JPH0618440B2 - Color system - Google Patents

Description

The present invention relates to a color system having reproduction means for processing an input color component signal and reproducing a color image.

[Prior Art] Conventionally, there is known a laser beam printer that forms an image by forming a latent image on a photoconductor and visualizing the latent image with toner. When a color image is formed by such a laser beam printer, first, a yellow toner image is formed on the photosensitive member and transferred to a transfer paper, then a magenta toner image is formed and transferred to the transfer paper, and similarly, a cyan toner image is formed. , It is necessary to repeat the same operation as black four times.

[Problems to be Solved by the Invention] However, according to the color image forming method as described above, for example, even when the original has only one black color as in a general document, four steps are performed. There was a waste of time.

Therefore, it is an object of the present invention to solve the above-mentioned drawbacks and to provide a color system capable of performing an efficient image reproduction process according to an input image without bothering humans.

[Means and Actions for Solving the Problems] In order to achieve the above object, the color system of the present invention is configured such that an input means (CCDs 14, 16, 18 in the embodiment) for inputting a plurality of color component signals, and the input means. Reproducing means for processing the color component signals inputted by the means to reproduce a color image (also a semiconductor laser 21, a polygon mirror 22, a photoconductor)
24), and a first determination unit (also a memory 128) for determining, in pixel units, whether or not the color component signal input by the input unit substantially indicates a specific color, Holding means (also holding circuit 130) for holding the result of the determination by the first determining means until a color component signal for at least one screen is input.
And based on the determination result held by the holding means,
Second determination means (also a hold circuit) for determining whether or not the color component signal for one screen input by the input means is an image signal formed by substantially only a specific color.
130, the OR gate 131, the control unit CPU 69) and the color component signal for one screen when it is determined that the color component signal for one screen is an image signal formed substantially only by a specific color. In reproducing the specific color, the first reproduction sequence in which the color other than the color necessary for reproducing the specific color is not reproduced is selected, and in other cases, the color other than the color necessary for reproducing the specific color is reproduced. Select the second playback sequence to
Control means for operating the reproducing means (also the control section CP
U69).

[Embodiment] In an embodiment of the present invention described below, a predetermined sequence is selected by determining that the input color signal is an image signal formed by a substantially specific color. In that case, when the black toner is transferred from the photoconductor to the copy paper, the copying operation for other colors is prohibited and the image reproduction time is shortened. Further, the image quality is not impaired because the color determination is performed and the image processing is selectively controlled. Also, the black judgment is judged by whether or not all the color component signals after the under color removal (hereinafter referred to as UCR) processing are at the peak level, or the maximum value of the input B, G, R signals (signal after γ conversion) or after masking correction. Y, M, C, (B, G, R)
It is determined whether or not the minimum value of the signal exceeds a predetermined level. Also, it is possible to regard the image as a line image by the black determination and not perform the design process so as not to impair the resolution.
Incidentally, it is also possible to judge whether the black is a line drawing or gradation with the black judgment, and in the latter case, the dither processing can be performed with a matrix pattern different from the color.

