JP2001309122A - Infrared ray image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared ray image sensor where a size of each pixel can be extended without incurring increase in the time constant or reduce the time constant without changing the size of each pixel. SOLUTION: A sensor array is formed on a silicon substrate 11 and bolometer type sensor elements 31, 32, 33, 34 are arranged in each pixel forming area 30 of the sensor array. The sensor elements 31, 32, 33, 34 are connected in series, and a voltage between both terminals in the series circuit is used for an output. An infrared day from an object whose temperature is to be measured is emitted onto the sensor array, from which thermal image data of each pixel can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an infrared image sensor.

[0002]

2. Description of the Related Art As an infrared sensor usable for general purposes, there is a thermal infrared sensor usable without cooling. Examples of such a sensor include a pyroelectric type, a thermopile type, and a bolometer type. As an example, a bolometer type is disclosed in Japanese Patent Application Laid-Open No. 8-43208. This is a bolometer-type infrared sensor that enables temperature measurement using a change in resistance value.

In such a bolometer-type infrared sensor, the output of an infrared detecting element and a temperature compensating element (reference element) having the same characteristics placed at a position where no infrared light is incident are compared to obtain a stable infrared image of a thermal image. I am trying to realize an image sensor.

In such a thermal infrared sensor,
One pixel is formed by one membrane structure (temperature-sensitive element), and the temperature of the pixel portion focused on one membrane region is obtained by the amount of infrared light incident on the membrane structure. I have. In such a sensor,
In some cases, such as when it is desired to increase the viewing angle of the entire sensor with a small number of pixel divisions, or when it is desired to reduce the load on the lens to form a low-magnification imaging system, the pixels of the sensor need to be enlarged. However, when the size of the pixel is increased, the time constant of the membrane structure is inevitably increased due to an increase in the heat capacity of the membrane structure and an improvement in heat insulation for increasing the sensitivity. However, if the time constant increases, the cycle of temperature detection becomes longer, the response of the sensor deteriorates, and the averaging process for reducing the noise of the sensor becomes difficult.

[0005]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and an object of the present invention is to increase the size of each pixel without increasing the time constant or to change the pixel size without changing the pixel size. Another object of the present invention is to provide an infrared image sensor capable of reducing a time constant.

[0006]

According to a first aspect of the present invention, a plurality of thermal sensor elements are provided in each pixel forming region. Therefore, the size of each pixel can be enlarged without increasing the time constant, or the time constant can be reduced without changing the pixel size.

According to the third aspect of the invention, the characteristics of the sensor elements in the pixel can be made the same, and the output correction and averaging can be simplified. According to the invention described in claim 4, the output of the sensor element in the pixel can be increased.

According to the fifth aspect of the present invention, the influence of variations in the sensor elements in the pixels can be reduced. According to the inventions described in claims 6 and 7, an output of the sensor element which is hardly affected by a change in environmental temperature can be obtained.

According to the present invention, it is possible to simultaneously measure the differential outputs of the sensor elements in the pixel. According to the ninth and tenth aspects, the output of each pixel can be obtained in a short time.

According to the eleventh and thirteenth aspects, the output of each pixel can be made less susceptible to noise. According to the twelfth aspect, the output of each pixel can be increased with respect to a temperature change.

According to the fourteenth aspect of the present invention, since each pixel has a temperature compensating element, the characteristic difference between the sensor element and the temperature compensating element can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, a bolometer-type sensor element is used as a thermal-type sensor element, and a large number of bolometer-type sensor elements are arranged in parallel to form a sensor array. FIG. 1 shows a configuration of an infrared image sensor.

The sensor has an infrared condensing lens 1, which is a high-density polyethylene,
It is made of chalcogen glass, BaF ₂ , ZnS or the like. This infrared condensing lens 1 may have any of a spherical surface, an aspherical surface, and a Fresnel lens shape.

An infrared sensor array 2 is arranged at a position separated from the infrared condenser lens 1. The infrared sensor array 2 includes a sensor element 2a, for example, 15 ×
It is shaped like a matrix of ten pieces. Further, a signal generation circuit 3 and selection circuits 4a and 4b are provided in the vicinity thereof. Then, a predetermined voltage is generated by the signal generation circuit 3 and the sensor elements 2a of the sensor array 2 are selected by the selection circuits 4a and 4b, and a signal corresponding to the amount of infrared light received is output.

The sensor element 2a in the infrared sensor array 2 will be described with reference to the longitudinal sectional view of FIG. A concave portion 12 is formed on the surface of the silicon substrate 11. An SiO ₂ thin film 13 is disposed on the upper surface of the silicon substrate 11 so as to cover the opening of the recess 12. A metal thin film resistor (metal resistor) 14 is disposed on the SiO ₂ thin film 13 at the opening of the concave portion 12, and a SiO ₂ thin film resistor is provided thereon.
Absorption film 16 is laminated via _two thin films 15. As described above, the films 13, 14, 15, 16 are provided in the openings of the concave portions 12.
Are stacked, and a closed region inside the concave portion 12 is a cavity 17. That is, the sensor element 2a has a membrane structure.

In FIG. 1, a signal detection / processing circuit 5 is connected to the infrared sensor array 2. The signal detection / processing circuit 5 includes a signal amplifier 6, a signal processing circuit 7, and a data transmission circuit 8. Various system control circuits 9 are connected to the signal detection / processing circuit 5.

FIG. 3 shows an example of use of the present sensor. In FIG. 3, a sensor 20 for a front seat is provided on a ceiling in a passenger car.
, And a rear seat sensor 21 are arranged, and two infrared sensor arrays are installed respectively. One sensor array includes, for example, 15 × 10 dot matrix sensor elements.

The operation of the sensor will be described. The infrared image sensors 20 and 21 attached as shown in FIG. 3 condense infrared light around the seat by the infrared light condensing lens 1 and form an image on the infrared sensor array 2 as a thermal image. At this time, the lens 1 is, for example, 750 × 50 at a position 500 mm away.
It is designed to be able to collect light in a range of 0 mm. When the number of sensor elements 2a of the sensor array 2 is 15 × 10, the range (position resolution) that can be detected by one sensor element 2a is 50 mm square.

In one sensor element, as shown in FIG. 2, the incident infrared light is absorbed by the absorbing film 16 and converted into heat. Since the SiO ₂ thin film 13 has a structure floating above the cavity 17 provided in the silicon substrate 11, it stores heat,
It can be insulated from outside. The metal thin film resistor 15 is
The resistance value changes with temperature. Therefore, by measuring the change in the resistance value, the temperature of the measured object can be detected.

As described above, the sensor array 2 in which many bolometer-type sensor elements 2a are formed on the silicon substrate 11 as a semiconductor substrate is formed, and the sensor array 2 is irradiated with infrared rays from the object to be measured. In the sensor array 2, thermal image data for each bolometer-type sensor element 2a can be obtained.

In the signal detection / processing circuit 5 of FIG. 1, a signal corresponding to the amount of infrared light received from the infrared sensor array 2 is amplified by the signal amplifier 6, and the signal processing circuit 7 compares the signal with a threshold value. The signal (image data) is sent from the data transmission circuit 8 to the various system control circuits 9
Sent to. In the various system control circuits 9, the air conditioning control in the vehicle, the deployment control of the airbag, the security control using the detection data of the presence or absence and the position of the occupant / intruder in each seat of the vehicle using the temperature detection function for each pixel in the vehicle. Used for etc.

Here, in order to obtain the absolute temperature using the change in the resistance value of the metal thin film resistor 15 in the sensor element 2a in FIG. 2, it is necessary to detect only the temperature change due to the incident infrared rays. Therefore, such a bolometer type sensor has a temperature compensation element (reference element) 25 on the silicon substrate 11 in addition to the sensor element 2a as shown in FIG. And the like, the absolute value can be obtained by taking the difference (difference in resistance change) between the sensor element 2a and the temperature compensation element 25. That is, the temperature of the output of the sensor element 2a is corrected by the temperature compensation element 25 which is not affected by infrared rays from the object to be measured.

However, usually, such a sensor array 2
Since one sensor element 2a forms one pixel (a part for detecting 50 mm square), the responsiveness of the element is determined by the heat capacity and heat insulation performance of the membrane. Therefore, if the heat insulating property is improved to increase the sensitivity, the response is inevitably reduced. In addition, since the heat capacity of the membrane also depends on the size of the membrane that forms the pixel, once the pixel size is determined, there is a limit even if the heat capacity is greatly reduced, and much improvement in responsiveness due to the reduced heat capacity cannot be expected. .

In this embodiment, the following configuration is employed. As shown in FIG. 5, in the sensor array 2 to which the infrared light condensed by the condenser lens 1 is applied, as shown in FIG. 6, the formation area of each pixel on the silicon substrate 11 (the detection area Z1 for one pixel in FIG. 5) ), A plurality of bolometer-type sensor elements 31 to 34 are arranged in the pixel formation region 30.
That is, the pixel formation region 30 is divided into a plurality of sensor elements having a membrane structure to form one pixel.

More specifically, in FIG. 6, the pixel forming region 30 is divided into four parts to form four sensor elements 31, 32, 3
3,34 are arranged. Therefore, the size of each sensor element (membrane structure) 31 to 34 in the pixel formation region 30 is 1/4 as compared with the case where one sensor element (membrane structure) is arranged in one pixel formation region. In this way, the size of the sensor element (membrane structure) is reduced, so that it becomes lighter than when one sensor element (membrane structure) is arranged in one pixel formation region,
Since the film supporting the membrane structure itself can be made thin, the heat capacity of the sensor elements (membrane structures) 31 to 34 can be significantly reduced (1/4 or less).

At this time, if the heat insulation performance of each sensor element (membrane structure) 31 to 34 is set to be substantially the same as in the case of one element per pixel, the responsiveness is improved by the decrease in heat capacity. (The time constant becomes smaller). The time constant is proportional to heat capacity / adiabatic performance (heat conductance).

As described above, since the response of the sensor element of each pixel can be improved, it is advantageous in performing output detection in a high-speed cycle, and an averaging process for reducing the output noise of the pixel. It is also advantageous in performing.

In FIG. 6, the sensor elements 31, 32, 33, and 34 in the pixel forming region 30 are connected in series by using conductor patterns 35a, 35b, and 35c. Outputs voltage. That is, the sum of the outputs of the sensor elements 31 to 34 in the pixel formation region 30 is defined as a pixel output. Therefore, the output of each pixel can be increased with respect to a temperature change.

As a result, the output of the sensor element in the pixel can be increased while obtaining the same resistance change as when one pixel is formed by one element, and the pixel output having a quick response can be obtained. Obtainable.

As described above, this embodiment has the following features. (A) The sensor array 2 is formed on the silicon substrate 11,
A bolometer-type sensor element is arranged in a large number of pixel forming regions 30 in the sensor array 2 and irradiates infrared rays from an object to be measured to the sensor array 2 to obtain thermal image data for each pixel. , A plurality of bolometer-type sensor elements 31
~ 34 were arranged. Therefore, the size of each pixel can be increased without increasing the time constant, or the time constant can be reduced without changing the pixel size.

That is, if the formation area of each pixel on the silicon substrate 11 is increased, the time constant of the bolometer-type sensor element (membrane structure) increases, which is disadvantageous for signal processing at the time of infrared detection. In the present embodiment, the response of one pixel can be made faster by having a plurality of sensor elements in one pixel, and the size of each pixel can be increased without increasing the time constant or without changing the pixel size. The time constant can be reduced. Further, it is less susceptible to the effects of noise in the detection processing circuit and variations in the resistance of the bolometer-type sensor element. (B) Since the bolometer-type sensor elements in the pixel formation region 30 have the same shape and structure (membrane structure), the characteristics of the sensor elements in the pixel can be made the same, and output correction and averaging can be simplified. . (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

This embodiment, which replaces FIG. 6, will be described with reference to FIG. As shown in FIG. 7, each of the sensor elements 31 to 34 in the pixel formation region 30 is connected to the conductor patterns 36a, 36b,
36c and 36d are connected in parallel. In this way, the influence of variations in the sensor elements 31 to 34 in the pixel can be reduced, and the average output of each of the sensor elements 31 to 34 can be extracted as the pixel output. (Third Embodiment) Next, a third embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

This embodiment, which replaces FIG. 6, will be described with reference to FIG. As shown in FIG. 8, a temperature compensation element (reference element) 37 is formed on a part of the silicon substrate 11. The temperature compensating element 37 is not affected by the collected infrared light. The temperature compensating element 37 is connected to the differential amplifier 38, and the differential amplifier 38 obtains a differential output from the output of each of the sensor elements 31 to 34 in the pixel formation region 30 from the temperature compensating element 37. It has become. As a result, an output of the sensor element that is hardly affected by a change in environmental temperature can be obtained.

In this embodiment, each of the sensor elements 31 to 31
The following two methods (i) and (ii) are used to sample the output of
There are different ways. As (i), as shown in FIG. 8, the output from each of the sensor elements 31 to 34 in the pixel formation region 30 is continuously detected (measured) to be a pixel output, and then the process proceeds to the next pixel. That is, after an output is obtained in the order of the sensor element 31 → the sensor element 32 → the sensor element 33 → the sensor element 34 in the predetermined pixel formation area, the sensor element 3
1 → sensor element 32 → sensor element 33 → sensor element 34
Get the output in the order of In this case, the output of each pixel can be obtained in a short time. As (ii), as shown in FIG. 9, among the sensor elements 31 to 34 in the pixel formation region, first, the first sensor element 31
Is continuously detected (measured) one after another for each pixel, and after that, the process proceeds to the second sensor element 32 in the pixel formation region. Hereinafter, the process proceeds from the third sensor element 33 to the fourth sensor element 34.

In the method (i), assuming that the sum of the outputs of the sensor elements 31 to 34 in the pixel formation area is a pixel output (assuming that the sum of the outputs from the sensor elements 31 to 34 is the output of the corresponding pixel). In addition, the output of each pixel can be increased with respect to a temperature change. Further, each of the sensor elements 31 to 31 in the pixel formation region
If the average of the outputs of the 34 is the output of the pixel (the average of the outputs of the sensor elements 31 to 34 is the output of the corresponding pixel), it is possible to reduce noise at the time of output detection.
That is, the output of each pixel can be made less susceptible to noise.

In the method (ii), averaging in a long cycle is also possible. (Fourth Embodiment) Next, the fourth embodiment will be described in the third embodiment.
The following description focuses on the differences from this embodiment.

This embodiment, which replaces FIG. 8, will be described with reference to FIG. In the case of FIG. 8, the difference between the output of each sensor element 31 to 34 in the pixel forming region 30 and the single temperature compensation element 37 is output, but in this embodiment, each sensor element is output. Differences from the temperature compensating elements 41 to 43 corresponding to 31 to 34 are output.

In FIG. 10, temperature compensating elements (reference elements) 41 to 43 corresponding to the respective sensor elements 31 to 34 in the pixel forming region 30 are formed on the silicon substrate 11. The temperature compensating element 41 is a differential amplifier 45
The temperature compensating element 42 is connected to the differential amplifier 46, the temperature compensating element 43 is connected to the differential amplifier 47, and the temperature compensating element 44 is connected to the differential amplifier 48. The difference between the output of the sensor element 31 in the pixel formation region 30 and the temperature compensation element 41 in the differential amplifier 45 is obtained. Similarly, the output of the sensor element 32 in the differential amplifier 46 is compared with the temperature compensation element 42. The output of the sensor element 33 in the differential amplifier 47 is different from that of the temperature compensating element 43, and the output of the sensor element 34 in the differential amplifier 48 is the temperature compensating element 4
4 is obtained.

In the case of FIG. 10, the outputs from the sensor elements 31 to 34 (the differential outputs of the sensor elements in the pixels) in the pixel forming area 30 are simultaneously detected (measured), and then the detection of the next pixel is started. Therefore, the time for obtaining each pixel output can be shortened. That is, the output of each pixel can be obtained in a short time.

The sum of the outputs of the sensor elements 31 to 34 in the pixel formation region 30 is used as a pixel output, and the output of each pixel is increased with respect to a temperature change, or the output of each sensor element 31 to 34 is changed. Using the average as the pixel output, the output of each pixel can be made less susceptible to noise. (Fifth Embodiment) Next, a fifth embodiment will be described with reference to a third embodiment.
The following description focuses on the differences from this embodiment.

This embodiment, which replaces FIG. 8, will be described with reference to FIG. 11, a temperature compensation element (reference element) 50 is arranged in each pixel formation region 30. Specifically, three sensor elements 31, 32, and 33 are formed in one pixel formation region 30, and one temperature compensation element 50 is formed. That is, one of the elements obtained by dividing one pixel forming region 30 is used as the temperature compensation element 50.

The temperature compensating element 50 is a differential amplifier 5
1 and output from each of the sensor elements 31 to 33 in the pixel formation region 30 of the differential amplifier 51 is different from the temperature compensation element 37. Similarly, a differential amplifier 52 is provided in an adjacent pixel formation region (indicated by a pixel N), and similarly, a differential amplifier is provided for each pixel.

In this embodiment, one pixel is formed in each pixel formation region 30.
Since one temperature compensation element 50 can be provided, the difference in characteristics between the sensor elements 31, 32, and 33 and the temperature compensation element 50 can be minimized (can be reduced).

In the above description, the case where a bolometer type sensor element is used as the thermal type sensor element has been described. However, the present invention is applied to a case where a pyroelectric type or a thermopile type sensor element is used as the thermal type sensor element. You may.

Further, the present invention can be used for control of various home electric appliances and industrial products using the acquisition of the position of a person in addition to those for automobiles.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an infrared image sensor.

FIG. 2 is a cross-sectional view illustrating a sensor element.

FIG. 3 is a perspective view showing a usage example.

FIG. 4 is a diagram illustrating an infrared image sensor.

FIG. 5 is a perspective view illustrating an infrared image sensor according to the first embodiment.

FIG. 6 is a perspective view illustrating an infrared image sensor according to the first embodiment.

FIG. 7 is a perspective view illustrating an infrared image sensor according to a second embodiment.

FIG. 8 is a perspective view illustrating an infrared image sensor according to a third embodiment.

FIG. 9 is a perspective view illustrating an infrared image sensor according to a third embodiment.

FIG. 10 is a perspective view illustrating an infrared image sensor according to a fourth embodiment.

FIG. 11 is a perspective view illustrating an infrared image sensor according to a fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Infrared condensing lens, 2 ... Sensor array, 2a ... Sensor element, 11 ... Silicon substrate, 30 ... Pixel formation area, 3
1, 32, 33, 34 ... sensor elements.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Katsumasa Nishii 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (Reference) 4M118 AA10 AB01 BA05 CA01 CA35 FB09 FB17 FB24 GD03 GD08 GD09 HA35 5C024 AX06 EX15 EX42 GX08 HX17 HX29 5C051 AA01 BA03 DA06 DA10 DB01 DB07 DB15 DE04

Claims (14)

[Claims] 1. A sensor array is formed on a semiconductor substrate,
An infrared image sensor in which thermal sensor elements are arranged in a large number of pixel forming regions in the sensor array, and infrared light from a temperature measurement object is irradiated on the sensor array to obtain thermal image data for each pixel. 3. The infrared image sensor according to claim 1, wherein a plurality of thermal sensor elements are arranged in each of the pixel formation regions. 2. The infrared image sensor according to claim 1, wherein each of the thermal sensor elements in the pixel formation region has a membrane structure. 3. The infrared image sensor according to claim 1, wherein each thermal sensor element in the pixel formation region has the same shape and structure. 4. The infrared image sensor according to claim 1, wherein the thermal sensor elements in the pixel formation region are connected in series. 5. The infrared image sensor according to claim 1, wherein the thermal sensor elements in the pixel formation region are connected in parallel. 6. The output of each thermal sensor element in the pixel formation region is a differential output from a temperature compensating element which is not affected by condensed infrared light.
4. The infrared image sensor according to any one of items 2 and 3. 7. The infrared image according to claim 6, wherein a difference between an output of each thermal sensor element in the pixel forming region and a single temperature compensation element is output. Sensor. 8. The apparatus according to claim 6, wherein a difference between an output of each thermal sensor element in the pixel forming region and a temperature compensating element corresponding to each sensor element is output. An infrared image sensor as described. 9. The method according to claim 1, wherein an output from each of the thermal type sensor elements in the pixel forming region is continuously detected, and then the detection of the next pixel is started. An infrared image sensor according to any one of claims 7 and 8. 10. The method according to claim 1, wherein an output from each of the thermal type sensor elements in the pixel forming region is simultaneously detected, and then the detection of the next pixel is started. Item 2. The infrared image sensor according to item 1. 11. The method according to claim 1, wherein, among the thermal sensor elements in the pixel formation region, first, the output of the first element is continuously detected for each pixel, and then the detection of the second element is started. An infrared image sensor according to any one of claims 1, 2, 3, 6, 7, and 8. 12. The infrared image sensor according to claim 9, wherein a sum of outputs of the thermal sensor elements in the pixel formation region is used as a pixel output. 13. The infrared image sensor according to claim 9, wherein an average of outputs of the thermal type sensor elements in the pixel formation region is set as an output of the pixel. 14. A device according to claim 6, wherein a temperature compensating element is provided in each of said pixel forming regions.
The infrared image sensor according to any one of claims 9 and 10.