JP4609423B2 - Projection optical system and projector - Google Patents

Description

  The present invention relates to a projection optical system and a projector, and more particularly to a technology of a projection optical system used for a projector.

  Conventionally, as a projection optical system used in a projector, a so-called shift optical system (axial shift optical system) in which light is shifted to a specific side with respect to an optical axis and travels has been proposed (for example, see Patent Document 1). 8). For example, in the case of a front projection type projector, by projecting light obliquely with respect to the irradiated surface by the shift optical system, there is an advantage that the projector main body can avoid blocking a part of the image when viewed from the observer. is there.

JP-A-5-241096

  In recent years, a technique for performing close-up projection using a front projection type projector has been proposed. By enabling the proximity projection, the projector can be disposed at a position close to the wall surface having the irradiated surface. When performing proximity projection, the projection optical system is configured to greatly shift light with respect to the optical axis. When the shift amount is increased, the diameter of the lens constituting the projection optical system is increased. Since the diameter of the lens, particularly the lens on the most exit side of the projection optical system, becomes large, it becomes very difficult to reduce the size of the projector. As described above, according to the conventional technique, there is a problem that it is difficult to make a small configuration when the light is largely shifted with respect to the optical axis. The present invention has been made in view of the above-described problems, and an object thereof is to provide a projection optical system and a projector that can have a small configuration when light is largely shifted with respect to an optical axis. To do.

  In order to solve the above-described problems and achieve the object, according to the present invention, there is provided a projection optical system that projects light, an optical element that is arranged with substantially the same optical axis, and a specified optical axis. A reflection part that reflects light traveling from the side toward the optical axis to a specific side, and the optical element and the reflection part transmit light incident from a specific side with respect to the optical axis to a specific side with respect to the optical axis. It is possible to provide a projection optical system characterized in that the projection optical system is shifted and moved forward.

  Light incident from a specific side with respect to the optical axis is reflected by the reflecting portion and then travels while being shifted to a specific side with respect to the optical axis. In the case where the reflecting portion is provided on the surface including the optical axis, a portion of the optical element opposite to the specific side with respect to the optical axis is not necessary. By omitting such unnecessary portions, the projection optical system can be downsized even when the light is largely shifted with respect to the optical axis. Thereby, it is possible to obtain a projection optical system capable of having a small configuration when the light is largely shifted with respect to the optical axis. Further, when only a specific side of the optical axis of the lens that is an optical element is used, it is possible to form two lenses from one lens material, thereby reducing the manufacturing cost. Even if the optical element is made slightly larger in order to improve the optical performance, the optical performance can be easily improved because the optical element can still be made smaller than the conventional one.

  Moreover, as a preferable aspect of the present invention, it is desirable that the reflecting portion reflects light at a position where the optical axis and the light beam intersect. Thereby, the light traveling from the specific side toward the optical axis with respect to the optical axis can be reflected to the specific side.

  Moreover, as a preferable aspect of the present invention, it is desirable that the reflecting portion is provided in an optical element disposed at a position where the optical axis and the light beam intersect. Thereby, in the configuration in which the optical element is arranged at a position where the optical axis and the light beam intersect, the light traveling from the specific side toward the optical axis with respect to the optical axis can be reflected to the specific side.

  Moreover, as a preferable aspect of the present invention, it is desirable that the reflecting portion is provided at the position of the stop. Thereby, at the position of the stop, light traveling from the specific side toward the optical axis with respect to the optical axis can be reflected to the specific side.

  Moreover, as a preferable aspect of the present invention, it is desirable to have an optical element other than the optical element arranged with the optical axes substantially coincided with each other. Thereby, it can be set as the structure provided with desired optical performance.

  Furthermore, according to the present invention, it is possible to provide a projector characterized by including a spatial light modulation device that modulates light according to an image signal and the projection optical system described above. By using the projection optical system described above, a small configuration can be achieved when the light is largely shifted with respect to the optical axis. Thus, a projector having a small configuration can be obtained when the light is largely shifted with respect to the optical axis.

  In a preferred aspect of the present invention, the projection optical system reflects an optical element arranged with the optical axes substantially coincided with each other and light traveling from the specific side toward the optical axis with respect to the optical axis to the specific side. The spatial light modulator is preferably disposed on a specific side with respect to the optical axis. Thereby, light can be incident on the projection optical system from a specific side with respect to the optical axis.

  Further, as a preferred aspect of the present invention, it is desirable to have a wide-angle optical element that widens the light from the projection optical system. The wide-angle optical element refers to an optical element that emits light in a wide angle range with respect to the angle range of incident light. By using a wide-angle optical element, it is possible to perform close-up projection using a projection optical system with an ultra-short focus. In the configuration in which light is shifted significantly with respect to the optical axis with an ultrashort focal point, a small configuration can be achieved.

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

  FIG. 1 shows a cross-sectional configuration of a main part of a projection optical system 10 according to Embodiment 1 of the present invention. The projection optical system 10 is a projection lens including a lens that is an optical element that deflects light by transmission. The projection optical system 10 includes a front group lens 11 and a rear group lens 12. The front lens group 11 is provided on the exit side of the diaphragm 14. The rear lens group 12 is provided on the incident side of the stop 14. The front lens group 11 is composed of three lenses LN. The rear lens group 12 is composed of five lenses LN. Each lens LN constituting the front group lens 11 and each lens LN constituting the rear group lens 12 are optical elements arranged with their optical axes substantially matched. The projection optical system 10 is a so-called coaxial optical system. The lenses LN constituting the front group lens 11 and the lenses LN constituting the rear group lens 12 are all arranged on a specific side with respect to the optical axis AX, that is, on the upper side of the drawing in FIG.

  The reflection unit 13 is provided on the surface that includes the optical axis AX at the position of the diaphragm 14. The reflection unit 13 reflects light traveling from the specific side toward the optical axis AX with respect to the optical axis AX to the specific side. The reflecting portion 13 can be configured by coating a parallel plate with a highly reflective member, for example, a metal member such as aluminum, a dielectric multilayer film, or the like.

  FIG. 2 shows a configuration example of a conventional projection optical system. Both the front group lens 21 and the rear group lens 22 are provided so that the center position of the lens LN and the optical axis AX substantially coincide with each other. Light is incident on the rear lens group 22 from the side opposite to the specific side with respect to the optical axis AX, that is, the lower side of the drawing in FIG. The light beam from the rear lens group 22 intersects the optical axis AX at the position of the stop 14. In the front lens group 21, light travels on a specific side with respect to the optical axis AX.

  Returning to FIG. 1, the projection optical system 10 of the present invention uses a portion corresponding to a specific half of the optical axis AX in the configuration shown in FIG. 2. Therefore, the front group lens 11 and the rear group lens 12 have shapes that are obtained by cutting the lens along a plane that passes through the center position of the lens. Specifically, the front group lens 11 shown in FIG. 1 has a shape obtained by cutting the front group lens 21 shown in FIG. 2 along a plane passing through the center position of the front group lens 21. Further, the rear group lens 12 shown in FIG. 1 has a shape obtained by cutting the rear group lens 22 shown in FIG. 2 along a plane passing through the center position of the rear group lens 22. The projection optical system 10 makes light incident from a specific side with respect to the optical axis AX. The light traveling on a specific side from the optical axis AX in the rear group lens 12 is incident on the reflecting portion 13 at a position where the optical axis AX and the light beam intersect. The reflection unit 13 reflects light at a position where the optical axis AX and the light beam intersect.

  The light reflected by the reflecting portion travels a specific side from the optical axis AX in the front group lens 11 and then exits from the projection optical system 10. As described above, the lens LN and the reflection unit 13 that are optical elements cause light incident from a specific side with respect to the optical axis AX to shift to a specific side with respect to the optical axis AX and travel.

