JP2016133633A - Optical unit, projection type display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical unit capable of reducing blur or color irregularity appearing in an outline portion of a display pattern, and a projection type display device and an electronic apparatus including the optical unit.SOLUTION: An optical unit 100 includes: a first light modulation part 121 including a first polarizing plate 81, a second polarizing plate 82 disposed to align a transmission axis or an absorption axis thereof to be orthogonal to that of the first polarizing plate 81, and a dimming liquid crystal panel 110A disposed between the first polarizing plate 81 and the second polarizing plate 82; and a second light modulation part 122 including a third polarizing plate 83 disposed to align a transmission axis or an absorption axis thereof to be orthogonal to that of the second polarizing plate 82, and a display liquid crystal panel 110B disposed between the second polarizing plate 82 and the third polarizing plate 83. A pixel of the dimming liquid crystal panel 110A is larger in size than a pixel of the display liquid crystal panel 110B. The optical unit also includes a retardation plate 91 that decreases a contrast ratio of the first light modulation part 121, on an incident side or an exit side for light of the dimming liquid crystal panel 110A.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical unit, a projection display device, and an electronic apparatus.

  As an optical unit, there is a light modulation means for modulating illumination light incident from a light source based on image information and emitting it as display light. Such light modulation means is used in, for example, a projection display device (projector) that enlarges and projects display light onto a screen or the like.

  For example, Patent Document 1 discloses a liquid crystal projector in which a correction liquid crystal panel and a display liquid crystal panel that modulates light according to a video signal are provided between a first polarizing plate and a second polarizing plate. ing. The liquid crystal panel for correction has the same twist direction of the liquid crystal molecules as the liquid crystal panel for display, and the orientation direction of the liquid crystal molecules (the direction in which the liquid crystal molecules are pretilted) is reversed 180 degrees around the optical axis. An example of arrangement with respect to a display liquid crystal panel is shown. Thereby, it is said that the reduction in contrast caused by the liquid crystal molecules being aligned with a pretilt angle in the display liquid crystal panel can be improved.

  Further, for example, in Patent Document 2, a first light modulation element that modulates light emitted from a light source, light that is arranged in series on the optical path with the first light modulation element, and is emitted from the first light modulation element And a second light modulation element that modulates the light intensity, and an image display device that is arranged so that the clear vision direction of the optical image of the first light modulation element substantially coincides with the clear vision direction of the second light modulation element is disclosed. ing. According to this image display device, the uniformity of the image emitted from the second light modulation element and the contrast are obtained by making the clear vision direction of the first light modulation element substantially coincide with the clear vision direction of the second light modulation element. It is said that the characteristics can be improved and a clear image can be obtained. In addition, a liquid crystal light valve (having a liquid crystal panel disposed between a pair of polarizing plates) is used as the first light modulation element and the second light modulation element.

JP 2001-142091 A JP 2006-251230 A

  In Patent Document 1 and Patent Document 2, when the pixel size of the liquid crystal panel for optical correction is larger than the pixel size of the liquid crystal panel for display, the optical pattern corresponding to the display pattern of the liquid crystal panel for display is optical. When the liquid crystal panel for correction is driven, there is a problem that a portion having a gradation state different from a preferable display state is generated around the display pattern due to a difference in size of the pixels. Such a portion having different gradation states is recognized as blur or color unevenness occurring in the contour portion of the display pattern, particularly when HDR (High Dynamic Range) processing close to human vision is performed in image processing. It is called “Hello”.

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

  [Application Example] An optical unit according to this application example includes a first polarizing plate, a second polarizing plate disposed so that a transmission axis or an absorption axis is orthogonal to the first polarizing plate, and the first polarizing plate. A light modulating liquid crystal panel disposed between the plate and the second polarizing plate, and a transmission axis or an absorption axis that is orthogonal to the second polarizing plate. A second light modulator including a third polarizing plate and a display liquid crystal panel disposed between the second polarizing plate and the third polarizing plate. The size of the pixel is larger than the size of the pixel of the liquid crystal panel for display, and a phase plate that lowers the contrast ratio of the first light modulator on the light incident side and / or the light exit side of the dimming liquid crystal panel. It is characterized by having.

  According to this application example, by reducing the contrast ratio of the first light modulation unit by the phase plate, a portion (halo) having a gradation state different from the preferable display state, which occurs around the display pattern of the display liquid crystal panel. It becomes inconspicuous. That is, an optical unit that can realize high contrast and excellent display quality can be provided.

In the optical unit according to the application example, the second light modulation unit is disposed between the second polarizing plate and the display liquid crystal panel, and has a transmission axis or an absorption axis with respect to the second polarizing plate. It is preferable to include the 4th polarizing plate arrange | positioned so that it may correspond.
According to this configuration, the contrast ratio in the second light modulation unit can be improved by providing the fourth polarizing plate. That is, an optical unit capable of realizing higher contrast and superior display quality can be provided.

In the optical unit according to the application example, the phase plate is an a-plate or a biaxial phase difference plate, and the azimuth direction of the slow axis of the liquid crystal layer of the light control liquid crystal panel and the phase plate It is preferable that they are arranged so that the azimuth direction of the slow axis coincides.
According to this configuration, the slow axis of the liquid crystal layer of the light control liquid crystal panel is aligned with the slow axis of the phase plate, thereby causing the slow axes to be shifted from each other. High contrast can be realized by preventing light leakage.

In the optical unit according to the application example, the phase plate is a c-plate, and is arranged so that a slow axis is inclined with respect to a normal line of a substrate surface of the light control liquid crystal panel. Is preferred.
According to this configuration, the contrast ratio of the first light modulation unit can be adjusted by adjusting the tilt angle of the c-plate on the slow axis. That is, it is possible to reduce the halo by adjusting the contrast ratio of the first light modulation unit according to the contrast ratio of the second light modulation unit, and to optimize the display state.

In the optical unit according to the application example, the phase plate is a λ / 2 plate, which is disposed on a light incident side and an emission side of the light control liquid crystal panel, and the slow axis of the λ / 2 plate. Is arranged with the azimuth direction slightly shifted from the transmission axis or absorption axis of the first polarizing plate on the incident side and the second polarizing plate on the emission side, and the slow axes of the λ / 2 plates intersect each other. The angle is preferably an angle other than 90 degrees.
According to this configuration, in the so-called white display in which the polarized light that has passed through the first polarizing plate is emitted from the second polarizing plate in the first light modulator, the λ / 2 plate is delayed with respect to the second polarizing plate on the emission side. Since the phase axis is only slightly shifted, the transmittance during white display is unlikely to decrease. On the other hand, in the so-called black display in which the polarized light that has passed through the first polarizing plate is not emitted from the second polarizing plate in the first light modulation unit, the retardation of the λ / 2 plate relative to the second polarizing plate on the emission side. Since the light is leaked when the axis is slightly shifted, the contrast ratio of the first light modulation unit is lowered. In other words, a portion (halo) having a gradation state different from a preferable display state that appears around the display pattern of the display liquid crystal panel is not conspicuous, and an optical unit capable of realizing high contrast and excellent display quality can be provided.

In the optical unit according to the application example, the phase plate may be formed integrally with the light control liquid crystal panel.
According to this configuration, since there is no gap between the phase plate and the light control liquid crystal panel, it is not affected by stray light incident from the gap. That is, it is possible to provide an optical unit that is structurally simple and capable of realizing excellent display quality.

In the optical unit described in the application example, it is preferable that a contrast ratio of the first light modulation unit is 1/10 or less with respect to a contrast ratio of the second light modulation unit.
According to this configuration, it is possible to realize the high contrast and the excellent display quality by making the portion (halo) of the gradation state different from the preferable display state inconspicuous surely generated around the display pattern of the display liquid crystal panel. An optical unit can be provided.

In the optical unit according to the application example described above, the alignment of liquid crystal molecules in the liquid crystal layer of the light control liquid crystal panel and the display liquid crystal panel is preferably a uniaxial substantially vertical alignment.
According to this configuration, the alignment mode of the liquid crystal molecules in the liquid crystal layer of the light control liquid crystal panel and the display liquid crystal panel is a uniaxial substantially vertical alignment (VA method). An optical unit capable of realizing high contrast and excellent display quality over a wider viewing angle range can be provided.

[Application Example] A projection display device according to this application example includes a light source, the optical unit according to the application example arranged on an optical axis of light emitted from the light source, and display light emitted from the optical unit. And a projection optical system that projects the image in an enlarged manner.
According to this application example, it is possible to provide a projection display device capable of realizing high contrast and excellent projection display quality.

[Application Example] An electronic apparatus according to this application example includes a light source and the optical unit described in the above application example arranged on an optical axis of light emitted from the light source.
According to this application example, it is possible to provide an electronic device capable of realizing high contrast and excellent display quality.

(A) is a schematic perspective view which shows the structure of the optical unit of 1st Embodiment, (b) is an optical schematic diagram which shows the phase plate in the optical unit of 1st Embodiment, (c) is another phase plate. The optical schematic diagram which shows. (A) is a schematic plan view which shows the structure of the liquid crystal panel for light control, (b) is a schematic sectional drawing which shows the structure of the liquid crystal panel for light control cut | disconnected by the H-H 'line | wire of (a). FIG. 3 is a schematic cross-sectional view illustrating an alignment state of liquid crystal molecules in an alignment film and a liquid crystal layer in a display region. The figure explaining the subject of the light modulation state in an optical unit. The table | surface which shows the relationship between each contrast ratio of the 1st light modulation part in an optical unit, and the 2nd light modulation part, and the brightness | luminance of the gray part around a display pattern. The figure which shows the light modulation state of the 1st light modulation part in the optical unit of 1st Embodiment. (A) is a schematic perspective view which shows the structure of the optical unit of 2nd Embodiment, (b) is a figure explaining the structure of the phase plate in the optical unit of 2nd Embodiment. The figure which shows the light modulation state of the 1st light modulation part in the optical unit of 2nd Embodiment. (A) is a schematic perspective view which shows the structure of the optical unit of 3rd Embodiment, (b) is a figure explaining the structure of the phase plate in the optical unit of 3rd Embodiment. The figure which shows the light modulation state of the 1st light modulation part in the optical unit of 3rd Embodiment. (A) is a schematic perspective view which shows the structure of the optical unit of 4th Embodiment, (b) is a schematic plan view which shows the orientation processing state of the liquid crystal panel for light control, (c) is the orientation state of the liquid crystal panel for display. FIG. The figure which shows the light modulation state of the 1st light modulation part in the optical unit of 4th Embodiment. Schematic which shows the structure of the projection type display apparatus as an electronic device. Schematic which shows the structure and light modulation state of the 2nd light modulation part of a modification.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced so that the part to be described can be recognized.

(First embodiment)
<Optical unit>
The optical unit of this embodiment will be described with reference to FIG. 1A is a schematic perspective view showing the configuration of the optical unit of the first embodiment, FIG. 1B is an optical schematic diagram showing a phase plate in the optical unit of the first embodiment, and FIG. FIG. 5 is an optical schematic diagram showing another phase plate.

  As shown in FIG. 1A, the optical unit 100 of the present embodiment includes a first light modulation unit 121 disposed on the light incident side on the optical axis L, and the light of the first light modulation unit 121. And a second light modulator 122 arranged on the emission side. That is, the optical unit 100 modulates the illumination light incident from the light source based on the image information and emits it as display light by the two light modulation units.

  The first light modulation unit 121 includes a first polarizing plate 81, a phase plate 91, a dimming liquid crystal panel 110 </ b> A, and a second polarizing plate 82. The first polarizing plate 81 and the second polarizing plate on the optical axis L so that the transmission axis (or absorption axis) of the second polarizing plate 82 is orthogonal to the transmission axis (or absorption axis) of the first polarizing plate 81. 82 are arranged. In the present embodiment, the transmission axis (or absorption axis) of the rectangular first polarizing plate 81 is a direction along the long side as indicated by an arrow. Hereinafter, the direction along the long side is defined as the X direction, the direction along the short side of the first polarizing plate 81 orthogonal to the X direction is defined as the Y direction, the direction orthogonal to the X direction and the Y direction, and along the optical axis L. This direction will be described as the Z direction. Further, viewing from the light incident side along the optical axis L is referred to as “plan view” or “planar”.

  The light control liquid crystal panel 110 </ b> A is disposed between the first polarizing plate 81 and the second polarizing plate 82 on the optical axis L. The optical design of the light control liquid crystal panel 110 </ b> A is such that the slow axis indicated by the arrow intersects the transmission axes (or absorption axes) of the first polarizing plate 81 and the second polarizing plate 82.

  The second light modulation unit 122 includes a third polarizing plate 83, a second polarizing plate 82, a third polarizing plate 83, and a second polarizing plate 83 that are arranged so that the transmission axis (or absorption axis) is orthogonal to the second polarizing plate 82. The display liquid crystal panel 110B disposed between the second polarizing plate 82 and the display liquid crystal panel 110B is arranged so that the transmission axis (or absorption axis) of the second polarizing plate 82 matches. And a fourth polarizing plate 84 disposed on the surface. Although the fourth polarizing plate 84 is not an essential component, the fourth polarizing plate 84 is used from the viewpoint of stabilizing the polarization direction of polarized light incident at various angles on the display liquid crystal panel 110B and ensuring a contrast ratio. It is preferable to provide it.

  The optical design of the display liquid crystal panel 110 </ b> B is such that the slow axis indicated by the arrow intersects the transmission axis (or absorption axis) of the fourth polarizing plate 84 and the third polarizing plate 83. The configuration and slow axis of the light control liquid crystal panel 110A and the display liquid crystal panel 110B will be described later.

For example, as shown in FIG. 1B, the phase plate 91 of the first light modulation unit 121 can be represented by a refractive index ellipsoid having refractive index anisotropy. when the refractive indices n _x in the plane defined by the direction, n _y, the refractive index along the Z-direction and n _z, satisfies the relation of _{n x> n y = n z} . The phase plate 91 which is such a refractive index ellipsoid is called an a-plate. The slow axis of the phase plate 91 is an axis of highest refractive index is larger n _x.

In the phase plate 91, the value of the front phase difference value R is set so that the contrast ratio of the first light modulation unit 121 is 1/10 or less with respect to the contrast ratio of the second light modulation unit 122. It is inserted between the plate 81 and the light control liquid crystal panel 110A. Further, it is arranged between the first polarizing plate 81 and the light control liquid crystal panel 110A so that the slow axis of the phase plate 91 and the slow axis of the light control liquid crystal panel 110A coincide. The front phase difference value R of the phase plate 91 is given by the following formula (1).
R = Δn · d (1)
Difference Δn is the refractive indices n _x and the refractive index n _y, d is the thickness of the portion causes a phase in the phase plate.
The front phase difference value R of the phase plate 91 in the present embodiment is, for example, 10 nm. As a specific example of such a phase plate 91, a uniaxially stretched film of triacetate, polycarbonate, polyester, polyvinyl alcohol or the like is applied to an optically isotropic transparent substrate (transparent support) such as glass or film. Examples thereof include a pasted substrate and a transparent substrate (transparent support) formed by vapor deposition of an inorganic material such as silicon oxide or aluminum oxide. Alternatively, the quartz plate may be polished to a predetermined thickness so that the front phase difference value becomes a predetermined value.

The phase plate 91 for reducing the contrast ratio of the first light modulation unit 121 is not limited to the a-plate described above. For example, as shown in FIG. 1 (c), may be a phase plate 92 is a refractive index ellipsoid satisfying a relationship of _{n x> n y> n z} . Such a phase plate 92 is called a biaxial retardation plate. As a specific example of the biaxial retardation plate, a biaxially stretched film such as triacetate, polycarbonate, polyester, or polyvinyl alcohol is attached to the transparent substrate described above, and silicon oxide, aluminum oxide, or the like is similarly applied to the transparent substrate. The thing which formed into a film by the vapor deposition method is mentioned. Alternatively, the quartz plates may be polished and overlapped to a predetermined thickness so that the front phase difference value becomes a predetermined value.

  The phase plate 91 (92) is not limited to be disposed between the first polarizing plate 81 and the dimming liquid crystal panel 110A, but between the dimming liquid crystal panel 110A and the second polarizing plate 82. May be arranged. Further, it may be disposed between the first polarizing plate 81 and the second polarizing plate 82 on the light incident side and the light exit side of the light control liquid crystal panel 110A. In this case, the total value of the front phase difference values of the respective phase plates is adjusted to be a desired front phase difference value R.

  The phase plate 91 (92) may be formed integrally with the counter substrate 20 on the light incident side of the counter substrate 20 constituting the light control liquid crystal panel 110A. Similarly, it may be formed integrally with the element substrate 10 on the light emission side of the element substrate 10 constituting the light control liquid crystal panel 110A.

<Light control LCD panel>
Next, an example of the light control liquid crystal panel 110A will be described with reference to FIGS. 2A is a schematic plan view showing the configuration of the light control liquid crystal panel, and FIG. 2B is a schematic cross section showing the structure of the light control liquid crystal panel taken along the line HH ′ in FIG. FIG. FIG. 3 is a schematic cross-sectional view showing the alignment state of the liquid crystal molecules in the alignment film and the liquid crystal layer in the display region.

  As shown in FIGS. 2A and 2B, the light control liquid crystal panel 110A according to the present embodiment includes an element substrate 10 and a counter substrate 20 which are arranged to face each other, and a liquid crystal layer sandwiched between the pair of substrates. 50. As the base material 10s of the element substrate 10 and the base material 20s of the counter substrate 20, for example, a quartz substrate or a glass substrate having translucency is used. Note that translucency in this specification refers to a property of transmitting light having a wavelength in the visible light region by at least 85%.

  The element substrate 10 is slightly larger than the counter substrate 20. The element substrate 10 and the counter substrate 20 are bonded together via a sealing material 40 arranged in a frame shape along the outer edge portion of the counter substrate 20, and liquid crystal having negative dielectric anisotropy is sealed in the gap. The liquid crystal layer 50 is configured. As the sealing material 40, for example, an adhesive such as a thermosetting or ultraviolet curable epoxy resin is employed. A spacer (not shown) is mixed in the sealing material 40 to keep the distance between the pair of substrates constant.

  Inside the sealing material 40, a display region E in which a plurality of pixels P are arranged in a matrix is provided. The counter substrate 20 is provided with a parting portion 21 that surrounds the display area E between the sealing material 40 and the display area E. The parting portion 21 is made of, for example, a light shielding metal or metal oxide. Note that the display area E may include dummy pixels arranged so as to surround the plurality of pixels P in addition to the plurality of pixels P contributing to display.

  The element substrate 10 is provided with a terminal portion in which a plurality of external connection terminals 104 are arranged. A data line driving circuit 101 is provided between the first side portion along the terminal portion of the element substrate 10 and the sealing material 40. In addition, an inspection circuit 103 is provided between the sealing material 40 and the display area E along the second side facing the first side. Further, a scanning line driving circuit 102 is provided between the seal material 40 and the display region E along the third side and the fourth side that are orthogonal to the first side and face each other. A plurality of wirings 105 that connect the two scanning line driving circuits 102 are provided between the sealing material 40 on the second side and the inspection circuit 103.

  Wirings connected to the data line driving circuit 101 and the scanning line driving circuit 102 are connected to a plurality of external connection terminals 104 arranged along the first side portion. The direction along the first side is the X direction, and the direction along the third side and the fourth side is the Y direction.

  As shown in FIG. 2B, the element substrate 10 includes a base material 10 s, a pixel electrode 15 provided for each pixel P on the surface of the base material 10 s on the liquid crystal layer 50 side, and an alignment film that covers the pixel electrode 15. 18. In addition, a pixel circuit that performs switching control of the pixel electrode 15 is provided on the base material 10s. The pixel circuit includes a thin film transistor (hereinafter referred to as TFT) 30 which is a switching element for switching control of the pixel electrode 15.

  The counter substrate 20 includes a base material 20s, a parting portion 21, a planarization layer 22, a counter electrode 23, an alignment film 24, and the like, which are sequentially stacked on the surface of the base material 20s on the liquid crystal layer 50 side.

  The parting part 21 surrounds the display area E as shown in FIG. 2A, and is provided at a position overlapping the scanning line driving circuit 102 and the inspection circuit 103 in plan view. Thus, the light incident on the peripheral circuit including these drive circuits from the counter substrate 20 side is blocked, and the peripheral circuit has a role of preventing malfunction due to the light. Further, unnecessary stray light is shielded so as not to enter the display area E, and a high contrast in the display of the display area E is ensured.

  The planarization layer 22 is made of an inorganic material such as silicon oxide, for example, and is provided so as to cover the parting portion 21 with translucency. Such a planarization layer 22 is a silicon oxide film formed by using, for example, a plasma CVD method, and has a thickness that can relax the surface unevenness of the counter electrode 23 formed on the planarization layer 22. Have.

  The counter electrode 23 is made of a transparent conductive film such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), for example, covers the planarization layer 22 and is formed at the four corners of the counter substrate 20 as shown in FIG. The vertical conduction portion 106 provided is electrically connected to the wiring on the element substrate 10 side.

  The alignment film 18 covering the pixel electrode 15 and the alignment film 24 covering the counter electrode 23 are set based on the optical design of the light control liquid crystal panel 110A, and are obliquely deposited films of inorganic materials such as silicon oxide (inorganic alignment film). Membrane) is employed. The alignment films 18 and 24 may employ an organic alignment film such as polyimide in addition to the inorganic alignment film.

  Such a light control liquid crystal panel 110A is of a transmissive type and an active drive type, and has an optical design of a normally white mode in which the pixel P is brightly displayed when not driven and a normally black mode in which the pixel P is darkly displayed when not driven. Is adopted. As described above, polarizing plates are arranged and used according to the optical design on the light incident side and the light emission side, respectively.

  As shown in FIG. 3, the alignment film 18 covering the pixel electrode 15 of the element substrate 10 is an aggregate of columnar crystal bodies 18a of silicon oxide obtained by, for example, oblique deposition of silicon oxide. The angle θb formed by the normal line of the substrate 10s and the film forming direction indicated by the solid line arrow is approximately 45 degrees. The angle θc formed by the direction in which the columnar crystal 18a grows from the surface of the substrate 10s and the normal line is not necessarily the same as the angle θb, and in this case, it is approximately 20 degrees. The liquid crystal molecules LC having negative dielectric anisotropy on such a film surface of the alignment film 18 are substantially vertically aligned with a pretilt whose major axis is inclined toward the film forming direction. The pretilt angle θp formed by the normal of the substrate 10s and the long axis of the liquid crystal molecules LC is about 4 degrees. In other words, the growth angle θc of the columnar crystal 18a with respect to the base material 10s is controlled so that the pretilt angle θp of the liquid crystal molecules LC is about 4 degrees. That is, the angle θb during film formation is controlled.

  Similarly, the alignment film 24 covering the counter electrode 23 on the counter substrate 20 side is an aggregate of columnar crystal bodies 24a of silicon oxide obtained by, for example, oblique deposition of silicon oxide. The angle θb formed by the normal line of the base material 20s and the film forming direction indicated by the broken-line arrow is approximately 45 degrees. The liquid crystal molecules LC are substantially vertically aligned with a pretilt in the film forming direction side with respect to the film surface (columnar crystal body 24a) of the alignment film 24. The growth directions of the columnar crystals 18a and 24a are parallel to each other in a sectional view and do not intersect. Hereinafter, the columnar crystal will be described as a column.

  The direction of the pretilt of the liquid crystal molecules LC in the alignment film 18 of the element substrate 10 as viewed from the counter substrate 20 side is a planar film formation direction (solid line) of oblique deposition in the alignment film 18 as shown in FIG. This is the same as the direction indicated by the arrow). Similarly, the predetermined direction of the pretilt of the liquid crystal molecules LC of the alignment film 24 viewed from the counter substrate 20 side is a planar film formation direction (indicated by a broken line) of oblique deposition in the alignment film 24 as shown in FIG. Azimuth direction). The direction of the pretilt of the liquid crystal molecules LC in such a uniaxial substantially vertical alignment method (VA method) is appropriately set based on the optical design conditions of the light control liquid crystal panel 110A. In the present embodiment, the pretilt direction intersects at an angle of 45 ° with respect to the transmission axis (or absorption axis) of the first polarizing plate 81 and the second polarizing plate 82 arranged on the light incident side and the light exit side. ing. In the present embodiment, the angle formed by the Y direction and the pretilt direction is referred to as a pretilt azimuth angle θa in the liquid crystal molecules LC. Thus, the maximum contrast is obtained when the liquid crystal layer 50 is driven by applying a predetermined potential between the pixel electrode 15 and the counter electrode 23.

  The slow axis of the liquid crystal molecule LC is the long axis of the liquid crystal molecule LC. Therefore, when a driving voltage is applied to the pixel electrode 15 and the counter electrode 23 of the light control liquid crystal panel 110A to generate an electric field and the liquid crystal molecules LC are tilted in the pretilt direction, the slow axis of the light control liquid crystal panel 110A is , The direction is 45 ° obliquely clockwise with respect to the Y direction (see FIG. 1A). In other words, in the present embodiment, the slow axis of the light control liquid crystal panel 110 </ b> A refers to the major axis orientation of the liquid crystal molecules LC when the liquid crystal layer 50 is driven.

<LCD panel for display>
The display liquid crystal panel 110B in the present embodiment has basically the same configuration as the transmissive and active drive type light control liquid crystal panel 110A, and is a uniaxial substantially vertical alignment method (VA method). It is driven based on image information of a display pattern to be displayed on the screen. However, the size of the pixel P in the display liquid crystal panel 110B is smaller than that of the light control liquid crystal panel 110A. In other words, the display liquid crystal panel 110B includes a plurality of pixels P arranged in the display region E with higher definition than the dimming liquid crystal panel 110A. In addition, the pretilt azimuth angle θa of the liquid crystal molecules LC having negative dielectric anisotropy in the display liquid crystal panel 110B is 135 °. As a result, like the liquid crystal panel for dimming 110A, the maximum contrast is obtained when the liquid crystal layer 50 is driven by applying a predetermined potential between the pixel electrode 15 and the counter electrode 23. Therefore, the slow axis of the display liquid crystal panel 110B is a direction of 135 ° obliquely clockwise with respect to the Y direction (see FIG. 1A).

  Next, problems to be solved by the present invention will be specifically described with reference to FIGS. FIG. 4 is a diagram for explaining the problem of the light modulation state in the optical unit, and FIG. 5 is the relationship between the contrast ratio of each of the first light modulation unit and the second light modulation unit in the optical unit and the luminance of the gray portion around the display pattern. It is a table | surface which shows.

  As shown in FIG. 4, an image desired to be displayed by the optical unit 100 is a display pattern including, for example, a circular white display (White) and a black display (Black) surrounding the circular white display (White). In the second light modulation unit 122, the display liquid crystal panel 110B is driven based on the display pattern. In the first light modulation unit 121, the pixel P of the light adjustment liquid crystal panel 110 </ b> A corresponding to the region including the portion that has been circular white display (White) in the second light modulation unit 122 is driven. Since the size of the pixel P of the light control liquid crystal panel 110A is larger than the size of the pixel P of the display liquid crystal panel 110B, the display pattern in the first light modulation unit 121 includes, for example, the above-described circular white display (White). The white display (White) of the touching square is obtained. Therefore, an image displayed by the first light modulation unit 121 and the second light modulation unit 122 includes a circular white display (White) and a square gray display (Gray) surrounding the circular white display (White). , And black display (Black) surrounding the gray display (Gray) of the square. This is because, in both the first light modulation unit 121 and the second light modulation unit 122, the black display (Black) portion is in a state where the light transmittance is reduced and the black level is improved. Further, the portion where the first light modulation unit 121 is white display (White) and the second light modulation unit 122 is black display (Black) is a gradation state with respect to the black display (Black) in the original image to be displayed. Is recognized as a different gray display (Gray).

