Autofocus device and autofocus method

Abstract

The application discloses an automatic focusing device and an automatic focusing method, and relates to the field of automatic focusing devices, and aims to realize fast focusing of a lens, reduce the situation of frequent focusing and out-of-focus in a shooting picture, keep the picture in a clear state for a long time, and improve the quality of the shooting picture. The automatic focusing device comprises a shooting device, a ranging module and a turntable. The shooting device is fixed on a base, is used for inquiring a focusing ranging table under a current magnification, and controls a focusing motor to adjust the focusing position of the lens according to the focusing step number corresponding to a current object distance, so that a clear image of a photographed object is formed on an image plane. The ranging module is used for measuring the current object distance between the optical center of the lens and the photographed object. The ranging module is fixed on the turntable, and the turntable is fixed on the base and is used for adjusting the position of the ranging module, so that the main optical axis of the ranging module is consistent with the main optical axis of the lens in the vertical direction, and the main optical axis of the ranging module is parallel to the main optical axis of the lens in the horizontal direction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of video monitoring, more particularly, to an automatic focusing device and an automatic focusing method. BACKGROUND

[0002] In the high-altitude monitoring scene of a safe city, a zoomable long-focus pan-tilt camera is needed.

[0003] The core components of the zoomable long-focus pan-tilt camera mainly include a mechanical rotating platform (also called a pan-tilt) that can realize vertical and horizontal axial rotation and a zoomable long-focus integrated core. Among them, the zoomable long-focus integrated core can realize large magnification optical zoom and focusing, and realize clear imaging of images several kilometers away. However, in the large magnification working scene, the focusing speed of the zoomable long-focus integrated core is much slower than that in the small magnification working scene, which leads to the imaging picture being easily blurred most of the time and cannot be clearly focused in the whole period. SUMMARY

[0004] The present application provides an automatic focusing device and an automatic focusing method to solve the problem of slow focusing speed of the zoomable long-focus integrated core, which leads to the imaging picture being easily blurred most of the time and cannot be clearly focused in the whole period.

[0005] According to a first aspect of the present application, an automatic focusing device is provided, comprising:

[0006] A shooting device is fixed on a base, used to query a focusing distance table at a magnification of a current lens, and control a focusing motor to adjust the focusing position of the lens according to the focusing step number corresponding to the current object distance, so that a clear image of the photographed object is formed on the image plane.

[0007] A distance measuring module is used to measure the current object distance between the optical center of the lens and the photographed object.

[0008] A rotating platform is fixed on the distance measuring module, and the rotating platform is fixed on the base. The rotating platform is used to adjust the position of the distance measuring module, so that the principal axis of the distance measuring module is consistent with the principal axis of the lens in the vertical direction, and the principal axis of the distance measuring module is parallel to the principal axis of the lens in the horizontal direction.

[0009] Optionally, the memory of the shooting device stores the focusing distance table, and the focusing distance table records the relationship among magnification, object distance and focusing step number.

[0010] Optionally, the rotating platform comprises:

[0011] a parallelism calibration assembly for adjusting a horizontal position of the distance measuring module so that a main optical axis of the distance measuring module is parallel to a main optical axis of the lens in a horizontal direction;

[0012] a height calibration assembly for adjusting a vertical position of the distance measuring module so that the main optical axis of the distance measuring module is in line with the main optical axis of the lens in a vertical direction.

[0013] Optionally, the parallelism calibration assembly comprises a parallelism stepper motor, a worm shaft, a worm wheel and a parallelism turntable,

[0014] the parallelism stepper motor is fixedly connected with the worm shaft, the worm wheel is fixedly connected with the parallelism turntable, and the worm shaft and the worm wheel are in transmission cooperation,

[0015] the parallelism stepper motor controls rotation of the worm shaft, the worm shaft drives rotation of the worm wheel, and the worm wheel drives rotation of the parallelism turntable in the horizontal direction.

[0016] Optionally, when an unwinding spiral angle of the worm shaft is less than a friction angle at which the worm shaft and the worm wheel are in contact, the parallelism calibration assembly is in position self-locking.

[0017] Optionally, the height calibration assembly comprises a wedge plate, a height control motor, a pressing plate and a sliding plate, a bottom surface of the wedge plate comprises a plurality of inclined surfaces, the height control motor comprises a gear reduction box, and the sliding plate comprises a plurality of rollers,

[0018] the height control motor is fixedly connected with the base, the sliding plate is fixedly connected with the base through the pressing plate, and an output gear of the gear reduction box is in meshing transmission with a sector gear of the sliding plate.

