A piezoelectric actuator driven optical system focusing device and its working method

Abstract

The application discloses a kind of piezoelectric actuator driven optical system focusing device and its working method, focusing device is equipped with several lens assemblies between objective lens and objective lens, the lens assembly includes fixed support, adjusting slide rail, slider, lens support, lens, bearing, actuator, first fixed bolt and second fixed bolt;The actuator includes metal matrix, first to fourth piezoelectric ceramic sheet, first to second stud, connecting rod, spring and adjusting bolt.Actuator can directly drive lens support movement, adjust optical path focal length.The application has simple structure, high precision, can be power-off self-locking, good versatility, and smaller circumferential size and adjustable stroke have higher application value and good economic benefits in optical system.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric drives, and more particularly to a focusing device for an optical system driven by a piezoelectric actuator and its operating method. Background Technology

[0002] Optical systems are affected by changes in ambient temperature, air pressure, and vibration during service. These environmental factors can cause the image plane of the optical system to defocus, reducing image resolution. Therefore, a focusing device is needed to adjust the amount of defocus and improve image quality. The focusing device is typically a linear motion mechanism that drives the focusing lens, changing the distance between the focusing lens and the eyepiece and objective lenses to adjust the focal length of the optical system. Currently, commonly used focusing devices in optical systems include cams, lead screws and nuts, and piezoelectric stack direct drive mechanisms. Cam focusing methods have disadvantages such as large size, easy cam wear, and inability to achieve self-locking; while lead screws and nuts can achieve high-precision focusing, they have high manufacturing requirements and require the configuration of reducers and other rotating mechanisms, resulting in a complex structure. With the continuous development of the microelectromechanical system (MEMS) field, the requirements for miniaturization and simplification of focusing devices in optical systems are constantly increasing, leading to the development of piezoelectric stack direct drive focusing devices. While piezoelectric stack-driven focusing devices offer the advantage of simple structure, their stroke is limited by the deformation of the piezoelectric stack, typically on the order of micrometers, thus restricting their applications. Therefore, ensuring that the focusing device achieves large stroke, high precision, and self-locking capabilities while reducing its structural complexity has become a major challenge for optical system focusing devices.

[0003] A piezoelectric actuator is a driver based on the inverse piezoelectric effect. It can excite high-frequency, low-amplitude vibrations of the stator through piezoelectric ceramics, thereby driving the rotor. Due to its simple structure, high precision, self-locking upon power failure, and good electromagnetic compatibility, it has extremely wide applications in fields such as bioengineering, aerospace, and precision engineering. Therefore, piezoelectric actuators are ideal drivers for focusing mechanisms. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a piezoelectric actuator-driven optical system focusing device and its working method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A piezoelectrically driven optical system focusing device has a plurality of lens assemblies between the eyepiece and the objective lens. The lens assembly includes a fixed bracket, an adjusting slide rail, a slider, a lens support, a lens, a bearing, an actuator, a first fixing bolt, and a second fixing bolt. The fixed bracket is L-shaped and includes a first fixed plate and a second fixed plate, with one end of the first fixed plate and one end of the second fixed plate being perpendicularly fixedly connected. The first fixing plate is provided with a first mounting hole for fixing the actuator; The adjusting slide rail is fixed to the second fixing plate and perpendicular to the first fixing plate; the slider is disposed on the adjusting slide rail and can slide freely on the adjusting slide rail. The lens holder is fixedly connected to the slider, and is provided with a second mounting hole for mounting the lens and a third mounting hole for mounting the bearing. The lens is fixed in the second mounting hole, and the outer ring of the bearing is fixed in the third mounting hole. The axes of the lens and the bearing are both perpendicular to the first fixing plate. The actuator includes a metal substrate, first to fourth piezoelectric ceramic plates, first to second studs, a connecting rod, a spring, and an adjusting bolt; The metal substrate is a regular square prism, including a first end face, a second end face, and first to fourth side walls connected end to end. The first end face is provided with a threaded through hole along the axis for cooperating with the adjusting bolt. The first to fourth piezoelectric ceramic sheets have the same structure and are arranged one-to-one on the first to fourth sidewalls. They are all polarized along the thickness direction. The first and third piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction, and the second and fourth piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction. The first stud and the second stud have the same outer diameter and are both provided with through holes along the axis for cooperating with the connecting rod; One end of the first stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the first end face and is threadedly connected to the metal substrate. One end of the second stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the second end face and is threadedly connected to the metal substrate. A gap is left between the first stud and the second stud. One end of the connecting rod is provided with an external thread for engaging with the adjusting bolt, and the threaded end passes through the first stud, the second stud and the adjusting bolt in sequence and is threadedly connected. The connecting rod and the first stud are coaxially fixed. The connecting rod and the second stud are keyed together, so that the connecting rod and the second stud are circumferentially fixed and axially free to slide. The spring is positioned between the adjusting bolt and the second stud, with one end abutting against the adjusting bolt and the other end abutting against the second stud, and is used to provide preload. The end of the connecting rod away from the adjusting bolt is coaxially fixed to the inner ring of the bearing; The metal substrate is disposed in the first mounting hole and is fixedly connected to the first fixing plate at the bending vibration nodes of its first to fourth sidewalls, such that the first fixing plate is located between the first to fourth piezoelectric ceramic sheets and the second end face, and the second fixing plate and the metal substrate are parallel. The lens assembly is fixed between the eyepiece and the objective lens, making the lens of the lens assembly coaxial with the eyepiece and the objective lens.

