JP2002365571A - Optical scanner and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical scanner having improved scanning efficiency, and to provide an imaging apparatus. SOLUTION: This optical scanner is provided with a light source means 1, a deflection means 6, having a plurality of deflection surfaces for reflecting and deflecting luminous flux from the light source means in the main scanning direction, and an optical system, guiding the luminous flux reflected and deflected by the deflection means to a surface to be scanned 8. In the optical scanner, the luminous flux is made incident on the deflection surface in a width larger than the width of the deflection surface in the main scanning direction, and the surface to be scanned has non-effective areas which needs to be irradiated with light on both sides across an effective area where an image is formed on a main scanning cross section. When the non-effective area on a scanning finishing side on the surface to be scanned is scanned with the luminous flux, based on either of two adjacent deflection surfaces of the deflection means, the non-effective area on a scanning starting side on the surface to be scanned, is scanned with the luminous flux based on the other deflection surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical scanning apparatus and an image forming apparatus which scan a photosensitive member with a light spot and form an image using an electrophotographic process. In particular, the image forming apparatus of the present invention is suitable for a laser beam printer (LBP), a digital copying machine, or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser beam printer or a digital copier, a light beam modulated in accordance with an image signal is emitted from a light source such as a semiconductor laser, and an image is formed using the light beam. Has formed.

FIG. 11 is a sectional view (main scanning sectional view) of a main portion of a conventional optical scanning device used in this type of image forming apparatus in the main scanning direction.

In FIG. 1, a parallel light beam emitted from a laser unit 61 including a semiconductor laser enters a cylindrical lens 62 having a predetermined refractive power only in the sub-scanning direction. The parallel light beam incident on the cylindrical lens 62 exits as a parallel light beam as it is in the main scanning section.

On the other hand, the above-mentioned parallel light beam is converged in the sub-scan section, and is formed on the deflecting surface 63a of the optical deflector 63 composed of a rotating polygon mirror (polygon mirror) as a long line image in the main scanning direction. The deflection surface 6 of the optical deflector 63
The light beam reflected and deflected at 3a is imaged as a light spot on the photosensitive drum surface 66, which is the surface to be scanned, by an imaging optical system (fθ lens system) 71 having fθ characteristics. The light spot repeatedly scans the photosensitive drum surface 66. The imaging optical system 71 includes a spherical lens 64 and a toric lens 65.

In the above-described optical scanning device, before scanning the photosensitive drum surface 66 with a light spot, the photosensitive drum surface 66 is scanned.
A BD (beam detector) sensor 69 as a photodetector is provided to adjust the timing of starting image formation above.

The BD sensor 69 scans a BD light beam which is a part of the light beam deflected by the optical deflector 63, that is, an area outside the image forming area before scanning the image forming area on the photosensitive drum surface 66. Receive the luminous flux when it is This B
The D light flux is reflected by a BD mirror 67, condensed by a BD lens (condensing lens) 68, and enters a BD sensor 69. Then, a BD signal (synchronous signal) is detected from the output signal of the BD sensor 69, and the scanning start timing of image recording on the photosensitive drum surface 66 is adjusted based on the BD signal.

The photosensitive drum rotates at a constant speed in synchronization with the drive signal of the semiconductor laser in the laser unit 61, and the photosensitive drum surface 66 moves in the sub-scanning direction with respect to the light spot to be scanned. Thus, an electrostatic latent image is formed on the photosensitive drum surface 66. The electrostatic latent image is developed by a well-known electrophotographic process, and is transferred to a transfer material such as paper to realize an image.

A photosensitive drum used in an image forming apparatus has an image forming area (effective image area) in the main scanning direction and blank areas (non-image forming areas) arranged on both sides of the image forming area. ing. The image forming area is an area where the toner image is finally transferred to the transfer material. When the light spot scans on the photosensitive drum in the main scanning direction, a period during which the image forming area is scanned in FIG. 12 is referred to as an image forming period. A period during which the light spot scans the blank area is referred to as a blank period. As can be seen from FIG. 12, a blank period exists before and after the image forming period in one scan of the light spot.

As shown in FIG. 12, a light beam emitted from a semiconductor laser during an image forming period is light-modulated in accordance with an image signal, and accordingly, a light spot for scanning on the surface of the photosensitive drum is turned on / off. I have. The surface of the photosensitive drum is charged in advance, and the irradiation of the intensity-modulated light spot causes a potential difference on the surface of the photosensitive drum, thereby forming an electrostatic latent image. That is, the charge is lost in the portion of the photosensitive drum surface irradiated with the light spot (exposed portion), and the charge is left in the portion not irradiated with the light spot (non-exposed portion).

In a conventional regular development image forming apparatus, a so-called reversal development is performed on an electrostatic latent image formed as described above by using a toner having a polarity opposite to a charge of a photosensitive drum in advance. . That is, the non-exposed portion becomes an image portion (a portion where toner adheres). In a regular development image forming apparatus, a light beam is turned on to prevent toner from adhering to a non-image area on the scanning start side and a non-image area on the scanning end side because toner adheres to a non-exposed portion. Exposure, that is, so-called blank exposure is performed.

