A miniaturized close-range imaging module with high imaging quality

Abstract

The present invention discloses a miniaturized short-distance imaging module with high imaging quality, comprising a first lens group, a second lens group and a photosensitive chip arranged in sequence from the object side to the image side; and a focusing motor used for driving only the first lens group or the second lens group to move to achieve focusing; wherein the first lens group and the second lens group constitute a lens group, the distance from the object plane to the image plane of the lens group on the optical axis is TTL, the distance from the object side surface to the image side surface of the lens group on the optical axis is TD, which satisfies the following relationship: 0.15≤TD / TTL≤0.9; the focal length f1 of the first lens group and the focal length f2 of the second lens group satisfy the following relationship: 0.1≤f1 / f2≤10; the optical tube length of the lens group satisfies the following relationship: 0.2≤TTL / (f1+f2)≤15; the distance L from the object side principal plane of the first lens group to the object plane Obj Satisfies the following relationship: 0.5f1≤L Obj ≤1.5f1; the distance from the image side principal plane of the second lens group to the image plane is L Ima Satisfies the following relationship: 0.5f2≤L Ima ≤1.5f2. By implementing the present invention, the volume of the entire module can be miniaturized.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging, and in particular to a miniaturized short-range imaging module with high imaging quality. Background Art

[0002] With the development of imaging technology, imaging devices have provided people with more and more convenience in daily life. People's requirements for imaging devices are not limited to imaging quality. Small size and portability have also become one of the important factors for people to choose imaging devices. Therefore, while ensuring high imaging quality, miniaturization is also crucial.

[0003] With the popularization of imaging devices, the world that people explore with imaging devices is no longer limited to the macroscopic world. The mysteries of the microscopic world are also attracting more and more people, and people also hope to observe tiny things at close range. At present, external macro lenses for mobile phones and special mobile phone macro cameras have appeared, allowing users to conveniently shoot microscopic objects anytime and anywhere.

[0004] The existing mobile phone macro camera adopts the method of increasing the distance from the lens to the detector to achieve macro imaging, that is, using the object distance and image distance relationship of optical imaging, the object distance is reduced by increasing the image distance to achieve macro imaging, such as the Chinese invention patent disclosure document with application number 201811206371.X. The main disadvantages of this scheme are: 1) The image distance must be increased to achieve super macro imaging (the distance from the object to the front face of the camera is less than or equal to 20 mm), resulting in a long distance from the lens to the detector, which is not conducive to the miniaturization of the camera, and in order to take into account both infinite imaging and super macro imaging, a large stroke focusing motor must be used, which also leads to a large overall size of the camera; 2) The optimal imaging range of the lens is limited. In order to take into account both infinite imaging and super macro imaging, the design requires the lens to optimize both infinite object distance and ultra-short object distance imaging, which is less feasible from the perspective of optical design. Even if the image distance is increased to achieve super macro, the imaging quality will be greatly lost, resulting in poor effect under super macro imaging.

[0005] Macro imaging can also be achieved by adding a positive focal length lens to the original mobile phone lens. For example, the Chinese invention patent with application number 201510275482.6 discloses a mobile phone with an external convex lens, which is movable. Macro photography can be achieved by moving the convex lens in front of the mobile phone camera. Compared with the aforementioned solution of increasing the distance of the lens to achieve super macro, the imaging quality of this solution can be better. For example, the Chinese invention patent publication with application number 201811003701.5 discloses a solution for achieving super macro imaging through an external lens, and its working distance is in the millimeter level. The advantage of this solution is that high-quality super macro imaging can be achieved by using a specially optimized external super macro lens. When imaging at super macro, the imaging depth of field is very shallow, and focusing is required during use. This solution uses the mobile phone's automatic focus camera module for focusing. When the magnification of ultra-macro imaging is close to 1 or greater than or equal to 1, it can be obtained from the optical system theory of geometric optics that the focusing range (i.e., the object plane movement range) is smaller than the motor stroke, resulting in wasted motor stroke. The motor stroke is an important factor restricting the size of the camera module. In order to achieve miniaturization, the motor stroke is usually not large, which ultimately leads to a too small focusing range.

[0006] The Chinese invention patent publication with application number 201910651974.9 discloses the structure of an ultra-macro lens, which has excellent ultra-macro imaging performance and can achieve the level of cell and subcellular resolution. The Chinese invention patent publication with application number 201910704120.2 discloses a camera module structure based on the ultra-macro lens. The module structure can work in a fixed focus mode without a focusing structure; it can also be combined with a focusing motor to realize an automatic focusing function to achieve clear imaging within a certain range of the object side. During automatic focusing, the focusing motor drives the entire module to move relative to the detection surface. According to the optical imaging theory, the focusing range is always smaller than the stroke of the focusing motor. As mentioned above, this causes the miniaturized ultra-macro camera module to have a focusing range that is too small in this working mode, which cannot meet the macro observation needs of different scenes.

[0007] The Chinese invention patent publication with application number 201910596432.6 discloses a mobile communication device with a microscopic imaging function, in which a camera module with a focusing function is provided. The module includes two lenses, and focusing can be achieved by moving the object lens alone. Compared with the aforementioned focusing solution, the focusing solution of the module can more effectively utilize the travel of the focusing mechanism, thereby facilitating the miniaturization of the module.

[0008] Miniaturized macro and micro imaging modules have great application prospects in the fields of biomedicine, especially in the field of portable biomedical imaging instruments. This field has special requirements for imaging quality, focusing distance, etc. At present, there is a lack of miniaturized macro and micro imaging modules suitable for this field. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a miniaturized short-range imaging module with high imaging quality in view of the defects of the prior art.

[0010] The technical solution adopted by the present invention to solve the technical problem is: constructing a miniaturized short-distance imaging module with high imaging quality, comprising a first lens group, a second lens group and a photosensitive chip arranged in sequence from the object side to the image side; and a focusing motor for driving only the first lens group or the second lens group to move to achieve focusing;

[0011] The first lens group and the second lens group form a lens group, the distance from the object plane to the image plane of the lens group on the optical axis is TTL, and the distance from the object side surface to the image side surface of the lens group on the optical axis is TD, which satisfies the following relationship: 0.15≤TD / TTL≤0.9;

[0012] The focal length f1 of the first lens group and the focal length f2 of the second lens group satisfy the following relationship: 0.1≤f1 / f2≤10;

[0013] The optical tube length of the lens group satisfies the following relationship: 0.2≤TTL / (f1+f2)≤15;

[0014] The distance L from the object principal plane of the first lens group to the object plane Obj Satisfies the following relationship: 0.5f1≤L Obj ≤1.5f1;

[0015] The distance L from the image side principal plane of the second lens group to the image plane Ima Satisfies the following relationship: 0.5f2≤L Ima ≤1.5f2.

[0016] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, both the first lens group and the second lens group have positive optical power and each include at least three lenses.

[0017] Preferably, in the miniaturized short-distance imaging module with high imaging quality described in the present invention, the object plane closest to the imaging module is a near-focus object plane, the object plane farthest from the imaging module is a far-focus object plane, and the object side of the lens group includes a limit surface, with the direction away from the imaging module as the positive direction;

[0018] The near-focus object plane is located within the range of ±50 μm from the limiting surface, and the distance between the far-focus object plane and the limiting surface is ≥220 μm.

[0019] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention,

[0020] When the focusing motor drives the first lens group to move, the second lens group is fixed in position; the near-focus object plane at this time is the object plane focused by the lens group when the distance between the first lens group and the second lens group is the smallest;

[0021] When the focusing motor drives the second lens group to move, the position of the first lens group is fixed; at this time, the near-focus object plane is the object plane focused by the lens group when the distance between the first lens group and the second lens group is the smallest.

[0022] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, the stroke of the focusing motor is ≥300 μm and ≤600 μm.

[0023] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, when the focusing motor drives the first lens group to move, the focusing distance is the same as the stroke of the focusing motor.

[0024] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, within the focusing range, the minimum distance between the first lens group and the second lens group is ≥50 μm.

