JP2008096985A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can reduce in size and speckle noise with a simple and low cost configuration. <P>SOLUTION: The image forming apparatus is provided with: a plurality of laser beam sources 1a, 1b, 1c; a rotary polygon mirror 3 which scans a plurality of beams from the plurality of laser beam sources 1a, 1b, 1c; and a multiplexing member 10 which multiplexes the plurality of laser beams scanned by the rotary polygon mirror 3. The rotary polygon mirror 3 is disposed above or below the multiplexing member 10 and the extension line of a rotary shaft of the rotary polygon mirror 3 passes through the multiplexing member 10. As the result, the apparatus size can be reduced and the speckle noise due to the plurality of laser beams can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a projector using light sources of a plurality of colors such as red (R), green (G), and blue (B).

  A display such as a projector that projects an image on a screen is known. Conventionally, a high-pressure mercury lamp has been mainly used as a light source, but recently, a laser display using a laser as a light source has been studied. When red (R), green (G), and blue (B) lasers are used as the light source, the color reproduction range can be greatly expanded and color representation close to the primary color can be achieved, and power consumption can be reduced. There are advantages.

On the other hand, as a need for a projector, there is a demand for downsizing the projector to a size that can be carried around. It has also been found that when a laser is used as the light source, image quality problems such as speckle noise occur. For such requests and problems, for example, proposals such as those in Patent Literature 1 and Patent Literature 2 have been proposed.
JP-A-2005-99160 Japanese Patent Laid-Open No. 11-64789

  However, in Patent Document 1, although the size of the apparatus can be reduced by downsizing the laser, there is a problem that the price increases. Further, in Patent Document 2, since a configuration for removing speckle noise is included for each of the R, G, and B light sources in order to remove speckle noise, there is a problem that the apparatus size becomes large. there were.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of simultaneously reducing the size of an apparatus and reducing speckle noise with a simple and inexpensive configuration.

  In order to achieve the above object, an image forming apparatus according to the present invention is scanned by a plurality of laser light sources, a rotating polygon mirror that scans a plurality of laser beams from the plurality of laser light sources, and the rotating polygon mirror. A multiplexing member for multiplexing a plurality of laser beams, and an extension line of the rotation axis of the rotary polygon mirror passes through the multiplexing member.

  In the above-described image forming apparatus, the extension of the rotation axis of the rotary polygon mirror that scans the laser beams from the plurality of laser light sources is arranged so as to pass through the multiplexing member, thereby achieving a significant reduction in the size of the apparatus. be able to. Furthermore, by scanning a plurality of laser beams with a single rotating polygonal mirror, speckle noise caused by the plurality of laser beams can be efficiently removed without hindering downsizing of the apparatus.

  The extension line of the rotation axis of the rotating polygon mirror is such that each optical path from the rotating polygon mirror corresponding to each of the plurality of laser beams to the combining member has substantially the same distance. It is preferable that it is deviated from the position by a predetermined distance.

  In this case, the distance of each optical path from the rotating polygon mirror corresponding to each of a plurality of laser beams to the combining member is obtained by shifting the extension line of the rotation axis of the rotating polygon mirror by a predetermined distance from the center position of the combining member. Can be made substantially the same. For this reason, the redundancy of each optical path is lost, and the apparatus size can be further reduced.

  A plurality of condensing elements arranged in the vicinity of the rotating polygon mirror on each optical path from each of the plurality of laser light sources to the rotating polygon mirror, wherein the condensing element is a laser from the laser light source; It is preferable that the light is condensed in the scanning direction of the laser beam by the rotary polygon mirror and emitted to the reflection surface of the rotary polygon mirror.

  In this case, the size and number of the reflecting surfaces of the rotating polygon mirror can be reduced by condensing the laser light incident on the rotating polygon mirror within the reflecting surface of the rotating polygon mirror. For this reason, the apparatus size can be further reduced.

  A plurality of spatial light modulators arranged on each optical path from the rotary polygon mirror corresponding to each of the plurality of laser beams to the combining member and irradiated with laser light scanned by the rotary polygon mirror; Each of the plurality of laser beams scanned by the rotary polygon mirror so that the moving speed of the irradiation position of the laser beam irradiated on the irradiated surface of the spatial modulation element is uniformized on the irradiated surface It is preferable that the light is converted into light substantially perpendicular to the irradiated surface of the spatial modulation element in the vicinity of the rotary polygon mirror.

  In this case, the laser beam scanned by the rotary polygon mirror is converted into light substantially perpendicular to the irradiated surface of the spatial modulation element, so that the moving speed of the irradiation position of the laser beam on the irradiated surface of the spatial modulation element is uniform Can be For this reason, an increase in the movement speed of the irradiation position at the end of the irradiated surface of the spatial modulation element is suppressed, and as a result, the uniformity of modulation on the irradiated surface is improved.

  A plurality of light collimating elements disposed in the vicinity of the rotating polygon mirror on each optical path from the rotating polygon mirror to the multiplexing member, and the light collimating element receives the incident laser light It is preferable to make it substantially perpendicular to the irradiated surface of the spatial modulation element.

  In this case, the laser beam can be converted into light substantially perpendicular to the irradiated surface of the spatial modulation element by arranging the light collimating element on each optical path. For this reason, it is not necessary to separately provide a complicated optical system, and the apparatus size can be reduced.

  The reflecting surface of the rotating polygon mirror has a predetermined curvature in the scanning direction of the laser light by the rotating polygon mirror, and the predetermined curvature is such that the light reflected by the reflecting surface is incident on the irradiated surface of the spatial modulation element. It is preferable to set the light so as to be substantially vertical.

  In this case, the laser beam can be converted into light substantially perpendicular to the irradiated surface of the spatial modulation element by giving the reflecting surface of the rotary polygon mirror a predetermined curvature. For this reason, it is not necessary to separately provide a complicated optical system, and the apparatus size can be reduced.

  It is preferable to further include a heat dissipating fan installed on the rotary polygon mirror, and the heat dissipating fan rotates integrally with the rotary polygon mirror.

  In this case, since the heat dissipation fan rotates in accordance with the rotation of the rotary polygon mirror, it is possible to cool the heat generated in the apparatus without separately providing a rotation drive unit dedicated to the heat dissipation fan. For this reason, the size of the apparatus can be reduced, and excess power consumption can be reduced.

  The range of variation in the amount of surface tilt of each reflecting surface of the rotary polygon mirror is preferably 0.12 degrees or more.

  In this case, the optical path of the laser light fluctuates due to the tilting of the reflecting surface of the rotary polygon mirror, so that the degree of visibility of speckle noise by the viewer can be reduced.

  A plurality of optical systems arranged on each optical path from the rotary polygon mirror to the multiplexing member corresponding to each of the plurality of laser beams, and the optical system includes a plurality of optical systems that propagate the laser beams. It is preferable that at least one of the plurality of optical elements vibrates in a direction substantially perpendicular to the optical path direction.

  In this case, since the optical path of the laser light varies due to the vibration of the optical element disposed on each optical path, the degree of visual recognition of speckle noise by the viewer can be reduced.

  It is preferable that a driving unit that rotates the rotary polygon mirror is further provided, and the vibrating optical element is connected to the driving unit and is vibrated by the driving unit.

  In this case, speckle noise can be reduced without separately providing a drive unit dedicated to vibration of the optical element by vibrating the optical element in conjunction with the rotation of the rotary polygon mirror. For this reason, the size of the apparatus can be reduced, and excess power consumption can be reduced.

  Each of the plurality of laser beams from the plurality of laser light sources is incident on the rotating polygon mirror from different directions from the periphery of the rotating polygon mirror, and each of the plurality of laser light sources is formed by the rotating polygon mirror. Arrange each emission direction of the plurality of laser beams so that the laser beam passing through the center position of the scanning range of the scanned laser beams reaches the center position of the irradiated surface of the spatial modulation element It is preferable that

  In this case, it becomes easy to design an optical system arranged on each optical path from the rotary polygon mirror to the multiplexing member. That is, the optical system may be designed so that the scanning direction of the laser beam scanned by the rotating polygon mirror is bilaterally symmetric with respect to the center direction of the scanning range of the laser beam.

  It is preferable to further include a liquid crystal display panel that displays an image when irradiated with the laser beam combined by the combining member.

  In this case, a liquid crystal display device with a reduced device size and reduced speckle noise can be realized.

  The multiplexing member is preferably a cross prism.

  In this case, it is possible to reduce the size of the projection optical system that multiplexes a plurality of laser beams and projects them on the screen.

  The multiplexing member is preferably two dichroic mirrors crossed at a predetermined angle.

  In this case, in this case, it is possible to reduce the size of the projection optical system that multiplexes a plurality of laser beams and projects them on the screen.

  It is preferable that the rotating polygon mirror is disposed on an upper portion or a lower portion of the multiplexing member.

  In this case, the apparatus size can be reduced more effectively.

  According to the present invention, it is possible to provide an image forming apparatus that can simultaneously reduce the size of the apparatus and reduce speckle noise with a simple and inexpensive configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part, and what attached the same code | symbol in drawing may abbreviate | omit description.

