JP2002288635A - Image inspection device and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image inspection device for correcting and collating slippage quantity by finding the slipping quantity of each of data, by analyzing the respectively read data by using a statistical method, when a print picture image, etc., on a recording medium pass two points and an imaging device furnished with the image inspection device. SOLUTION: An image reading sensor for providing an inspection data by reading the printed image, two sensors for speed detection to provide each of the data for speed detection by reading the changes in the gradation of a recording medium surface which are arranged with a specified interval in the moving direction, a speed change computing part for computing the rate of change of speed of the recording medium according to the data for speed detection and an inspection data and image data are collated in consideration of the speed change computed in the rate of change of speed computing part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image inspection apparatus for inspecting the quality of an image printed on a sheet and an image forming apparatus having the image inspection apparatus.

[0002]

2. Description of the Related Art Conventionally, an image printed by a copying machine, a printer, or the like is inspected using an automatic image inspection apparatus or the like.

An automatic image inspection apparatus generally uses a teaching image obtained from image data as a template, performs template matching based on read electronic data on a printed image to be inspected, obtains a residual, and obtains a residual. If the difference is large, it is determined that the printed matter has white spots or stains, and the presence or absence of a defect in the printed image is determined.

However, the position of the actually printed image does not have to be arranged at the same position in a strict sense as compared with the position of the teaching image, and it is necessary to allow a certain amount of deviation.

[0005] Japanese Patent Application Laid-Open No. 1-23818 discloses that when inspecting a traveling printed matter, a rotary encoder is attached to a drive system of the traveling printed matter to measure a speed fluctuation, and when the speed fluctuation is a predetermined value or more, a comparison is made. A technique has been disclosed in which target reference value data is rewritten in a memory so that the write positions of the reference value data and the inspection value data in the memory are matched.

[0006] According to this technique, it is possible to reduce the collation error caused by the speed fluctuation of the running printed matter.

Further, Japanese Patent Application Laid-Open No. 3-71263 discloses that
When comparing the inspection data with the reference data, the relative position of the reference data is set to 1 within the allowable range of the positional deviation.
A technique has been disclosed in which a plurality of sample row data shifted in units of pixels is created, and the sample row data and inspection data are collated.

According to this technique, there is an advantage that even if the printed image is slightly shifted from the original image, the inspection can be performed accurately.

[0009]

However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 23818/1990, when the recording medium is roll paper, the speed of the drive system of the printed material and the paper feed speed match. However, when the sheet is cut paper and the cut sheet is fed by a transport roll, there is a problem that the speed of the transport roll does not match the speed of the paper feed.

The technique disclosed in Japanese Patent Application Laid-Open No. 3-71263 cannot be applied when the reading position fluctuates greatly, and when there is a large blank portion without print data in the middle of the collation section, the amount of deviation between them is reduced. There is a problem that it cannot be dealt with because it accumulates and grows, and there is a problem that the processing time becomes longer if an attempt is made to solve the problem by expanding the collation range.

Further, in the case where a reading section for a printed image is provided at the subsequent stage of a fixing device in an electrophotographic high-speed printer or the like, the reading speed fluctuates greatly and the disclosed technique is not sufficient. On the other hand, a solution to measure the recording medium speed using laser Doppler is also conceivable,
There is a problem in terms of cost.

On the other hand, in Japanese Patent Application Laid-Open No. 10-42109, in a color image reading apparatus, a non-image portion is provided with oblique lines of equal pitch, read together with the original, and the deviation of data read based on the oblique line read information. A technique for correcting the amount is disclosed.

However, since the oblique lines having the same pitch as the reference of the reading position are formed in the non-image area and not formed in the image area, a partial change in magnification of the optical system for reading the print image and the inspection are performed. It is difficult to effectively correct the effect of local distortion due to the fluttering of the recording medium surface. Further, the mark serving as a reference for the position is an unnecessary mark for the user and is annoying.

The present invention has been made in consideration of the above circumstances, and has been described in detail.
By analyzing the data read at each point using a statistical method, the amount of deviation between the data is determined, and the amount of deviation is corrected and collated to reduce processing time and improve accuracy. It is an object to provide an image inspection apparatus and an image forming apparatus provided with the image inspection apparatus.

[0015]

According to the present invention, there is provided an image inspection apparatus for determining the quality of a print image recorded on a recording medium based on image data representing an original image. An image reading sensor that reads a print image recorded on the recording medium from a recording medium that moves in a predetermined moving direction and obtains inspection data; Two speed detection sensors that obtain the respective speed detection data by reading the change in speed, and a speed change calculation that calculates the speed change of the recording medium based on the speed detection data obtained by the two speed detection sensors By comparing the inspection data obtained by the image reading sensor with the image data, taking into account the speed change calculated by the speed change calculation unit, Characterized in that a quality deciding section that decides the quality of the recorded printed image on recording medium.

Here, the image reading sensor also serves as one of the two speed detecting sensors, and the speed change calculating section is obtained by the image reading sensor. It is preferable that the inspection data is used as one of the speed detection data to calculate the speed change of the recording medium.

In addition, a first image sensor in which a plurality of individual sensors are arranged in a width direction intersecting the moving direction and a line extending in the width direction on a print image read by the first image sensor are provided. A second line in which a plurality of individual sensors are arranged in the width direction to read a filling line.
And a three-line image sensor that reads the same line as the first image sensor and has a third image sensor in which a plurality of individual sensors are arranged in the width direction. Preferably, the second image sensor is used as the image reading sensor, and the first and third image sensors are used as the speed detecting sensors.

Further, it is preferable that the image reading sensor is an image sensor in which a plurality of individual sensors are arranged in a width direction intersecting the moving direction.

Further, the pass / fail judgment unit detects whether the print image matches the original image by pattern matching based on the inspection data and the image data, and judges pass / fail of the print image. In another preferred embodiment, the pattern change is performed by reflecting the speed change calculated by the speed change calculator on the shift amount of the pattern matching.

According to the image forming apparatus of the present invention for achieving the above object, there is provided an image forming apparatus for recording a print image on a recording medium based on image data representing an original image. An image reading sensor that reads a print image recorded on a recording medium to obtain inspection data, and is arranged at a predetermined interval in the moving direction,
Two speed detection sensors for obtaining each speed detection data by reading a change in the density of the recording medium surface; and a speed change of the recording medium based on the speed detection data obtained by the two speed detection sensors. A speed change calculating unit for calculating the speed change calculation unit, and comparing the inspection data obtained by the image reading sensor with the image data in consideration of the speed change calculated by the speed change calculating unit. And a quality determining unit for determining the quality of the printed image.

[0021]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic configuration diagram showing a first embodiment of the image inspection apparatus of the present invention.

The image inspection apparatus shown in FIG.
0 and a determination unit 20.

There are a print image 2 recorded on a sheet 1 by image processing of image data obtained from an original image, and a paper feed roller 3 for conveying the sheet 1 on which the print image 2 is recorded.

The image reading section 10 is provided with a fluorescent lamp 4 for irradiating the print image 2 of the paper 1 with light in parallel with the paper feed roller 3. The light reflected at 2 is condensed by the lens 5 and forms an image on the light receiving surface of the 2-line CCD sensor 6. 2
The line CCD sensor 6 includes two image sensors in which a plurality of individual sensors are arranged in a width direction intersecting with the paper conveyance direction.
Books and paper are arranged at predetermined intervals in the transport direction. One of them is an image reading sensor that reads a print image and obtains inspection data, and a light and shade such as a print image on a recording medium and a paper texture. One of the two speed detection sensors for reading the change and obtaining the speed detection data is also used as one of the speed detection sensors, and the other one is
It is the other speed detection sensor of the two speed detection sensors.

Each image sensor outputs two video signals having different time transitions.

The determination unit 20 includes an AD converter 21 for converting a video signal into a digital signal, and a correlation operation unit 22 for performing a correlation operation using two digital signals having different time transitions.
An inspection data memory 23 for temporarily storing inspection data obtained by reading a print image and digitally converted; an image data memory 24 for temporarily storing image data representing an original image; and an inspection data stored in the inspection data memory. For example, a reference registration calculation circuit 25 that calculates a positional shift amount in the inspection data by performing pattern matching with data in an upper left corner portion and determines a reference registration position (absolute position).
A position correction circuit 26 for correcting the amount of positional deviation in the inspection data, that is, the amount of positional deviation based on the amount of change in the speed of the recording medium calculated by the correlation calculating unit 22 and the amount of positional deviation calculated by the reference registration calculating circuit 25; It comprises a comparison operation determination circuit 27 for comparing and collating the inspection data subjected to the positional deviation correction by the position correction circuit 26 with the image data stored in the image data memory.

The two video signals output from the two-line CCD sensor and having different time transitions are respectively converted into digital signals by two AD converters 21, and one digital signal is stored in the test data memory 23 as test data. At the same time, the time-delayed speed detection data is input to the correlation operation unit 22, and the other digital signal without time delay is input to the correlation operation unit 22 as speed detection data.

