JP2007079482A - Optical scanner and image forming system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expose and scan with a plurality of beams with a simple and compact structure, in an optical scanner and an image forming system using the optical scanner. <P>SOLUTION: The optical scanner 1 has a laser light source 2 and a polygon scanner 6 for exposing and scanning with a laser beam 30 emitted from the laser light source 2. The optical scanner 1 also has a scanning face dividing mirror which guides the laser beam 30 deflected with the polygon scanner 6 in different directions according to the scanning angle of the laser beam and divides a scanning face into a plurality of scanning faces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming system using the same.

2. Description of the Related Art Conventionally, in an image forming system such as a copying machine or a laser printer, a plurality of scanning beams are modulated on the basis of color-separated image signals, exposure scanning is performed, and images of a plurality of colors are formed and superimposed. One that forms a full-color image by combining them is known.
For example, in Patent Document 1, four color beams are deflected by two rotary polygon mirrors and exposed and scanned on a photosensitive drum to form a four-color image, which is then superimposed to form a full-color image. A color image forming apparatus is described.
Japanese Examined Patent Publication No. 4-51829 (Figs. 1 and 4)

However, the conventional optical scanning apparatus as described above and the image forming system using the same have the following problems.
In the technique described in Patent Document 1, although the rotary polygon mirror and the motor that drives the rotary mirror can be shared, since the scanning optical system such as the light source and the fθ lens is separately provided, the number of parts is increased and the apparatus is There is a problem of increasing the size.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical scanning apparatus that performs exposure scanning of a plurality of beams with a simple and compact configuration, and an image forming system using the optical scanning apparatus. .

In order to solve the above problems, an optical scanning device of the present invention performs deflection scanning within a fixed scanning plane in order to perform exposure scanning with a light source that generates a light beam and a light beam emitted from the light source. An optical scanning device having an optical deflector, wherein the light beam deflected by the optical deflector is guided in different directions according to the scanning angle of view, and the scanning surface of the exposure scanning is changed to a plurality of scanning surfaces. A scanning plane dividing means for dividing is provided.
According to the present invention, the scanning plane dividing means guides the light beam deflected by the optical deflector in different directions according to the scanning angle of view, and divides the scanning plane for exposure scanning into a plurality of scanning planes. A plurality of exposure scans can be performed by one deflection scan. Therefore, a plurality of exposure scans can be performed using a single beam light source in common.

The image forming system of the present invention is configured to form an image by performing multi-beam exposure scanning using the optical scanning device of the present invention.
According to this invention, since the optical scanning device of the present invention is used, the same effects as the optical scanning device of the present invention are provided.

  According to the optical scanning device and the image forming system using the same according to the present invention, a plurality of exposure scans can be performed by using a beam light source in common by one deflection scan. There exists an effect that it can be set as a simple and small structure.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

[First Embodiment]
An optical scanning device according to a first embodiment of the present invention will be described.
1, 2, and 3 are schematic configuration explanatory diagrams of a top view, a front view, and a back view, respectively, for explaining the schematic configuration of the optical scanning device according to the first embodiment of the present invention. FIG. 4 is an optical layout diagram of the optical scanning device according to the first embodiment of the present invention. Here, in each figure, the light ray describes only the axial principal ray except for a part. Further, in FIG. 3, the optical path until it enters the optical deflector is shown expanded in the drawing.

  As shown in FIG. 1, the optical scanning device 1 of this embodiment has image planes 10A and 10B on the surfaces of photoconductors 11A and 11B, which are optical recording media used in a part of an image forming system, for example. It is a two-beam optical scanning device that matches and performs exposure scanning on each. The schematic configuration includes a control unit 100, a laser light source 2, a collimating lens 3, a beam shaping slit 4, a cylindrical lens 5, a polygon scanner 6, an fθ lens 7, scanning plane dividing mirrors 8A and 8B, and folding mirrors 9A and 9B. .

