JPS62299971A - Optical density measuring instrument for image inspection - Google Patents

Abstract

PURPOSE:To allow the titled instrument to reach the level of image inspection executed by an operator by setting up the sampling width for detecting optical density to a value smaller than visual resolution. CONSTITUTION:A measuring field adjusting mechanism 56 is arranged with an aperture plate 59 and a field lens 61 in an optical path and the aperture plate 59 is provided with a square aperture part. The image of a measuring portion on copying paper is formed on the aperture area of 50X2,500mum so that the expand image of 5 times is formed. A square area of 10X500mum on the copy paper is set up as one reading range. Thus, data indicating fine image status can be extracted by setting up the sampling width to a value smaller than the visual resolution and the discrimination to the density or resolution close to human senses can be attained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention "Field of Industrial Application" The present invention is used, for example, in an image inspection device for inspecting the quality of images reproduced by facsimile machines, printing machines, or copying machines. The present invention relates to an optical density measuring device for image inspection.

"Prior Art" In offices, various information devices output graphic information such as text and images. A typical example of this is a copying machine that copies original documents. A copying machine forms an electrostatic latent image on a photosensitive drum, reads image information using an image sensor such as a CCD, and develops the image using a developing device, or uses a recording head such as a thermal head. Images are reproduced on paper.

When designing such information devices or shipping these information devices from factories, reproduced images are inspected. There are two types of such tests:

(i) Inspection of whether the information equipment operates normally according to predetermined procedures and reproduces images.

(ii) Checking whether the quality of the reproduced image is within the market acceptable range or the specifications established when the equipment was designed.

For example, in the case of a copying machine, the inspection items include the position of the image relative to the copied paper, the density of the image relative to the original, and the resolution. The inspector inspects using scales, magnifying lenses, measuring instruments, or visually to check whether each process of the copying machine is working properly and that there are no errors in image reading or toner image transfer position. Determine whether or not.

In the case of copying machines, the latter inspection is also performed by an inspector. That is, the quality of the image is determined by the inspector directly comparing the image copied on the paper with the sample.

In conventional inspections as described above, the inspector is the main person, so
There were the following problems.

(1) Measured values or test results changed due to different testers.

(ii) Even for the same tester, the measured values or test results changed due to familiarity with the test or the psychological influence of the test subject tested previously.

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

In order to avoid such drawbacks, image inspection apparatuses have been proposed (Japanese Patent Application Laid-open No. 5-9-10345 and Japanese Patent Application Laid-open No. 59-10346).

This image inspection apparatus is provided with a table on which an object to be inspected having an image is positioned and placed.

The object to be inspected is set on this table, and the detection section is placed opposite to it. Then, the detection data output from this detection section is supplied to a data processing section, and the position, density, and resolution of the image are digitized based on the detection data.

``Problems to be Solved by the Invention'' However, the proposed image inspection apparatus uses a line sensor (image sensor) or a combination of a low density meter and a high density meter in the detection section. For this reason, the minimum area that can be measured has to be much larger than the minimum area that humans can sense. Therefore, with this image inspection device, the optical density in uniform density areas and the resolution in extremely high quality image areas are
Although it is possible to obtain somewhat good measurement results, image examinations under other conditions may result in a large discrepancy between the results and those perceived by humans.

The cause of this will be explained next.

FIG. 17 is an enlarged view of a part of the chart for resolution inspection. In this way, in this chart, black lines 201 with different intervals and line widths are drawn in parallel, and the resolution of the copied image is determined by how far the line width can be distinguished from the white background part 202. It is designed to be inspected.

FIG. 18 shows a further enlarged part of this chart, and FIG. 19 shows a sample of images copied by a copying machine in correspondence with this.

Here, FIG. 19A is an example in which relatively large unevenness occurs in the boundary area between the ground color portion 202 and the black line 202, and FIG.
This is an example of toner scattering at these boundary areas. Further, C in the same figure is an example in which a blank area 203 to which no toner is attached is generated inside the black line 201. In addition, various other situations may occur, such as the density of the black line 201 not changing all at once at the boundary but changing stepwise, or shading occurring inside the black line 201. Such delicate image conditions are a relatively large factor in image quality evaluation.

By the way, FIG. 20 shows the signal level of the read image signal when the outline of the black line has irregularities as shown in FIG. 19A, for example. This image signal 205
is a signal obtained by horizontally scanning the chart shown in FIG.
This corresponds to FIG. 4 of the publication. A 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. 19A, and has a thicker waveform than other portions indicated by a solid line. However, the image signal 205 .
If 205' is binarized and the image is inspected, the evaluation of the resolution will be exactly the same for both. This is because in conventional devices, the resolution is determined based on the location where a signal change occurs due to binarization and the number of times the signal changes at that location.

FIG. 21 shows an image signal for the image state shown in FIG. 19B, and FIG. 22 shows an example of an image signal for the image state shown in FIG. 19C. In the example shown in FIG. 21, the level of the image signal 205 becomes high in a portion 208 where the scattered toner is scanned. However, since the scattered portion is a relatively small area, the signal level does not increase sufficiently in this portion and is ignored in the binarization process.

FIG. 22 shows the opposite case, where the signal level at the arrow 209 is lowered due to the blank area 203 existing at the black line 201. However, even 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, the conventional apparatus has a problem in that images are judged at a level different from that perceived by the human eye.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an optical density measuring device for image inspection that can reach the level of image inspection performed by humans.

"Means for Solving the Problems" In the present invention, the above-mentioned object is achieved by setting the sampling width for detecting optical density to be smaller than the visual resolution.

-For example, a small aperture may be placed in the optical system to limit the area of light that enters the light receiving section, so that the area for detecting optical density is a rectangular area smaller than the visual resolution. . The rectangular area may be a square or a rectangle, and in the case of a rectangle, the short side may be set to be approximately 50 μm or less.

Of course, the shape of the region in the object to be inspected does not have to be rectangular, and can take various shapes such as circular and elliptical shapes.

According to the present invention, since images are sampled at minute intervals of, for example, 50 μm or less, it is possible to obtain image data that exceeds the visual resolution, and by processing this, it is possible to perform image inspections that are closer to human inspections. Become.

"Example" The present invention will be described in detail with reference to Examples below.

Overview of Apparatus FIG. 1 shows the external appearance of an optical density measuring apparatus for image inspection in one embodiment of the present invention.

This optical density measurement apparatus for image inspection is composed of an inspection section 1, a computer section 2, and a printer section 3.

Of these, the inspection section 1 is a section that continuously inspects copy paper 4 as an object to be inspected. The inspection section 1 includes a supply tray 5 and a discharge tray 6.

When inspecting a copying machine, a desired chart is set in the copying machine, and copy sheets 4 obtained thereby are stacked on a supply tray 5 as shown.

The copy sheets 4 are fed into a cylindrical chart holder 8 one by one by a feed roller 7. The surface of the chart holder 8 is covered with an insulating film, and the copy paper 4 is electrostatically attracted to this surface by a charging operation by an electrostatic charge supply device (not shown). In this state, an image inspection of the copy paper 4 as the object to be inspected is performed.

The copy paper 4 that has been inspected is peeled off from the chart holder 8 by a peeling mechanism that will be described later. The peeled copy sheets 4 are sequentially discharged onto the discharge tray 6.

An operation display panel 9 is arranged in this inspection section 1.
Disposed here are a power switch 11, a movement key 12 used when manually specifying the pattern of the object to be inspected, and a display 13 for displaying concentration data as a measurement result.

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

The printer section 3 is a section that outputs test results and the like, and in this embodiment a dot printer is used.

FIG. 2 shows an outline of the inspection section of this optical density measuring device for image inspection. The feed roller 7 of this inspection section 1
A shaft 21 that rotates receives driving force from a feed roller drive morph 23 via a chain 22. The supply tray 5 is adapted to be given a force to move upward by the excitation of a solenoid (not shown), and at the time of this excitation, the top layer surface of the copy paper 4 as the object to be inspected comes into contact with the feed roller 21. When the feed roller 21 rotates by a predetermined amount in this state, only one sheet of copy paper 4 in the uppermost layer is fed out. Prior to this feeding, the surface of the chart holder 8 is uniformly charged by a charging mechanism (not shown).

As a result, the fed-out copy paper 4 is electrostatically attracted to the chart holding section 8. The rotation of the cylindrical chart holder 8 in the circumferential direction (Y-axis direction) is performed by the driving force of a chart holder drive motor 26 connected to a decelerator 25 .

In this embodiment, the outer diameter of the chart holder 8 is 162 mm in diameter.
77 mm, the step angle of the chart holder drive motor 26 is 1.8 degrees, and the reduction ratio of the reducer 25 is 1/256.
And so. As a result, the chart holder drive motor 26 is driven one step, and the surface of the chart holder 8 is moved by 10 μm in the Y-axis direction. Control of the rotational position of the chart holder 8, that is, control of the position in the Y-axis direction, is performed using a point detected by a photo sensor 28 in a 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 Y-axis movement hole 34 of the optical head mounting block 33 is screwed into ball screws . . . -32. Therefore, when the X-axis stepping motor 31 rotates, it is guided by two guide bars 35 and 36 arranged parallel to the ball screw 32 and moves 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 set at 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 movement range of the optical head mounting block 33.

A density detection section 41, which will be described next, is attached to the optical head attachment block 33. A magnifying eyepiece lens 42 is also attached to the density detection unit 41, and the position of the image captured by the objective lens 43 can be checked during focus adjustment and especially during manual operation.

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

The concentration detection section 41 includes a tungsten lamp 51 for illumination. The light emitted from the tungsten lamp 51 is focused by the illumination lens 52 and
The measurement site 53 is illuminated. The reflected light from the measurement site 53 is collected by an objective lens 43 and split into two directions by a prism 54 equipped with a semi-transparent mirror (beam splitter).

One of the branched lights is reflected by a mirror 55, passes through a measurement field of view adjustment mechanism 56, has its wavelength component corrected by a color correction filter 57, and enters a photomultiplier tube 58. Here, the measurement field of view adjustment mechanism 56 has an aperture plate 59 and a field lens 61 disposed in the optical path.

The aperture plate 59 is a plate provided with a rectangular opening as shown in FIG. In this opening area of 50 μm x 2500 μm, an image of the measurement site on the copy paper is magnified five times and formed. A light beam reflected from a rectangular area (FIG. 4) with a long side of 500 μm and a short side of 10 μm on the chart, that is, in this embodiment, on the copy paper 4, passes through this opening and enters the photomultiplier tube 58 described above. will be done. The longitudinal direction of the opening of the aperture plate 59 can be set at an arbitrary angle by an aperture plate rotation solenoid 62.

The other light branched by the prism 54 has its traveling direction changed by the roof-shaped prism 64, and forms an erect image on the observation screen 65.

The image of the measurement site 53 thus formed can be enlarged and observed using the magnifying eyepiece 42.

Circuit Configuration of the Device (Principle Configuration of the Device) Before specifically explaining the device, the fundamental configuration of the circuit will be explained.

The following FIG. 5 shows an outline of the circuit configuration of the optical density measuring device for image inspection. This device is equipped with external signal input means 72 for instructing desired inspection items. The measurement control means 73 is configured to set 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 manual means 72. The pattern information storage means 74 stores the pattern to be inspected within the object to be inspected, and the processing procedure storage means 75 stores the inspection processing procedure for the pattern to be inspected.

The measurement means 76 scans the surface of the object 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 a processing procedure instructed by the measurement control means 73. The test results obtained thereby are outputted by the output means 83.

The output means 83 is typically the printer section 3 shown in FIG. 1, but the test results can also be displayed on the CRT screen of the computer section 2.

The operation of this optical density measuring device for image inspection will be explained in more detail. In the optical density measurement apparatus for image inspection, the type of the object to be inspected and the inspection items are converted into codes by the external signal input means 72 during inspection. Chart code 8 to identify the chart copied to the inspected object
4 and a test item code 85 representing the test 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 the 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. Of these, 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 pattern to be inspected and the arithmetic processing code 89 representing the arithmetic processing procedure are used to control the measurement. It will be read into the means 73.

At this stage, ■ the type of pattern to be inspected required for inspection, ■
Positional information on where the pattern exists on the copy paper, information on (1) an image density detection method for that pattern, and (2) information about a method for calculating and processing the results corresponding to the inspection items are stored in a code in the measurement control means 73. It will be set in a formatted state.

Among 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 measuring means 76.

The measuring means 76 moves to the representative point position 87 instructed by the measurement controlling means 73, and reads the image density detection format 8.
8, the image density to be measured is detected. The detection result is outputted to the arithmetic processing means 78 as a concentration data string 91. At the end of the concentration data string 91, an end signal 9
2 is added to instruct the start of arithmetic processing.

Upon receiving the end signal 92, the arithmetic processing means 78 executes the arithmetic processing code 89 previously supplied from the measurement control means 73.
Based on this, the corresponding calculation processing routine is selected. This arithmetic processing routine is then loaded into the internal arithmetic processing routine memory area. In the arithmetic processing means 78, the density data string 91 described above is stored in a density data string memory area. The arithmetic processing means 78 processes this concentration data string 91 using the routine loaded into the arithmetic processing routine memory area, and outputs the results according to the test items as the test results 9.
3 and is supplied to the output means 83.

The output means 83 will output this content.

The image density detection and density data arithmetic processing operations described above are sequentially performed for all patterns to be inspected that are preset in the measurement control means 73.

The arithmetic processing means 78 not only performs arithmetic processing on each pattern, but also performs statistical processing of the arithmetic processing results corresponding to all set patterns to be inspected. In this way, the desired test results for the object to be tested will be obtained.

(Configuration of External Signal Input Means) Next, the configuration of the external signal input means will be explained using FIG. 6.

The external signal input means 72 includes encoding means 101. The chart name 102 and test item 103 input by the operator are encoded by the encoding means 101. The code type discrimination means 10'4 receives the coded information and separates it into chart code and test item code. Then, it is output as a chart code 84 and a test 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 retrieval means 107. The pattern information storage position search means 107 searches for the position of the pattern to be inspected, and searches the pattern information storage unit 1.
08 as a pointer 109.

FIG. 8 shows the contents of the pattern information storage section. The pattern information storage unit 108 stores, as data, pattern codes as objects to be inspected within the corresponding chart, using the chart codes as keys, and representative point positions of the respective patterns represented by these pattern codes. . In this figure, for example, for chart code "xxx", there are three pattern codes a
1a and 1b are available. This means that two types of patterns specified by pattern codes a and b are displayed on the chart specified by this chart code "XXX", and the coordinates of a total of three patterns are displayed. is as shown in the representative point position.

Here, the pattern represented by the pattern code a is, for example, the electrophotographic society test chart "No. 1-
This is a resolution measurement pattern (not shown) for "R1975".This pattern is placed in the upper left and lower right parts of this test chart.In addition, pattern code b
The pattern represented by is a pattern for density measurement in this electrophotographic society test chart.

In this test chart, various density samples are displayed in a row at the bottom, forming a pattern for density measurement.

The pattern information output means 110 includes the pattern information storage section 1
08 is read out from the position indicated by the pointer 109 output by the pattern information storage position search means 107. The read content is the pointer 109
U is all pattern codes and their representative point positions for one chart code. The combination of the pattern code 86 and the corresponding representative point position 87 is sequentially read out under the control of the measurement control means 73 shown in FIG. 5, and sent into the measurement control means 73.

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

The processing procedure storage means 75 is supplied with an inspection item code 85 and a pattern code 86. Among these, the inspection item code 85 is detected by the inspection item code detection means 11.
2, and the pattern code 86 is detected by the pattern detection means 113. The detection result of the test item code detection means 112 is outputted as a first pointer 114 to the processing code storage means 115, and the detection result of the pattern detection means 113 is outputted as the second pointer 115 to the processing code storage means 116.

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

Returning to FIG. 9, the explanation will be continued. Inspection 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 “i”. Based on this, the third pointer 119 as address information is stored in the inspection procedure storage means 121.
Output for.

FIG. 11 shows the contents of the inspection procedure storage means. The inspection procedure storage means 121 stores image density detection formats for each image density detection code. There are multiple 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,
(iii) spacing, (iv) m number of points, and (V) slit direction.

Here, (i) the measurement start position is shown as a relative representative point. As described above, the representative point is indicated by the coordinates that serve as a reference for each pattern, whereas the counter representative point is the difference between the coordinate value of the starting position and the coordinate value of the representative point when scanning the pattern.

(ii) The direction is the direction of scanning, and there are two types of directions: the X-axis direction and the Y-axis direction. (iii > Interval is the sampling interval for concentration detection, (iv)
The total score is the total number of sampled data. (
V) The slit direction refers to the direction of the opening of the aperture plate 59 shown in FIG. In this example, is the opening parallel to the X axis?
It is set parallel to the Y axis rotated 90 degrees.

The third pointer 119 specifies 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 out the image density detection format 88 selected by the third pointer 119, and reads out the image density detection format 88 selected by the third pointer 119, and reads the image density detection format 88 from the measurement control means 7 shown in FIG.
3 to the measuring means 76 under the control of No. 3. On the other hand, the second code output means 123
The arithmetic processing code 89 is read from 6 and is similarly supplied to the arithmetic processing means 78 under the control of the measurement control means 73.

(Configuration of measurement means) The following FIG. 12 shows the contents of the measuring means.

The measuring means 75 can be roughly divided into three parts: (i) an image density detection section, (ii) a detection aperture control section, and (iii) a moving section. Measurement output terminal 7
5, the image density detection format 88 supplied from the measurement control means 73 is used to move over the object to be inspected (in this embodiment, the copy paper 4 on which the chart has been copied);
Image density will be detected in a predetermined format. 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 section 131, and based on the format 88 decoded here, the image density detection section and the detection aperture control section , and the moving part will be controlled accordingly.

By the way, the data sampling control section 131 controls the light receiving means 1 based on the data 133 obtained from the drive control section 132.
The current location of 33 is known. Therefore, the data sampling control section 131 determines the amount by which the light receiving means 133 should be moved by comparing it with the measurement start position obtained from the image density detection format 88. Data 134 regarding the determined movement amount etc. is sent to the drive control section 132.

The drive control unit 132 determines the amount of movement in the X-axis direction and the amount of movement in the Y-axis direction based on the data 134, and outputs an X-axis direction drive signal 135 and a Y-axis direction drive signal 136 with the corresponding number of pulses. 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 holder drive motor 26 (both shown in FIG. 2) which also serves as a stepping motor.

As already explained, the concentration detection section 41 (FIG. 2) is moved in the X-axis direction by the X-axis stepping motor 31.

Further, the drum-shaped chart holder 8 is rotated in the Y-axis direction by the drive of the chart holder drive motor 26, and the light receiving means 133 consisting of the photomultiplier tube 58 and the like is moved to a desired measurement position.

The data sampling control unit 131 then decodes the image density detection direction, sampling interval, total number of sampling points, and slit direction. First, the aperture direction is compared with the current aperture direction, and an angle signal 138 representing the comparison result with the designated angle is output. Angle signal 138
is supplied to an angle signal generator 139. Angle signal generator 139 supplies control signal 141 to aperture plate rotation solenoid 62 (see FIG. 3) to rotate aperture plate 61 by a desired angle.

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

The drive control section 132 moves the concentration detection section 41 or the chart holding section 8 by a predetermined amount in accordance with 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 detection section, and its output 145 is logarithmically converted by a logarithmic converter 146. Conversion output 147 is provided to A/D converter 148. A/D
The converter 148 has an A/D signal 15 for specifying the time at which the A/D converter is to be operated.
1 is supplied. The A/D signal generating section 149 generates the A/D signal 151 according to the A/'D start signal 152 supplied from the data sampling control section 131; The output of a counter (not shown) is used.

That is, this counter is preset with a count value corresponding to the measurement start position, and the light receiving means 1
As 33 begins to move, the count increases. When the count value of the counter reaches the preset value, the A/D
A start signal 152 will be output. When the A/D conversion is completed, the A/D signal generation section 149 completion signal 153
Output. When the data sampling control section 131 receives the end signal 153, it manages the above-mentioned counter and instructs the drive control section 132 to move the light receiving means 133, and if necessary, starts the next A/D at a predetermined timing. A D start signal 152 will be output. In this way,
It becomes 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 conversion output 147 from analog to digital. The converted density data 154 is sequentially stored in an image density buffer 155. The stored concentration data 154 is supplied to the arithmetic processing means 78 as a concentration data string 91, and is subjected to arithmetic processing.

Now, when the sampling of the concentration data progresses 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.

When the measurement control means 73 receives this end signal 156,
Data regarding the next block is supplied to the data sampling control section 131 as an image density detection format 88. In this way, concentration data is collected for each part to be measured.

(Configuration of arithmetic processing means) FIG. 13 shows the configuration of the arithmetic processing means. The calculation processing means includes a calculation control section 161. The calculation control section 161 receives the calculation processing code 8 from the measurement control means.
9 is supplied. The arithmetic processing code 89 is a code representing the arithmetic processing procedure. The arithmetic control unit 161 decodes the arithmetic processing code 89 and supplies the result as an arithmetic processing code 162 to the arithmetic processing address search means 163.

The arithmetic processing address search means 163 uses this arithmetic processing code 162 to search the arithmetic processing storage section 164.

The arithmetic processing storage unit 164 stores arithmetic processing data groups necessary for various tests. When the arithmetic processing address search means 163 moves the pointer 165 to the start address of the corresponding memory area by searching, the arithmetic processing address search means 163
A termination signal 166 is sent to 61. After receiving the end signal 166, the arithmetic control unit 161 generates a start signal 167,
Supply to loader starter 168.

When loader scooter 168 receives activation signal 167, it generates load signal 169.171.

(i) Pointer 1 in the arithmetic processing storage unit 164
A series of arithmetic processing contents 172 shown in 65 and (ii)
The density data string 91 stored in the image density buffer 155 (see FIG. 12) of the measuring means is transferred to the working area 1.
74. After loading, loader starter 1
68 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 contains the concentration data string 91.
The desired arithmetic processing is performed on the data. The result is stored in the calculation result output buffer 177 as the calculation result 176. The output means 83 shown in FIG. 5 inputs this stored content as an inspection result 93 and visualizes it.

l Details of Optical Density Measurement In this optical density measurement apparatus for image inspection, the copy paper 4 is first held in the chart holding section 8, and after its positioning is performed, the density measurement for each pattern is performed. Therefore,
Next, the positioning with respect to the copy paper 4 will be explained, and then the density measurement work for each pattern will be explained.

(Positioning for each measurement site) In order to measure an image from the copy paper on which the chart has been copied, the objective lens 43 of the optical head must correctly capture 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 paper 4 is ±5
An error of about mm occurs. This is due to the following reasons.

(i) Misalignment that occurs when a chart is copied using a copying machine.

In addition to alignment errors (registration misalignment) between the copy paper 4 and the photosensitive drum of the copying machine and magnification setting errors, there are also Contains errors due to skinny (rotation).

(ii) Misalignment when setting the chart in the chart holder 8.

This is a deviation that occurs when the copy paper 4 sent out from the supply tray 5 is set in the chart holding unit 8, and is caused by an error in the setting of the supply tray 5 or a misalignment in position alignment when the copy paper 4 is sent out. do.

In this embodiment, the target position can be reached with an accuracy of ±Q, 5 mm. For this purpose, as an example shown in FIG. 14, position detection patterns 192 to 194 are arranged at, for example, three locations on a chart 191 used in an optical density measuring device for image inspection. The coordinates of these position detection patterns 192 to 194 are known for each type of chart on the optical density measuring device for image inspection. The coordinate values of these patterns 192 to 194 on the chart are called actual coordinate values, and these are (XI, Yl, X2, Y2, X3,
Y3) It shall be expressed as te.

The device calculates these real coordinate values (X+, Yl, X2, Y2, X3, Y3
) is used to scan the surrounding copy paper 4 and detect changes in image density to detect these positions on the copy paper 4. The coordinate values of these position detection patterns 192 to 194 on the copy paper 4 are (xI +Vl
s x2 1V2 , x3 1V3 ).

By assembling the relational expressions of the plane coordinate system (X, Y) and (x, y), the actual position (X
, , yo) are calculated, and this coordinate value (Xa,
Yo ) is used to cause the density detection unit 41 to reach the target image area.

The position detection pattern does not need to be placed in three places on the copy paper; for example, by placing it in two places,
It is possible to understand the rotation and positional shift of the Further, by arranging more points, it is possible to grasp the elongation of each part of the copy paper 4, and it is possible to further improve the accuracy of reaching the measurement site.

(Pattern Scanning) FIG. 15 shows a certain pattern for density measurement. In this pattern 221, a point 223 is a representative point, and a point 224 is a detection start point in the X-axis direction. The detection starting point 224 is expressed as a relative coordinate value with respect to the representative point 223.

When scanning this pattern 221 also in the Y-axis direction,
A detection starting point different from point 224 may be provided for this purpose.

As described above, in the optical density measuring device for image inspection of this embodiment, a rectangular area of 10 μm x 500 μm on a copy sheet is set as a reading range at one time. 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, ie, the sampling width, is determined depending on the purpose of the measurement, etc. When the slit direction, that is, the longitudinal direction of the opening, is set in the Y-axis direction, the area for one concentration detection in the X-axis direction is 10 μm. Therefore, X
When scanning the copy paper 4 all over in the axial 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 minute image conditions as shown in Figure 19, and by processing this data, it is possible to understand the human sense of density and resolution. It becomes possible to make a discrimination close to .

The measurement does not necessarily require sampling at the same width as the short side of the rectangular area in which the optical density is to be detected, and can be freely set using the image density detection format. Therefore, depending on the inspection item, it is possible to roughly scan the image.

When scanning in the Y-axis direction, the slit direction is normally set in 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 already explained, in this embodiment, the X-axis stepping motor 31 or the chart holder driving moke 26 can be moved in units of 10 μm in the 1-pulse axis direction or the Y-axis direction, respectively.

In this manner, the optical density measuring device for image inspection of this embodiment measures the object to be inspected using the rectangular area as the minimum measurement range, so that the object to be inspected can be efficiently scanned without gaps. Of course, the rectangular area is not limited to a rectangle, but may be a square having four sides of equal length. In this case, it is necessary that these four sides be smaller than the minimum value of visual resolution (about 50 μm).

Furthermore, the basic area to be measured does not have to be rectangular, and may be circular or elliptical, for example. However, in these cases, in order to scan the entire image, some of the images are read overlappingly, so it is necessary to process these overlapping parts.

Although a photomultiplier tube is used as the light receiving means in the embodiment, the same optical density measurement operation can be performed using a photomultiplier using a semiconductor or a one-dimensional sensor such as a CCD. Further, in the embodiment, the optical density was detected using reflected light, but it may be detected using transparent light, for example, when inspecting the development state of photographic film.

"Effects of the Invention" As explained above, according to the present invention, at least a part of the area for detecting optical density is set smaller than the visual resolution, so it is possible to measure optical density with a sensation similar to visual perception. , it becomes possible to quickly obtain stable results.

[Brief explanation of the drawing]

Figures 1 to 16 are for explaining one embodiment of the present invention, of which Figure 1 is a perspective view of an optical density measuring device for image inspection, and Figure 2 shows the main parts of the inspection section. A schematic configuration diagram, FIG. 3 is an explanatory diagram showing the arrangement of optical components of the optical head,
FIG. 4 is an explanatory diagram showing the size of the area that is the measurement unit on copy paper, FIG. 5 is a block diagram showing the outline of the circuit configuration of the optical density measuring device for image inspection, and FIG. 6 is an external signal input means. 7 is a block diagram showing the structure of the pattern information storage means, FIG. 8 is an explanatory diagram showing the structure of the pattern information storage section, and FIG. 9 is a block diagram showing the structure of the processing procedure storage means. 10 is a block diagram showing the structure of the processing code storage means, FIG. 11 is a block diagram showing the structure of the inspection procedure storage means, FIG. 12 is a block diagram showing the structure of the measurement means, and FIG. 13 is a block diagram showing the structure of the measurement means. FIG. 14 is a block diagram showing the configuration of the processing means, FIG. 14 is a plan view of a chart showing the arrangement of position detection patterns, FIG. 15 is a plan view showing an example of a pattern for measuring density, and FIG. An explanatory diagram showing an example of scanning in the X-axis direction, Fig. 17 is a plan view showing an enlarged part of the chart for resolution inspection, and Fig. 18 is a further enlarged part of the chart shown in Fig. 17. FIGS. 19A to 19C are partially enlarged plan views showing various states of the copied image sample, and FIG. 20 is a waveform showing the signal level of the image signal obtained by reading the image portion shown in FIG. 19A. 21 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. 19B, and FIG. 22 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. 19C. n in the waveform diagram shown. ■...Inspection section, 2...Computer section, 3...Printer section, 4...Copy paper, 26...Chart holding section drive motor, 31
...X-axis stepping motor, 41...
・Concentration detection unit, 43...Objective lens, 51...
... Tungsten lamp, 58 ... Photomultiplier tube, 59 ... Aperture plate, 62 ... Aperture plate rotation solenoid. Applicant Fuji Xerox Co., Ltd.

Claims (1)

[Scope of Claims] 1. An optical density measurement device for image inspection that includes an illumination means and a photoelectric conversion means and detects the optical density of an image interposed between the illumination means and the photoelectric conversion means. An optical density measuring device for image inspection, characterized in that a sampling width for detection is set to be smaller than visual resolution. 2. The optical density measuring device for image inspection according to claim 1, wherein the area for detecting the optical density is determined to be a rectangular area smaller than the visual resolution. 3. The optical density measuring device for image inspection according to claim 2, wherein the rectangular area is a square. 4. The optical density measuring device for image inspection according to claim 2, wherein the rectangular area is a rectangle.