A gauge block measuring device and measuring method based on swept white light interference

Abstract

The application discloses a kind of based on swept frequency white light interference gauge block measuring device and measuring method, it is related to gauge block measuring technical field, the device includes swept frequency laser, third light splitting prism, first mirror, first light splitting prism, second mirror, to be measured block, third mirror, second light splitting prism, photoelectric detector, data processing end, the absolute measurement method of high sensitivity, high stability, strong anti-interference ability is used in the application, the length of gauge block can be obtained once measurement, measurement operation is simple, it is not necessary to compare with standard gauge block, not limited by the precision of standard gauge block, it can be used for the measurement of higher grade gauge block.

Description

Technical Field

[0001] This invention belongs to the field of gauge block measurement technology, specifically relating to a gauge block measurement device and method based on swept-frequency white light interferometry. Background Technology

[0002] Gauge blocks are one of the most widely used and important physical measuring instrument standards for length measurement internationally. They play a crucial role in product quality assurance systems, and gauge block calibration is an indispensable step in ensuring their proper use. Therefore, the requirements for gauge block length calibration are constantly increasing. Gauge block measurement technology is divided into contact measurement and non-contact measurement. With the development of gauge block measurement technology, contact measurement has gradually been phased out, and non-contact methods mainly rely on optical interferometry. Optical interferometry measures the optical path difference relative to a reference surface, and is therefore susceptible to interference from external factors such as airflow, temperature changes, and mechanical vibrations, requiring strict environmental conditions. Gauge block measurement based on optical interferometry can be further divided into comparative measurement and absolute measurement.

[0003] Comparative measurements require comparing the gauge block to a higher-order gauge block to calculate the difference. Chinese patent CN114608452A discloses a gauge block measurement system with an embedded etalon and no lapping mechanism. This system obtains the difference between the gauge block and the etalon by measuring the zero-order interference fringes of white light. This method is based on time-domain white light interferometry, which has low measurement accuracy. Moreover, the measurement process requires moving the reference arm, resulting in low stability and easy introduction of errors. Chinese patent document CN113251897A discloses a gauge block measurement device and method based on white light interferometry. This invention combines the frequency and phase of Fourier transform to obtain the optical path difference between the two end faces of the gauge block and the standard gauge block, thereby obtaining the difference between the gauge block and the standard gauge block. This method requires sequentially adjusting the positions of the gauge block and the standard gauge block during the measurement process, making absolute measurement impossible.

[0004] Absolute measurements currently often employ the fractional-number repetition method based on multiple wavelengths to increase the measurable range. This requires the use of multiple wavelengths to measure the same gauge block, which places strict requirements on the external environment, makes the system complex, and the measurement length is related to the wavelength of the light source, thus requiring the light source to have high stability.

[0005] The existing technology has the following problems:

[0006] 1. The accuracy of the comparative measurement method depends on the precision of the standard gauge block used, and the length of the gauge block to be measured is inversely proportional to the measurement precision. The position of the gauge block needs to be adjusted during the measurement process, which can easily cause measurement errors.

[0007] 2. The absolute measurement method based on the multi-wavelength small number repetition method is highly dependent on the light source, requiring the use of multiple light sources for multiple measurements, and has strict environmental requirements. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a gauge block measurement device and method based on frequency sweeping white light interferometry, thereby achieving absolute measurement of gauge blocks that is simple to operate, highly stable, and has strong anti-interference ability.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a block measurement device based on swept-frequency white light interferometry, comprising a swept-frequency laser, a third beam splitter, a first reflector, a second reflector, a block to be measured, a third reflector, a second beam splitter, a photodetector, and a data processing terminal;

[0010] The frequency-sweeping laser is used to provide a frequency-sweeping light source;

[0011] The third beam splitter is positioned in the propagation path of the swept frequency light source. The third beam splitter is used to split the passing light into transmitted light and reflected light. The swept frequency light source emitted by the swept frequency laser is split into a first test light and a second test light after passing through the third beam splitter. The light transmitted through the third beam splitter to the first reflecting mirror is the first test light, and the light reflected by the third beam splitter to the second beam splitter is the second test light.

[0012] The first reflector is positioned on the propagation path of the first test light. The first reflector is used to change the propagation path of the first test light so that the first test light is directed toward the first beam splitter.

