Multi-wavelength phase-shift interferometry apparatus

Abstract

The application provides a kind of multi-wavelength phase shift interferometry device, belongs to optical precision measurement technical field, specifically includes light source, for providing complex light;Measurement module, for dividing complex light into reference light and measurement light;The measurement light is transmitted to the measured article, and the light reflected by the measured article is spectrophotometric, to obtain transmission light and reflected light;Transmission light and reference light interfere, to obtain interference light;Filtering module, for filtering out a variety of wavelengths of monochromatic light from interference light;Detection module, for receiving filtered monochromatic light signal, and generating first photoelectric signal;Spectrometer, for receiving reflected light, and generating second photoelectric signal;Data acquisition card, for synchronously collecting first photoelectric signal and second photoelectric signal, and completing displacement operation, to obtain the measurement data of nanometer level precision of measured article. Through the processing scheme of the application, the nanometer level measurement precision measurement of more than 2mm even higher step 3D surface shape can be realized.

Description

Technical Field

[0001] This invention relates to the field of optical precision measurement technology, and specifically to a multi-wavelength phase-shifting interferometry measurement device. Background Technology

[0002] With the advancement of society and technology, the components used in various industries are gradually moving towards micro- and nano-structures, which poses new challenges to the current design and measurement fields. In some high-precision measurement fields, such as 3D surface shape detection of optical components and structural characterization of microelectromechanical devices, the requirements for measurement accuracy have reached the nanometer or even sub-nanometer level.

[0003] Currently, the surface shapes of components being measured on the market are diverse, including continuous surfaces and stepped surfaces. For 3D topography inspection of continuous surfaces, various high-precision measurement techniques have emerged, such as spectral confocal technology, area array interferometry, and multi-wavelength interferometry. However, measurement techniques for stepped surfaces are relatively limited. Although area array interferometry and multi-wavelength interferometry can achieve high-precision measurement of the 3D surface shape of stepped surfaces, the presence of 2π phase ambiguity limits their application to step heights, typically less than or equal to 1.5 mm (i.e., less than half the wavelength of a single wavelength, or less than half the wavelength of a single composite wavelength), making it difficult to meet the measurement requirements of higher stepped surfaces. While spectral confocal technology covers a measurement range from sub-millimeter to tens of millimeters, its measurement accuracy is generally at the sub-micrometer level, making it difficult to achieve true nanometer-level measurement accuracy. Currently, multi-wavelength interferometric phase-shifting measurement technology suffers from a small unambiguous measurement range while achieving nanometer-level measurement accuracy. Summary of the Invention

[0004] Therefore, in order to overcome the shortcomings of the prior art, the present invention provides a multi-wavelength phase-shifting interferometry measurement device that can achieve nanometer-level measurement accuracy of 3D surface shapes with steps greater than 2 mm or even higher.

[0005] To achieve the above objectives, the present invention provides a multi-wavelength phase-shifting interferometry measurement device, comprising: a light source for providing polychromatic light, the polychromatic light comprising at least four different wavelengths of monochromatic light; a measurement module for dividing the polychromatic light into reference light and measurement light; transmitting the measurement light to a test object and splitting the light reflected by the test object to obtain transmitted light and reflected light; the transmitted light and the reference light interfering to obtain interference light; a filtering module for filtering out monochromatic light of multiple wavelengths from the interference light; a detection module for receiving the filtered monochromatic light signal and generating a first photoelectric signal; a spectrometer for receiving the reflected light and generating a second photoelectric signal; and a data acquisition card for synchronously acquiring the first photoelectric signal and the second photoelectric signal, and performing displacement calculations to obtain measurement data of the test object with nanometer-level precision.

[0006] In one embodiment, the measurement module includes: a beam splitting unit for splitting the polychromatic light according to a certain ratio, wherein a portion of the polychromatic light is reflected as reference light and a portion of the polychromatic light is transmitted as measurement light; a modulation unit for driving a reflective surface reflecting the reference light to reciprocate according to a set frequency and amplitude; and a dispersion unit for dispersing the measurement light so that the various monochromatic lights in the measurement light are arranged according to wavelength along the optical axis; the dispersed measurement light illuminates the test object and is reflected by the test object, and is then collected by the dispersion unit as sample light; the sample light is split into transmitted light and reflected light by the beam splitting unit.

[0007] In one embodiment, the beam splitting unit includes a first coupler, a first optical fiber, and a first beam splitting plate fixedly connected to the measuring lens barrel and inclinedly disposed on the optical axis of the measuring light. The first coupler transmits the polychromatic light to the first optical fiber. The first optical fiber connects the first coupler and the measuring lens barrel. The first optical fiber has an end face near the measuring lens barrel. A portion of the polychromatic light is reflected at the end face of the optical fiber to become reference light, and a portion of the polychromatic light is transmitted at the end face of the optical fiber to become measuring light. The modulation unit includes a first motion module fixedly connected to the measuring lens barrel. The first motion module drives the end face of the optical fiber to reciprocate according to a set frequency and amplitude. The first beam splitting plate splits the sample light inside the measuring lens barrel to obtain transmitted light and reflected light.

[0008] In one embodiment, the beam splitting unit includes a first coupler, a second optical fiber, a first beam splitting plate inclined on the optical axis, and a second beam splitting plate perpendicularly disposed on the optical axis. The modulation unit includes a first motion module, wherein the first motion module and the second beam splitting plate are fixedly connected to the measuring lens barrel. The first coupler transmits the polychromatic light to the second optical fiber, and the first beam splitting plate transmits the polychromatic light to the second beam splitting plate. A portion of the polychromatic light is reflected by the second beam splitting plate to become reference light, and a portion of the polychromatic light is transmitted by the second beam splitting plate to become measuring light. The first motion module drives the second beam splitting plate to reciprocate according to a set frequency and amplitude. The first beam splitting plate splits the sample light outside the measuring lens barrel to obtain transmitted light and reflected light.

[0009] In one embodiment, the beam splitting unit includes a second coupler, a second optical fiber, a reflector, and a first beam splitting plate fixedly connected to the measuring lens barrel and tilted on the optical axis. The modulation unit includes a second motion module. The second coupler splits the polychromatic light into two paths. One path is reflected by the reflector to form a reference light collected by the second coupler. The other path is transmitted to the second optical fiber to become the measuring light. The second motion module drives the reflector to reciprocate according to a set frequency and amplitude. The first beam splitting plate splits the sample light inside the measuring lens barrel to obtain transmitted light and reflected light.

[0010] In one embodiment, the beam splitting unit and the modulation unit are a beam splitting modulation unit, which includes a second coupler, a second optical fiber, a reference lens, a modulation mirror, and a first beam splitting plate. The second coupler splits the polychromatic light into two paths. One path of light is reflected by the modulation mirror to form reference light collected by the second coupler; the other path of light is transmitted to the second optical fiber to become measurement light. The modulation mirror can reciprocate according to a set frequency and amplitude. The first beam splitting plate splits the sample light outside the measurement lens barrel to obtain transmitted light and reflected light.

[0011] In one embodiment, a collimating lens is further disposed between the first beam-splitting plate and the second optical fiber, and a converging objective lens is further disposed between the first beam-splitting plate and the spectrometer.

[0012] In one embodiment, the filtering module uses at least one of a filter, a grating, and a prism for filtering.

[0013] In one embodiment, the wavelength values ​​of the four monochromatic lights, from largest to smallest, are λ. (j) , λ (j+1) , λ (j+2) and λ (j+3) j represents the wavelength number, and the wavelength values ​​of the synthesized wavelengths, from largest to smallest, are as follows: i is the i-th order synthesized wavelength, calculated using the following formula:

[0014]

[0015]

[0016]

[0017] The wavelength synthesis conditions must meet the following requirements:

[0018] n takes values ​​from i and i-1. For the synthesized wavelength Uncertainty, For the synthesized wavelength The uncertainty.

[0019] In one embodiment,

[0020] Compared with the prior art, the advantages of the present invention are: it achieves coarse measurement of high step surface shape based on spectral confocal technology, and achieves nanometer-level measurement accuracy based on multi-wavelength interferometric phase-shifting measurement technology. In this process, it combines a stepwise refinement algorithm to achieve a smooth transition from coarse measurement results to fine measurement results, thereby achieving nanometer-level measurement accuracy of high step 3D surface shape. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the multi-wavelength phase-shifting interferometry device in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a multi-wavelength phase-shifting interferometry device in another embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of a multi-wavelength phase-shifting interferometry device in another embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of a multi-wavelength phase-shifting interferometry device in another embodiment of the present invention. Detailed Implementation

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that these aspects can be practiced without these specific details.

[0031] like Figure 1 As shown in the figure, this application provides a multi-wavelength phase-shifting interferometry measurement device, including a light source 100, a measurement module, a filter module 106, a detection module 107, a spectrometer 108, and a data acquisition card 109.

[0032] Light source 100 is used to provide polychromatic light. The wavelength of the polychromatic light can be visible light, infrared light, etc. The polychromatic light contains at least four different wavelengths of monochromatic light. To ensure better measurement results, there can be specific differences between the wavelengths of the monochromatic light.

