JPH01200775A - Picture recorder - Google Patents

Abstract

PURPOSE:To easily prepare a recording picture of which magnification in vertical and horizontal directions is changed by making variable a clock frequency for each laser beam, adjusting the scanning position of the beam and freely making changeable the magnification in the main scanning direction of a picture. CONSTITUTION:Picture information 47 read out from a memory buffer 41 is supplied to a semiconductor laser driving device 31 and picture information 48 read out from a buffer memory 42 is supplied to a semiconductor laser driving device 33. A laser beam 12 passing a scanning lens 18 is reflected on the mirror 51 of which section is of an arc shape, reaches an exposure spot 19, similarly a beam 13 is reflected on a mirror 52 and reaches an exposure spot 23. A frequency is adjusted like an expression where the scanning speed of the beam 12, the scanning speed of the beam 13, the frequency of a clock 43 and the frequency of a clock 45 are V1, V2, f1, and f2, respectively. The clocks 43 and 45 reading out a buffer picture corresponding to the laser beam to be scanned faster are also accelerated accordingly. Thus, the position of the beam in the main-scanning direction is adjusted and further the magnification of the picture in the main-scanning direction can be freely changed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an image recording apparatus for performing two-color or multicolor recording using multiple systems of laser beams.

"Prior Art" An image recording device that records an image by scanning a laser beam on a scanning medium such as a photoreceptor and forming an electrostatic latent image is used as a type of copying machine or computer output device. It has become widely used.

Such image recording devices have conventionally recorded in a single color such as black, but with the spread of color displays and the spread of color copying machines, two-color or multicolor recording has become possible. This is becoming more and more common.

FIG. 3 shows the main parts of a conventionally proposed image recording apparatus.

This image recording apparatus includes a photosensitive drum 11 for forming an electrostatic latent image. In this device, two systems of laser beams 12 and 13 reach the photosensitive drum 11. A first system of laser beam 12 is output from a first semiconductor laser 14 and is passed through a first collimating lens 1.
5 and enters one surface of the rotating polygon mirror 16. The rotating polygon mirror 16 is rotated at a constant speed by a scanner morph 17. The reflected light passes through the scanning lens 18 and reaches the first exposure location 19 on the photosensitive drum 11 . On the other hand, the laser beam 13 of the second system is output from the second semiconductor laser 21 and passed through the second collimating lens 22.
and enters the above-mentioned surface of the rotating polygon mirror 16. The reflected light passes through the scanning lens 18 and reaches the second exposure location 23 on the photosensitive drum 11 .

A charger (charge corotron) 25 is arranged around the photosensitive drum 11 in front of the first exposure location 19 . Further, a first developing device 26 is disposed between the first exposure location 19 and the second exposure location 23 . Further, behind the second exposure location 23, a second developing device 27, a static eliminator 28, and a transfer charger (transfer corotron) 2 are installed.
9 are arranged in this order. The photosensitive drum 11 rotates at a constant speed clockwise in the figure.

Therefore, the first semiconductor laser 14 is driven based on the first image information 32 input to the first semiconductor laser driving device 31, and the modulated first system laser beam 12 is applied to the first exposure location. When scanned at 19, the charger 25
The uniformly charged charges on the photosensitive drum 11 are selectively removed, and a first electrostatic latent image is formed. The first electrostatic latent image is developed by a first developing device 26, and the first electrostatic latent image is developed by a first developing device 26.
A toner image is formed using the recorded colors.

On the other hand, the second semiconductor laser 21 is driven based on the second image information 34 input to the second semiconductor laser driving device 33, and the modulated laser beam 13 of the second system is applied to the second exposure location. When scanned at 23, the photosensitive drum 1
The charge on one is selectively removed to form a second electrostatic latent image. The second electrostatic latent image is developed by the second developing device 27 to form a toner image in the second recording color.

Note that the first image information 32 and the second image information 34 are transferred by the same clock supplied from a clock generation circuit (not shown), and are transferred to the corresponding semiconductor laser driving device 3.
1 or 33.

After the two-color toner image is formed on the photosensitive drum 11, the charge is removed by the charge remover 28, and the two-color toner image is transferred onto the recording paper 36 by the action of the transfer charger 29. These toner images are fixed onto the recording paper 36 by a fixing device (not shown). In addition, the photosensitive drum 11
The toner that ultimately remains on the top is collected by a cleaning device, also not shown. By rotating the photosensitive drum 11 and repeating the above operations, it becomes possible to record various types of image information in two colors on a plurality of recording sheets 36. If three or more systems of semiconductor lasers are prepared, image information can be similarly recorded using three or more recording colors.