  In the projection optical system 10 according to the present invention, by providing the reflecting portion 13, a portion of the lens LN opposite to the specific side with respect to the optical axis AX becomes unnecessary. By omitting such unnecessary portions, the projection optical system 10 can be downsized even when light is largely shifted with respect to the optical axis AX. Thereby, there is an effect that a small configuration can be obtained when the light is largely shifted with respect to the optical axis AX. Further, by using only a specific side of the lens LN with respect to the optical axis, it is possible to form two lenses from one lens material, and the manufacturing cost can be reduced. Even if the lens LN is made slightly larger in order to improve the optical performance, it can still be made smaller compared to the conventional case, so that the optical performance can be easily improved.

  The configuration of the projection optical system 10 may be a shift optical system and a coaxial optical system, and is not limited to that described in the present embodiment. The projection optical system 10 can appropriately set the position, shape, number, and the like of the lens LN. For example, in the case of a configuration in which the lens LN is disposed at a position where the optical axis AX and the light beam intersect, the reflection unit 13 can be provided in the lens LN as shown in FIG. The reflection unit 13 is formed on the surface of the lens LN along the optical axis AX. In order to prevent an air layer from being formed between the reflecting portion 13 and the lens LN, it is desirable that the reflecting portion 13 is in close contact with the lens LN surface. For example, by depositing a highly reflective member such as aluminum on the lens LN surface, it is possible to form the reflecting portion 13 that is in close contact with the lens LN surface.

  The light that has entered the lens LN is reflected by the reflecting portion 13 and then exits from the lens LN. Thereby, the light traveling from the specific side toward the optical axis AX with respect to the optical axis AX can be reflected to the specific side. When light is incident on the interface of the lens LN at an angle greater than the critical angle, the light may be advanced to a specific side by total reflection at the interface of the lens LN. In this case, the interface of the lens LN functions as a reflection part.

  FIG. 4 illustrates a cross-sectional configuration of a main part of the projection optical system 30 according to the first modification of the first embodiment. In the projection optical system 30 of this modification, compared with the projection optical system 10 shown in FIG. 1, the rear group lens 32 and the reflecting unit 13 are arranged with the front group lens 31 on the lower side of the sheet, which is the side opposite to the specific side. Is moved to the upper side of the page, which is a specific side. The projection optical system 30 matches the optical axis of the lens LN constituting the front group lens 31 and matches the optical axis of the lens LN constituting the rear group lens 32. In this way, by appropriately moving the optical element, a configuration having desired optical performance can be obtained. The lens LN may be moved in units of the front group lens 31 and the rear group lens 32, or may be moved for each lens LN.

  FIG. 5 illustrates a cross-sectional configuration of a main part of the projection optical system 40 according to the second modification of the first embodiment. In the projection optical system 40 of this modification, one lens 43 is added to the front group lens 41 as compared with the projection optical system 10 shown in FIG. The rear group lens 42 is the same as the rear group lens 12 of the projection optical system 10 of FIG. The lens 43 is an optical element other than the optical element arranged with the optical axes substantially coincident with each other. In the conventional projection optical system shown in FIG. 6, the rear lens group 52 is the same as the rear lens group 22 shown in FIG. The front lens group 51 is provided with a single lens 53 disposed so that the optical axes do not coincide with each other between the lenses LN provided with the center position and the optical axis AX substantially coincident with each other.

  The projection optical system 40 of the present modification uses a portion corresponding to a specific side half of the optical axis AX in the configuration shown in FIG. As described above, by appropriately adding optical elements other than the optical elements arranged with the optical axes substantially matched, a configuration having desired optical performance can be obtained. Each projection optical system of the present embodiment may be configured to include an optical element other than a lens, for example, a mirror.

  FIG. 7 shows a schematic configuration of a projector 60 according to Embodiment 2 of the present invention. The projector 60 includes the projection optical system 10 of the first embodiment. The projector 60 is a front projection type projector that projects light according to an image signal. The projector 60 is disposed on the cabinet C near the wall surface W. The projector 60 performs close-up projection from a position close to the irradiated surface, for example, a position about several tens of centimeters from the wall surface W on which the screen 66 is disposed. The projector 60 has an optical engine 61.

  FIG. 8 shows a schematic configuration of the optical engine 61. The red (R) light LED 71R, which is a solid light source, is a light source unit that supplies R light. The R light from the R light LED 71R is collimated by the collimator lens 72 and then enters the R light spatial light modulator 73R. The spatial light modulator 73R for R light is a spatial light modulator that modulates R light according to an image signal, and is a transmissive liquid crystal display device. The R light modulated by the R light spatial light modulator 73R is incident on a cross dichroic prism 74 which is a color synthesis optical system.

  The green (G) light LED 71G, which is a solid light source, is a light source unit that supplies G light. The G light from the G light LED 71G is collimated by the collimator lens 72 and then enters the G light spatial light modulator 73G. The G light spatial light modulation device 73G is a spatial light modulation device that modulates G light according to an image signal, and is a transmissive liquid crystal display device. The G light modulated by the G light spatial light modulator 73G enters the cross dichroic prism 74 from a side different from the R light.

  The blue (B) light LED 71 </ b> B, which is a solid light source, is a light source unit that supplies B light. The B light from the B light LED 71B is collimated by the collimator lens 72 and then enters the B light spatial light modulator 73B. The B light spatial light modulation device 73B is a spatial light modulation device that modulates B light according to an image signal, and is a transmissive liquid crystal display device. The B light modulated by the B light spatial light modulator 73B enters the cross dichroic prism 74 from a side different from the R light and the G light. The optical engine 61 may be configured to use a uniformizing optical system that uniformizes the intensity distribution of the light beam, for example, a rod integrator, a fly-eye lens, or a superimposing lens.

  The cross dichroic prism 74 has two dichroic films 75 and 76 arranged so as to be substantially orthogonal to each other. The first dichroic film 75 reflects R light and transmits G light and B light. The second dichroic film 76 reflects B light and transmits R light and G light. The cross dichroic prism 74 combines R light, G light, and B light incident from different sides.

  As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used. The optical engine 61 is not limited to the case where a transmissive liquid crystal display device is used as the spatial light modulator. As the spatial light modulator, a reflective liquid crystal display (Liquid Crystal On Silicon; LCOS), DMD (Digital Micromirror Device), GLV (Grating Light Valve), or the like may be used. The projector 60 is not limited to a configuration including a spatial light modulator for each color light. The projector 60 may be configured to modulate two or three color lights with one spatial light modulator. The optical engine 61 is not limited to the case where an LED is used as the light source unit. As the light source unit, for example, a solid light source other than the LED, or a lamp such as an ultrahigh pressure mercury lamp may be used.

  Returning to FIG. 7, the projection optical system 10 is provided on the exit side of the optical engine 61. The aspherical mirror 64 is a wide-angle optical element that widens the light from the projection optical system 10 by reflection, and has an aspherical curved surface. The aspherical mirror 64 has a function of widening the light from the projection optical system 10 and a function of bending the light from the projection optical system 10 and traveling in the direction of the screen 66. The projector 60 enables an ultra-short focus by widening the light from the projection optical system 10 with the aspherical mirror 64. Thereby, close-up projection is possible.

  The aspherical mirror 64 can be configured, for example, by forming a reflective film on a substrate having a resin member or the like. As the reflective film, a highly reflective member layer, for example, a metal member layer such as aluminum, a dielectric multilayer film, or the like can be used. Further, a protective film having a transparent member may be formed on the reflective film. Since the aspherical mirror 64 has a curved surface shape, it is possible to simultaneously perform bending and widening of light.

