JP2000171770A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of contrast caused by black float and to obtain a high-quality display picture by forming a polarizing beam splitter of a member whose parameter value showing double refraction amount by thermal stress is equal to or under a specified value. SOLUTION: The polarizing beam splitter is formed of the member satisfying relation shown by an expression: 5.00×102>=K.α.E.∫(1-T)dλ/ρ/Cp. In the expression, K means the photoelastic constant (nm/mm.mm2/N) of the member, αmeans the linear expansion coefficient(10-6/K) of the member and E means the Young's modulus (103 N/mm2) of the member, and λ means the wavelength (mm) of illuminating light. T means the internal transmissivity of the member in the wavelength λ, ρ means the specific gravity (g/cm3) of the member, and Cp means the specific heat (J/g.k) of the member. An integration range in the expression is the range of the main light absorption wavelength band (420 nm to 500 nm) of the member. Thus, even when the double refraction is increased because temperature rises and the stress is increased, the increase degree thereof is restricted to a useful range in practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device, and can be applied to, for example, a projector device for projecting image light spatially modulated by a reflection type liquid crystal panel onto a screen. According to the present invention, by forming a polarizing beam splitter or the like using a member having a value of a birefringence amount due to thermal stress of 5.00 × 10 ² or less, it is possible to prevent a decrease in contrast due to black floating and to achieve high quality display. Be able to display images.

[0002]

2. Description of the Related Art Conventionally, in a projection type display device, spatially modulated image light is generated using a reflection type liquid crystal panel, and the image light is projected on a screen so that a desired color image can be formed. What was done is proposed.

FIG. 6 is a schematic diagram showing this type of projection display device. In the projection display device 1,
The light source 2 includes, for example, a discharge lamp 3 and a reflector 4, and emits illumination light of white light. Convex lens 5
Converts the illumination light emitted from the light source 2 into a substantially parallel light flux and emits it.

The color separation mirror 6 reflects the illumination light of a predetermined wavelength and transmits the remaining illumination light on the optical path of the illumination light emitted from the convex lens 5. Color separation mirror 7
Reflects the illumination light of a predetermined wavelength on the optical path of the illumination light reflected by the color separation mirror 6 and transmits the remaining illumination light. Thus, the projection display apparatus 1 separates the illumination light emitted from the light source 2 into blue, red, and green illumination lights.

The lens 8, the mirror 9, and the lens 10 bend the optical path of the illumination light transmitted through the color separation mirror 6 and guide the illumination light to the polarization beam splitter 11. Polarizing beam splitter 1
1 emits illumination light of a predetermined polarization plane out of the illumination light incident from the lens 10 toward the reflective liquid crystal panel 12, and transmits illumination light of a polarization plane orthogonal to the polarization plane.
Further, the polarizing beam splitter 11 is used for the reflection type liquid crystal panel 1.
The illumination light is spatially modulated in 2 and transmits a predetermined polarization component of the image light emitted to be emitted to the color combining prism 13.

Similarly, the polarization beam splitter 14 emits illumination light of a predetermined polarization plane out of the illumination light reflected by the color separation mirror 7 toward the reflection type liquid crystal panel 15, and a polarization plane orthogonal to the polarization plane. Illuminating light. The polarization beam splitter 14 spatially modulates the illumination light by the reflective liquid crystal panel 15 and transmits a predetermined polarization component of the image light emitted to the color combining prism 13.

Similarly, the polarization beam splitter 16 emits illumination light having a predetermined polarization plane out of the illumination light transmitted through the color separation mirror 7 toward the reflection type liquid crystal panel 17, and a polarization plane orthogonal to the polarization plane. Illuminating light. The polarization beam splitter 16 spatially modulates the illumination light by the reflective liquid crystal panel 17 and transmits a predetermined polarization component of the image light emitted to the color combining prism 13.

In this case, the reflection type liquid crystal panel 12,
In 15 and 17, the driving of a driving circuit (not shown) spatially modulates the illuminating light in accordance with each color signal corresponding to the wavelength of the illuminating light to be incident, and converts image light obtained by rotating a polarization plane with respect to the illuminating light. Polarization beam splitter 11,
The light is emitted toward 14 and 16.