  The control unit 100 performs overall control of the optical scanning device 1 and is electrically connected to at least the laser light source 2, the polygon scanner 6, and the synchronization detection sensor 14, and performs laser processing based on an information signal 101 input from the outside. The laser drive signal 102 for driving the light source 2 and the polygon scanner 6 are controlled to be turned ON / OFF, and the polygon scanner drive signal 103 that is rotated at a constant angular velocity when turned ON is sent to the laser light source 2 and the polygon scanner 6, respectively. In response to the supply of a synchronization detection signal 104 from a synchronization detection sensor 14 to be described later, the scanning start position is synchronously controlled.

  The laser light source 2 is for emitting a laser beam 30 composed of wavelength light having sufficient sensitivity with respect to the photoconductors 11A and 11B. The laser light source 2 is driven based on a laser drive signal 102 sent from the control unit 100. As a result, the laser beam 30 modulated based on the information signal 101 is emitted from the laser light source 2.

  The collimating lens 3 is an optical element that condenses the laser beam 30 emitted from the laser light source 2 into substantially parallel light.

  The beam shaping slit 4 is configured so that the laser beam 30 that has been made substantially parallel light by the collimating lens 3 has an appropriate imaging spot diameter in the main scanning direction and the sub-scanning direction on the image planes 10A and 10B. This is a member for shaping the beam shape. In the beam shaping slit 4, a member having an oval, rectangular or oval opening having an appropriate size on a light shielding plate according to the optical characteristics of an fθ lens 7 and a cylindrical lens 5 described later. Can be adopted.

  In the following, unless there is a risk of misunderstanding, the main scanning direction and the sub-scanning direction are used in a broad sense, and not only in the direction at the scanning position but also when referring to two directions of a cross section orthogonal to each optical path. I will use it. In other words, the direction that coincides with the main scanning direction and the sub-scanning direction on the image plane when traveling along the optical path and reaching the image plane is referred to as the main scanning direction and the sub-scanning direction, respectively, at any position on the optical path.

The cylindrical lens 5 is an optical element for forming an image of the laser beam 30 transmitted through the beam shaping slit 4 into a linear shape extending in the main scanning direction.
The polygon scanner 6 deflects a laser beam 30 that is substantially parallel to the main scanning direction transmitted through the cylindrical lens 5 and imaged in the sub-scanning direction in the main scanning direction. In the present embodiment, a motor (not shown) is used. A hexagonal polygon mirror is provided on the axis, and is rotated at a constant angular velocity in the direction of the arrow in FIG.
The position of the cylindrical lens 5 is adjusted so that the focal position substantially coincides with the polygon mirror surface 6 a that deflects the laser beam 30.

The fθ lens 7 is a scanning optical system having fθ characteristics for scanning the laser beam 30 deflected by the polygon scanner 6 and scanned at an equal angle on the fixed image planes 10A and 10B at a constant speed.
Further, the fθ lens 7 has a power different from that in the main scanning direction and deflects the laser beam 30 in order to perform so-called surface tilt correction that reduces the influence of the surface tilt of the polygon mirror surface 6a in the sub-scanning direction. The polygon mirror surface 6a and the image planes 10A and 10B have a conjugate positional relationship.
As long as the fθ lens 7 is an imaging optical system having fθ characteristics, a lens having an appropriate optical surface or a lens group in which appropriate optical surfaces are combined can be suitably employed.
In the present embodiment, the lens is composed of a single lens having an anamorphic lens surface.

As shown in FIG. 4, the fθ lens 7 is a scanning optical system that scans a range of image height ± H = ± f · θ _max around the optical axis 40 as an effective scanning half angle of view ± θ _max of the laser beam 30. A system is formed.
Here, the sign of the image height is the positive direction on the side where the laser light source 2 is positioned with respect to the optical axis 40.

