Phase modulator

Abstract

A phase modulator according to an embodiment of the present disclosure comprises: a phase modulation element that has a plurality of pixels and that can modulate the phase of light from a light source; a generation unit that can generate first data relating to a phase modulation amount for each of the pixels; and an adjustment unit that can adjust the first data so that a phase modulation range include a reference phase value based on the wavelength of the light from the light source. The phase modulation element can modulate the phase of the light from the light source on the basis of the first data adjusted by the adjustment unit.

Description

Phase Modulation Device

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

[0002] A liquid crystal display device has been proposed that has a glass substrate coated with an anti-reflection film to prevent multiple reflections in the liquid crystal layer (Patent Document 1).A phase modulation device using liquid crystal has also been proposed.

[0003] Japanese Patent Application Publication No. 5-66393

[0004] In a phase modulation device, it is required to suppress deterioration of image quality.

[0005] It is desirable to provide a phase modulation device that can suppress degradation of image quality.

[0006] According to an embodiment of the present disclosure, a phase modulation device includes a phase modulation element having a plurality of pixels and capable of modulating the phase of light from a light source, a generation unit capable of generating first data relating to a phase modulation amount for each pixel, and an adjustment unit capable of adjusting the first data so that a phase modulation range includes a reference phase value based on the wavelength of the light from the light source. The phase modulation element is capable of modulating the phase of the light from the light source based on the first data adjusted by the adjustment unit.

[0007] FIG. 1 is a diagram illustrating an example of a schematic configuration of a phase modulation device according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a configuration of a phase modulation element according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a relationship between a voltage applied to a pixel of the phase modulation element according to the first embodiment of the present disclosure and a phase modulation amount. FIG. 4 is a diagram illustrating an example of signal processing by the phase modulation device according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of a configuration of a phase modulation element according to the first embodiment of the present disclosure. FIG. 6 is a diagram illustrating another example of a configuration of a phase modulation element according to the first embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example of setting a phase adjustment range by the phase modulation device according to the first embodiment of the present disclosure. FIG. 8 is a diagram illustrating an example of setting a phase adjustment range by the phase modulation device according to the first embodiment of the present disclosure. FIG. 9 is a diagram illustrating an example of a schematic configuration of a phase modulation device according to a second embodiment of the present disclosure.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order: 1. First embodiment 2. Second embodiment 3. Modification

[0009] 1. First Embodiment FIG. 1 is a diagram illustrating an example of a schematic configuration of a phase modulation device according to a first embodiment of the present disclosure. The phase modulation device 1 is a device capable of modulating the phase of light. The phase modulation device 1 controls the phase of light using a phase modulation element. The phase modulation device 1 can control the wavefront of light and output any pattern of light. The phase modulation device 1 is applicable to various display devices and optical devices. The phase modulation device 1 can be applied to, for example, a 3D display device, a laser processing device, an ophthalmoscopic device, an astronomical observation device, etc.

[0010] The phase modulation device 1 has a signal processing unit 10, a driving unit 50, and a phase modulation element 100. Furthermore, as shown in FIG. 1 , the phase modulation device 1 may also be configured to include a light source 60. The signal processing unit 10 is configured to perform signal processing. The signal processing unit 10 has, for example, a processor and memories such as ROM and RAM, and performs signal processing (information processing) based on a program. The signal processing unit 10 can also be called a signal processing circuit. The signal processing unit 10 is also a control unit and is configured to be able to control each unit of the phase modulation device 1. The signal processing unit 10 can, for example, supply a signal that controls the driving unit 50 to the driving unit 50, thereby controlling the operation of the driving unit 50.

[0011] The signal processing unit 10 has a generating unit 11, a setting unit 12, and an adjusting unit 13. The generating unit 11 is configured to be able to generate data related to the phase modulation amount (hereinafter referred to as phase distribution data). The phase distribution data (phase distribution information) is data related to the phase modulation amount for each pixel of the phase modulation element 100. The phase distribution data is data related to the distribution of phase modulation amounts set in the phase modulation element 100, and can also be said to be data related to the magnitude of the voltage (potential difference) supplied between the electrodes of each pixel of the phase modulation element 100. The generating unit 11 is a phase distribution generating unit capable of generating phase distribution data.

[0012] The generator 11 generates phase distribution data D1 based on, for example, image data (image signals) input from an external source. The generator 11 can generate the phase distribution data D1 by performing light propagation calculations using the image data. The generator 11 calculates the phase modulation amount for each pixel required to display (reproduce) an image (e.g., a hologram reproduced image) based on the image data, and generates phase distribution data D1 related to the phase modulation amount for each pixel. The generator 11 can also be considered a calculation unit capable of calculating a phase distribution. The generator 11 outputs the generated phase distribution data D1 to the adjustment unit 13.

[0013] The setting unit 12 is configured to set a setting range of the phase modulation amount in the phase modulation element 100. The setting unit 12 generates data relating to the setting range of the phase modulation amount (hereinafter referred to as phase setting range data). The phase setting range data is data relating to the range of the phase modulation amount that can be set in the phase modulation element 100. The setting unit 12 is a phase modulation range setting unit that can set the phase modulation range.

[0014] The setting unit 12 determines, for example, the median, upper limit, lower limit, etc. of the setting range of the phase modulation amount, and generates phase setting range data indicating the median, upper limit, lower limit, etc. of the setting range. The setting unit 12 can also be said to be a determination unit that can determine the setting range of the phase modulation amount in the phase modulation element 100. The setting unit 12 outputs the generated phase setting range data to the adjustment unit 13.

[0015] The adjustment unit 13 is configured to be able to adjust the phase distribution data. As will be described later, the adjustment unit 13 adjusts the phase distribution data D1 so that the phase modulation range includes a phase value (reference phase value) based on the wavelength of light from the light source 60. The adjustment unit 13 is a phase distribution adjustment unit that can adjust the phase distribution. The adjustment unit 13 adjusts (corrects) the phase modulation amount for each pixel indicated by the phase distribution data D1 based on the reference phase value. The adjustment unit 13 can also be said to be a correction unit that can correct the phase distribution data. The adjustment unit 13 can generate phase distribution data D2 related to the distribution of the adjusted phase modulation amount and output it to the drive unit 50.

[0016] The driving unit 50 is configured to drive the phase modulation element 100. The driving unit 50 is a driving device (driving circuit) and can control the operation of the phase modulation element 100. The driving unit 50 is configured to be able to control, for example, the voltage to the phase modulation element 100. The driving unit 50 can supply a voltage to the phase modulation element 100 for driving each pixel of the phase modulation element 100 and control the phase modulation by the phase modulation element 100.

[0017] 1 , the driver 50 receives the phase distribution data D2 adjusted by the adjuster 13. Based on the phase distribution data D2, the driver 50 determines the magnitude (set value) of the voltage to be supplied to each pixel of the phase modulation element 100, and supplies the voltage to each pixel of the phase modulation element 100. The driver 50 can adjust the amount of phase modulation at each pixel by controlling the voltage to be supplied to each pixel of the phase modulation element 100, for example, so as to obtain a distribution of the amount of phase modulation indicated by the phase distribution data D2.

[0018] The phase modulation element 100 is an element capable of modulating the phase of incident light. The phase modulation element 100 is a liquid crystal phase modulation element, and controls the phase of light from the light source 60 by using liquid crystal. The phase modulation element 100 may be a transmissive liquid crystal element or a reflective liquid crystal element.

[0019] 2 is a diagram illustrating an example of the configuration of a phase modulation element according to the first embodiment. The phase modulation element 100 has a plurality of pixels P and is configured to be able to control the phase of light for each pixel P. In the phase modulation element 100, the plurality of pixels P are arranged two-dimensionally. As shown in FIG. 1, the phase modulation element 100 has a first substrate 101, a second substrate 102, and a liquid crystal layer 110.

[0020] The first substrate 101 and the second substrate 102 are fixed with a sealing material (not shown) with the liquid crystal layer 110 sandwiched therebetween. The pair of first substrate 101 and second substrate 102 are arranged spaced apart from each other in the stacking direction. Polarizers may be arranged above the first substrate 101 and below the second substrate 102, as necessary.

[0021] The first substrate 101 is a transparent substrate that transmits light and is made of, for example, a glass substrate. A first electrode 20a is provided on the first substrate 101. The second substrate 102 is disposed opposite the first substrate 101. The second substrate 102 is formed of, for example, a glass substrate, a semiconductor substrate (e.g., a silicon substrate), or the like. A second electrode 20b is provided on the second substrate 102. The second electrode 20b is disposed opposite the first electrode 20a, with a portion of the liquid crystal layer 110 sandwiched therebetween.

[0022] The first electrode 20a is a transparent electrode and is made of, for example, ITO (indium tin oxide). The first electrode 20a is an electrode common to a plurality of pixels P, and can also be called a counter electrode (or a common electrode).

