JP2001350114A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner which can be lowered in price and can reduce a noise and the power consumption. SOLUTION: This optical scanner has a plurality of light sources 1 and 1' which project luminous flux, optical systems 2 and 2' which image the luminous flux from those light sources 1 and 1' at specific positions, a deflector 3 which receives and deflects the luminous flux to make scans, a luminous flux splitting means 4 which splits the luminous flux from the deflector 3 so that they travel to surfaces to be scanned, and a scanning image formation optical system 5 which images the pieces of luminous flux from the deflector 3 on the scanned surfaces, and the luminous flux splitting means 4 is composed of a prism 4a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning apparatus used for an image forming apparatus such as a laser beam printer, a facsimile machine or a digital copying machine, and more particularly to an optical scanning apparatus used for a color image forming apparatus having a plurality of photosensitive members. Related to the device.

[0002]

2. Description of the Related Art Conventionally, as an optical scanning device, there has been known an optical scanning device in which one deflector receives a plurality of light velocities and scans a plurality of scanning surfaces. This type of optical scanning device is disclosed in
JP-A-9-54263, JP-A-10-73778 and JP-A-7-2
There is one described in 44247. The optical scanning device described in Japanese Patent Application Laid-Open No. 9-54263 is composed of multi-stage polygon mirrors corresponding to the number of light beams. The optical scanning device described in Japanese Patent Application Laid-Open No. H10-73778 is configured so that a plurality of light beams are obliquely incident on a deflection surface of a deflecting means in a sub-scanning cross section, and light beams can be separated by a mirror. JP 7-2442
The optical scanning device described in Japanese Patent Publication No. 47 is configured to use dichroic means as a means for dividing a plurality of beams.

[0003]

SUMMARY OF THE INVENTION
In the optical scanning device described in Japanese Patent Application Laid-Open No. 9-54263, since the deflector becomes large in the sub-scanning direction, the device becomes large, the weight also increases, and there is a problem that power consumption for rotation is increased. . Further, in the optical scanning device described in JP-A-10-73778, the scanning optical element needs to be largely deflected and incident on the scanning optical element in order to sufficiently separate the light beam. ,
There is a problem that not only the device becomes large and expensive, but also the scanning line bending increases. Also, JP-A-7-244247
The dichroic mirror is expensive in the optical scanning device described in Japanese Patent Application Laid-Open Publication No. H11-157, and thus has a problem that it becomes expensive as a whole. Further, in all of the conventional optical scanning devices, the distance on the optical axis between the light beam reflection point on the deflector and each surface to be scanned must be equal. There is a problem that miniaturization is difficult. An object of the present invention is to solve such problems. That is, an object of the present invention is to provide an optical scanning device capable of reducing cost and reducing noise and power consumption. It is another object of the present invention to provide an optical scanning device in which the angle of incidence of a light beam on a scanning optical element is made close to the vertical incidence, and the bending of a scanning line can be suppressed. Another object of the present invention is to
An object of the present invention is to provide an optical scanning device which eliminates restrictions on layout, does not complicate an optical system, and is suitable for miniaturization.

[0004]

In order to solve the above-mentioned problems, the invention according to the first aspect comprises a plurality of light sources for emitting light beams, and a deflector for imaging the light beams from these light sources at predetermined positions. A front optical system, a deflector that receives and deflects and scans a plurality of light beams from the deflector front optical system, and a light beam separation device that separates a plurality of light beams from the deflector toward a plurality of surfaces to be scanned Means, and a scanning image forming optical system for forming a plurality of light beams from the deflector on a plurality of scanned surfaces, wherein the light beam separating means is constituted by a prism. Features. The invention described in claim 2 is
2. The optical scanning device according to claim 1, wherein the prism is rotatable around an axis parallel to the main scanning direction as a rotation axis. According to a third aspect of the present invention, in the optical scanning device according to the first aspect, a shielding member that covers at least the deflector and has an opening on a side of the prism is provided, and the prism includes an opening of the shielding member. It is characterized by being arranged so as to cover the part. According to a fourth aspect of the present invention, a plurality of light sources for emitting light beams, a pre-deflector optical system for imaging the light beams from these light sources at predetermined positions, and a plurality of light beams from the pre-deflector optical system are provided. A deflector for receiving, deflecting and scanning, a light beam separating means for separating a plurality of light beams from the deflector toward a plurality of scanned surfaces, and a plurality of light beams from the deflector for a plurality of scanned surfaces. A scanning imaging optical system for forming an image on the optical scanning device, wherein a plurality of optical path lengths from the deflector to a plurality of surfaces to be scanned are different from each other, wherein the light beam separating means is constituted by a reflection mirror. ,
The scanning image forming optical system includes a first scanning image forming lens that forms a light beam on a first surface to be scanned, and a second lens that forms a light beam on a surface to be scanned other than the first surface to be scanned. A scanning imaging lens. According to a fifth aspect of the present invention, in the optical scanning device according to the fourth aspect, at least one synchronous light detecting means for receiving a light beam near a write start position and a write end position of each of the plurality of scanned surfaces; A synchronous control unit that independently controls light emission of the light sources corresponding to the respective scanned surfaces based on a light detection signal from the synchronous light detection unit.

[0005]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic front view showing the optical scanning device according to the first embodiment of the present invention. FIG.
FIG. 1 is a schematic diagram illustrating a main part of an optical scanning device according to a first embodiment of the present invention. As shown in FIGS. 1 and 2, the optical scanning device according to the first embodiment of the present invention includes a plurality of light sources 1 and 1 ′, a pre-deflector optical system 2 and 2 ′, and a deflector (polygon). (Mirror) 3, light beam separating means 4, and scanning image forming optical system 5. Each of the light sources 1 and 1 'emits a light beam. The light sources 1, 1 'are composed of semiconductor lasers. The pre-deflector optical systems 2 and 2 ′ form light beams from the light sources 1 and 1 ′ at predetermined positions. The pre-deflector optical system 2 includes a coupling lens 2 for coupling a light beam from the light source 1.
a, an aperture 2b for defining the size of the light beam from the coupling lens 2a, and a cylindrical lens 2c for forming the light beam from the aperture 2b as a line image near the reflection point of the polygon mirror 3. ing. The pre-deflector optical system 2 ′ includes a coupling lens 2 a ′ for coupling a light beam from the light source 1, an aperture 2 b ′ for defining the size of the light beam from the coupling lens 2 a ′, and an aperture 2 b ′. And a cylindrical lens 2c 'for forming a light beam as a line image near the reflection point of the polygon mirror 3. The cylindrical lenses 2c and 2c 'have refractive power only in the sub-scanning direction. Incidentally, the cylindrical lenses 2c, 2
The line image by c ′ may be slightly away from the reflection point of the polygon mirror 3. The polygon mirror 3 receives and reflects a plurality of light beams from the cylindrical lenses 2c and 2c 'for scanning while being rotated in a predetermined direction by a driving device (not shown). The light beam separating means 4 separates a plurality of light beams from the polygon mirror 3 toward a plurality of scanned surfaces. The light beam separating means 4 includes a prism 4a. The scanning image forming optical system 5 forms a plurality of light beams from the polygon mirror 3 on a plurality of surfaces to be scanned.

The scanning image forming optical system 5 comprises a first scanning image forming lens 5a and second scanning image forming lenses 5b and 5b '. The first scanning imaging lens 5a is disposed between the polygon mirror 3 and the prism 4a. Second
The scanning image forming lens 5b is disposed between the prism 4a and the surface of the first photoconductor 6 to be scanned. The second scanning imaging lens 5b 'is arranged between the prism 4a and the surface to be scanned of the second photoconductor 6'. First scanning imaging lens 5a
Receives a plurality of light beams from the polygon mirror 3. The prism 4a receives a plurality of light beams from the first scanning imaging lens 5a, separates the first light beam and the second light beam, and transfers the first light beam to the surface of the first photoconductor 6 to be scanned. The second light flux is directed to the surface to be scanned of the second photoconductor 6 '. Polygon mirror 3 and first scanning imaging lens 5
a is covered by the shielding member 7. An opening is formed on the side of the shielding member 7 on the side of the prism 4a. The prism 4 a is arranged so as to cover the opening of the shielding member 7. That is, the prism 4 a forms a part of the shielding member 7. Note that the shielding member 7 may be configured to cover only the polygon mirror 3. As described above, the two light beams reflected by the polygon mirror 3 pass through the first scanning and imaging lens 5a and enter the prism 4a. Here, assuming that the incident angles of the light fluxes a and b (FIG. 1) with respect to the inclined surface of the prism 4a are θa and θb, sin θ
a <1 / n <sin θb (n indicates the refractive index of the prism).
The light beam b is transmitted through the slope of a, the light beam b is totally reflected by the slope of the prism 4a, and the light beam a and the light beam b are separated. In addition, the first
In the embodiment of the present invention, when θa and θb do not satisfy the condition of the above equation (1) due to mounting error of the optical parts, the prism 4a can be rotated about an axis parallel to the main scanning direction as a rotation axis. Thus, adjustment can be made so as to satisfy the condition of the expression (1). Each light beam from the prism 4a is incident on the second scanning image forming lenses 5b and 5b ', and is imaged near the scanned surfaces of the first and second photoconductors 6 and 6'. Further, since the prism 4a forms a part of the shielding member 7, it prevents the foreign material such as toner from entering the inside of the shielding member 7 to prevent the foreign material from entering the polygon mirror 3 and the first scanning lens 5a. Can be prevented, and the sound of the polygon mirror 3 can be prevented from being transmitted to the outside.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic front view showing an optical scanning device according to a second embodiment of the present invention. FIG.
FIG. 9 is a schematic diagram illustrating a main part of an optical scanning device according to a second embodiment of the present invention. In the second embodiment of the present invention, the same components as those in the first embodiment of the present invention are denoted by the same reference numerals. As shown in FIGS. 3 and 4, the optical scanning device according to the second embodiment of the present invention comprises:
It has a plurality of light sources 1, 1 ', pre-deflector optical systems 2, 2', a deflector (polygon mirror) 3, a light beam separating means 8, and a scanning and imaging optical system 5 '. The light beam separating means 8 is constituted by a reflection mirror 8a. Scanning optical system 5 '
Is composed of a first scanning imaging lens 5a and a second scanning imaging lens 5c. First scanning imaging lens 5a
Is directed toward the first scanned surface of the first photoconductor 6 and forms an image on the first scanned surface of the first photoconductor 6. The second light beam from the first scanning imaging lens 5a is
The light is reflected by the reflection mirror 8a, separated from the first light beam, and directed to the second surface to be scanned of the second photosensitive member 6 '.
A second scanning imaging lens 5c is arranged between the reflection mirror 8a and the second surface to be scanned of the second photosensitive member 6 '. The second scanning imaging lens 5c receives the second light flux from the reflection mirror 8a and forms an image on the second scanned surface of the second photosensitive member 6 '. In the second embodiment of the present invention,
The optical path length from the polygon mirror 3 to the first surface to be scanned of the first photoconductor 6 is equal to the optical path length from the polygon mirror 3 to the second photoconductor 6.
′ Differs from the optical path length up to the second scanned surface. First
In the vicinity of the writing start position and the writing end position of the first scanned surface of the photosensitive member 6, first synchronous light detectors (synchronous light detecting means) 9 and 9 'are arranged to receive a light beam. . In the vicinity of the writing start position and the writing end position of the second scanned surface of the second photosensitive member 6 ', the second synchronous light detectors (synchronous light detecting means) 10, 10' receive light beams. Are located in Further, it is also possible to reduce the number of synchronous detectors by guiding the synchronous light at a plurality of locations to one synchronous detector with a mirror or the like so that the detection of the plural synchronous lights is also performed by one synchronous optical detector. First and second synchronous light detectors 9, 9 ',
Reference numerals 10 and 10 'are connected to a synchronization control device (synchronization control means) 11. The synchronization control device 11 is connected to the light sources 1, 1 '. The first synchronous light detector 9, 9 '
By detecting the light flux from the first photosensitive member 6, the first
And the time required for one scan. Further, the second synchronous light detectors 10, 10
′ Detects the light beam from the light source 1 ′, so that the writing timing on the second scanned surface of the second photosensitive member 6 ′ and the time required for one scan can be determined. Therefore, the synchronization control device 11 starts writing at the write timing obtained on the first and second scanned surfaces of the first and second photoconductors 6 and 6 ′, and sets the time required for one scan. By independently controlling the light emission of each of the light sources 1 and 1 'so that the writing is completed, the images of the light beams from each of the light sources 1 and 1' can be superimposed without deviation. The present invention can be applied to an optical scanning device that scans by focusing three or more light beams on three or more surfaces to be scanned.

[0008]

As described above, according to the first aspect of the present invention, since the light beam separating means is constituted by the prism, the reflection surface of the deflector can be made small, so that the cost can be reduced. , Noise and power consumption can be reduced. According to the first aspect of the present invention, since the light beam separating means is constituted by the prism, the light beam can be separated if the light beam angles are different, even if the light beam does not pass through completely different light paths. Therefore, the deflection of the light beam in the scanning optical system can be reduced and the scanning line bend can be suppressed, and the scanning optical system can be reduced in size, the cost can be reduced, and the apparatus can be downsized. . According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the prism can be rotated about an axis parallel to the main scanning direction as a rotation axis. Even if the angular relationship between the light beams changes, the light beams can be separated. According to the third aspect of the present invention, in addition to the effect of the first aspect, the prism has a role of separating a light beam and also serves as a part of a shielding member. Can be reduced. According to the fourth aspect of the present invention, the plurality of optical path lengths from the deflector to the plurality of scanned surfaces are different, the light beam separating means is constituted by a reflection mirror, and the scanning image forming optical system is constituted by the first scanned image. Since it has a first scanning imaging lens that forms a light beam on a scanning surface and a second scanning imaging lens that forms a light beam on a scanning surface other than the first scanning surface, Eliminates the layout constraint that the optical path length from the deflector to each scanned surface must be equal,
Moreover, miniaturization is enabled. According to the fifth aspect of the present invention, in addition to the effect of the fourth aspect, at least one synchronous light which is disposed near the write start position and the write end position of each of the plurality of scanned surfaces and receives the light beam. It has a detecting means and a synchronous control means for independently controlling the light emission of the light source corresponding to each scanned surface based on the light detection signal from the synchronous light detecting means. Can be matched.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a main part of the optical scanning device according to the first embodiment of the present invention.

FIG. 3 is a schematic front view showing an optical scanning device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a main part of an optical scanning device according to a second embodiment of the present invention.

[Explanation of symbols]

Reference numerals 1, 1 'light source, 2, 2' optical system before deflector, 3 deflector (polygon mirror), 4 light beam separation means, 4a prism, 5 scanning imaging optical system, 5a first scanning imaging lens, 5b, 5b ', 5c Second scanning imaging lens, 6
1st photoconductor, 6 '2nd photoconductor, 7 shielding member, 8
Light beam separating means, 8a Reflecting mirror, 9, 9 'First synchronous light detector (synchronous light detecting means), 10, 10' Second
Synchronous light detector (synchronous light detecting means), 11 Synchronous controller.

Claims (5)

[Claims] 1. A plurality of light sources for emitting light beams, a pre-deflector optical system for forming an image of the light beams from these light sources at predetermined positions, and a plurality of light beams from the pre-deflector optical system for receiving and deflecting the light beams. Deflector that scans the plurality of light beams from the deflector toward a plurality of scanning surfaces, and forms a plurality of light beams from the deflector on a plurality of scanning surfaces. An optical scanning device having a scanning image forming optical system, wherein the light beam separating means is constituted by a prism. 2. The optical scanning device according to claim 1, wherein
The optical scanning device according to claim 1, wherein the prism is rotatable around an axis parallel to a main scanning direction. 3. The optical scanning device according to claim 1, wherein
An optical scanning device, comprising: a shielding member that covers at least the deflector and has an opening on the side of the prism, wherein the prism is disposed so as to cover the opening of the shielding member. 4. A plurality of light sources for emitting light beams, a pre-deflector optical system for imaging light beams from these light sources at predetermined positions, and a plurality of light beams from the pre-deflector optical system for receiving and deflecting the light beams. Deflector that scans the plurality of light beams from the deflector toward a plurality of scanning surfaces, and forms a plurality of light beams from the deflector on a plurality of scanning surfaces. A scanning image forming optical system, wherein a plurality of optical path lengths from the deflector to a plurality of scanned surfaces are different optical scanning devices, wherein the light beam separating means is configured by a reflection mirror,
The scanning image forming optical system includes a first scanning image forming lens that forms a light beam on a first surface to be scanned, and a second lens that forms a light beam on a surface to be scanned other than the first surface to be scanned. An optical scanning device, comprising: a scanning imaging lens. 5. The optical scanning device according to claim 4, wherein
At least one synchronous light detecting means for receiving a light beam near the write start position and the write end position of each of the plurality of scanned surfaces, and corresponding to each of the scanned surfaces based on a light detection signal from the synchronous light detect means; An optical scanning device having synchronization control means for independently controlling light emission of the light source.