[0025] Preferably, the miniaturized short-range imaging module with high imaging quality described in the present invention further includes a filter arranged in front of the photosensitive chip for filtering out light of unnecessary wavelength bands.

[0026] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, it also includes a protective glass arranged in front of the lens group, and the object-side surface of the protective glass is a limiting surface.

[0027] Preferably, in the miniaturized short-range imaging module with high imaging quality described in the present invention, within the focusing range, the minimum distance between the first lens group and the protective glass is ≥50 μm.

[0028] By implementing the present invention, the following beneficial effects are achieved:

[0029] The structure of the miniaturized high-quality close-range imaging module does not need to increase the image distance to achieve close-range imaging, so the volume of the entire module can be miniaturized;

[0030] The entire lens group is divided into two parts, a first lens group and a second lens group. Different from the common whole lens focusing method, the focusing motor in the present invention only drives one of the lens groups to focus, which can effectively reduce the motor load. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0032] Figure 1 1 is a schematic diagram of a close-focus state of a first embodiment of a miniaturized close-range imaging module with high imaging quality according to the present invention;

[0033] Figure 2 1 is a schematic diagram of a far-focus state of a first embodiment of a miniaturized short-distance imaging module with high imaging quality according to the present invention;

[0034] Figure 3 2 is a schematic diagram of a close-focus state of a second embodiment of a miniaturized close-range imaging module with high imaging quality according to the present invention;

[0035] Figure 4 It is a schematic diagram of the far focus state of the second embodiment of the miniaturized short-distance imaging module with high imaging quality of the present invention. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0037] It should be understood that the directions or positional relationships indicated by "front", "rear", "upper" and "lower" etc. are based on the directions or positional relationships shown in the drawings, and are constructed and operated in specific directions. They are only for the convenience of describing the technical solution, and do not indicate that the device or element referred to must have a specific direction. Therefore, they should not be understood as a limitation on the present invention.

[0038] The present invention constructs a miniaturized short-range imaging module with high imaging quality, which is suitable for short-range imaging, including a first lens group 10, a second lens group 11 and a photosensitive chip 15 arranged in sequence from the object side to the image side; and a focusing motor 12 for driving only the first lens group 10 or the second lens group 11 to move to achieve focusing.

[0039] In some embodiments, a stop may be provided between the first lens group 10 and the second lens group 11. The first lens group 10 and the second lens group 11 each include at least three lenses. The first lens group 10 and the second lens group 11 form a nearly infinite correction microscope structure. The first lens group 10 and the second lens group 11 both have positive focal lengths. The first lens group 10 is equivalent to the objective lens of the microscope, and the second lens group 11 is equivalent to the tube lens of the microscope.

[0040] The focusing motor 12 drives the first lens group 10 or the second lens group 11 to achieve focusing, that is, to change the position of the object plane of the imaging module. Among them, the object plane closest to the imaging module is the near-focus object plane, and the object plane farthest from the imaging module is the far-focus object plane, and the direction away from the imaging module is the positive direction. The first lens group 10 and the second lens group 11 form a lens group, and the object side of the lens group includes a limiting surface. When there is a protective glass 17 on the object side of the lens group, the object surface of the protective glass 17 is the limiting surface; when there is no protective glass 17 on the object side of the lens group, the end face of the imaging module housing or other mechanical structures that cooperate with the imaging module is the limiting surface. The near-focus object plane is within ±50 μm of the limiting surface, and the distance between the far-focus object plane and the limiting surface is ≥220 μm.

[0041] In this embodiment, the stroke of the focus motor 12 is ≥300 μm and ≤600 μm, and when the focus motor 12 drives the first lens group 10 to move, the focusing distance is the same as the stroke of the focus motor 12. Within the focusing range, the minimum distance between the first lens group 10 and the second lens group 11 is ≥50 μm. When there is a protective glass 17, within the focusing range, the minimum distance between the first lens group 10 and the protective glass 17 is ≥50 μm.

[0042] The use of the above parameters has the following beneficial effects:

[0043] 1) The near-focus object plane can cover the close-range area of ​​the protective glass 17, and can image close objects. At the same time, the far-focus object plane can exceed the cover glass commonly used in microscopes, meeting the needs of biomedical imaging;

[0044] 2) The stroke of the focus motor 12 can effectively cover the dimensional tolerances of each component in the module due to processing and installation, improving the manufacturability of mass production;

[0045] 3) A minimum gap is retained between the first lens group 10 and the protective glass 17 and the second lens group 11, which improves the reliability of the imaging module and prevents the internal components of the module from colliding with each other and being damaged when the focus motor 12 exceeds the rated stroke;

[0046] 4) While achieving the above beneficial effects, the module is miniaturized.

[0047] When the focus motor 12 drives the first lens group 10 to move, the second lens group 11 is fixed. The near-focus object plane at this time is the object plane focused on by the lens group when the distance between the first lens group 10 and the second lens group 11 is the smallest;

[0048] When the focus motor 12 drives the second lens group 11 to move, the first lens group 10 is fixed. The near-focus object plane at this time is the object plane focused by the lens group when the distance between the first lens group 10 and the second lens group 11 is the smallest.

[0049] The distance between the object plane and the image plane of the lens group composed of the first lens group 10 and the second lens group 11 on the optical axis is TTL, and the distance between the object side surface and the image side surface of the lens group on the optical axis is TD, which satisfies the following relationship: 0.15≤TD / TTL≤0.9;

[0050] The focal length f1 of the first lens group 10 and the focal length f2 of the second lens group 11 satisfy the following relationship: 0.1≤f1 / f2≤10;

[0051] The optical tube length of the lens group satisfies the following relationship: 0.2≤TTL / (f1+f2)≤15;

[0052] The distance L between the object principal plane of the first lens group 10 and the object plane Obj Satisfies the following relationship: 0.5f1≤L Obj ≤1.5f1;

[0053] The distance L between the image side principal plane of the second lens group 11 and the image plane Ima Satisfies the following relationship: 0.5f2≤L Ima ≤1.5f2.

[0054] When the focusing motor 12 drives the first lens group 10 or the second lens group 11 to move, the imaging module meets the above conditions within the entire focusing stroke.

[0055] In some embodiments, the focus motor 12 may be a voice coil motor, an ultrasonic motor, a stepping motor, a memory alloy motor, or the like.

[0056] In some embodiments, the miniaturized high-quality short-range imaging module further includes a filter 18 disposed in front of the photosensitive chip 15 for filtering out light of unnecessary wavelengths to avoid affecting the imaging effect.

[0057] By implementing the present invention, the following beneficial effects are achieved:

[0058] 1) The structure of the miniaturized high-quality close-range imaging module does not need to increase the image distance to achieve close-range imaging, so the volume of the entire module can be miniaturized;

[0059] 2) The entire lens group is divided into two parts, the first lens group and the second lens group. Different from the common whole lens focusing method, the focusing motor in the present invention only drives one of the lens groups to focus, which can effectively reduce the motor load. And when the focusing motor drives the first lens group to move, the focusing distance is the same as the stroke of the focusing motor, and the focusing distance will not be less than the motor stroke, thus avoiding the waste of the motor stroke.

[0060] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation schemes. The described embodiments are only part of the embodiments of the present invention and are not limited to the protection scope of the present invention.

[0061] The first embodiment, as Figure 1 and 2 As shown, a miniaturized close-range imaging module with high imaging quality is provided, which is arranged according to the optical path and includes a first lens group 10, a second lens group 11 and a photosensitive chip 15 arranged in sequence from the object side to the image side, and a focusing motor 12 for driving the first lens group 10 to move to achieve focusing.

[0062] The first lens group 10 and the second lens group 11 form a lens group, the focal length f1 of the first lens group 10 is 2.2 mm, and the focal length f2 of the second lens group 11 is 3 mm. The distance TTL from the object surface to the image surface of the lens group on the optical axis is 8 mm, and the distance TD from the object side surface to the image side surface on the optical axis is 6 mm.

