JPH0814535B2 - Optical density measuring device for image inspection - Google Patents

Description

The present invention relates to an optical density measurement for image inspection used in an image inspection apparatus for inspecting the quality of an image reproduced by, for example, a facsimile machine, a printing machine or a copying machine. Regarding the device.

"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 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.

The above-described conventional inspection has the following problems because the inspector is the main subject.

(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 has been proposed (Japanese Patent Laid-Open No. 59-103464 and Japanese Patent Laid-Open No. 59-103464).
-103465 publication).

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, density and resolution of the image are digitized based on the detection data.

However, in the proposed image inspection apparatus, a line sensor (image sensor) or a combination of a low densitometer and a high densitometer is used for the detection unit. For this reason, the smallest measurable area has to be considerably larger than the smallest humanly perceptible area. Therefore, with this image inspection apparatus, although it is possible to obtain somewhat good measurement results for the optical density in a uniform density area and the resolution in an extremely high-quality image portion, it is possible to obtain results that humans feel in image inspection under other conditions. There was a case where a large gap was generated.

 The cause will be described below.

FIG. 17 is an enlarged view of a part of the chart for resolution inspection. Thus, 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 and the white background color portion 202 of the background. Is to be inspected.

FIG. 18 is a further enlargement of a part of this chart, and FIG. 19 shows a sample copy image of the copying machine corresponding to this. Here, FIG. 19A is an example in which relatively large unevenness is generated in the boundary region between the ground color portion 202 and the black line 202, and FIG. 19B is an example in which toner is scattered at these boundary portions. . Further, FIG. 6C shows an example in which a blank area 203 in which toner is not attached occurs inside the black line 201. In addition, various states such as a case where the density of the black line 201 does not change at the boundary portion at one time but changes stepwise, or a shade occurs inside the black line 201, and the like appear. Such a delicate state of an image becomes a relatively large factor in image quality evaluation.

By the way, FIG. 20 shows the signal level of the read image signal when the contour of the black line is uneven as shown in FIG. 19A, for example. This image signal 205 is the first
This is a signal obtained by scanning the chart shown in FIG. 7 in the horizontal direction in the figure, and corresponds to, for example, FIG. 4 of JP-A-59-103465. The signal part 20 shown in broken lines in this figure
Reference numeral 5'denotes an image signal obtained by scanning the protruding portion of the black line 201 in FIG. 19A, and the waveform is thicker 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 one-dot chain line 207 in the figure and the image is inspected, the evaluation as the resolution is the same in both cases. 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. 21 shows an image signal for the image state shown in FIG. 19R, and FIG. 22 shows an example of the 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 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. 22 shows the opposite case, that is, the blank area 2 existing in the black line 201.
Due to 03, the signal level at the portion indicated by arrow 209 is lowered. 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.

Therefore, an image automatic inspection apparatus has been proposed, which can perform an inspection that is almost equivalent to what an image inspector feels visually.

Japanese Patent Application No. 61-142976 filed on June 20, 1986
The issue has that description.

In this Japanese Patent Application No. 61-142976, the optical density of an object to be inspected is inspected using an opening of 10 μm × 500 μm. As a result, several inspection items of the inspection object can be inspected with an image at a level almost equal to the human interval.

"Problems to be Solved by the Invention" By the way, at the design or research stage of a copying machine or the like, it is necessary to perform image evaluation with an accuracy higher than human vision. However, the conventionally proposed optical density measuring device for image inspection has a limit for such highly accurate image evaluation, and it has not been possible to perform a sufficient inspection.

Further, when a plurality of different patterns are present in the measurement sample, it is difficult for the conventional device to perform highly accurate image evaluation unless an opening corresponding to each pattern is used.

For example, assume that a line pattern 211 as shown in FIG. 23A exists. In this case, this line pattern is inspected with the rectangular opening 212. If the width of the opening 212 is larger than the thickness of the line pattern 211 as shown in this figure, the detected signal level is the threshold TH as shown in FIG.
Will be lower than. That is, in the example shown in FIG. 23A, an accurate optical density cannot be known unless the opening has a width equal to or smaller than the thickness of the line pattern 211.

