CN114608472A - Wide spectrum interference microscopic measuring method, device, electronic equipment and medium - Google Patents
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Abstract
The invention provides a broad spectrum interference microscopic measurement method, a device, electronic equipment and a medium, wherein the broad spectrum interference microscopic measurement method comprises the following steps: acquiring an interference pattern of a sample to be detected; determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area which accords with a set threshold value; performing phase expansion on the first area to obtain a real phase diagram of a plurality of focal planes of the interference pattern; splicing the real phase images of the plurality of focal planes to obtain the phase distribution of the interference image; and determining the surface height distribution of the sample to be detected according to the phase distribution. The invention has the beneficial effects that: quantifying the fringe quality by the interference fringe modulation degree, and obtaining the sample height distribution in a set area by a phase expansion method; the sample heights acquired at different focal plane positions are spliced, so that a high-precision morphology measurement result with an expanded measuring range can be obtained, and the method is suitable for high-precision wide-range spectral interference microscopic measurement.
Description
Technical Field
The invention relates to the technical field of computer and high-precision detection, in particular to a wide-spectrum interference microscopic measurement method, a wide-spectrum interference microscopic measurement device, electronic equipment and a medium.
Background
Wide spectrum interference microscopy is widely applied to the field of high-precision detection due to the advantages of non-contact, no damage, rapidness and the like. System-resolved sample topography typically employs Vertical Scanning Interferometry (VSI) to measure sub-micron to millimeter features, and phase-shifting interferometry (PSI) to measure nanoscale features. The vertical scanning interferometry moves the focal plane of the microscope objective along the optical axis and collects an interference image sequence, and the height information of the sample is calculated according to the zero optical path difference position of the interference signal of each pixel point, although the precision is only submicron, the method has the advantage of larger measuring range. The principle of phase shift interferometry is to collect a plurality of interference fringe images with sample surface information at a single focal plane position, calculate the phase information of the interference fringe images to obtain the height distribution of the sample surface, wherein the precision can reach the nanometer level, but the interference fringe images are usually only used for smooth surfaces, and the phase information corresponding to height change is wrapped in an interval of [ -pi, pi ].
The quality of the fringes obtained by the spectral interference microscopic measurement method in the prior art at a designated focal plane position depends on the focal depth range of a microscope objective and the coherence length of a broad spectrum light source, when the surface fluctuation of a sample exceeds the limited range of the focal depth or the coherence length of the light source, the fringes are blurred or the contrast is lost, and a result obtained by wrapping phase unwrapping generates a large error or even an error.
Disclosure of Invention
The embodiment of the invention mainly aims to provide a method, a device, electronic equipment and a medium for wide-spectrum interference microscopic measurement, and the accuracy of the wide-spectrum interference microscopic measurement is improved.
The embodiment of the invention provides a broad spectrum interference microscopic measurement method on one hand, which is characterized by comprising the following steps: acquiring an interference pattern of a sample to be detected; determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area meeting a set threshold value; performing phase unwrapping on the first region to obtain real phase images of a plurality of focal planes of the interferogram; phase splicing the real phase images of the plurality of focal planes to obtain the phase distribution of the interference image; and determining the surface height distribution of the sample to be detected according to the phase distribution.
The wide-spectrum interference microscopic measurement method provided by the embodiment of the invention has at least the following beneficial effects:
a phase expansion and splicing method based on modulation degree is used as a wide spectrum interference microscopic measurement method: quantifying the fringe quality by the interference fringe modulation degree, and obtaining the sample height distribution in a set area by a phase unwrapping method; the sample heights acquired at different focal plane positions are spliced, so that a high-precision morphology measurement result with an expanded measuring range can be obtained, and the method is suitable for high-precision wide-range spectral interference microscopic measurement.
According to some embodiments of the invention, the determining a degree of modulation of the interferogram by which a first region of the interferogram is identified comprises:
acquiring pixels of the interference pattern;
performing a modulation degree calculation for each pixel of the interference pattern in such a manner
Where M (x, y) denotes a modulation degree of the pixel, and (x, y) denotes a position of the pixel, where N is the number of steps of phase shift measurement, and N is 1, 2n(x, y) is the gray value of the interference pattern of the nth frame;
and regarding the first region in which the modulation degree is not less than the set threshold as the phase expansion region according to the set threshold.
According to some embodiments of the invention, the performing phase unwrapping on the first region to obtain a true phase map of the interferogram for a plurality of focal planes comprises:
and performing phase unwrapping on the first area by using a diamond phase unwrapping algorithm, wherein the diamond phase unwrapping algorithm performs unwrapping on four adjacent pixels by using any pixel in the first area as a seed pixel, using the seed pixel as a center, and performing unwrapping in a diffusion manner until the phase unwrapping of all the pixels in the first area is completed to obtain real phase images of a plurality of focal planes.
According to some embodiments of the invention, phase-stitching the real phase patterns of the plurality of the focal planes to obtain a phase distribution of the interferogram comprises:
construction of the first focal plane R1And a secondary focal plane R2Is marked with a matrix Pv1And Pv2The coincidence region of the first focal plane and the second focal plane is R12Calculating the phase value mean difference delta phi of the overlapped area12
Wherein the content of the first and second substances,
is Hardmar product, N12For the number of pixels in the overlap region, the difference between the phase values is determined by delta phi12Performing splicing on the phase distribution maps at different positions by a splicing formula phistitch(x, y) is
After the first area unfolding phases in the focal planes at all positions are spliced, obtaining the phase distribution;
where φ (x, y) is the phase difference of the pixel (x, y).
According to some embodiments of the invention, the method further comprises:
constructing a mark matrix for representing the first area and the second area, wherein the mark matrix is
Pv(x, y) is the value of the flag matrix at the pixel (x, y), where M (x, y) is the modulation degree, k ismFor the set threshold, the region marked with 1 is the first region, and the region marked with 0 is the second region.
According to some embodiments of the invention, the determining the surface height distribution of the sample to be tested according to the phase distribution comprises:
subtracting the least squares fit plane from the phase distribution, and passing
Calculating to obtain the surface height distribution of the sample to be detected;
wherein λ is0Is the central wavelength of the white light source with wide spectrum, h (x, y) is the surface height distribution of the pixel (x, y), and phi (x, y) is the phase difference of the pixel (x, y).
Another embodiment of the present invention further discloses a wide-spectrum interference microscopy measurement apparatus, comprising: the interference acquisition module is used for acquiring an interference pattern of a sample to be detected; the interference identification module is used for determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area meeting a set threshold value; the phase unwrapping module is used for performing phase unwrapping on the first area to obtain a real phase diagram of a plurality of focal planes of the interferogram; the phase splicing module is used for phase splicing the real phase images of the plurality of focal planes to obtain the phase distribution of the interferogram; and the surface height distribution calculating module is used for determining the surface height distribution of the sample to be detected according to the phase distribution.
Another embodiment of the present invention further discloses an electronic device, which is characterized by comprising a processor and a memory; the memory is used for storing programs; the processor executes the program to implement the broad spectrum interferometric microscopy method as described.
Another embodiment of the present invention also discloses a computer-readable storage medium storing a program executed by a processor to implement the broad spectrum interferometric microscopy method as described.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic flow chart of a broad spectrum interferometric microscopy method according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a broad spectrum interferometric acquisition of an embodiment of the invention.
Fig. 3 is a schematic diagram of a distribution of modulation patterns of wrapped phase values according to an embodiment of the present invention.
FIG. 4 is a schematic flow chart of a broad spectrum interferometric microscopy method according to an embodiment of the present invention.
FIG. 5 is an unwrapped phase relationship diagram for two different focal plane positions for an embodiment of the present invention.
Fig. 6 is a simulation diagram of phase unwrapping and stitching according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a reconstructed three-dimensional structure according to an embodiment of the present invention.
Fig. 8 is a schematic diagram of a micro-nano structure measurement experiment result in the embodiment of the invention.
Fig. 9 is a schematic diagram of the reconstruction results of three algorithms according to the embodiment of the present invention.
FIG. 10 is a diagram of a broad spectrum interferometric microscopy analysis device according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. In the following description, suffixes such as "module", "part", or "unit" used to denote elements are used only for the convenience of description of the present invention, and have no peculiar meaning by themselves. Thus, "module", "component" or "unit" may be used mixedly. "first", "second", etc. are used for the purpose of distinguishing technical features only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the precedence of the indicated technical features. In the following description, the method steps are labeled in series for convenience of examination and understanding, and in combination with the overall technical solution of the present invention and the logical relationship among the steps, the implementation order among the steps is adjusted without affecting the technical effect achieved by the technical solution of the present invention. The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention.
Referring to fig. 1, it discloses a schematic flow chart of a wide spectrum interference microscopy measurement method, the flow chart includes:
s100, obtaining an interference pattern of a sample to be detected;
in some embodiments, referring to fig. 2, a schematic diagram of a sample acquisition under test for broad spectral interference is disclosed;
in some embodiments, optical symmetry is used to eliminate chromatic aberration by the reference and sample arms. The center wavelength of a broad spectrum white light source (LED, Thorlabs M730L4) is 730nm, the spectrum width is 30nm, and the uniform illumination of a sample surface is obtained by adopting a Kohler mode. The Beam Splitter (BS) respectively illuminates the reference mirror surface and the sample surface on the focal surfaces of the microscope objectives (50 x, NA 0.55, Nikon) in the reference arm and the sampling arm with the illumination beams, and combines the reflected light from the two arms to be focused on the photosensitive surface of the camera through an objective lens L (Nikon cylindrical lens, focal length 200mm), the red dotted line is in light source conjugate relation, and the black dotted line is in object image conjugate relation. The two-arm interference fringe image is acquired by a CCD (Baumer, VCXU-50M, pixel 3.45 μ M × 3.45 μ M, resolution 2448 × 2048) camera. A reference mirror mount piezoelectric actuator is used to generate periodic mechanical oscillations. And the one-dimensional displacement table Ts0 is used for vertically adjusting the sample table and the sample to realize the adjustment of the sampling focal plane. A two-dimensional displacement stage Ts1(Thorlabs, MSC202) was used to align the samples. The one-dimensional displacement table Ts2 is used for adjusting the reference arm length to make the optical path length of the reference mirror plane equal to the focal plane of the sample arm.
It should be noted that in fig. 2, Reference mirror is a reflector, Broadband light source is a Broadband light source, and Collimating lenses are illustrated.
In some embodiments, the interferogram is obtained by phase shift interferometry, which is a measurement technique that uses phase information to calculate the surface topography of a sample, and common phase shift algorithms include three-step phase shift, four-step phase shift, five-step phase shift, Carre phase shift, and the like. Taking a four-step phase shift method as an example, the technical principle of phase shift interferometry is briefly described below, and the light intensity i (n) of the wide-spectrum white light interference signal at the position n is:
I(n)＝I0{1+M(n)cos[φ(n)]} (1)
wherein I0For background light intensity, M (n) is the interference fringe modulation degree, and φ (n) is the two-arm phase difference.
In the four-step phase shift process, the micro-displacement step length is required to be
λ0Is the central wavelength of the broad spectrum light source, and the corresponding phase variation is
After the micro-displacement system finishes moving every time, the image acquisition system acquires an interference image, and the gray value of each pixel point of the interference image at different positions can be represented by a formula (2):
wherein, Ii(x, y) is the gray value of the interference image of the ith frame of the four-step phase shift, and the main phase distribution of each pixel point can be calculated by the formula (3)
In the calculation of
When the method is used, a four-quadrant arc tangent function arctan2f (x, y) is needed, and the phase calculated by the function is limited to [ - π, π]Internal, so phase information obtained by four-step phase shift algorithm
Is wrapped in [ -pi, pi [ -pi]In the interval, the number of the interval,
referred to as wrapped phase, phase unwrapping is required to obtain the true phase (x, y). The unfolded true phase can calculate the height distribution h (x, y) of the sample by equation 4.
Wherein phi (x, y) is the phase difference of the pixel (x, y), the phase shift interference has nanometer precision but is only suitable for smooth surface measurement, and the phase obtained by the height distribution is wrapped in the range of [ -pi, pi ].
S200, determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area which accords with a set threshold value;
in some embodiments, the first region is obtained by using the modulation degree as a evaluating function directly reflecting the quality of the interferogram and combining with the set threshold value, and each focal plane has a corresponding first region in a plurality of focal planes of the interferogram;
in some embodiments, the pixel (x, y) position fringe modulation M (x, y) is defined as,
wherein N isThe number of steps in the phase shift measurement, N1, 2nAnd (x, y) is the gray value of the interference image of the nth frame.
In some embodiments, a modulation degree is used as an interference pattern quality evaluation function, a region with good interference signal quality (an ideal region, a first region) and a region with poor interference quality (a problem region, a second region) are set by a threshold, pixel points with modulation degrees larger than the threshold are subjected to phase unwrapping, and no processing is performed when the modulation degree is smaller than the threshold.
Referring to FIG. 3, a schematic diagram of a distribution of modulation maps of calculated wrapped phase values at a scanning position, RaIn order to make the modulation degree greater than the set threshold region, RbThe modulation degree is smaller than the set threshold region.
In some embodiments, the selection of the set threshold is more critical, if the set threshold is too large, many points with good quality may be missed, and if the set threshold is too small, many pixels with poor quality may be considered as reliable pixels to perform phase unwrapping, which may result in failure of phase unwrapping.
In some embodiments, the setting threshold is correspondingly set according to the sample to be detected;
in some embodiments, the value P is taken at pixel (x, y) by inverting the sign matrix in the first regionv(x, y) is:
where M (x, y) is the degree of modulation, kmFor the set threshold, the region with flag 1 is the ideal region.
S300, performing phase expansion on the first region to obtain a real phase diagram of a plurality of focal planes of the interference pattern.
In some embodiments, phase unwrapping is performed through a diamond phase unwrapping algorithm, after a problem area and an ideal area are marked by setting a proper threshold value, only wrapping phases of the ideal area (a first area) are subjected to diamond unwrapping, the problem area is not unwrapped, interferograms are collected at different focal plane positions to resolve real phases, and the above operations are repeated.
Referring to fig. 4, the principle of diamond phase unwrapping is to take a certain starting point (point 1 in fig. 4) as a seed pixel, and to perform diffusion unwrapping on four adjacent pixels around the seed pixel, and after the four pixels in the neighborhood of the starting point are unwrapped, to sequentially perform phase unwrapping around the four pixels, to complete the next round of diamond phase unwrapping, and to not perform unwrapping on the last round of unwrapped pixels until all pixels are unwrapped.
Exemplarily, in fig. 4, 4 adjacent pixel points of the seed pixel 1 are 2, 3, 4, and 5, and a first round of expansion is performed;
and performing phase expansion by taking the pixel points 2, 3, 4 and 5 as seed pixels of the next round, and completing the phase expansion of all ideal areas in a diffusion mode.
S400, splicing the real phase diagrams of the multiple focal planes to obtain the phase distribution of the interference diagram.
In some embodiments, stitching is required to obtain a complete continuous phase distribution for the true phases resolved for different focal plane positions.
In some embodiments, referring to FIG. 5, the unwrapped phase matrix R corresponding to the focal plane position I, II is expanded1And R2， R1And R2Is denoted as R12. Overlapping region R12For measuring the region with the mark matrix 1 twice, the phase value average difference delta phi of the overlapped region needs to be calculated for phase splicing12：
Wherein, Pv1，Pv2Is the tag matrix corresponding to location I, II,
is Hardmar product, N12For the number of pixels in the overlap region, the phase values are averaged by an amount of delta phi12The phase distribution maps at different positions are spliced according to a formula 8,
wherein φ (x, y) is the phase difference of the pixel (x, y);
and S500, determining the surface height distribution of the sample to be detected according to the phase distribution.
In some embodiments, after the first region spread phases at all positions are spliced, the complete phase distribution of the sample can be obtained. And subtracting a plane fitted by a least square method to remove the inclination, and then obtaining the height distribution of the sample surface by a formula 4.
Referring to fig. 6, the embodiment of the present invention further discloses a simulation diagram of phase unwrapping and phase splicing, wherein in the vertical displacement process of the wide-spectrum interference microscopy mode (fig. 2) Ts0, the light intensity (formula 1) corresponding to the wide-spectrum white-light interference signal is,
wherein z is the vertical scan position, z0For interference of arm length,/cIs the coherence length, λ0Is the central wavelength of the white light source with broad spectrum, k is the tilt factor (the degree of the sample tilting relative to the optical axis), I0Is the background light intensity.
In the numerical simulation, the peak function of Matlab is used as the object to be measured, the height distribution of the object is shown in fig. 6 (a), and the tilt factor k is 0.02.
Interferograms 6(b) and 6(c) are acquired at the focal plane position I, II, respectively, and the interference fringes obtained by simulation are closer to those in actual measurement due to the introduction of the tilt factor k. The wrapping phases are obtained at the two focal plane positions by using a four-step phase shift algorithm, and the corresponding modulation degrees (formula 5) are calculated as shown in fig. 6(d) and 6(e), wherein the modulation degree is lower in the interference fringe fuzzy area.
It should be noted that the height of the surface of the test sample is shown by the z-axis height in the space coordinates in fig. 7 to 9 of the embodiment of the present invention, and correspondingly, the x-axis and the y-axis in the plane coordinates are used to represent the pixel coordinate.
Referring to fig. 7, the embodiment of the invention discloses splicing the unfolded phases of the ideal regions at each position, and obtaining a reconstructed three-dimensional structure after de-tilting by using a least square method. For comparison, the three-dimensional structure diagrams 7(a) and 7(b) restored by the minimum two-multiplication and the branch-and-cut method respectively show that the phase unwrapping and splicing result diagram 7(c) provided by the embodiment of the invention has obvious advantages, and can well overcome the problem caused by inaccurate wrapping phase under the conditions of fringe blurring and the like.
Referring to fig. 8, an embodiment of the present invention further provides a schematic diagram of a micro-nano structure measurement experiment result, the micro-nano structure to be measured is a hemispherical structure on the surface of a certain processed silicon wafer, the thickness of the micro-nano structure is 3-4 μm, and the experiment measures a certain hemisphere in the hemispherical array.
In the experimental process, the piezoelectric ceramics are driven to step into
Performing four-step displacement and acquiring interference images, totaling 12 interference images, acquiring wrapping phases of three different positions by using a four-step phase shift method, marking a problem area and an ideal area according to an evaluation function and a threshold value, performing phase expansion on the ideal area, and finally splicing the expanded phases of the ideal areas of the three positions according to a formula 11 to obtain a complete three-dimensional surface form of the whole object to be tested, so as to obtain a gray-scale image of a test sample shown in fig. 8(a), and modulation degree distribution of the test sample shown in fig. 8(b) and fig. 8(c) at the interference images of the different positions.
Illustratively, in the actual measurement process, due to the fact that the wrapping phase quality of a part of area is poor due to the focal depth limitation of a microscope objective lens, the partial reflection of an object to be measured is poor and the like, a proper threshold value is required to be set to distinguish a problem area from an ideal area, the threshold value is set to be 0.3 to carry out three-dimensional reconstruction after optimization, in order to enable the experimental result to be more visual, the method of least square, branch cutting, phase unfolding and splicing is adopted to carry out three-dimensional reconstruction on a micro-nano structure to be tested, and data when y is 500 are extracted to be compared.
Referring to fig. 9, the present embodiment illustrates three kinds of algorithm reconstruction results:
FIG. 9(a) least squares method, FIG. 9(b) branch cut method, FIG. 9(c) method provided by an embodiment of the present invention;
fig. 9(d), 9(e) and 9(f) correspond to the height curves of the marker sections (y is 500) of fig. 9(a), 9(b) and 9 (c).
Fig. 9(a) and 9(d) show the three-dimensional surface shape recovered by the least square method and the height distribution in the cross section shown, and the error is serious about 10 μm more than the rough height. Fig. 9(b) is a three-dimensional surface pattern recovered by the twitter method, which is clearly seen to have a stringiness phenomenon at the edge, and the cross section shown in fig. 9(e) shows that a large amount of noise is present in the cross section recovered by the twitter method. According to the method provided by the embodiment of the invention, the three-dimensional surface pattern 9(c) and the cross section pattern 9(f) are obtained, because the reflectivity of the bottom area of the test sample is too low and the interference fringes are not obvious, the acquired wrapped phase has errors, so that the noise is generated on the bottom of the cross section of the unfolded phase, but the noise has no influence on the reduction of the overall height, and the three-dimensional morphology of the test micro-nano structure is reduced with high precision.
Fig. 10 is a diagram of a broad spectrum interference microscopy measurement analysis apparatus according to an embodiment of the present invention, which includes an interference acquisition module 1001, an interference identification module 1002, a phase deployment module 1003, a phase splicing module 1004, and a surface height distribution calculation module 1005. The method comprises the following steps:
the interference acquisition module is used for acquiring an interference pattern of a sample to be detected;
the interference identification module is used for determining the modulation degree of the interference pattern, identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area which accords with a set threshold value;
the phase unwrapping module is used for performing phase unwrapping on the first area to obtain a real phase map of a plurality of focal planes of the interferogram;
the phase splicing module is used for phase splicing the real phase images of the multiple focal planes to obtain the phase distribution of the interferogram;
and the surface height distribution calculating module is used for determining the surface height distribution of the sample to be measured according to the phase distribution.
Exemplarily, under the cooperation of the interference acquisition module, the interference identification module, the phase deployment module, the phase splicing module and the surface height distribution calculation module in the device, the device of the embodiment can realize any one of the aforementioned wide-spectrum interference microscopic measurement methods, that is, obtain an interference pattern of a sample to be measured; determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area meeting a set threshold value; performing phase unwrapping on the first region to obtain real phase images of a plurality of focal planes of the interference image; phase-stitching the real phase maps of the plurality of focal planes to obtain a phase distribution of the interferogram; and determining the surface height distribution of the sample to be detected according to the phase distribution. The phase expansion and splicing method based on the modulation degree is used as a wide spectrum interference microscopic measurement method: quantifying the fringe quality by the interference fringe modulation degree, and obtaining the sample height distribution in a set area by a phase unwrapping method; the sample heights acquired at different focal plane positions are spliced, so that a high-precision shape measurement result of an extended range can be obtained, and the method is suitable for high-precision wide-range spectral interference microscopic measurement.
The wide spectrum interference microscopic measurement method provided by the technical scheme of the invention defines the areas with different focal plane fringe modulation degrees higher than the set threshold value as ideal areas, and calculates the height distribution of samples in the corresponding areas with nanometer precision. And different ideal regions are obtained by moving the focal plane of the microscope objective by the vertical displacement table. In the measuring process, the displacement distance corresponding to the adjacent ideal areas is ensured to have an overlapping area between the two areas so as to realize high-precision phase splicing. Due to the fact that the partial areas between the adjacent ideal areas are overlapped, the fact that the system measurement accuracy does not depend on the displacement component is guaranteed. The technical scheme of the invention provides a measuring method which can achieve nanoscale precision in the whole extended range and theoretically can extend the range to the full working distance of a microscope objective.
The embodiment of the invention also provides the electronic equipment, which comprises a processor and a memory;
the memory stores a program;
the processor executes a program to execute the wide spectrum interference microscopy method; the electronic device has a function of loading and operating a software system for wide-spectrum interferometric microscopy provided by the embodiment of the invention, for example, a Personal Computer (PC), a mobile phone, a smart phone, a Personal Digital Assistant (PDA), a wearable device, a pocket PC (ppc), a tablet PC, and the like.
Embodiments of the present invention also provide a computer-readable storage medium storing a program, the program being executed by a processor to implement the wide-spectrum interferometric microscopy method as described above.
In alternative embodiments, the functions/acts noted in the block diagrams may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Furthermore, the embodiments presented and described in the flow charts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented by the embodiments of the invention. Alternative embodiments are contemplated in which the order of various operations is changed and in which sub-operations, depicted as part of larger operations, are performed independently.
The embodiment of the invention also discloses a computer program product or a computer program, which comprises computer instructions, and the computer instructions are stored in a computer readable storage medium. The computer instructions may be read by a processor of a computer device from a computer-readable storage medium, and the computer instructions executed by the processor cause the computer device to perform the aforementioned broad-spectrum interferometric microscopy method.
Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise stated to the contrary, one or more of the described functions and/or features may be integrated in a single physical device and/or software module, or one or more functions and/or features may be implemented in a separate physical device or software module. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary for an understanding of the present invention. Rather, the actual implementation of the various functional blocks of the apparatus disclosed in the embodiments of the present invention will be understood within the ordinary skill of the engineer, taking into account the nature, function and inter-relationships of such blocks. Accordingly, those of ordinary skill in the art will be able to practice the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative of and not intended to limit the scope of the invention, which is defined by the appended claims and their full scope of equivalents.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the implementation of the present invention may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer (which may be a personal computer, a server, or a network device) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The logic and/or steps represented in the flowcharts or otherwise described herein, for example, may be considered as a sequential list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A method of wide-spectrum interferometric microscopy, comprising:
acquiring an interference pattern of a sample to be detected;
determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area which accords with a set threshold value;
performing phase unwrapping on the first region to obtain real phase images of a plurality of focal planes of the interferogram;
phase splicing the real phase images of the plurality of focal planes to obtain the phase distribution of the interference image;
and determining the surface height distribution of the sample to be detected according to the phase distribution.
2. The broad spectrum interferometric microscopy method of claim 1, wherein determining a degree of modulation of the interferogram by which to identify the first region of the interferogram comprises:
acquiring pixels of the interference pattern;
performing a modulation degree calculation for each pixel of the interference pattern in such a manner
Where M (x, y) denotes a modulation degree of the pixel, and (x, y) denotes a position of the pixel, where N is the number of steps of phase shift measurement, and N is 1, 2, …, N, In(x, y) is the gray value of the interference pattern of the nth frame;
and setting the first region in which the modulation degree is equal to or greater than the set threshold as the phase expansion region according to the set threshold.
3. The method of claim 1, wherein the performing phase unwrapping on the first region to obtain a true phase map of the interferogram for a plurality of focal planes comprises:
and performing phase unwrapping on the first area by using a diamond phase unwrapping algorithm, wherein the diamond phase unwrapping algorithm performs unwrapping on four adjacent pixels by using any pixel in the first area as a seed pixel and the seed pixel as a center, and performs unwrapping in a diffusion manner until phase unwrapping of all pixels in the first area is completed to obtain a real phase diagram of a plurality of focal planes.
4. The method of claim 1, wherein phase-stitching the real phase maps of the plurality of focal planes to obtain a phase distribution of the interferograms comprises:
construction of the first focal plane R1And a secondary focal plane R2Is marked with a matrix Pv1And Pv2The coincidence region of the first focal plane and the second focal plane is R12Calculating the phase value mean difference delta phi of the overlapped area12
Wherein, ° is Hardmar product, N12For the number of pixels in the overlap region, the phase values are averaged by an amount of delta phi12Performing splicing on the phase distribution maps at different positions by a splicing formula phistitch(x, y) is
After the first area unfolding phases in the focal planes at all positions are spliced, the phase distribution is obtained;
where φ (x, y) is the phase difference of the pixel (x, y).
5. The broad spectrum interferometric microscopy method of claim 4 wherein the method further comprises:
constructing a mark matrix for representing the first area and the second area, wherein the mark matrix is
Pv(x, y) is the value of the flag matrix at the pixel (x, y), where M (x, y) is the modulation degree, k ismFor the set threshold, the region marked with 1 is the first region, and the region marked with 0 is the second region.
6. The broad spectrum interferometric microscopy method of claim 4 wherein determining the surface height distribution of the sample to be measured from the phase distribution comprises:
subtracting the least squares fit plane from the phase distribution, and passing
Calculating to obtain the surface height distribution of the sample to be detected;
wherein λ is0Is the central wavelength of the white light source with wide spectrum, h (x, y) is the surface height distribution of the pixel (x, y), and phi (x, y) is the phase difference of the pixel (x, y).
7. A broad spectrum interferometric microscopy apparatus, comprising:
the interference acquisition module is used for acquiring an interference pattern of a sample to be detected;
the interference identification module is used for determining the modulation degree of the interference pattern, and identifying a first area of the interference pattern through the modulation degree, wherein the first area is used for representing a phase expansion area which accords with a set threshold value;
the phase unwrapping module is used for performing phase unwrapping on the first area to obtain a real phase image of a plurality of focal planes of the interferogram;
the phase splicing module is used for phase splicing the real phase images of the plurality of focal planes to obtain the phase distribution of the interferogram;
and the surface height distribution calculating module is used for determining the surface height distribution of the sample to be detected according to the phase distribution.
8. An electronic device comprising a processor and a memory;
the memory is used for storing programs;
the processor executes the program to implement the broad spectrum interferometric microscopy method of any one of claims 1-6.
9. A computer-readable storage medium, characterized in that the storage medium stores a program which is executed by a processor to implement the broad spectrum interferometric microscopy method of any one of claims 1-6.
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