Phase difference modulation device

Abstract

To provide a phase difference modulation device capable of shortening the time from a light refraction state to a change in the refraction state.SOLUTION: The phase difference modulation device 1 includes a first substrate 10 in which a first electrode 42 and a second electrode 43 are disposed at positions adjacent to each other in plan view, a second substrate 20 in which a third electrode 50 overlapping the first electrode 42 and the second electrode 43 in plan view is disposed, a liquid crystal layer 30 disposed between the first substrate 10 and the second substrate 20, and a control circuit 3 that applies a voltage to the first electrode 42, the second electrode 43, and the third electrode 50. When switching from a state in which the potential of the first electrodes 42 is the first potential E1 and the potential of the second electrodes 43 is the second potential E1 higher than the first potential E2 to a state in which the potential of the second electrodes 43 is the first potential E1 and the potential of the first electrodes 42 is the predetermined potential, the control circuit 3 sets the potential of the first electrodes 42 to the predetermined potential after setting the potential of the first electrodes 42 from the first potential E1 to the third potential E3 higher than the predetermined potential.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a phase difference modulation device. [Background technology]

[0002] Patent Document 1 discloses, as an example of a phase difference modulation device, a liquid crystal element that refracts and emits light. In the phase difference modulation device of Patent Document 1, when a voltage is applied to the first electrode and the second electrode and the potential of the first electrode differs from that of the second electrode, a potential gradient is generated in the high-resistance layer, causing the liquid crystal molecules to tilt. In this case, the tilt of the liquid crystal molecules causes light to be refracted. On the other hand, when no voltage is applied to the first electrode and the second electrode and the potential of the first electrode is equal to that of the second electrode, no potential gradient is generated in the high-resistance layer, causing the liquid crystal molecules to not tilt. In this case, light is not refracted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 117604 Summary of the Invention [Problem to be solved by the invention]

[0004] In the phase difference modulation device of Patent Document 1, when a voltage is applied to the first and second electrodes, causing light to be refracted, and the state changes from a state in which light is refracted to a state in which light is not refracted, the liquid crystal molecules change from a tilted state to a non-tilted state. At this time, the liquid crystal molecules move due to the elasticity of the liquid crystal layer, and therefore the movement speed of the liquid crystal molecules is slower than when a voltage is applied to the first and second electrodes, causing the tilted state of the liquid crystal molecules to change. Therefore, it takes a relatively long time for the state to change from a state in which light is refracted to a state in which light is refracted.

[0005] An object of the present disclosure is to provide a phase difference modulation device that can shorten the time it takes for light to change from a refracted state to a different refracted state. [Means for solving the problem]

[0006] The phase difference modulation device of the present disclosure comprises a first substrate on which a first electrode and a second electrode are arranged adjacent to each other in a planar view; a second substrate on which a third electrode is arranged so as to overlap the first electrode and the second electrode in a planar view; a liquid crystal layer arranged between the first substrate and the second substrate; and a control circuit that applies voltages to the first electrode, the second electrode, and the third electrode and imparts a phase difference to electromagnetic waves passing through the liquid crystal layer, wherein when switching from a state in which the potential of the first electrode is a first potential and the potential of the second electrode is a second potential higher than the first potential to a state in which the potential of the second electrode is the first potential and the potential of the first electrode is a predetermined potential, the control circuit changes the potential of the first electrode from the first potential to a third potential higher than the predetermined potential and then to the predetermined potential. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a conceptual diagram of a phase difference modulation device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view of a phase difference modulation element according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view of the phase difference modulation element taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a diagram showing the relationship between the potentials of the first electrode and the second electrode and the amount of change in the phase of emitted light passing through the liquid crystal layer. [Figure 5] FIG. 5 is a diagram showing the potential of the electrical resistance film and the phase difference of the emitted light passing through the liquid crystal layer when the phase difference modulation element refracts the emitted light along the fourth direction. [Figure 6] FIG. 6 is a diagram showing the potential of the electrical resistance film and the phase difference of the emitted light passing through the liquid crystal layer when the phase difference modulation element refracts the emitted light along the fifth direction. [Figure 7] FIG. 7 is a time chart of the potential of the first electrode and the potential of the second electrode in the first switching operation of the comparative example. [Figure 8] FIG. 8 is a time chart showing the amount of phase change of emitted light at the first liquid crystal portion and the second liquid crystal portion in the first switching operation of the comparative example. [Figure 9] FIG. 9 is a time chart of the phase difference between the light emitted from the first liquid crystal portion and the light emitted from the second liquid crystal portion in the first switching operation of the comparative example. [Figure 10] FIG. 10 is a time chart of the potential of the first electrode and the potential of the second electrode in the first switching operation according to the embodiment of the present disclosure. [Figure 11] FIG. 11 is a time chart showing the amount of phase change of emitted light at the first liquid crystal portion and the second liquid crystal portion in the first switching operation according to the embodiment of the present disclosure. [Figure 12] FIG. 12 is a time chart of the phase difference between the light emitted from the first liquid crystal portion and the light emitted from the second liquid crystal portion in the first switching operation according to the embodiment of the present disclosure. [Figure 13] FIG. 13 is a time chart of the potential of the first electrode and the potential of the second electrode in the second switching operation of the comparative example. [Figure 14] FIG. 14 is a time chart showing the amount of phase change of emitted light at the first liquid crystal portion and the second liquid crystal portion in the first switching operation of the comparative example. [Figure 15] FIG. 15 is a time chart of the phase difference between the light emitted from the first liquid crystal portion and the light emitted from the second liquid crystal portion in the second switching operation of the comparative example. [Figure 16] FIG. 16 is a time chart of the potential of the first electrode and the potential of the second electrode in the second switching operation according to the embodiment of the present disclosure. [Figure 17] FIG. 17 is a time chart showing the amount of phase change between the emitted light at the first liquid crystal portion and the second liquid crystal portion in the second switching operation according to the embodiment of the present disclosure. [Figure 18] FIG. 18 is a time chart of the phase difference between the light emitted from the first liquid crystal portion and the light emitted from the second liquid crystal portion in the second switching operation according to the embodiment of the present disclosure. [Figure 19] FIG. 19 is a plan view of a phase difference modulation element included in a phase difference modulation device according to a modified example of an embodiment of the present disclosure. [Figure 20]FIG. 20 is a cross-sectional view of the phase difference modulation element taken along the line XX-XX shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

[0009] It should be noted that the disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive of while maintaining the gist of the present disclosure are naturally included within the scope of the present disclosure. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with respect to the previous drawings may be given the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0010] The first direction D1 and second direction D2 shown in the drawings correspond to directions parallel to the plate surfaces of substrates included in the phase difference modulation element 2, which will be described later. The first direction D1 and second direction D2 correspond to the sides of the phase difference modulation element 2. In the first direction D1, the side indicated by the arrow is the +D1 side, and the side opposite the +D1 side is the -D1 side. In the second direction D2, the side indicated by the arrow is the +D2 side, and the side opposite the +D2 side is the -D2 side.

[0011] The third direction D3 corresponds to the thickness direction of the phase difference modulation element 2. In the third direction D3, the side indicated by the arrow is the +D3 side, and the side opposite the +D3 side is the -D3 side. The +D3 side of the third direction D3 corresponds to the front side of the phase difference modulation element 2, and the -D3 side of the third direction D3 corresponds to the rear side of the phase difference modulation element 2. In this specification, "plan view" means viewing the phase difference modulation element 2 along the third direction D3. Note that the first direction D1, the second direction D2, and the third direction D3 are merely examples, and the present disclosure is not limited to these directions.

[0012] 1 is a conceptual diagram of a phase difference modulation device 1 according to an embodiment of the present disclosure. The phase difference modulation device 1 includes a phase difference modulation element 2 and a control circuit 3.

[0013] The phase difference modulation element 2 is a refraction plate that refracts electromagnetic waves. Electromagnetic waves include visible light and radio waves. Below, a case will be described in which the phase difference modulation element 2 refracts emitted light L, which is visible light emitted from a light source S. The light source S is, for example, a lighting device such as a vehicle headlight or a spotlight. The emitted light L is incident on the phase difference modulation element 2.

[0014] The phase difference modulation element 2 has a state in which it transmits the emitted light L without changing the direction in which the emitted light L travels (emission direction), as indicated by the solid arrow, and a state in which it refracts the emitted light L along one of the two directions indicated by the dashed arrow (details will be described later).

[0015] Fig. 2 is a plan view of a phase difference modulation element 2 according to an embodiment of the present disclosure. Fig. 3 is a cross-sectional view of the phase difference modulation element 2 taken along line III-III shown in Fig. 2. The cross-sectional view of the phase difference modulation element 2 shown in Fig. 3 shows the cross-sectional shape of the phase difference modulation element 2 cut along a plane perpendicular to the first direction D1.

[0016] The phase difference modulation element 2 includes a first substrate 10, a second substrate 20, and a liquid crystal layer 30. The first substrate 10 and the second substrate 20 overlap each other in a planar view. The first substrate 10 and the second substrate 20 are light-transmitting. The first substrate 10 and the second substrate 20 are, for example, a glass substrate, a resin substrate, or a resin film.

[0017] A plurality of element groups 40, an insulating layer IL, and a first alignment film AL1 are arranged on the first substrate 10. Each element group 40 includes an electrically resistive film 41, a first electrode 42, and a second electrode 43.

[0018] 2, the multiple electrical resistance films 41 are arranged in a matrix along the first direction D1 and the second direction D2 in a plan view. In a plan view, the multiple electrical resistance films 41 have a rectangular shape whose length in the first direction D1 is longer than its length in the second direction D2. In a plan view, the multiple electrical resistance films 41 overlap with a refractive region RA that refracts the emitted light L.

[0019] The electrical resistance value of the electrical resistance film 41 is greater than the electrical resistance values ​​of the first electrode 42 and the second electrode 43. The material of the electrical resistance film 41 is a conductive material having light transmission properties, such as zinc oxide (ZnO) and IGZO (Indium Gallium Zinc Oxide).

[0020] The electrical resistance film 41 is electrically connected to the first electrode 42 and the second electrode 43 on the -D3 side.

[0021] The first electrode 42 extends in the first direction D1 in a plan view and overlaps with the electrically resistive film 41 on the first end side (+D2 side) of the electrically resistive film 41 in the second direction D2. The first electrode 42 is in contact with the electrically resistive film 41.

[0022] The second electrode 43 extends in the first direction D1 in plan view and overlaps with the electrical resistance film 41 on the second end side (-D2 side) of the electrical resistance film 41 in the second direction D2. The second electrode 43 is in contact with the electrical resistance film 41.

[0023] The first electrode 42 and the second electrode 43 are opposed to each other in the second direction D2 in a plan view and overlap with the electrically resistive film 41. In other words, the first electrode 42 and the second electrode 43 are disposed adjacent to each other in a plan view.

[0024] In the electrically resistive film 41, a portion overlapping with the first electrode 42 in a planar view is defined as a first overlapping portion 41a, a portion overlapping with the second electrode 43 in a planar view is defined as a second overlapping portion 41b, and a portion between the first overlapping portion 41a and the second overlapping portion 41b is defined as an intermediate portion 41c. In the second direction D2, the length of the intermediate portion 41c is longer than the combined length of the first overlapping portion 41a and the second overlapping portion 41b.

[0025] The plurality of element groups 40 are disposed on an insulating layer IL. The first alignment film AL1 is disposed on the +D3 side of the plurality of element groups 40 and the insulating layer IL.

[0026] On the second substrate 20, a third electrode 50 and a second alignment film AL2 are arranged.

[0027] The third electrode 50 overlaps, in plan view, the plurality of electrically resistive films 41. The third electrode 50 also overlaps, in plan view, the first electrode 42 and the second electrode 43.

[0028] The first electrode 42, the second electrode 43, and the third electrode 50 are made of a conductive material having light transmission properties, such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IGO (Indium Gallium Oxide), and IGZO (Indium Gallium Zinc Oxide).

[0029] The second alignment film AL2 is disposed on the −D3 side of the third electrode 50.

[0030] The liquid crystal layer 30 is disposed between the first substrate 10 and the second substrate 20. The liquid crystal layer 30 is sandwiched between a first alignment film AL1 and a second alignment film AL2. The first alignment film AL1 and the second alignment film AL2 determine the alignment (initial alignment) of the liquid crystal molecules LM contained in the liquid crystal layer 30 when no voltage is applied to the phase difference modulation element 2. The initial alignment of the liquid crystal molecules LM is a direction in which the long axes of the liquid crystal molecules LM are perpendicular to the third direction D3 (horizontal alignment). The alignment direction of the first alignment film AL1 and the alignment direction of the second alignment film AL2 are perpendicular to each other in a planar view.

[0031] The retardation modulation element 2 is a twisted nematic (TN) liquid crystal element, although it goes without saying that the retardation modulation element 2 is not limited to a twisted nematic liquid crystal element.

[0032] The control circuit 3 controls the phase difference modulation element 2. Specifically, the control circuit 3 applies a voltage (AC voltage) to the first electrode 42, the second electrode 43, and the third electrode 50, thereby imparting a phase difference to an electromagnetic wave (emitted light L) passing through the liquid crystal layer 30. As a result, the emitted light L is refracted by the phase difference modulation element 2. In this embodiment, the control circuit 3 applies a reference potential (0 V) to the third electrode 50. It goes without saying that the potential of the third electrode 50 is not limited to the reference potential (0 V). Below, a case will be described in which the alignment direction of the first alignment film AL1 is along the second direction D2, and the emitted light L is linearly polarized light having a polarization direction along the second direction D2.

[0033] FIG. 4 is a diagram showing the relationship between the potentials of the first electrode 42 and the second electrode 43 and the amount of phase change of the emitted light L passing through the liquid crystal layer 30. The potentials shown in FIG. 4 correspond to the effective values ​​of the AC voltage (this also applies to FIGS. 5, 6, 7, 10, 13, and 16, which will be described later). Note that the potentials shown in FIG. 4 may also be the maximum and average values ​​of the AC voltage. Specifically, FIG. 4 shows the relationship between the potentials of the first electrode 42 and the second electrode 43 and the amount of phase change (hereinafter referred to as the amount of phase change) of the emitted light L passing through the liquid crystal layer 30 when the potentials of the first electrode 42 and the second electrode 43 change with respect to the potential of the third electrode 50 while the potentials of the first electrode 42 and the second electrode 43 are equal to each other. In other words, the potentials shown in FIG. 4 correspond to the potential difference with respect to the potential of the third electrode 50 (which is the reference potential (0 V) in this embodiment) (this also applies to FIGS. 5, 6, 7, 10, 13, and 16, which will be described later).

[0034] 4, when the degree of tilt of the long axes of the liquid crystal molecules LM from the initial alignment (horizontal alignment) of the liquid crystal molecules LM is at its maximum (i.e., when the long axes of the liquid crystal molecules LM are parallel to the third direction D3), the amount of phase change of the output light L passing through the liquid crystal layer 30 is 0 (nm), and the phase of the output light L passing through the liquid crystal layer 30 does not change. As the long axes of the liquid crystal molecules LM tilt from a state parallel to the third direction D3 and approach the state of the initial alignment (horizontal alignment) of the liquid crystal molecules LM, the amount of phase change decreases from 0, and the phase of the output light L lags.

[0035] In this embodiment, when the potentials of the first electrode 42 and the second electrode 43 are at the reference potential (0 (V)), the liquid crystal molecules LM are initially aligned (horizontally aligned), and the amount of phase change of the emitted light L passing through the liquid crystal layer 30 is minimum (first phase P1). In other words, when the potentials of the first electrode 42 and the second electrode 43 are 0, the phase of the emitted light L passing through the liquid crystal layer 30 is delayed the most. Note that when no potential is applied to the phase difference modulation element 2, the potentials of the first electrode 42, the second electrode 43, and the third electrode 50 are 0, and the amount of phase change of the emitted light L passing through the liquid crystal layer 30 is minimum.

[0036] As the potentials of the first electrode 42 and the second electrode 43 increase, the degree of tilt of the liquid crystal molecules LM increases from the initial alignment (horizontal alignment), and the amount of phase change of the emitted light L passing through the liquid crystal layer 30 increases (i.e., the phase delay decreases). Note that the relationship between the potentials of the first electrode 42 and the second electrode 43 and the amount of phase change of the emitted light L passing through the liquid crystal layer 30 shown in Fig. 4 is an example, and it goes without saying that the relationship is not limited to that shown in Fig. 4.

[0037] When no voltage is applied to the phase difference modulation element 2, or when the potential of the first electrode 42 and the potential of the second electrode 43 are equal, the amount of phase change of the output light L passing through the liquid crystal layer 30 is equal at all parts of the liquid crystal layer 30, and no phase difference is generated in the output light L. Therefore, the phase difference modulation element 2 outputs the output light L without refracting it. Specifically, as shown in FIG. 3, the phase difference modulation element 2 outputs the output light L incident along the third direction D3 without refracting it. Note that the symbol in parentheses attached to the output light L indicates the traveling direction of the output light L. Also, in FIG. 3, the output light L output from the phase difference modulation element 2 is shown on the +D3 side of the phase difference modulation element 2.

[0038] On the other hand, when a voltage is applied to the phase difference modulation element 2 so that the potential of the first electrode 42 and the potential of the second electrode 43 are different from each other, the tilt degrees of the plurality of liquid crystal molecules LM in the liquid crystal layer 30 are different from each other, and as will be described later, a phase difference occurs in the outgoing light L passing through the liquid crystal layer 30. In this case, the phase difference modulation element 2 refracts the outgoing light L and emits it.

[0039] Next, the operation of the phase difference modulation element 2 when refracting the light L emitted from the light source S will be described. The light L is incident on the phase difference modulation element 2 from the back surface of the first substrate 10 along the third direction D3. The phase difference modulation element 2 refracts the light L and emits it along the fourth direction D4 or the fifth direction D5. In this embodiment, the angle between the third direction D3 and the fourth direction D4 is equal to the angle between the third direction D3 and the fifth direction D5.

[0040] 5 is a diagram showing the potential of the electrical resistance film 41 when the phase difference modulation element 2 refracts the emitted light L along the fourth direction D4, and the phase difference of the emitted light L passing through the liquid crystal layer 30. The fourth direction D4 is a direction inclined toward the +D2 side from the third direction D3 as shown in FIG.

[0041] The horizontal axis in Fig. 5 represents the position (coordinate) in the X direction. The symbols in parentheses are the symbols of the parts of the electrical resistance film 41 shown in Fig. 3, and the arrows corresponding to the symbols indicate the range of the parts of the electrical resistance film 41 corresponding to the symbols.

[0042] When the phase difference modulation element 2 refracts the emitted light L along the fourth direction D4, the control circuit 3 applies a first potential E1 to the first electrode 42 and a second potential E2 higher than the first potential E1 to the second electrode 43. In this embodiment, the first potential E1 is equal to the potential of the third electrode 50. That is, in this embodiment, the first potential E1 is the reference potential (0 (V)) of the control circuit 3 (i.e., in this embodiment, the first potential E1=0 (V)).

[0043] In this case, in one electrically resistive film 41, the potential of the second overlapping portion 41b in contact with the second electrode 43 is equal to the second potential E2. In addition, in one electrically resistive film 41, the potential of the intermediate portion 41c between the first electrode 42 and the second electrode 43 changes linearly from the second potential E2 to the first potential E1 from the −D2 side to the +D2 side in the second direction D2. Furthermore, in one electrically resistive film 41, the potential of the first overlapping portion 41a in contact with the first electrode 42 is equal to the first potential E1.

[0044] Furthermore, the control circuit 3 applies a first potential E1 (reference potential (0V)) to the third electrode 50. The potential difference between the first potential E1 and the second potential E2 is determined based on the angle between the third direction D3 and the fourth direction D4. In other words, the degree of inclination of the fourth direction D4 with respect to the third direction D3 can be adjusted by the potential difference between the first potential E1 and the second potential E2.

[0045] An electric field generated by applying a potential to the first electrode 42, the second electrode 43, and the third electrode 50 acts on the liquid crystal layer 30, tilting the liquid crystal molecules LM and imparting the phase shift amount shown in Fig. 4 to the emitted light L. This changes the refractive index of the emitted light L in the liquid crystal layer 30 in the second direction D2, and a phase difference is generated in the emitted light L passing through the liquid crystal layer 30.

[0046] Specifically, in the liquid crystal layer 30 shown in FIG. 3, the phase change amount of the output light L at the first liquid crystal portion 31 between the first electrode 42 and the third electrode 50 is a first phase P1 when the potential of the first electrode 42 is a first potential E1 (0 (V) in this embodiment) as shown in FIG. 4. Also, in the liquid crystal layer 30 shown in FIG. 3, the phase change amount of the output light L at the second liquid crystal portion 32 between the second electrode 43 and the third electrode 50 is a second phase P2 larger than the first phase P1 when the potential of the second electrode 43 is a second potential E2 larger than the first potential E1 as shown in FIG. 4. Therefore, the magnitude of the phase difference between the output light L passing through the first liquid crystal portion 31 and the output light L passing through the second liquid crystal portion 32 corresponds to a first phase difference PD1, which is the difference between the first phase P1 and the second phase P2. The first phase difference PD1 corresponds to the magnitude of the phase difference of the output light L corresponding to a first potential difference ED1 between the first potential E1 and the second potential E2.

[0047] The solid line shown in Figure 5 indicating the phase difference of the emitted light L passing through the liquid crystal layer 30 indicates a trajectory of the same phase as the reference phase, with the phase at the position corresponding to the end of the first liquid crystal portion 31 closest to -D2 in the second direction D2 being used as the reference (i.e., the phase difference is 0 (nm)).

[0048] The phase difference of the output light L passing through the liquid crystal layer 30 varies in a zigzag pattern between 0 and the first phase difference PD1 along the second direction D2. Specifically, the phase difference of the output light L at the second liquid crystal portion 32 corresponding to the second overlapping portion 41b is the first phase difference PD1. The phase difference of the output light L at the portion of the liquid crystal layer 30 corresponding to the intermediate portion 41c varies linearly from the first phase difference PD1 to 0 from the -D2 side to the +D2 side in the second direction D2. Furthermore, the phase difference of the output light L at the first liquid crystal portion 31 corresponding to the first overlapping portion 41a is 0.

[0049] The phase difference of the emitted light L between two adjacent electrical resistance films 41 in the second direction D2 changes linearly from 0 to the first phase difference PD1 from the −D2 side to the +D2 side in the second direction D2.

[0050] The degree of inclination of the phase difference of the output light L in the portion of the liquid crystal layer 30 corresponding to the intermediate portion 41c corresponds to the angle between the third direction D3 and the fourth direction D4. In addition, in the second direction D2, the length of the portion of the liquid crystal layer 30 corresponding to the intermediate portion 41c is longer than the combined length of the portions of the liquid crystal layer 30 corresponding to the first overlapping portion 41a and the second overlapping portion 41b.

[0051] As shown in FIG. 5, the phase difference of the emitted light L passing through the liquid crystal layer 30 changes, so that the emitted light L is refracted by the liquid crystal layer 30 and is emitted from the phase difference modulation element 2 along the fourth direction D4.

[0052] 6 is a diagram showing the potential of the electrical resistance film 41 when the phase difference modulation element 2 refracts the emitted light L along a fifth direction D5, and the phase difference of the emitted light L passing through the liquid crystal layer 30. The fifth direction D5 is a direction inclined from the third direction D3 toward the -D2 side as shown in FIG.

[0053] When the phase difference modulation element 2 refracts the emitted light L in the fifth direction D5, the control circuit 3 applies the second potential E2 to the first electrode 42 and the first potential E1 to the second electrode 43.

[0054] 6, in one electrical resistive film 41, the potential of the second overlapping portion 41b in contact with the second electrode 43 is equal to the first potential E1. In addition, in one electrical resistive film 41, the potential of the intermediate portion 41c changes linearly from the first potential E1 to the second potential E2 from the −D2 side to the +D2 side in the second direction D2. Furthermore, in one electrical resistive film 41, the potential of the first overlapping portion 41a in contact with the first electrode 42 is equal to the second potential E2.

[0055] Furthermore, a first potential E1 is applied to the third electrode 50 by the control circuit 3. The potential difference between the first potential E1 and the second potential E2 is determined based on the angle between the third direction D3 and the fifth direction D5. Therefore, the degree of inclination of the fifth direction D5 with respect to the third direction D3 can be adjusted by the potential difference between the first potential E1 and the second potential E2.

[0056] An electric field generated by applying a potential to the first electrode 42, the second electrode 43, and the third electrode 50 acts on the liquid crystal layer 30, tilting the liquid crystal molecules LM and imparting the phase shift amount shown in Fig. 4 to the emitted light L. This changes the refractive index of the emitted light L in the liquid crystal layer 30 in the second direction D2, and a phase difference is generated in the emitted light L passing through the liquid crystal layer 30.

[0057] Specifically, since the potential of the first electrode 42 is the second potential E2 and the potential of the second electrode 43 is the first potential E1, the magnitude of the difference between the phase of the emitted light L passing through the first liquid crystal portion 31 and the phase of the emitted light L passing through the second liquid crystal portion 32 corresponds to the first phase difference PD1, which is the magnitude of the difference between the first phase P1 and the second phase P2.

[0058] The solid line shown in Figure 6 indicating the phase difference of the emitted light L passing through the liquid crystal layer 30 indicates a trajectory of the same phase as the reference phase (i.e., the phase difference is 0) at the position corresponding to the end of the second liquid crystal portion 32 closest to +D2 in the second direction D2.

[0059] The phase difference of the output light L passing through the liquid crystal layer 30 varies in a zigzag pattern between 0 and the first phase difference PD1 along the second direction D2. Specifically, the phase difference of the output light L at the second liquid crystal portion 32 corresponding to the second overlapping portion 41b is 0. The phase difference of the output light L at the portion of the liquid crystal layer 30 corresponding to the intermediate portion 41c varies linearly from 0 to the first phase difference PD1 from the -D2 side to the +D2 side in the second direction D2. Furthermore, the phase difference of the output light L at the first liquid crystal portion 31 corresponding to the first overlapping portion 41a is the first phase difference PD1.

[0060] The phase difference of the emitted light L between two adjacent electrical resistance films 41 in the second direction D2 changes linearly from the first phase difference PD1 to 0 from the −D2 side to the +D2 side in the second direction D2.

[0061] The degree of inclination of the phase difference of the emitted light L in the portion of the liquid crystal layer 30 corresponding to the intermediate portion 41c corresponds to the angle formed between the third direction D3 and the fifth direction D5.

[0062] As shown in FIG. 6, the phase difference of the outgoing light L passing through the liquid crystal layer 30 changes, so that the outgoing light L is refracted by the liquid crystal layer 30 and is emitted from the phase difference modulation element 2 along a fifth direction D5.

[0063] Next, a first switching operation of the phase difference modulation element 2 will be described, in which the phase difference modulation element 2 switches from a state in which it emits the output light L along the fourth direction D4 to a state in which it emits the output light L along the third direction D3. In the first switching operation, the control circuit 3 switches from a state in which the potential of the first electrode 42 is the first potential E1 and the potential of the second electrode 43 is the second potential E2 higher than the first potential E1 to a state in which the potential of the second electrode 43 and the potential of the first electrode 42 are each the first potential E1 (corresponding to the "predetermined potential" in the first switching operation).

[0064] Fig. 7 is a time chart of the potential of the first electrode 42 and the potential of the second electrode 43 in the first switching operation of the comparative example. In Fig. 7 and Figs. 10, 13, and 16 described below, the potential of the first electrode 42 is indicated by a solid line, the potential of the second electrode 43 is indicated by a dashed dotted line, and the portion of the potential of the second electrode 43 that overlaps with the potential of the first electrode 42 is indicated by a solid line.

[0065] In the first switching operation of the comparative example, the control circuit 3 directly switches from a state in which the potential of the first electrode 42 is a first potential E1 and the potential of the second electrode 43 is a second potential E2 higher than the first potential E1 to a state in which the potential of the second electrode 43 and the potential of the first electrode 42 are each the first potential E1 at the switching timing.

[0066] That is, before the switching time t0 (switching timing) shown in FIG. 7, the potential of the first electrode 42 is the first potential E1 (reference potential: 0 (V)), and the potential of the second electrode 43 is the second potential E2, and as described above, the phase difference modulation element 2 emits the emitted light L along the fourth direction D4.

[0067] In the first switching operation of the comparative example, the control circuit 3 sets the potential of the second electrode 43 to the first potential E1 at switching time t0. On the other hand, the control circuit 3 does not change the potential of the first electrode 42 at switching time t0, leaving it at the first potential E1.

[0068] 8 is a time chart showing the phase change amount of the output light L at the first liquid crystal portion 31 and the second liquid crystal portion 32 in the first switching operation of the comparative example. In FIG. 8 and FIGS. 11, 14, and 17 described below, the phase change amount of the output light L at the first liquid crystal portion 31 is indicated by a solid line, the phase change amount of the output light L at the second liquid crystal portion 32 is indicated by a dashed dotted line, and the portion of the phase change amount of the output light L at the second liquid crystal portion 32 that overlaps with the phase change amount of the output light L at the first liquid crystal portion 31 is indicated by a solid line.

[0069] When the potential of the second electrode 43 is switched from the second potential E2 to the first potential E1 at switching time t0 (FIG. 7), the degree of tilt of the liquid crystal molecules LM in the second liquid crystal portion 32 corresponding to the second electrode 43 decreases toward the initial alignment state corresponding to the first potential E1 due to the elasticity of the liquid crystal layer 30. As a result, as shown in FIG. 8, the amount of phase change of the emitted light L in the second liquid crystal portion 32 decreases from the second phase P2 corresponding to the second potential E2 at switching time t0 to the first phase P1 corresponding to the first potential E1 at the first time t1, which is the first time T1 after the switching time t0. The first time T1 is determined by the viscosity of the liquid crystal layer 30, etc.

[0070] On the other hand, as shown in Fig. 7, the potential of the first electrode 42 remains at the first potential E1 even after switching time t0. Therefore, as shown in Fig. 8, the phase of the emitted light L at the first liquid crystal portion 31 remains at the first phase P1.

[0071] FIG. 9 is a time chart of the phase difference between the light L emitted from the first liquid crystal portion 31 and the light L emitted from the second liquid crystal portion 32 in the first switching operation of the comparative example.

[0072] 9 shows the difference in phase change amount of the output light L at the first liquid crystal portion 31 shown in FIG. 8 and the phase change amount of the output light L at the second liquid crystal portion 32. As shown in FIG. 9, the phase difference of the output light L is a value obtained by subtracting the first phase P1 from the second phase P2 at switching time t0. The magnitude of the phase difference of the output light L decreases from the first phase difference PD1 at switching time t0 and becomes 0 at the first time t1.

[0073] Therefore, the phase difference modulation element 2 emits the output light L along the fourth direction D4 before the switching time t0, and emits the output light L along the third direction D3 after the first time t1. From the switching time t0 to the first time t1, the direction of the output light L changes from the fourth direction D4 to the third direction D3 over the first time T1.

[0074] Thus, in the first switching operation of the comparative example, the switching time required for the direction of the emitted light L to switch from the fourth direction D4 to the third direction D3 corresponds to the first time T1. However, there is also a demand for a shorter switching time. Therefore, the control circuit 3 controls the voltages applied to the first electrode 42 and the second electrode 43 as described below.

[0075] FIG. 10 is a time chart of the potential of the first electrode 42 and the potential of the second electrode 43 in the first switching operation according to the embodiment of the present disclosure.

[0076] Before the switching time t0 shown in Figure 10, the potential of the first electrode 42 is the first potential E1 (reference potential: 0 (V)), and the potential of the second electrode 43 is the second potential E2, and as described above, the phase difference modulation element 2 emits the emitted light L along the fourth direction D4.

[0077] In the first switching operation of this embodiment, the control circuit 3 switches the potential of the second electrode 43 to the first potential E1 at switching time t0, similar to the first switching operation of the comparative example described above. Meanwhile, the control circuit 3 changes the potential of the first electrode 42 from the first potential E1 to a third potential E3 higher than the first potential E1 at switching time t0, and then returns it to the first potential E1.

[0078] In the first switching operation of this embodiment, the third potential E3 is determined as follows. As shown in FIG. 4, the third potential E3 is higher than the second potential E2. Furthermore, a third phase P3, which is the amount of phase change of the emitted light L corresponding to the third potential E3, is greater than the second phase P2. Furthermore, a second phase difference PD2, which is the difference between the second phase P2 and the third phase P3, is greater than or equal to the first phase difference PD1. In other words, the second phase difference PD2, which is the magnitude of the phase difference of the emitted light L corresponding to the second potential difference ED2 between the second potential E2 and the third potential E3, is greater than or equal to the first phase difference PD1, which is the magnitude of the phase difference of the emitted light L corresponding to the first potential difference ED1 between the first potential E1 and the second potential E2. Alternatively, the third potential E3 may be determined so that the second phase difference PD2 is smaller than the first phase difference PD1. Alternatively, the third potential E3 may be greater than the first potential E1 and less than or equal to the second potential E2.

[0079] 10, the control circuit 3 sets the potential of the first electrode 42 to the third potential E3 at switching time t0. Furthermore, the control circuit 3 sets the potential of the first electrode 42 from the third potential E3 to the first potential E1 at a second time t2, which is a second time T2 after the switching time t0. The second time T2 is shorter than the first time T1 and is set to a time at which the tilt degree of the liquid crystal molecules LM in the first liquid crystal portion 31 becomes substantially equal to the tilt degree of the liquid crystal molecules LM in the second liquid crystal portion 32 at the second time t2.

[0080] FIG. 11 is a time chart showing the amount of phase change of the emitted light L at the first liquid crystal portion 31 and the second liquid crystal portion 32 in the first switching operation according to the embodiment of the present disclosure.

[0081] As in the first switching operation of the comparative example described above, when the potential of the second electrode 43 is switched from the second potential E2 to the first potential E1 at switching time t0 (see Figure 10), the phase change amount of the emitted light L at the second liquid crystal portion 32 corresponding to the second electrode 43 decreases from the second phase P2 at switching time t0 to the first phase P1 at the first time t1, as shown in Figure 11.

[0082] On the other hand, when the potential of the first electrode 42 is switched from the first potential E1 to the third potential E3 at switching time t0 (see FIG. 10), the tilt degree of the liquid crystal molecules LM in the first liquid crystal portions 31 corresponding to the first electrode 42 increases from the initial alignment state corresponding to the first potential E1. Furthermore, at the second time t2, the tilt degree of the liquid crystal molecules LM in the first liquid crystal portions 31 becomes substantially equal to the tilt degree of the liquid crystal molecules LM in the second liquid crystal portions 32. As a result, as shown in FIG. 11, the amount of phase change of the emitted light L in the first liquid crystal portions 31 increases from the first phase P1 corresponding to the first potential E1 at switching time t0, and becomes substantially equal to the amount of phase change of the emitted light L in the second liquid crystal portions 32 at the second time t2.

[0083] Furthermore, at the second time t2, the potential of the first electrode 42 is switched from the third potential E3 to the first potential E1 (see FIG. 10), and the degree of tilt of the liquid crystal molecules LM in the first liquid crystal portion 31 decreases toward the initial alignment state due to the elasticity of the liquid crystal layer 30. As a result, as shown in FIG. 11, the amount of phase change of the emitted light L in the first liquid crystal portion 31 decreases from the second time t2 and becomes the first phase P1.

[0084] 12 is a time chart of the phase difference between the output light L at the first liquid crystal portion 31 and the output light L at the second liquid crystal portion 32 in the first switching operation of the embodiment of the present disclosure. In Fig. 12, the phase difference of the output light L in the first switching operation of the embodiment of the present disclosure is indicated by a solid line, and the phase difference of the output light L in the first switching operation of the comparative example shown in Fig. 9 is indicated by a dashed line.

[0085] 12 shows the phase difference between the amount of phase change of the output light L at the first liquid crystal portion 31 and the amount of phase change of the output light L at the second liquid crystal portion 32 shown in FIG. 11. As shown in FIG. 12, the phase difference of the output light L is a value obtained by subtracting the first phase P1 from the second phase P2 at switching time t0. The magnitude of the phase difference of the output light L decreases from the first phase difference PD1 at switching time t0 and becomes zero at a third time t3 between the second time t2 and the first time t1.

[0086] Therefore, the phase difference modulation element 2 emits the output light L along the fourth direction D4 before the switching time t0, and emits the output light L along the third direction D3 after the third time t3. From the switching time t0 to the third time t3, the direction of the output light L changes from the fourth direction D4 to the third direction D3 over the third time T3.

[0087] 12, between the third time t3 and the first time t1, the tilt degrees of the liquid crystal molecules LM in each of the first liquid crystal portion 31 and the second liquid crystal portion 32 change while the magnitude of the phase difference of the emitted light L remains at 0. As a result, the emitted light L is emitted along the third direction D3 after the third time t3.

[0088] As described above, with regard to the switching time required for the phase difference modulation element 2 to switch from a state in which it emits the output light L along the fourth direction D4 to a state in which it emits the output light L along the third direction D3, the switching time of the first switching operation in this embodiment corresponds to the third time T3 from the switching time t0 to the third time t3. The third time T3 is shorter than the first time T1, which corresponds to the switching time of the first switching operation in the comparative example. As described above, the phase difference modulation device 1 can shorten the time required for the output light L to change from a refracted state to a refractive state.

[0089] Next, a second switching operation of the phase difference modulation element 2 will be described, in which the phase difference modulation element 2 switches from a state in which it emits the outgoing light L along the fourth direction D4 to a state in which it emits the outgoing light L along the fifth direction D5. In the second switching operation, the control circuit 3 switches from a state in which the potential of the first electrode 42 is the first potential E1 and the potential of the second electrode 43 is the second potential E2 higher than the first potential E1 to a state in which the potential of the second electrode 43 is the first potential E1 and the potential of the first electrode 42 is the second potential E2 (corresponding to "predetermined potential" in the second switching operation).

[0090] FIG. 13 is a time chart of the potential of the first electrode 42 and the potential of the second electrode 43 in the second switching operation of the comparative example.

[0091] In the second switching operation of the comparative example, the control circuit 3 directly switches from a state in which the potential of the first electrode 42 is a first potential E1 and the potential of the second electrode 43 is a second potential E2 higher than the first potential E1 to a state in which the potential of the second electrode 43 is the first potential E1 and the potential of the first electrode 42 is the second potential E2 at the switching timing.

[0092] Before the switching time t0 shown in Figure 13, the potential of the first electrode 42 is the first potential E1 (reference potential: 0 (V)), and the potential of the second electrode 43 is the second potential E2, and as described above, the phase difference modulation element 2 emits the emitted light L along the fourth direction D4.

[0093] In the second switching operation of the comparative example, the control circuit 3 sets the potential of the second electrode 43 to the first potential E1 at switching time t0, while the control circuit 3 sets the potential of the first electrode 42 to the second potential E2 at switching time t0.

[0094] FIG. 14 is a time chart showing the amount of phase change of the emitted light L at the first liquid crystal portion 31 and the second liquid crystal portion 32 in the first switching operation of the comparative example.

[0095] When the potential of the second electrode 43 is switched from the second potential E2 to the first potential E1 at the switching time t0 (FIG. 13), the degree of tilt of the liquid crystal molecules LM in the second liquid crystal portion 32 corresponding to the second electrode 43 decreases toward the initial alignment state due to the elasticity of the liquid crystal layer 30. As a result, as shown in FIG. 14, the amount of phase change of the emitted light L in the second liquid crystal portion 32 decreases from the second phase P2 at the switching time t0 and becomes the first phase P1 at the first time t1, which is the first time T1 after the switching time t0.

[0096] On the other hand, by switching the potential of the first electrode 42 from the first potential E1 to the second potential E2 at switching time t0 (FIG. 13), the tilt degree of the liquid crystal molecules LM in the first liquid crystal portion 31 corresponding to the first electrode 42 increases from the initial alignment state. As a result, as shown in FIG. 14, the amount of phase change of the emitted light L in the first liquid crystal portion 31 increases from the first phase P1 at switching time t0, and becomes the second phase P2 at fourth time t4, which is the fourth time T4 after switching time t0. In this embodiment, the fourth time T4 is longer than the first time T1.

[0097] FIG. 15 is a time chart of the phase difference between the light L emitted from the first liquid crystal portion 31 and the light L emitted from the second liquid crystal portion 32 in the second switching operation of the comparative example.

[0098] 15 shows the phase difference between the amount of phase change of the output light L at the first liquid crystal portion 31 and the amount of phase change of the output light L at the second liquid crystal portion 32 shown in FIG. 14. As shown in FIG. 15, the phase difference of the output light L is a value obtained by subtracting the first phase P1 from the second phase P2 at the switching time t0. The magnitude of the phase difference of the output light L becomes smaller than the first phase difference PD1 at the switching time t0.

[0099] Furthermore, the phase difference of the output light L decreases from 0 between the switching time t0 and the fourth time t4, and becomes the first phase P1 minus the second phase P2 after the fourth time t4. The magnitude of the phase difference of the output light L is the first phase difference PD1 after the fourth time t4.

[0100] Therefore, the phase difference modulation element 2 emits the output light L along the fourth direction D4 before the switching time t0, and emits the output light L along the fifth direction D5 after the fourth time t4. Between the switching time t0 and the fourth time t4, the direction of the output light L changes from the fourth direction D4 to the fifth direction D5 over a fourth time T4.

[0101] Thus, the switching time required for the direction of the emitted light L to switch from the fourth direction D4 to the fifth direction D5 in the second operation of the comparative example corresponds to the fourth time T4. However, there is also a demand for a shorter switching time. Therefore, the control circuit 3 controls the voltages applied to the first electrode 42 and the second electrode 43 as described below.

[0102] FIG. 16 is a time chart of the potential of the first electrode 42 and the potential of the second electrode 43 in the second switching operation according to the embodiment of the present disclosure.

[0103] Before the switching time t0 shown in Figure 16, the potential of the first electrode 42 is the first potential E1 (reference potential: 0 (V)), and the potential of the second electrode 43 is the second potential E2, and as described above, the phase difference modulation element 2 emits the emitted light L along the fourth direction D4.

[0104] In the second switching operation of this embodiment, the control circuit 3 switches the potential of the second electrode 43 to the first potential E1 at switching time t0, similar to the second switching operation of the comparative example described above. Meanwhile, the control circuit 3 changes the potential of the first electrode 42 from the first potential E1 to a third potential E3 higher than the second potential E2 at switching time t0, and then changes the potential to the second potential E2.

[0105] In the second switching operation of this embodiment, the third potential E3 is determined as follows. As shown in FIG. 4, the third potential E3 is higher than the second potential E2. Furthermore, a third phase P3, which is the amount of phase change of the emitted light L corresponding to the third potential E3, is larger than the second phase P2. Furthermore, a second phase difference PD2, which is the magnitude of the difference between the second phase P2 and the third phase P3, is equal to or larger than the first phase difference PD1. Note that the third potential E3 may be determined so that the second phase difference PD2 is smaller than the first phase difference PD1.

[0106] 16 , the control circuit 3 sets the potential of the first electrode 42 to the third potential E3 at switching time t0. Furthermore, the control circuit 3 sets the potential of the first electrode 42 from the third potential E3 to the first potential E1 at fifth time t5, which is five time T5 after switching time t0. The fifth time T5 is set to be shorter than the fourth time T4, and to be such that the tilt degree of the liquid crystal molecules LM of the first liquid crystal portions 31 is greater than the tilt degree of the liquid crystal molecules LM of the second liquid crystal portions 32 at fifth time t5. Furthermore, the fifth time T5 is set to be such that the difference between the tilt degrees of the liquid crystal molecules LM of the first liquid crystal portions 31 and the second liquid crystal portions 32 at fifth time t5 is approximately equal to the difference between the tilt degrees of the liquid crystal molecules LM of the first liquid crystal portions 31 and the second liquid crystal portions 32 at switching time t0.

[0107] FIG. 17 is a time chart showing the amount of phase change between the first liquid crystal portion 31 and the second liquid crystal portion 32 and the output light L in the second switching operation according to the embodiment of the present disclosure.

[0108] Similar to the first switching operation of the comparative example described above, when the potential of the second electrode 43 is switched from the second potential E2 to the first potential E1 at switching time t0 (see FIG. 16), the phase change amount of the emitted light L at the second liquid crystal portion 32 corresponding to the second electrode 43 decreases from the second phase P2 to the first phase P1 at the first time t1, as shown in FIG. 17.

[0109] On the other hand, when the potential of the first electrode 42 is switched from the first potential E1 to the third potential E3 at switching time t0 (see FIG. 16), the tilt degree of the liquid crystal molecules LM in the first liquid crystal portion 31 corresponding to the first electrode 42 increases from the initial alignment corresponding to the first potential E1. As a result, as shown in FIG. 17, the phase change amount of the output light L at the first liquid crystal portion 31 increases from the first phase P1 and becomes larger than the phase change amount of the output light L at the second liquid crystal portion 32. Furthermore, when the fifth time T5 is determined as described above, at the fifth time t5, the phase change amount of the output light L at the first liquid crystal portion 31 is larger than the second phase P2, and the phase difference between the phase change amount of the output light L at the first liquid crystal portion 31 and the phase change amount of the output light L at the second liquid crystal portion 32 becomes approximately the first phase difference PD1.

[0110] Furthermore, at fifth time t5, the potential of the first electrode 42 is switched from the third potential E3 to the first potential E1 (see FIG. 16), and the degree of tilt of the liquid crystal molecules LM in the first liquid crystal portion 31 decreases toward the degree of tilt corresponding to the second potential E2 due to the elasticity of the liquid crystal layer 30. As a result, as shown in FIG. 17, the amount of phase change of the emitted light L in the first liquid crystal portion 31 decreases from the fifth time t5, and becomes the second phase P2 corresponding to the second potential E2.

[0111] 18 is a time chart showing the phase difference between the output light L at the first liquid crystal portion 31 and the output light L at the second liquid crystal portion 32 in the second switching operation of the embodiment of the present disclosure. In Fig. 18, the phase difference of the output light L in the second switching operation of the embodiment of the present disclosure is indicated by a solid line, and the phase difference of the output light L in the second switching operation of the comparative example shown in Fig. 15 is indicated by a dashed line.

[0112] 18 shows the phase difference between the amount of phase change of the output light L at the first liquid crystal portion 31 and the amount of phase change of the output light L at the second liquid crystal portion 32 shown in FIG. 17. As shown in FIG. 18, the phase difference of the output light L is a value obtained by subtracting the first phase P1 from the second phase P2 at switching time t0. The magnitude of the phase difference of the output light L becomes smaller than the first phase difference PD1 at switching time t0.

[0113] Furthermore, the phase difference of the output light L becomes smaller than 0 between the switching time t0 and the fifth time t5, and becomes the first phase P1 minus the second phase P2 at the sixth time t6 between the fifth time t5 and the fourth time t4. The magnitude of the phase difference of the output light L is the first phase difference PD1 from the sixth time t6 onwards.

[0114] Therefore, the phase difference modulation element 2 emits the output light L along the fourth direction D4 before the switching time t0, and emits the output light L along the fifth direction D5 after the sixth time t6. During the sixth time T6 between the switching time t0 and the sixth time t6, the direction of the output light L changes from the fourth direction D4 to the fifth direction D5 over the sixth time T6.

[0115] 18, between the sixth time t6 and the fourth time t4, the tilt degrees of the liquid crystal molecules LM in each of the first liquid crystal portion 31 and the second liquid crystal portion 32 change while the magnitude of the phase difference of the emitted light L remains the first phase difference PD1. As a result, the emitted light L is emitted along the fifth direction D5 after the sixth time t6.

[0116] As described above, with regard to the switching time required for the phase difference modulation element 2 to switch from a state in which it emits the output light L along the fourth direction D4 to a state in which it emits the output light L along the fifth direction D5, the switching time of the second switching operation in this embodiment corresponds to the sixth time T6 from switching time t0 to sixth time t6. The sixth time T6 is shorter than the fourth time T4, which corresponds to the switching time of the second switching operation in the comparative example. As described above, the phase difference modulation device 1 can shorten the time required for the output light L to change from a refracted state to a refractive state.

[0117] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible within the scope of the present disclosure. Appropriate modifications made within the scope of the present disclosure also naturally fall within the technical scope of the present disclosure.

[0118] For example, the emitted light L does not have to be polarized light, and may be natural light, for example. In this case, a polarizing plate having a transmission axis along the second direction D2 may be arranged in front of the phase difference modulation element 2.

[0119] Furthermore, the first electrode 42 and the second electrode 43 may be electrically connected to the electrical resistance film 41 while being separated from the electrical resistance film 41. Furthermore, the element group 40 does not necessarily have to include the electrical resistance film 41.

[0120] Furthermore, the initial alignment of the liquid crystal molecules LM may be a state in which the long axes of the liquid crystal molecules LM are parallel to the third direction D3 (vertical alignment). In this case, the direction in which the emitted light L is refracted is opposite to that of the phase difference modulation element 2 of the above embodiment. For example, when the potential of the first electrode 42 is the second potential E2 and the potentials of the second electrode 43 and the third electrode 50 are the first potential E1, the emitted light L is emitted along the fifth direction D5.

[0121] The element group 40 may also be annular. In this case, the element group 40 includes an annular electrically resistive film 41, a first electrode 42, and a second electrode 43. In this case, the first direction D1 corresponds to the radial direction, and the second direction D2 corresponds to the circumferential direction. A phase difference modulation element 2 including such an annular element group 40 functions like a Fresnel lens. The phase difference modulation element 2 may also include a plurality of annular element groups 40 having different diameters, and the plurality of annular element groups 40 may be arranged so that their centers overlap in a planar view.

[0122] Fig. 19 is a plan view of a phase difference modulation element 2 included in a phase difference modulation device 1 according to a modified example of the embodiment of the present disclosure. Fig. 20 is a cross-sectional view of the phase difference modulation element 2 taken along line XX-XX shown in Fig. 19.

[0123] The phase difference modulation element 2 of this modified example includes a plurality of rectangular electrodes 160 instead of the plurality of element groups 40. The plurality of rectangular electrodes 160 are rectangular in plan view. The plurality of rectangular electrodes 160 are arranged on the first substrate 10 in a matrix along the first direction D1 and the second direction D2 in plan view. The plurality of rectangular electrodes 160 overlap the third electrode 50 in plan view. Note that although the number of the plurality of rectangular electrodes 160 shown in FIG. 19 is 16, it goes without saying that the number is not limited to this.

[0124] In this modification, the control circuit 3 controls the potential of one of two rectangular electrodes 160 adjacent to each other in the second direction D2 in the same manner as the potential of the first electrode 42 in the above embodiment, and controls the potential of the other rectangular electrode 160 in the same manner as the potential of the second electrode 43 in the above embodiment. In this case, the control circuit 3 sets the potentials of the two rectangular electrodes 160 adjacent to each other in the first direction D1 to the same potential. In this case, the phase difference modulation element 2 of this modification can refract the emitted light L in the same manner as the phase difference modulation element 2 of the above embodiment.

[0125] In this modification, the control circuit 3 may control the potential of the rectangular electrode 160 furthest on the −D2 side in the second direction D2 in the same manner as the first electrode 42 in the above embodiment, and may control the potential of the rectangular electrode 160 furthest on the +D2 side in the second direction D2 in the same manner as the second electrode 43 in the above embodiment. In this case, the control circuit 3 sets the potentials of the multiple rectangular electrodes 160 between the rectangular electrode 160 furthest on the −D2 side and the rectangular electrode 160 furthest on the +D2 side in the second direction D2 to a potential between the potential of the rectangular electrode 160 furthest on the −D2 side and the rectangular electrode 160 furthest on the +D2 side. Specifically, the control circuit 3 controls the potential of the rectangular electrode 160 on the −D2 side of two rectangular electrodes 160 adjacent to each other in the second direction D2 in the multiple rectangular electrodes 160 between the rectangular electrode 160 furthest on the −D2 side and the rectangular electrode 160 furthest on the +D2 side in the second direction D2 to a potential closer to the potential of the rectangular electrode 160 furthest on the −D2 side than the potential of the rectangular electrode 160 on the +D2 side. Furthermore, in this case, the control circuit 3 sets the potentials of two rectangular electrodes 160 adjacent to each other in the first direction D1 to the same potential. Even in this case, the phase difference modulation element 2 of this modified example can refract the emitted light L in the same way as the phase difference modulation element 2 of the above embodiment.

[0126] Furthermore, other effects and advantages brought about by the aspects described in the above embodiments that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present disclosure. [Explanation of symbols]

[0127] 1 Phase difference modulation device 2 Phase difference modulation element 3 Control Circuit 10 First board 20 Second board 30 Liquid crystal layer 40 element sets 41 Electrical resistance film 42 1st electrode 43 2nd electrode 50 3rd electrode E1 First potential E2 2nd potential E3 3rd potential

Claims

1. a first substrate on which the first electrode and the second electrode are disposed adjacent to each other in a plan view; a second substrate on which a third electrode is disposed, the third electrode overlapping the first electrode and the second electrode in a plan view; a liquid crystal layer disposed between the first substrate and the second substrate; a control circuit that applies voltages to the first electrode, the second electrode, and the third electrode, and that imparts a phase difference to electromagnetic waves that pass through the liquid crystal layer; The control circuit When switching from a state in which the potential of the first electrode is a first potential and the potential of the second electrode is a second potential higher than the first potential to a state in which the potential of the second electrode is the first potential and the potential of the first electrode is a predetermined potential, changing the potential of the first electrode from the first potential to a third potential higher than the predetermined potential, and then changing the potential to the predetermined potential; Phase difference modulation device.

2. a magnitude of the phase difference of the electromagnetic wave corresponding to the potential difference between the second potential and the third potential is equal to or greater than a magnitude of the phase difference of the electromagnetic wave corresponding to the potential difference between the first potential and the second potential; 2. The phase difference modulation device according to claim 1.

3. further comprising an electrically resistive film disposed on the first substrate and electrically connected to the first electrode and the second electrode; 2. The phase difference modulation device according to claim 1.

4. The electromagnetic wave is visible light.

2. The phase difference modulation device according to claim 1.

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