JP3327668B2 - Infrared detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector for detecting temperature in a non-contact manner, and more particularly, to an infrared detector using a thermistor element and closely attached to a resin film having a high infrared absorption rate. The present invention relates to a high-sensitivity infrared detector including a thermistor element and a thermistor element for temperature compensation.

[0002]

2. Description of the Related Art Heretofore, as one of infrared detectors having improved detection sensitivity by using a thermistor, the present applicant has disclosed in Japanese Patent Application Laid-Open No. HEI 4-1992.
There is an infrared detector proposed in JP-A-183461.
FIG. 10 is a cross-sectional view of the infrared detector previously proposed by the present applicant. This infrared detector includes an envelope (case) 20 having an opening 21 in a part thereof, and an opening 21 of the envelope 20.
Film 22 made of a polymer material in which carbon black or an inorganic pigment is dispersed so as to close
And an infrared detecting thermistor element 23 disposed in the envelope 20 and closely adhered to the resin film, and a temperature compensation thermosensitive element 24 disposed in the envelope.

In the infrared detector, when infrared light enters a resin film 22 attached to an envelope 20, the infrared light is irregularly reflected and absorbed by carbon black or the like dispersed in the resin film 22, and the amount of resin is changed according to the amount of infrared light. The temperature of the film 22 increases. The temperature absorbed by the resin film 22 depends on the thermistor element
To change the resistance value. Since almost 100% of the infrared rays are absorbed by the resin film 22, the amount of the infrared rays transmitted through the resin film 22 is extremely small, and the effect on the temperature compensating thermistor element 24 can be ignored. Therefore, the temperature compensating thermistor element 24 can detect the ambient temperature without being affected by infrared rays. Therefore, by forming a bridge circuit using the infrared detecting thermistor element 22 and the temperature compensating thermistor element 24, a potential difference corresponding to the infrared ray is generated between the output terminals of the bridge circuit, and the infrared ray amount is detected based on the potential difference. It is something.

[0004]

However, FIG.
In the conventional infrared detector shown in FIG. 1, the thermistor element for infrared detection 23 is tightly fixed on the resin film 22, while the thermistor element for temperature compensation 24 is a resin for detecting the temperature inside the case 20. It has a structure in which the thermistor element is disposed alone without being tightly fixed to the film. Therefore, there is a structural disadvantage that the heat capacity of the infrared detecting thermistor element 22 is extremely large as compared with the temperature compensating thermistor element 24. is there. Further, if the temperature compensating thermistor element is embedded in the envelope, the heat capacity of the temperature compensating thermistor element becomes larger than that of the infrared thermistor element. For this reason, when the ambient temperature changes, a difference occurs in the response speed between the infrared detecting thermistor element and the temperature compensating thermistor element, so that there is a drawback that this difference becomes a detection error.

FIG. 8 is a bridge circuit diagram showing a detection circuit of the infrared detector. In FIG. 8, Th _1, Th ₂ are each infrared sensing thermistor element 5a and the temperature compensating thermistor element 5b, to form a bridge circuit by the resistor R _2, R _3, is positive electrode of the voltage source Ba via the resistor R ₁ is connected to the connection point of the infrared sensing thermistor element 5a and the temperature compensating thermistor element 5b, it is connected to the negative electrode of the voltage source Ba to the connection point between the resistor R ₂ and the resistor R _3, A and B are its output terminals. In a state where the infrared ray is not incident on the infrared detecting thermistor element, the output of the bridge circuit is in a balanced state and the output is zero. When there is a difference in heat capacity between the infrared detecting thermistor element 5a (Th ₁ ) and the temperature compensating thermistor element 5b (Th ₂ ), that is, in the infrared detector having the above structure, when the ambient temperature changes, the heat capacity becomes large. Since the element has poor response to a change in ambient temperature, there is a disadvantage that the balance of the bridge circuit is lost and a potential difference is generated between the output terminals A and B. There is a drawback that a temperature difference generated due to the difference in heat capacity becomes a temperature detection error and an accurate temperature cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an infrared detector having excellent thermal response characteristics, and having a stable and accurate temperature detecting ability.

