JPH07106643B2 - Image recorder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus using a semiconductor laser such as a laser beam printer, and more particularly to an image recording apparatus which outputs images with different scanning line densities by the same apparatus. .

(Prior Art) Conventionally, a laser beam printer, which is an image recording device,
It has a scanning line density specific to the machine, and it was difficult to change the scanning line density. Recently, the laser beam printer has been widely used in the market, and is used for output of personal computer, facsimile, plotter, etc., and its scanning line density is 200,240,300,400,480,500.
There are various types of (dot / inch).

(Problems to be Solved by the Invention) By the way, conventionally, when the scanning line densities are different, it is necessary to use printers having different scanning line densities. This is because an expensive printer is used as a dedicated machine for various hosts. There is a problem in that it is used and the amount of waste is extremely increased.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and the purpose thereof is to output images of different scanning line densities with the same device,
An object of the present invention is to provide an image recording apparatus that reduces costs and has good image quality.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a photosensitive member and a plurality of units for irradiating the photosensitive member with a laser beam modulated according to an image signal are provided. In the image recording apparatus having the laser light irradiating means, the laser light irradiated to the photoconductor from the plurality of laser light irradiating means has different spot diameters, and the photoconductor has high scanning line density. When forming an image, the laser light irradiating means for irradiating a laser beam having a spot diameter smaller than that when forming an image having a low scanning line density is used, and when forming an image having a low scanning line density on the photoreceptor. The laser light irradiating means for irradiating a laser light having a spot diameter larger than that for forming an image having a high scanning line density is used.

(Operation) In the present invention, the diameters of the respective spots irradiated onto the photoconductor by the plurality of laser light irradiation means are set to be different.

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example. 1 to 3 showing a laser beam printer as an image recording apparatus according to an embodiment of the present invention,
Reference numerals 1 and 2 denote a laser unit in which a semiconductor laser that is turned on and off according to image information and a collimator lens that converts a laser beam (laser light) emitted from the semiconductor laser into parallel light are integrated. 3 is the rotating shaft 3a
It is a polygon mirror as a scanner which rotates around the center of the laser. It reflects the laser beam emitted from each laser unit 1 and 2 and forms an image forming lens 4,5 and a folding mirror 6.
The laser beam is scanned over the photosensitive drum 7 as a recording medium (photoconductor) via the. Cylindrical lenses 8 and 8'are arranged between the laser units 1 and 2 and the polygon mirror 3, and the laser beam that has become a parallel light beam is formed into a linear shape at a right angle to the rotation axis 3a direction of the polygon mirror 3. An image is formed on the reflecting surface of the polygon mirror 3, and a laser beam is formed into a spot on the photosensitive drum 7 by the above-mentioned image forming lenses 4 and 5. The laser unit and the cylindrical lens constitute the laser light irradiation means. Further, 9 is a mirror for reflecting the laser beam to the fiber 10 which guides the light to the beam detector. The beam detector detects the passage of the laser beam, generates an image writing signal, and controls the timing of driving start by the image signal to be recorded by the laser so that the image writing position on the photosensitive drum 7 becomes constant. is there.

On the other hand, around the photosensitive drum 7, a primary charger 11, a developing device 12,
A transfer charger 13 and a cleaner 14 are provided, and an image is formed by a normal electrophotographic process. That is, the photosensitive drum 7 is uniformly charged by the primary charger 11 and is exposed and scanned by the laser beam to form an electrostatic latent image. Further, the developing device 12 forms a visible image with toner, and the transfer charging device 13 transfers the visible image to the transfer material 15 to transfer the transfer material.
The image transferred to 15 is fixed by a fixing device (not shown). On the other hand, the toner remaining on the photosensitive drum 7 is a cleaner.
Removed by 14.

FIG. 2 shows a scanner unit 15 in which an exposure unit such as a polygon mirror 3 and imaging lenses 4 and 5 is incorporated.
Dark box 1 that houses polygon mirror 3, imaging lenses 4 and 5
On the side wall of 6, two laser units 1 and 2 are mounted side by side in the horizontal direction. Reference numerals 17 and 17 are connectors for connecting the laser units 1 and 2 to a drive circuit (not shown), and 18 is a connector for energizing a motor (not shown) for rotationally driving the polygon mirror 3. Each laser unit 1,
Laser beams 1a and 2a incident on the polygon mirror 3 from 2
Are incident on the rotation shaft 3a of the polygon mirror 3 at substantially the same position in a direction perpendicular to the rotation axis 3a, and the respective incident angles differ by the distance between the laser units 1 and 2.

Regarding the scanning area L by the polygon mirror 3, Given in. Here, n is the number of surfaces of the polygon mirror 3, and f is the focal length of the optical system. For example, if a polygon mirror 3 having 6 surfaces is used and a lens having a focal length of 160 (mm) is used, L = 335 mm, which is sufficient to scan an A4 size width 210 mm.

