JPH05323221A - Optical device for optical scanning and image forming device therefor - Google Patents

Abstract

PURPOSE:To obtain an optical system for optical scanning appropriate for making the system compact by providing a measuring optical system composed of a reflecting part reflecting a reflected beam and an light receiving element receiving the reflected beam and providing the light receiving element on the opposite side of the surface to be scanned in the image forming optical system. CONSTITUTION:A mirror 108 and a slit 110 together with a photodiode mounted on a semiconductor laser 101 constitute the measuring optical system and are arranged so that a laser beam is incident on a mirror 108 at the position before image formation on the surface to be scanned is started. The mirror 108 is arranged so as to be perpendicular to the incident beam and optically conjugated with the semiconductor laser 101 and the reflected beam by the mirror 108 is arranged so as to be returned to the semiconductor laser 101. The slit 110 is provided so as to limit the moving incident beam on the mirror 108 and is formed with a slit 1mm wide. The detection timing of the image forming position is decided by moving the slit 110 in the main scanning direction and the position is adjusted so as to be matched with the detection timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning optical device,
In particular, the present invention relates to an optical scanning optical device effective for an image forming apparatus that forms an image by an electrophotographic process such as a laser beam printer or a color copying machine.

[0002]

2. Description of the Related Art FIG. 8 is a plan view showing the structure of a conventional example of an optical scanning optical device of this type.

A light flux emitted from a semiconductor laser 501 which is a light source is collimated by a collimator 502, and a diaphragm 503 is used.
After being shaped into a cylindrical lens 504 and made into a slender shape in the main scanning direction, it is irradiated onto a scan surface 507 through a polygon mirror 505 which is a deflecting means and an fθ lens 506 which is an image forming optical system in order. To do.

The polygon mirror 505 rotates about an axis perpendicular to the main scanning direction as shown by a driving means (not shown), and the laser light is reflected in the main scanning direction of the surface 507 to be scanned by the rotating operation. To be done. Semiconductor laser 50
Reference numeral 1 switches its output state in accordance with the rotation operation of the polygon mirror 505, whereby an image is formed on the surface 507 to be scanned in the main scanning direction.

A measuring optical system for detecting a position where an image is formed is provided between the fθ lens 506 and the surface 507 to be scanned. The measuring optical system includes a mirror 508 forming a reflecting portion and a slit 510. And a photodiode 509 which is a light receiving element. Among these members, the mirror 508 is arranged at a position before the start of image formation, and the slit 510 and the photodiode 5 are arranged.
09 is arranged so that the laser beam reflected by the mirror 508 enters the photodiode 509 through the slit 510. Since the detection timing for performing the image forming position is determined by the reflection direction of the mirror 508, the position of the mirror 508 is adjusted in advance so as to match the detection timing.

The laser beam reflected by the rotating polygon mirror forms a spot image by the fθ lens 506, and scans the surface to be scanned 507 such as the photosensitive drum at a constant speed.

[0007]

In the above-described conventional optical scanning optical device, since the measurement optical system for detecting the image forming position is arranged between the fθ lens and the surface to be scanned, the fθ lens There is a problem that it is difficult to make the device compact because the distance between the scanning surface and the surface to be scanned cannot be shortened.

Further, in the above-mentioned conventional example, the light source, or the collimator lens and the cylindrical lens, which are the first image forming system, from the deflecting means, although the outer diameter of the fθ lens which is the second image forming system is small. The optical scanning optical device cannot be downsized because it is provided separately.

The present invention has been made in view of the problems of the prior art as described above, and an object thereof is to realize an optical scanning optical system suitable for compactness.

[0010]

An optical scanning optical device according to the present invention comprises a deflecting means for deflecting a starting light beam of a light source, and an image forming optical system for forming an image of the deflected light by the deflecting means on a surface to be scanned. In an optical scanning optical device including a measuring optical system including a reflecting portion that reflects the deflected light and a light receiving element that receives the light reflected by the reflecting portion, the light receiving element has a side opposite to a surface to be scanned of the imaging optical system. It is provided in.

In this case, the reflecting portion may be provided on the side opposite to the surface to be scanned of the image forming optical system, and a semiconductor laser having a light receiving element for monitoring the output state is used as the light source. The light receiving element for monitoring the output state may also be used as the light receiving element forming the measurement optical system.