(Embodiment 1)
FIG. 1 is a top view showing a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a side view thereof. Hereinafter, the operation mechanism of the image forming apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2. The optical system of the image forming apparatus according to the present embodiment includes a plurality of laser light sources including a B light source 1a, a G light source 1b, and an R light source 1c, and cylindrical lenses 2a corresponding to the B light source 1a, the G light source 1b, and the R light source 1c, 2b, 2c, rotating polygon mirror 3, cylindrical lenses 4a, 4b, 4c, cylindrical mirror arrays 5a, 5b, 5c, reflecting mirrors 6a, 6b, 6c, diffusion plates 7a, 7b, 7c, and field lenses 8a, 8b, 8c, spatial modulation elements 9a, 9b, 9c, and a multiplexing member 10. Cylindrical lenses 4a, 4b, 4c, cylindrical mirror arrays 5a, 5b, 5c, reflection mirrors 6a, 6b, 6c, diffusers 7a, 7b, 7c, field lenses 8a, 8b, 8c, and spatial modulation elements 9a, 9b, Similarly to the cylindrical lenses 2a, 2b, and 2c, 9c corresponds to the B light source 1a, the G light source 1b, and the R light source 1c.

  As shown in FIG. 2, the optical system of the image forming apparatus according to the present embodiment has a two-story structure in which the rotating polygon mirror 3 is disposed on the upper part of the multiplexing member 10. That is, the laser light sources 1a, 1b, 1c, the cylindrical lenses 2a, 2b, 2c, the rotary polygon mirror 3, the cylindrical lenses 4a, 4b, 4c, and the cylindrical mirror arrays 5a, 5b, 5c are arranged on the second floor portion. The remaining members are arranged on the first floor. Of course, the present embodiment is not limited to this configuration. For example, laser light sources 1a, 1b, 1c, cylindrical lenses 2a, 2b, 2c, rotating polygon mirror 3, cylindrical lenses 4a, 4b, 4c, and cylindrical mirror arrays 5a, 5b, 5c are arranged on the first floor portion, and the rest These members may be arranged on the second floor. In short, one of the rotating polygon mirror 3 and the combining member 10 is arranged on the upper or lower portion of the other, and the laser light emitted from the laser light sources 1a, 1b and 1c and scanned by the rotating polygon mirror 3 is combined. Other members may be disposed so as to be guided to the member 10.

  Laser light emitted from the laser light sources 1a, 1b, and 1c is incident on the rotary polygon mirror 3 in a state of being converged in the main scanning direction by the cylindrical lenses 2a, 2b, and 2c. The light reflected by the reflecting surface of the rotating polyhedron 3 is scanned in the main scanning direction. The main scanning direction described here refers to the rotational scanning direction by the rotary polygon mirror 3. By converging the beam in the main scanning direction on the rotating polygon mirror 3, vignetting in the main scanning direction of the beam on the rotating polygon mirror 3 can be minimized. For this reason, it becomes possible to use a small-diameter rotating polygonal mirror as the rotating polygonal mirror 3, and it is possible to reduce the size of the apparatus.

  Since the beam reflected by the rotary polygon mirror 3 is diverging, it is returned to substantially parallel light by the cylindrical lenses 4a, 4b, 4c. In this case, it is advantageous to use meniscus lenses having power in the main scanning direction as the cylindrical lenses 4a, 4b, and 4c.

  Each beam that has become substantially parallel light by the cylindrical lenses 4a, 4b, and 4c is reflected by the cylindrical mirror arrays 5a, 5b, and 5c, and travels toward the reflecting mirrors 6a, 6b, and 6c disposed on the first floor. The intervals and curvatures of the cylindrical mirror arrays 5a, 5b, and 5c are set so that the exposure intensity on the spatial modulation elements 9a, 9b, and 9c is substantially uniform in the vertical direction. The beams reflected by the reflection mirrors 6a, 6b, and 6c enter the diffusion plates 7a, 7b, and 7c, and are transmitted and diffused within a predetermined angle range by the diffusion plates 7a, 7b, and 7c. Thereafter, the light is converted into telecentricity by the field lenses 8a, 8b, and 8c, and then incident on the spatial modulation elements 9a, 9b, and 9c. The light spatially modulated by the spatial modulation elements 9 a, 9 b, and 9 c is combined with the R, G, and B colors by the multiplexing member 10, then emitted to the projection lens 11, and then passes through the projection lens 11. The image is projected on the screen 12.

  Next, advantages of the optical system having the cylindrical lenses 2a, 2b, 2c and 4a, 4b, 4c of the present embodiment will be described. That is, in the present embodiment, the laser light emitted from the laser light sources 1a, 1b, and 1c is condensed in the main scanning direction of the rotary polygon mirror 3 by the cylindrical lenses 2a, 2b, and 2c, and the rotary polygon mirror 3 is used. The reflected light from the reflecting surface is made substantially parallel light again by the cylindrical lenses 4 a, 4 b, and 4 c and guided to the multiplexing member 10. The present embodiment has the following specific effects by the condensing by the cylindrical lenses 2a, 2b, and 2c and the parallelization by the cylindrical lenses 4a, 4b, and 4c. Hereinafter, this unique effect will be specifically described.

