JP2012137702A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid shading of effective light and transmission of unnecessary light in a light shielding mask when a projection optical system is shifted.SOLUTION: An image projection device comprises: an optical modulator LP for modulating light from a light source; a projection optical system 5 for projecting the light having been modulated by the optical modulator onto a projection surface; a first shifting mechanism 70, 71, 77 for moving the projection optical system against the optical modulator in a shift direction perpendicular to an optical axis AXL of the projection optical system; a light shielding mask 72 disposed between the optical modulator and the projection optical system and having an opening portion 72a for transmitting light and a shielding portion 72b formed in shift directions of the opening portion; and a second shifting mechanism 73, 86, 87 for moving the light shielding mask against the optical modulator in the same direction as the projection optical system moved by the first shifting mechanism out of the shift directions by a distance smaller than a distance of movement of the projection optical system.

Description

  The present invention relates to an image projection apparatus that projects an image onto a projection surface using a projection optical system, and more particularly to an image projection apparatus having a mechanism for shifting a projection optical system.

  Some image projection apparatuses such as liquid crystal projectors have a function of moving an image projection position on a projection surface such as a screen while fixing the position of the apparatus. This function makes the projection optical system in a direction perpendicular to the optical axis of the projection optical system with respect to a color combining optical element that combines light modulated by a light modulation element such as a liquid crystal panel or a plurality of light modulation elements. This is realized by a shift mechanism that moves (shifts) to.

  On the other hand, when unnecessary light that is not effective light used for image projection among the light from the light modulation element is irradiated to an optical element such as a lens constituting the projection optical system or a lens barrel that holds the projection optical system, This increases the temperature of the optical element and the lens barrel. As a result, there is a possibility that the optical performance of the projection optical system is lowered and the projected image is deteriorated. Further, unnecessary light incident on the projection optical system may be reflected in the projection optical system to generate a ghost. For this reason, as disclosed in Patent Document 1, the image projection apparatus includes a light modulation element and a color synthesis optical element (color synthesis prism) or a color synthesis optical element and a projection optical system. In some cases, a light-shielding mask having an opening that allows effective light to pass through and a light-shielding portion that blocks unnecessary light is disposed.

Patent No. 4055774

  However, in the above-described image projection apparatus having the shift mechanism of the projection optical system, when the position of the light shielding mask is fixed as in the image projection apparatus disclosed in Patent Document 1 and having no shift mechanism, the following Such a problem arises.

  FIG. 6A shows a non-shifted state in which the projection optical system 5 is not shifted with respect to the light modulation element 61. 6A (and FIG. 6B), the left diagram shows an optical cross section along the optical axis of the projection optical system, and the right diagram shows the projection optical system 5 viewed from the light modulation element side. The luminous flux is shown. In this non-shifted state, the light shielding mask 72 indicated by a solid line is appropriately disposed at a position where unnecessary light is shielded.

  As shown in FIG. 6B, when the projection optical system 5 is shifted with respect to the light modulation element 61, the cross-sectional shape of the light beam incident on the projection optical system 5 from the light modulation element 61 changes.

  The shape of the opening (hereinafter referred to as an aperture) 72 a of the light shielding mask 72 is determined by the cross-sectional shape of the light beam emitted from the light modulation element 61 and passing through the position where the light shielding mask 72 is disposed. Specifically, the shape of the aperture is determined so as to circumscribe the light beam reaching the end of the effective modulation area of the light modulation element 61 from the projection optical system 5 in the reverse ray tracing. Furthermore, the upper end of the aperture is determined by the light beam passing through the uppermost side (upper light beam) among the light beams that reach the upper end of the effective modulation area of the light modulation element 61, and the lowest light beam that reaches the lower end of the effective modulation area. The lower end of the aperture is determined by the ray passing through the side (bottom ray).

  By the way, in a general projection optical system (projection lens), the amount of luminous flux increases as it approaches the periphery from the center of the effective image circle. That is, the width of the light beam determined by the upper light beam and the lower light beam becomes thinner toward the periphery.

