Equivalent coding layered piezoelectric stack driver and stepping phase shift driving method thereof

Abstract

The invention discloses an equivalent coding layered piezoelectric stack driver and a stepping phase shift driving method thereof, and belongs to the technical field of phase shifters. According to the method, a piezoelectric stack is subjected to layering treatment, each layer is connected with a driving power supply through an independent electric control branch, an electric control branch module comprises an adjustable voltage dividing branch and a discharging branch, and binary switching of each piezoelectric layer between zero displacement and fixed displacement is achieved by combining a quick switch control module controlled by a single chip microcomputer. The step pitch consistency is ensured by adjusting the driving voltage layer by layer and accurately matching the step displacement of each layer, and the target phase shift step pitch can be adjusted according to the phase shift requirement. The method is simple in structure, does not need a complex closed-loop control system, effectively solves the problems of hysteresis and nonlinearity of a traditional piezoelectric stack, remarkably improves the system stability and the measurement precision, and is suitable for stepping phase shift control in high-precision interference measurement.

Description

Technical Field

[0001] This invention belongs to the field of phase shifter technology, specifically relating to an equivalent-coded layered piezoelectric stack driver and its step-type phase shift driving method. Background Technology

[0002] An interferometer is a precision measuring instrument based on the principle of optical interference. It uses the wavelength of light as its unit of measurement and boasts advantages such as high precision, high resolution, and good stability, making it widely used in optical processing and inspection, and micro / nano structure characterization. However, due to the low precision, low efficiency, and poor stability of interferograms in static conditions, phase-shifting interferometry has gradually developed. The basic principle of phase-shifting interferometry is to introduce an ordered phase change between two coherent beams in the interferometer, thereby obtaining multiple interference images under different phase states. Then, a phase reconstruction algorithm is used to solve for the precise phase distribution of the surface of the measured object, achieving nanometer-scale surface shape measurement.

[0003] Phase shift refers to the movement of the phase. It can be achieved by changing the optical path difference between the reference and test arms of the interferometer (mechanical phase shift) or by changing the wavelength of the light source (wavelength phase shift). The mechanical phase shifter is a crucial component of a phase-shifting interferometer; it is essentially a one-dimensional micro-displacer with ultra-high resolution, achieving phase shift by continuously micro-moving the lens along the optical axis. Most algorithms for recovering phase from phase-shifted interferograms share a common requirement: a constant step size for the phase shifter. Taking the commonly used four-step fixed-step phase shift as an example, the phase shifter drives the reference mirror to sequentially shift by a fixed optical path difference of 0°, 90°, 180°, and 270°, resulting in four interferograms with fixed phase shifts. The phase distribution is then obtained by solving a four-step phase shift algorithm. The performance of the phase shifter directly affects the measurement accuracy and precision of the phase-shifting interferometer; therefore, high requirements are placed on the phase shifter's motion resolution, linearity, stability, and anti-interference capabilities.

[0004] Piezoelectric stacks are widely used as driving elements in mechanical phase shifters. A piezoelectric stack is a high-performance micro-displacement actuator; under appropriate voltage, it can generate a displacement of approximately 0.1%-0.2% of its own length in the micrometer range, and possesses advantages such as high precision, high resolution, fast response, large driving force, small size, ease of control, stable performance, and no electromagnetic interference. However, due to the complex working mechanism of the piezoelectric effect, piezoelectric stacks have drawbacks such as nonlinearity, hysteresis, and creep. First, there is a significant nonlinearity between the piezoelectric stack displacement and the driving voltage, approximately 5%-10%; second, there is a large displacement difference between the voltage rise and fall curves of the piezoelectric stack, exhibiting significant hysteresis characteristics; third, when the driving voltage of the piezoelectric stack stabilizes, its displacement value changes slowly over time, reaching a stable value only after a certain period.

[0005] The aforementioned characteristics of piezoelectric stack drivers affect the overall accuracy and results of phase-shifting interferometry measurements. Therefore, nonlinear correction of the piezoelectric stack is crucial in practical applications. Currently, charge-driven methods, feedforward compensation methods, and feedback control methods are mainly used to achieve linear driving of piezoelectric stacks. The charge-driven method exhibits good linearity and resolution at high frequencies, but linearity decreases at low frequencies due to leakage current, drift, and other factors. Furthermore, practical charge amplifier circuits are complex and difficult to design. The feedforward compensation method can reduce hysteresis to some extent, but its model is complex, and real-time calculations place excessive demands on hardware. The feedback control method offers stable operation and good linear displacement output, but suffers from limitations in displacement resolution due to sensor resolution, low dynamic performance, and high sensor cost. Summary of the Invention