The scanning surface division mirrors 8A and 8B are reflection mirrors that deflect the laser beam 30 transmitted through the fθ lens 7 in different directions according to the scanning field angle, and divide the scanning surface of the laser beam 30 into a plurality of parts. This forms one embodiment of the dividing means.
The scanning plane dividing mirror 8A is a reflecting mirror that deflects the laser beam 30 obliquely toward the upper side of the fθ lens 7 in FIG. 2 within a range where the scanning angle of view θ satisfies the following expression.
θ _a ≦ θ ≦ θ _max (1)
Here, θ _a is a constant scanning angle of view near 0 °.
The scanning plane dividing mirror 8B is a reflecting mirror that deflects the laser beam 30 obliquely toward the lower side of the fθ lens 7 in FIG. 2 within a range in which the scanning angle of view θ satisfies the following expression.
−θ _max ≦ θ ≦ θ _b (2)
Here, the scanning field angles θ _a and θ _b are substantially equal values, and θ _b <θ _a .

  As shown in FIG. 2, the folding mirrors 9A and 9B deflect the laser beams 30 deflected by the scanning plane division mirrors 8A and 8B, respectively, so that the scanning lines become parallel lines separated by a distance L, and FIG. 3 is an optical path bending means for causing the scanning widths of the scanning lines to be in a positional relationship substantially overlapping when viewed in the sub-scanning direction. Therefore, the image planes 10A and 10B are on the same plane. In the present embodiment, the scanning range on each image plane is substantially symmetric with respect to the optical axis 40 in order to increase the overlapping range of the scanning widths of the scanning lines when viewed from the sub-scanning direction.

That is, the optical scanning device 1 includes a plurality of folding mirrors that respectively fold back the plurality of scanning planes divided by the scanning plane dividing unit, and each of the light beams that are scanned on the plurality of scanning planes by the plurality of folding mirrors. The beams are scanned in a scanning plane parallel to each other on a certain plane, and the scanning widths in the respective main scanning directions are formed so as to overlap each other when viewed from the sub-scanning direction orthogonal to the main scanning direction. It is an optical scanning device.
Therefore, the optical scanning device is suitable for an image forming system that superimposes the images of the scanning lines exposed and scanned by the respective scanning lines.

Further, the optical scanning device 1 is an optical scanning device in which two scanning plane dividing means are provided, and the optical paths after the division are provided in a positional relationship sandwiching the scanning plane before the division.
By arranging in this manner, it is easy to arrange the image planes 10A and 10B apart, and there is an advantage that it is easy to secure a space for arranging the photoconductors 11A and 11B and the image forming means around them.
Further, by arranging the folding mirrors 9A and 9B so as to overlap with the fθ lens 7 as in this embodiment, the space above and below the fθ lens 7 can be used effectively, and a compact device is configured. There is an advantage that can be. In other words, by arranging folding mirrors at positions opposite to each other across the scanning optical system so as to overlap the scanning optical system, the vertical space of the scanning optical system can be used effectively, and the compactness is achieved. There is an advantage that it can be made a simple device.

As shown in FIG. 3, the optical scanning device 1 includes a bending mirror 12, a synchronization detection lens 13, and a synchronization detection sensor 14 in order to perform synchronization control of the scanning start position of each scanning line.
The bending mirror 12 is for deflecting light having a scanning field angle of −θ _D (where θ _D > θ _max ) out of the laser beam 30 transmitted through the fθ lens 7 and guiding the light to the synchronization detection means.
The synchronization detection lens 13 is a condensing optical element for adjusting the image formation position and the spot diameter size so that the laser beam 30 whose optical path is bent by the bending mirror 12 is accurately detected by the synchronization detection means. It is.
The synchronization detection sensor 14 detects the arrival of the laser beam 30 collected by the synchronization detection lens 13 at a predetermined image height corresponding to the scanning angle of view −θ _D and generates a synchronization detection signal 104. Means. For example, it includes a PIN photodiode having an elongated rectangular light receiving surface and a synchronization detection signal generating circuit connected thereto.
The synchronization detection sensor 14 is electrically connected to the control unit 100 and can send a synchronization detection signal 104 to the control unit 100.

