Lens group position feedback device for zoom lens

Abstract

The utility model relates to the field of photoelectric technology application, in particular to a lens group position feedback device for a zoom lens. Comprising a direct-current gear motor, a motor driving gear, a zoom lens gear ring and a driven gear, the motor driving gear is located on an output shaft of the direct-current gear motor, the zoom lens gear ring is located at the tail end of an outer lens barrel of the zoom lens, and the zoom lens gear ring is meshed with the motor driving gear and the driven gear. The driven gear is connected with a non-contact magnetic encoder, the magnetic encoder comprises a permanent magnet and a magnetic coding plate, the permanent magnet is connected with the driven gear, and the magnetic coding plate and the permanent magnet are coaxially installed in a non-contact mode. According to the utility model, a multi-circle continuous rotation potentiometer is replaced by the non-contact magnetic encoder, the control and implementation modes are simple, the cost is lower, the problem of service life caused by a mechanical mode in the prior art is avoided, and the overall reliability is improved.

Description

Technical Field

[0001] The utility model relates to the field of optoelectronic technology applications, and particularly to a lens group position feedback device for a zoom lens. Background Art

[0002] The rapid development of the security industry has promoted the extensive use of various optical zoom lenses, including visible light, thermal imaging and other zoom imaging lenses, as well as zoom laser emission lenses. As a zoom lens, one of its basic functions is to accurately read and locate the field of view angle, focus clarity, laser emission angle, etc. of the lens. To achieve this function, it depends on the lens group position feedback device used in the zoom lens.

[0003] The existing conventional optical zoom lens group position feedback generally adopts the method of a DC reduction motor + a multi-turn continuous rotation potentiometer. A gear ring is installed at the end of the outer lens barrel of the zoom lens. The DC reduction motor and the multi-turn potentiometer are installed in parallel and respectively mesh with the gear ring at the end of the outer lens barrel of the zoom lens through the gears installed on their rotating shafts. When the motor rotates, it drives the outer lens barrel and the potentiometer of the zoom lens to rotate through the gear ring. The control board determines the lens group position by supplying power to both ends of the potentiometer and reading the feedback voltage at its tap end. This scheme is relatively simple to implement, but has relatively high installation requirements for the axial installation consistency of the motor and the potentiometer. Especially once the axial deviation of the potentiometer during installation is too large, it will cause increased wear on the internal coil during its continuous reciprocating rotation, resulting in a significant shortening of its service life. Secondly, limited by the rotation working mode of the potentiometer, there is a certain designed service life for the internal coil due to normal working wear. Coupled with the influence of factors such as high and low temperature changes, vibration, and long-term continuous operation in the whole machine application environment, the actual service life of the potentiometer is often significantly shorter than its designed service life, and the failure rate is relatively high. Content of the Utility Model

[0004] Aiming at the defects of the existing technology, the utility model provides a lens group position feedback device for a zoom lens, which replaces the multi-turn continuous rotation potentiometer with a non-contact magnetic encoder. The control and implementation method is simple and the cost is low. The non-contact installation method avoids the service life problem caused by the mechanical mode in the existing technology and improves the overall reliability.

[0005] To solve the above technical problems, the technical solution adopted by the present utility model is as follows: A lens group position feedback device for a zoom lens, comprising a DC reduction motor, a motor drive gear, a zoom lens gear ring, and a driven gear. The motor drive gear is located on the output shaft of the DC reduction motor. The zoom lens gear ring is located at the end of the outer barrel of the zoom lens. The zoom lens gear ring meshes with the motor drive gear and the driven gear respectively. The driven gear is connected with a non-contact magnetic encoder. The magnetic encoder includes a permanent magnet and a magnetic encoding plate. The permanent magnet is connected with the driven gear, and the magnetic encoding plate is coaxially and non-contactingly installed with the permanent magnet.

[0006] Further, the magnetic encoding plate is designed based on the AS5047P magnetic encoding chip, and the AS5047P magnetic encoding chip is coaxially and non-contactingly installed with the permanent magnet.

[0007] Further, the incremental output interface of the AS5047P magnetic encoding chip is connected to the control board through a connector J1.

[0008] Further, the SPI interface of the AS5047P magnetic encoding chip is connected to the control board through a connector J2.

[0009] Further, the permanent magnet is cylindrical.

[0010] Further, the magnetic encoding plate is fixed on a coding plate fixing bracket.

[0011] Further, this device is used for the zoom lens group and the focusing lens group of a zoom lens, or for the zoom lens group of a zoom laser emission lens.

[0012] The beneficial effects of the present utility model: On the basis of the existing lens group position feedback device, the present utility model replaces the multi-turn continuous rotation potentiometer with a non-contact magnetic encoder. The magnetic encoder consists of a small-volume circular permanent magnet and a magnetic encoding plate designed based on the AS5047P magnetic encoding chip. The magnetic encoding chip and the magnet are coaxially and non-contactingly installed, and the rotation angle information is obtained by converting the magnetic field component perpendicular to the chip surface generated by the magnet into voltage. On the basis of inheriting the simple control and implementation method and low cost of the existing technology, the non-contact installation method avoids the life problems caused by the mechanical mode in the existing technology and improves the overall reliability. Description of the Drawings

[0013] Figure 1 It is a structural schematic diagram of the present utility model;

[0014] Figure 2 It is a schematic diagram of the magnetic field generated by the permanent magnet;

[0015] Figure 3 It is a schematic diagram of obtaining angle information by the magnetic encoding chip through the magnetic field change generated by the rotation of the permanent magnet;

[0016] Figure 4 is the circuit schematic diagram of the magnetic encoding chip;

[0017] In the figure: 1. DC reduction motor, 2. Motor drive gear, 3. Zoom lens gear ring, 4. Driven gear, 5. Permanent magnet, 6. Magnetic encoding board, 7. Encoding board fixing bracket, 8. Outer barrel of the zoom lens, 9. Magnetic encoding chip. Specific embodiments

[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0019] Embodiment 1

[0020] This embodiment discloses a lens group position feedback device for a zoom lens, as Figure 1 shown, including a DC reduction motor 1, a motor drive gear 2, a zoom lens gear ring 3 and a driven gear 4. The motor drive gear 2 is located on the output shaft of the DC reduction motor 1. The zoom lens gear ring 3 is located at the end of the outer barrel of the zoom lens. The zoom lens gear ring 3 is respectively meshed with the motor drive gear 2 and the driven gear 4. The driven gear 4 is connected with a non-contact magnetic encoder. The magnetic encoder includes a permanent magnet 5 and a magnetic encoding board 6. The permanent magnet 5 is connected with the driven gear 4. The magnetic encoding board 6 is coaxially and non-contactingly installed with the permanent magnet 5, and the magnetic encoding board 6 is installed on the encoding board fixing bracket 7.

[0021] In this embodiment, the permanent magnet 5 is cylindrical. The magnetic encoder is implemented based on the AS5047P magnetic encoding chip 8. The magnetic encoding chip 8 and the permanent magnet 5 are coaxially and non-contactingly installed. The magnetic field component perpendicular to the surface of the magnetic encoding chip 8 generated by the permanent magnet 5 is converted into a voltage to obtain the rotation angle information.

[0022] The permanent magnet 5 is meshed with the zoom lens gear ring 3 through the driven gear 4. When the zoom lens barrel rotates, the permanent magnet 5 is driven to rotate through this gear meshing. The magnetic field generated by the magnet is evenly distributed around the magnet, and the distribution is as Figure 2 shown. Since the magnetic encoding chip 8 and the permanent magnet 5 are coaxially installed, the magnetic field perpendicular to the surface of the permanent magnet 5 will also be distributed perpendicular to the surface of the magnetic encoding chip 8. When the DC reduction motor 1 drives the zoom lens group to move, that is, the lens barrel rotates, the permanent magnet 5 rotates with the lens barrel, and at the same time the magnetic field generated by the permanent magnet 5 changes accordingly. The magnetic encoding chip 8 converts the magnetic field component perpendicular to the surface of the chip into a voltage to obtain the rotation angle information. The magnetic encoding chip 8 obtains the angle information through the magnetic field change generated by the rotation of the magnet as Figure 3 shown.

[0023] The AS5047P magnetic encoding chip used in this embodiment is a high-resolution magnetic rotary position sensor chip launched by AMS for motor and motion control applications. It is suitable for 360° full-angle measurement applications at a maximum rotational speed of up to 28k rpm. At a continuous rotational speed of 28k rpm, the maximum dynamic angle error is ±0.2°, fully meeting the requirements of the low-speed rotational angle measurement application of the optical zoom lens. This sensor chip supports both absolute and incremental angle measurements, with a 14-bit core resolution. In the decimal output mode, the maximum resolution per revolution can be as high as 4000 steps / 1000 pulses.

[0024] The sensor chip supports a standard 4-wire SPI communication interface. It is convenient to read 14-bit absolute angle data through the SPI interface by the main control module, and its non-volatile settings can be programmed without a dedicated programmer. At the same time, this sensor chip also supports the incremental ABI to output the running steps, and the output format is the same as that of a conventional standard encoder. Therefore, there is no need to change the control software or interface design in the application design, and it has high portability.

[0025] In addition, this sensor chip has extremely high immunity to stray magnetic fields and is not affected by dirt, dust, grease, moisture, and other pollutants. It has low requirements for the use environment and can effectively improve the reliability of the overall system.

[0026] The circuit schematic diagram of the magnetic encoding board designed based on the AS5047P magnetic encoding chip in this embodiment is as Figure 4 shown. The magnetic encoding board is powered by +5V provided by the zoom lens control board. Angle information can be obtained through the incremental output interface of connector J1 with the control board, or its absolute angle data can be obtained through the SPI interface communication of connector J2. The circuit interface is simple, flexible and convenient to use, and has strong applicability, fully meeting the requirements of the lens group position feedback of the optical zoom lens in security products.

[0027] The above description only presents the basic principles and preferred embodiments of the present invention. The improvements and substitutions made by those skilled in the art based on the present invention fall within the protection scope of the present invention.

Claims

1. A mirror group position feedback device for a zoom lens, comprising a DC reduction motor, a motor drive gear, a zoom lens gear ring and a driven gear. The motor drive gear is located on the output shaft of the DC reduction motor, and the zoom lens gear ring is located at the end of the outer barrel of the zoom lens. The zoom lens gear ring is meshed with the motor drive gear and the driven gear respectively. It is characterized in that: The driven gear is connected with a non-contact magnetic encoder, which includes a permanent magnet and a magnetic encoding plate. The permanent magnet is connected to the driven gear, and the magnetic encoding plate is coaxially and non-contactingly installed with the permanent magnet.

2. The lens group position feedback device for a zoom lens according to claim 1, characterized in that: The magnetic encoding plate is designed based on the AS5047P magnetic encoding chip, and the AS5047P magnetic encoding chip is coaxially and non-contactingly installed with the permanent magnet.

3. The lens group position feedback device for a zoom lens according to claim 2, wherein: The incremental output interface of the AS5047P magnetic encoding chip is connected to the control board through the connector J1.

4. The lens group position feedback device for a zoom lens according to claim 2, characterized in that: The SPI interface of the AS5047P magnetic encoding chip is connected to the control board through the connector J2.

5. The lens group position feedback device for a zoom lens according to claim 1 or 2, characterized in that: The permanent magnet is cylindrical.

6. The lens group position feedback device for a zoom lens according to claim 1 or 2, characterized in that: The magnetic encoding plate is fixed on the encoding plate fixing bracket.

7. The lens group position feedback device for a zoom lens according to claim 1, characterized in that: This device is used for the zoom lens group and the focusing lens group of a zoom lens, or for the zoom lens group of a zoom laser emitting lens.

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