CN109387949B

CN109387949B - Light beam control device based on polarization adjustment

Info

Publication number: CN109387949B
Application number: CN201710674927.7A
Authority: CN
Inventors: 徐伟科
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-08-09
Filing date: 2017-08-09
Publication date: 2020-12-01
Anticipated expiration: 2037-08-09
Also published as: CN109387949A

Abstract

A light beam control device based on polarization adjustment is composed of at least two layers of polarization control components and birefringent components with the same number of layers which are connected in series at intervals. Downstream of each layer of polarization control elements is a birefringent element. The polarization control component can change the polarization direction of the light, the polarization directions of the light in the birefringent component are different along the light paths of the light in the two reference directions, and the controller adjusts the polarization direction of the light by controlling the polarization control components of the layers, so that the light beam path and the final emergent position are controlled. The spatial pointing of the outgoing beam can be controlled if lenses or mirrors are added. The polarization control member may be made of a liquid crystal material, and the birefringent member may be made of a birefringent crystal. The invention realizes a light beam control scheme with low cost, miniaturization and no movable part.

Description

Light beam control device based on polarization adjustment

Technical Field

The invention relates to the field of light beam control, in particular to the field of free space optical communication and optical routing.

Background

Techniques for controlling the directional emission of a light beam have important applications in a number of areas. For example, in the fields of automatic driving, laser mapping, and the like, the laser scanning technology is one of the key technologies, and the work to be performed by laser scanning is to control the direction of a laser beam to change according to a designed track and obtain form information of a detected environment or an object according to a reflected laser signal. In the field of laser beam driving, a laser beam is emitted from a light source to a photoelectric converter on a receiving end as a carrier for energy transfer to complete energy transfer, and in order to improve the efficiency of energy transfer, the direction of the laser beam needs to be strictly controlled to be accurately directed to the receiving end. At present, laser beam direction control devices used in the fields are all based on traditional motor servo control, and are difficult to miniaturize and high in maintenance cost.

Techniques for controlling the directional emission of light beams may also have important applications in the field of wireless communications. The frequency selection of the existing wireless communication gives consideration to signal penetrability and communication bandwidth, if the frequency is higher, the penetrability and the capability of bypassing obstacles are deteriorated, and even becomes similar to that of visible light, a straight path is required; if the frequency is lower, the bandwidth is too narrow to support the communication requirements. The current 4G technology, WIFI technology, etc. have reached the theoretical bandwidth upper limit of the used carrier frequency, and even begin to provide a technology of single user and using multiple channels in order to further improve the bandwidth, but this method is limited by the access user density, the bandwidth that can be improved is limited, and this method of improving the communication bandwidth within the framework of the prior art has a negative effect, namely worsening the electromagnetic environment, aggravating the radiation problem, and making the adverse effect of wireless communication on human health increasingly prominent. The 5G technology under development plans to adopt a centimeter-level or even millimeter-level wavelength carrier, and theoretical bandwidth can be improved by one order of magnitude on the basis of 4G, but the radio wave penetrability and the obstacle bypassing capability of such a wavelength are poor, a straight line path is almost needed between a mobile terminal and a signal base station, if a 5G system is to be constructed comprehensively, more base stations are inevitably required to be constructed and the power of the base stations is improved, and if the existing large-angle broadcast signal transmission mode is continuously used, snow and frost are generated in the existing severe electromagnetic environment. It can be said that the existing wireless communication technologies such as mobile phone and WIFI face the bottleneck of communication bandwidth.

The development of mobile internet and internet of things will have higher and higher requirements on communication bandwidth, and the improvement of carrier frequency is the only way. Higher frequency electromagnetic waves, however, require a visual path between the mobile terminal and the signal base station, and between the terminal and the terminal, because of their poorer penetration and ability to bypass obstacles. Whether centimeter waves, millimeter waves, infrared light or visible light are used as carrier waves, a visible path is an important characteristic in future wireless communication, and the invention is applied to establishing the visible path of free space communication with a space angle as small as possible and reducing the influence of a communication link on an electromagnetic environment.

In general, current techniques for achieving directional emission of a light beam include the following: 1. a motor servo system or an MEMS driver and the like are used for controlling the reflector or the refraction crystal to rotate; 2. an electronic phased array or an optical phased array; 3. raster deflection, etc. The existing motor servo system or MEMS technology for three-dimensional space pointing servo has the problems of complex system, limited angle range and the like; the phased array technology has a limited deflection angle range due to the technical characteristics of the phased array technology, and particularly, the deflection angle of a light beam is smaller in the existing optical phased array technology; the blazed grating has different diffraction angles for electromagnetic waves with different wavelengths, and can realize directional emission of light beams by using the principle, but because the wavelength of the light waves is bound with the azimuth angle of the light beams, the requirement on adjustment of the frequency of the light waves is high, the emission end is required to perform accurate wavelength control, and the deflection angle is relatively limited.

The rapid development of optical fiber communication has higher and higher requirements on optical routing, and the reliability and the service life of the mode of mechanically switching the optical path are limited. Other optical routing techniques also have their own deficiencies. The invention can realize the selection of the optical path, so the invention can be used for designing the optical router.

The invention realizes the control of light beams by combining polarization adjustment and birefringent media, and is a novel device for controlling light beams.

