Automatic linear zoom lens and method based on servo lead screw dovetail groove transmission system

Abstract

The invention discloses an automatic linear zoom lens and method based on a servo lead screw dovetail groove transmission system, and relates to the technical field of automatic zoom lenses. The lens comprises a lens body, wherein a dovetail groove is formed in the axis direction of the top surface of the lens body; the dovetail groove sliding block is matched with the dovetail groove; the ball screw assembly is connected with the top of the dovetail groove sliding block; the zoom lens assembly is connected with the bottom of the dovetail groove sliding block; the servo motor is connected with a lead screw shaft of the ball screw assembly and drives the lead screw shaft to rotate to drive the dovetail groove sliding block to slide in the dovetail groove; and the encoder is connected with the servo motor and is used for detecting the difference value between the feeding amount of the servo motor and the target feeding amount and controlling the servo motor to complement. The servo motor is matched with the lead screw for transmission, the dovetail groove type sliding rail is adopted to ensure that the zooming component only performs single-degree-of-freedom linear motion on the axis, meanwhile, the encoder closed loop is arranged to prevent step loss of the servo motor, zooming calculation is simple, zooming precision is high, and the design period is shorter.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic zoom lens, and in particular to an automatic linear zoom lens and method based on a servo lead screw dovetail groove transmission system. Background Art

[0002] Traditional automatic zoom lenses usually use gear zoom and stepper motor drive. Gear zoom requires calculation of gear transmission ratio, cam zoom ratio, angle and feed ratio, etc. The design is cumbersome, and the strong correlation leads to poor interchangeability. In addition, during long-term use, the gear zoom will cause axial circular runout due to tooth wear, which will deteriorate the concentricity of the zoom lens. At the same time, the stepper motor is prone to step loss, and rotation errors exist at all times. In addition, during the production process, the mechanical parts of the lens group involve processes such as cam groove processing, which is difficult to process and cannot guarantee precision, and the accuracy is poor. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an automatic linear zoom lens and method based on a servo screw dovetail groove transmission system. The lens is based on a servo motor and a screw transmission, and a dovetail groove slide rail is used to ensure that the zoom component only moves linearly with a single degree of freedom on the axis. At the same time, an encoder closed loop is provided to prevent the servo motor from losing steps. The zoom calculation is simple and the zoom accuracy is high, and the design cycle is shorter.

[0004] In a first aspect, the present invention provides an automatic linear zoom lens based on a servo screw dovetail groove transmission system, comprising:

[0005] A lens body, wherein a dovetail groove is provided in the axial direction of the top surface of the lens body;

[0006] A dovetail groove slider, which matches the dovetail groove and can slide in the dovetail groove;

[0007] A ball screw assembly connected to the top of the dovetail groove slider;

[0008] A zoom lens assembly connected to the bottom of the dovetail groove slider;

[0009] A servo motor is connected to the screw shaft of the ball screw assembly, driving the screw shaft to rotate and drive the dovetail groove slider to slide in the dovetail groove, thereby driving the zoom lens assembly to move along the axis direction of the lens;

[0010] The encoder is connected to the servo motor and is used to detect the difference between the feed amount of the servo motor and the target feed amount, and control the servo motor to make up for it.

[0011] Furthermore, it also includes a fixed-focus lens assembly, which is fixed inside the lens body.

[0012] Furthermore, the servo motor is connected to the lens body via a fixing seat.

[0013] Furthermore, it also includes a protective window fixed on the image side of the lens body.

[0014] Furthermore, the protective window is fixed to the image side of the lens body by a fixing ring.

[0015] Furthermore, it also includes a dustproof focusing pressure ring fixed to the image side surface of the lens body.

[0016] Furthermore, it also includes a dust cover, which is fixed on the top surface of the dovetail groove of the lens body.

[0017] Furthermore, the zoom lens assembly is connected to the bottom of the dovetail groove slider via a locking pin.

[0018] In a second aspect, the present invention provides an automatic linear zoom method based on a servo screw dovetail groove transmission system, which requires providing the lens of the first aspect, and the method comprises:

[0019] The zoom factor is obtained through the MCU and the pulse wave value required for zooming to the corresponding object distance is calculated. Then, the pulse wave is sent through the motor drive module to drive the servo motor to drive the lead screw shaft to rotate, thereby driving the dovetail slot slider to slide in the dovetail slot;

[0020] The pulse wave is received by the encoder and compared with the difference with the required pulse wave value. If the difference is not 0, the difference is fed back to the MCU through the stroke detection switch and the AD conversion module. The MCU sends a pulse wave through the motor drive module again to drive the servo motor to drive the screw shaft to rotate until the dovetail slot slider reaches the focus.