[0023] The second electrode 20b is made of a transparent material such as ITO. The second electrode 20b may also be made of other metal materials such as aluminum (Al). The second electrode 20b is an electrode provided for each pixel P and can also be called a pixel electrode. Furthermore, elements such as transistors and wiring are formed on the second substrate 102. A circuit for driving each pixel P may be provided on the second substrate 102.

[0024] The liquid crystal layer 110 is a layer containing a plurality of liquid crystal molecules, and is provided between the first substrate 101 and the second substrate 102. The liquid crystal layer 110 is sealed between the first substrate 101 and the second substrate 102 by a sealing material. By applying a voltage between the first electrode 20a and the second electrode 20b, the liquid crystal molecules in the liquid crystal layer 110, which have dielectric anisotropy, respond, making it possible to control the orientation of the liquid crystal molecules.

[0025] The phase modulation element 100 also has an anti-reflection film 40 and an alignment film 30 (a first alignment film 30a and a second alignment film 30b in FIG. 2). The anti-reflection film 40 is made of, for example, a metal oxide. In the example shown in FIG. 2, the anti-reflection film 40 is provided between the first electrode 20a and the first alignment film 30a to reduce (suppress) reflection. The anti-reflection film 40 may also be provided between the second electrode 20b and the second alignment film 30b. Note that the phase modulation element 100 does not necessarily need to be provided with the anti-reflection film 40.

[0026] The alignment film 30 can align the liquid crystal molecules of the liquid crystal layer 110 in a specific direction. The alignment film 30 is a film (layer) that can control the alignment of the liquid crystal molecules. The alignment film 30 is made of, for example, a film formed by oblique evaporation (oblique evaporation film), a polymer, etc.

[0027] 2, the first alignment film 30a is located between the liquid crystal layer 110 and the first electrode 20a and is provided on the first electrode 20a. The second alignment film 30b is located between the liquid crystal layer 110 and the second electrode 20b and is provided on the second electrode 20b. The liquid crystal molecules of the liquid crystal layer 110 are held in a tilted state by the first alignment film 30a and the second alignment film 30b. That is, a predetermined pretilt angle (tilt angle) is imparted to the liquid crystal molecules of the liquid crystal layer 110.

[0028] In the phase modulation element 100, the electric field in the liquid crystal layer 110 changes depending on the voltage supplied between the first electrode 20 a and the second electrode 20 b, changing the orientation of the liquid crystal molecules. By controlling the voltage supplied to the second electrode 20 b of each pixel P, the orientation of the liquid crystal molecules can be adjusted for each pixel P, changing the refractive index and changing the optical path length.

[0029] Light incident on each pixel P of the phase modulation element 100 is emitted after being phase-modulated according to the tilt amount of the liquid crystal molecules of each pixel P. The phase modulation element 100 generates a phase delay that differs for each pixel P in the incident light, making it possible to propagate light with a desired wavefront.

[0030] 2 schematically represents multiple reflected light that may occur when the phase modulation element 100 is a reflective liquid crystal element. Furthermore, multiple reflected light W2 schematically represents multiple reflected light that may occur when the phase modulation element 100 is a transmissive liquid crystal element. Even when the phase modulation element 100 has the anti-reflection film 40, multiple reflected light may occur due to multiple reflections between the first substrate 101 and the second substrate 102 depending on the wavelength of the incident light, and this may cause disturbances in the wavefront of the emitted light.

[0031] Therefore, the phase modulation device 1 according to this embodiment adjusts the phase distribution data so that the phase modulation range of each pixel P of the phase modulation element 100 includes the reference phase value, and performs phase modulation of light by the phase modulation element 100. The reference phase value is a phase modulation amount that is set so that the phases of the light beams multiple-reflected by the phase modulation element 100 are the same. In this embodiment, it is possible to reduce the phase difference between the multiple-reflected light beams, and suppress wavefront disturbances caused by the multiple-reflected light beams.

[0032] 3 is a diagram showing an example of the relationship between the voltage applied to a pixel of the phase modulation element according to the first embodiment and the amount of phase modulation. In FIG. 3, the horizontal axis represents the applied voltage, and the vertical axis represents the amount of phase modulation. The reference phase value θc shown in FIG. 3 is determined according to the wavelength of light incident on the phase modulation element 100. In this embodiment, the reference phase value θc is set by the setting unit 12 or the adjustment unit 13 according to the wavelength of light from the light source 60, and is, for example, 0 or 2π.

