A laser temperature control device and method with proportional-integral correction unit

Abstract

This invention discloses a laser temperature control device and method with a proportional-integral (PI) correction unit. The device includes a PI correction unit, a TEC controller, and a laser. The TEC controller integrates an amplifier and a PWM driver, while the laser integrates a TEC and a thermistor. The PI correction unit includes resistors R1 and R2, a capacitor C, and the amplifier in the TEC controller. One end of resistor R1 is connected to the negative input of the amplifier, and the other end is connected to the feedback output of the thermistor. One end of resistor R2 is connected to the negative input of the amplifier, and the other end is connected in series with one end of capacitor C. The other end of capacitor C is connected to the output of the amplifier. The positive input of the amplifier is set to the reference voltage V corresponding to the set temperature. ref The proportional-integral correction unit of the laser temperature control system is connected to the PWM driver, TEC, and thermistor in sequence via wires.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a laser temperature control device and method with a proportional-integral correction unit. Background Technology

[0002] Lasers, capable of producing high-brightness, monochromatic, and highly directional beams, are ideal light sources for optical measurement and are widely used in this field. However, the performance of lasers is affected by ambient temperature and their own power consumption, leading to internal temperature variations. For example, the laser threshold current increases with temperature, while the external differential quantum efficiency decreases, thus affecting the laser's output power; the laser oscillation wavelength increases with temperature, resulting in mode hopping; and the size of the laser resonant cavity and the output transverse mode are affected by temperature, thus influencing the far-field intensity distribution, etc., severely impacting the laser's performance, stability, and lifespan, and consequently affecting the measurement accuracy and stability of the optical measurement system. Therefore, constant temperature control of lasers is necessary. Existing lasers generally have a built-in TEC (Thermoelectric Cooler) to maintain the stability of the laser's operating temperature. Based on the thermoelectric effect, it regulates and controls the laser temperature by controlling the current in the thermoelectric module. However, the built-in TEC temperature control is a first-order control system, with poor temperature control accuracy and static temperature errors. Therefore, by introducing a proportional-integral (PI) correction stage into the laser's built-in TEC (Transient Temperature Control), static errors are eliminated, and high-precision temperature control of the laser is achieved even without special requirements on the dynamic characteristics of temperature control. This has significant practical engineering implications for improving the measurement accuracy and stability of optical measurement systems. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a laser temperature control device and method with a proportional-integral correction unit.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A laser temperature control device with a proportional-integral correction unit includes a proportional-integral correction unit, a TEC controller, and a laser. The TEC controller integrates an amplifier and a PWM driver, and the laser integrates a TEC and a thermistor.

[0006] The proportional-integral correction unit includes resistors R1 and R2, capacitor C, and an amplifier in the TEC controller. One end of resistor R1 is connected to the negative input terminal of the amplifier, and the other end is connected to the feedback output of the thermistor. One end of resistor R2 is connected to the negative input terminal of the amplifier, and the other end is connected in series with one end of capacitor C. The other end of capacitor C is connected to the output terminal of the amplifier. The positive input terminal of the amplifier is set to the reference voltage V corresponding to the set temperature. ref The proportional-integral (PI) correction unit is connected in sequence to the PWM driver, TEC, and thermistor via wires. When controlling the laser's temperature, the thermistor senses the laser's temperature change and outputs a corresponding feedback voltage to the PI correction unit. The PI correction unit then adjusts the voltage based on the feedback voltage and the reference voltage V corresponding to the set temperature. ref A control voltage is output to the PWM driver. The PWM driver controls the TEC heating or cooling according to the magnitude of the control voltage to achieve temperature control of the laser and minimize the difference between the real-time temperature and the set temperature of the laser.

[0007] The present invention also provides a laser temperature control method with a proportional-integral correction unit, based on the above-mentioned temperature control device, comprising:

[0008] (1) Simplify the heat conduction network of the laser and establish a heat transfer model using the lumped parameter method; the thermal resistance between the laser cavity and the environment is R. θ Ignore the thermal resistance R between the TEC via the bottom of the cavity, the heat sink, and the environment. θA The real-time heat flow generated by TEC is Laser cavity heat capacity C y The ambient temperature is T A The real-time temperature inside the laser cavity is T0(t). The heat transfer time-domain model and heat transfer frequency-domain model are expressed as equations (1) and (2), respectively, where t represents time and s represents frequency response. The temperature control of the laser itself belongs to a first-order control system, where the time constant τ1 = R θ C y ;

[0009]

[0010]

[0011] (2) In order to improve the temperature control accuracy and eliminate static error, a proportional-integral correction unit is introduced. The transfer function of the proportional-integral correction unit is K1(τ2s+1) / s, where K1=1 / (R1C) and τ2=R2C.

