A surface profile and thickness measurement system and method based on high repetition rate optical comb

Abstract

The application provides a surface topography and thickness measurement system and method based on a high-repetition-rate optical comb, and belongs to the field of optical non-contact measurement. The system comprises a high-repetition-rate optical comb, a spectrum expansion and shaping module, a polarization maintaining optical fiber beam splitter, an optical switch, a fiber delay, a polarization maintaining optical fiber combiner, a polarization maintaining optical fiber circulator, a polarization maintaining optical fiber probe, a two-dimensional moving table, a spectrum detector and an upper computer. The system utilizes the characteristics of high wavelength stability, good coherence and real-time reference to the clock standard of the optical comb, realizes high-precision optical path difference resolution through spectrum interference technology, realizes simultaneous measurement of the surface topography and thickness of a target to be measured, has the advantages of high measurement precision, large measurement range and on-line traceability of measurement results, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of optical non-contact measurement, and particularly relates to a surface morphology and thickness measurement system and method based on a high repetition rate optical comb. Background Technology

[0002] Optical non-contact topography and thickness measuring instruments are widely used in thin film thickness measurement, semiconductor device inspection, optical device inspection, and medical device inspection. Current optical non-contact topography and thickness measuring instruments use SLDs (superluminescent diodes) as the light source. However, SLD light sources have poor wavelength stability, typically around 10 nm. -5 The magnitude of the difference between standard and standard measurements is significant. Spectroscopic interferometry uses a spectrometer as the detector, and the stability of the wavelength directly affects the accuracy and signal-to-noise ratio of the acquired signal, thus impacting measurement precision. Furthermore, SLD (Surface Diode Light) sources have poor coherence and a small coherence distance, resulting in a limited measurement range for morphology and thickness. Different instrument models are required to meet varying measurement ranges and precision requirements. Moreover, most current surface morphology and thickness measuring instruments cannot achieve online in-situ traceability and are significantly affected by thermal noise and environmental factors. Even the most advanced morphology and thickness measuring instruments, employing a built-in 633nm frequency-stabilized laser and using techniques such as beat frequency and phase-locked loop to calibrate the SLD source wavelength, suffer from complex technical methods and increased device size. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a surface morphology and thickness measurement system and method based on a high repetition rate optical comb.

[0004] The first aspect of this invention discloses a surface morphology and thickness measurement system based on a high repetition rate optical comb, the system comprising:

[0005] Electro-optic modulated optical frequency combs are used to generate optical comb pulses with repetition frequencies above gigahertz (GHz);

[0006] The spectral expansion and shaping module is used to expand and shape the spectrum of the optical comb pulses.

[0007] A polarization-maintaining fiber beam splitter is used to split the shaped optical comb pulse into a reference beam and a measurement beam. The reference beam is transmitted through a reference arm, and the measurement beam is transmitted through a measurement arm.

[0008] The optical switch and fiber delay unit are mounted on the reference arm; the polarization maintaining circulator is mounted on the measurement arm.

[0009] An optical switch is used to control the on / off state of the reference arm to switch measurement modes;

[0010] Fiber optic delay unit, used to adjust the optical path of the reference arm;

[0011] A polarization-maintaining circulator is used to separate forward and reverse propagating light, allowing the laser to propagate along a specified port sequence. The polarization-maintaining circulator has three ports; the measurement light enters through the first port and is transmitted to the polarization-maintaining fiber probe through the second port.

[0012] The polarization-maintaining fiber probe is used to emit measurement light and receive the target reflected light. The target reflected light enters the polarization-maintaining circulator through the second port and is input to the polarization-maintaining fiber combiner through the third port.

[0013] A polarization-maintaining fiber combiner is used to combine light entering under different measurement modes to produce interference.

[0014] A two-dimensional locator is used to carry and move the target to be tested.

[0015] A spectrometer is used to acquire the interference spectral signals of the polarization-maintaining fiber combiner.

[0016] The host computer is used to demodulate the interference spectral signal and calculate the morphology or thickness.

[0017] Optionally, the electro-optic modulated optical frequency comb includes a narrow linewidth continuous laser, an electro-optic intensity modulator, and an electro-optic phase modulator;

[0018] The laser signal emitted by the narrow linewidth continuous laser passes through an electro-optic intensity modulator and an electro-optic phase modulator in sequence to generate optical comb pulses with a repetition frequency of over gigahertz (GHz).

