A liquid crystal grating and a stereoscopic display device

Abstract

The present invention provides a liquid crystal grating and a stereoscopic display device, relating to the field of display technologies. The liquid crystal grating includes at least one liquid crystal cell, and the liquid crystal cell includes a first substrate, a first electrode, a first alignment layer, a liquid crystal layer, and a second substrate which are sequentially arranged; in a first state, the liquid crystal cell includes a plurality of first grating units arranged along a first direction, and the first grating units include a plurality of the first electrodes which are spaced apart from each other along the first direction; along the first direction, a first electric field is formed between two first electrodes which are respectively located in two adjacent first grating units and are the closest to each other. In the liquid crystal cell, the alignment direction of the first alignment layer is the same as the electric field direction of the first electric field. The present invention provides a liquid crystal grating and a stereoscopic display device to reduce the adverse effect of the lateral electric field on the rotation of liquid crystal molecules and improve the reverse domain problem.

Description

Technical Field

[0001] The present invention relates to the field of display technologies, and particularly to a liquid crystal grating and a stereoscopic display device. Background Art

[0002] Since two-dimensional display is difficult to clearly and accurately express the three-dimensional depth information, people have been committed to researching display technologies that can display three-dimensional scenes - three-dimensional image display technologies. Holographic three-dimensional display technology uses the diffraction or interference of light to record the amplitude and phase information of object light, and then reconstructs the information of object light through the diffraction of light. It is the only truly three-dimensional display technology among various display methods.

[0003] When a stereoscopic display device performs three-dimensional image display, after a spatial light modulator (SLM) modulates the optical signal in terms of phase and amplitude, generally, left-eye and right-eye images are formed through the diffraction function of a liquid crystal grating. How to improve the display effect has become an urgent problem to be solved. Summary of the Invention

[0004] The present invention provides a liquid crystal grating and a stereoscopic display device to reduce the adverse effects of the lateral electric field on the rotation of liquid crystal molecules and improve the reverse domain problem.

[0005] In a first aspect, an embodiment of the present invention provides a liquid crystal grating, including at least one liquid crystal cell. The liquid crystal cell includes a first substrate, a first electrode, a first alignment layer, a liquid crystal layer, and a second substrate arranged in sequence. In a first state, the liquid crystal cell includes a plurality of first grating units arranged along a first direction. The first grating unit includes a plurality of the first electrodes spaced apart from each other along the first direction.

[0006] Along the first direction, a first electric field is formed between the two first electrodes that are respectively located in two adjacent first grating units and are the closest to each other. In the liquid crystal cell, the alignment direction of the first alignment layer is the same as the electric field direction of the first electric field.

[0007] In a second aspect, an embodiment of the present invention provides a stereoscopic display device, including a light source, a spatial light modulator, and a grating assembly arranged in sequence.

[0008] The grating assembly includes at least one liquid crystal grating as described in the first aspect.

[0009] For the liquid crystal grating provided by the embodiment of the present invention, the electric field direction of the first electric field is the same as the alignment direction of the first alignment layer. The electric field direction received by the liquid crystal molecules adjacent to the first alignment layer faces the alignment direction of the first alignment layer and will not face the reverse direction of the alignment direction of the first alignment layer. The liquid crystal molecules adjacent to the first alignment layer will not have a reverse flip, reducing the adverse effects of the lateral electric field on the rotation of liquid crystal molecules and improving the reverse domain problem. Brief Description of the Drawings

[0010] Figure 1 It is a schematic cross-sectional structure diagram of a liquid crystal grating during the inventor's research process;

[0011] Figure 2 It is a schematic diagram of the voltage distribution of the first electrode and the second electrode of a liquid crystal grating during the inventor's research process;

[0012] Figure 3 It is a schematic cross-sectional structure diagram of a liquid crystal grating provided by an embodiment of the present invention;

[0013] Figure 4 It is a schematic diagram of the voltage distribution of the first electrode and the second electrode of a liquid crystal grating provided by an embodiment of the present invention;

[0014] Figure 5 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0015] Figure 6 It is a schematic diagram of the voltage distribution of the first electrode and the second electrode of another liquid crystal grating provided by an embodiment of the present invention;

[0016] Figure 7 It is a schematic three-dimensional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0017] Figure 8 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0018] Figure 9 It is a schematic diagram of the working process of a liquid crystal grating provided by an embodiment of the present invention;

[0019] Figure 10 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0020] Figure 11 It is a schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0021] Figure 12 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0022] Figure 13 It is a schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0023] Figure 14 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0024] Figure 15Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0025] Figure 16 Schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0026] Figure 17 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0027] Figure 18 Schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention;

[0028] Figure 19 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0029] Figure 20 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0030] Figure 21 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0031] Figure 22 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0032] Figure 23 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0033] Figure 24 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0034] Figure 25 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0035] Figure 26 Schematic diagram of the working timing of a liquid crystal grating provided by an embodiment of the present invention;

[0036] Figure 27 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0037] Figure 28 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention;

[0038] Figure 29 Schematic diagram of a stereoscopic display device provided by an embodiment of the present invention;

[0039] Figure 30 For Figure 29 Schematic diagram of the structure of area S2 in Detailed implementation mode

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the convenience of description, only the parts related to the present invention rather than all the structures are shown in the accompanying drawings.

[0041] Figure 1 It is a schematic cross-sectional structure diagram of a liquid crystal grating in the inventor's research process. Refer to Figure 1 , the liquid crystal grating includes a first substrate 11, a second substrate 12 and a liquid crystal layer 30. The liquid crystal layer 30 is located between the first substrate 11 and the second substrate 12. The liquid crystal layer 30 includes liquid crystal molecules. The liquid crystal grating includes a plurality of grating units 40. The plurality of grating units 40 are arranged along the first direction X. The grating unit 40 includes a plurality of first electrodes 21 and one second electrode 22. The plurality of first electrodes 21 are located between the first substrate 11 and the liquid crystal layer 30. The plurality of first electrodes 21 are spaced apart from each other along the first direction X. Along the first direction X, there is a certain distance between two adjacent first electrodes 21. The plurality of grating units 40 share the same second electrode 22, and the second electrode 22 is a full-surface electrode.

[0042] Figure 2 It is a schematic diagram of the voltage distribution of the first electrode and the second electrode of a liquid crystal grating in the inventor's research process. Refer to Figure 1 and Figure 2 , the inventor found through research that when performing three-dimensional display, there is a voltage difference between the first electrode 21 and the second electrode 22, and the longitudinal electric field formed by the first electrode 21 and the second electrode 22 can drive the rotation of liquid crystal molecules. There are at least two first electrodes 21 with different voltages, so as to form longitudinal electric fields with different intensities arranged along the first direction X. The longitudinal electric fields with different intensities cause the liquid crystal molecules to rotate by different angles, thereby forming a refractive index gradient and forming a plurality of grating units 40 arranged along the first direction X. Therefore, the grating unit 40 can also include liquid crystal molecules. However, a transverse electric field is formed between the first electrodes 21 with different voltages. The presence of the transverse electric field will cause the electro-flexure effect of the liquid crystal molecules, changing the rotation behavior of the liquid crystal molecules. The liquid crystal molecules in the liquid crystal grating cannot be flipped according to the ideal situation, and the liquid crystal molecules rotate in the direction opposite to the pretilt angle, resulting in the problem of reverse domains.

[0043] Refer to Figure 1 and Figure 2, the inventor found through research that there are some areas in the liquid crystal grating in an unsatisfactory state. The inventor further studied and found that along the first direction X, in two adjacent grating units 40 respectively, a first electric field TE1 is formed between the two first electrodes 21 that are closest to each other. The first electric field TE1 is a transverse electric field. The liquid crystal grating includes a first alignment layer 31, and the first alignment layer 31 is located between the first electrode 21 and the liquid crystal layer 30. In the liquid crystal grating, the alignment direction R1 of the first alignment layer 31 in some areas is opposite to the electric field direction of the first electric field TE1. Under the combined influence of the first electric field TE1 and the longitudinal electric field, the liquid crystal molecules at the position of the S1 region rotate along the Figure 1 the arrow direction in and produce a reverse flip, generating a bubble-like reverse domain in the S1 region. Among them, the liquid crystal molecules at the position of the S1 region are adjacent to the first electrode 21. The first alignment layer 31 can be in direct contact with the first electrode 21. In other embodiments, a protective layer can also be provided between the first alignment layer 31 and the first electrode 21. The first alignment layer 31 is located on the side of the protective layer away from the first electrode 21. The protective layer provides a flat surface for the first alignment layer 31 and improves the flatness of the first alignment layer 31.

