JP2023179039A - infrared sensor - Google Patents

Abstract

To suppress variation in a temperature of an infrared detector itself and stabilize an output signal in a reflection type infrared sensor.SOLUTION: An infrared sensor for detecting infrared rays radiated from an object includes a board having a detection surface oriented toward the object, a thermal type infrared detector mounted on a back face of the detection surface in the board, an infrared ray transmitting window that is formed on the board and transmits infrared rays in a predetermined wavelength region to the back face side, and a reflection part that is provided in a back face side of the board and reflects infrared rays transmitted through the infrared ray transmitting window and guiding them to the thermal type infrared detector, and is formed such that the infrared ray transmitting window does not overlap with the infrared detector when viewed from the detection surface side.SELECTED DRAWING: Figure 3

Description

The present invention relates to an infrared sensor using a thermal infrared detection element.

2. Description of the Related Art Conventionally, as a means for non-contactly measuring the temperature of an object, there is an infrared sensor using a thermal infrared detecting element such as a thermopile element. This infrared sensor is constructed so that a lens made of a material that transmits only infrared rays is installed in front of an infrared detection element, and the infrared rays emitted from an object are focused by the lens onto a thermal infrared detection element. It has been known. In addition, as shown in Patent Document 1, such an infrared sensor has an infrared detection element and a reflecting mirror arranged on the back side of a silicon substrate that transmits infrared rays, and the infrared rays that have passed through the silicon substrate are reflected by the reflecting mirror. A so-called reflective type is also known in which the light is focused on an infrared detection element.

Japanese Patent Application Publication No. 2002-048637

By the way, in the reflective infrared sensor described above, the temperature of the infrared detection element itself fluctuates more easily than in the type of infrared sensor in which a lens is placed in front of the infrared detection element, and the output signal from the infrared detection element may become unstable. There was a problem that it was easy to become stable.

The present invention has been made in view of the above-mentioned problems, and its main objective is to suppress fluctuations in the temperature of the infrared detection element itself and stabilize the output signal in a reflective infrared sensor. .

As a result of studies conducted by the present inventors to solve the above problems, it was found that in conventional reflective infrared sensors, a thermal infrared detection element is arranged on a silicon substrate that transmits infrared rays. The inventors discovered for the first time that a portion of the infrared rays directly reaches the back surface of the infrared detecting element without being reflected by a reflecting mirror, which causes the temperature of the infrared detecting element itself to fluctuate, leading to the present invention.

That is, the infrared sensor according to the present invention is an infrared sensor that detects infrared rays emitted from an object, and includes a substrate having a detection surface facing the object, and a substrate mounted on the back surface of the detection surface of the substrate. a thermal-type infrared detecting element; an infrared transmitting window formed on the substrate to transmit infrared rays in a predetermined wavelength range to the back surface side; and a reflecting part that reflects infrared rays and guides them to the thermal infrared detection element, and is formed such that the infrared transmission window does not overlap with the infrared detection element when viewed from the detection surface side. do.

According to the present invention, in a reflective infrared sensor, fluctuations in the temperature of the infrared detection element itself can be suppressed, and the output signal can be stabilized.

FIG. 1 is a perspective view of the overall configuration of an infrared sensor according to an embodiment of the present invention, viewed from the detection surface side. FIG. 2 is a perspective view of the overall configuration of the infrared sensor according to the embodiment, viewed from the back side. FIG. 3 is a cross-sectional view showing the internal configuration of the infrared sensor according to the embodiment. FIG. 3 is a plan view of the infrared sensor of the embodiment viewed from the detection surface side. FIG. 7 is a plan view of an infrared sensor according to another embodiment as viewed from the detection surface side.

EMBODIMENT OF THE INVENTION Below, the infrared sensor 100 based on one Embodiment of this invention is demonstrated with reference to drawings.

The infrared sensor 100 of this embodiment is configured to measure the temperature of an object in a non-contact manner by detecting infrared rays emitted from the object with a thermal infrared detection element 2.

Specifically, as shown in FIGS. 1 to 3, the infrared sensor 100 includes a substrate 1 having a detection surface 11 facing an object, and an infrared detection element 2 mounted on the back surface 12 of the detection surface 11 on the substrate 1. , a casing 3 attached to the back surface 12 of the substrate 1 so as to cover and accommodate the infrared detection element 2 , and an infrared transmission window formed on the substrate 1 that transmits only infrared rays in a predetermined wavelength range (measurement wavelength range). 4 and a calculation section 5. The casing 3 has a reflection part 31 inside that reflects the infrared rays that have passed through the infrared transmitting window 4 and guides them to the infrared detection element 2. When the detection surface 11 of the substrate 1 is directed toward the object, the rays emitted from the object are reflected. The infrared rays thus introduced are introduced into the casing 3 through the infrared transmitting window 4, and the introduced infrared rays are reflected by the reflection section 31 and detected by the infrared detection element 2. Each part will be explained below.

The substrate 1 is made of a resin material or the like that has low transmittance to infrared rays in the measurement wavelength range, and is specifically a printed circuit board (rigid board). This substrate 1 has a rectangular plate shape, and conductive wiring is provided on the back surface 12 of the detection surface 11 facing the object.

The infrared detection element 2 is a thermal type that detects a temperature change when absorbing infrared rays as a change in electromotive force, and specifically, it is a thermopile element made of a plurality of thermocouples arranged in series and made into a thin film. This infrared detection element 2 is directly mounted on the back surface 12 of the substrate 1. When viewed from above, this infrared detection element 2 has a planar light-receiving portion, which is a hot junction, set in the center thereof, and a plurality of cold contacts are set around the light-receiving portion. Note that the infrared detection element 2 may have a single pixel, or may have a plurality of pixels arranged in an array.

The casing 3 has a box shape that completely covers the infrared detection element 2 from the back surface 12 side of the substrate 1, and blocks external disturbance light from the back surface 12 side as well as outside air and wind. The casing 3 is made of a material that has a high light-shielding property against at least infrared rays in the measurement wavelength range, and here, the entire casing 3 is made of a metal material such as iron, stainless steel, or aluminum. The surface may be coated with gold plating, nickel plating, or the like.

The reflecting section 31 reflects the infrared rays that have passed through the infrared transmitting window 4 and focuses the reflected light on the infrared detecting element 2, and is provided at a position facing the infrared transmitting window 4 on the back surface 12 side of the substrate 1. Specifically, this reflective portion 31 is formed by machining the inner surface of the casing 3 into a concave shape, and the inner surface of the casing 3 functions as a reflective surface 31s. This reflective surface 31 is preferably mirror-finished, for example, so that it can reflect infrared rays, but is not limited thereto, and may be, for example, rough-finished. Note that the area of the inner surface of the casing 3 that does not constitute the reflective surface 31s is preferably configured to have a lower reflectance than the reflective surface 31s, and may be coated with, for example, black paint or resin. The surface may be processed to be extremely rough.

The infrared transmission window 4 includes a through hole 41 that penetrates the substrate 1 in the thickness direction and opens to the detection surface 11 and the back surface 12, and an optical filter 42 that closes the through hole 41. The optical filter 42 is made of a material that transmits only infrared rays in the measurement wavelength range, and is made of, for example, single crystal silicon. This optical filter 42 has a plate shape and is attached to the back surface 12 of the substrate 1 so as to cover the through hole 41.

The arithmetic unit 5 is an electronic circuit including a CPU, a memory, etc., and its functions are realized by making the CPU and peripheral devices work together according to a predetermined program stored in a predetermined area of the memory. The calculation unit 5 of this embodiment outputs a voltage proportional to the temperature of the object, and more specifically, it receives an electric signal output from the infrared detection element 2 and receives the electric signal that is received by the infrared detection element 2. It has the function of outputting a voltage proportional to the amount of infrared rays (or the temperature of the object). Furthermore, the calculation unit 5 has a function of amplifying the electrical signal output from the infrared detection element 2, a function of amplifying the output voltage, a function of measuring the ambient temperature, a function of correcting the output voltage based on the ambient temperature, etc. You can do it like this.

