JPH08271819A - Optical scanner - Google Patents

Abstract

PURPOSE: To provide an optical scanner whose number of parts is small, whose production stage is facilitated and which is easily optically assembled. CONSTITUTION: This optical scanner is provided with a laser beam source 2, a toroidal lens 5 condensing a laser beam L emitted from the laser beam source 2, a polygon mirror 6 reflecting the laser beam L transmitted through the lens 5, and a bowed fθ lens 8a condensing the laser beam L reflected from the mirror 6 and forming it into an image on a photoreceptor drum 11. In this scanner, the lens 5 is integrally constituted at one end of the lens 8a in a longitudinal direction, and a synchronizing signal condensing lens 8b is integrally constituted at the other end of the lens 8a. The lens 8a is formed symmetrical to the center. Furthermore, both ends of the lens 8a are fixed on an optical scanner main body 1 through lens holders 10a and 10b.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device equipped in a printer used as a peripheral device of a computer, other facsimiles, copiers and the like. Regarding the device. Conventionally, as an optical scanning device in a printer or the like used as a peripheral device of a computer,
The one shown in FIG. 3 is used. That is, the laser light emitted from the semiconductor laser 52 is collimated by the collimator lens 53 and shaped into an appropriate beam diameter by the aperture 54. The laser beam in the main scanning direction is slightly condensed by a toroidal lens 55 provided separately and is scanned in the main scanning direction by a polygon mirror 56 rotated by a scanner motor 57. At this time, the slightly condensed laser beam is subjected to a predetermined condensing in the main scanning direction by the fθ lens 58a, and a laser beam having an appropriate beam diameter is formed on the surface of the photosensitive drum 61. On the other hand, the beam diameter of the laser light in the sub-scanning direction is condensed on the polygon mirror 56 by the toroidal lens 55, at the same time reflected by the polygon mirror 56 to become a divergent light, and further collected by the fθ lens 58a. Be illuminated. Then, the focused laser light is imaged on the photosensitive drum 61 to have an appropriate beam diameter, as in the main scanning direction. The laser light reflected by the polygon mirror 56 is taken into the sync signal detecting sensor 59 through the sync signal condensing lens 58b. The captured laser light is
It is converted into an electric signal to control the emission timing of the image forming laser light. However, in the above-mentioned conventional example, the following inconveniences have occurred. That is, the toroidal lens 55 for slightly condensing the laser light is provided to the right of the fθ lens 58a and separately from the fθ lens 58a, as shown in FIG. Therefore, when the optical scanning device is properly set, each lens must be separately fixed to the device main body 51, which is very troublesome. In particular, high precision is required for fixing the lenses in the optical scanning device, and specifically, high precision is also required for the mutual positional relationship between the lenses, the distance, and the orientation of the lenses. For these reasons, it has been very difficult to reduce the manufacturing cost of the optical scanning device. Further, the conventional fθ lens 58a has a structure in which the synchronizing signal condensing lens 58b is integrally provided at one end portion thereof, and since it is not a bilaterally symmetrical shape, a large number of steps are required for its manufacture. In that respect, it is difficult to reduce the manufacturing cost. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical scanning device which improves the inconvenience of the conventional example, particularly has a small number of parts, a simple manufacturing process of the device itself, and an easy optical assembly. Is the purpose. In order to achieve the above object, in the invention according to claim 1, a laser light source, a toroidal lens for condensing the laser light emitted from this light source, and this toroidal lens. In the optical scanning device including a polygon mirror that reflects the laser light that has passed through and a bow-shaped fθ lens that collects the laser light reflected from the polygon mirror and forms an image on the photosensitive drum, the length of the fθ lens The toroidal lens is integrally formed at one end in the direction, and the synchronization signal condenser lens is integrally formed at the other end of the fθ lens. Further, the invention described in claim 2 adopts a configuration in which the fθ lens is formed symmetrically, and other configurations are the same as the invention described in claim 1. Further, in the invention described in claim 3, the both ends of the fθ lens are fixed to the main body of the optical scanning device through the lens holders, and other structures are the same as the invention described in claim 2. . According to the present invention, the toroidal lens and the synchronizing signal condensing lens are integrally formed at both ends of the fθ lens. Further, the fθ lens is fixed to the optical scanning device via lens holders at both ends thereof (ends of the toroidal lens and the synchronization signal condenser lens, respectively). And fθ
Laser light emitted from a semiconductor laser provided on the left side of the lens is collimated by a collimator lens and shaped into an appropriate beam diameter by an aperture. And
The laser light in the main scanning direction is slightly condensed by the toroidal lens and is scanned in the main scanning direction by the polygon mirror that is rotationally driven by the scanner motor. At this time,
