A digital holographic microscopy synchronous measurement method and device

Abstract

The present invention discloses a digital holographic microscopy synchronous measurement method and device, which relates to the field of optical interference measurement. It is used to solve the problems of complex measuring devices, complex operating modes and poor system stability when measuring objects using existing digital holography. It includes: a light source part, which is used to provide a plurality of coupled lights of different wavelengths to a spectroscopic prism; a spectroscopic prism, which is used to transmit and reflect the coupled light from the light source part, and the first reflected light is reflected by a first microscope objective lens and a sample to be measured to form a second reflected light; a tube lens, which is used to converge the second transmitted light and the fourth reflected light, so that the second transmitted light and the fourth reflected light interfere with each other on the camera surface; and a camera, which is used to collect the interference pattern formed by the second transmitted light and the fourth reflected light.

Description

Technical Field

[0001] The present invention relates to the field of optical interference measurement, and more specifically to a digital holographic microscopy synchronous measurement method and device. Background Art

[0002] Digital holography has the characteristics of non-contact, non-scanning, and high precision. It is widely used in biomedicine, surface morphology analysis, optical micromachining and other fields. General digital holographic measurement systems mostly use single-wavelength digital holography, but single-wavelength digital holography has the following shortcomings: in non-continuous surface morphology measurement, the measurable step height range is limited to half of the wavelength, and the effect is poor when measuring complex morphology, and the deformation measurement range is small; dual-wavelength digital holography is based on a single-wavelength phase map, and reconstructs the holographic image and obtains three-dimensional information through synthesis. Therefore, in order to overcome the problem of poor reproduction ability of single-wavelength digital holography for objects with complex morphology and high roughness surfaces and expand the measurement range of digital holography, multi-wavelength digital holography technology is proposed. On the basis of retaining the advantages of single-wavelength digital holography, the measurement range can be expanded from a few microns to tens of microns or even to the millimeter level, and objects with high roughness and morphology containing steps can be accurately measured.

[0003] The patented multi-wavelength adaptive digital holographic imaging system and method discloses a method that adopts a Mach Zehnder optical path configuration, uses a monochrome camera to collect holograms in steps and multiple times, and realizes multi-wavelength digital holographic imaging detection of the sample to be tested through wave-light correlation identification. However, the system requires the distributed collection of multiple holograms, which has the problems of poor stability and long time consumption; the patented multi-mode digital holographic microscopic quantitative phase measurement device discloses a multi-mode digital holographic microscopic quantitative phase measurement device, which has high comprehensive adaptability by manually switching the transmission / reflection mode and the single-wavelength measurement / dual-wavelength measurement mode. Since the measuring device can only manually switch the single-wavelength measurement / dual-wavelength measurement mode, it cannot be performed simultaneously, and the measuring device simply assembles the two systems together, which cannot improve the measurement accuracy and adaptability.

[0004] The current multi-wavelength digital holographic technology has a complicated data processing process, troublesome switching between multiple modes, and a complex measuring device with poor anti-interference performance. Furthermore, when a monochrome camera is used to collect holograms, it can only be achieved by recording the holograms in steps, and it is impossible to simultaneously record multi-wavelength digital holograms to achieve fast and accurate measurement of three-dimensional structures. Summary of the invention

[0005] The embodiment of the present invention provides a digital holographic microscopic synchronous measurement method and device, which are used to solve the problems of complex measuring device, complex operation mode and poor system stability when measuring objects using existing digital holography.

[0006] The embodiment of the present invention provides a digital holographic microscopy synchronous measurement device, comprising:

[0007] A light source part, which is used to provide a plurality of coupling lights of different wavelengths to the beam splitter prism;

[0008] A beam splitter prism is used to transmit and reflect the coupled light from the light source part to form a first transmitted light and a first reflected light; the first reflected light is reflected by the first microscope objective lens and the sample to be measured to form a second reflected light, and the second reflected light is passed through the beam splitter prism to form a second transmitted light; the first transmitted light is passed through the second microscope objective lens and the plane reflector to form a third reflected light, and the third reflected light is reflected by the beam splitter prism to form a fourth reflected light;

[0009] a tube lens, used for converging the second transmitted light and the fourth reflected light, so that the second transmitted light and the fourth reflected light generate interference on a camera surface;

[0010] A camera is used to collect an interference pattern formed by the second transmitted light and the fourth reflected light.

[0011] Preferably, the light source part includes a red fiber laser, a green fiber laser, a blue fiber laser, a fiber coupler, a clamp and an achromatic converging lens;

[0012] The optical fiber coupler is a multimode optical fiber; the wavelength of the optical fiber coupler matches the wavelength of the red optical fiber laser; the wavelength of the optical fiber coupler matches the wavelength of the green optical fiber laser; the wavelength of the optical fiber coupler matches the wavelength of the blue optical fiber laser;

[0013] The distance between the fixture and the achromatic converging lens is smaller than the focal length of the achromatic converging lens.

[0014] Preferably, the distance between the achromatic converging lens included in the light source part and the beam splitting prism is smaller than the focal length of the achromatic converging lens.

[0015] Preferably, the parameters of the first microscope objective lens and the second microscope objective lens are the same;

[0016] The distance between the first microscope objective lens and the sample to be measured is smaller than the focal length of the first microscope objective lens, and the spot diameter of the first reflected light entering the surface of the sample to be measured is larger than 1 mm.

[0017] Preferably, the distance between the beam splitter prism and the sample to be measured is equal to the distance between the beam splitter prism and the plane reflector.

[0018] The embodiment of the present invention provides a digital holographic microscopy synchronous measurement method, comprising:

[0019] An interference pattern matching the sample to be measured is obtained by a digital holographic microscopy synchronous measurement device, and data processing is performed on the interference pattern to obtain a plurality of single-wavelength digital holograms, and a single-wavelength phase pattern matching the plurality of single-wavelength digital holograms and a first height of the sample to be measured corresponding to each single wavelength are obtained according to a digital holographic angular spectrum phase reconstruction algorithm;

[0020] Combine multiple single wavelengths according to the synthetic wavelength formula to obtain multiple synthetic wavelengths, obtain a wrapped phase difference according to the wrapped phase of the single wavelength corresponding to each of the synthetic wavelengths, perform dual-wavelength phase reconstruction according to the phase difference corresponding to each of the single wavelength phase diagrams to obtain a true phase difference, and obtain a second height of the sample to be tested corresponding to the multiple synthetic wavelengths according to the second height formula;

[0021] The first height of the sample to be tested and the second height of the sample to be tested are compared in a combination manner, the wavelength corresponding to the comparison result with the highest number of times is determined as the final wavelength, and the final height of the sample to be tested is determined according to the final wavelength.

[0022] Preferably, the method of obtaining a single-wavelength phase map matching a plurality of single-wavelength digital holograms and a first height of the sample to be measured corresponding to each single wavelength according to the digital holographic angular spectrum phase reconstruction algorithm specifically includes:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] in, Representing the light wave of the reproduced object The angular spectrum expression after irradiating the digital hologram is: Represents the reconstructed object light wave, Express Perform Fourier transform, Representing the light wave of the reproduced object illuminating the acquired single-wavelength digital hologram; represents the angular spectrum transfer function, The expression of the angular spectrum of the light wave of the reconstructed object on the reconstruction plane; The complex amplitude expression of the reconstructed object light wave in the spatial domain; represents the phase distribution of the object light wavelength, Indicates taking The imaginary part of , express The real part of Indicates the first height of the sample to be tested, Indicates The true phase of a single wavelength, Represents the distance from the hologram to the reconstruction plane.

[0029] Preferably, the first height of the sample to be tested and the second height of the sample to be tested are compared in a combination manner, and the comparison result is determined according to the following formula:

[0030]

[0031] in, They represent the height of the samples to be tested at the same position. , Is a positive integer.

[0032] Preferably, the synthetic wavelength formula is as follows:

[0033]

[0034] The subtraction of the single wavelength wrapping phase to obtain the wrapping phase difference is as follows:

[0035]

[0036]

[0037] The second height formula is as follows:

[0038]

[0039] in, Indicates A single wavelength, Indicates A single wavelength, Indicated by and The synthesized wavelength, Indicates A single wavelength wrapping phase, , Indicates The true phase of a single wavelength, Indicates A single wavelength wrapping phase, , Indicates The true phase of a single wavelength, Indicates the second height of the sample to be tested, Indicates the package phase difference, represents the actual phase difference, and is an integer.

[0040] An embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes any one of the digital holographic microscopy synchronous measurement methods described above.