[0019] Optionally, the spectral spreading and shaping module includes: an erbium-doped fiber amplifier, a highly nonlinear fiber, a fiber filter, and a dispersion compensator;

[0020] Erbium-doped fiber amplifiers are used to amplify the energy of optical comb pulses; the amplified optical comb pulses are spectrally expanded through highly nonlinear optical fibers, and the target wavelength band is selected through fiber filters, while the pulse width is controlled through dispersion compensators.

[0021] Optionally, when the optical switch controls the reference arm to connect, the surface topography and thickness measurement system is in the surface topography measurement mode, and the reference light and the measurement light interfere with each other in the polarization-maintaining fiber combiner.

[0022] When the optical switch controls the reference arm to be disconnected, the surface topography and thickness measurement system is in thickness measurement mode, and only the measurement light is reflected on the upper and lower surfaces of the target and generates self-interference in the polarization-maintaining fiber combiner.

[0023] Optionally, the wavelength range of the spectral detector covers the output spectrum of the optical comb pulses, and the spectral resolution is less than or equal to the comb tooth spacing.

[0024] Optionally, in the topography measurement mode, the host computer reconstructs the surface topography by calculating the distance difference between the reference arm and the measuring arm and combining it with the scanning data of the two-dimensional moving stage;

[0025] In thickness measurement mode, the host computer reconstructs the thickness distribution of the target by calculating the optical path difference between the two reflected lights on the upper and lower surfaces of the target and combining the scanning data of the two-dimensional moving stage.

[0026] The second aspect of this invention discloses a method for measuring surface morphology and thickness based on a high repetition rate optical comb. The method is implemented using the surface morphology and thickness measurement system based on a high repetition rate optical comb as described in any one of the preceding claims. The method includes:

[0027] The on / off state of the reference arm is controlled by an optical switch, allowing the surface topography and thickness measurement system to operate in either topography measurement mode or thickness measurement mode.

[0028] In morphology mode, the fiber delay is adjusted to match the optical path of the reference light and the measurement light, and the interference signal of the reference light signal and the target reflected light is acquired and the morphology data is demodulated.

[0029] In thickness mode, the self-interference signals of the reflected light from the upper and lower surfaces of the target under test are acquired and the thickness data is demodulated.

[0030] By combining the scanning data from the two-dimensional moving stage, a three-dimensional surface morphology or thickness distribution map of the target under test is generated.

[0031] Optionally, in the topography measurement mode, the host computer reconstructs the three-dimensional surface topography by calculating the distance difference between the reference arm and the measuring arm and combining it with the scanning data of the two-dimensional moving stage.

[0032] Optionally, in thickness measurement mode, the host computer reconstructs the thickness distribution of the target by calculating the optical path difference between the two reflected lights on the upper and lower surfaces of the target and combining it with the scanning data of the two-dimensional moving stage.

[0033] In summary, the solution proposed in this invention has the following technical effects:

[0034] 1. This system uses an electro-optic modulated high-repetition-rate optical comb as a light source, which has the advantages of high wavelength stability, good coherence, and real-time reference to a clock standard. It can significantly improve the measurement accuracy and measurement range of the system, and enable online traceability of measurement results.

[0035] 2. This system can achieve different measurement ranges and different measurement resolutions by setting the parameters of the electro-optic modulation optical comb; it can also achieve the measurement of different parameters by replacing different types of polarization-maintaining fiber optic probes.

[0036] 3. This system can control the connection or disconnection of the reference arm laser through optical switching, and use a single system to simultaneously measure surface morphology and thickness parameters. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a structural diagram of an aero-engine blade tip clearance measurement system based on optical frequency comb spectral interferometry, according to an embodiment of the present invention.

