Focal plane detection device

Abstract

The utility model provides a focal plane detection device, comprising a laser light source used for providing illumination light; the first spectroscope is used for reflecting and transmitting the illumination light; wherein the illumination light transmitted by the first spectroscope irradiates a focal plane detection sample; the second spectroscope is used for reflecting and transmitting the illumination light rays reflected by the first spectroscope; the four-quadrant photoelectric detector is used for receiving the illumination light rays reflected by the second spectroscope so as to perform primary focusing on the focal plane detection sample; and the energy photoelectric detector is used for receiving the illumination light transmitted by the second spectroscope so as to carry out secondary focusing on the focal plane detection sample. The focal plane detection device provided by the utility model realizes quick, large-dynamic-range and high-precision defocus detection through the combined action of two paths of focal plane detection.

Description

Technical Field

[0001] This application belongs to the field of ultra-precision optical measurement technology, and particularly relates to a focal plane detection device. Background Art

[0002] It can be understood that the focal plane detector is the most critical component of the microscopic imaging technology and has been widely used in microscopic imaging, forming a closed-loop feedback control system with the light source, imaging optical path, and fluorescence detector. Currently, most of the related focusing instruments are based on visual inspection and manual focusing, and their disadvantages are low precision and slow speed.

[0003] The focal plane detection technology can realize non-contact real-time optical distance detection, which is an important technology in the optical processing and detection industry and plays a crucial role in fields such as laser direct writing, optical storage, semiconductor wafer defect inspection, three-dimensional topography detection, and fluorescence microscopy imaging. Key factors such as electronic and optical properties. Detection speed, detection range, and detection accuracy are the key factors for measuring the quality of defocus detection equipment. Existing defocus detection equipment is difficult to balance between detection range and detection accuracy, restricting its application range.

[0004] In summary, the existing focal plane detection technologies have relatively fast detection speeds and large focusing ranges, but there are problems with low accuracy. Summary of the Utility Model

[0005] The focal plane detection device provided by the present utility model realizes fast, large dynamic range, and high-precision defocus detection through the combined action of two-way focal plane detection.

[0006] The present utility model provides a focal plane detection device, which includes:

[0007] A laser light source for providing illumination light;

[0008] A first beam splitter for reflecting and transmitting the illumination light; wherein, the illumination light transmitted by the first beam splitter irradiates the focal plane detection sample;

[0009] A second beam splitter for reflecting and transmitting the illumination light reflected by the first beam splitter;

[0010] A quadrant photodetector for receiving the illumination light reflected by the second beam splitter to perform primary focusing on the focal plane detection sample;

[0011] An energy photodetector for receiving the illumination light transmitted by the second beam splitter to perform secondary focusing on the focal plane detection sample.

[0012] In some embodiments of the present application, a focal plane detection device further includes:

[0013] A light source beam expanding and collimating component, which is arranged on the optical path between the laser light source and the first beam splitter, and is used for converting the shape of the illumination light into a collimated state;

[0014] The light source beam expanding and collimating component includes:

[0015] A first lens, a first baffle, and a second lens that are sequentially arranged on the optical path from the laser light source to the first beam splitter; wherein, a small hole is provided on the first baffle.

[0016] In some embodiments of the present application, a focal plane detection device further includes:

[0017] A third lens, which is arranged on the optical path between the first beam splitter and the focal plane detection sample, and is used for focusing the illumination light in the collimated state onto the focal plane detection sample and for beam expanding and collimating the illumination light reflected by the focal plane detection sample, and then returning it to the first beam splitter.

[0018] In some embodiments of the present application, a focal plane detection device further includes:

[0019] A fourth lens and a second baffle that are sequentially arranged on the optical path from the second beam splitter to the energy photodetector; and are used for focusing the illumination light transmitted by the second beam splitter onto the energy photodetector; wherein, a small hole is provided on the second baffle and the fourth lens and the third lens are in a conjugate relationship.

[0020] In some embodiments of the present application, a focal plane detection device further includes:

[0021] An astigmatism module, which is arranged on the optical path between the second beam splitter and the quadrant photodetector, and is used for focusing the illumination light reflected by the second beam splitter onto the quadrant photodetector; wherein, the astigmatism module includes at least one of a single cylindrical lens, a biconvex lens, a double cylindrical lens, a cylindrical lens, and a convex lens.

[0022] In some embodiments of the present application, the astigmatism module includes: an aspherical lens and a circular plano-convex lens, and the concentric axes of the aspherical lens and the circular plano-convex lens coincide.

[0023] In some embodiments of the present application, the material of the aspherical lens is B270 glass, the radius is 9.577824 mm, and the thickness is 15.73693 mm;

[0024] The material of the circular plano-convex lens is H-K9L glass, and the thickness is 5 mm.

[0025] In some embodiments of the present application, the distance between the aspherical lens and the circular plano-convex lens is 10 mm.

[0026] In some embodiments of the present application, the first lens material is B270 glass, with a thickness of 5.831 mm, a radius of 4.174 mm, and a semi-aperture of 5 mm.

[0027] In some embodiments of the present application, the second lens material is N-BK7 glass, with a thickness of 8 mm, a radius of 113.656 mm, and a semi-aperture of 12.7 mm.

[0028] As can be seen from the above description, an embodiment of the present utility model provides a focal plane detection device, including: a laser light source for providing illumination light; a first beam splitter for reflecting and transmitting the illumination light; wherein, the illumination light transmitted by the first beam splitter irradiates a focal plane detection sample; a second beam splitter for reflecting and transmitting the illumination light reflected by the first beam splitter; a quadrant photodetector for receiving the illumination light reflected by the second beam splitter to perform a primary focusing on the focal plane detection sample; and an energy photodetector for receiving the illumination light transmitted by the second beam splitter to perform a secondary focusing on the focal plane detection sample.

[0029] The focal plane detection device provided by the embodiment of the present utility model integrates two off-focus detection optical paths. One path quickly locates the focal range of an object according to the astigmatic off-focus condition, and uses a photodetector to record astigmatic data, with a processing speed greater than 10KHz. The other path uses confocal measurement to determine the precise off-focus value of the object, and can improve the detection accuracy to within 100 nm. This device adopts a new integrated detection method, sharing a light source and a beam expander and collimator. With the most concise device, through the combined action of the two detections, it realizes fast, large dynamic range, and high-precision off-focus detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Schematic diagram of the principle of the astigmatic method focal plane detection device in the prior art Figure 1 ;

[0032] Figure 2 Schematic diagram of the principle of the astigmatic method focal plane detection device in the prior art Figure 2 ;

[0033] Figure 3Schematic structural diagram of a parallel astigmatic confocal detection device in the prior art;

[0034] Figure 4 Schematic principle diagram of a parallel astigmatic confocal detection device in the prior art;

[0035] Figure 5 Schematic structural diagram of a focal plane detection device in an embodiment of the present invention;

[0036] Figure 6 Schematic structural diagram of the astigmatic module 9 in an embodiment of the present invention;

[0037] Figure 7 Schematic structural diagram of the laser incident objective optical path module in a specific application example of the present invention;

[0038] Figure 8 Schematic structural diagram of the astigmatic module in a specific application example of the present invention;

[0039] Figure 9 Schematic structural diagram of the confocal module in a specific application example of the present invention.

[0040] Reference numerals in the drawings:

[0041] 1: Laser light source; 2: First lens; 3: First baffle; 4: Second lens; 5: First beam splitter; 6: Third lens; 7: Focal plane detection sample; 8: Second beam splitter; 9: Astigmatic module; 10: Quadrant photodetector; 11: Fourth lens; 12: Second baffle; 13: Energy photodetector; 14: Focus position; 901: Aspherical lens; 902: Circular plano-convex lens. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0043] Figure 1 And Figure 2What is displayed is the focal plane detection device of the astigmatism method in the prior art. The light beam emitted by the laser (LD) passes through the polarization beam splitter prism (PBS) to become S-polarized light, and the obtained S-polarized light is reflected by the surface of the workpiece. Since the light beam passes through the quarter-wave plate (QWP) twice, the polarization direction will be deflected 90° to become P-polarized light, which passes smoothly through the polarization beam splitter prism, and then is projected onto the four-quadrant detector (QD) through the astigmatism lens L2. Its detection accuracy is about 2um. Adjusting the system parameters can improve the theoretical detection sensitivity of the entire system, but it will cause the light spot detected on the four-quadrant detector to decrease, affecting the detection data. For example, the distance d between the objective lens and the cylindrical lens increases from 100mm to 200mm, and the QD spot radius decreases from 1.3248mm to 0.8085mm. Figure 2 As shown in (c), as the focal length f2 of the cylindrical lens increases from 16mm to 20mm, the radius of the spot decreases from 1.3176mm to 0.8112mm. As for the influence of the distance w between the cylindrical lens and the image plane, as w decreases from 24mm to 20mm, the spot radius decreases from 1.2973mm to 0.7692mm. Therefore, when selecting the size of these parameters, the size limit of the spot should be given priority to avoid blindly increasing the sensitivity and causing the spot size to be too small.

[0044] The above-mentioned astigmatic focal plane detection device has a fast detector response speed and can correspond to fast focal plane detection, but the detection area of ​​the four-quadrant detector is generally large, with a minimum of about 1mm, and there are gaps between the four quadrants, so the detection spot size cannot be too small. For astigmatic focal plane detection, the improvement of detection accuracy will inevitably cause the spot size to decrease. Therefore, it is difficult for actual astigmatic focal plane detection devices to achieve ultra-high accuracy.

[0045] Figure 3 as well as Figure 4 It is a parallel astigmatism confocal detection device in the prior art, and the nano-micro-motion stage realizes the movement and measurement in the Z direction. CCD is used to record images, and a series of sequential pictures are recorded during the measurement process. Based on the principle of astigmatism, the circular light field distribution of the positive focus measurement point on the sequential pictures, and the near focus and far focus are elliptical distributions. Its advantage is that it can measure multiple points at the same time, but the traditional CCD is different from the four-quadrant detector and cannot accurately calculate the defocus differential signal. The measurement range of confocal imaging is small, and it is difficult to achieve focus detection within a large dynamic and large measurement range.

[0046] Based on the above reasons, the embodiment of the present utility model provides a specific implementation of a focal plane detection device, see Figure 5 , the focal plane detection device specifically comprises:

[0047] A laser light source 1, used to provide illumination light;

[0048] The first beam splitter 5 is configured to reflect and transmit the illumination light; wherein, the illumination light transmitted by the first beam splitter 5 irradiates the focal plane detection sample 7.

[0049] The second beam splitter 8 is configured to reflect and transmit the illumination light reflected by the first beam splitter 5.

[0050] The quadrant photodetector 10 is configured to receive the illumination light reflected by the second beam splitter 8 to perform primary focusing on the focal plane detection sample 7.

[0051] The energy photodetector 13 is configured to receive the illumination light transmitted by the second beam splitter 8 to perform secondary focusing on the focal plane detection sample 7.

[0052] In some embodiments of the present application, the laser light source 1 may employ an LD semiconductor laser, and its function is to provide an illumination light source for defocus detection.

[0053] It can be understood that a beam splitter is also known as a beam splitter mirror, which is used to divide an incident light beam into two beams of transmitted and reflected light with a certain light intensity ratio.

[0054] The quadrant photodetector is a photodetection device formed by arranging four photodiodes with exactly the same performance according to the requirements of a rectangular coordinate. Specifically, it is a photodetection device formed by arranging four photodiodes with exactly the same performance according to the requirements of a rectangular coordinate and is used in laser guidance or laser collimation. It includes various specifications of silicon photocells and various types of quadrant photodiodes, such as quadrant PIN photodiodes, quadrant avalanche photodiodes, etc. The quadrant photodetector is used to convert an optical signal into an electrical signal and record the light intensity information of the four quadrants.

[0055] In some embodiments of the present application, referring to Figure 5 , a focal plane detection device further includes:

[0056] A light source beam expanding and collimating component, disposed on the optical path between the laser light source 1 and the first beam splitter 5, is configured to convert the shape of the illumination light into a collimated state.

[0057] The light source beam expanding and collimating component includes:

[0058] A first lens 2, a first baffle 3, and a second lens 4 sequentially disposed on the optical path from the laser light source 1 to the first beam splitter 5; wherein, the first baffle is provided with a small hole.

[0059] The first lens 2 focuses the light emitted by the laser light source 1 to a point. The small hole of the first baffle 3 is located at the light source focus position, thereby generating a point light source. The small hole of the first baffle 3 is located at the focal point of the second lens 4, and the point light source generates a collimated light source after passing through the second lens 4.

[0060] In some embodiments of the present application, referring further to Figure 5 , a focal plane detection device further includes:

[0061] A third lens 6, disposed on the optical path between the first beam splitter 5 and the focal plane detection sample 7, for focusing the illumination light in the collimated state onto the focal plane detection sample 7 and expanding and collimating the illumination light reflected by the focal plane detection sample 7, and returning it to the first beam splitter 5.

[0062] In some embodiments of the present application, referring further to Figure 5 , a focal plane detection device further includes:

[0063] A fourth lens 11 and a second baffle 12, which are sequentially disposed on the optical path from the second beam splitter 8 to the energy photodetector 13; for focusing the illumination light transmitted by the second beam splitter 8 onto the energy photodetector 13; wherein, the second baffle 12 is provided with a small hole and the fourth lens 11 and the third lens 6 are in a conjugate relationship.

[0064] The fact that the fourth lens 11 and the third lens 6 are in a conjugate relationship means that the image point formed by a point passing through the fourth lens 11 corresponds to the third lens 6.

[0065] In some embodiments of the present application, referring further to Figure 5 , a focal plane detection device further includes:

[0066] An astigmatism module 9, disposed on the optical path between the second beam splitter 8 and the quadrant photodetector 10, for focusing the illumination light reflected by the second beam splitter 8 onto the quadrant photodetector 10; wherein, referring to Figure 6 , the astigmatism module 9 includes at least one of a single cylindrical lens, a biconvex lens, a bi-cylindrical lens, a cylindrical lens, and a convex lens.

[0067] In some embodiments of the present application, referring to Figure 8 , the astigmatism module includes: an aspherical lens 901 and a circular plano lens 902, and the concentric axes of the aspherical lens 901 and the circular plano lens 902 coincide.

[0068] It can be understood that the design of the aspherical lens can effectively reduce or eliminate spherical aberration and other aberrations, thereby improving the imaging quality. The circular plano lens is usually a flat plate of glass or other transparent material, in a circular shape, with both surfaces being flat.

[0069] In some embodiments of the present application, the material of the aspherical lens is B270 glass, with a radius of 9.577824 mm and a thickness of 15.73693 mm;

[0070] The material of the circular plano-convex lens is H-K9L glass, with a thickness of 5 mm.

[0071] In some embodiments of the present application, the distance between the aspherical lens and the circular plano-convex lens is 10 mm.

[0072] In some embodiments of the present application, the material of the first lens is B270 glass, with a thickness of 5.831 mm, a radius of 4.174 mm, and a semi-aperture of 5 mm.

[0073] In some embodiments of the present application, the material of the second lens is N-BK7 glass, with a thickness of 8 mm, a radius of 113.656 mm, and a semi-aperture of 12.7 mm.

[0074] As can be seen from the above description, an embodiment of the present utility model provides a focal plane detection device, including: a laser light source for providing illumination light; a first beam splitter for reflecting and transmitting the illumination light; wherein, the illumination light transmitted by the first beam splitter irradiates a focal plane detection sample; a second beam splitter for reflecting and transmitting the illumination light reflected by the first beam splitter; a quadrant photodetector for receiving the illumination light reflected by the second beam splitter to perform a primary focusing on the focal plane detection sample; and an energy photodetector for receiving the illumination light transmitted by the second beam splitter to perform a secondary focusing on the focal plane detection sample.

[0075] The focal plane detection device provided by the embodiment of the present utility model integrates two off-focus detection optical paths. One path quickly locates the focal range of an object according to the astigmatic off-focus condition, and uses a photodetector to record astigmatic data, with a processing speed greater than 10KHz. The other path uses confocal measurement to determine the precise off-focus value of the object, and can improve the detection accuracy to within 100 nm. This device adopts a new integrated detection method, sharing a light source and a beam expander and collimator. With the most concise device, through the combined action of the two detections, it realizes fast, large dynamic range, and high-precision off-focus detection.

[0076] To further illustrate the solution, the present utility model provides a specific application example of a focal plane detection device to simultaneously meet the requirements of fast and high-precision focusing.

[0077] First, the focal plane detection device provided by the present utility model includes multiple optical elements as Figure 5 shown. Specifically, Figure 5Components 1 to 7 therein constitute the laser incident objective optical path module, components 5 to 10 constitute the astigmatism focal plane detection optical path module, component 9 is the astigmatism module, and 6, 7, 11, 12, 13 constitute the confocal focal plane detection optical path module.

[0078] Among them, 1 is a laser light source, and an LD semiconductor laser can be used. Its function is to provide an illumination light source for defocus detection. 2 is the first lens (optical lens), 3 is the first baffle (with a small hole), and 4 is the second lens (optical lens). 2, 3, and 4 form a laser beam expander and collimator. After passing through the second lens 4, a collimated laser beam is generated. 5 is the first beam splitter. The light emitted by the light source passes through the first beam splitter 5 and then irradiates the objective lens and the sample. The beam reflected by the sample passes through the beam splitter 5 again and then enters the defocus detection part. 6 is the third lens (objective lens). 7 is the focal plane detection sample, where 702 represents the object at the focus of the system z-axis, 701 represents moving to before the focus, and 702 represents the object moving to after the focus. 8 is the second beam splitter. The light reflected by the focal plane detection sample 7 is partially reflected into the left defocus detection module (9 and 10) after passing through the second beam splitter 8, and the other part is transmitted into the upper confocal detection module (11 to 13). 9 is the astigmatism module. The astigmatism module 9 can adopt various astigmatism module designs such as a single cylindrical lens, a biconvex lens, a double cylindrical lens, a cylindrical lens, and a convex lens. 10 is a quadrant photodetector, which converts the optical signal into an electrical signal and records the light intensity information of the four quadrants. The fourth lens 11 is the conjugate lens of the third lens 6. The second baffle 12 is provided with a small hole, and its function is to block the defocus light. 13 is an energy photodetector, which records the information of the in-focus object.

[0079] Actual optical system design and parameter design: Refer to Figure 7 In, 1 is a laser light source with parallel incidence, 2 is the first lens (focusing optical lens), and its material can be set as B270 glass, with a thickness of 5.831 mm, a radius of 4.174 mm, a semi-aperture of 5 mm, and the distance between the laser light source 1 and the first lens 2 is 5 mm. 14 is the focusing focal point position, and the distance from the first lens 2 is 4.22 mm. The distance between the laser light source 1 and the second lens 4 is 28.167 mm. The second lens 4 can adopt glass with the material of N-BK7, with a thickness of 8 mm, a radius of 113.656 mm, and a semi-aperture of 12.7 mm. 6 is the third lens (microscope objective lens). The distance between the second lens 4 and the third lens 6 is 100 mm, and the distance between the third lens 6 and the focal plane detection sample 7 is 20 mm (focal plane).

[0080] Figure 8It is an embodiment of the astigmatism module 9. 7 is the focal plane detection sample (in this embodiment, it is the light emission position of the focal plane detection sample), which includes two parts 901 and 902 in this embodiment. 901 is set as an aspherical lens with a radius of 9.577824 mm, a thickness of 15.73693 mm, and the material is B270 glass. The aspherical coefficients are successively r 2 : 0; r 4 : 7.1261963e -05 ; r 6 : -3.6757938e -08 ; r 8 : 2.276688e -09 ; r 10 : -1.5438247e -11 ; r 12 : 2.3870242e -14 ; r 14 : 0; r 16 : 0; 902 is a circular plano-convex lens with a thickness of 5 mm, and the material can be H-K9L glass. The distance between 901 and 902 is 10 mm. 10 is the astigmatism receiving plane, that is, the position of the quadrant photodetector.

[0081] Figure 9 It is an embodiment of the confocal module. The light rays schematically shown in the figure are the light rays emitted from the focus. The fourth lens 11 is a confocal aspherical lens conjugate to the third lens 6, and its radius can be set to 9.577824 mm, a thickness of 15.73693 mm, and the material is B270 glass. The aspherical coefficients are successively r 2 : 0; r 4 : 7.1261963e -05 ; r 6 : -3.6757938e -08 ; r 8 : 2.276688e -09 ; r 10 : -1.5438247e -11 ; r 12 : 2.3870242e -14 ; r 14 : 0; r 16 : 0; The small hole of the second baffle 12 is the confocal aperture position at this time, and its distance from the fourth lens 11 is 7.525153 mm.

[0082] As can be seen from the above description, a specific application example of the present utility model provides a focal plane detection device, which can achieve fast, high-dynamic-range, and high-precision optical defocus detection, and obtain the accurate object position through two-step defocus detection and calibration. First, the relationship between the astigmatism situation and the defocus information is established to achieve fast focus detection within the range of ±250um. Then, through confocal focal plane detection, the relationship between the focus and the confocal detection energy is established to achieve high-precision detection with an accuracy of less than 100nm.

[0083] In summary, the present utility model adopts a new integrated detection method, sharing a light source and a beam expanding and collimating device, and achieving fast, large-dynamic-range, and high-precision defocus detection through the combined action of two-way detection with the most concise device.

[0084] In the description of this specification, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise specified, the meaning of "a plurality" is two or more.

[0085] The description with reference to terms such as "an embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. The step sequences involved in each embodiment are used to schematically illustrate the implementation of the present utility model, and the step sequences are not limited and can be adjusted appropriately as needed.

[0086] In the description of the present utility model, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood through specific circumstances.

[0087] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present utility model. It should be understood that the above are only specific embodiments of the present utility model and are not used to limit the protection scope of the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A focal plane detection device, characterized in that: include: A laser light source, used to provide illumination light; A first beam splitter, used for reflecting and transmitting the illumination light; wherein the illumination light transmitted by the first beam splitter is irradiated onto the focal plane detection sample; a second beam splitter, used to reflect and transmit the illumination light reflected by the first beam splitter; A four-quadrant photoelectric detector, used for receiving the illumination light reflected by the second beam splitter, so as to focus the focal plane detection sample once; The energy photoelectric detector is used to receive the illumination light transmitted by the second beam splitter to perform secondary focusing on the focal plane detection sample.

2. The focal plane detection device according to claim 1, characterized in that: Also includes: A light source beam expansion and collimation component is arranged on the optical path between the laser light source and the first beam splitter, and is used to convert the shape of the illumination light into a collimated state; The light source beam expansion and collimation component comprises: A first lens, a first baffle and a second lens are sequentially arranged on the optical path from the laser light source to the first beam splitter; wherein the first baffle is provided with a small hole.

3. The focal plane detection device according to claim 2, characterized in that: Also includes: The third lens is arranged on the optical path between the first beam splitter and the focal plane detection sample, and is used to focus the illumination light in the collimated state onto the focal plane detection sample and to expand and collimate the illumination light reflected by the focal plane detection sample and return it to the first beam splitter.

4. The focal plane detection device according to claim 3, characterized in that: Also includes: A fourth lens and a second baffle are sequentially arranged on the optical path from the second beam splitter to the energy photoelectric detector; Used to focus the illumination light transmitted by the second beam splitter onto the energy photoelectric detector; wherein the second baffle is provided with a small hole and the fourth lens is in a conjugate relationship with the third lens.

5. The focal plane detection device according to claim 3, characterized in that: Also includes: An astigmatism module is arranged on the optical path between the second beam splitter and the four-quadrant photodetector, and is used to focus the illumination light reflected by the second beam splitter onto the four-quadrant photodetector; wherein the astigmatism module includes at least one of a single column lens, a double convex lens, a double column lens, a cylindrical lens and a convex lens.

6. The focal plane detection device according to claim 5, characterized in that: The astigmatism module comprises: an aspheric lens and a circular flat lens, and the concentric axis of the aspheric lens coincides with the concentric axis of the circular flat lens.

7. The focal plane detection device according to claim 6, characterized in that: The material of the aspheric lens is B270 glass, with a radius of 9.577824 mm and a thickness of 15.73693 mm; The material of the circular flat lens is H-K9L glass with a thickness of 5 mm.

8. The focal plane detection device according to claim 6, characterized in that: The distance between the aspherical lens and the circular flat lens is 10 mm.

9. The focal plane detection device according to claim 2, characterized in that: The first lens is made of B270 glass, and has a thickness of 5.831 mm, a radius of 4.174 mm, and a semi-aperture of 5 mm.

10. The focal plane detection device according to claim 2, characterized in that: The second lens is made of N-BK7 glass, has a thickness of 8 mm, a radius of 113.656 mm, and a semi-aperture of 12.7 mm.

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