JP5541204B2 - projector - Google Patents

Description

  The present invention relates to a projector that projects a light beam modulated by a light modulation device as an image.

  In projectors that use reflective LCD panels, there is a technology that improves the contrast by compensating the viewing angle of the reflective LCD panel by tilting the optical elements placed between the polarizing beam splitter and the reflective LCD panel. Exists.

JP 2007-4144 A

  In the projector disclosed in Patent Document 1, it is clearly stated that there are a plurality of optimum tilt directions when the optical element is tilted to improve contrast, but the light reflected from the optical element surface or projected. The relationship with the optical system is not described, and when the contrast is so high that reflection on the surface of the optical element cannot be ignored, there is a case where the contrast cannot be improved to the maximum depending on the tilt direction.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

となるように前記位相差素子が傾斜配置されていることを特徴とする。
The projector of the present invention includes an illumination optical system that emits illumination light having a system optical axis as a central axis, a polarization beam splitter that transmits and reflects light from the illumination optical system, and light that has passed through the polarization beam splitter. A reflective liquid crystal panel that modulates according to an image signal, a phase difference element disposed between the reflective liquid crystal panel and the polarizing beam splitter, and a projection optical system that projects light reflected from the polarizing beam splitter When, wherein the optical axis of the projection optical system is offset in parallel from the system optical axis, the polarization beam splitter, a normal direction to the system optical axis is approximately 45 degrees in the substrate plane of the polarization beam splitter are arranged to form a said a normal line drawn from the intersection of said system optical axis and the phase difference element a polarization beam splitter of the substrate plane Intersecting point of the A, the point at which the system optical axis with the substrate plane of the polarization beam splitter intersects and B, and that the optical axis of the projection optical system and the substrate plane of the polarization beam splitter intersects is C, and the point A the distance between the point C and AC, the distance between the point B and the point C and BC, the light flux of the phase difference element for a virtual face perpendicular to the system optical axis when the illumination light is incident on the retardation element The tilt angle of the incident surface is θ, the radius of the lens of the projection optical system is d, the deviation width between the lens optical axis of the projection optical system and the system optical axis is s, and the lens back focus of the projection optical system Is L, and the distance between the reflective liquid crystal panel and the intersection of the retardation element and the system optical axis is f,
AC> BC
And

The retardation element so that is characterized in that it is arranged obliquely.

According to the present invention, the distance BC is smaller than the distance AC and the phase difference element is tilted so as to satisfy the above formula (1). Therefore, the light reflected on the surface of the phase difference element is separated from the optical axis of the projection optical system. Proceed away. Therefore, since it becomes difficult to be swallowed by the projection optical system, the amount of light passing through the projection optical system when black is displayed on the reflective liquid crystal panel can be suppressed. That is, it is possible to improve the contrast represented by the ratio of the light amount projected when displaying a white image and the light amount projected when displaying a black image.

In the projector according to the aspect of the invention, the phase difference element is a phase difference element having a phase difference that compensates for a phase difference characteristic of the reflective liquid crystal panel in a state where a voltage is not applied. When the refractive indexes nx and ny are set to be the refractive index nz in the thickness direction, the following relational expression (4)
ny≈nx> nz (4)
It is preferable that the phase difference element satisfies the above.

  According to the present invention, it is possible to compensate the viewing angle of the liquid crystal by tilting the phase difference element, and there are two tilt directions that can be compensated in principle. In this case, it is possible to improve the contrast to the maximum by selecting a direction in which the reflected light is not easily swallowed by the projection optical system.

  In the projector according to the aspect of the invention, it is preferable that the retardation element is a structural birefringence retardation element constructed by laminating inorganic substances.

  According to the present invention, since the retardation element can be made of an inorganic substance, the reliability of the projector can be improved.