[0012] (3) The open-loop transfer function of the entire temperature control device with the addition of the proportional-integral correction unit is given by equation (3), which belongs to a second-order control system. In this system, the PWM driver controls the TEC, and the relationship between the TEC current and heat flow is considered linear, and is related to R... θ Together, they are equivalent to a proportional coefficient K2. The thermistor feeds back temperature information, converting temperature into voltage, with a proportional coefficient of K3. Next, all parameters involved in the temperature control device are designed and adjusted. The proportional coefficients K2, K3, and time constant τ1 are obtained experimentally by testing the unit step response without a proportional-integral correction unit. Specifically, a signal source capable of generating a unit step signal is connected to the input of the temperature control device without a proportional-integral correction unit. The unit step response is observed and recorded using data acquisition equipment such as an oscilloscope. K2, K3, and τ1 can be obtained from the recorded unit step response. Then, based on the set temperature and the corresponding reference voltage V... ref Design the proportional-integral (PI) correction unit parameters. Initialize the PI correction unit with appropriate resistors R1, R2, and capacitor C to obtain small initial values ​​for K1 (1 / R1C) and τ2 (R2C). Then observe the unit step response of the temperature control device. If the response is rapid but oscillations occur, increase R1 and gradually decrease K1. If the temperature control device responds slowly, decrease R1 and gradually increase K1. Continue until a K1 that can respond quickly without oscillations is found. Similarly, observe the unit step response of the temperature control device. If the temperature control device has a small steady-state error near the set temperature but oscillates or overshoots, decrease R2 and gradually decrease τ2. If the system's static error is large, increase R2 and gradually increase τ2. The goal is to find a τ2 that can eliminate steady-state error, making the actual temperature basically stable within the set temperature ±0.005℃ range, and minimizing oscillations.

[0013]

[0014] (4) After the temperature control device parameters are adjusted to the optimal level, the entire temperature control process is as follows: As the temperature control device continues to operate, the thermistor continuously monitors the laser temperature and feeds back the voltage corresponding to the actual temperature value to the proportional-integral correction unit. The proportional-integral correction unit compares the voltage corresponding to the actual temperature value with Vref, calculates the current temperature difference voltage signal, and outputs a control signal based on this temperature difference voltage signal to the TEC controller. According to the control signal, the TEC controller controls the TEC to heat or cool, adjusting the laser temperature accordingly. If the temperature is too low, the TEC will provide heating, and vice versa. This continues until the laser temperature stabilizes near the set value.

[0015] Furthermore, after adding a proportional-integral correction unit, the effect of ambient temperature change on laser temperature change in the temperature control device is less than 0.005℃.

[0016] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0017] 1. The temperature control device provided by this invention upgrades the original first-order control system to a second-order control system by introducing a proportional-integral correction unit into the commonly used TEC (Thermoelectric Cooler) temperature controller built into the laser. The proportional term handles the current error, and the integral term handles the accumulation of past errors. By observing the response of the temperature control device and continuously adjusting these two parameters, the laser temperature is ensured to remain stable near the set value, greatly improving the accuracy and stability of laser temperature control.

[0018] 2. The temperature control method of this invention involves a modeling method based on the lumped parameter method to establish a heat transfer model. The heat conduction network of the laser is simplified, and the heat transfer time-domain and frequency-domain models of the laser are obtained through parameters such as the thermal resistance between the laser cavity and the environment, the thermal resistance of the TEC through the bottom of the cavity and the heat sink and the environment, the real-time heat flow generated by the TEC, the heat capacity of the laser cavity, the ambient temperature, and the real-time temperature inside the laser cavity. This is a first-order model. Attached Figure Description

[0019] Figure 1 This is a simplified physical model diagram of the laser of the present invention, where T0 is the real-time temperature inside the laser cavity, and T... A Ambient temperature;

[0020] Figure 2 This is a thermal conductivity network diagram of the laser of the present invention, R. θ R is the thermal resistance between the laser cavity and the environment. θA The thermal resistance between the TEC via the bottom of the cavity, the heat sink, and the environment is negligible. For the real-time heat flow generated by TEC, C y For the heat capacity of the cavity;

[0021] Figure 3 This is a schematic diagram of the laser temperature control device of the present invention.

[0022] Figure 4 This is a system structure diagram of the laser temperature control device of the present invention;

[0023] Figure 5 This is a schematic diagram of the proportional-integral correction unit of the present invention;

[0024] Figures 6a to 6c These are the amplitude-frequency and phase-frequency characteristic curves of the original temperature control system, the temperature control device with a single proportional-integral correction unit, and the temperature control device with an added proportional-integral correction unit, respectively.

