JP2558268Y2 - Isothermal control calorimeter - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isothermal control calorimeter for measuring the power of light from a laser or the like, and more particularly to stabilization of a measuring operation.

[0002]

2. Description of the Related Art As an isothermal control calorimeter of this type, a calorimeter having the structure shown in FIG. 4 is well known.

In FIG. 1, reference numeral 1 denotes a photoreceptor forming a sensor portion, which comprises a cylindrical body 3 having an inner surface coated with a light absorbing paint 2 and a heat transfer plate 1a in which a heater 4 is embedded. 5
a and 5b are temperature difference detecting elements, 7 is a thermoelectric cooling element,
These elements are formed of Peltier elements having the same performance, and are fixed while being sandwiched between the heat transfer plate 1a and the temperature reference jacket 10. In addition, the outer periphery of the reference jacket 10 is surrounded by a first jacket 21 and a second jacket 22 as shown in FIG. 5 in order to stabilize the temperature, and a calorimeter 15 in which the sensor section is surrounded by a triple jacket. It is configured. The heat capacity of the heat transfer plate 1a including the cylindrical body 3 and the heat capacity of the reference jacket 10 are about 1: 1000, and the reference jacket 10 is larger.

[0004] Reference numeral 9 denotes a constant current source connected to the thermoelectric cooling element 7. Reference numeral 8 denotes a feedback amplifier for amplifying the output from the temperature difference detecting elements 5a and 5b, and this output is applied to the heater 4.

In the above configuration, when the measuring light is not input, the reference jacket 10 is kept at room temperature, and a constant current is constantly applied from the constant current source 9 to the thermoelectric cooling element 7 composed of a Peltier element. The hot plate 1a side is always cooled. In this case, the reference jacket 10 is heated, but the heat capacity of the reference jacket 10 is large and the heating amount of the thermoelectric cooling element 7 is small, so that the temperature of the temperature reference jacket 10 is not increased. Absent.

Therefore, in the apparatus shown in FIG. 4, the thermoelectric cooling element 7 and the constant current source 9 always act to increase the temperature on the reference jacket 10 side and decrease the temperature on the photoreceptor 1 side.

On the other hand, the temperature difference detecting elements 5a and 5b detect this temperature difference (nV level), and the preamplifier 11 amplifies the output to the mV level. Then, the main amplifier 12 performs a predetermined PID control operation based on the output of the preamplifier 11. In PID control, P (proportional), I
The respective constants of (integral) and D (differential) are determined and matched with the response time constant of the light detecting section (light absorber, temperature detecting element). Then, the output of the main amplifier 12 is applied to the heater 4 to increase the temperature of the heater 4 and control is performed so that the outputs of the temperature difference detecting elements 6, 6a become zero.

Accordingly, in the apparatus of Figure 4, the thermoelectric cooling element 7
The voltage from the main amplifier 12 to the cooled heat transfer plate 1a by the action of the constant current source 9 (current) in addition to the heater 4 heats the heat transfer plate 1a, the photoreceptor 1 temperature and temperature reference jacket 10 Are controlled so that their temperatures match.

In such a state, the laser beam L to be measured is
When a is incident from the upper part of the cylinder 3, the photoreceptor 1 absorbs light and the temperature rises according to the light power. The heat is conducted to the heat transfer plate 1a, and the heat transfer plate 1a is in a temperature equilibrium state.
And a reference jacket 10 causes a temperature difference. The temperature difference is detected by the temperature difference detecting elements 5a and 5b, and the main amplifier 12 reduces the voltage value sent to the heater 4. Therefore, the temperature of the heater 4 decreases, and the temperature of the heat transfer plate 1a and the temperature of the reference jacket 10 again match.

[0010]

As shown in FIG. 4, the feedback amplifier 8 is provided outside the sensor. Therefore, from the sensor to the feedback amplifier,
Usually, a signal cable 13 of about 2 m is used. The signal transmitted through the signal cable 13 is a minute signal of the nV level, and is the weakest part against external noise.

That is, noise picked up by the signal cable 13 is also amplified by the preamplifier 11. Therefore, it is not advisable to lengthen the signal cable 13.

In general, the input portion of the low-noise amplifier has a heat insulating structure with the outside to prevent noise due to thermoelectromotive force, and has an isothermal structure between terminals. Also, a technique for integrating a sensor portion and a preamplifier (head amplifier) to suppress the influence of external noise and improve NF is well known. However, if they are simply integrated, the heat generated by the power consumption of the preamplifier interferes with the calorimeter serving as the heat sensor, causing an adverse effect. For this reason, it was difficult to apply such a technique to an isothermal control calorimeter. Therefore, it was common to install the amplifier section away from the sensor.

The present invention has been made in view of such a point, and an object of the present invention is to provide an isothermal control calorimeter in which noise resistance is considered.

[0014]

According to the present invention, there is provided a photoreceptor having a heater embedded therein and a photoreceptor covering the photoreceptor.
And a temperature reference jacket
Cooling means disposed in contact with the bracket and said photoreceptor;
These are placed in contact with the photoreceptor and the temperature reference jacket.
A temperature difference detecting element for detecting a temperature difference between
A cell <br/> capacitors unit consisting placed insulating jacket over the jacket, the temperature of the photoreceptor of the optical detection unit by driving the heater based on the temperature difference detection signal from said temperature difference detection element constant a isothermal control type optical power meter comprising a control unit for controlling so as to keep the said installed in the insulation jacket, a chopper for modulating the chopping an output of said temperature difference detection element, wherein the sensor outside the insulation jacket <br/> support portion and is integrally installed, and a amplifier for demodulating and amplifying the modulated output of the chopper, is characterized in that integrating the preamplifier control unit and the sensor unit.

[0015]

In the present invention, the output of the temperature difference detecting element is modulated by the chopper in the heat insulation jacket. The modulation output of the chopper is demodulated and amplified by an amplifier integrated with the sensor unit. The chopper and the amplifier constitute a preamplifier, and the output of the amplifier is connected to an external control unit. The heater and the cooling means of the sensor unit are driven by the control unit, and the optical power is measured while performing isothermal control.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a state of measurement, and FIG. 3 is a time chart showing an operation at the time of measurement.

First, the overall operation of the apparatus will be described. FIG.
In this case, it is assumed that the laser beam output from the stabilized light source D is incident on the light receiving head A via the attenuator E and the shutter F.

In the first step of the measurement operation, the shutter F is closed, and no light enters the light receiving head A. In this state, the heater power is controlled so that the temperature reference jacket 10 and the photoreceptor 1 are in a thermal equilibrium state. At this time, the heater power consumption measured by the heater power meter is PH1.

In the second step, the heater power is controlled so that the temperature reference jacket 10 and the photoreceptor 1 are in thermal equilibrium with the shutter F open. At this time, the heater power consumption measured by the heater power measuring device 26 is set to PH2.

As a result, the incident light power PL is replaced by the difference in heater power consumption (PH1−PH2), and PH1 and P
By knowing H2, the incident light power PL can be known.

Next, the features of this embodiment will be described in detail with reference to FIG. In this embodiment, the conventional preamplifier with a built-in control unit apart from the photoreceptor is abolished and integrated with the sensor unit. However, if it is simply integrated with the sensor unit, the heat generated by the power consumption of the preamplifier adversely affects the calorimeter.

First, a chopper amplifier is used as a low noise amplifier, and a chopper 24 for performing chopping and an amplifier 25 for performing demodulation and amplification are installed separately. The chopper 24 is installed outside the temperature reference jacket 10. As a result, the chopper portion is placed in a thermally stable heat insulating jacket, and the minute signal output from the calorimeter is modulated by chopping, so that it is not affected by the thermoelectromotive force. After that, the amplifier 2 integrated with the head outside the insulation jacket
5, the heat due to the power consumption of the amplifier 25 does not adversely affect the calorimeter. Since the output of the amplifier 25 is amplified to, for example, about several mV, the influence of noise on the cable C is reduced. Further, noise reduction is further realized by making the input portion isothermal.

In the above embodiment, a triple insulation jacket structure is shown, but other structures (for example,
This can also be realized with a double structure.

As described above, an isothermal control calorimeter in which a preamplifier and a sensor are integrated can be realized in a state where thermal interference does not occur, and stable operation against electromagnetic disturbance can be realized as an optical power standard. Will be possible.

[0026]

As described above in detail, according to the present invention, a chopper that is installed in the heat insulating jacket of the sensor unit and modulates the output of the temperature difference detecting element by chopping, and the sensor unit outside the heat insulating jacket. It is installed integrally,
By providing an amplifier for demodulating and amplifying the modulation output of the chopper and integrating the preamplifier of the sensor unit and the control unit, an isothermal control calorimeter excellent in noise resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a measurement state of the device according to the embodiment of the present invention;

FIG. 3 is a time chart showing a measurement state of the apparatus according to the embodiment of the present invention;

FIG. 4 is a configuration diagram showing the entire configuration of a conventional example.

FIG. 5 is a configuration diagram showing a detailed configuration of a light receiving head portion.

[Explanation of symbols]

Reference Signs List 9 constant current source 10 temperature reference jacket 12 main amplifier 15 photoreceptor 21 first jacket 22 second jacket 23 optical conduction path 24 chopper 25 amplifier 26 heater power meter

Claims (1)

(57) [Scope of request for utility model registration] 1. A photoreceptor in which a heater is embedded,
A temperature reference jacket placed over the body and this temperature
Cooling hand placed in contact with the reference jacket and the photoreceptor
And a step, which is disposed in contact with the photoreceptor and the temperature reference jacket.
A temperature difference detecting element for detecting a temperature difference between them;
Insulation jacket placed over the reference jacket
And Ranaru sensor unit, before on the basis of the temperature difference detection signal from said temperature difference detection element
Serial A isothermal control type optical power meter comprising a control unit which drives the heater controls to keep the temperature of the photoreceptor of the optical detection unit constant, is installed in the insulating jacket, the temperature difference detection element a chopper for modulating the chopping an output, said insulating jacket outside the sensor portion and is integrally installed in, comprising an amplifier for demodulating and amplifying the modulated output of the chopper, integral and preamplifier control unit and the sensor unit An isothermally controlled calorimeter characterized by the following: