Auto focus system and auto focus method

Abstract

An auto-focusing system includes a focusing light source, an objective lens, a defocusing lens, a first image sensor, and a controller. The focusing light source is configured to emit a focusing light. The objective lens is disposed in a transmission path of the focusing light, wherein the focusing light is reflected from a sample after passing through the objective lens. The defocusing lens is disposed in the transmission path of the focusing light, such that the focusing light is defocused at a minimum point after passing through the objective lens. The first image sensor is configured to receive a focusing reflected light after the focusing light is reflected from the sample. The controller is electrically connected to the first image sensor. The controller drives the objective lens or the sample to move, such that a focal point of the objective lens is on the sample, according to a gravity center position, a position change, or an energy change of a light spot formed by the focusing reflected light on an imaging surface of the first image sensor.

Description

Technical Field

[0001] This invention relates to an autofocus system and an autofocus method. Background Technology

[0002] Generally, autofocus systems can be divided into two types: imaging-based and optical-based. Imaging-based autofocus systems are well-known in the industry, and their biggest advantage is their low cost. However, their disadvantages include slow response time and accuracy limited by depth of focus. Therefore, they have been gradually replaced by optical autofocus modules in recent years. Optical autofocus systems use changes in light shape (or light energy) detected by a light sensor as the basis for determining the defocus distance and direction. Their biggest advantages are high accuracy and fast response time. However, when the object is near the focal point, the light shape detected by the light sensor becomes severely distorted, leading to errors in the determination of defocus distance and direction, thus making it difficult for the autofocus system to make a judgment. Summary of the Invention

[0003] This invention provides an autofocus system and autofocus method, which have high focusing accuracy and shortened response time.

[0004] An embodiment of the present invention provides an autofocus system including a focusing light source, an objective lens, a defocusing lens, a first image sensor, and a controller. The focusing light source emits focusing light. The objective lens is positioned in the transmission path of the focusing light, wherein the focusing light passes through the objective lens and illuminates the sample. The defocusing lens is positioned in the transmission path of the focusing light, causing the minimum spot of the focusing light after passing through the objective lens to deviate from the focal point of the objective lens. The first image sensor receives the focused reflected light after the focusing light is reflected from the sample. The controller is electrically connected to the first image sensor. The controller drives the objective lens or the sample based on the centroid position, positional change, or energy change of the spot formed by the focused reflected light on the imaging surface of the first image sensor, so that the focal point of the objective lens falls on the sample.

[0005] An embodiment of the present invention provides an autofocus method comprising the following steps: Controlling a focusing light source to emit focusing light, such that the minimum spot of the focusing light after passing through the objective lens deviates from the focal point of the objective lens, wherein the focusing light sequentially passes through a defocusing lens and the objective lens before illuminating the sample. Receiving the focused reflected light after the focusing light is reflected from the sample. Based on the centroid position, positional change, or energy change of the spot formed by the focused reflected light on the imaging surface of the first image sensor, driving the objective lens or the sample to move, so that the focal point of the objective lens falls on the sample.

[0006] Based on the above, in one embodiment of the present invention, the autofocus system or autofocus method utilizes a defocus lens disposed on the transmission path of the focusing light to deviate the minimum spot of the focusing light after passing through the objective lens from the focal point of the objective lens. Therefore, the error in determining the distance between the focal point of the objective lens and the sample is reduced, further improving system accuracy and shortening response time. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of an autofocus system according to an embodiment of the present invention.

[0008] Figure 2 This is a schematic diagram showing multiple different light spots forming on the imaging surface of the first image sensor.

[0009] Figure 3 This is a graph showing the relationship between the calculated experimental defocus values ​​and theoretical values ​​at various defocus positions of the objective lens, according to an embodiment of the present invention.

[0010] Figure 4 This is a flowchart of an autofocus method according to an embodiment of the present invention.

[0011] Explanation of reference numerals in the attached figures

[0012] 10: Autofocus system;

[0013] 20, 20': Driver;

[0014] 30: Controller;

[0015] 100: Focusing light source;

[0016] 200, 800, 1000: Lens groups;

[0017] 300: Light-shielding components;

[0018] 400: Defocus lens;

[0019] 500, 600: Optical splitter;

[0020] 700: Objective lens;

[0021] 900: First image sensor;

[0022] 1100: Second image sensor;

[0023] C1: Line;

[0024] C2: Curve;

[0025] D: Distance;

[0026] F: Focus;

[0027] FL: Focusing light;

[0028] FRL: Focusing Reflection Light;

[0029] IL: Illuminating light;

[0030] IP: Imaging plane;

[0031] IRL: Parallel Image Light;

[0032] MS, MS': Minimum spot size;

[0033] O: Optical axis;

[0034] RS1, RS2: Light spots;

[0035] S: Sample;

[0036] S100, S120, S140: Steps. Detailed Implementation

[0037] Figure 1 This is a schematic diagram of an autofocus system according to an embodiment of the present invention. Please refer to... Figure 1 An embodiment of the present invention provides an autofocus system 10, which includes a focusing light source 100, an objective lens 700, a defocusing lens 400, a first image sensor 900, and a controller 30. The focusing light source 100 is used to emit focusing light FL. The focusing light source 100 is, for example, a laser diode (LD) light source, a light-emitting diode (LED) light source, or other suitable light source. The focusing light FL is, for example, infrared light or light of other wavelengths.

[0038] In this embodiment, the objective lens 700 is positioned in the transmission path of the focusing light FL, which illuminates the sample S after passing through the objective lens 700. The defocusing lens 400 is positioned in the transmission path of the focusing light FL, and is located between the focusing light source 100 and the objective lens 700. The defocusing lens 400 deflects the minimum light spot MS of the focusing light FL after passing through the objective lens 700 from the focal point F of the objective lens 700. The aforementioned focal point F is the minimum light spot of a parallel light beam that passes only through the objective lens 700, i.e., the focal length of the objective lens 700. For ease of explanation, Figure 1 This illustrates that the focal point F of objective lens 700 falls on sample S.

[0039] In this embodiment, the first image sensor 900 may be a thin film transistor (TFT), complementary metal oxide semiconductor (CMOS), charge coupled device (CCD), or other optical sensors, but the present invention is not limited thereto.

[0040] In addition, the controller 30 described above may include, for example, a microcontroller unit (MCU), a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a programmable controller, a programmable logic device (PLD), or other similar devices or combinations thereof, and the present invention is not limited thereto. Furthermore, in one embodiment, the functions of the controller 30 may be implemented as multiple program codes. These program codes are stored in memory and executed by the controller 30. Alternatively, in one embodiment, the functions of the controller 30 may be implemented as one or more circuits. The present invention does not limit the implementation of the functions of the controller 30 in software or hardware.

[0041] In this embodiment, the first image sensor 900 is used to receive the focused reflected light FRL after the focusing light FL is reflected from the sample S. The controller 30 is electrically connected to the first image sensor 900. The controller 30 determines the location of the center of gravity, positional changes, or energy changes of the light spot formed by the focused reflected light FRL on the imaging surface of the first image sensor 900 based on these factors. Figure 2 The light spot RS1 or RS2 on the imaging surface IP shown drives the objective lens 700 or the sample S to move along the optical axis O of the objective lens 700, so that the focal point F of the objective lens 700 falls on the sample S.

[0042] Figure 2 This is a schematic diagram showing multiple different light spots formed on the imaging surface of the first image sensor. Please also refer to... Figure 1 and Figure 2 For example, when the autofocus system does not have a 400° defocus lens, Figure 2The light spots in the image sensor 900, from left to right, can be the light spots formed on the imaging surface IP of the first image sensor 900, respectively, from the point of focus F of the objective lens 700, near the sample S (that is, when the minimum light spot MS after the focusing light FS passes through the objective lens 700 is closest to the sample S) to the point of distance from the sample S. When the autofocus system 10 is equipped with a defocus lens 400, the defocus lens 400 causes each light spot on the imaging surface IP to shift, for example... Figure 2 This illustrates a displacement of 500 μm (at which point the smallest light spot MS is displaced, but the focal length F is not). Spots RS1 and RS2 represent the light spots when the focal point F of objective lens 700 is closest to the sample S. However, due to... Figure 2 The light spots in the -250μm to 250μm range are nearly semi-circular, making it easy for the autofocus system 10 to analyze the centroid, positional changes, or energy changes of each light spot within this range. Therefore, analyzing the light spots in this range can reduce judgment errors, further improving system accuracy and shortening response time. Conversely, without a defocusing lens, and when the system is close to the sample S at the focal point F of the objective lens 700, the light spot acquired by the image sensor (e.g., Figure 2 The light spot (within the -250μm range) undergoes severe deformation, which increases the error in the system's judgment, further reducing the system's accuracy and increasing the response time.

