Method and device for determining liquid crystal phase compensation of liquid crystal on silicon

Abstract

The present invention discloses a method and a device for determining liquid crystal phase compensation of liquid crystal on silicon (LCOS). The method includes: characterizing a first polarization state and a second polarization state respectively according to a first Mueller matrix of the LCOS in a modulation state, a second Mueller matrix of the LCOS in a non-modulation state, and a Mueller matrix of the liquid crystal phase compensation unit; establishing a first contrast evaluation function according to a first polarization component in the first polarization state and a second polarization component in the second polarization state; converting independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase retardation according to the characterization relationship to obtain a second contrast evaluation function; and obtaining a target optical axis azimuth angle and a target phase retardation according to the second contrast evaluation function, so as to quickly determine parameters of liquid crystal phase compensation and improve the contrast of the bright field and the dark field of the LCOS optical engine.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of AR optical technologies, and in particular, to a method and a device for determining liquid crystal phase compensation of liquid crystal on silicon (LCOS). Background Art

[0002] In recent years, Augmented Reality (AR) technology has developed rapidly, and a series of related commercial products have been successively released. Among the most promising AR glasses solutions, the core optics includes two parts. One is an optical engine that generates virtual images, that is, an AR optical engine; the other is an optical waveguide that is used to blend the virtual image and the real world and transmit the virtual image to the human eye. The optical performance of the AR optical engine directly determines the performance level of the entire AR glasses. At present, the trend of miniaturization and portability of AR glasses has basically locked in the optical design solutions of liquid crystal on silicon (LCOS) chips or micro-LED self-luminous chips for the AR optical engine. Due to problems still existing in aspects such as the resolution and cost of micro-LED chips, the LCOS solution has become a very important AR optical engine solution in the short term.

[0003] Currently, LCOS chips can achieve a resolution of 2K, and each pixel is controlled by a separate liquid crystal. Currently, due to the residual "liquid crystal pretilt angle" that exists according to the orientation of the liquid crystal when manufacturing LCOS, this will directly cause light leakage when the AR optical engine projects a dark field, resulting in a decrease in the contrast of the optical engine. Summary of the Invention

[0004] The present invention provides a method and a device for determining liquid crystal phase compensation of liquid crystal on silicon, which can quickly determine the parameters of liquid crystal phase compensation and improve the contrast of the LCOS optical engine in bright and dark fields.

[0005] In a first aspect, embodiments of the present invention provide a method for determining liquid crystal phase compensation of liquid crystal on silicon, where a liquid crystal phase compensation unit is arranged on the output side of the liquid crystal on silicon;

[0006] The determining method includes:

[0007] Obtaining the characterization relationship of the first polarization state of the output light according to the first Mueller matrix of the liquid crystal on silicon in the modulation state and the Mueller matrix of the liquid crystal phase compensation unit, and obtaining the characterization relationship of the second polarization state of the output light according to the second Mueller matrix of the liquid crystal on silicon in the non-modulation state and the Mueller matrix of the liquid crystal phase compensation unit; wherein, the independent variables in the Mueller matrix include the optical axis azimuth angle and the phase retardation;

[0008] Obtain the first polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the first polarization state; obtain the second polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the second polarization state, and establish a first contrast evaluation function based on the first polarized light component and the second polarized light component;

[0009] According to the characterization relationship, convert the independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase retardation degree, and obtain a second contrast evaluation function;

[0010] Obtain the target optical axis azimuth angle and the target phase retardation degree according to the second contrast evaluation function.

[0011] Optionally, obtaining the characterization relationship of the first polarization state of the output light according to the first Mueller matrix of the liquid crystal on silicon in the modulation state and the Mueller matrix of the liquid crystal phase compensation unit, and obtaining the characterization relationship of the second polarization state of the output light according to the second Mueller matrix of the liquid crystal on silicon in the non-modulation state and the Mueller matrix of the liquid crystal phase compensation unit, includes:

[0012] Obtain the first Mueller matrix, the second Mueller matrix, and the Mueller matrix of the liquid crystal phase compensation unit;

[0013] Characterize the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of linearly polarized light;

[0014] Characterize the second polarization state according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of linearly polarized light.

[0015] Optionally, obtaining the first Mueller matrix and the second Mueller matrix includes:

[0016] Equivalent the liquid crystal on silicon to a phase retarder, and obtain the Mueller matrix of the phase retarder;

[0017] Measure the Stokes vector of the liquid crystal on silicon in the modulation state and the Stokes vector of the liquid crystal on silicon in the non-modulation state using a polarization measuring instrument;

[0018] Determine the first Mueller matrix according to the Stokes vector of linearly polarized light, the Stokes vector of the liquid crystal on silicon in the modulation state, and the Mueller matrix of the phase retarder;

[0019] Determine the second Mueller matrix according to the Stokes vector of linearly polarized light, the Stokes vector of the liquid crystal on silicon in the non-modulation state, and the Mueller matrix of the phase retarder.

[0020] Optionally, obtaining the Mueller matrix of the liquid crystal phase compensation unit includes:

[0021] Equivalent the liquid crystal phase compensation unit to a phase retarder, obtain the Mueller matrix of the phase retarder, and characterize the Mueller matrix of the liquid crystal phase compensation unit based on the Mueller matrix of the phase retarder. The independent variables in the Mueller matrix of the liquid crystal phase compensation unit include the optical axis azimuth angle and the phase retardation degree.

[0022] Optionally, obtain the first polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the first polarization state; obtain the second polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the second polarization state, and establish a first contrast evaluation function according to the first polarized light component and the second polarized light component, including:

[0023] According to the azimuth angle and ellipticity in the first polarization state, decompose the first polarization state in the target polarization direction to obtain the first polarized light component;

[0024] According to the azimuth angle and ellipticity in the second polarization state, decompose the second polarization state in the target polarization direction to obtain the second polarized light component;

[0025] The first contrast evaluation function is characterized as the ratio of the first polarized light component to the second polarized light component.

[0026] Optionally, obtaining the target optical axis azimuth angle and the target phase retardation degree according to the second contrast evaluation function includes:

[0027] Taking the value of the second contrast evaluation function as the first preset value as the target, with the value constraint condition of the optical axis azimuth angle being 0 to 180 and the value constraint condition of the phase retardation degree being 0 to 360, obtain the target optical axis azimuth angle and the target phase retardation degree.

[0028] Optionally, after obtaining the target optical axis azimuth angle and the target phase retardation degree, it further includes:

[0029] Determine the actual optical axis azimuth angle actually assembled of the liquid crystal phase compensation unit according to the target phase retardation degree;

[0030] Determining the actual optical axis azimuth angle actually assembled of the liquid crystal phase compensation unit according to the target phase retardation degree includes:

[0031] In the non-modulation state, by rotating the liquid crystal phase compensation unit to minimize the output second polarized light component, the corresponding optical axis azimuth angle at this time is the actually assembled optical axis azimuth angle.

