JP2008216520A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner and an image forming apparatus having high scanning accuracy at low cost. <P>SOLUTION: The optical scanner is provided with: a luminous flux split prism 202a which splits the light beam from a light source 152a into two light beams; a luminous flux split prism 202b which splits the light beam from a light source 152b into two light beams; two liquid crystal deflection elements (203a and 203b) which modulate the phase of the two light beams from the luminous flux split prism 202a, respectively; and two liquid crystal deflection elements (203c and 203d) which modulate the phase of the two light beams from the luminous flux split prism 202b, respectively. Thus high scanning accuracy is available at low cost. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus, and more particularly to an optical scanning device that scans a surface to be scanned with light, and an image forming apparatus including the optical scanning device.

  In electrophotographic image recording, an image forming apparatus using a laser is widely used. In this case, the image forming apparatus includes an optical scanning device, and forms a latent image by rotating the drum while scanning laser light using a polygon scanner (for example, a polygon mirror) in the axial direction of the photosensitive drum. Is common. In the field of electrophotography, an image forming apparatus is required to increase image density in order to improve image quality and to increase image output speed in order to improve operability.

  And the method of scanning a some line simultaneously using a some beam is proposed (for example, refer patent documents 1-3).

  For example, in Patent Document 1, optical scanning optical paths from one light source to n (≧ 2) optical scanning positions are formed, and the optical scanning optical paths to the n optical scanning positions are shifted in time. The light beams from the one light source are sequentially selected, and the light beam from the one light source is intensity-modulated by an image signal corresponding to the optical scanning position optically scanned by the selected optical scanning optical path. An optical scanning device that optically scans n optical scanning positions is disclosed. This optical scanning device includes m (1 ≦ m <n) light sources each emitting p (≧ 1) light beams, and q (2 ≦ q) each light beam from each light source in the sub-scanning direction. ≦ n) A light beam splitting unit that splits each light beam into a predetermined beam form, and a plurality of deflection reflection surfaces around the rotation axis, and q · mp light beams from the m light sources A polygon mirror type optical deflector that receives and deflects the beam, and n sets that form light spots by guiding n sets of light beams deflected by the polygon mirror type optical deflector to the corresponding optical scanning positions. And an optical path selection unit that selects an optical scanning optical path for each of the n sets of light beams, and the polygon mirror type optical deflector is at least a part of the optical path selection unit. It is characterized by making.

  Patent Document 2 discloses a light source that emits a laser beam, a deflection scanning unit that scans the laser beam from the light source in one direction, and a plurality of scanning imaging units that focus the deflected laser beam on a surface to be scanned. An optical scanning device having the following is disclosed. The optical scanning device is provided with a plurality of laser beam detectors each including the two systems of light receiving elements for detecting the laser beam in a region where the deflected laser beam passes for each scanning imaging unit. At least one system of the light receiving elements has two light receiving areas formed non-parallel to each other in an area through which the laser beam passes, and the two light receiving elements have a main scanning direction so that adjacent edges are parallel to each other. It is characterized by being arranged adjacent to

  Patent Document 3 includes a liquid crystal element capable of modulating the phase of a laser beam, and the liquid crystal element has a stripe-like electrode pattern arranged in one direction, and each stripe-like electrode pattern is individually provided. An optical scanning device having means for varying the effective value of the driving voltage is disclosed.

Japanese Patent Laying-Open No. 2005-092129 JP-A-2005-208513 JP 2005-292349 A

  In recent years, an image forming apparatus has been used for simple printing as an on-demand printing system, and accordingly, an image forming apparatus having a low price and excellent image quality is required.

  The present invention has been made under such circumstances, and a first object of the invention is to provide an optical scanning device that is low in price and excellent in scanning accuracy.

  A second object of the present invention is to provide an image forming apparatus capable of forming a high-quality image at high speed at a low price.

  According to a first aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with light, the light source; a light splitting element that splits light from the light source into a plurality of lights; and the plurality of lights. A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned; at least of the plurality of lights between the light splitting element and the deflector And a liquid crystal element that is arranged on the optical path of one light and modulates the phase of incident light.