That is, the optical scanning device 1 includes a single synchronization detection unit for performing synchronization control of the scanning start position of the exposure scan, and the synchronization detection signal of the synchronization detection unit is used to synchronize the exposure scans of the plurality of scanning surfaces. Commonly used for control.
Therefore, the synchronization detection means can be used for a plurality of exposure scans, and there is an advantage that the number of parts can be reduced.
In addition, since only one synchronization detection unit is used, the scan field angle range for performing the synchronization detection is small, so that there is an advantage that the effective image width can be widened.

Next, the operation of the optical scanning device 1 of the present embodiment will be described along the optical path.
When the information signal 101 is sent to the control unit 100, a laser drive signal 102 is sent from the control unit 100 to the laser light source 2, and a laser beam 30 modulated based on the information signal 101 is emitted. The emitted laser beam 30 is made into substantially parallel light by the collimating lens 3, enters the beam shaping slit 4, and enters the cylindrical lens 5 as substantially parallel light whose sectional shape is shaped by the shape of the beam shaping slit 4. The

  The laser beam 30 transmitted through the cylindrical lens 5 is condensed in the sub-scanning direction, is incident on a point P (see FIG. 4) on the polygon mirror surface 6a of the polygon scanner 6, and forms an image in a line extending in the main scanning direction. Is done.

On the other hand, the polygon scanner 6 starts rotating prior to the start of oscillation of the laser light source 2 by the control unit 100 and rotates at a constant angular velocity.
Therefore, when the laser beam 30 is incident, the laser beam 30 is repeatedly deflected and scanned at a constant angular velocity at least in the range of the scanning angle of view −θ _D to + θ _max .

The laser beam 30 having a scanning angle of view −θ _D is in a non-image area, and is condensed in the main scanning direction and the sub scanning direction by the fθ lens 7 and deflected by the bending mirror 12 as shown in FIG. The light passes through the lens 13, has a predetermined spot diameter, and is guided to the synchronization detection sensor 14.
The position of the synchronization detection sensor 14 corresponds to the image height at point A in FIG. 4 on the optical path layout. That is, f · θ _D = H + H ₀ .
When the laser beam 30 is received by the synchronization detection sensor 14, a synchronization detection signal 104 is generated and sent to the control unit 100.

On the other hand, in the range where the scanning angle of view θ satisfies the expression (2), the laser beam 30 transmitted through the fθ lens 7 is scanned at a constant speed from point B to point D on the optical layout (see FIG. 4).
In the range where the scanning angle of view θ satisfies the expression (1), the laser beam 30 transmitted through the fθ lens 7 is scanned at a constant speed from the point E to the point G on the optical layout (see FIG. 4).
In the actually formed optical path, when the scanning field angle θ is within the range of the expression (2), the laser beam 30 is deflected by the scanning plane dividing mirror 8B, and further folded by the folding mirror 9B, as viewed from the front (see FIG. 2). Thus, an optical path folded compactly in an inverted Z shape is formed, reaches the image plane 10B, and is scanned at a constant speed in the direction perpendicular to the plane of FIG.
When the scanning angle of view θ is within the range of the expression (1), the laser beam 30 is deflected by the scanning plane dividing mirror 8A, and further folded by the folding mirror 9A, and compact in a Z shape in front view (see FIG. 2). 2 is formed, reaches the image plane 10A, and is scanned at a constant speed in the direction perpendicular to the plane of FIG.

On the image planes 10A and 10B, the respective laser beams 30 are imaged with a predetermined spot diameter in the main scanning direction and the sub-scanning direction. These spot diameters are determined by the opening shape of the beam shaping slit 4 and the focal length of the fθ lens 7, and are set in advance according to the size of the exposure pixel required by the image forming system.
Further, in the sub-scanning direction, the deflection point of the polygon mirror surface 6a and the image plane are conjugate to each other, so that the surface tilt correction is performed. Even if there is a surface tilt error of the polygon mirror surface 6a, the sub-scan direction is corrected. All polygon mirror surfaces 6a are scanned on substantially the same scanning line without shifting the scanning position.

In this way, when the optical path is not folded, the laser beam 30 is scanned at a constant speed from the point B to the point G on the same scanning line between the image heights ± H as shown in FIG. On the other hand, it is divided into two scanning sections having a width of about H by the scanning plane dividing mirrors 8A and 8B, and is further folded on different image planes 10A and 10B by the folding mirrors 9A and 9B.
Although the positions of the image planes 10A and 10B depend on the arrangement of the folding mirrors 9A and 9B, in this embodiment, the scanning lines are arranged in parallel to each other, and the scanning range is substantially symmetric with respect to the optical axis 40. Has been.
For example, as shown in FIG. 4, the image plane 10 </ b> A is arranged at the position of the straight line eg where the midpoint F of the straight line EG is positioned at the point f on the optical axis 40 in plan view. Further, although not particularly illustrated, similarly, the image plane 10B is arranged at a position where the midpoint C of the straight line BD moves substantially at the same position as the point f and substantially overlaps the straight line eg.
Here, the positions of the scanning lines on the image planes 10A and 10B in the main scanning direction can be shifted within the correction limit because the writing position can be corrected by the synchronous control.

Next, exposure scanning control using the optical scanning device 1 will be described.
FIG. 5 is a timing chart for explaining control of exposure scanning of the optical scanning device according to the first embodiment of the present invention.
When the polygon scanner 6 is rotated by the polygon mirror surface 6a, the laser beam 30 deflected in the direction of the scanning field angle - [theta] _D is a mirror 12 bending, through the synchronization detection lens 13, is incident on the synchronism detecting sensor 14 The synchronization detection signal 104 is generated.
For example, as shown in FIG. 5, by the deflection of a polygon mirror surface 6a, the synchronization detection signal 104 is generated at time t _0, the next synchronization detection signal 104 at time t ₅ by the deflection of adjacent polygonal mirror surface 6a is It is assumed that the time for scanning at the angle of view ± θ _max is from time T ₁ to time T ₂ .

Optical scanning device 1, the period from time _{T 1} of the _{T 2,} draw the image surface 10B, on 10A, i.e. the photoreceptor 11B, a scanning line one by one on respective 11A. The information signal 101 used for each exposure is referred to as information signals B and A.
Therefore, when the synchronization detection signal 104 at time t ₀ is generated, the control unit 100 turns off the laser beam 30 and delays the laser beam 30 according to the information signal B by delaying Δt _B = t ₁ −t _0. Similarly, the laser drive signal 102 corresponding to the information signal A is generated with a delay of Δt _A = t ₃ −t ₀ .
Here, by adjusting the delay times Δt _B and Δt _A , synchronous control for adjusting the writing position of the information signals B and A can be performed.

With respect to the sub-scanning direction, the scanning line exposed with the information signal A is delayed by Δt _AB = t ₃ −t _{1 with} respect to the scanning line exposed with the information signal B, and is written at a position separated by a distance L. It is. Therefore, in order to superimpose the scanning line of the photoconductor 11B and the scanning line of the photoconductor 11A, the following equation should be satisfied.
L / V + Δt _AB = m / (n · N) (3)
Here, V is the common linear velocity of the photoconductors 11A and 11B, N is the number of rotations of the polygon scanner 6, n is the number of polygon mirror surfaces 6a, and m is a positive integer.

  As described above, the optical scanning device 1 of the present embodiment can be used as an exposure unit of an image forming system that superimposes exposed scanning lines.

Further, according to the optical scanning device 1 of the present embodiment, even with one laser light source 2, the scanning plane is divided into two by the scanning plane dividing mirrors 8A and 8B, and scanning lines are formed on two different image planes. Therefore, multi-beam exposure scanning can be performed.
Therefore, since the number of beam light sources can be reduced compared to the number of light beams, the number of parts such as the beam light source and its driving means can be reduced, so that the manufacturing cost can be reduced and the structure can be made compact. it can.

  In the present embodiment, since the scanning plane dividing mirrors 8A and 8B are disposed after the fθ lens 7, a multi-beam exposure scanning is performed with one scanning optical system. That is, both the beam light source and the scanning optical system are commonly used.

  In addition, since the scan for forming one scan line is divided into a plurality of scan lines, it is easy to make a multi-beam optical scanning device having a narrower width by using an existing wide scanning optical system. There is an advantage that it can be formed. For example, a general-purpose A3 vertical feed width scanning optical system can be diverted to an A5 vertical feed width two-beam scanning optical system.

Next, a modification of this embodiment will be described.
FIG. 6 is a schematic configuration explanatory diagram of a front view for explaining a schematic configuration of an optical scanning device according to a modification of the first embodiment of the present invention. Here, only a principal ray on the axis is shown except for some rays. In addition, the optical path until it enters the optical deflector is shown in a developed state in the drawing.

  The optical scanning device 20 of this modification includes a scanning surface division mirror 8C and a folding mirror 9C, respectively, instead of the scanning surface division mirror 8B and the folding mirror 9B of the optical scanning device 1 of the above embodiment. Hereinafter, a description will be given focusing on differences from the above embodiment.

The scanning plane division mirror 8C deflects the laser beam 30 transmitted through the fθ lens 7 within the range in which the scanning angle of view θ satisfies the expression (2) as shown in FIG. It deflects in an oblique direction on the same side as the direction.
The folding mirror 9C folds the laser beam 30 deflected by the scanning plane dividing mirror 8C to form a scanning line parallel to the scanning line formed on the image plane 10A and separated by a distance L on the image plane 10C. Therefore, on the image surface 10C, a photoconductor 11C arranged in parallel with the photoconductor 11A can be provided, and the surface can be exposed and scanned.

The optical scanning device 20 is different from the optical scanning device 1 in that the image planes 10 </ b> A and 10 </ b> C are formed in the same direction with respect to the fθ lens 7. That is, the present modification is an optical scanning device in which two scanning plane dividing means are provided, and the optical paths after the division are provided in a positional relationship in the same direction with respect to the scanning plane before the division. .
According to this modification, a member such as the fθ lens 7 is not sandwiched between the optical paths after being divided by the scanning plane dividing means, so that the separation distance L can be set smaller than that of the optical scanning device 1. There is an advantage that you can.

[Second Embodiment]
An image forming system according to a second embodiment of the present invention will be described.
FIG. 7 is a schematic configuration explanatory diagram of a front view for explaining a schematic configuration of an image forming system according to the second embodiment of the present invention.

The image forming system 200 according to the present embodiment forms a four-color image by performing exposure scanning with four beams using two optical scanning devices according to the first embodiment of the present invention, and superimposes them. A full color image is formed.
The schematic configuration of the image forming system 200 includes, for example, four laser beams 30Y, 30M that are modulated based on an information signal that is color-separated into yellow, magenta, cyan, and black color components, and are collected at appropriate spots. An image of each color is formed on the basis of the exposure information of the laser beam 30Y, 30M, 30C, 30K and the exposure unit 201 that emits 30C, 30K as mutually parallel scanning lines, and transferred onto the transfer paper 23. And an image forming unit 202 to be fixed.

  The exposure unit 201 is configured by using optical scanning devices 1A and 1B having the same configuration as that of the optical scanning device 1 according to the first embodiment of the present invention. The optical scanning device 1A emits laser beams 30Y and 30M, and the optical scanning device 1B emits laser beams 30C and 30K.

As long as the image forming unit 202 can form a full-color image by four-beam exposure, any image forming device may be used. In this embodiment, a 4-drum tandem image forming device using electrophotography is used. Used.
That is, the image forming units 15Y, 15M, 15C, and 15K are equally spaced from the upstream side in the transport direction along the transfer transport belt unit 21 that is an endless belt that is rotated in one direction to transport the transfer paper 23. Has been placed. A fixing unit 22 for performing heat roller fixing and a paper discharge tray 24 for discharging the transfer paper 23 are provided on the downstream side in the transport direction of the transfer transport belt unit 21.

The image forming unit 15Y (15M, 15C, 15K) exposes the laser beam 30Y (30M, 30C, 30K) to form a photosensitive drum 16 that forms an electrostatic latent image, and a charger that uniformly charges the photosensitive drum 16. 17, a developing unit 18Y (18M, 18C, 18K) for developing the electrostatic latent image, and a transfer unit 19 for transferring the developed toner image to the transfer paper 23.
The developing units 18Y, 18M, 18C, and 18K charge the color toners corresponding to yellow, magenta, cyan, and black, respectively, and in accordance with the electrostatic latent images formed on the respective photosensitive drums 16, respectively. For example, any known technique such as one-component development or two-component development may be used.
The arrangement positions with respect to the transfer / conveying belt unit 21 are formed by the respective scanning lines when the laser beams 30Y, 30M, 30C, and 30K are irradiated with an appropriate time delay in accordance with the color-separated information signal. The toner images are arranged in a positional relationship such that the toner images can be transferred on the same line on the transfer paper 23.

  Although not particularly illustrated, the image forming system 200 naturally includes an overall control unit for controlling the above-described components to perform an image forming operation, a paper feeding unit, and the like.

  According to the image forming system 200, the laser beams 30Y, 30M, 30C, and 30K modulated by the color-separated information signals are respectively irradiated with appropriate delays, and the photoreceptors of the image forming units 15Y, 15M, 15C, and 15K, respectively. An electrostatic latent image can be formed on the drum 16, developed with toner of each color, transferred onto the transfer paper 23 in a superimposed manner, and fixed by the fixing unit 22 to form a full color image.

In other words, the image forming system is characterized in that it includes the optical scanning device according to the first embodiment of the present invention to perform multi-beam exposure scanning to form an image.
Therefore, the same operational effects as those of the optical scanning device according to the first embodiment are provided.

  In the above description, the example in which the light beam emitted from one beam light source is divided into two by the scanning plane dividing means has been described. However, the number of division is not limited to two, but three or more It may be. For example, it may be divided into four to form an optical scanning device that performs four beam scanning with one beam light source.

  In the above description, an example in which the optical path after being divided by the scanning plane dividing unit is folded by one folding mirror, may be folded by more folding mirrors as necessary.

In the above description, the image plane after being folded by the folding mirror has been described as being parallel to the respective scanning lines. However, the image plane is not necessarily parallel unless it is an optical scanning device used in an image forming system for color superimposition. It does not have to be.
Similarly, the scanning ranges may not be arranged so as to overlap in the sub-scanning direction.
For example, when separate exposure scans are performed on optical recording media that are not related to each other, the positions of the respective scanning lines may be arranged in an appropriate positional relationship for convenience of layout.

In the above description, an example in which different image planes are formed on different optical storage media has been described. The light beam may be folded so that it is formed.
For example, a multi-beam optical scanning device that scans at a pixel pitch or an integer multiple of the pixel pitch in the sub-scanning direction may be formed on a single photosensitive drum. In this case, it is possible to configure a monochromatic image forming system that is accelerated by multi-beam scanning.

In the above description, the scanning optical system is a single lens, but the scanning optical system may be configured by a lens group. In that case, the scanning plane dividing means may be arranged at the subsequent stage of the scanning optical system, or may be arranged on the optical path between the lenses in the scanning optical system. In the latter case, it is necessary to provide a plurality of lenses or lens groups of the scanning optical system arranged after the scanning plane dividing means for each image plane of the optical path divided by the scanning plane dividing means. The lens or lens group of the scanning optical system arranged between the surface dividing means is commonly used for each light beam.
As an example of such a scanning optical system, a scanning optical system including a spherical fθ lens and a long cylindrical lens disposed in the vicinity of the image plane can be given. In this case, the scanning plane dividing unit can be disposed between the fθ lens and the long cylindrical lens.

  In the above description, the optical scanning device of the present invention has been described as being suitable for use in an image forming system. However, the application of the optical scanning device of the present invention is not limited to an image forming system.

  In the above description, an example in which a scanning optical system is included between the optical deflector and the scanning plane dividing unit has been described. However, depending on optical characteristics such as a scanning field angle and a spot diameter necessary for exposure scanning, scanning optical It is good also as a structure which does not include a system. Moreover, even if it includes a scanning optical system, it may be a scanning optical system that does not have fθ characteristics.

