JP3260821B2 - Light source device and projection type liquid crystal image display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device and a projection type liquid crystal image display device. INDUSTRIAL APPLICABILITY The light source device of the present invention can be used as a light source of a projection-type liquid crystal image display device, or as a light source of an optical device such as a polarization microscope that uses linearly polarized light.

[0002]

2. Description of the Related Art There are many optical devices that require linearly polarized illumination light, such as a projection type liquid crystal image display device, that is, a so-called "liquid crystal projector" or a polarizing microscope. As a method of obtaining a linearly polarized light beam, it is easiest to use a polarizing plate, but there is a problem that the use of a polarizing plate results in a large loss of light amount. When there is such a light amount loss, in a device requiring a large illumination light amount such as a projection type liquid crystal image display device,
The light source in the light source device needs to have an extremely large amount of light emission, and the amount of heat generated in the light source becomes enormous, so that measures against heat also become large.

As another example of converting a random polarization state into a linear polarization state, Japanese Patent Laid-Open Publication No.
There is a "polarization conversion module" disclosed in Japanese Patent No. 217814, but these publications do not disclose a specific structure and operation of the polarization conversion module, and what principle and mechanism perform polarization conversion. Not clear.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is very efficient to convert light from a white light source that emits light in a random polarization state into linearly polarized light and emit the light. It is an object of the present invention to provide a novel light source device which can be used and a projection type liquid crystal image display device which can realize a bright display image by using the light source device.

[0005]

A light source device according to the present invention is a light source device which "emits a linearly polarized light beam", and comprises a white light source, first and second polarization separation elements, a phase plate, and a dichroic. It has a mirror, a spectral unit, and a reflecting unit.

A "white light source" emits light in a random polarization state. As the white light source, in addition to a normal white light lamp, a combination of three LEDs that emit red, green, and blue light, or the like can be used.

[0007] The "first polarization separation element" is an optical element that separates light from a white light source into an S-polarized light component and a P-polarized light component. The “phase plate” transmits the P (or S) polarization component separated by the first polarization separation element.

[0008] The "second polarized light separating means" is provided "between the first polarized light separating element and the phase plate", and converts the P (or S) polarized light component separated by the first polarized light separating element into a phase. S of light returning from the phase plate side while passing to the plate side
The (or P) polarized light component is emitted in the same direction as the S (or P) polarized light component separated by the first polarization splitting element.

The "dichroic mirror" selectively transmits green light, and selectively transmits red light and blue light to the phase plate side, out of the light transmitted through the second polarization splitting means and transmitted through the phase plate. To reflect.

The "reflecting means" reflects the green light transmitted through the dichroic mirror in a predetermined direction.

The retardation of the phase plate is represented by (2l−) , where l, m, and n are natural numbers with respect to green wavelength: λ _G , red wavelength: λ _R , and blue wavelength: λ _B. 1) · λ _G / 2, {(2m ± 1) / 2} · λ _R / 2, {(2n ± 1) / 2} · λ _B / 2 .

The first and second polarization splitting means include:
A polarizing beam splitter or a polarizing beam plate can be used (claim 2). Further, a UV-IR filter (Claim 3) and / or a cold mirror for removing an ultraviolet light component and an infrared light component can be used between the white light source and the first polarization separation element (Claim 3). Item 4). As the phase plate, a birefringent crystal plate may be used (claim 5), or a metal plate in which a metal oxide film is obliquely deposited on one surface of a transparent parallel plate may be used (claim 6).

The phase plate and the dichroic mirror may be integrated with the second polarization splitting element.

The projection type liquid crystal image display device according to the present invention is characterized in that a light beam from a white light source is supplied to a two-dimensional liquid crystal shutter array which opens and closes a minute pixel shutter by turning a polarization plane according to an applied image signal. And projecting the light transmitted through the liquid crystal shutter array with a projection lens,
A projection type liquid crystal image display device for displaying an image in accordance with an image signal on a projection plane ", wherein the light source device is the light source device according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7. Features.

The projection type liquid crystal image display device can be implemented as a device for displaying a monochrome image or as a device for displaying a color image. In a projection type liquid crystal image display device for displaying a color image, a liquid crystal shutter array is disposed at a position optically equivalent to a projection lens, and is applied with a red image signal, a green image signal, and a blue image signal, respectively. , Red image, green image, and blue image shutter arrays. " Also,
The above-mentioned projection type liquid crystal image display device for displaying a color image includes a “color separation optical system” that separates a light beam from a light source into the three shutter arrays and irradiates each of the light beams, and transmits through the three shutter arrays. And a "color combining optical system" for combining the respective light beams into a single light beam incident on the projection lens.

[0016]

The light beam from the white light source is in a random polarization state, but is separated into a P-polarized light component and an S-polarized light component by the first polarization splitting element. One of the separated P and S polarized light components enters the second polarized light separating element. Here, for the sake of specificity, it is assumed that the P-polarized light component is incident on the second polarization separation element. Then, the P-polarized light component passes through the second polarization splitting element, is incident on the phase plate, and is transmitted therethrough.

The "retardance" of the phase plate is, as described above, green wavelength: λ _G , red wavelength: λ _R , blue wavelength: λ _B ,
Where l, m, and n are natural numbers, and (2l−1) · λ _G / 2, {(2m ± 1) / 2} · λ _R / 2, {(2n ± 1) / 2} -It is set to be λ _B / 2 . Accordingly, the green wavelength passes through the phase plate: from light lambda _G polarization plane previous incident state: The light lambda _G, phase difference of an odd multiple of a half wavelength is given, a green wavelength transmitted through the phase plate Turn 90 degrees, P before
The polarization state is converted from the polarization component to the S polarization component. Then, the light of the green wavelength: λ _G whose polarization state has been converted passes through the dichroic mirror.

On the other hand, the light of the red wavelength: λ _R and the light of the blue wavelength: λ _B pass through the phase plate, are reflected by the dichroic mirror, and pass through the phase plate again. Therefore, these lights reciprocately pass through the phase plate, but since the retardance for these lights is set as described above, these lights that reciprocately pass through the phase plate also have an order of an odd multiple of half a wavelength. A phase difference is given, and the polarization state is converted from the P polarization state at the time of incidence to the S polarization state. And these red wavelengths:
The light of λ _R , blue wavelength: λ _B returns to the second polarization separation element, passes through the second polarization separation element, and exits in the same direction as the S-polarized light component separated by the first polarization separation element. Will do.

Of course, in the above description, the light whose polarization plane rotates 90 degrees is light having wavelengths of λ _R , λ _G , and λ _B , and the light flux from the white light source is generally light having a wavelength other than the above-mentioned wavelengths. including. Therefore, the light transmitted through the dichroic mirror
The light returning to the second polarization separation element (which becomes elliptically polarized light having the long axis in the S direction) still has a P-polarized component, but the amount of the P-polarized component in the entire light is small. Thus, a significant part of the light transmitted through the dichroic mirror and the light returned to the second polarization splitting element can be used as S-polarized light.

[0020]

EXAMPLES Specific examples will be described below. FIG.
FIG. 3 is a view for explaining one embodiment of the light source device of the present invention. The white light source denoted by reference numeral 111 is constituted by a white lamp and a reflector, and emits a white light beam having a random polarization state. The white light flux is removed from the heat component by the cold mirror 112, the ultraviolet light component and the infrared light component are removed by the UV-IR filter 113, and is incident on the polarization beam splitter 121 as the first polarization separation element.
The polarizing beam splitter 121 reflects the incident S-polarized light component of the white light beam _W as a light beam SW, and transmits the P-polarized light component.

The transmitted light beam P _W of the P-polarized component passes through the polarization beam splitter 122 as a second polarization separation element joined to the polarization beam splitter 121 as it is. A wave plate 123 is adhered to the light exit surface of the polarization beam splitter 122, and a dichroic mirror 124 is adhered to the wave plate 123. The dichroic mirror 124 has a reflection wavelength region and a transmission reflection wavelength region as shown in FIG. 1B, and includes blue light including a blue wavelength: λ _B and red light including a red wavelength: λ _R. Is reflected.

The light beam P _W transmitted through the polarization beam splitter 122 transmits through the phase plate 123. Phase plate 123
Is a birefringent plate set to a retardance amount of 800 nm, and a phase difference given to transmitted light is represented by a solid curve T
, And the light that reciprocates through the phase plate 123 is given a phase difference as shown by a dashed curve R.

Therefore, the light transmitted through the phase plate 123 and the dichroic mirror 124 is green light including a green wavelength: λ _G , and this green light is given a phase difference almost equal to 波長 wavelength. the becomes light including a large amount of S-polarized light component, the light path direction is reversed 180 degrees by the prism 125 as a reflection means, and emits a light beam S _G. The light reflected by the dichroic mirror 124 is a blue light having a wavelength of λ _B and a red light having a wavelength of λ _R , both of which are given a phase difference close to 波長 wavelength and
When the light contains a large amount of polarized light components and enters the polarization beam splitter 123 as the second polarization splitting element, the S-polarized light components that occupy most of the light are reflected and emitted as light beams S _R and S _B.

2 and 3 show modified embodiments of the light source device. In order to avoid complication, the same reference numerals as in FIG. 1 are used for those which do not seem to be confused. The white light from the white light source 111 is
The light enters the polarization beam splitter 121 through the UV-IR filter 113 and the UV-IR filter 113, and the P-polarized light component is transmitted as it is and emitted as a white light flux _PW . The S-polarized light component separated by the reflection is a polarization beam splitter 122.
And is reflected, enters the phase plate 123, transmits the same, and enters the dichroic mirror 124. The phase plate 123 and the dichroic mirror 124 are the same as those in the example shown in FIG.

[0025] transmitted through the dichroic filter 124, the green light is deflected optical path direction by the prism 125 and emits as light P _S containing a large amount of P-polarized light component. Dichroic light reflected by dichroic mirror 124 is a blue light and red light, the light beam P _R P-polarized light component, which accounts for most of them is transmitted through the polarization beam splitter 122, P _B
Inject as

The example shown in FIG. 3 is an example in which the cold mirror is omitted from the embodiment shown in FIG. 1A and the reflecting means is changed from a prism to a mirror 126. Most of the light from the white light source 111 is converted into S-polarized light.

FIGS. 4 and 5 show embodiments of the projection type liquid crystal image display device for displaying a color image according to the present invention. In FIG. 4, reference numeral 1 denotes a light source device, reference numeral 2 denotes a projection image forming device, and reference numeral 3 denotes a projection lens device. Light source device 1 is the same as in Example 1, as described with reference to FIG. 1, S polarization state light beam S _W, S _R, S
_B, emit S _G. Reference numeral 12 denotes “polarization beam splitters 121 and 122, phase plate 123,
Dichroic mirror 124, prism 125 part "
Are collectively shown.

The projection image forming apparatus 2 includes dichroic mirrors 211, 212, 213, 214, a total reflection mirror 2
41, 242, shutter arrays 221, 222, 223 and liquid crystal shutter arrays, and condenser lenses 231, 232, 233 are combined as shown in the figure.

Dichroic mirrors 211 and 212, total reflection mirror 241, and condenser lens 23
1, 232 and 233 constitute a "color separation optical system", and include dichroic mirrors 213 and 214 and total reflection mirror 24.
Reference numeral 2 forms a “color combining optical system”.

The shutter arrays 221, 222, and 223 that constitute the liquid crystal shutter array have the same structure, and a two-dimensional liquid crystal shutter that opens and closes a minute pixel shutter by turning a polarization plane in accordance with an applied image signal. The linear polarization direction of the light flux emitted from the light source device 1 is set so as to correspond to the polarization direction of the polarizer on the incident side of each of the shutter arrays.

An image signal GS corresponding to a green component image is applied to the shutter array 221 and the shutter array 2
Image signals RS and BS corresponding to the red component image and the blue component image are applied to 22, 22 respectively. The dichroic mirror 211 selectively reflects green light and transmits light of another color. Dichroic mirrors 212 and 213
Selectively reflects red light and transmits other colors of light.
The dichroic mirror 214 selectively reflects blue light and transmits light of another color.

Accordingly, the liquid crystal shutter arrays 221, 221
When the light source 1 is operated while applying the image signals GS, RS, and BS to the liquid crystal shutter arrays 22, 223, respectively, a red image, a green image, and a blue image are obtained in the liquid crystal shutter arrays 221, 222, and 223. The respective shutter arrays are located at optically equivalent positions with respect to the projection lens of the projection lens device 3. Therefore, the image of each shutter array can be enlarged and projected on the screen 4 by the projection lens device 3 to display a color image.

In the embodiment shown in FIG. 5, the light source device 1A
Is the same as the embodiment shown in FIG. The projection image forming apparatus 2A includes a dichroic mirror prism 2
15, 116, total reflection mirrors 241, 242, 243,
244, shutter arrays 221, 222, and 223, which constitute a liquid crystal shutter array, and condenser lenses 231, 232, and 233 are combined as shown in the figure. Shutter arrays 221, 222,
223 is the same as that described with reference to the embodiment of FIG. 4, and the shutter array 221 receives the image signal GS corresponding to the green component image,
3, image signals RS and BS corresponding to the red component image and the blue component image, respectively, are applied. Both dichroic mirror prisms 215 and 116 selectively transmit red light and reflect light of other colors.

A dichroic mirror prism 215;
The total reflection mirrors 241, 242, 243, 244 and the condenser lenses 231, 232, 233 constitute a color separation optical system, and the dichroic mirror prism 116 constitutes a color synthesis optical system.

When the light source device 1A is turned on, the emitted light beam is linearly polarized light, and the green, red, and blue light components are applied to the shutter arrays 221, 222, and 223, respectively.

Shutter arrays 221, 222, 223
When the light source 1 is operated while applying the image signals GS, RS, and BS to the liquid crystal shutter arrays 221, 22 respectively.
2, 223, a red image, a green image, and a blue image are obtained, respectively. Each shutter array is located at an optically equivalent position with respect to the projection lens of the projection lens device 3, and the image of each shutter array is enlarged and projected on the screen 4 by the projection lens device 3 to display a color image. be able to.

The above description has been made of an example in which a color image is projected and displayed. However, if a monochrome image is projected and displayed, the liquid crystal shutter array can be constituted by one shutter array, and the light from the light source device is emitted. Is irradiated on the shutter array, a monochrome image according to the image signal is obtained on the shutter array, and this image is projected and displayed on the screen by the projection lens device.

[0038]

As described above, according to the present invention, a novel light source device and a projection type liquid crystal image display device can be provided. Since the light source device of the present invention is configured as described above, it is possible to convert light in a random polarization state from a white light source into light in a linear polarization state with high efficiency and emit the light.
Therefore, a projection type liquid crystal image display device using this light source device as a light source has extremely high light use efficiency and can realize bright image display without using a light source having a large light emission amount.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of a light source device.

FIG. 2 is a diagram showing another embodiment of the light source device.

FIG. 3 is a diagram showing another embodiment of the light source device.

FIG. 4 is a diagram schematically showing only a main part of one embodiment of a projection type liquid crystal image display device.

FIG. 5 is a diagram schematically showing only a main part of another embodiment of the projection type liquid crystal image display device.

[Explanation of symbols]

111 White light source 112 Cold mirror 113 UV-IR filter 121,1
22 polarizing beam splitter 123 phase plate
124 dichroic mirror 125
prism

Claims (9)

(57) [Claims] 1. A light source device for emitting a linearly polarized light beam, comprising: a white light source for emitting light in a random polarization state; and a light source for separating light from the white light source into an S-polarized light component and a P-polarized light component. P (or S) separated by the first polarized light separating element and the first polarized light separating element
A phase plate that transmits a polarized light component; and a P (or S) polarized light component that is provided between the first polarized light separating element and the phase plate and that is separated by the first polarized light separating element passes through the phase plate. A second polarization separating unit that emits the S (or P) polarized component of the light returning from the phase plate in the same direction as the S (or P) polarized component separated by the first polarization separating element; A dichroic mirror that selectively transmits green light and reflects red light and blue light to the phase plate side out of the light that has passed through the second polarization splitting means and transmitted through the phase plate; Reflecting means for reflecting the green light transmitted through the mirror in a predetermined direction, wherein the retardation of the phase plate is green light: λ _G , red light: λ _R , blue light: λ _B On the other hand, l, m, n As the number, respectively, set to be _{(2l-1) · λ G} / 2, {(2m ± 1) / 2} · λ R / 2, {(2n ± 1) / 2} · λ B / 2 A light source device, characterized in that: 2. The light source device according to claim 1, wherein the first and second polarization splitting means are a polarization beam splitter or a polarization beam plate. 3. The light source device according to claim 1, further comprising a UV-IR filter for removing an ultraviolet light component and an infrared light component between the white light source and the first polarization splitting element. Characteristic light source device. 4. The light source device according to claim 1, wherein a cold mirror is provided between the white light source and the first polarization splitting element. 5. The light source device according to claim 1, wherein the phase plate is a birefringent crystal plate. 6. The light source device according to claim 1, wherein the phase plate is formed by obliquely depositing a metal oxide film on one surface of a transparent parallel flat plate. 7. The light source device according to claim 1, wherein the phase plate and the dichroic mirror are integrated with the second polarization splitting element. Light source device. 8. A two-dimensional liquid crystal shutter array, which opens and closes a minute pixel shutter by turning a polarization plane according to an applied image signal, is irradiated with a light beam from a white light source, and the light transmitted through the liquid crystal shutter array. Is projected by a projection lens, and an image according to the image signal is displayed on a projection plane, wherein the light source device is a light source device. A projection type liquid crystal image display device, which is the light source device described in the above. 9. The projection type liquid crystal image display device according to claim 8, wherein the liquid crystal shutter array is disposed at an optically equivalent position with respect to the projection lens, and outputs a red image signal, a green image signal, and a blue image signal, respectively. A color separation optical system configured to be applied with shutter arrays for a red image, a green image, and a blue image. A color synthesizing optical system for synthesizing each light beam transmitted through the three shutter arrays into a single light beam incident on the projection lens.