JPH01216311A - Scanning optical device - Google Patents

Abstract

PURPOSE:To miniaturize a housing in which the scanning optical device is contained by outputting a light beam for showing the information from a light source, based on an output of a photodetecting means provided between a deflector and an ftheta lens. CONSTITUTION:A photodetecting means which is constituted by containing a reflecting mirror 73, a condensing lens 74 and a photodetector 75 is provided between a deflector 55 and an ftheta lens 56. In such a way, photodetecting means 73-75 for photodetecting a light beam in the beginning of a scanning start from the deflector 55 are provided, and based on outputs of these photodetecting means 73-75, a light beam for showing the information is outputted from a light source 53. Accordingly, it becomes unnecessary to contain a space between the ftheta lens 56 and the reflecting mirror 57 in a housing for containing a scanning optical device 51. In such a way, the housing 52 can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a scanning optical device suitably implemented in printing devices such as laser printers and facsimiles, and reading devices such as facsimiles, image scanners, and barcode leagues.

BACKGROUND OF THE INVENTION FIG. 3 is a plan view showing the basic structure of a scanning optical device 1 of a typical prior art laser printer. The light source 2 realized by a semiconductor laser device or the like is given a signal corresponding to information to be written on the photoreceptor 5 as a scanned medium from a processing circuit 8 that processes information from a host computer. generates a light beam in response to a given signal. The light beam is reflected and deflected by the deflection reflecting surface 3a of the deflector 3, and is formed into a point image on the photoreceptor 5 via the fθ lens 4.

The deflector 3 is a regular hexagonal prism whose axis-perpendicular cross section is, for example, a regular hexagon and is uniform in the direction of the axis 3b, and each side surface thereof constitutes a deflection reflecting surface 3a. Such a deflector 3 is rotationally driven around an axis 3b at a constant angular velocity by a configuration not shown. As a result, the angle between the normal line of the deflection-reflection surface 3a and the light beam from the light source 2, that is, the incident angle of the light beam, changes over time, and the reflection angle also changes accordingly. The incident position of the light beam reflected on the fθ lens 4 changes over time. As a result, the spot formed by the light beam as a dotted line image on the surface of the photoreceptor 5 moves in the direction of arrow 13. In this way, main scanning is performed on the photoreceptor 5,
Sub-scanning is performed by driving the photoreceptor 5 to rotate around its axis at a constant speed.

The fθ lens 4 converts the light beam reflected by the deflection reflection surface 3a of the deflector 3 into a dotted line image on the surface of the photoreceptor 5, and further ensures that the light beam scans the surface of the photoreceptor 5 in the direction of arrow 13 at a constant speed. formed and arranged as done in

Optical path 1 corresponding to writing start position W7 on photoreceptor 5
1 is shown in FIG. On the optical path 12 upstream in the direction of arrow 13 from the optical path 11, the fθ lens 4
A light-receiving element 6 is arranged between the photoreceptor 5 and the photoreceptor 5 .

The light-receiving element 6 receives the light beam passing through the optical path 12, converts it into a charge, and outputs a signal to the processing circuit 8.

In the processing circuit 8, in synchronization with the signal output by the light receiving element 6 upon receiving the light beam, the locus of the spot formed by the light beam on the surface of the photoreceptor 5 is determined as a signal corresponding to the f'F-ru-scanning line. Output. In accordance with this signal, the light source 2 outputs a light beam representing a signal corresponding to the information to be written on the -scanning line.

By sequentially performing such operations, an electrostatic latent image corresponding to information to be written is formed on the surface of the photoreceptor 5. This electrostatic latent image is visualized into, for example, a toner image by a developing device, and this toner image is transferred and fixed onto a recording paper or the like to perform printing.

FIG. 4 is a longitudinal sectional view showing the above-described scanning optical device 1 housed in the housing 21. As shown in FIG. The housing 21 consists of a lid body 21a and a housing body 21b, and a deflector 3, a motor 1o for rotationally driving the deflector 3, an fθ lens 4, a light receiving element 6, etc. are attached to the housing body 21b. The lid body 21a is the housing body 21b
will be installed on the Toner particles and the like are floating around the photoconductor 5, and in order to prevent such toner particles from adhering to the fθ lens 4, the deflection reflection surface 3a of the deflector 3, etc., the scanning optical device 1 Generally, it is housed in a sealed space within the housing 21. Further, in order to provide flexibility in the design of the apparatus, a reflecting mirror 22 extending along the length of the photoreceptor 5 is generally disposed in the optical path between the fθ lens 4 and the photoreceptor 5 .

FIG. 5 is a plan view showing the housing 21 with the lid 21a removed. For example, a cylindrical lens 31 is interposed in the optical path between the light source 2 and the deflection reflection surface 3a of the deflector 3. The cylindrical lens 31
The light beam generated from the light source 2 is formed into a linear image near the deflection reflection surface 3a of the deflector 3. The linearly imaged light beam is reflected on the deflection reflection surface 3 a and illuminates the surface of the photoreceptor 5 via the fθ lens 4 .