In the above description, the example in which the synchronization detection unit is used in common in a plurality of exposure scans has been described. You may make it perform synchronous control for every line.
In this case, since the delay time from the synchronization detection signal can be set to be short, there is an advantage that the delay time can be set with high accuracy.

  Further, all the constituent elements described above can be implemented in appropriate combination within the scope of the technical idea of the present invention, if technically possible. For example, the optical scanning device according to the modification of the first embodiment can be naturally adopted as the optical scanning device of the image forming system according to the second embodiment.

Here, a case will be described where the names of the correspondence relationship between the terminology of the above embodiment and the terminology of the claims are different.
The laser light source 2 and the polygon scanner 6 are embodiments of a beam light source and an optical deflector, respectively. The laser beam 30 corresponds to a light beam. Each of the scanning plane dividing mirrors 8A, 8B, and 8C is an embodiment of the scanning plane dividing means.
The synchronization detection sensor 14 is an embodiment of the synchronization detection means.

FIG. 2 is a schematic configuration diagram illustrating a schematic configuration of the optical scanning device according to the first embodiment of the present invention as viewed from above. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram in front view for explaining a schematic configuration of an optical scanning device according to a first embodiment of the present invention. 1 is a schematic configuration explanatory diagram in back view for explaining a schematic configuration of an optical scanning device according to a first embodiment of the present invention. 1 is an optical layout diagram of an optical scanning device according to a first embodiment of the present invention. It is a timing chart for demonstrating control of the exposure scanning of the optical scanning device concerning the 1st Embodiment of this invention. It is typical structure explanatory drawing of the front view for demonstrating schematic structure of the optical scanning device of the modification of the 1st Embodiment of this invention. It is a typical structure explanatory view of front view for demonstrating schematic structure of the image forming system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

1, 1A, 1B, 20 Optical scanning device 2 Laser light source (beam light source)
3 Collimating lens 4 Beam shaping slit 5 Cylindrical lens 6 Polygon scanner (optical deflector)
6a Polygon mirror surface 7 fθ lenses 8A, 8B, 8C Scanning surface dividing mirror (scanning surface dividing means)
9A, 9B, 9C Folding mirrors 10A, 10B, 10C Image planes 11A, 11B, 11C Photoconductor 14 Synchronization detection sensor (synchronization detection means)
30 Laser beam 100 Control unit 101 Information signal 102 Laser drive signal 104 Synchronization detection signal 200 Image forming system 201 Exposure unit 202 Image forming unit

Claims (5)

An optical scanning device comprising: a beam light source that generates a light beam; and an optical deflector that deflects and scans within a predetermined scanning plane in order to perform exposure scanning with the light beam emitted from the beam light source,
The apparatus further comprises a scanning plane dividing unit that guides the light beam deflected by the optical deflector in different directions according to the scanning angle of view and divides the scanning plane of the exposure scanning into a plurality of scanning planes. Optical scanning device. A plurality of folding mirrors that respectively fold back the plurality of scanning planes divided by the scanning plane dividing means;
With the plurality of folding mirrors, the respective light beams scanned on the plurality of scanning planes are main-scanned by forming parallel scanning lines on a certain plane, and the scanning width in each main-scanning direction is the main scanning direction. The optical scanning device according to claim 1, wherein the optical scanning device is formed so as to be substantially overlapped when viewed from a sub-scanning direction orthogonal to the scanning direction. A single synchronization detecting means for performing synchronization control of the scanning start position of the exposure scanning;
3. The optical scanning device according to claim 1, wherein the synchronization detection signal of the synchronization detection unit is commonly used for synchronization control of exposure scanning of the plurality of scanning surfaces.   The light according to any one of claims 1 to 3, wherein two scanning plane dividing means are provided, and each divided optical path is provided in a positional relationship sandwiching the scanning plane before division. Scanning device.   An image forming system, wherein the optical scanning device according to claim 1 is used to perform multi-beam exposure scanning to form an image.

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