CN113391489A

CN113391489A - Method and device for linearly polarized light polarization direction jump-free rotation

Info

Publication number: CN113391489A
Application number: CN202110676275.7A
Authority: CN
Inventors: 石锦卫; 蒋安雯; 于浩耘
Original assignee: Beijing Normal University
Current assignee: Beijing Normal University
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-09-14

Abstract

The invention relates to a linearly polarized light polarization direction jump-free rotation method and device applied to the related fields of image display, light field regulation and control, optical micro-manipulation, ophthalmic medical treatment and the like. The incident linearly polarized light is subjected to the birefringence effect of liquid crystal molecules, the components in the two directions of the fast axis and the slow axis of the incident linearly polarized light obtain half-wavelength phase difference, and the alternating voltage is utilized to control the liquid crystal molecules to rotate parallel to the liquid crystal substrate so as to emit the rotating linearly polarized light. The invention can realize controllable rotation rate of the rotating linearly polarized light and no jump in the rotating process. The uniform regulating array can be formed through the arrangement structure of the liquid crystal units, and can be applied to a Haidinge optical brush amblyopia therapeutic apparatus, an optical control device and other devices under specific conditions.

Description

Method and device for linearly polarized light polarization direction jump-free rotation

Technical Field

The invention relates to a linearly polarized light polarization direction jump-free rotation method and device applied to the related fields of image display, light field regulation and control, optical micro-manipulation, ophthalmic medical treatment and the like, and in a specific embodiment, relates to a Haiding optical brush amblyopia treatment instrument optimization device, a liquid crystal display device, a vector light field generation device and an optical manipulation device.

Background

The linearly polarized light rotates continuously without angle limitation, namely does not jump, and has wide application requirements in the fields of Haidinger amblyopia therapy, liquid crystal display, optical micro-manipulation and the like. Amblyopia is an ophthalmic common disease caused by visual development disorder of children. The Haidinger brush therapy is a method with good treatment effect for treating amblyopia, when blue linear polarized light with the rotation rate of 50-100r/min (namely 0.83-1.67Hz) is watched, a brush-shaped image can be generated in the field range to rotate at a slow speed, and the amblyopia can be treated by watching the rotating blue linear polarized light. In the field of optical micromanipulation, the angular momentum of circularly polarized light or vortex rotation can form an optical trap to capture or manipulate particles. The non-uniform polarization distribution of the independently regulated vector light field has important influence on the space-time evolution of the light field and the interaction between the light field and a substance. The screen display and the spatial light modulator need to adjust the transmittance by changing the direction of incident polarized light corresponding to the pixel points, so as to achieve the purpose of image display. Therefore, it is urgently required to develop a rotation device for linearly polarized light without jump in polarization direction.

At present, mainstream instruments for rotating the polarization direction of linearly polarized light comprise a liquid crystal phase retarder, a spatial light modulator, a photoelastic modulator and the like, but the polarization direction rotation regulating and controlling instruments can only realize continuous regulation and control in a limited angle range (usually within 180 degrees), and the polarization direction rotation jumping problem is encountered when the polarization direction rotation regulating and controlling instruments exceed the limited angle range, so that continuous rotation without angle limitation cannot be realized. The common design concept of the phase retarder is to change the polarization direction of emergent light by changing the optical rotation of liquid crystal or the birefringence of material. Taking the phase retarder as an example, a voltage is applied to the liquid crystal substrate ITO layer, so that liquid crystal molecules are longitudinally deflected along a light propagation direction, and birefringence and optical rotation are changed, thereby affecting the emergent polarization characteristic of incident linearly polarized light, and achieving the purpose of phase retardation.

The most direct device for linearly polarized light to rotate in the polarization direction without jumping is a half-wave plate (for linearly polarized light) or a polarizing plate (for natural light) driven by a mechanical motor, such as a Haidinge optical brush therapeutic apparatus (CN2875382Y), which works by the drive of the mechanical motor. However, the linear polarization light is driven by the mechanical motor to have the problems of inaccurate control and large mechanical disturbance, and the linear polarization light is large in size and cannot be integrated, so that the linear polarization light is not beneficial to developing portable equipment. High-speed jump-free polarization regulation and control can be realized based on an optical heterodyne interferometry, such ashttps://doi.org/10.29026/oea.2020.200022(OPTO-ELECTRONIC ADVANCES,2020，3(8), 200022) However, this method has high requirements for the accuracy of the optical path, the volume of the acousto-optic modulation device is still large, the efficiency is not high, and the cost is high, so that it is difficult to apply the method to the above various situations.

In addition, in devices that use a horizontal electric field to modulate liquid crystal and change the direction of linearly polarized light, such as IPS (CN101666949B) and FFS (CN1302450C) display panel technologies, the horizontal electric field provided by a single-layer electrode enables the liquid crystal to be aligned parallel to the substrate and rotate, and can modulate the polarization direction of polarized light, but still only can realize linear polarization rotation modulation of a limited angle to control gray scale, and still cannot realize no-jump rotation of the polarization direction of linearly polarized light. And the structure of the device only relates to a single-layer electrode, and is different from the structure of the device provided by the invention, so that the device is difficult to be applied to various scenes such as ophthalmic medical treatment, light field regulation, optical micro-manipulation and the like.

Disclosure of Invention

In order to solve the defects of the prior art in the field, the invention provides an electrically-driven linearly polarized light polarization direction jump-free rotating device based on a liquid crystal electro-optic effect principle.

To achieve the object of the present invention, a method is proposed, which comprises:

applying a voltage in a direction parallel to the first glass substrate plane; liquid crystal molecules in the liquid crystal layer are controlled to rotate parallel to the plane of the first glass substrate through voltage, so that the polarization direction of incident linearly polarized light can be continuously and controllably rotated.

In order to realize the purpose of the invention, the following technical scheme is adopted:

the liquid crystal display device comprises a liquid crystal unit, wherein a polarizing film is arranged on the light incidence side of the liquid crystal unit; wherein, the number of the liquid crystal units is one or more; the liquid crystal cell includes: the first glass substrate and the second glass substrate are oppositely arranged; and a liquid crystal layer between the first glass substrate and the second glass substrate; the electrodes are provided with a plurality of first electrode groups which are respectively arranged between the first glass substrate and the liquid crystal layer and are arranged in parallel, and a plurality of second electrode groups which are arranged between the liquid crystal layer and the second glass substrate and are arranged in parallel and have the direction orthogonal to the first electrode groups, and the distance between the electrodes in the electrode groups can be different; the electrodes are used for applying voltage to form a potential difference on the liquid crystal layer, and further the liquid crystal molecules are controlled to rotate on a plane parallel to the first glass substrate and the second glass substrate through the electric field.

Incident light is incident on the liquid crystal unit through the polaroid in a direction perpendicular to the first glass substrate, due to the fact that liquid crystal materials have birefringence, optical paths of the incident light passing through a fast axis polarization direction component and a slow axis polarization direction component are different, and the thickness of the liquid crystal layer is the thickness with the optical path difference of (m +1/2) wavelengths; wherein the thickness refers to the height of the glass substrate in the direction perpendicular to the plane; wherein m is any positive integer.

Optionally, the first electrode is formed by arranging two electrodes in parallel, one electrode is grounded, and an alternating voltage is applied to the other electrode; the second electrode group is formed by arranging two electrodes in parallel, one side electrode is grounded, and the phase difference between the applied electrode on one side and the applied electrode on the other side of the first electrode group is

The same frequency alternating voltage of (1); wherein n is any integer.

According to one embodiment, the first electrode group is formed by three electrodes which are arranged in parallel, two side electrodes are grounded, and an alternating voltage is applied to a middle electrode; the second electrode group is formed by three electrodes which are arranged in parallel, the electrodes at two sides are grounded, and the phase difference between the middle electrode and the first electrode group is applied

The same frequency alternating voltage of (1); wherein n is any integer. Alternatively, the middle electrode of the first and second electrode sets is grounded, and the alternating voltage is applied to the electrodes at both sides.

Optionally, a spacer layer may be made for some or all of the inactive areas to control the thickness of the liquid crystal material and help reduce negative electro-optic effects; the inactive area refers to a liquid crystal molecule area in which liquid crystal molecules are rotated reversely with respect to the exit deflection direction at the periphery of the active area due to the electrode arrangement being opposite to that of the active area.

According to another embodiment, the liquid crystal cells are repeated in a direction parallel to the electrodes of the first electrode group or parallel to the electrodes of the second electrode group to form an N x M array, the electrodes on the common boundary of adjacent liquid crystal cells being contiguous with adjacent electrodes in the electrode placement direction; the frequency and the phase of the alternating electrode applied to each liquid crystal unit can be uniformly regulated and controlled; wherein N and M are any positive integer. Optionally, adjacent electrodes are connected into a whole to form one electrode.

Optionally, a defined incident light wavelength, said incident light wavelength range being between 460nm-500 nm; the frequency of the alternating voltage applied by the electrode is between 0.41Hz and 0.83Hz, namely the rotation frequency of the emergent linear polarized light is between 50r/min and 100 r/min; the therapeutic apparatus is used for direct electric field driven Haidinge optical brush weak potential therapeutic apparatus.

