JP2008139530A - Projection optical system and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system capable of drastically switching picture size with simple constitution and equipped with adequate optical performance, and a projector using the projection optical system. <P>SOLUTION: The projection optical system 13 for projecting light can be switched to a first system and a second system having a different focal length from the first system. The first system and the second system are switched by replacing a first lens group that is a first optical element group constituting the first system with a second lens group that is a second optical element group constituting the second system. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 front projection type projector.

  Many front projection projectors that have been widely used in the past are installed at a position away from the screen to some extent in order to secure a projection distance. When the projector is installed at a position away from the screen, it is necessary to secure a place where there is no obstacle that blocks light in the optical path from the projector to the screen. Such restrictions on the installation position of the projector become more prominent as the display screen becomes larger. In particular, it is difficult to display a large screen in a small room. In recent years, a technique for performing close-up projection using a front projection type projector has been proposed. By enabling the close-up projection, for example, the projector can be arranged at a position close to the wall surface. By making it possible to place the projector at a position close to the wall surface, for example, within a few tens of centimeters of the wall surface, restrictions on the installation position of the projector can be reduced, and space can be saved. In addition, a large screen can be displayed even in a small room.

  Many front projection projectors that have been widely used in the past have a zoom function for adjusting the screen size. In general, the zoom function is realized by adjusting the position of an optical element constituting the optical system. For example, Patent Document 1 proposes a zoom lens technique for moving a lens that is an optical element.

Japanese Patent Laid-Open No. 5-19163

  In recent years, in order to be able to display a smaller screen and a larger screen, a projection optical system capable of realizing a high zoom ratio has been desired. However, it is difficult to design a projection optical system for enabling a high zoom ratio, and it is very difficult to realize a projection optical system having a high zoom ratio and sufficient optical performance. A projector that performs close-up projection employs a projection optical system with a very short focus. In the case of an ultra-short focal length optical system, a very high degree of difficulty is required for a design that enables a wide angle of view. For this reason, it is very difficult to design such that a zoom function is incorporated in a configuration that enables a wide angle of view. As described above, according to the conventional technique, it is possible to easily switch the screen size with a simple configuration, and it is difficult to obtain sufficient optical performance. The present invention has been made in view of the above-described problems, and uses a projection optical system capable of switching a large screen size with a simple configuration and having sufficient optical performance, and the projection optical system. An object is to provide a projector.

  In order to solve the above-described problems and achieve the object, according to the present invention, there is provided a projection optical system for projecting light, wherein the first system and the second system having a different focal length from the first system. It is possible to provide a projection optical system characterized in that it can be switched to each other.

  Since the first system and the second system can have different configurations, the design of the projection optical system is facilitated compared to the case where the zoom function is realized only by adjusting the position of the optical element, The projection optical system can be configured simply. In addition, sufficient optical performance can be easily realized. By eliminating the need for a design that incorporates a zoom function even in an ultra-short focus projection optical system, the screen size can be adjusted without encouraging the difficulty of design and the complexity of the configuration. Thereby, it is possible to obtain a projection optical system capable of drastically adjusting the screen size with a simple configuration and having sufficient optical performance.

  In a preferred aspect of the present invention, the first system and the second system interchange the first optical element group constituting the first system and the second optical element group constituting the second system. It is desirable to be able to switch by this. Thereby, it is possible to switch between the first system and the second system having different focal lengths.

  As a preferred embodiment of the present invention, the first system and the second system include at least one optical element constituting a part of the first system and at least one constituting a part of the second system. It is desirable to switch between two optical elements. Accordingly, the first system and the second system having different focal lengths can be switched with a simpler configuration.

