JPH10227699A - Noncontact temperature measuring sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sharp beam by a method wherein a light guide device having a taper-shaped inner face is arranged between an optical lens and a chipper and stray light is reduced. SOLUTION: A chopper 3 is arranged between an optical lens 2 and an infrared sensor 1, and a light guide device 5 which has a taper-shaped inner face is installed between the optical lens 2 and the chopper 3. Infrared rays which are radiated from an object to be measured are narrowed down by the optical lens 2 which uses a silicon diffraction-type plano lens so as to be incident on the infrared sensor 1. A beam which is condensed on the infrared sensor 1 from the optical lens 2 is shut off by the chopper 3 at constant intervals, and it can be measured continuously by a pyroelectric infrared sensor. An incident beam which has an angle is reflected by the tapered light guide device 5 so as to change its angle gradually, it does not reach the infrared sensor 1, and it does not becomes stray light. Since the stray light is reduced, it is possible to obtain an effect to invalidate the beam which is incident on the optical lens 2 but which is deviated from an optical axis, and the visual-field characteristic of the optical lens can be improved.

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, alarm devices, air conditioner indoor temperature control, etc., taking advantage of the fact that they can detect objects and detect temperatures in a non-contact manner. It is expected to do so. The pyroelectric infrared sensor is a sensor utilizing a pyroelectric effect of a pyroelectric body such as a LiTaO ₃ single crystal. The pyroelectric body has spontaneous polarization and always generates a surface charge. However, in a steady state in the atmosphere, the pyroelectric body is electrically neutral with the charge in the atmosphere. When infrared light is incident on the pyroelectric body, the temperature of the pyroelectric body changes, and accordingly, the charge state of the surface changes due to the neutral state being broken. A pyroelectric infrared sensor measures the amount of infrared radiation by detecting the charge generated on the surface. 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 order to detect temperature using a pyroelectric infrared sensor, it is necessary to intermittently transmit incident infrared rays (hereinafter, referred to as a beam). For this purpose, a mechanical chopper is used. The configuration of the chopper includes a rotary motor, an electromagnetic actuator, a piezoelectric actuator, and the like. A piezoelectric actuator is suitable for downsizing the sensor.

FIG. 4 shows a conventional non-contact temperature sensor. In FIG. 4, 11 is an infrared sensor, 12 is an optical lens, 1
Reference numeral 3 denotes a chopper formed of a piezoelectric actuator, 14 denotes a housing, and 15 denotes a sensor light receiving unit.

Here, the inner surface (hereinafter referred to as a cavity) of the casing 14 from the optical lens 12 to the infrared sensor 11 is substantially parallel to the optical axis, and is parallel to the optical axis such as a reflected beam indicated by a broken line. The other beam is reflected by the cavity and enters the infrared sensor 11. Therefore, it can be seen that the distribution at the position of the chopper 13 is wider than that of the direct beam indicated by the solid line.

[0006]

The purpose of the chopper 13 is to completely block and pass the beam incident on the infrared sensor 11. Therefore, if the beam is widely distributed, a larger amplitude is required. When the piezoelectric actuator has a relatively small amplitude and is used as the chopper 13, the piezoelectric actuator covers the weak point by being provided between the optical lens 12 and the infrared sensor 11 and intermittently interrupting the beam narrowed by the optical lens 12.

The incident infrared rays (hereinafter referred to as beams) parallel to the optical axis of the optical lens 12 are converged on the focal point by the light-converging effect of the optical lens 12 and guided to the infrared sensor 11 located substantially at the focal position. On the other hand, the beam that is not parallel to the optical axis passes through the optical lens 12 and is reflected on the peripheral wall (cavity) including the housing 14 of the infrared sensor 11 to become stray light and a part of the beam enters the infrared sensor 11. As a result, the range of the beam incident on the infrared sensor 11 is widened and the chopper 13 needs to have a large amplitude.

When the emissivity of the peripheral cavity is high, reflection is reduced and stray light is reduced. However, a radiation beam due to the temperature of the cavity itself enters the infrared sensor 11. In this case, if there is a temperature difference between the cavity and the infrared sensor 11, noise occurs and the measurement accuracy deteriorates.

In order to realize a small-sized and high-precision non-contact temperature sensor, there is a need for a structure which does not expand the beam and is not affected by a temperature difference from the cavity due to restrictions of the chopper 13.

An object of the present invention is to provide a non-contact temperature sensor which can obtain a sharp beam without stray light and can use a chopper having a small amplitude. I do.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an infrared sensor for detecting an infrared ray emitted from an object to be measured and generating an electric signal, and an infrared sensor for collecting an infrared ray emitted from the object to be measured. An optical lens that emits light and sends it to the infrared sensor, a self-temperature sensor that detects the temperature of the infrared sensor itself, and a chopper that is between the optical lens and the infrared sensor and that mechanically interrupts infrared light that enters the infrared sensor And a non-contact temperature sensor having a housing for mounting and supporting the infrared sensor, the optical lens, the self-temperature sensor, and the chopper, wherein a light guide having a tapered inner surface converging on the chopper side between the optical lens and the chopper. The container is arranged.

