JPH0537749A - Digital image forming device - Google Patents

Abstract

PURPOSE:To reduce contrast distortion of a picture by correcting an output distortion of a print section such as heat distribution of a heat resistor of a thermal printer head with a comparatively simple method. CONSTITUTION:A reference pattern is printed on paper P based on a prescribed reference pattern data 52a by using a print section such as a thermal head temperature control section 93 and a thermal head 31 or the like. The reference pattern is read by a photoelectric converter 11 and an A/D converter 91 or the like and compared with the original reference pattern data 52a to detects its difference. The detected value is outputted to an arithmetic operation circuit 53 to calculate the correction value of the output distortion of the print section and the output distortion of the print section is corrected based on the correction value at the print from an original.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a digital image forming apparatus for forming an image on an image forming medium by using a heating resistor of a thermal printer head.

[0002]

2. Description of the Related Art Generally, in this type of digital image forming apparatus, an image reading unit reads a document to generate digital image data, and then outputs the generated image data to an image processing circuit, where the image reading unit outputs the image data. Distortion correction is performed to create digital print data, and the created print data is output to the image forming unit, where an image is formed on the image forming medium. The distortion correction of the image reading unit is a shading in which the white reference and the black reference are read and stored in advance, and the exposure distortion in the reading unit and the sensitivity distortion of the photoelectric conversion element are corrected based on the read white reference and the black reference. This is called correction. As another distortion correction, for a contact-type reading sensor that uses multiple photoelectric conversion element chips, a reference pattern is read to correct the sensitivity distortion between the chips and the correction coefficient for each chip of the photoelectric conversion element is obtained. A means for applying a correction during a normal copying operation is known.

On the other hand, in the printing section, there are variations in the resistance value of the thermal printer head heating resistors (variations in heat generation distribution characteristics), and variations in the applied pressure,
Output is distorted. As this output distortion correction, there is known a means of storing the resistance value of the heating resistor in dot units and correcting the image data in dot units.

[0004]

In the conventional output distortion correction of the printing portion, the storage element ROM in which the variation in the resistance value of the thermal printer head heating resistor is stored in dot units and the image data is stored in dot units is used. It was treated as a set. Therefore, when the thermal printer head is damaged for some reason and is replaced with a new one, the storage element ROM in which the resistance value variation of the heating resistor is stored in dot units must be replaced at the same time, which causes a problem of high cost. there were. In addition, there is a problem that it is not sufficient to correct the printing distortion because the printing distortion due to the deviation from the plane of the resistor cannot be corrected only by the variation in the resistance value of the heating resistor. In addition, there is a problem that a circuit for correcting the image data in dot units is required.

In view of this, the present invention corrects the output distortion of the printing portion due to the variation in the heat generation distribution of the heat generating resistors of the thermal printer head with a relatively simple method to reduce the shading distortion of the image. The purpose is to provide a device. [Constitution of Invention]

[0006]

In order to achieve the above object, a digital image forming apparatus of the present invention comprises an image reading unit for reading a document to generate digital image data, and a digital image generated by the image reading unit. An image processing circuit that corrects data based on a correction value of the reading distortion of the image reading unit and a correction value of the output distortion of the image forming unit to create digital print data, and a digital processing circuit that creates the digital printing data. An image forming unit that forms an image on an image forming medium based on print data, a pattern generation unit that forms an image of a reference pattern by the image forming unit based on preset reference pattern data, and the pattern generation unit. A means for creating digital print data from the image of the reference pattern by the image reading means, and a reference pattern. Compared to the digital printing data created from over down image and the reference pattern data,
A means for detecting a value including a reading distortion of the image reading means and an output distortion of the image forming means, and an output distortion of the image forming means based on the detected value and a correction value of the reading distortion of the image reading means. It comprises means for calculating a correction value and means for outputting the correction value to the image processing circuit.