[0032] Second aspect, an embodiment of the present invention provides a device for determining the liquid crystal phase compensation of liquid crystal on silicon (LCOS), including: a characterization module, configured to obtain the characterization relationship of the first polarization state of the output light according to the first Mueller matrix of the LCOS in the modulation state and the Mueller matrix of the liquid crystal phase compensation unit, and obtain the characterization relationship of the second polarization state of the output light according to the second Mueller matrix of the LCOS in the non-modulation state and the Mueller matrix of the liquid crystal phase compensation unit; wherein, the independent variables in the Mueller matrix include the optical axis azimuth angle and the phase retardation;

[0033] a calculation module, configured to obtain the first polarization component in the target polarization direction according to the azimuth angle and the ellipticity in the first polarization state; obtain the second polarization component in the target polarization direction according to the azimuth angle and the ellipticity in the second polarization state, and establish a first contrast evaluation function according to the first polarization component and the second polarization component;

[0034] a conversion module, configured to convert the independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase retardation according to the characterization relationship, so as to obtain a second contrast evaluation function;

[0035] a target value acquisition module, configured to obtain the target optical axis azimuth angle and the target phase retardation according to the second contrast evaluation function.

[0036] Optionally, the characterization module includes: an acquisition unit, configured to acquire the first Mueller matrix, the second Mueller matrix, and the Mueller matrix of the liquid crystal phase compensation unit;

[0037] a first characterization unit, configured to characterize the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of linearly polarized light;

[0038] a second characterization unit, configured to characterize the second polarization state according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of linearly polarized light.

[0039] Optionally, the device for determining the liquid crystal phase compensation of the LCOS further includes: an assembly module, configured to determine the actual optical axis azimuth angle actually assembled by the liquid crystal phase compensation unit according to the target phase retardation;

[0040] The assembly module includes: a rotation unit, configured to rotate the liquid crystal phase compensation unit in the non-modulation state to minimize the output second polarization component, and the corresponding optical axis azimuth angle at this time is the actually assembled optical axis azimuth angle.

[0041] The method for determining liquid crystal phase compensation provided by the embodiments of the present invention establishes the characterization relationship between the Mueller matrix of the liquid crystal phase compensation unit in the modulation state and the first polarization state of the output light, and the characterization relationship between the Mueller matrix of the liquid crystal phase compensation unit in the non-modulation state and the second polarization state of the output light. Thus, the problem of converting the first polarization component in the first polarization state and the second polarization component in the second polarization state into the optical axis azimuth angle and phase retardation degree of the liquid crystal phase compensation unit can be realized. By optimizing the solution and simulation calculation, the target optical axis azimuth angle and target phase retardation degree are obtained, so that the parameters of the liquid crystal phase compensation can be quickly determined. By adding the liquid crystal phase compensation unit, the contrast of the bright field and dark field of the LCOS optical engine can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 FIG. is a schematic structural diagram of an imaging optical path of an LCOS in the related art;

[0043] Figure 2 FIG. is a schematic structural diagram of another imaging optical path of an LCOS in the related art;

[0044] Figure 3 FIG. is a schematic flow chart of a method for determining liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention;

[0045] Figure 4 FIG. is a schematic structural diagram of an imaging optical path of an LCOS optical engine provided by an embodiment of the present invention;

[0046] Figure 5 FIG. is a schematic flow chart of another method for determining liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention;

[0047] Figure 6 FIG. is a schematic structural diagram of a measurement structure of a Mueller matrix provided by an embodiment of the present invention;

[0048] Figure 7 FIG. is a schematic flow chart of a method for obtaining a first Mueller matrix and a second Mueller matrix provided by an embodiment of the present invention;

[0049] Figures 8 - 9 FIG. is a schematic structural diagram of a measurement structure of a Mueller matrix provided by an embodiment of the present invention;

[0050] Figure 10 FIG. is a schematic flow chart of another method for determining liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention;

[0051] Figure 11 and Figure 12 are the first polarization state and the second polarization state measured when the LCOS is incident with s-line polarized light;

[0052] Figure 13is the contrast value of the second contrast evaluation function at different phase delay degrees;

[0053] Figure 14 and Figure 15 is the detail of the change in the polarization state of the outgoing light after the phase compensation unit is added to the optical path;

[0054] Figure 16 is a schematic structural diagram of a device for determining the liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention;

[0055] Figure 17 is a schematic structural diagram of a device for determining the liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention;

[0056] Figure 18 is a schematic structural diagram of another device for determining the liquid crystal phase compensation of a liquid crystal on silicon provided by an embodiment of the present invention. Detailed implementation manners

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0058] Figure 1 is a schematic structural diagram of an imaging optical path of an LCOS in the related art. Under normal ideal conditions, when the LCOS is in the on-state modulation state, the input light is an s-line polarized light with a polarization direction perpendicular to the paper surface. The s-line polarized light can be reflected by a Polarizing Beam Splitter (PBS) to the LCOS, and after being modulated by the LCOS, the s-line polarized light is converted into a p-line polarized light. Among them, the polarization direction of the p-line polarized light is parallel to the paper surface and finally exits from the exit pupil 110 through the PBS. Figure 2 is a schematic structural diagram of another imaging optical path of an LCOS in the related art. In the off-state non-modulation state, the s-line polarized light passes through the LCOS without changing its polarization state and returns to the original path after being reflected by the PBS. Therefore, in the dark field at this time, there is no light leakage, and the ratio of the white field to the black field is infinite, and the contrast value is infinite, that is, the ideal contrast.

[0059] However, in fact, in combination with Figure 1, in the non-modulation state when powered off, after the s-line polarized light is reflected by the LCOS, due to the "liquid crystal pre-tilt angle" of the liquid crystal, the polarization state of the s-line polarized light changes. At this time, the polarization state output by the LCOS has light components of s-line polarized light and p-line polarized light. Therefore, when passing through the PBS, the s-line polarized light component in the light returns along the original path, and the p-line polarized light component passes through the PBS and finally exits from the exit pupil 110, resulting in dark field light leakage. At this time, the ratio of the white field to the black field is small, and the contrast value is low.

[0060] In the related art, the liquid crystal pre-tilt angle can be compensated by adding a liquid crystal compensation unit. For different LCOSs and liquid crystal compensation units with different design parameters, the performance of the contrast value is also different. In the prior art, the relevant design parameters of the liquid crystal compensation unit are obtained by measurement, and the acquisition efficiency of the design parameters of the liquid crystal compensation unit is low, and the accuracy also needs to be improved.

[0061] In view of this, Figure 3 The present invention provides a flowchart of a method for determining the liquid crystal phase compensation of a liquid crystal on silicon. This embodiment is applicable to the situation of determining the design parameters of a liquid crystal phase compensation unit. This method can be executed by a device for determining the liquid crystal phase compensation of a liquid crystal on silicon, and this device can be implemented in a hardware and / or software manner. The method specifically includes the following steps:

[0062] S110. Obtain the characterization relationship of the first polarization state of the output light according to the first Mueller matrix of the liquid crystal on silicon in the modulation state and the Mueller matrix of the liquid crystal phase compensation unit, and obtain the characterization relationship of the second polarization state of the output light according to the second Mueller matrix of the liquid crystal on silicon in the non-modulation state and the Mueller matrix of the liquid crystal phase compensation unit; wherein, the independent variables in the Mueller matrix include the optical axis azimuth angle and the phase retardation.