[0043] In this embodiment, as Figure 1 As shown, the distance D between the minimum spot MS of the focusing light FL after passing through the objective lens 700 and the focal point F of the objective lens 700 can be controlled by the focal length of the defocusing lens 400.

[0044] In this embodiment, the autofocus system 10 further includes actuators 20 and 20'. Actuators 20 and 20' are, for example, stages, but the invention is not limited thereto. Actuator 20 is connected to objective lens 700 or actuator 20' is used to carry sample S and is electrically connected to controller 30, wherein controller 30 drives objective lens 700 or sample S to move via actuators 20 and 20'.

[0045] In this embodiment, the autofocus system 10 further includes a light-shielding component 300. The light-shielding component 300 is disposed between the objective lens 700 and the focusing light source 100 in the transmission path of the focusing light FL, and is used to change the shape of the light spot illuminating the sample S by the focusing light FL. For example, the light spot emitted by the focusing light FL from the focusing light source 100 is nearly circular. After passing through the light-shielding component 300, the light spot of the focusing light FL can be nearly semi-circular. However, the present invention is not limited to this limitation in how the light-shielding component 300 changes the shape of the light spot of the focusing light FL.

[0046] In this embodiment, the autofocus system 10 further includes lens groups 200 and 800, and beam splitters 500 and 600. Lens group 200 is disposed between the focusing light source 100 and the light-shielding member 300, and is used to expand, shrink, or collimate the focusing light FL. Defocus lens 400 is disposed between beam splitter 500 and the light-shielding member 300, and beam splitter 500 is used to allow light with the same wavelength as the focusing light FL to partially pass through and partially reflect. Beam splitter 600 is disposed downstream of the optical path of beam splitter 500, and objective lens 700 is disposed between beam splitter 600 and driver 20'. Similarly, beam splitter 600 allows light with the same wavelength as the focusing light FL to reflect, or partially pass through and partially reflect. Lens group 800 is disposed between beam splitter 500 and first image sensor 900, and is used to image the focused reflected light FRL onto the first image sensor 900.

[0047] In this embodiment, the autofocus system 10 further includes a lens group 1000 and a second image sensor 1100 for receiving the image light (diffuse reflection) after the illumination light IL illuminates the sample S. The illumination light IL is emitted, for example, by an image acquisition light source, and the beam splitter 600 is adapted to allow light with the same wavelength as the illumination light IL to pass through, or partially pass through and partially reflect. The image acquisition light source can be disposed around the sample S, for example, disposed on the driver 20'. The lens group 1000 and the second image sensor 1100 are used by the autofocus system 10 to acquire an image of the sample S. After the controller 30 causes the focal point F of the objective lens 700 to fall on the sample S, a parallel image light IRL from the imaging plane of the second image sensor 1100 is traced backwards through the objective lens 700, and the minimum light spot MS' falls on the sample S.

[0048] Figure 3 This is an autofocus system according to an embodiment of the present invention, showing the relationship between calculated experimental defocus values ​​and theoretical values ​​at various defocus positions of the objective lens. The straight line C1 represents the theoretical value of the objective lens 700 at different defocus positions (i.e., the position of the focal point F of the objective lens 700 relative to the sample S), and the curve C2 represents the experimental defocus values ​​calculated by the controller 10 corresponding to different defocus positions on the straight line C1. Please refer to... Figure 3 The curve C2 is roughly close to the straight line C1, so the autofocus system 10 has good system accuracy.

[0049] Figure 4 This is a flowchart of an autofocus method according to an embodiment of the present invention. Please refer to... Figure 4An embodiment of the present invention provides an autofocus method comprising the following steps. In step S100, a focusing light source 100 is controlled to emit focusing light FL, such that the minimum spot MS of the focusing light FL after passing through the objective lens 700 deviates from the focal point F of the objective lens 700. The focusing light FL sequentially passes through the defocusing lens 400 and the objective lens 700 before illuminating the sample S. In step S120, the focusing reflected light FRL after the focusing light FL is reflected from the sample S is received. In step S140, based on the centroid position, positional change, or energy change of the light spots RS1 and RS2 formed by the focusing reflected light FRL on the imaging surface IP of the first image sensor 900, the objective lens 700 or the sample S is driven to move, so that the focal point F of the objective lens 700 falls on the sample S.

