JP2002131664A - Optical scanner and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical scanner with which a finer image is available by stabilizing the detection timing of a BD sensor and improving the precision of detection of the synchronized signal by the BD sensor and an image forming device using the scanner. SOLUTION: The optical scanner is provided with an incident optical means which leads a luminous flux emitted from a light source means into a deflection element, a scanning lens which forms an image of the luminous flux deflected by the deflection means on the plane to be scanned, a synchronized position detection means which converges a part of the luminous flux deflected by the deflection element on a slit by means of a focusing lens via a reflection mirror, leads the luminous flux from the slit on a synchronization detection element by means of a conjugate lens and controls the timing of the beginning position of scanning on the plane to be scanned by using a signal from the synchronization detection element, and the conjugation lens is composed of an anamorphic lens having different powers for a main scanning direction and for a subscanning direction.

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 and an image forming apparatus using the same, and more particularly to a laser beam printer, a digital copying machine, etc., which can perform high-speed and high-quality printing with a relatively simple structure. It is suitable.

[0002]

2. Description of the Related Art An optical scanning device conventionally used in an image forming apparatus such as a laser beam printer or a digital copying machine guides a light beam emitted from a light source to a deflecting element by an incident optical means, and the deflecting element uses the deflecting element. The deflected light beam is spot-formed on the photosensitive drum surface, which is the surface to be scanned, by the scanning optical means, and the light beam is optically scanned on the photosensitive drum surface.

In such an optical scanning device, a synchronous position detecting means (BD) is used immediately before an image signal is written in order to accurately control the image writing position on the photosensitive drum surface.
(Optical system) is generally provided.

FIG. 7 is a sectional view (main scanning sectional view) of a main part in a main scanning direction of a conventional optical scanning device having a synchronous position detecting means.
FIGS. 8A and 8B are cross-sectional views of main parts when only the optical path of the light beam toward the synchronous position detecting means in FIG. 7 is developed. FIG. 8A is a main scanning cross-sectional view, and FIG. 8B is a sub-scanning cross-sectional view. 8A and 8B, a solid line indicates a light beam, and a black shadow indicates a conjugate relationship by the BD conjugate lens 79.

In FIG. 1, reference numeral 71 denotes a light source means, which is composed of, for example, a semiconductor laser. Reference numeral 72 denotes an aperture stop, which shapes a light beam emitted from the light source means 71 into a desired optimum beam shape. Reference numeral 73 denotes a collimator lens, which converts a light beam passing through the aperture stop 72 into a substantially parallel light beam. Numeral 74 denotes a cylindrical lens having a predetermined refractive power only in the sub-scanning direction. The aperture stop 72, the collimator lens 73, and the cylindrical lens 7
Elements such as 4 constitute one element of the incident optical means 91.

Reference numeral 75 denotes an optical deflector as a deflecting element.
For example, it is composed of a rotating polygon mirror and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor. 81 is a single fθ lens having fθ characteristics,
By providing a conjugate relationship between the vicinity of the deflecting surface 75a of the optical deflector 75 and the vicinity of the photosensitive drum surface 82 as the surface to be scanned in the sub-scan section, a tilt correction function is provided.

Reference numeral 76 denotes an imaging lens (hereinafter, referred to as a “BD lens”).
It is written. ), A light beam (BD light beam) for detecting a synchronization signal for adjusting the timing of the scanning start position on the photosensitive drum surface 82 is placed on a surface of a BD slit 78 described later in both the main scanning section and the sub-scanning section. It is forming an image.

[0008] 77 is a reflection mirror (hereinafter referred to as "BD mirror")
It is written. ), And outputs the BD light flux to a synchronous detection element 8 described later.
The light is reflected to the 0 side. 78 is a slit (hereinafter referred to as “BD
Slit. " ), And is disposed at a position equivalent to the photosensitive drum surface 82.

Reference numeral 79 denotes a conjugate lens (hereinafter, referred to as a “BD conjugate lens”), which comprises a coaxial lens (spherical lens) having the same curvature in the main scanning direction and the sub-scanning direction. In order to correct surface tilt in the cross section, the surface of the synchronous detection element 80 and the surface of the BD mirror 77 are arranged in a substantially conjugate relationship in the main scanning cross section and the sub scanning cross section.

Reference numeral 80 denotes an optical sensor (hereinafter referred to as a "BD sensor") as a synchronization detecting element. In FIG. 1, a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 80 is shown. ) Using the photosensitive drum surface 82
The timing of the scanning start position for image recording on the upper side is adjusted.

The BD lens 76, BD mirror 77, B
Elements such as the D slit 78, the BD conjugate lens 79, and the BD sensor 80 are synchronized position detecting means (BD optical system)
Constitutes one element.

[0012]

The conjugate BD lens 79 composed of the above-mentioned coaxial lens is arranged so that the surface of the BD sensor 80 and the surface of the BD mirror 77 have a substantially conjugate relationship as described above. Therefore, in the main scanning section, the BD sensor 8
Since the luminous flux going to 0 scans not only on the surface of the BD slit 78 but also on the surface of the BD sensor 80, if there is a mounting error of the BD slit 78 and the BD sensor 80, a focusing error of the lens, etc. There is a problem that 80 detection unevenness occurs.

The present invention provides an optical scanning device capable of obtaining a higher definition image by stabilizing the timing of a scanning start position on a surface to be scanned and improving the detection accuracy of a synchronization signal by a BD sensor. With the goal.

Further, the present invention provides a multi-beam optical scanning device and an image having a plurality of optical scanning devices which can reduce scanning line jitter generated when a multi-beam laser is used as a light source means in the above optical scanning device. It is an object of the present invention to provide an image forming apparatus capable of reducing a color shift generated in a forming apparatus.

[0015]

According to a first aspect of the present invention, there is provided an optical scanning device, comprising: incident optical means for guiding a light beam emitted from a light source means to a deflecting element; A scanning lens to form an image on, and a part of the light beam deflected by the deflecting element is condensed on a slit via a reflecting mirror by the image forming lens, and the light beam from the slit is sent to a synchronous detection element by a conjugate lens. A synchronous position detecting means for guiding light and controlling a timing of a scanning start position on the surface to be scanned by using a signal from the synchronous detecting element, wherein the conjugate lens is disposed in the main scanning direction. And an anamorphic lens having different powers in the sub-scanning direction and the sub-scanning direction.

According to a second aspect of the present invention, in the first aspect of the present invention, the imaging lens includes an end of the scanning lens or is formed integrally with the scanning lens.

According to a third aspect of the present invention, in the first aspect, the imaging lens and the scanning lens are provided independently of each other.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the slit is arranged at or near an image forming position of the light beam from the deflection element by the image forming lens.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the conjugate lens has a refracting power that makes the surface of the synchronous detection element and the deflection surface of the deflection element substantially conjugate in the main scanning section. It is characterized by having.

According to a sixth aspect of the present invention, in the first aspect of the invention, the conjugate lens has a refracting power that makes the surface of the synchronous detection element and the surface of the reflecting mirror substantially conjugate in the sub-scanning cross section. It is characterized by:

According to a seventh aspect of the present invention, when the refractive power of the conjugate lens in the main scanning direction is φm and the refractive power in the sub-scanning direction is φs, the condition of φm <φs is satisfied. It is characterized by.

According to an eighth aspect of the present invention, in the first aspect, the light source means is a multi-beam laser.

According to a ninth aspect of the present invention, in the first aspect, the conjugate lens is manufactured by plastic molding.

According to a tenth aspect of the present invention, there is provided an image forming apparatus, comprising: the optical scanning device according to any one of the first to ninth aspects; a photosensitive member disposed on the surface to be scanned; A developing device for developing the electrostatic latent image formed on the photoreceptor as a toner image by the emitted light flux, a transfer device for transferring the developed toner image to a transfer material, and a transfer device for transferring the transferred toner image. A fixing device for fixing the material.

According to an eleventh aspect of the present invention, there is provided an image forming apparatus according to any one of the first to ninth aspects, wherein the optical scanning apparatus converts code data input from an external device into an image signal. And a printer controller that allows the user to input the data to the printer.

According to a twelfth aspect of the present invention, there is provided a color image forming apparatus comprising a plurality of optical scanning devices according to any one of the first to ninth aspects, each of which corresponds to a plurality of light beams emitted from each scanning optical device. Light is guided onto a plurality of image carriers, and the plurality of light beams are respectively scanned on the plurality of image carriers to form a color image.

According to a thirteenth aspect of the present invention, there is provided an optical scanning device, comprising: incident optical means for guiding a light beam emitted from a light source means to a deflecting element; and scanning for imaging the light beam deflected by the deflecting element on a surface to be scanned. A lens and a part of the light beam deflected by the deflecting element are condensed on a slit via a reflecting mirror by an imaging lens, and the light beam from the slit is guided to a synchronization detecting element by a conjugate lens, and A synchronous position detecting means for controlling timing of a scanning start position on the surface to be scanned by using a signal from a detecting element, wherein the conjugate lens comprises a coaxial lens, and A conjugate point of the axis lens with the surface of the synchronous detection element is located between the reflection mirror and the deflection element.

