JP3175169B2 - Buffer memory switching method of recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type recording apparatus such as a recording apparatus (1P2C), 1P3C, and 1P4C for sequentially developing a sub-color image and a main color image and simultaneously transferring and recording two colors, and multiple transfer. The present invention relates to a buffer memory switching method in a color recording device or the like.

[0002]

2. Description of the Related Art Generally, in an apparatus for recording a color image by a xerography, a heat-sensitive method, an ink-jet method or the like, for example, a color copying machine or the like, an IIT (image input device) 60 is used as shown in FIG. An original image is read, and if necessary, image data processed by an IPS (image processing system) is transferred to an IOT (image output device) 61, modulated with the image data, and the photosensitive material is image-exposed to form an electrostatic latent image. Writing is in progress. In this case, IO
The T61 is provided with a screen generator (SG) for processing image data, which is a part of the IPS, and a buffer memory (BM) for timing adjustment and gap correction in the case of 1P2C. The IOT 61 is shown in FIG.
As shown in (1), the image data sent from the IIT 60 is converted into image data of 2 to 3 bits by the SG 64 and taken into the system controller 63, the data is delayed by the buffer memory 65, and the image data output from the output interface 66 is output. Modulates the beams of the lasers 70 and 71, writes a sub-color image (color) from the laser 70 to the photosensitive material 75, and writes a main color image (black) to the photosensitive material 75 by the laser 71. The image is sequentially developed by the main developing unit 73, and transfer recording of two colors is performed simultaneously.

In this case, since there is a gap of 40 mm between the exposure point of the first beam by the laser 70 and the exposure point of the second beam by the laser 71, the timing of the first beam is adjusted by the line buffer in the buffer memory 65. For the second beam, the gap memory of the buffer memory 65 performs timing adjustment and gap correction for delaying by 40 mm, and performs exposure so that there is no displacement between the sub color and the main color.

[0004]

Normally, the buffer memory is provided with two types, a line buffer for a sub-color (color) and a gap memory for a main color (black). Uses a large gap memory. However, since the FIFO forming the gap memory is expensive, it is necessary to suppress the tone reproducibility in order to reduce the number of FIFOs used. As a result, there is a problem that high-definition printing cannot be performed in the case of black, which is frequently used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In a printing apparatus having a 1P2C function, a gap memory is not used for a frequently used black printing, and a sub-color buffer memory is used. Accordingly, it is an object of the present invention to provide a buffer memory switching method of a recording apparatus capable of improving gradation reproducibility and achieving a single-color high-definition mode.

[0006]

According to the present invention, the read image data is color-separated, and the sub-color image data and the main color image data are delayed through the sub-color buffer memory and the main-color buffer memory, respectively. The sub-color image and the main color image are sequentially developed by the sub-developing device and the main developing device arranged in
In a recording apparatus having a function of performing color transfer recording, a selector for switching and outputting image data to a sub-color buffer memory and a main-color buffer memory is provided.
The selector is switched by a mode signal, and image data is output to the sub-color buffer memory in the single-color high-definition mode.

[0007]

According to the present invention, of the image data read by the IIT, the sub-color image data is delayed through a small-capacity sub-color buffer memory, and the main-color image data is delayed by a large-capacity gap memory. In the recording apparatus having the function of sequentially developing the secondary developing device and the main developing device, respectively, and simultaneously performing two-color transfer recording,
In the single-color high-definition mode, the gap memory is not used, and a small-capacity sub-color buffer memory is used.The sub-color buffer memory has a small capacity and a sufficient number of bits, so it costs little. A high definition mode can be achieved.

[0008]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a configuration of a main part of a buffer memory switching system according to the present invention, FIG. 2 is a block diagram of a screen generator, and FIG.
FIG. 4 is a diagram for explaining the operation of the screen generator, FIG. 4 is a block diagram of a buffer memory, FIG. 5 is a diagram showing a color separation and photo flag reproducing circuit, and FIG. 6 is a block diagram of a gap memory and a line buffer. First, the screen generator will be described with reference to FIGS. As shown in FIG. 3 (a),
As shown in (b), one pixel to be used by switching between odd pixels and even pixels in the screen pattern 17 is 3 to
The pattern is divided into six blocks (four blocks in the figure) and a threshold value is set for each block as shown in the figure. The pattern is compared with the image data, and the density value of the image data is smaller than the threshold value. A large block is exposed by turning on a laser, and a gradation is produced according to the number of exposed blocks. For example,
If the value of the image data of the first pixel is 40, none of the blocks are lit, 70 is only one block, 130 is 2 blocks, 170 is 3 blocks, 200
If so, all four blocks are turned on, and gradation recording is performed. Therefore, the 8-bit image data sent from the IIT is expressed in five gradations when a 4-block screen pattern is used.

As described above, when recording is performed by dividing into 3 to 6 blocks per pixel, the gradation is naturally deteriorated. Therefore, the correction is performed by the error diffusion method. That is, the comparison circuit 15 detects the range of the image data in the block, and an error is detected by the difference generation circuit 18 based on the result, the image data from the latch circuit 14 and the pattern from the screen pattern 17. The error detection is the difference between the threshold value and the value of the image data. In practice, however, the difference between the average value of adjacent threshold values and the image data is determined. For example, if the image data is 80, the number of lighting blocks is 1, and the difference is 80− (50 + 100) / 2 = 5.
Becomes Next, the FIFO 19 delays one line, and the diffusion circuit 20 multiplies the previous three pixels by a correction coefficient to generate difference correction data. Then, when the pixel of interest is x and the three pixels of the previous line are a, b, and c, the diffusion circuit 20 outputs three pixels.
The correction coefficients k1, k2, and k3 of the pixel are multiplied, and these are added by the addition circuit 11. Also, the output of the latch circuit 14 is fetched and the look-up table (LU
T) 21, the correction data k4d of the immediately preceding pixel d is output and added by the addition circuit 13 to obtain x + k1a + k2b + k3.
c + k4d (k1 + k2 + k3 + k4 = 1) is obtained, and error correction is performed by three pixels in the previous line and the immediately preceding pixel. The immediately preceding pixel 21 may be obtained by simply reading out the correction value from a look-up table, or by calculating using the data of the screen pattern 17. Thus, in the example of FIG. 2 (in the case of 6 blocks), image data is output to the buffer memory as 3-bit data.

