JP2008026538A - Optical device and projector including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device in which an optical element for compensation is installed at low cost and with space savings, and with which excellent contrast and viewing angle characteristics are ensured. <P>SOLUTION: An indicatrix RIE11 of an end EP1 in the vicinity of an incident side surface is oriented to an intermediate direction between the x-axis and the y-axis with a certain inclined state, and an indicatrix RIE12 of an end EP2 in the vicinity of a light emitting side surface is oriented to an intermediate direction between the x-axis and the y-axis with an inclined state similar to that of the indicatrix RIE11. An approximate indicatrix RIE3 corresponds to a positive uniaxial material which is an average of both of the indicatrix RIE11 and the indicatrix RIE12. The retardation produced by the approximate indicatrix RIE3 is compensated with an optical compensation plate 84. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical device for image formation, and further relates to a projector incorporating the optical device.

As a conventional liquid crystal projector, a twisted nematic type liquid crystal panel is used, and the compensation between the liquid crystal panel and the incident polarizing plate and the outgoing polarizing plate has an optical axis that is oriented in the rubbing direction and tilted by a predetermined angle with respect to the incident surface. Some optical elements are arranged (see Patent Document 1). In such a liquid crystal projector, the pretilt of the liquid crystal can be compensated for by adjusting the optical axis and thickness of the compensating optical element arranged close to the liquid crystal panel, and the contrast and viewing angle can be improved.
JP 2004-198650 A

  However, in the liquid crystal projector as described above, it is caused by the pretilt formed on both surfaces of the liquid crystal layer by arranging one piece of compensation optical element on both the incident side and the exit side of the liquid crystal panel or on one side. Since the phase shift is compensated, the cost of the compensation optical element is greatly increased, it is not easy to secure a space for attaching the compensation optical element, and the attachment member and the process are complicated.

  Accordingly, an object of the present invention is to provide a light modulation device, that is, an optical device, which can incorporate a compensation optical element at low cost and save space and can ensure good contrast and viewing angle characteristics.

  In order to solve the above problems, an optical device according to the present invention includes (a) a liquid crystal that operates in a twisted nematic mode, and the optical axis of the liquid crystal adjacent to the incident surface and the emission surface is relative to the incident surface and the emission surface. A liquid crystal cell that is tilt-aligned by a predetermined pretilt angle, and (b) disposed on either the incident side or the exit side of the liquid crystal cell, and formed of a uniaxial crystal having a negative uniform optical axis, A predetermined intermediate direction that forms a non-zero angle with respect to the first rubbing direction corresponding to the tilt alignment direction of the liquid crystal adjacent to the incident surface and the second rubbing direction corresponding to the tilt alignment direction of the liquid crystal adjacent to the exit surface. One type of optical compensation element having an orientation orientation of the optical axis, and (c) a pair of polarizing elements arranged so as to sandwich the liquid crystal cell and the optical compensation member.

  In the above optical device, the optical axis of the liquid crystal adjacent to the entrance surface and the exit surface in the liquid crystal cell is inclined with respect to the normal of the entrance surface by a predetermined pretilt angle, but either the entrance side or the exit side. Negative uniaxiality in which the optical compensator arranged in the optical axis is a predetermined intermediate direction that forms a non-zero angle with respect to the first rubbing direction on the incident side and the second rubbing direction on the exit side, respectively. Since it is formed of crystals, the adjustment of the predetermined intermediate direction can approximately cancel or reduce the retardation of the image light in the front direction caused by each pretilt formed on the incident side and the emission side of the liquid crystal. Thereby, for example, it is possible to suppress a phenomenon in which black rises in the front direction of the liquid crystal cell when the electric field is applied and the contrast of the image is lowered.

  In addition, in the off-state of the twisted nematic liquid crystal cell (that is, the state in which no voltage is applied), the liquid crystal adjacent to the entrance surface and the exit surface is tilted with respect to the normal to the entrance surface. Pretilt occurs. Such a pretilt of the liquid crystal near the entrance surface and the exit surface is maintained in substantially the same state even when the liquid crystal cell is turned on. In the present invention, when an object to be compensated by the optical compensation element is an on-state liquid crystal, an average tilt state remaining in the liquid crystal adjacent to the entrance surface and the exit surface in the on state is referred to as a pretilt, and the compensation object Is an off-state liquid crystal, the average tilt state remaining in the liquid crystal adjacent to the entrance surface and the exit surface in this off state is referred to as pre-tilt.

  According to a specific aspect or aspect of the present invention, in the optical device, the optical axis of the optical compensation element has a predetermined inclination angle with respect to the normal direction of the incident surface and the exit surface parallel to each other of the liquid crystal cell. Just tilted. In this case, since the influence of the pretilt can be compensated for the direction inclined with respect to the front direction, it is possible to suppress the occurrence of bias in the viewing angle characteristics within a certain range.

  In yet another aspect of the present invention, the optical compensation element has an incident plane and an emission plane parallel to the incident surface and the emission surface of the liquid crystal cell, and the optical axis is inclined with respect to the normal line of the incident plane and the emission plane. Flat plate element. In this case, since the optical compensation element is arranged in parallel to the liquid crystal cell or the like, the optical compensation element can be simply and accurately fixed in a stable state.

  In yet another aspect of the present invention, the optical compensation element has an entrance plane and an exit plane parallel to each other that are inclined with respect to the entrance plane and the exit plane of the liquid crystal cell, and is in the normal direction of the entrance plane and the exit plane. It includes a flat element with an optical axis. In this case, the optical axis of the optical compensation element can be set in a direction perpendicular to the incident plane and the like, and the processing and production of the optical compensation element are relatively easy.

  In yet another aspect of the present invention, the optical compensation element has a thickness that effectively cancels the retardation caused by the liquid crystal present in the vicinity of the entrance surface and the exit surface of the liquid crystal in the liquid crystal cell. In this case, the retardation can be effectively reduced not only in the front direction of the liquid crystal cell but also in the range including the vicinity thereof, and the image quality of the image formed by the optical device can be improved.

  According to a specific aspect or aspect of the present invention, in the optical device, the optical compensation element is disposed on the emission surface side of the liquid crystal cell. In this case, even if the microlens array for adjusting the luminous flux is arranged on the incident side, a sufficient effect can be obtained with respect to improvement in contrast and viewing angle characteristics.

  In yet another aspect of the present invention, the liquid crystal cell includes a microlens array at least on the incident side. In this case, the angle of the light beam incident on the liquid crystal cell can be adjusted.

