JP6375167B2 - Optical device, projector, manufacturing method, and manufacturing support apparatus - Google Patents

Description

  The present invention relates to an optical device that generates laser light, a projector, a manufacturing method, and a manufacturing support apparatus.

  2. Description of the Related Art Conventionally, there is known a projector that modulates light emitted from an illumination device by a spatial light modulator and enlarges and projects the modulated image light onto a screen by a projection optical system such as a projection lens. A wave plate that adjusts the polarization direction of laser light is used in such projectors. For example, in a laminated wave plate in which quarter wave plates are provided on both sides of a half wave plate, the thickness of the half wave plate is adjusted to use a high-order phase difference, and in the vicinity of each wavelength used. Is known to operate locally as a half-wave plate (see, for example, Patent Document 1 below).

International Publication No. 2013/015066

  However, the above-described prior art has a problem that when the laminated wave plate is operated as a half-wave plate, the liquid crystal cell becomes thick and the switching characteristics of the liquid crystal cell are deteriorated.

  In order to solve the above-described problems caused by the prior art, the present invention provides an optical device, a projector, a manufacturing method, and manufacturing support capable of realizing a laminated wavelength plate that operates as a half-wave plate while suppressing deterioration in switching characteristics. An object is to provide an apparatus.

  In order to solve the above-described problems and achieve the object, according to one aspect of the optical device, the projector, the manufacturing method, and the manufacturing support apparatus according to the present invention, a plurality of laser beams having a polarization state in a predetermined direction and different wavelengths are provided. A liquid crystal cell that allows the direction of the director relative to the predetermined direction to be switched between a first direction and a second direction parallel to the substrate surface, and a first wavelength plate that allows each laser beam emitted from the liquid crystal cell to pass therethrough, Pass each laser beam emitted from the first wave plate, pass a second wave plate whose slow axis is parallel to the first wave plate, and pass each laser beam emitted from the second wave plate, A third wavelength plate whose slow axis is parallel to the first direction or the second direction, and a control circuit that periodically switches the direction of the director, the liquid crystal cell, the first wavelength plate, the first 2 Outputs each laser beam passed through the long plate and the third wave plate.

  Accordingly, by increasing the thickness of the laminated wave plate that is different from the liquid crystal cell, the laminated wave plate can be operated as a half-wave plate while suppressing the thickness of the liquid crystal cell.

  According to the present invention, it is possible to realize a laminated wave plate that operates as a half-wave plate while suppressing a decrease in switching characteristics.

FIG. 1A is a diagram illustrating a configuration example of an optical device according to an embodiment. FIG. 1B is a diagram illustrating a first modification of the optical device. FIG. 1C is a diagram illustrating a second modification of the optical device. FIG. 1D is a diagram illustrating a third modification of the optical device. FIG. 2A is a diagram illustrating Example 1 of an electrode structure of a liquid crystal cell. FIG. 2B is a diagram illustrating Example 2 of the electrode structure of the liquid crystal cell. FIG. 2C is a diagram illustrating Example 3 of the electrode structure of the liquid crystal cell. FIG. 2D is a diagram illustrating Example 4 of the electrode structure of the liquid crystal cell. FIG. 3 is a diagram illustrating an example of the operation of the laminated wave plate. FIG. 4 is a graph showing a first example of retardation characteristics with respect to wavelength when a liquid crystal device is used as a half-wave plate. FIG. 5 is a graph showing a first example of azimuth angle characteristics when a liquid crystal device is used as a half-wave plate. FIG. 6 is a diagram illustrating an example of a laminated wave plate in which retardation films are combined. FIG. 7A is a graph illustrating an example of wavelength dispersion characteristics of a retardation film. FIG. 7B is a diagram illustrating an example of a change in retardation characteristics caused by a retardation film. FIG. 7C is a diagram illustrating an example of a change in azimuth angle characteristics due to the retardation film. FIG. 8 is a graph showing an example of crosstalk characteristics with respect to wavelength. FIG. 9 is a perspective view showing an example of an optical device. FIG. 10 is a graph showing an example of retardation characteristics with respect to the thickness of the wave plate at each wavelength. FIG. 11 is a diagram illustrating an example of a hardware configuration of the manufacturing support apparatus according to the embodiment. FIG. 12 is a cross-sectional view showing a specific example of a liquid crystal cell using a ferroelectric liquid crystal. FIG. 13 is an explanatory diagram (part 1) illustrating the relationship between the direction of the molecular major axis of the ferroelectric liquid crystal and the electric field. FIG. 14 is an explanatory diagram (part 2) illustrating the relationship between the molecular major axis direction of the ferroelectric liquid crystal and the electric field.

  Exemplary embodiments of an optical device, a projector, a manufacturing method, and a manufacturing support apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1A is a diagram illustrating a configuration example of an optical device according to an embodiment. As illustrated in FIG. 1A, the optical device 100 according to the embodiment includes a light source unit 110, a liquid crystal device 120, and a control circuit 130. However, the light source unit 110 and the control circuit 130 may be external to the optical device 100. In this case, the optical device 100 may not include the light source unit 110 and the control circuit 130.

  The light source unit 110 emits laser light having a predetermined wavelength in a predetermined polarization state. The laser light is, for example, linearly polarized laser light that includes a plurality of primary color lights spatially or temporally. Specifically, the light source unit 110 includes an RGB laser light source 111 and a polarization maintaining fiber 112. The RGB laser light source 111 includes light of a plurality of primary colors (red, green, and blue) and emits linearly polarized laser light. The light source unit 110 is, for example, a field sequential type light source unit that emits light sources of respective colors in a time division manner.

  The polarization maintaining fiber 112 is a PMF (Polarization Maintaining Fiber) that holds the polarization state (linearly polarized light) of the laser light emitted from the RGB laser light source 111 and emits it to the liquid crystal device 120. A polarization direction 101 indicates a polarization direction (for example, 0 °) of laser light emitted from the polarization maintaining fiber 112 to the liquid crystal device 120.

  The liquid crystal device 120 includes a wave plate 121 (fourth wave plate), a liquid crystal cell 122 (first liquid crystal cell), a wave plate 123 (first wave plate), a wave plate 124 (second wave plate), a wavelength A plate 125 (third wave plate) and a wave plate 126 (fifth wave plate) are included.

  The liquid crystal cell 122 can be made of, for example, a ferroelectric liquid crystal (FLC) cell. Wave plate 125 is, for example, a half-wave plate. The wave plate 125 can be made of, for example, a nematic liquid crystal cell, a retardation film, a ferroelectric liquid crystal cell, or the like. In the example shown in FIG. 1A, the wave plate 125 is formed of a wave plate whose direction of the slow axis is fixed.

  Wave plates 121, 123, 124, and 126 are quarter wavelength plates having the same configuration, for example. Wave plates 121, 123, 124, and 126 can be made of, for example, a nematic liquid crystal (NLC) cell or a retardation film.

  The wave plate 121 passes the laser light emitted from the polarization maintaining fiber 112 and emits it to the liquid crystal cell 122. The slow axis direction 121 a indicates the direction of the slow axis (slow axis) of the wave plate 121. The slow axis is the axis with the highest birefringence refractive index. The slow axis direction 121a is set at an angle of about 0 ° with respect to the polarization direction 101 of the laser beam emitted from the polarization maintaining fiber 112 in a predetermined direction. For this reason, the polarization state of the laser light does not change in the wave plate 121.

  The liquid crystal cell 122 passes the laser beam emitted from the wave plate 121 and emits it to the wave plate 123. In addition, the liquid crystal cell 122 rotates the polarization direction of the laser beam to be transmitted by a switchable rotation amount. The director direction 122 a indicates the direction of the director of liquid crystal molecules in the liquid crystal cell 122. The angle of the director direction 122 a with respect to the slow axis direction 121 a of the wave plate 121 is about 22.5 ° (first direction) and about −22.5 ° (second direction) in the direction parallel to the substrate surface of the liquid crystal cell 122. It is possible to switch to (± π / 8).

  When the director direction 122a of the liquid crystal cell 122 is switched to 22.5 °, the polarization state of the laser light emitted from the liquid crystal cell 122 rotates by 22.5 × 2 = 45 °. When the director direction 122 a of the liquid crystal cell 122 is switched to −22.5 °, the polarization state of the laser light emitted from the liquid crystal cell 122 rotates by −22.5 ° × 2 = −45 °.

  The wave plate 123 allows the laser light emitted from the liquid crystal cell 122 to pass through and is emitted to the wave plate 124. The slow axis direction 123 a indicates the direction of the slow axis (slow axis) of the wave plate 123. The slow axis direction 123 a is set at an angle of about 0 ° with respect to the polarization direction 101 of the laser light emitted from the polarization maintaining fiber 112. For this reason, when the director direction 122a of the liquid crystal cell 122 is switched to 22.5 ° and −22.5 °, the polarization state of the laser light in the wave plate 123 is circularly polarized in the opposite direction.

  The wave plate 124 passes the laser beam emitted from the wave plate 123 and emits it to the wave plate 125. The slow axis direction 124 a indicates the direction of the slow axis of the wave plate 124. The slow axis direction 124 a is set at an angle of about 0 ° with respect to the polarization direction 101 of the laser light emitted from the polarization maintaining fiber 112 in a predetermined direction. For this reason, when the director direction 122 a of the liquid crystal cell 122 is switched to 22.5 °, the polarization direction of the laser light in the wave plate 124 is linearly polarized at 45 ° with respect to the polarization direction 101. When the director direction 122 a of the liquid crystal cell 122 is switched to −22.5 °, the polarization direction of the laser light in the wave plate 124 is linearly polarized light of −45 ° with respect to the polarization direction 101. Thus, the wave plate 124 is set so that the slow axis is parallel to the wave plate 123.

  The wave plate 125 passes the laser beam emitted from the wave plate 124 and emits it to the wave plate 126. The slow axis direction 125 a indicates the direction of the slow axis of the wave plate 125. The slow axis direction 125a is set at an angle of about 22.5 ° with respect to the polarization direction 101 of the laser light emitted from the polarization maintaining fiber 112 in a predetermined direction. For this reason, when the director direction 122 a of the liquid crystal cell 122 is switched to 22.5 °, the polarization direction of the laser light in the wave plate 124 is linearly polarized at 0 ° with respect to the polarization direction 101. When the director direction 122 a of the liquid crystal cell 122 is switched to −22.5 °, the polarization direction of the laser light in the wave plate 124 is linearly polarized at 90 ° with respect to the polarization direction 101. Further, the slow axis direction 125 a of the wave plate 125 may be set to an angle of about −22.5 ° with respect to the polarization direction 101 of the laser beam emitted from the polarization maintaining fiber 112. Thus, the wave plate 125 is set so that the slow axis is parallel to about 22.5 ° (first direction) or about −22.5 ° (second direction) (± π / 8).

  The wave plate 126 passes the laser beam emitted from the wave plate 125 and emits it to the subsequent stage of the optical device 100. The slow axis direction 126 a indicates the direction of the slow axis of the wave plate 126. The slow axis direction 126 a is set at an angle of about 0 ° with respect to the polarization direction 101 of the laser light emitted from the polarization maintaining fiber 112. For this reason, when the director direction 122 a of the liquid crystal cell 122 is switched to 22.5 °, the polarization direction of the laser light does not change in the wave plate 126. Even when the director direction 122 a of the liquid crystal cell 122 is switched to −22.5 °, the polarization direction of the laser light does not change in the wave plate 126.

  Polarization states 102 and 103 indicate the polarization direction of the laser light emitted from the wave plate 126. When the director direction 122 a of the liquid crystal cell 122 is switched to 22.5 °, the polarization state of the laser light emitted from the wave plate 126 is a straight line of 0 ° with respect to the polarization direction 101 as shown in the polarization state 102. Become polarized. When the director direction 122 a of the liquid crystal cell 122 is switched to −22.5 °, the polarization state of the laser light emitted from the wave plate 126 is 90 ° with respect to the polarization direction 101 as shown in the polarization state 103. It becomes linearly polarized light.

  The change in the polarization state described here is a change in the wavelength designed so that the liquid crystal cell 122 and the wave plate 125 operate as a half-wave plate, and the wave plates 123 and 124 operate as quarter-wave plates. . For example, when the liquid crystal cell 122 and the wave plate 125 are designed to operate as half-wave plates and the wave plates 123 and 124 operate as quarter-wave plates at the green laser wavelength of the RGB laser light source 111, the RGB laser light source 111 The polarization state of each of the red and blue laser beams becomes elliptically polarized light close to ± 45 ° by the liquid crystal cell 122, but becomes circularly polarized light by the wave plate 123.

  The control circuit 130 periodically switches the angle of the director direction 122a of the liquid crystal cell 122 with respect to the slow axis direction 121a of the wave plate 121 between 22.5 ° and −22.5 °. For example, the control circuit 130 switches the director direction 122 a of the liquid crystal cell 122 by controlling the voltage applied to the electrode of the liquid crystal cell 122.

  As shown in FIG. 1A, the liquid crystal device 120 operates as a half-wave plate for the laser light emitted from the polarization maintaining fiber 112. Further, by switching the director direction 122 a of the liquid crystal cell 122, the polarization state of the laser light emitted from the liquid crystal device 120 is alternately switched to orthogonal linearly polarized light.

  Further, by adopting a configuration in which the liquid crystal cell 122 is sandwiched between the wave plate 121 and the wave plate 123, the laser light emitted from the liquid crystal device 120 is not dependent on the polarization state of the laser light incident on the liquid crystal device 120. It can be operated as a half-wave plate.

  Further, in the configuration shown in FIG. 1A, the angle of the director direction 122a of the liquid crystal cell 122 with respect to the slow axis direction 121a of the wave plate 121 is set to 67.5 ° and 112.5 in the direction parallel to the substrate surface of the liquid crystal cell 122. It may be possible to switch to ° (3π / 8, 5π / 8). In this case, the slow axis direction 125 a of the wave plate 125 is set to 67.5 ° or 112.5 ° with respect to the polarization direction 101.

  FIG. 1B is a diagram illustrating a first modification of the optical device. In FIG. 1B, the same parts as those shown in FIG. 1A are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 1B, the wave plate 125 may be made of a ferroelectric liquid crystal cell (second liquid crystal cell), and the slow axis direction 125 a (director direction) of the wave plate 125 may be switched by the control circuit 130.

  In the configuration shown in FIG. 1B, the director direction 122a of the liquid crystal cell 122 is set to 0 ° and −22.5 ° with respect to the slow axis direction 121a (the liquid crystal cell 122 and the wave plate 125 having a phase difference of 3π / 2 are used. In this case, it is possible to switch to 22.5 °. Then, the control circuit 130 controls the liquid crystal cell 122 and the wave plate 125 in synchronization so that the slow axis direction 125 a of the wave plate 125 is the same as the director direction 122 a of the liquid crystal cell 122.

  When the director direction 122 a and the slow axis direction 125 a (director direction) are switched to 0 °, the polarization state of the laser light does not change in the liquid crystal device 120. For this reason, as shown in the polarization state 102, the polarization state of the laser light emitted from the wave plate 126 is linearly polarized at 0 ° with respect to the polarization direction 101.

  When the director direction 122 a and the slow axis direction 125 a (director direction) are switched to −22.5 °, the operation is the same as that shown in FIG. 1A, and the light is emitted from the wave plate 126 as shown in the polarization state 103. The polarization state of the laser beam is 90 ° linear polarization with respect to the polarization direction 101.

  In the configuration shown in FIG. 1B, the director direction 122a and the slow axis direction 125a may be switched between 90 ° and 67.5 °. In the configuration shown in FIG. 1B, the director direction 122a and the slow axis direction 125a may be switched between 90 ° and 112.5 °.

  FIG. 1C is a diagram illustrating a second modification of the optical device. In FIG. 1C, the same parts as those shown in FIG. 1A are denoted by the same reference numerals and description thereof is omitted. When the polarization state of the laser light incident on the liquid crystal device 120 can be limited to 0 ° or 90 ° with respect to the slow axis direction 123a, the wave plates 121 and 126 of the liquid crystal device 120 are omitted as shown in FIG. 1C. It is good also as a structure. Also in this case, the same effect as that of the optical device 100 shown in FIG. 1A can be obtained, and the number of parts can be reduced.

  FIG. 1D is a diagram illustrating a third modification of the optical device. In FIG. 1D, parts similar to those shown in FIG. 1B are denoted by the same reference numerals and description thereof is omitted. When the polarization state of the laser light incident on the liquid crystal device 120 can be limited to 0 ° or 90 ° with respect to the slow axis direction 123a, the wave plates 121 and 126 of the liquid crystal device 120 are omitted as shown in FIG. 1D. It is good also as a structure. Also in this case, the same effect as that of the optical device 100 shown in FIG. 1B can be obtained, and the number of parts can be reduced.

(Chromatic dispersion characteristics of liquid crystal devices)
Next, the wavelength dispersion characteristic of the liquid crystal device 120 will be described. Here, the characteristics of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 in the liquid crystal device 120 will be mainly described, but the same applies to the characteristics of the wave plates 124 to 126 (the same applies hereinafter).

