JP2018189450A - Visual inspection device, and lighting device for visual inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure that light and darkness on image side is kept constant over time even when a wavelength shift occurs.SOLUTION: The present invention comprises: a lighting unit 10, having a plurality of LEDs 1 that generate light of different wavelengths, for irradiating a workpiece with light by the plurality of LEDs 1; a filter unit 200 having light transmission characteristics that differ depending on wavelength of light, with part of light of each wavelength generated individually from the plurality of LEDs 1 of the lighting unit 10 passing therethrough; a light-receiving unit 20 for receiving the light having passed through the filter unit 200 and having sensitivity characteristics differing from an imaging unit 30 depending on the wavelength of received light; and a control unit for controlling the lighting unit 10 so that the amount of irradiated light becomes approximately the same for each of the plurality of LEDs 1 on the basis of a signal representing the amount of received light for each wavelength, output from the light-receiving unit 20. The light transmission characteristics of the filter unit 200 are set in such a way that the sensitivity characteristics of light received by the light-receiving unit 20 via the filter unit 200 are approximately the same as the sensitivity characteristics of the imaging unit 30, in each wavelength region of light irradiated by the lighting unit 10.SELECTED DRAWING: Figure 13

Description

  The present invention relates to an appearance inspection apparatus and an appearance inspection illumination apparatus that perform an appearance inspection of a workpiece by multispectral imaging using a light source composed of a plurality of light emitting diodes (LEDs) that emit light of different wavelengths.

  There is known an appearance inspection apparatus that prepares an illumination device in which a plurality of color LEDs are arranged in a ring shape, and inspects the appearance of the workpiece by processing a captured image of the workpiece illuminated by the illumination device (for example, a patent). See reference 1.)

  In such an appearance inspection, it is desirable for the LED to prevent a decrease in the inspection accuracy of the workpiece, so that the light emission amount of each LED does not change with time, but the light emission amount decreases due to deterioration over time. For this reason, it is conceivable to provide a light receiving element for sensing such as a photodiode in the vicinity of the LED, and to correct the LED drive current so as to cancel the decrease in the amount of light emission based on the output from the light receiving element. For example, when the amount of light received by the light receiving element decreases, the LED drive current is increased. If the amount of light received by the light receiving element increases, the LED drive current is decreased.

JP 2006-047290 A

  By the way, this method is feedback control for preventing the light emission intensity of each LED itself from changing with time, and particularly in appearance inspection, it is important that the brightness of the captured image does not change with time. It is assumed that the change rate of the received light amount of the light receiving element for sensing is substantially the same as the change rate of the received light amount of the image pickup element for acquiring a captured image. For example, when the light emission intensity of the LED itself is reduced by 5%, the amount of light received by the light receiving element is reduced by 5%, and similarly, the amount of light received by the imaging element is reduced by 5%. If the directions match, feedback correction can be performed accurately.

  However, a phenomenon called wavelength shift in which the peak wavelength of emitted light shifts when the temperature of the LED rises is known, and when this wavelength shift occurs, even if there is no change over time in the emission intensity of each LED itself, As a result of a change in the amount of light received by the image sensor for acquiring the captured image and a change in brightness of the captured image, there is a possibility that the inspection accuracy may be reduced. In this regard, even if an attempt is made to reduce the influence of wavelength shift by the light receiving element for sensing, the light receiving element and the image pickup element have different wavelength light receiving sensitivity characteristics depending on the wavelength of the emitted light from the LED, so the increase / decrease direction of the received light amount does not match In some cases, it is not easy to know how to correct the LED drive current. An object of the present invention is to provide an appearance inspection apparatus, an appearance inspection illumination apparatus, and an appearance that can easily suppress a decrease in inspection accuracy even when the peak wavelength of emitted light emitted from a light source is shifted. It is providing the filter attached to the illuminating device for a test | inspection.

Means for Solving the Problems and Effects of the Invention

  According to the visual inspection apparatus according to the first aspect of the present invention, the illumination unit has a plurality of light emitting elements that generate light of different wavelengths, and irradiates the inspection object with the plurality of light emitting elements, Inspection having a sensitivity characteristic of receiving reflected light of each wavelength reflected from the inspection object irradiated by the illuminating unit and outputting a signal having different intensity according to the wavelength of the received reflected light, and inspection based on the sensitivity characteristic An appearance inspection apparatus that inspects the appearance of an inspection object by processing an inspection image generated by the imaging unit, and having different light transmission characteristics depending on the wavelength of light A filter unit through which a part of the light of each wavelength generated individually from the plurality of light emitting elements passes, and the imaging unit that receives the light that has passed through the filter unit and according to the wavelength of the received light Have different sensitivity characteristics An optical unit, and a control unit that controls the illuminating unit based on a signal that is output from the light receiving unit and that indicates the amount of light received at each wavelength, so that the amount of irradiation light is substantially constant for each of the plurality of light emitting elements. And the light transmission characteristic of the filter unit is the sensitivity characteristic of the light that has passed through the filter unit and received by the light receiving unit in each wavelength range of the light irradiated by the illuminating unit. Can be set to be approximately the same. According to the above configuration, even if a wavelength shift occurs in the emitted light from the LED, the brightness of the captured image to be subjected to the appearance inspection becomes constant over time based on the one-dimensional information of the change in the amount of light received by the light receiving unit. Thus, it becomes possible to accurately feedback correct the LED drive current.

  According to the visual inspection apparatus according to the second aspect of the present invention, the light transmission characteristic of the filter unit can be configured such that the light transmission characteristic decreases continuously or stepwise as the wavelength of light increases.

  Furthermore, according to the appearance inspection apparatus according to the third aspect of the present invention, the filter unit can be attached to a light receiving surface on which the light receiving unit receives light.

Furthermore, according to the visual inspection apparatus according to the fourth aspect of the present invention, the sensitivity characteristic of the imaging unit having a wavelength having a peak value of the sensitivity characteristic of light that has passed through the filter unit and received by the light receiving unit. The width of the wavelength λ _MAX having the peak value, which means a deviation width from the wavelength having the peak value, can be configured to be within ± 20% of the wavelength having the peak value of the sensitivity characteristic of the imaging unit.

Furthermore, according to the visual inspection apparatus according to the fifth aspect of the present invention, the sensitivity characteristic of the imaging unit having a wavelength having a peak value of the sensitivity characteristic of the light passing through the filter unit and received by the light receiving unit. The width of the wavelength λ _MAX having the peak value, which means a deviation width from the wavelength having the peak value, can be configured to be within ± 10% of the wavelength having the peak value of the sensitivity characteristic of the imaging unit.

  Furthermore, according to the visual inspection apparatus according to the sixth aspect of the present invention, the absolute value of the inclination of the inclined portion of the sensitivity characteristic graph of the light passing through the filter unit and received by the light receiving unit is the imaging unit. The sensitivity characteristic graph can be configured to be between 0.5 and 2 times the absolute value of the slope of the slope portion.

  Furthermore, according to the illumination device for appearance inspection according to the seventh aspect of the present invention, the reflected light of each wavelength reflected from the inspection object irradiated with light of different wavelengths is received, and the received reflected light of It has a sensitivity characteristic that outputs signals having different intensities according to wavelengths, and includes an imaging unit that generates an inspection image based on the sensitivity characteristic, and processes the inspection image generated by the imaging unit, thereby processing the inspection object. Illumination device for appearance inspection used in an appearance inspection apparatus for inspecting appearance, having a plurality of light emitting elements that generate light of different wavelengths, and illuminating an inspection object with the plurality of light emitting elements Part, a filter part having different light transmission characteristics depending on the wavelength of light, and a part of the light of each wavelength generated individually from the plurality of light emitting elements of the illumination part, and the filter part Received light A light receiving unit having a sensitivity characteristic different from that of the imaging unit according to the wavelength of the received light, and an amount of irradiation light for each of the plurality of light emitting elements based on a signal output from the light receiving unit and indicating a received light amount of each wavelength And a control unit that controls the illumination unit such that the light transmission characteristics of the filter unit pass through the filter unit in each wavelength region of light irradiated by the illumination unit and The sensitivity characteristic of the light received by the light receiving unit can be set to be substantially the same as the sensitivity characteristic of the imaging unit.

It is a graph which shows the temperature characteristic of the emission spectrum of UV-LED which uses AlGaN as a luminescent material. FIG. 2A is a schematic diagram for explaining the influence of the wavelength shift of the LED emitted light, FIG. 2A is a graph showing the emission intensity characteristic with respect to the wavelength of the LED emitted light, and FIG. 2B is a CMOS which is an imaging element on the imaging side FIG. 2C is a graph showing the light receiving sensitivity of the photodiode PD which is the light receiving element on the light receiving side. It is a schematic diagram for demonstrating feedback correction. It is a schematic diagram for demonstrating feedback correction. It is a mimetic diagram for explaining feedback amendment concerning this embodiment. FIGS. 6A and 6B are schematic diagrams for explaining a method for making the wavelength light receiving sensitivity characteristics of PD and CMOS substantially the same, FIG. 6A is a wavelength light receiving sensitivity characteristic of CMOS, and FIG. 6B is a wavelength light receiving sensitivity characteristic of PD. 6C shows the wavelength light transmission characteristic of the filter, and FIG. 6D shows the wavelength light receiving sensitivity characteristic of the PD when this filter is installed before light enters the PD. FIG. 7A is a schematic diagram for explaining the influence of wavelength shift of LED emission light when an ideal filter is applied to a PD, and FIG. 7A is a graph showing emission intensity characteristics with respect to the wavelength of LED emission light; FIG. 7B is a graph showing the light reception sensitivity of the CMOS, and FIG. 7C is a graph showing the light reception sensitivity of the PD after applying an ideal filter. It is a system configuration figure showing the composition of the appearance inspection device concerning a 1st embodiment of the present invention. It is a block diagram which shows the structure of the external appearance inspection apparatus which concerns on the 1st Embodiment of this invention. It is a schematic plan view which shows the illumination part which concerns on the 1st Embodiment of this invention. It is a figure which shows the internal structure of the illumination part for demonstrating arrangement | positioning of the filter part which concerns on this embodiment. It is a figure which shows the internal structure of the illumination part for demonstrating arrangement | positioning of the filter part which concerns on this embodiment. FIG. 13A is a graph showing the wavelength light reception sensitivity characteristic in which the light reception sensitivity of the PD is plotted, and FIG. 13B is a graph showing the light transmittance of the filter unit. 13C is a graph showing the wavelength light transmission characteristics of the PD to which the filter unit is applied, which is obtained by multiplying the light reception sensitivity of the PD and the light transmittance of the filter unit. FIG. 13D is a graph showing the wavelength light receiving sensitivity characteristic in which the light receiving sensitivity of the CMOS is plotted. It is a block diagram which shows the structure of the input management part and memory | storage part which concern on the 1st Embodiment of this invention. It is a flowchart of the setting method in the visual inspection which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the image inspection method in the external appearance inspection which concerns on the 1st Embodiment of this invention. It is a figure which shows the light receiving element corresponding | compatible table which concerns on the 1st Embodiment of this invention. FIG. 4 is a schematic diagram illustrating that images for each wavelength are acquired by irradiating a work piece with illumination light having different wavelengths one by one in order in order to explain the basic principle of multispectral imaging in full lighting mode. . It is a schematic diagram for demonstrating setting mode. It is a schematic diagram for demonstrating inspection mode. It is a schematic diagram for demonstrating the method of producing one gray image from the three gray images corresponding to R, G, and B. FIG. It is a figure which shows the positional relationship of the diffuse reflection surface S and illumination for demonstrating the basic principle of a photometric stereo method. It is a figure which shows the state which irradiated the light from the 1st lighting block. It is a figure which shows the state which irradiated the light from the 2nd lighting block. It is a figure for demonstrating estimating the direction of the surface from the combination of an irradiation direction and the brightness of reflected light. It is a figure which shows an example of the inclination image differentiated to the orthogonal | vertical direction for demonstrating the production | generation method of an outline extraction image. It is a figure which shows an example of the inclination image differentiated in the horizontal direction. It is a figure which shows an example of an outline extraction image. It is a top view which shows the illumination part which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows 1st Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a schematic diagram which shows 2nd Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a schematic diagram which shows 3rd Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a schematic diagram which shows 4th Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a top view which shows the illumination part which concerns on the 3rd Embodiment of this invention. It is a circuit diagram of the lighting circuit incorporated in the illumination part which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows 5th Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a schematic diagram which shows 6th Embodiment of the positional relationship of the light source unit of this invention, and a light-receiving part. It is a model perspective view of the light-receiving part which concerns on the 2nd Embodiment of this invention. It is a schematic cross section of the light-receiving part which concerns on the 2nd Embodiment of this invention. It is a schematic cross section of 2nd Embodiment regarding arrangement | positioning of the illumination board | substrate of this invention. It is a schematic cross section of 3rd Embodiment regarding arrangement | positioning of the illumination board | substrate of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below is an example for embodying the technical idea of the present invention, and the present invention is not limited to the following. Moreover, this specification does not specify the member shown by the claim as the member of embodiment. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the embodiments are not intended to limit the scope of the present invention only to specific examples unless otherwise specifically described. Only. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and reference sign indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.