  A projector according to the present invention includes (a) the optical device for light modulation described above, (b) an illumination device that illuminates the optical device, and (c) a projection lens that projects an image formed by the optical device. .

  The projector includes the above-described optical device, and can suppress, for example, a phenomenon in which black rises in the front direction of the liquid crystal cell and the contrast of the image decreases when the projector is turned on. As a result, it is possible to improve the dimming, that is, the accuracy of light modulation by the liquid crystal cell while saving space and suppressing an increase in cost. Therefore, it is possible to provide a projector that can project a high-quality image with a simple structure.

[First Embodiment]
FIG. 1 is an enlarged cross-sectional view illustrating the structure of a liquid crystal light valve (light modulation device) that is an optical device according to a first embodiment of the present invention.

  In the illustrated liquid crystal light valve 31, the first polarizing filter 31b, which is an incident-side polarizing plate, and the second polarizing filter 31c, which is an exit-side polarizing plate, form crossed Nicols. The polarization modulator 31a sandwiched between the first and second polarizing filters 31b and 31c is a liquid crystal panel that changes the polarization direction of incident light in units of pixels in accordance with an input signal.

  The polarization modulation unit 31a sandwiches a liquid crystal layer 71 composed of liquid crystal operating in a twisted nematic mode (that is, twisted nematic liquid crystal), and a transparent first substrate 72a on the incident side and a second transparent on the emission side. And a substrate 72b. Further, the polarization modulator 31a includes an incident side cover 74a outside the incident side first substrate 72a, and includes an emission side cover 74b outside the second substrate 72b on the emission side. Although not shown, the first substrate 72a is formed so as to embed a microlens array composed of, for example, microlenses arranged corresponding to liquid crystal cells (pixels) described later.

  A transparent common electrode 75 is provided on the surface of the first substrate 72a on the liquid crystal layer 71 side, and an alignment film 76 is formed thereon, for example. On the other hand, on the surface of the second substrate 72b on the liquid crystal layer 71 side, there are a plurality of transparent pixel electrodes 77 arranged in a matrix and thin film transistors (not shown) electrically connected to the transparent pixel electrodes 77. And an alignment film 78 is formed thereon, for example. Here, the first and second substrates 72a and 72b, the liquid crystal layer 71 sandwiched therebetween, and the electrodes 75 and 77 form a liquid crystal cell for changing the polarization state of incident light. Each pixel constituting the liquid crystal cell includes one pixel electrode 77, a common electrode 75, and a liquid crystal layer 71 sandwiched therebetween. A grid-like black matrix 79 is provided between the first substrate 72a and the common electrode 75 so as to partition each pixel.

  Here, the alignment films 76 and 78 are for aligning the liquid crystal compounds constituting the liquid crystal layer 71 in a necessary direction. The alignment film 76 aligns the liquid crystalline compound in contact with the first rubbing direction (X-axis direction), and the alignment film 78 aligns the liquid crystalline compound in contact with the second rubbing direction (Y-axis direction). In the off state where no voltage is applied to the liquid crystal layer 71, the alignment film 76 has a role of aligning the optical axis of the liquid crystalline compound in a direction including the XZ plane which is the polarization plane of the first polarizing filter 31b. 78 has a role of aligning the optical axis of the liquid crystalline compound in a direction including the YZ plane which is the polarization plane of the second polarizing filter 31c. As a result, the optical axis of the liquid crystal compound in the liquid crystal layer 71 is arranged so as to be gradually twisted from the first substrate 72a to the second substrate 72b. That is, when the optical axes of a pair of liquid crystal compounds disposed on both ends of the liquid crystal layer 71 adjacent to the first and second substrates 72a and 72b, that is, the alignment films 76 and 78, are projected on the XY plane, For example, they form a twist angle of 90 °. As a result, the liquid crystal layer 71 sandwiched between the pair of polarizing filters 31b and 31c is operated in a normally-on mode, and a maximum transmission state (light-on state) can be secured in an off state in which no voltage is applied. it can. As will be described in detail later, at the both ends of the liquid crystal layer 71, that is, in the vicinity of the alignment films 76 and 78, the optical axis of the liquid crystalline compound is on the XY plane, that is, the incident surface and the output surface facing the alignment films 76 and 78. They are not parallel and are arranged in a state inclined by a certain pretilt angle with respect to the incident surface and the exit surface.

  On the other hand, in the ON state where the voltage is applied to the liquid crystal layer 71, that is, in the light shielding state (light OFF state), the optical axis of the liquid crystalline compound located away from the alignment films 76 and 78 is at the normal line of the first substrate 72a. Oriented in a parallel direction (specifically, the Z direction). However, the optical axis of the liquid crystalline compound is maintained substantially at the both ends of the liquid crystal layer 71, that is, in the vicinity of the alignment films 76 and 78. In other words, the optical axes of the liquid crystal compounds on both end sides are aligned in the X direction and the Y direction along the polarization planes of the first and second polarizing filters 31b and 31c, but on the XY plane, that is, the alignment films 76 and 78. It is not horizontal to the opposite entrance and exit surfaces, but is maintained in a state tilted by a fixed tilt angle with respect to the entrance and exit surfaces. Note that, in the off state where no voltage is applied to the liquid crystal layer 71 and the on state where a voltage is applied, the optical axis of the liquid crystalline compound existing in the vicinity of the alignment films 76 and 78 varies somewhat, but the XY plane. It is maintained in an inclined state inclined with respect to. Therefore, when the objective is optical compensation for the liquid crystal layer 71 in the on state, that is, the light shielding state, the tilt angle corresponding to such a tilt state is also referred to as a pretilt angle.

  In this polarization modulator 31a, a thin optical compensator 84 having a thickness of, for example, about 1 to 200 μm is attached to the exit surface of the exit side cover 74b, that is, one flat surface facing the second polarization filter 31c. Yes. Here, the optical compensation plate 84 is affixed on the flat surface on the exit side of the incident side cover 74a with an optical adhesive to constitute the optical compensation element OC. It is affixed by the optical adhesive on the injection | emission surface of the board | substrate 72b.

  The optical compensator 84 is a flat plate element in which the light incident end face and the light exit end face are parallel, and is formed of a transparent negative uniaxial crystal. The optical axis of the optical compensator 84 is arranged so as to form a fixed angle with respect to the XZ plane and the YZ plane, and to form a predetermined inclination angle with respect to the Z axis. That is, the optical axis of the optical compensation plate 84 forms a non-zero angle with respect to the intermediate direction between the X axis and the Y axis, that is, the X direction along the polarization plane of the first polarizing filter 31b, and the polarization of the second polarizing filter 31c. The orientation direction is an intermediate direction that forms a non-zero angle with respect to the Y direction along the plane.

