JPH1137847A - Narrow-field thermistor bolometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to make a detection area a narrow field of sight to make the constitution simple and small-sized, and to generate an output canceling the thermal error component of a sensing element. SOLUTION: A sensing space and a reference space are formed in a package 1 independently, and sensing elements Rs and reference elements Rr having the same structure are put in to them. In the sensing space and opening 1b of a specified diameter is formed, and a sensing-side detecting element 2 of a specified diameter corresponding to this opening 1b and a circular correcting element 3 having an inside diameter larger than the diameter of the opening 1b are provided. These detecting and correcting elements 2 and 3 output signals of a photodetection level corresponding to the incidence of infrared rays. An outputting means is composed by bridge-connecting individual sensing and reference elements Rs, Rr, cancels the thermal error component of the sensing element Rs, output the difference between the output of the detecting element 2 of the sensing element and the output of the correcting element 3, and outputs a photodetection level in a narrow field-of-sight range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor bolometer for use in a radiation thermometer or the like for measuring the temperature of an object in a non-contact manner, and more particularly to a narrow-field thermistor bolometer having a narrow detection field and a disturbance. .

[0002]

2. Description of the Related Art A thermistor, whose electric resistance varies greatly with temperature, is sealed in a package provided with a window through which infrared rays pass, and the amount of infrared rays is measured based on a change in resistance due to a rise in temperature due to incident infrared rays. It can be converted to temperature and output. In non-contact temperature detection using such a thermistor bolometer, the field of view becomes wider as the distance increases, but there is a demand to limit the detection area in which the temperature is to be detected. The narrow field of view makes it possible to improve the accuracy of measuring the temperature of the object in the limited detection area and reduce the influence from the surroundings of the object.

Further, the thermistor bolometer has a configuration in which the same thermistor for detection and correction is provided inside the package, and infrared rays are incident only on the detection side. Those that remove components are widely used.

[0004]

In order to narrow the detection area of the conventional thermistor bolometer to a narrow field of view, a condensing optical system using a lens, a mirror, or the like, or an aperture is used outside the package of the sensor. There was a problem that the configuration was large and expensive.

Also, when viewed from the sensor side, infrared radiation from a structure such as a lens, a mirror, or an aperture is also received, and the error factor increases. This is not a problem if the temperature of the light-receiving part of the sensor is equal to the temperature of the structure. There is also a problem that a transient shift occurs between the change in temperature and the temperature of the structure, and this appears as an error in the output.

[0006] Thermistor bolometers of this type, which are classified as thermal sensors, use the amount of infrared energy received by an object and the amount of infrared energy subtracted from the energy emitted by the light receiving section of the sensor itself. When the temperature of the light receiving portion changes, the amount of infrared rays (temperature) is output based on the temperature difference between the object and the light receiving portion itself. Therefore, for example, when an attempt is made to measure body temperature near room temperature (25 ° C.), the output is small due to the small temperature difference, making it difficult to obtain an accurate temperature output (corresponding to the resolution of the temperature output). Therefore, there is a demand for a configuration that can reduce the size so that the temperature change of the material and the light receiving portion that undergo a large change in state even with a smaller incident energy and that provides a sufficient resolution can be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can provide a narrow detection field of view, a simple and small-sized detection area, and can cancel and output a thermal error component of a sensing element. It is intended to provide a narrow-field thermistor bolometer.

[0008]

According to the present invention, there is provided a narrow-field thermistor bolometer according to the present invention.
As described, in a thermistor bolometer in which a sensing element and a reference element having the same shape as the sensing element are provided inside the package to cancel and output a thermal error component of the sensing element, a predetermined diameter through which infrared rays pass is provided. A package in which a sensing space in which a window is formed as an opening, a reference space having the same shape as the sensing space and having no window, and a sealed whole area, are formed independently of each other; A thermistor film which is provided inside the sensing space, has a shape corresponding to the window, and has a resistance value changed by a temperature rise due to infrared rays incident through the window, and the incident angle is parallel light (α0) Outputs the highest light receiving level and the light receiving level corresponding to the incident angle up to the critical angle (α3) A sensing side detecting element (Rsm) for outputting a sensing signal, and an annular thermistor provided inside the sensing space of the package, having the same area as the sensing detecting element and having an inner diameter larger than the opening diameter of the window. A sensing side correction element (Rss) for detecting infrared rays having an incident angle in a predetermined angle range (α0 <α <α3), and a sensing side correction element (Rss) provided inside the reference space of the package; Reference side detection element (Rrm) with the thermistor film formed in the same shape as the reference element
A reference-side correction element (Rrs) provided inside the reference space of the package and having the same shape as the sensing-side correction element and formed with a thermistor film; and detecting the sensing side and the reference side. Element and the correction element on the sensing side and the reference side are bridge-connected to cancel the thermal error component generated on the sensing side and the reference side, and the output of the detection element and the correction element on the sensing side is corrected. Output means for outputting the difference.

According to a second aspect of the present invention, the thermistor films of the detection element and the correction element are aligned on the front and back of a single substrate, and the same thermistor films are formed after the same ones are formed. By removing a part of the substrate by the etching process, a minute cross-linked structure may be formed at an interval corresponding to the thickness of the substrate.

The sensing element 2 (Rs
m) detects infrared light from an object to be detected through the opening 1b of the package 1 and outputs a signal of a corresponding light receiving level, and outputs a signal of the highest light receiving level when the incident light is parallel light α0. I do. Correction element 3 (R
ss) detects infrared light while the incident light reaches a critical angle α3 other than the parallel light (α0). Inside the package 1, in addition to the sensing side detection element 2 and the correction element 3 on the sensing side, the reference side detection element 2 (Rrm) and the correction element 3 (R
rs) are provided, and the two elements on the reference side are hermetically sealed inside the package 1 without opening.
The output means 7 bridges both elements on the sensing side and the reference side to cancel an error component due to thermal characteristics on the sensing side and the reference side, thereby improving the temperature drift characteristics. Then, only by outputting the difference between the output of the detection element 2 and the output of the correction element 3 on the sensing side, it is possible to obtain only the output corresponding to the angle at which the incident light has a narrow field of view.

[0011]

FIG. 1 is a side sectional view showing a configuration of a narrow-field thermistor bolometer according to the present invention. The inside of the package 1 is airtight and the inside is sealed with a vacuum or gas as required. Inside the package 1, a sensing element Rs and a reference element Rr having the same configuration are accommodated. These sensing elements R
s and the reference element Rr are the detection element 2 (Rsm, Rrm) and the correction element 3 (R
ss, Rrs). Sensing element R
An opening 1b is formed in a circular shape with an opening diameter L1 on the upper surface 1a of the package 1 on the s side, and a window 4 is provided in the opening 1b. The window 4 used is one that has been subjected to a surface reflection prevention treatment for infrared light or a filter treatment for transmitting only a predetermined wavelength (infrared light).

The detection element 2 (Rsm) on the sensing element Rs side will be described. The detection element 2 is formed in a circular shape having an outer diameter L2 about the opening diameter L1 of the opening 1b. The detection element 2 is provided with a predetermined thermistor film 2 a on the surface of a substrate using a wafer such as a single crystal silicon constituting the package 1.
Is formed. The thermistor bolometer changes its resistance value by a temperature change reflecting the difference between the amount of infrared energy incident on the detection element 2 and the infrared energy emitted by self-radiation.

The detecting element 2 is supported on the package 1 by a beam 2b which is sufficiently narrow in four directions from the outer edge. Here, the detection element 2 is disposed at a predetermined distance H1 on the coaxial position of the opening 1b of the package 1.

A predetermined distance H2 (H1) is coaxial with the opening 1b.
<H2) A correction element 3 (Rss) is disposed at a distance. Here, the detecting element 2 and the correcting element 3 are separated by a predetermined distance H3 (H2-H1). The correction element 3 is a detection element 2
A thermistor film 3a is formed on a substrate by the same manufacturing method as described above. The correction element 3 has an inner diameter L3 equal to or larger than the opening diameter L1 of the opening 1b of the package 1 and an outer diameter L4 having a predetermined diameter.
And has an area equal to the area of the detection element 2.

The correction element 3 is supported on the package 1 by a beam 3b which is sufficiently narrow in four directions from the outer edge. The detecting element 2 and the correcting element 3
May be supported by three beam portions 2b and 3b.

Here, the effective ranges of the shapes of the detection element 2 and the correction element 3 will be described. The inner diameter L3 of the correction element 3> the opening diameter L1 of the opening 1b of the package 1. When the incident light has a critical angle (α3 in FIG. 7 described later), the edge of the opening 1b, the outer diameter edge of the detection element 2, and the outer diameter edge of the correction element 3 are each obliquely incident. Must be collinear with the incident light. The areas of the detection element 2 and the correction element 3 are the same.

The detection element 2 (Rrm) on the reference element Rr side and the correction element 3 (Rrm)
rs) is configured in the same manner as the sensing element Rs, but the reference element Rr is
The package 1 is sealed inside the package 1 by a partition 1c, and an opening 1b is provided on the side of the reference element Rr.
Are not formed, and external light is blocked. As a result, both the sensing element Rs and the reference element Rr are housed in the same package 1 so that the sensing element Rs and the reference element Rr have the same configuration (the same material, manufacturing method, and area). Since the noise component and the time axis component of the temperature change of both elements can be considered to be almost the same, the same thermal characteristics (thermal conduction characteristics via the beam from the element, thermal conduction characteristics in the element) And the thermal characteristics such as heat conduction from the element to the surrounding atmosphere and the radiant heat balance between the element and the surrounding structure (package or the like) are the same.

FIG. 2 is a plan view showing the detecting element 2 and the correcting element 3 used in the sensing element Rs and the reference element Rr. The thermistor films 2a and 3a of the respective elements 2 and 3 are formed in, for example, intersecting comb-teeth shapes as shown in the figure. These thermistor films 2a, 3a have lead patterns 2c, 3c extending at both ends, respectively, and are respectively passed over the beam portions 2b, 3b and led out of the package 1 via wire bonds. In the figure, the inner diameter L3 of the correction element 3 is equal to the opening diameter L of the opening 1b of the package 1.
1 and those having a larger diameter than the outer diameter L2 of the detecting element 2 are described.

FIG. 3 is a diagram showing a connection state between the sensing element Rs and the reference element Rr.
FIG. 1A is a perspective view showing the structure of each element, and FIG. 1B is a diagram showing a circuit configuration of electrical connection. Sensing element Rs detection element 2 (Rsm)
One end of the lead pattern 2c and the lead pattern 2 of the detection element 2 (Rrm) of the reference element Rr.
The other end of the lead pattern 2c of each detecting element 2 (Rsm, Rrm) is led out of the package 1 at terminals 5a and 5b, and the correcting element 3 (Rss, Rrs). Correction element 3 (Rss, R
The other ends of rs) are connected to each other and grounded to the package 1.

As shown in FIG. 2B, each element constitutes a bridge circuit 7a by the above-mentioned connection, and is connected to a subtraction means 7b outside the package 1, and these constitute an output means 7. The bridge circuit 7a outputs the light receiving level V1 of the detecting element 2 and the light receiving level V2 of the correcting element 3, respectively. Here, since the sensing element Rs and the reference element Rr are bridge-connected, the thermal characteristics of these two elements are the same, so that a thermal error component can be canceled and the temperature drift characteristic can be improved. . The outputs V1 and V2 indicate only the light receiving levels based on the infrared rays incident on the sensing element Rs. The light receiving level V1 of the detecting element 2 and the light receiving level V2 of the correcting element 3 are input to the subtracting means 7b, and the difference (V1-V2) between the two is output from the output terminal Vout. This subtraction means 7b can be configured by using a comparator or using a CPU and subtraction processing software.

Next, the operation of a narrow visual field according to the above configuration will be described. 4 to 7 are explanatory diagrams showing detection states of the narrow-field thermistor bolometer for different viewing angles.
The sensing element Rs is shown. FIG. 4 is a diagram showing a light receiving state when the incident angle of the incident light is α0. When the angle that is the optical axis of the incident infrared light (incident light) is an incident angle α, the incident angle of the incident light is α0 (parallel light:
When the incident light is incident on the surface of the detecting element 2 at a right angle), the detecting element 2 obtains the maximum light receiving energy. At this time, since the inner diameter L3 of the correcting element 3 is equal to or larger than the opening diameter L1 of the opening 1b, incident light that is parallel light is blocked by the opening 1b and does not enter the correcting element 3. (Light reception level of detection element 2 = max, light reception level of correction element 3 = 0)

FIG. 5 shows that the incident angle of the incident light is α1 (α0 <α).
It is a figure which shows the light receiving state at the time of 1 <(alpha) 2). When the device is at a slight angle with respect to the surface of the detection element 2, the distance H1 between the opening 1b and the detection element 2
As a result, the received light energy incident on the detection element 2 is slightly reduced. At this time, the light incident on the correction element 3 is incident on a part of the correction element 3.
(Light reception level of detection element 2> light reception level of correction element 3)

FIG. 6 shows that the incident angle of the incident light is α2 (α1 <α
It is a figure which shows the light receiving state at the time of 2 <(alpha) 3). When it is at an angle to the surface of the detecting element 2,
The received light energy incident on the detection element 2 by the opening 1b is reduced by half. At this time, the incident light also partially enters the correction element 3. (Light reception level of detection element 2 ≥ light reception level of correction element 3)

FIG. 7 shows that the incident angle of the incident light is α3 (α2 <α
It is a figure which shows the light receiving state at the time of 3). When the optical element has a critical angle with respect to the surface of the detection element 2, the incident light is not incident on either the detection element 2 or the correction element 3 by the opening 1b. (Light receiving level of detection element 2 = 0, light receiving level of correction element 3 = 0)

As shown in FIGS. 4 to 7, the detecting element 2 and the correcting element 3 are configured to receive light differently depending on the incident angle α of the incident light. When the incident angle α0 is as shown, only the detecting element 2 is in the light receiving state,
Infrared rays radiated from an object located in the direction of the incident angle α0 can be limitedly detected.

FIG. 8 is a diagram showing angles of incident light and light receiving levels. The light receiving level of the detecting element 2 is the highest when the incident angle α of the incident light is in the parallel light state α0 (described in FIG. 3), as shown by the solid line in FIG. It is getting lower until now. on the other hand,
The light receiving level of the correction element 3 is the lowest when the incident light is at the incident angle α0, as shown by the middle dotted line in FIG.
Incidence angle α gradually increases as the incident angle increases
It is the highest at 2 and thereafter gradually lowers up to the incident angle α3.

Therefore, the output means 7 cancels the light receiving output of the portion where the incident angle α is large by subtracting the output of the correcting element 3 from the output of the detecting element 2, and the direction of α 0 where the incident angle is small is obtained. Thus, it is possible to limit the detection to only the incident light from the camera and to perform the narrow field of view detection (see FIG. 3B). At the same time, since the detection element 2 and the correction element 3 are formed of the same material, manufacturing method, and area, the noise components of both elements 2 and 3 and the time axis component of the temperature change are considered to be substantially equal. Therefore, these error components can be removed by the difference operation.

In the above description, the detection element 2 and the correction element 3 are described as being provided on different substrates, but the present invention is not limited to this.
FIG. 9 is a side sectional view showing a specific structure of the configuration described in the above embodiment. The thermistor film 2a of the detecting element 2 is formed on the surface (upper surface) of the substrate 10 using a wafer such as a single crystal silicon, and the thermistor film 3a of the correcting element 3 is formed on the back surface (lower surface). Here, the thickness of the substrate is set to the distance H3. Thermistor film 2a,
Explaining the production method of 3a, vapor deposition, sputtering or C
An insulating film such as silicon oxide or silicon nitride with low thermal conductivity is formed by a thin film forming method such as VD, and a thermistor film and an electrode metal film with a large resistance temperature coefficient are also formed and patterned by a thin film on the insulating film. Thermistor film 2
a and 3a are formed. In addition, in FIG.
Although the portions a and 3a are described as being thicker for convenience, in actuality, the portions have a uniform thickness like the lead patterns 2c and 3c.

Thereafter, the portion of the substrate 10 on which the thermistor films 2a and 3a are provided is removed by a wet etching method using a corrosive liquid or a reactive ion etching method using a corrosive gas to form a minute crosslinked structure. Thereby, the thermistor films 2a and 3a can be arranged at a distance H3 from each other, the heat capacity of both elements 2 and 3 can be made sufficiently small, and the thermal insulation from the surrounding structure can be achieved. You can take it. Substrates made of the same material are used for the upper and lower surfaces of both elements 2 and 3, respectively, and thermistor films 2a and 3a are used.
Package 1 sealed with covers 11 and 12 having a predetermined space formed only by etching or the like in the same manner as described above.
Is configured. In this package 1, the window 1 is formed by forming the opening 1b with the opening diameter L1 only on the thermistor films 2a and 3a (Rsm, Rss) on the sensing side as described above. In this configuration, the beam portions 2b and 3b are not formed on both elements 2 and 3, and the lead patterns 2c and 3c are not formed.
Is sandwiched and fixed to the substrate 10 and the upper and lower covers 11 and 12 in a sandwich manner, and supports the thermistor films 2a and 3a.

The central substrate 10 is provided with a heat sink 1
The lead patterns 2c and 3c are supported and fixed on the substrate 4, and the lead patterns 2c and 3c are connected to a substrate terminal or the like via a wire 15. Incidentally, the package 1 is housed in a bolometer housing 16, and the housing 16 has openings 16 corresponding to the openings of the openings 1 b of the package 1.
b is opened and a window 17 is provided.

Although the detection area can be made narrower by merely reducing the opening diameter L1 of the opening 1b of the package 1, the opening diameter L1 of the opening 1b can be reduced.
Simply reducing the incident energy also decreases at the same time (see FIG. 8).
(While the width of the waveform becomes narrower, the height also decreases.) This is not preferable because the sensitivity decreases. In this regard,
According to the above configuration of the present invention, a narrow visual field can be obtained without lowering the sensitivity.

[0032]

According to the present invention, it is possible to narrow the detection area with a simple structure, thereby performing detection with a narrow detection target, and eliminating the influence from the surroundings of the detection target. . Further, the present invention has a configuration in which an output of a narrow-field detection area can be obtained only by taking the difference between the detection element and the correction element, so that the configuration can be made simple and compact. Further, it is possible to detect a small area without using a mirror or a lens. Then, elements of the same configuration are provided for sensing and for reference, respectively,
Since both are housed in the same package and connected in a bridge, it is possible to cancel the thermal error component generated in the sensing element,
The temperature drift characteristics are good and the detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a narrow-field thermistor bolometer of the present invention.

FIG. 2 is a diagram showing a thermistor film.

FIG. 3 is a diagram showing a connection state of each element on a sensing side and a reference side. (A) is a perspective view showing a structure.
FIG. 2B is a diagram illustrating an electric circuit configuration.

FIG. 4 is a diagram showing a light receiving state for each incident angle of incident light (part 1).

FIG. 5 is a diagram (part 2) illustrating a light receiving state for each incident angle of incident light.

FIG. 6 is a diagram showing a light receiving state for each incident angle of incident light (part 3).

FIG. 7 is a diagram illustrating a light receiving state of incident light by incident angle (part 4).

FIG. 8 is a diagram showing an incident angle and a light receiving level of incident light.

FIG. 9 is a side sectional view showing a specific configuration example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Package, 1b ... Opening part, 2 ... Detection element, 3 ... Correction element, 4 ... Window, 7 ... Output means, R
s: sensing element, Rr: reference element.

Claims (2)

[Claims] 1. A thermistor bolometer in which a sensing element and a reference element having the same shape as the sensing element are provided inside a package to cancel and output a thermal error component of the sensing element. A package in which a sensing space in which a window is formed as an opening, a reference space having the same shape as the sensing space and having no window, and a sealed whole area, are formed independently of each other; A thermistor film which is provided inside the sensing space, has a shape corresponding to the window, and has a resistance value changed by a temperature rise due to infrared rays incident through the window, and the incident angle is parallel light (α0) Outputs the highest light receiving level and the light receiving level corresponding to the incident angle up to the critical angle (α3) A sensing side detecting element (Rsm) for outputting a sensor, and an annular thermistor provided inside the sensing space of the package, having the same area as the sensing detecting element and having an inner diameter larger than the opening diameter of the window. A film is formed, and the incident angle is within a predetermined angle range (α0 <α <α).
3) a sensing-side correction element (Rss) for detecting infrared rays, which is provided inside a reference space of the package;
A reference-side detection element (Rrm) having the same shape as the sensing-side detection element and formed with a thermistor film, provided inside the reference space of the package;
A reference-side correction element (Rrs) having the same shape as the sensing-side correction element and a thermistor film formed thereon; a sensing-side and reference-side detection element; and a sensing-side and reference-side correction element Output means for bridge-connecting the elements, canceling a thermal error component generated on the sensing side and the reference side, and outputting a difference between outputs of the detection element and the correction element on the sensing side. Characteristic narrow-field thermistor bolometer. 2. The thermistor films of the detection element and the correction element are aligned respectively on the front and back of a single substrate, and after the same one is formed, the substrate at the thermistor film portion is removed by etching. 2. The narrow-field thermistor bolometer according to claim 1, wherein each of the narrow-field thermistor bolometers has a minute cross-linking structure at intervals corresponding to the thickness of the substrate.