JP2017227747A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device that reduces flare components occurring within a prism unit to thereby improve image quality.SOLUTION: A projector PJ1 has: a digital micromirror device DP; a first prism unit PU1; and a projection optical system PO. The first prism unit PU1 has an air gap AG that tilts at a prescribed angle with respect to a principal light ray of image light L2 emitted from a center of an image screen surface DS of the digital micromirror device DP, in which the image light L2 transmits the air gap AG. In the first prism unit PU1, a normal line of at least one prism surface of a first prism surface S1 where the image light L2 is incident in a prism P1 and a second prism surface S2 where the image light L2 emerges outward a prism P2 tilts with respect to an optical axis AX of the projection optical system PO.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a projection display device, for example, a projection display device including a reflective image display element such as a digital micromirror device.

  In a DLP (digital light processing; registered trademark of Texas Instruments, USA) type projector, image projection is performed using an optical semiconductor called a DLP chip in which millions of small mirrors (micromirrors) are incorporated. In the case of a three-chip type DLP system using three DLP chips, a special prism separates the lamp light into the three primary colors of RGB light and illuminates each DLP chip to display a color image. In the case of a one-chip type DLP system using one DLP chip, the lamp light is separated into the three primary colors of RGB light by one color wheel that is color-coded into three colors of RGB, and one DLP chip. Illuminate and display a color image. Since the color wheel rotates at a high speed and the micromirrors are switched at a high speed accordingly, the human eye can see a color image in which RGB is synthesized by the afterimage effect. .

  Digital micromirror devices typified by the DLP chip are generally used as reflective image display elements for projectors. The digital micromirror device has an image display surface composed of a plurality of minute micromirrors. The image display surface controls the tilt of each mirror surface and modulates the intensity of the illumination light. Form. In other words, ON / OFF of each pixel of the digital micromirror device is, for example, rotation of a mirror surface of ± 12 ° about a rotation axis that forms an angle of 45 ° with respect to each side of the image display surface ( That is, it is expressed by micromirror driving for one axis. Regarding the movement of the micromirror, a new operation type digital micromirror device (Tilt & Roll Pixel DMD) that performs micromirror driving about two orthogonal axes has also been proposed in Non-Patent Document 1.

  Conventionally, various types of projection display devices have been proposed as projectors equipped with reflective image display elements such as the above-described digital micromirror devices (see, for example, Patent Documents 1 and 2). A bright and high-definition projector is required.

JP 2002-049094 A JP 2003-149414 A

DLP (R) TRP pixel architecture and chipsets, Internet <URL: http://www.ti.com/lsds/ti/dlp/video-and-data-display/trp-technology.page#0.2>

  However, in a conventional projection display device using a reflective image display element, an air gap for totally reflecting illumination light and guiding it to the image display element causes image degradation (flare) in transmitted image light. End up. For this reason, there is a limit to high definition as it is.

  For example, in the projection display device described in Patent Document 1, the occurrence of aberration is suppressed by making the air gap wedge-shaped. However, if the prism is not collided on the narrow side of the air gap, It is necessary to widen the gap sufficiently, and as a result, flare may increase. Further, in the projection type display device described in Patent Document 2, the air gap is narrowed by controlling the vapor deposition film thickness using metal or the like to suppress the occurrence of aberration, but if the air gap is too narrow, the temperature change Sometimes the prism is deformed and the opposing glass surfaces come into contact with each other, making total reflection impossible.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a projection display device in which flare components generated in a prism unit are reduced to improve image quality.

In order to achieve the above object, a projection display device according to a first aspect of the present invention includes a reflective image display element that converts illumination light to image light by reflecting the illumination light on an image display surface, and an optical path of the illumination light. A projection type display device comprising: a prism unit that performs bending and transmission of image light; and a projection optical system that projects image light transmitted through the prism unit onto a screen,
The prism unit has an air gap inclined at a predetermined angle with respect to a principal ray of image light emitted from the center of the image display surface, and the image light is transmitted through the air gap.
In the prism unit, a normal line of at least one prism surface other than the prism surface constituting the air gap among the prism surface on which the image light is incident on the prism and the prism surface on which the image light is emitted outside the prism is projected. Inclined with respect to the optical axis of the optical system.

The projection display device of the second invention is the projection display device according to the first invention, wherein the image display element is provided for each of a plurality of wavelength bands.
The prism unit bends the optical path of the illumination light including the plurality of wavelength bands by reflection on the prism surface constituting the air gap, and the illumination light emitted by being bent by the first prism unit. And a second prism unit that divides the light into the plurality of wavelength bands and makes each incident on the plurality of image display elements, and synthesizes the image light emitted from each image display element and makes it incident on the first prism unit. It is characterized by that.

  According to a third aspect of the present invention, there is provided the projection display device according to the first or second aspect, wherein the prism surface on which the image light enters the prism is the first prism surface, and the prism surface from which the image light is emitted to the outside of the prism. Is the second prism surface, the length in the optical axis direction from the first prism surface to the second prism surface is longer on the side closer to the air gap than the second prism surface, The first and second prism surfaces are both perpendicular to the optical axis of the projection optical system so that the air gap is shorter on the side closer to the first prism surface. At least one of the second prism surfaces is inclined.

In a projection display device according to a fourth aspect of the present invention, in any one of the first to third aspects, the image display surface includes a plurality of micromirrors, and the inclination of each micromirror surface is ON in the image display surface. An image is formed by controlling the intensity of the illumination light under the control of / OFF,
The following conditional expressions (1) and (2) are satisfied.
0.85 × Cg <G <1.15 × Cg (1)
(0.05 × T / P−0.05) <K <0.2 × T / P (2)
However, when a plane including the chief ray of the illumination light just before the incidence with respect to the center of the image display surface and the chief ray of the image light just after the reflection is a reference plane,
Cg = arcsin (1 / N) − (R-arcsin (1 / (2F))) / N
N: Refractive index at the d-line of the prism through which image light passes,
R: Angle (degrees) formed when the chief ray of illumination light immediately before entering the center of the image display surface and the chief ray of image light immediately after being reflected at the center of the image display surface are projected onto the reference plane.
F: Minimum F number of the projection optical system,
G: Angle (degree) of air gap with respect to a plane perpendicular to the principal ray of image light emitted from the center of the image display surface,
T: Air gap thickness (mm)
P: distance between centers of adjacent micromirror surfaces (mm),
K: Angle (degrees) formed by the normal of the inclined prism surface with respect to the optical axis of the projection optical system,
It is.

According to a fifth aspect of the present invention, there is provided a projection-type display device that includes a reflection-type image display element that converts illumination light to image light by reflecting the illumination light on an image display surface, emits light, folds the optical path of the illumination light, and transmits image light. A projection type display device comprising: a prism unit that performs the projection; and a projection optical system that projects image light transmitted through the prism unit onto a screen,
The image display element is provided for each of a plurality of wavelength bands,
The prism unit includes a plurality of first prism units that respectively bend the optical paths of the plurality of illumination lights divided into the plurality of wavelength bands and enter the plurality of image display elements, and the plurality of image display elements. A second prism unit that combines a plurality of image lights reflected and transmitted through the first prism unit to be incident on the projection optical system, and
The plurality of first prism units each have an air gap inclined at a predetermined angle with respect to a principal ray of image light emitted from the center of the image display surface,
The image light respectively incident on the plurality of first prism units passes through the air gap, exits from the first prism unit, and enters the second prism unit.
In the second prism unit, a normal line of a prism surface from which image light is emitted out of the prism is inclined with respect to the optical axis of the projection optical system.

  A projection display device according to a sixth aspect of the present invention is the projection display device according to any one of the first to fifth aspects, wherein the prism surface having a normal line inclined with respect to the optical axis of the projection optical system is more than the air gap. It is located on the projection optical system side.

  According to the present invention, the flare component generated by the image light passing through the air gap in the prism unit can be canceled by the prism surface having a normal line inclined with respect to the optical axis of the projection optical system. Therefore, flare components generated in the prism unit can be reduced to improve the image quality, and a bright and high-definition projection display device can be realized.

The schematic block diagram which shows 1st Embodiment of a projection type display apparatus. The schematic block diagram which shows 2nd Embodiment of a projection type display apparatus. The top view which shows an example of the principal part of 2nd Embodiment. The schematic block diagram which shows 3rd Embodiment of a projection type display apparatus. The top view which shows an example of the principal part of 3rd Embodiment. The figure for demonstrating the distance P between the centers of the adjacent micromirrors in a digital micromirror device. The optical path figure which shows the optical path separation of the illumination light and image light in 2nd Embodiment. The figure for demonstrating the separation angle R of illumination light and image light. The optical path figure which expands and shows the principal part M1 in FIG. The figure for demonstrating the inclination of the prism surface in 2nd Embodiment. The graph which shows MTF before and after flare correction | amendment in 2nd Embodiment. The graph which shows the lateral aberration before and after flare correction | amendment in 2nd Embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a projection display device according to the present invention will be described below with reference to the drawings. Note that the same or corresponding parts in the embodiment and the like are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  FIG. 1 shows a one-chip type projector PJ1 as the first embodiment of the projection display device. FIG. 2 shows a three-chip type projector PJ2 as a second embodiment of the projection display apparatus, and FIG. 3 shows an example of a main part thereof. FIG. 4 shows a three-chip type projector PJ3 as a third embodiment of the projection display apparatus, and FIG.

  1, 2, and 4, the global Cartesian coordinate system coincides with the local Cartesian coordinate system (X, Y, Z) whose origin is the center of the image display surface DS of the digital micromirror device DP. In the coordinate system, the X direction is a direction parallel to the surface normal of the image display surface DS, the Z direction is a direction parallel to the axis of inclination of the air gap AG, and the Y direction is It is a direction orthogonal to the X direction and the Z direction. Therefore, the paper surface of FIGS. 1, 2 and 4 corresponds to the XY plane, and the paper surfaces of FIGS. 3 and 5 correspond to the XZ plane.

  The one-chip type projector PJ1 (FIG. 1) has a configuration including a light source device 1, a color wheel 2, an integral rod 3, an illumination optical system IL, a projection optical system PO, a digital micromirror device DP, and the like. Yes. The three-chip type projectors PJ2 and PJ3 (FIGS. 2 and 4) include a light source device 1, an integral rod 3, an illumination optical system IL, a projection optical system PO, a digital micromirror device DP, and the like. It has become.

  Examples of the light source device 1 that generates the illumination light L1 in the projectors PJ1, PJ2, and PJ3 include a xenon lamp and a laser light source. The light source device 1 used in the projectors PJ1 and PJ2 is a white light source, and the light source device 1 used in the projector PJ3 generates colored light in three wavelength bands: R (red), G (green), and B (blue), respectively. It is a color light source.

  In the light source device 1, a light emitting point is arranged at the focal position of the reflecting surface of the lamp reflector formed of an elliptical surface, and the convergent light emitted from the light source device 1 is integrated with the integral rod 3 (FIGS. 2 and 4) or the color wheel. 2 (FIG. 1). In other words, the projectors PJ2 and PJ3 are configured to cause convergent light to be incident on the integral rod 3, and the projector PJ1 is configured to cause convergent light to be incident on the color wheel 2. The light beam that has passed through the color wheel 2 is incident on the integral rod 3. Will do.

  The color wheel 2 mounted on the projector PJ1 includes three types of color filters that transmit R, G, and B color light. By rotating the color wheel 2, the color light to be illuminated is sequentially switched over time, and the image information corresponding to each color is displayed on the digital micromirror device DP, so that the projected image can be colored. Become.

  The integral rod 3 assumed here is a hollow rod type light intensity uniformizing element formed by bonding four plane mirrors. The illumination light L1 that has entered from the entrance-side end surface (rod entrance surface) of the integral rod 3 is mixed by being repeatedly reflected by the side surface (that is, the inner wall surface) of the integral rod 3, and the illumination light L1 The spatial energy distribution is made uniform and the light is emitted from the outlet side end face (rod outlet face) R0.

  The shape of the exit-side end surface R0 of the integral rod 3 is a quadrangle (which may be rectangular or trapezoidal) substantially similar to the image display surface DS of the digital micromirror device DP, and the integral rod 3, the exit-side end surface R0 is conjugated or substantially conjugated to the image display surface DS of the digital micromirror device DP. Therefore, the luminance distribution at the exit side end face R0 is made uniform by the mixing effect, so that the digital micromirror device DP is efficiently and uniformly illuminated.

  The integral rod 3 is not limited to a hollow rod, but may be a glass rod made of a quadrangular prism-shaped glass body. Further, as long as it matches the shape of the image display surface DS of the digital micromirror device DP, the side surfaces are not limited to four. That is, the cross-sectional shape is not limited to a quadrilateral such as a rectangle or a trapezoid. Accordingly, examples of the integral rod 3 to be used include a hollow cylinder formed by combining a plurality of reflection mirrors, and a polygonal columnar glass body.

  The illumination light L1 emitted from the exit side end face R0 of the integral rod 3 enters the illumination optical system IL. The illumination optical system IL is a catadioptric optical system that guides the incident illumination light L1 to the digital micromirror device DP and illuminates the image display surface DS. Then, the first lens unit LN (consisting of a lens, a plane mirror, etc.) that condenses the illumination light L1 and a prism unit that performs bending of the optical path of the illumination light L1 and transmission of the image light L2 are used. The prism unit PU1 or the first and second prism units PU1 and PU2 are provided, and the exit-side end surface R0 of the integral rod 3 and the image display surface DS are conjugated or substantially conjugated. The optical paths in FIGS. 1 to 5 indicate central principal rays (corresponding to the optical axis AX and passing through the center of the image display surface DS) of the illumination light L1 and the image light L2.

  The illumination light L1 incident on the illumination optical system IL is collected by the condenser lens system LN and then enters the first prism unit PU1. The first prism unit PU1 includes a TIR (Total Internal Reflection) prism composed of two substantially triangular prisms P1 and P2, and an air gap AG is provided between the prisms P1 and P2. As will be described later, the air gap AG is inclined by a predetermined angle (90 ° -G) with respect to the central principal ray L2p (FIG. 7) of the image light L2 emitted from the center of the image display surface DS. Optical path separation between illumination light (input light) L1 and image light (output light) L2 for the micromirror device DP is performed.

  In the projector PJ1, the first prism unit PU1 bends the optical path of the illumination light L1, and causes the illumination light L1 to enter the digital micromirror device DP. The bending of the optical path is performed when the illumination light L1 is incident on the slope of the prism P1 forming the air gap AG at an angle satisfying the total reflection condition and totally reflected. The image light L2 reflected by the digital micromirror device DP and incident on the first prism unit PU1 passes through the air gap AG, exits from the first prism unit PU1, enters the projection optical system PO, and enters the screen. Projected.

  In the projector PJ2, the first prism unit PU1 bends the optical path of the illumination light L1 including the RGB wavelength bands, and causes the illumination light L1 to enter the second prism unit PU2. The bending of the optical path is performed when the illumination light L1 is incident on the slope of the prism P1 forming the air gap AG at an angle satisfying the total reflection condition and totally reflected.

  The second prism unit PU2 mounted on the projector PJ2 is composed of a color prism for color separation / synthesis composed of three prisms PR, PG, and PB. For example, as shown in FIG. 3, the illumination light L1 emitted from the first prism unit PU1 is separated into RGB wavelength bands and incident on three digital micromirror devices DR, DG, and DB, respectively. The image light L2 emitted from the mirror devices DR, DG, and DB is combined and incident on the first prism unit PU1. Then, the image light L2 incident on the first prism unit PU1 passes through the air gap AG, exits from the first prism unit PU1, enters the projection optical system PO, and is projected onto the screen.

  The color separation / synthesis in the second prism unit PU2 will be described in more detail. FIG. 3 shows the first and second prism units PU1, PU2 as viewed from the upper surface side along the Y direction (FIG. 2). As shown in FIG. 3, the second prism unit PU2 has a configuration in which a substantially triangular prismatic blue prism PB and a red prism PR, and a block-shaped green prism PG are sequentially combined. Further, as a digital micromirror device DP (FIG. 2) that modulates the illumination light L1 on the image display surface DS according to an image signal, a red digital micromirror device DR and a green digital micromirror. A device DG and a blue digital micromirror device DB are provided.

  Between the blue prism PB and the red prism PR, a blue dichroic surface that reflects blue light and an air gap layer are provided adjacent thereto. The air gap layer is inclined with respect to the optical axis AX. Further, between the red prism PR and the green prism PG, a red dichroic surface that reflects red light and an air gap layer adjacent thereto are provided. This air gap layer is also inclined with respect to the optical axis AX. The inclination direction is opposite to the inclination direction of the air gap layer formed by the blue prism PB and the red prism PR.

  The illumination light L1 incident from the entrance / exit surface of the blue prism PB is reflected by the blue dichroic surface, and the other green light and red light are transmitted. The blue light reflected by the blue dichroic surface is totally reflected by the incident / exiting surface of the blue prism PB and is emitted from the blue incident / exiting surface which is the side surface of the blue prism PB to illuminate the blue digital micromirror device DB. . Of the green light and red light transmitted through the blue dichroic surface, red light is reflected by the red dichroic surface and green light is transmitted. The red light reflected by the red dichroic surface is totally reflected by the air gap layer provided adjacent to the blue dichroic surface, and is emitted from the red incident / exit surface which is the side surface of the red prism PR. • Illuminate device DR. The green light transmitted through the red dichroic surface is emitted from the green incident / exit surface which is the side surface of the green prism PG, and illuminates the green digital micromirror device DG.

  The blue image light L2 reflected by the blue digital micromirror device DB enters the blue incident / exit surface, is totally reflected by the incident / exit surface of the blue prism PB, and then reflected by the blue dichroic surface. The red image light L2 reflected by the red digital micromirror device DR enters the red incident / exit surface and is totally reflected by an air gap layer provided adjacent to the blue dichroic surface. Reflected by the red dichroic surface and further transmitted through the blue dichroic surface. Further, the green image light L2 reflected by the green digital micromirror device DG is incident on the green incident / exit surface and is transmitted through the red dichroic surface and the blue dichroic surface.

  The red, blue, and green image lights L2 are combined on the same optical axis AX, emitted from the prism surface SB that is the entrance / exit surface of the blue prism PB, and enter the first prism unit PU1. Since the image light L2 incident on the first prism unit PU1 does not satisfy the total reflection condition here, it passes through the air gap AG (FIG. 2), and an image is projected onto the screen by the projection optical system PO.

  In the projector PJ3, the light source device 1, the integral rod 3, the condensing lens system LN, and the first prism unit PU1 are provided for each of the RGB wavelength bands without using a color separation prism. Therefore, for example, as shown in FIG. 5, the three first prism units PU1 fold the optical paths of the illumination light L1 divided into the RGB wavelength bands into three digital micromirror devices DR, DG, and DB, respectively. Make each incident. The bending of the optical path is performed when the illumination light L1 is incident on the slope of the prism P1 forming the air gap AG at an angle satisfying the total reflection condition and totally reflected.

  The second prism unit PU2 mounted on the projector PJ3 is made up of a color prism for color synthesis that includes three prisms PR, PG, and PB. For example, as shown in FIG. 5, three image lights L2 reflected by three digital micromirror devices DR, DG, and DB, respectively, transmitted through the first prism unit PU1, and then emitted are combined into the projection optical system PO. Make it incident. At this time, the image light L2 incident on each of the three first prism units PU1 passes through the air gap AG, exits from the first prism unit PU1, and enters the second prism unit PU2. Then, the image light L2 incident on the projection optical system PO is projected on the screen.

  The color composition in the second prism unit PU2 will be described in more detail. FIG. 5 shows the first and second prism units PU1 and PU2 as viewed from the upper surface side along the Y direction (FIG. 4). As shown in FIG. 5, the second prism unit PU <b> 2 has a configuration in which a substantially triangular prismatic blue prism PB and red prism PR, and a block-shaped green prism PG are sequentially combined. Further, as a digital micromirror device DP (FIG. 4) that modulates the illumination light L1 on the image display surface DS according to an image signal, a red digital micromirror device DR and a green digital micromirror. A device DG and a blue digital micromirror device DB are provided.

  Between the blue prism PB and the red prism PR, a blue dichroic surface that reflects blue light and an air gap layer are provided adjacent thereto. The air gap layer is inclined with respect to the optical axis AX. Further, between the red prism PR and the green prism PG, a red dichroic surface that reflects red light and an air gap layer adjacent thereto are provided. This air gap layer is also inclined with respect to the optical axis AX. The inclination direction is opposite to the inclination direction of the air gap layer formed by the blue prism PB and the red prism PR.

  The blue image light L2 reflected by the blue digital micromirror device DB passes through the first prism unit PU1, enters the blue incident surface, and is totally reflected by the exit surface of the blue prism PB. Reflected by dichroic surface. The red image light L2 reflected by the red digital micromirror device DR passes through the first prism unit PU1, enters the red incident surface, and is provided adjacent to the blue dichroic surface. After being totally reflected by the gap layer, it is reflected by the red dichroic surface and further passes through the blue dichroic surface. Further, the green image light L2 reflected by the green digital micromirror device DG is transmitted through the first prism unit PU1, is incident on the green incident surface, and is transmitted through the red dichroic surface and the blue dichroic surface.

  The red, blue, and green image lights L2 are combined on the same optical axis AX, emitted from the prism surface SB that is the emission surface of the blue prism PB, and incident on the projection optical system PO. An image is projected onto the screen by the PO. The image light L2 reflected by the digital micromirror devices DR, DG, and DB and incident on the first prism unit PU1 does not satisfy the total reflection condition, and thus passes through the air gap AG (FIG. 4).

  The digital micromirror device DP; DR, DG, DB is a reflective image display element that modulates light to generate an image, and an image display surface DS that forms a two-dimensional image by intensity modulation of the illumination light L1. And the cover glass CG etc. which are arrange | positioned on it. For example, as shown in FIG. 6, the image display surface DS includes a plurality of micromirrors MR, and the inclination of each micromirror surface (pixel reflection surface) MS is controlled to be ON / OFF on the image display surface DS, so that the illumination light L1 An image is formed by modulating the intensity. That is, in the digital micromirror device DP, each micromirror surface MS is ON / OFF controlled on the image display surface DS composed of a plurality of rectangular micromirror surfaces MS, and the micromirror MR is in an image display state (ON State) and an image non-display state (OFF state), the illumination light L1 can be intensity-modulated to form a desired image.

  The well-known digital micromirror device DP; DR, DG, and DB pixels have a rotation axis that forms an angle of 45 ° with respect to each side of the rectangular image display area formed by the image display surface DS. ON / OFF is expressed by rotating, for example, ± 12 ° around the axis. Only the light reflected by the micromirror in the ON state passes through the projection optical system PO. On the other hand, in the case of a new operation type digital micromirror device DP; DR, DG, DB (see Non-Patent Document 1, etc.), the rotation of the mirror surface is not centered on one rotation axis but is orthogonal. It is centered on two rotating shafts.

  FIG. 7 shows an optical path of the axial light beam of the image light L2 in the projector PJ2. When the illumination light L1 enters the prism P1, the optical path is bent by total reflection at the air gap AG in the first prism unit PU1. The illumination light L1 is emitted from the prism P1, and is irradiated on the image display surface DS of the digital micromirror device DP through the second prism unit PU2. When the illumination light L1 is irradiated on the image display surface DS of the digital micromirror device DP, the image light L2 is emitted from the digital micromirror device DP by reflection on the illuminated image display surface DS. At this time, as shown in FIG. 8, the chief ray L2p of the image light L2 just reflected at the center of the image display surface DS with respect to the chief ray L1p of the illumination light L1 just before entering the center of the image display surface DS is The image light L2 is separated from the illumination light L1 at an angle R.

  As shown in FIG. 7, the image light L2 passes through the first prism unit PU1 via the second prism unit PU2. At this time, the image light L2 passes through the air gap AG inclined by an angle G with respect to the optical axis AX, exits the second prism unit PU2 from the prism P2, enters the projection optical system PO, and is projected onto the screen. The The lower end of the air gap AG is preferably set below the lower limit position that does not block the image light L2.

  Of the image light L2, the light ray incident on the air gap AG at the incident angle α2 is greatly inclined with respect to the air gap AG (α1 <α2), and is thus largely refracted by the air gap AG. FIG. 9 shows an enlarged main part M1 where the refraction occurs. As can be seen from FIG. 9, the light beam incident on the air gap AG at the incident angle α2 in the image light L2 is largely refracted by the air gap AG. The flare component Δ generated by this refraction is imaged by the projection optical system PO. Sometimes flare occurs. Note that the direction of the flare component Δ is parallel to the screen surface, and the flare is evaluated as a distance on the screen surface.

  The first prism unit PU1 mounted on the projector PJ1 (FIG. 1) has a prism surface on which the image light L2 enters or exits in addition to the prism surfaces A1 and A2 (FIG. 9) that form the air gap AG. To do. Specifically, a prism surface S1 on which the image light L2 is incident on the prism P1 and a prism surface S2 on which the image light L2 is emitted outside the prism P2. In the projector PJ1, the normal line of at least one of the prism surfaces S1 and S2 is inclined with respect to the optical axis AX of the projection optical system PO. By tilting the prism surface in this way, the flare can be canceled as a result. Therefore, the flare component Δ generated in the first prism unit PU1 can be reduced to improve the projected image quality, and a bright and high-definition projector PJ1 can be realized.

  The first and second prism units PU1 and PU2 mounted on the projector PJ2 (FIGS. 2 and 3) include all RGB colors in addition to the prism surfaces A1 and A2 (FIG. 9) constituting the air gap AG. There is a prism surface on which the image light L2 enters or exits. Specifically, a prism surface S1 on which the image light L2 is incident on the prism P1, a prism surface S2 on which the image light L2 is emitted to the outside of the prism P2, and a prism surface on which the image light L2 enters and exits the blue prism PB. SB. In the projector PJ2, the normal line of at least one of the prism surfaces S1, S2, and SB is inclined with respect to the optical axis AX of the projection optical system PO. By tilting the prism surface in this way, the flare can be canceled as a result. Therefore, the flare component Δ generated in the first prism unit PU1 can be reduced to improve the projected image quality, and a bright and high-definition projector PJ2 can be realized.

  In the second prism unit PU2 of the projector PJ2, as can be seen from FIG. 3, the prisms PR, PG, and PB have prism surfaces that face the digital micromirror devices DR, DG, and DB, respectively. The image light L2 of each color of RGB is configured to enter. Therefore, it is possible to cancel the flare component Δ even if the prism surfaces facing the digital micromirror devices DR, DG, DB are arranged so that their normal lines are inclined with respect to the optical axis AX. However, since it is necessary to incline three prism surfaces corresponding to RGB colors, the configuration becomes complicated. Therefore, in the second prism unit PU2 of the projector PJ2, it is preferable to perform flare correction on the prism surface SB.

  In the first and second prism units PU1 and PU2 mounted on the projector PJ3 (FIGS. 4 and 5), in addition to the prism surfaces A1 and A2 (FIG. 9) constituting the air gap AG, all RGB colors are included. There is a prism surface on which the image light L2 enters or exits. Specifically, the prism surface SB from which the image light L2 is emitted to the outside of the blue prism PB. In the projector PJ3, the normal line of the prism surface SB is inclined with respect to the optical axis AX of the projection optical system PO. By tilting the prism surface in this way, the flare can be canceled as a result. Accordingly, the flare component Δ generated in the first prism unit PU1 can be reduced to improve the projected image quality, and a bright and high-definition projector PJ3 can be realized.

  In addition, as can be seen from FIG. 5, the first and second prism units PU1 and PU2 of the projector PJ3 have prism surfaces on which the RGB image light L2 enters or exits in addition to the prism surface SB. As described above with respect to the projector PJ2, it is possible to cancel the flare component Δ even if these prism surfaces are arranged such that the normal line is inclined with respect to the optical axis AX. However, since it is necessary to incline three prism surfaces corresponding to RGB colors, the configuration becomes complicated. Therefore, it is preferable to perform flare correction on the prism surface SB in the projector PJ3.

  Each of the projectors PJ1, PJ2, and PJ3 described above is a digital micromirror device DP that converts the illumination light L1 into the image light L2 by reflecting the illumination light L1 on the image display surface DS, and bends the optical path of the illumination light L1. And a first prism unit PU1 that transmits the image light L2, and a projection optical system PO that projects the image light L2 transmitted through the first prism unit PU1 onto a screen. The first prism unit PU1 has an air gap AG inclined by a predetermined angle (90 ° -G) with respect to the principal ray L2p of the image light L2 emitted from the center of the image display surface DS, and the air gap AG Through which the image light L2 passes. In the prism unit including the first prism unit PU1, at least one of the prism surface on which the image light L2 enters the prism and the prism surface on which the image light L2 exits the prism other than the prism surface constituting the air gap AG. The normal line of one prism surface is inclined with respect to the optical axis AX of the projection optical system PO.

  When the normal of the prism surface is tilted with respect to the optical axis AX of the projection optical system PO, the incident angle of the image light L2 with respect to the projection optical system PO changes, so coma aberration occurs. When coma aberration is generated in the direction opposite to the flare component Δ (FIG. 9) generated by the image light L2 passing through the air gap AG, the flare is canceled, so that the flare of the projected image is eliminated and the image quality is improved. Can be realized. In addition, since the coma that cancels the flare is generated instead of cutting the flare, this flare correction has an advantage that the brightness does not decrease. Therefore, it is possible to achieve high definition while maintaining brightness.

  Here, the inclination of the prism surface for canceling the flare component Δ will be described using the prism surfaces S1 and S2 of the projector PJ2 as an example. In FIG. 10A, the slopes of the prism surfaces S1 and S2 are compared with a state parallel to each other (that is, a state where the prism surfaces S1 and S2 are both perpendicular to the optical axis AX of the projection optical system PO). Show. Further, FIG. 10B shows an angle K formed by the normal line NL of the inclined prism surfaces S1 and S2 with respect to the optical axis AX.

  As shown in FIG. 10 (A), the tilt direction is different between the prism surface S1 on which the image light L2 enters the prism P1 and the prism surface S2 on which the image light L2 exits the prism P2. Since the axis of inclination of the air gap AG and the axis of inclination of the prism surfaces S1 and S2 are parallel, the prism surface S2 has the same inclination direction (counterclockwise) as the air gap AG, and the prism surface S1 has the air gap AG. The direction of inclination is opposite (clockwise). In addition, the axis of inclination of these surfaces is perpendicular (Z direction) to the paper surface (XY plane).

  Considering the distance between the prism surfaces S1 and S2, the length in the optical axis AX direction from the prism surface S1 to the prism surface S2 is long on the side where the air gap AG is close to the prism surface S2 (distance d2). The prism surface S1 is based on the condition that the prism surfaces S1 and S2 are both perpendicular to the optical axis AX so that the air gap AG is shorter on the side closer to the prism surface S1 (distance d1) (d1 <d2). , S2 is preferably inclined. That is, only the prism surface S1 on which the image light L2 enters the prism P1 may be tilted with respect to the optical axis AX of the projection optical system PO, and only the prism surface S2 on which the image light L2 is emitted out of the prism P2 is tilted. Alternatively, both the prism surfaces S1 and S2 may be inclined.

  Setting the inclination directions of the prism surfaces S1 and S2 as described above can effectively cancel flare caused by the image light L2 being transmitted through the air gap AG. In the projectors PJ2 and PJ3, the flare can be effectively canceled out similarly to the prism surface S2 with respect to the prism surface SB from which the image light L2 is emitted to the outside of the blue prism PB. Further, since flare cancellation is completed with only the prisms P1, P2, and PB, there is an advantage that it is not necessary to change other components. Note that the inclinations of the prism surfaces S1, S2, and SB are relative to the optical axis AX of the projection optical system PO, so that even if the projection optical system PO is inclined with respect to the prism surface S1, S2, or SB. Good. In FIG. 10A, the arrangement of the tilted projection optical system PO instead of the prism surface S2 is indicated by a dotted line.

In order to further improve the image quality by reducing the flare component Δ generated in the first prism unit PU1, as in the projectors PJ1, PJ2, and PJ3, a digital micromirror device DP is provided as an image display element, and the following conditions are satisfied. It is preferable to satisfy the expressions (1) and (2).
0.85 × Cg <G <1.15 × Cg (1)
(0.05 × T / P−0.05) <K <0.2 × T / P (2)
However, a plane including the principal ray L1p of the illumination light L1 just before incidence with respect to the center of the image display surface DS and the principal ray L2p of the image light L2 just after reflection is a reference plane (FIGS. 1, 2, 4, and 4). (Corresponding to the XY plane which is the paper surface of FIG. 7).
Cg = arcsin (1 / N) − (R-arcsin (1 / (2F))) / N
N: Refractive index at the d-line of the prisms P1, P2 through which the image light L2 passes,
R: When the principal ray L1p of the illumination light L1 immediately before entering the center of the image display surface DS and the principal ray L2p of the image light L2 immediately after reflection at the center of the image display surface DS are projected onto the reference plane. Angle formed (unit is degree, angle R is shown in FIG. 8),
F: Minimum F number of the projection optical system PO,
G: The angle of the air gap AG with respect to a plane perpendicular to the principal ray L2p (optical axis AX) of the image light L2 emitted from the center of the image display surface DS (the unit is degrees, and the angle G is shown in FIG. 7).
T: Air gap thickness (mm)
P: distance between centers of adjacent micromirror surfaces MS (unit is mm, distance P is shown in FIG. 6),
K: angle (degree) formed by the normal line NL of the inclined prism surfaces S1, S2, SB with respect to the optical axis AX of the projection optical system PO,
It is.

  Conditional expression (1) defines an appropriate angle G of the air gap AG, and conditional expression (2) defines an appropriate inclination angle K of the flare correcting prism surface. The air gap AG provided in the first prism unit PU1 for guiding the illumination light L1 to the digital micromirror device DP satisfies the conditional expression (1), so that the illumination light L1 is totally reflected and image light. L2 can be appropriately transmitted, and the light utilization efficiency can be maximized. In addition, if the normal line NL of the prism surfaces S1, S2, and SB is tilted with respect to the optical axis AX of the projection optical system PO within a range that satisfies the conditional expression (2), the flare component Δ is effectively generated in the air gap AG. The image quality can be further improved.

  If the lower limit of conditional expression (1) is not reached, the total reflection condition of the illumination light L1 is not satisfied, and the light utilization efficiency tends to decrease. If the upper limit of the conditional expression (1) is exceeded, flare due to the air gap AG occurs greatly, and the image quality tends to deteriorate. If the lower limit of conditional expression (2) is not reached, the flare cannot be completely removed and it becomes difficult to cancel the flare. If the upper limit of conditional expression (2) is exceeded, overcorrection may occur and new flare may occur.

In relation to conditional expression (1), it is desirable to satisfy the following conditional expression (1a), and it is more desirable to satisfy conditional expression (1b).
0.9 × Cg <G <1.1 × Cg (1a)
0.95 × Cg <G <1.05 × Cg (1b)
These conditional expressions (1a) and (1b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (1). Therefore, the above-mentioned effect can be further enhanced by preferably satisfying conditional expression (1a), more preferably satisfying conditional expression (1b).

In relation to conditional expression (2), it is desirable to satisfy the following conditional expression (2a).
(0.05 × T / P−0.05) <K <0.15 × T / P (2a)
This conditional expression (2a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (2). Therefore, preferably, the above-described effect can be further increased by satisfying conditional expression (2a).

As a configuration satisfying conditional expressions (1) and (2),
N = 1.5168,
R = 24,
F = 2.5,
Cg = 33.029,
G = 33 (= 0.999 × Cg),
T = 0.01 mm,
P = 0.01 mm,
K = 0.1,
Is mentioned.

The above data is conditional expression (1):
0.85 × Cg <G <1.15 × Cg
To correspond to
0.85 × 33.029 <0.999 × 33.029 <1.15 × 33.029
0.85 <0.999 <1.15
It becomes. Similarly, when corresponding to the conditional expressions (1a) and (1b),
0.9 <0.999 <1.1
0.95 <0.999 <1.05
It becomes.

The above data is conditional expression (2):
(0.05 × T / P−0.05) <K <0.2 × T / P
To correspond to
(0.05 × 0.01 / 0.01−0.05) <K <0.2 × 0.01 / 0.01
0 <0.1 <0.2
It becomes. Similarly, when corresponding to the conditional expression (2a),
0 <0.1 <0.15
It becomes.

  11 and 12 show the optical performance before and after flare correction using the above data in the projector PJ2 (flare correction prism surface S2 (front tilt), K = 0.1 deg, wavelength: 550 nm). FIG. 11 is a graph showing changes in MTF (Modulation Transfer Function) due to defocus (mm) (solid line: MTF value on XY plane, broken line: MTF value on XZ plane; spatial frequency: 90 cycles / mm). FIG. 11A shows the MTF before flare correction, and FIG. 11B shows the MTF after flare correction. 12 is a graph showing lateral aberration. FIGS. 12A and 12B show lateral aberration before flare correction, and FIGS. 12C and 12D show lateral aberration after flare correction. (Maximum scale: ± 25 μm). The solid line shown in FIGS. 12A and 12C is the lateral aberration ey (Py: incident height) on the XY plane, and the broken line shown in FIGS. 12B and 12D is the lateral aberration ez (on the XZ plane). Pz: incident height).

  In the three-chip type projector PJ2, digital micromirror devices DR, DG, and DB (FIG. 3) are provided for each of a plurality of wavelength bands RGB, and the illumination includes a plurality of wavelength bands RGB as a prism unit. The first prism unit PU1 that bends the optical path of the light L1 by reflection on the prism surface A1 that forms the air gap AG, and the illumination light L1 that is bent and emitted by the first prism unit PU1 is separated into a plurality of wavelength bands RGB. Are incident on the plurality of digital micromirror devices DR, DG, DB, respectively, and the image light L2 emitted from each of the digital micromirror devices DR, DG, DB is combined and incident on the first prism unit PU1. 2 prism unit PU2 (color prism for color separation / synthesis) And, it includes a. The air gap AG included in the first prism unit PU1 is inclined at a predetermined angle (90 ° -G) with respect to the principal ray L2p of the image light L2 emitted from the center of the image display surface DS. The image light L2 incident on the PU1 passes through the air gap AG, is emitted from the first prism unit PU1 and enters the projection optical system PO.

  As described above, the occurrence of flare in the air gap AG is canceled by the at least one inclined prism surface S1, S2, SB as a result. Therefore, the image quality is improved, and high definition can be achieved while maintaining brightness. In the three-chip type projection display device, since higher luminance is required, it is necessary to set the air gap AG relatively wide so as to cope with a large temperature change. Since the generated flare is increased accordingly, the above effect is also great.

  The three-chip type projector PJ3 includes digital micromirror devices DR, DG, and DB (FIG. 5) for each of a plurality of wavelength bands RGB, and is divided into a plurality of wavelength bands RGB as a prism unit. A plurality of first prism units PU1 that respectively bend the optical paths of the plurality of illumination lights L1 and enter the plurality of digital micromirror devices DR, DG, DB, respectively, and a plurality of digital micromirror devices DR, DG, A second prism unit PU2 (color prism for color synthesis) that combines the plurality of image lights L2 reflected by the DB and transmitted through the first prism unit PU1 to enter the projection optical system PO. Yes. Each of the plurality of first prism units PU1 has an air gap AG inclined at a predetermined angle (90 ° -G) with respect to the principal ray L2p of the image light L2 emitted from the center of the image display surface DS. The image light L2 respectively incident on the first prism unit PU1 passes through the air gap AG, exits from the first prism unit PU1, and enters the second prism unit PU2.

  As described above, the occurrence of flare in the air gap AG is canceled by the inclined prism surface SB in the second prism unit PU2. Therefore, the image quality is improved, and high definition can be achieved while maintaining brightness. Moreover, since the prism surface SB is located farthest from the digital micromirror devices DR, DG, DB in the first and second prism units PU1, PU2, there is almost no blurring due to the inclination of the prism surface. .

  In the projectors PJ1, PJ2, and PJ3 described above, it is preferable that the prism surface having the normal line NL inclined with respect to the optical axis AX of the projection optical system PO is located on the projection optical system PO side with respect to the air gap AG. For example, in the prism units PJ1 and PJ2, inclining the prism surface S2 is effective in preventing the occurrence of one-sided blur due to the inclination.

PJ1, PJ2, PJ3 Projector (Projection type display device)
IL illumination optical system LN condenser lens system PU1 first prism unit PU2 second prism unit PR red prism PG green prism PB blue prism P1, P2 prism S1 prism surface (first prism surface)
S2 Prism surface (second prism surface)
SB Prism surface A1, A2 Prism surface AG Air gap DP Digital micromirror device (Reflective image display device)
DR Red digital micromirror device (reflective image display device)
DG Green digital micromirror device (reflective image display device)
DB Digital micromirror device for blue (reflective image display device)
DS Image display surface MR Micromirror MS Micromirror surface L1 Illumination light L2 Image light L1p, L2p Central principal ray PO Projection optical system XY Reference plane NL Normal line AX Optical axis 1 Light source device 2 Color wheel 3 Integral rod R0 Rod exit surface

Claims (6)

A reflective image display element that converts illumination light to image light by reflecting it on the image display surface and emits it, a prism unit that performs bending of the optical path of illumination light and transmission of image light, and transmission through the prism unit. A projection optical system that projects projected image light onto a screen,
The prism unit has an air gap inclined at a predetermined angle with respect to a principal ray of image light emitted from the center of the image display surface, and the image light is transmitted through the air gap.
In the prism unit, a normal line of at least one prism surface other than the prism surface constituting the air gap among the prism surface on which the image light is incident on the prism and the prism surface on which the image light is emitted outside the prism is projected. A projection display device, wherein the projection display device is tilted with respect to an optical axis of an optical system. The image display element is provided for each of a plurality of wavelength bands,
The prism unit bends the optical path of the illumination light including the plurality of wavelength bands by reflection on the prism surface constituting the air gap, and the illumination light emitted by being bent by the first prism unit. And a second prism unit that divides the light into the plurality of wavelength bands and makes each incident on the plurality of image display elements, and synthesizes the image light emitted from each image display element and makes it incident on the first prism unit. The projection type display device according to claim 1.   From the first prism surface to the second prism surface, the prism surface on which the image light enters the prism is the first prism surface, and the prism surface from which the image light is emitted out of the prism is the second prism surface. The length in the optical axis direction of the second prism surface is longer on the side closer to the air gap with respect to the second prism surface, and shorter on the side closer to the air gap with respect to the first prism surface. 2. At least one of the first and second prism surfaces is inclined with reference to a state in which both the first and second prism surfaces are perpendicular to the optical axis of the projection optical system. Or the projection type display apparatus of 2 description. The image display surface is composed of a plurality of micromirrors, and on the image display surface, the inclination of each micromirror surface is ON / OFF controlled to form an image by modulating the intensity of illumination light,
The projection type display device according to claim 1, wherein the following conditional expressions (1) and (2) are satisfied:
0.85 × Cg <G <1.15 × Cg (1)
(0.05 × T / P−0.05) <K <0.2 × T / P (2)
However, when a plane including the chief ray of the illumination light just before the incidence with respect to the center of the image display surface and the chief ray of the image light just after the reflection is a reference plane,
Cg = arcsin (1 / N) − (R-arcsin (1 / (2F))) / N
N: Refractive index at the d-line of the prism through which image light passes,
R: Angle (degrees) formed when the chief ray of illumination light immediately before entering the center of the image display surface and the chief ray of image light immediately after being reflected at the center of the image display surface are projected onto the reference plane.
F: Minimum F number of the projection optical system,
G: Angle (degree) of air gap with respect to a plane perpendicular to the principal ray of image light emitted from the center of the image display surface,
T: Air gap thickness (mm)
P: distance between centers of adjacent micromirror surfaces (mm),
K: Angle (degrees) formed by the normal of the inclined prism surface with respect to the optical axis of the projection optical system,
It is. A reflective image display element that converts illumination light to image light by reflecting it on the image display surface and emits it, a prism unit that performs bending of the optical path of illumination light and transmission of image light, and transmission through the prism unit. A projection optical system that projects projected image light onto a screen,
The image display element is provided for each of a plurality of wavelength bands,
The prism unit includes a plurality of first prism units that respectively bend the optical paths of the plurality of illumination lights divided into the plurality of wavelength bands and enter the plurality of image display elements, and the plurality of image display elements. A second prism unit that combines a plurality of image lights reflected and transmitted through the first prism unit to be incident on the projection optical system, and
The plurality of first prism units each have an air gap inclined at a predetermined angle with respect to a principal ray of image light emitted from the center of the image display surface,
The image light respectively incident on the plurality of first prism units passes through the air gap, exits from the first prism unit, and enters the second prism unit.
In the second prism unit, the projection type display device is characterized in that a normal line of a prism surface from which image light is emitted out of the prism is inclined with respect to an optical axis of the projection optical system.   The prism surface having a normal line inclined with respect to the optical axis of the projection optical system is located on the projection optical system side with respect to the air gap. Projection type display device.

Images