Another example will be described with reference to FIG. FIG. 24A shows a case where the optical density of a dot 213 of a certain size composed of a set of several toner particles is measured. Also in this case, if the opening 212 is larger than the size of the dot 212, sufficient optical density cannot be obtained as shown in FIG.

In the technique disclosed in the above-mentioned Japanese Patent Application No. 61-142976, 10
All samples were measured using one opening of μm × 500 μm. Therefore, as shown in FIG. 23 and FIG. 24B, there is a problem that the measurement may be performed at a density lower than the actual optical density.

Therefore, an object of the present invention is to provide an optical density measuring device for image inspection, which is capable of measuring the optical density suitable for various patterns in a sample to be measured.

"Means for Solving Problems" In the present invention, (i) a light source for illuminating a measurement site of an image, and (ii) photoelectric conversion of a light beam incident from the measurement site as data for optical density detection. And (iii) an optical density inspection area switching means capable of switching the type of each unit inspection area to be converted by the photoelectric conversion means to a plurality of types. Let That is, when the unit inspection area is set by the opening of the optical system, the size and shape of the opening can be selected to be a desired one, so that an optical pattern suitable for various patterns in the sample to be measured can be selected. Allows measurement of concentration.

Here, the optical density inspection area switching means includes a pattern determination means for determining the measurement target pattern and an inspection area setting means for selecting the type of the unit inspection area according to the determination result of the pattern determination means, Enables automation of measurement.

It is desirable that the sampling width for detecting the optical density is set so as to match the unit inspection area switched by the optical density inspection area switching means and smaller than the visual resolution.

Taking the case of measuring toner particles as an example,
As the unit inspection area, a rectangular area smaller than the size of the toner particles, a rectangular area about the size of the toner particles, and a rectangular area larger than the rectangular area can be prepared. When a rectangular area having a size larger than the toner particles is used, if it is too large, the noise level with respect to the level of the image signal obtained from the photoelectric conversion means increases and the S / N ratio deteriorates. Also, if the unit inspection area is too large, the sensitivity will be worse than the visual resolution, so
It is also necessary to pay attention to this point.

The unit inspection area for detecting the optical density is a circular area, a rectangular area, or another shape area smaller than the visual resolution. In the case of a rectangular area, it may be square or rectangular.

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

Outline of Apparatus FIG. 1 shows an appearance of an optical density measuring apparatus for image inspection according to an embodiment of the present invention. This optical density measuring device for image inspection comprises an inspection unit 1, a computer unit 2 and a printer unit 3.

Of these, the inspection unit 1 uses the copy paper 4 as the inspection object.
Is a part for continuously inspecting. 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, and a power switch 11, a moving key 12 used when manually specifying an inspection object pattern and density data as a measurement result are displayed. A display 13 is 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, and a disk drive device for driving a floppy disk.
Equipped with 17 etc., CPU for data processing inside
(Central processing unit) etc. are installed.

The printer unit 3 is a unit that outputs inspection results and the like.
In this embodiment, a dot printer is used.

FIG. 2 shows an outline of the inspection section of the optical density measuring device for image inspection. The shaft 21 for rotating the feed roller 7 of the inspection unit 1 is adapted to receive the transmission of 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. Feed roller 21 in this state
Is rotated by a predetermined amount, only the uppermost copy sheet 4 is fed out. Prior to this feeding, the chart holding portion 8 has its surface uniformly charged by a charging mechanism (not shown). As a result, the copy paper 4 sent out is electrostatically adsorbed to the chart holding unit 8. The rotation of the cylindrical chart holder 8 in the circumferential direction (Y-axis direction) is
This is performed by the driving force of the chart holding unit drive motor 26 connected to the speed reducer 25.

In this embodiment, the outer diameter of the chart holder 8 is 162.77.
mm and the step angle of the chart holder drive motor 26 is 0.
5 degrees or 1.8 degrees, and the reduction ratio of the speed reducer 25 was 1/256. 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 in the Y-axis direction by 5 μm or 10 μm. The control of the rotational position of the chart holding unit 8, that is, the position control in the Y-axis direction is performed with 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 two guide bars 35 arranged parallel to the ball screw 32,
Guided by 36, it moves in the X-axis direction.

