CN109931885B - Device for accurately measuring incidence angle of light beam - Google Patents
Device for accurately measuring incidence angle of light beam Download PDFInfo
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- CN109931885B CN109931885B CN201910169429.6A CN201910169429A CN109931885B CN 109931885 B CN109931885 B CN 109931885B CN 201910169429 A CN201910169429 A CN 201910169429A CN 109931885 B CN109931885 B CN 109931885B
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- 239000004973 liquid crystal related substance Substances 0.000 claims abstract description 48
- 239000004988 Nematic liquid crystal Substances 0.000 claims abstract description 6
- 210000002858 crystal cell Anatomy 0.000 claims description 6
- 238000001514 detection method Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 12
- 239000013078 crystal Substances 0.000 abstract description 3
- 238000000034 method Methods 0.000 description 10
- 230000003287 optical effect Effects 0.000 description 6
- 238000000691 measurement method Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004556 laser interferometry Methods 0.000 description 2
- 238000012634 optical imaging Methods 0.000 description 2
- 238000001028 reflection method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005316 response function Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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Abstract
The invention discloses a device for accurately measuring the incidence angle of a light beam, which relates to the technical field of G02F optics, and comprises a laser, a beam splitter, a reflecting mirror, a liquid crystal box and a detector, wherein the laser is used for generating Gaussian light beams and transmitting the Gaussian light beams into the beam splitter, the beam splitter is used for splitting the Gaussian light beams into two Gaussian light beams with equal intensity, one Gaussian light beam is transmitted to the liquid crystal box, the other Gaussian light beam is transmitted into the liquid crystal box through the reflecting mirror at a certain incidence angle, the detector is used for measuring the light intensity of the light beam after passing through the liquid crystal box, PT symmetrical crystal lattice formed by nematic liquid crystal and strong non-local nonlinearity thereof are utilized, the incidence angle of reflected light is directly determined by measuring the light intensity of the transmitted light after passing through the liquid crystal box according to the one-to-one correspondence relation between the light intensity of the transmitted light after passing through the liquid crystal box and the incidence angle of the reflected light; the environment adaptability is good, the cost is low, the measurement accuracy is high, and the measurement requirement of a micro angle can be met.
Description
Technical Field
The invention relates to the technical field of G02F optics, in particular to a device for accurately measuring the incident angle of a light beam.
Background
Precise angle measurement is always a problem in the engineering field, and an optical method is an important method for accurately measuring small angles. The currently applied optical small angle measurement methods mainly comprise an optical internal reflection method, a CCD optical angle measurement method, a circular grating method, a double-frequency laser interferometry method, an optical imaging auto-collimation method, a precise photoelectric small angle measurement method and the like. The main advantage of the optical internal reflection method is small volume, which can be made into pocket angle meter, but its measuring accuracy is not high. The main advantage of the CCD optical goniometry method is that the operation is simpler, but the measurement accuracy is not high enough. The main advantage of the round grating method is that the measurement accuracy is high, but the manufacturing and processing of the high-accuracy grating are difficult. The dual-frequency laser interferometry has high accuracy in small-angle measurement, but is bulky. Although the optical imaging auto-collimation method has high measurement precision, the method has poor environmental adaptability and high requirements on measurement environment, and is more suitable for being carried out in a laboratory with good environment. Although the precision photoelectric small-angle measurement method has high measurement precision, has the functions of measuring the attitude angle and transmitting the space reference, the cost is high.
Disclosure of Invention
The invention provides a device for accurately measuring the incident angle of a light beam aiming at the problems of the background technology, and solves the problems that the existing small-angle measuring technology cannot achieve high measuring accuracy, simple operation, good environmental adaptability and low cost.
In order to achieve the above-mentioned objective, the present invention provides a device for precisely measuring the incident angle of a light beam, which comprises a laser, a beam splitter, a reflecting mirror, a liquid crystal box and a detector, wherein the laser is used for generating a gaussian light beam and emitting the gaussian light beam into the beam splitter, the beam splitter is used for splitting the gaussian light beam into two gaussian light beams with equal intensity, one of the gaussian light beams is emitted to the liquid crystal box, the other gaussian light beam is emitted to the liquid crystal box through the reflecting mirror at a certain incident angle, the detector is used for measuring the light intensity of the light beam after passing through the liquid crystal box, and the corresponding light intensities are respectively obtained by adjusting different incident angles so as to obtain the corresponding relation between the incident angle and the light intensity; during detection, the incident angle to be measured is determined according to the light intensity measured by the detector.
Preferably, the two Gaussian beams with equal intensity are adopted, wherein one beam is transmitted light, and the other beam is reflected light.
Preferably, the detector is used for measuring the light intensity of the light beam after passing through the liquid crystal box, specifically: the intensity of the transmitted light after passing through the cell is measured.
Preferably, the liquid crystal box has its internal nematic liquid crystal constituting PT symmetrical lattice.
Preferably, the corresponding relation between the incident angle and the light intensity is determined by a non-local nonlinear schrodinger equation.
Preferably, the one light beam is emitted to the liquid crystal box, specifically: a light beam is emitted vertically to the liquid crystal cell.
The invention provides a device for precisely measuring the incident angle of a light beam, which can utilize PT symmetrical crystal lattice formed by nematic liquid crystal and strong non-local nonlinearity thereof, directly determine the incident angle of reflected light by measuring the light intensity of transmitted light passing through a liquid crystal box according to the one-to-one correspondence relationship between the light intensity of the transmitted light passing through the liquid crystal box and the incident angle of the reflected light. The method is a good non-contact angle measurement method, has good environmental adaptability, low cost and high measurement accuracy, can meet the measurement requirement of a small angle, and provides a good measurement means for a plurality of engineering fields.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an apparatus for accurately measuring an incident angle of a light beam according to an embodiment of the present invention;
FIG. 2 is a graph showing gain obtained when tan θ= + -0.5 is applied to transmitted light in PT symmetrical lattice according to one embodiment of the present invention;
FIG. 3 is a schematic diagram showing the intensity of the transmitted light passing through the liquid crystal cell according to the different incident angles θ of the reflected light according to an embodiment of the present invention;
description of the reference numerals:
1-laser, 2-beam splitter, 3-reflector, 4-liquid crystal box, 5-detector;
the achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.
In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
The invention provides a device for accurately measuring the incidence angle of a light beam;
in a first preferred embodiment of the present invention, as shown in fig. 1, the laser device comprises a laser device 1, a beam splitter 2, a reflecting mirror 3, a liquid crystal box 4 and a detector 5, wherein the laser device 1 is used for generating gaussian beams and emitting the gaussian beams into the beam splitter 2, the beam splitter 2 is used for splitting the gaussian beams into two gaussian beams with equal intensity, one beam of the gaussian beams is transmitted (as reference light), one beam of the gaussian beams is transmitted, the other beam of the gaussian beams is transmitted vertically to the liquid crystal box 4, the reflected light is transmitted into the liquid crystal box 4 through the reflecting mirror 3 at a certain incident angle θ, the detector 5 is used for measuring the light intensity of the transmitted light after passing through the liquid crystal box 4, and the corresponding light intensities are respectively obtained by adjusting different incident angles θ so as to obtain the corresponding relationship between the incident angle θ and the light intensity; the incident angle theta to be measured is determined according to the light intensity measured by the detector 5 during detection.
In the embodiment of the invention, a liquid crystal box is used, and nematic liquid crystal filled in the liquid crystal box can form PT symmetrical lattices and has strong non-local nonlinearity; based on the characteristic that the incident angles of the reflected light are different and the gains obtained by the transmitted light are different in the PT symmetrical crystal lattice, the one-to-one correspondence relationship between the light intensity of the transmitted light passing through the liquid crystal box and the incident angle of the reflected light can be obtained, and then the incident angle of the reflected light can be determined by measuring the light intensity of the transmitted light after being transmitted through the liquid crystal box. Here, the liquid crystal cell may be replaced with another material having strong non-local nonlinearity and capable of constituting a PT symmetric lattice.
In the embodiment of the invention, the corresponding relation between the incident angle θ and the light intensity is determined by a non-local nonlinear schrodinger equation, and is specifically as follows:
the Gaussian beam emitted by the laser is divided into two Gaussian beams with equal intensity by a beam splitter, the transmitted light vertically enters the liquid crystal box and is marked as a beam 1, the reflected light is used as reference light and enters the liquid crystal box through a reflecting mirror at an incident angle theta, and the reflected light is marked as a beam 2, and an initial light field u (x, 0) entering the front surface of the liquid crystal box can be expressed as:
wherein A is 1 ，A 2 Normalized amplitudes, w, of transmitted and reflected light, respectively 1 ，w 2 Is the spatial beam width of the transmitted and reflected light, d is the distance between the transmitted and reflected light when they impinge on the front surface of the cell, tan θ is dimensionless and is measured by 1/kw 0 Performing dimensionless transformation;
the liquid crystal material in the liquid crystal box is PT symmetrical lattice formed by nematic liquid crystal, and meanwhile has strong non-local nonlinearity, and the transmission of light beams in the liquid crystal box meets the following dimensionless non-local nonlinearity schrodinger equation:
the nonlinear response function of the liquid crystal material is:
wherein w is NCL Is the dimensionless spatial feature of liquid crystal materialA length;
the PT symmetry potential function of the liquid crystal material is as follows:
V PT (x)＝A PT [cos 2 (x)+iVsin(2x)] (4)
since the incident angle θ of reflected light is different in the PT symmetric lattice, the gain obtained by transmitted light is also different as shown in fig. 2. Therefore, by changing the magnitude of θ, a one-to-one correspondence between the light intensity of the transmitted light passing through the liquid crystal cell and the incident angle θ of the reflected light can be obtained, as shown in fig. 3.