Disclosure of Invention

The invention aims to provide a light beam control device based on polarization adjustment, so as to meet the requirements of the light beam control technology in the fields of light routing, light communication, unmanned driving, laser scanning, laser beam driving, light routing, space positioning and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

a light beam control device based on polarization adjustment, characterized in that: the polarization control units and the birefringence units are arranged in a mode of being arranged at intervals layer by layer along the propagation direction of the light beam, each layer of polarization control unit is positioned at the upstream of the corresponding layer of birefringence unit according to the sequence of the light beam passing, and each layer of birefringence unit is positioned at the downstream of the corresponding layer of polarization control unit;

each layer of polarization control unit is provided with a light polarization adjusting medium, is connected with the controller and is controlled by the controller to change the polarization direction of light;

each layer of the birefringent units is provided with a birefringent medium, a light beam enters from a certain incident position of the birefringent unit, a part of light with the polarization direction along the polarization direction of the ordinary light in the birefringent medium exits from a first position of the birefringent unit, a part of light with the polarization direction along the polarization direction of the extraordinary light in the birefringent medium exits from a second position of the birefringent unit, the direction of the connection line of the first position and the second position is called the light beam offset direction of the birefringent unit at the incident position, and the length of the connection line of the first position and the second position is called the light beam offset distance of the birefringent unit at the incident position;

the propagation direction of the light beam passing through each layer of polarization control unit is uniquely determined by the passing position;

the controller adjusts the polarization direction of the light by controlling the polarization control units of each layer, so that the position of the light beam emitted from the downstream birefringent unit corresponding to the polarization control units of each layer is controlled, and the controller determines the position of the light beam emitted from the birefringent unit of the last layer by controlling the polarization control units of all the layers.

Optionally, the number of layers of the polarization control unit and the number of layers of the birefringence units of the light beam control device are both even numbers, the birefringence units of each layer are numbered with natural numbers according to the sequence of light beam passing, locally, the light beam offset direction of the birefringence unit with the odd number is vertical to the light beam offset direction of the birefringence unit with the even number of the first layer of the downstream, and the controller controls the two-dimensional exit position of the light beam on the light beam exit surface of the birefringence unit of the last layer by controlling the polarization control units of all the odd layers and the even layers.

Optionally, at least one layer of the light polarization adjusting medium of the polarization control unit is twisted nematic liquid crystal, the polarization control unit has two transparent liquid crystal alignment films, the two liquid crystal alignment films are respectively located on the inner side of the light beam incident surface of the polarization control unit and the inner side of the light beam emergent surface of the polarization control unit, the twisted nematic liquid crystal is filled between the two liquid crystal alignment films, and the molecular orientation of the twisted nematic liquid crystal is influenced by the liquid crystal alignment films; the polarization control unit is also provided with a pair of electrodes or a plurality of pairs of electrodes, each pair of electrodes comprises two electrodes and is electrically connected with the controller, the light beam entering the polarization control unit is vertical to the light beam incidence surface of the polarization control unit, the polarization direction of the light entering the polarization control unit is parallel to or vertical to the orientation direction of the two layers of liquid crystal orientation films, and the controller controls the molecular orientation of the twisted nematic liquid crystal between the two electrodes to be in one of two states by controlling the voltage between the two electrodes: the polarization direction of the light which exits the polarization control unit is parallel to the polarization direction of the light which enters the polarization control unit, or the polarization direction of the light which exits the polarization control unit is perpendicular to the polarization direction of the light which enters the polarization control unit;

the specific mode is one of the following two modes:

the first mode is that two electrodes of a pair of electrodes are respectively positioned on a light beam incidence surface and a light beam emergence surface of the polarization control unit, and the orientation directions of two layers of liquid crystal orientation films are vertical to each other;

in the second mode, two electrodes of the pair of electrodes are simultaneously positioned on the light beam incidence surface of the polarization control unit or the light beam emergence surface of the polarization control unit, the orientation directions of the two layers of liquid crystal orientation films are parallel to each other, and the connection direction of the two electrodes is vertical to the orientation direction of the liquid crystal orientation film.

Optionally, the light polarization adjusting medium of at least one layer of the polarization control unit is an electro-optic crystal, the propagation direction of the light beam in the electro-optic crystal is parallel to the optical axis direction, the light beam is linearly polarized, and the included angles between the polarization direction and the ordinary light polarization direction and the extraordinary light polarization direction of the electro-optic crystal are both 45 degrees, the polarization control unit has a pair of electrodes or is distributed with a plurality of pairs of electrodes in the lateral direction of the light beam propagation direction, each pair of electrodes includes two electrodes and is electrically connected with the controller, if the controller controls the voltage between the two electrodes to enable the phase difference between the ordinary light and the extraordinary light to be pi, the polarization direction of the light emitted out of the polarization control unit is perpendicular to the polarization direction of the light emitted into the polarization control unit; if the controller controls the voltage between the two electrodes so that the phase difference between the ordinary light and the extraordinary light is 0, the polarization direction of the light exiting the polarization control unit is parallel to the polarization direction of the light entering the polarization control unit.

Optionally, the light polarization adjusting medium of at least one layer of the polarization control unit is a magneto-optical crystal with a magneto-optical rotation effect, the polarization control unit has a magnetic field control unit, and the controller controls a magnetic field in the magneto-optical crystal along a light beam propagation direction through the magnetic field control unit, so as to adjust a rotation angle of a polarization direction of light exiting the polarization control unit relative to a polarization direction of light entering the polarization control unit.

