A method and device for pixel-level full-vector full-range polarization control

Abstract

The present invention provides a pixel-level full-vector, full-range polarization control device, comprising: an aperture, a radial polarization converter, a first phase-type liquid crystal spatial light modulator, a second phase-type liquid crystal spatial light modulator, a PC control terminal, a converging lens, and a polarization camera. Specifically, the aperture, the radial polarization converter, the first phase-type liquid crystal spatial light modulator, the second phase-type liquid crystal spatial light modulator, the converging lens, and the polarization camera are arranged in sequence along the horizontal direction and share a common rotational symmetry axis. The present invention relates to the technical field of vector light beam polarization control. The pixel-level full-vector, full-range polarization control device of the present invention can achieve full-range polarization control of the ellipticity angle [‑π / 4, π / 4] and the azimuth angle [‑π / 2, π / 2] for light incident in any polarization state.

Description

Technical Field

[0001] The present invention relates to the technical field of vector beam polarization control, and in particular to a method and device for pixel-level full-vector full-range polarization control. Background Art

[0002] Polarization is another crucial property of light besides intensity, phase, and frequency. Currently, the most common devices on the market that can control the polarization characteristics of light are polarizers, wave plates, and depolarizers. However, these polarization devices can only achieve a single polarization conversion. For example, a quarter-wave plate can only achieve the conversion between linearly polarized light and circularly / elliptically polarized light; a half-wave plate can only control the azimuth of polarized light, but cannot control its ellipticity; and a depolarizer can only control the degree of polarization, depolarizing polarized light into partially polarized light or depolarizing it to return it to natural light. In addition, the polarization control of the incident light beam by these polarization devices is isotropic within the pupil plane, but this is far from meeting the current application requirements of polarized light, such as polarization illumination, super-resolution imaging, precision machining, micro-manipulation, and other fields.

[0003] In recent years, radially / angularly polarized light has been widely used in polarization applications. This new type of light beam with anisotropic polarization distribution within the beam cross section is called a vector beam. However, in addition to vector beams with radially / angular polarization distribution, exploring how to generate vector beams with other forms of anisotropic polarization distribution has become one of the research hotspots in the field of polarization control. Currently, the most cutting-edge polarization control devices are micro-nano optical structures such as metasurfaces and superlenses. However, most micro-nano optical structures are only designed for a more complex polarization control and are often limited in actual use. In addition, micro-nano optical structures have high technical requirements, are difficult to process, have high production costs, and cannot achieve dynamic continuous polarization control. Therefore, the popularity, flexibility, and versatility of such micro-nano structures are relatively poor. Summary of the Invention

[0004] In view of this, the present invention aims to propose a pixel-level full-vector full-range polarization control device to achieve full-range polarization control for light incident in any polarization state.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A pixel-level full-vector, full-range polarization control device comprises an aperture, a radial polarization converter, a first phase-type liquid crystal spatial light modulator, a second phase-type liquid crystal spatial light modulator, a PC control terminal, a converging lens, and a polarization camera. The aperture, the radial polarization converter, the first phase-type liquid crystal spatial light modulator, the second phase-type liquid crystal spatial light modulator, the converging lens, and the polarization camera are arranged in sequence along the horizontal direction and share a common rotational symmetry axis.

[0007] Furthermore, the first phase-mode liquid crystal spatial light modulator and the second phase-mode liquid crystal spatial light modulator are placed side by side.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] The pixel-level full-vector full-range polarization control device described in the present invention uses the most common optical components in the field of polarization. The device has a simple structure, is easy to operate, has good optical path stability, and is highly practical.