And measuring the light intensity of the transmitted light after being transmitted by the liquid crystal box by using a detector, and obtaining the reflected light incident angle theta according to the one-to-one correspondence between the light intensity of the obtained transmitted light after passing through the liquid crystal box and the reflected light incident angle theta.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.
Claims (1)
1. The device is characterized by comprising a laser, a beam splitter, a reflecting mirror, a liquid crystal box and a detector, wherein the laser is used for generating Gaussian beams and emitting the Gaussian beams into the beam splitter, the beam splitter is used for splitting the Gaussian beams into two Gaussian beams with equal intensity, one Gaussian beam is emitted to the liquid crystal box, the other Gaussian beam is emitted into the liquid crystal box through the reflecting mirror at a certain incidence angle, and the detector is used for measuring the light intensity of the Gaussian beams after the light beams pass through the liquid crystal box, and corresponding light intensities are respectively obtained by adjusting different incidence angles so as to obtain the corresponding relation between the incidence angle and the light intensity; during detection, the incidence angle to be measured is judged according to the light intensity measured by the detector;
the two Gaussian beams with equal intensity are characterized in that one Gaussian beam is transmitted light, and the other Gaussian beam is reflected light;
the detector is used for measuring the light intensity of the light beam after passing through the liquid crystal box, and specifically comprises the following components: measuring the intensity of the transmitted light after passing through the liquid crystal cell;
the nematic liquid crystal in the liquid crystal box forms PT symmetrical lattice;
the corresponding relation between the incident angle and the light intensity is determined by a non-local nonlinear Schrodinger equation;
the light beam is emitted to the liquid crystal box, and specifically comprises the following steps: a light beam is emitted vertically to the liquid crystal cell.
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Citations (7)
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| US6081337A (en) * | 1998-05-05 | 2000-06-27 | The Hong Kong University Of Science & Technology | Method and apparatus for measuring liquid crystal cell properties |
| CN1804586A (en) * | 2005-10-28 | 2006-07-19 | 华南师范大学 | Method for precisely measuring incident angle by means of laser feedback and application thereof |
| CN101825785A (en) * | 2009-03-03 | 2010-09-08 | 大塚电子株式会社 | The inclination angle determination method of reflective type liquid crystal cell and determinator |
| CN102147536A (en) * | 2011-03-11 | 2011-08-10 | 中国科学院上海光学精密机械研究所 | Dual-path controllable one-dimensional optic crystal lattice device |
| CN104914585A (en) * | 2015-07-08 | 2015-09-16 | 湖南大学 | Non-local-media-based spatial frequency beam splitter |
| CN106885787A (en) * | 2017-04-07 | 2017-06-23 | 华南师范大学 | A kind of method and apparatus for measuring the coarse film complex refractivity index of glass surface |
| CN209802321U (en) * | 2019-03-06 | 2019-12-17 | 华南师范大学 | Device for accurately measuring light beam incident angle |
-
2019
- 2019-03-06 CN CN201910169429.6A patent/CN109931885B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6081337A (en) * | 1998-05-05 | 2000-06-27 | The Hong Kong University Of Science & Technology | Method and apparatus for measuring liquid crystal cell properties |
| CN1804586A (en) * | 2005-10-28 | 2006-07-19 | 华南师范大学 | Method for precisely measuring incident angle by means of laser feedback and application thereof |
| CN101825785A (en) * | 2009-03-03 | 2010-09-08 | 大塚电子株式会社 | The inclination angle determination method of reflective type liquid crystal cell and determinator |
| CN102147536A (en) * | 2011-03-11 | 2011-08-10 | 中国科学院上海光学精密机械研究所 | Dual-path controllable one-dimensional optic crystal lattice device |
| CN104914585A (en) * | 2015-07-08 | 2015-09-16 | 湖南大学 | Non-local-media-based spatial frequency beam splitter |
| CN106885787A (en) * | 2017-04-07 | 2017-06-23 | 华南师范大学 | A kind of method and apparatus for measuring the coarse film complex refractivity index of glass surface |
| CN209802321U (en) * | 2019-03-06 | 2019-12-17 | 华南师范大学 | Device for accurately measuring light beam incident angle |
Non-Patent Citations (1)
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| 棱镜晶体旋转法测量液晶器件大预倾角;范志新等;光学学报;第26卷(第11期);第1671-1675页 * |
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