JP2002031845A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a projection lens for a projector. SOLUTION: This projector is provided with plural liquid crystal panels 410R, 410G and 410B to respectively modulate plural color light beams, a cross dichroic prism 420 to synthesize a color light beam modulated by an optical modulating device and the projection lens 40 to project a synthesized light beam synthesized by the cross dichroic prism, and field lenses 411, 412 and 413 to condense the synthesized light beam of the color light beam on the entrance pupil of the projection lens 40 are arranged between the liquid crystal panels 410R, 410G and 410B and the cross dichroic prism 420, and color light beam selecting films 421 and 422 of the cross dichroic prism 420 is provided with shading.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projector (projection display device), and particularly to an optical system thereof.

[0002]

2. Description of the Related Art FIG. 10 is a perspective view showing the appearance of a general projector. Here, the projector 501
An upper case 503 defining its upper surface and having operation buttons 502 disposed thereon, and a lower case 50 defining its lower surface.
4. A rectangular parallelepiped shape having a front case 505 defining the front surface thereof is formed, and a front end portion of the projection lens 506 protrudes from the front case 505.

A known optical system in such a projector has, for example, a configuration as shown in FIG.
That is, the illuminance distribution of the light from the light source 510 is made uniform,
The liquid crystal panels 550R, 550R, 5
A first lens array 521, a second lens array 522, and a polarization conversion element 52 for allowing the light to be incident on 50G and 550B.
3 and an illumination optical system 520 including a superimposing lens 524;
The light beam W emitted from the illumination optical system 520 is red,
A color light separation optical system 530 that separates the green and blue light beams R, G, and B, and a liquid crystal panel 550 that corresponds to the blue light beam B among the color light beams separated by the color light separation optical system 530.
B, a relay optical system 540, three liquid crystal panels 550R, 550G and 550B as light modulating means for modulating each color light beam according to given image information, and a color light combining optical system for combining the modulated color light beams. And a projection lens 506 for enlarging and projecting the combined light beam on a projection surface. In addition,
In front of each liquid crystal panel, parallelizing lenses 534, 535, 545 for parallelizing divergent light are arranged.

[0004] Here, the illumination optical system 520 includes:
Each liquid crystal panel is uniformly illuminated and brightened to every corner when an image is displayed by the projector, which contributes to providing a clear image with high contrast over the entire area.

[0005]

As shown in FIG. 12, the light emitted from the illumination optical system 520 is collimated by collimating lenses 534, 535, and 545. Since the light passes through the projection lens 560 and is guided to the projection lens 506, when the size of the illumination optical system and the characteristics such as the light collection characteristics are determined, the position farthest from the projection surface among the plurality of lenses constituting the projection lens is determined. There is a problem that the diameter of the lens (rear lens) 506A disposed in the lens is determined, and the projection lens cannot be made smaller, and the degree of freedom in designing the projection lens is limited. In particular, in an illumination optical system using a uniform illumination optical system, light incident on the projection lens tends to diverge in various directions, so that the degree of freedom in designing the projection lens is likely to be limited. SUMMARY An advantage of some aspects of the invention is to provide a projector that can reduce the size of a projection lens without being influenced by the characteristics of an illumination optical system.

[0006]

According to the present invention, there is provided a projector comprising: an illumination optical system for emitting illumination light; a color separation optical system for separating light emitted from the illumination optical system into a plurality of color lights; A plurality of collimating lenses for respectively collimating the color lights emitted from the optical system, and a plurality of light modulators for respectively modulating the plurality of color lights emitted from the collimating lens,
A color light combining prism that combines the color lights modulated by these light modulation devices, and a projector that includes a projection lens that projects the light combined by the color light combination prism, and each of the plurality of light modulation devices A light traveling direction adjusting means for condensing the combined light toward an entrance pupil of the projection lens is arranged between the color light combining prism. In addition, the light traveling direction adjusting means can be configured by a convex lens or a combination of lenses.

As described above, by using the light traveling direction adjusting means such as a convex lens or the like, the combined light exiting the color light combining prism is efficiently condensed toward the entrance pupil of the projection lens.
Regardless of the characteristics of the illumination optical system, the size of the projection lens can be selected, so that the size of the projection lens and thus the projector itself can be reduced.

Further, in order to correct color unevenness caused by the provision of the light traveling direction adjusting means, the color synthesizing prism includes a dielectric multilayer film and is caused by the light traveling direction adjusting means. It is preferable to include a color non-uniformity correction unit that corrects a wavelength shift generated in the dielectric multilayer film due to a change in a light incident angle.

As a means for correcting color unevenness, for example, by giving shading to a dielectric multilayer film formed in the cross dichroic prism 420, it is possible to respond to a change in the incident angle of light on these dielectric multilayer films. By changing the characteristics of the film according to the position, it is possible to cancel the wavelength shift caused by the installation of the field lens.

[0010]

Next, embodiments of the present invention will be described based on examples. In the following description, unless otherwise specified, the traveling direction of light is the z direction, and the direction at 12 o'clock as viewed from the z direction is the y direction, and the direction at 3 o'clock is the x direction.

FIG. 1 is a schematic plan view showing an optical system configuration of a projector (projection display device) according to one embodiment of the present invention. This optical system includes three main parts: a light source unit 20, an optical unit 30, and a projection lens 40.

The optical unit 30 includes an integrator optical system 300, which will be described later, and dichroic mirrors 382, 3
86, color light separation optical system 380 having reflection mirror 384
And a relay optical system 390 having an incident side lens 392, a relay lens 396, and reflection mirrors 394, 398, and three parallelizing lenses 400, 402, and 40.
4, three liquid crystal panels (liquid crystal light valves) 410R, 410G, 410B as light modulation devices, and field lenses 411, 412, as light traveling direction adjusting means.
413 and a cross dichroic prism 420 as a color light combining prism.

The light source unit 20 is disposed on the incident surface side of the first lens array 320 of the optical unit 30,
The projection lens 40 is arranged on the exit surface side of the cross dichroic prism 420 of the optical unit 30.

FIG. 2 is an explanatory diagram showing an illumination optical system for illuminating three liquid crystal panels which are illumination areas of the projector shown in FIG. The illumination optical system includes a light source 200 provided in the light source unit 20 and an integrator optical system 300 provided in the optical unit 30. The integrator optical system 300 includes a first lens array 320 and a second lens array 320.
It has a lens array 340, a light blocking plate 350, a polarization conversion element array 360, and a superimposing lens 370. In FIG. 2, for the sake of simplicity, only the main components for explaining the function of the illumination optical system are shown.

The light source 200 includes a light source lamp 210 and a concave mirror 212. Radial light rays (radiated light) emitted from the light source lamp 210 are reflected by the concave mirror 212 and emitted in the direction of the first lens array 320 as substantially parallel light beams. Here, as the light source lamp 210,
A halogen lamp, a metal halide lamp, or a high-pressure mercury lamp can be used. As the concave mirror 212, a parabolic mirror is preferably used.

FIG. 3 is a front view (A) and a side view (B) showing the appearance of the first lens array 320. This first
In the lens array 320, small small lenses 321 having a rectangular outline are arranged in N × 2 rows (here, N = 2).
4), which are arranged in a matrix of M rows (here, M = 10) in the horizontal direction, and the external shape of each small lens 321 viewed from the z direction is each of the liquid crystal panels 410R, 410G,
The shape is set to be substantially similar to the shape of 410B. For example, if the aspect ratio (the ratio between the horizontal and vertical dimensions) of the image forming area of the liquid crystal panel is 4: 3, the aspect ratio of each small lens 321 is also set to 4: 3.

The second lens array 340 has a function of guiding a plurality of partial light beams emitted from the first lens array 320 so as to overlap the liquid crystal panel via the polarization separation films 366 of the two polarization conversion element arrays 361 and 362. And the first
The lens array 320 includes the same number of small lenses 341 as the number of lenses. The first lens array 32
0 and the lens orientation of the second lens array 340 are +
They may face either the z direction or the −z direction, or they may face different directions as shown in FIG.

As shown in FIG. 2, the polarization conversion element array 360 has two polarization conversion element arrays 361 and 362 arranged symmetrically with respect to the optical axis. FIG. 4 is a perspective view showing the appearance of one polarization conversion element array 361.
The polarization conversion element array 361 includes a polarization beam splitter array 363 composed of a plurality of polarization beam splitters and a λ / 2 phase difference plate 364 (λ is selectively disposed on a part of the light exit surface of the polarization beam splitter array 363. Light wavelength). Polarizing beam splitter array 36
3 has a shape in which a plurality of columnar translucent members 365 each having a parallelogram cross section are sequentially bonded.
Polarized light separating films 366 and reflective films 367 are alternately formed on the interface of the light transmitting member 365. λ / 2 phase difference plate 3
Reference numeral 64 is selectively affixed to the x-direction mapped portion of the light exit surface of the polarization separation film 366 or the reflection film 367. In this example, a λ / 2 retardation plate 364 is attached to the x-direction mapped portion of the light exit surface of the polarization separation film 366.

The polarization conversion element array 361 has a function of converting an incident light beam into one type of linearly polarized light (for example, s-polarized light or p-polarized light) and emitting the same. FIG. 5 is a schematic diagram illustrating the operation of the polarization conversion element array 361. When non-polarized light (incident light having a random polarization direction) including an s-polarized component and a p-polarized component is incident on the incident surface of the polarization conversion element array 361, the incident light is
66 separates the light into s-polarized light and p-polarized light. The s-polarized light is reflected almost vertically by the polarization splitting film 366,
The light is emitted after being further reflected by the reflection film 367. On the other hand, the p-polarized light passes through the polarization separation film 366 as it is. A λ / 2 retardation plate 364 is disposed on the exit surface of the p-polarized light transmitted through the polarization separation film 366.
The polarized light is converted into s-polarized light and emitted. Therefore, most of the light that has passed through the polarization conversion element array 361 is emitted as s-polarized light. When light emitted from the polarization conversion element array 361 is desired to be p-polarized light, the λ / 2 retardation plate 364 may be disposed on the emission surface from which the s-polarized light reflected by the reflection film 367 is emitted. Good.
Further, as long as the polarization directions can be aligned, a λ / 4 retardation plate may be used, or a desired retardation plate may be provided on both the exit surfaces of the P-polarized light and the S-polarized light.

In the polarization conversion element array 361, one adjacent polarization separation film 366 and one reflection film 36
7, and one block composed of one λ / 2 retardation plate 364 can be regarded as one polarization conversion element 368. In the polarization conversion element array 361, such polarization conversion elements 368 are arranged in a plurality of rows in the x direction. Note that the polarization conversion element array 362 has exactly the same configuration as the polarization conversion element array 361, and a description thereof will be omitted.

FIG. 6 is a front view showing the light shielding plate 350. The light shielding plate 350 includes two polarization conversion element arrays 36.
Of the 1,362 light incident surfaces, the light incident surface is used so that light is incident only on the light incident surface corresponding to the polarization separation film 366.
It has a configuration in which a plurality of openings 351 are provided in a substantially rectangular plate.

The unpolarized light emitted from the light source 200 shown in FIG. 2 is divided into a plurality of partial light beams 202 by a plurality of small lenses 321 of a first lens array 320 constituting an integrator optical system 300, The two polarization conversion element arrays 361, 361 are provided via the lens array 340.
The light is condensed near the polarization separation film 366. The plurality of partial light beams incident on the two polarization conversion element arrays 361 and 362 are converted into one type of linearly polarized light and emitted.
The plurality of partial light beams emitted from the two polarization conversion element arrays 361 and 362 are superimposed on liquid crystal panels 410R, 410G, and 410B described later by the superimposing lens 370.