[0010] Another object of the present invention is to provide a method for pixel-level full-vector full-range polarization control, comprising the following steps:

[0011] Step 1: The collimated incident light passes through the aperture and is vertically incident on the radial polarization converter, generating radial vector polarized light with a radial regular distribution of polarization states in the pupil plane;

[0012] Step 2: The generated radial vector polarized light is vertically incident on the active window of the first phase-mode liquid crystal spatial light modulator;

[0013] Step 3: Load a specially designed grayscale image on the PC control terminal to adjust the polarization azimuth and ellipticity of the radial vector polarized light within the full range, and obtain a vector beam with a specific polarization state distribution in the pupil plane;

[0014] Step 4: The obtained vector light beam with a specific polarization state distribution in the pupil plane is vertically incident on the second phase-mode liquid crystal spatial light modulator;

[0015] Step 5: Load a specially designed grayscale image through the PC control terminal to adjust the polarization azimuth and ellipticity of the incident vector polarized light beam within the full range again;

[0016] Step 6: Obtain the final desired vector polarized beam.

[0017] Furthermore, the grayscale image generated by the specific design loaded by the PC control terminal needs to be designed in accordance with the polarization distribution requirements of the outgoing vector light beam.

[0018] Compared with the existing technology, the pixel-level full-vector full-range polarization control method proposed in this invention has the following advantages:

[0019] By combining a first phase-mode liquid crystal spatial light modulator (LC-SLM), a second phase-mode LC-SLM, and a radial polarization converter, the device can dynamically control the polarization azimuth angle of incident light of any polarization state within the full range of [-π / 2, π / 2], and the ellipticity angle within the full range of [-π / 4, π / 4]. This device not only offers excellent real-time dynamic control but also enables full-range polarization control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 This is an overall schematic diagram of the pixel-level full-vector full-range polarization control device according to an embodiment of the present invention;

[0022] Figure 2 The sampling pixels A, B, C and D in the pupil plane of the radial polarization converter of the method and apparatus for pixel-level full-vector full-range polarization control according to the embodiment of the present invention are:

[0023] Figure 3 An enlarged view of sampling pixels A, B, C, and D of the method and apparatus for pixel-level full-vector, full-range polarization control according to an embodiment of the present invention;

[0024] Figure 4 The sampling pixels A, B, C and D corresponding to the pupil plane of the first phase-mode liquid crystal spatial light modulator of the method and apparatus for pixel-level full-vector full-range polarization control according to an embodiment of the present invention;

[0025] Figure 5 The sampling pixels A, B, C and D corresponding to the second phase-mode liquid crystal spatial light modulator pupil plane of the method and apparatus for pixel-level full-vector full-range polarization control according to an embodiment of the present invention;

[0026] Figure 6 The polarization control mode implemented on the first phase-type liquid crystal spatial light modulator and the second phase-type liquid crystal spatial light modulator for each sampling pixel point of the method and apparatus for pixel-level full-vector full-range polarization control according to the embodiment of the present invention;

[0027] Description of reference numerals:

[0028] 1. Aperture; 2. Radial polarization converter; 3. First phase-type liquid crystal spatial light modulator; 4. Second phase-type liquid crystal spatial light modulator; 5. PC control terminal; 6. Converging lens; 7. Polarization camera. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," and "back" and other terms indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0032] This embodiment relates to a method and device for pixel-level full-vector full-range polarization control, such as Figure 1 As shown, it includes an aperture 1, a radial polarization converter 2, a first phase-type liquid crystal spatial light modulator 3, a second phase-type liquid crystal spatial light modulator 4, a PC control terminal 5, a converging lens 6, and a polarization camera 7. Specifically, the aperture 1, the radial polarization converter 2, the first phase-type liquid crystal spatial light modulator 3, the second phase-type liquid crystal spatial light modulator 4, the converging lens 6, and the polarization camera 7 are arranged in sequence along the horizontal direction and share a common rotational symmetry axis. Among them, the first phase-type liquid crystal spatial light modulator 3 and the second phase-type liquid crystal spatial light modulator 4 are placed side by side. Since the optical components mentioned above are the most common in the field of polarization, the device structure is simple and easy to operate, the optical path is stable, and it is highly practical.