[0044] Figure 3 is a schematic cross-sectional structure diagram of a liquid crystal grating provided by an embodiment of the present invention, Figure 4 is a schematic voltage distribution diagram of the first electrode and the second electrode of a liquid crystal grating provided by an embodiment of the present invention. Refer to Figure 3 and Figure 4 , the liquid crystal grating includes at least one liquid crystal cell 100. The liquid crystal cell 100 includes a first substrate 11, a first electrode 21, a first alignment layer 31, a liquid crystal layer 30, and a second substrate 12 arranged in sequence. In the first state ST1, the liquid crystal cell 100 includes a plurality of first grating units 401 arranged along the first direction X. The first grating unit 401 includes a plurality of first electrodes 21 spaced apart from each other along the first direction X. Along the first direction X, there is a certain distance between two adjacent first electrodes 21. Along the first direction X, in two adjacent first grating units 401 respectively, a first electric field TE1 is formed between the two first electrodes 21 that are closest to each other. In the liquid crystal cell 100, the alignment direction R1 of the first alignment layer 31 is the same as the electric field direction of the first electric field TE1.

[0045] For a liquid crystal grating provided by an embodiment of the present invention, the electric field direction of the first electric field TE1 is the same as the alignment direction R1 of the first alignment layer 31. The electric field direction received by the liquid crystal molecules adjacent to the first alignment layer 31 is towards the alignment direction R1 of the first alignment layer 31 and will not be towards the reverse alignment direction of the first alignment layer 31. The liquid crystal molecules adjacent to the first alignment layer 31 will not produce a reverse flip, reducing the adverse effect of the transverse electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem.

[0046] Exemplarily, referring to Figure 3 and Figure 4 , the liquid crystal cell 100 further includes a second electrode 22, and the second electrode 22 is located between the second substrate 12 and the liquid crystal layer 30. When performing a stereoscopic display, there is a voltage difference between the first electrode 21 and the second electrode 22, and the longitudinal electric field formed by the first electrode 21 and the second electrode 22 can drive the liquid crystal molecules to rotate, forming a plurality of first grating units 401, and the plurality of first grating units 401 are arranged repeatedly along the first direction X. The liquid crystal grating is used for light diffraction and deflection. When not performing a stereoscopic display, the first grating units 401 are not formed, and the liquid crystal grating is not used or is used as an auxiliary for light diffraction and deflection. Among them, the direction of the longitudinal electric field can be the third direction Z or the opposite direction of the third direction Z.

[0047] Optionally, referring to Figure 3 , in the same first grating unit 401, the first grating unit 401 includes a plurality of first electrode groups 51 arranged along the first direction X. The first electrode group 51 includes at least one first electrode 21 and at least one second electrode 22. In the same first electrode group 51, the first electrode 21 and a second electrode 22 at least partially overlap, the first electrode 21 and a second electrode 22 overlap, or the first electrode 21 and a second electrode 22 partially overlap. The voltage difference between the first electrode 21 and the second electrode 22 is a first voltage difference. The longitudinal electric field formed by the first voltage difference can drive the liquid crystal molecules to rotate. Among them, the first voltage difference is the difference between the voltage of the first electrode 21 and the voltage of the second electrode 22 in the first grating unit 401, that is, the first voltage difference is the voltage of the first electrode 21 minus the voltage of the second electrode 22.

[0048] Exemplarily, referring to Figure 3 , a first electrode group 51 includes a first electrode 21 and a second electrode 22. There is a first voltage difference between the voltages of the first electrode 21 and the second electrode 22 in the same first electrode group 501. In other embodiments, a first electrode group 51 includes a plurality of first electrodes 21 and a second electrode 22.

[0049] Optionally, referring to Figure 3 and Figure 4 , each of the first voltage differences has the same polarity. The longitudinal electric field formed by the first electrode 21 and the second electrode 22 ( Figure 3 the arrow in which indicates the longitudinal electric field) has the same electric field direction. The longitudinal electric field formed by the first electrode 21 and the second electrode 22 drives the liquid crystal molecules to rotate in the same direction.

[0050] Exemplarily, referring to Figure 3 and Figure 4, a plurality of first electrodes 21 include a first sub-first electrode 211, a second sub-first electrode 212, a third sub-first electrode 213, and a fourth sub-first electrode 214. The voltage of the first sub-first electrode 211 is greater than the voltage of the second electrode 22, and the first sub-first electrode 211 and the second electrode 22 form a first voltage difference with a positive polarity. The voltage of the second sub-first electrode 212 is greater than the voltage of the second electrode 22, and the second sub-first electrode 212 and the second electrode 22 form a first voltage difference with a positive polarity. The voltage of the third sub-first electrode 213 is greater than the voltage of the second electrode 22, and the third sub-first electrode 213 and the second electrode 22 form a first voltage difference with a positive polarity. The voltage of the fourth sub-first electrode 214 is greater than the voltage of the second electrode 22, and the fourth sub-first electrode 214 and the second electrode 22 form a first voltage difference with a positive polarity. Figure 3 The arrows in Figure 3 indicate the longitudinal electric field. The thickness of the arrow represents the magnitude of the longitudinal electric field. The thicker the arrow, the greater the longitudinal electric field and the greater the first voltage difference.

[0051] Optionally, referring to Figure 3 and Figure 4 , in the same first grating unit 401, along the first direction X, each of the first voltage differences gradually decreases, the intensity of the longitudinal electric field formed by each first electrode group 51 gradually decreases, and the rotation angle of the liquid crystal molecules gradually decreases. In other embodiments, in the same first grating unit 401, along the first direction X, the first voltage difference gradually increases, and correspondingly, the alignment direction R1 of the first alignment layer 31 is changed so that the alignment direction R1 of the first alignment layer 31 is the same as the electric field direction of the first electric field TE1. It can be understood that since in the same first grating unit 401, along the first direction X, the first voltage difference gradually increases or gradually decreases, the first voltage differences of two adjacent first grating units 401 undergo a jump. Correspondingly, the refractive index formed by the liquid crystal molecules gradually changes within the same first grating unit 401 and undergoes a jump at the boundary between two adjacent first grating units 401, thus forming a grating with a diffraction function.

[0052] Exemplarily, referring to Figure 3 and Figure 4 , the first grating unit 401 includes M (exemplarily, Figure 3Among them, M = 4) the first electrode group 51, where M is a positive integer greater than 1. In the same first grating unit 401, along the first direction X, the first voltage differences corresponding to the first electrode group 51 from the first one to the Mth one show a linear change. In the same first grating unit 401, the intensity of the longitudinal electric field formed by each first electrode group 51 increases linearly or decreases linearly. Since the rotation angle of the liquid crystal molecules is proportional to the intensity of the longitudinal electric field, the linearly changing first voltage differences cause the liquid crystal molecules to form a linearly changing refractive index, simplifying the optical path. In other embodiments, the first voltage differences corresponding to the first electrode group 51 from the first one to the Mth one show other variation rules.

[0053] Optionally, referring to Figure 3 , a plurality of first grating units 401 share a second electrode 22. In the direction perpendicular to the plane of the first substrate 11, a second electrode 22 overlaps with the first electrodes 21 in a plurality of first grating units 401. The second electrode 22 can be a full-surface electrode.

[0054] Figure 5 is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention, Figure 6 is a schematic diagram of the voltage distribution of the first electrode and the second electrode of another liquid crystal grating provided by an embodiment of the present invention. Referring to Figure 5 and Figure 6 , the liquid crystal cell 100 further includes a second alignment layer 32. The second alignment layer 32 is located between the second electrode 22 and the liquid crystal layer 30. In the first state ST1, the first grating unit 401 includes a plurality of second electrodes 22 spaced apart from each other along the first direction X. Along the first direction X, there is a certain distance between two adjacent second electrodes 22. Along the first direction X, a second electric field TE2 is formed between the two second electrodes 22 that are respectively located in two adjacent first grating units 401 and are the closest to each other. The second electric field TE2 is a transverse electric field. In the liquid crystal cell 100, the alignment direction R2 of the second alignment layer 32 is the same as the electric field direction of the second electric field TE2. In the embodiment of the present invention, the electric field direction of the second electric field TE2 is the same as the alignment direction R2 of the second alignment layer 32. The electric field direction received by the liquid crystal molecules adjacent to the second alignment layer 32 is towards the alignment direction R2 of the second alignment layer 32, and will not be towards the reverse alignment direction of the second alignment layer 32. The liquid crystal molecules adjacent to the second alignment layer will not have a reverse flip, reducing the adverse effect of the transverse electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem.

[0055] Exemplarily, referring to Figure 5 and Figure 6, there are at least two first electrodes 21 with different voltages, and a transverse electric field is generated between the first electrodes 21. There are at least two second electrodes 22 with different voltages, and a transverse electric field is generated between the second electrodes 22. Thus, the transverse electric field is dispersed among the first electrodes 21 and the second electrodes 22, and the transverse electric field is dispersed between the first substrate 11 and the second substrate 12, rather than concentrated on a single substrate (the substrate includes the first substrate 11 and the second substrate 12), thereby reducing the transverse electric field intensity of a single substrate. The adverse effect of the transverse electric field on the rotation of liquid crystal molecules is reduced, and the reverse domain problem is improved.

[0056] Exemplarily, referring to Figure 5 and Figure 6 , in the same first grating unit 401, there are at least two first electrodes 21 with different voltages, and there are at least two second electrodes 22 with different voltages. In the same first grating unit 401, the transverse electric field is dispersed between the first substrate 11 and the second substrate 12, the adverse effect of the transverse electric field on the rotation of liquid crystal molecules is reduced, and the reverse domain problem is improved.

