Lens group driving device and autofocus lens

Abstract

The present invention provides a lens group driving device and an automatic focusing lens, comprising: a driving coil fixedly connected to the lens group; a closed magnetic ring, through which the driving coil passes to form a cross structure; at least two guide rods for limiting the moving direction of the lens group, with any guide rod being parallel to the optical axis of the lens group; and the driving coil driving the lens group to move along the guide rods when energized. When the driving coil is energized and drives the lens group, there is no contact between the driving coil and the closed magnetic ring, thereby reducing noise caused by friction or vibration, and reducing noise generated during zooming or focusing. Compared with the problems of noise caused by the high-frequency vibration of the stepping motor itself and slow focusing speed caused by the driving frequency limitation of the stepping motor, the present application utilizes the interaction force between the magnetic field generated by the driving coil and the closed magnetic ring to drive the driving coil to produce non-contact movement with the closed magnetic ring, which can effectively avoid noise and increase the focusing speed.

Description

Technical Field

[0001] The present invention relates to an optical imaging device, and in particular to a lens group driving device and an automatic focusing lens. Background Art

[0002] In recent years, due to the impact of the epidemic, video equipment has become more and more commonly used in human life. With the development of imaging chip technology, image processing, and network transmission technology, video conferencing equipment, live broadcasts, and educational recording and broadcasting equipment have higher and higher requirements for imaging. Because the subjects of the shots are mainly people and voice recording is required, the camera lens is directly required to gradually develop towards high pixels, large aperture, fast focus and low noise. In order to meet this trend, the focusing structure of the optical lens installed on video conferencing equipment, live broadcast equipment, educational recording and broadcasting equipment and other products also requires further fast and precise focusing and low noise performance.

[0003] The traditional automatic focusing method of optical lenses generally uses the screw connection guide structure of the stepper motor to drive the lens to achieve linear motion as the automatic focusing transmission function; the optical coupling element is used to realize the position detection function. Although this method is simple in design, the stepper motor has large vibrations when it is actuated, which produces unavoidable noise; the stepper motor drives the automatic focusing structure, and there is the inherent transmission backlash of the motor and the inherent stepping phenomenon of the stepper motor, which affects the focusing accuracy. Due to the inherent driving frequency of the stepper motor, the focusing speed cannot be further improved. In addition, the response speed of the optical coupling also affects the focusing speed. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a lens group driving device and an autofocus lens, which can reduce the noise generated by focusing and improve the focusing speed.

[0005] The object of the present invention is to provide a lens group driving device, comprising: a driving coil fixedly connected to the lens group; a closed magnetic ring, through which the driving coil passes to form a cross structure; at least two guide rods for limiting the moving direction of the lens group, any one of the guide rods being parallel to the optical axis of the lens group; the driving coil drives the lens group to move along the guide rods when powered on.

[0006] In some embodiments, the lens group driving device is configured with a precision device, and the precision device further includes: an array magnetic strip fixed on the lens group; and a giant magnetoresistive sensor for detecting position changes of the array magnetic strip.

[0007] In some embodiments, the closed magnetic ring includes: two U-shaped iron plates, which are arranged to be buckled in an opposite direction with their openings facing each other, and a limiting rod for limiting the driving coil is provided between the two U-shaped iron plates, and the two U-shaped iron plates and the limiting rod form a "sun" shape;

[0008] Two permanent magnets are respectively arranged in the two U-shaped iron plates.

[0009] The present invention also proposes an autofocus lens, comprising: a lens barrel; a zoom lens group and a focus lens group arranged in the lens barrel, wherein the zoom lens group and the focus lens group are both equipped with the above-mentioned lens group driving device; and a controller for controlling the movement of the zoom lens group and controlling the focus lens group to move according to the movement distance of the zoom lens group.

[0010] In some embodiments, it also includes: three fixed lens groups arranged in the lens barrel, the fixed lens groups are respectively a first fixed lens group, a second fixed lens group and a third fixed lens group along the direction from the object side to the image side of the optical axis; the focusing lens group is arranged between the third fixed lens group and the second fixed lens group; the zoom lens group is arranged between the first fixed lens group and the second fixed lens group; and the aperture is arranged between the zoom lens group and the second fixed lens group.