The optical scanning optical device of the present invention comprises a light source and a first light beam from the light source, which linearly forms an image at a first image forming position.
Image forming means, a deflecting means having a reflecting surface in the vicinity of the first image forming position for deflecting and scanning the light beam from the light source, and a light beam deflected by the deflecting means on the surface to be scanned. Second image forming means for forming and scanning in a dot shape at the image forming position of the second image forming means, and image formation in the sub scanning direction between the first and second image forming positions by the second image forming means. The magnification is equal to or more than 1 ×, and the first image forming unit is arranged at a position that does not exceed the outer diameter of the second image forming unit in the scanning direction.

In the optical scanning optical device of the present invention, the image forming magnification between the first image forming point and the second image forming position by the second image forming means is 10 times or less in the sub scanning direction. preferable.

In some optical scanning optical devices of the present invention, the light source is arranged at a position that does not exceed the outer diameter of the second image forming means in the scanning direction.

The optical scanning optical device of the present invention has means for detecting passage of scanning light in order to obtain a scanning direction synchronizing signal,
The means may be arranged at a position that does not exceed the outer diameter of the second image forming means in the scanning direction.

An image forming apparatus of the present invention comprises a photoconductor which is a surface to be scanned by a light beam, the optical scanning optical device of the present invention which scans the light beam on the photoconductor to form a latent image, and the photoconductor. And a visualization means for visualizing the latent image formed above.

[0017]

Since the light receiving element for detecting the scanning line writing position is not provided between the image forming optical system and the surface to be scanned, the apparatus is suitable for downsizing.

When a semiconductor laser provided with a light receiving element for monitoring the output state is used as a light source and the light receiving element is also used as a light receiving element which constitutes the measurement optical system, a light receiving element which newly constitutes the measurement optical system is used. It is not necessary to provide an element.

In the optical scanning optical device according to the present invention, the light source or the first image forming system is placed in a region restricted by the outer diameter of the second image forming system with respect to the scanning direction. It is possible to realize compactness, which in turn reduces the size and cost of the entire image forming apparatus.

[0020]

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

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, and FIG. 2 is a plan view thereof.

The illustrated collimator 102, slit 1
03, cylindrical lens 104, polygon mirror 1
05, fθ lens 106 and scanned surface 107 are the conventional collimator 502, slit 503, cylindrical lens 504, polygon mirror 505, and fθ shown in FIG.
The description is omitted because it has the same configuration and arrangement as the lens 506 and the surface 507 to be scanned.

The semiconductor laser 101 in this embodiment is provided with a photodiode for adjusting the output,
A measurement optical system for detecting an image forming position is configured by using the photodiode. The mirror 108 and the slit 110 constitute a measurement optical system together with a photodiode provided in the semiconductor laser 101, and the laser light is mirrored via the slit 110 at a position before the image formation on the surface 107 to be scanned is started. It is arranged so as to be incident on 108. The mirror 108 is provided so as to be perpendicular to the incident light beam and optically conjugate with the semiconductor laser 101, and the light reflected by the mirror 108 is arranged to be returned to the semiconductor laser 101.

The slit 110 is provided to limit the incident light that enters the mirror 508 while moving.
A slit hole having a width of 1 mm is formed. The detection timing for performing the image forming position is determined by moving the slit 110 in the main scanning direction, and the position of the slit 110 is adjusted so as to match the predetermined detection timing.

FIG. 3 is a sectional view showing the structure of the semiconductor laser 101 shown in FIG.

Since the output characteristics of the semiconductor laser generally strongly depend on the ambient temperature, a photodiode for measuring the amount of light is often provided inside.
The semiconductor laser 101 shown in FIG.
The anti-polygon mirror 105 of the laser light emitted by
A photodiode 302 for monitoring the laser light emitted to the side is provided. Usually the photodiode 30
The current supplied to the laser element 301 is controlled according to the monitor output of No. 2 to keep the laser output constant.
Although only the Power Control control is performed, in this embodiment, the image forming position is confirmed in addition to the APC control.

When the laser light emitted toward the surface 107 to be scanned (see FIG. 1) and reflected by the mirror 108 (see FIG. 1) returns to the semiconductor laser 101, the return light is incident on the photodiode 302. For the photodiode 30
The output of 2 temporarily increases significantly. Therefore, by comparing the output of the photodiode 302 with a predetermined value, the reflection by the mirror 108 can be confirmed, and the image forming position can be confirmed. It is not necessary to perform the APC control when the reflection by the mirror 108 is confirmed, but since the APC control does not always have to be performed, there is no particular problem.

