Photoelastic modulation type high-precision quantitative phase demodulation device and method

Abstract

The invention belongs to the field of optical measurement, relates to a photoelastic modulation type high-precision quantitative phase demodulation device and a photoelastic modulation type high-precision quantitative phase demodulation method, and aims to realize stable and accurate interference type phase measurement. Comprising a light source, an interference light path system and a detection and signal demodulation system. A polarization light splitting unit in the interference light path system divides a detection light beam from a light source into a reference light beam and a measurement light beam with mutually orthogonal polarization directions, and respectively guides the reference light beam and the measurement light beam to a reference light path and a measurement light path; a photoelastic modulator is arranged in the reference light path, and a sample area for bearing a sample to be measured is arranged in the measuring light path; a beam combining unit in the interference light path system combines the emergent light beams to generate an interference light signal; the detection and signal demodulation system comprises a polarization analyzer, a photoelectric detector and a signal processing module; the signal processing module is electrically connected with the photoelectric detector and the photoelastic modulator; the signal processing module comprises a field programmable gate array.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement, in particular to a high-precision quantitative phase demodulation device and method based on photoelastic modulation. BACKGROUND

[0002] Quantitative phase measurement technology, as a non-contact and high-sensitivity optical detection method, has wide application requirements in biomedical imaging, material science and precision measurement. This technology can detect the phase change of light caused by the slight change of sample thickness or refractive index, so as to realize high-contrast observation and quantitative analysis of transparent or weakly absorbing samples.

[0003] At present, the phase measurement method based on interference principle is the mainstream technical scheme in this field. Although the typical interferometer structure such as Mach-Zehnder type can provide high phase detection sensitivity, its discrete optical path structure is extremely sensitive to environmental micro-vibration and air flow disturbance, resulting in poor system stability, significant random phase noise, and difficulty in realizing long-term reliable measurement in conventional laboratory or industrial environment. Another common Michelson type interference structure improves the optical path symmetry to some extent, but the reference light and signal light are difficult to completely separate in space, which limits the flexibility and accuracy of the system in dynamic measurement or complex sample detection. SUMMARY

[0004] In order to solve the problems mentioned in the background, the present application provides a high-precision quantitative phase demodulation device and method based on photoelastic modulation, aiming to realize stable and accurate interferometric phase measurement.

[0005] The application adopts the following technical scheme: the application provides a high-precision quantitative phase demodulation device of an elastic light modulation type, comprising a light source, an interference light path system and a detection and signal demodulation system; the light source is used for providing a detection light beam; the interference light path system comprises a polarization beam splitting unit, a reference light path, a measurement light path and a beam combining unit; the polarization beam splitting unit is used for splitting the detection light beam from the light source into a reference light beam and a measurement light beam with mutually orthogonal polarization directions and guiding them to the reference light path and the measurement light path respectively; an elastic light modulator is arranged in the reference light path and used for applying periodic phase modulation to the passing reference light beam; a sample region for carrying a sample to be measured is arranged in the measurement light path; the beam combining unit is used for combining the light beams respectively emitted through the reference light path and the measurement light path to generate an interference light signal; the detection and signal demodulation system comprises an analyzer, a photodetector and a signal processing module; the analyzer is arranged on the exit light path of the beam combining unit and used for analyzing the interference light signal; the photodetector is used for receiving the light signal passing through the analyzer and converting it into an electric signal; the signal processing module is electrically connected with the photodetector and the elastic light modulator; the signal processing module comprises a field programmable gate array, which is configured to: provide a modulation driving signal to the elastic light modulator, and perform digital lock-in amplification processing on the electric signal output by the photodetector based on a reference signal with the same frequency and source as the modulation driving signal, so as to demodulate the phase information introduced by the sample to be measured.

[0006] The polarization beam splitting unit comprises a half-wave plate and a polarization beam splitting prism arranged in sequence along the light path.

[0007] The reference light path further comprises a first polarizer arranged in the light path of the elastic light modulator and a first mirror for changing the light path direction; the measurement light path further comprises a second polarizer arranged in the light path of the sample region and a second mirror for changing the light path direction.

[0008] The beam combining unit is a non-polarization beam splitting prism.

[0009] The elastic light modulator comprises an elastic light crystal and an LC resonant high-voltage driving circuit connected with the elastic light crystal, and the LC resonant high-voltage driving circuit is connected with the field programmable gate array of the signal processing module.

[0010] The first polarizer, the second polarizer and the analyzer are all calcite Glan-Taylor polarizers with an extinction ratio of more than 100000:1.

[0011] The signal processing module further comprises an acquisition unit connected with the field programmable gate array and used for acquiring the electric signal output by the photodetector.

[0012] The high-precision quantitative phase demodulation device of the elastic light modulation type further comprises a computer in communication connection with the signal processing module and used for receiving, displaying and storing the demodulated phase information.

[0013] The application also provides a high-precision quantitative phase demodulation method of elastic light modulation type, which is realized based on the high-precision quantitative phase demodulation device of elastic light modulation type and comprises the following steps: separating a detection light beam emitted by a light source into a reference light beam and a measurement light beam with mutually orthogonal polarization directions; making the reference light beam pass through an elastic light modulator to apply periodic phase modulation to the elastic light modulator, and making the measurement light beam pass through a sample to be measured to carry phase information of the sample to be measured; combining the modulated reference light beam and the measurement light beam carrying the phase information of the sample to generate an interference light signal; converting the interference light signal into an electric signal; generating a modulation driving signal for driving the elastic light modulator by using a field programmable gate array, and synchronously using a reference signal with the same frequency and source as the modulation driving signal to perform digital phase-locked amplification processing on the electric signal to demodulate a phase delay introduced by the sample to be measured.

[0014] The phase delay of the sample to be measured is solved by extracting the amplitude of a fundamental frequency component related to the modulation frequency of the elastic light modulator in the electric signal and calculating the ratio of the amplitudes of the fundamental frequency components.

[0015] Compared with the prior art, the application has the following beneficial effects: 1. The application introduces the elastic light modulator into the optical path of the Mach-Zehnder interferometer, applies high-frequency and stable known phase modulation to the reference arm, and carries the small and quasi-static phase information to be measured on a specific harmonic of the modulation signal. Combined with the digital phase-locked amplification technology realized by the field programmable gate array, the harmonic components can be accurately extracted, the low-frequency noise and DC drift can be effectively suppressed, and therefore, very high measurement sensitivity and precision are realized. Meanwhile, compared with the traditional Michelson interferometer, the reference light and the object light are separated in the interference structure, the crosstalk caused by the superposition of the optical paths is avoided, and the flexibility and long-term stability of the system are improved.

[0016] 2. The application uses the field programmable gate array as the core processing unit, and the hardware parallel processing architecture enables the signal generation (modulation driving signal), data acquisition (electric signal) and digital phase-locked calculation to be synchronized and performed at high speed. This method overcomes the speed bottleneck of the traditional software phase-locked or analog phase-locked, can realize microsecond-level phase demodulation and output, and meets the harsh requirements of high speed and real time for dynamic process and transient phenomenon measurement.

[0017] 3. The application uses the elastic light modulator combined with a specific optical path design and signal processing algorithm, does not need the mechanical scanning components or complex frequency shift devices commonly used in traditional phase measurement systems, and reduces the dependence on multi-channel and high-cost phase-locked amplifiers. This not only significantly simplifies the optical path structure and the electronic system, reduces the hardware cost and the complexity of system debugging and maintenance, but also has stronger anti-vibration ability, longer service life and higher reliability because there is no moving mechanical component in the system, and is easier to integrate and apply with the existing industrial automation platform. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Figure 1 is a structural schematic diagram of a photoelastic modulation type high-precision quantitative phase demodulation device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0020] Reference Figure 1 The present embodiment provides a photoelastic modulation type high-precision quantitative phase demodulation device, which comprises a light source 1, an interference optical path system, and a detection and signal demodulation system. The light source 1 is used to provide a detection light beam. The interference optical path system comprises a polarization beam splitting unit, a reference light path, a measurement light path, and a beam combining unit. The polarization beam splitting unit is used to split the detection light beam from the light source 1 into a reference light beam and a measurement light beam with mutually orthogonal polarization directions, and guide them to the reference light path and the measurement light path, respectively. A photoelastic modulator 5 is arranged in the reference light path, and is used to apply periodic phase modulation to the passing reference light beam.

[0021] A sample region for carrying a sample to be measured 9 is arranged in the measurement light path. The beam combining unit is used to combine the light beams respectively emitted via the reference light path and the measurement light path to generate an interference light signal. The detection and signal demodulation system comprises an analyzer 11, a photodetector 12, and a signal processing module 13. The analyzer 11 is arranged on the exit light path of the beam combining unit, and is used to analyze the interference light signal. The photodetector 12 is used to receive the light signal passing through the analyzer 11 and convert it into an electrical signal. The signal processing module 13 is electrically connected with the photodetector 12 and the photoelastic modulator 5. The signal processing module 13 comprises a field programmable gate array, which is configured to: provide a modulation driving signal to the photoelastic modulator 5, and perform digital lock-in amplification processing on the electrical signal output by the photodetector 12 based on a reference signal with the same frequency and source as the modulation driving signal, so as to demodulate the phase information introduced by the sample to be measured 9.

[0022] In some embodiments, the polarization beam splitting unit comprises a half-wave plate 2 and a polarization beam splitting prism 3 arranged in sequence along the light path.

[0023] As a possible implementation, the reference light path further comprises a first polarizer 4 arranged in the light path of the photoelastic modulator 5, and a first mirror 6 for changing the direction of the light path. The measurement light path further comprises a second polarizer 7 arranged in the light path of the sample region, and a second mirror 8 for changing the direction of the light path.

[0024] In some embodiments, the beam combining unit is a non-polarization beam combining prism 10.

[0025] As a possible implementation, the photoelastic modulator 5 comprises a photoelastic crystal and an LC resonant high-voltage driving circuit connected to the photoelastic crystal, which is connected to the field programmable gate array of the signal processing module 13.

[0026] As a possible implementation, the first polarizer 4, the second polarizer 7 and the polarimeter 11 are all calcite Glan-Taylor polarizers with an extinction ratio better than 100000:1.

[0027] As a possible implementation, the signal processing module 13 further comprises a collection unit connected to the field programmable gate array, for collecting the electrical signal output by the photodetector 12.

[0028] As a possible implementation, the photoelastic modulator type high-precision quantitative phase demodulation device further comprises a computer 14 in communication connection with the signal processing module 13, for receiving, displaying and storing the demodulated phase information.

[0029] The detection light beam emitted by the light source 1 first passes through the polarization splitting unit, i.e. the half-wave plate 2 and the polarization splitting prism 3. The half-wave plate 2 is used to fine-tune the polarization angle of the incident light to optimize the splitting efficiency. Subsequently, the polarization splitting prism 3 precisely splits the incident light into two beams of linearly polarized light with mutually orthogonal polarization directions, i.e. the reference light beam and the measurement light beam, and respectively delivers the reference light beam and the measurement light beam to the reference light path and the measurement light path.

[0030] In the reference light path, the reference light beam passes through the first polarizer 4 and the photoelastic modulator 5 in turn. The first polarizer 4 ensures that the light beam incident on the photoelastic modulator 5 is in a determined polarization state. The photoelastic modulator 5, under the driving of its LC resonant high-voltage driving circuit, which is exemplarily provided with a driving signal by the FPGA, imposes a high-frequency, sinusoidal periodic phase delay on the passing light beam. Thereafter, the light beam is reflected by the first mirror 6 and guided to the beam combining unit.

[0031] In the measurement light path, the measurement light beam passes through the second polarizer 7, the second mirror 8 and the sample to be measured 9 in turn. The second polarizer 7 is also used to optimize the polarization state of the light beam. The sample to be measured 9 will introduce a small phase delay to be measured into the light beam due to its thickness or refractive index distribution. The light beam carrying the phase information of the sample is then guided to the beam combining unit.

[0032] The two beams are combined at a non-polarization beam combiner 10. Since their polarization directions are orthogonal, they do not interfere immediately. The combined light then passes through a polarizer 11, which only allows the polarization component parallel to its own transmission axis to pass. The two components have the same polarization direction, thus interfere to form an intensity-varying interference light signal. The intensity of this light signal contains both the high-frequency modulation introduced by the photoelastic modulator and the phase information introduced by the sample under test. A photodetector 12 then converts this intensity-modulated interference light signal into an electrical signal containing rich frequency components in real time.

[0033] The signal processing module 13, as the core of the entire device, generates the driving and reference signals simultaneously and performs digital phase-locked amplification. The FPGA generates a high-frequency digital signal, which drives the photoelastic modulator 5 on one hand and provides a reference signal to the internal digital phase-locked amplifier on the other hand. This completely eliminates the frequency drift and phase jitter between the driving signal and the reference signal. The FPGA collects the electrical signal from the photodetector 12. Through its hardware parallel processing capability, it performs the digital phase-locked amplification algorithm in real time: it multiplies and integrates (filters) the collected signal with the reference signal (and its 90° phase-shifted signal) it generates itself. This process can accurately extract the amplitude of the base frequency component in the signal that has the same frequency as the reference signal.

[0034] Instead of directly using a single amplitude, the system calculates the ratio of the amplitudes of the two base frequency components. According to optical principles (such as Jones matrix derivation), this ratio is only related to the fixed modulation depth of the photoelastic modulator (corresponding to the known Bessel function value) and the phase delay to be measured , and is independent of common interference factors such as intensity fluctuations of the light source and gain changes of the detector. By solving this ratio equation, the high-precision phase delay to be measured can be finally calculated, which is not affected by environmental interference.

[0035] The calculated phase information is transmitted by the FPGA to the computer 14 for real-time display, storage, and further analysis, achieving monitoring of the entire measurement process.

[0036] The application further provides a high-precision quantitative phase demodulation method of the elastic light modulation type, which is realized based on the high-precision quantitative phase demodulation device of the elastic light modulation type and comprises the following steps: separating the detection light beam emitted by the light source 1 into a reference light beam and a measurement light beam with mutually orthogonal polarization directions; making the reference light beam pass through the elastic light modulator 5 to apply periodic phase modulation to the reference light beam, and making the measurement light beam pass through the sample 9 to be measured to carry phase information of the sample 9 to be measured; combining the modulated reference light beam and the measurement light beam carrying the phase information of the sample to generate an interference light signal; converting the interference light signal into an electrical signal; generating a modulation driving signal for driving the elastic light modulator 5 by using a field programmable gate array, and synchronously generating a reference signal with the same frequency and source as the modulation driving signal to perform digital lock-in amplification processing on the electrical signal to demodulate the phase delay introduced by the sample 9 to be measured; and extracting the amplitude of the fundamental frequency component related to the modulation frequency of the elastic light modulator 5 in the electrical signal and calculating the ratio of the amplitudes of the fundamental frequency components to obtain the phase delay of the sample 9 to be measured.

[0037] Based on the device and method provided above, the application further provides a matching use instruction and principle explanation. First, the high-precision quantitative phase demodulation device of the elastic light modulation type is calibrated: the modulation fast axis direction of the elastic light modulator 5 in the reference arm is adjusted to coincide with the horizontal direction; the polarization axis direction of the first polarizer 4 in the reference arm and the polarization axis direction of the polarization analyzer 11 after beam combination are adjusted to specific preset angles relative to the modulation fast axis direction of the elastic light modulator, for example, to 45° and -45°, respectively; and the polarization axis direction of the second polarizer 7 in the measurement arm is also adjusted to coincide with the horizontal direction.

[0038] Through the above adjustment, the entire optical system can be accurately mathematically modeled and analyzed by using the Jones matrix formalism. The incident detection light beam is divided into a reference light beam and a measurement light beam with mutually orthogonal polarization directions after passing through the half-wave plate 2 and the polarization beam splitter prism 3. Exemplarily, the Jones vector of the incident detection light beam after passing through the half-wave plate 2 is: (1) For the reference arm, the Jones matrix after passing through the polarization beam splitter prism 3 is: (2) In the above formula, is the total intensity of the detection light beam passing through the half-wave plate 2. The Jones matrices of the elastic light modulator 5 and the first polarizer 4 are respectively: (3) (4) In the above formula, , is the phase modulation amplitude of the elastic light modulator 5, is the modulation circular frequency of the photoelastic modulator 5.

[0039] The photoelastic modulator 5 applies an alternating voltage to its interior piezoelectric driver, which is consistent with the mechanical resonance frequency of the photoelastic crystal. The crystal is driven to produce a periodic micro-deformation, thereby periodically changing its refractive index, and finally introducing a high-frequency, controllable phase modulation to the reference light beam passing through it.

[0040] Neglecting the loss of the detection light beam in the propagation process, the exit light Jones vector of the reference arm is: (5) For the measurement arm, the Jones matrix after the polarizing beam splitter 3 is: (6) The Jones matrices of the sample 9 to be measured and the second polarizer 7 are respectively: (7) (8) Neglecting the loss of the detection light beam in the propagation process, the exit light Jones vector of the measurement arm is: (9) The reference arm and the measurement arm perform vector superposition at the non-polarization beam combiner 10, and the Jones vector is: (10) The Jones matrices of the polarizer 11 and the non-polarization beam combiner 10 are respectively: (11) (12) Neglecting the loss of the detection light beam in the propagation process, the exit light Jones vector after the polarizer 11 is: (13) The reference light beam and the measurement light beam are reflected by the first mirror 6 and the second mirror 8 respectively, and are combined at the non-polarization beam combiner 10 to generate an interference light signal. After passing through the polarizer 11, the interference light signal is received by the photodetector 12 and converted into an electrical signal.

[0041] By performing Jones matrix analysis on the entire optical path, the total light intensity expression received by the photodetector 12 can be derived. The expression contains a direct current component and an alternating current component. The alternating current component contains information related to the phase delay of the sample to be measured due to the high-frequency modulation of the photoelastic modulator.

[0042] Specifically, equations (1) to (12) are brought into equation (13) to obtain the light intensity detected by the photodetector 12: (14) in, , These represent the total intensity of the detection beam emitted through the reference arm and the measuring arm, respectively. The above equation... and Using the expansion of the first kind of Bessel series, we get: (15) (16) in, It is a positive integer. It is a 0th order Bessel series. , They are respectively order and Substituting the above two equations into equation (14), and omitting higher-order Bessel series of order 3 and above, we obtain equation (17): To simplify calculations and optimize the signal-to-noise ratio, the phase modulation amplitude of the elastic modulator is... Set to a specific value such that the zeroth-order Bessel function Specifically, the phase modulation amplitude of the optical modulator 5 is set to... Make In this case, the DC signal term output by photodetector 12 is: (18) in, , The total intensity of the laser emitted through the reference arm and the measuring arm is respectively measured. For the AC term in equation (17), the fundamental frequency term of the elastic-optical modulation is extracted using digital lock-in amplification technology: (19) (20) This invention extracts the fundamental frequency component from the interference signal through signal acquisition and the field-programmable gate array (FPGA) in the digital phase-locked loop module 13. The FPGA synchronously generates a modulation signal to drive the photoelectric modulator, and uses this signal as a reference standard of the same frequency and origin to perform digital phase-locked amplification on the electrical signal output from the photodetector 12, thereby obtaining the amplitude of the fundamental frequency component. and Their mathematical expressions correspond to equations (19) and (20), respectively.

[0043] To eliminate the influence of common-mode noise such as light source intensity fluctuations, this invention employs a ratio method for data processing. The ratio of the amplitudes of the two fundamental frequency components is calculated as follows: (21) From formula (21), the instability of the detection beam is eliminated, and the phase retardation of the sample 9 to be measured can be solved as: (22) The present application introduces an elasto-optic modulator into the optical path of a Mach-Zehnder interferometer, applies high-frequency and stable known phase modulation on the reference arm, and carries the small quasi-static phase information to be measured on a specific harmonic of the modulation signal. Combined with the digital phase-locked amplification technology realized by the field programmable gate array, the harmonic components can be accurately extracted, the low-frequency noise and DC drift can be effectively suppressed, and therefore the measurement sensitivity and accuracy are extremely high. At the same time, compared with the traditional Michelson interferometer, the reference light and the object light are separated, the crosstalk caused by the coincidence of the optical paths is avoided, and the flexibility and long-term stability of the system are improved.

[0044] The present application uses a field programmable gate array as a core processing unit, and the hardware parallel processing architecture enables the signal generation (modulation driving signal), data acquisition (electrical signal) and digital phase-locked calculation to be synchronized and high-speed. This method overcomes the speed bottleneck of traditional software phase-locked or analog phase-locked, and can realize microsecond-level phase demodulation and output, which meets the harsh requirements of high speed and real-time for dynamic process and transient phenomenon measurement.

[0045] The present application uses an elasto-optic modulator combined with a specific optical path design and signal processing algorithm, without the need for mechanical scanning components or complex frequency shift devices commonly used in traditional phase measurement systems, and also reduces the dependence on multi-channel and high-cost phase-locked amplifiers. This not only significantly simplifies the optical path structure and electronic system, reduces the complexity of hardware cost and system debugging and maintenance, but also has stronger anti-vibration ability, longer service life, higher reliability, and is easier to integrate and apply with existing industrial automation platforms.

[0046] The above is a further detailed description of the preferred technical solutions of the present application, and cannot be considered as the specific implementation of the present application. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, simple deductions and substitutions can also be made, and all should be considered as the protection scope of the present application.

Claims

1. A high-precision quantitative phase demodulation device of elastic-optical modulation type, characterized in that, The system includes a light source, an interferometric optical path system, and a detection and signal demodulation system. The light source provides a detection beam. The interferometric optical path system includes a polarization beam splitting unit, a reference optical path, a measurement optical path, and a beam combining unit. The polarization beam splitting unit splits the detection beam from the light source into a reference beam and a measurement beam with mutually orthogonal polarization directions, and guides them to the reference optical path and the measurement optical path, respectively. A photoelectric modulator is provided in the reference optical path to apply periodic phase modulation to the passing reference beam. The measurement optical path includes a sample area for carrying the sample to be tested. The beam combining unit combines the beams emitted from the reference optical path and the measurement optical path to generate an interferometric light signal. The detection and signal demodulation system... The modulation system includes an analyzer, a photodetector, and a signal processing module. The analyzer is disposed in the output optical path of the beam combiner unit and is used to analyze the polarization of the interference optical signal. The photodetector is used to receive the optical signal passing through the analyzer and convert it into an electrical signal. The signal processing module is electrically connected to the photodetector and the photoelastic modulator. The signal processing module includes a field-programmable gate array (FPGA), which is configured to: provide a modulation drive signal to the photoelastic modulator and, based on a reference signal that is of the same frequency and origin as the modulation drive signal, perform digital phase-locked amplification on the electrical signal output by the photodetector to demodulate the phase information introduced by the sample under test.

2. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, The polarization beam splitting unit includes a half-wave plate and a polarization beam splitting prism arranged sequentially along the optical path.

3. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, The reference optical path further includes a first polarizer disposed in the optical path of the elastic modulator, and a first reflector for changing the direction of the optical path; the measurement optical path further includes a second polarizer disposed in the optical path of the sample region, and a second reflector for changing the direction of the optical path.

4. The elastic-optical modulation type high-precision quantitative phase demodulation device according to claim 1, characterized in that, The beam combining unit is a non-polarizing beam splitter prism.

5. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, The photoelastic modulator includes a photoelastic crystal and an LC resonant high-voltage driving circuit connected to the photoelastic crystal. The LC resonant high-voltage driving circuit is connected to the field-programmable gate array of the signal processing module.

6. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, The first polarizer, the second polarizer, and the analyzer are all calcite Glan Taylor polarizers with an extinction ratio better than 100,000:

1.

7. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, The signal processing module also includes a data acquisition unit connected to the field-programmable gate array (FPGA) for acquiring the electrical signals output by the photodetector.

8. The high-precision quantitative phase demodulation device of elastic-optical modulation type according to claim 1, characterized in that, It also includes a computer that is communicatively connected to the signal processing module, used to receive, display and store the demodulated phase information.

9. A high-precision quantitative phase demodulation method based on elastic-optical modulation, characterized in that, The device based on any one of claims 1-8, characterized by high precision quantitative phase demodulation using elastic-optical modulation, comprises: The detection beam emitted by the light source is separated into a reference beam and a measurement beam with mutually orthogonal polarization directions. The reference beam is passed through an elastic-optical modulator to apply periodic phase modulation to the elastic-optical modulator. Simultaneously, the measurement beam is passed through the sample under test to carry the phase information of the sample under test. The modulated reference beam and the measurement beam carrying the sample phase information are combined to generate an interference light signal. The interference light signal is converted into a corresponding electrical signal. A modulation drive signal for driving the elastic-optical modulator is generated using a field-programmable gate array (FPGA). Simultaneously, a reference signal with the same frequency and origin as the modulation drive signal is used to digitally lock-in amplify the electrical signal to demodulate the phase delay introduced by the sample under test.

10. The high-precision quantitative phase demodulation method of elastic-optical modulation according to claim 9, characterized in that, The phase delay of the sample under test is determined by extracting the amplitude of the fundamental frequency component in the electrical signal that is related to the modulation frequency of the photoelastic modulator and calculating the ratio of the amplitude of the fundamental frequency component.

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