[0012]

However, in order to perform blank exposure, the drawing area of the scanning optical system is correspondingly increased, and the scanning lens and the optical deflector (polygon mirror) are enlarged accordingly. There is a problem that the size is increased and the cost is increased. Also, in a so-called overfilled scanning optical system in which the width of a light beam incident on the polygon mirror is made wider than the deflection surface (reflection surface) of the polygon mirror, the number of polygon mirror surfaces is increased to increase scanning efficiency. Although the mirror diameter can be made smaller, the deflection angle of the light beam becomes smaller as the number of surfaces increases, and it is necessary to increase the focal length in order to secure the scanning width. There was a point.

According to the present invention, a blank area (non-effective area) is formed on a scanning start side and a scanning end side, and a part of a light beam emitted from a light source for exposing the blank area on the scanning end side is used for scanning. It is an object of the present invention to provide an optical scanning device and an image forming apparatus that can increase the scanning efficiency by exposing a blank area.

Further, the present invention uses a part of the light beam emitted from the light source means for exposing the blank area on the scanning end side, and
An object of the present invention is to provide an optical scanning device and an image forming apparatus capable of improving scanning efficiency by performing D detection.

[0015]

According to a first aspect of the present invention, there is provided an optical scanning device comprising: a light source; a deflecting unit having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source in a main scanning direction;
An optical system for guiding a light beam reflected and deflected by the deflecting means to a surface to be scanned, wherein the light beam is incident on the deflecting surface with a width wider than the width of the deflecting surface in the main scanning direction. The scanning surface has an ineffective area that needs to be irradiated with light on both sides of an effective area for image formation in the main scanning section, and one of two adjacent deflecting surfaces of the deflecting means. When the light beam based on the deflection surface scans the non-effective area on the scanning end side on the surface to be scanned, the light beam based on the other deflection surface scans the non-effective area on the scanning start side on the surface to be scanned. It is characterized by:

According to a second aspect of the present invention, there is provided an optical scanning device, comprising: light source means; deflecting means having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source means in the main scanning direction; and a light beam reflected and deflected by the deflecting means. An optical system that guides light to the surface to be scanned, wherein a light beam is incident on the deflecting surface at a width wider than the width of the deflecting surface in the main scanning direction. A non-effective area that needs to be irradiated with light on both sides of an effective area for image formation in the cross section is provided, and a light beam based on one of the two deflecting surfaces adjacent to the deflecting means is irradiated with the light beam. When scanning the non-effective area on the scanning end side on the scanning surface, the light beam based on the other deflection surface scans the synchronization detection area set on the scanning start side on the scanning surface.

According to a third aspect of the present invention, there is provided an image forming apparatus, comprising: a light source unit; a deflecting unit having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source unit in the main scanning direction; And an optical system for guiding the light onto the photoreceptor,
An image forming apparatus comprising an exposure process in which a light beam is incident on the deflecting surface at a width wider than the width of the deflecting surface in the main scanning direction, and a toner image is formed on a portion where the light beam is not irradiated on the photoconductor. The photoreceptor has blank areas on both sides of the image forming area in the main scanning cross section, and a light beam based on one of the two deflecting surfaces adjacent to the deflecting means emits light on the scanning end side on the photoreceptor surface. When scanning the blank area, the light beam based on the other deflection surface scans the blank area on the scanning start side on the photoconductor surface.

According to a fourth aspect of the present invention, there is provided an image forming apparatus, comprising: a light source; a deflecting unit having a plurality of deflecting surfaces for reflecting and deflecting the luminous flux from the light source in the main scanning direction; And an optical system for guiding the light onto the photoreceptor,
An image forming apparatus comprising an exposure process in which a light beam is incident on the deflecting surface at a width wider than the width of the deflecting surface in the main scanning direction, and a toner image is formed on a portion where the light beam is not irradiated on the photoconductor. The photoreceptor has blank areas on both sides of the image forming area in the main scanning cross section, and a light beam based on one of the two deflecting surfaces adjacent to the deflecting means emits light on the scanning end side on the photoreceptor surface. When scanning the blank area, the light beam based on the other deflection surface scans the synchronous detection area set on the scanning start side on the photosensitive member surface.

According to a fifth aspect of the present invention, there is provided an image forming apparatus, comprising: light source means for emitting a light beam modulated in accordance with an image signal; deflection means for repeatedly deflecting the light beam emitted from the light source means; An imaging optical system for forming an image on the surface to be scanned as a light spot, a photosensitive member arranged on the surface to be scanned, repeatedly scanned by the light spot, and selectively exposed; and A driving unit that moves in a sub-scanning direction orthogonal to the main scanning direction, a developing unit that forms an image by attaching toner to a selectively exposed photoconductor, and a light source driving unit that drives and controls the light source unit. An image forming apparatus having an image forming area in the main scanning direction and a blank area on both sides of the image forming area, wherein the developing unit is a non-exposed portion of the selectively exposed photosensitive body. To toner An image forming process for attaching the light source, wherein the light source driving unit drives the light source unit in accordance with an image signal during a period in which the light spot scans the image forming area on the photoconductor, and the light spot is formed on the photoconductor. The light source is turned on during the entire period of scanning the blank area, and when the blank area on the scan end side is exposed, a part of the blank area on the scan start side is exposed.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the deflecting means has a plurality of deflecting surfaces, and a width of the light beam incident on one deflecting surface in the main scanning direction is equal to the width of the deflecting surface in the main scanning direction. It is characterized by being wider than the width.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, when the light beam from the one deflection surface is exposing the blank area on the scanning end side, the light beam from the deflection surface adjacent to the deflection surface is exposed. Are incident on a part of the blank area on the scanning start side.