  FIG. 2 is a conceptual side sectional view for explaining the refractive index of the liquid crystal layer 71 and the refractive index of the optical compensator 84 in the ON state. 3A is a perspective view conceptually illustrating the refractive index of the liquid crystal layer 71, and FIG. 3B is a perspective view illustrating approximation of the refractive index at the incident / exit end of the liquid crystal layer 71. FIG. 3C is a perspective view for explaining a further approximation of the refractive index in the liquid crystal layer 71. 2 and the like, the incident surface 71a and the emission surface 71b of the liquid crystal layer 71 and the incident plane 84a and the emission plane 84b of the optical compensation plate 84 are all parallel to each other.

  In the liquid crystal layer 71 in the ON state shown in FIG. 2, the major axis of the refractive index ellipsoid RIE1 of the liquid crystalline compound, that is, the optical axis OA1 is arranged substantially parallel to the Z axis, and is incident on the incident surface 71a and the emission surface 71b. It is generally perpendicular to it. However, at a position close to the entrance surface 71a and the exit surface 71b, the optical axis OA1 of the refractive index ellipsoid RIE1 is inclined to some extent with respect to the Z axis, and the liquid crystal properties are extremely close to the entrance surface and the exit surface. The compound is equal to the tilt angle before the voltage is applied, and generally the angle with respect to the incident surface is less than about 10 degrees. Further, the optical axis of the liquid crystalline compound abruptly approaches an angle that is parallel to the normal direction of the incident surface as it goes toward the center of the liquid crystal layer.

  On the other hand, in the optical compensator 84, the minor axis of the refractive index ellipsoid RIE2 of the negative uniaxial crystal composing the optical compensator 84, that is, the optical axis OA2, is a plane including the Z axis and inclined at substantially the same angle between the XZ plane and the YZ plane. And has a constant tilt angle that is not so large with respect to the Z-axis. More specifically, the tilt direction of the refractive index ellipsoid RIE2, that is, the orientation direction is an intermediate direction between the polarization planes of the first and second polarizing filters 31b and 31c. The angle is about 45 ° and about 45 ° with respect to the Y direction.

  Here, with reference to FIGS. 3A to 3C, an approximate process of the refractive index anisotropy of the liquid crystal layer 71 will be described. As shown in FIG. 3A, in the central portion CP of the liquid crystal layer 71 that responds straightly to an electric field, the refractive index ellipsoid RIE10 of the liquid crystalline compound is in a state along the Z axis, Birefringence action is not given to the front light beam traveling along. However, in the end portion EP1 of the liquid crystal layer 71 close to the incident surface 71a, the refractive index ellipsoids RIE111 and RIE112 of the liquid crystal compound are inclined by a pretilt angle with respect to the Z axis, and along the Z axis. A birefringence action is given to the traveling front beam. The refractive index ellipsoid RIE111 closer to the incident surface 71a has a major axis oriented in the X-axis direction with a relatively small inclination with respect to the incident surface 71a, and is a refractive index ellipse relatively far from the incident surface 71a. The body RIE 112 is oriented in an intermediate direction between the X axis and the Y axis with a relatively large inclination with respect to the incident surface 71a. Similarly, in the end portion EP2 of the liquid crystal layer 71 close to the exit surface 71b, the refractive index ellipsoids RIE121 and RIE122 of the liquid crystal compound are inclined by a pretilt angle with respect to the Z axis, and along the Z axis. Birefringence action is given to the front light flux that travels. Note that the refractive index ellipsoid RIE121 closer to the exit surface 71b has a long axis oriented in the Y-axis direction with a relatively small inclination with respect to the exit surface 71b, and is a refractive index ellipse relatively far from the exit surface 71b. The body RIE 122 is oriented in the intermediate direction between the X axis and the Y axis with a relatively large inclination with respect to the emission surface 71b.

  Here, the approximation of the refractive index of the liquid crystal layer 71 shown in FIG. 3A will be considered with reference to FIG. The refractive index ellipsoid RIE11 approximately representing the average refractive index of the liquid crystalline compound in the incident side end portion EP1 of the liquid crystal layer 71 shown in FIG. 3B is a refractive index ellipse shown in FIG. The bodies RIE111 and RIE112 are averaged according to the thickness. Similarly, the refractive index ellipsoid RIE12 that approximately represents the average refractive index of the liquid crystal compound in the emission-side end portion EP2 of the liquid crystal layer 71 shown in FIG. 3B is shown in FIG. The refractive index ellipsoids RIE121 and RIE122 are averaged according to the thickness. As a result, the refractive index ellipsoid RIE11 of the end portion EP1 that is in the vicinity of the surface on the incident side is oriented in the intermediate direction between the X axis and the Y axis but closer to the X axis direction in a certain inclined state, and near the surface on the exit side. The refractive index ellipsoid RIE12 of the end portion EP2 is oriented in the middle direction between the X axis and the Y axis but closer to the Y axis direction in the same inclined state as the refractive index ellipsoid RIE11. In the above description, the upper and lower end portions EP1 and EP2 are described so that the refractive index changes in two steps. However, in actuality, the refractive index changes continuously in multiple steps, and both refractive index ellipses. The sizes, inclination amounts, and the like of the bodies RIE11 and RIE12 are approximately determined based on simulations, experiments, and the like on the assumption of the known characteristics of the liquid crystal layer 71.

  Next, with reference to FIG. 3C, a further approximation of the refractive index of the liquid crystal layer 71 shown in FIG. 3B will be considered. The end portions EP1 and EP2 of the liquid crystal layer 71 shown in FIG. 3B exist separately, but can be considered to be approximately a single layer. Accordingly, the refractive index of the two end portions EP1 and EP2 of the liquid crystal layer 71 shown in FIG. 3B, that is, the approximate refractive index ellipsoid RIE3 shown in FIG. 3C is an average of both refractive index ellipsoids RIE11 and RIE12. It corresponds to a positive uniaxial material. Such an approximate refractive index ellipsoid RIE3 is oriented in an intermediate direction DA between the X axis and the Y axis with a relatively large inclination with respect to the XY plane, and the major axis of the approximate refractive index ellipsoid RIE3, that is, the optical axis OAC1. Is inclined by the approximate pretilt angle TA with respect to the intermediate direction DA. The approximate pretilt angle TA corresponds to the vertical approximate tilt angle θ1 with respect to the Z axis. In addition, it is assumed that the intermediate direction DA in which the approximate refractive index ellipsoid RIE3 is oriented forms an angle α with respect to the X-axis direction. This angle α is about 45 ° due to the symmetry of the liquid crystal layer 71. Note that the approximate refractive index ellipsoid RIE3 in FIG. 3C is described as representing the average refractive index of the end portions EP1 and EP2, but represents the average refractive index of the entire liquid crystal layer 71. You can also In this case, the approximate refractive index ellipsoid RIE3 is formed by the portions EP1, EP2 and CP, and is a composite of the refractive index ellipsoids RIE11, RIE12, and RIE10 shown in FIG.

