CN114200723A - Liquid crystal variable phase delay device without transverse deviation of light beam - Google Patents
Liquid crystal variable phase delay device without transverse deviation of light beam Download PDFInfo
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- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 173
- 230000003287 optical effect Effects 0.000 claims abstract description 32
- 230000000694 effects Effects 0.000 claims abstract description 14
- 230000010287 polarization Effects 0.000 claims description 19
- 239000004988 Nematic liquid crystal Substances 0.000 claims description 18
- 230000008859 change Effects 0.000 claims description 16
- 238000003384 imaging method Methods 0.000 claims description 12
- 230000010363 phase shift Effects 0.000 claims description 12
- 230000005540 biological transmission Effects 0.000 claims description 10
- 238000005305 interferometry Methods 0.000 claims description 10
- 230000001419 dependent effect Effects 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 230000002441 reversible effect Effects 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 2
- 230000001934 delay Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
- G02F1/133531—Polarisers characterised by the arrangement of polariser or analyser axes
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133553—Reflecting elements
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- Crystallography & Structural Chemistry (AREA)
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Abstract
The invention provides a liquid crystal variable phase retarder without transverse beam deviation, which consists of one or two liquid crystal variable phase retarders with the same thickness, optical axes in the same plane and mutually symmetrical orientation, and can compensate beam deviation caused by the birefringence effect of the liquid crystal variable phase retarders. The liquid crystal variable phase delay device without the transverse deviation of the light beam mainly comprises a polarizer, one or two symmetrically arranged liquid crystal variable phase delays with the same thickness and a driving power supply. The compensation device realizes the transverse offset compensation of light beams and simultaneously increases the phase delay amount in a combined mode according to the electric control birefringence effect of liquid crystal, and realizes the pure phase modulation of the liquid crystal variable phase retarder.
Description
Technical Field
The invention relates to the technical field of nematic liquid crystal devices, in particular to a liquid crystal variable phase delay device without transverse deviation of light beams.
Background
Nematic liquid crystals are composed of elongated rod-like molecules, and their spontaneous alignment characteristics, in which the long axes of the molecules are parallel to each other, make the nematic liquid crystals highly birefringent, and by using this characteristic, they can be fabricated into a variety of electrically controlled optical devices. One characteristic commonly used in nematic liquid crystal devices is that the amount of phase retardation between the extraordinary and ordinary light can be varied by controlling the voltage, making a liquid crystal variable phase retarder that not only avoids mechanical adjustments, but also has a response time on the order of milliseconds. Compared with other electro-optical crystal devices, the liquid crystal variable phase retarder has the advantages of convenience in phase retardation adjustment, low working voltage, low power consumption, large birefringence effect, convenience in manufacturing and the like, and is widely applied to the fields of liquid crystal display, interferometry, optical communication and the like.
When the nematic liquid crystal device is used as a phase retarder, all liquid crystal molecules tend to keep consistent with an external field electric field to generate an inclination angle along with the change of driving voltage, and after a light beam is emitted from the nematic liquid crystal device due to the birefringence effect of the liquid crystal molecules, a certain phase difference is generated between the ordinary light and the extraordinary light, and the spatial position of the extraordinary light also generates transverse offset, so that the ordinary light and the extraordinary light cannot be completely superposed.
Disclosure of Invention
In view of the above, in order to solve the above problems in the prior art, the present invention provides a liquid crystal variable phase retarder without lateral shift of light beams, which compensates the lateral shift of the extraordinary rays and doubles the phase shift amount by using a combination of two liquid crystal variable phase retarders. Pure phase modulation of the liquid crystal variable phase retarder is achieved.