The reference register calculation circuit 25 stores image data raster-converted based on the original image created by the personal computer or image data read from the original image by the scanner in the image data memory 24. The image data is taken out from the image data memory 24 and the inspection data is taken out from the inspection data memory 23, and the data of the small area corresponding to the upper left corner of the print image in the inspection data is stored in the upper left corner of the original image in the image data. The data of the corresponding relatively large area is subjected to pattern matching by the so-called residual sequential test method, and the reference position deviation amount of the print image from the original image is calculated.

Here, the reference position shift amount is calculated by performing pattern matching based on the data of the small area corresponding to the upper left corner, but the present invention is not limited to this.
Further, pattern matching is performed by the so-called residual sequential test method, but the present invention is not limited to this.

The correlation calculating section 22 converts the speed reading data having different time transitions read by two image sensors arranged at a predetermined interval in the moving direction of the recording medium.
Input from the AD converter 21 of the system, and the input 2
A correlation calculation between the speed reading data of the systems is performed to obtain a change in the line gap when each line of the print image moves, and the reading speed fluctuation calculated from the change is used as a unit of a block to be inspected. The shift amount of each line is calculated by cumulative addition.

The position correction circuit 26 calculates the shift amount of each line of the print image based on the change in the speed of the recording medium calculated by the correlation operation unit 22 and the reference registration shift amount of the print image calculated by the reference registration calculation circuit 25. At the same time, the inspection data is taken out from the inspection data memory 23, and the positional deviation amount of the inspection data is corrected for each block to be inspected.

The comparison operation judging circuit 27 includes a position correcting circuit 2
The inspection data whose positional deviation has been corrected in 6 is compared with the image data stored in the image data memory 24,
The quality of the print image recorded on the recording medium is determined.

Here, the comparison operation determination circuit 27 may perform pattern matching with the image data based on the inspection data whose positional deviation has already been corrected by the position correction circuit 26, so that the collation range can be reduced. Thus, the operation time can be reduced.

FIG. 2 is a conceptual diagram for comparing two speed detection data read by a two-line CCD sensor.

The two-line CCD sensor 6 shown in FIG.
Two image sensors 6a and 6b in which a plurality of individual sensors are arranged in a width direction intersecting the moving direction of the recording medium are arranged, and a printed image is recorded on the two image sensors. The recording medium moves in the direction of arrow A with the surface facing the sensor.

A portion (part of the recording medium) 7 indicated by a dotted line in the figure is read by an image sensor 6a disposed on the upstream side in the direction of arrow A in which the recording medium moves. The read data 6c of the column, which is read by the image sensor 6b disposed on the downstream side in the direction of the arrow A in which the recording medium moves, becomes the read data 6d of the succeeding pixel column shown in the lower right part of the figure.

The read data 6c of the preceding pixel column and the read data 6d of the succeeding pixel column are a Y coordinate indicating the position of the recording medium in the direction of arrow A, and the position in the width direction intersecting with the direction of the arrow A in which the recording medium moves. Are displayed three-dimensionally by an X-coordinate representing the data and a Z-coordinate representing the size of each read data.

The read data 6c of the preceding pixel row and the read data 6d of the succeeding pixel row are the Y coordinate corresponding to the time transition of the same pixel on the surface of the recording medium passing over each image sensor of the two-line CCD sensor 6. The position is incorrect. Further, in the read data, even if the plain portion of the recording medium is read, the coordinate scale indicating the boundary between the pixel values is bent as a result of reading the paper fiber pattern.

Since the read data of the preceding pixel column and the read data of the subsequent pixel column read a random pattern of paper fibers with a shift corresponding to the time transition, the read data of the preceding pixel column and the read data of the subsequent pixel column are read. A speed change or the like can be calculated by performing a correlation operation with the read data in the column and obtaining a correlation peak.

FIG. 3 is a diagram showing a two-line CCD sensor.

The two-line CCD sensor 6 shown in FIG.
Image sensor 6 in which individual sensors of 000 pixels are arranged
The two a and 6b are arranged in parallel, and the interval between the image sensors is 10 pixels at a pixel pitch and 10 lines apart.

Now, the two image sensors 6a, 6a
If the deviation of the read data obtained by the correlation operation based on the speed detection data obtained in b is 9.8 pixels,
This means that the moving speed of the recording medium is 2% faster than the original moving speed.

FIG. 4 is a diagram showing a correlation operation section for performing a correlation operation for calculating a change in the speed of the recording medium.

A correlation calculation unit 22 shown in FIG. 4 includes a read value calculation unit 30 for performing a calculation using the speed detection data as a parameter when performing a correlation calculation based on two systems of speed detection data; And an ASIC unit 31 for calculating a constant part which is not affected by the data for use and multiplying the value calculated by the read value calculation unit 30 to obtain a correlation function.
To 0, the video signal of 2 is output from the line CCD sensor time course is different two systems and digital signal I ₁ is converted by the AD converter and I ₂ are inputted.

