JP2010160409A - Image projection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projection apparatus that projects a high contrast image with high luminance, and shifts a projection optical system while maintaining high resolution performance. <P>SOLUTION: The image projection apparatus has: an image forming element LP for forming an original image; an illuminating optical system α for emitting light from a light source 1 to the image forming element; the projection optical system 5 for projecting light from the image forming element to a target projection surface; and a shifting mechanism S for shifting the projection optical system in a first direction corresponding to the direction of a short side of the image forming element in relation to the image forming element and a second direction corresponding to the long side of the image forming element. In the illuminating optical system, the F number in the first direction is greater than that in the second direction. The amount in which the projection optical system can be shifted by the shifting mechanism in the first direction is larger than that in the second direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image projection apparatus such as a liquid crystal projector, and more particularly to an image projection apparatus having a shift mechanism that shifts a projection optical system that projects light from an image forming element such as a liquid crystal panel onto a projection surface.

  In the image projection device, illumination optics that can project high-brightness and high-contrast images by using light from the light source with high efficiency and illuminating the image forming element with uniform illuminance, thereby reducing unevenness in brightness and color. A system is needed.

  In the illumination optical system disclosed in Patent Document 1, the F-number is different between the short side direction and the long side direction of the image forming element. The F number is a numerical value indicating the brightness of the illumination optical system, and is inversely proportional to the magnitude of the incident angle of the light beam with respect to the image forming element. In this illumination optical system, since the polarization beam splitter used in the color separation / synthesis optical system has an incident angle characteristic, the cross section including the normal line of the polarization separation surface of the polarization beam splitter (hereinafter referred to as the first cross section). The F number is increased as much as possible to reduce the influence of incident angle characteristics. Thereby, the contrast of a projection image is improved. On the other hand, the F number in the second cross section orthogonal to the first cross section is made as small as possible to increase the amount of light. This realizes an illumination optical system capable of projecting a high-brightness and high-contrast image.

  In addition, in the image projection apparatus, the projection position of the image can be moved by shifting the projection optical system in the short side direction and the long side direction with respect to the image forming element in order to improve the installation property. Some have a projection shift function.

Furthermore, in order to reduce the size of the image projection apparatus and increase the resolution of the projected image, the image forming element is reduced in size while increasing in the number of pixels. For this reason, the pixel pitch is becoming increasingly smaller. ing.
JP 2004-245977 A

  As the pixel pitch of the image forming element becomes smaller, it is necessary to improve the resolution performance of the projection optical system. In general, the depth of focus of the projection optical system is proportional to the product of the pixel pitch and the F number of the illumination optical system. In other words, the depth of focus of the projection optical system is reduced by improving the brightness and reducing the pixel pitch.

  As the depth of focus of the projection optical system decreases, the influence of mechanical errors such as tilting and decentering of the projection optical system increases, and the projected image is likely to be blurred. For this reason, a shift mechanism for realizing the above-described projection shift function is required to shift the projection optical system in a state where the mechanical error of the projection optical system is as small as possible.

  However, it is difficult to realize a shift mechanism having a sufficient shiftable amount and having such a small mechanical error at a low cost.

  The present invention provides an image projection apparatus capable of projecting a high-brightness and high-contrast image, and further capable of shifting a projection optical system while maintaining high resolution performance.

  An image projection apparatus according to one aspect of the present invention projects an image forming element that forms an original image, an illumination optical system that irradiates the image forming element with light from a light source, and light from the image forming element onto a projection surface. The projection optical system and the projection optical system are shifted relative to the image forming element in a first direction corresponding to the short side direction of the image forming element and a second direction corresponding to the long side direction of the image forming element. And a shift mechanism. In the illumination optical system, the F number in the first direction is larger than the F number in the second direction. The shiftable amount in the first direction of the projection optical system by the shift mechanism is larger than the shiftable amount in the second direction.

  According to the present invention, an image projection apparatus capable of projecting a high-brightness and high-contrast image and capable of shifting the projection optical system in the first and second directions while maintaining high resolution performance. Can be realized. In addition, a shiftable amount in the first and second directions can be sufficiently secured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Overall configuration of projector)
FIG. 5 shows the configuration of a liquid crystal projector (image projection apparatus) that is Embodiment 1 of the present invention.

  In this figure, reference numeral 1 denotes a light source lamp (hereinafter simply referred to as a lamp), and a high-pressure mercury discharge lamp is used in this embodiment. However, as the light source lamp 1, a discharge lamp (for example, a halogen lamp, a xenon lamp, or a metal halide lamp) other than the high-pressure mercury discharge lamp may be used.

  2 is a lamp holder for holding the lamp 1, 3 is explosion-proof glass, and 4 is a glass presser. α is an illumination optical system that converts the luminous flux from the lamp 1 into a parallel luminous flux having a uniform brightness distribution, β is a color separation of the light from the illumination optical system α, and is applied to a liquid crystal panel for RGB, which will be described later. A color separation / synthesis optical system for guiding and color-combining light from the liquid crystal panel.

