JP2006038550A - Painted surface inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a painted surface inspection device capable of inspecting the painted surface finely corresponding to the imaging characteristic of an image sensor entered flatly by regularly reflected light relative to light irradiation. <P>SOLUTION: This device is equipped with a surface light source 10 for performing light irradiation flatly onto an inspection object painted surface, an avalanche multiplication type imaging camera 21 as the image sensor entered by the regularly reflected light from the inspection object painted surface, and an image processing device 20 for inspecting existence of a defect on the painted surface by image processing for detecting a level change of the image signal. The surface light source 10 is equipped with a light source comprising a light emitting diode group formed by arraying a plurality of light emitting diodes arrayed circularly in the depth direction so that each optical axis agrees with the arc center point, and a Fresnel lens facing to the light source on the front of the arc center point and having the arc center point as a focal point, and the Fresnel lens emits in parallel along the optical axis surface, irradiation light of each light emitting diode passing the focal point along the optical axis surface including each optical axis of the plurality of light emitting diodes in the arc-shaped array. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a surface light source that irradiates a coating surface in a planar shape, an image sensor that makes regular reflection light incident on the coating surface to be inspected, and image processing that detects a level change of an image signal of the image sensor. The present invention relates to a coating surface inspection apparatus including an image processing apparatus that inspects for the presence or absence of surface defects.

  Patent Document 1 discloses that a vehicular coating surface inspection apparatus in which a straight tube fluorescent lamp as a surface light source that illuminates the surface of a vehicle being conveyed and a CCD camera that images an illumination area are arranged on a vehicle conveyance line is well known. It has become. This makes it possible to discriminate from the yuzu skin without reducing the reflected light level for the yuzu skin with a gentle reflection angle by an optical system with a simple configuration that uses the diffused light of the surface light source without depending on the laser light. Based on the decrease in the reflected light level due to the change in the reflection angle, irregular micro-defects such as burrs and scratches caused by dust can be detected by image processing.

  However, since this coating surface inspection device is premised on imaging reflected light on the coating surface of diffused light, the light irradiation range for the coating surface in the horizontal width direction of the straight tube fluorescent lamp can be expanded to some extent. There remains room for improvement in terms of detection sensitivity with respect to the amount of irradiation light. Therefore, according to Patent Document 2, the surface light source is disposed in front of the straight tube fluorescent lamp, and has a vertically long slit having a width approximately equal to or narrower than the width thereof, and is disposed in front of the slit, and has a straight tube shape. It has a width that is wider than the width of the fluorescent lamp, and a vertically long Fresnel lens that converts the incident light in the width direction incident through the slit into parallel light, and the image signal level output from the image sensor is on the normal coating surface. There has been disclosed a coating surface inspection device for a vehicle that detects a minute defect occurring on a coating surface of a vehicle outer surface by detecting a drop from a corresponding high signal level.

  Further, as a light source, a vehicular lamp such as a tail lamp or a stop lamp in which light emitting diode groups are arranged in a planar shape is well known. According to Patent Document 3, a Fresnel lens is formed on the front surface of a light emitting diode arranged in a planar shape along an outer lens. A vehicular lamp is also disclosed in which each of the lamps is arranged to control light distribution. When a light emitting diode is used in this way, a maintenance-free light source with a long life is realized without requiring time until the illuminance becomes constant from the time of lighting as in a fluorescent lamp.

On the other hand, as an image sensor, according to Patent Document 4 or Patent Document 5, a first conductivity type carrier blocking layer and a second conductivity type carrier are formed on a signal reading substrate having a plurality of pixel electrodes disposed on the upper surface. A solid-state imaging device in which a light-receiving layer having an avalanche multiplication effect under a high S / N ratio is interposed by application of a bias between the blocking layers is well known. Furthermore, according to Patent Document 6, an endoscope using a solid-state imaging device that can greatly improve the resolution, the S / N ratio, and the sensitivity is well known, and the target portion is observed with a resolution comparable to a microscope. It is possible.
Japanese Patent Laid-Open No. 3-10150 JP 2000-250625 A JP 2000-123610 A JP-A-5-129649 JP-A-5-335549 Japanese Patent Laid-Open No. 9-21963

  According to Patent Document 2, in the case of a surface light source in which a slit and a Fresnel lens are arranged in front of a straight tube fluorescent lamp, specular reflection light from a microdefect such as a chip that suppresses diffusion in the width direction and changes a reflection angle. However, the range of conversion to parallel light in the horizontal width direction is limited by the shape of the straight tube fluorescent lamp, and as long as a fluorescent lamp is assumed, the luminance is stable. There is a problem that does not reach the light source of the light emitting diode group in terms of the degree of maintenance or maintainability. Therefore, according to Japanese Patent Application No. 2003-384778, the applicant of the present invention has a light source by a light emitting diode group in which a plurality of light emitting diodes arranged in an arc shape are arranged in the depth direction so that each optical axis coincides with the arc center point. And a Fresnel lens facing the light source in front of the arc center point and focusing on the arc center point, and the Fresnel lens includes optical axes of a plurality of light emitting diodes arranged in an arc shape. A surface light source for surface inspection has been proposed that emits the irradiation light of each light emitting diode passing through the focal point along the optical axis plane in parallel along the optical axis plane. Accordingly, it is possible to irradiate a parallel light having a stable luminance over a wide range via the Fresnel lens, and thus processing a captured image of specularly reflected light in which diffusion in the arc arrangement direction is suppressed, so that a wide range in the arc arrangement direction is obtained. Small defects on the coating surface can be inspected with high sensitivity by changing the reflected light.

  However, if it is assumed that a normal CCD camera is used, there is a limit to the fine detection sensitivity. Therefore, by improving the surface light source alone, it is possible to detect minute defects, etc. due to foreign matter contamination or scratches on the surface to be painted with high accuracy. Even so, minute recesses (so-called repellency) caused by fluctuations in the surface tension of the coating film, minute projections (so-called sagging) caused by paint dripping, ring-like projections (so-called waks) generated when bubbles bounce, etc. There is still room for improvement in that it is difficult to detect minute defects in the coating film itself having a relatively gentle uneven slope.

  In view of such a point, the present invention provides a coating surface inspection apparatus that can inspect a coating surface more finely according to the imaging characteristics of an image sensor that makes regular reflection light incident on light in a plane shape. With the goal.

  In order to achieve this object, the present invention pays attention to the fine imaging performance with respect to the coating surface of the avalanche multiplication type solid-state imaging camera provided with the light receiving layer having an avalanche multiplication effect. The surface light source that illuminates the paint surface in a planar shape, the image sensor that makes specular reflection light incident on the paint surface to be inspected, and the image processing that detects the level change of the image signal of this image sensor, the defect of the paint surface In a coating surface inspection apparatus including an image processing apparatus for inspecting presence or absence, a plurality of light emitting diodes arranged in an arc shape in the depth direction are arranged so that each surface light source coincides with an arc center point. A light source by the group of light emitting diodes arranged, and a Fresnel lens facing the light source in front of the arc center point and focusing on the arc center point, and the Fresnel lens, The irradiation light of each light emitting diode passing through the focal point along the optical axis plane including the optical axis of each of the plurality of light emitting diodes arranged in an arc shape is emitted in parallel along the optical axis plane, and the image sensor performs avalanche multiplication. It is a type imaging camera.

  As a result, the irradiation light that passes through the focal point of the Fresnel lens, which is the arc center point of each light-emitting diode in the arc-shaped array, enters the Fresnel lens and is emitted as parallel light, and regular reflection in which diffusion in the arc array direction is suppressed. By processing an image picked up under high resolution and high sensitivity of light, a minute defect on the coating surface in a wide range in the arc arrangement direction is finely inspected by a change in the reflected light. Therefore, according to claim 2, the image processing apparatus detects the micro defect caused by the defect of the coating film itself on the normal coating target surface in addition to the micro defect caused by the scratch or adhering dust on the coating surface to be inspected. It becomes possible to provide a defect determination means.

  In order to easily display a minute defect on the premise of an analog image signal having a high S / N ratio that can be output by an avalanche multiplication type imaging camera, the image processing apparatus according to claim 3, the avalanche multiplication type imaging camera Differential processing means for outputting an analog differential signal by differential processing of an analog image signal output by reading scanning of the picked-up image, and an analog differential signal exceeding a predetermined level includes a plurality of continuous read scanning lines and in the read scanning direction. Defect determination means for determining the presence / absence of a defect based on the width of a differential signal detection area detected next to each other within a scanning range defined by a predetermined scanning width, and an analog differential signal generated with respect to a coating surface to be inspected Screen display means for displaying a screen. In order to further increase the parallelism of the emitted light, a slit is formed in the focal position along the depth direction. In order to smooth the amount of light emitted between the light emitting diodes, according to the invention of claim 5, a diffusing plate that widens the directivity angle of the light emitted from the light emitting diodes is disposed at either the light emitting diode group or the focal position.

  According to the first aspect of the present invention, the light emitting diodes arranged in an arcuate plane can irradiate parallel light having a stable brightness over a wide range via the Fresnel lens, and thus the positive diffusion in which the diffusion in the arc arrangement direction is suppressed. By processing the captured image of the reflected light, a small defect on the coating surface in a wide range in the arc arrangement direction can be detected with high detection accuracy by the change of the reflected light, and can be stably inspected by a stable light source. A surface light source having an arbitrary shape can be manufactured by the arc arrangement of the light emitting diode group. In addition, by using an avalanche multiplication type solid-state imaging camera with high resolution, high S / N ratio, and high sensitivity as an image sensor, the unevenness of the coating film itself on the normal coating target surface, which was difficult to detect conventionally It is also possible to detect minute defects whose inclination is relatively gentle compared to so-called bumps. That is, according to the second aspect of the invention, it is possible to detect minute defects in the coating film itself caused by fluctuations in the surface tension of the coating film, dripping of paint, bounce of bubbles, and the like. According to the third aspect of the present invention, an analog image signal having a high S / N ratio can be obtained, so that the edge of the image signal of a minute defect is emphasized brightly and darkly with respect to the standard luminance by a simple analog differential process. Display on the screen as it is. According to the fourth aspect of the present invention, the parallelism is further improved and the resolution is improved by shielding the irradiation light diffused by the light emitting diode. According to the invention of claim 5, the brightness of the light emitting diode group can be made uniform by accepting a slight decrease in parallelism.

A coating surface inspection apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a coating surface inspection apparatus configured for a vehicle, in which robots 39 and 39a are arranged on both sides of a conveyance path of the vehicle 1, and a base 29 attached to the tip of each robot arm 9 and 9a. HARP (High-gain Avalanche Rushing amorphous Photoconductor) as an area light source 10 and an image sensor, that is, an avalanche multiplication type solid-state imaging camera equipped with an avalanche light-receiving layer (manufactured by Hamamatsu Photonics Co., Ltd., trade name AP)
An imaging device 20 comprising an imager camera, model name C9148) 21 is attached. The robots 39 and 39a scan the coating surface so as to sequentially shift the imaging device 20, and can arbitrarily control the three-dimensional position facing the coating surface and the angle in the three axial directions at each scanning position. . The avalanche multiplication type solid-state imaging camera 21 is oriented so that specular reflection light having a width wider than the irradiation area on the coating surface of the Fresnel lens 15 at a front position, for example, 50 cm, and a vertical width of about 200 mm is incident. ing.

