Multi-light-spot automatic focusing device and automatic focusing method thereof

Abstract

The invention provides a multi-light-spot automatic focusing device and an automatic focusing method thereof. The multi-spot automatic focusing device comprises a light source; the spatial light modulation structure is located on the light emitting side of the light source, and the spatial light modulation structure is used for dividing one beam of light into multiple beams of light; the reflector is located on the side, away from the light source, of the spatial light modulation structure, and the edge of the reflector is tangent to the optical axis of the light source, so that only half of the multiple light beams are reflected by the reflector; the microscope objective is located on a downstream light path of the reflector, light beams reflected by the reflector irradiate the surface of a sample through the microscope objective to form array light spots, the sample reflects the light beams on the surface of the sample to form array light beams, then the array light beams enter the focus detection structure, and the defocusing amount of the light spots is judged according to the light spots received in the focus detection structure. Therefore, focusing is realized. The problem that an automatic focusing device in the prior art is limited in focus detection application scene is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic focusing equipment, and in particular to a multi-spot automatic focusing device and an automatic focusing method thereof. Background Art

[0002] At present, autofocus technology is widely used in the fields of optical inspection, semiconductors, and biochips. In the process of detecting the object to be inspected by the microscope, in order to achieve the image requirements of a large field of view when observing the object to be inspected using the microscope, the object to be inspected must be scanned in steps. After the imaging system completes the exposure of an area of ​​the object to be inspected, the stage will perform a stepping motion to move the next imaging area of ​​the object to be inspected into the field of view of the microscope. During the movement, defocusing may occur, so the autofocus device is required to monitor and adjust in real time to ensure that the object to be inspected is always in the optimal focal plane position of the microscope during the imaging process.

[0003] Existing autofocus devices mainly use two methods. One is to mainly use image clarity or image spatial frequency to achieve automatic focus detection. Usually, a series of images need to be collected and the clarity of each frame of image is evaluated. The focus detection speed of this method is related to the algorithm. Generally, the more images are collected, the longer the focus detection time is, and the higher the focus detection accuracy is. This method has a simple system structure and low cost, but it is often slow and has low accuracy. It can only be applied to objects with certain optical characteristics (such as cells), so it has poor versatility. The other is to use laser or LED light to determine the defocus distance and direction to achieve focusing. It has the advantages of high accuracy, high speed, and high versatility, but it usually increases the cost and complexity of the equipment. In addition, this autofocus device usually determines the defocus amount based on a single light spot. In some application scenarios, there will be focus detection errors. For example, the surface reflectivity of the object to be detected is very different, or the surface is uneven, or the focus detection light spot is placed on the edge of the object to be detected. These situations may cause the focus to be detected on the wrong focal plane, thereby affecting the accuracy of the focus detection.

[0004] That is to say, the auto-focus device in the prior art has the problem of limited focus detection application scenarios. Summary of the invention

[0005] The main purpose of the present invention is to provide a multi-spot autofocus device and an autofocus method thereof, so as to solve the problem that the autofocus device in the prior art has limited focus detection application scenarios.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a multi-spot autofocus device, comprising: a light source; a spatial light modulation structure, the spatial light modulation structure is located on the light emitting side of the light source, and the spatial light modulation structure is used to divide a beam of light into multiple beams of light; a reflector, the reflector is located on the side of the spatial light modulation structure away from the light source, and the edge of the reflector is tangent to the optical axis of the light source, so that only half of the multiple beams of light are reflected by the reflector; a microscope objective lens, the microscope objective lens is located in the downstream optical path of the reflector, the light beam reflected by the reflector passes through the microscope objective lens and irradiates the surface of the sample to form an array of light spots, the sample reflects the light beam on its surface to form an array of light spots, and then enters the focusing detection structure, and the defocus amount of the multiple light spots is judged according to the multiple light spots received in the focusing detection structure, thereby achieving focusing.

[0007] Furthermore, the light source is a laser diode.

[0008] Furthermore, the spatial light modulation structure is a one-dimensional Dammann grating.