  Reference numeral 5 denotes a projection lens that projects light (image) from the color separation / synthesis optical system β onto a screen (projected surface) (not shown). A projection optical system (not shown) is accommodated in the projection lens 5.

  Reference numeral 6 denotes an optical box that houses the lamp 1, the illumination optical system α, and the color separation / synthesis optical system β and to which the projection lens 5 is fixed. The optical box 6 is formed with a lamp case 6 a surrounding the lamp 1.

  Reference numeral 7 denotes an optical box lid that covers the optical box 6 with the illumination optical system α and the color separation / synthesis optical system β accommodated therein. Reference numeral 8 denotes a PFC power supply board that creates a DC power supply from a commercial power supply to each board. Reference numeral 9 denotes a power supply filter board. Reference numeral 10 denotes a ballast power supply board that operates with the PFC power supply board 8 to drive the lamp 1 to light.

  Reference numeral 11 denotes a control board that performs driving of the liquid crystal panel and lighting control of the lamp 1 by electric power from the PFC power supply board 8. 12A and 12B are first and second for cooling optical elements such as a liquid crystal panel and a polarizing plate in the color separation / synthesis optical system β by sucking air from an air inlet 21a of the lower exterior case 21 described later. It is an optical system cooling fan. Reference numeral 13 denotes a first RGB duct for guiding the wind from both the optical system cooling fans 12A and 12B to the optical elements in the color separation / synthesis optical system β.

  Reference numeral 70 denotes a first dust removal filter that covers a first air inlet, which will be described later, formed in the first RGB duct 13.

  Reference numeral 14 denotes a lamp cooling fan that sends a blowing air to the lamp 1 to cool the lamp 1. A first lamp duct 15 guides the cooling air to the lamp 1 while holding the lamp cooling fan 14. Reference numeral 16 denotes a second lamp duct that holds the lamp cooling fan 14 and forms a duct together with the first lamp duct 15.

  Reference numeral 17 denotes a power supply cooling fan for cooling air by sucking air from an air inlet 21b provided in the lower exterior case 21 and allowing air to flow through the PFC power supply board 8 and the ballast power supply board 10. Reference numeral 18 denotes an exhaust fan, which discharges hot air that has been sent from the lamp cooling fan 14 to the lamp 1 and has cooled it, from an exhaust port 24a formed in a second side plate B24 described later.

  The lower exterior case 21 houses the lamp 1, the optical box 6, the power supply system boards 8 to 10, the control board 11, and the like. Reference numeral 22 denotes an upper outer case for covering the lower outer case 21 with the optical box 6 and the like stored therein. Reference numeral 23 denotes a first side plate, which closes a side opening formed by the outer cases 21 and 22 together with the second side plate 24. The lower exterior case 21 has the above-described intake ports 21a and 21b, and the second side plate 24 has the above-described exhaust port 24a. The lower exterior case 21, the upper exterior case 22, the first side plate 23, and the second side plate 24 constitute a housing of the projector.

  Reference numeral 25 denotes an IF board on which a connector for taking in various signals is mounted. Reference numeral 26 denotes an IF reinforcing plate attached to the inside of the first side plate 23.

  Reference numeral 27 denotes an exhaust duct for guiding the exhaust heat from the lamp 1 to the exhaust fan 18 so as not to diffuse the exhaust air into the housing. The exhaust duct 27 holds lamp exhaust louvers 19 and 20 having a light shielding function for preventing light from the lamp 1 from leaking outside the apparatus.

  Reference numeral 28 denotes a lamp lid. The lamp lid 28 is detachably disposed on the bottom surface of the lower exterior case 21 and is fixed by a screw (not shown). Reference numeral 29 denotes a set adjustment leg. The set adjustment leg 29 is fixed to the lower exterior case 21, and the height of the leg part 29a can be adjusted. The tilt angle of the projector can be adjusted by adjusting the height of the leg 29a.

  Reference numeral 30 denotes an RGB intake plate for holding a second dust removal filter 71 attached to the outside of the intake port 21a of the lower exterior case 21.

  Reference numeral 31 denotes a prism base that holds the color separation / synthesis optical system β. Reference numeral 32 denotes a box side cover having a duct-shaped portion for guiding cooling air from the first and second optical system cooling fans 12A and 12B in order to cool the optical elements and the liquid crystal panel in the color separation / synthesis optical system β. Reference numeral 33 denotes a second RGB duct that forms a duct together with the box side cover 32.

  Reference numeral 34 denotes an RGB substrate connected to the control substrate 11 to which a flexible substrate extending from a liquid crystal panel disposed in the color separation / synthesis optical system β is connected.

  Reference numeral 35 denotes an RGB substrate cover for preventing electrical noise from entering the RGB substrate 34.

(Optical configuration)
Next, the configuration of the optical system including the lamp 1, the illumination optical system α, the color separation / synthesis optical system β, and the projection lens (projection optical system) 5 will be described with reference to FIG. 6A shows a horizontal section of the optical system, and FIG. 6B shows a vertical section.

