Method and apparatus for non-jump rotation of polarization direction of linearly polarized light

Abstract

This invention relates to a method and apparatus for non-jumping rotation of the polarization direction of linearly polarized light, applicable to fields such as image display, light field modulation, optical micromanipulation, and ophthalmic medicine. Incident linearly polarized light is subjected to the birefringence effect of liquid crystal molecules, resulting in a half-wavelength phase difference between its fast and slow axis components. Alternating voltage is used to control the rotation of liquid crystal molecules parallel to the liquid crystal substrate, thereby emitting rotated linearly polarized light. This invention enables controllable rotation rate of the linearly polarized light without any jumps during the rotation process. A unified control array can be formed through the arrangement of liquid crystal cells, which can be applied in specific situations to devices such as the Haidinger brush amblyopia treatment instrument and optical manipulation devices.

Description

Technical Field

[0001] This invention relates to a method and apparatus for rotating the polarization direction of linearly polarized light without jumping, applicable to fields such as image display, light field modulation, optical micromanipulation, and ophthalmic medical treatment. In specific embodiments, it relates to a Haidinger light brush amblyopia treatment instrument optimization device, a liquid crystal display, a vector light field generator, and an optical manipulation device. Background Technology

[0002] The continuous rotation of linearly polarized light without angular limitations, i.e., rotation without jumps, has wide applications in fields such as Haidinger brush amblyopia therapy, liquid crystal displays, and optical micromanipulation. Amblyopia is a common ophthalmic disease caused by visual developmental disorders in children. Haidinger brush therapy is a relatively effective treatment for amblyopia. When fixating on blue linearly polarized light with a rotation rate of 50-100 r / min (i.e., 0.83-1.67 Hz), a brush-like image appears slowly rotating within the field of view. Fixating on the rotating blue linearly polarized light can treat amblyopia. In the field of optical micromanipulation, the angular momentum of circularly polarized or vortex light can form optical traps to capture or manipulate particles. The non-uniform polarization distribution of independently controllable vector light fields has a significant impact on the spatiotemporal evolution of the light field and the interaction between the light field and matter. Screen displays and spatial light modulators require adjusting the transmittance by changing the direction of incident polarized light corresponding to each pixel to achieve image display. Therefore, there is an urgent need to develop devices for rotating linearly polarized light without jumps in polarization direction.

[0003] Currently, mainstream instruments for rotating the polarization direction of linearly polarized light include liquid crystal phase retarders, spatial light modulators, and photoelastic modulators. However, these instruments can only achieve continuous control within a limited angular range (usually within 180°). Beyond this range, they all face the problem of abrupt changes in polarization direction rotation, making continuous rotation without angular limitations impossible. This is because the general design concept of phase retarders is to change the polarization direction of the emitted light by altering the optical rotation of the liquid crystal or the magnitude of the birefringence of the material. Taking a phase retarder as an example, applying a voltage to the ITO layer of a liquid crystal substrate causes the liquid crystal molecules to deflect longitudinally along the direction of light propagation, changing the birefringence and optical rotation, thereby affecting the polarization characteristics of the emitted linearly polarized light and achieving the purpose of phase delay.

[0004] The most direct device for rotating the polarization direction of linearly polarized light without abrupt changes is a mechanically driven half-wave plate (for linearly polarized light) or polarizer (for natural light), such as the Haidinger phototherapy brush (CN2875382Y), which operates by a mechanical motor. However, mechanically driven rotation of linearly polarized light suffers from imprecise control and significant mechanical disturbances, and its large size makes integration difficult, hindering the development of portable devices. High-speed, non-abrupt polarization control can be achieved using optical heterodyne interferometry, such as... https: / / doi.org / 10.29026 / oea.2020.200022(OPTO-ELECTRONIC ADVANCES, 2020, 3(8), 200022). However, this method requires high precision in the optical path, the acousto-optic modulation device is still very large, the efficiency is not high, and the cost is high, making it difficult to apply to the above-mentioned situations.

[0005] Furthermore, devices that use a horizontal electric field to modulate liquid crystals and change the direction of linearly polarized light, such as IPS (CN101666949B) and FFS (CN1302450C) display panel technologies, utilize a horizontal electric field provided by a single-layer electrode to allow the liquid crystals to align parallel to the substrate and rotate, thus modulating the polarization direction of polarized light. However, these devices can only achieve linear polarization rotation modulation within a limited angle to control grayscale, and cannot achieve a non-abrupt rotation of the polarization direction of linearly polarized light. Moreover, their structure involves only a single-layer electrode, which differs from the device structure proposed in this invention, making them difficult to apply to the aforementioned ophthalmic medical, light field modulation, and optical micromanipulation applications. Summary of the Invention

[0006] To address the shortcomings of existing technologies in this field, this invention proposes an electrically driven linearly polarized light polarization direction rotation device without abrupt changes, based on the principle of liquid crystal electro-optic effect. This device uses alternating voltage to control the rotation of liquid crystal molecules and sets the thickness of the liquid crystal layer to be equivalent to a rotating half-wave plate. Thus, the polarization direction of linearly polarized light can be continuously rotated without a motor, the rotation rate is controllable, and there are no polarization abrupt changes during the rotation process.

