JP2004170375A - Thermopile array sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermopile array sensor which is superior in S/N, by ingeniously removing the white noise of the sensor itself, noise due to the temperature variation of the surroundings, and the 1/f noise caused by a DC amplifier. <P>SOLUTION: In the thermopile array sensor 3, in which the plurality of measurement thermopiles A<SB>1</SB>-A<SB>4</SB>, B<SB>1</SB>-B<SB>4</SB>, C<SB>1</SB>-C<SB>4</SB>, and D<SB>1</SB>-D<SB>4</SB>are arranged on a semiconductor substrate 5, light-shielded compensating thermopiles X<SB>1</SB>-X<SB>4</SB>are provided to the semiconductor substrate 5. The measurement thermopiles A<SB>1</SB>-A<SB>4</SB>, B<SB>1</SB>-B<SB>4</SB>, C<SB>1</SB>-C<SB>4</SB>, and D<SB>1</SB>-D<SB>4</SB>and the compensating thermopiles X<SB>1</SB>-X<SB>4</SB>are provided, with respective switches Q<SB>r11</SB>-Q<SB>r45</SB>and Q<SB>c11</SB>-Q<SB>c45</SB>for extracting signals. The operational processing is performed, on the basis of the differences between the outputs of the measurement thermopiles A<SB>1</SB>-A<SB>4</SB>, B<SB>1</SB>-B<SB>4</SB>, C<SB>1</SB>-C<SB>4</SB>, and D<SB>1</SB>-D<SB>4</SB>and of the compensating thermopiles X<SB>1</SB>-X<SB>4</SB>. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermopile array sensor used for a temperature measuring device for non-contact temperature measurement of an object having a two-dimensional spread.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-22652 As the thermopile array sensor, for example, as described in Patent Document 1, it is used by being incorporated in a device for analyzing an infrared two-dimensional image or the like. I have. FIG. 7 schematically shows an example of a conventional thermopile array sensor 70. The thermopile array sensor 70 has a plurality of measurement thermopiles 72 arranged side by side on a sensor chip 71 made of a semiconductor substrate such as a Si substrate. . In the thermopile array sensor 70 having such a configuration, the output from each thermopile 72 for measurement is sequentially extracted by performing switching by a switch 73 provided on the sensor chip 71, and the extracted signal is output to a DC amplifier 74. After the amplification, the data is taken into the CPU 76 through the AD converter 75.
[0003]
However, in the thermopile array sensor 70 having the above-described structure, white noise caused by the intrinsic resistance component 72R of the thermopile 72 itself for measurement and noise caused by a change in the ambient temperature of the thermopile array sensor 70. Further, 1 / f noise and the like due to the DC amplifier 74 are generated, and these noises are superimposed on the output of the thermopile array sensor 70, and as a result, the S / N has to be deteriorated.
[0004] The present invention has been made in consideration of the above-mentioned matters, and its object is to take advantage of the influence of white noise of the sensor itself, noise caused by a change in ambient temperature, and 1 / f noise caused by a DC amplifier. To provide a thermopile array sensor excellent in S / N.
[0005]
According to a first aspect of the present invention, there is provided a thermopile array sensor in which a plurality of thermopiles for measurement are arranged in parallel on a semiconductor substrate. A semiconductor substrate is provided with a light-shielded compensating thermopile, and a switch for extracting a signal is provided in each of the measuring thermopile and the compensating thermopile, and arithmetic processing is performed based on a difference between outputs of the measuring thermopile and the compensating thermopile. Is configured to be performed.
An amplifier has a voltage / current offset and 1 / f noise, and the offset varies depending on the ambient temperature. Also, the 1 / f noise increases as the frequency decreases. Therefore, as described above, by providing a compensation thermopile on a semiconductor substrate provided with a plurality of measurement thermopiles, the measurement thermopile and the compensation thermopile have the same resistance value and have the same characteristics. The influence of each of the noises can be significantly reduced by operating the switch formed on the semiconductor substrate, for example, at a high speed to extract each signal and taking the difference between them. When the ambient temperature changes, a signal proportional to the differential value of the temperature change is added to the original signal.However, by taking the difference between the signal of the measuring thermopile and the signal of the compensating thermopile, The effects of ambient temperature changes are also eliminated.
According to a second aspect of the present invention, in the thermopile array sensor according to the first aspect, the thermopile for measurement includes a plurality of m rows and n columns (m and n are integers of 1 or more and not simultaneously 1). ), A compensating thermopile may be provided for each row, and the output of the compensating thermopile may be extracted for each row scan.
According to a third aspect of the present invention, in the thermopile array sensor according to the first aspect, the output of the measuring thermopile and the output of the compensating thermopile may be alternately taken out.
Further, as described in claim 4, in the thermopile array sensor according to claim 1, the thermopile for measurement is a plurality of m rows and n columns (m and n are integers of 1 or more and not simultaneously 1). ), One compensation thermopile may be provided in common to the plurality of measurement thermopiles, and the output of the compensation thermopile may be taken out after taking out the outputs of all the measurement thermopiles.
According to a fifth aspect of the present invention, in the thermopile array sensor according to the first to fourth aspects, based on a difference between a non-inverted output and an inverted output of the outputs of the measuring thermopile and the compensating thermopile. In the case where the arithmetic processing is performed by using such a method, an offset due to a bias current of an external circuit such as a DC amplifier can be canceled.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. 1 to 6 show one embodiment of the present invention. FIG. 1 schematically shows a temperature measuring device incorporating a thermopile array sensor of the present invention. In this figure, reference numeral 1 denotes a temperature measuring device, which is a cylindrical body 2 formed to block infrared light IR. The thermopile array sensor 3 is accommodated therein, and an infrared light focusing lens 4 is provided on one end side of the cylindrical body 2, that is, on the front side of the thermopile array sensor 3. The infrared light condensing lens 4 is formed of, for example, from the IR transmission materials such as chalcogenide glass and BaF _2. In addition, the infrared light focusing lens 4 may have any shape such as a spherical surface, an aspherical surface, and a Fresnel lens shape.
The thermopile array sensor 3 comprises a plurality of thermopiles 6 arranged in a matrix, for example, 4 rows × 5 columns, on a silicon substrate (silicon chip) 5 as a semiconductor substrate (semiconductor chip). 4 rows × 4 columns are thermopiles for measurement (hereinafter, denoted by reference symbols A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 to} D ₄ ), and 4 rows × 1 column compensation thermopile pile (hereinafter, represented by the symbol _X 1 to X ₄₎ are.
The structure of the thermopile array sensor 3 will be described in more detail with reference to FIG. 2. The upper surface of the silicon substrate 5 is formed with 4 × 5 rectangular recesses 7 in plan view. A thermopile element 6a is provided below each of the recesses 7, and the thermopile 6 is formed. The thermopile element 6a is formed by connecting in series a plurality of thermocouples 9 in which a thermoconductive material is connected to the upper surface of an insulating thin film 8 provided horizontally so as to cross the concave portion 7, and is provided below the thermopile element 6a. Are open to the outside so as to form a heat release space 10. Further, the side surface 11 of the concave portion 7 on the upper surface side of the thermopile element 6a is formed on the mirror surface and is inclined upward and divergent so as to enter the concave portion 7 from above (infrared light IR). Is formed so as to converge light in the direction of the thermopile element 6a.
In the thermopile 6, 4 × 4 thermopile units denoted by reference signs A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 to} D ₄ (only D _{4 in} FIG. 2) (Shown), the upper surface of the concave portion 7 is opened, and the infrared light IR passing through the infrared light condensing lens 4 is formed as it is or on a thermopile for measurement which is reflected by the mirror surface 11 and enters the thermopile element 6a. On the other hand, with respect to 4 × 1 pieces indicated by reference signs X _{1 to} X ₄ (only X ₄ is shown in FIG. 2), the infrared light IR is incident on the upper surface of the recess 7 into the recess 7. For example, a light-shielding film 12 such as an aluminum film is provided to prevent the infrared rays IR from being incident on the thermopile element 6a.
That is, the thermopile array sensor 3 according to the present embodiment includes thermopile for measurement A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , D _{1 to} D ₄ composed of 4 × 4 elements, 4 × 1 compensating thermopiles X _{1 to} X ₄ are formed in a matrix on one silicon substrate 5, and the measuring thermopile and the compensating thermopile are mutually shaped except for the light shielding film 12. (Size) and structure are identical and have the same properties. The thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , D _{1 to} D ₄ and the thermopiles X _{1 to} X ₄ for compensation are simply referred to as thermopiles 6.
FIG. 3 shows an example of an electric circuit of the thermopile array sensor 3. In this figure, reference numeral 13 denotes a measuring unit, and 14 denotes a signal output unit connected to the measuring unit 13. First, the measurement unit 13 is mainly constituted from the respective thermopile 6 and row select switch _Q r11 _{to Q r45} and column select switch _Q c11 _{to Q c45} serving as a respective signal output switch provided on each thermopile 6 . These switches _Q r11 _{~Q r45, Q} c11 to _{to Q c45,} the row selecting switch SW-1~SW-X, the row selection signal input via respective switches SW-through SW-D for column selection , Is controlled on and off by a column selection signal. Incidentally, when collectively row select switch _Q r11 _{to Q r45} and column select switch _Q c11 _{to Q c45} respectively, row select switch _{Q r,} as the column selection switch _{Q c.}
The signal output section 14 outputs signals obtained by the respective thermopiles 6 in the measuring section 13. In this embodiment, the signal output section 14 includes an inverting / non-inverting section 15 and an output terminal section 16. . The inverting / non-inverting unit 15 inverts or non-inverts the polarity of the signal of each thermopile 6 and is a combination of inverting connection switches Q _i1 and Q _i2 and non-inverting connection switches Q _n1 and Q _n2. The connection switches Q _i1 , Q _i2 , Q _n1 , and Q _n2 are turned on and off by an inverted signal and a non-inverted signal input via an inverted signal input switch SW-INV and an inverted signal input switch SW-NINV, respectively. Controlled. The output terminal section 16 includes a positive terminal 16P and a negative terminal 16N. Also, Q _s is shorting switch, the positive terminal 16P and a negative terminal 16N provided to short-circuit at their input side, controlled by a short-circuit signal input through the short-circuit signal input switch SW-SHORT Is done.
[0018] Incidentally, the switches _{Q r, Q c, Q i1} , Q i2, Q n1, Q n2, Q s is constituted for example by MOS-FET (analog switch). Also, in FIG. 3, CA _{1 to} CA ₄ , CB _{1 to} CB ₄ , CC ₁ to CC ₄ , CD _{1 to} CD ₄ , CX ₄ -C-X _4, the capacitor, C-COM is connected to one end of each thermopile 6, wherein a capacitor is commonly connected to the other end of each thermopile 6.
Further, in FIG. 3, 17 is an operational amplifier, 18 is an AD conversion circuit, and 19 is a CPU.
Next, the operation of the thermopile array sensor 3 having the above configuration will be described with reference to FIGS. For example, infrared light IR from an object to be measured (not shown) travels to the thermopile array sensor 3 via the infrared light focusing lens 4. In this case, the infrared light IR that has entered the concave portion 7 in which the thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 to} D ₄ for measurement are incident on the thermopile element 6 a. However, since the light-shielding film 12 is formed on the entrance side of the concave portion 7 in which the compensating thermopiles X _{1 to} X ₄ are formed, the infrared light IR may not enter the thermopile element 6 a. Absent.
Signals are generated in the thermopile 6 in the measuring section 13 of the thermopile array sensor 3 by the incidence of the infrared light IR. These signals in each thermopile 6, as shown in FIG. 3, each row select switch Q _r and each row selection signal to each column selection switch Q _c, on the column select signal, by turning off control, are taken out one . That is, in the example shown in FIG. 3, for example, after the signals in the measurement thermopiles A _{1 to} D ₁ in the first row are extracted, the output of the compensation thermopile X ₁ is extracted, and the thermopile in the second row and below is also extracted. I do the same. That is, the signals of the compensating thermopiles X _{1 to} X ₄ located in the row are taken out every row scanning. In FIG. 3, _Tr indicates the measurement time of each row, and _Tf indicates the measurement time of all rows.
As described above, the signals extracted from each of the thermopiles 6 are sequentially sent to a signal output section 14, and the inversion / non-inversion section 15 undergoes inversion or non-inversion processing to output the signal to an output terminal section. It is output to 16 negative terminals 16N or 16P. More specifically, the inversion connection switches Q _i1 , Q _i2 and the non-inversion connection switches Q _n1 , Q _n2 are connected to the inversion signal input through the inversion signal input switch SW-INV, the inversion signal input switch SW-NINV, or the inversion signal. The connection switches Q _i1 , Q _i2 , Q _n1 , and Q _n2 are appropriately turned on or off by performing on / off control by the inversion signal. The connection switch _{Q n1, Q n2} is on, the connection when the switch _{Q i1, Q i2} is off, the thermopile _{A 1 ~D 1, A 2 ~D} 2, A 3 ~D 3, A 4 ~D _4, the signal of _X 1 to X ₄ is output to the positive terminal 16P as it polarities. When the connection switches _Qn1 and _Qn2 are off and the connection switches _Qi1 and _Qi2 are on, the polarity of the signal is inverted and output to the negative terminal 16N.
The output signals of the thermopiles 6 output to the positive terminal 16P and the negative terminal 16N are sequentially input to the CPU 19 via the operational amplifier 17 and the AD conversion circuit 18. In the CPU 19, as shown in FIG. 5, arithmetic processing is performed based on the difference between the AD conversion output at the time of non-inversion and the AD conversion output at the time of inversion. As a result, an offset caused by a bias current of an external circuit such as the operational amplifier 17 and the AD conversion circuit 18 is skillfully canceled.
As described above, in the thermopile array sensor 3 according to the above embodiment, the thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 are} placed on one silicon substrate 5. the to D ₄ with a plurality parallel, the compensation thermopile _X 1 to X _4, which is shielded provided, the measuring thermopile _{a 1 ~A 4, B 1 ~B} 4, C 1 ~C 4, D 1 ~D 4 since the output of that to perform arithmetic processing on the basis of the difference between the outputs of the compensation thermopile X ₁ to X _4, it exhibits the following excellent effects.
[0025] That is, now, r rows, AD conversion data of the thermopile for measuring c-th column (the difference upon non-inversion output and the inverting on output) and V _rc, AD conversion data of the compensation thermopile r rows ( _Assuming that the difference between the non-inverted output and the inverted output) is V _rx , the difference between the AD conversion data V _rc and V _rx (V _rc −V _rx ) is used to calculate the temperature of the measurement object, and the silicon substrate 5, the electromotive force of the thermopile 6 due to a sudden change in the ambient temperature of the thermopile array sensor 3 (due to the thermal resistance between the cold junction and the hot junction, and the heat capacity of the hot junction / light receiving portion). Error factors based on the above are canceled. Therefore, a measurement result excellent in S / N can be obtained.
In the above-described embodiment, as shown in FIG. 3, a signal generated in each thermopile 6 of the measuring section 13 of the thermopile array sensor 3 is converted into a row selection switch _Qr and a column selection switch Qr. each row selection signal _c, on the column select signal, by turning off the control, sequentially takes out, in inverted and non-inverted portions 15 of the signal output section 14, reversing the connection switch Q _i1, Q _i2 and non-inverting connection By switching the switches Q _n1 and Q _n2 , an inverted output and a non-inverted output are taken out. However, the row selection switch Q _r and the switches Q _i1 , Q _i2 , Q _n1 and Q _n2 for polarity inversion are switched. Charge injection at the time of switching may occur.
In this embodiment, the gate voltages of the switches Q _r , Q _i1 , Q _i2 , Q _n1 , and Q _n2 are shown by enlarging the portions indicated by symbols a and b in FIG. As shown in FIGS. 6A and 6B, the column selection switch _Qc is turned off and then changed, so that charge injection does not occur at the time of the switching. At this time, in order to suppress the input impedance of the operational amplifier 17 is an external circuit low, leaving the shorting switch Q _s in the ON state. Thus, a discharge path for charge injection of the row selection switch _Qr and the polarity inversion switches Q _i1 , Q _i2 , Q _n1 , and Q _n2 is formed.
The present invention is not limited to the above-described embodiment, but can be implemented in various modifications. The thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , and C _{1 to} C ₄ for measurement are used. , D _{1 to} D _{4 and} the outputs of the compensating thermopiles X _{1 to} X ₄ may be alternately taken out. That is, for example, in FIG. 3, when reading the outputs of the measurement thermopiles A _{1 to} D _{1 in} the first row, A ₁ → X ₁ → B ₁ → X ₁ → C ₁ → X ₁ → D ₁ → X ₁ In this way, signals are alternately extracted from the thermopile for measurement and the thermopile for compensation. In this case, chopping may be added. In such a case, noise can be further reduced.
One compensation thermopile X is provided in common for all the measurement thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 to} D ₄ . The output of the compensating thermopile X may be extracted after extracting the outputs of the thermopiles A _{1 to} A ₄ , B _{1 to} B ₄ , C _{1 to} C ₄ , and D _{1 to} D ₄ .
A capacitor may be provided in parallel with each thermopile 6. In this case, white noise of the thermopile 6 itself can be further reduced, and spike noise can be reduced. .
[0031]
As described above, in the thermopile array sensor of the present invention, a plurality of thermopiles for measurement are provided on a single semiconductor substrate, a thermopile for compensation is provided which is shielded from light, and the output of the thermopile for measurement and the thermopile for compensation are provided. The arithmetic processing is performed based on the difference between the outputs of the sensors, so that the effects such as white noise of the sensor itself, noise caused by changes in ambient temperature, and 1 / f noise caused by the DC amplifier can be skillfully removed. , S / N can be obtained.
That is.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing a temperature measuring device incorporating a thermopile array sensor of the present invention.
FIG. 2 is a diagram schematically showing a configuration of the thermopile array sensor.
FIG. 3 is a diagram showing an example of an electrical configuration of the thermopile array sensor.
FIG. 4 is a timing chart for explaining signal extraction from a thermopile.
FIG. 5 is a timing chart for explaining inversion / non-inversion at the time of signal extraction.
6A is an enlarged view of a portion a in FIG. 5, and FIG. 6B is an enlarged view of a b portion in FIG.
FIG. 7 is a diagram schematically showing a conventional thermopile array sensor.
[Reference Numerals] 3 ... thermopile array sensor, 5 ... semiconductor _{substrate, A 1 ~A 4, B 1} ~B 4, C 1 ~C 4, D 1 ~D 4 ... measuring _thermopile, X 1 to X ₄ ... Compensation thermopile, Q _{r11 to} Q _r45 , Q _{c11 to} Q _c45 ... switches for extracting signals.

Claims (5)

In a thermopile array sensor in which a plurality of thermopiles for measurement are arranged side by side on a semiconductor substrate, a switch for extracting signals is provided for each of the thermopile for measurement and the thermopile for compensation while providing a light-shielded compensating thermopile on the semiconductor substrate. A thermopile array sensor configured to perform arithmetic processing based on a difference between outputs of the thermopile for measurement and the thermopile for compensation. The thermopile for measurement is arranged in a plurality of m rows and n columns (m and n are 1 or more and not an integer at the same time), a thermopile for compensation is provided in each row, and the output of the thermopile for compensation is taken out every row scan. The thermopile array sensor according to claim 1. 3. The thermopile array sensor according to claim 1, wherein an output of the measurement thermopile and an output of the compensation thermopile are alternately taken out. The thermopiles for measurement are arranged in a plurality of m rows and n columns (m and n are at least 1 and are not integers at the same time), and one thermopile for compensation is provided in common for the plurality of thermopiles for measurement. 2. The thermopile array sensor according to claim 1, wherein an output of said compensating thermopile is taken out after taking out an output of the thermopile. The thermopile array sensor according to any one of claims 1 to 4, wherein arithmetic processing is performed based on a difference between a non-inverted output and an inverted output of the outputs of the measurement thermopile and the compensation thermopile.

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