[0007]

In order to achieve the above object, an infrared detector according to the present invention comprises a thermosensitive element for detecting infrared rays and a thermosensitive element for compensating temperature, a thermosensitive element for detecting infrared rays, and the thermosensitive element for detecting infrared rays. A resin film for tightly fixing the compensation heat-sensitive elements, a substantially thermally conductive plate or frame for fixing at least portions of the resin film on the infrared detection side and the temperature compensation side, and the infrared detection A case in which the plate portion or the frame is provided so that the thermal sensing element for temperature and the thermal sensing element for temperature compensation are arranged inside thereof, an incident window through which infrared rays are incident, and a shielding section that shields the infrared rays. Wherein the entrance window is disposed on the side of the thermal element for use, and the shielding section is disposed on the side of the thermal element for temperature compensation.

Further, the infrared detector of the present invention comprises a thermosensitive element for infrared detection and a thermosensitive element for temperature compensation, and a resin film in which the thermosensitive element for infrared detection and the thermosensitive element for temperature compensation are fixed to the same surface. A substantially thermally conductive plate or frame for fixing at least a boundary portion of the resin film on the infrared detection side and the temperature compensation side, and the infrared detection thermosensitive element and the temperature compensation thermosensitive element inside thereof. A case for accommodating the frame so as to be disposed at the same, an incident window through which infrared rays are incident, and a shielding portion for shielding the infrared rays, wherein the incident window is disposed on the infrared sensing thermal element side, and the temperature compensation is performed. An infrared detector, wherein the shielding portion is arranged on the side of the heat-sensitive element.

In addition, the infrared detector of the present invention comprises a thermosensitive element for detecting infrared rays, a thermosensitive element for temperature compensation, a case provided with a window for incident infrared rays on one side, the thermosensitive element for detecting infrared rays and the temperature compensating element. A first and a second resin film provided with a reflective film on the back surface thereof, and a surface of the first resin film on which the infrared detecting thermosensitive element is closely fixed. To the window side, with the surface of the second resin film on which the temperature-compensating thermosensitive element is tightly fixed facing the reflective film formed on the first resin film. Characterized in that at least a part of the infrared detector is fixed by a thermally conductive frame and disposed in the case. Further, in the infrared detector, the case and the frame are integrally formed, and a component insertion hole is provided in the case.

[0010]

The infrared detector according to the present invention uses a resin film having substantially the same shape as a resin film in which the infrared sensing thermal element and the temperature compensating thermal element absorb infrared rays, and a thermal element having substantially the same heat capacity and the same characteristics. In this way, the structure is made to be equally affected by the temperature change due to the temperature change around the infrared detector, for example, heat conduction, radiation, convection, etc. inside the case, and offset by the change in the surrounding temperature. The temperature is accurately detected in such a manner as to obtain the temperature. Also,
Since the heat-sensing part and the temperature compensation part, which are composed of the thermal element for infrared detection and the resin film and the thermal element for temperature compensation and the resin film, respectively, have the same heat capacity, the applied voltage of the bridge circuit composed of the infrared detector must be increased. Can maintain an equilibrium state even if the
The N ratio increases and the detection sensitivity can be increased. In addition, a plate having substantially good thermal conductivity that prevents heat of the infrared detecting unit from conducting to the resin film of the temperature compensating unit is provided at a portion or a boundary portion of the resin film of the infrared detecting unit and the temperature compensating unit. By providing a part or a frame, temperature detection is performed such that the temperature gradient at the facing part or the boundary part is made substantially zero.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the infrared detector according to the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of the infrared detector of the present invention, and FIG. 2 is a side sectional view showing an assembled state. 1 and 2, reference numeral 1 denotes a case made of resin or metal. 2 is a resin film 3
A frame for fixing a and 3b, the material of which is made of resin or metal. The frame 2 is fixed in the case by an adhesive or the like by an overhang 4 provided in the case 1. The case 1 and the frame 2 are materials having good thermal conductivity, for example,
If it is metal, the case 1 and the frame 2 may be formed integrally. The resin films 3a and 3b are made of a polymer material such as polyester having a thickness of 0.2 mm as a base material and carbon black or an inorganic pigment dispersed therein.