The invention solves the problems through the following technical means:
in one aspect, the present invention provides a liquid crystal variable phase retarder device without a lateral shift of a light beam, comprising: the polarizer, a first liquid crystal variable phase delayer, a second liquid crystal variable phase delayer, a first driving power supply and a second driving power supply;
the first driving power supply generates a first driving voltage;
the second driving power supply generates a second driving voltage;
the slow axis of the polarizer is in the x-y plane of the coordinate axis and the included angle of the slow axis of the polarizer and the x axis is 45 degrees;
the slow axis of the first liquid crystal variable phase delayer is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the first driving voltage;
the slow axis of the second liquid crystal variable phase retarder is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the second driving voltage and is arranged in axial symmetry with the first liquid crystal variable phase retarder.
Further, the first driving power supply and the second driving power supply output alternating-current voltage, the adjustable range is 0-25V, and the minimum adjustable voltage is 0.001V.
Further, the compensation of the offset by the liquid crystal variable phase delay device without the transverse shift of the light beam specifically comprises the following processes:
step 1: a beam of linearly polarized light is incident to the polarizer, and the polarizer adjusts the polarization state of the incident light to enable the included angle between the polarization direction of the incident light and the slow axis direction of the first liquid crystal variable phase retarder to be 45 degrees;
step 2: linearly polarized light vertically enters the surface of the first liquid crystal variable phase retarder after passing through the polarizer and can be decomposed into o light and e light which are vertical to the optical axis direction and vibrate along the optical axis direction, and after two beams of linearly polarized light with mutually vertical vibration directions pass through the first liquid crystal variable phase retarder, the e light can be shifted for a certain distance along the positive direction of the y axis due to the birefringence effect of nematic liquid crystal; by adjusting the voltage of the first driving power supply, the deflection angle alpha of the long axis of the liquid crystal molecules in the first liquid crystal phase variable retarder is changed, and the refractive index n of the e light is simultaneously changedkeThe magnitude of e-light is changed along with the change of the magnitude of the e-light, and the lateral offset of the e-light after the e-light is transmitted out of the first liquid crystal variable phase retarder is changed along with nkeIs changed;
and 3, step 3: the o light and the e light separated by the first liquid crystal variable phase retarder by a certain distance are incident to a second liquid crystal variable phase retarder, wherein the second liquid crystal variable phase retarder and the first liquid crystal variable phase retarder are symmetrically arranged, and then the e light passes through the second liquid crystal variable phase retarder and then shifts by a certain distance along the negative direction of the y axis; after incident light passes through the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer, the e light respectively shifts once along the positive direction and the negative direction of the y axis, and the shifting distance is related to the driving voltage applied by the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer;
and 4, step 4: and controlling the driving voltages of the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer to be always equal, so that the offset of the e light along the positive direction and the negative direction of the y axis is always equal, the compensation of the offset is realized, and the phase delay amount is multiplied.
In another aspect, the present invention provides a liquid crystal variable phase retarder without a lateral shift of a light beam, including: the liquid crystal variable phase retarder comprises a polarizer, a liquid crystal variable phase retarder, a reflecting mirror and a driving power supply;
the driving power supply is used for generating driving voltage;
the slow axis of the polarizer is in the x-y plane of the coordinate axis and the included angle of the slow axis of the polarizer and the x axis is 45 degrees;
the slow axis of the liquid crystal variable phase retarder is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the driving voltage;
the reflector is used for reflecting the light transmitted to the reflector and then entering the liquid crystal variable phase retarder again.
Further, the driving power supply outputs alternating voltage, the adjustable range is 0-25V, and the minimum adjustable voltage is 0.001V.
Further, the compensation of the offset by the liquid crystal variable phase delay device without the transverse shift of the light beam specifically comprises the following processes:
step 1: after a beam of linearly polarized light is incident to the polarizer, the included angle between the polarization direction of the incident light and the slow axis of the liquid crystal variable phase retarder is adjusted to be 45 degrees, the linearly polarized light is vertically incident to the surface of the liquid crystal variable phase retarder, and the incident light can be decomposed into o light and e light which are vertical to the optical axis direction and vibrate along the optical axis direction;
step 2: when a driving power supply is used for applying voltage to the liquid crystal phase variable retarder, the long axis direction of nematic liquid crystal molecules is deflected, the deflection angle is alpha, and the refractive index of e light is nkeThe deflection angle of the long axis of the nematic liquid crystal molecules is changed by changing the magnitude of the driving voltage, so as to obtain different e-light refractive indexes nkeDue to the birefringence effect of the nematic liquid crystal, the e-light will shift a certain distance delta in the positive y-axis direction after passing through the liquid crystal variable phase retarder1And the offset is dependent on the e optical refractive index nkeWhile the propagation of o-light has no change in direction and position;
and 3, step 3: two beams of light are transmitted to the reflector and reflected by the reflector to enter the liquid crystal variable phase retarder again, and according to the reversible principle of the light path, the e light can shift a certain distance delta along the negative direction of the y axis after passing through the liquid crystal variable phase retarder again2And Δ1＝Δ2Accordingly, the light deviation caused by the liquid crystal variable phase retarder is compensated for by the combination of the liquid crystal variable phase retarder and the mirror.
In another aspect, the present invention provides a phase-shift interferometry system for measuring a relationship between a phase shift amount and a voltage of a liquid crystal variable phase retarder without a lateral shift of a light beam, including: the device comprises a light source, a polarizer, a beam expanding collimating mirror, a first plane reflector, a liquid crystal variable phase retarder, a first beam splitter, a polarization beam splitting element, a second plane reflector, a third plane reflector, an infinite imaging microscope objective, a tube lens, a second beam splitter, an analyzer and a monochromatic black-and-white image sensor;
the light source emits linearly polarized light along the x-axis direction of the coordinate axis;
the light transmission axis of the polarizer is in the xy plane of the coordinate axis, and the included angle between the light transmission axis of the polarizer and the x axis is 45 degrees;
the slow axis direction of the liquid crystal variable phase retarder is the x axis direction of the coordinate axis, and the optical axis deflects in an xz plane along with the change of the driving voltage;
the transmission axis of the analyzer is in the xy plane of the coordinate axis and forms an included angle of 45 degrees with the x axis;
the monochromatic black-and-white image sensor is placed at the equivalent air focal length of the lens barrel lens;
when the liquid crystal variable phase retarder works, light emitted by the light source passes through the polarizer and the beam expanding collimating mirror, is reflected by the first beam splitting mirror, enters the liquid crystal variable phase retarder and is divided into P light and S light; at this time, due to the birefringence effect of the liquid crystal, the P light and the S light will be separated by a minute distance, and then incident on the first plane mirror, reflected by the first plane mirror into the liquid crystal variable phase retarder, where the deviation of the light will be compensated; the P light and the S light after the offset compensation enter a polarization beam splitting element after penetrating through a first beam splitter, two beams of light are split by the polarization beam splitting element and then are respectively incident on a second plane reflector and a third plane reflector, and then the S light passes through an infinite imaging microscope objective and a tube lens and is further converged on the second beam splitter; the light transmitted through the second beam splitter is collected by the monochrome black and white image sensor after the polarization direction of the light is adjusted by the analyzer.
Further, the light source is a semiconductor laser with a wavelength of 639.
Compared with the existing liquid crystal variable phase delayer, the invention has the advantages that: the combination of the liquid crystal variable phase delayer compensates the light deviation caused by the liquid crystal variable phase delayer, and increases the phase shift amount to twice of the original amount, thereby realizing pure phase modulation of the liquid crystal variable phase delayer.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a structural view of a liquid crystal variable phase retarder device without a lateral shift of a light beam according to a first embodiment of the present invention;
FIG. 2 is a structural view of a liquid crystal variable phase retarder device without a lateral shift of a light beam according to a second embodiment of the present invention;
FIG. 3 is an image of a resolution plate according to the present invention;
FIG. 4 shows the maximum shift of e-ray in the present invention;
FIG. 5 shows the result of the invention after the e-ray offset is compensated;
FIG. 6 is a phase-shifting interferometry system used in the present invention;
FIG. 7 is a phase-shifting interferogram acquired by a phase-shifting interferometry system of the present invention;
FIG. 8 is a diagram showing the relationship between the driving voltage and the phase shift amount of the liquid crystal variable phase retarder without lateral shift of light beam according to the present invention;
FIG. 9 is a diagram of the phase distribution of a phase-shifted interferogram acquired by a phase-shifting interferometry system of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work based on the embodiments of the present invention belong to the protection scope of the present invention.
Example one
Referring to fig. 1, a liquid crystal variable phase retarder without a lateral shift of a light beam according to an embodiment of the present invention includes: polarizer 1, first liquid crystal variable phase retarder 2, second liquid crystal variable phase retarder 3, first driving power supply 4 and second driving power supply 5.
The first driving power supply 4 generates a first driving voltage.
The second driving power supply 5 generates a second driving voltage.
The slow axis of the polarizer 1 is in the x-y plane of the coordinate axis shown in the figure and the included angle of the slow axis and the x axis is 45 degrees.
The slow axis of the first liquid crystal variable phase retarder 2 is along the y-axis direction of the coordinate axis shown in the figure, and the optical axis deflects in the y-z plane along with the change of the driving voltage.
The slow axis of the second liquid crystal variable phase retarder 3 is along the y-axis direction of the coordinate axis shown in the figure, and the optical axis deflects in a y-z plane along with the change of the driving voltage and is arranged in axial symmetry with the first liquid crystal variable phase retarder 2.
The first driving power supply 4 and the second driving power supply 5 output alternating-current voltage, the adjustable range is 0-25V, and the minimum adjustable voltage is 0.001V.
When the variable-phase retarder works, a beam of linearly polarized light enters the polarizer 1, after the included angle between the polarization direction of the incident light and the slow axis of the first liquid crystal variable-phase retarder 2 is adjusted to be 45 degrees, the linearly polarized light vertically enters the surface of the first liquid crystal variable-phase retarder 2, and then the incident light can be decomposed into o light and e light which are vertical to the optical axis direction and vibrate along the optical axis direction. When a first driving power supply 4 is used for applying voltage to the first liquid crystal variable phase delayer 2, the long axis direction of liquid crystal molecules is deflected, the deflection angle is alpha, and the refractive index of e light is nkeChanging the driving voltage changes the deflection angle of the long axis of the liquid crystal molecules, wherein the e-light refractive index nkeWill also change accordingly. Due to the birefringence effect of the nematic liquid crystal, e-light will shift a certain distance delta in the positive y-axis direction after passing through the liquid crystal variable phase retarder1And the offset is dependent on the e optical refractive index nkeWhile the propagation of o-light has no changes in direction and position. After the two beams of light enter the second liquid crystal variable phase delayer 3, the voltage output by the second driving power supply 5 is controlled to be the same as the voltage output by the first driving power supply 4, and the deflection angle of the long axis of the liquid crystal molecules of the liquid crystal variable phase delayer is-alpha because the first liquid crystal variable phase delayer 2 and the second liquid crystal variable phase delayer 3 are symmetrically arranged. e light will shift a certain distance delta along the negative direction of the y axis after passing through the second liquid crystal variable phase retarder 32And Δ1＝Δ2Therefore, the light deviation caused by the liquid crystal variable phase retarder is compensated by the combination of the two liquid crystal variable phase retarders.
Second embodiment
Referring to fig. 2, a liquid crystal variable phase retarder without a lateral shift of a light beam according to a second embodiment of the present invention includes: polarizer 101, liquid crystal variable phase retarder 102, mirror 103, and driving power supply 104.
The driving power source 104 is used for generating a driving voltage.
The slow axis of polarizer 101 is in the x-y plane of the coordinate axis shown and has an included angle of 45 DEG with the x-axis.
The slow axis of the liquid crystal variable phase retarder 102 is along the y-axis direction of the illustrated coordinate axis, and the optical axis is deflected in the y-z plane as the driving voltage is changed.
The mirror 103 is used to reflect the light propagating thereon and then enter the liquid crystal variable phase retarder 102 again.
The driving power supply 104 outputs alternating voltage, the adjustable range is 0-25V, and the minimum adjustable voltage is 0.001V.
During operation, after a beam of linearly polarized light enters the polarizer 101, the included angle between the polarization direction of the incident light and the slow axis of the liquid crystal variable phase retarder 102 is adjusted to 45 °, the linearly polarized light is perpendicularly incident on the surface of the liquid crystal variable phase retarder 102, and the incident light can be decomposed into o light and e light which are perpendicular to the optical axis direction and vibrate along the optical axis direction. When a voltage is applied to the liquid crystal variable phase retarder 102 by the driving power supply 104, the long axis direction of the nematic liquid crystal molecules is deflected by an angle α, and the refractive index of e light is nkeThe deflection angle of the long axis of the nematic liquid crystal molecules is changed by changing the magnitude of the driving voltage, so as to obtain different e-light refractive indexes nkeDue to the birefringence effect of the nematic liquid crystal, the e-light will shift a certain distance Δ in the positive y-axis direction after passing through the liquid crystal variable phase retarder 1021And the offset is dependent on the e optical refractive index nkeWhile the propagation of o-light has no changes in direction and position. The two beams of light are transmitted to the reflector 103, reflected by the reflector 103 and enter the liquid crystal variable phase retarder 102 again, and according to the principle that the light path is reversible, the e-beam passes through the liquid crystal variable phase retarder 102 again and then shifts for a certain distance delta along the negative direction of the y-axis2And Δ1＝Δ2Accordingly, the light deviation caused by the liquid crystal variable phase retarder is compensated for by the combination of the liquid crystal variable phase retarder and the mirror.
Results of the experiment
In order to test the liquid crystal variable phase delay device without transverse beam offset, an imaging light path is built and a resolution plate is imaged, a black-and-white image sensor receives an image formed by the resolution plate at an image surface of the imaging light path as shown in fig. 3, then a liquid crystal variable phase retarder is added into the imaging light path, e light in the imaging light beam can be shifted for a certain distance after the imaging light beam passes through the liquid crystal variable phase retarder, the image formed by the e light on the resolution plate is shifted accordingly, and the relation between the offset and the voltage formed by the e light is obtained by adjusting the driving voltage of the liquid crystal variable phase retarder, so that the relation between the offset and the voltage of the e light is obtained. The shift distance of the e-ray imaged by the e-ray is monitored by drawing a cross-sectional view of the e-ray imaged along the direction of the straight line A, and the shift amount of the e-ray at different voltages is obtained, and the maximum value is obtained when the driving voltage is 1.12V, as shown in FIG. 4. After the liquid crystal variable phase retarder without lateral beam shift according to the first and second embodiments of the present invention is added to the imaging optical path, the driving voltage of the liquid crystal variable phase retarder is changed, and the shift phenomenon of e-light is effectively compensated, and the result is shown in fig. 5.
The liquid crystal variable phase retardation device without lateral shift of light beam of the second embodiment was then added to a phase-shifting interferometry system to measure its phase shift amount versus voltage. A phase-shifting interferometry system is shown in fig. 6, comprising: the device comprises a light source 201, a polarizer 202, a beam expanding collimator 203, a first plane mirror 204, a liquid crystal variable phase retarder 205, a first beam splitter 206, a polarization beam splitting element 207, a second plane mirror 208, a third plane mirror 209, an infinity imaging microscope objective 210, a tube lens 211, a second beam splitter 212, an analyzer 213 and a monochrome black and white image sensor 214.