Optionally, at least one layer of the birefringent units is a birefringent crystal, and an included angle between two propagation directions of a light beam in the birefringent crystal and an optical axis of the birefringent crystal is not 0 degree nor 90 degrees;

the three optical principal axes of the birefringent crystal are respectively a first principal axis, a second principal axis and a third principal axis, the relation of the refractive index Ng of the first principal axis, the refractive index Nm of the second principal axis and the refractive index Np of the third principal axis is that Ng is more than or equal to Nm and more than or equal to Np, and the incident direction of the light beam for obtaining the maximum light beam separation angle is required to be as follows: in the birefringent crystal, the polarization direction of the ordinary rays is along the second main axis, and the included angle between the propagation direction and the third main axis is arctan (Ng/Np); the polarization direction of the extraordinary ray is in a plane formed by the first main axis and the third main axis, and the included angle between the propagation direction and the third main axis is arctan (Np/Ng).

Optionally, at least one layer of the birefringent unit is a polarization splitting prism of one of a Wollaston prism, a Nicol prism, a Nomarski prism, and a Glan prism.

Optionally, there are two reference directions perpendicular to each other, a first reference direction and a second reference direction;

the light beam incidence surfaces and the light beam emergence surfaces of all the polarization control units and the birefringent units are planes and are parallel to a plane formed by the first reference direction and the second reference direction;

the light beam entering the first layer of polarization control unit is linearly polarized light, and the polarization direction is along a first reference direction or a second reference direction;

the controller controls all polarization control units in one of two states: the polarization direction of the light which exits the polarization control unit is parallel to the polarization direction of the light which enters the polarization control unit, or the polarization direction of the light which exits the polarization control unit is perpendicular to the polarization direction of the light which enters the polarization control unit;

the beam offset directions of the birefringent units in the same layer at all incident positions are the same, and the beam offset distances are also the same;

the beam shift direction of the birefringent unit is along a first reference direction or along a second reference direction;

for all the birefringent units with the beam offset direction along the first reference direction, the ratio of the beam offset distance of each layer to the layer nearest to the downstream of each layer is the same and is a first proportionality coefficient;

for all birefringent elements with beam shift directions along the second reference direction, the ratio of the beam shift distance of each layer to the layer nearest to the layer downstream is the same, and is the second proportionality coefficient.

Optionally, the first scaling factor or the second scaling factor is 2.

Optionally, the last layer of birefringent crystal of the beam steering arrangement has a lens or mirror downstream thereof, which refracts or reflects the beams emerging from different positions into different directions.

Optionally, an antireflection film is arranged between at least one layer of polarization control unit and an adjacent layer of birefringent unit, and the thickness of the antireflection film is obtained by dividing the 1/4 wavelength of light by the refractive index of the antireflection film.

Based on the technical scheme, the invention realizes the light beam control device based on polarization adjustment, and has the following outstanding technical effects: (1) the invention has no movable part, and avoids the problems of mechanical abrasion, material failure and the like in the light beam control containing the movable part. (2) The invention can use liquid crystal as light polarization adjusting medium, thereby reducing the size of the device, facilitating miniaturization and having lower polarization control voltage. (3) If the birefringent crystal is selected as the birefringent unit, one layer of birefringent unit can be a whole birefringent crystal, and compared with other prior art, the processing cost of the birefringent crystal is lower. (4) The one-layer polarization control unit can be a large or even a whole liquid crystal or electro-optic crystal or magneto-optic medium, and does not need to process a fine structure like the prior art, so the processing cost is lower. (5) The invention has low power consumption and is suitable for application occasions with sensitive power consumption, such as mobile communication and the like. (6) The invention can be used not only for free space optical communication but also for optical routing, and can be combined with other free space optical communication technologies or optical routing technologies to obtain a more optimized design.

Drawings

Fig. 1 is a schematic diagram of a first embodiment of the invention.

Fig. 2 is a schematic diagram of a first embodiment of the invention.

FIG. 3 is a view in the-X direction of the first embodiment of the present invention.

Fig. 4 is a view in the + Y direction according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of a second embodiment of the present invention.

FIG. 6 is a cross-sectional view of a twisted nematic liquid crystal polarization control unit according to a first embodiment of the present invention.

FIG. 7 is a cross-sectional view of a twisted nematic liquid crystal polarization control unit according to a second embodiment of the present invention.

FIG. 8 is a schematic diagram of a birefringent element using birefringent crystals according to the present invention.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings.

The first embodiment is as follows:

twisted nematic liquid crystals are used as the light polarization adjusting medium of the polarization control unit, calcite crystals are used as the birefringent units, and a concave lens is used as the optical lens downstream of the last layer of birefringent units.

As shown in fig. 1 and 2, an incident light beam enters the first-layer polarization control unit 109, passes through the polarization control unit 109, the birefringent unit 101, the polarization control unit 110, the birefringent unit 102, the polarization control unit 111, the birefringent unit 103, the polarization control unit 112, the birefringent unit 104, the polarization control unit 113, the birefringent unit 105, the polarization control unit 114, the birefringent unit 106, the polarization control unit 115, the birefringent unit 107, the polarization control unit 116, and the birefringent unit 108 in this order, exits from a predetermined position on the light beam exit surface of the birefringent unit 108 along the Z-axis direction, and exits at a predetermined angle after being deflected by the concave lens 117.

As shown in fig. 1, 2, 3, and 4, X, Y, Z is a space orthogonal coordinate system, and the chirality of three coordinate axes is: x, Y, Z is a left-handed coordinate system. The X-axis direction is a first reference direction, and the Y-axis direction is a second reference direction. The incident beam enters the first layer polarization control unit 109 along the Z-axis direction, perpendicular to the XY plane. The incident light beam is linearly polarized with a polarization direction along the X-axis direction or along the Y-axis direction. The

polarization control units

109, 110, 111, 112, 113, 114, 115, and 116 are sheet-like, liquid crystal alignment films are parallel to the XY plane, and twisted nematic liquid crystal is filled between the two liquid crystal alignment films. The design of the polarization control unit is shown in fig. 6, wherein 301 is two layers of liquid crystal alignment films, 303 is two layers of electrodes, the electrodes are parallel to the XY plane and are transparent, the electrode material is indium tin oxide ITO or indium zinc oxide IZO, the two layers of electrodes are respectively electrically connected with a controller, and the controller controls the voltage between the two electrodes. The twisted nematic liquid crystal 302 is filled between two liquid crystal orientation films 301, the orientation directions of the two liquid crystal orientation films of one polarization control unit are vertical to each other, and in 301, the orientation direction of the upstream liquid crystal orientation film is along the X axis; 301, the alignment direction of the downstream liquid crystal alignment film is along the Y-axis. In order to ensure reliable operation of the liquid crystal molecules, the twisted nematic liquid crystal molecules of the present embodiment have a small pretilt angle of 2 to 8 degrees with respect to the XY plane. When the controller applies a voltage of 0 to the electrode pair 303, the molecular orientation of the twisted nematic liquid crystal is affected only by the liquid crystal orientation film, 301, the liquid crystal molecular orientation is along the X axis in the vicinity of the liquid crystal orientation film located upstream; 301, in the vicinity of the liquid crystal alignment film located downstream, the liquid crystal molecular alignment is along the Y axis, and the liquid crystal molecular alignment is continuously changed in the Z direction. Therefore, due to the characteristics of the twisted nematic liquid crystal, when the controller applies a voltage of 0 to the electrode pair 303, the polarization direction of the polarized light having the polarization direction along the X axis or the Y axis is rotated by 90 degrees after passing through the polarization control unit. After the controller applies several volts between the electrode pair 303, an electric field is established between the electrode pair 303, and since molecules of the twisted nematic liquid crystal have a significant polarity, the arrangement is changed in the electric field to be along the line direction of the electric field, i.e., the Z-axis direction, so that when the controller applies several volts between the electrode pair 303, polarized light having a polarization direction along the X-axis or the Y-axis does not change the polarization state after passing through the polarization control unit.

As shown in fig. 1, 2, 3, and 4, 101, 102, 103, 104, 105, 104, 107, and 108 are birefringent units, all of which are rectangular parallelepiped-shaped birefringent crystals processed from calcite, which is a uniaxial crystal and a negative birefringence crystal. The first principal axis refractive index Ng, the second principal axis refractive index Nm, and the third principal axis refractive index Np have a relationship of Ng > Nm > Np.

Third main axes of the

birefringent crystals

101, 103, 105 and 107 with odd numbers are all parallel to the XZ plane, the included angles between the third main axes and the X axis are all arctan (Np/Ng), and the included angles between the third main axes and the positive direction of the Z axis are all acute angles. It can be proved that the design can obtain the maximum polarized beam splitting angle arctan (Ng/Np) -arctan (Np/Ng), namely the polarization direction of the ordinary ray is along the Y direction, and the beam of the ordinary ray passes through the birefringent crystal along the Z axis direction; and the polarization direction of the extraordinary ray is parallel to an XZ plane, and the propagation direction of the extraordinary ray in the birefringent crystal is deflected to the X-axis direction by an angle of arctan (Ng/Np) -arctan (Np/Ng) relative to the Z-axis. Because the incident light beams are linearly polarized light, the polarization direction is along the X axis or the Y axis, and all the polarization control units either do not change the polarization direction or rotate the polarization direction by 90 degrees, the light incident on each layer of birefringent crystals is linearly polarized light with the polarization direction along the X axis direction or the Y axis direction, so that the propagation paths of the light beams in the

birefringent crystals

101, 103, 105 and 107 are only two, or the light beams are deflected to the X axis by an angle of arctan (Ng/Np) -arctan (Np/Ng) along the original direction, namely the light beam deflection direction is the X axis direction, and the light beam deflection distance is tan [ arctan (Ng/Np) -arctan (Np/Ng) ] multiplied by the length of the Z axis direction of the birefringent crystals.

The third major axes of the even-numbered

birefringent crystals

102, 104, 106, and 108 are all parallel to the YZ plane, and the angles between the third major axes and the Y axis are arctan (Np/Ng), and the angles between the third major axes and the positive direction of the Z axis are all acute angles. It can be proved that the design can obtain the maximum polarized beam splitting angle arctan (Ng/Np) -arctan (Np/Ng), namely the polarization direction of the ordinary ray is along the X direction, and the beam of the ordinary ray passes through the birefringent crystal along the Z axis direction; and the polarization direction of the extraordinary ray is parallel to a YZ plane, and the propagation direction of the extraordinary ray in the birefringent crystal is deflected to the Y axis direction by an angle of arctan (Ng/Np) -arctan (Np/Ng) relative to the Z axis. Because the incident light beams are linearly polarized light, and the polarization direction is along the X axis or the Y axis, and all the polarization control units either do not change the polarization direction or rotate the polarization direction by 90 degrees, the light incident on each layer of birefringent crystals is linearly polarized light with the polarization direction along the X axis direction or the Y axis direction, so that the propagation paths of the light beams in the

birefringent crystals

102, 104, 106 and 108 are only two kinds, or the light beams are deflected to the Y axis by an angle of arctan (Ng/Np) -arctan (Np/Ng) along the original direction or relative to the original direction, namely the light beam deflection direction is the Y axis direction, and the light beam deflection distance is tan [ arctan (Ng/Np) -arctan (Np/Ng) ] multiplied by the length of the Z axis direction of the birefringent crystals.

The beam shift directions of the odd-numbered

birefringent crystals

101, 103, 105, and 107 are perpendicular to the beam shift directions of the even-numbered

birefringent crystals

102, 104, 106, and 108.

The

birefringent crystals

101 and 102 have the same length in the X-axis and Z-axis directions, and the length of 102 in the Y-axis direction is greater than 101. The

birefringent crystals

103 and 104 have the same length in the X-axis and Z-axis directions, and the length of 104 in the Y-axis direction is greater than 103. The

birefringent crystals

105 and 106 have the same length in the X-axis and Z-axis directions, and the length of 106 in the Y-axis direction is greater than 105. The

birefringent crystals

107 and 108 have the same length in the X-axis and Z-axis directions, and the length of 108 in the Y-axis direction is greater than 107. The ratio of the lengths of the

birefringent crystals

101 and 103 in the Z-axis direction is 2, the ratio of the lengths of the

birefringent crystals

103 and 105 in the Z-axis direction is 2, the ratio of the lengths of the

birefringent crystals

105 and 107 in the Z-axis direction is 2, and referring to the calculation formula of the beam shift distance in the previous stage, it is known that the first proportionality coefficient is 2. The ratio of the lengths of the

birefringent crystals

102 and 104 in the Z-axis direction is 2, the ratio of the lengths of the

birefringent crystals

104 and 106 in the Z-axis direction is 2, and the ratio of the lengths of the

birefringent crystals

106 and 108 in the Z-axis direction is 2, and referring to the calculation formula of the beam shift distance in the previous paragraph, it can be seen that the second proportionality coefficient is also 2. The

birefringent crystals

102 and 103 have the same length in the Y-axis direction, and the length of 103 is greater than 102 in the X-axis direction. The

birefringent crystals

104 and 105 have the same length in the Y-axis direction, and the length of 105 in the X-axis direction is greater than 104. The

birefringent crystals

106 and 107 have the same length in the Y-axis direction, and the length of 107 in the X-axis direction is greater than 106.

As shown in fig. 3, the beam shift directions of the

birefringent crystals

102, 104, 106, and 108 of even numbers are the Y-axis direction, the thicknesses of the birefringent crystals are reduced proportionally, and the second proportionality coefficients are all 2, so that the ratio of the beam shift distances of the

birefringent crystals

102, 104, 106, and 108 is 8:4:2: 1. The controller controls the polarization direction of the light beam entering the birefringent crystal 102 by controlling the polarization control unit 110, and if the light polarization direction is along the X-axis, the light beam continues to propagate along the Z-axis; if the polarization direction of light is along the Y axis, the light beam deflects the angle of arctan (Ng/Np) -arctan (Np/Ng) to the Y axis after entering the birefringent crystal 102, when exiting the birefringent crystal 102, the propagation direction of the light beam is restored to the original direction according to the symmetry of the light beam, and continues along the Z axis, so that the propagation path of the light beam in the birefringent crystal 102 and the position of the exiting crystal 102 are changed in the Y axis direction without affecting the propagation direction of the exiting light beam. Similarly, the controller controls the polarization direction of the light beam incident into the birefringent crystal 104, and controls the propagation path of the light beam within the birefringent crystal 104 and the position of the light beam exiting 104 in the Y-axis direction by controlling the polarization control unit 112; the controller controls the polarization direction of the light beam incident into the birefringent crystal 106 by controlling the polarization control unit 114, and controls the propagation path of the light beam in the birefringent crystal 106 and the position of the light beam exiting 106 in the Y-axis direction; the controller controls the polarization direction of the light beam incident into the birefringent crystal 108, and controls the propagation path of the light beam within the birefringent crystal 108 and the position of the light beam exiting 108 in the Y-axis direction by controlling the polarization control unit 116. The controller can control the emergent position of the light beam at 108 to be 2 in the Y-axis direction by controlling the

polarization control units

110, 112, 114 and 116⁴One of 16 distances.

As shown in fig. 4, the beam shift direction of the

birefringent crystals

101, 103, 105, 107 of odd number is the X-axis direction,since the thickness of the birefringent crystals is scaled down and the first scale factors are all 2, the ratio of the beam shift distances of the

birefringent crystals

101, 103, 105, 107 is 8:4:2: 1. The controller controls the polarization direction of the light beam incident on the birefringent crystal 101 by controlling the polarization control unit 109, and if the light polarization direction is along the Y axis, the light beam continues to propagate along the Z axis; if the light polarization direction is along the X axis, the light beam deflects the angle of arctan (Ng/Np) -arctan (Np/Ng) to the X axis after entering the birefringent crystal 101, when exiting the birefringent crystal 101, the light beam propagation direction returns to the original direction according to the symmetry of the light beam, and continues along the Z axis, thereby changing the propagation path of the light beam in the birefringent crystal 101 and the position of the exiting crystal 101 in the X axis direction without affecting the propagation direction of the exiting light beam. Similarly, the controller controls the polarization direction of the light beam incident into the birefringent crystal 103, and controls the propagation path of the light beam within the birefringent crystal 103 and the position of the light beam exiting 103 in the X-axis direction by controlling the polarization control unit 111; the controller controls the polarization direction of the light beam incident into the birefringent crystal 105 by controlling the polarization control unit 113, and controls the propagation path of the light beam within the birefringent crystal 105 and the position of the light beam exiting 105 in the X-axis direction; the controller controls the polarization direction of the light beam incident into the birefringent crystal 107 by controlling the polarization control unit 115, and controls the propagation path of the light beam within the birefringent crystal 107 and the position of the light beam exiting 107 in the X-axis direction. The controller can control the exit position of the light beam at 108 to be 2 in the X-axis direction by controlling the

polarization control units

109, 111, 113, 115⁴One of 16 distances.

The light beam incident surface of the polarization control unit 109 has a certain area, theoretically having an infinite number of light beam incident positions, but for a fixed incident position, light beams are incident from it to the polarization control unit 109, and then the controller can control the light beams to be emitted from the 16 × 16 to 256 possible two-dimensional arrays of possible emission positions of the light beam emission surface of the birefringent crystal 108 by controlling 109, 110, 111, 112, 113, 114, 115, and 116. If only the optical path of a layer of birefringent elements is to be changed, the states of the polarization control elements upstream and downstream of the layer of birefringent elements should be switched simultaneously, while keeping all other polarization control elements unchanged.

The design of the polarization control unit of this embodiment can also be as shown in fig. 7. 401 is a two-layer liquid crystal alignment film, and 403 is a pair of electrodes. To reduce the control voltage, the polarization control unit may have a plurality of electrode pairs. Two electrodes in one electrode pair are positioned on the same side surface of the polarization control unit, and the material of the electrodes is a metal sputtering layer with the thickness of 0.2 mu m. The twisted nematic liquid crystal 402 is filled between two liquid crystal alignment films 401, and the alignment directions of the two liquid crystal alignment films of one polarization control unit are parallel to each other, both along the X-axis direction. When the controller does not apply a voltage to the electrode pair 403, the molecular orientation of the twisted nematic liquid crystal is affected by the liquid crystal alignment film, and the liquid crystal molecular orientation is along the X axis. So when the controller does not apply a voltage to the electrode pairs 403, the polarization direction of the polarized light having the polarization direction along the X-axis or the Y-axis is not changed after passing through the polarization control unit. When the controller applies a voltage of several volts between the pair of electrodes 403, an electric field is established between 403, and since the molecules of twisted nematic liquid crystal have a significant polarity, the alignment in the electric field is changed along the direction of the electric field lines, i.e., the Y-axis direction, while the orientation of the liquid crystal molecules along the Z-axis direction is continuously changed. Therefore, when the controller applies a voltage of several volts between the pair of electrodes 403, the polarized light having the polarization direction along the X axis or the Y axis is rotated by 90 degrees after passing through the polarization control unit.

In fig. 3 and 4, arrows indicate beamlets. For a light beam with a certain width and not linear polarization, beamlets with different incidence positions may pass through the same position in the light beam steering apparatus of the present invention, as shown in fig. 8, 501 is a birefringent unit, 502 is an incident light beam, there are two possible output light beams 503, 504 after passing through 501 according to the polarization direction, and if the input light beams are shown as 505, 506, the input light beams 505, 506 may cross in 501. This does not affect the control of the individual beamlets, however, because the photons are bosons, the beams incident at different locations within the material carrying capacity do not interfere with each other.

The wavelength range of the light in this embodiment is visible light, i.e., 0.4 μm to 0.76 μm.

If the included angle between the polarization direction of the linearly polarized light and the orientation direction of the liquid crystal orientation film is not 0 degree nor 90 degrees, then after passing through the twisted nematic liquid crystal of fig. 6 or 7, the linearly polarized light may become elliptically polarized light, two light beams are resolved in the birefringent crystal, and finally the emitted light beam 108 also becomes two light beams, so if one output light beam is to be obtained, the input light beam is required to be linearly polarized along the X-axis direction or the Y-axis direction.

Twisted nematic liquid crystals are widely used in liquid crystal display screens, and are generally classified into TN liquid crystals, IPS liquid crystals, VA liquid crystals, and the like, according to the manner of changing the orientation of liquid crystal molecules before and after application of an electric field. The liquid crystal display screen has polarizing films on the upper and lower surfaces in order to control the brightness of light of each pixel, whereas the polarization control unit of the present invention has no polarizing film and uses only the light polarization adjusting property of twisted nematic liquid crystal.

The polarization control unit of the invention can also be made of an electro-optical crystal, although the thickness is thicker, and the half-wave voltage of the electro-optical crystal with the existing size and material is higher, the polarization control unit can be used under the condition of higher requirement on the light beam control speed because the adjustment speed of the electro-optical crystal is fast.

The polarization control unit based on the magneto-optical crystal has high requirement on the magnetic field intensity, but has the advantages that the polarization direction of incident light is not limited, and for a beam of light with a certain wavelength, no matter which direction the polarization direction faces, the magneto-optical rotation is generated by the optically active crystal in the magnetic field, and the polarization direction can rotate by the same angle.

For the selection of birefringent crystals, in addition to calcite crystals, other crystals having a large difference between the maximum refractive index and the minimum refractive index can be used for manufacturing the birefringent crystals of the present invention, such as yttrium vanadate crystals, lithium niobate crystals, and the like.

