JPS61281214A - Laser recorder - Google Patents

Abstract

PURPOSE:To correct the face inclination of a rotary polyhedral mirror and to execute laser recording without uneven optical scanning pitches by providing a slit plate having a slit for passage of laser light in the main scanning direction at the width smaller than the beam diameter of laser light to a photosensitive body and the rotary polyhedral mirror. CONSTITUTION:The slit plate 18 is formed with the slit S of the width corresponding to the diameter of the dot to be printed, for example, 0.1mm width in the main scanning direction and is juxtaposed with a photosensitive drum 17 at an approximately equal length. The slit plate is juxtaposed with the rotary polyhedral mirror 14 in the positional relation with which the center of the laser light LB-1 of the longitudinally long elliptical beam shape reflected from said mirror is coincident with the center of the slit S. The slit width is smaller than the length of the elliptical beam spot of the laser light LB-1. If the face inclination of the mirror 4 arises from the deviation of the revolving shaft thereof, the laser light LB-1 emitted from the mirror 14 is made incident on the slit plate 18 in the form of the beam deviating in the auxiliary scanning direction but the laser light and the slit S overlap on each other and the printing and recording are executed at the specified pitch on the recording surface of the drum 17 in the auxiliary scanning direction Y regardless of the face inclination of the mirror 17.

Description

[Detailed Description of the Invention] [Summary] The laser recording device of the present invention uses a laser beam having a long cross-section in the sub-scanning direction perpendicular to the main-scanning direction, and converts the laser beam deflected by a rotating polygonal mirror into the laser beam. The photoreceptor is scanned through a slit in the main scanning direction that is narrower than the beam diameter, making it possible to perform laser recording without any unevenness in the optical scanning pitch regardless of the surface tilt of the rotating polygon mirror.

[Industrial application field]

The present invention relates to a device that records information using a laser beam, and more particularly to a new laser beam scanning system that corrects the tilting of a rotating polygon mirror.

In laser recording devices known as laser printers and the like, it is important to improve optical scanning pitch unevenness caused by the surface tilt of a rotating polygon mirror that deflects modulated laser light.

(Prior Art) A conventional laser printer uses a cylindrical lens to correct the tilt of the rotating polygon mirror.

[Problem that the invention seeks to solve]

However, the above cylindrical lens is quite expensive.

An object of the present invention is to provide a laser recording apparatus which has an inexpensive configuration, corrects the surface tilt of a rotating polygon mirror, and thereby enables laser recording without unevenness in the optical scanning pitch.

[Means for solving problems]

In the laser recording apparatus of the present invention, as shown in FIG. A slit plate 18 having a slit S in the main scanning direction (axis direction of the photoconductor) having a width smaller than the length of the elliptical laser beam spot is provided between the polygon mirror 14 and the photoconductor 17, and the rotating polygon mirror 14 The laser beam is deflected by a vertically elongated ellipse and is scanned onto the photoreceptor through the Surin+-S.

[Effect]

The slit plate constricts the vertically elongated elliptical spot-shaped laser beam incident from the rotating polygon mirror, transforms it into a substantially square laser beam spot corresponding to a predetermined printing dot, and emits the laser beam onto the photoreceptor. In addition, the circular slit plate should be used by aligning the center of the slit with the center of the laser beam bond in advance (this may cause the rotating polygon mirror to be tilted inadvertently and the laser beam to be incident in a manner deviated in the sub-scanning direction). However, unless the laser beam spot deviates from the slit 7, the laser beam is emitted onto the photoreceptor in the spot shape described above.

Moreover, since the emitting position is a fixed position, pinch unevenness in the sub-scanning direction does not occur at all.

〔Example〕

FIG. 1 is a schematic diagram of a laser beam scanning system of a laser printer to which the present invention is applied.