Reference numerals 5a and 5b denote thermosensitive elements, which will be described as thermistor elements in this embodiment. Of course, any thermosensitive element such as a thermocouple or a platinum resistor may be used. The same characteristics are used for the thermal elements 5a and 5b. The heat-sensitive elements 5a and 5b have substantially the same shape and are fixed so as to be in close contact with one surface of the resin films 3a and 3b having the same heat capacity. Reference numeral 6 denotes a lid having an infrared incident window 7 attached to one surface of the case 1 and an infrared shielding portion 6a. Needless to say, the case 1 and the lid 6 may be formed as an integral structure. The lid 6 has a structure in which an infrared incident window 7 is located at a portion of the resin film 3a to which a thermal element for infrared detection is attached, and an infrared shielding portion 6a is located at a portion of the resin film 3b to which a thermal element for temperature compensation is attached. It has a structure to do. The resin films 3a and 3b need not have the same shape as long as they have the same heat capacity. The frame 2 in FIG. 1 is a means for fixing the resin film on the infrared detection side and the temperature compensation side to the inside of the case, and aims to eliminate the thermal gradient between the infrared detection side and the temperature compensation side due to the resin film. Therefore, it is not necessary to use a frame as shown in FIG. 1, and a recess is formed in a part of the overhang 4 as shown in the embodiment of FIG. 2 ′ is fitted in the concave portion of the overhang portion 4 and disposed.
3b may be arranged and fixed to the overhang portion 4 and the plate portion 2 '. The plate portion 2 'may be provided only at a portion where the resin film on the infrared detection side and the resin film on the temperature compensation side face and contact each other. Lid 6
Is fixed to the case 1 with the infrared incident window 7 side as the infrared detecting side.

Next, infrared detection by the infrared detector of the present invention will be described. First, the infrared rays are transmitted through the lid 6 of the case 1.
Incident on the infrared incident window 7 provided in the
a. The resin film 3a is a resin film 3a made of polyester in which carbon black is dispersed and having an infrared absorptivity of approximately 100%, and the temperature of the resin film 3a increases according to the amount of infrared rays. A rise in the temperature of the resin film 3a changes the resistance value of the thermistor element 5a that is in close contact with the back surface of the resin film 3a. Therefore, the temperature rise of the resin film 3a according to the amount of infrared rays is output as a change in resistance value. Of course, the change in the resistance value includes the influence of the temperature around the infrared detector.

On the other hand, the temperature compensating thermistor element 5b
The temperature compensating thermistor element 5b is not affected by the infrared rays and has a resistance value with respect to the temperature of the surrounding atmosphere, because the temperature compensating thermistor element 5b is tightly fixed to the resin film 3b and has a structure of blocking the infrared rays by the lid 6. Changes. The thermistor elements 5 on the infrared detection side and the temperature compensation side
The heat capacities of the respective heat capacities a and 5b and the heat capacities of the resin films 3a and 3b to which they are applied are the same.

Therefore, the resistance value of the thermistor element changes in the same manner with respect to the temperature change of the ambient atmosphere of the infrared detector, and by canceling this change, the temperature change according to the incident infrared ray amount can be accurately detected. can do. This cancellation of the ambient temperature can be achieved by the bridge circuit shown in FIG. Using the infrared detecting thermistor element 5a (Th ₁ ) and the temperature compensating thermistor element 5b (Th ₂ ) of the infrared detector according to the present invention, the above-described bridge circuit is formed, and the infrared detecting thermistor element 5a
Is detected as a voltage change between the terminals A and B, and a temperature change corresponding to the amount of infrared rays is accurately detected.

FIG. 9 shows the output characteristics when the surface of an object (heating element) having the infrared detectors of the prior art and the present invention is viewed. As shown in the characteristic curve (a) of FIG. 9, in the conventional case, an overshoot is observed at the rising portion,
This means that it takes time to reach a stable state due to the difference in heat capacity between the infrared detecting thermistor element and the temperature compensating thermistor element, in other words, to reach a state where accurate temperature can be detected. I can say that. On the other hand, as shown in the characteristic curve (b), in the case of the infrared detector of the present invention, since there is no overshoot, it is possible to set a state where accurate temperature detection can be performed in a short time.

FIG. 4 is an exploded perspective view showing another embodiment of the infrared detector according to the present invention. The embodiment of FIG.
Is different from the infrared detector shown in (1) in that the resin film 8 to which the infrared detecting thermistor element 5a and the temperature compensating thermistor element 5b are tightly fixed is constituted by a single plate. Case 1 formed, infrared incident window 7
The lid 6 and the frame 2 provided with the infrared ray shielding portion 6a are the same as those in the embodiment of FIG. In this embodiment, when the temperature of the surface of the resin film 8 on the side of the infrared detecting thermistor element 5a rises due to the incidence of infrared light, the heat flows through the resin film 8 to the side of the temperature compensating thermistor element 5b and the temperature compensating thermistor 5b. Since the resistance value of the element 5b is to be changed, a metal frame (cold junction for absorbing heat) 2 is adhered to the back side of the resin film 8 in order to prevent this, and the boundary between the infrared detection side and the temperature compensation side is formed. The temperature gradient of the portion is eliminated. That is, heat is prevented from flowing through the resin film 8 and flowing toward the temperature compensating thermistor element 5b. The frame 2 may be made of resin instead of metal as long as the material has good thermal conductivity. In this case, it is necessary to increase the heat capacity as compared with metal to reduce the temperature gradient and thermally insulate the two. For example, it is necessary to increase the thickness of the resin film 8 and increase the width thereof. There is. Needless to say, similarly to the embodiment of FIG. 3, a structure may be adopted in which the plate portion 2 'as shown in FIG. 3 is arranged at least at the boundary between the infrared detection side and the temperature compensation side without providing the frame 8.

FIG. 5 is an exploded perspective view showing another embodiment of the infrared detector according to the present invention, and FIG. 6 is a side sectional view showing a state where the components of FIG. 5 are assembled. 5 and 6, an overhang 4 is formed in the case 1 and the frame 2 is placed and fixed on the overhang 4. The frame 2 has windows 2a and 2b, respectively.
There is. Reference numeral 3a denotes a resin film, and the infrared detecting thermistor 5a is adhered and fixed to the back surface thereof. Similarly,
Temperature compensation thermistor 5b on the back of resin film 3b
Are adhered and fixed, and a reflective film 9 is adhered to the surface thereof. It is stuck so that the surface of the resin film 3a is exposed from the window 2a. The resin film 3b is stuck so that the reflection film 9 is exposed from the window 2b. In this manner, the infrared detector has a structure in which the reflection film 9 is formed on the infrared incident surface of the resin film 3b of the temperature compensating thermistor 5b to shield the infrared light. Also, without forming the window 2b of the frame 2,
An infrared shielding portion may be used, and a reflection film may be formed on the infrared shielding portion. Needless to say, in this embodiment, for the same reason, a recess may be provided in the overhang portion 4 and a plate portion 2 'as shown in FIG. 3 may be provided.

FIG. 7 (a) is a side view showing another embodiment of the infrared detector according to the present invention. The infrared detector of the above embodiment has an infrared detecting thermistor element 5a and a temperature compensating element. This is a structure in which resin films 3a and 3b that tightly fix the thermistor element 5b are arranged in a plane. However, in FIG. 7A, in order to make the infrared detecting unit and the temperature compensating unit compact, the front surface of the resin film 3a having the reflective film 9a on the back surface is placed in the case 10 having the infrared incident window formed on one surface. Thermistor element 5 for infrared detection
a, and a resin film 3b is arranged in a pair with the resin film 3a. The resin film 3b has a reflection film 9b on its back surface (preferably formed on the bottom surface side to avoid the influence of infrared radiation from the bottom surface of the case 10).
Is formed, and the temperature compensating thermistor element 5b is formed on the surface thereof.
Are tightly fixed. These resin films 3a, 3b
Is held by the support frame 11 having good thermal conductivity. The resin films 3a and 3b have the same heat capacity as a resin film having the same shape.

The spaces 12a and 12b in the case 10 facilitate heat convection in spaces that are continuous with each other.
5, the infrared detecting thermistor element 5a and the temperature compensating thermistor element 5b must have the same influence on the change of the ambient temperature. In the infrared detector having this structure, the reflection film 9a prevents heat radiation from the back surface due to the temperature rise of the resin film 3a due to infrared rays, thereby preventing the temperature of the resin film on the temperature compensation side from rising. As for the material of the case 10 of the infrared detector of this embodiment, a resin may be used in the same manner as in the above embodiment, but if a case made of a metal having good heat conductivity is used, the reflection film 9b of the resin film 3b is used. Is not necessary, and is used as a cold junction for eliminating the thermal gradient of the support frame 11 between the ends of the resin films 3a and 3b for detecting infrared rays and for compensating temperature, so that the temperature detection error of infrared rays can be ignored. As a result, accurate temperature detection becomes possible. Needless to say, when the case is formed of a resin, a support frame made of a metal may be provided between the resin films for infrared detection and temperature compensation, as in the previous embodiment. Needless to say, the support frame 11 may be a circular frame or a rectangular frame, as long as the resin films 3a and 3b can be stretched and fixed to the support frame 11. For example, as shown in FIG. In order to stretch and support 3b, any structure that supports at least two sides may be used.

In the infrared detector according to the present invention, the resin film to which the infrared detecting thermistor element and the temperature compensating thermistor element are fixed in close contact has substantially the same shape.
The temperature is easily detected by equalizing the heat capacities of the thermistor element for infrared detection and the resin film and the thermistor element for temperature compensation and the resin film, but the shape of the resin film is different but the heat capacity is equal It is clear that it is sufficient. Of course, even if the heat capacity of the heat sensitive part and the temperature compensation part are slightly different,
Although it is possible to cancel with a bridge circuit, productivity is better if the resin films have the same shape, and the positional conditions of the infrared detecting thermistor element and the temperature compensating thermistor element, for example, symmetry It is clear that it is convenient to keep Further, the frame and the case to which the resin film on which the heat-sensitive part and the temperature compensation part are formed are bonded may be integrally formed. In this case, it is necessary to provide a component insertion hole on the bottom of the case.

[0022]

As described above, the infrared detector of the present invention has a resin film in which the thermosensitive element for detecting the infrared ray and the thermosensitive element for temperature compensation are fixed in the same shape or the same heat capacity. The thermal capacity of the infrared detector and the temperature compensator, including the same, is made equal, so that the influence of the surrounding temperature can be easily canceled, and the temperature of the infrared radiator is accurately measured to detect the amount of infrared. There are advantages that can be done. Further, instead of separately providing the resin film for tightly fixing the thermosensitive element for infrared detection and the thermosensitive element for temperature compensation as described above, a single plate may be used, in which case the heat sensitive surface on the thermosensitive element side for infrared detection is used. It is necessary to prevent the heat absorbed by the heat-sensing element for temperature compensation from being conducted to the side of the resin film, so that the heat gradient of the resin film becomes zero at the center of the resin film. It has an advantage that the temperature of the infrared radiator can be accurately measured to detect the amount of infrared radiation. In addition, the infrared detector of the present invention is designed to prevent the heat of the infrared detecting thermosensitive element from affecting the temperature compensating thermosensitive element as radiant heat in order to enhance the infrared detection sensitivity. The element and the thermal compensation element for temperature compensation are arranged at the same distance to the infrared radiator, or the heat of the infrared detection thermal sensitive section does not affect the thermal compensation element for the infrared radiation body. There is an advantage that a reflection plate is provided on the back surface of the resin film on which the infrared detecting thermosensitive element is adhered so that the infrared ray of the infrared radiator can be accurately detected.