[0057] Exemplarily, referring to Figure 1 and Figure 2 , the voltage of the first sub-first electrode 211 is +1V, the voltage of the second sub-first electrode 212 is +2V, the voltage of the third sub-first electrode 213 is +3V, and the voltage of the fourth sub-first electrode 214 is +4V. The voltage of the second electrode 22 is 0V. The voltage difference formed between the first sub-first electrode 211 and the second electrode 22 is 1V, the voltage difference formed between the second sub-first electrode 212 and the second electrode 22 is 2V, the voltage difference formed between the third sub-first electrode 213 and the second electrode 22 is 3V, and the voltage difference formed between the fourth sub-first electrode 214 and the second electrode 22 is 4V. The voltage difference formed between the fourth sub-first electrode 214 and the first sub-first electrode 211 in the adjacent grating unit 40 is 3V. The transverse electric field formed between the first electrodes 21 is relatively large. When the alignment direction R1 of the first alignment layer 31 is opposite to the electric field direction of the first electric field TE1, the greater the electric field intensity of the first electric field TE1, the more likely it is that the liquid crystal molecules cannot flip as ideally, and the liquid crystal molecules rotate in the direction opposite to the pretilt angle, resulting in the reverse domain problem.

[0058] Exemplarily, referring to Figure 5 and Figure 6, the multiple second electrodes 22 include a first sub-second electrode 221, a second sub-second electrode 222, a third sub-second electrode 223, and a fourth sub-second electrode 224. The voltage of the first sub-first electrode 211 is +0.5V, the voltage of the second sub-first electrode 212 is +1V, the voltage of the third sub-first electrode 213 is +1.5V, and the voltage of the fourth sub-first electrode 214 is +2V. The voltage of the first sub-second electrode 221 is -0.5V, the voltage of the second sub-second electrode 222 is -1V, the voltage of the third sub-second electrode 223 is -1.5V, and the voltage of the fourth sub-second electrode 224 is -2V. The voltage difference formed by the first sub-first electrode 211 and the first sub-second electrode 221 is 1V, the voltage difference formed by the second sub-first electrode 212 and the second sub-second electrode 222 is 2V, the voltage difference formed by the third sub-first electrode 213 and the third sub-second electrode 223 is 3V, and the voltage difference formed by the fourth sub-first electrode 214 and the fourth sub-second electrode 224 is 4V. The voltage difference formed by the fourth sub-first electrode 214 and the first sub-first electrode 211 in the adjacent grating unit 40 is 1.5V. The voltage difference formed by the fourth sub-second electrode 224 and the first sub-second electrode 221 in the adjacent grating unit 40 is 1.5V. The lateral electric field formed between the first electrodes 21 is reduced. Even when the alignment direction R1 of the first alignment layer 31 is opposite to the electric field direction of the first electric field TE1, the adverse effect of the lateral electric field on the rotation of liquid crystal molecules can be reduced, and the reverse domain problem can be improved.

[0059] Exemplarily, referring to Figure 5 and Figure 6 , in each grating unit 40 (including the first grating unit 401), the first electrodes 21 with the same ordinal number have the same voltage, and the second electrodes 22 with the same ordinal number have the same voltage. The voltage distribution rules of the multiple first electrodes 21 in each grating unit 40 are the same, and the voltage distribution rules of the multiple second electrodes 22 in each grating unit 40 are the same. Thus, the first electrodes 21 with the same voltage in the multiple grating units 40 can be connected to the same power supply terminal, and the second electrodes 22 with the same voltage in the multiple grating units 40 can be connected to the same power supply terminal, reducing the number of power supply terminals. Herein, the ordinal number of the first electrode 21 or the second electrode 22 in the grating unit 40 refers to the number of the first electrode 21 or the second electrode 22 in the grating unit 40. Herein, the voltage distribution rule of the first electrode 21 or the second electrode 22 refers to the distribution rule presented by the voltages of the multiple first electrodes 21 or the multiple second electrodes 22 along the first direction X.

[0060] Exemplarily, referring to referring to Figure 5 and Figure 6, the grating unit 40 includes a first sub-grating unit 41 and a second sub-grating unit 42. Both the first sub-grating unit 41 and the second sub-grating unit 42 include 4 electrode groups 50. One electrode group 50 (including the first electrode group 51) includes a first electrode 21 and a second electrode 22. In the grating unit 40, the 4 first electrodes 21 are arranged in sequence, and the 4 second electrodes 22 are arranged in sequence. The first first electrode 21 in the first sub-grating unit 41 has the same voltage as the first first electrode 21 in the second sub-grating unit 42, and the second first electrode 21 in the first sub-grating unit 41 has the same voltage as the second first electrode 21 in the second sub-grating unit 42. The first second electrode 22 in the first sub-grating unit 41 has the same voltage as the first second electrode 22 in the second sub-grating unit 42, and the second second electrode 22 in the first sub-grating unit 41 has the same voltage as the second second electrode 22 in the second sub-grating unit 42.

[0061] Figure 7 is a schematic three-dimensional structure diagram of another liquid crystal grating provided by an embodiment of the present invention, Figure 8 is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention, Figure 9 is a schematic diagram of the working process of a liquid crystal grating provided by an embodiment of the present invention. Refer to Figures 7 - 9 , the liquid crystal grating includes two stacked liquid crystal cells 100, and the two liquid crystal cells 100 are a first liquid crystal cell 101 and a second liquid crystal cell 102 respectively. In the first state ST1, the first liquid crystal cell 101 includes a first grating unit 401, and the voltages of any two first electrodes 21 in the second liquid crystal cell 102 are the same. In the second liquid crystal cell 102, the voltage differences formed by any two first electrodes 21 and the second electrode 22 are the same, and the electric field intensities of the longitudinal electric fields formed between any two first electrodes 21 and the second electrode 22 are the same. Along the first direction X, the intensity of the longitudinal electric field does not change. The longitudinal electric fields with the same intensity cause the liquid crystal molecules to rotate by the same angle, no refractive index gradient is formed, and no grating with a diffraction function is formed. Therefore, the second liquid crystal cell 102 will not diffract and deflect the light passing through it.

[0062] Exemplarily, refer to Figures 7 - 9 , the two liquid crystal cells 100 are stacked along the optical axis of the liquid crystal grating, and the light passes through the two liquid crystal cells 100. That is to say, the same light ray passes through both the first liquid crystal cell 101 and the second liquid crystal cell 102. Among them, the optical axis of the liquid crystal grating is perpendicular to the plane where the first substrate 11 is located. Figure 9The dashed arrow indicates the propagation direction of light. The light incident vertically is deflected to the right after passing through the first liquid crystal cell 101 and the second liquid crystal cell 102. In the first state ST1, in the first liquid crystal cell 101, the voltage of the first electrode 21 is a positive voltage, the voltage of the second electrode 22 is 0V, and the first electrode 21 and the second electrode 22 form a first longitudinal electric field VE1. The direction of the first longitudinal electric field VE1 is the third direction Z, pointing from the first electrode 21 to the second electrode 22. Along the first direction X, the first longitudinal electric field VE1 gradually decreases. The first longitudinal electric fields VE1 with different intensities cause the liquid crystal molecules to rotate by different angles, thereby forming a refractive index gradient and forming a plurality of first grating units 401 arranged along the first direction X. The plurality of first grating units 401 form a grating with a diffraction deflection function. In the embodiment of the present invention, it is the first liquid crystal cell 101 that deflects the light. In the first liquid crystal cell 101, the alignment direction R1 of the first alignment layer 31 is the same as the electric field direction of the first electric field TE1. The alignment direction of the first alignment layer 31 in the first liquid crystal cell 101 is denoted as the first alignment direction R11. In the first state ST1, in the first liquid crystal cell 101, the first alignment direction R11 is the same as the electric field direction of the first electric field TE1.

[0063] In the second liquid crystal cell 102, the voltage of all the first electrodes 21 is 0V, the voltage of the second electrodes 22 is 0V, and no longitudinal electric field is formed between the first electrodes 21 and the second electrodes 22. Along the first direction X, the intensity of the longitudinal electric field does not change. In other embodiments, the voltage of all the first electrodes 21 in the second liquid crystal cell 102 is 1V, the voltage of the second electrodes 22 is 0V, and the voltage difference formed between the first electrodes 21 and the second electrodes 22 is 1V. Along the first direction X, the intensity of the longitudinal electric field does not change, and no refractive index gradient is formed. In the first state ST1, the second liquid crystal cell 102 is not used for light deflection. In the second liquid crystal cell 102, since the voltages of all the first electrodes 21 are the same, no transverse electric field is generated between adjacent first electrodes 21, thereby avoiding the adverse effect of the transverse electric field on the rotation of the liquid crystal molecules. In the first state ST1, the second liquid crystal cell 102 does not have the problem of reverse domains. In the second state, the first liquid crystal cell 101 is not used for light deflection, and the second liquid crystal cell 102 deflects the light. Thus, the function of deflecting the light is split between two liquid crystal cells 100 and completed separately in two states, so that in the liquid crystal cell 100 mainly used for diffraction deflection (including the first liquid crystal cell 101 in the first state ST1 or the second liquid crystal cell 102 in the second state), the alignment direction R1 of the first alignment layer 31 is the same as the electric field direction of the first electric field TE1. The adverse effect of the transverse electric field on the rotation of the liquid crystal molecules is reduced, and the problem of reverse domains is improved.

[0064] Figure 10 It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by the embodiment of the present invention.Figure 11 Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention. Refer to Figure 10 and Figure 11 , in the second state ST2, the second liquid crystal cell 102 includes at least one second grating unit 402. The second grating unit 402 includes a plurality of first electrodes 21 arranged at intervals in a first direction. The voltage change trend of the first electrodes 21 of the second grating unit 402 in the second state ST2 is opposite to the voltage change trend of the first electrodes 21 of the first grating unit 401 in the first state ST1. Among them, in the second state ST2, a third electric field TE3 is formed between the two first electrodes 21 that are respectively located in two adjacent second grating units 402 and are the closest to each other. The third electric field TE3 is a transverse electric field. In the second liquid crystal cell 102, the alignment direction of the first alignment layer 31 is the same as the electric field direction of the third electric field TE3. In the embodiment of the present invention, in the second liquid crystal cell 102, the electric field direction of the third electric field TE3 is the same as the alignment direction of the first alignment layer 31. The electric field direction received by the liquid crystal molecules adjacent to the first alignment layer 31 is towards the alignment direction of the first alignment layer 31, and will not be towards the opposite direction of the alignment of the first alignment layer 31. The liquid crystal molecules adjacent to the first alignment layer 31 will not have a reverse flip, reducing the adverse effect of the transverse electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem.

[0065] Exemplarily, refer to Figure 10 and Figure 11 , in the second state ST2, in the second liquid crystal cell 102, the first electrode 21 and the second electrode 22 form a second longitudinal electric field VE2. The direction of the second longitudinal electric field VE2 is the third direction Z, pointing from the first electrode 21 to the second electrode 22. Along the first direction X, the second longitudinal electric field VE2 gradually increases. Different intensities of the second longitudinal electric field VE2 cause the liquid crystal molecules to rotate different angles, thereby forming a refractive index gradient and forming a plurality of second grating units 402 arranged along the first direction X. The plurality of second grating units 402 form a grating with a diffraction and deflection function. In the embodiment of the present invention, it is the second liquid crystal cell 102 that deflects the light. In the second liquid crystal cell 102, the alignment direction R1 of the first alignment layer 31 is the same as the electric field direction of the first electric field TE1. The alignment direction of the first alignment layer 31 in the second liquid crystal cell 102 is denoted as the second alignment direction R21. In the second state ST2, in the second liquid crystal cell 102, the second alignment direction R21 is the same as the electric field direction of the third electric field TE3.

[0066] In the second state ST2, the voltages of any two first electrodes 21 in the first liquid crystal cell 101 are the same. In the first liquid crystal cell 101, the voltage differences formed by any two first electrodes 21 and the second electrode 22 are the same, and the electric field strengths of the longitudinal electric fields formed between any two first electrodes 21 and the second electrode 22 are the same. Along the first direction X, the intensity of the longitudinal electric field does not change. The longitudinal electric fields with the same intensity cause the liquid crystal molecules to rotate by the same angle, without forming a refractive index gradient and without forming a grating with a diffraction function. In the second state ST2, the first liquid crystal cell 101 does not diffract and deflect the light passing through it. In the first liquid crystal cell 101, since the voltages of all the first electrodes 21 are the same, no transverse electric field is generated between adjacent first electrodes 21, thus avoiding the adverse effects of the transverse electric field on the rotation of the liquid crystal molecules. In the second state ST2, the first liquid crystal cell 101 does not have the problem of reverse domains. The functions of setting the first liquid crystal cell 101 and the second liquid crystal cell 102 are not elaborated here. Please refer to Figures 7 - 9 the description of the embodiments involved.

[0067] Through the above embodiments, while ensuring that the liquid crystal grating can provide images for the left and right eyes respectively, the problem of reverse domains can be avoided. At the same time, the refresh frequency of a liquid crystal cell can be reduced, and the power consumption can be reduced.

[0068] Exemplarily, refer to Figures 7 - 11 , along the same first direction X: In the first state ST1, the voltage change trend of the first electrodes 21 of the first grating unit 401 gradually decreases. In the second state ST2, the voltage change trend of the first electrodes 21 of the second grating unit 402 gradually increases.

[0069] Figure 12 FIG. is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention. Figure 13 FIG. is a schematic working process diagram of another liquid crystal grating provided by an embodiment of the present invention. Refer to Figure 12 and Figure 13, the liquid crystal grating includes two stacked liquid crystal cells 100, which are respectively a first liquid crystal cell 101 and a second liquid crystal cell 102. In the first state ST1, the first liquid crystal cell 101 includes a first grating unit 401, and the second liquid crystal cell 102 includes at least one third grating unit 403. The third grating unit 403 includes a plurality of first electrodes 21 spaced apart from each other along the first direction X. Along the first direction X, a fourth electric field TE4 is formed between two adjacent first electrodes 21 located in the same third grating unit 403, and the electric field direction of the fourth electric field TE4 is opposite to that of the first electric field TE1. In the embodiment of the present invention, in the first state ST1, along the first direction X, the voltage change trend of the first electrodes 21 in the first grating unit 401 is the same as that of the first electrodes 21 in the third grating unit 403. Both the first liquid crystal cell 101 and the second liquid crystal cell 102 are used to deflect light toward the first side of the optical axis of the liquid crystal grating. In the first state ST1, the first liquid crystal cell 101 is mainly used for light diffraction deflection, and the second liquid crystal cell 102 is used to assist in light deflection. The first liquid crystal cell 101 deflects the light to a preset position or near a preset angle as soon as possible, and the second liquid crystal cell 102 corrects the deflection angle slightly to deflect the light to the preset position or preset angle.

[0070] Optionally, referring to Figure 12 and Figure 13 , along the first direction X, a fifth electric field TE5 is formed between the two first electrodes 21 that are respectively located in two adjacent third grating units 403 and are the closest to each other. The fifth electric field TE5 is a transverse electric field. In the second liquid crystal cell 102, the alignment direction R1 of the first alignment layer 31 (i.e., the second alignment direction R21) is opposite to the electric field direction of the fifth electric field TE5. The absolute value of the fifth electric field TE5 is less than the absolute value of the first electric field TE1. In the embodiment of the present invention, on the one hand, in the first state ST1, the second liquid crystal cell 102 is used to assist in light deflection, and the second liquid crystal cell 102 has the same light deflection direction as the first liquid crystal cell 101. On the other hand, the electric field strength of the fifth electric field TE5 is small. Even if the second alignment direction R21 is opposite to the electric field direction of the fifth electric field TE5, the fifth electric field TE5 is less than the transverse threshold electric field at which the liquid crystal molecules are reversely flipped, and the fifth electric field TE5 is less than the value of the transverse electric field when bubble domains are generated. In the second liquid crystal cell 102, the liquid crystal molecules adjacent to the first alignment layer 31 will not be reversely flipped, reducing the adverse effect of the transverse electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem.

[0071] Optionally, referring to Figure 12 and Figure 13, in the same third grating unit 403, a plurality of second electrode groups 52 arranged along the first direction X are included. The second electrode group 52 includes at least one first electrode 21 and at least one second electrode 22. In the same second electrode group 52, the first electrode 21 and the second electrode 22 at least partially overlap. The first electrode 21 overlaps with one second electrode 22, or a part of the first electrode 21 overlaps with one second electrode 22. The voltage difference between the first electrode 21 and the second electrode 22 is the second voltage difference, and a sixth electric field VE6 is formed between the first electrode 21 and the second electrode 22. The sixth electric field VE6 is a longitudinal electric field. The absolute value of the fifth electric field TE5 is less than the absolute value of the maximum value of the sixth electric field VE6. Wherein, the second voltage difference is the difference between the voltage of the first electrode 21 and the voltage of the second electrode 22 in the third grating unit 403, that is, the first voltage difference is the voltage of the first electrode 21 minus the voltage of the second electrode 22. It can be understood that along the first direction X, the distance between two adjacent first electrodes 21 is small, so that in the case of a given voltage difference (for example, 1V), it is easy to generate a stronger electric field. Along the third direction Z, since a certain cell gap needs to be reserved for the liquid crystal layer 30, the distance between the first electrode 21 and the second electrode 22 is large, so that in the case of a given voltage difference (for example, 1V), it is easy to generate a weaker electric field. In the embodiment of the present invention, the absolute value of the fifth electric field TE5 is less than the absolute value of the maximum value of the sixth electric field VE6, and the electric field intensity of the fifth electric field TE5 is much smaller than the electric field intensity of the first electric field TE1. Even if the second alignment direction R21 is opposite to the electric field direction of the fifth electric field TE5, the second liquid crystal cell 102 will not have the problem of reverse domains.

[0072] Optionally, referring to Figure 12 and Figure 13 , the liquid crystal layer 30 includes liquid crystal molecules. The absolute value of the maximum value of the sixth electric field VE6 is less than the threshold electric field value for driving the rotation of the liquid crystal molecules. The absolute value of the maximum value of the sixth electric field VE6 is less than the value of the longitudinal electric field when bubble domains are generated. In the second liquid crystal cell 102, the liquid crystal molecules adjacent to the first alignment layer 31 will not have reverse flipping, reducing the adverse effect of the lateral electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem.

[0073] Exemplarily, referring to Figure 12 and Figure 13, in the first state ST1, in the second liquid crystal cell 102, the voltage of the second electrode 22 is a common voltage. For example, the voltage of the second electrode 22 can be a ground voltage or 0V, so that the voltages of the positive and negative frames can be exactly symmetrical. When the voltage of the second electrode 22 is 0V, the absolute value of the sixth electric field VE6 is proportional to the absolute value of the voltage of the second electrode 22. The larger the absolute value of the sixth electric field VE6, the larger the absolute value of the voltage of the second electrode 22, and the smaller the absolute value of the sixth electric field VE6, the smaller the absolute value of the voltage of the second electrode 22. When the voltage of the second electrode 22 is 0V and the voltage of the sixth electric field VE6 is a non-negative voltage (including 0V and positive voltage), the voltage of the first electrode 21 corresponding to the maximum value of the sixth electric field VE6 (i.e., ​ the first sub-first electrode 211 in ​ ) is denoted as V1, and the voltage difference between the first sub-first electrode 211 and the second electrode 22 is: V1 - 0 = V1. The voltage of the first electrode 21 corresponding to the minimum value of the sixth electric field VE6 (i.e.,

[0074] the fourth sub-first electrode 214 in ​ and ​ ) is denoted as V2, V2 = V, and the voltage difference between the fourth sub-first electrode 214 and the second electrode 22 is: V2 - 0 = V2 = 0V. The transverse voltage difference corresponding to the fifth electric field TE5 is: V1 - V2 = V1 - 0 = V1.

[0075] Optionally, referring to ​ and ​ , the number of the first electrodes 21 in one first grating unit 401 is the same as the number of the first electrodes 21 in one third grating unit 403. In the two liquid crystal cells 100, the division of the first grating unit 401 and the third grating unit 403 remains unchanged. Thus, while ensuring the above prevention of reverse domains, the two liquid crystal cells 100 can assist each other in deflecting light, reducing the burden on a single liquid crystal cell 100, and enabling the two liquid crystal cells 100 to adopt two circuits with the same function, reducing the circuit design difficulty.

[0076] In other embodiments, the sixth electric field VE6 may not drive the liquid crystal molecules to rotate, may not form a refractive index gradient, and may not form a grating with a diffraction function. The second liquid crystal cell 102 may also not diffract and deflect the light passing through it.

[0077] It should be noted that, in this embodiment, ​ and ​Represents the current states of two liquid crystal cells 100 in the same frame. That is, the states of the two liquid crystal cells 100 when providing the picture for one eye, namely the states of the two liquid crystal cells 100 in the same frame. At this time, the first liquid crystal cell 101 mainly deflects light. Of course, in some embodiments of the present application, when displaying another frame of picture, the liquid crystal grating is used to provide the picture for the other eye. At this time, the states of the two liquid crystal cells 100 are swapped. That is to say, the second liquid crystal cell 102 mainly deflects light. At this time, the second liquid crystal cell 102 needs to refer to the requirements for the first liquid crystal cell 101 above, and the first liquid crystal cell 101 needs to refer to the requirements for the second liquid crystal cell 102 in the above embodiments. In addition, the voltage change trend of the first electrode 21 in the same grating unit 40 of the first liquid crystal cell 101 and the second liquid crystal cell 102 is that it gradually increases along the first direction X.

[0078] ​ It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention. ​ It is a schematic working process diagram of another liquid crystal grating provided by an embodiment of the present invention. Refer to ​ and ​ In the first liquid crystal cell 101, the number of the first grating units 401 is greater than the number of the third grating units 403 in the second liquid crystal cell 102. Along the first direction X, the change period of the first longitudinal electric field VE1 is less than the change period of the sixth electric field VE6. The sixth electric field VE6 changes slowly, thereby forming a smaller number of the fifth electric fields TE5, which can reduce the adverse effects of the fifth electric field TE5 on the rotation of liquid crystal molecules and improve the reverse domain problem.

[0079] Exemplarily, refer to ​ and ​ In the first grating unit 401, the number of the first electrodes 21 is less than the number of the first electrodes 21 in the third grating unit 403. The number of the first grating units 401 in the first liquid crystal cell 101 is L times the number of the third grating units 403 in the second liquid crystal cell 102, and L is a positive integer greater than 1.

[0080] ​ It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by an embodiment of the present invention. ​ It is a schematic working process diagram of another liquid crystal grating provided by an embodiment of the present invention. Refer to ​ and ​, in the first state ST1, the first liquid crystal cell 101 includes a plurality of first grating units 401, and the second liquid crystal cell 102 includes a third grating unit 403. In the third grating unit 403, the voltage gradually increases or gradually decreases from the first first electrode 21 to the last first electrode 21. In the embodiment of the present invention, since there is only one third grating unit 403, the fifth electric field TE5 will not be generated, which can avoid the adverse effect of the fifth electric field TE5 on the rotation of liquid crystal molecules and avoid the problem of reverse domains in the second liquid crystal cell 102.

[0081] That is to say, there is only one third grating unit 403 in the second liquid crystal cell 102. That is to say, all the first electrodes 21 in the second liquid crystal cell 102 form a grating unit 40. Along the first direction X, the voltage change trend of all the first electrodes 21 in the second liquid crystal cell 102 shows a gradual change.

[0082] Through such a design, the excessive lateral electric field between two grating units 40 in the second liquid crystal cell 102 is directly avoided. While borrowing the second liquid crystal cell 102 to assist the first liquid crystal cell 101 in deflecting light, the reverse domains in the second liquid crystal cell 102 can also be avoided.

[0083] ​ It is a schematic cross-sectional structure diagram of another liquid crystal grating provided by the embodiment of the present invention. ​ It is a schematic working process diagram of another liquid crystal grating provided by the embodiment of the present invention. Refer to ​ and ​, the liquid crystal grating includes two stacked liquid crystal cells 100, which are the first liquid crystal cell 101 and the second liquid crystal cell 102 respectively. In the first state ST1, the first liquid crystal cell 101 includes a first grating unit 401, and the second liquid crystal cell 102 includes at least one third grating unit 403. The third grating unit 403 includes a plurality of first electrodes 21 arranged at intervals from each other along the first direction X. Along the first direction X, in two adjacent third grating units 403 respectively, a fifth electric field TE5 is formed between the two closest first electrodes 21. In the second liquid crystal cell 102, the alignment direction R1 of the first alignment layer 31 (i.e., the second alignment direction R21) is the same as the electric field direction of the fifth electric field TE5. Since the second alignment direction R21 is the same as the electric field direction of the fifth electric field TE5, in the second liquid crystal cell 102, the electric field direction received by the liquid crystal molecules adjacent to the first alignment layer 31 is toward the second alignment direction R21, and the liquid crystal molecules adjacent to the first alignment layer 31 will not produce reverse flipping. In the embodiment of the present invention, in the first state ST1, along the first direction X, the voltage change trend of the first electrodes 21 in the first grating unit 401 is opposite to the voltage change trend of the first electrodes 21 in the third grating unit 403. The first liquid crystal cell 101 is used to deflect light toward the first side of the optical axis of the liquid crystal grating, and the second liquid crystal cell 102 is used to deflect light toward the second side of the optical axis of the liquid crystal grating. In the first state ST1, the first liquid crystal cell 101 is mainly used for light diffraction deflection, and the second liquid crystal cell 102 is used for light deflection as an auxiliary.

[0084] Optionally, referring to ​ and ​, the alignment direction R1 of the first alignment layer 31 in the first liquid crystal cell 101 is different from the alignment direction R1 of the first alignment layer 31 in the second liquid crystal cell 102, that is, the first alignment direction R11 is different from the second alignment direction R21. In the first state ST1, the electric field direction of the first electric field TE1 is opposite to the electric field direction of the fifth electric field TE5. In the first state ST1, the voltage of the first electrode 21 in the first liquid crystal cell 101 has the opposite polarity to the voltage of the first electrode 21 in the second liquid crystal cell 102. The direction of the first longitudinal electric field VE1 is the third direction Z, and in the first liquid crystal cell 101, it points from the first electrode 21 to the second electrode 22. Along the first direction X, the first longitudinal electric field VE1 gradually decreases, and different intensities of the first longitudinal electric field VE1 cause the liquid crystal molecules to rotate by different angles, thereby forming a refractive index gradient. In the embodiment of the present invention, the first liquid crystal cell 101 mainly deflects the light. The direction of the sixth electric field VE6 is the opposite direction of the third direction Z, and in the second liquid crystal cell 102, it points from the second electrode 22 to the first electrode 21. Along the first direction X, the sixth electric field VE6 gradually increases, and different intensities of the sixth electric field VE6 cause the liquid crystal molecules to rotate by different angles, thereby forming a refractive index gradient. In the embodiment of the present invention, the second liquid crystal cell 102 assists in deflecting the light. In the embodiment of the present invention, in the first liquid crystal cell 101, the electric field direction of the first electric field TE1 is the same as the first alignment direction R11, and the first liquid crystal cell 101 will not have the problem of reverse domains. In the second liquid crystal cell 102, the electric field direction of the fifth electric field TE5 is the same as the second alignment direction R21, and the second liquid crystal cell 102 will not have the problem of reverse domains.

[0085] Exemplarily, referring to ​ and ​ , the first alignment direction R11 is opposite to the second alignment direction R21, the electric field direction of the fourth electric field TE4 is opposite to the electric field direction of the first electric field TE1, and the electric field direction of the first longitudinal electric field VE1 is opposite to the electric field direction of the sixth electric field VE6. In the first state ST1, along the first direction X, the voltage change trend of the first electrode 21 in the first grating unit 401 is the same as the voltage change trend of the first electrode 21 in the third grating unit 403. Both the first liquid crystal cell 101 and the second liquid crystal cell 102 are used to deflect the light toward the first side of the optical axis of the liquid crystal grating.

[0086] In the first state ST1, the voltage of the first electrode 21 in the first grating unit 401 can be a positive voltage or a negative voltage. The following will be described in detail. The first state ST1 represents the current states of the two liquid crystal cells 100 in the same frame F (for example, in the first frame F1). In the first state ST1, the first liquid crystal cell 101 mainly deflects light, and the second liquid crystal cell 102 does not deflect light or plays an auxiliary role in deflecting light. The second state ST2 represents the current states of the two liquid crystal cells 100 in the same frame F (for example, in the second frame F2). In the second state ST2, the second liquid crystal cell 102 mainly deflects light, and the first liquid crystal cell 101 does not deflect light or plays an auxiliary role in deflecting light.

[0087] Exemplarily, referring to ​ and ​ , in the first state ST1, along the first direction X, the voltage of the first electrode 21 in the first grating unit 401 gradually decreases, and the voltage of the first electrode 21 in the first grating unit 401 is a positive voltage.

[0088] ​ FIG. ​ and ​ is a schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention. Referring to

[0089] In the first state ST1, along the first direction X, the voltage of the first electrode 21 in the first grating unit 401 gradually decreases, and the voltage of the first electrode 21 in the first grating unit 401 is a negative voltage. The electric field direction of the first electric field TE1 is the same as the first alignment direction R11, and the first liquid crystal cell 101 will not have the problem of reverse domains.

[0090] Exemplarily, referring to ​ , in the first liquid crystal cell 101, the impurities in the liquid crystal layer 30 move toward the second electrode 22 under the drive of the longitudinal electric field in the third direction Z. Referring to ​, in the first liquid crystal cell 101, impurities in the liquid crystal layer 30 move toward the first electrode 21 side under the drive of the longitudinal electric field in the opposite direction of the third direction Z. The working time of the liquid crystal grating includes multiple frames. In different frames, the longitudinal electric field in the first liquid crystal cell 101 can be alternately oriented in the third direction Z and in the opposite direction of the third direction Z, thereby preventing impurities from accumulating on one side.

[0091] In the second state ST2, the voltage of the first electrode 21 in the second grating unit 402 can be a positive voltage or a negative voltage. Details will be described below.

[0092] Exemplarily, referring to ​ and ​ , in the second state ST2, along the first direction X, the voltage of the first electrode 21 in the second grating unit 402 gradually increases, and the voltage of the first electrode 21 in the second grating unit 402 is a positive voltage.

[0093] ​ Another schematic diagram of the working process of the liquid crystal grating provided by an embodiment of the present invention, referring to ​ and ​ , in the second state ST2, along the first direction X, the voltage of the first electrode 21 in the second grating unit 402 gradually increases, and the voltage of the first electrode 21 in the second grating unit 402 is a negative voltage. The electric field direction of the third electric field TE3 is the same as the second alignment direction R21, and the second liquid crystal cell 102 will not have the problem of reverse domains.

[0094] Details of the operation of the second liquid crystal cell 102 in positive and negative frames will be described below. Exemplarily, referring to ​ , in the second liquid crystal cell 102, impurities in the liquid crystal layer 30 move toward the second electrode 22 side under the drive of the longitudinal electric field in the third direction Z. Referring to ​ , in the second liquid crystal cell 102, impurities in the liquid crystal layer 30 move toward the first electrode 21 side under the drive of the longitudinal electric field in the opposite direction of the third direction Z. The working time of the liquid crystal grating includes multiple frames. In different frames, the longitudinal electric field in the second liquid crystal cell 102 can be alternately oriented in the third direction Z and in the opposite direction of the third direction Z, thereby preventing impurities from accumulating on one side.

[0095] In the above embodiments, the first alignment direction R11 is different from the second alignment direction R21. In other embodiments, the first alignment direction R11 and the second alignment direction R21 can be the same.

[0096] ​ Another schematic diagram of the working process of the liquid crystal grating provided by an embodiment of the present invention, referring to ​, the first alignment direction R11 is the same as the second alignment direction R21. The electric field direction of the first longitudinal electric field VE1 is the reverse direction of the third direction Z. In the first state ST1, along the first direction X, the voltage of the first electrode 21 in the first grating unit 401 gradually increases, and the voltage of the first electrode 21 in the first grating unit 401 is a negative voltage. The electric field direction of the first electric field TE1 is the same as the first alignment direction R11, and the first liquid crystal cell 101 will not have the problem of reverse domains.

[0097] ​ Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention, refer to ​ , the first alignment direction R11 is the same as the second alignment direction R21. The electric field direction of the second longitudinal electric field VE2 is the reverse direction of the third direction Z. In the second state ST2, along the first direction X, the voltage of the first electrode 21 in the second grating unit 402 gradually increases, and the voltage of the first electrode 21 in the second grating unit 402 is a negative voltage. The electric field direction of the third electric field TE3 is the same as the second alignment direction R21, and the second liquid crystal cell 102 will not have the problem of reverse domains.

[0098] As an implementation manner, the liquid crystal cell 100 may include a plurality of first electrodes 21 and a plurality of second electrodes 22. The alignment direction and the electric field direction in the liquid crystal cell 100 with this structure will be further explained below.

[0099] ​ Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention, refer to ​ and ​ , in the first state ST1, in the first liquid crystal cell 101, the first alignment direction R11 is the same as the electric field direction of the first electric field TE1, and the liquid crystal molecules adjacent to the first alignment layer 31 will not have reverse flipping. The alignment direction of the second alignment layer 32 in the first liquid crystal cell 101 is denoted as the third alignment direction R12. In the first state ST1, in the first liquid crystal cell 101, the third alignment direction R12 is the same as the electric field direction of the second electric field TE2, and the liquid crystal molecules adjacent to the second alignment layer 32 will not have reverse flipping. The first alignment direction R11 is opposite to the third alignment direction R12.

[0100] ​ Schematic diagram of the working process of another liquid crystal grating provided by an embodiment of the present invention, refer to ​ and ​, in the second state ST2, in the second liquid crystal cell 102, the second alignment direction R21 is the same as the electric field direction of the third electric field TE3, and the liquid crystal molecules adjacent to the first alignment layer 31 will not have reverse flipping. The alignment direction of the second alignment layer 32 in the second liquid crystal cell 102 is denoted as the fourth alignment direction R22. In the second state ST2, in the second liquid crystal cell 102, the fourth alignment direction R22 is the same as the electric field direction of the seventh electric field TE7, and the liquid crystal molecules adjacent to the second alignment layer 32 will not have reverse flipping. The second alignment direction R21 is opposite to the fourth alignment direction R22. Among them, in the second liquid crystal cell 102, in the second state ST2, along the first direction X, the seventh electric field TE7 is formed between the two second electrodes 22 that are respectively located in two adjacent grating units 40 and are the closest to each other. The seventh electric field TE7 is a transverse electric field.

[0101] ​ is a schematic diagram of the working timing of a liquid crystal grating provided by an embodiment of the present invention. Refer to ​ , and ​ , the liquid crystal grating includes two stacked liquid crystal cells 100. The working time of the liquid crystal grating includes multiple frames F. In the same frame F, one of the two liquid crystal cells 100 is mainly used for light diffraction and deflection, and the other is not used or is used to assist in light deflection. The deflection angle of the light is mainly determined by one of the two liquid crystal cells 100.

[0102] Exemplarily, refer to ​ , one frame F is the period when a kind of color light irradiates one eye of the observer. For a stereoscopic display scheme that uses RGB three primary colors for color display, six frames are required for a complete picture. These six frames are the left-eye green frame LG, the left-eye blue frame LB, the left-eye red frame LR, the right-eye green frame RG, the right-eye blue frame RB, and the right-eye red frame RR. ​ The dashed box in

[0103] Optionally, refer to ​ , and ​, the two liquid crystal cells 100 are the first liquid crystal cell 101 and the second liquid crystal cell 102 respectively. The multiple frames F include a first frame F1 and a second frame F2, and the second frame F2 is after the first frame F1. In the first frame F1, the first liquid crystal cell 101 operates in a first state ST1, and the first liquid crystal cell 101 is configured to mainly diffract and deflect light toward the first side of the optical axis of the liquid crystal grating. In the second frame F2, the second liquid crystal cell 102 operates in a second state ST2, and the second liquid crystal cell 102 is configured to mainly diffract and deflect light toward the second side of the optical axis of the liquid crystal grating, and the first side and the second side are located on opposite sides of the optical axis of the liquid crystal grating. Wherein, the optical axis of the liquid crystal grating is perpendicular to the plane where the first substrate 11 is located.

[0104] Exemplarily, referring to ​ , and ​ , in the first frame F1, the first liquid crystal cell 101 operates in a first state ST1, and the first liquid crystal cell 101 is configured to mainly diffract and deflect light toward the first side of the optical axis of the liquid crystal grating. The first side of the optical axis of the liquid crystal grating is the right side of the optical axis of the liquid crystal grating. For an observer facing the light propagation direction, the green light (schematically shown by green light, but not limited thereto) is deflected into the observer's left eye.

[0105] Exemplarily, referring to ​ , ​ and ​ , in the second frame F2, the second liquid crystal cell 102 operates in a second state ST2, and the second liquid crystal cell 102 is configured to mainly diffract and deflect light toward the second side of the optical axis of the liquid crystal grating. The second side of the optical axis of the liquid crystal grating is the left side of the optical axis of the liquid crystal grating. For an observer facing the light propagation direction, the green light (schematically shown by green light, but not limited thereto) is deflected into the observer's right eye.

[0106] Optionally, referring to ​ , and ​ , in the first frame F1, in the same first grating unit 401 of the first liquid crystal cell 101, along the first direction, the voltages of the respective first electrodes 21 gradually decrease. The first liquid crystal cell 101 is configured to mainly diffract and deflect light toward the first side of the optical axis of the liquid crystal grating. In the second frame F2, in the same second grating unit 402 of the second liquid crystal cell 102, along the first direction X, the voltages of the respective first electrodes 21 gradually increase. The second liquid crystal cell 102 is configured to mainly diffract and deflect light toward the second side of the optical axis of the liquid crystal grating.

[0107] Optionally, referring to ​ , and ​, the voltage of the first electrode 21 in the first liquid crystal cell 101 in the first frame F1 has the same polarity as the voltage of the first electrode 21 in the second liquid crystal cell 102 in the second frame F2. As an example, the voltage of the first electrode 21 in the first liquid crystal cell 101 in the first frame F1 is a positive voltage, and the voltage of the first electrode 21 in the second liquid crystal cell 102 in the second frame F2 is a positive voltage.

[0108] Optionally, refer to ​ , the extending direction of the first electrode 21 in the first liquid crystal cell 101 is the same as the extending direction of the first electrode 21 in the second liquid crystal cell 102. The first electrode 21 in the first liquid crystal cell 101 is arranged in parallel with the first electrode 21 in the second liquid crystal cell 102, and both the first electrode 21 in the first liquid crystal cell 101 and the first electrode 21 in the second liquid crystal cell 102 extend along the second direction Y. The first liquid crystal cell 101 and the second liquid crystal cell 102 form a liquid crystal grating.

[0109] It should be noted that in addition to using two liquid crystal cells 100 to form a liquid crystal grating as provided in the above embodiments, in other embodiments, one liquid crystal cell 100 can also be used to form a liquid crystal grating. When using one liquid crystal cell 100 to form a liquid crystal grating, it is necessary to control the voltage change trend of the first electrode 21 so that the direction of the first electric field TE1 is the same as the alignment direction of the first alignment layer 31.

[0110] ​ This is a schematic diagram of the working process of another liquid crystal grating provided by the embodiment of the present invention. ​ This is a schematic diagram of the working process of another liquid crystal grating provided by the embodiment of the present invention. Refer to ​ 、 ​ and ​, the two first states ST1 include a first sub-state ST11 and a second sub-state ST12. That is, the two first states ST1 are the first sub-state ST11 and the second sub-state ST12 respectively. The first sub-state ST11 represents the current state of a single liquid crystal cell 100 in the same frame F (for example, in the first frame F1). In the first sub-state ST11, the liquid crystal cell 100 diffracts and deflects light toward the first side of the optical axis of the liquid crystal grating. The second sub-state ST12 represents the current state of a single liquid crystal cell 100 in the same frame F (for example, in the second frame F2). In the second sub-state ST12, the liquid crystal cell 100 diffracts and deflects light toward the second side of the optical axis of the liquid crystal grating. For the same liquid crystal cell 100, the voltage of the first electrode 21 in the first sub-state ST11 is opposite in polarity to the voltage of the first electrode 21 in the second sub-state ST12. For the same liquid crystal cell 100, the electric field direction of the first electric field TE1 in the first sub-state ST11 is the same as the electric field direction of the first electric field TE1 in the second sub-state ST12. In the first sub-state ST11 and the second sub-state ST12, the direction of the first electric field TE1 is the same as the alignment direction of the first alignment layer 31, and the liquid crystal molecules adjacent to the first alignment layer 31 will not have a reverse flip, reducing the adverse effect of the lateral electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem. In the embodiment of the present invention, in a single liquid crystal cell 100, by switching positive and negative voltages, light deflection in two directions is achieved, and in both frames, the direction of the first electric field TE1 is the same as the alignment direction of the first alignment layer 31, and the liquid crystal molecules adjacent to the first alignment layer 31 will not have a reverse flip, reducing the adverse effect of the lateral electric field on the rotation of the liquid crystal molecules and improving the reverse domain problem. The voltage of the first electrode 21 in the first sub-state ST11 is opposite in polarity to the voltage of the first electrode 21 in the second sub-state ST12. Thus, the same liquid crystal cell 100 can operate in a positive and negative frame transformation mode, and the longitudinal electric field directions formed in the positive frame and the negative frame are opposite, so that in the positive frame, impurities move toward the first electrode 21, and in the negative frame, impurities move toward the second electrode 22; or, in the positive frame, impurities move toward the second electrode 22, and in the negative frame, impurities move toward the first electrode 21, thereby preventing the enrichment of impurities on one side. It can be understood that in the embodiment of the present invention, the liquid crystal grating only includes a single liquid crystal cell 100. Thus, the thickness of the liquid crystal grating is reduced, the light transmittance is increased, and the cost of the liquid crystal grating is reduced.

[0111] Exemplarily, referring to ​ and ​, in the first sub-state ST11, the voltage of the first electrode 21 is a positive voltage. Within the same first grating unit 401, along the first direction X, the voltage of the first electrode 21 gradually decreases. The liquid crystal cell 100 is configured to diffract and deflect light toward the first side of the optical axis of the liquid crystal grating. The first side of the optical axis of the liquid crystal grating is the right side of the optical axis of the liquid crystal grating. For an observer facing the light propagation direction, the light is deflected into the observer's left eye.

[0112] Exemplarily, refer to ​ and ​ , in the second sub-state ST12, the voltage of the first electrode 21 is a negative voltage. Within the same first grating unit 401, along the first direction X, the voltage of the first electrode 21 gradually decreases. The liquid crystal cell 100 is configured to diffract and deflect light toward the second side of the optical axis of the liquid crystal grating. The second side of the optical axis of the liquid crystal grating is the left side of the optical axis of the liquid crystal grating. For an observer facing the light propagation direction, the light is deflected into the observer's right eye.

[0113] ​ is a schematic diagram of a stereoscopic display device provided by an embodiment of the present invention. Refer to ​ , the stereoscopic display device includes a light source 61, a spatial light modulator 62, and a grating assembly 64 arranged in sequence. The grating assembly 64 includes at least one liquid crystal grating in the above embodiments.

[0114] Exemplarily, refer to ​ , the light source 61 is used to sequentially emit coherent red, green, and blue backlights. The spatial light modulator 62 includes a first spatial light modulator 621 for phase modulation and a second spatial light modulator 622 for amplitude modulation. The stereoscopic display device further includes a field lens 63, and the field lens 63 is located between the spatial light modulator 62 and the grating assembly 64. The field lens 63 is at least used to improve the ability of the marginal light rays emitted by the spatial light modulator 62 to enter the grating assembly 64. The grating assembly 64 is used to form a left-eye image and a right-eye image based on the incident light.

[0115] Exemplarily, refer to ​ , the grating assembly 64 includes three liquid crystal gratings, which are a first liquid crystal grating 641, a second liquid crystal grating 642, and a third liquid crystal grating 643 respectively. The extending directions of the first electrodes 21 of any two of the first liquid crystal grating 641, the second liquid crystal grating 642, and the third liquid crystal grating 643 can be different. In other embodiments, the grating assembly 64 may further include other numbers of liquid crystal gratings.