In this figure, 11 is a motor 12 that processes print information.
and a signal processing circuit that drives the semiconductor laser 13 and the like. Reference numeral 14 denotes a rotating polygon mirror that is rotated by the motor 12, modulated by the modulator 15, and focused by the lens 16, and moves the laser beam LB-1 in the main scanning direction X to be incident on the recording surface of the photosensitive drum 17. be.

Up to this point, the process is the same as in conventional laser printers. In conventional printers, the photosensitive drum 17 is
A cylindrical lens (not shown) was placed in front of the lens.

However, in the present invention, the spot shape of the modulated laser beam incident on the rotating polygon mirror 14 is a vertically elongated ellipse in cross section, for example, a vertically 0.
3~Q, 4svr, oval shape with width of about 0.1m. The following means can be adopted to create this vertically elongated elliptical beam of laser light. In other words, in the case of the semiconductor laser used in this example, since it originally emits an elliptical laser beam, if it is arranged with the laser beam emission direction in the vertical direction, the vertically elongated elliptical laser spot can be obtained. This is adopted. Incidentally, another method is to arrange a light guide plate having a predetermined vertically elliptical aperture hole in front of the rotating polygon mirror so that the laser light passing therethrough is formed into a vertically elliptical spot shape.

Further, in this invention, a slit plate 18 is provided in place of the cylindrical lens. This slit plate 18 has a slit S having a width corresponding to the print dot diameter, for example, a width of about 0.1 mm.
is formed in the main scanning direction, and is arranged in parallel with the photosensitive drum 17 with approximately the same length, and the rotating polygon mirror 14 is located between the center of the vertically elliptical beam-shaped laser beam LB-1 reflected from the rotating polygon mirror 14 and the slit S. They are placed side by side in a positional relationship that matches the centers of the two. Note that the slit width is smaller than the length of the elliptical beam spot of the laser beam L8-1 (0.3 to 0.40).

In such a configuration, assuming that the rotating polygon mirror 14 is installed correctly, the laser beam LB-1 in the shape of a vertically elongated ellipse reflected by the rotating polygon mirror 14 is shown in FIG. 2(a). The light enters the slit plate 18 as shown in FIG. The incident laser beam LB-1 sufficiently overlaps the slit S, and the slit S narrows down this vertically elongated elliptical beam spot only in the vertical direction, and the laser beam LB-2 having a substantially regular square beam spot shape is delivered to the photosensitive drum 17. emitted to.

However, suppose that the rotation axis of the rotating polygon mirror 14 is deviated in a predetermined direction, causing a surface tilt. In this case, rotating polygon mirror 1
The laser beam LB-1 emitted from the laser beam LB-1 enters the slit plate 18 in a shifted manner in the sub-scanning direction as shown in FIG. 2(b). However, if there is a slight scanning deviation, the laser beam and the slit S overlap, and therefore, in this case as well, the laser beam LB- has a substantially regular square beam spot shape.
2 can be emitted onto the photosensitive drum 17.

Therefore, printing is performed on the recording surface of the photosensitive drum 17 at a constant pitch in the sub-scanning direction Y, regardless of the surface tilt of the rotating polygon mirror 17.

〔effect〕

As is clear from the above description, according to the laser recording apparatus of the present invention, it is possible to correct the surface tilt of the rotating polygon mirror and perform laser recording without uneven optical scanning. In addition, the surface tilt correction means is extremely practical because it has a simple and inexpensive structure that only requires a slit plate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram conceptually showing a laser beam scanning system according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining the effect of a slit plate. In the figure,

Claims (1)

[Scope of Claims] A laser recording configuration in which a modulated laser beam is moved in a main scanning direction by a rotating polygon mirror (14) to scan a recording surface of a photoreceptor (17), wherein the laser beam (LB-1) has a long cross-sectional shape in the sub-scanning direction perpendicular to the main-scanning direction, and has a main-scanning width smaller than the beam diameter of the laser beam (LB-1) on the photoreceptor (17) and the rotating polygon mirror (14). A slit plate (1) having a slit (S) for laser beam passage in the direction
8) A laser recording device characterized by comprising: