JPH06191086A - Optical scanning recorder - Google Patents

Abstract

PURPOSE:To enhance quality of an image irrespective of a writing density and to reduce manhour of regulating, inspecting of an apparatus by writing image data for one or more scannings based on one scanning at variable deflecting period of an optical deflector together with a recording density on a photosensitive member according to an input signal. CONSTITUTION:This entire apparatus records an image based on an image signal from a host computer. The signal from the computer has a variable recording density of a range of 240-600dpi. At the time of inputting, for example, 240dpi, a motor speed and an image clock of 480dip are used to write the same image information for twice scannings. Thus, a change rate of the motor speed can be set to 1.5-fold, the number of image clocks is set to three, and the change rate can be set to 2.2-fold by using the speed control of a motor 4 and repetition of one line information of the image. Further, since an interval of pixels is variable in a partial range, uniformity of solid black and high resolution can be actually measured in all ranges of 240-60odpi.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning recording apparatus such as a laser beam printer for recording information such as characters on a recording material such as a photosensitive drum which is a surface to be scanned by scanning a light beam.

[0002]

2. Description of the Related Art Conventionally, an optical scanning recording apparatus of this type generally records on a photosensitive drum by an optical deflecting device as disclosed in Japanese Patent Publication No. 62-36210. Since this type of recording apparatus receives and records an image signal from a computer or the like, the instruction of the image recording density from the computer or the like is 240 dpi, 300 dpi, 40
There are several types such as 0 dpi, and the deflection frequency of the optical deflector, the clock frequency for image writing, the laser light amount, the writing spot diameter, and the like are made to correspond so as to satisfy the performance at the specified writing density of a certain value.

[0003]

Recently, it has been desired to improve the image quality of an output image, and the writing density is 600 dpi, 800.
dpi and more are beginning to emerge. As another direction, one product has a specification in which the recording density can be changed by the recording device by a signal for changing the image writing density from the host computer. In order to support various writing densities as described above, for performance-oriented products, prepare as many optical scanning devices as there are product writing densities, and for writing-capable write density changeable products, there is a wide range. Since it is necessary to use an optical scanning device that satisfies the performance in the range, the cost is increased.

Further, regarding the cost-oriented one, since one write density compatible one is coped with only by forcibly changing the deflection frequency and the image clock of the deflector, image deterioration is caused.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to obtain a high quality image at any writing density, and an apparatus corresponding to the writing density. An object of the present invention is to provide an optical scanning recording apparatus which can reduce the number of adjustment and inspection steps.

[0006]

In order to achieve the above object, according to the present invention, a light source and a light deflector for deflecting and scanning a light beam generated from the light source are provided to scan light on a surface of a photoconductor. In an optical scanning recording device including a scanning device, a recording density on a photoconductor is variable by an input signal, a deflection cycle of an optical deflector is variable, and one scanning is performed based on image data for one scanning. Or, it is characterized in that two or more scans are written as image data.

It is preferable that the variable range of the deflection period of the optical deflector is not more than twice.

[0008]

In the optical scanning recording apparatus having the above structure, the writing of the image data on the surface to be scanned can be switched by the same data for one scanning or a plurality of scannings, and the deflection cycle of the optical deflector can be changed. Thus, a single optical scanning device can handle a wide range of image writing densities on the surface to be scanned.

Further, the quality of the output image is improved by setting the variation range of the deflection frequency of the optical deflector to be twice or less.

[0010]

1 to 6 show a first embodiment according to the present invention, and FIG. 1 shows a schematic structure. In FIG. 1, reference numeral 1 denotes a semiconductor laser which is a light source, and a light beam emitted from the semiconductor laser passes through a first lens system 2 so that the beam diameter and the degree of focusing are adjusted, and a rotating polyhedral surface 3 Incident on the mirror. The rotary polygon mirror 3 is fixed to a motor 4 and rotates at a high speed in the direction of A in FIG. The light beam that is incident along with the rotation of the rotary polygon mirror 3 is deflected and scanned at high speed and is incident on the fθ lens system 5. By passing through the fθ lens 5, the linearity of the scanning speed and the light condensing property are adjusted, and the photosensitive drum 6 is linearly scanned in the direction of arrow C. Here, the photosensitive drum 6 rotates in the direction of arrow B at a constant speed, and image information repeatedly scanned in the direction C can be continuously and two-dimensionally recorded on the surface thereof.

Here, the entire apparatus records an image based on an image signal from a host computer,
The image signal from the host computer has a variable recording density in the range of 240 dpi to 600 dpi. For example, if the recording density is 240, 300, 400, 48
Assuming that there are five types of 0,600 dpi, it is necessary to change the number of rotations of the motor 4, a clock for writing an image, or a pixel size for obtaining an appropriate image according to each density. Table 1 below shows the relationship between the writing density, the motor rotation number, the pixel size, and the writing image clock when the number of images of the rotary polygon mirror 3 is 6 and the focal length of the fθ lens 5 is 150 mm.