With the above configuration, stray light is reduced, and a chopper having a small amplitude can be used.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an infrared sensor for detecting an infrared ray radiated from an object to be measured and generating an electric signal, and collecting infrared rays radiated from the object to be measured. An optical lens that emits light and sends it to the infrared sensor;
A self-temperature sensor for detecting the temperature of the infrared sensor itself, a chopper between the optical lens and the infrared sensor for mechanically interrupting infrared light incident on the infrared sensor, the infrared sensor, the optical lens, A temperature sensor, a non-contact temperature sensor having a housing for mounting and supporting a chopper, wherein a tapered lumen connecting the outer shape of the optical lens and the edge of the infrared light receiving portion is provided between the optical lens and the chopper. This is a configuration having a light guide, so that the beam passing through the chopper can be sharpened.

According to a second aspect of the present invention, the surface of the cavity and the opening surface of the cavity on the chopper side are infrared reflecting surfaces, so that the influence of the temperature difference between the surface and the infrared sensor can be reduced. .

According to a third aspect of the present invention, the surfaces of the lumen and the wall are non-reflective surfaces of infrared rays, so that a change in surface reflectance with time can be reduced.

According to a fourth aspect of the present invention, the surface of the lumen is a non-reflection surface of infrared rays and the surface of the wall is a smooth reflection surface, so that the influence of a temperature difference between the surface and the infrared sensor is reduced. In addition, the change with time of the reflectance of the surface of the lumen can be reduced.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the present invention. 1 is an infrared sensor, 2 is an optical lens, 3 is a chopper, 4 is a housing (chassis), 5 is a light guide, and 6 is a sensor light receiving unit.

An infrared ray (hereinafter referred to as a beam) emitted from an object to be measured (not shown) is converged by an optical lens 2 using a silicon diffraction type flat lens and is incident on an infrared sensor 1. The chopper 3 cuts off the beam condensed from the optical lens 2 to the infrared sensor 1 at regular intervals and enables continuous measurement by a pyroelectric infrared sensor. In the present embodiment, a mechanical reciprocating motion is performed by a piezoelectric actuator. What is adopted.

In this embodiment, as shown in FIG. 2, an incident beam having a similar angle is gradually reflected by a tapered cavity, that is, a light guide 5 to gradually change the angle. Is not reached. Therefore, the beam distribution at the position of the chopper 3 does not become stray light and remains narrow due to the direct beam, and the chopper amplitude can be small.

The reduction of stray light is caused by the fact that the optical lens 2
This also has the effect of nullifying a beam incident on the optical axis deviating from the optical axis, and also contributes to the improvement of the visual field characteristics.

Until now, the surface condition of the inner surface of the light guide 5 has been considered as a smooth reflecting surface. However, if minute irregularities are actually unavoidable, a black non-reflecting surface may be used. In this case, the light guide 5 has no angle changing effect due to the taper, but does not generate any stray light because it is originally a non-reflective surface. However, there is no ideal non-reflection surface, so that it is effective to use it together with a taper. However, if the vertical wall surface 7 in FIG. 3 is a black non-reflective surface, a radiation beam is generated, and a temperature difference between the cavity and the infrared sensor 1 causes a measurement error. Therefore, a smooth reflective surface is desirable.

Generally, a polished lens such as silicon or germanium is used as the optical lens 3. In the case of a small lens as in the present invention, a flat lens using the principle of diffraction is effective. This is because the area is reduced because it is cut out from a large-sized wafer and directly connected to the cost.

A self-temperature sensor for detecting the temperature of the infrared sensor 1 itself is not shown here but is arranged in the vicinity of the infrared sensor 1 or in the case of the infrared sensor 1.

[0024]

As described above, the present invention realizes a small non-contact temperature measuring sensor by obtaining a sharp beam without stray light by a light guide having a taper and utilizing a chopper by a small piezoelectric actuator. is there.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing functions of an embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating functions of an embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional non-contact temperature sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared sensor 2 Optical lens 3 Chopper 4 Housing 5 Light guide 6 Sensor light-receiving part 7 Vertical wall surface

Claims (4)

[Claims] An infrared sensor for detecting an infrared ray radiated from the object to generate an electric signal; an optical lens for condensing the infrared ray radiated from the object to send to the infrared sensor; A self-temperature sensor for detecting the temperature of the sensor itself, a chopper between the optical lens and the infrared sensor for mechanically interrupting infrared light incident on the infrared sensor, and the infrared sensor, an optical lens, a self-temperature sensor, and a chopper A non-contact temperature sensor having a housing for mounting and supporting a light guide having a tapered lumen between the optical lens and the chopper that connects an outer shape of the optical lens and an edge of the infrared light receiving unit. A non-contact temperature sensor having: 2. The non-contact temperature sensor according to claim 1, wherein the surface of the lumen and the opening surface of the lumen on the chopper side are infrared reflecting surfaces. 3. The non-contact temperature sensor according to claim 1, wherein the surface of the lumen and the wall are non-reflective surfaces of infrared rays. 4. The surface of the lumen is an infrared non-reflective surface,
The non-contact temperature sensor according to claim 3, wherein the surface of the wall is a smooth reflecting surface.