JPH0523070U - Infrared detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a highly reliable infrared detector that suppresses malfunctions due to temperature changes as much as possible and protects the infrared transmission filter. [Structure] The printed wiring board 2 is provided on a base 3 having a plurality of lead terminals 31, 32. On this printed wiring board 2, necessary circuit components 21, 22 and a support 6 are provided.
A pyroelectric substrate 1 having electrodes formed via 1, 62 is provided. Each of the above components is hermetically sealed by a cap 4 having an infrared transmission filter 5 provided on the top. Then, a coating film 7 made of a resin having a large infrared ray transmittance is formed on the entire surface except a part of the lead terminal. This coating film may be formed on the upper surface of the cap 4 in a hemispherical shape, a Fresnel lens may be formed, or a hemispherical Fresnel lens may be formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an infrared detector that detects infrared rays emitted from a human body or the like.

[0002]

[Prior Art]

 As is well known, pyroelectric elements, thermopiles and the like can be mentioned as elements for detecting infrared rays. For example, when a pyroelectric element receives infrared rays, it absorbs its heat energy to cause a temperature change, spontaneous polarization changes, and electric charges are generated on the surface. In this way, an electric charge is induced on the surface in proportion to the minute temperature change, and this electric charge is detected as a current or a voltage by an external circuit.

As shown in FIGS. 6 and 7, for example, a conventional pyroelectric infrared detector has a structure in which three lead terminals 83a, 83b, and 83c are projected on the upper surface of a metal base 83, and these lead terminals 83a, 83b, and 83c are projected. The printed wiring board 82 is supported on the terminals at three points, and the circuit components 85 and 86 and the support 84 are mounted on the upper and lower surfaces of the board, and the pyroelectric board 81 is supported on the support. Each of these parts was covered with a metal cap 87 having a transmission filter 88. Although not shown, the infrared detector was coated with a hollow hemispherical Fresnel lens that collects infrared rays.

[0004]

[Problems to be solved by the device]

 The metal case, that is, the metal base and cap is used to improve the airtightness.However, since the metal case is made of metal, the thermal conductivity is high and the ambient environmental temperature of the infrared detector is prevented from changing. It is easy to convey to the inside of this detector. Therefore, if a sudden change in environmental temperature occurs, the temperature may change in all or part of the pyroelectric element (infrared detection element) in the detector, which causes the infrared detector to operate incorrectly. There was a chance that it would end up. Further, the infrared transmission filter generally has a structure in which an antireflection film and an infrared transmission filter film are provided on a Si or Ge substrate by vapor deposition, and each of these films is mechanically or chemically attacked and Therefore, the function as a filter may not be able to be exhibited. Further, when used for a long period of time or under high temperature and high humidity, moisture may intrude from the bonding part of the infrared transmission filter or the joint part of the cap and the base, which may cause noise.

The present invention has been made in order to solve the above-mentioned problems. Even when a rapid temperature change occurs in the surrounding environment surrounding the infrared detector, malfunction caused by this temperature change is suppressed as much as possible. Another object of the present invention is to provide an infrared detector that protects the infrared transmission filter and can obtain high reliability over a long period of time.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the infrared detector according to the present invention accommodates the infrared detecting element in a metal case having a plurality of electrically independent lead terminals, and at the same time, the upper surface of the metal case is covered. An infrared entrance window is provided on this, and an optical filter that transmits infrared rays of a desired wavelength is installed in this infrared entrance window. A coating film made of a resin having a high infrared transmittance is formed on the entire surface except a part of the lead terminals. It is characterized by what has been done. Examples of the resin to be coated include high density polyethylene, polyamide and the like.

In the above structure, the coating film may be formed in a hemispherical shape on the upper surface of the metal case having an infrared ray incident window, a Fresnel lens may be formed, or a combination thereof. It may be a hemispherical Fresnel lens. The Fresnel lens is used to collect external light and is designed by dividing it into several strips.

[0008]

[Action]

 Even if the ambient temperature changes, the resin coating film, which has a high infrared transmittance, moderates the rate of temperature transfer inside the infrared detector. In addition, this coating film protects the filter film of the infrared transmission filter and prevents moisture from entering the detector. Of course, since this coating film is selected to have a high infrared transmittance, it does not pose a problem in the detection of the infrared detector in practical use. Further, infrared rays can be focused by forming the coating film into a hemispherical shape, using a Fresnel lens, or using a combination of these.

[0009]

【Example】

 First Embodiment A first embodiment according to the present invention will be described with reference to the drawings, taking a pyroelectric infrared detector as an example. FIG. 1 is a sectional view showing the structure of a pyroelectric infrared detector. The pyroelectric substrate 1 is made of lead titanate-based pyroelectric ceramic, is polarized in the plate thickness direction, and is cut into a rectangular shape. Metal film electrodes (Cr or Ni—Cr) 11 and 12 for light reception are provided at a predetermined interval on the surface of the pyroelectric substrate 1 by means such as vapor deposition, and on the back surface thereof, a metal film electrode 13 is provided. , 14 (Ag etc.) are provided. The light-receiving electrodes 11 and 12 are commonly connected.