[0039] Among them, 1-high repetition rate optical comb, 2-spectrum spreading and shaping module, 3-polarization-maintaining fiber beam splitter, 4-optical switch, 5-fiber delayer, 6-polarization-maintaining circulator, 7-polarization-maintaining fiber probe, 8-two-dimensional moving stage, 9-target under test, 10-polarization-maintaining fiber combiner, 11-spectral detector, 12-host computer. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The first aspect of this invention discloses a surface morphology and thickness measurement system based on a high repetition rate optical comb, such as... Figure 1 As shown, the system includes: a high-repetition-rate optical comb 1, a spectral spreading and shaping module 2, a polarization-maintaining fiber beam splitter 3, an optical switch 4, a fiber delay unit 5, a polarization-maintaining circulator 6, a polarization-maintaining fiber probe 7, a two-dimensional moving stage 8, the target under test 9, a polarization-maintaining fiber bundler 10, a spectral detector 11, and a host computer 12. All fiber optic devices are connected via polarization-maintaining fibers, and the spectral detector and the host computer are connected via a network cable. Based on the principle of spectral interferometry, this system collects spectral interference fringes and accurately distinguishes the optical path difference between the reference light and the measurement light, thereby achieving the measurement of the surface morphology and thickness of the target under test. Employing an all-polarization-maintaining fiber structure, it has advantages such as high measurement accuracy, a large measurement range, and online traceability of measurement results, and has broad application prospects.

[0042] The high repetition rate optical comb is an electro-optic modulated optical comb 1, which outputs a high-stability laser pulse with a repetition rate of over 1 GHz. The electro-optic modulated optical comb can be generated by intensity and phase modulation of the laser output from a narrow-linewidth continuous laser. Electro-optic modulated optical combs have advantages such as tunable comb tooth spacing, high repetition rate, good stability, good coherence, and high integration, and are widely used in optical communication, distance measurement, spectral measurement, frequency measurement, and arbitrary waveform generation.

[0043] The spectral spreading and shaping module 2 is used to spectrally spread and shape the optical comb pulse. The polarization-maintaining fiber beam splitter 3 is used to split the shaped optical comb pulse into reference light and measurement light. The reference light is transmitted through the reference arm, and the measurement light is transmitted through the measurement arm. The optical switch 4 and the fiber delay unit 5 are located on the reference arm; the polarization-maintaining circulator 6 is located on the measurement arm. The optical switch 4 is used to control the pass-through or open-end state of the reference arm to achieve different measurement modes. The fiber delay unit 5 is used to precisely adjust the optical path of the reference arm to make the optical path of the reference arm and the measurement arm equal to obtain a spectral interference signal. The polarization-maintaining circulator 6 is used to separate the forward and reverse transmission light, so that the laser is transmitted along a specified port sequence. The polarization-maintaining circulator 6 includes three ports; the measurement light enters through the first port and is transmitted to the polarization-maintaining fiber probe through the second port. The polarization-maintaining fiber probe 7 is used to emit the measurement light and receive the target reflected light. The target reflected light enters the polarization-maintaining circulator 6 through the second port and is input to the polarization-maintaining fiber combiner 10 through the third port. The polarization-maintaining fiber combiner 10 is used to combine light entering under different measurement modes to generate interference. The two-dimensional moving stage 8 is used to carry and move the target 9 under test, achieving scanning functionality through a two-dimensional moving stage. The spectrometer 11 is used to acquire the interference spectrum signal from the polarization-maintaining fiber combiner 10. The host computer 12 is used to demodulate the interference spectrum signal and calculate the morphology or thickness.

[0044] Optionally, the electro-optic modulated optical frequency comb 1 includes a narrow linewidth continuous laser, an electro-optic intensity modulator, and an electro-optic phase modulator.

[0045] The laser signal emitted by a narrow-linewidth continuous laser is sequentially passed through an electro-optic intensity modulator and an electro-optic phase modulator to generate an optical comb pulse with a repetition frequency of over gigahertz (GHz). The modulation signals of the electro-optic intensity modulator and the electro-optic phase modulator are referenced to a clock standard, and the repetition frequency of the electro-optic modulated optical comb can be adjusted by setting the modulation signal frequency.

[0046] Optionally, the spectral spreading and shaping module 2 includes: an erbium-doped fiber amplifier, a highly nonlinear fiber, a fiber filter, and a dispersion compensator. The erbium-doped fiber amplifier amplifies the electro-optic modulated optical frequency comb, enabling the frequency comb pulses to obtain higher energy. The amplified pulses are then spectrally spread through the highly nonlinear fiber. The fiber filter selects the desired laser wavelength band, and the dispersion compensator controls the pulse width.

[0047] Optionally, when the optical switch 4 controls the reference arm to connect, the surface topography and thickness measurement system is in the surface topography measurement mode, and the reference light and the measurement light interfere with each other in the polarization-maintaining fiber combiner 10.