  4A is a side view for explaining the refractive index of the liquid crystal layer 71, and FIG. 4B is a plan view for explaining the refractive index of the liquid crystal layer 71. 5A is a side view for explaining the refractive index of the optical compensation plate 84, and FIG. 5B is a plan view for explaining the refractive index of the optical compensation plate 84. As shown in FIG.

となっている。よって、垂直入射光に対する液晶層７１のリタデーションＲｅ１は、液晶層７１の厚みをｄ１として、

となる。同様に、光学補償板８４について考えると、この光学補償板８４は、負の一軸性結晶からなり、屈折率を基準とする各軸方向の屈折率をｎｘ，ｎｙ，ｎｚとすると、一般にｎｘ＝ｎｙ＞ｎｚの関係が成り立ち、屈折率ｎｚの長軸短軸に対応する光学軸ＯＡ２が、光学補償板８４の入射平面８４ａに法線方向から入射する光線（垂直入射光）の光路ＶＰに対して、近似配向方向に傾斜角θ２＝θ１だけ傾いた状態となっている。ここで、図５（ａ）に示すように正常屈折率がＮ_ｏで異常屈折率がＮ_ｅであり、図５（ｂ）に示すように近似配向方向に対応する配向方位（垂直入射光の進相軸方向）に振動する光の近似配向方向屈折率がｎ_４で遅相軸方向に振動する光の垂直方向屈折率がｎ_３であるとすると、

となっている。よって、垂直入射光に対する光学補償板８４のリタデーションＲｅ２は、光学補償板８４の厚みをｄ２として、

となる。ここで、液晶層７１の近似屈折率ｎｚ（ｎ_ｅ）の長軸と光学補償板８４の屈折率ｎｚ（Ｎ_ｅ）の短軸とは平行に配置されており、それぞれの遅相軸及び進相軸は互いに入れ替わっている。したがって、垂直入射光に対するトータルのリタデーションＲＥは、式（３）で与えられるＲｅ１と、式（６）で与えられるＲｅ２との差の絶対値で与えられる。つまり、Ｒｅ１＝Ｒｅ２のとき、第１偏光フィルタ３１ｂから射出された偏光と第２偏光フィルタ３１ｃに入射する偏光は同一状態となり、垂直入射光に対する偏光フィルタ３１ｃでの遮光が完全となり、液晶ライトバルブ３１の透過及び遮光によって決定される画像のコントラストは最大となる。 First, considering the liquid crystal layer 71, the approximate refractive index ellipsoid RIE3 corresponds to a positive uniaxial material as described with reference to FIG. Assuming that the refractive index in the axial direction is nx, ny, nz, the relationship of nx = ny <nz is approximately established, and the optical axis OAC1 corresponding to the major axis of the refractive index nz is a modulus on the incident surface 71a of the liquid crystal layer 71. The optical path VP of light rays (vertical incident light) incident from the linear direction is inclined by the vertical approximate tilt angle θ1 in the approximate orientation direction. Here, an extraordinary refractive index _{n e} with ordinary index as shown in FIG. 4 (a) is _{n o,} that is nx ₌ ny ₌ n o, an nx = _{n e,} shown in FIG. 4 (b) Thus, if the approximate orientation direction refractive index of light oscillating in the approximate orientation direction (slow axis direction of normal incident light) is n ₂ and the vertical refractive index of light oscillating in the fast axis direction is n ₁ ,

It has become. Therefore, the retardation Re1 of the liquid crystal layer 71 with respect to the normal incident light is expressed as follows:

It becomes. Similarly, when considering the optical compensator 84, the optical compensator 84 is made of a negative uniaxial crystal, and generally nx = ny, nz where the refractive index in each axial direction with respect to the refractive index is nx, ny, nz. The relationship of ny> nz holds, and the optical axis OA2 corresponding to the major axis and the minor axis of the refractive index nz is relative to the optical path VP of the light ray (vertical incident light) incident on the incident plane 84a of the optical compensator 84 from the normal direction. Thus, the tilt angle θ2 = θ1 in the approximate orientation direction. Here, ordinary refractive index as shown in FIG. 5 (a) is abnormal refractive index N _e in N _o, FIG. 5 (b) to the orientation direction corresponding to the approximate alignment direction, as shown (for normally incident light If the approximate orientation direction refractive index of light oscillating in the fast axis direction is n ₄ and the vertical refractive index of light oscillating in the slow axis direction is n ₃ ,

It has become. Therefore, the retardation Re2 of the optical compensator 84 with respect to the normal incident light is set to d2 as the thickness of the optical compensator 84.

It becomes. Here, the major axis of the approximate refractive index nz (n _e ) of the liquid crystal layer 71 and the minor axis of the refractive index nz (N _e ) of the optical compensator 84 are arranged in parallel, and the slow axis and the fast axis of each are arranged. The phase axes are interchanged. Therefore, the total retardation RE with respect to the normal incident light is given by the absolute value of the difference between Re1 given by Expression (3) and Re2 given by Expression (6). That is, when Re1 = Re2, the polarized light emitted from the first polarizing filter 31b and the polarized light incident on the second polarizing filter 31c are in the same state, and the light blocking by the polarizing filter 31c with respect to the vertically incident light becomes complete, and the liquid crystal light valve The contrast of the image determined by the transmission and shading of 31 is maximized.