[0009] Furthermore, the multi-spot autofocus device also includes a beam expansion and collimation structure, which is located between the light source and the spatial light modulation structure, and is used to expand and collimate the light emitted by the light source.

[0010] Furthermore, the multi-spot autofocus device also includes a collimator, which is located between the reflector and the microscope objective lens.

[0011] Furthermore, the multi-spot autofocus device also includes a dichroic mirror, which is located between the collimating lens and the microscope objective lens to achieve reflection of the light beam between the collimating lens and the microscope objective lens.

[0012] Furthermore, the focus detection structure includes a multi-quadrant photoelectric sensor for determining the defocus amounts of the multiple light spots.

[0013] Furthermore, there are one or more multi-quadrant photoelectric sensors. When there are multiple multi-quadrant photoelectric sensors, the focusing structure also includes a semi-transparent and semi-reflective mirror, at least one multi-quadrant photoelectric sensor is located on the reflection path of the semi-transparent and semi-reflective mirror, and at least another multi-quadrant photoelectric sensor is located on the transmission path of the semi-transparent and semi-reflective mirror.

[0014] Furthermore, the multi-spot autofocus device also includes a light absorbing layer, which is located on a side of the reflector away from the spatial light modulation structure, and is used to absorb the other half of the multiple beams of light that are not reflected by the reflector.

[0015] According to another aspect of the present invention, there is provided an autofocus method for a multi-spot autofocus device. The autofocus method is the autofocus method for the multi-spot autofocus device described above. The multi-spot autofocus device also includes a stage, the stage carries a sample of the multi-spot autofocus device, the stage is movably arranged relative to the microscope objective lens, and the autofocus method includes: a pre-adjustment step: manually adjusting the distance between the microscope objective lens and the stage so that the clarity of the sample meets a preset threshold; an autofocus step: turning on the multi-spot autofocus device, judging the defocus amount of the multiple light spots according to the multiple light spots received in the focusing detection structure of the multi-spot autofocus device, and then adjusting the distance between the sample and the microscope objective lens, thereby achieving focusing.

[0016] By applying the technical solution of the present invention, a multi-spot autofocus device includes a light source, a spatial light modulation structure, a reflector and a microscope objective lens. The spatial light modulation structure is located on the light output side of the light source, and is used to divide a beam of light into multiple beams of light. The reflector is located on the side of the spatial light modulation structure away from the light source, and the edge of the reflector is tangent to the optical axis of the light source, so that only half of the multiple beams of light are reflected by the reflector. The microscope objective lens is located in the downstream optical path of the reflector. The light beam reflected by the reflector passes through the microscope objective lens and irradiates the surface of the sample to form an array of light spots. The sample reflects the light beam on its surface to form an array of light spots, and then enters the focusing detection structure. The defocus amount of the multiple light spots is judged according to the multiple light spots received in the focusing detection structure, thereby achieving focusing.

[0017] By setting up a spatial light modulation structure, the spatial light modulation structure can divide a beam of light emitted by a light source into multiple beams of light, which are then reflected by a reflector so that half of the multiple beams of light are irradiated onto the surface of the sample through a microscope objective lens, forming an array of light spots on the surface of the sample, and then reflected by the sample so that the formed array of light beams enters the focusing structure, and the defocus amounts of the multiple light spots are judged according to the multiple light spots received in the focusing structure. Each light spot can obtain a defocus amount, and by increasing the number of light beams entering the focusing structure, focusing is achieved by the defocus amounts of the multiple light spots, which can better ensure the accuracy of focusing, and can greatly avoid the risk of focusing errors in some scenes, so that the focusing measurement value can be found more accurately, which is conducive to increasing the application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A schematic diagram of the optical path of a multi-spot autofocus device according to an optional embodiment of the present invention is shown;

[0020] Figure 2A schematic diagram of the optical path of a multi-spot autofocus device according to another optional embodiment of the present invention is shown;

[0021] Figure 3 A schematic diagram showing light spots received by a multi-quadrant photoelectric sensor of a multi-spot auto-focusing device under different defocus amounts in an optional embodiment of the present invention is shown;

[0022] Figure 4 Shows Figure 2 A local optical path diagram of a multi-spot autofocus device;

[0023] Figure 5 A schematic diagram showing a light spot at a sample of a multi-spot autofocus device according to an optional embodiment of the present invention is shown;

[0024] Figure 6 Shows Figure 2 Schematic diagram of the light spots received by the two multi-quadrant photoelectric sensors of the multi-spot autofocus device.

