JPH0363691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pyroelectric sensor that detects light or infrared rays.

[Technical background of the invention and its problems] Conventionally, as shown in FIG. 1, a pyroelectric sensor has a blackened film 2 formed on the upper surface of a pyroelectric body 1 and an electrode layer 3 formed on the lower surface. hole 4 in the center
It is known that the electrode layer 3 is fixed to the upper surface of a flat substrate 5 with a hole 4 so as to close the hole 4. In the figure, 6 is an FET (field effect transistor), and 7 and 8 are resistors, which are fixed to the lower surface of the substrate 5. FIG. 2 is a basic circuit diagram of a pyroelectric sensor, in which the field effect transistor 6
The drain and source of are connected to the terminals T1 and T2, respectively, and the source is connected to the terminal T through the resistor 8.
3, and its gate is further connected to the terminal T3 via a parallel circuit of the pyroelectric body 1 and the resistor 7. That is, in this sensor, the pyroelectric body 1
When the blackened film 2 receives light or infrared rays, it is converted into heat, the polarization changes slightly, and charges are generated. The impedance of this is converted using FET6 and a signal is output.

By the way, in order to obtain high sensitivity in this sensor, the pyroelectric material 1 needs to cause a thermal change even with a small amount of light or infrared rays. Therefore, the heat capacity must be reduced, and it is made extremely thin with a thickness of 100 μm or less. In addition, it was necessary to make holes 4 in the substrate 5 to prevent heat from escaping through the substrate 5. However, when a hole is drilled like this, it is difficult to place and fix the pyroelectric material directly above the hole, so if the pyroelectric material is displaced, heat will be transferred from the pyroelectric material to the board. This caused the problem of decreased sensitivity due to the increased contact surface between the pyroelectric body and the substrate.

Furthermore, since pyroelectric materials are extremely thin, they break easily and are difficult to handle, creating difficulties in the manufacturing process.

[Purpose of the invention] This invention was made to solve such problems, and it is possible to always obtain stable and high sensitivity.
Moreover, the purpose is to provide a pyroelectric sensor with high strength.

[Summary of the Invention] This invention forms a concave central portion on the side opposite to the light-receiving surface of a pyroelectric substance, forms an electrode layer in the concave portion, and fixes the peripheral portion outside the concave portion on a flat substrate. This is a pyroelectric sensor made by

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 11 denotes a pyroelectric material having a U-shaped cross section with a concave central portion on the side opposite to the light-receiving surface. After forming a concave shape, it is cut to a predetermined size, and the light-receiving surface side is polished to form a central portion thin enough to have a sufficiently small heat capacity. By doing so, the central portion can be formed extremely thin while maintaining sufficient strength. A blackened film 12 is formed at the center of the light-receiving surface of the pyroelectric body 11, and an electrode layer 14 is formed in a recess 13 formed on the opposite side of the light-receiving surface.
Then, a conductive paste is applied to the outer peripheral edge of the recess 13 of the pyroelectric body 11, and the pyroelectric body 11 is fixed to the substantially central portion of the flat substrate 15. On the opposite side of the substrate 15
FET (field effect transistor) 16, resistor 1
7 and 18 are fixed.

Note that the operation of the pyroelectric sensor of this embodiment is the same as the conventional one, so a description thereof will be omitted.

With such a configuration, the recess 1 of the pyroelectric body 11
3 can sufficiently prevent heat from escaping. Moreover, since the peripheral portion is thick, sufficient strength can be maintained, and the central portion, which is irradiated with light and infrared rays, can be made extremely thin. Therefore, the heat capacity of the pyroelectric body 11 can be made sufficiently small, and a highly sensitive sensor can be manufactured. Further, in order to fix the pyroelectric body 11 on the substrate 15, it is sufficient to apply the conductive paste only to the outer peripheral edge of the recess 13, and the paste does not protrude. Furthermore, the fixed positioning of the pyroelectric body 11 to the substrate 15 can be easily done since there are no holes, and there is no positional displacement of the pyroelectric body with respect to the hole as in the conventional case. There will be no change or decline in

In the above embodiments, a pyroelectric body having a U-shaped cross section was used, but the present invention is not necessarily limited to this, and the pyroelectric body may have a curved shape as a whole. Even in such a case, the stress applied to the pyroelectric body is dispersed to the periphery, resulting in strong strength.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a pyroelectric sensor that always provides stable high sensitivity and has improved strength.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional example, FIG. 2 is a basic circuit diagram of a sensor, and FIG. 3 is a sectional view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11...Pyroelectric substance, 12...Blackened film, 13...Recessed part, 14...Electrode layer, 15...Substrate.

Claims (1)

[Scope of Claims] 1. A central part of the pyroelectric body opposite to the light-receiving surface is formed into a concave shape, an electrode layer is formed in the concave part, and a peripheral part outside the concave part is fixed on a flat substrate. A pyroelectric sensor characterized by the formation of 2. The pyroelectric sensor according to claim 1, wherein the pyroelectric body is formed so that its central portion is thinner than its peripheral portion.