  According to this, since the light splitting element that splits the light from the light source into a plurality of lights is provided, the number of light sources can be reduced as compared with the prior art. In addition, since the liquid crystal element that modulates the phase of at least one of the plurality of lights from the light splitting element is included, the scanning accuracy can be improved. Therefore, it is possible to realize cost reduction with high scanning accuracy.

  According to a second aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device of the present invention that scans the at least one image carrier with light containing image information. An image forming apparatus provided.

  According to this, since at least one optical scanning device of the present invention is provided, as a result, it is possible to form a high-quality image at high speed at low cost.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a printer 10 according to an embodiment of the present invention. In this specification, the main scanning direction will be described as the Y-axis direction, the sub-scanning direction as the Z-axis direction, and the direction orthogonal to these will be described as the X-axis direction.

  The printer 10 is a tandem multicolor printer that forms a full-color image by superimposing four colors (yellow, magenta, cyan, and black), and includes an optical scanning device 100, four photosensitive drums (30a, 30a, 30b, 30c, 30d), four charging chargers (32a, 32b, 32c, 32d), four developing rollers (33a, 33b, 33c, 33d), and four toner cartridges (34a, 34b, 34c, 34d). ) Four cleaning cases (31a, 31b, 31c, 31d), transfer belt 40, paper feed tray 60, paper feed roller 54, registration roller pair 56, fixing roller 50, paper discharge tray 70, paper discharge roller 58, And a control device (not shown) for comprehensively controlling the above-described units.

  The photosensitive drum 30a, the charging charger 32a, the developing roller 33a, the toner cartridge 34a, and the cleaning case 31a are used as a set, and form an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image. Constitute.

  The photosensitive drum 30b, the charging charger 32b, the developing roller 33b, the toner cartridge 34b, and the cleaning case 31b are used as a set, and an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image. Constitute.

  The photosensitive drum 30c, the charging charger 32c, the developing roller 33c, the toner cartridge 34c, and the cleaning case 31c are used as a set, and form an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image. Constitute.

  The photosensitive drum 30d, the charging charger 32d, the developing roller 33d, the toner cartridge 34d, and the cleaning case 31d are used as a set, and form an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image. Constitute.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is the surface to be scanned. The photosensitive drums are arranged at equal intervals in the X-axis direction with the longitudinal direction as the Y-axis direction. Each photosensitive drum is rotated clockwise (in the direction of the arrow) within the plane in FIG. 1 by a rotation mechanism (not shown).

  Each charging charger uniformly charges the surface of the corresponding photosensitive drum.

  The optical scanning device 100 converts light modulated for each color based on multicolor image information (yellow image information, magenta image information, cyan image information, black image information) from a host device (for example, a personal computer). The surface of the corresponding charged photosensitive drum is irradiated. As a result, on the surface of each photoconductive drum, the charge disappears only in the portion irradiated with light, and a latent image corresponding to the image information is formed on the surface of each photoconductive drum. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates. The configuration of the optical scanning device 100 will be described later.

  Yellow toner is stored in the toner cartridge 34a, and the toner is supplied to the developing roller 33a. Magenta toner is stored in the toner cartridge 34b, and the toner is supplied to the developing roller 33b. Cyan toner is stored in the toner cartridge 34c, and the toner is supplied to the developing roller 33c. Black toner is stored in the toner cartridge 34d, and the toner is supplied to the developing roller 33d.

  As each developing roller rotates, the toner from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (hereinafter referred to as “toner image” for convenience) moves in the direction of the transfer belt 40 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 40 at a predetermined timing, and are superimposed to form a color image.

  Recording paper is stored in the paper feed tray 60. A paper feed roller 54 is arranged in the vicinity of the paper feed tray 60, and the paper feed roller 54 takes out the recording paper one by one from the paper feed tray 60 and conveys it to the registration roller pair 56. The registration roller pair 56 feeds the recording paper toward the transfer belt 40 at a predetermined timing. As a result, the color image on the transfer belt 40 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing roller 50.

  In the fixing roller 50, heat and pressure are applied to the recording paper, whereby the toner is fixed on the recording paper. The recording paper fixed here is sent to the paper discharge tray 70 via the paper discharge roller 58 and is sequentially stacked on the paper discharge tray 70.