The infrared sensor 100 also has a connector 6 for connecting to a power source (not shown) or the like. This connector 6 is attached to the detection surface 11 side of the board 1. Note that the connector 6 may be attached to the back surface 12 side of the board 1.

In the infrared sensor 100 of this embodiment, as shown in FIG. It is formed. Specifically, in this infrared sensor 100, the infrared transmitting window 4 is formed around the infrared detecting element 2 on the substrate 1 in an area outside the cold junction of the infrared detecting element 2. Further, the infrared transmitting window 4 is formed so as not to surround the entire circumference of the infrared detecting element 2. The through hole 41 constituting the infrared transmitting window 4 has a round hole shape, and only one through hole 41 is formed at a position that does not entirely overlap with the infrared detecting element 2 when viewed from the detection surface 11 side.

Further, in this infrared sensor 100, the reflecting portion 31 is formed so that its reflecting surface 31s is not parabolic but spherical (concave spherical). The reflective surface 31s is formed so that the inclination in the region facing the infrared transmitting window 4 is approximately the same as the inclination of an ideal paraboloid having the light receiving surface of the infrared detecting element 2 as its focal point.

Further, on the detection surface 11 of the substrate 1, a reflective film 7 that reflects light including infrared radiation in the measurement wavelength range is laminated. The reflective film 7 is formed at least in a region corresponding to the back side of the infrared detecting element 2 , and here, it is formed over the entire region corresponding to the back side of the casing 3 . The reflective film 7 is made of, for example, copper foil or gold plating.

According to the infrared sensor 100 of the present embodiment configured in this manner, the infrared detection element 2 is directly mounted on the printed circuit board through which infrared rays are difficult to pass, and the infrared transmitting window 4 is transparent when viewed from the detection surface 11 side. It is formed so as not to overlap with the detection element 2, and furthermore, a reflective film 7 is formed on the detection surface 11 of the printed circuit board, so that the infrared rays transmitted through the infrared transmission window 4 reach the infrared detection element 2 from the back surface. By doing so, the cold junction of the thermopile can be prevented from being heated, and the output signal can be stabilized.

Note that the present invention is not limited to the above embodiments.

For example, the through hole 41 constituting the infrared transmitting window 4 is not limited to a round hole shape, and as long as it is formed at a position that does not overlap with the infrared detecting element 2, it may have an elongated hole shape, a square hole shape, etc., as shown in FIG. may be of any shape.

Further, a plurality of infrared transmission windows 4 may be provided around the infrared detection element 2 as long as they do not overlap with the infrared detection element 2 when viewed from the detection surface 11 side.

Further, in the embodiment described above, the reflective surface 31s of the reflective section 31 is formed in a spherical shape, but the present invention is not limited to this. In other embodiments, the reflective surface 31s may be formed in a parabolic shape.

Further, although the infrared sensor 100 in the embodiment described above measures the temperature of an object, the present invention is not limited thereto. The infrared sensor 100 of other embodiments may be used for applications such as human body detection and non-contact operation.

Further, although the infrared detection element 2 in the embodiment described above is a thermopile element, it is not limited to this. In other embodiments, the infrared detection element 2 may be a bolometer or a pyroelectric sensor.

In addition, it goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made without departing from the spirit thereof. For example, the infrared sensor of the present invention includes the following aspects.

(Aspect 1) An infrared sensor that detects infrared rays emitted from an object, including a substrate having a detection surface facing the object, and a thermal infrared sensor mounted on the back side of the detection surface of the substrate. an infrared transmitting window formed on the substrate to transmit infrared rays in a predetermined wavelength range to the back side; and an infrared transmitting window provided on the back side of the substrate to reflect the infrared rays transmitted through the infrared transmitting window. an infrared sensor that is provided with a reflective portion that leads to a thermal infrared detection element, and is formed such that the infrared transmission window does not overlap with the infrared detection element when viewed from the detection surface side.