  As a preferred aspect of the present invention, light is projected from the optical axis by shifting to a specific side, and the first system is one of the optical elements provided on the exit side from the stop with respect to the surface including the optical axis. Preferably, the second system is configured using a second portion which is a side different from the first portion with respect to the surface including the optical axis of the optical element. . When the shift optical system is employed, for example, one of the circular lenses used for light deflection is one semicircular portion obtained by dividing the circular shape into two equal parts by the diameter. Therefore, it is possible to configure the first system using only the first part of the optical element and configure the second system using only the second part of the optical element. By replacing the part where the light is incident in the optical element with the first part and the second part, it is possible to switch between the first system and the second system with a simple configuration. Further, the optical element including the first part and the second part can be accommodated in one lens barrel, and space saving can be achieved. As a result, the screen size can be significantly adjusted with a simpler and more compact configuration, and sufficient optical performance can be realized.

  As a preferable aspect of the present invention, it is desirable that the optical element has different optical characteristics between the first portion and the second portion. Accordingly, the first system and the second system can be configured using the same optical element.

  As a preferred embodiment of the present invention, it is desirable that the first system and the second system are switched by rotating at least one optical element provided on the exit side from the stop around the optical axis. . Thereby, it is possible to switch between the first system and the second system having different focal lengths.

  As a preferred embodiment of the present invention, light from a position opposite to the specific side with respect to the optical axis is projected to be shifted to a specific side, and the first system and the second system are projected. It is desirable to switch the optical element group constituting the optical system by rotating it around the optical axis. Thereby, it is possible to switch between the first system and the second system having different focal lengths.

  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, the screen size can be greatly adjusted with a simple configuration, and sufficient optical performance can be obtained. As a result, a projector capable of greatly adjusting the screen size with a simple configuration and displaying a high-quality image can be obtained.

  In a preferred aspect of the present invention, the projection optical system can be switched between a first system and a second system having a focal length different from that of the first system. It is desirable to stop the emission of light according to the image signal while switching between the two systems. During switching between the first system and the second system, the image changes regardless of the image signal. By stopping the emission of light during switching between the first system and the second system, discomfort given to the observer can be reduced.

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

  FIG. 1 shows a schematic configuration of a projector 10 according to Embodiment 1 of the present invention. The projector 10 is a front projection type projector that projects light according to an image signal. The projector 10 is disposed on the cabinet C near the wall surface W. The projector 10 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 16 is arranged. The projector 10 has an optical engine 11.

  FIG. 2 shows a schematic configuration of the optical engine 11. The red (R) light LED 21 </ b> R, which is a solid light source, is a light source unit that supplies R light. The R light from the R light LED 21R is collimated by the collimator lens 22 and then enters the R light spatial light modulator 23R. The spatial light modulator 23R 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 23R is incident on a cross dichroic prism 24 which is a color synthesis optical system.

  The green (G) light LED 21G, which is a solid light source, is a light source unit that supplies G light. The G light from the G light LED 21G is collimated by the collimator lens 22 and then enters the G light spatial light modulator 23G. The G light spatial light modulation device 23G 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 23G enters the cross dichroic prism 24 from a different side from the R light.

  The blue (B) light LED 21 </ b> B that is a solid light source is a light source unit that supplies B light. The B light from the B light LED 21B is collimated by the collimator lens 22 and then enters the B light spatial light modulator 23B. The B light spatial light modulation device 23B 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 23B enters the cross dichroic prism 24 from a side different from the R light and the G light. The optical engine 11 may be configured to use a uniformizing optical system that makes the intensity distribution of the light beam uniform, for example, a rod integrator, a fly-eye lens, or a superimposing lens.

  The cross dichroic prism 24 has two dichroic films 25 and 26 arranged so as to be substantially orthogonal to each other. The first dichroic film 25 reflects R light and transmits G light and B light. The second dichroic film 26 reflects B light and transmits R light and G light. The cross dichroic prism 24 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 11 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 10 is not limited to a configuration including a spatial light modulator for each color light. The projector 10 may be configured to modulate two or three color lights with one spatial light modulator. The optical engine 11 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. 1, the projection optical system 13 is provided on the exit side of the optical engine 11. The projection optical system 13 is a projection lens including a lens that is an optical element that deflects light by transmission. The aspherical mirror 14 is a wide-angle reflecting part that widens the light from the projection optical system 13 by reflection, and has an aspherical curved surface. The aspherical mirror 14 has a function of widening the light from the projection optical system 13 and a function of bending the light from the projection optical system 13 and traveling in the direction of the screen 16. The projector 10 enables an ultra-short focus by widening the light from the projection optical system 13 with the aspherical mirror 14. Thereby, close-up projection is possible.

  The aspherical mirror 14 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. By making the aspherical mirror 14 into a curved surface shape, it becomes possible to simultaneously perform bending and widening of light.

  By widening the light not only by the projection optical system 13 but also by the aspherical mirror 14, the projection optical system 13 can be made smaller than when the light is widened only by the projection optical system 13. The projection optical system 13 and the aspherical mirror 14 perform image enlargement and image formation on the screen 16. The projection optical system 13 functions to enlarge an image and form an image on the screen 16. The aspherical mirror 14 functions to enlarge an image. The aspherical mirror 14 may be appropriately deformed so that image distortion can be corrected.

  The casing 17 houses the optical engine 11, the projection optical system 13, and the aspherical mirror 14. The emitting unit 15 emits light modulated according to the image signal from the housing 17 toward the screen 16. The emitting unit 15 is configured by covering an opening provided in the housing 17 with a transparent member. The screen 16 is a reflective screen that reflects the light from the emitting portion 15. The screen 16 can have good viewing angle characteristics by making it possible to diffuse light in a desired range where an observer exists.

  In addition to the cabinet C, the projector 10 may be installed on a floor surface, a desk, a rack, or the like. Since the projector 10 has a compact configuration, an installation location can be easily secured. By enabling the projector 10 to be installed near the wall surface W, a large screen can be displayed even in a narrow room. The projector 10 may cause the aspherical mirror 14 to protrude from the housing 17. In this case, the housing 17 is formed with an opening through which the light incident on the aspherical mirror 14 passes, instead of the emitting portion 15.

  The projector 10 may be provided with a mirror for bending the optical path between the projection optical system 13 and the aspherical mirror 14. When the optical path is bent by about 90 degrees with a mirror, the optical engine 11 and the projection optical system 13 are arranged so as to emit light in the vertical direction or the depth direction in FIG. Thereby, each part from the optical engine 11 to the aspherical mirror 14 can be further arranged near the wall surface W.

  FIG. 3 schematically shows the optical system of the projector 10. The projection optical system 13 and the aspherical mirror 14 are arranged so that their optical axes are substantially coincident. The normal line N of the screen 16 is substantially parallel to the optical axis of the projection optical system 13 and the optical axis of the aspherical mirror 14. The projection optical system 13, the aspherical mirror 14, and the screen 16 all constitute a so-called coaxial optical system having a common optical axis AX. The projector 10 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. 3 with respect to the optical axis AX. On the other hand, the center normal of the image plane virtually formed on the exit surface of the cross dichroic prism 24 in the optical engine 11 is parallel to the optical axis AX and opposite to a specific side, that is, light. The axis AX is shifted to the lower side in FIG. With this configuration, the projector 10 makes light having a large incident angle incident on the screen 16. The incident angle is an angle formed by the normal line N of the screen 16 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 14 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 of the conical shape. By making the aspherical mirror 14 substantially rotationally symmetric with respect to the optical axis AX, the optical axis of the aspherical mirror 14 and the optical axes of other configurations can be easily matched. Since the aspherical mirror 14 has an axisymmetric aspherical shape, it can be processed by a simple method such as a lathe. Therefore, the aspherical mirror 14 can be manufactured easily and with high accuracy.

  The projector 10 employs a super wide-angle optical system that uses the projection optical system 13 and the aspherical mirror 14 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 16 is 70 degrees and the maximum incident angle is 80 degrees. By adopting the shift optical system, it is possible to make the angle difference of the light incident on the screen 16 within about 10 degrees.

