JP2900536B2 - Resolution switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a resolution switching device in a laser printer or the like, a plurality of polygon mirrors having different numbers of reflection surfaces on a spindle are intended to quickly and reliably switch an image to each resolution. And, a plurality of laser light emitters that are different from each other in diameter of the laser light according to the number of reflection surfaces and are different from each other, and select a combination of the polygon mirror and the laser light emitter according to resolution, and select the laser light emitter. The resolution is switched by selectively emitting light.

[Industrial applications]

The present invention relates to a resolution switching device in a laser printer or the like.

Recently, demands for high-speed printing and high image quality have increased, and laser printers using laser light have been used as printers.

[Conventional technology]

As shown in the perspective view of the main part of FIG.
A semiconductor laser light emitting device (hereinafter referred to as LD) 1 for emitting a laser beam modulated according to an image signal; a polygon mirror 2 having a large number of reflecting surfaces 2a for reflecting the laser beam of the LD 1; Spindle 3 supporting the center of the motor, and a DC motor 4 for rotating the spindle 3 at a constant speed.
A lens 6 for scanning the laser beam reflected by the polygon mirror 2 on the surface of the optical drum 5 at a constant speed, and a reflecting mirror 7 for reflecting the light from the lens 6 and guiding the light onto the surface of the optical drum 5. Etc.

Therefore, the laser light scans the surface of the optical drum 5 for each reflecting surface 2a by the rotation of the polygon mirror 2, and forms an electrostatic latent image based on the image signal.

Thereafter, the toner is put on the optical drum 5 by a developing device (not shown) and visualized, and the visualized image is transferred to recording paper or the like and fixed by a fixing device.

LD1 uses a semiconductor diode as a light source, and the light emitted from the light source is converted into a parallel light by a collimating lens.

There is a slit in front of the semiconductor diode, which functions to narrow the laser beam to a required beam diameter, and this portion is integrally formed.

[Problems to be solved by the invention]

In a series of printing operations, when there is a demand for a high-density image in a part of the printing operation, it is necessary to increase the rotation speed of the spindle each time, and to decrease the rotation speed after completion.

However, the motor is a DC motor, and it takes ten and several seconds to stabilize the speed, during which the image cannot be formed.

For this reason, there is a problem that the resolution can be switched for each sheet, but it is actually impossible to switch the resolution during printing of one sheet.

SUMMARY OF THE INVENTION It is an object of the present invention to quickly and reliably switch an image to each resolution.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, as shown in a perspective view of a main part of FIG. 1, a plurality of polygon mirrors 8a to 8n having different numbers of reflection surfaces on a spindle 3 and a pair of polygon mirrors 8a to 8n are provided. Equipped with a plurality of laser light emitters whose diameter of the laser light is different from the diameter of the laser light depending on the number of surfaces, select a combination of the polygon mirrors 8a to 8n and the laser light emitter according to the resolution, and selectively emit light by the laser light emitter. Is switched.

[Action]

A plurality of polygon mirrors having different numbers of reflection surfaces are rotated by one spindle, and an image of a desired resolution is formed by selecting a polygon mirror that reflects laser light modulated by an image signal. I can do it.

In other words, by selecting a polygon mirror having a large number of reflecting surfaces, the number of scanning lines is increased, a small-diameter laser beam is emitted, and a high-resolution image can be formed. The number of lines is reduced and a large-diameter laser beam is emitted to form a low-resolution image.

〔Example〕

 1 and 2 show one embodiment of the present invention.

 The same reference numerals are given to the same parts throughout the country.

In the present invention, as shown in the perspective view of the main part of FIG. 1, when the resolution is required in two levels, the spindle 3 has two polygons having different numbers of reflecting surfaces such as six and twelve. Mirrors 8a and 8b are provided, and the polygon mirrors 8a and 8b are selected from those irradiated by the laser light of the laser light emitter 9 or 10 according to the requirement of resolution.

As a method for switching the laser light, two LDs 9 and 10 having the same configuration as in the prior art are provided, and a polygon mirror 8a (small diameter) having a small number of reflection surfaces is provided with an LD 9 having a large laser light diameter. On the polygon mirror 8b (large diameter) having a large number of reflection surfaces, an LD 10 having a small diameter of the laser light is disposed to be opposed from the beginning.

Usually, a low-resolution electrostatic latent image is formed on the photosensitive drum 5 using a combination of the LD 9 and the polygon mirror 8a.

If there is a request for a high resolution, the combination of the LD 9 and the polygon mirror 8a is immediately changed to the combination of the LD 10 and the polygon mirror 8b by a switch mechanism or the like not shown.

Then, the rotation speed of polygon mirror 8b is polygon mirror
Even if the number of rotations is the same as 8a, the number of scanning lines on the photosensitive drum 5 increases as the number of reflection surfaces increases, and a high-resolution electrostatic latent image can be formed.

By this, a low-resolution image 11a and a high-resolution image 11b can be alternately formed on one sheet of recording paper 11, as shown in the plan view of FIG.

In the case of low resolution, the beam diameter of the laser beam is large, and in the case of high resolution, the beam diameter is small. This is done so that no gap is felt.

In the above description, the case where the resolution is switched to two stages has been described. However, when the resolution is switched to three or more stages, the combination of the LD and the polygon mirror is increased corresponding to the stage,
It can be easily realized by performing the same control.

〔The invention's effect〕

According to the present invention, switching of images can be performed easily and accurately, which has a great economical and industrial effect.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a resolution switching device of the present invention, FIG. 2 is a plan view of a recording paper to which the present invention is applied, and FIG. 3 is a perspective view of a main portion of a conventional resolution switching device. In the figure, 1, 9 and 10 are LDs, 2, 8a and 8b are polygon mirrors, 3 is a spindle, 4 is a DC motor, 5 is a photosensitive drum, 6 is a lens, 7 is a reflection mirror, 11 is recording paper, 11a is a low resolution image, and 11b is a high resolution image.

Claims (1)

(57) [Claims] A plurality of polygon mirrors (8a to 8n) having different numbers of reflecting surfaces on a spindle (3), and a plurality of polygon mirrors which are paired with each other and have different laser beam diameters depending on the number of reflecting surfaces. A resolution switching device comprising a laser light emitter, wherein a combination of the polygon mirrors (8a to 8n) and the laser light emitter is selected according to the resolution, and the laser light emitter is selectively emitted to switch the resolution.