Has the advantages that:

1. the invention can realize linearly polarized light rotation without jumping.

2. The invention can arbitrarily regulate and control the rotation frequency of linearly polarized light.

3. Compared with mechanical drive, the invention has the advantages of no mechanical vibration, small occupied space and low energy consumption.

Drawings

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic top view of a liquid crystal cell structure according to an embodiment of the invention.

Fig. 2 is a schematic front view of a liquid crystal cell structure according to an embodiment of the invention.

FIG. 3 is a schematic side view (left side view) of a liquid crystal cell structure according to an embodiment of the invention.

FIG. 4 is a schematic front view of a spacer structure for a liquid crystal cell according to another embodiment of the present invention.

FIG. 5 shows the electric field distribution of the liquid crystal cell in the embodiment of the present invention.

FIG. 6 shows the distribution of the electric field of the liquid crystal cell observed at another angle in the embodiment of the present invention.

FIG. 7 is a top view of an electric field distribution of a liquid crystal cell in an embodiment of the present invention.

Fig. 8 is a schematic diagram illustrating a unified array control and a relationship between the array control and a corresponding area of a liquid crystal cell according to another embodiment of the present invention.

Detailed Description

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which this application belongs.

This example is merely to provide a further understanding of the inventive concept, the liquid crystal material n being incident at a wavelength of 630nm_o＝1.479， n_e1.573 is for illustration and not as a limitation of the claims.

Fig. 1 to 3 are schematic views of an embodiment and three views of a liquid crystal cell, and as seen from the plan view of fig. 1, the electrodes divide one liquid crystal cell into 4 regions, i.e., a region 01, a region 02, a region 03, and a region 04. The electrode 101, the electrode 102 and the electrode 103 are arranged below the upper liquid crystal glass substrate 121. The electrode 111, the electrode 112, and the electrode 113 are disposed above the lower glass substrate 122. Between the two glass substrates is a liquid crystal material 125. The positional relationship of the structures can be clearly seen from fig. 2 and 3, and the insulating film 123 covers the electrodes and the contact surfaces of the glass substrates and the liquid crystal, because the electrode arrays are provided on both the upper and lower glass substrates in the present invention, which is provided for preventing the leakage current. However, in the current commercial liquid crystal cell structure, only one side of the glass substrate is provided with the electrode array, and the other side is grounded, so that the requirement is not met.

Grounding the electrodes 101, 103, 111 and 113, applying sine alternating current voltage to the electrode 102, applying cosine alternating current voltage with the same frequency to the electrode 112, generating potential difference between the two voltages and the grounding electrode in the horizontal direction, generating electric field action on liquid crystal molecules, and subjecting the liquid crystal molecules to the electric field action, wherein when the applied voltage exceeds the threshold voltage, the axial direction of the liquid crystal molecules is consistent with the direction of the electric field. The resultant electric field generated by the two electrodes is a rotating electric field with constant amplitude and the rotating frequency is the frequency of the applied alternating voltage. The liquid crystal molecular alignment is aligned with the electric field direction and rotated at the applied alternating voltage frequency.

The thickness of the liquid crystal material 125, i.e. the distance between the two glass substrates, is the thickness of the liquid crystal birefringence that generates the half-wavelength optical path difference corresponding to the incident wave wavelength. In this embodiment, to make the liquid crystal as a zero-order half-wave plate, the thickness of the liquid crystal is calculated according to the birefringence parameter

Since the alternating voltage electrode has the effect of the electric field on the liquid crystal molecules in the two side areas, the analysis shows that the rotating direction of the liquid crystal molecules in the area 02 and the area 03 is opposite to the rotating direction of the liquid crystal molecules in the area 01 and the area 04 in the plane, the electric field direction of the area 01 is opposite to that of the area 04, and the liquid crystal molecules are aligned uniformly. Taking the larger area 04 as the active area, the areas 02, 03 are considered as inactive areas, which may have a negative electro-optic effect on the beneficial effect.

Therefore, the areas of the regions 02 and 03 are as small as possible, and as shown in fig. 1, the effective output region of the rotationally linearly polarized light is a region 04. In the present embodiment, the areas of the regions 02 and 03 are 1/10 of the region 04, and the ratio can be adjusted according to the specific application.

To address this problem, as shown in fig. 4, the regions 01, 02 and 03 may be made into spacers (spacers) in whole or in part, such as spacers 126 and 127 in fig. 4, for controlling the thickness of the liquid crystal cell and for reducing the negative electro-optic effect of the inactive region. The spacer layer may be made opaque to reduce interference without rotational components.

Fig. 5, fig. 6 are schematic diagrams of electric fields inside the liquid crystal cell observed from two directions after the visualization is solved by using the MATLAB numerical value, and fig. 7 is a schematic diagram of electric field distribution of the 3-dimensional liquid crystal cell observed from a top view angle after the visualization is solved by using the MATLAB numerical value. Each layer in the figure represents the electric field in the liquid crystal at a different location along the direction of light propagation. Since the liquid crystal molecules are influenced by the electric field exceeding the threshold voltage, and the liquid crystal molecular axis orientation is the same as the electric field, it can be considered that the electric field direction in fig. 5-6 is the liquid crystal molecular orientation here.

In this embodiment, the distance between the electrodes 101 and 102 is equal to the distance d between the

electrodes

111 and 112₁The distance between the electrodes 102 and 103 is equal to the distance d between the electrodes 112 and 113₂The thickness of the liquid crystal layer is d₀In FIGS. 5-6, the distance ratio is d₁:d₂:d₀1:10: 1. As can be seen from fig. 5 to 6, since the sine 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 by the electrode positions. Therefore, the liquid crystal molecules in the regions 01, 02 and 03 are difficult to maintain parallel to the substrate due to the influence of the electrodes, and the negative influence on the incident linearly polarized light is limited even without the spacer of fig. 4, but similarly, as can be seen from fig. 5 to 6, the liquid crystal molecules in 80% of the regions 04 are inclined only in the vertical direction at a small angle. As can be seen from the top view of fig. 7, the liquid crystal molecular alignment of the region 04 is mainly affected by the in-plane electric field and can be rotated substantially uniformly in the horizontal direction.

After incident light passes through the polaroid, the incident light is vertically incident on the structure, liquid crystal molecules in the liquid crystal unit rotate along with the direction of an electric field, and the area 04 can be regarded as a rotating half-wave plate directly driven by the electric field. Incident linearly polarized light passes through the liquid crystal unit, emergent light is deflected by an angle, the deflection angle changes along with time, and the rotated linearly polarized light is obtained, and according to the half-wave plate principle, the rotation frequency of the linearly polarized light is twice of the rotation frequency of liquid crystal molecules, namely twice of the rotation frequency of alternating voltage. The rotating linear polarized light modulated by the liquid crystal unit rotating at high speed (such as above 50 Hz) can be used as a means for capturing and controlling particles by the optical micro-manipulation technology. The method can also be used as a light field regulation and control technology and a vector light field generation means.

In another embodiment, as shown in fig. 8, the liquid crystal cells in the M-th row and the N-th column and the adjacent cell electrodes of the liquid crystal cells in the above embodiments are formed into an array. The adjacent liquid crystal cells share the ground electrode. The electrodes 301, 311 are grounded, and the electrodes 302, 312 are respectively connected with different alternating voltages.

The voltages of the lower substrate electrodes of the liquid crystal cells in the same row are the same, and the voltages of the upper substrate electrodes of the liquid crystal cells in the same row are the same. Sine voltage with the same frequency phase is applied to the lower substrate electrode, cosine voltage with the same frequency as the lower substrate electrode is applied to the upper substrate electrode, and the phases of the electrodes of the upper substrate are the same, so that the uniformly regulated liquid crystal array is obtained. The sine and cosine voltages of the upper and lower substrates can be exchanged to change the rotating direction according to requirements. Furthermore, the voltage and the phase of the upper substrate and the lower substrate can be controlled at will, so that various vector electric field distributions changing along with time are generated and are used for special occasions such as light field regulation.

Embodiments may be used as a means for trapping, controlling particles, or vector light field manipulation using optical micromanipulation techniques.

When the embodiment is applied to the Haidinger optical brush, the voltage frequency is between 0.41Hz and 0.83Hz, and the wavelength range of the incident light is 460nm to 500 nm. The light source can be a blue light LED light source meeting the above conditions or a white light source filtered by a blue cobalt glass filter, and the blue linearly polarized light is obtained by a liquid crystal array light incidence side polarizer and emits the rotating linearly polarized light after entering the liquid crystal unit, and the rotating brush-shaped image can be seen by watching the emergent light.

As an optimization device of the Haidinge optical brush amblyopia therapeutic instrument, the device has the characteristics of portability, easy carrying, low energy consumption, controllable frequency and no mechanical disturbance, and is particularly suitable for being integrated with VR and the like.

The array redundant area can be made into a spacer layer (spacer) in whole or in part, and the spacer layer is used for controlling the thickness of a liquid crystal box on one hand and is helpful for reducing the negative electro-optic effect of the invalid area on the other hand. The spacer layer may be made opaque to reduce interference without rotational components.