[0063] Specifically, Figure 4 The present invention provides a structural schematic diagram of the imaging optical path of an LCOS optical engine. Refer to Figure 4 , the liquid crystal phase compensation unit 210 is arranged on the output side of the LCOS, and the PBS is arranged on the side of the liquid crystal phase compensation unit 210 away from the LCOS. The modulation state refers to the state in which the LCOS modulates the first polarized light with the first polarization direction into the second polarized light with the second polarization direction in the working states such as when powered on. The non-modulation state refers to the state in which the LCOS does not modulate the first polarized light with the first polarization direction in the working states such as when powered off. Exemplarily, the first polarized light can be s-line polarized light, and the second polarized light can be p-line polarized light.

[0064] It can be seen from the imaging optical path that the s-line polarized light is reflected by the PBS, passes through the liquid crystal phase compensation unit 210 and the LCOS, and then passes through the LCOS again and is reflected and passes through the liquid crystal phase compensation unit 210 again to reach the reflection interface of the PBS. In the modulation state, the LCOS corresponds to the first Mueller matrix. By characterizing with the first Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210, the Stokes vector of the output light after the light beam passes through the LCOS and the liquid crystal phase compensation unit 210 can be obtained, that is, the first polarization state of the output light in the modulation state. It should be noted that the Mueller matrix is a 4x4 matrix, which can be used to describe the propagation and interaction of linearly polarized light on optical elements. It can relate the polarization state of the incident light to the properties of the optical elements, so as to calculate the polarization state of the outgoing light.

[0065] Similarly, in the non-modulation state, the LCOS corresponds to the second Mueller matrix. By characterizing with the second Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210, the Stokes vector of the output light after the light beam passes through the LCOS and the liquid crystal phase compensation unit 210 can be obtained, that is, the second polarization state of the output light in the non-modulation state. Due to the existence of the liquid crystal pretilt angle in the LCOS, in the non-modulation state, the second polarization state will also include a partial p-line polarized light component. Therefore, both the first polarization state and the second polarization state here can be regarded as elliptically polarized light with a certain degree of ellipticity.

[0066] S120. Obtain the first polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the first polarization state; obtain the second polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the second polarization state, and establish a first contrast evaluation function according to the first polarized light component and the second polarized light component;

[0067] Specifically, the first contrast evaluation function can characterize the light intensity contrast between the first polarization state and the second polarization state in the target polarization direction. For an LCOS optical engine, the light in the target polarization direction can be p-line polarized light. In an ideal state, the second polarization state does not include a p-line polarized light component. That is to say, in the dark field condition, there should be no light leakage. In the actual state, the phase compensation of the liquid crystal phase compensation unit 210 is used to minimize the p-line polarized light component in the second polarization state. Therefore, a first contrast evaluation function of the p-line polarized light component (the first polarized light component) in the first polarization state and the p-line polarized light component (the second polarized light component) in the second polarization state is established to evaluate the contrast between the bright field and the dark field of the LCOS. That is to say, when the ratio of the p-line polarized light component of the first polarization state to the p-line polarized light component of the second polarization state is larger, it indicates that the contrast between the bright field and the dark field is higher, and it also reflects that the light intensity of the p-line polarized light component in the second polarization state is smaller. Among them, both the first polarization state and the second polarization state can be regarded as elliptically polarized light with a certain ellipticity. Therefore, the p-line polarized light component can be obtained by decomposition according to the azimuth angle and ellipticity in the first polarization state; the p-line polarized light component can be obtained by decomposition according to the azimuth angle and ellipticity in the second polarization state.

[0068] S130. According to the characterization relationship, convert the independent variables in the first contrast evaluation function from the azimuth angle and ellipticity to the optical axis azimuth angle and phase retardation to obtain the second contrast evaluation function.

[0069] Specifically, the first polarization state is characterized by the first Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210. Among them, the first Mueller matrix can be measured by a Mueller matrix measuring instrument. The Mueller matrix of the liquid crystal phase compensation unit 210 can be characterized by an expression. The independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 include the optical axis azimuth angle and phase retardation, and the independent variables in the first polarization state include the azimuth angle and ellipticity. According to the characterization relationship, the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the independent variables in the first polarization state have a corresponding relationship. Through the solution and conversion of mathematical methods, the relationship between the first polarized light component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 can be obtained.

[0070] Similarly, the second polarization state is characterized by the second Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210. Among them, the second Mueller matrix can be measured by a Mueller matrix measuring instrument. The Mueller matrix of the liquid crystal phase compensation unit 210 can be characterized by an expression. The independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 include the optical axis azimuth angle and the phase retardation. The independent variables in the second polarization state include the azimuth angle and the ellipticity. According to the characterization relationship, the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the independent variables in the second polarization state have a corresponding relationship. Through the solution and conversion of mathematical methods, the relationship between the second polarization component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 can be obtained.

[0071] According to the relationship between the first polarization component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the relationship between the second polarization component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210, the first contrast evaluation function can be converted into a second contrast evaluation function. The independent variables of the second contrast evaluation function include the optical axis azimuth angle and the phase retardation of the liquid crystal phase compensation unit 210.

[0072] S140. Obtain the target optical axis azimuth angle and the target phase retardation according to the second contrast evaluation function.

[0073] Specifically, at this time, the problem of obtaining the optical axis azimuth angle and the phase retardation can be converted into a problem of solving the optimal solution of nonlinear programming. Exemplarily, taking the maximum value of the second contrast evaluation function as the objective function, constraint conditions are established for the optical axis azimuth angle and the phase retardation. Thus, through optimal solution, the target optical axis azimuth angle and the target phase retardation can be obtained. The optimal solution process here can adopt the optimal solution methods of existing related technologies, which will not be elaborated here.

[0074] The method for determining liquid crystal phase compensation provided by the embodiments of the present invention, by establishing the characterization relationship between the Mueller matrix of the liquid crystal phase compensation unit in the modulation state and the first polarization state of the output light, and the characterization relationship between the Mueller matrix of the liquid crystal phase compensation unit in the non-modulation state and the second polarization state of the output light, can thus realize the problem of converting the first polarization component in the first polarization state and the second polarization component in the second polarization state into the optical axis azimuth angle and the phase retardation of the liquid crystal phase compensation unit. Through optimal solution and simulation calculation, the target optical axis azimuth angle and the target phase retardation are obtained, so that the parameters of liquid crystal phase compensation can be quickly determined, and thus by adding a liquid crystal phase compensation unit, the contrast of the bright and dark fields of the LCOS optical engine can be improved.

[0075] Figure 5 It is a schematic flowchart of another method for determining liquid crystal phase compensation of liquid crystal on silicon provided by the embodiments of the present invention. Refer to Figure 5 , including:

[0076] S210. Obtain the first Mueller matrix, the second Mueller matrix, and the Mueller matrix of the liquid crystal phase compensation unit 210. Among them, the first Mueller matrix is denoted as Mr1, the second Mueller matrix is denoted as Mr2, and the Mueller matrix of the liquid crystal phase compensation unit 210 is denoted as Mc(θ|φ), where θ and φ respectively represent the independent variable optical axis azimuth angle and the phase retardation. The first Mueller matrix and the second Mueller matrix can be obtained by measuring with a Mueller matrix measuring instrument platform. Figure 6 The following is a schematic diagram of the measurement structure of the Mueller matrix provided by the embodiment of the present invention. Refer to Figure 6 , Place the LCOS on the Mueller matrix measuring instrument platform. The output end 610 and the input end 620 of the Mueller matrix measuring instrument are set at a certain angle. The LCOS is powered on and works, and is respectively switched to the modulation state and the non-modulation state. Using the Mueller matrix measuring instrument, the first Mueller matrix of the LCOS in the modulation state and the second Mueller matrix of the LCOS in the non-modulation state can be directly read out.

[0077] S220. Characterize the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit 210, and the Stokes vector of the linearly polarized light. Among them, for the S linearly polarized light of the LCOS optical engine as the incident light, the Stokes vector of the linearly polarized light takes the Stokes vector of the S linearly polarized light, denoted as Sin, Sin = [1, 0, 0, 0]. According to the optical path relationship, in the modulation state, the Stokes vector S01 output by the liquid crystal phase compensation unit 210 can be expressed as:

[0078] S01 = Mc(-θ|φ) * Mr1 * Mc(θ|φ) * Sin; which characterizes the first polarization state.

[0079] The S linearly polarized light incident light first passes through the liquid crystal phase compensation unit 210, is reflected by the LCOS, and then passes through the liquid crystal phase compensation unit 210 again. Here, Mc(-θ|φ) means that the optical axis is opposite when the first incident light exits, so the optical axis azimuth angle takes the opposite value.

[0080] S230. Characterize the second polarization state according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit 210, and the Stokes vector of the linearly polarized light. Among them, according to the optical path relationship, in the non-modulation state, the Stokes vector S02 output by the liquid crystal phase compensation unit 210 can be expressed as:

[0081] S02 = Mc(-θ|φ) * Mr2 * Mc(θ|φ) * Sin; which characterizes the second polarization state.

[0082] The incident S linearly polarized light first passes through the liquid crystal phase compensation unit 210, is reflected by the LCOS, and then passes through the liquid crystal phase compensation unit 210 again. Here, Mc(-θ|φ) means that the optical axis is in the reverse direction when the light is incident for the first time compared to when it exits, so the optical axis azimuth angle takes the opposite value for representation.

[0083] S240. Obtain the first polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the first polarization state; obtain the second polarized light component in the target polarization direction according to the azimuth angle and ellipticity in the second polarization state, and establish a first contrast evaluation function based on the first polarized light component and the second polarized light component;

[0084] S250. According to the characterization relationship, convert the independent variables in the first contrast evaluation function from the azimuth angle and ellipticity to the optical axis azimuth angle and phase retardation degree to obtain a second contrast evaluation function;

[0085] S260. Obtain the target optical axis azimuth angle and the target phase retardation degree according to the second contrast evaluation function.

[0086] Based on the above embodiments, Figure 7 The present invention provides a schematic flowchart of a method for obtaining a first Mueller matrix and a second Mueller matrix. Refer to Figure 7 , including:

[0087] S310. Equivalent the liquid crystal on silicon to a phase retarder and obtain the Mueller matrix of the phase retarder;

[0088] Specifically, for the imaging optical path of the LCOS optical engine, the function of the LCOS is to modulate the s linearly polarized light into p linearly polarized light in the modulation state and maintain the s linearly polarized state in the non-modulation state. When there is light leakage in the non-modulation state, the light reflected by the LCOS forms elliptically polarized light. Therefore, the LCOS can be equivalent to a phase retarder with an azimuth angle. Therefore, according to the phase retarder, the Mueller matrix Mwp(θ) of the phase retarder can be obtained, where the Mueller matrix Mwp(θ) of the phase retarder is expressed as:

[0089]

[0090] Among them, θ is the optical axis azimuth angle, and the value range of θ is [0, 180]; φ is the phase retardation degree, and the value range of φ is [0, 360].

[0091] S320. Use a polarization measuring instrument to measure the Stokes vector of the liquid crystal on silicon in the modulation state and the Stokes vector of the liquid crystal on silicon in the non-modulation state;

[0092] Specifically, Figures 8 - 9 The present invention provides a schematic diagram of a measurement structure of a Mueller matrix. Refer to Figure 8, by adjusting the azimuth angle of the polarizer 810 to make the reading of the polarimeter 820 be s-line polarized light, and its Stokes vector is Sin = [1, 0, 0, 0]. See Figure 9 , place the LCOS in the test optical path, switch the modulation state and non-modulation state of the LCOS respectively, and the Stokes vectors Sout1 of the LCOS in the modulation state and Sout2 of the LCOS in the non-modulation state can be obtained through the polarimeter 820.

[0093] S330. Determine the first Mueller matrix according to the Stokes vector of linearly polarized light, the Stokes vector of liquid crystal on silicon in the modulation state, and the Mueller matrix of the phase retarder;

[0094] Specifically, the Stokes vector Sout1 of the LCOS in the modulation state can be expressed as the product of the first Mueller matrix expressed as Mr1 and the Stokes vector of s-line polarized light, that is, Sout1 = Mr1 * Sin.

[0095] Sout1 can be rewritten as: Sout1 = Mwp(θ) * Sin. At this time, there are only two variables, the optical axis azimuth angle θ and the phase retardation degree φ, in the equation. According to the fact that the Stokes vector Sout1 of the LCOS in the modulation state is corresponding equal to the calculated result vector of Mwp(θ) * Sin, a set of values of θ and φ can be obtained, and then the first Mueller matrix Mr1 can be obtained.

[0096] S340. Determine the second Mueller matrix according to the Stokes vector of linearly polarized light, the Stokes vector of liquid crystal on silicon in the non-modulation state, and the Mueller matrix of the phase retarder.

[0097] Specifically, the Stokes vector Sout2 of the LCOS in the non-modulation state can be expressed as the product of the second Mueller matrix expressed as Mr2 and the Stokes vector of s-line polarized light, that is, Sout2 = Mr2 * Sin.

[0098] Sout2 can be rewritten as: Sout2 = Mwp(θ) * Sin. At this time, there are only two variables, the optical axis azimuth angle θ and the phase retardation degree φ, in the equation. According to the fact that the Stokes vector Sout2 of the LCOS in the modulation state is corresponding equal to the calculated result vector of Mwp(θ) * Sin, a set of values of θ and φ can be obtained, and then the second Mueller matrix Mr2 can be obtained.

[0099] Based on the above embodiments, optionally, obtaining the Mueller matrix of the liquid crystal phase compensation unit 210 includes;

[0100] The liquid crystal phase compensation unit 210 is equivalent to a phase retarder, and the Mueller matrix of the phase retarder is obtained. The Mueller matrix of the liquid crystal phase compensation unit 210 is characterized based on the Mueller matrix of the phase retarder. The independent variables in the Mueller matrix of the liquid crystal phase compensation unit 210 include the optical axis azimuth angle and the phase retardation degree.

