JPH0669210B2 - Image playback device - Google Patents

Description

The present invention relates to a color system such as a printer of a color copying machine.

A printer that reproduces color using a photosensitive drum will be described below as an example. It processes color signals B, G, R to control the laser, forms a latent image of Y, M, C, BK on the photosensitive drum, develops it with the developer of Y, M, C, BK and transfers it. To form a color image. In this case, the color image quality is likely to be deteriorated due to fatigue, aging, and the like. For that reason, service maintenance is often required.

The present invention eliminates such drawbacks, and enables stable color reproduction of good image quality by generating a reference gradation signal and outputting the processed reference gradation signal.

This embodiment is shown in FIG. The document 1 is fixed by a document mat 3 placed on the transparent plate 2 of the document table. The photosensitive drum 24 and the transfer drum 53 rotate in the arrow direction to execute the color process. Reference numeral 12 is a spectroscopic dichroic mirror, and reference numerals 14, 16 and 18 are CCDs that sense the spectrum and generate color signals B, G, and R, respectively. The lamp 8 and the mirrors 9 and 10 reciprocate to scan the original 1 and simultaneously output color signals B, G, and R from each CCD to generate a Y signal for reproduction, and then reciprocate again to output an M signal. The above scanning is repeated four times to form Y, M, C, and BK signals, and the laser is controlled to sequentially form each color latent image on the drum 24. Each color is sequentially developed, and the transfer drum 53 is rotated four times to repeatedly transfer the paper onto the paper to obtain a full-color copy.

The optical system emits light from the illumination lamps 5 and 6, and is combined with the light from the reflecting mirrors 7 and 8 to illuminate the original, and the reflected light is reflected by the moving reflecting mirrors 9 and 10 and the lens 11 Pass through the 12 dichro filters. Here, it is split into light of blue wavelength, light of green wavelength, and light of red wavelength. The blue wavelength of the split light of each split light passes through the blue filter 13 and the solid-state image sensor.
Received by 14. Similarly, light of a green wavelength passes through the green filter 15 and is received by the solid-state image sensor 16. The light of the red wavelength is received by the solid-state image sensor 18 through the red filter 17. That is, the manuscript 3 is moved together with the illumination lamps 5 and 6, and is moved by the moving reflecting mirror 9 and 1 / the
An image is formed on the solid-state image pickup devices 14, 15, 16 of each color through the lens 11 and the dichro filter 12 while maintaining the optical path length by the moving reflection mirror 10 that moves in the same direction with the moving speed of 2. A test chart 4 for automatically controlling color balance and gradation described later is provided in front of the original. When the copy key 166 is turned on under the condition that the test mode switch 165 is turned on, the test chart 4 is also scanned when the illumination lamp moves along the document, and the CCD generates the reference signal. The output of each of the solid-state image pickup devices 14, 16 and 18 is applied as a light output from the semiconductor laser 21 to the polygon mirror 22 via an image processing unit 27 described later. Since the polygon mirror 22 is rotated by the scanner motor 23, the laser light is scanned perpendicularly to the rotation direction of the photosensitive drum 24. A photo sensor 64 is located at a position of 11 mm where the laser beam starts scanning on the drum, and when the laser beam hits the photo sensor 64, B and D signals are generated.

The photosensitive drum 24 is negatively charged by the negative charger 25, which is supplied with a negative high voltage current from the high voltage power supply 25. Then, when it reaches the exposure unit 26, the original 1 on the transparent plate 2 of the original table is illuminated by the illumination lamps 5 and 6, and the moving reflecting mirrors 9 and 10 are moved.
And lens 11, dichro filter 12, blue filter 1
3, images are formed on the solid-state image pickup devices 14, 16 and 18 by the green filter 15 and the red filter 17. The image output from the CCD is subjected to the aging correction by the siding unit 28 for each color from the block diagram of the image processing unit 27 of FIG.
Γ correction (gradation linearization) by the correction unit 29, turbidity correction by the masking processing unit 30, undercolor removal correction by the UCR processing unit 31, gradation reproduction correction by the dither processing unit 32, multi-value processing unit. The gradation up is further corrected by 33, the laser 21 is modulated from the laser driver unit 34, and the laser light is imaged on the photosensitive drum 24. There, an electrostatic latent image is formed and four color developing devices 36, 37,
Enter 38,39. Here, the above processes are performed by separating the three colors with one exposure scan, but the UCR process output is output for each scan of B, G, R, and BK (black). When the one-color separation optical signal in the image processing unit 27 is selected by the signal of the control unit, the corresponding developing device is selected.
The developing device selected there is carried out by powder development by the magnetic flade method, and the electrostatic latent image is visualized. After that, the ghost miniature lamp 40 for erasing the electrostatic latent image and the negative post electrode 41 supplied from the negative voltage power source 25 negatively charge the electrostatic latent image.

Next, the upper and lower cassettes 43 and 44 are selected from the cassette selected from the operation unit 45, and the copy paper 48 sent by rotating the paper feed rollers 46 and 47 passes through the upper and lower 49, 50 of the first registration roller. The transfer roller 51 passes through the second registration roller 52 and is wound around the transfer drum 53. Therefore, the toner on the photosensitive drum 24 is transferred to the copy paper 48 by the transfer electrode 54. The transfer is performed the number of times of the selected color, and each time the copy paper 48 is transferred by the static elimination electrode 55 supplied with a high voltage from the AC high voltage generator 25.
To remove the electricity. When the transfer is completed the selected number of times, the paper is peeled off from the gripper 57 and the belt is conveyed by the conveyor fan 58.
It is adsorbed on 59 and guided to fixing unit 60.

In the test mode, the reference color signal by the test chart is reproduced on the paper and discharged through the above-mentioned image processing and process sequence. In this case, the scanning movement is less than the maximum document size distance and is near the test chart, which shortens the time.

FIG. 2 shows a block diagram of the image processing unit. The light of the original separated into three colors from the dichroic filter is received by the solid-state image pickup devices 14, 16 and 18. The output is amplified by CCD light receiving units 61, 62 and 63 to increase the information of a plurality of pixels in the CCD, and A /
It is converted to a D converter and sent to the next seeding unit 28.
Next, when the optical system passes through the white part of the chart 4 from the main body control part 64, a signal is sent, and the shading unit 28 corrects the output level of the CCD so as to be constant. CCD from the sheathing unit 28 to the γ correction unit 29
The input sensitivity of is switched by the signal of the main body control unit 64. The B, G, and R signals are simultaneously processed in the masking processing unit 30 for the signals, and the color correction is performed by changing the mixing ratio of each color component. The mixing ratio of each color is performed by switching the signal of the main body control unit. The signal in UCR processing unit
The minimum value signal of B, G, R is discriminated, and the value obtained by multiplying the minimum signal by an arbitrary coefficient with the main body control signal is taken as the black level signal.
Whether or not the value is subtracted from each color depends on the control signal of the main body. Here, among the signals of each color B, G, R, BK, the main body control unit 64
The signal of one color is sent to the dither processing unit 32 by the select signal of. In the dither processing unit 32, each color signal is compared with a deep signal, for example, a 6-bit signal by using a ROM of a table reference, and is converted into a digital signal of 1.0 to facilitate laser modulation. Next, in the dither processing unit 32, a block for parallel dither processing, that is, a dither ROM in which ones having a high threshold level are arranged and a dither ROM in which ones having a low threshold value are arranged are provided, and a multi-value processing unit 33 for selecting an output by this is provided. Pass through. This is one pixel for example 3
It is designed so that it can be expressed by the density of the value (high, medium, low), and the select control of this processing unit is performed by the main body control section. The multi-value processing unit is intended to output one pixel with a pulse width of 1,0.5,0, and the laser driver unit 34 drives the laser 21 by the output. This compares the input signal with the two dither ROMs at the same time by their comparators, and sequentially controls their respective outputs temporally with timing to output them in an OR relationship. The pattern of the dither ROM is different for each color.

Next, FIG. 3 shows a block diagram of the main body control unit 64. When the user operates the main control unit 72 to be operated and the sub control unit 73 to be operated by a service person or the like, operation data is input from the bus controller 69 through the control bus CBUS of the CPU 65 via the key I / O 66 to perform a copy operation. It operates according to the contents of the memory 68. By this operation, the CPU 65 inputs signals from the input interface 75 to the input devices I ₁ to Ij by using the I / O port 74 by the bus controller CBUS, and moves the signals from the output driver 76 to the output devices O _{1 to} Oj. In addition, the CPU sends the operation data from the main control 72 or the sub-control 73 to the image processing controller I / I using a bus controller.
Output to O 71 and send control data to the image processing unit. The sequence of this copying machine is controlled by inputting the clock from the reference pulse generator 70 driven by the drum motor to the INT of the CPU 65.

The command input signal related to the test mode and each signal of the input switch sensor are input through the input interface 75.

A photosensor unit 170 including a light emitting diode and a phototransistor is provided on the path to the fixing device 60 to read the chart image formed on the copy paper.

FIG. 5 shows the image position of the chart 4 formed on the copy paper and the arrangement of the photosensor unit 170, which is a reflection type sensor configuration, in which the phototransistors and the light emitting diodes are alternately arranged.

