JP2008015300A - Optical apparatus and projector equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical apparatus with a small footprint, while suppressing cost increase and improving optical modulation accuracy of contrast or the like, and to provide a projector equipped therewith. <P>SOLUTION: In an inside support layer 84, the minor axis or the optical axis OA2 of an index ellipsoid RIE2 is in XZ surface and has a constant tilt angle θ2 with respect to a Z axis. The tilt angle θ2 is substantially equal to a pre-tilt angle θ1 that is given to a liquid crystal layer 71. By adjusting the index ellipsoid RIE2 and the thickness d2 of the inside support layer 84, integrated value of retardation can be minimized for a lighting device, and the contrast of an image formed by a liquid crystal light valve 31 can be enhanced. <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 vertical alignment type liquid crystal panel is used for the purpose of improving the contrast ratio, and an optical anisotropy element for compensation is arranged between the liquid crystal panel and the incident polarizing plate. There is one in which an element is inclined at an angle according to the alignment direction of liquid crystal molecules in a liquid crystal panel (see Patent Document 1).
JP 2006-11298 A

  However, when using the optically anisotropic element as described above, it is necessary to secure a sufficient space for disposing the optically anisotropic element between the liquid crystal panel and the incident polarizing plate. Further, the cost increases due to the special incorporation and fixing of the optically anisotropic element.

  The polarizing plates disposed before and after the liquid crystal panel usually have a structure in which PVA (polyvinyl alcohol) is sandwiched between support layers called TAC (triacetyl cellulose). Although this TAC is not large, it has birefringence, and even when the polarizing plate is arranged in crossed Nicols, a phenomenon occurs in which oblique incident light leaks and the contrast is lowered.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical device capable of improving light modulation accuracy such as contrast while saving space and suppressing an increase in cost, and a projector including the optical device.

  In order to solve the above problems, an optical device according to the present invention is disposed on at least one of (a) a liquid crystal cell including a liquid crystal operating in a vertical alignment mode, and (b) an incident side and an emission side of the liquid crystal cell. (C) the polarizing plate includes a polarizing film and an inner support layer provided on the liquid crystal cell side of the polarizing film to support the polarizing film, and (d) the inner support layer is a liquid crystal It is made of a negative uniaxial refractive material having an optical axis inclined with respect to the normal direction of the incident surface of the panel.

  In the above optical device, the orientation of the optical axis of the inner support layer of the polarizing plate separate from the liquid crystal cell can be adjusted in advance even when a pretilt variation occurs in the optical axis of the liquid crystal in the liquid crystal cell. By doing so, it is possible to cope with such a pretilt variation by utilizing the refractive index characteristic of the inner support layer which is a negative uniaxial refractive material. This makes it possible to effectively utilize the birefringence of the polarizing plate, which was previously considered undesirable, and improves the dimming or light modulation accuracy of the liquid crystal cell while saving space and increasing costs. Can be made.

  According to a specific aspect or aspect of the present invention, in the optical device, the liquid crystal cell is configured such that the optical axis of the liquid crystal in the off state is tilted and aligned by a predetermined pretilt angle with respect to the normal of the incident surface. The inner support layer has a uniform optical axis in the orientation direction of the off-state liquid crystal in the liquid crystal cell and in the direction inclined with respect to the incident surface. In this case, a so-called pretilt is generated in the liquid crystal as a result of the optical axis of the liquid crystal being tilted with respect to the normal of the incident surface in the off state of the liquid crystal cell (that is, in the state where no voltage is applied). By utilizing the refractive index characteristic, it is possible to cancel or reduce the retardation of the image light in the front direction caused by the pretilt of the liquid crystal. As a result, it is possible to suppress a phenomenon in which black rises in the front direction of the liquid crystal cell and the contrast of the image decreases when the liquid crystal cell is turned off. Note that the pretilt remaining in the liquid crystal cell in the off state is uniform within the liquid crystal layer, and the refractive index characteristic of the inner support layer is made uniform and the orientation is adjusted, so that the image light generated in the front direction due to the pretilt of the liquid crystal is adjusted. Retardation can be compensated effectively.

  In another aspect of the present invention, the inner support layer is a flat plate having an incident plane and an emission plane parallel to the incident plane of the liquid crystal cell and having an optical axis inclined with respect to the normal line of the incident plane and the emission plane. is there. In this case, since the polarizing plate is arranged in parallel to the liquid crystal cell or the like, the polarizing plate can be easily and precisely fixed in a stable state.

  In yet another aspect of the present invention, the inner support layer has an entrance plane and an exit plane parallel to each other inclined with respect to the entrance plane of the liquid crystal cell, and the optical axis is in the normal direction of the entrance plane and the exit plane. It is an existing flat plate. In this case, the optical axis of the inner support layer of the polarizing plate can be set in a direction perpendicular to the incident plane or the like, and the inner support layer can be processed and manufactured relatively easily.

  In yet another aspect of the invention, the inner support layer has a thickness that substantially cancels retardation due to the off-state liquid crystal in the liquid crystal cell. In this case, the inner support layer of the polarizing plate can suppress the phenomenon in which black rises in the front direction of the liquid crystal cell due to the pretilt of the liquid crystal and the contrast of the image decreases.

  In yet another aspect of the present invention, the inner support layer substantially cancels the retardation caused by the off-state liquid crystal in the liquid crystal cell corresponding to the range of the tilt angle of the illumination light with respect to the incident surface of the liquid crystal cell. Has a thickness. In this case, the retardation can be 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.

  In yet another aspect of the present invention, polarizing plates are disposed on both the incident side and the emission side of the liquid crystal cell. In this case, illumination light having a high degree of polarization can be incident on the liquid crystal cell by the polarizing plate arranged on the incident side, and specific linearly polarized light is selectively transmitted from the liquid crystal cell by the polarizing plate arranged on the emission side. Thus, image light that is light-modulated as transmitted light can be obtained. In addition, for both or one of the incident-side and emission-side polarizing plates, the inner support layer is a negative uniaxial refractive material having an optical axis inclined with respect to the normal direction of the incident surface of the liquid crystal panel. be able to.

  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 optical device described above, and cancels out the retardation of the image light generated by the tilt even when manufacturing pre-tilt variation occurs on the optical axis of the liquid crystal in the liquid crystal cell. Or it can be reduced. 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 vertical alignment mode (that is, a vertical alignment type 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.

  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 compound constituting the liquid crystal layer 71 in a necessary direction, and in the off state where no voltage is applied to the liquid crystal layer 71, the optical axis of the liquid crystal compound. In the on-state in which a voltage is applied to the liquid crystal layer 71, the optical axis of the liquid crystal compound is the first in the ON state. It is allowed to be oriented in a specific direction (specifically, X direction) perpendicular to the normal line of one substrate 72a.

  FIG. 2 is a cross-sectional structure diagram illustrating the structure of the first polarizing filter 31b and the like. The first polarizing filter 31b is a polarizing element including a polarizing film 81, an outer support layer 83, and an inner support layer 84. Here, the polarizing film 81 is held in a sandwiched state between the outer support layer 83 and the inner support layer 84. The polarizing film 81 is for passing only light that vibrates in a certain direction, and is formed by adsorbing a dye to a PVA (polyvinyl alcohol) film and stretching it in a specific direction. The outer support layer 83 is formed of a TAC (triacetyl cellulose) film. The inner support layer 84 can be formed of a thin plate of an organic material such as TAC, but can also be formed of a thin plate of an inorganic material such as a sapphire plate. Here, the inner support layer 84 is a flat plate that is formed of a negative uniaxial refracting material and has a light incident end face and a light exit end face that are parallel to each other. The optical axis is inclined with respect to the normal direction of the incident surface of the first polarizing filter 31b and the polarization modulator 31a because of the arrangement inside (that is, the side facing the polarization modulator 31a in FIG. 1). Is set. That is, the polarizing film 81 is disposed so that its optical axis is in the XZ plane including the alignment direction (specifically, the X direction) of the liquid crystal layer 71 shown in FIG. A predetermined inclination angle is formed with respect to the axis. The outer support layer 83 is also a flat element made of a negative uniaxial refractive material, but its optical axis is relative to the normal direction of the incident surface of the first polarizing filter 31b or the polarization modulator 31a. There is no need to tilt.

