JP3049469B2 - Laser output detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical detection type laser output detection apparatus.

[0002]

2. Description of the Related Art In the field of laser processing, for example, in order to automatically control the processing quality, the output of laser light (light intensity)
Is used. In general, laser output detection devices are roughly classified into those of a calorimetric type using a photothermal converter such as a calorimeter and those of a photodetection type using a photoelectric conversion element such as a photodiode. The calorimetric measurement method has the disadvantage that the response speed is low because it converts the output of the laser light into heat once, and it takes several seconds to obtain the measured value.
Recently, the photodetection method has become mainstream.

FIG. 8 and FIG. 9 are views showing the configuration of a conventional laser output detection device based on a light detection method. FIG. 8 is a cross-sectional view and FIG. 9 is a front view.

In this laser output detecting device, a housing 102 having a laser light introducing window 102a on one side is provided upright on a mounting substrate 100. Housing 1
In 02, a reflection mirror 104 is disposed at an angle of 45 ° with respect to the laser light introduction window 102a. An opening 102b is provided on a side surface of the housing 102 located in the reflection direction when viewed from the reflection mirror 104, and one opening ( The laser beam entrance 108a is fixed with bolts (not shown) or the like. And the first
The other opening (laser light exit) 108 of the holder 108
One opening (laser beam entrance) 110a of the cylindrical second holding body 110 made of metal is fixed by fitting into b.
The other opening (laser beam exit) 1 of the second holder 110
The circuit board 112 is mounted on the 10b side. At four corners of the mounting substrate 100, mounting holes 100 for passing bolts are provided.
a is provided.

The laser beam entrance 108 of the first holder 108
At a, a plano-convex lens 114 is arranged with its convex surface facing the reflection mirror 104 side. A plurality of, for example, three ND filters 1 are provided in the laser beam entrance 110a of the second holder 110.
16 and one visible light cutoff filter or one infrared transmission filter 118 are arranged side by side in the optical axis direction.
A photoelectric conversion element, for example, a photodiode 120 is mounted on the circuit board 112 with the light receiving surface facing the filter side at the laser light exit portion 110b of 10.

In such a configuration, the laser light introduction window 10
2a, a laser beam emitted from, for example, a laser oscillation unit (not shown) is passed through a beam splitter (not shown), and a part (for example, 1%) of the laser beam L reflected therefrom is reflected.
B is incident. The laser light LB entering the housing 102 bends the optical path by 90 ° by the reflection mirror 104, passes through the plano-convex lens 114, the ND filter 116, and the visible light cutoff filter 118 and enters the light receiving surface of the photodiode 120.

At this time, the plano-convex lens 114 has a laser beam LB
Is focused on the light receiving surface of the photodiode 120, and ND
The filter 116 attenuates the light intensity of the laser light LB at a predetermined attenuation rate.
, The visible light component is removed as a noise component. From the output terminal of the photodiode 120, the received laser light L
An electric signal representing the output of B, and thus the output of the laser light LB incident on the laser light introduction window 102a or the output of the laser light LB emitted from the laser oscillation unit, is obtained.

[0008]

Incidentally, the photoelectric conversion characteristics of a photoelectric conversion element such as a photodiode change in accordance with the ambient temperature, and the output signal changes even if a laser beam having the same light intensity is received. Also, optical filters such as an ND filter and a visible light cutoff filter are liable to change in filter characteristics depending on the ambient temperature. For this reason, the conventional laser output detection device as described above has a drawback that, for example, the output signal of the photodiode 120 is different between the morning and the afternoon in the laser processing plant even if the output of the laser light LB is the same. No stable laser output measurement value was obtained. In particular, immediately after the start of measurement, that is, immediately after the transmission or incidence of the laser light, the transmittance of the optical filter and the photoelectric conversion rate of the photoelectric conversion element are likely to fluctuate greatly,
For this reason, the laser output measured value was liable to fluctuate greatly.

[0009]

[0010] The present invention has been made in view of such problems.
Intended, and aims to provide a laser output detection device in combination with a simple and small temperature control mechanism and a temperature compensating mechanism so as to obtain a stable and highly accurate laser output measured value
I do .

[0011]

In order to achieve the above object, a first laser output detecting apparatus according to the present invention comprises a laser light detecting device.
In a laser output detection device that detects the output of, a photoelectric conversion element that receives the laser light and converts the output of the laser light into an electric signal, and a holder having high thermal conductivity that holds the photoelectric conversion element, Heating or cooling the holder
A temperature adjusting means for changing a resistance value according to a temperature of the holder;
Temperature of the first resistor and the holding body to a predetermined temperature.
In order to maintain the resistance, the temperature adjusting means is connected to the resistance of the first resistor.
Temperature control controlled by on / off control method according to resistance value change
Control means, and the photoelectric conversion element according to a temperature of the holder.
Resistor whose resistance value changes with a temperature coefficient of opposite polarity
And the electrical signal obtained from the photoelectric conversion element is
Temperature compensation circuit for compensating for a change in the resistance value of the second resistor
And a road .

[0012] The second laser output detector of the present invention are
In a laser output detection device that detects the output of laser light,
An optical filter that passes the laser light, and the optical filter
Receiving the laser light passing therethrough and changing the output of the laser light
A photoelectric conversion element for converting into an electric signal, and the optical filter
Holding body having high thermal conductivity for holding the substrate and the photoelectric conversion element
And temperature adjusting means for heating or cooling the holder,
A first resistor whose resistance value changes according to the temperature of the holder
Body and the holder so as to maintain the temperature of the holder at a predetermined temperature.
Temperature control means for changing the resistance value of the first resistor
Temperature control means for controlling by an on / off control method;
A temperature coefficient having a polarity opposite to that of the photoelectric conversion element according to the temperature of the holding body.
A second resistor whose resistance value changes with the number, and the photoelectric conversion element
The electric signal obtained from the second resistor to the resistance of the second resistor.
A temperature compensating circuit for compensating according to the value change is provided.

[0013]

[0014]

[0015]

[Action] In the laser output detector of the above configuration, the holding member for holding the photoelectric conversion element is controlled to a predetermined temperature by the temperature control means, and the output signal is the temperature compensator of the photoelectric conversion element
Since the temperature is compensated by the structure (the second resistor and the temperature compensating circuit) , the photoelectric conversion element operates without being influenced by the ambient temperature, the state of the laser beam, and the like, and the high-precision representing the laser beam output accurately An electric signal is obtained. In addition,
The temperature control mechanism (first resistance and temperature control means)
Performs temperature control using the on / off control method,
Compensation mechanism (second resistance and temperature compensation circuit)
Compensates for temperature ripple caused by control
A simple and small temperature control mechanism and temperature compensation mechanism
Obtaining stable and accurate laser output measurements combined
Can be.

[0016]

[0017]

[0018]

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view showing the overall configuration of a laser output detection device according to an embodiment of the present invention, and FIG. 2 is a side cross-sectional view showing the configuration of a main part of the laser output detection device.

In this laser output detection device 10, a box-shaped housing 12 having a laser light introduction window 12a on one side is provided on a mounting substrate 11. In the housing 12, a reflection mirror 14 is attached to a mirror support 16 at an angle of 45 ° with respect to the laser light introduction window 12a. An opening 12b is provided on a side surface of the housing 12 located in the reflection direction when viewed from the reflection mirror 14.

At the center of the housing 12, a pair of rod-shaped support members 18 are fixed to the side surfaces of the housing 12 with bolts 20 in a direction perpendicular to the optical axis. One opening (laser beam entrance) 22 of a first cylindrical holder 22 made of a light-shielding insulating material, for example, resin, is provided on these rod-shaped support members 18.
a is fixed by bolts 24.

Near the opening 12b of the housing 12, the first
The other opening (laser beam outlet) 22b of the holder 22 is provided with a four-tube connecting member 26 made of a light-shielding insulating material such as a resin through a four-tube connecting member 26. One opening (laser light entrance) 28a of the second holder 28 is connected, and a circuit board 30 is connected to the other opening (laser light exit) 28b of the second holder 28. The rod-shaped support member 18 has four parallel to the optical axis.
One ends of the rod-shaped support members 32 are fixed, and the circuit board 30 is fixed to the other ends of the rod-shaped support members 32 with bolts 34. At four corners of the mounting board 11, mounting holes 11a for passing bolts are formed.

A dustproof glass plate 36 is attached to the laser beam inlet 22 a of the first holder 22, and a light diffusion plate 40 is attached to the inside of the glass plate 36 via an O-ring 38. The second holder 28 includes a plurality of, for example, three N
A D filter 42 and one visible light cutoff filter or infrared transmission filter 44 are arranged side by side in the optical axis direction, and a photoelectric conversion element such as a photodiode 46 has a light receiving surface facing the filter near the laser light exit portion 28b. 3
Mounted on 0.

On the inner wall surface of the second holder 28, a step 28c is formed at a position slightly closer to the center than the light receiving surface of the photodiode 46, and the optical filters 42 and 44 are cylindrically shaped using the step 28c as a stopper. The optical filters 42 and 44 are firmly held in the second holding body 28 by being pushed in at the end face of the connecting member 26.

In the laser optical system having such a configuration, for example, a laser beam emitted from a laser oscillating unit (not shown) is passed through a beam splitter (not shown) to a laser beam introducing window 12a, and a part reflected therefrom is reflected. (For example, 1%) of the laser light LB is incident. The laser beam LB entering the housing 12 bends the optical path by 90 ° by the reflection mirror 14, passes through the glass plate 36, the light diffusion plate 40, the ND filter 42 and the visible light cutoff filter 44, and reaches the light receiving surface of the photodiode 46. Incident.

At this time, the light diffusion plate 40 diffuses the laser light LB. Thereby, the light beam cross-sectional area of the laser light LB is expanded. Since the first holder 22 and the connecting member 26 are light-blocking, the laser light LB does not leak to the outside, no external light enters the laser light path, and all of the laser light LB The light enters the ND filter 42 disposed at the laser beam inlet 28a of the holder 2. The ND filter 42 attenuates the light intensity of the laser light LB at a predetermined attenuation rate. The visible light blocking filter 44 removes a visible light component from the laser light LB as a noise component. The photodiode 46 converts the intensity of the received laser beam LB into an electric signal. This electric signal indicates the output of the laser light LB incident on the laser light introduction window 12a, and thus indicates the output of the laser light LB emitted from the laser oscillation unit.

The laser output detecting apparatus of this embodiment is provided with a temperature control mechanism and a temperature compensation mechanism as described below in order to stably operate the above-mentioned laser optical system without being affected by the ambient temperature.

The four side walls of the second holding member 28 are composed of a pair of thin side walls facing each other as shown in FIG. 1 and a pair of thick side walls facing each other as shown in FIG.

As shown in FIG. 2, a heating element 48 made of, for example, a metal film resistor is adhered or attached to the outer wall surface of one thick side wall 28d of the second holding member 28. The resistance heating element 48 is provided with a power supply (not shown) under the control of a circuit board (not shown) on which the mounting board 10 is mounted or a temperature control circuit (not shown) mounted on the circuit board 30. ) By receiving more power and resistive heating
The second holder 28 is heated.

Thick side walls 28e, 28d of the second holding member 28
In the figure, two thermistors 50 and 52 are embedded at positions close to the photodiode 46. The terminals 50a, 52a of these thermistors 50, 52 protrude outside the circuit board 30 and are connected to a temperature control circuit and a temperature compensation circuit via wiring on the circuit board 30, respectively.

FIG. 3 shows the configuration of the temperature control circuit in this embodiment. This temperature control circuit comprises a thermistor 50 and three resistors 54, 56, 5 between the DC power supply VC and the ground.
8 is connected to a bridge circuit, a pair of intermediate connection points NA and NB in the bridge circuit are connected to both input terminals of the operational amplifier 60, and the output terminal of the operational amplifier 60 is connected to a switch 62 inserted in the heating element power supply circuit. Are connected to the control terminal. Series resistors 56 and 58 in the bridge circuit
Constitutes a reference voltage generating circuit.

The thermistor 50 has a negative temperature coefficient N
In the case of the TC thermistor, when the temperature of the second holder 28 rises due to the heat generated by the resistance heating element 48, the resistance value of the thermistor 50 decreases, and the voltage VA at the intermediate connection point NA rises. When the voltage VA exceeds the reference voltage VS,
The output voltage of the operational amplifier 60 becomes H level, the switch 62 is opened, and the resistance heating element 48 is turned off. As a result, heat generation of the resistance heating element 48 stops. Second holder 28
As the temperature decreases, the resistance value of the thermistor 50 increases, and the voltage VA at the intermediate connection point NA decreases. And
When the voltage VA falls below the reference voltage VS, the operational amplifier 6
The output voltage of 0 becomes the L level, the switch 62 is closed, and the power supply to the resistance heating element 48 is restarted.

As described above, the temperature control mechanism in the present embodiment comprises the optical filters 42 and 44 and the photodiode 4
High heat conductive second holding body 28 holding body 6 integrally
Is controlled by a feedback control method so as to maintain the temperature (for example, 40 ° C.) corresponding to the reference voltage VS. Thereby, the optical filters 42, 4
The photodiode 4 and the photodiode 46 operate at a substantially constant temperature regardless of the ambient temperature and without being affected by the energy of the laser beam LB. Accordingly, a highly accurate laser output measurement value can be obtained immediately after the start of laser oscillation.

Further, the temperature control mechanism in the present embodiment
Since the heating of the holder 28 is controlled by the on / off control method, the temperature control circuit is made small and inexpensive.

However, according to the on / off control method, the opening and closing of the switch 62 are frequently repeated, so that the resistance heating element 48 generates heat intermittently. Therefore, as shown in FIG. A ripple rp appears at the temperature of the holder 28. This temperature ripple rp affects the photoelectric conversion of the photodiode 46.

In this embodiment, such a second holding member 28 is used.
The following temperature compensation circuit is provided to cancel the effect of the temperature ripple rp on the photodiode 46 and stabilize the measured value of the laser output.

FIG. 4 shows the configuration of the temperature compensation circuit in this embodiment. This temperature compensating circuit includes the photodiode 4
6, the cathode terminal is connected to the ground, the anode terminal is connected to the non-inverting input terminal (+) of the operational amplifier 64, the inverting input terminal (-) of the operational amplifier 64 is connected to the ground, and the non-inverting A series-parallel resistance circuit including a thermistor 52 and resistors 66 and 68 is connected as a feedback resistor between the input terminal (+) and the output terminal.

In this temperature compensation circuit, the laser light LB
Is incident on the photodiode 46 and a current ILB corresponding to the light intensity of the laser beam LB flows through the photodiode 46, and a voltage signal SLB corresponding to the current ILB is obtained at the output terminal of the operational amplifier 64.

Generally, the photoelectric conversion characteristic of the photodiode 46 has a positive temperature coefficient as shown by a curve PL in FIG. 5, and the output (photocurrent) level tends to increase as the ambient temperature increases. The temperature characteristic of the photoelectric conversion is approximated by the following equation. SLB (△ T) = R ・ ILB ・ exp (α △ T) (1) where α is the temperature coefficient of the photosensitivity, and の T is an arbitrary reference temperature (for example, 25 ° C.) Indicates the temperature difference.

In this temperature compensating circuit, the thermistor 52 is constituted by an NTC thermistor having a negative temperature coefficient, and the resistance values (R66, R68) of the feedback resistors 66, 68 are selected in accordance with optimization conditions such as the least square method.

In the circuit of FIG. 4, the above equation (1) becomes the following equation (2). SLB (△ T) = [R66 + [R68 ・ R52 ・ exp ｛−B △ {T / T0 ・ (T0 + △ T)｝] / [R68 + R52 ・ exp ｛-B △ T / T0 ・ (T0 + △ T) ｝]] · ILB · exp (α △ T) (2) where T0 is a reference temperature of 298 ° K (25 ° C), and B is a thermistor constant.

In order to compensate for the temperature characteristic, a condition (parameter value) satisfying the following equation (3) may be obtained. d [SLB (ΔT)] / d (ΔT) = 0 (3)

However, there may be no value (solution) that satisfies this condition. Further, there is a value (solution) at a specific temperature, but it may not be possible to cope with a wide range of temperatures. To solve these, d
[SLB (△ T)] / d (△ T) = εi, and Σεi ²
The condition (parameter value) for minimizing may be selected.

In this manner, the temperature characteristic of the photodiode 46 is compensated, and the output signal SLB of the operational amplifier 64 is changed to the operating temperature range of the photodiode 46 (normally 20 to 50 ° C.) as shown by the curve QL in FIG. Can be stabilized within.

As described above, in the temperature compensation circuit according to the present embodiment, the resistor (thermistor) 52 having a temperature coefficient opposite to that of the photodiode 46 is attached to the second holder 28,
The resistor (thermistor) 52 is incorporated in a feedback resistor of a photocurrent-voltage conversion circuit for converting a photocurrent output from the photodiode 46 into a voltage signal, and the resistance values of the feedback resistors 66 and 68 are set to appropriate values. By selecting this, the photoelectric conversion characteristics of the photodiode 46 are temperature-compensated, and the laser output measurement signal SLB independent of the ambient temperature is output.

As a result, even if the temperature of the second holder 28 fluctuates as shown in FIG. 6A due to the on / off control of the temperature control mechanism, the laser output output from the temperature compensating circuit can be obtained. As shown in FIG. 6B, no ripple appears in the measurement signal SLB, and a stable and accurate laser output measurement value is obtained.

In the laser output detecting device of this embodiment, a thermal guard or a thermal protector 53 is attached to the outer wall surface of the thick side wall 28e of the second holder 28. The thermal guard 53 has a built-in thermoresponsive element such as a thermostat. When the temperature of the second holder 28 rises to a predetermined overheating temperature (for example, about 65 ° C.) due to a runaway temperature control mechanism or the like, the thermostat of the thermal guard 53 operates to cut off the power supply to the heating element 48. It has become.

Further, in the laser output detection device of this embodiment, the laser beam LB whose light beam cross-sectional area is increased by the light diffusing plate 40 is made to enter the photodiode 46 through the optical filters 42 and 44. The optical filters 42 and 44 can be arranged at an arbitrary position behind the light diffusion plate 40, and preferably the photodiode 4
By disposing the second holding member 28 at a position close to 6, the second holding member 28 having high thermal conductivity can be configured to be small in size and small in heat capacity. When the heat capacity of the second holding member 28 is small as described above, the time required to start up to the set temperature is short, and the power required for temperature control is small.

In this regard, in the conventional laser output detection device (FIG. 8), since the laser light condensed near the light receiving surface of the photoelectric conversion element 120 by the condenser lens 114 passes through the optical filters 116 and 118, In order to avoid fluctuations due to heat generation, the optical filters 116 and 118 are positioned at a position where the laser beam cross section is as large as possible, that is, the condenser lens 11.
In this case, the second holding member 110 is inevitably lengthened and increased in size, and its heat capacity is increased.

FIG. 7 is a block diagram showing the configuration of a YAG laser processing system to which the laser output detection device according to this embodiment is applied. 7, portions corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals.

This YAG laser processing system is a YAG laser processing system.
The output of the laser light LB oscillated and output from the laser oscillator 72 is controlled by a feedback method. The YAG laser oscillator 72 includes a YAG rod, an excitation lamp, an optical resonator, and the like.
The excitation lamp is turned on in response to the lamp current from 0, light having a predetermined wavelength component is emitted from the YAG rod excited by the light energy, and light of a specific wavelength is resonance-amplified by the optical resonator. Light LB is output. The laser light LB passes through the beam splitter 74, and a part of the laser light LB reflected there is guided to the laser output detection device 10 of the present embodiment. As described above, the electrical signal ILB representing the output of the laser light LB is obtained from the photodiode 46 of the laser output detection device 10.

Most of the laser beam LB transmitted through the beam splitter 74 is directly irradiated onto a workpiece (not shown) via an optical lens (not shown), or is once irradiated with an incident unit (not shown). ), From which the light is sent to a remote output unit via an optical fiber (not shown), and the output unit irradiates the workpiece.

The electric signal (photocurrent) ILB output from the photodiode 46 of the laser output detection device 10 is converted into a voltage signal SLB by a photocurrent-voltage conversion circuit 76. This conversion circuit 76 corresponds to the temperature compensation circuit (FIG. 4). Voltage signal SLB obtained from conversion circuit 76
Is converted into a digital signal by a sample- and-hold circuit 78 and a digital / analog conversion circuit 80 before being input to the CPU 82.

The CPU 82 operates according to a program stored in the memory 84, performs predetermined calibration or correction operation on the input laser output detection signal SLB, and obtains a measured value of the output of the laser beam LB. And CPU8
2. A comparison error is obtained by comparing the obtained laser output measurement value with the laser output set value input from the input unit 88 and stored in the memory 84, and a control signal CS for making the comparison error zero is output to the laser. Power supply 70. Also, the laser output measurement value and other data are displayed through the display unit 86 as necessary. Further, the CPU 82 controls the temperature control control circuit 9.
For 0, data such as a temperature set value input from the input unit 88 and a required control signal TS are given.

In this laser processing system, the laser output detection signal ILB accurately representing the output of the laser beam LB is obtained from the laser output detection device 10 immediately after the start of the oscillation of the YAG laser oscillator 72 without being affected by the ambient temperature. Therefore, a desired laser output waveform can be obtained by highly accurate and stable feedback control.

In the above-described embodiment, the two thermistors 50 and 52 are separately mounted in the second holding member 28.
Both thermistors 50 and 52 may be attached together (at one location). In addition, although a simple and small-scale temperature control circuit using an on / off control method is used, a temperature control circuit using a PID control method may be used.

In the above embodiment, the cylindrical connecting portion 26 is provided separately in order to reduce the heat capacity of the second holding member 28 as much as possible. However, these members may be formed integrally.
The types and the numbers of the optical filters 42 and 44 in the above embodiment are merely examples, and an arbitrary number of optical filters of any type can be used. A photoelectric conversion element other than a photodiode can also be used. The laser beam to be detected is not limited to the YAG laser beam, but may be another laser beam such as a CO2 laser beam or a semiconductor laser beam.

In the above embodiment, the temperature of the second holding member 28 is adjusted to a set temperature higher than the normal temperature by using the resistance heating element 48 as a means for adjusting the temperature. It is also possible to provide a cooling-type temperature adjusting means using the same or the like to adjust the temperature to a set temperature lower than the normal temperature.

[0060]

As described above, according to the laser output detecting apparatus of the present invention, by using a simple and small temperature control mechanism and a temperature compensation mechanism together, a high temperature which is not affected by the ambient temperature, the laser output state and the like can be obtained. Accurate and reliable laser power measurements can be guaranteed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the overall configuration of a laser output detection device according to one embodiment of the present invention.

FIG. 2 is a side sectional view showing a configuration of a main part of the laser output detection device according to the embodiment.

FIG. 3 is a circuit diagram illustrating a configuration of a temperature control circuit according to the embodiment.

FIG. 4 is a circuit diagram illustrating a circuit configuration of a temperature compensation circuit according to an embodiment.

FIG. 5 is a diagram showing temperature-output characteristics of a photoelectric conversion element and a temperature compensation circuit in an example.

FIG. 6 is a diagram illustrating a time-temperature characteristic of a second holder and a time-output characteristic of a temperature compensation circuit in the example.

FIG. 7 is a block diagram illustrating a configuration of a YAG laser processing system to which the laser output detection device according to the embodiment is applied.

FIG. 8 is a longitudinal sectional view showing a configuration of a conventional laser output detection device.

FIG. 9 is a rear view showing the configuration of a conventional laser output detection device.

[Explanation of symbols]

 Reference Signs List 10 laser output detection device 28 second holder 42 ND filter 44 visible light cutoff filter 46 photodiode 48 resistance heating element 50 thermistor 52 thermistor 60, 64 operational amplifier 66, 68 resistance

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 1/02 G01J 1/42 B23K 26/00 H01S 3/00

Claims (2)

(57) [Claims] 1. A laser output detection device for detecting an output of a laser beam, comprising: a photoelectric conversion element that receives the laser beam and converts the output of the laser beam into an electric signal; and a heat conductor that holds the photoelectric conversion element. A holding member having a high rate, a temperature adjusting means for heating or cooling the holding member, and a first resistor having a resistance value that changes according to the temperature of the holding member.
Body and the temperature controller so as to maintain the temperature of the holder at a predetermined temperature.
The adjusting means is turned on / off in response to a change in the resistance value of the first resistor.
Temperature control means for controlling by an off control method, and a reverse polarity of the photoelectric conversion element according to the temperature of the holding body.
A second resistor whose resistance value at temperature coefficient changes, the photoelectric conversion the second said electrical signal obtained from the element
And a temperature compensating circuit for compensating according to a change in the resistance value of the resistor . 2. A laser output detection device for detecting an output of a laser beam, comprising: an optical filter that passes the laser beam;
A photoelectric conversion element for converting an output of laser light into an electric signal; and a heat transfer element for holding the optical filter and the photoelectric conversion element.
A holding member having a high conductivity, a temperature adjusting means for heating or cooling the holding member, and a first resistor having a resistance value that changes according to the temperature of the holding member
Body and the temperature controller so as to maintain the temperature of the holder at a predetermined temperature.
The adjusting means is turned on / off in response to a change in the resistance value of the first resistor.
Temperature control means for controlling by an off control method, and a reverse polarity of the photoelectric conversion element according to the temperature of the holding body.
A second resistor whose resistance value at temperature coefficient changes, the photoelectric conversion the second said electrical signal obtained from the element
And a temperature compensating circuit for compensating according to a change in the resistance value of the resistor .