The light source 201 is a semiconductor laser with a wavelength of 639, and emits linearly polarized light along the x-axis of the coordinate axis shown in the figure.
The transmission axis of the polarizer 202 is in the xy plane of the coordinate axis in the figure and the included angle of the transmission axis and the x axis is 45 degrees.
The slow axis direction of the liquid crystal variable phase retarder 205 is the x axis direction of the coordinate axis shown in the figure, and the optical axis deflects in the xz plane as the driving voltage changes.
The analyzer 213 is arranged such that its transmission axis is in the xy-plane of the coordinate axis and has an included angle of 45 ° with respect to the x-axis.
The monochrome black and white image sensor 214 should be placed at the equivalent air focal length of the tube lens 211.
In operation, after passing through the polarizer 202 and the beam expanding collimator 203, light emitted from the light source 201 is reflected by the first beam splitter 206, enters the liquid crystal variable phase retarder 205, and is divided into P light and S light; at this time, the P light and the S light will be separated by a minute distance due to the birefringence effect of the liquid crystal, and then incident on the first plane mirror 204, reflected by the first plane mirror 204 into the liquid crystal variable phase retarder 205, where the deviation of the light will be compensated; the offset-compensated P light and S light enter the polarization beam splitter 207 after passing through the first beam splitter 206, the polarization beam splitter 207 splits the two beams of light and then respectively enters the second plane mirror 208 and the third plane mirror 209, and then the S light passes through the infinity imaging microscope objective 210 and the tube lens 211, and the two beams of light are further converged on the second beam splitter 212; the light transmitted through the second beam splitter 212 is polarized by the analyzer 213, and then collected by the monochrome black and white image sensor 214.
By adjusting the driving voltage of the liquid crystal variable phase retarder 205, a series of phase-shifting interferograms can be acquired by the phase-shifting interferometry system as shown in FIG. 7. Then, the phase shift amount and the phase distribution of the phase-shifted interferogram are calculated by using an improved iterative algorithm (AIA algorithm) based on the least square principle as shown in fig. 8 and 9, respectively. In fig. 8, the dotted line shows the relationship between the phase shift amount of the liquid crystal variable phase retarder and the voltage when the light beam offset compensation is not performed, and the solid line shows the relationship between the phase shift amount and the voltage obtained by the liquid crystal variable phase retarder without the lateral beam offset according to the present invention.
As can be seen from fig. 5 and 8, the liquid crystal variable phase retarder without lateral shift of light beam according to the present invention not only compensates the lateral shift of light beam, but also doubles the phase shift amount to realize pure phase modulation of the liquid crystal variable phase retarder.
The liquid crystal variable phase retarder without the light beam transverse shift compensates the light shift caused by the liquid crystal variable phase retarder by properly combining the liquid crystal variable phase retarder and the reflecting mirror according to the electric control birefringence effect of the liquid crystal, thereby not only eliminating the influence of the liquid crystal variable phase retarder on the light transmission, but also doubling the phase delay amount.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (8)
1. A liquid crystal variable phase retarder without lateral shift of light beams, comprising: the polarizer, a first liquid crystal variable phase delayer, a second liquid crystal variable phase delayer, a first driving power supply and a second driving power supply;
the first driving power supply generates a first driving voltage;
the second driving power supply generates a second driving voltage;
the slow axis of the polarizer is in the x-y plane of the coordinate axis and the included angle of the slow axis of the polarizer and the x axis is 45 degrees;
the slow axis of the first liquid crystal variable phase delayer is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the first driving voltage;
the slow axis of the second liquid crystal variable phase retarder is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the second driving voltage and is arranged in axial symmetry with the first liquid crystal variable phase retarder.
2. The liquid crystal variable phase retardation device without lateral shift of light beam according to claim 1, wherein the first driving power supply and the second driving power supply output an alternating voltage with an adjustable range of 0 to 25V and a minimum adjustable voltage of 0.001V.
3. The device for liquid crystal variable phase retardation without beam lateral shift according to claim 1, wherein the compensation of the shift amount by the device for liquid crystal variable phase retardation without beam lateral shift specifically comprises the following processes:
step 1: a beam of linearly polarized light is incident to the polarizer, and the polarizer adjusts the polarization state of the incident light to enable the included angle between the polarization direction of the incident light and the slow axis direction of the first liquid crystal variable phase retarder to be 45 degrees;
step 2: linearly polarized light vertically enters the surface of the first liquid crystal variable phase retarder after passing through the polarizer and can be decomposed into o light and e light which are vertical to the optical axis direction and vibrate along the optical axis direction, and after two beams of linearly polarized light with mutually vertical vibration directions pass through the first liquid crystal variable phase retarder, the e light can be shifted for a certain distance along the positive direction of the y axis due to the birefringence effect of nematic liquid crystal; by adjusting the voltage of the first driving power supply, the deflection angle alpha of the long axis of the liquid crystal molecules in the first liquid crystal phase variable retarder is changed, and the refractive index n of the e light is simultaneously changedkeThe magnitude of e-light is changed along with the change of the magnitude of the e-light, and the lateral offset of the e-light after the e-light is transmitted out of the first liquid crystal variable phase retarder is changed along with nkeIs changed;
and 3, step 3: the o light and the e light separated by the first liquid crystal variable phase retarder by a certain distance are incident to a second liquid crystal variable phase retarder, wherein the second liquid crystal variable phase retarder and the first liquid crystal variable phase retarder are symmetrically arranged, and then the e light passes through the second liquid crystal variable phase retarder and then shifts by a certain distance along the negative direction of the y axis; after incident light passes through the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer, the e light respectively shifts once along the positive direction and the negative direction of the y axis, and the shifting distance is related to the driving voltage applied by the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer;
and 4, step 4: and controlling the driving voltages of the first liquid crystal variable phase delayer and the second liquid crystal variable phase delayer to be always equal, so that the offset of the e light along the positive direction and the negative direction of the y axis is always equal, the compensation of the offset is realized, and the phase delay amount is multiplied.
4. A liquid crystal variable phase retarder without lateral shift of light beams, comprising: the liquid crystal variable phase retarder comprises a polarizer, a liquid crystal variable phase retarder, a reflecting mirror and a driving power supply;
the driving power supply is used for generating driving voltage;
the slow axis of the polarizer is in the x-y plane of the coordinate axis and the included angle of the slow axis of the polarizer and the x axis is 45 degrees;
the slow axis of the liquid crystal variable phase retarder is along the direction of the y axis of the coordinate axis, and the optical axis deflects in the y-z plane along with the change of the driving voltage;
the reflector is used for reflecting the light transmitted to the reflector and then entering the liquid crystal variable phase retarder again.
5. The liquid crystal variable phase retardation device without lateral shift of light beam according to claim 4, wherein the driving power supply outputs an alternating voltage with an adjustable range of 0 to 25V and a minimum adjustable voltage of 0.001V.
6. The device for liquid crystal variable phase retardation without beam lateral shift according to claim 4, wherein the compensation of the shift amount by the device for liquid crystal variable phase retardation without beam lateral shift specifically comprises the following processes:
step 1: after a beam of linearly polarized light is incident to the polarizer, the included angle between the polarization direction of the incident light and the slow axis of the liquid crystal variable phase retarder is adjusted to be 45 degrees, the linearly polarized light is vertically incident to the surface of the liquid crystal variable phase retarder, and the incident light can be decomposed into o light and e light which are vertical to the optical axis direction and vibrate along the optical axis direction;
step 2: when a voltage is applied to the liquid crystal variable phase retarder by a driving power supply, the nematic liquid crystal molecules are emitted in the long axis directionIs deflected by an angle alpha, at which time the refractive index of e light is nkeThe deflection angle of the long axis of the nematic liquid crystal molecules is changed by changing the magnitude of the driving voltage, so as to obtain different e-light refractive indexes nkeDue to the birefringence effect of the nematic liquid crystal, the e-light will shift a certain distance delta in the positive y-axis direction after passing through the liquid crystal variable phase retarder1And the offset is dependent on the e optical refractive index nkeWhile the propagation of o-light has no change in direction and position;
and 3, step 3: two beams of light are transmitted to the reflector and reflected by the reflector to enter the liquid crystal variable phase retarder again, and according to the reversible principle of the light path, the e light can shift a certain distance delta along the negative direction of the y axis after passing through the liquid crystal variable phase retarder again2And Δ1＝Δ2Accordingly, the light deviation caused by the liquid crystal variable phase retarder is compensated for by the combination of the liquid crystal variable phase retarder and the mirror.
7. A phase shift interferometry system for measuring the relationship between the amount of phase shift and voltage of the liquid crystal variable phase retarder device without lateral shift of light beam according to any of claims 4 to 6, comprising: the device comprises a light source, a polarizer, a beam expanding collimating mirror, a first plane reflector, a liquid crystal variable phase retarder, a first beam splitter, a polarization beam splitting element, a second plane reflector, a third plane reflector, an infinite imaging microscope objective, a tube lens, a second beam splitter, an analyzer and a monochromatic black-and-white image sensor;
the light source emits linearly polarized light along the x-axis direction of the coordinate axis;
the light transmission axis of the polarizer is in the xy plane of the coordinate axis, and the included angle between the light transmission axis of the polarizer and the x axis is 45 degrees;
the slow axis direction of the liquid crystal variable phase retarder is the x axis direction of the coordinate axis, and the optical axis deflects in an xz plane along with the change of the driving voltage;
the transmission axis of the analyzer is in the xy plane of the coordinate axis and forms an included angle of 45 degrees with the x axis;
the monochromatic black-and-white image sensor is placed at the equivalent air focal length of the lens barrel lens;
when the liquid crystal variable phase retarder works, light emitted by the light source passes through the polarizer and the beam expanding collimating mirror, is reflected by the first beam splitting mirror, enters the liquid crystal variable phase retarder and is divided into P light and S light; at this time, due to the birefringence effect of the liquid crystal, the P light and the S light will be separated by a minute distance, and then incident on the first plane mirror, reflected by the first plane mirror into the liquid crystal variable phase retarder, where the deviation of the light will be compensated; the P light and the S light after the offset compensation enter a polarization beam splitting element after penetrating through a first beam splitter, two beams of light are split by the polarization beam splitting element and then are respectively incident on a second plane reflector and a third plane reflector, and then the S light passes through an infinite imaging microscope objective and a tube lens and is further converged on the second beam splitter; the light transmitted through the second beam splitter is collected by the monochrome black and white image sensor after the polarization direction of the light is adjusted by the analyzer.
8. A phase-shifting interferometry system according to claim 7, wherein said light source is a semiconductor laser having a wavelength of 639.
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| CN109470173A (en) * | 2018-12-29 | 2019-03-15 | 华南师范大学 | A kind of binary channels simultaneous phase shifting interference microscopic system |
| CN113196154A (en) * | 2018-12-07 | 2021-07-30 | 复合光子美国公司 | Liquid crystal display with external retarder |
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| JPH11311784A (en) * | 1998-03-26 | 1999-11-09 | Sharp Corp | Liquid crystal display device and display |
| WO2001022155A1 (en) * | 1999-09-17 | 2001-03-29 | Nippon Mitsubishi Oil Corporation | Reflection liquid crystal display |
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| CN109031737A (en) * | 2018-09-06 | 2018-12-18 | 北京航空航天大学 | A kind of fast-response phase delay device based on the double-deck nematic liquid crystal |
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