FIG. 4 shows the two incident beams 1a and 2a of the laser light on the polygon mirror 3 and the reflected beams 1b and 2b thereof. The two incident beams 1a and 2a are incident with a slight deviation in the vertical direction on one surface 3b of the polygon mirror 3 (deviation amount H),
At the same time, the angle of incidence on the polygon mirror surface 3b will also be slightly shifted.

On the other hand, the laser beam from the laser unit 1 is formed on the optical path surface formed by the incident light 1a and the reflected light 1b on the polygon mirror 3, and the incident light 2a and the reflected light 2b of the laser beam from the other laser unit 2 are formed. It is parallel to the optical path surface.

Next, FIG. 5 shows the semiconductor laser 101 and the semiconductor laser 1 after receiving the laser light signal by the beam detector 100.
FIG. 4 is a block diagram until driving 02, in which a signal obtained by receiving a laser beam by the beam detector 100 is sent to the control circuit 103, and each semiconductor laser 101, 102 emits light in accordance with an image signal after a predetermined time has elapsed from the light receiving signal of the beam detector 100.

Here, the scanning line density of the laser unit 1 is, for example, 240
The cylindrical lens 8 as the spot diameter changing means is adjusted so that the spot diameter on the photosensitive drum 7 is 100 to 150 (μm) so as to be suitable for (dot / inch), and the laser unit 2 is For example, the cylindrical lens 8'as the spot diameter varying means is adjusted so that the spot diameter is 60 (μm) to 100 (μm) so as to be suitable for 400 (dot / inch). (Here, the spot diameter measures the width of 1 / e ² of the maximum value.) The planes forming the laser beams of the laser unit 1 and the laser unit 2 are on the same plane. Then, the substantially same surface of the photosensitive drum 7 is scanned.

However, since the laser units 1 and 2 are displaced from each other in the incident position on the polygon mirror 3, the laser units 1 and 2 scan the photosensitive drum 7 while being displaced from each other in the axial direction of the photosensitive drum 7. The part corresponding to is overlapped with both laser units 1 and 2.

On the other hand, in the above embodiment, 240 (dot / inch) and 400 (do
t / inch) When switching the semiconductor laser used,
It is necessary to simultaneously switch the rotation speed of the polygon motor and the drive frequency for driving the semiconductor laser.

Incidentally, in the above embodiment, the photosensitive drum 7 corresponding to the scanning line density is used.
Although the structure of the semiconductor laser is changed so as to change the above spot diameter, the laser output may be changed by changing the driving current applied to each semiconductor laser at the same time.

Further, the laser exposure method may be an image scan method in which a portion to which toner is attached is irradiated with a laser, or a background scan method in which the outside of a portion to which toner is attached is exposed. In particular, the background method has a remarkable effect. By the way, this is because, in the background method, the overlapping of laser spots is an important factor for preventing fogging in a white background.

Further, in the above-mentioned embodiment, the distance between the cylindrical lenses 8 and 8 ′ and the laser units 1 and 2 was changed as the spot diameter varying means, but the radiation angle θ of the semiconductor laser is not limited to this.
It may be adjusted with (Far Field Pattern). The semiconductor laser has an emission angle θ in the range of about 6 ° to 40 ° depending on its individual body. The smaller the emission angle θ, the larger the spot diameter, and conversely, the larger the emission angle θ, the smaller the spot diameter. Therefore, the semiconductor laser may be selected according to the size of the radiation angle θ, and the spot diameter may be changed by this.

(Effects of the Invention) The image forming apparatus according to the present invention has the above-described configuration and operation, and the laser beams emitted from the plurality of laser beam irradiating means have different spot diameters. When a high scanning line density image is formed on the image, a laser beam irradiating unit that emits a laser beam having a smaller spot diameter than when a low scanning line density image is formed is used. The laser beam irradiation means that irradiates a laser beam with a spot diameter larger than that when forming an image with a high scanning line density, so that the same device outputs images with different scanning line densities. Therefore, the cost can be reduced and good image quality can be obtained.

[Brief description of drawings]

1 is a schematic configuration diagram of an image recording apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of a scanner unit of the apparatus of FIG. 1, and FIG. 3 is scanning by a polygon mirror of the apparatus of FIG. FIG. 4 is a schematic plan view of an optical system showing a region, FIG. 4 is an explanatory view showing how a laser enters a polygon mirror, and FIG. 5 is a block diagram showing a control mode of the same embodiment. Explanation of symbols 1,2 …… Laser unit (semiconductor laser) 3 …… Polygon mirror 7 …… Photosensitive drum (recording medium) 8,8 ′ …… Cylindrical lens

Claims (1)

[Claims] 1. An image recording apparatus comprising a photoconductor and a plurality of laser light irradiation means for irradiating the photoconductor with laser light modulated according to an image signal. The laser light applied to the photoconductor has different spot diameters, and when forming an image having a high scanning line density on the photoconductor, the laser beam having a spot diameter larger than that when forming an image having a low scanning line density is used. Using the laser light irradiation means for irradiating a small laser beam, when forming an image with a low scanning line density on the photoconductor, a laser beam with a larger spot diameter is irradiated than when forming an image with a high scanning line density. An image recording apparatus using the above laser light irradiation means.