JPS604110Y2 - Light detection unit for infrared gas analyzer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a light detection section of an infrared gas analyzer that analyzes components contained in gas using absorption of infrared rays.

In an infrared gas analyzer in which a semiconductor optical sensor receives the reference light transmitted through a reference cell and the measurement light transmitted through a measurement cell, an infrared interference filter is placed so that it is almost in contact with the measurement cell of the reference cell. .

Therefore, even though the optical sensor is maintained at a constant temperature, the temperature of the interference filter changes according to changes in the external temperature, and the optical sensor outputs a signal influenced by the external temperature.

Especially when using two or more filters, the difference in temperature characteristics between the filters causes changes in external temperature.

It will have a big impact.

An object of the present invention is to provide a photodetector that combines an optical sensor and an interference filter so as not to be affected by the temperature characteristics of the optical sensor and the interference filter.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an outline view showing an embodiment of a photodetector according to the present invention, and FIG. 2 is a sectional view of FIG. 1.

In FIGS. 1 and 2, 1 is a metal block, and this metal block 1 is formed with a reference light side light introduction hole 11 and a measurement light side light introduction hole 12 for guiding reference light and measurement light.

Further, an optical sensor mounting hole 13 is formed at the intersection of the light introduction holes 11 and 12 of the metal block 1, and a ring-shaped groove 14 and a temperature sensor mounting hole 15 are formed on the peripheral surface.

Reference numeral 2 denotes an optical sensor inserted and fixed into the mounting hole 13 of the metal block 1, and a photosensitive element 21 such as a thermistor or bolometer.
and a substrate 22.

3 is an infrared interference filter attached to the metal block 1 so as to block the reference light side light introduction hole 11, and 4 is an infrared interference filter attached to the metal block 1 so as to block the measurement light side light introduction hole 12. be.

5 is a heater or cooler (hereinafter referred to as heat/absorbing element) that is attached to the groove 14 and heats or cools the metal block 1;
is a temperature sensor placed in the mounting hole 15 to detect the temperature of the metal block 1.

7 is a control circuit that controls the heat-absorbing element 5 so that the output of the temperature sensor 6 is constant.

The control circuit 7, the heat/absorbing element 5, and the temperature sensor 6 are
It constitutes a temperature control means that keeps the temperature of the metal block 1 constant.

In the light detection unit of the present invention configured in this way, the reference light passes through the filter 3 and the light introduction hole 11 on the reference light side and reaches the optical sensor 2, and the measurement light passes through the filter 4 and the light introduction hole on the measurement light side and reaches the optical sensor 2. reaches sensor 2.

In reality, the reference light and measurement light are alternately applied to the optical sensor 2 due to the function of sectors (not shown).

In this device of the present invention, the interference filter 3゜4 is placed near the light sensor 2, which is the light condensing part, so its area can be made extremely small, and a light detection part with a small heat capacity can be obtained. .

Therefore, by restricting the temperature of the metal block 1 to a constant value by using a small-sized heat absorption element 5, the optical sensor 2 and the interference filters 3 and 4 can be kept at a constant temperature.

In addition, in the above description, a device having two types of light introduction holes, the reference light side light introduction hole 11 and a measurement light side light introduction hole 12, was described, but the present invention is applicable to a device having one type of light introduction hole. Of course, it can be used.

Furthermore, if the photosensitive element 21 is also used as a temperature detection element as in the invention of Japanese Patent Application No. 50-82620,
Temperature sensor 6 becomes unnecessary.

As explained above, according to the present invention, since the optical sensor and the infrared interference filter can be kept at a constant temperature, it is possible to realize a photodetecting section that is not affected by these temperature characteristics.

[Brief explanation of drawings]

FIG. 1 is an outline view showing an embodiment of the photodetection section according to the present invention, and FIG. 2 is a sectional view of the photodetection section shown in FIG. 1. 1...Metal block, 11...Reference light side light introduction hole, 12...Measurement light side light introduction hole, 2.
..... Optical sensor, 3, 4 ..... Infrared interference filter, 5 ..... Heat absorption and heat absorption element, 6 ..... Temperature sensor, 7 ..... Control circuit.

Claims (2)

[Scope of utility model registration request] (1) A metal block in which a light introduction hole is formed, an optical sensor attached to the light introduction hole of this metal block, and an infrared interference filter attached to the metal block so as to block the light introduction hole. , and temperature control means for keeping the metal block at a constant temperature. (2) The light detection unit according to claim 1, which has a reference light side light introduction hole and a measurement light side light introduction hole as the light introduction holes.