  As shown in FIG. 5, for example, it is assumed that the contrast ratio of the first light modulation unit 121 and the second light modulation unit 122 is both 100: 1, and the illuminance of white display (White) of the first light modulation unit 121 is 100000. Lux (lx). Then, the illuminance of black display (Black) in the first light modulation unit 121 is 1000 lux (lx). The illuminance of gray display (Gray) in the images displayed by the first light modulation unit 121 and the second light modulation unit 122 is set to the illuminance of white display (White) of the first light modulation unit 121. A value obtained by multiplying the Black ratio. Similarly, the illuminance of black display (Black) in the displayed image is a value obtained by multiplying the illuminance of black display (Black) of the first light modulator 121 by the Black ratio of the second light modulator 122. Accordingly, the illuminance of the images displayed by the first light modulation unit 121 and the second light modulation unit 122 is white display (White) is 100000 lux (lx), and gray display (Gray) is 1000 lux (lx). Black display (Black) becomes 10 lux (lx). The illuminance of gray display (Gray) is 100 times the illuminance of black display (Black).

  The gray display portion of the displayed image is originally different in gradation state from the black display portion of the image to be displayed, so that the gray display portion is conspicuous. Reduces display quality. Specifically, in recent years, since display with high definition and excellent color reproducibility has been demanded, when HDR (High Dynamic Range) processing close to human vision is performed in image processing, gray display ( Since the portion of (Gray) is recognized as blur or color unevenness occurring in the contour portion of the display pattern, improvement is required.

  As shown in FIG. 5, for example, the contrast ratio of the first light modulation unit 121 is 50: 1, the contrast ratio of the second light modulation unit 122 is 200: 1, and white display (White) of the first light modulation unit 121 is performed. ) Is set to 100,000 lux (lx). Then, the illuminance for black display (Black) in the first light modulation unit 121 is 2000 lux (lx), which is twice that of the case where the contrast ratio is 100: 1. Therefore, the illuminance of the image displayed by the first light modulation unit 121 and the second light modulation unit 122 is white display (White) is 100,000 lux (lx), and gray display (Gray) is 500 lux (lx). Black display (Black) becomes 10 lux (lx). Therefore, the illuminance of black display (Black) does not change, but the illuminance of gray display (Gray) decreases. However, the illuminance of gray display (Gray) is 50 times the illuminance of black display (Black) and still stands out. In this case, the contrast ratio of the first light modulation unit 121 is ¼ of the contrast ratio of the second light modulation unit 122.

  In contrast, for example, the contrast ratio of the first light modulation unit 121 is 31.62: 1, the contrast ratio of the second light modulation unit 122 is 316.2: 1, and the white display of the first light modulation unit 121 is performed. The illuminance of (White) is set to 100,000 lux (lx). Then, the illuminance of black display (Black) in the first light modulation unit 121 is 3162 lux (lx). Therefore, the illuminance of the image displayed by the first light modulation unit 121 and the second light modulation unit 122 is white display (White) is 100,000 lux (lx), and gray display (Gray) is 316 lux (lx). Black display (Black) becomes 10 lux (lx). Therefore, the illuminance of the black display (Black) does not change, but the illuminance of the gray display (Gray) is 31.6 times as high as the illuminance of the black display (Black), and the gray display (Gray) becomes inconspicuous. In this case, the contrast ratio of the first light modulation unit 121 is 1/10 of the contrast ratio of the second light modulation unit 122.

  Further, for example, the contrast ratio of the first light modulation unit 121 is further reduced to 10: 1, the contrast ratio of the second light modulation unit 122 is increased to 1000: 1, and white display of the first light modulation unit 121 is performed. The illuminance of (White) is set to 100,000 lux (lx). Then, the illuminance of black display (Black) in the first light modulation unit 121 is 10,000 lux (lx). Therefore, the illuminance of the images displayed by the first light modulation unit 121 and the second light modulation unit 122 is 100000 lux (lx) for white display (White) and 100 lux (lx) for gray display (Gray). Black display (Black) becomes 10 lux (lx). Therefore, the illuminance of black display (Black) does not change, but the illuminance of gray display (Gray) becomes 10 times the illuminance of black display (Black), and the gray display (Gray) becomes more inconspicuous. In this case, the contrast ratio of the first light modulation unit 121 is 1/100 of the contrast ratio of the second light modulation unit 122. Note that the illuminance of black display (Black) in the displayed image is preferably as small as possible from the viewpoint of ensuring gradation and realizing excellent display quality.

  In order to improve the blur and color unevenness in the contour portion of the display pattern described above, the optical unit 100 of the present embodiment has a contrast ratio of the first light modulation unit 121 of 1/10 or less as compared with the second light modulation unit 122. Therefore, the phase plate 91 of the first light modulation unit 121 is configured. Hereinafter, the light modulation state in the first light modulation unit 121 will be described with reference to FIG. FIG. 6 is a diagram illustrating a light modulation state of the first light modulation unit in the optical unit according to the first embodiment. Specifically, it is a diagram illustrating polarization states of white display and black display in the first light modulation unit 121.

  As shown in FIG. 6, for example, the transmission axis of the first polarizing plate 81 in the first light modulation unit 121 is in a direction along the X direction. The angle of the transmission axis around the optical axis (broken line) at this time is set to 0 °. The second polarizing plate 82 is disposed so that the transmission axis of the second polarizing plate 82 is orthogonal to the transmission axis of the first polarizing plate 81. The slow axis of the phase plate 91 which is an a-plate is 45 °, and the front phase difference value R is, for example, 10 nm. When the light control liquid crystal panel 110A is driven to display white, the slow axis of the white display portion is 45 ° as described above. That is, the slow axis of the light control liquid crystal panel 110 </ b> A and the slow axis of the phase plate 91 at the time of white display coincide with each other. Actually, the slow axis of the liquid crystal panel for dimming 110A during white display has some variation with respect to 45 °. Therefore, it is sufficient that the slow axis of the light control liquid crystal panel 110A and the slow axis of the phase plate 91 are substantially matched.

  In white display, light transmitted through the first polarizing plate 81 is linearly polarized light having an angle of 0 ° with the optical axis as the center. When this linearly polarized light is transmitted through the phase plate 91, it becomes elliptically polarized light whose major axis direction is 0 °. Further, when the elliptical polarized light is transmitted through the light control liquid crystal panel 110A, the driven light control liquid crystal panel 110A has the same effect as the λ / 2 plate. It becomes. Since the major axis direction of the elliptically polarized light coincides with the direction of the transmission axis of the second polarizing plate 82, the light incident on the first polarizing plate 81 as a result is transmitted through the second polarizing plate 82 to display white. Is made. Even if the phase plate 91 is omitted, the light incident on the first polarizing plate 81 is transmitted through the second polarizing plate 82 and is displayed in white. Since the front phase difference value R of the phase plate 91 is relatively small, the illuminance is hardly lowered in white display even if the phase plate 91 is arranged.

  On the other hand, assuming that the liquid crystal molecules LC are in a substantially vertical alignment state without driving the light control liquid crystal panel 110A, elliptical polarized light having a major axis direction of 0 ° transmitted through the phase plate 91 has a major axis direction of The light control liquid crystal panel 110A is transmitted with almost no change. Therefore, elliptically polarized light whose major axis direction is 0 ° is incident on the second polarizing plate 82, and only the polarization component in the direction along the transmission axis of the second polarizing plate 82 is transmitted through the second polarizing plate 82 to display black. Is made. If the phase plate 91 is removed, linearly polarized light having an angle of 0 ° centered on the optical axis transmitted through the first polarizing plate 81 is transmitted through the dimming liquid crystal panel 110A as it is and enters the second polarizing plate 82. Therefore, the second polarizing plate 82 having a transmission axis of 90 ° can hardly be transmitted. That is, compared with the case where the phase plate 91 is deleted, the contrast ratio of the first light modulation unit 121 including the phase plate 91 is reduced. Since the configuration in which the phase plate 91 is deleted from the first light modulation unit 121 is the same as the second light modulation unit 122, the contrast ratio of the first light modulation unit 121 is the second by providing the phase plate 91. It is lower than the contrast ratio of the light modulator 122. As described with reference to FIG. 5, the front phase difference value R of the phase plate 91 is such that the contrast ratio of the first light modulation unit 121 is 1/10 or less than the contrast ratio of the second light modulation unit 122. It is preferable to adjust to.

According to the optical unit 100 of the first embodiment, the following effects can be obtained.
(1) The size of the pixel P of the light control liquid crystal panel 110 </ b> A in the first light modulation unit 121 is larger than the size of the pixel P of the display liquid crystal panel 110 </ b> B of the second light modulation unit 122. The first light modulation unit 121 includes a phase plate 91 that sets the contrast ratio of the first light modulation unit 121 to 1/10 or less of the contrast ratio of the second light modulation unit 122. Therefore, in the contour portion of the display pattern by the optical unit 100, the gray display having a gradation state different from the desired display state is less noticeable. That is, the optical unit 100 that can realize high contrast and excellent display quality can be provided.
(2) Since the size of the pixel P of the dimming liquid crystal panel 110A in the first light modulation unit 121 is larger than the size of the pixel P of the display liquid crystal panel 110B of the second light modulation unit 122, it is on the optical axis L. The light control liquid crystal panel 110A can be easily positioned with respect to the display liquid crystal panel 110B.
(3) If the phase plate 91 is formed integrally with the light control liquid crystal panel 110A, the optical unit 100 having a simpler structure can be realized.

(Second Embodiment)
<Optical unit>
Next, an optical unit according to a second embodiment will be described with reference to FIGS. FIG. 7A is a schematic perspective view showing the configuration of the optical unit of the second embodiment, and FIG. 7B is a diagram for explaining the configuration of the phase plate in the optical unit of the second embodiment. FIG. 8 is a diagram illustrating a light modulation state of the first light modulation unit in the optical unit according to the second embodiment.
In the optical unit of the second embodiment, the configuration of the phase plate 91 (92) is different from that of the optical unit 100 of the first embodiment. Therefore, the same components as those of the optical unit 100 are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 7A, the optical unit 200 of the present embodiment includes a first light modulation unit 221 disposed on the light incident side on the optical axis L, and the light of the first light modulation unit 221. And a second light modulator 122 arranged on the emission side. The optical unit 200 modulates the illumination light incident from the light source based on the image information by the first light modulation unit 221 and the second light modulation unit 122 and emits it as display light.

  The first light modulator 221 includes a first polarizing plate 81, a phase plate 93, a light control liquid crystal panel 110 </ b> A, and a second polarizing plate 82. The first polarizing plate 81 and the second polarizing plate on the optical axis L so that the transmission axis (or absorption axis) of the second polarizing plate 82 is orthogonal to the transmission axis (or absorption axis) of the first polarizing plate 81. 82 are arranged.

  The light control liquid crystal panel 110 </ b> A is disposed between the first polarizing plate 81 and the second polarizing plate 82 on the optical axis L. The optical design of the light control liquid crystal panel 110 </ b> A is such that the slow axis indicated by the arrow intersects the transmission axes (or absorption axes) of the first polarizing plate 81 and the second polarizing plate 82.

  The second light modulation unit 122 includes a third polarizing plate 83, a second polarizing plate 82, a third polarizing plate 83, and a second polarizing plate 83 that are arranged so that the transmission axis (or absorption axis) is orthogonal to the second polarizing plate 82. The display liquid crystal panel 110B disposed between the second polarizing plate 82 and the display liquid crystal panel 110B is arranged so that the transmission axis (or absorption axis) of the second polarizing plate 82 matches. And a fourth polarizing plate 84 disposed on the surface.

In the first light modulator 221, the phase plate 93 disposed between the first polarizing plate 81 and the light control liquid crystal panel 110 </ b> A exhibits refractive index anisotropy as shown in FIG. 7B. in the index ellipsoid, a satisfies the relation of _{n x = n y> n z} , viewed from the direction along the n _z axis when optically refractive index is isotropic circular. Such a refractive index ellipsoid is called a c-plate. The phase plate 93 of the present embodiment is obtained by inclining the c-plate with respect to the optical axis L clockwise at a predetermined angle about an axis of 45 °. Therefore, the phase plate 93 is a refractive index ellipsoid having a slow axis in the direction of the optical axis L, that is, in the direction of an azimuth angle of 45 ° when viewed from the Z direction. Therefore, the slow axis of the phase plate 93 coincides with the slow axis of the liquid crystal panel 110A for light control when driven. The front phase difference value R in the phase plate 93 varies depending on the tilt angle with respect to the optical axis L of the c-plate.
As a specific example of the phase plate 93, that is, a specific example of the c-plate, a film of triacetate, polycarbonate, polyester, polyvinyl alcohol or the like having a different refractive index in the thickness direction ( _nz axis direction) is pasted on the transparent substrate described above. Can be mentioned. Moreover, what laminated | stacked and laminated | stacked the inorganic material on the transparent substrate is mentioned.

  Similarly to the phase plate 91 (92) of the first embodiment, the phase plate 93 is not limited to be disposed between the first polarizing plate 81 and the light control liquid crystal panel 110A, and the light control liquid crystal panel. 110A and the 2nd polarizing plate 82 may be arrange | positioned.

  As shown in FIG. 8, the light modulation state (polarization state) at the time of white display and black display in the first light modulation unit 221 is basically the same as that of the first light modulation unit 121 of the first embodiment. That is, when linearly polarized light that is transmitted through the first polarizing plate 81 and has an angle around the optical axis of 0 ° is transmitted through the phase plate 93, it becomes elliptically polarized light whose major axis direction is 0 °. When the elliptical polarized light is transmitted through the light control liquid crystal panel 110A, the driven light control liquid crystal panel 110A has the same effect as the λ / 2 plate, so that the major axis direction of the elliptical polarization is 90 °. Direction. Since the major axis direction of the elliptically polarized light coincides with the direction of the transmission axis of the second polarizing plate 82, the light incident on the first polarizing plate 81 as a result is transmitted through the second polarizing plate 82 to display white. Is made. Even if the phase plate 93 is omitted, the light incident on the first polarizing plate 81 is transmitted through the second polarizing plate 82 and is displayed in white. If the front retardation value R of the phase plate 93 is set to a small value of about 10 nm, the illuminance is hardly lowered in white display even if the phase plate 93 is arranged.

  On the other hand, assuming that the liquid crystal molecules LC are in a substantially vertical alignment state without driving the light control liquid crystal panel 110A, elliptical polarized light having a major axis direction of 0 ° transmitted through the phase plate 93 has a major axis direction of The light control liquid crystal panel 110A is transmitted with almost no change. Therefore, elliptically polarized light whose major axis direction is 0 ° is incident on the second polarizing plate 82, and only polarized light in the direction along the transmission axis of the second polarizing plate 82 is transmitted through the second polarizing plate 82, thereby displaying black. Made. When the phase plate 93 is omitted, the linearly polarized light whose angle around the optical axis transmitted through the first polarizing plate 81 is 0 ° is transmitted through the dimming liquid crystal panel 110A as it is and is incident on the second polarizing plate 82. Therefore, the second polarizing plate 82 having a transmission axis of 90 ° can hardly be transmitted. That is, compared with the case where the phase plate 93 is deleted, the contrast ratio of the first light modulator 221 having the phase plate 93 is lowered. Since the configuration in which the phase plate 93 is omitted from the first light modulation unit 221 is the same as the configuration of the second light modulation unit 122, the contrast ratio of the first light modulation unit 221 is the second by providing the phase plate 93. It is lower than the contrast ratio of the light modulator 122. As described with reference to FIG. 5, the front phase difference value R of the phase plate 93 is such that the contrast ratio of the first light modulation unit 221 is 1/10 or less than the contrast ratio of the second light modulation unit 122. Furthermore, it is preferable to adjust the inclination angle of the c-plate with respect to the optical axis L. Further, since the contrast ratio in the light control liquid crystal panel 110A and the display liquid crystal panel 110B depends on temperature, it is preferable to adjust the inclination angle of the c-plate with respect to the optical axis L in accordance with the operating temperature condition.

According to the optical unit 200 of the second embodiment, in addition to the same effects as the effects (1) and (2) of the first embodiment, the following effects can be obtained.
(4) When the inclination angle of the c-plate with respect to the optical axis L is changed, the front phase difference value R of the phase plate 93 changes. That is, it is possible to provide the optical unit 200 that can adjust the contrast ratio of the first light modulation unit 221 by adjusting the inclination angle of the c-plate. In other words, it is possible to provide the optical unit 200 capable of adjusting the display state (display quality) such as bleeding and color unevenness in the contour portion of the actual display pattern.

(Third embodiment)
<Optical unit>
Next, an optical unit according to a third embodiment will be described with reference to FIGS. FIG. 9A is a schematic perspective view showing the configuration of the optical unit of the third embodiment, and FIG. 9B is a diagram for explaining the configuration of the phase plate in the optical unit of the third embodiment. FIG. 10 is a diagram illustrating a light modulation state of the first light modulation unit in the optical unit according to the third embodiment.
The optical unit of the third embodiment is different from the optical unit 100 of the first embodiment in the configuration of the first light modulation unit 121. Therefore, the same components as those of the optical unit 100 are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 9A, the optical unit 300 of the present embodiment includes a first light modulation unit 321 disposed on the light incident side on the optical axis L, and the light of the first light modulation unit 321. And a second light modulator 122 arranged on the emission side. The optical unit 300 uses the first light modulation unit 321 and the second light modulation unit 122 to modulate the illumination light incident from the light source based on image information and emit it as display light.

  The first light modulation unit 321 includes a first polarizing plate 81, a phase plate 94, a light control liquid crystal panel 110 </ b> A, a phase plate 95, and a second polarizing plate 82. The first polarizing plate 81 and the second polarizing plate on the optical axis L so that the transmission axis (or absorption axis) of the second polarizing plate 82 is orthogonal to the transmission axis (or absorption axis) of the first polarizing plate 81. 82 are arranged.

  The light control liquid crystal panel 110 </ b> A is disposed between the first polarizing plate 81 and the second polarizing plate 82 on the optical axis L. The optical design of the light control liquid crystal panel 110 </ b> A is such that the slow axis indicated by the arrow intersects the transmission axes (or absorption axes) of the first polarizing plate 81 and the second polarizing plate 82.

  The second light modulation unit 122 includes a third polarizing plate 83, a second polarizing plate 82, a third polarizing plate 83, and a second polarizing plate 83 that are arranged so that the transmission axis (or absorption axis) is orthogonal to the second polarizing plate 82. The display liquid crystal panel 110B disposed between the second polarizing plate 82 and the display liquid crystal panel 110B is arranged so that the transmission axis (or absorption axis) of the second polarizing plate 82 matches. And a fourth polarizing plate 84 disposed on the surface.

  In the first light modulator 321, the phase plate 94 disposed between the first polarizing plate 81 and the light control liquid crystal panel 110 </ b> A is a λ / 2 plate as shown in FIG. When viewed from the direction along the optical axis L, the linearly polarized light incident at an angle θ with respect to the slow axis is rotated to a double angle 2θ and transmitted. The phase plate 95 disposed between the light control liquid crystal panel 110A and the second polarizing plate 82 is also the same λ / 2 plate as the phase plate 94, and the angle setting of the slow axis is different from that of the phase plate 94. .

  As shown in FIG. 10, in the first light modulator 321, the phase plate 94 includes the first polarizing plate 81 and the light control liquid crystal panel 110 A so that the slow axis is 1 ° counterclockwise around the optical axis. It is arranged between. The phase plate 95 is disposed between the light adjustment liquid crystal panel 110A and the second polarizing plate 82 so that the slow axis is 89 ° counterclockwise around the optical axis. In white display in the first light modulation unit 321, when linearly polarized light that is transmitted through the first polarizing plate 81 and has an angle of 0 ° centered on the optical axis is incident on the phase plate 94, the linearly polarized light of 0 ° and the phase plate 94 Since the angle formed by the slow axis is 1 °, it is emitted as linearly polarized light having a counterclockwise angle of 2 ° around the optical axis. When transmitted through the light control liquid crystal panel 110A driven with 2 ° linearly polarized light, the driven light control liquid crystal panel 110A also produces the same effect as the λ / 2 plate. Since the angle formed by the slow axis of the optical liquid crystal panel 110A is 43 °, the light is emitted as linearly polarized light having a counterclockwise angle of 88 ° around the optical axis. When 88 ° linearly polarized light is incident on the phase plate 95, the angle formed by the 88 ° linearly polarized light and the slow axis of the phase plate 95 is 1 °, so that the counterclockwise angle about the optical axis is 90 °. The linearly polarized light is emitted. Accordingly, since the 90 ° linearly polarized light matches the direction of the transmission axis of the second polarizing plate 82, the light incident on the first polarizing plate 81 as a result is transmitted through the second polarizing plate 82 and displayed in white. Is made. Even if the phase plates 94 and 95 are omitted, the light incident on the first polarizing plate 81 is transmitted through the second polarizing plate 82 and is displayed in white. Therefore, even if the phase plates 94 and 95 which are λ / 2 plates are arranged, the illuminance does not decrease in the white display.

  On the other hand, in the black display in the first light modulation unit 321, when linearly polarized light that is transmitted through the first polarizing plate 81 and has an angle of 0 ° about the optical axis is incident on the phase plate 94, Since the angle formed by the slow axis of the phase plate 94 is 1 °, the light is emitted as linearly polarized light having a counterclockwise angle of 2 ° around the optical axis. When the 2 ° linearly polarized light is incident on the non-driven dimming liquid crystal panel 110A, the liquid crystal molecules LC are substantially vertically aligned in the non-driven dimming liquid crystal panel 110A. The light is emitted as linearly polarized light with a clockwise angle of approximately 2 °. When 2 ° linearly polarized light is incident on the phase plate 95, the angle formed by the 2 ° linearly polarized light and the slow axis of the phase plate 95 is 87 °, so that the counterclockwise angle about the optical axis is 176 °. It is emitted as linearly polarized light. Accordingly, since the 176 ° linearly polarized light and the direction of the transmission axis of the second polarizing plate 82 do not match and are not orthogonal to each other, the light incident on the first polarizing plate 81 as a result Black is displayed through part of 82. Even if the phase plates 94 and 95 are omitted, the light incident on the first polarizing plate 81 does not pass through the second polarizing plate 82 and is displayed in black. That is, in the black display, the first light modulation unit 321 including the phase plates 94 and 95 has a lower black level than the case where the phase plates 94 and 95 are deleted, so that the contrast ratio is lowered. As described with reference to FIG. 5, the phase plate 94 centered on the optical axis so that the contrast ratio of the first light modulation unit 321 is 1/10 or less than the contrast ratio of the second light modulation unit 122. , 95 is preferably adjusted.

According to the optical unit 300 of the third embodiment, the following effects can be obtained.
(1) The size of the pixel P of the light control liquid crystal panel 110A in the first light modulation unit 321 is larger than the size of the pixel P of the display liquid crystal panel 110B of the second light modulation unit 122. The first light modulation unit 321 includes phase plates 94 and 95 that make the contrast ratio of the first light modulation unit 321 1/10 or less of the contrast ratio of the second light modulation unit 122. The phase plates 94 and 95 are λ / 2 plates, which are arranged on the light incident side and the light exit side of the light control liquid crystal panel 110A, and the slow axis of the λ / 2 plate is the first polarizing plate on the incident side. The angle at which the azimuth direction is slightly shifted with respect to the transmission axis of 81 and the second polarizing plate 82 on the exit side, and the angle at which the slow axes of the mutual λ / 2 plates intersect is an angle other than 90 degrees. Accordingly, in the case of white display in which the linearly polarized light transmitted through the first polarizing plate 81 is emitted from the second polarizing plate 82 in the first light modulation unit 321, the λ / 2 plate is delayed with respect to the second polarizing plate 82 on the emission side. Since the phase axis is only slightly shifted, the transmittance during white display is unlikely to decrease. On the other hand, in the case of black display in which the linearly polarized light transmitted through the first polarizing plate 81 is not emitted from the second polarizing plate 82 in the first light modulation unit 321, λ / 2 with respect to the second polarizing plate 82 on the emission side. Since light leakage occurs when the slow axis of the plate is slightly shifted, the contrast ratio of the first light modulator 321 is reduced. Therefore, the gray display having a gradation state different from the desired display state is hardly noticeable in the contour portion of the display pattern by the optical unit 300. That is, the optical unit 300 that can realize high contrast and excellent display quality can be provided.
(2) The contrast ratio of the first light modulator 321 can be adjusted by adjusting the angle of the slow axis around the optical axis of the phase plates 94 and 95 which are λ / 2 plates.
(3) Since the size of the pixel P of the light control liquid crystal panel 110A in the first light modulation unit 321 is larger than the size of the pixel P of the display liquid crystal panel 110B of the second light modulation unit 122, it is on the optical axis L. The light control liquid crystal panel 110A can be easily positioned with respect to the display liquid crystal panel 110B.

(Fourth embodiment)
<Optical unit>
Next, an optical unit according to a fourth embodiment will be described with reference to FIGS. FIG. 11A is a schematic perspective view showing the configuration of the optical unit of the fourth embodiment, FIG. 11B is a schematic plan view showing the alignment processing state of the light control liquid crystal panel, and FIG. 11C is for display. It is a schematic plan view which shows the orientation state of a liquid crystal panel. FIG. 12 is a diagram illustrating a light modulation state of the first light modulation unit in the optical unit according to the fourth embodiment.
The optical unit of the fourth embodiment is different from the optical unit 100 of the first embodiment mainly in the configuration of the display liquid crystal panel 110B. Specifically, the alignment method of the liquid crystal layer of the display liquid crystal panel is a twisted nematic method (TN method).

  As shown in FIG. 11A, the optical unit 400 of the present embodiment includes a first light modulation unit 421 disposed on the light incident side on the optical axis L, and the light of the first light modulation unit 421. And a second light modulator 422 disposed on the emission side. The optical unit 400 modulates the illumination light incident from the light source based on the image information by the first light modulation unit 421 and the second light modulation unit 422 and emits it as display light.

  The first light modulation unit 421 includes a first polarizing plate 85, a phase plate 96, a light control liquid crystal panel 110 </ b> C, and a second polarizing plate 86. The first polarizing plate 85 and the second polarizing plate on the optical axis L so that the transmission axis (or absorption axis) of the second polarizing plate 86 is orthogonal to the transmission axis (or absorption axis) of the first polarizing plate 85. 86 are arranged. The transmission axis of the first polarizing plate 85 is 135 ° clockwise around the optical axis L. The transmission axis of the second polarizing plate 86 is 45 ° clockwise around the optical axis L.

The dimming liquid crystal panel 110C has basically the same configuration as the transmissive and active drive type dimming liquid crystal panel 110A of the first embodiment, and is a uniaxial substantially vertical alignment method (VA method). On the optical axis L, it is disposed between the first polarizing plate 85 and the second polarizing plate 86. The optical design of the light control liquid crystal panel 110C is such that the slow axis indicated by the arrow intersects the transmission axes (or absorption axes) of the first polarizing plate 85 and the second polarizing plate 86.
As shown in FIG. 11B, the angle θa indicating the film forming direction of the inorganic alignment film in the light control liquid crystal panel 110C is 90 ° with respect to the Y direction. That is, the slow axis of the light control liquid crystal panel 110C is a direction along the X direction.

  As shown in FIG. 11A, the phase plate 96 of the first light modulator 421 is an a-plate, and the slow axis (indicated by a solid arrow) of the phase plate 96 is a liquid crystal panel for dimming. It is arranged between the first polarizing plate 85 and the light control liquid crystal panel 110C so as to coincide with the slow axis of 110C (indicated by the solid line arrow). The front phase difference value R of the phase plate 96 is, for example, 10 nm. A specific example of the phase plate 96 is the same as the phase plate 91 of the first embodiment described above, and is formed on an optically isotropic transparent substrate (transparent support) such as glass or film, with triacetate, polycarbonate, Examples include those obtained by attaching a uniaxially stretched film such as polyester or polyvinyl alcohol, and those obtained by depositing an inorganic material such as silicon oxide or aluminum oxide on a transparent substrate (transparent support). Alternatively, the quartz plate may be polished to a predetermined thickness so that the front phase difference value becomes a predetermined value.

Phase plate 96 is not limited to a a- plate, as described in the first embodiment, in n _x> n _y> is the refractive index ellipsoid satisfying a relationship of n _z 2 axis retardation plate There may be. Further, the phase plate 96 is not limited to being disposed between the first polarizing plate 85 and the light control liquid crystal panel 110C, and is disposed between the light control liquid crystal panel 110C and the second polarizing plate 86. It may be. Further, it may be disposed between the first polarizing plate 85 and the second polarizing plate 86 on the light incident side and the emission side of the light control liquid crystal panel 110C. In this case, the total value of the front phase difference values of the respective phase plates is adjusted to be a desired front phase difference value R.

  The phase plate 96 may be formed integrally with the counter substrate 20 on the light incident side of the counter substrate 20 constituting the light control liquid crystal panel 110C. Similarly, it may be formed integrally with the element substrate 10 on the light emission side of the element substrate 10 constituting the light control liquid crystal panel 110C.

  The second light modulator 422 includes a third polarizing plate 87, a second polarizing plate 86, a third polarizing plate 87, and a second polarizing plate 86 arranged so that the transmission axis (or absorption axis) is orthogonal to the second polarizing plate 86. The display liquid crystal panel 110 </ b> D disposed between the second polarizing plate 86 and the display liquid crystal panel 110 </ b> D is arranged so that the transmission axis (or the absorption axis) matches the second polarizing plate 86. And a fourth polarizing plate 88. The transmission axis of the fourth polarizing plate 88 is 45 ° clockwise around the optical axis L. The transmission axis of the third polarizing plate 87 is 135 ° clockwise around the optical axis L.

The display liquid crystal panel 110D is a TN system, and basically has the same configuration as the transmissive and active drive type display liquid crystal panel 110B of the first embodiment. The size of the pixel P of the display liquid crystal panel 110D is smaller than the size of the pixel P of the light control liquid crystal panel 110C.
As shown in FIG. 11C, the alignment treatment direction of the alignment film on the counter substrate of the display liquid crystal panel 110D is a direction from the lower left to the upper right as indicated by the dashed arrow when viewed from the direction along the optical axis L. Thus, it coincides with the transmission axis of the fourth polarizing plate 88 disposed on the light incident side. The alignment processing direction of the alignment film on the element substrate of the display liquid crystal panel 110D is a direction from the lower right to the upper left indicated by the solid line arrow when viewed from the direction along the optical axis L, and is disposed on the light emission side. The transmission axis of the third polarizing plate 87 coincides with the transmission axis. The liquid crystal layer is composed of liquid crystal molecules LC having positive dielectric anisotropy, and the twist direction of the liquid crystal molecules LC is counterclockwise when viewed from the direction along the optical axis L, and the twist angle θt is 90 °. The twist angle θt is not necessarily limited to 90 °, and may be, for example, 89 ° close to 90 °.

  In the second light modulator 422 provided with such a display liquid crystal panel 110D, the display liquid crystal panel 110D is driven in accordance with a display pattern to be actually displayed. In the second light modulation unit 422 of the present embodiment, when white display is performed, no driving voltage is applied to the pixel P of the display liquid crystal panel 110D, and when black display is performed, the pixel P of the display liquid crystal panel 110D is applied. A drive voltage is applied.

  As shown in FIG. 12, when linearly polarized light having an angle of 135 ° clockwise with respect to the optical axis passing through the first polarizing plate 85 is transmitted through the phase plate 96, elliptically polarized light having a major axis direction of 135 ° clockwise. It becomes. When the dimming liquid crystal panel 110C driven with the elliptically polarized light of 135 ° is transmitted, the driven dimming liquid crystal panel 110C has the same effect as the λ / 2 plate, so that the major axis direction of the elliptically polarized light is clockwise. The direction is 45 ° around. Since the 45 ° major axis direction of the elliptically polarized light matches the direction of the transmission axis of the second polarizing plate 86, the light incident on the first polarizing plate 85 as a result is transmitted through the second polarizing plate 86. White display is made. Even if the phase plate 96 is omitted, the light incident on the first polarizing plate 85 is transmitted through the second polarizing plate 86 and is displayed in white. If the front phase difference value R of the phase plate 96 is set to a small value of about 10 nm, the illuminance is hardly lowered in white display even if the phase plate 96 is arranged.

  On the other hand, assuming that the liquid crystal molecules LC are in a substantially vertically aligned state without driving the light control liquid crystal panel 110C, the elliptically polarized light whose major axis direction transmitted through the phase plate 96 is 135 ° clockwise is long. The light adjustment liquid crystal panel 110C is transmitted in a state where the axial direction hardly changes. Therefore, elliptically polarized light whose major axis direction is 135 ° clockwise enters the second polarizing plate 86, and only polarized light in the direction along the transmission axis of the second polarizing plate 86 is transmitted through the second polarizing plate 86. Black display is made. When the phase plate 96 is omitted, the linearly polarized light whose angle about the optical axis transmitted through the first polarizing plate 85 is clockwise and 135 ° is transmitted through the dimming liquid crystal panel 110C as it is and transmitted through the second polarizing plate 86. , The transmission axis is hardly transmitted through the second polarizing plate 86 having a clockwise angle of 45 °. That is, compared with the case where the phase plate 96 is deleted, the contrast ratio of the first light modulator 421 having the phase plate 96 is lowered. As described with reference to FIG. 5, the front phase difference value R of the phase plate 96 is such that the contrast ratio of the first light modulation unit 421 is 1/10 or less than the contrast ratio of the second light modulation unit 422. Further, it is preferable to adjust the front phase difference value R of the phase plate 96.

  As a measure for increasing the contrast ratio of the second light modulation unit 422 as compared with the first light modulation unit 421, the alignment of the liquid crystal molecules LC in the liquid crystal layer on the light incident side and / or emission side of the display liquid crystal panel 110D. For example, an optical compensator such as a c-plate may be arranged to prevent light leakage caused by the state (pretilt or twist).

According to the fourth embodiment, the following effects can be obtained.
(1) The size of the pixel P of the light control liquid crystal panel 110C in the first light modulation unit 421 is larger than the size of the pixel P of the display liquid crystal panel 110D of the second light modulation unit 422. The first light modulation unit 421 includes a phase plate 96 that sets the contrast ratio of the first light modulation unit 421 to 1/10 or less with respect to the contrast ratio of the second light modulation unit 422. Therefore, in the contour portion of the display pattern by the optical unit 400, the gray display having a gradation state different from the desired display state is hardly noticeable. That is, the optical unit 400 that can realize high contrast and excellent display quality can be provided.
(2) Since the size of the pixel P of the dimming liquid crystal panel 110C in the first light modulation unit 421 is larger than the size of the pixel P of the display liquid crystal panel 110D of the second light modulation unit 422, it is on the optical axis L. The light control liquid crystal panel 110C can be easily positioned with respect to the display liquid crystal panel 110D.
(3) If the phase plate 96 is formed integrally with the light control liquid crystal panel 110C, the optical unit 400 having a simpler structure can be realized.

(Fifth embodiment)
<Electronic equipment>
Next, an electronic apparatus to which the optical unit of this embodiment is applied will be described with reference to FIG. FIG. 13 is a schematic diagram illustrating a configuration of a projection display device as an electronic apparatus.

  As shown in FIG. 13, a projection display apparatus 1000 as an electronic apparatus according to the present embodiment includes a polarization illumination apparatus 1100 arranged along the system optical axis L, and two dichroic mirrors 1104 and 1105 as light separation elements. And. In addition, three reflection mirrors 1106, 1107, 1108 and five relay lenses 1201, 1202, 1203, 1204, 1205 are provided. Further, three transmissive liquid crystal light valves 1210, 1220, and 1230, a cross dichroic prism 1206 as a light combining element, and a projection lens 1207 as a projection optical system are provided.

  The polarized light illumination device 1100 is generally configured by a lamp unit 1101 as a light source composed of a white light source such as an ultra-high pressure mercury lamp or a halogen lamp, an integrator lens 1102, and a polarization conversion element 1103.

  The dichroic mirror 1104 reflects red light (R) and transmits green light (G) and blue light (B) among the polarized light beams emitted from the polarization illumination device 1100. Another dichroic mirror 1105 reflects the green light (G) transmitted through the dichroic mirror 1104 and transmits the blue light (B).

The red light (R) reflected by the dichroic mirror 1104 is reflected by the reflection mirror 1106 and then enters the liquid crystal light valve 1210 via the relay lens 1205.
Green light (G) reflected by the dichroic mirror 1105 enters the liquid crystal light valve 1220 via the relay lens 1204.
The blue light (B) transmitted through the dichroic mirror 1105 enters the liquid crystal light valve 1230 via a light guide system including three relay lenses 1201, 1202, 1203 and two reflection mirrors 1107, 1108.