[0007]

According to the digital image forming apparatus of the present invention, the original is read by the image reading means to generate digital image data, and the digital image data generated by the image reading means is read by the image processing circuit and read by the image reading means. And the output distortion correction value of the image forming means to make digital print data, and the image forming means forms an image on the image forming medium based on the digital print data created by the image processing circuit. When forming on the above, the image of the reference pattern is formed from the image forming means based on the reference pattern data by the pattern generation means, and the digital print data is created from the image of the reference pattern by the pattern generation means, and the image of the reference pattern is formed. Comparing the digital print data created from the reference pattern data with the image A value including the reading distortion of the image pickup means and the output distortion of the image forming means is detected, and the correction value of the output distortion of the image forming means is calculated based on the detected value and the correction value of the reading distortion of the image reading means. Then, the correction value is output to the image processing circuit.

[0008]

FIG. 2 shows a thermal transfer type color copying machine capable of selectively producing multicolor color copying as an example of the image forming apparatus of the present invention. That is, reference numeral 1 is a main body of the copying machine, and an operation panel 50 is provided on the front portion of the upper surface of the main body 1. The upper part of the main body 1 is an image reading section 3 for scanning and reading the original O set on the original table (transparent glass) 2, an image processing section 4 for processing an image read by the image reading section 3, and a lower part. Is the image forming unit 5. Reference numeral 100 denotes an original cover provided on the original table 2 so as to be openable and closable, and has an original pocket 100a. A shading correction white reference plate 31 and a document size indicator 32 are provided on the upper end surface of the document table 2.

As shown in FIGS. 2 and 3, the image reading section 3 includes a first carriage 7 having an exposure lamp 6 as a light source, a second carriage 8 for bending an optical path by a mirror, a lens 16a and color correction. The lens section 16 provided with the filter 16b, the mirror section 10 for guiding the reflected light from the original O to the photoelectric converter 11 and correcting the optical path length at the time of zooming, the original O.
A photoelectric converter (conversion means) 11 for receiving the reflected light from the
And a drive system (not shown) for changing the position of each part.

The first carriage 7 has an exposure lamp 6 for irradiating the original O with light, a reflector 12 as a reflecting mirror for collecting the light from the exposure lamp 6 on the surface of the original, and a light radiated from the exposure lamp 6. A filter 17 for absorbing heat rays,
A mirror 13 that guides the reflected light from the document O to the second carriage 8 side is mounted. Reference numeral 19 in the drawing denotes a gloss detector for detecting the glossiness of the original O.

The second carriage 8 is provided with mirrors 8a and 8b for guiding the light guided by the mirror 13 to the lens 16. The first and second carriages 7 and 8 are
The second carriage 8 is connected to each other by a timing belt (not shown) and is driven by the scanning motor 18, so that the second carriage 8 moves in the same direction at half the speed of the first carriage 7. There is. This allows scanning so that the optical path length to the lens 16a is constant. The mirror section 10 has two mirrors 10.
a, 10b, and guides the light to the photoelectric converter 11.

The photoelectric converter 11 photoelectrically converts the reflected light from the original O to convert the image of the original O into cyan,
Green and yellow (or red, green, blue) light signals are separately output as color signals, and are mainly composed of, for example, a CCD type line image sensor. In this case, one pixel of the document O corresponds to three continuous elements (C, G, Y) of the CCD sensor. The output of the photoelectric converter 11 is output to the signal processing unit 4 described later.

The image forming section 5 has a platen drum 22 arranged substantially in the center thereof. This platen drum 22
The periphery of the is formed of an elastic body such as rubber and has a function as a platen roller of the thermal head portion 24. The platen drum 22 winds the sheet P around itself by rotating itself in the clockwise direction, so that the sheet P does not shift during overlay printing. A pinch roller 2 is provided around the platen drum 22 to prevent the paper P from floating above the platen drum 22 at a predetermined interval.
5a and 25b are provided. Platen drum 2
The circumference of 2 is slightly longer than the length of the maximum paper size in the longitudinal direction.

A thermal head portion 24 is disposed on the lower left portion of the platen drum 22. The thermal head portion 24 is attached to a radiator integrally formed on the rear end surface of the holder, and the thermal printer head 24
a, heat sink 24b, pressure spring 24c, cam 24
d, and a cam switch 24e. Further, a ribbon cartridge 26 is mounted between the platen drum 22 and the thermal head portion 24 so as to interpose an ink ribbon 26a as an image forming medium.