When the temperature of the atmosphere around the infrared detector changes, for example, the effects of heat conduction, radiation, convection, etc. inside the case due to the change in the ambient temperature of the infrared detector are compared with the temperature detecting element for infrared detection and the temperature compensation. If the heat-sensitive element is received,
In the infrared detector of the present invention, the heat-sensitive portions having the same heat capacity are equally affected, and the change in the resistance value of the heat-sensitive element with respect to the ambient temperature change also becomes the same value. Since the equilibrium state can be maintained even when the ambient temperature is changed, the balance of the bridge circuit is not lost, and the influence of the ambient temperature change can be ignored. Therefore, there is an advantage that the amount of infrared rays can be accurately measured. In addition, since the infrared detecting section and the temperature compensating section, which are composed of the infrared sensing thermal element and the temperature compensating thermal element and the resin film, have the same heat capacity, even when the applied voltage of the bridge circuit is increased, the balance of the circuit is not increased. Since the state can be maintained, the SN ratio can be increased by increasing the voltage applied to the bridge circuit, and an infrared detector with good detection sensitivity can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing one embodiment of an infrared detector according to the present invention.

FIG. 2 is a side sectional view of the embodiment of FIG. 1 in an assembled state.

FIG. 3 is an exploded perspective view showing another embodiment of the infrared detector according to the present invention.

FIG. 4 is an exploded perspective view showing another embodiment of the infrared detector according to the present invention.

FIG. 5 is an exploded perspective view showing another embodiment of the infrared detector according to the present invention.

FIG. 6 is a side sectional view of the embodiment of FIG. 5 in an assembled state.

FIGS. 7A and 7B are side sectional views showing another embodiment of the infrared detector according to the present invention.

FIG. 8 is a circuit diagram in which an infrared detector is incorporated in a bridge circuit.

FIG. 9 is a diagram comparing characteristics of the present invention and a conventional infrared detector.

FIG. 10 is a sectional view showing an example of a conventional infrared detector.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 case 2 frame 2 ′ plate 3a, 3b, 8 resin film 4 overhang 5a infrared detecting thermistor element 5b temperature compensating thermistor element 6 lid 6a infrared shielding section 7 infrared incident window

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 5/00-5/62 G01J 1/00-1/60

Claims (4)

(57) [Claims] 1. A thermosensitive element for infrared detection and a thermosensitive element for temperature compensation, a resin film for closely fixing the thermosensitive element for infrared detection and the thermosensitive element for temperature compensation, and the resin on the infrared detection side and the temperature compensation side A plate or frame having substantially thermal conductivity for fixing at least an opposing portion of the film; and the plate or frame so that the infrared detecting thermal element and the temperature compensating thermal element are disposed inside the thermal detecting element. A case provided with a body, an incident window through which infrared rays are incident, and a shielding unit that shields infrared rays, wherein the incident window is arranged on the infrared sensing thermal element side, and the shielding unit is arranged on the temperature compensating thermal element side. An infrared detector characterized by disposing. 2. A thermosensitive element for detecting an infrared ray and a thermosensitive element for temperature compensation, a resin film in which the thermosensitive element for detecting an infrared ray and the thermosensitive element for temperature compensation are fixed to the same surface, an infrared detecting side and a temperature compensating side. A substantially thermally conductive plate portion or frame for fixing at least a boundary portion of the resin film, and the frame so that the infrared detecting thermosensitive element and the temperature compensating thermosensitive element are arranged inside thereof. And a shielding part for shielding the infrared ray, wherein the incident window is arranged on the infrared sensing thermal element side, and the shielding section is arranged on the temperature compensating thermal element side. An infrared detector characterized by disposing. 3. A thermosensitive element for detecting an infrared ray, a thermosensitive element for temperature compensation, a case provided with a window for incident infrared light on one surface, and a thermosensitive element for detecting an infrared ray and the thermosensitive element for temperature compensation, which are tightly fixed to each other. And a first film having a reflection film on the back surface thereof.
And a second resin film, wherein the surface of the first resin film on which the infrared detecting thermosensitive element is fixedly adhered faces the window, and the temperature compensation thermosensitive element of the second resin film is closely adhered to the window side. With the fixed surface facing the reflective film formed on the first resin film, at least a portion of the first and second resin films was fixed with a thermally conductive frame and disposed in the case. An infrared detector, characterized in that: 4. The infrared detector according to claim 1, wherein the case and the frame are integrally formed, and a component insertion hole is provided in the case.