  Each cleaning case removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position of the corresponding charging charger again.

  Next, the configuration of the optical scanning device 100 will be described.

  As shown in FIG. 2 as an example, the optical scanning device 100 includes two light sources (152a and 152b), two coupling lenses (154a and 154b), two optical elements (201a and 201b), 2 beam splitting prisms (202a, 202b), 4 liquid crystal deflecting elements (203a, 203b, 203c, 203d), 4 cylinder lenses (204a, 204b, 204c, 204d), polygon mirror 104, 4 fθ lens (105a, 105b, 105c, 105d), 8 folding mirrors (106a, 106b, 106c, 106d, 108a, 108b, 108c, 108d), 4 toroidal lenses (107a, 107b, 107c, 107d), And 8 light detection sensors (205a, 205b, 205c, 205d, 2 6a, it comprises 206b, 206c, 206d) and the like.

  Each light source is a surface emitting semiconductor laser array in which 32 light emitting portions v are formed on one substrate, as shown in FIG. 3 as an example.

  This laser array is inclined by an angle γ from a direction corresponding to the main scanning direction (hereinafter also referred to as “M direction” for convenience) to a direction corresponding to the sub-scanning direction (here, the Z-axis direction) ( In the following, there are four light emitting part rows in which eight light emitting parts are arranged at equal intervals (interval d) along the “T direction” for convenience. These four light emitting unit rows are arranged at equal intervals (intervals d) in a direction orthogonal to the T direction (hereinafter referred to as “S direction” for convenience). That is, the 32 light emitting units are two-dimensionally arranged along the T direction and the S direction, respectively. In the present specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  In addition, the polarization state of the light from each light emission part is mutually the same, and is any of a random polarization, a circular polarization, and a linear polarization.

  The coupling lens 154a makes light from the light source 152a substantially parallel light. The coupling lens 154b makes light from the light source 152b substantially parallel light.

  The optical element 201a is disposed on the optical path of light via the coupling lens 154a, and outputs light in a polarization state according to the modulation characteristics of the liquid crystal deflection element 203a and the liquid crystal deflection element 203b. The optical element 201b is disposed on the optical path of light via the coupling lens 154b, and outputs light in a polarization state corresponding to the modulation characteristics of the liquid crystal deflection element 203c and the liquid crystal deflection element 203d.

  Here, each optical element outputs linearly polarized light in the Z-axis direction (see FIGS. 4 to 6).

  The light beam splitting prism 202a is disposed on the optical path of the light passing through the optical element 201a, and splits the light passing through the optical element 201a into two lights that are parallel to each other at a predetermined interval in the Z-axis direction. The beam splitting prism 202b is disposed on the optical path of the light that passes through the optical element 201b, and splits the light that passes through the optical element 201b into two lights that are parallel to each other at a predetermined interval in the Z-axis direction.

  Here, each of the light beam splitting prisms has the same configuration. Therefore, the light beam splitting prism 202a will be described as a representative, and the description of the light beam splitting prism 202b will be omitted.

  The beam splitting prism 202a includes a half mirror Hm and a reflection mirror Rm as shown in FIGS. 4 to 6 as an example. The half mirror Hm receives light that has passed through the optical element 201a, reflects half of the light in the + Z direction, and transmits the remaining light as it is. The reflection mirror Rm is arranged in parallel to the half mirror Hm on the + Z side of the half mirror Hm, and bends the optical path of light from the half mirror Hm so as to be parallel to the optical path of light transmitted through the half mirror Hm. FIG. 4 shows a case where the polarization state of light from the light source 152a is random polarization, and a polarizer can be used as the optical element 201a. FIG. 5 shows a case where the polarization state of light from the light source 152a is circularly polarized light, and a λ / 4 plate can be used as the optical element 201a. FIG. 6 shows a case where the polarization state of light from the light source 152a is linearly polarized light inclined by 45 ° with respect to the Z-axis direction, and a λ / 2 plate can be used as the optical element 201a. In the case of linearly polarized light, the polarization is not limited to 45 ° with respect to the Z-axis direction.