  The inner support layer 84 functions as an optical compensator for enhancing the function of the polarization modulator 31a shown in FIG. That is, by utilizing the refractive index characteristic of the inner support layer 84, the retardation of the image light in the front direction caused by the pretilt of the liquid crystal in the liquid crystal layer 71 can be canceled or reduced, and the polarization modulation unit 31a can turn off when turned off. It is possible to suppress the phenomenon in which black rises in the formed image and the contrast is lowered. For example, when the inner support layer 84 is formed of sapphire, the refractive index ellipsoid has a refractive difference of about 0.008 and is adjusted to a thickness of about 30 to 100 μm. For example, when the inner support layer 84 is formed of TAC, the refractive difference of the refractive index ellipsoid depends on the stretching force at the time of manufacture, and thus the thickness is appropriately set according to the refractive index difference.

  The second polarizing filter 31c also has a three-layer structure including the polarizing film 81 and the support layers 83 and 84, similarly to the first polarizing filter 31b. However, for convenience of explanation, the second polarizing filter 31c will be described on the assumption that the inner support layer 84 is first formed of an isotropic material having no refractive index anisotropy.

  FIG. 3 is a conceptual side sectional view for explaining the refractive index of the liquid crystal layer 71 and the refractive index of the inner support layer 84. Here, the entrance surface 71a and the exit surface 71b of the liquid crystal layer 71 and the entrance plane 84a and the exit plane 84b of the inner support layer 84 are all parallel to each other.

  In the liquid crystal layer 71 in the off state to which no voltage is applied, the major axis of the refractive index ellipsoid RIE1 of the liquid crystal compound, that is, the optical axis OA1 has a small tilt angle with respect to the Z axis in the XZ plane, but a constant tilt angle. ing. At this time, the tilt direction of the refractive index ellipsoid RIE1 is the X direction, and this X direction is referred to as the alignment direction of the liquid crystal layer 71. The tilt angle in the orientation direction of the refractive index ellipsoid RIE1 is called a pretilt angle θ1. On the other hand, in the inner support layer 84, the minor axis of the refractive index ellipsoid RIE2 of the negative uniaxial crystal constituting the inner support layer 84, that is, the optical axis OA2, is in the XZ plane and has a small tilt angle with respect to the Z axis. Have. More specifically, the tilt direction, that is, the azimuth angle of the refractive index ellipsoid RIE2 is the same X direction as the alignment direction of the liquid crystal layer 71, and the tilt angle θ2, ie, polar angle, at the azimuth angle at which the refractive index ellipsoid RIE2 tilts. Is substantially equal to the pretilt angle θ1 given to the liquid crystal layer 71 in the present embodiment. Here, the inclination angle θ2 of the minor axis of the refractive index ellipsoid RIE2 of the inner support layer 84 and the pretilt angle θ1 of the liquid crystal layer 71 are assumed to be substantially equal. The refractive index of the inner support layer 84 and the refraction of the liquid crystal layer 71 In principle, when the refractive index is equal, the minor axis inclination angle θ2 of the refractive index ellipsoid RIE2 of the inner support layer 84 and the pretilt angle θ1 of the liquid crystal layer 71 are equal, but the refractive index of the inner support layer 84 If the refractive index of the liquid crystal layer 71 is different from that of the liquid crystal layer 71, the difference in the refractive index is taken into consideration (when the light incident on the polarization modulator 31a at a certain incident angle is transmitted through the inner support layer 84 and the liquid crystal layer 71). The angle of increase / decrease with respect to the pretilt angle θ1 of the liquid crystal layer 71 is such that the minor axis inclination angle θ2 of the refractive index ellipsoid RIE of the inner support layer 84 is such that the light beam becomes parallel when passing through the inside. It is because it is set as.

  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. FIG. 5A is a side view for explaining the refractive index of the inner support layer 84, and FIG. 5B is a plan view for explaining the refractive index of the inner support layer 84.

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、内側支持層８４について考えると、この内側支持層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の短軸に対応する光学軸ＯＡ２が内側支持層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、傾き角θ２（θ２はθ１と等しいか近い値）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）に示すように垂直入射光の進相軸方向に振動する光の屈折率がｎ_４で遅相軸方向に振動する光の屈折率が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内側支持層８４のリタデーションＲｅ２は、内側支持層８４の厚みをｄ２として、

となる。ここで、液晶層７１の屈折率ｎｚの長軸と内側支持層８４の屈折率ｎｚの短軸とは平行又は略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第２偏光フィルタ３１ｃでの遮光が完全となる。 First, considering the liquid crystal layer 71, the refractive index ellipsoid of the liquid crystal compound corresponds to a positive uniaxial material, and the refractive index in each axial direction based on the refractive index is expressed as nx, ny, Assuming nz, generally, the relationship of nx = ny <nz is established, and the optical path OA1 corresponding to the major axis of the refractive index nz is the optical path of the light beam (normally incident light) incident on the incident surface 71a of the liquid crystal layer 71 from the normal direction. It is in a state tilted by a pretilt angle θ1 with respect to VP. Here, a FIGS. 4 (a) are shown as ordinary refractive index at _{n o} extraordinary refractive index _{n e,} that is _{nx = ny = n o, nz} = n e, as shown in FIG. 4 (b) If the refractive index of light oscillating in the slow axis direction of normal incident light is n ₂ and the 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 inner support layer 84, the inner support layer 84 is made of a negative uniaxial crystal, and when the refractive indexes in the respective axial directions based on the refractive index are nx, ny, and nz, generally nx = The relationship of ny> nz holds, and the optical axis OA2 corresponding to the minor axis of the refractive index nz is inclined with respect to the optical path VP of the light ray (normally incident light) incident on the incident plane 84a of the inner support layer 84 from the normal direction. It is inclined by an angle θ2 (θ2 is equal to or close to θ1). Here, FIG. 5 extraordinary refractive index ordinary refractive index as shown in (a) is in N _o is N _e, the light vibrating in the fast axis direction perpendicular incident light as shown in FIG. 5 (b) If the refractive index is n ₄ and the refractive index of light oscillating in the slow axis direction is n ₃ ,

It has become. Therefore, the retardation Re2 of the inner support layer 84 with respect to the normal incident light has the thickness of the inner support layer 84 as d2.

It becomes. Here, the major axis of the refractive index nz of the liquid crystal layer 71 and the minor axis of the refractive index nz of the inner support layer 84 are arranged in parallel or substantially in parallel, and the slow axis and the fast axis are interchanged with each other. Yes. 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 second polarizing filter 31c with respect to the vertically incident light becomes complete.

で与えられる。上式でｄ２／ｃｏｓ（η２）は、傾斜した入射光の内側支持層８４における実効光路長であり、ｄ１／ｃｏｓ（η１）は、傾斜した入射光の液晶層７１における実効光路長である。 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 beam L1 that is obliquely incident on the liquid crystal light valve 31 from the air, the inclination angle in the air is η0, the inclination angle in the inner support layer 84 is η1, and the inclination in the liquid crystal layer 71 is Let the angle be η2. In this case, since the difference between N _o and N _e in the inner support layer 84 is small, N _o ≈N _e , so that the light flux incident on the inner support layer 84 from the air at the inclination angle η0 is as follows: Follow the optical path that satisfies the conditions.
sin (η0): sin (η1) = 1: 1 / N _o
sin (η1) = sin (η0) / N _o (7)
Further, in the liquid crystal layer 71, since the n _o ≒ n _e, for the light beam incident at an inclination angle η2 to the liquid crystal layer 71 inclination angle η1 in the inner support layer 84, 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 X-axis direction, the tilt angle η0 described above 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 OA1 in the inner support layer 84 and the angle w2 formed with the optical axis OA2 in the liquid crystal layer 71 are the variables η0, φ and the above. It can be obtained geometrically from η1 and η2 obtained based on this. When the refractive index of the inner support layer 84 and the refractive index of the liquid crystal layer 71 are equal, the tilt angle θ2 and the pretilt angle θ1 shown in FIG. 3 are equal, and the light flux passing through the liquid crystal light valve 31 is optical axis OA1, The angles w1 and w2 formed with OA2 are also equal to each other (OA1 = OA2, w1 = w2). The retardation Re ′ when the oblique incident light as described above passes through the inner support layer 84 and the liquid crystal layer 71 is expressed by the following formula.

Given in. In the above equation, d2 / cos (η2) is the effective optical path length of the inclined incident light in the inner support layer 84, and d1 / cos (η1) is the effective optical path length of the inclined incident light in the liquid crystal layer 71.

がゼロに近づくように内側支持層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との関係をφが傾斜方向から９０°ずれている場合に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と内側支持層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、内側支持層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。 Consequently, the retardation Re of passing through the liquid crystal light valve 31 or inner support layer 84 and the liquid crystal layer 71 ', the refractive index _{n o, n e, N o} , a N e, d1, d2 are constants, Since the values η1, η2, 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 inner support layer 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 maximized. 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 inner support layer 84 is set so that is close to zero. Here, W (η0, φ) is a weighting function given by the angular distribution of incident light. FIG. 6A is a visual explanation of the relationship between the retardation Re ′ = f (η0, φ) of the passing light and the tilt angle η0 when φ is shifted by 90 ° from the tilt direction. The retardation Re ′ is the smallest for the light in the front direction where the angle η0 is 0, but the retardation Re ′ gradually increases as the inclination angle η0 increases. FIG. 6B visually illustrates the relationship between the weighting function W (η0, φ) of the incident light and the inclination angle η0, and the light density in the front direction where the inclination 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 the retardation Re ′ = f (η0, φ) is determined by the optical characteristics of the liquid crystal layer 71 and the inner support layer 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 inner support layer 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 inner support layer 84. The thickness d2 and the inclination angle θ2 of the inner support layer 84 can be determined quickly.

  In the above description, the inner support layer 84 is a negative uniaxial refractive material, and the inner support layer 84 itself functions as an optical compensator for canceling the retardation caused by the pretilt of the liquid crystal layer 71. The second polarizing filter 31c can have the same function instead of the first polarizing filter 31b, or both the first and second polarizing filters 31b and 31c can share the function as an optical compensator. . When the second polarizing filter 31c is made to function alone as an optical compensation plate, the refractive index characteristic of the inner support layer 84 of the second polarizing filter 31c is made the same as that shown in FIG. 5 and the like, and the retardation given by the above formula (3) Re1 is set to be equal to the retardation Re2 inside the second polarizing filter 31c given by the above formula (6). Further, when both polarizing filters 31b and 31c share the function as an optical compensator, the refractive index characteristics of the inner support layer 84 of both polarizing filters 31b and 31c are the same as those shown in FIG. ) And the retardation Re2 of the sum of the retardations inside the polarizing filters 31b and 31c given by the above equation (6).

  An example of a method for manufacturing the inner support layer 84 will be described. When the inner support layer 84 is made of sapphire, first, PVA is pasted on the TAC to adsorb the dye, then the PVA is stretched together with the TAC, and the polarizing film 81 and the outer support layer 83 in the first polarizing filter 31b. A laminated portion made of is formed. Thereafter, sapphire as the material of the inner support layer 84 is cut as thin as possible, and the tilt direction (azimuth angle) and tilt angle (polar angle) θ2 of the refractive index ellipsoid RIE2 are the same as those of the refractive index ellipsoid RIE1 of the liquid crystal layer 71. To be. Next, a process such as polishing is performed on a pair of opposed planes of the cut sapphire plate to smooth the surface. Next, after preparing a flat support substrate having high transmittance such as quartz and white plate glass and having no birefringence, and pasting the cleaned sapphire plate on the support substrate after cleaning through an ultraviolet curable resin Fix by curing. Thereafter, the sapphire plate on the support substrate is further polished to a target thickness. The inner support layer 84 is attached to a laminated portion composed of the polarizing film 81 and the outer support layer 83 via an appropriate adhesive. When the sapphire plate is polished to the target thickness, if the target thickness is about 50 μm, the sapphire plate can be polished with a single sapphire plate without being fixed to the support substrate.

When the inner support layer 84 is formed of TAC, PVA is pasted on the TAC to adsorb the dye, and then the PVA is stretched together with the TAC to form the polarizing film 81 and the outer support layer 83 in the first polarizing filter 31b. A laminated part is formed. Then, the extending | stretching material which extended | stretched TAC used as the inner side support layer 84 is prepared, and the inner side support layer 84 is produced by cutting out this extending | stretching material in a required direction. This inner side support layer 84 is affixed on the laminated part which consists of the polarizing film 81 and the outer side support layer 83, for example via a PVA-type adhesive agent. Note that the refractive index ellipsoid of the inner support layer 84 formed of TAC generally has nx> ny, where nx, ny, nz are the refractive indexes in the respective axial directions with respect to the refractive index and the thickness of the stretched film is d2. > nz holds, and parameters Re and Rth generally regarded as the characteristics of the stretched film are as follows.
Re = (nx−ny) · d2 (12)
Rth = {(nx + ny) / 2−nz} · d2 (13)
Here, Re corresponds to the difference in refractive index on the major axis side of the ellipsoid, and is preferably 0 nm. Rth corresponds to the difference from the shortest diameter, and is about 80 nm, for example. However, with TAC's current manufacturing technology, it is very difficult to set Re to 0 nm, and a similar function is achieved even if Re is not 0 nm. However, it can be incorporated in the liquid crystal light valve 31 as the inner support layer 84.

[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. 7 is a side sectional view for explaining the inner support layer 184 of the first polarizing filter 31b incorporated in the liquid crystal light valve of the second embodiment. In this case, the first polarizing filter 31b 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 inner support layer 184, which is a flat plate element, with a similar inclination angle from the emission plane 184b. Inject at. Here, as in the case of the first embodiment, the inner support layer 184 is a flat element formed of a transparent negative uniaxial crystal, but the direction of the optical axis OA2 is perpendicular to the incident plane 184a. It is processed as follows. The first polarizing filter 31b is fixed to the main body side of the liquid crystal panel including the liquid crystal layer 71 and the like by a holder (not shown).

  In the present embodiment, in the inner support layer 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. . The tilt angle θ2 is substantially equal to the pretilt angle θ1 given to the liquid crystal layer 71. Here, the reason that the minor axis tilt angle θ2 of the refractive index ellipsoid RIE2 of the inner support layer 184 and the pretilt 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 with respect to the liquid crystal layer 71 is taken into consideration, there may be a slight difference between θ1 and θ2.

The inner support layer 184 as described above can be formed of a stretched film such as TAC. The stretched film is suitable for mass production. In the case of a stretched film, the refractive index ellipsoid generally has a relationship of nx>ny> nz, where nx, ny, nz are the refractive indexes in the respective axial directions with reference to the refractive index and the thickness of the stretched film is d2. Thus, the parameters Re and Rth generally regarded as the characteristics of the stretched film are as follows.
Re = (nx−ny) · d2 (12)
Rth = {(nx + ny) / 2−nz} · d2 (13)
Here, Re corresponds to the difference in refractive index on the major axis side of the ellipsoid, and is preferably 0 nm. Rth corresponds to the difference from the shortest diameter, and is about 80 nm, for example. However, it is very difficult for the stretched film to have Re of 0 nm with the current manufacturing technology, and even if Re is not 0 nm, approximately the same function is achieved. Even if it exists, it can be incorporated in the liquid crystal light valve 31 as the inner support layer 184.