According to an eighth aspect of the present invention, in the invention of the fifth or sixth aspect, the image height of the outermost part of the blank area on the scanning start side is Ybtop, and the image height of the outermost part of the blank area on the scanning end side is Ybtop. Ybend, the image height on the scanning start side at the end of the image forming area is Ygtop, the image height on the scanning end side at the end of the image forming area is Ygend, and the fθ coefficient of the imaging optical system is f. ,

[0023]

(Equation 3)

Is satisfied.

According to a ninth aspect of the present invention, in the fifth aspect of the present invention, the BD detection for detecting the light beam by the sensor is performed outside the blank area in order to take the timing of starting the scanning.
Ybtop is the image height of the outermost part of the blank area on the scanning start side, Ybend is the image height of the outermost part of the blank area on the scanning end side, and scanning starts at the end of the image forming area. Ygtop is the image height on the side, Ygend is the image height on the scan end side of the end of the image forming area, Ybd is the image height on the outermost part of the timing detection of scanning start, and f is the fθ coefficient of the imaging optical system. and when,

[0026]

(Equation 4)

It is characterized by satisfying the following.

According to a tenth aspect of the present invention, there is provided an image forming apparatus comprising: light source means for emitting a light beam modulated in accordance with an image signal; deflection means for repeatedly deflecting the light beam emitted from the light source means;
An imaging optical system for forming an image of a light beam deflected by the deflecting means as a light spot on a surface to be scanned, and a photoreceptor arranged on the surface to be scanned and repeatedly scanned by the light spot and selectively exposed A driving unit for moving the photoconductor in a sub-scanning direction orthogonal to the main scanning direction; a developing unit for forming an image by adhering toner to the photoconductor selectively exposed; and a driving control of the light source unit Light source driving means, the photosensitive member has an image forming area in the main scanning direction, a blank area on both sides of the image forming area, and a BD signal for detecting a synchronization signal outside the blank area on the scanning start side. Area and
Wherein the developing means has an exposure process for adhering toner to the non-exposed portions of the selectively exposed photoreceptor, and the light source driving means causes a light spot to illuminate the image forming area on the photoreceptor. During the scanning period, the light source unit is driven according to the image signal, and the light source is turned on during the entire period in which the light spot scans the blank area and the BD detection area on the photoconductor, and the scanning is completed. When the blank area on the side is exposed, a light beam is guided through a deflecting means to a part of the BD detection area.

According to an eleventh aspect of the present invention, in the invention of the tenth aspect, the deflecting means has a plurality of deflecting surfaces, and the width of the light beam incident on one deflecting surface in the main scanning direction is equal to the width of the deflecting surface in the main scanning direction. It is characterized by being wider than the width.

According to a twelfth aspect of the present invention, in the tenth or eleventh aspect, the light beam guided to the BD detection area via the deflecting means is a light beam separated by a light beam separating means. .

According to a thirteenth aspect of the present invention, in the invention of the tenth or eleventh aspect, when the light beam from the one deflecting surface is exposing the blank region on the scanning end side, the deflecting surface is adjacent to the deflecting surface. Is incident on a part of the BD detection area.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to any one of the fifth to thirteenth aspects, the code data input from an external device is converted into an image signal to convert the image data into an image signal. It is characterized by having a printer controller for inputting to the forming apparatus.

[0033]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[Image Forming Apparatus] FIG. 1 is a cross-sectional view (sub-scanning cross-sectional view) of a main portion in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In FIG. 1, reference numeral 204 denotes an image forming apparatus. The image forming apparatus 204 receives code data Dc from an external device 217 such as a personal computer.
Enter. The code data Dc is converted into image data (dot data) Di by the printer controller 211 in the apparatus. The image data Di is input to the optical scanning device 200. The optical scanning unit (optical scanning device) 200 emits a light beam (light flux) 203 modulated in accordance with the image data Di, and the light beam 203 causes the photosensitive surface of the photosensitive drum 201 to move in the main scanning direction. Scanned.

The photosensitive drum 201 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 215. Then, with this rotation, the photosensitive surface of the photosensitive drum 201 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 203. Above the photosensitive drum 201, a charging roller 202 for uniformly charging the surface of the photosensitive drum 201 is provided so as to contact the surface.
The light beam 203 scanned by the optical scanning device 200 is applied to the surface of the photosensitive drum 201 charged by the charging roller 202.

As described above, the light beam 203 is
The light is modulated based on the image data Di, and by irradiating the light beam 203, an electrostatic latent image is formed on the surface of the photosensitive drum 201. The electrostatic latent image is further transferred to the photosensitive drum 201 from the irradiation position of the light beam 203.
Is developed as a toner image by a developing device 207 disposed so as to be in contact with the photosensitive drum 201 on the downstream side in the rotational cross section of FIG.

The toner particles used here have a sign opposite to that of the charge charged by the charging roller 202. Then, so-called regular development, in which the non-exposed portion of the photosensitive drum becomes a portion (image portion) where the toner adheres, is performed.

The toner image developed by the developing device 207 is transferred onto a sheet 212 as a transfer material by a transfer roller (transfer device) 208 disposed below the photosensitive drum 201 so as to face the photosensitive drum 201. Is done. Paper 2
Reference numeral 12 is stored in a paper cassette 209 in front of the photosensitive drum 201 (right side in FIG. 1), but can be fed manually. A paper feed roller 210 is provided at an end of the paper cassette 209, and feeds the paper 212 in the paper cassette 209 to a transport path.