[0041] The embodiment of the present invention provides a digital holographic microscopy synchronous measurement method and device, the device comprising: a light source part, which is used to provide a plurality of coupled lights of different wavelengths to a beam splitter prism; a beam splitter prism, which is used to transmit and reflect the coupled light from the light source part to form a first transmitted light and a first reflected light; the first reflected light is reflected by a first microscope objective lens and a sample to be measured to form a second reflected light, and the second reflected light is passed through the beam splitter prism to form a second transmitted light; the first transmitted light is passed through a second microscope objective lens and a plane reflector to form a third reflected light, and the third reflected light is reflected by the beam splitter prism to form a fourth reflected light; a tube lens, which is used to converge the second transmitted light and the fourth reflected light so that the second transmitted light and the fourth reflected light generate interference on the camera surface; and a camera, which is used to collect the interference pattern formed by the second transmitted light and the fourth reflected light. The device uses a fiber coupler to couple three beams of light of different wavelengths together and emit them. After a Twyman-Green optical path configuration, the camera can synchronously record a multi-wavelength digital hologram in a single frame, simplifying the multi-wavelength and multi-range operation mode. Furthermore, based on the device, six measurement ranges can be obtained using a digital holographic interference pattern. Six wavelengths can be obtained simultaneously in the measurement of the sample to be measured for phase reconstruction to obtain six phase maps. Through a self-comparison phase selection algorithm, a high-precision final phase map is obtained after phase compensation, which improves the measurement efficiency and reduces the measurement error. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 A schematic diagram of the structure of a digital holographic microscopy synchronous measurement device provided by an embodiment of the present invention;

[0044] Figure 2 A schematic diagram of a height cross section of a sample to be tested provided in an embodiment of the present invention;

[0045] Figure 3The single wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0046] Figure 4 The single wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0047] Figure 5 The single wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0048] Figure 6 The synthetic wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0049] Figure 7 The synthetic wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0050] Figure 8 The synthetic wavelength provided by the embodiment of the present invention Schematic diagram of the height cross section obtained by measurement;

[0051] Fig. 9 A schematic diagram of a final height cross section of a sample to be tested provided in an embodiment of the present invention;

[0052] Among them, 1-red fiber laser 1, 2-green fiber laser 2, 3-blue fiber laser 3, 4-fiber coupler 4, 5-clamp 5, 6-achromatic converging lens 6, 7-beam splitter prism 7, 8-first microscope objective lens 8, 9-sample to be tested 9, 10-tube lens 10, 11-second microscope objective lens 11, 12-reflector 12, 13-camera 13, 14-computer 14. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Figure 1 A schematic diagram of the structure of a digital holographic microscopy synchronous measurement device provided by an embodiment of the present invention; Figure 1 As shown, the digital holographic microscopic synchronous measurement device provided by the embodiment of the present invention mainly includes: a light source part, a beam splitter prism 7, a tube lens 10 and a camera 13.

[0055] Specifically, the light source part is used to provide a plurality of coupled lights of different wavelengths to the beam splitter prism 7. In the embodiment of the present invention, the light source part includes a plurality of red fiber lasers 1, green fiber lasers 2, blue fiber lasers 3, fiber couplers 4, fixtures 5, achromatic converging lenses 6, etc., which can provide different wavelengths. Among them, a plurality of fiber lasers of different wavelengths are connected to the fiber coupler, and coupled light is formed after being coupled in the fiber coupler at a ratio of 1:1:1. The coupled light is emitted from the fixture in a divergent state, and the coupled light is converged in front of the beam splitter prism after passing through the achromatic converging lens.

[0056] In this embodiment, the beam splitter prism is used to partially transmit and partially reflect the coupled light from the light source part, and then form a first transmitted light and a first reflected light. Specifically, the first reflected light passing through the beam splitter prism 7 is irradiated to the surface of the sample 9 to be tested through the first microscope objective lens 8, and is reflected by the surface of the sample 9 to be tested to form a second reflected light. Further, the second reflected light passes through the beam splitter prism 7 to form a second transmitted light; accordingly, the first transmitted light is irradiated to the surface of the plane reflector 12 through the second microscope objective lens 11, and is reflected by the plane reflector 12 to form a third reflected light. The third reflected light is reflected again by the beam splitter prism 7 to form a fourth reflected light.

[0057] The tube lens 10 located in the light emitting direction of the dichroic prism 7 is used to converge the second transmitted light and the fourth reflected light from the dichroic prism 7 . The converged second transmitted light and the fourth reflected light generate interference on the surface of the camera 13 .

[0058] In the embodiment of the present invention, the camera 13 is used to collect the interference pattern formed by the second transmitted light and the fourth reflected light, and the camera 13 is electrically connected to the computer 14. In practical applications, the second transmitted light from the beam splitter prism carries the surface information of the sample to be tested, and the fourth reflected light from the beam splitter prism can be used as a reference light to interfere with the second transmitted light to form an interference pattern, and the camera can record a color digital holographic interference pattern in a single frame.

[0059] For example, in this embodiment, the wavelengths of the red fiber laser 1, the green fiber laser 2, and the blue fiber laser 3 are in the red, green, and blue spectral ranges, respectively, that is, the wavelengths of the three lasers can be respectively ,in, is the red spectrum, is the green spectrum, The blue spectrum.

[0060] Furthermore, the fiber coupler 4 is a multimode optical fiber, and the wavelength of the fiber coupler 4 matches the wavelength of the red fiber laser 1, the wavelength of the green fiber laser 2, and the wavelength of the blue fiber laser 3 respectively; the distance between the clamp 5 and the achromatic converging lens 6 is less than the focal length of the achromatic converging lens 6.

[0061] Further, the distance between the achromatic converging lens 6 and the beam splitting prism 7 included in the light source part is smaller than the focal length of the achromatic converging lens 6 .

[0062] For example, in this embodiment, the parameters of the first microscope objective lens 8 and the second microscope objective lens 11 are the same; the distance between the first microscope objective lens 8 and the sample 9 to be measured is less than the focal length of the first microscope objective lens 8, and the spot diameter of the first reflected light entering the surface of the sample 9 to be measured is greater than 1 mm. Furthermore, the distance between the sample 9 to be measured and the beam splitter prism 7 is equal to the distance between the plane reflector 12 and the beam splitter prism 7. Based on the above settings, it can be ensured that the state of the second transmitted light carrying the surface information of the sample to be measured is the same as the state of the fourth reflected light.

[0063] Figure 2 A schematic flow chart of a digital holographic microscopy synchronous measurement method provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, the method comprises the following steps:

[0064] Step 101, obtaining an interference pattern through a digital holographic microscopy synchronous measurement device, performing data processing on the interference pattern to obtain a plurality of single-wavelength digital holograms corresponding to the single wavelengths, and obtaining a single-wavelength phase map and a first height of a sample to be measured corresponding to the plurality of single wavelengths according to a digital holographic angular spectrum phase reconstruction algorithm;

[0065] Step 102, combining multiple single wavelengths according to a synthetic wavelength formula to obtain multiple synthetic wavelengths, obtaining a wrapped phase difference according to the wrapped phase of the single wavelength corresponding to each of the synthetic wavelengths, performing dual-wavelength phase reconstruction according to the phase difference corresponding to each of the single wavelength phase diagrams to obtain a true phase difference, and obtaining a second height of the sample to be measured corresponding to the multiple synthetic wavelengths according to a second height formula;

[0066] Step 103, the first height of the sample to be tested and the second height of the sample to be tested are compared in combination, the wavelength corresponding to the comparison result with the highest number of times is determined as the final wavelength, and the final height of the sample to be tested is determined according to the final wavelength.

[0067] In step 101, a plurality of single-wavelength interference patterns are obtained by a digital holographic microscopic synchronous measurement device. Further, by using a filter in a camera included in the digital holographic microscopic synchronous measurement device, holograms of different wavelengths in a color digital hologram can be separated to obtain a single-wavelength digital hologram corresponding to each single wavelength. In this embodiment, the digital holographic microscopic synchronous measurement device includes three fiber lasers of different wavelengths, so three single-wavelength digital holograms are obtained accordingly. Furthermore, by using a digital holographic angular spectrum phase reconstruction algorithm, phase patterns corresponding to the three wavelengths and a first height of the sample to be measured corresponding to each single wavelength can be obtained.

[0068] Specifically, the digital holographic reconstruction process is achieved by computer simulation of the diffraction propagation of light waves in the traditional optical holographic reconstruction process. According to the angular spectrum theory, after the single-wavelength digital hologram corresponding to the single wavelength is illuminated by the reconstructed object light wave, its angular spectrum expression can be obtained by Fourier transform, as shown in formula (1):

[0069] (1)

[0070] in, Representing the light wave of the reproduced object The angular spectrum expression after irradiating a single-wavelength digital hologram is: Represents the reconstructed object light wave, Express Perform Fourier transform, Representing the light wave of the reproduced object Illuminate the acquired single-wavelength digital hologram.

[0071] Furthermore, the distance between the hologram and the reconstruction plane is determined, and the light field distribution of the reconstructed image is obtained on the reconstruction plane. At this time, the angular spectrum expression of the reconstructed object light wave is obtained as shown in formula (2):

[0072] (2)

[0073] in, represents the angular spectrum transfer function, An expression representing the angular spectrum of the reconstructed object light wave on the reconstruction plane.

[0074] Furthermore, by performing an inverse Fourier transform on formula (2), we can obtain the complex amplitude expression of the reconstructed object light wave in the spatial domain, as shown in formula (3):

[0075] (3)

[0076] in, Represents the complex amplitude expression of the reconstructed object light wave in the spatial domain, represents the inverse Fourier transform.

[0077] Furthermore, the angular spectrum theory is used to obtain the complex amplitude expression of the reconstructed object light wave in the spatial domain: After that, the phase distribution of the reconstructed light wave can be calculated, that is, the phase distribution of each single wavelength can be obtained. The corresponding phase diagram , as shown in formula (4):

[0078] (4)

[0079] in, represents the phase distribution of the reconstructed object light wave, Indicates taking The imaginary part of , express The real part of .

[0080] In the embodiment of the present invention, after the phase diagram corresponding to each single wavelength is obtained, the first height of the sample to be tested corresponding to each wavelength is obtained by phase unwrapping and de-tilting, wherein the first height of the sample to be tested can be determined by the following formula:

[0081] (5)

[0082] in, Indicates the first height of the sample to be tested, Indicates The true phase of a single wavelength, Represents the distance from the hologram to the reconstruction plane.

[0083] In step 102, multiple single wavelengths are combined with each other according to the following synthetic wavelength formula to obtain multiple synthetic wavelengths, wherein the synthetic wavelength formula is as follows:

[0084] (6)

[0085] in, Indicates A single wavelength, Indicates A single wavelength, Indicated by and Synthesized synthetic wavelength.

[0086] Furthermore, two wrapping phases can be obtained according to the phases of multiple single wavelengths in the input synthetic wavelength formula: , and then the package phase difference can be obtained according to the following formula:

[0087] (7)

[0088] in, Indicates the package phase difference, Indicates A single wavelength wrapping phase, , Indicates The true phase of a single wavelength, Indicates A single wavelength wrapping phase, , Indicates The true phase of a single wavelength.

[0089] Furthermore, the real phase difference can be obtained by performing dual-wavelength phase reconstruction according to the phase difference corresponding to each single-wavelength phase image, and then the second height of the sample to be tested corresponding to multiple synthetic wavelengths can be obtained according to the second height formula, wherein the real phase difference and the second height formula are as follows:

[0090] (8)

[0091] (9)

[0092] in, represents the actual phase difference, and is an integer, Indicates the package phase difference, Indicates the second height of the sample to be tested, Indicated by and Synthesized synthetic wavelength.

[0093] In step 103, after obtaining the first height of the sample to be tested and the second height of the sample to be tested, the first height of the sample to be tested and the second height of the sample to be tested are compared and processed in a combination manner, that is, they are processed according to the following formula (10), and then the wavelength corresponding to the comparison result with the highest number of times is determined as the final wavelength. For example, if there are 3 single wavelengths, 3 first heights of the sample to be tested and 3 second heights of the sample to be tested will be generated accordingly. After comparing the above 3 first heights of the sample to be tested and the 3 second heights of the sample to be tested in a combination manner, 15 comparison results can be obtained.

[0094] In an embodiment of the present invention, after the comparison results are obtained, the comparison results obtained by formula (10) can be screened according to the method provided by the following formula (10), and the wavelength corresponding to the comparison result with the highest number of times is determined as the final wavelength according to the screening results, and then the measurement result based on the final wavelength is determined as the final height of the sample to be measured.

[0095] (10)

[0096] in, They represent the height of the samples to be tested at the same position. , Is a positive integer.

[0097] The following combination Figure 2~Figure 9 Taking this as an example, the specific process of determining the final height of the sample to be tested is introduced: Figure 2As shown, a height cross-sectional diagram of a sample to be tested is provided in an embodiment of the present invention. In this embodiment, it is necessary to determine the final wavelength based on the height of the first step, and then determine the final height of the sample to be tested based on the final wavelength.