[0019] Optionally, the height control motor drives rotation of the output gear, and in turn drives rotation of the sliding plate, in the process of rotation of the sliding plate, the plurality of rollers of the sliding plate move along the plurality of inclined surfaces of the wedge plate, so that the wedge plate moves in the vertical direction, and in turn so that the distance measuring module moves in the vertical direction.

[0020] Optionally, when an inclination angle of the plurality of inclined surfaces of the wedge plate is less than a friction coefficient between the plurality of rollers and the plurality of inclined surfaces, the height calibration assembly is in position self-locking.

[0021] Optionally, the turntable further comprises a connecting plate, a plurality of springs and a plurality of fasteners,

[0022] The connecting plate is located between the distance measuring module and the parallelism calibration assembly, the plurality of springs are located between the parallelism calibration assembly and the inclined wedge plate, and the distance measuring module, the connecting plate, the parallelism calibration assembly, the plurality of springs, the height calibration assembly and the base are fixedly connected through the plurality of fasteners.

[0023] Optionally, the photographing device comprises a variable focal length telephoto integrated machine core.

[0024] The distance measuring module comprises a laser distance measuring module.

[0025] According to a second aspect of the present application, an automatic focusing method is provided, comprising:

[0026] Controlling a zoom motor of the photographing device to adjust a magnification of a lens;

[0027] Measuring a current object distance between an optical center of the lens and a photographed object at a current magnification by using a distance measuring module;

[0028] Querying a focusing distance table at the current magnification, and controlling a focusing motor to adjust a focusing position of the lens according to a focusing step number corresponding to the current object distance, so that the photographed object forms a clear image on an image plane.

[0029] Optionally, the automatic focusing method further comprises:

[0030] Calibrating a relative position of a main optical axis of the distance measuring module and a main optical axis of the lens;

[0031] Establishing the focusing distance table.

[0032] Optionally, the calibration of the relative position of the main optical axis of the distance measuring module and the main optical axis of the lens comprises:

[0033] Placing a calibration plate at a first distance from the lens, the calibration plate comprising a first calibration frame and a second calibration frame;

[0034] Adjusting a position of the lens so that an image of a center point of the first calibration frame is located at an optical center of the lens;

[0035] Determining, by using an image analysis algorithm, whether a laser spot formed by laser emitted by the distance measuring module on the calibration plate is located within the second calibration frame,

[0036] When the laser spot is located within the second calibration frame, locking the position of the distance measuring module by using a self-locking function of the parallelism calibration assembly and the height calibration assembly.

[0037] Optionally, the establishment of the focusing distance table comprises:

[0038] controlling the zoom motor of the photographing device to adjust the magnification of the lens;

[0039] determining the nearest distance and the farthest distance at which the lens can take a clear image according to the depth of field of the object focal point at each magnification;

[0040] placing a reference object at the nearest distance, controlling the focus motor to finely adjust the focus position of the lens so that the reference object forms a clear image on the image focal plane, and recording the object distance of the reference object and the focus step number of the focus motor;

[0041] moving the reference object to the farthest distance at each interval of a second distance until the reference object is moved to the farthest distance,

[0042] judging whether the reference object forms a clear image on the image focal plane at each interval of the second distance,

[0043] if a clear image is not formed, controlling the focus motor to finely adjust the focus position of the lens so that the reference object forms a clear image on the image focal plane, and recording the object distance of the reference object and the focus step number of the focus motor;

[0044] recording the object distance of the reference object and the focus step number of the focus motor at each magnification, and obtaining the focus distance table in which the relationship among the magnification, the object distance and the focus step number is recorded.

[0045] The automatic focusing device and the automatic focusing method provided by the embodiment of the application, the automatic focusing device comprises a photographing device, a distance measuring module, a turntable and a base. The distance measuring module is fixed on the turntable, the photographing device and the turntable are fixed on the base, and the turntable comprises a parallelism calibration assembly and a height calibration assembly with a position self-locking function. During use, the horizontal and vertical positions of the distance measuring module can be adjusted by the parallelism calibration assembly and the height calibration assembly, so that the main optical axis of the distance measuring module is parallel to the main optical axis of the lens in the horizontal direction, and the main optical axis of the distance measuring module is consistent with the main optical axis of the lens in the vertical direction. The mechanical error caused by the installation of the automatic focusing device is magnified when the lens works in a long-focus mode, which causes the main optical axis of the distance measuring module to be non-parallel to the main optical axis of the lens, or even intersect, thereby improving the accuracy of the object distance measured by the distance measuring module.