[0101] Specifically, to compensate for the pretilt angle of the LCOS liquid crystal in the LCOS optical engine, a liquid crystal phase compensation unit 210 can be added. The Mueller matrix of the liquid crystal phase compensation unit 210 can be expressed as Mc(θ|φ). The liquid crystal phase compensation unit 210 is equivalent to a phase retarder. Therefore, the Mueller matrix Mc(θ|φ) of the liquid crystal phase compensation unit 210 can be characterized by the Mueller matrix Mwp(θ) of the phase retarder. At this time, the independent variables of the Mueller matrix Mc(θ|φ) of the liquid crystal phase compensation unit 210 include two variables: the optical axis azimuth angle θ and the phase retardation degree φ.

[0102] Figure 10 The flowchart of another method for determining the liquid crystal phase compensation of silicon-based liquid crystal provided by the embodiment of the present invention is shown in Figure 10 , including:

[0103] S410. Obtain the first Mueller matrix, the second Mueller matrix, and the Mueller matrix of the liquid crystal phase compensation unit 210;

[0104] S420. Characterize the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit 210, and the Stokes vector of the linearly polarized light. Among them, for the S linearly polarized light of the LCOS optical engine as the incident light, the Stokes vector of the linearly polarized light is the Stokes vector of the S linearly polarized light, denoted as Sin, and Sin = [1, 0, 0, 0]. According to the optical path relationship, in the modulation state, the first Stokes vector S01 output after passing through the liquid crystal phase compensation unit 210 can be expressed as:

[0105] S01 = Mc(−θ|φ) * Mr1 * Mc(θ|φ) * Sin; which characterizes the first polarization state.

[0106] The S linearly polarized light incident light first passes through the liquid crystal phase compensation unit 210, is reflected by the LCOS, and then passes through the liquid crystal phase compensation unit 210 again. Here, Mc(−θ|φ) means that the optical axis is opposite to the outgoing direction during the first incidence, so the optical axis azimuth angle takes the opposite value.

[0107] S430. Characterize the second polarization state according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit 210, and the Stokes vector of the linearly polarized light. Among them, according to the optical path relationship, in the non-modulation state, the second Stokes vector S02 output after passing through the liquid crystal phase compensation unit 210 can be expressed as:

[0108] S02 = Mc(−θ|φ) * Mr2 * Mc(θ|φ) * Sin; which characterizes the second polarization state.

[0109] S440. Decompose the first polarization state in the target polarization direction according to the azimuth angle and ellipticity in the first polarization state to obtain the first polarized light component;

[0110] Specifically, the first Stokes vector S01 is a vector including four elements, and the first Stokes vector S01 can be expressed as:

[0111]

[0112] Among them, S0 represents the total light intensity, S1 represents the difference between the horizontal linearly polarized light component and the vertical linearly polarized light component, S2 represents the difference between the 45° linearly polarized light component and the -45° linearly polarized light component, and S3 represents the difference between the right-handed circularly polarized light component and the left-handed circularly polarized light component; is the ellipticity of the first polarization state, is the azimuth angle of the first polarization state. According to the fact that the calculation result vectors of the first Stokes vector S01 and Mc(−θ|φ) * Mr1 * Mc(θ|φ) * Sin are correspondingly equal, for different optical axis azimuth angles θ and phase retardation degrees φ of the liquid crystal phase compensation unit 210, different first Stokes vectors S01 can be obtained, and the ellipticity of the first polarization state can be calculated one by one and the azimuth angle of the first polarization state .

[0113] In the embodiment of the present invention, the target polarization direction is the polarization direction of the p-linearly polarized light. To characterize the p-linearly polarized light component (the first polarized light component) of the polarized light in the first polarization state, the polarized light in the first polarization state can be decomposed in the polarization direction of the p-linearly polarized light. Figure 8 This is a schematic diagram of the coordinate axes of an elliptically polarized light provided by the embodiment of the present invention. Exemplarily, the Y-axis direction is the polarization direction of the p-linearly polarized light, and the X-axis is the polarization direction of the s-linearly polarized light. Then, the major axis a and the minor axis b of the elliptically polarized light in the figure can be decomposed into the X and Y axis directions:

[0114] Among them, the p-linearly polarized light component on the Y-axis can be expressed as:

[0115] ;

[0116] a1 is the major axis of the polarized light in the first polarization state, b1 is the minor axis of the polarized light in the first polarization state, is the azimuth angle of the first polarization state. It should be noted that Figure 8 the shape of the elliptically polarized light in is not the actual polarized light in the first polarization state, but only serves as a decomposition example.

[0117] S450. Decompose the second polarization state in the target polarization direction according to the azimuth angle and ellipticity in the second polarization state to obtain a second polarized light component;

[0118] Specifically, the second Stokes vector S02 is a vector including four elements, and the second Stokes vector S02 can be expressed as:

[0119]

[0120] where S0 represents the total light intensity, S1 represents the difference between the horizontal linearly polarized light component and the vertical linearly polarized light component, S2 represents the difference between the 45° linearly polarized light component and the -45° linearly polarized light component, and S3 represents the difference between the right-handed circularly polarized light component and the left-handed circularly polarized light component; is the ellipticity of the second polarization state, is the azimuth angle of the second polarization state. According to the fact that the second Stokes vector S02 is equal to the calculated result vector corresponding to Mc(-θ|φ) * Mr2 * Mc(θ|φ) * Sin, for different optical axis azimuth angles θ and phase retardation degrees φ of the liquid crystal phase compensation unit 210, different second Stokes vectors S02 can be obtained, and the ellipticity of the second polarization state and the azimuth angle of the second polarization state .

[0121] In the embodiment of the present invention, the target polarization direction is the polarization direction of p-line polarized light. To characterize the p-line polarized light component (second polarized light component) of the polarized light in the second polarization state, the polarized light in the second polarization state can be decomposed in the polarization direction of p-line polarized light. Combining Figure 8 , exemplarily, the Y-axis direction is the polarization direction of p-line polarized light, and the X-axis is the polarization direction of s-line polarized light. Then, the major axis a and the minor axis b of the elliptically polarized light in the figure can be decomposed into the X and Y axis directions:

[0122] where the p-line polarized light component on the Y-axis can be expressed as:

[0123] ;

[0124] a2 is the major axis of the polarized light in the second polarization state, b2 is the minor axis of the polarized light in the second polarization state, is the azimuth angle of the second polarization state.

[0125] S460. The first contrast evaluation function is characterized as the ratio of the first polarized light component to the second polarized light component. Among them, the first contrast evaluation function:

[0126] ;

[0127] S470. According to the representation relationship, convert the independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase retardation to obtain the second contrast evaluation function;

[0128] Specifically, according to the above process, it can be understood that for different optical axis azimuth angles θ and phase retardations φ of the liquid crystal phase compensation unit 210, different first Stokes vectors S01 and second Stokes vectors S02 can be obtained. Therefore, the ellipticity of the first polarization state and the azimuth angle of the first polarization state have a mathematical relationship with the optical axis azimuth angle θ and the phase retardation φ of the liquid crystal phase compensation unit 210. The ellipticity of the second polarization state and the azimuth angle of the second polarization state have a mathematical relationship with the optical axis azimuth angle θ and the phase retardation φ of the liquid crystal phase compensation unit 210. Therefore, through the solution and conversion of mathematical methods, the independent variables in the first contrast evaluation function can be converted from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase retardation of the liquid crystal phase compensation unit 210. That is, the second contrast evaluation function where T is the transformation from the independent variables of the azimuth angle and the ellipticity in the first contrast evaluation function to the optical axis azimuth angle θ and the phase retardation φ of the liquid crystal phase compensation unit 210.

