JPH08275925A - Radiative clinical thermometer - Google Patents

Abstract

PURPOSE: To realize high accuracy in a small type by setting a dimension of a light receiving part of an infrared ray sensor of a radiative clinical thermometer to measure an eardrum temperature and a diameter of an optical lens not more than a specific value. CONSTITUTION: An infrared ray emitted from an eardrum 7 is condensed through an optical lens 3, and enters an infrared ray sensor 1 from an opening part 8, and forms an image in a sensor light receiving part 2. An angle of visibility is determined by the size of the sensor light receiving part and a distance between this light receiving part and the optical lens, and since the size of a visual field on a measuring object is determined by this angle of visibility and a distance between the measuring object and the optical lens, a sufficiently small visual field and sufficient optical sensitivity are obtained to the eardrum by a combination of the infrared ray sensor on which a light receiving diameter or one side of a square is not more than 0.3mm and the optical lens whose diameter is not more than 6mm, and influence of disturbance is hardly exerted. Therefore, a smaller angle of visibility is obtained, and a visual field is limited within a range of the eardrum, and measuring accuracy can be improved by eliminating temperature information except the eardrum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation thermometer using an infrared sensor.

[0002]

2. Description of the Related Art The light receiving part of a radiation thermometer that measures the temperature of the eardrum, which is said to reflect the body temperature of a person most faithfully, by an infrared sensor is conventionally a thermopile infrared sensor and the like. It is composed of a metal waveguide directly connected. The infrared sensor has a unique viewing angle, and the infrared energy taken in from this viewing angle range is converted to an electrical signal to determine the temperature, but when the area of the DUT exceeds this range. Although the temperature of the object to be measured is indicated correctly, if it is smaller than this range, it becomes an average temperature including the ambient temperature of the object to be measured, and the measurement error increases.

Therefore, as shown in FIG. 3, an object to be measured 14 is provided by using a waveguide 13 having an inner surface of a mirror surface in front of an infrared sensor 12 mounted in a housing 10 via a chassis 11.
(In this case, the eardrum) is approached equivalently and the area of the eardrum occupying the viewing angle range is made to be as large as possible. However, it is dangerous for the body to bring the outlet of the waveguide 13 too close to the eardrum 14, and the distance is 5 to 10 mm. In this case, the difference between the eardrum and its surrounding temperature causes a measurement error, and the variation in the depth at which the radiation thermometer is inserted into the ear canal also causes an error. Further, immediately after inserting the radiation thermometer into the ear canal, the heat from the ear canal is transferred to the housing 10 that abuts on the ear canal, and this is transferred to the internal waveguide tube 13.
The temperature of the waveguide 13 gradually rises, which also causes a measurement error. In order to solve this, a method has been proposed in which the housing 10 is heated in advance to around the body temperature, but it is obvious that it is not suitable as a portable device.

[0004]

The infrared sensor generally has a wide viewing angle of 50 to 90 °, and assuming that the eardrum has a diameter of φ5, the above problem occurs unless the distance is approached to 5 to 2.5 mm. However, when the viewing angle is about 3 °, the distance is dramatically increased to about 95 mm. A lens is used to reduce the viewing angle, but in this case, the size of the light receiving portion of the infrared sensor becomes a problem. That is, the size of the light receiving portion of the thermopile is about 1 mm, the distance between the eardrum and the optical lens is 40 mm, and the visual field on the eardrum is 3 m.
When m, the viewing angle is about 4.3 °, and the distance between the optical lens and the light receiving part is about 13 mm. At this time, φ5 mm
An optical lens diameter of about φ15 mm is required to obtain the same sensitivity as when directly viewing the eardrum at a distance of 5 mm. However, it is difficult to incorporate such a large optical lens in the eardrum thermometer.

An object of the present invention is to solve the above problems and to provide a small and highly accurate radiation thermometer using an optical lens.

[0006]

In order to achieve the above-mentioned object, the present invention comprises an infrared sensor having a sensor light receiving portion having a diameter of 0.3 mm or less and an optical lens having a diameter of 6 mm or less.