  By widening the light not only by the projection optical system 10 but also by the aspherical mirror 64, the projection optical system 10 can be made smaller than when the light is widened only by the projection optical system 10. The projection optical system 10 and the aspherical mirror 64 perform image enlargement and image formation on the screen 66. The projection optical system 10 functions to enlarge an image and form an image on the screen 66. The aspherical mirror 64 functions to enlarge an image. The aspherical mirror 64 may be appropriately modified so as to correct image distortion.

  The casing 67 houses the optical engine 61, the projection optical system 10, and the aspherical mirror 64. The emitting unit 65 emits light modulated according to the image signal from the housing 67 toward the screen 66. The emitting unit 65 is configured by covering an opening provided in the housing 67 with a transparent member. The screen 66 is a reflective screen that reflects the light from the emitting portion 65. The screen 66 can have good viewing angle characteristics by making it possible to diffuse light in a desired range where the observer exists.

  In addition to the cabinet C, the projector 60 may be installed on a floor surface, a desk, a rack, or the like. Since the projector 60 has a compact configuration, an installation place can be easily secured. By enabling the projector 60 to be installed near the wall surface W, a large screen can be displayed even in a narrow room. The projector 60 may cause the aspherical mirror 64 to protrude from the housing 67. In this case, an opening through which light incident on the aspherical mirror 64 passes is formed in the housing 67 in place of the emitting portion 65.

  The projector 60 may be provided with a mirror for bending the optical path between the projection optical system 10 and the aspherical mirror 64. When the optical path is bent by about 90 degrees with a mirror, the optical engine 61 and the projection optical system 10 are arranged so as to emit light in the vertical direction or the depth direction in FIG. Thereby, each part from the optical engine 61 to the aspherical mirror 64 can be further arranged near the wall surface W.

  FIG. 9 schematically shows the optical system of the projector 60. The projection optical system 10 and the aspherical mirror 64 are arranged so that the optical axes substantially coincide. The normal line N of the screen 66 is substantially parallel to the optical axis of the projection optical system 10 and the optical axis of the aspherical mirror 64. Both the projection optical system 10 and the aspherical mirror 64 constitute a so-called coaxial optical system having a common optical axis AX. The projector 60 constitutes a so-called shift optical system in which light modulated in accordance with an image signal is shifted to a specific side with respect to the optical axis AX and travels.

  Specifically, the light modulated in accordance with the image signal is shifted to the upper side of the paper surface of FIG. Each spatial light modulator (not shown) is arranged on a specific side with respect to the optical axis AX. The center normal of the image plane virtually formed on the exit surface of the cross dichroic prism 74 in the optical engine 61 is parallel to the optical axis AX and shifted to a specific side. With such a configuration, the projector 60 makes light having a large incident angle incident on the screen 66. The incident angle is an angle formed by the normal line N of the screen 66 and the incident light beam.

  By employing a coaxial optical system, it is possible to adopt a normal coaxial system design method. Therefore, it is possible to realize an optical system with a small number of man-hours for designing the optical system and with few aberrations. The aspherical mirror 64 may have a shape that is substantially rotationally symmetric with respect to the optical axis AX, for example, a shape obtained by cutting out a part other than the apex portion of the conical shape. By making the aspherical mirror 64 substantially rotationally symmetric with respect to the optical axis AX, the optical axis of the aspherical mirror 64 and the optical axes of other configurations can be easily matched. Since the aspherical mirror 64 has an asymmetrical aspherical shape, it can be processed by a simple method such as a lathe. Therefore, the aspherical mirror 64 can be manufactured easily and with high accuracy.

  The projector 60 employs a super-wide-angle optical system that uses the projection optical system 10 and the aspherical mirror 64 so that the angle of view θ is at least 150 degrees, for example, 160 degrees. Furthermore, by adopting a shift optical system that uses only a part of the angle range of the ultra-wide angle, it is possible to align the light traveling direction. In this embodiment, for example, the minimum incident angle on the screen 66 is 70 degrees and the maximum incident angle is 80 degrees. By adopting the shift optical system, the angle difference of the light incident on the screen 66 can be within about 10 degrees.

