JPS62146655A - Image recording apparatus - Google Patents

Abstract

PURPOSE:To output images different in scanning line density by the same apparatus, by setting the spot diameters of a plurality of semiconductive lasers so as to differentiate the same. CONSTITUTION:Laser beams emitted from laser units, 1, 2 in a parallel luminous flux are linearily formed into an image on the reflective surface of a polygon mirror 3 at a right angle to the direction of the rotary shaft 3a of the polygon mirror 3 and formed into an image on a photosensitive drum 7 in a spot form by image forming lenses 4, 5. A cylindrical lens 8 as a spot diameter variable means is adjusted so that the scanning line density of the laser unit 1 is fitted, for example, to 240 (dot/inch) and the spot diameter on the photosensitive drum 77 comes to 100-150(mum) and a cylindrical lens 8' as a spot diameter variable means is adjusted so that the scanning line density of the laser unit is fitted, for example, to 400 (dot/inch) and the spot diameter comes to 60-100(mum).

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an image recording device using a semiconductor laser such as a laser beam printer, and more particularly to an image recording device that outputs images with different scanning line densities using the same device. .

(Prior art) Conventionally, laser beam printers, which are image recording devices,
The scanning line density is unique to the machine, and it is difficult to change the scanning line density.

Recently, laser beam printers have become a widespread market for personal computer output.

Used in facsimiles, plotters, etc.

The scanning line density is also 200, 240, 300°400,
There are various types of 480 and 500 (dat/1nch).

(Problems to be Solved by the Invention) In the past, printers with different scanning line densities had to be used for different scanning line densities, and this meant that expensive printers were used as dedicated machines for various hosts. There was a problem in that this resulted in an extremely large amount of waste.

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

(Means for Solving the Problems) In order to achieve the above object, the present invention has a plurality of semiconductor lasers, and each of the laser beams irradiated onto a recording medium by the plurality of semiconductor lasers has a plurality of semiconductor lasers. A variable means for varying the spot diameter is provided, and the variable means sets the spot diameters of the plurality of conductor lasers to be different.

(Function) In the present invention, the diameters of the spots irradiated onto the recording medium by a plurality of semiconductor lasers are set to be different.

(Embodiments) The present invention will be explained in detail below based on illustrated embodiments. In Figs. 1 to 3 showing a laser beam printer as an image recording device according to an embodiment of the present invention, 1
, 2 is a laser unit that combines a semiconductor laser that is turned on and off in accordance with image information and a collimator lens that converts the laser beam emitted from the semiconductor laser into parallel light. Reference numeral 3 denotes a polygon mirror as a scanner which rotates around a rotation axis 3a, and reflects the laser beam emitted from each laser unit 1.2 to a recording medium via an imaging lens 4.5 and a folding mirror 6. The photosensitive drum 7 is scanned with a laser beam. Cylindrical lenses 8 and 8' are disposed between the laser unit 1.2 and the polygon mirror 3, and they convert the parallel laser beam into a line perpendicular to the rotation axis 3a direction of the polygon mirror 3. The laser beam is imaged on the reflective surface of the polygonal mirror 3, and is imaged as a spot on the photosensitive drum 7 by the above-mentioned imaging lenses 4 and 5. Further, 9 is a mirror that reflects the laser beam onto a fiber 10 that guides the light to a beam detector. The beam detector detects the passage of the laser beam and generates an image writing signal, and controls the timing at which the laser starts driving with the recorded image signal so that the image writing position on the photosensitive drum 7 is constant. be.

On the other hand, around the photosensitive drum 7, there is a primary charger 11 and a developer 1.
2. A transfer charger 13 and a cleaner 14 are provided,
The image is formed by a conventional electrophotographic process. That is, the photosensitive drum 7 is uniformly charged by the charger 11 and exposed and scanned by a laser beam to form an electrostatic latent image.

Furthermore, a visible image is formed using toner by the developing device 12, and is transferred onto the transfer material 15 by the transfer charger 13, and the image transferred to the transfer material 15 is fixed by a fixing device (not shown). - The toner remaining on the photosensitive drum 7 is removed by the cleaner 14.

FIG. 2 shows a scanner unit 15 incorporating an exposure section such as a polygon mirror 3 and an imaging lens 4.5. Two laser units 1.2 are mounted horizontally on the side wall of a dark box 16 in which a polygon mirror 3, an imaging lens 4.5, etc. are housed. 17.17 is a connector for connecting the laser unit 1.2 to a drive circuit (not shown), and 18 is a connector for energizing a motor (not shown) for rotationally driving the polygon mirror 3. A laser beam la enters the polygon mirror 3 from each laser unit 1.2.