  Here, the parallel beam diameter of the R light source 1c in the main scanning direction is 2 mm, and the distance from the rotary polygon mirror 3 to the spatial modulation element 9c via the cylindrical lens mirror array 5c, the reflection mirror 6c, the diffusion plate 7c, and the field lens 8c. An example in which the width of the spatial modulation element 9c is 15 mm in the main scanning direction will be described. First, consider an optical system without the cylindrical lenses 2c and 4c of the present embodiment.

  When the cylindrical lens 2c does not collect light in the main scanning direction and does not pass through the cylindrical lens 4c, if the duty ratio of the laser scanning period is kept at about 90%, the number of surfaces of the rotary polygon mirror 3 needs to be about 36. become. Further, if the reflecting surface of the rotating polygon mirror 3 has a width of 2 mm in the main scanning direction, the radius of the inscribed circle of the rotating polygon mirror 3 is required to be at least 12 mm. Will be huge. As a result, the size of the rotary polygon mirror 3 increases the size of the entire apparatus. If the combining member 10 is a cuboid cross prism of 20 mm × 20 mm × 20 mm, the size of the rotary polygon mirror 3 arranged on the upper side or the lower side of the cross prism is larger than the projected area when the cross prism is viewed from above. The size of the rotary polygon mirror 3 becomes the rate-determining device size.

  Next, consider the case where the cylindrical lenses 2 c and 4 c of the present embodiment are arranged before and after the rotary polygon mirror 3. In this case, if the light is condensed in the main scanning direction by the cylindrical lens 2c and further passed through the cylindrical lens 4c, the number of surfaces required for the rotary polygon mirror 3 is about 12, which may be reduced compared to the above case. it can. If the radius of the inscribed circle of the rotating polygon mirror 3 is also about 5 mm, the size of the reflecting surface of the rotating polygon mirror 3 has a width of 2 mm or more in the main scanning direction. Since the beam is focused in the main scanning direction on the rotary polygon mirror 3, it can be said that the size of the reflecting surface is sufficient. If it is this size, even if the size of the multiplexing member 10 is the same 20 mm × 20 mm × 20 mm as described above, the rotary polygon mirror 3 does not protrude from the projected area, and the device size is not limited. In addition, rotary polygon mirrors having about 12 faces are widely mass-produced by general-purpose laser printers and the like, and are more advantageous than 36-face polygons in terms of availability and cost. Furthermore, since the cylindrical lenses 4a, 4b, and 4c are inserted, an increase in scanning speed at the left and right scanning ends on the spatial modulation elements 9a, 9b, and 9c can be suppressed, so that the exposure is uniform in the main scanning direction. Improves.

  As described above, the condensing by the cylindrical lens 2c and the parallelization by the cylindrical lens 4c are advantageous in many aspects such as space, cost, availability, and exposure uniformity. In the above example, the system of the R light source 1c is described as an example, but the same can be said for the G light source 1b and the B light source 1a.

  In this embodiment, the cylindrical lenses 2c and 4c having power only in the main scanning direction are used. However, depending on the beam diameter in the thickness direction of the rotary polygon mirror 3, the cylindrical lenses 2c and 4c are also formed in the thickness direction of the reflecting surface. Of course, it is also possible to have a configuration that provides power and eliminates vignetting in the thickness direction.

  Next, advantages of the optical system having the rotary polygon mirror 3 of the present embodiment will be described.

  Generally, as a means for removing speckle noise, as disclosed in Japanese Patent Laid-Open No. 11-64789 described in the background art, it is considered to arrange a lenticular lens that rotates in each optical path of a plurality of light sources. . In this case, motors for rotating the lenticular lens are required for the number of light sources, and therefore, adoption in a small projector having a plurality of light sources is particularly problematic in terms of apparatus size and cost. Further, speckle noise can be reduced by scanning with a galvano scanner or the like other than a lenticular lens as disclosed in JP-A-11-64789. However, when a galvano scanner is inserted into each optical path of a plurality of light sources as in JP-A-11-64789, it is difficult to reduce the size and cost for the same reason as the above lenticular lens.