[0006] As a further optimization of the piezoelectric-driven optical system focusing device of the present invention, the first to fourth piezoelectric ceramic sheets are glued one-to-one to the first to fourth sidewalls with epoxy resin adhesive.

[0007] As a further optimization of the piezoelectrically driven optical system focusing device of the present invention, chamfers are provided between the first to fourth sidewalls of the metal substrate.

[0008] As a further optimization of the piezoelectrically driven optical system focusing device of the present invention, the connecting rod is provided with a first keyway parallel to its axis, and the inner wall of the second stud is provided with a second keyway that cooperates with the first keyway. A flat key is provided between the connecting rod and the second stud; part of the flat key is located in the first keyway and the other part is located in the second keyway, so that the connecting rod and the second stud are circumferentially fixed and can slide freely in the axial direction.

[0009] As a further optimization of the piezoelectrically driven optical system focusing device of the present invention, the present invention also includes a first fixing bolt and a second fixing bolt. The first fixing plate includes a first end face, a second end face, and first to fourth side faces connected end to end in sequence. The first fixing plate is perpendicularly fixed to the second fixing plate at its fourth side face. The first mounting hole penetrates through the first end face and the second end face of the first fixing plate; The first fixing plate has a first threaded hole on its first side that communicates with the first mounting hole and matches the first fixing bolt. The first fixing bolt is threadedly connected to the first fixing plate through the first threaded hole, and the first fixing bolt abuts against the metal substrate. The second side of the first fixing plate is provided with a second threaded hole that communicates with the first mounting hole and matches the second fixing bolt. The second fixing bolt is threadedly connected to the first fixing plate through the second threaded hole, and the second fixing bolt abuts against the metal substrate. The first fixing bolt and the second fixing bolt work together to fix the metal substrate in the first mounting hole.

[0010] The present invention also discloses a method for operating the piezoelectrically driven optical system focusing device, comprising the following steps: If it is necessary to control the forward translation of the lens in the lens assembly between the eyepiece and the objective lens: A first signal is applied to the first and third piezoelectric ceramic sheets, and a second signal is applied to the second and fourth piezoelectric ceramic sheets. The first and second signals are sinusoidal voltage signals with a phase difference of π / 2, which cause the particles on the threads of the metal substrate to vibrate at high frequency and micro-amplitude, thereby driving the first and second studs to rotate through friction. The lens support moves in the positive direction along the adjustment slide rail under the drive of the first stud, thereby driving the lens to translate in the positive direction between the eyepiece and the objective lens. If it is necessary to control the lens in the lens assembly to shift in the opposite direction between the eyepiece and the objective lens, the phase difference between the first and second signals can be adjusted to -π / 2.

