JP2001050818A - Non-contact temperature-measuring sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate non-contact temperature-measuring sensor by arranging an optical filter with characteristic for cutting the long-wavelength side for the fundamental wavelength of a diffraction optical lens on an optical axis. SOLUTION: A diffraction optical lens 3 for condensing infrared rays is provided inside an enclosure 1 on the optical axis of an infrared light reception part 2. Also, a filter 5 for cutting a long-wavelength side for the fundamental wavelength of the optical lens 3 is arranged at incidence light-limiting window 4 on the optical axis of infrared rays at the other end of the enclosure 1. Infrared rays emitted from an object to be measured pass through the filter 5, are condensed by the optical lens 3, and enter the infrared light reception part 2. In this manner, the long-wavelength side is relaxed by the filter 5 for cutting the long-wavelength side. Further, by relaxing the short-wavelength side with the incidence light-limiting window, a visual field is narrowed, thus using an inexpensive diffraction-type lens and at the same tiem acquiring a small visual field angle and improving measurement accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact temperature sensor using an infrared sensor.

[0002]

2. Description of the Related Art In recent years, infrared sensors have been used for automatic doors, alarms, indoor temperature control of air conditioners, and the like, taking advantage of the fact that they can detect objects and detect temperatures in a non-contact manner. To go. An object emits infrared rays according to its temperature, and by using this sensor, the position and temperature of the object can be detected. In particular, an ear canal thermometer as a non-contact temperature sensor is expected to be able to measure body temperature in a short time.

[0003] The light receiving part of the ear canal thermometer is conventionally generally composed of an infrared sensor such as a thermomobile and a metallic waveguide directly connected thereto. Infrared sensors have a unique viewing angle and convert the energy of infrared rays taken from this range into electrical signals to determine the temperature.If the area of the measured object exceeds this range, the Although the temperature is correctly indicated, if the temperature is lower than this range, the average temperature including the ambient temperature of the object to be measured is obtained, and the measurement error increases. For this reason, an attempt is made to make the area of the eardrum occupying the viewing angle range as large as possible by equivalently approaching the object to be measured (the eardrum in this case) using a waveguide. However, it is dangerous to bring the entrance of the waveguide too close to the eardrum.
It is actually 10 mm apart. In this case, the difference between the eardrum and the surrounding temperature becomes a measurement error, and the variation in the depth at which the radiation thermometer is inserted into the ear canal also becomes an error. Immediately after the radiation thermometer is inserted into the ear canal, heat from the ear canal is transmitted to the exterior part (probe) in contact with the ear canal, and this is transmitted to the internal waveguide, so that the temperature of the waveguide gradually increases. A measurement error results. In order to solve this, a method has been proposed in which the probe is heated to near body temperature in advance, but it is not suitable as a portable device.

[0004]

The viewing angle of the infrared sensor is generally as wide as 50 to 90 °, and if the diameter of the eardrum is φ5 mm, the above problem occurs unless the distance is reduced to 5 to 2.5 mm. However, when the viewing angle is about 3 °, the distance is greatly increased and can be extended to about 95 °. A lens is used to reduce the viewing angle, but in this case, the characteristics of the lens are problematic.

An object of the present invention is to solve the above problems and to provide a highly accurate non-contact temperature sensor.

[0006]

According to the present invention, there is provided an optical filter having a characteristic of cutting a long wavelength side with respect to a fundamental wavelength of a diffractive optical lens on an optical axis.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an infrared light receiving section for detecting an infrared ray radiated from an object to be measured and generating an electric signal, and an infrared ray radiating from the object to be measured. A diffractive optical lens for condensing and sending the light to the infrared light receiving unit, and a non-contact temperature sensor having a housing for mounting and supporting the infrared light receiving unit and the diffractive optical lens; An optical filter having a characteristic of cutting the side is arranged on the optical axis.

According to a second aspect of the present invention, a member for limiting the amount of incident light is provided on the opposite side of the diffractive optical lens, and the member is thermally coupled to the infrared light receiving portion.

According to a third aspect of the present invention, a light guide having a tapered inner surface converging toward the lens is provided between the member for limiting the amount of incident light and the diffractive optical lens.

According to a fourth aspect of the present invention, the inner surface of the light guide has a sawtooth cross section.

According to a fifth aspect of the present invention, a substantially optically closed lumen is formed between the infrared ray receiving section and the diffractive optical lens, and the surface of the lumen has a sawtooth cross section. It is.

With the above-described structure, the short wavelength light is eliminated by a mechanical limiter, and the long wavelength light is eliminated by an optical filter, thereby improving the visual field characteristics. .

Hereinafter, a non-contact temperature measurement sensor according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a non-contact temperature sensor according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a cylindrical housing. One end of the housing 1 is provided with an infrared light receiving section 2. An optical lens 3 for condensing optical lines is provided inside the housing 1 on the optical axis of the infrared light receiving section 2. The incident light limiting window 4 on the optical axis of the infrared light, which is the other end of the housing 1, is provided with a filter 5 for cutting off the long wavelength side of the infrared light.

The principle of operation will be described below.

Infrared light radiated from an object to be measured (not shown) passes through a filter 5 and passes through an optical lens 3 using the principle of diffraction.
And the light is condensed by the optical lens 3 and enters the infrared light receiving unit 2.

FIG. 2 shows only the lens and the infrared ray receiving section. Here, A is the distance between the object to be measured (not shown) and the optical lens 3, and B is the optical lens 3 and the infrared light receiving unit 2.
, C indicates the size of the infrared light receiving unit 2, and B and C
The line extending the angle determined by the above forms a field of view having a size of D at the position of the measured object. The visual field between the measured object and the optical lens 3 can be represented by a line connecting D and the outer diameter of the optical lens 3. Assuming that the focal length of the optical lens 3 is f, B between A, B, and f
When there is a relation of = 1 / (1 / f-1 / A), an image is formed at the position of the infrared receiving section 2. Here, considering a beam from a point X outside the range of the visual field D, an image is formed at a point Y on a distance B, but the beam (broken line) from the lens toward the image forming point does not enter the infrared light receiving unit. .

At this time, in a diffractive lens using the principle of diffraction, the light condensing characteristic has wavelength dependence. Assuming that the wavelength of the incident light is λ, λ × f = constant. Therefore, when light having a different wavelength from the design wavelength, that is, the fundamental wave, is incident, an image is formed at a position different from the original image forming point. In FIG. 2, the input by the fundamental wave is imaged on Y, but the input with a longer wavelength than the fundamental wave is imaged on a point Y1 at a distance E shorter than B as shown in FIG. At this time, since the beams after the image forming point diverge as shown by the meshes in the figure, there is a case where the beams enter the infrared receiving unit 2. On the other hand, an input with a wavelength shorter than the main wave forms an image at a point Y2 at a distance G longer than B as shown in FIG. Also in this case, the beam is incident on the infrared receiving unit. Both of these indicate that the field of view has expanded.

In FIG. 1 of the present embodiment, the long wavelength side is alleviated by the filter 5 for cutting the long wavelength side. Further, by reducing the short wavelength side by the incident light limiting window 4, as shown in FIG.

The housing 1 not only supports the optical lens 3, the infrared ray receiving section 2, the filter 3, and the like, but also has a function of thermally coupling. The inner surface of the housing 1 is subjected to a blackening process to prevent reflection. If there is reflection, the effect of narrowing the field of view by the incident light limiting window 4 as shown in FIG. 6 is reduced by half. Although the reflection is suppressed by the blackening process, the radiation increases, so that if the temperature of the housing 1 is different from that of the infrared light receiving unit 2, a temperature error occurs. Therefore, by thermally coupling them, the temperature difference between the housing 1 and the infrared receiving unit 2 can be reduced, and the influence of the energy radiated by the housing 1 can be reduced. For this reason, it is desirable that the housing 1 be made of a metal material having a low thermal conductivity.

FIG. 7 shows a second embodiment of the present invention. The difference from the first embodiment is that the inner surface shape of the housing 1 is changed from a cylinder to a cone. By changing the shape of the inner surface from a cylinder to a cone, the angle is changed by repeating the reflection even for a slight reflection, thereby making it difficult to enter the lens. As a result, the slight sensitivity for a wide field of view can be further reduced.

FIG. 8 shows a third embodiment of the present invention, in which the conical inner surface of the second embodiment has a saw-tooth shape. In the present embodiment, the outer diameter of the housing 21 increases due to the conical inner surface shape. In order to improve this, the conical inner surface shape is sliced and the cross-sectional shape is arranged in a sawtooth shape. Thus, the outer diameter can be made substantially the same as that of the first embodiment while maintaining the effect of the conical inner surface shape.

FIG. 9 shows a fourth embodiment of the present invention. In the third embodiment, the inner cavity between the optical lens 3 and the infrared receiver 2 has a sawtooth conical inner surface.
Thereby, it is possible to reduce disturbance light from entering the infrared light receiving unit 2.

[0025]

As described above, the present invention improves the measurement accuracy by obtaining a small viewing angle while using an inexpensive diffractive lens with a filter that cuts the long wavelength side and an incident light limiting window. This is to realize a temperature measurement sensor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a non-contact sensor according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram illustrating the principle.

FIG. 3 is a schematic view illustrating the principle.

FIG. 4 is a schematic view illustrating the principle.

FIG. 5 is a schematic view illustrating the principle.

FIG. 6 is a sectional view of a non-contact sensor according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a non-contact sensor according to Embodiment 2 of the present invention.

FIG. 8 is a sectional view of a non-contact sensor according to Embodiment 3 of the present invention.

FIG. 9 is a sectional view of a non-contact sensor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Infrared light receiving part 3 Optical lens 4 Incident light limiting window 5 Filter

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Nomura, Inventor 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2G065 AB02 AB24 BA11 BA36 BA37 BB04 BB26 BB46 CA01 CA11 DA10 2G066 AC13 BA08 BA22 BA23 BA30 BA57 BB01

Claims (5)

[Claims] 1. An infrared light receiving section for detecting an infrared ray emitted from an object to be measured and generating an electric signal, and a diffractive optical lens for condensing infrared light emitted from the object to be sent to the infrared light receiving section. In the non-contact temperature measurement sensor having a housing for mounting and supporting the infrared light receiving section and the diffractive optical lens, an optical filter having a characteristic of cutting a long wavelength side with respect to a fundamental wavelength of the diffractive optical lens is provided on an optical axis. Non-contact temperature measurement sensor arranged. 2. The non-contact temperature sensor according to claim 1, further comprising a member on the opposite side of the diffractive optical lens for limiting the amount of incident light, wherein the member is thermally coupled to the infrared light receiving unit. 3. The non-contact temperature sensor according to claim 2, further comprising a light guide having a tapered inner surface converging on the lens side between the member for limiting the amount of incident light and the diffractive optical lens. 4. The non-contact temperature sensor according to claim 3, wherein the inner surface of the light guide has a sawtooth cross section. 5. The non-contact measurement method according to claim 1, wherein a substantially optically closed lumen is formed between the infrared ray receiving section and the diffractive optical lens, and the surface of the lumen has a sawtooth cross section. Temperature sensor.