で与えられる。上式でｄ１／ｃｏｓη１は、傾斜した入射光の液晶層７１における実効光路長であり、ｄ２／ｃｏｓη２は、傾斜した入射光の光学補償板８４における実効光路長である。なお、以上では、光学補償板８４と液晶層７１とにおける遅相軸と進相軸との大小関係が垂直入射光と同様であるとしたが、これに該当しない場合もある。すなわち、液晶層７１を垂直近似チルト角θ１に対応する傾き角η１よりも大きな傾斜角で通過する光束等については、上記式（９）中の符号の正負を適宜入れ替えることで、正確なリタデーションＲｅ’を求めることができる。 Below, the case where the incident light to the liquid crystal light valve 31 has an angular distribution will be considered. First, consider a certain light flux L1 incident obliquely on the liquid crystal light valve 31 from the air. The inclination angle in the air is η0, the inclination angle in the liquid crystal layer 71 is η1, and the inclination in the optical compensator 84 is as follows. Let the angle be η2. In this case, in the liquid crystal layer 71, so since the difference between n _o and n _e is small becomes n _o ≒ n _e, for the light beam incident at an inclination angle η0 to the liquid crystal layer 71 from the air, the following conditions Follow a satisfying optical path.
sin (η0): sin (η1) = 1: 1 / n _o
sin (η1) = sin (η0 ) / n o ... (7)
Further, since N _o ≈N _{e in the} optical compensator 84, the light flux that has entered the optical compensator 84 from the liquid crystal layer 71 at an inclination angle η 1 is as follows.
sin (η1): sin (η2) = 1 / n _o : 1 / N _o
sin (η2) = sin (η1 ) (n o / N o) ... (8)
In the above, the light beam incident on the incident surface 71a with the inclination angle η0 with respect to the normal line has been considered, but the direction of the incident light inclination is also a problem. Here, assuming that the tilt direction is considered with reference to the approximate orientation direction, that is, the intermediate direction DA, the tilt angle η0 is a polar angle, and the azimuth angle of the incident light beam is φ. In this case, the angle w1 formed by the light beam passing through the liquid crystal light valve 31 with the optical axis OAC1 in the liquid crystal layer 71 and the angle w2 formed by the light beam with the optical axis OA2 in the optical compensator 84 are the variables η0 and φ. And η1 and η2 obtained based on these values can be obtained geometrically. The retardation Re ′ when such obliquely incident light passes through the liquid crystal layer 71 and the optical compensator 84 is given by

Given in. In the above equation, d1 / cos η1 is the effective optical path length of the tilted incident light in the liquid crystal layer 71, and d2 / cos η2 is the effective optical path length of the tilted incident light in the optical compensator 84. In the above, the magnitude relationship between the slow axis and the fast axis in the optical compensator 84 and the liquid crystal layer 71 is the same as that in the normal incident light, but this may not be the case. That is, for a light beam or the like that passes through the liquid crystal layer 71 at a tilt angle larger than the tilt angle η1 corresponding to the vertical approximate tilt angle θ1, an accurate retardation Re can be obtained by appropriately changing the sign of the formula (9). 'Can be asked.

がゼロに近づくように光学補償板８４を設定する。ここで、Ｗ（η０，φ）は、入射光の角度分布によって与えられる重み関数である。図６（ａ）は、通過光のリタデーションＲｅ’＝ｆ（η０，φ）と傾き角η０との一般的な関係を視覚的に説明したものであり、傾き角η０が０となる正面方向の光に対してリタデーションＲｅ’が最も小さくなっているが、傾き角η０が増加するに従ってリタデーションＲｅ’が徐々に増加する。また、図６（ｂ）は、入射光の重み関数Ｗ（η０，φ）と傾き角η０との関係を視覚的に説明したものであり、傾き角η０が０となる正面方向の光の密度が最も高くなっており、これに伴って重み関数が最大値となっている。以上は例示であり、リタデーションＲｅ’＝ｆ（η０，φ）の特性は、液晶層７１と光学補償板８４の光学特性によって定まり、Ｗ（η０，φ）は、光源の放射特性、均一化光学系の光学特性、液晶のマイクロレンズの特性等によって定まる。つまり、光学補償板８４の屈折率楕円体ＲＩＥ２や厚みｄ２を調節することで、様々なＷ（η０，φ）の照明装置に対してリタデーションＲｅ’＝ｆ（η０，φ）の積分値を極小化することができ、液晶ライトバルブ３１によって形成される画像のコントラストを最大限高めることができる。 As a result, the retardation Re ′ when passing through the liquid crystal light valve 31 and the optical compensator 84 is such that the refractive indexes n _o , n _e , N _o , N _e , d 1 and d 2 are constants, and the values η 1, η 2 Since w1 and w2 are parameters determined by the above values η0 and φ, the following function f
Re ′ = f (η0, φ) (10)
Can be processed. Therefore, the thickness d2 of the optical compensator 84 can be optimized based on the above formula (10) so that the retardation Re ′ is obtained for all incident rays and the sum of these is minimized. The contrast of the image determined by the transmission and shading of the liquid crystal light valve 31 is approximately maximum. For example, in the case of a light beam perpendicularly incident on the liquid crystal light valve 31 with a certain NA, η0 corresponding to the opening angle is 0 to ηmax and the azimuth angle φ is 0 to 360 °.

The optical compensator 84 is set so as to approach zero. Here, W (η0, φ) is a weighting function given by the angular distribution of incident light. FIG. 6A visually illustrates a general relationship between the retardation Re ′ = f (η0, φ) of the passing light and the inclination angle η0. The front direction in which the inclination angle η0 is 0 is illustrated in FIG. Although the retardation Re ′ is the smallest with respect to light, the retardation Re ′ gradually increases as the tilt angle η0 increases. FIG. 6B visually illustrates the relationship between the weighting function W (η0, φ) of the incident light and the tilt angle η0, and the light density in the front direction where the tilt angle η0 is zero. Is the highest, and accordingly, the weighting function has the maximum value. The above is an example, and the characteristic of retardation Re ′ = f (η0, φ) is determined by the optical characteristics of the liquid crystal layer 71 and the optical compensator 84, and W (η0, φ) is the emission characteristic of the light source and the homogenizing optics. It is determined by the optical characteristics of the system and the characteristics of the liquid crystal microlenses. That is, by adjusting the refractive index ellipsoid RIE2 and the thickness d2 of the optical compensator 84, the integral value of the retardation Re ′ = f (η0, φ) is minimized for various illumination devices of W (η0, φ). The contrast of the image formed by the liquid crystal light valve 31 can be maximized.

  The integral value (total retardation) represented by the above equation (11) can be quickly obtained by a simulation that performs high-speed calculation, and by inputting the characteristics of the liquid crystal layer 71 and the refractive index characteristics of the optical compensator 84. The thickness d2 and the inclination angle θ2 of the optical compensation plate 84 can be determined quickly.

