JP2001091354A - Pyroelectric infrared thin-film element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pyroelectric infrared thin-film element by which infrared rays can be measured with stable accuracy without being influenced by an ambient temperature even when the ambient temperature is changed. SOLUTION: In this pyroelectric infrared thin-film element, an upper-part electrode 4 and a lower-part electrode 5 are formed respectively on the surface and the rear surface of a pyroelectric thin film 3, and an infrared detection part 6 is formed. A heater 9 is installed at the infrared detection part 6, the heater 9 is electrified, and the temperature of the pyroelectric thin film 3 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared thin-film element in which an infrared detector is formed by providing an upper electrode and a lower electrode on the upper and lower surfaces of a pyroelectric thin film, respectively.

[0002]

2. Description of the Related Art As the above-mentioned pyroelectric infrared thin film element, for example, there is one described in Japanese Patent Application Laid-Open No. 9-318454. FIG. 5 schematically shows a pyroelectric infrared thin film element described in this publication, where 1 is MgO.
A single crystal substrate made of (magnesium oxide) 2 is a minute concave portion formed by etching in the surface layer of the substrate 1. Reference numeral 3 denotes a pyroelectric thin film, for example, a PZT ferroelectric thin film or a PLZT ferroelectric thin film. On the upper and lower surfaces of the pyroelectric thin film 3, an upper electrode 4 and a lower electrode 5 made of, for example, Pt (platinum) are provided so as to correspond to each other. When viewed in the direction of arrow A, a portion where the upper electrode 4, the lower electrode 5, and the pyroelectric thin film 3 overlap each other is referred to as an infrared detector 6.

An insulating thin film 7 is formed around the infrared detecting section 6 and holds the infrared detecting section 6 with respect to the substrate 1. The insulating thin film 7 is, for example, an organic insulating thin film such as a polyimide resin thin film, a SiO ₂ thin film or a Si thin film. an inorganic insulating film such as ₃ N _4. Reference numeral 8 denotes an infrared absorbing film provided so as to cover the upper surface of the upper electrode 4, which is formed by appropriately mixing an infrared absorbing material such as carbon black into a photosensitive organic thin film capable of photolithography.

In the above-described pyroelectric infrared detector, since the infrared absorption film 8 is formed on the upper surface of the infrared detector 6, there is an advantage that the sensitivity is good and the response speed is excellent.

[0005]

However, in general, the pyroelectric infrared detector is also applicable to a pyroelectric infrared detector in which the pyroelectric infrared thin-film element having the above structure is incorporated in a container having an infrared transmission window. , Generally, has a temperature coefficient for sensitivity. FIG. 6 is a plot of the output status when the ambient temperature is changed for three pyroelectric infrared detectors (indicated by ●, □, and Δ in the figure). 100% sensitivity
And

Therefore, when a plurality of pyroelectric infrared detectors having a temperature coefficient for sensitivity as described above are used in, for example, a gas analyzer, it is desirable to use ones whose temperature coefficients are substantially equal to each other. It is fixed to a temperature-controlled metal block.

In the gas analyzer using the plurality of pyroelectric infrared detectors, the temperature coefficient is measured to improve the measurement accuracy and to make the temperature coefficient of the pyroelectric infrared detector substantially equal. However, this measurement requires considerable time and effort. In addition, when the temperature of the metal block is adjusted, a warm-up time is required until the temperature is adjusted to a constant temperature. This is because the heat capacity of the metal block is large. However, if the heat capacity of the metal block is reduced, there is a disadvantage that the temperature of the metal block depends on the ambient temperature. Further, in order to control the temperature of the metal block having a large heat capacity, a considerably large-capacity temperature control heater is required. However, the power consumption is correspondingly increased, which leads to an increase in running costs and other costs.

The present invention has been made in consideration of the above-mentioned circumstances, and provides a pyroelectric infrared thin-film element which can be measured with stable accuracy without being affected by the influence of the ambient temperature. It is intended to be.

[0009]

In order to achieve the above object, the present invention provides a pyroelectric infrared thin film element in which an infrared detector is formed by providing an upper electrode and a lower electrode on the upper and lower surfaces of a pyroelectric thin film, respectively. In the above, a heater is provided in the infrared detection section, and the heater is energized to control the temperature of the pyroelectric thin film.

In the pyroelectric infrared thin film element having the above-mentioned structure, the heat capacity of the pyroelectric thin film is small. Therefore, even if the infrared detecting section including the thin film is heated by the heater, it takes only a few seconds until the temperature is stabilized. Requires only a short time. Further, since a block for adjusting the temperature is not required, the configuration is simplified.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a pyroelectric infrared thin-film element of the present invention. The pyroelectric infrared thin-film element shown in FIG. 1 is significantly different from that shown in FIG. A heater is provided in the infrared detecting section including the upper electrode and the lower electrode, and the heater is energized to control the temperature of the pyroelectric thin film.

That is, in FIG. 1, reference numeral 9 denotes a heater provided in the infrared detecting unit 6, for example, Pt, Ni, NiC.
1 and more specifically, the infrared detecting unit 6
Is provided on the upper surface of the insulating thin film 7 for holding the substrate 1 against the substrate 1. Reference numeral 10 denotes an insulating thin film provided so as to cover the heater 9. The insulating thin film 10 is an insulating thin film 7 for holding the infrared detecting unit 6 with respect to the substrate 1.
Similarly to the above, for example, it is composed of an organic insulating thin film such as a polyimide resin thin film or an inorganic insulating thin film such as a SiO ₂ thin film or Si ₃ N ₄ . The infrared absorbing film 8 is provided on the upper surface of the insulating thin film 10.

The pyroelectric infrared thin-film element having the above-described structure is incorporated as a pyroelectric infrared detector in a container having an infrared transmission window. FIG. 2 is a diagram schematically showing an electrical configuration of the pyroelectric infrared detector. In FIG.
11 is a circuit for amplifying the detection signal of the infrared detection unit 6, 12
Is a circuit for adjusting the temperature of the heater 9.

FIG. 3 schematically shows a configuration for examining the sensitivity of a pyroelectric infrared detector incorporating the above-described pyroelectric infrared thin film element. In FIG. 3, reference numeral 13 denotes a pyroelectric infrared detector. , And is arranged to face the black body furnace 14 whose temperature is to be measured. A chopper 15 is interposed between the pyroelectric infrared detector 13 and the black body furnace 14, and is driven to rotate by a motor (not shown). Reference numeral 16 denotes a power supply for driving the pyroelectric infrared detector 13, and reference numeral 17 denotes a measuring device.

In FIG. 3, the current flowing through the heater 9 provided in the infrared detector 6 of the pyroelectric infrared thin-film element incorporated in the pyroelectric infrared detector 13 is controlled by the temperature control circuit 12. By controlling the temperature of the pyroelectric thin film 3 of the infrared detecting section 6 to be always 60 ° C., for example, and measuring the output when the ambient temperature of the pyroelectric infrared detector 13 is changed. As a result, the result as shown in FIG. 4 was obtained.

In FIG. 4, the sensitivity when the ambient temperature is 20 ° C. is set to 100%. In the pyroelectric infrared thin film element of the present invention, the pyroelectric thin film 3 and the upper electrode 4 are used.
The heater 9 is provided in the infrared detecting section 6 including the lower electrode 5 and the lower electrode 5, and the heater 9 is energized so that the temperature adjustment of the pyroelectric thin film 3 is always constant (for example, 60 ° C.). Even if the ambient temperature changes, the influence of the change can be canceled, an output of 100% is always obtained, and the measurement can be performed with stable accuracy.

As described above, in the pyroelectric infrared thin film element of the present invention, the heat capacity of the pyroelectric thin film 3 is small. Only a very short time, such as a few seconds, is required for the temperature to stabilize, the power consumption is reduced, and the desired measurement can be performed in a short time. In addition, since a block for temperature control is not required, the configuration is simplified, and a small and compact device can be obtained.

[0018]

As described above, the pyroelectric infrared thin film element of the present invention is constructed as described above, so that even if the influence of the ambient temperature changes, the measurement can be performed with stable accuracy. The desired measurement can be performed in a short time after the power is turned on. Further, the configuration is simplified, and a compact pyroelectric infrared detector can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an example of a pyroelectric infrared thin film element of the present invention.

FIG. 2 is a view schematically showing an electrical configuration of a pyroelectric infrared detector incorporating the pyroelectric infrared thin film element.

FIG. 3 is a schematic configuration diagram of an apparatus for measuring an output of the pyroelectric infrared detector.

FIG. 4 is a diagram showing the temperature dependence of the sensitivity of the pyroelectric infrared detector.

FIG. 5 is a longitudinal sectional view schematically showing a conventional pyroelectric infrared thin film element.

FIG. 6 is a diagram showing the temperature dependence of sensitivity of a conventional pyroelectric infrared detector incorporating a pyroelectric infrared thin film element.

[Explanation of symbols]

3 ... pyroelectric thin film, 4 ... upper electrode, 5 ... lower electrode, 6 ... infrared detector, 9 ... heater.

Claims (1)

[Claims] 1. A pyroelectric infrared thin-film element having an infrared detector formed by providing an upper electrode and a lower electrode respectively on an upper surface and a lower electrode of a pyroelectric thin film, wherein the infrared detector is provided with a heater, and the heater is energized. The pyroelectric infrared thin film element is characterized in that the temperature of the pyroelectric thin film is adjusted by performing the following.