JPH05223632A - Calibrating system for light power meter - Google Patents

Abstract

PURPOSE:To enable accurate calibration free from changes in light outputs of a light source by a method wherein two lights divided with a halfmirror are allowed to pass and break simultaneously with a shutter and the luminous flux passed is received with light power meters, the one on the side of a reference device and the other on the side of a device to be inspected. CONSTITUTION:The luminous flux of a laser light radiated from a light source 1 is attenuated down to a certain level with a halfmirror 7 and further, in two directions with a halfmirror 2. Then, the shutters 3 and 4 are opened or closed simultaneously by an indication from a control section body 8 to introduce the luminous flux to a reference device 5 and a device 6 to be inspected and a light power from the light source 1 is measured simultaneously with the reference device 5 and the device 6 to be inspected. The simultaneous opening or closing of the shutters 3 and 4 enables the measurement of the power of the laser light at the simultaneous timing with the reference device 5 and the device 6 to be inspected. In this case, the measurement at the same time allows the removal of instability of the light source free from changes in the light power of the light source 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical power meter calibration system for calibrating an optical power meter for measuring the power of laser light, and more particularly to improving the stability of a light source.

[0002]

2. Description of the Related Art As an optical power meter calibration system of this type, the configuration shown in FIG. 4 is well known. FIG. 5 is a diagram showing details of the light receiving head portion.

In these figures, reference numeral 11 denotes a light receiving body forming the sensor section S, which is composed of a cylindrical body 13 having an inner surface coated with a light absorbing paint 12 and a heat transfer plate 15 having a heater 14 embedded therein. .. 16, 16a are temperature difference detecting elements, 17
Is a thermoelectric cooling element, and these elements are formed of Peltier elements having equivalent performance, and are fixed in a state of being sandwiched between the heat transfer plate 15 and the reference jacket 18. The outer circumference of the reference jacket 18 is surrounded by an intermediate jacket 19 and an outer jacket 20 as shown in FIG. 5 in order to stabilize the temperature, and the sensor section S is constructed as a light receiving head A surrounded by a triple jacket. ing. The heat capacity of the heat transfer plate 15 including the cylindrical body 13 and the heat capacity of the reference jacket 18 are about 1: 1000, and the reference jacket 18 is larger.

Reference numeral 21 is a constant current source connected to the thermoelectric cooling element 17. Reference numeral 22 is a feedback amplifier which obtains heater power for isothermal control from the outputs from the temperature difference detecting elements 16 and 16a. This feedback amplifier 22
Is applied to the heater 14 and is output to the outside in order to obtain the incident optical power. The feedback amplifier 22 includes the preamplifier 23 and the PID amplifier 2
It is composed of four.

In the above structure, when the measuring light is not input, the reference jacket 18 is kept at room temperature, and the thermoelectric cooling element 17 composed of the Peltier element is constantly supplied with a constant current IA from the constant current source 21. The heat transfer plate 15 side is always cooled. In this case, the reference jacket 18 side is heated, but the heat capacity of the reference jacket 18 is large and the heating amount of the thermoelectric cooling element 17 is small. Therefore, in the apparatus shown in FIG. 4, the thermoelectric cooling element 17 and the constant current source 21 always act in the direction of lowering the temperature of the light receiving body 21 side.

On the other hand, the temperature difference detecting elements 16 and 16a have this temperature difference (temperature difference between the reference jacket 18 and the heat transfer plate 15: n.
V level), the preamplifier 23 outputs its output (m
V level) and add to the PID amplifier 24. Then, the PID amplifier 24 performs a predetermined calculation (this calculation is a known PID calculation for controlling the temperatures of the heat transfer plate 15 and the reference jacket 18 to quickly match each other). This P
The output of the ID amplifier 24 is applied to the heater 14 to raise the temperature of the heater 14, and the temperature difference detecting elements 16a, 16b
The output of is controlled to be zero.

Therefore, in the apparatus of FIG. 4, the thermoelectric cooling element 1
The voltage (current I) is applied from the PID amplifier 24 to the heat transfer plate 15 cooled by the action of the constant current source 21 and the constant current source 21.
In addition to the above, the heat transfer plate 15 is heated to control the temperature of the light receiving body 11 and the temperature of the temperature reference jacket 18 to be the same.

In such a state, the laser light L to be measured
When a is incident from the upper part of the cylindrical body 13, the light receiving body 11 absorbs light, and the temperature rises according to the light power. The heat is conducted to the heat transfer plate 15, and a temperature difference is generated between the heat transfer plate 15 and the reference jacket 18 which are in a temperature equilibrium state. This temperature difference is detected by the temperature difference detection elements 16a and 16b, and PI
The D amplifier 24 reduces the voltage value sent to the heater 14. Therefore, the temperature of the heater 14 drops, and the heat transfer plate 1
5 and the temperature of the reference jacket 18 again coincide.

[0009]

Consider a case where the above isothermal control type calorimeters are compared and calibrated. In such a case, the light flux from the light source is divided into two, and calibration is performed with a pre-calibrated calorimeter for standard measurement (standard instrument) and a calorimeter for measurement (test instrument) that has not been calibrated yet. .. The two calorimeters (standard device and test device) receiving the light flux from the light source alternately repeat the measurement to calibrate the test device.

When the device under test is calibrated in this manner, the stability of the light source may greatly affect the calibration accuracy. That is, if the optical output of the light source fluctuates between when the measurement is performed with the standard device and when the measurement and calibration are performed with the device under test, the calibration accuracy (measurement accuracy and linearity) is significantly reduced. ..

The present invention has been made in view of such a point, and an object thereof is to provide an optical power meter calibration system capable of performing accurate calibration.

[0012]

According to the present invention for solving the above-mentioned problems, the accuracy of the optical power meter on the device under test side is measured by measuring the optical power meter as the standard device and the optical power meter as the device under test. And an optical power meter calibration system for measuring linearity, a light splitting means for splitting light from a light source into two, a shutter means for simultaneously passing / blocking two lights split by the light splitting means, and a shutter means for passing the light. The optical power meter on the standard device side and the optical power meter on the test device side that receive the light flux respectively, and the difference E1 in the accuracy of the optical power measured by the optical power meter on the standard device side and the optical power meter on the test device side, and By referring to the difference E2 in the accuracy of the optical power measured by exchanging the standard device and the device under test, the accuracy of the device under test is calculated from the half value of the sum of the differences in accuracy (E1, E2). It is characterized in that a control means for determining.

[0013]

In the present invention, the light beam split by the light splitting means is controlled to be blocked / passed by the shutter means at the same time. The light flux passing through this shutter means is received by the standard device and the device under test, and the respective accuracy of Find the difference. The control means obtains the accuracy of the device under test from the half value of the sum of the differences in accuracy. Therefore, it is not affected by the instability of the light source.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the calibration of one embodiment of the present invention. In this figure, 1 is a light source such as a HeNe laser, 2 is a half mirror whose reflectance and transmittance are variable, 3 is a first shutter for transmitting / blocking the light flux from the light source 1, and 4 is a light source from the light source 1. Second shutter for transmitting / blocking the light flux, 5 is a calorimeter as a standard device, 6 is a calorimeter as a device under test, 7 is a variable half mirror for controlling the optical power from the light source 1, and 8 is a calorimeter. It is a control unit main body for controlling. 2 is a timing chart showing the opening / closing timing of the shutters 3 and 4, and FIG. 3 is an explanatory diagram showing the division ratio of the optical power in the half mirror 2.

The operation of the apparatus of this embodiment thus constructed is as follows. The luminous flux of the laser light emitted from the light source 1 is attenuated to a certain level by the half mirror 7,
Further, it is divided into two directions by the half mirror 2. It is set in advance so that the light quantity becomes 1: 1 during this division. Then, the shutters 3 and 4 are simultaneously opened and closed according to an instruction from the control unit main body 8 to guide the luminous flux to the standard device 5 and the device under test 6. Then, the optical power from the light source 1 is simultaneously measured by the standard device 5 and the device under test 6.

As shown in FIG. 2, by simultaneously opening and closing the shutters 3 and 4, the power of the laser light at the same timing can be measured by the standard device 5 and the device under test 6. In this case, even if the optical power of the light source 1 varies,
Since the measurements are made at the same time, the instability of the light source can be eliminated.

The difference ε in accuracy between the standard device 5 and the device under test 6 is
The influence of the non-uniformity of the power of the light flux divided into two is included. Therefore, to obtain ε accurately from this measurement result,
It is necessary to exchange the locations of the standard device 5 and the device under test 6 and measure again. Here, the optical power split by the half mirror 2 is P + Δ in the 90 ° reflection direction as shown in FIG.
It is assumed that P [mW] and P [mW] in the straight traveling direction. The measured values of the standard device and the device under test obtained in the first measurement are P and p.
1, P + the measured value obtained in the second measurement after the position exchange
Let ΔP, p2.

In this case, the difference (E1) between the (test device) and the (standard device) at the first time is: E1 = p1-P, and the difference E2 between the (test device) and the (standard device) at the second time
Is E2 = p2 + δ (P / (2P + ΔP)) − P−ΔP−δ
((P + ΔP) / (2PΔP)). Where δ
The term is the fluctuation of the optical power between the first and second times,
These values are offset and become almost negligible. I want to obtain ε (ε ＝
The value of (test device)-(standard device)) can be represented by the first time: ε = p1-P, the second time: ε = p2-P-ΔP, and thus ε = 1/2 (p1 + p2-ΔP-2P) = It becomes 1/2 (E1 + E2). That is, the accuracy difference ε between the standard device 5 and the device under test 6 can be obtained by dividing the sum of the accuracy differences between the first and second times by 2.

In this way, the control unit main body 8 performs the calculation in accordance with the above procedure to obtain the accuracy difference ε. As a result, highly accurate measurement can be performed without being affected by the instability of the light source.

As described above, according to the present embodiment, in measuring the accuracy and linearity of the optical power measuring device, the influence of the instability of the light source is almost eliminated, and the accuracy can be improved. Become.

[0021]

As described in detail above, according to the present invention, there is provided an optical power meter calibration system capable of performing accurate calibration even when the optical output of a light source fluctuates. can do.

[Brief description of drawings]

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

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

FIG. 3 is an explanatory diagram showing a measurement state of the device according to one example of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a conventional optical power meter.

FIG. 5 is a configuration diagram showing a configuration of a main part of a conventional optical power meter.

[Explanation of reference numerals] 1 light source 2 half mirror 3,4 shutter 5 standard device 6 test device 7 half mirror 8 control unit main body

Claims (1)

[Claims] 1. The accuracy and linearity of the optical power meter (6) on the device under test are measured by measuring the optical power meter (5) as a standard device and the optical power meter (6) as a device under test. In the optical power meter calibration system, the light splitting means (2) for splitting the light from the light source (1) into two and the shutter means (3) for simultaneously passing / blocking the two lights split by the light splitting means (2). , 4), the optical power meter (5) on the standard device side and the optical power meter (6) on the test device side, which receive the light fluxes passing through the shutter means (3, 4), respectively, and the optical power meter on the standard device side. See (5) and the difference E1 in the accuracy of the optical power measured by the optical power meter (6) on the side of the device under test, and the difference E2 in the accuracy of the optical power measured by replacing the standard device and the device under test. Then, the difference in accuracy (E
1. An optical power meter calibration system, comprising: a control means (8) for obtaining the accuracy of the device under test from the half value of the sum of (1, E2).