  FIG. 4 shows a cross-sectional configuration of the projection optical system 13. FIG. 5 shows a plane configuration on the incident side of the projection optical system 13. The projection optical system 13 includes a first lens group 31 and a second lens group 32. The first lens group 31 is a first optical element group including four lenses LN fixed by a first lens barrel 33, and constitutes a first system. The second lens group 32 is a second optical element group including six lenses LN fixed by a second lens barrel 34 longer than the first lens barrel 33, and constitutes a second system. The focal length of the first lens group 31 is longer than the focal length of the second lens group 32.

  Both the first lens group 31 and the second lens group 32 are fixed to the rotary substrate 30. An incident side portion of each of the first lens group 31 and the second lens group 32 is fixed to the rotary substrate 30. The rotary substrate 30 is a circular plate-like member provided so as to be rotatable about the rotation axis TX. The first lens group 31 and the second lens group 32 are arranged at positions symmetrical to each other with respect to the rotation axis TX on the rotating substrate 30. When the first lens group 31 is arranged so that the optical axis AX and the optical axis of the first lens group 31 coincide, the second lens group 32 is arranged at a position different from the optical axis AX. When the first lens group 31 which is the first system is on the optical axis AX, the projector 10 displays a screen having a diagonal length of, for example, 40 inches on the screen 16 (a white double arrow in FIG. 6). On the left side of

  When the rotary substrate 30 is rotated approximately 180 degrees from the state shown in FIGS. 4 and 5, the first lens group 31 and the second lens group 32 are interchanged. The rotating substrate 30 may have a configuration for fixing the position of the second lens group 32 when the second lens group 32 reaches the optical axis AX. When the second lens group 32 is disposed so that the optical axis AX and the optical axis of the second lens group 32 coincide with each other, the first lens group 31 is disposed at a position different from the optical axis AX.

  Since the focal length of the second lens group 32 is shorter than the focal length of the first lens group 31, a larger screen is displayed when the second lens group 32 is used than when the first lens group 31 is used. When the second lens group 32, which is the second system, is on the optical axis AX, the projector 10 displays, for example, an 80-inch screen on the screen 16 (see the right side of the white double arrow in FIG. 6). By switching between the first system and the second system in the projection optical system 13, as shown in FIG. 6, a significant screen size switching can be realized.

  The projection optical system 13 can be switched between the first system and the second system having a focal length different from that of the first system by exchanging the first lens group 31 and the second lens group 32. . For example, in the case of a projector 10 for consumer use, it is possible to enjoy viewing on a large screen and a content according to the content when it is desired to obtain a sense of reality such as a small screen or a movie for a normal television program. The projector 10 is not limited to switching the screen size between 40 inches and 80 inches. For example, the projector 10 can display a 30 to 40 inch screen by the first system and an 80 to 100 inch screen by the second system. The image size that can be displayed by the projector 10 can be appropriately set according to the configuration of the projector 10.

  Since the first system and the second system can have different configurations, the design of the projection optical system 13 is facilitated compared to the case where the zoom function is realized only by adjusting the position of the optical element. The projection optical system 13 can be configured simply. For example, the projection optical system 13 is capable of high resolution, for example, full high-definition in the case of the second system, and lower resolution than that of the second system in the case of the first system. The corresponding design becomes possible. Therefore, sufficient optical performance can be easily realized.

  By eliminating the need for a design that incorporates a zoom function in an ultra-short focus optical system, it is possible to adjust the screen size without encouraging the difficulty of design and the complexity of the configuration. Costs can be reduced by reducing design man-hours and simplifying lens construction. As a result, the screen size can be greatly adjusted with a simple configuration, and sufficient optical performance can be obtained. The projector 10 can greatly adjust the screen size with a simple configuration, and can display a high-quality image.

