JPH11271684A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable polarized light conversion without the need of a microlens array. SOLUTION: Instead of the microlens array, a hologram optical element 50 is used. The light emitted from a light source 40 is converted in its advancing direction by the hologram optical element 50 and is made incident on a polarized light conversion optical system 60. In the polarized light conversion optical system 60, the polarized light conversion is performed by a polarized beam splitter array 62, a reflection mirror array 63 and a λ/2 plate array 64. The light converted to linearly polarized light in the polarized light conversion optical system 60 generates image by an image display optical system 70.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device. In particular, the present invention relates to an image display device that performs polarization conversion by spatially modulating light using a hologram optical element.

[0002]

2. Description of the Related Art A conventional image display device is disclosed in
There is a polarized light illumination device described in Japanese Patent No. 304739. Hereinafter, a conventional image display device will be described with reference to the drawings and descriptions described in this publication. FIG.
It is the schematic block diagram which looked at the principal part of the conventional polarized light illuminating apparatus in planar view. The polarized light illuminating device 1 of the present example is roughly constituted by a light source unit 2, a first lens plate 3, and a second lens plate 4 arranged along the system optical axis L. The light emitted from the light source unit 2 is condensed into the second lens plate 4 by the first lens plate 3, and in the process of passing through the second lens plate 4, the randomly polarized light has a polarization direction of The light is converted into one kind of uniform polarized light, and reaches the illumination area 5.

The light source section 2 is generally constituted by a light source lamp 201 and a parabolic reflector 202. The randomly polarized light emitted from the light source lamp 201 is reflected in one direction by the parabolic reflector 202, and is incident on the first lens plate 3 as a substantially parallel light flux. here,
Instead of the parabolic reflector 202, an elliptical reflector, a spherical reflector, or the like can be used. The light source optical axis R is inclined by a certain angle with respect to the system optical axis L.

FIG. 5 shows the appearance of the first lens plate 3. As shown in this figure, the first lens plate 3 has a configuration in which a plurality of minute rectangular condenser lenses 301 having a rectangular outline are arranged vertically and horizontally. The light incident on the first lens plate 3 forms the same number of condensed images as the number of the rectangular condensing lenses 301 in a plane perpendicular to the system optical axis L by the condensing action of the rectangular condensing lens 301. Since the plurality of condensed images is nothing but a projection image of the light source lamp, it is hereinafter referred to as a secondary light source image.

Next, with reference to FIG. 4 again, the second lens plate 4 of this embodiment will be described. The second lens plate 4 includes a condenser lens array 410 and a polarization separation prism array 42
0, a λ / 2 retardation plate 430 and an emission side lens 440, and is a composite laminate including a second light source image formed by the first lens plate 3 with respect to the system optical axis L near the position. It is located in a vertical plane. This second
The lens plate 4 has a function as a second lens plate of the integrator optical system, a function as a polarization separation element, and a function as a polarization conversion element.

The condensing lens array 410 has substantially the same configuration as the first lens plate 3. That is, a plurality of condensing lenses 411 of the same number as the rectangular condensing lens 301 constituting the first lens plate 3 are arranged, and have an action of condensing light from the first lens plate 3. Condensing lens array 4
Reference numeral 10 corresponds to a second lens plate of the integrator optical system.

The condenser lens 411 constituting the condenser lens array 410 and the rectangular condenser lens 301 constituting the first lens plate 3 do not need to have exactly the same dimensions, shape and lens characteristics. It is desirable that each be optimized in accordance with the characteristics of the light from the light source unit 2. However, it is ideal that the light incident on the polarization splitting prism array 420 has a chief ray inclined parallel to the system optical axis L. From this point, the condenser lens 411 has the same lens characteristics as the rectangular condenser lens 301 constituting the first lens plate 3 or has a shape similar to that of the rectangular condenser lens 301. In many cases, they have the same lens characteristics.

FIG. 6 shows a polarization separating prism array 420.
Is shown. As shown in this figure, a polarized light separating prism array 420 includes a polarizing beam splitter 421 formed of a prismatic prism composite having a polarization separating film inside, and a rectangular prismatic prism composite also having a reflecting film inside. And a reflection mirror 422 composed of a plurality of reflection mirrors 422 as a basic structural unit, and a plurality of the pairs arranged in a plane (arranged in a plane on which a secondary light source image is formed).
A pair of basic constituent units are regularly arranged so as to correspond to the condenser lens 411 constituting the condenser lens array 410. Also, the width Wp of one polarization beam splitter 421 and the width Wm of one reflection mirror 422
Are equal. Further, in this example, the condenser lens array 410
Although the values of Wp and Wm are set so as to be の of the width of the condenser lens 411 constituting the above, the present invention is not limited to this.

Here, the second lens plate 4 including the polarization separation prism array 420 is arranged so that the secondary light source image formed by the first lens plate 3 is located at the portion of the polarization beam splitter 421. I have. For this purpose, the light source unit 2 is arranged such that the light source optical axis R makes a slight angle with respect to the system optical axis L.

Referring to FIGS. 4 and 6, the randomly polarized light incident on the polarization splitting prism array 420 is converted into two types of polarized light, P-polarized light and S-polarized light, having different polarization directions by a polarization beam splitter 421. Separated into light. The P-polarized light passes through the polarization beam splitter 421 without changing the traveling direction. On the other hand, S-polarized light is
The light is reflected by the polarization splitting film 423 of the polarization beam splitter 421 to change the traveling direction by about 90 degrees, and the adjacent reflection mirror 4
The light is reflected by the reflection surface 424 of the reflection mirror 22 (a pair of reflection mirrors), changes the traveling direction by about 90 degrees, and is finally emitted from the polarization separation prism array 420 at an angle substantially parallel to the P-polarized light.

On the exit surface of the polarization separating prism array 420, a λ / 2 retardation film 431 is regularly arranged,
A retardation plate 430 is provided. That is, the polarization beam splitter 4 constituting the polarization separation prism array 420
The λ / 2 retardation film 431 is disposed only on the exit surface portion of the optical disk 21, and the λ / 2 retardation film 431 is not disposed on the exit surface portion of the reflection mirror 422. Therefore, the P-polarized light emitted from the polarization beam splitter 421 is converted into S-polarized light by rotating the polarization plane when passing through the λ / 2 retardation film 431. On the other hand, since the S-polarized light emitted from the reflection mirror 422 does not pass through the λ / 2 retardation film 431, it does not receive any rotation of the polarization plane and passes through the λ / 2 retardation plate 430 as S-polarized light. I do. To summarize the above,
Polarization separation prism array 420 and λ / 2 retardation plate 430
Thus, the randomly polarized light is converted into one type of polarized light (in this case, S-polarized light).

In this manner, the luminous flux aligned to the S-polarized light is guided to the illumination area 5 by the exit lens 440, and is superposed and coupled on the illumination area 5. That is, the image plane cut out by the first lens plate 3 is superimposed and formed on the illumination area 5 by the second lens plate 4. At the same time, the random polarized light is spatially separated into two types of polarized lights having different polarization directions by the polarized light separating prism array 420 in the middle, and when passing through the λ / 2 retardation plate 430, the random polarized light becomes one.
Is converted into various kinds of polarized light, and almost all the light is
To reach. Therefore, the illumination region 5 is almost uniformly illuminated with one type of polarized light.

FIG. 7 shows an example of a projection display device in which the polarized light illumination device 1 shown in FIG. 4 is incorporated. As shown in FIG. 7, the polarization illuminating device 1 of the projection display device 3400 of the present example includes a light source unit 2 that emits randomly polarized light in a position direction, and the random polarized light emitted from the light source unit 2. After being condensed by the first lens plate 3 and guided to a predetermined position on the second lens plate 4, two types of polarized light are polarized by the polarization separation prism array 420 in the second lens plate 4. Separated into light. Further, among the separated polarized lights, the P-polarized light is converted into the S-polarized light by the λ / 2 retardation plate 430.

The light beam emitted from the polarized light illuminating device 100 is first reflected by a blue-green reflecting dichroic mirror 340.
At 1, red light is transmitted and blue light and green light are reflected. The red light is reflected by the reflection mirror 3402, and
To the liquid crystal light valve 3403. On the other hand, of the blue light and the green light, the green light is reflected by the green reflecting dichroic mirror 3404 and reaches the second liquid crystal light valve 3405.

Here, since the blue light has the longest optical path length of each color light, the incident side lens 34 for the blue light.
06, relay lens 3408 and emission side lens 3410
Light guide means 3450 comprising a relay lens system comprising
Is provided. That is, after transmitting the blue light through the green reflecting dichroic mirror 3404, first, the incident side lens 3
406 and the reflection mirror 3407, the relay lens 3
After being guided to 408 and converged by the relay lens 3408, the light exit side lens 341 is reflected by the reflection mirror 3409.
0, and then the third liquid crystal light valve 34
Reach 11. Here, the first to third liquid crystal valves 3
403, 3405, and 3411 modulate the respective color lights and include video information corresponding to each color, and then convert the modulated color lights into a dichroic prism 3413 (color combining unit).
Incident on. In the dichroic prism 3413, a dielectric multilayer film for red reflection and a dielectric multilayer film for blue reflection are formed in a cross shape, and synthesize modulated light beams. The light flux synthesized here passes through the projection lens 3414 (projection unit), and forms an image on the screen 3415. The above is the conventional apparatus disclosed in Japanese Patent Application Laid-Open No. H8-304739.

[0016]

Since the conventional polarized light illuminating device is configured as described above, it is necessary to incline the light beam with respect to the optical axis. Also, when performing polarization conversion,
There is a disadvantage that a microlens array is required and the structure becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an image display apparatus which does not need to tilt a light beam from a light source with respect to an optical axis and does not need a microlens array. The purpose is to gain.

[0018]

An image display device according to the present invention has the following elements. (A)
A light source that outputs light, (b) a hologram optical element that receives light from the light source and changes the traveling direction of the light, and (c) a polarization light that receives light output from the hologram optical element and performs polarization conversion. A conversion optical system, and (d) an image display optical system that displays an image using light output from the polarization conversion optical system.

The hologram optical element receives light having a wavelength λ, modulates the light having a wavelength λ with a frequency f _i , changes the traveling direction of the input light to λf _i and −λf _i , and outputs it. It is a computer generated hologram.

The polarization conversion optical system is arranged at a position where light from the hologram optical element is input and condensed, and at a position where light from the condensing lens is condensed. A polarizing beam splitter array that separates any one of the following linearly polarized lights, a reflecting mirror array that reflects one of the P- and S-wave linearly polarized lights separated by the polarizing beam splitter array, and light reflected by the reflecting mirror array. And a λ / 2 plate array for converting the light into the other linearly polarized light.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a principle diagram of the present invention. The image display device of the present invention includes a light source 40
And a hologram optical element 50, a polarization conversion optical system 60, and an image display optical system 70. The polarization conversion optical system 60 includes a condenser lens 61, a polarization beam splitter array 62, a reflection mirror array 63, and a λ / 2 plate array 64. The image display optical system 70 includes an emission lens 71 and a liquid crystal panel 72. Since the configuration of the polarization conversion optical system 60 is the same as that shown in the conventional example, a detailed description will not be given here.

Next, the hologram optical element 50 will be described. FIG. 2 is a diagram illustrating the principle of a hologram. A hologram is originally a dry plate on which interference fringes (amplitude and phase) of two lights are recorded. Here, a computer generated hologram (computer generated hologram) on which a calculated digital pattern is recorded will be considered. When a laser beam having a wavelength λ is incident on a phase plate modulated at a frequency f _i , the laser light is split in the directions of angles λf _i and −λf _i . A computer generated hologram is a kind of diffractive optical element, and can be considered as a phase plate that gives a periodic optical path difference to the wavefront of incident laser light and performs spatial modulation in a direction in which light is to be propagated. Due to the principle of superposition, many frequencies f1, f
., F3,... Can be divided in the direction of each frequency. Here, the hologram optical element 50 and the condenser lens 61 are arranged as shown in FIG.
(The focal length is F), if the polarizing beam splitter array 62 is arranged, the polarizing beam splitter array 6
You can shift the focal point at a position away Efuramudaf _i and -Efuramudaf _i from the optical axis on the two.

Hologram optical element (HOE: Holog)
In the design of the Optical Optical Element, the Fourier transform spectrum of the HOE pattern is
A computer is designed to have a sharp peak at a frequency corresponding to a position where an image is to be placed. For example, as the HOE, a surface relief type transmission phase hologram (Kinoform) that directly etches synthetic quartz to provide a multi-stage phase difference is employed. The HOE pattern has a pixel size of 1
256 × 256 to 10 with a square of 〜2 μm as a unit
It is composed of 24 × 1024 pixels. In the actual calculation,
First, a random phase is given to each pixel, and an error function (evaluation function) that can be determined to be close to the target value when the Fourier transform spectrum has a high peak at a required frequency is set. Convergence calculation is performed so as to minimize the error function by sequentially changing the phases of the pixels.

Next, the multi-zone homogenizer of the hologram will be described. The feature of the hologram-based homogenizer is that a conventional general prism or a kaleidoscope-type homogenizer simply forms a uniform irradiation area in one place, whereas a required area (zone) is required. The ability to irradiate a homogenized beam at the same time. The irradiation area can be adjusted to the arrangement of the polarizing beam splitter array 62 and can have any shape. For example, as shown in the example shown in FIG. 1, when there are openings (positions of the polarizing beam splitters) through which light is transmitted in nine regions,
The beam spot can be divided into nine regions.
By doing so, the light transmittance at the opening can be improved as compared with the case where the entire region is irradiated. The irradiation method that makes the most of this feature is to perform beam irradiation in accordance with the pattern of the opening as shown in FIG. And one
Since irradiating one split beam to one aperture may cause variations in the intensity distribution of the focused spot, several beams should be superimposed on each aperture to homogenize the intensity distribution. Can be. Such a technique of simultaneously irradiating a beam having an arbitrary shape and a homogenized intensity distribution in a large number of regions is called a multi-zone homogenizer.

The light emitted from the light source 40 is preferably a parallel light. The hologram optical element 50 converts the traveling direction of the incident light to a predetermined angle with respect to the traveling direction of the incident light. Therefore, the higher the degree of parallelism of the light beam incident from the light source 40, the more desirable.

As described above, in this embodiment, a parallel light beam from the light source 40 is spatially modulated using the hologram optical element 50 designed by a computer based on the principle of the hologram, that is, The light is guided to the polarization beam splitter array 62 prepared as the polarization conversion optical system 60 by changing the traveling direction. Polarization conversion optical system 6
The light converted to linearly polarized light by 0 is applied to the liquid crystal panel 72 from the exit lens 71. When the light is emitted from the emission lens 71 to the liquid crystal panel 72, the light emitted from the emission lens 71 is superimposed on the liquid crystal panel 72, and the luminance distribution can be made flat and uniform. LCD panel 72
Is output by a conventionally known configuration. Note that the polarization conversion optical system is not limited to the one shown in FIG. 1, and another configuration may be used.

[0027]

As described above, according to the present invention, by employing a hologram, a microlens array which has been conventionally required can be eliminated, and the optical system can be simplified.

According to the present invention, as in the prior art,
Since it is not necessary to tilt the optical axis of the light beam, there is an effect that the arrangement and adjustment of the optical system are simplified.

Further, according to the present invention, the luminance distribution can be made uniform by using a hologram.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a diagram showing the principle of the hologram of the present invention.

FIG. 3 is a diagram showing the principle of a hologram projection system according to the present invention.

FIG. 4 is a diagram showing a conventional polarized light illumination device.

FIG. 5 is a diagram showing a conventional microlens array.

FIG. 6 is a diagram showing a conventional polarization conversion optical system.

FIG. 7 is a diagram showing a conventional projection display device.

[Explanation of symbols]

Reference Signs List 40 light source, 50 hologram optical element, 60 polarization conversion optical system, 61 condenser lens, 62 polarization beam splitter array, 63 reflection mirror array, 64λ / 2 plate array, 70 image display optical system, 71 emission lens, 7
2 Liquid crystal panel.

Claims (3)

[Claims] 1. An image display device having the following elements: (a) a light source that outputs light; (b) a hologram optical element that receives light from the light source and changes the traveling direction of the light;
(C) a polarization conversion optical system that receives the light output from the hologram optical element and performs polarization conversion, and (d) an image display optical system that displays an image using the light output from the polarization conversion optical system. 2. The hologram optical element receives light having a wavelength λ, modulates light having a wavelength λ at a frequency f _i , and changes the traveling direction of the input light to λf _i and −λf _i. 2. A computer generated hologram for output.
The image display device as described in the above. 3. A polarization conversion optical system, comprising: a condenser lens for inputting light from a hologram optical element and condensing the light; and a light condensing lens disposed at a position where the light from the condenser lens is condensed. A polarizing beam splitter array that separates any linearly polarized light from the S wave, a reflecting mirror array that reflects one of the P wave and the S wave separated by the polarizing beam splitter array, and a reflecting mirror array that reflects the reflected light. 3. The image display device according to claim 2, further comprising a λ / 2 plate array for converting the reflected light into the other linearly polarized light.