[0021] The technical solution provided in the embodiments of the present invention has at least the following technical effects:

[0022] The servo motor drives the ball screw to achieve linear zoom. The servo motor will not lose steps, and the encoder closed-loop control is further used to eliminate pulse errors caused by energy loss to ensure zoom accuracy. The movement of the zoom lens assembly is limited to the axial direction of the lens through the cooperation of the dovetail groove slider and the dovetail groove, avoiding radial runout errors and ensuring the concentricity of the lens, making the lens focus more accurate. The zoom structure is simple and interchangeable, and the use of the ball screw increases the service life.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0025] Figure 1 An exploded view of the lens structure in the first embodiment of the present invention;

[0026] Figure 2 is a cross-sectional view of the lens structure in the first embodiment of the present invention;

[0027] Figure 3 It is a partial schematic diagram of a dovetail groove and a dovetail groove slider in the first embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the principle of the ball screw assembly in the first embodiment of the present invention;

[0029] Figure 5 It is a schematic diagram of the process of the method in the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] The embodiment of the present invention provides an automatic linear zoom lens and method based on a servo screw dovetail groove transmission system, which is based on a servo motor and a screw transmission, and adopts a dovetail groove slide rail to ensure that the zoom component only moves linearly with a single degree of freedom on the axis. At the same time, an encoder closed loop is provided to prevent the servo motor from losing steps. The zoom calculation is simple and the zoom accuracy is high, and the design cycle is shorter.

[0031] The technical solution in the embodiment of the present invention has the following general idea:

[0032] 1. Use servo screw to replace the traditional cam slot zoom solution. You only need to calculate the ratio of zoom object distance and screw feed, which is simple to calculate; 2. Use dovetail slot slide to replace the traditional cam slot slide to ensure that the zoom component only moves in a single degree of freedom linearly on the axis to prevent radial circular runout and form and position errors; 3. Use ball screw pair transmission to effectively reduce feed resistance; 4. Equipped with anti-step loss servo motor closed-loop encoder, the servo motor can detect the feed amount in time through the AD conversion module and timely feedback the decoding in the encoder. After decoding, the pulse is re-issued to accurately make up for the feed error caused by the servo screw transmission pair.

[0033] Embodiment 1

[0034] This embodiment provides an automatic linear zoom lens based on a servo screw dovetail groove transmission system, such as Figure 1 and Figure 2 As shown, including:

[0035] A lens body 1, wherein a dovetail groove 2 is provided in the axial direction of the top surface of the lens body 1;

[0036] A dovetail groove slider 3, which matches the dovetail groove 2 and can slide in the dovetail groove 2;

[0037] A ball screw assembly 4 is connected to the top of the dovetail groove slider 3;

[0038] A zoom lens assembly 5 connected to the bottom of the dovetail groove slider 3;

[0039] The servo motor 6 is connected to the screw shaft 41 of the ball screw assembly 4, and drives the screw shaft 41 to rotate forward and reversely to drive the dovetail groove slider 3 to slide in the dovetail groove 2, thereby driving the zoom lens assembly 5 to reciprocate along the lens axis direction (a corresponding groove is also provided at the bottom of the dovetail groove 2 for moving the zoom lens assembly 5).

[0040] The encoder is connected to the servo motor 6 and is used to detect the difference between the feed amount of the servo motor 6 and the target feed amount, and control the servo motor 6 to make up for it.

[0041] Specifically, it also includes a fixed-focus lens assembly 7, which is fixed inside the lens body.

[0042] The servo motor 6 is connected to the lens body 1 via a fixing seat 8 .

[0043] The protective window sheet 9 is also included, and the protective window sheet 9 is fixed to the image side of the lens body 1 through a fixing ring 10.

[0044] The lens body 1 further comprises a dustproof focusing pressure ring 11 which is fixed to the image side surface of the lens body 1 .

[0045] The lens body 1 further comprises a dust cover 12 which is fixed on the top surface of the dovetail groove 2 of the lens body 1 .

[0046] In a possible implementation, the zoom lens assembly 5 is connected to the bottom of the dovetail groove slider 3 via a locking pin A. Figure 3 In other implementations, the connection can also be made in an integrated manner.

[0047] like Figure 4 As shown, to realize the movement of the zoom lens assembly 5, it is necessary to control the feeding of the ball screw assembly 4, and the feeding of the ball screw assembly 4 is to convert the rotation of the servo motor 6 into a linear feeding motion through the ball screw pair. During the feeding motion, the motion is limited to a straight line through the cooperation of the dovetail groove 2 slide rail to avoid radial runout and ensure the concentricity of the lens. Therefore, during the automatic zooming process, the servo motor 6 drives the screw shaft 41 of the ball screw assembly 4 to rotate forward and reverse, thereby driving the dovetail groove slider 3 to slide in the dovetail groove 2, and then driving the zoom lens assembly 5 connected to the dovetail groove slider 3 to reciprocate along the axis of the lens.

[0048] The lens sleeve of the lens of this embodiment can be designed according to the center thickness and curvature of different zoom lenses, while the servo screw part can remain unchanged, so the same zoom system can be applied to zoom lenses of various specifications and has strong interchangeability.

[0049] Based on the same inventive concept, the present application also provides a zoom method corresponding to the lens in the first embodiment, see the second embodiment for details.

[0050] Embodiment 2

[0051] In this embodiment, an automatic linear zoom method based on a servo screw dovetail groove transmission system is provided, and a lens as described in the first embodiment is required, such as Figure 5 As shown, the method includes:

[0052] The MCU obtains the zoom factor and calculates the pulse wave value required for zooming to the corresponding object distance, and then sends a pulse wave through the motor drive module to drive the servo motor 6 to drive the screw shaft 41 to rotate, thereby driving the dovetail groove slider 3 to slide in the dovetail groove 2;

[0053] The pulse wave is received by the encoder and compared with the difference with the required pulse wave value. If the difference is not 0, the difference is fed back to the MCU through the stroke detection switch and the AD conversion module. The MCU sends a pulse wave through the motor drive module again to drive the servo motor to drive the screw shaft to rotate until the dovetail slot slider reaches the focus.

[0054] Adjust the feed ratio of the ball screw assembly 4 according to the actual zoom requirement. For example, for a 2x zoom, the object distance is 35mm (here understood as the distance between the zoom lens and the imaging object), and the preset origin is 0. At this time, the lens object distance is also zero. To achieve a 2x zoom, the zoom lens needs to be moved to 35mm, and so on. The servo motor is controlled by pulse waves. For example, a pulse wave is preset to correspond to an axial feed of 1mm. At this time, to achieve a 2x zoom, 35 pulses need to be sent; but in actual situations, the energy loss of the pulse will cause a pulse error, which will cause the preset position to fail. Therefore, an encoder is equipped to form a closed-loop control with the servo motor. For example, 35 pulse waves are given, but only 34.8 are actually received. The photoelectric coupling stroke detection switch can be fed back to the encoder through the AD conversion module to decode the actual missing pulses and make up for them through the encoder until they are accurate.

[0055] The present invention realizes linear zoom by driving a ball screw through a servo motor, and the servo motor will not lose steps. The pulse error caused by energy loss is further eliminated through encoder closed-loop control to ensure zoom accuracy. The movement of the zoom lens assembly is limited to the axial direction of the lens through the cooperation of the dovetail groove slider and the dovetail groove, thereby avoiding radial runout errors and ensuring the concentricity of the lens, making the lens focus more accurate. The zoom structure is simple and has strong interchangeability, and the use of the ball screw increases the service life.

[0056] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. An automatic linear zoom lens based on a servo screw dovetail groove transmission system, characterized in that: include: A lens body, wherein a dovetail groove is provided in the axial direction of the top surface of the lens body; A dovetail groove slider, which matches the dovetail groove and can slide in the dovetail groove; A ball screw assembly connected to the top of the dovetail groove slider; A zoom lens assembly connected to the bottom of the dovetail groove slider; A servo motor is connected to the screw shaft of the ball screw assembly, driving the screw shaft to rotate and drive the dovetail groove slider to slide in the dovetail groove, thereby driving the zoom lens assembly to move along the axis direction of the lens; The encoder is connected to the servo motor and is used to detect the difference between the feed amount of the servo motor and the target feed amount, and control the servo motor to make up for it.

2. The lens according to claim 1, characterized in that: It also includes a fixed-focus lens assembly, which is fixed inside the lens body.

3. The lens according to claim 1, characterized in that: The servo motor is connected to the lens body via a fixing seat.

4. The lens according to claim 1, characterized in that: It also includes a protective window sheet, which is fixed to the image side of the lens body.

5. The lens according to claim 4, characterized in that: The protective window is fixed to the image side of the lens body through a fixing ring.

6. The lens according to claim 1, characterized in that: It also includes a dustproof focusing pressure ring, which is fixed on the image side of the lens body.

7. The lens according to claim 1, characterized in that: It also includes a dust cover, which is fixed on the top surface of the dovetail groove of the lens body.

8. The lens according to claim 1, characterized in that: The zoom lens assembly is connected to the bottom of the dovetail groove slider through a locking pin.

9. An automatic linear zoom method based on a servo screw dovetail transmission system, characterized in that: A lens as described in any one of claims 1 to 8 is required, and the method comprises: The MCU obtains the zoom factor and calculates the pulse wave value required for zooming to the corresponding object distance, and then sends a pulse wave through the motor drive module to drive the servo motor to drive the screw shaft to rotate, drive the dovetail slot slider to slide in the dovetail slot, and thus drive the zoom lens assembly to move along the axis of the lens; The pulse wave is received by the encoder and compared with the difference with the required pulse wave value. If the difference is not 0, the difference is fed back to the MCU through the stroke detection switch and the AD conversion module. The MCU sends a pulse wave through the motor drive module again to drive the servo motor to drive the screw shaft to rotate until the dovetail slot slider reaches the focus.

Images