  The action of a general wavelength plate on the polarization state of laser light can be expressed as a Jones matrix, for example, by the following equation (1). Γe indicates retardation (phase difference) of the wave plate. Ψe indicates the azimuth angle of the wave plate. (Vx, Vy) indicates incident polarized light.

  The retardation (phase difference) of the wave plates 121 and 123 is γ1 (= π / 2). The retardation of the liquid crystal cell 122 is γ2 (= π). The azimuth angle Ψ of the liquid crystal cell 122 is an angle of the director direction (slow axis direction) of the liquid crystal cell 122 with respect to the slow axis direction of the wave plates 121 and 123.

  The Jones matrix in the wave plate 121, the liquid crystal cell 122, and the wave plate 123 can be expressed by, for example, the following equation (2). In the following formula (2), “x” indicates a matrix product.

  When the action of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 is regarded as the action of one general wave plate, the Jones matrix shown in the above equation (1) and the Jones matrix shown in the above equation (2) The equation holds in between. From this equation, the retardation Γe of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 can be expressed, for example, by the following equation (3). Further, the azimuth angle Ψe with respect to the incident polarization of the laser light of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 can be expressed by, for example, the following equation (4).

  Here, a case will be described in which the liquid crystal cell 122 is thickened to realize a half-wave plate in the laminated wave plate including the wave plate 121, the liquid crystal cell 122, and the wave plate 123 without using the wave plates 124 to 126. In this case, for example, in order to perform switching between 0 ° and 45 ° in the liquid crystal cell 122, when the ferroelectric liquid crystal is used for the liquid crystal cell 122, the liquid crystal cell 122 is made thick (for example, 18 [μm]). Manufacturing is difficult. Similarly, when a liquid crystal cell having radial electrodes is used for the liquid crystal cell 122, it is necessary to make the liquid crystal cell 122 thick (for example, 20 [μm]), which makes manufacturing difficult. Further, the voltage required for driving for switching needs to be set to be considerably large (± 50 [V] or more).

  On the other hand, the optical device 100 implement | achieves a half-wave plate with the laminated wave plate also including the wave plates 124-126 (or wave plate 124,125), for example as shown in FIG. 1A When switching ± π / 8 (cone angle is 45 °), even if the liquid crystal cell 122 (ferroelectric liquid crystal) is thin (for example, 2 [μm]), switching of linearly polarized light is possible. In addition, the voltage required for driving for switching can be reduced (for example, 2 to 3 [V]).

  For example, when switching between 0 ° and π / 8 (cone angle is 22.5 °) as shown in FIG. 1B, for example, a radial electrode that switches in a lateral electric field is used instead of a ferroelectric liquid crystal. A liquid crystal cell (NLC) can be used. In this case, since the liquid crystal cell (NLC) having radial electrodes is designed as a half-wave plate like the ferroelectric liquid crystal, the thickness is as thin as the ferroelectric liquid crystal (for example, several [μm]) )can do. However, in this case, the voltage required for driving for switching is larger than that of the ferroelectric liquid crystal (approximately ± 50 [V]).

  Further, by increasing the wavelength plate (for example, the wavelength plate 121) of the liquid crystal device 120 (laminated wave plate) different from the liquid crystal cell 122, the thickness of the liquid crystal cell 122 is suppressed and the liquid crystal device 120 is reduced to ½ wavelength. It can be operated as a plate. Therefore, it is possible to realize the liquid crystal device 120 (laminated wave plate) that operates as a half-wave plate while suppressing a decrease in switching characteristics.

  Further, by switching the polarization state between, for example, 0 ° linear polarization and 90 ° linear polarization, it is possible to improve the image quality by reducing the speckle of the image projected with the laser light on the screen. In addition, a polarization filter type three-dimensional image can be generated by switching the polarization state of an image between, for example, 0 ° linear polarization and 90 ° linear polarization.

  Further, the polarization state of laser light including a plurality of primary colors can be controlled by the liquid crystal device 120. For this reason, compared with the case where a polarization control device is provided for each primary color light, for example, the number of parts can be reduced and the device can be downsized.

  The liquid crystal cell 122 may be a liquid crystal cell having a plurality of electrodes that hold the directors in different directions (see, for example, FIGS. 2A to 2D). The direction of the director of the liquid crystal molecules can be switched by rotating parallel to the substrate surface, and the movement of the liquid crystal molecules can be controlled only by the electric field response speed of the liquid crystal using a lateral electric field, so the polarization state of the laser light can be switched at high speed. It can be carried out. By switching the polarization state of the laser light at high speed, it is possible to improve the speckle reduction effect and generate a three-dimensional image with a high frame rate.

(Example of electrode structure of liquid crystal cell)
FIG. 2A is a diagram illustrating Example 1 of an electrode structure of a liquid crystal cell. The liquid crystal cell 122 illustrated in FIG. 2A is the liquid crystal cell 122 viewed from the traveling direction of the laser light (the same applies to FIGS. 2B to 2D). Moreover, the wave plate 125 in the configuration shown in FIG. 1B or the like can also employ the same configuration as the liquid crystal cell 122 (the same applies hereinafter). The electrodes 211 to 218 are electrodes of the liquid crystal cell 122. The electrodes 211 to 218 are provided at angles of 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 °, respectively.

  The electrode 211 and the electrode 215, the electrode 212 and the electrode 216, the electrode 213 and the electrode 217, and the electrode 214 and the electrode 218 are a pair of electrodes. By applying a voltage to the pair of electrodes, the director of the liquid crystal molecules in the liquid crystal cell 122 can be rotated in parallel with the substrate surface, and the director direction 122a can be controlled. For example, by applying a voltage to the electrode 211 and the electrode 215, the director direction 122a of the liquid crystal cell 122 can be controlled to 0 °. Moreover, you may apply a voltage also to electrodes other than the electrode used as a group. Thereby, the director direction 122a of the liquid crystal cell 122 can be controlled over a wider range by balancing the voltage values applied to the electrodes. Thus, since the movement of the liquid crystal molecules can be controlled only by the electric field response speed of the liquid crystal, it can be operated at high speed.

  In this case, the polarization direction of the laser light incident on the liquid crystal device 120 and the slow axis directions 121a and 123a of the wave plates 121 and 123 are 22.5 °, 67.5 °, 112. The direction is either 5 ° or 157.5 °. Thus, by controlling the voltage applied to the electrodes 211 to 218, the director direction 122 a of the liquid crystal cell 122 is set to 22.5 ° and −22.5 ° (or to the slow axis directions 121 a and 123 a of the wave plates 121 and 123 (or 0 ° and −22.5 °) and the like.

  As for the liquid crystal cell 122 shown in FIG. 2A, for example, non-patent literature (Yasuo Ohtera, Takashi Chiba, Shojiro Kawakami, “Liquid Crystal Polarization Control Device by Rotating Electric Field Drive”, Optics, Vol. 30, No. 1, pp. 29-30, The liquid crystal polarization control device described in January 10, 2001) can be used.

  FIG. 2B is a diagram illustrating Example 2 of the electrode structure of the liquid crystal cell. Electrodes 221 to 224 shown in FIG. 2B are electrodes of the liquid crystal cell 122. The electrodes 221 to 224 are provided at angles of 45 °, 90 °, 225 °, and 270 °, respectively. In the liquid crystal cell 122, the director direction 122a may be switched between two directions of 22.5 ° and −22.5 °, for example. Therefore, as shown in FIG. Good.

  In this case, the polarization direction of the laser light incident on the liquid crystal device 120 and the slow axis directions 121a and 123a of the wave plates 121 and 123 are 22.5 °, 67.5 °, 112. The direction is either 5 ° or 157.5 °. Thus, by controlling the voltage applied to the electrodes 221 to 224, the director direction 122a of the liquid crystal cell 122 is set at 22.5 ° and −22.5 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123. You can switch to

  In the configuration shown in FIG. 1B and the like, for example, the electrodes 221 to 224 are provided at angles of 67.5 °, 90 °, 247.5 °, and 270 °, respectively, so that the director direction 122a is set to 0 ° and −22. It is possible to switch to two directions of 5 °.

  FIG. 2C is a diagram illustrating Example 3 of the electrode structure of the liquid crystal cell. Electrodes 231 to 234 shown in FIG. 2C are electrodes of the liquid crystal cell 122. The electrodes 231 to 234 are provided at angles of 0 °, 90 °, 180 °, and 270 °, respectively.

  In this case, the polarization direction of the laser light incident on the liquid crystal device 120 and the slow axis directions 121a and 123a of the wave plates 121 and 123 are 22.5 °, 67.5 °, 112. The direction is either 5 ° or 157.5 °. Thus, by controlling the voltage applied to the electrodes 231 to 234, the director direction 122a of the liquid crystal cell 122 is set at 22.5 ° and −22.5 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123. You can switch to

  1B and the like, the director direction 122a of the liquid crystal cell 122 is set to 0 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123 by controlling the voltage applied to the electrodes 231 to 234. It can be switched to an angle of -22.5 °.

  FIG. 2D is a diagram illustrating Example 4 of the electrode structure of the liquid crystal cell. Electrodes 241 to 248 illustrated in FIG. 2D are electrodes of the liquid crystal cell 122. The electrodes 241 to 248 are provided at angles of 22.5 °, 67.5 °, 112.5 °, 157.5 °, 202.5 °, 247.5 °, 292.5 °, and 337.5 °, respectively. It has been. That is, the electrodes 241 to 248 are obtained by inclining the electrodes 211 to 218 shown in FIG. 2A by 22.5 °, respectively.

  In this case, the polarization direction of the laser light incident on the liquid crystal device 120 and the slow axis directions 121a and 123a of the wave plates 121 and 123 are 0 °, 45 °, 90 °, and 135 ° as shown in the polarization direction 240. Either direction. Thus, by controlling the voltage applied to the electrodes 241 to 248, the director direction 122 a of the liquid crystal cell 122 is set at 22.5 ° and −22.5 ° with respect to the slow axis directions 121 a and 123 a of the wave plates 121 and 123. You can switch to

  1B and the like, the director direction 122a of the liquid crystal cell 122 is set to 0 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123 by controlling the voltage applied to the electrodes 241 to 248. It can be switched to an angle of -22.5 °.

  As shown in FIGS. 2A to 2D, the liquid crystal cell 122 includes a plurality of electrode sets that hold the director direction 122a, so that the director direction 122a can be switched at high speed.

  Specifically, the liquid crystal cell 122 includes a first electrode that holds the director direction 122a in the direction of 22.5 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123, and the direction of the director. , 123 with respect to the slow axis directions 121a, 123a, and a second electrode held in a direction of −22.5 °. The same applies to the wave plate 125 shown in FIG. 1B and the like.

  Further, as in the configuration shown in FIG. 1B, the director direction 122a of the liquid crystal cell 122 is switched to 0 ° and −22.5 ° with respect to the slow axis directions 121a and 123a of the wave plates 121 and 123. For example, the liquid crystal cell 122 and the wave plate 125 may be the liquid crystal cell 122 having radial electrodes with lateral electric fields shown in FIGS. 2A to 2D, for example, instead of the ferroelectric liquid crystal.

(Design of laminated wave plate)
FIG. 3 is a diagram illustrating an example of the operation of the laminated wave plate. 3, the same parts as those shown in FIGS. 1A and 1B are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 3, the x-axis corresponds to the predetermined direction (0 °). The z axis corresponds to the traveling direction of light. It is assumed that retardations of the wave plates 121, 123, 124, and 126 shown in FIG. Further, it is assumed that the azimuth angle (azimuth angle) between the slow axis directions 121a, 123a, 124a, 126a and the predetermined direction in the wave plates 121, 123, 124, 126 is Ψ1.

  The retardation of the liquid crystal cell 122 and the wave plate 125 is assumed to be γ2. Further, it is assumed that the azimuth angle between the director direction 122a and the slow axis direction 125a and the predetermined direction is Ψ2. Here, the directions of the slow axis directions 121a and 123a of the wave plates 121 and 123 are defined as the reference 0 °. In this case, the azimuth angle Ψ1 of the wave plates 121 and 123 is 0 °. Therefore, the azimuth angle Ψ between the wave plates 121 and 123 and the liquid crystal cell 122 is Ψ = Ψ2-Ψ1 = Ψ2.

  The laminated wave plate 120a shown in FIG. 3 virtually illustrates a liquid crystal device including the wave plate 121, the liquid crystal cell 122, and the wave plate 123 as one wave plate (laminated wave plate). A slow axis direction 301 indicates a virtual slow axis direction of the laminated wave plate 120a. An azimuth angle between the slow axis direction 301 of the laminated wave plate 120a and a predetermined direction is Ψe.

  The retardation Γe of the laminated wave plate 120a and the azimuth angle Ψe between the slow axis direction 301 and the predetermined direction of the laminated wave plate 120a are the retardations γ1, γ2 and azimuth angles of the wave plate 121, the liquid crystal cell 122, and the wave plate 123, respectively. By the calculation based on Ψ and Jones matrix, it can be expressed as the above formulas (3) and (4).

  In the above formulas (3) and (4), the retardation γx of the wave plate x (the wave plate 121, the liquid crystal cell 122 and the wave plate 123) changes as shown in the following formula (5) depending on the wavelength of the light passing therethrough. In the following equation (5), Δnx is the refractive index (birefringence) of the wave plate x. Δnx is determined by, for example, the material of the wave plate x and the wavelength λ of light passing therethrough. The wavelength dependence of Δnx will be described later. dx is the thickness of the wave plate x.

  In order to use the laminated wave plate 120a as a quarter wave plate, the retardation of the laminated wave plate 120a may be set to Γe = ± π / 2 × (2n−1) (n is a natural number, ± is + or −). Therefore, cos (Γe / 2) = ± 1 / √2 and sin (Γe / 2) = ± 1 / √2. The liquid crystal cell 122 is designed to be a half-wave plate at a predetermined wavelength (for example, a green wavelength), and γ2 = π. Therefore, sin (γ2 / 2) = 1.

  For example, in order to switch the polarization direction between clockwise circularly polarized light and counterclockwise circularly polarized light, Ψe = 45 ° is required. Therefore, the above equation (4) can be expressed by the above cos (Γe / 2) = ± 1. / √2 and sin (Γe / 2) = ± 1 / √2 and sin (γ2 / 2) = 1, so that sin (2Ψe) = ± √2 · sin (2Ψ) = 1. Therefore, the azimuth angle Ψ between the wave plates 121 and 123 and the liquid crystal cell 122 is 22.5 °, 67.5 °, 112.5 °, or 157.5 °, that is, ψ = π / 8 × (2n− 1).

  Substituting the above equation (5), Ψ = π / 8 × (2n−1), and the wavelength of each laser beam emitted from each light source into the above equation (3), the above equation (3) The material of the wave plates 121 and 123 and the thickness d1 are selected so as to approach ± 1 / √2. Thereby, the laminated wave plate 120a (laminated wave plate) can be operated as a quarter wave plate at the wavelength of each laser beam emitted from each light source.

  For example, it is assumed that the azimuth angle Ψ between the wave plates 121 and 123 and the liquid crystal cell 122 is set to 67.5 ° so that the switching in the liquid crystal cell 122 is easy. Here, the wavelengths of the blue, green, and red laser beams are λB, λG, and λR, respectively. The retardations for the blue, green, and red laser beams in the wave plates 121 and 123 are γ1B, γ1G, and γ1R, respectively. The retardations γ1B, γ1G, and γ1R can be obtained by the above equation (5), the refractive index Δn1 of the wave plates 121 and 123, the thickness d1 of the wave plates 121 and 123, and the wavelengths λB, λG, and λR.

  The retardations for the blue, green, and red laser beams in the liquid crystal cell 122 are γ2B, γ2G, and γ2R, respectively. The retardations γ2B, γ2G, and γ2R can be obtained by the above equation (5), the refractive index Δn2 of the liquid crystal cell 122, the thickness d2 of the liquid crystal cell 122, and the wavelengths λB, λG, and λR.

  By substituting the double angle formula shown in the following equation (6), Ψ = 67.5 °, γ1 = γ1B, γ1G, γ1R, and γ2 = γ2B, γ2G, γ2R into the above equation (3), The following equation (7) can be obtained.

  The above equation (7) can be transformed into the following equation (8) by the product-sum formula.

Further, the refractive index Δn also changes according to the wavelength λ. For example, the refractive index Δn can be approximated by Δn = a + b / λ ² + c / λ ⁴ + d / λ ⁶ ... From the Cauchy dispersion formula. a, b, c, d,... are coefficients inherent to the material of the wave plate. In the following description, the refractive index Δn is approximated by a + b / λ ² + c / λ ⁴ (up to the third term).

  [gamma] 1B, [gamma] 1G, [gamma] 1R, [gamma] 2B, [gamma] 2G, [gamma] 2R can be expressed by the above equation (5) as the following equation (9). However, the coefficients a, b, and c in the wave plates 121 and 123 are a1, b1, and c1, respectively. The coefficients a, b, and c in the liquid crystal cell 122 are a2, b2, and c2, respectively.

  Further, since the liquid crystal cell 122 operates as a half-wave plate at a predetermined wavelength (for example, λG), the thickness d2 of the liquid crystal cell 122 is determined by the coefficients a2, b2, c2 in the liquid crystal cell 122 and the above equation (9).

  Further, by modifying the equation (7), the retardation Γe for the wavelengths λB, λG, and λR in the laminated wave plate 120a can be expressed as the following equation (10).

  The above equation (10) can be transformed into the following equation (11) by the product-sum formula.

  Therefore, the thicknesses d1 of the wave plates 121 and 123 are selected so that the retardation Γe with respect to the wavelengths λB, λG, and λR in the above equation (10) or (11) approaches ± π / 2 × (2n−1). Thus, the laminated wave plate 120a can be operated as a quarter wave plate for each wavelength component of the wavelengths λB, λG, and λR.

  Here, the design of the laminated wave plate 120a made up of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 has been described. However, the laminated wave plate made up of the wave plates 124 to 126 is similarly set, so The laminated wave plate made of can be operated as a quarter wave plate. Therefore, the liquid crystal device 120 including the wave plate 121, the liquid crystal cell 122, and the wave plates 123 to 126 can be operated as a half-wave plate.

  FIG. 4 is a graph showing a first example of retardation characteristics with respect to wavelength when a liquid crystal device is used as a half-wave plate. In FIG. 4, the horizontal axis indicates the wavelength λ [nm] of light. The vertical axis represents the retardation Γe (phase difference) of the liquid crystal device 120.

  The retardation characteristic 411 indicates the change characteristic of the retardation Γe with respect to the wavelength in the liquid crystal device 120 constituted by the wave plate 121, the liquid crystal cell 122, and the wave plates 123 to 126. As shown in the retardation characteristic 411, in the liquid crystal device 120, the retardation Γe periodically changes with respect to the wavelength.

  For example, in the vicinity of 452 [nm] corresponding to blue laser light, the retardation Γe is about π. The retardation Γe is about π even in the vicinity of 518 [nm] corresponding to the green laser beam. Further, also in the vicinity of 640 [nm] corresponding to the red laser beam, the retardation Γe is about π.

  In this way, by designing the thickness d1 of the wave plates 121 and 123 to 126 so that the retardation Γe has a desired value at a plurality of wavelengths to be used, the liquid crystal device 120 is halved at each wavelength component to be used. It can be operated as a wave plate. In this case, the polarization directions of the laser beams incident on the liquid crystal device 120 are aligned (see FIG. 9).

  FIG. 5 is a graph showing a first example of azimuth angle characteristics when a liquid crystal device is used as a half-wave plate. In FIG. 5, the horizontal axis indicates the wavelength λ [nm] of light. The vertical axis represents the azimuth angle Ψe of the liquid crystal device 120.

  An azimuth angle characteristic 511 illustrated in FIG. 5 indicates a change characteristic of the azimuth angle ψe with respect to the wavelength when the liquid crystal cell 122 and the wave plate 125 have the same alignment direction in the liquid crystal device 120. In the liquid crystal device 120, when the alignment directions of the liquid crystal cell 122 and the wave plate 125 are different between + π / 8 and −π / 8, respectively, a laminated wave plate 120a including the wave plate 121, the liquid crystal cell 122, and the wave plate 123 And the laminated wave plate composed of the wave plates 124 to 126 cancel each other, so that the azimuth angle Ψe is substantially 0 °.

  As shown in the azimuth characteristic 511, the liquid crystal device 120 in this case has an azimuth angle Ψe of about 45 ° at each wavelength used (452 [nm], 518 [nm] and 640 [nm]). It has become.

  As shown in FIGS. 4 and 5, the retardation of the liquid crystal device 120 at each wavelength (452 [nm], 518 [nm] and 640 [nm]) to be used is determined by the design of the thickness d1 of the wave plates 121 and 123. Γe can be set to π, and the azimuth angle Ψe of the liquid crystal device 120 can be set to 45 °. For this reason, the polarization direction at the time of emission of each wavelength can be set to 0 ° or 90 °, and each wavelength component output from the liquid crystal device 120 can be made the same linearly polarized light.

  As shown in FIGS. 4 and 5, the laminated wave plate 120a can be operated as a quarter wave plate at each wavelength to be used by designing the thickness d1 of the wave plates 121 and 123. In the example shown in FIGS. 4 and 5, the value of retardation Γe is obtained by switching the azimuth by a combination of Ψ = 3π / 8 and Ψ = 5π / 8 or a combination of Ψ = π / 8 and Ψ = 7π / 8. Can switch the azimuth angle Ψe at each wavelength used to ± 45 °, and the laminated wave plate 120a can be used as a circularly polarized light switching device.

  This is because a ferroelectric liquid crystal having a cone angle of 45 ° or a liquid crystal cell 122 as shown in FIG. It can be realized by switching by a combination of ° and 112.5 ° or a combination of 22.5 ° and 157.5 ° (-22.5 °).

  The laminated wave plate composed of the wave plates 124 to 126 is similarly set and operated as a quarter wave plate, so that the liquid crystal device 120 is operated as a half wave plate and used as a linearly polarized light switching device. can do.

(Configuration using retardation film)
In the above example, a retardation film (for example, a λ / 4 film) having an arbitrary retardation γ3 different from the wave plates 121 and 123 may be used in combination with the wave plates 121 and 123. This makes it possible to perform more flexible adjustment so that the phase difference characteristic and the azimuth angle characteristic match each wavelength used.

  FIG. 6 is a diagram illustrating an example of a laminated wave plate in which retardation films are combined. In FIG. 6, the description of the same parts as those shown in FIG. 3 is omitted. As shown in FIG. 6, for example, a retardation film 601 can be provided between the wave plate 121 and the liquid crystal cell 122. Further, the retardation film 602 can be provided between the wave plate 123 and the wave plate 124.

  Further, the retardation film 603 can be provided between the wave plate 124 and the wave plate 125. Further, the retardation film 604 can be provided at the subsequent stage of the wave plate 126. Moreover, when it is set as the structure which does not provide the wavelength plates 121 and 126, the phase difference films 601 and 604 do not need to be provided.

  The optical axes of the retardation films 601 to 604 can be parallel or perpendicular to the wave plates 121, 123, 124, and 126.

  First, a case where the slow axis of the retardation film (for example, the retardation films 601 to 604) and the slow axis of the wave plates 121 and 123 are made parallel will be described.

  FIG. 7A is a graph illustrating an example of wavelength dispersion characteristics of a retardation film. A retardation characteristic 711 in FIG. 7A indicates a change characteristic of the retardation Γe with respect to the wavelengths of the wave plates 121, 123, 124, and 126. A retardation characteristic 712 indicates a change characteristic of the retardation Γe with respect to the wavelength of the retardation films 601 to 604.

  As the retardation films 601 to 604, a retardation film having a wavelength dispersion different from that of the wave plates 121, 123, 124, and 126 can be applied as in the retardation characteristic 712. And it is designed so that the slow axes of the retardation films 601 to 604 and the wave plates 121, 123, 124, 126 are aligned.

  FIG. 7B is a diagram illustrating an example of a change in retardation characteristics caused by a retardation film. In FIG. 7B, the horizontal axis indicates the wavelength λ [nm] of light. The vertical axis represents retardation Γe (phase difference). A retardation characteristic 721 in FIG. 7B indicates a change characteristic of the retardation Γe when the retardation films 601 to 604 are not provided.

  The retardation characteristic 722 is an appropriate number of retardation films (for example, retardation films 601 to 604) having a retardation characteristic 712 (see FIG. 7A), and the retardation films and the wave plates 121, 123, 124, and 126 are slow. The change characteristic of retardation (GAMMA) e when an axial direction becomes parallel is shown.

  The retardation characteristic 723 is an appropriate number of retardation films (for example, retardation films 601 to 604) having a retardation characteristic 712 (see FIG. 7A), and the retardation films and the wave plates 121, 123, 124, and 126 are slow. The change characteristic of the retardation Γe when the axial directions are orthogonal is shown.

  The characteristics of the retardation Γe of the liquid crystal device 120 can also be adjusted by changing the number of retardation films and the slow axis direction. For example, when the slow axis of the retardation film and the slow axis of the wave plates 121, 123, 124, 126 are orthogonal to each other, the slow axis of the retardation film and the slow axes of the wave plates 121, 123, 124, 126 are Compared to the parallel case, the peak position of the change characteristic of the azimuth angle Ψe can be shifted in the opposite direction as the peak position of the change characteristic of the retardation Γe.

  FIG. 7C is a diagram illustrating an example of a change in azimuth angle characteristics due to the retardation film. In FIG. 7C, the horizontal axis indicates the wavelength λ [nm] of light. The vertical axis represents the azimuth angle Ψe of the liquid crystal device 120. An azimuth angle characteristic 731 illustrated in FIG. 7C indicates a change characteristic of the azimuth angle Ψe when the retardation films 601 to 604 are not provided.

  The azimuth angle characteristic 732 is an appropriate number of retardation films (for example, retardation films 601 to 604) having retardation characteristics 712 (see FIG. 7A), and the retardation film and the wave plates 121, 123, 124, 126 The change characteristic of the azimuth angle Ψe when the slow axis direction is parallel is shown. The azimuth angle characteristic 733 is an appropriate number of retardation films (for example, retardation films 601 to 604) having retardation characteristics 712 (see FIG. 7A), and the retardation film and the wave plates 121, 123, 124, 126 The change characteristic of the azimuth angle Ψe when the slow axis directions are orthogonal is shown.

  FIG. 8 is a graph showing an example of crosstalk characteristics with respect to wavelength. In FIG. 8, the horizontal axis indicates the wavelength λ [nm] of light, and the vertical axis indicates the ratio (crosstalk value) of the outgoing light (I) to the incident light Io of the liquid crystal device 120. The crosstalk characteristic 810 is a characteristic of the crosstalk value with respect to the wavelength after selecting the thickness d1 of the wave plates 121, 123, 124, and 126. The crosstalk characteristic 820 is a characteristic of the crosstalk value with respect to the wavelength when the thickness d1 of the wave plates 121, 123, 124, 126 is not adjusted.

  FIG. 9 is a perspective view showing an example of an optical device. 9, the same parts as those shown in FIG. 1A are denoted by the same reference numerals, and description thereof is omitted. A red light source 901, a green light source 902, and a blue light source 903 shown in FIG. 9 are light sources of respective colors included in the light source unit 110. As illustrated in FIG. 9, polarizing plates 911 to 913 may be provided between the red light source 901, the green light source 902, the blue light source 903, and the liquid crystal device 120.

  Laser beams output from the red light source 901, the green light source 902, and the blue light source 903 are incident on the polarizing plates 911 to 913, respectively. The polarizing plate 911 is a polarizer that transmits only the linearly polarized light component in the transmission polarization direction 921 out of the laser light emitted from the red light source 901 and emits it to the liquid crystal device 120. The polarizing plate 912 is a polarizer that transmits only the linearly polarized light component in the transmission polarization direction 922 out of the laser light emitted from the green light source 902 and emits it to the liquid crystal device 120.

  The polarizing plate 913 is a polarizer that transmits only the linearly polarized light component in the transmission polarization direction 923 out of the laser light emitted from the blue light source 903 and emits it to the liquid crystal device 120. For example, as in the first example shown in FIG. 4, when the retardation Γe matches at each wavelength used, as shown in FIG. 9, the transmission polarization direction 921 of the linearly polarized light component transmitted by the polarizing plates 911 to 913 is shown. -923 are aligned in a predetermined direction. Thereby, each wavelength component output from the liquid crystal device 120 can be made into the same linearly polarized light.

  When the red light source 901, the green light source 902, and the blue light source 903 emit linearly polarized laser light, the polarization directions of the laser beams from the red light source 901, the green light source 902, and the blue light source 903 are respectively transmitted polarization directions. You may adjust the angle of the red light source 901, the green light source 902, and the blue light source 903 so that it may correspond with 921-923 substantially. In this case, the polarizing plates 911 to 913 may be omitted. Thereby, the optical loss in the polarizing plates 911-913 can be suppressed.

  Polarization directions 931 to 933 indicate the polarization directions of the red, green, and blue wavelength components in the laser light emitted from the liquid crystal device 120, respectively. In the example shown in FIG. 9, the polarization directions of the respective wavelength components are linearly polarized light in the same direction.

  FIG. 10 is a graph showing an example of retardation characteristics with respect to the thickness of the wave plate at each wavelength. In FIG. 10, the horizontal axis indicates the thickness d1 of the wave plates 121 and 123. The vertical axis represents the retardation Γe of the laminated wave plate 120 a composed of the wave plate 121, the liquid crystal cell 122, and the wave plate 123. Retardation characteristics 1001 to 1003 indicate the characteristics of retardation Γe with respect to the thickness d1 of the wave plates 121 and 123 at blue, green, and red wavelengths, respectively. A retardation 1004 indicates a retardation of π / 2.

  The manufacturing support apparatus according to the embodiment includes a refractive index Δn1 (λ) of the wave plates 121 and 123, a thickness d2 of the liquid crystal cell 122, a refractive index Δn2 (λ) of the liquid crystal cell 122, the wave plate 121, and the liquid crystal cell. 122 and the retardation Γe for each thickness d1 of the wave plates 121 and 123 based on the angle Ψ between the slow axes of the wave plate 123 and the above formula (10) or (11). Calculate and output the calculation result of retardation Γe for each thickness d1. For example, the manufacturing support apparatus outputs the calculation result of the retardation Γe for each thickness d1 by displaying it as in the graph shown in FIG.

  Thereby, the designer of the liquid crystal device 120 can easily select the thickness d1 of the wave plates 121 and 123 at which the retardation Γe of the laminated wave plate 120a is close to a desired retardation in each wavelength component. For example, by selecting the thickness d1 at the positions indicated by reference numerals 1005 and 1006, the retardation Γe of the laminated wave plate 120a is close to π / 2 at each wavelength component, and the laminated wave plate 120a is ¼ wavelength at each wavelength component. Designs that operate as plates can be made.

  In addition, the wave plates 124 to 126 can be designed to operate as quarter wave plates by adopting configurations corresponding to the wave plate 121, the liquid crystal cell 122, and the wave plate 123 of the laminated wave plate 120a, respectively. .

  Alternatively, the manufacturing support apparatus according to the embodiment includes the refractive index Δn1 (λ) of the wave plates 124 and 126, the thickness d2 of the wave plate 125, the refractive index Δn2 (λ) of the wave plate 125, the wave plate 124, Based on the angle Ψ between the slow axes of the wave plate 125 and the wave plate 126 and the above equation (10) or (11), the retardation for each thickness d1 of the wave plates 124 and 126 for each wavelength component. Γe may be calculated, and the calculation result of retardation Γe for each thickness d1 may be output.

  As described above, the manufacturing support apparatus according to the embodiment outputs the calculation result of the retardation Γe for each thickness d1 for at least one of the laminated wave plate 120a and the laminated wave plate including the wave plates 124 to 126. . Thereby, each of the laminated wave plate 120a and the laminated wave plate composed of the wave plates 124 to 126 is operated as a quarter wave plate, and the liquid crystal device 120 is easily designed as a half wave plate. be able to.

<General conditional expression>
Here, the laminated wave plate 120a including the wave plate 121, the liquid crystal cell 122, and the wave plate 123 will be described, but the same applies to the laminated wave plate including the wave plates 124 to 126. In the above formulas (10) and (11), retardation Γe is shown as Ψ = 67.5 °, but more generally, retardation Γe with respect to wavelength λ can be expressed by the following formula (12).

  That is, the thicknesses d1 of the wave plates 121 and 123 are designed so that the retardation Γe calculated by the following equation (12) approaches ± π / 2 × (2n−1) at each wavelength to be used. Thereby, the laminated wave plate 120a can be operated as a quarter wave plate at each wavelength to be used.

In the equation (12), the refractive index Δn1 (λ) of the wave plates 121 and 123 can be approximated by a1 + b1 / λ ² + c1 / λ ⁴ ... From the above Cauchy dispersion formula. In addition, the refractive index Δn2 (λ) of the liquid crystal cell 122 can be approximated by a2 + b2 / λ ² + c2 / λ ⁴ .

That is, if the coefficients inherent to the materials of the wave plates 121 and 123 are A1, A2, A3,... Am (m is a natural number), the refractive index Δn1 (λ) of the wave plates 121 and 123 is A1 + A2 / λ ² + A3 / It can be approximated by λ ⁴ + A4 / λ ⁶ ... + A (m) / λ ^ (2 (m−1)). Further, if the coefficients inherent to the material of the liquid crystal cell 122 are B1, B2, B3,... Bm, the refractive index Δn2 (λ) of the liquid crystal cell 122 is B1 + B2 / λ ² + B3 / λ ⁴ + B4 / λ ⁶ . m) / λ ^ (2 (m−1)).

  Thus, in the manufacturing method according to the embodiment, first, the thickness d2 of the liquid crystal cell 122 is determined as the first determination step. Further, as the second determination step, the angle Ψ between the slow axes of the wave plate 121, the liquid crystal cell 122, and the wave plate 123 is determined. And as a 3rd determination process, based on each determination result by a 1st determination process and a 2nd determination process, the thickness d1 of the wavelength plates 121 and 123 is 1/4 wavelength for the laminated wavelength plate 120a in each wavelength to use. The thickness is determined to operate as a plate. In addition, you may replace the order of a 1st determination process and a 2nd determination process.

  The thickness d1 of the wave plates 124 and 126 in which the laminated wave plate made of the wave plates 124 to 126 operates as a quarter wave plate is determined by making the same determination for the laminated wave plate made of the wave plates 124 to 126. Can be determined.

  Thereby, the liquid crystal device 120 operates as a half-wave plate at each wavelength to be used, and variation in the polarization direction for each wavelength can be suppressed. Therefore, for example, when the liquid crystal device 120 is used in a projector, the polarization state of each wavelength component of the laser light can be controlled with higher accuracy. Therefore, variation in the extinction ratio of each wavelength component of the laser beam can be suppressed, and the image quality of the image obtained by projecting the laser beam on the screen can be improved.

  For each wavelength component, the polarization state can be switched to, for example, linearly polarized light orthogonal to each other. For this reason, the speckle of each wavelength component of the image which projected the laser beam on the screen can be reduced, and an image quality can be improved more. Also, a linear polarization filter type three-dimensional image can be generated by switching the polarization state of the video to linearly polarized light orthogonal to each other.

  In each wavelength used, the thickness d1 of the wave plates 121, 123, 124, and 126 where the retardation Γe calculated by the above equation (12) is ± π / 2 × (2n−1) may not be determined. obtain. On the other hand, for example, at least one thickness d1 of the wave plates 121, 123, 124, and 126 having a retardation Γe of ± π / 2 × (2n−1) exists in each wavelength band of each laser beam. Thus, it is desirable to design the material of the wave plates 121, 123, 124, 126 and the liquid crystal device 120.

  As each wavelength band of each laser beam, for example, the wavelength band of the blue laser beam is set to 435 to 480 [nm], the wavelength band of the green laser beam is set to 500 to 560 [nm], and the wavelength of the red laser beam is set. The band can be 610 to 750 [nm].

  FIG. 11 is a diagram illustrating an example of a hardware configuration of the manufacturing support apparatus according to the embodiment. The manufacturing support apparatus according to the embodiment can be realized, for example, by an information processing apparatus 1100 illustrated in FIG. The information processing apparatus 1100 includes a CPU 1110, a main memory 1120, an auxiliary memory 1130, a user interface 1140, and a communication interface 1150. The CPU 1110, main memory 1120, auxiliary memory 1130, user interface 1140, and communication interface 1150 are connected by a bus 1101.

  A CPU 1110 (Central Processing Unit) controls the entire information processing apparatus 1100. The main memory 1120 is, for example, a RAM (Random Access Memory). The main memory 1120 is used as a work area for the CPU 1110. The auxiliary memory 1130 is, for example, a nonvolatile memory such as a hard disk, an optical disk, or a flash memory. Various programs for operating the information processing apparatus 1100 are stored in the auxiliary memory 1130. The program stored in the auxiliary memory 1130 is loaded into the main memory 1120 and executed by the CPU 1110.

  The user interface 1140 includes, for example, an input device that receives an operation input from the user, an output device that outputs information to the user, and the like. The input device can be realized by a key (for example, a keyboard) or a remote controller, for example. The output device can be realized by, for example, a display or a speaker. Further, an input device and an output device may be realized by a touch panel or the like. The user interface 1140 is controlled by the CPU 1110.

  The communication interface 1150 is a communication interface that performs communication with the outside of the information processing apparatus 1100 by, for example, wireless or wired communication. The communication interface 1150 is controlled by the CPU 1110.

  For example, the auxiliary memory 1130 stores an arithmetic program for performing an arithmetic operation according to the above formula (10) or (11) or the formula (10) or (11). Further, from the user interface 1140 and the communication interface 1150, the thickness d2, the angle Ψ, the operating wavelengths λB, λG, and λR of the liquid crystal cell 122 (wavelength plate 125) are calculated according to the above formula (10) or (11). Each parameter is input. Each parameter input from the user interface 1140 or the communication interface 1150 is stored in the main memory 1120.

  The CPU 1110 uses the above equation (10) or (11) and the arithmetic program stored in the auxiliary memory 1130 and each parameter stored in the main memory 1120 to retardation each wavelength component for each thickness d1. Γe is calculated. Then, CPU 1110 outputs the relationship between thickness d1 and retardation Γe, for example, via user interface 1140 or communication interface 1150.

  However, the configuration of the information processing apparatus 1100 is not limited to the above. For example, the expression (10) or the expression (11) and the arithmetic program are not stored in the information processing apparatus 1100 but may be stored in an external simulation apparatus. The information processing apparatus 1100 may transmit each parameter to an external simulation apparatus, for example, via the communication interface 1150, receive the calculation result of the retardation Γe for each thickness d1, and output the received calculation result.

(Specific example of liquid crystal cell using ferroelectric liquid crystal)
Next, a specific example of the liquid crystal cell 122 using ferroelectric liquid crystal instead of the liquid crystal cell having the electrode shape shown in FIGS. 2A to 2D will be described. Here, a case where a ferroelectric liquid crystal is used for the liquid crystal cell 122 will be described. Although the liquid crystal cell 122 will be described, the same applies to the wave plate 125 shown in FIG. 1B and the like.

  FIG. 12 is a cross-sectional view showing a specific example of a liquid crystal cell using a ferroelectric liquid crystal. As shown in FIG. 12, in the liquid crystal cell 122, for example, a pair of glass substrates 1231 and 1232 sandwiching a liquid crystal layer 1220 having a thickness of about 2 [μm] and these two glass substrates 1231 and 1232 are bonded. And a sealing material 1270. Electrodes 1241 and 1242 are formed on the opposing surfaces of the glass substrates 1231 and 1232, and alignment films 1251 and 1252 are disposed on the electrodes 1241 and 1242. The electrodes 1241 and 1242 are solid electrodes such as ITO, for example.

  Next, the electro-optic effect of the ferroelectric liquid crystal will be described. 13 and 14 are explanatory views showing the relationship between the molecular major axis direction of the ferroelectric liquid crystal and the electric field. 13 and 14 schematically show liquid crystal molecules when the liquid crystal cell 122 is viewed from the laser light incident side, and the average molecular major axis direction of the liquid crystal will be described with reference to FIGS. 13 and 14. To do. Although the liquid crystal cell 122 will be described, the same applies to the wave plate 125 shown in FIG. 1B and the like.

  As shown in FIG. 13, when an electric field E is applied from the drawing table (the first glass substrate 1231 of the liquid crystal cell 122) toward the back (the second glass substrate 1232 of the liquid crystal cell 122), the liquid crystal molecules LCM The average molecular major axis direction M, which is the first ferroelectric state, is stable at an angle “θ1” about the alignment axis OA of the alignment film. On the other hand, as shown in FIG. 14, when the electric field E is applied from the back to the front, the average molecular major axis direction M, which is the second ferroelectric state of the liquid crystal molecules LCM, is the orientation of the alignment film. It is stable by tilting the angle “θ2” clockwise with respect to the axis OA.

  That is, the liquid crystal molecules LCM are transferred on the cone-shaped side surface that draws the molecular major axis direction M as a moving straight line. The sum (θ1 + θ2) of the angles “θ1” and “θ2” is the average molecular long axis direction of the liquid crystal in the first ferroelectric state and the average molecular length of the liquid crystal in the second ferroelectric state. This is the angle between the axial direction, that is, the central angle θ of the cone (ie, cone angle). By considering various materials for the ferroelectric liquid crystal, the angle of the central angle θ can be set to 45 °. As a result, the director direction 122a (the direction of the liquid crystal molecules) can be switched to the direction parallel to the substrate surface of the liquid crystal cell 122 as described above.

  Further, the wave plates 121, 123, 124, and 126 described above can be formed by a liquid crystal element. Further, electrodes are formed on both surfaces of the liquid crystal layer so that a voltage can be applied in the liquid crystal element. Thereby, the voltage applied to the liquid crystal element can be controlled, and the phase difference of the wave plates 121, 123, 124, 126 can be finely adjusted. In addition, the design and manufacture of the wave plates 121, 123, 124, and 126 are facilitated, and it is possible to cope with changes in the usage environment such as a wavelength shift of the laser beam due to temperature changes.

  As described above, according to the optical device, the projector, the manufacturing method, and the manufacturing support apparatus, a broadband laminated wave plate that operates as a half-wave plate while suppressing a decrease in switching characteristics by reducing the thickness of the liquid crystal cell is realized. can do.

  As described above, the optical device, the projector, the manufacturing method, and the manufacturing support apparatus according to the present invention are useful for the optical device, the projector, the manufacturing method, and the manufacturing support apparatus that project images and images. Suitable for small optical devices.

DESCRIPTION OF SYMBOLS 100 Optical device 101,210,220,230,240,931-933 Polarization direction 102,103 Polarization state 110 Light source part 111 RGB laser light source 112 Polarization-maintaining fiber 120 Liquid crystal device 120a Laminated wave plate 121,123-126 Wave plate 121a , 123a, 124a, 125a, 126a, 301 Slow axis direction 122 Liquid crystal cell 122a Director direction 130 Control circuit 211-218, 221-224, 231-234, 241-248, 1241, 1242 Electrode 411, 711, 712, 721 723, 1001 to 1003 Retardation characteristics 511, 731 to 733 Azimuth angle characteristics 601 to 604 Retardation film 810,820 Crosstalk characteristics 901 Red light source 902 Green light source 903 Blue light source 91 ～913 polarizer 921 to 923 transmitting polarization direction 1004 retardation 1100 information processing apparatus 1101 bus 1110 CPU
1120 Main memory 1130 Auxiliary memory 1140 User interface 1150 Communication interface 1220 Liquid crystal layer 1231, 1232 Glass substrate 1251, 1252 Alignment film 1270 Sealing material

Claims (10)

A polarization state in a predetermined direction and is passed through a plurality of laser beams of different wavelengths, it is possible to switch the direction of the director relative to the predetermined direction in the first direction and the second direction parallel to the substrate surface, the laser beam passing through A liquid crystal cell operating as a half-wave plate at a wavelength of
Operates as a quarter-wave plate at the wavelength of the laser beam, allows each laser beam emitted from the liquid crystal cell to pass, and has a slow axis parallel to the polarization direction of each laser beam incident on the liquid crystal cell or A first vertical wave plate;
A second wavelength that operates as a quarter-wave plate at the wavelength of the laser beam, passes each laser beam emitted from the first wavelength plate, and has a slow axis parallel to the slow axis of the first wave plate The board,
A third wavelength that operates as a half-wave plate at the wavelength of the laser beam, passes each laser beam emitted from the second wavelength plate, and has a slow axis parallel to the first direction or the second direction. The board,
A control circuit that periodically switches the direction of the director;
And outputs each laser beam that has passed through the liquid crystal cell, the first wave plate, the second wave plate, and the third wave plate, and outputs the predetermined direction, the direction of the director, and the delay of the first wave plate. An optical device, wherein a phase axis, a slow axis of the second wave plate, and a slow axis of the third wave plate are directions orthogonal to the traveling directions of the respective laser beams .   The thicknesses of the first wave plate, the second wave plate, and the third wave plate are set such that the liquid crystal cell, the first wave plate, the second wave plate, and the third wave plate have wavelengths of the plurality of laser beams. The optical device according to claim 1, wherein the laminated wave plate constituted by the wave plate is adjusted to a thickness that operates as a half-wave plate. A fourth wave plate provided in a front stage of the liquid crystal cell, allowing each laser beam to pass through the liquid crystal cell, and having the same configuration as the first wave plate;
A fifth wave plate that is provided at a subsequent stage of the third wave plate, passes each laser beam emitted from the third wave plate, and has the same configuration as the second wave plate;
The optical device according to claim 1, further comprising:   The optical device according to claim 1, wherein the third wave plate is a wave plate having a fixed slow axis direction.   The direction of the director can be switched between about 22.5 ° and about −22.5 ° with respect to the predetermined direction, or the angle between the predetermined direction is about 112.5 ° and about 67.67. The optical device according to claim 4, wherein the optical device is switchable so as to be 5 °. The third wave plate is composed of a second liquid crystal cell in which the direction of the director relative to the predetermined direction can be switched between the first direction and the second direction same as the liquid crystal cell (hereinafter referred to as “first liquid crystal cell”). And
The optical device according to claim 1, wherein the control circuit switches the direction of each director of the first liquid crystal cell and the second liquid crystal cell in the same direction in synchronization.   The direction of each director is switchable so that the angle between the predetermined direction is about 0 ° and about 22.5 °, or the angle between the predetermined direction is about 90 ° and about 112.degree. The optical device according to claim 6, wherein the optical device can be switched so as to be 5 °. The optical device according to any one of claims 1 to 7,
A modulator that spatially modulates the laser light;
And a laser beam emitted from the optical device and modulated by the modulator. A polarization state in a predetermined direction and is passed through a plurality of laser beams of different wavelengths, it is possible to switch the direction of the director relative to the predetermined direction in the first direction and the second direction parallel to the substrate surface, the laser beam passing through A liquid crystal cell that operates as a half-wave plate at the wavelength of the liquid crystal, and a liquid crystal cell that operates as a quarter-wave plate at the wavelength of the laser light, passes each laser light emitted from the liquid crystal cell , and the slow axis is the liquid crystal A first wavelength plate that is parallel or perpendicular to the polarization direction of each laser beam incident on the cell, and each laser beam that operates as a quarter-wave plate at the wavelength of the laser beam and is emitted from the first wavelength plate And the second phase plate whose slow axis is parallel to the slow axis of the first wave plate and the half wave plate at the wavelength of the laser beam, and emitted from the second wave plate Each A third wavelength plate that transmits light and whose slow axis is parallel to the first direction or the second direction, and a control circuit that periodically switches the direction of the director, the liquid crystal cell, the first Each laser beam that has passed through the wave plate, the second wave plate, and the third wave plate is output, and the predetermined direction, the director direction, the slow axis of the first wave plate, and the slow wave of the second wave plate. In the method of manufacturing an optical device, wherein the phase axis and the slow axis of the third wavelength plate are directions orthogonal to the traveling directions of the laser beams, respectively .
A first determining step for determining a thickness of the liquid crystal cell and the third wave plate ;
A second determining step of determining an angle between each slow axis of the first wave plate and the liquid crystal cell and an angle between each slow axis of the second wave plate and the third wave plate; ,
Based on the thickness determined by the first determination step and the angle determined by the second determination step, the thicknesses of the first wavelength plate and the second wavelength plate are determined for each of the emitted laser beams. A third determining step for determining a thickness at which a laminated wave plate constituted by the liquid crystal cell, the first wave plate, the second wave plate, and the third wave plate operates as a half wave plate at a wavelength;
The manufacturing method characterized by including. A laser beam having a wavelength λ1 and a polarization state in a predetermined direction and a laser beam having a wavelength λ2 and a polarization state different from the wavelength λ1 are passed, and the direction of the director relative to the predetermined direction is the first direction and the first direction parallel to the substrate surface A liquid crystal cell that can be switched in two directions and operates as a half-wave plate at the wavelength of the passing laser beam, and operates as a quarter-wave plate at the wavelength of the laser beam and is emitted from the liquid crystal cell. A first wavelength plate that transmits laser light and whose slow axis is parallel or perpendicular to the polarization direction of the laser light incident on the liquid crystal cell, and operates as a quarter wavelength plate at the wavelength of the laser light, Each laser beam emitted from the first wavelength plate is allowed to pass, and operates as a second wavelength plate whose slow axis is parallel to the slow axis of the first wavelength plate, and a ½ wavelength plate at the wavelength of the laser beam. and, A third wavelength plate that passes each laser beam emitted from the second wavelength plate and whose slow axis is parallel to the first direction or the second direction, and a control circuit that periodically switches the direction of the director; And outputs each laser beam that has passed through the liquid crystal cell, the first wave plate, the second wave plate, and the third wave plate , the predetermined direction, the direction of the director, and the first wave plate In a manufacturing support apparatus for supporting the manufacture of an optical device in which the slow axis, the slow axis of the second wave plate, and the slow axis of the third wave plate are directions orthogonal to the traveling directions of the laser beams, respectively . ,
About at least one of the liquid crystal cell and the first wave plate, the second wave plate and the third wave plate,
The thickness d1 of the first wave plate or the second wave plate, the refractive index Δn1 (λ) of the first wave plate or the second wave plate that changes according to the wavelength λ of the light passing therethrough, the liquid crystal cell or the The thickness d2 of the third wave plate, the refractive index Δn2 (λ) of the liquid crystal cell or the third wave plate that changes according to the wavelength λ of the light passing therethrough, and the slow axes of the first wave plate and the liquid crystal cell Or the angle ψ between the slow axes of the second wave plate and the third wave plate, respectively, the first wave plate at λ = λ1 and λ = λ2, respectively, A storage unit storing a program for calculating the following equation for each thickness d1 of the second wave plate ;
A calculation unit that performs the calculation according to the program stored in the storage unit and outputs a result of the calculation;
Production support device, characterized in that it comprises a.

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