JP2010078627A - Projection type display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type display equipped with a micromirror display element in which the quality of an image projected on a screen is improved. <P>SOLUTION: The projection type display 1 includes: an projection lens 8 for projecting a predetermined image on a screen 3; a light source 4 for generating illumination light; and a micromirror display element 2 for modulating the illumination light from the light source 4. The micromirror type display element 2 includes a micromirror element which tilts to an ON position at which the illumination light is reflected toward the projection lens 8 and an OFF position at which the illumination light is reflected toward a position outside the entrance pupil of the projection lens 8. The optical axis L2 of the ON light reflected by the micromirror element at the ON position is tilted with respect to the optical axis L3 of the projection lens 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection display device including a micromirror display device.

  In this specification, the “micro mirror type display element” is a light modulation element in which a large number of micro mirror elements (reflecting mirrors) of about several μm square are arranged on a silicon substrate, and the inclination of the micro mirror element is determined. A light modulation element that controls whether or not the illumination light from the light source is reflected in the screen direction by changing the electrostatic attraction. This micro mirror type display element has the same function as an element called DMD which is a trade name of Texas Instruments.

  2. Description of the Related Art Conventionally, as a projection display device that enlarges and projects a predetermined image on a screen via a projection lens, a projection display device that uses a micromirror display element that is a reflective light modulation element is known. In this projection type display device, the micro mirror element constituting the micro mirror type display element reflects the illumination light from the light source toward the entrance pupil of the projection lens, and the illumination light from the light source is incident on the projection lens. It tilts to the off position where it reflects towards a position off the pupil. Further, an image on the screen is constituted by a set of on-lights reflected by the micro mirror elements at the on-position.

  In this projection display device, it is known that flat light reflected by a cover glass or the like for protecting the micromirror element is generated. When flat light enters the entrance pupil of the projection lens, the contrast of the image projected on the screen decreases, or a so-called ghost phenomenon occurs where a weak ghost image overlaps the original image, resulting in a decrease in the image quality of the projected image. To do.

  Here, as shown in FIG. 5A, the optical axis L11 of the flat light is formed by the optical axis L21 of the on light and the optical axis L31 of the off light reflected by the micro mirror element at the off position. It is generally known that it becomes a substantially bisector of a corner. Therefore, in order to prevent flat light from entering the entrance pupil of the projection lens, the illumination optical system has an ON light spread angle (that is, flat light spread angle) θ11 that is equal to or less than the swing angle (tilt angle) θ21 of the micromirror element. It is set to become. That is, the illumination optical system is set so that its F number is equal to or greater than “1 / (2 sin (θ21))”. In general, in order to improve the image quality of the image on the screen, the illumination optical system is configured such that the F number is “1 / (2 sin (θ21))”. Further, the swing angle θ21 is 12 °, for example.

  As a projection display device capable of preventing uneven brightness of the projected image due to flat light, a projection display device in which a diaphragm plate is installed between the illumination optical system and the total reflection prism has been proposed ( For example, see Patent Document 1).

JP 2005-309337 A

  In recent years, in order to improve the image quality of a projected image, the use of a brighter illumination optical system has been studied in a projection display device. However, if the swing angle θ21 of the micromirror element is constant and a brighter illumination optical system is used (that is, if the F-number of the illumination optical system is reduced), as shown in FIG. Enters the entrance pupil of the projection lens. Therefore, despite the use of an illumination optical system having a small F number in order to improve the image quality of the projected image, the contrast is lowered or a ghost phenomenon occurs, and the image quality of the projected image is lowered.

  Accordingly, an object of the present invention is to provide a projection display device that can improve the image quality of an image projected on a screen in a projection display device including a micromirror display device.

  In order to solve the above problems, a projection display device according to the present invention includes a projection lens for projecting a predetermined image on a screen, a light source for generating illumination light, and a micro mirror for modulating illumination light from the light source. The micro mirror type display element is inclined to an on position where the illumination light is reflected toward the projection lens and an off position where the illumination light is reflected toward a position outside the entrance pupil of the projection lens. An optical axis of ON light reflected by the micro mirror element at the ON position is inclined with respect to the optical axis of the projection lens.

  In the projection display device of the present invention, the optical axis of on-light is inclined with respect to the optical axis of the projection lens. Therefore, even when an illumination optical system with a small F number is used, the amount of the flat light entering the entrance pupil of the projection lens is suppressed by tilting the optical axis of the on-light in a direction in which the flat light moves away from the entrance pupil of the projection lens. It becomes possible. That is, in the present invention, while using an illumination optical system having a small F-number, it is possible to suppress the amount of flat light entering the entrance pupil of the projection lens, thereby suppressing the reduction in the contrast of the projected image and the occurrence of the ghost phenomenon. become. Therefore, according to the present invention, it is possible to improve the image quality of the image projected on the screen.

  In the present invention, the flat light whose optical axis is the substantially bisector of the angle formed by the optical axis of the off-light and the optical axis of the on-light reflected by the micromirror element in the off position is the entrance pupil of the projection lens. It is preferable that the optical axis of the on-light is inclined with respect to the optical axis of the projection lens so as to be out of the range. If comprised in this way, it can prevent that flat light enters into the entrance pupil of a projection lens. Accordingly, it is possible to improve the image quality of the projected video by preventing the decrease in contrast and the ghost phenomenon.

  In the present invention, it is preferable that the edge of the entrance pupil of the projection lens and the edge of the flat light are substantially circumscribed. In the present invention, since the optical axis of the on-light is tilted with respect to the optical axis of the projection lens, a part of the on-light deviates from the entrance pupil of the projection lens. It is possible to minimize the amount of on-light that deviates from the entrance pupil of the projection lens while preventing the occurrence of the ghost phenomenon. Therefore, it is possible to suppress the deterioration of the image quality of the projected video that occurs when a part of the on-light deviates from the entrance pupil of the projection lens.

  In the present invention, the projection display device includes an internal total reflection prism having a transmission surface through which illumination light traveling from the light source to the micromirror display device is transmitted or a reflection surface from which illumination light traveling from the light source to the micromirror display device is reflected. When the reference illumination light is the light whose optical axis after being reflected by the micromirror element at the ON position is parallel to the optical axis of the projection lens, the incident angle of the illumination light incident on the transmission surface is the reference illumination light The on-light optical axis is tilted with respect to the optical axis of the projection lens so that the incident angle is smaller than the incident angle or the incident angle of the illumination light incident on the reflecting surface is larger than the incident angle of the reference illumination light. It is preferable. If comprised in this way, reflection of the illumination light which injects into a transmission surface toward a micromirror type | mold display element, and transmission of the illumination light which injects into a reflection surface toward a micromirror type display element can be suppressed. That is, it is possible to suppress the illumination light reflection loss due to reflection on the transmission surface or the illumination light transmission loss due to transmission on the reflection surface.

  In the present invention, it is preferable that the optical axis of the illumination light directed from the light source to the micro mirror type display element is substantially linear. Compared with the case where an optical path from the light source to the micromirror type display element is formed by using refraction or the like, this configuration can increase the efficiency of light incident on the micromirror type display element and The image quality of the video can be improved.

  As described above, in the projection display device of the present invention, it is possible to improve the image quality of the image projected on the screen.

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

(Schematic configuration of the projection display device)
FIG. 1 is a schematic configuration diagram for explaining a schematic configuration of a projection display device 1 according to an embodiment of the present invention.

  The projection display device 1 according to this embodiment is a display device that enlarges and projects a predetermined image on a screen 3 by using a micro-mirror display device 2 that is a reflective light modulation device. As shown in FIG. 1, the projection display device 1 includes a light source 4 that generates illumination light, an illumination optical system 5, a color wheel (CW) 6, and an internal total, in addition to the micromirror display element 2. A reflection prism 7 and a projection lens 8 for projecting a predetermined image on the screen 3 are provided.

  The light source 4 is, for example, an ultra-high pressure mercury lamp, and includes a bright spot 10 such as a filament part or a discharge part and an elliptical reflecting mirror 11. The light source 4 emits white illumination light toward the illumination optical system 5. The light source 4 may be an LED. When the light source 4 is a white LED, it can be used as it is in place of the ultra high pressure mercury lamp, and when the light source 4 is a three-color (RGB) LED, the three colors are blinked at high speed. Can be omitted.

  The CW 6 is formed in a thin disk shape and is disposed between a condenser lens 13 (to be described later) and the rod integrator 14 constituting the illumination optical system 5. The CW 6 is fixed to an output shaft of a motor (not shown) and is rotated by the power of the motor. In addition, the CW 6 includes, for example, three filter units including a red filter unit, a blue filter unit, and a green filter unit which are not illustrated.

  The illumination optical system 5 of this embodiment includes a condenser lens 13, a rod integrator (light pipe) 14, and a relay lens 15. As shown in FIG. 1, the illumination optical system 5 is directed from the light source 4 toward the minute mirror type display element 2. The condenser lens 13, CW6, rod integrator 14, and relay lens 15 are arranged in this order. In this embodiment, the illumination optical system 5 is configured so that the optical axis L1 of the illumination optical system 5 is substantially linear.

  The internal total reflection prism 7 includes a prism 17 and a prism 18 formed in a triangular prism shape. The prism 17 and the prism 18 are fixed to each other with the facing surface 17 a formed on the prism 17 and the facing surface 18 a formed on the prism 18 facing each other. As will be described later, in this embodiment, the illumination light incident on the internal total reflection prism 7 passes through the opposing surfaces 17a and 18a. Further, the light reflected by the minute mirror type display element 2 is totally reflected by the facing surface 17a. That is, the internal total reflection prism 7 of this embodiment is an RTIR (Reverse Total Internal Reflection) prism.

  The micro mirror type display element 2 includes a plurality of micro mirror elements (reflecting mirrors, not shown) that reflect the illumination light from the light source 4 toward the internal total reflection prism 7, and a control circuit for driving and controlling the micro mirror elements. (Not shown). The micro mirror type display element 2 includes a cover glass (not shown) for protecting the micro mirror element.

  In the micromirror type display element 2, the inclination of each of the plurality of micromirror elements is controlled based on the drive signal from the control circuit. Specifically, the micromirror element to which the “ON” driving signal is given from the control circuit is inclined so that the reflected light is directed to the projection lens 8 via the internal total reflection prism 7. Further, the micromirror element to which the “OFF” driving signal is given from the control circuit is inclined so that the reflected light is directed to the position deviated from the entrance pupil of the projection lens 8 via the internal total reflection prism 7. That is, the micromirror element is inclined to an ON position where the illumination light is reflected toward the projection lens 8 and an OFF position where the illumination light is reflected toward a position outside the entrance pupil of the projection lens 8. For example, the micromirror element is inclined by ± 12 ° with respect to a predetermined reference position.

  The projection lens 8 is held by a lens barrel 19. The projection lens 8 functions to make the micromirror element of the micromirror type display element 2 and the screen 3 have an optically conjugate relationship, and the image formed on the micromirror element of the micromirror type display element 2 is The projection lens 8 enlarges and projects on the screen 3.

  In the projection display device 1 configured as described above, the illumination light emitted from the light source 4 and passing through the illumination optical system 5 and the CW 6 enters the internal total reflection prism 7. The illumination light that has entered the internal total reflection prism 7 passes through the opposing surfaces 17 a and 18 a and enters the micromirror type display element 2. The opposing surfaces 17a and 18a in this embodiment are transmission surfaces through which illumination light traveling from the light source 4 toward the micromirror display device 2 is transmitted.

  The illumination light incident on the micromirror display element 2 is reflected by the micromirror element. Specifically, the light reflected by the micromirror element at the ON position (ON light) is reflected by the micromirror element so as to go to the projection lens 8 after being totally reflected by the facing surface 17a of the internal total reflection prism 7. Is done. Further, the light reflected by the micro mirror element in the off position (off light) is totally reflected by the facing surface 17a of the internal total reflection prism 7 and then travels to a position away from the projection lens 8 so that the light is reflected by the micro mirror element. Reflected.

(Tilt of optical axis of illumination optical system)
FIG. 2 is a diagram for explaining the inclination of the optical axis L2 of the ON light from the EE direction in FIG. 3A is a schematic diagram showing the relationship between the entrance pupil of the projection lens 8 and the on-light from the FF direction of FIG. 1, and FIG. 3B is the projection lens 8 from the FF direction of FIG. It is a schematic diagram which shows the relationship between this entrance pupil and flat light. FIG. 4 is a diagram for explaining the angle of the illumination light incident on the internal total reflection prism 7 shown in FIG.

  In this embodiment, the illumination optical system 5 is arranged so that the optical axis L2 of the ON light reflected by the micromirror element at the ON position is inclined with respect to the optical axis L3 of the projection lens 8. Specifically, the on-light optical axis L2 is shifted to the right of the optical axis L3 of the projection lens 8 when viewed from the FF direction in FIG. It is inclined with respect to the axis L3. In this embodiment, the illumination optical system 5 is arranged so that the illumination light is incident on the minute mirror type display element 2 obliquely from above in order to appropriately reflect the illumination light by the minute mirror element. As shown in FIG. 4, the ON light optical axis L2 is inclined with respect to the optical axis L3 of the projection lens 8 so that the ON light optical axis L2 is shifted to the lower side of the optical axis L3 of the projection lens 8.

  More specifically, as shown in FIG. 3B, the optical axis of the on-light is set so that the flat light reflected by the cover glass or the like for protecting the micromirror element deviates from the entrance pupil of the projection lens 8. L2 is inclined with respect to the optical axis L3 of the projection lens 8. In this embodiment, the optical axis L2 of the on-light is inclined with respect to the optical axis L3 of the projection lens 8 so that the edge of the entrance pupil of the projection lens 8 and the edge of the flat light are substantially circumscribed. Therefore, the inclination angles θ1 and θ2 of the on-light optical axis L2 with respect to the optical axis L3 of the projection lens 8 become larger as the F number of the illumination optical system 5 becomes smaller (that is, the illumination optical system 5 becomes brighter). Become.

  As described above, the optical axis of the flat light is a substantially bisector of an angle formed by the optical axis L2 of the on light and the optical axis of the off light. Further, since the ON light optical axis L2 is inclined with respect to the optical axis L3 of the projection lens 8, a part of the ON light deviates from the entrance pupil of the projection lens 8 as shown in FIG. In this embodiment, the F number of the illumination optical system 5 is set so that the ON light has an elliptical shape.

  As described above, the optical axis L2 of the ON light reflected by the micromirror element at the ON position is inclined with respect to the optical axis L3 of the projection lens 8. That is, when the light whose optical axis after being reflected by the micromirror element in the ON position is parallel to the optical axis L3 of the projection lens 8 is used as the reference illumination light, as shown in FIG. The optical axis L1 of the illumination optical system 5 (that is, the optical axis L1 of the illumination light) is inclined with respect to L0. Specifically, as shown in FIG. 4, with respect to the optical axis L0 of the reference illumination light, the incident angle α1 of the illumination light incident on the facing surfaces 17a and 18a is smaller than the incident angle α2 of the reference illumination light. The optical axis L1 of the illumination optical system 5 is inclined.

(Main effects of this form)
As described above, in this embodiment, the illumination optical system 5 is arranged so that the ON-light optical axis L2 is inclined with respect to the optical axis L3 of the projection lens 8. Therefore, even when the illumination optical system 5 having a small F-number is used, the flat light entering the entrance pupil of the projection lens 8 is tilted by tilting the optical axis L2 of the on-light in a direction away from the entrance pupil of the projection lens 8. The amount of light can be suppressed. In particular, in this embodiment, the on-light optical axis L2 is tilted with respect to the optical axis L3 of the projection lens 8 so that the flat light deviates from the entrance pupil of the projection lens 8. It is possible to prevent light from entering. Therefore, in this embodiment, while using the illumination optical system 5 having a small F number, it is possible to prevent the flat light from entering the entrance pupil of the projection lens 8 and to suppress the decrease in contrast of the projected image and the occurrence of the ghost phenomenon. Can do. As a result, in this embodiment, the image quality of the projected image on the screen 3 can be improved.

  Here, in this embodiment, since the optical axis L2 of the on-light is inclined with respect to the optical axis L3 of the projection lens 8, a part of the on-light deviates from the entrance pupil of the projection lens 8 (FIG. 3A )reference). However, in this embodiment, since the optical axis L2 of the flat light is inclined with respect to the optical axis L3 of the projection lens 8 so that the edge of the entrance pupil of the projection lens 8 and the edge of the flat light are substantially circumscribed, the projection is performed. While preventing flat light from entering the entrance pupil of the lens 8, the amount of on-light that deviates from the entrance pupil of the projection lens 8 can be minimized. Therefore, it is possible to suppress the deterioration of the image quality of the projected video that occurs when a part of the ON light deviates from the entrance pupil of the projection lens 8.

  In this embodiment, the optical axis of the illumination optical system 5 with respect to the optical axis L0 of the reference illumination light so that the incident angle α1 of the illumination light incident on the opposing surfaces 17a and 18a is smaller than the incident angle α2 of the reference illumination light. L1 is inclined. Therefore, it is possible to suppress the reflection of the illumination light that is incident on the facing surfaces 17a and 18a toward the micromirror type display element 2. That is, the reflection loss of illumination light due to reflection on the facing surfaces 17a and 18a can be suppressed. Therefore, the image quality of the projected image on the screen 3 can be improved.

  In this embodiment, the optical axis L1 of the illumination light directed from the light source 4 to the micromirror type display element 2 is substantially linear. Therefore, the efficiency of light incident on the micromirror display element 2 can be increased compared to the case where an optical path from the light source 4 toward the micromirror display element 2 is formed using refraction or the like, and the screen 3 The image quality of the projected image can be improved.

(Other embodiments)
In the embodiment described above, the illumination optical system 5 is arranged so that the illumination light is incident on the minute mirror type display element 2 from obliquely above. However, the illumination light is incident on the minute mirror type display element 2 from obliquely below. The illumination optical system 5 may be arranged so as to be incident. In this case, the on-light optical axis L2 may be inclined with respect to the optical axis L3 of the projection lens 8 so that the on-light optical axis L2 is shifted to the upper side of the optical axis L3 of the projection lens 8.

  In the form described above, the internal total reflection prism 7 is an RTIR in which the illumination light incident from the light source 4 is transmitted through the opposing surfaces 17a and 18a, and the light reflected by the micromirror display element 2 is totally reflected by the opposing surface 17a. It is a prism. In addition to this, for example, the internal total reflection prism 7 is a TIR in which the illumination light incident from the light source 4 is totally reflected by the facing surface 17a and the light reflected by the micromirror type display element 2 is transmitted through the facing surfaces 17a and 18a. A (Total Internal Reflection) prism may be used. In this case, if the on-light optical axis L2 is inclined with respect to the optical axis L3 of the projection lens 8 so that the incident angle of the illumination light incident on the facing surface 17a is larger than the incident angle of the reference illumination light. good. By doing so, it is possible to suppress the transmission of the illumination light incident on the facing surface 17a toward the micro mirror type display element 2, and thus it is possible to suppress the transmission loss of the illumination light due to the transmission through the facing surface 17a. .

  In the embodiment described above, the optical axis L2 of the flat light is inclined with respect to the optical axis L3 of the projection lens 8 so that the edge of the entrance pupil of the projection lens 8 and the edge of the flat light are substantially circumscribed. In addition to this, for example, the flatness is slightly larger or slightly smaller than the inclination of the optical axis L2 of the flat light with respect to the optical axis L3 of the projection lens 8 when the edge of the entrance pupil of the projection lens 8 and the edge of the flat light are substantially circumscribed. The optical axis L2 of light may be tilted. In the embodiment described above, the optical axis L1 of the illumination light directed from the light source 4 toward the micromirror display device 2 is substantially linear, but refraction is used (that is, the optical axis direction of the illumination light). The illumination light from the light source 4 may be incident on the minute mirror type display element 2.

It is a schematic block diagram for demonstrating schematic structure of the projection type display apparatus concerning embodiment of this invention. It is a figure for demonstrating the inclination of the optical axis of the optical axis of ON light from the EE direction of FIG. (A) is a schematic diagram showing the relationship between the entrance pupil of the projection lens and ON light from the FF direction in FIG. 1, and (B) is the entrance pupil and flat light of the projection lens from the FF direction in FIG. It is a schematic diagram which shows the relationship. It is a figure for demonstrating the angle of the illumination light which injects into the internal total reflection prism shown in FIG. It is a figure for demonstrating the problem of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projection type display apparatus 2 Micro mirror type display element 3 Screen 4 Light source 7 Internal total reflection prism 8 Projection lens 17a, 18a Opposite surface (transmission surface)
L1 Optical axis of illumination light L2 Optical axis of on-light L3 Optical axis of projection lens α1 Incident angle of illumination light α2 Incident angle of reference illumination light

Claims (5)

A projection lens for projecting a predetermined image on a screen, a light source that generates illumination light, and a micro-mirror type display element that modulates illumination light from the light source,
The minute mirror type display element is a minute mirror that is inclined to an on position that reflects the illumination light toward the projection lens and an off position that reflects the illumination light toward a position away from the entrance pupil of the projection lens. With elements,
The projection display device, wherein an optical axis of on-light reflected by the minute mirror element at the on-position is inclined with respect to an optical axis of the projection lens.   Flat light whose optical axis is an approximately bisector of an angle formed by the optical axis of off-light reflected by the micromirror element at the off-position and the optical axis of on-light is the entrance pupil of the projection lens. The projection display device according to claim 1, wherein the optical axis of the on-light is inclined with respect to the optical axis of the projection lens so as to be out of the range.   The projection display device according to claim 2, wherein an edge of an entrance pupil of the projection lens and an edge of the flat light are substantially circumscribed. An internal total reflection prism having a transmission surface through which the illumination light traveling from the light source toward the micromirror display device is transmitted or a reflection surface from which the illumination light from the light source toward the micromirror display device is reflected;
When the illumination light in which the optical axis after being reflected by the micromirror element in the ON position is parallel to the optical axis of the projection lens is used as reference illumination light,
The incident angle of the illumination light incident on the transmission surface is smaller than the incident angle of the reference illumination light, or the incident angle of the illumination light incident on the reflection surface is greater than the incident angle of the reference illumination light. 4. The projection display device according to claim 1, wherein an optical axis of the on-light is inclined with respect to an optical axis of the projection lens so that the optical axis of the projection lens is larger.   5. The projection display device according to claim 1, wherein an optical axis of the illumination light directed from the light source toward the minute mirror type display element is substantially linear. 6.

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