JPH1195172A - Polarized light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarized light source device which is small and compact to make the device suitable for utilization as a light source for a liquid crystal projector, etc., and is inexpensively producible. SOLUTION: The half of the circular exit opening 3b of the light source lamp 4 of the polarization light source device 1 is shielded by a reflection plate 6 and light I is emitted from an opening part 3c of the remaining semi-circular shape. The light I(s) of the S polarized light component of the light I is reflected by a polarized light separating film 11 and the light I(p) of the P polarizing plate component transmits the first and second polarized light separating films 11, 12. The transmitted light is reflected by a total reflection plate 14, by which the light is passed twice through a quarter-wave plate 13 and is made to the light I'(s) of the S polarizing plate component. This light is reflected by the second polarized light separating film 12. The polarized luminous flux I(out) which is obtd. via a condenser lens 15 and is aligned in the polarization direction is made into the polarized luminous flux of a circular shape consisting of the light I(s) and I'(s). The size of the optical element for polarized light conversion is made small and the increase of the optical path length for the polarized light conversion is suppressed. Even more, the smaller number of the times that the light which is the object for the polarized light conversion passes the optical element is necessitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polarized light source device that emits outgoing light consisting of only a specific polarization component and is used as a light source device for a liquid crystal projector or the like.

[0002]

2. Description of the Related Art In a liquid crystal display device such as a liquid crystal projector, a parallel light from a light source lamp such as an arc lamp such as a metal halide lamp or a halogen lamp is radiated to a light valve formed of a liquid crystal panel, and a display image is formed in the light bubble. After the corresponding modulation, a projection image is formed on a projection surface via a projection optical system. Here, the liquid crystal light valve for modulating the light corresponding to the image information uses only a specific polarization component, and even if the liquid crystal light valve is irradiated with the parallel light emitted from the light source lamp as it is, the polarization direction is changed. However, half of the light components that differ from each other are not used, so that the light use efficiency is low and the projected image cannot be brightened.

Therefore, conventionally, parallel light emitted from a light source lamp is guided to a polarization conversion optical system, the polarization direction is adjusted through the parallel light, and then irradiated to a liquid crystal light valve, thereby increasing the light use efficiency. To obtain a bright projected image. For example, JP-A-8-29734 discloses a light source of a display device having such a polarization conversion optical system. Also, Japanese Patent Application Laid-Open No. 3-13983 discloses a projection type liquid crystal display device provided with a polarization conversion optical system.

[0004]

FIG. 4 shows the structure of Japanese Patent Application Laid-Open No. Hei 8-2.
No. 9734 discloses a light source.
The polarization conversion optical system 00 has a quarter-wave plate 102 arranged on the incident side and a quarter-wave plate 103 arranged on the emission side, sandwiching the polarization beam splitter 101 arranged on the optical axis of the light source. It includes a total reflection mirror 104 disposed behind the 波長 wavelength plate 103 and a total reflection mirror 105 disposed on the side of the polarization beam splitter 101.
The polarization beam splitter 101 reflects the S-polarized light component of the parallel light emitted from the light source lamp 106 in the orthogonal direction, and transmits the P-polarized light component as it is.
a, and the P-polarized light component included in the parallel light emitted from the light source lamp 106 is at least 1 /
It is necessary to pass through the four-wavelength plate seven times and pass through the polarizing beam splitter 101 five times.

[0005] In the polarization conversion optical system having this configuration, the light of one polarization component is emitted many times as described above for the polarization conversion.
It is necessary to pass through a 波長 wavelength plate and a polarizing beam splitter, and therefore, loss of light amount and deterioration of polarization efficiency generated when passing through these optical elements cannot be ignored. Therefore, there is a problem to be solved that the utilization efficiency of light emitted from the light source lamp is low.

On the other hand, FIG. 5 shows a projection type liquid crystal display device described in JP-A-3-13983.
The polarization conversion optical system of the projection type liquid crystal display device 200 includes a polarization beam splitter 201, an optical path changing prism 203 arranged in parallel with the polarization beam splitter 201 in a direction orthogonal to the optical axis of the light source, and an optical path changing prism. And a half-wave plate 204 disposed at a position facing the exit surface of the light-emitting device 203. In this optical system, the parallel light emitted from the light source lamp 205 transmits one polarization component in the polarization beam splitter 201, and the polarization component orthogonal to the parallel light is reflected at a right angle to form the optical path changing prism 20.
3, the light is again reflected in a direction parallel to the optical axis of the light source, and the polarization direction is rotated by 90 degrees via a half-wave plate.

However, in the polarization conversion optical system having this configuration, the light source lamp 205 is required to perform the polarization conversion.
The width of the parallel light beam emitted from the light source is doubled in the lateral direction with respect to the exit aperture. For this reason, there is a problem to be solved that an installation area is required to arrange the optical system. In addition, in order to return the polarized light beam that has spread in one direction to the original shape of the used light beam, a cylindrical conversion lens is required, which leads to an increase in the size of the optical system and an increase in cost. is there.

An object of the present invention is to propose a polarized light source device capable of performing polarization conversion with a small loss of light amount and without causing a decrease in polarization efficiency.

It is another object of the present invention to provide a polarized light source device which requires a small number of optical elements for performing polarization conversion and can realize miniaturization of the optical elements.

[0010]

In order to solve the above-mentioned problems, the present invention provides a light source lamp including a light emitting tube and a reflector for reflecting divergent light from the light emitting tube toward an emission opening. The following configuration is employed in a polarized light source device having a polarization conversion optical system that aligns the polarization direction of light emitted from the emission opening of the light source lamp to generate polarized light.

That is, the light source lamp has a reflecting plate that shields the emission opening on one side portion about one axis of symmetry of the opening shape and reflects a light component emitted from the portion in the same direction. It has a configuration.

[0012] The polarization conversion optical system may include one of a P-polarized light component and an S-polarized light component included in the outgoing light emitted through the portion of the emission opening that is not shielded by the reflector. A first polarization separation film that reflects only the light at right angles and transmits the light of the other polarization component, a total reflection plate that reflects the polarization component transmitted through the first polarization separation film in the opposite direction, A quarter-wave plate disposed on an optical path between a first polarization splitting film and the total reflection plate, and the first polarization splitting film on an optical path between the first polarization splitting film and the quarter-wave plate And a second polarization splitting film having the same polarization splitting characteristic as the first polarization splitting film.

[0013] In the polarized light source device of the present invention configured as described above, the actual emission light exit opening of the light source lamp is a one side portion that is not shielded by the reflector. Accordingly, each optical element constituting the polarization conversion optical system arranged to convert the emitted light emitted therefrom into a polarized light can be half the size of the conventional one, so that the optical system can be made small and compact. .

The cross-sectional shape of the light emitted from the light source lamp is a half cross-sectional shape of the shape of the exit opening of the light source lamp. Is reflected by the first polarization splitting film. The other polarized light component (the second polarized light component) also passes through the second polarized light separating film having the same polarized light separating characteristic, then reaches the total reflection plate through the に wavelength plate, where it is reflected in the same direction. Then, the light passes through the quarter-wave plate again, so that the polarization direction is 9
By rotating by 0 degrees, the polarization direction becomes the same as the first polarization component.
As a result, the second polarized light component is reflected at right angles by the second polarized light separating film, and exits in the same direction as the first polarized light component.

Accordingly, since the number of times that the polarized light component to be polarization-converted passes through each optical element is small, it is possible to suppress loss of light amount and decrease in polarization efficiency.

Further, the light flux composed of the first polarized light component having a half cross-sectional shape of the exit opening shape of the light source lamp and the light flux of the second polarized light component having a symmetrical half cross-sectional shape after polarization conversion are synthesized. Thus, it is possible to obtain a combined light beam having the same shape as the emitted light beam directly emitted from the light source lamp without being blocked by the reflector.

The light emitted from the light source lamp can be made substantially parallel light by selecting the shape of the reflecting mirror and the like.

Here, in the polarization conversion optical system of the polarized light source device of the present invention, instead of disposing the quarter-wave plate and the total reflection plate, the polarized light after passing through the second polarized light separating film is used. It is also possible to adopt a configuration in which the reflection type liquid crystal device that rotates the polarization direction of the component light by 90 degrees and totally reflects the component light toward the second polarization splitting film is arranged. If this configuration is adopted, the number of times that the polarization component to be subjected to the polarization conversion passes through the optical element can be reduced, and the number of optical elements required for the polarization conversion can be reduced. It is possible to realize an inexpensive optical system with little decrease in polarization efficiency.

Further, in the polarization conversion optical system of the polarized light source device of the present invention, instead of disposing the second polarized light separating film, the quarter-wave plate, and the total reflection plate, the first polarized light is used. A first and a second total reflection plate for reflecting the polarized light component transmitted through the separation surface and emitting the polarized light component in the same direction as the polarized light component reflected by the first polarization separation film; and the first total reflection plate And a half-wave plate disposed between the first and second total reflection plates or on the emission side of the second total reflection plate. it can. If this configuration is adopted, one polarization beam splitter having a generally expensive polarization separation film is omitted, and
Since an inexpensive reflector can be used, the optical system can be configured at a low cost as a whole.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows an optical system of a polarized light source device to which the present invention is applied. As shown in this figure,
The polarized light source device 1 includes a light source lamp 4 having an arc tube 2 and a reflecting mirror 3 for reflecting divergent light from the arc tube 2 so as to become parallel light, and a polarization direction of the parallel light from the light source lamp 4. And a polarization conversion optical system 5 that emits the polarized light as aligned light.

The arc tube 2 of the light source lamp 4 is an arc lamp such as a metal halide lamp or a halogen lamp. The reflecting mirror 3 may have an elliptical reflecting surface 3a or a parabolic reflecting surface. The divergent light from the arc tube 2 is reflected directly or on the reflecting surface 3a to be a substantially parallel light beam as a whole, and the circular exit opening 3b of the reflecting surface.
Are emitted through However, in this example, one side of the circular emission opening 3b around one axis of symmetry is closed by a reflector. That is, the circular injection opening 3
The lower semicircular portion in FIG. 1B is closed off by a semicircular reflector 6 having a shape corresponding to the semicircle. The reflecting surface 6a of the reflecting plate 6 is orthogonal to the light source optical axis 4a. Therefore, the parallel light flux having a semicircular cross section irradiated on the reflecting surface 6a of the reflecting plate 6 is reflected in the same direction, is reflected again by the reflecting surface 3a of the reflecting mirror 3, and is returned to the other side (in FIG. The light is emitted toward the polarization conversion optical system 5 through the (upper) semicircular opening 3c.

In this embodiment, an infrared removal filter 7 is disposed on the emission side of the semicircular opening 3c.
In the figure, a parallel light flux I having a semicircular cross section indicated by a hatched portion.
Is emitted to the polarization conversion optical system 5 through this filter 7.

Next, the polarization conversion optical system 5 includes a polarization beam splitter 8 composed of a prism composite. The polarization beam splitter 8 includes a first polarization separation film 11 orthogonal to the light source optical axis 4a, This first polarization separation film 11
And a second polarization separation film 12 extending in the direction orthogonal to the one end. The polarization separation characteristics of the first and second polarization separation films 11 and 12 are the same. For example, only the light I (s) of the S-polarized component included in the parallel light flux I is reflected, and the light I of the P-polarized component is reflected. The characteristic is set so as to transmit (p). Such a polarization separation film can be configured as, for example, a dielectric multilayer film.

Behind the polarizing beam splitter 8 in the direction of the light source optical axis 4a, a quarter-wave plate 13 and a total reflection plate 14 are arranged in this order. Further, a condenser lens 15 is disposed on the rear side of the optical path with respect to the S-polarized light exit surface 8a of the polarization beam splitter 8 parallel to the light source optical axis 4a.

The polarized light source device 1 of the present embodiment configured as described above.
In the above, the parallel light flux I having a semicircular cross section emitted from the light source lamp 4 is subjected to polarization conversion in the following manner, and emitted as a polarized light flux I (out) whose polarization direction is aligned with the S polarization direction. Is done.

First, the parallel light flux I having a semicircular cross section is passed through the first polarization separation film 11 of the polarization beam splitter 8.
Only the S-polarized light I (s) is reflected, and the P-polarized light I (p) is transmitted as it is. The reflected S-polarized light component I (s) is emitted through the emission surface 8a and the condenser lens 15. After the light I (p) of the P-polarized light component has passed through the first polarization separation film 11, it also transmits through the second polarization separation film 12 having the same polarization separation characteristics. Thereafter, after the polarization direction is rotated by 45 degrees via the quarter-wave plate 13, the light is reflected in the same direction by the total reflection plate 14 and transmits through the quarter-wave plate 13 again. As a result, since the light I (p) of the P-polarized light component passes through the quarter-wave plate 13 twice,
The polarization direction is rotated by 90 degrees, and the light I ′ of the S-polarized component
(S). Accordingly, the light is reflected at a right angle by the second polarization separation film 12 and is emitted through the emission surface 8 a of the polarization beam splitter 8 and the condenser lens 15.

Here, the light I '(s) of the S-polarized light component obtained by the polarization conversion is in a state where its cross-sectional shape is inverted. As a result, the polarized light flux I (out) obtained through the condenser lens 15 has a circular cross section corresponding to the circular emission opening 3b of the light source lamp 4.

As described above, in the polarized light source device 1 of the present embodiment, the emitted light beam to be subjected to polarization conversion may be half the size of the emission opening of the light source lamp. Therefore, as in the prior art, a polarizing prism having a size corresponding to the emission aperture of the light source lamp or 1 /
Compared to an optical system having a four-wavelength plate, the size of the optical element can be halved, and the entire optical system can be made small and compact. Also, the price will be lower.

Furthermore, the optical path length required for the polarization conversion can be shortened, and the number of times that the polarization component to be subjected to the polarization conversion passes through the quarter-wave plate only needs to be two times. Also, a decrease in polarization efficiency can be suppressed.

(Second Embodiment) FIG. 2 shows an optical system of a polarized light source device having another configuration to which the present invention is applied. The polarization light source device 20 is different from the polarization light source device 1 according to the first embodiment in that the quarter-wave plate 13 and the total reflection plate 15 are arranged in the polarization conversion optical system 5A. Instead, the second polarization separation film 1
The polarization direction of the polarization component light I (p) transmitted through the second polarization separation film 1 is rotated by 90 degrees and the second polarization separation film 1 is again rotated.
That is, the reflection type liquid crystal device 21 that totally reflects the light toward 2 is disposed. Since other configurations are the same, corresponding portions are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

In the polarized light source device 20 having this configuration,
The same operation and effects as those of the polarized light source device 1 can be obtained. In addition, the number of times that the polarization component to be subjected to polarization conversion passes through the optical element can be reduced, and the number of optical elements required for polarization conversion can be reduced. There is an advantage that an optical system with a small decrease in the image quality can be realized.

(Third Embodiment) FIG. 3 shows an optical system of a polarized light source device having still another configuration to which the present invention is applied. The polarization light source device 30 is different from the polarization light source device 1 according to the first embodiment in that the second polarization separation film 12, the quarter-wave plate 13, and the total reflection plate 14 are provided.
, The light I (p) of the polarized light component transmitted through the first polarization splitting film 11 is reflected, and the light I (s) of the polarized light component reflected by the first polarization splitting film 11 is reflected. First and second total reflection plates 31 and 32 that emit light in the same direction as
The half-wave plate 33 is arranged on the optical path reflected by the total reflection plate 32 and reaching the condenser lens 15.

The number of the reflecting plates 31 and 32 may be three or more, as long as the shape of the emitted light I ′ (s) is symmetrical to the light I (s). Further, the arrangement position of the half-wave plate 33 is on the incident side of the first total reflection plate 31, that is, the first
May be on the optical path between the total reflection plate 31 and the first polarization separation film 11 or on the optical path between the first and second total reflection plates 31 and 32.

In the polarization light source device 30 configured as described above, since an inexpensive reflector is used instead of the expensive second polarization separation film 12, there is an advantage that an increase in the manufacturing cost of the optical system can be suppressed. is there.

(Other Embodiments) In each of the above embodiments, as a characteristic of the polarization splitting film, S-polarized light is reflected,
Although it is assumed to transmit the P-polarized light, it is needless to say that a light having the opposite separation characteristic may be used.

In the above description, the light source lamp has a circular emission opening. However, the light source lamp may have a shape other than a circle.

On the other hand, the polarized light source device according to the present invention can be used not only as a light source for a front type liquid crystal projector and a rear type liquid crystal projector, but also as a light source for an optical device requiring other polarized light sources.

[0038]

As described above, in the polarized light source device of the present invention, light is emitted from one half of the exit opening of the light source lamp, and the emitted light is subjected to polarization conversion. Therefore, compared with the case where the polarization conversion optical element having a size corresponding to the emission aperture of the light source lamp is conventionally used, a small optical element can be used, and the optical system can be configured to be small and compact. This has the effect of being able to be manufactured at low cost.

Further, it is possible to suppress the increase in the optical path length for the polarization conversion and to reduce the number of times that the light to be subjected to the polarization conversion passes through the optical element, so that it is possible to suppress the light loss and the decrease in the polarization efficiency as a whole. This has the effect.

Further, by combining the polarized component light emitted without the polarization conversion and the light emitted after the polarization conversion, a combined luminous flux having a shape corresponding to the emission aperture of the light source lamp is obtained. Therefore, there is an effect that the same polarized light beam as in the conventional case can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an optical system of a polarized light source device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an optical system of a polarized light source device according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating an optical system of a polarized light source device according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram for explaining a conventional polarization conversion optical system.

FIG. 5 is a schematic configuration diagram for explaining another example of a conventional polarization conversion optical system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polarized light source device 2 arc tube 3 reflecting mirror 3 a reflecting surface 3 b circular emission opening of light source lamp 3 c semicircular emission opening not shielded by reflector 4 light source lamp 4 a light source optical axis 5 polarization conversion optical system 6 reflector 6 a Reflection surface 7 UV cutoff filter 8 Polarization beam splitter 8a Emission surface 11 First polarization separation film 12 Second polarization separation film 13 Quarter wave plate 14 Total reflection plate 15 Condenser lens 20 Polarized light source device 21 Reflective liquid crystal device 30 Polarized light source device 31 First total reflection plate 32 Second total reflection plate 33 波長 wavelength plate I (s) S-polarized light I (p) P-polarized light I ′ (s) Obtained S-polarized light component I (out) Emitted light beam after polarization conversion

[Procedure amendment]

[Submission date] November 10, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

FIG. 5

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/74 H04N 5/74 A

Claims (4)

[Claims] 1. A light source lamp comprising a light emitting tube and a reflecting mirror for reflecting divergent light from the light emitting tube toward an emission opening, and a polarization direction of light emitted from the emission opening of the light source lamp being aligned. In the polarized light source device having a polarization conversion optical system for converting light, the light source lamp shields the emission opening on one side portion around one symmetry axis of the opening shape, and an emission light component emitted from the portion. And a polarization conversion optical system, wherein the polarization conversion optical system includes a P-polarized light component and a S-polarized light component, which are included in emission light emitted through a portion of the emission opening that is not shielded by the reflection plate. A first polarized light separating film that reflects one polarized light component of the polarized light components at a right angle and transmits the other polarized light component, and a polarized light component transmitted through the first polarized light separating film in the opposite direction. Total anti-reflection A quarter wavelength plate disposed on an optical path between the first polarization splitting film and the total reflection plate; and a first quarter wavelength plate disposed on an optical path between the first polarization splitting film and the quarter wavelength plate. And a second polarization separation film having the same polarization separation characteristics as the first polarization separation film, the polarization light source device being disposed orthogonal to the polarization separation film. 2. The polarization conversion optical system according to claim 1, wherein the polarization conversion optical system is replaced with the quarter-wave plate and the total reflection plate.
The light of the polarization component after passing through the second polarization separation film,
A polarized light source device comprising: a reflection type liquid crystal device that rotates its polarization direction by 90 degrees and totally reflects toward the second polarization separation film. 3. The polarization conversion optical system according to claim 1, wherein the polarization conversion optical system transmits through the first polarization separation surface instead of the second polarization separation film, the quarter-wave plate, and the total reflection plate. First and second total reflection plates that reflect the polarized component light after the reflection and emit the polarized component light reflected by the first polarization separation film in the same direction as the first total reflection plate Incident side of
Between the first and second total reflection plates or the second
か に arranged on any one of the emission sides of the total reflection plate
A polarized light source device comprising: a wave plate. 4. The polarized light source device according to claim 1, wherein light emitted from the emission opening of the light source lamp is parallel light.