[0033] 3 is the phase modulation range indicated by the above-described phase setting range data, and is the setting range of the phase modulation amount in the phase modulation element 100. The setting unit 12 sets a range including the reference phase value θc within the range of the phase modulation amount that can be set in the phase modulation element 100 as the phase modulation range R1, and generates phase setting range data indicating the phase modulation range R1.

[0034] The phase modulation range R2 is the phase modulation range indicated by the above-mentioned phase distribution data D2, and is the range of phase modulation amounts required for image display. The adjustment unit 13 shifts and adjusts the phase distribution data D1 generated by the generation unit 11 so that the phase modulation range indicated by the phase distribution data D1 includes the reference phase value θc. The phase modulation range indicated by the phase distribution data D2 generated by the shift adjustment becomes the phase modulation range R2 including the reference phase value θc, as in the example shown in FIG.

[0035] The driver 50 supplies a voltage to each pixel P of the phase modulation element 100 so as to obtain the phase distribution indicated by the phase distribution data D2. Since the phase modulation amount in the phase modulation element 100 is a value within a range including the reference phase value θc, it is possible to reduce the difference in phase between the light beams that are multiple-reflected by the phase modulation element 100. This makes it possible to suppress wavefront distortion caused by multiple-reflected light.

[0036] 4, the adjustment unit 13 according to the present embodiment shifts and adjusts the phase modulation amount for each pixel P. The adjustment unit 13 can adjust the phase distribution data D1 so that the difference between the phase modulation amount for each pixel P and the reference phase value θc becomes smaller. The adjustment unit 13 may also shift and adjust the phase modulation amount so that the sum S1 (see the following equation (1)) of the squared values ​​of the differences between the phase modulation amount Ψ for each pixel P and the reference phase value θc becomes smaller.

[0037] In this case, the adjustment unit 13 may adjust the phase modulation amount Ψ so that the sum S1 is minimized. This makes it possible to reduce the difference between the phase modulation amount Ψ of each pixel P and the reference phase value θc, thereby effectively suppressing wavefront disturbances caused by multiple reflected light. This makes it possible to improve the image quality. Note that when adjusting the phase modulation amount within the phase modulation range R1, the adjustment unit 13 may perform a wrapping (folding) process on the phase modulation amount according to the phase modulation range R1.

[0038] The generation unit 11 of the phase modulation device 1 is configured to generate the phase distribution data D1 by performing a single light propagation calculation, for example. The generation unit 11 can generate the phase distribution data D1 by performing a single light propagation calculation between the image plane of the phase modulation element 100 and the reproduction plane under the condition that a uniform phase is set as an initial phase on the reproduction plane, which is an image plane formed by phase-modulated light.

[0039] ​In this case, the generation unit 11 may use, as a propagation calculation method, a Sommerfeld diffraction integral, an angular spectrum method, a Fresnel diffraction, etc. Furthermore, for example, the generation unit 11 may use, as a method for converting amplitude information obtained by the light propagation calculation into phase information, a double phase (DP) method, a complex field encoding (CFE) method, etc.

[0040] The generator 11 can bias the phase distribution of the phase distribution data D1 by the above-described light propagation calculation, thereby reducing the effect of multiple reflections on image quality. Furthermore, since the light propagation calculation is performed in one step, the calculation speed can be kept high.

[0041] The generation unit 11 may generate the phase distribution data D1 by performing light propagation calculations multiple times. The generation unit 11 may use the Gerchberg-Saxton method, the Wirtinger Holography method, the Stochastic Gradient Descent (SGD) method, or the like as a propagation calculation method. The generation unit 11 can optimize the phase distribution on the image plane of the phase modulation element 100 by performing light propagation calculations at least two times.

[0042] Even when light propagation calculations are performed multiple times, it is possible to generate a bias in the phase distribution of the phase distribution data D1, thereby reducing the impact of multiple reflections on image quality. Furthermore, the width of the phase distribution can be controlled by the initial phase set during light propagation calculation, which allows for increased freedom in setting. This is expected to improve image quality.

[0043] Fig. 5 is a diagram showing an example of the configuration of a phase modulation element according to the first embodiment. Fig. 5 shows an example in which the phase modulation element 100 is a reflective liquid crystal element. When no phase modulation is performed in the phase modulation element 100, the optical path length L between the first electrode 20a and the second electrode 20b can be expressed by the following equation (2) using the refractive index nk of each layer and the thickness dk of each layer.

[0044] The total phase shift θall at a certain wavelength λ can be expressed by the following equation (3) using the change in refractive index Δn in the liquid crystal layer 110 and the thickness d of the liquid crystal layer 110.