The read value calculating section 30 has a plurality of first-in first-out delay circuits FIFO 30a. FIFO30a2
Reference numeral 30a4 has a capacity for accommodating one line of data obtained by one image sensor.
Has a capacity of 10 lines that is delayed by 10 lines corresponding to the interval between two image sensors. A line memory 30b is connected to the subsequent stage of the FIFO 30a, and the line memory 30b can temporarily store data for 100 pixels. Two line memories 30b of the line memo 30b are provided with two switches 30 of a switching unit 30c having three switching switches 30e.
e, is switched and connected at the same time as the multiplier 30d. The multiplier 30d multiplies the data stored in the two connected line memories 30b by one another. Adder circuit 30f
And the multiplied value is stored in the memory of the accumulation circuit 30f.

ASI comprising a dedicated IC for performing a correlation operation
The C unit 31 reads out the cumulative addition value stored in the cumulative addition circuit 30f and calculates the correlation function C (i, j).

Here, for example, N1 × N in the input image
The upper left corner position of the template image consisting of one pixel is (a,
b), a partial image of the input image composed of M1 × M1 pixels is I (a, b) (m1, n1), and a template image is T
When (m1, n1) is set, the cross-correlation function between the input image and the template image is given by Equation 1 (Page 709 of Image Analysis Handbook: University of Tokyo Press).

[0049]

(Equation 1)

Now, the equation (1) is replaced, and the cross-correlation function C (i, j) between the two speed detection data is obtained by the equation (2).

[0051]

(Equation 2)

Here, the change in the speed of the recording medium can be obtained by obtaining i and j at which the correlation function becomes maximum. In order to improve the accuracy, the pixel density is interpolated by, for example, 10 When focusing only on the shift in the moving direction, the correlation function C (i, j) can be obtained by Expression (3).

[0053]

(Equation 3)

When the formula (3) is developed and calculated, the first term of the numerator can be developed into the formula (4) when, for example, 1 <j ≦ 10.

[0055]

(Equation 4)

The correlation function C (0, j) can be divided into a portion that changes using the speed detection data as a parameter and a constant portion that is irrelevant to the speed detection data. 30 and the constant part is A
The calculation is performed by the SIC unit 31.

In the read value calculation unit 30, when the speed detection data I _{2 of} the preceding pixel row is input, the first stage FIFO 3
0a1 over the I ₂ to the 10 lines delayed by inputs the output of FIFO30a1 of the first stage multiplied by the delay line memory 30b, FIFO in the second stage
Input to 30a2. In the second stage FIFO 30a2,
Further, a delay of one line is applied, and the output of the delayed second stage FIFO 30a2 is input to the line memory and also input to the third stage FIFO 30a3. The third-stage FIFO 30a3 further delays by one line and inputs the output to a line memory. Thus, calculation of the part which varies in accordance with the speed detection data output I ₂ of the correlation function is performed. Similarly, for the speed detection data I ₁ of the succeeding pixel column, the FI
FO 30a4 and 2 for temporarily storing data for 100 pixels
Calculating part which changes the speed detection data I ₂ of the correlation function is performed using One line memory 30b.

Although the image sensor has an array of individual sensors for reading data corresponding to 5000 pixels, the operation is performed using the data corresponding to 100 pixels in the first half, and the result of repeating these cumulative operations for 10 lines is obtained. Is stored in the memory of the accumulation circuit 30f.

The ASIC unit 31 is provided for each of the accumulative adding circuits 30f.
The correlation function C (0, j) is obtained by multiplying the calculated value stored in the memory of (1) and the numerical value of the constant part calculated in advance with the read calculated value.
By comparing the magnitude of the correlation function C (0, j) thus obtained with respect to each j, j is obtained in which the value of the correlation function is maximized.

For example, if j is +2, it means that there is a displacement of +0.2 lines with respect to 10 lines between the image sensors, and that there is a speed change of -2%.

FIG. 5 is a schematic diagram showing a change in the reading speed of the recording medium read by the speed detecting sensor.

In FIG. 5, the vertical axis represents the reading speed (mm / s) of the speed detecting sensor, and the horizontal axis represents the length (mm) of the recording medium in the moving direction.

Here, the reading speed of the sensor is set to 15.7 dots / mm and the frequency of the line sync signal of the sensor is set to 6.3 kHz. Actually, as can be seen from the figure, it fluctuates up and down around 400 mm / s.

FIG. 6 is a diagram showing the reading position shift amount of the recording medium.

