JP2001318335A - Device and method for optical scanning and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To makes light reflected by a transparent plate, closing the window of the housing of an optical deflector, not operate as ghost light during an optical scan. SOLUTION: The luminous flux from the side of a light source 1 is made incident on the deflecting and reflecting surface of the optical deflector 11 through the parallel flat plate type transparent plate 9 closing the window provided to the housing 7 containing the optical deflector 11 deflecting reflected luminous flux by swinging or rotating its deflecting and reflecting surface and the deflected luminous flux from the deflecting and reflecting surface is projected and converged on a scanned surface 17 by scanning image formation optical systems 13 and 15 to form a light spot on the scanned surface, thus optically scanning the scanned surface 17. Between the incidence position D of the luminous flux from the side of the light source 1 and the projection area of the deflected luminous flux on the transparent plate 9, a light shield member 31 which shields the scanning image formation optical systems from the reflected luminous flux from the transparent plate 9 as to the luminous flux from the light source side is arranged closely to or in contact with the external surface of the transparent plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical scanning device, an optical scanning method, and an image forming apparatus.

[0002]

2. Description of the Related Art A light beam from a light source is deflected by an optical deflector, and the deflected light beam is condensed toward a surface to be scanned by a scanning image forming optical system to form a light spot on the surface to be scanned. Optical scanning devices that optically scan a surface are widely known in relation to digital copying machines, optical printers, facsimile machines, and the like. As a light deflector used in such an optical scanning device, a light deflector generally reflecting a light beam from a light source side by a deflecting / reflecting surface and rotating or swinging the deflecting / reflecting surface at high speed is generally used. . Such an optical deflector has a housing to prevent dust from adhering to the drive unit and the deflecting / reflecting surface, or to prevent mechanical noise and wind noise accompanying high-speed rotation and high-speed swing from leaking to the outside. In many cases, a light beam enters from a light source side and a deflected light beam is emitted through a parallel plate-shaped transparent plate that is housed in a housing and covers a window provided in a housing. In such a case, light reflected by the transparent plate closing the window of the housing may become ghost light and reach the surface to be scanned, forming a so-called ghost image. In this case, the ghost image is generally a “straight black streak” extending in the sub-scanning direction.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent light reflected by the transparent plate from acting as ghost light in optical scanning.

[0004]

An optical scanning apparatus to which the present invention is applied is a "parallel flat plate for closing a window provided in a housing for housing an optical deflector for deflecting a reflected light beam by swinging or rotating a deflecting / reflecting surface. The light beam from the light source is made incident on the deflecting / reflecting surface of the optical deflector through the transparent plate, and the deflecting light beam is emitted by the deflecting / reflecting surface. The emitted deflecting light beam is scanned by the scanning image forming optical system. An optical scanning device that forms a light spot on the surface to be scanned by converging light toward the surface and performs optical scanning on the surface to be scanned ”. As the “light source”, an appropriate one conventionally known as a light source for an optical scanning device,
For example, various gas lasers, solid-state lasers, LEDs and the like can be used, and a semiconductor laser can be mentioned as the most practical and general light source. When a semiconductor laser is used as a light source, the emitted divergent light beam is converted into a light beam form (parallel light beam, condensed light beam, weakly divergent light beam, etc.) suitable for an optical scanning optical system, A coupling optical system such as a coupling lens is used.
The "optical deflector" is of the type "deflecting the reflected light beam by swinging or rotating the deflecting / reflecting surface" as described above. As a device that performs deflection by swinging the deflection reflection surface, a well-known “galvanometer mirror” can be used. In addition, examples of a device that performs deflection by rotating the deflecting reflection surface include a rotating polygon mirror, a rotating single mirror, and a rotating two-surface mirror. The optical deflector is housed in a housing to prevent dust from adhering to the deflecting / reflecting surface and to prevent driving noise and wind noise from the outside. The emission of the deflecting light beam by the deflecting reflection surface is performed through a “parallel flat transparent plate that closes a window provided in the housing”. As the “parallel plate-shaped transparent plate”, a transparent glass plate or a transparent plastic plate can be used. The deflected light beam is converged toward the surface to be scanned by the scanning image forming optical system. Then, a light spot formed on the surface to be scanned by the condensed light beam optically scans the surface to be scanned. The “scanning optical system” can be composed of one or more lenses, can be composed of an imaging mirror having an imaging function, or can be one or more lenses and one or more imaging mirrors. It can also be configured as a complex system. In order to correct "surface tilt" in the optical deflector, a "line image forming optical system"
By using, a light beam from the light source side is imaged as a `` long line image in the main scanning direction '' at a position near the deflecting reflection surface of the optical deflector,
The scanning image forming optical system can be an anamorphic optical system that sets the “scanned surface and the position of the deflecting / reflecting surface to be geometrically optically conjugate” in the sub-scanning direction.