  On the other hand, according to the rotating polygonal mirror 3 of the present embodiment, a plurality of beams from the plurality of light sources 1a, 1b, 1c are incident on the rotating polygonal mirror 3 from the periphery thereof, thereby rotating as a single scanning means. A plurality of beams can be scanned by the polygon mirror 3. For this reason, speckle noise can be obtained without increasing the number of scanning means even with a plurality of light sources, which is advantageous in terms of cost and space. Furthermore, in the rotary polygon mirror 3 of the present embodiment, the rotary polygon mirror 3 and the multiplexing member 10 are vertically moved so that the extension line of the rotation axis of the rotary polygon mirror 3 passes through the multiplexing member 10. Deploy. By doing so, it becomes possible to make the optical path of each of the plurality of beams from the rotary polygon mirror 3 to the multiplexing member 10 substantially the same, eliminating the redundancy in the optical path of each beam, and enabling further significant downsizing. Become.

  Next, the positional relationship between the rotary polygon mirror 3 and the multiplexing member 10 of the present embodiment will be described. Here, a case where a cross prism is used as the multiplexing member 10 will be described. Of course, the present embodiment is not limited to one in which the multiplexing member 10 is a cross prism. For example, R, G, and B laser beams may be combined by crossing two dichroic mirrors at a predetermined angle.

  In the optical system of the image forming apparatus according to the present embodiment, as shown in FIG. 1, the R, G, and B light sources 1a, 1b, and 1c are arranged inside dead spaces 13a and 13b. This effectively utilizes the installation location of the device. When the R, G, B light sources 1a, 1b, 1c are arranged in the dead spaces 13a, 13b, as shown in FIG. 3, the R, G, B deflection center directions 16a, 16b, 16c The incident beams 17a, 17b, and 17c for G and B are incident on the reflecting surface of the rotary polygon mirror 3 at an angle. Specifically, the incident beam 17a from the B light source 1a is incident at an incident angle θ1 with respect to the deflection center direction 16a, and the incident beam 17b from the G light source 1b is incident at an incident angle θ2 with respect to the deflection center direction 16b. The incident beam 17c from the R light source 1c is incident at an incident angle θ3 with respect to the deflection center direction 16c. Each incident beam 17a, 17b, 17c is scanned around each deflection center direction 16a, 16b, 16c by the rotation of the rotary polygon mirror 3. Here, the R, G, and B light sources 1a, 1b, and 1c are set so that the beams reflected by the rotary polygon mirror 3 in the deflection center directions 16a, 16b, and 16c are directed toward the centers of the spatial modulation elements 9a, 9b, and 9c. What is necessary is just to arrange. Specifically, the incident angles θ1, θ2, and θ3 may be adjusted. By doing so, the optical system subsequent to the rotating polygonal mirror 3 may be designed so that each beam from the rotating polygonal mirror 3 scans a symmetrical angle with respect to the deflection center directions 16a, 16b, 16c, The design of the optical system becomes easy.

  When the incident angles θ1, θ2, and θ3 are adjusted as described above, as shown in FIG. 3, the rotation center 14 of the rotary polygon mirror 3 and the center 15 of the cross prism 10 are shifted by a predetermined distance. Will be. Specifically, as shown in FIG. 3, when the R, G, and B incident beams 17 a, 17 b, and 17 c are incident on the rotary polygon mirror 3 from three directions, the distance from the diagonal center 15 of the cross prism 10 is a distance. The rotation center 14 of the rotary polygon mirror 3 may be arranged at a position shifted from X and Y.

  Note that the diameter of the inscribed circle of the rotary polygon mirror 3 needs to be equal to or less than the vertical and horizontal length of the cross prism 10 because the rotation center 14 of the rotary polygon mirror 3 is deviated from the center 15 of the cross prism 10. As described above, the incident beams 17a, 17b, and 17c are condensed on the rotary polygon mirror 3 in the main scanning direction, so that the diameter of the inscribed circle of the rotary polygon mirror 3 is made smaller than the vertical and horizontal lengths of the cross prism 10. can do. Specifically, for example, the angle formed by the incident beams 17a, 17b, and 17c and the deflection center directions 16a, 16b, and 16c of the R, G, and B lasers in FIG. When the size of the prism is 20 mm × 20 mm × 20 mm as described above, the radius of the inscribed circle of the rotary polygon mirror 3 can be 7 mm and the number of surfaces can be twelve. Further, the rotational center 14 of the rotary polygon mirror 3 is best positioned to be located at a position of X = Y = 2.85 mm from the center 15 of the cross prism 10 so that the deflection center directions 16a, 16b, and 16c can be scanned equally to the left and right. At this time, the rotating polygonal mirror 3 does not protrude beyond the cross prism 10 and does not become the rate limiting device size.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. The present embodiment is a form in which the heat dissipation mechanism is realized with a simple configuration in the image forming apparatus of the first embodiment. FIG. 4 is a side view showing a schematic configuration of the image forming apparatus according to the present embodiment.

