JPS5938756A - Controlling method of scanning for color printer - Google Patents

Abstract

PURPOSE:To enable the image formation from the home position of a drum, by comparing the timing for arriving of a rotating drum at a prescribed angle position when a beam approaches the prescribed distance at the end of a photosensitive drum and suspending the scanning for the 1st line if there is too much space. CONSTITUTION:The latent image on a photosensitive drum 8 is developed with toners of three primary colors YMC, and is transferred three times superposedly on the same sheet, whereby a color copy is obtd. When the home position 11 of the drum is detected within the prescribed time after arrival of the beam 7 of a laser 5 deflected by a mirror 6 at a prescribed position 10, the beam is modulated by an image signal from the point apart by l from the position 10 for the beginning end of the beam, and the formation of the image is started. When the timings for both detection are apart too much, the formation of the image is stopped in the scanning of that time and the scanning is accomplished from the next second line. Since the pitch of the lines is small, there is no influence on the image quality even if one line is dropped out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color printer scanning control method for controlling the scanning of a light beam in a color printer that forms a color image by overlapping dot patterns of each color using an electrostatic electrophotographic method, and in particular, It is possible to superimpose yellow, magenta, and cyan color images with high precision.

In general, in order to form a color image by subtractive color mixing of yellow, magenta, and cyan (C), which are complementary colors to the three primary colors, the dot-turns of each of these complementary colors are superimposed and recorded on the same recording paper. The color printer is
It can be roughly divided into the following types. That is, one type of color printer prints a recording paper traveling at a constant speed at right angles to its traveling direction, as shown in FIG.
A color image is formed by scanning the recording head 1 in which the nozzles of each complementary color Y1M%C are densely arranged, and ejecting the coloring material of each complementary color from each nozzle to deposit each complementary color on the recording paper 3 at the same time. In this type of color printer, the configuration of the recording head is complicated and large, but since recording is performed for each complementary color at the same time, no deviation occurs in the superposition of images of each color. On the other hand, the other type of color printer modulates the laser light beam by supplying image data read out one line at a time from an image memory (not shown) to a laser generator, as shown in FIG. The laser beam causes a photosensitive drum (not shown) to be
First, for example, a yellow (7) latent image is formed, and after that yellow (7) latent image is developed and transferred, a magenta (b) latent image is formed and developed. , is transferred, and furthermore, a latent image of cyan (C) is formed, development and transfer are repeated, and the transferred images of the three complementary colors are superimposed on the same recording paper, using an electrostatic electrophotographic method, In this type of color printer, a color image is formed by overlapping images formed separately for each complementary color, but yellow (
2), magenta (goods), cyan (C) latent images 4 (-/
, lI−,2,&−,? must be formed with extremely high precision and uniformity.

An object of the present invention is to provide a color printer scanning control method for controlling the scanning of a light beam so that latent images of each complementary color can be superimposed and formed on a photosensitive drum with extremely high precision in the latter type of color printer described above. It is about providing.

The present invention will be described in detail below with reference to the drawings.

An example of the configuration of a color printer scanning control device according to the present invention for achieving the above-mentioned object is shown in FIG. 3(A). A scanning control device according to the present invention having the configuration shown in the figure, a means for generating an image leading edge, that is, an image leading edge signal, which is provided at the scanning start side edge of the photosensitive drum g and instructs the writing start position of a latent image according to image data. Similarly, the scan start signal generating means 10 is arranged close to the scan start side edge of the photosensitive drum and instructs the start of line scanning by the light beam 7, and starts modulation of the light beam 7 by image data. It was designed to be controlled. That is, in the illustrated configuration, 7942 minutes of image data for each complementary color Y, M, and C are read out from the image memory /co in parallel for /line by the parallel-to-serial converter /3.
After converting it into a time-series signal, the modulator/lI
is applied to the laser oscillator S to modulate the intensity of the laser beam. The laser beam 7 is deflected from the left to the right in the figure on the horizontal line A by the rotation of the rotating polygon mirror B to perform line scanning, and at the same time, the photosensitive drum g is rotated in the direction of the arrow to form the latent image 9. . A light beam detector 10 is provided at the scanning start point of the light beam 7 near the left end surface of the photosensitive drum g to detect the starting end of line scanning of the light beam 7, and detects the starting point of the line scan of the light beam 7 from a position a distance l from the scanning start point. Modulation of the light beam 7 by the image data is started to start forming a latent image.

In order to detect the starting point of latent image formation, an image tip signal generator is provided at the edge of the photosensitive drum 8.

For example, as shown in FIG. 3(B), this image tip signal generator // causes the light beam 16 from the emitted light i (th) to be detected by the closely opposed photoreceiver /7. It is configured in the form of a beam interceptor in which the light beam is blocked by passing through a light shielding piece attached to the edge, and an image tip signal is generated by blocking the light beam from the photoreceiver/7. The image tip signal indicates the starting point of latent image formation in accordance with only the rotation of the photosensitive drum, regardless of the line scanning of the laser beam peak.

On the other hand, as shown in FIG. 7, the image memory 7.2 contains /
[Image data for N lines of 1IIi image is converted to yellow (2
) about memory/,? -/address AY/~AY
7942 minutes each are stored in memory/, 2-.H for magenta (goods). 2 address AM/-AMH
are stored for 7942 minutes each, and in addition, cyan (C
), address AC/~ACH of memory saw-3
Each line is stored in .

