JP2018017670A - Spectral characteristic acquisition device, image evaluation device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a spectral characteristic related to a field of measurement on a measurement target object by using a comparatively simple constitution.SOLUTION: A pinhole array 11 allows a light flux reflected by a measurement target object 1 to pass through a plurality of pinholes 11 arrayed in the lateral direction. A lens array 13 condenses each light flux passing through each pinhole 11a toward an imaging surface 17s of an imaging device 17. A diffraction element 15 forms on the imaging surface 17s, a plurality of diffraction images obtained by diffracting each light flux passing through the lens array 13 in the longitudinal direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a spectral characteristic acquisition device, an image evaluation device, and an image forming device.

In the commercial printing field, when a color image is formed on a recording medium by an electrophotographic image forming apparatus, the color of the color image formed on the recording medium is measured, and color management is performed for reproducibility and stability. So-called color management is performed.
At this time, it is necessary to accurately measure the color of the color image formed on the recording medium, and a spectrocolorimeter is generally used. Since the spectrocolorimeter measures the color of one point in a predetermined region, it takes time to measure the color of a plurality of points such as a color chart, which is an operational problem.
Therefore, as a method for acquiring spectral characteristics from a color image formed on the entire surface of a recording medium in a short time, a large number of spectral sensors are arranged, and spectral data is acquired from the spectral sensors arranged in parallel. A method using a spectral imaging module that enables high-precision color measurement of the entire surface of a recording medium is known.

Specifically, for example, spectral imaging modules as disclosed in Patent Documents 1 to 3 are disclosed.
In Patent Document 1, a plurality of apertures are transmitted through, diffracted obliquely while forming an image, and a plurality of diffraction images are captured by a line sensor, so that spectral characteristics at a plurality of points are acquired in parallel, and the openings are slit-shaped. For this reason, “OPTICAL SENSOR DEVICE AND METHOD FOR SPECTRAL ANALYSIS” is disclosed, in which when the light intensity changes at the passing position in the slit, an error is added to the detected spectral characteristic and a false color is generated.
In Patent Document 2, a plurality of oblique slit openings arranged in the longitudinal direction are transmitted, diffracted in the short direction while being imaged, and detected by an imaging means in which a plurality of pixels are arranged in the longitudinal direction. Spectral characteristics are acquired in parallel. Disclosure of “spectral characteristic acquisition device, image evaluation device, image forming device” with technical content that if the light intensity changes at the passing position in the oblique slit-shaped opening, an error is added to the acquired spectral property and false color is generated Has been.
Japanese Patent Laid-Open No. 2004-133867 describes an imaging unit in which a plurality of pixels arranged in the longitudinal direction are transmitted through a plurality of openings arranged in the longitudinal direction, diffracted in the lateral direction while forming an image, and diffracted images transmitted through the oblique slit-shaped openings. A “spectral characteristic acquisition apparatus, image evaluation apparatus, and image forming apparatus” having a technical content of acquiring a plurality of spectral characteristics in parallel by detection is disclosed. In Patent Document 3, it is difficult to adjust the positions of the oblique slit-shaped opening and the imaging means arranged in front of the image sensor and the plurality of openings.

However, as in the inventions disclosed in Patent Document 1 and Patent Document 2, when the opening is substantially slit-shaped in an oblique direction, the light intensity varies depending on the passing position in the opening (for example, black / white boundary). There is a problem that an error occurs in the spectral characteristic detected by the sensor, and a greatly different color is output.
On the other hand, in the invention disclosed in Patent Document 2, since there is an optical system that makes the light intensity uniform depending on the passing position in the opening, the influence of the optical system is small, and therefore, it is affected by the problems described above. Hateful. However, in order to acquire spectral characteristics, it is necessary to accurately adjust the position of the oblique slit aperture arranged immediately before the image sensor, the imaging element, and the aperture, and a large amount of spectral characteristic acquisition devices are produced at low cost. There was a problem that was difficult.
The present invention has been made in view of the above, and an object thereof is to acquire spectral characteristics relating to a measurement region on a measurement object using a relatively simple configuration.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided with an imaging unit having a plurality of pixels arranged in a matrix in the vertical direction and the horizontal direction, and the measurement on the object to be measured using the imaging unit. A spectral characteristic acquisition device that measures spectral characteristics of the object to be measured by capturing a diffraction image of the region, wherein a plurality of pinholes that allow light beams reflected by the object to pass through are in the lateral direction A pinhole array arranged in a row, a condensing means for condensing each light flux that has passed through each pinhole toward an imaging surface of the imaging means, and each light flux that has passed through the condensing means in the vertical direction Diffracting means for forming a plurality of diffracted diffraction images on the imaging surface.