In FIG. 6, the vertical axis represents the read position deviation amount (mm) of the recording medium, and the horizontal axis represents the length (mm) of the recording medium in the moving direction.

The curve in the figure represents the amount of deviation from the standard reading position obtained by cumulatively adding the speed change shown in FIG. 5 in the direction of movement of the recording medium. If the inspection data and the image data are compared and collated in consideration of the deviation amount, the quality of the printed image can be determined with high accuracy.

FIG. 7 is a diagram showing a flow for calculating the amount of deviation from the standard position.

In FIG. 7, first, two lines C
The ASIC unit of the correlation operation unit calculates the correlation function C (0, j) based on the speed detection data read by the two image sensors of the CD sensor (S-1).

Next, each value of the calculated correlation function is compared.
The j at which the value becomes the maximum is determined (S-2).

Next, after dividing j by the product of the multiple value 10 of the pixel density and the line gap 10, 1 is added, and the reciprocal thereof is calculated to obtain the ratio to the standard reading speed. By multiplying and subtracting 10 pixels as a standard gap, a shift amount between 10 pixels as a calculation unit is obtained (S-3).

Further, the shift amount between the 10 pixels obtained in (S-3) is cumulatively added for every 10 lines to obtain the position shift correction amount for each inspection block (S-
4).

Then, the inspection data is compared with the image data,
At the time of collation, the inspection data is corrected based on the obtained positional deviation correction amount (S-5).

FIG. 8 is a diagram showing an example of a print image having a long blank section.

In the print shown in FIG. 8 in which the image is interrupted in the middle part, conventionally, data for calculating the speed change cannot be obtained, and the speed change during this period cannot be captured.
In some cases, misregistration has been accumulated, and collation when a printed image appears again has been difficult in some cases. However, in the present embodiment, the speed change is obtained by the correlation calculation, and the positional deviation amount is calculated. Since the probability variable for performing the correlation operation can be obtained from the grayscale information such as the print image and the texture on the surface of the recording medium, the change in the speed of the recording medium is captured even if the image is interrupted in the middle part, and the position is captured. Since the shift amount can be calculated, comparison and collation can be performed.

At this time, the collation position is ±± with respect to the reference position.
When used together with the movement of about 0.5 mm, it is possible to compensate for the calculation error of the accumulated deviation amount, and conversely, the range in which the collation position is moved can be reduced. In addition, the calculation of the displacement amount by the correlation operation is performed not only on the data obtained in the first half of the individual sensor array of the image sensor but also on the data obtained in the second half of the image sensor, thereby reducing the skew of the recording medium. Can also respond. In this case, the skew can be corrected by associating the accumulated calculation amounts of the first half and the second half in proportion to the position in the width direction intersecting with the moving direction of the recording medium.

Next, a second embodiment of the present invention will be described.

FIG. 9 is a schematic configuration diagram of an image inspection apparatus according to the second embodiment.

The second embodiment differs from the image inspection of the first embodiment shown in FIG. 1 in that a three-line CCD sensor used for reading a color image is used without a filter, and two lines are used. The image sensor of No. 1 achieves high speed by alternately reading each line of the print image, and one of the remaining one image sensor and one of the two read the print image is used for speed detection. Different, but otherwise common. Therefore, the same components are denoted by the same reference numerals, and only the differences will be described.

The three-line CCD sensor 8 includes three image sensors in which a plurality of individual sensors are arranged in the width direction intersecting the sheet conveyance direction, and is arranged at predetermined intervals in the sheet conveyance direction. The two image sensors are image reading sensors that read a printed image or paper texture and obtain inspection data, and perform high-speed reading by alternately reading each line on a recording medium with the two image sensors. I have. One of the two image sensors also serves as one of the two speed detection sensors for reading the change in the density of the recording medium surface and obtaining the speed detection data. The other image sensor is a speed detecting sensor of the other of the two speed detecting sensors.

The three image sensors output three video signals having different time transitions.

The three video signals output from the three-line CCD sensor 8 and having different time transitions are converted into digital signals by a first AD converter 21a, a second AD converter 21b, and a third AD converter 21c, respectively. To the first AD
The digital signal converted by the converter 21a and the second AD converter 21b is stored as test data in the test data memory 23, and the digital signal converted by the third AD converter 21c and the first AD converter 21a The converted digital signal is input to the correlation calculator 22 as speed detection data.

FIG. 10 is a diagram showing a three-line CCD sensor.

The three-line CCD sensor 8 shown in FIG.
Three image sensors 8a, 8b, and 8c in which individual sensors of 7,500 pixels are arranged are arranged in parallel, and the distance between the image sensors is four lines wide as measured at the pixel pitch.