In the screen pattern 17, FIG.
As shown in FIG. 3A, the threshold value of the pattern of the adjacent pixel is the same in the scanning direction, and the threshold value of the pattern of the adjacent pixel is the same in the scanning direction as shown in FIG. A pattern that increases in the scanning direction and a pattern that decreases in the scanning direction are prepared, and the pattern A and the pattern B are sequentially switched and output between odd-numbered pixels and even-numbered pixels.

The pattern shown in FIG. 3A is a case of 400 spi applied to character data, and the pattern of FIG. 3B is a case of 200 spi applied to a photographic image. When the pattern shown in FIG. 3A is used, for example, as shown in FIG. 3C, when the density value of the image data becomes large, such as G1, G2, and G3 patterns, Since each block is turned on as indicated by oblique lines and the threshold value differs between pattern A and pattern B, recording can be apparently performed with a higher gradation. On the other hand, when the screen pattern shown in FIG. 3B is used, as shown in FIG. 3D, the G1, G2, and G3 patterns are such that each block is turned on sequentially from the boundary between the pattern A and the pattern B. It looks like two dots form one dot in appearance. Therefore, since the resolution is reduced, it is possible to record, for example, blurring a halftone dot of a photograph.

Image data from such a screen generator is input to a buffer memory shown in FIG. Image data is subjected to color separation by a main color / sub color separation circuit 31 via a photo flag decoder 30. The main color / sub color separation circuit 31 has an IPS
The 1-bit color flag from is added. This specific circuit includes two selectors 4 as shown in FIG.
0, 41, one of the selectors is selected by a color flag to extract a sub color or a main color,
Output to the line buffer and gap memory respectively. Thus, the sub-color image data is input to the line buffer 32, and the main color image data is input to the photo flag encoder 33. The photo flag encoder 33 is provided so as to be able to separate the photo data from the normal data without providing a signal line for the photo flag data.
00), and at the end of the picture data, a prohibition code (100)
The starting point and the ending point of the photograph data can be understood.

As shown in FIG. 5B, the photo flag decoder 35 detects the prohibition code (100) by the logic circuit 43, adjusts the timing by the latch circuit 44, and outputs the photo flag from the flip-flop 45. ing. The gap memory 1 is for delaying and outputting photographic data or normal character data by 40 mm, and is controlled by a page synchronization signal (ROS / PSYNC) on the IOT side and a line synchronization signal, and the page synchronization signal is a sheet on the IOT side. Generated based on the length and timing signals. Also,
The control of the line buffer 32 is performed by a line synchronization signal from the IOT side. Then, a page start signal is sent from the IIT to the IOT side, and writing is started.

The image data from the screen generator is separated into sub-color image data or main image data by a color flag in the selector 3 in FIG. 1, and the sub-color image data is stored in a small-capacity sub-color buffer memory (line). Buffer) 1 and output. The main color image data, which is normally black, is delayed through a large-capacity main color buffer memory (gap memory) 2 and output as main color data. These output data are subjected to pulse width modulation to obtain a first beam and a second beam, respectively.
It becomes a beam modulation signal. In this embodiment, the selector 3 is switched by the mode signal, and when the single-color high-definition mode is selected, the image data always passes through the sub-color buffer memory 1 and the gap memory is not used. The sub-color buffer memory has a small capacity and a sufficient number of bits. As a result, in the single-color high-definition mode, the number of blocks in the screen generator can be increased, the number of bits can be improved, and the gradation reproducibility can be improved.

In the above embodiment, a 1P2C color copying machine has been described as an example. However, the present invention is not limited to this. It is applicable to recording devices, etc., and the recording method is not limited to xerography.
It is also applicable to a heat-sensitive method, an ink-jet method, and the like.

[0016]

As described above, according to the present invention, in a printing apparatus having a 1P2C function, a gap memory is not used for a frequently used black image and a sub-color buffer memory is used. It is possible to achieve a high definition mode at little cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a buffer memory switching system of the present invention.

FIG. 2 is a block diagram of a screen generator.

FIG. 3 is a diagram for explaining an operation in a screen generator.

FIG. 4 is a block diagram of a buffer memory.

FIG. 5 is a diagram showing a color separation and photo flag reproduction circuit.

FIG. 6 is a block diagram of a gap memory and a line buffer.

FIG. 7 is a diagram illustrating an overall configuration of a 1P2C copying machine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sub-color buffer memory, 2 ... Main color buffer memory, 3 ... Selector, 4 ... OR circuit, 5 ... Selector

Claims (1)

(57) [Claims] The image data read is color-separated,
The sub-color image data and the main color image data are delayed through the sub-color buffer memory and the main color buffer memory, respectively, and the sub-color image and the main color image are sequentially developed by the sub-developing device and the main developing device arranged at predetermined intervals. A recording apparatus having a function of simultaneously transferring and recording two colors, a selector for switching and outputting image data to a buffer memory for sub-color and a buffer memory for main color, and switching the selector according to a mode signal to obtain a single-color high-definition. A buffer memory switching method for a printing apparatus, wherein image data is output to a sub-color buffer memory in a mode.