Optical Imaging System, Imaging Module, Electronic Device, and Optical Imaging Method

Abstract

The present invention discloses an optical imaging system, an imaging module, an electronic device, and an optical imaging method. The optical imaging system at least includes a single-frame imaging system and a laser marking system. The single-frame imaging system includes an objective lens, a first beam splitter, a mirror scanning unit, and a tube lens sequentially arranged along the optical axis from the object plane to the image plane. The laser marking system includes a first laser for emitting laser light, and a first lens, a pinhole array, a second lens, and an aperture sequentially arranged along the optical path of the first laser. The laser light emitted by the first laser is shaped into a parallel beam by the first lens to illuminate the pinhole array, and then the pinhole array is projected onto the object plane via the second lens, the first aperture, the first beam splitter, and the objective lens. By adding a laser marking system on the basis of the single-frame imaging system, the positions of each single-frame sub-field are marked with laser marking points, providing precise alignment accuracy for sub-field stitching, thereby compensating for the field-of-view stitching error caused by the drift of the scanning mirror.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular, to an optical imaging system, an imaging module, an electronic device, and an optical imaging method. Background Art

[0002] The optical resolution and the field of view of an optical system are two important optical indicators. The formula for calculating the field of view (FOV) is

[0003] Horizontal field of view L:

[0004] L = PR × n h

[0005] Vertical field of view W:

[0006] W = PR × n v

[0007] Where PR is the pixel resolution, and nh and nv are the number of pixels in a row or a column in the effective photosensitive area of the photosensitive element (sensor), respectively.

[0008] The formula for calculating the optical resolution (OR):

[0009]

[0010] Where λ is the wavelength of the light source, and NA is the numerical aperture of the lens.

[0011] To satisfy the sampling theorem, generally OR = 2PR,

[0012] Then

[0013] L = 0.5 × OR × n h

[0014] W = 0.5 × OR × n v

[0015] High resolution requires the optical resolution OR to be smaller and smaller, and a large field of view requires the field of view FOV to be larger and larger. From the above formula, it can be seen that the field of view FOV and the optical resolution OR are proportional to each other. Therefore, it is difficult to achieve a large field of view and high resolution simultaneously.

[0016] To simultaneously meet the requirements of a large field of view and high resolution, currently there are mainly two methods: spatial expansion and time expansion.

[0017] Spatial expansion is usually achieved by means of optical hardware splicing. Specifically, it is to form a large field of view and high-resolution optical system through the splicing of multiple high-resolution optical subsystem arrays. Hardware splicing does not require multiple photo shootings, and the image capture speed is fast. However, it has a large volume, and non-telecentric lenses are often used to form adjacent field of view overlaps. Non-telecentric lenses have perspective errors. Scanning splicing can use telecentric lenses to eliminate perspective errors, but it requires multiple photo shootings, and the speed is lower than that of hardware splicing.

[0018] Temporal expansion is usually achieved by means of scanning. With the help of a scanning mirror, each fine sub-field of view is taken separately at different times, and finally a large field of view and high-resolution image is obtained through image splicing. However, for the mirror scanning system, the alignment accuracy requirements for adjacent sub-fields of view to be spliced are very high. After the scanning mirror runs for a long time, there are often uncontrollable temperature drifts that are difficult to measure in real time, which reduces the alignment accuracy of adjacent sub-fields of view and causes relatively large field of view splicing errors. Secondly, for high-resolution optical systems, their depth of field is often small. When the detected object has height fluctuations, the object is easily out of focus, resulting in a reduction in the imaging level. Summary of the Invention

[0019] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an optical imaging system, an imaging module, an electronic device and an optical imaging method, which can meet the 2D optical imaging requirements of a large field of view, high resolution and real-time focusing.

[0020] An optical imaging system includes a single-frame imaging system and a laser marking system;

[0021] The single-frame imaging system includes an objective lens, a first beam splitter, a mirror scanning unit and a tube lens arranged in sequence along the optical axis from the object plane to the image plane; the reflection scanning unit includes a first scanning mirror, a second scanning mirror and a relay module. The first scanning mirror is arranged at the aperture of the objective lens, the second scanning mirror is arranged at the aperture of the tube lens, and the relay module is arranged between the first scanning mirror and the second scanning mirror for relaying the imaging of the aperture of the objective lens to the aperture of the tube lens; by adjusting the angles of the first scanning mirror and the second scanning mirror, the single-frame imaging field of view of the single-frame imaging system can be scanned and moved along the X direction and the Y direction;

[0022] The laser marking system includes a first laser for emitting laser to the object plane and a first lens, a pinhole array, a second lens and an aperture arranged in sequence along the optical path of the first laser; the laser emitted by the first laser is shaped into a parallel beam by the first lens to illuminate the pinhole array, and then the pinhole array is projected onto the object plane through the second lens, the first aperture, the first beam splitter and the objective lens.