[0006] To eliminate the nonlinearity, hysteresis, and creep defects of piezoelectric stack drivers in mechanical phase shifters, and to solve the problems of complex driving circuits and control models, limited resolution and dynamic characteristics, and high hardware costs in existing charge-driven methods, feedforward compensation methods, and feedback control methods, this invention proposes an equivalent-coded hierarchical piezoelectric stack driver and its step-type phase-shifting driving method.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An equivalent-coded layered piezoelectric stack driver is used for displacement driving of mechanical phase shifters in a phase-shifting interferometer, comprising an equivalent-coded layered piezoelectric stack, a drive power supply module, an electrical control branch module, and a switch control module; The layered piezoelectric stack comprises sequentially connected in series. n piezoelectric layer P i Each layer is connected to the drive power supply module via parallel electronic control branch modules, and the control terminal of each electronic control branch module is connected to the respective control port I / O of the switch control module. i Corresponding connection, i =1, 2, ..., n ; Each electronic control branch module corresponds to the piezoelectric layer P of the corresponding layer. i displacement step D i Make precise adjustments to achieve the target phase shift step. D 0. The switch control module controls the rapid switching of each electronic control branch module to control the corresponding piezoelectric layer P. i Charging or discharging causes each piezoelectric layer P to... i The output displacement is within the target phase shift step. D Binary switching between 0 and zero; The switch control module sequentially controls the connection of the piezoelectric layers P applied to each layer. iThe voltage applied to each piezoelectric layer P i The displacement output is generated sequentially to achieve overall step-by-step phase shifting of the layered piezoelectric stack driver, and the phase applied to each piezoelectric layer P is disconnected sequentially or simultaneously. i The voltage on the piezoelectric layer P i Displacement reset.

[0008] Furthermore, the electronic control branch module includes a voltage divider branch, a discharge branch, and a switch control signal; the voltage divider branch is a fixed resistor. R i Adjustable resistor Ra i and charging switch S i A series of fixed resistors connected in series. R i The other end is connected to the negative terminal of the drive power module and grounded, charging switch S i The other end is connected to the positive terminal of the drive power module; Discharge branch is the discharge resistor Rc i and discharge switch Sc i The circuit consists of a series connection, a discharge branch, and a piezoelectric layer P. i Both ends are connected in parallel to a fixed resistor. R i The two ends; The fast switch module includes the charging switch S i and the discharge switch Sc i Control port I / O of the switch control module i Connect to the touch terminal of the fast switch module respectively, so that the charging switch S i and discharge switch Sc i Control port I / O i control signals K i They are in a complementary conduction state under high / low levels.

[0009] Furthermore, the fixed resistor R i The resistance range is 100kΩ to 1GΩ, and it is an adjustable resistor. Ra i The maximum resistance is R i 10% to 20%.

[0010] Furthermore, the driving power supply module is an amplitude-adjustable DC regulated power supply used to adjust all piezoelectric layers P i The driving reference voltage.

[0011] Furthermore, the fast-switching module includes at least 2 nA switching device, wherein the switching device is a power transistor or a solid-state relay.

[0012] Furthermore, the switch control module includes a microcontroller (MCU), and the MCU contains at least... n One control port, its control port I / O i Road control signals K i One-way control charging switch S i The on / off state of the circuit is controlled by one circuit, and the other circuit controls the discharge switch Sc via the inverter. i The on / off state of the charging switch S i With discharge switch Sc i They exhibit a complementary conduction relationship.

[0013] Furthermore, in the control signal K i When in a high-level state, the charging switch S i Close and discharge switch Sc i Disconnect, piezoelectric layer P i Fast charging and outputting the corresponding step displacement D i In control signal K i When in a low-level state, the charging switch S i Disconnect and discharge switch Sc i Closed, piezoelectric layer P i Rapid discharge and displacement reset via the discharge branch; Adjustable resistors of each electronic control branch module Ra i Used for fine adjustment of the corresponding piezoelectric layer P i Voltage U i This makes the piezoelectric layer P i At this voltage U i The step displacement below D i Phase shift step with target D 0. Strictly consistent.

[0014] Furthermore, each piezoelectric layer P i displacement step D i Precisely adjust to the target phase shift step D The specific steps for 0 are as follows: Step 11: Determine the number of phase shifting steps based on the phase shifting algorithm actually used in the phase shifting interferometer. m That is, the number of piezoelectric layers involved in the driving process, and then based on the wavelength of the laser light source used. λ Calculate the target phase shift step of a single piezoelectric layer D 0= λ / m ,in m ≤ n ; Step 12: The target phase shift step distance calculated above. D 0, combined with a single piezoelectric layer P i The amplitude of the output voltage of the drive power supply module is adjusted proportionally to the rated displacement data under rated voltage, so that when the adjustable resistor... Ra i When =0, the single-layer piezoelectric layer P i step displacement D i Slightly larger than the target phase shift step D 0; Step 13: The switch control module outputs periodic control signals. K i For piezoelectric layer P i Driven independently, while its displacement step size is monitored by a high-precision displacement sensor. D i And calculate the displacement step. D i relative to the target phase shift step D 0 error δ i =( D i - D 0) / D 0; Step 14: Based on the piezoelectric layer P i displacement step error δ i Fine adjustment of the corresponding adjustable resistor Ra i The size of the step error, until the step error is determined. δ i To achieve the required phase shift accuracy; Step 15: Repeat steps 13 and 14 until all piezoelectric layers P are formed. i displacement step error δ i All achieved the phase shift accuracy requirement, i.e., all piezoelectric layers P i In control signal K i Under its action, a constant displacement step can be generated. D i = D 0.