  In the figure, reference numeral 41 denotes a discharge arc tube (hereinafter simply referred to as an arc tube) that emits white light in a continuous spectrum. Reference numeral 42 denotes a reflector having a concave mirror that condenses light from the arc tube 41 in a predetermined direction. The light source lamp 1 is constituted by the arc tube 41 and the reflector 42.

  Reference numeral 43a denotes a first cylinder array in which a plurality of cylindrical lens cells having refractive power in the horizontal direction shown in FIG. 6A are arranged. 43b is a second cylinder array having a plurality of cylindrical lens cells corresponding to the individual lens cells of the first cylinder array 43a. 44 is an ultraviolet absorption filter, and 45 is a polarization conversion element that converts non-polarized light into predetermined polarized light.

  Reference numeral 46 denotes a front compressor composed of a cylindrical lens having a refractive power in the vertical direction shown in FIG. Reference numeral 47 denotes a reflection mirror for bending the optical axis from the lamp 1 by approximately 90 degrees (more specifically, 88 degrees).

  43c is a third cylinder array in which a plurality of cylindrical lens cells having refractive power in the vertical direction are arranged. 43d is a fourth cylinder array having a plurality of cylindrical lens arrays corresponding to individual lens cells of the third cylinder array 43c.

  Reference numeral 50 denotes a color filter for returning the color in a specific wavelength region to the lamp 1 in order to adjust the color coordinates to a predetermined value. Reference numeral 48 denotes a condenser lens. Reference numeral 49 denotes a rear compressor composed of a cylindrical lens having a refractive power in the vertical direction. The illumination optical system α is configured as described above.

  58 is a dichroic mirror that reflects light in the wavelength region of blue (B: for example 430 to 495 nm) and red (R: for example 590 to 650 nm) and transmits light in the wavelength region of green (G: for example 505 to 580 nm). is there. 59 is an incident side polarizing plate for G in which a polarizing element is bonded to a transparent substrate, and transmits only P-polarized light. Reference numeral 60 denotes a first polarization beam splitter that transmits P-polarized light and reflects S-polarized light on a polarization separation surface constituted by a multilayer film.

  61R, 61G, and 61B are a reflective liquid crystal panel for red, a reflective liquid crystal panel for green, and a reflective liquid crystal panel for blue as light modulation elements (or image forming elements) that reflect incident light and modulate the image, respectively. is there. 62R, 62G, and 62B are a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue, respectively.

  A trimming filter 64a returns orange light to the lamp 1 in order to increase the color purity of the R light. Reference numeral 64b denotes an incident-side polarizing plate for RB in which a polarizing element is attached to a transparent substrate and transmits only P-polarized light.

  65 is a color selective phase difference plate that converts the polarization direction of the R light by 90 degrees and does not convert the polarization direction of the B light. Reference numeral 66 denotes a second polarization beam splitter that transmits P-polarized light and reflects S-polarized light on the polarization separation surface.

  Reference numeral 68B denotes a B-use exit side polarizing plate (polarizing element) that rectifies only the S-polarized component of the B light. 68G is a G output-side polarizing plate that transmits only the S-polarized light component of the G light. Reference numeral 69 denotes a dichroic prism that transmits R light and B light and reflects G light.

  The above dichroic mirror 58 to dichroic prism 69 constitute a color separation / synthesis optical system β.

  In this embodiment, the polarization conversion element 45 converts P-polarized light to S-polarized light. The P-polarized light and S-polarized light described here are described with reference to the polarization direction of light in the polarization conversion element 45. On the other hand, the light incident on the dichroic mirror 58 is assumed to be P-polarized light considering the polarization directions in the first and second polarization beam splitters 60 and 66 as a reference. That is, in this embodiment, the light emitted from the polarization conversion element 45 is S-polarized light, but when the same S-polarized light is incident on the dichroic mirror 58, it is defined as P-polarized light.

(Optical action)
Next, the optical action will be described.

  Light emitted from the arc tube 41 is collected in a predetermined direction by the reflector 42. The reflector 42 has a parabolic concave mirror, and light from the focal position of the paraboloid becomes a light beam parallel to the symmetry axis of the paraboloid. However, since the light source from the arc tube 41 is not an ideal point light source and has a finite size, the condensed light flux includes many light components that are not parallel to the symmetry axis of the paraboloid. ing. These light beams are incident on the first cylinder array 43a. The light beam incident on the first cylinder array 43a is divided into a plurality of light beams corresponding to the number of cylinder lens cells and collected to form a plurality of strip-shaped light beams arranged in the vertical direction. The plurality of split light beams pass through the ultraviolet absorption filter 44 and the second cylinder array 43b to form a plurality of light source images in the vicinity of the polarization conversion element 45.

  The polarization conversion element 45 has a polarization separation surface, a reflection surface, and a half-wave plate. A plurality of light beams are incident on a polarization separation surface corresponding to each column, and are divided into a P-polarized component that transmits the light and an S-polarized component that is reflected there. The reflected S-polarized component is reflected by the reflecting surface and is emitted in the same direction as the P-polarized component. On the other hand, the P-polarized component transmitted through the polarization splitting surface is transmitted through the half-wave plate and converted into the same polarized component as the S-polarized component. Thus, a plurality of light beams having the same polarization direction are emitted.

  The plurality of light beams that have undergone polarization conversion are emitted from the polarization conversion element 45, compressed by the front compressor 46, reflected by the reflection mirror 47, and incident on the third cylinder array 43 c.

  The light beam incident on the third cylinder array 43c is divided into a plurality of light beams corresponding to the number of cylinder lens cells and collected to form a plurality of strip-shaped light beams arranged in the horizontal direction. The plurality of split light beams enter the rear compressor 49 via the fourth cylinder array 43d and the condenser lens 48.

  By the optical action of the front compressor 46, the condenser lens 48, and the rear compressor 49, rectangular images formed by a plurality of light beams overlap each other to form a rectangular uniform brightness illumination area. Reflective liquid crystal panels 61R, 61G, and 61B are disposed in this illumination area.

  The light converted to S-polarized light by the polarization conversion element 45 enters the dichroic mirror 58. Hereinafter, the optical path of the G light transmitted through the dichroic mirror 58 will be described.

  The G light transmitted through the dichroic mirror 58 enters the incident side polarizing plate 59. Even after being decomposed by the dichroic mirror 58, the G light remains P-polarized light (S-polarized light when the polarization conversion element 45 is used as a reference). The G light exits from the incident-side polarizing plate 59, then enters the first polarizing beam splitter 60 as P-polarized light, passes through the polarization separation surface, and reaches the G reflective liquid crystal panel 61G.

  Here, an image supply device 80 such as a personal computer, a DVD player, or a TV tuner is connected to the IF board 25 of the projector. The control board 11 drives the reflective liquid crystal panels 61R, 61G, and 61B based on the image information input from the image supply device 80, and forms an original image for each color on them. Thereby, the light incident on each reflective liquid crystal panel is reflected and modulated (image modulation) according to the original image. The image supply device 80 and the projector constitute an image display system.

  In the G reflective liquid crystal panel 61G, the G light is image-modulated and reflected. The P-polarized component of the image-modulated G light is again transmitted through the polarization separation surface of the first polarization beam splitter 60, returned to the light source side, and removed from the projection light. On the other hand, the S-polarized component of the image-modulated G light is reflected by the polarization separation surface of the first polarization beam splitter 60 and travels toward the dichroic prism 69 as projection light.

  At this time, in a state where all the polarization components are converted to P-polarized light (in a state where black is displayed), a quarter-wave plate 62G provided between the first polarizing beam splitter 60 and the G-use reflective liquid crystal panel 61G. The slow axis is adjusted in a predetermined direction. Thereby, the influence of the disorder of the polarization state which generate | occur | produces with the 1st polarizing beam splitter 60 and the reflective liquid crystal panel 61G for G can be restrained small.

  The G light emitted from the first polarization beam splitter 60 enters the dichroic prism 69 as S-polarized light, is reflected by the dichroic surface of the dichroic prism 69, and reaches the projection lens 5.

  On the other hand, the R light and B light reflected by the dichroic mirror 58 enter the trimming filter 64a. R light and B light are still P-polarized light after being decomposed by the dichroic mirror 58. Then, after the orange light component is cut by the trimming filter 64a, the R light and the B light are transmitted through the incident side polarizing plate 64b and are incident on the color selective phase difference plate 65.

  The color-selective phase difference plate 65 has an action of rotating only the polarization direction of the R light by 90 degrees, so that the R light is incident on the second polarization beam splitter 66 as S-polarized light and the B light is incident on P-polarized light.

  The R light incident on the second polarization beam splitter 66 as S-polarized light is reflected by the polarization separation surface of the second polarization beam splitter 66 and reaches the R-use reflective liquid crystal panel 61R. The B light incident on the second polarization beam splitter 66 as P-polarized light is transmitted through the polarization separation surface of the second polarization beam splitter 66 and reaches the B-use reflective liquid crystal panel 61B.

  The R light incident on the R reflective liquid crystal panel 61R is image-modulated and reflected. The S-polarized component of the image-modulated R light is reflected again by the polarization separation surface of the second polarization beam splitter 66, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized component of the image-modulated R light passes through the polarization separation surface of the second polarization beam splitter 66 and travels toward the dichroic prism 69 as projection light.

  The B light incident on the B-use reflective liquid crystal panel 61B is image-modulated and reflected. The P-polarized component of the image-modulated B light is transmitted again through the polarization separation surface of the second polarization beam splitter 66 and returned to the light source side, and is removed from the projection light. On the other hand, the S-polarized component of the image-modulated B light is reflected by the polarization separation surface of the second polarization beam splitter 66 and travels toward the dichroic prism 69 as projection light.

  At this time, by adjusting the slow axes of the quarter-wave plates 62R and 62B provided between the second polarizing beam splitter 66 and the R and B reflective liquid crystal panels 61R and 61B, As in the case, the adjustment in the black display state of each of the R and B lights can be performed.

  The R light and B light that are combined into one light beam and emitted from the second polarization beam splitter 66 are analyzed by the exit-side polarizing plate 68B and enter the dichroic prism 69. Further, the R light is transmitted through the exit-side polarizing plate 68 </ b> B as P-polarized light and enters the dichroic prism 69.

  By being analyzed by the exit-side polarizing plate 68B, the B light is ineffective generated by the B light passing through the second polarizing beam splitter 66, the B reflective liquid crystal panel 61B, and the quarter wavelength plate 62B. The light is cut from the components.

  The R light and B light incident on the dichroic prism 69 are transmitted through the dichroic surface and are combined with the G light reflected by the dichroic surface to reach the projection lens 5.

  The combined R, G, B light is enlarged and projected onto a projection surface such as a screen by the projection lens 5.

  The optical path described above is when the reflective liquid crystal panel is in the white display state. Hereinafter, the optical path when the reflective liquid crystal panel is in the black display state will be described.

  First, the optical path of G light will be described. The P-polarized light of the G light that has passed through the dichroic mirror 58 enters the incident-side polarizing plate 59, then enters the first polarizing beam splitter 60, is transmitted through the polarization separation surface, and is transmitted to the G reflective liquid crystal panel 61G. And so on. However, since the reflective liquid crystal panel 61G is in the black display state, the G light is reflected without being image-modulated. For this reason, even after being reflected by the reflective liquid crystal panel 61G for G, the G light remains P-polarized light. Accordingly, the G light again passes through the polarization separation surface of the first polarization beam splitter 60, passes through the incident side polarizing plate 59, returns to the light source side, and is removed from the projection light.

  Next, the optical paths of R light and B light will be described. The P-polarized light of R light and B light reflected by the dichroic mirror 58 is incident on the incident side polarizing plate 64b. Then, after exiting from the incident side polarizing plate 64 b, the light enters the color selective phase difference plate 65. Since the color-selective phase difference plate 65 has an action of rotating only the polarization direction of the R light by 90 degrees, the R light is incident on the second polarization beam splitter 66 as S-polarized light and the B light is incident on P-polarized light.

  The R light incident on the second polarization beam splitter 66 as S-polarized light is reflected by the polarization separation surface and reaches the R-use reflective liquid crystal panel 61R. The B light incident on the second polarization beam splitter 66 as P-polarized light passes through the polarization separation surface and reaches the B-use reflective liquid crystal panel 61B.

  Here, since the R reflective liquid crystal panel 61R is in a black display state, the R light incident on the R reflective liquid crystal panel 61R is reflected without being image-modulated. For this reason, even after being reflected by the reflective liquid crystal panel 61R for R, the R light remains S-polarized light. Accordingly, the R light is reflected again by the polarization separation surface of the second polarization beam splitter 66, passes through the incident-side polarizing plate 64b, returns to the light source side, and is removed from the projection light. Thereby, black display is performed.

  On the other hand, the B light incident on the B reflective liquid crystal panel 61B is reflected without being image-modulated because the B reflective liquid crystal panel 61B is in the black display state. For this reason, even after being reflected by the reflective liquid crystal panel 61B for B, the B light remains P-polarized light. Therefore, the B light again passes through the polarization separation surface of the second polarizing beam splitter 66, is converted to P-polarized light by the color-selective retardation plate 65, passes through the incident-side polarizing plate 64b, and is returned to the light source side. Removed from the projected light.

  A dotted line OP1 in FIG. 6B indicates an optical path in a first cross section including a first direction (hereinafter referred to as a panel short side direction) corresponding to the short side direction of each liquid crystal panel. A dotted line OP2 in FIG. 6A indicates an optical path in a second cross section including a second direction (hereinafter referred to as a panel long side direction) corresponding to the long side direction of each liquid crystal panel.

  Here, the color separation / synthesis optical system β is an optical system including a plurality of color separation surfaces (polarization separation surfaces and dichroic surfaces), and decomposes light from the illumination optical system α into a plurality of color lights. Are guided to a plurality of liquid crystal panels 61R, 61G, and 62B. The color separation / synthesis optical system β combines a plurality of color lights from the plurality of liquid crystal panels 61R, 61G, and 62B and guides them to the projection lens 5. The normal line of each color separation surface (see n in FIG. 2) is included in a cross section (first cross section) parallel to the panel short side direction 81.

  In the panel short side direction (first cross section), each polarization beam splitter has an incident angle characteristic. For this reason, in the panel short side direction, the incident angle of the light beam incident from the illumination optical system α to the polarization separation surface of each polarization beam splitter and each liquid crystal panel is larger than the incident angle in the panel long side direction (second cross section). Small (large as F number) is set.

  On the other hand, in the panel long side direction, in order to capture more light from the lamp 1, the incident angle is set larger (smaller as F number) than in the panel short side direction.

  Thus, in the illumination optical system α of the present embodiment, the F number is larger in the panel short side direction than in the panel long side direction.