In order to reduce the size of the birefringent unit, a dispersion prism based on the light polarization direction, such as a Wollaston prism (Wollaston prism), a Nicol prism (Nicol prism), a Nomarski prism (Nomarski prism), a Glan prism (Glan-Foucault prism, Glan-Taylor prism), or the like, may be used as the birefringent unit. In particular, at the incident beam, two or more beam steering devices as shown in fig. 1, 2, 3 and 4, which are respectively along different directions, can be combined by using the polarization splitting prism and the polarization control unit to form a beam steering device with a wider beam steering angle range.

For clarity of explanation of the inventive content, fig. 1, 2, 3, 4 are not drawn strictly to scale.

Example two:

as shown in fig. 5, an input light beam sequentially passes through an antireflection film 209, a polarization control unit 205, an antireflection film 209, a birefringent unit 201, an antireflection film 209, a polarization control unit 206, an antireflection film 209, a birefringent unit 202, an antireflection film 209, a polarization control unit 207, an antireflection film 209, a birefringent unit 203, an antireflection film 209, a polarization control unit 208, an antireflection film 209, a birefringent unit 204, and an antireflection film 209, and then is emitted. The light beam incident surfaces and the light beam exit surfaces of all the polarization control units and the birefringent units are parallel to a plane formed by the first reference direction and the second reference direction. FIG. 5 is a cross-sectional view of the second embodiment, wherein the first reference direction is horizontally to the left and the second reference direction is vertically.

All the polarization control elements and the birefringent elements have the same length in the second reference direction. The light polarization adjusting media of the

polarization control units

205, 206, 207, 208 are twisted nematic liquid crystals, the structure is the same as that of the first embodiment, and the alignment direction of the liquid crystal alignment film is parallel to the first reference direction or the second reference direction. The

birefringent elements

201, 202, 203 and 204 are all lithium niobate crystals, optical axes of all the birefringent elements are along the same direction and are parallel to the section plane, and the optical axes and the first reference direction have included angles which are not 0 and not 90 degrees.

The polarization direction of the ordinary rays is along the second reference direction, and the polarization direction of the extraordinary rays is parallel to the section plane. The length ratio of the

birefringent elements

201, 202, 203, 204 in the direction perpendicular to both the first reference direction and the second reference direction is 8:4:2: 1. The beam shift directions of the

birefringent elements

201, 202, 203, 204 are the same, and the ratio of the beam shift distances is 8:4:2: 1. The controller controls the voltages of the electrodes in the

polarization control units

205, 206, 207, 208 so as to control the twisted nematic liquid crystal not to change the light polarization direction or to rotate the light polarization direction by 90 degrees. For the beam entrance position shown in fig. 5, all possible beam propagation directions are as shown in fig. 5, and the control of the

polarization control units

205, 206, 207, 208 by the controller determines the position where the beam exits the beam exit surface of 204 to be one of 16 possible positions. Unlike the two-dimensional control of the beam of the first embodiment, the 16 possible positions of the second embodiment are arranged along the first reference direction, and therefore are one-dimensional control of the beam.

The wavelength of the incident beam was 1.06 μm. 209 is an antireflection film, if the light beam is incident perpendicularly to the first reference direction and the second reference direction, the thickness of 209 should be 1/4 wavelength divided by the refractive index of the antireflection film, and the principle of antireflection is that the reflected light phases of the front and back surfaces of 209 are different by pi, so that the reflected light phases of the front and back surfaces cancel each other out, and the light transmittance is increased. For multilayer optical devices, the role of the antireflection film is very important, since the change in light transmission affects the transmission of the entire device geometrically.

The terms used in the present invention should be understood in accordance with their specification and literal meaning. Some terms are described in more detail herein.

The "light" may be not only visible light but also electromagnetic waves having various possible wavelengths such as infrared light, ultraviolet light, X-rays, and microwaves.

"light beam" is not limited to visible light only, but is understood to mean electromagnetic waves of a wavelength that is small compared to the cross-section of light propagation, exhibiting geometrical optical properties. Lower frequency electromagnetic waves, such as infrared light, microwaves, etc., are within the scope of the beam of the present invention if the propagation cross section is sufficiently large.

The meaning of "ordinary light" refers to the definition of optics, which refers to light that follows the law of refraction.

The meaning of "very light" refers to the optical definition, meaning light that does not follow the law of refraction.

"upstream" and "downstream" mean that, in the direction of light propagation, the light arrives upstream first and downstream later.

The "beam incident surface" and "beam exit surface" mean a spatial position, and do not particularly denote a certain surface material.

An "electrode" is understood to be a spatial configuration of electrically conductive material. The electrodes in the present invention are mostly plate-shaped, sheet-shaped, and strip-shaped. An "electrode pair" is understood to mean two electrodes which are spatially located opposite one another and are each connected to a pair of positive and negative electrodes.

"electrically connected" is to be understood as being connected by means of a conductor.

By "transparent" it is understood that the medium may at least partially transmit electromagnetic waves of that wavelength.

The controller can be a microelectronic control device, a control circuit, a computer, a PLC, a single chip microcomputer, an FPGA, an industrial personal computer, a mobile device and the like, and other elements or devices with control functions. The controller is provided with a corresponding driving module to drive the controlled device.

Many modifications and variations are possible in light of the above teaching. The particular embodiments were chosen and described in order to best explain the principles of the disclosure and its practical application, to thereby enable others skilled in the art to best utilize the various embodiments with various modifications as are suited to the particular use contemplated.

The embodiments are not intended to be restrictive, and various technical features of the invention can be combined according to actual needs. In the specific embodiments, combination, structural design, parameter selection, etc. are not specifically listed, and a person skilled in the art may flexibly select the combination according to specific situations. However, any technical solutions, technical designs, etc. including the technical features of the present invention fall within the scope of the present invention.

Claims

1. A light beam control device based on polarization adjustment, characterized in that: the polarization control units and the birefringence units are arranged in a mode of being arranged at intervals layer by layer along the propagation direction of the light beam, each layer of polarization control unit is positioned at the upstream of the corresponding layer of birefringence unit according to the sequence of the light beam passing, and each layer of birefringence unit is positioned at the downstream of the corresponding layer of polarization control unit;

2. A polarization adjustment based beam steering apparatus according to claim 1, wherein: the number of layers of the polarization control units and the number of layers of the birefringence units of the light beam control device are both even numbers, the birefringence units of each layer are numbered with natural numbers according to the sequence of light beam passing, locally, the light beam offset direction of the birefringence unit with the odd number is vertical to the light beam offset direction of the birefringence unit with the even number of the first layer of the downstream, and the controller controls the two-dimensional emergent position of the light beam on the light beam emergent surface of the birefringence unit of the last layer by controlling the polarization control units of all the odd layers and the even layers.

3. A polarization adjustment based beam steering apparatus according to claim 1, wherein: at least one layer of light polarization adjusting medium of the polarization control unit is twisted nematic liquid crystal, the polarization control unit is provided with two layers of transparent liquid crystal orientation films, the two layers of liquid crystal orientation films are respectively positioned on the inner side of the light beam incidence surface of the polarization control unit and the inner side of the light beam emergence surface of the polarization control unit, the twisted nematic liquid crystal is filled between the two layers of liquid crystal orientation films, and the molecular orientation of the twisted nematic liquid crystal is influenced by the liquid crystal orientation films; the polarization control unit is also provided with a pair of electrodes or a plurality of pairs of electrodes, each pair of electrodes comprises two electrodes and is electrically connected with the controller, the light beam entering the polarization control unit is vertical to the light beam incidence surface of the polarization control unit, the polarization direction of the light entering the polarization control unit is parallel to or vertical to the orientation direction of the two layers of liquid crystal orientation films, and the controller controls the molecular orientation of the twisted nematic liquid crystal between the two electrodes to be in one of two states by controlling the voltage between the two electrodes: the polarization direction of the light which exits the polarization control unit is parallel to the polarization direction of the light which enters the polarization control unit, or the polarization direction of the light which exits the polarization control unit is perpendicular to the polarization direction of the light which enters the polarization control unit;

the specific mode is one of the following two modes:

4. A polarization adjustment based beam steering apparatus according to claim 1, wherein: the light polarization adjusting medium of at least one layer of the polarization control unit is an electro-optic crystal, the propagation direction of a light beam in the electro-optic crystal is parallel to the direction of an optical axis, the light beam is linearly polarized, the included angles between the polarization direction and the ordinary light polarization direction and between the polarization direction and the extraordinary light polarization direction of the electro-optic crystal are both 45 degrees, the polarization control unit is provided with a pair of electrodes or is distributed with a plurality of pairs of electrodes in the lateral direction of the light beam propagation direction, each pair of electrodes comprises two electrodes and is electrically connected with a controller, and if the controller controls the voltage between the two electrodes to enable the phase difference between the ordinary light and the extraordinary light to be pi, the polarization direction of the light emitted out of the polarization control unit is perpendicular to the polarization direction of the light; if the controller controls the voltage between the two electrodes so that the phase difference between the ordinary light and the extraordinary light is 0, the polarization direction of the light exiting the polarization control unit is parallel to the polarization direction of the light entering the polarization control unit.

5. A polarization adjustment based beam steering apparatus according to claim 1, wherein: the light polarization adjusting medium of at least one layer of the polarization control unit is a magneto-optical crystal with a magneto-optical rotation effect, the polarization control unit is provided with a magnetic field control unit, and the controller controls a magnetic field in the magneto-optical crystal along the propagation direction of the light beam through the magnetic field control unit so as to adjust the rotation angle of the polarization direction of the light emitted out of the polarization control unit relative to the polarization direction of the light emitted into the polarization control unit.

6. A polarization adjustment based beam steering apparatus according to claim 1, wherein: at least one layer of the birefringent units is a birefringent crystal, and included angles between two propagation directions of light beams in the birefringent crystal and an optical axis of the birefringent crystal are not 0 degree or 90 degrees;

7. A polarization adjustment based beam steering apparatus according to claim 1, wherein: at least one layer of the birefringent units is a polarization beam splitting prism of one of a Wollaston prism, a Nicol prism, a Nomarski prism and a Glan prism.

8. A polarization adjustment based beam steering apparatus according to claim 1, wherein: having two reference directions perpendicular to each other, a first reference direction and a second reference direction;

9. A polarization adjustment based beam steering apparatus according to claim 8, wherein: the first scaling factor or the second scaling factor is 2.

10. A polarization adjustment based beam steering apparatus according to claim 1, wherein: downstream of the last layer of birefringent crystals of the beam steering arrangement there are lenses or mirrors that refract or reflect the beams emerging from different positions into different directions.

11. A polarization adjustment based beam steering apparatus according to claim 1, wherein: an antireflection film is arranged between at least one layer of polarization control unit and the adjacent layer of birefringent unit, and the thickness of the antireflection film is obtained by dividing the 1/4 wavelength of light by the refractive index of the antireflection film.