[0007] To achieve the objectives of this invention, a method is proposed, the method comprising:

[0008] A voltage is applied in a direction parallel to the plane of the first glass substrate; the liquid crystal molecules in the liquid crystal layer are rotated parallel to the plane of the first glass substrate by controlling the voltage, thereby continuously and controllably rotating the polarization direction of the incident linearly polarized light.

[0009] To achieve the objectives of this invention, the following technical solution is adopted:

[0010] A liquid crystal cell, wherein a polarizer is disposed on the light-incident side of the liquid crystal cell; wherein there are one or more liquid crystal cells; the liquid crystal cell includes: a first glass substrate and a second glass substrate disposed opposite to each other; and a liquid crystal layer between the first glass substrate and the second glass substrate; electrodes, wherein there are multiple electrodes respectively disposed between the first glass substrate and the liquid crystal layer, forming a first electrode group arranged in parallel with each other, and a second electrode group arranged in parallel with each other and orthogonal to the first electrode group between the liquid crystal layer and the second glass substrate, and the spacing between the electrodes in the electrode group may be different; the electrodes are used to apply voltage to form a potential difference in the liquid crystal layer, thereby controlling the liquid crystal molecules to rotate in a plane parallel to the first and second glass substrates through an electric field.

[0011] Incident light passes through the polarizer and enters the liquid crystal cell perpendicular to the first glass substrate. Due to the birefringence of the liquid crystal material, the optical path lengths of the fast-axis polarization component and the slow-axis polarization component of the incident light are different. The thickness of the liquid crystal layer is the thickness of the optical path difference being (m+1 / 2) wavelengths. The thickness refers to the height of the glass substrate in the direction perpendicular to the plane. Where m is any positive integer.

[0012] Optionally, the first electrode consists of two parallel electrodes, one grounded and the other subjected to an alternating voltage; the second electrode group consists of two parallel electrodes, one grounded and the other subjected to an alternating voltage that is phase-different from that of the first electrode group. The alternating voltage of the same frequency; where n is any integer.

[0013] According to one embodiment, the first electrode group consists of three electrodes arranged in parallel, with the two side electrodes grounded and an alternating voltage applied to the middle electrode; the second electrode group consists of three electrodes arranged in parallel, with the two side electrodes grounded and an alternating voltage applied to the middle electrode that is phase-differential from that applied to the first electrode group. An alternating voltage of the same frequency is applied; where n is any integer. An alternative is to ground the middle electrode of the first and second electrode groups and apply the aforementioned alternating voltage to the electrodes on both sides.

[0014] Optionally, spacer layers can be made for some or all of the invalid regions to control the thickness of the liquid crystal material and help reduce negative electro-optic effects; invalid regions refer to liquid crystal molecule regions outside the working region where the liquid crystal molecules rotate in the opposite direction to the emission deflection direction due to the opposite electrode arrangement to the working region.

[0015] According to another embodiment, an N*M array of liquid crystal cells is formed by repeating the above-described method along a direction parallel to the electrodes of the first electrode group or parallel to the electrodes of the second electrode group. Adjacent liquid crystal cells share electrodes on their boundaries, and adjacent electrodes are connected along the electrode placement direction. The frequency and phase of the alternating electrodes applied to each liquid crystal cell can be uniformly controlled. N and M are arbitrary positive integers. Optionally, the connection of adjacent electrodes constitutes a single electrode.

[0016] Optionally, it has a defined incident light wavelength, the incident light wavelength being in the range of 460nm-500nm; the electrode applies an alternating voltage frequency between 0.41Hz and 0.83Hz, i.e., the output polarized light rotation frequency is between 50r / min and 100r / min; it is used for a Haidinger light brush weak therapy device driven by a direct electric field.

[0017] Beneficial effects:

[0018] 1. This invention enables linearly polarized light rotation without jumps.

[0019] 2. This invention can arbitrarily adjust the rotation frequency of linearly polarized light.

[0020] 3. Compared with mechanical drive, the present invention has no mechanical vibration, occupies less space, and consumes less energy. Attached Figure Description

[0021] To gain a more complete understanding of the invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 The diagram shown is a top view of the liquid crystal cell structure in an embodiment of the present invention.

[0023] Figure 2 The image shown is a front view schematic diagram of the liquid crystal cell structure in an embodiment of the present invention.

[0024] Figure 3 The diagram shown is a side view (left view) of the liquid crystal cell structure in an embodiment of the present invention.

[0025] Figure 4 The diagram shown is a front view of a liquid crystal cell with an added spacer substructure in another embodiment of the present invention.

[0026] Figure 5 The figure shows the electric field distribution of the liquid crystal cell in an embodiment of the present invention.

[0027] Figure 6 The image shows the distribution of the electric field of the liquid crystal cell from another angle in an embodiment of the present invention.

[0028] Figure 7 The image shown is a top view of the electric field distribution of the liquid crystal cell in an embodiment of the present invention.

[0029] Figure 8 The diagram shown is a schematic diagram of the unified array control and a schematic diagram of the relationship between the corresponding areas of the liquid crystal cells in another embodiment of the present invention. Detailed Implementation

[0030] The following sections will discuss in detail the making and use of the presently preferred embodiments. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in various specific texts. The specific embodiments discussed are merely illustrative of particular ways of carrying out and using the invention, and do not limit the scope of the invention.

[0031] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0032] This embodiment is only provided as a further understanding of the invention. With incident light at a wavelength of 630nm, the liquid crystal material n... o =1.479, n e=1.573 is used as an example for illustration, and is not intended to limit the claims.

[0033] Figure 1-3 This is a schematic diagram of an embodiment, and also a three-view drawing of a liquid crystal cell. Figure 1 As seen in the top view, the electrodes divide a liquid crystal cell into four regions: region 01, region 02, region 03, and region 04. Electrodes 101, 102, and 103 are positioned below the upper liquid crystal glass substrate 121. Electrodes 111, 112, and 113 are positioned above the lower glass substrate 122. Liquid crystal material 125 lies between the two glass substrates. Figure 2 and Figure 3 The positional relationship of each structure can be clearly seen. An insulating film 123 is covered on the contact surfaces between the electrodes, the glass substrate, and the liquid crystal. This is because electrode arrays exist on both the upper and lower glass substrates of this invention, and this film is designed to prevent leakage. Currently, commercial liquid crystal cell structures typically only have an electrode array on one side of the glass substrate while the other side is grounded, thus eliminating this requirement.

[0034] Electrodes 101, 103, 111, and 113 are grounded. A sinusoidal alternating voltage is applied to electrode 102, and a cosine alternating voltage of the same frequency is applied to electrode 112. A potential difference is generated between the two voltages and the horizontally grounded electrode, creating an electric field that acts on the liquid crystal molecules. When the applied voltage exceeds a threshold voltage, the axial direction of the liquid crystal molecules aligns with the direction of the electric field. Because the molecules are simultaneously subjected to the aforementioned phase difference of the potential applied by the upper and lower substrate electrodes, the combined electric field generated by the two electrodes is a rotating electric field with constant amplitude and a rotation frequency equal to the frequency of the applied alternating voltage. The liquid crystal molecules align with the direction of the electric field and rotate at the frequency of the applied alternating voltage.

[0035] The thickness of the liquid crystal material, 125, which is the distance between the two glass substrates, is the thickness of the liquid crystal birefringence corresponding to the half-wavelength optical path difference of the incident wave wavelength. In this specific embodiment, as an example, to make the liquid crystal act as a zero-order half-wave plate, the liquid crystal thickness is calculated based on the aforementioned birefringence parameters.

[0036] Since the alternating voltage electrode exerts an electric field on the liquid crystal molecules in both regions, analysis shows that the rotation direction of the liquid crystal molecules in regions 02 and 03 is opposite to the in-plane rotation direction of the liquid crystal molecules in regions 01 and 04. The electric field directions in regions 01 and 04 are opposite, and the liquid crystal molecules are oriented in the same direction. Region 04, with its larger area, is considered the effective region, while regions 02 and 03 are considered ineffective regions, potentially having a negative electro-optic effect on the beneficial results.

[0037] Therefore, the areas of regions 02 and 03 should be as small as possible, such as... Figure 1As shown, the effective output region for the rotated linearly polarized light is region 04. In this embodiment, as an example, the areas of regions 02 and 03 are both 1 / 10 of the area of ​​region 04. This ratio can be adjusted according to the specific application.