  According to the present invention, it is possible to acquire spectral characteristics related to a measurement region on the DUT 1 using a relatively simple configuration.

(A) is a figure which shows the structure of the optical system of the spectral characteristic acquisition apparatus which concerns on 1st Embodiment of this invention, (b) is the hardware constitutions of the spectral characteristic acquisition apparatus which concerns on 1st Embodiment of this invention. FIG. (A) is sectional drawing which looked at the spectral imaging module from the Y-axis direction, (b) is sectional drawing which looked at the spectral imaging module from the X-axis direction. It is a block diagram for demonstrating the hardware constitutions of the image pick-up element which concerns on 1st Embodiment of this invention. It is a schematic diagram for demonstrating the relationship between the image pick-up element which concerns on 1st Embodiment of this invention, and a diffraction image. (A) is a figure which shows the relationship between the vertical shift register of an image pick-up element, each pixel, and a diffraction image, (b) has shifted each vertical direction pixel by 1 pixel in the vertical shift register by the vertical transfer process. (C) is a diagram showing that the horizontal shift register has shifted by one pixel in the horizontal transfer process, and (d) shows that the spectral intensity information of the diffraction image is stored in the horizontal shift register. FIG. It is a timing chart which shows the operation | movement with respect to an image pick-up element by the control part shown in FIG.1 (b). It is a schematic diagram for demonstrating the step-shaped diffraction element which concerns on 4th Embodiment of this invention. It is a figure which shows the structure of the image evaluation apparatus which concerns on 5th Embodiment of this invention. It is a figure which shows the structure of the image forming apparatus which concerns on 6th Embodiment of this invention.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
The present invention has the following configuration in order to acquire spectral characteristics related to a measurement region on a measurement object using a relatively simple configuration.
That is, the spectral characteristic acquisition apparatus of the present invention includes an imaging unit having a plurality of pixels arranged in a matrix in the vertical direction and the horizontal direction, and uses the imaging unit to obtain a diffraction image related to the measurement region on the object to be measured. A spectral characteristic acquisition device that measures spectral characteristics of an object to be measured by imaging, a pinhole array in which a plurality of pinholes that allow light beams reflected by the object to pass through are arranged in a horizontal direction; Condensing means for condensing each light flux that has passed through each pinhole toward the imaging surface of the imaging means and a plurality of diffraction images obtained by diffracting each light flux that has passed through the condensing means in the vertical direction are formed on the imaging surface. And diffracting means.
With the above configuration, it is possible to acquire the spectral characteristics related to the measurement region on the object to be measured using a relatively simple configuration.
Hereinafter, the features of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
<Configuration of spectral characteristic acquisition device>
With reference to FIGS. 1A and 1B, the configuration of the spectral characteristic acquisition apparatus according to the first embodiment of the present invention will be described. FIG. 1A is a diagram showing a configuration of an optical system of a spectral characteristic acquisition apparatus 10 according to the first embodiment of the present invention, and FIG. 1B is a spectral characteristic acquisition apparatus according to the first embodiment of the present invention. 10 is a diagram illustrating a hardware configuration of 10. FIG.
The spectral characteristic acquisition apparatus 10 includes a light source 3, an imaging lens 5, a spectral imaging module 7, and a control unit 9.
A measured object 1 shown in FIG. 1 is a recording medium such as a recording sheet, and is conveyed in a direction opposite to the Y-axis direction at a constant speed. The measurement area 1a of the DUT 1 is a measurement area having a predetermined width at least in the Y-axis direction. The measurement area 1a may be the entire width of the DUT 1. The spectral characteristic acquisition device 1 can simultaneously acquire spectral characteristics at a plurality of positions in the measurement region 1 a of the DUT 1.

The light source 3 irradiates the device under test 1 with illumination light 3a. The light flux reflected from each position of the measurement region 1a of the DUT 1 reaches the imaging lens 5 respectively.
The imaging lens 5 constitutes imaging means, transmits the incident light beam, and condenses it toward the spectral imaging module 7.
The spectral imaging module 7 is arranged on the optical axis of the imaging lens 5, and is a module of optical system parts and imaging elements for acquiring the spectral characteristics of the DUT 1. Be controlled.
The control unit 9 controls the ON / OFF timing of the light source 3 and the operation timing of the spectral imaging module 7.

<Spectral imaging module>
Next, the spectral imaging module according to the first embodiment of the present invention will be described with reference to FIGS. 2A is a cross-sectional view of the spectral imaging module 7 viewed from the Y-axis direction, and FIG. 2B is a cross-sectional view of the spectral imaging module 7 viewed from the X-axis direction.
The spectral imaging module 7 includes a pinhole array 11, a lens array 13, a diffraction element 15, and an imaging element 17.
The light beam that has passed through the imaging lens 5 shown in FIG. 1 enters the pinhole array 11. In the pinhole array 11, a plurality of pinholes 11a having a predetermined opening area are arranged in the x-axis direction, and light beams reflected from respective positions in the measurement region 1a shown in FIG.

Each light beam that has passed through each pinhole 11 a of the pinhole array 11 is incident on each lens 13 a of the lens array 13. The lens array 13 constitutes a condensing unit, and a plurality of lenses 13 a are arranged in the x-axis direction, and the optical axis of the lens surface of each lens 13 a corresponds to each pinhole 11 a on the pinhole array 11. Are arranged as follows. Each light beam that has passed through each lens 13a of the lens array 13 passes through the diffraction element 15 and forms an image on the imaging surface 17s of the imaging element 17 to form a diffraction image.
The diffraction element 15 has a plurality of diffraction gratings 15a arranged on the xy plane so as to be diffracted in the y-axis direction, and forms an image on the image pickup surface 17s of the image pickup element 17 while being refracted at a diffraction angle corresponding to the wavelength. Thus, a plurality of diffraction images are formed on the imaging surface 17s.
The imaging element 17 is configured by a charge coupled device (CCD) area image sensor, and has an imaging plane on the xy plane.

<Hardware configuration of image sensor>
With reference to FIG. 3, the hardware configuration of the image sensor according to the first embodiment of the present invention will be described. FIG. 3 is a configuration diagram for explaining a hardware configuration of the image sensor according to the first embodiment of the present invention.
The image sensor 17 is a CCD area image sensor having n pixels in the horizontal direction (x direction) and m pixels in the vertical direction (y direction).
Specifically, the image sensor 17 includes vertical shift registers 17a1 to 17an, a horizontal shift register 17b, and an A / D converter 17c.

Each of the vertical shift registers 17a1 to 17an includes a plurality of unit light receiving units that are pixels arranged in the vertical direction (y direction), and shifts the charge accumulated in each pixel in the vertical direction (−y direction). It is.
The horizontal shift register 17b is a shift register that is arranged in the horizontal direction (x direction) and shifts charges in the horizontal direction (−x direction).
The A / D converter 17c performs A / D conversion on the charge (voltage signal) transported in the horizontal direction by the horizontal shift register 17b to convert it into a digital signal.

<Relationship between image sensor and diffraction pattern>
With reference to FIG. 4, the relationship between the image sensor and the diffraction image according to the first embodiment of the present invention will be described. FIG. 4 is a schematic diagram for explaining the relationship between the imaging element and the diffraction image according to the first embodiment of the present invention.
In FIG. 4, as an example of the present invention, the light receiving region 17 r of the image sensor 17 having 40 pixels in the horizontal direction (x direction) and 6 pixels in the vertical direction (y direction), and three diffraction images 17 _i−1 , 17. _i-2 and _17i-3 are shown. However, the present invention is not limited to the number of pixels, the number of diffraction images, and the interval between diffraction images shown in FIG.
Since the interval between the pinholes 11a is at least the length of each diffraction image 17i in the vertical direction, a plurality of diffraction images 17i can be independently formed on the imaging surface 17s.

The diffraction images 17i corresponding to the pinholes 11a of the pinhole array 11 shown in FIG. 2 are arranged in the horizontal direction (x direction) and diffracted in the vertical direction (y direction). Therefore, by appropriately adjusting the grating pitch p of the diffraction grating of the diffraction element 15, it is possible to arrange only a predetermined diffraction image component in the light receiving region 17 r of the imaging element 17.
In FIG. 4, since only the first-order diffracted image is adjusted to form an image on the light receiving region 17r, the transmitted image that is the 0th-order diffracted light is formed outside the light receiving region.

<Method of reading signal from image sensor>
With reference to FIG. 5, a method of reading a signal from the image sensor according to the first embodiment of the present invention will be described. FIG. 5A is a diagram illustrating the relationship between the vertical shift registers 17a1 to 17a7 of the image sensor 17, each pixel, and the diffraction image 17i. FIG. 5B is a diagram illustrating the vertical direction of each of the vertical shift registers 17a1 to 17a7 in the vertical transfer process. It is a figure which shows having shifted the pixel by 1 pixel, (c) is a figure which shows having shifted only 1 pixel in the horizontal shift register 17b by the horizontal transfer process, (d) is the spectral intensity of a diffraction image It is a figure which shows having stored information in the horizontal shift register 17b.
Note that the number of pixels and the number of diffraction images of the image sensor 17 shown in FIGS. 5A to 5D are examples, and the present invention is not limited to this.

FIG. 5A is a diagram illustrating the relationship between the vertical shift registers 17a1 to 17a7 of the image sensor 17, each pixel, and the diffraction image 17i. In FIG. 5A, a full frame transfer type CCD area image sensor in which the vertical shift registers 17a1 to 17a7 also serve as pixels is tried.
The control unit 9 executes a combination of a vertical transfer process and a horizontal transfer process as a signal reading process for the image sensor 17.
In the vertical transfer process, the controller 9 transports the charges accumulated in the pixels arranged in the vertical direction in the vertical direction in the vertical shift registers 17a1 to 17a7 and accumulates them in the respective registers of the horizontal shift register 17b.
In the horizontal transfer process, the controller 9 carries the charges accumulated in the respective registers in the horizontal shift register 17b in the horizontal direction, and converts the analog signal into a digital signal in the A / D converter 17c.

For example, in the area mode, the control unit 9 reads the signals of all the pixels accumulated in the image sensor 17 independently. In this area mode, one vertical transfer process is performed for each pixel, followed by a horizontal transfer process for horizontal pixels, and this vertical transfer process and horizontal transfer process are alternately repeated for the vertical pixels. .
Further, for example, in the full line binning mode, the control unit 9 performs the vertical transfer process for the vertical direction pixels when the image sensor 17 is used as a line sensor having pixels that are long in the vertical direction, thereby performing the horizontal shift register 17b. By accumulating the added charges in each of the registers, and then performing a horizontal transfer process for the horizontal pixels, reading can be realized in a much faster time than in the area mode.
In the present invention, since the first-order diffraction image diffracted in the vertical direction is formed in the light receiving region of the image sensor 17, charges corresponding to the light intensity of each wavelength corresponding to the vertical direction of the image sensor 17 are accumulated in each pixel. The

Next, as shown in FIG. 5B, when the control unit 9 shifts each vertical pixel by one pixel in the vertical shift registers 17a1 to 17a7 by the vertical transfer process, the charge of each pixel is sequentially reduced. In addition to shifting in the direction, the charge of the lowermost pixel is transferred to the horizontal shift register 17b.
Next, as shown in FIG. 5C, when the control unit 9 shifts by one pixel in the horizontal shift register 17b by the horizontal transfer process, the charge accumulated in each register in the horizontal shift register 17b becomes one pixel. Shift by minutes. By alternately repeating the vertical transfer process and the horizontal transfer process, the spectral intensity information of the diffraction image can be stored in the horizontal shift register 17b as shown in FIG.
Here, as shown in FIG. 4, the control unit 9 appropriately arranges the arrangement pitch of the plurality of diffraction images 17 i so that the optical signals of the diffraction images are not mixed, and the independent diffraction images 17 i are mixed. Are stored in the horizontal shift register 17b as charge signals related to the optical signal.

Finally, the control unit 9 shifts the horizontal pixel in the horizontal shift register 17b by the horizontal transfer process, whereby the A / D converter 17c converts the charge signal related to the optical signal of each independent diffraction image 17i to A / D. Since D conversion is performed, the spectral characteristics of the diffraction image can be read out as a digital signal.
The signal readout cycle according to the present invention is the same as the readout time in the above-described full line binning mode, and high-speed readout is possible.
As a specific example, a CCD area image sensor “S11071-1104” manufactured by Hamamatsu Photonics has 2048 × 16 pixels. Therefore, for example, when the arrangement pitch of the diffraction images 17i is 20 pixels, it is possible to acquire the spectral characteristic signals of about 100 diffraction images at high speed and with high accuracy.

<Timing chart>
Next, with reference to FIG. 6, the timing chart which shows the operation | movement with respect to the image pick-up element 17 by the control part 9 mentioned above is demonstrated. FIG. 6 is a timing chart showing the operation of the image sensor 17 by the control unit 9.
As an exposure process, the controller 9 forms an image on the image sensor 17 with the light emitted from the light source 3 at time t1 to t2 to form a diffraction image 17i. Charges are accumulated in each pixel of the image sensor 17.
In the vertical transfer process, the controller 9 transports charges accumulated in each pixel in the vertical direction in the vertical shift registers 17a1 to 17an by the shift clock at time t2 to t3 and accumulates them in the respective registers of the horizontal shift register 17b. To do.

In the horizontal transfer process, the control unit 9 performs horizontal transfer by shifting the horizontal shift register 17b by one pixel in the horizontal direction at times t2 to t3.
Here, at time t2 to t3, the control unit 9 alternately repeats the vertical transfer process and the horizontal transfer process, thereby obtaining the spectral intensity information of the diffraction image 17i as shown in FIG. 5D. 17b is stored in each register.
In the A / D converter 17c, at time t3 to t4, the charge signal related to the optical signal of each independent diffracted image 17i stored in each register of the horizontal shift register 17b is shifted by the shift clock and input. D conversion is performed.

Second Embodiment
<Image-side telecentric characteristics>
As the imaging lens according to the second embodiment of the present invention, the imaging lens 5 shown in FIG. 1 has an image side telecentric characteristic.
In general, since the light beam that has passed through the front focal point of the convex lens travels in parallel after exiting the convex lens, the optical axis and the light beam are parallel on the image side. That the light beam is parallel to the optical axis is called telecentric, and that the light beam and the optical axis are parallel on the image side is called image-side telecentric.
In this way, by arranging the imaging lens 5 having the image side telecentric characteristic in the front stage of the pinhole array 11, all the principal rays of the respective light beams that have passed through the pinhole array 11 shown in FIG. Parallel to the optical axis.
Therefore, each pinhole 11a of the pinhole array 11 shown in FIG. 2 and each lens surface 13a of the lens array 13 corresponding to the pinhole array 11 may be arranged on a parallel plane orthogonal to the optical axis. Thus, since the imaging lens 5 has the image side telecentric characteristic, the spectral imaging module 7 can be configured with lenses having various magnifications and angles of view.

<Third Embodiment>
<Equal magnification erecting element>
As a lens array according to the third embodiment of the present invention, the lens array 13 shown in FIG. 2 is replaced with an equal-magnification erecting imaging element using a GRIN lens array.
As a specific product, there is a SELFOC (registered trademark) lens array manufactured by Nippon Sheet Glass. By using the GRIN lens array as the light condensing means, the positioning accuracy of the lens array 13 and the pinhole array 11 can be greatly relaxed.
Further, when a GRIN lens array is used as the light condensing means, each of the pinhole arrays 11 is caused by the optical characteristics of the GRIN lens array even if the image side telecentric characteristics of the imaging lens 5 employed in the second embodiment are not sufficient. Since the influence of the chief ray inclination of each light beam passing through the pinhole 11a is canceled out, the spectral imaging module 7 is configured with lenses of various magnifications and angles of view as in the second embodiment. Is possible.

<Fourth embodiment>
<Stair-like diffraction element>
With reference to FIG. 7, a stepped diffraction element according to a fourth embodiment of the present invention will be described. FIG. 7 is a schematic diagram for explaining a stepped diffraction element according to a fourth embodiment of the present invention.
A feature of the fourth embodiment resides in that a step-like diffraction element 150A is arranged on the optical axis after the lens array 13.
The stepped diffraction element 150A is a kind of blazed diffraction grating, in which all the blaze surfaces are orthogonal to the optical axis, and a predetermined step is formed at a predetermined pitch on the surface opposite to the incident surface. is there. This is considered to be a combination of a blazed diffraction grating and a prism.

The stepped diffraction element 150A can emit the first-order diffracted light _BL having a predetermined wavelength parallel to the optical axis of the incident light L by appropriately selecting the grating pitch and the step. In FIG. 5, A _L indicates the 0th-order diffracted light, and C _L indicates the second-order diffracted light.
As described above, by arranging the step-like diffractive element 150A on the optical axis going from the lens array 13 to the subsequent stage, the first-order diffracted light _BL becomes parallel to the optical axis, so that the adjustment of the optical system becomes easy. The spectral imaging module 7 can be configured.

<Fifth Embodiment>
<Configuration of image evaluation apparatus>
With reference to FIG. 8, the structure of the image evaluation apparatus which concerns on 5th Embodiment of this invention is demonstrated. FIG. 8 is a diagram showing a configuration of an image evaluation apparatus according to the fifth embodiment of the present invention.
The image evaluation device 30 includes the light source 3, the control unit 9, the spectral characteristic acquisition device 10 described in any one of the first to third embodiments, and the transport unit 20.
A feature of the image evaluation apparatus 30 according to the fifth embodiment is that the conveyance unit 20 is provided.
For example, in accordance with a command from the control unit 9, while the transport unit 20 transports the device under test 1 at a constant speed, the spectroscopic characteristics of the device under test 1 are continuously measured at a constant period in the spectroscopic property acquisition apparatus 10. By acquiring, the spectral characteristics of the entire surface of the DUT 1 can be obtained.
Based on the acquired spectral characteristics of the entire surface of the device under test 1, the image evaluation apparatus 30, for example, the spectral reflectance distribution of the device under test 1, tristimulus values XYZ, and color measurement results such as L * a * b *. Calculate and output the value. The image evaluation apparatus 30 enables high-precision measurement on the entire surface of the DUT 1 in a short time.

For this reason, even when there are many evaluation objects on the surface of the DUT 1 such as a color chart, it is possible to perform high-precision measurement in a shorter time compared to the conventional method.
By using the measurement result acquired by the image evaluation device 30, it is possible to make a pass / fail determination for the device under test 1 by comparing it with a separately prepared reference value and for the manufacturing process of the device under test 1. Can be urged to adjust.
In the present embodiment, the conveyance unit 20 is configured to move the DUT 1 with respect to the spectral characteristic acquisition device 10, but the conveyance unit 20 moves the spectral characteristic acquisition device 10 with respect to the DUT 1. Therefore, the spectral characteristics of the entire surface of the DUT 1 can be acquired in a short time.

<Sixth Embodiment>
<Image forming apparatus>
With reference to FIG. 9, a configuration of an image forming apparatus according to the sixth embodiment of the present invention will be described. FIG. 9 is a diagram showing a configuration of an image forming apparatus according to the sixth embodiment of the present invention.
A feature of the sixth embodiment is that the image evaluation apparatus 30 is built in the image forming apparatus 100.
The image forming apparatus 100 shown in FIG. 9 includes an image evaluation apparatus 30, paper feed cassettes 101a and 101b, paper feed rollers 102, a controller 103, a scanning optical system 104, a photoconductor 105, an intermediate transfer body 106, a fixing roller 107, paper discharge. A roller 108. The image forming apparatus 100 is, for example, an electrophotographic full-color image forming apparatus. In addition, the image forming apparatus 100 is a full-color image forming apparatus equipped with an electrophotographic inkjet.
In the image forming apparatus 100, the object 200 conveyed by the guide and paper feed roller 102 from the paper feed cassettes 101a and 101b is exposed to the photoconductor 105 by the scanning optical system 104, and a color material is applied and developed. The developed image is transferred onto the intermediate transfer member 106 and then from the intermediate transfer member 106 onto the object 200.

The image transferred onto the object 200 is fixed by the fixing roller 107, and the object 200 on which the image is formed is discharged by the paper discharge roller 108. The image evaluation device 30 is installed at the subsequent stage of the fixing roller 107.
As described above, according to the sixth embodiment, an object 200 after image formation (an image after printing) is measured in-line, and an image forming apparatus that enables adjustment of a printing process based on the measurement is realized. Can do. That is, by installing the image evaluation apparatus 30 including the spectral characteristic acquisition apparatus 10 at a predetermined position of the image forming apparatus 100, it is possible to acquire the spectral characteristics at an arbitrary position of the printed image.
Further, based on the acquired spectral characteristics, it is possible to calculate the colorimetric results such as tristimulus values XYZ and CIELAB. Therefore, the printing process is monitored using a colorimetric result from an arbitrary image, and if it deviates from the assumed color, the operator is notified, printing is interrupted, or changes in the printing process are offset. Thus, the printing process can be adjusted as described above, and more accurate color images can be stably produced.

<Configuration, operation and effect of exemplary embodiment of the present invention>
<First aspect>
The spectral characteristic acquisition apparatus 10 according to this aspect includes an imaging device 17 (imaging means) having a plurality of pixels arranged in a matrix in the vertical direction and the horizontal direction, and uses the imaging device 17 to measure on the DUT 1. A spectral characteristic acquisition apparatus 10 that measures the spectral characteristics of the device under test 1 by capturing a diffraction image of the region 1a, and a plurality of pinholes 11a that allow the light beam reflected by the device under test 1 to pass therethrough. The pinhole array 11 arranged in the horizontal direction, the lens array 13 (light condensing means) for condensing the light beams that have passed through the pinholes 11a toward the image pickup surface 17s of the image pickup device 17, and the lens array 13 And a diffraction element 15 (diffractive means) for forming a plurality of diffraction images obtained by diffracting each light beam in the vertical direction on the imaging surface 17s.
According to this aspect, the pinhole array 11 allows the light beam reflected by the DUT 1 to pass through the plurality of pinholes 11a arranged in the horizontal direction. The lens array 13 condenses the light beams that have passed through the pinholes 11 a toward the image pickup surface 17 s of the image pickup device 17. The diffraction element 15 forms a plurality of diffraction images obtained by diffracting the light beams that have passed through the lens array 13 in the vertical direction on the imaging surface 17 s.
As a result, a plurality of diffraction images diffracted in the vertical direction are formed on the imaging surface 17 s, and by imaging the diffraction image related to the measurement region 1 a on the DUT 1 using the imaging device 17, the DUT 1 can be measured.
A spectral characteristic relating to the measurement region 1a on the DUT 1 can be obtained using a configuration that is relatively simpler than that of the prior art, and a high-speed and high-precision spectral imaging module can be provided in a compact and inexpensive manner. it can.