[0025] The above drawings include the following reference numerals:

[0026] 10. Light source; 20. Beam expander; 30. Collimating lens; 40. Spatial light modulation structure; 50. Reflector; 60. Collimating lens; 70. Dichroic mirror; 80. Microscope objective; 90. Sample; 100. Multi-quadrant photoelectric sensor; 110. Semi-transparent and semi-reflective mirror; 120. Light-absorbing layer. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0029] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0030] In order to solve the problem that the autofocus device in the prior art has limited focus detection application scenarios, the present invention provides a multi-spot autofocus device and an autofocus method thereof.

[0031] like Figures 1 to 6As shown, the multi-spot autofocus device includes a light source 10, a spatial light modulation structure 40, a reflector 50 and a microscope objective 80. The spatial light modulation structure 40 is located on the light output side of the light source 10, and the spatial light modulation structure 40 is used to divide a beam of light into multiple beams of light; the reflector 50 is located on the side of the spatial light modulation structure 40 away from the light source 10, and the edge of the reflector 50 is tangent to the optical axis of the light source 10, so that only half of the multiple beams of light are reflected by the reflector 50; the microscope objective 80 is located in the downstream optical path of the reflector 50, and half of the light beam reflected by the reflector 50 passes through the microscope objective 80 to irradiate the surface of the sample 90 to form an array of light spots, and the sample 90 reflects the light beam on its surface to form an array of light spots, and then enters the focusing structure, and the defocus amount of the multiple light spots is judged according to the multiple light spots received in the focusing structure, thereby achieving focusing.

[0032] By setting up the spatial light modulation structure 40, the spatial light modulation structure 40 can divide a beam of light emitted by the light source 10 into multiple beams of light, and then after reflection by the reflector 50, half of the multiple beams of light are irradiated to the surface of the sample 90 through the microscope objective 80, forming an array of light spots on the surface of the sample 90, and then the formed array of light beams enters the focusing structure through reflection by the sample 90, and the defocus amounts of the multiple light spots are judged according to the multiple light spots received in the focusing structure, and each light spot can obtain a defocus amount. By increasing the number of light beams entering the focusing structure, focusing is achieved by the defocus amounts of multiple light spots, which can better ensure the accuracy of focusing, and can greatly avoid the risk of focusing errors in some scenes, so that the focusing measurement value can be found more accurately, which is conducive to increasing the application scenarios.

[0033] Specifically, the light source 10 is a laser diode. This configuration allows the laser diode to emit a laser beam, which facilitates subsequent light splitting. More specifically, the light source 10 is a 660nm semiconductor laser diode, which can avoid interference of the light source 10 with microscopic imaging.

[0034] Specifically, the spatial light modulation structure 40 is a one-dimensional Dammann grating. A one-dimensional Dammann grating can divide a beam of light into multiple beams in a single row. Of course, in practical applications, a two-dimensional grating can also be selected according to specific needs to achieve the splitting of the array beam.

[0035] In a specific embodiment of the present application, in order to ensure the homogenization effect of the one-dimensional Dammann grating on light, the grating frequency of the one-dimensional Dammann grating is set to be greater than or equal to 100lp / mm and less than or equal to 140lp / mm, and the divergence angle of the one-dimensional Dammann grating is greater than 0° and less than or equal to 5°. Preferably, the grating frequency of the one-dimensional Dammann grating is 120lp / mm, and the divergence angle is 1.2°. By reasonably setting the specific parameters of the one-dimensional Dammann grating, it is beneficial to ensure the light splitting effect while ensuring the uniformity of the light spot, thereby improving the focusing accuracy.

[0036] refer to Figure 1and Figure 2 The multi-spot autofocus device also includes a beam expansion and collimation structure, which is located between the light source 10 and the spatial light modulation structure 40. The beam expansion and collimation structure is used to expand and collimate the light emitted by the light source 10. In a specific embodiment of the present application, the beam expansion and collimation structure includes a beam expander 20 and a collimator lens 30, which are sequentially arranged at intervals on the light exit side of the light source 10. The beam expander 20 is convenient for the subsequent reflector 50 to reflect half of the light and avoid the other half of the light, so that only half of the target pupil is illuminated, satisfying the focus detection principle.

[0037] Specifically, the multi-spot autofocus device further includes a collimator 60 and a dichroic mirror 70. The collimator 60 is located between the reflector 50 and the microscope objective 80, and the dichroic mirror 70 is located between the collimator 60 and the microscope objective 80, so as to realize the reflection of the light beam between the collimator 60 and the microscope objective 80. Half of the multiple light beams reflected by the reflector 50 are sequentially collimated by the collimator 60 and reflected by the dichroic mirror 70, and reach the microscope objective 80, and then appear as an array of light spots on the surface of the sample 90. After the sample 90 reflects the light beam to form an array of light beams, it is sequentially reflected by the dichroic mirror 70 and the collimator 60, and then enters the focusing structure from the outside of the reflector 50, that is, the reflector 50 avoids the return path of the light beam. The dichroic mirror 70 realizes the reflection of the focusing beam and the transmission of the imaging beam, so that the imaging beam and the focusing beam will not interfere with each other.

[0038] In addition, the central axis of the collimator 60 and the optical axis of the microscope objective 80 coincide on the dichroic mirror 70, and the edge of the side of the reflector 50 away from the light source 10 is on the central axis of the collimator 60, so that the light beam returned by the sample 90 can avoid the reflector 50 and enter the focus detection structure after passing through the collimator 60. Since only half of the target pupil is illuminated when the light beam is irradiated on the sample 90, the point spread function of the microscope objective 80 is highly tilted, so that the reflected light spot will be laterally displaced as the focus moves.

[0039] Specifically, the focus detection structure includes a multi-quadrant photoelectric sensor 100 for determining the defocus amount of multiple light spots. The multi-quadrant photoelectric sensor 100 is conducive to focusing the multiple light spots irradiated thereon. In a specific embodiment of the present application, the multi-quadrant photoelectric sensor 100 is a four-quadrant photoelectric sensor. In order to realize the focus detection function of multiple beams and multiple light spots, the four-quadrant photoelectric sensor is used to process the focus detection information of multiple light spots.

[0040] In an optional embodiment of the present application, the multi-quadrant photoelectric sensor 100 is one or more. Figure 1 In the specific embodiment shown, there is one multi-quadrant photoelectric sensor 100. Figure 2In the specific embodiment shown, there are multiple multi-quadrant photoelectric sensors 100, specifically two. When there are multiple multi-quadrant photoelectric sensors 100, the focus detection structure also includes a semi-transparent and semi-reflective mirror 110. The semi-transparent and semi-reflective mirror 110 is located on the back side of the reflector 50 and between the two multi-quadrant photoelectric sensors 100. At least one multi-quadrant photoelectric sensor 100 is located on the reflection path of the semi-transparent and semi-reflective mirror 110, and at least another multi-quadrant photoelectric sensor 100 is located on the transmission path of the semi-transparent and semi-reflective mirror 110. By adding the semi-transparent and semi-reflective mirror 110, the light beam can be split to form a multi-channel detection form, so as to realize the focus detection of more light spot arrays. In other words, the two multi-quadrant photoelectric sensors 100 can receive multiple light spots, thereby realizing the judgment of the defocus amount.

[0041] exist Figure 1 and Figure 2 In the embodiment, the multi-spot autofocus device further includes a light absorbing layer 120, which is located on a side of the reflector 50 away from the spatial light modulation structure 40, and is used to absorb the other half of the multiple beams of light that are not reflected by the reflector 50. Specifically, the multi-spot autofocus device further includes a stage, on which a sample 90 is mounted, and the stage is movably arranged relative to the microscope objective lens 80. A computer algorithm is used to determine the defocus amount of the multiple light spots received in the focus detection structure, and then the stage is controlled to move up and down according to the defocus amount to adjust the distance between the sample 90 and the microscope objective lens 80, thereby achieving focusing.

[0042] The present invention also provides an auto-focusing method for a multi-spot auto-focusing device. The auto-focusing method is the auto-focusing method for the multi-spot auto-focusing device described above. The auto-focusing method includes:

[0043] Pre-adjustment step: manually adjusting the distance between the microscope objective lens 80 and the stage so that the clarity of the sample 90 meets a preset threshold;

[0044] Autofocusing step: Turn on the multi-spot autofocusing device, determine the defocusing amount of the multiple light spots according to the multiple light spots received in the focus detection structure of the multi-spot autofocusing device, and then adjust the distance between the sample 90 and the microscope objective lens 80 to achieve focusing.

[0045] like Figure 3 As shown, the light spot received by the multi-quadrant photoelectric sensor 100 will shift and change with the movement of the focus. Through software simulation, the present invention can achieve the focus detection requirement, and multiple light spots appear on the focal plane and the multi-quadrant photoelectric sensor 100, and the multiple light spots will change with the change of the defocus amount. Figure 3The shapes of multiple light spots reaching the four-quadrant photoelectric sensor under different defocus values ​​are shown. The four-quadrant photoelectric sensor can be regarded as a combination of two two-quadrant photoelectric sensors, which can simultaneously obtain the DIV signals of two light spots. Figure 2 In the embodiment, two light spots can be detected on each four-quadrant photoelectric sensor, and each light spot will have different lateral displacements depending on the defocus amount.

[0046] Figure 4 Shows Figure 2 Local light path diagram of the optical system in . Figure 5 Multiple light spots formed by multiple light beams received at the sample 90 are shown. Figure 6 They are shown respectively Figure 2 The two light spots are respectively received by the two four-quadrant photosensors in the embodiment.

[0047] During the focusing test, the sample 90 is first placed on the stage, a microscope objective lens 80 with a suitable magnification is selected, and the lens is manually adjusted until the sample 90 presents a clear image. Then open the focusing structure, connect the signal processing module of the multi-quadrant photoelectric sensor 100 and the control module that controls the movement of the stage. At this time, the light reflected by the sample 90 is obtained by the multi-quadrant photoelectric sensor 100, and the multi-quadrant photoelectric sensor 100 obtains the output signals of the light spot, which are SUM, DIFF and DIV respectively. SUM represents the sum of the light intensities PD1 and PD2 obtained by two of the quadrants of the four-quadrant photoelectric sensor, SUM=PD1+PD2, DIFF represents the difference between the two light intensities, DIFF=PD1-PD2, when the sample 90 is at the focal plane, DIFF is approximately 0 and SUM is the maximum value, DIV=(DIFF / SUM)*K (K is the signal amplification factor), which is expressed as the focusing measurement value, which is linearly related to the defocus amount. According to the DIV values ​​obtained at different defocus planes, we can obtain the displacement of the microscope objective 80 or the stage.

[0048] Usually, the signal processing module first processes whether the sum signal SUM is greater than the threshold. If it is greater than the threshold, it is determined that focus can be achieved. If it is less than the threshold, it means that the focus range is exceeded and focus cannot be achieved. If SUM is greater than the threshold, the defocus amount and defocus direction will be calculated based on the obtained DIV value, thereby pushing the stage to move and complete autofocus.

[0049] In actual application, when some parts of sample 90 deviate from the optimal focal plane position, the reflected light spot position will shift left and right on the multi-quadrant photoelectric sensor 100, and the PD1 and PD2 values ​​will change. At this time, the DIV value will change with the DIV value we set at the optimal focal plane. The DIV change is used as a feedback signal for the focusing direction. The up and down movement of the stage is used to quickly compensate for the defocus amount and adjust the sample 90 to the optimal focal plane position. Light spots at different positions can obtain defocus information of different focal planes, and the sample 90 can be adjusted to different focal plane positions. In this way, we can effectively expand the application scope of the multi-spot autofocus device. For example, if the surface of sample 90 is very uneven, a lot of focal plane information can be obtained through multiple light spots; for example, when inspecting the edge of sample 90, some focus detection spots are unavailable, and we can process these available points and damaged points through DIP.

[0050] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0052] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-spot autofocus device, characterized in that: include: Light source (10); A spatial light modulation structure (40), the spatial light modulation structure (40) being located on the light output side of the light source (10), and the spatial light modulation structure (40) being used to divide a beam of light into multiple beams of light; a reflector (50), the reflector (50) being located on a side of the spatial light modulation structure (40) away from the light source (10), and an edge of the reflector (50) being tangent to the optical axis of the light source (10), so that only half of the multiple light beams are reflected by the reflector (50); A microscope objective lens (80) is located in a downstream optical path of the reflector (50). The light beam reflected by the reflector (50) passes through the microscope objective lens (80) and irradiates the surface of a sample (90) to form an array of light spots. The sample (90) reflects the light beam on its surface to form an array of light beams, which then enter a focusing structure. The defocus amounts of the multiple light spots received in the focusing structure are determined, thereby achieving focusing.

2. The multi-spot autofocus device according to claim 1, characterized in that: The light source (10) is a laser diode.

3. The multi-spot autofocus device according to claim 1, characterized in that: The spatial light modulation structure (40) is a one-dimensional Dammann grating.

4. The multi-spot autofocus device according to claim 1, characterized in that: The multi-spot autofocus device further comprises a beam expansion and collimation structure, which is located between the light source (10) and the spatial light modulation structure (40), and is used to expand and collimate the light emitted by the light source (10).

5. The multi-spot autofocus device according to claim 1, characterized in that: The multi-spot automatic focusing device further comprises a collimator (60), wherein the collimator (60) is located between the reflector (50) and the microscope objective lens (80).

6. The multi-spot autofocus device according to claim 5, characterized in that: The multi-spot autofocus device further comprises a dichroic mirror (70), wherein the dichroic mirror (70) is located between the collimating mirror (60) and the microscope objective lens (80) and is used to realize reflection of the light beam between the collimating mirror (60) and the microscope objective lens (80).

7. The multi-spot autofocus device according to claim 1, characterized in that: The focus detection structure comprises a multi-quadrant photoelectric sensor (100) for determining the defocus amounts of a plurality of light spots.

8. The multi-spot autofocus device according to claim 7, characterized in that: There are one or more multi-quadrant photoelectric sensors (100). When there are more than one multi-quadrant photoelectric sensors (100), the focusing structure further comprises a semi-transparent and semi-reflective mirror (110), at least one of the multi-quadrant photoelectric sensors (100) is located on the reflection path of the semi-transparent and semi-reflective mirror (110), and at least another multi-quadrant photoelectric sensor (100) is located on the transmission path of the semi-transparent and semi-reflective mirror (110).

9. The multi-spot autofocus device according to claim 1, characterized in that: The multi-spot autofocus device further comprises a light absorbing layer (120), the light absorbing layer (120) being located on a side of the reflector (50) away from the spatial light modulation structure (40), and the light absorbing layer (120) being used to absorb the other half of the multiple beams of light that are not reflected by the reflector (50).

10. An autofocus method for a multi-spot autofocus device, the autofocus method being the autofocus method for the multi-spot autofocus device according to any one of claims 1 to 9, the multi-spot autofocus device further comprising a stage, the stage carrying a sample (90) of the multi-spot autofocus device, the stage being movably arranged relative to a microscope objective lens (80), the autofocus method comprising: Pre-adjustment step: manually adjusting the distance between the microscope objective lens (80) and the stage so that the clarity of the sample (90) meets a preset threshold; Automatic focusing step: turning on the multi-spot automatic focusing device, judging the defocus amount of the multiple light spots according to the multiple light spots received in the focus detection structure of the multi-spot automatic focusing device, and then adjusting the distance between the sample (90) and the microscope objective lens (80), thereby achieving focusing.

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