By using the three-line CCD sensor 8, the reading speed can be increased to 8/3 times. In this case, when the standard reading density is 600 dpi and reading is performed at 8/3 times the standard reading speed, the reading density of each reading line becomes 225 dpi, and the reading position is shifted by 1.5 lines.

The two adjacent image sensors 8a and 8b located on the lower side of the figure are image reading sensors, and are at reading positions that are half-phase shifted from each other. The density can be read. Also, the uppermost image sensor 8c and the lowermost image sensor 8a of the three image sensors 8a, 8b, 8c shown in FIG.
Is a speed detection sensor, and the standard displacement amount between the two sensors is equivalent to three lines twice as large as 1.5 lines.

A shift amount due to a speed change with respect to the standard position shift amount for three lines is calculated by a correlation operation, and the shift amount from the standard position is obtained by accumulatively adding the shift amounts. Similarly, it is reflected on the position correction amount at the time of performing collation.

As described above, since the reading speed can be increased by using two image reading sensors, an image printed by a high-speed printer or the like can be read, and one of the image reading sensors can be used. Correlation calculation can be performed between the read data and the data read by the remaining one of the three speed detection sensors to cope with a collation position shift caused by a change in the reading speed.

Next, a description will be given of a third embodiment of the image inspection apparatus according to the present invention.

FIG. 11 is a schematic configuration diagram showing an image inspection apparatus according to the third embodiment. The third embodiment differs from the second embodiment in that all the three image sensors of the three-line CCD sensor 8 are used to alternately read each line of a printed image or texture in parallel to obtain inspection data. The difference is that the speed is increased and the data read by two of the image sensors is used for speed detection, but the other points are common. Therefore, the same components are denoted by the same reference numerals, and only the differences will be described.

The three-line CCD sensor 8 includes three image sensors in which a plurality of individual sensors are arranged in the width direction intersecting the paper transport direction, and is arranged at a predetermined interval in the paper transport direction. The image sensor is an image reading sensor that obtains inspection data by reading a printed image, paper texture, or the like, and achieves high speed by alternately reading each line on a recording medium in parallel with three image sensors.

Two of the three image sensors also serve as two speed detection sensors for obtaining speed detection data.

The three image sensors output three video signals having different time transitions.

The three video signals output from the three-line CCD sensor 8 and having different time transitions are converted into digital signals by the first AD converter 21d, the second AD converter 21e, and the third AD converter 21f, respectively. The digital signal converted by each AD converter is stored in the test data memory 23 as test data, and the digital signal converted by the first AD converter 21d and the digital signal converted by the third AD converter 21f are converted. The digital signal is input to the correlation operation unit 22 as speed detection data.

When performing three-line parallel reading using the three-line CCD 8, the reading phase of each line is shifted.
The reading phase of each line taking the reading speed into account is 1/3 of each other
So that they shift one by one. For example, when reading at three times the standard speed, the reading lines of the three-line CCD 8 shown in FIG. 10 are shifted by 4/3 lines.

In this case, the positional deviation amount of the two lines for which the correlation operation is performed is no longer an integer. For example, the multiple value of the pixel density is changed from 10 to 15, and the delay of three lines is -−１. By using the position (where j is −5) as a reference, the same collation as in the first embodiment and the second embodiment can be performed.

In the first to third embodiments, the positional deviation amount is calculated by utilizing the correlation between the positional information of each read line of the plurality of line sensors. It is not necessary to be limited to line sensors,
For example, it can also be calculated by arranging two area sensors at an interval in the moving direction of the recording medium, calculating the correlation between the read images, and calculating the difference from the original time transition.

Next, an embodiment of the image forming apparatus of the present invention will be described.

FIG. 12 is a schematic configuration diagram showing an embodiment of the image forming apparatus of the present invention.

The image forming apparatus shown in FIG. 12 supplies an image forming section 50 for forming a print image on a sheet,
A paper feeding and transporting unit 51 for transporting, and a finishing processing unit 52 for discriminating the quality of the print image and sorting the printed paper into good print images for each page
A print image creation unit 53 that performs image processing of image data or generates a signal obtained by pulse modulation, reads a print image printed on paper and coordinate scales, converts the read data into inspection data and position data, and converts the inspection data. Obtain corrected inspection data by correcting with position data, compare with image data,
A reading determination unit 54 that determines whether or not the printed image matches the original image by collation, and based on the determination result of the reading determination 54, eliminates a sheet on which a defective print has been made, or returns the image to the image forming unit 50. The printer controller 55 instructs printing. The print image creation unit 53 performs image processing on image data raster-converted based on the original image created by the personal computer or image data read from the original image by the scanner, binarizes the image data, and converts the pulse-modulated signal. It is generated and transmitted to the laser exposure device 56 of the image forming unit 50.

The image forming section 50 has a photosensitive drum 57 on which a toner image is formed, a charger 59 uniformly charges the photosensitive drum 57, and a laser exposure device 56 controls the print image forming section 53. The developing device 58 irradiates a uniformly charged photosensitive drum 57 with a laser beam pulse-modulated based on the generated signal to form an electrostatic latent image. The image is developed with toner to form a toner image on the surface of the photosensitive drum 57. The toner image formed on the surface of the photoconductor drum 57 is
The fixing device 62 transfers the toner image on the sheet 61 transferred from 1 to the printing position 60 and fixes the transferred toner image on the sheet 61 by applying heat and pressure. The sheet on which the print image is formed is transported to the print image reading position 63 by the paper feed transport unit 51.

The paper feeder 51 has three paper trays 1 to 3 for supplying sheets of different sizes according to the size of an image to be printed. Is provided with a double-sided tray 65 for temporarily storing the paper that has been finished. The paper accommodated in each tray is put on a line of a paper transport belt 67 that is driven by paper transport rollers 66 and circulates, and is printed at a print position 60, a fixing position where the fixing device 62 fixes the image, and a print image reading position. The paper conveyed to 63 and printed on one side but printed on the other side is placed in the tray 65 for both sides, and the paper that has been printed on both sides or printed on only one side is further divided into sheets for each page. The sheet is conveyed to the processing section 52 or the purge tray 68 that stores the defective print.

The reading determination section 54 is arranged at the print image reading position 63 and reads the print image, which has been fixed on the sheet, to obtain the inspection data, and
Two speed detection sensors 41 that are arranged at predetermined intervals in the moving direction of the paper and that read the print image on the surface of the printed paper or the density of the paper texture to obtain each speed detection data; A speed change calculating means 42 for calculating a speed change of the paper moving by correlation based on the speed detection data obtained by the two speed detection sensors 41 and a small area at the upper left corner of the print image The inspection data is subjected to pattern matching on image data corresponding to a slightly larger area in the upper left corner of the original image to calculate a reference position deviation amount of the print image, and the reference position deviation amount and the speed change calculator 42 calculate the reference position deviation amount. The quality of the printed image recorded on the paper is checked by comparing the inspection data with the image data in consideration of the positional deviation amount due to the speed change. And a determination unit 43 for the constant to.

Note that the read determination unit 54 can determine the pass / fail by correcting the positional deviation of the inspection data to obtain the corrected inspection data, and comparing and comparing the corrected inspection data with the image data.

If the result of the comparison and collation by the reading determination section 54 is that the print image has a character or graphic that does not match the original image, the printer controller 55
The print image creating unit 53 rejects the paper whose print image is determined to be mismatched based on the determination information and stores it in the purge tray 68, and reprints the print image determined to be mismatched to obtain a good print image. Issue an image formation command.

As described above, the inspection data is subjected to the processing for correcting the amount of positional deviation due to the change in the speed of the recording medium, and the determination as to whether or not the print image matches the original image can be made at high speed and with high accuracy. Therefore, based on the determination result, a defective print can be eliminated, or a good substitute print can be formed again and stored in a predetermined section shelf, so that a manual check can be eliminated.

In the present embodiment, the image forming apparatus of the electrophotographic recording type has been described. However, the image forming apparatus is not limited to the electrophotographic recording type, but may be a thermosensitive recording type image forming apparatus. The image forming apparatus used may be a printing apparatus. Further, the image forming apparatus includes:
It may be a printer or a copier.

[0107]

As described above, according to the image inspection apparatus of the present invention, even when the moving speed of the recording medium to be inspected is largely changed, it is possible to perform the collation in consideration of the displacement amount. In addition to this, the processing time can be significantly reduced as compared with the conventional matching method using pattern matching. In addition, by providing this image inspection apparatus in the image forming apparatus, it is possible to save labor particularly in a high-speed printer or the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an image inspection apparatus of the present invention.

FIG. 2 is a conceptual diagram for comparing two speed detection data read by a two-line CCD.

FIG. 3 is a diagram showing a two-line CCD sensor.

FIG. 4 is a diagram illustrating a correlation operation unit that performs a correlation operation for calculating a speed change of a recording medium.

FIG. 5 is a schematic diagram showing a change in reading speed of a recording medium read by a speed detection sensor.

FIG. 6 is a diagram illustrating a reading position shift amount of a recording medium.

FIG. 7 is a diagram illustrating a flow for calculating a shift amount from a standard position.

