JP4736550B2 - Optical device and projection display apparatus using the same - Google Patents

Description

  The present invention relates to an optical device in which a reflective spatial light modulator and a peripheral optical member of the reflective spatial light modulator are integrated, and a projection display apparatus using the optical device.

  The color projection display device decomposes R (red), G (green), and B (blue) color lights related to the three primary color lights from a white light source and leads them to the corresponding spatial light modulation elements. Color light modulated according to the video signal is synthesized and projected to display a color video on the screen.

  In the above-described color projection display device, in a projection display device using a reflective spatial light modulation element, the decomposed color light is incident on the reflective spatial light modulation element to modulate the light, and the modulated color light is synthesized. And an optical system formed by combining a plurality of polarizing beam splitters.

  In the projection display device using this reflective spatial light modulation element, there is a problem that shading (color unevenness) occurs due to birefringence in the optical path of a polarizing beam splitter or other optical components. That is, the temperature of the glass rises when the light from the light source is irradiated onto the glass constituting the polarizing beam splitter, and the resulting distortion causes optical anisotropy and birefringence. In order to solve the problem, it has been proposed to use a glass having a small photoelastic coefficient for a polarizing beam splitter (see, for example, Patent Document 1).

  In addition, in a projection display device using a reflective spatial light modulation element, in order to achieve high contrast, normally two or more polarization beam splitters act on one spatial light modulation element. The optical configuration of the type projection display device was complicated. Therefore, by arranging four polarizing beam splitters between two ceramic bases at a close distance and fixing them to form an optical system, three polarized light beams are formed for one reflective spatial light modulator. While a beam splitter is operated, a device that has a relatively simple optical configuration and can realize a high-contrast projection display device has been proposed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 9-054213 Japanese Patent Laid-Open No. 2004-070202

By the way, in the proposal of patent document 1, it is disclosed that glass with a small photoelastic coefficient is used for a polarization beam splitter. Specifically, for incident light with a wavelength of 0.4 μm to 0.7 μm, it is composed of a member made of a translucent material whose absolute value of the photoelastic constant is 1.5 × 10 −8 cm ² / N or less. Is. However, even in these configurations, since the photoelastic coefficient is not 0, there remains a problem that shading occurs.

The proposal of Patent Document 2 adopts a structure in which four optical members such as a polarizing beam splitter are sandwiched between ceramic bases. Therefore, even if the thermal expansion coefficients of the polarizing beam splitter and the ceramic base are configured as approximate values as much as possible, there is a problem that stress is easily generated and shading remains due to the sandwiched structure.
Furthermore, since the sheet metal member that holds the reflective spatial light modulation element has a structure of iron and stainless steel, there is a problem in that it is distorted when exposed to a temperature change due to long-time irradiation from a light source, and the registration changes. It was.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an optical device that can reduce the occurrence of shading and registration changes and obtain high image quality, and a projection display apparatus using the optical device. And

In order to solve the above-mentioned problems, the present invention comprises means described in the following 1) to 3).
That is,
1) Aluminum base (1), glass base (2a) fixed on the aluminum base (1), two glass spacers (2b) fixed on the glass base, and two triangular prisms A polarizing beam splitter in which glass prisms having a shape are bonded to each other through a polarization separating thin film surface, and two first and fourth polarizing beam splitters (the bottom surfaces of the triangles of the glass prism are fixed on a glass base) 102, 105) and two triangular prism-shaped glass prisms are bonded to each other through a polarization separation thin film surface, and are second and third polarizing beam splitters smaller than the first and fourth polarizing beam splitters. , triangular base of the second and third of the glass prisms of the polarization beam splitter is secured to the Garasusupe Sa, the first and The center in the height direction of the four polarizing beam splitters and the center in the height direction of the second and third polarizing beam splitters are substantially coincided with each other and are disposed adjacent to the first and fourth polarizing beam splitters. The second and third polarizing beam splitters (103, 104), and reflective spatial light modulators (161, 162, 163) disposed on the side surfaces of the second and third polarizing beam splitters, An optical device for a projection display device.
2) In the optical device for a projection display device according to 1),
A first support member (4a) fixed to the upper surface of one glass prism of the second and third polarizing beam splitters (103, 104), and a second support member fixed to the first support member. A support member (5), a third support member (4b) fixed to the bottom surface of one of the glass prisms of the second and third polarizing beam splitters, and one end of the second support member One end of the fourth support member (6) at the one end on the opposite side of the other end to which the first support member and the second support member are fixed And the other end is fixed to the third support member, and the fourth support member (6) holding the reflective spatial light modulator is provided, The thermal expansion coefficient of the second support member is the thermal expansion coefficient of the fourth support member. Optical device for a projection display device characterized by greater than coefficients.
3) A projection display device characterized by using the optical device for a projection display device according to 1) or 2) in a color separation / synthesis optical system.

According to the optical device of the present invention and the projection display apparatus using the optical device, a plurality of polarizing beam splitters having different cross-sectional heights orthogonal to the optical axis are arranged on the glass base. In addition, a small polarizing beam splitter is formed by laminating a glass plate made of the same material on the glass base and arranging the optical axis so as to match the position required for the design. By using the glass plate, the effect of thermally blocking from the metal base is obtained.
That is, the stress is reduced as much as possible by fixing all the polarization beam splitters on the glass material. This produces an effect that shading is reduced.
Further, by matching the linear expansion coefficient of the fixing member of the optical component, the difference in thermal expansion when the temperature of the environment changes is reduced, and as a result, distortion is reduced, so that the registration is stabilized. .

  Hereinafter, the best mode for carrying out the invention of an optical device according to the present invention and a projection display apparatus using the same will be described with reference to preferred embodiments.

  FIG. 1 shows a schematic configuration diagram of an optical device applied to this embodiment. The optical device 30 includes first, second, and third polarizing beam splitters 102, 103, and 104 that function as a cubic or prismatic polarization separation element in which two right triangular prisms are bonded via a polarization separation surface. A fourth polarization beam splitter 105 that functions as a polarization beam combiner is arranged such that its polarization separation surfaces 121, 131, 141, and 151 as a whole are substantially X-shaped. Further, although not shown, the light transmitting surface (the upper side surface of the first polarizing beam splitter) on the incident side of the first polarizing beam splitter 102 has a function of rotating the polarization planes of the R light and the G light by 90 degrees. The first color polarizer is provided between the first and second polarization beam splitters 102 and 103 with a second color polarizer having a function of rotating the polarization plane of the G light by 90 °. Further, a third color polarizer having a function of rotating the polarization plane of the R light by 90 ° is provided between the second and fourth polarizing beam splitters 103 and 105, and the third and fourth polarizing beam splitters 104 and 105. A fourth color polarizer having a function of rotating the polarization plane of the B light by 90 ° is provided in between.

The optical device 30 applied to this embodiment operates as follows. Although described with reference to FIG. 2, main optical components are extracted for easy understanding.
Indefinitely polarized white light emitted from a light source (not shown) is incident on the integrator optical system. Then, the white light is made uniform and aligned with the S-polarized light and enters the first color polarizer. Since the first color polarizer is wavelength selective polarization conversion means for rotating the planes of polarization of the R light and the G light by 90 °, the S polarization according to the R light and the G light transmitted through the first color polarizer. Is converted to P-polarized light. Further, since the first color polarizer has no effect on the B light, they remain S-polarized light.
Hereinafter, the transition of the optical path and the plane of polarization of each color light will be described individually.

  First, the P-polarized G light that has passed through the first color polarizer travels straight through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the second color polarizer (not shown). Since the second color polarizer is wavelength-selective polarization conversion means for rotating the polarization plane of the G light by 90 °, the P-polarized light related to the G light transmitted through the second color polarizer is converted to S-polarized light. The S-polarized G light transmitted through the second color polarizer is incident on the second polarization beam splitter 103, reflected by the polarization separation surface 131 of the second polarization beam splitter 103, and emitted from the light transmission surface 103a. The light enters the reflective spatial light modulator 161 corresponding to G. Then, the reflection type spatial light modulation element 161 receives light modulation according to the video signal corresponding to G and reflects the light.

  The P-polarized component of the G light generated by the light modulation travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and enters a third color polarizer (not shown). The third color polarizer is a wavelength-selective polarization converter that rotates the polarization plane of the R light by 90 °, and therefore does not act on the G light and the P-polarized component of the G light is transmitted as P-polarized light. It goes straight and enters the fourth polarization beam splitter 105. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the R light will be described. The P-polarized R light transmitted through the first color polarizer passes straight through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the second color polarizer. Since the second color polarizer is a wavelength-selective polarization conversion unit that rotates the polarization plane of the G light by 90 °, it does not act on the R light, and the R light remains P-polarized and the second polarized beam. The light enters the splitter 103. The P-polarized R light incident on the second polarization beam splitter 103 travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and exits from the light transmission surface 103b to be reflected in R-type spatial light. The light enters the modulation element 162. Then, the reflection type spatial light modulation element 162 receives the light modulation corresponding to the video signal corresponding to R and is reflected.

  The S-polarized component of the R light generated by the light modulation is reflected by the polarization separation surface 131 of the second polarization beam splitter 103 and enters the third color polarizer. Since the color polarizer is wavelength selective polarization conversion means for rotating the polarization plane of the R light by 90 °, the S polarization component of the R light is converted into P polarization and incident on the fourth polarization beam splitter 105. . Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the B light will be described. Since the first color polarizer does not act on the B light, the B light remains as S-polarized light. Therefore, the S-polarized B light is reflected on the polarization separation surface 121 of the first polarization beam splitter 102. It is reflected and enters the third polarization beam splitter 104.

  The S-polarized B light is reflected by the polarization separation surface 141 of the third polarization beam splitter 104, exits from the light transmitting surface 104 d, and enters the B-type reflective spatial light modulator 163. Then, the reflection type spatial light modulation element 162 receives light modulation according to the video signal corresponding to B and is reflected.

  The P-polarized component of the B light generated by the light modulation passes through the polarization separation surface 141 of the third polarization beam splitter 104 and enters the fourth color polarizer. Since the color polarizer is a wavelength-selective polarization conversion unit that rotates the polarization plane of the B light by 90 ° as described above, the P-polarized component of the B light is converted into the S-polarized light, and the fourth polarizing beam splitter 105. Is incident on. Then, the light is reflected by the polarization separation surface 151 of the fourth polarization beam splitter 105, passes through the light transmission surface 105 c of the fourth polarization beam splitter 105, and exits from the projection lens 130.

  The configuration of the optical device 30 will be described in detail with reference to FIG. For the sake of explanation, the first polarizing beam splitter 102, the fourth polarizing beam splitter 105, and the reflective spatial light modulation element 161 corresponding to G are focused. As shown in the figure, a glass plate 2 a is laminated on an aluminum base 1, and a first polarizing beam splitter 102 and a fourth polarizing beam splitter 105 made of glass are disposed thereon. Blue plate soda glass is used for the glass plate.

  Table 1 shows the thermal conductivity (unit: w / mK) of various materials. Since aluminum has a high thermal conductivity, when it is in direct contact, the glass on the aluminum side is cooled by heat conduction, and each polarization beam splitter is cooled asymmetrically in the vertical direction. Therefore, birefringence is likely to occur. Therefore, the shading problem occurs for the reason described above. Therefore, as described later, a glass having a low thermal conductivity and the same thermal expansion coefficient as that of each polarizing beam splitter is sandwiched between each polarizing beam splitter and the aluminum base 1.

  The thermal conductivity of the optical glass is in the range of 0.546 to 1.126 (w / mK). It can be seen that the optical glass has a thermal conductivity of about 1/200 that of a metal such as aluminum, and the thermal conductivity is the smallest compared with ceramics such as alumina, silicon nitride, and ALN.

  The four polarizing beam splitters have different dimensions. Specifically, large polarizing beam splitters 102 and 105 are used for the optical path with a large illumination area, and small polarizing beam splitters 103 and 104 are used for the optical path with a small illumination area. This is because the illumination light from the light source is converged toward the effective pixel area of the reflective spatial light modulation element, and the modulated light having a cone angle diffuses toward the projection lens. Because. That is, in the polarization beam splitters 103 and 104 to which the reflection type spatial light modulation elements are attached, it is only necessary to have a size corresponding to the effective pixel area of the reflection type spatial light modulation elements. The polarizing beam splitters 102 and 105 installed on the projection lens side require a larger size.

  At this time, if the size of the larger one is unified, when light from a small illumination area is irradiated onto a large polarizing beam splitter, there will be places in the glass where light is irradiated and where light is not irradiated, resulting in uneven temperature rise. However, since the birefringence easily occurs, the size is set according to the optical path.

  The small polarizing beam splitters 103 and 104 are arranged by laminating the glass plate 2b made of the same material on the glass plate 2a and aligning the optical axes. Since each polarizing beam splitter is not placed directly on the aluminum base 1 and is interposed through the glass plates 2a and 2b, an effect of thermally blocking the aluminum base 1 is obtained.

  Moreover, the stress is reduced as much as possible by fixing each polarization beam splitter on the glass plate. As the glass plates 2a and 2b, soda glass is used. As will be described later, the thermal expansion coefficients of the glass plates 2a and 2b of the optical glass and the thermal expansion of the glass of the polarizing beam splitter are almost equal values, and the stress is reduced as much as possible.

The upper and lower surfaces of the polarization beam splitter 103, a first support member and is L-shaped Rejibesu 4a respectively, Rejibesu 4b of the third L-shaped as a supporting member is bonded. Two guide pins 4b1 are provided at the lower part of the lower registration base 4b. A focus adjuster 5 that is a second support member formed of a brass member is screwed to the upper registration base 4a. The focus adjuster 5 has two pin holes for receiving the guide pins 61.

Here, the registration bases 4 a and 4 b are fixed only to the right triangular prism 1030 on one side of the two right triangular prism glasses constituting the polarizing beam splitter 103. When the two right triangular prism glasses 1030 and 1031 are fixed to each other, the two right triangular prism glasses 1030 and 1031 expand differently due to the difference in the heating situation of the two right triangular prism glasses, and thus there is much distortion. Because it becomes.
That is, the polarization beam splitter 103 selectively reflects light by the polarization separation surface 131, so that the amounts of light passing through the two right triangular prism glasses 1030 and 1031 are different.

  The reflective spatial light modulator 161 is assembled by a reflective liquid crystal element 13, an aperture assembly 11, an aperture packing 12, a wave plate holder 9, a top packing 8, and a top plate 7. The aperture assembly 11 is an opening for irradiating light only to the portion corresponding to the pixel of the reflective liquid crystal. The aperture packing 12 prevents entry of dust or the like. The wave plate holder holds the wave plate 10. The top packing 8 is in contact with the polarizing beam splitter 103 on the side of the loose packing, and is provided to seal around the reflective liquid crystal element 13 and prevent dust from entering. The top plate 7 is for holding these assemblies.

The reflective spatial light modulator 161 adjusts the focus and registration of the screen while projecting an image using a registration and focus adjustment system.
The focus is set by adjusting the two guide pins 61 standing on the upper side of the registration plate 6 as the fourth support member and the two guide pins 4b1 standing on the lower registration base 4b. 5 is passed through the two pin holes at the bottom of the registration plate 6, and an adhesive is injected into the pin hole in a focused state, and the stud and the pin hole are bonded and fixed.

  Registration is set as follows. First, the top plate 7 is brought into contact with the registration plate 6 (sliding the position is shifted) so that the registration of the three colors is matched. While maintaining this state, the top plate 7 and the registration plate 6 are fixed by injecting an adhesive into the registration plate upper hole and the top plate lower hole.

  The focus adjuster 5 is provided in order to adjust the variation in the mounting pitch between the two upper and lower guide pins 61 and 4b1.

  Next, conventionally, a sheet metal member for holding an element has a structure of iron and stainless steel. That is, the registration bases 4a and 4b are made of iron, and the members of the registration plate 6, the top plate 7, and the aperture assembly 11 are disposed in the vicinity of the reflective liquid crystal element 13, and therefore SUS (stainless steel) from the viewpoint of rust prevention performance and processing accuracy. ) Was used.

Table 2 compares the thermal expansion coefficients of various materials. Various optical glasses have substantially the same thermal expansion coefficient regardless of their compositions. However, it can be seen that the thermal expansion coefficient of the metal material is larger than that of the glass material, and the value varies depending on the metal type.
It has been clarified that the conventional structure and its material have the following problems regarding the thermal expansion coefficient. (In the following discussion, the coefficient of thermal expansion is in units of (* 10-6 / K).)

  In FIG. 3, focusing on the thermal expansion coefficients of the polarizing beam splitter 103, the upper and lower registration bases 4a and 4b attached thereto, and the focus adjuster 5, the thermal expansion coefficients of the glass of the polarizing beam splitter 103 and the blue plate float glass 2a and 2b are as follows. Both are approximately equal to about 8.1. The thermal expansion coefficient of the registration bases 4a and 4b is 12.1.

On the other hand, the thermal expansion coefficient of the members of the registration plate 6, the top plate 7 and the aperture assembly 11 provided to mount the reflective liquid crystal element 13 so as to face them is 17.3.
That is, the average thermal expansion coefficient of the members (glass, iron) existing on the polarizing beam splitter side is “a value between 8.1 and 12.1”, whereas the registration plate 6 existing on the reflective liquid crystal element 13 side. The coefficient of thermal expansion of the members of the top plate 7 and the aperture assembly 11 is 17.3. There is a difference in coefficient of thermal expansion of about 7 between the two.

Therefore, the coefficient of thermal expansion on the polarizing beam splitter 103 side is smaller than the coefficient of thermal expansion on the registration plate 6 side, and as a result, there is a problem that distortion occurs when exposed to temperature changes for a long time and registration changes. It was revealed.
That is, in such a state, when a change in temperature occurs after adjusting the focus and registration of the screen to match the registration of the three color screens, the registration shift (three-color registration Phenomenon). For example, when the temperature rises, the registration plate 6 on the reflective liquid crystal element 13 side expands compared to the polarizing beam splitter 103 side. Conversely, when the temperature is lowered, the registration plate 6 on the reflective liquid crystal element 13 side relatively contracts. As the heat stress accumulates, the position of the reflective liquid crystal element 13 with respect to the polarization beam splitter 103 may be slightly shifted. The deviation becomes a phenomenon of registration deviation when the directions of deviation do not coincide in each polarization beam splitter corresponding to light of three colors.

  Therefore, in this embodiment, the linear expansion coefficient on the structure is matched to reduce the distortion and stabilize the registration. As a means for achieving this object, the focus adjuster 5 is changed from iron material to brass.

  The thermal expansion of brass applied to this embodiment is 20. As a result, the average coefficient of thermal expansion of the members (glass, iron, brass) existing on the polarizing beam splitter 103 side was “a value between 8.1 and 12.1”. The thermal expansion coefficient of the plate 6 etc. approaches 17.1. As a result, the difference in thermal expansion when the temperature of the environment changes is reduced, so that distortion is reduced and as a result, registration displacement is reduced.

  In the experiment, the registration deviation after 10 times of “−20 degrees → 70 degrees heat cycle” was reduced from a maximum of 0.5 pixels to 0.3 pixels in the present embodiment.

  As described above, the use of a brass adjuster as the focus adjuster achieves uniform linear expansion, reduces distortion, and achieves the effect of stabilizing registration.

  The schematic block diagram of the projection display apparatus applied to a present Example is demonstrated using FIG. In the projection display device 50, an optical device 30, a mirror 51, and a screen 52 are installed in an exterior cabinet 53. The R light, G light, and B light emitted from the light transmitting surface 105 c of the fourth polarization beam splitter 105 of the optical device 30 are transmitted through the projection lens 130, reflected by the mirror 51, and enlarged to display a color image on the screen 52. .

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the optical device applied to a present Example is shown. 1 is a main schematic configuration diagram of an optical device applied to the present embodiment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic assembly diagram for explaining an optical device applied to this embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The schematic for demonstrating the optical device applied to a present Example is shown. BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the projection display apparatus applied to a present Example is shown.

Explanation of symbols

30 ... Optical device 1 ... Aluminum base 5 ... Focus adjuster 6 ... Registration plate 7 ... Top plate 11 ... Aperture assembly 13 ... Reflective liquid crystal elements 161, 162, 163 ... Reflective spatial light modulators 102, 103, 104, 105 ... Polarization beam splitters 121, 131, 141, 151...
1030, 1031 ... right triangular prism glass 50 ... projection display device 53 ... exterior cabinet 51 ... mirror 52 ... screen

Claims (3)

An aluminum base,
A glass base fixed on the aluminum base;
Two glass spacers fixed on the glass base;
A polarizing beam splitter in which two triangular prism-shaped glass prisms are bonded to each other via a polarization separation thin film surface, and two first and fourth polarized light beams each having a triangular bottom surface fixed on a glass base. A beam splitter,
Two triangular prism-shaped glass prisms are bonded to each other through a polarization separation thin film surface, and the second and third polarization beam splitters are smaller than the first and fourth polarization beam splitters. 3 of triangular base of the glass prisms of the polarization beam splitter, fixed to said Garasusupe Sa, the first and fourth said height direction of the center of the polarization beam splitter of the second and third polarization beam splitter The second and third polarizing beam splitters, the height direction centers of which are substantially coincident with each other and disposed adjacent to the first and fourth polarizing beam splitters;
A reflective spatial light modulator disposed on a side surface of the second and third polarizing beam splitters;
An optical device for a projection display device. A first support member fixed to the upper surface of one of the glass prisms of the second and third polarizing beam splitters;
A second support member fixed to the first support member;
A third support member fixed to the bottom surface of one of the glass prisms of the second and third polarizing beam splitters;
A fourth end of the second support member is located at one end of the second support member, which is on the opposite side of the other end to which the first support member and the second support member are fixed. The support member has one end fixed, the other end fixed to the third support member, and the fourth support member holding the reflective spatial light modulator; With
The optical device for a projection display device according to claim 1, wherein a thermal expansion coefficient of the second support member is larger than a thermal expansion coefficient of the fourth support member.     A projection display device, wherein the optical device for a projection display device according to claim 1 or 2 is used in a color separation / synthesis optical system.

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