JP2009002739A - Radiation thermometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation thermometer capable of acquiring fully satisfactory result, from the viewpoint of not only high-speed response performance but also measurement accuracy and measurement reproducibility by organizing and using the optimum optical system for an infrared sensor having a large light receiving domain, and realizing high-speed and high-accuracy measurement. <P>SOLUTION: A circular conical condensing mirror 7, having an inner circumferential surface 7a with a gradually widened opening toward the infrared lens 5 side, is arranged between a high-speed response thermopile type infrared sensor 1 and an infrared lens 5 for refracting infrared light from a measuring object toward the light-receiving domain of the infrared sensor 1, so that the narrow opening end of the inner circumferential surface is in contact with or is very close to the light-receiving region of the infrared sensor 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used when, for example, measuring the surface temperature of various objects that are difficult to measure in a contact type, such as food or drinking water, or that are difficult to measure in a contact manner, such as an operating part in a factory. The present invention relates to a radiation thermometer that measures the surface temperature of an object to be measured by measuring the amount of infrared rays emitted from the surface of the object to be measured.

  As this type of radiation thermometer, it is desired to increase the response speed in moving object measurement applications. For example, in a high-speed line that continuously controls the temperature while continuously producing drinking water, the measurable time for one sample is 30 to 40 msec. Under such conditions, a response of 10 msec or less is required to exhibit a response characteristic of 95% or more. Speed is required. The response speed of the radiation thermometer depends on the response speed of the infrared sensor mounted inside. From this point of view, various researches have been conducted to increase the response speed of the infrared sensor. An infrared sensor having a response speed sufficiently corresponding to a continuous production high-speed line of drinking water has been developed and has already reached a practical level.

  On the other hand, an infrared sensor having a high-speed response performance has a relatively large light receiving area due to its structure. In the radiation thermometer using the infrared sensor having such a large light receiving area, the fluctuation of the indicated value and the field of view. An optical system that can efficiently collect light with satisfactory characteristics has not been developed. Therefore, as an optical system of an infrared sensor having high-speed response performance, an optical system generally known from the past, that is, a large light reception on the front side of the infrared sensor 21, as schematically shown in FIG. An infrared lens 22 having a size corresponding to the region 21a (see, for example, Patent Document 1) or a cone-shaped inner portion immediately before the light receiving region 21a of the infrared sensor 21 as schematically shown in FIG. The actual condition is that only the condensing mirror 23 having a peripheral surface is arranged.

JP-A-4-104080

  However, as shown in FIG. 5, in the case of a radiation thermometer using only a large infrared lens 22 as an optical system, not only a large but thick lens is required, which is not only expensive but also transmission loss corresponding to the thickness. As a result, the efficiency of capturing infrared light from the object to be measured is at most about 30%, which is satisfactory in terms of measurement accuracy and measurement reproducibility while using an infrared sensor with excellent high-speed response performance. Cannot be obtained. In addition, in the case of a radiation thermometer using only the conical condensing mirror 23 as shown in FIG. 6 as an optical system, a narrow visual field characteristic suitable for the light receiving region of the infrared sensor cannot be obtained, and measurement accuracy and measurement reproduction are achieved. There is a problem that satisfactory results cannot be obtained in terms of sex.

  The present invention has been made in view of the above circumstances, and its purpose is not only to have excellent high-speed response performance by constructing an optimal optical system for an infrared sensor having a large light receiving area, but also to provide measurement accuracy and measurement. An object is to provide a radiation thermometer that can achieve satisfactory results in terms of reproducibility and can realize high-speed and high-accuracy measurement.

  In order to achieve the above object, a radiation thermometer according to the present invention is a radiation thermometer for measuring the surface temperature of an object to be measured by measuring the amount of infrared light emitted from the surface of the object to be measured. Condensation in the form of a weight having an inner peripheral surface with a gradually wider opening toward the infrared lens side between the sensor and an infrared lens that refracts infrared light from the measurement object toward the light receiving region of the infrared sensor. The mirror is characterized in that the narrow opening end of its inner peripheral surface is in contact with or in close proximity to the light receiving region of the infrared sensor.

  According to the present invention having the above-described characteristic configuration, by using an infrared sensor having a large light receiving area, the response speed of the radiation thermometer can be increased, and the moving object can be sufficiently measured. As an optical system for the large light receiving area of the infrared sensor, an optical system consisting of a combination of an infrared lens and a weight-shaped condensing mirror is used, and the thickness and curvature of the lens, the opening angle and the length of the condensing mirror, etc. Selection by optical simulation and verification by experiment to obtain efficient condensing characteristics that can capture nearly 100% of infrared light from the measurement object and narrowed field of view characteristics. As a result, it is optimal for a large light receiving area. The construction of a simple optical system was completed. Therefore, not only is it excellent in high-speed response performance, but by constructing (adopting) an optical system that is optimal for the high-speed response infrared sensor, sufficiently satisfactory results can be obtained in terms of measurement accuracy and measurement reproducibility. There is an effect that a radiation thermometer capable of realizing high-speed and high-precision measurement can be obtained.

  As an infrared sensor in the radiation thermometer according to the present invention, as described in claim 2, a plurality of strip-like thin thin film portions are arranged in parallel to each other on a substrate, and each length of the plurality of thin thin film portions is arranged. It is preferable to use a thermopile provided with a plurality of thermocouples connected in series along the side.

  In the thermopile infrared sensor having the above configuration, the thermal conductance between the thin film portion and the substrate that is the heat sink is defined by the size in the short side direction, so that the response speed can be increased while the long side direction of the thin film portion is aligned. By increasing the number of installed thermocouples, the faster the response speed, the lower the temperature reached by the heat sensitive part due to the trade-off relationship described later, which can compensate for the decrease in sensitivity, and the response is in a trade-off relationship. It is possible to achieve both speed and practical level sensitivity. By combining a thermopile infrared sensor with such a high-speed response and high sensitivity with an optimal optical system, it can be used effectively for measuring moving objects such as high-speed lines that control temperature while continuously producing drinking water. can do.

Note that the trade-off relationship between the response speed and the sensitivity is that the thermal time constant τ when C is the heat capacity of the heat sensitive portion and G is the thermal conductance with the substrate,
τ = C / G (1)
In order to increase the response speed, it is necessary to decrease the heat capacity C and increase the thermal conductance G. On the other hand, when the thermal conductance G increases, the sensitivity decreases.

  Further, in the radiation thermometer using the thermopile type infrared sensor, as described in claim 3, a light receiving region of the infrared sensor is formed in a circular shape or a substantially circular shape, and an inner peripheral surface of the condenser mirror is a cone. It is desirable to form in a shape. In this case, regardless of the shape of the object to be measured, it is possible to measure with high sensitivity, high speed, and high accuracy, and to improve versatility.

  Further, in the radiation thermometer according to the present invention, as described in claim 4, the condensing mirror is disposed so as to form a space between the wide opening end of the inner peripheral surface and the infrared lens. It is possible to avoid that the infrared light refracted by the lens is diffusely reflected on the inner peripheral surface on the wide opening end side of the condensing mirror and deteriorate the visual field characteristic, and the condensing characteristic and the visual field characteristic are further improved. Can be.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a lens barrel portion which is a main part of a radiation thermometer according to the present invention. In FIG. 1, reference numeral 1 denotes an infrared sensor, which is detachably assembled and fixed to the bottom of the lens barrel 2 via a mounting seat plate 3 and a bolt 4. An infrared lens 5 that refracts infrared light IR from a measurement object toward a light receiving region of the infrared sensor 1 is fixed to the opening end side of the lens barrel 2 via an annular presser 6.

  In the lens barrel 2 between the infrared sensor 1 and the infrared lens 5, a conical condensing mirror 7 having an inner peripheral surface 7a having an opening gradually wider toward the infrared lens 5 side is disposed. The condensing mirror 7 is configured to form a virtual light receiving surface 8 having an area approximately 15 times as large as a light receiving region (described later) of the infrared sensor 1 at the widest opening end of the inner peripheral surface 7a. The narrowest opening end of the inner peripheral surface 7a is fixed so as to be in contact with the can 9 that accommodates the infrared sensor 1, and the distance from the light receiving region of the infrared sensor 1 is made as short as possible. . The condensing mirror 7 is formed to have the shortest length L so that there is a space between the widest opening end of the inner peripheral surface 7 a, that is, the virtual light receiving surface 8 and the infrared lens 5. Yes.

  On the outer surface of the mounting base plate 3 at the bottom of the lens barrel 2, a conductive printed circuit board 12 for electrically connecting lead pins 11 led out from a silicon substrate 10 serving as a heat sink of the infrared sensor 1 is fastened together with the bolts 4. It is fixed.

The infrared sensor 1 is formed by forming an insulating film 13 such as SiO _{2 on} the upper surface of the silicon substrate 10 and etching the back surface of the silicon substrate 10 as shown in the principle configuration diagrams of FIGS. Three thin strips of thin strips 14a, 14b, 14c having a diaphragm structure are arranged in parallel with each other to form a heat sensitive part, and these thin film parts 14a, 14b, 14c form a substantially circular light receiving region 1A.

  Then, along each long side of the three rows of thin film portions 14a, 14b, and 14c, a plurality of, for example, a total of 144 thermocouples 15 made of aluminum and polycrystalline silicon are connected to their hot junctions 15h. Is located on the thin film portions 14a, 14b, 14c, and the cold junctions 15c are arranged in parallel so as to be located on the silicon substrate 10, and the thermocouples 15 are connected in series. It consists of a thermopile.

  The radiation thermometer has an alarm output function and a peak hold / bottom by gate input in a lens barrel portion on which an optical system composed of a combination of the above-described high-speed response thermopile infrared sensor 1 and infrared lens 5 and condenser mirror 7 is mounted. A case body incorporating a hold, a moving average function, an interface circuit with the outside, and the like are joined. However, since these are well known, detailed description thereof is omitted.

  In the radiation thermometer configured as described above, as the infrared sensor 1, a structure in which strip-like long thin film portions 14a, 14b, and 14c are arranged in parallel to each other as a heat sensitive portion, and a plurality of heat sensitive portions, For example, by using a thermopile type infrared sensor in which a total of 144 thermocouples 15 are connected in series, a rapid response of 2 msec or more and 10 msec or less is evident from the trade-off relational expression (1) described above. It is possible to achieve both speed and practical level sensitivity, and for example, it can be effectively applied to moving object measurement applications such as a high-speed line for temperature control while continuously producing drinking water.

  In addition, as an optical system for the relatively large light receiving area 1A of the thermopile type infrared sensor 1 having a high-speed response and high sensitivity as described above, an infrared lens 5 and a conical condensing mirror 7 are combined. Optics for obtaining an efficient condensing characteristic and a narrow visual field characteristic capable of capturing nearly 100% of the infrared light IR from the measurement object with respect to the thickness, curvature, opening angle and length of the condensing mirror 7, etc. By selecting by simulation and verifying by experiment, and using an optimal optical system constructed so that the fluctuation of the indicated value and the visual field characteristics can be satisfied even for a large light receiving area 1A, it has only excellent high-speed response performance. In addition, it is possible to obtain a radiation thermometer capable of realizing high-precision measurement with a measurement accuracy within ± 2 ° C (0 to 200 ° C) and a measurement reproducibility within 1 ° C That.

  Further, as in the above embodiment, the light receiving region 1A of the thermopile infrared sensor 1 is formed in a substantially circular or circular shape, and the inner peripheral surface 7a of the condenser mirror 7 is formed in a conical shape. Regardless of the shape of the object to be measured, it can be measured with high sensitivity, high speed and high accuracy, and versatility can be enhanced.

  Further, the condensing mirror 7 may be formed in such a length that the widest open end of the conical inner peripheral surface 7a contacts the infrared lens 5 as shown by the phantom line in FIG. However, as shown in the above-described embodiment, the lens 5 is formed with a short length L in which a space exists between the widest opening end of the inner peripheral surface 7a and the infrared lens 5. It is possible to avoid that the refracted infrared light IR is irregularly reflected by the inner peripheral surface 7a on the wide opening end side of the condensing mirror 7 to deteriorate the visual field characteristic, and the condensing characteristic and the visual field characteristic are further improved. Can be.

  In the above embodiment, three rows of strip-like thin thin film portions 14a, 14b, 14c having a diaphragm structure on the silicon substrate 10 are arranged in parallel with each other to form a heat sensitive portion, and the thin film portions 14a, 14b, 14c are substantially circular. The thermopile infrared sensor 1 formed with the light receiving region 1A is used, but instead of this, as shown in FIG. 4, two rows of elongated thin film portions 14a, 14b having the same length as the strip structure are arranged in parallel. A plurality of thermocouples 15 made of aluminum and polycrystalline silicon are juxtaposed along the long sides of the two rows of thin film portions 14a and 14b. A fast response thermopile type infrared sensor 1 having a rectangular light receiving region 1A connected in series may be used.

It is a longitudinal cross-sectional view of the lens-barrel part which is the principal part of the radiation thermometer which concerns on this invention. It is a top view which shows the principle structure of the infrared sensor used for the radiation thermometer which concerns on this invention. It is sectional drawing which shows the principle structure of the infrared sensor used for the radiation thermometer which concerns on this invention. It is a top view which shows the principle structure of the other infrared sensor used for the radiation thermometer which concerns on this invention. It is the schematic which shows an example of the optical system of the infrared sensor used for the conventional radiation thermometer. It is the schematic which shows the other example of the optical system of the infrared sensor used for the conventional radiation thermometer.

Explanation of symbols

1 Infrared sensor (thermopile infrared sensor)
1A Light-receiving area 5 Infrared lens 7 Condensing mirror 7a Conical inner peripheral surface 14a, 14b, 14c Strip-shaped elongated thin film portion 15 Thermocouple IR Infrared light

Claims (4)

A radiation thermometer that measures the surface temperature of the measurement object by measuring the amount of infrared rays emitted from the surface of the measurement object,
Between the infrared sensor and the infrared lens that refracts infrared light from the object to be measured toward the light receiving region of the infrared sensor, a weight-shaped collection having an inner peripheral surface with an opening gradually wider toward the infrared lens side. A radiation thermometer characterized in that the optical mirror is arranged in such a manner that the narrow opening end of its inner peripheral surface is in contact with or in close proximity to the light receiving region of the infrared sensor.   The infrared sensor has a plurality of strips of thin thin film portions arranged in parallel to each other on a substrate, and a plurality of thermocouples are connected in series along each long side of the thin film portions of the plurality of rows. The radiation thermometer according to claim 1, wherein the radiation thermometer is composed of a thermopile.   The radiation thermometer according to claim 2, wherein a light receiving region of an infrared sensor constituted by the thermopile is formed in a circular shape or a substantially circular shape, and an inner peripheral surface of the condenser mirror is formed in a conical shape. The radiation thermometer according to any one of claims 1 to 3, wherein the condensing mirror is disposed so as to form a space between an open end having a large inner peripheral surface and an infrared lens.

Images