[0046] In addition, when the current distance is obtained, the shooting device queries the focusing distance table, and controls the focusing motor to adjust the focusing position of the lens according to the focusing step number corresponding to the current distance, so that the photographed object forms a clear image on the image plane. When the focusing motor moves, the clearness characteristic value of the image is not constantly obtained according to a certain focusing evaluation function, the rapid focusing of the lens can be realized, the out-of-focus and frequent focusing in the photographed picture are reduced, the picture is kept clear for a long time, and the quality of the photographed picture is improved. BRIEF DESCRIPTION OF DRAWINGS

[0047] The above and other objects, features and advantages of the present application will become more clearly understood from the following description of the embodiments of the present application taken with reference to the accompanying drawings.

[0048] Figure 1 A control table of the zoom motor and the focusing motor of the shooting device of the embodiment of the present application is shown.

[0049] Figure 2 A structure diagram of the automatic focusing device of the embodiment of the present application is shown.

[0050] Figure 3 An exploded view of the automatic focusing device of the embodiment of the present application is shown.

[0051] Figure 4 A structure diagram of the parallelism calibration assembly of the embodiment of the present application is shown.

[0052] Figure 5 A structure diagram of the height calibration assembly of the embodiment of the present application is shown.

[0053] Figure 6 A flowchart of the automatic focusing method of the first embodiment of the present application is shown.

[0054] Figure 7 A flowchart of the automatic focusing method of the second embodiment of the present application is shown.

[0055] Figure 8 A calibration block diagram of the automatic focusing method of the second embodiment of the present application is shown. DETAILED DESCRIPTION

[0056] The present application will be described in more detail by referring to the attached drawings. In each of the drawings, like elements are designated by like reference numerals for the sake of clarity. Furthermore, some parts can not be shown.

[0057] In the following, many specific details of the present application are described in order to provide a more thorough understanding of the present application. However, as will be readily apparent to one skilled in the art, the present application can be practiced without these specific details.

[0058] Lens is a very important component in image capturing devices such as cameras, internet protocol cameras (IPCs), etc. The lens of current image capturing devices often includes multiple lenses (concave and convex lenses), i.e. imaging through multiple lens combinations. Generally, multiple lenses in the lens that play a role in adjusting focal length are combined into one whole, referred to as a zoom group, and the zoom group corresponds to a zoom motor, through which the position of the zoom group is adjusted, and in turn the magnification is adjusted. Multiple lenses that play a role in adjusting imaging are combined into one whole, referred to as a focus group, and the focus group also corresponds to a focus motor, through which the position of the focus group is adjusted, and in turn the focus position is adjusted.

[0059] Zoom motor is an indispensable component in image capturing devices (especially variable focus image capturing devices). Multiple lenses in the lens of the image capturing device for changing focal length constitute a lens group, referred to as a zoom group, and the position of the lens group is moved by the zoom motor.

[0060] Focus motor is also an indispensable component in image capturing devices (especially variable focus image capturing devices). Multiple lenses in the lens of the image capturing device for changing distance constitute a lens group, referred to as a focus group, and the position of the lens group is moved by the focus motor.

[0061] Shooting device, the shooting device involved in the embodiments of the present application includes a variable focal length telephoto integrated machine core. The variable focal length telephoto integrated machine core, for example, is a 55x variable focal length telephoto integrated machine core, a 60x variable focal length telephoto integrated machine core, and a 70x variable focal length telephoto integrated machine core, can do large magnification optical zoom and focusing, and realize clear imaging of images several kilometers away.

[0062] Figure 1 The control table of the zoom motor and the focus motor of the shooting device of the embodiments of the present application is shown. Specifically, the control table of the zoom motor and the focus motor of the 55x variable focal length telephoto integrated machine core. The lens of the 55x variable focal length telephoto integrated machine core has the functions of 1x-55x optical zoom, focusing, aperture control, and filter switching.

[0063] From Figure 1From the control table shown, it can be seen that when the lens is at optical magnification 1x, the number of steps of the focusing motor (focus steps) differs by 767-765=2 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 1x (Zoom=1x), the focusing motor takes a maximum of only 2 steps to complete the journey, and within the 2 steps, a certain point is the focusing position at which the image has the best sharpness; when the lens magnification is at optical magnification 2x (Zoom=2x), the number of steps of the focusing motor (focus steps) differs by 1054-1046=8 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 2x (Zoom=2x), the focusing motor takes a maximum of only 8 steps to complete the journey, and within the 8 steps, a certain point is the focusing position at which the image has the best sharpness; when the lens magnification is at optical magnification 3x (Zoom=3x), the number of steps of the focusing motor (focus steps) differs by 1219-1202=17 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 3x (Zoom=3x), the focusing motor takes a maximum of only 17 steps to complete the journey, and within the 17 steps, a certain point is the focusing position at which the image has the best sharpness.