  The first lens group 31 and the second lens group 32 are not limited to being replaced by the rotation of the rotary substrate 30. For example, the first lens group 31 and the second lens group 32 may be provided in parallel, and the first lens group 31 and the second lens group 32 may be interchanged by moving in parallel. The first lens group 31 and the second lens group 32 may be configured to perform zoom adjustment and focus adjustment by moving the lens LN in the optical axis AX direction. When either one of the first lens group 31 and the second lens group 32 is disposed on the optical axis AX for projection, not only those used for projection but also those not used for projection are housing 17. It is desirable to be in a state of being housed inside. As a result, it is possible to eliminate damage or the like caused by the user directly touching the lens LN, and to prevent dust and scratches.

  The first lens group 31 and the second lens group 32 are not limited to the configuration shown in the figure, and the position, shape, number, and the like of the lens LN can be set as appropriate. The projection optical system 13 is not limited to the configuration in which the first lens group 31 and the second lens group 32 including the lens LN are interchanged. The first optical element group and the second optical element group that are switched in switching between the first system and the second system may be configured to include an optical element other than the lens LN, for example, a mirror.

  The projection optical system 13 is not limited to the case where it can be switched between two systems having different focal lengths. The projection optical system 13 may be configured to be switchable between three or more systems having different focal lengths. As the number of systems that can be switched in the projection optical system 13 increases, the projector 10 can perform display with a larger number of screen sizes, and can respond to various contents and requests.

  The replacement of the first lens group 31 and the second lens group 32 may be performed automatically according to an input operation for changing the screen size, or may be performed manually. For example, if an input operation for changing the screen size is performed in the operation unit 35 illustrated in FIG. 7, the control unit 36 exchanges the first lens group 31 and the second lens group 32 in the projection optical system 13. Further, the control unit 36 controls the light source driving unit 37 in accordance with the input to the operation unit 35.

  While the first lens group 31 and the second lens group 32 are exchanged, the light source driving unit 37 stops the supply of light from the color light LEDs 21R, 21G, and 21B under the control of the control unit 36. While the projection optical system 13 is switched between the first system and the second system, emission of light corresponding to the image signal is stopped. During switching between the first system and the second system, the image changes regardless of the image signal. By stopping the emission of light during switching between the first system and the second system, discomfort given to the observer can be reduced.

  The control unit 36 is not limited to the case where the emission of light is stopped by the control of the light source driving unit 37. For example, the control unit 36 may stop the emission of light according to the image signal by controlling the configuration in which light is blocked in the optical path from each of the color light LEDs 21R, 21G, and 21B to the emission unit 15. Also, when the first lens group 31 and the second lens group 32 are manually replaced, the emission of light according to the image signal can be stopped. In this case, the rotation of the rotating substrate 30 is detected and the supply of light is stopped. In addition, the rotation substrate 30 can be rotated to detect that the replacement of the first lens group 31 and the second lens group 32 is completed, and the emission of light according to the image signal can be restarted.

  FIG. 8 shows a cross-sectional configuration of a projection optical system 40 according to a modification of the present embodiment. FIG. 9 shows the incident side plane configuration of the projection optical system 40 of this modification. The projection optical system 40 has a plurality of lenses LN fixed by a lens barrel 44. The first switching lens 41 and the second switching lens 42 are provided so as to be interchangeable between the lenses LN in the lens barrel 44. When the first switching lens 41 is on the optical axis AX, the projection optical system 40 is the first system. The first switching lens 41 is an optical element that forms part of the first system. When the second switching lens 42 is on the optical axis AX, the projection optical system 40 is a second system. The second switching lens 42 is an optical element that constitutes a part of the second system.

  Both the first switching lens 41 and the second switching lens 42 are fixed to the rotating substrate 43. The first switching lens 41 and the second switching lens 42 are interchanged by rotating the rotating substrate 43 around the rotation axis TX. The projection optical system 40 can switch between the first system and the second system having a focal length different from that of the first system by exchanging the first switching lens 41 and the second switching lens 42. .

  The projection optical system 40 can switch between the first system and the second system by exchanging the single lenses 41 and 42. Compared with the case where each lens group housed in the lens barrel is replaced, the number of parts can be reduced and the cost can be reduced. Accordingly, the first system and the second system having different focal lengths can be switched with a simpler configuration. The first switching lens 41 and the second switching lens 42 are not limited to being interchangeable at the illustrated positions, and may be interchangeable at any position in the projection optical system 40.

