JP2014174355A - Optical system and projection display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To project a high contrast image.SOLUTION: An optical system comprises: a polarization light separation element 7 transmitting P polarization light therethrough and reflecting S polarization light; a first dichroic prism 9 having a first color separation surface 9a transmitting blue color light therethrough and reflecting all other color light; and a retardation plate 8 arranged between the polarization light separation element 7 and the first dichroic prism 9. The optical axis of the retardation plate is located within a plane including both a normal line of the first color separation surface 9a of the first dichroic prism 9 and a normal line of an incidence/emission surface of a reflection liquid crystal display element 13G, and inclined with respect to the normal line of the incidence/emission surface of the reflection liquid crystal display element 13G.

Description

  The present invention relates to an optical system and a projection display device using the same.

  Patent Documents 1 and 2 propose a projection display device having a dichroic mirror or dichroic prism that separates and combines three color lights after a polarization separation element, and three reflective liquid crystal display elements.

JP 2003-121793 A JP 2009-237565 A

  However, in the configurations of Patent Documents 1 and 2, since the actual polarization axis direction of the dichroic film functioning as the color separation surface or the color synthesis surface is shifted from the polarization direction of the incident light, the light passing through the dichroic film is elliptical. Polarized light causes a reduction in contrast of the projected image.

  An object of the present invention is to provide an optical system capable of projecting a high-contrast image and a projection display device using the same.

  The optical system of the present invention includes an image modulation element that modulates and reflects color light, a polarization separation unit that transmits the first polarized light and reflects the second polarized light orthogonal to the first polarized light, First color separation means having a first color separation surface that transmits first color light and reflects second color light having a wavelength region different from that of the first color light, the polarization separation means, and the color separation A first retardation plate disposed between the means, and an optical axis of the first retardation plate is a normal line of the first color separation surface of the first color separation means It is in a plane including both normal lines of the incident / exiting surface of the image modulation element, and is inclined with respect to the normal line of the incident / exiting surface of the image modulation element.

  ADVANTAGE OF THE INVENTION According to this invention, the optical system which can project a high contrast image, and a projection type display apparatus using the same can be provided.

It is a block diagram of the projection type display apparatus of this invention. Example 1 It is a figure which shows the direction of the optical axis of the phase difference plate shown in FIG. Example 1 It is a figure which shows the light ray which injects into the color separation surface of the 1st dichroic prism shown in FIG. 1 in contrast with a prior art example. Example 1 It is a figure which shows the effect of the phase difference plate shown in FIG. 1 in contrast with a prior art example. Example 1 It is a block diagram of the projection type display apparatus of this invention. (Example 2) It is a figure which shows the structure of the color filter shown in FIG. (Example 2)

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

  FIG. 1 is a block diagram of a projection display device (image projection device, projection display device) according to the first embodiment. The projection display device includes a light source unit, an illumination optical system, a color separation / synthesis optical system, and a projection lens (projection optical system) 14.

  The light source unit includes a light source 1 and a parabolic reflector 2, and a light beam emitted from the light source (light emitting unit of the lamp) 1 in all directions is emitted by the parabolic reflector 2 as substantially parallel light. The light source 1 of the present embodiment is an ultrahigh pressure mercury lamp, but is not limited thereto, and an LED or a laser light source may be used.

  The illumination optical system illuminates image modulation means (reflection liquid crystal display element, reflection liquid crystal panel), UV-IR (ultraviolet / infrared light) cut filter 3, first lens array 4, and second lens. It has an array 5 and a condenser lens 6.

  The parallel light beam from the paraboloid reflector 2 enters the UV-IR cut filter 3, is divided into a plurality of partial light beams by the first lens array 4, and each partial light beam is condensed. Each divided light beam is condensed near the second lens array 5, and each partial light beam forms a light source image (secondary light source image). The split luminous flux emitted from the second lens array 5 is collected by the condenser lens 6 and illuminates the reflective liquid crystal display element 13 in a superimposed manner.

  The color separation / synthesis optical system splits incident light into a plurality of color components, modulates and reflects the light of each color component (color light) in accordance with the video signal, and synthesizes the light of the color components that have been light-modulated. The color separation / synthesis optical system includes a polarization separation element 7, a phase difference plate 8, a first dichroic prism 9, a second dichroic prism 10, a prism 11, and light modulation means.

  The polarization separation element 7 is a polarization separation means having a polarization separation surface having characteristics of transmitting P-polarized light (first polarized light) and reflecting S-polarized light (second polarized light). Composed. Thereby, the illumination light is aligned with the P-polarized light. The polarization directions of the first polarized light and the second polarized light are orthogonal.

  The P-polarized light transmitted through the polarization separation element 7 is incident on a phase difference plate (first phase difference plate) 8 and enters a first dichroic prism (first color separation means) 9 having a first color separation surface. Incident. The first color separation surface 9a of the first dichroic mirror 9 reflects the blue band (B) color light (first color light), the red band (R) color light and the green band (G) color light (these And the second color light) is transmitted. R color light (third color light), G color light (fourth color light), and B color light have different wavelength regions.

  Conventionally, the phase difference plate 8 is not provided, and the polarization directions of the rays a to i shown in FIG. 3B incident on the color separation surface 9a of the first dichroic prism 9 are those shown in FIG. The light rays a to i shown in FIG. 4C did not coincide with the P-polarized light direction formed of the color separation surface. As a result, the light beam that has passed through the color separation surface 9a is affected by the phase difference between the S-polarized light and the P-polarized light generated on the color separation surface 9a, and becomes elliptically polarized light as shown in FIG. This was a cause of a decrease in the contrast of the projected image.

  On the other hand, in the present embodiment, as shown in FIG. 2, the phase difference plate 8 has an optical axis normal to the color separation surface of the first dichroic prism 9 and a method of an incident / exit surface of a reflection type image display element described later. It is in a plane including both of the lines and is inclined with respect to the normal line of the incident / exit surface of the reflective image display element 13. Thereby, the polarization directions of the light rays a to i shown in FIG. 3A that have passed through the phase difference plate 8 change as shown in FIG. 4A to FIG. 4B. As a result, the polarization directions of the light beams a to i that have passed through the phase difference plate 8 substantially coincide with the P polarization direction formed by the light beams a to i and the color separation surface 9a shown in FIG. A decrease in contrast can be prevented.

  The blue light reflected by the first dichroic prism 9 passes through the prism 11 and the quarter wavelength plate 12B and enters the reflective image display element 13B. In the case of black display in which the background color of the projection surface is black, the image is not reflected by the reflective image display element 13B but is reflected as P-polarized light, passes through the quarter-wave plate 12B and the prism 11, 1 dichroic prism 9 is reflected.

  The role of the quarter wavelength plate that functions as the second retardation plate will be described below. For example, the light beam a shown in FIG. 3A is a light beam in the i direction with respect to the color separation surface of the first dichroic prism 9 after being reflected by the reflective image display elements 13R, 13G, and 13B. For this reason, as shown in FIG. 4C, if the polarization direction of the light beam a remains the same, a shift occurs with respect to the polarization direction of the light beam in the i direction, leading to a decrease in contrast.

  Therefore, the light is converted so as to substantially match the polarization direction with respect to i by passing through the quarter-wave plate twice. When the P-polarized light reflected by the first dichroic prism 9 passes through the phase difference plate 8, the polarization direction changes as shown in FIGS. 4 (e) to 4 (f) and passes through the polarization separation element 7. And returned to the light source side. In the case of white display in which the background color of the projection surface is white, the reflection-type image display element 13B is image-modulated and reflected by S-polarized light, passes through the quarter-wave plate 12B and the prism 11, and passes through the first display. Reflects the dichroic prism 9. Thereafter, the light is transmitted through the phase difference plate 8, reflected by the polarization separation element 7, and displayed on the projection surface via the projection lens 14.

  The light modulation means modulates and reflects the light of each color component (color light) according to the video signal, reflects the red reflective liquid crystal display element 13R, the green reflective liquid crystal display element 13G, and the blue reflective liquid crystal. It is comprised from the display element 13B. Each liquid crystal display element functions as an image modulation element (liquid crystal panel). 12R, 12G, and 12B are a quarter wavelength plate for red (1 / 4λ plate), a quarter wavelength plate for green, and a quarter wavelength plate for blue, respectively. The red quarter-wave plate 12R is disposed between the second dichroic prism 10 and the red reflective liquid crystal display element 13R. The green quarter-wave plate 12G is disposed between the second dichroic prism 10 and the green reflective liquid crystal display element 13G. The blue quarter wave plate 12B is disposed between the prism 11 and the blue reflective liquid crystal display element 13B.

  The projection lens 14 is a projection unit (projection optical system) that projects light from the polarization separation element 7 onto a projection surface (not shown).

  The green light transmitted through the first dichroic prism 9 transmits a green band light and reflects a red band light, and a second dichroic prism (second color separation means) 10 having a second color separation surface. Transparent. Thereafter, the light passes through the quarter-wave plate 12G and enters the reflective image display element 13G. The normal line of the color separation surface 10 a of the second dichroic prism 10 is preferably substantially parallel to the normal line of the color separation surface 9 a of the first dichroic prism 9.

  By changing the polarization direction by the phase difference plate 8, the same effect as that of the color separation surface 9a of the first dichroic prism 9 can be obtained, and the decrease in contrast can be prevented. When the reflective image display element 13G displays black, the image is not modulated by the reflective image display element 13G, but is reflected as P-polarized light, passes through the quarter-wave plate 12G and the second dichroic prism 10, The light passes through the first dichroic prism 9. When the light transmitted through the first dichroic prism 9 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4 (e) to FIG. 4 (f), passes through the polarization separation element 7, and passes through the light source. Back to the side. On the other hand, when the reflective image display element 13G displays white, the reflective image display element 13G is image-modulated and reflected by the S-polarized light, passes through the quarter-wave plate 12G and the dichroic prism B10, and is transmitted through the first image display element 13G. The light passes through the dichroic prism 9. Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  The red light transmitted through the first dichroic prism 9 is reflected by the second dichroic prism 10 that transmits green band light and reflects red band light. Thereafter, the light passes through the quarter-wave plate 12R and enters the reflective image display element 13R. When the reflective image display element 13 </ b> R displays black, the image is not modulated by the reflective image display element 13 </ b> R but is reflected as P-polarized light, is transmitted through the quarter-wave plate 12 </ b> R, and is reflected by the second dichroic prism 10. Then, the light passes through the first dichroic prism 9. When the light transmitted through the first dichroic prism 9 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4 (e) to FIG. 4 (f), passes through the polarization separation element 7, and passes through the light source. Back to the side. On the other hand, when the reflective image display element 13R displays white, the reflective image display element 13R is image-modulated and reflected by S-polarized light, passes through the quarter-wave plate 12R, and is reflected by the dichroic prism B10. The light passes through the first dichroic prism 9. Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  FIG. 5 is a block diagram of the projection type display apparatus according to the second embodiment. Example 2 is a time-division display device that is associated with two image display elements instead of three image display elements. Since the configuration from the light source 1 to the condenser lens 6 is the same as that of the first embodiment, description thereof is omitted.

  The light that has passed through the condenser lens 6 passes through the color filter 21 and then enters the polarization separation element 7. Since the color filter 21 has the configuration shown in FIG. 6 and is rotated by a rotating unit (not shown), a certain time zone is yellow (red band and green band), and a certain time zone is magenta (red band and blue band). Is incident on the polarization separation element 7. The polarization separation element 7 and the phase difference plate 8 are the same as those in the first embodiment.

  The P-polarized light transmitted through the polarization separation element 7 is incident on the phase difference plate 8, transmits red band light (first color light), and reflects blue and green band light (second color light). The light enters the third dichroic prism 22 having the separation surface 22a.

  When yellow (red and green band) light is incident on the third dichroic prism 22, the green band light (second color light) of the yellow light is reflected by the third dichroic prism 22, and 1 / The light passes through the four-wavelength plate 23BG and enters the reflective image display element 24BG. When the reflective image display element 24BG displays black, the image is not modulated by the reflective image display element 24BG but is reflected as P-polarized light, passes through the quarter-wave plate 23BG, and passes through the third dichroic prism 22. reflect. The role of the quarter wave plate is the same as that of the first embodiment. When the light reflected by the third dichroic prism 22 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4 (e) to FIG. 4 (f) and passes through the polarization separation element 7. Returned to the light source side. When the reflective image display element 24BG performs white display, the image is modulated and reflected by the reflective image display element 24BG into S-polarized light, passes through the quarter-wave plate 23BG, and reflects the third dichroic prism 22. . Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  When yellow light is incident on the third dichroic prism 22, the red light (first color light) transmitted through the third dichroic prism 22 is transmitted through the quarter-wave plate 23R, and the reflective image display element 24R. Is incident on. When the reflective image display element 24R displays black, the image is not modulated by the reflective image display element 24R but is reflected as P-polarized light, and passes through the quarter-wave plate 23R and the third dichroic prism 22. When the light transmitted through the third dichroic prism 22 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4E to FIG. Back to the side. When the reflective image display element 24 </ b> R displays white, the reflective image display element 24 </ b> R is image-modulated and reflected by the S-polarized light and passes through the quarter-wave plate 23 </ b> R and the third dichroic prism 22. Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  When magenta (red and blue band) light is incident on the third dichroic prism 22, the blue band light (second color light) of the magenta light is reflected by the third dichroic prism 22, and 1 / The light passes through the four-wavelength plate 23BG and enters the reflective image display element 24BG. When the reflective image display element 24BG displays black, the image is not modulated by the reflective image display element 24BG but is reflected as P-polarized light, passes through the quarter-wave plate 23BG, and is reflected by the third dichroic prism 22. Reflected. When the light reflected by the third dichroic prism 22 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4 (e) to FIG. 4 (f) and passes through the polarization separation element 7. Returned to the light source side. When the reflective image display element 24BG performs white display, the image is modulated and reflected by the reflective image display element 24BG into S-polarized light, passes through the quarter-wave plate 23BG, and reflects the third dichroic prism 22. . Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  When magenta light is incident on the third dichroic prism 22, the red light (first color light) transmitted through the third dichroic prism 22 is transmitted through the quarter-wave plate 23R, and the reflective image display element 24R. Is incident on. When the reflective image display element 24R displays black, the image is not modulated by the reflective image display element 24R but is reflected as P-polarized light, and passes through the quarter-wave plate 23R and the third dichroic prism 22. When the light transmitted through the third dichroic prism 22 passes through the phase difference plate 8, the polarization direction changes as shown in FIG. 4E to FIG. Back to the side. When the reflective image display element 24 </ b> R displays white, the reflective image display element 24 </ b> R is image-modulated and reflected by the S-polarized light and passes through the quarter-wave plate 23 </ b> R and the third dichroic prism 22. Thereafter, the light passes through the phase difference plate 8, is reflected by the polarization separation element 7, and is displayed on the projection surface via the projection lens 14.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, the image display element is not limited, and the second retardation plate is not limited to a quarter wavelength plate. The color separation means is not limited to a dichroic prism such as a dichroic mirror.

  The projection display device can be applied to a liquid crystal projector.

7 ... polarization separation element (polarization separation means), 8 ... phase difference plate (first phase difference plate), 9 ... first dichroic prism (first color separation means), 9a ... first color separation surface, 13G, 13R, 13B ... reflective liquid crystal display element (image modulation element), 14 ... projection lens (projection means)

Claims (7)

An image modulation element that modulates and reflects color light; and
Polarization separation means for transmitting the first polarized light and reflecting the second polarized light orthogonal to the first polarized light;
First color separation means having a first color separation surface that transmits first color light and reflects second color light having a wavelength region different from that of the first color light;
A first retardation plate disposed between the polarization separation means and the color separation means;
Have
The optical axis of the first retardation plate is in a plane including both the normal line of the first color separation surface of the first color separation means and the normal line of the incident / exit surface of the image modulation element. And an optical system which is inclined with respect to a normal line of the incident / exit surface of the image modulation element.   The optical system according to claim 1, further comprising a second retardation plate disposed between the first color separation unit and the image modulation element.   The optical system according to claim 2, wherein the second retardation plate is a ¼ wavelength plate. Second color separation means having a second color separation surface that transmits third color light and reflects fourth color light having a wavelength region different from that of the third color light;
2. The normal line of the first color separation surface of the first color separation unit and the normal line of the second color separation surface of the second color separation unit are parallel to each other. 4. The optical system according to any one of items 3 to 3.   The polarization separation means has a polarization separation surface, wherein the first polarized light is P-polarized light and the second polarized light is S-polarized light with respect to the polarization separation surface. The optical system according to any one of claims 1 to 4.   The polarization separation unit reflects the second polarized light modulated and reflected by the image modulation element to a projection unit, and the projection unit projects the second polarized light onto a projection surface. The optical system according to any one of claims 1 to 5.   A projection display device comprising the optical system according to claim 1.