JPH0443783Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a photodetector that detects infrared rays and the like.

(Prior technology) In recent years, in the far-infrared region, unlike quantum-type infrared sensors, sensors have been developed to operate at room temperature, have no wavelength dependence, and are relatively inexpensive. , thermal infrared sensor,
In particular, pyroelectric infrared sensors are used in various fields.

A pyroelectric infrared sensor is a type of temperature sensor that detects temperature by utilizing the pyroelectric effect, in which when a temperature change is applied to a pyroelectric crystal, a charge is generated on the surface due to a change in spontaneous polarization. It is used for human body detection, flame detection, temperature detection, etc.

In this type of pyroelectric detector, as shown in FIG. 3, electrodes 2 and 3 are formed on the opposing main surfaces of a pyroelectric crystal substrate 1, respectively, and a heat generating source is placed on the electrode 2. It has an element 5 on which a heat absorbing film 4 called a blackening film is formed. The heat absorbing film 4 absorbs infrared rays and the like incident from a heat generating source and converts them into heat. This heat generates charges on the surface of the pyroelectric crystal substrate 1. The generated charge is detected by a source follower circuit using a field effect transistor (FET).

By the way, element 5 of the above pyroelectric detector
For example, as shown in FIG. 4, a hermetic seal case 8 consisting of a base 6 and a cap 7
Inside, a part of the lead terminal 9 is supported on the base 6 as a support, and this element 5 includes:
Infrared rays are incident through a filter 11 made of silicon or the like attached to the window 7a of the cap 7.

Conventionally, the filter 11 is bonded to the periphery of the window 7a of the cap using an optical resin adhesive 12, as shown in FIG. 5, but since the periphery of the window 7a is flat, it is difficult to position it. Therefore, as shown in FIG. 6, the filter 11 was often adhered to the window 7a of the cap 7 in a shifted position.

In this way, the filter 11 is connected to the window 7 of the cap 7.
Moisture enters into the hermetic seal case 8 from the cap, etc. that occurs between the cap and the periphery of a, and due to this moisture, it has a very high impedance, usually on the order of 10 ¹¹ ohm to 10 ¹² ohm. There was a problem in that the impedance between the electrodes 2 and 3 of the element 5 decreased, and the generated charge leaked due to this decreased impedance, resulting in poor characteristics of the infrared sensor.

In order to solve this problem, as shown in FIG.
1a, and the filter 11 is formed at this stepped portion 11a.
It is also practiced to position the filter 11 with respect to the window 7a.
The stepped portion 11a must be formed in the filter 11, which not only increases the cost of the filter but also increases the cost of the filter 11.
Due to the stepped portion 11a, the thickness of the peripheral edge portion becomes thinner and the strength becomes lower. Therefore, as in the case where the infrared sensor is used in a pressure vessel, the filter 11
If an external force is applied to the filter 11, the filter 11 needs to be thicker.
There was a problem where the cost of 1 became even higher.

(Purpose of the invention) The present invention was made to solve the above-mentioned problems in photodetectors such as infrared sensors, and the filter that selects the wavelength of light incident on the element is accurately positioned in the cap that covers the element. The purpose of the present invention is to provide a highly reliable photodetector that can be reliably attached in a fixed state.

(Structure of the invention) Therefore, in the present invention, a window is formed in the recess formed at the bottom of the cap that covers the element, and a rectangular filter that is fixed by fitting into this recess is located at the four corners of the window. It is characterized in that the apex is positioned so as to abut against the inner wall of the recess. The filter is accurately positioned with the vertices of its four corners abutting the side walls of a recess formed in the bottom of the cap.

(Effects of the invention) According to the invention, the polygonal filter that selects the wavelength of light incident on the element is accurately positioned with the apex of the polygon in contact with the inner wall of the recess formed at the bottom of the cap. This makes it possible to reliably bond the filter of the photodetector to the cap, eliminate malfunctions caused by the intrusion of light with wavelengths other than the required wavelength, and prevent the sealing of the photodetector case. Since the stop can be made perfect, a highly reliable photodetector with less characteristic deterioration can be obtained. Also, according to the present invention,
Since the filter of the photodetector is fitted into a recess formed in the bottom of the cap, its gluing operation is also facilitated.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

For example, in the infrared sensor shown in FIG.
As shown in FIGS. 1 and 2, a recess 13 into which a rectangular filter 11 fits is formed, and a window 7a is formed within this recess 13. The recess 13 is located between a pair of opposing sides 11 of the filter 11.
Inner walls 13a, 13a substantially parallel to a, 11a,
A pair of opposing sides 11b, 1 of the filter 11
It has inner walls 13b, 13b substantially parallel to the filter 1b, and four inner walls 13c facing the apexes S at the four corners of the filter 11, respectively. In this embodiment, the depth d (see FIG. 2) of the recess 13 is set to 0.1 mm to 0.2 mm when the thickness of the filter 11 is 0.4 mm.

When the filter 11 is fitted into the recess 13 formed at the bottom of the cap 7, the four corner vertices S of the filter 11 abut against the side walls 13c of the recess 13 and are positioned using optical resin such as epoxy resin. It is glued to the bottom of the cap 7 with adhesive 12.

By doing this, the filter 11 can be connected to the cap 7.
When the filter 11 is attached to the bottom of the cap 7, the vertices S of the four corners of the filter 11 are attached to the recesses 1 formed at the bottom of the cap 7.
They are positioned in contact with the inner walls 13c of No. 3, respectively. Therefore, when the filter 11 is bonded to the bottom of the cap 7, the filter 11 will not be misaligned, thereby eliminating poor characteristics due to unnecessary light intrusion due to misalignment of the filter 11, and reliability deterioration due to poor sealing. be able to.

In the above embodiment, the recess 13 may have an elliptical shape in which the apexes S of the four corners of the filter 11 abut against the inner wall, or the filter 11 may be hexagonal or octagonal. good.

The present invention is not limited to infrared sensors having a filter mounting structure as shown in FIGS. 1 and 2, but can be widely applied to photodetectors in general.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a filter mounting structure of an embodiment of a photodetector according to the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 is an element of a pyroelectric detector. , FIG. 4 is a partially sectional front view of a conventional photodetector, FIG. 5 is an explanatory diagram of the filter mounting structure of the photodetector in FIG. 4, and FIG. 6 is a filter mounting structure in FIG. 5. FIG. 7 is an explanatory diagram of another filter mounting structure of the photodetector shown in FIG. 4. FIG. 5...Element, 7...Cap, 7a...
Window, 11... Filter (S... four corner vertices), 1
2... Optical resin adhesive, 13... Concave portion (13c
...the inner wall that the four corner vertices of the filter come into contact with).

Claims (1)

[Scope of utility model registration request] A cap that covers a light detection element has a window in a recess formed at its bottom, and light enters the element through a polygonal filter that is fitted and fixed in this recess. A photodetector, characterized in that the filter is positioned so as to be in contact with the inner wall of the recess at the apex of the polygon.