Focusing method and system based on turn-back type optical device, computer equipment and storage medium

Abstract

The invention provides a focusing method and system based on a turn-back type optical device, computer equipment and a storage medium, and the method comprises the steps: obtaining the intensity of an electric field currently acting on single electro-optical tuning plate glass, so as to determine the refractive index change of the single electro-optical tuning plate glass; acquiring an incident angle of the marginal light of the light beam on the electro-optical tuning plate glass group; determining the refraction angle of the edge light of the light beam in the electro-optical tuning plate glass group according to the incidence angle and the refractive index change of the single electro-optical tuning plate glass; and determining the focusing amount of the current electro-optical tuning plate glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning plate glass group and the refractive index change of the single electro-optical tuning plate glass. Accurate real-time focusing can be provided for different wafers to be detected, the influence of pattern shapes, reflectivity differences and the like of points to be detected on the wafers in the focusing process only depending on the defocusing relation calibration curve on the measurement result is overcome, and the defect detection sensitivity is improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor detection technology, and in particular relates to a focusing method, system, computer equipment and storage medium based on a folding optical device. Background Art

[0002] In the semiconductor wafer manufacturing process, defect detection plays a vital role in chip manufacturing. With the urgent market demand and the ultimate pursuit of chip cost and power consumption, it is the main driving force for the continuous increase in chip process requirements, which makes the chip defect size requirements higher and higher. Therefore, accurately identifying the type and size of defects is an important factor in improving product yield. In order to improve product yield and reduce production costs, the wafer defect detection system is one of the keys to process control and yield management in the semiconductor manufacturing process.

[0003] During the wafer inspection process, the focal depth of the high-resolution objective lens is short and is affected by the flatness of the platform supporting the wafer, platform floating, and wafer warping. In order to obtain better imaging quality and defect detection sensitivity, it is necessary to keep the wafer surface in the focal plane or focal depth range of the objective lens.

[0004] The focusing of the wafer surface is usually achieved based on a defocus calibration curve, but different wafers have different pattern shapes and different reflectivities. The defocus calibration curves obtained based on wafers with different pattern shapes and different reflectivities will also be different, which will affect the focusing of the wafer surface. Summary of the invention

[0005] The present invention provides a focusing method, system, computer equipment and storage medium based on a folding optical device to solve the problem in the prior art that different wafers have different pattern shapes and different reflectivities, which affects the focusing of the wafer surface.

[0006] In a first aspect, the present invention provides a focusing method based on a reentrant optical device, wherein the reentrant optical device sequentially comprises a tube lens group, a focusing lens group, a field lens group, an electro-optical tuning flat glass group, and a reentrant lens group;

[0007] The focusing lens group is used to form an intermediate image plane; the field lens group is used to perform chromatic aberration correction on the intermediate image; the reentrant lens group is used to converge the intermediate image to the final image plane; the tube lens group is used to magnify the intermediate image; the electro-optic tuning flat glass group is used to adjust the equivalent focal length of the focusing lens group;

[0008] The focusing method comprises:

[0009] In the electro-optical tuning flat glass group, obtaining the intensity of the electric field currently acting on a single electro-optical tuning flat glass as the first electric field intensity;

[0010] Determining a refractive index change of a single electro-optical tunable flat glass according to a first electric field intensity;

[0011] When the light beam passing through the focusing lens group is incident on the electro-optic tuning flat glass group, the incident angle of the edge light of the light beam on the electro-optic tuning flat glass group is obtained;

[0012] Determine the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of the single electro-optical tuning flat glass;

[0013] The focusing amount of the current electro-optical tuning flat glass group is determined according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group and the refractive index change of a single electro-optical tuning flat glass.