The core of the ribbon cartridge 26 is connected to a drive shaft (not shown) of the motor through a drive force transmission mechanism (not shown) and is rotatively driven as necessary, whereby The ink ribbon 26a is a ribbon guide 26b,
Guided by 26b, it runs between the platen drum 22 and the thermal head portion 24. The ribbon cartridge 26 is slidable by a slide rail 26c. In the figure, 22a is a grip sensor, 22b is a paper width sensor, 22c is a motor for driving the platen drum, and 22d is a paper discharge scraper.

A paper feed cassette 20 is detachably attached to the lower portion of the main body 1, and a pickup roller 41a, a paper feed roller 41b, and a separation roller 41 are correspondingly attached thereto.
c, an intermediate roller 41d is arranged. The sheets P as the image forming medium accommodated in the sheet feeding cassette 20 are taken out one by one by these rollers 41a to 41d, and after the leading end alignment is performed, they are transported toward the platen drum 22 and are pinched by the pinch roller 25a. Thus, the platen drum 22 is wound around. Reference numeral 29a is a paper empty switch for detecting the presence or absence of the paper P, 29b is a paper size switch for detecting the paper size, and 29c.
Is a paper top switch that detects the leading edge of the paper, 29
d is an OH that detects whether the paper is a plastic sheet
It is a P detection switch. Reference numeral 21 is a manual feed guide for guiding the manually fed paper P.

The paper P is wound around the platen drum 22 by clockwise rotation, and after the leading edge passes through the printing area, the thermal head 24 is pressed against the platen drum 22 to perform printing.

When the printing of the first color is completed, the platen drum 22 is supposed to have rotated almost once. here,
The thermal head 24 is released once, and the ink ribbon 26
Is taken up and the next color is cued. Then, the platen drum 22 starts to rotate clockwise again, the thermal head 24 performs printing, and the next color is overprinted (printed).

Thus, in the case of full color copying,
Image formation is performed by four operations of yellow, magenta, cyan, and black, or three operations of yellow, magenta, and cyan. In the case of a single color such as black, the operation is performed once.

At the time of discharging the paper, the paper P is separated from the platen drum 22 by the paper discharge scraper 16a and is discharged onto the paper discharge tray 28 by the paper discharge rollers 27. In the figure, 27a is an exit switch.

FIG. 1 is a schematic control system block diagram of a digital image forming apparatus showing an embodiment of the present invention.
1, a first control unit 82 and a second sub control unit 83. The main control unit 81 includes an operation panel 50 and a display panel 5.
1, memory 52, arithmetic circuit 53, correction circuit 84, luminance / color difference separation circuit 85, image quality improvement circuit 86, color signal conversion circuit 8
7, the binarization circuit 88, the first sub-control unit 82, the second sub-control unit 83, and the switching circuits 97, 98, respectively, and controls these.

The first sub controller 82 is a light source controller 8
9, the motor drive unit 90, the photoelectric converter 11, the A / D converter 91, and the resolution conversion unit 92, which are connected to each other and control these. The light source controller 89 is connected to the exposure lamp 6 and controls the lighting and the light amount of the exposure lamp 6.
That is, the exposure lamp 6 is turned on during a normal image reading operation. The motor drive unit 90 drives the scanning motor 18. The second sub control unit 83 includes a thermal head temperature control unit 93 and the thermal head 3
1, various detection switches 94, and drive units 95 and 97, respectively, and control these. Driver 95
Is connected to and drives a drive system 96 such as a motor and a solenoid.

The correction circuit 84 performs shading correction on the image data (after resolution conversion) obtained by A / D conversion of the reflected light from the original O, that is, the variation correction of the photoelectric converter 11. The correction circuit 84 outputs the red R, green G, and blue B signals in synchronization with a clock signal from an oscillator (not shown).

The color signal conversion circuit 87 receives the luminance signal (I) and the color difference signal 1 sent from the image quality improvement circuit 86.
(C1), the color difference signal 2 (C2), Y, M, C, and B are output according to the color signal selection signal from the main control unit 81.
One of the color signals is sent to the binarization circuit 88. The color signal conversion circuit 87 is composed of, for example, a ROM and outputs a color signal corresponding to an address designated by each of the signals.

