JPS59163967A - Image reproducing system - Google Patents

Abstract

PURPOSE:To attain color reproduction with stable and excellent picture quality by generating a reference gradation signal with a diagnostic command signal and applying gradation correction with an output processing its signal. CONSTITUTION:When a test mode switch 165 is turned on, the diagnostic command signal is generated, lighting lamps 5, 6 are moved along an original 1, then a test chart 4 is scanned and image pickup elements 14, 16, 18 generate three color reference signals of blue B, green G and red R, respectively. Outputs of the elements 14, 16, 18 are subjected to prescribed processing at an image processor 27, laser light from a semiconductor laser 21 scans a photosensitive drum 24 via a polygon mirror 22 to form an electrostatic latent image on the drum 24. This latent image is transferred on a sheet of copy paper 48 wound on a transfer drum 53. The image on the chart 4 tranferred on the copy paper is read by a photo sensor unit 170 and the gradation is corrected by four phototransistors sensing the pattern with different gradation difference.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reproduction system for a printer such as a color copying machine.

A printer that reproduces color using a photosensitive drum will be described below as an example. This processes the color signals B, G, R to control the laser and sends Y, M, C to the photosensitive drum.

A BK latent image is formed, developed with Y, M, C, and BK developers, and transferred to transfer paper to form a color image. In this case, the color image quality is likely to deteriorate due to fatigue, aging, etc. Therefore, frequent service mate maintenance is required. .

The present invention eliminates these drawbacks by generating a reference gradation signal and making it possible to stably reproduce color with good image quality by outputting the processed signal.

FIG. 1 shows this embodiment. A document 1 is placed on a transparent plate 2 of a document table and fixed to a document mat 3. The photosensitive drum 24 and the transfer drum 53 rotate in the direction of the arrow to perform a color process.

12 is a dichroic mirror for spectroscopy, and 14, 16, and 18 are CODs that sense spectral light and generate color signals B, G, and R. The second amplifier 8, Mi 7-9, and 10 reciprocate to scan the original 1, and at the same time output color signals B, G, and R from each CCD, actuate the Y signal for reproduction, and then reciprocate again to scan the M Output the signal and repeat the above scanning 4 times to obtain Y, M, C, BK.
A signal is generated and the laser is controlled to sequentially form latent images of each color on the drum 24. Each color is developed sequentially and the transfer drum 56 is
The image is then rotated and transferred onto the paper on top of it, creating a full-color copy.

The optical system emits light from illumination lamps 5 and 6, and reflects light from a reflecting mirror 7.
. Here, the light is split into blue wavelength light, green wavelength light, and red wavelength light. Of the respective decomposed lights, the decomposed light of blue wavelength passes through each filter 16 and is received by the solid-state image sensor 14 . Similarly, light with a green wavelength passes through a green filter 15 and passes through a solid-state image sensor 16.
The light is received by the The light with the red wavelength passes through the red filter 17 and is received by the solid-state image sensor 18 . That is, the document 3 is moved by the movable reflection mirror 9 that moves together with the illumination panels 5 and 6.
The moving reflection mini 17-10, which moves in the same direction at a moving speed of % of the moving reflection mirror 9, further condenses the light onto the solid-state image sensors 14, 15, 16 of each color via the lens 11 and dichroic filter 12 while maintaining the optical path length. imaged.

A test chart 4 for automatically controlling color balance and gradation, which will be described later, is provided in front of the original. Copy key 1 with test mode switch 1650 on condition
When the illumination lamp 66 is turned on, this test chart 4 is also scanned when the illumination lamp moves along the document, and the COD generates a reference signal. Each solid-state image sensor 14.1<i,
The output of 18 passes through an image processing section 27, which will be described later, and is irradiated from a semiconductor laser 21 to a polygon mirror 22 as a light output. Since the polygon mirror 22 is rotated by a scanner motor 26, the laser beam is scanned perpendicularly to the rotation direction of the photosensitive drum 24. A photosensor 64 is located at a position 11 days before the laser beam starts scanning the drum, and when the laser beam hits this, it generates B and D signals.

The photosensitive drum 24 is negatively charged by a negative charger 25 that is supplied with a negative high voltage current from a high voltage power source 25. Next, when reaching the exposure section 26, the transparent plate 2 of the document table is exposed.
The document 1 above is illuminated by illumination lamp 5. A movable reflecting mirror 9, 10, a lens 11, a dichroic filter 12,
Solid-state image sensor 14 . IS, imaged at 18. As shown in the block diagram of the image processing unit 27 in FIG. 2, the image output from the COD is subjected to shading correction by the shading unit 2 for each color, and the γ correction unit 2
9 performs gamma correction (gradation linearization), masking processing unit 30 performs turbidity correction, UCR processing unit 31 performs undercolor removal correction, and buzzer processing unit 32 performs p
The gradation reproduction is corrected, the gradation is further corrected by the multilevel processing unit 33, the laser 21 is modulated from the laser driver unit 34, and the laser beam is sent to the photosensitive drum 2.
is imaged.

There, an electrostatic latent image is formed and the four color developers 36, 57
.

Enter 38.59. Here, each of the above processes is performed by separating the three colors in one exposure scan, and a UCR processing output is output for each scan of B, G, R, and BK (blank). 1 in the image processing unit 27 according to the signal from the control section.
The configuration is such that when a color separation optical signal is selected, a corresponding developer is selected.

The developer selected thereupon performs powder development using a magnetic freding method, and the electrostatic latent image is visualized. After that, the ghost lamp 40 for erasing the electrostatic latent image and the negative post electrode 41 supplied with the negative voltage power supply 25 are used to remove the negative (next, the upper and lower parts) 4
5. The copy paper 4B fed by rotating paper feed rollers 46 and 47 passes through the upper and lower rollers 49 and 50, and then passes through the transport roller 51.
After passing through the second registration roller 52, the transfer drum 53
wrapped around. Thereupon, the toner on the photosensitive drum 24 is transferred onto the copy paper 48 by the transfer electrode 54. The transfer is performed several times for the selected color, and each time the copying paper 48 is neutralized by a static eliminating electrode 55 to which a high voltage is supplied from the AC high voltage generator 25. When the selected number of transfers is completed, the paper is peeled off from the gripper 57, adsorbed onto the belt 59 by the conveyor belt 58, and guided to the fixing section 60.

In the test mode, the reference color signal from the test chart is reproduced on paper through the above-described image processing and gross sequence, and then discharged.

In this case, the scanning movement is less than the distance of the maximum document size and is near the test chart, which is intended to shorten the time.

FIG. 2 shows a schematic diagram of the image processing unit and knit. The light from the document separated into three colors by the dichroic filter is received by the solid-state image sensors 14i11i5 and 18.

The output is sent to the COD light receiving unit (Sf, 62.63
The information of a plurality of pixels in the CCD is amplified, converted into a digital converter, and sent to the next seeding unit 28. Next, a signal is sent from the main body control section 64 when the optical system passes through the white portion of the chart 4, and the shading unit 28 adjusts the output level of the COD to a constant level. From the shading unit 28, the r correction unit 29
The input sensitivity of the OD is switched according to the signal from the main body control section 64. The signals are subjected to arithmetic processing on each of the B, G, and R signals simultaneously in a masking processing unit 30, and color correction is performed by changing the mixing ratio of each color component.

The mixing ratio of each color is determined by switching signals in the main body control section. The signal is processed by the UCR processing unit.

The minimum value signal of G and R is determined, and the value obtained by multiplying the minimum signal by an arbitrary coefficient using one main body control section is set as a black level signal.

Whether that value is subtracted from each color or not depends on the main body control signal. Here each color B, G.

Among the R and BK signals, one color signal is sent to the buzzer processing unit 32 by a select signal from the main body control section 64.
sent to. The buzzer processing unit 62 uses a table reference ROM to compare each color signal as a deep signal, for example, an 1-bit signal, and converts it into a 1.0 digital signal, making it easier to modulate the laser. Make it. Next, the buzzer processing unit 32 is provided with a buzzer ROM that processes the buzzers in parallel, that is, a buzzer ROM in which high threshold levels are arrayed and a buzzer ROM in which low threshold levels are arrayed, and multi-level processing is performed in which the outputs thereof are selected. Pass unit 33. This allows one pixel to be represented by, for example, three values (high, medium, low) density, and the main body control section performs selection control of this processing section knit. The multilevel processing unit is designed to output one pixel with a pulse width of 1° OoS, O, and the laser driver unit 34 drives the laser 21 based on the output. This is the input signal and the two buzzers R mentioned above.
Simultaneously compare and process OM and those controllers,
Each of these outputs is timed and sequentially controlled and output in an OR relationship. Buzzer R for each color
OM's turn is different.

Next, a block diagram of the main body control section 64 is shown in FIG. When the user operates the main control unit 72 and the sub-control unit 73 operated by a service person, the control bus CBU of the CPU 65 is transmitted from the bus controller 69 through the key I1066.
The copy data is input to S and the copying operation is performed in the memory section 6.
Operate according to the contents of 8. This operation consumes 65 CPU
is connected to port 7 by the controller CBUEI.
4 to input the input device from the input interface 75.

The signals from ~Oj are input, and the output device [0, ~Oj] is operated from the output driver 76. Further, the CPU outputs operation data from the main control 72 or sub-control 73 to the image processing controller V071 using the bus controller, and sends the control data to the image processing section. The sequence of this copying machine is that the clock from the reference pulse generator 7o driven by the drum motor is sent to the CPU.
It is controlled by inputting it to the 65-unit NT.

Command input signals and input switch sensor signals related to the test mode are input via the input interface 75.

A photosensor unit 170 consisting of a light emitting diode and a phototransistor is provided on the path leading 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 has a reflective illumination sensor configuration, in which phototransistors and light emitting diodes are arranged alternately as shown.

FIG. 7 is a flowchart showing the cover correction control in the test mode, which is programmed in the memory 68 (FIG. 3) of the microcomputer CPU of the main body control section of FIG. 2. The CPU has a test mode switch 165, a copy key 166, a warning IS7. X) Lag lamp 168 and sensor unit 170 are connected.

Generally, when a photosensitive drum or developer becomes tired, the density decreases, and the difference in density between dark and thin areas becomes smaller.

In the example of the present invention, when it is detected that this difference is small, γ increases even more than the current memory.l) A memory with a large change in output data relative to a change in input data is selected. A constant gradation is always obtained.

When the test mode switch 165 is turned on, the input of the reset button is first determined (step ja).

For example, there are ROM memories for each of the three colors in which four types of γ curves are set for each color, but among these, the memory with a gentler slope of the γ curve cannot be selected for each color. , switch 8WB1. , 5
Select WQI and SWR1.

For example, the switch that determines γ of a blue image is 5WB1.
5WB2.5WB5.8WB4 The slope of γ is steeper when the 4-digit number is large.

For maintenance, for example, immediately after drum replacement, the Kl serviceman presses the reset button (not shown) to reset 5WB1°SWG, , S at steps 2a and 3a.
Turn on WB4 and reset r.

During this time, the main body control unit 64 controls the photo sensor 170 by counting clock input from the reference pulse generator 70 synchronized with the drum drive motor from the start of forming the latent image on the drum.
Step 4a) Read the signal from the photosensor '170 (5a) For example, ld'0. If there is a difference of 1V or more (6a), adjust the current flowing to the light emitting diode (7a) to eliminate the difference. This can be done by automatically controlling the light emitting diode of 1c170 with a D/A conversion signal. In addition, without adjusting the above difference to zero, it is also possible to memorize the variation between the phototransistors and perform pre-correction by υ every time the value is corrected when reading the B, G, and H images. .

Next, in the same way as in step 4a, when the patch image reaches the center of the bull part (8a), read the signal from the photo sensor (9a). It is difficult to judge if there are enough gradations.1
0a), if it is 0.59 V or less, the γ selection switch SWB 1 to 4 of the currently selected color-specific γ memory
Please judge which one is ON (11a, 12a, 13a)
, for example, when SWB is ON, 8WB1 is turned OFF and the next 5WB2 is turned ON. If 8WB is ON, turn EIWB off and turn on SWB4. 5
Since WB4 does not have a memory with a rapid r value, the alarm 2 amplifier 167 notifies the user that correction is not possible if the image quality is any worse (18a).

When it is no longer formed (13a), the stop lamp 168 is set to 0NL (14), and the next copying operation is prohibited until the reset button is pressed.The same applies to green and red.

Note that it is possible to determine whether a predetermined voltage exists between the transistors by determining whether each output of an analog operational amplifier provided between two phototransistors is 1 or not. In this way, γ for each color is obtained from the test chart.
Select a specific memory of the correction unit 29.

Note that when the threshold array of the aforementioned design ROM is selected according to the gradation judgment signal, the multi-value processing level (binary, 3-value) of the multi-value processing unit is determined.
It is also possible to faithfully reproduce the gradation by selecting one of the following values:

Backup means is provided in the image processing unit 27 so that once the γ memory is selected, the same correction circuit can be selected at the next copying operation even if the main SW is turned off.

Note that the present invention can also be applied to a color printer that prints with 4 dots per pixel. Furthermore, even if the B, G, and R signals are transmitted from the host computer, the standard color signals as described above can be generated from the host or generated internally and input to the input 2 inputs B, G, and R. It can be achieved.

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

It is also possible to display the above-mentioned gradation deviation determination output and perform manual adjustment.

Another example is not to transfer the chart image to copy paper.
By creating the image at the drum position shown in FIG. 6 and detecting the image of the chart on the drum with a photosensor, correction can be made during normal copying without providing a test mode.

It can also be achieved by measuring the potential of the drum surface corresponding to Test Char) K. Also, an output signal Y corresponding to the test chart from the UCR processing unit.

It is also possible to measure and correct M and C. Furthermore, by increasing the distance between the housing unit 2B and the housing unit 2B, it can be used as a communication device, for example, spanning buildings. Also, instead of pasting a chart, a circuit that generates the same signal as when reading a chart may be stored.

The gamma curve was changed by changing the memory used to read and select the chart image, but the correction range was further improved by changing the lighting voltage of the illumination lamp 5゜6, the voltage of the charging electrode 63, the light intensity of the laser 21, and the gain of the COD amplifier. can be made wider.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the force 2-copying machine, Fig. 2 is a block diagram of the image processing section, Fig. 3 is a block diagram of the main body processing unit,
FIG. 4 is a test chart diagram, and FIG. 5 is a copy of the chart and a photosensor. In the diagram, 170 is a sensor unit, 24
is a photosensitive drum. 4th review No. 5 (Foundation) Ne1 copy and the direction of the chosen helmet of the people

Claims (2)

[Claims] (1) It has a reference gradation signal generation means and a diagnostic command signal generation means, and can generate the reference gradation signal based on the diagnostic command signal and perform gradation correction using the output of the processed signal. An image reproduction system characterized by: (2) The image reproduction system according to item 1, wherein the gradation of each color is controlled by the processed output of the reference color signal.