The pyroelectric substrate 1 is mounted on a printed wiring board 2 on which printed wiring is provided via supports 61 and 62. The supports 61 and 62 are made of the same material as the pyroelectric substrate 1. Further, on the back surface of the printed wiring board 2, circuit components 21 and 22 such as FETs and resistors forming an external circuit are attached, and through holes 2a and 2b are provided in accordance with the arrangement of lead terminals described later. In the base 3, lead terminals 31 and 32 as shown in FIG. 3 are planted on a metal shell 3a via insulating glass. Collar portions 31a and 32a having a size such that the through hole does not penetrate are provided above the lead terminals, and the collar portions are exposed on the upper surface of the base. The printed wiring board is locked and held by the collar portion. The uppermost part of the lead terminal protruding from the surface of the base penetrates through holes 2a and 2b provided in the printed wiring board 2 and is exposed on the surface of this board. The exposed portion and the printed wiring are made of solder or the like. Electrical joining is performed by joining with a conductive joining material.

The cap 4 that seals each of these components is made of metal, and an infrared entrance window 41 is provided on the upper surface. Below the infrared entrance window, an infrared transmission filter 5 that transmits only infrared rays in a certain wavelength range is attached by a bonding material 5a. This is because the sensitivity of the pyroelectric substrate does not depend on wavelength, and it is necessary to select a desired wavelength region in advance. After sealing the pyroelectric substrate and the like with this cap, a high-density polyethylene having high infrared transmittance and good mechanical strength is coated. The thickness of the coating film 7 may be determined according to the usage environment of the infrared detector.

Second Embodiment A second embodiment according to the present invention will be described with reference to the drawings, taking a pyroelectric infrared detector as an example. In this embodiment, the main constituent parts are the same as those in the first embodiment, so the description of this part will be omitted. FIG. 2 is a sectional view showing the structure of the pyroelectric infrared detector. After the base 3 and the cap 4 are hermetically joined by resistance welding, a high-density polyethylene is formed in a hemispherical shape 71 on the upper surface of the metal case having an infrared entrance window. This hemispherical shape can be manufactured by setting a detector in a female hemispherical mold and projecting high-density polyethylene into this mold. The hemispherical shape improves the light condensing ability.

Third Embodiment A third embodiment according to the present invention will be described with reference to the drawings, taking a pyroelectric infrared detector as an example. In this embodiment, the main constituent parts are the same as those in the first embodiment, so the description of this part will be omitted. FIG. 3 is a sectional view showing the structure of a pyroelectric infrared detector. After the base 3 and the cap 4 are airtightly joined by resistance welding, high-density polyethylene is formed in a Fresnel lens shape 72 on the upper surface of the metal case having an infrared incident window. The Fresnel lens-shaped formation may be performed by setting a detector in a Fresnel lens-shaped mold and injecting high-density polyethylene into the mold. Further, a configuration in which the second and third embodiments are combined, that is, a convex Fresnel lens may be configured. According to this embodiment, the ability to collect light is improved and an infrared detector with higher sensitivity can be obtained.

Next, with respect to changes in ambient temperature, a comparative example between the conventional product and the device of the present invention will be shown below. The compared product is the one shown in the first embodiment, which does not have a high-density polyethylene coating film, and the product of the present invention has a high-density polyethylene film with an average film thickness of about 0.5 mm. It is provided with a coating film. We applied several levels of temperature shock (rapid temperature change in a short time) to both and observed the noise generation situation. FIG. 4 shows the noise generation state of the conventional product, and FIG. 5 shows the noise generation state of the present invention product. It is clearly understood from FIGS. 4 and 5 that the device of the present invention does not malfunction even if a temperature shock is applied until a certain temperature change occurs.

[0015]

[Effect of the device]

 According to the present invention, the high-density polyethylene coating film relaxes the speed of temperature transfer to the inside of the infrared detector, so that even if the ambient temperature changes, a part of the infrared detection element undergoes rapid temperature fluctuations. No malfunction is caused, and only temperature fluctuations due to the incidence of infrared rays can be detected. Further, since this coating film protects the filter film of the infrared transmission filter, only desired infrared rays can be transmitted, and the reliability of the infrared detector is improved. . Furthermore, by making this coating film a hemispherical surface shape, using a Fresnel lens, or using a combination of these, it is possible to focus the infrared rays, so that it is highly reliable and highly sensitive infrared rays. You can get a detector. Further, due to the improved moisture resistance, the characteristics of the detector, particularly the generation of noise, can be suppressed even when it is used in a high temperature and high humidity atmosphere for a long time, and a highly reliable infrared detector can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an infrared detector according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the infrared detector according to the present invention.

FIG. 3 is a sectional view showing an infrared detector according to a third embodiment of the present invention.

FIG. 4 is a graph showing comparative data.

FIG. 5 is a graph showing comparative data.

FIG. 6 is a perspective view showing a conventional example.

FIG. 7 is a sectional view showing a conventional example.

[Explanation of symbols]

 1 Pyroelectric Substrate 2 Printed Wiring Board 3 Base 31, 32 Lead Terminals 31a, 32a Collar 4 Cap 5 Infrared Transmission Filter 5a Bonding Material 7 Coating Film

Claims (3)

[Scope of utility model registration request] 1. An infrared detecting element is housed in a metal case having a plurality of electrically independent lead terminals and an infrared incident window is provided on the upper surface of the metal case.
In an infrared detector in which an optical filter that transmits infrared rays of a desired wavelength is installed in the infrared entrance window, a coating film made of a resin having a high infrared transmittance is formed on the entire surface except a part of the lead terminals. Characteristic infrared detector. 2. The infrared detector according to claim 1, wherein the coating film is formed in a hemispherical shape on the upper surface of a metal case having an infrared incident window. 3. The infrared detector according to claim 1 or 2, wherein the coating film forms a Fresnel lens on the upper surface of a metal case having an infrared incident window.