[0045] Furthermore, if the refractive index of the first electrode 20a is r1, the refractive index of the second electrode 20b is r2, and the phase of the incident wave is α, then the composite wave Φ1 of the multiple-reflected light W1 can be expressed by the following equation (4).

[0046] The following equation (5) is obtained from the above equations (3) and (4): In equation (5), m is an integer. When the optical path length (L+Δnd) between the substrates is an integer multiple of half the wavelength of the incident light, the composite wave Φ1 becomes a composite wave of the same wavefront, making it possible to prevent wavefront distortion.

[0047] When the phase modulation element 100 is a reflective liquid crystal element, the setting unit 12 (or adjustment unit 13) of the phase modulation device 1 can set, as the reference phase value θc, the phase modulation amount in the phase modulation element 100 when the optical path length between the first substrate 101 and the second substrate 102 is an integer multiple of the half wavelength of the light from the light source 60. The phase modulation amount is shifted and adjusted as described above in accordance with this reference phase value θc, thereby reducing the phase difference between the multiple reflected light beams. This makes it possible to prevent wavefront distortion caused by multiple reflected light beams and suppress deterioration in image quality.

[0048] Fig. 6 is a diagram showing another example of the configuration of the phase modulation element according to the first embodiment. Fig. 6 shows an example in which the phase modulation element 100 is a transmissive liquid crystal element. In this case, the total phase amount θall at a certain wavelength λ can be expressed by the following equation (6).

[0049] Furthermore, the composite wave Φ2 of the multiple-reflected light W2 can be expressed by the following equation (7).

[0050] The following equation (8) is obtained from the above equations (6) and (7): In equation (8), m is an integer. ​When the optical path length (L+Δnd) between the substrates is an integer multiple of the wavelength of the incident light, the composite wave Φ2 becomes a composite wave of the same wavefront, making it possible to prevent the occurrence of wavefront disturbance.

[0051] When the phase modulation element 100 is a transmissive liquid crystal element, the setting unit 12 (or adjustment unit 13) of the phase modulation device 1 can set, as the reference phase value θc, the phase modulation amount in the phase modulation element 100 when the optical path length between the first substrate 101 and the second substrate 102 is an integer multiple of the wavelength of the light from the light source 60. By shifting and adjusting the phase modulation amount as described above in accordance with this reference phase value θc, the difference in phase between each of the multiple reflected light beams becomes smaller. This makes it possible to prevent wavefront distortion caused by multiple reflected light beams and suppress deterioration in image quality.

[0052] 7 and 8 are diagrams illustrating an example of setting the phase adjustment range by the phase modulation device according to the first embodiment. The setting unit 12 can set a median value of the setting range of the phase modulation amount based on the optical path length for each pixel P. For example, the setting unit 12 may set the median value of the setting range so that the sum S2 (see the following equation (9)) of the squared values ​​of the differences between the remainder when the phase amount θk based on the optical path length at the pixel P is divided by 2π and the reference phase value θc is small.

[0053] In this case, the setting unit 12 may set the median of the setting range of the phase modulation amount so that the sum S2 is minimized. This makes it possible to effectively suppress wavefront disturbances caused by multiple reflections even when there is a difference in the optical path length for each pixel P in the phase modulation element 100. It is possible to prevent degradation of image quality when the optical path lengths of the pixels P are non-uniform.

[0054] ​8, the setting unit 12 may set the setting range so that the difference between the median and upper limit of the setting range of the phase modulation amount is a phase difference of at least half a wavelength (a phase difference of at least π). The setting unit 12 may also set the setting range so that the difference between the median and lower limit of the setting range of the phase modulation amount is a phase difference of at least half a wavelength. This prevents a large potential difference from occurring between pixels of the phase modulation element 100, making it impossible to obtain the desired phase modulation amount. It is also possible to prevent deterioration in image quality due to disclination.

[0055] [Actions and Effects] A phase modulation device (phase modulation device 1) according to this embodiment includes a phase modulation element (phase modulation element 100) having a plurality of pixels and capable of modulating the phase of light from a light source (light source 60), a generation unit (generation unit 11) capable of generating first data (phase distribution data) related to the phase modulation amount for each pixel, and an adjustment unit (adjustment unit 13) capable of adjusting the first data so that the phase modulation range includes a reference phase value (reference phase value θc) based on the wavelength of the light from the light source. The phase modulation element is capable of modulating the phase of the light from the light source based on the first data adjusted by the adjustment unit.

