JP2000059640A - Color image generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the output data buffer capacity of a tandem electrophotographic device, to provide an arbitration system by a simple logic and to reduce a circuit scale without damaging image processing. SOLUTION: The timing of reading data inputted from an image data input part 10 from an input data buffer 11 and inputting them to a conversion part for converting them to image data for respective image generation parts is synchronized with an image generation timing for respective output colors. In this case, by sharing one color conversion part 12 by the respective image generation parts 17-20 in a time division manner and changing the parameter set to the color conversion part 12 the image data to be inputted to the respective image generation parts 17-20 are generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus which is a tandem type electrophotographic apparatus, and more particularly to a tandem type electrophotographic apparatus which can reduce the capacity of an output data buffer and at low cost. The present invention relates to a color image generating apparatus.

[0002]

2. Description of the Related Art In a color electrophotographic apparatus, generally, a method of generating three color images of cyan, magenta, and yellow, or four colors including black in a frame-sequential manner, and successively superimposing colors to generate a color image. Is often used,
In this method, the time required for generating the monochrome image is multiplied by the number of colors (generally four times). Therefore, for products emphasizing speed performance, those of the tandem type having image generation units for the number of colors are widely used. In the tandem system, data read from an input data buffer is simultaneously converted into YMCK data by four color converters and output to respective image generators. The data in the output data buffer is sent to the image generator at different timings for each of YMCK. In this case, it is necessary to match the timing of reading from the input data buffer with the timing of needing data of the image generation unit.
The operation timings of the CK image generation units are different from each other, and the operation timings are partially overlapped. In practice, it is not possible to match the timings of the image generation units for all colors. Therefore,
It is necessary to provide an output data buffer for each color to absorb a difference in data output timing to the image generation unit. As described above, in the tandem type color electrophotographic apparatus, not only four image generation units are required, but also the writing timing of each color is different, so that a buffer memory for compensating the writing timing is required, thereby increasing the cost. There was a problem that would invite.

A method for reducing the output data buffer of the tandem system is disclosed in, for example, JP-A-8-30510.
No. 9 has proposed a color image forming apparatus. In this apparatus, the exposure position on the photoreceptor belt is adjusted for each color, so that the exposure timing of each color is matched, and the size of the output data buffer is reduced.
Specifically, a single-color image of each color is formed on a belt-shaped photoconductor, and the belt photoconductor is supported in tension by a driving roll and a tension roll, respectively. If the drive roll has eccentricity, the speed of the belt-shaped photosensitive member changes in speed, but if the tension roll has eccentricity, the speed does not change. Due to the eccentricity of the driving roll,
The amplitude and frequency are the same, and the phase is shifted by the wrap angle (180 °) at which the belt-shaped photoconductor wraps around the drive roll. As a result, the position fluctuation of the exposed image and the position fluctuation of the transfer image are added, and the position fluctuations of the two are 180 ° different from each other, so that the position fluctuation on the recording paper is canceled out to zero. Therefore, it is possible to prevent or reduce the fluctuation of the image forming position due to the eccentricity of all the rolls on which the belt-shaped photoconductor is stretched.

[0004]

As described above, in the conventional tandem type color image forming apparatus, not only four image generating units are required, but also the writing timing of each color is different, thereby compensating for this. Therefore, there is a problem that a buffer memory is required, which leads to an increase in cost. On the other hand, in the color image forming apparatus described in the above-mentioned publication, it is necessary to provide the belt photoreceptor by a length necessary for timing adjustment, so that there is a problem that the outer shape of the device becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image generating apparatus which solves these conventional problems and which can realize a tandem type electrophotographic apparatus at a low cost by suppressing the capacity of an output data buffer. . Another object of the present invention is to provide a color image generating apparatus capable of realizing an arbitration method capable of reducing the required output data buffer capacity with simple logic.
Still another object of the present invention is to provide a color image generating apparatus capable of reducing a circuit scale without deteriorating image processing performance.

[0006]