FIG. 1 shows an embodiment of the invention. The original 1 is placed on the transparent plate 2 of the original table and fixed by the original mat 3. The photosensitive drum 24 and the transfer drum 53 rotate in the arrow direction to execute the color process. 12 is a spectroscopic dichroic mirror,
CCDs 14, 16 and 18 generate color signals B, G and R by sensing the spectrum. The lamp 8 and the mirrors 9 and 10 are reciprocally moved 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. , Repeating the above scanning 4 times, Y, M, C, BK
A signal is formed, a laser is controlled, and each color latent image is sequentially formed 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 the reflecting mirror 7,
The light from the document 8 is combined with the light from 8, and the reflected light is reflected by the moving reflection mirrors 9 and 10, passes through the lens 11, and passes through the dichroic filter 12. Here, it is split into light of blue wavelength, light of green wavelength, and light of red wavelength. The decomposed light of the blue wavelength of each decomposed light passes through the blue filter 13 and is received by the solid-state imaging device 14. Similarly, light having a green wavelength passes through the green filter 15 and is received by the solid-state image sensor 16. Light of red wavelength is red filter 1
The solid-state image pickup device 18 receives the light through the line 7. That is, manuscript 3
While maintaining the optical path length by the moving reflecting mirror 9 that moves integrally with the illumination lamps 5 and 6 and the moving reflecting mirror 10 that moves in the same direction with a moving speed of 1/2 of this moving reflecting mirror 9. Furthermore, lens 11 and dichro filter 12
After that, the solid-state image pickup elements 14, 16 and 18 of each color are imaged. An image processing unit 2 which will be described later on the output of each solid-state image pickup device 14, 16, 18.
After that, the semiconductor laser 21 irradiates the polygon mirror 22 as light output. Since the polygon mirror 22 is rotated by the scanner motor 23, the photosensitive drum 2
Laser light is scanned perpendicular to the rotation direction of 4. Further, there is a photo sensor 64 at a position 11 mm before the laser beam starts scanning on the drum, and B and D signals are generated when the laser beam hits the photo sensor 64.

The photosensitive drum 24 is negatively charged by the negative charging device 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 transparent plate 2 of the document table
The upper original 1 is illuminated by the illumination lamps 5 and 6, and is moved to the solid-state image pickup devices 14, 16 and 18 by the movable reflecting mirrors 9 and 10 and the lens 11, the dichro filter 12, the blue filter 13, the green filter 15 and the red filter 17. Imaged CC
The image output from D passes through the shading unit 104 for each color, through the γ correction unit 105, the masking unit 109, the UCR processing unit 119, the dither processing unit 124, The laser light output from the multi-value processing unit 125 and the laser driver unit 126 to the laser 21 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 three colors are separated by one exposure scan, and the above respective processes are performed, but the output of each UCR is B, G, R,
It is sequentially selected for each black ski. Image processing unit 2 by the signal of the body control (E signal to UCR)
When the one-color separated optical signal in 7 is selected, the developing device corresponding to it is selected. The developing device selected there develops the electrostatic latent image into a visible image. 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 are negatively charged to erase the electrostatic latent image.

Next, the upper and lower cassettes 43, 44 are selected from the cassette selected from the operation section 45, and the copy paper 48 sent by rotating the paper feed rollers 46, 47 passes through the first registration roller, the lower 49, 50, 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 4 by the transfer electrode 54.
Transfer to 8. After the transfer, the photosensitive drum 25 removes electricity from the copy paper 48 by the electricity removing electrode 55 supplied with a high voltage from the high voltage generator 25.

In the case of a normal color original, the above operation is repeated four times for four colors and the transfer drum is rotated four times to superimpose each color. If black 1
In the case of an original with only colors, if it is detected that the original has only one black color at the time when one optical movement is completed, as described below, G, R scan, development, transfer, etc. are skipped to obtain a black image. The copying operation of is started. That is, in the case of a color original, the operating time for four colors is required, but in the case of an original of one black color, the operating time for two or one color can be shortened. 2 times or 4
The copy sheet, which has been completely transferred, is peeled off from the gripper 57, adsorbed on the belt 59 by the conveyance fan 58, guided to the fixing section 60, fixed, and then sent out of the apparatus.

2 and 3 show image processing circuit diagrams. The light of the original separated into three colors from the dichro filter is CCD 14,16,18
When the light is emitted, its output is amplified by the CCD substrates 101, 102 and 103, A / D converted, and sent to the next shading unit 104 in 8 bit parallel. When the incident light quantity of the CCD is the same (when it is white), the output data for each bit of the CCD is equal, and further correction is made so that the variations of the CCDs 14, 16 and 18 for the three colors are eliminated. In 104, the RAM configuration is used, and the data is used as an address and is properly output.

Next, an optimum γ curve is selected by switching the values of the switches 106, 107 and 108 in order to linearize the gradation property between the input and output by the γ correction unit 105. Incidentally, from 8 bits to the top 6
The bit processing is used for processing in a significant level area.