The color synthesizing prism 13 synthesizes and emits the image light incident from the polarization beam splitters 11, 14 and 16, and the projection lens 19 adjusts the color synthesizing prism 1
The image light emitted from 3 is projected on the screen 20.
As a result, in the projection display device 1, the images formed by the reflective liquid crystal panels 12, 15, and 17 are enlarged and projected on the screen 20, so that a desired color image can be displayed.

[0010]

By the way, in this type of projection type display device 1, black is displayed with white floating (so-called black floating), and the contrast is sufficiently ensured in the displayed image on the screen. There was a problem that could not be done.

That is, the polarizing beam splitter is formed by bonding the inclined surfaces of the right-angle prisms, and detects the incident light by laminating a dielectric film on the bonded surface. Therefore, in the transmitted light and the reflected light of the polarization beam splitter, linearly polarized light due to this detection should be emitted.

However, the glass material constituting this kind of right-angle prism has a birefringent property, whereby reflected light and transmitted light which are originally emitted as linearly polarized light are emitted as elliptically polarized light. That is, in the reflected light and the transmitted light, light having a polarization plane orthogonal to the intended polarization plane is included. In addition, light incident by linearly polarized light is analyzed by elliptically polarized light, and a portion of light that is originally transmitted or reflected is reflected or transmitted by the opposite way and emitted. .

[0013] Looking at this with respect to the image light emitted from each reflection type liquid crystal panel toward the polarization beam splitter,
In a reflective liquid crystal panel, incident light on a predetermined polarization plane is spatially modulated, and image light is reflected as a combined light of a P-polarized component and an S-polarized component. The image light emitted in this way is
Originally, the P-polarized light component and the S-polarized light component are separated by the polarization beam splitter, and only the image light of the P-polarized light component is projected on the screen. However, the image light becomes elliptically polarized light due to the birefringence of the polarizing beam splitter, and as a result, a part of the S-polarized light component that is not spatially modulated is projected on the screen.

Further, regarding the illumination light emitted from the polarizing beam splitter toward the reflection type liquid crystal panel, the illumination light of a predetermined polarization plane spatially modulated by the reflection type liquid crystal panel is compared with the illumination light of a polarization plane orthogonal to the predetermined polarization plane. The components leak, and the leaked illumination light is directly projected on the screen.

If such black floating occurs unevenly, the projection type display device 1 causes
Uniformity will be degraded.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a projection display device capable of displaying a high-quality display image with improved contrast.

[0017]

According to the present invention, there is provided a polarizing beam splitter having a configuration of 5.00.
× 10 ² ≧ K · α · E · ∫ (1-T) dλ / ρ / Cp

Further, the polarizing beam splitter and / or the dichroic prism are made of a member satisfying the relational expression.

In a member that satisfies the above relationship, even if the birefringence increases due to an increase in temperature and an increase in stress, the degree of the birefringence can be kept within a practically sufficient range. As a result, the floating of black due to birefringence can be reduced, and accordingly, the contrast can be improved and a high-quality display image can be displayed.

[0020]

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

(1) First Embodiment (1-1) Overall Configuration of First Embodiment FIG. 1 is a schematic diagram showing a projection type display apparatus according to a first embodiment of the present invention. It is. In the projection display device 30, the light source 31 is configured by arranging a xenon lamp 32 on a reflector 33, which is a substantially parabolic mirror, and illuminating white light emitted from the xenon lamp 32 with an opening of the reflector 33. It emits more. In the light source 31, a pair of fly-eye lenses 34A and 34B are arranged on the optical path of the illumination light, thereby making the light amount distribution of the illumination light uniform.

Further, in the light source 31, a polarization plane conversion sheet 35 is disposed between the fly-eye lenses 34A and 34B. Here, the polarization plane conversion sheet 35 is a reflection type liquid crystal panel 36B, 36R in the projection type display device 30,
36G mainly selectively transmits an S-polarized light component, which is a polarized light that can be spatially modulated effectively, and has a P
It is an optical element that converts a polarization component into an S-polarization component.

As a result, the light source 31 is connected to the xenon lamp 3
2 for illumination light emitted by various polarization planes,
A polarized light component effective for image display is increased, and a polarized light component orthogonal to the polarized light component is reduced to emit the illumination light, thereby improving the utilization efficiency of the illumination light and improving the contrast of the displayed image.

The convex lens 37 is a fly-eye lens 34B
The illumination light is condensed and emitted on the optical path of the emitted illumination light, and the mirror 38 bends the optical path of the illumination light emitted from the convex lens 37 by 90 degrees and emits it. The convex lens 39 condenses and emits the illumination light reflected by the mirror 38.

The polarizing beam splitter 41 selectively reflects an S-polarized component effective for displaying an image and selectively transmits a P-polarized component orthogonal to the S-polarized component. Accordingly, the polarizing beam splitter 41 reflects most of the illumination light incident from the convex lens 39 and folds the optical path by 90 degrees, whereas the reflective liquid crystal panel 3 that follows the optical path in reverse.
With respect to image light by P-polarized light and S-polarized light from 6B, 36R, and 36G, the P-polarized light component is selectively transmitted.

The dichroic mirror 42B is formed by laminating a transparent dielectric film on a plate glass, and selectively reflects a predetermined wavelength component of incident light and selectively transmits the remaining component. Is configured. The dichroic mirror 42B selectively reflects the illumination light component in the blue band out of the illumination light emitted from the polarization beam splitter 41, emits it toward the reflective liquid crystal panel 36B, and transmits the remaining components.

The reflection type liquid crystal panel 36B is driven by a blue color signal to form a blue image among the images displayed by the projection display device 30. The reflection type liquid crystal panel 36B transmits the illuminating light incident from the dichroic mirror 42B, reflects the light from the reflection plate disposed on the back surface, transmits the illuminating light again, and emits the light, thereby rotating the polarization plane according to the blue image. And emits modulated light. Thereby, the reflection type liquid crystal panel 36B emits the image light by the combined light of the P-polarized light and the S-polarized light to the dichroic mirror 42B with respect to the illuminating light incident by the S-polarized light.

The dichroic mirror 42B selectively reflects the modulated light incident from the reflective liquid crystal panel 36B and emits the modulated light to the polarization beam splitter 41, and transmits the modulated light incident from the subsequent dichroic mirror 42R. And exits to the polarization beam splitter 41.

As described above, in the dichroic mirror 42B that selectively reflects only the incident light having a desired wavelength, the cutoff wavelength at which the S-polarized light component and the P-polarized light component that are obliquely transmitted and reflected are selectively changed. Different. On the other hand, in this type of projection display device 30, incident light of the S-polarized component is reflected on the reflective liquid crystal panel 36B, and P-polarized and S-polarized image light incident from the reflective liquid crystal panel 36B. To reflect the polarization beam splitter 41
Out. As a result, if the wavelength of the cut-off for selectively transmitting the S-polarized light component and the P-polarized light component is different, the utilization efficiency of the spectrum is reduced.

However, the difference in the cutoff wavelength between the reflected light of the S-polarized light component and the P-polarized light component is characterized in that it decreases as the incident angle of the incident light decreases. As a result, in the projection display device 30, the dichroic mirror 42B is connected to the optical axis of the incident light and the reflection type liquid crystal panel 36.
B with respect to the optical axis of the incident light so that the angle θ1 with the optical axis of the image light obtained from B becomes smaller than 90 degrees.
It is arranged to be inclined at an angle of 5 degrees. In addition, the reflection type liquid crystal panel 36B is disposed closer to the polarization beam splitter 41 side by that amount, so that the shape of the entire projection display device 30 can be reduced.

The dichroic mirror 42R is formed by laminating a transparent dielectric film on a plate glass, and selectively reflects a predetermined wavelength component of incident light and selectively transmits the remaining component. Is configured. The dichroic mirror 42R selectively reflects the illumination light component of the red band out of the illumination light transmitted through the dichroic mirror 42B and emits it toward the reflective liquid crystal panel 36R.
The remaining components are transmitted and emitted toward the reflective liquid crystal panel 36G.

The reflection type liquid crystal panel 36R is driven by a red color signal to form a red image among the images displayed by the projection display device 30. The reflection type liquid crystal panel 36R transmits the illumination light incident from the dichroic mirror 42R, and then reflects and reflects again by the reflection plate disposed on the back surface and emits it again, whereby the polarization plane is rotated according to the red image. Emit modulated light. As a result, the reflective liquid crystal panel 36R emits image light of P-polarized light and S-polarized light to the dichroic mirror 42R with respect to the illumination light of S-polarized light.

The reflection type liquid crystal panel 36G is driven by a green color signal to form a green image among the images displayed by the projection display device 30. The reflection type liquid crystal panel 36G transmits the illumination light incident from the dichroic mirror 42R, reflects the light from the reflection plate disposed on the back surface, transmits the illumination light again, and emits the light, thereby rotating the polarization plane according to the green image. Emit modulated light. Thereby, the reflection type liquid crystal panel 36G emits the image light by the P-polarized light and the S-polarized light to the dichroic mirror 42R with respect to the illumination light incident by the S-polarized light.

The dichroic mirror 42R selectively reflects the modulated light incident from the reflection type liquid crystal panel 36R and emits the modulated light to the dichroic mirror 42B.
Further, the modulated light incident from the reflective liquid crystal panel 36G is transmitted and emitted to the dichroic mirror 42B.

In the dichroic mirror 42R that combines and emits the green and red modulated lights in this way, the cutoff wavelengths of the reflected lights of the S-polarized component and the P-polarized component are different, and the incident angle of the incident light is reduced. When it gets smaller,
The difference in the cutoff wavelength is reduced accordingly. Thereby, the dichroic mirror 42R is disposed in parallel with the dichroic mirror 42B so that the angle θ2 between the optical axis of the incident light and the optical axis of the video light obtained from the reflective liquid crystal panel 36R is smaller than 90 degrees. Are arranged at an angle of 45 degrees with respect to the optical axis of the incident light. In addition, the reflection type liquid crystal panel 36R has a polarization beam splitter 41 correspondingly.
The projection type display device 30 is arranged close to the side, so that the shape of the entire projection display device 30 can be reduced.

Thus, the polarizing beam splitter 41 is provided to the dichroic mirrors 42B, 42R, etc.
Illuminating light mainly emitted by S-polarized light, and as a result, reflective liquid crystal panels 36B, 36R, 36G
The P-polarized light component of the P-polarized light and the S-polarized light generated by the above is selectively transmitted and emitted toward the screen. The projection lens 45 projects the transmitted light of the polarization beam splitter 41 on a screen 46 in an enlarged manner.

(1-2) Structure of Polarizing Beam Splitter The polarizing beam splitter 41 is formed by bonding the inclined surfaces of a right-angle prism, and a dielectric film is laminated on the bonding surface to analyze incident light. A surface is formed. The polarizing beam splitter 41 is such that the bottom surface of each right-angle prism has a length of 5
0 [mm], thereby forming a square having a length of 50 [mm] on one side as a whole. The polarization beam splitter 41 has a parameter A represented by the following equation.
Is formed of a glass material having a value of 3.71 × 10 ² , whereby birefringence due to thermal stress is reduced.

[0038]

(Equation 3)

Here, K is the photoelastic constant (nm / mm · mm ² / N) of this glass material, α is the linear expansion coefficient (10 ⁻⁶ / K) of this glass material, and E is the Young's modulus of this glass material. Rate (10 ³
N / mm ² ), λ is the wavelength (nm) of the illumination light, and T is the wavelength λ
, Ρ is the specific gravity of this glass material (g / cm ³ ), and Cp is the specific heat of this glass material (J / g · k).
The integration range in the expression (3) is in the range of the light absorption wavelength band (420 [nm] to 500 [nm]) of the glass material.

(1-3) Operation of First Embodiment In the configuration described above, in the projection display device 30, the reflective liquid crystal panels 36B, 36R, and 36G are driven by blue, red, and green color signals, respectively. The images corresponding to the blue, red, and green color signals are respectively reflected on the reflective liquid crystal panel 3.
6B, 36R and 36G. Projection display device 3
0 decomposes the illumination light emitted from the light source 31 into blue, red, and green wavelengths and supplies them to the corresponding reflective liquid crystal panels 36B, 36R, and 36G, respectively, so that these blue, red, and green colors are emitted. The polarization planes of the blue, red, and green illumination lights are rotated according to the image corresponding to the signal to generate image light, and the projection optical system 45 selectively projects the P-polarized component of the image light onto the screen 46. Then, a color display image is projected.

That is, the illuminating light emitted from the light source 31 enters the polarizing beam splitter 41 via the mirror 38, where the reflective liquid crystal panels 36B, 36R, 36
The G component reflects the S-polarized component used to form image light, and is decomposed into blue, red, and green illumination light by the subsequent dichroic mirrors 42B and 42R. These blue, red, and green illumination lights are respectively reflected by the reflective liquid crystal panel 36B,
The blue, red, and green image light is generated by the combined light of the P-polarized light and the S-polarized light and is reflected by 36R and 36G, and the image light enters the polarization beam splitter 41 via the dichroic mirrors 42B and 42R. These modulated lights are
The P-polarized component selectively passes through the polarization beam splitter 41 and enters the projection optical system 45, and is projected on a screen 46 by the projection optical system 45.

At this time, the illumination light enters the dichroic mirrors 42B and 42R obliquely with S-polarized light, and the modulated light obliquely enters the dichroic mirrors 42B and 42R as combined light of P-polarized light and S-polarized light. On the other hand, the dichroic mirrors 42B and 42R have different reflection characteristics with respect to wavelength between the S-polarized light and the P-polarized light, so that the reflection characteristics with respect to the wavelength of the illumination light and the reflection characteristics with respect to the modulated light are different. .

However, in this embodiment, the angle between the optical axis of the illumination light for the dichroic mirrors 42B and 42R and the optical axis of the modulated light incident on each of the dichroic mirrors 42B and 42R is set to be smaller than 90 degrees. Since the dichroic mirrors 42B and 42R are inclined, the difference in the cutoff wavelength between the S-polarized reflected light and the P-polarized reflected light can be reduced. That is, each dichroic mirror 42B, 42
R for reflective liquid crystal panels 36B, 36R, 36G
For blue, red, green illumination light emitted toward
The modulated light by the blue, red, and green P-polarized light corresponding to the illumination light can be emitted toward the projection optical system 45 without any waste, and the utilization efficiency of the illumination light is improved by that much to increase the bright height. A high quality display image can be formed.

In the projection type display device 30, the illumination light by the S-polarized light is spatially modulated in this manner, so that the P-polarized light and the S
A reflective liquid crystal panel 36B that emits light modulated by polarized light;
In 36R and 36G, the component of the image light due to the S-polarized light should be originally separated from the image light due to the P-polarized light and not projected on the screen 46 in the polarization beam splitter 41.

However, when the component of the S-polarized light is transmitted through the right-angle prism constituting the polarization beam splitter 41, the polarization plane of the S-polarized light component changes due to birefringence. The light is analyzed as a component on an analysis surface. Thereby, the projection display device 3
At 0, a part of the S-polarized light component is
And is projected onto the screen 46, and the contrast of the displayed image is reduced accordingly.

The illumination light emitted from the light source 31 is analyzed by the analysis surface of the polarization beam splitter 41, and the P-polarized component is reflected by the reflection type liquid crystal panels 36B, 36R, 36G.
However, at this time, due to the birefringence of the right-angle prism constituting the polarization beam splitter 41, the S-polarized component is mixed with the P-polarized component and emitted, and the S-polarized component is reflected by the reflective liquid crystal panels 36B and 36R. , 36G, is transmitted through the polarizing beam splitter 41 and projected on the screen 46, and the contrast of the displayed image is reduced accordingly.

However, in this embodiment,
The parameter A represented by the equation (3) has a value of 3.71 × 1.
By right-angle prism is formed by 0 ² of the glass material, P-polarized light component increases due to the birefringence, can be kept to practically sufficient range S-polarized light component, reduction in contrast is prevented by that amount black float You.

That is, from the cause of the occurrence of the black floating described above,
If the degree of birefringence can be reduced in the right-angle prism constituting the polarization beam splitter 41, the floating of black can be reduced accordingly. This birefringence occurs due to the stress inside the glass material, and can be determined by using the value of optical path length × photoelastic constant × stress indicating the distortion amount of the glass material as a guide.

Since the photoelastic constant is a constant value according to the glass material, it is considered that this type of black floating can be reduced by managing the photoelastic constant. However, even if the photoelastic constant is reduced, it is difficult to reduce the birefringence by using a glass material having a large stress.

Considering the stress, in this type of glass material, the stress is represented by thermal stress + initial stress + mounting stress. Here, the thermal stress is a stress that is displaced by a rise in the temperature of the glass material, and is generated in the projection display device 30 by a rise in temperature due to heat convection, heat conduction, loss of illumination light, and the like inside the set. The initial stress is a residual stress at the time of forming the polarizing beam splitter 41, a residual stress when the glass material is hardened, a residual stress at the time of cutting out and polishing the glass material, a residual stress at the time of forming the analysis surface, This is caused by shrinkage of the adhesive during bonding. The mounting stress is a stress applied to the polarization beam splitter 41 by disposing the polarization beam splitter 41.

When the power of the projection type display device 30 was turned on while the internal temperature was sufficiently low, and a display image was observed, immediately after the power was turned on, as shown in FIG. However, it was found that black floating increased with time. This indicates that the stress having the greatest effect on birefringence among the stresses represented by thermal stress + initial stress + mounting stress is thermal stress, and the amount of distortion due to this thermal stress is controlled. This indicates that black floating can be sufficiently reduced.

By further studying the thermal stress, the thermal stress can be expressed by physical constants defining the characteristics of this type of glass material, and can be expressed by temperature difference × linear expansion coefficient × Young's modulus. Temperature difference is specific heat, specific gravity,
It can be represented by transmittance.

Taking these factors into consideration, the degree of black floating due to birefringence can be determined from the parameter A according to the relational expression of equation (3).

Actually, a comparison is made between the polarizing beam splitter 41 made of a glass material having a parameter A of 3.71 × 10 ^{2 and} the polarizing beam splitter made of a glass material having a parameter A of 5.44 × 10 ^{2 according to} this embodiment. As a result, as shown in FIG. 2, the parameter A has a value of 5.44 × 1.
0 than ² ones, decrease in contrast by black floating and black level in a few hours is increased is perceived. On the other hand, when the parameter A has a value of 3.71 × 10 ² , it is difficult to perceive a decrease in contrast due to floating of blacks even when used for a long time, and a sufficiently high-quality image can be displayed for practical use. I understood.

By judging these evaluation results comprehensively,
In order to keep the decrease in contrast due to the birefringence of the polarizing beam splitter within a practically sufficient range, if a glass material having a parameter A of 5.00 × 10 ² or less is used in practice, the deterioration of contrast and uniformity is reduced. Projection type display device with a small number can be obtained.

As described above, in the projection type display device 30, a decrease in contrast is prevented in this way, and the fly-eye lens 34A
And 34B, illumination light can be supplied with a uniform amount of light, and accordingly, uneven brightness of a display image can be prevented, whereby a high-quality display image can be displayed.

The fly-eye lenses 34A and 34
By the polarization plane conversion sheet 35 disposed between B and B, the P-polarized light component that is transmitted through the polarization beam splitter 41 and is not used for displaying an image is partially converted into the S-polarized light component and emitted, so that the illumination is reduced accordingly. The use efficiency of light is increased, and the luminance level of the display image is improved, whereby it is possible to display a high-quality display image.

(1-4) Effects of the First Embodiment According to the above configuration, the parameter A indicating the degree of birefringence due to thermal stress represented by the equation (3) is a value of 5.00 × 10 ² or less. By creating a polarizing beam splitter using a glass material having a value of 3.71 × 10 ² , it is possible to keep the reduction in contrast due to floating black in a practically sufficient range, thereby displaying a high-quality display image. can do.

In particular, since there is little change in contrast due to heat, it is possible to obtain stable contrast and uniformity even after long lighting. Further, with respect to an increase in the amount of light accompanying an increase in the luminance of the display screen, the ripening stress characteristics of the material are improved, so that it is possible to easily cope with an increase in the luminance.

(2) Second Embodiment FIG. 3 is a schematic diagram showing a projection display device according to a second embodiment. In this projection display device 50, a dichroic prism 51 is used instead of the dichroic mirrors 42B and 42R in the projection display device 30 described above.
To decompose the illumination light into blue, red, and green illumination light, and synthesize blue, red, and green image light.

Here, in the projection type display device 50, in addition to the polarization beam splitter 41, the dichroic prism 51 is formed using a glass material having a parameter A expressed by the equation (3) with a value of 3.71 × 10 ^2. .

As shown in FIG. 3, even if the dichroic prism 51 is formed using a glass material whose parameter A indicating the degree of birefringence due to thermal stress is 3.71 × 10 ² ,
The same effect as that of the embodiment can be obtained.

(3) Third Embodiment FIG. 4 is a schematic diagram showing a projection type display device according to a third embodiment. In the projection display device 60, a polarization beam splitter 61 having a different polarization plane for transmitting and reflecting from the polarization beam splitter 41 according to the configuration of the above-described first embodiment is arranged. Change the placement of In the projection display device 60, the same components as those of the projection display device 30 described above are denoted by the corresponding reference numerals, and redundant description will be omitted.

That is, in the projection type display device 60, the polarization beam splitter 61 is made of a glass material having a parameter A indicating the degree of birefringence due to thermal stress with a value of 3.71 × 10 ² and transmitting S-polarized light. , P-polarized light. In response to this, the dichroic mirror 42B etc.
It is arranged on the optical path of the illumination light transmitted through the polarization beam splitter 61.

Further, in the projection type display device 60, polarization splitters 62 and 63 are disposed on the light source side and the projection optical system side of the polarization beam splitter 61, respectively. Here, the polarization separation elements 62 and 63 are formed by laminating films of a predetermined thickness having optical anisotropy, and as shown in FIG.
It selectively transmits incident light on a predetermined polarization plane and selectively reflects incident light on a polarization plane orthogonal to the predetermined polarization plane.

The polarization separation element 62 is disposed between the convex lens 39 and the polarization beam splitter 61, and selectively transmits the S-polarized light component of the illumination light incident from the light source 31.
The P-polarized component is selectively reflected. On the other hand, the polarization separation element 63 includes the projection optical system 45 and the polarization beam splitter 6.
1 and selectively transmits the P-polarized light component and selectively reflects the S-polarized light component of the incident light from the polarization beam splitter 61.

Thus, the polarization splitting elements 62 and 63 are
In order to improve the contrast of the displayed image and to efficiently use the illumination light, the brightness level of the displayed image can be improved by reflecting the component of the polarization plane that causes black floating to the light source side so that it can be reused. It has been done.

Further, the polarization splitters 62 and 63 are held by being attached to the entrance surface and the exit surface of the polarization beam splitter 61 with an optical adhesive. Accordingly, in the projection display device 60, the air layer between the polarization separation element 62 and the polarization beam splitter 61 and the air layer between the polarization separation element 63 and the polarization beam splitter 61 are omitted, and the light generated by the air layer is omitted. To prevent loss. Further, heat generated by the polarization splitters 62 and 63 is efficiently radiated to reduce a rise in temperature.

According to the configuration shown in FIG. 4, in addition to the configuration according to the first embodiment, between the light source 31 and the polarization beam splitter 61 and between the projection optical system 45 and the polarization beam splitter 61 By arranging the polarization separation elements 62 and 63, the floating of black can be further prevented, whereby the contrast is improved and a high-quality display image can be formed.

Further, since the polarization splitting elements 62 and 63 are adhered to and held by the polarization beam splitter 61, light loss due to an air layer can be prevented and a bright high-quality display image can be displayed. In addition, since the rise in temperature can be reduced, reliability can be improved accordingly, change over time can be prevented, and work required for arrangement can be simplified.

(4) Other Embodiments In the above embodiment, the case where the present invention is applied to the projection type display device using one polarization beam splitter has been described, but the present invention is not limited to this. Instead, as shown in FIG. 6, the present invention can be widely applied to a case where a polarization beam splitter is assigned to each color.

[0072]

As described above, according to the present invention, a polarizing beam splitter or the like is formed by using a member having a parameter A representing birefringence of 5.00 × 10 ² or less.
It is possible to display a high-quality display image while preventing a decrease in contrast due to floating black.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a projection display device according to a first embodiment of the present invention.

FIG. 2 is a characteristic curve diagram for explaining the operation of the projection display device of FIG.

FIG. 3 is a schematic diagram illustrating a projection display device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a projection display device according to a third embodiment of the present invention.

FIG. 5 is a perspective view for describing a polarization splitting element.

FIG. 6 is a schematic diagram illustrating a conventional projection display device.

[Explanation of symbols]

1, 30, 50, 60 ... Projection display device, 2, 31 ...
... Light source, 12, 15, 17, 36R, 36G, 36B ...
... Reflection type liquid crystal panel, 11, 14, 15, 41, 61 ...
... Polarizing beam splitters, 42R, 42G, 42B ...
Dichroic mirror, 62, 63 ... polarization splitter,
45 Projection optical system

Claims (2)

[Claims] 1. A reflection type image forming means for spatially modulating illumination light having a predetermined polarization plane and emitting image light obtained by rotating the polarization plane with respect to the polarization plane of the illumination light, and projecting the image light. A projection optical system, and the illumination light emitted from a predetermined light source is emitted toward the reflection-type image forming means, and a predetermined polarization component of the image light incident from the reflection-type image formation means is converted into the light. A projection type display device, comprising: a polarizing beam splitter that emits light to a projection optical system, wherein the polarizing beam splitter is made of a member satisfying the following relational expression. (Equation 1) Here, K is the photoelastic constant (nm / mm) of the member.
· Mm ² / N), α is the linear expansion coefficient of said member (10 ^-6
/ K) and E are the Young's modulus of the member (10 ³ N / mm)
² ), λ is the wavelength (nm) of the illumination light, T is the internal transmittance of the member at wavelength λ, and ρ is the specific gravity of the member (g / g).
cm ³ ) and Cp are the specific heat (J / g · k) of the member, and the integral range in the expression (1) is the main light absorption wavelength band (420 [nm] to 500 [nm]) of the member. Range. 2. The method according to claim 1, wherein each of the incident lights having a predetermined wavelength is spatially modulated.
A plurality of reflection-type image forming means for emitting image light obtained by rotating the polarization plane with respect to the polarization plane of the incident light; and the plurality of reflection-type illumination light emitted from a predetermined light source based on a wavelength. A dichroic prism that emits the image light from the plurality of reflective image forming units and emits the image light so as to trace the optical path of the illumination light in reverse, and a projection optical system that projects the image light. A polarizing beam splitter that emits the illumination light emitted from the light source toward the dichroic prism and emits a predetermined polarization component of the image light incident from the dichroic prism to the projection optical system. And wherein the polarizing beam splitter and / or the dichroic prism is made of a member satisfying the following relational expression. Projection display device. (Equation 2) Here, K is the photoelastic constant (nm / mm) of the member.
· Mm ² / N), α is the linear expansion coefficient of said member (10 ^-6
/ K) and E are the Young's modulus of the member (10 ³ N / mm)
² ), λ is the wavelength (nm) of the illumination light, T is the internal transmittance of the member at wavelength λ, and ρ is the specific gravity of the member (g / g).
cm ³ ) and Cp are the specific heat (J / g · k) of the member, and the integral range in the expression (2) is the main light absorption wavelength band (420 [nm] to 500 [nm]) of the member. Range.