[0023] Optionally, a second beam splitter is further provided between the second scanning mirror and the tube lens;

[0024] The imaging module further includes a real-time focusing system, which includes a second laser for emitting laser to the object surface, and a third lens, a pinhole, and a fourth lens sequentially arranged along the optical path of the second laser. The laser emitted by the second laser forms a converging beam through the third lens to illuminate the pinhole, and then projects the pinhole onto the object surface through the fourth lens, the second beam splitter, the mirror scanning unit, the first beam splitter, and the objective lens;

[0025] The size of the projection of the pinhole on the object surface changes with the distance between the objective lens and the object surface.

[0026] Optionally, the relay module includes a first relay lens and a second relay lens. The first relay lens is arranged between the first scanning mirror and the second scanning mirror, and the second relay lens is arranged between the first relay lens and the second scanning mirror and can move along the optical axis between the first relay lens and the second scanning mirror.

[0027] Optionally, the objective lens is an object-side telecentric lens conjugate to infinity on the image side, and the tube lens is an image-side telecentric lens conjugate to infinity on the object side.

[0028] Optionally, the colors of the lasers emitted by the first laser and the second laser are different, and / or the shape of the holes in the pinhole array is different from the shape of the pinhole.

[0029] An imaging module includes a photosensitive element and the above optical imaging system, and the photosensitive element is arranged behind the tube lens.

[0030] An electronic device includes a housing and the above imaging module, and the imaging module is arranged in the housing.

[0031] An optical imaging method applied to the above imaging module includes:

[0032] Dividing a large field of view into multiple sub-fields of view;

[0033] Taking images separately for each sub-field of view in a time-sharing manner to obtain a first sub-field image and a second sub-field image for each sub-field of view. Among them, the first sub-field image is an image obtained when the laser marking system is in the on state, and the laser marking points projected by the laser marking system on the object surface are recorded in the first sub-field image. The second sub-field image is an image obtained when both the laser marking system and the real-time focusing system are in the off state;

[0034] According to the positions of the laser marking points in each first sub - field image, image stitching is performed on the second sub - field image corresponding to the first sub - field image to obtain a large - field image.

[0035] Optionally, the obtaining of the first sub - field image and the second sub - field image of each sub - field by taking images separately in a time - sharing manner includes:

[0036] Drive the first scanning mirror and the second scanning mirror to step to the target sub - field;

[0037] Turn on the laser marking system to form laser marking points on the object surface, and turn on the real - time focusing system to form laser focusing points on the object surface, where the laser marking points and the laser focusing points do not overlap;

[0038] Collect the first sub - field image through the single - frame imaging system, and the first sub - field image records the positions of the laser marking points and the sizes of the laser focusing points simultaneously;

[0039] Determine the focusing compensation amount according to the size of the laser focusing point, and control the movement of the second relay lens based on the focusing compensation amount, where the focusing compensation amount is the movement direction and distance corresponding to moving the second relay lens along the optical axis from the zero position to the position where the object surface is imaged clearly;

[0040] Turn off the laser marking system and the real - time focusing system, and collect the second sub - field image through the single - frame imaging system;

[0041] Control the second relay lens to return to the zero position, take the next sub - field as the target sub - field, and return to execute the step of driving the first scanning mirror and the second scanning mirror to step to the target sub - field.

[0042] Optionally, before dividing the large - field into multiple sub - fields, it further includes: calibrating the laser marking system to obtain a laser point calibration image;

[0043] The performing of image stitching on the second sub - field image corresponding to the first sub - field image according to the positions of the laser marking points in each first sub - field image to obtain a large - field image includes:

[0044] Compare each first sub - field image with the laser point calibration image, determine whether the positions of the laser marking points in the first sub - field image change compared with their positions in the laser point calibration image, and record the drift amount of the laser marking points when the change occurs; perform image stitching on the second sub - field image corresponding to the first sub - field image according to the positions of the laser marking points and the corresponding drift amounts in each first sub - field image to obtain a large - field image.