[0013] The first and second beam splitters are arranged opposite each other on the same axis. The first and second beam splitters are used to split the passing light into transmitted light and reflected light. The first beam splitter is arranged on the propagation path of the first test light, and the first test light is split into a first side reference light and a first side test light after passing through the first beam splitter. The second beam splitter is arranged on the propagation path of the second test light, and the second test light is split into a second side reference light and a second side test light after passing through the second beam splitter. The first side test light and the second side test light are coaxial and share the same path.

[0014] The second reflector is positioned on the propagation path of the first side reference light, and the second reflector is used to reflect the first side reference light along the original path;

[0015] The third reflector is positioned on the propagation path of the reference light from the second side, and is used to reflect the reference light from the second side along the original path.

[0016] The block to be measured is placed between the first beam splitter and the second beam splitter, and the first side test light and the second side test light are respectively perpendicularly incident on the first side and the second side of the block to be measured.

[0017] The photodetector is located on the side of the third beam splitter away from the second beam splitter and is electrically connected to the data processing terminal. The photodetector is used to collect the reference light from the first side, the reference light from the second side, the test light from the first side, and the test light from the second side of the third beam splitter, generate an interference signal, and transmit the interference signal to the data processing terminal.

[0018] The data processing terminal is used to calculate the optical path difference of the interference light based on the interference signal, and then calculate the length between the first side and the second side of the block to be measured.

[0019] A measurement method for a gauge block measuring device based on the above-mentioned frequency-sweeping white light interferometry includes a system calibration process and a measurement process, the specific steps of which are as follows:

[0020] System calibration process:

[0021] S1: Without placing the block to be measured, the path from the first beam splitter to the second reflector is blocked by a light shield, interrupting the optical path of the first side reference light. The first side test light is reflected by the second beam splitter and then passes through the third beam splitter to enter the photodetector. The second side reference light is reflected by the third reflector and then passes through the second and third beam splitters to enter the photodetector. The second side test light is reflected by the first beam splitter, the first reflector, and the third beam splitter to enter the photodetector. The detector records the interference signal and transmits it to the data processing terminal. The interference spectrum is denoted as I1. The optical paths of the first and second side test lights are the same. The light synthesized by the first and second side test lights is denoted as the enhancement light. The optical path difference s1 between the second side reference light and the enhancement light is calculated based on I1.

[0022] S2: Move the light shield to block the path from the second beam splitter to the third mirror, interrupting the optical path of the second side reference light and opening the optical path of the first side reference light. The first side reference light is reflected by the second mirror and passes through the first beam splitter. After being reflected by the first mirror and the third beam splitter, it enters the photodetector. The first side test light and the second side test light also enter the photodetector. The first side test light and the second side test light have the same optical path. The light synthesized by the first side test light and the second side test light is called the enhancement light. The photodetector records the interference signal and transmits it to the data processing terminal. The interference spectrum is called I2. The optical path difference s2 between the first side reference light and the enhancement light is calculated based on I2.

[0023] Measurement process:

[0024] S3: Place the block to be measured between the first beam splitter and the second beam splitter, so that the first side test light and the second side test light are perpendicularly incident on the first side and the second side of the block to be measured, respectively. Use a light shield to block the path from the third beam splitter to the first reflector. The reference light on the second side is reflected by the third reflector and then passes through the second beam splitter and the third beam splitter before entering the photodetector. The test light on the second side is reflected by the corresponding side of the block to be measured and the second beam splitter, and then passes through the third beam splitter before entering the photodetector. The photodetector records the interference signal and transmits it to the data processing terminal. Record the interference spectrum as I3. Calculate the optical path difference s3 between the reference light on the second side and the test light on the second side based on I3.

[0025] S4: Move the light-shielding plate to block the path from the third beam splitter to the second beam splitter. The reference light from the first side is reflected by the second mirror and then passes through the first beam splitter. After being reflected by the first mirror and the third beam splitter, it enters the photodetector. The test light from the first side is reflected by the corresponding side of the block to be measured, the first beam splitter, the first mirror, and the third beam splitter before entering the photodetector. The photodetector records the interference signal and transmits it to the data processing terminal. The interference spectrum is denoted as I4. The optical path difference s4 between the reference light from the first side and the test light from the first side is calculated based on I4.

[0026] S5: The data processing end uses the system calibration values ​​s1 and s2 and the measured values ​​s3 and s4 to calculate the length l between the first and second sides of the block to be measured.

