JP2841406B2 - Color image inspection method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a color image inspection method for inspecting, in particular, the quality of a color image among the qualities of an image reproduced by, for example, a copying machine, a printer or a printing machine. In particular, the present invention relates to a color image inspection method and apparatus capable of determining a color shift amount as one of the color reproducibility inspection items.

[Related Art] In an office, various information devices output image information such as characters and images. A typical example is a copying machine for copying a document. Copiers form an electrostatic latent image on a photosensitive drum, read image information using an image sensor such as a CCD, and develop using a developing device, or use a recording head such as a thermal head. The image is being reproduced on paper.

When designing such an information device or shipping such an information device from a factory, an inspection of a reproduced image is performed. Such an inspection is roughly classified into the following two types.

(1) Inspection of whether or not the information device normally operates according to a predetermined procedure and reproduces an image.

(2) Inspection of whether the quality of the reproduced image is within an acceptable range in the market or within a range of specifications determined at the time of designing the device.

For example, in the case of a copying machine, the inspection items include the position of the image on the copied paper, the density of the image on the document, and the resolution. The inspector conducts the inspection by using a scale, a magnifying lens, or a measuring machine, or visually, and confirms that the respective processes of the copying machine are operating normally, and that the reading of the image and the transfer position of the toner image are correct. Whether or not is determined.

In the case of a copying machine, the latter inspection is also performed by the inspector. That is, the degree of the image is determined by the inspector directly comparing the image transferred to the sheet with the sample.

Since the conventional inspection as described above is mainly performed by the inspector, there are the following problems.

(1) The measurement value or test result changed when the examiner was different.

(2) Even in the same examiner, the measurement value or the test result changed due to the familiarity of the test or due to the psychological effect of the test object tested before.

(3) Measured values or test results also changed due to physical and mental fatigue of the examiner.

In order to avoid such a drawback, an image inspection apparatus for automatically performing an inspection has been proposed (JP-A-59-10345).
And JP-A-59-10346).

In this image inspection apparatus, a table for positioning and mounting an inspection object having an image is prepared. An object to be inspected is set on this table, and the detection unit is arranged to face the object. Then, the detection data output from the detection unit is supplied to the data processing unit, and the position, density, and resolution of the image are digitized based on the detection data.

However, in the proposed image inspection apparatus, since the detection unit sequentially detects several predetermined patterns, only a standardized inspection can be performed. For example, it is assumed that only a density inspection is required for a certain information device to be inspected, and a resolution inspection is required at many places on the inspection target for other information devices. In the proposed image inspection apparatus, a uniform inspection is performed for all the inspected objects, so that the former information equipment is subjected to useless inspection, and the inspection time is wasted. Also, with the latter information equipment, there is a possibility that the inspection location may be insufficient.

Of course, the latter inspection can be satisfied if a program is incorporated so as to perform many inspections at many places on the inspection object. However, such an image inspection apparatus requires a simple inspection. There has been a problem that more inefficient inspection is performed on the inspection object.

As described above, the general image inspection has been described. However, recently, color copying or color recording has been generalized, and it is necessary to inspect the image for these.
When the inspected object is a color image, the reproduction is performed by mixing some colors other than the predetermined color.

That is, generally xerographic copying machines (electrostatic copying machines)
When a color image is reproduced in an apparatus such as a thermal transfer type recording apparatus or the like, an image is formed using three color materials of cyan, magenta, and yellow, or four color materials obtained by adding black (black) thereto. Will do it.

FIG. 27 illustrates this principle. The photosensitive drum 301 is subjected to slit exposure in the direction indicated by an arrow 302 after image information on a document (not shown) is selectively absorbed by a filter (not shown). Photoconductor drum 3
Although not shown, a charge corotron (charging device) is arranged around 01, and an electrostatic latent image is formed by this exposure operation. The formed electrostatic latent image is developed by the developing device 303 to form a toner image. This toner image is transferred onto a recording paper 305 wound around a transfer drum 304 arranged close to the photosensitive drum 301. For this purpose, a transfer device 306 is used.

In the case of performing color printing, the above-described filters are sequentially set to desired ones, the color material is selected to correspond to the filters, and the toner image is transferred onto the recording paper 305 one by one.

When color reproduction is performed by sequentially overlapping color materials as described above, the amount of color misregistration as one factor that affects color reproducibility becomes a problem. That is, if a color misregistration occurs in the process of reproducing colors for each color, the quality of the image is remarkably deteriorated, especially in a line image or a character portion.

For example, blue characters are reproduced by subtractive mixing of magenta and cyan colors. If the positions of these two colors are shifted during the printing process, the characters are blurred and very difficult to read. Further, in the case of a picture image, there is a problem that the effect of the positional deviation appears in the picture itself to be reproduced, and accurate color reproduction cannot be performed.

Therefore, conventionally, the amount of color misregistration has been measured for an image reproduced. Conventionally, such a color shift amount is measured by a method in which a color image to be inspected is magnified and projected using a microscope, and an inspector directly reads the color shift. As described above, there is a problem that the inspection error is easily generated when the inspector himself inspects the image visually.

Therefore, in order to solve the above problem, the above-described proposed image inspection apparatus detects the density of three primary colors in addition to the detection of black and white density, thereby performing a unique inspection of a color image such as a color shift. It is considered. However, simply 3
When the color misregistration is measured by detecting the density of each color, the influence of unnecessary absorption of the used color material appears, and the recording position of each color material cannot be obtained accurately.

For example, the yellow color material actually used includes a small amount of magenta and cyan in addition to yellow. Therefore, when trying to detect the color separation density of blue to inspect the yellow color, two colors, magenta and cyan, which are simultaneously contained in the color material, have absorption in the blue region, and magenta and cyan colors are absorbed. Is also detected at the same time. As a result, only the yellow portion cannot be ideally separated from other colors.
Thus, simply expanding the proposed image inspection apparatus for three colors cannot completely separate the images of cyan, magenta, and yellow, and as a relative error of the recording position of each color material. Inspection of the "color shift amount" is incomplete.

Therefore, the present applicant has solved the above problems, and can freely set the inspection content according to the inspection object.
In addition, an automatic color image inspection apparatus capable of accurately inspecting the amount of color misregistration has already been proposed (JP-A-63-1936).
No. 73).

The automatic color image inspection apparatus includes an inspection object holding unit that holds an inspection object having an image formed of a plurality of inspection patterns, and a supply unit that supplies the inspection object to the inspection object holding unit. Means, inspection pattern selection means for selecting a pattern to be inspected from the inspection object held by the inspection object holding means, and reading of an image to change the optical density of the portion to an achromatic color Alternatively, an optical density measuring unit that detects the density of a predetermined chromatic color, a moving unit that moves the optical density measuring unit to an image reading position, and a color in a color image using data obtained from the optical density measuring unit. And a color shift amount detecting means for obtaining the shift amount.

In this apparatus, as shown in FIG. 28, the maximum value max (d1, d2, d
3) is detected and a color image inspection can be automatically performed.

[Problems to be Solved by the Invention] However, the above-described conventional technology has the following problems. That is, in the case of the color image automatic inspection apparatus, the maximum value of the color shift amount of the image is detected by the color shift amount detecting means, and the color image is inspected based on the maximum value of the color shift amount. ing. However, the present inventors have studied the correlation between the amount of color misregistration measured as described above and the feeling of color misregistration received when an actual color image is visually observed. It was found that there was a difference between the color misregistration and the color misregistration.

In other words, it has been found that even when the maximum value of the color shift amount is the same, the effect on human vision differs greatly depending on the shift amount between the two colors of cyan, magenta, yellow, and black. For example, as shown in FIG. 29A, if magenta, yellow, and black overlap each other and only cyan is displaced from these colors by a distance equal to the maximum displacement d0, The deviation is most noticeable.
In comparison, as shown in FIG. 29B, the maximum amount of color misregistration
Even if d0 is the same, the magenta color and the yellow color overlap and deviate from black, and if the cyan color deviates from these magenta and yellow colors by about 3/4 of the maximum deviation d0, the color deviation Will be of a noticeable standard. Further, as shown in FIG. 29C, if the maximum amount of color shift d0 is the same and the magenta and yellow colors overlap with black and are shifted by about 1/2 of the maximum amount of shift d0, the color shift is Is the least noticeable.

Therefore, if only the maximum value of the color shift amount of the color image is detected, there is a problem that the color shift amount corresponding to human vision cannot be detected.

[Means for Solving the Problems] Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a color shift amount that more accurately corresponds to human vision. An object of the present invention is to provide a color image inspection method and apparatus capable of inspection.

That is, the color image inspection method according to the present invention reads a specific inspection pattern on an inspection object, detects the optical density of the inspection pattern as an achromatic color and a density of a predetermined chromatic color, and then performs the achromatic optical inspection. Based on the peak position of the density and the peak position of the predetermined chromatic optical density, the maximum deviation amount between the colors that are the farthest out of the achromatic color and the predetermined chromatic color, and the deviation amount between the two colors The maximum value is obtained, and the color shift in the color image is inspected based on the maximum shift amount and the maximum value of the shift amounts between the two colors.

Further, the color image inspection apparatus according to the present invention reads a specific inspection pattern on the inspection object, and detects an optical density of the inspection pattern as an achromatic color and a predetermined chromatic color density, The peak position of the achromatic optical density and the peak position of the predetermined chromatic optical density detected by the optical density detecting means are obtained, and the maximum deviation between the colors which are the farthest away from the achromatic color and the predetermined chromatic color is determined. And a color shift amount detecting means for detecting a maximum value of the shift amount between the two colors, and a maximum value of the maximum shift amount detected by the color shift amount detecting means and the maximum shift amount between the two colors. Inspection of color misregistration in a color image is performed based on the values.

 As the achromatic color, for example, black is used.

Further, as the predetermined chromatic color, cyan, magenta, and yellow are used, for example, but are not limited thereto, and it goes without saying that other chromatic colors may be used. Also, the number of chromatic colors is not limited to three.

Further, as the shift amount between the two colors, for example, how much other colors such as cyan, magenta, and yellow are shifted with reference to black is considered, but is not limited thereto. It goes without saying that a shift amount between any two colors may be used.

[Operation] According to the color image inspection apparatus of the present invention, as described in the configuration of the color image inspection method, the specific inspection pattern on the inspection object is read, and the optical density of the inspection pattern is set to achromatic. And after detecting as the density of the predetermined chromatic color, based on the peak value of the achromatic optical density and the peak position of the predetermined chromatic optical density, the distance between the achromatic color and the predetermined chromatic color is the longest. The maximum deviation between the colors and the maximum value of the deviation between the two colors are obtained, and the color deviation in the color image is inspected based on the maximum deviation and the maximum value of the deviation between the two colors. ing.

As described above, in the color image inspection method and apparatus according to the present invention, of the achromatic color and the predetermined chromatic color, the largest deviation amount between the colors that are the farthest apart from each other and the largest deviation amount between the two colors. The color shift in the color image is inspected based on the maximum shift amount and the maximum value of the shift amount between the two colors. Therefore, the maximum value of the color shift amount is simply obtained and the maximum color shift amount is determined. Compared to the case of inspecting color misregistration in a color image based on the amount of misalignment, the maximum value of the amount of misalignment between two colors that has a large effect on human eyes is also detected, and the color misregistration in the color image is inspected including this. Therefore, it is possible to automatically perform an inspection for color misregistration in a color image closer to human vision.

[Embodiments] The present invention will be described below based on the illustrated embodiments.

FIG. 1 shows the appearance of a color image inspection apparatus according to an embodiment of the present invention. This color image inspection apparatus includes an inspection unit 1, a computer unit 2, and a printer unit 3.

The inspection unit 1 is a unit that continuously inspects the copy paper 4 as an inspection target. The inspection unit 1 includes a supply tray 5 and a discharge tray 6. When inspecting the copying machine, a desired chart is set in the copying machine, and the copy paper 4 obtained by this is stacked on the supply tray 5 as shown. The copy paper 4 is fed one by one to a cylindrical chart holding unit 8 by a feed roller 7. The surface of the chart holding unit 8 is covered with an insulating film, and the copy sheet 4 is electrostatically attracted to the surface by a charging operation by an electrostatic charge supply device (not shown). In this state, the image inspection of the copy sheet 4 as the inspection object is performed. The copy paper 4 that has been inspected is
It is peeled from the chart holding unit 8 by a peeling mechanism described later. The copy paper 5 after peeling is sequentially discharged to the discharge tray 6.

An operation display panel 9 is disposed in the inspection unit 1. The operation switch panel 9 has a power switch 11, a key 12 used for manually specifying a pattern to be inspected, and density data as a measurement result. An indicator 13 for displaying is arranged.

The computer unit 2 can be constituted by a commercially available computer, and specifies test items, processes data such as density data, and performs various displays. This part includes a keyboard 15 as input means, a CRT 16 as display means, and a disk drive device for driving a floppy disk.
17 etc., with a CPU for data processing inside
(Central processing unit) and the like.

The printer section 3 is a section for outputting inspection results and the like. In this embodiment, a dot printer is used.

FIG. 2 shows the outline of the inspection section of the color image inspection apparatus. A shaft 21 for rotating the feed roller 7 of the inspection unit 1 receives a driving force transmitted from a feed roller drive motor 23 via a chain 22. The supply tray 5 is provided with a force to move upward by excitation of a solenoid (not shown), and the uppermost surface of the copy sheet 4 as the inspection object comes into contact with the feed roller 7 at the time of excitation. When the feed roller 7 rotates by a predetermined amount in this state, only one copy sheet 4 of the uppermost layer is sent out. Prior to this feeding, the surface of the chart holding unit 8 is uniformly charged by a charging mechanism (not shown). The fed copy sheet 4 is electrostatically attracted to the chart holding unit 8 as a result. The rotation of the cylindrical chart holder 8 in the cylindrical direction (Y-axis direction) is performed by a chart holder drive motor 26 connected to a speed reducer 25.
Is performed by the driving force.

In this embodiment, the outer diameter of the chart holding section 8 is set to a diameter of 162.
77 mm, and the step angle of the chart holder drive motor 26
1.8 degrees, and the reduction ratio of the reducer 25 was set to 1/256. As a result, the chart holding unit driving motor 26 is driven one step, so that the surface of the chart holding unit 8 is moved in the Y-axis direction by 10 steps.
It will move by μm. The control of the rotational position of the chart holding unit 8, that is, the position control in the Y-axis direction, is performed using a point at which the photosensor 28 detects the notch 27 provided at the end of the cylinder as a reference point.

A ball screw 32 rotated by an X-axis stepping motor 31 is arranged above the chart holder 8 so that its axis is parallel to the rotation axis of the cylindrical chart holder 8. The optical head mounting block 33 has a Y-axis direction moving hole 34 screwed with the ball screw 32. Therefore, when the X-axis stepping motor 31 rotates,
It is guided by two guide bars 35 and 36 arranged in parallel with the ball screw 32 and moves in the X-axis direction.

In this embodiment, the pitch of the ball screw 32 is 5 mm. Set the step angle of the stepping motor 31 in the X-axis direction to 0.
With the configuration of 27 degrees, the optical head mounting block 33 moves in the X-axis direction by 10 μm by one-step driving. Two limit switches 37 and 38 are arranged in the X-axis direction to limit the moving range of the optical head mounting block 33.

The optical head mounting block 33 has a density detecting unit 41 described below mounted thereon. The density detecting section 41 is also provided with an enlarged eyepiece 42 so that the position of an image captured by the objective lens 43 during focus adjustment and particularly during manual operation can be confirmed.

In the color image inspection apparatus of this embodiment, the density detector 41 is moved at a pitch of 10 μm in both the X-axis direction and the Y-axis direction. However, a finer pitch may be set. . In this case, for example, the pitch of the ball screw 32 in the X-axis direction and the reduction ratio in the Y-axis direction may be further reduced.

FIG. 3 shows the optical structure of the optical head.

The concentration detector 41 includes a tungsten lamp 51 for illumination. Light emitted from the tungsten lamp 51 is condensed by the illumination lens 52, and the measurement site 53 of the chart holding unit 8 is illuminated. The reflected light from the measurement site 53 is collected by the objective lens 43 and split in two directions by a prism 54 having a semi-transmissive mirror (beam splitter).

One light after the branch is reflected by the mirror 55 and passes through the measurement visual field adjusting mechanism 56. Here, the measurement visual field adjustment mechanism 56 has an aperture plate 59 and a field lens 61 arranged in the optical path.

The opening plate 59 is a plate having a rectangular opening as shown in FIG. In this 50 μm × 2500 μm opening area,
The image of the measurement site on the copy paper is magnified five times and formed. Then, on the chart, that is, in this embodiment, the short side on the copy paper 4 is 10 μm and the long side is 50 μm.
The light beam reflected from the rectangular region of 0 μm (FIG. 4) is incident on the photomultiplier tube 58 through this opening. The opening plate 59 is an opening plate rotating step motor 62
Thus, the direction of the opening can be set to an arbitrary angle in units of one degree.

The light that has passed through the measurement field adjustment mechanism 56 is subjected to a color correction filter.
After the infrared wavelength component is cut by 57, the light reaches the filter unit 66. Filter unit 66 is cylindrical
Around 67, seven types of color filters 68-1 to 68-7 and one type of light-blocking filter 69 are arranged one by one at 45 ° intervals. The rotary solenoid 70 transmits a driving force to the cylinder 67 via a gear, a ratchet, and a stopper (not shown), rotates the cylinder at an angle of 45 degrees as one step, and sets the filter unit 66 at a predetermined position. In this state, light that has passed through any of the color filters 68-1 to 68-7 is incident on the photomultiplier tube 58, and the optical density is measured.

By the way, a light-blocking filter 69, which plays a role of completely blocking light from entering the photomultiplier tube 58, is a filter unit.
These are prepared for 66 initial settings. That is, the cylinder 67 rotates and the light shielding filter 69 is
At the time when the photomultiplier tube 57 is arranged to face the photomultiplier tube 58, no light beam enters the photomultiplier tube 58. This state is an initial position of the filter unit 66, and a desired color filter is set for selective absorption of light by a predetermined step operation. The signal level is also adjusted based on the output of the photomultiplier tube 58 in the initial state in which the light-blocking filter 69 is arranged to face the color correction filter 57.

Now, as the seven types of color filters 68-1 to 68-7,
The following filters are used.

Color filter 68-1: Red filter WRATTEN # 25 manufactured by Kodak Corporation Color filter 68-2: Green filter WRATTEN # 58 Color filter 68-3: Blue filter WRATTEN # 47 Color filter 68-4 manufactured by Kodak Corporation … B / W filter FUJIFILM Corporation SP 18 color filter 68-5… Red filter Toshiba Glass Co., Ltd. KL-63 color filter 68-6… Green filter Toshiba Glass Co., Ltd. KL-54 color filter 68-7… Green filter KL-44 manufactured by Toshiba Glass Co., Ltd. Here, the color filter 68-4 is a visual filter for changing the wavelength characteristic in order to match the output of the photomultiplier tube 58 with human visual perception. Therefore, the filter 68-4 is inserted before the photomultiplier tube 58 when measuring the optical density in black and white.

In this filter unit 66, two sets of color separation filters 68-1 to 68-3, 68-
5-68-7 are prepared. One of these filters 68
-1 to 68-3 are for a wide band, and the other filter 68-5
6868-7 are for narrow band. These may be used properly according to the inspection item, and depending on the device, only one set of a filter and a visual filter may be prepared.

The other light branched by the prism 54 is changed its traveling direction by the roof-shaped prism 64, and is
An erect image is formed on 65 to form an image. The image of the measurement site 53 formed in this way can be enlarged and observed by the magnifying eyepiece 42.

Circuit Configuration of Apparatus (Principle Configuration of Apparatus) Prior to specifically describing the apparatus, the principle configuration of the circuit will be described.

FIG. 5 shows an outline of a circuit configuration of the automatic color image inspection apparatus. This device includes external signal input means 72 for designating a desired inspection item.
The measurement control means 73 sets the position and type of the pattern to be inspected and the inspection processing procedure according to the inspection item indicated by the external signal input means 72. The pattern information storage means 74 stores the pattern to be inspected in the inspection object, and the processing procedure storage means 75 stores the inspection processing procedure for the pattern to be inspected. The measuring means 76
The surface of the object to be inspected is scanned under the control of the measurement control means 73 to detect the image density. In the processing procedure instructed by the arithmetic processing means 78 and the measurement control means 73, the data obtained from the measuring means 76 is arithmetically processed. The inspection result obtained by this is output by the output means 83. The output means 83 includes a first
Although the printer unit 3 shown in the figure is typical, the inspection result can be displayed on the CRT screen of the computer unit 2 as well.

The operation of the automatic color image inspection apparatus will be described in more detail. In the automatic color image inspection apparatus, the type of the inspection object and the inspection item are coded by the external signal input means 72 at the time of inspection. The chart code 84 for specifying the chart copied to the object to be inspected and the inspection item code 85 representing the inspection item are sent to the measurement control means 73. The measurement control means 73 sends the chart code 84 to the pattern information storage means 74. The pattern information storage means 74 outputs a representative point position 87 representing the pattern to be inspected included in the chart represented by the chart code 84. The pattern code 86 also contains information representing the color of each pattern. The pattern code 86 is sent to the processing procedure storage means 75 together with the inspection item code 85, and an image density detection format 88 corresponding to the inspection item and the pattern to be inspected and an arithmetic processing code 89 representing the arithmetic processing procedure are read by the measuring means 73. Will be infested.

At this stage, the type of the pattern to be inspected required for the inspection, the position information on the position of the pattern on the copy sheet, and the result corresponding to the image density detection method and the inspection item for the pattern are calculated. Information about the method will be set in the measurement control means 73 in a coded state.

Among these information, a representative point position 87 representing the coordinates of the position where the pattern exists and an image density detection format 88
Is sent to the measuring means 76. The measuring unit 76 moves to the representative point position 87 specified by the measurement control unit 73, and detects the image density to be measured according to the image density detection format 88. The detection result is output to the arithmetic processing means 78 as a density sequence 91. At the end of the density data sequence 91, an end signal 92 is added to instruct the start of arithmetic processing.

Upon receiving the end signal 92, the arithmetic processing means 78 selects a corresponding arithmetic processing routine based on the arithmetic processing code 89 previously supplied from the measurement control means 73. Then, the arithmetic processing routine is loaded into an internal arithmetic processing routine memory area. The arithmetic processing means 78 stores the above-described density data string 91 in a density data string memory area. The arithmetic processing means 78 processes the density data string 91 by the routine loaded in the arithmetic processing routine memory area, and supplies a result corresponding to the inspection item to the output means 83 as an inspection result. The output means 83 outputs this content.

The above-described image density detection and density data calculation processing are sequentially performed on all the patterns to be inspected set in the measurement control unit 73 in advance. The arithmetic processing means 73 performs arithmetic processing on each pattern, and also performs statistical processing of the arithmetic processing results corresponding to all the set patterns to be inspected. In this way, an inspection result for the inspection object is obtained.

(Configuration of External Signal Input Means) Next, the configuration of the external signal input means will be described with reference to FIG.

The external signal input means 72 includes a coding means 101. The chart name 102 and the inspection item 103 input by the operator are coded by the coding means 101. When receiving the coded information, the code type determining means 104 separates the coded information into a chart code and an inspection item code. Then, the chart and the
This is output as the code 84 and the inspection item code 85.

(Configuration of Pattern Information Storage Unit) FIG. 7 shows a configuration of the pattern information storage unit. The pattern information storage means 74 stores the chart code
84 is supplied to the pattern information storage position search means 107. The pattern information storage position search means 107 searches the position of the pattern to be inspected and sends it to the pattern information storage unit 108 as a pointer 109.

FIG. 8 shows the contents of the pattern information storage unit. The pattern information storage unit 108 stores, as data, the pattern codes as all the inspection targets in the corresponding chart and the representative point positions of the patterns represented by these pattern codes, using the chart code as a key. . In this figure, for example, for the chart code "XXX", three pattern codes a, a,
b is prepared. This is the chart code "XX
This means that two types of patterns specified by the pattern codes a and b are displayed on the chart specified by X ", and the coordinates of the three total patterns are as shown at the representative point positions. Note that the pattern codes a and b
Is coded taking into account the color represented by the pattern.

Here, the pattern represented by the pattern code a is, for example, a test item such as an optical density of one color and a reproducibility of a fine line. (Not shown) is used. In this test chart, this pattern is arranged in the upper left or lower right part. The pattern represented by the pattern code b is a pattern for density measurement in an electrophotographic society test chart. In this test chart, various density samples are displayed in a row below the test chart, thereby forming a pattern for density measurement. Thus, even in color inspection,
In many cases, test charts expressed in black and white are used, but if the reproducibility of mixed colors is listed as an inspection item, a chart represented by these mixed colors will be used. .

The pattern information unit 110 reads the contents stored in the pattern information storage unit 108 from the position indicated by the pointer 109 output from the pattern information storage position search unit 107. The read contents are all pattern codes related to one chart code indicated by the pointer 109 and their representative point positions. Pattern code 86,
The combinations of the representative point positions 87 are sequentially read out under the control of the measuring means 73 shown in FIG.
73 Sent inside.

(Configuration of Processing Procedure Recording Means) Next, the contents of the processing procedure storage means 75 are shown in FIG.

The inspection procedure code 85 and the pattern code 86 are supplied to the processing procedure recording means 75. The test item code 85 is detected by the test item code detection means 112, and the pattern code 86 is detected by the pattern detection means 113. The detection result of the inspection item code detection means 112 is used as a first pointer 114 as a processing code storage means 116.
And the detection result of the pattern detection means 113 is similarly output to the processing code storage means 116 as a second pointer 115.

FIG. 10 shows the contents of the processing code storage means. The processing code storage means 116 stores (1) an operation processing code, (2) a pattern code, and (3) an image density detection code for each inspection item code. An inspection item code for specifying an inspection item is designated by the first pointer 114 output from the inspection item code detecting means 112 described above. Then, the operation processing code in the inspection item code is selected by the second pointer 115 output from the pattern detection means 113. In the example shown in FIG. 10, for the pattern specified by the pattern code “a”, the image density detection specified by the image density detection code “a” and the arithmetic processing specified by the arithmetic processing code “A” are performed. You can see what happens. The code contents designated by the two pointers 114 and 115 are temporarily stored in a storage area in the processing code storage means 116.

Returning to FIG. 9, the description will be continued. Inspection means Grinding means 11
7 reads out the image density detection code 118 stored in the processing code storage means 116. In the example shown in FIG. 10, the image density detection code 118 is “A”. Based on this, a third pointer 119 as address information is obtained.
Is output to the inspection procedure storage means 121.

FIG. 11 shows the contents of the inspection procedure storage means. The inspection procedure storage unit 121 stores an image density detection format for each image density detection code. There are a plurality of image density detection formats, each of which is stored in a block unit. The contents of these block units are, for example, (1) measurement start position, (2) direction, (3)
The interval, (4) total number of points, (5) slit direction, and (6) filter set.

Here, (1) the measurement start position is indicated by a position as a representative point. As described above, the representative point is indicated by the reference coordinates for each pattern. On the other hand, the representative point is the difference between the coordinate value of the start position and the coordinate value of the representative point when scanning the pattern. (2) The direction is the direction of scanning, and there are two types, the X-axis direction and the Y-axis direction.
(3) The interval is a sampling interval for density detection, and (4) the total number of points is the total number of data to be sampled. (5) The slit direction refers to the direction of the opening of the opening plate 59 shown in FIG. In this embodiment, the opening is set to a position parallel to the X-axis at the time of initial setting or a position rotated by 90 degrees from this. The opening is set at a desired rotational position in steps of one at the time of measurement. With this angle setting, measurement of oblique lines and the like can be effectively performed.

Finally, (6) the filter set is a signal for selecting the light blocking filter 69 or the seven types of color filters 68-1 to 68-7 in the filter unit 66 shown in FIG.
According to this signal, one or more of the red, green, and blue color filters and the white / black filter are selected. When a plurality of filters are selected based on the signal for this filter set, the above-described (1) to (1) to
Each data of (5) is supplied to the measuring means 76 via the code output means 122 by the number of times. In response to this, the measuring unit 76 sets the filter unit 66 to a desired filter position, and repeats the operations determined in the above (1) to (5).

The third pointer 119 specifies an image density detection code. In the example shown in FIG. 11, the image density detection code "A" is selected. The first code output means 122 is a third code output means.
The image density detection format 88 selected by the pointer 119 is read out and supplied to the measuring means 76 under the control of the measuring control means 73 shown in FIG. On the other hand, the second code output means 123 reads the processing code 89,
Similarly, it is supplied to the arithmetic processing means 78 under the control of the measurement control means 73.

(Structure of the measuring means) FIG. 12 shows the contents of the measuring means.

The measuring means 76 can be roughly divided into three parts: an image density detecting unit, a detecting aperture control unit, and a moving unit. The measuring means 76 moves on the inspection object (the copy sheet 4 on which the chart is copied in this embodiment) based on the image density detection format 88 supplied from the measurement control The concentration is to be detected. That is, the image density detection format 88 (see FIG. 11) supplied from the measurement control means 73 is supplied to the data sampling control unit 131, and based on the decoded format 88, the image density detection unit, the detection aperture control unit , And the moving part is controlled.

By the way, the data sampling control unit 131 knows the current position of the light receiving unit 133 based on the data 133 obtained from the drive control unit 132. Therefore, the data sampling control unit 131 compares the light receiving unit 133 with the measurement start position obtained from the image density detection format 88.
Find the amount to move. Data on the obtained movement amount and the like is sent to the movement control unit 132.

The drive control unit 132 calculates the X-axis direction movement amount and the Y-axis direction movement amount based on the data 134, and determines the X-axis direction driving signal 135 and the Y-axis direction driving signal 136 of the pulse number corresponding thereto.
Is output. The X-axis direction drive signal 135 is supplied to the X-axis stepping motor 31, and the Y-axis direction drive signal 136 is supplied to the chart holding section drive motor 26 (also see FIG. 2), which is also a stepping motor.

As described above, the density detector 41 (FIG. 2) is moved in the X-axis direction by the X-axis stepping motor 31. Further, the chart holding unit 8 on the drum is rotated in the Y-axis direction by the driving of the chart holding unit drive motor 26, and the light receiving means 133 including the photomultiplier tube 58 and the like is moved to a desired measurement position.

Next, the data sampling control unit 131 decodes the image density detection direction, sampling interval, total number of sampling points, slit direction, and filter set. First, the opening direction is compared with the current opening direction, and an angle signal 138 indicating the result of comparison with the designated angle is output.
The angle signal 138 is supplied to an angle signal generator 139. The angle signal generator 139 is connected to the aperture plate rotating step motor 62 (third
A control signal 141 is supplied in response to the control signal 141 to rotate the aperture plate 61 by a desired angle.

Next, data sampling control section 131 compares the filter position indicated by the filter set with the currently set filter position, and outputs a filter switching signal 140 for setting the designated filter position. The filter switching signal 140 is supplied to a switching pulse generator 142.
The switching pulse generator 142 supplies a pulse signal 150 to the rotary solenoid 70 for driving filter switching,
A desired one of the filters 69, 68-1 to 68-7 in the filter unit 66 is inserted into the optical path.

When the setting of the light receiving means 133 is completed as described above,
The data sampling controller 131 sets the total number of points obtained from the image density detection format 88 in a counter (not shown) in the controller. Then, the image density detection direction and the sampling interval are output to the drive control unit 132 as data 134,
set.

The drive control unit 132 moves the density detection unit 41 or the chart holding unit 8 by a predetermined amount according to the specified detection direction.

Incidentally, the detection output 143 output from the light receiving means 133 is amplified by an amplifier 144 in the image density detection unit, and the output 145 is output.
Is logarithmically converted by the logarithmic converter 146, and the conversion output 147 is A / D
It is provided to converter 148. The A / D converter 148 has an A / D converter 148 for specifying an A / D conversion time.
The D signal 151 is supplied. The A / D signal generator 149 is an A / D signal supplied from the data sampling controller 131.
The A / D signal 151 is generated by the D start signal 152.
As the start signal 152, an output of a counter (not shown) in the data sampling control unit 131 is used.

That is, the counter is preset with a count value corresponding to the measurement start position.
The count value increases as the movement of 133 starts. Then, when the count value of the counter reaches the preset value, the A / D start signal 152 is output. When the A / D conversion ends, the A / D signal generation unit 149 outputs an end signal 153. When receiving the end signal 153, the data sampling control unit 131 manages the above-described counter and sends a light receiving unit 133 to the drive control unit 132.
The A / D start signal 152 is output at a predetermined timing when necessary.
In this way, it is possible to manage the sampling interval of the density data.

On the other hand, the A / D converter 148 outputs the conversion output 14
7 is converted from analog to digital. Converted density data 1
54 are sequentially stored in the image density buffer 155. The stored density data 154 is supplied to the arithmetic processing means 78 as a density data string 91, and arithmetic processing is performed.

When the sampling of the density data proceeds and the built-in counter counts a certain value as the final value, the data sampling control section 131 outputs an end signal 156 to the measurement control means 73. The measurement control means 73 outputs the end signal 156
Is received, the data for the next block is supplied to the data sampling control unit 131 as the image density format 88. In this way, concentration data is collected for each part to be measured.

(Configuration of arithmetic processing means) FIG. 13 shows a configuration of the arithmetic processing means. The arithmetic processing means 78 includes an arithmetic control unit 161. The arithmetic control unit 161 receives the arithmetic processing code 8 from the measurement control unit 73.
9 is supplied. The operation processing code 89 is a code representing an operation processing procedure. The arithmetic control unit 161 decodes the arithmetic processing code 89 and outputs the result to the arithmetic processing code 162.
Is supplied to the arithmetic processing address search means 162.

The arithmetic processing address search means 163 searches the arithmetic processing storage unit 164 using the arithmetic processing code 162. In the arithmetic processing storage unit 164, arithmetic processing data groups necessary for various inspections are stored. Arithmetic processing address search means 16
3 moves the pointer 165 to the start address of the corresponding memory area by searching, and then sends an end signal 1 to the arithmetic processing unit 161.
Send 66. After receiving the end signal 166, the arithmetic control unit 161
A start signal 167 is generated and supplied to the loader / starter 168.

When the loader / starter 168 receives the start signal 167, it generates load signals 169 and 171. And an arithmetic processing storage unit
A series of arithmetic processing contents indicated by the pointer 165 in 164
172 and the image density buffer 155 of the measuring means (see FIG. 12)
Example 91 of density data stored in the working area 17
Load 4 After the loading is completed, the loader / starter 168 supplies a start signal 175 to the working area 174, activates it and transfers control to the working area 174 itself.

At the same time, the working area 174 performs a desired operation on the density data sequence 91. The result is the result of the operation
176 is stored in the operation result output buffer 177. The output means 83 shown in FIG. 5 inputs the stored content as the inspection result 93 and visualizes it.

Details of Optical Density Measurement In one embodiment of the color image inspection method according to the present invention,
The color image inspection is automatically performed by the color image inspection apparatus configured as described above. In this color image inspection apparatus, first, the copy sheet 4 is held in the chart holding section 8, and after the positioning thereof, the density of each pattern is measured. Therefore, the positioning of the copy paper 4 will be described next, followed by the density measuring operation and the color shift amount measuring operation for each pattern.

(Positioning for Each Measurement Site) In order to measure an image from a copy sheet on which the chart is copied, the objective lens 43 of the optical head must correctly detect the target measurement site. by the way,
Assuming that the density detecting unit 41 is unilaterally set to a predetermined coordinate position, the desired position on the copy paper 4 is ± 5 m.
An error of about m occurs. This is due to the following reasons.

(1) Deviation that occurs when copying a chart with a copying machine.

This includes misalignment (registration misalignment) between the copy sheet 4 and the photosensitive drum of the copying machine, a setting error of the magnification, and a skew when the copy sheet 4 is conveyed inside the copying machine. (Rotation) is included.

(2) Misalignment when set on the chart holding unit 8.

This is the copy paper 4 sent from the supply tray 5.
Is a shift that occurs when the sheet is set in the chart holding unit 8, and corresponds to a setting error of the supply tray 5 or a positional alignment shift when the copy sheet 4 is sent out.

In this embodiment, the target position can be reached with an accuracy of ± 0.5 mm. Therefore, as shown in an example in FIG. 14, the chart 191 used in the automatic color image inspection apparatus has, for example, position detection patterns 192 to 194 arranged at three places. The coordinates of these position detection patterns 192 to 194 are grasped for each chart type on the automatic color inspection apparatus side. The coordinate values of these patterns 192 to 194 on the chart will be called actual coordinate values, and these will be referred to as (X ₁ , Y ₁ , X ₂ ,
Y ₂ , X ₃ , Y ₃ ).

In the device, these real coordinate values (X ₁ , Y ₁ , X ₂ , Y ₂ , X ₃ , Y ₃ )
Is used to scan the surroundings of the copy paper 4 and detect a change in the density of the image to detect the positions on the copy paper 4. The coordinate values of these position detection patterns 192 to 194 on the copy paper 4 are represented by (x ₁ , y ₁ , x ₂ , y ₂ , x ₃ ,
y ₃ ). By assembling the relational expressions of the two coordinate systems (X, Y) and (x, y), the actual position (X ₀ , Y ₀ ) corresponding to the coordinates of the measured pattern (x ₀ , y ₀ ) on the copy paper 4 ₀ ) is calculated, and the density detection section 41 is caused to reach the target image section using the coordinate values (X ₀ , Y ₀ ).

The position detection patterns need not be arranged at three places on the copy paper. For example, by arranging them at two places, the rotation and displacement of the copy paper 4 can be grasped. Further, by arranging more points, it is possible to grasp the elongation of each part of the copy paper 4 and the like, and it is possible to further improve the accuracy of reaching the measurement site.

(Scanning of Pattern) FIG. 15 shows a pattern for performing density measurement. In this pattern 221, point 223 is a representative point,
Point 224 is the detection start point in the X-axis direction. The detection start point 224 is represented as a coordinate value relative to the representative point 223. If the pattern 221 is also scanned in the Y-axis direction, a starting point different from the point 224 may be prepared for this purpose.

As described above, in the automatic color image inspection apparatus of this embodiment, the rectangular area of 10 μm × 500 μm on the copy paper is
This is the reading range. The reading mode is determined by the image density detection format shown in FIG. That is, in this example, the point 224 is the measurement start position, and the measurement direction is the X-axis direction. The measurement interval, that is, the sampling width, is determined depending on the purpose of the measurement and the like. In the automatic color image inspection apparatus of this embodiment, the opening is 10 μm × 500 μm.
Is a rectangular (rectangular) area of
The density detection area per time becomes 10 μm. Therefore, when scanning the copy paper 4 throughout the X-axis direction, the measurement interval is 10 μm.

FIG. 16 shows the state of scanning in this case. When the sampling width is set to be smaller than the luminous resolution in this way, data representing a fine image state substantially matching the luminous perception of a human can be obtained. This will be described later as an effect of the color image inspection apparatus of this embodiment.

of course. The measurement does not necessarily need to be performed at the same width as the short side of the rectangular area for detecting the optical density, and can be set freely in the image density detection format.
Therefore, it is possible to scan the image roughly depending on the inspection item.

When scanning in the Y-axis direction, the slit direction is usually set to the X-axis direction. Thus, in the case of this embodiment, sampling of an image with a width of 10 μm is possible. As described above, in this embodiment, the density detecting unit 41 is moved in the X-axis direction or the Y-axis direction in units of 10 μm by stepping the X-axis stepping motor 31 or the chart holding unit driving motor 26 one by one. be able to.

(Inspection of Color Shift Amount) Now, the pattern 221 as the inspection object shown in FIG.
Is a pattern in which the color materials of cyan C, magenta M, yellow Y, and black K are sequentially adjacently arranged on a straight line. At this time, an enlarged schematic view of the inspection object having the pattern in FIG. 17A is as shown in FIG. 17B as an example. The color shift amounts to be inspected in FIG. 17B are d0 to d3. That is, cyan color material 225, magenta color material 226,
Of the relative distances between the center positions of the respective lines of the yellow color material 227 and the black color material 228, not only the maximum deviation amount d0 of the colors that are the farthest apart from each other, but also each color material centered on black. The distance d1, d2, d3 between the two colors and the maximum value d of these distances
Also ask for _Wm . Even if the value of d0 is the same, the larger the value of _{dWm, the more} the appearance of the color shift becomes more worrisome. Therefore, by obtaining the value of _dWm , it is possible to more accurately evaluate the amount of color shift.

In the color image inspection method of this embodiment, in order to perform such an inspection of the amount of color misregistration, the color misregistration amount inspection is coded in the inspection item code AA shown in FIG. Coded as a. As a filter set in the image density detection format corresponding to the image density detection code "A" shown in FIG. 11, filters of four colors are coded. As a result, in the inspection of the amount of color misregistration, the image density detection operation is repeated four times in total for the color materials of cyan, magenta, yellow, and black while being sequentially switched to the designated four color filters. Become.

This will be described in detail with reference to the flowchart for the color shift amount inspection shown in FIG.

First, the measuring means 76 shown in FIGS. 5 and 12 sequentially scans the pattern 221 according to the image density detection format, and sequentially inspects the density data sequence for four colors (FIG.
18 steps). Then, the result is sent to the arithmetic processing means 78 via the image density buffer 155.

This is shown in FIG. 19a. In this FIG.
For the cyan, magenta, yellow, and black color materials of the image shown in the figure, cyan has a red separation density of 231, magenta has a green separation density of 232, yellow has a blue separation density of 233, and black has a luminous density of 10 μm pitch. 5 shows a scanned profile.

The arithmetic processing means 78 converts threshold values C _T , M _T , for binarizing each image signal from each of the cyan, magenta, yellow, and black profiles as shown in FIG.
Y _T and K _T are set, and the center positions C ^* , M ^* , Y ^* , and K ^* of the lines made of the respective color materials are set (step in FIG. 18).

First, the threshold level _{C T, M T, Y T} , K T is determined by the following equation (1).

TH _i = (DATA _MAXi −DATA _MINi ) × 0.5 + DATA _MINi (1) where i = 1, 2, 3, 4 and TH ₁ = C _T , TH ₂ =
M _T , TH ₃ = Y _T , TH ₄ = K _T.

This determined threshold level C _T , M _T , Y _T , K _T
And the intersection of the four color material density profiles corresponding to
From the arithmetic mean of the obtained intersections of the two points, the center positions C ^* and M of the respective color materials for each line as shown in FIG.
^* , Y ^* , K ^* are required.

Next, the arithmetic processing means 78 determines the center positions C ^* , M ^* ,
The following values are calculated using Y ^* and K ^* (step in FIG. 18).

d1 = | C ^* -K ^* | d2 = | M ^* -K ^* | d3 = | K ^* -Y ^* | d0 = | C ^* -Y ^* | Furthermore, based on the above d1, d2, d3, its maximum value _Find d _Wm (step in FIG. 18).

d _Wm = max (d1, d2, d3) In this way, the maximum deviation amount d0 and the maximum value d _Wm of the distance between two colors with respect to black are obtained. The output unit 83 visualizes these shift amounts as necessary.

Further, the arithmetic processing means 78 calculates the color shift evaluation amount H based on the maximum shift amount d0 and the maximum value _dWM . here,
H is given by the following equation, and is a value for evaluating how color misregistration of a color image affects human visual perception. The correlation value with the psychological amount of color shift received when seen by the eye is 1
, The color misregistration evaluation amount H more accurately corresponds to the impression of color misregistration when a color image is actually viewed by a human eye.

_{H = f (d0, d WM} ) = 8.54E -6 × d0 2 -9.72E -3 × d0 -3.36E -3 × d WM +6.0013 However, E ^-1 represents 10 ^-1.

 The output means 83 visualizes this value H.

As described above, when inspecting the color shift amount of the color image, the maximum shift amount between the colors that are the farthest apart from each other and the maximum value of the shift amount between the two colors with respect to black are obtained. Since the inspection of the color shift in the color image is performed based on the maximum value of the shift amount between the colors, it is possible to perform the inspection of the color shift suitable for the actual human visual field.

In order to confirm the effect of the present invention, the present inventors actually copied various patterns having different maximum deviation amounts and the maximum deviation amounts between the two colors on the copy paper 4, and 17 subjects who are experts who are familiar with color images to some extent have 5 points (I do not understand the color shift), 4 points (I do not care about the color shift) Scored in 5 points: 3 points (color shift is annoying but not intrusive), 2 points (color shift is an obstructive), 1 point (color shift is very annoying). The correlation between the color shift evaluation amount H = f (d0) when only the shift amount is considered, and the color when the maximum value of the shift amount between the two colors is also considered in addition to the scoring result and the maximum shift amount. An experiment was conducted to examine the correlation with the deviation evaluation amount H = f (d0, _dWM ).

Here, the following equation is used as the color shift evaluation amount H = f (d0) when only the maximum shift amount is considered.

H = f (d0) = 1.01E -5 × d0 2 -1.35E -3 × d0 + 5.45 however, E ^-1 is likewise represents 10 ^-1.

FIG. 26 shows the results of this experiment. The vertical axis of this figure is a value indicating the correlation between the color shift evaluation amount H and the color shift actually perceived by human eyes and visually.
The closer this value is to 1, the more accurately the color misregistration evaluation amount H and the color misregistration that a person actually sees and sees visually correspond.

As is clear from this figure, the maximum deviation
In the case where the color shift was evaluated only by d0, the correlation value was about 0.90, which was quite close to the color shift actually felt by human eyes and visually, but insufficient, whereas the present invention In this case, the value was as high as about 0.94, which was almost equal to the color shift actually perceived by human eyes and was visually satisfactory.

Note that the present inventors performed an experiment similar to the above, in consideration of the element CC indicating the color having the largest color shift amount in addition to the maximum shift amount d0 and the maximum value _dWM. Done.

The color shift evaluation amount H used in this case is given by the following equation.

_{H = f (d0, d WM} , CC) = 8.54E -6 × d0 2 -9.72E -3 × d0 -3.36E -3 × d WM -2.08E -1 × CC + 6.0013 However, E ^-1 10 ^{Represents -1} .

As described above, in addition to the maximum shift amount d0 and the maximum value _dWM , the color shift evaluation amount H that takes into account the color CC having the largest color shift amount, which is all of the possible elements, and the human eye actually sees the color shift evaluation amount H. The correlation value with the color shift felt by the eye is about 0.95,
Correlation value in consideration of the maximum displacement amount d0 and the maximum value d _WM described above, 0.94 is seen whether those going of how satisfactory.

Here, as the value of the color CC having the largest color shift amount, for example, in the case of a halftone image, green (G) is 5, cyan (C) is 4, magenta (M) is 2,
Black (K), which is a mixture of cyan, magenta and yellow, is 1.
5. Red (R) is set to 1, and in the case of a line or solid image, black (K), which is a mixture of cyan, magenta and yellow, is set to 1, and other colors are set to 2. I have.

By the way, in the color image inspection method of this embodiment, the region where the object to be inspected is scanned is set to a very small rectangle of 10 μm × 500 μm. Therefore, unlike a conventional apparatus for image inspection similar to that of the related art, it is possible to perform an inspection that is closer to human visual perception. This will be described in detail below.

First, FIG. 20 is an enlarged view of a part of the resolution inspection chart. Thus, in this chart,
The black line 201 with the interval and the ship width set in several stages is drawn in parallel, and the resolution of the copied image is inspected according to the white background color portion 202 of the background and the line width to which it can be identified. ing.

FIG. 21 is an enlarged view of a part of this chart, and FIG. 22 shows a sample of a copy image of a copying machine corresponding thereto. Here, FIG. 22 is an example in which relatively large unevenness occurs in the boundary region between the ground color portion 202 and the black line 202, and FIG. 22B is an example in which toner scatters at these boundary portions. FIG. 9C shows an example in which a blank area 203 where no toner is attached occurs inside the black line 201. In addition, various states such as a case where the density of the black line 021 does not change at once at the boundary portion but changes stepwise, and a case where shading occurs inside the black line 201 appear. Such a delicate state of an image is a relatively large factor in image quality evaluation.

By the way, FIG. 23 shows the signal level of the image signal read by the conventional apparatus when the contour of the black line has irregularities as shown in FIG. 22A, for example. The image signal 205 is a signal obtained by scanning the chart shown in FIG. 20 in the horizontal direction in the figure, and corresponds to, for example, FIG. 4 of JP-A-59-103465. The signal portion 205 'indicated by a broken line in this figure is an image signal obtained by scanning the protruding portion of the black line 201 in FIG. 22A, and has a thicker waveform than the other portions shown in practice. However, if the image signals 205 and 205 'are binarized at the threshold level indicated by the one-dot chain line 207 in the figure and the image is inspected, the evaluation as the resolution becomes completely the same. This is because in the conventional apparatus, the resolution is determined based on the location where the signal change occurs due to the binarization and the number of signal changes at that location.

FIG. 24 is an image signal obtained by the conventional apparatus for the image state shown in FIG. 22B, and FIG. 25 is an image signal obtained by the conventional apparatus for the image state shown in FIG. 22C. This is an example. In the example shown in FIG. 24, the level of the image signal 205 is high in the portion 208 where the scattered toner is scanned. However, since the scattered portion is a relatively small region, the signal level does not increase sufficiently at this portion, and
It is ignored during the process of value conversion. FIG. 25 shows the opposite case, where the signal level at the arrow 209 is reduced by the blank area 203 existing at the black line 201. However, also in this case, since the signal change in the minute portion is not sufficient, this change is ignored in the binarization process. According to such a conventional apparatus, there is a problem that the image is determined at a different level from the quality of the image perceived by human eyes.

However, in the color image inspection apparatus of this embodiment, the fourth
As shown in the figure, the inspection of the optical density of the inspection object is performed using the opening of 10 μm × 500 μm. Since the diameter of the toner particles after fixing is approximately 10 to 20 μm, it can be seen that this makes it possible to inspect the object to be inspected at a level substantially equal to the interval between humans.

Further, in the color image inspection apparatus of this embodiment, the inspection target is measured with the rectangular area as the minimum measurement range, so that the inspection target can be efficiently scanned without gaps. Of course, the rectangular area is not limited to a rectangle of 10 μm × 500 μm. For example, it may be a rectangle having a larger size, a square having the short sides having the same length, or a square having a larger size. In the case of a square, it is not necessary to incline (rotate) the opening in accordance with the scanning of a pattern formed of obliquely inclined line segments.

Of course, the shape of the opening used for measurement need not be a strict rectangle, but may be, for example, a rectangle close to a circle or an ellipse. However, in these cases, in order to scan the entire image, the images are partially read in an overlapping manner, so that a process for dealing with these overlapping portions is necessary.

Although the photomultiplier tube is used as the light receiving means in the embodiment, the same optical density measuring operation can be performed by using a photomultiplier using a semiconductor or a one-dimensional sensor such as a CCD. In the embodiment, the optical density is detected by the reflected light. However, for example, when the development state of the photographic film is inspected, the optical density may be detected by the transmitted light.

Further, in the embodiments, toner particles have been described as an example of units constituting an image to be inspected. In other non-impact type devices or impact type devices, the size and the rotation angle of the opening may be considered in consideration of the size and shape of the ink and the like used in these devices.

[Effects of the Invention] As described above, according to the color image inspection method according to the present invention, in addition to the maximum shift amount between the colors that are the farthest apart from each other, the color difference between two colors that greatly affects human vision. Since the maximum value of the shift amount is obtained, and the color shift in the color image is inspected based on the maximum shift amount and the maximum value of the shift amount between the two colors, the color shift amount inspection more accurately corresponds to human vision. Becomes possible.

According to the color image inspection apparatus of the present invention,
As described above, it is possible to provide an apparatus capable of automatically inspecting a color shift amount more accurately corresponding to human vision.

[Brief description of the drawings]

FIG. 1 is a perspective view of an automatic color image inspection apparatus, FIG. 2 is a schematic configuration diagram showing a main part of an inspection section, FIG. 3 is an explanatory view showing an arrangement of optical components of an optical head, and FIG. FIG. 5 is an explanatory view showing the size of an area serving as a unit of measurement on a sheet;
FIG. 6 is a block diagram schematically showing the circuit configuration of the automatic color image inspection apparatus, FIG. 6 is a block diagram showing the configuration of external signal input means, FIG. 7 is a block diagram showing the configuration of pattern information storage means, and FIG. Is an explanatory diagram showing a configuration of a pattern information storage unit, FIG. 9 is a block diagram showing a configuration of a processing procedure storage unit, FIG. 10 is an explanatory diagram showing a configuration of a processing code storage unit,
11 is an explanatory diagram showing the configuration of the inspection procedure storage means, FIG. 12 is a block diagram showing the configuration of the setting means, FIG. 13 is a block diagram showing the configuration of the arithmetic processing means, and FIG. 14 is a pattern for position detection. FIG. 15 is a plan view showing an example of a pattern for performing density measurement, and FIG.
FIG. 16 is an explanatory view showing an example of scanning in the X-axis direction.
FIGS. A and B are a plan view and an enlarged plan view showing a color shift state of a pattern portion shown in a circle in FIG. 15, FIG. 18 is a flowchart showing a color shift amount inspection process, and FIG. FIG. 9 is an explanatory diagram showing a process of processing an image signal obtained by reading the image portion shown in FIG.
Is a waveform diagram showing a profile of each color material of red separation density, green separation density, blue separation density, and luminous density, FIG. 20B is an explanatory diagram showing a center position of each color material, and FIG. FIG. 21 is a plan view in which a part of the chart is enlarged.
FIG. 20 is an enlarged plan view of a part of the chart shown in FIG.
22A to 22C are partially enlarged plan views showing various states of a sample of a copy image, FIG. 23 is a waveform diagram showing a signal level of an image signal obtained by reading the image portion shown in FIG. 22A, and FIG. Is the 22nd
FIG. 25 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. B. FIG. 25 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. 22C. Is a graph showing experimental results of this embodiment, FIG. 27 is a principle diagram showing a copying principle of a color xerographic copying machine, FIG. 28 is an explanatory diagram showing a state of detecting a color shift amount of a conventional apparatus, and FIG. A,
FIGS. 4B and 4C are explanatory diagrams respectively showing states in which the amounts of color misregistration are different. [Explanation of Symbols] 1 ... Inspection unit 2 ... Computer unit 4 ... Copy paper 5 ... Supply tray 8 ... Chart holding unit 41 ... Density detection unit 58 ... Photomultiplier tube 66 ... Filter unit 68 …… Color filter 76 …… Measurement means 78 …… Operation processing means 221 …… Pattern 231 …… Red separation density 232 …… Green separation density 233 …… Blue separation density 234 …… Cyan color material amount 235 …… Magenta color material Amount 236: Yellow color material amount C, M, Y: Center position of each color material amount d: Color shift amount

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hisae Goto 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/40- 1/409 H04N 1/46-1/62 G06T 7/00

Claims (2)

(57) [Claims] A specific inspection pattern on an object to be inspected is read, and the optical density of the inspection pattern is detected as a density of an achromatic color and a predetermined chromatic color. Based on the peak position of the chromatic optical density, of the achromatic color and the predetermined chromatic color, the maximum deviation between the colors that are the farthest apart and the maximum value among the deviations between the two colors are obtained, A color image inspection method for inspecting color misregistration in a color image based on the maximum deviation amount and the maximum value of the deviation amount between two colors. 2. An optical density detecting means for reading a specific inspection pattern on an object to be inspected and detecting an optical density of the inspection pattern as a density of an achromatic color and a predetermined chromatic color, and detecting the optical density by the optical density detecting means. The peak position of the obtained achromatic color optical density and the peak position of the predetermined chromatic color optical density are obtained, and the maximum deviation amount of the colors which are the farthest away from the achromatic color and the predetermined chromatic color is calculated. Color shift amount detecting means for detecting the maximum value of the shift amounts,
A color image inspection apparatus for inspecting a color image for color misregistration based on the maximum amount of misregistration detected by the color misregistration amount detection means and the maximum value of the misregistration amount between two colors.