The sheet 212 on which the unfixed toner image has been transferred as described above is further moved to the rear of the photosensitive drum 201 (FIG. 1).
At the left side). The fixing device includes a fixing roller 213 having a fixing heater (not shown) therein and a pressure roller 214 disposed so as to be in pressure contact with the fixing roller 213, and is sent from the transfer unit. The sheet 212 is fixed to the fixing roller 213 and the pressure roller 21.
The paper 2 is heated by applying pressure at the pressure contact portion 4
12 to fix the unfixed toner image. Further, a paper discharge roller 216 is disposed behind the fixing roller 213, and discharges the fixed paper 212 out of the image forming apparatus.

Although not shown in FIG. 1, the print controller 211 performs not only the above-described data conversion, but also a motor 215, various parts in the image forming apparatus, a polygon motor in the optical scanning apparatus 200, and the like. Control.

[Optical Scanning Apparatus] FIG. 2 is a sectional view (main scanning sectional view) of a main part in the main scanning direction showing the configuration of the optical scanning apparatus in the image forming apparatus of FIG. FIG. 3 is a sectional view (sub-scan sectional view) of a main part of the optical scanning device in FIG. 2 in the sub-scan direction.
FIG. 4 is a developed view in which the optical system of the optical scanning device of FIG. 2 is developed along a light beam in a main scanning section, and FIG. 5 is an expanded view of the optical system of the optical scanning device in FIG. 2 along a light beam in a sub-scanning section. Each of the developed views is shown. 2 to 5, the same members are denoted by the same reference numerals.

In this specification, the direction in which a light beam (light beam) is reflected and deflected (deflection scanning) by the deflecting means is defined as the main scanning direction, and the direction orthogonal to the optical axis of the imaging optical system and the main scanning direction is defined as sub-scanning. Defined as direction.

In this embodiment, a so-called overfilled field suitable for application to a high-speed, high-definition image forming apparatus
(0verfilled) Optical system (OFS) is used. OFS means that the width of the light beam incident on the rotary polygon mirror in the main scanning direction is larger than the width in the main scanning direction of one of a plurality of deflection surfaces (reflection surfaces) of the rotary polygon mirror.

2 to 5, reference numeral 1 denotes a semiconductor laser as a light source. The semiconductor laser 1 is driven by a laser drive signal and emits a light beam. Reference numeral 2 indicates a collimator lens. The collimator lens 2 converts a divergent light beam emitted from the semiconductor laser 1 into a parallel light beam or a convergent light beam. The semiconductor laser 1 and the collimator lens 2 may be integrated.

Reference numeral 3 denotes an aperture stop. This aperture stop 3
Restricts the passing light flux (light quantity). Reference numeral 4 denotes a cylindrical lens (cylinder lens). The cylindrical lens 4 has a predetermined refractive power only in the sub-scanning direction, and causes the light beam that has passed through the aperture stop 3 to main-scan the deflecting surface (reflection surface) 6a of the optical deflector 6 described later in the sub-scanning section. The image is formed as a long line image in the direction. Reference numeral 9 denotes a folding mirror. The return mirror 9 returns the incident light beam to the optical deflector 6 side. In addition, the collimator lens 2,
Each element such as the aperture stop 3, the cylindrical lens, and the reflection mirror 9 constitutes one element of the incident optical system 21.

Reference numeral 6 denotes an optical deflector as a deflecting means. The optical deflector 6 is composed of, for example, a rotating polygon mirror (polygon mirror), and is rotated at a constant speed in the direction of arrow A by a polygon motor (not shown).

In the present embodiment, the light beam emitted from the light source means 1 is made incident on the reflection surface 6a of the polygon mirror 6 via the incident optical system 21, but a structure without the incident optical system 21 is used. That is, the light beam emitted from the light source means 1 may be directly incident on the reflection surface 6a of the polygon mirror 6.

Reference numeral 22 denotes an imaging optical system having a light collecting function and fθ characteristics. The imaging optical system 22 has a single fθ lens (fθ lens system) 5 and a cylindrical mirror 7 having a predetermined power only in the sub-scanning direction. An image is formed on the surface 8. The imaging optical system 22 optically forms a substantially conjugate relationship between the deflecting surface 6a of the optical deflector 6 and the surface 8 to be scanned in the sub-scanning section. Such a configuration provides the deflecting surface 6 of the optical deflector 6.
This is to compensate for the processing error a and the inclination of the deflecting surface 6a due to the inclination of the rotation axis of the optical deflector, and is called tilt correction.

The light beam incident on the optical deflector 6 has once passed through a part of the fθ lens 5. That is, the fθ lens 5 is also a part of the components of the incident optical system 21.
Further, the imaging optical system 22 may be constituted by a plurality of lenses instead of a single lens as in the present embodiment. Scanned surface 8
Corresponds to the photosensitive drum surface of the photosensitive drum 201 in FIG.

In the optical scanning device according to the present embodiment, before the image forming area on the surface to be scanned (photosensitive drum surface) 8 is scanned with a light spot, the optical scanning device is used as a photodetector to adjust the timing of starting image formation. (Beam detector) sensor 12 is provided. The BD sensor 12 is a BD light flux which is a part of the light beam deflected by the light deflector 6.
That is, it receives a light beam when scanning an area (blank area) outside the image forming area before scanning the image forming area on the photosensitive drum surface 8. The BD light flux is reflected by a BD mirror (mirror for detecting a synchronization signal) 10, condensed by a BD lens (condensing lens) 11, and enters a BD sensor 12. Then, a BD signal (synchronization signal) is detected from the output signal of the BD sensor 12, and the scanning start timing of image recording on the scanned surface (photosensitive drum surface) 8 is adjusted based on the BD signal.

The BD mirror 10, BD lens 11, B
Each element such as the D sensor 12 constitutes one element of the BD optical system (synchronous detection optical system).

FIG. 6 is an explanatory diagram for explaining that the scanning efficiency is improved by the present embodiment.

In the same drawing, reference numeral 81 denotes a near-parallel light in the main scanning direction by an incident optical system (not shown), and a light beam to a polygon mirror 82 which temporarily forms an image near the polygon mirror reflecting surface (deflecting surface) in the sub-scanning direction. Incident light, 82 is a polygon mirror, 83 is an fθ lens, 84 is a photosensitive drum, 84a is an image forming area (image drawing area) as an effective area, 8
5, 86 are polygon reflection surfaces adjacent to each other, and 87 is a blank area (BAE) as an ineffective area on the scanning start side.
Area, 88 is a blank area (BAE area) as an ineffective area on the scanning end side; 90, 92 are principal rays of the light beam reflected by the polygon reflecting surface 85;
Indicates the principal ray of the light beam reflected by the polygon reflecting surface 86. Numerals 90 and 91 denote light rays from the respective polygon reflecting surfaces at the rotation angle of the polygon mirror 82, and similarly, light rays 92 and 93 denote the light rays when the polygon reflecting surface is further rotated from the rotation angle of the polygon mirror 82. Is shown.

The light 81 incident on the polygon mirror 82 is wider than the surface width (width in the main scanning direction) of the polygon reflection surface (deflection surface). Reflected light is generated. After the incident light 81 that has entered the polygon reflection surface 86 scans the image drawing area (image forming area) 84a, the light beam 91 reaches a point 88a of the blank area 88. At this time, the light source is continuously lit, and the polygon is turned on. With the rotation of the mirror 82, the entire area of the blank area 88 is scanned while being exposed, and the light beam 93 is further scanned to scan the position (end) 88b of the blank area 88.

At the same time, the polygon mirror 8 of the incident light 81
The light beam 90 reflected and deflected by the reflection surface (deflection surface) 85 adjacent to the second reflection surface 86 enters a part of the blank area 87 on the scanning start side and starts exposing. The beam 90 scans while exposing a point 87a of the blank area 87, and the light beam 92 reaches a position 87b of the blank area 87.

Accordingly, the blank area 87 on the scanning start side can be exposed simultaneously with the light beam 90 and the blank area 88 on the scanning end side can be exposed simultaneously with the light beam 93, so that the scanning efficiency can be improved.

At this time, as shown in FIG. 6, the height from the optical axis La to the maximum image height 87c, which is the image height of the outermost part of the blank area 87 on the scanning start side of the scanning optical device, is Ybtop, and the scanning is completed. The height from the optical axis La up to the maximum image height 88c, which is the image height of the outermost part of the blank area 88 on the side, is Ybend, and the maximum image that is the image height of the outermost part on the scanning start side of the image drawing area 84a. When the height from the optical axis La to the height 84b is Ygtop, and the height from the optical axis La to the maximum image height 84c, which is the image height of the outermost peripheral portion on the scanning end side of the image drawing area 84a, is Ygend, The fθ coefficient f of the imaging optical system 83 is given by the following equation (1).
To (3), the blank area 8 on the scanning start side is satisfied.
This is a condition for simultaneously exposing the whole area or a part of the blank area 88 on the scanning end side with a light beam.

[0058]

(Equation 5)

Here, the fθ coefficient f is the polygon mirror 82
Is the value of f (fθ coefficient) that satisfies Y = fθ, where θ is the deflection angle of the light beam and Y is the image height (height from the scanning center) of the light beam incident on the photosensitive drum surface. .

If the expression (1) is not satisfied, when the light beam is scanning the scanning end side of the image drawing area 84a,
The light beam scans the blank area 87 on the scanning start side, and if it is continuously turned on, it is not possible to draw an image on the scanning end side.

If the expression (2) is not satisfied, the reflected light is incident on the image drawing area 84a by the adjacent surface when the blank area 88 on the scanning end side is exposed, so that the scanning of the image drawing area 84a is performed. You cannot draw on the start side.

If the expression (3) is not satisfied, both of the blank areas 87 and 88 cannot be simultaneously exposed on the reflection surface adjacent to the polygon mirror.

Embodiment 2 FIG. 7 shows Embodiment 2 of the present invention.
FIG.

In the figure, reference numeral 101 denotes an incident optical system (not shown) which is substantially parallel light in the main scanning direction and is incident on the polygon mirror 102 which forms an image near the reflection surface of the polygon mirror 102 in the sub-scanning direction. Light, 102 is a polygon mirror, 103 is an fθ lens, 104 is a photosensitive drum,
104a is an image forming area (image drawing area) as an effective area, 105 and 106 are polygon reflecting surfaces adjacent to each other, and 107 is a blank area (BAE) on the scanning start side.
Area), 108 is a blank area (BAE area) on the scanning end side, 110 and 112 are principal rays of the light beam reflected by the polygon reflection surface 105, and 111 and 113 are light beams reflected by the polygon reflection surface 106, respectively. , 114 is a synchronization detection area (BD) set on the scanning start side.
(Detection area), which is located outside the blank area 107 on the scanning start side.