  By using the projection optical system 10 described above, the projector 60 can have a small configuration when the light is largely shifted with respect to the optical axis AX. Thereby, in the structure which shifts light largely with respect to an ultra short focus and an optical axis, there exists an effect that it can be made a small structure. By using the projection optical system 10 described above, the projector 60 has a feature that the spatial light modulation device that is the object plane and the screen 66 that is the image plane are on the same side with respect to the optical axis AX.

  In addition to using the aspherical mirror 64 as the wide-angle optical element, the projector 60 may use a super-wide-angle lens, a diffractive optical element, or the like. The projector may be a so-called rear projector that supplies laser light to one surface of the screen and observes an image by observing light emitted from the other surface of the screen. The projection optical system of Example 1 may be applied to, for example, an imaging optical system used for an imaging apparatus.

  As described above, the projection optical system according to the present invention is suitable for use in a projector that shifts light to a specific side with respect to the optical axis.

1 is a diagram showing a cross-sectional configuration of a main part of a projection optical system according to Example 1 of the present invention. The figure which shows the structural example of the conventional projection optical system. The figure which shows the structure which provides a reflection part in a lens. FIG. 5 is a diagram illustrating a cross-sectional configuration of a main part of a projection optical system according to Modification Example 1 of Example 1. FIG. 7 is a diagram illustrating a cross-sectional configuration of main parts of a projection optical system according to Modification Example 2 of Example 1. The figure which shows the structural example of the conventional projection optical system. FIG. 5 is a diagram illustrating a schematic configuration of a projector according to a second embodiment of the invention. The figure which shows schematic structure of an optical engine. The figure which represented typically the optical system of the projector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Projection optical system, 11 Front group lens, 12 Rear group lens, 13 Reflection part, 14 Aperture, AX optical axis, LN lens, 21 Front group lens, 22 Rear group lens, 30 Projection optical system, 31 Front group lens, 32 Rear group lens, 40 projection optical system, 41 front group lens, 42 rear group lens, 43 lens, 51 front group lens, 52 rear group lens, 53 lens, 60 projector, 61 optical engine, 64 aspherical mirror, 65 emitting part , 66 screen, 67 housing, C cabinet, W wall surface, LED for 71R R light, LED for 71G G light, LED for 71B B light, 72 collimator lens, spatial light modulator for 73R R light, space for 73G G light Light modulator, spatial light modulator for 73B light, 74 cross dichroic prism, 75 first dichroic film, 6 second dichroic film, N normal

Claims (8)

A projection optical system for projecting light,
An incident-side optical element that is arranged with its optical axes substantially coincident and deflects light by transmission ;
An optical element on the exit side that is arranged on the rear side of the optical path of the optical element on the incident side so that the optical axes are substantially coincided with each other, and deflects light by transmission;
Light which is provided on a surface including the optical axis of the incident-side optical element and is incident from a specific side with respect to the optical axis of the incident-side optical element and travels toward the optical axis is transmitted on the specific side . A reflection part that reflects the optical element on the emission side ;
Have
The projection optical system according to claim 1, wherein the optical elements on the incident side and the emission side have a shape in which a side opposite to the specific side is cut . The projection optical system according to claim 1, wherein the reflection unit reflects light at a position where an optical axis of the optical element on the incident side and a light beam intersect.   The projection optical system according to claim 2, wherein the reflection unit is provided in an optical element disposed at a position where the optical axis and the light beam intersect.   The projection optical system according to claim 1, wherein the reflection unit is provided at a position of a stop.   5. The projection optical system according to claim 1, further comprising an optical element other than the optical element arranged so that the optical axes substantially coincide with each other. A spatial light modulator that modulates light according to an image signal;
A projector comprising: the projection optical system according to claim 1. Before SL spatial light modulator, a projector according to claim 6, wherein said being arranged on a particular side with respect to the optical axis.   The projector according to claim 6, further comprising a wide-angle optical element that widens light from the projection optical system.

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