[0045] Implementing the above solution has the following beneficial effects:

[0046] In the design of the single-frame imaging system of this solution, the first scanning mirror and the second scanning mirror are respectively placed at the aperture of the objective lens and the aperture of the tube lens, which can ensure that the focal lengths in the X and Y scanning directions are equal; the relay module relays the aperture of the objective lens to the aperture of the tube lens, ensuring that when the two scanning mirrors are working, the object-space telecentricity of the single-frame imaging system will not change, and ensuring that when the working distance between the object plane and the objective lens changes, the position image of the laser marking point in the first sub-field image will not generate perspective errors.

[0047] Adding a laser marking system on the basis of the single-frame imaging system, projecting the pinhole array onto the object plane through the laser, forming stable and unchanging laser marking points at fixed positions in the large field of view in the object space, and each object-space sub-field has a corresponding marking point. The calibrated laser marking system can monitor the drift of the scanning mirror, that is, if the first scanning mirror and the second scanning mirror have a small drift, then the imaging position of the laser marking point in each single-frame field of view will change compared with the calibrated laser point position, so as to monitor the specific drift amount, provide a basis for subsequent field stitching, compensate for the field stitching error caused by the drift of the scanning mirror, and improve the alignment accuracy of field stitching.

[0048] Set up a real-time focusing system, project the pinhole onto the object plane through the laser, form a laser focus point that can reflect the working distance between the objective lens and the object plane, monitor the change of the object plane height through the size of the laser focus point, and then calculate the focusing compensation amount, and drive the second relay lens to perform focusing compensation. After the focusing compensation, the imaging system focuses on the new object plane height for clear imaging, realizing the functions of mechanical fast focusing and real-time focusing.

[0049] This solution can meet the 2D optical imaging requirements of large field of view, high resolution and real-time focusing. Description of the Drawings

[0050] Figure 1 is a schematic structural diagram of the imaging module provided by an embodiment of the present invention;

[0051] Figure 2 is a schematic diagram of field division provided by an embodiment of the present invention;

[0052] Figure 3 is a schematic structural diagram of the pinhole array provided by an embodiment of the present invention;

[0053] Figure 4 is a schematic flowchart of the optical imaging method provided by an embodiment of the present invention;

[0054] Figure 5It is a schematic flowchart of a method for taking images of each sub - field by time - sharing according to an embodiment of the present invention.

[0055] In the figure: 100 is a single - frame imaging system, 101 is an object plane, 102 is an objective lens, 103 is a first beam splitter, 104 is a second beam splitter, 105 is a tube lens, 400 is a mirror scanning unit, 401 is a first scanning mirror, 402 is a second scanning mirror, 403 is a first relay lens, 404 is a second relay lens, 200 is a laser marking system, 201 is a first laser, 202 is a first lens, 203 is a pinhole array, 204 is a second lens, 205 is an aperture, 300 is a real - time focusing system, 301 is a second laser, 302 is a third lens, 303 is a pinhole, 304 is a fourth lens. Detailed implementation manners

[0056] 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. The components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected 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 creative efforts fall within the scope of protection of the present invention.

[0058] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0059] In the description of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships in which the invention product is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0060] In the description of the present invention, it should also be noted that unless otherwise clearly defined and limited, the terms "arranged" and "connected" 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. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0061] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "under" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0062] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0063] This embodiment provides an optical imaging system, which at least includes a single-frame imaging system 100 and a laser marking system 200.

[0064] The single-frame imaging system 100 includes an objective lens 102, a first beam splitter 103, a mirror scanning unit 400, a tube lens 105, and a photosensitive element 106 that are sequentially arranged along the optical axis from the object plane 101 to the image plane; the reflection scanning unit includes a first scanning mirror 401, a second scanning mirror 402, and a relay module. The first scanning mirror 401 is arranged at the aperture of the objective lens 102, the second scanning mirror 402 is arranged at the aperture of the tube lens 105, and the relay module is arranged between the first scanning mirror 401 and the second scanning mirror 402 for relaying the imaging of the aperture of the objective lens 102 to the aperture of the tube lens 105. By adjusting the angles of the first scanning mirror 401 and the second scanning mirror 402, the single-frame imaging field of view of the single-frame imaging system 100 can be scanned and moved in the X direction and the Y direction. Among them, the objective lens 102 is an object-space telecentric lens with an image-space infinity conjugate, and the tube lens 105 is an image-space telecentric lens with an object-space infinity conjugate. The relay module may include a first relay lens 403 and a second relay lens 404. The first relay lens 403 is arranged between the first scanning mirror 401 and the second scanning mirror 402, and the second relay lens 404 is arranged between the first relay lens 403 and the second scanning mirror 402 and can move along the optical axis between the first relay lens 403 and the second scanning mirror 402.