Next, the masking processing unit 109 performs arithmetic processing on each B, G, R signal at the same time to change the mixing ratio of each color component to perform color correction. This calculation is performed by the coefficient multiplication ROM and the addition / subtraction ROM. The mixing ratio of each color is a value between 110 and 118 (switch)
By switching. Incidentally, the reason that the calculated value is set to the upper 4 bits is that it is limited to a significant area level.

Next, in the UCR processing unit 119, the minimum value signals of B, G and R are discriminated by the logic of each comparator COMP and each gate MiN. A value obtained by multiplying the minimum signal by an arbitrary coefficient according to the value of the switch 120 is used as a black level signal. The value is subtracted from each color by each UCR. The signal is branched into two systems, and one of them is sent to the dither processing unit 124 by a select signal 121, 122, 123 from the main body control unit. In the dither processing unit 124, each color, for example, 6BiT
The multi-gradation signals are compared using a table-referenced dither ROM to be converted into one-bit digital signals of 1 or 0 so that the laser can be easily modulated. Next, this signal is passed through the R / W line memory to be multi-valued by the multi-value processing unit 125, and the laser 21 is driven by the laser driver unit 126. It should be noted that the dither processing unit is an RO with low threshold levels arranged.
It has M ₁ , a high array of ROMs ₃ , and an intermediate ROM ₂ , which compares the input signal to these ROM outputs at the same time, puts the output from each comparator into memory, latches it, and divides it into three equal pixels. That is, one pixel is divided by pulses having different widths of φ ₁ to φ ₃ and output corresponding to ROMs ₁ to ₃ , respectively, whereby one pixel can be represented by four values.

On the other hand, a part of the output of each UCR ROM of B, G, and R is input to the black signal determination circuit 127. What is input here is the upper 4 BiT of the 6 BiT. This is because a color signal with little density is ignored, and 6BiT may be left as it is.

The memory 128 has a function of a conversion table, and has 000
0 is stored in the address, and F is stored in all other addresses. Here, if the values of the R, G, and B signals after UCR processing are r, g, and b, respectively, the rgb address is addressed, and since r, g, and b are 4 bits each, the FFF from the 000 address. There is an address to the address. 0
At address 00, all R, G, B signals after UCR processing are 0
, (In the case of representing a black pixel), the memory 128 outputs 0 in this case. If at least one of the R, G, and B signals after UCR processing is not 0 (when representing a pixel other than a black pixel), the memory 128
Outputs F. For example, R signal is 1 and G and B signals are 0
In the case of, the address 100 is addressed and the memory 128 outputs F. In this way, in the memory 128, a black pixel is determined on a pixel-by-pixel basis, and the output is latched by the latch circuit 129 and input to the hold circuit 130 in synchronization with the clock. Using this output 140, the control unit CP
U69 (FIG. 1) determines by software described below and contributes to sequence control. This will be described with reference to the flowchart of FIG.

The flow chart shown in FIG. 4 is programmed in the microcomputer of the control unit CPU 69. First, the RESET signal is output immediately before the optical scan for scanning the original, and the outputs Q _{1 to} Q ₄ of the hold circuit 130 are output. Reset (step 1).

If there is a color signal even once before the completion of the first optical scanning, the hold circuit 130 outputs FF, and as a result, the output 140 of the OR gate 131 becomes H level.

The control circuit CPU69 checks this signal immediately after the completion of the optical scanning (3) (4), and if it is an H level signal, performs a normal full color copying operation (4).

If the gate 131 remains at the L level, it is determined that the original is black and the B, G, and R processes are omitted, and a sequence selection signal is output to complete the process only by the black copying operation.
(6). Therefore, a sequence controller (not shown) makes only the black developing device movable to form and develop a latent image. When the transfer drum rotates once, the gripper 57 is released and the transfer paper is ejected.

In this case, the process rotations for G and R are omitted when scanning and developing are performed in the order of B, G, R, and black, so that the processing time for two colors is sufficient.

Further, when the original is subjected to a preliminary blank scan, the color can be judged at the end of the blank scan, and the developing time for one black color is sufficient.