"Problem to be Solved by the Invention" By the way, in this proposed image recording device, the rotating polygon mirror 16 and the scanning lens 18 are shared by the two systems of laser beams 12 and 13. Therefore, the scanning conditions of these laser beams 12 and 13 on the photosensitive drum 11 are similar to each other, which is an ideal condition for combining two-color images.

However, even under such circumstances, the rotating polygon mirror 16
The reality is that the distances from the reflection position of the laser beam to the respective exposure points 19 and 23 do not exactly match. Furthermore, the scanning lens 18 is not necessarily processed so that it exhibits exactly the same optical characteristics for these laser beams 12 and 13. Due to these subtle differences in optical conditions, both laser beams 12.1
The speed at which the photoreceptor is scanned by the photoreceptors 3 and 3 is different, which may cause a shift in the position of the image.

FIGS. 4 and 5 are for explaining such a situation. As shown in FIG. 4, the speeds at which the two laser beams 12 and 13 deflected by the rotating polygon mirror 16 scan the photosensitive drum are V+ and V2, respectively, and these are in the relationship V, <V2. shall be. In this case, the electrostatic latent image “Δ
If BCDEJ is to be formed, the latent image formed by the first system of laser beam 12 is the second system as shown in FIG.
The latent image is formed with a width shorter than that of the latent image by the laser beam 13 of the system. In this figure, both laser beams 12
．． The formation position of the electrostatic latent image according to No. 13 is shown shifted in the sub-scanning direction for convenience, and in order to clarify the positional shift of the formed latent image, the left edge of the image part of the electrostatic latent image is shown to be coincident. it's shown.

As described above, if the irradiation positions of the two laser beams in the main scanning direction are different, color shift occurs when recording with different recording colors, and an image that is difficult to see is formed.

A similar problem occurs when performing multicolor recording using three or more systems of laser beams.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an image recording apparatus that can prevent the recording position from shifting due to differences in the scanning speed of laser beams.

"Means for Solving the Problems" The present invention includes (1) a laser beam generation source that generates multiple systems of laser beams, and (ii) inputting image signals prepared for each system to modulate the laser beams for each system. (iii) a clock frequency setting means capable of setting the frequency of the clock for transmitting the image signal to the modulation means for each system; and (IV) a laser beam modulated by the modulation means is incident and deflected for scanning. The image recording device is equipped with a rotating polygon mirror.

Note that the laser beams of each system may be irradiated onto the same photoreceptor as shown in FIG. 3, or may be irradiated onto separate photoreceptors.

According to the present invention, when the scanning speeds of laser beams are different, the positions of each pixel on the scanned medium can be matched by changing the clock frequency accordingly.

"Example" The present invention will be described in detail with reference to Examples below.

FIG. 1 shows the main part of the circuit configuration of an image recording apparatus according to an embodiment of the present invention. Components that are the same as those in FIG. 3 are designated by the same reference numerals, and their description will be omitted as appropriate.

Now, in this image recording apparatus, the first image information 32 consisting of binary data is sequentially supplied to the first memory buffer 41 and is temporarily stored there. Similarly, 2
The second image information 34 consisting of value data is sequentially supplied to a second memory buffer 42 and is temporarily stored there.

The first clock 43 used for writing and reading the image information 32 to and from the first memory buffer 41 is
The signal is output from the first voltage controlled oscillator (■C○) 44. Further, a second clock 45 used for writing and reading image information 34 into and from the second memory buffer 42 is output from a second voltage controlled oscillator 46 . First voltage controlled oscillator 4
A control voltage ■1 is applied to the second voltage controlled oscillator 46, and a control voltage ■2 is applied to the second voltage controlled oscillator 46, respectively. These control voltages (1) and (2) can be adjusted freely by the operator using a slider (not shown) or the like. First image information 47 read out from the first memory buffer 41. is the first
is supplied to the semiconductor laser driving device 31 of. Also, second image information 48 read out from the second memory buffer 42
is supplied to the second semiconductor laser driving device 33.

The subsequent circuit portions of the image recording apparatus of this embodiment are basically the same as those shown in FIG.

However, in the case of the apparatus of this embodiment, the laser beam 12 of the first system passes through the scanning lens 18 as an fθ lens.
is once reflected by a mirror 51 having an arcuate cross section and reaches the first exposure location 19, and similarly the laser beam 1 of the second system is emitted.
3 is reflected by the mirror 52 and exposed to the second exposed area 23
It is designed to reach.