[0015] Furthermore, in step 12, when the adjustable resistor Ra i When =0, the piezoelectric layer P i displacement stepD i satisfy: D 0< D i ≤1.05 D 0.

[0016] Furthermore, each piezoelectric layer P i It is composed of several piezoelectric ceramic sheets of the same size, polarized along the thickness direction, stacked together, with adjacent ceramic sheets having opposite polarization directions.

[0017] Furthermore, the piezoelectric ceramic sheet is a circular sheet structure polarized along the thickness direction.

[0018] Furthermore, an equivalent-coded layered piezoelectric stack driver step-shift phase-shifting method is proposed, which utilizes the aforementioned equivalent-coded layered piezoelectric stack to implement a mechanical phase shifter. m Step-size phase shift drive, where m ≤ n The specific steps are as follows: Step 21: After receiving the trigger signal, the switch control module uses it as the starting point for timing and connects all control port I / O ports. i Output control signal K i Set to low level, so that all piezoelectric layers P i The output displacement is zero; Step 22, every interval Δ t The delay time, the switch control module will switch in a preset order m One control port I / O i Output control signal K i Sequentially set to high level to control each piezoelectric layer P i The corresponding phase shift step is generated sequentially. D 0, m P piezoelectric layer i Corresponding generation m Phase shift step D 0, driving a mechanical phase shifter to achieve step-by-step phase shifting; Step 23, when the last piezoelectric layer P m Generate the corresponding phase shift step D 0 and continue Δ t After the delay time, the layered piezoelectric stack drives the phase shifter to complete one cycle. m Step-by-step phase shifting with equal step spacing; subsequently, the switch control module will control all control port I / O. i Output m Road control signals K i Simultaneously set to low level, enabling all piezoelectric layers P in the layered piezoelectric stack to... iThe step displacement simultaneously decreases to zero; or at intervals Δ t The delay time is used to sequentially connect the pin I / O pins. i Output m Road control signals K i Set to low level to control each piezoelectric layer P i The step displacements are successively reduced to zero, thereby driving the phase shifter to achieve step-by-step phase shifting in the opposite direction.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are reflected in the following aspects: (1) This invention divides the traditional piezoelectric stack into equal parts. n By layering piezoelectric layers and digitally switching each piezoelectric layer, the output displacement of a single piezoelectric layer can be binary-switched between zero and a certain fixed value, thereby effectively eliminating the hysteresis of the output displacement of the piezoelectric stack under traditional analog voltage control.

[0020] (2) The present invention is achieved through n Each voltage divider circuit finely adjusts the driving voltage applied to each piezoelectric layer in the layered piezoelectric stack, which can achieve strict consistency in the displacement step of all piezoelectric layers, thereby effectively eliminating the displacement nonlinearity caused by the inconsistency of electromechanical parameters between piezoelectric layers.

[0021] (3) By adjusting the amplitude of the DC regulated power supply, the displacement step of each piezoelectric layer in the layered piezoelectric stack can be adjusted over a wide range, or by setting the number of piezoelectric layers involved in the drive, the cumulative displacement output can be changed, i.e. the overall displacement output of the layered piezoelectric stack. This can meet the requirements of different phase shifting interferometers for the phase shift step of the laser light source wavelength and different phase shifting algorithms, and has a wide range of applications.

[0022] (4) The present invention can realize high-precision step phase shifting of the phase shifter with simple open-loop digital drive. The drive circuit is simple and stable, requiring only common electronic components such as microcontroller, digital switch, and DC regulated power supply. It does not require complex closed-loop controller, digital-to-analog conversion circuit, expensive analog high-voltage amplifier, etc., and can effectively save circuit cost while ensuring accuracy, stability and anti-interference performance. Attached Figure Description

[0023] Figure 1 This is a block diagram illustrating the control principle of the equivalent-encoded layered piezoelectric stack driver and its step-phase-shifting driving method of the present invention. Figure 2 (a) is a schematic diagram of the traditional piezoelectric stack wiring method; Figure 2 (b) shows the relationship between the output displacement and the driving voltage of a conventional piezoelectric stack under analog voltage drive; Figure 2(c) is the equal-step analog voltage drive signal; Figure 2 (d) is a traditional piezoelectric stack in Figure 2 (c) The step displacement curve generated under the driving voltage; Figure 3 (a) is a schematic diagram of the wiring method for a 4-layer equivalent coding layered piezoelectric stack; Figure 3 (b) is a timing diagram of the step displacement of the layered piezoelectric stack and the driving voltage of each piezoelectric layer; Figure 4 This is one of the specific circuit diagrams for an equivalent-encoded layered piezoelectric stack driver and its step-type phase-shifting driving method. Detailed Implementation

[0024] To further illustrate the technical features of the present invention, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. These embodiments are merely preferred examples of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0025] like Figure 1 As shown, an equivalent-coded layered piezoelectric stack driver is used for displacement driving of the mechanical phase shifter in a phase-shifting interferometer. It includes an equivalent-coded layered piezoelectric stack 1, a drive power supply module 2, an electrical control branch module 3, and a switch control module 4. The drive power supply module 2 supplies power to the layered piezoelectric stack 1, and the switch control module 4 controls the on / off state of each branch within the electrical control branch module 3, thereby controlling the on / off state of each piezoelectric layer within the layered piezoelectric stack 1 to achieve charging displacement and discharging reset.

[0026] Layered piezoelectric stack 1 includes sequentially connected piezoelectric stacks 1 n piezoelectric layer P i , i =1, 2, ..., n Specifically, in this embodiment, each piezoelectric layer P i It is composed of several piezoelectric ceramic sheets of uniform size, polarized along the thickness direction, stacked together, with adjacent ceramic sheets having opposite polarization directions. The piezoelectric ceramic sheets are circular discs polarized along the thickness direction. Each piezoelectric layer P... i Mechanically, they are connected in series; electrically, they have independent positive and negative electrodes. Each layer is connected to the drive power supply module 2 via parallel and identically structured electronic control branch modules 3. The control terminals of each electronic control branch module 3 are respectively connected to the respective control ports (I / O) of the switch control module 4. i Corresponding connections. Thus, the various control port I / O ports of the switch control module 4 can be accessed. i The on / off state of each electrical control branch module 3 is controlled independently, and a digital switching control method is used to realize the corresponding piezoelectric layer P. i Charging or discharging.

[0027] Switch control module 4 controls the fast switching module of electrical control branch module 3 to switch on and off to control the piezoelectric layer P of the corresponding layer. i Charging or discharging causes each piezoelectric layer P to... i The output displacement is within the target phase shift step. D Binary switching between 0 and zero. Specifically, the electronic control branch module 3 includes a voltage divider branch 31, a discharge branch 32, and a switch control signal 33. The voltage divider branch 31 consists of a fixed resistor. R i Adjustable resistor Ra i and charging switch S i A series of fixed resistors connected in series. R i The other end is connected to the negative terminal of the drive power module 2 and grounded, charging switch S i The other end is connected to the positive terminal of the drive power module 2. The discharge branch 32 consists of a discharge resistor Rc. i and discharge switch Sc i The system is configured in series, consisting of discharge branch 32 and piezoelectric layer P. i Both ends are connected in parallel to a fixed resistor. R i The two ends.

[0028] In this embodiment, the driving power module 2 is used to adjust all piezoelectric layers P i The driving reference voltage includes an adjustable DC regulated power supply whose amplitude is continuously adjustable between zero and the rated voltage of the piezoelectric stack, thereby enabling control of the piezoelectric layer P. i Applying different driving voltages to achieve different phase shift steps D Wide range of adjustment (0). Fixed resistors in each voltage divider branch. R i The same resistance value can be used, ranging from 100kΩ to 1GΩ. The specific resistance value needs to be selected based on the DC amplitude of the DC regulated power supply to ensure the fixed resistor... R i Low power consumption; adjustable resistor Ra i The maximum resistance is approximately that of a fixed resistor. R i 10%-20% of the resistance value.

[0029] The fast-switching module includes a charging switch S i and discharge switch Sc i Corresponding to n A piezoelectric layer, charging switch S i and discharge switch Sc i The quantities are each n Therefore, the fast switch module includes at least 2 nThe switching device must be able to withstand the high voltage required for piezoelectric ceramic actuation; therefore, the switching device can be a power MOSFET or a solid-state relay. The control port I / O of the switch control module 4 is also included. i Connect to the touch terminal of the fast switch module respectively, so that the charging switch S i and discharge switch Sc i Control port I / O i control signals K i They exhibit complementary conduction states under high / low levels. In this embodiment, the switch control module 4 is mainly composed of a microcontroller (MCU), which contains at least... n One control port (I / O pin). n Circuit switch control signal K i From the I / O of the microcontroller MCU i The output is connected to the corresponding charging switch S. i The control terminal, and the other path through inverter I i After inverting the voltage level, connect it to the corresponding discharge switch Sc. i The control terminal, corresponding to the piezoelectric layer P i Charging switch S i With discharge switch Sc i They exhibit a complementary conduction relationship, i.e., charging switch S i and discharge switch Sc i The opening and closing states are opposite. In this embodiment, the charging switch S i With discharge switch Sc i If the control logic of the two switches is the same, that is, both are normally open; if the control logic of the two switches is opposite, that is, one is normally open and the other is normally closed, then the switch control signal... K i It can be connected to the charging switch S at the same time. i With discharge switch Sc i The control terminal, without the inverter I i Preferably, based on the control signal requirements of the fast switching module, n Circuit switch control signal K i From the port I / O of the microcontroller MCU i After output, the power can be amplified first, and then connected to the control terminal of the fast switching module.