[0050] In this embodiment, the movement of the objective lens 700 or the sample S includes the following steps: The objective lens 700 or the sample S is moved by the drivers 20, 20' electrically connected to the controller 30.

[0051] In summary, in one embodiment of the present invention, the autofocus system or method utilizes a defocusing lens positioned along the transmission path of the focusing light to deviate the minimum spot of the focusing light from the objective lens's focal point. Therefore, the autofocus system or method avoids using a severely distorted light spot to determine the center of gravity, positional changes, or energy changes of the light spot, reducing the error in the system's calculation of the distance between the objective lens's focal point and the sample, further improving system accuracy and shortening response time.

Claims

1. An autofocus system, characterized in that, include: A focusing light source, used to emit focusing light; An objective lens is positioned in the path of the focusing light, wherein the focusing light passes through the objective lens and illuminates the sample. A defocusing lens is disposed on the transmission path of the focusing light to deviate the focal point of the objective lens at the minimum spot of the focusing light after passing through the objective lens. A first image sensor is used to receive the focused reflected light after the focusing light is reflected from the sample; as well as The controller is electrically connected to the first image sensor. The controller drives the objective lens or the sample to move based on the centroid position, position change, or energy change of the light spot formed by the focused reflected light on the imaging surface of the first image sensor, so that the focal point of the objective lens falls on the sample. The defocusing lens is further used to displace the light spots on the imaging surface of the first image sensor, making it easier to analyze changes in the center of gravity, position, or energy of the light spots. The autofocus system also includes: The second image sensor is used to receive image light after illumination light shines on the sample, wherein after the controller focuses the objective lens onto the sample, the smallest point of light after the parallel image light from the imaging surface of the second image sensor passes through the objective lens falls onto the sample.

2. The autofocus system according to claim 1, characterized in that, The distance between the minimum light spot after the focusing light passes through the objective lens and the focal point of the objective lens is controlled by the focal length of the defocus lens.

3. The autofocus system according to claim 1, characterized in that, Also includes: A driver, connected to the objective lens or used to carry the sample, and electrically connected to the controller, wherein the controller drives the objective lens or the sample to move via the driver.

4. The autofocus system according to claim 1, characterized in that, Also includes: A light-shielding component is disposed between the objective lens and the focusing light source on the transmission path of the focusing light, in order to change the shape of the light spot illuminating the sample.

5. An autofocus method, characterized in that, include: The focusing light source is controlled to emit focusing light, so that the minimum light spot after the focusing light passes through the objective lens deviates from the focal point of the objective lens, wherein the focusing light passes through the defocus lens and the objective lens in sequence and then illuminates the sample. Receive the focused reflected light after the focusing light is reflected from the sample; By using the defocus lens, each light spot on the imaging surface of the first image sensor is displaced, making it easier to analyze the changes in the center of gravity, position, or energy of each light spot; as well as Based on the centroid position, positional change, or energy change of the light spot formed by the focused reflected light on the imaging surface of the first image sensor, the objective lens or the sample is driven to move, so that the focal point of the objective lens falls on the sample. The second image sensor is used to receive the image light after the illumination light shines on the sample. After the controller makes the focus of the objective lens fall on the sample, the parallel image light from the imaging surface of the second image sensor is traced backward through the objective lens to the smallest point of light that falls on the sample.

6. The autofocus method according to claim 5, characterized in that, The distance between the minimum light spot after the focusing light passes through the objective lens and the focal point of the objective lens is controlled by the focal length of the defocus lens.

7. The autofocus method according to claim 5, characterized in that, Driving the objective lens or the sample to move includes: The objective lens or the sample is moved by a driver electrically connected to a controller, characterized in that the driver is connected to the objective lens or is used to carry the sample.

8. The autofocus method according to claim 5, characterized in that, A light-shielding component is disposed between the objective lens and the focusing light source in the transmission path of the focusing light to change the shape of the light spot illuminating the sample.

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