  Also in this embodiment, by appropriately adjusting the refractive index ellipsoid RIE2, the thickness d2, the inclination, and the like of the inner support layer 184, the retardation Re ′ = f (η0, Since the integral value of φ) can be minimized, the contrast of the image formed by the liquid crystal light valve 31 can be maximized.

  In the above description, the inner support layer 184 of the first polarizing filter 31b is a negative uniaxial refractive material and functions as an optical compensator that cancels out retardation caused by the pretilt of the liquid crystal layer 71 by itself. However, the second polarizing filter 31c (see FIG. 3) can have the same function, or the first and second polarizing filters 31b and 31c can share the function as an optical compensator. .

[Third Embodiment]
FIG. 8 is a diagram for explaining the configuration of the optical system of the 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 to 25c and three sets of polarizing filters 25e, 25f, and 25g arranged so as to sandwich the liquid crystal panels 25a to 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 polarizing filters 31b and 31c, that is, an inner support layer 84 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. In the third liquid crystal panel 25c for red light, the red light branched by passing through the second dichroic mirror 23b enters through the field lens 23h. Each of the liquid crystal panels 25a to 25c is a non-light-emitting light modulation device that modulates the spatial intensity distribution of incident illumination light, and the three colors of light incident on each of the liquid crystal panels 25a to 25c ˜25c is modulated in accordance with the drive signal or image signal inputted as an electrical signal. 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 inner support layer 84 has been described, but 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, the polarizing film 81 is not limited to the above-described PVA, and can be formed of other resin materials.

  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 of the polarizing plate integrated in the liquid crystal light valve of FIG. It is side sectional drawing explaining the refractive index of a liquid crystal layer and the inner side support layer of a polarizing filter. (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 inner side support layer. (A), (b) shows the inclination angle dependency of retardation and the weight function of incident light. It is a sectional side view explaining the polarizing filter in 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, 75, 77 ... electrode, 76, 78 ... alignment film, 77 ... transparent pixel electrode, 81 ... polarizing film, 83 ... outer support layer, 84 ... inner support layer, 84a ... incident plane, 84b ... exit plane, OA1, OA2 ... optical axis, .theta.1 ... pretilt angle, .theta.2 ... tilt.

Claims (8)

A liquid crystal cell including a liquid crystal operating in a vertical alignment mode;
An optical device comprising a polarizing plate disposed on at least one of the incident side and the emission side of the liquid crystal cell,
The polarizing plate includes a polarizing film and an inner support layer provided on the liquid crystal cell side of the polarizing film to support the polarizing film,
The inner support layer is an optical device formed of a negative uniaxial refractive material having an optical axis inclined with respect to the normal direction of the incident surface of the liquid crystal panel. The liquid crystal cell is one in which the optical axis of the liquid crystal in the off state is tilted by a predetermined pretilt angle with respect to the normal of the incident surface,
The optical device according to claim 1, wherein the inner support layer has a uniform optical axis in an orientation direction of the liquid crystal in an off state in the liquid crystal cell and in a direction inclined with respect to the incident surface.   The inner support layer is a flat plate having an incident plane and an emission plane parallel to the incident plane 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 any one of Items 2 to 3.   The inner support layer is a flat plate having an incident plane and an emission plane parallel to each other inclined with respect to the incident plane of the liquid crystal cell, and an optical axis in the normal direction of the incident plane and the emission plane. The optical device according to any one of claims 1 and 2.   5. The optical device according to claim 1, wherein the inner support layer has a thickness that substantially cancels retardation caused by an off-state liquid crystal in the liquid crystal cell. 6.   The inner support layer has a thickness that substantially cancels retardation caused by off-state liquid crystal in the liquid crystal cell in correspondence with a range of an inclination angle of illumination light with respect to an incident surface of the liquid crystal cell. The optical device according to any one of claims 1 to 5.   The optical device according to any one of claims 1 to 6, wherein the polarizing plate is disposed on both an incident side and an emission side of the liquid crystal cell. An optical device for light modulation according to any one of claims 1 to 7,
An illumination device for illuminating the optical device;
A projection lens for projecting an image formed by the optical device;
A projector comprising:

Images