  Normally, when an image forming apparatus such as a projector is miniaturized, the surface area of the apparatus becomes smaller, and thus heat radiation in the apparatus becomes important. However, if a new fan or the like is added for that purpose, it goes against miniaturization.

  Therefore, the image forming apparatus according to the present embodiment further includes a fan 18 attached to the rotary polygon mirror 3 as shown in FIG. The fan 18 rotates at a high speed together with the rotary polygon mirror 3, generates air by the high speed rotation, and releases heat generated in the apparatus to the outside. In the present embodiment, the rotary polygon mirror 3 is disposed at the upper or lower portion of the multiplexing member 10 and is located at the center of the apparatus. For this reason, the air generated by the rotation of the fan 18 integrated with the rotary polygon mirror 3 spreads from the center of the apparatus to the entire apparatus. As a result, heat generated from the inside of the apparatus is efficiently discharged outside the apparatus. Furthermore, since the fan 18 can be rotated by the rotation of the rotary polygon mirror 3, it is not necessary to separately provide a drive mechanism dedicated to the rotation of the fan 18, and a heat dissipation mechanism can be realized with an inexpensive configuration.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. This embodiment is a form in which the speckle noise is removed by using the surface tilt generated on the reflecting surface of the rotary polygon mirror in the image forming apparatuses of the first and second embodiments. FIG. 5 is an enlarged side view of a rotary polygon mirror used in the image forming apparatus according to the present embodiment. Hereinafter, a method for removing speckle noise using surface tilt of the rotary polygon mirror 3 will be described with reference to FIG.

  As shown in FIG. 5, the rotary polygon mirror 3 is processed so that the reflection surface and the rotation axis are substantially parallel in the manufacturing process, but the reflection surface is generally slightly tilted. For example, the reflecting surface 19a is substantially parallel to the rotation axis, but the reflecting surface 19b falls downward, and the reflecting surface 19c falls upward. In general, this is called troublesome. If the reflecting surface of the rotating polygon mirror 3 is tilted in this way, the beam reflected by the reflecting surfaces 19a, 19b, 19c of the rotating polygon mirror 3 has a slight optical path in the vertical direction as shown in FIG. It will shift. For example, the beam reflected by the reflecting surface 19a travels substantially horizontally in the direction 20a, but the beam reflected by the reflecting surface 19b travels downward in the direction 20b, and the beam reflected by the reflecting surface 19c faces upward in the direction 20c. Will progress.

  When the rotating polygonal mirror 3 rotates and scans in this state, the beam is scanned in the main scanning direction, and the optical path is shifted in the vertical direction (thickness direction of the rotating polygonal mirror 3) by the amount of surface tilt for each surface. Irradiation areas on the diffusion plates 7a, 7b, and 7c are also shifted. For this reason, the speckle pattern fluctuates for each reflecting surface 19a, 19b, 19c. Thereby, the speckle noise visually recognized is reduced. Specifically, it is known that the speckle noise is usually difficult to be visually recognized when there is a position variation of about 200 μm on the diffusion plates 7a, 7b, and 7c, and the diffusion plates 7a, 7b, Assuming that the distance to 7c is 50 mm, speckle noise is difficult to be visually recognized if there is a surface tilt of about 0.12 ° within one rotation of the rotary polygon mirror 3. This is also very effective because speckles of a plurality of beams can be reduced at a time by defining only the surface tilt accuracy of the single rotating polygonal mirror 3.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. The present embodiment is a form in which speckle noise is removed by vibrating the members constituting the optical system in the image forming apparatuses of the first and second embodiments.

  In the image forming apparatus according to the present embodiment, in FIGS. 1 and 2, cylindrical lenses 4a, 4b, 4c, cylindrical mirror arrays 5a, 5b, 5c, reflection mirrors arranged in the optical paths of R, G, B, respectively. Speckle noise is reduced by vibrating one or more members of 6a, 6b, 6c, diffuser plates 7a, 7b, 7c, and field lenses 8a, 8b, 8c vertically and horizontally. Is possible. Even if there is no surface tilt of the reflecting surface of the rotary polygon mirror 3 in FIG. 5, the speckle noise that is visually recognized by changing the speckle pattern is reduced by vibrating any one of the members. Can be made. However, in the case of multiple beams, it is necessary to vibrate in each optical path, so a motor or the like is attached to a part that vibrates in each optical path, or a member that vibrates in each optical path is moved in conjunction with a single motor or the like. Etc. are required.

  In the present embodiment, the surface tilt accuracy of the rotary polygon mirror 3 of the above-described third embodiment may be defined simultaneously. By doing so, speckle noise can be further reduced.

  In the present embodiment, it is also conceivable to use a motor for vibrating the vibrating member in combination with the motor of the rotary polygon mirror 3. For example, as shown in FIG. 6, a disk-shaped member 21 having a different thickness in the circumferential direction is attached to the rotation axis of the rotary polygon mirror 3, and the cylindrical lenses 4 a, 4 b, and 4 c immediately after the rotary polygon mirror 3 are attached to the thickness of the member 21. Move up and down in conjunction with. The rotary polygon mirror 3 is rotationally driven by a drive unit 31 having a motor connected to the rotary shaft of the rotary polygon mirror 3. By doing so, when the rotary polygon mirror 3 rotates, the member 21 also rotates in conjunction with it, and the cylindrical lenses 4a, 4b, 4c also vibrate up and down accordingly, thereby the optical path fluctuates and the speckle pattern changes. It fluctuates and speckle noise is reduced. This makes it possible to further reduce speckle noise easily at low cost without adding a new motor.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. In the first embodiment, the reflected light from the reflecting surface of the rotary polygon mirror 3 is again made into substantially parallel light by the cylindrical lenses 4 a, 4 b, and 4 c and then guided to the multiplexing member 10. In the present embodiment, in the first embodiment, the cylindrical lenses 4a, 4b, and 4c are not required by making them substantially parallel at the time of reflection by the reflecting surface of the rotary polygon mirror 3. FIG. 7 is a top view showing a schematic configuration of the image forming apparatus according to the present embodiment.

  As shown in FIG. 7, the rotating polygon mirror 22 of the present embodiment has a reflecting surface having a predetermined curvature in the main scanning direction. Therefore, the laser light emitted from the laser light sources 1a, 1b, and 1c is condensed in the main scanning direction of the rotary polygon mirror 22 by the cylindrical lenses 2a, 2b, and 2c, and the condensed beam is reflected by the rotary polygon mirror 22. It is converted into a substantially parallel beam upon reflection by the surface. By doing so, the cylindrical lenses 4a, 4b, and 4c immediately after the rotary polygon mirror 3 that are necessary in the first embodiment are not required. Although it becomes impossible to suppress the uniformity of exposure intensity due to an increase in scanning speed at the scanning end on the spatial modulation elements 9a, 9b, 9c, the cylindrical lenses 4a, 4b, which are provided for the laser light sources 1a, 1b, 1c, respectively. Since 4c can be eliminated, the number of parts can be reduced.

(Embodiment 6)
Although the first to fifth embodiments of the present invention have been described using a display device such as a projector that projects an image on a screen as the image forming device, the present invention is not limited to this. For example, a liquid crystal display device that illuminates a liquid crystal display screen from the back may be used. FIG. 8 shows a schematic configuration of an image forming apparatus according to Embodiment 6 of the present invention.

  In the image forming apparatus according to the present embodiment, as shown in FIG. 8, the laser beams emitted from the laser light sources 1a, 1b, and 1c are converged in the main scanning direction by the cylindrical lenses 2a, 2b, and 2c. Then, the light enters the rotary polygon mirror 3. The light reflected by the reflecting surface of the rotating polyhedron 3 is scanned in the main scanning direction.

  The beams reflected by the rotating polygon mirror 3 are returned to substantially parallel light by the cylindrical lenses 4a, 4b, and 4c, and the beams that have become substantially parallel light are reflected by the cylindrical mirror arrays 5a, 5b, and 5c, It goes to the reflection mirrors 6a, 6b, 6c arranged on the first floor. The beams reflected by the reflection mirrors 6a, 6b, 6c are converted into telecentricity by the field lenses 8a, 8b, 8c, and then multiplexed by the multiplexing member 10, and then the liquid crystal display panel unit by the illumination optical system 23. 24 is irradiated.

  As described above, according to Embodiments 1 to 6 of the present invention, it is possible to simultaneously achieve downsizing and speckle countermeasures of an image forming apparatus such as a projector with a simple and inexpensive configuration.

  The image forming apparatus according to the present invention can be applied as a portable small projector.

1 is a top view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a side view showing a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is a figure for demonstrating the positional relationship of a multiplexing member and a rotary polygon mirror, and the incident angle of each laser beam with respect to a rotary polygon mirror. It is a side view which shows schematic structure of the image forming apparatus in Embodiment 2 of this invention. It is an enlarged side view of the rotary polygon mirror used in the image forming apparatus in Embodiment 3 of the present invention. It is a side view which shows schematic structure of the image forming apparatus in Embodiment 4 of this invention. It is a top view which shows schematic structure of the image forming apparatus in Embodiment 5 of this invention. It is a top view which shows schematic structure of the image forming apparatus in Embodiment 6 of this invention.

Explanation of symbols

1a, 1b, 1c Light source 2a, 2b, 2c, 4a, 4b, 4c Cylindrical lens 3, 22 Rotating polygon mirror 5a, 5b, 5c Cylindrical mirror array 6a, 6b, 6c Reflective mirror 7a, 7b, 7c Diffuser plate 8a, 8b 8c Field lens 9a, 9b, 9c Spatial modulation element 10 Combined member 11 Projection lens 12 Screen 13a, 13b Dead space 14 Center of rotation 15 Center 16a, 16b, 16c Direction of deflection center 17a, 17b, 17c Incident beam 18 Fan 19a, 19b, 19c Reflective surfaces 20a, 20b, 20c Reflection direction 21 Disc-shaped member 23 Illumination optical system 24 Liquid crystal display panel unit 31 Drive unit

Claims (15)

A plurality of laser light sources;
A rotating polygon mirror that scans a plurality of laser beams from the plurality of laser light sources;
A multiplexing member that combines a plurality of laser beams scanned by the rotary polygon mirror,
An image forming apparatus, wherein an extension line of a rotation axis of the rotary polygon mirror passes through the multiplexing member.   The extension line of the rotation axis of the rotating polygon mirror is such that each optical path from the rotating polygon mirror corresponding to each of the plurality of laser beams to the combining member has substantially the same distance. The image forming apparatus according to claim 1, wherein the image forming apparatus is deviated from the position by a predetermined distance. A plurality of condensing elements arranged in the vicinity of the rotating polygon mirror on each optical path from each of the plurality of laser light sources to the rotating polygon mirror;
The said condensing element condenses the laser beam from the said laser light source in the scanning direction of the laser beam by the said rotary polygon mirror, and radiate | emits it to the reflective surface of the said rotary polygon mirror. The image forming apparatus described. A plurality of spatial light modulators arranged on each optical path from the rotary polygon mirror corresponding to each of the plurality of laser beams to the combining member and irradiated with laser light scanned by the rotary polygon mirror; Prepared,
Each of the plurality of laser beams scanned by the rotary polygon mirror is the rotating polyhedron so that the moving speed of the irradiation position of the laser light irradiated on the irradiated surface of the spatial modulation element is made uniform on the irradiated surface. The image forming apparatus according to claim 3, wherein the image forming apparatus is converted into light substantially perpendicular to an irradiated surface of the spatial modulation element in the vicinity of a mirror. A plurality of light collimating elements disposed in the vicinity of the rotating polygon mirror on each optical path from the rotating polygon mirror to the multiplexing member;
The image forming apparatus according to claim 4, wherein the light collimating element makes incident laser light substantially perpendicular to an irradiated surface of the spatial modulation element. The reflecting surface of the rotating polygon mirror has a predetermined curvature in the scanning direction of the laser light by the rotating polygon mirror,
The image forming apparatus according to claim 4, wherein the predetermined curvature is set so that light reflected by the reflecting surface becomes light substantially perpendicular to an irradiated surface of the spatial modulation element. . A heat dissipating fan installed on the rotary polygon mirror,
The image forming apparatus according to claim 1, wherein the heat dissipating fan rotates integrally with the rotary polygon mirror.   The image forming apparatus according to claim 1, wherein the range of variation in the amount of surface tilt of each reflecting surface of the rotary polygon mirror is 0.12 degrees or more. A plurality of optical systems disposed on each optical path from the rotary polygon mirror corresponding to each of the plurality of laser beams to the multiplexing member;
The optical system includes a plurality of optical elements that propagate the laser light, and at least one of the plurality of optical elements vibrates in a direction substantially perpendicular to the optical path direction. Item 9. The image forming apparatus according to any one of Items 1 to 8. A drive unit for rotating the rotary polygon mirror;
The image forming apparatus according to claim 9, wherein the vibrating optical element is connected to the driving unit and is vibrated by the driving unit. Each of the plurality of laser beams from the plurality of laser light sources is incident on the rotating polygon mirror from different directions from the periphery of the rotating polygon mirror,
Each of the plurality of laser light sources includes the plurality of laser light sources so that the laser light passing through the center position of the scanning range of the laser light scanned by the rotary polygon mirror reaches the center position of the irradiated surface of the spatial modulation element. 7. The image forming apparatus according to claim 4, wherein each of the laser beams is arranged in a set emission direction.   The image forming apparatus according to claim 1, further comprising a liquid crystal display panel that displays an image when irradiated with laser light combined by the combining member.   The image forming apparatus according to claim 1, wherein the multiplexing member is a cross prism.   The image forming apparatus according to claim 1, wherein the multiplexing member is two dichroic mirrors intersecting at a predetermined angle.   The image forming apparatus according to claim 1, wherein the rotary polygon mirror is disposed at an upper portion or a lower portion of the multiplexing member.

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