[0030] If the charging switch S i With discharge switch Sc i The piezoelectric layer P closes when the control signal is high and opens when the control signal is low. i The working process is as follows: The microcontroller (MCU) connects to the pin I / O... iOutput control signal K i When the voltage is high, the charging switch S i Close and discharge switch Sc i Disconnected, the DC regulated power supply (DC) supplies voltage to the piezoelectric layer P through voltage divider branch 31. i Fast charging to voltage U i Piezoelectric layer P i In voltage U i A fixed step displacement is generated under the action. D i When the control signal K i When switched to a low level, the charging switch S i Disconnect and discharge switch Sc i Closed, piezoelectric layer P i The voltage is rapidly discharged to zero through discharge branch 32, and its output displacement D i It also quickly drops to zero, achieving displacement reset. The function of discharge branch 32 is to... i Provides a rapid discharge path when power is off, enabling the piezoelectric layer P i The voltage across the terminals drops rapidly to zero, thus causing the step displacement of that layer to drop rapidly to zero. Discharge resistor Rc i The resistance value can be determined based on the piezoelectric layer P. i equivalent capacitance C i The required size and discharge time are calculated.

[0031] Adjustable resistors of each electronic control branch module Ra i Used for fine adjustment of the corresponding piezoelectric layer P i Voltage U i This makes the piezoelectric layer P i At this voltage U i The step displacement below D i Phase shift step with target D 0. Strictly consistent. Specifically, in the charging switch S... i When closed, adjust the adjustable resistor. Ra i The size of the material applied to the piezoelectric layer P can be precisely adjusted. i Both ends (i.e., fixed resistors) R i Voltage at both ends U i Size, thus affecting the piezoelectric layer P i displacement stepD i Fine adjustments are made to achieve the displacement steps of all piezoelectric layers. D i Strict consistency. In the piezoelectric layer P i displacement step D i After fine-tuning, during subsequent operation, the charging switch S i After closure, the single-layer piezoelectric layer P can be i The output displacement is between zero and a certain fixed value (target phase shift step). D The binary switching between 0 and 0 eliminates the hysteresis of the piezoelectric stack output displacement under traditional analog voltage control.

[0032] The equivalent-encoded layered piezoelectric stack of the present invention is used in mechanical phase shifters. m Before the fixed-step phase shift operation, each piezoelectric layer P needs to be... i displacement step D i Precisely adjust to the target phase shift step D 0. The specific steps are as follows: Step 11: Determine the number of phase shifting steps based on the phase shifting algorithm actually used in the phase shifting interferometer. m That is, the number of piezoelectric layers involved in the driving process, and then based on the wavelength of the laser light source used. λ Calculate the target phase shift step of a single piezoelectric layer D 0= λ / m ,in m ≤ n .

[0033] Step 12: The target phase shift step distance calculated above. D 0, combined with a single piezoelectric layer P i The amplitude of the output voltage of the drive power supply module 2 (DC regulated power supply) is adjusted proportionally to the rated displacement data under rated voltage, so that when the adjustable resistor... Ra i When =0, the single-layer piezoelectric layer P i step displacement D i Greater than the target phase shift step D 0 represents the step displacement. D i The precise adjustment leaves a margin. Preferably, when the adjustable resistor... Ra i When =0, it corresponds to the voltage U i The underlying piezoelectric layer P i displacement step D i satisfy: D 0<D i ≤1.05 D 0.

[0034] Step 13: Switch control module 2 outputs periodic control signals. K i For piezoelectric layer P i It is driven independently, while its displacement step size is monitored by a high-precision displacement sensor (such as a laser interferometer, capacitive displacement sensor, etc.). D i And calculate the displacement step. D i relative to the target phase shift step D 0 error δ i =( D i - D 0) / D 0.

[0035] Step 14: Based on the piezoelectric layer P i displacement step error δ i Fine adjustment of the corresponding adjustable resistor Ra i The size of the step error, until the step error is determined. δ i To achieve phase shift accuracy requirements (such as error threshold | δ i (∣≦0.05%).

[0036] Step 15: Repeat steps 13 and 14 until all piezoelectric layers P are formed. i displacement step error δ i All achieved the phase shift accuracy requirement, i.e., all piezoelectric layers P i In control signal K i Under its action, a constant displacement step can be generated. D i = D 0.

[0037] The above steps are used to separate each piezoelectric layer P of the layered piezoelectric stack 1. i displacement step D i Precisely adjust to the target phase shift step D After 0, the switch control module 2 sequentially controls the connection of the piezoelectric layers P applied to each layer. i The voltage applied to each piezoelectric layer P i The displacement output is generated sequentially to achieve overall step-by-step phase shifting of the layered piezoelectric stack driver, and the phase applied to each piezoelectric layer P is disconnected sequentially or simultaneously.i The voltage on the piezoelectric layer P i Displacement reset. (Through...) n Each voltage divider circuit finely adjusts the driving voltage applied to each piezoelectric layer in the layered piezoelectric stack 1, achieving strict consistency in the displacement step of all piezoelectric layers, and further eliminating the displacement nonlinearity caused by the inconsistency of electromechanical parameters between piezoelectric layers.

[0038] This layered piezoelectric stack driver is applied to high-precision step-shift phase shifting of mechanical phase shifters in phase-shifting interferometers. This invention proposes an equivalent-encoded layered piezoelectric stack driver step-shift phase shifting method, applying the aforementioned equivalent-encoded layered piezoelectric stack driver to realize the mechanical phase shifter... m Step-size phase shift drive, where m ≤ n The specific steps are as follows: Step 21: After receiving the trigger signal, the switch control module 4 (MCU) uses it as the timing start point and connects all control port I / O ports. i Output control signal K i Set to low level, so that all piezoelectric layers P i The output displacement is zero.

[0039] Step 22, every interval Δ t Delay time (Δ) t Based on the exposure time setting of the CCD sampling the interferogram, the switch control module 4 will switch in a preset sequence. m One control port I / O i Output control signal K i Sequentially set to high level to control each piezoelectric layer P i The corresponding phase shift step is generated sequentially. D 0, m P piezoelectric layer i Corresponding generation m Phase shift step D 0, driving a mechanical phase shifter to achieve step-by-step phase shifting; Step 23, when the last piezoelectric layer P m Generate the corresponding phase shift step D 0 and continue Δ t After the delay time, the layered piezoelectric stack 1 drives the phase shifter to complete one cycle. m Step-by-step phase shifting with equal step spacing; subsequently, switch control module 4 will control all control port I / O... i Output m Road control signals K i Simultaneously set to low level, enabling all piezoelectric layers P of the layered piezoelectric stack 1 to...i The step displacement simultaneously decreases to zero; or at intervals Δ t During the delay time, the switch control module 4 sequentially switches the pin I / O pins. i Output m Road control signals K i Set to low level to control each piezoelectric layer P i The step displacements are successively reduced to zero, thereby driving the phase shifter to achieve step-by-step phase shifting in the opposite direction. At the same time, another set of interferometric images is acquired for analysis or phase reconstruction.

[0040] Through the above adjustment and driving methods, the consistent adjustment of the output displacement step of each layer of the layered piezoelectric stack and the high-precision stepping phase shifting drive of the mechanical phase shifter can be achieved.

[0041] The following uses a piezoelectric stack structure with 4 piezoelectric layers as an example to conduct performance tests and comparisons between the traditional voltage-driven wiring method and the layered digital-driven wiring method of the present invention.

[0042] like Figure 2 As shown in (a), this is a schematic diagram of a traditional piezoelectric stack wiring method, in which all piezoelectric layers are electrically connected in parallel and connected using the same simulated voltage source. U drive. Figure 2 (b) shows the relationship between the output displacement and the driving voltage of a traditional piezoelectric stack under analog voltage drive. It can be seen that the output displacement exhibits significant hysteresis and nonlinearity as the driving voltage changes. When the output displacement is... Figure 2 When the equal-step analog voltage drive signal shown in (c) is applied to a conventional piezoelectric stack, the piezoelectric stack will output as follows: Figure 2 As shown in (d), the step displacement shows that there is a significant nonlinear error between each step, and there is a significant misalignment of the step displacement in different directions, i.e., hysteresis characteristics.

[0043] like Figure 3 As shown in (a), this is a schematic diagram of a 4-layer equivalent-coded layered piezoelectric stack wiring method. Figure 3 As shown in (b), to drive the layered piezoelectric stack to move in a step-like manner in different directions, and each piezoelectric layer P i Timing diagram of the driving voltage. Due to the voltage applied to each piezoelectric layer P i The voltage on it is only zero and zero. U i Two values, P for each piezoelectric layer i The output displacement is only zero and... D i Two values ​​eliminate displacement hysteresis. Then, the driving voltage for each piezoelectric layer is applied through a voltage divider branch. U i Fine-tuning allows each piezoelectric layer P istep displacement D i Strict consistency is achieved, thereby further eliminating the nonlinearity of the displacement.

[0044] like Figure 4 As shown, this is to adopt the following Figure 3 (a) shows a specific embodiment of the circuit schematic of the high-precision step-by-step phase-shifting driving method of the present invention when a four-layer equivalent-coded piezoelectric stack is used. Each piezoelectric layer P i The equivalent capacitance is C i , i =1, 2, 3, 4. The switch control module 4 is mainly composed of an STM32 microcontroller, and the switch control signals are... K i From the pin I / O of the STM32 microcontroller i The output, after being amplified by a transistor, is connected to the charging optocoupler relay S. i One control terminal, the other via inverter I i The voltage level is inverted, then amplified by a transistor, and finally connected to the discharge optocoupler relay Sc. i One of the control terminals. Optocoupler relay S i and Sc i The other control terminal is connected to a +5V external bias power supply.

[0045] When control signal K i When the signal is high, the charging optocoupler relay S i With both output terminals in the ON state, the discharge optocoupler relay Sc i Both output terminals are disconnected; the DC regulated power supply supplies power to the piezoelectric layer P through a voltage divider branch. i Fast charging to voltage U i Piezoelectric layer P i In voltage U i A fixed step displacement is generated under the action. D i When the control signal K i When the level is low, the charging optocoupler relay S i With both output terminals in the open state, the discharge optocoupler relay Sc i Both output terminals are in the ON state. Piezoelectric layer P i The output displacement is rapidly discharged to zero through the discharge branch. D i It also quickly dropped to zero.

[0046] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An equivalent-encoded layered piezoelectric stack driver, applied to the displacement driving of a mechanical phase shifter in a phase-shifting interferometer, characterized in that: It includes a hierarchical piezoelectric stack with equivalent encoding, a drive power supply module, an electronic control branch module, and a switch control module; The layered piezoelectric stack comprises sequentially connected in series. n piezoelectric layer P i Each layer is connected to the drive power supply module via parallel electronic control branch modules, and the control terminal of each electronic control branch module is connected to the respective control port I / O of the switch control module. i Corresponding connection, i =1, 2, ..., n ; Each electronic control branch module corresponds to the piezoelectric layer P i displacement step D i Make precise adjustments to achieve the target phase shift step. D 0. The switch control module controls the rapid switching of each electrical control branch module to control the piezoelectric layer P of the corresponding layer. i Charging or discharging causes each piezoelectric layer P to... i The output displacement is within the target phase shift step. D Binary switching between 0 and zero; The switch control module sequentially controls the connection of the piezoelectric layers P applied to each layer. i The voltage on the surface causes each piezoelectric layer P to... i The displacement output is generated sequentially to achieve overall step-by-step phase shifting of the layered piezoelectric stack driver, and the phase applied to each piezoelectric layer P is disconnected sequentially or simultaneously. i The voltage on the piezoelectric layer P i Displacement reset.

2. The equivalent-encoded layered piezoelectric stack driver according to claim 1, characterized in that: The electronic control branch module includes a voltage divider branch, a discharge branch, and a switch control signal. The voltage divider branch is a fixed resistor. R i Adjustable resistor Ra i and charging switch S i A series of fixed resistors connected in series. R i The other end is connected to the negative terminal of the drive power module and grounded, charging switch S i The other end is connected to the positive terminal of the drive power module; Discharge branch is the discharge resistor Rc i and discharge switch Sc i The circuit consists of a series connection, a discharge branch, and a piezoelectric layer P. i Both ends are connected in parallel to a fixed resistor. R i The two ends; The fast switch module includes the charging switch S i and the discharge switch Sc i Control port I / O of the switch control module i Connect to the touch terminal of the fast switch module respectively, so that the charging switch S i and discharge switch Sc i Control port I / O i control signals K i They are in a complementary conduction state under high / low levels.

3. The equivalent-encoded layered piezoelectric stack driver according to claim 2, characterized in that: The fixed resistor R i The resistance range is 100kΩ to 1GΩ, and it is an adjustable resistor. Ra i The maximum resistance is R i 10% to 20%.

4. The equivalent-encoded layered piezoelectric stack driver according to claim 2, characterized in that: The driving power supply module is an amplitude-adjustable DC regulated power supply used to adjust all piezoelectric layers P i The driving reference voltage.

5. The equivalent-encoded layered piezoelectric stack driver according to claim 2, characterized in that: The fast-switching module includes at least 2 n A switching device, wherein the switching device is a power transistor or a solid-state relay.

6. The equivalent-encoded layered piezoelectric stack driver according to claim 5, characterized in that: The switch control module includes a microcontroller MCU, and the microcontroller MCU contains at least... n One control port, its control port I / O i Road control signals K i One-way control charging switch S i The on / off state of the circuit is controlled by one circuit, and the other circuit controls the discharge switch Sc via the inverter. i The on / off state of the charging switch S i With discharge switch Sc i They exhibit a complementary conduction relationship.

7. The equivalent-encoded layered piezoelectric stack driver according to any one of claims 2-6, characterized in that: In control signal K i When in a high-level state, the charging switch S i Close and discharge switch Sc i Disconnect, piezoelectric layer P i Fast charging and outputting the corresponding step displacement D i In control signal K i When in a low-level state, the charging switch S i Disconnect and discharge switch Sc i Closed, piezoelectric layer P i Rapid discharge and displacement reset via the discharge branch; Adjustable resistors of each electronic control branch module Ra i Used for fine adjustment of the corresponding piezoelectric layer P i Voltage U i This makes the piezoelectric layer P i At this voltage U i Step displacement D i Phase shift step with target D 0. Strictly consistent.

8. The equivalent-encoded layered piezoelectric stack driver according to claim 7, characterized in that: Each piezoelectric layer P i displacement step D i Precisely adjust to the target phase shift step D The specific steps for 0 are as follows: Step 11: Determine the number of phase shifting steps based on the phase shifting algorithm actually used in the phase shifting interferometer. m That is, the number of piezoelectric layers involved in the driving process, and then based on the wavelength of the laser light source used. λ Calculate the target phase shift step of a single piezoelectric layer D 0= λ / m ,in m ≤ n ; Step 12: The target phase shift step distance calculated above. D 0, combined with a single piezoelectric layer P i The amplitude of the output voltage of the drive power supply module is adjusted proportionally to the rated displacement data under rated voltage, so that when the adjustable resistor... Ra i When =0, the single-layer piezoelectric layer P i step displacement D i Greater than the target phase shift step D 0; Step 13: The switch control module outputs periodic control signals. K i For piezoelectric layer P i Driven independently, while its displacement step size is monitored by a high-precision displacement sensor. D i And calculate the displacement step. D i relative to the target phase shift step D 0 error δ i = ( D i - D 0) / D 0; Step 14: Based on the piezoelectric layer P i displacement step error δ i Fine adjustment of the corresponding adjustable resistor Ra i The size of the step error, until the step error is determined. δ i To achieve the required phase shift accuracy; Step 15: Repeat steps 13 and 14 until all piezoelectric layers P are formed. i displacement step error δ i All piezoelectric layers P have met the phase shift accuracy requirements, i.e., all Piezoelectric layers P have achieved the required phase shift accuracy. i In control signal K i Under its action, a constant displacement step can be generated. D i = D 0。 9. The equivalent-encoded layered piezoelectric stack driver according to claim 8, characterized in that: In step 12, when the adjustable resistor Ra i When =0, the piezoelectric layer P i displacement step D i satisfy: D 0< D i ≤1.05 D 0.

10. The equivalent-encoded layered piezoelectric stack driver according to any one of claims 1 to 6, or 8 or 9, characterized in that: Each piezoelectric layer P i It is composed of several piezoelectric ceramic sheets of the same size, polarized along the thickness direction, stacked together, with adjacent ceramic sheets having opposite polarization directions.

11. The equivalent-encoded layered piezoelectric stack driver according to claim 10, characterized in that: The piezoelectric ceramic sheet is a circular sheet structure polarized along the thickness direction.

12. A step-type phase-shifting driving method using an equivalent-coded layered piezoelectric stack driver, employing an equivalent-coded layered piezoelectric stack driver as described in any one of claims 1 to 11 to realize a mechanical phase shifter. m Step-size phase shift drive, where m ≤ n The specific steps are as follows: Step 21: After receiving the trigger signal, the switch control module uses it as the starting point for timing and connects all control port I / O ports. i Output control signal K i Set to low level, so that all piezoelectric layers P i The output displacement is zero; Step 22, every interval Δ t The delay time, the switch control module will switch in a preset order m One control port I / O i Output control signal K i Sequentially set to high level to control each piezoelectric layer P i The corresponding phase shift step is generated sequentially. D 0, m P piezoelectric layer i Corresponding generation m Phase shift step D 0, driving a mechanical phase shifter to achieve step-by-step phase shifting; Step 23, when the last piezoelectric layer P m Generate the corresponding phase shift step D 0 and continue Δ t After the delay time, the layered piezoelectric stack drives the phase shifter to complete one cycle. m Step-by-step phase shifting with equal step spacing; subsequently, the switch control module will control all control port I / O. i Output m Road control signals K i Simultaneously set to low level, enabling all piezoelectric layers P in the layered piezoelectric stack to... i The step displacement simultaneously decreases to zero; or at intervals Δ t The delay time is used to sequentially connect the pin I / O pins. i Output m Road control signals K i Set to low level to control each piezoelectric layer P i The step displacements are successively reduced to zero, thereby driving the phase shifter to achieve step-by-step phase shifting in the opposite direction.

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