[0065] In the design of the single-frame imaging system 100, the first scanning mirror 401 and the second scanning mirror 402 are respectively placed at the aperture of the objective lens 102 and the aperture of the tube lens 105, which can ensure that the focal lengths in the X and Y scanning directions are equal; the relay module relays the imaging of the aperture of the objective lens 102 to the aperture of the tube lens 105, ensuring that when the two scanning mirrors work, the object-space telecentricity of the single-frame imaging system 100 does not change, and ensuring that when the working distance between the object plane and the objective lens changes, the position image of the laser marking point in the first sub-field image will not produce perspective errors.

[0066] The laser marking system 200 includes a first laser 201 that emits laser light to the object plane 101, and a first lens 202, a pinhole array 203, a second lens 204, and an aperture 205 that are sequentially arranged along the optical path of the first laser 201; the laser light emitted by the first laser 201 is shaped into a parallel beam by the first lens 202 to illuminate the pinhole array 203, and then the pinhole array 203 is projected onto the object plane 101 through the second lens 204, the first aperture 205, the first beam splitter 103, and the objective lens 102.

[0067] Based on the single-frame imaging system 100, a laser marking system 200 is added. The pinhole array 203 is projected onto the object surface 101 by laser, and stable and invariant laser marking points are formed at fixed positions in the large field of view on the object side. Each sub-field of view on the object side has a corresponding marking point. After calibration, the laser marking system 200 can monitor the drift of the scanning mirrors. That is, if the first scanning mirror 401 and the second scanning mirror 402 have a small drift, the imaging position of the laser marking point in each single-frame field of view will change compared to the calibrated laser point position, thereby monitoring the specific drift amount, providing a basis for subsequent field stitching, compensating for the field stitching error caused by the drift of the scanning mirrors, and improving the alignment accuracy of field stitching.

[0068] In a possible implementation, a second beam splitter 104 is further provided between the second scanning mirror 402 and the tube lens 105. The optical imaging system further includes a real-time focusing system 300. The real-time focusing system 300 includes a second laser 301 that emits laser towards the object surface 101, and a third lens 302, a pinhole 303, and a fourth lens 304 that are sequentially arranged along the optical path of the second laser 301. The laser emitted by the second laser 301 forms a converging beam through the third lens 302 to illuminate the pinhole 303, and then projects the pinhole 303 onto the object surface 101 through the fourth lens 304, the second beam splitter 104, the mirror scanning unit 400, the first beam splitter 103, and the objective lens 102. The size of the projection of the pinhole 303 on the object surface 101 changes with the distance between the objective lens 102 and the object surface 101. Among them, since the pinhole array 203 of the laser marking system 200 and the pinhole 303 of the real-time focusing system 300 are both projected onto the object surface 101, it is necessary to distinguish between the two. In actual implementation, the colors of the lasers emitted by the first laser 201 and the second laser 301 can be set to be different, for example, one is green light and the other is red light, or the shape of the holes in the pinhole array 203 can be designed to be different from the shape of the pinhole 303, for example, one is circular and the other is cross-shaped.

[0069] In this embodiment, a real-time focusing system 300 is provided. The pinhole 303 is projected onto the object surface 101 by laser to form a laser focus point that can reflect the working distance between the objective lens 102 and the object surface 101. The change in the height of the object surface 101 is monitored through the size of the laser focus point, and then the focusing compensation amount is calculated, and the second relay lens 404 is driven for focusing compensation. After the focusing compensation, the imaging system focuses on the new height of the object surface 101 to achieve clear imaging and realize the functions of mechanical rapid focusing and real-time focusing.

[0070] Please refer to Figure 1, this embodiment provides an optical imaging system, including a single-frame imaging system 100, a laser marking system 200, and a real-time focusing system 300, which can meet the 2D optical imaging requirements of large field of view, high resolution, and real-time focusing. The optical imaging system of this embodiment can divide the large field of view into m×n sub-fields of view with the help of the first scanning mirror 401 and the second scanning mirror 402, where m refers to the number of rows, n refers to the number of columns, and both m and n are integers greater than or equal to 1. Each sub-field of view is taken separately at different times, and then a large field of view and high-resolution image is obtained through image stitching.