[0116] ​ is ​ a schematic diagram of the structure of the S2 region in ​ , ​ and​ , the first substrate 11 is located between the second substrate 12 and the spatial light modulator 62 in the same liquid crystal cell 100. The first electrode 21 is located between the second electrode 22 and the spatial light modulator 62 in the same liquid crystal cell 100. In other embodiments, the positions of the first electrode 21 and the second electrode 22 can also be swapped, that is, the second substrate 12 is located between the first substrate 11 and the spatial light modulator 62 in the same liquid crystal cell 100. The second electrode 22 is located between the first electrode 21 and the spatial light modulator 62 in the same liquid crystal cell 100. After the positions of the first electrode 21 and the second electrode 22 are swapped, it does not affect the light propagation path and the deflection direction compared with before the position swap.

[0117] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A liquid crystal grating, characterized in that, Comprising at least one liquid crystal cell, the liquid crystal cell including a first substrate, a first electrode, a first alignment layer, a liquid crystal layer, and a second substrate disposed in sequence; in a first state, the liquid crystal cell includes a plurality of first grating units arranged along a first direction, the first grating units including a plurality of the first electrodes spaced apart from each other along the first direction; Along the first direction, a first electric field is formed between the two first electrodes that are respectively located in two adjacent first grating units and are the closest to each other. In the liquid crystal cell, the alignment direction of the first alignment layer is the same as the electric field direction of the first electric field; The liquid crystal cell further includes a second electrode, the second electrode being located between the second substrate and the liquid crystal layer; In the same first grating unit, there are a plurality of first electrode groups arranged along the first direction, the first electrode groups each including at least one first electrode and at least one second electrode; in the same first electrode group, the first electrode and the second electrode at least partially overlap, and the voltage difference therebetween is a first voltage difference; The liquid crystal cell further includes a second alignment layer, the second alignment layer being located between the second electrode and the liquid crystal layer; The first grating unit includes a plurality of the second electrodes spaced apart from each other along the first direction; Along the first direction, a second electric field is formed between the two second electrodes that are respectively located in two adjacent first grating units and are the closest to each other. In the liquid crystal cell, the alignment direction of the second alignment layer is the same as the electric field direction of the second electric field; 2. The liquid crystal grating according to claim 1, wherein Each of the first voltage differences has the same polarity.

3. The liquid crystal grating according to claim 1, wherein In the same first grating unit, along the first direction, the first voltage difference gradually increases or gradually decreases.

4. The liquid crystal grating according to claim 1, wherein A plurality of the first grating units share one second electrode.

5. The liquid crystal grating according to claim 1, wherein Comprising two stacked liquid crystal cells, the two liquid crystal cells being a first liquid crystal cell and a second liquid crystal cell respectively; In the first state, the first liquid crystal cell includes the first grating unit, and the voltages of any two first electrodes in the second liquid crystal cell are the same.

6. The liquid crystal grating according to claim 5, wherein In a second state, the second liquid crystal cell includes at least one second grating unit, the second grating units including a plurality of the first electrodes spaced apart from each other along the first direction; The voltage change trend of the first electrodes of the second grating units in the second state is opposite to the voltage change trend of the first electrodes of the first grating units in the first state; Wherein, in the second state, a third electric field is formed between the two first electrodes that are respectively located in two adjacent second grating units and are the closest to each other. In the second liquid crystal cell, the alignment direction of the first alignment layer is the same as the electric field direction of the third electric field.

7. The liquid crystal grating according to claim 1, wherein Comprising two stacked liquid crystal cells, the two liquid crystal cells being a first liquid crystal cell and a second liquid crystal cell respectively; In the first state, the first liquid crystal cell includes the first grating unit, and the second liquid crystal cell includes at least one third grating unit, the third grating units including a plurality of the first electrodes spaced apart from each other along the first direction; Along the first direction, a fourth electric field is formed between two adjacent first electrodes located in the same third grating unit, and the electric field direction of the fourth electric field is opposite to that of the first electric field.

8. The liquid crystal grating according to claim 7, wherein, Along the first direction, a fifth electric field is formed between the two first electrodes that are closest to each other and are respectively located in two adjacent third grating units. In the second liquid crystal cell, the alignment direction of the first alignment layer is opposite to the electric field direction of the fifth electric field. The absolute value of the fifth electric field is less than the absolute value of the first electric field.

9. The liquid crystal grating according to claim 8, wherein In the same third grating unit, there are multiple second electrode groups arranged along the first direction. Each second electrode group includes at least one first electrode and at least one second electrode. In the same second electrode group, the first electrode and the second electrode at least partially overlap, and the voltage difference between them is a second voltage difference, forming a sixth electric field. The absolute value of the fifth electric field is less than the absolute value of the maximum value of the sixth electric field.

10. The liquid crystal grating according to claim 9, wherein The liquid crystal layer includes liquid crystal molecules. The absolute value of the maximum value of the sixth electric field is less than the threshold electric field value for driving the rotation of the liquid crystal molecules.

11. The liquid crystal grating according to claim 8, wherein, The number of first electrodes in one first grating unit is the same as the number of first electrodes in one third grating unit.

12. The liquid crystal grating according to claim 7, characterized in that, The number of first grating units in the first liquid crystal cell is greater than the number of third grating units in the second liquid crystal cell.

13. The liquid crystal grating according to claim 1, characterized in that, It includes two stacked liquid crystal cells, which are the first liquid crystal cell and the second liquid crystal cell respectively. In the first state, the first liquid crystal cell includes the first grating unit, and the second liquid crystal cell includes at least one third grating unit. The third grating unit includes multiple first electrodes arranged at intervals along the first direction. Along the first direction, a fifth electric field is formed between the two first electrodes that are closest to each other and are respectively located in two adjacent third grating units. In the second liquid crystal cell, the alignment direction of the first alignment layer is the same as the electric field direction of the fifth electric field.

14. The liquid crystal grating according to claim 13, wherein The alignment direction of the first alignment layer in the first liquid crystal cell is different from the alignment direction of the first alignment layer in the second liquid crystal cell. The electric field direction of the first electric field is opposite to the electric field direction of the fifth electric field. In the first state, the voltages of the first electrodes in the first liquid crystal cell and the first electrodes in the second liquid crystal cell have opposite polarities.

15. The liquid crystal grating according to claim 1, characterized in that, It includes two stacked liquid crystal cells. The working time of the liquid crystal grating includes multiple frames. In the same frame, one of the two liquid crystal cells is mainly used for light diffraction and deflection, and the other is not used or is used to assist in light deflection.

16. The liquid crystal grating according to claim 15, characterized in that, The two liquid crystal cells are the first liquid crystal cell and the second liquid crystal cell respectively. The multiple frames include a first frame and a second frame, and the second frame is after the first frame. In the first frame, the first liquid crystal cell operates in the first state and is configured to mainly diffract and deflect light toward the first side of the optical axis of the liquid crystal grating. In the second frame, the second liquid crystal cell operates in a second state and is configured to mainly diffract and deflect light toward a second side of the optical axis of the liquid crystal grating, where the first side and the second side are located on opposite sides of the optical axis of the liquid crystal grating.

17. The liquid crystal grating according to claim 16, characterized in that, In the first frame, in the same first grating unit of the first liquid crystal cell, along the first direction, the voltages of the respective first electrodes gradually decrease; In the second state, the second liquid crystal cell includes at least one second grating unit, and the second grating unit includes a plurality of the first electrodes arranged at intervals from each other along the first direction; in the second frame, in the same second grating unit of the second liquid crystal cell, along the first direction, the voltages of the respective first electrodes gradually increase.

18. The liquid crystal grating according to claim 17, wherein The voltages of the first electrodes in the first liquid crystal cell in the first frame and the voltages of the first electrodes in the second liquid crystal cell in the second frame have the same polarity.

19. The liquid crystal grating according to claim 1, characterized in that, It includes two stacked liquid crystal cells, which are a first liquid crystal cell and a second liquid crystal cell respectively; The extending direction of the first electrodes in the first liquid crystal cell is the same as that of the first electrodes in the second liquid crystal cell.

20. The liquid crystal grating according to claim 1, characterized in that, The two first states include a first sub-state and a second sub-state; For the same liquid crystal cell, the polarities of the voltages of the first electrodes in the first sub-state and the voltages of the first electrodes in the second sub-state are opposite; For the same liquid crystal cell, the directions of the electric fields of the first electric fields in the first sub-state and the directions of the electric fields of the first electric fields in the second sub-state are the same.

21. A stereoscopic display device, characterized in that, It includes a light source, a spatial light modulator, and a grating assembly arranged in sequence; The grating assembly includes at least one liquid crystal grating according to any one of claims 1-20.

22. The stereoscopic display device according to claim 21, wherein, The first substrate is located between the second substrate in the same liquid crystal cell and the spatial light modulator; or, The second substrate is located between the first substrate in the same liquid crystal cell and the spatial light modulator.

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