JP2008145483A - Image projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector which can reachly uniformize the projected light beams coming through various paths to illuminate the whole liquid crystal display panel, without making most of the structures of the polarizer complex. <P>SOLUTION: Since the first main light beam PL 1 and the second main light beam PL 2 are both made to converge with predetermined angles on the polarizer 34, the polarized light beam from the first prism 91 and the second prism 92 can be prevented from shifting from each other caused by their being emitted in different directions, with respect to the direction perpendicular to the light axis. Thus, the illumination light, from the first and second prisms 91, 92, can be directed overlapping one another with less displacements to the liquid crystal display panels 61b, 61g, and 61r. In other words, it is possible to obtain a uniform illumination light, by effectively using the light from the light source with less light loss and high quality images can be projected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a projector incorporating a polarization conversion device for aligning a light beam from a light source with polarized light in a specific direction.

As an illuminating device incorporated in a projector, there is an illuminating device incorporating a polarization conversion device that can illuminate a liquid crystal display panel with polarized light in a specific direction without waste.

In such a polarization conversion device, for example, a columnar first prism and a second prism are stacked,
By providing a polarization separation film and a reflection film on a pair of surfaces on the joint side of the first prism, a structure in which the polarization separation film and the reflection film are alternately interposed between the stacked prisms is obtained (Patent Document). 1
reference).

In another polarization conversion device, the optical path length differs between polarized light that travels straight when passing through the polarization separating prism array and polarized light that is reflected twice and emitted in the front direction when passing through the polarization separating prism array. Therefore, a correction glass block is provided on the side of the longer optical path length to adjust the imaging position of the passing light of the polarization conversion device (see Patent Document 2).
JP 10-39136 A Japanese Patent Laid-Open No. 11-101956

However, in the method of providing a correction glass block on the side with a long optical path length in the polarization separation prism array, the structure of the polarization conversion device becomes complicated by the provision of the glass block in an array, and the accuracy of the polarization conversion device can be easily improved. The manufacturing cost increases.

Accordingly, the present invention provides a projector capable of illuminating a liquid crystal display panel without waste by making the projection states of light beams having different optical path lengths coincide with each other without complicating the structure of the polarization conversion device. Objective.

In order to solve the above problems, a projector according to the present invention includes (a) a light source that generates light source light, (b) a polarization conversion device that aligns the polarization direction of the light source light, and illumination light that has passed through the polarization conversion device. And (c) a projection optical system that projects the light modulated by the light modulation device. The polarization conversion device has (b1) a quadrangular prism outer shape having a parallelogram-shaped cross section, and is substantially parallel to each other with the incident surface and the exit surface being substantially parallel to each other and inclined with respect to the entrance surface and the exit surface. A first prism having a parallel separation surface and a reflection surface; and (b2) formed on the separation surface of the first prism, and transmits first polarized light and reflects second polarized light from incident light from the incident surface. (B3) a reflection element that is formed on the reflection surface of the first prism and that bends the optical path of the second polarization reflected by the polarization separation element;
4) having a second prism arranged so as to form a substantially complementary angle on the opposite side of the first prism via the polarization separation element. Then, the polarization conversion device reflects the first principal ray of the polarized light reflected by the reflecting element and emitted from the exit surface of the first prism, and the polarized light emitted from the exit surface of the second prism after passing through the polarization separating element. The second principal rays converge or diverge from each other at a predetermined angle.

In the projector, since the polarization conversion device converges or diverges the first principal ray and the second principal ray at a predetermined angle, the polarized light emitted from the first prism and the polarized light emitted from the second prism It is possible to prevent or reduce the displacement of the illumination light caused by being emitted at different positions with respect to the direction perpendicular to the optical axis.

According to a specific aspect or aspect of the present invention, in the projector, the first principal ray and the second principal ray are incident substantially perpendicularly on the incident surface of the first prism through the same optical path. In this case, a single principal ray incident on the polarization conversion device substantially along the optical axis is divided into a first principal ray and a second principal ray, and emitted from the first principal ray. The principal ray and the second principal ray emitted from the second prism can converge or diverge from each other while being emitted substantially along the optical axis. Therefore, it is possible to perform illumination that is superimposed with a small positional deviation between the illumination light from the first prism and the illumination light from the second prism.

According to another aspect of the present invention, the polarization conversion device crosses the first principal ray and the second principal ray at the position of the illuminated region of the light modulation device. In this case, it is possible to uniformly illuminate the illuminated area of the light modulation device by the illumination light from the first prism and the illumination light from the second prism without positional deviation.

According to still another aspect of the present invention, the entrance surface of the first prism, the exit surface of the first prism, and the exit surface of the second prism are parallel to each other, and the refractive index of the first prism is It is different from the refractive index of two prisms. In this case, only by providing a difference in refractive index between the first prism and the second prism, it is possible to reduce the deviation of the irradiation position between the polarized light emitted from the first prism and the polarized light emitted from the second prism. .

According to still another aspect of the present invention, the polarization separating element and the reflecting element are not parallel to each other and form a predetermined wedge angle. In this case, by adjusting the wedge angle formed by the polarization separation element and the reflection element, it is possible to reduce the deviation of the irradiation position between the polarized light emitted from the first prism and the polarized light emitted from the second prism.

According to still another aspect of the present invention, the exit surface of the first prism and the exit surface of the second prism are not parallel to each other and form a predetermined folding angle. In this case, the deviation of the irradiation position between the polarized light emitted from the first prism and the polarized light emitted from the second prism is reduced by adjusting the folding angle formed by the exit surface of the first prism and the exit surface of the second prism. can do.

According to still another aspect of the present invention, the polarization direction of the light emitted from one of the exit surfaces is opposite to either the exit surface of the first prism or the exit surface of the second prism, and the other exit surface. And a retardation plate that matches the polarization direction of the light emitted from the light source. In this case, the polarized light emitted from the first prism and the polarized light emitted from the second prism can be aligned and emitted from the polarization conversion device.

According to still another aspect of the invention, the polarization conversion device includes a plurality of units each including a first prism, a polarization separation element, a reflection element, and a second prism in a predetermined direction perpendicular to the optical axis. It further includes a superimposing lens that is repeatedly arranged and superimposes the light emitted from the plurality of sets in the illuminated region of the light modulation device. In this case, it is possible not only to prevent or reduce the positional deviation of the illumination light emitted from the first and second prisms for each unit, but also to superimpose the emitted light from a plurality of sets in the illuminated area. .

[First Embodiment]
FIG. 1 is a schematic diagram showing an optical system of a projector 10 according to the first embodiment of the present invention.
The projector 10 is an optical device that modulates a light beam emitted from a light source according to image information to form an optical image, and enlarges and projects the optical image on a screen. The light source lamp unit 20 and the illumination optical system 30 , A color separation device 40, a light modulator 60, a cross dichroic prism 70, and a projection optical system 80.

The light source lamp unit 20 is a light source that collects and emits light beams emitted from the light source lamp 21 to the surroundings and illuminates the light modulation unit 60 via the illumination optical system 30 and the like, and the light source lamp 21 that is an arc tube. An elliptical concave mirror 22 that reflects the light source light emitted from the light source lamp 21;
And a concave lens 23 for collimating light source light reflected by the concave mirror 22. In the light source lamp unit 20, the light source light emitted from the light source lamp 21 is collimated through the concave mirror 22 and the concave lens 23 and emitted to the front side, that is, the illumination optical system 30 side. Instead of the elliptical concave mirror 22 described above, various concave mirrors such as a paraboloid can be used. When a parabolic concave mirror is used, a parallel light beam can be emitted from the light source lamp unit 20 without providing the concave lens 23 or the like after the concave mirror 22.

The illumination optical system 30 divides the light beam emitted from the light source lamp unit 20 into a plurality of partial light beams, and causes the plurality of light beams to overlap and enter the target illumination area, and the in-plane illuminance of the illumination area is uniform. The first lens array 31, the second lens array 32,
A polarization conversion device 34 and a superimposing lens 35 are provided.

The first lens array 31 has a function as a light beam splitting optical element that splits a light beam emitted from the light source lamp 21 into a plurality of partial light beams, and is arranged in a matrix in a plane orthogonal to the system optical axis OA. A plurality of small lenses are provided. The contour shape of each small lens is set so as to be almost similar to the shape of the image forming area, that is, the illuminated area of the liquid crystal display panels 61b, 61g, 61r constituting the light modulation unit 60 described later. Second lens array 32
Is an optical element that condenses a plurality of partial light beams divided by the first lens array 31 described above, and is arranged in a matrix in a plane perpendicular to the system optical axis OA as in the first lens array 31. Although a plurality of small lenses are provided, the purpose is to collect light. Therefore, the contour shape of each small lens does not need to correspond to the shape of the image forming area of the liquid crystal display panels 61b, 61g, 61r.

