JP2009025424A - Temperature control method and wavelength conversion laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify constitution by preventing temperature of an object to be temperature controlled from overshooting the target temperature and rising immediately after the turning-on of power. <P>SOLUTION: A wavelength conversion laser device includes a PID circuit (25) to PID control a Peltier device (27) based on a difference (ΔT) between a set temperature (Ts') and a temperature (Tx) of the object, and a temperature control circuit (20) to make the set temperature (Ts') be equal to the surrounding temperature (Tc) at the turning-on of the power, and subsequently to change the set temperature (Ts') from the surrounding temperature (Tc) into the target temperature (Ts) with a first order lag function of a predetermined time constant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a temperature control method and a wavelength conversion laser device, and more specifically, a temperature at which the temperature of a temperature control target can be suppressed from being excessively higher than a target temperature immediately after power is turned on and the configuration can be simplified. The present invention relates to a control method and a wavelength conversion laser device.

  In order to keep the wavelength-converted optical output above a certain level, there is known a “wavelength conversion laser” that performs temperature control to keep an optical resonator including a semiconductor laser and a nonlinear optical element in a predetermined temperature range (for example, a patent) Reference 1).

On the other hand, when the deviation is larger than the deviation width corresponding to the proportional band, the integration operation is turned off, and within the deviation width, the deviation is in the range of 0 to 1 and the smaller the deviation is, the larger the coefficient is, the larger the deviation is, and the integral operation is performed. A method for cutting the integration operation of a PID controller ”is known (for example, see Patent Document 2).
JP-A-8-171106 JP-A-8-16204

As a temperature control method in the conventional wavelength conversion laser device, PI control or PID control is generally used. In temperature control by PI control or PID control, if the deviation between the set temperature and <-control target temperature is large when the power is turned on, when the deviation decreases, that is, when the set temperature reaches the set temperature <- Since the operation amount due to the integral operation becomes excessive, an excessive amount of control is generated (because the undershoot is also taken into account).
However, when performing control to keep the light output constant, if an excessive amount of overshoot occurs in the temperature to be controlled, the light output deviates from a temperature region where the light output exceeds a certain level, causing a temporary decrease in output. This is a particular problem in applications that require stability of light output immediately after power-on. Also, if the light output has a hysteresis characteristic with respect to the control target temperature, the control target temperature that is temporarily overrun is in a steady state, that is, no output exceeding a certain level can be obtained even if it reaches the set temperature. Problems arise.

On the other hand, if the technique disclosed in Patent Document 2 is used, the integration operation is turned off at the time of rising, so that it is possible to suppress the temperature of the control target from exceeding the set temperature. This suppression effect becomes higher when the deviation width corresponding to the proportional band is smaller.
However, since the optical resonator of a wavelength conversion laser device ⇒ Proportional operation cannot be increased, a thermal load that does not allow the proportional operation to be increased so much that the deviation width corresponding to the proportional band has a certain size. There is a problem that a sufficient suppression effect cannot be obtained.

Moreover, in patent document 2, it has the structure which changes the coefficient which controls integral operation | movement continuously according to a deviation.
However, when it is desired to simplify the structure of the laser head including the drive system in the wavelength conversion laser device, it is difficult to mount programmable circuit elements, and the circuit configuration is as compact as possible using general-purpose or dedicated discrete elements. Therefore, it is not realistic to change the coefficient for controlling the integration operation continuously according to the deviation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control method and a wavelength conversion laser device that can suppress the temperature control target temperature from exceeding the set temperature and increase immediately after the power is turned on, and can simplify the configuration. It is in.

In a first aspect, the present invention is a temperature control method for controlling a target temperature (Tx) by PID control based on a deviation (ΔT) between a set temperature (Ts ′) and a target temperature (Tx), the power source of the target At the time of charging, the environmental temperature (Tc) is set as the set temperature (Ts ′), and then the set temperature (Ts ′) is changed from the environmental temperature (Tc) to the target temperature (Ts) by a first-order lag function of a predetermined time constant. A temperature control method characterized by changing the temperature is provided.
In the temperature control method according to the first aspect, the environmental temperature (Tc) becomes the set temperature (Ts ′) when the power is turned on when the target temperature (Tx) matches the environmental temperature (Tc). ΔT) becomes zero. After the power is turned on, the target temperature (Tx) changes. If the time constant of the first-order lag function is set appropriately, the set temperature (Ts') becomes the target temperature at almost the same rate of change as the target temperature (Tx). Since the deviation (ΔT) is always maintained at a small value, the target temperature (Tx) converges to the target temperature (Ts). Thus, since the deviation (ΔT) is always maintained at a small value, it is possible to suppress the target temperature (Tx) from exceeding the target temperature (Ts) due to overintegration immediately after the power is turned on. In addition, the configuration can be simplified.