<Second aspect>
The interval between the pinholes 11a of this aspect is at least equal to or longer than the length of each diffraction image 17i in the vertical direction.
According to this aspect, since the interval between the pinholes 11a is at least the longitudinal length of each diffraction image 17i, a plurality of diffraction images 17i can be independently formed on the imaging surface 17s. .

<Third aspect>
The lens array 13 (light condensing means) of this aspect constitutes an erecting equal-magnification imaging system using a lens array in which a plurality of gradient index lenses are arranged in the horizontal direction.
According to this aspect, the lens array 13 (condensing means) constitutes an erecting equal-magnification imaging system by a lens array in which a plurality of gradient index lenses are arranged in the horizontal direction, so that a pinhole can be formed at the time of manufacturing the optical system. Since adjustment of the biaxial direction orthogonal to the optical axis of the array 11 and the lens array 13 is almost unnecessary, manufacture at a lower cost is possible.

<4th aspect>
The spectral characteristic acquisition device 10 according to this aspect is arranged in front of the pinhole array 11 and forms an image of each measurement region 1a of the device under test 1 on each pinhole 11a (imaging means). ).
According to this aspect, the spectral characteristic acquisition device 10 is disposed in the front stage of the pinhole array 11, and the imaging lens 5 that forms an image related to each measurement region 1a of the DUT 1 on each pinhole 11a. By providing, the spectral imaging module can be manufactured in a compact and inexpensive manner.

<5th aspect>
The imaging lens 5 (imaging means) of this aspect has an image side telecentric characteristic.
According to this aspect, the imaging lens 5 has image-side telecentric characteristics, so that a plurality of optical axes corresponding to the pinholes 11a of the pinhole array 11 at the rear stage of the imaging lens 5 are parallel. Therefore, the optical system after the pinhole array 11 can be shared by one design. As a result, the optical system downstream of the pinhole array 11 can be shared with a plurality of reduction imaging lenses having different measurement pitches on the DUT 1, and thus the spectral imaging module can be manufactured in a compact and inexpensive manner. Can do.

<Sixth aspect>
The diffraction element 15 (diffractive means) of this aspect is a step-like diffraction element that forms a first-order diffraction image on the optical axis of the lens array 13 (condensing means).
According to this aspect, the diffractive element 15 is a step-like diffractive element that forms a first-order diffraction image on the optical axis of the lens array 13, so that, for example, the first-order diffracted light can be parallel to the optical axis, As a result, the position adjustment at the time of manufacturing the optical system is simplified, and the optical system can be manufactured at a lower cost.

<Seventh aspect>
In the spectral characteristic acquisition apparatus 10 of this aspect, the image sensor 17 (imaging means) includes a horizontal shift register 17b.
Vertical shift registers 17a1 to 17an (vertical transfer means) for shifting the charge accumulated in each pixel by one pixel in the vertical direction;
A horizontal shift register 17b (horizontal transfer means) for inputting charges accumulated in the lowermost pixel to the horizontal shift register 17b and shifting the inputted charges by one pixel in the horizontal direction;
And a control unit 9 that controls the vertical shift registers 17a1 to 17an and the horizontal shift register 17b to be alternately repeated.
According to this aspect, the image sensor 17 includes the horizontal shift register 17b, and the vertical shift registers 17a1 to 17an shift the charge accumulated in each pixel by one pixel in the vertical direction. The horizontal shift register 17b inputs the charge accumulated in the lowermost pixel to the horizontal shift register 17b, and shifts the input charge by one pixel in the horizontal direction. The control unit 9 controls the vertical shift registers 17a1 to 17an and the horizontal shift register 17b to repeat alternately.
As a result, the charges related to the plurality of diffraction images in the vertical direction formed on the imaging surface 17 s can be converted into the horizontal direction and output, and the spectral characteristics related to the DUT 1 can be measured.

<Eighth aspect>
The image evaluation apparatus 30 according to this aspect includes a spectral characteristic acquisition apparatus 10 according to any one of the first aspect to the sixth aspect, and a conveyance unit 20 that moves the DUT 1 relative to the spectral characteristic acquisition apparatus 10 ( Moving means) and a control unit 9 (second control means) for controlling to acquire the spectral characteristics of the entire surface of the DUT 1.
According to this aspect, the transport unit 20 moves the DUT 1 with respect to the spectral characteristic acquisition device 10. The control unit 9 performs control so as to acquire the spectral characteristics of the entire surface of the DUT 1.
Thereby, the spectral characteristics of the entire surface of the DUT 1 can be acquired in a short time.

<Ninth aspect>
The image evaluation apparatus 30 according to the present aspect includes the spectral characteristic acquisition apparatus 10 according to any one of the first aspect to the sixth aspect, and a conveyance unit 20 that moves the spectral characteristic acquisition apparatus 10 relative to the DUT 1 ( Moving means) and a control unit 9 (second control means) for controlling to acquire the spectral characteristics of the entire surface of the DUT 1.
According to this aspect, the conveyance unit 20 moves the spectral characteristic acquisition device 10 with respect to the DUT 1. The control unit 9 performs control so as to acquire the spectral characteristics of the entire surface of the DUT 1.
Thereby, the spectral characteristics of the entire surface of the DUT 1 can be acquired in a short time.

<10th aspect>
An image forming apparatus 100 according to this aspect includes the image evaluation apparatus 30 according to the nineteenth aspect.
According to this aspect, since the image forming apparatus 100 includes the image evaluation apparatus 30, it is possible to acquire spectral characteristics of the entire surface of the recording medium related to the image formed by the image forming apparatus, for example, accurate color information. The color variation between the mediums and the deviation from the predetermined color can be evaluated in the printing process, and the image forming apparatus 100 is adjusted based on the evaluation information, so that the predetermined value can be more stably determined. Can be formed.

DESCRIPTION OF SYMBOLS 1 ... Object to be measured, 1a ... Measurement area, 5 ... Imaging lens, 9 ... Control part, 10 ... Spectral characteristic acquisition apparatus, 11 ... Pinhole array, 11a ... Pinhole, 13 ... Lens array, 15 ... Diffraction element, DESCRIPTION OF SYMBOLS 17 ... Image pick-up element, 17a ... Vertical shift register, 17b ... Horizontal shift register, 17i ... Diffraction image, 17s ... Imaging surface, 20 ... Conveyance part, 30 ... Image evaluation apparatus, 100 ... Image forming apparatus

WO / 02/050783 JP 2014-238385 A JP 2014-153078 A

Claims (10)

An imaging means having a plurality of pixels arranged in a matrix in the vertical direction and the horizontal direction is provided, and a diffraction image relating to a measurement region on the measurement object is picked up by using the imaging means. A spectral characteristic acquisition device for measuring such spectral characteristics,
A pinhole array in which a plurality of pinholes that allow light beams reflected by the object to be measured to pass therethrough are arranged in the lateral direction;
Condensing means for condensing the light beams that have passed through the pinholes toward the imaging surface of the imaging means;
A spectral characteristic acquisition apparatus comprising: a diffractive unit that forms, on the imaging surface, a plurality of diffraction images obtained by diffracting the light beams that have passed through the condensing unit in the vertical direction.   The spectral characteristic acquisition apparatus according to claim 1, wherein the interval between the pinholes is at least equal to or longer than the length in the vertical direction of each diffraction image.   2. The spectral characteristic acquisition apparatus according to claim 1, wherein the condensing unit constitutes an erecting equal-magnification imaging system using a lens array in which a plurality of gradient index lenses are arranged in the lateral direction.   2. The spectral characteristic according to claim 1, further comprising an image forming unit that is arranged in front of the pinhole array and forms an image of each measurement region of the object to be measured on each pinhole. Acquisition device.   The spectral characteristic acquisition apparatus according to claim 4, wherein the imaging unit has an image side telecentric characteristic.   6. The spectral characteristic acquisition apparatus according to claim 1, wherein the diffraction unit is a stepped diffraction element that forms a first-order diffraction image on an optical axis of the light collecting unit. The imaging means includes a horizontal shift register,
Vertical transfer means for shifting the charge accumulated in each pixel by one pixel in the vertical direction;
Horizontal transfer means for inputting charges accumulated in the lowermost pixel to the horizontal shift register and shifting the inputted charges by one pixel in the lateral direction;
The spectral characteristic acquisition apparatus according to claim 1, further comprising a control unit configured to control the vertical transfer unit and the horizontal transfer unit to alternately repeat. The spectral characteristic acquisition device according to any one of claims 1 to 7,
Moving means for moving the object to be measured with respect to the spectral characteristic acquisition device;
An image evaluation apparatus comprising: a second control unit that performs control so as to acquire spectral characteristics of the entire surface of the object to be measured. The spectral characteristic acquisition device according to any one of claims 1 to 7,
Moving means for moving the spectral characteristic acquisition device with respect to the object to be measured;
An image evaluation apparatus comprising: a second control unit that performs control so as to acquire spectral characteristics of the entire surface of the object to be measured.   An image forming apparatus comprising the image evaluation apparatus according to claim 9.

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