[0056] In the phase modulation device 1 according to this embodiment, the phase of the light from the light source 60 is modulated based on the phase distribution data D2, which has been adjusted so that the phase modulation range includes the reference phase value θc based on the wavelength of the light from the light source 60. This makes it possible to prevent wavefront distortion caused by multiple reflected light, and to prevent degradation of image quality.

[0057] 2. Second Embodiment Next, a second embodiment of the present disclosure will be described. In the following, components similar to those in the above-described embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0058] 9 is a diagram showing an example of a schematic configuration of a phase modulation device according to a second embodiment of the present disclosure. In this embodiment, the phase modulation device 1 further includes a measurement unit 70 and a calculation unit 80. The measurement unit 70 is configured to be able to measure light from the phase modulation element 100. The measurement unit 70 is configured using, for example, a photodiode sensor, a CCD image sensor, a CMOS image sensor, or the like.

[0059] The measuring unit 70 is configured to photoelectrically convert incident light to generate a signal. The measuring unit 70 receives light phase-modulated by the phase modulation element 100, and can generate and output a signal D11, which is an electrical signal based on the amount of received light, as a measurement result. The measuring unit 70 outputs, for example, the signal D11 to the calculating unit 80, which corresponds to the intensity of the light phase-modulated by the phase modulation element 100 and emitted.

[0060] The calculation unit 80 is configured to calculate the amount of phase modulation based on the signal D11 input from the measurement unit 70. For example, the calculation unit 80 calculates (detects) the amount of phase modulation θ1 in the phase modulation element 100 when the intensity of light from the phase modulation element 100 is highest based on the signal D11. The calculation unit 80 generates a signal D12 indicating the calculated amount of phase modulation θ1 and outputs it to the setting unit 12 of the signal processing unit 10. Note that the measurement unit 70 and the calculation unit 80 may be configured integrally. Alternatively, the signal processing unit 10 may be configured to include the calculation unit 80.

[0061] The setting section 12 is configured to be able to change the phase setting range data of the phase modulation amount based on the measurement results by the measuring section 70. The setting section 12 can adjust the median, upper limit, lower limit, etc. of the setting range of the phase modulation amount based on the signal D12 input from the calculating section 80. For example, the setting section 12 sets the phase modulation amount θ1 indicated by the signal D12 as the median of the setting range, and adjusts the phase setting range data. The setting section 12 outputs the adjusted phase setting range data to the adjusting section 13.

[0062] The adjustment unit 13 is configured to be able to adjust the phase distribution data based on the measurement results by the measurement unit 70. In the example shown in Fig. 9, the adjustment unit 13 receives the phase setting range data changed by the setting unit 12. The adjustment unit 13 adjusts the phase distribution data D1 in accordance with the phase setting range data to generate phase distribution data D2. Note that the adjustment unit 13 may also change the phase distribution data D2 in accordance with the phase setting range data. The drive unit 50 supplies a voltage to each pixel P of the phase modulation element 100 so as to obtain the phase distribution indicated by the phase distribution data D2.

[0063] In this way, in this embodiment, the amount of phase modulation in each pixel P of the phase modulation element 100 can be adjusted according to the measurement results by the measurement unit 70. Even if the characteristics of the phase modulation element 100 change over time, the phase modulation range can be adjusted, and wavefront disturbance caused by multiple reflected light can be suppressed. The amount of phase modulation can be optimized, making it possible to improve image quality.

[0064] [Actions and Effects] The phase modulation device (phase modulation device 1) according to this embodiment has a measurement unit (measurement unit 70) capable of measuring light from the phase modulation element (phase modulation element 100). The adjustment unit (adjustment unit 13) can adjust the first data (phase distribution data) based on the measurement result by the measurement unit.

[0065] In the phase modulation device 1 according to this embodiment, the phase distribution data is adjusted based on the measurement results from the measurement unit 70, and the phase of the light from the light source 60 is modulated. This makes it possible to suppress the occurrence of wavefront disturbances caused by multiple reflected light, and to suppress degradation of image quality.

[0066] Next, a modified example of the present disclosure will be described. In the following, the same components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0067] <3. Modifications> In the above-described embodiment, an example configuration of the phase modulation device has been described, but the configuration of the phase modulation device is not limited to this. The phase modulation device 1 may have a light source separate from the light source 60, and this light source may be used as a light source for measuring light phase-modulated by the phase modulation element 100. The wavelength of the light from the measurement light source may be determined so that it is largely reflected by the electrodes (first electrode 20 a, second electrode 20 b) of the phase modulation element 100. This makes it possible to measure the intensity of light from the phase modulation element 100 with high accuracy. The wavelength of the measurement light source may be a wavelength outside the wavelength range of visible light.