[0033] The measurement module is used to split the polychromatic light into a reference light and a measurement light; it transmits the measurement light to the object under test and splits the light reflected from the object to obtain transmitted light and reflected light; the transmitted light and the reference light interfere to obtain interference light. The measurement module has the dual function of simultaneously performing multi-wavelength interferometry and spectral confocal measurement. In this measurement module, the polychromatic light is first split into two independent optical paths. One measurement light illuminates the object under test and is reflected by the object. The light reflected by the object is the sample light, which is split into transmitted light and reflected light. The reflected light enters the spectrometer, and this optical path is the spectral confocal measurement optical path; the transmitted light interferes with the other reference light, and this optical path is the multi-wavelength interferometry measurement optical path.

[0034] A beam splitter unit can split a light beam in a certain proportion, with some light reflected and some light transmitted. The measurement module contains at least two beam splitter units or beam splitting optics. One beam splitter unit or beam splitting optics splits the polychromatic light into a reference light and a measurement light; another beam splitter unit or beam splitting optics changes the direction of the measurement light path, causing part of the measurement light to return to the multi-wavelength interferometric measurement path and the other part of the measurement light to return to the spectral confocal measurement path.

[0035] The filter module 106 is used to filter out monochromatic light of multiple wavelengths from the interference light. The filter module 106 can use at least one of the following: a filter, a grating, a prism, etc., to filter the interference light. The filter module 106 can obtain several specific wavelengths of monochromatic light (the number of wavelengths is greater than or equal to four) according to the needs of multi-wavelength interferometry. The interval between the wavelength values ​​can be adjusted as needed, which facilitates the subsequent step-by-step refinement processing of the multi-wavelength interferometry signal.

[0036] The detection module 107 is used to receive the filtered monochromatic light signal and generate a first photoelectric signal.

[0037] The spectrometer 108 is used to receive reflected light and generate a second photoelectric signal. The spectrometer 108 detects the confocal signal of the spectral field and collects the spectrum of light signals reflected back by the object at different times.

[0038] The data acquisition card 109 synchronously acquires signals from the detection module (obtaining multi-wavelength interference signals) and the spectrometer (obtaining spectral confocal signals), and performs subsequent displacement calculations. The data acquisition card 109 is used to synchronously acquire the first photoelectric signal and the second photoelectric signal, and perform displacement calculations to obtain measurement data of nanometer-level precision for the object under test.

[0039] The principle of spectral confocal ranging is determined based on the wavelength value returned by the measured object. Assuming the peak wavelength of the returned spectral signal obtained at time t is λ... (t) The peak wavelength of the spectral signal obtained at time t+1 is λ. (t+1)The change in morphology of the surface of the object being measured at this time is CL. (t+1) The specific relationships are as follows:

[0040]

[0041] In the above formula, k is a calibration coefficient that needs to be calibrated in advance.

[0042] In spectral confocal techniques, there is a simplified theoretical relationship between axial resolution and spectrometer resolution, assuming the spectrometer resolution is δλ, the effective spectral bandwidth of the light source is Δλ, the designed axial resolution is δd, and the designed axial chromatic difference is Δd. The specific relationship is shown in the following formula:

[0043]

[0044] To obtain a larger measurement range, conventional settings require increasing the axial chromatic difference Δd, which correspondingly reduces the spectral resolution δλ. However, since spectral confocalization is a coarse measurement method in this application, the requirements for the accuracy and resolution of this level of spectral confocalization measurement are not high, thereby reducing the manufacturing cost of the spectrometer in the confocal direction. This calculation can determine the fuzzy range of the 3D morphology of the measured object (such as large steps, steep morphologies, etc.) and achieve the measurement of the non-fuzzy range. Subsequently, this application uses multi-wavelength interferometry to achieve high-precision measurement of the 3D morphology of the measured object (such as large steps, steep morphologies, etc.).

[0045] The method employs at least four wavelengths, synthesizing at least three wavelength orders to facilitate large-scale, high-precision measurements. The number of wavelength orders synthesized equals the number of wavelengths minus 1. Taking x wavelengths as an example, the wavelength values ​​of the x monochromatic lights, from largest to smallest, are λ... (j) , λ (j+1) , λ (j+2) ... and λ (j+(x-1)) j represents the wavelength number, and the wavelength values ​​of the synthesized wavelengths, from largest to smallest, are as follows: i is the i-th order synthesized wavelength, calculated using the following formula:

[0046]

[0047] The wavelength synthesis conditions must meet the following requirements:

[0048] n takes values ​​from i, ..., i-(x-3), For the synthesized wavelength Uncertainty, For the synthesized wavelength The uncertainty.

[0049] In one embodiment, This facilitates the transition between stages of different synthesis wavelengths and avoids placing excessively high demands on any one stage.

[0050] The morphological change of the measured object obtained based on the spectral confocal technique is CL, and the synthesized wavelength values ​​from largest to smallest are as follows: From the formula for measuring the synthesized wavelength, it can be seen that when measuring distance L using the i-th order synthesized wavelength, the following equation holds:

[0051] In the above formula, L (i) Indicates the use of synthesized wavelength The measured value at time, m (i) ε represents the integer part of the phase of the synthesized wave. (i) The fractional part of the phase of the synthesized wave, where 0 < ε (i) <1.

[0052] Using the measured surface morphology change CL of the object as a coarse measurement result, and then transitioning to the first-order synthetic wavelength, the m value can be obtained. (i) , ε (i) It can be calculated from the measured data that INT[] represents the floor function, as detailed below:

[0053]

[0054] The distance calculated based on the first-order synthesized wavelength is as follows:

[0055]

[0056] The distance calculated based on the second-order synthesized wavelength is as follows:

[0057]

[0058]

[0059] The distance calculated based on the (x-1)th order synthesized wavelength is as follows:

[0060]

[0061]

[0062] Obtain L (i-(x-2)) Finally, it is determined by the wavelength λ. (j) The final calculation result is determined, and the accuracy of the final calculation result is determined by λ. (j) Decide:

[0063]

[0064]

[0065] L(i-(x-1)) This is the final measurement result after step-by-step refinement. Thus, the goal of achieving coarse measurement of the 3D morphology of the object under test using spectral confocal technology and fine measurement using multi-wavelength interferometry is achieved. The measurement accuracy of this device is related to the measurement accuracy of a single wavelength, and theoretically, it can achieve nanometer-level measurement accuracy.

[0066] The aforementioned device achieves coarse measurement of high-step surface shapes based on spectral confocal technology and nanometer-level measurement accuracy based on multi-wavelength interferometric phase-shifting measurement technology. During this process, a step-by-step refinement algorithm ensures a smooth transition from coarse to fine measurement results, thereby achieving nanometer-level measurement accuracy for the 3D surface shapes of high-step surfaces. Furthermore, the spectral confocal technology determines a large unambiguous measurement range, while the multi-wavelength interferometric phase-shifting measurement technology guarantees high measurement accuracy. Combining the large range of spectral confocal technology and the high precision of multi-wavelength interferometric measurement technology, an unambiguous measurement range greater than 2 mm can be achieved while maintaining nanometer-level measurement accuracy, thus enabling large unambiguous range and high-precision measurement of the 3D morphology of optical elements. Moreover, the device possesses dual functions of multi-wavelength interferometric measurement and spectral confocal measurement, ensuring that multi-wavelength interferometric signals and spectral confocal signals are acquired through a common optical path, resulting in strong system stability and anti-interference capabilities.

[0067] In one embodiment, such as Figure 1 As shown, the measurement module includes a beam splitting unit, a modulation unit, and a dispersion unit 103c.

[0068] A beam-splitting unit is used to split the polychromatic light according to a certain ratio. A portion of the polychromatic light is reflected as reference light, and a portion is transmitted as measurement light. In one embodiment, using... Figure 1 For example, the beam splitting unit includes a first optical fiber 102 and a first beam splitting plate 103a. The first optical fiber 102 splits the polychromatic light according to a certain ratio; a portion of the polychromatic light is reflected to become reference light, and a portion is transmitted to become measurement light. The sample light is split into transmitted light and reflected light by the first beam splitting plate 103a. One end of the first optical fiber 102 is fixed to the measuring lens barrel 103, and the first beam splitting plate 103a is fixed inside the measuring lens barrel 103 and tilted along the optical axis of the measurement light.

[0069] The modulation unit drives the reflecting surface of the reference light to reciprocate at a set frequency and amplitude. The modulation unit can be fixed to the measuring lens barrel 103, using the fiber optic end face as the reflecting surface, and fixed to the modulation module. The fiber optic end face vibrates synchronously with the modulation module. In another embodiment, the modulation unit may not be mounted on the measuring lens barrel 103, but rather integrated with the optical element containing the reflecting surface, driving the optical element to reciprocate at a set frequency and amplitude. The modulation unit can be a piezoelectric ceramic motor, a linear motor, etc. The modulation unit can be controlled by the data acquisition card 109.

[0070] The dispersion unit 103c is used to disperse the measurement light, so that the various monochromatic lights 104 in the measurement light are arranged according to their wavelengths along the optical axis; the focal points of light of different wavelengths are distributed at different axial positions, and the axial color difference produced by the dispersion ranges from a few millimeters to tens of millimeters. The dispersed measurement light 104 illuminates the object to be measured and is reflected by the object, and then collected by the dispersion unit as sample light.

[0071] The aforementioned device uses a modulation unit to determine the vibration frequency and amplitude of the reflecting surface, thereby modulating the reference optical signal.

[0072] In one embodiment, such as Figure 1 As shown, the beam splitting unit includes a first coupler 101, a first optical fiber 102, and a first beam splitting plate 103a that is fixedly connected to the measuring lens barrel and tilted on the measuring optical axis.

[0073] The first coupler 101 transmits polychromatic light from the light source 100 to the first optical fiber 102.

[0074] The first optical fiber 102 connects the first coupler 101 and the measuring lens barrel 103. The first optical fiber 102 has an optical fiber end face at one end near the measuring lens barrel 103. A portion of the polychromatic light is reflected at the optical fiber end face to become reference light, and a portion of the polychromatic light is transmitted at the optical fiber end face to become measuring light.

[0075] The modulation unit includes a first motion module 103b that is fixedly connected to the measuring lens barrel 103.

[0076] The first motion module 103b drives the fiber end face to reciprocate according to the set frequency and amplitude.

[0077] The first spectroscopic plate separates the sample light inside the measuring lens tube, obtaining transmitted light and reflected light.

[0078] In one embodiment, the multi-wavelength phase-shifting interferometry device further includes a computer 110, which receives data processed by the data acquisition card 109 and displays the results.

[0079] The working principle of the above device is as follows:

[0080] Light emitted from light source 100 reaches first optical fiber 102 via first coupler 101. The light passing through first optical fiber 102 is split into two parts: one part is reflected by the fiber end face as reference light, and the other part passes through the fiber end face as measurement light. The measurement light reaches measurement tube 103, then passes through first beam splitter 103a and dispersive objective lens 103c. The dispersed light 104 reaches the object under test 105. The light reflected by the object under test 105 is collected by dispersive objective lens 103c to obtain sample light. The sample light reaches first beam splitter 103a, and a portion of the sample light is transmitted through the dispersive objective lens 103c. The light is transmitted, and a portion of the sample light is reflected to form reflected light. The transmitted light interferes with the reference light at the end face of the first optical fiber 102. The interference signal reaches the filter module 106 after passing through the first coupler 101. After passing through this module, monochromatic light of different wavelengths can be obtained. The monochromatic light is received by the detection module 107 and the signal is transmitted to the data acquisition card 109. The reflected light is received by the spectrometer 108 and the signal is transmitted to the data acquisition card 109. The data acquisition card 109 can control the power of the light source 100 and the vibration frequency and amplitude of the first motion module 103b. The data acquisition card 109 uploads the processed data to the computer 110 for result display.

[0081] In one embodiment, such as Figure 2 As shown, the beam splitting unit includes a first coupler 101, a second optical fiber 113, a first beam splitting plate 103a inclined on the optical axis, and a second beam splitting plate 103f vertically disposed on the optical axis. The modulation unit includes a first motion module 103b.

[0082] The first motion module 103b and the second beam-splitting plate 103f are fixedly connected to the measuring lens barrel 103 and are both fixed on the measuring lens barrel 103. The second beam-splitting plate 103f is fixed inside the measuring lens barrel 103. The first motion module 103b can be fixed on the inner wall of the measuring lens barrel 103 or on the outer wall of the measuring lens barrel 103.

[0083] The first coupler 101 transmits the polychromatic light to the second optical fiber 113, the second optical fiber 113 transmits the polychromatic light to the first beam splitter 103a, the first beam splitter 103a transmits the polychromatic light to the second beam splitter 103f, a portion of the polychromatic light is reflected by the second beam splitter 103f to become reference light, and a portion of the polychromatic light is transmitted by the second beam splitter to become measurement light.

[0084] The first motion module 103b drives the second beam-splitting plate 103f to reciprocate according to a set frequency and amplitude. The first beam-splitting plate 103a splits the sample light outside the measuring lens tube to obtain transmitted light and reflected light.

[0085] In one embodiment, a collimating lens 103d is provided between the first beam-splitting plate and the second optical fiber, and a converging objective lens 103e is provided between the first beam-splitting plate and the spectrometer.

[0086] The working principle of the above device is as follows:

[0087] The light emitted by the light source 100 passes sequentially through the second optical fiber 113, the collimating lens 103d, and the first beam splitting plate 103a, and reaches the second beam splitting plate 103f.

[0088] The second beam-splitting plate 103f reflects part of the light as reference light for multi-wavelength interferometry and transmits part of the light as measurement light. The second beam-splitting plate 103f has no effect on the measurement results of spectral confocal measurement.

[0089] The modulation module 103b drives the second beam splitter 103f to reciprocate at a set frequency and amplitude (the data acquisition card 109 can control the frequency and amplitude of the modulation module 103b) to achieve the purpose of modulating the optical path of the reference light.

[0090] The first spectrophotometer plate 103a separates the sample light outside the measuring lens tube to obtain transmitted light and reflected light.

[0091] The transmitted light interferes with the reference light at the first coupler 101. The interference signal, after passing through the first coupler 101, reaches the filter module 106. After passing through this module, monochromatic light of different wavelengths can be obtained. The monochromatic light is received by the detection module 107 and the signal is transmitted to the data acquisition card 109. The reflected light is received by the spectrometer 108 and the signal is transmitted to the data acquisition card 109. The data acquisition card 109 can control the power of the light source 100 and also control the vibration frequency and amplitude of the first motion module 103b. The data acquisition card 109 uploads the processed data to the computer 110 for result display.

[0092] In one embodiment, such as Figure 3 As shown, the beam splitting unit includes a second coupler 114, a second optical fiber 113, a reflector 112a, and a first beam splitting plate 103a that is fixedly connected to the measuring lens barrel and tilted on the optical axis.

[0093] In one embodiment, the beam splitting unit further includes a reference head 111, which collimates the light in the optical fiber, enabling the light to propagate parallel in space. The reference head 111 collimates a portion of the light from the second coupler 114. The collimated light is reflected by the mirror 112a, re-enters the reference head 111, and then returns to the second coupler 114.

[0094] The modulation unit includes a second motion module 112b.

[0095] The second coupler 114 splits the polychromatic light into two paths. One path is reflected by the mirror 112a to form the reference light collected by the second coupler; the other path is transmitted to the second optical fiber 113 to become the measurement light.

[0096] The second motion module 112b drives the reflector 112a to reciprocate according to the set frequency and amplitude.

[0097] The first spectroscopic plate 103a splits the sample light inside the measuring lens tube to obtain transmitted light and reflected light.

[0098] The working principle of the above device is as follows:

[0099] The light emitted by the light source 100 passes through the second coupler 114. Part of the light travels through the second optical fiber 113 to the measuring lens tube 103, while another part travels through the reference head 111 to the reflecting mirror 112a. The light reflected by the reflecting mirror 112a serves as the reference light. This reference light interferes with the sample light reflected from the object under test 105 at the second coupler 114.

[0100] The reflector 112a reciprocates with a set frequency and amplitude under the drive of the second motion module 112b, thereby modulating the optical path of the reference light. The second motion module 112b can be a piezoelectric ceramic motor, a linear motor, or the like.

[0101] The measuring light reaches the measuring tube 103, then passes through the first beam-splitting plate 103a and the dispersive objective lens 103c. The dispersed light 104 reaches the object under test 105. The light reflected by the object under test 105 is collected by the dispersive objective lens 103c to obtain the sample light. The sample light reaches the first beam-splitting plate 103a, where part of the sample light is transmitted to form transmitted light, and part of the sample light is reflected to form reflected light. The transmitted light interferes with the reference light at the second coupler 114, and the interference signal reaches the filter module 106. After passing through this module, monochromatic light of different wavelengths can be obtained. The monochromatic light is received by the detection module 107 and the signal is transmitted to the data acquisition card 109. The reflected light is collected by the converging objective lens 103e and received by the spectrometer 108, and the signal is transmitted to the data acquisition card 109. The data acquisition card 109 can control the power of the light source 100 and also control the vibration frequency and amplitude of the first motion module 103b. The data acquisition card 109 uploads the processed data to the computer 110 for result display.

[0102] In one embodiment, such as Figure 4 As shown, the beam splitting unit and the modulation unit are a beam splitting modulation unit, which includes a second coupler 114, a second optical fiber 113, a reference lens 111, a modulation mirror 112, and a first beam splitting plate 103a.

[0103] The second coupler 114 splits the polychromatic light into two paths. One path is reflected by the modulation mirror 112 to form the reference light collected by the second coupler 114; the other path is transmitted to the second optical fiber 113 to become the measurement light.

[0104] The modulation mirror 112 can reciprocate according to a set frequency and amplitude. The modulation mirror 112 includes a mirror and a motion unit.

[0105] The first spectroscopic plate 103a separates the sample light outside the measuring tube 103 to obtain transmitted light and reflected light.

[0106] The working principle of the above device is as follows:

[0107] The light emitted by the light source 100 passes through the second coupler 114. Part of the light travels through the second optical fiber 113 to the measuring lens tube 103, while another part travels through the reference head 111 to the modulation mirror 112. The light reflected by the modulation mirror 112 serves as the reference light. This reference light interferes with the sample light reflected from the object under test 105 at the second coupler 114.

[0108] The light emitted by the light source 100 passes sequentially through the second optical fiber 113, the collimating lens 103d, and the first beam-splitting plate 103a, and reaches the dispersive objective lens 103c. The dispersed light 104 reaches the object under test 105; the light reflected by the object under test 105 is collected by the dispersive objective lens 103c to obtain the sample light.

[0109] The first spectrophotometer plate 103a separates the sample light outside the measuring microscope tube, resulting in transmitted light and reflected light. When the sample light reaches the first spectrophotometer plate 103a, part of the sample light is transmitted and part of the sample light is reflected.

[0110] The transmitted light interferes with the reference light at the second coupler 114. The interference signal reaches the filter module 106, and after passing through this module, monochromatic light of different wavelengths can be obtained. The monochromatic light is received by the detection module 107, and the signal is transmitted to the data acquisition card 109. The reflected light is collected by the converging objective lens 103e and received by the spectrometer 108, and the signal is transmitted to the data acquisition card 109. The data acquisition card 109 can control the power of the light source 100 and also control the vibration frequency and amplitude of the first motion module 103b. The data acquisition card 109 uploads the processed data to the computer 110 for result display.

[0111] In one embodiment, the wavelength values ​​of the four monochromatic lights, from largest to smallest, are λ... (j) , λ (j+1) , λ (j+2) and λ (j+3)j represents the wavelength number, and the wavelength values ​​of the synthesized wavelengths, from largest to smallest, are as follows: i is the i-th order synthesized wavelength, calculated using the following formula:

[0112]

[0113]

[0114]

[0115] The wavelength synthesis conditions must meet the following requirements:

[0116] n takes values ​​from i and i-1. For the synthesized wavelength Uncertainty, For the synthesized wavelength The uncertainty.

[0117] The morphological change of the measured object obtained based on the spectral confocal technique is CL. Four composite wavelengths are used, and the composite wavelength values ​​from largest to smallest are: From the formula for measuring the synthesized wavelength, it can be seen that when measuring distance L using the i-th order synthesized wavelength, the following equation holds:

[0118]

[0119] In the above formula, L (i) Indicates the use of synthesized wavelength The measured value at time, m (i) ε represents the integer part of the phase of the synthesized wave. (i) The fractional part of the phase of the synthesized wave, where 0 < ε (i) <1.

[0120] Using the measured surface morphology change CL of the object as a coarse measurement result, and then transitioning to the first-order synthetic wavelength, the m value can be obtained. (i) , ε (i) It can be calculated from the measured data that INT[] represents the floor function, as detailed below:

[0121]

[0122] The distance calculated based on the first-order synthesized wavelength is as follows:

[0123]

[0124] The distance calculated based on the second-order synthesized wavelength is as follows:

[0125]

[0126]

[0127] The distance calculated based on the third-order synthesized wavelength is as follows:

[0128]

[0129]

[0130] Obtain L (i-2) Finally, it is determined by the wavelength λ. (j) The final calculation result is determined, and the accuracy of the final calculation result is determined by λ. (j) Decide:

[0131]

[0132]

[0133] L (i-3) This is the final measurement result after step-by-step refinement, achieving the goal of coarse measurement using spectral confocal technology and fine measurement using multi-wavelength interferometry. The measurement accuracy of this device is related to the measurement accuracy of a single wavelength, and theoretically, it can achieve nanometer-level measurement accuracy.

[0134] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A multi-wavelength phase-shifting interferometric measurement device, characterized in that, include: A light source for providing polychromatic light, said polychromatic light comprising at least four different wavelengths of monochromatic light; The measurement module is used to split the polychromatic light into a reference light and a measurement light; transmit the measurement light to the object under test, and split the light reflected by the object under test to obtain transmitted light and reflected light; the transmitted light and the reference light interfere to obtain interference light, wherein the measurement module is configured to simultaneously form a multi-wavelength interferometric measurement optical path and a spectral confocal measurement optical path, the transmitted light enters the multi-wavelength interferometric measurement optical path, and the reflected light enters the spectral confocal measurement optical path; A filter module is used to filter out monochromatic light of multiple wavelengths from the interference light; The detection module is used to receive the filtered monochromatic light signal and generate the first photoelectric signal; A spectrometer is used to receive the reflected light and generate a second photoelectric signal. Based on the principle of spectral confocal ranging, the spectrometer obtains the morphological change of the surface of the object under test based on the second photoelectric signal, thereby achieving a large-scale coarse measurement. A data acquisition card is used to synchronously acquire the first photoelectric signal and the second photoelectric signal, and to complete displacement calculation to obtain measurement data of the test object with nanometer-level precision. The data acquisition card is configured to: use the morphological change obtained by the spectrometer as the coarse measurement result, and obtain the final measurement result through a step-by-step refinement algorithm based on the interference phase information of at least four wavelengths contained in the first photoelectric signal. The progressive refinement algorithm is based on multi-wavelength synthesis and phase unwrapping. It uses the wavelength values ​​of the at least four monochromatic lights to generate at least three levels of synthesized wavelengths, and progressively refines the coarse measurement results by utilizing the constraint conditions between adjacent synthesized wavelengths.

2. The multi-wavelength phase-shifting interferometric measurement device according to claim 1, characterized in that, The measurement module includes: The beam splitting unit is used to split the polychromatic light according to a certain ratio. A portion of the polychromatic light is reflected as reference light, and a portion of the polychromatic light is transmitted as measurement light. The modulation unit is used to drive the reflective surface that reflects the reference light to reciprocate according to a set frequency and amplitude; The dispersion unit is used to disperse the measurement light so that the various monochromatic lights in the measurement light are arranged in accordance with the wavelength along the optical axis; the dispersed measurement light illuminates the test object and is reflected by the test object, and is then collected by the dispersion unit into sample light; the sample light is divided into transmitted light and reflected light by the beam splitting unit.

3. The multi-wavelength phase-shifting interferometric measurement device according to claim 2, characterized in that, The beam splitting unit includes a first coupler, a first optical fiber, and a first beam splitting plate that is fixedly connected to the measuring lens barrel and inclinedly disposed on the optical axis of the measuring light. The first coupler transmits the polychromatic light to the first optical fiber. The first optical fiber connects the first coupler and the measuring lens barrel. The first optical fiber has an end face near the measuring lens barrel. A portion of the polychromatic light is reflected at the end face to become reference light, and a portion of the polychromatic light is transmitted through the end face to become measuring light. The modulation unit includes a first motion module that is fixedly connected to the measuring lens barrel. The first motion module drives the optical fiber end face to reciprocate according to a set frequency and amplitude. The first spectrophotometer plate splits the sample light inside the measuring lens barrel to obtain transmitted light and reflected light.

4. The multi-wavelength phase-shifting interferometry measuring device according to claim 2, characterized in that, The beam splitting unit includes a first coupler, a second optical fiber, a first beam splitting plate inclined on the optical axis, and a second beam splitting plate perpendicular to the optical axis. The modulation unit includes a first motion module. The first motion module and the second beam-splitting plate are fixedly connected to the measuring lens barrel. The first coupler transmits the polychromatic light to the second optical fiber. The first beam-splitting plate transmits the polychromatic light to the second beam-splitting plate. A portion of the polychromatic light is reflected by the second beam-splitting plate to become reference light, and a portion of the polychromatic light is transmitted through the second beam-splitting plate to become measurement light. The first motion module drives the second beam-splitting plate to reciprocate according to a set frequency and amplitude; The first beam splitter plate separates the sample light outside the measuring lens tube to obtain transmitted light and reflected light.

5. The multi-wavelength phase-shifting interferometric measurement device according to claim 2, characterized in that, The beam splitting unit includes a second coupler, a second optical fiber, a reflector, and a first beam splitting plate that is fixedly connected to the measuring lens barrel and inclinedly arranged on the optical axis. The modulation unit includes a second motion module. The second coupler splits the polychromatic light into two paths. One path is reflected by the mirror to form the reference light collected by the second coupler; the other path is transmitted to the second optical fiber to become the measurement light. The second motion module drives the reflector to reciprocate according to a set frequency and amplitude; The first spectrophotometer plate splits the sample light inside the measuring lens barrel to obtain transmitted light and reflected light.

6. The multi-wavelength phase-shifting interferometric measurement device according to claim 2, characterized in that, The beam splitting unit and the modulation unit constitute a beam splitting modulation unit. The beam splitting and modulation unit includes a second coupler, a second optical fiber, a reference lens, a modulation mirror, and a first beam splitting plate. The second coupler splits the polychromatic light into two paths. One path is reflected by the modulation mirror to form the reference light collected by the second coupler; the other path is transmitted to the second optical fiber to become the measurement light. The modulation mirror can reciprocate according to a set frequency and amplitude; The first spectrophotometer plate separates the sample light outside the measuring lens tube to obtain transmitted light and reflected light.

7. The multi-wavelength phase-shifting interferometric measurement device according to claim 4 or 6, characterized in that, A collimating lens is also provided between the first beam-splitting plate and the second optical fiber, and a converging objective lens is also provided between the first beam-splitting plate and the spectrometer.

8. The multi-wavelength phase-shifting interferometric measurement device according to claim 1, characterized in that, The filtering module uses at least one of a filter, a grating, and a prism for filtering.

9. The multi-wavelength phase-shifting interferometric measurement device according to claim 1, characterized in that, The wavelength values ​​of the four monochromatic lights, from largest to smallest, are λ （j） , λ （j+1） , λ （j+2） and λ （j+3） , j The wavelengths are numbered, and the wavelength values ​​of the synthesized wavelengths, from largest to smallest, are as follows: , , , i For the first i The formula for calculating the synthesized wavelength is as follows: The wavelength synthesis conditions must meet the following requirements: n takes values ​​from i and i-1. For the synthesized wavelength Uncertainty, For the synthesized wavelength The uncertainty.

10. The multi-wavelength phase-shifting interferometric measurement device according to claim 9, characterized in that, 。

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