Focal length dynamic regulation device and regulation method based on thermal driving and pressure control

Abstract

The present application relates to a kind of focal length dynamic regulation and control device and regulation and control method based on heat drive and pressure control, mainly solve the technical problems such as the existing single drive mode being difficult to consider wide range and high stability for electrowetting drive.This application adopts the technical scheme: the focal length dynamic regulation and control device, it includes microlens array, heat drive module, pressure control module and collaborative control unit;The microlens array is to set several microlens units on transparent substrate, the microlens unit is filled with optical liquid;The heat drive module is a thin film heater array formed by several thin film heaters, the thin film heater is integrated below the microlens array by microfabrication technology, each thin film heater is connected with external drive circuit by independent lead, realizes independent addressing control;The pressure control module includes micro pressure pump, sealed cavity, fluid pipeline, thermal expansion compensation cavity and micro fluid control valve array.

Description

Technical Field

[0001] This invention belongs to the field of optical and precision instrument technology, specifically relating to a dynamic focal length control device and control method based on thermal drive and pressure control. Background Technology

[0002] Microlens arrays, as core components of modern optical systems, have wide applications in imaging, beam shaping, light field manipulation, and three-dimensional sensing. Traditional microlens arrays are mostly made of solid materials, with fixed focal lengths, which cannot meet the demands of dynamic zoom. Therefore, researchers have developed various adjustable-focus microlens technologies.

[0003] Currently, the main types of adjustable focus microlens technologies include:

[0004] Electrowetting drive technology, such as the patent with publication number CN116300047A, adjusts the focus by changing the contact angle of the liquid on the hydrophobic dielectric layer by changing the applied voltage. This type of technology has advantages such as fast response speed and low power consumption, but it has problems such as limited adjustment range, easy droplet adhesion, contact angle hysteresis, and poor long-term working stability.

[0005] Pressure-driven technology: such as the patent with publication number CN117631104A, achieves focal length adjustment by changing the droplet volume or film deformation through adjusting fluid pressure. This type of technology has the advantages of a large adjustment range and strong driving force, but the response speed is relatively slow, and pressure fluctuations can easily lead to focal length instability.

[0006] Thermally driven technology: This technology alters the surface tension of a liquid (thermocapillary effect) or the refractive index of a material (thermo-optic effect) through localized heating. While this type of technology is easy to integrate and has a fast response time, its single thermal drive has a limited adjustment range and suffers from problems such as high thermal inertia and difficulty in controlling temperature uniformity.

[0007] Therefore, existing single-drive methods have the following drawbacks: electrowetting drives struggle to balance wide range and high stability; pressure drives struggle to achieve rapid response and high-precision control; and thermal drives are limited by a finite adjustment range and thermal management challenges. More importantly, due to inherent differences in structural design, process implementation, and control logic among different drive mechanisms, there is a technical bias in the field that makes it difficult to overcome obstacles to effectively integrating multiple drive methods.

[0008] Therefore, developing a novel microlens array that can effectively integrate the advantages of multiple driving methods and achieve wide-range, high-precision, and fast-response focal length adjustment through coordinated control has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of existing single driving methods, such as the difficulty in achieving both wide range and high stability in electrowetting drive, the difficulty in achieving fast response and high precision control in pressure drive, and the limitation of limited adjustment range and thermal management problems in thermal drive. The invention provides a focal length dynamic control device and control method based on thermal drive and pressure control.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A dynamic focal length control device based on thermal drive and pressure control includes a microlens array (1), a thermal drive module (2), a pressure control module (3), and a collaborative control unit (4). The microlens array (1) consists of several microlens units (6) arranged on a transparent substrate, and the microlens units (6) are filled with optical liquid. The thermal drive module (2) is a thin-film heater array composed of several thin-film heaters (8). The thin-film heaters (8) are integrated below the microlens array (1) through microfabrication technology and are arranged one-to-one with the microlens units (6). Each thin-film heater (8) is connected to an external drive circuit through an independent lead (9) to achieve independent addressing control. The pressure control module (3) includes a micro pressure pump (11), a sealed cavity (12), a fluid pipeline (13), a thermal expansion compensation cavity (10), and a micro flow control valve array (7). The thermal expansion compensation cavity (10) is provided inside the sealed cavity (12). The container is equipped with a thermal expansion medium (14). The output end of the micro pressure pump (11) is connected to the sealed cavity (12). The sealed cavity (12) is connected to the microlens unit (6) via the fluid pipe (13) and the micro flow control valve array (7) to achieve independent control of the fluid pressure inside different microlens units. The collaborative control unit (4) includes a microprocessor and a drive circuit. The microprocessor receives focal length adjustment instructions from the outside and generates control signals according to a preset control strategy. The drive circuit includes a thermal drive circuit, a pressure drive circuit, and a valve drive circuit. The thermal drive circuit is connected to the thin film heater array, the pressure drive circuit is connected to the micro pressure pump, and the valve drive circuit is connected to the micro flow control valve array to drive the thin film heater array, the micro pressure pump, and the micro flow control valve array to work. A highly thermally conductive transparent heat dissipation layer (5) is provided between the thermal drive module (2) and the pressure control module (3) to accelerate the removal of local Joule heat after the thermal drive module works.

[0012] Furthermore, the transparent substrate is any one of polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), or quartz glass.

[0013] Further, the optical liquid (7) is any one of silicone oil, fluorinated liquid or ionic liquid with a refractive index in the range of 1.3-1.7; and when the optical liquid (7) is silicone oil and the transparent substrate is polydimethylsiloxane (PDMS), the inner wall of the microlens unit (6) is coated with an anti-swelling barrier layer, or when the transparent substrate is polydimethylsiloxane (PDMS), the optical liquid (7) is limited to fluorinated liquid or ionic liquid.

[0014] Furthermore, the thin-film heater (8) is an indium tin oxide (ITO) transparent heating film or a metal nanowire heating network with a thickness of 50-200 nm.

[0015] Furthermore, the preset control strategy is: a pressure-then-heat driven strategy and a parallel collaborative strategy; the pressure-then-heat driven strategy is: the collaborative control unit (4) opens the micro-flow control valve corresponding to the target microlens unit, drives the micro pressure pump (11) to perform coarse focus adjustment, and closes the corresponding micro-flow control valve to lock the fluid pressure after reaching the preset range; then the focus is finely adjusted through the heat driven module (2); the parallel collaborative strategy is: according to the preset focus-pressure-temperature mapping model, the parameters of the pressure control module and the heat driven module are adjusted synchronously.

[0016] A control method applied to any of the above-described devices, the control method comprising:

[0017] Step S1: Obtain the focus adjustment command;

[0018] Step S2: Based on the focal length adjustment command, generate a cooperative control signal through the cooperative control unit;

[0019] Step S3: Based on the coordinated control signal, drive the pressure control module and the thermal drive module to change the focal length of the microlens unit to the target value through the coordinated effect of independent flow control and pressure maintenance and thermal deformation of the microflow control valve array.

[0020] This invention integrates a thermal drive module and a pressure control module. By coordinating the control unit, driving the pressure control module, and the thermal drive module, the focal length of the microlens unit is changed. This solves the technical problems of existing single-drive methods, such as the difficulty in achieving both wide range and high stability with electrowetting drive, the difficulty in achieving fast response and high-precision control with pressure drive, and the limitations of thermal drive in terms of limited adjustment range and thermal management. Compared with the prior art, the beneficial effects of this invention are:

[0021] 1. Breakthrough in overcoming the performance bottleneck of a single driving method: By organically combining thermal drive and pressure control, a working mode of "pressure coarse adjustment + thermal drive fine adjustment" is achieved. Experiments show that this invention can achieve a wide range of adjustment from 50-500μm, while maintaining millisecond-level response speed (<15ms) and submicron-level adjustment accuracy (±0.3μm), which is a comprehensive performance that no single driving method can achieve.

[0022] 2. It creates a synergistic technical effect: thermal drive and pressure control are not simply superimposed, but deeply coupled through a collaborative control unit. Pressure control solves the problem of limited adjustment range of thermal drive, while thermal drive makes up for the shortcomings of slow response and low accuracy of pressure control. The combination of the two produces a synergistic effect of "1+1>2".

[0023] 3. Improved system stability and reliability: "Coarse adjustment pressure latching" is achieved through a micro-flow control valve array, completely eliminating the interference of local thermal expansion on the main fluid path during thermally driven fine adjustment. The thermal expansion compensation chamber effectively suppresses the impact of ambient temperature fluctuations on the pressure control system; and the independently addressable thermally driven array enables precise control of individual microlens units, avoiding droplet adhesion and cross-interference problems, significantly improving long-term operational stability.