[0129] S480. Obtain the target optical axis azimuth angle and the target phase retardation according to the second contrast evaluation function.

[0130] Specifically, based on the above process, the solution process is converted into a process of solving the optimal solution of nonlinear programming. Taking the value of the second contrast evaluation function as the first preset value as the goal, where the second contrast evaluation function is used to characterize the contrast between the bright field and the dark field. When the ratio of the p-line polarized light component of the first polarization state to the p-line polarized light component of the second polarization state is larger, it means that the contrast between the bright field and the dark field is higher. In order to obtain a higher contrast and reduce the light leakage in the non-modulation state, the first preset value can take the variable parameter corresponding to the maximum value of the second contrast evaluation function as the optimal solution. Therefore, the objective function can be set as: Max f(θ,φ); where the value constraint condition of the optical axis azimuth angle: 0 ≤ θ ≤ 180; the value constraint condition of the phase retardation: 0 ≤ φ ≤ 360. The optimization solution process here can adopt the optimization solution methods of existing related technologies, which will not be elaborated here.

[0131] Optionally, after obtaining the target optical axis azimuth angle and the target phase retardation, it further includes:

[0132] Determine the actual optical axis azimuth angle actually assembled by the liquid crystal phase compensation unit 210 according to the target phase retardation;

[0133] Specifically, for the optical axis azimuth angle θ, during the calculation process, the optical axis azimuth angle θ is only used to calculate the phase retardation φ. After selecting the actual model of the liquid crystal phase compensation unit 210 according to the phase retardation φ, in actual application, the optical axis azimuth angle θ of the liquid crystal phase compensation unit 210 needs to be determined according to specific assembly requirements.

[0134] Optionally, determining the actual optical axis azimuth angle of the actual assembly of the liquid crystal phase compensation unit 210 according to the target phase retardation includes:

[0135] In the non-modulation state, by rotating the liquid crystal phase compensation unit 210 to minimize the output second polarized component, the corresponding optical axis azimuth angle is the actual assembly optical axis azimuth angle.

[0136] Specifically, select the liquid crystal phase compensation unit 210 with the phase retardation φ as the target phase retardation. Power on the LCOS and operate it in the non-modulation state. Set the liquid crystal phase compensation unit 210 on the output side of the liquid crystal on silicon. By rotating the liquid crystal phase compensation unit 210, minimize the output second polarized component. Among them, the second polarized component can be characterized by the light intensity at the exit pupil 110 of the imaging optical path of the LCOS optical engine. That is to say, by measuring the optical power of the exit pupil 110, when the optical power is the smallest, the leakage light in the non-modulation state is the smallest, and the corresponding optical axis azimuth angle is the actual assembly optical axis azimuth angle.

[0137] Based on the above embodiments, an embodiment is provided to determine the parameters of liquid crystal phase compensation. In the embodiment of the present invention, the liquid crystal type of the LCOS screen is TN type. The first polarization state and the second polarization state of multiple LCOSs under the incidence of s-line polarized light are measured with a polarization measuring instrument, as Figure 11 and Figure 12 shown. According to the method for obtaining the first Mueller matrix and the second Mueller matrix, the first Mueller matrix Mr1 can be obtained:

[0138] Mr1 = [ 1 0 0 0;

[0139] 0 -0.9373 0.3416 -0.0687;

[0140] 0 -0.3416 -0.9398 -0.0121;

[0141] 0 -0.0687 0.0121 0.9976;]

[0142] The second Mueller matrix Mr2 can be obtained:

[0143] Mr2 = [ 1 0 0 0;

[0144] 0 0.9364 -0.1304 -0.3258;

[0145] 0 0.1304 -0.7327 0.6679;

[0146] 0 -0.3258 -0.6679 -0.6691;]

[0147] Based on steps S420 - S470, the contrast values of the second contrast evaluation function at different phase delay degrees can be obtained, and the results are as Figure 13 shown (curve 1). It can be seen from this that for this LCOS, the phase delay degree of the optimal phase compensation unit is between 18 - 25 nm, while ensuring that the white - field brightness attenuation is not significant; at this time Figure 14 and Figure 15 are the details of the change in the polarization state of the output light after adding the phase compensation unit to the optical path. Among them, the phase delay degree is 21 nm, and the optical axis azimuth angle is 152°.

[0148] Figure 16 FIG. is a schematic structural diagram of a device for determining liquid - crystal phase compensation of a liquid - crystal on silicon provided by an embodiment of the present invention. Refer to Figure 16 , and it includes: a characterization module 510, configured to obtain the characterization relationship of the first polarization state of the output light according to the first Mueller matrix of the liquid - crystal on silicon in the modulation state and the Mueller matrix of the liquid - crystal phase compensation unit 210, and obtain the characterization relationship of the second polarization state of the output light according to the second Mueller matrix of the liquid - crystal on silicon in the non - modulation state and the Mueller matrix of the liquid - crystal phase compensation unit 210; wherein, the independent variables in the Mueller matrix include the optical axis azimuth angle and the phase delay degree;

[0149] a calculation module 520, configured to obtain the first polarized light component in the target polarization direction according to the azimuth angle and the ellipticity in the first polarization state; obtain the second polarized light component in the target polarization direction according to the azimuth angle and the ellipticity in the second polarization state, and establish a first contrast evaluation function according to the first polarized light component and the second polarized light component;

[0150] a conversion module 530, configured to convert the independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity to the optical axis azimuth angle and the phase delay degree according to the characterization relationship, so as to obtain a second contrast evaluation function;

[0151] a target - value acquisition module 540, configured to obtain the target optical axis azimuth angle and the target phase delay degree according to the second contrast evaluation function.

[0152] Specifically, the modulation state refers to the state in which the LCOS modulates the first polarized light with the first polarization direction into the second polarized light with the second polarization direction when in working states such as power-on. The non-modulation state refers to the state in which the LCOS does not modulate the first polarized light with the first polarization direction when in working states such as power-off. Exemplarily, the first polarized light can be an s-line polarized light, and the second polarized light can be a p-line polarized light.

[0153] It can be seen from the imaging optical path that the s-line polarized light is reflected by the PBS, passes through the liquid crystal phase compensation unit 210 and the LCOS, and then passes through the LCOS and is reflected again through the liquid crystal phase compensation unit 210 to reach the reflection interface of the PBS. In the modulation state, the LCOS corresponds to the first Mueller matrix. The characterization module 510 can obtain the Stokes vector of the output light after the light beam passes through the LCOS and the liquid crystal phase compensation unit 210 by characterizing through the first Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210, that is, the first polarization state of the output light in the modulation state. Similarly, in the non-modulation state, the LCOS corresponds to the second Mueller matrix. The characterization module 510 can obtain the Stokes vector of the output light after the light beam passes through the LCOS and the liquid crystal phase compensation unit 210 by characterizing through the second Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210, that is, the second polarization state of the output light in the non-modulation state. Due to the existence of the liquid crystal pretilt angle in the LCOS, in the non-modulation state, the second polarization state also includes a partial p-line polarized light component. Therefore, both the first polarization state and the second polarization state here can be regarded as elliptically polarized lights with a certain degree of ellipticity.