  A specific example will be described. When a sapphire crystal is used as the optical compensator 84 for the twisted nematic liquid crystal layer 71, the thickness d2 is in the range of about 1 to 100 μm. In particular, as a result of the simulation performed on the liquid crystal light valve 31 including the general twisted nematic liquid crystal layer 71, the thickness d2 = 50 μm of the optical compensator 84 is appropriate, and the integral value given by the above equation (11) is minimized. Value and could. The results are shown in the graph of FIG. In this graph, the vertical axis indicates the gain, the horizontal axis “no compensation” indicates the case where the optical compensation plate 84 is not provided, and “sapphire compensation” indicates the case where the optical compensation plate 84 made of sapphire crystal is provided. .

  FIG. 8 shows the result of simulation with data corresponding to a specific liquid crystal light valve 31. FIG. 8A shows the viewing angle characteristics of the liquid crystal light valve 31 of the example, and FIG. 8B shows the viewing angle characteristics of the liquid crystal light valve of the comparative example. The liquid crystal light valve of the comparative example corresponds to “no compensation” in the graph of FIG. 7, and the liquid crystal light valve of the comparative example corresponds to “sapphire compensation” of the graph. In both viewing angle characteristics, the contour line means an inclination angle with respect to the normal direction of the incident surface. As is apparent from the figure, in the case of the liquid crystal light valve 31 of the embodiment, the viewing angle characteristics are good in a wide range with respect to the normal direction of the incident surface, and the contrast in the front direction of the liquid crystal light valve 31 is remarkably improved. I understand that.

  Hereinafter, a method for manufacturing the optical compensation element OC including the optical compensation plate 84 will be described. First, materials for the optical compensation plate 84 and the emission side cover 74b, which are constituent elements of the optical compensation element OC, are prepared. That is, sapphire as a material of the optical compensator 84 is cut out as thin as possible, and the tilt direction (alignment orientation) and tilt angle (polar angle) θ2 of the refractive index ellipsoid RIE2 are the same as the approximate refractive index ellipsoid RIE3 of the liquid crystal layer 71. Try to be the same. Next, a process such as polishing is performed on a pair of opposed planes of the cut sapphire plate to smooth the surface. Next, a parallel plate-like support substrate having a high transmittance such as quartz or white glass, which is a material of the emission side cover 74b, and having no birefringence is prepared. Next, the cleaned sapphire plate is bonded to the cleaned support substrate via an ultraviolet curable resin, and then fixed by curing. Thereafter, the sapphire plate on the support substrate is polished with relatively coarse abrasive grains so that the sapphire layer becomes an optical compensation plate 84 of, for example, about 60 μm. At this time, if double-side polishing or the like is used, the thickness of the optical compensator 84 that is a sapphire layer can be determined by measuring retardation. If single-side polishing is used, an optical that is a sapphire layer using a micro gauge. The thickness of the compensation plate 84 can be determined. Note that even with single-side polishing, if the supporting substrate to be bonded is transparent and has no birefringence (for example, white plate or quartz), the thickness can be measured by retardation while the sapphire plate is bonded. Since the polished surface has fine scratches, the scratches are filled with an adhesive having a refractive index similar to that of the optical compensation plate 84, or polished again with relatively fine abrasive grains. Smooth the surface.

  In the first embodiment described above, the optical compensation plate 84 is attached to the emission side cover 74b. However, if the optical compensation plate 84 is disposed between the pair of polarizing filters 31b and 31c, a certain effect can be achieved. Therefore, the optical compensator 84 can be attached to the incident side cover 74a, for example.

[Second Embodiment]
Hereinafter, a liquid crystal light valve which is an optical device according to a second embodiment of the present invention will be described. The liquid crystal light valve of the second embodiment is a modification of the liquid crystal light valve of the first embodiment, and the portions that are not specifically described are the same as those of the first embodiment, and redundant description is omitted.

  FIG. 9 is a side sectional view for explaining the optical compensation element OC incorporated in the liquid crystal light valve of the second embodiment. In this case, the optical compensation element OC is inclined with respect to the incident surface 71a of the liquid crystal layer 71. That is, the optical path VP of the light beam perpendicularly incident on the incident surface 71a of the liquid crystal layer 71 is incident on the incident plane 184a of the optical compensator 184, which is a flat plate element, with a similar inclination angle from the emission plane 184b. Inject at. Here, the optical compensation plate 184 is a flat element formed of a transparent negative uniaxial crystal, as in the case of the first embodiment, but the direction of the optical axis OA2 is perpendicular to the incident plane 184a. It is processed as follows. The optical compensation plate 184 is supported by a transparent plate 181 made of an isotropic material such as glass. The optical compensation element OC as a whole is a main body of a liquid crystal panel including a liquid crystal layer 71 and the like by a holder (not shown). It is fixed on the side.

  In the present embodiment, in the optical compensator 184, the minor axis of the refractive index ellipsoid RIE2, that is, the optical axis OA2, has a constant inclination angle θ2 with respect to the optical path VP of the light beam perpendicularly incident on the liquid crystal layer 71. This tilt angle θ2 is substantially equal to the vertical approximate tilt angle θ1 given to the liquid crystal layer 71. Here, the reason why the minor axis tilt angle θ2 of the refractive index ellipsoid RIE2 of the optical compensation plate 184 and the vertical approximate tilt angle θ1 of the liquid crystal layer 71 are substantially equal are the same as in the first embodiment. This is because when a difference in refractive index between 184 and the liquid crystal layer 71 is taken into consideration, a slight difference may occur between θ1 and θ2.

  The optical compensation plate 184 as described above can be easily formed not only by sapphire but also by a stretched film such as TAC because one of the three main refractive indexes exists in the normal direction of the compensation element surface. . The stretched film is suitable for mass production.

  Also in this embodiment, the retardation Re described in the first embodiment for various illumination devices by appropriately adjusting the refractive index ellipsoid RIE2, the thickness d2, the inclination, etc. of the optical compensation plate 184 in the optical compensation element OC. Since the integral value of '= f (η0, φ) can be minimized, the contrast of an image formed by the liquid crystal light valve 31 can be maximized. In the present embodiment, the optical compensation element OC is arranged at the front stage of the liquid crystal layer 71. However, the optical compensation element OC can be arranged at the rear stage of the liquid crystal layer 71, and the same effect can be obtained.

[Third Embodiment]
Hereinafter, a liquid crystal light valve (light modulation device) which is a liquid crystal device according to a third embodiment of the present invention will be described. The liquid crystal light valve of the third embodiment is a modification of the liquid crystal light valve of the second embodiment, and parts that are not specifically described are the same as those of the second embodiment, and redundant description is omitted.