[0071] The single-frame imaging system 100 is sequentially provided with an objective lens 102, a first beam splitter 103, a mirror scanning unit 400, a second beam splitter 104, a tube lens 105, and a photosensitive element along the optical axis from the object plane 101 to the image plane. The mirror scanning unit 400 includes a first scanning mirror 401, a relay module, and a second scanning mirror 402 sequentially arranged from the first beam splitter 103 to the second beam splitter 104. The function of the single-frame imaging system 100 is to achieve high-resolution imaging of each single-frame sub-field of view. Among them, the objective lens 102 is an object-space telecentric lens with an image-space infinity conjugate, and the tube lens 105 is an image-space telecentric lens with an object-space infinity conjugate. The relay module is composed of a first relay lens 403 and a second relay lens 404. The relay module relays the aperture of the objective lens 102 to the aperture of the tube lens 105. The first scanning mirror 401 is placed at the aperture of the objective lens 102, and the second scanning mirror 402 is placed at the aperture of the tube lens 105, so as to ensure that the focal lengths in the X and Y scanning directions are equal. The non-coincidence of the scanning mirror and the aperture position often causes the object-space telecentricity of the single-frame imaging system 100 to be damaged. The relay module can ensure that when the first scanning mirror 401 and the second scanning mirror 402 are working, the object-space telecentricity of the single-frame imaging system 100 will not change.

[0072] The function of the mirror scanning unit 400 is to achieve time-sharing imaging of each sub-field of view. The principle is as follows: Both the first scanning mirror 401 and the second scanning mirror 402 are scanning mirrors. By controlling the angles of the first scanning mirror 401 and the second scanning mirror 402, the single-frame imaging field of view is scanned and moved in the X and Y directions. Specifically, the first scanning mirror 401 can be used to scan the single-frame sub-field of view in the X direction, and the second scanning mirror 402 can be used to scan the single-frame sub-field of view in the Y direction. As Figure 2As shown, the entire large field of view is divided into m×n sub - fields of view. The black dots within each sub - field of view represent the laser focus points, which are generated by the real - time focusing system 300; the light - colored dots represent the laser marking points, which are generated by the laser marking system 200. When the first scanning mirror 401 and the second scanning mirror 402 start to work, first, the first scanning mirror 401 is used to perform a sub - field - by - sub - field scan along the X - direction (from A11, A12, A13.... to A1n), and then the second scanning mirror 402 is used to perform a line - by - line scan along the Y - direction, from A1n to A2n; then the first scanning mirror 401 is used to perform a scan along the reverse X - direction (from A2n....A23, A22, to A21), and so on, to complete the scan of the entire large field of view.

[0073] The function of the laser marking system 200 is to monitor the drift of the scanning mirror. As Figure 1 shown, the laser marking system 200 includes a first laser 201, a first lens 202, a pinhole array 203, a second lens 204, and an aperture 205. The laser emitted by the first laser 201 passes through the first lens 202 to form a parallel light beam, which illuminates the pinhole array 203. The structure of the pinhole array 203 is as Figure 3 shown. The pinhole array 203 has m×n small holes (m rows and n columns), which is consistent with the number of rows and columns of the sub - fields of view. Then, through the projection optical system composed of the second lens 204, the aperture 205, the first beam splitter 103, and the objective lens 102, the pinhole array 203 is projected onto the object plane 101 to form stable and invariant laser marking points at fixed positions in the large object - side field of view. There is a corresponding laser marking point in each object - side sub - field of view. After calibration of the laser marking system 200, when the first scanning mirror 401 and the second scanning mirror 402 have a small drift, the imaging positions of the laser marking points B11, B12...Bmn in each single - frame field of view will change compared with the calibrated laser point positions, so as to monitor the specific drift amount and provide a basis for subsequent image stitching.