Since the toroidal lens is integrally formed at one end of the fθ lens, the laser light is emitted from the vicinity of the end of the fθ lens. As a result, the laser light is incident on the polygon mirror at a large incident angle without being affected by the lens holder, so that the degree of freedom in optical design is improved. Then, the laser beam slightly condensed and reflected by the polygon mirror is subjected to a predetermined condensing in the main scanning direction by the f.theta. Lens, and a laser beam having an appropriate beam diameter is formed on the surface of the photosensitive drum. . On the other hand, the beam diameter of the laser beam in the sub-scanning direction is condensed on the polygon mirror by the toroidal lens, at the same time as being reflected by the polygon mirror to become divergent light, and further condensed by the fθ lens. Then, the condensed laser light is imaged on the photosensitive drum 11 to have an appropriate beam diameter as in the main scanning direction. Further, the laser light reflected by the polygon mirror is taken into the sync signal detection sensor through the sync signal condenser lens. The captured laser light is converted into an electric signal, and the emission timing of the image forming laser light is controlled. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. First, in FIG. 1, the optical scanning device is provided with an arch-shaped member substantially parallel to the photosensitive drum 11. Shape f
The θ lens 8a is equipped. Also, the fθ lens 8a
Is formed by bending both ends thereof, and the toroidal lens 5 is integrally formed at one end (the left end in the drawing). Further, a synchronization signal condenser lens 8b is integrally formed at the other end (right end in the figure). A polygonal mirror 6 having a rectangular shape is rotatably provided near the fθ lens 8a and on the side opposite to the side where the photosensitive drum 11 is provided. Explaining these in more detail, the fθ lens 8a is formed in an arcuate shape, and both ends thereof are formed to be bent toward the polygon mirror 6 side. That is, both ends thereof have a V-shape. A toroidal lens 5 is formed at one end on the left side of the both ends, and a synchronization signal condenser lens is formed at the other end. Further, the lens holder 1 is provided at the outermost ends of the fθ lens 8a.
It is fixed to the optical scanning device body 1 by 0a and 10b. At this time, since the toroidal lens 5 centered on the fθ lens 8a and the synchronizing signal condensing lens 8b are symmetrically configured, they can be easily fixed to the optical scanning device. A laser light source 2 for generating a laser light L for forming an electrostatic latent image on the photoconductor drum 11 is provided on the opposite side of the toroidal lens 5 to the side where the polygon mirror 6 is located. Has been done. The laser light source 2 is arranged so as to pass through the toroidal lens 5 and reach the polygon mirror 6. Further, a collimator lens 3 for collimating the laser light L is arranged on the downstream side of the laser light L of the laser light source 2 and on the upstream side of the toroidal lens 5. Further, on the downstream side of the collimator lens 3,
An aperture 4 for reducing the diameter of the laser light L is provided. As described above, since the toroidal lens 5 is formed integrally with the fθ lens 8a, precise alignment with each other is unnecessary. On the other hand, at the other end (right end in the figure) of the fθ lens 8a, there is provided a sync signal focusing lens 8b for focusing the laser light L and making it enter the sync signal detecting sensor 9. ing. The synchronizing signal condensing lens 8b is formed in a shape that is symmetrical to the toroidal lens 5 described above. Further, on the extension line of the synchronization signal condensing lens 8b, the above-mentioned synchronization signal detection sensor 9 for detecting a synchronization signal for image formation and transmitting it to a control unit (not shown) is arranged. It is set up. The polygon mirror 6 is arranged on the extension line of the toroidal lens 5 on the downstream side of the laser light L from the laser light source 2. The polygon mirror 6 is formed in a square shape in a plan view and in a plate shape having a predetermined thickness (see FIG. 2), and is rotatably arranged in a horizontal direction (paper surface direction in the drawing). Then, the received laser light L is reflected by the side mirror. The polygon mirror 6 is rotationally driven by a scanner motor 7 which is arranged in engagement with the toroidal lens 5. Further, the fθ lens 8a is provided on the opposite side of the polygon mirror 6 (upper part in FIG. 1) with the fθ lens 8a interposed therebetween.
The photoconductor drum 11 is rotatably arranged so as to be substantially parallel to. Then, the laser beam L reflected from the polygon mirror 6 irradiates the surface of the photoconductor drum 11 to form an electrostatic latent image on the photoconductor drum 11. Next, the operation of the optical scanning device configured as described above will be described with reference to FIG. 2. First, the laser light source 2 is set to a predetermined position based on an image signal transmitted from a controller (not shown). Laser light L for image formation is generated. The laser light L is diffused light, but is collimated by the collimator lens 3 provided on the downstream side. Then, the donut-shaped aperture 4 arranged further downstream is used to reduce the light diameter to an appropriate one. The light diameter of the laser light L in the main scanning direction is slightly condensed by the toroidal lens 5 provided integrally with the fθ lens 8a. Then, it reaches the polygon mirror 6 arranged on the downstream side of the toroidal lens 5 and is reflected by the polygon mirror 6. A scanner motor 7 for rotationally driving the polygon mirror 6 is engaged with the polygon mirror 6, and the polygon mirror 6 is rotated in response to a rotation signal from a control section, whereby the photosensitive drum 11 is rotated.