[0007]

With the above configuration, the viewing angle is determined by the size of the sensor light-receiving part and the distance between the light-receiving part and the optical lens, and the size of the field of view on the object to be measured is Since it depends on the distance between the object to be measured and the optical lens, an infrared sensor with a light receiving diameter of 0.3 mm or less and a diameter of 6 m
By combining optical lenses of m or less, a sufficiently small field of view and sufficient optical sensitivity can be obtained for the eardrum, and a highly accurate radiation thermometer that is not easily affected by disturbance can be realized.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a side sectional view of a first embodiment of the present invention. 1 is an infrared sensor, 2 is a sensor light receiving part, 3 is an optical lens, 4 is a chopper, 5 is a chassis, 6 is a housing, and 7 is an eardrum. The infrared sensor 1 is provided with an opening 8.

Infrared rays emitted from the eardrum 7 are condensed through the optical lens 3 and enter the infrared sensor 1 through the opening 8 and form an image on the sensor light receiving section 2. This infrared ray causes the infrared sensor 1 to generate a voltage, and this voltage is connected to an electronic circuit (not shown) by a lead wire (not shown). This electronic circuit amplifies / converts / calculates the sensor voltage to convert it into temperature and The temperature is displayed on a display (not shown).

The opening 8 determines the viewing angle of the infrared sensor 1 itself together with the sensor light receiving portion 2, and here covers substantially the effective diameter of the optical lens 3. As the infrared sensor 1, there are a thermopile, a pyroelectric sensor and the like, but a thin film type pyroelectric sensor is used here. For this reason, it is necessary to interrupt the incident infrared rays, and the chopper 4 interrupts the infrared ray bundle immediately before entering the opening 8. The infrared sensor 1, the optical lens 3, and the chopper 4 are almost the same chassis 5
The chassis 5 is built in the housing 6. The casing 6 has a tubular portion 9 formed in the direction of incidence of infrared rays, and the tubular portion 9 is inserted into the ear canal when measuring the body temperature.

The viewing angle of the optical lens system is determined by the size of the sensor light receiving portion 2 and the distance between the sensor light receiving portion 2 and the optical lens 3. FIG. 2 is a schematic diagram of the lens optical system. Here, a is the distance between the object to be measured on the eardrum 7 and the optical lens 3, b is the distance between the sensor light receiving unit 2 and the optical lens 3, f is the focal length of the optical lens 3, θ is the viewing angle of the lens system, and d is the viewing angle of the lens system. Is the diameter of the sensor light receiving portion 2, D is the effective diameter of the optical lens 3, e is the field diameter on the object to be measured, and ω is the solid angle of the optical lens 3 viewed from the infrared sensor 1. If the image forming conditions are satisfied, the following relationships are established among the parameters.

That is, the sensor light receiving portion 2 and the optical lens 3
And the viewing angle θ of the lens system is (Equation 2), the solid angle ω of the optical lens 3 seen from the infrared sensor 1 is
Becomes as shown in (Equation 3).

[0014]

[Equation 1]

[0015]

[Equation 2]

[0016]

(Equation 3)

Here, a = 40 mm, f = 6 mm, d =
If 0.24 mm and D = 5 mm, θ = 1.95 °, ω
= 0.394. At this time, assuming that the infrared sensor 1 has a large light receiving element such as a thermopile or a bulk-type ceramic pyroelectric sensor, and D = 1 mm, θ =
9.1, e becomes φ5.66 and the eardrum 7 becomes φ5 m
If m, this cannot be covered. Where θ
In order to approach = 1.95, f = 16.9 mm may be set, but at this time, ω = 0.023, which is extremely reduced. Since the solid angle ω determines the optical sensitivity, ω is 0.394.
In order to get closer to, it is necessary to set D = 20.7. However, if such a large optical lens 3 is mounted on a thermometer, the diameter of the tubular portion 9 to be inserted into the ear canal of the housing 6 needs to be increased accordingly, so that it cannot be inserted into the ear canal.