[0025] Figure 7a and Figure 7bThese are graphs showing the temperature change of the laser as a function of ambient temperature in the original temperature control system and the temperature control device with added proportional-integral correction unit. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0027] like Figures 1 to 5 As shown, this embodiment provides a laser temperature control device with a proportional-integral correction unit, including a proportional-integral correction unit, a TEC controller, and a laser; the TEC controller integrates an amplifier 4 and a PWM driver 5, and the laser integrates a TEC 6 and a thermistor 7.

[0028] The proportional-integral correction unit consists of resistor R11, resistor R22, capacitor C3, and amplifier 4 in the TEC controller. One end of resistor R11 is connected to the negative input terminal of the amplifier in the TEC controller, and the other end is connected to the feedback output of the thermistor in the laser. One end of resistor R22 is connected to the negative input terminal of the amplifier, and the other end is connected in series with one end of capacitor C3. The other end of capacitor C3 is connected to the output terminal of the amplifier. The positive input terminal of the amplifier is set to the reference voltage V corresponding to the set temperature. ref .

[0029] The proportional-integral (PI) correction unit is connected sequentially to the PWM driver, the TEC (thermal arrester) in the laser, and the thermistor via wires. For high-precision temperature control of the laser, the thermistor senses temperature changes and outputs a corresponding feedback voltage to the PI correction unit. The PI correction unit then adjusts the voltage based on this feedback voltage and the reference voltage V corresponding to the set temperature. ref A high-precision control voltage is output to the PWM driver. The PWM driver controls the TEC (heating or cooling) according to the magnitude of the control voltage to achieve high-precision temperature control of the laser, that is, the difference between the laser temperature and the set temperature is very small.

[0030] Specifically, this embodiment also provides a laser temperature control method with a proportional-integral correction unit, and a laser temperature control device with a proportional-integral correction unit, comprising:

[0031] First, see Figure 2 A simplified heat conduction network for the laser is constructed, and a heat transfer model is established using the lumped parameter method. The thermal resistance between the laser cavity and the environment is R. θ The thermal resistance of TEC between the bottom of the laser cavity, the heat sink, and the environment is R. θA The heat flux generated by the TEC is negligible; Cavity heat capacity C yThe ambient temperature is T A If the real-time temperature inside the cavity is T0(t), then the heat transfer time-domain and frequency-domain models can be expressed as equations (1) and (2), respectively. It can be seen that the temperature control of the laser itself is a first-order control system with low temperature control accuracy. The time constant τ1 = R θ C y .

[0032]

[0033]

[0034] Then, in order to improve the temperature control accuracy and eliminate static error, a proportional-integral correction unit is introduced. The transfer function of the proportional-integral correction unit is K1(τ2s+1) / s, where K1=1 / (R1C) and τ2=R2C.

[0035] Finally, all system parameters involved in the temperature control device are designed and adjusted. The proportional coefficient K2K3 and time constant τ1 can be obtained by testing the step response of the system without a proportional-integral correction unit. Then, the parameters of the proportional-integral correction unit are designed to ensure the stability and accuracy of the system. The open-loop transfer function of the entire temperature control device system is given by equation (3), which shows that it is a second-order control system. By adjusting its system parameters, the temperature control accuracy can be greatly improved. Among them, the PWM driver controls the TEC. The relationship between the TEC current and the heat flow is considered linear, and it is related to R. θ Together, they are equivalent to a proportional coefficient K2. The thermistor feeds back temperature information and converts the temperature into voltage, with a proportional coefficient of K3.

[0036]

[0037] This embodiment also conducted a laser temperature control experiment based on the aforementioned apparatus and method. By testing the transfer function of the original laser temperature control system without a proportional-integral (PI) correction unit, K2K3 = 88 and τ1 = 12 were obtained. Then, suitable resistors and capacitors were selected for the PI correction unit to ensure that the amplitude-frequency response curve of the overall open-loop transfer function crossed the 0dB point at -20dB / dec, obtaining sufficient phase margin. In this embodiment, the resistors and capacitors used correspond to K1 = 0.0455 and τ2 = 11.22. The amplitude-frequency and phase-frequency response curves of the original temperature control system, the PI correction unit, and the temperature control device with the PI correction unit are as follows: Figures 6a to 6c As shown in the figure. The laser was placed in a constant temperature chamber, and the chamber temperature was increased from 10℃ to 45℃ in 5℃ increments. The laser temperature of the original temperature control system and the temperature control device after adding a proportional-integral correction unit were tested respectively. The results are as follows. Figure 7a and Figure 7bAs shown, in the original temperature control system, for every 1°C change in ambient temperature, the laser temperature changes by 0.005°C, meaning an ambient temperature suppression ratio of 0.5%, which provides some temperature control. However, in the temperature control device with the added proportional-integral correction unit, changes in ambient temperature have almost no impact on the laser temperature. After each change in ambient temperature, the laser temperature recovers quickly, with the overall change not exceeding 0.005°C. Temperature control accuracy is significantly improved.

[0038] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A laser temperature control method with a proportional-integral correction unit, based on a laser temperature control device with a proportional-integral correction unit, comprising a proportional-integral correction unit, a TEC controller and a laser, wherein the TEC controller integrates an amplifier and a PWM driver, and the laser integrates a TEC and a thermistor; The proportional-integral correction unit includes resistors R1 and R2, capacitor C, and an amplifier in the TEC controller. One end of resistor R1 is connected to the negative input terminal of the amplifier, and the other end is connected to the feedback output of the thermistor. One end of resistor R2 is connected to the negative input terminal of the amplifier, and the other end is connected in series with one end of capacitor C. The other end of capacitor C is connected to the output terminal of the amplifier. The positive input terminal of the amplifier is set to the reference voltage V corresponding to the set temperature. ref The proportional-integral (PI) correction unit is connected in sequence to the PWM driver, TEC, and thermistor via wires. When controlling the laser's temperature, the thermistor senses the laser's temperature change and outputs a corresponding feedback voltage to the PI correction unit. The PI correction unit then adjusts the voltage based on the feedback voltage and the reference voltage V corresponding to the set temperature. ref A control voltage is output to a PWM driver, which controls the TEC (thermal energy storage device) for heating or cooling based on the control voltage to achieve temperature control of the laser, minimizing the difference between the real-time laser temperature and the set temperature. Its key feature is... include: (1) Simplify the heat conduction network of the laser and establish a heat transfer model using the lumped parameter method; the thermal resistance between the laser cavity and the environment is R. θ Ignore the thermal resistance R between the TEC via the bottom of the cavity, the heat sink, and the environment. θA The real-time heat flux generated by TEC is Laser cavity heat capacity C y The ambient temperature is T A The real-time temperature inside the laser cavity is T0(t). The heat transfer time-domain model and heat transfer frequency-domain model are expressed as equations (1) and (2), respectively, where t represents time and s represents the frequency response. The laser's temperature control is a first-order control system, where the time constant... τ 1= R θ C y ; （1）； （2）； (2) To improve temperature control accuracy and eliminate static error, a proportional-integral correction unit is introduced. The transfer function of the proportional-integral correction unit is given by equation (2). K 1( τ 2 s +1) / s In the formula K 1 = 1 / ( R 1 C ), τ 2= R 2 C ; (3) The open-loop transfer function of the entire temperature control device with a proportional-integral correction unit is given by equation (3), which belongs to a second-order control system; in which the PWM driver controls the TEC, and the relationship between the TEC current and the heat flow is considered linear, and... R θ Together they are equivalent to a proportionality coefficient. K 2. The thermistor provides temperature feedback, converting the temperature into voltage, with a proportionality coefficient of... K 3; Next, adjust all parameters involved in the temperature control device, including the proportional coefficient. K 2. K 3. Time constant τ 1. The unit step response of the uncorrected proportional-integral (PI) correction unit is obtained through experimental testing. Specifically, a signal source capable of generating a unit step signal is connected to the input terminal of the temperature control device without the PI correction unit. The unit step response is observed and recorded using data acquisition equipment, and the result is obtained from the recorded unit step response. K 2. K 3. τ 1; Then, based on the set temperature and the corresponding reference voltage V ref Set the parameters of the proportional-integral correction unit; （3）； (4) As the temperature control device continues to operate, the thermistor continuously monitors the temperature of the laser and feeds back the voltage corresponding to the actual temperature value to the proportional-integral correction unit. The proportional-integral correction unit compares the voltage corresponding to the actual temperature value with V. ref The system compares and calculates the current temperature difference voltage signal, and outputs a control signal based on this signal to the TEC controller. The TEC controller then controls the TEC to heat or cool to adjust the laser temperature until the laser temperature stabilizes near the set value.

2. The laser temperature control method with a proportional-integral correction unit according to claim 1, characterized in that, The process of setting the parameters of the proportional-integral correction unit is as follows: Select resistor R1, resistor R2, and capacitor C to initialize the proportional-integral correction unit, and obtain a... K 1. τ 2. Initial value; then observe the difference between the actual temperature and the set temperature of the temperature control device, and adjust accordingly. R 1. R 2 to change K 1. τ 2. The goal is to find a method that ensures the actual temperature remains essentially stable within ±0.005℃ of the set temperature. K 1. τ The value of 2.

3. The laser temperature control method with a proportional-integral correction unit according to claim 1, characterized in that, After adding a proportional-integral correction unit, the effect of ambient temperature change on laser temperature change in the temperature control device is less than 0.005℃.

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