JP2012159528A - Optical scanning device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanning device that can suppress influence of reflection light and scattered light without causing increase of the number of parts and size of the device, and an image forming device including the optical scanning device.SOLUTION: A printer 1 comprises: a laser diode 111 for outputting a light beam; a polygon mirror 130 for deflecting and scanning the light beam; a system 150 having a first fθ lens 151 arranged while facing the polygon mirror 130, and a second fθ lens 153 arranged apart from the polygon mirror 130 than the first fθ lens 151, guiding the light beam deflected and scanned by the polygon mirror 130 onto a surface to be scanned, and imaging the light beam; and a light shielding section 230 arranged between the polygon mirror 130 and the first fθ lens 151 and on a light path of the light beam deflected and scanned by the polygon mirror 130, and suppressing reflection of the light beam toward the first fθ lens 151.

Description

  The present invention relates to an optical scanning device and an image forming apparatus including the optical scanning device.

  Conventionally, as an image forming apparatus such as a printer or a copier, a photosensitive drum whose surface is chargeable, an optical scanning device (optical writing device) that forms an electrostatic latent image on the surface of the photosensitive drum, and an electrostatic latent image There is a type provided with a developing device for developing the toner.

The optical scanning device deflects and scans the light beam output from the light source with an optical deflector, thereby forming an electrostatic latent image on the surface (scanned surface) of the photosensitive drum.
Here, in the optical scanning device, a ghost image or the like may be generated due to reflected / scattered light (stray light, flare light) generated when the light beam is reflected / scattered by various members or the like.

  On the other hand, an image forming apparatus that suppresses the influence of reflected light and scattered light by attaching a light shielding member to the fθ lens has been proposed (see, for example, Patent Document 1).

JP 2006-106694 A

However, in the image forming apparatus of Patent Document 1, since the light shielding member is attached to the fθ lens, there are problems that the cost increases due to an increase in the number of parts and the assemblability deteriorates.
Further, in the image forming apparatus, in order to suppress the generation of reflected light / scattered light, it is necessary to increase the size of the shielding member itself, which makes it difficult to reduce the size.

An object of the present invention is to provide an optical scanning device capable of suppressing the influence of reflected light and scattered light without increasing the number of parts and increasing the size.
Another object of the present invention is to provide an image forming apparatus including the optical scanning device.

  The present invention relates to a light source that outputs a light beam, an optical deflector that deflects and scans the light beam output from the light source, a first lens disposed opposite to the optical deflector, and the first lens. An optical system having a second lens spaced apart from the optical deflector and guiding the light beam deflected and scanned by the optical deflector onto a scanned surface; and the optical deflector. An optical scanning device comprising: a light shielding portion disposed on an optical path of the light beam deflected and scanned by the optical deflector between the first lens and suppressing reflection of the light beam toward the first lens side; Relates to the device.

  In the optical scanning device, it is preferable that the light shielding portion is disposed on the upstream side of the scanning, outside the effective scanning region and in proximity to the outer edge of the effective scanning region.

  Further, in the optical scanning device, the light shielding portion is disposed to face the optical deflector, and is subjected to a rough surface treatment for preventing the light beam from the optical deflector from being reflected toward the first lens side. It preferably has a light shielding surface.

  In the optical scanning device, the light shielding unit is disposed to face the optical deflector, and is a planar or curved light shield for preventing the light beam from the optical deflector from being reflected toward the first lens. It is preferable to have a surface.

  In the optical scanning device, the light shielding surface is formed such that an angle formed between the light beam from the optical deflector and a portion closer to the effective scanning area than the position irradiated with the light beam is vertical or acute. It is preferred that

  In the optical scanning device, it is preferable that the light shielding portion has a sharp end on the effective scanning region side.

  Preferably, the optical scanning device includes a case member that accommodates the light source, the optical deflector, and the optical system, and the light shielding portion is formed integrally with the case member.

  The present invention relates to an image forming apparatus comprising the optical scanning device described above and an image carrier having the scanned surface.

ADVANTAGE OF THE INVENTION According to this invention, the optical scanning apparatus which can suppress the influence of reflected light and scattered light can be provided, without causing the increase in a number of parts, or enlarging.
In addition, according to the present invention, an image forming apparatus including the optical scanning device can be provided.

FIG. 3 is a diagram for explaining an arrangement of components in the printer 1 as an embodiment of the present invention. 2 is a front view illustrating a laser scanner unit 4. FIG. FIG. 3 is a diagram illustrating a configuration of a laser scanner unit 4. FIG. 3 is an enlarged view of a region A in FIG. 2. It is an enlarged view of the area | region B in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus according to the present embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component of the printer 1.

As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a sheet T as a sheet-like transfer material based on predetermined image information. And a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (scanned body), a charging unit 10, and a laser scanner unit as an optical scanning device (optical writing device, exposure unit). 4, a developing device 16, a toner cartridge 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8, and a fixing unit 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a conveyance path H for paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side along the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8. Then, static elimination by the static eliminator 12 and cleaning by the drum cleaning unit 11 are performed.

The photosensitive drum 2 is a cylindrical member. The photosensitive drum 2 has a surface 2a (scanned surface) which is a side surface in a cylindrical shape. The photoreceptor drum 2 functions as a photoreceptor or an image carrier.
The photosensitive drum 2 is disposed so as to be rotatable in the direction of an arrow about a rotation axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path H. An electrostatic latent image can be formed on the surface 2 a of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface 2 a of the photosensitive drum 2. The charging unit 10 uniformly charges the surface 2a of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

The laser scanner unit 4 (optical scanning device) is arranged at a predetermined distance from the surface 2 a of the photosensitive drum 2.
The laser scanner unit 4 includes a laser unit 110, a polygon mirror 130 (light deflector), and an optical system 150 (see FIG. 3).

  The laser scanner unit 4 scans and exposes the surface 2a of the photosensitive drum 2 based on image information input from an external device such as a PC (personal computer). By performing scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface 2 a of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface 2 a of the photosensitive drum 2. The configuration and operation of the laser scanner unit 4 will be described in detail later.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface 2 a of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner contained in the toner cartridge 5 to the developing device 16. The toner supply unit 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a transfer bias applying unit (not shown). The transfer roller 8 is configured to be rotatable while in contact with the photosensitive drum 2.

  A sheet T conveyed through the conveyance path H is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The static eliminator 12 is disposed so as to face the surface 2 a of the photosensitive drum 2. The static eliminator 12 irradiates the surface 2a of the photosensitive drum 2 with light, thereby neutralizing the surface of the photosensitive drum 2 after the transfer is performed (removing charges).

  The drum cleaning unit 11 is disposed to face the surface 2 a of the photosensitive drum 2. The drum cleaning unit 11 removes toner and deposits remaining on the surface 2a of the photosensitive drum 2, and transports the removed toner and the like to a predetermined recovery mechanism for recovery.

  The fixing unit 9 melts and presses the toner constituting the toner image transferred to the paper T and fixes the toner on the paper T. The fixing unit 9 includes a heating rotator 9a heated by a heater and a pressure rotator 9b pressed against the heating rotator 9a. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize the paper T on which the toner image has been transferred, and convey the paper T. By transporting the paper T while being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred onto the paper T is melted and pressurized, and is fixed to the paper T.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. The paper feed cassette 52 is configured to be drawable in the horizontal direction from the right side (the right side in FIG. 1) of the apparatus main body M. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path H by the cassette paper feed unit 51 disposed at the end of the paper feed cassette 52 on the paper feed side (the right end in FIG. 1). The cassette paper feeding unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path H. Is provided.

  On the right side (right side in FIG. 1) of the apparatus main body M, a manual paper feed unit 64 is provided. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the front surface of the apparatus main body M in the closed state, and a paper feed roller 66. The manual feed tray 65 is attached at its lower end to the apparatus body M in the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The paper feed roller 66 feeds the paper T placed on the open manual feed tray 65 to the manual feed path Ha.

  A paper discharge unit 50 is provided on the upper side of the apparatus main body M. The paper discharge unit 50 discharges the paper T to the outside of the apparatus main body M by the third roller pair 53. Details of the paper discharge unit 50 will be described later.

  The transport path H for transporting the paper T includes a first transport path H1 from the cassette paper feeding unit 51 to the transfer nip N, a second transport path H2 from the transfer nip N to the fixing unit 9, and a discharge from the fixing unit 9. A third conveyance path H3 to the section 50, a manual conveyance path Ha that joins the paper supplied from the manual sheet feeding unit 64 to the first conveyance path H1, and a third conveyance path H3 from the downstream side to the upstream side. And a return transport path Hb that reverses the sheet and returns it to the first transport path H1.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path H1. A first branch portion Q1 is provided in the middle of the third transport path H3.
The first joining part P1 is a joining part where the manual feed path Ha joins the first transport path H1. The second junction P2 is a junction where the return conveyance path Hb merges with the first conveyance path H1.
The first branch portion Q1 is a branch portion where the return transport path Hb branches from the third transport path H3, and includes a first roller pair 54a and a second roller pair 54b. One roller of the first roller pair 54a and one roller of the second roller pair 54b are combined.

  In the middle of the first transport path H1 (specifically, between the second joining portion P2 and the transfer roller 8), a sensor for detecting the paper T, skew correction of the paper T, and image correction A registration roller pair 80 for aligning the timing of forming the toner image in the forming unit GK and the conveyance of the paper T is disposed. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the paper T (upstream in the transport direction). The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

The return conveyance path Hb is a conveyance path that is provided to make the opposite surface (unprinted surface) opposite to the already printed surface to the photosensitive drum 2 when performing duplex printing on the paper T.
According to the return conveyance path Hb, the sheet T conveyed from the first branching section Q1 to the sheet discharge section 50 side by the first roller pair 54a is reversed and returned to the first conveyance path H1 by the second roller pair 54b. , And can be conveyed to the upstream side of the pair of registration rollers 80 arranged on the upstream side of the transfer roller 8. A predetermined toner image is transferred onto the unprinted surface at the transfer nip N on the paper T that is reversed upside down by the return conveyance path Hb.

  A paper discharge unit 50 is formed at the end of the third transport path H3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The paper discharge unit 50 discharges the paper T conveyed on the third conveyance path H3 to the outside of the apparatus main body M by the third roller pair 53.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T formed with a predetermined toner image and discharged from the paper discharge unit 50 are stacked and stacked.
A sheet detection sensor is disposed at a predetermined position in each conveyance path.

Next, the operation of the printer 1 will be briefly described with reference to FIG.
First, a case where single-sided printing is performed on the paper T stored in the paper feed cassette 52 will be described.
The paper T accommodated in the paper feed cassette 52 is sent out to the first transport path H1 by the forward feed roller 61 and the paper feed roller pair 63, and then the registration rollers via the first junction P1 and the first transport path H1. Transported to pair 80.
In the registration roller pair 80, skew correction of the paper T and timing adjustment with the toner image are performed.

The paper T discharged from the registration roller pair 80 is introduced between the photosensitive drum 2 and the transfer roller 8 (transfer nip N) via the first conveyance path H1. A toner image is transferred onto the paper T between the photosensitive drum 2 and the transfer roller 8.
Thereafter, the paper T is discharged from between the photosensitive drum 2 and the transfer roller 8, and the fixing nip between the heating rotator 9a and the pressure rotator 9b in the fixing unit 9 via the second conveyance path H2. To be introduced. Then, the toner TN is melted in the fixing nip, and the toner TN is fixed on the paper T.

Next, the paper T is transported to the paper discharge unit 50 through the third transport path H3 by the first roller pair 54a, and is discharged from the paper discharge unit 50 to the paper discharge stacking unit M1 by the third roller pair 53.
In this way, single-sided printing of the paper T stored in the paper feed cassette 52 is completed.

  When single-sided printing is performed on the paper T placed on the manual feed tray 65, the paper T placed on the manual feed tray 65 is sent out to the manual feed path Ha by the paper feed roller 66, and then the first junction unit It is conveyed to the registration roller pair 80 via P1 and the first conveyance path H1. Subsequent operations are the same as the one-side printing operation of the paper T accommodated in the paper feed cassette 52 described above, and a description thereof will be omitted.

Next, the configuration of the laser scanner unit 4 will be described with reference to FIGS.
FIG. 2 is a front view illustrating the laser scanner unit 4. FIG. 2 is a view of the laser scanner unit 4 seen from the direction of arrow S in FIG. FIG. 3 is a diagram illustrating the configuration of the laser scanner unit 4. FIG. 3 is a diagram in which the case member 200 and the like are removed from the laser scanner unit 4 of FIG. 4 is an enlarged view of region A in FIG. FIG. 5 is an enlarged view of region B in FIG.

  2 and 3, the laser scanner unit 4 includes a laser unit 110, a polygon mirror 130 (light deflector), a polygon mirror driving unit 132 (not shown), an optical system 150, and dust-proof glass. 155, an aspherical mirror 171 and a detection sensor 173.

  The outer shape of the laser scanner unit 4 is formed by the case member 200. In the case member 200, the laser unit 110, the polygon mirror 130 (light deflector), the polygon mirror driving unit 132 (not shown), the optical system 150, the dustproof glass 155, the aspherical mirror 171 and the detection sensor 173 are predetermined. It is accommodated and arranged in a state of being positioned.

  The laser scanner unit 4 operates based on instructions from the image forming control unit 310, the LD control unit 320, the motor control unit 330, and the like.

As shown in FIG. 2 and FIG. 3, the laser unit 110 is arranged with the light output portion facing the polygon mirror 130.
The laser unit 110 includes a laser diode 111 (light source), a collimator lens 112, a first aperture member 113, a cylindrical lens 114, and a second aperture member 115.
In the laser unit 110, the laser diode 111 (light source), the collimator lens 112, the first aperture member 113, the cylindrical lens 114, and the second aperture member 115 are arranged in this order from the upstream side to the downstream side in the optical path direction.

  The laser diode 111 outputs a light beam. The light beam output from the laser diode 111 is output to the polygon mirror 130 via the collimator lens 112, the first aperture member 113, the cylindrical lens 114, and the second aperture member 115.

The laser diode 111 is controlled by the LD control unit 320.
The laser diode 111 is controlled by the LD control unit 320 that receives an instruction from the image formation control unit 310.
The laser diode 111 is controlled by the LD control unit 320 based on a signal from the detection sensor 173.

The polygon mirror 130 (light deflector) deflects and scans the light beam output from the laser scanner unit 4 (laser diode 111).
The polygon mirror 130 is a regular pentagon and is formed in a flat plate shape in a plan view (a direction perpendicular to the paper surface in FIG. 3).
Each surface constituting the side surface of the polygon mirror 130 is processed so as to suitably reflect the light beam (for example, mirror processing).

The polygon mirror 130 is rotated at a constant speed in a predetermined direction (counterclockwise direction in FIGS. 2 and 3) by a polygon mirror driving unit 132 (not shown).
The polygon mirror 130 deflects (reflects) the light beam L0 from the laser unit 110 toward a first fθ lens 151 described later while rotating at a predetermined speed.
The light beam L0 reflected and deflected by the polygon mirror 130 passes through the first fθ lens 151 and the second fθ lens 153, and rotates while being horizontally scanned in a predetermined scanning direction (main scanning direction SC direction in FIGS. 2 and 3). It is guided to an effective exposure position on the surface 2a of the photosensitive drum 2 (see FIG. 1) that rotates about the axis.

  Polygon mirror 130 is not limited to a regular pentagon in plan view, and may be a regular polygon. Further, the rotation direction and rotation speed of the polygon mirror 130 can be appropriately set according to the specifications of the laser scanner unit 4.

The polygon mirror drive unit 132 includes a motor (not shown), a gear (not shown), and the like.
The polygon mirror drive unit 132 drives the polygon mirror 130 to rotate in a predetermined direction (counterclockwise direction in FIGS. 2 and 3) at a constant speed.
The polygon mirror drive unit 132 starts rotation of the polygon mirror 130 and stops rotation of the polygon mirror 130 based on an instruction from the image formation control unit 310.

The optical system 150 includes a first fθ lens 151 (first lens) and a second fθ lens 153 (second lens).
The first fθ lens 151 is disposed to face the polygon mirror 130.
The first fθ lens 151 is disposed at a position closer to the polygon mirror 130 than the second fθ lens 153. The first fθ lens 151 is disposed upstream of the second fθ lens 153 in the optical path direction.
The second fθ lens 153 is arranged farther from the polygon mirror 130 than the first lens. The second fθ lens 153 is disposed downstream of the first fθ lens 151 in the optical path direction.
The optical system 150 guides the light beam deflected and scanned from the polygon mirror 130 onto the surface 2a (scanned surface) of the photosensitive drum 2 to form an image.

Here, the light beam reflected and deflected by the polygon mirror 130 exposes the effective exposure area RA on the surface 2 a of the photosensitive drum 2 through the optical system 150.
The light beam reflected and deflected by the polygon mirror 130 is scanned in the effective scanning area SA. The effective scanning area SA is a scanning area of the light beam when the light beam exposes the effective exposure area RA.

  The dustproof glass 155 is disposed on the downstream side of the optical system 150 in the optical path direction. The dust-proof glass 155 is arranged to prevent toner, dust, and dust from entering the optical system 150. The light beam that has passed through the dustproof glass 155 exposes the surface 2 a of the photosensitive drum 2.

The aspherical mirror 171 has a reflecting surface that reflects the light beam L2 (L2b) toward the detection sensor 173 in order to detect the scanning start position (upstream side in the main scanning direction SC, writing start position) of the effective scanning area SA. It is an aspherical mirror.
The aspherical mirror 171 is disposed outside the effective scanning area SA and on the scanning start position side.
A prism or the like can be used instead of the aspherical mirror.

The detection sensor 173 detects the light beam reflected by the aspherical mirror 171. Accordingly, the detection sensor 173 detects that the light beam is scanned outside the effective scanning area SA and in the vicinity of the scanning start position.
When detecting the light beam, the detection sensor 173 outputs a detection result to the LD control unit 320. The detection sensor 173 is arranged outside the effective scanning area SA and on the scanning end position (downstream side in the main scanning direction SC, writing end position) side.
Note that as the detection sensor 173, various optical sensors such as a photodiode, a phototransistor, and a photo IC can be used.

The image formation control unit 310 controls the image formation unit GK. Further, the image formation control unit 310 controls the LD control unit 320 and the motor control unit 330.
The image formation control unit 310 is based on image information output from an external device (for example, a PC) and input is received by an input reception unit (for example, an input interface unit). The motor control unit 330 is controlled.

The LD control unit 320 controls the laser diode 111.
The LD control unit 320 controls the laser diode 111 based on an instruction from the image formation control unit 310. The LD control unit 320 controls the light emission state of the laser diode 111 based on an instruction from the image formation control unit 310. The LD control unit 320 controls the light emission state during scanning based on an instruction from the image formation control unit 310 based on the image information.

Further, the LD control unit 320 controls the light emission state in the laser diode 111 based on the detection result from the detection sensor 173.
When the LD control unit 320 receives a detection result indicating that the light beam output from the detection sensor 173 has been detected, the LD control unit 320 changes the laser diode 111 from emitting light to not emitting light after a predetermined first time has elapsed. Then, after a predetermined second time longer than the first time elapses, the laser diode 111 is changed from the non-light emitting state to the light emitting state.

The motor control unit 330 controls the polygon mirror driving unit 132. The motor control unit 330 controls a motor that is a drive source constituting the polygon mirror drive unit 132.
The motor control unit 330 controls the motor (polygon mirror driving unit 132) based on an instruction from the image formation control unit 310.
The motor control unit 330 instructs the motor (polygon mirror driving unit 132) to start outputting the rotational driving force that rotates the polygon mirror 130 at a constant speed based on an instruction from the image formation control unit 310, and Instructs the motor to stop outputting the rotational driving force.

  The case member 200 has the laser unit 110, the polygon mirror 130 (light deflector), the polygon mirror driving unit 132 (not shown), the optical system 150, the dust-proof glass 155, the aspherical mirror 171 and the detection sensor 173 at predetermined positions. Is positioned and accommodated.

The case member 200 has a light shielding portion 230.
The light shielding unit 230 is formed integrally with the case member 200. The light shielding portion 230 is formed so as to extend from the polygon mirror holding portion 210 constituting the case member 200.
The light shielding unit 230 is disposed between the polygon mirror 130 and the first fθ lens 151 on the optical path of the light beam L1a (see FIG. 4) deflected and scanned by the polygon mirror 130. The light shielding unit 230 suppresses reflection of the light beam L1a toward the first fθ lens 151 side.

The light shielding unit 230 is disposed outside the effective scanning area SA and in proximity to the outer edge of the effective scanning area SA. The light shielding unit 230 is disposed close to the scanning upstream (writing start position) side of the outer edge of the effective scanning area SA.
The light blocking unit 230 is a portion that is irradiated immediately before the light beam subjected to polarization scanning is irradiated onto the aspherical mirror 171.

The light shielding unit 230 has a light shielding surface 232.
The light shielding surface 232 is disposed to face the polygon mirror 130.
The light shielding surface 232 is a planar light shielding surface for preventing the light beam L1a from the polygon mirror 130 from being reflected toward the first fθ lens 151 side.

The light shielding surface 232 is set to an angle at which the reflected light of the light beam L1a does not enter the first fθ lens 151.
The light shielding surface 232 is, for example, the light beam L1a from the polygon mirror 130 and the portion on the side of the effective scanning area SA from the position irradiated with the light beam L1a (in FIG. 5, the position left of the position irradiated with the light beam L1a Is formed so that the angle formed with the portion (portion on the tip side of the light shielding portion 230) is vertical or acute (in the present embodiment, acute).

The light shielding surface 232 may be subjected to a predetermined process so that the light beam is not easily reflected. For example, the light shielding surface 232 may be subjected to a rough surface treatment such that the surface becomes rough.
The light shielding surface 232 may be formed in a curved surface shape. In this case, the angle formed with the light beam is set by replacing the virtual plane having the normal to the optical path of the light beam with the planar inclined surface.

Further, the end of the light shielding portion 230 on the effective scanning area SA side has a sharp shape.
For example, the end portion of the light shielding unit 230 is formed so that the radius of curvature is 2 to 3 mm. Since the end portion of the light shielding portion 230 has a sharp shape and is not a planar shape, the light beam applied to the end portion may be reflected to the first fθ lens 151 side with a predetermined intensity. It is suppressed.

Next, the operation of the laser scanner unit 4 will be described.
First, the user outputs predetermined image information to the printer 1 from an external device (for example, a PC). Image information output from an external device is input to the image formation control unit 310 via an input interface (for example, a connector).

  The image formation control unit 310 that has received the image information outputs a predetermined instruction to each part of the image forming unit GK and outputs a predetermined instruction to the LD control unit 320 and the motor control unit 330.

  Upon receiving an instruction from the image formation control unit 310, the motor control unit 330 instructs a motor (not shown) to rotate the polygon mirror 130 at a constant speed.

  Upon receiving an instruction from the image formation control unit 310, the LD control unit 320 controls the light emission state of the laser diode 111. The LD control unit 320 controls the light emission state of the laser diode 111 based on the image information.

The laser diode 111 that has received an instruction from the LD control unit 320 first starts emitting a light beam and continuously emits the light beam.
The light beam emitted from the laser diode 111 is reflected by one reflecting surface (one of the five mirrors constituting the side surface) constituting the polygon mirror 130.
On the scanning upstream side (writing start side), the light beam L1a before being irradiated onto the aspherical mirror 171 is reflected to the opposite side of the first fθ lens 151 by the light shielding surface 232 of the light shielding unit 230 (L1b in FIG. 5). ).

  By rotating the polygon mirror 130, the irradiation position of the light beam reflected by the polygon mirror 130 moves to the end side of the light shielding unit 230. Here, the light beam applied to the end of the light shielding unit 230 is not substantially reflected toward the first fθ lens 151 side.

  When the polygon mirror 130 is further rotated, the light beam L2a reflected by the polygon mirror 130 passes through the first fθ lens 151 and is irradiated on the aspherical mirror 171. The light beam applied to the aspherical mirror 171 is reflected toward the detection sensor 173.

The detection sensor 173 detects the light beam L2b from the aspherical mirror 171 and outputs the detection result to the LD control unit 320.
Here, when receiving a detection result from the detection sensor 173, the LD control unit 320 starts measuring time.

When the polygon mirror 130 is further rotated, the light beam L3 reflected by the polygon mirror 130 is transmitted through the first fθ lens 151, the second fθ lens 153, and the dustproof glass 155, and the surface 2a of the photosensitive drum 2 is obtained. An upper predetermined position is exposed.
The light beam L3 is bent by the first fθ lens 151 and the second fθ lens 153 to expose a predetermined position (within the effective exposure area RA) on the surface 2a of the photosensitive drum 2.

Further, when the polygon mirror 130 is further rotated, the light beam (L 3 → L 4) reflected by the polygon mirror 130 is scanned on the surface 2 a of the photosensitive drum 2.
While the light beam is scanned in the main scanning direction SC, the laser diode 111 repeats turning on and off based on the control from the LD control unit 320.

Then, the LD control unit 320 switches (turns off) the laser diode 111 from the light emitting state to the non-light emitting state when the measured time exceeds a predetermined first time.
In other words, the LD control unit 320 turns off the laser diode 111 when the light beam is positioned at the writing end position.

Further, the LD control unit 320 switches (lights up) the laser diode 111 from a non-light emitting state to a light emitting state when the measured time further exceeds a predetermined second time.
In other words, the LD control unit 320 turns on the laser diode 111 at a predetermined timing after the reflecting surface that reflects the light beam is switched from the reflecting surface that has reflected the light beam to another reflecting surface. .

The laser scanner unit 4 repeats the above operation to form an electrostatic latent image on the surface 2 a of the photosensitive drum 2.
In this case, the laser scanner unit 4 can suppress generation of flare light or the like. Further, the laser scanner unit 4 can suppress generation of a ghost image or the like.

  According to this embodiment, the laser scanner unit 4 can suppress the influence of reflected light and scattered light. Thus, the laser scanner unit 4 can form a high-quality electrostatic latent image. The printer 1 having the laser scanner unit 4 can form a high-quality toner image.

  Further, according to the present embodiment, the light shielding unit 230 is disposed between the polygon mirror 130 and the first fθ lens 151. The light shielding unit 230 is disposed on the upstream side in the traveling direction of the light beam. Thereby, even if the light-shielding part 230 is small (it does not enlarge), it can suppress the influence of reflected light or scattered light suitably. Thereby, the laser scanner unit 4 can be reduced in size.

  Further, the laser scanner unit 4 has a planar or curved light shielding surface 232 for preventing the light beam from being reflected toward the first fθ lens 151. The light shielding surface 232 is formed such that the angle formed between the light beam from the polygon mirror 130 and the portion closer to the effective scanning region than the position irradiated with the light beam is vertical or acute. Thereby, the laser scanner unit 4 can suppress an unnecessary light beam from traveling toward the photosensitive drum 2. The laser scanner unit 4 can preferably suppress the influence of reflected light and scattered light.

  In the present embodiment, the end portion of the light shielding portion 230 is formed so that the end portion on the effective scanning area SA side is sharp. Accordingly, the laser scanner unit 4 can suppress irregular reflection of the light beam at the end when the light beam is switched from the state shielded by the light shielding unit 230 to the state irradiated to the aspherical mirror 171.

  In the present embodiment, the light shielding unit 230 is arranged on the scanning upstream side (writing start side). In the present embodiment, the detection sensor 173 is configured to detect a light beam on the scanning upstream side (writing start side). Specifically, the detection sensor 173 is configured to detect a light beam that is irradiated on the aspherical mirror 171 that is a light beam on the upstream side of scanning (writing start side). In the present embodiment, the light shielding unit 230 suppresses generation of flare light or the like that occurs between the time when the laser diode 111 is turned on and the time when the aspherical mirror 171 is irradiated.

  In the present embodiment, the light shielding portion 230 is formed integrally with the case member 200. Thereby, the laser scanner unit 4 can suppress the influence of reflected light or scattered light without causing an increase in the number of parts or an increase in size.

  In the present embodiment, since the printer 1 includes the laser scanner unit 4, the above-described effects are similarly obtained.

As mentioned above, although preferred embodiment was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the present embodiment, the monochrome printer 1 is described as the image forming apparatus. However, the present invention is not limited to this, and the image forming apparatus may be a color printer, a monochrome copier, a color copier, a facsimile, or a complex machine thereof. Etc.
The sheet-shaped transfer material is not limited to the paper T, and may be a film sheet, for example.

  Further, the laser scanner unit 4 may have a folding mirror on the downstream side of the second fθ lens 153 in the optical path direction of the light beam. The laser scanner unit 4 may include a folding lens that bends the light beam transmitted through the second fθ lens 153 in a predetermined direction according to the size and arrangement of the laser scanner unit 4.

  In the present embodiment, the printer 1 is a monochrome type. However, as described above, the printer 1 is not limited to this. For example, the printer 1 may be a tandem type or the like. Here, when the printer 1 is a tandem type, the printer 1 may be configured to have a plurality of laser scanner units 4 corresponding to each photosensitive drum.

DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum, 2a ... Surface (surface to be scanned), 4 ... Laser scanner unit (optical scanning device), 110 ... Laser unit, 111 ... Laser diode (Light source), 130... Polygon mirror (light deflector), 150... Optical system, 151... First f.theta. Lens 151 (first lens), 153... Second f.theta. Lens 153 (second lens), 171. Aspherical mirror, 173 ... detection sensor, 200 ... case member, 230 ... light shielding part, 232 ... light shielding surface, SA ... effective scanning area, SC ... main scanning direction, RA ... effective exposure area

Claims (8)

A light source that outputs a light beam;
An optical deflector that deflects and scans the light beam output from the light source;
Light having a first lens arranged opposite to the optical deflector and a second lens arranged farther from the optical deflector than the first lens and deflected and scanned by the optical deflector An optical system for guiding the beam onto the surface to be scanned and forming an image;
A light shielding portion disposed between the light deflector and the first lens on an optical path of a light beam deflected and scanned by the light deflector and suppressing reflection of the light beam toward the first lens; An optical scanning device. 2. The optical scanning device according to claim 1, wherein the light shielding unit is disposed outside the effective scanning region and in the vicinity of the outer edge of the effective scanning region and upstream of the scanning. The said light-shielding part has a light-shielding surface which is arrange | positioned facing the said optical deflector, and the rough surface process for preventing the light beam from the said optical deflector to reflect in the said 1st lens side is carried out. 2. The optical scanning device according to 2. The said light shielding part is arrange | positioned facing the said optical deflector, and has a planar or curved light-shielding surface for not reflecting the light beam from the said optical deflector to the said 1st lens side. The optical scanning device according to 1. 5. The light shielding surface according to claim 4, wherein an angle formed between the light beam from the optical deflector and a portion closer to the effective scanning region than the position irradiated with the light beam is vertical or acute. Optical scanning device. The optical scanning device according to claim 5, wherein the light shielding portion has a sharp end on the effective scanning region side. A case member that houses the light source, the optical deflector, and the optical system;
The optical scanning device according to claim 1, wherein the light shielding portion is formed integrally with the case member. An optical scanning device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image carrier having the surface to be scanned.

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