[0064] When the lens magnification is at optical magnification 46x (Zoom=46x), the number of steps of the focusing motor (focus steps) differs by 2035-956=1079 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 46x (Zoom=46x), the focusing motor takes a maximum of 1079 steps to complete the journey, and within the 1079 steps, a certain point is the focusing position at which the image has the best sharpness; when the lens magnification is at optical magnification 47x (Zoom=47x), the number of steps of the focusing motor (focus steps) differs by 2035-942=1093 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 47x (Zoom=47x), the focusing motor takes a maximum of 1093 steps to complete the journey, and within the 1093 steps, a certain point is the focusing position at which the image has the best sharpness; when the lens magnification is at optical magnification 48.8x (Zoom=48.8x), the number of steps of the focusing motor (focus steps) differs by 2035-918=1117 (steps) when the object distance changes from 10m to 2m, that is, when the lens magnification is at optical magnification 48.8x (Zoom=48.8x), the focusing motor takes a maximum of 1117 steps to complete the journey, and within the 1117 steps, a certain point is the focusing position at which the image has the best sharpness.

[0065] Therefore, it can be concluded that when the lens is working at an optical telephoto lens, the focusing motor needs to take more than 1000 more steps to find the optimal focusing position for image sharpness compared to when the lens is working at a short focal length. During its movement, the focusing motor continuously acquires image sharpness feature values ​​based on a certain focus evaluation function (e.g., in the image processing module of the shooting device). It then controls the focusing motor based on these sharpness feature values, moving the corresponding focus group and re-acquiring the image sharpness feature values ​​at the new position until these feature values ​​meet a pre-defined condition, thus achieving autofocus. During this autofocus process, each step taken by the focusing motor and the re-acquisition of the image sharpness feature value takes approximately 1ms. The fact that the focusing motor needs to take more than 1000 more steps when the lens is working at a telephoto lens means that the focusing time is increased by more than 1 second, significantly impacting the speed at which the image focuses and becomes sharp.

[0066] Figure 2 A schematic diagram of the structure of an autofocus device according to an embodiment of the present invention is shown.

[0067] like Figure 2 The autofocus device shown includes: a shooting device 1000, a rangefinder module 2000, a turntable 3000, and a base 4000.

[0068] The shooting device 1000 includes a lens, a focusing motor, a zoom motor, and a memory. The memory stores a focus rangefinder table, which records the relationship between magnification, object distance, and focus step count. The shooting device 1000 is fixed on the base 4000 and is used to look up the focus rangefinder table at the current magnification. Based on the focus step count corresponding to the current object distance, it controls the focusing motor to adjust the lens's focus position so that the subject is formed in a sharp image on the image-side focal plane.

[0069] The ranging module 2000, such as a laser ranging module, is used to measure the current object distance between the optical center of the lens and the subject being photographed.

[0070] The turntable 3000 includes a parallelism calibration component 3100 and a height calibration component 3200. A ranging module 2000 is fixed on the turntable 3000, which is fixed to a base 4000. The turntable 3000 is used to adjust the position of the ranging module 2000 using the parallelism calibration component 3100 and the height calibration component 3200, ensuring that the principal optical axis of the ranging module 2000 is aligned with the principal optical axis of the lens in the vertical direction, and parallel to the principal optical axis of the lens in the horizontal direction. The base 4000 of the autofocus device can be fixed to a rotating gimbal for high-altitude monitoring scenarios. The rotating gimbal drives the autofocus device to rotate, thereby achieving high-altitude monitoring.

[0071] Figure 3 An exploded view of the autofocus device of the embodiment of the present application is shown. Figure 4 A structural schematic view of the parallelism calibration assembly of the embodiment of the present application is shown. Figure 5 A structural schematic view of the height calibration assembly of the embodiment of the present application is shown.