If the process is performed in the order of black, B, G, and R, the black latent image is already formed at the time of color determination (at the end of scanning), so by blocking the subsequent processing,
Processing time for one color is enough.

In the case of the type in which each color is reproduced on four of the photosensitive drums and the resist is sequentially transferred onto one sheet of paper, the paper feeding speed can be increased and the time can be shortened after finishing the black process.

The present invention is effective even if the input signals B, G and R in FIG. 2 are from the host computer, and X, Y and Z are also effective.
You can switch between the host and CCD reader as needed at the connection point. In this case, if a monochrome command signal is added to the head of the signal sent from the host, this can be judged and regarded as a black image. Further, even in the case of a 1-pixel 4-dot type printer, it is effective in shortening the time when there is a difference between the monochrome process and the full-color process. Further, since the full-color signal processing step can be omitted, the black image quality can be reproduced well.

Even if it is determined that the input signal is a monochromatic image of B, G, R, Y, M, or C other than black, sequence processing and signal processing can be omitted in the same manner. This judgment is the output B of UCR,
It is possible to monitor G and R independently and detect that there is almost no output for any of the colors.

When black is determined, it can be determined as a character image and the dither unit can be output in an output manner without impairing the resolution. Further, in this case, a static threshold value (three levels) is set _to the signal a for the dither ROMs ₁ to 3 in order to reproduce a slight halftone by using the pulse width modulation of the laser drive signal by the above-mentioned four values.
_The above pulse width modulation or brightness modulation can be performed by setting _{1 to} a ₃ .

Also, by judging the output from the hold circuit 130 for each line and applying the reset, black judgment can be made for each line and selective control of signal processing such as a dither can be sequentially performed. Further, it is possible to make a determination for every several pixels, so that the synchronization can be accurately performed and the partial selection control described above can be performed.

As described above, according to the embodiment of the present invention, a specific color such as black is judged in a color system such as a color copying machine so that about 1/2 to 1/4 is copied to a black original. You can save time. Further, it is possible to perform signal processing that enhances the resolution of characters and the like. Since unnecessary color signal processing is not performed, the quality of the specific color does not deteriorate.

In addition, useless charging, laser irradiation, development,
Since the transfer and cleaning processes are prohibited, the life of the machine can be extended without giving unnecessary fatigue.

EFFECTS OF THE INVENTION As described above, according to the present invention, there is provided first determination means for determining whether or not the color component signal input by the input means substantially indicates a specific color, and the above determination. And a holding unit that holds the determination result by the means until at least the color component signal for one screen is input by the input unit. Therefore, based on the determination result held by the holding unit, the color component for one screen is obtained. Whether or not the signal is an image signal formed substantially only by a specific color can be automatically determined by the second determination means, and it is efficient according to the input image without human labor. It is possible to perform efficient image reproduction in a short time by performing various image reproduction processes, for example, by omitting unnecessary reproduction sequences.

[Brief description of drawings]

FIG. 1 is a sectional view of a color copying machine to which the present invention can be applied, FIGS. 2 and 3 are circuit diagrams of an image processing unit, and FIG. 4 is a flow chart for determining color signals. ...... Image processing unit 127 …… Black judgment circuit

Claims (1)

[Claims] 1. A color system having an input means for inputting a plurality of color component signals and a reproducing means for processing the color component signals input by the input means to reproduce a color image, wherein the input means First determination means for determining whether or not the input color component signal substantially indicates a specific color on a pixel-by-pixel basis, and the determination result by the first determination means for at least one screen by the input means. Holding means for holding the color component signal until the color component signal is input, and based on the judgment result held by the holding means, the color component signal for one screen input by the input means is substantially a specific color. Second determining means for determining whether or not the image signal is formed by only one image, and the color component signal for one screen is determined to be an image signal formed by substantially only a specific color. When the color component signal for one screen is reproduced, the first reproduction sequence in which the color other than the color necessary for reproducing the specific color is not reproduced is selected. A color system comprising: a control unit for selecting a second reproduction sequence for reproducing a color other than a color necessary for reproducing a specific color and operating the reproduction unit.