Next, the scanning start signal BD from the light beam detector 10 instructs the scanning start timing for each scanning line as shown in FIG. After 'ftT, the light beam 7 reaches the latent image formation start point AS, and immediately modulation of the light beam 7 by the image data starts from the first line, ? It is desirable that the scan start signal BD and the image tip signal P be generated almost simultaneously, as shown in FIG. That is, after the light beam 7 irradiates the light beam detector/θ and generates the ax scan mJ start signal RD, the distance! It is desirable that the line scanning of the light beam 7 is performed at a timing such that the image tip signal P is generated just before the light beam 7 reaches the latent image formation starting point P after scanning by J. However, since the photosensitive drum g rotates independently of the line scanning timing of the light beam 7, it is difficult to determine at which timing of the line scanning by the light beam 7 the image tip signal P is generated. It is unknown which position on the horizontal line A the light beam 7 is irradiating when the signal P is generated. therefore,
If the scan start signal BD and the image tip signal P do not occur almost simultaneously, the modulation of the optical peak by the first yellow image data will be performed at the next light beam detector after the image tip signal P is generated. After a time corresponding to the distance l has elapsed since the generation of the scanning start signal BD/ by 10, the modulation of the light beam 7 is started using the image data of the fourth row, and the latent image is changed from the starting point AS' of the fourth row in the latent image. begins to form. Thereafter, in the second modulation of the light beam 7 by the magenta image data and the third modulation of the light beam 7 by the cyan image data, when the scan start signal BD and the image tip signal P are generated almost simultaneously, Immediately, the modulation of the light beam is started from the /th row of the image data to start forming the latent image from the /th row, and when the image tip signal P is generated much later than the generation of the scanning start signal BD. , after a time corresponding to the distance rIAl has elapsed from the generation of the next scanning start signal BD, the modulation of the light beam is started from the first row of the image data, and the formation of the latent image is started from the λ-th row. Avoid misalignment of lines between latent images.

Next, for the modulation of the light beam by yellow image data and cyan image data, the image tip signal P and the scan start signal BD are generated almost simultaneously, and for the modulation of the light beam by magenta image data, the image tip signal P starts scanning. Signal B
To explain specifically with reference to FIG. 6, taking as an example a case where the occurrence is much later than D, when modulating with yellow image data, the image tip signal P and the scan start signal BD almost match, so the photosensitive drum A yellow latent image C/row AY/ of g l is formed, and when modulated by the next magenta image data, when the image tip signal P is generated, the light beam 7
is located at, for example, point B on the horizontal line A, so wait until the next scanning start signal BD/ is generated and scan the magenta latent image 2.
If the modulation is started from the row AM, 2, the first row AY- of the yellow latent image and the λ-th row AM2 of the magenta latent image almost perfectly match and overlap. Furthermore, when modulating with cyan image data, since the image tip signal P and the scan start signal BD are generated almost simultaneously, modulation is immediately started from the /th row of the cyan image data to generate a cyan latent image! When the formation is started from line AC/, no deviation occurs between the lines after the first line of each complementary color latent image. Note that the scanning line spacing in this type of color printer is usually g lines/1.
1S/-2 lines/1111176 lines/dragon etc. are extremely fine, so as mentioned above, even if only the magenta latent image is missing in the 7th line of the J complementary color latent image, it will not cause any problems in practice. do not have.

As is clear from the above description, according to the present invention, a light beam detector is provided at the start point of light beam scanning in a color printer to generate a scanning start signal, and a light beam ink detector or the like is placed on the photosensitive drum. In step 4-1, an image tip signal is generated, and when both signals have a predetermined relationship, modulation of the light beam starts from the /th row of image data, and when they do not have a predetermined relationship, the modulation of the light beam starts from the second row of image data. By starting the modulation of the light beam from the row, there is no row shift between complementary color images that should be superimposed to form a color image, thereby preventing deterioration of the recording S quality due to color shift, etc. It is possible to obtain extraordinary effects.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the recording head and recording paper of an inkjet color printer, Fig. 1 is a diagram schematically showing the outline of a color printer using three complementary color image superimposition, Fig. 3, o3) 1 is a block diagram showing an example of the configuration of a color printer scan control device according to the present invention, FIG. 1 is a diagram showing an example of the configuration of an image memory thereof, and FIGS. FIG. l...recording head, c...nozzle, 3...recording paper, Ku/-1I-3...latent image, left...laser oscillator, 6...rotating polygon mirror, 7...・Laser light beam, S...Photosensitive drum, 9...Latent image, IO...Light beam detector, l/...Light beam interrupter, /Co...Image memory, /3... Series/parallel converter, /4'...Modulator, 1g...Emitter, /A...Light beam, 17...Light receiver, /Z...Light shielding piece.

Claims (1)

[Claims] A color image is recorded by alternately repeating the process of line scanning with a light beam modulated by an image signal to form a latent image on a photosensitive drum, and the process of developing the latent image and transferring it to recording paper. The color printer includes means for generating an image tip signal for indicating the first line of the latent image, and means for generating a scan start signal for indicating the start end of line scanning of the light beam, When the image tip signal is in a predetermined relationship, modulation of the light beam is started from the /th row of the image, and when the scan start signal and the image tip signal are not in a predetermined relationship, the modulation is applied to the subsequent scan start signal. Accordingly, the modulation of the light beam is started from the first row of the image.