Automatic focusing method, device, equipment, storage medium and program product

Abstract

The present application discloses an autofocus method, apparatus, device, storage medium, and program product, relating to the field of optical interferometry technology. The autofocus method includes: obtaining an interference signal generated by the interference of a first light beam and a second light beam at predetermined time intervals to obtain a corresponding interference signal set; calculating the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference; and automatically focusing the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens; the present application eliminates errors caused by different objective lenses by precalculating the wavefront phase difference, thereby improving the accuracy of autofocus, and can use a microscope objective lens with lower parameter specifications than the imaging microscope objective lens as a reference microscope objective lens to reduce the cost of autofocus. Therefore, the present application can reduce the cost of autofocus and improve the accuracy of autofocus.

Description

Technical Field

[0001] The present application relates to the field of optical interferometry technology, and in particular to autofocus methods, devices, equipment, storage media and program products. Background Art

[0002] During wafer inspection, the depth of field of the high-resolution objective lens is very small. The wafer warping and jitter during scanning will cause defocus and affect the measurement accuracy. Therefore, wafer inspection requires real-time focusing.

[0003] Current focusing methods typically require using two identical objective lenses to achieve symmetry in the optical paths of the interferometer arms. However, high-resolution objective lenses are expensive, and using two identical high-resolution objective lenses increases costs. Furthermore, differences between the lenses can still cause incomplete symmetry in the optical paths, leading to reduced focusing accuracy. Consequently, current focusing methods suffer from high costs and insufficient focusing accuracy. Summary of the Invention

[0004] The main purpose of this application is to provide an automatic focusing method, device, equipment, storage medium and program product, aiming to solve the technical problems of the current focusing method, such as high cost and insufficient focusing accuracy.

[0005] To achieve the above objectives, the present application proposes an autofocus method, which is applied to an autofocus device, and the method includes:

[0006] At every preset time period, an interference signal generated by the interference of a first light beam and a second light beam is acquired to obtain a corresponding interference signal set, wherein the first light beam is directed to a reference microscope objective lens, and the second light beam is directed to an imaging microscope objective lens, and the reference microscope objective lens has been focused and has parameter specifications lower than that of the imaging microscope objective lens;

[0007] Calculating a defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens;

[0008] The imaging microscope objective lens is automatically focused based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0009] In one embodiment, the interference signal set includes a plurality of phase-shifted interference signals having different phase shift amounts, and the step of calculating the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference includes:

[0010] Based on the wavefront phase difference, phase compensation is performed on the phase-shifted interference signal to calculate and obtain a compensated interference signal that eliminates the wavefront phase difference;

[0011] Based on different numbers of adjacent compensation interference signals, the defocus amount of the imaging microscope objective lens is calculated.

[0012] In one embodiment, before the step of acquiring the interference signal generated by the interference of the first light beam and the second light beam at every preset time period, the method further includes:

[0013] Acquire a first distance between each point on the reference microscope objective and the optical axis of the first light beam when the first light beam passes through the reference microscope objective, and acquire a first angle of each point on the reference microscope objective relative to the origin of the light beam;

[0014] Acquire a second distance between each point on the imaging microscope objective and the optical axis of the second light beam when the second light beam passes through the imaging microscope objective, and acquire a second angle of each point on the imaging microscope objective relative to the origin of the second light beam;

[0015] The wavefront phase difference between the imaging microscope objective and the reference microscope objective is calculated based on the first distance, the first angle, the second distance, and the second angle.

[0016] In one embodiment, the step of calculating the wavefront phase difference between the imaging microscope objective and the reference microscope objective based on the first distance, the first angle, the second distance, and the second angle comprises:

[0017] calculating a reference objective wavefront of the reference microscope objective lens based on the first distance and the first angle;

[0018] Based on the second distance and the second angle, an imaging objective lens wavefront of the imaging microscope objective lens is calculated;

[0019] Based on the imaging objective lens wavefront and the reference objective lens wavefront, calculating the wavefront optical path difference between the imaging microscope objective lens and the reference microscope objective lens;

[0020] Based on the wavefront optical path difference, the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens is calculated.

[0021] In one embodiment, the step of automatically focusing the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens includes:

[0022] Determining whether the defocus amount is within the range of the depth of field;

[0023] If the focus is not within the range of the depth of field, determining the displacement of the corresponding object translation stage based on the defocus amount;

[0024] Based on the displacement, the corresponding object displacement stage is moved to complete the automatic focusing of the microscope objective lens.