On the other hand, the conventional radiation thermometer is composed of an infrared sensor 12, a waveguide 13, a casing 10 and the like as shown in FIG. 3, but the inner surface of the waveguide 13 is mirror-finished by polishing and plating. However, it is optically effective to shorten the space by this length. Therefore, infrared sensor 1
2 is almost the same as looking directly into the DUT 14 from the entrance of the waveguide 13. The terms that determine the optical sensitivity at this time are as follows.

When the distance between the inlet of the waveguide 13 and the object 14 to be measured is L and the viewing angle of the infrared sensor 12 itself is θ, the sensitivity coefficient A is (Equation 4) and the effective diameter D of the optical lens is (Equation 5). ).

[0020]

[Equation 4]

[0021]

(Equation 5)

When L = 10 mm and the eardrum diameter is φ5 mm, the viewing angle covering this is θ = 28 ° and A = 0.
It becomes 059.

To compare this with the lens system, in the case of the lens system, 1 / π is added to the lens efficiency in addition to the above ω, so that the lens efficiency is set to 0.6 and the above ω = 0.394.
Is used, the sensitivity coefficient of the lens system becomes 0.075, and it can be seen that this embodiment is more advantageous in terms of sensitivity.

Further, in the case of the waveguide 13, even if the polishing or plating treatment is performed as described above, the reflectance does not become completely 1, so that the temperature information of the waveguide itself also enters the infrared sensor 12.
At this time, if the temperature of the waveguide 13 is the same as that of the infrared sensor 12, there is no problem. However, even if one end is thermally coupled, the other end is distant from the outer peripheral portion and the disturbance heat is transferred through the housing 10. Hard to be the same. For this reason, the measured value changes immediately after inserting the thermometer into the ear canal and after a while, which is recognized as poor reproducibility. In the present embodiment, similarly, the temperature of the tubular portion 9 changes, but since the viewing angle is narrowed by the optical lens 3, the inner surface of the tubular portion 9 does not enter the visual field and this influence is eliminated.

The opening 8 limits the viewing angle of the infrared sensor 1 itself as described above, but this has the effect of preventing the entry of thermal information other than the incident from the optical lens 3, and in the present embodiment it is 30. It is supposed to be °. When using the chopper 4, there is also an effect that the required value of the amplitude of the chopper 4 can be reduced by this visual field.

A polished lens made of silicon or germanium is generally used as the optical lens 3, but a flat lens applying the diffraction principle is effective in the case of a small lens as in the present invention. This is because the area is directly linked to the cost because it is cut out from a large-sized wafer.

[0027]

As described above, the present invention improves the measurement accuracy by obtaining a smaller viewing angle in the optical lens, limiting the field of view within the range of the eardrum, and excluding temperature information other than the eardrum, and a small sensor. The infrared thermometer having a light receiving section realizes a radiation thermometer having a feature that a sensitivity equal to or higher than that of a conventional one is secured with a small optical lens.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a radiation thermometer according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the operation of the embodiment.

FIG. 3 is a side sectional view showing a configuration of a conventional radiation thermometer.

[Explanation of symbols]

 1 infrared sensor 2 sensor light receiving part 3 optical lens 4 chopper 5 chassis 6 housing 7 eardrum 8 opening 9 tubular part

Claims (4)

[Claims] 1. A radiation thermometer for detecting body temperature by detecting infrared rays radiated from an object to be measured, and a rectangular infrared sensor having a sensor light-receiving portion having a diameter of 0.3 mm or less or one side of 0.3 mm or less, A radiation thermometer having an optical lens with a diameter of 6 mm or less. 2. The radiation thermometer according to claim 1, wherein a flat plate lens utilizing a diffraction effect is used as the optical lens. 3. The radiation thermometer according to claim 1, wherein a pyroelectric thin film is used as the infrared sensor. 4. The radiation thermometer according to claim 1, wherein the infrared sensor has a viewing angle of 30 ° or less.