[0027] Furthermore, the specific calculation method for the length l of the block to be measured in step S5 is as follows:

[0028]

[0029] Furthermore, the steps for calculating the optical path lengths s1, s2, s3, and s4 from the interference spectra I1, I2, I3, and I4 are as follows:

[0030] P1: The acquired interference spectrum is first processed to remove the DC component and high-frequency noise, and then the power spectral density coefficient S(k) of the light source is used. i The interference spectrum was normalized.

[0031] P2: Complex interference spectra are obtained by performing a Hilbert transform on the processed interference spectra;

[0032] P3: Using trigonometric functions to obtain the i-th wavenumber k in the interference spectrum i The corresponding phase θ i Dewind it to obtain the optical path difference with respect to k. i and θ i The slope of the equation is calculated using the least squares method to obtain a low-precision solution for the optical path difference.

[0033] P4: Perform a Fast Fourier Transform on the complex interference spectrum to obtain the roll-up phase θ of the interference spectrum. w and using θ w Calculate the unwound phase θ uw And a high-precision solution for optical path difference.

[0034] Furthermore, in step P4, θ is utilized w Calculate the unwound phase θ uw The specific method for obtaining a high-precision solution for the optical path difference is as follows:

[0035]

[0036]

[0037] Where Round represents the rounding operation, k c Represents the center wave number, s n This represents the optical path difference of the light rays in the nth interference spectrum.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. This invention does not require the use of multi-wavelength fractional number repetition method, nor does it require the use of multiple wavelengths to measure the same gauge block. It is simple to operate and has a fast measurement speed.

[0040] 2. The frequency-sweeping white light interferometry used in this invention is a frequency-domain white light interferometry method. Compared with time-domain based white light interferometry, it has better demodulation accuracy and does not require moving the reference arm, resulting in higher system stability.

[0041] 3. This invention employs an absolute measurement method with high sensitivity, high stability, and strong anti-interference capability. The length of the gauge block can be obtained in a single measurement. The measurement operation is simple, does not require comparison with standard gauge blocks, and is not limited by the accuracy of standard gauge blocks. It can be used for the measurement of higher-grade gauge blocks. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0043] The labels in the diagram represent: 1. Sweeping laser; 2. Third beam splitter; 3. First reflector; 4. First beam splitter; 5. Second reflector; 6. Measured block; 7. Third reflector; 8. Second beam splitter; 9. Photodetector; 10. Data processing terminal. Detailed Implementation

[0044] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, a block measurement device based on swept white light interferometry includes a swept laser 1, a third beam splitter 2, a first reflector 3, a first beam splitter 4, a second reflector 5, a block to be measured 6, a third reflector 7, a second beam splitter 8, a photodetector 9, and a data processing terminal 10.

[0046] The frequency-sweeping laser 1 is used to provide a frequency-sweeping light source;

[0047] The third beam splitter 2 is set on the propagation path of the swept light source. The third beam splitter 2 is used to split the passing light into transmitted light and reflected light. The swept light source emitted by the swept laser 1 is split into a first test light and a second test light after passing through the third beam splitter 2. The optical paths of the first test light and the second test light are perpendicular to each other.

[0048] The first reflector 3 is disposed on the propagation path of the first test light. The first reflector 3 is used to change the propagation path of the first test light so that the first test light is directed toward the first beam splitter 4.

[0049] The first beam splitter 4 and the second beam splitter 8 are arranged opposite each other on the same axis. The first beam splitter 4 and the second beam splitter 8 are used to split the passing light into transmitted light and reflected light. The first beam splitter 4 is arranged on the propagation path of the first test light. After passing through the first beam splitter 4, the first test light is split into a first side reference light and a first side test light. The second beam splitter 8 is arranged on the propagation path of the second test light. After passing through the second beam splitter 8, the second test light is split into a second side reference light and a second side test light. The first side test light and the second side test light are coaxial and share the same path.

[0050] The second reflector 5 is disposed on the propagation path of the first side reference light, and the second reflector 5 is used to reflect the first side reference light along the original path;

[0051] The third reflector 7 is disposed on the propagation path of the reference light on the second side, and the third reflector 7 is used to reflect the reference light on the second side along the original path.

[0052] The block to be measured 6 is placed between the first beam splitter 4 and the second beam splitter 8, and the first side test light and the second side test light are respectively perpendicularly incident on the first side and the second side of the block to be measured 6.

[0053] The photodetector 9 is disposed on the side of the third beam splitter 2 away from the second beam splitter 8 and is electrically connected to the data processing terminal 10. The photodetector 9 is used to collect the first side reference light, the second side reference light, the first side test light and the second side test light passing through the third beam splitter 2, generate an interference signal and transmit the interference signal to the data processing terminal 10.

[0054] The data processing terminal 10 is used to calculate the optical path difference of the interference light based on the interference signal, and then calculate the length between the first side and the second side of the block to be measured 6.

[0055] The measurement method based on the above-mentioned swept-frequency white light interferometry gauge block measuring device includes a system calibration process and a measurement process, the specific steps of which are as follows:

[0056] System calibration process:

[0057] S1: Without placing the measurement block 6, the path from the first beam splitter 4 to the second reflector 5 is blocked by a light-shielding plate. The first side test light is reflected by the second beam splitter 8 and then passes through the third beam splitter 2 to enter the photodetector 9. The second side reference light is reflected by the third reflector 7 and then passes through the second beam splitter 8 and the third beam splitter 2 to enter the photodetector 9. The second side test light is reflected by the first beam splitter 4, the first reflector 3, and the third beam splitter 2 to enter the photodetector 9. The detector 9 records the interference signal and transmits it to the data processing terminal 10. The interference spectrum is denoted as I1. Among the three beams of light that make up the interference spectrum I1, the first side test light and the second side test light both pass through the closed optical path formed by the third beam splitter 2, the first reflector 3, the first beam splitter 4, and the second beam splitter 8. That is, the optical path lengths of the first side test light and the second side test light are equal. The light synthesized by the first side test light and the second side test light is denoted as the enhancement light. The optical path difference s1 between the second side reference light and the enhancement light is calculated according to I1. Then:

[0058] 2a1-c1=s1 (1)

[0059] Where a1 is the distance traveled by light from the third beam splitter 2 to the reflecting mirror 7, and c1 is the distance traveled by light from the third beam splitter 2 around the closed light path.

[0060] S2: Move the light shield to block the path from the second beam splitter 8 to the third reflector 7, interrupting the optical path of the second side reference light and opening the optical path of the first side reference light. The first side reference light is reflected by the second reflector 5 and passes through the first beam splitter 4, and after being reflected by the first reflector 3 and the third beam splitter 2, it enters the photodetector 9. The first side test light and the second side test light also enter the photodetector (9). The first side test light and the second side test light have the same optical path. The light synthesized by the first side test light and the second side test light is called the enhanced light. The photodetector 9 records the interference signal and transmits it to the data processing terminal 10. The interference spectrum is denoted as I2. The optical path difference s2 between the first side reference light and the enhanced light is calculated based on I2. Then:

[0061] 2a²-c₁=s² (2)

[0062] Where a2 is the distance traveled by light from the third beam splitter 2 to the reflecting mirror 5.

[0063] Measurement process:

[0064] S3: As Figure 1 As shown, the block to be measured 6 is placed between the first beam splitter 4 and the second beam splitter 8, so that the first side test light and the second side test light are perpendicularly incident on the first side and the second side of the block to be measured 6, respectively. The path from the third beam splitter 2 to the first reflector 3 is blocked by a light shield. The reference light from the second side is reflected by the third reflector 7 and then passes through the second beam splitter 8 and the third beam splitter 2 before entering the photodetector 9. The test light from the second side is reflected by the second side of the block to be measured 6 and the second beam splitter 8, and then passes through the third beam splitter 2 before entering the photodetector 9. The photodetector 9 records the interference signal and transmits it to the data processing terminal 10. The interference spectrum is denoted as I3. The optical path difference s3 between the reference light from the second side and the test light from the second side is calculated based on I3. Then:

[0065] 2a1-2b1=s3 (3)

[0066] Where b1 is the distance that light travels from the third beam splitter 2 to the second side of the block 6 to be measured.

[0067] S4: Move the light-shielding plate to block the path from the third beam splitter 2 to the second beam splitter 8. The reference light from the first side is reflected by the second reflector 5 and then passes through the first beam splitter 4. After being reflected by the first reflector 3 and the third beam splitter 2, it enters the photodetector 9. The test light from the first side is reflected by the first side surface of the block to be measured 6, the first beam splitter 4, the first reflector 3, and the third beam splitter 2 before entering the photodetector 9. The photodetector 9 records the interference signal and transmits it to the data processing terminal 10. The interference spectrum is denoted as I4. The optical path difference s4 between the reference light from the first side and the test light from the first side is calculated based on I4. Then:

[0068] 2a² - 2b² = s⁴ (4)

[0069] Where b2 is the distance that light travels from the third beam splitter 2 to the first side of the block to be measured 6.

[0070] Let l be the length between the first and second sides of the block 6 to be measured. Then the following relationship exists:

[0071] b1 + b2 + l = c1. (5)

[0072] By combining equations (1), (2), (3), (4), and (5) above, the length between the first and second sides of the block 6 to be measured can be obtained.

[0073] The principle for calculating optical path lengths s1, s2, s3, and s4 from interference spectra I1, I2, I3, and I4 is the same. Taking the calculation of s1 using I1 as an example, the steps for calculating optical path length from interference spectra are as follows:

[0074] The collected interference spectrum can be expressed as:

[0075]

[0076] Where, k i For the i-th wave number, S(k) i ) represents the power spectral density coefficient of the light source, I r (k i ) and I s (k i ) are the light intensities of the reference light and the enhancement light on the second side, respectively, and s1 is the optical path difference.

[0077] The acquired interference spectrum was first processed to remove the DC component and high-frequency noise, using S(k i After normalizing the spectrum, the complex interference spectrum is obtained by performing a Hilbert transform, and the wavenumber k is obtained using trigonometric functions. i The corresponding phase is de-wound to obtain:

[0078] θ i =k i s1+θ0 (7)

[0079] Where θ0 is the initial phase.

[0080] The slope of formula (7) is calculated using the least squares method to obtain the low-precision solution s′1 of the optical path. A fast Fourier transform is then performed on the interference spectrum to obtain the roll-up phase θ of the interference spectrum. w Then the dewinding phase θ is obtained. uw And a high-precision solution for optical path difference:

[0081]

[0082] Where Round represents the rounding operation, k c Indicates the center wave number.

[0083] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A method for measuring gauge blocks based on swept-frequency white light interferometry, which is implemented using a gauge block measuring device based on swept-frequency white light interferometry. The device includes a swept-frequency laser (1), a third beam splitter (2), a first reflector (3), a first beam splitter (4), a second reflector (5), a gauge block (6), a third reflector (7), a second beam splitter (8), a photodetector (9), and a data processing terminal (10). The swept-frequency laser (1) is used to provide a swept-frequency light source; The third beam splitter (2) is set on the propagation path of the sweeping light source. The third beam splitter (2) is used to split the passing light into transmitted light and reflected light. The sweeping light source emitted by the sweeping laser (1) is split into the first test light and the second test light after passing through the third beam splitter (2). The light transmitted through the third beam splitter (2) to the first reflector (3) is the first test light, and the light reflected by the third beam splitter (2) to the second beam splitter (8) is the second test light. The first reflector (3) is set on the propagation path of the first test light. The first reflector (3) is used to change the propagation path of the first test light so that the first test light is directed toward the first beam splitter (4). The first beam splitter (4) and the second beam splitter (8) are arranged opposite each other on the same axis. The first beam splitter (4) and the second beam splitter (8) are used to split the passing light into transmitted light and reflected light. The first beam splitter (4) is arranged on the propagation path of the first test light. After passing through the first beam splitter (4), the first test light is split into a first side reference light and a first side test light. The second beam splitter (8) is arranged on the propagation path of the second test light. After passing through the second beam splitter (8), the second test light is split into a second side reference light and a second side test light. The first side test light and the second side test light are coaxial and share the same path. The second reflector (5) is disposed on the propagation path of the first side reference light, and the second reflector (5) is used to reflect the first side reference light along the original path; The third reflector (7) is positioned on the propagation path of the reference light from the second side, and the third reflector (7) is used to reflect the reference light from the second side along the original path; The block to be measured (6) is placed between the first beam splitter (4) and the second beam splitter (8), and the first side test light and the second side test light are respectively perpendicularly incident on the first side and the second side of the block to be measured (6); The photodetector (9) is located on the side of the third beam splitter (2) away from the second beam splitter (8) and is electrically connected to the data processing terminal (10). The photodetector (9) is used to collect the first side reference light, the second side reference light, the first side test light and the second side test light that pass through the third beam splitter (2), generate an interference signal and transmit the interference signal to the data processing terminal (10). The data processing terminal (10) is used to calculate the optical path difference of the interference light based on the interference signal, and then calculate the length between the first side and the second side of the block to be measured (6); Its features are, The system calibration process and measurement process are included, and the specific steps are as follows: System calibration process: S1: Without placing the test block (6), the path from the first beam splitter (4) to the second reflector (5) is blocked with a light shield. The test light from the first side is reflected by the second beam splitter (8) and then passes through the third beam splitter (2) into the photodetector (9). The reference light from the second side is reflected by the third reflector (7) and then passes through the second beam splitter (8) and the third beam splitter (2) into the photodetector (9). The test light from the second side is reflected by the first beam splitter (4), the first reflector (3), and the third beam splitter (2) into the photodetector (9). The photodetector (9) records the interference signal and transmits it to the data processing terminal (10). The interference spectrum is recorded as... The first and second side test lights have the same optical path. The light synthesized from the first and second side test lights is called the enhanced light. According to... Calculate the optical path difference between the reference light and the enhancement light on the second side. ; S2: Move the light-shielding plate to block the path from the second beam splitter (8) to the third reflector (7), interrupting the optical path of the second side reference light and opening the optical path of the first side reference light. The first side reference light is reflected by the second reflector (5) and passes through the first beam splitter (4), and after being reflected by the first reflector (3) and the third beam splitter (2), it enters the photodetector (9). The first side test light and the second side test light also enter the photodetector (9). The first side test light and the second side test light have the same optical path. The light synthesized by the first side test light and the second side test light is called the enhanced light. The photodetector (9) records the interference signal and transmits it to the data processing terminal (10). The interference spectrum is recorded as... ,according to Calculate the optical path difference between the reference light and the enhancement light on the first side. ; Measurement process: S3: Place the block to be measured (6) between the first beam splitter (4) and the second beam splitter (8), so that the first side test light and the second side test light are perpendicularly incident on the first side and the second side of the block to be measured (6), respectively. Use a light shield to block the path from the third beam splitter (2) to the first reflector (3). The reference light from the second side is reflected by the third reflector (7) and then passes through the second beam splitter (8) and the third beam splitter (2) before entering the photodetector (9). The test light from the second side is reflected by the corresponding side of the block to be measured (6) and the second beam splitter (8) and then passes through the third beam splitter (2) before entering the photodetector (9). The photodetector (9) records the interference signal and transmits it to the data processing terminal (10). Record the interference spectrum as . ,according to Calculate the optical path difference between the reference light from the second side and the test light from the second side. ; S4: Move the light-shielding plate to block the path from the third beam splitter (2) to the second beam splitter (8). The reference light from the first side is reflected by the second reflector (5) and then passes through the first beam splitter (4). After being reflected by the first reflector (3) and the third beam splitter (2), it enters the photodetector (9). The test light from the first side is reflected by the corresponding side of the block to be measured (6), the first beam splitter (4), the first reflector (3), and the third beam splitter (2) and then enters the photodetector (9). The photodetector (9) records the interference signal and transmits it to the data processing terminal (10). The interference spectrum is recorded as follows. ,according to Calculate the optical path difference between the reference light and the test light on the first side. ; S5: Data processing end (10) uses system calibration value and and measured values and Calculate the length between the first and second sides of the block to be measured (6). .

2. A measurement method according to claim 1, characterized in that, The length of the block to be measured (6) in step S5 The specific calculation method is as follows: 。 3. A measurement method according to claim 1, characterized in that, The steps for calculating the optical path difference from the interference spectrum are as follows: P1: The acquired interference spectrum is first processed to remove the DC component and high-frequency noise, and then the power spectral density coefficient of the light source is used. The interference spectrum was normalized. P2: Complex interference spectra are obtained by performing a Hilbert transform on the processed interference spectra; P3: Using trigonometric functions to obtain the first... Number of waves Corresponding phase Dewind it to obtain the optical path difference about and The slope of the equation is calculated using the least squares method to obtain a low-precision solution for the optical path difference. ; P4: Perform a Fast Fourier Transform on the complex interference spectrum to obtain the roll-up phase of the interference spectrum. and utilize Calculate the unwound phase and high-precision solution of optical path difference .

4. A measurement method according to claim 3, characterized in that, In step P4, and utilizing Calculate the unwound phase The specific method for obtaining a high-precision solution for the optical path difference is as follows: ； ； in This indicates the rounding operation. Indicates the center wave number. This represents the optical path difference of the light rays in the nth interference spectrum. This is a low-precision solution for the optical path difference.

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