[0072] As shown in the autofocus device comprises a shooting device 1000, a distance measuring module 2000, a turntable 3000 and a base 4000. The turntable 3000 comprises a parallelism calibration assembly 3100, a height calibration assembly 3200, a connecting plate 3300, a plurality of springs 3400 and a plurality of fasteners. As shown in the parallelism calibration assembly 3100 comprises a parallelism stepper motor 3110, a worm shaft 3120, a worm wheel (not shown) and a parallelism turntable 3130. As shown in the height calibration assembly 3200 comprises a wedge plate 3220, a height control motor 3210, a pressing plate 3230 and a sliding plate 3240. The bottom surface of the wedge plate 3220 comprises a plurality of inclined surfaces, the height control motor 3210 comprises a gear reduction box, and the sliding plate 3240 comprises a plurality of rollers. The connecting plate 3300 is located between the distance measuring module 2000 and the parallelism calibration assembly 3100, the plurality of springs 3400 are located between the parallelism calibration assembly 3100 and the wedge plate 3220, and the distance measuring module 2000, the connecting plate 3300, the parallelism calibration assembly 3100, the plurality of springs 3400, the height calibration assembly 3200 and the base 4000 are fixedly connected by the plurality of fasteners. Figure 3 Figure 4 Figure 3 Figure 5

[0073] The parallelism calibration assembly 3100 is used to adjust the horizontal position of the distance measuring module 2000, so that the main optical axis of the distance measuring module 2000 is parallel to the main optical axis of the lens in the horizontal direction. The parallelism stepper motor 3110 is fixedly connected with the worm shaft 3120, the worm wheel is fixedly connected with the parallelism turntable 3130, and the worm shaft 3120 and the worm wheel are cooperatively driven. The parallelism stepper motor 3110 controls the rotation of the worm shaft 3120, the worm shaft 3120 drives the rotation of the worm wheel, and then the worm wheel drives the rotation of the parallelism turntable 3130 in the horizontal direction. When the unwinding spiral angle of the worm shaft 3120 is less than the friction angle of the contact between the worm shaft 3120 and the worm wheel, the position of the parallelism calibration assembly 3100 is self-locked.

[0074] ​​​​The height calibration assembly 3200 is used to adjust the vertical position of the distance measuring module 2000, so that the main optical axis of the distance measuring module 2000 is highly consistent with the main optical axis of the lens in the vertical direction. The height control motor 3210 is fixedly connected with the base 4000, the sliding plate 3240 is fixedly connected with the base 4000 through the pressing plate 3230, and the output gear of the gear reduction box is meshed and driven with the sector gear of the sliding plate 3240. The height control motor 3210 drives the output gear to rotate, and then drives the sliding plate 3240 to rotate. In the process of rotating the sliding plate 3240, since the sliding plate 3240 is fixed on the base 4000, the plurality of rollers of the sliding plate 3240 move along the plurality of inclined surfaces of the inclined wedge plate 3220, so that the inclined wedge plate moves in the vertical direction, and then the distance measuring module 2000 moves in the vertical direction. When the inclination angle of the plurality of inclined surfaces of the inclined wedge plate 3220 is less than the friction coefficient between the plurality of rollers and the plurality of inclined surfaces, the height calibration assembly 3200 is self-locked in position.

[0075] Figure 6 A flowchart of an automatic focusing method of the first embodiment of the application is shown. Specifically, the automatic focusing method of the automatic focusing device in the embodiment of the application comprises the following steps:

[0076] In step S610, the zoom motor of the photographing device is controlled to adjust the magnification of the lens.

[0077] In this step, the automatic focusing device in the embodiment of the application can be installed in a monitoring holder for use. The holder operator controls the zoom motor of the photographing device to adjust the magnification of the lens, for example, to adjust the magnification of the lens to x5.

[0078] In step S620, the distance measuring module is used to measure the current object distance between the optical center of the lens and the photographed object under the current magnification.

[0079] In this step, when the magnification of the lens changes, the distance measuring module immediately starts to measure the current object distance between the optical center of the lens and the photographed object under the current magnification.

[0080] In step S630, the focusing distance table is queried under the current magnification, and the focusing motor is controlled according to the focusing step corresponding to the current object distance to adjust the focusing position of the lens, so that the photographed object forms a clear image on the image side focal plane.

[0081] In this step, the memory of the photographing device stores the focusing distance table recording the relationship between the magnification, the object distance and the focusing step number. When the current object distance measured by the distance measuring module is obtained, the photographing device (for example, the main control board of the photographing device drives the focusing motor to query the focusing distance table) queries the focusing distance table, and controls the focusing motor to adjust the focusing position of the lens according to the focusing step number corresponding to the current object distance so that the photographed object forms a clear image on the image plane.

[0082] Figure 7 The flowchart of the automatic focusing method of the second embodiment of the present application is shown. Specifically, the automatic focusing method using the automatic focusing device in the embodiment of the present application comprises the following steps:

[0083] In step S710, the relative position of the main optical axis of the distance measuring module and the main optical axis of the lens is calibrated.

[0084] In this step, the calibration board is placed at a first distance from the lens, for example, 100 meters in front of the lens. Figure 8 The schematic diagram of the calibration frame of the automatic focusing method of the second embodiment of the present application is shown. As shown in Figure 8 The calibration board 800 includes a first calibration frame 810 and a second calibration frame 820. The first calibration frame 810 is the calibration frame of the main optical axis of the lens of the photographing device, and the second calibration frame 820 is the calibration frame of the main optical axis of the distance measuring module. The laser spot formed by the laser emitted by the distance measuring module on the calibration board 800 spreads to the size of the circle frame of the second calibration frame 820 at the first distance. The relative position of the first calibration frame 810 and the second calibration frame 820 is determined by the relative position of the photographing device and the distance measuring module of the automatic focusing device.

[0085] The position of the lens is adjusted so that the image of the center point of the first calibration frame 810 is located at the optical center of the lens. For example, a "+" is superimposed at the center of the display image of the lens, and the position of the photographing device is manually moved so that the "+" falls on the center point of the first calibration frame 810.

[0086] The image analysis algorithm determines whether the laser spot formed by the laser emitted by the distance measuring module on the calibration plate 800 is located within the second calibration frame 820. If the laser spot is located within the second calibration frame 820, the main optical axis of the distance measuring module is parallel to the main optical axis of the lens in the horizontal direction and is consistent with the main optical axis of the lens in the vertical direction. If the laser spot is not located within the second calibration frame 820, the positional deviation of the laser spot from the center of the second calibration frame 820 is calculated, and the positional deviation is converted into the number of steps of the parallelism stepper motor and the height control motor of the turntable. The horizontal position and the vertical position of the distance measuring module are adjusted so that the main optical axis of the distance measuring module is parallel to the main optical axis of the lens in the horizontal direction and is consistent with the main optical axis of the lens in the vertical direction. The drive of the parallelism stepper motor and the height control motor is disconnected, and the position of the distance measuring module is locked by the position self-locking function of the parallelism calibration assembly and the height calibration assembly.

[0087] In step S720, the focusing distance table is established.

[0088] In this step, the zoom motor of the shooting device is controlled to adjust the magnification of the lens. For example, after the shooting device is powered on, the main control board of the shooting device sends a command to the zoom motor, and the zoom motor drives the zoom group in the lens to move to positions, and the magnification of the lens is adjusted to 1x, 2x, 3x, …, 55x in sequence.

[0089] At each magnification, the nearest distance and the farthest distance at which the lens can shoot a clear image are determined according to the depth of field of the object focal point. The reference object is placed at the nearest distance, the focusing motor is controlled to fine-tune the focusing position of the lens so that the reference object forms a clear image on the image focal plane, and the object distance of the current reference object and the focusing step number of the focusing motor are recorded.

[0090] The reference object is moved in the direction of the farthest distance every second distance (for example, 1 meter) until the reference object moves to the position of the farthest distance. At each second distance interval, it is determined whether the reference object forms a clear image on the image focal plane. If a clear image is formed, the focusing motor does not need to be controlled to fine-tune the focusing position of the lens. If a clear image is not formed, the focusing motor is controlled to fine-tune the focusing position of the lens so that the reference object forms a clear image on the image focal plane, and the object distance of the current reference object and the focusing step number of the focusing motor are recorded.

[0091] The recorded object distance of the reference object and the focusing step number of the focusing motor at each magnification are sorted to obtain a focusing distance table in which the relationship between the magnification, the object distance, and the focusing step number is recorded.

[0092] In step S730, the zoom motor of the shooting device is controlled to adjust the magnification of the lens.

[0093] In step S740, the ranging module is used to measure the current object distance between the optical center of the lens and the photographed object at the current magnification.

[0094] In step S750, the focusing ranging table is queried at the current magnification, and the focusing motor is controlled according to the focusing step number corresponding to the current object distance to adjust the focusing position of the lens so that the photographed object forms a clear image on the image-side focal plane.

[0095] Steps S730 to S750 are consistent with steps S610 to S630 in Figure 6 Therefore, details are not repeated here.

[0096] In some optional embodiments of the present application, ranging can be performed based on the automatic focusing device in the embodiments of the present application. When the display image of the photographing device of the automatic focusing device has been seen to be in a clear focusing state, the object distance of the photographed object in the image can be found by reading the focusing ranging table stored in the memory, and by inversely searching the current magnification and the focusing motor step number of the lens.

[0097] According to the automatic focusing device and the automatic focusing method provided in the embodiments of the present application, the automatic focusing device comprises a photographing device, a ranging module, a turntable and a base. The ranging module is fixed on the turntable, and the photographing device and the turntable are fixed on the base. The turntable comprises a parallelism calibration assembly and a height calibration assembly with a position self-locking function. During use, the horizontal and vertical positions of the ranging module can be adjusted by the parallelism calibration assembly and the height calibration assembly, so that the main optical axis of the ranging module is parallel to the main optical axis of the lens in the horizontal direction, and the main optical axis of the ranging module is consistent with the main optical axis of the lens in the vertical direction. The mechanical error caused by the installation of the automatic focusing device is amplified when the lens works in the long-focus mode, so that the main optical axis of the ranging module is not parallel to the main optical axis of the lens, or even intersects, thereby improving the accuracy of the object distance measured by the ranging module.

[0098] In addition, at the current magnification, when the current object distance measured by the ranging module is obtained, the photographing device queries the focusing ranging table, and controls the focusing motor to adjust the focusing position of the lens according to the focusing step number corresponding to the current object distance so that the photographed object forms a clear image on the image-side focal plane. When the focusing motor moves, it is not necessary to constantly obtain the clearness characteristic value of the image according to a certain focusing evaluation function, the rapid focusing of the lens can be realized, the out-of-focus and frequent focusing in the photographed image are reduced, the photographed image is kept in a clear state for a long time, and the quality of the photographed image is improved.

[0099] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended that the scope of the application be limited to the detailed description contained herein or the specific examples described therein but rather that the scope of the application be determined by the appended claims, preferably by the claims, as interpreted according to the principles of patent law including 35 U.S.C. § 112. Furthermore, it is intended that the scope of the application include all alternatives, modifications and equivalents falling within the true spirit and scope of the application as recited in the claims hereafter. It is also to be understood that the use of "a" or "an", "the" or similar referents in the context of describing the application are to be construed to cover both the singular and plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein and each separate value is incorporated into the specification as if it were individually recited herein. The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated otherwise, should be understood to mean one or more. The use of the term "or" in the context of describing the application is to be construed as inclusive and not exclusive, unless otherwise indicated herein or unless clearly indicated otherwise by context. The use of the term "based on" or "operatively connected" herein is to be construed as permitting a wide variety of enhancements and modifications.

[0100] In accordance with the practice of the present application, such embodiments will not be described in detail with reference to every single feature or step, nor are the embodiments limited to only the specific embodiments described herein. The foregoing description merely exemplifies the general nature of the application and is not intended to limit the application to only the particular embodiments described herein. The description of these embodiments is intended for the purpose of aiding in the understanding of the application for those of ordinary skill in the art, and is not intended to limit the application to only the specific embodiments described herein. Any modification, equivalent replacement or improvement made without departing from the spirit and principle of the application shall fall within the scope of the application. The embodiments are selected and described in this specification in order to better explain the principles and practical applications of the application, so that those skilled in the art can well utilize the application and make modifications and uses on the basis of the application.

Claims

1. An automatic focusing device, characterized in that, include: The shooting device, fixed on the base, is used to look up the focus range table at the current magnification of the lens, and control the focus motor to adjust the focus position of the lens according to the focus step number corresponding to the current object distance so that the subject is formed in a clear image on the image-side focal plane. The focus range table records the relationship between magnification, object distance and focus step number. The ranging module is used to measure the current object distance between the optical center of the lens and the subject being photographed; A turntable is provided, on which the ranging module is fixed, and the turntable is fixed to the base. The turntable is used to adjust the position of the ranging module. The turntable includes a parallelism calibration component and a height calibration component. The height calibration component is used to adjust the vertical position of the ranging module so that the principal optical axis of the ranging module is at the same height as the principal optical axis of the lens in the vertical direction. The parallelism calibration component is used to adjust the horizontal position of the ranging module so that the principal optical axis of the ranging module is parallel to the principal optical axis of the lens in the horizontal direction.

2. The autofocus device according to claim 1, characterized in that, The focusing distance measurement table is stored in the memory of the shooting device.

3. The autofocus device according to claim 2, characterized in that, The parallelism calibration assembly includes: a parallelism stepper motor, a worm shaft, a worm gear, and a parallelism rotary table. The parallelism stepper motor is fixedly connected to the worm shaft, and the worm gear is fixedly connected to the parallelism turntable. The worm shaft and the worm gear cooperate to transmit power. The parallelism stepper motor controls the rotation of the worm shaft, the worm shaft drives the turbine to rotate, and the turbine drives the parallelism turntable to rotate in the horizontal direction.

4. The autofocus device according to claim 3, characterized in that, When the unfolded helix angle of the worm shaft is less than the friction angle at which the worm shaft and the turbine contact, the parallelism calibration component engages in position self-locking.

5. The autofocus device according to claim 2, characterized in that, The height calibration assembly includes: a wedge plate, a height control motor, a pressure plate, and a sliding plate. The bottom surface of the wedge plate includes multiple inclined surfaces. The height control motor includes a gear reducer. The sliding plate includes multiple rollers. The height control motor is fixedly connected to the base, the sliding plate is fixedly connected to the base through the pressure plate, and the output gear of the gear reducer meshes with the sector gear of the sliding plate for transmission.

6. The autofocus device according to claim 5, characterized in that, The height control motor drives the output gear to rotate, which in turn drives the sliding plate to rotate. During the rotation of the sliding plate, the multiple rollers of the sliding plate move along the multiple inclined surfaces of the wedge plate, causing the wedge plate to move in the vertical direction, which in turn causes the ranging module to move in the vertical direction.

7. The autofocus device according to claim 6, characterized in that, When the inclination angle of the plurality of inclined surfaces of the wedge plate is less than the coefficient of friction between the plurality of rollers and the plurality of inclined surfaces, the height calibration component engages in position self-locking.

8. The autofocus device according to claim 7, characterized in that, The turntable also includes: a connecting plate, multiple springs, and multiple fasteners. The connecting plate is located between the ranging module and the parallelism calibration component, the plurality of springs are located between the parallelism calibration component and the wedge plate, and the ranging module, the connecting plate, the parallelism calibration component, the plurality of springs, the height calibration component and the base are fixedly connected by the plurality of fasteners.

9. The autofocus device according to claim 8, characterized in that, The shooting device includes: a zoom and telephoto integrated camera mechanism; The ranging module includes a laser ranging module.

10. An autofocus method, characterized in that, include: Control the zoom motor of the shooting equipment to adjust the magnification of the lens; The distance between the optical center of the lens and the subject is measured using a ranging module at the current magnification. At the current magnification, the focus range table is consulted, and the focus motor is controlled to adjust the focus position of the lens according to the focus step number corresponding to the current object distance so that the subject is formed in a clear image on the image-side focal plane. The focus range table records the relationship between magnification, object distance and focus step number. The ranging module is fixed on a turntable, which is fixed to a base. The turntable is used to adjust the position of the ranging module. The turntable includes a parallelism calibration component and a height calibration component. The height calibration component is used to adjust the vertical position of the ranging module so that the principal optical axis of the ranging module is at the same height as the principal optical axis of the lens in the vertical direction. The parallelism calibration component is used to adjust the horizontal position of the ranging module so that the principal optical axis of the ranging module is parallel to the principal optical axis of the lens in the horizontal direction.

11. The autofocus method according to claim 10, characterized in that, The autofocus method further includes: The relative position of the principal optical axis of the ranging module and the principal optical axis of the lens is calibrated. Establish the focusing distance measurement table.

12. The autofocus method according to claim 11, characterized in that, The calibration of the relative position between the principal optical axis of the ranging module and the principal optical axis of the lens includes: A calibration plate is placed at a first distance from the lens, the calibration plate including a first calibration frame and a second calibration frame; Adjust the position of the lens so that the image of the center point of the first calibration frame is located at the optical center of the lens; The image analysis algorithm determines whether the laser spot formed by the laser emitted by the ranging module on the calibration plate is located within the second calibration frame. When the laser spot is located within the second calibration frame, the position of the ranging module is locked by the position self-locking function of the parallelism calibration component and the height calibration component.

13. The autofocus method according to claim 11, characterized in that, Establishing the focus rangefinder table includes: Control the zoom motor of the shooting device to adjust the magnification of the lens; At each magnification, the closest and furthest distances at which the lens can capture a clear image are determined based on the depth of field of the object's focal point. Place the reference object at the closest distance position, control the focusing motor to fine-tune the focusing position of the lens so that the reference object forms a clear image on the image-side focal plane, and record the current object distance of the reference object and the focusing step number of the focusing motor; The reference object is moved towards the farthest distance position at every second interval until the reference object reaches the farthest distance position. At each interval of the second distance, it is determined whether the reference object forms a sharp image on the image-side focal plane. If a clear image is not formed, the focusing motor is controlled to fine-tune the focusing position of the lens so that the reference object forms a clear image on the image-side focal plane, and the current object distance of the reference object and the focusing step number of the focusing motor are recorded. Record the object distance of the reference object and the focusing step number of the focusing motor at each magnification to obtain the focusing distance measurement table, which records the relationship between magnification, object distance and focusing step number.

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