[0068] The phase modulation device 1 may have an optical system that separates the optical path and measure the light from the phase modulation element 100 using the optical system. Furthermore, the measurement unit 70 of the phase modulation device 1 may perform measurement using higher-order diffracted light. Furthermore, the phase modulation device 1 may have, as the measurement unit 70, a measuring instrument that can measure the luminance distribution in the image plane of the phase modulation element 100.

[0069] In the above-described embodiment, an example of the configuration of the phase modulation element 100 has been described, but this is merely an example, and the configuration of the phase modulation element 100 is not limited to the above-described example. For example, the phase modulation element 100 does not need to have the antireflection film 40.

[0070] Although the present disclosure has been described above by way of embodiments and modifications, the present technology is not limited to the above embodiments, etc., and various modifications are possible. For example, although the modifications described above have been described as modifications of the above embodiments, the configurations of the modifications can be combined as appropriate.

[0071] According to an embodiment of the present disclosure, a phase modulation device includes a phase modulation element, a generator capable of generating first data relating to a phase modulation amount for each pixel, and an adjuster capable of adjusting the first data so that a phase modulation range includes a reference phase value based on the wavelength of light from a light source. The phase modulation element is capable of modulating the phase of light from the light source based on the first data adjusted by the adjuster. This makes it possible to suppress wavefront distortion caused by multiple reflections and to suppress degradation of image quality.

[0072] Note that the effects described in this specification are merely examples and are not limited to those described, and other effects may be present. The present disclosure may also have the following configurations: (1) A phase modulation device comprising: a phase modulation element having a plurality of pixels and capable of modulating the phase of light from a light source; a generation unit capable of generating first data related to a phase modulation amount for each pixel; and an adjustment unit capable of adjusting the first data so that a phase modulation range includes a reference phase value based on the wavelength of the light from the light source, wherein the phase modulation element is capable of modulating the phase of the light from the light source based on the first data adjusted by the adjustment unit. (2) The phase modulation device described in (1) above, wherein the reference phase value is a phase modulation amount set so that the phases of the light beams multiple-reflected by the phase modulation element are identical. (3) The phase modulation device described in (1) or (2) above, wherein the adjustment unit is capable of adjusting the first data so that the difference between the phase modulation amount for each pixel and the reference phase value is small. (4) The phase modulation device according to any one of (1) to (3), wherein the adjustment unit is capable of shifting the phase modulation amount so as to reduce a sum of squares of the difference between the phase modulation amount for each pixel and the reference phase value. (5) The phase modulation device according to any one of (1) to (4), wherein the generation unit is capable of generating the first data by performing a single light propagation calculation. (6) The phase modulation device according to any one of (1) to (4), wherein the generation unit is capable of generating the first data by performing a plurality of light propagation calculations. (7) The phase modulation device according to any one of (1) to (6), wherein the phase modulation element has a first substrate, a second substrate facing the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate and containing liquid crystal molecules, and the phase modulation element is a reflective liquid crystal element. (8) The phase modulation device described in (7), wherein the reference phase value is a phase modulation amount in the phase modulation element when the optical path length between the first substrate and the second substrate is an integer multiple of half the wavelength of the light from the light source.(9) The phase modulation device according to (7) or (8), further comprising: a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting a median value of the setting range based on the optical path length for each pixel. (10) The phase modulation device according to any one of (7) to (9), further comprising: a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting the setting range so that a difference between the median value and an upper limit value of the setting range and a difference between the median value and a lower limit value of the setting range each become a phase difference of at least half a wavelength. (11) The phase modulation device according to any one of (1) to (6), further comprising: a first substrate, a second substrate facing the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate and containing liquid crystal molecules, wherein the phase modulation element is a transmissive liquid crystal element. (12) The phase modulation device according to (11), wherein the reference phase value is the phase modulation amount in the phase modulation element when the optical path length between the first substrate and the second substrate is an integer multiple of the wavelength of the light from the light source. (13) The phase modulation device according to (11) or (12), further comprising a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting a median value of the setting range based on the optical path length for each pixel. (14) The phase modulation device according to any one of (11) to (13), further comprising a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting the setting range so that the difference between the median and an upper value of the setting range and the difference between the median and a lower value of the setting range each become a phase difference of at least half a wavelength. (15) The phase modulation device according to any one of (1) to (14), further comprising a measurement unit capable of measuring light from the phase modulation element, wherein the adjustment unit is capable of adjusting the first data based on a measurement result by the measurement unit.(16) The phase modulation device according to any one of (1) to (15), comprising: a measurement unit capable of measuring light from the phase modulation element; and a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting the setting range based on a measurement result by the measurement unit. (17) The phase modulation device according to any one of (1) to (16), comprising: a measurement unit capable of measuring light from the phase modulation element; and a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting the phase modulation amount in the phase modulation element when the intensity of the light from the phase modulation element is highest as a median of the setting range.

