JPS5850558A - Color image recording apparatus - Google Patents

Abstract

PURPOSE:To execute high precision registering of each transferred color image, by providing a detector of the position of a recording paper conveyed, and adjusting output timing of color image information in accordance with this detection signal. CONSTITUTION:A recording paper 20 is held on a conveyer belt 7, and receives transfer of each color toner image from a toner image formed by developing an electrostatic latent image with a color toner on each photosensitive drum arranged along the conveyance route in succession. Information of color images is thus formed. As the position detection system of the paper 20 brought with the belt 7 a light source 22 is arranged above the belt 7, and an optical system 23 for receiving light from the iight source 22 and a line sensor 24 are arranged on the reverse side of the belt 7. Slip of registering of each color image transferred on the paper 20 can be eliminated by adjusting output timing of the color image information in accordance with the output signals sent from this line sensor 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color image recording device, and more particularly, to a color image recording device that conveys a color image formed based on color image information.
A color planning recording device (related to 1) that sequentially transfers and records each color onto recording paper.

As a method for recording color images, color image information is output using an electronic copying device (laser beam printer) that includes a plurality of photosensitive drums arranged in parallel, and the color images formed by this electronic copying device are sequentially printed in different colors. Conventionally, methods have been proposed in which images are recorded in overlapping colors.

FIG. 1 is an explanatory diagram of such a recording method. Reference numerals 1a to 1d are scanning optical systems, and the scanning optical system extracts required image information from an image memory, etc. (not shown) as a light beam (laser beam). Photosensitive drums arranged in parallel corresponding to cyan (C), magenta M, yellow (Y), and black (Be)! It is configured to form images on a to 2d.

Developing units 3a to 3d are located near the photosensitive drums 2a to 2d.
At the same time, chargers 48 to 4d are arranged on the side of a conveyor belt 7 for conveying paper (not shown), facing each of the photosensitive drums 2a to 2d. To explain the operation of the above configuration, the modulated light beams output from the scanning optical systems 1a to 1d form an optical image on each of the photosensitive drums 2a to 2d. A one-color electrostatic latent image is formed, which is developed by developers 53a to 3d, and each color is sequentially transferred by chargers 4a to 4d to the recording paper held on the conveying belt 7-1 to form a color image.

FIG. 2 is a schematic perspective view showing details of one of the four scanning optical systems 1 shown in FIG.
The light is collimated by the rotating polygon mirror 12 and deflected by the rotating polygon mirror 12. The polarized light beam forms an image on the photosensitive drum 3F by an imaging lens 13 called an fθ lens to perform beam scanning. During this beam scanning, the tip of the one-line scanning light beam is reflected by a mirror 14 and guided to a detector 15 . As is well known, the detection signal from the detector 15 is the ID of the image signal.
It is used as an output timing control signal (index) or as a cue signal.

Conventional color image recording is performed by the method described above, but when images corresponding to each color are superimposed on the conveyed recording paper one after another, the output timing of the image f signal depends on the recording paper. Since it is set in advance regardless of the positional state, the overlapping of images of each color transferred to the recording paper may shift due to positional deviation of the recording paper caused by deviation of the conveyance belt or the like.

That is, there is a drawback that registration may not be achieved and a high-quality color image rt cannot be obtained.

The present invention has been made in view of the above points, and provides a color image recording device that can form high-quality color images by making it possible to perform image registration with high precision. The purpose is to

In order to achieve this object, the present invention is characterized in that a means for detecting the position of the recording medium being conveyed is provided, and the output timing of color image information is adjusted in accordance with a detection signal from the position detecting means. There is.

An embodiment of the present invention will be described below with reference to the attached drawings. FIG. 3 is a schematic perspective view showing a paper position detection system employed in the color image recording apparatus of the present invention.

Before explaining this paper position detection system, the reason why the position of the transported paper shifts will be explained. Recording paper 20 is conveyed by a conveyance bell)? -Jl and is conveyed along each of the photosensitive drums 2a to 2d shown in FIG. 1, and undergoes a copying process of electrostatic latent image, development, and transfer by a charger as shown in FIG. . In this case, in order to facilitate corona transfer by the chargers 4a to 4d shown in FIG. The position of the belt 7 is easily changed due to the deformation of the belt 7. Therefore, as mentioned above, in order to accurately match each color, it is necessary to detect the position of the recording paper and adjust the output timing of the image information. is important.

For this purpose, the recording paper 20 transported by the transport belt 7
As shown in FIG. 3, a light source 22 is placed on the conveyor belt 7 as a position detection system, and an optical system 23 that receives light from the light source 22 and a line sensor such as a CCD are installed on the back side of the conveyor belt 7. 24 are placed. FIG. 4 shows details of this paper position detection system. The same reference numerals as in FIG. 3 indicate the same parts, and an image of the recording paper 20 illuminated by a light source 22 such as a lamp is transmitted to a line sensor 20 by an optical system 23 composed of a SELFOC lens array.
formed on top. Assuming that the recording paper 20 is now being fed in the direction of the arrow, the output signal from the line sensor 24 will have a waveform as shown in FIG.

Now set the repetition frequency of one line of the line sensor 24 to fl
, then - line period △T1 is △T1= '/J'
It becomes LSeC. The image on the recording paper 20 is the line sensor 24
When I- is not reached, repetitive pulses A, B, and C having a predetermined duty ratio of, for example, about 80 chi are output within the line period ΔT1 described above. In this case, the rise of each pulse, that is, from n L II to H' (from the point of 1 change to H
The number of bits maintained at ' is counted as will be described later, and if this count is greater than a predetermined value, it is determined that the image of the recording paper 20 has not reached the line sensor H. On the other hand, when the leading edge of the recording paper 20 reaches the line sensor 24, a predetermined period of time e.g.
As in case (E), respectively ΔT2tΔT and later n Hl
Falling from + to II L II. In this case as well, H”
If the counted value does not exceed a predetermined value, the number of bits maintained in By detecting whether the level is "L", the amount of lateral deviation of the recording paper 20 can be known.

Next, the details of detecting the amount of lateral shift will be explained. now,
The optical system 23 has an equal pressure of 1'! , in the case of an optical system that creates an image, the paper position Y is given by Y=PXN, assuming that it is measured from the tip of the line sensor.

However, P is the pitch of the line sensor, and N is 'H°.

This is the number of bits of the output line sensor.

If the optical system is composed of a normal lens with a magnification β (β × 0), the direction of the line sensor must be reversed because it is an inverted image. Therefore, in this case, reverse the reading direction of the line sensor to find Y = PXN Adjust output timing.

FIG. 6 is a solo diagram of a circuit for adjusting the output timing of this image signal. First, the vertical synchronization signal obtained by signal processing from the line sensor 24 is delayed by a predetermined number of counts by the counter 31, and then This becomes a directional image synchronization signal. On the other hand, the horizontal position correction ζ signal 33 obtained by processing No. 14 from the line sensor 24 is set in a counter 35 to a value proportional to the amount of horizontal deviation Y, and the horizontal synchronization signal 33 shown in FIG.
A subtraction count is started based on , and when it reaches 0, the above-mentioned image synchronization signal is output.

If the repetition frequency f of the line sensor 24 is synchronized with the line frequency of the optical scanning of the laser beam printer, horizontal deviation correction for each line is possible. A method of reading each of multiple lines may also be used.

Next, we will explain how to give the vertical synchronization signal of the image signal in this embodiment (2. Time △To
is ΔT(1=50X10-"/30-4.7m5ec. Therefore, when synchronized with the reading cycle of one line by the line sensor, one cycle of the line sensor ΔT1 is also Δl", = 1.7772 sec. , if a 512-bit CCD sensor is used, the drive clock frequency H for each bit is H>512
/1.7X10-";l; 301 KHz. FIG. The bits are read out synchronously one by one and binarized by the binarization circuit 40.

Next, among the outputs from the binarization circuit 40, only the "H" level is counted. The final count from the counter 41 is compared with a set value by a comparator 42, and if it is smaller than a predetermined number, it is assumed that the recording paper is coming and a vertical synchronizing signal is generated. The predetermined number required for the comparison by the comparator 42 described above is 51.
Although a value smaller than 2 is sufficient, it is preferable to give it experimentally in order to increase the accuracy of the stroke of the paper's lateral displacement and the authenticity of the data. The vertical synchronization signal can be obtained in the following manner, but the horizontal position correction signal is obtained by counter 4.
The output of 1 may be used as is or after being multiplied by a constant.

As described above, in one embodiment of the present invention, the output timing of the image synchronization signal is controlled based on the detection signal from the recording paper position detection means, and the vertical synchronization signal and horizontal synchronization signal for this image signal are controlled. Since the image is generated, registration of a single color image can be performed with high precision regardless of the positional deviation of the recording paper.

Note that in the above-mentioned embodiment, the skew (tilt) of the recording paper was not mentioned in relation to the positional shift of the recording paper, but if the horizontal shift 1LIY from the line sensor is fixed after a certain time t (here △
t is taken within the range of the same recording paper)
From the measured Y', the oblique angle θ (rod) becomes θ=(Y'-Y)/v·Δt. However, y is a value determined from the paper feeding speed.

Such skewing of paper can be corrected by software by appropriately changing the way the scanning optical system retrieves the image information from the image memory contents.

As described above, the color image recording apparatus according to the present invention is provided with a recording paper position detecting means when transferring and recording a color image sequentially for each color onto a conveyed recording paper. Since the output timing of the color image update is adjusted in accordance with the detection signal of , color image registration can be performed with high precision even if there is a positional shift of the recording paper.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a color image forming method on recording paper via a plurality of photosensitive drums by a laser beam printer; Fig. 2 is a schematic perspective view of a scanning optical system adopted in the method shown in Fig. 1; FIG. 3 is a schematic perspective view of a paper position detection system employed in the color image recording apparatus according to the present invention, FIG. 4 is a perspective view showing details of the paper position detection system shown in FIG. 3, and FIG. The figure is a waveform diagram of the output signal from the line sensor shown in Figures 3 and 4, and Figure 6 is the image 1 adopted in the present invention.
FIG. 7 is a block diagram of the vertical synchronizing signal generating circuit employed in the present invention. 1... Scanning optical system 2... Sensor drum 3
...Developer, 4...Charger 7...Transport belt 20...Recording paper 22...Light source
23...Optical system 24...Line sensor

Claims (3)

[Claims] (1) In a color image recording apparatus that sequentially transfers and records a color image formed based on color image information onto a conveyed recording medium for each color, a position detection means for the recording medium is provided, and detection from the position detection means is provided. A color image recording apparatus characterized in that the output timing of the color image information is adjusted according to a signal. (2) The color image recording apparatus according to claim 1, wherein the position detecting means is an optical position detecting means provided on a conveyance path of a conveyed recording medium. (3) Color image recording according to claim 2, characterized in that the optical position detection means detects a predetermined passing position of the recording medium and a deviation of the recording medium from the predetermined position. Device.