FIG. 8 is a diagram illustrating an example of a print image having a long blank section.

FIG. 9 is a schematic configuration diagram of an image inspection device according to a second embodiment.

FIG. 10 is a diagram showing a three-line CCD sensor.

FIG. 11 is a schematic configuration diagram illustrating an image inspection apparatus according to a third embodiment.

FIG. 12 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper 2 Print image 3 Paper feed roller 4 Fluorescent lamp 5 Lens 6 2-line CCD sensor 6a Image sensor arranged on the upstream side 6b Image sensor arranged on the downstream side 6c Read data of the preceding pixel row 6d The following pixel row Read data 7 A portion represented by a dotted line 8 3-line CCD sensor 8a Lowermost image sensor 8c Uppermost image sensor 10 Image reading unit 20 Judging unit 21 AD converters 21a and 21d First AD converters 21b and 21e 2 AD converters 21c, 21f Third AD converter 22 Correlation operation unit 23 Inspection data memory 24 Image data memory 25 Reference registration calculation circuit 26 Position correction circuit 27 Comparison operation determination circuit 30 Read value operation unit 30a FIFO 30a1, 30a4 First-stage FIFO 30a2 Second-stage FIFO 30a3 3-stage FIFO 30b Line memory 30c Switching unit 30d Multiplier 30e Switch 30f Cumulative addition circuit 31 ASIC unit 40 Image reading sensor 41 Speed detecting sensor 42 Speed change calculating unit 43 Judging unit 50 Image forming unit 51 Paper feed unit 52 Finishing Processing unit 53 Print image creation unit 54 Read determination unit 55 Printer controller 56 Laser exposure device 57 Photoconductor drum 58 Developing device 59 Charger 60 Printing position 61 Paper 62 Fixing device 63 Print image reading position 64 Paper tray 65 Double-sided tray 66 Paper transport Roller 67 Paper transport belt 68 Purge tray

Claims (6)

[Claims] An image inspection apparatus for judging the quality of a print image recorded on a recording medium based on image data representing an original image, wherein the image is recorded on the recording medium from a recording medium moving in a predetermined moving direction. An image reading sensor that reads a print image to obtain inspection data; and two speed detection sensors that are arranged at a predetermined interval in the moving direction and that read a change in density on the surface of the recording medium to obtain each speed detection data. A sensor, a speed change calculation unit that calculates a speed change of the recording medium based on speed detection data obtained by the two speed detection sensors, inspection data and the image data obtained by the image reading sensor Are compared with each other in consideration of the speed change calculated by the speed change calculator, thereby determining whether the print image recorded on the recording medium is good or not. An image inspection apparatus, comprising: a fixing unit. 2. The image reading sensor according to claim 1, wherein said image reading sensor doubles as one of said two speed detecting sensors, and said speed change calculating section is obtained by said image reading sensor. 2. The image inspection apparatus according to claim 1, wherein the inspection data is used as one of the speed detection data to calculate a speed change of the recording medium. 3. A first image sensor having a plurality of individual sensors arranged in a width direction intersecting the moving direction, and a line extending in the width direction on a print image read by the first image sensor. Reading a line to fill, a second image sensor in which a plurality of individual sensors are arranged in the width direction, and reading the same line as the first image sensor;
A three-line image sensor having a third image sensor in which a plurality of individual sensors are arranged in the width direction, wherein the first and second image sensors are used as the image reading sensors; The image inspection apparatus according to claim 1, wherein a third image sensor is used as the speed detection sensor. 4. The image inspection apparatus according to claim 1, wherein the image reading sensor is an image sensor in which a plurality of individual sensors are arranged in a width direction intersecting the moving direction. 5. A pass / fail judgment unit which detects whether or not the print image matches the original image by pattern matching based on the inspection data and the image data, and judges pass / fail of the print image. 5. The method according to claim 1, wherein the pattern matching is performed by reflecting the speed change calculated by the speed change calculating unit on a shift amount of the pattern matching. 6. 2. The image inspection apparatus according to claim 1. 6. An image forming apparatus for recording a print image on a recording medium based on image data representing an original image, comprising reading a print image recorded on the recording medium from a recording medium moving in a predetermined moving direction. An image reading sensor that obtains inspection data; two speed detection sensors that are arranged at predetermined intervals in the movement direction and that read changes in the density of the recording medium surface to obtain each speed detection data; A speed change calculation unit that calculates a speed change of the recording medium based on speed detection data obtained by the two speed detection sensors; and an inspection data and the image data obtained by the image reading sensor. A quality judgment unit for judging the quality of the print image recorded on the recording medium by collating in consideration of the speed change calculated by the change calculation unit. An image forming apparatus comprising: