JP2852807B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is capable of transferring an image signal obtained by scanning a document image and performing photoelectric conversion on each pixel to an external device such as a host computer. The present invention relates to an image reading device.

(Prior art) Conventionally, in this type of image reading apparatus, a CCD image sensor is generally used as a photoelectric conversion element.
It takes the form of a reduction optical system. Therefore, in order to improve the reading accuracy, it is necessary to increase the accuracy of assembling the optical system. In a factory, a means for inspecting the accuracy of the assembly is output by reading a test chart corresponding to an inspection item. Inspection was carried out by the images.

(Problems to be Solved by the Invention) However, in such an inspection means, the inspection itself takes a long time, and an operator directly looks at an output image to judge. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus capable of inspecting the accuracy of assembling an optical system in a scanner main body without relying on an operator.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a reference plate for detecting the assembling accuracy of the scanning optical system outside the image reading area of the platen glass. In the image reading apparatus, a reference plate for detecting the assembling accuracy of the scanning optical system is provided outside the image reading area of the scanning optical system, and the assembling accuracy of the scanning optical system can be self-diagnosed by reading the reference plate with the image reading element. On the reference plate, at least one line is printed at the center and three lines are printed near both ends, each of which is perpendicular to the arrangement direction of the image reading elements. The center line of the two lines is overlapped by a predetermined pixel in a direction perpendicular to the arrangement direction of the image reading elements.

(Operation) In the present invention having the above structure, at least one of the reference plate provided outside the image reading area of the platen glass and three of the reference plates provided near the both ends of the image reading element. Lines perpendicular to the arrangement direction are printed, and the center line with respect to two of the three lines near the end is perpendicular to the arrangement direction of the image reading elements. It overlaps by a predetermined pixel. Thereby, the inclination of the image reading element, the positional deviation in the main scanning direction, and the main scanning magnification deviation can be self-diagnosed only by reading the reference plate, and the inspection of the assembling accuracy of these scanning optical systems can be performed without depending on the operator. Since the scanning can be performed by the scanner itself, the assembling time can be reduced and the inspection accuracy can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

 1 and 2 show one embodiment of the present invention.

Reference numeral 1 denotes a document image reading device that reads a document image.

Reference numeral 2 denotes a scanning optical system, which includes a document illumination unit 15 and a reflection mirror.
16, a lens 14, a CCD 12, and a CCD driver 13.

The document illuminating unit 15 has a document illuminating lamp FL and is movable in the direction A in the figure. The reflection mirror 16 regulates the optical path L of the light reflected from the document surface. The lens 14 converges the reflected light. The CCD 12 is arranged in an array corresponding to one line in the main scanning direction of the document, and photoelectrically converts the reflected light converged by the lens 14. The CCD driver 13 drives the CCD 12.

Reference numeral 11 denotes a control unit for controlling each unit, and reference numeral 17 denotes a platen glass for regulating a document surface to be read flat.
Reference numeral 18 denotes a document placed on the platen glass 17, and 19 denotes a platen cover. Reference numeral 20 denotes a stepping motor, which constitutes moving means together with a stepping motor drive circuit 31 shown in FIG. Stepping motor drive circuit 31 is CP
The stepping motor 20 is driven according to the excitation signal from U208.

2, 12, 14, and 18 indicate the same parts as those in FIG. Hereinafter, the CCD driver 13 and the control unit 11 will be described.

(CCD Driver 13) 201 is an amplifier (AMP) for amplifying the output of the CCD 12. An A / D converter (A / D) 202 converts an analog signal from the amplifier 201 into a 6-bit digital signal. Reference numeral 203 denotes a CCD drive circuit which drives the CCD 12 in accordance with a timing signal supplied from the control unit 11 to regulate read timing.

(Control unit 11) Reference numeral 204 denotes a shading RAM which stores the light distribution characteristics of the document illumination lamp FL. Reference numeral 205 denotes a shading control unit which includes a shading ROM 208A storing a shading correction coefficient and a circuit for controlling the shading RAM 204, and outputs a signal from the A / D converter 202 based on the light distribution data of the document illumination lamp FL stored in the shading RAM 204. Is subjected to shading correction. 20
Reference numeral 6 denotes a binarization circuit. Reference numeral 207 denotes an interface circuit serving as a transfer unit for receiving a control signal and outputting an image signal with an external device 250 serving as a host device such as a personal computer. Reference numeral 208 denotes a microcomputer-type CPU which has a ROM 208A storing a control program and a working RAM 208B, and controls each unit according to the control program stored in the ROM 208A. Here, the shading RAM 204, shading control circuit 205, binarization circuit 206, and CPU 208
Is configured.

 Next, an actual self-diagnosis method will be described.

FIG. 3 is a view of the platen glass 17 viewed from the back. A
Is a white reference plate for shading, and B is a plate on which a pattern for checking the assembling accuracy is printed. FIG. 4 shows signals when the pattern is read, and C, D, and E correspond to C, D, and E in FIG. As shown in FIG. 4, the three lines in sections C and E are lines each having a thickness of one pixel, and have an interval of 10 pixels in the main scanning direction. The center line of two of the three lines intersects two pixels in the sub-scanning direction, which corresponds to a CCD 12 (shown in FIG. 1).
This is to check the inclination of the attachment. Next, D is a line indicating the center of the effective area, which checks whether the CCD 12 is correctly assembled in the main scanning direction, and further measures the intervals between D and C and between D and E The main scanning magnification can be measured to check the mounting accuracy of the lens 14 (shown in FIG. 1).

Next, an actual self-diagnosis processing method will be described with reference to the flowchart of FIG.

Upon receiving the self-diagnosis command, the scanner turns on the illumination lamp FL in S1 and waits 600 msec for the amount of light to stabilize in S2, and then moves the scanning optical system 2 to the center of the part B shown in FIG. Move to part D. The image signal read in S4 is written in the pseudo RAM 204, and the illumination lamp FL is turned off in S5. In S6, shading RAM2
SHDCNT, which is an address counter when reading the data of 04, and PEAKCNT, which is a counter for counting the number of detected black peak portions, are each cleared to zero. S7 in shading RAM 204 at S7
Is taken into the accumulator in the CPU 208, and if the value is larger than 32 in S8, the process proceeds to S9; otherwise, the process proceeds to S12. In S12, +1 is added to SHDCNT, and if the value does not exceed 2000 in S13, S
Returning to 7, if so, since seven lines could not be detected, an error 1 indicating that the CCD is tilted and assembled is set in S14, and the self-diagnosis is terminated.
Next, in S9, since a line is detected, the count value at that time is set to PEAK which is an address for storing the address where the peak value is detected in the internal RAM 208B of the CPU 208.
Store at the address where PEAKCNT × 2 is added to ADR,
If PEAKCNT is increased by 1 and the value is 8 in S11
Proceed to S15, otherwise return to S7.

In S15, the address corresponding to the line located on the most reference side is loaded into the BC register.In S16, the address corresponding to the line located at the rear end is loaded into the DE register.
Loads the address corresponding to the line located at the center into the double accumulator EA. The value is 100 in S18
If it is within 0 ± 2, proceed to S19; otherwise, store the value of the double accumulator EA at the address indicated by ERRCNT, which is the error value of the center pit, and confirm that the CCD12 is not installed in the main scanning direction. Error 2 shown
Is set in S20, and the process proceeds to S19. At S19, the BC register is subtracted from the double accumulator EA. If the value is within 800 ± 2 at S21, the process proceeds to S22. Otherwise, the error 3 indicating that the main scanning magnification is not appropriate is obtained.
Is set in S26, and the processing ends. At S22, the contents of the DE register are stored in the double accumulator EA, at S23, the address corresponding to the line located at the center is loaded into the BC register, and at S24, the BC is read from the double accumulator EA.
If the value is within 800 ± 2 in S25 after pulling the register, the process is terminated. Otherwise, error 3 is returned in S26.
And exit.

Next, as a result, in order to obtain a host computer as an external device, it is possible to obtain a self-diagnosis result by transmitting a command for reporting a self-diagnosis result.

Next, a description will be given, with reference to FIG. 6, of a method of correcting when the main scanning magnification is correct and only the position of the center bit is an error in the self-diagnosis described above.

In the figure, HSYNC is a main scanning synchronization signal of the CCD 12 output from the timing signal generation circuit 209 as a change means, and ARWE is a buffer RAM in the interface circuit 207.
(Not shown) to control writing, and it is assumed that writing to the buffer RAM is started when the signal becomes "H".

For example, in the self-diagnosis, if the contents of the center bit error value ERRCNT is 10, as shown in the figure
By causing the ARWE signal to be delayed by 10 pixels, the read start position can be corrected.

In the previous embodiment, the reference for performing the self-diagnosis was provided only on the home position side. However, as shown in FIG.
It can be said that it is also an effective means to check the skew by comparing the center line address at the home position side with the center line address at the rear end side.

(Effects of the Invention) According to the present invention, the inclination of the image reading element, the positional deviation in the main scanning direction, and the main scanning magnification deviation can be self-diagnosed only by reading the reference plate. Since the operation can be performed by the scanner itself without depending on the operator, the assembly time can be reduced and the inspection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to one embodiment of the present invention, FIG. 2 is a block diagram showing the operation of the apparatus, and FIG. 3 is a reference plate used for self-diagnosis on a platen glass of the apparatus. FIG. 4 is a waveform diagram of a signal when the device reads the reference plate, FIG. 5 is a flowchart for explaining a self-diagnosis procedure of the device, FIG. 7 is a timing chart of correction based on the result of self-diagnosis of the apparatus, and FIG. 7 is an external view for explaining a reference plate of a platen glass of an image forming apparatus according to another embodiment of the present invention. EXPLANATION OF SYMBOLS 2 Scanning optical system 12 CCD 14 Lens 16 Reflector mirror 17 Platen glass 207 Interface (transfer means) 209 Timing signal generation circuit (change means) 250 ... external device, A ... reference plate W ... accuracy detection means

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 1/00 H04N 1/04 G03G 15/00

Claims (1)

(57) [Claims] A reference plate for detecting the assembling accuracy of the scanning optical system outside the image reading area of the platen glass;
An image reading apparatus capable of self-diagnosing the assembling accuracy of the scanning optical system by reading the reference plate with an image reading element, wherein the reference plate has at least one image at the center and three images near each end. Lines perpendicular to the arrangement direction of the reading elements are printed, and the center line with respect to two of the three lines near the end is perpendicular to the arrangement direction of the image reading elements. An image reading device, which overlaps by a predetermined number of pixels in different directions.