[0098] Specifically, the digital holographic microscopic synchronous measurement device provided by the embodiment of the present invention is used to measure Figure 2 The provided sample to be tested is measured to obtain an interference pattern. Since the light source part in the digital holographic microscopy synchronous measurement device includes a red fiber laser, a green fiber laser and a blue fiber laser, according to the method provided in step 101 and step 102, the first heights of three samples to be tested and the second heights of three samples to be tested can be obtained, which are: single wavelength Corresponding to the first height of the sample to be tested, single wavelength Corresponding to the first height of the sample to be tested, single wavelength The corresponding first height of the sample to be tested, the synthetic wavelength The corresponding second height of the sample to be tested, the synthetic wavelength The corresponding second height of the sample to be tested, the synthetic wavelength The corresponding second height of the sample to be tested.

[0099] In this embodiment, the wavelength of the red fiber laser is , wavelength of green fiber laser , wavelength of blue fiber laser , synthetic wavelength , synthetic wavelength , synthetic wavelength . Figure 2 The step heights of the multiple steps included in the provided sample to be tested are: , , , , , .

[0100] In practical applications, in non-continuous surface topography measurement, the range of step height that can be measured is limited to about half of the wavelength. In an embodiment of the present invention, , , , , and Therefore, the maximum heights that can be measured by the above wavelengths are 225nm, 266nm, 316nm, 1459nm, 781nm and 1681nm respectively.

[0101] For the reasons mentioned above, single wavelength The height cross-section diagram is measured as follows Figure 3 As shown, due to the single wavelength It can only measure the lowest step, which is the third step, and the result can only be the lowest height, which is the height of the third step. In this embodiment, since a single wavelength is used , in order to make the single wavelength Corresponding to the numerical value in the following algorithm, here it will be based on a single wavelength The step height is measured using Indicates that Here Indicates that a single wavelength The determined first height of the sample to be tested does not represent the actual height of the step.

[0102] Accordingly, a single wavelength The height cross-section diagram is measured as follows Figure 4 As shown, due to the single wavelength Due to the wavelength range limitation, it can only measure the height of the third and fifth steps, that is, and , where the single wavelength The step height is measured using and Indicates that and , here and Indicates that a single wavelength The determined first height of the sample to be tested does not represent the actual height of the step.

[0103] Single wavelength The height cross-section diagram is measured as follows: Figure 5 As shown, due to the single wavelength Due to the wavelength range limitation, it can only measure the heights of the third, fifth and sixth steps, that is, and , where the single wavelength The step height is measured using , and Indicates that , and , here , and Indicates that a single wavelength The determined first height of the sample to be tested does not represent the actual height of the step.

[0104] Synthetic wavelength The height cross-section diagram is measured as follows: Figure 6 As shown, the synthetic wavelength The heights of the third step, the fifth step, the sixth step, the second step, and the fourth step can be measured, that is, , , and , where the synthesized wavelength The step height is measured using , , , and Indicates that , , , and , here , , , and Indicates that the synthetic wavelength The determined second height of the sample to be tested does not represent the actual height of the step.

[0105] Synthetic wavelength The height cross-section diagram is measured as follows: Figure 7 As shown, the synthetic wavelength The heights of the third step, the fifth step, the sixth step and the second step can be measured, that is, , and , where the synthesized wavelength The step height is measured using , , and Indicates that , , and , here , , and Indicates that the synthetic wavelength The determined second height of the sample to be tested does not represent the actual height of the step.

[0106] Synthetic wavelength The height cross-section diagram is measured as follows: Figure 8 As shown, the synthetic wavelength The heights of the third step, the fifth step, the sixth step, the second step, the fourth step and the first step can be measured, that is, , , , , and , where the synthesized wavelength The step height is measured using , , , , and Indicates that , , , , and , here , , , , and Indicates that the synthetic wavelength The determined second height of the sample to be tested does not represent the actual height of the step.

[0107] In this embodiment, based on the above 6 wavelengths, 6 cross-sectional line height diagrams can be obtained, that is, for the same position, there will be 3 first heights of 3 samples to be tested corresponding to 3 single wavelengths and 3 second heights of 3 samples to be tested corresponding to 3 synthetic wavelengths, that is, respectively: , , , , and .

[0108] Further, after obtaining the first heights of multiple samples to be tested and the second heights of multiple samples to be tested at the same position, a comparison process is performed in a combination manner, and the following 15 results can be obtained, which are: ; ; ; ; ; ; ; ; ; ; ; ; ; and .

[0109] Furthermore, according to formula (10), the above 15 results can be screened, including the following:

[0110] because , so remove ,Sure is the correct height.

[0111] because , so remove ,Sure is the correct height.

[0112] because , so remove ,Sure is the correct height.

[0113] because , so remove ,Sure is the correct height.

[0114] because , so remove ,Sure is the correct height.

[0115] because , so remove ,Sure is the correct height.

[0116] because , so remove ,Sure is the correct height.

[0117] because , so remove ,Sure is the correct height.

[0118] because , so remove ,Sure is the correct height.

[0119] because , so remove ,Sure is the correct height.

[0120] because , so remove ,Sure is the correct height.

[0121] because , so remove ,Sure is the correct height.

[0122] because , so remove ,Sure is the correct height.

[0123] because , so remove ,Sure is the correct height.

[0124] because , so remove ,Sure is the correct height.

[0125] In this embodiment, after 15 comparison calculations, it can be determined that Has the highest number of times in the measurement range, removing , , , , The corresponding height map will eventually Determined as the final height of the first step, the final height of the sample to be tested is According to the above embodiments, represents the height of the first step, i.e. .

[0126] Furthermore, when determining After the highest number of times in the measurement range, the obtained The wavelength at the time is determined as the final wavelength. In this embodiment, The wavelength used is the synthetic wavelength When the final wavelength is determined, the heights of other steps determined by the final wavelength are also confirmed as the final heights of other steps. Figure 2 The steps shown in the figure can determine the final height of the first step as , the final height of the second step is , the final height of the third step is , the final height of the fourth step is , the final height of the fifth step is , the final height of the sixth step is . Fig. 9 A schematic diagram of the final height cross section of the sample to be tested is provided for this embodiment.

[0127] In summary, an embodiment of the present invention provides a digital holographic microscopy synchronous measurement method and device, which includes: a light source part, which is used to provide a plurality of coupled lights of different wavelengths to a dichroic prism; a dichroic prism, which is used to transmit and reflect the coupled light from the light source part to form a first transmitted light and a first reflected light; the first reflected light is reflected by a first microscope objective lens and a sample to be measured to form a second reflected light, and the second reflected light is passed through the dichroic prism to form a second transmitted light; the first transmitted light is passed through a second microscope objective lens and a plane reflector to form a third reflected light, and the third reflected light is reflected by the dichroic prism to form a fourth reflected light; a tube lens, which is used to converge the second transmitted light and the fourth reflected light so that the second transmitted light and the fourth reflected light produce interference on the camera surface; a camera, which is used to collect the interference pattern formed by the second transmitted light and the fourth reflected light. The device uses a fiber coupler to couple three beams of light of different wavelengths together and emit them. After a Twyman-Green optical path configuration, the camera can synchronously record a multi-wavelength digital hologram in a single frame, simplifying the multi-wavelength and multi-range operation mode. Furthermore, based on the device, six measurement ranges can be obtained using a digital holographic interference pattern. Six wavelengths can be obtained simultaneously in the measurement of the sample to be measured for phase reconstruction to obtain six phase maps. Through a self-comparison phase selection algorithm, a high-precision final phase map is obtained after phase compensation, which improves the measurement efficiency and reduces the measurement error.

[0128] Another embodiment of the present invention also provides a computer device, which includes: a processor and a memory; the memory is used to store computer program code, and the computer program code includes computer instructions; when the processor executes the computer instructions, the electronic device executes each step of the digital holographic microscopy synchronous measurement method shown in the above method embodiment.

[0129] Another embodiment of the present invention further provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed on a computer device, the computer device executes each step of the digital holographic microscopy synchronous measurement method shown in the above method embodiment.

[0130] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0131] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A digital holographic microscopy synchronous measurement method, characterized in that: include: An interference pattern matching the sample to be measured is obtained by a digital holographic microscopy synchronous measurement device, the interference pattern is data processed to obtain a plurality of single-wavelength digital holograms, and a single-wavelength phase map matching the plurality of single-wavelength digital holograms and a first height of the sample to be measured corresponding to each single wavelength are obtained according to a digital holographic angular spectrum phase reconstruction algorithm; Combining multiple single wavelengths according to a synthetic wavelength formula to obtain multiple synthetic wavelengths, obtaining a wrapped phase difference according to the wrapped phase of the single wavelength corresponding to each synthetic wavelength, performing dual-wavelength phase reconstruction according to the phase difference corresponding to each single wavelength phase diagram to obtain a true phase difference, and obtaining a second height of the sample to be measured corresponding to the multiple synthetic wavelengths according to a second height formula; The first height of the sample to be tested and the second height of the sample to be tested are compared in a combination manner, the wavelength corresponding to the comparison result with the highest number of times is determined as the final wavelength, and the final height of the sample to be tested is determined according to the final wavelength; The step of obtaining a single-wavelength phase map matching a plurality of single-wavelength digital holograms and a first height of the sample to be measured corresponding to each single wavelength according to the digital holographic angular spectrum phase reconstruction algorithm specifically includes: O(f x ,f y )=F{C(x,y)H(x,y)} U(f x ,f y )=F{C(x,y)H(x,y)}G(f x ,f y ) U(x′,y′)=F -1 {F{C(x,y)H(x,y)}G(f x ,f y )} The first height of the sample to be tested and the second height of the sample to be tested are compared in combination, and the comparison result is determined according to the following formula: The synthetic wavelength formula is as follows: The subtraction of the single wavelength wrapping phase to obtain the wrapping phase difference is as follows: The second height formula is as follows: Among them, O(f x ,f y ) represents the angular spectrum expression after the digital hologram is illuminated by the reconstructed object light wave C(x,y), C(x,y) represents the reconstructed object light wave, F{C(x,y)H(x,y)} represents the Fourier transform of C(x,y)H(x,y), H(x,y) represents the single-wavelength digital hologram collected by the reconstructed object light wave C(x,y); G(f x ,f y ) represents the angular spectrum transfer function, U(f x ,f y ) represents the angular spectrum expression of the reconstructed object light wave on the reconstruction plane; U(x′,y′) represents the complex amplitude expression of the reconstructed object light wave in the spatial domain; represents the phase distribution of the object light wavelength, Im(U(x′,y′)) represents the imaginary part of U(x′,y′) divided by i, Re(U(x′,y′)) represents the real part of U(x′,y′), H 1 Indicates the first height of the sample to be tested, λ i represents the i-th single wavelength, represents the true phase of the i-th single wavelength, d represents the distance between the hologram and the reconstruction plane; h i ,h j Respectively represent the height of the sample to be tested at the same position, i, j are positive integers, λ i represents the i-th single wavelength, y j represents the jth single wavelength, λ ij Indicated by λ i and λ j The synthesized wavelength, represents the wrapped phase of the i-th single wavelength, represents the true phase of the i-th single wavelength, represents the wrapped phase of the jth single wavelength, represents the true phase of the jth single wavelength, H 2 Indicates the second height of the sample to be tested, Indicates the package phase difference, Indicates the true phase difference, l i and l j is an integer; The digital holographic microscopy synchronous measurement device comprises: A light source part, which is used to provide a plurality of coupled lights of different wavelengths to the beam splitter prism; a beam splitter prism configured to transmit and reflect the coupled light from the light source portion to form a first transmitted light and a first reflected light; the first reflected light is reflected by the first microscope objective lens and the sample to be measured to form a second reflected light, and the second reflected light is passed through the beam splitter prism to form a second transmitted light; the first transmitted light is passed through the second microscope objective lens and the plane reflector to form a third reflected light, and the third reflected light is reflected by the beam splitter prism to form a fourth reflected light; a cylindrical lens for converging the second transmitted light and the fourth reflected light so as to cause interference between the second transmitted light and the fourth reflected light on a camera surface; A camera is used to collect an interference pattern formed by the second transmitted light and the fourth reflected light.

2. The method according to claim 1, wherein The light source part includes a red fiber laser, a green fiber laser, a blue fiber laser, a fiber coupler, a clamp and an achromatic converging lens; The fiber coupler is a multimode fiber; the wavelength of the fiber coupler matches the wavelength of the red fiber laser; the wavelength of the fiber coupler matches the wavelength of the green fiber laser; the wavelength of the fiber coupler matches the wavelength of the blue fiber laser; A distance between the fixture and the achromatic converging lens is smaller than a focal length of the achromatic converging lens.

3. The method according to claim 1, wherein The distance between the achromatic converging lens included in the light source part and the beam splitting prism is smaller than the focal length of the achromatic converging lens.

4. The method according to claim 1, wherein The parameters of the first microscope objective lens and the second microscope objective lens are the same; The distance between the first microscope objective lens and the sample to be measured is smaller than the focal length of the first microscope objective lens, and the spot diameter of the first reflected light entering the surface of the sample to be measured is larger than 1 mm.

5. The method according to claim 1, wherein The distance between the beam splitter prism and the sample to be measured is equal to the distance between the beam splitter prism and the plane reflector.

6. A computer-readable storage medium, characterized in that A computer program is stored, and when the computer program is executed by a processor, the processor is caused to execute the digital holographic microscopy synchronous measurement method according to any one of claims 1 to 5.

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