[0014] Optionally, determining the refractive index change of a single electro-optical tunable flat glass according to the first electric field intensity includes:

[0015] The refractive index change Δn of a single electro-optical tunable flat glass is calculated according to the following formula:

[0016]

[0017] Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

[0018] Optionally, determining the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of a single electro-optical tuning flat glass comprises:

[0019] The refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set is calculated according to the following formula:

[0020]

[0021] Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; n0 is the refractive index of a single electro-optical tuning flat glass without the effect of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

[0022] Optionally, determining the focusing amount of the current electro-optical tunable flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tunable flat glass group, and the refractive index change of a single electro-optical tunable flat glass includes:

[0023] The shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam is calculated according to the following formula:

[0024] d = h × tanα2;

[0025] Wherein, h is the thickness of the electro-optic tuning flat glass set;

[0026] The focal length f of the electro-optical tuning flat glass set is calculated according to the following formula:

[0027] f = d × tan(90°-α1);

[0028] Obtaining the focal length of the electro-optic tuning flat glass set when there is no electric field applied, as a first focal length;

[0029] Obtaining the focal length of the current electro-optical tuning flat glass set as the second focal length;

[0030] The absolute value of the difference between the first focal length and the second focal length is used as the focusing amount of the current electro-optic tuning flat glass set.

[0031] In a second aspect, the present invention provides a focusing system based on a reentrant optical device, wherein the reentrant optical device sequentially comprises a tube lens group, a focusing lens group, a field lens group, an electro-optical tuning flat glass group, and a reentrant lens group;

[0032] The focusing lens group is used to form an intermediate image plane; the field lens group is used to perform chromatic aberration correction on the intermediate image; the reentrant lens group is used to converge the intermediate image to the final image plane; the tube lens group is used to magnify the intermediate image; the electro-optic tuning flat glass group is used to adjust the equivalent focal length of the focusing lens group;

[0033] The focusing system comprises:

[0034] A first acquisition module, used for acquiring the intensity of the electric field currently acting on a single electro-optical tuning flat glass in the electro-optical tuning flat glass group as a first electric field intensity;

[0035] A first determination module, used to determine the refractive index change of a single electro-optical tuning flat glass according to the first electric field intensity;

[0036] A second acquisition module is used to acquire the incident angle of the edge light of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group;

[0037] A second determination module is used to determine the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of the single electro-optical tuning flat glass;

[0038] The third determination module is used to determine the focusing amount of the current electro-optical tuning flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group and the refractive index change of a single electro-optical tuning flat glass.

[0039] Optionally, the first determining module includes:

[0040] The first calculation unit is used to calculate the refractive index change Δn of a single electro-optical tuning flat glass according to the following formula:

[0041]

[0042] Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

[0043] Optionally, the second determining module includes:

[0044] The second calculation unit is used to calculate the refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set according to the following formula:

[0045]

[0046] Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; n0 is the refractive index of a single electro-optical tuning flat glass without the effect of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

[0047] Optionally, the third determining module includes:

[0048] The third calculation unit is used to calculate the shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam according to the following formula:

[0049] d = h × tanα2;

[0050] Wherein, h is the thickness of the electro-optic tuning flat glass set;

[0051] The fourth calculation unit is used to calculate the focal length f of the electro-optic tuning flat glass set according to the following formula:

[0052] f = d × tan(90°-α1);

[0053] A first acquisition unit is used to acquire the focal length of the electro-optic tuning flat glass group when there is no electric field, as a first focal length;

[0054] A second acquisition unit, used for acquiring the focal length of the current electro-optical tuning flat glass group as a second focal length;

[0055] The first determining unit is configured to use the absolute value of the difference between the first focal length and the second focal length as the focusing amount of the current electro-optical tunable flat glass set.

[0056] In a third aspect, the present invention provides a computer device, comprising a processor and a memory; wherein, when the processor executes a computer program stored in the memory, the steps of the focusing method based on the reentrant optical device described in the first aspect are implemented.

[0057] In a fourth aspect, the present invention provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, the steps of the focusing method based on the reentrant optical device described in the first aspect are implemented.