[0074] The function of the real - time focusing system 300 is to monitor the height change of the object plane 101 in real time and capture clear images through mechanical focusing. As Figure 1As shown, the real-time focusing system 300 includes a second laser 301, a third lens 302, a pinhole 303, and a fourth lens 304. The light emitted by the second laser 301 forms a converging beam after passing through the third lens 302, illuminating the pinhole 303. The pinhole 303 is projected onto the object surface 101 through a projection system composed of the fourth lens 304, the second beam splitter 104, the second scanning mirror 402, the second relay lens 404, the first relay lens 403, the first scanning mirror 401, the second beam splitter 104, and the objective lens 102. When the working distance WD between the objective lens 102 and the object surface 101 changes, the size of the laser focus point (i.e., the projection of the pinhole 303 on the object surface 101) observed by the single-frame imaging system 100 will change. According to the size of the laser focus point, the change amount of the working distance WD can be judged, and then the focusing compensation amount can be accurately calculated by software to drive the second relay lens 404 for focusing compensation. After the focusing compensation, the single-frame imaging system 100 focuses on the new height of the object surface 101 for clear imaging. It should be noted that the laser marking point B set (B11, B12... Bmn) and the laser focus point C set (C11, C12... Cmn) need to be distinguishable, including but not limited to color distinction and shape distinction. Color distinction can be, for example: the first laser 201 emits green laser, the second laser 301 emits red laser, the B set is green, and the C set is red. At this time, the photosensitive element is an image sensor capable of sensing color images, such as a color camera. Shape distinction can be, for example: the shape of the holes on the pinhole array 203 in the laser marking system 200 is circular, and the shape of the pinhole 303 in the real-time focusing system 300 is cross-shaped. At this time, the laser colors emitted by the first laser 201 and the second laser 301 can be the same or different, and the photosensitive element can be an image sensor for sensing black and white or color images, that is, it can be a black and white camera or a color camera.

[0075] It should be noted that the number of rows and columns of the holes on the pinhole array 203 is the same as the number of rows and columns of the sub-fields of view obtained after the large field of view is divided. The laser marking system 200 projects the pinhole array 203 onto the object plane 101 to form stable and unchanging laser marking points at fixed positions in the large field of view in the object space. There is a corresponding laser marking point in each sub-field of view in the object space. By adjusting the first scanning mirror 401 and the second scanning mirror 402 to step into a single sub-field of view, at this time, the image that the photosensitive element can capture is the image of a single sub-field of view, and there is a corresponding laser marking point in this sub-field of view; since the real-time focusing system 300 forms an image through the first scanning mirror 401 and the second scanning mirror 402, the laser focus point projected by the real-time focusing system 300 onto the object plane 101 moves with the adjustment of the first scanning mirror 401 and the second scanning mirror 402, so there is a laser focus point in each sub-field of view. Therefore, the image of a single sub-field of view captured by the photosensitive element has a laser marking point and a laser focus point. Figure 2 For a vivid illustration, the corresponding laser marking point and laser focus point are shown in each sub-field of view.

[0076] Taking a large field of view of 50×50 mm as an example, in this embodiment, with the help of the first scanning mirror 401 and the second scanning mirror 402, the entire large field of view is subdivided into sub-fields of 25 rows and 25 columns. Each sub-field (2.2×2.2 mm) takes images separately in time division, and finally a large field of view and high-resolution image are obtained through image stitching. Specifically, when the driving mirror scanning unit 400 steps into a certain single-frame sub-field of view, first, the laser marking system 200 and the real-time focusing system 300 are turned on to form two laser points with non-overlapping positions on the object plane 101 (one is a laser marking point and the other is a laser focus point). The single-frame imaging system 100 takes the first photo to record the position of the laser marking point and the size of the laser focus point at the same time. The software judges the required focusing compensation amount according to the size of the laser focus point, and then controls the second relay lens 404 to move along the optical axis from the zero position to a certain accurate position to obtain a clear image of the object. Then, the laser marking system 200 and the real-time focusing system 300 are turned off, and the single-frame imaging system 100 takes the second photo. Then, when the scanning mirror steps into the adjacent sub-field of view, the second relay lens 404 synchronously returns to the zero position to take two photos of the adjacent field of view. Repeat the above actions until the entire large field of view is scanned. The software completes the sub-field image stitching according to the positions of each laser marking point that have been recorded and combines the images taken each time.

[0077] This embodiment provides an imaging module, which includes an optical imaging system and a photosensitive element. The structure and function of the optical imaging system are the same as those in the above embodiment and will not be elaborated here. The photosensitive element can be an image sensor, and the photosensitive element is arranged behind the lens of the single-frame imaging system 100 for recording images.

[0078] This embodiment provides an electronic device, which includes a housing and the imaging module described in the foregoing embodiment, and the imaging module is disposed within the housing.

[0079] This embodiment provides an optical imaging method applied to the imaging module described in the foregoing embodiment. Please refer to Figure 4 and this optical imaging method includes steps S401 - S405.

[0080] S401: Divide the large field of view into multiple sub - fields of view.

[0081] Among them, the number of rows and columns of the sub - field of view is the same as the number of rows and columns of the holes on the pinhole array. The pinhole array of the laser marking system is projected onto the object plane, and stable and invariant laser marking points are formed at fixed positions in the large field of view on the object side. Each object sub - field of view has a corresponding laser marking point.

[0082] S403: Take images of each sub - field of view separately in a time - division manner to obtain a first sub - field image and a second sub - field image of each sub - field of view. Among them, the first sub - field image is an image obtained when the laser marking system is in the on state, and the laser marking points projected by the laser marking system onto the object plane are recorded in the first sub - field image. The second sub - field image is an image obtained when both the laser marking system and the real - time focusing system are in the off state.

[0083] Please refer to Figure 5 and taking images of each sub - field of view separately in a time - division manner may include steps S501 - S511.

[0084] S501: Drive the first scanning mirror and the second scanning mirror to step to the target sub - field of view;

[0085] S503: Turn on the laser marking system to form laser marking points on the object plane, and turn on the real - time focusing system to form laser focus points on the object plane. The positions of the laser marking points and the laser focus points do not overlap;

[0086] S505: Collect a first sub - field image through the single - frame imaging system. The first sub - field image records the positions of the laser marking points and the sizes of the laser focus points at the same time;

[0087] S507: Determine the focusing compensation amount according to the size of the laser focus point, and control the movement of the second relay lens based on the focusing compensation amount. Among them, the focusing compensation amount is the moving direction and moving distance corresponding to moving the second relay lens along the optical axis from the zero position to the position where the object plane is imaged clearly;

[0088] S509: Turn off the laser marking system and the real - time focusing system, and collect a second sub - field image through the single - frame imaging system;

[0089] S511. Control the second relay lens to return to the zero position, and take the next sub-field of view as the target sub-field of view.

[0090] Repeat steps S501 - S511 until the first sub-field of view image and the second sub-field of view image corresponding to each sub-field of view are acquired.

[0091] S405: According to the positions of the laser marking points in each first sub-field of view image, perform image stitching on the second sub-field of view image corresponding to the first sub-field of view image to obtain a large field of view image.

[0092] Before dividing the large field of view into multiple sub-fields of view, it further includes: calibrating the laser marking system to obtain a laser point calibration image. Further, step S405 may include: comparing each first sub-field of view image with the laser point calibration image to determine whether the positions of the laser marking points in the first sub-field of view image change compared to their positions in the laser point calibration image, and recording the drift amount of the laser marking points when a change occurs; according to the positions of the laser marking points and the corresponding drift amounts in each first sub-field of view image, perform image stitching on the second sub-field of view image corresponding to the first sub-field of view image to obtain a large field of view image.

[0093] By adding a laser marking system, using laser marking points to mark the positions of each single-frame sub-field of view, providing precise alignment accuracy for field of view stitching, thereby compensating for the field of view stitching error caused by the drift of the scanning mirror; also monitoring the change in the object surface height through a real-time focusing system, and then feeding back to the piezoelectric ceramic through software to drive the second intermediate (relay) lens to achieve mechanical rapid focusing, thereby realizing the function of real-time focusing. This embodiment can meet the 2D optical imaging requirements of a large field of view (50mm × 50mm), high resolution (1 - 2um / pixel), and real-time focusing. This solution can be applied to wafer inspection, mini LED, and micro LED inspection.

[0094] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An optical imaging system that obtains a large field-of-view image through image stitching, characterized in that it includes a single-frame imaging system (100) and a laser marking system (200); The single-frame imaging system (100) includes an objective lens (102), a first beam splitter (103), a mirror scanning unit (400), and a tube lens (105) sequentially arranged along the optical axis from the object plane (101) to the image plane; the reflection scanning unit includes a first scanning mirror (401), a second scanning mirror (402), and a relay module. The first scanning mirror (401) is arranged at the aperture of the objective lens (102), the second scanning mirror (402) is arranged at the aperture of the tube lens (105), and the relay module is arranged between the first scanning mirror (401) and the second scanning mirror (402) for relaying the imaging of the aperture of the objective lens (102) to the aperture of the tube lens (105); by adjusting the angles of the first scanning mirror (401) and the second scanning mirror (402), the single-frame imaging field of view of the single-frame imaging system (100) can be scanned and moved in the X direction and the Y direction; the function of the single-frame imaging system (100) is to achieve high-resolution imaging of a single-frame sub-field of view; wherein, the relay module includes a first relay lens (403) and a second relay lens (404), and the second relay lens (404) is arranged between the first relay lens (403) and the second scanning mirror (402) and can move along the optical axis between the first relay lens (403) and the second scanning mirror (402); The laser marking system (200) includes a first laser (201) that emits laser light towards the object plane (101), and a first lens (202), a pinhole array (203), a second lens (204), and an aperture (205) sequentially arranged along the optical path of the first laser (201); the laser light emitted by the first laser (201) is shaped into a parallel beam by the first lens (202) to illuminate the pinhole array (203), and then the pinhole array (203) is projected onto the object plane (101) through the second lens (204), the aperture (205), the first beam splitter (103), and the objective lens (102).

2. The optical imaging system according to claim 1, characterized in that a second beam splitter (104) is further arranged between the second scanning mirror (402) and the tube lens (105); The imaging module further includes a real-time focusing system (300). The real-time focusing system (300) includes a second laser (301) that emits laser light towards the object surface (101), and a third lens (302), a pinhole (303), and a fourth lens (304) that are sequentially arranged along the optical path of the second laser (301). The laser light emitted by the second laser (301) forms a converging beam through the third lens (302) to illuminate the pinhole (303), and then projects the pinhole (303) onto the object surface (101) through the fourth lens (304), the second beam splitter (104), the mirror scanning unit (400), the first beam splitter (103), and the objective lens (102); The size of the projection of the pinhole (303) on the object surface (101) varies with the distance between the objective lens (102) and the object surface (101).

3. The optical imaging system according to claim 2, wherein The first relay lens (403) is disposed between the first scanning mirror (401) and the second scanning mirror (402).

4. The optical imaging system according to claim 2, wherein The objective lens (102) is an object-space telecentric lens with an image-space infinity conjugate, and the tube lens (105) is an image-space telecentric lens with an object-space infinity conjugate.

5. The optical imaging system according to claim 2, wherein The colors of the laser lights emitted by the first laser (201) and the second laser (301) are different, and / or, the shape of the holes in the pinhole array (203) is different from the shape of the pinhole (303).

6. An imaging module, wherein It includes a photosensitive element and the optical imaging system according to any one of claims 1-5. The photosensitive element (106) is disposed behind the tube lens (105).

7. An electronic device, wherein It includes a housing and the imaging module according to claim 6. The imaging module is disposed within the housing.

8. An optical imaging method applied to the imaging module according to claim 6, wherein It includes: Dividing a large field of view into a plurality of sub-fields of view; Taking images of each sub-field of view separately in a time-sharing manner to obtain a first sub-field image and a second sub-field image of each sub-field of view. Among them, the first sub-field image is an image obtained when the laser marking system is in an on state, and the laser marking points projected by the laser marking system on the object surface are recorded in the first sub-field image. The second sub-field image is an image obtained when both the laser marking system and the real-time focusing system are in an off state; According to the positions of the laser marking points in each first sub-field image, image stitching is performed on the second sub-field image corresponding to the first sub-field image to obtain a large field of view image.

9. The method according to claim 8, wherein The taking images of each sub-field of view separately in a time-sharing manner to obtain a first sub-field image and a second sub-field image of each sub-field of view includes: Drive the first scanning mirror and the second scanning mirror to step to the target sub-field of view; Turn on the laser marking system to form laser marking points on the object surface, and turn on the real-time focusing system to form laser focusing points on the object surface. The positions of the laser marking points and the laser focusing points do not overlap; Collect the first sub-field of view image through the single-frame imaging system. The first sub-field of view image records the position of the laser marking point and the size of the laser focusing point at the same time; Determine the focusing compensation amount according to the size of the laser focusing point, and control the movement of the second relay lens based on the focusing compensation amount. The focusing compensation amount is the movement direction and distance corresponding to moving the second relay lens along the optical axis from the zero position to the position where the object surface is imaged clearly; Turn off the laser marking system and the real-time focusing system, and collect the second sub-field of view image through the single-frame imaging system; Control the second relay lens to return to the zero position, take the next sub-field of view as the target sub-field of view, and return to execute the step of driving the first scanning mirror and the second scanning mirror to step to the target sub-field of view.

10. The method according to claim 8, wherein Before dividing the large field of view into multiple sub-fields of view, it further includes: calibrating the laser marking system to obtain a laser point calibration image; The image stitching of the second sub-field of view image corresponding to the first sub-field of view image according to the positions of the laser marking points in each first sub-field of view image to obtain a large field of view image includes: Compare each first sub-field of view image with the laser point calibration image, determine whether the position of each laser marking point in the first sub-field of view image has changed compared with its position in the laser point calibration image, and record the drift amount of the laser marking point when it changes; according to the positions of the laser marking points and the corresponding drift amounts in each first sub-field of view image, perform image stitching on the second sub-field of view image corresponding to the first sub-field of view image to obtain a large field of view image.

Images