FIG. 7 is a flow chart showing the color correction control in the test mode, which is the microcomputer of the main body control unit in FIG.
It is programmed in the CPU memory 68 (FIG. 3). CPU
A test mode switch 165, a copy key 166, a warning lamp 167, a stop lamp 168, and a sensor unit 170 are connected to the.

Generally, when the photosensitive drum and the developer are fatigued, the density is lowered and the density difference between the dark portion and the thin portion is reduced.

In the present invention example, when it is detected that this difference is small, a memory in which γ stands still further than the current memory, that is, a memory in which the amount of change in the output data is large relative to the amount of change in the input data is selected is always constant. Gradation can be obtained.

When the test mode switch 165 is turned on, the input of the reset button is first judged (step 1a). This is, for example, for each color, there are three types of ROM memories in which four types of γ-curves are set, but among these, the γ-curve has a gradual inclination and is used to select a gradual memory for each color. Select switches SWB ₁ , SWG ₁ , and SWR ₁ . For example, the switches that determine γ in the blue image are SWB ₁ , SWB ₂ , SWB ₃ , and SWB.
_{There are four} and four. The larger the number, the steeper the γ slope.

Immediately after the maintenance, for example, the drum is replaced, a serviceman pushes a reset button (not shown) to turn on SWB ₁ , SWG ₁ , and SWR ₁ at steps 2a and 3a to reset γ.

During this time, the main body control unit 64 counts the clock input from the reference pulse generator 70 synchronized with the drum drive motor from the start of latent image formation on the drum, so that the white center of the patch image arrives under the photo sensor 170. (Step 4a), the signal from the photo sensor 170 is read (5
a) If there is a difference of 0.1 V or more among the four phototransistors that sense patterns of different gradations (6a), adjust the current flowing through the light emitting diode (7a) to eliminate the difference. This can be done by automatically controlling 170 light emitting diodes with D / A conversion signals. It is also possible to perform the precorrection by storing the variation between the phototransistors without adjusting the difference to zero and correcting the values when the B, G, and R images are read. Next, as in step 4a, when the center of the blue part of the patch image is reached (8a), the signal from the photosensor is read (9a). If the difference between the four phototransistors is a constant value, such as 0.6V or more, It is judged that the tone is sufficient (10a), and if it is 0.59V or less, it is judged which one of the γ selection switches SWB1 to SWB4 of the currently selected γ memory for each color is ON (11a, 12a, 13a), For example, when SWB ₁ is ON, turn SWB ₁ OFF and then turn SWB ₂ ON. If SWB ₃ is ON, turn SWB ₃ OFF and turn SWB ₄ ON. SWB
Since there is no memory of γ that is steeper than ₄ , the warning lamp 167 informs that the correction cannot be made if the image quality is worse (18a).

If the normal image is not formed due to further fatigue or the illumination lamps 5 and 6 are known (13a), the stop plump 168 is turned on (14a) and the next copying operation is performed. It is prohibited until you press the reset button. The same applies to greens and reds.

Whether or not there is a predetermined voltage between the phototransistors can be determined by determining whether or not each output of the analog operational amplifier provided between the two phototransistors is one. In this way, γ for each color from the test chart
Select a specific memory for the correction unit 29.

It is to be noted that the gradation judgment signal is used to select the threshold value array of the above-mentioned dither ROM, or the level (binary, 3
It is also possible to faithfully reproduce the gradation by selecting the value or the four values.

Once the .gamma. Memory is selected, a back-up means is provided in the image processing unit 27 so that the same correction circuit can be selected in the next copying operation even if the main switch is turned off.

It can also be applied to a color printer that prints with 4 dots per pixel. Even when the B, G, R signals are transmitted from the host computer, the reference color signal as described above is generated from the host or internally generated and the input line B,
It can be achieved by inputting to G and R.

This example can also be applied to a reproduction system using monochrome digital processing.

It is also possible to display by the output of the above-mentioned gradation shift and manually adjust.

As another example, without transferring the image of the chart to the copy paper,
It is also possible to make corrections during normal copying without providing a test mode by creating the image at the drum position in FIG. 6 and detecting the image of the chart on the drum with a photo sensor.
It can also be achieved by measuring the potential of the drum surface corresponding to the test chart. It is also possible to measure and correct the output signals Y, M and C corresponding to the test chart from the UCR processing unit. The photo sensor has a combination of a lamp and a CCD.

It is also possible to make the distance between the CCD light receiving units 61, 62, 63 and the shielding unit 28 of FIG. 2 longer so as to be used as a communication device, for example, across buildings. Also, a circuit for generating the same signal as when the chart is read may be incorporated instead of attaching the chart.

The γ curve was changed by changing the memory for reading and selecting the chart image, but the correction range can be further changed by changing the lighting voltage of the illumination lamps 5 and 6, the light quantity of the voltage laser 21 of the band electrode 63, and the gain of the CCD amplifier. It can be widened.

(Effects of the Invention) As described above, according to the present invention, gradation correction is performed on an input image signal, and an image is formed on a recording medium according to the image signal after the gradation correction. In the image reproducing apparatus, a signal generating means (corresponding to the chart 4 in FIG. 1 in the embodiment) for generating a reference signal composed of a pattern having different gradations, and a reference image or gradation corresponding to the reference signal. The image forming means (also the laser 21 in FIG. 2) for forming the corrected reference image on the recording medium, and a plurality of elements for reading the image of the portion of the recording medium having different gradations. A conversion unit for reading the reference image formed on the recording medium by the image forming unit and converting the reference image into an electric signal according to a gradation pattern of the image (photosensor 170 in FIG. 2); Output from conversion means Tone correction means for setting the tone correction characteristic for the image signal based on the difference signal of the electric signal to be performed, and the tone correction means for performing the tone correction of the image signal by the tone correction characteristic (also in FIG. 2). The gradation correction unit 29) and the first judgment means for judging whether or not the gradation correction means can change the gradation correction characteristics (also the main body control section 64 in FIG. 2).
And a first display unit (also an alarm lamp 167 in FIG. 2) for displaying that the gradation correction characteristic cannot be changed by the first judgment unit, and the image forming unit. Second determining means (also the main body control section 64 in FIG. 2) for determining whether or not proper image formation by
Second display means (also stop lamp 168 in FIG. 2) for displaying the fact that proper image formation cannot be performed by the image forming means by the second determining means.
When the first judging means judges that the gradation correcting characteristic cannot be changed by the gradation correcting means, the image forming means permits the image formation, and the second judging means makes the image. By forming the image on the recording medium according to the input image signal, it is possible to have a control means for prohibiting the image formation by the image forming means when it is determined that the image formation by the forming means cannot be performed properly. It is possible to improve the image quality and operability when performing.

In particular, according to the present invention, since a plurality of elements are provided for reading an image of a portion having different gradations on the recording medium, high-speed reading is possible, and whether or not the gradation correction characteristics can be changed and whether the gradation correction characteristics are appropriate or not can be changed. Since the display means for distinguishing whether image formation is possible and displaying the determination result is provided, it is easy for the operator to take an appropriate action according to either of them, and moreover, the gradation correction characteristic is simply changed. If it is not possible to prevent the image formation, it is possible to provide a device which is easy to use because the image formation is not prohibited.

[Brief description of drawings]

FIG. 1 is a sectional view of a color copying machine, FIG. 2 is a block diagram of an image processing unit, and FIG. 3 is a block diagram of a main body processing unit.
FIG. 4 is a test chart, FIG. 5 is a diagram showing a copy of the chart and the positional relationship of the photosensor, and FIG. 6 is a diagram showing a copy of the chart of another embodiment and the positional relationship of the photosensor.
The figure is a control flow chart, in which 170 is a sensor unit and 24 is a photosensitive drum.

Claims (1)

[Claims] 1. An image reproducing apparatus for performing gradation correction on an input image signal and forming an image on a recording medium according to the image signal after the gradation correction, from a pattern having different gradations. A signal generating means for generating a reference signal, an image forming means for forming a reference image or a reference image after gradation correction according to the reference signal on a recording medium, and a gradation on the recording medium. Is composed of a plurality of elements for reading images of different portions, and reads the reference image formed on the recording medium by the image forming unit,
Converting means for converting into an electric signal according to the gradation pattern of the image; and setting a gradation correction characteristic for the image signal based on a difference signal between the electric signals outputted from the converting means, Gradation correction means for correcting the gradation of the image signal according to the gradation correction characteristics, and first judgment means for judging whether the gradation correction characteristics can be changed by the gradation correction means. If the first judgment means judges that the gradation correction characteristic cannot be changed by the gradation correction means, a first display means for displaying the fact and a proper image formation by the image forming means Second determination means for determining whether or not the image formation is possible, and the second determination means for displaying, when the second determination means determines that proper image formation cannot be performed by the image forming means. The display means and the first determination means When it is determined that the gradation correction characteristic cannot be changed by the gradation correction unit, the image formation by the image formation unit is permitted, and the proper image formation by the image formation unit cannot be formed by the second determination unit. An image reproducing apparatus comprising: a control unit that prohibits image formation by the image forming unit when it is determined that