As the line image forming optical system, a cylindrical lens having a positive power, a concave cylindrical mirror, or the like can be used. The “scanned surface” is a surface that receives light scanning by a light spot, and is actually a photosensitive surface of a “photosensitive medium” such as a photoconductive photosensitive member. The moving direction of the light spot on the surface to be scanned is the main scanning direction, and the direction orthogonal to the main scanning direction on the surface to be scanned is the sub-scanning direction, but in this specification, the light path from the light source to the surface to be scanned is At any position, directions corresponding to the main / sub scanning directions are referred to as a main scanning direction and a sub scanning direction. The photosensitive surface of the photosensitive medium as the substance to be scanned undergoes sub-scanning while being displaced in the sub-scanning direction. The optical scanning device according to the first aspect has the following features. That is, when the principal ray of the deflected light beam deflected by the deflecting reflection surface is in a direction orthogonal to the main scanning line (trajectory of the light spot) on the surface to be scanned, the direction matching the principal ray is referred to as a “reference principal ray”. Direction. The angle formed between the principal ray of the light beam incident from the light source (via the transparent plate) on the deflecting reflecting surface and the reference principal ray direction is defined as “θ ₂ ”. Further, in the deflecting surface (the surface swept by the principal ray of the deflected light beam ideally deflected by the optical deflector), the inclination angle of the transparent plate with respect to the direction orthogonal to the reference principal ray direction is “θ ₃ ” the reference principal ray direction and angle principal rays in the deflection plane of the reflected light beam by the transparent plate of the light beam from the side "theta ₁ '
And Angle: θ ₁ = θ ₂ -2θ ₃ . Regarding the optical axis of the scanning image forming optical system, the angle formed by the “principal ray of the deflected light beam toward the end of the scanning area on the same side as the reflected light beam” with the reference principal ray direction is “θ ₀ ”. These corners: and theta ₁ and theta ₀ is the relation: ₍₁₎ θ 1> so as to satisfy theta _0, angle: theta _0, transparent plate tilt angle with respect to theta _1: theta ₃ is set . In the optical scanning device according to the first aspect, with respect to the optical axis of the scanning and imaging optical system, the side on which the light beam from the light source enters can be referred to as the "optical scanning start side" (claim 2).

The optical scanning device according to claim 3 has the following features.
Have signs. That is, various angles defined as above: θ
₀, Θ₁, Θ_Two, Θ_ThreeAt the angle: θ ₁And θ₀Is related to: (2) θ₁≤θ₀ So that the angle: θ₀, Θ₁The inclination of the transparent plate against
Angle: θ_ThreeIs set. Then, the "light source"
Between the incident position of the light beam from the side and the exit area of the deflected light beam.
`` Between '', the light flux reflected from the light source side by the transparent plate
The light-shielding member that shields the image forming optical system
It has it close to or in contact with the surface. This claim 3
In the optical scanning device, the light shielding member is referred to as a “transparent plate
Part of the fixing member to be fixed to the
(Claim 4). The optical scanning device according to claim 5 is an optical scanning device.
3. The optical scanning device according to claim 3, wherein the scanning image forming optical system is a lens.
System, and “the deflection area of the deflected light beam emitted from the transparent plate
Along the outside, the most light polarization of the scanning imaging
A pair of radiators formed radially toward the lens surface on the director side
Wall-shaped member ". One end of each of the pair of wall members
Position the transparent plate in contact with the outer surface of the transparent plate.
The other end touches the lens surface to position the lens surface
Has ability. Then, of the pair of wall-shaped members,
Are located on the side where these light beams enter the transparent plate ''
Also serves as a member. In the optical scanning device according to claim 5,
Has assembled a pair of wall-like members with the optical system of the optical scanning device.
Can be formed as part of a casing that is
(Claim 6). The optical scanning method according to the present invention is based on the following:
Optical deflector that deflects the reflected light beam by swinging or rotating
Parallel plate that closes the window provided in the housing that houses
The light flux from the light source side passes through the transparent plate of
Incident on the reflective surface and deflection by the reflective surface
The light beam is emitted and the emitted deflected light beam is sent to the scanning imaging optical system.
The light is focused toward the surface to be scanned, and the light spot
Optical scanning method of forming a slit and performing optical scanning of the surface to be scanned "
is there. The optical scanning method according to claim 7 is such an optical scanning method.
The method uses the optical scanning device according to claim 1 or 2.
9. The optical scanning method according to claim 8, wherein
An optical scanning method according to any one of claims 3 to 6, wherein the optical scanning method is an optical scanning method.
It is characterized by performing using an apparatus.

An image forming apparatus according to the present invention is configured such that “optical scanning is performed by an optical scanning device on a photosensitive surface of a photosensitive medium to form a latent image,
An image forming apparatus that visualizes a latent image to obtain an image. According to a ninth aspect of the present invention, there is provided an image forming apparatus using the optical scanning device according to the first or second aspect as an optical scanning device for optically scanning a photosensitive surface of a photosensitive medium. An image forming apparatus according to a tenth aspect is characterized in that the optical scanning device for optically scanning a photosensitive surface of a photosensitive medium uses the optical scanning device according to any one of the third to sixth aspects. 11. The image forming apparatus according to claim 9, wherein the photosensitive medium is a "photoconductive photoreceptor", and an electrostatic latent image formed by uniform charging of a photosensitive surface and optical scanning by an optical scanning device is a toner image. It can be configured to be visualized as (claim 11). The toner image is recorded on a sheet-shaped recording medium (transfer paper or “OHP sheet (plastic sheet for overhead projector)
Etc.). In the image forming apparatus according to the ninth or tenth aspect, for example, a "silver salt photographic film" can be used as the photosensitive medium. In this case, the latent image formed by the optical scanning by the optical scanning device can be visualized by a normal silver halide photographic process. Such an image forming apparatus can be implemented as, for example, an "optical plate making apparatus" or an "optical drawing apparatus". An image forming apparatus according to claim 11, specifically, a laser printer, a laser plotter, a digital copying apparatus,
It can be implemented as a facsimile machine or the like.

[0008]

Embodiments of the present invention will be described below. In FIG. 1A, a light source 1 is a “semiconductor laser” and emits a divergent light beam. This divergent light beam is converted into a light beam form suitable for the following optical system by a coupling lens 3 forming a “coupling optical system”, for example, a “parallel light beam”, a condensed light beam, or a “slightly divergent light beam”. Is done. In the following description, for the sake of specificity, it is assumed that the operation of the coupling lens 3 is a collimating operation, and the coupled light beam is a parallel light beam. The coupled light flux is then condensed in a sub-scanning direction (a direction perpendicular to the drawing) by a cylindrical lens 5 which is a “line image forming optical system”, and a rotating polygon mirror 11 as an “optical deflector”. Incident on the deflecting / reflecting surface. A rotating polygon mirror 11 as an optical deflector is housed in a housing 7, and a window provided in the housing 7 is closed by a transparent plate 9 which is a “parallel flat glass plate”. The light beam from the light source side converges in the sub-scanning direction, passes through the transparent plate 9, and forms a long line image in the main scanning direction near the deflection reflection surface. The light beam reflected by the deflecting reflection surface is emitted as a parallel light beam in the main scanning direction and as a divergent light beam in the sub-scanning direction, passes through the transparent plate 9 and exits out of the housing. Are sequentially transmitted through the lenses 13 and 15, and are condensed toward the surface to be scanned 17 by the action of the lenses 13 and 15 to form a light spot on the surface to be scanned 17. When the rotary polygon mirror 11 rotates at a constant speed in the direction of the arrow, the light beam reflected by the deflecting / reflecting surface becomes a deflecting light beam deflected at a constant angular speed, and the light spot optically scans the surface 17 to be scanned. The scanning image forming optical system constituted by the lenses 13 and 15 has an “fθ function” in order to make the optical scanning uniform. In FIG. 1A, an area indicated by a symbol L is a “scanning area”. The position indicated by the symbol A is a position where writing by optical scanning is started. To align the writing start position A, a deflection light beam is detected by the photo sensor 20 via the mirror 19 prior to the start of writing, and the photo sensor 20
, A synchronization signal for starting writing is issued. The write start position A is determined by the synchronization signal. The position indicated by the symbol B is the write end position. Therefore, the “scanning area” is an area where the deflected light beam optically scans from when the photosensor 20 detects the deflected light beam to when writing is completed.

The optical scanning device described above with reference to FIG. 1A is a parallel plate that closes a window provided in a housing 7 that houses an optical deflector 11 that deflects a reflected light beam by rotating a deflecting / reflecting surface. A light beam from the light source 1 side is made incident on the deflecting / reflecting surface of the optical deflector 11 through the transparent plate 9 in the shape of
The deflecting light beam is emitted by the deflecting reflection surface, and the emitted deflecting light beam is condensed toward the surface to be scanned 17 by the scanning and imaging optical systems 13 and 15 to form a light spot on the surface to be scanned 17 and to be scanned. 17 is an optical scanning device that performs optical scanning.
FIG. 1B is a diagram for explaining a characteristic portion of the embodiment shown in FIG. When the principal ray of the deflected light beam deflected by the deflecting reflection surface is in a direction orthogonal to the main scanning line on the surface to be scanned, the “direction that matches the principal ray” is referred to as a reference principal ray direction. This is indicated by PL in FIG. The reference principal ray direction PL corresponds to the lens 13 in the embodiment being described.
And the optical axis of The angle between the reference principal ray direction PL and the principal ray of the light beam incident on the deflecting reflection surface from the light source side is “θ ₂ ”, and the reference principal ray in the deflecting plane (in the drawing of FIG. 1B). The angle of inclination of the transparent plate 9 with respect to the direction N perpendicular to the light beam direction PL is “θ ₃ ”,
The angle formed by the principal ray R of the reflected light beam with the reference principal ray direction PL in the deflection plane is “θ ₁ ”. Angle: θ ₁ is the angle:
θ ₂ , θ ₃ and θ ₁ = θ ₂ -2θ ₃ . Further, with respect to the optical axis (matching PL) of the scanning image forming optical system, on the same side as the reflected light beam (having the main light beam R), the main light beam F of the deflected light beam heading toward the end B of the scanning area is used as a reference. Principal ray direction P
The angle formed with L is “θ ₀ ”. In the optical scanning device according to the embodiment shown in FIG. 1, the angles: θ ₁ and θ ₀ are related by:
(1) An angle: θ ₀ and an inclination angle: θ ₃ of the transparent plate 9 with respect to θ ₁ are set so as to satisfy θ ₁ > θ ₀ (claim 1). When the above condition is satisfied, as shown in FIG. 1A, “a light beam reflected by the transparent plate 9 from the light source side”
Is located outside the writing end position B in the scanning area L, so that a ghost image is not generated for an image written by optical scanning. That is, the light beam reflected by the transparent plate 9 is rendered harmless.

In the embodiment shown in FIG. 1, writing by optical scanning is started at a writing start position A. This writing start side is determined by the "optical axis of the scanning imaging optical system (coordinate with the reference principal ray direction PL). (A side on which the light beam from the light source 1 enters). In the embodiment of FIG. 1, it is possible to reverse the direction of rotation of the rotary polygon mirror 11 and set the side at position B in the drawing as the writing start side. However, the angles: θ ₁ and θ ₀ are related as follows: (1) Since θ ₁ > θ ₀ is satisfied, the light beam reflected by the transparent plate 9 and the deflected light beam traveling to the position B intersect near the position B.
For this reason, the arrangement of the detection system is limited in order to prevent the reflected light flux from entering the detection system (similar to the mirror 19 and the photo sensor 20) for detecting the synchronization light. As shown in FIG. 1, if the position A is the write start side, there is no such restriction on the arrangement of the detection system, and the degree of freedom of the layout of the detection system is large. FIG. 2 shows another embodiment of the present invention. In order to avoid complication, the same reference numerals as those in FIG. In this embodiment, as shown in FIG. 2A, the principal ray of the deflected light beam deflected by the deflective reflection surface is:
When a direction that matches the principal ray when the direction is orthogonal to the main scanning line on the scanned surface 17 is referred to as a reference principal ray direction, the reference principal ray direction PL and the light source 1 side incident on the deflecting / reflecting surface will be referred to. The angle between the light beam and the principal ray is “θ ₂ ”, the inclination angle of the transparent plate 9 with respect to the direction N orthogonal to the reference principal ray direction PL in the deflection plane is “θ ₃ ”, and the angle of the light beam from the light source 1 is The angle between the principal ray R of the light beam reflected by the transparent plate 9 and the reference principal ray direction PL in the deflection plane is represented by “θ ₁ (= θ ₂ −2).
θ ₃ ) ", with respect to the optical axis (PL) of the scanning image forming optical system, on the same side as the reflected light beam (R), the angle formed by the principal ray F of the deflected light beam toward the end of the scanning area L with the reference principal ray direction. To “θ
₀ ", the angle: θ ₁ and θ ₀ are related by: (2)
In order to satisfy θ ₁ ≦ θ ₀ , the angle θ ₀ and the inclination angle θ ₃ of the transparent plate 9 with respect to θ ₁ are set (claim 3).

Therefore, the position C at which the “light flux from the light source side” reflected by the transparent plate 9 reaches the surface to be scanned 17 is
This is inside the writing end position B in the scanning area L, and therefore, unless some precautionary measures are taken, the reflected light beam acts as ghost light and generates a ghost image in the written image. Therefore, in this embodiment, FIG.
As shown in (b), between the incident position D of the light beam (having a light beam width of about 4.5 mm in the main scanning direction) from the light source 1 side and the emission area E of the deflected light beam on the transparent plate 9. A light-shielding member 31 that shields a light beam reflected by the transparent plate 9 from the transparent plate 9 with respect to the scanning image forming optical system is brought into contact with the outer surface of the transparent plate 9 (if the reflected light beam can be blocked, the light-shielding member 31 is brought into proximity instead of being brought into contact) (Claim 3). This makes it possible to completely prevent the “light flux from the light source side” reflected by the transparent plate 9 from acting as ghost light. As shown in FIG.
1 is formed as a part of the frame 30. The frame 30 is a fixing member for fixing the transparent plate 9 to the housing 7 as shown in FIG. That is, the light blocking member 3
1 is formed as a part of a fixing member for fixing the transparent plate 9 to the housing 7 (claim 4). FIG. 3 shows another embodiment of the present invention. In order to avoid complication, the same reference numerals as those in FIG. Angles in the drawing: θ ₀ , θ ₁ , θ ₂ , and θ ₃ are the same as those in FIG. 2, and the luminous flux from the light source 1 is
Since the light is reflected from the transparent plate 92 so as to “incident at the position C of the scanning area”, the light acts as ghost light and generates a ghost image unless some preventive measures are taken. In this embodiment, the scanning image forming optical system is a lens 1
Since the lens system is composed of lenses 3 and 15, FIG.
As shown in (b), along the outside of the deflection region of the deflected light beam emitted from the transparent plate 9, radially from the transparent plate 9 side toward the lens surface 13 A of the scanning image forming optical system closest to the optical deflector. A pair of the formed wall members 41 and 42 were provided.

One end of each of the pair of wall members 41 and 42 contacts the outer surface of the transparent plate 9 to position the transparent plate 9, and the other end thereof contacts the lens surface 13A to form a lens. Face 13
A has a function of positioning A, and a pair of wall-shaped members 41, 4
Of the two, the one located on the side where the light flux from the light source side enters the transparent plate (the wall-shaped member 41) also serves as a light shielding member (claim 5). The wall members 41 and 42 are formed as a part of a casing into which the optical system of the optical scanning device is assembled (claim 6). That is, in the case of a resin casing, for example, the wall-shaped member is formed as a part of the casing by "molding integrally with the casing body". Since the wall-shaped member 41 also functions as a light-shielding member, it is possible to prevent the light beam reflected by the transparent plate 9 from acting as ghost light. When the optical scanning device (the first and second aspects) shown in the embodiment in FIG. 1 is used, a window provided in the housing 7 that houses the optical deflector 11 that deflects the reflected light beam by rotating the deflecting / reflecting surface is closed. The light beam from the light source 1 is made incident on the deflecting / reflecting surface of the optical deflector 11 via the parallel plate-shaped transparent plate 9 and the deflecting light beam is emitted by the deflecting / reflecting surface. Optical system 13,
3. The light scanning method according to claim 1, wherein the light is converged toward the surface to be scanned 17 by a light source 15 to form a light spot on the surface to be scanned 17, and optically scans the surface to be scanned 17. What is performed using a scanning device (claim 7) is implemented.
When the optical scanning device (claims 3 to 6) according to the embodiment shown in FIG. 2 or FIG. The light beam from the light source 1 is made incident on the deflecting / reflecting surface of the optical deflector 11 via the parallel plate-shaped transparent plate 9 closing the window provided, and the deflecting light beam by the deflecting / reflecting surface is emitted. The light beam is scanned by the scanning imaging optical systems 13 and 15.
The light is condensed toward the scanned surface 17 by the
An optical scanning method in which an optical spot is formed thereon and an optical scanning of the scanned surface 17 is performed using the optical scanning device according to any one of claims 3 to 6 (claim 8). Will be implemented.

Finally, an embodiment of the image forming apparatus will be described with reference to FIG. This image forming apparatus is a “laser printer”. The laser printer 100 uses the photosensitive medium 1
Reference numeral 11 denotes a “photoconductive photoconductor formed in a cylindrical shape”. Around the photosensitive medium 111, a charging roller 112 as a charging unit, a developing device 113, a transfer roller 1
14. A cleaning device 115 is provided. A well-known "corona charger" can be used as the charging means. Further, the optical scanning device 11 using the laser beam LB
7 is provided to perform “exposure by optical writing” between the charging roller 112 and the developing device 113.
In FIG. 4, reference numeral 116 denotes a fixing device, reference numeral 118 denotes a cassette, reference numeral 119 denotes a pair of registration rollers, reference numeral 120 denotes a paper feed roller, reference numeral 121 denotes a conveyance path, reference numeral 122 denotes a pair of discharge rollers, reference numeral 123 denotes a tray, and reference numeral P Denotes transfer paper as a recording medium. When performing image formation, the photosensitive medium 111, which is a photoconductive photoconductor, is rotated clockwise at a constant speed, and the surface thereof is uniformly charged by the charging roller 112.
An electrostatic latent image is formed by exposure of the laser beam LB of the optical scanning device 117 by optical writing. The formed electrostatic latent image is a so-called “negative latent image”, and the image portion is exposed.
This electrostatic latent image is reversely developed by the developing device 113,
A toner image is formed on the image carrier 111. Transfer paper P
Is detachable from the main body of the image forming apparatus 100. When the cassette 118 is mounted as shown in FIG.
0 is fed. The fed transfer paper P has its leading end held by a pair of registration rollers 119. The registration roller pair 119 sends the transfer paper P to the transfer portion in synchronization with the timing at which the toner image on the image carrier 111 moves to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer section, and the toner image is electrostatically transferred by the operation of the transfer roller 114. The transfer paper P on which the toner image has been transferred is sent to the fixing device 116 and the fixing device 1
At 16, the toner image is fixed, and is discharged onto a tray 123 by a discharge roller pair 122 through a conveyance path 121. The surface of the image carrier 111 after the transfer of the toner image is cleaned by the cleaning device 115 to remove residual toner, paper dust, and the like.

The above-described OHP sheet or the like can be used instead of the transfer paper, and the transfer of the toner image can be performed via an “intermediate transfer medium” such as an intermediate transfer belt. As the optical scanning device 117, FIG.
Alternatively, good image formation can be performed by using the optical scanning device described with reference to FIG. Therefore,
This image forming apparatus is an image forming apparatus that forms a latent image by performing optical scanning by a light scanning device 117 on a photosensitive surface of a photosensitive medium 111 and visualizes the latent image to obtain an image. As the optical scanning device 117 that performs the optical scanning of (1), the device described in claim 1 or 2 can be used (claim 9), and the device described in any one of claims 3 to 6 can be used. (Claim 10). In this image forming apparatus, the photosensitive medium 111 is a photoconductive photoconductor, and an electrostatic latent image formed by uniform charging of the photosensitive surface and optical scanning by the optical scanning device is visualized as a toner image. (Claim 11). Although the single beam system has been described above as the optical scanning device, the present invention can also be applied to a multi-beam optical scanning device. As the optical deflector, a rotating single-sided mirror or a rotating two-sided mirror can be used instead of the rotating polygonal mirror described in each of the embodiments. It can also be used.

[0015]

As described above, according to the present invention, a novel optical scanning device, optical scanning method, and image forming apparatus can be realized. According to the optical scanning device and the optical scanning method of the present invention,
As described above, since the reflected light beam by the parallel flat transparent plate provided in the housing of the optical deflector does not act as ghost light, it is possible to realize good optical scanning without generation of a ghost image, and the image forming apparatus of the present invention By using such an optical scanning device, it is possible to realize good image formation without generating a ghost image.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of the invention of an optical scanning device.

FIG. 2 is a diagram for explaining another embodiment of the invention of the optical scanning device.

FIG. 3 is a diagram for explaining another embodiment of the invention of the optical scanning device.

FIG. 4 is a diagram for explaining an embodiment of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source (semiconductor laser) 3 Coupling lens 5 Cylindrical lens 7 Housing 9 Transparent plate 11 Rotating polygon mirror 13, 15 Lens which comprises a scanning imaging optical system 17 Scanning surface 19 Mirror 20 Photo sensor

Claims (11)

[Claims] 1. Reflection by swinging or rotation of a deflecting / reflecting surface
Provided in the housing that houses the light deflector that deflects the light beam
Through the parallel plate-shaped transparent plate that covers the window
When these light beams are incident on the deflecting and reflecting surface of the optical deflector,
In both cases, the deflecting light beam from the deflecting reflection surface is emitted and emitted.
The emitted deflection light beam is directed to the surface to be scanned by the scanning image forming optical system.
To form a light spot on the surface to be scanned,
In the optical scanning device for optically scanning the surface to be scanned, the principal ray of the deflecting light beam deflected by the deflecting reflecting surface is
When the direction is orthogonal to the main scanning line on the inspection surface,
When the direction matching the ray is called the reference chief ray direction,
From the direction of the principal ray and from the light source side incident on the deflecting reflection surface
The angle between the light beam and the principal ray is θ_TwoIn the plane of deflection
Of the transparent plate in a direction orthogonal to the reference principal ray direction.
The tilt angle is θ_ThreeAnd the transparent plate of the light flux from the light source side.
The principal ray of the reflected light beam is reflected in the deflection plane by the reference principal ray.
Angle between the direction and θ₁(= Θ_Two-2θ _Three), The scanning image light
On the same side of the optical axis of the academic system as the reflected light beam,
The principal ray of the deflected light beam traveling toward the end of the inspection area is the reference principal light.
Angle between the line direction and θ₀And the angle: θ₁And θ₀And
Relationship: (1) θ₁> Θ₀ So that the above angle: θ₀, Θ₁Transparent above
Plate tilt angle: θ_ThreeOptical scanning characterized by the setting
apparatus. 2. The optical scanning device according to claim 1, wherein a side on which a light beam from a light source side enters is an optical scanning start side with respect to an optical axis of the scanning image forming optical system. . 3. Reflection by swinging or rotation of a deflecting / reflecting surface.
Provided in the housing that houses the light deflector that deflects the light beam
Through the parallel plate-shaped transparent plate that covers the window
When these light beams are incident on the deflecting and reflecting surface of the optical deflector,
In both cases, the deflecting light beam from the deflecting reflection surface is emitted and emitted.
The emitted deflection light beam is directed to the surface to be scanned by the scanning image forming optical system.
To form a light spot on the surface to be scanned,
In the optical scanning device for optically scanning the surface to be scanned, the principal ray of the deflecting light beam deflected by the deflecting reflecting surface is
When the direction is orthogonal to the main scanning line on the inspection surface,
When the direction matching the ray is called the reference chief ray direction,
From the direction of the principal ray and from the light source side incident on the deflecting reflection surface
The angle between the light beam and the principal ray is θ_TwoIn the plane of deflection
Of the transparent plate in a direction orthogonal to the reference principal ray direction.
The tilt angle is θ_ThreeAnd the transparent plate of the light flux from the light source side.
The principal ray of the reflected light beam is reflected in the deflection plane by the reference principal ray.
Angle between the direction and θ₁(= Θ_Two-2θ _Three), The scanning image light
On the same side of the optical axis of the academic system as the reflected light beam,
The principal ray of the deflected light beam traveling toward the end of the inspection area is the reference principal light.
Angle between the line direction and θ₀And the angle: θ₁And θ₀And
Relation: (2) θ₁≤θ₀ So that the above angle: θ₀, Θ₁Transparent above
Plate tilt angle: θ_ThreeThe incident position of the light flux from the light source side on the transparent plate,
The light flux from the light source side between the deflected light flux emission area
Shields the light beam reflected by the transparent plate from the scanning image forming optical system
The light shielding member close to or in contact with the outer surface of the transparent plate.
An optical scanning device, comprising: 4. The optical scanning device according to claim 3, wherein the light shielding member is formed as a part of a fixing member for fixing the transparent plate to the housing. 5. The optical scanning device according to claim 3, wherein the scanning image forming optical system is a lens system, and the scanning image forming optical system is arranged from the transparent plate side along the outside of the deflection area of the deflected light beam emitted from the transparent plate. The system has a pair of wall members formed radially toward the lens surface closest to the optical deflector, and one end of each of the pair of wall members is in contact with the outer surface of the transparent plate. The other end portion has a function of positioning the lens surface by abutting on the lens surface, and the light flux from the light source side of the pair of wall members is transparent plate. An optical scanning device, wherein the device located on the side where light is incident also serves as a light blocking member. 6. The optical scanning device according to claim 5, wherein the pair of wall members are formed as a part of a casing into which an optical system of the optical scanning device is assembled. 7. A light beam from a light source side is transmitted through a parallel plate-shaped transparent plate that covers a window provided in a housing that houses a light deflector that deflects a reflected light beam by swinging or rotating a deflecting / reflecting surface. While being incident on the deflecting / reflecting surface of the optical deflector, the deflecting light beam from the deflecting / reflecting surface is emitted, and the emitted deflecting light beam is condensed toward the surface to be scanned by the scanning image forming optical system, and is converged on the surface to be scanned. Form a light spot on the
An optical scanning method for optically scanning the surface to be scanned, wherein the optical scanning method is performed using the optical scanning device according to claim 1. 8. A light beam from a light source side is transmitted through a parallel plate-shaped transparent plate that covers a window provided in a housing that houses a light deflector that deflects a reflected light beam by swinging or rotating a deflecting / reflecting surface. While being incident on the deflecting / reflecting surface of the optical deflector, the deflecting light beam from the deflecting / reflecting surface is emitted, and the emitted deflecting light beam is condensed toward the surface to be scanned by the scanning image forming optical system, and is converged on the surface to be scanned. Form a light spot on the
An optical scanning method for optically scanning the surface to be scanned, wherein the optical scanning method is performed using the optical scanning device according to any one of claims 3 to 6. 9. An image forming apparatus for forming a latent image by performing optical scanning on a photosensitive surface of a photosensitive medium with an optical scanning device and visualizing the latent image to obtain an image, wherein the light on the photosensitive surface of the photosensitive medium is provided. An image forming apparatus comprising: an optical scanning device that performs scanning; 10. An image forming apparatus for forming a latent image by performing optical scanning on a photosensitive surface of a photosensitive medium by an optical scanning device and visualizing the latent image to obtain an image, wherein the light on the photosensitive surface of the photosensitive medium is obtained. An image forming apparatus, comprising: an optical scanning device that performs scanning, wherein the optical scanning device according to any one of claims 3 to 6 is used. 11. An image forming apparatus according to claim 9, wherein the photosensitive medium is a photoconductive photoreceptor, and an electrostatic latent image formed by uniform charging of a photosensitive surface and optical scanning by an optical scanning device. But,
An image forming apparatus which is visualized as a toner image.