[0024] 4. Enhanced application flexibility and adaptability: This invention supports independent control of individual microlens units, enabling advanced functions such as multi-focal distribution and complex wavefront modulation; at the same time, the device has a compact structure, is easy to integrate, and can be widely used in various scenarios such as AR / VR devices, medical endoscopes, mobile phone camera modules, and laser processing systems. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the micro-flow control valve array and thermal expansion compensation cavity of the present invention;

[0027] In the diagram: 1-Microlens array, 2-Thermal drive module, 3-Pressure control module, 4-Cooperative control unit, 5-High thermal conductivity transparent heat dissipation layer, 6-Microlens unit, 7-Micro flow control valve array, 8-Thin film heater, 9-Independent lead wire, 10-Thermal expansion compensation chamber, 11-Micro pressure pump, 12-Sealed cavity, 13-Fluid channel, 14-Thermal expansion medium, 15-Micro flow control valve outlet. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] like Figure 1 and Figure 2 As shown in this embodiment, a dynamic focal length control device based on thermal drive and pressure control includes a microlens array 1, a thermal drive module 2, a pressure control module 3, and a collaborative control unit 4. The microlens array 1 consists of several microlens units 6 arranged on a transparent substrate, each filled with an optical liquid. The thermal drive module 2 is a thin-film heater array composed of several thin-film heaters 8. These thin-film heaters 8 are integrated below the microlens array 1 using microfabrication technology and are arranged one-to-one with each of the microlens units 6. Each thin-film heater 8 is connected to an external drive circuit via an independent lead 9, enabling independent addressing control. The pressure control module 3 includes a micro pressure pump 11, a sealed cavity 12, a fluid pipeline 13, a thermal expansion compensation cavity 10, and a micro flow control valve array 7. The thermal expansion compensation cavity 10 is located inside the sealed cavity 12 and contains a thermal expansion medium. 14. The output end of the micro pressure pump 11 is connected to the sealed cavity 12. The sealed cavity 12 is connected to the microlens unit 6 via the fluid pipe 13 and the microfluidic valve array 7 to achieve independent control of the fluid pressure inside different microlens units. The collaborative control unit 4 includes a microprocessor and a drive circuit. The microprocessor receives focus adjustment commands from the outside and generates control signals according to a preset control strategy. The drive circuit includes a thermal drive circuit, a pressure drive circuit, and a valve drive circuit. The thermal drive circuit is connected to the thin-film heater array, the pressure drive circuit is connected to the micro pressure pump, and the valve drive circuit is connected to the microfluidic valve array to drive the thin-film heater array, the micro pressure pump, and the microfluidic valve array. A highly thermally conductive transparent heat dissipation layer 5 is provided between the thermal drive module 2 and the pressure control module 3 to accelerate the removal of local Joule heat after the thermal drive module is working. The microfluidic valve outlet 15 in the microfluidic valve array 7 is connected to the microlens unit 6 via a pipe.

[0030] The collaborative control unit is responsible for receiving external commands and precisely controlling the thermal drive module, pressure control module, and micro-flow control valve array through various internally integrated drive circuits. The thermal drive circuit uses an OPA4171 series multi-channel operational amplifier array, which features multi-channel independent control capability and good thermal stability, supporting high-precision power output and independent addressing of individual heaters. The pressure drive circuit uses a DRV2700 piezoelectric drive chip, capable of generating the specific waveform, frequency, and high-pressure signal required for pumping. The valve drive circuit uses a ULN2003A Darlington transistor array chip, featuring multiple outputs, high response speed, and sufficient drive current, suitable for driving micro-solenoid valves, piezoelectric valves, or other types of micro-valvees.

[0031] Furthermore, the transparent substrate is any one of polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), or quartz glass.

[0032] Furthermore, the optical liquid 7 is any one of silicone oil, fluorinated liquid, or ionic liquid with a refractive index in the range of 1.3-1.7; and when the optical liquid 7 is silicone oil and the transparent substrate is polydimethylsiloxane (PDMS), the inner wall of the microlens unit 6 is coated with an anti-swelling barrier layer, or when the transparent substrate is polydimethylsiloxane (PDMS), the optical liquid 7 is limited to fluorinated liquid or ionic liquid.

[0033] Furthermore, the thin-film heater 8 is an indium tin oxide (ITO) transparent heating film or a metal nanowire heating network with a thickness of 50-200 nm.

[0034] Furthermore, the preset control strategy is: a pressure-first-heat-later drive strategy and a parallel collaborative strategy; the pressure-first-heat-later drive strategy is: the collaborative control unit 4 opens the micro-flow control valve corresponding to the target microlens unit, drives the micro pressure pump 11 to perform coarse focus adjustment, and closes the corresponding micro-flow control valve to lock the fluid pressure after reaching the preset range; then the focus is finely adjusted through the heat drive module 2; the parallel collaborative strategy is: according to the preset focus-pressure-temperature mapping model, the parameters of the pressure control module and the heat drive module are adjusted synchronously.

[0035] A control method applied to any of the above-described devices, the control method comprising:

[0036] Step S1: Obtain the focal length adjustment command; the command may come from user input or the upper-level control system, and it contains the target focal length information;

[0037] Step S2: Based on the focus adjustment command, a cooperative control signal is generated through the cooperative control unit; specifically:

[0038] First, determine the adjustment mode: Based on the difference between the target focal length and the current focal length, select the corresponding adjustment mode. When the difference is greater than the preset threshold (e.g., 50μm), enter the composite drive mode; when the difference is less than the threshold, enter the single thermal drive mode.

[0039] When using the composite drive adjustment: In the composite drive mode, coarse adjustment is first performed through the pressure control module: the micro pressure pump is controlled to output the corresponding pressure so that the focal length is adjusted to within ±10% of the target range; then fine adjustment is performed through the thermal drive module: the corresponding thin film heater is controlled to work, and the droplet curvature is finely adjusted through the thermocapillary effect so that the focal length accurately reaches the target value.

[0040] When using single thermal drive adjustment: In single thermal drive mode, the thin film heater is directly controlled to achieve rapid fine adjustment of the focal length.

[0041] Step S3: Based on the coordinated control signal, drive the pressure control module and the thermal drive module to change the focal length of the microlens unit to the target value through the coordinated effect of independent flow control and pressure maintenance and thermal deformation of the microflow control valve array.

[0042] Step S4: Stability Maintenance; To address slow changes in ambient temperature, adaptive adjustment is achieved using a thermal expansion compensation chamber located within the sealed cavity. When fluctuations in ambient temperature cause the fluid inside the system to expand or contract, the thermal expansion medium (such as paraffin) in the compensation chamber undergoes synchronized volume expansion and contraction, passively absorbing and offsetting the reference pressure drift in the main fluid path. For each independently operating microlens unit, after the focal length is adjusted, its corresponding micro-flow control valve is completely closed, forming a rigid physical flow cutoff. This physical isolation fundamentally cuts off fluid exchange between the microlens unit and the main fluid path, ensuring that the focal length does not drift even under prolonged continuous operation or severe vibration.

[0043] This invention relates to the application of multi-focal control. By implementing independent composite drive control of microlens units in different groups through a collaborative control unit, multiple focusing regions with different focal lengths can be formed on the same microlens array. For example, the microlens units in the central region of the array can be adjusted to a shorter focal length (e.g., 100 μm), while the microlens units in the edge regions can be adjusted to a longer focal length (e.g., 300 μm), thereby achieving the effect of simultaneously imaging objects at different depths clearly.

[0044] To verify the technical effects of the present invention, a systematic experimental test was conducted. The test sample was prepared according to the apparatus of Example 1, with a microlens array specification of 10×10 and a unit size of 100μm.

[0045] Performance comparison tests show that:

[0046] The present invention (composite drive) can achieve continuous focal length adjustment of 50-500μm, with a response time of <15ms and steady-state accuracy of ±0.3μm.

[0047] Single pressure-driven comparison samples: The adjustment range is similar (50-480μm), but the response time is >50ms and the steady-state accuracy is only ±2.5μm.

[0048] Single thermally driven comparison sample: Fast response time (<10ms), but limited adjustment range (80-150μm).

[0049] Long-term stability tests show that:

[0050] After 1000 hours of continuous operation, the focal length drift of this invention is <1μm, while the focal length drift of the comparison sample driven by single electrowetting reaches >5μm.

[0051] The above experimental results fully demonstrate the significant advantages of this invention in terms of adjustment range, response speed, control accuracy, and long-term stability.

Claims

1. A dynamic focus control device based on thermal drive and pressure control, characterized in that: The system includes a microlens array (1), a thermal drive module (2), a pressure control module (3), and a collaborative control unit (4). The microlens array (1) consists of several microlens units (6) arranged on a transparent substrate, and each microlens unit (6) is filled with an optical liquid. The thermal drive module (2) is a thin-film heater array consisting of several thin-film heaters (8). The thin-film heaters (8) are integrated below the microlens array (1) using microfabrication technology and are arranged one-to-one with each of the microlens units (6). Each thin-film heater (8) is connected to an external drive circuit through an independent lead (9) to achieve independent addressing control. The pressure control module (3) includes a micro pressure pump (11), a sealed cavity (12), a fluid pipeline (13), a thermal expansion compensation cavity (10), and a micro flow control valve array (7). The thermal expansion compensation cavity (10) is located inside the sealed cavity (12), and a thermal expansion medium (14) is located in the thermal expansion compensation cavity (10). The output end of the micro pressure pump (11) is connected to the sealed cavity (12). The sealed cavity (12) is connected to the microlens unit (6) via the fluid pipe (13) through the micro flow control valve array (7) to achieve independent control of the fluid pressure inside different microlens units. The collaborative control unit (4) includes a microprocessor and a drive circuit. The microprocessor receives focal length adjustment instructions from the outside and generates control signals according to a preset control strategy. The drive circuit includes a thermal drive circuit, a pressure drive circuit, and a valve drive circuit. The thermal drive circuit is connected to the thin film heater array, the pressure drive circuit is connected to the micro pressure pump, and the valve drive circuit is connected to the micro flow control valve array to drive the thin film heater array, the micro pressure pump, and the micro flow control valve array to work. A high thermal conductivity transparent heat dissipation layer (5) is provided between the thermal drive module (2) and the pressure control module (3) to accelerate the removal of local Joule heat after the thermal drive module works.

2. The focal length dynamic adjustment device based on thermal drive and pressure control according to claim 1, characterized in that: The transparent substrate is any one of polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), or quartz glass.

3. The focal length dynamic adjustment device based on thermal drive and pressure control according to claim 1, characterized in that: The optical liquid (7) is any one of silicone oil, fluorinated liquid or ionic liquid with a refractive index in the range of 1.3-1.7; and when the optical liquid (7) is silicone oil and the transparent substrate is polydimethylsiloxane (PDMS), the inner wall of the microlens unit (6) is coated with an anti-swelling barrier layer, or when the transparent substrate is polydimethylsiloxane (PDMS), the optical liquid (7) is limited to fluorinated liquid or ionic liquid.

4. The focal length dynamic adjustment device based on thermal drive and pressure control according to claim 1, characterized in that: The thin-film heater (8) is an indium tin oxide (ITO) transparent heating film or a metal nanowire heating network with a thickness of 50-200 nm.

5. The focal length dynamic adjustment device based on thermal drive and pressure control according to claim 1, characterized in that: The preset control strategy is: a pressure-then-heat driven strategy and a parallel collaborative strategy; the pressure-then-heat driven strategy is: the collaborative control unit (4) opens the micro-flow control valve corresponding to the target microlens unit, drives the micro pressure pump (11) to perform coarse focus adjustment, and closes the corresponding micro-flow control valve to lock the fluid pressure after reaching the preset range; then the focus is finely adjusted through the heat driven module (2); the parallel collaborative strategy is: according to the preset focus-pressure-temperature mapping model, the parameters of the pressure control module and the heat driven module are adjusted synchronously.

6. A method for controlling the device according to any one of claims 1-5, characterized in that, The control method includes: Step S1: Obtain the focus adjustment command; Step S2: Based on the focal length adjustment command, generate a cooperative control signal through the cooperative control unit; Step S3: Based on the coordinated control signal, drive the pressure control module and the thermal drive module to change the focal length of the microlens unit to the target value through the coordinated effect of independent flow control and pressure maintenance and thermal deformation of the microflow control valve array.

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