  Further, the projection optical system 40 is not limited to a configuration that allows the single lenses 41 and 42 to be interchanged with each other. The projection optical system 40 only needs to replace at least one optical element constituting a part of the first system and at least one optical element constituting a part of the second system. The position, the number, and the shape of the optical elements interchangeable between the first system and the second system are not limited to the same, and may be different.

  FIG. 10 shows a sectional configuration of the projection optical system 50 according to the second embodiment of the present invention. The projection optical system 50 of the present embodiment is characterized in that the first system and the second system are switched by rotating the front lens group 51. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The front lens group 51 includes four lenses LN1, LN2, LN3, and LN4 that are optical elements provided on the exit side from the stop 53.

  FIG. 11 shows a planar configuration of the lens LN1 disposed on the most exit side of the front group lens 51. The lens LN1 has a circular shape. The lens LN1 has different refractive indexes at the first portion 54 and the second portion 55. The first portion 54 is one side of the lens LN1 with respect to the surface S including the optical axis AX. In FIG. 11, the surface S is a surface that includes the optical axis AX and is substantially perpendicular to the paper surface. The second portion 55 is on the side different from the first portion 54 with respect to the surface S. The first portion 54 and the second portion 55 have substantially the same semicircular shape in the planar configuration. The first portion 54 and the second portion 55 of the lens LN1 cause light to travel in different directions by making the refractive index of the first portion 54 different from the refractive index of the second portion 55. Thus, the lens LN1 has different optical characteristics between the first portion 54 and the second portion 55.

  Returning to FIG. 10, the three lenses LN2, LN3, and LN4 other than the lens LN1 on the most exit side of the front group lens 51 are similar to the lens LN1 on the most exit side, as the first portion 54 and the second portion 55. Thus, they have different optical characteristics. The first system of the projection optical system 50 is configured using the first portion 54 of the front group lens 51. The second system of the projection optical system 50 is configured using the second portion 55 of the front group lens 51.

  The light from the cross dichroic prism 24 passes through only the upper half of the front group lens 51 from the optical axis AX by shifting from the optical axis AX to the upper side of the paper, which is a specific side. At this time, the lower half of the front group lens 51 from the optical axis AX is not used. The illustrated projection optical system 50 is a first system that allows light to pass through the first portion 54 of the front group lens 51. From this state, when the front lens group 51 is rotated approximately 180 degrees around the optical axis AX, the positions of the first portion 54 and the second portion 55 are switched. When light is allowed to pass through the second portion 55 of the front group lens 51, the projection optical system 50 becomes the second system. The first system and the second system are switched by rotating the front lens group 51 about the optical axis AX. For example, the front lens group 51 can be configured to be rotatable about the optical axis AX for each portion of the lens barrel that supports the lenses LN1 to LN4.

  Thus, by employing the shift optical system, it is possible to use optical elements having the first system optical characteristics for the first portion 54 and the second system optical characteristics for the second portion 55, respectively. it can. Replacing the portion of the optical element that makes light incident with the first portion 54 and the second portion 55 makes it possible to switch between the first system and the second system with a simple configuration. Further, the optical element including the first portion 54 and the second portion 55 can be housed in one lens barrel (not shown), and space saving can be achieved. The cost can be further reduced by reducing the number of parts. As a result, it is possible to greatly adjust the screen size and to realize sufficient optical performance with a simpler and smaller configuration.

  The lenses LN1 to LN4 can be easily formed by mold transfer to a resin, glass or the like using a mold. In order to give the first portion 54 and the second portion 55 different optical characteristics, the refractive index of the first portion 54 and the refractive index of the second portion 55 are not limited. The curvature of the curved surface of the first portion 54 and the curvature of the curved surface of the second portion 55 may be made different so as to have different optical characteristics.

  Also, when different coatings are applied to the first portion 54 and the second portion 55, or different thicknesses are used for the first portion 54 and the second portion 55, different optical characteristics can be provided. The lenses LN <b> 1 to LN <b> 4 having such a configuration may be formed by bonding a first part 54 and a second part 55 that are separately molded, in addition to being formed by mold transfer.

  Further, in the front group lens 51, the positions, the number, and the shape of the lenses LN1 to LN4 may be different between the first portion 54 and the second portion 55. Also in this case, the first portion 54 and the second portion 55 can have different optical characteristics. The front lens group 51 is not limited to a configuration in which any of the lenses LN1 to LN4 has different optical characteristics between the first portion 54 and the second portion 55. For some lenses, both the first portion 54 and the second portion 55 may have the same optical characteristics.

  The projection optical system 50 is not limited to a configuration in which the first system and the second system are switched by rotating all the lenses LN1 to LN4 constituting the front lens group 51. Any structure may be used as long as at least one of the lenses LN1 to LN4 that are optical elements constituting the front lens group 51 is rotated. In this case, the entire lens other than the lens to be rotated can be configured with uniform optical characteristics.

  FIG. 12 shows a cross-sectional configuration of a projection optical system 60 according to a modification of the present embodiment. The projection optical system 60 of this modification is characterized in that the first system and the second system are switched by rotating all the lenses LN that are optical element groups constituting the projection optical system 60. The front lens group 61 includes three lenses LN that are optical elements provided on the light exit side from the diaphragm 63. The rear lens group 62 is composed of five lenses LN which are optical elements provided on the incident side from the stop 63.

  The light from the cross dichroic prism 24 enters the projection optical system 60 from a position shifted from the optical axis AX to the lower side of the drawing, which is the side opposite to the specific side. The light incident on the projection optical system 60 passes through only the lower half of the rear group lens 62 from the optical axis AX. At this time, the upper half of the rear group lens 62 from the optical axis AX is not used. The light beam from the rear group lens 62 crosses the optical axis AX at a position outside the lens LN and in the vicinity of the stop 63, and enters the front group lens 61 from a position shifted from the optical axis AX to the upper side of the paper, which is a specific side. . The light incident on the front group lens 61 passes through only the upper half of the front group lens 61 from the optical axis AX. At this time, the lower half of the front lens group 61 from the optical axis AX is not used.

  The projection optical system 60 shown in the figure is a first system that allows light to pass through using the first portion 64 of the front group lens 61 and the second portion 67 of the rear group lens 62. From this state, when the projection optical system 60 is rotated approximately 180 degrees around the optical axis AX, the positions of the first portion 64 and the second portion 65 of the front lens group 61 are switched. Further, the positions of the second portion 67 and the first portion 66 of the rear group lens 62 are interchanged. When light passes through the second portion 65 of the front lens group 61 and the first portion 66 of the rear lens group 62, the projection optical system 60 becomes the second system. The first system and the second system are switched by rotating all the lenses LN collectively around the optical axis AX.

  Each lens LN of the front lens group 61 has different optical characteristics in the first portion 64 and the second portion 65. Each lens LN of the rear group lens 62 has different optical characteristics in the first portion 66 and the second portion 67. The configuration for giving different optical characteristics is the same as in the case of the projection optical system 50 (see FIG. 10). In this case as well, as in the case of the projection optical system 50 (see FIG. 10), the screen size can be greatly adjusted and a sufficient optical performance can be realized with a simpler and smaller configuration.

  The projection optical system 60 is not limited to a configuration in which both the front group lens 61 and the rear group lens 62 have different optical characteristics in the first portions 64 and 66 and the second portions 65 and 67. For example, the optical characteristics of the first portion 64 and the second portion 65 may be different only for the front group lens 61. Further, only the lens LN constituting the front group lens 61 and the lens LN constituting the rear group lens 62 are only part of the lens LN, and the optical characteristics of the first portions 64 and 66 and the second portions 65 and 67 are the same. It is also possible to make them different.