  The liquid crystal light valves 1210, 1220, and 1230 are disposed to face the incident surfaces of the cross dichroic prism 1206 for each color light. The color light incident on the liquid crystal light valves 1210, 1220, and 1230 is modulated based on video information (video signal) and emitted toward the cross dichroic prism 1206. In this prism, four right-angle prisms are bonded together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface thereof. The three color lights are synthesized by these dielectric multilayer films, and the light representing the color image is synthesized. The synthesized light is projected onto the screen 1300 by the projection lens 1207, which is a projection optical system, and the image is enlarged and displayed.

  The liquid crystal light valve 1210 is one to which the optical unit 100 (see FIG. 1) of the first embodiment is applied. The same applies to the other liquid crystal light valves 1220 and 1230.

  According to such a projection display apparatus 1000, since the optical unit 100 of the first embodiment is used as the liquid crystal light valves 1210, 1220, and 1230, high contrast and excellent display quality are realized. The projection display apparatus 1000 can be provided. The same effect can be obtained even if the optical unit 200 of the second embodiment, the optical unit 300 of the third embodiment, and the optical unit 400 of the fourth embodiment are used as the liquid crystal light valves 1210, 1220, and 1230. can get.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. A projection display device and an electronic apparatus to which the optical unit is applied are also included in the technical scope of the present invention. Various modifications other than the above embodiment are conceivable. Hereinafter, a modification will be described.

(Modification 1) In the first to third embodiments, the configuration of the second light modulation unit is not limited to this. FIG. 14 is a schematic diagram illustrating a configuration and a light modulation state of a second light modulation unit according to a modification. For example, as illustrated in FIG. 14, the second light modulation unit 122 </ b> B according to the modification includes a third polarizing plate 83 and a fourth polarization that are arranged so that the transmission axes (or absorption axes) are orthogonal to each other on the optical axis. Plate 84, display liquid crystal panel 110B disposed between third polarizing plate 83 and fourth polarizing plate 84, and phase plate 97 disposed between fourth polarizing plate 84 and display liquid crystal panel 110B. And have. That is, the second light modulation unit 122B according to the modification is different from the second light modulation unit 122 according to the first embodiment in that the phase plate 97 is provided.
The phase plate 97 is disposed for the purpose of canceling (optically compensating) a phase difference caused by a pretilt in the uniaxial substantially vertically aligned liquid crystal molecules LC of the liquid crystal layer 50 in the display liquid crystal panel 110B. As a specific example of such a phase plate 97, the c-plate is inclined with respect to the optical axis in the same manner as the phase plate 93 described in the second embodiment, and is rotated 45 ° clockwise around the optical axis. An example of generating a slow axis in the azimuth direction is given. In addition, a biaxial retardation plate similar to the phase plate 92 described in the first embodiment is inclined with respect to the optical axis, and a slow axis is generated in a 45 ° azimuth direction clockwise around the optical axis. O-plates may be used.

  As shown in FIG. 14, when linearly polarized light having an angle of 90 ° centered on the optical axis and transmitted through the fourth polarizing plate 84 is transmitted through the phase plate 97, it becomes elliptically polarized light having a major axis direction of 90 °. When the elliptically polarized light is transmitted through the driven display liquid crystal panel 110B, the slow axis of the driven display liquid crystal panel 110B is 135 ° clockwise around the optical axis, and the display liquid crystal panel 110B is λ / Since the same effect as that of the two plates is produced, the major axis direction of the elliptically polarized light becomes the direction of 0 °. Since the major axis direction of the elliptically polarized light coincides with the direction of the transmission axis of the third polarizing plate 83, the light incident on the fourth polarizing plate 84 as a result is transmitted through the third polarizing plate 83 to display white. Is made.

On the other hand, if the liquid crystal molecules LC are in a substantially vertical alignment state without driving the display liquid crystal panel 110B, the elliptically polarized light having a major axis direction of 90 ° transmitted through the phase plate 97 is displayed on the display liquid crystal panel 110B. Since the phase difference of the liquid crystal molecules LC in the liquid crystal layer 50 is optically compensated, the liquid crystal layer 50 is emitted from the display liquid crystal panel 110B as linearly polarized light of approximately 90 °. Therefore, 90 ° linearly polarized light enters the third polarizing plate 83, and no light is emitted from the third polarizing plate 83 having a transmission axis of 0 °, resulting in black display.
By providing such a phase plate 97, it is possible to realize the second light modulation unit 122B with improved viewing angle characteristics and a high contrast ratio. The phase plate 97 may be disposed between the display liquid crystal panel 110B and the third polarizing plate 83.

  (Modification 2) In the above embodiment, the second polarizing plate between the light control liquid crystal panel and the display liquid crystal panel may be included in the first light modulation unit, or the second polarizing plate and the fourth polarizing plate. Since the transmission axis or absorption axis of the polarizing plate is in the same azimuth direction, either the second polarizing plate or the fourth polarizing plate may be included in the second light modulation unit.

  (Modification 3) In the first embodiment, the phase plate 91 is arranged so that the slow axis of the phase plate 91 coincides with the slow axis of the light control liquid crystal panel 110A. Therefore, when forming the alignment film 18 (alignment film 24) of the light control liquid crystal panel 110A by oblique vapor deposition using an inorganic material, the alignment film 18 is controlled by controlling the film thickness of the alignment film 18 (alignment film 24). A phase difference (birefringence) may be given to the (alignment film 24), and the alignment film 18 (alignment film 24) may function as the phase plate 91.

  (Modification 4) An electronic apparatus to which any one of the optical units of the first to fourth embodiments is applied is not limited to the projection display apparatus 1000 of the fifth embodiment. For example, projection-type HUD (head-up display), HMD (head-mounted display), electronic book, personal computer, digital still camera, LCD TV, viewfinder type or monitor direct-view type video recorder, car navigation system, electronic notebook The optical unit of the above embodiment can be suitably used as a display unit of an information terminal device such as POS. Further, the optical unit of the present embodiment is not limited to being used as a display unit, and may be used as a shutter for an exposure apparatus or the like.

  50 ... Liquid crystal layer, 81, 85 ... First polarizing plate, 82, 86 ... Second polarizing plate, 83 ... Third polarizing plate, 84 ... Fourth polarizing plate, 91, 92, 93, 94, 95, 96, 97 ... phase plate, 100, 200, 300, 400 ... optical unit, 110A, 110C ... liquid crystal panel for dimming, 110B, 110D ... liquid crystal panel for display, 121, 221, 321, 421 ... first light modulator, 122, 122B, 422 ... second light modulation unit, 1000 ... projection display device, 1101 ... lamp unit as light source, 1207 ... projection lens as projection optical system, L ... optical axis, P ... pixel.

Claims (10)

Between the first polarizing plate, the second polarizing plate disposed so that the transmission axis or the absorption axis is orthogonal to the first polarizing plate, and disposed between the first polarizing plate and the second polarizing plate. A first light modulation unit including a dimming liquid crystal panel;
A third polarizing plate disposed such that a transmission axis or an absorption axis is orthogonal to the second polarizing plate, and a display liquid crystal panel disposed between the second polarizing plate and the third polarizing plate, A second light modulator including
The pixel size of the liquid crystal panel for light control is larger than the pixel size of the liquid crystal panel for display,
An optical unit comprising a phase plate for reducing a contrast ratio of the first light modulation unit on a light incident side and / or an emission side of the light control liquid crystal panel.   The second light modulation unit is arranged between the second polarizing plate and the display liquid crystal panel, and is a fourth polarization arranged so that a transmission axis or an absorption axis coincides with the second polarizing plate. The optical unit according to claim 1, further comprising a plate.   The phase plate is an a-plate or a biaxial retardation plate, and the azimuth direction of the slow axis of the liquid crystal layer of the liquid crystal panel for light control matches the azimuth direction of the slow axis of the phase plate. The optical unit according to claim 1, wherein the optical unit is arranged as described above.   The said phase plate is a c-plate, Comprising: It arrange | positions so that a slow axis may incline with respect to the normal line of the board | substrate surface of the said liquid crystal panel for light control. The optical unit described.   The phase plate is a λ / 2 plate and is disposed on the light incident side and the light exit side of the light control liquid crystal panel, and the slow axis of the λ / 2 plate is the first polarizing plate on the incident side and The azimuth direction is slightly shifted from the transmission axis or absorption axis of the second polarizing plate on the exit side, and the angle at which the slow axes of the mutual λ / 2 plates intersect is an angle other than 90 degrees. The optical unit according to claim 1 or 2.   The optical unit according to any one of claims 1 to 5, wherein the phase plate is formed integrally with the light control liquid crystal panel.   7. The optical device according to claim 1, wherein a contrast ratio of the first light modulation unit is 1/10 or less of a contrast ratio of the second light modulation unit. unit.   8. The optical unit according to claim 1, wherein the alignment of liquid crystal molecules in the light control liquid crystal panel and the liquid crystal layer of the display liquid crystal panel is a uniaxial substantially vertical alignment. 9. . A light source;
The optical unit according to any one of claims 1 to 8 disposed on an optical axis of light emitted from the light source;
A projection display system, comprising: a projection optical system that magnifies and projects display light emitted from the optical unit. A light source;
An electronic device comprising: the optical unit according to claim 1 disposed on an optical axis of light emitted from the light source.

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