An electrostatic latent image is sequentially formed along the longitudinal direction of the surface of the.
More specifically, first, the laser light L emitted from the laser light source 2 is related to the rotational position of the polygon mirror 6,
The light is transmitted through the sync signal condenser lens 8b and detected by the sync signal detection sensor 9. Then, a predetermined signal is transmitted from a control unit (not shown) based on this detection signal, and the laser light source 2 starts emitting light according to the image to be formed, and at the same time, the polygon mirror 6 starts rotating. That is, in the initial stage of the optical scanning process, the right side of the photosensitive drum 11 is irradiated. At this time, the laser light L reflected from the polygon mirror 6 receives a predetermined light condensing in the main scanning direction due to the lens effect of the fθ lens 8a and forms an image on the surface of the photosensitive drum 11. . And the polygon mirror 6
With the rotation of, the optical scanning process proceeds from the right side of the photosensitive drum 11 to the left side sequentially (in the direction of the arrow in FIG. 2). After that, as the photosensitive drum 11 rotates,
The polygon mirror 6 also rotates and the next optical scanning process is repeated. On the other hand, the beam diameter of the laser light L in the sub-scanning direction (direction perpendicular to the main scanning direction) is condensed on the polygon mirror 6 by the toroidal lens 5 and, at the same time, is reflected by the polygon mirror 6 and once diverged. And fθ
It is again focused by the lens 8a. Then, the focused laser beam L is imaged on the photosensitive drum 11 to have an appropriate beam diameter, as in the main scanning direction. The laser light L reflected by the polygon mirror 6 is taken into the sync signal detecting sensor 9 through the sync signal condenser lens 8b. The captured laser light L is converted into an electric signal, and the emission timing of the next image forming laser light is controlled. Since the present invention is constructed and functions as described above, according to the invention of claim 1, the toroidal lens and the synchronizing signal condensing lens are formed integrally with the fθ lens. In addition, when manufacturing each lens, the manufacturing process can be simplified as compared with the conventional method, and the number of parts of the optical scanning device itself can be reduced. Further, there is no need for precise adjustment work of the positions and orientations of the lenses. Further, even when the fθ lens is fixed to the optical scanning device, the fθ lens, the toroidal lens, and the synchronizing signal condensing lens can be fixed at the same time in one step, so that the efficiency of the assembling work is also improved. , Which produces an excellent effect. Further, since the toroidal lens is integrally formed at one end of the fθ lens, the laser light can be incident on the polygon mirror at a large angle. Therefore, the optical design is facilitated, and the size reduction of the device can be realized, which is an excellent effect. According to the second aspect of the invention, since the fθ lens is formed symmetrically, the manufacturing process thereof is simplified as compared with the conventional bilaterally asymmetric lens, and the fθ lens is Even when the lens holder is fixed to the optical scanning device via the lens holder, the shape of the lens holder can be made common to the left and right, so that an excellent effect that the manufacturing cost can be reduced can be obtained. Further, according to the invention of claim 3, fθ
Since both ends of the lens (the portion of the toroidal lens and the synchronizing signal condensing lens) are fixed to the optical scanning device via the lens holder, even if the laser light source is arranged near both ends of the fθ lens, Since the light is not blocked by the lens holder and is not optically affected, there is an excellent effect that the degree of freedom in optical design is greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing an embodiment of the present invention. FIG. 2 is a perspective view showing the optical scanning device disclosed in FIG. FIG. 3 is a plan view showing a conventional example. [Description of Reference Signs] 1 Optical scanning device body 2 Laser light source 5 Toroidal lens 6 Polygon mirror 8a fθ lens 8b Synchronous signal condensing lenses 10a and 10b Lens holder 11 Photosensitive drum L Laser light

Claims (1)

Claim: What is claimed is: 1. A laser light source, a toroidal lens that collects laser light emitted from the light source, a polygon mirror that reflects the laser light that has passed through the toroidal lens, and a reflection from the polygon mirror. In an optical scanning device including an arc-shaped fθ lens that collects the focused laser light and forms an image on a photosensitive drum, the toroidal lens is integrally formed at one longitudinal end of the fθ lens. An optical scanning device characterized in that a sync signal condensing lens is integrally formed at the other end of the fθ lens. 2. The light scanning device according to claim 1, wherein the fθ lens is formed symmetrically. 3. The optical scanning device according to claim 2, wherein both ends of the fθ lens are fixed to the optical scanning device main body through lens holders.