Since the light 101 incident on the polygon mirror 102 is wider than the surface width (width in the main scanning direction) of the polygon reflection surface, light reflected by the adjacent reflection surfaces 105 and 106 of the polygon mirror is generated. After the incident light 101 incident on the polygon reflecting surface 106 scans the image drawing area 104a, the light beam 111 is changed to a point 108a of the blank area 108.
At this time, the light source is in a continuous lighting state, scans while exposing the entire blank area 108 with the rotation of the polygon mirror 102, and further scans the light beam 1
13 scans to the position 108b of the blank area 108.

At the same time, the reflection surface 10 of the polygon mirror 102
6, the reflected beam 110 from the adjacent reflecting surface 105 reaches the BD detection area 114 for detecting the timing of scanning on the scanning start side, enters the BD photodetector 114a,
As a result, a signal for BD is output. Further, with the rotation of the polygon mirror 102, the light beam 110 passes through the BD detection area 114 and then enters the blank area 107 on the scanning start side.
Are scanned while exposing, and the light beam 112 reaches the end 104b of the image drawing area 104a (the end 107b of the blank area 107).

Accordingly, B on the scanning start side is
The D detection can be performed while exposing the blank area 108 on the scanning end side with the light beam 112 or the light beam 113 at the same time as the D detection, and the scanning efficiency can be improved.

At this time, as shown in FIG. 7, the optical axis La at the outermost portion of the BD detection area 114 on the scanning start side of the scanning optical device.
Ybd, the height from the optical axis La up to the maximum image height 107c which is the image height of the outermost part of the blank area 107 on the scanning start side, and the outermost part of the blank area 108 on the scanning end side. The height from the optical axis La up to the maximum image height 108c, which is the image height of Ybend, is defined as Ybend, and the height from the optical axis La up to the maximum image height 104b, which is the image height of the outermost peripheral portion of the image drawing area 104a on the scanning start side. Assuming that the height is Ygtop and the height from the optical axis La to the maximum image height 104c which is the image height of the outermost peripheral portion of the image drawing area 104a on the scanning end side is Ygend, the fθ coefficient f of the imaging optical system 103 Satisfying the following equations (4) to (6) is a condition for simultaneously exposing the whole or a part of the BD detection area 114 on the scanning start side and the blank area 108 on the scanning end side with a light beam.

[0069]

(Equation 6)

If the expression (4) is not satisfied, the light beam scans the BD detection area 114 on the scanning start side while the light beam is scanning the scanning end side of the image drawing area 104a, and the BD detection is not performed. Therefore, in the case of continuous lighting, an image on the scanning end side cannot be drawn.

If the expression (5) is not satisfied, the reflected light is incident on the image drawing area 104a by the adjacent surface when the blank exposure area 108 on the scanning end side is exposed, so that the drawing on the scanning start side is performed. Can not be done.

If the expression (6) is not satisfied, the BD signal cannot be detected simultaneously on two adjacent reflection surfaces of the polygon mirror while scanning the blank exposure area 108 on the scanning end side.

FIG. 8 is an explanatory diagram for explaining a decrease in the amount of light in the BD detection area according to the present invention. FIG. 9 is a graph in which a light quantity drop in the present embodiment is calculated.

FIG. 8 is a diagram showing the distribution of the light beam incident on the polygon mirror and the amount of light reflected by the reflection surface of the polygon mirror at that time. In the graph, the vertical axis represents the amount of light on the surface to be scanned, and the horizontal axis represents the image height. The curve in the graph shows the light amount distribution. Normally, the light quantity distribution of the laser is represented by a Gaussian distribution.

In the present embodiment, the light ray on the axis La draws the center of the image. At this time, the polygonal reflection surface is perpendicular to the incident light beam in the main scanning section at the center of the incident light beam. The amount of light reflected by the polygon reflecting surface used in this state is the integrated amount of light in the range 121 indicated by the hatched portion in the figure. In addition, the polygon reflection surface at the time of BD detection moves within the incident light beam, and has the integrated light amount in the area 122 indicated by another oblique line in the figure. Therefore, as is clear from the figure, the integrated light amount at the time of BD detection is smaller than the integrated light amount at the time of drawing the center of the image. The change in the amount of light due to the movement of the polygon reflection surface in the incident light beam is mainly caused by the laser far field pattern in the main scanning direction and the FN of the optical system that forms the incident light beam.
It is determined by o, the polygon diameter, the number of polygon surfaces, and the focal length of the scanning optical system. For example, as shown in FIG. 9, the exposure light quantity gradually decreases from the scanning center to the scanning periphery.

In a conventional underfilled scanning optical system (a type in which the diameter of a light beam incident on the polygon reflection surface is smaller than the width of the polygon reflection surface), the diameter of the polygon is usually designed to be as small as possible. Therefore, as the image height increases, a part of the light beam outside the effective scanning width cannot be covered by the polygon facet surface, and the light amount on the image surface rapidly decreases.

However, in the overfilled scanning optical system as in this embodiment, when a certain amount of uniformity of the light amount distribution is ensured within the effective scanning width, a light beam for BD detection uses as shown in FIG. Even in the range, since a part of the light beam whose light distribution decreases in a Gaussian distribution is used, the light amount does not decrease so much that BD detection cannot be performed.

That is, the BD detection system has a large detection light amount width which can usually cope with the light amount decrease by increasing the electric gain, and there is no problem even if the light beam on the adjacent surface in the present invention is used.

[Third Embodiment] FIG. 10 is an explanatory view of a part of a third embodiment of the present invention. In the figure, 121 is a photosensitive drum surface, 122 is a half mirror as a light beam separating means, 123 is a slit, 124 is a lens for BD, 12
5 is a BD sensor for BD, 126 is scanning light incident on the BD detection area, and 127 is scanning light incident on the image drawing area 121a. Reference numeral 121b denotes a blank area on the scanning start side.

The scanning light 126 is separated by the half mirror 122 into a light beam heading for the BD sensor-125 and a light beam heading for the photosensitive drum surface 121.
The light beam incident on 1 exposes the blank exposure area 121b.

On the other hand, the light beam reflected by the half mirror 122 in the direction of the BD sensor 125
, And refracted and condensed by the lens 124 for BD.
The timing of drawing is given by being incident on the surface of the sensor 125.

As shown in FIG.
, The focus position of the spot on the photosensitive drum surface 121 shifts, but the blank exposure area 121b
In this case, it is important that the amount of light can be secured, and there is no problem.

There is no problem if the transmittance of the half mirror is increased and the amount of light is temporarily increased.

According to the present embodiment, since the BD detection is performed during the blank exposure, there is no need to sacrifice the efficiency for the BD detection. Simultaneous exposure makes it possible to improve the scanning efficiency.

[0085]

According to the present invention, a blank area (ineffective area) is formed on the scanning start side and the scanning end side as described above, and a part of the light beam emitted from the light source means for exposing the blank area on the scanning end side. By exposing the blank area on the scanning start side by using the above, an optical scanning device and an image forming apparatus that can increase the scanning efficiency can be achieved.

According to the present invention, as described above, BD detection is performed by using a part of the light beam emitted from the light source for exposing the blank area on the scanning end side, so that the scanning efficiency can be improved. And an image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a sub-scan sectional view showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a main scanning cross-sectional view of the optical scanning device according to the first embodiment of the present invention.

FIG. 3 is a sub-scan sectional view of the optical scanning device according to the first embodiment of the present invention.

FIG. 4 is a developed view in the main scanning direction according to the first embodiment of the present invention.

FIG. 5 is a developed view in the sub-scanning direction according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating an improvement in scanning efficiency according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an improvement in scanning efficiency according to the second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a change in a light amount distribution according to the second embodiment of the present invention.

FIG. 9 is a graph showing a change in light amount distribution according to the second embodiment of the present invention.

FIG. 10 is a sub-scan sectional view around the BD optical system according to a third embodiment of the present invention.

FIG. 11 is a main scanning sectional view of a scanning optical system of a conventional optical scanning device.

FIG. 12 is an explanatory diagram of blank exposure.

[Explanation of symbols]

 Reference Signs List 1 light source means (semiconductor laser) 2 collimator-lens 3 aperture stop 4 cylindrical lens 5 fθ lens 6 deflecting means (optical deflector) 6a deflecting surface 7 cylindrical mirror 8 scanned surface (photosensitive drum surface) 9 folding mirror 10 BD mirror 11 BD lens 12 BD sensor 21 Incident optical means 22 Imaging optical system 200 Optical scanning device 201 Photosensitive drum 202 Charging roller 203 Light beam 204 Image forming device 207 Developing device 208 Transfer roller 209 Paper cassette 210 Feed roller 211 Printer controller 212 Transfer material (Paper) 213 Fixing roller 214 Pressure roller 215 Motor 216 Discharge roller 217 External device

Claims (14)

[Claims] 1. A light source means, a deflecting means having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source means in a main scanning direction, and an optical device for guiding a light beam reflected and deflected by the deflecting means to a surface to be scanned. A light beam incident on the deflecting surface in a width wider than the width of the deflecting surface in the main scanning direction, wherein the surface to be scanned has an effective area for forming an image in a main scanning section. On both sides of the deflecting means, a light beam based on one of the two deflecting surfaces adjacent to the deflecting means is irradiated with a non-effective area on the scanning end side on the surface to be scanned. An optical scanning device wherein, while scanning an effective area, a light beam based on the other deflection surface scans a non-effective area on the scanning start side on the surface to be scanned. 2. A light source means, a deflecting means having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source means in a main scanning direction, and an optical device for guiding the light beam reflected and deflected by the deflecting means to a surface to be scanned. A light beam incident on the deflecting surface in a width wider than the width of the deflecting surface in the main scanning direction, wherein the surface to be scanned has an effective area for forming an image in a main scanning section. On both sides of the deflecting means, a light beam based on one of the two deflecting surfaces adjacent to the deflecting means is irradiated with a non-effective area on the scanning end side on the surface to be scanned. An optical scanning device, wherein, while scanning an effective area, a light beam based on the other deflection surface scans a synchronization detection area set on the scanning start side on the surface to be scanned. 3. A light source means, a deflecting means having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source means in the main scanning direction, and an optical device for guiding the light beam reflected and deflected by the deflecting means onto a photosensitive member. A light beam is incident on the deflecting surface with a width wider than the width of the deflecting surface in the main scanning direction, and a toner image is formed on a portion where the light beam is not irradiated on the photoconductor. In the image forming apparatus, the photoreceptor has blank areas on both sides of the image forming area in the main scanning section, and a light beam based on one of the two deflecting surfaces adjacent to each other of the deflecting means receives the light beam. An image forming apparatus, wherein when scanning a blank region on a scanning end side on a body surface, a light beam based on the other deflection surface scans a blank region on a scanning start side on the photosensitive member surface. 4. A light source means, a deflecting means having a plurality of deflecting surfaces for reflecting and deflecting a light beam from the light source means in the main scanning direction, and an optical device for guiding the light beam reflected and deflected by the deflecting means onto a photosensitive member. A light beam is incident on the deflecting surface with a width wider than the width of the deflecting surface in the main scanning direction, and a toner image is formed on a portion where the light beam is not irradiated on the photoconductor. In the image forming apparatus, the photoreceptor has blank areas on both sides of the image forming area in the main scanning section, and a light beam based on one of the two deflecting surfaces adjacent to each other of the deflecting means receives the light beam. An image forming apparatus characterized in that when scanning a blank area on the scanning end side on a body surface, a light beam based on the other deflection surface scans a synchronization detection area set on the scanning start side on the photoconductor surface. 5. A light source means for emitting a light beam modulated in accordance with an image signal, a deflecting means for repeatedly deflecting a light beam emitted from the light source means, and a light beam deflected by the deflecting means is projected onto a surface to be scanned. An imaging optical system for forming an image as a spot, a photoconductor arranged on the surface to be scanned, repeatedly scanned by the light spot, and selectively exposed, and a sub-scanning direction orthogonal to the main scanning direction of the photoconductor. Drive means for moving the toner to the photosensitive member selectively exposed,
An image forming apparatus comprising: a developing unit for forming an image; and a light source driving unit for driving and controlling the light source unit, wherein the photoconductor has an image forming region in a main scanning direction and blank regions on both sides of the image forming region. In the forming apparatus, the developing unit has an image forming process of attaching toner to a non-exposed portion of the photoconductor selectively exposed, and the light source driving unit scans an image forming area on the photoconductor with a light spot. During this period, the light source means is driven according to the image signal, and the light source is turned on during the entire period in which the light spot scans the blank area on the photoconductor, exposing the blank area on the scanning end side. An image forming apparatus that exposes a part of a blank area on a scanning start side during the scanning. 6. The deflecting means has a plurality of deflecting surfaces,
6. The width of a light beam incident on one deflection surface in the main scanning direction is wider than the width of the deflection surface in the main scanning direction.
Image forming apparatus. 7. When the light beam from the one deflecting surface is exposing the blank region on the scanning end side, the light beam from the deflecting surface adjacent to the deflecting surface is part of the blank region on the scanning start side. The image forming apparatus according to claim 6, wherein the light is incident on the image forming apparatus. 8. The image height of the outermost part of the blank area on the scanning start side is Ybtop, the image height of the outermost part of the blank area on the scanning end side is Ybend, and the scanning start side of the edge of the image forming area is Ybtop. Where Ygtop is the image height of the image, Ygend is the image height of the end of the image forming area on the scanning end side, and f is the fθ coefficient of the imaging optical system. The image forming apparatus according to claim 5, wherein the following condition is satisfied. 9. In order to take the timing of the start of scanning, there is provided a BD detecting means for performing a BD detection for detecting a light beam by a sensor outside the blank area, and an image height of the outermost part of the blank area on the scanning start side. Ybtop, Ybend is the image height at the outermost periphery of the blank area on the scanning end side, Ygtop is the image height on the scanning start side at the end of the image forming area, and Ygtop is the image height on the scanning end side at the end of the image forming area. Where Ygend is the height, Ybd is the image height at the outermost periphery of the scan start timing detection, and f is the fθ coefficient of the imaging optical system. 6. The image forming apparatus according to claim 5, wherein: 10. A light source means for emitting a light beam modulated in accordance with an image signal, a deflecting means for repeatedly deflecting a light beam emitted from the light source means, and a light beam deflected by the deflecting means is projected onto a surface to be scanned. An imaging optical system for forming an image as a spot, a photoconductor arranged on the surface to be scanned, repeatedly scanned by the light spot, and selectively exposed, and a sub-scanning direction orthogonal to the main scanning direction of the photoconductor. A light source driving means for driving and controlling the light source means, and a driving means for moving the light source, a developing means for adhering toner to a selectively exposed photoconductor to form an image, and a light source driving means for controlling the light source means. An image forming apparatus having an image forming area, a blank area on both sides of the image forming area, and a BD detection area for detecting a synchronization signal outside the blank area on the scanning start side. A light source driving unit that emits light in accordance with an image signal during a period in which a light spot scans an image forming area on the photoconductor. The light source is turned on during the entire period in which the light spot scans the blank area and the BD detection area on the photoconductor, and when the blank area on the scan end side is exposed, the BD detection is performed. An image forming apparatus, wherein a light beam is guided to a part of a region through a deflection unit. 11. The deflecting means has a plurality of deflecting surfaces,
The image forming apparatus according to claim 10, wherein a width of the light beam incident on one deflecting surface in the main scanning direction is wider than a width of the deflecting surface in the main scanning direction. 12. The image forming apparatus according to claim 10, wherein the light beam guided to the BD detection area via the deflection unit is a light beam separated by a light beam separation unit. 13. When a light beam from the one deflecting surface is exposing the blank area on the scanning end side, a light beam from a deflecting surface adjacent to the deflecting surface enters a part of the BD detection area. 12. The method according to claim 10, wherein
Image forming apparatus. 14. An image forming apparatus according to claim 5, further comprising a printer controller for converting code data input from an external device into an image signal and inputting the image signal to said image forming apparatus. An image forming apparatus comprising: