JPH11237572A - Optical writer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical writer capable of reducing the cost and size. SOLUTION: In the optical writer provided with a light source for projecting an optical beam modulated in accordance with a recording signal, a scanning deflection means for deflecting the optical beam and scanning the surface of a photosensitive body with the deflected beam, an optical element formed between a light source and the photosensitive body, and an optical beam writing synchronizing signal generating means and constitued so as to form an exposed image by optically writing the optical beam on the surface of the photosensitive body in accordance with a synchronizing signal generated from the synchronizing signal generating means, a folded mirror 3 for detecting synchronization and a long lens 2 for correcting plane tilt are held and positioned by one plate spring (holding member) 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing device which scans a photoreceptor with a modulated light beam and forms an exposure image on the photoreceptor, and more particularly to a support structure of a synchronization detecting mirror. Related to an optical writing device.

[0002]

2. Description of the Related Art In recent years, electrophotographic image forming apparatuses which perform laser writing, such as digital copiers and laser printers, have become widespread. FIG. 8 shows a schematic configuration of an optical writing apparatus having a general optical writing system of this type of image forming apparatus. Referring to FIG. 8, a conventional optical writing apparatus includes an fθ lens 1 and a long lens 2 between a polygon mirror 5 and a photosensitive member 12 and emits light from an LD (laser diode) unit 8 as a light source. The laser beam is irradiated to a polygon mirror 5 composed of a polygon mirror rotating at a high speed as a light deflecting means via a cylindrical lens 9, and the laser beam deflected at a constant angular velocity by the polygon mirror 5 is converted into a constant velocity deflection by the fθ lens 1. Then, the surface of the photoconductor 12 is scanned by correcting the surface tilt by the long lens 2. The cylindrical lens 9 corrects the surface tilt of the polygon mirror 5, and forms a part of a mirror surface tilt optical system together with the long lens 2. The long lens 2 is formed of a toroidal lens, also called a BTL lens.

At a position outside the scanning area on the photosensitive member 12 and at which a scanning beam from the polygon mirror 5 can enter, a folding mirror for synchronization detection (hereinafter referred to as a "mirror for synchronization detection").
Called. 3) is provided, the light beam reflected by the synchronization detecting mirror 3 is detected by a light receiving element 4 as a synchronization detecting means, and a synchronization detection signal is output based on the incident timing of the detected light beam. The LD unit 8 is driven based on the signal to synchronize the image writing of each scanning line.

By the way, in terms of cost, an optical writing unit having such an optical system occupies a large specific gravity in a lens system which guarantees constant light beam speed and imaging performance. The most effective way to reduce the cost of the lens system is to reduce the size of each lens. Naturally, a lens system having a size that can achieve the effective image width on the photoreceptor 12 is the smallest, but what matters at that time is the layout of the synchronous optical system.

Now, considering the optical writing system shown in FIG. 8, the synchronizing beam is composed of the fθ lens 1 and the long lens 2.
Is passed back through the mirror 3 for synchronization detection, the fθ lens 1 and the long lens 2 are large because the light beam needs to scan out of the scanning area of the photoconductor 12. In this synchronization detection, when the beam for synchronization detection reaches the light receiving element 4, it passes through the lens system and
Since it is desirable that the beam has the same beam shape as that of the beam that reaches the photodetector 2, the distance L1 between the synchronization detecting mirror 3 and the light receiving element 4 does not turn back by the synchronization detecting mirror 3 so that the beam reaches the photosensitive member 12. It is set to be equal to the path L2 when performing the operation. In the case of folding back at an acute angle as shown in FIG. 8, the distance L3 between the light receiving element 4 and the polygon mirror 5 is made as small as possible, and when the synchronization detecting mirror 3 is moved to the left in FIG. And cost can be further reduced.

[0006]

However, in order to reduce the cost, for example, the long lens 2 is downsized as shown in FIG. 9 and the synchronization detecting mirror 3 is provided between the fθ lens 1 and the long lens 2. If the lens is arranged and folded at an acute angle, the long lens 2 can be formed in a small size.
When 1 and L2 are made equal, the unit width W becomes large as shown by the broken line. Thus, the unit width W
When the size of the writing unit increases, the size of the housing and cover of the writing unit increases, and the cost cannot be denied.

[0007] Recently, A3 Novi (330 mm x 470)
mm) paper is required in the market. However, it is difficult for a conventional lens system compatible with A3 (297 mm × 420 mm) to pass an optical path for synchronization detection through the lens system as shown in FIG. For this reason, the fθ lens 1 as shown in FIG.
Although a synchronous mirror can be arranged between the lens and the long lens 2, there is a problem of cost increase as described above, and at the same time, in the configuration of FIG. 9 compared with the configuration of FIG. There is also a problem that it becomes difficult to separate the beam from the light beam for synchronization detection in terms of space.

Therefore, as shown in a detailed view of a portion A in FIG. 9 of FIG. 9, the synchronization detecting mirror 3 is cantilevered so as to protrude to a position close to the area of the image writing beam. Flare light 6a reflected by the end face (edge portion) 3a of the light-emitting device, and flare light 6b generated by the reflection component of the image writing beam once entering the long mirror 2 entering the back surface 3b of the synchronization detecting mirror 3 and being reflected. Is incident on the photoreceptor 12, and an abnormality such as a black streak in the sub-scanning direction appears.

Providing a dedicated leaf spring 7 for supporting the synchronization detecting mirror 3 is disadvantageous in terms of cost and increase in the number of assembly steps.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide a low-cost and small-sized optical writing device capable of copying a larger size.

[0011]

In order to achieve the above object, a first means comprises a light source for emitting a light beam modulated according to a recording signal, and a light beam deflected to scan a photosensitive member. A scanning deflecting unit, an optical element provided between the light source and the photoconductor, and a light beam writing synchronizing signal generating unit, wherein light is written on the photoconductor based on a synchronizing signal generated from the synchronizing signal generating unit. And an optical writing device for forming an exposure image on the photoreceptor, wherein a folding mirror for synchronization detection for guiding a light beam to the synchronization signal generating means and a lens for correcting surface tilt are provided by one holding member. It is characterized by holding and positioning.

A second means is the first means, wherein the holding member is formed of a leaf spring, and the lens and the folding mirror for synchronization detection are elastically held at one end side of the lens. .

The third means is characterized in that, in the first means, the end face and the back face of the synchronization detecting folding mirror are subjected to non-reflection processing.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a cross section at the center of an optical writing device according to an embodiment of the present invention, and FIG. 2 is a plan view. In the following description, the same parts as those in the above-described conventional example will be denoted by the same reference numerals, and redundant description will be omitted as appropriate.

In this embodiment, an fθ mirror 1a and a first folding mirror 10 are provided in place of the fθ lens 1 in the conventional example shown in FIG. 8, and the beams reflected by the two mirrors 1a and 10 are taken care of by the long lens 2. After performing the correction, the light is reflected by the second folding mirror 11 and is incident on the photoconductor 12. That is, the light beam emitted from the LD unit 8 including the aperture passes through the cylindrical lens 9 and is deflected by the polygon mirror 5, and fθ
The light is reflected twice by the mirror 1a and the first folding mirror 10. Thereafter, the light passes through the long lens 2 and is reflected by the second folding mirror 11, and then enters the photoconductor. The incident beam fully uses the effective area of the long mirror 2, is reflected by the first folding mirror 10, and is deflected by widening the angle.
It is configured to be able to cope with 3 mm and A3 Nobi.

FIG. 3 is a plan view showing a specific configuration of an optical unit having the optical writing system shown in FIGS. 1 and 2, and FIG.
FIG. 5 is an enlarged view showing the configuration near the synchronization detecting mirror. As shown in these figures, a polygon mirror 5 is arranged below the optical box main body 20 of the optical unit in FIG. 3, and the laser beam emitted from the LD unit 8 arranged at the right end of the center is shown in FIG.
As shown in FIG. 2, the light is reflected by the fθ mirror 1a and the first folded lens 10, transmitted through the long lens 2, and guided from the second folded lens 11 to the photoconductor (not shown). 3 and 4, each mirror 1a, 1
Although the positional relationship between 0 and 11 and the lens 2 in the height direction is not clear, it goes without saying that these components are arranged in a positional relationship as shown in the schematic diagram of FIG.

The synchronization detecting mirror 3 is the same as that of the long lens 2 shown in FIG.
4 and FIG. 4, the light receiving element 4 is located at the lowermost position in the optical box 20 (FIG. 4).
In the perspective view of FIG.
The distance L1 between the light receiving element 4 and the light receiving element 4 is kept small. Thus, the unit width W can be reduced, and the entire unit can be formed small and compact. Further, the separation between the image writing beam and the synchronization detection beam does not need to be performed at a close position as shown in FIG.

Further, in this embodiment, as shown in FIG. 6, an end face (edge face) 3a and a back face 3a of the synchronization detecting mirror 3 are provided.
b is subjected to non-reflection processing so that flare light does not enter the photoconductor 12. In particular, performing non-reflection processing on the end face 3a eliminates the need to control so that the light beam does not turn on at the timing of passing through the end face 3a. Therefore, when the interval between the synchronization detection and the start of image writing is short, This means that the design margin increases.

In this embodiment, one end (the left end in the figure) of the long lens 2 and the synchronization detecting mirror 3 are simultaneously held by a leaf spring 13 having a shape as shown in FIG. The spring 13 functions as a holding member. That is, the leaf spring 13 elastically holds the vertical side (upper side-see FIG. 5) of the long lens 2 with the elastic piece 13a, and projects the horizontal side from the side surface of the long lens 2 (flange portion) 2a. In FIG. 5, the elastic member is elastically held from the rear side. 5 and 6 of the synchronization detecting mirror 3, the abutting portion 2 protruding from the base 20 a side of the optical box 20 by the elastic piece 13 c from the back side (the back surface 3 b).
0b. Then, while being held by this one leaf spring 13, the screw 14
By this, it is fixed to the base 20a of the optical box, and both are positioned. With this configuration, the relative position of the long lens 2 and the synchronization detecting mirror 3 is defined by the leaf spring 13, and the positioning of the two in the optical system is performed by the screw 14, so that good accuracy can be maintained. At the same time, the number of assembly steps can be reduced, and the cost can be further reduced.

[0021]

As described above, according to the first aspect of the present invention, the folding mirror for detecting synchronization and the long lens for correcting surface tilt are held and positioned by one holding member. Since the number of components can be minimized and the size can be reduced, and the relative position adjustment between the two is not required, the assembly can be simplified, and a low-cost optical writing device can be provided.

According to the second aspect of the present invention, the holding member is formed of a leaf spring, and the holding member holds the long lens and the folding mirror for synchronization detection at one end of the long lens. In particular, it is not necessary to set a space in which the folding mirror for synchronizing detection is to be set up, so that downsizing can be promoted, assembly can be simplified, and assembly costs can be reduced.

According to the third aspect of the present invention, since the end face and the back face of the return mirror for synchronization detection are subjected to anti-reflection processing, the occurrence of image contamination caused by the return mirror for synchronization detection is suppressed even if the size is reduced. can do.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a path of a light beam when an optical writing system of an optical writing apparatus according to an embodiment of the present invention is sectioned at a central portion.

FIG. 2 is a schematic plan view of an optical writing device including the optical writing system of FIG.

FIG. 3 is a plan view of the optical writing unit according to the embodiment of the present invention.

FIG. 4 is a perspective view of the optical writing unit of FIG. 3;

FIG. 5 is an enlarged view showing details of a portion B in FIG. 4;

FIG. 6 is a perspective view of a synchronization detecting mirror.

FIG. 7 is a perspective view of a holding member that holds both the long lens and the synchronization detecting mirror at the same time.

FIG. 8 is a plan view showing a schematic configuration of an optical writing system of an optical writing device according to a conventional example.

FIG. 9 is a plan view showing a schematic configuration of an optical writing system of an optical writing device according to another conventional example.

FIG. 10 is an enlarged view showing details of a portion A in FIG. 9;

[Explanation of symbols]

 Reference Signs List 1 fθ lens 1a fθ mirror 2 long lens 3 synchronization detecting mirror 4 light receiving element 5 polygon mirror 10 first folding mirror 11 second folding mirror 12 photoconductor 13 leaf spring (holding member)

Claims (3)

[Claims] A light source for emitting a light beam modulated in accordance with a recording signal; a scanning deflecting unit for deflecting the light beam to scan on a photosensitive member; and an optical element provided between the light source and the photosensitive member. And a light beam writing synchronization signal generating means, wherein an optical writing device performs optical writing on the photoconductor based on a synchronization signal generated from the synchronization signal generating means, and forms an exposed image on the photoconductor. An optical writing apparatus characterized in that a folding mirror for detecting a synchronization for guiding a light beam to the synchronization signal generating means and a lens for correcting surface tilt are held and positioned by one holding member. 2. The optical writing apparatus according to claim 1, wherein the holding member is made of a leaf spring, and the lens and the folding mirror for synchronization detection are elastically held at one end of the lens. 3. The reflection detecting mirror according to claim 1, wherein an end face and a back face of the folding mirror for synchronization detection are subjected to non-reflection processing.
An optical writing device according to claim 1.