JP2002158382A - Method and device for deciding appropriate driving temperature of laser source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the process time, related to a device for deciding an appropriate driving temperature at which the output power of laser beam is maximum. SOLUTION: An appropriate driving temperature deciding device 5 comprises a temperature characteristics information acquiring means 52 which acquires the temperature characteristics information representing the temperature characteristics of an output power, by detecting the output power of laser beam L3 emitted from a laser source 1 while a Peltier element 24 is so driven that the temperature of the laser source 1 provided on the Peltier element 24 changes at an almost constant gradient; and an appropriate driving temperature deciding means 54 which decides the appropriate driving temperature based on the acquired temperature characteristics information.

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 which maximizes the output power of the laser light emitted from the laser light source disposed on a heat source such as a Peltier device. It concerns the device.

[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.

[0009]

Since the optical output has a temperature dependency, it is necessary to set the final target temperature at the time of this temperature adjustment to an appropriate driving temperature (appropriate operating temperature) at which the optical output becomes substantially maximum. is there. For this reason, conventionally, an appropriate driving temperature has been determined (temperature search) as follows. That is, the light emitting source used for the laser light source such as a laser diode is driven at a constant current, and the heat source such as a Peltier element is driven to wait until the laser light source (particularly the laser diode as the light emitting source) is stabilized at a substantially constant temperature. The light output at this certain stable temperature is detected. Next, the control temperature is raised or lowered slightly to wait for the temperature to stabilize, and the light output is detected again. By repeatedly detecting the light output while slightly changing the temperature, temperature characteristic information indicating the relationship between the temperature and the light output is obtained. Then, based on the acquired temperature characteristic information, a temperature at which the optical output becomes substantially maximum is determined, and this is determined as an appropriate driving temperature. Once the proper driving temperature is determined, if this laser light source is to be used again, it is adjusted from the beginning to the previously determined proper driving temperature before use.

Further, since the proper driving temperature may change with time, even after the proper driving temperature is once determined,
The temperature characteristic information is acquired periodically (for example, every other month) in the same manner as described above, and the appropriate driving temperature is determined again.

However, as can be seen from the above description, the conventional method has a problem that it takes time to determine an appropriate driving temperature because light detection is performed while waiting for temperature stabilization to acquire temperature characteristic information. . For example,
When temperature characteristics information is acquired by changing the temperature in a temperature range of 2 ° C., it may take about 6 minutes to determine an appropriate driving temperature. For this reason, in the various devices using the laser light source, there has been a problem that the device cannot be used until the proper driving temperature is determined after the device is started.

The present invention has been made in view of the above circumstances, and has as its object to provide a method and an apparatus capable of determining an appropriate driving temperature of a laser light source in a short time.

[0013]

According to the present invention, a method of determining an appropriate driving temperature obtains temperature characteristic information of an optical output by detecting an optical output while changing the temperature of a laser light source with a substantially constant temperature gradient. It is characterized in that an appropriate driving temperature is determined based on temperature characteristic information.

That is, the method for determining an appropriate driving temperature of the present invention is 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 the heat source becomes substantially maximum. Then, while driving the heat source so that the temperature of the laser light source changes at a substantially constant gradient, the output power of the laser light emitted from the laser light source is detected to obtain temperature characteristic information indicating the temperature characteristics of the output power. It is characterized in that an appropriate driving temperature is determined based on the acquired temperature characteristic information.

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.

Further, 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.

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

If the acquired temperature characteristic information shows a plurality of peaks (maximum values) when re-determining the proper driving temperature, the one closer to the previously determined proper driving temperature is set as the present proper driving temperature. Good.

There is a laser light source disposed on a heat source.
The present invention is not limited to the configuration in which the laser light source is directly disposed on the heat source for temperature adjustment, but may be any configuration that determines the appropriate driving temperature at which the output power of the laser light is maximized.
For example, the heat source and the laser light source may be arranged close to each other, and the laser light source may be substantially arranged on the heat source.

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. By detecting the output power of the laser light 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, the temperature characteristic information indicating the temperature characteristics of the output power can be obtained. It is characterized by comprising temperature characteristic information acquiring means for acquiring and proper driving temperature determining means for deciding a proper driving temperature based on the acquired temperature characteristic information.

In the apparatus for determining an appropriate driving temperature according to the present invention, the temperature characteristic information acquiring means is provided with a laser light source having a temperature of 0.
It is desirable to drive the heat source so as to change at a substantially constant gradient within a range of 1 ° C./sec or less.

In the apparatus for determining an appropriate driving temperature according to the present invention, it is preferable that the laser light source has a laser diode.

Further, in the proper driving temperature determining apparatus of the present invention, it is preferable that the laser light source has a laser diode pumped solid laser such as an SHG laser. That is, the laser diode is used as an excitation source for exciting the solid-state laser crystal of the excitation solid-state laser.

In order to fully enjoy the effects of the present invention, it is desirable that the range of the output power at an appropriate driving temperature of the laser light source is 0.05 mW to 20 mW.

For the same reason, it is desirable that the range which can be adopted as the proper driving temperature is 10 ° C. to 45 ° C. and the operating environment temperature of the laser light source is 0 ° C. to 50 ° C.

[0028]

According to the method and the apparatus for determining an appropriate driving temperature of the present invention, the temperature characteristic information of the light output is obtained by detecting the light output while changing the laser light source with a substantially constant temperature gradient. Since the proper drive temperature is determined based on the characteristic information, there is no waiting time until the temperature of the laser light source stabilizes after the temperature is slightly changed, and the temperature characteristic information can be acquired at high speed. Specifically, the processing time for determining the appropriate driving temperature can be reduced.

Thus, it is also possible to solve the problem that the apparatus cannot be used before the appropriate driving temperature is determined after starting the various apparatuses using the laser light source.

[0030]

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 constituting 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, which is divergent light, are provided. (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 formed by the Nd: YAG crystal 13 and the resonator mirror 14, and the 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, and the condenser lens 12 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 the 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.
Is provided.

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.

The photodiode 33 fixed on the reference plate 22 is also connected to the portion of the above-described resonator and the laser diode 1.
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 drive temperature determining device 5 is configured to control the laser beam L3 (substantially the light beam L3) emitted from the laser light source 1 disposed on the Peltier element 24 as a heat source.
3a) for determining an appropriate driving temperature of the laser light source 1 at which the output power becomes maximum, wherein 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) is substantially constant. Peltier element 24
A temperature characteristic information acquiring means 52 for acquiring temperature characteristic information indicating a temperature characteristic of the output power by detecting the output power of the laser beam L3 emitted from the laser light source 1 while driving the laser; Proper drive temperature determining means 5 for determining a proper drive temperature based on the characteristic information
4 is provided. The temperature characteristic information obtaining means 52 and the proper drive temperature determining means 54 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 detect the detection light L3b with the photodiode 33, thereby substantially detecting the output power of the laser beam L3.

When the Peltier element 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 acquiring means 52 stops the feedback control of the temperature control circuit 42 and drives the Peltier element 24 so as to change the temperature of the laser light source 1 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.

It is sufficient that the laser light source 1 changes 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 is a flow chart showing a specific example of the proper driving temperature determining method of the present invention, which is performed in the proper driving temperature determining device 5 having the above-described configuration.

First, 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). # 1). At this time, the data accuracy of the control temperature for the temperature control circuit 42 may be, for example, about 12 bits.

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 # 2). 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 # 3). The accuracy of the optical output data acquired at this time is, for example, about 16 bits. In order to improve 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).
And

When the acquisition of the current temperature Tn in step # 2 and the acquisition of the current power Pn in step # 3 are completed, control is performed toward the temperature control circuit 42 so that the temperature of the laser light source 1 increases by about 0.03 ° C. The signal J0 is issued, and the temperature control circuit 42 drives the Peltier element 24 (step # 4).

Approximately 0.3 to 1.0 after step # 2
After about a second, the laser light source 1
, And the processing up to step # 4 is sequentially repeated in the same manner. The process is repeated until a desired number (here, N) of data is obtained (step # 5). That is, the processes of steps # 2 to # 5 are repeated in a repetition cycle of about 0.3 to 1.0 seconds.

As described above, the temperature characteristic of the light output can be obtained by obtaining the temperature data and the light output data for each repetition cycle while changing the temperature of the laser light source 1. Then, when the temperature characteristic information is obtained, a drive temperature at which the light output can be substantially maximized is obtained based on the result (step # 6).

Since the temperature characteristic information of the light output is generally obtained as having one maximum value (peak) as shown in step # 6 of FIG. 3, for example, the temperature exhibiting the peak is determined as the appropriate driving temperature. Or the median value of the temperature at the 90% position across the peak is taken as the appropriate drive temperature.
Further, when the acquired temperature characteristic information exhibits a plurality of peaks (maximum) as output power, the one closer to the previously determined proper driving temperature is set as the present proper driving temperature.

Here, the median value of the temperature at the 90% position across the peak is set as the appropriate driving temperature, for example, because of 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.

A signal J1 indicating the determined proper drive temperature is issued 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 drive temperature.

The information on the proper driving temperature determined in this way and the referred temperature characteristic information are stored in a storage element such as a memory, and are referred to in the next activation of the laser light source and the proper driving temperature determination processing at that time. It shall be.

In the above embodiment, in step # 4, the temperature of the laser light source 1 is increased at a rate of 0.03 ° C./sec or less, that is, changed at a constant gradient from the low temperature side to the high temperature side. The drive signal is issued to the Peltier element 24. Conversely, the drive signal is sent 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. In the same manner as described above, the temperature characteristic information of the light output may be acquired, and the drive temperature at which the light output can be maximized may be obtained based on the result.

Here, as can be seen from the description with reference to FIG. 3, in the method for determining an appropriate driving temperature of the present invention, the light output is detected by changing the laser light source 1 at a substantially constant temperature gradient. Temperature characteristic information (continuous data sampling to obtain temperature characteristic information),
Since the proper drive temperature is determined based on this temperature characteristic information, the temperature characteristic information can be acquired at high speed without waiting time until the laser light source stabilizes after a slight change in temperature. Can determine an appropriate driving 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.

Next, an embodiment to which the proper driving temperature determining method of the present invention is applied and a comparative example to which a conventional proper driving temperature determining method is applied will be described.

In the comparative experiment, it was examined how the proper driving temperature indicated when the environmental temperature and the temperature search sequence were changed under the condition using the conventional method at 23 ° C. and 50% was changed. And

As environmental conditions, 5 ° C., 50% RH, 23
The measurement is performed under three conditions of 50 ° C and 50% RH.

As a search sequence (a process for acquiring temperature characteristic information) when determining an appropriate drive temperature, when the conventional method is used, the temperature is raised every 0.03 ° C. to stabilize the temperature, and then the output of the photodiode is set. Data 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). On the other hand, when the method of the present invention is used, the temperature of the laser light source rises (indicated by “low → high” in a table described later) or decreases (in a table described below) at a constant gradient of about 0.03 ° C./sec. , The Peltier element is driven so as to perform “high → low”, 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, the central value of the temperature at the 90% position across the peak is determined as the appropriate driving temperature based on the obtained temperature characteristic information.

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

[0094] 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, one of the peaks (maximum value) is exhibited as a temperature characteristic of the light output under each environmental temperature in any of the search methods. 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 can be seen from Table 1, when the conventional method is used, it takes about 6 minutes to determine the appropriate driving temperature by sweeping within the range of 2 ° C. According to the method of the present invention, 2 ° C./0.03° C. = 66 samples, 0.5
If the above steps are repeated at a rate of about seconds / cycle, the time required for data sampling is about 33 seconds, and the appropriate driving temperature is determined even if processing other than data sampling for acquiring temperature characteristics is included. The time required for this could be made within 50 seconds. That is, if an appropriate driving temperature is determined by applying the present invention, the time can be reduced.

At 5 ° C. below B3-231, abnormal data (approximately twice as large) is obtained by any of the methods. 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 appropriate driving temperature can be obtained by referring to the temperature characteristic obtained again by giving the temperature change in the opposite direction. Because it was decided.

According to the experiment, when the speed of the temperature sweep was increased to 0.1 ° C./sec or more, the deviation from the result determined by using the conventional method became large, and a preferable result was not necessarily obtained. Therefore, when the present invention 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 driving temperature determined by the conventional method and the proper driving temperature determined by the method of the present invention in all standard environments is ± 0. It is within 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. The use of the method of the present invention for performing the processing is substantially equivalent to performing the temperature control by the conventional method, and the processing time of the SHG proper drive temperature search can be reduced.

In other words, in the conventional method and the method of the present invention, there is no problem even if the present invention is applied to determine an appropriate driving temperature without causing a difference within 0.1 ° C. The side effect of shortening the time, that is, a large deviation occurs in the peak detection result, does not occur.

Thus, if the method for determining an appropriate driving temperature of the present invention is applied to the above-described various devices using a laser light source,
The problem that the device cannot be used until the proper drive temperature is determined after the device is started can be solved.
That is, it is possible to quickly start up the device using the laser light source.

Even if the method of determining an appropriate driving temperature according to the present invention is carried out every time the power of the apparatus is turned on, the processing time is short as described above, so that the laser light source, especially the S
It does not affect the life of the HG laser.

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 conventional method, the temperature search range may be increased, but the processing time is correspondingly longer. On the other hand, according to the present invention, even if the temperature search range is widened, the temperature search can be completed in a short time. Therefore, even when the proper drive temperature is largely deviated due to a change with time, it is possible to easily find the appropriate drive temperature. it can.

Although the preferred embodiment of the method and apparatus for determining an appropriate drive 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 standard output power is about 1 to 3 mW. However, the present invention provides that the output power range under the proper driving temperature of the laser light source is 0.05 mW.
It is suitable to apply to those of about 20 mW.

In the above embodiment, the laser power (optical output) is at the time of the 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.

In the above embodiment, the laser light source using the SHG laser was used. However, the present invention is not limited to this.
A laser light source is disposed on a heat source, such as a laser, and can be applied to any device that needs to determine an appropriate driving temperature at which the output power of the laser light is maximized in actual use.

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 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.

[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 drive temperature determining device 9 Package case 10 LD-excited solid-state laser 11 Laser diode (semiconductor laser) 12 Condensing lens 13 Nd: YAG crystal 14 Resonator mirror 15 Wavelength conversion unit 22 Reference plate 24 Peltier device 31 Optical Filter 32 Beam Splitter 33 Photodiode 34 APC Circuit 40 Temperature Sensor 42 Temperature Control Circuit 52 Temperature Characteristic Information Acquisition Means 54 Appropriate Driving Temperature Determination Means L1 Laser Beam (for Excitation) L2 Laser Beam (Fundamental Wave) L3 Laser Beam (No. L3a Used light L3b Detection light

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Moroboshi 798, Miyadai, Kaisei-cho, Ashigara-gun, Kanagawa F-Term (in reference) 5F072 AB02 JJ20 KK01 KK05 KK08 KK12 KK15 KK30 PP07 TT05 TT14 TT27

Claims (6)

[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 maximum, wherein the temperature of the laser light source is By detecting the output power of the laser light emitted from the laser light source while driving the heat source so as to change at a substantially constant gradient, temperature characteristic information indicating the temperature characteristic of the output power is obtained, and the obtained temperature is obtained. A proper driving temperature determining method, wherein the proper driving temperature is determined based on 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 temperature of the laser light source is Temperature characteristic information for obtaining temperature characteristic information indicating the temperature characteristic of the output power by detecting the output power of the laser light emitted from the laser light source while driving the heat source so as to change at a substantially constant gradient. An appropriate driving temperature determining apparatus comprising: an obtaining unit; and an appropriate driving temperature determining unit that determines the appropriate driving temperature based on the obtained temperature characteristic information. 3. 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 apparatus for determining an appropriate driving temperature according to claim 2. 4. The apparatus according to claim 2, wherein the laser light source has a laser diode. 5. The apparatus according to claim 4, wherein the laser light source includes a laser diode-pumped solid-state laser. 6. The apparatus according to claim 2, wherein an output power of the laser light source at the appropriate driving temperature is in a range of 0.05 mW to 20 mW.