阅读说明：本技术 一种显微成像设备以及纳米尺度三维形貌测量系统 (Microscopic imaging equipment and nanoscale three-dimensional shape measurement system ) 是由 吴征宇 于 2021-09-27 设计创作，主要内容包括：本申请涉及一种显微成像设备以及纳米尺度三维形貌测量系统,显微成像设备包括显微镜、4F系统以及相机；所述4F系统包括两个透镜组以及电控变焦透镜；两个所述透镜组分别为第一透镜组和第二透镜组；两个所述透镜组均为反远距结构的傅里叶变换物镜；所述显微镜的镜片、第一透镜组、电控变焦透镜、第二透镜组以及相机的镜片依次设置于同一光轴上；所述第一透镜组以及所述第二透镜组对称设置于所述电控变焦透镜两侧；所述显微镜的像平面位于所述第一透镜组的前焦面,所述电控变焦透镜位于所述第一透镜组的后焦面以及所述第二透镜组的前焦面,所述相机位于所述第二透镜组的后焦面。本申请具有成像像差小、效率高的技术效果。(The application relates to a microscopic imaging device and a nanoscale three-dimensional shape measurement system, wherein the microscopic imaging device comprises a microscope, a 4F system and a camera; the 4F system comprises two lens groups and an electric control zoom lens; the two lens groups are respectively a first lens group and a second lens group; the two lens groups are both Fourier transform objective lenses with an inverse teledistance structure; the lens of the microscope, the first lens group, the electric control zoom lens, the second lens group and the lens of the camera are sequentially arranged on the same optical axis; the first lens group and the second lens group are symmetrically arranged on two sides of the electric control zoom lens; the image plane of the microscope is located on the front focal plane of the first lens group, the electronic control zoom lens is located on the rear focal plane of the first lens group and the front focal plane of the second lens group, and the camera is located on the rear focal plane of the second lens group. The imaging optical system has the technical effects of small imaging aberration and high efficiency.)

1. A microscopic imaging apparatus comprising a microscope, a 4F system and a camera; the 4F system comprises two lens groups and an electric control zoom lens; the two lens groups are respectively a first lens group and a second lens group; the two lens groups are both Fourier transform objective lenses with an inverse teledistance structure;

the lens of the microscope, the first lens group, the electric control zoom lens, the second lens group and the lens of the camera are sequentially arranged on the same optical axis; the first lens group and the second lens group are symmetrically arranged on two sides of the electric control zoom lens; the image plane of the microscope is located on the front focal plane of the first lens group, the electronic control zoom lens is located on the rear focal plane of the first lens group and the front focal plane of the second lens group, and the camera is located on the rear focal plane of the second lens group.

2. A microscopic imaging apparatus according to claim 1, wherein said lens group comprises two symmetrical units;

the symmetrical unit comprises a positive meniscus lens, a double-cemented positive lens and a double-cemented negative lens; the positive meniscus lens, the double-cemented positive lens and the double-cemented negative lens are sequentially arranged on the same optical axis, the concave surface of the positive meniscus lens faces the double-cemented positive lens, and the crown glass of the double-cemented positive lens and the crown glass of the double-cemented negative lens both face the positive meniscus lens;

the two symmetrical units are symmetrically arranged, and the positive meniscus lenses of the two symmetrical units are positioned on the outer side.

3. The microscopic imaging apparatus according to claim 1, wherein the microscope comprises a light source, a condenser, a filter, a first relay lens, an aperture stop, a second relay lens and a spectroscope coaxially arranged in this order, the objective lens is arranged on a reflection optical path of the spectroscope, the reflector is arranged on one spectroscopic optical path of the spectroscope, and the imaging tube lens, the 4F system and the camera are arranged on the other spectroscopic optical path in this order.

4. A nanoscale three-dimensional topography measurement system comprising the microscopic imaging apparatus according to any one of claims 1 to 3, further comprising a computer device;

the microscopic imaging equipment is used for acquiring a plurality of sample images with different focal lengths along an optical axis and adjusting the focal lengths through the electric control zoom lens;

the computer equipment is used for acquiring the sample image and carrying out three-dimensional topography measurement based on the sample image.

5. The system according to claim 4, wherein the three-dimensional topography measurement is performed based on the sample image, in particular:

carrying out differential estimation on the basis of the sample image to obtain light intensity axial differential;

obtaining phase distribution according to an optical energy transmission equation;

and solving the depth of the sample according to the phase distribution to construct the three-dimensional appearance of the sample.

6. The nanoscale three-dimensional topography measurement system according to claim 5, wherein the light intensity axial differential is obtained by performing differential estimation based on the sample image, specifically:

the sample image comprises a forward out-of-focus image, a focus image and a reverse out-of-focus image, and differential estimation is carried out;

；

wherein the content of the first and second substances,for the axial differential of the light intensity,is the light intensity distribution of the forward defocused image,in order to reverse the light intensity distribution of the out-of-focus image,is the defocus distance;

；

wherein the content of the first and second substances,in order to electrically control the focal length of the zoom lens,is the focal length of the lens group,to electrically control the focal length of the concave lens in the zoom lens,is the distance between the concave lens and the electrically controlled zoom lens.

7. The system according to claim 4, wherein the focal length adjustment is performed by the electrically controlled zoom lens, specifically:

and selecting a change area of the electric control zoom lens, wherein the current of the electric control zoom lens is proportional to the focal length, and carrying out focal length adjustment.

8. The system of claim 5, wherein the differential estimation based on the sample image yields an axial differential of light intensity, further comprising:

and carrying out multiple differential estimation, and calculating the average value of the light intensity axial differentials obtained by the multiple differential estimation as the final light intensity axial differential.

9. The system of claim 5, wherein the phase distribution is obtained according to an optical energy transfer equation, specifically:

the optical energy transfer equation is:

；

wherein the content of the first and second substances,in terms of the wave number, the number of waves,is the axial differential of the light intensity,in order to be the light intensity distribution,to act onThe hamiltonian of the plane is calculated,is a phase distribution;

obtaining a phase distribution:

；

wherein the content of the first and second substances,which represents the inverse of the laplace operator,is the inverse matrix of the light intensity distribution.

10. The system according to claim 5, wherein the depth of the sample is obtained according to the phase distribution, and the three-dimensional shape of the sample is constructed, specifically:

for any two points in the phase distributionAndcalculating the phase difference between two pointsAnd further calculating the height difference between the two points:

；

wherein the content of the first and second substances,in order to be the difference in height,is the wavelength;

and obtaining the relative height information of the surface of the sample by combining the height difference between the points, namely the three-dimensional shape information of the surface of the sample.

Technical Field

The application relates to the technical field of microscopic imaging, in particular to a microscopic imaging device and a nanoscale three-dimensional shape measurement system.

Background

In the field of industrial manufacturing, three-dimensional shape information of an object has important significance for manufacturing process control. When light irradiates on an object, the three-dimensional shape of the object can influence the wave front and phase distribution of light waves. Therefore, depth information of the object can be obtained by calculating the phase. However, currently, all optical signal detection devices, such as cmos type and ccd type cameras, can record only light intensity, and cannot record phase information. Therefore, the phase information must be demodulated from the intensity detection signal using a specific method. The optical energy transfer equation technique is a typical optical phase extraction method. Unlike the conventional phase measurement method based on the optical interference technique, the optical energy transfer equation is essentially a partial differential equation describing a first order partial derivative relationship that is satisfied between the phase and intensity of light in the paraxial approximation state. In principle, the optical energy transmission equation can be solved by using the light field intensity on a plurality of axial displacement planes, and then phase information can be obtained. This makes optical system designs based on optical energy transfer equations much more compact and compact than optical interference-based methods.

Most of the existing optical imaging systems based on the optical energy transmission equation are directed at transparent or semitransparent objects, but are not suitable for opaque objects, so that a reflective phase imaging system needs to be constructed to acquire a multifocal image of an opaque object, and then a method based on the optical energy transmission equation is used to acquire a reflection phase of the object to reconstruct three-dimensional topography information of the object to be measured.

However, it should be noted that the conventional phase measurement system based on the optical energy transmission equation often depends on an electrically controlled displacement stage to obtain multiple light intensity maps by mechanically moving the sample or the camera, which greatly reduces the imaging rate of the system, and thus it is difficult to apply the optical imaging system to an industrial online measurement scenario. Although research reports recently show that the high-speed phase measurement system based on the adjustable focusing lens has a large influence on imaging quality, namely a typical 4F system, of a relay system in an Abbe imaging system, and depth measurement in a nanometer level is difficult to realize. This is because the combination of the conventional 4F system and the adjustable focusing lens fails to take into account the aberration factors of the system, and the aberration variation of the system introduced by the adjustable focusing lens is difficult to reduce and eliminate while the adjustable focusing lens is deformed in shape to generate different focal lengths. In addition, the aberration of the 4F system is coupled with the phase difference of the zoom lens in a superimposed manner, which further reduces the imaging quality of the phase imaging system, and thus it is difficult to obtain a high-precision phase measurement result. Therefore, a new set of optical imaging system must be designed to fit the adjustable zoom lens from the perspective of the whole imaging system, so as to minimize the system aberration and improve the accuracy of phase measurement.

Disclosure of Invention

In view of this, the present application provides a microscopic imaging apparatus and a nanoscale three-dimensional topography measurement system, so as to solve the technical problems of large aberration and low efficiency in phase measurement microscopic imaging.

In order to solve the above-described problems, in a first aspect, the present invention provides a microscopic imaging apparatus including a microscope, a 4F system, and a camera; the 4F system comprises two lens groups and an electric control zoom lens; the two lens groups are respectively a first lens group and a second lens group; the two lens groups are both Fourier transform objective lenses with an inverse teledistance structure;

the lens of the microscope, the first lens group, the electric control zoom lens, the second lens group and the lens of the camera are sequentially arranged on the same optical axis; the first lens group and the second lens group are symmetrically arranged on two sides of the electric control zoom lens; the image plane of the microscope is located on the front focal plane of the first lens group, the electronic control zoom lens is located on the rear focal plane of the first lens group and the front focal plane of the second lens group, and the camera is located on the rear focal plane of the second lens group.

Optionally, the lens group comprises two symmetrical units;

the symmetrical unit comprises a positive meniscus lens, a double-cemented positive lens and a double-cemented negative lens; the positive meniscus lens, the double-cemented positive lens and the double-cemented negative lens are sequentially arranged on the same optical axis, the concave surface of the positive meniscus lens faces the double-cemented positive lens, and the crown glass of the double-cemented positive lens and the crown glass of the double-cemented negative lens both face the positive meniscus lens;

the two symmetrical units are symmetrically arranged, and the positive meniscus lenses of the two symmetrical units are positioned on the outer side.

Optionally, the microscope includes light source, condensing lens, light filter, first relay lens, aperture diaphragm, second relay lens and the spectroscope of coaxial setting in proper order, be provided with objective on the reflection light path of spectroscope, be provided with the speculum on the beam splitting light path of spectroscope, another beam splitting light path has set gradually the formation of image section of thick bamboo mirror 4F system and the camera.

In a second aspect, the present application further provides a system for measuring a nanoscale three-dimensional topography, comprising a microscopic imaging device and a computer device;

the microscopic imaging equipment is used for acquiring a plurality of sample images with different focal lengths along an optical axis and adjusting the focal lengths through the electric control zoom lens;

the computer equipment is used for acquiring the sample image and carrying out three-dimensional topography measurement based on the sample image.

Optionally, the three-dimensional topography measurement is performed based on the sample image, specifically:

carrying out differential estimation on the basis of the sample image to obtain light intensity axial differential;

obtaining phase distribution according to an optical energy transmission equation;

and solving the depth of the sample according to the phase distribution to construct the three-dimensional appearance of the sample.

Optionally, performing differential estimation based on the sample image to obtain an axial differential of light intensity, specifically:

the sample image comprises a forward out-of-focus image, a focus image and a reverse out-of-focus image, and differential estimation is carried out;

；

wherein the content of the first and second substances,for the axial differential of the light intensity,is the light intensity distribution of the forward defocused image,in order to reverse the light intensity distribution of the out-of-focus image,is the defocus distance;

；

wherein the content of the first and second substances,in order to electrically control the focal length of the zoom lens,is the focal length of the lens group,to electrically control the focal length of the concave lens in the zoom lens,is the distance between the concave lens and the electrically controlled zoom lens.

Optionally, the focal length adjustment is performed through the electronic control zoom lens, specifically:

and selecting a change area of the electric control zoom lens, wherein the current of the electric control zoom lens is proportional to the focal length, and carrying out focal length adjustment.

Optionally, performing differential estimation based on the sample image to obtain an axial differential of light intensity, specifically:

and carrying out multiple differential estimation, and calculating the average value of the light intensity axial differentials obtained by the multiple differential estimation as the final light intensity axial differential.

Optionally, the phase distribution is obtained according to an optical energy transmission equation, specifically:

the optical energy transfer equation is:

；

wherein the content of the first and second substances,in terms of the wave number, the number of waves,is the axial differential of the light intensity,in order to be the light intensity distribution,to act onThe hamiltonian of the plane is calculated,is a phase distribution;

obtaining a phase distribution:

；

wherein the content of the first and second substances,which represents the inverse of the laplace operator,is the inverse matrix of the light intensity distribution.

Optionally, the depth of the sample is obtained according to the phase distribution, and a three-dimensional shape of the sample is constructed, specifically:

for any two points in the phase distributionAndcalculating the phase difference between two pointsAnd further calculating the height difference between the two points:

；

wherein the content of the first and second substances,in order to be the difference in height,is the wavelength;

and obtaining the relative height information of the surface of the sample by combining the height difference between the points, namely the three-dimensional shape information of the surface of the sample.

The invention has the beneficial effects that: the invention optimizes the 4F system, adopts the electric control zoom lens to focus, does not contain mechanical moving parts, has simple structure and accurate measurement; the lens group of the reverse telegroup structure with a symmetrical structure is adopted to realize Fourier transform, the optimally designed 4F system almost has no damage to the imaging of the microscope, the relay of a high-quality light intensity image can be realized, and the aberration of the formed microscopic image is extremely small, so that the high-quality rapid imaging of the three-dimensional appearance of an object can be realized; meanwhile, a system formed by the 4F system and the adjustable zoom lens can be directly inherited with a traditional bright field microscope without additional equipment, and compared with a technology based on optical interference phase measurement, the most compact optical structure design can be realized.

Drawings

FIG. 1 is a schematic diagram of one embodiment of a microscopic imaging apparatus provided herein;

FIG. 2 is a schematic structural diagram of an embodiment of a microscopic imaging apparatus provided herein;

FIG. 3 is a diagram illustrating simulation results of modulation transfer function of an embodiment of the microscopic imaging apparatus provided in the present application;

FIG. 4 is a diagram illustrating a simulation result of a dot-column diagram of an embodiment of the microscopic imaging apparatus provided in the present application;

fig. 5 is a diagram of a simulation result of an imaging effect of an embodiment of a microscopic imaging apparatus provided in the present application.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the application and together with the description, serve to explain the principles of the application and not to limit the scope of the application.

In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

The present application provides a microscopic imaging device and a nanoscale three-dimensional topography measurement system, which are described in detail below.

First, as shown in fig. 1 and fig. 2, an embodiment of the present application provides a microscopic imaging apparatus, including a microscope 100, a 4F system 200, and a camera 300; the 4F system 200 includes two lens groups and an electronically controlled zoom lens 15; the two lens groups are respectively a first lens group and a second lens group; the two lens groups are both Fourier transform objective lenses with an inverse teledistance structure;

the lens of the microscope 100, the first lens group, the electrically controlled zoom lens 15, the second lens group and the lens of the camera 300 are sequentially arranged on the same optical axis; the first lens group and the second lens group are symmetrically arranged on two sides of the electronic control zoom lens 15; the image plane of the microscope 100 is located at the front focal plane of the first lens group, the electronically controlled zoom lens 15 is located at the back focal plane of the first lens group and the front focal plane of the second lens group, and the camera 300 is located at the back focal plane of the second lens group.

The microscopic imaging apparatus provided in this embodiment specifically includes: a microscope 100, a first lens group, an electrically controlled zoom lens 15, a second lens group, a camera 300; the microscope 100 is a reflection microscope; the first lens group, the electric control zoom lens 15 and the second lens group form a 4F system 200, and the electric control zoom lens 15 is positioned on the back focal plane of the first lens group and the front focal plane of the second lens group; the image plane of the microscope 100 is located at the front focal plane of the first lens group of the 4F system 200; camera 300 is located at the back focal plane of the second lens group of 4F system 200. The present embodiment has the following features in the design of the 4F system 200: the two lens groups adopt an anti-telephoto group structure to realize Fourier transform, and are symmetrically arranged on two sides of the electric control zoom lens 15, the design of the symmetrical Fourier transform objective lens naturally eliminates distortion, improves imaging quality, and simultaneously, the anti-telephoto group is used, so that the image space focal distance of the objective lens is reduced relative to the focal distance of the objective lens, and the overall dimension of the optical processing system is reduced.

Compared with the prior art, the embodiment has the remarkable advantages that: (1) the electronic control zoom lens 15 is adopted for focusing, mechanical moving parts are not contained, and compared with other methods of optical energy transmission equations, the method does not need any mechanical moving device, and is simple in structure and accurate in measurement; (2) different from the existing optical energy transmission equation calculation imaging method, the optimally designed 4F system 200 almost has no damage to the imaging of the microscope 100, can realize high-quality light intensity image relay, and the aberration of the formed microscope 100 image is extremely small, so that high-quality rapid imaging of the three-dimensional appearance of an object can be realized; (3) the system formed by the 4F system 200 and the adjustable focus lens of the present invention can be directly inherited from the conventional bright field microscope 100 without additional equipment. The most compact design of the optical structure can be achieved compared to techniques based on optical interferometric phase measurements.

As shown in FIG. 1, in one embodiment, the lens group includes two symmetric units;

the symmetrical unit comprises a positive meniscus lens, a double-cemented positive lens and a double-cemented negative lens; the positive meniscus lens, the double-cemented positive lens and the double-cemented negative lens are sequentially arranged on the same optical axis, the concave surface of the positive meniscus lens faces the double-cemented positive lens, and the crown glass of the double-cemented positive lens and the crown glass of the double-cemented negative lens both face the positive meniscus lens;

the two symmetrical units are symmetrically arranged, and the positive meniscus lenses of the two symmetrical units are positioned on the outer side.

In this embodiment, the 4F system 200 is a symmetrical structure formed by combining four positive meniscus lenses, four double-cemented positive lenses, and four double-cemented negative lenses, wherein the two positive meniscus lenses, the two double-cemented positive lenses, and the two double-cemented negative lenses are combined into a symmetrical 2F structure, a symmetrical unit is formed by the one meniscus lens, the one double-cemented positive lens, and the one double-cemented negative lens, and the electrically controlled zoom lens 15 is placed on the frequency spectrum surface of the standard 4F relay system.

Specifically, as shown in fig. 1, a first lens group is taken as an example for description, the first lens group includes a first symmetric unit and a second symmetric unit, the first symmetric unit 101 includes a positive meniscus lens 121, a double-cemented positive lens 131, and a double-cemented negative lens 141, the second symmetric unit includes a positive meniscus lens 122, a double-cemented positive lens 132, and a double-cemented negative lens 142, and two focal planes of the lens groups are located outside the positive meniscus lens 121 and outside the positive meniscus lens 122, respectively.

The positive meniscus lens has a convex surface facing the light source to reduce curvature of field and correct spherical aberration. The crown glass is arranged close to the positive meniscus lens to correct the sine difference and the spherical aberration, and the positive and negative double cemented lens group is used to correct the sine difference and the spherical aberration and simultaneously effectively correct the off-axis aberration and the image surface curvature. The other parts adopt symmetrical structures, as shown in figure 1, and the symmetrical structures are beneficial to naturally correcting image plane distortion. All the lenses are arranged on the same optical axis and are coaxially arranged with the imaging tube lens of the microscope 100.

As shown in fig. 1, in an embodiment, the microscope 100 includes a light source 1, a condenser 2, a filter 3, a first relay lens 4, an aperture stop 5, a second relay lens 6, and a spectroscope 9 coaxially disposed in sequence, an objective lens 8 is disposed on a reflection light path of the spectroscope 9, a reflector 10 is disposed on one light splitting path of the spectroscope 9, and an imaging tube 11, the 4F system 200, and the camera 300 are sequentially disposed on the other light splitting path.

In this embodiment, an olympus BX35M microscope 100 is selected, and specifically includes an LED light source 1 of 455nm in fig. 1, a condenser 2, an optical filter 3, a first relay lens 4, an aperture stop 5, a second relay lens 6, a spectroscope 9, an objective lens 8, a reflector 10, and an imaging tube lens 11. The microscope 100 is equipped with the 4F system 200 of the previous embodiment. The microscope 100 is equipped with a Soranbo camera 300, model number Thorlabs CS165MU1, resolution 1440pixels × 1080pixels, 3.45 μm/pixel, and the camera 300 achieves image acquisition. During imaging, the back focal plane of the objective lens 8 coincides with the front focal plane of the imaging barrel lens 11, light of a light source passes through the objective lens 8, is reflected by the sample 7, enters the 4F system 200 through the objective lens 8 and the imaging barrel lens 11 to form an infinite correction imaging system, and then is modulated by the electric control zoom lens 15 to irradiate the camera 300, so that a series of intensity images can be collected.

In order to verify the imaging quality of the microscopic imaging device provided by the embodiment, the imaging is simulated, and the modulation simulation is performed by adopting different Modulation Transfer Functions (MTFs), so that the OTF module value simulation result is shown in FIG. 3, and the imaging quality is better from the OTF module value; the dot-column diagram imaging simulation diagram is shown in fig. 4, a central area, a belt area and an edge area are respectively subjected to simulation imaging in fig. 4, the central area, the belt area and the edge area respectively correspond to image surfaces of 0.000mm, 1.756mm and 2.484mm, light spots of simulation imaging all fall in Airy spots, and the better imaging quality is also shown, wherein the Airy spots are shown by circular parts in fig. 4. The imaging effect simulation results are shown in fig. 5.

The embodiment also provides a system for measuring the nanoscale three-dimensional topography, which comprises microscopic imaging equipment and computer equipment;

the microscopic imaging equipment is used for acquiring a plurality of sample images with different focal lengths along an optical axis and adjusting the focal lengths through the electric control zoom lens;

the computer equipment is used for acquiring the sample image and carrying out three-dimensional topography measurement based on the sample image.

The computer equipment is used for building the three-dimensional shape based on sample imaging, and can be equipment such as a mobile terminal, a desktop computer, a notebook computer, a palm computer and a server.

In one embodiment, the three-dimensional topography measurement is performed based on the sample image, specifically:

carrying out differential estimation on the basis of the sample image to obtain light intensity axial differential;

obtaining phase distribution according to an optical energy transmission equation;

and solving the depth of the sample according to the phase distribution to construct the three-dimensional appearance of the sample.

The embodiment is a quantitative phase imaging system based on an optical energy transmission equation, an electric control zoom lens and a high-performance Abbe imaging optical lens module. The method is suitable for measuring the three-dimensional shape of the micro-nano object at high speed, quantitatively and in real time.

The present embodiment requires the following steps to complete one measurement: controlling an electrically controlled zoom lens, collecting three images along an optical axis, respectively requiring a forward defocusing image, a focusing image and a reverse defocusing image, and obtaining the differential of light intensity along the axial direction by utilizing differential estimation; obtaining phase distribution according to an optical energy transmission equation; and according to the obtained phase distribution, obtaining the depth of the sample and constructing the three-dimensional appearance of the sample.

The phase change caused by the object can be accurately obtained through the steps, so that the accuracy of the three-dimensional shape of the object obtained through reconstruction is guaranteed, multi-step differential estimation can be carried out due to the characteristic that the electronic control zoom lens is continuously and accurately changed, and the precision of calculation imaging is improved.

In an embodiment, the difference estimation is performed based on the sample image to obtain an axial differential of light intensity, specifically:

the sample image comprises a forward out-of-focus image, a focus image and a reverse out-of-focus image, and differential estimation is carried out;

；

wherein the content of the first and second substances,for the axial differential of the light intensity,is the light intensity distribution of the forward defocused image,in order to reverse the light intensity distribution of the out-of-focus image,is the defocus distance;

；

wherein the content of the first and second substances,in order to electrically control the focal length of the zoom lens,is the focal length of the lens group,to electrically control the focal length of the concave lens in the zoom lens,is a distance between the concave lens and the electrically controlled zoom lens.

In an embodiment, the adjusting the focal length by the electrically controlled zoom lens specifically includes:

and selecting a change area of the electric control zoom lens, wherein the current of the electric control zoom lens is proportional to the focal length, and carrying out focal length adjustment.

The ETL changes the focal length according to the current change, and there is a region where the current changes in proportion to the focal length in a certain section, and this embodiment selects this region to correct forAnd carrying out difference.

In an embodiment, the difference estimation is performed based on the sample image to obtain an axial differential of light intensity, specifically:

and carrying out multiple differential estimation, and calculating the average value of the light intensity axial differentials obtained by the multiple differential estimation as the final light intensity axial differential.

And carrying out multi-step differential estimation, and improving the precision of differential estimation so as to improve the imaging precision.

In one embodiment, the phase distribution is obtained according to an optical energy transfer equation, specifically:

the optical energy transfer equation is:

；

wherein the content of the first and second substances,in terms of the wave number, the number of waves,is the axial differential of the light intensity,in order to be the light intensity distribution,to act onThe hamiltonian of the plane is calculated,is a phase distribution;

obtaining a phase distribution:

；

wherein the content of the first and second substances,which represents the inverse of the laplace operator,is the inverse matrix of the light intensity distribution.

In an embodiment, the depth of the sample is obtained according to the phase distribution, and a three-dimensional shape of the sample is constructed, specifically:

for any two points in the phase distributionAndcalculating the phase difference between two pointsAnd further calculating the height difference between the two points:

；

wherein the content of the first and second substances,in order to be the difference in height,is the wavelength;

and obtaining the relative height information of the surface of the sample by combining the height difference between the points, namely the three-dimensional shape information of the surface of the sample.

The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application.