[0012]

[Table 1] As can be seen from Table 1, in order to correspond to the range of 240 to 600 dpi, the change in the rotation speed of the motor 4 is 2.5.
2 times, the pixel size is 2.5 times, and the image clock must be changed in the range of 6.25 times.

Although it is technically possible to change the rotation speed of the motor 4 in this manner, considering the rotation jitter characteristics of the motor 4 and the precession movement of the rotation axis, the characteristics are improved at all rotation speeds. It is difficult to do so, and the change in the number of revolutions should be less than double. In addition, it becomes necessary to properly use five types of image clocks. A particular problem is that the appropriate writing pixel density changes depending on the writing density.

On the other hand, the size of the laser spot on the surface of the photoconductor drum 6 may be controlled, but it is technically and costly difficult. For example, if the pixel size is 63.5
FIGS. 2 to 6 show the state of the pixel arrangement when fixed to μm and 240 to 600 dpi are drawn with the same pixel size.

24 compared to the range of 400 to 600 dpi
It can be seen that the pixel array of 0,300 dpi is too far apart. Although the pixel size may be increased in order to reduce the pixel interval, on the contrary, the resolution at high density is deteriorated. Further, if an attempt is made to increase the resolving power, density unevenness will occur when an attempt is made to output uniform black at a low density.

Regarding the scanning direction of the light beam, if the image clock is lengthened as shown by the broken line in FIG. 3, the pixel interval in the main scanning direction can be made small, but the pixel interval in the sub scanning direction is made small. I can't do it.

As a method of enlarging pixels in the sub-scanning direction, there is a method of increasing the laser light amount by writing at a low density. However, if the rate of change of the light amount is too large, the image power in the main scanning direction deteriorates. It is not preferable because it is influenced by the characteristic change due to the large change in the amount of light on the laser chip surface.

Therefore, in the present invention, for example, when inputting 240 dpi, the same image information is written twice for scanning by using the motor rotation speed and the image clock of 480 dpi.
Similarly, in the case of dpi, the motor rotation speed of 600 dpi,
The same image information is written twice using the image clock. Table 2 below shows the correspondence between the motor rotation speed, the pixel clock, and the number of image repetitions for 240 to 600 dpi. The same pixel information is output twice in the main scanning direction.

[0019]

[Table 2] As is apparent from Table 2, by using the rotation speed control of the motor 4 and the repetition of one line information of the image together, the change rate of the motor rotation speed is 1.5 times, the number of image clocks is 3 types, and the change rate is 2. It can be doubled. Further, since the interval between pixels is only the change in the range of FIGS. 2, 5 and 6 of FIGS. 2 to 6, the uniformity of solid black and the high resolution are 240
It is realized in the entire range of up to 600 dpi. Further, even when the resolution and the black solid are adjusted by changing the pixel spacing by changing the laser light amount, the rate of change of the light amount can be made extremely small.

The first embodiment of the present invention is 240-600d.
An example of repeating the scan line once or twice in the range of pi is shown, but by using the repetition of three times or more, it is possible to cope with a density range of more than that.

Instead of the deflector using the rotary polygon mirror 3 and the motor 4, other deflectors such as a resonance type galvano can be used to achieve the object of the present invention.

Instead of writing the same data a plurality of times, it is also possible to smooth the output image by generating and outputting inner information based on the image information before and after.

[0023]

As described above, in the optical scanning recording apparatus in which the writing density can be changed, the beam deflection cycle is made variable and the number of times of writing the image information of one line is made variable. It is possible to obtain a high image quality having both black solid uniformity and high resolution at the writing density. In addition, since the number of rotations of the motor to be controlled and the frequency of the image clock are reduced, the man-hours for adjustment and inspection can be reduced, which is effective in cost reduction.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical scanning recording apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing pixel intervals at a constant pixel size at a recording density of 400 dpi.

FIG. 3 is a schematic diagram showing a pixel interval at a constant pixel size at a recording density of 240 dpi.

FIG. 4 is a schematic diagram showing pixel intervals at a fixed pixel size at a recording density of 300 dpi.

FIG. 5 is a schematic diagram showing pixel intervals at a fixed pixel size at a recording density of 480 dpi.

FIG. 6 is a schematic diagram showing pixel intervals at a fixed pixel size at a recording density of 600 dpi.

[Explanation of symbols]

 1 semiconductor laser (light source) 2 first light source system 3 rotating polygon mirror 4 motor 5 fθ lens 6 photoconductor drum

Claims (2)

[Claims] 1. An optical scanning recording apparatus including a light source and an optical deflector for deflecting and scanning a light beam generated from the light source, the optical scanning apparatus including an optical scanning device for scanning on a surface of a photoconductor. Optical scanning recording characterized in that the density is variable, the deflection cycle of the optical deflector is variable, and one scan or two or more scans are written as image data based on the image data for one scan. apparatus. 2. The variable range of the deflection period of the optical deflector is 2
The optical scanning recording apparatus according to claim 1, wherein the number is not more than double.