JPH01910A - Optical device in image forming apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to a non-impact printer, a copying machine, or other device that forms an image using a laser beam, in which a plurality of laser beams are directed onto an image carrier. irradiate.

The present invention relates to improvements in optical devices in image forming apparatuses.

(Prior Art) In image forming apparatuses such as copying machines and printers, in order to form a multicolor image on a photoreceptor which is an image carrier using a plurality of developers, in recent years, as shown in FIG. A device that forms a plurality of electrostatic latent images on a photoreceptor using a laser beam is often used. That is, this device consists of two
The two laser beams (lla) and (llb) emitted from the laser oscillation devices (10a) and (LOb) are guided to a polygon mirror (12) rotating at high speed via a collimator lens and a beam compressor (not shown). , and as the polygon mirror (12) rotates, the reflection angles of the laser beams (lla) and (ltb) are changed, and the laser beams (13) are scanned in the longitudinal direction of the photoreceptor (13). On the other hand, an imaging lens system (17) consisting of a first lens (14) and a second lens (16) is provided between the polygon mirror (12) and the photoreceptor (13).
Two laser beams (lla).

(llb) is imaged on the photoreceptor (13).

However, in such a device, the two laser beams (lla) and (llb) are irradiated to different positions on the photoreceptor (13), so the optical paths must be separated. Book laser beam (lla).

(llb) is the light 4111 (17) of the imaging lens system (17).
The image is formed through a symmetrical and parallel optical path or a symmetrical and outwardly tilted optical path with respect to a). That is, since the two laser beams (lla) and (llb) pass through the imaging lens system (17) separately, the first lens (lla) and (llb) pass through the imaging lens system (17).
The effective scanning area of the second lens (14) and the second lens (16) becomes larger;
This causes distortion in the image formed on top, leading to a decrease in image quality.
This method has a problem in that it cannot be applied to fine images. Furthermore, in the case where the lens is a plastic lens that is easily affected by temperature changes, the distortion of the lens due to environmental changes increases the distortion of the image and significantly degrades the quality of the image.

On the other hand, although the effective scanning area is large, it is possible to reduce image distortion by increasing the lens diameter.
For plastic lenses that are integrally molded by pouring into a mold, as the diameter increases, the precision of molding with the mold deteriorates, creating new problems such as difficulty in manufacturing and increased costs.

(Problem to be Solved by the Invention) Conventionally, a plurality of laser beams are imaged at symmetrical positions about the optical axis of an imaging lens system through parallel or outwardly inclined optical paths. Therefore, the effective scanning area of the lens in the imaging lens system becomes larger, which increases image distortion and degrades the image.However, in order to reduce image distortion, attempts were made to increase the diameter of the plastic lens. In this case, the molding is difficult and the cost increases.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and by reducing the effective scanning area of the lens of the imaging lens system, it is possible to reduce image distortion and improve the image, and it is also possible to apply it to fine images. The object of the present invention is to provide an optical device for an image forming apparatus that can perform the following steps.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an oscillation section that oscillates a laser beam so as to tilt the laser beam in the direction of the optical axis of the imaging lens system.

(Function) The present invention uses the above means to bring a plurality of laser beams close to the optical axis near the imaging lens system or within the imaging lens system, thereby reducing the effective scanning area of the lens by the plurality of laser beams. Therefore, it is possible to reduce image distortion without increasing the size of the lens, thereby improving the image quality and preventing an increase in the cost of the lens.

(Example) An example of the present invention will be described below with reference to FIG. (ta) is an optical device in a non-impact printer (not shown) which is a terminal of a host system such as an electronic computer, and includes a first oscillation unit (20) consisting of a semiconductor laser that oscillates a first laser beam (20a). and an oscillation section (21) made of a semiconductor laser that oscillates a second laser beam (21a). And the first oscillation part (2
0) and a second oscillating unit (21), the first and second laser beams (20a) and (21a) both have an inclination angle in the optical axis (24a) direction of an imaging lens system (24), which will be described later. ψ
It is provided at an angle so that the beam is incident at an angle of 2.5 [degrees]. Further, (23) is a polygon mirror rotated at 6000 degrees (7 minutes of rotation), and after being oscillated by the first oscillation unit (20) and the second oscillation unit (21), a collimator lens (not shown) and a beam A first laser beam (20a) and a second laser beam (20a) are focused and deflected through a compressor.
is irradiated with a laser beam (21a). Each laser beam (20) is further reflected by a polygon mirror (23).
The imaging lens system (24) for condensing the aL (21a) onto the photoreceptor (26), which is an image carrier, and forming an image uniformly on the scanning line, which is the longitudinal direction thereof, is made of integrally molded plastic. The first lens (24b) and the second lens (24b)
4c). or,.

(27a) and (27b) are the first laser beam (2
First and second mirrors that deflect the optical path of 0a) toward the photoreceptor (26).

(27c) and (27d) are the second laser beam (2
These are third and fourth mirrors that deflect the optical path 1a) toward the photoreceptor (26). Note that (28) is the first developing device (30) is the second developing device, (31) is the first charger, and (32) is the second charger.

When multicolor printing is started in a non-impact printer (not shown) based on information from a host system (not shown), each device is driven, and the photoreceptor (26) is rotated in the direction of arrow X. Each charger (32), (
33) becomes charged, the developing device (za), (30
) can also be developed. In this state, the host system (
each oscillator (20) in response to a print signal from (not shown),
(21) from the first and second laser beams (20a)
.

(21a) is oscillated, each laser beam (20a)
.

(21a) are each guided to a polygon mirror (23) via a collimator lens and a beam compressor (not shown), and as they rotate, they are each scanned in the longitudinal direction of the photoreceptor (26) via an imaging lens system (24).

On the other hand, in the imaging lens system (24), the first and second laser beams (20a) and (21a) reflected from the polygon mirror (23) are oriented 2 times in the optical axis (24a) direction.
．． The first lens (24b) has an inclination angle of 5 [degrees].
The optical axis intersects with the optical axis at approximately the middle position of the second lens (24c), and after passing through the second lens (24c), it is reflected and deflected by the first mirror (27a) and the second mirror (27b), respectively. The light is then imaged and irradiated onto the photoreceptor (26).

And in this way, both laser beams (20a), (
When the scanning of 21a) is completed and the electrostatic latent images are formed, each electrostatic latent image is transferred to the first developer (28) and the second developer (3o
), and then the laser beam (20a
) is re-charged by the second charger (32) and scanned again by the second laser beam (21a), while the developing part by the second laser beam (21a) is transferred by one transfer unit (not shown). After the transfer is performed in the section, the next printing is made possible after passing through a cleaning device and a static eliminator.

With this configuration, the first laser beam (20a) and the second laser beam (21a)
Each oscillating unit (20) faces toward the optical axis (24a) of 4).
.

(21), is reflected by the polygon mirror (23), and intersects the optical axis within the imaging lens system (24).
One laser beam (2) in the imaging lens system (24)
0a) and (21a) can be reduced compared to the conventional method, the first lens (24b) and the second lens (21a)
In 4c), the passing width of both laser beams, that is, the effective scanning area of the lens, can be reduced, without using a large-diameter lens that is difficult to manufacture and expensive, and even with the same diameter lens as the conventional one. Can reduce distortion of one image,
It is possible to improve image quality without incurring the cost increase caused by using a lens with a large diameter, and it is also possible to apply it to fine images.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the angle between the optical axis of the imaging lens system and the plurality of laser beams may be arbitrary, and the intersection position of the plurality of laser beams may be changed. is also arbitrary, and may be located not within the imaging lens system, but may be in the vicinity thereof, or within the imaging lens system, as shown in the modification shown in FIG. 2, first. That is, in this device, the first laser beam (33a) and the second laser beam (33b) are transmitted only through the first lens (34a) as the first stage lens of the imaging lens system (34). , and a dedicated third lens (35a) and fourth lens (35b) are used as the second-stage lenses, so the effective scanning area of the first lens (34a) is reduced. , both laser beams (33a), (33b
) intersect within the first lens (34a).

Moreover, the number of laser beams is also arbitrary, and as in the second modification shown in FIG.
.

(37), (38), (39), the first to fourth laser beams (36a), (
37a), (38a), and (39a) on the photoreceptor (
A device that irradiates different positions (not shown) may also be used. In this modification, four laser beams (
36a)...The first lens (42a) according to (39a)
) and the second lens (42b), the first and second laser beams (36a
), (37a), and the third and fourth laser beams (38a) and (39a) are each reflected by a polygon mirror (43) and then intersect near the front of the imaging lens system (42).

[Effects of the Invention] As explained above, according to the present invention, the plurality of laser beams can be made symmetrical and parallel to the optical axis of the imaging lens system, or tilted outward, as in the past. , is tilted toward the optical axis of the imaging lens system, and intersects near or within the imaging lens system, so the effective scanning area of each lens in the imaging lens system is reduced compared to conventional methods. It is possible to reduce image distortion and improve images even though the lens has the same diameter as before, without using a lens with a large diameter, which increases costs because it is difficult to manufacture, and can be applied to fine images. This also makes it possible to expand the functionality of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one embodiment of the present invention, and FIG. 2 is a schematic explanatory diagram showing a first modification of the present invention. FIG. 3 is a schematic explanatory diagram showing a second modified example of the present invention, and FIG.
The figure is a schematic explanatory diagram showing a conventional device. 20...First oscillation part 20a...First laser beam 21...Second oscillation part 21a
...Second laser beam 23...Polygon mirror
24...Imaging lens system 24a...Optical axis
24b...first lens 24c...second lens

Claims (3)

[Claims] (1) Laser beams emitted from a plurality of oscillation units are scanned by the same polygon mirror, and a plurality of static images are displayed on the image carrier using a shared imaging lens system provided between the polygon mirror and the image carrier. In those that form an electrolatent image,
An optical device for an image forming apparatus, wherein at least one laser beam among the laser beams emitted from the plurality of oscillation units is tilted in a direction toward the optical axis of the imaging lens system. (2) An optical device in an image forming apparatus according to claim 1, wherein the laser beams oscillated from a plurality of oscillating units are crossed within an imaging lens system. (3) An optical device in an image forming apparatus according to claim 1, wherein the laser beams oscillated from a plurality of oscillating units intersect in the vicinity of an imaging lens system.