[0025] In addition, to achieve the above-mentioned purpose, the present application also proposes an automatic focusing device, which includes:

[0026] a signal acquisition module, configured to acquire, at every preset time period, an interference signal generated by the interference of a first light beam and a second light beam, to obtain a corresponding interference signal set, wherein the first light beam is directed toward a reference microscope objective lens, and the second light beam is directed toward an imaging microscope objective lens, the reference microscope objective lens being in focus and having parameter specifications lower than that of the imaging microscope objective lens;

[0027] a defocus calculation module, configured to calculate the defocus of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens;

[0028] An automatic focusing module is used to automatically focus the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0029] In addition, to achieve the above-mentioned purpose, the present application also proposes an autofocus device, which includes:

[0030] a light source for forming a first light beam directed toward the reference microscope objective and a second light beam directed toward the imaging microscope objective;

[0031] an interference unit, configured to generate an interference signal based on the first light beam and the second light beam;

[0032] a detection unit, configured to acquire the interference signal at every preset time period, obtain a corresponding interference signal set, and send the interference signal set to a processing control unit;

[0033] A processing control unit is used to receive the interference signal set sent by the detection unit, calculate the defocus amount of the imaging microscope objective lens based on the interference signal set and the pre-calculated wavefront phase difference, and automatically focus the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0034] In a possible implementation manner of the present application, the autofocus device further includes:

[0035] a feedback actuator, configured to receive the displacement sent by the processing control unit and, based on the displacement, move the corresponding object stage to complete automatic focusing of the imaging microscope objective lens;

[0036] The processing control unit is further used to: determine whether the defocus amount is within the range of the depth of field; if not, determine the displacement of the corresponding object displacement stage based on the defocus amount, and send the displacement to the feedback actuator.

[0037] In addition, to achieve the above-mentioned purpose, the present application also proposes a storage medium, which is a computer-readable storage medium. A computer program is stored on the storage medium, and when the computer program is executed by a processor, the steps of the autofocus method described above are implemented.

[0038] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the auto-focusing method described above are implemented.

[0039] One or more technical solutions proposed in this application have at least the following technical effects:

[0040] The present application obtains the interference signal generated by the interference of the first light beam and the second light beam at every preset time period, obtains the corresponding interference signal set, calculates the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, and automatically focuses the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0041] Because the present application first calculates the wavefront phase difference based on the wavefront of the reference microscope objective lens and the imaging microscope objective lens, and additionally calculates the defocus amount based on the wavefront phase difference, the error caused by the different objective lenses can be eliminated when calculating the defocus amount, so that the defocus amount of the imaging microscope objective lens can be accurately calculated based on the reference microscope objective lens that has been focused, thereby improving the accuracy of autofocus. And because the present application eliminates the error caused by the different objective lenses through the above method, there is no need to use two expensive identical high-resolution objective lenses when focusing. Instead, a microscope objective lens with parameter specifications lower than the imaging microscope objective lens can be used as a reference microscope objective lens to reduce the cost of autofocus. Therefore, the present application can reduce the cost of autofocus and improve the accuracy of autofocus. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] Figure 1 A flowchart of the first embodiment of the auto-focus method of the present application is provided;

[0045] Figure 2 A schematic diagram of a first scene provided in Example 1 of the autofocus method of this application;

[0046] Figure 3 A schematic diagram of a second scenario provided in Example 1 of the autofocus method of this application;

[0047] Figure 4 A schematic diagram of the process flow of the second embodiment of the auto-focus method of this application;

[0048] Figure 5 Schematic diagram of the module structure of the autofocus device according to an embodiment of the present application.

[0049] The purpose, features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0050] It should be understood that the specific embodiments described herein are merely used to explain the technical solutions of the present application and are not intended to limit the present application.

[0051] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0052] It should be noted that the execution subject of this embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, mobile phone, etc., or an electronic device capable of implementing the above functions, an autofocus device, etc. The following uses an autofocus device as an example to illustrate this embodiment and the following embodiments.

[0053] During wafer inspection, high-resolution objective lenses have a very small depth of field. Wafer warpage and wafer jitter during scanning can cause defocus, affecting measurement accuracy, necessitating real-time focusing. Linnik microfocusing (Linnik, the originator of Linnik microfocusing) is commonly used in microscopic inspection. Linnik microfocusing (Linnik, the originator of Linnik microfocusing) typically requires symmetry in the optical paths of the two interferometer arms. However, in high-resolution brightfield imaging systems, high-NA (numerical aperture) imaging objectives are expensive, making Linnik focusing difficult to implement. Furthermore, variations between identical high-resolution objective lenses can lead to incomplete symmetry in the optical path used for focusing, resulting in reduced focusing accuracy.

[0054] Based on this, the embodiment of the present application provides an auto-focus method, which is applied to an auto-focus device, referring to Figure 1 , Figure 1 This is a flowchart of the first embodiment of the auto-focusing method of the present application.

[0055] In this embodiment, the auto-focus method includes steps S10 to S30:

[0056] Step S10: acquiring, at every preset time period, an interference signal generated by the interference of the first light beam and the second light beam to obtain a corresponding interference signal set, wherein the first light beam is a light beam directed toward a reference microscope objective lens, and the second light beam is a light beam directed toward an imaging microscope objective lens, and the reference microscope objective lens has been focused and has parameter specifications lower than that of the imaging microscope objective lens;

[0057] It should be noted that the first and second light beams are obtained by splitting parallel light beams using a beam splitter prism. The interference signal is the interference image produced by the interference of the first and second light beams, which contains phase information and can be used to reflect the defocus state of the microscope objective lens. The interference signal set is a set of interference image data collected at multiple time points and / or positions, which can be used for subsequent phase demodulation and defocus calculation.

[0058] The reference microscope objective lens is the reference arm of the interference system of this embodiment, and the imaging microscope objective lens is the measurement arm of the interference system of this embodiment. The parameter specifications include the NA, magnification, focal length and other parameters of the microscope objective lens. The price of a microscope objective lens with low parameter specifications will be lower than that of a microscope objective lens with high parameter specifications.

[0059] It can be understood that the interference phenomenon is the phenomenon that when two or more coherent light beams meet, corresponding interference signals are generated. The light intensity at the interference point is:

[0060]

[0061] Where, I is the light intensity at the interference point, I r is the intensity of the first beam (i.e., the reference beam), I m is the intensity of the second beam (i.e., the measuring beam), is the phase difference between the reference beam and the measurement beam. In the case of using a broadband light source, the spectral distribution of the broadband light source is:

[0062]

[0063] Among them, B(v) is a function that describes the relationship between the wavelength and light intensity of a broadband light source, v is the frequency, and v c is the center frequency of the light source, is the half-width of the light source spectrum. The function of the coherent intensity of light as a function of distance is:

[0064]

[0065] Among them, g( ) is the coherence intensity envelope function, is the height of the objective lens from the focal point, is the distance between the wafer and the focal plane of the objective lens, is the coherence length of the light source, The specific calculation formula is: , is the central wavelength of the light source. The relationship between the relative optical path difference between the reference arm and the measuring arm and the interference light intensity can be referred to Figure 2 .

[0066] According to the above formula, the coherence intensity of light is related to the phase difference between the two beams of light. The coherence intensity of the two beams of light passing through the phase objective lens is related to the distance between the objective lens and the focal point. In other words, the distance between the objective lens and the focal point can be determined based on the phase difference between the two beams of light. Therefore, this embodiment requires obtaining the interference signal generated by the interference of the first and second beams at predetermined time intervals to obtain a corresponding set of interference signals. This set of interference signals can then be used to determine the defocus of the corresponding microscope objective lens for focusing.

[0067] In one embodiment, the process of forming the first light beam and the second light beam and obtaining the interference signal is performed on an autofocus device. The setting of the autofocus device can refer to Figure 3 The autofocus device includes a light source, an interference unit and a detection unit, and the process of beam formation and interference includes:

[0068] The light source is provided with a broadband light source, a collimator and an aperture. Low-coherence light is emitted by the broadband light source. The low-coherence light first passes through the collimator to become a parallel beam. The parallel beam then passes through the aperture to become a parallel beam with a preset spot size and is emitted to the beam splitter prism in the interference unit.

[0069] The interference unit is provided with an imaging microscope objective lens, a reference microscope objective lens and a beam splitter prism. The parallel light beam first passes through the beam splitter prism to be split into a first light beam and a second light beam, wherein the beam splitter prism has a preset beam splitting ratio, and in this embodiment, the beam splitting ratio is 50:50. An object to be imaged is provided in front of the imaging microscope objective lens. The object to be imaged is an object to be imaged placed on an object stage. In this embodiment, the object to be imaged is a wafer. A reflector is provided in front of the reference microscope objective lens. The first light beam passes through the reference objective lens and converges on the reflector. The reflector reflects the converged first light beam, so that the first light beam passes through the reference objective lens again and returns to the beam splitter prism. The second light beam passes through the imaging objective lens and converges on the object to be imaged. The object to be imaged reflects the converged second light beam, so that the second light beam passes through the imaging objective lens again and returns to the beam splitter prism. After passing through the beam splitter prism, the first and second light beams are projected toward the tube lens in the detection unit.

[0070] The detection unit is provided with a tube lens and a camera. The detection surface of the camera is located at the focus of the tube lens. After the first light beam and the second light beam are emitted to the tube lens, the tube lens shortens the optical path of the first light beam and the second light beam, so that the first light beam and the second light beam interfere with each other at the focus of the tube lens, generating an interference signal. The camera obtains the interference signal every preset time period and transmits the corresponding interference signal set to the processing control unit, wherein the interference signal obtained by the camera is an optical signal. Before transmitting the interference signal, the optical signal gain will be amplified and converted into a corresponding electrical signal.

[0071] Step S20, calculating the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens;

[0072] It should be noted that the wavefront is the equiphase surface at each point in the propagation process of the light beam, and the wavefront phase difference is the phase difference between different wavefronts of different light beams. In this embodiment, it is the phase distribution difference between the reference arm and the measuring arm caused by the difference in objective lens parameters. The defocus amount is the distance deviation between the focus of the imaging microscope objective lens and the object to be imaged.

[0073] Understandably, traditional Linnik-style interferometric autofocus methods typically use two identical large-aperture, high-resolution microscope lenses to ensure high-quality interference fringes, thereby achieving accurate focusing. However, due to the high cost of large-aperture, high-resolution microscope lenses, they are difficult to apply to Linnik-style interferometric autofocus methods. Furthermore, different microscope lenses result in different optical paths through the lens, making it impossible to use the phase difference of the interference signal for focusing. Therefore, it is not possible to simply replace the two identical microscope lenses in the above method with different microscope lenses.

[0074] Furthermore, there are still some differences between the same microscope objective lenses due to reasons such as manufacturing process, which makes the light paths through the two microscope objective lenses not completely symmetrical. Therefore, the focusing method using the Linnik method will still have errors, resulting in a decrease in focusing accuracy.

[0075] Therefore, this embodiment first calculates the wavefront phase difference between the reference and imaging microscopes before calculating the defocus of the imaging microscope. By introducing this wavefront phase difference, the phase error caused by lens asymmetry is effectively eliminated, thereby improving the accuracy of defocus calculation and, in turn, focusing accuracy. Furthermore, since the error caused by lens differences is eliminated, this embodiment allows the use of an objective lens with lower parameter specifications than the imaging microscope as a reference lens, effectively reducing focusing costs while improving focusing accuracy.

[0076] Furthermore, conventional measurement methods use monochromatic light sources for focusing. However, monochromatic light sources have a long coherence length, which produces clear interference fringes even with a large optical path difference between the two beams. Consequently, they fail to produce a distinct envelope feature, limiting focus to a narrow range. However, this embodiment utilizes a broadband light source with a wider spectral range and shorter coherence length, which produces a clear interference envelope during interference, enabling precise focusing over a wider range and extending the focus range.

[0077] In a feasible embodiment, the interference signal set includes multiple phase-shifted interference signals with different phase shift amounts. The specific implementation of calculating the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference may also be:

[0078] Based on the wavefront phase difference, phase compensation is performed on the phase-shifted interference signal to calculate a compensation interference signal that eliminates the wavefront phase difference. Based on different numbers of adjacent compensation interference signals, the defocus amount of the imaging microscope objective lens is calculated.

[0079] It should be noted that the phase-shift interference signal is obtained when the object displacement stage moves rapidly and continuously in a direction parallel to the light beam based on a preset displacement setting when receiving a focus operation instruction.

[0080] It should also be noted that phase compensation is an operation that corrects the phase-shifted interference signal based on the calculated wavefront phase difference to eliminate the error caused by the asymmetry of the objective lens. Through phase compensation, a compensated interference signal can be obtained. The interference light intensity of the compensated interference signal is:

[0081]

[0082] Among them, I ris the intensity of the first beam, I m is the intensity of the second beam, is the calculated wavefront phase difference, is the distance from a point on the objective lens to the optical axis passing through the objective lens, and its range is [0, R], where R is the radius of the objective lens surface. It is the angle between the point on the objective lens and the origin of the light beam on the objective lens surface, ranging from [0, 2 ], which is the angular range of the circle formed by the objective lens surface.

[0083] It is understood that after calculating the wavefront phase difference, the calculated wavefront phase difference needs to be used to eliminate errors. The errors are caused by the different optical paths of the light beams caused by different objective lenses, which manifest as phase differences between the different light beams. Therefore, in this embodiment, when resolving the interference signal, phase compensation is performed based on the calculated wavefront phase difference, so that the calculated defocus amount is the defocus amount after eliminating the wavefront phase difference.

[0084] The defocus amount can be calculated using a Fourier transform method or a phase-shift interferometry method. The phase-shift interferometry method can be a three-frame method, a four-frame method, or a five-frame method. This embodiment uses a three-frame method as an example.

[0085] Taking three adjacent interference signals as a solution unit, the light intensity of adjacent interference signals is:

[0086]

[0087]

[0088]

[0089] in, is the phase difference between adjacent interference signals. The phase difference between the first and second beams can be calculated using three adjacent interference signals:

[0090]

[0091] And since the phase difference refers to the difference in relative position between two coherent light waves at a certain moment, and the reference microscope objective is the objective in the focusing state, the phase difference is calculated as The defocus amount can be obtained, and the focus can be performed according to the defocus amount.

[0092] Step S30 : automatically focusing the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0093] It should be noted that the defocus is the distance deviation between the focus of the imaging microscope objective lens and the object to be imaged, and the depth of field is the maximum range in which the object plane is allowed to deviate from the ideal focal plane while maintaining image clarity.

[0094] It can be understood that this embodiment eliminates the error caused by different objective lenses through the pre-calculated wavefront phase difference when calculating the defocus amount. Therefore, focusing based on the calculated defocus amount can effectively improve the focusing accuracy.

[0095] In a feasible implementation manner, the specific implementation manner of automatically focusing the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens may also be:

[0096] Determine whether the defocus amount is within the range of the depth of field. If not, determine the displacement of the corresponding object displacement stage based on the defocus amount, and move the corresponding object displacement stage based on the displacement to complete automatic focusing of the microscope objective lens.

[0097] It should be noted that the depth of field range is a distance interval extending half the depth of field above and below the ideal focal plane, and the object displacement stage is an actuator for accurately moving the position of the object to be imaged in the vertical direction (Z axis).

[0098] It is understood that if the defocus amount is within the depth of field range, the object to be imaged is still clear and no focusing is required. However, if the defocus amount is not within the depth of field range, it is necessary to move the stage to focus so that the object to be imaged is in focus within the imaging microscope objective lens. This embodiment determines whether the defocus amount is within the depth of field range before focusing. Therefore, the stage is activated for adjustment only when the defocus amount exceeds the depth of field range, avoiding frequent focusing and improving the stability and response efficiency of the focusing system.

[0099] In one embodiment, the calculation of the defocus amount, the determination of whether to focus, and the focusing operation process are performed on an autofocus device, and the autofocus device further includes a processing control unit and a feedback execution mechanism. The specific processing of the defocus amount calculation, focus determination, and focusing operation includes:

[0100] The processing control unit is provided with a host computer, which receives the interference signal sent by the camera, calculates the focus position of the imaging objective lens and the defocus amount between the focus position and the position of the object to be observed according to the interference signal, determines whether focusing is required based on the defocus amount and the depth of field range of the imaging microscope objective lens, and if so, calculates a corresponding displacement amount according to the defocus amount, and sends the corresponding displacement amount to the feedback actuator to complete focusing;

[0101] The feedback actuator is provided with a displacement stage. The feedback actuator receives the displacement amount sent by the host computer and displaces the displacement stage based on the displacement amount to complete the automatic focusing of the imaging microscope objective lens.

[0102] In summary, in this embodiment, an interference signal generated by the interference of the first light beam and the second light beam is obtained at every preset time period to obtain a corresponding interference signal set; based on the interference signal set and the wavefront phase difference, the defocus amount of the imaging microscope objective lens is calculated; and based on the defocus amount and the depth of field of the imaging microscope objective lens, the imaging microscope objective lens is automatically focused.

[0103] Because this embodiment first calculates the wavefront phase difference based on the wavefronts of the reference microscope and the imaging microscope, and additionally calculates the defocus amount based on the wavefront phase difference, the error caused by different objective lenses can be eliminated when calculating the defocus amount. Therefore, the defocus amount of the imaging microscope can be accurately calculated based on the reference microscope that has been focused, thereby improving the accuracy of autofocus. Moreover, because this embodiment eliminates the error caused by different objective lenses through the above-mentioned method, there is no need to use two expensive, identical high-resolution objective lenses when focusing. Instead, a microscope with lower parameter specifications than the imaging microscope can be used as the reference microscope, thereby reducing the cost of autofocus. Therefore, this embodiment can reduce the cost of autofocus and improve the accuracy of autofocus.

[0104] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above embodiment 1 can be referred to the above introduction and will not be described in detail later. Figure 4 Before step S10, the auto-focusing method further includes steps S01 to S03:

[0105] Step S01, obtaining a first distance between each point on the reference microscope objective and the optical axis of the first light beam when the first light beam passes through the reference microscope objective, and obtaining a first angle of each point on the reference microscope objective relative to the origin of the light beam;

[0106] It should be noted that the optical axis is the central propagation path of the focusing system of this embodiment, the first distance is the set of distances between each point in the reference microscope objective and the optical axis, and the first angle is the set of angles of each point in the reference microscope objective relative to the origin of the light beam in the mirror surface.

[0107] It is understood that in this embodiment, because the imaging microscope objective lens and the reference microscope objective lens are different, there will be a large wavefront difference, which requires compensation to eliminate the error caused by the wavefront difference. Therefore, this embodiment samples the first distance and first angle of each point on the objective lens surface to perform subsequent wavefront calculations. This embodiment also quantifies the position information of each sampling point using the first distance and first angle, thereby improving the accuracy of subsequent wavefront fitting calculations.

[0108] Step S02, obtaining a second distance between each point on the imaging microscope objective and the optical axis of the second light beam when the second light beam passes through the imaging microscope objective, and obtaining a second angle of each point on the imaging microscope objective relative to the origin of the second light beam;

[0109] It should be noted that the second distance is the set of distances between each point in the imaging microscope objective and the optical axis, and the second angle is the set of angles of each point in the imaging microscope objective relative to the origin of the light beam in the mirror surface.

[0110] Step S03 : calculating the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the first distance, the first angle, the second distance, and the second angle.

[0111] It should be noted that the wavefront phase difference in this embodiment is calculated before focusing, and the wavefront phase difference is independent of the light source used in the focusing process, the movement frequency of the object displacement stage, and the acquisition frequency of the interference signal, and is only related to the imaging microscope objective lens and the reference microscope objective lens.

[0112] It is understood that the wavefront phase difference is a phase difference caused by the different specifications of the reference microscope and the imaging microscope. Therefore, it is only related to the reference microscope and the imaging microscope themselves. To calculate the wavefront phase difference, it is necessary to sample information at each point on the reference microscope and the imaging microscope. Therefore, this embodiment first obtains the first distance, the first angle, the second distance, and the second angle to calculate the corresponding wavefront phase difference.

[0113] In a feasible implementation manner, the specific implementation manner of calculating the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the first distance, the first angle, the second distance, and the second angle may also be:

[0114] Based on the first distance and the first angle, the reference objective lens wavefront of the reference microscope objective lens is calculated; based on the second distance and the second angle, the imaging objective lens wavefront of the imaging microscope objective lens is calculated; based on the imaging objective lens wavefront and the reference objective lens wavefront, the wavefront optical path difference between the imaging microscope objective lens and the reference microscope objective lens is calculated; based on the wavefront optical path difference, the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens is calculated.

[0115] It should be noted that the wavefront optical path difference refers to the actual distance difference between two waves on their propagation paths. The wavefront is the set of geometric positions of waves with the same phase at a specific point in time. In this embodiment, the wavefront is represented by a seventh-order, thirty-six-term Zernike polynomial (Zernike, the originator of the polynomial). The seventh-order, thirty-six-term Zernike polynomial is a set of orthogonal polynomials defined on the unit circle. By defining the order and the number of terms, a specific type of description of the wavefront can be performed. The description expression is:

[0116]

[0117] in, ) is the fitted wave surface, is the distance from a point on the objective lens to the optical axis passing through the objective lens, and its range is [0, R], where R is the radius of the objective lens surface. It is the angle between the point on the objective lens and the origin of the light beam on the objective lens surface, ranging from [0, 2 ], which is the angle range of the circle formed by the objective lens surface, are the coefficients of the polynomial, and s is a combination of polynomials of different orders and numbers of terms. The specific Zenike overall polynomial part can be divided into three parts:

[0118]

[0119] in, is a radial polynomial, n represents the total order, m represents the angular frequency, and the wavefront of the reference microscope objective can be calculated separately Wavefront imaging microscope objective , the optical path difference of the two wavefronts after passing through the reflective beam splitter prism is:

[0120]

[0121] The wavefront phase difference can be calculated for:

[0122]

[0123] It will be appreciated that this embodiment uses two objective lenses with different parameter specifications. Therefore, the wavefronts of the first and second light beams after passing through the reference objective lens and the imaging microscope objective lens are not simple plane waves, but rather complex wavefronts. Furthermore, because this embodiment pre-samples each point on the reference microscope objective lens and the imaging microscope objective lens and calculates the corresponding first distance, first angle, second distance, and second angle, this embodiment can accurately calculate the wavefronts of the reference microscope objective lens and the imaging microscope objective lens, and further calculate the wavefront phase difference, thereby eliminating focus errors caused by different objective lenses and improving focus accuracy.

[0124] In summary, this embodiment obtains a first distance between each point on the reference microscope objective lens and the optical axis of the first light beam when the first light beam passes through the reference microscope objective lens, and obtains a first angle of each point on the reference microscope objective lens relative to the origin of the light beam; obtains a second distance between each point on the imaging microscope objective lens and the optical axis of the second light beam when the second light beam passes through the imaging microscope objective lens, and obtains a second angle of each point on the imaging microscope objective lens relative to the origin of the second light beam; and calculates the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the first distance, the first angle, the second distance, and the second angle.

[0125] When using two objective lenses with different parameter specifications, the wavefronts of the first and second light beams after passing through the reference objective lens and the microscope objective lens are not simple plane waves, but rather complex wavefronts. Therefore, this embodiment calculates the wavefront phase difference and uses it to eliminate the corresponding focusing error. Furthermore, since the generated wavefront phase difference is only related to the objective lens itself, this embodiment samples and quantifies each point on the objective lens surface, thereby accurately calculating the wavefront and, therefore, the wavefront phase difference, using the calculated first distance, first angle, second distance, and second angle. This allows for accurate calculation of the wavefront, thereby eliminating the focusing error and improving focusing accuracy.

[0126] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the autofocus method of the present application. More simple transformations based on this technical concept are all within the scope of protection of the present application.

[0127] The present application also provides an autofocus device, comprising:

[0128] a light source for forming a first light beam directed toward the reference microscope objective and a second light beam directed toward the imaging microscope objective;

[0129] an interference unit, configured to generate an interference signal based on the first light beam and the second light beam;

[0130] a detection unit, configured to acquire the interference signal at every preset time period, obtain a corresponding interference signal set, and send the interference signal set to a processing control unit;

[0131] A processing control unit is used to receive the interference signal set sent by the detection unit, calculate the defocus amount of the imaging microscope objective lens based on the interference signal set and the pre-calculated wavefront phase difference, and automatically focus the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

[0132] In a possible implementation manner of the present application, the autofocus device further includes:

[0133] a feedback actuator, configured to receive the displacement sent by the processing control unit and, based on the displacement, move the corresponding object stage to complete automatic focusing of the imaging microscope objective lens;

[0134] The processing control unit is further used to: determine whether the defocus amount is within the range of the depth of field; if not, determine the displacement of the corresponding object displacement stage based on the defocus amount, and send the displacement to the feedback actuator.

[0135] This application also provides an automatic focusing device, please refer to Figure 5 , the automatic focusing device comprises:

[0136] A signal acquisition module 10 is configured to acquire, at predetermined time intervals, an interference signal generated by the interference of a first light beam and a second light beam, to obtain a corresponding interference signal set, wherein the first light beam is directed toward a reference microscope objective lens, and the second light beam is directed toward an imaging microscope objective lens, wherein the reference microscope objective lens is already in focus and has lower parameter specifications than the imaging microscope objective lens;

[0137] a defocus calculation module 20, configured to calculate the defocus of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens;

[0138] The auto-focus module 30 is configured to automatically focus the imaging microscope based on the defocus amount and the depth of field of the imaging microscope.

[0139] In one embodiment, the defocus amount calculation module further includes:

[0140] a compensation signal calculation submodule, configured to perform phase compensation on the phase-shifted interference signal based on the wavefront phase difference, and calculate a compensation interference signal that eliminates the wavefront phase difference;

[0141] The defocus amount calculation submodule is used to calculate the defocus amount of the imaging microscope objective lens based on different numbers of adjacent compensation interference signals.

[0142] In one embodiment, the auto-focusing device further includes:

[0143] a first acquisition module, configured to acquire a first distance between each point on the reference microscope objective lens and the optical axis of the first light beam when the first light beam passes through the reference microscope objective lens, and to acquire a first angle of each point on the reference microscope objective lens relative to the origin of the light beam;

[0144] a second acquisition module, configured to acquire a second distance between each point on the imaging microscope objective lens and the optical axis of the second light beam when the second light beam passes through the imaging microscope objective lens, and to acquire a second angle of each point on the imaging microscope objective lens relative to the origin of the second light beam;

[0145] The phase difference calculation module calculates the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the first distance, the first angle, the second distance, and the second angle.

[0146] In one embodiment, the phase difference calculation module further includes:

[0147] A first wavefront calculation submodule, configured to calculate a reference objective wavefront of the reference microscope objective lens based on the first distance and the first angle;

[0148] A second wavefront calculation submodule, configured to calculate an imaging objective lens wavefront of the imaging microscope objective lens based on the second distance and the second angle;

[0149] an optical path difference calculation submodule, configured to calculate the wavefront optical path difference between the imaging microscope objective lens and the reference microscope objective lens based on the imaging objective lens wavefront and the reference objective lens wavefront;

[0150] The phase difference calculation submodule is used to calculate the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the wavefront optical path difference.

[0151] In one embodiment, the auto-focus module further includes:

[0152] A range judgment submodule, configured to judge whether the defocus amount is within the range of the depth of field;

[0153] a displacement calculation submodule, configured to determine the displacement of the corresponding object displacement stage based on the defocus amount if the object is not within the range of the depth of field;

[0154] The auto-focus submodule is used to move the corresponding object displacement stage based on the displacement amount to complete the auto-focusing of the microscope objective lens.

[0155] The autofocus device provided in this application utilizes the autofocus method of the aforementioned embodiment, and can address the technical issues of existing focusing methods, such as high cost and insufficient focusing accuracy. Compared to the prior art, the beneficial effects of the autofocus device provided in this application are the same as those of the autofocus method provided in the aforementioned embodiment, and the other technical features of the autofocus device are the same as those disclosed in the aforementioned embodiment, and are not further described here.

[0156] The present application provides a computer-readable storage medium having computer-readable program instructions (ie, a computer program) stored thereon, wherein the computer-readable program instructions are used to execute the auto-focus method in the above-mentioned embodiment.

[0157] The computer-readable storage medium provided herein may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems, or devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to, an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including, but not limited to, wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0158] The computer-readable storage medium may be included in the auto-focus device, or may exist independently without being assembled into the auto-focus device.

[0159] The computer-readable storage medium carries one or more programs. When the one or more programs are executed by the auto-focus device, the auto-focus device is enabled to perform the auto-focus method.

[0160] Computer program code for performing the operations of the present application may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0161] The flow charts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to the various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, program segment or a part of code, and the module, program segment or a part of code contains one or more executable instructions for realizing the prescribed logical functions. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order than that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the prescribed function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0162] The modules described in the embodiments of the present application may be implemented in software or hardware, wherein the name of a module does not necessarily limit the unit itself.

[0163] The computer-readable storage medium provided in this application stores computer-readable program instructions (i.e., a computer program) for executing the aforementioned autofocus method. This computer-readable storage medium can address the technical issues of existing focusing methods, which suffer from high costs and insufficient focusing accuracy. Compared to the prior art, the beneficial effects of the computer-readable storage medium provided in this application are similar to those of the autofocus method provided in the aforementioned embodiments and are not further elaborated here.

[0164] The present application also provides a computer program product, comprising a computer program, which implements the steps of the above-mentioned auto-focusing method when executed by a processor.

[0165] The computer program product provided in this application can address the technical issues of current focusing methods, which suffer from high costs and insufficient focusing accuracy. Compared to the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the autofocus method provided in the above-mentioned embodiments, and will not be elaborated upon here.

[0166] The user-related data involved in this application (for example, user attribute data, user behavior data, and user geographic location, etc., please adapt the data type here according to the content of the plan) are all obtained after obtaining the user's permission or consent; that is, when this application is applied to specific products or technologies, it is necessary to obtain user permission to obtain and process the relevant data, and the processing of the relevant data must comply with the relevant laws, regulations and regulatory standards of the relevant countries and regions.

[0167] The above description is only part of the embodiments of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. An autofocus device, characterized in that: The autofocus device comprises: A light source, configured to form a first light beam directed toward a reference microscope objective lens and a second light beam directed toward an imaging microscope objective lens, wherein the light source is a broadband light source, and the reference microscope objective lens is a lens that has been focused and has lower parameter specifications than the imaging microscope objective lens; an interference unit, configured to generate an interference signal based on the first light beam and the second light beam; a detection unit, configured to acquire the interference signal at every preset time period to obtain a corresponding interference signal set, amplify the gain of the interference signal set, convert it into a corresponding electrical signal, and send it to a processing control unit, wherein the interference signal is an optical signal before conversion; A processing control unit is used to receive the interference signal set sent by the detection unit, calculate the defocus amount of the imaging microscope objective lens based on the interference signal set and the pre-calculated wavefront phase difference, and automatically focus the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

2. The autofocus device according to claim 1, wherein: The autofocus device also includes: a feedback actuator, configured to receive the displacement sent by the processing control unit and, based on the displacement, move the corresponding object stage to complete automatic focusing of the imaging microscope objective lens; The processing control unit is further used to: determine whether the defocus amount is within the range of the depth of field; if not, determine the displacement of the corresponding object displacement stage based on the defocus amount, and send the displacement to the feedback actuator.

3. An automatic focusing method, characterized in that: Applied to an autofocus device, the method includes: At every preset time period, an interference signal generated by the interference of a first light beam and a second light beam is acquired to obtain a corresponding interference signal set, wherein the first light beam is directed to a reference microscope objective lens, and the second light beam is directed to an imaging microscope objective lens, and the reference microscope objective lens has been focused and has parameter specifications lower than that of the imaging microscope objective lens; Calculating a defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens before focusing, and the wavefront phase difference is only related to the imaging microscope objective lens and the reference microscope objective lens; The interference signal set includes a plurality of phase-shifted interference signals with different phase shift amounts, and the step of calculating the defocus amount of the imaging microscope objective lens based on the interference signal set and the wavefront phase difference includes: Based on the wavefront phase difference, phase compensation is performed on the phase-shifted interference signal to calculate and obtain a compensated interference signal that eliminates the wavefront phase difference; Calculating the defocus amount of the imaging microscope objective lens based on different numbers of adjacent compensation interference signals; The imaging microscope objective lens is automatically focused based on the defocus amount and the depth of field of the imaging microscope objective lens.

4. The method according to claim 3, wherein Before the step of obtaining the interference signal generated by the interference of the first light beam and the second light beam at every preset time period, the method further includes: Acquire a first distance between each point on the reference microscope objective and the optical axis of the first light beam when the first light beam passes through the reference microscope objective, and acquire a first angle of each point on the reference microscope objective relative to the origin of the light beam; Acquire a second distance between each point on the imaging microscope objective and the optical axis of the second light beam when the second light beam passes through the imaging microscope objective, and acquire a second angle of each point on the imaging microscope objective relative to the origin of the second light beam; The wavefront phase difference between the imaging microscope objective and the reference microscope objective is calculated based on the first distance, the first angle, the second distance, and the second angle.

5. The method according to claim 4, wherein The step of calculating the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens based on the first distance, the first angle, the second distance, and the second angle comprises: calculating a reference objective wavefront of the reference microscope objective lens based on the first distance and the first angle; Based on the second distance and the second angle, an imaging objective lens wavefront of the imaging microscope objective lens is calculated; Based on the imaging objective lens wavefront and the reference objective lens wavefront, calculating the wavefront optical path difference between the imaging microscope objective lens and the reference microscope objective lens; Based on the wavefront optical path difference, the wavefront phase difference between the imaging microscope objective lens and the reference microscope objective lens is calculated.

6. The method according to claim 3, wherein The step of automatically focusing the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens comprises: Determining whether the defocus amount is within the range of the depth of field; If the focus is not within the range of the depth of field, determining the displacement of the corresponding object translation stage based on the defocus amount; Based on the displacement, the corresponding object displacement stage is moved to complete the automatic focusing of the microscope objective lens.

7. An automatic focusing device, characterized in that: The device comprises: a signal acquisition module, configured to acquire, at every preset time period, an interference signal generated by the interference of a first light beam and a second light beam, to obtain a corresponding interference signal set, wherein the first light beam is directed toward a reference microscope objective lens, and the second light beam is directed toward an imaging microscope objective lens, the reference microscope objective lens being in focus and having parameter specifications lower than that of the imaging microscope objective lens; a defocus calculation module, configured to calculate a defocus of the imaging microscope objective lens based on the interference signal set and a wavefront phase difference, wherein the wavefront phase difference is pre-calculated based on the wavefront of the reference microscope objective lens and the wavefront of the imaging microscope objective lens before focusing, and the wavefront phase difference is only related to the imaging microscope objective lens and the reference microscope objective lens; a compensation signal calculation submodule, configured to perform phase compensation on the phase-shifted interference signal based on the wavefront phase difference, and calculate a compensation interference signal that eliminates the wavefront phase difference; a defocus amount calculation submodule, configured to calculate the defocus amount of the imaging microscope objective lens based on different numbers of adjacent compensation interference signals; An automatic focusing module is used to automatically focus the imaging microscope objective lens based on the defocus amount and the depth of field of the imaging microscope objective lens.

8. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the auto-focusing method according to any one of claims 3 to 6 are implemented.

9. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the steps of the auto-focus method according to any one of claims 3 to 6 are implemented.

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