In this embodiment, the pitch of the ball screw 32 is 5 mm. With the configuration in which the step angle of the X-axis stepping motor 31 is set to 0.36 degrees or 0.72 degrees, the optical head mounting block 33 moves in the X-axis direction by 5 μm or 10 μm in one step of driving. Two limit switches 37 and 38 are arranged in the X-axis direction, and the optical head mounting block
It is designed to limit the movement range of 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 manual operation.

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 in 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 visual field adjusting mechanism 56, is corrected in wavelength component by a color correction filter 57, and is incident on a photomultiplier tube 58.
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 aperture plate 59 is a rotatable disc as shown in FIG. 4, in which four types of aperture regions 60-1 to 60-4 are arranged. In the first opening area 60-1, 25 μm × 25 μ
The opening of m is set. Second opening area 60-2
Has an opening of 50 μm × 50 μm. Third
In the opening area 60-3, an opening of 50 μm × 500 μm is set. 50 μm in the fourth opening region 60-4
An opening of × 1250 μm is set. In each of the opening regions 60-1 to 60-4, the image of the measurement site on the copy sheet is magnified 5 times and formed. Then, on the chart, that is, in this embodiment, a light beam reflected from a rectangular area (unit inspection area) having long sides of 5 μm, 10 μm, 100 μm and 250 μm and short sides of 5 μm or 10 μm on the copy paper 4 passes through this opening. Then, the light is incident on the photomultiplier tube 58 described above. As for the aperture plate 59, the aperture region corresponding to the object to be measured is selected by the aperture selection step motor 62-1 shown in FIG. 3, and the longitudinal direction of the aperture is set to an arbitrary angle by the aperture plate rotation step motor 62-2. It is supposed to be done.

The other light split by the prism 54 has its traveling direction changed by the roof prism 64, and the observation screen
The image is formed as an erect image on 65. The image of the measurement site 53 thus formed can be magnified and observed by the magnifying eyepiece 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 optical density measuring device for image inspection. This device 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. Measuring means
The control unit 73 controls the measurement control unit 73 to inspect the surface to be inspected and detect 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 be displayed on the CRT screen of the computer unit 2.

The operation of the optical density measuring device for image inspection will be described in more detail. In the optical density measuring device for image inspection, the type and the inspection item of the inspection object 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 includes 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 representing a representative position of the pattern to be inspected.
Outputs 87. 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 the pattern to be inspected and the operation processing code 89 representing the operation processing procedure are used for measurement control. It will be read by the means 73.

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 88
Is sent to the measuring means 76. The measurement means 76 is a measurement control means
After moving to the representative point position 87 designated by 73, the image density to be measured is detected 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 string 91 to instruct the start of arithmetic processing.

Upon receiving the end signal 92, the arithmetic processing means 78 selects the arithmetic processing routine corresponding to this based on the arithmetic processing code 89 supplied before from the measurement control means 73. Then, this arithmetic processing routine is loaded into the internal arithmetic processing routine memory area. In the arithmetic processing means 78, the above-mentioned density data string 91 is stored in the density data string memory area. The arithmetic processing means 78 processes the density data sequence 91 by the routine loaded in the arithmetic processing routine memory area, and outputs the result according to the inspection item as the inspection result 93.
Supply to 83. The output means 83 will output this content.

The image density detection and the calculation processing of the density data described above are sequentially performed for all the inspection patterns preset in the measurement control unit 73. The arithmetic processing means 78 performs arithmetic processing on each pattern and also statistical processing of arithmetic processing results corresponding to all the set patterns to be inspected. In this way, the desired inspection result for the inspection object can be 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. Each chart 102 and inspection item 103 input by the operator are coded by this 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 is a chart code
84 is supplied to the pattern information storage position searching means 107. The pattern information storage position retrieval means 107 retrieves 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 position of each pattern represented by these pattern codes. . In this figure, for example, for the chart code "XXX", three pattern codes a, a,
b is prepared. This is this chart code "XX
This means that two types of patterns specified by pattern codes a and b are displayed on the chart specified by X ", and the coordinates of the three patterns are as shown in the representative point position. ing.

Here, the pattern represented by the pattern code a is, for example, the Electrophotographic Society test chart “No. 1-R”.
This is a pattern for resolution measurement (not shown) in 1975 ". In this test chart, this pattern is arranged in the upper left and lower right parts. Also, the pattern represented by the pattern code b is this electronic photograph. This is a pattern for density measurement in an academic conference test chart.In this test chart, various density samples are displayed in a row below the test chart, which constitutes a pattern for density measurement.

The pattern information output means 110 includes a pattern information storage unit 108.
The contents stored in the pattern information storage position searching means 107
Is read from the position indicated by the pointer 109 output by The read contents are all patterns related to one chart code indicated by the pointer 109.
The codes and their representative point positions are shown. The combination of pattern code 86 and representative point position 87 for this is
The data is sequentially read 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 detected by the inspection item code detecting means 112, and the pattern code 86 is the pattern detecting means 11
Detected by 3. The detection result of the inspection item code detection means 112 is used as the first pointer 114 by the processing code storage means 1
And the detection result of the pattern detection means 113 is output to the second
It is also output to the processing code storage means 116 as the pointer 115 of.

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. First output from the inspection item code detection means 112 described above
An inspection item code for specifying an inspection item is designated by the pointer 114 of the. And the pattern detection means 113
The operation processing code in the inspection item code is selected by the second pointer 115 output by. In the example shown in FIG. 10, for the pattern specified by the pattern code “a”, the image density detection specified by the image density detection code “a” and the arithmetic processing specified by the arithmetic processing code “A” are performed. You know that it will be done. The code contents designated by the two pointers 114 and 115 are stored in the processing code storage means 116.
It is temporarily stored in the internal storage area.

Returning to FIG. 9, the explanation will be continued. Inspection procedure search means 11
Reference numeral 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 score, (v) opening type, and (v
i) Slit direction.

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) Opening type is the type of opening selected for the sample. As shown in FIG. 4, since the aperture plate 59 of this embodiment is provided with four types of aperture regions 60-1 to 60-4, the aperture plates are 25 μm × 25 μm and 50 μm.
It is possible to select one from four types of openings of x50 μm, 50 μm × 500 μm and 50 μm × 1250 μm. (Vi) The slit direction means the direction of the opening of the opening plate 59 shown in FIG. In this embodiment, the opening is set parallel to the X axis or parallel to the Y axis rotated by 90 degrees.

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 uses the image density detection format 8 selected by the third pointer 119.
8 is read out and supplied to the measuring means 76 under the control of the measuring control means 73 shown in FIG. On the other hand, the second code output means 123 reads 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) FIG. 12 below shows the contents of the measuring means.

The measuring means 75 is roughly divided into three parts, (i) an image density detecting section, (ii) a detection aperture control section, and (iii) a moving section.
It can be divided into two parts. At the measurement output terminal 75,
On the basis of the image density detection format 88 supplied from the measurement control means 73, the object to be inspected (copy paper 4 on which the chart is copied in this embodiment) is moved to detect the image density in a predetermined format. It will be. That is,
The image density detection format 88 (see FIG. 11) supplied from the measurement control means 73 is supplied to the data sampling control unit 131, and based on the format 88 decoded here,
The image density detection unit, the detection aperture control unit, and the moving unit are controlled.

The data sampling control unit 131 grasps the current position of the light receiving unit 133 based on the data 133 obtained from the drive control unit 132. Therefore, the data sampling control unit 131 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. 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
Similarly, it is supplied to a chart holding unit drive motor 26 (both see FIG. 2) as 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.
The light receiving means 133 composed of 58 or the like moves to a desired measurement position.

The data sampling control unit 131 next detects the image density, the sampling interval, the total number of sampling points,
Decode the type of opening and the slit direction. Then, first, the type of pattern to be measured is detected, and it is determined whether or not the currently set opening is suitable for this. This determination result is the opening type selection signal 137-
It is output as 1. The opening type selection signal 137-1 is
It is supplied to the opening type selection signal generator 138. The opening type selection signal generator 138 is an opening selection step motor 62-
The drive signal 137-2 is sent to the control unit 1 to select a desired opening from the four types of opening areas 60-1 to 60-4 of the opening plate 59.

Next, the data sampling control unit 131 compares the instructed opening direction and the current opening direction for the selected opening 60, and outputs the angle signal 137-3 representing the comparison result with the instructed angle. The angle signal 137-3 is supplied to the angle signal generator 139. The angle signal generator 139 sends a control signal to the aperture plate rotation step motor 62-2 (see FIG. 3).
141 will be provided to rotate the selected opening 60 by the desired angle.

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,
set.

The drive control unit 132 moves the concentration 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 143 output from the light receiving unit 133 is amplified by the amplifier 144 in the image density detection unit, and its output 145 is obtained.
Is logarithmically converted by the logarithmic converter 146. Conversion output 147 is A / D
It is supplied to the converter 148. The A / D converter 148 uses the A / D signal generator 149 to specify an A / D converter for specifying the time at which the A / D converter operates.
The D signal 151 is supplied. The A / D signal generator 149 receives the A / D signal supplied from the data sampling controller 131.
The A / D signal 151 is generated by the D start signal 152, but the A / D
The start signal 152 uses the output of a counter (not shown) in the data sampling control unit 131.

That is, the counter is preset with a count value corresponding to the measurement start position.
The count value increases with the start of movement of 133. Then, when the count value of the counter reaches the preset value, the A / D start signal 152 is output. When the A / D conversion ends, the A / D signal generator 149 outputs the end signal 153. When the data sampling control unit 131 receives the end signal 153,
The light receiving means 1 is provided to the drive control unit 132 by managing the counter described above.
The movement of 33 is instructed, and the next A / D start signal 152 is output at a predetermined timing when necessary.
In this way, it becomes possible to manage the sampling interval of the density data.

On the other hand, when A / D conversion is instructed by the A / D signal 151, A
The / D converter 148 converts the converted output 147 from analog to digital. The converted density data 154 is the image density buffer 155.
Are stored in sequence. 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. The measurement control means 73 outputs this end signal 156.
Data, the data for the next block is converted into the image density detection format 88 and the data sampling control unit
Supply to 131. In this way, the concentration data is collected for each part to be measured.

(Arrangement of Arithmetic Processing Means) FIG. 13 shows the arrangement of the arithmetic processing means. The arithmetic processing means includes an arithmetic control unit 161. The arithmetic processing section 89 is supplied with the arithmetic processing code 89 from the measurement control means. The arithmetic processing code 89 is a code representing an arithmetic processing procedure. The arithmetic control unit 161 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 means 163 searches the arithmetic processing storage unit 164 using this arithmetic processing code 162. The arithmetic processing memory unit 164 stores arithmetic processing data groups necessary for various inspections. Arithmetic processing address searching means 163
Moves the pointer 165 to the start address of the corresponding memory area by searching, and sends the end signal 1 to the arithmetic control unit 161.
Sends 66. The arithmetic control unit 161 receives the end signal 166,
A start signal 167 is generated and supplied to the loader starter 168.

When the loader / starter 168 receives the start signal 167, it generates load signals 169 and 171. Then, (i) the series of arithmetic processing contents 172 indicated by the pointer 165 in the arithmetic processing storage unit 164, and (ii) the image density buffer 155 of the measuring means (the twelfth
The density data string 91 stored in the working area 174 is loaded. After the loading is completed, the loader / starter 168 supplies the start signal 175 to the working area 174, activates it and transfers control to the working area 174 itself.

At the same time, a desired calculation process is performed on the density data sequence 91 in the working area 174. The result is the operation result
It is stored in the calculation result output buffer 177 as 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 optical density measuring apparatus for image inspection, first, the copy paper 4 is held in the chart holding unit 8 and positioned, and then the density is measured for each pattern. Therefore, next, the positioning with respect to the copy sheet 4 will be described, and then the density 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 at a predetermined coordinate position, the desired position on the copy paper 4 is ± 5 mm.
There is some error. This is due to the following reasons.