In this embodiment, since only the mirror 108 and the slit 110, which can be made extremely small, are provided between the fθ lens and the surface 107 to be scanned,
The image forming apparatus can be made compact. Also,
Since the photodiode for detecting the image forming position is incorporated in the semiconductor laser, the size can be further reduced and the manufacturing cost can be reduced.

FIG. 4 is a plan view showing the configuration of the second embodiment of the present invention.

In this embodiment, a mirror 408 and a slit 410 having the same structure as the mirror 108 and the slit 110 in FIG. 1 are provided between the polygon mirror 105 and the fθ lens 106 in FIG. Since other configurations and operations are similar to those of the embodiment shown in FIG. 1, the same reference numerals as those in FIG.

In the present embodiment, there is nothing provided between the fθ lens 106 and the surface 107 to be scanned, so that further compactness can be achieved.

In each of the embodiments described above, the photodiode incorporated in the semiconductor laser has been described as being used for detecting the image forming position, but the semiconductor laser is not used as the light source for image forming. When using a semiconductor laser that does not have a built-in object or a photodiode, a half mirror having a very high transmittance is tilted between the fθ lens and the light source, and the photodiode is placed at a position where the return light is reflected by the half mirror. It should be provided.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 5 shows a third embodiment of the present invention, in which (a) is a main scanning section of the optical arrangement of the optical scanning device,
FIG. 3B is a schematic view of a main part of a sub-scan section. Figure 5
In (a) and (b), the same members are indicated by the same numbers.

In FIGS. 5A and 5B, the light source 21 made of a semiconductor laser or the like is provided in a range smaller than the outer diameter of the toric lens 27 described later. The aperture stop 24 may be provided anywhere between the light source 21 and the deflection means described later, but in the present embodiment, it is provided behind the collimator lens 22. This collimator lens 2
2. The first imaging system is composed of the cylindrical lens 23 and the aperture stop 24 which have power only in the sub-scanning direction.

A rotary polygon mirror 25, which is a deflecting means.
Rotates at a constant rotation speed in the direction of arrow A. The spherical lens 26 and the anamorphic toric lens 27 having different refractive powers in the main scanning direction and the sub-scanning direction form a second image forming system. The photosensitive drum 28, which is the surface to be scanned, rotates in the direction of arrow B at a constant rotation speed during image formation.

In FIG. 5A, the light beam emitted from the light source 21 becomes a substantially parallel light beam by the collimator lens 22, and the light beam width is regulated by the aperture stop 24.
The light passes through the cylinder lens 23 and enters the reflecting surface of the rotary polygon mirror 25. At this time, since the cylinder lens 22 has no refracting power in the main scanning direction, it does not contribute to the image formation in FIG. The rotary polygon mirror rotates in the direction of arrow A, whereby the reflected light beam is deflected and scanned within the main scanning cross section and is incident on the second image forming system including the spherical lens 27 and the toric lens 28.

The second image forming system has a function of forming an image of an incident light beam on the position of the surface to be scanned which is proportional to the incident angle thereof, whereby the surface of the surface to be scanned is illuminated in accordance with the rotation of the rotary polygon mirror. It can be scanned in spots.

Here, the locus through which the light spot passes on the surface to be scanned is called a scanning line. Further, generally, the central axis of the light flux of each angle of view is called an optical axis, and in particular, the central axis L of the light flux that is incident perpendicularly to the scanning line is called an “axial optical axis”.

In FIG. 5B, the light beam emitted from the light source 21 becomes a substantially parallel light beam by the collimator lens 22, and the light beam width is regulated by the aperture stop 24.
It is incident on the cylinder lens 23. The cylinder lens 22 has a refractive power in the sub-scanning direction, and illuminates the reflecting surface with a light beam that converges at the first image forming point P near the reflecting surface of the rotary polygon mirror 25. Spherical lens 26, toric lens 27
In the sub-scanning cross section, the second image forming system having the function of making the rotary polygon mirror reflecting surface and the surface to be scanned form an image forming relationship, whereby the rotary polygon mirror reflecting surface is rotated. Even if the scanning line is tilted with respect to the axis, the position of the scanning line in the sub-scanning direction does not change.

The optical scanning optical device is generally the same as that shown in FIG.
The arrangement including the light source 1 to the second image forming system in (a) and (b) is configured as one unit. By reducing the size of this device, the optical scanning optical device can be
The size of the image forming apparatus included as one unit can be made compact, and the degree of freedom in arranging other necessary units is increased, which leads to downsizing of the apparatus, simplification of assembly, and cost reduction.

Among the sizes of the optical scanning optical device, the factor that limits the length in the direction from the optical deflector to the surface to be scanned is the position of the second image forming system, and the closer the optical deflector is, the more the device. Can be small. However, if the distance is too close, the image forming magnification between the reflecting surface and the surface to be scanned shown in FIG. 6 becomes large, and the image forming relationship by the second image forming system becomes sensitive to the position variation of the reflecting surface. The deterioration of the function and the enlargement of the light spot due to the curvature on the image plane in the sub-scanning direction occur.

Considering these points, it is desirable that the vertical imaging magnification between the reflecting surface and the surface to be scanned by the second imaging system is from 1 × to 10 ×. When the image forming magnification is 1 ×, the second image forming system is located substantially in the center between the reflecting surface and the surface to be scanned.

Providing the second image forming system close to the reflecting surface is also effective for reducing the width (outer diameter) of the constituent lens in the main scanning direction.

In FIG. 5A, the one having the largest size in the main scanning direction is the toric lens 7 constituting the second image forming system, and in the present embodiment, the first image forming system and the light source 1 are made toric. The size of the optical scanning optical device can be minimized by installing the lens 7 in a region sandwiched by straight lines m and m ′ drawn from both ends of the outer diameter of the lens 7 in parallel with the axial optical axis L. Has become.

FIG. 6 is a schematic diagram of a main scanning section of an optical arrangement of an optical scanning optical device according to a fourth embodiment of the present invention.

In the figure, the light source 21 made of a semiconductor laser or the like is provided in a range smaller than the outer diameter of a toric lens 36 described later. In this embodiment, the collimator lens 33 having an anamorphic image forming performance and the aperture stop 34 form a first image forming system.
The rotating polygon mirror 35, which is a deflecting means, rotates in the direction of arrow A at a constant rotation speed.

The anamorphic toric lens 36 having different refracting powers in the main scanning direction and the sub-scanning direction constitutes a second image forming system with this one lens. The photosensitive drum 28, which is the surface to be scanned, rotates in the direction of arrow B at a constant rotation speed during image formation. Furthermore, in this embodiment,
A light beam detection (hereinafter, BD: BEAM DETECT) folding mirror 37, a BD lens 38, and a BD light detection element 39 are provided.

In FIG. 6, the light emitting point of the light source 21 is within the range m, m ′ regulated by the outer diameter of the second image forming system, and the light flux emitted from the light source 21 is passed through the collimator lens 33 to the main and sub sides. The light beams become substantially parallel light beams that converge at different positions, the light beam width is regulated by the aperture stop 34, and then the light beams enter the reflecting surface of the rotary polygon mirror 35.

The rotary polygon mirror rotates in the direction of arrow A,
As a result, the reflected light beam is deflected and scanned within the main scanning section, and is incident on the second image forming system constituted by the toric lens 36.

The single toric lens 36 has a function of forming an image of an incident light beam on the surface to be scanned, which is proportional to the incident angle, whereby the surface to be scanned is rotated in accordance with the rotation of the rotary polygon mirror. It can be scanned with a light spot.

The image forming point of the collimator lens 33 in the sub-scanning direction is located at a point P near the reflecting surface of the rotary polygon mirror 35, and the reflecting surface is illuminated with a light beam that converges there. As in the third embodiment, the toric lens 37 has a function of forming an image-forming relationship between the rotary polygon mirror reflecting surface and the surface to be scanned in the sub-scan section, which causes the rotary polygon mirror reflecting surface to rotate. Even if the scanning line is tilted with respect to the axis, the position of the scanning line in the sub-scanning direction does not change.

In the fourth embodiment, since the first imaging system is a single anamorphic lens, the light source can be arranged closer to the reflecting surface of the light deflecting means.

Further, in this embodiment, BD detecting means for obtaining a synchronizing signal in the scanning direction is also installed in the area regulated by the outer diameter of the second image forming system. The folding mirror 37 folds the light flux that forms an image outside the scanning start end of the scanning line on the photoconductor 28 and guides it to the BD lens 38.
The light is collected by 8 and its passage is detected by the light detecting element 39, and the electric signal generated by the light detecting element at this time is used as a synchronizing signal.

FIG. 7 is a diagram showing a fifth embodiment in which the present invention is implemented by providing a reflecting surface in the optical path of the first image forming system.

In the present embodiment, the folding mirror 47, which is a reflecting surface, is provided, and it is possible to reduce the size of the device without shortening the optical path length between the collimator lens 2 and the rotary polygon mirror 5.

[0057]

Since the present invention is constructed as described above, it has the following effects.

According to the first aspect of the invention, there is an effect that the optical scanning optical device suitable for compactness can be obtained.

According to the second aspect, there is an effect that the above effect can be further improved.

According to the third aspect of the present invention, the above effect can be further improved and the manufacturing cost can be reduced by utilizing the light receiving element provided in advance in the light source as the light receiving element constituting the measurement optical system. There is an effect that can be lowered.

According to a fourth aspect of the present invention, the image forming magnification of the second image forming means in the optical scanning optical device in the optical axis direction in the sub-scanning direction is equal to or more than 1 ×, and the light source section and the light detecting section are arranged to be the same. Two
The optical scanning optical device can be miniaturized by providing it in a range smaller than the outer diameter of the image forming system. Further, as a result, in the image forming apparatus equipped with the optical scanning optical device,
The degree of freedom in arranging the parts is increased, the assembling property is improved, the device is downsized, and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is a plan view of the embodiment shown in FIG.

FIG. 3 is a sectional view showing a configuration of a semiconductor laser 101 in FIG.

FIG. 4 is a plan view showing a configuration of a second exemplary embodiment of the present invention.

5A is a schematic configuration diagram in a main scanning cross section of an optical scanning optical device according to a third embodiment of the present invention, and FIG. 5B is a schematic configuration diagram in a sub scanning cross section in the third embodiment. is there.

FIG. 6 is a diagram showing a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a fifth embodiment of the present invention.

FIG. 8 is a plan view showing a configuration of a conventional example.

[Explanation of symbols]

 101 Semiconductor Laser 102 Collimator 103, 110, 410 Slit 104 Cylindrical Lens 105 Polygon Mirror 106 fθ Lens 107 Scanned Surface 108, 408 Mirror 301 Laser Element 302 Photodiode

Claims (8)

[Claims] 1. A deflecting means for deflecting a light flux emitted from a light source, an imaging optical system for forming an image of the deflected light by the deflecting means on a surface to be scanned, a reflecting portion for reflecting the deflected light, and a reflecting portion. An optical scanning optical device including a measurement optical system including a light receiving element that receives reflected light, wherein the light receiving element is provided on the side opposite to the surface to be scanned of the imaging optical system. Optical device. 2. The optical scanning optical device according to claim 1, wherein a reflecting portion is provided on a side of the imaging optical system opposite to the surface to be scanned. 3. The optical scanning optical device according to claim 1, wherein a semiconductor laser having a light receiving element for monitoring an output state is used as a light source, and the light receiving element for monitoring the output state. Is used as a light receiving element constituting a measurement optical system. 4. A light source, a first image forming means for linearly forming a light beam from the light source on a first image forming position, and a reflecting surface in the vicinity of the first image forming position. Deflection means for deflecting and scanning the light flux from the light source, and a second light flux on the surface to be scanned for deflecting the light flux deflected by the deflection means.
Second image forming means for forming and scanning point-like images at the image forming position in the sub scanning direction between the first and second image forming positions by the second image forming means. An optical scanning optical device, wherein the magnification is equal to or more than 1 ×, and the first image forming unit is arranged at a position not exceeding the outer diameter of the second image forming unit in the scanning direction. 5. The sub-scanning direction image forming magnification between the first image forming point and the second image forming position by the second image forming means is 10 times or less. Optical scanning optical device. 6. The optical scanning optical device according to claim 4, wherein the light source is arranged at a position that does not exceed the outer diameter of the second image forming means in the scanning direction. 7. A means for detecting passage of scanning light in order to obtain a scanning direction synchronization signal, said means being arranged at a position not exceeding an outer diameter of the second image forming means in the scanning direction. The optical scanning optical device according to claim 4. 8. A photosensitive member which is a surface to be scanned by a light beam, and a latent image is formed by scanning the light beam on the photosensitive member.
An image forming apparatus comprising: the optical scanning optical device described in 5, 6, or 7; and a visualization unit that visualizes a latent image formed on the photoconductor.