According to a fourteenth aspect, in the thirteenth aspect, a conjugate point of the coaxial lens with the surface of the synchronous detection element is located between the deflection element and the imaging lens. I have.

According to a fifteenth aspect, in the thirteenth aspect, a conjugate point of the coaxial lens with the surface of the synchronous detection element is located between the imaging lens and the reflection mirror. And

According to a sixteenth aspect, in the thirteenth aspect, the imaging lens comprises an end of the scanning lens or is formed integrally with the scanning lens.

A seventeenth aspect of the present invention is characterized in that, in the thirteenth aspect, the imaging lens and the scanning lens are provided independently of each other.

An eighteenth aspect of the present invention is characterized in that, in the thirteenth aspect, the slit is arranged at or near the image forming position of the light beam from the deflection element by the image forming lens.

The invention of claim 19 is the invention of claim 13, wherein the light source means is a multi-beam laser.

According to a twentieth aspect, in the thirteenth aspect, the conjugate lens is manufactured by plastic molding.

According to a twenty-first aspect of the present invention, there is provided an image forming apparatus comprising: the optical scanning device according to any one of the thirteenth to twentieth aspects;
A photoreceptor disposed on the surface to be scanned, a developing device for developing an electrostatic latent image formed on the photoreceptor by a light beam scanned by the optical scanning device as a toner image, and a developed toner image. The image forming apparatus is characterized in that it has a transfer device for transferring to a transfer material and a fixing device for fixing the transferred toner image to the transfer material.

According to a twenty-second aspect of the present invention, there is provided an image forming apparatus comprising: the optical scanning device according to any one of the thirteenth to twentieth aspects;
A printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device.

According to a twenty-third aspect of the present invention, a color image forming apparatus is provided with a plurality of optical scanning devices according to any one of the thirteenth to twentieth aspects, and corresponds to a plurality of light beams emitted from each scanning optical device. Light is guided onto a plurality of image carriers, and the plurality of light beams are respectively scanned on the plurality of image carriers to form a color image.

[0038]

[First Embodiment] FIG. 1 is a sectional view (main scanning sectional view) of a main portion of a first embodiment of the present invention in a main scanning direction. 2A and 2B are cross-sectional views of main parts when only the optical path of a light beam heading to a synchronous position detecting unit in FIG. 1 is developed, and FIG. 2A is a cross-sectional view of main parts in the main scanning direction. FIG. 2B is a sectional view of a main part in the sub-scanning direction (sub-scanning sectional view). 2A and 2B, a solid line indicates a light beam, and a black shadow indicates a conjugate relationship by the BD conjugate lens 9.

In this specification, the plane formed by the optical axis of the scanning lens and the light beam deflected by the optical deflector is defined as a main scanning section, and the plane including the optical axis of the scanning lens and orthogonal to the main scanning section is defined as a sub-scanning section. Defined as a scanning section.

In the figure, reference numeral 1 denotes a light source means, which comprises, for example, a semiconductor laser (single beam laser) for emitting a single light beam. Reference numeral 2 denotes an aperture stop.
Is shaped into a desired optimal beam shape. Reference numeral 3 denotes a collimator lens, which converts a light beam passing through the aperture stop 2 into a substantially parallel light beam. Reference numeral 4 denotes a cylindrical lens having a predetermined refractive power only in the sub-scanning direction. In addition, the aperture stop 2, the collimator lens 3,
Each element such as the cylindrical lens 4 constitutes one element of the incident optical means 51.

Reference numeral 5 denotes an optical deflector as a deflecting element, which is, for example, a polygon mirror (rotating polygon mirror), and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor.

Numeral 11 denotes a single scanning lens (f.theta. Lens) having f.theta. Characteristics, and a deflecting surface 5a of the optical deflector 5 or its vicinity and a photosensitive drum surface 12 as a surface to be scanned or its vicinity in the sub scanning section. The optical deflector has a surface tilt correcting function by making a substantially conjugate relationship between the optical deflector and the optical deflector.