[0011] Furthermore, the lens barrel includes a first lens barrel for fixing the first fixed lens group, a second lens barrel for fixing the second fixed lens group, and a third lens barrel for fixing the third fixed lens group. The first lens barrel, the second lens barrel, and the third lens barrel are fixed in sequence by screws.

[0012] In some embodiments, the focusing lens group is arranged in a focusing housing; the lens group driving device for driving the focusing lens is a first driving device, and the driving coil corresponding to the first driving device is fixed on the focusing housing; the zoom lens group is arranged in a zoom housing; the lens group driving device for driving the zoom lens is a second driving device, and the driving coil corresponding to the second driving device is fixed on the zoom housing.

[0013] Furthermore, there are two guide rods, including a first guide rod and a second guide rod, and the first guide rod and the second guide rod are arranged between the first lens barrel and the third lens barrel.

[0014] In some embodiments, there are four guide rods, including a first guide rod, a second guide rod, a third guide rod and a fourth guide rod. The first guide rod and the third guide rod are arranged between the first lens barrel and the second lens barrel for guiding the zoom lens group; the second guide rod and the fourth guide rod are arranged between the second lens barrel and the third lens barrel for guiding the focusing lens group.

[0015] In some embodiments, any of the guide rods is fixed on the lens barrel, the focusing lens group and the zoom lens group are provided with guide arms, the guide arms are provided with U-shaped grooves, and the guide rods pass through the U-shaped grooves.

[0016] When the drive coil is powered and driving the lens assembly, there is no contact between the drive coil and the enclosed magnetic ring, thereby reducing noise caused by friction or vibration, and thus reducing the noise generated during zooming or focusing. Compared to the problems of stepper motors causing noise due to their own high-frequency vibrations and slow focusing speeds caused by the limited drive frequency of stepper motors, this application utilizes the interaction between the drive coil and the magnetic field generated by the enclosed magnetic ring to drive the drive coil to produce non-contact movement within the enclosed magnetic ring, which can effectively avoid noise and increase focusing speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic diagram of a focus driving device in an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of a lens structure in an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of the optical principle of an embodiment provided by the present invention;

[0021] Figure 4 A schematic diagram of an array magnetic stripe in an embodiment of the present invention;

[0022] Figure 5 A schematic diagram of the output signal of a giant magnetoresistive sensor in an embodiment of the present invention.

[0023] Reference numerals:

[0024] Autofocus lens 100; lens group driving device 10; driving coil 11; lens group 12; closed magnetic ring 13; guide rod 14; array magnetic strip 15; giant magnetoresistance sensor 16; first lens barrel 21; second lens barrel 22; third lens barrel 23; zoom lens group 30; zoom housing 31; focusing lens group 40; focusing housing 41; aperture 50; first fixed lens group 60; second fixed lens group 70; third fixed lens group 80. DETAILED DESCRIPTION

[0025] The description of the embodiments in this specification should be combined with the corresponding drawings, which should be considered a complete part of this specification. In the drawings, the shapes and thicknesses of the embodiments may be exaggerated and indicated for simplicity or convenience. Furthermore, the various structural components in the drawings will be described separately. It is worth noting that components not shown in the drawings or not described in words are known to those of ordinary skill in the art.

[0026] The description of the embodiments herein and any references to directions and orientations are for ease of description only and are not to be construed as limiting the scope of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination. The present invention is not specifically limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0028] See also Figures 1 to 5 A lens group driving device 10 and an autofocus lens 100 according to an embodiment of the present invention are described.

[0029] like Figure 1 As shown, the lens group driving device 10 includes: a driving coil 11, which is fixedly connected to the lens group 12. Normally, the lens group 12 includes at least a lens and an outer shell, and the driving coil 11 is fixedly connected to the lens group 12 through the outer shell; a closed magnetic ring 13, and the driving coil 11 passes through the closed magnetic ring 13 to form a cross structure, which is usually in a vertical form, that is, the surface formed by any circle of the driving coil 11 is perpendicular to the magnetic field of the closed magnetic ring 13; at least two guide rods 14, which are used to limit the moving direction of the lens group 12, and any guide rod 14 is parallel to the optical axis of the lens group 12; the driving coil 11 drives the lens group 12 to move along the guide rods 14 when powered on.

[0030] The drive coil 11, which holds the lens assembly 12, forms a cross structure with the enclosed magnetic ring 13. A magnetic field is formed around the enclosed magnetic ring 13. When the coil is energized, the magnetic field generated by the enclosed magnetic ring 13 interacts with the magnetic field generated by the drive coil 11 to generate a driving force, causing the drive coil 11 and the lens assembly 12 fixed thereto to move. The lens assembly 12 is mounted on a guide rod 14, which is arranged parallel to the optical axis of the lens assembly 12. The lens assembly 12 can move along the direction of the guide rod 14. When the lens assembly driving device 10 is energized, the interaction between the magnetic fields causes the drive coil 11 and the lens assembly 12 to move along the guide rod 14. It is understood that by changing the direction and magnitude of the current passing through the drive coil 11, the magnitude of the magnetic field generated by the drive coil 11 can be changed, thereby changing the driving direction and movement speed of the lens assembly 12 by the drive coil 11. The direction and magnitude of the current in the drive coil 11 can be adjusted based on the actual minimum driving force.

[0031] When the drive coil 11 is energized and drives the lens group 12, there is no contact between the drive coil 11 and the closed magnetic ring 13, thereby reducing noise caused by friction or vibration, and reducing the noise generated during zooming or focusing. Compared with the problems of stepper motors causing noise due to their own high-frequency vibrations and slow focusing speed due to the limitation of the stepper motor drive frequency, the present application utilizes the interaction force between the magnetic field generated by the drive coil 11 and the closed magnetic ring 13 to drive the drive coil 11 to produce non-contact movement within the closed magnetic ring 13, which can effectively avoid noise and increase the focusing speed.

[0032] In some embodiments, the lens group driving device 10 is equipped with a precision device, which further includes: an array of magnetic strips 15, the arrangement of the array of magnetic strips 15 is as follows: Figure 4 As shown, it is fixed on the lens group 12; the giant magnetoresistive sensor 16 is used to detect the position change of the array magnetic strip 15.

[0033] When the driving coil 11 is energized and moves, the array magnetic strip 15 fixed on the lens group 12 also moves along the guide rod 14 with the lens group 12. When each magnetic pole of the array magnetic strip 15 passes through the giant magnetoresistive sensor 16, a two-phase magnetic field Gaussian curve is generated, as shown in FIG. Figure 5As shown, the Gaussian curve is a sine wave. The back-end circuit and algorithm of the giant magnetoresistive sensor 16 amplify the Gaussian curve signal and then process it. The phase difference of the two-phase sine wave is divided into several parts, and the back-end algorithm is used to identify it to obtain higher displacement accuracy. For example, in some embodiments, the interval of the array magnetic strips 15 is selected to be 264um, the phase difference of the feedback sine wave is 66um, and the back-end circuit algorithm divides the phase difference into 64 parts, and the accuracy of each part is 66um / 64=1.03um. The focusing accuracy reaches 1um focusing accuracy, which effectively improves the problem of insufficient accuracy of traditional stepper motor transmission caused by its stepping accuracy, screw transmission accuracy, and the inherent backlash of the stepper motor. It can be understood that in some embodiments, the number of parts into which the back-end circuit divides the phase difference can be determined according to the required accuracy, and it is not limited to dividing it into 64 parts.

[0034] In some embodiments, the closed magnetic ring 13 includes: two U-shaped iron plates, the openings of which are arranged to be opposite to each other and buckled together, and a limiting rod for limiting the driving coil 11 is provided between the two U-shaped iron plates. The limiting rod is used to quickly position the closed magnetic ring 13 and the driving coil 11 when assembling, and also to prevent the driving coil 11 from falling off. The two U-shaped iron plates and the limiting rod form a "sun" shape;

[0035] Two permanent magnets are respectively arranged in two U-shaped iron plates.

[0036] After the two U-shaped iron plates are fastened together with their openings facing each other, two permanent magnets are placed within each U-shaped plate to form a magnetic field. The U-shaped plates consist of a horizontal portion and two vertical portions, with each permanent magnet positioned within the corresponding horizontal portion, located on the inner side of the U-shaped plate. The magnetic field within the enclosed magnetic ring 13 interacts with the magnetic field formed by the energized drive coil 11, driving the drive coil 11 to move along the optical axis, with the limit rod parallel to the optical axis.

[0037] The driving coil 11 can be installed into the closed magnetic ring 13 through the opening of the two U-shaped iron plates to form a cross structure with the closed magnetic ring 13. The two permanent magnets are arranged at the horizontal parts of the corresponding U-shaped iron plates, that is, the two permanent magnets are arranged opposite to each other to generate a vertical magnetic field.

[0038] The present invention also provides an auto-focus lens 100, such as Figure 3 As shown, it includes: a lens barrel; a zoom lens group 30 and a focus lens group 40 arranged in the lens barrel, and the zoom lens group 30 and the focus lens group 40 are both equipped with the above-mentioned lens group driving device 10; a controller for controlling the movement of the zoom lens group 30, and controlling the focus lens group 40 to move according to the moving distance of the zoom lens group 30.

[0039] The zoom lens group 30 and the focusing lens group 40 equipped with the lens group driving device 10 are capable of performing linear motion parallel to the optical axis. When the image plane and the object distance are fixed and the position of the zoom lens group 30 is determined, the focusing lens group 40 has a unique position corresponding thereto in optical theory, so that a clear image is obtained. And when the zoom lens group 30 moves, the focusing lens group 40 also changes according to the position and moving distance of the zoom lens group 30, so as to obtain a clear image. By configuring the lens group driving device 10 on the zoom lens group 30 and the focusing lens group 40, the driving force formed by the interaction between the driving coil 11 of the lens group driving device 10 and the magnetic field generated by the closed magnetic ring 13 drives the zoom lens group 30 and the focusing lens group 40 to move. Since there is no contact between the driving coil 11 and the closed magnetic ring 13 during the movement, the noise generated by friction or vibration is prevented, and the noise problem of the lens during the zooming and focusing process is effectively alleviated. Furthermore, because the lens drive device does not have transmission backlash and step-out phenomena, the focusing accuracy is improved. The driving coil 11 and the closed magnetic ring 13 generate driving force through the interaction between the magnetic fields, which also effectively improves the problem of the inability to increase the focusing speed due to the inherent driving frequency of the traditional stepping motor and the slow response speed of the optical coupler.

[0040] It is understandable that the zoom lens group 30 can be configured with a driving device according to actual conditions, and those skilled in the art can select the lens group driving device 10 or an ordinary stepping motor according to actual usage conditions.

[0041] Automatic focusing is achieved through the software algorithm of the controller. When the camera detects defocus, the controller controls the lens driving device to search for the clearest focus point according to the set algorithm requirements, and drives the focusing lens group 40 to the specified position based on the difference between the current position of the focusing lens group 40 and the target position fed back by the position and displacement feedback device.

[0042] In some embodiments, the lens assembly further includes: three fixed lens groups arranged in the lens barrel, such as Figure 3 As shown, the fixed lens groups along the direction from the object side to the image side of the optical axis are respectively the first fixed lens group 60, the second fixed lens group 70 and the third fixed lens group 80; the focusing lens group 40 is arranged between the third fixed lens group 80 and the second fixed lens group 70; the zoom lens group 30 is arranged between the first fixed lens group 60 and the second fixed lens group 70; and the aperture 50 is arranged between the zoom lens group 30 and the second fixed lens group 70.

[0043] The distance between the first fixed lens group 60 and the zoom lens group 30 is L1, and the distance between the third fixed lens group 80 and the focus lens group 40 is L2. When the image plane and object distance are fixed and L1 changes, L2 has a unique corresponding value in optical theory to achieve optimal imaging resolution, and the entire lens has a corresponding focal length value. When the object distance changes significantly, L2 can be adjusted to regain a clear image.