The polarization conversion device 34 is formed of a PBS array and a phase difference plate, and has a role of aligning the polarization direction of each partial light beam divided by the first lens array 31 with one direction of linearly polarized light.
As will be described in detail later, the PBS array of the polarization converter 34 has a structure in which polarization separation films and reflection mirrors that are inclined with respect to the system optical axis OA are alternately arranged via a plurality of prisms. One of the two kinds of polarized light beams separated by the polarization separation film and the reflection mirror and emitted in the same direction is polarized by a phase difference plate (not shown) provided in a stripe shape, and the polarization directions of all the polarized light beams Are aligned. By using such a polarization conversion device 34, the light beam emitted from the lamp main body 21 can be aligned with a polarized light beam in one direction without waste, so the utilization factor of the light source light used in the light modulation unit 60 is improved. Can be made.

The superimposing lens 35 condenses a plurality of partial light beams that have passed through the first lens array 31, the second lens array 32, and the polarization conversion device 34, and corresponds to the image forming areas of the liquid crystal display panels 61b, 61g, 61r. It is an optical element for making it overlap and inject on an illumination area | region. The light beam emitted from the superimposing lens 35 is emitted to the color separation device 40 at the next stage while being made uniform.
That is, the illumination light that has passed through both the lens arrays 31 and 32 and the superimposing lens 35 passes through the color separation device 40 described in detail below, and then the illumination region of the light modulator 60, that is, the liquid crystal display panel 61b for each color.
The 61g and 61r image forming areas are uniformly superimposed and illuminated.

The color separation device 40 includes first and second dichroic mirrors 41 a and 41 b and a reflection mirror 4.
2a, 42b, 42c, condenser lenses 43r, 43b, 43g, and relay lens 4
5 and 46. Among these, the color separation optical system including the first and second dichroic mirrors 41a and 41b uses illumination light as blue (B) light, green (G) light, and red (R).
) Separated into three luminous fluxes of colored light. Each dichroic mirror 41a, 41b is an optical element obtained by forming on a transparent substrate a dielectric multilayer film having a wavelength selection function of reflecting a light beam in a predetermined wavelength region and transmitting a light beam in another wavelength region. Yes, they are arranged in an inclined state with respect to the system optical axis OA. The first dichroic mirror 41a is red, blue, green (R
Of the three colors G and B), the blue light LB is reflected, and the green light LG and the red light LR are transmitted. The second dichroic mirror 41b reflects the green light LG out of the incident green light LG and red light LR and transmits the red light LR. The condenser lenses 43r, 43b, and 43g for each color provided on the emission side of the color separation device 40 have each partial light beam emitted from the second lens array 32 and incident on the light modulation unit 60 with respect to the system optical axis OA. It is provided so as to have an appropriate degree of convergence or divergence. The pair of relay lenses 45 and 46 are disposed on the third optical path OP3 for red which is relatively longer than the first optical path OP1 for blue and the second optical path OP2 for green. These relay lenses 45 and 46 transmit the image formed immediately before the incident-side first relay lens 45 to the condenser lens 43r on the exit side almost as it is, so that the light use efficiency due to light diffusion or the like is achieved. Is prevented.

In the color separation device 40, the illumination light incident from the light source lamp unit 20 via the illumination optical system 30 first enters the first dichroic mirror 41a. The blue light LB reflected by the first dichroic mirror 41a is guided to the first optical path OP1 and enters the final stage condenser lens 43b via the reflection mirror 42a. The first dichroic mirror 41a
The green light LG that has been transmitted through and reflected by the second dichroic mirror 41b is reflected by the second optical path OP2.
Is incident on the last condenser lens 43g. Further, the red light LR that has passed through the second dichroic mirror 41b is guided to the third optical path OP3, and the reflection mirrors 42b and 42c.
Then, the light enters the condenser lens 43r at the final stage through the relay lenses 45 and 46.

The light modulation unit 60 includes three liquid crystal display panels (liquid crystal display panels) 61b, 61g, and 61r on which the three colors of illumination lights LB, LG, and LR are incident, and the liquid crystal display panels 61b, 61g, and 61r, respectively.
Three sets of polarizing filters 62b, 62g, and 62r are arranged so as to sandwich 61r.
Here, for example, the liquid crystal display panel 61b for blue light LB and the pair of polarizing filters 62b and 62b sandwiching the liquid crystal display panel 61b constitute a liquid crystal light valve for two-dimensionally modulating the luminance of illumination light based on image information. To do. Similarly, the liquid crystal display panel 61g for green light LG and the corresponding polarizing filters 62g and 62g also constitute a liquid crystal light valve, and the liquid crystal display panel 61r for red light LR and the polarizing filters 62r and 62r are also liquid crystal lights. Configure the valve. Each of the liquid crystal display panels 61b, 61g, 61r is a liquid crystal which is an electro-optical material hermetically sealed between a pair of transparent glass substrates. For example, according to a given image signal using a polysilicon TFT as a switching element, The polarization direction of the polarized light beam incident on each of them is modulated.

In the light modulation unit 60, the blue light LB guided to the first optical path OP1 enters the illumination area provided at the position of the liquid crystal display panel 61b via the condenser lens 43b, and passes through the image forming area in the liquid crystal display panel 61b. Illuminate. The green light LG guided to the second optical path OP2 enters the illumination area provided at the position of the liquid crystal display panel 61g via the condenser lens 43g and illuminates the image forming area in the liquid crystal display panel 61g. The red light LR guided to the third optical path OP3 enters the illumination area provided at the position of the liquid crystal display panel 61r via the first and second relay lenses 45 and 46 and the condenser lens 43r, and enters the liquid crystal display panel 61r. Illuminate the image forming area. Each of the liquid crystal display panels 61b, 61g, and 61r is a non-light-emitting and transmissive light modulation device for changing the spatial distribution of the polarization direction of incident illumination light. Each liquid crystal display panel 61b, 6
The color lights LB, LG, and LR incident on 1g and 61r are respectively transmitted to the liquid crystal display panels 61b and 61b.
The polarization state is adjusted in units of pixels in accordance with drive signals or control signals input as electrical signals to 61g and 61r. At this time, the polarization direction of the illumination light incident on the liquid crystal display panels 61b, 61g, 61r is adjusted by the polarizing filters 62b, 62g, 62r, and the light emitted from the liquid crystal display panels 61b, 61g, 61r is adjusted. Modulated light having a predetermined polarization direction is extracted.

The cross dichroic prism 70 includes exit side polarization filters 62b, 62g, and 62r.
1 is a light combining optical system that forms a color image by combining optical images modulated for each color light emitted from the light source. The cross dichroic prism 70 has a substantially square shape in plan view in which four right angle prisms are bonded together, and a pair of dielectric multilayer films 71 and 72 intersecting in an X shape are formed at the interface where the right angle prisms are bonded to each other. Is formed. One first dielectric multilayer film 71 reflects blue light, and the other second dielectric multilayer film 72 reflects red light. The cross dichroic prism 70 reflects the blue light LB from the liquid crystal display panel 61b by the first dielectric multilayer film 71 and emits the green light LG from the liquid crystal display panel 61g to the first and second sides.
The red light L emitted from the liquid crystal display panel 61r is emitted straight through the dielectric multilayer films 71 and 72.
R is reflected by the second dielectric multilayer film 72 and emitted to the left in the traveling direction.

The image light combined by the cross dichroic prism 70 in this way is projected as a color image on a screen (not shown) at an appropriate magnification through a projection optical system 80 as a magnification projection lens.

FIG. 2 is an enlarged plan view for explaining the structure and the like of the polarization conversion device 34 incorporated in the illumination optical system 30 of FIG. The polarization conversion device 34 includes first and second prisms 91 and 92, a polarization separation film 93, a reflection film 94, a phase difference plate 95, and a mask 96.

The first and second prisms 91 and 92 are both translucent members formed of glass or the like, and each has a quadrangular prism shape whose bottom surface (surface parallel to the paper surface) is a parallelogram. ing. The first and second prisms 91 and 92 are alternately connected to form a thick square plate perpendicular to the system optical axis OA, and form the outer shape of the polarization conversion device 34. Here, the first prism 91 includes an entrance surface 91a and an exit surface 91b that are parallel to each other, and a separation surface 91c and a reflection surface 91d that form a predetermined angle with respect to these surfaces 91a and 91b and are parallel to each other. Here, the separation surface 91c supports the polarization separation film 93, and the reflection surface 91d supports the reflection film 94. Although detailed description is omitted, the second prism 92 similarly has an entrance surface, an exit surface, a separation surface, and a reflection surface. Both prisms 91 and 92 are alternately joined by an optical adhesive.

The polarization separation film 93 is disposed between the adjacent prisms 91 and 92 in a state inclined by 45 ° with respect to the system optical axis OA. The polarization separation film 93 transmits one of the P-polarized light beam and the S-polarized light beam included in the light beam of the incident light IL emitted from each small lens constituting the second lens array 32 and transmits the other polarized light. Reflects light flux. Here, the polarization separation film 9
Reference numeral 3 denotes an incident light I incident on the polarization conversion device 34 as a polarization separation element made of a dielectric multilayer film.
Of the L polarization components, the S polarization is bent as the first polarization by reflection, and the P polarization is separated by passing straight as the second polarization by transmission. The polarization separation film 93
Is formed on the separation surface 91c, which is one inclined side surface of the prism 91, using various film forming methods including vapor deposition.

The reflective film 94 is 4 to the system optical axis OA between the adjacent prisms 91 and 92.
It is arranged in an inclined state of 5 °. That is, the reflective film 94 is disposed in parallel to face the polarization separation film 93 with the first prism 91 interposed therebetween. The reflective film 94 further reflects the first polarized light reflected by the polarization separation film 93 as a reflective element made of a dielectric multilayer film,
The optical path is converted in the same direction as the second polarized light. The reflective film 94 is formed of the first prism 9.
1 is formed on the reflecting surface 91d, which is the other inclined side surface, using various film forming methods including vapor deposition.

The phase difference plate 95 is provided to face the exit surface 91b of the first prism 91, and converts the first polarized light, which is S-polarized light reflected by the reflective film 94, into P-polarized light as a half-wave phase difference plate. To do.
The phase difference plate 95 can be provided on the exit side of the second prism 92, but in this case,
The second polarized light that is P-polarized light transmitted through the polarization separation film 93 is converted into S-polarized light.

The mask 96 is provided on the incident side of the second prism 92 and blocks unnecessary light as a light shielding plate made of a light shielding material.

In the polarization converter 34 described above, of the incident light IL incident on the first prism 91, the principal ray PL0 as the illumination optical system 30 is the first polarized light reflected by the polarization separation film 93. The light is branched into a principal ray PL1 and a second principal ray PL2, which is the other polarized light passing through the principal ray PL1. Both the principal rays PL1 and PL2 are both emitted from the polarization conversion device 34 along the system optical axis OA and incident on the superimposing lens 35. Here, the first principal ray PL1 and the second principal ray PL2 are completely separated. They are not parallel but form a small angle α that converges toward each other in the traveling direction. In this case, the first principal ray PL1 is parallel to the system optical axis OA, and the second principal ray PL2 is inclined by a minute angle α with respect to the system optical axis OA. As a result, the first principal ray PL1 and the second principal ray PL2 pass through the system optical axis OA in the illuminated area IS corresponding to the position of the image forming area provided in the liquid crystal display panels 61b, 61g, 61r. Both incident on one point. In the illustrated example, the principal ray PL0 incident on the polarization conversion device 34 is parallel to the system optical axis OA. However, depending on the specifications of the first and second lens arrays 31, 32, the principal ray PL0 may be the system. In some cases, the optical axis OA may have a certain angle. Also in this case, the principal rays PL1 and PL2 are made incident on one place on the illuminated area IS by adjusting the relative inclination between the first principal ray PL1 and the second principal ray PL2.

Hereinafter, the reason why the principal rays PL1 and PL2 are relatively inclined and converged will be described. Since the superimposing lens 35 of the present embodiment has a characteristic of converging the incident light beam that converges on a predetermined point (on the illuminated area IS), the first principal light beam PL1 emitted from the polarization conversion device 34 and Second
When the principal ray PL2 converges at a small angle α adapted to the characteristics of the superimposing lens 35, they are superimposed at the same position on the illuminated area IS by the superimposing lens 35. However, due to the configuration of the polarization converter, the inclination of the principal rays PL0 of the plurality of partial light beams, etc., the superimposing lens that converges the incident light beam that converges on a predetermined point (on the illuminated area IS) For example, when both principal rays PL1 and PL2 are emitted from the polarization conversion device 34 in parallel with each other, they are incident on different positions on the illuminated area IS. In such a case, generally, both principal rays PL1 and PL2 intersect at the rear surface of the illuminated area IS, and the incident light IL divided through the lens arrays 31 and 32 is accurately aligned. Therefore, the effective illumination range is narrowed. As a result, a sufficient illumination margin cannot be secured, and coloring or the like may occur at the end of the projected image. Therefore, in the present embodiment, the first principal ray PL2 is emitted in the first direction so as to be adapted to the characteristics of the superimposing lens 35 that collects the converged incident light beam at a predetermined point (on the illuminated area IS). Shift to the principal ray PL1 side. That is, the first chief ray PL1
A small refraction difference is provided between the first prism 91 and the second prism 92 so that the second principal ray PL2 and the second principal ray PL2 converge at a small angle α.

FIG. 3 is a partial enlarged view of a specific cell constituting the polarization conversion device 34, and the first principal ray PL1.
And a method of emitting the second principal ray PL2 so as to converge with each other. When the principal ray PL0 is incident on the first prism 91, it is separated into the first principal ray PL1 and the second principal ray PL2 by the polarization separation film 93. At this time, the first principal ray PL1 is separated from the first prism. Since the cross section of 91 is a parallelogram, the optical path is shifted with respect to the paper surface direction perpendicular to the traveling direction and emitted in the same direction. On the other hand, for the second principal ray PL2, the refractive index n2 of the second prism 92 is slightly smaller than the refractive index n1 of the first prism 91, and the exit angle I2 is slightly smaller than the incident angle I1. Is getting bigger. More specifically, as is well known, the relationship between the incident angle I1 and the exit angle I2 is given by Snell's law, and n1 · sin (I1) = n2 · sin (I2). Therefore, if n1> n2, I1 <I2 is established, and the first principal ray P of the second principal ray PL2 emitted from the second prism 92 is satisfied.
The small angle α which is the convergence angle with respect to L1 can be arbitrarily set within a certain range, and the second principal ray PL2 can be brought closer to the first principal ray PL1 side. That is, the first principal ray PL1 and the second principal ray PL2 are illuminated in consideration of the power of the superimposing lens 35, the distances to the liquid crystal display panels 61b, 61g, 61r, and the like under the refractive index conditions as described above. The light is incident on the same position on the region IS. The material of the first prism 91 and the material of the second prism 92 can be appropriately selected as a combination of existing materials in order to achieve the target refractive index difference.

The polarization conversion device 34 includes a plurality of cells made up of prisms 91, 92 and the like in an array so as to be symmetrical on both sides with respect to the system optical axis OA. Although not described in detail, these cells also have the same structure as that shown in FIG. 3. In each cell, the reflected first principal ray PL1 and the transmitted second principal ray PL2 are the same. , It is set so as to be incident on the same position on the illuminated area IS.

As is apparent from the above description, according to the projector 10 of the present embodiment, the converged incident light is adapted to the characteristics of the superimposing lens 35 that focuses the light at a predetermined point (on the illuminated area IS). In addition, since the first principal ray PL1 and the second principal ray PL2 are converged at a predetermined angle in the polarization converter 34, the polarized light emitted from the first prism 91 and the polarized light emitted from the second prism 92 are light. It is possible to prevent the displacement of the illumination light caused by being emitted at different positions with respect to the direction perpendicular to the axis. Therefore, the first and second prisms 91,
The illumination light from 92 can be incident on the liquid crystal display panels 61b, 61g, 61r with a small positional shift. That is, it is possible to obtain uniform illumination light that effectively uses light source light with a small amount of light loss, and to project a high-quality image.

Hereinafter, a specific example of the polarization conversion device 34 incorporated in the projector 10 of the embodiment will be described. FIGS. 4A to 4F are diagrams for explaining the results of simulation for a specific projector 10. FIG. 4A illustrates a case where the first and second prisms 91 and 92 have the same refractive index and have an old-type configuration. That is, the distribution on the liquid crystal display panel of the illumination light corresponding to the second principal ray PL2 that travels straight through the conventional specific cell is shown. In this case, the illumination image II is biased to the right with respect to the black frame corresponding to the illuminated area IS. FIG. 4B is a diagram for explaining the positional relationship between the illuminated area IS and the illumination image II in an easy-to-understand manner. FIG. 4C corresponds to FIG. 4A, and shows the distribution on the liquid crystal display panel of the illumination light corresponding to the first principal ray PL1 that passes through the same specific cell while being reflected. The illumination image II is not biased left and right with respect to the black frame corresponding to the illumination area IS. FIG.
FIG. 4D corresponds to FIG. 4B and illustrates the positional relationship between the illuminated region IS and the illumination image II in an easy-to-understand manner. FIG. 4E corresponds to the second principal ray PL2 that goes straight through the specific cell of the embodiment in which the illumination state shown in FIG. 4A is corrected, and illuminates the black frame corresponding to the illuminated area IS. Image II is not biased left and right. FIG. 4F is a diagram for explaining the positional relationship between the illuminated area IS and the illumination image II in an easy-to-understand manner. That is, the polarization conversion device 3 of the embodiment
4, the illuminated area IS of the liquid crystal display panel is illuminated without deviation by the illumination light of FIG. 4 (c) and the illumination light of FIG. 4 (e), so that the light source light is effectively utilized with little light loss. Uniform illumination light can be obtained. In the above simulation, the refractive index difference n1-n2
= 0.003, a small angle α corresponding to the angle correction amount of the principal ray is set to 0.07 °, and a distance from the polarization conversion device 34 to the illuminated area IS is 110 mm.

[Second Embodiment]
Hereinafter, a projector according to a second embodiment of the invention will be described. Note that the projector according to the second embodiment is obtained by partially changing the projector according to the first embodiment, and parts that are not particularly described are the same as those of the first embodiment.

FIG. 5 is a partially enlarged view illustrating the configuration of the polarization conversion member incorporated in the projector according to the second embodiment. In the case of this polarization conversion member 134, the refractive index of the first prism 191 and the refractive index of the second prism 192 are equal, but the polarization separation film 93 and the reflection film 94 are not parallel to each other and form a wedge angle β. is doing. That is, the first prism 191 and the second prism 192.
Means that the light incident surface and the light exit surface are arranged so as to form a complementary angle with each other so that each cross section is not a parallelogram. Polarized light separation film 9
3 and the reflection film 94 are adjusted to adjust the incident light beam converged to a predetermined 1
A small angle α, which is a convergence angle of the first principal ray PL1 emitted from the first prism 91 with respect to the second principal ray PL2, so as to be adapted to the characteristics of the superimposing lens 35 focused on the point (on the illuminated area IS). It can be arbitrarily set, and the first principal ray PL1 can be brought closer to the second principal ray PL2. Accordingly, the first principal ray PL1 and the second principal ray PL2 can be incident on the same position on the illuminated area IS, and uniform illumination light that effectively utilizes the light source light with a small amount of light loss can be obtained. it can.

[Third Embodiment]
Hereinafter, a projector according to a third embodiment of the invention will be described. Note that the projector according to the third embodiment is obtained by partially changing the projector according to the first embodiment, and parts that are not particularly described are the same as those of the first embodiment.

FIG. 6 is a partially enlarged view illustrating the configuration of the polarization conversion member incorporated in the projector according to the third embodiment. In the case of this polarization conversion member 234, the refractive index of the first prism 291 and the refractive index of the second prism 292 are equal, but the exit surfaces 291b and 292b of both prisms 291 and 292 are not parallel to each other and the folding angle γ is set. It is made. That is, the first prism 29
The first and second prisms 292 do not have an accurate parallelogram cross section. Therefore, by adjusting the folding angle γ formed by the exit surfaces 291b and 292b of both the prisms 291 and 292, the characteristics of the superimposing lens 35 that collects the converged incident light beam at a predetermined point (on the illuminated area IS). A small angle α that is a convergence angle of the first principal ray PL1 emitted from the first prism 91 with respect to the second principal ray PL2 emitted from the second prism 92 so as to be adapted to The first principal ray PL1 and the second principal ray PL2 can be brought close to each other. Accordingly, the first principal ray PL1 and the second principal ray PL2 can be incident on the same position on the illuminated area IS, and uniform illumination light that effectively utilizes the light source light with a small amount of light loss can be obtained. it can.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments.
For example, in the above embodiment, the incident light beam that converges is a predetermined point (on the illuminated area IS).
The first principal ray PL1 emitted from the first prism 91 and the second principal ray PL2 emitted from the second prism 92 are converged at a small angle α so as to adapt to the characteristics of the superimposing lens 35 that collects light on the lens. However, in the case where the incident light beam from which the characteristic of the superimposing lens diverges is condensed at a predetermined point (on the illuminated area IS), both principal rays PL1 are adapted to the characteristics of the superimposing lens.
, PL2 can be diverged by a small angle α. Similarly, the principal rays of the plurality of partial light beams incident on the polarization conversion member are not parallel to the system optical axis OA, and the characteristic of the superimposing lens is the system optical axis OA.
In the case where incident light parallel to the light beam is condensed at a predetermined point (on the illuminated area IS), both principal rays PL1 and PL2 are made parallel to the system optical axis OA in accordance with the characteristics of such a superimposing lens. You can also

In the above-described embodiment, each cell including the first prism 91, the second prism 92, and the like has the same structure. However, a plurality of portions where the refractive index setting and the like enter each polarization conversion member in each cell. It is also possible to have a different structure according to the incident angle of the principal ray of the light beam.

In the above embodiment, an example of the projector 10 using three light modulation devices has been described. However, the present invention can also be applied to a projector using one, two, or four or more light modulation devices. .

In the above embodiment, an example in which the present invention is applied to a transmissive projector has been described. However, the present invention can also be applied to a reflective projector. here,"
“Transmission type” means that the light valve including the liquid crystal display panel is a type that transmits light, and “reflection type” means that the light valve is a type that reflects light. ing. In the case of a reflection type projector, the light valve can be constituted only by a liquid crystal display panel, and a pair of polarizing plates is unnecessary. The light modulation device is not limited to a liquid crystal display panel or the like, and may be a light modulation device using a micromirror, for example.

Further, as the projector, there are a front projector that projects an image from the direction of observing the projection surface and a rear projector that projects an image from the side opposite to the direction of observing the projection surface. Is applicable to both.

It is a schematic diagram which shows the optical system of the projector which concerns on 1st Embodiment. It is a top view for demonstrating the polarization conversion member which comprises a projector. It is the elements on larger scale explaining the behavior of the light beam which injects into a polarization conversion member. (A)-(f) is a figure explaining an Example. It is a figure explaining the polarization conversion member in the projector which concerns on 2nd Embodiment. It is a figure explaining the polarization conversion member in the projector which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 20 ... Light source lamp unit, 30 ... Illumination optical system, 31 ... 1st lens array, 32 ... 2nd lens array, 34 ... Polarization converter, 34,134,
234: Polarization conversion device, 35: Superposition lens, 40 ... Color separation device, 41a, 41b ...
Dichroic mirrors, 42a, 42b, 42c ... reflective mirrors, 43r, 43b, 4
3g ... condenser lens, 45, 46 ... relay lens, 60 ... light modulation part, 61b,
61g, 61r ... liquid crystal display panel, 62b, 62g, 62r ... polarizing filter, 70 ...
Cross dichroic prism, 80 ... projection optical system, 91 ... first prism, 91a
Reference surface 91b: exit surface 91c ... separation surface 91d ... reflection surface 92 ... second prism 93 ... polarization separation film 94 ... reflection film 95 ... phase difference plate 96 ... mask I
DESCRIPTION OF SYMBOLS 1 ... Incident angle, I2 ... Ejection angle, IS ... Illuminated area, OA ... System optical axis, PL0 ...
Chief ray, PL1 ... first chief ray, PL2 ... second chief ray, α ... small angle, β ... wedge angle,
γ ... Folding angle

Claims (8)

A light source that generates source light;
A polarization conversion device for aligning the polarization direction of the light source light;
A light modulation device that modulates illumination light that has passed through the polarization conversion device according to image information;
A projection optical system for projecting light modulated by the light modulation device,
The polarization converter is
It has a quadrangular prism outer shape having a parallelogram-shaped cross section, and includes an entrance surface and an exit surface that are substantially parallel to each other, and a separation surface and a reflection surface that are both inclined and substantially parallel to the entrance surface and the exit surface. A first prism having,
The first prism is formed on the separation surface of the first prism, and the first of the incident light from the incident surface.
A polarization separation element that separates polarized light by transmitting the polarized light and reflecting the second polarized light,
The second prism formed on the reflection surface of the first prism and reflected by the polarization separation element.
A reflective element that bends the optical path of the polarized light,
A second prism arranged to form a substantially complementary angle on the opposite side of the first prism via the polarization separation element;
A first principal ray of polarized light reflected by the reflecting element and emitted from the exit surface of the first prism, and a second principal light of polarized light that passes through the polarization separation element and exits from the exit surface of the second prism. A projector that converges or diverges light rays at a predetermined angle. The projector according to claim 1, wherein the first principal ray and the second principal ray are incident on the incident surface of the first prism substantially perpendicularly with the same optical path. The projector according to any one of claims 1 and 2, wherein the polarization conversion device intersects the first principal ray and the second principal ray at a position of an illuminated region of the light modulation device. The entrance surface of the first prism, the exit surface of the first prism, and the exit surface of the second prism are parallel to each other, and the refractive index of the first prism is the refractive index of the second prism. The projector according to claim 1, which is different from the refractive index. The projector according to any one of claims 1 to 3, wherein the polarization separation element and the reflection element are not parallel to each other and form a predetermined wedge angle. 4. The projector according to claim 1, wherein the exit surface of the first prism and the exit surface of the second prism are not parallel to each other and form a predetermined folding angle. 5. Opposing the exit surface of the first prism and the exit surface of the second prism, the polarization direction of the exit light from the one exit surface is changed to the polarization direction of the exit light from the other exit surface. The projector according to any one of claims 1 to 6, further comprising a phase difference plate that matches the phase difference plate. In the polarization conversion device, a plurality of sets each including the first prism, the polarization separation element, the reflection element, and the second prism are repeatedly arranged in a predetermined direction perpendicular to an optical axis, The projector according to any one of claims 1 to 7, further comprising a superimposing lens that superimposes light emitted from a set of units in an illuminated area of the light modulation device.

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