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What is claimed is:
1. A polarizing apparatus comprising:
a first transparent block (11, 21) having at least three plane surfaces for
transmitting light,
a second transparent block (12, 22) having at least three transparent
surfaces for transmitting light,
first and second polarization separation films (19, 20) having mutually
different spectral transmittances of S-polarization component (15, 25) the
films being evaporation-deposited on opposite planes of a transparent
glass substrate (18), respectively, thereby forming a polarization
separation means (13, 23) which is located between one plane of said first
transparent block (11, 21) and one plane of said second transparent block
(12, 22).
2. A polarizing apparatus in accordance with claim 1 wherein
at least one of said first transparent block and said second transparent
block is of a triangular prism shape.
3. A polarizing apparatus in accordance with claim 1 wherein
said first transparent block and second transparent block are glass.
4. A polarizing apparatus in accordance with claim 1 wherein
said second transparent block has a light absorption means at a P-polarized
light outgoing plane.
5. A polarizing apparatus in accordance with claim 1 wherein
said polarization separation means comprises multi-layer thin films on both
sides of said transparent substrate,
each multi-layer thin film comprising lamination of optical thin films.
6. A polarizing apparatus in accordance with claim 5 wherein
said multi-layer thin films each comprise an alternate lamination of two
kinds of optical thin films each having mutually different refractive
indices.
7. A projection display apparatus comprising:
a light source,
a pre-polarizer which takes out a substantially linearly polarized light
from light emitted from said light source,
a polarizing apparatus of claim 1 for serving in common as a polarizer and
an analyzer, a reflection type light valve which reflects said light
modulating its polarization state, and
a projection lens for projecting optical images formed at said light valve.
8. A projection display apparatus in accordance with claim 7 wherein
said pre-polarizer comprises a plural number of transparent substrates
disposed parallelly with intermediating thin air gap layers inbetween,
said transparent substrates each having on both surfaces thereof optical
thin films of a refractive index which is higher than that of said
substrate.
9. A projection display apparatus in accordance with claim 7 wherein
said light valve is a liquid crystal display device.
10. A projection display apparatus in accordance with claim 7 wherein
a quarter-wave plate is provided between said polarizing apparatus and said
light valve, said quarter-wave plate being disposed in a manner that a
fast optic axis or slow optic axis crosses perpendicularly with a plane
including the incident light optical axis and reflected light optical axis
of said polarizing apparatus.
11. A projection display apparatus in accordance with claim 10 wherein
said polarizing apparatus and said quarter-wave plate are cemented to each
other.
12. A projection display apparatus comprising:
a light source for emitting light color components of three primary colors,
a pre-polarizer for taking out a substantially linearly polarized light
from light emitted from said light source,
a polarizing apparatus of claim 1 for serving in common as a polarizer and
an analyzer,
a color decomposition means for decomposing the output light from said
polarizing apparatus into three primary colors,
three reflection type light valves for reflecting the light modulating the
polarization state, and
a projection lens for projecting optical images formed at said light valve
onto a screen.
13. A projection display apparatus in accordance with claim 12 wherein
said pre-polarizer comprises a plural number of parallelly disposed
transparent substrates with intermediating thin air gap layers inbetween,
said transparent substrates each having on both surfaces thereof optical
thin films of a refractive index which is higher than that of said
substrate.
14. A projection display apparatus in accordance with claim 12 wherein
said light valve is a liquid crystal display device.
15. A projection display apparatus in accordance with claim 12 wherein
a quarter-wave plate is provided between said polarizing apparatus and said
light valve, said quarter-wave plate being disposed in a manner such that
a fast optic axis or slow optic axis crosses perpendicularly with a plane
including the incident light optical axis and reflected light optical axis
of said polarizing apparatus.
16. A projection display apparatus in accordance with claim 15 wherein
said polarizing apparatus and said quarter-wave plate are cemented to each
other.
17. A polarizing apparatus comprising:
at least three transparent plates (32, 33, 35) for transmitting light,
a frame (31),
first and second polarization separation films (19, 20) having mutually
different spectral transmittances of S-polarization component (42), the
films being formed on opposite planes of a transparent glass substrate
(18), respectively, thereby forming a polarization separation means (38),
said at least three transparent plates (32, 33, 35), said frame (31) and
said polarization separation means (38) constituting a vessel having two
chambers separated by said polarization separation means (38), said three
transparent plates (32, 33, 35) being located on three sides of said
vessel for transmitting light therethrough, and,
at least a transparent material (39, 40) which is in a liquid state at
least at one time and subsequently in a gel phase or solid phase and
filled in said two chambers, respectively.
18. A polarizing apparatus in accordance with claim 17 wherein
said transparent filler material is ethylene glycol solution, or a mixed
solution of ethylene glycol, diethylene glycol, and glycerin, or a
transparent silicone resin which is transformable to solid phase or gel
phase with time.
19. A polarizing apparatus in accordance with claim 17 wherein
said frame has a light absorption means on the inner surface where an
P-polarization component is incident.
20. A polarizing apparatus in accordance with claim 17 wherein said
polarization separation means (38) comprises multi-layer thin films (19,
20) on both sides of said transparent planes of said substrate (18),
each multi-layer films comprising laminations of optical thin films.
21. A polarizing apparatus in accordance with claim 20 wherein
said multi-layer thin films each comprise an alternate lamination of two
kinds of optical thin film each having mutually different refractive
indices.
22. A projection display apparatus comprising:
a light source,
a pre-polarizer which takes out a substantially linearly polarized light
from light emitted from said light source,
a polarizing apparatus of claim 17 for serving in common as a polarizer and
an analyzer, a reflection type light valve which reflects said light
modulating its polarization state, and
a projection lens for projecting optical images formed at said light valve.
23. A projection display apparatus comprising:
a light source for emitting the light color components of three primary
colors,
a pre-polarizer for taking out a substantially linearly polarized light
from light emitted from said light source,
a polarizing apparatus of claim 17 for serving in common as a polarizer and
an analyzer,
a color decomposition means for decomposing the output light from said
polarizing apparatus into three primary colors,
three reflection type light valves for reflecting the light modulating the
polarization state, and
a projection lens for projecting optical images formed at said light valve
onto a screen. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polarizing apparatus that acts both as a
polarizer and an analyzer and also to a projection display apparatus that
enlarges and projects optical images formed on a reflection type light
valve using the above-mentioned polarizing apparatus.
2. Description of the Prior Art
In order to obtain large-size picture images, a hitherto known method is to
form optical images on a light valve operating by video signals,
illuminate a projection light on this optical images and project the
optical images in enlarged size on a screen through a projection lens. In
recent years, a projection display apparatus using a liquid crystal
display as a light valve attracts much attention. And upon aiming at the
high resolution capability, the Japanese unexamined Patent publication
(Tokkai Sho) 61-13885t (M. Himuro) proposed a reflection type liquid
crystal display that is easily expandable to a large capacity apparatus
with regard to the pixel number without spoiling the pixel aperture factor
of a liquid crystal display.
An outline configuration of a conventional projection display apparatus
using the above-mentioned liquid crystal display is shown in FIG. 19. A
light beam 2 emitted from a light source 1 is collimated into a nearly
parallel beam, and then the light beam is separated into an S-polarization
component 4 which is reflected by a polarization beam splitter 3 and a
P-polarization component 5 which transmits therethrough. The
S-polarization component 4 is incident upon a liquid crystal display 6.
The liquid crystal display 6 is of the kind that utilizes a property of
the birefringence of a liquid crystal, and each picture element has
individual reflecting electrode for reflecting light. In case that no
voltage is applied to the liquid crystal layer, no birefringence property
is exhibited actually, whereas when voltage is applied, the birefringence
property takes place. Therefore, when a linearly polarized light having
its polarization direction in a specified direction is incident, its
reflected light becomes an elliptically polarized light.
The S-polarization component 4 is partially converted into the
P-polarization component by the liquid crystal display 6 and is incident
again into the polarization beam splitter 3. The P-polarization component
included in the reflected light from the liquid crystal display 6
transmits through the polarization beam splitter 3 and incident into a
projection lens 7, whereas the S-polarization component is reflected
thereby and proceeds toward the light source 1. In such the manner, an
optical image formed as the change of the birefringence property on the
liquid crystal display 6 is expanded and projected onto a screen (not
shown) by a projection lens 7.
In the reflection type liquid crystal display device, the switching
elements can be disposed behind the picture element electrodes. Therefore,
the picture element pitch can be reduced without reducing the size of the
switching elements, and hence the high density integration of the picture
element is not a difficult task. Therefore, by the use of the reflection
type liquid crystal display device, a brighter and higher resolution
projection image in comparison with the use of the transmitting type
liquid crystal display device can be obtained.
In the configuration shown in FIG. 19, when black is to be displayed, the
S-polarization component 4 incident onto the liquid crystal display 6 is
reflected back as it was (S-polarization component) without receiving any
conversion into the P-polarization component. The more the amount of
residual S-polarization component transmitting through the polarization
beam splitter 3 and being incident onto the projection lens 7, the less
the resultant contrast of the projection image becomes. Therefore, in
order to obtain a high contrast projection image, it is required to make
the S-polarization component transmittance of the polarization beam
splitter 3 very low.
In general, as for the polarization beam splitter 3, those type as that
proposed by S. M. MacNEILLE in the U.S. Pat. No. 2,403,731 are mostly
used. The U.S. Patent discloses an optical device in which two glass
prisms are joined together to form a cubic shape or a rectangular
parallelo-piped shape, and therein an optical multi-layers thin film is
formed on the joining surfaces. The optical multi-layers thin film is
formed by alternately laminating two different kinds of thin films each of
which has a mutually different refractive index from the others. This
configuration has an action of separating the natural light into two
polarization components having mutually-orthogonal planes of polarization.
Materials and the film thicknesses of those two thin films are selected to
fulfill the Brewster's angle condition that the transmittance of the
P-polarization component becomes 100% at a specified wavelength. This
Brewster's angle condition is expressed with the incident angle
.theta..sub.G onto the multi-layers thin film, the refractive index
n.sub.G of the glass prisms, the refractive index n.sub.L of the lower
refractive index thin film, and the refractive index n.sub.H of the higher
refractive index thin film, as follows:
##EQU1##
When the condition of EQ.(1) is fulfilled, it is possible, with keeping the
transmittance of the P-polarization component to 100%, to reduce the
transmittance of the S-polarization component by increasing the number of
layers of the multi-layers thin film.
However, the wavelength bandwidth of the polarization beam splitter wherein
separation of the two polarization components are carried out is
relatively narrow. Therefore, in case of a projection display apparatus
using white light, it is difficult to keep the transmittance of the
S-polarization component low over the whole wavelength bandwidth over the
visible light range.
For this problem there has been such a proposal that the white, light
emitted from a light source is decomposed into three primary colors of
red, green, and blue, and three polarization beam splitters respectively
corresponding to those three wavelength band ranges are provided.
According to such conventional configuration, even though transmittances of
those respective S-polarization components at respective wavelength ranges
of particular color components can be kept low, cost naturally rises and
also the size of apparatus and weight increase since three of joined block
of glass prisms are used. Moreover, since it is usually the case that the
incident light is not perfectly parallel, in such a case, wavelength shift
is liable to take place owing to an incident angle dependence of the
light. And a narrow wavelength bandwidth of the transmittance of the
S-polarization component becomes practically further narrower.
Accordingly, when it is intended to obtain a high contrast projection
image with such configuration, the substantially parallel light only must
be used. Therefore, a difficulty arises in producing sufficient bright
picture images.
SUMMARY OF THE INVENTION
The present invention is to solve the above-mentioned problems, and
purposes to offer a polarizing apparatus that is capable of keeping the
reflectance for the S-polarization component high over a wide wavelength
range and also has little dependence to light incident angle dependence.
And it purposes also to offer a projection display apparatus capable of
displaying a bright and high quality projection image using the
above-mentioned polarizing apparatus.
In order to accomplish the above-mentioned purpose, the polarizing
apparatus of the present invention comprises a first transparent body, a
second transparent body, at least one transparent plane parallel
substrate, and at least two polarization component separation means. Both
of the above-mentioned first and second transparent bodies respectively
have at least three plane surfaces, and the transparent plane parallel
substrate and the polarization component separation means are held between
the first transparent body and the second transparent body. And spectral
transmittance characteristics for the S-polarization component of those
two, at lest, polarization component separation means are different to
each other.
And it is also possible to build the polarizing apparatus by instructing a
liquid holding vessel with at least three transparent plates and a frame,
and by using a transparent material which is in liquid phase at least at
the time of assembly as the transparent bodies, and then by filling a
transparent material in the above-mentioned vessel.
By forming respective polarization component separating means having
mutually different spectral transmittance of S-polarization component on
two interfaces formed between respective transparent bodies and the
transparent parallel planed substrate, the light polarizing apparatus of
the present invention acts as a polarization beam splitter whose
transmittance of totally integrated S-polarization component can be kept
very low over a wide wavelength range and, and at the same time, whose
incident angle dependence is kept very little. If this polarizing
apparatus is used for a projection display apparatus using a reflection
type birefringent light valve, the S-polarization component that is
reflected by the light valve as for the black display part can be shut out
effectively, and hence projection image of a high contrast can be
displayed.
Since the transmittance of the S-polarization component can be made very
low over all the visible wavelength range by a single polarizing
apparatus, even when white light is decomposed into three primary colors
of red, green, and blue, and three light valves corresponding to those
three primary colors are used, there is no necessity to use a plural
number of polarizing apparatus. As a result, a projection display
apparatus using this polarizing apparatus can be made in a compact size.
And, if a material which is liquid at lest at the time of assembly is used
as for a transparent body, materials of lower cost than that of the glass
prism can be chosen. Since those assembly process and liquid filling
process are rather easily workable, a light polarizer using the liquid
materials can be produced in a lower cost in comparison with the
polarization beam splitter using glass prisms.
In the polarizing apparatus of the present invention, in case that the
P-polarization component is reflected by its outgoing plane or the like,
resulting in a main cause of lowering the contrast, arrival of unnecessary
light component to the screen can be avoided by providing a light
absorbing means in place of or the inside of the outgoing plane.
Advantages of the light polarizer of the present invention are, as is
evident as described above, that the transmittance of the S-polarization
component can be kept low over a wide wavelength bandwidths, and besides
that the incident angle dependence is little. And advantages of the
projection display apparatus using the polarizing apparatus of the present
invention are that the bright and high contrast projection image can be
displayed and that the size of the apparatus is compact.
The feature and the effect of the present invention will be made more
evident by referring to the later-described embodiments and their
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A and FIG. 1B are perspective views of embodiments of polarizing
apparatus of the present invention.
FIG. 2 is an outline drawing of the constitution of a polarization
separation mirror.
FIG. 3 is a characteristic curve for explaining a spectral transmittance of
the polarizing apparatus of the present invention.
FIG. 4 is a characteristic curve for explaining another spectral
transmittance of the polarizing apparatus of the present invention.
FIG. 5 is a cross-sectional side view of the polarizing apparatus of the
present invention.
FIG. 6 is a characteristic curve for explaining a spectral transmittance of
the polarizing apparatus of the present invention.
FIG. 7 is a characteristic curve for explaining another spectral
transmittance of the polarizing apparatus of the present invention.
FIG. 8 is a partially broken perspective view of the polarizing apparatus
of the present invention.
FIG. 9 is a cross-sectional side view of the polarizing apparatus of the
present invention.
FIG. 10 is a characteristic curve for explaining a spectral transmittance
of the polarizing apparatus of the present invention.
FIG. 11 is a characteristic curve for explaining another spectral
transmittance of the polarizing apparatus of the present invention.
FIG. 12 is a cross-sectional side view of the polarizing apparatus of the
present invention.
FIG. 13 is a perspective view of a projection display apparatus of the
present invention.
FIG. 14 is a characteristic curve for explaining a spectral transmittance
of a pre-polarizer.
FIG. 15 is a characteristic curve for explaining another spectral
transmittance of the pre-polarizer of the present invention.
FIG. 16 is a perspective view showing an outline constitution of a
projection display apparatus of the present invention.
FIG. 17 is a perspective view showing an outline constitution of the
projection display apparatus of the present invention.
FIG. 18 is a perspective view showing an outline constitution of the
projection display apparatus of the present invention.
FIG. 19 is a perspective view showing an outline constitution of a
projection display apparatus of prior art.
It will be recognized that some or all of the Figures are schematic
representations for purposes of illustration and do not necessarily depict
the actual relative sizes or locations of the elements shown.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, Explanation is given on embodiments of the present invention referring
to the drawings.
FIG. 1A is a drawing showing the constitution of a polarizing apparatus of
the present invention, wherein two triangular pillar shaped prisms are
used for glass prisms 11 and 12. They are joined to each other sandwiching
a polarization separation mirror 13 therebetween. Light incident on the
prism 11 is separated into an S-polarization component 15 and a
P-polarization component 16 by the polarization separation mirror 13.
Constitution of the polarization separation mirror 13 is shown in FIG. 2.
On both surfaces of the glass substrate 18 of a thickness of 1 mm, a first
multi-layer thin film 19 and a second multi-layers thin film 20 are
evaporation-deposited respectively. The multi-layer thin films 19 and 20
are made by respective laminating of low refractive index film and high
refractive index film. By sandwiching the thus prepared polarization
separation mirror 13 tightly between the glass prisms 11 and 12, a
resulted composite body works as a polarization beam splitter. The thin
films configuration and the layer number of the first multi-layer thin
film 19 and those of second multi-layer thin film 20 are selected to be
same to each other. And by relatively shifting the film thickness, the
wavelength ranges for reflecting the S-polarization component are varied
from each other. By such configuration, it became possible to keep a total
spectral transmittance for the S-polarization component very low over a
wide wavelength range, and moreover the incident angle dependence over
usable wavelength range can be made very little.
The configurations of the multi-layers thin films 19, 20 of the present
embodiment in accordance with the combination based on the condition
equation (1) mentioned before are shown in TABLE 1. Setting the standard
incident angle onto the polarization separation mirror 13 to be
45.degree., the materials are selected that a dense flint glass of a
refractive index of 1.755 for the glass prisms 11 and 12, a float glass
plate of a refractive index of 1.52 for the glass substrate 18 of the
polarization separation mirror 13, and silicon dioxide of a refractive
index of 1.46 for the low refractive index films and titanium dioxide of a
refractive index of 2.3 for the high refractive index films. The film
thickness d is the physical film thickness.
TABLE 1
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Standard Incident Angle 45.degree.
First Multi- Second Multi-
Layer Thin Film
Layer Thin Film
Refractive Film Thickness
Film Thickness
Index d (nm) d (nm)
______________________________________
1.52 -- --
1 1.46 143.8 107.9
2 2.30 91.3 68.5
3 1.46 143.8 107.9
4 2.30 91.3 68.5
5 1.46 143.8 107.9
6 2.30 91.3 68.5
7 1.46 143.8 107.9
8 2.30 91.3 68.5
9 1.46 143.8 107.9
10 2.30 91.3 68.5
11 1.46 143.8 107.9
12 2.30 91.3 68.5
13 1.46 143.8 107.9
1.755 -- --
______________________________________
Spectral transmittance of the polarization separation mirror of the
configuration of TABLE 1 over a wavelength range from 400 nm to 700 nm is
shown in FIG. 3 and FIG. 4. FIG. 3 shows spectral transmittance of the
P-polarization component and the S-polarization component, wherein the
total P-polarization component transmittance (P) is shown by a solid
curve, whereas the S-polarization component transmittance of the first
multi-layers thin film (S1) is shown by a broken curve, and the
S-polarization component transmittance of the second multi-layers thin
film (S2) is shown by a dotted broken curve (a chain line curve). As is
understood from the curves, transmittance of the P-polarization component
is as high as more than 90%, and the transmittance concerning the
S-polarization component, the first multi-layer thin film has low
transmittance in the longer wavelength side (about 490 nm-700 nm) while
the second multi-layer thin film has low transmittance in the shorter
wavelength side (400 nm-550 nm). Thereby the total transmission for the
S-polarization component is kept as low as less than 0.1%.
FIG. 4 shows the incident angle dependency of the S-polarization component
transmittance (S) of the polarization separation mirarot. Numerals in the
figure represent incident angles onto the polarization separation mirror.
Thus those three curves in the figure illustrate the behavior of
variations of transmission induced by .+-.5.degree. deviations in the
incident angle, expressed in the angle converted to that of the air, from
the standard incident angle of 45.degree.. From this figure, the
transmittance of the S-polarization component can be kept as low as less
than 0.4% over 400-700 nm even at the time when the incident angle of the
light leans as much as .+-.5.degree., meaning that the incident angle
dependency is very little.
For the first multi-layer thin film 19 and the second multi-layer thin film
20, also by evaporation-depositing them respectively on those two glass
prisms 11 and 12, the same result can be obtained.
In case where the polarizing apparatus of the present invention is used in
a projection display apparatus using a reflection type birefringent light
valve, although the most part of the unnecessary P-polarization component
16 outgoes from the outgoing plane shown in FIG. 1A, a part thereof is
reflected by this outgoing plane and propagates toward the screen. Such
reflection often happens to cause an unfavorable influence of lowering the
contrast of the projection image. In that case, it is possible to prevent
such lowering of the contrast by providing a light absorbing layer 17 by
forming a minute roughness on the outgoing plane and coating an absorbing
material over the outside surface thereon shown in FIG. 1B. A preferred
example of such light absorbing layer is made by sand blasting the bottom
face 17 of the prism 12 and then applying a block coating thereon.
Constitution of another embodiment of the present invention is shown in
FIG. 5.
A glass prism 21 is a square pillar shaped prism having a cross-sectional
form of trapezoid that is obtainable by cutting a tip part of an
equilateral triangle, and a glass prism 22 is a triangular pillar shaped
prism. These glass prisms 21 and 22 are joined including a polarization
separation mirror 23 therebetween. The glass prism 21 is prepared such
that the incident angle of the incident light 24 on the polarization
separation mirror 23 becomes 50.degree.. Similarly as in the constitution
of FIG. 1, the incident light 24 is separated into an S-polarization
component 25 and a P-polarization component 26.
For the polarization separation mirror 23 as in the aforementioned
embodiment, on both surfaces of a glass substrate, a first multi-layers
thin film and a second multi-layer thin film are formed. Those
multi-layers films are respectively formed by laminating low refractive
index films and high refractive index films alternately. The configuration
of the multi-layer thin films used for the polarization separation mirror
used in the constitution of FIG. 5 is shown in TABLE 2. Taking a standard
incident angle on the polarization separation mirror 23 to be 50.degree.,
the following materials are used:
borosilicate crown glass of a refractive index of 1.516 for the glass
prisms 21 and 22,
a float glass plate of refractive index of 1.52 for the glass substrate of
the polarization separation mirror 23,
magnesium difluoride of a refractive index of 1.39 for the low refractive
index films, and
zinc sulfate of a refractive index of 2.3 for the high refractive index
films.
TABLE 2
______________________________________
Standard Incident Angle: 50.degree.
First Multi- Second Multi-
Layer Thin Film
Layer Thin Film
Refractive Film Thickness
Film Thickness
Index d (nm) d (nm)
______________________________________
1.52 -- --
1 1.39 151.1 113.3
2 2.30 91.3 68.5
3 1.39 151.1 113.3
4 2.30 91.3 68.5
5 1.39 151.1 113.3
6 2.30 91.3 68.5
7 1.39 151.1 113.3
8 2.30 91.3 68.5
9 1.39 151.1 113.3
10 2.30 91.3 68.5
11 1.39 151.1 113.3
12 2.30 91.3 68.5
13 1.39 151.1 113.3
1.516 -- --
______________________________________
Spectral transmittance of the polarization separation mirror of TABLE 2
over a wavelength range of 400 nm to 700 nm is shown in FIG. 6 and FIG. 7.
In these graphs, as in FIG. 3 and FIG. 4, in FIG. 6, the total
P-polarization component transmittance (P) is shown by a solid curve, the
S-polarization component transmittance of the first multi-layer thin film
(S1) is shown by a broken curve, and the S-polarization component
transmittance of the second multi-layer thin film (S2) is shown by a
dotted broken curve. In FIG. 7, on the total S-polarization component
transmission, its incident angle dependency is shown. It is understood
from FIG. 6 and FIG. 7, similarly as in the constitution of FIG. 1, that
the transmission of the P-polarization component is kept as high as more
than 90% whereas the transmission of the S-polarization component is kept
as low as less than 0.4% over a wavelength range of 400 nm to 700 nm even
for the incident angle of the light leans as much as .+-.5.degree. (in
air) from the standard incident angle (50.degree.). Accordingly, it is
also understood that the incident angle dependency is also very little.
Also in the constitution shown in FIG. 5, the first multi-layer thin film
and the second multi-layers thin film can be made similarly by
evaporation-depositing them respectively on those two glass prisms 21 and
22.
Furthermore, in the constitution of FIG. 5, similarly as in the
constitution shown in FIG. 1A, when the polarizing apparatus of the
present invention is used in a projection display apparatus using a
reflection type bire | | |