In a second aspect, the present invention relates to a semiconductor laser (1), a solid-state laser medium (3) that is excited by the semiconductor laser (1) and outputs fundamental light, and a nonlinear optical element (4) that converts the wavelength of the fundamental light. ) Including an optical resonator (6), heat generating means (27) capable of heating the semiconductor laser (1) and the optical resonator (6), the semiconductor laser (1) and the optical resonator (6) The target temperature detecting means (28) for detecting the target temperature (Tx), which is the temperature of the target temperature, and the PID of the heat generating means (27) based on the deviation (ΔT) between the set temperature (Ts ′) and the target temperature (Tx) The PID control means (25, 26) to be controlled, and when the power is turned on, the environmental temperature (Tc) is set to the set temperature (Ts ′), and the target temperature (Tc) is determined from the environmental temperature (Tc) as a function of a first-order lag. Ts) to the set temperature Provided is a wavelength conversion laser device (100, 100 ′) characterized by comprising set temperature control means (21, 22, 23) for changing the degree (Ts ′).
In the wavelength conversion laser device (100, 100 ′) according to the second aspect, the environmental temperature (Tc) is set to the set temperature (Ts ′) when the target temperature (Tx) coincides with the environmental temperature (Tc). ), The deviation (ΔT) becomes zero. After the power is turned on, the target temperature (Tx) changes. If the time constant of the first-order lag function is set appropriately, the set temperature (Ts') becomes the target temperature at almost the same rate of change as the target temperature (Tx). Since the deviation (ΔT) is always maintained at a small value, the target temperature (Tx) converges to the target temperature (Ts). In this way, since the deviation (ΔT) is always maintained at a small value, it is possible to suppress the target temperature (Tx) from exceeding the target temperature (Ts) immediately after the power is turned on by overintegration. Further, since the first-order lag function can be realized with a simple circuit configuration, the configuration can be simplified, and it is also useful in a small and portable wavelength conversion laser device such as battery drive.

  According to the temperature control method and the wavelength conversion laser apparatus of the present invention, it is possible to suppress the temperature control target temperature from exceeding the set temperature and increasing immediately after the power is turned on. In addition, the configuration can be simplified.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is an explanatory diagram illustrating a wavelength conversion laser device 100 according to the first embodiment.
This wavelength conversion laser device 100 includes a semiconductor laser 1 that generates excitation laser light, a condensing lens system 2 that condenses the excitation laser light, a reflection surface formed on the incident surface of the excitation laser light, and the excitation laser light. An optical resonator 6 is formed between the solid-state laser medium 3 that is excited to generate fundamental wave light, the nonlinear optical element 4 that generates second harmonic light when the fundamental wave light is incident, and the reflecting surface of the solid-state laser medium 3. An output-side mirror 5 having a reflecting surface, a beam splitter 7 that transmits a part of the output laser light output from the output-side mirror 5 to the outside and branches the remainder, and a photodiode that receives the branched light and converts it into an electrical signal 8, a temperature control unit 9 having a Peltier element 27 and a target temperature sensor 28 for controlling the temperature of the semiconductor laser 1 and the optical resonator 6, and a half for supplying a driving current to the semiconductor laser 1. The body laser drive circuit 12, the Peltier element drive circuit 26 that supplies a drive current to the Peltier element 27, the environmental temperature sensor 29 that detects the environmental temperature Tc, and the target temperature Tx detected by the target temperature sensor 28 become the target temperature Ts. The temperature control circuit 20 that controls the Peltier element driving circuit 26 so as to match, and the semiconductor laser driving circuit 12 are controlled so that the intensity of the branched light received by the photodiode 8 is constant, and the target temperature Ts is supplied to the temperature control circuit 20. And a control unit 11 for providing the above.