The color signal conversion circuit 87 receives the luminance signal (I) and the color difference signal 1 sent from the image quality improvement circuit 86.
(C1), the color difference signal 2 (C2), and the color signal selection signal from the main controller 81.
One of Magenta M, Cyan C, or Black B
One color signal is a clock signal from an oscillator (not shown)
It is output in synchronization with the clock divided by / 3. Switching between yellow Y, magenta M, cyan C, and black B is performed by a count value obtained by counting a page synchronization signal supplied from the main controller 81 by a counter (not shown).

The operation panel 50 includes a shading correction switch 50b for correcting deterioration distortion of an image signal of the image reading section 3 and an output distortion correction switch 50c for correcting output distortion of the printing section 5. There is. Memory 52
Is a storage unit 52a that stores reference pattern data, and M that stores the read black reference for shading correction.
0, and M1 which stores the read white standard for shading correction. The arithmetic circuit 53 is a circuit that calculates the output distortion of the printing unit 5. The switching circuits 97 and 98 are circuits that switch the signal flow between normal image processing, shading correction, and output distortion correction of the printing unit 5. Next, the operation of the copying machine will be described with reference to FIGS.

After setting the copying conditions, the copy key 50a
When is pressed, copying is performed according to the various copying conditions that have been set. That is, the reflected light of the light emitted from the exposure lamp 6 to the original O is imaged on the photoelectric converter 11. The photoelectric converter 11 separates the light into cyan (C), green (G), and yellow (Y) analog color signals, and sends them to the A / D converter 91. The A / D converter 91 converts each analog color signal into a digital signal and outputs the digital signal to the resolution conversion unit 92.

The resolution conversion unit 92 performs resolution conversion so that the resolution of the photoelectric converter 11 and the resolution of the thermal head 24 match, and the result is sent to the correction circuit 84 via the switching circuit 97. In addition, the correction circuit 84 has a memory 51
Input the correction values stored in M0 and M1. This correction value is a value obtained by adding the correction value of the reading distortion of the image reading section 3 (shading correction value) and the correction value of the output distortion of the printing section. In the correction circuit 84, the photoelectric converter 1 is applied to each of the C, G, and Y color signals sent from the resolution conversion unit 92.
The variation of 1 is corrected based on this correction value. Therefore, the correction processing here is performed along with the shading correction (correction of exposure distortion in the image reading unit 3, variation in sensitivity of the photoelectric conversion element, etc.) as described above, and the resistance value of the heating resistance element in the printing unit 5. Corrects variations and variations in pressure. The result is sent to the luminance / color difference separation circuit 85. The luminance / color difference separation circuit 85 performs various arithmetic processes on the C, G, and Y color signals sent from the correction circuit 84,
Luminance signal (I), color difference signal 1 (C1), color difference signal 2 (C
It is separated into each signal of 2) and sent to the image quality improving circuit 86. The image quality improving circuit 86 analyzes the luminance signal, the color difference signal 1, and the color difference signal 2 sent from the luminance color difference separating circuit 85, performs image quality improving processing such as edge enhancement and character specification, and sends them to the color signal converting circuit 87. .. As a result, the color signal conversion circuit 87
Performs color conversion based on the luminance signal, the color difference signal 1, and the color difference signal 2 that have been subjected to the image quality improvement processing, and according to the color selection signal from the main control unit 81, yellow (Y), magenta (M), It is converted into any one color signal (a signal corresponding to the density) of cyan (C) and black (B) [the three primary colors (Y, M, C) at the time of printing plus B] and sent to the binarization circuit 88. The binarization circuit 88 is a color signal sent from the color signal conversion circuit 87 (any one of Y, M, C and B).
On the other hand, area gradation conversion, that is, binarization is performed by a dither method or the like, and the binarized signal is passed through a switching circuit 98 to a server.
It is sent to the round head temperature control unit 93. The thermal head temperature control unit 93 sends a print signal to the thermal head 24 based on the binarized signal supplied from the binarization circuit 88. On the other hand, the paper P in the paper feed cassette 20 is taken out and conveyed by the pickup roller 41a, the paper feed roller 41b, the separation roller 41c, and the intermediate roller 41d. Then, the conveyed paper P is guided to the platen drum 22 and wound around the platen drum 22.

In accordance with such a state, the thermal head 24 responds to the print signal by the platen drum 22.
Printing (that is, image formation) is performed on the paper P that is wound around. In the obtained print, the correction circuit 84 corrects the image reading unit 3 and the printing unit 5, so that a copy more faithful to the original image can be obtained. Next, a means for correcting the deterioration distortion of the output signal in the printing unit 5 will be described.

First, deterioration distortion of an image signal in the image reading section 3 is corrected in advance (shading correction). That is,
Shading correction switch 50b of operation panel 50
When is pressed and a signal is output to the main control unit 81, the main control unit 8
1 is output to the display panel 51, and a display to that effect is displayed. Then, the light source control unit 89 of the sub control unit 82 is controlled to turn off the exposure lamp 6. In this state, the black reference value is read and the shading correction value is stored in M0 of the memory 52. Next, the light source control unit 89 of the sub-control unit 82 is controlled to turn on the exposure lamp 6, and in this state, the white reference plate 31 is read and stored in M1 of the memory 51.

Then, when the switch 50c for correcting the deterioration distortion of the printing portion of the operation panel 50 is pressed and the signal is output to the main control portion 81, the signal is output from the main control portion 81 to the display panel 51, and a message to that effect is displayed. Then, the reference data stored in the memory 52a is called. As an example of the reference data, when "00" is black and "FF" is white, the reference data is gray which is indicated by a numerical value of "80". Main controller 81
Outputs the reference data stored in the memory 52a to the thermal head temperature control unit 93 via the switching circuit 98. The sub controller 83 includes a thermal head temperature controller 93,
The thermal head 31, the drive unit 95 and the like are controlled to print a reference pattern on the paper P based on the reference pattern data. That is, the paper P taken out from the paper feed roller 41 is guided to the platen drum 22, where the thermal pad 2
4 is printed based on the print signal corresponding to the reference pattern data, and after the printing is completed, it is discharged to the paper discharge tray 28 via the paper discharge guide 27. This print does not pass through the image reading unit 3, and thus the output reference pattern data shows the recording characteristic of the print unit 5, that is, the output distortion of the print unit 5 including the heat generation distribution characteristic of the thermal printer head. ..

Next, the reading unit 3 reads the output reference pattern (that is, the pattern that includes the distortion of the printing unit 5 but does not include the deterioration distortion of the image signal in the image reading unit 3). That is, the photoelectric control unit 89 of the sub-control unit 82 is controlled to turn on the exposure lamp 6, and the motor driving unit 90 is controlled to drive the traveling motor 18. Then, the printed reference pattern is read by the photoelectric converter 11, the A / D converter 91, etc.,
The read reference pattern is output to the main controller 81 via the switching circuit 97. The read reference pattern includes the distortion of the printing unit 5 and the deterioration distortion of the image signal in the image reading unit 3. The deterioration distortion of the image signal has already been read, and M
0 and M1, the distortion of the printing section 5 (heat distribution characteristic of the thermal printer head) is calculated by the arithmetic circuit 53 from the correction value of the deterioration distortion in the known image reading section 3 and the read reference pattern. Is converted into a white reference value for shading and a black reference value for shading in a form corresponding to the correction value of the deterioration distortion in the image reading unit 3 and digitized. Then, this value is added to M0 and M1 of the memory 52, respectively.

Accordingly, the correction in the correction circuit 84 is
The printing unit 5 together with the correction value of the reading distortion in the image reading unit 3
The processing is performed based on the output distortion correction value in (1), and thus a copy more faithful to the original image can be obtained.

In this embodiment, the example of correcting the variation of the thermal transfer type printing apparatus by the thermal printer head has been described, but it can be applied to the correction of the laser printer scanner exposure apparatus.

[0035]

According to the present invention, the output distortion in the printing portion including the variation of the heat generation distribution of the heating resistor of the thermal printer head is relatively simple in the printing distortion due to the deviation from the plane of the resistor. It is possible to reduce the grayscale distortion of the image by performing the correction including the correction of. Further, unlike the conventional case, it is not necessary to replace the storage element ROM that stores the resistance value variation of the heating resistor in a dot unit when the thermal printer head is damaged, and a circuit for correcting the image data in a dot unit is also required. No longer needed.

[Brief description of drawings]

FIG. 1 is a schematic control system block diagram of a digital image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a digital image forming apparatus showing an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of an image reading unit of the apparatus.

FIG. 4 is a flowchart for obtaining a correction value for output distortion of a printing unit of the same device.

[Explanation of symbols]

1 ... Copier main body, 2 ... Document table, 3 ... Image reading unit, 4 ...
Image processing unit, 5 ... Image forming unit, 6 ... Exposure lamp, 7 ... First carriage, 8 ... Second carriage, 8a, 8b ... Miller, 9 ... 10 ... Miller unit, 10a, 10b ... Miller,
11 ... Photoelectric converter, 12 ... Reflector, 13 ... Mirror,
16 ... Lens part, 16a ... Lens, 16b ... Color correction filter, 17 ... Heat ray absorption filter, 18 ... Scanning motor, 19 ... Gloss detector, 20 ... Paper feed cassette, 21
... Manual feed guide, 22 ... Platen drum, 22a ... Grip sensor, 22b ... Paper width sensor, 22c ... Platen drum drive motor, 22d ... Paper discharge scraper, 24 ... Ser
Round head part, 24a ... Thermal printer head, 24
b ... heat sink, 24c ... pressure spring, 24d ... cam,
24e ... cam switch, 25a, 25b ... pinch-
La, 26 ... Ribbon cartridge, 26a ... Ink ribbon, 26b ... Ribbon guide, 26c ... Slide rail,
27 ... Paper discharge roller, 27a ... Exit switch, 28
... Paper ejection tray, 29a ... Paper empty switch,
29b ... Paper size switch, 29c ... Paper top switch, 29d ... OHP detection switch, 31 ... Shading correction white reference plate, 32 ... Original size indicator, 41a ... Pickup roller, 41b ... Paper feeding roll
La, 41c ... Separation roller, 41d ... Intermediate roller, 50 ...
Operation panel, 50a ... Copy key, 50b, 50c ... Switch, 51 ... Display panel, 52 ... Memory, 52a ... Reference pattern data storage section, 53 ... Arithmetic circuit, 81 ... Main control section, 82 ... First control section, 83 ... Second sub-control unit, 84
Compensation circuit, 85 ... Luminance color difference separation circuit, 86 ... Image quality improvement circuit, 87 ... Color signal conversion circuit, 88 ... Binarization circuit, 89
... light source control section, 90 ... motor drive section, 91 ... A / D converter, 92 ... resolution conversion section, 93 ... thermal head temperature control section, 94 ... various detection switches, 95 ... drive section, 96 ...
Drive system, 97, 98 ... Switching circuit, 100 ... Original cover,
100a ... manuscript pocket.

Claims (1)

Claim: What is claimed is: 1. An image reading unit for reading a document to generate digital image data; and a digital image data generated by the image reading unit, a correction value of a reading distortion of the image reading unit, and an image. An image processing circuit that corrects based on the correction value of the output distortion of the forming unit to create digital print data, and an image that forms an image on an image forming medium based on the digital print data created by the image processing circuit. Forming means; pattern generation means for forming an image of the reference pattern by the image forming means based on preset reference pattern data; and digital printing data by the image reading means from the image of the reference pattern by the pattern generation means Means, the digital print data created from the image of the reference pattern, and A means for detecting a value including the reading distortion of the image reading means and the output distortion of the image forming means by comparing with the reference pattern data; and the detected value and the correction value of the reading distortion of the image reading means. A digital image forming apparatus comprising: a unit that calculates a correction value of output distortion of an image forming unit based on the output unit; and a unit that outputs the correction value to the image processing circuit.