  The avalanche multiplication type solid-state imaging camera 21 has a high resolution of 512 × 512 pixels, and performs electronic amplification at a high S / N ratio with respect to a normal CCD camera to detect a coating film with high sensitivity. be able to. In the imaging apparatus 20, the level of the continuous analog image signal output by the avalanche multiplication type solid-state imaging camera 21 reading out the imaging screen at a high speed in the scanning direction is output due to a minute defect. An image processing device 30 for detecting a drop from a high signal level is attached.

  This image processing apparatus, for example, as shown in FIG. 2, amplifies an analog image signal supplied from an avalanche multiplication type solid-state imaging camera 21 and performs a differential process by an analog differential circuit of CR (capacitor, resistor). And a differential processing means 31 for outputting an analog differential waveform signal, a screen display device 32 for displaying the image signal of the differentiated imaging screen of the coating surface to be inspected, and reading scanning along the readout scanning line. Each of the positive and negative pulses generated by differentiation is defined as image data obtained by reading out and scanning an image signal in a width direction of about 8 cm and a depth direction of 20 cm slightly narrower than the width of the Fresnel lens 15 in the width direction. By detecting the amplitude between peaks and using an image signal exceeding a predetermined level as a defect candidate signal, an address corresponding to a minute pixel between the peaks is obtained. The area of the differential signal detection area in which the defect candidate signal is detected next to each other within the scanning range defined by the defect candidate detection unit 33a to be stored, a plurality of continuous readout scanning lines, and a predetermined scanning width in the readout scanning direction An area determination unit 33b for determining whether or not there is a defect, and an inspection data storage unit 34 for storing inspection data.

  The inspection data storage means and the defect determination means 33 are constituted by a personal computer, and the screen display device 32 receives image signals from both of the robot arms 9 and 9a and is common to this personal computer as a screen display means. It constitutes an accessory device. This screen display device uses a personal computer that digitizes and stores the analog differential waveform signals to which it belongs together with the robot scanning position data of the robots 39 and 39a that scan the coating surface so that the imaging device 20 is sequentially shifted. The display data storage means 32a is attached, and graphic display data of the contour of the vehicle body to be inspected and mark data to be described later indicating the defective part are incorporated, and the differential waveform of the entire coating surface to be inspected or the designated area is included. The signal is D / A converted again, and the minute defect is displayed together with the mark at the corresponding coating surface position on the vehicle body.

The CR time constant of the differential processing means 31 is a fall due to a decrease in the level of a thin pulse signal detected in a minute region in the readout scanning direction corresponding to a minute defect having a width of, for example, about 0.2 mm on the coating surface, and its It is set sufficiently small so that the rise due to the return can be detected. The defect candidate detection unit 33a performs A / D conversion on the differential waveform signal, and generates positive and negative pulses generated in pairs in a minute region in the readout scanning direction corresponding to about 0.2 mm to 1.5 mm of the coating surface. When the amplitude between peaks is calculated and exceeds a predetermined amplitude, it is stored as a defect candidate signal together with the address of the region to which it belongs. The area determination unit 33b determines whether or not the defect candidate signal exceeds the area, for example, 0.5 mm ^{2 when} viewed on the coating surface based on the size of the block region or linear region detected adjacently. When turning, a defect signal indicating the part is output. The inspection data storage means 34 stores the coating surface position specified at the robot scanning position where the defect signal is output as defect position data.

  4 and 5 show a surface light source 10 for inspecting a painted surface for a vehicle. The surface light source 10 is based on a plurality of light emitting diodes 11a arranged in an arc shape so that each optical axis coincides with the arc center point. A light source 11 composed of a group of light emitting diodes further arranged in the depth direction on the surface 12, a Fresnel lens 15 facing the light source in front of the arc center point and having the arc center point as a focal point F, and a focal point F And a slit plate 17 that forms a vertically long slit 16 in the depth direction at each position, and each is housed in a case 13.

  The Fresnel lens 15 is set to be wider than the horizontal width of the plurality of light emitting diodes 11a arranged in an arc shape with a radius of about 8 cm, and is arranged symmetrically with respect to a symmetry plane that divides the light source 11 into two in the depth direction through the focal point F. The incident light passing through the focal point F along the optical axis plane including each optical axis of the plurality of arc-shaped light emitting diodes 11a, that is, the plane orthogonal to the above-described symmetry plane is deflected in parallel along the optical axis plane. To do. Further, the width of the Fresnel lens 15 is 10 cm, the depth is about 30 cm corresponding to the straight tube fluorescent lamp, and the light emitting diodes 11a passing through the slits 16 having a width of about 1 cm along the optical axis surface described above. A number of Fresnel surfaces significantly larger than the number of light emitting diodes are formed in the width direction so as to emit the irradiated light in parallel. The light emitting diode 11a emits blue light, and irradiates light with a directivity angle of an emitted light amount of about ± 10 ° in the lateral direction and about ± 20 ° in the depth direction with respect to the optical axis.

  The operation of the coating surface inspection apparatus configured as described above is as follows. Due to the arc arrangement of the light emitting diodes 11a and the aperture of the slit 16, irradiation light passing through the focal point or the vicinity thereof is incident on the Fresnel lens 15, and the coating surface to be inspected is irradiated with parallel light or substantially parallel light. The imaging device 20 images the reflected light with the avalanche multiplication type solid-state imaging camera 21 and supplies an analog image signal in the imaging range to the image processing device 30. In a captured image of specularly reflected light in which the diffusion in the arc arrangement direction is suppressed, a minute defect on the coating surface to be inspected is detected with high sensitivity and high resolution by the reflected light, and is detected on the optical axis surface of the light emitting diode 11a in the arc arrangement. A wide range can be efficiently inspected with high accuracy by the horizontal scanning in the horizontal direction. Moreover, it is detected with a more sensitive amplitude change by blue light having a short wavelength.

  That is, in FIG. 3, the above-mentioned irregularity, repelling, sagging, and sword (on the third stage in FIG. 2), the differential waveform signal shown in the second row of FIG. 2 is generated at the center by scanning in the horizontal direction as viewed in the figure. The projections and sagging are convex, but the image signal is detected dark, so that it first falls and rises in pairs. Similarly, a differential waveform signal corresponding to the shape of a minute defect is generated each time readout scanning is performed from the top to the bottom in order as viewed in the figure.

  On the screen of the screen display device 32, as shown in FIG. 1, an image of a differential waveform is displayed on the image of the vehicle body contour after the inspection is completed. At that time, micro-defects are displayed by the differential waveform signal, as schematically shown in five stages, in which the fourth level in FIG. The image sizes are aligned for convenience). If the horizontal width is narrow, the differential waveform itself is displayed according to the luminance, but if the width is widened, the intermediate area once becomes the standard luminance. That is, when the image signal level rises at the edge of the minute defect, the luminance rises from the standard luminance level, and falls at the falling edge, so that the minute defect is clearly displayed by the brightness of the edges on both sides in the scanning direction. . In addition, an X mark is displayed at an image position determined to be a minute defect. By instructing the screen display device 32, the inspection surface in the specific area can be enlarged and displayed.

  As a screen display device according to another embodiment, when the coating surface inspection device is configured to perform the coating surface inspection in a stationary state, the imaging is performed in a synchronized state with the imaging of the avalanche multiplication type solid-state imaging camera 21. A range of analog image signals may be displayed as they are without being stored once. In the surface light source according to the above-described embodiment, even if the slit at the focal position is abolished, the optical axis of all the light emitting diodes is directed to the focal point of the Fresnel lens. A wide range of parallel conversion is possible. Further, as shown in FIG. 6, in FIG. 1, a diffusion plate 19 that widens the directivity angle in the lateral width direction with respect to the optical axis of each light emitting diode 11a is arranged in the slit 16, so that a slight decrease in parallelism is accepted. Thus, the luminance in the width direction of the light source 11 can be made uniform. Similarly, it is also conceivable to arrange the diffusion plate 19a in place of the diffusion plate 19 along the light source 11 as shown in FIG.

  As an image processing apparatus according to another embodiment, a digital image signal is once taken into a memory as before without performing the above-described differential processing of a continuous analog waveform, and a sharp level change of the image signal level is detected by a CPU. In this way, the above-described various micro defects can be detected. For example, as shown in FIG. 7, as the defect determination means, a falling point Tf and a rising point Tr from a high image level caused by a minute defect are detected from an image signal in the readout scanning direction, and the difference between them is determined as a reference. If the value is exceeded, the pixel line data is determined as a candidate for a minute defect. Further, a rectangle R formed by circumscribing a minute defect candidate region formed by data of readout scanning lines of adjacent minute defect candidates in order is calculated, and the vertical and horizontal lengths are respectively calculated, and one of them has a predetermined length. If it exceeds, it is judged as a micro defect.

It is a figure explaining the structure of the coating surface test | inspection apparatus by embodiment of this invention. It is a figure explaining operation | movement of the image processing apparatus of the same coating surface inspection apparatus. It is a schematic front view of the coating surface inspection apparatus for vehicles. It is sectional drawing of the surface light source of the same coating surface inspection apparatus. It is a perspective view of the same surface light source. It is a schematic sectional drawing of the surface light source by another embodiment. Processing operations of the image processing apparatus according to another embodiment will be described.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Surface light source 11 Light source 11a Light emitting diode 15 Fresnel lens 16 Slit 21 Avalanche multiplication type solid-state imaging camera 32 Screen display apparatus

Claims (5)

A surface light source that illuminates the surface to be inspected in a plane, an image sensor that makes regular reflection light incident on the surface to be inspected, and image processing that detects a change in the level of the image signal of the image sensor. In a coating surface inspection apparatus provided with an image processing apparatus that inspects for the presence or absence of defects,
The surface light source includes a light source by the light emitting diode group in which a plurality of light emitting diodes arranged in an arc shape are arranged in the depth direction so that each optical axis coincides with the arc center point, and the arc center point on the light source. And a Fresnel lens that faces the arc center point, and the Fresnel lens extends along an optical axis plane that includes the optical axis of each of the plurality of light emitting diodes arranged in an arc shape. The coating surface inspection apparatus is characterized in that the light emitted from each of the light emitting diodes passing through the focal point is emitted in parallel along the optical axis surface, and the image sensor is an avalanche multiplication imaging camera.   The image processing apparatus includes defect determination means for detecting a micro defect caused by a defect of a coating film itself on a normal coating target surface in addition to a micro defect caused by a scratch or attached dust on the coating surface to be inspected. The coating surface inspection apparatus according to claim 1, wherein   The image processing apparatus has a differential processing means for outputting an analog differential signal by differential processing of an analog image signal output by reading and scanning a captured image of an avalanche multiplication imaging camera, and an analog differential signal exceeding a predetermined level is continuous. A defect judging means for judging presence / absence of a defect based on a width of a differential signal detection area detected adjacent to a plurality of readout scanning lines and a scanning range defined by a predetermined scanning width in the readout scanning direction; 3. The coating surface inspection apparatus according to claim 1, further comprising screen display means for displaying an analog differential signal generated on the coating surface on a screen.   The coating surface inspection apparatus according to any one of claims 1 to 3, wherein a slit is formed at a focal position along a depth direction.   The coating surface inspection apparatus according to any one of claims 1 to 4, wherein a diffusing plate that widens the directivity angle of the light emitted from the light emitting diodes is disposed at any one of the light emitting diode group and the focal position. .

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