It should be noted that in the description of the present specification, the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention.

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

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A linearly polarized light rotating apparatus, characterized by comprising:

the liquid crystal display device comprises a liquid crystal unit, wherein a polarizing film is arranged on the light incidence side of the liquid crystal unit; wherein, the number of the liquid crystal units is one or more;

the liquid crystal cell includes:

the first glass substrate and the second glass substrate are oppositely arranged;

and a liquid crystal layer between the first glass substrate and the second glass substrate;

electrodes having a plurality of first electrode groups arranged in parallel with each other and respectively interposed between the first glass substrate and the liquid crystal layer, and a plurality of second electrode groups arranged in parallel with each other and oriented orthogonally to the first electrode groups and interposed between the liquid crystal layer and the second glass substrate; the electrode spacing in the first electrode group and the second electrode group can be different;

the electrodes are used for applying voltage, potential difference parallel to the first glass substrate is formed in the liquid crystal layer, and then liquid crystal molecules are controlled to rotate on a plane parallel to the first glass substrate and the second glass substrate through the direction of an electric field;

incident light is incident on the liquid crystal unit through the polaroid in a direction perpendicular to the first glass substrate, the optical paths of the incident light passing through the fast axis polarization direction component and the slow axis polarization direction component are different, and the thickness of the liquid crystal layer is the thickness with the optical path difference of (m +1/2) wavelengths; wherein the thickness refers to the height of the glass substrate in the direction perpendicular to the plane; wherein m is any positive integer.

2. Linearly polarized light rotating device according to claim 1,

the first electrode group is formed by arranging two electrodes in parallel, wherein one electrode is grounded, and an alternating voltage is applied to one electrode;

the second electrode group is formed by arranging two electrodes in parallel, one side electrode is grounded, and the phase difference between the applied electrode on one side and the applied electrode on the other side of the first electrode group is

The same frequency alternating voltage of (1); wherein n is any integer.

3. Linearly polarized light rotating device according to claim 1,

the first electrode group is formed by arranging three electrodes in parallel, the electrodes on two sides are grounded, and alternating voltage is applied to the middle electrode;

the second electrode group is formed by three electrodes which are arranged in parallel, two side electrodes are grounded, and the middle electrode is applied to the electrode groupPhase difference of the first electrode group

The same frequency alternating voltage of (1); wherein n is any integer.

4. The linearly polarized light rotating apparatus according to claim 3, having the first electrode group and the second electrode group structure according to claim 3, further comprising:

in any one of said groups of electrodes, the middle electrode is grounded and the two side electrodes are supplied with an alternating voltage according to claim 3.

5. The linearly polarized light rotating apparatus according to claim 3, characterized by having the structure according to any one of claims 3 to 4, further comprising:

a spacer layer can be made for part or all of the inactive area to control the thickness of the liquid crystal material and help reduce negative electro-optic effects; the inactive area refers to a liquid crystal molecule area in which liquid crystal molecules are rotated reversely with respect to the exit deflection direction at the periphery of the active area due to the electrode arrangement being opposite to that of the active area.

6. A linearly polarized light rotating device, characterized by satisfying the linearly polarized light rotating device of any one of claims 3 to 5; characterized in that the liquid crystal cell repeat arrangement of any of claims 3 to 5 is satisfied;

the repeating liquid crystal cells may be arranged in a direction parallel to the first electrode group electrodes or parallel to the second electrode group electrodes;

the electrodes on the boundary are shared by adjacent liquid crystal cells;

adjacent electrodes are connected along the electrode placement direction to form an N-M array;

the frequency and the phase of the alternating electrode applied to each liquid crystal unit can be uniformly regulated and controlled; wherein N and M are any positive integer.

7. The linearly polarized light rotating apparatus according to claim 6, further comprising:

having a defined incident light wavelength in the range of 460nm to 500 nm; the frequency of the alternating voltage applied by the electrode is between 0.41Hz and 0.83Hz, namely the rotation frequency of the emergent linear polarized light is between 50r/min and 100 r/min; the Haidinge optical brush amblyopia therapeutic instrument is driven by an electric field.

8. A linearly polarized light rotating method applied to the linearly polarized light rotating apparatus according to any one of claims 1 to 7, characterized by comprising:

applying a voltage in a direction parallel to the plane of the first glass substrate, i.e. in the plane perpendicular to the incident light;

controlling liquid crystal molecules in the liquid crystal layer to rotate parallel to the plane of the first glass substrate through voltage;

the linearly polarized light is rotated by rotating the liquid crystal molecules.