[0073] This application claims priority based on Japanese Patent Application No. 2022-082327, filed on May 19, 2022 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0074] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A phase modulation device comprising: a phase modulation element having a plurality of pixels and capable of modulating the phase of light from a light source; a generation unit capable of generating first data relating to the amount of phase modulation for each pixel; and an adjustment unit capable of adjusting the first data so that the phase modulation range includes a reference phase value based on the wavelength of the light from the light source, wherein the phase modulation element is capable of modulating the phase of the light from the light source based on the first data adjusted by the adjustment unit.

2. A phase modulation device according to claim 1, wherein the reference phase value is a phase modulation amount that is set so that the phases of the light beams multiple-reflected by the phase modulation element are the same.

3. The phase modulation device according to claim 1, wherein the adjustment section is capable of adjusting the first data so that the difference between the phase modulation amount for each pixel and the reference phase value becomes small.

4. The phase modulation device according to claim 1, wherein the adjustment section is capable of shifting the phase modulation amount so that the sum of squares of the differences between the phase modulation amount for each pixel and the reference phase value becomes smaller.

5. The phase modulation device according to claim 1, wherein the generation unit is capable of generating the first data by performing a single light propagation calculation.

6. The phase modulation device according to claim 1, wherein the generation unit is capable of generating the first data by performing light propagation calculations multiple times.

7. The phase modulation device according to claim 1, wherein the phase modulation element has a first substrate, a second substrate facing the first substrate, and a liquid crystal layer containing liquid crystal molecules provided between the first substrate and the second substrate, and the phase modulation element is a reflective liquid crystal element.

8. A phase modulation device according to claim 7, wherein the reference phase value is the amount of phase modulation in the phase modulation element when the optical path length between the first substrate and the second substrate is an integer multiple of half the wavelength of the light from the light source.

9. A phase modulation device according to claim 8, further comprising a setting section capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting section is capable of setting a median value of the setting range based on the optical path length for each pixel.

10. A phase modulation device according to claim 8, further comprising a setting section capable of setting a setting range for the amount of phase modulation in the phase modulation element, wherein the setting section is capable of setting the setting range so that the difference between the median value and the upper limit value of the setting range and the difference between the median value and the lower limit value of the setting range each result in a phase difference of at least half a wavelength.

11. The phase modulation device according to claim 1, wherein the phase modulation element has a first substrate, a second substrate facing the first substrate, and a liquid crystal layer containing liquid crystal molecules provided between the first substrate and the second substrate, and the phase modulation element is a transmissive liquid crystal element.

12. A phase modulation device according to claim 11, wherein the reference phase value is the amount of phase modulation in the phase modulation element when the optical path length between the first substrate and the second substrate is an integer multiple of the wavelength of the light from the light source.

13. A phase modulation device according to claim 12, further comprising a setting section capable of setting a setting range of the amount of phase modulation in the phase modulation element, wherein the setting section is capable of setting a median value of the setting range based on the optical path length for each pixel.

14. A phase modulation device according to claim 12, further comprising a setting section capable of setting a setting range for the amount of phase modulation in the phase modulation element, wherein the setting section is capable of setting the setting range so that the difference between the median value and the upper limit value of the setting range and the difference between the median value and the lower limit value of the setting range each result in a phase difference of at least half a wavelength.

15. The phase modulation device according to claim 1, further comprising a measurement unit capable of measuring light from the phase modulation element, wherein the adjustment unit is capable of adjusting the first data based on the measurement results of the measurement unit.

16. A phase modulation device according to claim 1, comprising: a measurement unit capable of measuring light from the phase modulation element; and a setting unit capable of setting a setting range for the amount of phase modulation in the phase modulation element, wherein the setting unit is capable of setting the setting range based on the measurement results by the measurement unit.

17. A phase modulation device according to claim 1, comprising: a measurement unit capable of measuring light from the phase modulation element; and a setting unit capable of setting a setting range of the phase modulation amount in the phase modulation element, wherein the setting unit is capable of setting the phase modulation amount in the phase modulation element when the intensity of the light from the phase modulation element is highest as the median value of the setting range.

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