  FIG. 10 is a side sectional view for explaining the optical compensation element OC incorporated in the liquid crystal light valve of the third embodiment. In this case, the optical compensation element OC has an optical compensation plate 184 processed so that the direction of the optical axis OA2 is perpendicular to the incident plane 184a, and a pair of wedges joined so as to sandwich the optical compensation plate 184. And prisms 281a and 281b. Here, the refractive indexes of the wedge-shaped prisms 281 a and 281 b are substantially equal to the refractive index of the optical compensation plate 184. As a result, the light beam VP perpendicularly incident on the incident surface 71a of the liquid crystal layer 71 is perpendicularly incident on the incident surface 285a of the optical compensation element OC, but the incident plane 184a of the optical compensation plate 184 is Incident at an angle.

  In the present embodiment, in the optical compensator 184, the minor axis of the refractive index ellipsoid RIE2, that is, the optical axis OA2, has a constant inclination angle θ2 with respect to the light beam VP perpendicularly incident on the liquid crystal layer 71. The tilt angle θ2 is equal to the vertical approximate tilt angle θ1 given to the liquid crystal layer 71.

  Also in this embodiment, the retardation Re described in the first embodiment for various illumination devices by appropriately adjusting the refractive index ellipsoid RIE2, the thickness d2, the inclination, etc. of the optical compensation plate 184 in the optical compensation element OC. Since the integral value of '= f (η0, φ) can be minimized, the contrast of an image formed by the liquid crystal light valve 31 can be maximized. In the present embodiment, the optical compensation element OC is disposed in the previous stage of the liquid crystal layer 71. However, the optical compensation element OC may be disposed in the subsequent stage of the liquid crystal layer 71.

[Fourth Embodiment]
FIG. 11 is a diagram for explaining the configuration of an optical system of a projector incorporating the liquid crystal light valve 31 shown in FIG.

  The projector 10 includes 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 illumination of each color emitted from the color separation optical system 23. A light modulator 25 illuminated by light, a cross dichroic prism 27 that combines image light of each color from the light modulator 25, and a projection for projecting image light that has passed through the cross dichroic prism 27 onto a screen (not shown). And a projection lens 29 which is an optical system. Among these, the light source device 21, the color separation optical system 23, the light modulation unit 25, and the cross dichroic prism 27 are image forming apparatuses that form image light to be projected onto the screen.

  In the projector 10 described above, the light source device 21 includes a light source lamp 21a, a concave lens 21b, a pair of fly-eye optical systems 21d and 21e, a polarization conversion member 21g, and a superimposing lens 21i. 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. The pair of fly-eye optical systems 21d and 21e is 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 by these element lenses to be individually condensed and diverged. Let The polarization conversion member 21g converts the light source light emitted from the fly-eye optical system 21e into, for example, only the S-polarized component perpendicular to the paper surface of FIG. The superimposing lens 21i enables superimposing illumination on the light modulation devices of the respective colors provided in the light modulation unit 25 by appropriately converging the illumination light that has passed through the polarization conversion member 21g as a whole. That is, the illumination light that has passed through both the fly-eye optical systems 21d and 21e and the superimposing lens 21i passes through the color separation optical system 23 that will be described in detail below, and each color liquid crystal panel 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 23j, 23m, 23n, and 23o, and a light source device. 21 together with the illumination device. Here, the first dichroic mirror 23a reflects, for example, red light and green light among the three colors of red, green, and blue, and transmits blue light. In addition, the second dichroic mirror 23b reflects, for example, green light and transmits red light out of the two incident colors of red and green. In this color separation optical system 23, the substantially white light source light from the light source device 21 is incident on the first dichroic mirror 23a after the optical path is bent by the reflection mirror 23j. The blue light that has passed through the first dichroic mirror 23a enters the field lens 23f through the reflection mirror 23m, for example, as S-polarized light. Further, the green light reflected by the first dichroic mirror 23a and further reflected by the second dichroic mirror 23b is incident on the field lens 23g as S-polarized light, for example. Further, the red light that has passed through the second dichroic mirror 23b remains as S-polarized light, for example, and enters the field lens 23h for adjusting the incident angle via the lenses LL1 and LL2 and the reflecting mirrors 23n and 23o. The lenses LL1 and LL2 and the field lens 23h constitute a relay optical system. This relay optical system has a function of transmitting the image of the first lens LL1 almost directly to the field lens 23h via the second lens LL2.

  The light modulation unit 25 includes three 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, 25b, and 25c. Here, the liquid crystal panel 25a for blue light and the pair of polarizing filters 25e and 25e sandwiching the liquid crystal panel 25a are used for two-dimensionally modulating the blue light of the image light after the luminance modulation based on the image information. A liquid crystal light valve for blue is constructed. The blue liquid crystal light valve has the same structure as the liquid crystal light valve 31 shown in FIG. 1, and incorporates an optical compensation element OC, that is, an optical compensation plate 84 and the like for improving contrast. 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 red light liquid crystal panel 25c and the polarizing filters 25g and 25g are also red liquid crystals. Configure the light valve. The green and red liquid crystal light valves also have the same structure as the liquid crystal light valve 31 shown in FIG.

  The blue light branched by passing through the first dichroic mirror 23a of the color separation optical system 23 enters the first liquid crystal panel 25a for blue light 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. The red light branched by passing through the second dichroic mirror 23b is incident on the third liquid crystal panel 25c for red light through the field lens 23h. Each of the liquid crystal panels 25a to 25c is a non-light emitting type light modulation device that modulates the spatial intensity distribution of incident illumination light in units of pixels, and the three colors of light incident on the liquid crystal panels 25a to 25c are respectively Modulation is performed according to a drive signal or an image signal input as an electrical signal to the liquid crystal panels 25a to 25c. At that time, the polarization filters 25e, 25f, and 25g adjust the polarization direction of the illumination light incident on the liquid crystal panels 25a to 25c, and have a predetermined polarization direction from the modulated light emitted from the liquid crystal panels 25a to 25c. Component light is extracted as image light.

  The cross dichroic prism 27 is a photosynthetic member, has a substantially square shape in plan view in which four right angle prisms are bonded together, and a pair of dielectric multilayer films that intersect in an X shape at the interface where the right angle prisms are bonded to each other. 27a and 27b are formed. One first dielectric multilayer film 27a reflects blue light, and the other second dielectric multilayer film 27b reflects red light. The cross dichroic prism 27 reflects the blue 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 red light from the liquid crystal panel 25c is reflected by the second dielectric multilayer film 27b and emitted to the left in the traveling direction.