  Aperture in which the shape determined in the non-shifted state shown in FIG. 6 (a) (here, the optical axis position of the projection optical system coincides with the center of the effective modulation area of the light modulation element 61) is determined. On the other hand, consider a case where the projection optical system is shifted upward as shown in FIG. In the non-shifted state, the flux splitting is vertically symmetric, so the shape of the aperture is also vertically symmetric with respect to the center of the effective modulation region of the light modulation element 61.

  However, in the upward shift state in which the projection optical system is shifted upward as shown in FIG. 6B, the optical axis of the projection optical system is also shifted upward with respect to the effective modulation region of the light modulation element 61. The light flux taken into the projection optical system from the light modulation element 61 increases on the upper side and decreases on the lower side. That is, in the reverse ray tracing, the upper ray of the luminous flux reaching the upper end of the effective modulation region of the light modulation element 61 that determines the aperture and the lower ray of the luminous flux reaching the lower end move upward. As a result, effective light is emitted on the upper side and unnecessary light is allowed to pass on the lower side by the light-shielding mask whose aperture is appropriately set so as to correspond to the non-shift state.

  The present invention provides an image projection apparatus capable of avoiding effective light shifting and unnecessary light passing through a light shielding mask when a projection optical system is shifted.

  An image projection apparatus according to one aspect of the present invention includes a light modulation element that modulates light from a light source, a projection optical system that projects light modulated by the light modulation element onto a projection surface, and the projection optical system. A first shift mechanism that moves the light modulation element in a shift direction orthogonal to the optical axis of the projection optical system, an opening that is disposed between the light modulation element and the projection optical system, and passes light. A light-shielding mask having a light-shielding part formed in the shift direction with respect to the opening, and the light-shielding mask on the side where the projection optical system is moved by the first shift mechanism in the shift direction with respect to the light modulation element And a second shift mechanism for moving the projection optical system by a movement amount smaller than the movement amount of the projection optical system.

According to the present invention, when the projection optical system is moved (shifted), the light shielding mask is also moved to the same side by a movement amount smaller than the movement amount of the projection optical system. Or unnecessary light can be avoided. Thereby, in the image projection apparatus having the shift mechanism of the projection optical system, it is possible to suppress deterioration of the projected image and occurrence of ghost due to unnecessary light increased by the shift of the projection optical system.

1 is an external view of a liquid crystal projector that is Embodiment 1 of the present invention. FIG. FIG. 2 is a cross-sectional view illustrating an optical configuration of a liquid crystal projector of an example. FIG. 3 is an exploded perspective view illustrating configurations of a lens shift mechanism and a mask shift mechanism provided in the liquid crystal projector of the embodiment. The perspective view which shows the structure of the said lens shift mechanism and a mask shift mechanism. FIG. 6 is a perspective view illustrating a configuration of a lens shift mechanism and a mask shift mechanism provided in a liquid crystal projector that is Embodiment 2 of the present invention. The figure which shows the relationship between the projection lens and the light shielding mask in the prior art and each Example.

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

  FIG. 1 shows an appearance of a liquid crystal projector (image projection apparatus) 100 that is Embodiment 1 of the present invention. A projection lens barrel 5 holds a projection lens 5a as a projection optical system inside.

  In this embodiment, a liquid crystal projector using a liquid crystal panel as a light modulation element will be described. However, an image projection apparatus using another light modulation element such as a digital micromirror device (DMD) is also included in the embodiment of the present invention. included.

  FIG. 2 shows a part of the optical configuration of the liquid crystal projector 100. White non-polarized light from a light source lamp (not shown) enters a color separation / synthesis optical system β including a polarization conversion element, a dichroic mirror, and a polarization beam splitter PBS (not shown). The color separation / synthesis optical system β separates incident light into light of three colors R, G, and B, converts the light into polarized light having a specific polarization direction, and guides it to the liquid crystal panel LP. FIG. 2 shows only the liquid crystal panel LP corresponding to one color of the three colors.

  The liquid crystal panel LP forms an original image corresponding to a video signal input from the outside to the liquid crystal projector 100, and modulates incident light by the original image (that is, according to the input video signal). The one color light L1 modulated by the liquid crystal panel LP enters the dichroic prism DP included in the color separation / synthesis optical system β via the polarization beam splitter PBS. In addition, light of two colors modulated by another liquid crystal panel (not shown) is also guided to the dichroic prism DP.

  The dichroic prism DP combines the incident three colors of modulated light and guides them to the projection lens 5 a in the projection lens barrel 5. A light shielding mask 72 is disposed between the dichroic prism DP and the projection lens barrel 5, that is, between the liquid crystal panel LP and the projection lens 5a. The light shielding mask 72 includes an opening 72a (hereinafter referred to as an aperture) 72a through which light from the dichroic prism DP (liquid crystal panel LP) passes, and a light shielding portion formed in an upward direction and a downward direction as a shift direction with respect to the aperture 72a. 72b. The shape of the aperture 72a is set in accordance with the shape of the region where light is actually emitted on the exit surface of the dichroic prism DP.

  The light shielding portion 72b of the light shielding mask 72 of this embodiment is also formed in the left-right direction with respect to the aperture and surrounds the aperture 72a, but the light shielding portion is formed at least in the shift direction with respect to the aperture. Just do it.

  The projection lens 5a projects the combined three-color modulated light onto a projection surface such as a screen (not shown). Thereby, the projection image corresponding to the input video signal is displayed on the projection surface.

  The projection lens barrel 5 is fixed to a shift plate 71 which is a part of a lens shift mechanism (first shift mechanism) described later. The shift plate 71 is held by the shift base 70 so as to be movable upward and downward in FIG. The upward direction and the downward direction are directions orthogonal to the optical axis AXL of the projection lens 5a. Hereinafter, these are also referred to as shift directions. In this way, the projection lens barrel 5 and the shift plate 71 are held so as to be movable (shiftable) in the shift direction with respect to the color separation / synthesis optical system β, the liquid crystal panel LP, and the shift base 70. Further, the light shielding mask 72 is moved by a mask shift mechanism (second shift mechanism) described later along with the movement of the projection lens barrel 5 in the shift direction (however, independent of the movement of the projection lens barrel 5). ) And move in the shift direction.

  Next, the configuration of the lens shift mechanism will be described with reference to FIGS. FIG. 3 shows the lens shift mechanism in an exploded manner. 4A shows the lens shift mechanism as seen from the projection lens barrel 5 side, and FIG. 4B shows the lens shift barrel as seen obliquely from the light shielding mask 72 side. In the following description, the projection lens barrel 5 side in the lens shift mechanism is referred to as a front side, and the light shielding mask 72 side that is the opposite side is referred to as a rear side. Further, as shown in FIGS. 3 and 4A, the left side and the right side when viewed from the projection lens barrel 5 side are referred to as the left side and the right side, respectively.

  As described above, the projection lens barrel 5 is attached to the shift plate 71 movable in the vertical direction. At the four corners of the shift plate 71, elongated holes 71b extending in the vertical direction are formed.

  A shift base 70 is disposed on the rear side of the shift plate 71. At the four corners of the front surface of the shift base 70, flanged pins 74 are attached by screws, and each pin 74 is inserted into each elongated hole portion 71b of the shift plate 71 from the rear side. The flange portion of each pin 74 contacts the rear surface of the shift plate 71.

  Each pin 74 protruding from the long hole portion 71b has a sliding member 75a having a hole portion through which the pin 74 passes, a coil spring 76, and a sliding member 75a fixed to the tip of the pin 74 with a screw. A spring pressing member 75b that compresses and sandwiches the coil spring 76 therebetween is attached. The coil spring 76 in a compressed state presses the shift plate 71 against the shift base 70 (the flange portion of the pin 74) via the sliding member 75a. In this way, the shift plate 71 and the projection lens barrel 5 attached thereto are held by the shift base 70 so as to be movable in the vertical direction.

  A motor (first actuator) 77 is attached to the right end of the shift base 70 via a motor base plate 78. A lead screw 79 is rotatably held on the motor base plate 78, and a nut portion of the drive member 80 is engaged with the lead screw 79. The driving member 80 is held by a holding portion 71 a formed at the left end portion of the shift plate 71. A small gear 81 is attached to the tip (upper end) of the output shaft of the motor 77 so as to be rotatable integrally with the output shaft. The small gear 81 is fixed to the upper end of the lead screw 79 so as to be rotatable integrally therewith. It meshes with the large gear 82. For this reason, when the motor 77 operates and the lead screw 79 rotates, the driving member 80, the shift plate 71, and the projection lens barrel 5 move (shift) in the vertical direction.

  Next, the mask shift mechanism will be described. The light shielding mask 72 is held by a mask holding member 73 on the rear side of the shift base 70, and is disposed between the dichroic prism DP and the projection lens barrel 5 (the incident surface of the projection lens 5a). The mask holding member 73 has a mask holding portion for holding the light shielding mask 72 and leg portions formed on both left and right sides of the mask holding portion, and the leg portions extend in the optical axis direction and are held by the mask holding portion. The light-shielding mask 72 to be used is disposed a predetermined amount away from the incident surface of the projection lens 5a. Long hole portions 73a extending in the vertical direction are formed at four positions on the mask holding portion in the vertical and horizontal directions.

  Flange pins 83 are attached to the four positions on the rear surface of the shift base 70 with screws, and the pins 83 are inserted into the long hole portions 73a of the mask holding member 73 from the front side. The flange portion of each pin 83 comes into contact with the front surface of the mask holding member 73 (leg portion).

  Each pin 83 protruding from the elongated hole portion 73a has a sliding member 84a having a hole portion through which the pin 83 passes, a coil spring 85, and a pin 83 fixed to the tip of the pin 83 with a screw and between the sliding member 84a. Then, a spring holding member 84b that compresses and sandwiches the coil spring 85 is attached. The coil spring 85 in a compressed state presses the mask holding member 73 (leg part) against the shift base 70 (flange part of the pin 83) via the sliding member 84a. In this way, the mask holding member 73 and the light shielding mask 72 held thereby are held by the shift base 70 so as to be movable in the vertical direction.

  A shift plate rack 71 </ b> R is formed at the left end of the shift plate 71. A mask rack 73R is formed at the left end of the mask holding member 73. The gear holding portion 70a that protrudes from the left end of the shift base 70 has a gear connecting shaft 88 that rotatably connects the large gear 86 that meshes with the shift plate rack 71R and the small gear 87 that meshes with the mask rack 73R. The bearing member 89 is rotatably held.

  When the shift plate 71 moves in the shift direction, the large gear 86, the gear coupling shaft 88 and the small gear 87 are rotated by the shift plate rack 71R, and the rotation of the small gear 87 moves the mask holding member 73 via the mask rack 73R. . That is, the shift plate rack 71R, the large gear 86, the gear coupling shaft 88, the small gear 87, and the mask rack 73R transmit the movement of the lens shift mechanism driven by the motor 77 to the mask shift mechanism to drive the mask shift mechanism. The interlocking mechanism is configured.

  By this interlocking mechanism, the mask holding member 73 also moves in conjunction with the shift plate 71 moving in the shift direction. The direction in which the mask holding member 73 moves is the same side as the side in which the shift plate 71 moves in the shift direction (upward and downward directions). However, since the diameter of the small gear 87 is smaller than the diameter of the large gear 86, the movement amount of the mask holding member 73 is smaller than the movement amount of the shift plate 71. The amount of movement of the mask holding member 73 with respect to the amount of movement of the shift plate 71 is set by the reduction ratio of the speed reduction mechanism constituted by the large gear 86 and the small gear 87.

  FIG. 6B shows the relationship between the movement direction and the movement amount of the projection lens barrel 5 (shift plate 71) and the light shielding mask 72 (mask holding member 73) in this embodiment. When the projection lens barrel 5 moves upward from the non-shift state shown in FIG. 6A to the shift state shown in FIG. 6B, the light-shielding mask 72 also moves upward (two-dot chain line 72 in the figure). However, the movement amount B is smaller than the movement amount A of the projection lens barrel 5 (A> B).

  Due to the relationship between the direction of movement and the amount of movement between the projection lens barrel 5 and the light shielding mask 72, the effective light on the upper side and the unnecessary light on the lower side are scattered by the light shielding mask 72 not only in the non-shifted state but also in the shifted state. Can be avoided. Therefore, when the projection lens barrel 5 is moved in the shift direction, it is possible to suppress the deterioration of the projected image and the generation of ghosts due to reflection in the projection lens 5a.

  FIG. 5 shows a mask shift mechanism in a projector that is Embodiment 2 of the present invention. In the first embodiment, the case where the movement of the shift plate 71 is transmitted to the mask holding member 73 (light shielding mask 72) and moved is described. However, in this embodiment, a motor (second actuator) 91 for moving the light shielding mask 72 is provided separately from a motor (first actuator) 77 for moving the shift plate 71 (projection lens barrel 5). . In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof is omitted.

  A first linear encoder 90 as a first position detector is attached to the shift plate 71, and the first linear encoder 90 is a position of the shift plate 71 (projection lens barrel 5) in the shift direction. Is detected.

  Further, a second linear encoder 93 that is a second position detector is attached to the mask holding member 73, and the second linear encoder 93 is shifted in the shift direction of the mask holding member 73 (light shielding mask 72). The position of is detected.

  A motor 91 is attached to the rear surface of the shift base 70. The output shaft of the motor 91 is a lead screw 92, and a nut portion 73 n formed on the mask holding member 73 is engaged with the lead screw 92. For this reason, when the motor 91 operates and the lead screw 92 rotates, the mask holding member 73 and the light shielding mask 72 move (shift) in the vertical direction.

  Reference numeral 50 denotes a controller composed of a CPU or the like. The controller 50 determines a target position of the light shielding mask 72 (mask holding member 73) according to the position of the projection lens barrel 5 (shift plate 71) detected by the first linear encoder 90. The target position may be determined by reading from data indicating the position of the light shielding mask 72 with respect to the position of the projection lens barrel 5 stored in advance in a memory in the controller 50, or detected by the first linear encoder 90. You may determine by the calculation using a result. Then, the controller 50 operates the motor 91 so that the position of the light shielding mask 72 detected by the second linear encoder 93 reaches the determined target position.

  The relationship between the movement direction and the movement amount of the projection lens barrel 5 and the light shielding mask 72 in this embodiment is the same as that in the first embodiment (A> B). Then, due to the relationship between the movement direction and the movement amount of the projection lens barrel 5 and the light shielding mask 72, the upper effective light is emitted by the light shielding mask 72 or the lower side in the shift state as well as in the non-shift state. An increase in unnecessary light can be avoided. Therefore, when the projection lens barrel 5 is moved in the shift direction, it is possible to suppress the deterioration of the projected image and the generation of ghosts due to reflection in the projection lens 5a.

  In each of the above embodiments, the case where the mask shift mechanism is held by the shift base 70 that is the base member of the lens shift mechanism has been described. However, the mask shift mechanism may be held by the casing (main body) of the projector.

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

An image projection apparatus capable of projecting a high-quality image while having a shift function of the projection optical system can be provided.

70 Shift base 71 Shift plate 72 Shading mask 73 Mask holding member 77 Motor

Claims (3)

A light modulation element for modulating light from the light source;
A projection optical system that projects the light modulated by the light modulation element onto the projection surface;
A first shift mechanism that moves the projection optical system with respect to the light modulation element in a shift direction orthogonal to the optical axis of the projection optical system;
A light shielding mask that is disposed between the light modulation element and the projection optical system and has an opening that allows light from the light modulation element to pass therethrough and a light shielding part that is formed in the shift direction with respect to the opening;
Movement of the light shielding mask with respect to the light modulation element is smaller than the movement amount of the projection optical system on the same side as the side of the projection optical system being moved by the first shift mechanism in the shift direction. An image projection apparatus comprising: a second shift mechanism that moves by an amount. A first actuator for driving the first shift mechanism;
The image projection apparatus according to claim 1, further comprising an interlocking mechanism that transmits the movement of the first shift mechanism to the second shift mechanism to drive the second shift mechanism. A first actuator for driving the first shift mechanism;
A first position detector for detecting a position of the projection optical system in the shift direction;
A second actuator for driving the second shift mechanism;
A second position detector for detecting the position of the light shielding mask in the shift direction;
The position of the light shielding mask detected by the second position detector reaches the target position of the light shielding mask corresponding to the position of the projection optical system detected by the first position detector. The image projection apparatus according to claim 1, further comprising a controller that operates the second actuator.