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

This includes an error in registration between the copy paper 4 and the photosensitive drum of the copying machine (misregistration),
In addition to the magnification setting error, an error due to skew (rotation) occurring when the copy sheet 4 is conveyed inside the copying machine is included. (Ii) Misalignment when set on the chart holding unit 8.

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

In this embodiment, the target position can be reached with an accuracy of ± 0.5 mm. To this end, the chart used in the optical density measuring device for image inspection as shown in FIG.
191 includes, for example, position detection patterns 192 to 19 at the three positions.
Placed 4 The coordinates of these position detection patterns 192 to 194 are grasped by the chart type on the image inspection optical density measuring device side. These patterns on the chart
The coordinate values of 192 to 194 will be called real coordinate values, and these will be represented by (X ₁ , Y ₁ , X ₂ , Y ₂ , X ₃ , Y ₃ ).

The apparatus scans the copy paper 4 around it using these actual coordinate values (X ₁ , Y ₁ , X ₂ , Y ₂ , X ₃ , Y ₃ ) and detects the density change of the image. The position on the copy paper 4 is detected. The coordinate values of these position detection patterns 192 to 194 on the copy paper 4 are (x ₁ , y ₁ , x ₂ , y ₂ , x ₃ , y ₃ ). By constructing the relational expressions of both coordinate systems (X, Y) and (x, y), the actual position (X ₀ , Y ₀ ) corresponding to the coordinate (x ₀ , y ₀ ) of the pattern to be measured on the copy paper 4 is obtained. ₀ ) is calculated, and the density detecting unit 41 is made to reach the target image portion using this coordinate value (X ₀ , Y ₀ ).

It is not necessary to arrange the position detection patterns on the copy sheet at three positions. For example, by arranging the position detection patterns at two positions, the rotation and the positional deviation of the copy sheet 4 can be grasped. 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.

(Pattern scanning) FIG. 15 shows a certain pattern for density measurement. In this pattern 221, point 223 is the representative point and point 22
4 is the detection start point in the X-axis direction. Detection start point 224
Are represented as relative coordinate values 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 optical density measuring device for image inspection of this embodiment, 25 μm × 25 μm, 50 μm × 50 μm, 50 μm ×
Select one of the four types of openings of 500 μm and 50 μm x 1250 μm, which results in 5 μm x on copy paper
5μm, 10μm × 10μm, 10μm × 100μm or 10μ
Reading is performed once by using a rectangular area of m × 250 μm as a unit inspection area. The reading mode is defined by the image density detection format shown in FIG. That is, in this example, the point 224 is the measurement start position and the measurement direction is the X-axis direction. The measurement interval, that is, the sampling width is determined by the purpose of measurement and the like. When the slit direction, that is, the longitudinal direction of the opening is set to the Y-axis direction, the concentration detection region for one time in the X-axis direction is 5 μm or 10 μm.
Therefore, when scanning the copy sheet 4 in the X-axis direction, the measurement interval is 5 μm or 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 the data that represents the minute image state as shown in Fig. 19, and by processing this, the human sense of density and resolution can be obtained. It is possible to discriminate closer to. 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 5 μm or 10 μm. As described above, in this embodiment, the X-axis stepping motor 31 or the chart holding unit driving motor 26 is advanced by one pulse each, so that the concentration detecting unit 41 is moved in the X-axis direction or the Y-axis direction in units of 5 μm or 10 μm. It can be moved.

As described above, in the optical density measuring device for image inspection of this embodiment, the object to be inspected is measured with the rectangular region as the minimum measurement range, so that the object to be inspected can be efficiently scanned without gaps.

The basic region to be measured does not have to be rectangular, and may be circular or elliptical, 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 measurement work 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 transparent light when inspecting the development state of a photographic film.

"Effects of the Invention" As described above, according to the present invention, a plurality of unit inspection areas for detecting optical density are prepared, and an appropriate one can be selected from these. Therefore, for example, for a large measurement area, 10 μm × 100 μm or 1
It is possible to select a rectangular area of 0 μm × 250 μm and make it 5 μm × 5 μm or 10 μm × 10 μm for a narrow measurement area. Of course, since the shape and size of the unit inspection area can be set variously, even for inspection targets including various patterns, it is possible to select the area according to that and measure the optical density, and to obtain accurate and stable results quickly. You will be able to get it.

[Brief description of drawings]

1 to 16 are for explaining one embodiment of the present invention, in which FIG. 1 is a perspective view of an optical density measuring device for image inspection, and FIG. 2 shows a main part of an inspection unit. Schematic configuration diagram, third
FIG. 4 is a layout explanatory view showing the layout of optical components of the optical head, FIG. 4 is an explanatory view showing the size of a region as a unit of measurement on the copy paper, and FIG. 5 is a circuit configuration of optical density measurement for image inspection. FIG. 6 is a block diagram showing the outline, FIG. 6 is a block diagram showing the configuration of the external signal input means, FIG. 7 is a block diagram showing the configuration of the pattern information storage means, and FIG. 8 is an explanatory diagram showing the configuration of the pattern information storage section. FIG. 9 is a block diagram showing the configuration of the processing procedure storage means, FIG. 10 is a block diagram showing the configuration of the processing code storage means, FIG. 11 is a block diagram showing the configuration of the inspection procedure storage means, and FIG. FIG. 13 is a block diagram showing the configuration of the measuring means, 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, and FIG. 15 is density measurement. Plan view showing an example of a pattern for FIG. 16 is an explanatory view showing an example of scanning in the X-axis direction, FIG. 17 is a plan view showing an enlarged part of the resolution inspection chart, and FIG. 18 is a further illustration of the chart shown in FIG. A partially enlarged plan view, FIGS. 19A to 19C.
Is a partially enlarged plan view showing various states of the sample copy image, FIG. 20 is a waveform diagram showing the signal level of the image signal obtained by reading the image part shown in FIG. 19A, and FIG. 21 is FIG. 19B. 22 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. 22, FIG. 22 is a waveform diagram showing the signal level of the image signal obtained by reading the image portion shown in FIG. 19C, and FIG. FIG. 9B is a diagram showing a state of inspecting a conventional unit inspection area.
Is a characteristic diagram of a signal obtained by this inspection, FIG. 24A is an explanatory diagram showing how a group of dots is inspected in a conventional unit inspection area, and FIG. 24B is a characteristic diagram of a signal obtained by this inspection. Is. 1 ... Inspection unit, 4 ... Copy paper, 41 ... Density detection unit, 43 ... Objective lens, 51 ... Tungsten lamp, 58 ... Photomultiplier tube, 59 ... Aperture plate, 60-1 to 60 -4 ... Aperture area, 62-1 ... Aperture selection step motor

Continuation of the front page (56) References JP-A-63-174074 (JP, A) JP-A-61-209470 (JP, A) Actually developed JP-A-58-62250 (JP, U)

Claims (7)

[Claims] 1. A light source for illuminating a measurement site of an image,
A photoelectric conversion unit that photoelectrically converts a light beam incident from the measurement site as data for detecting optical density, and a plurality of types of each unit inspection region of the measurement site that is converted by the photoelectric conversion unit. An optical density measuring device for image inspection, comprising: an optical density inspection area switching means capable of performing the same. 2. The optical density inspection area switching means comprises pattern discrimination means for discriminating a pattern to be measured and inspection area setting means for selecting the type of the unit inspection area according to the discrimination result of the pattern discrimination means. The optical density measuring device for image inspection according to claim 1, wherein 3. The sampling width for detecting the optical density is set so as to match the unit inspection area switched by the optical density inspection area switching means, and is smaller than the visual resolution. An optical density measuring device for image inspection as set forth in claim 1. 4. The optical density measuring device for image inspection according to claim 3, wherein the unit inspection area for detecting the optical density is a circular area smaller than the visual resolution. 5. The optical density measuring device for image inspection according to claim 3, wherein the unit inspection area for detecting the optical density is a rectangular area smaller than the visual resolution. 6. The optical density measuring device for image inspection according to claim 5, wherein the rectangular region is a square. 7. The optical density measuring device for image inspection according to claim 5, wherein the rectangular region is rectangular.