Reference numeral 6 denotes an imaging lens (hereinafter, referred to as a “BD lens”), which is a light beam (B) for detecting a synchronization signal for adjusting the timing of a scanning start position on the photosensitive drum surface 12.
D light beam) is imaged on a BD slit 8 surface described later in both the main scanning section and the sub-scanning section. That is,
The BD lens 6 has a BD slit 8 in the main scanning section.
By scanning the surface and making the deflecting surface 5a of the optical deflector 5 and the surface of the BD slit 8 substantially conjugate in the sub-scanning cross section, a surface tilt correction function of the optical deflector (surface tilt correction system) )have.

Reference numeral 7 denotes a reflection mirror (hereinafter, referred to as a “BD mirror”), which detects a BD light beam from a synchronous detection element 10 described later.
Reflected to the side. The BD mirror 7 is for turning back the light beam guided to the synchronous position detecting means described later, and is arranged to reduce the size of the entire apparatus.

Reference numeral 8 denotes a slit (hereinafter, referred to as a “BD slit”), which is arranged at or near the image forming position of the BD lens 6. The BD slit 8 has a knife edge at its end and is scanned in the main scanning direction.
The position where the spot substantially formed by the D lens 6 enters the surface of the BD sensor 10 is determined. The reason why the edge of the BD slit 8 is formed in a knife edge shape is that the BD detection accuracy is higher when the edge is formed by the knife edge of the BD slit 8 than when the BD light beam is emitted at the end of the light receiving surface of the BD sensor 10. It is.

Reference numeral 9 denotes a conjugate lens (hereinafter referred to as a "BD conjugate lens"), which is made of an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction, and is manufactured by plastic molding. The BD conjugate lens 9 according to the present embodiment is configured such that the surface of the synchronous detection element 10 and the deflection surface 5a of the optical deflector 5 have a substantially conjugate relationship in the main scanning section, and the surface of the synchronous detecting element 10 in the sub-scanning section. The refractive power, the arrangement position, and the like are set so that the and the BD mirror 7 have a substantially conjugate relationship.

Reference numeral 10 denotes an optical sensor (hereinafter, referred to as a “BD sensor”) as a synchronization detection element. In this embodiment, a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 10 is provided. Is used to adjust the timing of the scanning start position for image recording on the photosensitive drum surface 12.

The BD lens 6, the BD mirror 7, the BD slit 8, the BD conjugate lens 9, and the BD sensor 10
And the like constitute one element of a synchronous position detecting means (BD optical system).

In this embodiment, the light beam emitted from the light source means 1 is modulated in accordance with the image information, the cross section of the light beam is restricted by the aperture stop 2, and the collimator lens 3 converts the light beam into a substantially parallel light beam. The light enters the lens 4. The light beam incident on the cylindrical lens 4 is emitted as it is in the main scanning section. In the sub-scan section, the light converges and converges.
Is formed as a substantially linear image (a linear image elongated in the main scanning direction) on the deflecting surface 5a. The light beam reflected and deflected by the deflecting surface 5a of the optical deflector 5 is scanned by the scanning lens 11 on the photosensitive drum surface 12a.
An image is formed on the photosensitive drum surface 12 at a constant speed by rotating the optical deflector 5 in the direction of arrow A in the direction of arrow B (main scanning direction). Thus, an image is recorded on the photosensitive drum surface 12 which is a recording medium.

At this time, in order to adjust the timing of the scanning start position on the photosensitive drum surface 12 before optical scanning on the photosensitive drum surface 12, a part of the light beam reflected and deflected by the optical deflector 5 is After being condensed on the surface of the BD slit 8 via the BD mirror 7 by the light 6, the light is guided to the BD sensor 10 via the BD conjugate lens 9. Then, a synchronization signal (BD) obtained by detecting an output signal from the BD sensor 10 is output.
The timing of the scanning start position of the image recording on the photosensitive drum surface 12 is adjusted using the signal (signal).

Table 1 shows design values of the synchronous position detecting means in this embodiment.

[0052]

[Table 1]

In the present embodiment, as shown in Table 1, the BD conjugate lens 9 is composed of an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction. By arranging the surface of the BD sensor 10 and the deflecting surface 5a of the optical deflector 5 so as to be substantially conjugate in the cross section, the BD sensor is scanned on the surface of the BD slit 8 even though the BD light beam is scanned. On the tenth surface, the BD light beam is stopped. Thereby, in the present embodiment, for example, the BD slit 8
In addition, even if there is an error in mounting the BD sensor 10 or a focusing error of the lens, it is possible to prevent the detection unevenness of the BD sensor 10 from occurring.

In this embodiment, when the power (refractive power) in the main scanning direction of the BD conjugate lens 9 is φm and the power (refractive power) in the sub-scanning direction is φs, φm <φsｓ (1) The following conditions are satisfied. Conditional expression (1) relates to the ratio between the power of the BD conjugate lens 9 in the main scanning direction and the power in the sub-scanning direction. If the conditional expression (1) is not satisfied, the timing of the scanning start position on the photosensitive drum surface 12 is determined. It is not good because it becomes difficult to stabilize. In the present embodiment, the power φm of the BD conjugate lens 9 in the main scanning direction is φm = 0.054 (focal length = 18.4 mm), and the power φs in the sub-scanning direction is φs = 0.064 (focal length = 15.6 mm). Equation (1) is satisfied.

In the main scanning section, a reduction system in the longitudinal direction of the line image is formed on the surface of the BD sensor 10, and the BD light flux is imaged on the surface of the BD slit 8. On the surface, the beam diameter is larger than the beam diameter on the surface of the BD slit 8, stabilizing the position of the light beam on the sensor surface, and making it difficult to pick up unevenness in sensitivity of the BD sensor 10.

The BD conjugate lens 9 is disposed so that the surface of the BD sensor 10 and the surface of the BD mirror 7 have a substantially conjugate relationship in the sub-scanning section as described above. This is a system that corrects the displacement of the light beam due to the tilt of the light beam.

This system is particularly effective in a multi-beam optical scanning apparatus in which scanning line jitter is likely to cause a problem and a color image forming apparatus in which color misregistration is likely to occur.

As described above, in the present embodiment, the BD conjugate lens 9 is constituted by an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction as described above, thereby having a function of correcting the tilt of the BD mirror 7. Together with stabilizing the detection timing of the BD sensor 10,
By increasing the detection accuracy of the synchronization signal by the BD sensor 10, a high-definition image can be obtained.

In the present embodiment, the BD lens 6 and the scanning lens 11 are provided independently of each other.
1 may be used, or may be formed integrally with the scanning lens 11. At this time, BD slit 8
Is disposed at a position equivalent to the surface of the photosensitive drum 12.

In the present embodiment, the light source means 1 is constituted by a single beam laser. However, the light source means 1 may be constituted by a multi-beam laser to scan the surface to be scanned with a plurality of light beams in the same manner as in the first embodiment. The effect can be obtained.

[Embodiment 2] FIGS. 3A and 3B are cross-sectional views of essential parts when only the optical path of a light beam toward a synchronous position detecting means is developed in Embodiment 2 of the present invention. FIG. 3A is a main scanning sectional view, and FIG. 3B is a sub-scanning sectional view. In the figures (A) and (B), the solid line represents the luminous flux,
A black shadow indicates a conjugate relationship by the BD conjugate lens 19. 2A and 2B, the same elements as those shown in FIGS. 2A and 2B are denoted by the same reference numerals.

This embodiment is different from the first embodiment in that the BD conjugate lens 19 is constituted by a coaxial lens (spherical lens or aspherical lens) having the same curvature in the main scanning direction and the sub-scanning direction. The configuration is such that the conjugate point of the coaxial lens 19 with the surface of the BD sensor 10 is located upstream of the BD mirror 7 (between the BD mirror 7 and the optical deflector 5). In other respects, the configuration and the optical function are substantially the same as those of the first embodiment, and thus the same effects are obtained.

That is, in the figure, reference numeral 19 denotes a BD conjugate lens, which is formed of a coaxial lens, and deflects the conjugate point of the coaxial lens 19 with the BD sensor 10 in both the main scanning section and the sub-scanning section. It is configured to be located between the deflecting surface 5a of the device 5 and the BD lens 6.

In this embodiment, the coaxial lens 19 is used in both the main scanning section and the sub-scanning section as described above, and the conjugate point of the coaxial lens 19 with the BD sensor 10 is determined by the deflecting surface 5a of the optical deflector 5. And the BD lens 6, the BD light beam is almost stopped on the surface of the BD sensor 10 in the main scanning section, and the BD mirror 7 is tilted in the sub-scanning section. , The sensitivity to the movement of the BD light beam in the sub-scanning direction on the surface of the BD sensor 10 is suppressed. The coaxial lens 19 is a system that substantially corrects the detection unevenness of the BD sensor 10.

In the present embodiment, the use of a coaxial lens as the BD conjugate lens 19 not only improves the detection accuracy of the BD sensor 10 but also facilitates manufacture and achieves cost reduction.

Table 2 shows design values of the synchronous position detecting means in this embodiment.

[0067]

[Table 2]

[Embodiment 3] FIGS. 4A and 4B are cross-sectional views of main parts when only the optical path of a light beam toward a synchronous position detecting means is developed in Embodiment 3 of the present invention. FIG. 3A is a main scanning sectional view, and FIG. 3B is a sub-scanning sectional view. In the figures (A) and (B), the solid line represents the luminous flux,
The black shadow indicates a conjugate relationship by the BD conjugate lens 29. 1A and 1B, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment is different from the second embodiment in that the conjugate point of the coaxial lens 29 with the surface of the BD sensor 10 is located between the BD lens 6 and the BD mirror 7. . In other respects, the configuration and the optical function are substantially the same as those of the second embodiment, and the same effects are obtained.

That is, in the figure, reference numeral 29 denotes a BD conjugate lens, which is composed of a coaxial lens, and sets the conjugate point of the coaxial lens 29 with the surface of the BD sensor 10 in the main scanning section and the sub-scanning section. It is configured to be located between the lens 6 and the BD mirror 7.

In this embodiment, the coaxial lens 29 is set in the main scanning section and the sub-scanning section as described above, and the conjugate point of the coaxial lens 29 with the surface of the BD sensor 10 is set to BD.
By being configured to be located between the lens 6 and the BD mirror 7, the BD light flux is
It is almost stopped on the surface of the sensor 10, and in the sub-scan section, the BD light beam BD
The sensitivity to the movement in the sub-scanning direction on the surface of the sensor 10 can be suppressed lower than that in the second embodiment. This coaxial lens 29 has a B
This is a system for correcting the detection unevenness of the D sensor 10.

Further, in the present embodiment, similarly to the above-described second embodiment, by using a coaxial lens for the BD conjugate lens 29, not only the detection accuracy of the BD sensor 10 is improved, but also the manufacturing is facilitated and the cost is reduced. Down can also be achieved.

Table 3 shows design values of the synchronous position detecting means in this embodiment.

[0074]

[Table 3]

[Image Forming Apparatus] FIG. 5 is a sectional view of a main portion in the sub-scanning direction showing an embodiment of an image forming apparatus (electrophotographic printer) using any one of the optical scanning apparatuses according to the first to third embodiments. It is. In FIG. 5, reference numeral 104 denotes an image forming apparatus. The image forming apparatus 104 receives code data D from an external device 117 such as a personal computer.
c is input. The code data Dc is converted into image data (dot data) Di by the printer controller 111 in the apparatus. This image data Di is input to the optical scanning unit 100. The optical scanning unit (optical scanning device) 100 outputs image data Di.
A light beam (light beam) 103 modulated according to the light beam is emitted, and the light beam 103 scans the photosensitive surface of the photosensitive drum 101 in the main scanning direction.

The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. Then, along with this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction orthogonal to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface.
The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with a light beam 103 scanned by the optical scanning unit 100.

As described above, the light beam 103 is
The light is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. This electrostatic latent image is further moved from the irradiation position of the light beam 103 to the photosensitive drum 101.
Is developed as a toner image by a developing device 107 disposed so as to contact the photosensitive drum 101 on the downstream side in the rotation direction of the photosensitive drum 101. The toner particles used here have, for example, the opposite sign to the charge charged by the charging roller 102,
Then, so-called regular development, which is a portion (image area) where the toner adheres to the non-exposed portion of the photosensitive drum, or reversal development where the toner adheres to the exposed portion of the photosensitive drum may be performed.

The toner image developed by the developing device 107 is transferred below the photosensitive drum 101 by a transfer roller 108 disposed opposite to the photosensitive drum 101 onto a sheet 112 as a material to be transferred. The paper 112 is stored in a paper cassette 109 in front of the photosensitive drum 101 (right side in FIG. 5), but can be fed manually. At the end of the paper cassette 109, a paper feed roller 11 is provided.
0 is provided, and the paper 11 in the paper cassette 109 is
2 to the transport path.

The sheet 112 onto which the unfixed toner image has been transferred as described above is further moved to the rear of the photosensitive drum 101 (FIG. 5).
At the left side). The fixing device is composed of a fixing roller 113 having a fixing heater (not shown) therein and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and is sent from the transfer unit. The sheet 112 is fixed to the fixing roller 113 and the pressure roller 11.
The paper 1 is heated by applying pressure at the pressing portion
12 to fix the unfixed toner image. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and discharges the fixed paper 112 to the outside of the image forming apparatus.

Although not shown in FIG. 5, the print controller 111 not only converts the explanation data, but also controls the motor 115 and other components in the image forming apparatus and the polygon motor in the optical scanning unit 100. Perform control.

[Color Image Forming Apparatus] FIG. 6 shows a case where a plurality of the optical scanning apparatuses of the first to third embodiments are used at the same time and image information of each color is recorded on different photosensitive drum surfaces. FIG. 2 is a schematic view of a main part of a tandem type color image forming apparatus on which an image is formed.

In the figure, reference numerals 41, 42, 43, and 44 denote any one of the optical scanning devices according to the first to third embodiments,
Reference numerals 21, 22, 23, and 24 denote photosensitive drums as image carriers, 31, 32, 33, and 34 denote developing units, and 45 denotes a transport belt.

The color image forming apparatus shown in the figure is an optical scanning device (41, 42, 4) according to any one of the first to third embodiments.
3,44), each of which corresponds to each color of C (cyan), M (magenta), Y (yellow), and B (black), and is in parallel with each of the photosensitive drums (21, 22, 23, 2).
4) An image signal is recorded on a surface, and then multiple-transferred onto a recording material to print one full-color image at high speed.

As described above, by configuring a color image forming apparatus using a plurality of optical scanning devices of the present invention, it is possible to increase the speed, and at the same time, to achieve high image quality with little registration deviation (color deviation) between each color. A color image can be obtained.

[0085]

According to the present invention, as described above, the conjugate lens is constituted by an anamorphic lens having different powers in the main scanning direction and the sub-scanning direction.
By stabilizing the detection timing of the sensor and increasing the detection accuracy of the synchronization signal by the BD sensor, an optical scanning device capable of obtaining a high-definition image can be achieved.

Further, according to the present invention, as described above, the conjugate point of the BD conjugate lens with the BD sensor surface in the main scanning section is located upstream of the BD mirror, so that the detection timing of the BD sensor can be reduced. Stabilize,
By improving the detection accuracy of the synchronization signal by the BD sensor, an optical scanning device capable of obtaining a high-definition image can be achieved.

Further, according to the present invention, an image forming apparatus capable of reducing scanning line jitter generated when a multi-beam laser is used and color shift generated in a color image forming apparatus having a plurality of optical scanning devices. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is a main scanning sectional view and a sub-scanning sectional view after the deflection element according to the first embodiment of the present invention.

FIG. 3 is a main scanning cross-sectional view and a sub-scanning cross-sectional view after a deflection element according to a second embodiment of the present invention.

FIG. 4 is a main scanning sectional view and a sub-scanning sectional view after a deflection element according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a main part in a sub-scanning direction showing a configuration example of an image forming apparatus (electrophotographic printer) using the optical scanning device of the present invention.

FIG. 6 is a schematic view of a main part of a tandem type color image forming apparatus of the present invention.

FIG. 7 is a schematic diagram of a main part of a conventional optical scanning device.

FIG. 8 is a main scanning sectional view and a sub-scanning sectional view after the deflection element of the conventional optical scanning device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source means (semiconductor laser) 2 Aperture stop 3 Collimator lens 4 Cylindrical lens 5 Deflection element (optical deflector) 6 BD lens 7 BD mirror 8 BD slit 9 BD conjugate lens 10 BD sensor 11 Scanning lens 12 Scanning surface (photosensitive Drum surface) 41, 42, 43, 44 Optical scanning device 21, 22, 23, 24 Image carrier (photosensitive drum) 31, 32, 33, 34 Developing device 45 Conveying belt 100 Optical scanning device 101 Photosensitive drum 102 Charging roller 103 Light beam 104 Image forming device 107 Developing device 108 Transfer roller 109 Paper cassette 110 Feed roller 111 Printer controller 112 Transfer material (paper) 113 Fixing roller 114 Pressure roller 115 Motor 116 Discharge roller 117 External device

Claims (23)

[Claims] 1. An incident optical means for guiding a light beam emitted from a light source means to a deflecting element, a scanning lens for forming an image of the light beam deflected by the deflecting element on a surface to be scanned, and a scanning lens deflected by the deflecting element. A part of the luminous flux is condensed on the slit via the reflecting mirror by the imaging lens, the luminous flux from the slit is guided to the synchronization detecting element by the conjugate lens, and the signal is used by using the signal from the synchronous detecting element. A synchronous position detecting means for controlling timing of a scanning start position on a surface to be scanned, wherein the conjugate lens comprises an anamorphic lens having different powers in a main scanning direction and a sub-scanning direction. An optical scanning device, comprising: 2. The optical scanning device according to claim 1, wherein the imaging lens comprises an end of the scanning lens or is formed integrally with the scanning lens. 3. The optical scanning device according to claim 1, wherein the imaging lens and the scanning lens are provided independently of each other. 4. The optical scanning device according to claim 1, wherein the slit is disposed at or near an image forming position of the light beam from the deflection element by the image forming lens. 5. The conjugate lens according to claim 1, wherein the conjugate lens has a refracting power in a main scanning cross section to make a surface of the synchronous detection element and a deflecting surface of the deflecting element substantially conjugate. Optical scanning device. 6. The conjugate lens according to claim 1, wherein the conjugate lens has a refracting power that makes the surface of the synchronous detection element and the surface of the reflection mirror substantially conjugate in a sub-scan section.
The optical scanning device according to claim 1. 7. The optical scanning device according to claim 1, wherein when the refractive power of the conjugate lens in the main scanning direction is φm and the refractive power in the sub-scanning direction is φs, the condition of φm <φs is satisfied. apparatus. 8. The optical scanning device according to claim 1, wherein said light source means is a multi-beam laser. 9. The optical scanning device according to claim 1, wherein said conjugate lens is manufactured by plastic molding. 10. An optical scanning device according to claim 1, further comprising: a photosensitive member disposed on the surface to be scanned.
A developing unit that develops an electrostatic latent image formed on the photoconductor as a toner image by a light beam scanned by the optical scanning device, a transfer unit that transfers the developed toner image to a transfer target material, An image forming apparatus, comprising: a fixing device for fixing the transferred toner image to the transfer material. 11. An optical scanning device according to claim 1, further comprising: a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device. An image forming apparatus comprising: 12. A plurality of optical scanning devices according to claim 1, wherein a plurality of light beams emitted from each scanning optical device are guided on a corresponding plurality of image carrier surfaces. A color image forming apparatus that forms a color image by scanning each of the plurality of image carriers with the plurality of light beams. 13. An incident optical means for guiding a light beam emitted from a light source means to a deflecting element, a scanning lens for forming an image of the light beam deflected by the deflecting element on a surface to be scanned, and a scanning lens deflected by the deflecting element. A part of the luminous flux is condensed on the slit via the reflecting mirror by the imaging lens, the luminous flux from the slit is guided to the synchronization detecting element by the conjugate lens, and the signal is used by using the signal from the synchronous detecting element. A synchronous position detecting means for controlling a timing of a scanning start position on the surface to be scanned, wherein the conjugate lens comprises a coaxial lens, and a surface of the synchronous detecting element formed by the coaxial lens. Wherein the conjugate point of the optical scanning device is located between the reflection mirror and the deflection element. 14. The optical scanning device according to claim 13, wherein a conjugate point of the coaxial lens with the surface of the synchronous detection element is located between the deflection element and the imaging lens. 15. The optical scanning device according to claim 13, wherein a conjugate point of the coaxial lens with a surface of the synchronization detecting element is located between the imaging lens and the reflection mirror. 16. The optical scanning device according to claim 13, wherein the imaging lens comprises an end of the scanning lens or is formed integrally with the scanning lens. 17. The image forming apparatus according to claim 1, wherein the imaging lens and the scanning lens are provided independently of each other.
3. The optical scanning device according to 3. 18. The optical scanning device according to claim 13, wherein the slit is disposed at or near an image forming position of the light beam from the deflection element by the image forming lens. 19. The optical scanning device according to claim 13, wherein said light source means is a multi-beam laser. 20. The optical scanning device according to claim 13, wherein the conjugate lens is manufactured by plastic molding. 21. The optical scanning device according to claim 13, a photoconductor disposed on the surface to be scanned, and a light beam scanned by the optical scanning device, the photoconductor being placed on the photoconductor. It has a developing device for developing the formed electrostatic latent image as a toner image, a transfer device for transferring the developed toner image to a transfer material, and a fixing device for fixing the transferred toner image to the transfer material. An image forming apparatus comprising: 22. An optical scanning device according to claim 13, further comprising: a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device. An image forming apparatus comprising: 23. A plurality of optical scanning devices according to claim 13, wherein a plurality of light beams emitted from each scanning optical device are guided on a corresponding plurality of image carrier surfaces. A color image forming apparatus that forms a color image by scanning each of the plurality of image carriers with the plurality of light beams.