[0033] The method for pixel-level full-vector full-range polarization control includes the following steps:

[0034] Step 1: The collimated incident light passes through the aperture 1 and is vertically incident on the radial polarization converter 2, generating radial vector polarized light with a radially regular distribution of polarization states in the pupil plane;

[0035] Step 2: The generated radial vector polarized light is vertically incident on the active window of the first phase-mode liquid crystal spatial light modulator 3;

[0036] Step 3: Loading a specially designed grayscale image through the PC control terminal 5 to adjust the polarization azimuth and ellipticity of the radial vector polarized light within the full range, thereby obtaining a vector beam with a specific polarization state distribution in the pupil plane;

[0037] Step 4: The obtained vector light beam with a specific polarization state distribution in the pupil plane is vertically incident on the second phase-mode liquid crystal spatial light modulator 4;

[0038] Step 5: Load a specially designed grayscale image through the PC control terminal 5 to adjust the polarization azimuth angle [-π / 2, π / 2] and the ellipticity angle [-π / 4, π / 4] of the incident vector polarized light beam again within the full range;

[0039] Step 6: Obtain the final desired vector polarized beam.

[0040] Specifically, the grayscale image generated by the specific design loaded by the PC control terminal 5 needs to be designed in accordance with the polarization distribution requirements of the outgoing vector light beam.

[0041] Based on the foregoing, the radially polarized light can be converted into a vector light beam having a uniform or non-uniform polarization distribution in the pupil plane after passing through the first phase-type liquid crystal spatial light modulator 3 and the second phase-type liquid crystal spatial light modulator 4. That is, the polarization state in the entire pupil plane can be uniformly distributed linear polarization, circular polarization, or elliptical polarization. Of course, it can also be non-uniformly distributed linear polarization, circular polarization, elliptical polarization, or a combination of the three.

[0042] Specifically, any collimated incident light passes through the aperture 1 and is vertically incident on the radial polarization converter 2, generating radial vector polarized light with a radially regular polarization state distribution in the pupil plane, and then vertically incident on the working window of the first phase-type liquid crystal spatial light modulator 3. The polarization azimuth and ellipticity angle of the radial vector polarized light are regulated within the full range by loading a specially designed grayscale image through the PC control terminal 5, so as to obtain a vector light beam with a specific polarization state distribution in the pupil plane, and then vertically incident on the second phase-type liquid crystal spatial light modulator 4. Similarly, the method of loading a specially designed grayscale image through the PC control terminal 5 is used to again regulate the polarization azimuth and ellipticity angle of the incident vector polarized light beam within the full range, so as to obtain the final desired vector polarized light beam.

[0043] That is, by combining the first phase-type liquid crystal spatial light modulator 3, the second phase-type liquid crystal spatial light modulator 4 and the radial polarization converter 2, the polarization azimuth angle of light incident in any polarization state can be dynamically controlled within the full range of [-π / 2, π / 2], and the ellipticity angle can also be dynamically controlled within the full range of [-π / 4, π / 4].

[0044] Based on the above, the 4*4 order Mueller matrix corresponding to the polarization conversion effect of the phase-type liquid crystal spatial light modulator is:

[0045]

[0046] Where θ is the fast axis direction and δ is the phase delay.

[0047] A collimated incident light passes through the aperture 1 and is vertically incident on the radial polarization converter 2, generating radial vector polarized light with a radial regular distribution of polarization states in the pupil plane, such as Figure 2-3 As shown, the sampled pixels A, B, C and D in the pupil of the radial polarization converter 2 and their enlarged views, specifically, the polarization azimuth angles of the pixels A, B, C and D are 0°, 45°, 90° and -45° respectively.

[0048] like Figure 4-5 The figure shows the corresponding pixels A, B, C and D in the pupil of the first phase-type liquid crystal spatial light modulator 3 and the second phase-type liquid crystal spatial light modulator 4. The polarization control mode implemented by each sampling pixel on the first phase-type liquid crystal spatial light modulator 3 and the second phase-type liquid crystal spatial light modulator 4 is as follows Figure 6 shown.

[0049] Assuming that we want to obtain left-handed circularly polarized light at a certain pixel point in the pupil plane, that is, the incident light is modulated into radially polarized light after passing through the radial deflection converter, and the radially polarized light is finally modulated into the desired left-handed circularly polarized light after passing through the first phase-type liquid crystal spatial light modulator and the second phase-type liquid crystal spatial light modulator. Then we can know that: γ A =0°,γ B =45°,γ C =90° and γ D =-45°.