  The temperature adjustment circuit 20 includes a subtractor 21 that outputs a temperature difference between the target temperature Ts and the environmental temperature Tc, a primary delay circuit 22 that transmits the output of the subtractor 21 as a function of a primary delay of a predetermined time constant, and a primary delay. An adder 23 that adds the environmental temperature Tc to the output of the circuit 22 to obtain a set temperature Ts ′, a difference unit 24 that outputs a deviation ΔT between the set temperature Ts ′ and the target temperature Tx, and a Peltier so that the deviation ΔT becomes zero. And a PID circuit 25 that performs PID control of the element driving circuit 26.

The set temperature Ts ′ is expressed by the following equation, where t is the elapsed time since the power is turned on, and τ is the time constant of the first-order lag function corresponding to the thermal time constant of the semiconductor laser 1 and the optical resonator 6. It is.
Ts ′ = (Ts−Tc) {1−exp (−t / τ)} + Tc

FIG. 2 is a graph showing changes in the set temperature Ts ′.
When the power is turned on, Ts ′ = Tc, and then the time constant τ changes from Ts ′ = Tc to Ts ′ = Ts.

FIG. 3 is a graph showing an actual measurement result of a change in target temperature in an actual machine.
The solid line is the result of τ = 9 seconds, the dotted line is τ = 8 seconds, and the broken line is the result of τ = 7 seconds. A two-dot chain line is a comparative example in the case where Ts ′ = Ts at the same time when the power is turned on.
In the comparative example, the target temperature Tx is much higher than the target range Ts and is high, but all of τ = 9 seconds, τ = 8 seconds, and τ = 7 seconds are improved from the comparative example. Therefore, if it sets in the range of (tau) = 9 second-7 second, it can suppress that temperature control object temperature goes too much and becomes higher than preset temperature immediately after power-on.

FIG. 4 is a graph showing another actual measurement result of the change in the target temperature in the actual machine.
The solid line is the result of τ = 9 seconds, the dotted line is τ = 8 seconds, and the broken line is the result of τ = 7 seconds. A two-dot chain line is a comparative example in the case where Ts ′ = Ts at the same time when the power is turned on.
In the comparative example, the target temperature Tx is much higher than the target range Ts and is high, but all of τ = 9 seconds, τ = 8 seconds, and τ = 7 seconds are improved from the comparative example. Therefore, if it sets in the range of (tau) = 9 second-7 second, it can suppress that temperature control object temperature goes too much and becomes higher than preset temperature immediately after power-on.

According to the wavelength conversion laser device 100 of the first embodiment, the following effects can be obtained.
(1) When the power is turned on when the target temperature Tx matches the environmental temperature Tc, the environmental temperature Tc becomes the set temperature Ts ′, and thus the deviation ΔT becomes zero. After the power is turned on, the target temperature Tx changes, but if the time constant τ is set appropriately, the set temperature Ts ′ changes to the target temperature Ts at almost the same rate of change as the change in the target temperature Tx. Is kept at a small value while the target temperature Tx converges to the target temperature Ts. In this way, since the deviation ΔT is always maintained at a small value, it is possible to suppress the target temperature Tx from exceeding the target temperature Ts immediately after the power is turned on due to overintegration.
(2) Since the first-order lag circuit 22 can be realized with a simple circuit configuration, the configuration can be simplified, and it is also useful in a small and portable wavelength conversion laser device such as a battery drive.

FIG. 5 is an explanatory diagram of a wavelength conversion laser device 100 ′ according to the second embodiment.
This wavelength conversion laser device 100 ′ includes a semiconductor laser 1 that generates excitation laser light, a condenser lens system 2 that condenses the excitation laser light, a reflection surface formed on the incident surface of the excitation laser light, and the excitation laser light. An optical resonator 6 is formed between the solid-state laser medium 3 that generates the fundamental wave light by being excited by the laser, the nonlinear optical element 4 that generates the second harmonic light when the fundamental wave light is incident, and the reflecting surface of the solid-state laser medium 3. An output-side mirror 5 having a reflecting surface, a beam splitter 7 that transmits a part of the output laser light output from the output-side mirror 5 to the outside and branches the remainder, and receives the branched light and converts it into an electrical signal. A temperature control unit 9 having a photodiode 8, a Peltier element 27, and a target temperature sensor 28 for controlling the temperature of the semiconductor laser 1 and the optical resonator 6, and a half for supplying a drive current to the semiconductor laser 1 The conductor laser drive circuit 12, the Peltier element drive circuit 26 that supplies a drive current to the Peltier element 27, and the Peltier element drive circuit 26 are controlled so that the target temperature Tx detected by the target temperature sensor 28 matches the set temperature Ts'. A temperature control circuit 20 ′ that controls the semiconductor laser drive circuit 12 so that the intensity of the branched light received by the photodiode 8 is constant, and a controller 11 ′ that supplies the temperature control circuit 20 ′ with a set temperature Ts ′. It has.

  The temperature control circuit 20 ′ includes a differentiator 24 that outputs a deviation ΔT between the set temperature Ts ′ and the target temperature Tx, and a PID circuit 25 that performs PID control of the Peltier element driving circuit 26 so that the deviation ΔT becomes zero. Yes.

  The control unit 11 ′ is a microprocessor, and stores an ambient temperature memory 29 ′ that stores the target temperature Tx when the power is turned on and outputs it as the ambient temperature Tc, and a differencer 21 that outputs a temperature difference between the target temperature Ts and the ambient temperature Tc. A first-order lag element 22 ′ that transmits the output of the subtractor 21 as a function of a first-order lag with a predetermined time constant, and an adder 23 that adds the environmental temperature Tc to the output of the first-order lag element 22 ′ to obtain a set temperature Ts ′. As a function of the processing program.

  According to the wavelength conversion laser device 100 ′ of the second embodiment, the same effect as that of the first embodiment can be obtained.

  The wavelength conversion laser device of the present invention can be used in the bioengineering field and the measurement field. In particular, it is useful for, for example, a laser pointer driven by a dry battery.

1 is a configuration explanatory view showing a wavelength conversion laser device according to Example 1. FIG. 3 is a graph showing changes in set temperature according to Example 1. 3 is a graph showing a change in target temperature according to Example 1. 6 is another graph showing a change in target temperature according to Example 1. FIG. 6 is an explanatory diagram illustrating a wavelength conversion laser device according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Condensing lens system 3 Solid state laser medium 4 Nonlinear optical element 5 Output side mirror 6 Optical resonator 7 Beam splitter 8 Photodiode 9 Temperature control unit 11, 11 'Control part 12 Semiconductor laser drive circuit 20, 20' Temperature control Circuits 21, 24 Differentiator 22 Primary delay circuit 22 'Primary delay element 23 Adder 26 Peltier element drive circuit 27 Peltier element 28 Target temperature sensor 29 Environmental temperature sensor 29' Environmental temperature memory 100, 100 'Wavelength conversion laser device

Claims (2)

A temperature control method for controlling a target temperature (Tx) by PID control based on a deviation (ΔT) between a set temperature (Ts ′) and a target temperature (Tx), wherein the environmental temperature (Tc) is set when the target is turned on. A temperature control method characterized in that the set temperature (Ts ′) is changed from the environmental temperature (Tc) to the target temperature (Ts) as a function of a first-order delay with a predetermined time constant. . An optical resonator (6) including a semiconductor laser (1), a solid-state laser medium (3) that is excited by the semiconductor laser (1) and outputs fundamental light, and a nonlinear optical element (4) that converts the wavelength of the fundamental light; A heating means (27) capable of heating the semiconductor laser (1) and the optical resonator (6), and a target temperature (Tx) which is a temperature of the semiconductor laser (1) and the optical resonator (6). Target temperature detecting means (28) for detecting, and PID control means (25, 26) for PID controlling the heat generating means (27) based on a deviation (ΔT) between a set temperature (Ts ′) and the target temperature (Tx). When the power is turned on, the ambient temperature (Tc) is set to the preset temperature (Ts ′), and then the preset temperature (Ts ′) from the ambient temperature (Tc) to the target temperature (Ts) as a function of a first-order lag of a predetermined time constant. ) Set temperature control means (21, 22, 23) and a wavelength conversion laser device being characterized in that comprising a (100, 100 ').

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