[0058] The present invention provides a focusing method, system, computer equipment and storage medium based on a reentrant optical device, wherein the method includes obtaining the intensity of the electric field currently acting on a single electro-optical tuning flat glass in an electro-optical tuning flat glass group as a first electric field intensity; determining the refractive index change of the single electro-optical tuning flat glass according to the first electric field intensity; obtaining the incident angle of the edge light of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; determining the refractive angle of the edge light of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of the single electro-optical tuning flat glass; determining the focusing amount of the current electro-optical tuning flat glass group according to the incident angle, the current refractive angle, the thickness of the electro-optical tuning flat glass group and the refractive index change of the single electro-optical tuning flat glass. The present invention can provide accurate real-time focusing for different wafers to be tested, overcome the influence of the pattern shape and reflectivity difference of the test point on the wafer on the measurement result in the process of focusing only relying on the defocus relationship calibration curve, and improve the imaging quality and defect detection sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 A schematic flow chart of a focusing method based on a folding optical device provided in an embodiment of the present invention;

[0061] Figure 2 A schematic structural diagram of a folding optical device provided by an embodiment of the present invention;

[0062] Figure 3 A schematic diagram of electro-optical modulation focusing provided by an embodiment of the present invention;

[0063] Figure 4 A schematic structural diagram of a focusing system based on a folding optical device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] 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.

[0065] Example 1

[0066] like Figure 1 As shown, this embodiment provides a focusing method based on a folding optical device, such as Figure 2 and Figure 3 As shown, the reentrant optical device comprises a tube lens group 1, a focusing lens group 2, a field lens group 3, an electro-optic tuning flat glass group 4 and a reentrant lens group 5 in sequence;

[0067] The focusing lens group 2 is used to form an intermediate image plane; the field lens group 3 is used to perform chromatic aberration correction on the intermediate image; the reentrant lens group 5 is used to converge the intermediate image to the final image plane; the tube lens group 1 is used to magnify the intermediate image; and the electro-optical tuning flat glass group 4 is used to adjust the equivalent focal length of the focusing lens group 2.

[0068] The Schupmann principle (placing an element with the same dispersion but opposite optical power at the conjugate image position of the optical system to correct the chromatic aberration of any optical element with chromatic aberration) is used in combination with the Offner field lens (using the spherical aberration of the compensating lens to balance the aspherical normal aberration and reducing higher-order aberrations by adjusting the position of the field lens) to correct axial chromatic aberration and first-order lateral chromatic aberration, and the achromatic field lens group corrects higher-order lateral chromatic aberration.

[0069] The optical system optimizes monochromatic aberration and chromatic aberration. The optimization range of chromatic aberration can be 0.2μm-0.5μm, covering the deep ultraviolet band, which is a band that conventional NA0.9 objective lenses cannot reach.

[0070] The focusing lens group 2 includes seven lenses, wherein the interval between the first two lenses and the last five lenses is generally half of the total thickness of the last five lenses. The first two lenses are low-power lenses, and the purpose is to correct monochromatic aberrations, such as coma and astigmatism. By the relatively large interval between the first two lenses and the last five lenses, the spatial translation of the light beams in different angular fields will be maximized, which is very conducive to the correction of chromatic aberration.

[0071] The field lens group 3 is generally a three-lens achromatic combination. The material is generally a combination of fused quartz and calcium fluoride. Other deep ultraviolet transparent materials can also be selected, such as magnesium fluoride, lanthanum fluoride and lithium fluoride glass. In addition to using refractive surface lenses, diffractive surface lenses can also be used. Because the dispersion of calcium fluoride and fused quartz in the ultraviolet band is quite different, the curvature radius of a single lens of the field lens group 3 is relatively small. The field lens group 3 is mainly used for the complete correction of redundant lateral chromatic aberration. The correction of the main chromatic aberration still needs to be done through the recursive lens group 5 and the focusing lens group 2.

[0072] The recursive lens group 5 includes a spherical reflector coated with a reflective film, a fused silica meniscus lens, and a plano-convex fused silica lens close to the final imaging surface. Most of the plane area of ​​the plano-convex lens is coated with a reflective film, and the uncoated area is the area where the light beam needs to be projected. The reflective film material is generally aluminum, and a dielectric film can also be coated to enhance the reflectivity. There is a small hole in the center area of ​​the spherical reflector, so the area coated with the reflective film avoids this small hole to allow the light beam corresponding to the intermediate image to pass through the spherical reflector. The field lens group 3 is close to the position of this small hole. The recursive lens group 5 has a strong field curvature correction capability, which is one of the reasons why the optical system has a large field of view.

[0073] A focusing method based on a folding optical device, comprising:

[0074] Step 101: In the electro-optical tunable flat glass group, the intensity of the electric field currently acting on a single electro-optical tunable flat glass is obtained as a first electric field intensity.

[0075] Step 102: determining the refractive index change of a single electro-optical tunable flat glass according to the first electric field intensity.

[0076] Exemplarily, the refractive index change Δn of a single electro-optical tunable flat glass is calculated according to the following formula:

[0077]

[0078] Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

[0079] Step 103, when the light beam passing through the focusing lens group is incident on the electro-optic tuning flat glass group, the incident angle of the edge light of the light beam on the electro-optic tuning flat glass group is obtained.

[0080] Step 104, determining the refraction angle of the edge ray of the light beam in the electro-optic tuning flat glass group according to the incident angle and the refractive index change of the single electro-optic tuning flat glass.

[0081] Exemplarily, the refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set is calculated according to the following formula:

[0082]

[0083] Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passes through the focusing lens group and is incident on the electro-optical tuning flat glass group; n0+Δn represents the refractive index of the current single electro-optical tuning flat glass; n0 is the refractive index of a single electro-optical tuning flat glass without the action of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

[0084] Step 105 , determining the focusing amount of the current electro-optical tuning flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group, and the refractive index change of a single electro-optical tuning flat glass.

[0085] Exemplarily, this step includes:

[0086] The shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam is calculated according to the following formula:

[0087] d = h × tanα2.

[0088] Wherein, h is the thickness of the electro-optic tuning flat glass set.

[0089] The focal length f of the electro-optical tuning flat glass set is calculated according to the following formula:

[0090] f = d × tan(90° - α1).

[0091] The focal length of the electro-optic tuning flat glass group when there is no electric field is obtained as the first focal length.

[0092] The focal length of the current electro-optic tuning flat glass group is obtained as the second focal length.

[0093] The absolute value of the difference between the first focal length and the second focal length is used as the focusing amount of the current electro-optic tuning flat glass set.

[0094] In order to make the solution of this embodiment clearer, this embodiment further discloses specific examples.

[0095] The electro-optic tuning flat glass selected is quartz glass, the thickness of the entire quartz glass is 5 mm, the refractive index n0 of quartz without an applied electric field is 1.54, and the linear electro-optic coefficient is 30.8. The quartz glass is layered in the thickness direction to set transparent electrodes to apply an electric field, which can reduce the voltage required to cause a large refractive index change.

[0096] In this embodiment, the entire quartz glass is divided into 100 layers. The thickness of a single layer of quartz glass is 50 μm. The voltage applied to the single layer of quartz glass is 200 V. The electric field strength is E = 200 V / 50 μm = 4000 V / mm. Then Δn is 0.225×10 -3 .

[0097] like Figure 3 As shown, the focusing lens group is equivalent to an objective lens. The incident angle of the edge ray of the light beam in the objective lens is 45 degrees. When no voltage is applied to the single-layer quartz glass, the edge ray is refracted through the entire quartz glass. The lateral distance from the center of the light beam at the exit (that is, the shortest distance between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass group and the axis of the light beam) is d1, and the distance from the focus point to the lower surface of the entire quartz glass is f1; after the voltage is applied, the edge ray is refracted through the electro-optic crystal. The distance from the center of the light beam at the exit is d2, and the distance from the convergence point to the lower surface of the entire quartz glass is f2. According to the law of refraction, the incident light and the outgoing light of the entire quartz glass are parallel, but there is a translation. This translation is related to the crystal refractive index and thickness, and the incident angle. Here, the crystal thickness and the incident angle are fixed. By changing the refractive index, the translation can be changed. Different translations will result in different final convergence positions, thereby achieving the purpose of focusing.

[0098] When no voltage is applied, the refractive index of the entire quartz glass is 1.54, and the refraction angle of the edge light in the entire quartz glass is 27.33 degrees; after applying a voltage of 200V, the corresponding refractive index is 1.54+Δn=1.54225, and the refraction angle of the edge light in the entire quartz glass is 27.29 degrees. d2-d1=h×(tan27.33°-tan27.29°)=0.0045mm. f2-f1=d2-d1=0.0045mm, that is, the focusing amount is 0.0045 mm.

[0099] In summary, the focusing method based on the reentrant optical device provided in this embodiment utilizes the photoelectric modulation of the internal components of the optical system to achieve automatic focusing without moving parts, avoiding the complex control system required for the mobile optical system or the motion stage, and can provide accurate real-time focusing for different wafers to be tested. It overcomes the influence of the pattern shape and reflectivity differences of the test points on the wafer on the measurement results during the focusing process that relies solely on the defocus relationship calibration curve, thereby improving the imaging quality and defect detection sensitivity.

[0100] Example 2

[0101] Based on the same inventive concept as Example 1, this example provides a focusing system based on a reflective optical device. Since the principle of solving the problem by this system is similar to the focusing method based on a reflective optical device provided in the aforementioned Example 1, the implementation of this system can refer to the implementation of the focusing method based on a reflective optical device provided in Example 1.

[0102] like Figure 4 As shown, the focusing system based on the reentrant optical device includes:

[0103] The first acquisition module 10 is used to acquire the intensity of the electric field currently acting on a single electro-optical tuning flat glass in the electro-optical tuning flat glass group as the first electric field intensity.

[0104] The first determination module 20 is used to determine the refractive index change of a single electro-optical tuning flat glass according to the first electric field intensity.

[0105] The second acquisition module 30 is used to acquire the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group.

[0106] The second determination module 40 is used to determine the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of a single electro-optical tuning flat glass.

[0107] The third determination module 50 is used to determine the focusing amount of the current electro-optical tunable flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tunable flat glass group and the refractive index change of a single electro-optical tunable flat glass.

[0108] Exemplarily, the first determining module includes:

[0109] The first calculation unit is used to calculate the refractive index change Δn of a single electro-optical tuning flat glass according to the following formula:

[0110]

[0111] Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

[0112] Exemplarily, the second determining module includes:

[0113] The second calculation unit is used to calculate the refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set according to the following formula:

[0114]

[0115] Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; n0 is the refractive index of a single electro-optical tuning flat glass without the effect of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

[0116] Exemplarily, the third determining module includes:

[0117] The third calculation unit is used to calculate the shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam according to the following formula:

[0118] d = h × tanα2.

[0119] Wherein, h is the thickness of the electro-optic tuning flat glass set.

[0120] The fourth calculation unit is used to calculate the focal length f of the electro-optic tuning flat glass set according to the following formula:

[0121] f = d × tan(90° - α1).

[0122] The first acquisition unit is used to acquire the focal length of the electro-optic tuning flat glass group when there is no electric field, as a first focal length.

[0123] The second acquisition unit is used to acquire the focal length of the current electro-optical tuning flat glass group as the second focal length.

[0124] The first determining unit is configured to use the absolute value of the difference between the first focal length and the second focal length as the focusing amount of the current electro-optical tunable flat glass set.

[0125] For more specific working processes of the above modules, please refer to the corresponding contents disclosed in Example 1, which will not be repeated here.

[0126] Example 3

[0127] This embodiment provides a computer device, including a processor and a memory; wherein the processor implements the steps of the focusing method based on the reentrant optical device described in Embodiment 1 when executing the computer program stored in the memory.

[0128] For more specific details of the above method, please refer to the corresponding contents disclosed in Example 1, which will not be repeated here.

[0129] Example 4

[0130] This embodiment provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, the steps of the focusing method based on the reentrant optical device described in Embodiment 1 are implemented.

[0131] For more specific details of the above method, please refer to the corresponding contents disclosed in Example 1, which will not be repeated here.

[0132] Example 5

[0133] This embodiment provides a computer program product, including computer executable instructions or a computer program. When the computer executable instructions or the computer program are executed by a processor, the steps of the focusing method based on the reentrant optical device described in Example 1 are implemented.

[0134] For more specific details of the above method, please refer to the corresponding contents disclosed in Example 1, which will not be repeated here.

[0135] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the systems, devices, storage media, and computer program products disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0136] Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solution in the embodiments of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a disk, an optical disk, etc., and includes a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention or some parts of the embodiments.

[0137] In some embodiments, computer executable instructions may be in the form of a program, software, software module, script or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine or other unit suitable for use in a computing environment.

[0138] As an example, computer-executable instructions may, but need not, correspond to a file in a file system, may be stored as part of a file that stores other programs or data, such as in one or more scripts in a HyperText Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or code portions).

[0139] As an example, computer executable instructions may be deployed to be executed on one electronic device, or on multiple electronic devices located at one site, or on multiple electronic devices distributed at multiple sites and interconnected by a communication network.

[0140] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A focusing method based on a reentrant optical device, characterized in that: The reentrant optical device comprises in sequence a tube lens group, a focusing lens group, a field lens group, an electro-optic tuning flat glass group and a reentrant lens group; The focusing lens group is used to form an intermediate image plane; the field lens group is used to perform chromatic aberration correction on the intermediate image; and the folding lens group is used to converge the intermediate image to the final image plane; The tube lens assembly is used to magnify the intermediate image; The electro-optic tuning flat glass group is used to adjust the equivalent focal length of the focusing lens group; The focusing method comprises: In the electro-optical tuning flat glass group, obtaining the intensity of the electric field currently acting on a single electro-optical tuning flat glass as the first electric field intensity; Determining a refractive index change of a single electro-optical tunable flat glass according to a first electric field intensity; When the light beam passing through the focusing lens group is incident on the electro-optic tuning flat glass group, the incident angle of the edge light of the light beam on the electro-optic tuning flat glass group is obtained; Determine the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of the single electro-optical tuning flat glass; The focusing amount of the current electro-optical tuning flat glass group is determined according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group and the refractive index change of a single electro-optical tuning flat glass.

2. The focusing method based on the reentrant optical device according to claim 1, characterized in that: The step of determining the refractive index change of a single electro-optical tuning flat glass according to the first electric field intensity comprises: The refractive index change Δn of a single electro-optical tunable flat glass is calculated according to the following formula: Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

3. The focusing method based on the reentrant optical device according to claim 1, characterized in that: The method of determining the refraction angle of the edge light of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of a single electro-optical tuning flat glass comprises: The refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set is calculated according to the following formula: Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; n0 is the refractive index of a single electro-optical tuning flat glass without the effect of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

4. The focusing method based on the reentrant optical device according to claim 3, characterized in that: The step of determining the focusing amount of the current electro-optical tuning flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group, and the refractive index change of a single electro-optical tuning flat glass includes: The shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam is calculated according to the following formula: d = h × tanα2; Wherein, h is the thickness of the electro-optic tuning flat glass set; The focal length f of the electro-optical tuning flat glass set is calculated according to the following formula: f = d × tan(90°-α1); Obtaining the focal length of the electro-optic tuning flat glass set when there is no electric field applied, as a first focal length; Obtaining the focal length of the current electro-optical tuning flat glass set as the second focal length; The absolute value of the difference between the first focal length and the second focal length is used as the focusing amount of the current electro-optic tuning flat glass set.

5. A focusing system based on a reentrant optical device, characterized in that: The reentrant optical device comprises in sequence a tube lens group, a focusing lens group, a field lens group, an electro-optic tuning flat glass group and a reentrant lens group; The focusing lens group is used to form an intermediate image plane; the field lens group is used to perform chromatic aberration correction on the intermediate image; and the folding lens group is used to converge the intermediate image to the final image plane; The tube lens assembly is used to magnify the intermediate image; The electro-optic tuning flat glass group is used to adjust the equivalent focal length of the focusing lens group; The focusing system comprises: A first acquisition module, used for acquiring the intensity of the electric field currently acting on a single electro-optical tuning flat glass in the electro-optical tuning flat glass group as a first electric field intensity; A first determination module, used to determine the refractive index change of a single electro-optical tuning flat glass according to the first electric field intensity; A second acquisition module is used to acquire the incident angle of the edge light of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; A second determination module is used to determine the refraction angle of the edge ray of the light beam in the electro-optical tuning flat glass group according to the incident angle and the refractive index change of the single electro-optical tuning flat glass; The third determination module is used to determine the focusing amount of the current electro-optical tuning flat glass group according to the incident angle, the current refraction angle, the thickness of the electro-optical tuning flat glass group and the refractive index change of a single electro-optical tuning flat glass.

6. The focusing system based on the folding optical device according to claim 5, characterized in that: The first determining module comprises: The first calculation unit is used to calculate the refractive index change Δn of a single electro-optical tuning flat glass according to the following formula: Wherein, n0 is the refractive index of a single electro-optic tuning flat glass without the effect of an electric field; γ is the linear electro-optic coefficient; and E is the first electric field intensity.

7. The focusing system based on the folding optical device according to claim 5, characterized in that: The second determining module comprises: The second calculation unit is used to calculate the refraction angle α2 of the edge ray of the light beam in the electro-optic tuning flat glass set according to the following formula: Wherein, α1 is the incident angle of the edge ray of the light beam on the electro-optical tuning flat glass group when the light beam passing through the focusing lens group is incident on the electro-optical tuning flat glass group; n0 is the refractive index of a single electro-optical tuning flat glass without the effect of an electric field; Δn is the refractive index change of a single electro-optical tuning flat glass.

8. The focusing system based on the folding optical device according to claim 7, characterized in that: The third determination module comprises: The third calculation unit is used to calculate the shortest distance d between the exit point of the edge ray of the light beam on the electro-optic tuning flat glass set and the axis of the light beam according to the following formula: d = h × tanα2; Wherein, h is the thickness of the electro-optic tuning flat glass set; The fourth calculation unit is used to calculate the focal length f of the electro-optic tuning flat glass set according to the following formula: f = d × tan(90°-α1); A first acquisition unit is used to acquire the focal length of the electro-optic tuning flat glass group when there is no electric field, as a first focal length; A second acquisition unit, used for acquiring the focal length of the current electro-optical tuning flat glass group as a second focal length; The first determining unit is configured to use the absolute value of the difference between the first focal length and the second focal length as the focusing amount of the current electro-optical tunable flat glass set.

9. A computer device, characterized in that: It comprises a processor and a memory; wherein, when the processor executes the computer program stored in the memory, the steps of the focusing method based on the reentrant optical device described in any one of claims 1 to 4 are implemented.

10. A computer-readable storage medium, characterized in that: Used to store computer programs; when the computer programs are executed by the processor, the steps of the focusing method based on the reentrant optical device described in any one of claims 1 to 4 are implemented.

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