It is a figure explaining the structure of the optical system of the projector which concerns on 1st Embodiment. It is an enlarged view of the liquid crystal light valve for G optical paths explaining the light modulation device of the projector shown in FIG. FIG. 3 is a comparative example of FIG. 2 and is an enlarged view of a liquid crystal light valve for a G optical path. It is an enlarged view of the liquid crystal light valve for R optical paths which comprises the projector of FIG. FIG. 2 is an enlarged view of a liquid crystal light valve for a B optical path constituting the projector of FIG. 1. It is the schematic diagram which showed the B optical path in this embodiment linearly. It is a conceptual diagram of the refractive-index ellipsoid of the liquid crystal light valve for G light paths which comprises the projector of FIG. It is an enlarged view of the phase difference element for G optical paths which comprises the projector of FIG.

(First embodiment)
The configuration of the optical system of the projector according to the first embodiment of the invention will be described below with reference to FIG. In FIG. 1, X, Y, and Z mean three coordinate axes that constitute a three-dimensional orthogonal coordinate system.

  The illustrated projector 100 includes an illumination optical system 20 that emits illumination light, and a color separation light guide optical that separates the illumination light from the illumination optical system 20 into three color lights of blue (b), green (g), and red (r). A system 40, a light modulator 60 that modulates the three color lights emitted from the color separation light guide optical system 40 according to image information, and a light combiner that combines the image light of each color emitted from the light modulator 60 70 and a projection optical system 80 that projects the image light combined by the light combining unit 70 onto a screen (not shown). Of these, the portions from the illumination optical system 20 to the light combining unit 70 are accommodated in an optical component casing (not shown). In the case of the projector 100, the system optical axis SA corresponding to the central axis of the light beam from the illumination optical system 20 to the light combining unit 70 is two-dimensionally arranged parallel to the XZ plane (reference plane).

In the projector 100, the illumination optical system 20 includes a light source device 10, a concave lens 14, a first lens array 15, a second lens array 16, a polarization conversion device 17, and a superimposing lens 18. Among these, the light source device 10 is a light source that emits a light beam for illumination. For example, a light-emitting tube 11 that is a high-pressure mercury lamp or the like, and a light beam emitted forward from the light-emitting tube 11 such as a superimposing lens 18 to the light-emitting tube. And a concave mirror 12 that collects the light beam emitted backward from the arc tube 11 and emits it forward.
The concave lens 14 has a role of collimating the light beam from the light source device 10, but may be omitted when the concave mirror 12 is a parabolic mirror, for example.
The first lens array 15 is composed of a plurality of element lenses 15a arranged in a matrix, and divides the light beam emitted from the concave lens 14 corresponding to the sections of the element lenses 15a. The second lens array 16 includes a plurality of element lenses 16a arranged corresponding to the plurality of element lenses 15a, respectively, and adjusts the divergence state of the divided light flux from each element lens 15a.
The polarization conversion device 17 converts the split light beam emitted from the second lens array 16 into only linearly polarized light having a polarization plane parallel to the first direction (Z direction in the present embodiment) and supplies the linearly polarized light to the next stage optical system. This is a polarization conversion unit.
The superimposing lens 18 appropriately superimposes the illumination light IL as linearly polarized light that has passed through the polarization converter 17 as a whole, so that the superimposing lens 18 is superimposed on the liquid crystal light valves 60b, 60g, and 60r of the respective colors provided in the illuminated region, that is, the light modulation unit 60. Enable lighting.
That is, the illumination light IL that has passed through both the lens arrays 15 and 16 and the superimposing lens 18 passes through a color separation light guide optical system 40 that will be described in detail below, and is a reflective liquid crystal panel for each color provided in the light modulator 60. 61b, 61g, and 61r are uniformly superimposed and illuminated.

  The polarization conversion device 17 includes a plurality of prism elements 17a each having a structure incorporating a polarizing beam splitter (PBS) and a mirror, and a plurality of prism elements 17a attached to one of the light exit surfaces of the prism elements 17a. And a wave plate 17b. Each prism element 17a is a rod-shaped member extending in the Y direction, and the plurality of prism elements 17a are arranged in the Z direction and arranged in a plate shape extending in parallel to the YZ plane as a whole. The illumination light IL that is linearly polarized light in the first direction is emitted from the polarization conversion device 17 as described above. Here, the first direction is a polarization plane when the optical path of the projector 100 is linearly developed. Or the direction of vibration of the electric field, the linearly polarized light in the first direction can be switched to a state parallel to the second direction rotated by 90 ° by passing through the reflective liquid crystal panels 61b, 61g, 61r.

The color separation light guide optical system 40 includes a cross dichroic mirror 21, a dichroic mirror 22, bending mirrors 23a and 23b, first lenses 31a and 31b, and second lenses 32b, 32g, and 32r. Here, the cross dichroic mirror 21 includes a first dichroic mirror 21a and a second dichroic mirror 21b as a pair of separation surfaces. The first dichroic mirror 21a and the second dichroic mirror 21b are orthogonal to each other, and their intersecting axis 21c extends in the Y direction.
The first dichroic mirror 21a reflects, for example, blue (B) as one color component included in the illumination light IL, and transmits green (G) and red (R) colors as the other color components. The second dichroic mirror 21b reflects the green (G) and red (R) colors, which are the other color components, and transmits the blue (B) color, which is the one color component. The dichroic mirror 22 reflects, for example, green (G) color as one of the two incident color components, green red (GR) color, and transmits red (R) color as the other.
Thereby, the blue light LB, the green light LG, and the red light LR constituting the illumination light IL emitted from the illumination optical system 20 are respectively guided to the first optical path OP1, the second optical path OP2, and the third optical path OP3. Each incident on different objects.
More specifically, the illumination light IL from the illumination optical system 20 enters the cross dichroic mirror 21. The blue light LB reflected and branched by the first dichroic mirror 21a of the cross dichroic mirror 21 is incident on the polarization beam splitter 62b of the liquid crystal light valve 60b via the bending mirror 23a and the like.
Further, the green light LG reflected / branched by the second dichroic mirror 21b of the cross dichroic mirror 21 and further reflected / branched by the dichroic mirror 22 through the bending mirror 23b and the like is applied to the polarization beam splitter 62g of the liquid crystal light valve 60g. Incident. Further, the red light LR reflected and branched by the second dichroic mirror 21b of the cross dichroic mirror 21 and branched by the passage of the dichroic mirror 22 is incident on the polarization beam splitter 62r of the liquid crystal light valve 60r.

  The first lens 31a and the second lens 32b arranged on the first optical path OP1 are provided to adjust the angle state of the blue light LB incident on the reflective liquid crystal panel 61b. The first lens 31b and the second lens 32g arranged on the second optical path OP2 are provided to adjust the angle state of the green light LG incident on the reflective liquid crystal panel 61g. The first lens 31b and the second lens 32r arranged on the third optical path OP3 are provided to adjust the angular state of the red light LR incident on the reflective liquid crystal panel 61r. Here, the color filters 25g and 25r provided in association with the second lenses 32g and 32r are not essential, but the brightness balance between the green light LG and the red light LR incident on the reflective liquid crystal panels 61g and 61r is adjusted. Provided to adjust.

  The light modulation unit 60 includes three liquid crystal light valves 60b, 60g, and 60r corresponding to the first optical path OP1, the second optical path OP2, and the third optical path OP3, which are the three optical paths for each color. Each of the liquid crystal light valves 60b, 60g, and 60r is a non-light-emitting light modulator that modulates the spatial distribution of the intensity of incident illumination light.

A liquid crystal light valve 60g for G color will be described with reference to FIG. 2 in addition to FIG. FIG. 2 is an enlarged view of a liquid crystal light valve for G color (for G optical path) as a light modulation device.
The liquid crystal light valve 60g for G color includes a reflective liquid crystal panel 61g illuminated by the green light LG, a polarizing beam splitter 62g disposed on the light incident / exit side of the reflective liquid crystal panel 61g, the reflective liquid crystal panel 61g, and a polarized beam. A phase difference element 64g disposed between the splitter 62g and a polarizing element 63g disposed on the light emission side of the liquid crystal light valve 60g is provided.

The reflective liquid crystal panel 61g is not illustrated, but a light-transmitting substrate having a transparent electrode or the like, a driving substrate having a reflective pixel electrode or the like, and liquid crystal sealed and sealed between the light-transmitting substrate and the driving substrate And a layer.
The polarization beam splitter 62g is a structural birefringence type polarization separation element, specifically, a wire grid polarizing plate in which a grid of a conductive material is formed in a stripe shape on a light transmissive main plate. The polarization beam splitter 62g is in a state where its substrate plane is inclined by approximately 45 ° around the Y axis from a state perpendicular to the system optical axis SA. That is, the normal to the substrate plane of the polarizing beam splitter 62g is inclined by approximately 45 ° with respect to the system optical axis SA. The polarizing beam splitter 62g selectively transmits the linearly polarized light in the first direction (in this case, the Z direction) with respect to the incident green light LG and guides it to the reflective liquid crystal panel 61g.
The reflective liquid crystal panel 61g converts the polarization state of the green light LG incident thereon into linearly polarized light in a second direction (in this case, Y direction) that is partially perpendicular to the first direction, according to the image signal, Reflected toward the polarizing beam splitter 62g. The polarization beam splitter 62g selectively reflects only the linearly polarized light component in the second direction (Y direction in this case) of the light modulated through the reflective liquid crystal panel 61g. At this time, by providing the phase difference element 64g between the polarizing beam splitter 62g and the reflective liquid crystal panel 61g, the phase shift caused by the pretilt or the like of the liquid crystal layer of the reflective liquid crystal panel 61g is compensated, and the polarizing beam splitter The degree of polarization or extinction ratio on the light exit side of 62 g can be increased, and the contrast of the liquid crystal light valve 60 g can be further improved.

  The phase difference element 64g is an element that modulates the polarization state of light in order to compensate for the phase shift caused by the pretilt or the like of the liquid crystal layer of the reflective liquid crystal panel 61g as described above, and the phase difference element 64g is the substrate plane. Are arranged at a predetermined angle with respect to the system optical axis SA. Details of the inclined arrangement of the phase difference element 64g will be described later.

The R color liquid crystal light valve 60r will be described with reference to FIG. FIG. 4 is an enlarged view of a liquid crystal light valve for R color (for R optical path) as a light modulation device.
The R color liquid crystal light valve 60r includes a reflective liquid crystal panel 61r illuminated by the red light LR, a polarizing beam splitter 62r disposed on the light incident / exit side of the reflective liquid crystal panel 61r, and the reflective liquid crystal panel 61r. A phase difference element 64r disposed between the beam splitter 62r and a polarizing element 63r disposed on the light emission side of the liquid crystal light valve 60r is provided. The constituent elements of the liquid crystal light valve 60r for R color correspond to the constituent elements of the liquid crystal light valve 60g for G color, and the configuration and operation thereof are the same, and thus detailed description thereof is omitted. .

A liquid crystal light valve 60b for B color will be described with reference to FIG. FIG. 5 is an enlarged view of a liquid crystal light valve for B color (for B optical path) as a light modulation device.
The B-color liquid crystal light valve 60b includes a reflective liquid crystal panel 61b illuminated by blue light LB, a polarization beam splitter 62b disposed on the light incident / exit side of the reflective liquid crystal panel 61b, a reflective liquid crystal panel 61b, and a polarized light. A phase difference element 64b disposed between the beam splitter 62b and a polarizing element 63b disposed on the light emission side of the liquid crystal light valve 60b is provided. The components of the liquid crystal light valve 60b for B color correspond to the components of the liquid crystal light valve 60g for G color, and the configuration and operation thereof are the same, so detailed description thereof will be omitted. .

Referring to FIG. 1, the light combining unit 70 has a substantially square shape in plan view in which four right-angle prisms are bonded together, and intersects in an X shape as a combined surface at the interface where the right-angle prisms are bonded together. In addition, a pair of a first dichroic mirror 71a and a second dichroic mirror 71b extending in the Y direction with an intersecting axis 71c are formed. Both dichroic mirrors 71a and 71b are formed of dielectric multilayer films having different characteristics. That is, one first dichroic mirror 71a reflects blue light LB, and the other second dichroic mirror 71b reflects red light LR.
The light combining unit 70 transmits the modulated green light LG from the liquid crystal light valve 60g through the first and second dichroic mirrors 71a and 71b so as to go straight in the X direction, and the modulated red light from the liquid crystal light valve 60r. The light LR is reflected by the second dichroic mirror 71b and bent in the X direction by bending the optical path, and the modulated blue light LB from the liquid crystal light valve 60b is reflected by the first dichroic mirror 71a and bent. To inject in the X direction. On the light emitting side of the light combining unit 70, the green light LG, the blue light LB, and the red light LR of each color light are superimposed to perform color composition. A half-wave plate (not shown) is disposed between the light combining unit 70 and the G-color polarizing element 63g. In this case, the green light LG can be incident on the first and second dichroic mirrors 71a and 71b in the P-polarized state, and the synthesis efficiency of the blue light LB, green light LG, and red light LR of each color light in the light combining unit 70 is increased. And the occurrence of color unevenness can be suppressed.

  The projection optical system 80 projects the color image light combined by the light combining unit 70 on a screen (not shown) at a desired magnification. That is, a color moving image or a color still image with a desired magnification corresponding to the drive signal or image signal input to each of the reflective liquid crystal panels 61b, 61g, 61r is projected on the screen. The optical axis LA of the projection optical system 80 is shifted in the −Z direction parallel to the system optical axis SA by a predetermined width. Therefore, the projector 100 is configured to be able to project a projected image with a bias in the −Z direction with respect to the system optical axis.

Next, the inclined arrangement of the phase difference element 64g will be described in detail with reference to FIG. A point where the normal line drawn from the center of the substrate plane of the phase difference element 64g and the substrate plane of the polarization beam splitter 62g intersect is A, and B is the point where the substrate plane of the polarization beam splitter 62g intersects the system optical axis SA. When the point where the 62 g substrate plane and the optical axis LA of the projection optical system 80 intersect is C, the distance AC between the point A and the point C and the distance BC between the point B and the point C satisfy the following formula (2). The phase difference element 64g is inclined.
AC> BC (2)
Consider the reflected light RG reflected by the surface of the phase difference element 64g in the green light LG. The reflected light RG travels away from the optical axis LA of the projection optical system 80 and is less likely to be swallowed by the projection optical system 80. That is, the amount of light leaked during black display can be reduced, and the contrast of the liquid crystal light valve 60g can be increased.

FIG. 3 shows a liquid crystal light valve 60g, a light combining unit 70, and a projection optical system 80 as a comparative example. In this case, it is assumed that the distance AC between the point A and the point C and the distance BC between the point B and the point C are inclined so as to satisfy the following formula (3).
AC <BC (3)
Consider the reflected light RG reflected by the surface of the phase difference element 64g in the green light LG. Since the reflected light RG travels closer to the optical axis LA of the projection optical system 80, the reflected light RG is easily swallowed by the projection optical system 80. That is, the amount of light leaked during black display increases and the contrast of the liquid crystal light valve 60g decreases.

  FIG. 4 shows the liquid crystal light valve 60r, the light combining unit 70, and the projection optical system 80. In this case as well, the liquid crystal light valve 60g (see FIG. 2) of the present embodiment is inclined so as to satisfy the above formula (2). As a result, the amount of light leaked during black display can be reduced, and as a result, the contrast of the liquid crystal light valve 60r can be increased.

  FIG. 5 shows the liquid crystal light valve 60b, the light combining unit 70, and the projection optical system 80. In this case as well, the liquid crystal light valve 60g (see FIG. 2) of the present embodiment is inclined so as to satisfy the above formula (2). As a result, the amount of light leaked during black display can be reduced, and as a result, the contrast of the liquid crystal light valve 60b can be increased.

  Similar to the phase difference element 64g of the present embodiment, the phase difference elements 64b and 64r are inclined so as to satisfy the above formula (2), whereby the contrast of the liquid crystal light valves 60b and 60r can be similarly increased.

As is clear from the above description, the projector 100 according to the present embodiment includes the illumination optical system 20 that emits the illumination light IL having the system optical axis SA as the central axis, and the light emitted from the illumination optical system 20. Substrate-like (plate-like) polarizing beam splitters 62b, 62g, and 62r that transmit light in a predetermined polarization direction and reflect light in a polarization direction perpendicular to the predetermined polarization direction, and emitted from the illumination optical system 20 Reflective liquid crystal panels 61b, 61g, 61r that modulate light according to image signals, and phase difference elements 64b disposed between the reflective liquid crystal panels 61b, 61g, 61r and the polarization beam splitters 62b, 62g, 62r, 64g, 64r, and a projection optical system 80 that projects the light reflected from the polarization beam splitters 62b, 62g, 62r.
Further, in the present embodiment, the optical axis LA of the projection optical system 80 and the system optical axis SA are shifted in parallel, the normal direction of the substrate plane of the polarization beam splitters 62b, 62g, and 62r, and the system optical axis SA. There are arranged so as to form an approximately 45 degrees, the phase difference element 64b, 64 g, normal to the polarization beam splitter 62b drawn from the substrate plane center of 64r, 62 g, the point of intersection is the substrate plane 62r is a, polarization A point where the substrate plane of the beam splitters 62b, 62g and 62r and the system optical axis SA intersect is B, and a point where the substrate plane of the polarization beam splitters 62b, 62g and 62r and the optical axis LA of the projection optical system 80 intersect is C. In addition, the phase difference elements 64b, 64g, and 64r are in the direction in which the distance AC between the points A and C and the distance BC between the points B and C satisfy the relational expression AC> BC. Is inclined arrangement. Since the projector 100 according to the present embodiment has such a configuration, the amount of light when a black image is displayed can be suppressed, and the contrast can be improved.

FIG. 6 is a schematic diagram showing an optical path between the phase difference element 64b (64g, 64r) and the projection optical system 80. As shown in FIG. The optical path is actually bent through the polarization beam splitter 62b (62g, 62r), but is shown as a straight optical path in FIG. In FIG. 6, x, y, and z mean three coordinate axes constituting a three-dimensional orthogonal coordinate system, and the z axis is parallel to the system optical axis SA. FIG. 6 illustrates a blue (B) optical path, but the present invention is also applicable to a green (G) optical path and a red (R) optical path.
Here, the tilt angle θ of the light incident surface and the light exit surface of the phase difference element 64b (64g, 64r) with respect to a virtual plane ( xy plane) perpendicular to the system optical axis SA (z axis) is the lens of the projection optical system 80. Where d is the radius of the projection optical system 80, and s is the deviation width between the lens optical axis of the projection optical system 80 and the system optical axis SA, the lens back focus of the projection optical system 80 is L, and the reflective liquid crystal panel 61b (61g, 61r) When the distance from the phase difference element 64b (64g, 64r) is f and the F number of the lens of the projection optical system 80 is Fno, the following formula (1) is satisfied.

  The tilt angle of the phase difference element 64b (64g, 64r) with respect to the system optical axis SA is equal to the pretilt angle of the liquid crystal layer of the corresponding reflective liquid crystal panel 61b (61g, 61r) (the tilt of the main axis of liquid crystal molecules with respect to the system optical axis SA). Angle). The phase difference element 64b (64g, 64r) is a plate-like member having birefringence in which the light incident surface and the light exit surface are parallel, and the main axis of the birefringence ellipsoid is substantially perpendicular to the light incident surface. It is.

The relationship between the refractive index of the reflective liquid crystal panel and the phase difference element will be described with reference to FIG. FIG. 7 is a conceptual diagram showing the relationship between the refractive indexes of the reflective liquid crystal panel 61g and the phase difference element 64g of the projector 100 according to the present embodiment.
The reflective liquid crystal panel 61g includes a liquid crystal layer 61c and a mirror 61d. The liquid crystal layer 61c contains a liquid crystal compound 65.
Here, the liquid crystal compound 65 of the liquid crystal layer 61c has a positive uniaxial property, and its birefringence characteristic is expressed by a rugby ball type refractive index ellipsoid as shown in FIG. It is oriented in a slightly tilted direction (angle) with respect to. By orienting at an angle slightly inclined with respect to the X axis, the liquid crystal light valve 60g can ensure the maximum transmission state in the on state in which a voltage is applied to the liquid crystal layer 61c. Furthermore, the phase difference element 64g has a negative uniaxial property of the following formula (4) when the refractive index in the normal direction of the substrate surface is nz and the refractive indexes in the substrate surface are ny and nx. The birefringence characteristic is expressed by a disc-shaped refractive index ellipsoid as shown in FIG.
ny≈nx> nz (4)

  FIG. 7A shows a case where the phase difference element 64g is inclined so that the optical axis of the liquid crystal compound 65 is inclined in the same direction as the optical axis of the liquid crystal compound 65 is slightly inclined. The green light LG passes through the retardation element 64g and the liquid crystal layer 61c, and is reflected by the mirror 61d inside the reflective liquid crystal panel 61g. After the reflection, it passes through the liquid crystal layer 61c and the retardation element 64g again.

  FIG. 7B is a schematic representation of FIG. 7A in a transmission type. The liquid crystal layer 61e is a liquid crystal layer corresponding to the liquid crystal layer 61c that passes after the green light LG is reflected by the mirror 61d, and the phase difference element 64c is equivalent to the phase difference element 64g that passes after the green light LG is reflected by the mirror 61d. The phase difference element. Since the positive uniaxial and negative uniaxial birefringent substances having the same optical axis direction have the effect of canceling each influence, the influences generated by the liquid crystal layer 61c and the retardation element 64g cancel each other, and the liquid crystal layer 61e The effects caused by the phase difference element 64c cancel each other. Thus, in black display when no voltage is applied to the reflective liquid crystal panel 61g, the influence of birefringence due to the pretilt of the liquid crystal layer 61c on the green light LG is reduced, and the amount of black light can be suppressed. As a result, the contrast of the liquid crystal light valve 60g can be improved.

In FIGS. 7C and 7D, the phase difference element 64g is inclined so that the optical axis of the phase difference element 64g is inclined in a direction opposite to the direction in which the optical axis of the liquid crystal compound 65 is slightly inclined. This corresponds to FIGS. 7A and 7B.
Even when the phase difference element 64g is tilted so that the optical axis is tilted in the direction opposite to the tilt direction of the optical axis of the liquid crystal compound 65, it occurs in the liquid crystal layer 61c and the phase difference element 64c as shown in FIG. The effects of birefringence cancel each other, and the effects of birefringence generated by the liquid crystal layer 61e and the retardation element 64g cancel each other. Thereby, the contrast can be improved as in the case where the phase difference element 64g is tilted so that the optical axis is tilted in the same direction as the tilt direction of the liquid crystal compound 65.

As is clear from the above description, in the reflective liquid crystal panels 61b, 61g, 61r of the present embodiment, the liquid crystal molecules (liquid crystalline compound 65) are in a state perpendicular to the substrate surface when no voltage is applied. The phase difference elements 64b, 64g, and 64r are slightly inclined and aligned, and the phase difference having a phase difference that compensates for the phase difference characteristics of the reflective liquid crystal panels 61b, 61g, and 61r in a state where no voltage is applied. It is an element. Further, the phase difference elements 64b, 64g, and 64r have the following refractive expressions (4) when the refractive indexes nx and ny in the substrate plane are set to the refractive index nz in the thickness direction.
ny≈nx> nz (4)
It is possible to select the phase difference elements 64b, 64g, and 64r to be inclined in the direction in which the light reflected from the surfaces of the phase difference elements 64b, 64g, and 64r is not swallowed by the projection optical system 80. .

  FIG. 8 is an enlarged view of the phase difference element 64g of the projector 100 according to the present embodiment. In the case of the phase difference element 64g, an inorganic film 642g having a thickness equal to or smaller than the wavelength of light on at least one surface of the phase difference element substrate 641g, and an inorganic film having a lower refractive index than the inorganic film 642g 643g is alternately stacked.

  In the case of this phase difference element 64g, since all the constituent materials can be constructed with inorganic materials, the reliability of the liquid crystal light valve 60g can be reliably increased.

  DESCRIPTION OF SYMBOLS 10 ... Light source device, 20 ... Illumination optical system, 40 ... Color separation light guide optical system, 60 ... Light modulation part, 61b, 61g, 61r ... Reflective type liquid crystal panel, 62b, 62g, 62r ... Polarization beam splitter, 63b, 63g , 63r ... Polarizing element, 64b, 64g, 64r ... Phase difference element, 65 ... Liquid crystal compound, 70 ... Photosynthesis unit, 80 ... Projection optical system, SA ... System optical axis, LA ... Optical axis of projection optical system, RG ... reflected light.

Claims (3)

An illumination optical system that emits illumination light whose central axis is the system optical axis;
A polarizing beam splitter that transmits and reflects light from the illumination optical system;
A reflective liquid crystal panel that modulates light transmitted through the polarizing beam splitter according to an image signal;
A retardation element disposed between the reflective liquid crystal panel and the polarizing beam splitter;
A projection optical system that projects the light reflected from the polarization beam splitter,
The optical axis of the projection optical system are displaced in parallel from the system optical axis,
The polarization beam splitter, the polarization beam normal direction and the system optical axis of the substrate plane of the splitter is arranged so as to form an approximately 45 degrees,
Wherein the phase difference element and a normal line drawn from the intersection of said system optical axis polarization beam splitter a point where the substrate plane intersects is A, a point where the polarization beam splitter of the substrate plane and the system optical axis intersects the B , the point at which the optical axis of the projection optical system and the substrate plane of the polarization beam splitter intersects a C, the distance between the point a and the point C and AC, and the distance between the point B and the point C and BC, the illumination light Is the inclination angle of the light beam incident surface of the phase difference element with respect to a virtual plane perpendicular to the system optical axis when entering the phase difference element, and d is the radius of the lens of the projection optical system. The deviation width between the lens optical axis of the system and the system optical axis is s, the lens back focus of the projection optical system is L, the intersection of the reflective liquid crystal panel, the phase difference element and the system optical axis Between If the remote is f,
AC> BC
And

Projector said retardation element is inclined arranged so that. The phase difference element is a phase difference element having a phase difference that compensates for a phase difference characteristic of the reflective liquid crystal panel in a state where no voltage is applied, and the phase difference element has a refractive index nx, ny in a substrate plane. And when the refractive index nz is in the thickness direction,
The following relational expression ny≈nx> nz
The projector according to claim 1, which is a phase difference element that satisfies the above. The projector according to claim 1, wherein the phase difference element is a structural birefringence type phase difference element constructed by laminating inorganic substances.

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