  The projection lens 29 projects the color image light synthesized by the cross dichroic prism 27 on a screen (not shown) at a desired magnification. That is, a color moving image or a color still image having a desired magnification corresponding to the drive signal or image signal input to each of the liquid crystal panels 25a to 25c is projected on the screen.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Such modifications are also possible.

  That is, in the above-described embodiment, an example in which sapphire or TAC is used as the optical compensation plate 84 has been described. However, a negative uniaxial material other than sapphire or TAC can be used. Specifically, inorganic materials such as calcite, KDP (potassium dihydrogen), and ADP (ammonium dihydrogen phosphate) can be used, and various olefin organic materials can be used.

  Further, in the above embodiment, the contrast is improved by compensating the retardation in the on state where the voltage is applied to the liquid crystal layer 71, that is, the light off state, but the off state where the voltage is not applied to the liquid crystal layer 71, that is, the light. Retardation can also be compensated for in the on state. Also in this case, the approximate refractive index ellipsoid RIE3 is obtained for the liquid crystal layer 71 in the off state, and the transmission luminance can be increased.

  In the projector 10 of the above-described embodiment, the light source device 21 includes the light source lamp 21a, the pair of fly's eye optical systems 21d and 21e, the polarization conversion member 21g, and the superimposing lens 21i, but the fly eye optical systems 21d and 21e. The polarization conversion member 21g and the like can be omitted, and the light source lamp 21a can be replaced with another light source such as an LED.

  Further, in the above embodiment, the color separation optical system 23 is used to perform color separation of illumination light, the light modulation unit 25 modulates each color, and then the cross dichroic prism 27 synthesizes each color image. However, an image can also be formed by a single liquid crystal panel, that is, the liquid crystal light valve 31.

  In the above embodiment, only the example of the projector 10 using the three liquid crystal panels 25a to 25c has been described. However, the present invention is a projector using only one liquid crystal panel, a projector using two liquid crystal panels, or The present invention can also be applied to a projector using four or more liquid crystal panels.

  In the above embodiment, only an example of a front type projector that projects from the direction of observing the screen is given, but the present invention is also applicable to a rear type projector that projects from the side opposite to the direction of observing the screen. Is possible.

It is a side sectional view explaining the structure of the liquid crystal light valve concerning a 1st embodiment. It is a sectional side view explaining the refractive index of the liquid crystal layer and optical compensator of a liquid crystal light valve. (A)-(b) is a perspective view explaining the approximation of the refractive index of a liquid-crystal layer. (A), (b) is the side view and top view explaining the refractive index of a liquid crystal layer. (A), (b) is the side view and top view explaining the refractive index of an optical compensation board. (A), (b) shows the inclination angle dependency of retardation and the weight function of incident light. It is a graph explaining the result of simulation. (A), (b) shows an Example and a comparative example about the viewing angle by simulation. It is a sectional side view explaining the liquid crystal light valve of 2nd Embodiment. It is a sectional side view explaining the liquid crystal light valve of 2nd Embodiment. It is a figure explaining the optical system of the projector incorporating the liquid crystal light valve of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 21 ... Light source device, 21g ... Polarization conversion member, 23 ... Color separation optical system, 23a, 23b ... Dichroic mirror, 25 ... Light modulation part, 25a, 25b, 25c ... Liquid crystal panel, 25e, 25f, 25g ... Polarizing filter, 27 ... Cross dichroic prism, 27a, 27b ... Dielectric multilayer film, 29 ... Projection lens, 31 ... Liquid crystal light valve, 31a ... Polarization modulator, 31b ... First polarizing filter, 31c ... Second polarizing filter, 71 ... liquid crystal layer, 71a ... incident surface, 71b ... exit surface, 72a, 72b ... substrate, 74a, 74b ... cover, 75, 77 ... electrode, 76, 78 ... alignment film, 77 ... transparent pixel electrode, 84 ... optical compensation plate 84a ... incidence plane, 84b ... emission plane, CP ... center part, DA ... middle direction, EP1, EP2 ... end part, A1, OA2 ... optical axis, OAC1 ... optical axis, OC ... optical compensation element, RIE1, RIE2 ... refractive index ellipsoid, RIE11, RIE12, RIE10 ... refractive index ellipsoid

Claims (8)

A liquid crystal cell that includes a liquid crystal that operates in a twisted nematic mode, and in which the optical axis of the liquid crystal adjacent to the entrance surface and the exit surface is tilt-aligned by a predetermined pretilt angle with respect to the entrance surface and the exit surface;
The liquid crystal cell is disposed on one of the incident side and the emission side, is formed of a uniaxial crystal having a negative uniform optical axis, and corresponds to a tilt alignment direction of liquid crystal adjacent to the incident surface. One kind of optical compensation in which a predetermined intermediate direction that forms a non-zero angle with respect to one rubbing direction and a second rubbing direction corresponding to the tilt alignment direction of the liquid crystal adjacent to the exit surface is the alignment direction of the optical axis. Elements,
An optical apparatus comprising a pair of polarizing elements arranged so as to sandwich the liquid crystal cell and the optical compensation member.   The optical apparatus according to claim 1, wherein an optical axis of the optical compensation element is inclined by a predetermined inclination angle with respect to a normal direction of an incident surface and an emission surface parallel to each other of the liquid crystal cell.   The optical compensation element is a flat plate element having an incident plane and an emission plane parallel to the incident surface and the emission surface of the liquid crystal cell and having an optical axis inclined with respect to a normal line of the incident plane and the emission plane. Item 3. The optical device according to Item 2.   The optical compensation element has a plane of incidence and an emission plane parallel to each other inclined with respect to the incidence plane and the emission plane of the liquid crystal cell, and an optical axis in the normal direction of the incidence plane and the emission plane. The optical device according to claim 2.   5. The thickness of the optical compensation element according to claim 1, wherein the optical compensation element has a thickness that effectively cancels retardation caused by liquid crystal present in the vicinity of an incident surface and an emission surface among liquid crystals in the liquid crystal cell. An optical device according to claim 1.   The optical apparatus according to claim 1, wherein the optical compensation element is disposed on an emission surface side of the liquid crystal cell.   The optical device according to claim 6, wherein the liquid crystal cell includes a microlens array at least on an incident side. An optical device for light modulation according to any one of claims 1 to 7,
An illumination device for illuminating the optical device;
A projector comprising: a projection lens that projects an image formed by the optical device.

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