JP2007264007A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of easily switching contrast priority operation and brightness priority operation and hardly causing the deterioration in image quality and the loss of light quantity when switching them. <P>SOLUTION: Since a second retardation plate 59 is arranged to advance/retreat on an optical path by a driving device 91 so as to switch the polarization direction of modulated light from a first optical modulation part 25, the path of modulated light from the first optical modulation part 25 can be easily switched between a first optical path PA1 shortcut to straight advance through a polarizing beam splitter 51 and a second optical path PA2 folded by the polarizing beam splitter 51, going and returning in a relay optical system 60 or the like and detouring to be submitted to luminance modulation in a second optical modulation part 70. Thus, the contrast priority operation using the first and the second optical modulation parts 25 and 70 and the brightness priority operation using only the first optical modulation part 25 are easily switched, and the deterioration in image quality and the loss of light quantity in projection are effectively restrained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a projector including a liquid crystal panel for adjusting luminance separately from a liquid crystal panel for image formation in order to improve the contrast of an image.

As a conventional projector, it modulates the transmittance of the liquid crystal panels for each color arranged on the RGB three-color optical path, and is arranged on the optical path after combining the dispersed light via an imaging lens. There is a device that modulates the transmittance of a high-definition liquid crystal panel and makes the transmittance of light of each component emitted from the high-precision liquid crystal panel proportional to the inverse γ correction values of R, G, and B when displaying color images ( Patent Document 1).

As a similar projector, a projector including a video display liquid crystal panel and an illuminance display liquid crystal panel (see Patent Document 2), first to third light modulators for each color, and a light modulator for combined light are provided. There are some (see Patent Document 3), and those equipped with a first optical modulator and a second optical modulator (see Patent Document 4).
JP-A-6-167690 JP-A-9-116840 European Patent Publication No. EP1427271 US Pat. No. 5,987,142

However, in a projector using a liquid crystal panel for each color and a high-definition liquid crystal panel, the projection image tends to be dark because the illumination light passes through the liquid crystal panel twice. For this reason, when brightness is required, it is conceivable to temporarily retract the high-definition liquid crystal panel from the optical path and dispose a glass plate or the like equivalent thereto. However, it is not always easy to accurately arrange the high-definition liquid crystal panel on the optical path, and the image quality may be deteriorated due to pixel shift or the like occurring between the plurality of panels, and the image is transferred between the plurality of panels. Therefore, a light loss is also caused by the imaging lens.

Accordingly, an object of the present invention is to provide a projector that can easily switch between a contrast-priority operation and a brightness-priority operation, and that is less susceptible to image quality deterioration and light quantity loss upon switching.

In order to solve the above problems, a projector according to the present invention includes: (a) a first liquid crystal light valve that modulates light from an illumination device according to image information and emits it as polarized light; and (b) a first liquid crystal light valve. Light guiding means capable of guiding the modulated light from the first light path short-circuited according to the polarization direction of the modulated light and the second light path detoured, and (c) a front stage of the light guide means A polarization switching means for switching the polarization direction of the modulated light from the first liquid crystal light valve; and (d) a second switching element arranged on the second optical path of the light guiding means,
A relay optical system that temporarily forms an image of the modulated light modulated by the liquid crystal light valve; and (e) an image light that is disposed on the second optical path of the light guide and is imaged by the relay optical system in accordance with image information. A second liquid crystal light valve that modulates and emits as polarized light; and (f) modulated light that is at least modulated by the first liquid crystal light valve and is emitted from the light guide means through one of the first and second optical paths. A projection optical system that projects light.

In the projector described above, the polarization switching unit includes a phase element that can be moved back and forth on the optical path preceding the light guide unit, and switches the polarization direction of the modulated light from the first liquid crystal light valve.
The first optical path and the second optical path in the light guide means can be easily switched. This
After the modulated light of the first liquid crystal light valve is guided to the second liquid crystal light valve on the second optical path,
The modulated light of the liquid crystal light valve can be enlarged and projected by the projection optical system, or the modulated light of the first liquid crystal light valve can be enlarged and projected directly by the projection optical system via the first optical path. Therefore, the contrast priority operation using the first and second liquid crystal light valves and the brightness priority using only the first liquid crystal light valve are performed only by moving the phase element while the first and second liquid crystal light valves are fixed. The operation can be easily switched, and image quality deterioration and light amount loss can be suppressed.

According to a specific aspect or aspect of the present invention, in the projector, the light guiding unit includes a polarizing beam splitter disposed at a branch point of the first and second optical paths, and a second stage subsequent to the polarizing beam splitter. A phase element disposed on the second optical path, and a mirror that is disposed on the second optical path with the phase element interposed between the polarization beam splitter and reverses the light beam from the polarization beam splitter on the second optical path, The first liquid crystal light valve has a transmissive liquid crystal panel, and the second liquid crystal light valve has a reflective liquid crystal panel that causes image light out of the light beam from the polarization beam splitter to travel backward on the second optical path. . In this case, the second optical path can be branched from the first optical path by a simple optical system using a polarizing beam splitter, a phase element, a mirror, and the like.

In another aspect of the present invention, when the relay optical system is developed with respect to the second optical path, the first liquid crystal light valve and the second liquid crystal light valve are substantially symmetric with respect to the mirror of the light guide means. It has a configuration. In this case, the transmission of the image from the first liquid crystal light valve to the second liquid crystal light valve can be made precise, for example, the relay optical system is a double-sided telecentric optical system.

In yet another aspect of the present invention, the first liquid crystal light valve includes three color light valves that perform three-color modulation and a color synthesis prism that synthesizes the color lights modulated by the color light valves. The light guiding means has a compensating prism that realizes an optical path equivalent to the color combining prism on the second optical path between the polarizing beam splitter and the second liquid crystal light valve. In this case, a color synthesizing prism and a compensation prism equivalent thereto can be arranged between each color light valve in the preceding stage and the second liquid crystal light valve in the succeeding stage, and the first liquid crystal light valve and the second liquid crystal light valve can be arranged. The symmetry of the optical path between the two can be increased.

According to still another aspect of the present invention, when the phase element is disposed on the optical path, the light guide means guides the modulated light from the first liquid crystal light valve to the first optical path, and the phase element from the optical path. When retracted, the light guide means guides the modulated light from the first liquid crystal light valve to the second optical path. In this case, since the phase element is retracted from the optical path when the modulated light from the first liquid crystal light valve is guided to the second optical path, it is easy to improve the projection accuracy from the first liquid crystal light valve to the second liquid crystal light valve.

[First Embodiment]
FIGS. 1 and 2 are schematic views showing the respective parts by dividing the optical system of the projector 10 according to the first embodiment of the present invention into two parts.

The projector 10 according to the present embodiment is an optical device for modulating a light beam emitted from a light source in one or two stages according to image information to form an optical image, and enlarging and projecting the optical image on a screen. is there. The projector 10 includes, as optical components, a light source device 21 that generates light source light, a color separation optical system 23 that divides the light source light from the light source device 21 into three colors of red, green, and blue, and a color separation optical system 23. A first light modulator 25 illuminated by the emitted illumination light of each color;
A light guide 50 that guides image light from the light modulator 25 to one of two optical paths described later;
A relay optical system 60 that is incorporated in 0 to transmit image light from the first light modulation unit 25, a second light modulation unit 70 that remodulates the image transmitted by the relay optical system 60, and a second light modulation A projection optical system 80 that projects the image light that has passed through the unit 70 onto a screen (not shown).

In the projector 10 described above, the light source device 21 includes the light source lamp 21a and the concave lens 2.
1b, a pair of lens arrays 21d and 21e, a polarization conversion member 21g, and a superimposing lens 21
i. Among these, the light source lamp 21a is composed of, for example, a high-pressure mercury lamp, and includes a concave mirror that collects the light source light and emits it forward. The concave lens 21b has a role of collimating the light source light from the light source lamp 21a, but may be omitted. A pair of lens arrays 21
d and 21e are fly-eye optical systems composed of a plurality of element lenses arranged in a matrix, and the light source light from the light source lamp 21a that has passed through the concave lens 21b is divided into partial light beams by these element lenses and collected individually. Light and diverge. The polarization conversion member 21g converts the light source light emitted from the lens array 21e into, for example, only the S-polarized component perpendicular to the paper surface of FIG. The superimposing lens 21i appropriately superimposes the illumination light having passed through the polarization conversion member 21g as a whole, thereby enabling superimposing illumination on the light modulation devices of the respective colors provided in the first light modulation unit 25. In other words, the illumination light that has passed through both the lens arrays 21d and 21e and the superimposing lens 21i passes through the color separation optical system 23 that will be described in detail below, and then the liquid crystal panels 25a, 25b, 25c is uniformly superimposed and illuminated.

The color separation optical system 23 includes first and second dichroic mirrors 23a and 23b, three field lenses 23f, 23g, and 23h that are correction optical systems, and reflection mirrors 23m and 23n.
, 23o, and constitutes an illumination device together with the light source device 21. Here, the first dichroic mirror 23a reflects, for example, red light and transmits green light and blue light among the three colors of red, green, and blue. The second dichroic mirror 23b reflects, for example, green light and transmits blue light out of the two incident colors of blue and green. In the color separation optical system 23, the substantially white light source light from the light source device 21 first enters the first dichroic mirror 23a. The red light reflected by the first dichroic mirror 23a is incident on the field lens 23f via the reflection mirror 23m, for example, as S-polarized light. Further, the green light transmitted through the first dichroic mirror 23a and reflected by the second dichroic mirror 23b is, for example, a field lens 23g as S-polarized light.
Is incident on. Furthermore, the blue light that has passed through the second dichroic mirror 23b is incident on the field lens 23h for adjusting the incident angle through the lenses LL1 and LL2 and the reflecting mirrors 23n and 23o, for example, as S-polarized light. The lenses LL1 and LL2 and the field lens 23h constitute a relay lens system. This relay lens system includes the first lens LL1.
Is transmitted to the field lens 23h almost as it is through the second lens LL2.

The first light modulation unit 25 includes three transmission-type liquid crystal panels 25a, 25b, and 25c and three sets of polarizing filters 25e, 25f, and 25g arranged so as to sandwich the liquid crystal panels 25a to 25c.
With. Here, a red light liquid crystal panel 25a and a pair of polarizing filters 25 sandwiching the liquid crystal panel 25a.
e and 25e constitute a red transmissive liquid crystal light valve for two-dimensionally modulating the luminance of red light of illumination light based on image information. Similarly, the green light liquid crystal panel 25b and the corresponding polarizing filters 25f and 25f also constitute a green liquid crystal light valve, and the blue light liquid crystal panel 25c and the polarizing filters 25g and 25g are also transparent for blue. Type liquid crystal light valve. The first light modulator 25 described above constitutes a first liquid crystal light valve for image information modulation that forms a color image.

The first liquid crystal panel 25a for red light includes the first dichroic mirror 2 of the color separation optical system 23.
The red light branched off by being reflected by 3a enters through the field lens 23f. Green light branched by being reflected by the second dichroic mirror 23b of the color separation optical system 23 enters the second liquid crystal panel 25b for green light via the field lens 23g. Blue light branched by passing through the second dichroic mirror 23b is incident on the third liquid crystal panel 25c for blue light through the field lens 23h. Each of the liquid crystal panels 25a to 25c is a non-light-emitting light modulation device that modulates the spatial intensity distribution of incident illumination light, and the three colors of light incident on each of the liquid crystal panels 25a to 25c ˜25c is modulated in accordance with the drive signal or image signal input as an electrical signal. At that time, each of the liquid crystal panels 25a to 25 by the polarizing filters 25e, 25f, and 25g.
The polarization direction of the illumination light incident on c is adjusted, and component light in a predetermined polarization direction is extracted as image light from the modulated light emitted from the liquid crystal panels 25a to 25c.

The cross dichroic prism 27 is a light combining member, that is, a color combining prism.
A pair of dielectric multilayer films 27a and 27b intersecting in an X shape are formed at the interface where the right-angle prisms are bonded together.
One first dielectric multilayer film 27a reflects red light, and the other second dielectric multilayer film 27b reflects blue light. The cross dichroic prism 27 reflects the red light from the liquid crystal panel 25a by the first dielectric multilayer film 27a and emits it to the right in the traveling direction, and the green light from the liquid crystal panel 25b to the first and second dielectric multilayer films 27a. , 27b, the liquid crystal panel 25c
Is reflected by the second dielectric multilayer film 27b and emitted to the left in the traveling direction.

The light guide 50 includes a polarizing beam splitter 51, a first retardation plate 52, a mirror 54, a compensation prism 57, and a second retardation plate 59. Among these, the polarization beam splitter 51, the first retardation plate 52, and the mirror 54 are short in the modulated light from the first light modulation unit 25 synthesized through the cross dichroic prism 27 according to the polarization direction. It functions as a light guiding means for guiding to either one of the first optical path PA1 and the long second optical path PA2.

In the light guide 50 described above, the polarization beam splitter 51 has a substantially square shape in plan view in which two right angle prisms are bonded together, and a dielectric multilayer film 51a is formed on the interface where both right angle prisms are bonded. Yes. The polarization beam splitter 51 reflects, for example, S-polarized light and transmits P-polarized light in the incident modulated light. For example, when S-polarized modulated light is incident on the polarization beam splitter 51, the modulated light is transmitted through the dielectric multilayer film 5 of the polarization beam splitter 51.
The light is reflected by 1a and emitted to the left in the traveling direction, that is, to the first phase difference plate 52 side. The first phase difference plate 52 is a phase element that gives a necessary phase difference to transmitted light in different polarization directions around the system optical axis OA, and is formed of, for example, a quarter wavelength plate. The light beam from the polarization beam splitter 51 that has entered the first retardation plate 52 enters the mirror 54 via the relay optical system 60. The mirror 54 has a reflecting surface arranged perpendicular to the system optical axis OA, and reverses the light beam from the polarization beam splitter 51. Reflected light from the mirror 54 enters the incident / exit port (on the right side of the drawing) provided on the opposite side of the polarizing beam splitter 51 through the relay optical system 60, the first phase plate 52, and the polarizing beam splitter 51. The compensating prism 57 is disposed adjacent to the incident / outgoing port of the polarization beam splitter 51, is formed of the same material as the right-angle prism constituting the cross dichroic prism 27, and has the same size as the cross dichroic prism 27 as a whole. Have.

The operation of the light guide unit 50 will be described. When the modulated light from the first light modulation unit 25 is incident on the polarization beam splitter 51 as P-polarized light, for example, the modulated light passes through the dielectric multilayer film 51a of the polarization beam splitter 51. Since it passes, it passes through the first optical path PA1 that is short-circuited so as to travel straight through the polarization beam splitter 51. On the other hand, when the modulated light from the first light modulator 25 is incident on the polarization beam splitter 51 as, for example, S-polarized light, the modulated light is reflected by the dielectric multilayer film 51a of the polarization beam splitter 51. It passes through the second optical path PA2 that makes a detour as described below. More specifically, the S-polarized light beam incident on the polarization beam splitter 51 is reflected by the dielectric multilayer 51 a of the polarization beam splitter 51 to be reflected on the first retardation plate 52.
Injected to the side. The light beam incident on the first retardation plate 52 is converted from, for example, linearly polarized light into circularly polarized light, passes through the relay optical system 60, and enters the mirror 54. The light beam reflected by the mirror 54 passes through the relay optical system 60 again from the reverse direction and reenters the first phase difference plate 52. The first retardation plate 52 returns, for example, circularly polarized light to linearly polarized light. At this time, the polarization direction is rotated by 90 °. That is, the light beam reflected by the dielectric multilayer film 51a in the outward path toward the mirror 54 is S
In the case of polarized light, the light beam that re-enters the dielectric multilayer film 51a in the return path becomes P-polarized light. Therefore,
The light flux on the return path goes straight through and passes through the dielectric multilayer film 51a, that is, the polarization beam splitter 51,
The light passes through the compensation prism 57 and enters the second light modulation unit 70 for modulating luminance information. The second light modulator 70 constitutes a reflective liquid crystal light valve that performs luminance modulation on the color image formed by the first light modulator 25, and the light flux from the second phase difference plate 56 and the compensation prism 57. Is modulated in luminance and folded in the incident direction. The light beam modulated and folded by the second light modulator 70 passes through the compensation prism 57 again from the reverse direction. That is, the forward light beam toward the second light modulation unit 70 passes through the dielectric multilayer film 51a, but is modulated in the second light modulation unit 70 in the return path, for example, from P-polarized light to S-polarized light. The light flux that is converted into the light and re-enters the dielectric multilayer film 51a is reflected by the dielectric multilayer film 51a, that is, the polarization beam splitter 51, and is emitted to the left in the traveling direction, that is, to the projection optical system 80 side.

The second retardation plate 59 that constitutes a part of the light guide unit 50 is a phase element that gives a necessary phase difference to transmitted light of different polarization directions, and is formed with a ½ wavelength, for example. The second retardation plate 59 is supported by a guide mechanism (not shown), and the operation position (one-dot chain line) between the cross dichroic prism 27 and the polarization beam splitter 51 and the cross dichroic prism 27.
And a retracted position (solid line) deviated from between the polarizing beam splitter 51 and the polarizing beam splitter 51. The second phase difference plate 59 is driven by the driving device 91 to operate at a necessary timing, and can be freely switched between the operating position and the retracted position. The second retardation plate 59 is
As will be described in detail below, it functions as a polarization switching unit that switches the polarization direction of the modulated light from the first light modulation unit 25 in cooperation with the drive device 91.

When the second retardation plate 59 is disposed at the operating position on the system optical axis OA, the image information modulation light from the first light modulation unit 25 is converted from S-polarized light to P-polarized light. The light passes through the dielectric multilayer film 51a of the polarizing beam splitter 51 and passes through the first optical path PA1 that is short-circuited so as to travel straight through the polarizing beam splitter 51. On the other hand, when the second retardation plate 59 is disposed at the retracted position off the system optical axis OA, the image information modulated light from the first light modulation unit 25 is maintained as S-polarized light. The image information modulated light is reflected by the dielectric multilayer film 51a of the polarization beam splitter 51, and travels back and forth through the relay optical system 60 and the like and passes through the second optical path PA2 subjected to luminance modulation by the second light modulation unit 70. That is, by operating the driving device 91 and arranging the second retardation plate 59 on the optical path, the image information modulated light from the first light modulation unit 25 can be directly incident on the projection optical system 80, and the driving is performed. By operating the device 91 and removing the second retardation plate 59 from the optical path, the image information modulated light from the first light modulation unit 25 is modulated in luminance by the second light modulation unit 70 and then applied to the projection optical system 80. It can be made incident.

The relay optical system 60 uses the cross dichroic prism 27 in the middle of three-color image light (light intensity distribution) formed on the image forming area of the three liquid crystal panels 25a, 25b, 25c or a liquid crystal light valve including the liquid crystal panels 25a, 25b, 25c. While synthesizing, the light is accurately projected on the image forming area of the second light modulation unit 70 with the light intensity distribution substantially preserved and almost without any light loss. At this time, the projection magnification by the relay optical system 60 is set to, for example, 1 ×, that is, equal magnification. The relay optical system 60 is composed of a plurality of lens elements including a spherical surface and an aspherical surface so that a projected image can be formed at the same magnification, for example, on the order of several tens of microns. It is a highly accurate relay lens corrected to. Further, in the light guide unit 50, the optical path from the mirror 54 to the first light modulation unit 25, and the mirror 54 to the second light modulation unit 7.
Since the optical paths up to 0 are equivalent, the relay optical system 60 has a mirror 54 as an aperture stop having an intermediate two lens groups with respect to the first light modulator 25 and the second light modulator 70. It functions as if it is placed mirror-symmetrically across the screen. As a result, the image of the first light modulator 25 is
It is possible to provide a double-sided telecentric high-resolution projection lens, that is, a relay optical system 60 that transfers to the light modulation unit 70 at the same magnification. At this time, the cross dichroic prism 27 and the compensation prism 57 are arranged at symmetrical positions with the mirror 54 interposed therebetween, and the first light modulation unit 2
The symmetry of the optical path length between 5 and the second light modulator 70 is made more precise.

The second light modulation unit 70 includes a reflective liquid crystal panel 72a and functions as a second light modulation device. Here, the liquid crystal panel 72a constitutes a second liquid crystal light valve for two-dimensionally modulating the luminance of the color image light after the image information modulation by the first light modulator 50 based on the image information. The second liquid crystal light valve constituting the second light modulator 70 has a configuration in which a plurality of pixels whose reflectance can be controlled independently are arranged in a matrix, and is provided in the first light modulator 25 described above. The synthesized light obtained by synthesizing the three image lights from the liquid crystal panels 25a, 25b, and 25c is again optically modulated based on the display image data, and the modulated light corresponding to the image light to be finally projected is emitted.
Here, the outline of the image forming area (effective area) of the liquid crystal panel 72a has, for example, the same shape as the outline of the image forming areas (effective area) of the liquid crystal panels 25a, 25b, and 25c provided in the first light modulator 25. The image light formed by the liquid crystal panels 25a, 25b, and 25c for image information modulation is projected onto the liquid crystal panel 72a for luminance modulation at a magnification of 1 × with the same image size.

The image light that has passed through the second light modulation unit 70 as described above is modulated in two stages by the combination with the first light modulation unit 25, and the two-stage modulation has extremely high contrast.

Although a detailed description is omitted, the projection optical system 80 includes a plurality of lens elements including a spherical surface and an aspheric surface, and image formation of the liquid crystal panel 72a of the second light modulation unit 70 or a liquid crystal light valve including the same. Screen light (not shown) of image light of optical image formed on area at appropriate magnification
Project as a color image on top.

As is clear from the above description, in the projector 10 of the present embodiment, the second retardation plate 5
9 is arranged to be movable back and forth on the optical path by the driving device 91 and the polarization direction of the modulated light from the first light modulation unit 25 is switched. Therefore, the path of the modulated light from the first light modulation unit 25 is changed to the polarization beam splitter 51. Between the first optical path PA1 that is short-circuited so as to travel straight and the second optical path PA2 that is bent by the polarization beam splitter 51 and reciprocates through the relay optical system 60 and the like and is subjected to luminance modulation by the second optical modulation unit 70. You can easily switch between them. That is, the contrast priority operation using the first and second light modulators 25 and 70 and the first light modulators 25 and 70 are fixed only by the advancement and retraction of the second phase difference plate 59 while the first and second light modulators 25 and 70 are fixed. Brightness priority operation using only the one light modulator 25 can be easily switched, and image quality deterioration and light amount loss during projection can be effectively suppressed.

[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. 3 is a schematic diagram showing the projector 110 according to the second embodiment. In the case of the projector 110 according to the second embodiment, the first light modulator 125 is configured by a so-called single-plate transmissive liquid crystal light valve. The first light modulation unit 125 includes a transmissive liquid crystal panel 125 a and the liquid crystal panel 12.
And a pair of polarizing filters 125e arranged so as to sandwich 5a. Here, the liquid crystal panel 125a has a color filter in each pixel, and the illumination light that has passed through the first light modulation unit 125 is converted into a color image that has undergone image information modulation.

In the projector 110 of the present embodiment, the first light modulator 125 needs to be illuminated with substantially white light, and the color separation optical system 23 (see FIG. 1) is provided between the light source device 21 and the first light modulator 125.
Is not provided. In addition, since the color image is directly formed by the first light modulation unit 125,
The cross dichroic prism 27 (see FIG. 1) between the first light modulator 125 and the polarization beam splitter 51 is omitted. Accordingly, the compensation prism 57 (see FIG. 2) for compensating the optical path of the cross dichroic prism 27 is also simplified.

In the above description, the first light modulator 125 is a color liquid crystal light valve for modulating image information, and the second light modulator 70 is a liquid crystal light valve for luminance modulation. The light modulator 125 may be used for luminance modulation, and the second light modulator 70 may be used for image information modulation.

In addition, this invention is not restricted to said embodiment, In the range which does not deviate from the summary, it can implement in a various aspect, For example, the following deformation | transformation is also possible.

For example, in the above embodiment, the lens array 2 is used to divide the light beam in the illumination device.
Although 1d and 21e are used, the present invention is also applicable to a projector that does not use such a lens array. Further, the lens arrays 21d and 21e can be replaced with rod integrators. Furthermore, although the polarization conversion member 21g that converts the light from the light source lamp 21a into a specific direction of polarization is used, the present invention is also applicable to a projector that does not use such a polarization conversion member 21g.

In the above-described embodiment, the second modulation unit 70 has been described with a method in which the emitted light changes the polarization direction with respect to the incident light during white display. However, a method in which the polarization direction is not changed may be used. In that case, a phase element formed of a quarter-wave plate is provided between the polarization beam splitter 51 and the second modulator.

Moreover, in the said embodiment, the 1st light modulation part 25, ie, liquid crystal panel 25a, 25b, 25.
Although the liquid crystal light valves made of c and the like are transmissive, these liquid crystal light valves can be replaced with digital micromirror devices or the like.

In the first and fifth embodiments, the blue liquid crystal panel 2 is used in the first light modulator 25.
Although 5c is arranged in the relatively long third optical path OP3, it is also possible to guide other blue and green colors to the relatively long third optical path OP3.

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. The projector 10 shown in FIG. , 110 can be applied to both.

It is a figure explaining the part of the optical system of the projector which concerns on 1st Embodiment. It is a figure explaining the part of the optical system of the projector which concerns on 1st Embodiment. It is a figure explaining the optical system of the projector which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 21 ... Light source device, 21a ... Light source lamp, 23 ... Color separation optical system, 23a, 23b ... Dichroic mirror, 25 ... 1st light modulation part, 25a ... Liquid crystal panel, 25a, 25b, 25c ... Liquid crystal panel, 25e, 25f, 25g ... polarizing filter, 27 ... cross dichroic prism, 27a, 27b ... dielectric multilayer, 5
DESCRIPTION OF SYMBOLS 0 ... Light guide part, 51 ... Polarization beam splitter, 51a ... Dielectric multilayer film, 52 ... 1st phase difference plate, 54 ... Mirror, 57 ... Compensation prism, 59 ... 2nd phase difference plate, 60 ... Relay optical system, 70: second light modulator 72a: liquid crystal panel 80: projection optical system 91
... Driver, OA ... System optical axis, PA1 ... First optical path, PA2 ... Second optical path

Claims (5)

A first liquid crystal light valve that modulates light from the illumination device according to image information and emits the polarized light;
A light guide means capable of guiding the modulated light from the first liquid crystal light valve to one of a first optical path that is short-circuited according to a polarization direction of the modulated light and a second optical path that is bypassed;
A polarization switching means for switching the polarization direction of the modulated light from the first liquid crystal light valve, including a phase element movably disposed on an optical path upstream of the light guide means;
A relay optical system that is disposed on the second optical path of the light guide and that forms an image of the modulated light modulated by the first liquid crystal light valve;
A second liquid crystal light valve arranged on the second optical path of the light guiding means and modulating the image light imaged by the relay optical system according to image information and emitting it as polarized light;
At least modulated by the first liquid crystal light valve, the first and second from the light guide means
A projection optical system that projects the modulated light emitted through one of the optical paths as image light;
A projector comprising: The light guiding means includes a polarizing beam splitter disposed at a branch point of the first and second optical paths, a phase element disposed on the second optical path downstream of the polarizing beam splitter, and the polarizing beam splitter; A mirror disposed on the second optical path with the phase element interposed therebetween to reverse the light beam from the polarization beam splitter on the second optical path,
The first liquid crystal light valve has a transmissive liquid crystal panel,
2. The projector according to claim 1, wherein the second liquid crystal light valve includes a reflective liquid crystal panel that reverses image light of the light beam from the polarization beam splitter on the second optical path. When the relay optical system is unfolded with respect to the second optical path, the relay optical system has a substantially symmetric configuration with respect to the first liquid crystal light valve and the second liquid crystal light valve with the mirror of the light guide means interposed therebetween. The projector according to claim 2. The first liquid crystal light valve includes three color light valves that perform three-color modulation, and a color synthesis prism that synthesizes the color lights modulated by the color light valves.
The projector according to claim 3, wherein the light guiding unit includes a compensation prism that realizes an optical path equivalent to the color combining prism on the second optical path between the polarizing beam splitter and the second liquid crystal light valve. When the phase element is disposed on the optical path, the light guide means guides the modulated light from the first liquid crystal light valve to the first optical path, and when the phase element is retracted from the optical path,
The light guide means guides modulated light from the first liquid crystal light valve to the second optical path.
The projector according to claim 4.

Images