[0044] Further, if Figure 3 As shown, the lens barrel includes a first lens barrel 21 for fixing the first fixed lens group 60, a second lens barrel 22 for fixing the second fixed lens group 70, and a third lens barrel 23 for fixing the third fixed lens group 80. The first lens barrel 21, the second lens barrel 22 and the third lens barrel 23 are fixed in sequence by screws.

[0045] The first lens barrel 21, the second lens barrel 22, and the third lens barrel 23 are secured together by a locking mechanism, securing the first, second, and third fixed lens groups 60, 70, and 80 to each other and protecting the fixed lens groups from damage due to collisions. This ensures a constant distance between the first, second, and third fixed lens groups 60, 70, and 80, and provides support and movement space for the focus lens group 40 and the zoom lens group 30. The giant magnetoresistive sensor 16 is mounted on the third lens barrel 23.

[0046] In some embodiments, the focusing lens group 40 is arranged in a focusing housing 41; the lens group driving device 10 for driving the focusing lens is a first driving device, and the driving coil 11 corresponding to the first driving device is fixed on the focusing housing 41; the zoom lens group 30 is arranged in a zoom housing 31; the lens group driving device 10 for driving the zoom lens is a second driving device, and the driving coil 11 corresponding to the second driving device is fixed on the zoom housing 31.

[0047] The focusing housing 41 and the zoom housing 31 protect the focusing lens group 40 and the lens and zoom lens group in the zoom lens group 30, and also have the function of supporting the lenses to prevent the focusing lens group 40 and the zoom lens from being damaged or destroyed due to collision or friction with external parts or devices. At the same time, the focusing housing 41 and the zoom housing 31 are conducive to the rapid assembly of the focusing lens group 40 and the zoom lens group 30, and are convenient for the installation of the driving device.

[0048] Furthermore, when the focusing lens group 40 and the zoom lens group 30 have different masses and sizes, the driving coil corresponding to the first driving device and the driving coil corresponding to the second driving device also have different size parameters. Similarly, the corresponding closed magnetic rings will also have different size parameters.

[0049] Furthermore, there are two guide rods 14 , including a first guide rod and a second guide rod, and the first guide rod and the second guide rod are disposed between the first lens barrel 21 and the third lens barrel 23 .

[0050] The first guide rod is used to guide the zoom lens group 30, and the second guide rod is used to guide the focusing lens group 40. The focusing lens group 40 and the zoom lens group 30 enable the zoom lens group 30 and the focusing lens group 40 to move between the first lens barrel 21 and the third lens barrel 23, limiting the movement range of the zoom lens group 30 and the focusing lens group 40.

[0051] In some embodiments, there are four guide rods 14, including a first guide rod, a second guide rod, a third guide rod and a fourth guide rod. The first guide rod and the third guide rod are arranged between the first lens barrel 21 and the second lens barrel 22, for guiding the zoom lens group 30; the second guide rod and the fourth guide rod are arranged between the second lens barrel 22 and the third lens barrel 23, for guiding the focusing lens group 40.

[0052] The first guide rod, the second guide rod, the third guide rod and the fourth guide rod are arranged parallel to the optical axis of the lens. While guiding the zoom lens group 30 and the focusing lens group 40, they fix the moving routes of the zoom lens group 30 and the focusing lens group 40 so that the zoom lens group 30 and the focusing lens group 40 can move along the direction of the lens optical axis, and make the optical axes of the zoom lens group 30 and the focusing lens group 40 coincide with the optical axis of the entire lens to meet the requirements of the optical system.

[0053] In some embodiments, any guide rod 14 is fixed on the lens barrel, and the focusing lens group 40 and the zoom lens group 30 are provided with guide arms, and the guide arms are provided with U-shaped grooves, and the guide rod 14 passes through the U-shaped grooves.

[0054] By setting a guide arm and a U-shaped groove, the focusing lens group 40 and the zoom lens group 30 are set on the guide rod 14, so that the fixation of the focusing lens group 40 and the zoom lens group 30 to the guide rod 14 is more stable, and the requirement of moving the focusing lens group 40 and the zoom lens group 30 on the guide rod 14 is met.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lens group driving device, characterized in that: Comprising: A driving coil (11), fixedly connected to a lens group (12); A closed magnetic ring (13), the driving coil (11) passing through the closed magnetic ring (13) to form a cross structure; At least two guide rods (14), used to limit the moving direction of the lens group (12), any one of the guide rods (14) being parallel to the optical axis of the lens group (12); The driving coil (11) drives the lens group (12) to be movable along the guide rod (14) in the powered-on state; The closed magnetic ring (13) comprises: Two U-shaped iron plates, arranged with their opening directions facing each other and buckled, a limiting rod for limiting the driving coil (11) being arranged between the two U-shaped iron plates, the two U-shaped iron plates and the limiting rod forming a "day" character shape; Two permanent magnets, respectively arranged inside the two U-shaped iron plates.

2. The lens group driving device according to claim 1, characterized in that: The lens group driving device is configured with a precision device, and the precision device further comprises: An array magnetic strip (15), fixed on the lens group (12); A giant magnetoresistive sensor (16), used to detect the position change of the array magnetic strip (15).

3. An autofocus lens, characterized in that: Comprising: A lens barrel; A zoom lens group (30) and a focusing lens group (40) arranged inside the lens barrel, both the zoom lens group (30) and the focusing lens group (40) being configured with the lens group driving device as described in any one of claims 1 to 2; A controller, used to control the movement of the zoom lens group (30) and to control the focusing lens group (40) to move according to the moving distance of the zoom lens group (30).

4. The autofocus lens according to claim 3, wherein: Further comprising: Three fixed lens groups arranged inside the lens barrel, the fixed lens groups being the first fixed lens group (60), the second fixed lens group (70), and the third fixed lens group (80) in sequence from the object side to the image side along the optical axis; The focusing lens group (40) is arranged between the third fixed lens group (80) and the second fixed lens group (70); The zoom lens group (30) is arranged between the first fixed lens group (60) and the second fixed lens group (70); An aperture (50), arranged between the zoom lens group (30) and the second fixed lens group (70).

5. The autofocus lens according to claim 4, wherein: The lens barrel includes a first lens barrel (21) for fixing the first fixed lens group (60), a second lens barrel (22) for fixing the second fixed lens group (70), and a third lens barrel (23) for fixing the third fixed lens group (80), the first lens barrel (21), the second lens barrel (22), and the third lens barrel (23) being fixedly locked in sequence by screws.

6. The autofocus lens according to claim 3, wherein: The focusing lens group (40) is arranged inside a focusing housing (41); The lens group driving device for driving the focusing lens is a first driving device, and the driving coil (11) corresponding to the first driving device is fixed on the focusing housing (41); The zoom lens group (30) is arranged inside a zoom housing (3)1); The lens group driving device for driving the zoom lens is a second driving device, and the driving coil (11) corresponding to the second driving device is fixed on the zoom housing (31).

7. The autofocus lens according to claim 5, wherein: There are two guide rods (14), including a first guide rod and a second guide rod, and the first guide rod and the second guide rod are arranged between the first lens barrel (21) and the third lens barrel (23).

8. The autofocus lens according to claim 5, wherein: There are four guide rods (14), including a first guide rod, a second guide rod, a third guide rod and a fourth guide rod. The first guide rod and the third guide rod are arranged between the first lens barrel (21) and the second lens barrel (22) and are used to guide the zoom lens group (30); The second guide rod and the fourth guide rod are arranged between the second lens barrel (22) and the third lens barrel (23) and are used to guide the focusing lens group (40).

9. The autofocus lens according to claim 3, wherein: Any of the guide rods (14) is fixed on the lens barrel, and the focusing lens group (40) and the zoom lens group (30) are provided with guide arms, each of which is provided with a U-shaped groove, and the guide rod (14) passes through the U-shaped groove.

Images