The image recording apparatus configured as described above measures the scanning speed of the two systems of laser beams 12 and 13 during adjustment after its manufacture. Such measurements are carried out by arranging photodetectors at the start and rear ends of the laser beam scanning area of the photosensitive tram 11, respectively.
This can be done by measuring the distance between these photodetectors and the photodetection timing. Now, it is assumed that the scanning speed of the laser beam 12 of the first system is 1, and the scanning speed of the laser beam 13 of the second system is 2. Also, the frequency of the first clock 43 at this time is f, and the frequency of the second clock 43 is f.
Let the frequency of the clock 45 be f2.

In this case, the frequency fl or the frequency f2 or both are adjusted so as to satisfy the following equation. Such adjustment is performed by changing the control voltage (1) or (2) as described above.

V , V 2 f, f2 As an example, the scanning speed ■1 is 1', 71X106 mm
/S, the scanning speed is 1.74X106mm/S.
and the frequency f1 is 20. It is assumed that the frequency is set to OOMHz. In this case, the worker changes the frequency f2 to 2
The adjustment is completed by setting it to 0.35MHz.

When such an adjustment is made, for a laser beam that is scanned faster, the clock 4 that reads image information from the corresponding buffer of the memory buffers 41 and 42
3 or 45 will also be faster in proportion to this. As a result, the image signal generated by the other laser beam and the recording position of the electrostatic latent image always match in pixel units.

FIG. 2, which corresponds to FIG. 5, shows the state of formation of an electrostatic latent image after adjusting the clock frequency in this embodiment. It can be seen that the electrostatic latent image rABcDEJ is aligned in the main scanning direction with either laser beam.

In the embodiments described above, two types of electrostatic latent images are formed on the same photosensitive drum using one rotating polygon mirror, and the images are transferred in one transfer operation. The present invention is not limited to such a case, but can also be applied to a case where the respective laser beams are simultaneously deflected and scanned on different scanned media. Furthermore, the medium to be scanned is not limited to the photosensitive drum as in the embodiment, but a photosensitive belt may also be used, for example.

In addition, although two systems of laser beams were used in the example, three systems of laser beams were used.
The present invention can also be applied when performing multicolor recording using more than one system of beams.

"Effects of the Invention" As described above, according to the present invention, the clock frequency can be changed for each laser beam. Therefore, according to the present invention, it is not only possible to simply adjust the scanning position of the beam, but also to freely change the magnification of the image in the main scanning direction. Another advantage is that it can be easily created.

Further, in the present invention, if all the laser beams are irradiated onto the same photoreceptor, there is an advantage that the configuration of the image recording apparatus can be simplified and the cost can be reduced. Furthermore, in the present invention, by irradiating each system of laser beams onto separate photoreceptors, it is possible to prevent toners of different colors from being mixed together, and the quality of images can be stabilized over a long period of time.

[Brief explanation of the drawing]

Figures 1 and 2 are for explaining one embodiment of the present invention, of which Figure 1 is a schematic configuration diagram showing the main parts of an image recording device, and Figure 2 is a diagram showing the main parts of an image recording device. An explanatory diagram showing the state of formation of an electrostatic latent image, FIG. 3 is a schematic configuration diagram showing the main parts of a conventionally proposed image recording device, and FIG. 4 is an explanatory diagram showing the state of deflection scanning of a rotating polygon mirror. FIG. 5 is an explanatory diagram showing an example of the formation state of an electrostatic latent image when the scanning speed of the laser beam is different. 11... Photoreceptor, 12... First system laser beam, 13...
...Second system laser beam, 14...First
semiconductor laser, 16... Rotating polygon mirror, 21... Second semiconductor laser, 31...
・First semiconductor laser drive device, 33...Second
semiconductor laser driving device, 43... first clock, 44... first voltage controlled oscillator, 45...
...Second clock, 46...Second voltage controlled oscillator. Applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney ± 5 Umeo Yamauchi Figure 2 Figure 5 Figure 4

Claims (1)

[Scope of Claims] A laser beam generation source that generates a plurality of systems of laser beams, a modulation means that inputs an image signal prepared for each system and modulates the laser beam for each system, and a modulation means that modulates the image signal for each system. An image recording apparatus comprising: a clock frequency setting means that can set the frequency of a clock to be transferred for each system; and a rotating polygon mirror that receives a laser beam modulated by the modulation means and deflects and scans the laser beam.