JP2835047B2 - Reading waveform inspection device for image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a reading waveform inspection apparatus of an image reading apparatus which inspects a reading image waveform of an image reading apparatus and performs an automatic product inspection. .

(Prior Art) In a facsimile, an image scanner, or the like, an image reading device portion for reading an image is a line type (one-dimensional array) in which a plurality of minute imaging elements are arranged in a line at a high density of, for example, 16 dots / mm. ) Is configured using the image sensor. Then, while sending the original to such a line type image sensor in a direction orthogonal to the original,
An image of a document is read at each imaging element position, and is sequentially sent out in the form of an image signal corresponding to the density information, thereby obtaining an image signal continuous in a pixel position order in units of one line. By the way, in such an image reading apparatus, since an image signal is obtained by a line-type image sensor which is an aggregate of an extremely large number of imaging elements, variations in characteristics of each imaging element become a problem. That is, if the readout characteristics of the individual imaging elements are not uniform to some extent, the reproducibility of the obtained image becomes poor,
Resolution and fidelity are compromised. Therefore, it is necessary to inspect the output image signal of the image reading apparatus, measure the variation, determine the quality, and perform product selection and output correction.

Conventionally, when performing this type of inspection, for example, an image waveform obtained by reading an original image of a white pattern is input to a synchroscope, and an inspector visually observes the displayed waveform. The observation waveform obtained in this case is as shown in FIG. 2, and the fine fluctuation indicates the white level output of each imaging element. Therefore, it is possible to roughly know the state of the variation of the imaging element and the state of the shift of the overall white level, and it is possible to judge whether or not the quality is good. Therefore, only subjective inspections, which are influenced by factors such as the above, could not be carried out to perform physically precise objective waveform inspections. That is, in the waveform observation by the synchroscope, it is not possible to precisely calculate the uniformity, resolution, and reading width of the waveform. Also,
It is difficult to handle the waveform inspection using a high-frequency synchroscope, and the price of the measuring instrument is high.

(Problems to be Solved by the Invention) As described above, the inspection of the read image waveform for knowing the quality and characteristics of the conventional image reading apparatus is a visual inspection for observing the image waveform output from the image reading apparatus with a synchroscope. Therefore, the inspection is performed subjectively by the inspector, and accordingly, the inspection result also has individual differences, and is easily affected by the angle at which the waveform is viewed and the degree of concentration. In addition, waveform inspection using a high-frequency synchroscope is difficult to handle, and is greatly affected by measurement results. In addition, there is a problem that the price of a measuring instrument is high. In addition, objective waveform inspection cannot be performed, and precise calculation of waveform uniformity, resolution, and reading width cannot be performed. Objective performance measurement means that you can objectively know the performance of a product.It is not only important for product quality control, but also a technology for product improvement and performance improvement. Since it is also important as a material, development of an inspection device capable of realizing such objective precision measurement is expected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of reading an image reading device such as a line-type image sensor, in which the performance of the image reading device can be objectively measured and necessary physical information can be easily obtained. It is to provide a waveform inspection device.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows. That is, storage means for receiving and sequentially storing the output image signals of the image reading apparatus which has read the reference pattern, and reading out the information stored in the storage means and inputting the signal between adjacent pixels of the received image signal. Means for sequentially searching for extreme-point pixels by comparing values, and searching for a singular pixel that deviates beyond a predetermined range from the average value of the signal values of the searched pixels, and a limited pixel located before and after this singular pixel. Correction means for obtaining a corrected image signal by obtaining an average value of the signal values of the predetermined number of pixels and replacing the specific pixel with the average value, the corrected image signal obtained by the correction means The uniformity and resolution of signal values taken by each pixel are calculated, and the calculated values are compared with a predetermined standard value to determine and output an inspection result.

(Operation) The present apparatus having such a configuration sequentially stores the image signals obtained from the image reading device that has read the reference pattern in the storage means, reads out the image signals, and indicates the abnormal value in the image signals by the correction means. After correcting the signals of a small number of pixels to an average value, the calculating means calculates the uniformity and resolution of the read signal from the corrected image signal, and compares them with predetermined standard values by the determining means to determine the inspection result. Output. Therefore, in the evaluation, the number of the pixels is small and the influence on the entire screen formation is small, but the value of the uniformity can be calculated by suppressing the influence of the abnormal pixel which has a large influence on the measurement result. Independent of individual differences and observation conditions,
Objective inspection with high reproducibility according to the actual situation becomes possible.

As described above, since the present invention is not a visual inspection using a synchroscope but a measurement inspection based on numerical processing, a precise inspection result can be obtained, and the inspection result may vary due to individual differences or differences in work conditions. As a result, inspection results at a certain level can be obtained, and stable product management can be performed. In addition, a reading image inspection device of an image reading device that has features such as easy collection and processing of inspection results is provided. Can be provided.

Further, according to the present invention, when inspecting a specific pixel, a pixel which deviates from the average value by more than a predetermined range is set as a specific pixel. Therefore, not only a pixel having an abnormally low signal level but also an abnormally large pixel is searched as a specific pixel. Can be
As a result, a black pixel due to dust or an abnormal white pixel due to irregular reflection such as a scratch can be detected as a specific pixel without fail.

Further, according to the present invention, when removing a peculiar pixel, an average value of signal values of a limited number of pixels located before and after the peculiar pixel is obtained, and the peculiar pixel is replaced with this average value. For this reason, even in the case where the pixel level of one line varies depending on the area due to the influence of lens distortion or the like, according to the present invention, the pixel level is corrected to an appropriate pixel level considering only the peripheral pixel level of the specific pixel. Can be. On the other hand, for example, if a singular pixel is simply deleted or corrected based on the average value of all pixel levels in one line, the corrected singular pixel level will be significantly different from the level of its surrounding pixels. As a result, the pixel remains as an abnormal pixel and adversely affects the determination of uniformity or the like.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the present apparatus.
In the figure, reference numeral 1 denotes an input image signal which is an image signal read by an image reading device; 2 denotes a measuring instrument for waveform observation such as a synchroscope for displaying a waveform of the input image signal 1 input;
Reference numeral 3 denotes an amplifier which receives the input image signal 1 and corrects and amplifies the input image signal 1. Reference numeral 4 denotes an A / D converter which converts the output of the amplifier 3 into digital data. Reference numeral 5 denotes a clock control unit. Reference numeral 6 denotes an A / D converter. The storage unit stores output data of the converter 4. The A / D converter 4 and the storage unit 6 perform A / D conversion and fetch conversion data in synchronization with a clock signal output from the clock control unit 5. Reference numeral 7 denotes an arithmetic control unit which is configured by, for example, a microcomputer or the like which performs data processing on the data stored in the storage unit 6, analyzes and tabulates, and inputs / outputs and displays data. A CRT display 9 for displaying the display output information as an image, and a keyboard 9 for inputting data and commands to the arithmetic and control unit 7.

In such a configuration, for example, when a read image signal 1 for a white pattern original image is input from an inspection target image reading device using a line type image sensor, the image signal as shown in FIG. While the waveform is observed, it is input to the amplifier 3 and amplified.