[0038] Regarding this issue, such as Figure 4 As shown, regions 01, 02, and 03 can be entirely or partially made into spacers, such as... Figure 4 The intermediate spacers 126 and 127 serve two purposes: firstly, to control the thickness of the liquid crystal cell, and secondly, to help reduce the negative electro-optic effects in ineffective areas. The spacer layer can be made opaque to reduce interference from non-rotational components.

[0039] Figure 5 , Figure 6 This is a visualized schematic diagram of the internal electric field of a liquid crystal cell, viewed from two directions, obtained using MATLAB numerical solution. Figure 7 This diagram illustrates the electric field distribution of a 3D liquid crystal cell, viewed from a top-down angle, after numerical solution using MATLAB. Each layer in the diagram represents the electric field at different locations along the light propagation direction within the liquid crystal. Because the liquid crystal molecules are affected by an electric field exceeding a threshold voltage, the molecular axis orientation is aligned with the applied electric field; therefore, it can be assumed that... Figure 5-6 The direction of the electric field is the orientation of the liquid crystal molecules at this location.

[0040] In this specific embodiment, the distance between electrode 101 and electrode 102 is equal to the distance between electrode 111 and electrode 112, which is d1; the distance between electrode 102 and electrode 103 is equal to the distance between electrode 112 and electrode 113, which is d2; and the thickness of the liquid crystal layer is d0. Figure 5-6 In this context, the distance ratio is d1:d2:d0 = 1:10:1. (From...) Figure 5-6 As can be seen, because the sinusoidal voltage is located on the upper substrate and the cosine voltage is located on the lower substrate, the liquid crystal molecules near the electrodes are severely tilted due to the electrode positions. Therefore, the liquid crystal molecules in regions 01, 02, and 03 are difficult to keep parallel to the substrate due to the electrode influence, even without... Figure 4 The spacer has a limited negative impact on the polarization of incident rays, and can also be used to... Figure 5-6 As observed, 80% of the liquid crystal molecules in region 04 are tilted at only a small angle in the vertical direction. From... Figure 7 As can be seen from the top view, the orientation of liquid crystal molecules in region 04 is mainly affected by the in-plane electric field, and they can rotate in a basically consistent manner in the horizontal direction.

[0041] After incident light passes through the polarizer, it is incident perpendicularly onto the above structure. The liquid crystal molecules inside the liquid crystal cell rotate in the direction of the electric field. Region 04 can be considered a rotating half-wave plate directly driven by the electric field. The incident linearly polarized light passes through the liquid crystal cell and exits deflected at an angle. This deflection angle changes over time, resulting in rotating linearly polarized light. According to the half-wave plate principle, the rotation frequency of the linearly polarized light is twice the rotation frequency of the liquid crystal molecules, which is also twice the rotation frequency of the alternating voltage. The rotating linearly polarized light modulated by a high-speed rotating liquid crystal cell (e.g., above 50Hz) can be used as a means of capturing and controlling particles in optical micromanipulation technology. It can also be used as a means of generating vector light fields in light field modulation technology.

[0042] Another specific embodiment, such as Figure 8 This is a schematic diagram of the electrode structure of the liquid crystal cells in the Mth row and Nth column of the above embodiment after the liquid crystal cells are arranged into an array. Adjacent liquid crystal cells share a ground electrode. Electrodes 301 and 311 are grounded, while electrodes 302 and 312 are connected to different alternating voltages.

[0043] The lower substrate electrode voltages of liquid crystal cells in the same column are identical, and the upper substrate electrode voltages of liquid crystal cells in the same row are identical. A sinusoidal voltage of the same frequency and phase is applied to the lower substrate electrode, while a cosine voltage of the same frequency and phase is applied to the upper substrate electrode, with all electrodes on the upper substrate having the same phase, thus achieving a uniformly regulated liquid crystal array. If needed, the sinusoidal and cosine voltages of the upper and lower substrates can be interchanged to change the rotation direction. Furthermore, the voltages and phases of the upper and lower substrates can be arbitrarily controlled, thereby generating various time-varying vector electric field distributions for special applications, such as light field manipulation.

[0044] The embodiments can serve as a means of capturing and controlling particles or modulating vector light fields using optical micromanipulation techniques.

[0045] When this embodiment is applied to a Haidinger brush, the voltage frequency is between 0.41Hz and 0.83Hz, and the wavelength range of the incident light is 460nm to 500nm. The light source can be a blue LED light source that meets the above conditions, or a white light source filtered by a blue cobalt glass filter. After passing through the incident light-side polarizer of the liquid crystal array, blue linearly polarized light is obtained. After entering the liquid crystal cell, rotating linearly polarized light is emitted. By observing the emitted light, a rotating brush-like image can be seen.