[0154] The first contrast evaluation function can characterize the light intensity contrast between the first polarization state and the second polarization state in the target polarization direction. For the LCOS optical engine, the light in the target polarization direction can be p-line polarized light. In the ideal state, the second polarization state does not include a p-line polarized light component. That is to say, in the dark field condition, there should be no light leakage. In the actual state, the phase compensation of the liquid crystal phase compensation unit 210 is used to minimize the p-line polarized light component in the second polarization state. Therefore, the calculation module 520 establishes the first contrast evaluation function of the p-line polarized light component (the first polarized light component) in the first polarization state and the p-line polarized light component (the second polarized light component) in the second polarization state to evaluate the contrast between the bright field and the dark field of the LCOS. That is to say, when the ratio of the p-line polarized light component of the first polarization state to the p-line polarized light component of the second polarization state is larger, it indicates that the contrast between the bright field and the dark field is higher, and it also reflects that the light intensity of the p-line polarized light component in the second polarization state is smaller. Among them, both the first polarization state and the second polarization state can be regarded as elliptically polarized lights with a certain degree of ellipticity. Therefore, the calculation module 520 can decompose to obtain the p-line polarized light component according to the azimuth angle and the ellipticity rate in the first polarization state; the calculation module 520 can decompose to obtain the p-line polarized light component according to the azimuth angle and the ellipticity rate in the second polarization state.

[0155] The first polarization state is characterized by the first Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210. Among them, the first Mueller matrix can be measured by a Mueller matrix measuring instrument. The Mueller matrix of the liquid crystal phase compensation unit 210 can be characterized by an expression. The independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 include the optical axis azimuth angle and the phase retardation. The independent variables in the first polarization state include the azimuth angle and the ellipticity. According to the characterization relationship, the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the independent variables in the first polarization state have a corresponding relationship. The conversion module 530 can obtain the relationship between the first polarized light component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 through the solution conversion of mathematical methods.

[0156] Similarly, the second polarization state is characterized by the second Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit 210. Among them, the second Mueller matrix can be measured by a Mueller matrix measuring instrument. The Mueller matrix of the liquid crystal phase compensation unit 210 can be characterized by an expression. The independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 include the optical axis azimuth angle and the phase retardation. The independent variables in the second polarization state include the azimuth angle and the ellipticity. According to the characterization relationship, the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the independent variables in the second polarization state have a corresponding relationship. The conversion module 530 can obtain the relationship between the second polarized light component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 through the solution conversion of mathematical methods.

[0157] The conversion module can convert the first contrast evaluation function into the second contrast evaluation function according to the relationship between the first polarized light component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210 and the relationship between the second polarized light component and the independent variables of the Mueller matrix of the liquid crystal phase compensation unit 210. The independent variables of the second contrast evaluation function include the optical axis azimuth angle and the phase retardation of the liquid crystal phase compensation unit 210.

[0158] At this time, the problem of obtaining the optical axis azimuth angle and the phase retardation can be converted into a problem of solving the optimal solution of nonlinear programming. Exemplarily, the target value acquisition module 540 takes the maximum value of the second contrast evaluation function as the objective function, and establishes constraint conditions for the optical axis azimuth angle and the phase retardation, so as to obtain the target optical axis azimuth angle and the target phase retardation through optimal solution. The optimal solution process here can adopt the optimal solution methods of existing related technologies, which will not be elaborated here.

[0159] Optionally, the device for determining the liquid crystal phase compensation of liquid crystal on silicon (LCOS) further includes an assembly module configured to determine the actual optical axis azimuth angle actually assembled by the liquid crystal phase compensation unit 210 according to the target phase retardation. Specifically, for the optical axis azimuth angle θ, during the calculation process, the optical axis azimuth angle θ is only used to cooperate with the calculation of the phase retardation φ. After selecting the actual model of the liquid crystal phase compensation unit 210 according to the phase retardation φ, the assembly module needs to determine the actual optical axis azimuth angle θ according to the specific assembly requirements.

[0160] Optionally, the assembly module includes a rotation unit configured to minimize the output second polarization component by rotating the liquid crystal phase compensation unit 210 in the non-modulation state. At this time, the corresponding optical axis azimuth angle is the actually assembled optical axis azimuth angle. Specifically, select the liquid crystal phase compensation unit 210 with the phase retardation φ as the target phase retardation, power on the LCOS and operate it in the non-modulation state, set the liquid crystal phase compensation unit 210 on the output side of the LCOS, and the rotation unit rotates the liquid crystal phase compensation unit 210 to minimize the output second polarization component. Among them, the second polarization component can be characterized by the light intensity of the exit pupil 110 of the imaging optical path of the LCOS optical engine. That is to say, by measuring the optical power of the exit pupil 110, when the optical power is the smallest, the leakage light in the non-modulation state is the smallest, and the corresponding optical axis azimuth angle at this time is the actually assembled optical axis azimuth angle.

[0161] Figure 17 The following is a schematic structural diagram of a device for determining the liquid crystal phase compensation of liquid crystal on silicon provided by an embodiment of the present invention. Refer to Figure 17, including the LOCS positioning platform 830, the optical-mechanical fixing structure 840, and the power meter platform 850; the arrows therein are schematic diagrams of the optical path. In actual production, the LCOS optical machine is held by the optical-mechanical fixing structure to ensure the repeatability accuracy of the picking and placing of the optical machine. A rotating unit is also provided on the LOCS positioning platform 830. The rotating unit holds the liquid crystal phase compensation unit 210, and the rotating unit can rotate the liquid crystal phase compensation unit 210 around the center of the LCOS light-emitting surface. The LOCS is fixed on the LOCS positioning platform 830, and the liquid crystal phase compensation unit 210 rotates against the LCOS protective glass surface. The vertical distance between the liquid crystal phase compensation unit 210 and the lower edge of the LOCS optical machine should be as short as possible. Exemplarily, the distance from the optical machine is at least within 1 cm. The optical path from the light output port of the optical machine to the power meter 851 should be ensured to avoid being affected by stray light. The shape of the aperture 860 can be made rectangular, and the specific dimensions depend on the specific project. The entire operation environment should be carried out in a closed darkroom as much as possible. Select the liquid crystal phase compensation unit 210 with the phase retardation φ as the target phase retardation. Power on the LCOS and keep it in the non-modulation state. The rotating unit rotates the liquid crystal phase compensation unit 210 until the light power measured by the power meter 851 is minimized. At this time, the leakage light in the non-modulation state is the smallest, and the corresponding optical axis azimuth angle is the actual assembly optical axis azimuth angle.

[0162] Figure 18 The following is a schematic structural diagram of another device for determining the liquid crystal phase compensation of silicon-based liquid crystals provided by an embodiment of the present invention. Refer to Figure 18 , including a light source 870, an aperture 860, a polarizer 810, a PBS, a rotating unit, and a power meter 851; among them, the light source 870, the aperture 860, the polarizer 810, and the PBS are on the same optical axis. Power on the LCOS and keep it in the non-modulation state. The light source 870 can select a laser light source with good collimation. After being polarized into s-line polarized light by the polarizer 810, it is reflected to the LCOS through the PBS. By rotating the optical axis azimuth angle of the liquid crystal phase compensation unit through the rotating unit until the reading of the power meter 851 is minimized, the corresponding optical axis azimuth angle at this time is the actual assembly optical axis azimuth angle.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining liquid crystal phase compensation of liquid crystal on silicon, characterized in that: The liquid crystal phase compensation unit is arranged at the output side of the silicon-based liquid crystal; The determination method comprises: A characterization relationship of a first polarization state of the output light is obtained according to a first Mueller matrix of the silicon-based liquid crystal in a modulated state and a Mueller matrix of the liquid crystal phase compensation unit, and a characterization relationship of a second polarization state of the output light is obtained according to a second Mueller matrix of the silicon-based liquid crystal in a non-modulated state and a Mueller matrix of the liquid crystal phase compensation unit; wherein the independent variables in the Mueller matrix include an optical axis azimuth and a phase delay; Obtaining a first polarization component in a target polarization direction according to the azimuth and ellipticity in the first polarization state; obtaining a second polarization component in the target polarization direction according to the azimuth and ellipticity in the second polarization state, and establishing a first contrast evaluation function according to the first polarization component and the second polarization component; According to the characterization relationship, the independent variables in the first contrast evaluation function are converted from the azimuth angle and the ellipticity into the optical axis azimuth angle and the phase delay degree to obtain a second contrast evaluation function; A target optical axis azimuth and a target phase delay are obtained according to the second contrast evaluation function.

2. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 1, characterized in that: The method comprises: obtaining a characterization relationship of a first polarization state of output light according to a first Mueller matrix of the silicon-based liquid crystal in a modulated state and a Mueller matrix of the liquid crystal phase compensation unit, and obtaining a characterization relationship of a second polarization state of output light according to a second Mueller matrix of the silicon-based liquid crystal in a non-modulated state and a Mueller matrix of the liquid crystal phase compensation unit, including: Acquire the first Mueller matrix, the second Mueller matrix, and the Mueller matrix of the liquid crystal phase compensation unit; characterizing the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of the linearly polarized light; The second polarization state is characterized according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of the linearly polarized light.

3. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 2, characterized in that: Acquiring the first Mueller matrix and the second Mueller matrix includes: Treating the silicon-based liquid crystal as a phase retarder to obtain a Mueller matrix of the phase retarder; Using a polarimeter to measure the Stokes vector of the silicon-based liquid crystal in a modulated state and the Stokes vector of the silicon-based liquid crystal in a non-modulated state; Determine the first Mueller matrix according to the Stokes vector of the linearly polarized light, the Stokes vector of the silicon-based liquid crystal in a modulation state, and the Mueller matrix of the phase retarder; The second Mueller matrix is ​​determined according to the Stokes vector of the linearly polarized light, the Stokes vector of the silicon-based liquid crystal in a non-modulated state, and the Mueller matrix of the phase retarder.

4. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 3, characterized in that: Obtaining the Mueller matrix of the liquid crystal phase compensation unit, comprising: The liquid crystal phase compensation unit is equivalent to a phase retarder, and the Mueller matrix of the phase retarder is obtained. The Mueller matrix of the liquid crystal phase compensation unit is characterized based on the Mueller matrix of the phase retarder, and the independent variables in the Mueller matrix of the liquid crystal phase compensation unit include the optical axis azimuth and the phase retardation degree.

5. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 1, characterized in that: Obtaining a first polarization component in a target polarization direction according to the azimuth and ellipticity in the first polarization state; obtaining a second polarization component in the target polarization direction according to the azimuth and ellipticity in the second polarization state, and establishing a first contrast evaluation function according to the first polarization component and the second polarization component, including: Decomposing the first polarization state in a target polarization direction to obtain a first polarization component according to the azimuth angle and the ellipticity in the first polarization state; Decomposing the second polarization state in a target polarization direction to obtain a second polarization component according to the azimuth and ellipticity in the second polarization state; The first contrast evaluation function is characterized by a ratio of the first polarization component to the second polarization component.

6. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 1, characterized in that: Obtaining a target optical axis azimuth and a target phase delay according to the second contrast evaluation function includes: Taking the second contrast evaluation function value as the first preset value as the target, the optical axis azimuth value constraint condition is 0 to 180, the phase delay value constraint condition is 0 to 360, and the target optical axis azimuth and target phase delay are obtained.

7. The method for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 6, characterized in that: After obtaining the target optical axis azimuth and target phase delay, the following steps are also included: Determining the actual optical axis azimuth angle of the liquid crystal phase compensation unit actually assembled according to the target phase retardation; Determining the actual optical axis azimuth angle of the liquid crystal phase compensation unit actually assembled according to the target phase retardation includes: In the non-modulation state, the liquid crystal phase compensation unit is rotated to minimize the output second polarization component, and the corresponding optical axis azimuth angle is the actual assembly optical axis azimuth angle.

8. A device for determining liquid crystal phase compensation of liquid crystal on silicon, characterized in that: include: A characterization module, used for obtaining a characterization relationship of a first polarization state of the output light according to a first Mueller matrix of the silicon-based liquid crystal in a modulated state and a Mueller matrix of a liquid crystal phase compensation unit, and obtaining a characterization relationship of a second polarization state of the output light according to a second Mueller matrix of the silicon-based liquid crystal in a non-modulated state and a Mueller matrix of the liquid crystal phase compensation unit; wherein the independent variables in the Mueller matrix include an optical axis azimuth and a phase delay; A calculation module, used to obtain a first polarization component in a target polarization direction according to the azimuth and ellipticity in the first polarization state; obtain a second polarization component in the target polarization direction according to the azimuth and ellipticity in the second polarization state, and establish a first contrast evaluation function according to the first polarization component and the second polarization component; A conversion module, configured to convert the independent variables in the first contrast evaluation function from the azimuth angle and the ellipticity into the optical axis azimuth angle and the phase delay degree according to the characterization relationship, so as to obtain a second contrast evaluation function; A target value acquisition module is used to obtain a target optical axis azimuth and a target phase delay according to the second contrast evaluation function.

9. The device for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 8, characterized in that: The characterization modules include: An acquisition unit, used to acquire the first Mueller matrix, the second Mueller matrix and the Mueller matrix of the liquid crystal phase compensation unit; A first characterization unit, configured to characterize the first polarization state according to the first Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit, and the Stokes vector of the linearly polarized light; The second characterization unit is used to characterize the second polarization state according to the second Mueller matrix, the Mueller matrix of the liquid crystal phase compensation unit and the Stokes vector of the linearly polarized light.

10. The device for determining liquid crystal phase compensation of liquid crystal on silicon according to claim 8, characterized in that: Also includes: An assembly module, used for determining an actual optical axis azimuth angle of the actual assembly of the liquid crystal phase compensation unit according to the target phase retardation; The assembly module comprises: The rotating unit is used to minimize the output second polarization component by rotating the liquid crystal phase compensation unit in a non-modulation state. At this time, the corresponding optical axis azimuth angle is the actual assembly optical axis azimuth angle.

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