JP2011179828A - Multi-wavelength infrared array sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small infrared array sensor which can detect the positions, sizes, and the number of objects having different properties at a low cost without providing an associated image processing means. <P>SOLUTION: In the infrared array sensor 1 in which a plurality of sensor pixels 2 including respective infrared light receiving parts 4 and first and second temperature detection parts 5A, 5B are two-dimensionally arranged, adjacent sensor pixels 2 are thermally and electrically isolated, and absorption wavelength bands are different from each other. The first temperature detection parts 5A of the sensor pixels 2 absorbing light of the same absorption wavelength bands in each row are connected in series with each other, and the second temperature detection parts 5B in each column are connected in series with each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an infrared array sensor in which a plurality of arrayed sensor pixels are used in association with each other.

  If one sensing device is sensitive to light in a plurality of wavelength bands, it is convenient to detect objects having different properties. For example, a sensor that is sensitive to both infrared rays in the wavelength band of 4.4 to 5.5 μm and infrared rays in the wavelength band of 8 to 14 μm, which are generally called atmospheric windows, can detect both flames and human bodies.

  Thus, in the field of image sensors, a thermal infrared array sensor has been proposed in which sensors with different infrared wavelength bands to be detected are arranged for each row or column of an array (Patent Document 1). In this infrared array sensor, each sensor pixel has a reflective film and a diaphragm facing each other through a cavity, and the diaphragm is composed of a bolometer material thin film and upper and lower protective films formed so as to sandwich the thin film. . However, the protective film of one sensor pixel A is made of silicon nitride, and the protective film of the sensor pixel B in the adjacent row (or column) is made of silicon oxide that is transparent to infrared rays. An absorption film is provided on the protective film on the opposite side. In the sensor pixel A, the protective film itself absorbs infrared light having a wavelength of 10 μm, and in the sensor pixel B, the absorption film absorbs infrared light having a wavelength of 4 μm based on interference between incident light and reflected light.

  The absorbed infrared rays become heat to change the temperature of the diaphragm, and accordingly, the resistance of the bolometer is changed and converted into an electric signal, and the signal is imaged by digital image processing (Patent Document 1, Paragraph 0022). ).

  On the other hand, as an array sensor that can specify the position of a detection target without performing image processing, first and second temperature sensors are provided in one pixel, and the first temperature sensors are connected in series for each row. One in which a second temperature sensor is connected in series for each column has been proposed (Patent Document 2). In this array sensor, the position of the pixel that detected the object is specified by the change in the output extracted from the row end and the column end, and the position of the object is specified based on the position.

JP 2000-205944 A WO2007 / 135850

Providing image processing means as in Patent Document 1 eventually increases the area occupied by the entire apparatus and increases the cost.
Therefore, an object of the present invention is to further improve the array sensor of Patent Document 2, and to detect a position, size, and number of objects having different properties without providing an image processing means. It is to provide a sensor at a low cost.

In order to solve the problem, the infrared array sensor of the present invention is
In an infrared array sensor in which a plurality of sensor pixels each having an infrared light receiving part and first and second temperature detection parts are two-dimensionally arranged,
The first temperature detection units of the sensor pixels that separate adjacent sensor pixels thermally and electrically and have different absorption wavelength bands to absorb light in the same absorption wavelength band are connected in series for each row. The second temperature detectors are connected in series for each column.

  According to the infrared array sensor of the present invention, when the light receiving unit of a certain pixel receives infrared light in the absorption wavelength band of the pixel from the object, the light receiving unit generates heat, and the temperature rise of the first and second of the pixel is detected. The temperature detector reads and outputs a detection signal. As the temperature detection unit, a thermopile, a bolometer, a diode, or the like can be used. And since the 1st, 2nd temperature detection part of the sensor pixel which absorbs the light of the same absorption wavelength band is connected in series for every row and every column, according to the above-mentioned output, The output of the row and column to which it belongs changes, and the position of the pixel that detected the object is specified. As shown in FIG. 1, the position of each pixel is associated with each position in the field of view of the sensor by association means such as a lens, and the position information of the object is obtained from the detected pixel position. At the same time, information for determining the property of the object based on the absorption wavelength band of the pixel is obtained.

  The sensor pixel may include a filter, and the wavelength band to be absorbed may be different among the sensor pixels depending on the difference in the pass band of the filter. In this case, the same infrared light receiving unit can be applied to all sensor pixels.