It is difficult to obtain desired characteristics when the fθ lens 4 is composed of a single lens, and is generally composed of a plurality of lenses. That is, it is composed of, for example, a first fθ lens portion 41 and a second fθ lens portion 42 .

An optical path 12 upstream in the direction of arrow 13 from the optical path 11 of the light beam corresponding to the position indicated by reference numeral 32 on the surface of the reflecting mirror 22 corresponding to the writing start position 7 of the photoreceptor 5
A reflecting mirror 33 is provided above. The light beam reflected by the reflecting mirror 33 forms an image on the light receiving surface 6a of the light receiving element 6 via the optical path 13. At this time, the optical path 1
3 is selected to be equal to the length of the optical path between the reflecting mirror 33 and the surface of the photoreceptor 5, which is assumed to be an extension of the optical path 12, so that on the light receiving surface 6a of the light receiving element 6, The light beam will become a dotted line image.

What is shown in FIG. 3 is the basic configuration of the scanning optical device 1, and generally, as shown in FIG. 5, a reflecting mirror 33 is used to guide the light beam to the light receiving element 6.

Problems to be Solved by the Invention In the prior art as described above, a light receiving means including a reflecting mirror 33 and a light receiving element 6 is interposed between the fθ lens 4 and the reflecting mirror 22. Optical device 1 is housed within housing 21 . However, although the above-mentioned light receiving means is only installed in the space between the reflecting mirror 22 and the fθ lens 4, the space between the fθ lens 4 and the reflecting mirror 22 is limited to the housing 21. It may occupy more than half of the space inside.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scanning optical device that is advantageous in reducing the size of a housing in which the scanning optical device is housed.

Means for Solving the Problems The present invention provides a scanning optical device that scans a scanned medium by focusing a light beam generated from a light source on the scanned medium through a deflector and an fθ lens. A light receiving means for receiving a light beam from the deflector at the initial stage of scanning is provided between the deflector and the fθ lens, and a light beam representing information is output from the light source based on the output of the light receiving means. This is a scanning optical device.

Function In the present invention, a light beam at the initial stage of scanning is received,
A light receiving means for regulating the timing at which a light beam representing information is output from the light source is provided between the deflector and the fθ lens. As a result, the space between the fθ lens and the medium to be scanned does not need to be a space within the housing that houses the scanning optical device, and the housing can be made smaller.

Embodiment FIG. 1 is a plan view showing the basic configuration of a laser printer using a scanning optical device 51 according to an embodiment of the present invention.

The scanning optical device 51 is housed in a housing 52, and the first
The figure shows a plan view with the lid removed. The scanning optical device 51 includes a light source 53 that includes a semiconductor laser device, etc., a cylindrical lens 54 that linearly focuses a light beam generated from the light source 53, and a light beam that is focused by the cylindrical lens 54. Deflector 55 having a deflection reflecting surface 55a near the line image of the beam
, an fθ lens 56, which will be described later, and the like. The light beam reflected on the deflection reflecting surface 55a is f
It enters the reflecting mirror 57 via the θ lens 56, and the reflecting mirror 5
The light is reflected at 7 and illuminates the surface of a right cylindrical photoreceptor 58, which is a scanned medium.

The deflector 55 is, for example, a regular hexagonal prism whose axis-perpendicular cross section is a regular hexagon and is uniform in the direction of the axis 55b, and its side surfaces are used as reflecting mirrors to form a deflection reflection surface 55a. Such a deflector 55 is rotationally driven by a motor 59 around its axis 55b in the direction of an arrow 71 at a constant speed. As a result, the optical path of the light beam generated from the light source 53 and passing through the cylindrical lens 54 and the steel beam incidence surface 55
The angle formed by the normal line of a, that is, the angle of incidence of the light beam on the deflection reflecting surface 55a changes over time, and the reflection angle changes accordingly, so the light beam is condensed on the photoreceptor 58 and formed. The spot that is displayed moves in the direction of arrow 60.

The fθ lens 56 focuses the light beam reflected on the deflection reflecting surface 55a so as to form a spot as a dotted line image on the surface of the photoreceptor 58, and the scanning speed of the spot in the direction of the arrow 60 is constant. It is designed to be kept. In order to obtain such characteristics of the fθ lens 56, the fθ lens 56 is often composed of a plurality of lenses, and in this embodiment, the fθ lens 56 includes a first fθ lens portion 61 and a second fθ lens portion 62. It is composed of:

By rotating the deflector 55 in the direction of arrow 71, the photoreceptor 58
A main scan is performed on the surface of the photoreceptor 58 by a light beam, and a sub-scan is performed by driving the photoreceptor 58 to rotate around its axis at a constant speed. In this way, the photoreceptor 5
An electrostatic latent image is formed on the surface of 8.

Around the photoreceptor 58, there is a main corona discharger for uniformly charging the surface of the photoreceptor 58, and a developing device for visualizing the electrostatic latent image formed on the surface of the photoreceptor 58 into a toner image. , a transfer corona discharger (none of which is shown) for transferring the toner image onto the recording paper, and the like, and by the action of these, information corresponding to the light beam generated by the light source 53 is transferred onto the recording paper. printed.

The first fθ lens portion 61 of the fθ lens 56 is located on the optical path L2 corresponding to the upstream side in the direction of the arrow 60 from the optical path L1 corresponding to the writing start position 72 on the surface of the photoreceptor 58.
A reflecting mirror 7 is provided between the deflecting reflection surface 55a of the deflector 55 and
3 are arranged.

The light beam reflected by the reflecting mirror 73 forms a point image via a condenser lens 74 on a light receiving surface 75a of a light receiving element 75 including a photodiode or the like. Due to the function of the condensing lens 74, the light receiving element 75 can output a signal that changes sharply when its light receiving surface 75a is irradiated with the light beam.

The condensing lens 74 and the light receiving element 75 are arranged between the first fθ lens portion 61 of the fθ lens 56 and the deflector 55, so that the optical path L3 between the reflecting mirror 73 and the condensing lens 74 is , the first fθ lens portion 61 and the deflector 5
It exists between 5 and 5.

The reflecting mirror 73, the condensing lens 74, and the light receiving element 75
The light receiving means includes the following.

The light source 53 generates a light beam in response to a signal given from a processing circuit 81 that processes information from the host computer. The signal given to the light source 53 is! 5 light body 58
As a result, an electrostatic latent image corresponding to the desired information is formed on the photoreceptor 58. The processing circuit 81 provides the light source 53 with a signal representing information corresponding to one scanning line, which is a locus formed by a spot formed by a light beam on the surface of the photoreceptor 58, as a unit; however, the output of such a signal is , are performed in synchronization with a signal provided from the light receiving element 75 via the line 76.

FIG. 2 is a longitudinal sectional view of a laser printer using the stain scanning optical device 51 described above. The housing 52 has a lid 52a
and a housing body 52b, the housing body 5
With the deflector 55, fθ lens 56, motor 59, etc. attached to the housing body 52b, the lid body 52a is attached to the housing body 52.
b.

A motor 59 is attached to the bottom surface of the housing 52, and the deflector 55 is attached to a drive shaft 59a of the motor 59. The fθ lens 56 is also attached to the bottom surface of the housing 52, and a light receiving means including the aforementioned reflecting mirror 73, condensing lens 74, and light receiving element 75 is attached at a position indicated by reference numeral 82. The housing 52 is provided with an opening 83 , and the light beam passing through the fθ lens 56 enters the reflecting mirror 57 through the opening 83 .

The housing 52 includes a zero reflector 5 fixedly disposed on a support plate 86 attached to a base 85 of the laser printer.
7 is a support means 87 disposed in relation to the base body 86;
Supported by

The support means 87 is configured so that the angle and position of the reflecting mirror 57 can be adjusted.

A light-transmitting dustproof member 88 is attached to a portion corresponding to the optical path between the reflecting mirror 57 and the photoreceptor 58 in association with a through hole 86a formed in the support plate 86. The function of the dustproof member 88 allows the light beam reflected by the reflecting mirror 57 to be guided to the surface of the photoreceptor 58, and prevents foreign matter such as toner floating around the photoreceptor 58.
adhering to the surface of the reflector 57 and the housing 5
2 is prevented from entering.

As described above, in this embodiment, the light receiving means including the reflecting mirror 73, the condensing lens 74, and the light receiving element 75 is disposed between the deflector 55 and the fθ lens 56. The space between the fθ lens 56 and the reflecting mirror 57 is
There is no need to accommodate the scanning optical device 51 in the housing 52, and therefore the housing 52 can be made smaller. In addition, in such a configuration, the sum of the distance W1 between the fθ lens 56 and the reflecting mirror 57 and the distance W2 between the reflecting mirror 57 and the surface of the photoreceptor 58 (W1+W2)
The distance Wl is kept constant.

Since W2 can be changed, there is an advantage that laser printers and the like can be designed flexibly.

Furthermore, since the housing 52 can be made smaller,
For example, when the housing 52 is molded by injection molding, the dimensional accuracy can be improved.

Effects of the Invention As described above, according to the present invention, it is possible to downsize the housing that houses the scanning optical device, and for example, it becomes possible to design a laser printer etc. flexibly.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the basic configuration of an embodiment of the present invention, FIG. 2 is a vertical sectional view thereof, FIG. 3 is a plan view showing the basic configuration of the prior art, and FIG. 4 is a prior art. Vertical section of technology, 5th
The figure is a plan view showing the prior art. 51... Scanning optical device, 52... Housing, 53
... Light source, 55... Deflector, 56... fθ lens, 58... Photoreceptor, 73... Reflector, 74... Condensing lens, 75... Light receiving element, 81... ...Processing circuit agent Patent attorney Keibu Saikyo Figure 3

Claims (1)

[Claims] In a scanning optical device that scans a scanned medium by focusing a light beam generated from a light source on the scanned medium via a deflector and an fθ lens, What is claimed is: 1. A scanning optical device comprising: a light receiving means for receiving a light beam at the beginning of scanning, and a light beam representing information is output from the light source based on the output of the light receiving means.