JPH0648853B2 - Color image inspection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to an automatic color image inspection capable of inspecting especially the quality of a color image among the quality of an image reproduced by a facsimile machine, a printing machine or a copying machine. The present invention relates to an inspection device, and more particularly to a color image automatic inspection device capable of obtaining a trapping rate as one of inspection items of color reproducibility.

"Conventional technology" In the office, various information devices output image information such as characters and images. A typical example of this is a copying machine for copying a document. A copying machine forms an electrostatic latent image on a photosensitive drum, reads image information using an image pickup device such as a CCD, develops using a developing device, or uses a recording head such as a thermal head. The image is reproduced on paper.

When designing such information devices or shipping these information devices from the factory, inspection of reproduced images is performed. Such inspections are roughly classified into the following two types.

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

(Ii) Inspection of whether or not the quality of the reproduced image is acceptable in the market or within the specifications specified at the time of designing the device.

For example, in the case of a copying machine, the inspection item includes the position of the image on the copied sheet, the density of the image on the original, the resolution, and the like. The inspector makes full use of the scale, magnifying lens or measuring device, or visually inspects to make sure that the processes of the copier are operating normally, and there is no error in reading the image or transferring the toner image. Whether or not it 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 copied on the sheet with the sample.

Since the inspector is the main body of the above conventional inspection,
There were the following problems.

(I) When the inspector is different, the measured value or the inspection result changes.

(Ii) Even in the same inspector, the measurement value or the inspection result changed due to the familiarity of the inspection or the psychological influence of the previously inspected object.

(Iii) The measured values or test results also changed depending on the physical and mental fatigue of the inspector.

In order to avoid such a defect, an image inspection apparatus that automatically inspects has been proposed (Japanese Patent Laid-Open No. 59-1034).
5 and JP-A-59-10346).

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

However, in the proposed image inspection apparatus, the detection unit sequentially detects some predetermined patterns, so that only a standardized inspection can be performed. For example, it is assumed that only the density inspection is required for a certain information device to be inspected, and the resolution inspection is required for other information devices in many places of the inspection object. Since the proposed image apparatus performs a uniform inspection on all the inspection objects, the former information equipment is wastefully inspected and the inspection time is wasted. Moreover, in the latter information device, there is a possibility that the inspection location may be insufficient.

Of course, the latter inspection can be satisfied by incorporating a program that performs many inspections at many places on the inspection object, but such an image inspection apparatus requires a simple inspection. There is a problem that a more inefficient inspection is performed on the inspection object.

So far, general image inspection has been explained, but recently color copying or color recording has become popular,
There is also a need for image inspection of these. When the object to be inspected is a color image, an inspection item for checking the color reproducibility is necessary. Conventionally, color image inspection has also been performed visually. That is, the inspector compares the color of the object to be inspected with the color sample to determine whether the color reproducibility is acceptable.

However, the color characteristic in a color image has three elements of saturation, hue and lightness. Therefore, the inspector needs to visually compare each element when comparing with the color sample, which may cause excessive fatigue.
Therefore, the visual inspection of the color image has a problem that an inspection error is likely to occur.

Therefore, it is considered that the above-mentioned proposed image inspection apparatus detects the density of the three primary colors in addition to the detection of the black-and-white density, thereby checking the color reproducibility. According to such a color image automatic inspection apparatus, even if sufficient results are obtained for the inspection items for the black-and-white image or the image composed of a single color already described, the color generated by the superposition of a plurality of colors Is insufficient for the inspection of.

This point will be described in detail below.

Generally, when a color image is reproduced by a device such as a xerographic copying machine (electrostatic copying machine) or a thermal transfer recording device, it is made of three color materials of cyan, magenta, and yellow, or black (black). An image is formed by the four color materials to which is added.

FIG. 26 is for explaining this principle. Image information on a document (not shown) is selectively absorbed by the photoconductor drum 301 by a filter (not shown), and then slit exposure is performed in a direction indicated by an arrow 302. Although not shown, a charge corotron (charger) is arranged around the photoconductor drum 301, 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 recorded on a recording sheet 305 wound around a transfer drum 304 arranged close to the photoconductor drum 301.
Is transcribed to. For this purpose, the transfer unit 306 is used.

When performing color recording, the above filters are sequentially set to desired ones, a color material corresponding to this is selected, and toner images are transferred to the recording paper 305 one by one.

In the case of reproducing colors by sequentially superimposing color materials in this way, the trapping rate becomes a problem as one factor that influences the color reproducibility. Where trapping
Is a term mainly used in the field of printing, and refers to the influence when a layer of ink or toner (hereinafter simply referred to as a color material) printed earlier in multicolor printing receives a color material printed later. . For example, in the case of overlapping the color materials on the recording paper in the order of cyan, magenta, and yellow, in the recording of the magenta of the second color, the color material of the part where the cyan color material of the first color exists The amount of overlapping changes, which is called trapping.

Usually, a color that is important for reproduction in a color image is often formed by superimposing three colors like the color of human skin. Therefore, when trapping occurs, the desired color material amount is transferred in the single-color recording area, but the desired color material amount is transferred in the overlapping portion of the three colors to reproduce the desired color. Can't do it.

Therefore, it is necessary to define the trapping rate as one of the performances of the recording device and the like, and perform the inspection for each device. However, even if the density detection inspection items for the three primary colors are added during this inspection, there is the effect of unnecessary absorption components of the individual color materials actually used,
Accurate trapping rates cannot be measured due to the fact that well-known additive and proportional laws are not established.

Therefore, an object of the present invention is to provide an automatic color image inspection apparatus capable of freely setting inspection contents according to an object to be inspected and capable of accurately inspecting the trapping rate.

"Means for Solving Problems" In the present invention, (i) an inspection object holding means for holding an inspection object having an image composed of a plurality of inspection patterns, and (ii) this inspection object Supply means for supplying the object to be inspected to the object holding means; and (iii) pattern to be inspected selecting means for selecting a pattern to be inspected from the object to be inspected held by the object to be inspected holding means. , (Iv) optical density measuring means for reading the image and detecting the optical density of the portion as the density of an achromatic color or a predetermined chromatic color, and (v) moving the optical density measuring means to an image reading position. The color image automatic inspection apparatus is provided with a moving means and (vi) a trapping rate detecting means for obtaining a trapping rate in a color image using the data obtained from the optical density measuring means.

According to the present invention, since the trapping rate is determined by measuring the optical density of the required color material, it is possible to accurately grasp the trapping rate, and the inspection items can be freely set without changing the chart. Therefore, unnecessary inspection can be omitted.

[Examples] The present invention will be described in detail below with reference to Examples.

[Examples] The present invention will be described in detail below with reference to Examples.

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

Of these, the inspection unit 1 is a unit for continuously inspecting the copy paper 4 as the inspection object. The inspection unit 1 includes a supply tray 5 and a discharge tray 6. When the copier is inspected, a desired chart is set on the copier, and the copy paper 4 thus obtained is stacked on the supply tray 5 as shown. The copy papers 4 are fed one by one to the cylindrical chart holding unit 8 by the feed roller 7. The surface of the chart holding portion 8 is covered with an insulating film, and the copy sheet 4 is electrostatically adsorbed to this surface by a charging operation by an electrostatic charge supply device (not shown). In this state, the image inspection of the copy paper 4 as the inspection object is performed.

The copy paper 4 that has been inspected is peeled from the chart holding unit 8 by a peeling mechanism described later. The copy paper 4 after peeling is sequentially discharged to the discharge tray 6.

An operation display panel 9 is arranged in the inspection unit 1,
Here, a power switch 11, a moving key 12 used when manually specifying a pattern of an object to be inspected, and a display 13 for displaying density data as a measurement result are arranged.

The computer unit 2 can be configured by a commercially available computer, and performs specification of inspection items, processing of data such as concentration data, and various displays. This part includes a keyboard 15 as an input means, a CRT 16 as a display means,
A disk drive device 17 for driving a floppy disk is provided, and a CPU (central processing unit) for data processing is installed inside.

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

FIG. 2 shows the outline of the inspection unit of this automatic color image inspection apparatus. The shaft 21 that rotates the feed roller 7 of the inspection unit 1 receives the driving force from the feed roller drive motor 23 via the chain 22. The supply tray 5 is given a force to move upward by the excitation of a solenoid (not shown),
At the time of this excitation, the surface of the uppermost layer of the copy paper 4 as the inspection object comes into contact with the feed roller 21. When the feed roller 21 rotates by a predetermined amount in this state, only one copy sheet 4 of the uppermost layer is fed out. Prior to this feeding, the chart holding portion 8 has its surface uniformly charged by a charging mechanism (not shown). The copy paper 4 sent out is
As a result, it is electrostatically adsorbed on the chart holder 8. Circumferential direction of the cylindrical chart holder 8 (Y-axis direction)
Is rotated by the driving force of the chart holding unit drive motor 26 connected to the speed reducer 25.

In the present embodiment, the chart holder 8 has an outer diameter of 162.
77 mm, the step angle of the chart holding unit drive motor 26 is 1.8 degrees, and the speed reduction ratio of the speed reducer 25 is 1/256.
And As a result, when the chart holding unit drive motor 26 is driven by one step, the surface of the chart holding unit 8 moves by 10 μm in the Y-axis direction. The control of the rotational position of the chart holding unit 8, that is, the position control in the Y-axis direction is performed by using the point where the notch 27 provided at the end of the cylinder is detected by the photo sensor 28 as a reference point.

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

In this embodiment, the pitch of the ball screw 32 is 5 mm. The step angle of the X-axis stepping motor 31 is set to 0.
With the configuration of 72 degrees, the optical head mounting block 33 moves by 10 μm in the X-axis direction in one step of 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 is mounted with a density detecting section 41 described below. A magnifying eyepiece lens 42 is also attached to the density detecting unit 41, so that the position of the image captured by the objective lens 43 can be confirmed during focus adjustment and particularly during manual operation.

In the color image automatic 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, but it may be set at a finer pitch. 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 made finer.

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

The concentration detector 41 includes a tungsten lamp 51 for illumination. The 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 into two directions by a prism 54 equipped with a semitransparent mirror (beam splitter).

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

The opening plate 59 is a plate having a rectangular opening as shown in FIG. In the 50 μm × 2500 μm opening area, the image of the measurement site on the copy sheet is magnified 5 times and formed. Then, the light flux reflected from a rectangular area (FIG. 4) on the chart, that is, in this embodiment, on the copy paper 4 having a short side of 10 μm and a long side of 500 μm passes through this opening, and the photomultiplier tube 58 described above is used.
Will be incident on. The aperture plate 59 can be set to an arbitrary angle in units of 1 degree by the aperture plate rotation step motor 62.

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

By the way, the light blocking filter 69 which plays a role of completely blocking the incidence of light rays on the photomultiplier tube 58 is prepared for initial setting of the filter unit 66. That is, when the cylinder 67 rotates and the light blocking filter 69 is arranged so as to face the color correction filter 57, no light beam enters the photomultiplier tube 58. This state becomes the 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 shielding filter 69 is arranged so as to face the color correction filter 57.

By the way, as the seven kinds of color filters 68-1 to 68-7, the following filters are used.

Color filter 68-1 Red filter Kodak WRATTEN # 25 Color filter 68-2 Green filter Kodak WRATTEN # 58 Color filter 68-3 Blue filter Kodak WRATTEN # 47 Color filter 68-4 B / W filter SP 18 color filter 68-5 manufactured by Fuji Film Co., Ltd. Red filter KL-63 color filter 68-6 manufactured by Toshiba Glass Co., Ltd. Green filter KL-54 color filter 68-7 manufactured by Toshiba Glass Co., Ltd. Blue 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 the human visual sense. Therefore, the filter 68-4 is inserted in front of the photomultiplier tube 58 when the optical density is measured in black and white.

Further, in this filter unit 66, two sets of color separation filters 68-1 to 68-3 are provided for color separation of two colors, respectively.
68-5 to 68-7 are prepared. One of the filters 68-1 to 68-3 is for wide band, and the other filter 68-5 to 68-7 is for narrow band. These may be used properly depending on the inspection item, and depending on the apparatus, only one set of filters and visual filters may be prepared.

The other light split by the prism 54 has its traveling direction changed by the roof prism 64 and is formed as an erect image on the observation screen 65. The image of the measurement site 53 thus formed can be magnified and observed by the magnifying eyepiece lens 42.

Circuit Configuration of Device (Principle Configuration of Device) Prior to a specific description of the device, the principle configuration of the circuit will be described.

Next, FIG. 5 shows an outline of the circuit configuration of the color image automatic inspection apparatus. This apparatus is provided with an external signal input means 72 for instructing a desired inspection item.
The measurement control means 73 is adapted to set the position, type and inspection processing procedure of the pattern to be inspected according to the inspection item represented by the external signal input means 72. The pattern information storage means 74 stores the inspection pattern in the inspection object, and the processing procedure storage means 75 stores the inspection processing procedure for the inspection pattern. The measuring means 76 scans the surface to be inspected under the control of the measurement control means 73 and detects the image density. The arithmetic processing means 78 performs arithmetic processing on the data obtained from the measuring means 76 according to the processing procedure instructed by the measurement control means 73. The inspection result thus obtained is output by the output means 83.
The output unit 83 is typically the printer unit 3 shown in FIG. 1, but the inspection result can also be displayed on the CRT screen of the computer unit 2.

The operation of this color image automatic inspection apparatus will be described in more detail. In the color image automatic inspection apparatus, the type of the inspection object and the inspection item are coded by the external signal input means 72 during the 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 pattern code 86 representing a pattern to be inspected included in the chart represented by the chart code 84 and a representative point position 87 representing a representative position of the pattern to be inspected. The pattern code 86 is
It 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 the image density detection format 88 corresponding to the inspection item and the pattern to be inspected and the operation processing code 89 representing the operation processing procedure are sent to the measurement control means 73. Will be read.

At this stage, the kind of the pattern to be inspected necessary for the inspection, the position information of the position of the pattern on the copy paper, and the result corresponding to the image density detecting method and the inspection item for the pattern are arithmetically processed. Information about the method will be set in the measurement control means 73 in coded form.

Of these pieces of information, the representative point position 87 representing the coordinates of the position where the pattern exists and the image density detection format 8
8 is sent to the measuring means 76. The measuring means 76 moves to the representative point position 87 designated by the measurement control means 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 the density data string 91. An end signal 92 is added to the end of the density data sequence 91 to instruct the start of arithmetic processing.

When the arithmetic processing means 78 receives the end signal 92, the arithmetic processing code 89 supplied from the measurement control means 73 before that.
Based on, the arithmetic processing routine corresponding to this is selected. Then, this arithmetic processing routine is loaded into the internal arithmetic processing routine memory area. The above-mentioned density data string 91 is stored in the density data string memory area of the arithmetic processing means 78. The arithmetic processing means 78 processes the density data sequence 91 by the routine loaded in the arithmetic processing routine memory area, and supplies the result according to the inspection item as the inspection result 93 to the output means 83. The output means 83 will output this content.

The image density detection and the density data calculation processing operation described above are sequentially performed on all the inspection patterns preset in the measurement control unit 73. The arithmetic processing means 78 performs arithmetic processing on individual patterns and also statistical processing of arithmetic processing results corresponding to all the set inspection patterns. In this way, the inspection result of the inspection object is obtained.

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

The external signal input means 72 comprises a coding means 101. The chart name 102 and the inspection item 103 input by the operator are coded by the coding means 101. Upon receiving the coded information, the code type discrimination means 104 separates the coded information into a chart code and an inspection item code. Then, it is output as the chart code 84 and the inspection item code 85 via the code control unit 105.

(Structure of Pattern Information Storage Means) FIG. 7 shows the structure of the pattern information storage means. The pattern information storage means 74 supplies the chart code 84 to the pattern information storage position searching means 107. The pattern information storage position searching 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 section. The pattern information storage unit 108 stores, as data, all the pattern codes to be inspected in the corresponding chart using the chart code as a key and the representative point positions of the patterns represented by these pattern codes. . In this figure, for example, for the chart code "XXX", three pattern codes a,
a and b are prepared. This means that two types of patterns specified by the pattern codes a and b are displayed in the chart specified by this chart code "XXX", and the coordinates of a total of three patterns are representative. It is as shown in the dot position. The pattern codes a and b are coded in consideration of the color represented by the pattern.

Here, the pattern represented by the pattern code a is, for example, for the inspection items such as the optical density of one color and the reproducibility of the fine line, for the resolution measurement in the Electrophotographic Society test chart “NO.1-R 1975”. A pattern (not shown) is used. In this test chart, this pattern is arranged in the upper left and lower right parts.
Further, the pattern represented by the pattern code b is a pattern for density measurement in this Electrophotographic Society test chart. In this test chart, various concentration samples are displayed in a row below the test chart to form a concentration measurement pattern. In this way, even in color inspection, a test chart expressed in black and white is often used, but when the reproducibility of mixed colors itself is listed as an inspection item, it is expressed by these mixed colors. You will use the chart that was created.

The pattern information output means 110 is the pattern information storage unit 1.
The contents stored in 08 are read from the position indicated by the pointer 109 output by the pattern information storage position searching means 107. The read content is the pointer 109
All pattern codes for one chart code indicated by and their representative point positions. The combination of the pattern code 86 and the representative point position 87 corresponding thereto is sequentially read out by the control of the measurement control means 73 shown in FIG.

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

The inspection item code 85 and the pattern code 86 are supplied to the processing procedure storage means 75. Of these, the inspection item code 85 is the inspection item code detecting means 11
2 and the pattern code 86 is detected by the pattern detecting means 113. The detection result of the inspection item code detection means 112 is output to the processing code storage means 115 as the first pointer 114, and the detection result of the pattern detection means 113 is also output to the processing code storage means 116 as the second pointer 115.

FIG. 10 shows the contents of the processing code storage means. The processing code storage means 116 stores (i) calculation processing code, (ii) pattern code, and (iii) image density detection code for each inspection item code.
The inspection item code for specifying the inspection item is designated by the first pointer 114 output from the inspection item code detecting means 112. Then, the arithmetic processing code in the inspection item code is selected by the second pointer 115 output from the pattern detecting means 113.
In the example shown in FIG. 10, for the pattern specified by the pattern code "a", the image density detection code "a"
It can be seen that the image density detection specified by and the calculation processing specified by the calculation processing code "A" are performed. The code contents designated by the two pointers 114 and 115 are
It is temporarily stored in the storage area in the processing code storage means 116.

Returning to FIG. 9, the explanation will be continued. Detection procedure search means 11
7 reads out the image density detection code 118 stored in the processing code storage means 116. In the example of FIG. 10 described above, the image density detection code 118 is “A”. Then, based on this, the third pointer 119 as address information is output to the inspection procedure storage means 121.

FIG. 11 shows the contents of the inspection procedure storage means. The inspection procedure storage means 121 stores an image density detection format for each image density detection code. There are a plurality of sets of image density detection formats, each of which is stored in block units. The contents of these block units are, for example, (i) measurement start position, (ii) direction, (ii
i) interval, (iv) total number of points, (v) slit direction, (vi)
It is a filter set.

Here, (i) the measurement start position is shown as a position as a pair representative point. The representative point is indicated by the reference coordinates for each pattern, as described above, whereas the representative point is the difference between the coordinate value of the start position and the representative point coordinate value when the pattern is scanned. The (ii) direction is the scanning direction, and there are two types, the X-axis direction and the Y-axis direction. (Ii
i) Interval is the sampling interval for density detection, and (iv) Total score is the total number of sampled data. (V) The slit direction means the direction of the opening of the opening plate 59 shown in FIG. In this embodiment, the opening is set at a position parallel to the X axis or rotated by 90 degrees from the initial setting. In addition, this opening is set at a desired rotational position in steps of once during measurement. By setting this angle, it is possible to effectively measure diagonal lines and the like.

Finally, (vi) filter set means the light blocking filter 69 or 7 in the filter unit 66 shown in FIG.
This is a signal for selecting the type of color filters 68-1 to 68-7. This signal will select one or more of the red, green and blue color filters and the white / black filter. When a plurality of filters are selected by the signal for this filter set, the respective data of (i) to (v) described above are supplied to the measuring means 76 via the code output means 122 in the predetermined order. To be done. The measuring means 76 accordingly sets the filter unit 66 at a desired filter position and repeats the operations determined in the above (i) to (v).

The third pointer 119 identifies the 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 reads the image density detection format 88 selected by the third pointer 119 and supplies it to the measuring means 76 under the control of the measurement control means 73 shown in FIG. On the other hand, the second code output means 123 reads out the arithmetic processing code 89 from the processing code storage means 116 and similarly supplies it to the arithmetic processing means 78 under the control of the measurement control means 73.

(Structure of Measuring Means) Next, FIG. 12 shows the contents of the measuring means.

The measuring means 76 is roughly classified into (i) image density detecting section, (ii) detection aperture control section, and (iii) moving section.
It can be divided into two parts. The measuring means 76 moves on the object to be inspected (copy paper 4 on which the chart is copied in this embodiment) based on the image density detection format 88 supplied from the measurement control means 73, and the image is formed in a predetermined format. The concentration will be detected. That is, the image density detection format 88 (see FIG. 11) supplied from the measurement control unit 73 is supplied to the data sampling control unit 131, and based on the format 88 decoded here, the image density detection unit and the detection aperture control unit. , And the moving part will be controlled.

By the way, the data sampling control unit 131 uses the data 133 obtained from the drive control unit 132 to detect the light receiving unit 1.
Knowing 33 currently existing locations. Therefore, the data sampling control unit 131 obtains the amount of movement of the light receiving unit 133 by comparison with the measurement start position obtained from the image density detection format 88. The data 134 regarding the obtained movement amount and the like is sent to the drive control unit 132.

The drive control unit 132 obtains the X-axis direction movement amount and the Y-axis direction movement amount based on the data 134, and outputs the X-axis direction drive signal 135 and the Y-axis direction drive signal 136 having the corresponding pulse numbers. 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 unit drive motor 26 (also see FIG. 2) which is also a stepping motor.

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

The data sampling control unit 131 then detects the image density detection direction, the sampling interval, the total number of sampling points,
Decode slit direction and filter set. Then, first, the opening direction is compared with the current opening direction, and the angle signal 138 representing the comparison result with the instructed angle is output. The angle signal 138 is supplied to the angle signal generator 139. The angle signal generator 139 supplies the control signal 141 to the aperture plate rotation step motor 62 (see FIG. 3) to rotate the aperture plate 61 by a desired angle.

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

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

By the way, the detection output 14 output from the light receiving means 133
3 is amplified by an amplifier 144 in the image density detecting section, and its output 145 is logarithmically converted by a logarithmic converter 146. The converted output 147 is supplied to the A / D converter 148. A / D
The converter 148 is supplied with an A / D signal 151 from the A / D signal generator 149 for designating the time at which A / D conversion is performed. A / D signal generator 149
Is A / supplied from the data sampling control unit 131
Although the A / D signal 151 is generated by the D start signal 152, the output of a counter (not shown) in the data sampling control unit 131 is used as the A / D start signal 152.

That is, the count value corresponding to the measurement start position is preset in this counter.
The count value increases with the start of movement of 33. When the count value of the counter reaches the preset value, A / D
The start signal 152 will be output. When the A / D conversion is completed, the A / D signal generator 149 outputs the end signal 153.
Is output. Upon receiving the end signal 153, the data sampling control unit 131 manages the above-mentioned counter to instruct the drive control unit 132 to move the light receiving unit 133, and when necessary, starts the next A / D at a predetermined timing. The signal 152 will be output. In this way
It is possible to manage the sampling interval of concentration data.

On the other hand, when A / D conversion is instructed by the A / D signal 151, the A / D converter 148 converts the converted output 147 from analog to digital. The converted density data 154 is
It is sequentially stored in the image density buffer 155. The stored density data 154 is supplied to the arithmetic processing means 78 as the density data string 91, and the arithmetic processing is performed.

When the sampling of the density data progresses and the built-in counter counts a certain value as the final value, the data sampling control unit 131 outputs the end signal 156 to the measurement control unit 73. Upon receiving the end signal 156, the measurement controller 73 supplies the data for the next block to the data sampling controller 131 as the image density detection format 88. In this way, the concentration data is collected for each part to be measured.

(Structure of Arithmetic Processing Unit) FIG. 13 shows the structure of the arithmetic processing unit. The arithmetic processing means 78 includes an arithmetic control unit 161. The arithmetic processing section 89 is supplied with the arithmetic processing code 89 from the measurement control means 73. The arithmetic processing code 89 is
It is a code representing a calculation processing procedure. Arithmetic control unit 16
1 decodes the arithmetic processing code 89 and supplies the result as the arithmetic processing code 162 to the arithmetic processing address searching means 163.

The arithmetic processing address searching unit 163 searches the arithmetic processing storage unit 164 using the arithmetic processing code 162.
The arithmetic processing storage unit 164 stores arithmetic processing code groups required for various inspections. The arithmetic processing address search means 163 moves the pointer 165 to the start address of the corresponding memory area by the search, and then the arithmetic control unit 1
The end signal 166 is sent to 61. After receiving the end signal 166, the arithmetic control unit 161 generates a start signal 167,
Supply to the loader / starter 168.

When the loader / starter 168 receives the activation signal 167, it generates load signals 169 and 171. Then, (i) a series of arithmetic processing contents 172 indicated by the pointer 165 in the arithmetic processing storage unit 164, and (ii) working the density data string 91 stored in the image density buffer 155 (see FIG. 12) of the measuring means. Load in area 174. 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.

Along with this, the working area 174 has a concentration data string 91.
Then, the desired arithmetic processing is executed for. The result is stored in the operation result output buffer 177 as the operation result 176. The output means 83 shown in FIG. 5 inputs this stored content as an inspection result 93 and visualizes it.

Details of Optical Density Measurement In this color image automatic inspection apparatus, first, the copy paper 4 is held in the chart holding unit 8 and after positioning the copy paper 4,
Density measurement is performed for each pattern. Therefore, next, the positioning with respect to the copy sheet 4 will be described, and subsequently, the density measuring operation and the trapping rate measuring operation for each pattern will be described.

(Positioning with respect to each measurement site) In order to measure an image from a copy paper on which a chart is copied, the objective lens 43 of the optical head must correctly grasp the target measurement site. By the way, if the density detection unit 41 side is unilaterally set to a predetermined coordinate position, the desired position on the copy sheet 4 is ± 5.
An error of about mm occurs. This is due to the following reasons.

(I) Misalignment that occurs when copying a chart with a copying machine.

This includes not only the alignment error (registration deviation) between the copy paper 4 and the photosensitive drum of the copying machine, the setting error of the magnification, but also when the copy paper 4 is conveyed inside the copying machine. The error due to the occurrence of skew (rotation) is included.

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

This is a deviation that occurs when the copy paper 4 delivered from the supply tray 5 is set in the chart holding unit 8, and an error in the setting of the supply tray 5 or a positional alignment deviation when the copy paper 4 is delivered is applicable. To do.

In this embodiment, the target position can be reached with an accuracy of ± 0.5 mm. For this reason, as shown in FIG. 14 by way of example, in the chart 191 used in the color image automatic inspection apparatus, for example, the position detection patterns 19 are provided at the three positions.
2-194 were placed. These position detection patterns 1
The coordinates 92 to 194 are known for each chart type on the color image automatic inspection device side. The coordinate values of these patterns 192 to 194 on the chart will be referred to as actual coordinate values, and these will be expressed as (X ₁ , Y ₁ , X ₂ , Y ₂ , X ₃ , Y).
₃ ).

The device uses these real coordinate values (X ₁ , Y ₁ , X ₂ , Y ₂ , X
₃ , Y ₃ ) is used to scan the copy paper 4 around it, and the position on these copy papers 4 is detected by detecting the density change of the image. The coordinate values of these position detection patterns 192 to 194 on the copy paper 4 are defined as (x ₁ , y ₁ , x ₂ , y ₂ , x ₃ , y ₃ ). By assembling the relational expressions of both coordinate systems (X, Y) and (x, y), the actual position (X ₀ , Y) corresponding to the coordinate (x ₀ , y ₀ ) of the measured pattern on the copy paper 4 is obtained. ₀ )
Is calculated, and the density detection unit 41 is caused to reach the target image portion using this coordinate value (X ₀ , Y ₀ ).

The position detection pattern does not need to be arranged at three places on the copy sheet, and by arranging the position detection pattern at two places, the copy sheet 4
It is possible to grasp the rotation and displacement of the. Further, by arranging more points, it is possible to grasp the elongation of each portion of the copy sheet 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 certain pattern for density measurement. In this pattern 221, the point 223 is the representative point and the point 224 is the detection start point in the X-axis direction. The detection start point 224 is represented as a relative coordinate value with respect to the representative point 223. When the pattern 221 is also scanned in the Y-axis direction, a detection start point different from the point 224 may be prepared for this purpose.

As described above, in the color image automatic inspection apparatus of this embodiment, the rectangular area of 10 μm × 500 μm on the copy paper is set as the reading range for one reading. The reading mode is the 11th
It is defined by the image density detection format shown in the figure. 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 by the purpose of measurement and the like. In the color image automatic inspection apparatus of this embodiment, the opening is 10 μm × 50.
Since the area is a rectangular area having a size of 0 μm, one density detection area in the X-axis direction is 10 μm. Therefore, when scanning the copy sheet 4 in the X-axis direction, the measurement interval is 10 μm.

FIG. 16 shows the scanning situation in this case. By setting the sampling width smaller than the visual resolution in this way, it is possible to extract data representing a fine image state that substantially matches the human visual perception. This will be described later as an effect of the color image automatic inspection apparatus of the present embodiment.

Of course, the measurement does not necessarily need to be sampled with the same width as the short side of the rectangular area for detecting the optical density, and can be freely set in the image density detection format. Therefore, the image can be roughly scanned depending on the inspection item.

When scanning in the Y-axis direction, the slit direction is normally set to the X-axis direction. As a result, in the case of this embodiment, it is possible to sample an image with a width of 10 μm.
As described above, in this embodiment, the X-axis stepping motor 31 or the chart holding unit drive motor 26 is stepped up one by one, so that the density detection unit 41 is moved.
Can be moved in units of 10 μm in the X-axis direction or the Y-axis direction.

(Inspection of Trapping Rate) Now, the pattern 22 as the inspection object shown in FIG.
As shown in FIG. 17, 1 is a cyan single color 225, a magenta single color 226, a yellow single color 227, and these three.
It is assumed that it is composed of a black color 228 that is created by sequentially superposing various types of color materials. At this time, the following three types of inspection results for the trapping rate are required.

In the automatic color image inspection apparatus of the present embodiment, the inspection of the trapping rate is coded into the inspection item code AA shown in FIG. 10, and the above-mentioned pattern 221 similar to that shown in FIG. 15 is designated as a in the pattern code. Coded.
Also, as the filter set in the image density detection format corresponding to the image density detection code "a" shown in FIG. 11, three color filters are coded. Therefore, for the patch portions of the respective colors 225 to 228, the image density detection operation by the same operation is repeated a total of three times by sequentially switching the filters as shown by the solid line and the broken line in FIG.

This will be described in detail with reference to the flow chart for the trapping rate inspection shown in FIG.

First, the measuring means 76 shown in FIG. 5 and FIG. 12 forms the first pattern 228 according to the image density detection format.
Sequential scanning is performed in the direction shown in FIG. 7, and the density data sequence is sequentially scanned for three colors (step). Then, the result is processed by the arithmetic processing means 78 via the image density buffer 155.
Send to. The scanning at this time is roughly performed on the patch portions of the respective colors 225 to 228. Specifically, 10 mm x
Inspection area of 10 mm is 100 μm in the X-axis direction
Pitch, and in 2 mm steps in the Y-axis direction. As a result, 500 density data strings are obtained for the patch portions of the respective colors 225 to 228.

Next, the arithmetic processing means 78 performs averaging processing on the densities of the three colors obtained for the patch portions of the respective colors 225 to 228. Thereafter, using the averaged density data obtained in each patch portion of the cyan single color 225, the magenta single color 226, and the yellow single color 227, the masking matrix generation as shown in the following equation is performed. (First
(Fig. 8 step).

Here, for example, the reference D _CR represents the red separated average density in the patch portion of the cyan single color 225, and the reference D _MG represents the green separated average density in the magenta single color 226. The same applies to other symbols.

The equation (1) is a pre-procedure for calculating the trapping rate, and is performed in order to correct the unnecessary absorption effect of the color material described as the problem of the conventional technique.

Next, the arithmetic processing means 78 uses the averaged density data of the three colors in the black 228 portion, and the respective color material amounts C _REL , M _REL of cyan, magenta, and yellow in the portion where the colors are superimposed, Y _REL is calculated (step in FIG. 18).

According to this equation (2), cyan, magenta, and yellow in the patch portion of black 228 obtained by superimposing three colors when the color material amount of each patch portion of each of the colors 225 to 227 is set to "1". Each content of is required.

However, by the processing of this step, it is impossible to avoid the failure of the well-known additive rule and proportional law, which have been pointed out as a problem of the prior art. Therefore, in this embodiment, the trapping rate is detected using the equation (3) (step in FIG. 18).

Here, the symbols T _C , T _M, and T _Y are cyan,
The trapping rates of the magenta and yellow color materials are shown. In this equation (3), the coefficient a ₁₁ , ... a ₃₉
The 3 × 9 coefficient matrix represented by is converted into a ROM (Read Only Memory) and is arranged in the arithmetic processing means 78. The content of this coefficient matrix may differ depending on the recording method performed on the recording paper to be inspected. Therefore, when a color image is inspected for a plurality of recording methods, a ROM may be prepared for each recording method, and these may be appropriately switched and used. Of course, one ROM may be divided into a plurality of storage areas, and these storage areas may be selectively called according to the type of recording method.

The calculation result of the trapping rate in the automatic color image inspection apparatus according to the present embodiment will be described with reference to FIG.

The measured trapping rate shown on the horizontal axis of FIG. 19 is obtained as follows.

First, a color toner as a color material used in color xerography is uniformly dispersed by changing the weight per unit area on a recording paper to prepare a test piece. At this time, the weights of the cyan, magenta, and yellow toners are measured by a balance, and then test pieces for single color, for superimposing two colors, and for superimposing three colors are prepared.

Once the test pieces have been created, cyan for each test piece,
Magenta and yellow toner weights W _C , W _M , W _Y
Are the weights W _C0 , W _M0 , and
Calculate the actual trapping rate by dividing by W _Y0 .

After the measured trapping rate is calculated, the toner on the test piece is fixed by the fixing device used in the copying machine. The test piece after fixing is set in the color image automatic inspection apparatus of this embodiment, and the trapping rate is measured. In this embodiment,
For the toners of cyan, magenta, and yellow, 0.66 mg / cm ² was set as the reference value of the measured trapping rate.

The trapping rate shown on the vertical axis in FIG. 19 is a value obtained by calculation. The 24 points indicated by the circles in the figure are the values obtained by the color image automatic inspection apparatus of this embodiment plotted in relation to the measured trapping rate. On the other hand, the 24 points indicated by X in the figure are plots of the values obtained up to the operation of steps in FIG. 18 in relation to the actually measured trapping rate for reference. In this figure, some of the circles and crosses are duplicated at the origin.

In FIG. 19, a straight line 311 indicates an ideal case in which the calculated value perfectly matches the measured trapping rate. As can be seen from this, according to the present embodiment, the trapping rate is obtained with an accuracy of ± 2% even in the high density region by adding the processing of the steps in FIG.

By the way, in the color image automatic inspection apparatus of this embodiment, the rectangular area for scanning the inspection object is 10 μm × 500 μm.
It was set to a rectangle with a very small size of m. Therefore,
Unlike a conventional apparatus for image inspection similar to the above, it is possible to perform an inspection close to the human visual sense. This will be described in detail below.

First, FIG. 20 is an enlarged view of a part of the chart for resolution inspection. As described above, in this chart, the black lines 201 in which the intervals and the line widths are set in several stages are drawn in parallel, and the resolution of the copied image depends on the line width that can be identified from the white background color portion 202 of the background. Is to be inspected.

FIG. 21 is an enlarged view of a part of this chart, and FIG. 22 shows a sample copy image of a copying machine corresponding to this. Here, FIG. 22A shows
This is an example in which relatively large unevenness is generated in the boundary area between the ground color portion 202 and the black line 202, and FIG. 9B is an example in which toner is scattered at these boundary portions. Further, FIG. 6C shows a blank area 203 where toner is not attached inside the black line 201.
Is an example of occurrence. In addition, the density of the black line 201 does not change at the boundary portion at a time but changes gradually, or
Various states appear such as when light and shade occur inside. Such a delicate state of an image becomes 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. This image signal 205 is a signal obtained by scanning the chart shown in FIG.
This corresponds to FIG. 4 of Japanese Patent No. 03465. A signal portion 205 'shown 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 by the solid line. However, when the image signals 205 and 205 'are binarized at the threshold level shown by the alternate long and short dash line 207 and the image is inspected,
Both of them have the same resolution evaluation. This is because in the conventional device, the resolution is determined based on the location where the signal has changed due to binarization and the number of times the signal has changed at that location.

FIG. 24 shows an image signal obtained by the conventional apparatus for the image state shown in FIG. 22B, and FIG. 25 shows 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 becomes high at the portion 208 where the scattered toner is scanned. However, since the scattered portion is a relatively small area, the signal level does not rise sufficiently in this portion and is ignored in the binarization process. FIG. 25 shows the opposite case, in which the blank area 203 existing in the black line 201 portion lowers the signal level in the arrow 209 portion. However, also in this case, since the signal change in the minute portion is not sufficient, this change is ignored in the binarization process. As described above, according to the conventional device, there is a problem that the image is discriminated at a level different from the quality of the image perceived by human eyes.

However, in the color image automatic inspection apparatus of the present embodiment, the fourth
As shown in the figure, the optical density of an object to be inspected is inspected using an opening of 10 μm × 500 μm. The diameter of the toner particles after fixing is approximately 10 to 20.
Since it is μm, it can be understood that this allows the image inspection to be performed at a level almost the same as a human sense in inspecting the inspection object.

Further, in the color image automatic inspection apparatus of the present embodiment, since the rectangular region is measured with the rectangular region as the minimum measurement range,
The object to be inspected can be efficiently scanned without a gap. 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 size larger than this, a square having a side having the same length as the short side described above, or a square having a size larger than this. In the case of a square, it is not necessary to tilt (rotate) the opening in accordance with the pattern even when inspecting a pattern composed of obliquely inclined line segments.

Of course, the shape of the opening used for the measurement does not have to be a strict rectangle, and may be a rectangle having a shape close to a circle or an ellipse, for example. However, in these cases, since the images are partially overlapped and read in order to scan the entire image, it is necessary to process the overlapped parts.

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 the photomultiplier means using a semiconductor or a one-dimensional sensor such as CCD. Further, although the optical density is detected by reflected light in the embodiment, it may be detected by transmitted light when inspecting, for example, the development state of a photographic film.

Further, in the embodiment, as a unit forming the image to be inspected,
The toner particles have been described as an example. In other non-impact type devices, or in impact type devices, the size and rotation angle of the openings may be considered in consideration of the size and shape of the ink or the like used therein.

[Advantages of the Invention] As described above, according to the present invention, it is possible to automate the inspection of the optical density of a plurality of colors on an object to be inspected, such as copy paper, and reduce the burden on the operator. . Moreover, since the pattern to be inspected can be selected according to the measurement content, efficient work can be performed. Especially for the inspection of the "trapping rate", which is one of the important items that affect the color reproducibility when the object to be inspected is a color image, these color materials are unnecessary from the density data obtained by reading each color material independently. When the absorption effect is corrected, and when the trapping rate is calculated using the corrected amount of each color material and each amount of color material in the portion where the color materials are superposed,
We decided to perform linear correction by matrix calculation according to the recording method. Therefore, the trapping rate can be accurately inspected, which is of great practical value when evaluating a color image.

[Brief description of drawings]

The drawings are for explaining one embodiment of the present invention, in which FIG. 1 is a perspective view of an automatic color image inspection apparatus, FIG. 2 is a schematic configuration diagram showing an essential part of an inspection section, and FIG. FIG. 4 is a layout explanatory view showing the layout of optical components of the optical head, and FIG.
5 is a block diagram showing a schematic circuit configuration of a color image automatic inspection apparatus, FIG. 6 is a block diagram showing a configuration of external signal input means, and FIG. 7 is a block diagram showing a configuration of pattern information storage means. 8 is an explanatory view showing the structure of the pattern information storage unit, FIG. 9 is a block diagram showing the structure of the processing procedure storage unit, FIG. 10 is a block diagram showing the structure of the processing code storage unit, and FIG. 11 is the inspection procedure. FIG. 12 is a block diagram showing the configuration of the storage means, FIG. 12 is a block diagram showing the configuration of the measuring means, and FIG. 13 is a block diagram showing the configuration of the arithmetic processing means.
FIG. 14 is a plan view of a chart showing the location of the position detection pattern, FIG. 15 is a plan view showing an example of a pattern for density measurement, and FIG. 16 is an example of scanning in the X-axis direction. Explanatory diagram, FIG. 17 is an explanatory diagram showing the scanning state of the patch portion of each color, FIG. 18 is a flow chart showing the calculation procedure of the trapping rate, and FIG. 19 is the actual trapping rate and the trapping rate obtained by calculation. Fig. 20 is a characteristic diagram comparing the example with the conventional example. Fig. 20 is a plan view showing an enlarged part of a chart for resolution inspection. Fig. 21 is an enlarged part of the chart shown in Fig. 20. 22A to 22C are partially enlarged plan views showing various states of a sample copy image, and FIG. 23 is a waveform diagram showing a signal level of an image signal obtained by reading the image part shown in FIG. 22A. , Fig. 24 shows 22 Waveform diagram showing a signal level of the image signal obtained by reading the image portion indicated by B, FIG. 25 is a 22
FIG. 26 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. C, and FIG. 26 is a principle diagram showing the copying principle of the color xerographic copying machine. 1 ... inspection unit, 2 ... computer unit, 4 ... copy paper, 5 ... supply tray, 8 ... chart holding unit, 41 ... concentration detection unit, 58 ... photomultiplier tube, 66 ... filter Unit: 68 ... Color filter, 76 ... Measuring means, 78 ... Arithmetic processing means, 221 ... Pattern, 225 ... Cyan mono color, 226 ... Magenta mono color, 227 ... Yellow mono color, 228 ... Black.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Ohashi 2274 Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd. Ebina Business Office (56) References JP-A-61-277248 (JP, A) JP-A-59- 103464 (JP, A) "Printing Engineering Handbook" edited by The Japan Printing Association (SHO 58-7-20) 256 ~ 257

Claims (1)

[Claims] 1. An inspected object holding means for holding an inspected object having an image composed of a plurality of inspection patterns, and a supply means for supplying the inspected object to the inspected object holding means. A pattern to be inspected for selecting a pattern to be inspected among the objects to be inspected held by the means to be inspected, and a single color material in the pattern selected by the pattern to be inspected Optical density measuring means for measuring the optical density of each area and the area where these color materials are superposed by sequentially switching filters of predetermined three primary colors, and the optical density measuring means is selected by the inspected pattern selecting means. Moving means for moving to the reading position by using the coordinate values corresponding to the formed pattern, the parts of the individual color materials and the overlapping of these color materials. Averaging processing means for averaging the densities of the three primary colors obtained for each of the divided parts, and the averaged data of each of the parts of the individual coloring material and the overlapping parts of these coloring materials. Using,
In the unnecessary absorption effect correction means for correcting the unnecessary absorption effect of these color materials, and in the area where these color materials are superposed when the amount of each color material in each area of the single color material is "1". The color material amount calculating means for obtaining each color material amount and each color material amount for each overlapping portion of the color material obtained by the color material amount calculating means are corrected by the unnecessary absorption effect correcting means. Trapping for each color material is performed by linearly converting each value obtained by dividing by the corresponding color material amount in the part with a matrix operation formula having a coefficient matrix preset for each recording method of these color materials. And a trapping rate calculating means for calculating a rate.