[0011] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects: 1. This invention uses a threaded piezoelectric actuator as the driver for focusing a lens assembly. The threaded piezoelectric actuator is directly connected to the lens holder, eliminating the need for a transmission mechanism and achieving direct drive of the lens. The device requires fewer assembly parts, effectively reducing structural complexity. The stator and rotor of the threaded piezoelectric actuator are threadedly engaged, and this threaded engagement has a self-locking function. Utilizing this characteristic, the focusing device proposed in this invention can be powered off during the focus-holding phase of the optical system, reducing device power consumption. 2. This invention adopts a modular design. In different optical system designs, several lens assemblies can be arranged in series along the axis to realize the adjustment of multiple focusing lenses in the optical path. The device can be adapted to the adjustment needs of various optical systems and has stronger versatility. 3. The effective stroke of the device in this invention depends on the lengths of the first stud and the second stud in the threaded piezoelectric actuator. Therefore, the lengths of the first stud and the second stud can be adjusted according to the stroke requirements of different optical systems, making the device more versatile. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is an exploded structural diagram of the present invention; Figure 3 This is a schematic diagram of the actuator in this invention; Figure 4 This is a schematic diagram of the structure of the first stud, the second stud, the connecting rod, the spring, and the adjusting bolt in this invention. Figure 5 This is a cross-sectional structural diagram of the actuator in this invention; Figure 6 This is a schematic diagram showing the polarization direction of the first to fourth piezoelectric ceramic sheets and the applied driving voltage in this invention; Figure 7 This is a schematic diagram of the driving signal of the present invention; Figure 8This is a schematic diagram of the state of the metal substrate of the present invention when it is driven; Figure 9 This is a schematic diagram of the driving lens moving in the forward direction according to the present invention; Figure 10 This is a schematic diagram of the driving lens moving in the reverse direction according to the present invention.

[0013] In the diagram, 1-first fixed plate, 2-second fixed plate, 3-adjusting slide rail, 4-slider, 5-lens bracket, 6-lens, 7-bearing, 8-actuator, 9-first fixing bolt, 10-second fixing bolt, 11-metal substrate, 12-first piezoelectric ceramic sheet, 13-fourth piezoelectric ceramic sheet, 14-first stud, 15-second stud, 16-connecting rod, 17-spring, 18-adjusting bolt, 19-flat key. Detailed Implementation

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings: This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0015] like Figure 1 , Figure 2 As shown, the present invention discloses a piezoelectrically driven optical system focusing device, which has a plurality of lens assemblies between the eyepiece and the objective lens. The lens assembly includes a fixed bracket, an adjusting slide rail, a slider, a lens bracket, a lens, a bearing, an actuator, a first fixing bolt, and a second fixing bolt. like Figure 2 As shown, the fixed bracket is L-shaped and includes a first fixed plate and a second fixed plate, with one end of the first fixed plate and one end of the second fixed plate being perpendicularly fixed together. The first fixing plate is provided with a first mounting hole for fixing the actuator; The adjusting slide rail is fixed to the second fixing plate and perpendicular to the first fixing plate; the slider is disposed on the adjusting slide rail and can slide freely on the adjusting slide rail. The lens holder is fixedly connected to the slider, and is provided with a second mounting hole for mounting the lens and a third mounting hole for mounting the bearing. The lens is fixed in the second mounting hole, and the outer ring of the bearing is fixed in the third mounting hole. The axes of the lens and the bearing are both perpendicular to the first fixing plate. like Figure 3 As shown, the actuator includes a metal substrate, first to fourth piezoelectric ceramic plates, first to second studs, a connecting rod, a spring, and an adjusting bolt; The metal substrate is a regular square prism, including a first end face, a second end face, and first to fourth side walls connected end to end. The first end face is provided with a threaded through hole along the axis for cooperating with the adjusting bolt. The first to fourth piezoelectric ceramic sheets have the same structure and are arranged one-to-one on the first to fourth sidewalls. They are all polarized along the thickness direction. The first and third piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction, and the second and fourth piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction. like Figure 4 As shown, the first stud and the second stud have the same outer diameter and are both provided with through holes along the axis for cooperating with the connecting rod; One end of the first stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the first end face and is threadedly connected to the metal substrate. One end of the second stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the second end face and is threadedly connected to the metal substrate. A gap is left between the first stud and the second stud. One end of the connecting rod is provided with an external thread for engaging with the adjusting bolt, and the threaded end passes sequentially through the first stud, the second stud, and is threadedly connected to the adjusting bolt. The connecting rod and the first stud are coaxially fixed together; the connecting rod and the second stud are keyed together, so that the connecting rod and the second stud are circumferentially fixed but axially free to slide. Figure 5 As shown; The spring is positioned between the adjusting bolt and the second stud, with one end abutting against the adjusting bolt and the other end abutting against the second stud, and is used to provide preload. The end of the connecting rod away from the adjusting bolt is coaxially fixed to the inner ring of the bearing; The metal substrate is disposed in the first mounting hole and is fixedly connected to the first fixing plate at the bending vibration nodes of its first to fourth sidewalls, such that the first fixing plate is located between the first to fourth piezoelectric ceramic sheets and the second end face, and the second fixing plate and the metal substrate are parallel. The lens assembly is fixed between the eyepiece and the objective lens, making the lens of the lens assembly coaxial with the eyepiece and the objective lens.

[0016] The first to fourth piezoelectric ceramic sheets are glued to the first to fourth sidewalls one by one using epoxy resin adhesive; each of the first to fourth sidewalls of the metal substrate has a chamfer. Let the length of the metal substrate be L, then the length T of the first to fourth piezoelectric ceramic sheets is preferably less than 0.75L.

[0017] The connecting rod and the second stud can be keyed together in the following way: the connecting rod is provided with a first keyway parallel to its axis, and the inner wall of the second stud is provided with a second keyway that mates with the first keyway; A flat key is provided between the connecting rod and the second stud; part of the flat key is located in the first keyway and the other part is located in the second keyway, so that the connecting rod and the second stud are circumferentially fixed and can slide freely in the axial direction.

[0018] The metal substrate can be fixed in the first mounting hole in the following manner: The present invention also includes a first fixing bolt and a second fixing bolt; The first fixing plate includes a first end face, a second end face, and first to fourth side faces connected end to end in sequence. The first fixing plate is perpendicularly fixed to the second fixing plate at its fourth side face. The first mounting hole penetrates through the first end face and the second end face of the first fixing plate; The first fixing plate has a first threaded hole on its first side that communicates with the first mounting hole and matches the first fixing bolt. The first fixing bolt is threadedly connected to the first fixing plate through the first threaded hole, and the first fixing bolt abuts against the metal substrate. The second side of the first fixing plate is provided with a second threaded hole that communicates with the first mounting hole and matches the second fixing bolt. The second fixing bolt is threadedly connected to the first fixing plate through the second threaded hole, and the second fixing bolt abuts against the metal substrate. The first fixing bolt and the second fixing bolt work together to fix the metal substrate in the first mounting hole.

[0019] The present invention also discloses a method for operating the piezoelectrically driven optical system focusing device, comprising the following steps: If it is necessary to control the forward translation of the lens in the lens assembly between the eyepiece and the objective lens: A first signal is applied to the first and third piezoelectric ceramic sheets, and a second signal is applied to the second and fourth piezoelectric ceramic sheets. The first and second signals are sinusoidal voltage signals with a phase difference of π / 2, such as... Figure 6 , Figure 7 As shown, this causes the particles on the metal matrix thread to undergo high-frequency micro-amplitude vibrations, such as... Figure 8 As shown, the first and second studs are then driven to rotate through friction; the lens holder moves along the adjusting slide rail in the positive direction under the action of the first stud, thereby causing the lens to translate in the positive direction between the eyepiece and the objective lens, as shown. Figure 9 As shown; If it is necessary to control the lens in the lens assembly to shift in opposite directions between the eyepiece and the objective lens, the phase difference between the first and second signals can be adjusted to -π / 2. Figure 10 As shown.

[0020] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0021] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific 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 within the protection scope of the present invention.

Claims

1. A piezoelectrically driven focusing device for an optical system, comprising a plurality of lens assemblies disposed between the eyepiece and the objective lens, characterized in that, The lens assembly includes a fixed bracket, an adjusting slide rail, a slider, a lens bracket, a lens, a bearing, an actuator, a first fixing bolt, and a second fixing bolt; The fixed bracket is L-shaped and includes a first fixed plate and a second fixed plate, with one end of the first fixed plate and one end of the second fixed plate being perpendicularly fixedly connected. The first fixing plate is provided with a first mounting hole for fixing the actuator; The adjusting slide rail is fixed to the second fixing plate and perpendicular to the first fixing plate; the slider is disposed on the adjusting slide rail and can slide freely on the adjusting slide rail. The lens holder is fixedly connected to the slider, and is provided with a second mounting hole for mounting the lens and a third mounting hole for mounting the bearing. The lens is fixed in the second mounting hole, and the outer ring of the bearing is fixed in the third mounting hole. The axes of the lens and the bearing are both perpendicular to the first fixing plate. The actuator includes a metal substrate, first to fourth piezoelectric ceramic plates, first to second studs, a connecting rod, a spring, and an adjusting bolt; The metal substrate is a regular square prism, including a first end face, a second end face, and first to fourth side walls connected end to end. The first end face is provided with a threaded through hole along the axis for cooperating with the adjusting bolt. The first to fourth piezoelectric ceramic sheets have the same structure and are arranged one-to-one on the first to fourth sidewalls. They are all polarized along the thickness direction. The first and third piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction, and the second and fourth piezoelectric ceramic sheets are symmetrically arranged and have the same polarization direction. The first stud and the second stud have the same outer diameter and are both provided with through holes along the axis for cooperating with the connecting rod; One end of the first stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the first end face and is threadedly connected to the metal substrate. One end of the second stud extends into the metal substrate from the side of the threaded through hole in the metal substrate located at the center of the second end face and is threadedly connected to the metal substrate. A gap is left between the first stud and the second stud. One end of the connecting rod is provided with an external thread for engaging with the adjusting bolt, and the threaded end passes through the first stud, the second stud and the adjusting bolt in sequence and is threadedly connected. The connecting rod and the first stud are coaxially fixed. The connecting rod and the second stud are keyed together, so that the connecting rod and the second stud are circumferentially fixed and axially free to slide. The spring is positioned between the adjusting bolt and the second stud, with one end abutting against the adjusting bolt and the other end abutting against the second stud, and is used to provide preload. The end of the connecting rod away from the adjusting bolt is coaxially fixed to the inner ring of the bearing; The metal substrate is disposed in the first mounting hole and is fixedly connected to the first fixing plate at the bending vibration nodes of its first to fourth sidewalls, such that the first fixing plate is located between the first to fourth piezoelectric ceramic sheets and the second end face, and the second fixing plate and the metal substrate are parallel. The lens assembly is fixed between the eyepiece and the objective lens, making the lens of the lens assembly coaxial with the eyepiece and the objective lens.

2. The piezoelectrically driven optical system focusing device according to claim 1, characterized in that, The first to fourth piezoelectric ceramic sheets are glued to the first to fourth sidewalls one by one using epoxy resin adhesive.

3. The piezoelectrically driven optical system focusing device according to claim 1, characterized in that, The metal substrate has chamfers between its first to fourth sidewalls.

4. The piezoelectrically driven optical system focusing device according to claim 1, characterized in that, The connecting rod is provided with a first keyway parallel to its axis, and the inner wall of the second stud is provided with a second keyway that mates with the first keyway; A flat key is provided between the connecting rod and the second stud; part of the flat key is located in the first keyway and the other part is located in the second keyway, so that the connecting rod and the second stud are circumferentially fixed and can slide freely in the axial direction.

5. The piezoelectrically driven optical system focusing device according to claim 1, characterized in that, It also includes a first fixing bolt and a second fixing bolt; The first fixing plate includes a first end face, a second end face, and first to fourth side faces connected end to end in sequence; The first mounting hole penetrates through the first end face and the second end face of the first fixing plate; The first fixing plate has a first threaded hole on its first side that communicates with the first mounting hole and matches the first fixing bolt. The first fixing bolt is threadedly connected to the first fixing plate through the first threaded hole, and the first fixing bolt abuts against the metal substrate. The second side of the first fixing plate is provided with a second threaded hole that communicates with the first mounting hole and matches the second fixing bolt. The second fixing bolt is threadedly connected to the first fixing plate through the second threaded hole, and the second fixing bolt abuts against the metal substrate. The first fixing bolt and the second fixing bolt work together to fix the metal substrate in the first mounting hole.

6. The operating method of the piezoelectrically driven optical system focusing device according to claim 1, characterized in that, Includes the following processes: If it is necessary to control the forward translation of the lens in the lens assembly between the eyepiece and the objective lens: A first signal is applied to the first and third piezoelectric ceramic sheets, and a second signal is applied to the second and fourth piezoelectric ceramic sheets. The first and second signals are sinusoidal voltage signals with a phase difference of π / 2, which cause the particles on the threads of the metal substrate to vibrate at high frequency and micro-amplitude, thereby driving the first and second studs to rotate through friction. The lens support moves in the positive direction along the adjustment slide rail under the drive of the first stud, thereby driving the lens to translate in the positive direction between the eyepiece and the objective lens. If it is necessary to control the lens in the lens assembly to shift in the opposite direction between the eyepiece and the objective lens, the phase difference between the first and second signals can be adjusted to -π / 2.

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