  Returning to FIG. 2, each of the liquid crystal deflecting elements has a configuration in which liquid crystal is sealed between two transparent glass plates, and electrodes are formed above and below the surface of one glass plate. When a potential difference is applied between the electrodes, the orientation of the liquid crystal changes in the Z-axis direction, and as a result, a refractive index gradient (tilt) occurs in the Z-axis direction. Thereby, the light emission axis can be slightly tilted with respect to the Z-axis direction (see JP-A-2005-292349).

  The liquid crystal deflecting element 203a is arranged on the optical path of the −Z side light (hereinafter also referred to as “yellow light” for convenience) of the two lights from the light beam splitting prism 202a, and converts the yellow light to Z according to the applied voltage. It can be deflected with respect to the axial direction.

  The liquid crystal deflecting element 203b is arranged on the optical path of + Z side light (hereinafter also referred to as “magenta light” for convenience) out of the two lights from the light beam splitting prism 202a. Can be deflected with respect to direction.

  The liquid crystal deflecting element 203c is arranged on the optical path of + Z side light (hereinafter also referred to as “cyan light” for convenience) of the two lights from the light beam splitting prism 202b, and converts the cyan light into the Z axis according to the applied voltage. Can be deflected with respect to direction.

  The liquid crystal deflecting element 203d is arranged on the optical path of light on the −Z side (hereinafter also referred to as “black light” for convenience) of the two lights from the light beam splitting prism 202b, and converts the black light to Z according to the applied voltage. It can be deflected with respect to the axial direction.

  The cylinder lens 204 a is disposed on the optical path of light (yellow light) via the liquid crystal deflecting element 203 a and converges the yellow light in the vicinity of the deflection reflection surface of the polygon mirror 104 in the sub-scanning direction.

  The cylinder lens 204b is disposed on the optical path of light (magenta light) via the liquid crystal deflecting element 203b, and converges the magenta light in the vicinity of the deflection reflection surface of the polygon mirror 104 in the sub-scanning direction.

  The cylinder lens 204c is disposed on the optical path of light (cyan light) via the liquid crystal deflecting element 203c, and converges cyan light in the vicinity of the deflection reflection surface of the polygon mirror 104 in the sub-scanning direction.

  The cylinder lens 204d is disposed on the optical path of light (black light) via the liquid crystal deflecting element 203d, and converges the black light in the vicinity of the deflection reflection surface of the polygon mirror 104 in the sub-scanning direction.

  The polygon mirror 104 has a four-stage mirror having a two-stage structure (see FIGS. 2 and 7), and each mirror serves as a deflection reflection surface. The light from the cylinder lens 204a and the light from the cylinder lens 204d are respectively deflected on the first (lower) deflecting / reflecting surface, and the light and cylinder from the cylinder lens 204b are deflected on the second (upper) deflecting / reflecting surface. It arrange | positions so that the light from the lens 204c may be deflected, respectively. Further, the first-stage deflecting / reflecting surface and the second-stage deflecting / reflecting surface rotate with a phase shift of 45 °, and light scanning is alternately performed in the first and second stages.

  The fθ lens 105 a and the fθ lens 105 b are disposed on the −X side of the polygon mirror 104, and the fθ lens 105 c and the fθ lens 105 d are disposed on the + X side of the polygon mirror 104.

  The fθ lens 105a and the fθ lens 105b are stacked in the Z-axis direction, the fθ lens 105a faces the first-stage deflection reflection surface, and the fθ lens 105b faces the second-stage deflection reflection surface (see FIG. 7). Further, the fθ lens 105c and the fθ lens 105d are stacked in the Z-axis direction, the fθ lens 105c faces the second-stage deflection reflection surface, and the fθ lens 105d faces the first-stage deflection reflection surface (see FIG. 7).

  Therefore, the yellow light deflected by the polygon mirror 104 enters the fθ lens 105a, the black light enters the fθ lens 105d, the magenta light enters the fθ lens 105b, and the cyan light enters the fθ lens 105c.

  The yellow light transmitted through the fθ lens 105a forms an image in a spot shape on the photosensitive drum 30a via the folding mirror 106a, the toroidal lens 107a, and the folding mirror 108a. That is, the folding mirror 106a, the toroidal lens 107a, and the folding mirror 108a can be regarded as a part of the Y station.

  The magenta light transmitted through the fθ lens 105b forms a spot image on the photosensitive drum 30b via the folding mirror 106b, the toroidal lens 107b, and the folding mirror 108b. That is, the folding mirror 106b, the toroidal lens 107b, and the folding mirror 108b can be regarded as a part of the M station.

  The cyan light transmitted through the fθ lens 105c forms a spot image on the photosensitive drum 30c via the folding mirror 106c, the toroidal lens 107c, and the folding mirror 108c. That is, the folding mirror 106c, the toroidal lens 107c, and the folding mirror 108c can be regarded as a part of the C station.

  The black light transmitted through the fθ lens 105d forms a spot image on the photosensitive drum 30d via the folding mirror 106d, the toroidal lens 107d, and the folding mirror 108d. That is, the folding mirror 106d, the toroidal lens 107d, and the folding mirror 108d can be regarded as a part of the K station.

  Further, each fθ lens has a non-arc surface shape having such a power that the light spot moves at a constant speed in the main scanning direction on the corresponding photosensitive drum surface as the polygon mirror 104 rotates. Yes.

  The folding mirrors are arranged so that the optical path lengths from the polygon mirror 104 to the photosensitive drums coincide with each other, and the incident position and the incident angle of light on the photosensitive drums are equal to each other. ing.

  Each of the light detection sensors is disposed at a position equivalent to the image plane. Each light detection sensor outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  The light detection sensor 205a is disposed at a position where yellow light that has passed through the toroidal lens 107a immediately before the start of scanning enters. Therefore, it is possible to detect the start of scanning on the photosensitive drum 30a from the output signal of the light detection sensor 205a.

  The light detection sensor 205b is disposed at a position where magenta light that has passed through the toroidal lens 107b and immediately before the start of scanning enters. Therefore, it is possible to detect the start of scanning on the photosensitive drum 30b from the output signal of the light detection sensor 205b.

  The light detection sensor 205c is disposed at a position where cyan light that has passed through the toroidal lens 107c and immediately before scanning starts enters. Therefore, it is possible to detect the start of scanning on the photosensitive drum 30c from the output signal of the light detection sensor 205c.

  The light detection sensor 205d is disposed at a position where black light that has passed through the toroidal lens 107d and immediately before scanning starts enters. Therefore, it is possible to detect the start of scanning on the photosensitive drum 30d from the output signal of the light detection sensor 205d.

  The light detection sensor 206a is arranged so that yellow light that has passed through the toroidal lens 107a and has just finished scanning enters. Therefore, the end of scanning on the photosensitive drum 30a can be detected from the output signal of the light detection sensor 206a.

  The light detection sensor 206b is arranged so that magenta light that has passed through the toroidal lens 107b and has just finished scanning enters. Therefore, the end of scanning on the photosensitive drum 30b can be detected from the output signal of the light detection sensor 206b.

  The light detection sensor 206c is arranged so that cyan light that has passed through the toroidal lens 107c and has just finished scanning enters. Therefore, the end of scanning on the photosensitive drum 30c can be detected from the output signal of the light detection sensor 206c.

  The light detection sensor 206d is arranged so that black light that has passed through the toroidal lens 107d and has just finished scanning enters. Therefore, the end of scanning on the photosensitive drum 30d can be detected from the output signal of the light detection sensor 206d.

  As described above, according to the optical scanning device 100 according to the present embodiment, the light beam splitting prism 202a that splits the light from the light source 152a into two lights, and the light beam splitting that splits the light from the light sources 152b into two lights. And a prism 202b. Thereby, the number of light sources can be reduced more than before. Also, two liquid crystal deflecting elements (203a, 203b) that respectively modulate the phases of the two lights from the beam splitting prism 202a, and two liquid crystal deflections that respectively modulate the phases of the two lights from the beam splitting prism 202b. Element (203c, 203d). Thereby, scanning accuracy can be improved. Therefore, it is possible to realize cost reduction with high scanning accuracy.

  In addition, since the number of light sources can be reduced as compared with the prior art, it is possible to reduce the size.

  Further, the printer 10 according to the present embodiment includes the optical scanning device 100 that is low in price and excellent in scanning accuracy. As a result, it is possible to form a high-quality image at high speed at a low price. It becomes.

  In the above embodiment, as shown in FIG. 8 as an example, the optical element 201a and the light beam splitting prism 202a may be integrated. Thereby, size reduction can be further promoted.

  Moreover, in the said embodiment, it replaces with the said half mirror Hm, and as shown in FIGS. 9-11 as an example, the component of the Z-axis direction in incident light is permeate | transmitted, and in any of an optical axis direction and Z-axis direction Alternatively, a polarization beam splitter PBS that reflects the component in the orthogonal direction in the + Z direction may be used. As a result, linearly polarized light whose polarization state is in the Z-axis direction and linearly polarized light whose polarization state is orthogonal to both the optical axis direction and the Z-axis direction are emitted from the light beam splitting prism. In this case, the optical element 201a is disposed on the optical path of the light from the reflection mirror Rm. FIG. 9 shows a case where the polarization state of light from the light source is random polarization, and a λ / 2 plate can be used as the optical element 201a. FIG. 10 shows a case where the polarization state of light from the light source is circularly polarized light, and a λ / 2 plate can be used as the optical element 201a. FIG. 11 shows a case where the polarization state of light from the light source is linearly polarized light inclined by 45 ° with respect to the Z-axis direction, and a λ / 2 plate can be used as the optical element 201a. In this case, as shown in FIG. 12 as an example, the optical element 201a and the light beam splitting prism 202a may be integrated. Thereby, size reduction can be further promoted.

  Further, in this case, when modulating the phase of only one of the two lights from the light beam splitting prism, for example, as shown in FIG. 13, the liquid crystal deflection is performed corresponding to only the light transmitted through the polarization beam splitter PBS. An element may be arranged. Thereby, the number of parts can be further reduced.

  Moreover, in the said embodiment, as FIG. 14 shows as an example, when the polarization state of the light from the said light source is a linearly polarized light parallel to a Z-axis direction, the said optical element is unnecessary. Thereby, cost reduction and size reduction can be further promoted.

  Moreover, although the said embodiment demonstrated the case where each light source had 32 light emission parts, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where the light emission part space | interval regarding T direction and the light emission part space | interval regarding S direction were mutually equal, it is not restricted to this, The light emission part space | interval regarding T direction and the light emission part space | interval regarding S direction are They may be different from each other.

  In the above embodiment, the S direction may coincide with the Z-axis direction.

  In the above embodiment, the case of a tandem color printer as the image forming apparatus has been described. However, the present invention is not limited to this. For example, even if an image forming apparatus other than a printer (copying machine, facsimile, or multifunction machine in which these are integrated), an image forming apparatus provided with the optical scanning device 100 can be manufactured at a low price and with high quality multicolor. A color image can be formed at high speed.

  Further, an image forming apparatus using a color developing medium (positive photographic paper) that develops color by the heat energy of a beam spot as an image carrier may be used. In this case, a visible image can be directly formed on the image carrier by optical scanning.

  In the above embodiment, the case of a multi-color printer is described as the image forming apparatus. However, the present invention is not limited to this, and the image forming apparatus is a single-color image forming apparatus that forms a high-quality image at a low price and at a high speed. Is possible.

  As described above, the optical scanning device of the present invention is suitable for realizing low cost with high scanning accuracy. The image forming apparatus according to the present invention is suitable for forming a high-quality image at a high speed at a low price.

1 is a diagram illustrating a schematic configuration of a printer 10 according to an embodiment of the present invention. It is a perspective view which shows the optical scanning device 100 in FIG. It is a figure for demonstrating each light source in FIG. FIG. 3 is a diagram (No. 1) for describing an optical element, a light beam splitting prism, and a liquid crystal deflecting element in FIG. FIG. 3 is a diagram (No. 2) for explaining the optical element, the light beam splitting prism, and the liquid crystal deflecting element in FIG. FIG. 3 is a third diagram illustrating the optical element, the light beam splitting prism, and the liquid crystal deflecting element in FIG. It is a side view which shows the optical scanning device 100 in FIG. It is a figure for demonstrating integration of an optical element and a light beam splitting prism. It is FIG. (1) for demonstrating the light beam splitting prism which has PBS. It is FIG. (2) for demonstrating the light beam splitting prism which has PBS. It is FIG. (3) for demonstrating the light beam splitting prism which has PBS. It is a figure for demonstrating integration of the optical element and the light beam splitting prism which has PBS. It is a figure for demonstrating the case where the phase of only one of the two lights from a light beam splitting prism is modulated. It is a figure for demonstrating the case where the polarization state of the light from a light source is a linearly polarized light parallel to a subscanning direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Printer (image forming apparatus), 30a-30d ... Photosensitive drum (image carrier), 100 ... Optical scanning device, 104 ... Polygon mirror (deflector), 105a-105d ... f (theta) lens (a part of scanning optical system) ), 106a to 106d ... folding mirror (part of the scanning optical system), 107a to 107d ... toroidal lens (part of the scanning optical system), 108a to 108d ... folding mirror (part of the scanning optical system), 152a ... light source , 152b ... light source, 201a ... optical element, 201b ... optical element, 202a ... light beam splitting prism (light splitting element), 202b ... light beam splitting prism (light splitting element), 203a ... liquid crystal deflecting element (liquid crystal element), 203b ... liquid crystal Deflection element (liquid crystal element), 203c ... Liquid crystal deflection element (liquid crystal element), 203d ... Liquid crystal deflection element (liquid crystal element), Hm ... Half mirror , PBS ... polarized beam splitter.

Claims (12)

An optical scanning device that scans a surface to be scanned with light,
With a light source;
A light splitting element for splitting light from the light source into a plurality of lights;
A deflector for deflecting the plurality of lights;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned;
An optical scanning device comprising: a liquid crystal element that is disposed on an optical path of at least one of the plurality of lights and modulates a phase of incident light between the light splitting element and the deflector. The light splitting element has a half mirror that splits incident light into two parts,
The optical element which is arrange | positioned on the optical path of the light which goes to the said light splitting element from the said light source, and outputs the light of the polarization state according to the modulation characteristic of the said liquid crystal element is characterized by the above-mentioned. Optical scanning device.   The optical scanning device according to claim 2, wherein the polarization state of the light incident on the half mirror is any one of random polarization, circular polarization, and linear polarization. The liquid crystal element has a modulation characteristic such that a gradient of refractive index occurs in a direction corresponding to the sub-scanning direction,
The optical scanning device according to claim 2, wherein the optical element outputs linearly polarized light in a direction corresponding to a sub-scanning direction. The light splitting element has a polarization beam splitter that splits incident light into two,
The optical device further comprising: an optical element that is disposed on an optical path of at least one light from the light splitting element toward the liquid crystal element, and that outputs light in a polarization state corresponding to a modulation characteristic of the liquid crystal element. 2. An optical scanning device according to 1.   The optical scanning device according to claim 5, wherein the polarization state of the light incident on the polarization beam splitter is one of random polarization, circular polarization, and linear polarization. The light splitting element has a polarization beam splitter that splits incident light into two,
2. The optical scanning device according to claim 1, wherein the light reflected by the polarization beam splitter reaches the deflector without passing through the liquid crystal element.   The optical scanning device according to claim 2, wherein the light splitting element and the optical element are integrated. The liquid crystal element has a modulation characteristic such that a gradient of refractive index occurs in a direction corresponding to the sub-scanning direction,
The optical scanning device according to claim 1, wherein the polarization state of light from the light source is linearly polarized light in a direction corresponding to a sub-scanning direction. The light source is a surface emitting semiconductor laser having a plurality of light emitting units,
The optical scanning device according to claim 1, wherein polarization states of light from the plurality of light emitting units are the same. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 1 to 10 that scans light including image information on the at least one image carrier.   The image forming apparatus according to claim 11, wherein the image information is multicolor image information.

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