[0050]

[0051]

[0052] Combined with the 4*4 order Mueller matrix corresponding to the polarization conversion effect of the phase-type liquid crystal spatial light modulator described above, the polarization conversion effect of the sampling pixels A, B, C, and D after the dual-phase liquid crystal spatial light modulator is expressed in the form of a Stokes-Mueller matrix as follows:

[0053] 1. Sampling pixel A:

[0054]

[0055] 2. Sampling pixel B:

[0056]

[0057] 3. Sampling pixel C:

[0058]

[0059] 4. Sampling pixel D:

[0060]

[0061] The present invention utilizes a combination of a first phase-type liquid crystal spatial light modulator (3), a second phase-type liquid crystal spatial light modulator (4), and a radial polarization converter (2). This allows for dynamic control of the polarization azimuth angle of incident light of any polarization state within the full range [-π / 2, π / 2], and dynamic control of the ellipticity angle within the full range [-π / 4, π / 4]. This allows for full vector and full-range polarization control of each pixel within the pupil plane for any incident light beam. This method and device can generate vector beams with arbitrary polarization distribution patterns. This device not only offers excellent real-time dynamic control but also enables full-range polarization control. The first phase-type liquid crystal spatial light modulator (3) and the second phase-type liquid crystal spatial light modulator (4) utilize a PC control terminal (5) to load different grayscale images, enabling comprehensive design of the fast axis direction and phase delay for each pixel. This method produces vector polarized beams with either isotropic or anisotropic polarization distribution within the pupil plane. This method offers high flexibility and control precision, down to a single pixel.

[0062] The proposed method and device for pixel-level, full-vector, full-range polarization control utilizes the most commonly used optical components in the field of polarization. The device boasts a simple, easy-to-use structure, excellent optical path stability, and strong practicality. This method and device for pixel-level, full-vector, full-range polarization control is of great significance for the application and widespread adoption of vector beams in applications such as polarization illumination, super-resolution imaging, precision machining, and optical micromanipulation.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pixel-level full-vector full-range polarization control device, comprising: An aperture (1), a radial polarization converter (2), a first phase-type liquid crystal spatial light modulator (3), a second phase-type liquid crystal spatial light modulator (4), a PC control terminal (5), a converging lens (6) and a polarization camera (7), characterized in that: The aperture (1), the radial polarization converter (2), the first phase-type liquid crystal spatial light modulator (3), the second phase-type liquid crystal spatial light modulator (4), the converging lens (6), and the polarization camera (7) are arranged in sequence along a horizontal direction and share a common rotational symmetry axis.

2. The pixel-level full-vector full-range polarization control device according to claim 1, characterized in that: The first phase-type liquid crystal spatial light modulator (3) and the second phase-type liquid crystal spatial light modulator (4) are placed side by side.

3. A method for pixel-level full-vector full-range polarization control, characterized by: Step 1: collimated incident light passes through the aperture (1) and is vertically incident on the radial polarization converter (2), generating radial vector polarized light with a radially regular polarization state in the pupil plane; Step 2: The generated radial vector polarized light is vertically incident on the active window of the first phase-type liquid crystal spatial light modulator (3); Step 3: Loading a specially designed grayscale image through the PC control terminal (5) to adjust the polarization azimuth and ellipticity of the radial vector polarized light within the full range, and obtaining a vector beam with a specific polarization state distribution in the pupil plane; Step 4: The obtained vector light beam with a specific polarization state distribution in the pupil plane is vertically incident on the second phase-type liquid crystal spatial light modulator (4); Step 5: Load a specially designed grayscale image through the PC control terminal (5) to adjust the polarization azimuth and ellipticity angle of the incident vector polarized light beam within the full range again; Step 6: Obtain the final desired vector polarized beam.

4. The method for pixel-level full-vector full-range polarization control according to claim 3, characterized in that: The grayscale image generated by the specific design loaded on the PC control terminal (5) needs to be designed in accordance with the polarization distribution requirements of the outgoing vector light beam.

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