In order to achieve the above object, in a color image generating apparatus according to the present invention, data input from an image input unit is stored in an input data buffer, and data is read from the input data buffer. The output data buffer for holding the data after the color conversion is required by performing the timing of inputting to the color conversion unit for converting the image data into the image data for each image generation unit at the timing synchronized with the image generation timing for each output color. Keep capacity small (Fig. 2
reference). As a result, the capacity of the output data buffer can be reduced, and a tandem-type electrophotographic apparatus can be realized at low cost. Further, in the present invention, a conventional photosensitive drum can be used instead of the belt photosensitive member as in the apparatus described in the above-mentioned publication, so that there is no problem related to the belt. Further, in the above-described electrophotographic apparatus, acceptance of a data read request from the plurality of color conversion units to the input data buffer is performed for the color conversion unit that has issued the request first (see FIG. 6). This makes it possible to realize an arbitration method that can reduce the required output data buffer capacity with a simple logic. Further, one color conversion unit is shared by each image generation unit in a time-division manner, and by changing parameters set in the color conversion unit, image data to be input to each image generation unit is generated (see FIG. 1). . As a result, the number of color conversion units, which conventionally required four sets, can be reduced to one set, and the circuit scale can be reduced without deteriorating image processing performance. Therefore, a tandem type electrophotographic apparatus can be realized at low cost. it can.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 5 is a diagram showing an example of a unit layout of a tandem-type color electrophotographic apparatus. In FIG. 5, A is a paper supply unit, B is an image forming (developing) unit, C is a photoreceptor, D is a fixing unit, E is a paper discharging unit, F is a paper transport belt, L is yellow, magenta, and cyan. , The distance between each transfer point for each color of black. In the color electrophotographic apparatus, as shown in FIG. 5, in each image forming unit B, yellow (Y), magenta (M), cyan (C), black A single-color image of each color (K) is formed on the photoconductor C. The image formed on the photoreceptor C is electrostatically transferred from the paper feeding unit A to the recording paper fed and fed from the paper feeding unit A by the action of the transfer charger. Although not shown in the figure, the cleaning device operates after the transfer to the photosensitive member C.
Unnecessary images remaining on the upper surface are cleaned to prepare for the next image forming step. Further, the charge removing device removes the electric charge on the sheet conveying belt F applied in the suction transfer process. The recording paper on which the image synthesized in the four colors is transferred is subjected to a fixing process in a fixing unit D, and then is discharged to a paper discharge unit E. Image data input from an image data input unit such as an image scanner / printer controller is temporarily stored in an input data buffer, and is converted from an image format (generally RGB) of the input data by a color conversion unit to an image format of an image generation unit. (Generally YMCK) and sent to an image generation unit via an output data buffer, whereby an image is formed by an electrophotographic process.

FIG. 4 is an image data transfer timing chart of the tandem type color electrophotographic apparatus of the present invention,
For comparison, a conventional tandem transfer timing is shown in FIG. Conventionally, as shown in FIG. 3, at the timing "color conversion", data read from an input buffer is simultaneously input to all color conversion circuits, and outputs converted to respective colors are output to respective outputs. Input to the data buffer. Here, the time t1 from the color conversion of the first color to the image data output 1 is a time for synchronizing timings, so that the output data buffer 1 has a small capacity of about several lines, but the output of the second and subsequent colors is required. Since the data buffers 2, 3, and 4 each take a long time until the exposure start time t2, a larger capacity is required for the buffer for the rear image generating apparatus. That is, the time until the second color is output to the output data buffer 2 is t1 + t2,
The time until the third color is output is t1 + 2 × t2 = t3 +
t2, and the time until the fourth color is output is t1 + 3 ×
t2 = t4 + t2. Here, t2 is a time obtained by multiplying the interval L between the image generation units of each color shown in FIG. 5 by the moving speed of the image product such as the paper to be written or the intermediate transfer belt, that is, the image space between the colors. It is the time for the product to move.

On the other hand, in the electrophotographic apparatus of the present invention, as shown in FIG. 4, the timing at which data is transferred from the input data buffer to the output data buffer via the color conversion unit is determined by the timing of each image generation unit. By performing the operation in synchronization with the operation, the capacity of all output data buffers can be suppressed to about several lines as in the case of the first color. That is, the second color conversion 2 is performed after the time t2 from the first color conversion 1, the third color conversion 3 is performed after the time t2, and the fourth color conversion 4 is performed after the time t2. For all four colors, the time from color conversion to data output is short. Here, since the time t1 from the color conversions 1 to 4 to the image data outputs 1 to 4 is a time for synchronizing timings, each of the output data buffers 1 to 4 has a small capacity of about several lines. As described above, t2 is the time obtained by multiplying the moving distance of the image-forming product such as the paper to be written or the intermediate transfer belt by the interval L between the image generating units of each color shown in FIG. This is the time during which the image product moves.

FIG. 6 is an operation flowchart of the arbitration circuit showing one embodiment of the present invention. The request from the color conversion unit for each color is entered in a FIFO type queue, and is processed from the request of the color conversion unit that issued the request first. The arbitration circuit is a high-performance circuit that employs an arbitration (arbitration) function capable of competing for bus occupation rights among a plurality of devices (boards) in consideration of a multiprocessor configuration. First, it is determined whether or not there is a request (step 101). If so, it is determined again whether or not the request can be accepted (step 10).
2) If possible, accept the request (step 103). If it is currently being accepted and cannot be accepted, it is added to the queue (step 104). Then, it is determined whether or not the reading being executed is completed (step 1).
05) If completed, respond to the request at the head of the queue (step 106). Thus, after returning to the beginning and detecting the presence or absence of the request, the operation of responding to the head of the queue is repeatedly performed.

