JP2002158383A - Method and device for deciding appropriate driving temperature of laser source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always decide an appropriate temperature independent of the ambient temperature in actual use, related to a device for deciding an appropriate driving temperature at which an output power is almost maximum. SOLUTION: An appropriate driving temperature deciding device 5 comprises a temperature sensor 60 which is provided outside a case 9 to measure the ambient temperature; a temperature characteristics information acquiring means 52 which acquires the temperature characteristics information representing the temperature characteristics of an output power for each of a plurality of ambient temperatures; an ambient temperature dependent characteristics information acquiring means 62 wherein the appropriate driving temperature at each ambient temperature is decided based on the acquired temperature characteristics information, and then, based on the result, the ambient temperature dependent characteristics information of the appropriate driving temperature is acquired; a memory 64 in which the acquired ambient temperature dependent characteristics information is stored; and an appropriate driving temperature deciding means 54 which decides the appropriate driving temperature in actual use based on the ambient temperature measured with the temperature sensor 60 in actual use, and the ambient temperature dependent characteristics information stored in the memory 64.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining an appropriate driving temperature of a laser light source, at which the output power of the laser light emitted from the laser light source disposed on a heat source such as a Peltier device becomes substantially maximum. And devices.

[0002]

2. Description of the Related Art For example, a reading light source of a pickup section of a compact disk player, a mini disk player, or the like,
Radiation image reader (for example, Japanese Patent Publication No. 3-79695,
7-191421, etc.), a fluorescence diagnostic apparatus (for example,
No. 30, JP-A-7-59783, etc.) or a fluorescence detection device for performing gene expression analysis using a macroarray, a microarray, a DNA chip, etc. (for example, “Gene expression analysis using microarray; Yodosha Publishing Co., Ltd.), Volume 17 (1999), 1
Monthly Issue, P61-P65 ”and“ Gene Medicine; Vol.4, No.1 2000
It is well known that a laser light source is used as an excitation light source of "Medical Do Co., Ltd.").

[0003] Among laser light sources, particularly, a laser light source using a laser diode (semiconductor laser) is small in size, inexpensive, and easy to handle. It has been increasingly used, and its demand is rapidly increasing.

For example, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-189783, a solid-state laser crystal to which a rare earth element such as neodymium is added is irradiated with a laser (a laser beam) emitted from a laser diode to excite the solid-state laser beam. A diode-pumped solid-state laser (hereinafter, also referred to as an LD-pumped solid-state laser) is also known. This LD-pumped solid-state laser is also suitable for obtaining a high-output optical output, and thus is, for example, a MOPA laser (Master Oscillator-Power Amplifier).
A MOPA type laser diode, Electronics Lett;
ers Vol.28 No.2 p 2011-2013, Optics & Photonics
As well as News Mch. '93p 11-13, JP-A-6-291400), its use as a high-power laser is expanding.

In this LD-pumped solid-state laser, in order to obtain a laser beam having a shorter wavelength, a non-linear optical crystal is arranged in the resonator to convert the solid-state laser beam to a second harmonic, a sum frequency, or the like. Wavelength conversion is also widely performed. For example, a second harmonic is used to obtain visible light or ultraviolet light by frequency doubling using a nonlinear optical crystal based on near-infrared output light (solid laser beam). The thing that takes out the waves is SHG (Second Harmonic Generati)
on) It is called a laser.

On the other hand, when a laser light source is used as a light source of the above-described various devices, the light output (light emission amount) of the laser light source is kept constant in a steady state in order to stabilize reading accuracy and the like. In general, APC (Automatic Power Control) control is performed so that the output signal of the photodetector is detected by a photodetector such as a diode and the output signal of the photodetector has a constant value.

A laser light source capable of obtaining a relatively high output light, such as a laser using an LD-pumped solid-state laser (including the one that converts the wavelength as described above; the same applies hereinafter), is used. In order to suppress variations in the optical output (output power) and oscillation wavelength of the laser diode as the pump source, and to maintain a predetermined phase matching state in the nonlinear optical crystal in the case of performing the above-described wavelength conversion, Generally, the temperature of each part of the solid-state laser crystal or the resonator is adjusted to a predetermined temperature. For example, in the case of an SHG laser, since it is affected by the mode control by the etalon, it is necessary to strictly control the temperature control.

This temperature adjustment is usually carried out by placing the above-mentioned parts on an electronic cooling element such as a Peltier element (heat-absorbing / absorbing element), detecting the temperature in a laser diode or a resonator, and based on the detected temperature. In this case, the electronic cooling element is driven by feedback control so as to keep the above-mentioned parts at the final target temperature.

The final target temperature for this temperature adjustment is:
Since the optical output has a temperature dependency, it is necessary to set an appropriate driving temperature (appropriate operating temperature) so that the optical output becomes substantially the maximum. For this reason, the temperature characteristic of the light output is measured at a predetermined environmental temperature, and a drive temperature (operating temperature) at which the light output becomes substantially maximum is obtained based on the measurement result, and this is determined as an appropriate drive temperature. Once the proper drive temperature is determined, when using this laser light source again, even if the ambient temperature is different from that when the proper drive temperature was determined, the proper drive temperature determined as described above is used. The drive temperature is adjusted from the beginning and used.

[0010]

However, when the system is used at an appropriate operating temperature determined in advance at a predetermined environmental temperature, if the actual operating condition is different from the predetermined environmental temperature, the set temperature may be reduced. Is not necessarily an appropriate driving temperature at the actual operating environment temperature. For example, 5
When an appropriate driving temperature is determined under an environmental temperature of 40 ° C. and the operating temperature is set to the appropriate driving temperature under an environmental temperature of 40 ° C.,
There has been a problem that the light output is lower than the maximum output level.

According to the investigation by the present inventors, for example, SH
In the case of a G laser, when the ambient temperature changes by about + 1 ° C,
The appropriate driving temperature according to the environmental temperature tended to decrease by -0.01 ° C. In other words, the appropriate driving temperature to be set is
That is, the laser light source is affected by the environmental temperature in the actual use state.

When the cause of the SHG laser was examined, it was found that the temperature difference between the two surfaces of the Peltier element was different depending on the environmental temperature, and the degree of distortion of the Peltier element was different for each environmental temperature. Specifically, since the installation state of a resonator or the like formed on a Peltier element (and a reference plate on the Peltier element) changes depending on the environmental temperature factor, the resonance point shifts. It is considered that there is a difference in the appropriate driving temperature to be set for each case.

If the light output falls below the maximum output level, a problem arises because the reading accuracy of an apparatus using a laser light source cannot be stabilized. In particular, in the case of a fluorescence detection device for performing the above-mentioned gene expression analysis, which often has a chance to handle weak light, the deviation of the appropriate driving temperature is ±
The temperature must be within 0.1 ° C., and the above problem cannot be neglected. Also, every time the ambient temperature changes in actual use,
It is difficult to determine the proper driving temperature by measuring the temperature characteristics of the optical output.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method and an apparatus which can always set an appropriate driving temperature regardless of an ambient temperature of an actual use state of a laser light source. It is intended for.

[0015]

According to the present invention, there is provided a method for determining a proper driving temperature of a laser light source, the output power of the laser light emitted from the laser light source provided on the heat source being substantially maximum. In this method, environmental temperature dependent characteristic information indicating an environmental temperature dependent characteristic of an appropriate driving temperature is stored in a predetermined storage means such as a memory in advance, and the environmental temperature in the actual use state of the laser light source is measured. In addition, an appropriate driving temperature in an actual use state is determined based on the measured environmental temperature and the environmental temperature dependent characteristic information stored in the storage means. That is, the environmental temperature dependence of the proper driving temperature is investigated in advance, and the proper driving temperature according to the actual operating environment temperature is determined.

The ambient temperature means the temperature around the laser light source. Since the laser light source is usually configured by housing main parts such as a light emitting source and a resonator in a predetermined case, the environmental temperature may be a temperature outside the case. When the laser light source whose main part is housed in the case is used in the above-described radiation image reading apparatus or fluorescence diagnostic apparatus, the temperature outside the radiation image reading apparatus or the inside of the apparatus and outside the case Is the environmental temperature.

The environmental temperature dependence of the proper driving temperature means that the output power of the laser light is substantially maximum because the structural arrangement of the resonator and the like inside the laser light source changes according to the change in the environmental temperature surrounding the laser light source. Means the temperature-dependent characteristic of the change of the appropriate driving temperature.
In other words, the present invention is not concerned with temperature-dependent characteristics that do not include structural factors.

The environmental temperature dependent characteristic information stored in the storage means may be unique to each laser light source and acquired for each laser light source. Alternatively, the environmental temperature-dependent characteristic information acquired for a typical laser light source may be stored in the same manner for other laser light sources.

The environmental temperature-dependent characteristic information stored in the storage means includes, for example, a look-up table (LUT) in which each environmental temperature is associated with an appropriate driving temperature at each environmental temperature. It may be table data. Further, for example, the function may be in the form of a function indicating the environmental temperature dependence such as a linear function or a cubic function.

An apparatus for determining an appropriate driving temperature according to the present invention is an apparatus for determining an appropriate operating temperature of a laser light source at which the output power of the laser light emitted from the laser light source disposed on the heat source becomes substantially maximum. A storage means for storing environmental temperature dependence characteristic information indicating an environmental temperature dependence characteristic of an appropriate driving temperature; an environmental temperature measurement means for measuring an environmental temperature in an actual use state of a laser light source; And an appropriate driving temperature determining means for determining an appropriate driving temperature in an actual use state based on the environmental temperature dependent characteristic information stored in the means.

In the proper drive temperature determining apparatus of the present invention, the storage means stores the proper drive temperature at a predetermined environmental temperature and a coefficient indicating a change in the proper drive temperature with respect to a change in the environmental temperature as environmental temperature dependent characteristic information. It is desirable to keep it.

Here, storing the appropriate driving temperature at a predetermined environmental temperature and the coefficient indicating the change in the appropriate driving temperature with respect to the change in the environmental temperature as the environmental temperature dependent characteristic information means that the environmental temperature dependent characteristic is stored. This means that the environmental temperature dependent characteristic information is stored in the form of the function shown.
For example, the environmental temperature at the time of the exploration, the appropriate driving temperature determined at that time, and the displacement of the appropriate driving temperature per 1 ° C. of the environmental temperature change (change rate corresponding to the gradient of the linear function) are stored. . The proper drive temperature according to the actual use environment temperature can be calculated by using the proper drive temperature and the change rate at the predetermined environment temperature stored in the storage means. When a higher-order function form is used, the number of coefficients stored in the memory may be increased according to the order.

In the proper driving temperature determining apparatus of the present invention, the proper driving temperatures at a plurality of environmental temperatures are determined in advance to acquire the environmental temperature dependent characteristic information indicating the environmental temperature dependent characteristics. It is preferable that the apparatus further includes an environmental temperature dependent characteristic information acquisition unit that stores the characteristic information in the storage unit. In other words, the configuration is such that the environmental temperature dependent characteristic information is acquired for each laser light source and the result is stored in the storage means.

In such a configuration, the laser light emitted from the laser light source is driven while driving the heat source so that the temperature of the laser light source changes at a substantially constant gradient at each of a plurality of environmental temperatures. The apparatus further includes temperature characteristic information acquiring means for acquiring temperature characteristic information indicating a temperature characteristic of the output power by detecting the output power. It is desirable that the appropriate driving temperature at each environmental temperature is determined based on the characteristic information, and the environmental temperature dependent characteristic information is acquired based on the determined result. In this case, it is desirable that the temperature characteristic information acquiring means drives the heat source so that the temperature of the laser light source changes at a substantially constant gradient within a range of 0.1 ° C./sec or less.

The temperature characteristic information indicating the temperature characteristic of the output power means information indicating the relationship between the temperature change and the output power change.

In obtaining temperature characteristic information by detecting the output power of the laser beam while driving the heat source, it is desirable to detect the output power of the laser beam at predetermined temperature intervals. Although there is a predetermined temperature interval, since the temperature is changed at a substantially constant gradient, the output power may be detected at substantially constant time intervals. Here, detecting the output power of the laser beam at a predetermined temperature interval means detecting the output power at each temperature of the laser light source corresponding to the predetermined temperature interval.

Since the temperature characteristic information of the output power of the laser light is acquired, the APC control is not activated even if the laser light source is small at the time of acquiring the temperature characteristic information.

In order to obtain accurate temperature characteristic information, it is desirable to perform constant current driving for maintaining the amount of current flowing to a light emitting source such as a semiconductor laser at a constant value in order to maintain data continuity. In this case, it is preferable to perform the constant current drive so that the current value becomes substantially equal to the steady current amount corresponding to the reference power (reference light output value) of the laser light source in the steady state. That is, the light-emitting source is driven in an appropriate driving state as much as possible.

In determining the proper drive temperature based on the temperature characteristic information, for example, the temperature at which the output power (light output) becomes substantially maximum may be set as the proper drive temperature, or the temperature at which the substantially maximum output power is set The median value of the temperature at a predetermined position (for example, a position at approximately 90% of the maximum value) may be set as the appropriate drive temperature.

According to the present invention, the structure of the laser light source is deformed depending on the environmental temperature (generates structural distortion), whereby the structural arrangement of the resonator and the like is changed, and the optimum driving temperature is reduced. It is intended for laser light sources that exhibit temperature-dependent characteristics.

As such a laser light source, for example,
A laser diode-pumped solid-state laser such as an SHG laser or another laser diode having a main part as a laser diode is applicable.

[0032]

According to the method and apparatus for determining an appropriate driving temperature according to the present invention, environmental temperature dependency characteristic information indicating the environmental temperature dependency of the proper driving temperature is stored in a memory or the like in advance, and the measured actual operating state is determined. Since the proper drive temperature in the actual use state is determined based on the environmental temperature and the environmental temperature dependent characteristic information stored in the memory, the proper drive temperature according to the actual operating environmental temperature can be easily and simply determined. Can be determined fast.

Further, since the proper drive temperature is determined in accordance with the environmental temperature actually used based on the environmental temperature dependency characteristic obtained in advance, the proper drive temperature is changed every time the environmental temperature in actual use changes. It is not necessary to re-measure the temperature characteristic for determination each time, and the start-up of the apparatus using the laser light source (the time until it becomes actually usable) can be shortened, which is convenient.

In addition, if the appropriate driving temperature under a predetermined environmental temperature and the rate of change thereof are stored in a memory or the like as the environmental temperature dependent characteristic, a relatively small capacity memory can be used. In addition, a calculation using the appropriate driving temperature and the change rate stored in a memory or the like makes it possible to determine the appropriate driving temperature according to the environmental temperature in actual use in a very short time.

Further, if environmental temperature dependence characteristic information acquiring means is provided to acquire the environmental temperature dependence characteristic information for each laser light source and the result is stored in a memory or the like, the environmental temperature dependence characteristic information can be obtained. It is no longer affected by individual differences.

In this case, if the temperature characteristic information is obtained by detecting the output power while changing the temperature of the laser light source at a substantially constant gradient, each environmental temperature at the time of obtaining the environmental temperature dependent characteristic can be obtained. The lower appropriate driving temperature determination process can be performed at high speed.

[0037]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view showing one embodiment of a laser light source including a proper driving temperature determining device according to the present invention, and FIG. 2 is a diagram showing a circuit portion and a light emitting source which constitute the proper driving temperature determining device together with this laser light source. FIG. 3 is a block diagram illustrating a circuit portion to be driven.

In the package case 9 of the laser light source 1, a laser diode (semiconductor laser) 11 for emitting a laser beam L1 for excitation, and a refractive index distribution type rod lens for condensing the laser beam L1 as divergent light, for example. (Selfoc lens) Condensing lens 12
And a YAG crystal (hereinafter, Nd: a solid laser medium) doped with neodymium (Nd).
13) and the Nd: YAG crystal 13
Resonator mirror 14 disposed on the front side (right side in the figure) of
Between the resonator mirror 14 and the Nd: YAG crystal 13, in order from the crystal 13 side.
LiNbO ₃ crystal (hereinafter referred to as LNb)
An LD-pumped solid-state laser 10 having a wavelength conversion unit 15 in which a crystal 15b and an etalon 15c are sequentially arranged is provided.

The laser diode 11 has a wavelength of 80
One that emits a 9 nm laser beam L1 is used. The Nd: YAG crystal 13 receives the incident laser beam L1.
Excites neodymium ions, and emits light having a wavelength of 946 nm as a fundamental wave. Nd: YAG crystal 13
The light of 946 nm wavelength is reflected well (reflectance of 99.9% or more) and the excitation laser beam L1 of 809 nm wavelength is satisfactorily transmitted (transmittance of 99%) on the end face on the side of the excitation light incident side.
Above) coating is applied. On the other hand, the mirror surface of the resonator mirror 14 is provided with a coating that satisfactorily reflects light having a wavelength of 946 nm and transmits light having a wavelength of 473 nm described below.

As a result, a Fabry-Perot resonator is constituted by the Nd: YAG crystal 13 and the resonator mirror 14, and light having a wavelength of 946 nm is confined between the above-described surfaces to cause laser oscillation. The (fundamental wave) L2 is converted by the wavelength conversion unit 15 into a laser beam L3, which is a second harmonic having a wavelength of す な わ ち, that is, 473 nm.
Harmonics) L3 are emitted from the resonator mirror 14. That is, the LD-pumped solid-state laser 1 of the laser light source 1 of the present embodiment
0 functions as an SHG laser.

Note that, instead of the Nd: YAG crystal 13, Y
When a VO crystal is used, a second harmonic having a wavelength of 532 nm can be obtained as a laser beam L3.

The Nd: YAG crystal 13, the wavelength conversion unit 15, and the resonator mirror 14 are fixed to a resonator holder 95, and the resonator holder 95 is fixed to the reference plate 22. The reference plate 22 is used not only for improving the positional accuracy of the resonator structure but also for efficiently conducting the heat of the Peltier element to the Nd: YAG crystal 13 and the like, and has a thermal conductivity. It is made of a metal body such as copper, which is high in temperature and hardly generates an in-plane temperature gradient.

The laser light source 1 has a built-in temperature control function for controlling the temperature so that substantially the entire laser light source 1 is maintained at a substantially constant temperature. That is, in the package case 9 of the laser light source 1, a Peltier device 24 as a heat source composed of an element body 24a, an upper surface 24b, and a bottom surface 24c is provided, and the Peltier device 24 is placed on the device mounting surface (package case bottom surface). The bottom surface 24c is fixed. The reference plate 22 is fixed to the upper surface 24b of the Peltier element 24. Between the reference plate 22 and the Peltier element 24, a heat conductive sheet having elasticity may be arranged in order to improve adhesion and heat conductivity between the two.

The Nd: YAG crystal 13 on the reference plate 22
A temperature sensor 40 for temperature detection is fixed in the vicinity. This temperature sensor 40 is connected to a temperature control circuit 42 provided on the drive board 3. In FIG. 1, the temperature sensor 40 and the drive board 3 are not shown. As the temperature sensor 40, for example, a thermistor, a thermocouple, or the like can be used.

As described above, in this embodiment, N
The d: YAG crystal 13 and the resonator mirror 14 constitute a Fabry-Perot resonator, and the temperature near the Nd: YAG crystal 13 in this resonator is detected by a temperature sensor 40 fixed to the reference plate 22. You. The temperature control circuit 42 is a feedback type circuit, and the temperature sensor 40
Temperature control circuit 42 so that the detected temperature of
Drives the Peltier element 24. By such temperature control, the temperature in the vicinity of the Nd: YAG crystal 13 is maintained at a predetermined temperature. As described above, since the reference plate 22 is a metal body having a high thermal conductivity and hardly causing an in-plane temperature gradient, as a result, not only the portion of the resonator near the Nd: YAG crystal 13 but also the wavelength Main parts of the laser light source 1 including the respective parts of the conversion unit 15 (for example, the etalon 15c), the laser diode 11, the condenser lens 12, and the like are kept at a constant temperature.

Here, when driving and controlling the Peltier element 24, it goes without saying that the Peltier element 24 is caused to generate heat or absorb heat depending on the relationship between the target predetermined temperature and the detected temperature.

Next, the configuration of an APC control system for keeping the light output (output power) of the laser light source 1 constant will be described. An optical filter 31 having wavelength selectivity and a beam splitter 3 such as a dichroic mirror are further forward (rightward in the figure) of the wavelength conversion unit 15 on the reference plate 22.
2 are fixed in this order with respect to the traveling direction of the laser beam L3. The laser beam L on the reference plate 22
APC in a position that does not interfere with the direction of travel
A photodiode 33 as a photodetector is fixed. The main part of the laser light source 1 and this APC control system are housed in a package case 9. A window member 7 for emitting laser light (light L3a to be described later) is provided on the front side of the optical path of the package case 9. Thereby, the influence of the convection outside the case hardly affects the inside, and the temperature fluctuation inside the case is configured to be as small as possible.

The optical filter 31 is provided with a laser beam (second
The laser beam L1 and the laser beam L2 emitted from the resonator mirror 14 are cut while transmitting the higher harmonic (L3). The beam splitter 32 disposed at an angle to the traveling direction of the laser beam L3 transmits most of the laser beam L3 as the use light L3a, while partially transmitting the photodiode 33 as the detection light L3b.
Reflect toward.

The detection light L3b is applied to the photodiode 33
And an output signal S indicating the light amount monitor current is input to the APC circuit 34 provided on the drive board 3. The APC circuit 34 controls the drive current of the laser diode 11 based on the output signal S so that the output signal S is constant. Thereby, the light output of the laser beam L1 is stabilized, and finally the laser beam (second
The output of the (harmonic) L3 also becomes substantially stable.

Note that the photodiode 33 fixed on the reference plate 22 also has
The temperature is adjusted together with the lens 1 and the condenser lens 12 so as to be maintained at a predetermined temperature.

Next, the proper drive temperature determining device 5 of the present invention included in the laser light source 1 will be described.

The proper driving temperature determining device 5 is capable of controlling a laser beam L3 (substantially the light beam L3) emitted from a laser light source 1 disposed on a Peltier element 24 as a heat source.
The configuration is such that the appropriate driving temperature of the laser light source 1 at which the output power of 3a) becomes substantially maximum can be determined appropriately regardless of the environmental temperature.

That is, the proper drive temperature determining device 5 is provided outside the case 9 of the laser light source 1 and serves as an environmental temperature measuring means for measuring the environmental temperature outside the case 9; The laser beam L3 emitted from the laser light source 1 while driving the Peltier element 24 so that the temperature of the main part of the laser light source 1 (hereinafter simply referred to as the temperature of the laser light source 1) changes at a substantially constant gradient. By detecting the output power,
Temperature characteristic information acquiring means 52 for acquiring temperature characteristic information indicating a temperature characteristic of output power for each of the plurality of environmental temperatures, and after determining an appropriate driving temperature under each environmental temperature based on the acquired temperature characteristic information. An environmental temperature dependent characteristic information acquiring unit 62 for acquiring the environmental temperature dependent characteristic information of the appropriate driving temperature based on the result, and the environmental temperature dependent characteristic information acquired by the environmental temperature dependent characteristic information acquiring unit 62 are stored. A memory 64 as storage means;
The appropriate driving temperature in the actual use state is determined based on the environmental temperature measured by the temperature sensor 60 in the actual use state (environmental temperature in actual use) and the environmental temperature dependent characteristic information stored in the memory 64. And an appropriate driving temperature determining means 54.

The temperature characteristic information acquiring means 52, the proper driving temperature determining means 54, the environmental temperature dependent characteristic information acquiring means 62, and the memory 64 are provided on the drive board 3 in a circuit configuration. It goes without saying that an A / D converter for acquiring temperature data and optical output data, a CPU for data processing, and the like are provided as the circuit configuration.

The temperature characteristic information acquiring means 52 is configured to substantially detect the output power of the laser beam L3 by detecting the detection light L3b with the photodiode 33.

When the Peltier device 24 is driven so that the temperature of the laser light source 1 changes at a substantially constant gradient in a state where the APC control is operated, the APC control causes the light output to be constant. And proper temperature characteristics cannot be obtained. For this reason, when acquiring the temperature characteristics of the output power of the laser beam (characteristics indicating the relationship between the temperature change and the optical output change) as described above, the APC control is stopped and the current flowing through the laser diode 11 is stopped. ACC control (constant current drive) for keeping the amount of current approximately equal to the amount of steady current corresponding to the reference light output value of the laser light source 1 in the steady state
Perform

As the reference light output value, the maximum output power of the laser beam L3 in an appropriate driving temperature state at a predetermined environmental temperature can be used. More specifically, for example, a representative value provided by a manufacturer may be used. Alternatively, a current value flowing through the laser diode 11 at an appropriate driving temperature or an appropriate operating temperature recommended by a manufacturer may be used, which is determined in advance using the appropriate operating temperature determination method of the present invention or a conventional appropriate temperature determining method.

The temperature characteristic information acquisition means 52 stops the feedback control of the temperature control circuit 42 and drives the reference to drive the Peltier element 24 so that the temperature of the laser light source 1 changes at a substantially constant gradient. The temperature of the laser light source 1 is detected (monitored) by the temperature sensor 40 fixed to the plate 22, and the Peltier element 24 is moved so that the temperature sweep (temperature change of the laser light source 1) is as fast as 0.1 ° C./sec or less. It is to be driven. Thus, the output power of the laser beam can be detected while driving the Peltier element 24, and appropriate temperature characteristic information can be obtained.

Note that the laser light source 1 only needs to change its temperature at a substantially constant temperature, and the driving of the Peltier element 24 may be pulsed.

Since the temperature of the laser light source 1 is changed at a substantially constant gradient, the output power may be detected (sampled) at substantially constant time intervals. Since only one data sampling circuit is actually provided, only single task processing can be performed, and data sampling of temperature and light output cannot be performed simultaneously. However, by reducing the time difference per sample between the temperature change monitor by the temperature sensor 40 and the light output monitor by the photodiode 33, both monitors can be performed substantially simultaneously. Of course, a configuration in which the temperature change monitor and the optical output monitor are performed separately (parallel task processing)
It may be.

FIG. 3 shows a method for determining an appropriate driving temperature at each environmental temperature (# 10s) and an appropriate driving in an actual use state, which are performed for each environmental temperature when acquiring the environmental temperature dependency of the appropriate driving temperature. It is the flowchart which showed the specific example of the temperature determination method (# 20s).

First, the environmental temperature at the time of performing the following processing is measured by the temperature sensor 60 (step # 10). The measurement data accuracy need not be so high. During the following processing, a constant environmental temperature is maintained. This is for properly acquiring the environmental temperature dependence of the appropriate driving temperature.

Next, as described above, the laser diode 1
1 and a steady-state current corresponding to the reference light output value is passed, and the Peltier element 24 is driven so that the temperature of the laser light source 1 becomes substantially equal to a predetermined appropriate driving temperature (the initial temperature value) (step). # 11). The data accuracy of the control temperature for the temperature control circuit 42 at this time is, for example, 12
It only needs to be about a bit.

Next, with the temperature of the laser light source 1 substantially stabilized, temperature data indicating the temperature (current temperature) of the laser light source 1 is obtained (step # 12). The accuracy of the temperature data acquired at this time is, for example, about 16 bits. In order to improve accuracy, for example, an average value at five sampling points is obtained, and the average value is set as a current temperature Tn (n indicates a sampling point).

Next, the laser beam L at the current temperature Tn
Light output data indicating the light output (current power) of No. 3 is obtained (step # 13). The accuracy of the optical output data acquired at this time is, for example, about 16 bits. In order to improve the accuracy, for example, an average value at five sampling positions is obtained, and this average value is used as the current power Pn (n indicates a sampling point).

The current temperature Tn in the above step # 12
When the acquisition of the current power Pn in step # 13 is completed, a control signal J0 is sent to the temperature control circuit 42 so that the temperature of the laser light source 1 rises by about 0.03 ° C. The element 24 is driven (Step # 14).

Approximately 0.3-1.
After about 0 seconds, the temperature data of the laser light source 1 is obtained in the same manner as in step # 12, and thereafter, in step # 14.
The above process is sequentially repeated. The process is repeated until a desired number (here, N) of data is obtained (step # 15). That is, the processes of steps # 12 to # 15 are repeated in a repetition cycle of about 0.3 to 1.0 seconds.

As described above, while the temperature of the laser light source 1 is changed, the temperature data and the light output data are obtained for each repetition cycle, so that the temperature characteristic information of the light output can be obtained. When the temperature characteristic information is obtained, a drive temperature at which the light output can be substantially maximized is determined based on the result (step # 16).

As the temperature characteristic information of the light output, generally, a maximum value (peak) as shown in step # 16 of FIG.
Therefore, for example, the temperature at which a peak is present is set as the appropriate driving temperature, or the median value of the 90% position across the peak is set as the appropriate driving temperature. Further, when the acquired temperature characteristic information exhibits a plurality of peaks (maximum) as output power, the one closer to the appropriate driving temperature determined under the same environmental temperature last time is set as the current appropriate driving temperature.

Here, the reason why the median value of the temperature at the 90% position across the peak is set as the appropriate driving temperature is, for example, a substantially flat characteristic with a slightly inclined peak or a characteristic with a plurality of subtle peaks. Even in the case where there is, by setting them at almost the center value, it is possible to prevent the output from largely changing due to temperature fluctuation.

The information on the appropriate driving temperature under a certain environmental temperature determined in this way and the temperature characteristic information referred to together with the information indicating the environmental temperature at the time of the main measurement are provided in the environmental temperature dependent characteristic information acquiring means 62 (not shown). It is stored in a storage element such as a memory (which may also be used as the memory 64 for storing the environmental temperature dependent characteristic information).

The above processing is performed in the same manner while changing the environmental temperature (steps # 17 and # 18). Thereby, an appropriate drive temperature for each of the plurality of environmental temperatures is determined. The environmental temperature to be measured may be two or more of the lower limit and the upper limit assumed as the actual use state of the laser light source 1, and may be measured at, for example, 5 ° C. and 40 ° C.

Next, the environmental temperature dependent characteristic information acquisition means 62
Based on the obtained appropriate driving temperature at each environmental temperature,
Environmental temperature dependence characteristic information on the proper driving temperature of the laser light source 1 is acquired and stored in the memory 64 (step # 1).
9). For example, if the measurement is performed at two points of 5 ° C. and 40 ° C. as in the above-described example, the appropriate driving temperature per 1 ° C. of environmental temperature change is obtained from the difference of the environmental temperature between the two points and the difference of each appropriate driving temperature. (The coefficient corresponding to the slope of the linear function) is obtained. Then, the obtained change rate and the appropriate driving temperature of at least one of the two points (hereinafter also referred to as a reference appropriate driving temperature) are stored in the memory 64 as environmental temperature dependent characteristic information.

In the above embodiment, step # 14
In the above, the drive signal is issued to the Peltier element 24 so that the temperature of the laser light source 1 rises at 0.03 ° C./sec or less, that is, changes from a low temperature side to a high temperature side at a constant gradient. Conversely, a drive signal is issued to the Peltier element 24 so that the temperature of the laser light source 1 changes (falls) from a high temperature side to a low temperature side at a constant gradient, and the temperature characteristic information of the light output is generated as described above. May be obtained, and a drive temperature at which the light output can be substantially maximized may be obtained based on the result.

When the laser light source 1 is actually driven and used, first, the ambient temperature of the laser light source 1 in the actual use state is measured by the temperature sensor 60 (step # 20). The appropriate drive temperature determining means 54 determines an appropriate drive temperature according to the actual use state environmental temperature based on the measured environmental temperature and the environmental temperature dependent characteristic information stored in the memory 64. A signal J1 indicating the proper driving temperature is sent to the temperature control circuit 42, and the Peltier device 24 is driven by the temperature control circuit 42 so as to reach the determined proper driving temperature (step # 21).

By the calculation using the reference proper drive temperature and the change rate stored in the memory 64, the proper drive temperature corresponding to the environmental temperature in actual use can be determined in a very short time. Thereby, the start-up of the device using the laser light source can be accelerated.

Further, as can be seen from the description with reference to FIG.
By detecting the light output while changing the temperature at a substantially constant temperature gradient, the temperature characteristic information of the light output is obtained (continuous data sampling is performed to obtain the temperature characteristic information). Since the proper driving temperature under the temperature is determined, there is no waiting time until the laser light source stabilizes after the temperature is slightly changed, so that the temperature characteristic information can be acquired at high speed. It is possible to determine an appropriate driving temperature at a lower temperature in a short time.

The temperature characteristic information acquiring means 52 for acquiring the temperature characteristic information measures the output power of the laser light by the photodiode 33 provided in the package case 9 of the laser light source 1 and the temperature sensor 40.
, The temperature of the laser light source 1 is measured, so that there is no influence of individual differences and the configuration of the entire light source can be made compact.

If the above processing is performed for each laser light source 1 to obtain the environmental temperature dependence, the environmental temperature dependence will not be affected by individual differences.

Next, effects of applying the present invention will be described with reference to specific examples.

As environmental conditions, 5 ° C., 50% RH, 23
It measured on three conditions of 50 degreeC of 50% RH, and 42 degreeC 50% RH.

The search sequence (processing for acquiring temperature characteristic information) when determining the appropriate drive temperature is 0.03
After the temperature is stabilized by increasing the temperature every ° C., the output data of the photodiode is sampled (shown as “low → high” in a table described later). Further, under the same conditions, the temperature is lowered and the output data of the output of the photodiode is sampled (shown as “high → low” in a table described later). Note that such a search method (a method generally performed conventionally) is hereinafter referred to as a discontinuous search mode.

On the other hand, when the method shown in the above-mentioned flowchart (FIG. 3) (hereinafter referred to as a continuous search mode) is used, the temperature of the laser light source rises at a constant gradient of about 0.03 ° C./sec (see the table below). At "low → high")
Alternatively, the Peltier element is driven so as to descend (indicated by “high → low” in a table described later), and the output data of the photodiode and the output data of the temperature sensor during that time are sampled almost simultaneously.

In either method, based on the obtained temperature characteristic information, the median value of the temperature at the 90% position across the peak is determined as the appropriate driving temperature under the environmental temperature.

As a laser light source (measurement sample), B
B0052S, B0100S, B0103S, B3 as lue-SHG (SHG laser emitting blue light; hereinafter referred to as blue SHG)
-231, Green-SHG (SH emitting green light)
G0098S is measured as G laser (hereinafter referred to as green SHG). These SHG lasers are manufactured by Fuji Photo Optical Co., Ltd.

As an example of the temperature characteristics, temperature characteristic diagrams (temperature map, temperature characteristic information) for B0103S are shown in FIGS.
Shown in In the figure, the exploration method, the direction of temperature rise and fall, and the environmental temperature are distinguished by the last three letters written after the model number, P is the temperature exploration of the conventional method, N is the temperature exploration of the present invention,
F is from low temperature to high temperature side, R is from high temperature to low temperature side, L is 5
50% RH at 50 ° C., 50% RH at 23 ° C., 42 ° C. 50 at H
% RH is shown.

Table 1 shows the processing time (exploration time) required to acquire the temperature characteristic diagram for each SHG laser (measurement sample). Table 2 shows an appropriate driving temperature for each SHG laser determined based on the obtained temperature characteristic diagram, and Table 3 shows a standard output of each SHG laser.

[Table 1]

[Table 2]

[Table 3]

In FIGS. 5 and 6, the suffix M is the data (type data) at 23 ° C. and 50% RH shown in FIG. 4 and is shown for reference (reference).

Further, the “PD output” on the vertical axis in the figure indicates the output value of the photodiode 33 monitoring the output power. The output power (mW) and PD output (au)
The peak value shown in each temperature characteristic diagram corresponds to the standard output in Table 3. For example, in the case of B0103S, the standard output is 1.837 mW, which is about 180% of the peak in the diagram.
00a. u.

As shown in the figure, in any of the search methods, one peak (maximum value) is exhibited as the temperature characteristic of the light output under each environmental temperature. It can also be seen that the peak position and shape are slightly different depending on the search method and conditions.

Although not shown, almost the same characteristics were obtained for SHG lasers other than B0103S.

As shown in Table 2, for example, in the case of B0052S, the appropriate driving temperature determined in the discontinuous search mode is 5 ° C.
23.35 ° C under the environment, 23.26 ° C under the 23 ° C environment,
It was 23.12 ° C in a 42 ° C environment. Therefore, the change rate (displacement) of the appropriate driving temperature with respect to the change of the environmental temperature + 1 ° C. is approximately −0.006 ° C. The difference between the proper driving temperature in a 5 ° C environment and the proper driving temperature in a 42 ° C environment is 0.23.
° C. In a fluorescence detector or the like, the deviation of the proper driving temperature is required to be within ± 0.1 ° C.
Even if the temperature is set at 2 ° C., if it is set to the proper driving temperature determined at 5 ° C., it cannot be used.

On the other hand, as shown in the above-mentioned flowchart (FIG. 3), by acquiring the environmental temperature dependence of the proper driving temperature in advance, after setting the proper driving temperature under the temperature condition at 5 ° C., When the laser light source is moved below 23 ° C., −0.006 × (23 ° C.-5 ° C.) = − 0.1
From 1 ° C., 23.35 ° C.−0.11 ° C. = 23.24 ° C., and an appropriate driving temperature under 23 ° C. can be obtained. The difference from the actual measured value shown in Table 2 is also 0.02 ° C.
So you can almost ignore it. If used at 35 ° C., −0.006 × (35 ° C.-5 ° C.) = − 0.18 ° C.
Therefore, the proper driving temperature at 35 ° C. is required to be 23.17 ° C. Similarly, if used at 42 ° C., −
0.006 x (42 ° C-5 ° C) = -0.22 ° C,
The proper driving temperature at 42 ° C. is determined to be 23.13 ° C. (the difference from the actually measured value is 0.01 ° C.).

By determining the displacement coefficient of the appropriate drive temperature with respect to the environmental temperature in this way, even if the environmental temperature in the actual use state changes, an optimal drive temperature suitable for the environmental temperature in the actual use state is set. be able to.

In the above embodiment, the laser power (optical output) is at the time of standard output. For example, the same method is used when the output power in the actual use state is 1/10 of the standard output. It goes without saying that you can do it.

As can be seen from Table 1, in the discontinuous search mode, it takes about 6 minutes to determine the appropriate drive temperature by sweeping within the range of 2 ° C. However, in the case of the continuous search mode, Is 2 ° C./0.03° C. = 66 samples. If the above steps are repeated at about 0.5 seconds / cycle, the time required for data sampling becomes about 33 seconds, and temperature characteristics are obtained. Even if processing other than data sampling is included, the time required to determine an appropriate driving temperature can be reduced to 50 seconds or less. That is, if the appropriate driving temperature is determined in the continuous search mode, the processing time can be reduced.

Here, at 5 ° C. below B3-231, abnormal data (about twice as large as other data) is obtained in any of the search modes. This is because the peak point cannot be found in the temperature characteristic obtained by giving the temperature change only in one direction, and the temperature characteristic obtained by giving the temperature change in the opposite direction and reacquiring the temperature characteristic can be reduced by 5 ° C. Is determined.

According to the experiment, when the speed of the temperature sweep was increased to 0.1 ° C./sec or more in the continuous search mode, the deviation from the result determined in the discontinuous search mode became large.
Not always good results were obtained. Therefore, when the continuous search mode is applied, it is preferable that the temperature of the laser light source be changed at a substantially constant gradient within a range of 0.1 ° C./sec or less.

As can be seen from Table 2, the difference between the proper drive temperature determined in the discontinuous search mode and the proper drive temperature determined in the continuous search mode in all standard environments is ±. It is within 0.1 ° C. In other words, without waiting for temperature stabilization while changing the laser light source at a constant temperature gradient, the output of the photodiode in the SHG module and the temperature sensor signal (temperature sensor signal) are acquired almost simultaneously, and the temperature characteristics of the optical output are obtained. Using the processing method is substantially equivalent to controlling the temperature in the continuous exploration mode. In other words,
In both exploration modes, there is no problem even if the proper driving temperature is determined by applying the continuous exploration mode without causing a difference within 0.1 ° C.
That is, there is no side effect of shortening the time that a large deviation occurs in the peak detection result of the temperature characteristic diagram.

If the temperature of the laser light source is changed in a narrow temperature range, the appropriate driving temperature may deviate from the temperature search range due to a change over time. In this case, even in the discontinuous search mode, it is sufficient to extend the temperature search range, but it takes much processing time. On the other hand, in the continuous search mode, the temperature search can be completed in a short time even if the temperature search range is widened. Easy to find.

Although the preferred embodiment of the method and apparatus for determining an appropriate driving temperature according to the present invention has been described above, the present invention is not necessarily limited to the above-described embodiment.

For example, in the above embodiment, the reference proper drive temperature and the change rate are stored in the memory as environmental temperature dependent characteristic information, and the proper drive temperature corresponding to the actual use state environmental temperature is determined by calculation using these. Although the configuration has been described, a configuration using a look-up table in which each environmental temperature at every several degrees Celsius and an appropriate driving temperature in the environmental temperature are associated may be employed. Although the memory capacity is increased, the appropriate driving temperature can be determined faster because the calculation does not need to be performed. In this case, when the environmental temperature in the actual use state does not exist in the table data, the nearby table data may be used. Of course, it can also be obtained by interpolation calculation.

In the above-described embodiment, the laser light source using the SHG laser is used. However, the present invention is not limited to this.
A laser light source is provided on a heat source such as a laser, and in actual use, it is necessary to determine an appropriate driving temperature at which the output power of the laser light becomes substantially maximum. Therefore, the present invention can be applied to any structure in which the structural arrangement state of the resonator and the like changes, and the optimum driving temperature exhibits environmental temperature dependent characteristics.

In the above embodiment, the standard output power is 1
However, according to the present invention, the range of the output power at an appropriate driving temperature of the laser light source is 0.05 mW to
It is preferable to apply the present invention to one having about 20 mW.

In the above-described embodiment, the temperature characteristic information acquiring means 52 measures the output power of the laser light by the photodiode 33 provided in the package case 9 of the laser light source 1 and the laser sensor by the temperature sensor 40. Although the configuration is such that the temperature of the light source 1 is measured, such a configuration is not necessarily required. For example,
The measurement of the output power and / or the temperature measurement of the laser light source 1 itself is performed using an external measuring instrument. The temperature characteristic information acquisition means 52 exclusively acquires the measurement results (manual input by an operator or a measurement system). May be used, for example, may be used as an automatic input), or may be configured to acquire temperature characteristic information based on the acquired measurement result.

In the above embodiment, each laser light source is provided with a means for acquiring environmental temperature dependent characteristic information. However, for example, only a representative laser light source is actually measured to obtain the environmental temperature dependent characteristic information. Dependency characteristic information (representative information) may be acquired, the representative information may be stored in the memory of another laser light source (by manual input), and the representative information may be shared by all models.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a laser light source including a proper drive temperature determining device according to the present invention.

FIG. 2 is a block diagram showing a circuit portion forming an appropriate driving temperature determining device and a circuit portion driving a light emitting source and the like;

FIG. 3 is a flowchart showing a specific example of a method for determining an appropriate driving temperature according to the present invention.

FIG. 4 is a temperature characteristic diagram of blue SHG (B0103S) (23 ° C.)

FIG. 5 is a temperature characteristic diagram (5 ° C.) of blue SHG (B0103S).

FIG. 6 is a temperature characteristic diagram (42 ° C.) of blue SHG (B0103S).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 3 Drive board 5 Appropriate driving temperature determining device 9 Package case 10 LD-excited solid-state laser 11 Laser diode (semiconductor laser) 12 Condenser lens 13 Nd: YAG crystal 14 Resonator mirror 15 Wavelength conversion unit 22 Reference plate 24 Peltier device DESCRIPTION OF SYMBOLS 31 Optical filter 32 Beam splitter 33 Photodiode 34 APC circuit 40 Thermistor 42 Temperature control circuit 52 Temperature characteristic information acquisition means 54 Proper driving temperature determination means 60 Temperature sensor (environment temperature measurement means) 62 Environmental temperature dependence characteristic information acquisition means 64 Memory ( Storage means) L1 laser beam (for excitation) L2 laser beam (fundamental wave) L3 laser beam (second harmonic) L3a working light L3b detection light

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2K002 AB12 BA01 CA03 DA01 HA20 5F072 AB02 AB13 HH02 HH03 JJ05 KK06 KK12 KK15 PP07 QQ02 RR01 RR03 TT15 TT22 TT27 YY16 5F073 AB23 BA04 EA15 FA02 FA25 GA02 GA12 GA14

Claims (7)

[Claims] 1. A method for determining an appropriate driving temperature of a laser light source at which an output power of a laser light emitted from a laser light source disposed on a heat source is substantially maximized, comprising: Environmental temperature-dependent characteristic information indicating the temperature-dependent characteristic is stored in a predetermined storage unit in advance, the environmental temperature of the laser light source in an actual use state is measured, and the measured environmental temperature and the storage unit are stored in the storage unit. Determining an appropriate driving temperature in the actual use state based on the environmental temperature dependent characteristic information. 2. An apparatus for determining an appropriate driving temperature of a laser light source at which an output power of a laser light emitted from a laser light source disposed on a heat source is substantially maximum, wherein the environment of the appropriate driving temperature is determined. A storage unit for storing environmental temperature-dependent characteristic information indicating temperature-dependent characteristics; an environmental temperature measuring unit for measuring an environmental temperature in an actual use state of the laser light source; and the measured environmental temperature and stored in the storage unit. A proper driving temperature determining device for determining a proper driving temperature in the actual use state based on the environmental temperature dependent characteristic information. 3. The storage means stores, as the environmental temperature dependent characteristic information, a proper driving temperature at a predetermined environmental temperature and a coefficient indicating a change in the proper driving temperature with respect to the change in the environmental temperature. 3. The apparatus for determining an appropriate driving temperature according to claim 2, wherein: 4. An environmental temperature dependent characteristic information indicating the environmental temperature dependent characteristic is obtained by previously determining an appropriate driving temperature at a plurality of environmental temperatures, and the obtained environmental temperature dependent characteristic information is stored in the storage means. 4. The apparatus according to claim 2, further comprising an environmental temperature dependent characteristic information obtaining unit for causing the apparatus to determine the temperature. 5. An output power of a laser beam emitted from the laser light source while driving the heat source so that the temperature of the laser light source changes at a substantially constant gradient at each of the plurality of environmental temperatures. A temperature characteristic information acquisition unit that acquires temperature characteristic information indicating a temperature characteristic of the output power, wherein the environmental temperature dependent characteristic information acquisition unit acquires the plurality of environmental temperatures based on the acquired temperature characteristic information. The apparatus according to claim 4, wherein an appropriate driving temperature is determined for each of them, and the environmental temperature dependent characteristic information is obtained based on the determined result. 6. The apparatus according to claim 2, wherein the laser light source has a laser diode. 7. The apparatus according to claim 6, wherein the laser light source includes a laser diode-pumped solid-state laser.