An appearance inspection device and an appearance inspection illumination device to which the present invention is applied include an illumination device in which a plurality of color LEDs (light emitting diodes) that emit light of different wavelengths are arranged in a ring shape, and the amount of light emitted from the plurality of LEDs is determined. A system for feedback correction using a photodiode includes a configuration for reducing the influence of the wavelength shift of the LED when visual inspection of a workpiece is performed by multispectral imaging. Therefore, the description of this embodiment is based on an illumination device in which a plurality of color LEDs that emit light of different wavelengths are arranged in a ring shape, and a system that feedback-corrects the amount of light emitted from the plurality of LEDs by a photodiode. As appropriate, the configuration for reducing the influence of the wavelength shift of the LED and the appearance inspection by multispectral imaging will be mentioned.
(Basic principle)

  FIG. 1 is a graph showing temperature characteristics of an emission spectrum of a UV-LED using AlGaN as a light emitting material. As shown in this figure, unlike a laser diode, an LED emits light in a wide wavelength range, and when the temperature rises due to ambient temperature or heat generation during energization, the emission spectrum shifts to the longer wavelength side. This phenomenon is called wavelength shift, and occurs with LED emitted light of all wavelengths.

  FIG. 2 is a schematic diagram for explaining the influence of the wavelength shift of the LED emission light. FIG. 2A is a graph showing the emission intensity characteristic with respect to the wavelength of the LED emission light, and FIG. 2B and FIG. 5 is a graph showing the light receiving sensitivity of a CMOS (Complementary MOS) that is an image pickup element on the image pickup side and a photodiode PD that is a light receiving element on the light receiving side. In these figures, for convenience of explanation, an LED having an emission spectrum with a short wavelength is referred to as a B-LED, an LED having an emission spectrum with a long wavelength is referred to as an R-LED, and an LED positioned therebetween is referred to as a G-LED. In FIG. 2A, the solid line shows the emission spectrum of the LED before the wavelength shift, and the broken line shows the emission spectrum of the LED after the wavelength shift.

Here, as shown in FIG. 2A, as the temperature rises, the emission spectrum of the B-LED is in the wavelength range from λ ₀ to λ ₁ and the emission spectrum of the G-LED is in the wavelength range from λ ₂ to λ _3. Consider a case where the emission spectrum of the R-LED is shifted in wavelength by a little (for example, 5 μm) in the wavelength range of λ ₄ to λ ₅ .

The captured image is determined not by the amount of light emitted by the LED but by the amount of light received by the CMOS, and as shown in FIG. 2B, the amount of light that can actually be sensed by the CMOS differs depending on the wavelength of the light. For example, in the B-LED, the light reception sensitivity of the CMOS increases from S ₀ to S ₁ despite the fact that the light emission intensity does not change due to the wavelength shift from λ ₀ to λ ₁ , so that the amount of S ₁ -S ₀ is increased. The captured image becomes brighter by the corresponding amount. For example, in the G-LED, even if there is a wavelength shift from λ ₂ to λ ₃ , the light receiving sensitivity of the CMOS remains unchanged at S ₂ (S ₃ = S ₂ ), so the brightness of the captured image does not change. For example, in R-LED, the wavelength shift from lambda ₄ lambda to _5, the light receiving sensitivity of the CMOS is lowered to _{S 5} from _{S 4,} the captured image becomes darker by an amount corresponding to the amount of S 4 -S _5.

On the other hand, when the change in the actual light emission amount at the LED is estimated by the change in the light reception amount at the PD that performs sensing, as shown in FIG. 2C, the light amount that can actually be sensed by the PD depends on the wavelength of the light. From the difference, for example, in the B-LED, the light receiving sensitivity of the PD increases from S ′ ₀ to S ′ ₁ due to the wavelength shift from λ ₀ to λ ₁ , which corresponds to the amount of S ′ ₁ -S ′ _0. It is estimated that the actual amount of light emitted from the LED has increased by that amount. For example G-LED, similarly in R-LED, the amount of S _'3 -S' _2, by an amount corresponding to the amount of S _'4 -S' _5, respectively, the actual amount of light emitted by the LED is increased presume.

Therefore, in the B-LED, the captured image to be subjected to the appearance inspection becomes bright as estimated based on the PD, but in the G-LED and R-LED, the captured image does not change contrary to the estimation based on the PD. Or it will be dark. In the case of the R-LED, as shown in FIG. 3, in the feedback correction, it is estimated that the actual light emission amount in the R-LED is increased by an amount corresponding to the amount of S ′ ₄ -S ′ _5. For the R-LED, the LED driving current is controlled so as to reduce the light emission amount. On the imaging side, as shown in FIG. 4, the captured image is darkened by an amount corresponding to the amount of S ₄ -S _{5 due} to the wavelength shift, and the light emission amount of the R-LED itself by feedback correction. Decreases, the captured image becomes darker.

  This defect is due to the wavelength shift of the emitted light from the LED, and as an actual phenomenon, the influence of the change in the light emission intensity of the LED itself over time is added, so accurate feedback based on the change in the amount of light received by the PD In order to correct, it is necessary to grasp whether the change in the amount of light received by the PD is caused by the wavelength shift of the emitted light from the LED or the influence of the change in the emission intensity of the LED itself over time.

  Here, in the wavelength range of the B-LED in which the wavelength sensitivity characteristics of the PD and the CMOS are similar, it is necessary to pay attention to the fact that the captured image to be subjected to the appearance inspection becomes bright as estimated based on the PD. If the wavelength sensitivity characteristics of PD and CMOS are the same in the wavelength range to be used, the increase / decrease direction of the amount of received light due to the wavelength shift always matches, so the influence of the wavelength shift and the emission intensity of the LED itself There is no need to distinguish the effects of changes over time. This makes it possible to accurately feedback-correct the LED drive current based on one-dimensional information about the change in the amount of light received by the PD so that the brightness of the captured image that is the subject of the appearance inspection is constant over time. It is not easy to match the wavelength sensitivity characteristics of both by the design of the material of the PD itself.

  Therefore, in this embodiment, as shown in FIG. 5, it is considered that a filter is installed before light enters the PD. FIG. 6 is a schematic diagram for explaining a method for making the wavelength light receiving sensitivity characteristics of PD and CMOS substantially the same, FIG. 6A is a wavelength light receiving sensitivity characteristic of CMOS, and FIG. 6B is a wavelength light receiving characteristic of PD. FIG. 6C shows the wavelength light transmission characteristic of the filter. FIG. 6D shows the wavelength light reception sensitivity characteristic of the PD when this filter is installed before light enters the PD.

6A is a target for which the wavelength sensitivity characteristic of the CMOS shown in FIG. 6A is a target, and the light reception sensitivity value of the PD shown in FIG. 6B is multiplied by the light transmittance of the filter shown in FIG. Match. As shown in FIG. 6B, the light receiving sensitivity of the PD is low in the short wavelength light receiving sensitivity and increases to the right, so that the light transmittance is high on the short wavelength side and the light transmittance on the long wavelength side. For example, a filter having a wavelength light transmission characteristic as shown in FIG. 6C is designed or adopted, and this filter is disposed in front of the PD. The waveform of the light receiving sensitivity characteristic can be made to be similar to the waveform of the CMOS wavelength light receiving sensitivity characteristic shown in FIG. 6A. When such a similar filter can be arranged in front of the PD, the light receiving sensitivity values S ″ _{0 to} S ″ ₅ corresponding to the peak wavelengths of B-LED to R-LED shown in FIG. Since this is a value, it corresponds to the relative values S _{0 to} S ₅ of the light receiving sensitivity in the CMOS shown in FIG. 6A.

FIG. 7 is a schematic diagram for explaining the influence of the wavelength shift of the LED emission light when an ideal filter is applied to the PD, and FIG. 7A shows the emission intensity characteristic with respect to the wavelength of the LED emission light. FIG. 7B is a graph showing the light receiving sensitivity of the CMOS, and FIG. 7C is a graph showing the light receiving sensitivity of the PD after applying an ideal filter. 7B and 7C, as described above, S _{0 to} S ₅ and S ″ _{0 to} S ″ ₅ coincide with each other, and therefore any of B-LED to R-LED is a target for visual inspection. The brightness of the captured image is as estimated based on the PD. In other words, if an ideal filter is applied to a PD, whether or not a wavelength shift occurs in the emitted LED light, the object of appearance inspection is determined based on one-dimensional information such as a change in the amount of light received by the PD. Thus, it becomes possible to accurately feedback-correct the LED drive current so that the brightness of the captured image becomes constant over time.

  In this embodiment, while keeping the amount of illumination constant over time, it is not limited to high-resolution color inspection, and spectral analysis on the imaging side is not performed so that appearance inspection of a workpiece can be performed by multispectral imaging described later, Since eight LEDs with different wavelengths of emitted light are provided on the illumination side, and a configuration for performing feedback correction with one PD arranged in the vicinity of the eight LEDs, the filter includes eight LEDs. In all the wavelength ranges of the emitted light, a wavelength light transmission characteristic is required so that the increase / decrease direction of the received light amount accompanying the wavelength shift always matches between PD and CMOS.

  Note that the wavelength-sensitivity characteristic (first sensitivity characteristic) of CMOS and the filter pass between the shortest wavelength and the longest wavelength (hereinafter referred to as “irradiation wavelength band”) among the wavelengths emitted by the light emitting element. The transmission characteristics for each wavelength of the filter are designed so that the wavelength-sensitivity characteristics (second sensitivity characteristics) of the PDs that have received the light after being processed are substantially the same. In the wavelength band outside the wavelength, the first sensitivity characteristic and the second sensitivity characteristic are not necessarily the same.

  It is preferable that the continuous curve of the first sensitivity characteristic in the irradiation wavelength band and the continuous curve of the second sensitivity characteristic are the same. Thereby, even if the wavelength which each light emitting element emits shifts by the change of temperature, the change width of the sensitivity of the CMOS and the change width of the sensitivity of the PD due to the shift can be made substantially the same.

The irradiation wavelength band does not necessarily have to be defined between the shortest wavelength and the longest wavelength strictly, and is defined by a bandwidth in consideration of a wavelength shift due to a temperature change. The wavelength shift due to the temperature change occurs, for example, plus or minus 1% to 5% for each wavelength. Here, the temperature change is, for example, a change in operating temperature (for example, 0 to 100 degrees).
(System configuration of visual inspection equipment)

FIG. 8 is a diagram illustrating an example of an appearance inspection system. The appearance inspection line has a conveyance belt HB that conveys a workpiece W that is an inspection object. The illumination device includes an annular illumination unit 10 that illuminates the workpiece W, and includes a plurality of LEDs 1 (basic light sources) having different wavelengths. The illumination part 10 has an annular part and is divided into a plurality of lighting blocks TB1 to TB4 in the circumferential direction, and a plurality of LEDs 1 having different wavelengths are arranged in each of the lighting blocks TB1 to TB4. The illumination unit 10 can switch between lighting and extinguishing with the lighting block TB as a minimum unit. The camera is an imaging unit 30 that receives reflected light from the illuminated workpiece W and generates a luminance image, and is disposed on the central axis of the annular illumination unit 10. The image treatment device 40 controls the illumination device and the camera, performs image processing such as edge detection and area calculation on the image acquired by the camera, and determines the quality of the workpiece W. A PLC 70 (Programmable Logic Controller) is connected to the image processing apparatus. A photoelectric sensor 90 or the like connected to the PLC 70 and provided at a predetermined position on the appearance inspection line detects that the work W has arrived on the central axis of the annular illumination device or at a predetermined upstream position of the illumination device. Then, the PLC 70 transmits a trigger signal to the image processing device 40. When the image treatment device 40 receives the trigger signal from the PLC 70, the image processing device 40 turns on the illumination device at a timing at which the work W is conveyed to the illumination device, preferably at the center of the annular illumination unit 10, and illumination is performed. The camera is controlled to take an image at the timing when the work W is illuminated by the apparatus. The image processing apparatus 40 executes image processing using an image acquired by the camera, and determines whether or not the work W is a non-defective product as a result of an appearance inspection with respect to an externally connected control device such as the PLC 70. A determination signal is output as a signal indicating the result. The display unit 50 is connected to the image processing apparatus 40 and displays a user interface for setting control parameters related to the examination, an image of the workpiece W, a result of an appearance inspection of the workpiece W, and the like. The input unit 60 is a pointing device 61, a keyboard 62, a console, and the like, and is connected to the image processing apparatus 40 and used to set control parameters.
(Configuration of appearance inspection equipment)

FIG. 9 shows a block diagram of the appearance inspection apparatus according to the first embodiment of the present invention. The visual inspection apparatus shown in this figure is arranged on the annular illumination device and on the approximate center axis of the annular illumination device and above the illumination device, and when the workpiece W is positioned at the approximate center of the annular illumination unit 10. An image pickup unit 30 for picking up an image of the work W, a display unit 50 for displaying a setting screen, an image of the picked-up work W, and a pass / fail judgment result, an input unit 60 for making various settings such as control parameters, and various control processes. The image processing apparatus 40 which performs is provided. The lighting device is composed of a plurality of lighting blocks TB, and an annular lighting unit 10 in which a plurality of LEDs 1 emitting light of different wavelengths are arranged in each lighting block TB, and when the lighting unit 10 is turned on And a light receiving unit 20 that receives light. The image processing device 40 is set by the input management unit 41 that manages various settings such as the illumination method, wavelength selection, and light amount setting, and the light amount received by the light receiving unit and the light amount setting unit for each lighting block TB. A light amount correction value setting unit 42 for setting a light amount correction value by comparing the light amount, an illumination control unit 43 for turning on the illumination unit 10, and an imaging control unit 44 for controlling the timing of imaging by the imaging unit 30. The image processing unit 45 that performs image processing using the image acquired by the imaging unit 30 and determines whether the workpiece W is acceptable or not using the image data that has been subjected to image processing, and the content that is displayed on the display unit 50 are controlled. And a storage unit 47 for storing various settings. Furthermore, the image processing apparatus 40 can be connected to an external device such as the PLC 70 or the computer 80 as required. Note that the image processing apparatus 40 can be connected to a controller or the like as necessary, and various control processes other than image processing can be assigned to the controller or the like.
(Lighting part)

As shown in FIG. 10, the illumination unit 10 includes a plurality of LEDs 1 arranged in an annular shape on the illumination substrate 3 constituting a single plane, and at least in the center of the annular illumination unit 10, The hollow portion is formed so that the image pickup unit 30 can pick up an image of the workpiece W positioned at the center. A single plane including all the LEDs 1 arranged in the illumination unit 10 is substantially parallel to a conveyance surface such as a conveyance belt HB that conveys the workpiece W or a surface of the workpiece W to be inspected. The illumination unit 10 is arranged. And it becomes the structure which can irradiate illumination light to the center part of the cyclic | annular illumination part 10 simultaneously and from the different illumination directions, or to change a direction sequentially for every lighting block TB with respect to the workpiece | work W positioned below. Yes. In the present embodiment, a plurality of LEDs 1 each emitting different wavelengths are used as one light source unit KT, and the annular body is divided substantially equally in the circumferential direction to form a plurality of lighting blocks TB1 to TB4. At least one light source unit KT is arranged for the blocks TB1 to TB4. In the present embodiment, the illumination unit 10 is divided into four. Thereby, the illumination unit 10 of the present embodiment is configured by four lighting blocks TB1 to TB4 of the first lighting block TB1, the second lighting block TB2, the third lighting block TB3, and the fourth lighting block TB4, and each At least one light source unit KT is arranged in the lighting blocks TB1 to TB4. In the embodiment shown in FIG. 10, one light source unit KT is arranged in each of the lighting blocks TB <b> 1 to TB <b> 4, but the number of light source units KT may be increased or decreased according to the size of the illumination unit 10, for example. Good. As will be described in detail later, when there are a plurality of light source units KT in one lighting block TB, LEDs 1 having the same properties are arranged for each light source unit KT, and they are connected in series and lit by the same control circuit. Therefore, the characteristic of the light emitted from the LED 1 of the light source unit KT that cannot be received by the light receiving unit 20 can be regarded as the same as the characteristic of the light emitted from the LED 1 of the light source unit KT that can be received by the light receiving unit 20. Accordingly, if at least one light source unit KT can be received by the light receiving unit 20 without receiving light emitted from all the light source units KT by the light receiving unit 20, the lighting block TB including the light source unit KT. The characteristics of the emitted light from the other light source unit KT can be grasped. Moreover, as shown in FIG. 8, each lighting block TB1-TB4 is irradiated so that the light irradiated from each lighting block TB1-TB4 may be irradiated toward the workpiece | work W positioned in the center of the cyclic | annular illumination part 10. As shown in FIG. The optical axis is configured to be directed to the central portion obliquely below.
(Light receiving section)

As shown in FIG. 10, the light receiving unit 20 is installed corresponding to a plurality of lighting blocks TB arranged substantially equally in the circumferential direction of the annular body of the lighting unit 10, and is arranged in each of the lighting blocks TB1 to TB4. The light emitted from all the LEDs 1 as the light source unit KT to be received is configured to be received. In the present embodiment, the first light receiving unit 21 is provided in the first lighting block TB1, the second light receiving unit 22 is provided in the second lighting block TB2, and the third light receiving unit 23 is provided in the third lighting block TB3. The fourth light receiving unit 24 is arranged in the fourth lighting block TB4. Each of the light receiving units 20 is arranged on the outer peripheral side of the light source unit KT at the central portion in the circumferential direction of each of the lighting blocks TB1 to TB4 in correspondence with the light source unit KT, but in each of the lighting blocks TB1 to TB4. For example, the light source unit KT may be disposed at the end of the lighting block TB in the circumferential direction as long as it can receive light from all the LEDs 1 appropriately. Each light receiving unit 20 has one light receiving element 2 that receives light of the LED 1 of each wavelength and outputs a light receiving signal indicating the amount of light. Each light receiving unit 20 may be composed of a plurality of light receiving elements 2. In that case, the light receiving unit 20 outputs a light reception signal indicating one light quantity such as an average value of values received by the plurality of light receiving elements 2. The light source unit KT includes at least one LED 1 of each wavelength that receives light at the light receiving unit 20 and emits light of different wavelengths, and each LED 1 can independently correct the amount of light for each wavelength. Is. The lighting block TB is composed of a plurality of LEDs 1 having different wavelengths including at least one light source unit KT, and lights up for each wavelength by one signal from the illumination control unit 43.
(Filter part)

  The filter unit 200 is a filter having a wavelength light transmission characteristic as shown in FIG. 6C as an ideal type that has a high light transmittance on the short wavelength side and a low light transmittance on the long wavelength side. As shown in FIGS. 11 and 12, for example, it has a plate shape, and is arranged in contact with the light receiving surface of the light receiving unit 20 so that the thickness direction matches the light receiving direction of the light receiving unit 20. With this arrangement, as shown in FIG. 5, the filter unit 200 is interposed between the LED 1 and the light receiving unit 20 (PD), and the light transmittance is distributed with respect to the wavelength according to its own wavelength light transmission characteristic. Thus, the light emitted from all the LEDs 1 as the light source unit KT disposed in each of the lighting blocks TB1 to TB4 is transmitted.

  In the present embodiment, the first light receiving unit 21 in the first lighting block TB1 has the first filter unit 201 (see FIG. 11), and the second light receiving unit 22 in the second lighting block TB2 has the second light receiving unit 22. The filter unit 202 (see FIGS. 11 and 12) is provided in the third light receiving unit 23 in the third lighting block TB3, the third filter unit 203 is provided in the fourth lighting block TB4, and the fourth light receiving unit 24 in the fourth lighting block TB4. A fourth filter unit 204 (see FIG. 11) is arranged. In addition, although the filter part 200 receives light emitted from the LED 1 directly by the light receiving part 20, if the filter part does not intervene in the light toward the workpiece W, the light may be received indirectly via a mirror, for example. Good.

  13A and 13B illustrate wavelength light transmission characteristics of the filter unit 200 used in the present embodiment. FIG. 13A illustrates wavelength light reception sensitivity characteristics in which the light reception sensitivity of the PD used as the light receiving element in the light receiving unit 20 is plotted. FIG. 13B is a graph showing wavelength light transmission characteristics in which the light transmittance of the filter unit 200 used in this embodiment is plotted. FIG. 13C is a graph showing the light reception sensitivity of the PD and the light transmittance of the filter unit 200. FIG. 13D is a graph showing the wavelength light transmission characteristics of a PD to which the filter unit 200 according to this embodiment is applied, and FIG. 13D is a wavelength plotting the light receiving sensitivity of a CMOS used as an image sensor in this embodiment. It is a graph which shows a light reception sensitivity characteristic.

  In the description of the basic principle, an ideal filter is assumed, and the wavelength light receiving sensitivity characteristics are completely similar between the PD side and the CMOS side. However, in order to obtain the effect of the present invention, the filter unit 200 is used. It is sufficient if the wavelength having the peak value of the wavelength light transmission characteristic of the PD to which is applied and the wavelength having the peak value of the wavelength sensitivity characteristic of the CMOS are substantially the same and substantially similar. In other words, as shown in FIG. 13D, the wavelength sensitivity characteristic of the CMOS generally has a lower light receiving sensitivity as it goes away from the wavelength having the peak value. Therefore, the filter unit 200 according to this embodiment shown in FIG. The wavelength light transmission characteristics of the applied PD need only be the same as the wavelength sensitivity characteristics of the CMOS according to the present embodiment shown in FIG. .

More specifically, it has a peak value that means a deviation width between a wavelength having a peak value of the wavelength light transmission characteristic of a PD to which the filter unit 200 is applied and a wavelength having a peak value of the wavelength sensitivity characteristic of the CMOS. The width of the wavelength λ _MAX is preferably within ± 20% of the wavelength having the peak value of the CMOS wavelength light receiving sensitivity characteristic, and more preferably within ± 10%. Also, the absolute value of the slope of the slope of the wavelength light transmission characteristic graph of the PD to which the filter unit 200 is applied is from 0.5 times (50%) the absolute value of the slope of the slope of the wavelength sensitivity characteristic graph of the CMOS. It is preferably between 2 times (200%).

The reason why it is more preferable if the width of the wavelength λ _MAX having the peak value is within ± 10% is as follows. The wavelength light receiving sensitivity characteristic of the CMOS according to the present embodiment has a peak value in the vicinity of 600 nm. In the present embodiment, as described above, eight LEDs having different wavelengths of emitted light are provided on the illumination side, and the interval between the peaks of each of the eight LED emitted lights is 70 to 80 nm. This is because it is considered that the emitted light from the LEDs does not interfere with each other even if the deviation is ± 10%. In addition, it is preferable that the width of the wavelength λ _MAX having the peak value is within ± 20%. If the increase / decrease direction of the received light amount due to the wavelength shift coincides with each other, the purpose can be achieved by feedback control. Even if there is a slight deviation, if the convex shape as shown in the graph can be realized, a certain degree of effect can be expected, and it is acceptable if it is within ± 20% of the wavelength having the peak value of the wavelength sensitivity characteristic of CMOS. It is possible.

  Also, the absolute value of the slope of the slope portion of the wavelength light transmission characteristic graph of the PD to which the filter unit 200 is applied is 0.5 times (50%) the absolute value of the slope portion of the wavelength sensitivity characteristic graph of the CMOS. The reason why it is preferable to be between 2 times (200%) is that the increase / decrease direction of the received light amount accompanying the wavelength shift coincides with each other. Because it is considered to be.

Based on the above, when focusing on the wavelength light transmission characteristics of the PD to which the filter unit 200 according to the present embodiment shown in FIG. 13C is applied and the wavelength sensitivity characteristics of the CMOS according to the present embodiment shown in FIG. However, since both have substantially the same wavelength with peak values and are substantially similar, the filter unit 200 used in this embodiment is sufficiently practical. Conceivable.
(Imaging part)

The imaging unit 30 receives a control signal from the image processing device based on the trigger signal from the PLC 70, and acquires an image of the workpiece W by imaging the workpiece W at the timing when the light from the illumination unit 10 is irradiated. To do. It is preferable that the optical axis of the imaging unit 30 and the central axis of the annular illumination unit 10 are arranged to coincide with each other. As the imaging unit 30, for example, an imaging element such as a CCD or a CMOS can be used. The imaging unit 30 images the workpiece W and outputs an image signal, converts the output image signal into a luminance signal, and outputs the luminance signal to the image processing unit 45 connected by an imaging cable.
(Display section)

The display unit 50 displays a screen that accepts various settings such as control parameters from the input unit 60 and displays a captured image. The display unit 50 is connected to the image processing apparatus via a cable or the like. You may comprise so that the screen which receives various settings, and the imaged image may be displayed on the screen of the computer 80 which can be connected to an image treatment apparatus.
(Flow of appearance inspection method)

The flow of the appearance inspection method in the present invention is roughly divided into three steps. The first step is a setting step. Before the appearance inspection apparatus is operated and the workpiece W is visually inspected, various control parameters such as selection of the wavelength and setting of the amount of light irradiated at the selected wavelength are set. This is the setting step. The next step is a tuning step. When the irradiation of light from the illumination unit 10 is instructed based on the light amount set in the setting step, the light emitted from the illumination unit 10 may not be the set light amount due to deterioration of the LED 1 or wavelength shift. is there. In this case, the light amount is corrected so that the light emitted from the illumination unit 10 becomes the set light amount. The last step is an operation step, in which the workpiece W is imaged using light emitted from the illumination unit 10 based on the corrected light quantity, and an appearance inspection of the workpiece W is performed.
(Input Management Department)

FIG. 14 is a block diagram showing a configuration example of the input management unit 41 in FIG. In the setting step, the input management unit 41 selects an illumination method selection unit 411 for selecting an illumination method and a wavelength for selecting a wavelength necessary for the inspection from each wavelength of the LED 1 arranged in the illumination unit 10. A selection unit 412 and a light amount setting unit 413 for setting the light amount of light emitted from the LED 1 having the wavelength selected using the wavelength selection unit 412 are provided.
(Lighting method selector)

In the setting step, the illumination method selection unit 411 receives any one of a plurality of irradiation methods of light emitted from the illumination unit 10 from the user. In the irradiation method, all the lighting blocks TB1 to TB4 provided in the illumination unit 10 are turned on while sequentially switching the lighting blocks TB1 to TB4 to illuminate the work W, and each time the lighting block TB is turned on. The partial switching lighting mode in which the imaging unit 30 captures the workpiece W and all the lighting blocks TB1 to TB4 of the lighting unit 10 that are simultaneously turned on to illuminate the workpiece W, and the imaging unit 30 captures the workpiece W. There is a lighting mode. In the partial switching lighting mode, it is possible to acquire an image for each irradiation direction of the workpiece W irradiated with light sequentially from a plurality of different directions by turning on the illumination for each lighting block TB. In the all lighting mode, it is possible to acquire an image of the work W in a state where all the lighting blocks TB1 to TB4 are turned on simultaneously. The partial switching lighting mode is suitable for detecting scratches and the like because light is emitted from a plurality of directions. The full lighting mode is suitable for detecting color unevenness and the like because uniform light is emitted by simultaneously lighting all the lighting blocks TB1 to TB4. Therefore, the user selects one mode from the viewpoint of whether detection of scratches or color unevenness is desired. Further, regarding the partial switching lighting mode, the lighting is performed for each lighting block TB, and in addition to the mode for performing imaging, an image captured for each lighting block TB is presented to the user at the time of setting, so that the user desires. A function for designating lighting of only the lighting block TB effective for checking the inspection contents, for example, the presence or absence of scratches on a specific part of the work W (function of always turning off the lighting block TB determined to be unnecessary) is further provided. May be. However, in this case, when the workpiece W is arranged at a position illuminated by the illumination unit 10, it is preferably positioned and supplied. The illumination method selected by the illumination method selection unit 411 is stored in the storage unit 47.
(Wavelength selector)

  The wavelength selection unit 412 is a selection unit for selecting at least one wavelength among the wavelengths of the LEDs 1 arranged in the illumination unit 10 in the setting step. After the illumination method is selected by the illumination method selection unit 411, the wavelength selection unit 412 accepts the selection of the wavelength. The wavelength selected by the wavelength selection unit 412 is stored in the storage unit 47.

  As described above, the wavelength can be set with respect to the illumination unit 10 using the wavelength selection unit 412. However, it is important that the user in advance has a plurality of wavelengths provided by the illumination unit 10. It is to grasp which wavelength is effective for the inspection content of the work W provided by the user. Therefore, in the present embodiment, at the time of setting before inspection, a plurality of wavelength selection units 412 are provided based on a plurality of images obtained by sequentially irradiating the workpiece W with a plurality of light beams having different wavelengths. Provides a function of selecting one of the wavelengths. For example, after the illumination method is selected, the illumination unit 10 irradiates a defective product having scratches or uneven color, respectively, with light of a plurality of different wavelengths, and the imaging unit 30 acquires images irradiated at the respective wavelengths. To do. When a plurality of obtained images are compared, there may be an image in which a flaw or color unevenness is detected and an image in which a flaw or color unevenness to be detected is not detected. Therefore, the wavelength selection unit 412 extracts an image in which scratches or color unevenness is detected from a plurality of images, specifically, an image having a variation in the luminance value of the luminance image, and is used for the extracted image. Select a wavelength.

In addition, when the wavelength is selected, the wavelength selecting unit 412 automatically selects the wavelength, and the user can manually select the wavelength based on his / her own judgment. At that time, the display unit 50 simultaneously displays a plurality of images respectively irradiated with a plurality of wavelengths so that the user can select one or more appropriate wavelengths that are easy to detect scratches and color unevenness. I have to. When a specific wavelength is not selected by the wavelength selection unit 412, a state in which all provided wavelengths are selected as the initial value set in the image processing apparatus 40 is employed. As the initial value, a specific limited wavelength may be adopted instead of all wavelengths.
(Light intensity setting part)

  The light amount setting unit 413 is a setting unit for setting the light amount of light emitted from the LED 1 having the wavelength selected by the wavelength selection unit 412 in the setting step. When the selection of the illumination method and the selection of the wavelength are completed, the light amount setting unit 413 receives the setting of the light amount of the selected wavelength. When the light amount is set by the light amount setting unit 413, the current value corresponding to the light amount set by the light amount setting unit 413 flows through the LED 1 having the selected wavelength, so that the LED 1 having the selected wavelength has the light amount setting unit 413. Lights with the light intensity set in. The light amount set by the light amount setting unit 413 is stored in the storage unit 47. When the wavelength selection unit 412 selects a plurality of wavelengths, the light amount setting unit 413 can set a different light amount for each wavelength. When a different light amount is set for each wavelength, the light amount for each wavelength is stored.

  As described above, the light amount setting unit 413 can be used to set the light amount for the selected wavelength, but what is important is how the user can set the optimal light amount in advance. For this reason, in the following embodiments, a plurality of different light amounts of light are sequentially irradiated onto the workpiece W, and the light amount setting unit 413 refers to a plurality of images obtained for each irradiation. Therefore, it is possible to set an appropriate amount of light.

  Specifically, in the setting step, after the selection of the illumination method and the selection of the wavelength are completed, a plurality of light amounts of light are sequentially irradiated onto the workpiece W at the selected wavelength, and the light is irradiated with the plurality of light amounts. Each of the workpieces W is captured, and based on the plurality of captured images, the light amount setting unit 413 adjusts the light amount so that the image to be captured or the inspection region set for the image becomes an image suitable for inspection. Set automatically. In detail, when taking a picture with a monochrome camera, if the illumination is too bright, there will be many white parts (so-called whiteout) in the picture, and conversely if it is too dark, there will be many black parts (so-called blackout) in the picture. There is a high possibility that the inspection cannot be performed accurately with either image. In this embodiment, an LED having a specific wavelength can be selected and irradiated from among a plurality of LEDs having different wavelengths of emitted light. For example, a red LED is applied to a bright red workpiece W. In this case, the received image sensitivity is affected by the irradiation target and the wavelength of the emitted light. The light amount adjustment when a plurality of LEDs can be selected is more difficult than the light amount adjustment when irradiating with only one color LED.

  That is, it is preferable that the entire captured image or at least a region to be inspected in the image is reflected in gray with little overexposure or blackout. Therefore, the illumination unit 10 emits light to the workpiece W with a plurality of brightnesses, the imaging unit 30 captures the workpiece W for each illumination having different brightness, and the image processing unit 45 generates respective luminance images. . The light quantity setting unit 413 sets the brightness to 0 from among the plurality of captured images, or from an image in which at least an area to be inspected is a gray tone, for example, a 256-gradation brightness image. A luminance image with few pixels close to and 255 pixels is extracted. The light amount setting unit 413 determines that the light amount at the time of capturing the extracted luminance image has a brightness suitable for the inspection, and automatically sets the light amount. As another example, when a plurality of light amounts are irradiated on the defective product in advance by the illumination unit 10, the light amount setting unit 413 performs image processing to be described later from among the obtained plurality of luminance images. It is possible to select the light amount of an image in which scratches and the like are detected by the average gradation processing by the unit 45.

  When setting the light amount, the light amount setting unit 413 automatically sets the light amount, and the user can manually set the light amount based on his / her own judgment. At that time, the display unit 50 can simultaneously display images of a plurality of workpieces W captured for each light amount of different brightness within the range that the illumination unit 10 can provide, so that the user can select an appropriate light amount. I am doing so.

In the above-described embodiment, the various parameters of the setting step are set in the order of selection of the illumination method, selection of the wavelength, and then setting of the amount of light, but the setting order is not limited to this.
(Light intensity correction value setting section)

  In the tuning step, the light amount correction value setting unit 42 receives light emitted from the LED corresponding to the wavelength selected by the wavelength selection unit 412 with the light amount set by the light amount setting unit 413 for each lighting block TB. 20 by comparing the value based on the amount of light received by each light receiving unit 20 and the value based on the amount of light set by the light amount setting unit 413, by the light receiving unit 20 for each lighting block TB. A correction value is set such that the value based on the received light amount is equal to the value based on the light amount set by the light amount setting unit 413. This is because even if the LED 1 is turned on with a current value corresponding to the light amount set by the light amount setting unit 413, the LED 1 is deteriorated with time, and thus is not necessarily turned on with the light amount set by the light amount setting unit 413. Therefore, by setting the correction value by the light amount correction value setting unit 42 and updating the setting at an appropriate timing, each of the lighting blocks TB1 to TB4 always approximates the set light amount or the set light amount. It can be turned on with light.

  The comparison between the value based on the light amount received by the light receiving unit 20 and the value based on the light amount set by the light amount setting unit 413 is basically set by the light amount received by the light receiving unit 20 and the light amount setting unit 413. This is done by comparing the amount of light. However, the light from the LED 1 received by each light receiving unit 20 may receive a part of the light diffused from the LED 1 instead of the main light amount emitted from the LED 1 toward the workpiece W. For this reason, the magnitude of the amount of light applied to the workpiece W set by the light amount setting unit 413 and the amount of light received by the light receiving unit 20 may be different. In order to cope with such a case, as an example, the correlation between the received light amount received by the light receiving unit 20 and the main emitted light amount toward the work W of the LED 1 in the case of the received light amount is generated and held as a correspondence table, By using the correspondence table, there is a method for comparing the main light emission amount calculated by the correspondence table based on the light reception amount detected from the light receiving unit 20 and the light amount set by the light amount setting unit 413. . In the specific example, the correspondence table is used to obtain the calculated value. However, the calculated value may be based on a coefficient obtained based on an experiment. On the contrary, the comparison here may be a method of comparing the light amount received by the light receiving unit 20 with a value based on the light amount set by the light amount setting unit 413 (for this method, the light receiving element correspondence table). As will be described later).

Here, a specific example of the correction value is given. For example, a difference value between a value based on the light amount set by the light amount setting unit 413 and a value based on the light amount received by the light receiving unit 20, set by the light amount setting unit 413. When the current value calculated from the difference between the value based on the light amount and the value based on the light amount received by the light receiving unit 20, the light amount received by the light receiving unit 20 is corrected to the light amount set by the light amount setting unit 413 Or the current value when the light amount received by the light receiving unit 20 is corrected to a reference value corresponding to the light amount set by the light amount setting unit 413 of the light receiving element correspondence table described later. That is, the correction value is determined based on the light amount set by the light amount setting unit 413 and the light amount received by the light receiving unit 20, and the light quantity set by the light amount setting unit 413 is used for each of the lighting blocks TB1 to TB4. It is a value for lighting LED1 of each wavelength.
(Lighting control unit)

  In the tuning step, the illumination control unit 43 selects the wavelength selected by the wavelength selection unit 412 for each lighting block TB based on the wavelength selected by the wavelength selection unit 412 and the light amount set by the light amount setting unit 413. LED1 corresponding to is made to emit light. Thereby, the correction value is obtained by the light quantity correction value setting unit 42 described above. Further, the illumination control unit 43 corresponds to the wavelength selected by the wavelength selection unit 412 for each lighting block TB based on the correction value in the operation step after the light amount correction value setting unit 42 sets the correction value. LED1 to emit light. That is, the process of setting the correction value is a tuning step, and the process of performing illumination based on the set correction value corresponds to the operation step.

  In the partial switching lighting mode, the illumination control unit 43 sets the LED 1 having the wavelength selected by the wavelength selection unit 412 to the light amount set by the light amount setting unit 413 or the correction value in the lighting of each of the lighting blocks TB1 to TB4. Based on this, the lighting blocks TB1 to TB4 are caused to emit light while being sequentially switched. While one lighting block TB is on, the other lighting blocks TB are off. Further, when the partial switching lighting mode for sequentially lighting only the selected lighting block TB described in the column of the lighting method selection unit is provided, only the selected lighting block TB is set by the light amount setting unit 413. The light is turned on based on the amount of light or the correction value. When a plurality of wavelengths are selected by the wavelength selection unit 412, the first wavelength LED 1 is caused to emit light while sequentially switching the lighting blocks TB 1 to TB 4, and then the second wavelength LED 1. Is made to emit light while sequentially switching the lighting blocks TB1 to TB4.

  A configuration in which the light receiving unit 20 provided in each of the lighting blocks TB1 to TB4 is not affected by the light emission of the LEDs 1 of the other lighting blocks TB (for example, the light emission in each of the lighting blocks TB1 to TB4 is transmitted to the other lighting blocks TB). If the light receiving unit 20 is shielded from light, or the light receiving units 20 of the lighting blocks TB1 to TB4 are arranged at positions that do not affect the light emission in the other lighting blocks TB), the tuning step is performed. In FIG. 5, the plurality of lighting blocks TB1 to TB4 can be turned on at the same time, and the light amount correction control can be performed in units of the lighting blocks TB.

On the other hand, in the full lighting mode, the illumination control unit 43 simultaneously sets the light amount set by the light amount setting unit 413 or the correction value of the LED 1 having the wavelength selected by the wavelength selection unit 412 in all the lighting blocks TB1 to TB4. The light is emitted based on the above.
(Imaging control unit)

The imaging control unit 44 causes the imaging unit 30 to image the workpiece W in synchronization with the timing of illumination by the illumination control unit 43. In other words, in the operation step, the illumination control unit 43 irradiates the workpiece W with illumination based on the illumination method selected by the illumination method selection unit 411 and the correction value set by the light amount correction value setting unit 42. The imaging control unit 44 controls the imaging unit 30 so that the workpiece W is imaged at the timing when the illumination is irradiated. In the partial switching lighting mode, the imaging control unit 44 controls the imaging unit 30 so that the imaging unit 30 captures the workpiece W at the timing when each of the lighting blocks TB1 to TB4 is lit. In the all lighting mode, the imaging control unit 44 controls the imaging unit 30 so that the imaging unit 30 captures the workpiece W at the timing when all the lighting blocks TB1 to TB4 are turned on.
(Image processing unit)

  The image processing unit 45 is used based on an image processing flow configured by selecting and combining various image processing tools of the image processing unit 45 with respect to the image acquired from the imaging unit 30 in the operation step. The image inspection desired by the person is performed. For example, when the user selects the all lighting mode, the imaging unit 30 acquires an image in a state where illumination light is irradiated from all directions surrounding the workpiece W, and the image is supplied to the image processing unit 45. The As an example, there are the following cases for selecting the full lighting mode. When the user wants to detect the presence or absence of scratches on the workpiece W, it has been found that ultraviolet rays are effective as the wavelength. Moreover, if it is determined that the presence or absence of scratches can be detected in images acquired in the full lighting mode or in a plurality of images acquired in the partial switching lighting mode, the user can turn on the lighting with a short processing speed, that is, a short inspection time. Select a mode.

  In such a case, in the image processing apparatus 40, the user designates an area designation window for an area in the work W on which an inspection is to be performed for the presence or absence of scratches on the acquired image including the work W. The inspection area is specified using a function called "." Next, a search window of, for example, 4 pixels × 4 pixels is set in the area designated by the area designating window, and is shifted to the right by, for example, 1 pixel unit from the upper left corner of the area designating window. When moving to the right corner of the window, the region designating window automatically moves to the right corner in the window by shifting rightward by one pixel from the position shifted by one pixel downward from the position of the upper right corner. In addition to setting the function to shift to the lower right corner of the area specified in, an image processing tool is set at each shift position to perform average gradation processing on the image information in the search window. The average gradation process is to obtain an average value of gradations of all the pixels in the search window. The average gradation value in the search window at a specific shift position is set to 1 for the position of the search window. A function for checking whether or not there is a change in gradation in this area is added by comparing with average gradation values obtained at four diagonal positions in the vertical and horizontal directions for each pixel. By executing such evaluation in the entire area designated by the area designating window, it is determined that there is a scratch at a place where the gradation has changed.

  In this way, by selecting a plurality of image processing tools held by the image processing apparatus 40 and setting the conditions for the tools, the inspection content desired by the user is selected for the image acquired in the all lighting mode. An inspection for the presence or absence of scratches in the acquired image can be performed. On the other hand, when the partial switching lighting mode is selected, the imaging unit 30 acquires an image at each timing when the selected LED 1 in each lighting block TB is lit, and at least a plurality of images corresponding to the lighting block TB are images. It is supplied to the processing device 40.

In the partial switching lighting mode, it is possible to perform image processing as performed in the full lighting mode on each of a plurality of acquired images to check the presence or absence of scratches. The following processing is also possible with different image processing settings. Using the image signals of a plurality of partial illumination images input from the imaging unit 30, a normal vector image (hereinafter referred to as “tilt image”) of a surface at each pixel is generated, and the X direction and Y direction of the tilt image are generated. The second-order inclination image (hereinafter referred to as “contour extraction image”) is created, and processing for inspecting scratches or the like is performed using these images. Then, the image processing unit 45 performs the inspection of the presence / absence and size of the scratch based on the processed image. For example, if the size of the scratch is equal to or greater than a predetermined threshold, it is determined that the product is defective.
(Setting before inspection)

FIG. 15 shows an example of a flowchart at the time of setting of an inspection method or the like adapted to the workpiece W as an inspection object in the setting step. This flowchart corresponds to a setting step in the flow of the appearance inspection method. First, the user selects an illumination method of either the partial switching lighting mode or the full lighting mode (ST101). Next, the user selects a wavelength suitable for inspection of at least one workpiece W from a plurality of different wavelengths (ST102). Next, the user sets the amount of light emitted from the lighting block TB of light of the selected wavelength (ST103).
(Light intensity correction control)

  FIG. 16 shows an example of a flowchart of the first embodiment of a flow of a series of appearance inspection methods for light amount correction control. The first embodiment is control in which the tuning step and the operation step are repeated for each lighting block TB in the partial switching lighting mode. That is, a tuning step is performed prior to each operation step. In the tuning step, the image processing apparatus 40 performs the following control. The image treatment device reads the partial switching lighting mode stored in the storage unit 47 (ST201). Next, the image treatment apparatus reads out the wavelength selected by the wavelength selection unit 412 from the storage unit 47 (ST202). Then, the image processing apparatus reads the light amount set by the light amount setting unit 413 from the storage unit 47 (ST203).

  In the tuning step, the illumination control unit 43 turns on the LED 1 with the selected wavelength while switching it for each lighting block TB so as to obtain a set light amount (ST204). Specifically, among the plurality of lighting blocks TB1 to TB4, for example, the LED 1 having a selected wavelength arranged in the first lighting block TB1 is turned on. When the first lighting block TB1 is turned on, the first light receiving unit 21 disposed in the first lighting block TB1 receives the amount of light (ST205).

  Next, the light amount correction value setting unit 42 compares the light amount set by the light amount setting unit 413 with the light amount received by the first light receiving unit 21 (ST206). When the amount of light received by the first light receiving unit 21 deviates from the set amount of light, the first light receiving unit 21 is based on the method described in the section of “Light amount correction value setting unit” described above. A correction value for setting the amount of light received in step 1 to the set amount of light is set (ST207). When the received light quantity does not deviate from the set light quantity, the light quantity correction value setting unit 42 sets the correction value to zero. This completes the setting of the correction value for the LED 1 having the selected wavelength in the first lighting block TB1.

  In the operation step after setting the correction value, the image processing apparatus 40 performs the following control. Based on the correction value set by the light quantity correction value setting unit 42, the illumination control unit 43 performs control so that the first lighting block TB1 of the lighting unit 10 is lit (ST208). The imaging unit 30 images the workpiece W while the LED 1 of the first lighting block TB1 is lit with the light amount corrected by the correction value (ST209). Thereafter, for the second lighting block TB2 to the fourth lighting block TB4 for which the correction value has not been set, the process returns to the tuning step ST204, and the tuning step and the operation step up to step ST209 are turned on. If the light amount correction is completed in all the lighting blocks TB1 to TB4, the process proceeds to step ST211 (ST210). In the case where there are still wavelengths for which light amount correction and imaging of the workpiece W have not been completed among the wavelengths selected by the wavelength selection unit 412, the process returns to step ST202, which is a tuning step, and has been completed for all wavelengths. Advances to step ST212 (ST211).

  Here, the procedure of performing the illumination control (ST208) and the imaging (ST209) in the operation step after the light amount correction (ST207) in the tuning step is completed has been described, but the light amount correction and illumination control (hereinafter referred to as light amount control). ) Is overwhelmingly shorter than the time required for imaging (normally about several tens of times during imaging, and about twice at the shortest is possible during imaging), light quantity control is always performed during imaging. You may continue to do. Thereby, even if the LED light emission efficiency deteriorates or the wavelength shift occurs due to the self-heating of the LED during imaging, the most recent light amount control can be reflected in the captured image.

  The imaging unit 30 transfers the obtained plurality of image data to the image processing unit 45. Specifically, when a plurality of partial illumination images or a plurality of wavelengths are selected, a plurality of partial illumination images for each wavelength are transferred. As an example of image processing, the image processing unit 45 performs image processing on a plurality of partial illumination images by a photometric stereo method (details will be described later), and the work W is a non-defective product based on the plurality of image processed images. It is determined whether or not (ST212).

  When the next workpiece W reaches the central axis of the illumination unit 10, the appearance inspection apparatus performs an appearance inspection on the next workpiece W. Even after the correction value is set once by the light amount correction value setting unit 42, the light amount may be reduced due to deterioration of the LED 1, and therefore the light amount correction value setting unit 42 needs to update the correction value at an appropriate frequency. is there. In this embodiment, tuning is performed prior to the operation step for each lighting block TB, and illumination is performed using the updated correction value in the subsequent operation step. However, the present invention is not limited to this configuration, and it is also possible to irradiate illumination using the correction value of each lighting block TB updated in the operation step after tuning in all the lighting blocks TB prior to the operation step. is there.

  Note that tuning need not be performed prior to all operation steps. For example, an embodiment in which light amount correction control is performed at the start of the appearance inspection apparatus, an embodiment in which light amount correction control is performed at a rate of once every several lighting blocks TB are lit, a timer is provided, and a fixed time elapses. Embodiment in which light amount correction control is performed, a temperature sensor is provided in the LED 1 arranged in the light source unit KT, and the light amount correction control is performed when the temperature change from the previous light amount correction control becomes equal to or greater than a certain level. There are forms, etc.

  Further, there are two embodiments for a specific method for updating the correction value. In the first embodiment, in the tuning step after the correction value is set, the LED 1 is caused to emit light based on the set correction value, and the new correction value is based on the amount of light received by the light receiving unit 20. Set. In other words, this is a method in which the correction value previously set by the light amount correction value setting unit 42 is used and updated to a new correction value. In the second embodiment, in the tuning step after the correction value is set, the LED 1 is caused to emit light based on the setting value set by the light amount setting unit 413 and based on the light amount received by the light receiving unit 20. To set a new correction value. That is, this is a method in which the correction value previously set by the light amount correction value setting unit 42 is not used, and the setting value set by the light amount setting unit 413 is used to update to a new correction value.

  With the above configuration, the visual inspection apparatus according to the present invention irradiates the light of the wavelength selected by the wavelength selection unit 412 from the annular illumination unit 10 for each of the lighting blocks TB1 to TB4 with the light amount set by the light amount setting unit 413. Then, the light receiving unit 20 corresponding to each of the lighting blocks TB1 to TB4 receives the light, and the received light amount is received by the light receiving unit 20 by comparing the received light amount with the set light amount for each lighting block TB. The light amount is corrected so that the received light amount approaches the set light amount, and the workpiece W can be imaged at a timing when the corrected amount of light is irradiated onto the workpiece W.

In the present embodiment, the light amount correction control in the case where the respective lighting blocks TB1 to TB4 are sequentially turned on in the partial switching lighting mode has been described. However, the full lighting mode in which all the lighting blocks TB1 to TB4 are turned on simultaneously. The same light quantity correction control is possible in In the all lighting mode, the light amount correction value setting unit 42 compares the light amount set by the light amount setting unit 413 with the light amount received by each lighting block TB for each lighting block TB, and the lighting block TB. A correction value is set for each, and the illumination control unit 43 lights all the lighting blocks TB1 to TB4 simultaneously based on the set correction value. In this case, after the tuning step is completed in all the lighting blocks TB1 to TB4, the operation step is started. As in the partial switching lighting mode, tuning does not have to be performed prior to all operation steps, and in this case, the above-described embodiments can be employed.
(Correction correction between light receiving element and LED)

In addition to the problem of deterioration with time described above, the LED 1 may emit different amounts of light even when the same current is passed due to individual characteristics even when the LED 1 is not used. In addition, there are individual differences in the light receiving elements 2 arranged in the light receiving unit 20, and the light receiving elements 2 having different sensitivities may be arranged in the same lighting device. Therefore, consideration may be necessary for variations in the light amount of the LED 1 and the light receiving sensitivity of the light receiving element 2.
(Light emitting element correspondence table)

  First, the variation of the LED 1 will be described. Even if a current for emitting light with a light amount set by the light amount setting unit 413 is supplied, if a light is emitted only with a light amount less than or equal to the set light amount, a larger amount of current must be supplied in consideration thereof. On the contrary, when a current for emitting light with the light amount set by the light amount setting unit 413 is supplied, if a light amount exceeding the set light amount is emitted, a small amount of current must be supplied in consideration thereof. .