The reflection mirror 372 shown in FIG.
The light beam emitted from the superimposing lens 370 is provided to guide the light beam toward the color light separation optical system 380. Therefore, it is not always necessary depending on the configuration of the optical system.

The color light separation optical system 380 includes first and second
It has dichroic mirrors 382 and 386 and has a function of separating light emitted from the illumination optical system into three color lights of red, green, and blue. First dichroic mirror 38
2 transmits the red light component of the light emitted from the superimposing lens 370 and reflects the blue light component and the green light component. The red light transmitted through the first dichroic mirror 382 is reflected by the reflection mirror 384 and passes through the collimating lens 400 to reach the liquid crystal panel 410R for red light. The parallelizing lens 400 converts each partial light beam emitted from the superimposing lens 370 into a light beam parallel to the central axis (principal ray). Other liquid crystal panels 410G, 41
The collimating lenses 402 and 404 provided before 0B operate similarly.

Further, the first dichroic mirror 382
Of the blue light and the green light reflected by the green light, the green light is reflected by the second dichroic mirror 386, passes through the collimating lens 402, and reaches the liquid crystal panel 410G for green light. On the other hand, the blue light is transmitted to the second dichroic mirror 386.
Through the relay optical system 390, that is, the incident side lens 392, the reflection mirror 394, the relay lens 396, and the reflection mirror 398, and further to the collimating lens 40
4 and reaches the liquid crystal panel 410B for blue light. The reason why the relay optical system 390 is used for blue light is that the optical path length of blue light is longer than the optical path lengths of other color lights, so that a reduction in light use efficiency due to light diffusion or the like is prevented. To do that. That is, it is for transmitting the partial light beam incident on the incident side lens 392 to the parallelizing lens 404 as it is.

The three liquid crystal panels 410R, 410G, 4
10B has a function as an electro-optical device that modulates incident light in accordance with given image information (image signal). Thereby, the three liquid crystal panels 410R, 41
Each color light incident on 0G and 410B is modulated in accordance with given image information to form an image of each color light. In addition,
Polarizing plates (not shown) are provided on the light incident surface side and the light emitting surface side of the three liquid crystal panels 410R, 410G, and 410B.

The three liquid crystal panels 410R, 410G, 4
The modulated light of three colors emitted from 10B is transmitted through the field lenses 411, 412, and 413, the focusing direction is narrowed, and is incident on the cross dichroic prism 420. Here, the modulated lights of three colors are combined to form a color. Synthetic light for projecting an image is formed. Further, the combined light generated by the cross dichroic prism 420 is
The projection lens 40 has a function of projecting the combined light on a projection screen, and displays a color image on the projection screen.

Next, the field lenses 411, 412,
413 will be described. As shown in FIG. 7, these field lenses 411, 412, and 413 are provided with three liquid crystal panels for efficiently condensing the combined light emitted from the cross dichroic prism 420 to the entrance pupil 43 of the projection lens 40. (Liquid crystal light valve) 410R,
It is arranged between each of 410G and 410B and the cross dichroic prism 420. These field lenses 411, 412, 413 function as light traveling direction adjusting means. That is, the direction of the light collimated by the collimating lenses 400, 402, and 404 is adjusted by the field lenses 411, 412, and 413, and the light is directed toward the center of the pupil of the projection lens 40. Therefore, the size of the projection lens can be selected regardless of the characteristics of the illumination optical system. In general, convex lenses are used as the field lenses 411, 412, and 413 as in the present embodiment, and the detailed shape is determined by the relationship with the entrance pupil 43 of the projection lens 40. In FIG. 7, reference numerals 41 and 42 denote a lens (rear ball) disposed at a position farthest from the projection surface among a plurality of lenses constituting the projection lens 40, respectively.
Lens (front lens) located closest to the projection surface
Are shown.

The field lens may be constructed by combining a plurality of lenses as shown in FIG. 8 in addition to the single convex lens as described above.

By the way, such a field lens 4
Since 11, 412, and 413 change the incident angle of light to the cross dichroic prism 420, the telecentric system collapses in the cross dichroic prism 420, causing a wavelength shift. That is, the cross dichroic prism 420 has red, green,
It functions as a color light combining optical system for forming a color image by combining modulated light of three colors of blue, and includes a dielectric multilayer film (light selective film) that reflects red light and a dielectric film that reflects blue light. A body multilayer film (light selective film) is formed in an approximately X-shape at the interface between the four right-angle prisms. These derivative multilayer films
Wavelength selection characteristics (color selection characteristics) depending on the angle of incident light
Changes. In this manner, the shift of the selection characteristic from a predetermined set wavelength due to a change in the incident angle of light is called a wavelength shift. When this wavelength shift occurs, the wavelength of the light selected by the dielectric multilayer film partially changes, so that color unevenness occurs in the projected image.

In this embodiment, a correction means for canceling such a wavelength shift is provided. That is,
In the present embodiment, the cross dichroic prism 420
By giving shading to the dielectric multilayer film formed therein, the characteristics of the film are changed according to the position according to the change of the incident angle of light to these dielectric multilayer films, and the field lens 411, The shift in wavelength caused by the installation of 412 and 413 is canceled.

This shading can be realized, for example, by changing the thickness of the dielectric multilayer film in accordance with the wavelength shift caused by the field lenses 411, 412, 413. The thickness of the dielectric multilayer film is determined by the cross dichroic prism 420 shown in FIG.
When arranged as shown in the plan view of FIG. 9A, the red light-reflecting dielectric multilayer increases as the distance from the projection lens increases, as indicated by the hatched portion shown in the cross-dichroic prism 420 plan view of FIG. The film 421 and the blue light reflecting dielectric multilayer film 422 are changed so as to increase at a fixed rate. Since a method of forming a film for performing shading and a method of manufacturing a cross dichroic prism are well known, a detailed description of these methods will be omitted.

In the projector of this embodiment described above, the field lenses 411, 412, 413 disposed between the liquid crystal panels 410R, 410G, 410B and the cross dichroic prism 420 project regardless of the characteristics of the illumination optical system. The lens 40 can be formed, and the cross dichroic prism 42
By providing appropriate shading to the color light selection film included in 0, generation of color unevenness is also prevented.

In the above embodiment, an example in which the present invention is applied to a projection display device using a transmissive liquid crystal panel has been described. However, the present invention relates to a projection type display device using a reflective liquid crystal panel. The present invention can be applied to a display device. Further, as described later, the electro-optical device is not limited to a liquid crystal panel. Here, “transmissive” means that an electro-optical device such as a liquid crystal panel transmits light, and “reflective” means that an electro-optical device such as a liquid crystal panel reflects light. It is a type. In a projection display device employing a reflection type electro-optical device, a dichroic prism is used as color light separating means for separating light into three colors of red, green, and blue, and modulated light of three colors is used. May be used also as a color light combining unit that combines and emits in the same direction.

The electro-optical device for light modulation is not limited to a liquid crystal panel (eg, a liquid crystal light valve).
For example, an apparatus using a micro mirror may be used.
Also, the prism that is a color light combining optical system is not limited to a dichroic prism in which two types of color selection surfaces are formed along the bonding surface of the four triangular prisms, but a dichroic prism with one type of color selection surface and a polarization type. It may be a beam splitter. Alternatively, the prism may be such that a light-selecting surface is arranged in a substantially hexahedral light-transmitting box and a liquid is filled therein.

Further, as the projection type display device, a front projection type display device for projecting from a direction in which a projected image is observed,
There is a rear-projection display device that performs projection from the side opposite to the direction in which a projected image is observed, but the configuration described in the above embodiment can be applied to any of them.

[0037]

According to the present invention, it is possible to obtain a projector capable of further reducing the size of the projection lens, regardless of the characteristics of the illumination optical system. At this time, color unevenness can be corrected.

[Brief description of the drawings]

FIG. 1 is a plan view showing an optical system of a projector according to an embodiment of the invention.

FIG. 2 is an explanatory diagram of an illumination optical system constituting the optical system of FIG. 1;

FIGS. 3A and 3B are a front view (A) and a side view (B) of a first lens array constituting an illumination optical system. FIGS.

FIG. 4 is a perspective view showing an appearance of a polarization conversion element array constituting the illumination optical system.

FIG. 5 is a schematic view showing the operation of the polarization conversion element array of FIG.

FIG. 6 is a front view showing an example of a light shielding plate constituting the illumination optical system.

FIG. 7 is a schematic view showing the operation of a field lens (convex lens).

FIG. 8 is an exemplary view showing another configuration of the field lens.

9A is a plan view showing an arrangement around the cross dichroic prism, and FIG. 9B is a plan view of the cross dichroic prism showing a shading state of the color light selection film.

FIG. 10 is a perspective view showing the appearance of a general projector.

FIG. 11 is a configuration diagram showing an optical system of a known projector.

FIG. 12 is a schematic diagram showing a telecentric system in the optical system shown in FIG. 11;

[Explanation of symbols]

Reference Signs List 20 light source unit 30 optical unit 40 projection lens 200 light source 202 partial light beam 210 light source lamp 212 concave mirror 300 integrator optical system 320 first lens array 321 small lens forming first lens array 340 second lens array 341 forming second lens array Small lens 350 Light shield plate 360, 361, 362 Polarization conversion element array 363 Polarization beam splitter array 364 λ / 2 phase difference plate 365 Translucent member 366 Polarization separation film 367 Reflection film 368 Polarization conversion element 370 Superposition lens 380 Color light separation optics System 382 First dichroic mirror 384 Reflecting mirror 386 Second dichroic mirror 390 Relay optical system 394,398 Reflecting mirror 400,402,404 Parallelizing lens 410R, 410G, 410B Liquid crystal panel 411, 412, 413 Field lens (convex lens) 420 Cross dichroic prism 421 Red light reflecting dielectric multilayer 422 Blue light reflecting dielectric multilayer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/74 H04N 5/74 A 9/31 9/31 A CF term (Reference) 2H088 EA15 HA13 HA14 HA16 HA18 HA20 HA21 HA24 HA25 HA28 MA04 MA20 2H091 FA05X FA26X FB02 LA11 LA16 5C058 AA06 AB06 BA06 BA23 BA35 5C060 BA04 BA07 BB13 BC05 BD02 DA05 GA02 GB06 GB10 HC01 HC12 HC24 HC25 JA19 JB06

Claims (5)

[Claims] An illumination optical system for emitting illumination light; a color separation optical system for separating light emitted from the illumination optical system into a plurality of color lights; and a color light emitted from the color separation optical system being parallel to each other. A plurality of collimating lenses to be converted, a plurality of light modulators respectively modulating a plurality of color lights emitted from the collimating lens, a color light combining prism for combining the color lights modulated by these light modulators, A projector lens for projecting the light combined by the color light combining prism, wherein the combined light passes through the projection lens between each of the plurality of light modulators and the color light combining prism. A projector, comprising a light traveling direction adjusting means for converging light toward an entrance pupil. 2. The projector according to claim 1, wherein said light traveling direction adjusting means comprises a convex lens. 3. The projector according to claim 1, wherein said light traveling direction adjusting means comprises a combination of a plurality of lenses. 4. The color combining prism includes a dielectric multilayer film, and corrects a color shift that is generated in the dielectric multilayer film by a change in an incident angle of light caused by the light traveling direction adjusting means. The projector according to claim 1, further comprising a unit. 5. The projector according to claim 4, wherein the dielectric multilayer film is provided with shading as a means for correcting the color unevenness.