[0063] The first lens group 10 is mounted on a movable carrier (not shown) of the focus motor 12 by dispensing glue or other fixing methods. The focus motor 12 can be a voice coil motor, an ultrasonic motor, a memory alloy motor, etc. The stroke of the focus motor 12 is 300 μm.

[0064] In this embodiment, a lens barrel 13 is further included for fixing the second lens group 11. The lens barrel 13 has internal threads, and the second lens group 11 has external threads, and the two are connected by threads. During actual imaging, the focus motor 12 drives the first lens group 10 to move to achieve the focusing function, and the position of the second lens group 11 in the imaging optical path is fixed.

[0065] In this embodiment, the photosensitive chip 15 is disposed on a circuit board 16, and the circuit board 16 includes but is not limited to a printed circuit board, a flexible circuit board, etc. The photosensitive chip 15 is fixedly placed at the image focal plane of the second lens group 11, and the light converged by the second lens group 11 is incident on the photosensitive chip 15, and the photosensitive chip 15 performs photoelectric conversion on the sensed light.

[0066] In some embodiments, the photosensitive chip 15 is a planar array photoelectric device. Preferably, the photosensitive chip 15 is a CMOS image sensor or a CCD image sensor.

[0067] In addition, the miniaturized high-quality close-range imaging module also includes a housing 14 for fixing the first lens group 10, the second lens group 11, the focusing motor 12, the photosensitive chip 15, etc.

[0068] In this embodiment, if Figure 1As shown, the near-focus object plane 21 is located 50 μm inside the upper surface of the housing 14. Figure 2 As shown, the far-focus object plane 22 is located 300 μm outside the upper surface of the housing 14. In the near-focus state, the distance between the first lens group 10 and the upper surface of the housing 14 is 900 μm, and the distance between the first lens group 10 and the second lens group 11 is 0.15 mm. In the far-focus state, the distance between the first lens group 10 and the upper surface of the housing 14 is 550 μm.

[0069] The second embodiment, as Figure 3 and 4 As shown, compared with the first embodiment, a filter 18 is added in front of the photosensitive chip 15, and a protective glass 17 is added at the front of the imaging module. The focusing method is that the focusing motor 12 drives the second lens group 11 to move, and the first lens group 10 is fixed on the lens barrel 13. The lens barrel 13 has an internal thread, and the first lens group 10 has an external thread. The two are connected by threads. During actual imaging, the focusing motor 12 drives the second lens group 11 to move to achieve the focusing function, and the position of the first lens group 10 in the imaging optical path is fixed.

[0070] The first lens group 10 and the second lens group 11 form a lens group, the focal length f1 of the first lens group 10 is 2.5 mm, and the focal length f2 of the second lens group 11 is 5 mm. The distance TTL from the object surface to the image surface of the lens group on the optical axis is 10 mm, and the distance TD from the object side surface to the image side surface on the optical axis is 7 mm.

[0071] The filter 18 is disposed between the second lens group 11 and the photosensitive chip 15, and can be fixed to the housing 14 by glue or other means, or can be directly glued to the second lens group 11 like the side, or can be placed closely above the photosensitive chip 15. The filter 18 is used to filter out light that is not desired to be detected by the photosensitive chip, and in some embodiments, it can be a reflective filter or an absorptive filter.

[0072] The protective glass 17 is installed in front of the first lens group 10, with a thickness of 0.5 mm, and plays a role in protecting the lens. In order to prevent the protective glass from making hard contact with the ground when the module falls, thereby damaging the internal motor mechanism and lens and other components, a preferred solution is to add a layer of buffer material between the protective glass 17 and the focus motor 12, including but not limited to foam plastic and other materials.

[0073] It should be noted that the filter 18 and the protective glass 17 can be selected according to the actual needs of the user, and whether the two are used does not affect the core imaging function of the module. For example, when the protective glass 17 is added in front of the imaging module, the closest imaging surface of the imaging module should at least start from the outer surface of the protective glass 17 to ensure that the object surface is outside the protective glass 17 in the entire focusing range. Similarly, when adding the filter 18, it should also be ensured that there is enough space on the image side to reasonably set the position of the filter 18 without affecting the imaging.

[0074] like Figure 3 As shown in FIG. 1 , the near-focus object plane 21 of this embodiment is located above the upper surface of the protective glass 17. Figure 4 As shown, the far-focus object plane is located about 200 μm outside the upper surface of the protective glass 17. In the near-focus state, the distance between the first lens group 10 and the second lens group 11 is 0.4 mm. In the far-focus state, the distance between the first lens group 10 and the second lens group 11 is 0.05 mm.

[0075] The present invention is described by specific embodiments, and it should be understood by those skilled in the art that various changes and equivalent substitutions may be made to the present invention without departing from the scope of the present invention. In addition, various modifications may be made to the present invention for specific situations or specific circumstances without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all implementation methods falling within the scope of the claims of the present invention.

Claims

1. A miniaturized short-range imaging module with high imaging quality, characterized in that: It comprises a first lens group (10), a second lens group (11) and a photosensitive chip (15) which are arranged in sequence from the object side to the image side; and a focusing motor (12) for driving only the first lens group (10) or the second lens group (11) to move to achieve focusing; Wherein, the first lens group (10) and the second lens group (11) both have positive focal power and each include at least three lenses; Within the focusing range, the minimum distance between the first lens group (10) and the second lens group (11) is ≥50 μm; The first lens group (10) and the second lens group (11) form a lens group, the distance from the object plane to the image plane of the lens group on the optical axis is TTL, and the distance from the object side surface to the image side surface of the lens group on the optical axis is TD, which satisfies the following relationship: 0.15≤TD / TTL≤0.9; The focal length f1 of the first lens group (10) and the focal length f2 of the second lens group (11) satisfy the following relationship: 0.1≤f1 / f2≤10; The optical tube length of the lens group satisfies the following relationship: 0.2≤TTL / (f1+f2)≤15; The distance L between the object principal plane of the first lens group (10) and the object plane Obj Satisfies the following relationship: 0.5f1≤L Obj ≤1.5f1; The distance L between the image-side principal plane of the second lens group (11) and the image plane Ima Satisfies the following relationship: 0.5f2≤L Ima ≤1.5f2.

2. The miniaturized short-range imaging module with high imaging quality according to claim 1, characterized in that: The object plane closest to the imaging module is the near-focus object plane, the object plane farthest from the imaging module is the far-focus object plane, and the object side of the lens assembly includes a limiting surface, with the direction away from the imaging module as the positive direction; The near-focus object plane is located within the range of ±50 μm from the limiting surface, and the distance between the far-focus object plane and the limiting surface is ≥220 μm.

3. The miniaturized short-range imaging module with high imaging quality according to claim 2, characterized in that: When the focus motor (12) drives the first lens group (10) to move, the second lens group (11) is fixed in position; the near-focus object plane at this time is the object plane focused on by the lens group when the distance between the first lens group (10) and the second lens group (11) is the smallest; When the focusing motor (12) drives the second lens group (11) to move, the position of the first lens group (10) is fixed; at this time, the near-focus object plane is the object plane focused on by the lens group when the distance between the first lens group (10) and the second lens group (11) is the smallest.

4. The miniaturized short-range imaging module with high imaging quality according to claim 1, characterized in that: The stroke of the focusing motor (12) is ≥300 μm and ≤600 μm.

5. The miniaturized short-range imaging module with high imaging quality according to claim 4, characterized in that: When the focus motor (12) drives the first lens group (10) to move, the focus distance is the same as the stroke of the focus motor (12).

6. The miniaturized short-range imaging module with high imaging quality according to claim 1, characterized in that: It also includes a filter (18) arranged in front of the photosensitive chip (15) and used to filter out light of unnecessary wavelengths.

7. The miniaturized short-range imaging module with high imaging quality according to claim 1, characterized in that: It also comprises a protective glass (17) arranged in front of the lens group, wherein the object-side surface of the protective glass (17) is a limiting surface.

8. The miniaturized short-range imaging module with high imaging quality according to claim 7, characterized in that: In the focusing range, the minimum distance between the first lens group (10) and the protective glass (17) is ≥50 μm.

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