FIG. 2 is a block diagram of an image data transfer circuit of a tandem color electrophotographic apparatus according to an embodiment of the present invention. In the case of FIG. 2, the data input to the image data input unit 21 is stored in one input data buffer 22, and the data is transferred from the input data buffer 22 to the output data buffers 27 to 30 via the color conversion units 23 to 26. The data transfer timing is synchronized with the operation of each of the image generation units 31 to 34. That is, the arbitration circuit receives requests in order from the requested color, and sequentially adds to the queue those requested during color conversion processing. The color conversion is performed on the first color in synchronization with the operation of the image generation unit, and after the time t1, the color is output to the output data buffer for that color. For example, if there is a request from the color converter 23 first, the arbitration circuit accepts the request, transfers the data from the input data buffer 22 to the color converter 23, executes the color conversion process, and then executes the output data buffer 27. Output the converted data. Next, if the request at the head of the queue is from the color conversion unit 26, the request is accepted, the data is transferred from the input data buffer 22 to the color conversion unit 26, and the data is output after performing the color conversion processing. Output to the data buffer 30. After that, for the remaining two colors,
In the same way, the operation of receiving and performing color conversion processing and outputting to the output data buffer is repeated.

FIG. 1 is a block diagram of an image data transfer circuit of a tandem color electrophotographic apparatus according to another embodiment of the present invention. Many color conversion circuits represent each color of input image data as input data and express the output data as a function of one color of output image data. Therefore, changing the output color with the same circuit can be easily realized by changing the parameters of the conversion function. In FIG. 1, only one color conversion unit 12 is provided in common for each color. The data requests from the output data buffers 13 to 16 are arbitrated according to the algorithm shown in FIG. 6, and when one output data buffer is selected, parameters suitable for the selected output data buffer are sent to the color conversion unit 12. The data set and read from the input data buffer 11 are color-converted and written to the output data buffers 13-16. In the present invention, the YMCK image generation unit 17
Data is read from the input data buffer 11 at the operation timings of 〜20. Since the timing for reading the data of each color is shifted, the read data cannot be shared for each color as in the conventional method. However, the reading from the input data buffer 11 must be performed at a speed four times or more the speed of the conventional method. To perform time sharing separately. That is, the contention is solved by reading the input data buffer 11 of each of the YMCKs in small pieces. YMCK input data buffer 1
1 is read from another address of the input data buffer 11 at the same time in a macro manner, but is performed by time sharing, and is not performed at the same time in a micro manner. Use with time sharing.

[0013]

As described above, according to the present invention,
Since the capacity of the output data buffer can be reduced with simple logic, a tandem-type electrophotographic apparatus can be realized at low cost. Further, by employing the arbitration method, the circuit scale can be reduced without impairing the image processing performance.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image data transfer circuit of a color image generating apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an image data transfer circuit of a color image generation device according to a second embodiment of the present invention.

FIG. 3 is a time chart showing image data transfer timing of a conventional tandem color electrophotographic apparatus.

FIG. 4 is a time chart showing image data transfer timing of the tandem color electrophotographic apparatus according to the present invention.

FIG. 5 is a unit layout diagram of a tandem-type color electrophotographic apparatus to which the present invention is applied.

FIG. 6 is a block diagram of an arbitration circuit showing one embodiment of the present invention.

[Explanation of symbols]

10, 21 ... image data input unit, 11, 22 ... input data buffer, 12, 23-26 ... color conversion unit, 13-1
6, 27-30: output data buffer, 17-20, 3
1 to 34: an image generating unit, A: a paper feeding unit, B: an image forming unit,
C: photoconductor, D: fixing unit, E: paper discharge unit, F: paper transport belt.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuichi Yokota 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H030 AA01 AA05 AB02 AD12 AD17 BB02 BB23 5C077 LL17 LL18 LL20 MP08 NP01 PP32 PP33 PQ22 TT02 TT06 5C079 HB01 HB03 HB12 KA03 MA02 NA10 NA11 NA25

Claims (3)

[Claims] 1. A tandem-type color image generation device having image generation units for the number of colors, wherein the data input from an image data input unit is stored, and the image generation unit for each output color at a different timing. A color image generating apparatus comprising: an input buffer capable of reading data in synchronization with the generation timing of the image data in parallel; and a color conversion unit that converts the image data into image data for each image generation unit. 2. The color image generation device according to claim 1, wherein the input data buffer receives a data read request from a plurality of color conversion units, and receives the data read request from a color conversion unit that has issued the request first. And sequentially responding to the read request connected to the head of the queue when the execution of the color conversion processing is completed. 3. The color image generation apparatus according to claim 1, wherein the color conversion unit sets a different parameter for each image generation unit each time, so that the image generation units share the parameters in a time-sharing manner. A color image generation device that generates image data to be input to each image generation unit.