[0048] When the optical switch 4 controls the reference arm to be disconnected, the surface topography and thickness measurement system is in thickness measurement mode, and only the measurement light is reflected on the upper and lower surfaces of the target and generates self-interference in the polarization-maintaining fiber combiner 10.

[0049] Optionally, the polarization-maintaining fiber optic probe has a coaxial transceiver structure for transmitting measurement optical pulses and receiving the reflected light from the surface of the target and different dielectric layers.

[0050] Optionally, a spectrometer is used to collect spectral interference fringes. The wavelength range of the spectrometer 11 covers the output spectrum of the optical comb pulse, and the spectral resolution is less than or equal to the comb tooth spacing.

[0051] Optionally, in the topography measurement mode, the host computer 12 reconstructs the surface topography by calculating the distance difference between the reference arm and the measuring arm and combining it with the scanning data of the two-dimensional moving stage;

[0052] In thickness measurement mode, the host computer 12 reconstructs the thickness distribution of the target by calculating the optical path difference between the two reflected lights on the upper and lower surfaces of the target and combining the scanning data of the two-dimensional moving stage.

[0053] The second aspect of this invention discloses a method for measuring surface morphology and thickness based on a high repetition rate optical comb. The method is implemented using the surface morphology and thickness measurement system based on a high repetition rate optical comb as described in any one of the preceding claims. The method includes:

[0054] The on / off state of the reference arm is controlled by optical switch 4, which selects whether the surface topography and thickness measurement system is working in topography measurement mode or thickness measurement mode.

[0055] In morphology mode, the fiber delay unit 5 is adjusted to match the optical path of the reference light and the measurement light, and the interference signal of the reference light signal and the target reflected light is collected and the morphology data is demodulated.

[0056] In thickness mode, the self-interference signals of the reflected light from the upper and lower surfaces of the target 9 are acquired and the thickness data is demodulated.

[0057] By combining the scanning data from the two-dimensional moving stage 8, a three-dimensional surface morphology or thickness distribution map of the target 9 to be tested is generated.

[0058] Optionally, in the topography measurement mode, the host computer 12 reconstructs the three-dimensional surface topography by calculating the distance difference between the reference arm and the measuring arm and combining it with the scanning data of the two-dimensional moving stage.

[0059] Optionally, in thickness measurement mode, the host computer 12 reconstructs the thickness distribution of the target by calculating the optical path difference between the two reflected lights on the upper and lower surfaces of the target and combining the scanning data of the two-dimensional moving stage.

[0060] When the optical switch is in the pass state, the system is in the surface morphology measurement mode, which can realize the surface morphology measurement of the target. The linearly polarized pulsed laser emitted by the electro-optic modulated optical frequency comb 1 enters the spectrum spreading and shaping module 2, and is then split into two beams by the polarization-maintaining fiber beam splitter 3. One beam serves as the reference light, passing sequentially through the optical switch 4 and the fiber delay unit 5 on the reference arm; the other beam serves as the measurement light, entering one port of the polarization-maintaining circulator 6 on the measurement arm. The measurement light output from the second port of the polarization-maintaining circulator 6 is incident on the target under test via the polarization-maintaining fiber probe 7. The polarization-maintaining fiber probe 7 is fixed above the target under test 9, which is fixed on the two-dimensional moving stage 8 and scanned by the two-dimensional moving stage. The measurement light reflected from the target under test re-enters the polarization-maintaining fiber probe 7 and the second port of the polarization-maintaining circulator 6, and is output from the third port of the polarization-maintaining circulator 6. The reference light output from the fiber delay unit on the reference arm and the measurement light output from the third port of the polarization-maintaining circulator 6 are combined and enter the polarization-maintaining fiber beam combiner 10, causing interference. The spectral detector 11 collects the interference fringes and sends them to the host computer 12 for demodulation to obtain the morphology.

[0061] At this time, the intensity of the interference fringes collected by the spectral detector I for:

[0062]

[0063] in, I 0 represents the background light intensity (DC component). f The frequency of the interference signal, nL The optical path difference between the reference arm and the measuring arm. n For group refractive index, L The distance difference between the reference arm and the measuring arm. c It is the speed of light.

[0064] When the two-dimensional moving stage moves the target under test in two dimensions, the polarization-maintaining fiber optic probe emits a laser to measure the target under test, and a set of distance difference data between the reference arm and the measuring arm can be obtained. Combined with the corresponding position information of the two-dimensional moving stage, a set of three-dimensional coordinate information can be obtained. Based on this set of three-dimensional coordinate information, the surface morphology of the target under test can be calculated.

[0065] When the optical switch is in the off state, the system is in thickness measurement mode, which can measure the thickness between the optical surfaces of the object to be measured, such as the thickness of optical devices and thin films. The linearly polarized pulsed laser emitted by the electro-optic modulated optical frequency comb 1 enters the spectral spreading and shaping module 2, and is then split into two beams by the polarization-maintaining fiber beam splitter 3. One beam serves as a reference beam; since the optical switch is off, the laser on the reference arm cannot pass through. The other beam serves as the measurement beam, entering one port of the polarization-maintaining circulator 6 on the measurement arm. The measurement beam output from the second port of the polarization-maintaining circulator 6 is incident on the target to be measured via the polarization-maintaining fiber probe 7. The polarization-maintaining fiber probe 7 is fixed above the target to be measured 9, which is fixed on the two-dimensional moving stage 8. The two-dimensional moving stage performs scanning. The measurement beam reflected from the target to be measured re-enters the polarization-maintaining fiber. The two ports of the fiber optic probe 7 and the polarization-maintaining circulator 6 are output from the three ports of the polarization-maintaining circulator 6. When the measurement light shines on the upper surface of the transparent object to be measured, part of the measurement light is reflected back to the polarization-maintaining fiber optic probe 7 through the upper surface, and is recorded as the upper surface reflected light. Another part of the measurement light passes through the upper surface and shines on the lower surface of the transparent object. After being reflected by the lower surface, part of the measurement light returns to the polarization-maintaining fiber optic probe, and is recorded as the lower surface reflected light. The upper surface reflected light and the lower surface reflected light enter the polarization-maintaining fiber optic combiner 10 and interfere. The spectral detector 11 collects the interference fringes and sends them to the host computer 12 for demodulation to obtain the thickness of the transparent object.

[0066] Intensity of interference fringes collected by the spectral detector I’ for:

[0067]

[0068] in, I 0 represents the background light intensity (DC component). f The frequency of the interference signal, nd The optical path difference between the upper and lower surfaces of a transparent object. n For group refractive index, d The thickness of a transparent object. c It is the speed of light.

[0069] To achieve thickness measurement at different locations, a two-dimensional moving stage can be used to move the target under test in two dimensions. A polarization-maintaining fiber optic probe emits a laser to measure the target under test, obtaining a set of thickness data for the transparent object. By combining this with the corresponding position information of the two-dimensional moving stage, a set of three-dimensional coordinate information can be obtained, thus enabling the measurement of thickness parameters at any location of the transparent object under test.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surface morphology and thickness measurement system based on a high repetition rate optical comb, characterized in that, The system includes: An electro-optic modulated optical frequency comb (1) is used to generate optical comb pulses with repetition frequencies above gigahertz. The spectral expansion and shaping module (2) is used to perform spectral expansion and shaping on the optical comb pulses; The spectral spreading and shaping module (2) includes: an erbium-doped fiber amplifier, a highly nonlinear fiber, a fiber filter, and a dispersion compensator; Erbium-doped fiber amplifiers are used to amplify the energy of optical comb pulses; the amplified optical comb pulses are spectrally expanded through highly nonlinear optical fibers, and the target wavelength band is selected by an optical fiber filter, while the pulse width is controlled by a dispersion compensator. The polarization-maintaining fiber beam splitter (3) is used to split the shaped optical comb pulse into reference light and measurement light. The reference light is transmitted through the reference arm, and the measurement light is transmitted through the measurement arm. The reference arm is equipped with an optical switch (4) and an optical fiber delayer (5); the measurement arm is equipped with a polarization maintaining circulator (6). Optical switch (4) is used to control the on / off state of the reference arm to switch the measurement mode; Fiber optic delay unit (5) is used to adjust the optical path of the reference arm; The polarization-maintaining circulator (6) is used to separate the forward and reverse transmission light, so that the laser is transmitted along the specified port sequence; the polarization-maintaining circulator (6) includes three ports; the measurement light enters through the first port and is transmitted to the polarization-maintaining fiber probe (7) through the second port. The polarization-maintaining fiber probe (7) is used to receive the measurement light and emit the target reflected light. The target reflected light enters the polarization-maintaining circulator (6) through the second port and is input to the polarization-maintaining fiber combiner (10) through the third port. A polarization-maintaining fiber combiner (10) is used to combine light entering under different measurement modes to produce interference. A two-dimensional mobile station (8) is used to carry and move the target under test (9); A spectrometer (11) is used to collect the interference spectrum signal of the polarization-maintaining fiber combiner (10); the wavelength range of the spectrometer (11) covers the optical comb pulse output spectrum, and the spectral resolution is less than or equal to the comb tooth spacing. The host computer (12) is used to demodulate the interference spectrum signal and calculate the morphology or thickness; When the optical switch (4) controls the reference arm to connect, the surface topography and thickness measurement system is in the surface topography measurement mode, and the reference light and the measurement light interfere with each other in the polarization-maintaining fiber combiner (10). When the optical switch (4) controls the reference arm to be disconnected, the surface topography and thickness measurement system is in thickness measurement mode, and only the measurement light is reflected on the upper and lower surfaces of the target and then generates self-interference in the polarization-maintaining fiber combiner (10); In the topography measurement mode, the host computer (12) reconstructs the surface topography by calculating the distance difference between the reference arm and the measuring arm and combining it with the scanning data of the two-dimensional moving stage; In the topography measurement mode, the intensity of the interference fringes acquired by the spectral detector I for: in, I 0 represents the background light intensity. f The frequency of the interference signal, nL The optical path difference between the reference arm and the measuring arm. n For group refractive index, L The distance difference between the reference arm and the measuring arm. c The speed of light; When the two-dimensional moving stage moves the target under test in two dimensions, the polarization-maintaining fiber optic probe emits laser light to measure the target under test and obtains a set of distance difference data between the reference arm and the measuring arm. Combined with the corresponding position information of the two-dimensional moving stage, a set of three-dimensional coordinate information is obtained. Based on this set of three-dimensional coordinate information, the surface morphology of the target under test is calculated. In the thickness measurement mode, the host computer (12) reconstructs the thickness distribution of the target by calculating the optical path difference between the two reflected lights on the upper and lower surfaces of the target and combining the scanning data of the two-dimensional moving stage. In thickness measurement mode, the intensity of interference fringes acquired by the spectral detector I’ for: in, nd The optical path difference between the upper and lower surfaces of a transparent object. d The thickness of a transparent object; To measure thickness at different locations, a two-dimensional moving stage is used to move the target under test in two dimensions. A polarization-maintaining fiber optic probe emits a laser to measure the target under test, obtaining a set of thickness data for the transparent object. This data is then combined with the corresponding position information of the two-dimensional moving stage to obtain a set of three-dimensional coordinate information, thus enabling the measurement of thickness parameters at any location of the transparent object under test.

2. The surface morphology and thickness measurement system according to claim 1, characterized in that, The electro-optic modulated optical frequency comb (1) includes a narrow linewidth continuous laser, an electro-optic intensity modulator, and an electro-optic phase modulator; The laser signal emitted by the narrow linewidth continuous laser passes through an electro-optic intensity modulator and an electro-optic phase modulator in sequence to generate optical comb pulses with a repetition frequency of over gigahertz.

3. A method for measuring surface morphology and thickness based on a high-repetition-rate optical comb, characterized in that, The method is implemented using the surface topography and thickness measurement system based on a high repetition rate optical comb as described in any one of claims 1-2. The method includes: The on / off state of the reference arm is controlled by the optical switch (4), and the surface morphology and thickness measurement system is selected to work in morphology measurement mode or thickness measurement mode. In morphology mode, the fiber delay device (5) is adjusted to match the optical path of the reference light and the measurement light, and the interference signal of the reference light signal and the target reflected light is collected and the morphology data is demodulated. In thickness mode, the self-interference signal of the reflected light from the upper and lower surfaces of the target (9) is acquired and the thickness data is demodulated; Combined with the scanning data of the two-dimensional moving stage (8), a three-dimensional surface morphology or thickness distribution map of the target to be tested (9) is generated.

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