  In the front group lens 61 and the rear group lens 62, the position, the number, and the shape of the lens LN may be different between the first portions 64 and 66 and the second portions 65 and 67. The projection optical system 60 includes the first system and the second system in the case where the light beam and the optical axis AX intersect at a position outside the lens LN, as well as the case where the light beam and the optical axis AX intersect in the lens LN. It is possible to switch between systems. The configuration of the projection optical systems 50 and 60 in the present embodiment is not limited to that described in the present embodiment, and the position, shape, number, and the like of the lenses can be set as appropriate. The projection optical system of each of the above embodiments may be applied to an imaging optical system used in an imaging apparatus.

  As described above, the projection optical system according to the present invention is suitable for use in a projector that performs close-up projection.

1 is a diagram illustrating a schematic configuration of a projector according to a first 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. The figure which shows the cross-sectional structure of a projection optical system. The figure which shows the incident side plane structure of a projection optical system. The figure explaining switching of a screen size. The figure which shows the structure for controlling a projection optical system and an optical drive part. FIG. 6 is a diagram illustrating a cross-sectional configuration of a projection optical system according to a modification of Example 1. The figure which shows the incident side plane structure of a projection optical system. FIG. 5 is a diagram showing a cross-sectional configuration of a projection optical system according to Example 2 of the invention. The figure which shows the planar structure of the lens which comprises a front group lens. FIG. 6 is a diagram showing a cross-sectional configuration of a projection optical system according to a modification of Example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Projector, 11 Optical engine, 13 Projection optical system, 14 Aspherical mirror, 15 Output part, 16 Screen, 17 Case, C cabinet, W wall surface, LED for 21R R light, LED for 21G G light, For 21B B light LED, 22 collimator lens, spatial light modulator for 23R R light, spatial light modulator for 23G G light, spatial light modulator for 23B B light, 24 cross dichroic prism, 25 first dichroic film, 26 second dichroic film, AX optical axis, N normal, 30 rotation substrate, 31 first lens group, 32 second lens group, 33 first lens barrel, 34 second lens barrel, LN lens, TX rotation axis, 35 operation unit, 36 control unit 37 light source drive unit, 40 projection optical system, 41 first switching lens, 42 second switching lens, 43 rotating substrate, 44 Cylinder, 50 projection optical system, 51 front lens group, 53 stop, 54 first part, 55 second part, LN1-4 lens, S surface, 60 projection optical system, 61 front group lens, 62 rear group lens, 63 stop 64 First part 65 Second part 66 First part 67 Second part

Claims (9)

  A projection optical system for projecting light, wherein the projection optical system is switchable between a first system and a second system having a focal length different from that of the first system.   The first system and the second system are switched by exchanging the first optical element group constituting the first system and the second optical element group constituting the second system. The projection optical system according to claim 1, wherein:   The first system and the second system interchange at least one optical element that forms part of the first system and at least one optical element that forms part of the second system. The projection optical system according to claim 1, wherein the projection optical system is switched accordingly. Project light by shifting from the optical axis to a specific side,
The first system is configured by using a first portion on one side with respect to a surface including the optical axis among optical elements provided on the exit side from the stop,
2. The projection according to claim 1, wherein the second system is configured by using a second portion of the optical element that is different from the first portion with respect to a plane including the optical axis. Optical system.   The projection optical system according to claim 4, wherein the optical element has optical characteristics different from each other in the first part and the second part.   6. The first system and the second system can be switched by rotating at least one optical element provided on the exit side from the stop around the optical axis. The projection optical system described in 1. The light from the position opposite to the specific side with respect to the optical axis is shifted to the specific side and projected,
6. The switch according to claim 4, wherein the first system and the second system are switched by rotating an optical element group constituting the projection optical system around the optical axis. Projection optical system. A spatial light modulator that modulates light according to an image signal;
A projector comprising: the projection optical system according to claim 1.   The projection optical system is switchable between a first system and a second system having a focal length different from the first system, and is between the first system and the second system. The projector according to claim 8, wherein emission of light corresponding to the image signal is stopped while switching is performed.

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