Here, in the measuring device 2, the inspector performs a rough waveform observation as described in FIG. 2 (a pass / fail inspection by grasping the overall tendency). In the amplifier 3, the A / D converter 4
The offset adjustment and the level adjustment are performed so as to meet the input condition of (1). The image signal that has passed through the amplifier 3 is sent to an A / D converter 4, which converts the image signal into digital data for each image in the original image signal while being controlled by a clock control unit 5. To the storage unit 6 for storage. The data of the image signal stored in the storage unit 6 is sent to the arithmetic control unit 7, and the arithmetic control unit 7 shows the singular point of the waveform indicated by the reference numeral 10 in FIG. The lowest point is searched for and corrected to signal waveform data as shown in FIG. 4 in which this is corrected to a nearby average value. Then, the arithmetic control unit 7 further performs the fourth
The uniformity of the image signal is calculated from the reading width and resolution indicated by reference numeral 13 in the drawing and the distribution width of the data indicated by reference numeral 14, and it is determined whether or not these are within a predetermined standard range. This inspection result is output to and displayed on the CRT display 8, filed in an external storage device (not shown), and output to a printer (not shown).

Here, the waveform analysis by the arithmetic control unit 7 will be described in more detail. The image signal data is read from the storage unit 6 into the arithmetic control unit 7, and the image signal data at the read stage is the original image signal as it is without any correction. This is schematically shown in FIG. 3, which directly reflects the difference in the output characteristics of the individual imaging elements. However, FIG. 3 shows an image signal for a white pattern, where 10 is a singular point, 11
Is the upper limit point, 12 is the lower limit point, and 13 is the reading width. The singular point 10 is an image that is shifted by a predetermined value or more from the average value of the poles of a predetermined number of images before and after the image, the upper limit point 11 is a pixel at the upper limit in the image signal, and the lower limit. Point 12, on the contrary, is the lowest pixel in the image signal. The read width 13 is a pixel obtained by subtracting a dummy pixel from the entire image signal. In general, the image sensor has a lens on the input surface side to form an image of a pixel, and the output of the image sensor in both side regions of the image sensor which is out of the image formation region by the lens. In the case of a contact type without using a lens, the reading width 13 does not matter.

For such image signal data, the singular point 10, the upper limit point 11, the lower limit point 12, and the reading width 13 are examined, and the data is obtained and the singular point 10 is removed. 12
And make corrections. The corrected white level image signal data is schematically represented as a waveform shown in FIG. 4, and the arithmetic control unit 7 uses the corrected data to obtain a range 14 indicating white level uniformity, a reading width 13, and a resolution. Is calculated. The calculated value is compared with a predetermined standard value given to the arithmetic control unit 7 to make a determination, and the result is displayed.

FIG. 5 is a diagram for explaining a data correction method in the arithmetic control unit 7. In the figure, 15 is the upper limit pole, 16
Is a lower limit pole, 17 is a pixel at an intermediate level, 18 is an average value of 10 upper and lower poles for each of the front and rear, and is a value obtained by correcting the singular point 10. Here, the maximum value where the image signal data rises, that is, the maximum value is the upper limit pole 15, and the minimum value where the image signal data falls conversely is the lower limit pole 16, which are many as shown in the figure.

The method of correcting the singular point 10 will be described. First, as shown in FIG. 5A, an upper limit pole 15 and a lower limit pole 16 are found.
This compares the data of the preceding and following pixels, finds the maximum value of the rising image signal data, stores it as the pixel of the upper limit pole 15 each time it is found, and conversely, the minimum value of the falling pixel Each time the
Are stored as pixels. In this way, the data of the preceding and succeeding pixels are sequentially compared, and the pixels indicating the upper and lower extreme points 15, 16 are obtained in order, ignoring the pixels indicating the value of the intermediate level 17. Next, a singular point 10 is found from these.
For this, a predetermined standard value is set, and a value exceeding that value is applied. Using these singular points 10, upper limit poles 15, and lower limit poles 16, the singular points 10 as shown by reference numeral 18 in FIG.
The average value of the upper limit poles 15 (or the lower limit pole 16 in the case of the lower limit singular point) of each of ten values before and after the singular point is calculated from the value of. In addition, the calculation of the reading width is obtained by finding the pixels showing the lowest value in the regions at both ends and calculating the number of pixels between them. For the singular point, the upper limit pole, and the lower limit pole, sort the data of the upper limit pole 15 and the lower limit pole 16 in FIG. 5 by the sorting method and find the maximum value from the upper limit pole 15 and the minimum value from the lower limit pole 16 Find out by doing.

As a result, in the evaluation, it is possible to calculate the values such as the reading width and the uniformity while suppressing the influence of the data of the singular point 10 having a small number and having a small influence on the entire screen formation, and an inspection with high reproducibility in accordance with the actual situation. Will be possible.

As described above, in the present apparatus, a storage means for receiving an output image signal of an image reading apparatus which reads a reference pattern such as a white pattern and sequentially storing the output image signal, and reading and inputting information stored in the storage means to input and receive the received image Means for sequentially searching for extreme pixels by comparing signal values between adjacent pixels of the signal, and searching for specific pixels that deviate beyond a predetermined range from the average value of the searched signal values of each pixel, Correcting means for obtaining a corrected image signal by calculating an average value of signal values of a limited number of pixels located before and after the specific pixel and replacing the specific pixel with the average value. Calculate the uniformity and resolution of the signal value taken by each pixel based on the corrected image signal obtained by the above, compare the calculated value with a predetermined standard value set in advance to determine and output an inspection result. Is Therefore, based on the white level image signal obtained by reading the white pattern, the signal of a small number of pixels indicating an abnormal value is corrected to an average value, and then the read width of the image reading device and the uniformity of the read signal are obtained from the corrected image signal. , The resolution is calculated and compared with a predetermined standard value, and the inspection result is determined as to whether or not it is a non-defective product within a predetermined standard range.
In the evaluation, the number of pixels is small and the influence on the overall screen formation is small, but the value of the reading width, uniformity, etc. can be calculated by suppressing the influence of abnormal pixels which have a large effect on the measurement result. This makes it possible to carry out an objective test with high reproducibility and in accordance with the actual situation, without being influenced by individual differences or observation conditions.

The present invention is not limited to the embodiment described above and shown in the drawings, and can be carried out by appropriately modifying it without departing from the scope of the invention. In particular, measurement items and calculation conditions are appropriately set. Can be used. In addition, the reference pattern is not limited to the white pattern, and the target image reading device is not limited to the line-type image sensor, but can be applied to a two-dimensional array.

[Effects of the Invention] As described above, according to the present invention, since the measurement inspection is not a visual inspection using a synchroscope but a numerical processing, a precise inspection result can be obtained. Images that have characteristics such that inspection results at a certain level can be obtained without variation due to differences in the product, stable product management can be performed, and inspection results can be easily collected and processed. A read image inspection device of the reader can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a read image signal of an image reading apparatus, and FIGS. 3 to 5 are views for explaining an embodiment of the present invention. FIG. 1 ... input image signal, 2 ... measuring instrument, 3 ... amplifier, 4
... A / D converter, 6 ... Storage unit, 7 ... Calculation control unit, 8 ... CRT display, 10 ... Singular point, 11 ... Upper limit point, 12 ... Lower limit point, 15 ... Upper limit pole, 16… Lower limit pole.

Claims (1)

(57) [Claims] A storage means for receiving and sequentially storing output image signals of an image reading apparatus which has read a reference pattern, and reading and storing information stored in the storage means and inputting each pixel adjacent to the received image signal. Means for sequentially searching for extreme pixels by comparing signal values between the pixels; and searching for a singular pixel that deviates beyond a predetermined range from an average value of the searched signal values of each pixel, and that is located before and after the singular pixel. Correcting means for obtaining a corrected image signal by obtaining an average value of the signal values of a limited number of pixels to be limited and replacing the specific pixel with the average value; and a corrected image signal obtained by the correcting means. Calculating means for calculating the uniformity and resolution of the signal value taken by each pixel; means for comparing the calculated value with a predetermined standard value to determine an inspection result; means for outputting the determination result When Reading waveform inspection system of the image reading apparatus characterized by comprising.