[0046] As an optimized device for the Haidinger light brush amblyopia treatment device, it features lightweight portability, low energy consumption, controllable frequency, and no mechanical disturbance, making it particularly suitable for integration with VR and other technologies.

[0047] Excess areas in the array can be entirely or partially made into spacers. This serves two purposes: firstly, to control the thickness of the liquid crystal cell, and secondly, to help reduce the negative electro-optic effects in inactive areas. The spacers can be made opaque to reduce interference from non-rotational components.

[0048] It should be noted that in the description of this specification, the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0049] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A linearly polarized light rotation device, characterized in that, include: A liquid crystal cell, wherein a polarizer is disposed on the light-incident side of the liquid crystal cell; wherein the liquid crystal cell is one or more; The liquid crystal unit includes: A first glass substrate and a second glass substrate disposed opposite to each other; And the liquid crystal layer between the first glass substrate and the second glass substrate; The electrodes include a first electrode group consisting of multiple electrodes arranged in parallel between the first glass substrate and the liquid crystal layer, and a second electrode group arranged in parallel between the liquid crystal layer and the second glass substrate, with its direction orthogonal to the first electrode group. The electrodes are used to apply voltage to form a potential difference in the liquid crystal layer parallel to the first glass substrate, thereby controlling the rotation of liquid crystal molecules in a plane parallel to the first and second glass substrates by the direction of the electric field. Incident light, after passing through the polarizer, enters the liquid crystal cell perpendicular to the first glass substrate. The fast-axis polarization component and the slow-axis polarization component of the incident light have different optical path lengths, and the thickness of the liquid crystal layer is such that the optical path difference is... The thickness of each wavelength; where thickness refers to the height of the glass substrate in the vertical direction; where m is any positive integer.

2. The linearly polarized light rotating device according to claim 1, characterized in that, The first electrode group consists of two parallel electrodes, with one electrode grounded and the other electrode subjected to an alternating voltage; The second electrode group consists of two parallel electrodes, one electrode grounded and the other electrode applied with a phase difference from the first electrode group. The alternating voltage of the same frequency; where n is any integer.

3. The linearly polarized light rotating device according to claim 1, characterized in that, The first electrode group consists of three electrodes arranged in parallel, with the two side electrodes grounded and an alternating voltage applied to the middle electrode; The second electrode group consists of three parallel electrodes, with the two side electrodes grounded and the middle electrode applying an electrode with a phase difference from that of the first electrode group. The alternating voltage of the same frequency; where n is any integer.

4. The linearly polarized light rotating device according to claim 1, characterized in that, The first electrode group consists of three electrodes arranged in parallel, with the middle electrode grounded and alternating voltage applied to the two side electrodes; The second electrode group consists of three parallel electrodes, with the middle electrode grounded and the two side electrodes applying an electrode with a phase difference from that of the first electrode group. The alternating voltage of the same frequency; where n is any integer.

5. The linearly polarized light rotating device according to any one of claims 3 to 4, characterized in that... Also includes: Part or all of the invalid regions are made into spacer layers to control the thickness of the liquid crystal material and help reduce negative electro-optic effects; the invalid region refers to the liquid crystal molecule region outside the working region where the liquid crystal molecules rotate in the opposite direction to the emission deflection direction due to the opposite electrode arrangement to the working region.

6. The linearly polarized light rotating device according to any one of claims 3 to 5, characterized in that... Also includes: The liquid crystal cells are arranged repeatedly; The repeating liquid crystal cells are arranged in a direction parallel to the electrodes of the first electrode group or parallel to the electrodes of the second electrode group; The adjacent liquid crystal cells share the electrodes on the boundary; Along the electrode placement direction, adjacent electrodes are connected to form an N*M array; The frequency and phase of the alternating electrodes applied to each liquid crystal cell can be uniformly controlled; where N and M are arbitrary positive integers.

7. The linearly polarized light rotating device according to claim 6, characterized in that, Also includes: It has a defined incident light wavelength, the incident light wavelength being between 460 nm and 500 nm; the electrodes apply an alternating voltage with a frequency between 0.41 Hz and 0.83 Hz, i.e., the output polarized light rotation frequency is between 50 r / min and 100 r / min; it is a Haidinger light brush amblyopia treatment device driven by an electric field.

8. A method for rotating linearly polarized light, applied to the linearly polarized light rotating device as described in any one of claims 1-7, characterized in that, The method includes: A voltage is applied in a direction parallel to the plane of the first glass substrate, i.e., in the plane perpendicular to the incident light. The liquid crystal molecules within the liquid crystal layer are rotated parallel to the plane of the first glass substrate by voltage control.

Images