2a are incident at substantially the same position from a direction perpendicular to the rotation axis 3a of the polygon mirror 3, and their respective incident angles differ by the fact that the laser units 1 and 2 are spaced apart from each other.

Regarding the scanning area by the polygon mirror 3, L =
-! --X is given by f. Here, n represents the number of surfaces of the polygon mirror 3, and f represents the focal length of the optical system. For example, if a polygon mirror 3 with 6 surfaces is used and the focal length is
[If a lens of l 60 (am) is used, L=335
mm, which is sufficient to scan an A4-sized intestine with a width 210a.

FIG. 4 shows the state of two laser beams incident on the polygon mirror 3, la and 2a, and their reflected beams lb and 2b. The angles of incidence on the two incident mirror surfaces 3b are also slightly shifted.

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

Next, FIG. 5 is a block diagram from when the beam detector 100 receives a laser beam signal to when the semiconductor laser 101 and the semiconductor laser 102 are driven.
The signal of the laser beam received by the beam detector 100 is sent to the control circuit 103, and after a certain period of time from the received signal of the beam detector 100, each semiconductor laser 101.1
02 emits light in response to an image signal.

Here, the scanning line density of the laser unit 1 is, for example, 24
0 (dat/1nch)
The symmetrical lens 8 as a spot diameter variable means is adjusted so that the upper spot diameter is 100 to 150 (gm), and the laser unit 2 is adjusted so that the upper spot diameter is 100 to 150 gm.
The symmetrical lens 8' as a spot diameter variable means is adjusted so that the spot diameter is 60 (IL) to 100 (Lm) suitable for 0 (dat/1 nch). (Here, the spot diameter is 1/e2 of the maximum value
The width of the part is measured. ) Further, the planes on which the laser beams of the laser unit 1 and the laser unit 2 are formed are on the same plane, and scan substantially the same surface of the photosensitive drum 7.

However, since the laser units 1 and 2 are incident on the polygon mirror 3 at different positions, they scan the photosensitive drum 7 with deviations from each other in the axial direction of the photosensitive drum 7. The portion corresponding to the width overlaps with both laser units 1 and 2.

On the other hand, in the above embodiment, 240 (dat/1nc
h) and 400 (dat/1nch) Te When switching the semiconductor laser to be used, it is necessary to simultaneously switch the rotational speed of the polygon motor and the driving frequency for driving the semiconductor laser.

In the above embodiment, the photosensitive drum 7 is
The structure of the semiconductor laser was changed to change the upper spot diameter, but at the same time, the laser output may be changed by changing the drive current applied to each semiconductor laser.

Further, the laser exposure method may be an image scan method in which a portion to which toner adheres is irradiated with a laser beam, or a background scan method in which a portion other than the portion to which toner adheres is exposed to light; however, the present invention In particular, this method has a remarkable effect on the background method. Incidentally, this is because in the background method, overlapping of laser spots is an important factor to prevent fog from occurring in the white background area.

Furthermore, in the above embodiment, the spot diameter variable means is used to change the distance between the symmetrical lens 8.8' and the laser unit 1.2, but the invention is not limited to this. You may also use the vA clause. Semiconductor lasers have a radiation angle θ in the range of about 6° to 40° depending on the individual semiconductor laser, but the smaller the radiation angle θ, the larger the spot diameter, and conversely, the larger the radiation angle θ, the smaller the spot diameter. Radiation angle θ
Semiconductor lasers may be selected depending on the size of the spot diameter, thereby varying the spot diameter.

(Effects of the Invention) The image forming apparatus according to the present invention has the above-described configuration and operation, and has a plurality of semiconductor lasers, and the diameter of each laser spot irradiated onto a recording medium by the plurality of semiconductor lasers is Since a variable means is provided, and the variable means sets the diameters of each of the plurality of semiconductor lasers to be different, images with different scanning line densities can be output with the same device, and costs can be reduced. This has the effect that good image quality can be obtained by reducing the amount of image.

[Brief explanation of drawings]

FIG. 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 shown in FIG. 1, and FIG. 3 is a scanning by a polygon mirror of the apparatus shown in FIG. 1. FIG. 4 is an explanatory diagram showing how a laser is incident on a polygon mirror, and FIG. 5 is a block diagram showing a control form of the same embodiment. Explanation of symbols 1.2... Laser unit (semiconductor laser) 3.
・Polygon mirror

Claims (1)

[Claims] A plurality of semiconductor lasers are provided, and a variable means is provided for varying the spot diameter of each laser beam irradiated onto a recording medium by the plurality of semiconductor lasers, and the variable means is configured to vary the spot diameter of each of the plurality of semiconductor lasers. An image recording device characterized by being configured.