(Shift mechanism)
Next, the shift mechanism of the projection lens 5 will be described with reference to FIGS. 1, 2, 3, 4, 7, 8, and 9. 1 shows the color separation / synthesis optical system β (however, only the second polarizing beam splitter 66 and the dichroic prism 69 are shown: the same applies to FIG. 2), the shift mechanism S, and the panel long side direction (second cross section) 76. Indicates. FIG. 2 shows the color separation / synthesis optical system β and the shift mechanism S in the panel short side direction (first cross section) 81. Further, in FIG. 1 and FIG. 2, only one liquid crystal panel is shown as LP for the sake of simplicity (corresponding to the reflective liquid crystal panel for R 61R or the reflective liquid crystal panel for B 61B).

  The spread angle 77 of the principal ray emitted from the liquid crystal panel LP in the panel long side direction 76 shown in FIG. 1 is larger than the spread angle 82 of the principal ray emitted from the liquid crystal panel LP in the panel short side direction 81 shown in FIG. large. Although this is not shown in FIGS. 1 and 2, the F number of the illumination optical system α that irradiates the liquid crystal panel LP with the light from the lamp 1 is smaller than the panel long side direction 76 in the panel short side direction 81. It means big.

  In FIG. 1 and FIG. 2, the chief ray emitted while spreading from the liquid crystal panel LP is guided to the projection lens 5 via the second polarizing beam splitter 66 and the dichroic prism 69. The second polarizing beam splitter 66 and the dichroic prism 69 (actually the entire color separation / synthesis optical system β) are positioned and attached to a prism base 78 as a support member. That is, the prism base 78 supports the second polarization beam splitter 66 and the dichroic prism 69.

  If the projection lens 5 is tilted with respect to the second polarizing beam splitter 66 and the dichroic prism 69, it causes image deterioration. The depth of focus is proportional to the pixel pitch × F number of the liquid crystal panel LP. For this reason, if the F number is doubled, the focal depth is also doubled.

  The shift mechanism S is a mechanism that shifts the projection lens 5 in the panel short side direction 81 and the panel long side direction 76 with respect to each liquid crystal panel while holding the projection lens 5. As can be seen from FIG. 6B, the long side direction of the actual reflective liquid crystal panel 61B for B is different from the shift direction of the projection lens 5 by the shift mechanism S. However, the projection lens 5 shifts in a cross section (second cross section) including the long side direction of the B-use reflective liquid crystal panel 61B. Including this case, the shift mechanism S shifts the projection lens 5 in the panel long side direction 76 in this embodiment. This is the same regardless of the orientation of the liquid crystal panel.

  The shift mechanism S is attached to the prism base 78. Specifically, the shift mechanism S includes a first shift plate 79 attached to the prism base 78 so as to be shiftable in the panel long side direction 76 with respect to the prism base 78 (that is, the liquid crystal panel LP). . Further, the shift mechanism S includes a second shift plate 80 attached to the first shift plate 79 so as to be shiftable in the panel short side direction 81 with respect to the prism base 78. The first shift plate 79 and the second shift plate 80 are stacked in the optical axis direction of the projection lens 5, and the panel long side direction 76 is a direction orthogonal to the optical axis direction of the projection lens 5. And it shifts in the panel short side direction 81.

  The shift mechanism S is configured such that the shiftable amount of the projection lens 5 in the panel short side direction 81 (the shiftable amount of the second shift plate 80) is the shiftable amount in the panel long side direction 76 (first shift). It is configured to be larger than the shiftable amount of the plate 79. In other words, the shiftable amount of the projection lens 5 in the panel long side direction 76 is configured to be smaller than the shiftable amount in the panel short side direction 81.

  Since the shift plate has a smaller shiftable amount, the change in the area of the shift seating surface is smaller, so the amount of play can be reduced. The smaller the amount of backlash, the more the tilt of the projection lens 5 can be reduced. For this reason, in this embodiment, the first shift plate 79 that shifts the shiftable amount of the second shift plate 80 that shifts in the panel short side direction 81 with a large F number in the panel long side direction 76 with a small F number. It is set larger than the possible shift amount.

  As a result, the shift direction in which the shiftable amount is large and the projection lens 5 is easily tilted and the direction in which the depth of focus is deep because the F number is large in the illumination optical system α and the projection lens 5 is allowed to tilt are large. Match. In other words, a shift direction in which the shiftable amount is small and the projection lens 5 is not easily tilted and a direction in which the depth of focus is shallow because the F number is small in the illumination optical system α and the tilting tolerance of the projection lens 5 is small. Match. With such a setting, it is possible to realize a projector that is hardly affected by the tilt of the projection lens 5 caused by the shift mechanism S and has little image deterioration. Further, a sufficient shiftable amount of the projection lens 5 can be ensured in each of the panel short side direction 81 and the panel long side direction 76.

  FIG. 3 shows the relationship between the image circle 73 of the projection lens 5 and the liquid crystal panel 72 in which the ratio of the length of the long side to the length of the short side is 4: 3 and the length of the short side is A. Yes. Note that the projection lens actually shifts with respect to the liquid crystal panel, but here the description will be made assuming that the liquid crystal panel shifts with respect to the projection lens. This is the same in the description of FIG.

  3, the liquid crystal panel 72 can be shifted from the center of the image circle 73 (the optical axis position of the projection lens 5) by 50% (0.5 A) of the length of the short side in the short side direction. In this case, the radius of the image circle 73 is required to be at least 1.2A.

  The right diagram of FIG. 3 shows a case where the liquid crystal panel 72 is shifted in the long side direction from the center of the image circle 73 with respect to the same image circle 73 as the left diagram. In this case, the shiftable amount is 0.43 A, which is smaller than the shiftable amount (0.5 A) in the short side direction.

  FIG. 4 shows the relationship between the image circle 75 of the projection lens 5 and the liquid crystal panel 74 in which the ratio of the length of the long side to the length of the short side is 16: 9 and the length of the short side is A. Yes.

  As shown in the left diagram of FIG. 4, when the liquid crystal panel 74 can be shifted from the center of the image circle 75 by 50% (0.5 A) of the length of the short side in the short side direction, the radius of the image circle 75 Requires at least 1.3A.

  4 shows a case where the liquid crystal panel 74 is shifted from the center of the image circle 75 in the long side direction with respect to the same image circle 75 as the left diagram. In this case, the shiftable amount is 0.34 A, which is smaller than the shiftable amount (0.5 A) in the short side direction.

  As can be seen from this, when a liquid crystal panel with different long and short sides is shifted within the image circle of the projection lens, the shiftable amount in the long side direction is always shiftable in the short side direction. Smaller than the amount. Therefore, it is preferable to match the direction in which the shiftable amount is large and the direction in which the shiftable amount is small with the direction in which the F number is large and the direction in which the aforementioned F number is small.

  In this embodiment, the shift mechanism in which the two shift plates 79 and 89 that can shift in two different directions are stacked is described. However, a shift mechanism in which one shift plate can shift in the two directions is used. Also good.

  FIG. 7 shows a more specific configuration of the shift mechanism S described in the first embodiment as the second embodiment of the present invention. FIG. 7 is a view showing the shift mechanism S ′ as seen from the optical axis direction of the projection lens 5. In the present embodiment, the same reference numerals as those in the first embodiment are assigned to components common to the first embodiment.

  The first shift plate 79 is in contact with the prism base 78 at three seating surfaces 89, 90, 91. In the side view shown on the right side in the drawing, a seat surface 91 is formed on the first shift plate 79, and the seat surface 91 is in contact with the prism base 78.

  The second shift plate 80 is in contact with the first shift plate 79 at three seating surfaces 92, 93, 94.

  Long hole portions 82, 83, 84 extending in the long side direction of the panel are formed at the center of the seating surfaces 89, 90, 91 of the first shift plate 79, and the prism base 78 is formed in each long hole portion. A boss protruding from is inserted. The long hole portion 82 and the boss are engaged with each other in the panel short side direction. On the other hand, the long hole portions 83 and 84 and the boss are not engaged in the panel short side direction, and the engagement accuracy in the panel short side direction is achieved by the width L2 between the outer surfaces of the long hole portions 83 and 84. I'm out.

  Long hole portions 85, 86, 87 extending in the short side direction of the panel are formed in the center portions of the seating surfaces 92, 93, 94 of the second shift plate 80. Each long hole portion has a first hole portion. A boss protruding from the shift plate 79 is inserted. The long hole portion 85 and the boss are engaged with each other in the panel long side direction. On the other hand, the long hole portions 86 and 87 and the boss are not engaged in the long side direction of the panel, and the engagement accuracy in the long side direction of the panel is obtained by the width L3 between the outer surfaces of the long hole portions 85 and 87. I'm out.

  7 is a side view of the shift mechanism S ′. The first shift plate 79 and the second shift plate 80 are pressed against the prism base 78 and the first shift plate 79 by springs 95 to 99 with friction, respectively.

  In FIG. 7, the first shift plate 79 and the second shift plate 80 are respectively held so as to be shiftable in the panel long side direction and the panel short side direction by inserting bosses into the long hole portions. showed that. However, this is only an example, and the first shift plate and the second shift plate may be held so as to be shiftable in the panel long side direction and the panel short side direction by the rail structure. FIG. 8 shows the configuration.

  As shown in FIG. 8, rail portions 104 to 109 are provided on the outer portions of the prism base 78 and the first shift plate 79, and the first shift plate 79 and the second shift plate 80 are connected by the rail portions 104 to 109. Holds shiftable. The first shift plate 79 and the second shift plate 80 are biased to one side in the panel short side direction and one side in the panel long side direction by the biasing springs 102 and 103 provided on the rail portion 108 and the rail portion 105, respectively. Has been.

  With such a configuration, the contact area between the prism base 78 and the first shift plate 79 and between the first shift plate 79 and the second shift plate 80 can be easily increased. An advantageous configuration can be realized.

  Further, a side view of a portion surrounded by a dotted circle in the upper diagram of FIG. 8 is shown on the right side of FIG. A leaf spring 108 is attached to the second shift plate 80. A part of the leaf spring 108 has a curved surface shape, and the curved surface portion is bent to press the first shift plate 79 against the prism base 78. Further, since the curved portion is bent in the direction along the shift direction of the first shift plate 79 (indicated by an arrow in the drawing), the leaf spring 108 is not moved even when the first shift plate 79 is shifted. 1 shift plate 79 is not damaged.

  The projector described in the first embodiment is installed so that the short side direction of the panel coincides with the direction of gravity. Such an installation method includes a normal installation method that is placed on a table and an installation method that is suspended from the top and bottom. In the ceiling-suspended state, the gravity direction is reversed in the panel short-side direction with respect to the normal installation state, and the tilting amount of the projection lens 5 changes due to the difference in the amount of play due to the difference in the gravity direction of the shift mechanism.

  However, as described in the first embodiment, the F-number of the illumination optical system is large and the depth of focus is deep in the direction of the short side of the panel, which is advantageous for changes in the tilt amount of the projection lens 5.

  In FIG. 9, as a third embodiment of the present invention, the shift mechanism shown in FIG. 8 has a function capable of changing the shift amounts of the first shift plate 79 and the second shift plate 80 using an actuator. The added shift mechanism S "'is shown.

  In the shift mechanism S ′ ″, the first shift plate 79 is provided with a notch 112, and a rack gear 111 extending in the long side direction of the panel is formed inside the notch 112. Further, the first shift plate 79 is provided with a first gear. The second shift plate 80 is also provided with a notch 113, and a rack gear 114 extending in the short side direction of the panel is formed inside the notch 113.

  The rack gear 111 meshes with a drive gear 110 attached to the output shaft of the motor 109. As the motor 109 rotates, the first shift plate 79 shifts in the panel long side direction.

  The rack gear 114 meshes with a drive gear 120 attached to an output shaft of a motor (not shown). As the motor rotates, the second shift plate 80 shifts in the panel short side direction.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment when the present invention is implemented.

1 is a top view illustrating a color separation / synthesis optical system, a projection lens, and a shift mechanism of a projector that is Embodiment 1 of the present invention. FIG. FIG. 2 is a side view illustrating a color separation / synthesis optical system, a projection lens, and a shift mechanism thereof in Embodiment 1. FIG. 3 is a diagram illustrating a relationship between an image circle of a projection lens and a liquid crystal panel having an aspect ratio of 4: 3 in Example 1. FIG. 3 is a diagram illustrating a relationship between an image circle of a projection lens and a liquid crystal panel having an aspect ratio of 16: 9 in Example 1. FIG. 3 is an exploded perspective view of the projector according to the first embodiment. FIG. 3 is a diagram illustrating an optical configuration of the projector according to the first embodiment. FIG. 6 is a diagram illustrating a color separation / synthesis optical system, a projection lens, and a shift mechanism of a projector that is Embodiment 2 of the present invention. FIG. 6 is a diagram illustrating another example of a color separation / synthesis optical system, a projection lens, and a shift mechanism of a projector that is Embodiment 2 of the present invention. FIG. 10 is a diagram illustrating a color separation / synthesis optical system, a projection lens, and a shift mechanism of a projector that is Embodiment 3 of the present invention.

DESCRIPTION OF SYMBOLS 1 Light source lamp 5 Projection lens 59, 64b, 68B, 68G Polarizing plate 61R, 61G, 61B Reflective type liquid crystal panel 62R, 62G, 62B 1/4 wavelength plate 73, 75 Image circle 78 of projection lens 78 Prism base 78
79, 80 Shift plate S Shift mechanism

Claims (3)

An image forming element for forming an original image;
An illumination optical system for irradiating the image forming element with light from a light source;
A projection optical system for projecting light from the image forming element onto a projection surface;
Shift for shifting the projection optical system with respect to the image forming element in a first direction corresponding to the short side direction of the image forming element and a second direction corresponding to the long side direction of the image forming element A mechanism,
The illumination optical system has an F number in the first direction larger than an F number in the second direction,
An image projection apparatus characterized in that a shiftable amount in the first direction of the projection optical system by the shift mechanism is larger than a shiftable amount in the second direction. The projection optical system is configured to decompose light from the illumination optical system into a plurality of color lights, guide the plurality of color lights to the plurality of image forming elements, and combine the plurality of color lights from the plurality of image forming elements. Color separation and synthesis optical system leading to
A support member for supporting the color separation / synthesis optical system,
The image projection apparatus according to claim 1, wherein the shift mechanism is attached to the support member. An optical system including a plurality of color separation surfaces, wherein the light from the illumination optical system is decomposed into a plurality of color lights, and the plurality of color lights are guided to the plurality of image forming elements, from the plurality of image forming elements A color separation / synthesis optical system that combines the plurality of color lights and guides them to the projection optical system,
The image projection apparatus according to claim 1, wherein the normal line of each color separation surface is included in a cross section parallel to the first direction.