  In addition, the infrared light receiving unit may include an absorption film that absorbs infrared light in a specific range of wavelength bands, and may absorb infrared light in different wavelength bands between sensor pixels due to the difference in the absorption film. Furthermore, the absorbing film is combined with the reflecting film so that the absorbing film absorbs the interference light between the incident light and the reflected light, and the wavelength band absorbed by the difference in optical distance between the absorbing film and the reflecting film is changed between the sensor pixels. It may be different. In this case, an additional member such as a filter is not required.

  In order to detect the position of the object, it is not necessary to provide an image processing means, and a single sensor is sufficient to detect a plurality of wavelengths. Therefore, downsizing and cost reduction can be realized.

It is a figure explaining the method of matching the position of a sensor pixel, and the position of a target object. FIG. 3 is a plan view block diagram schematically showing the infrared array sensor according to the first embodiment. It is the A section top view in FIG. It is BB sectional drawing in FIG. It is a top view block diagram which shows typically the state which detected the target object in the infrared array sensor. It is a graph which shows the relationship between the infrared radiation amount and wavelength of the object which this sensor makes object. (A) is sectional drawing which shows the principal part of the infrared array sensor which concerns on Embodiment 2, (b) is the B section enlarged view of (a). It is sectional drawing which shows the principal part of the infrared array sensor which concerns on Embodiment 3. FIG. It is a figure explaining the permeation | transmission area | region of the filter applied to the sensor. It is a top view block diagram which shows typically the infrared array sensor which concerns on Embodiment 4. FIG. It is a figure which shows operation | movement of the infrared array sensor. It is a figure which shows another operation | movement of the infrared array sensor. It is a figure which shows the use condition of the infrared array sensor.

Embodiment 1
2 is a plan view block diagram schematically showing the infrared array sensor according to the first embodiment, FIG. 3 is a plan view of a portion A in FIG. 2, and FIG. 4 is a cross-sectional view along BB in FIG.
As shown in FIG. 2, the infrared array sensor 1 is arranged in a 4 × 4 grid, and includes 16 sensor pixels 2 corresponding to one of the wavelength bands λ1 and λ2 and a lens (not shown). Here, λ1 = 4.4 to 5.5 μm and λ2 = 8 to 14 μm. Then, the pixels 2 corresponding to the wavelength band λ2 are arranged next to the row direction and the column direction of the pixels 2 corresponding to the wavelength band λ1, so that the sensor pixels 2 corresponding to the wavelength bands λ2 are evenly arranged. Yes. When the light from the object is focused by a lens (not shown) and condensed, each position of the object in the field of view of the sensor is adjusted so as to be incident on one of the pixels 2.

  As shown in FIGS. 3 and 4, the infrared array sensor 1 includes 16 sets of infrared light receivers 4, first temperature detectors 5A, and second on the main surface of a single crystal silicon substrate 3 by photolithography. The temperature detecting portion 5B and the beam 6 are formed and etched while being covered with an unillustrated etching protection mask. Each set of the infrared light receiving unit 4, the temperature detecting units 5 </ b> A and 5 </ b> B, the beam 6, and the surrounding substrate 3 constitute one sensor pixel 2.

  In each sensor pixel 2, the infrared light receiving unit 4 is supported by the substrate 3 through a beam 6 in a cavity 7 of an inverted quadrangular pyramid formed by anisotropic wet etching. The infrared light receiving portion 4 itself is made of a thin film material that absorbs infrared rays in a specific wavelength range. For example, a silicon oxide film absorbs a wavelength band having a peak at a wavelength of about 10 μm, and a silicon nitride film absorbs a wavelength band having a peak at a wavelength of about 13 μm. As described above, the thin film material is selected for each pixel 2 so that the absorption wavelength band is different between the pixels 2 adjacent in the row direction and the column direction. Other configurations are not different between the pixels 2.

  The temperature detectors 5A and 5B are thermopile type temperature sensors, each of which has a hot contact formed in the infrared light receiving unit 4 and a cold contact formed in the substrate 3 around the infrared light receiving unit 4, respectively. Reference numeral 4 denotes a voltage value corresponding to the received infrared energy. The hot junction and the cold junction are connected through the beam 6. The cold junction of each temperature detection unit 5A is connected in series with the cold junction of the temperature detection unit 5A of the adjacent pixel 2 in the row direction through one aluminum wiring formed in the substrate 3. Similarly, one temperature detection unit 5B is connected to the temperature detection unit 5B of the adjacent pixel 2 in the column direction. One end of the series circuit is then connected to a common ground terminal and the other end is connected to a separate output terminal for that row or column.

  Therefore, the beam 6 has a function of supporting both the infrared light receiving unit 4 and the temperature detecting units 5A and 5B. In addition, each infrared light receiving unit 4 and each temperature detecting unit 5A, 5B are thermally and electrically separated by the adjacent infrared light receiving unit 4 and temperature detecting units 5A, 5B and the cavity 7 in a certain wavelength band. The output change accompanying the light absorption of the corresponding pixel 2 does not affect the change of the pixel 2 corresponding to another wavelength band.

  According to the infrared array sensor 1, when the detection object enters the field of view of any pixel 2 corresponding to the wavelength, the infrared light receiving unit 4 absorbs infrared rays emitted from the object and generates heat. Along with this, the output voltage of the temperature detectors 5A, 5B changes, and a voltage signal indicating detection of the object is obtained. As shown in FIG. 5, for example, if the pixel 2 located at the position of the second row and the first column detects the object W, the output terminal of the series circuit of the second row and the output terminal of the series circuit of the first column respectively. A predetermined voltage signal is obtained. In this way, the position of the pixel 2 that detected the object W is specified as being in the second row and first column, and at the same time, information for determining the property of the object W based on the absorption wavelength band λ2 of the pixel 2, that is, the object Information suggesting that the object W is a human body is obtained.

  There may be a portion where the absorption band of a sensor pixel corresponding to a certain wavelength band overlaps with the absorption band of a sensor pixel corresponding to another wavelength band. For example, a flame (FIG. 6 (a)) in which specific strong radiation due to CO2 resonance radiation is observed at a wavelength of 4.4 μm and a curve in which the radiation amount is broad with respect to the wavelength based on Planck's radiation law. Assume that two objects, a high-temperature object (FIG. 6B), are detection targets. Then, in general, in FIG. 6, the sensor pixel P corresponding to the wavelength band p1 and the sensor pixel Q corresponding to the wavelength band q are combined, and the pixel P is output large and the pixel Q is output small. A high temperature object is detected by a large output from both of the pixels P and Q. However, even if the pixel P corresponds to the wavelength band p2, only the pixel P outputs a large flame. This is because it can be detected.

Embodiment 2
Fig.7 (a) is sectional drawing which shows the principal part of the infrared array sensor which concerns on 2nd embodiment, FIG.7 (b) is the B section enlarged view of (a).
As in the first embodiment, the infrared array sensor 10 is regularly arranged in a 4 × 4 grid and includes 16 sensor pixels 12 corresponding to one of the wavelength bands λ1 and λ2 and a lens (not shown). .

  However, unlike the first embodiment, the infrared light receiver 14 includes an absorption film 14a made of a titanium nitride thin film having a sheet resistance of 377Ω from the light receiving surface side (ie, the upper side of the drawing), a transmission film 14b made of a silicon oxide thin film having a thickness d, and It is a laminated body of reflective films 14c made of aluminum. The thickness d is determined for each pixel 12 so that n · d = (2m + 1) λ / 4 is satisfied, where n is the refractive index of silicon oxide, λ is the wavelength to be absorbed, and m is an integer. .

  The infrared light transmitted through the absorption film 14a and the transmission film 14b is reflected by the reflection film 14c, the incident light and the reflected light interfere with each other, and the resonance wavelength is absorbed by the absorption film 14a, whereby the absorption film 14a generates heat. To do. Along with this, the output voltage from the temperature detectors 5A and 5B changes. In this way, as in the first embodiment, the position of the pixel 12 that detected the object is specified, and at the same time, information for determining the property of the object is obtained.

Embodiment 3
FIG. 8 is a cross-sectional view showing a main part of an infrared array sensor according to the third embodiment.
As in the first embodiment, the infrared array sensor 20 is regularly arranged in a 4 × 4 grid and includes 16 sensor pixels 22 corresponding to one of the wavelength bands λ1 and λ2 and a lens (not shown). .

  Each sensor pixel 22 includes the infrared light receiving unit 4, the temperature detection units 5 </ b> A and 5 </ b> B, and the beam 6 as in the first embodiment, and further includes a filter 8 installed above the infrared light receiving unit 4. The infrared light receiving unit 4 itself is made of a thin film material that absorbs infrared rays in a specific wavelength range, as in the first embodiment, but may be made of a laminate as in the second embodiment. In addition, the infrared light receiving unit 4 may be configured such that the absorption wavelength band is different between adjacent pixels 22, or all of them may be the same.

  For example, even if the infrared light receiving units 4 are all the same and absorb uniformly in a wide wavelength band, one filter 8 (referred to as filter 8A) and the filter 8 (filter 8B) of the adjacent pixel are used. ), The absorption wavelength band can be made different between the adjacent pixels 22 (FIG. 9B). As described in the first embodiment, since there may be a portion where the absorption band of a sensor pixel corresponding to a certain wavelength band overlaps with the absorption band of a sensor pixel corresponding to another wavelength band, the infrared array The sensor 20 may have a configuration in which a sensor pixel provided with a filter and a sensor pixel not provided with a filter are combined.

Embodiment 4
FIG. 10 is a plan view block diagram schematically showing an infrared array sensor according to the fourth embodiment. The infrared array sensor 30 of this embodiment can measure not only the position of an object but also the area or the number of objects. For this purpose, in addition to the configuration of the infrared array sensor 1 of the first embodiment, row addition circuits 31 and 32 and Column addition circuits 33 and 34 are provided. When one object enters the field of view of a plurality of pixels 2 corresponding to the same wavelength band, their output voltage values are added together.

  The row addition circuit 31 outputs the output taken out from the output terminal of the series circuit corresponding to the wavelength λ1 of each row when the object is not detected, and the series corresponding to the wavelength λ1 of each row when the object is detected. The difference from the output extracted from the output terminal of the circuit is added for all rows. Similarly, the row addition circuit 32 performs an operation corresponding to the wavelength λ2. The column addition circuits 33 and 34 similarly perform calculations corresponding to the wavelengths λ1 and λ2 for all columns, respectively.

  The operation of the infrared array sensor 30 will be described with reference to FIGS. FIG. 11 is a plan view showing the operation of the infrared array sensor 30 when measuring the area. For convenience of illustration, all the pixels 2 are sensitive to an object having the same wavelength, not one of a plurality of wavelengths of λ1 and λ2. It shall be. In the figure, the numbers “0”, “1” and “2” written at the end of the arrows at the right end of each row and the lower end of each column conceptually represent the output levels to be extracted. “0” indicates that there is no object in the detection range of any pixel 2 in the row or column, and “1” or “2” indicates that there is an object in the detection range of one or two pixels 2, respectively. Show.

  As shown in the figure, when the object W is detected across the pixel 2 in the second row and the third column and the pixel 2 in the second row and the fourth column, the output level taken out from the output terminal of the second row is “ 2 ”, the output levels taken out from the output terminals of the third column and the fourth column are“ 1 ”, respectively. If it is known in advance that there is one object in the field of view of the infrared array sensor 30, the area of the object W can be specified as a size corresponding to the detection range of the two adjacent pixels 2.

  FIG. 12 is a plan view showing the operation of the infrared array sensor 30 when counting the number, and it is assumed that all the pixels 2 are sensitive to an object having the same wavelength as in FIG. In the figure, among the 16 pixels 2, a filled one indicates that light from the object is irradiated. It is assumed that the temperature of the object is constant to some extent, such as a person. If the output change amount “1” when one person enters the visual field of the sensor 30 is grasped in advance, when four persons enter the visual field as shown in FIG. By dividing the added value “4” and the added value “4” of the outputs for all the columns by the output change amount “1” for one person, it is measured that the number of persons entering the field of view is four.

1, 10, 20, 30 Infrared array sensor 2, 12, 22 Sensor pixel 3 Substrate 4, 14 Infrared light receiver 5A, 5B Temperature detector 6 Beam 7 Cavity 8 Filters 31, 32, 33, 34

Claims (5)

In an infrared array sensor in which a plurality of sensor pixels each having an infrared light receiving part and first and second temperature detection parts are two-dimensionally arranged,
The first temperature detection units of the sensor pixels that separate adjacent sensor pixels thermally and electrically and have different absorption wavelength bands to absorb light in the same absorption wavelength band are connected in series for each row. An infrared array sensor, wherein the second temperature detectors are connected in series for each column.   The infrared array sensor according to claim 1, wherein the sensor pixel includes a filter, and a wavelength band absorbed by the filter is different among the sensor pixels.   2. The infrared ray according to claim 1, wherein the infrared light receiving unit has an absorption film that absorbs infrared light in a wavelength band in a specific range, and the wavelength band to be absorbed is different among sensor pixels due to the difference in the absorption film. Array sensor.   The infrared light receiving unit has an absorption film and a reflection film, and the absorption film absorbs the interference light between the incident light and the reflected light, and the wavelength band absorbed by the difference in optical distance between the absorption film and the reflection film is a sensor. The infrared array sensor according to claim 1, wherein the infrared array sensor is different among pixels.   One end of the group of first and second temperature detection units connected in series is connected to a common ground terminal, and the other end is connected to an individual output terminal for each wavelength band. The infrared array sensor according to claim 1.

Images