  Therefore, at the time of completion inspection at the time of manufacturing the lighting device, the distance from the light source unit KT of each of the lighting blocks TB1 to TB4 in addition to the light receiving unit 20 provided for each lighting block TB incorporated in the lighting device, respectively. A single inspection light receiving device (not shown) is provided which is arranged to be equal and receives light from each light source unit KT. Specifically, a single inspection light-receiving device is provided at substantially the center of the hollow portion at the center of the illumination device. As another light receiving method, the light receiving device for inspection is moved to the vicinity of the light receiving unit 20 of the lit lighting block TB every time the lighting blocks TB1 to TB4 are turned on, and the light from each light source unit KT is moved. It may receive light. What is important in either method is that the inspection light receiving device having the same light receiving element is used, and the light receiving environment of the illumination unit 10 is almost the same (the light receiving environment is the same for each light receiving unit 20). The light receiving device for inspection receives the light from each block at the position).

  Using the inspection light receiving device, only the first lighting block TB1 is turned on with a light amount set by the light amount setting unit 413 for a certain wavelength, and the inspection light receiving device receives light. When there is a discrepancy between the amount of light received by the inspection light receiving device and the amount of light set by the light amount setting unit 413, the amount of light received by the inspection light receiving device becomes the amount of light set by the light amount setting unit 413. As described above, the light emission amount of the LED 1 of the first lighting block TB1 is adjusted. An instruction value (for example, a current value) for the LED 1 when emitting light with the adjusted light amount is set as an adjustment value corresponding to the light amount set in the first lighting block TB1. The reference values of the second lighting block TB2 to the fourth lighting block TB4 are calculated in the same manner, and the adjustment values for the other light amounts that can be set by the light amount setting unit 413 are also calculated for each lighting block TB. Then, the light emitting element correspondence table creating unit creates a light emitting element correspondence table in which the light amount settable by the light amount setting unit 413 and each adjustment value are associated with each lighting block TB. That is, the correction for each LED 1 is performed by evaluating and adjusting the light emission performance of the LED 1 of each lighting block TB using an inspection light receiving device having a single light receiving element. The correction of the variation of the LED 1 is performed prior to the correction of the variation of the light receiving element 2 described later.

In other words, the light emitting element correspondence table creation unit applies to the lighting blocks TB1 to TB4 when the light amounts of the lighting blocks TB1 to TB4 received by the inspection light receiving device become the light amounts set by the light amount setting unit 413. Using the instruction value as an adjustment value, each adjustment value corresponding to the light amount that can be set by the light amount setting unit 413 is calculated for each lighting block TB, and the light amount that can be set by the light amount setting unit 413 and each adjustment value are turned on. A light emitting element correspondence table associated with each block TB is created for each wavelength. The light emitting element correspondence table created for each wavelength is stored in a storage device provided in the illumination device.
(Light receiving element correspondence table)

  Next, the variation of the light receiving element 2 will be described. For example, by using the created light emitting element correspondence table, even if the light amount emitted by the LED 1 in the first lighting block TB1 is the same as the set light amount, the first light emitting block TB1 arranged in the first lighting block TB1 is used. When the sensitivity of the light receiving element 2a is poor, only the light amount equal to or less than the set light amount is received. Conversely, even if the light quantity emitted by the LED 1 in the second lighting block TB2 is the same as the set light quantity, it is set when the sensitivity of the second light receiving element 2b arranged in the second lighting block TB2 is good. Receives light that exceeds the light level.

  In order to correct the variation of the light receiving elements 2, after the light emitting element correspondence table is created at the time of completion inspection or the like, a light receiving device similar to the inspection light receiving device used when creating the light emitting element correspondence table is used.

  An example of a method for creating the light receiving element correspondence table will be described. For example, for a certain wavelength, when 10 light amounts are set by the light amount setting unit 413, the illumination control unit 43 lights only the first lighting block TB1 with 10 light amounts using the light emitting element correspondence table. The first light receiving element 2a disposed in the first lighting block TB1 and the inspection light receiving device receive the light. In this case, the light receiving device for inspection receives 10 light amounts, but the first light receiving element 2a has a low sensitivity, and therefore detects that the brightness is 9. Therefore, the reference value of the first lighting block TB1 when the light amount set by the light amount setting unit 413 is 10 is stored as 9. That is, the reference value is the amount of light received by the light receiving unit 20 arranged in the lit lighting block TB when the lighting block TB emits light with the light amount set by the light amount setting unit 413. The reference values of the second lighting block TB2 to the fourth lighting block TB4 are calculated in the same manner, and the reference values are similarly calculated for each lighting block TB for other light amounts that can be set by the light amount setting unit 413. Then, the light receiving element correspondence table creating unit creates, for each wavelength, the light receiving element correspondence table shown in FIG. 7 in which the light amount settable by the light amount setting unit 413 and the respective reference values are associated with each lighting block TB. The vertical axis of the light receiving element correspondence table indicates the light amount that can be set by the light amount setting unit 413, and the horizontal axis indicates the lighting block TB. That is, the correction for each light receiving element 2 is performed by evaluating and adjusting the light receiving performance of the light receiving elements 2 of the lighting blocks TB1 to TB4 using an inspection light receiving device having a single light receiving element.

  That is, the light receiving element correspondence table creation unit can be set by the light amount setting unit 413 using the light amount received by the light receiving unit 20 in a state where the LED 1 is illuminated with the light amount settable by the light amount setting unit 413 as a reference value. Each reference value corresponding to the amount of light is calculated for each lighting block TB, and a light receiving element correspondence table in which the amount of light that can be set by the light amount setting unit 413 and each reference value is associated for each lighting block TB is created for each wavelength. . The light receiving element correspondence table created for each wavelength is stored in a storage device provided in the illumination device.

  In addition, the light emitting element correspondence table creation unit and the light receiving element correspondence table creation unit may be provided in any of the illumination device or the inspection device used at the time of completion inspection of the illumination device.

Further, in the embodiment in which the light amount is detected by the inspection light receiving device, in addition to the embodiment in which light from each of the lighting blocks TB1 to TB4 is received by the light receiving element and the light amount is detected, the light amount is acquired by the imaging unit 30. In another embodiment, the amount of light is detected based on the luminance image thus obtained. For example, a reference plate such as a blank sheet is imaged by sequentially irradiating light for each lighting block TB, and a plurality of luminance images for each lighting block TB are generated from the plurality of captured images. And the light quantity of each lighting block TB is detected based on the some luminance image for every lighting block TB. That is, the light receiving device for inspection can be replaced by the imaging unit 30 instead of a light receiving element provided separately for inspection. In addition, the light receiving element correspondence table is created at the time of completion inspection of the lighting device, but may be updated so as to be able to cope with changes in variation of the light receiving elements 2 due to deterioration with time. In this case, the light receiving element correspondence table creation unit may be provided in the illumination device, the image processing unit 45, the computer 80 connected to the outside, or the like.
(Light intensity correction value setting using correspondence table)

  The light amount correction value setting using the correspondence table will be described with reference to FIG. 17 which is a light receiving element correspondence table. When the user sets 10 light amounts with the light amount setting unit 413, the illumination control unit 43 performs the first lighting. A current having an adjustment value corresponding to 10 light amounts on the light emitting element correspondence table is supplied to the LED 1 having a specific wavelength in the block TB1. However, since the light quantity of the LED 1 is reduced due to the deterioration of the LED 1 with time, the first light receiving element 2a detects the light quantity of 8. The light amount correction value setting unit 42 includes the reference value (9 in this case) of the first lighting block TB1 corresponding to the light amount (10 in this case) set by the light amount setting unit 413 in the light receiving element correspondence table, and the first light reception. The correction value is set so that the amount of light received by the first light receiving element 2a becomes 9, which is the reference value, by comparing the amount of light received by the element 2a (8 in this case). The illumination control unit 43 corrects the light amount so that the light amount received by the first light receiving element 2a becomes 9 based on the set correction value. Accordingly, the first lighting block TB1 can be lit with 10 light amounts. That is, the light amount correction value setting unit 42 is configured to use the light amount received by the light receiving unit 20 and the light receiving element correspondence table when each of the lighting blocks TB1 to TB4 is turned on with the light amount adjusted using the light emitting element correspondence table. A reference value corresponding to the set light amount is compared for each lighting block TB, and a correction value is set for each lighting block TB so that the light amount received by the light receiving unit 20 approaches the reference value.

In the present embodiment, the illumination control unit 43 uses the light emitting element correspondence table and the light receiving element correspondence table so that the light amount received by the light receiving unit 20 approaches the reference value corresponding to the light amount set by the light amount setting unit 413. Although the amount of light is controlled, it is not limited to this method. For example, when the variation of the LED 1 and the light receiving element 2 can be tolerated, the light amount received by the light receiving unit 20 is not used without using the light emitting element correspondence table or the light receiving element correspondence table, or using only one of the correspondence tables. The light amount may be controlled so as to be the light amount set by the light amount setting unit 413.
(Multispectral imaging)

  Here, the basic principle of multispectral imaging will be described with reference to FIGS. Multispectral imaging detects scratches or the like on the workpiece W using a plurality of images irradiated with light having different wavelengths in all lighting modes in which all the lighting blocks TB1 to TB4 in the present embodiment are turned on simultaneously. This is an example of an effective image processing tool. That is, multispectral imaging is one of many image processing tools set in the image processing unit 45, is selected by the user, and is incorporated into the image processing flow.

  In multispectral imaging, as shown in FIG. 18, illumination light having different wavelengths is sequentially irradiated onto the workpiece W one by one in the full lighting mode, and an image for each wavelength is acquired. For example, when irradiating illumination light with eight wavelengths from UV to IR, eight spectral images can be acquired. In this figure, UV is an ultraviolet wavelength, B is a blue wavelength, G is a green wavelength, AM is an amber wavelength, OR is an orange wavelength, R is a red wavelength, and IR1 and IR2 (wavelengths longer than IR1) indicate infrared wavelengths. ing.

  Some visual inspections may not require all eight images. In this case, the work W is irradiated with only illumination light having a necessary wavelength. In general, eight images are rarely used for appearance inspection as they are, and one gray image is created from eight images by color shading conversion, and this gray image is used for appearance inspection. For example, binarization processing, edge detection processing, blob processing, etc. are performed on a gray image that has undergone color shading conversion, and the position and dimensions (length and area) and color of features (eg, pins) on the work W are respectively Inspect whether it is within tolerance.

  In order to create a gray image of the workpiece W, a non-defective product (model) registration color is required. This is because a gray image is created by converting eight spectral images based on color information of registered colors.

  First, as shown in FIG. 19, in the setting mode, color information of registered colors is extracted from image areas (designated areas) designated by the user in eight spectral images acquired from non-defective products. For example, when the non-defective product is an instant food (eg, ramen) and the number of certain ingredients (eg, shrimp) is counted by visual inspection, the good image is presented by the user, When a specified rectangular area is specified, color information of registered colors including the average pixel matrix, variance-covariance matrix, and the number of pixels included in the specified area is extracted from the pixels included in the specified area. To do.

Next, in the inspection mode, as shown in FIG. 20, eight spectral images for the workpiece W are acquired. The distance d (x) with respect to the registered color is obtained by the following equation for all the pixels included in each spectral image. Note that x is an 8-dimensional vector whose elements are the pixel values of the eight spectral images.

Further, as shown in the following equation, a product is obtained by multiplying the distance d (x) by a predetermined gain g, and an offset a is added if necessary, and subtracted from the maximum gradation G _max that each pixel can take. Thus, a single gray image is created in which the difference G obtained is the gray gradation of the pixel of interest x. When there are a plurality of registered colors, a plurality of gray images are created with each registered color as a reference.

  Actually, the difference G obtained by this mathematical formula is calculated in eight dimensions using eight gray images to create one gray image. To make the image easier, refer to FIG. This will be described by visualizing in three dimensions of RGB. Each pixel has, for example, three components R, G, and B, and a vector having (R, G, B) as a component is obtained in each pixel. Usually, since the actual background image is dark, when all the pixels are plotted, the pixels in the dark portion are gathered around the background image. On the other hand, the pixels where the workpiece W is actually gathered in a different location from the location of the background image.

When the distance between the (R, G, B) coordinates and the coordinates in the background image is the longest, the contrast between the color to be extracted and the background image is the largest, so for all pixels, One gray image is completed by associating 256 levels of gradation according to the longest distance. The gray image created in this way is an image that brightens the color that the user wants to extract. Therefore, for example, in the previous example, by performing multispectral imaging, it is possible to find shrimp that would be buried by normal image processing.
(Photometric stereo method)

  Next, the basic principle of the photometric stereo method will be described with reference to FIGS. The photometric stereo method is an image processing tool that is effective for detecting scratches or the like on the workpiece W using a plurality of images irradiated with light from a plurality of illumination directions acquired in the partial switching lighting mode in the present embodiment. It is an example. Therefore, the photometric stereo method is one of many image processing tools set in the image processing unit 45, and is selected by the user and incorporated in the image processing flow.

First, as shown in FIG. 22, it is assumed that there is an unknown diffuse reflection surface S and a plurality of illuminations whose brightness and position are known (in this example, two of the first lighting block TB1 and the second lighting block TB2). To do. For example, as shown in FIG. 23, when light is emitted from the first lighting block TB1, the diffuse reflection light on the surface of the diffuse reflection surface S is (1) brightness of illumination (known), (2) direction of illumination (known) ), (3) the surface orientation of the workpiece W (normal vector n), and (4) the albedo parameters of the workpiece W surface. Therefore, as shown in FIG. 23 and FIG. 24, each of the partial illumination images including the diffuse reflected light when the illumination light is projected from a plurality of different illumination directions, specifically, three or more illumination directions, Shoot at 30. Then, as shown in FIG. 25, by using three or more partial illumination images as input images, unknown (3) orientation of the workpiece W surface (normal vector n), (4) albedo of the workpiece W surface, It can be calculated based on the following relational expression.
I = ρLSn
In the above formula,
ρ: albedo L: illumination brightness S: illumination direction matrix n: surface normal vector I: image gradation value

From the above equation, when there are three illumination units 10, it can be expressed by the following equation.

Moreover, when the illumination part 10 is four, it can represent with following Formula.
(Normal vector n)

From the above equation, the normal vector n can be expressed by the following equation.
n = 1 / ρL · S ⁺ I
In the above formula,
If S ^{+ is a} square matrix, the normal inverse matrix S ⁺ : The inverse matrix of the vertically long matrix is the Moore-Penrose pseudo-inverse matrix S ⁺ = (S ^t S) ⁻¹ S ^t
Ask for.
(Albedo)

Further, the albedo ρ can be expressed by the following equation.
ρ = | I | / | LSn |
(Outline extraction image)

  Next, a method of generating a tilt image by the photometric stereo method and obtaining surface information of the workpiece W such as a scratch or a contour from the obtained tilt image will be described.

First, a tilt image generation method will be described. When the curved surface of the workpiece W is S, the tilt image is given by the following equation.
x direction: δs / δx, y direction: δs / δy

  Here, as an example of the tilt image, an example in which a one-yen coin is used as the work W is shown in FIGS. FIG. 26 shows a Y coordinate component image in the normal direction, and FIG. 27 shows an X coordinate component image in the normal direction. Here, using the partial illumination images captured from the four illumination directions, the tilt image shown in FIG. 26 is differentiated in the X direction (horizontal direction in the figure) by differentiating in the Y direction (vertical direction in the figure). Thus, the tilt images shown in FIG. 27 are obtained.

Here, since the scratches, contours, and the like are places where the tilt of the surface of the workpiece W changes, the tilt image is differentiated in each direction. The second-order tilt image is given by the following equation.
x direction: δ ² s / δx ² , y direction: δ ² s / δy ²

From the above, the portions δ ² s / δx ² and δ ² s / δy ² of the tilt images in the x direction and the y direction are synthesized to generate a contour extraction image including the contour of the workpiece W and flaw information. The contour extraction image E is given by the following equation.
E = δ ² s / δx ² + δ ² s / δy ²

  In the above equation, E indicates contour information, and S indicates the curved surface of the workpiece W. An example of the contour extraction image calculated from FIGS. 26 and 27 is shown in FIG. In the contour extracted image, the height is expressed by shading (brightness) of the image so that the high portion is white and the low portion is black.

Based on this contour extraction image and a non-defective image registered in advance in the image processing apparatus 40, the image processing unit 45 determines whether or not the work W is non-defective.
(Details of lighting section)

  FIG. 29 is a plan view of the interior of the illumination unit 10 according to the first embodiment. Hereinafter, the direction in which the light from the LED 1 is emitted will be described as a downward direction. The illumination unit 10 includes an annular case 4 having an opening in the downward direction, an annular illumination substrate 3 accommodated in the case 4, and a diffusion plate (not shown) that covers the opening of the case 4 and diffuses light. Consists of. In the illustrated example, the case 4 has a circular shape, but may have a polygonal shape. The case 4 has an opening for allowing the imaging optical axis of the imaging unit 30 to be arranged at the center, an illumination board support 5 made of an annular body that supports the illumination board 3, and an opening located at the center. An outer wall 6 extending in a direction orthogonal to the plane of the annular body is formed on the outer peripheral portion of the annular body most distant from the section.

On the illumination board 3, a plurality of LEDs 1 that emit light of different wavelengths are arranged adjacent to each other along the circumferential direction of the annular illumination unit 10. In this embodiment, an LED 1 that emits light of eight colors of wavelengths is provided, and green (520 nm), red (720 nm), blue (450 nm), infrared (850 nm), ultraviolet (405 nm), yellow (590 nm), red The LEDs 1 that emit white light (650 nm) are arranged in the described order to constitute one light source unit KT, and one light source unit KT is arranged in the lighting block TB. In the present embodiment, one LED 1 of each wavelength is arranged in the light source unit KT, but a plurality of LEDs 1 of any wavelength may be arranged. In addition, each LED 1 has a low sensitivity or a high sensitivity due to the wavelength of the light receiving element 2. Considering this point, the LED 1 having a lower sensitivity than the light receiving element 2 is selected in the light source unit KT. It is preferable to dispose the LED 1 that is close and sensitive. Here, for example, red or the like has good sensitivity to the light receiving element 2, and blue, infrared, ultraviolet, or the like has relatively low sensitivity.
(Details of light receiving part)

  As shown in FIG. 29, in the first embodiment, the light receiving element 2 directly receives the light emitted from the LED 1. That is, the light receiving element 2 is disposed with its light receiving surface facing the LED 1 disposed on the illumination substrate 3. In the first embodiment, the light emitting surface of the LED 1 is disposed downward and the light receiving surface of the light receiving element 2 is disposed upward. The light receiving element 2 receives light emitted from the LED 1 through the filter unit 200. The light receiving element 2 may receive the light emitted from the LED 1 through an optical member such as a lens.

  In addition, the light receiving unit 20 is arranged corresponding to the light source unit KT, but “correspondingly arranged” includes the following embodiments. In the first embodiment, the light receiving unit 20 is provided in the illumination unit 10 on the outer periphery side of the light source unit KT arranged in the arc-shaped lighting block TB, and in the circumferential direction of the annular illumination unit 10, The light source units KT are arranged in an overlapping manner. However, the present invention is not limited to this configuration, and the light receiving unit 20 may be disposed anywhere in the illumination unit 10 as long as it can receive light from the LED 1 to be received.

The light receiving element 2 is arranged offset to the outer peripheral side from the plurality of LEDs 1 arranged in a ring shape on the illumination substrate 3. Here, “the light receiving element 2 is disposed offset from the plurality of LEDs 1 on the outer peripheral side” means that not only the light receiving element 2 does not overlap the LED 1 in a plan view but also the light receiving element 2 is one of the LEDs 1. This includes a state in which the center of the optical axis of the LED 1 and the light receiving element 2 do not overlap. Thereby, the light emitted perpendicularly from the LED 1 important for appearance inspection is not obstructed by the light receiving element 2.
(Another embodiment of relationship between light source unit and light receiving unit)

  In the first embodiment described based on FIG. 29, as shown in FIG. 30, one light source unit KT is arranged in one lighting block TB, and one light receiving unit 20 is associated with the light source unit KT. Arranged. In each lighting block TB1 to TB4, the light receiving unit 20 is provided for one light source unit KT, as in the second embodiment shown in FIG. 31, and a plurality of light receiving units 20 corresponding to one light source unit KT. Can also be arranged. As an example, when two light receiving units 20 are arranged for one light source unit KT, a first light receiving unit 20a is provided corresponding to the LEDs 1 of some wavelengths in the light source unit KT, and the light source unit KT is provided. A second light receiving portion 20b is provided in correspondence with the LED 1 having the other wavelength. In this case, the light from the LED 1 having some wavelengths is received by the first light receiving unit 20a, and the light from the LED 1 having other wavelengths is received by the second light receiving unit 20b. The light receiving unit 20b outputs a light receiving signal of the light source unit KT.

  Further, when a plurality of light source units KT are provided for each of the lighting blocks TB1 to TB4, the plurality of light source units KT1 to KT2 in the lighting block TB are provided as in the third embodiment shown in FIG. A method of providing a single light receiving unit 20 can be considered. As another method, a method of providing the light receiving unit 20 for each of the plurality of light source units KT1 to KT2 in the lighting block TB as in the fourth embodiment shown in FIG. When a plurality of light receiving units 20 are provided in one lighting block TB, a light reception signal indicating one light quantity such as an average value of values received by the plurality of light receiving units 20 is output.

  Here, an embodiment having four light source units KT1 to KT4 in each of the lighting blocks TB1 to TB4 as a third embodiment will be described with reference to FIG. In the present embodiment, the annular illumination unit 10 is divided into four lighting blocks TB1 to TB4, and one light receiving unit 20 is arranged at the center in the circumferential direction of each of the lighting blocks TB1 to TB4. And LED8 of 8 wavelengths of 1st light source unit KT1 is arrange | positioned in the center part of the circumferential direction of lighting block TB. In FIG. 34, on the right side in the circumferential direction of the first light source unit KT1, there are a total of 12 LEDs 1 of 8 wavelengths of the second light source unit KT2 and LEDs 1 of 4 wavelengths of the 8 wavelengths of the fourth light source unit KT4. LEDs 1 are arranged, and on the left side in the circumferential direction of the first light source unit KT, the eight-wavelength LEDs 1 of the third light source unit KT3 and the other four-wavelength LEDs 1 out of the eight wavelengths of the fourth light source unit KT4. A total of 12 LEDs 1 are arranged. Therefore, four LEDs 1 of each wavelength are arranged in each of the lighting blocks TB1 to TB4, and the four LEDs 1 of each wavelength are connected in series to be turned on and off in conjunction with each other. The light of the four LEDs 1 of each wavelength that is lit in conjunction with each other is received by the single light receiving unit 20 through the filter unit 200.

  Next, a one-wavelength lighting circuit according to the illumination unit 10 of the third embodiment will be described with reference to FIG. In the lighting circuit shown in FIG. 35, at each wavelength, four LEDs 1 in the lighting block TB described above are connected in series to form an LED group. A switch SW that can be turned on / off to turn on / off the lighting block TB is connected in series to the LED group. Further, a variable resistor R capable of correcting the light amount by adjusting the resistance value based on the correction value set by the light amount correction value setting unit 42 described above is connected in series to the LED group. As described above, since the illumination unit 10 is divided into four lighting blocks TB1 to TB4, four LED groups, a switch SW, and four variable resistors R connected in series are provided, and these are arranged in parallel by a power cable. Connected to. A power source is connected to the power cable, and power is supplied to each LED group through the power cable. In this embodiment, since the 8-wavelength LED 1 is used, the above-described eight lighting circuits are provided. The four LEDs 1 of each LED group become the LED 1 of the light source unit KT, and the light is received by the light receiving unit 20.

The light quantity correction control will be described based on the circuit configuration described above. In the tuning step, each light receiving unit 20 arranged for each lighting block TB receives light from a plurality of LEDs 1 connected in series for each lighting block TB. To do. The light amount correction value setting unit 42 compares the light amount set by the light amount setting unit 413 with the light amount of the LED 1 received by the light receiving unit 20 in each of the lighting blocks TB1 to TB4, and for each lighting block TB. Set the correction value of the light quantity of LED1. And in an operation step, the illumination control part 43 makes all LED1 connected in series in each lighting block TB1-TB4 with the light quantity correct | amended based on the set correction value.
(Another embodiment of the illumination unit)

  In the first to fourth embodiments, each of the lighting blocks TB1 to TB4 includes a plurality of light sources that do not belong to the light source unit KT other than at least one light source unit KT. A unit UN (a plurality of LEDs 1 constituting eight wavelengths) composed of the LEDs 1 may be additionally arranged. In this case, the light quantity of the LED 1 of the unit UN that does not belong to the light source unit KT is corrected so that it is lit with the same light quantity as the light quantity corrected by the light quantity correction value setting unit 42 in the light source unit KT arranged in the same lighting block TB. Is done.

FIG. 36 shows a fifth embodiment in which units UN that do not belong to the light source unit KT are additionally arranged. In the fifth embodiment, a configuration in which only the light of one light source unit KT is received by the light receiving unit 20 and the light of the unit UN is not received by the light receiving unit 20 (for example, the unit UN with respect to the light receiving unit 20). A configuration in which a light-shielding plate for shielding the light is provided, a lighting circuit for tuning, and a configuration in which only the light source unit KT is lit during tuning). Further, even if a light shielding plate and a lighting circuit for tuning are not provided, if the light of the unit UN received by the light receiving unit 20 is sufficiently smaller than the light of the light source unit KT, only the light source unit KT is used. Tuning can be performed assuming that light is received by the light receiving unit 20. In addition, when there exists LED1 of the wavelength with little light quantity, you may arrange | position more LED1 of the wavelength in LED UN of other wavelengths in unit UN.
(Another embodiment of the relationship between the lighting block and the light source unit)

  In the first to fifth embodiments, at least one light source unit KT is arranged in the lighting block TB. However, in the sixth embodiment shown in FIG. 37, one light source unit KT is arranged across the adjacent lighting blocks TB, and one light receiving unit 20 is arranged corresponding to the light source unit KT arranged over the lighting blocks TB. The The light receiving unit 20 receives the light when the LED 1 having the wavelength arranged in one lighting block TB among the plurality of LEDs 1 of the light source unit KT arranged across the two lighting blocks TB is turned on. When the LED 1 having the wavelength arranged in the lighting block TB is turned on, the light is received and a light reception signal is output.

  In this embodiment, since the illumination part 10 is divided | segmented into four lighting block TB1-TB4, the four light source units KT are arrange | positioned ranging over each lighting block TB which adjoins. For example, one light source unit KT is arranged across the adjacent first lighting block TB1 and second lighting block TB2, and among the eight wavelengths LED1 of the light source unit KT, the LED1 having 1 to 4 wavelengths is the first lighting block. When arrange | positioned at TB1, LED1 of 5-8 wavelengths is arrange | positioned at 2nd lighting block TB2. Then, another light source unit KT is arranged across the adjacent second lighting block TB2 and third lighting block TB3, and LEDs 1 to 4 wavelengths are arranged in the second lighting block TB2, and the third lighting block TB3. The LED 1 having 5 to 8 wavelengths is arranged in the. The same applies to the third lighting block TB3 and the fourth lighting block TB4, and the fourth lighting block TB4 and the first lighting block TB1, which are adjacent to each other. That is, 1 to 8 wavelength LED1 is arrange | positioned at each lighting block TB. Therefore, also in the sixth embodiment, it can be considered that one light source unit KT is provided in each lighting block TB.

Further, the first to fifth embodiments can be used in combination with the configuration of the sixth embodiment. For example, in the second embodiment in which a plurality of light receiving units 20 are provided corresponding to one light source unit KT, one light source unit KT is arranged across the adjacent first lighting block TB1 and second lighting block TB2. In this case, one light receiving unit 20 is arranged corresponding to the LED 1 having 1 to 4 wavelengths arranged in the first lighting block TB1, and corresponding to the LED 1 having 5 to 8 wavelengths arranged in the second lighting block TB2. Another light receiving unit 20 can be arranged. The other light source unit KT is arranged so as to straddle the adjacent second lighting block TB2 and third lighting block TB3, and receives one light corresponding to the 1 to 4 wavelength LEDs 1 arranged in the second lighting block TB2. The part 20 is arrange | positioned, and the other light-receiving part 20 is arrange | positioned corresponding to LED1 of 5-8 wavelengths arrange | positioned at 3rd lighting block TB3. The same applies to the third lighting block TB3 and the fourth lighting block TB4, and the fourth lighting block TB4 and the first lighting block TB1, which are adjacent to each other.
(Another embodiment of the light receiving unit)

  There are roughly two forms for receiving light from the LED 1 by the light receiving unit 20. The first is a direct light receiving mode in which the light receiving unit 20 directly receives the light from the LED 1, and the second is a light receiving element in which the light emitted from the LED 1 is reflected by a reflecting member that changes the light irradiation angle. 2 is an indirect light receiving mode for receiving light. The light receiving unit 20 of the first embodiment described above corresponds to a direct light receiving mode.

  As a specific example of another direct light receiving mode, the light receiving element 2 is arranged between the LEDs 1 arranged in a line and directly receives the light of the plurality of LEDs 1 arranged on both sides of the light receiving element 2. There are embodiments.

  In both the direct light receiving mode and the indirect light receiving mode, an embodiment in which a light guide member is provided to guide light to the light receiving element 2 or a light collecting member is provided to collect light while collecting light. It is possible to adopt an embodiment in which the light is received.

As a specific example, a second embodiment in which a condensing member is provided in the indirect light receiving mode will be described. FIG. 38 is a schematic cross-sectional view of the second embodiment which is an indirect light receiving mode, and FIG. 39 is a schematic perspective view of the second embodiment. In the second embodiment, the light receiving element 2 indirectly receives light from the LED 1 collected by a light collecting member that reflects and collects light. For example, a hole is provided in the illumination board 3, and the light receiving element 2 is mounted in a hole portion on the surface of the illumination board 3 on the side opposite to the LED 1 placement surface with the light receiving surface facing upward. The light receiving member 205 is provided on the illumination substrate 3, and the upper member 206 whose surface on the illumination substrate 3 side is coated with a reflective material, and a transparent or translucent diffusion member having a truncated pyramid shape that diffuses light inside. 207. The diffusing member 207 is recessed in an inverted conical shape with the upper surface facing downward, and the upper member 206 is attached to the upper surface of the diffusing member 207 so that the light receiving member 205 forms a hollow cone inside. . The light emitted from the LED 1 is incident from the trapezoidal surface of the diffusing member 207, reflected by the reflecting surface of the upper member 206, the surface of the diffusing member 207, etc., and then condensed by the hollow conical portion, The light enters the light receiving element 2 through the hole. Thereby, the light receiving element 2 can receive light while eliminating the influence of disturbance light.
(Other variations)

  In the above-described embodiment, the LED 1 is arranged on the illumination board 3 constituting a single plane. However, as shown in FIG. 40, the illumination board 3 is placed on the entire circumference of the case 4 configured in an annular shape. A plurality of LEDs 1 may be arranged in an annular shape on a plane having the same height on the illumination board 3.

  In the above-described embodiment, the plurality of LEDs 1 are arranged in a row on the annular illumination substrate 3, but the LEDs 1 may be arranged in a plurality of rows in the radial direction. When the LEDs 1 are arranged in a plurality of rows on the illumination substrate 3 arranged obliquely, the LEDs 1 that emit light of the same wavelength are positioned on a plane having the same height.

  In the embodiment described above, the plurality of LEDs 1 are arranged on the illumination board 3 constituting a single plane. However, as shown in FIG. The LED 1 having 1 to 4 wavelengths may be annularly arranged in the upper stage, and the LEDs 1 having 5 to 8 wavelengths may be annularly arranged in the lower stage. In this case, the inner diameter of the upper illumination board 3 is smaller than the inner diameter of the lower illumination board 3, and the upper illumination board 3 is wider. Then, the upper LED 1 is arranged offset to the center axis side of the annular illumination unit 10 with respect to the lower LED 1.

  In the embodiment described above, the lighting unit 10 is divided into four and includes four lighting blocks TB1 to TB4. However, at least two lighting blocks TB are provided so that the workpiece W can be illuminated from two or more different lighting directions. If there is enough. When the number of lighting blocks TB is increased to eight lighting blocks TB or the like, partial illumination images can be obtained from more illumination directions, so that the accuracy of image inspection can be improved.

  In the present embodiment, the description has been made on the premise of the ring illumination device in which the light from the LEDs 1 arranged in an annular shape is irradiated toward the workpiece W below the illumination device, but the LEDs 1 are arranged in an annular shape and the surface of the workpiece W is arranged. A low-angle illuminating device that illuminates light from the entire circumference at a shallow angle, or light emitted from the LEDs 1 arranged in a ring shape is irradiated upward, and is reflected by a dome-shaped reflecting mirror to diffuse the light. The present invention can also be applied to a dome-type illumination device that irradiates diffused light to the workpiece W below.

  Furthermore, the illumination part 10 can arrange | position the lighting block TB comprised by the bar shape to a rectangular shape, or can arrange | position to a polygonal shape.

  The LED 1 is one embodiment of a light emitting element, and a light emitting element that emits light in response to an electrical signal can be employed. For example, organic EL, laser light, quantum dots, and the like can be used as the light emitting element.

  The light receiving element 2 is, for example, a photodiode. In addition, a phototransistor, a photoelectric cell, an image sensor, or the like that can convert light brightness into an electrical signal can be used as the light receiving element 2.

  The visual inspection device, the visual inspection illumination device, and the filter attached to the visual inspection illumination device according to the present invention use a light source composed of a plurality of light emitting diodes (LEDs) that emit light of different wavelengths, and perform multispectral imaging. Applicable for visual inspection.

1 ... LED
2 ... light receiving element 3 ... illumination substrate 10 ... illuminating unit 20 ... light receiving unit 200 ... filter unit 30 ... imaging unit 40 ... image processing device 41 ... input management unit 42 ... light quantity correction value setting unit 43 ... illumination control unit 44 ... imaging control Unit 45 ... Image processing unit 411 ... Illumination method selection unit 412 ... Wavelength selection unit 413 ... Light amount setting unit TB ... Lighting block KT ... Light source unit UN ... Unit HB not belonging to light source unit ... Conveying belt

Claims (7)

A plurality of light emitting elements that generate light of different wavelengths, an illumination unit that emits light to the inspection object by the plurality of light emitting elements, and each wavelength reflected from the inspection object irradiated by the illumination unit An imaging unit that receives the reflected light and has a sensitivity characteristic that outputs a signal having a different intensity according to the wavelength of the received reflected light, and generates an inspection image based on the sensitivity characteristic, and is generated by the imaging unit. An appearance inspection apparatus for inspecting the appearance of an inspection object by processing the inspection image,
A filter unit having different light transmission characteristics according to the wavelength of light, and a part of the light of each wavelength generated individually from the plurality of light emitting elements,
A light receiving unit that receives light that has passed through the filter unit, and has a sensitivity characteristic different from that of the imaging unit according to the wavelength of the received light;
A control unit that controls the illumination unit so that the amount of irradiation light is substantially constant for each of the plurality of light emitting elements based on a signal that is output from the light receiving unit and indicates a received light amount of each wavelength;
With
The light transmission characteristic of the filter unit is substantially the same as the sensitivity characteristic of the imaging unit in the wavelength range of the light irradiated by the illuminating unit, and the sensitivity characteristic of the light passing through the filter unit and received by the light receiving unit. Appearance inspection apparatus characterized by being set to be. The appearance inspection apparatus according to claim 1,
The appearance inspection apparatus according to claim 1, wherein the light transmission characteristics of the filter section are continuously or stepwise lowered as the wavelength of light increases. The appearance inspection apparatus according to claim 1 or 2,
The appearance inspection apparatus, wherein the filter unit is attached to a light receiving surface on which the light receiving unit receives light. The appearance inspection apparatus according to any one of claims 1 to 3,
A wavelength having a peak value that means a deviation width between a wavelength having a peak value of sensitivity characteristic of light passing through the filter unit and received by the light receiving unit and a wavelength having a peak value of sensitivity characteristic of the imaging unit. The width of λ _MAX is within ± 20% of the wavelength having the peak value of the sensitivity characteristic of the imaging unit. It is an external appearance inspection apparatus as described in any one of Claims 1-4,
A wavelength having a peak value that means a deviation width between a wavelength having a peak value of sensitivity characteristic of light passing through the filter unit and received by the light receiving unit and a wavelength having a peak value of sensitivity characteristic of the imaging unit. The width of λ _MAX is within ± 10% of the wavelength having the peak value of the sensitivity characteristic of the imaging unit. It is an external appearance inspection apparatus as described in any one of Claims 1-5,
The absolute value of the slope of the slope of the sensitivity characteristic graph of the light passing through the filter unit and received by the light receiving unit is 0.5 to 2 times the absolute value of the slope of the slope of the sensitivity characteristic graph of the imaging unit. Appearance inspection device characterized by being in between. It has a sensitivity characteristic that receives the reflected light of each wavelength reflected from the inspection object irradiated with light of different wavelengths, and outputs a signal of different intensity according to the wavelength of the received reflected light. An illumination device for appearance inspection used in an appearance inspection device that includes an imaging unit that generates an inspection image based on the image, and inspects the appearance of an inspection object by processing the inspection image generated by the imaging unit;
An illumination unit that has a plurality of light emitting elements that generate light of different wavelengths, and irradiates light on an inspection object with the plurality of light emitting elements,
A filter unit having different light transmission characteristics depending on the wavelength of light, and a part of the light of each wavelength generated individually from the plurality of light emitting elements of the illumination unit,
A light receiving unit that receives light that has passed through the filter unit, and has a sensitivity characteristic different from that of the imaging unit according to the wavelength of the received light;
A control unit that controls the illumination unit so that the amount of irradiation light is substantially constant for each of the plurality of light emitting elements based on a signal that is output from the light receiving unit and indicates a received light amount of each wavelength;
With
The light transmission characteristic of the filter unit is substantially the same as the sensitivity characteristic of the imaging unit in the wavelength range of the light irradiated by the illuminating unit, and the sensitivity characteristic of the light passing through the filter unit and received by the light receiving unit. Illumination device for visual inspection characterized by being set to be.