With this configuration, the infrared detection element is formed so that the infrared transmission window does not overlap with the infrared detection element when viewed from the detection surface side, so the infrared rays transmitted through the infrared transmission window are directed to the back surface of the infrared detection element. It cannot be reached from This can prevent the infrared detection element from heating up and stabilize the output signal.

(Aspect 2) In aspect 1, the infrared transmitting window includes a through hole penetrating the substrate around the infrared detecting element, and an optical filter that blocks the through hole and transmits infrared rays in the predetermined wavelength range. Infrared sensor as described.

(Aspect 3) The infrared sensor according to aspect 1 or 2, wherein the substrate is a printed circuit board.
In this way, since the infrared detection element is mounted on a printed circuit board that does not easily transmit infrared rays, it is possible to prevent infrared rays emitted from the object from passing through the board and reaching the back side of the infrared detection element. I can do it.

(Aspect 4) The infrared sensor according to any one of aspects 1 to 3, wherein a reflective film is laminated on the detection surface of the substrate in a region corresponding to the back side of the infrared detection element.
In this way, infrared rays that pass through the substrate and reach the infrared detection element can be further reduced.

(Aspect 5) The infrared sensor according to any one of aspects 1 to 4, wherein the reflective surface of the reflective portion has a concave spherical shape.
In this way, dimensions can be easily measured to check the workmanship compared to the case where the reflecting surface is made into a parabolic shape during manufacturing.

(Aspect 6) The infrared sensor according to Aspect 5, wherein the infrared transmission window is formed so as not to surround the entire circumference of the infrared detection element when viewed from the detection surface side.
By doing so, it is not necessary to use the reflective surface to condense light from the entire circumferential direction surrounding the infrared detecting element, so that the reflective surface can be formed into a spherical shape without having to be a paraboloid.

(Aspect 7) The infrared sensor according to any one of aspects 1 to 6, wherein the infrared detection element is a thermopile element.
If the thermopile element, which needs to suppress the temperature change of the cold junction due to the principle of measurement, is used as an infrared detection element, the effects of the present invention can be more pronounced.

100...Infrared sensor 1...Substrate 11...Detection surface 12...Back surface 2...Infrared detection element 3...Casing 31...Reflection part 31s...Reflection surface 4... Infrared transmission window 41...Through hole 42...Optical filter 5...Calculation unit 6...Connector

Claims (7)

An infrared sensor that detects infrared rays emitted from an object,
a substrate having a detection surface facing the object;
a thermal infrared detection element mounted on the back side of the detection surface of the substrate;
an infrared transmitting window formed on the substrate and transmitting infrared rays in a predetermined wavelength range to the back surface side;
a reflecting part provided on the back side of the substrate to reflect infrared rays that have passed through the infrared transmitting window and guide them to the infrared detection element;
The infrared sensor is formed such that the infrared transmission window does not overlap with the infrared detection element when viewed from the detection surface side. The infrared rays according to claim 1, wherein the infrared rays transmitting window comprises a through hole penetrating the substrate around the infrared detecting element, and an optical filter that blocks the through hole and transmits infrared rays in the predetermined wavelength range. sensor. The infrared sensor according to claim 1, wherein the substrate is a printed circuit board. The infrared sensor according to claim 1, wherein a reflective film is laminated on the detection surface of the substrate in a region corresponding to the back side of the infrared detection element. The infrared sensor according to claim 1, wherein the reflective surface of the reflective section has a concave spherical shape. The infrared sensor according to claim 5, wherein the infrared transmission window is formed so as not to surround the entire circumference of the infrared detection element when viewed from the detection surface side. The infrared sensor according to claim 1, wherein the infrared detection element is a thermopile element.