JP2012251776A - Detection device, sensor device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device which is adjustable in sensitivity, a sensor device, and an electronic apparatus.SOLUTION: The detection device includes a pyroelectric element 10, a sensitivity adjustment circuit 30 which is connected to the pyroelectric element 10 and adjusts the voltage sensitivity for the output voltage of the pyroelectric element 10, and a detection circuit 20 which is connected to the pyroelectric element 10. The sensitivity adjustment circuit 30 includes a variable capacity circuit 40 for sensitivity adjustment, and further includes a variable resistance circuit 50 which is connected in parallel with the variable capacity circuit 40. The resistance value of the variable resistance circuit 50 is set to a large value when the capacity value of the variable capacity circuit 40 is set to a small value, or to a small value when the capacity value of the variable capacity circuit 40 is set to a large value.

Description

  The present invention relates to a detection apparatus, a sensor device, an electronic apparatus, and the like.

  Conventionally, an infrared detecting device using a pyroelectric element is known. For example, infrared rays having a wavelength in the vicinity of 10 μm are radiated from the human body, and by detecting this, information on the presence and temperature of the human body can be acquired without contact. Therefore, intrusion detection and physical quantity measurement can be realized by using such an infrared detection circuit.

  As a prior art of an infrared detection device, for example, a technique disclosed in Patent Document 1 is known. In the prior art of Patent Document 1, a pyroelectric current is generated by changing the temperature of the pyroelectric element while repeatedly irradiating and blocking infrared rays on the pyroelectric element using a chopper. It detects as a voltage signal by making it charge.

  However, this prior art has a problem that it is difficult to control and adjust the sensitivity of the detection device according to the intensity of infrared light because the voltage sensitivity of the pyroelectric element cannot be adjusted.

JP 59-142427 A

  According to some embodiments of the present invention, it is possible to provide a detection device, a sensor device, an electronic apparatus, and the like that can adjust sensitivity.

  One embodiment of the present invention includes a pyroelectric element, a sensitivity adjustment circuit that is connected to the pyroelectric element and adjusts voltage sensitivity of an output voltage of the pyroelectric element, and a detection circuit that is connected to the pyroelectric element. The sensitivity adjustment circuit includes a detection device including a variable capacitance circuit for sensitivity adjustment.

  According to one aspect of the present invention, the detection device can variably set the capacitance connected to the pyroelectric element by variably setting the capacitance value of the variable capacitance circuit. By doing so, the voltage sensitivity can be adjusted, so that the voltage sensitivity suitable for the temperature range of the object can be adjusted, for example. As a result, it is possible to detect, for example, an object image at night and a temperature distribution of an object with high accuracy and stability.

  In the aspect of the invention, the sensitivity adjustment circuit may further include a variable resistance circuit connected in parallel to the variable capacitance circuit.

  According to this configuration, the detection device variably sets the capacitance value and resistance value connected to the pyroelectric element by variably setting the capacitance value of the variable capacitance circuit and the resistance value of the variable resistance circuit. be able to. In this way, the voltage sensitivity can be adjusted.

  In one aspect of the present invention, the resistance value of the variable resistance circuit may be set to a larger value as the capacitance value of the variable capacitance circuit is smaller.

  In this way, the detection device can variably set the capacitance value and the resistance value while keeping the product of the capacitance value of the variable capacitance circuit and the resistance value of the variable resistance circuit substantially constant. As a result, it is possible to adjust the voltage sensitivity of the detection device without changing the chopping frequency region where the voltage sensitivity becomes substantially constant.

  In the aspect of the invention, the capacitance value of the variable capacitance circuit and the resistance value of the variable resistance circuit may be set so that a product of the capacitance value and the resistance value is constant.

  In this way, the detection device can variably set the capacitance value and the resistance value while keeping the product of the capacitance value of the variable capacitance circuit and the resistance value of the variable resistance circuit constant. As a result, it is possible to adjust the voltage sensitivity of the detection device without changing the frequency region in which the voltage sensitivity is substantially constant.

  In the aspect of the invention, the sensitivity adjustment circuit may be any one of the plurality of adjustment units having capacitance elements having different capacitance values as the variable capacitance circuit, and the adjustment units. One adjustment unit and a switch circuit for selectively connecting the pyroelectric element may be included.

  In this way, the detection device can set the capacitance value of the variable capacitance circuit variably by selecting and connecting any one of the plurality of adjustment units with the switch circuit.

  In the aspect of the invention, each of the plurality of adjustment units may further include a resistance element connected in parallel to the capacitance element.

  According to this configuration, the detection device can variably set the capacitance value and the resistance value by selecting and connecting any one of the plurality of adjustment units with the switch circuit.

  In one aspect of the present invention, a control unit that outputs an adjustment signal for sensitivity adjustment may be included, and a capacitance value of the variable capacitance circuit may be set variably based on the adjustment signal.

  In this way, the detection device can adjust the voltage sensitivity by setting the capacitance value of the variable capacitance circuit to be variable based on the adjustment signal output from the control unit.

  In one aspect of the present invention, a resistance value of the variable resistance circuit may be variably set based on the adjustment signal.

  In this way, the detection device can adjust the voltage sensitivity by variably setting the capacitance value and the resistance value based on the adjustment signal output from the control unit.

  In one aspect of the present invention, the maximum value of the voltage sensitivity is Rvmax, the absorption rate of the pyroelectric element is ε, the pyroelectric coefficient is p, the area of the pyroelectric element is S, and the thermal resistance of the pyroelectric element is Rth, where the combined capacitance value of the internal capacitance of the pyroelectric element and the variable capacitance circuit is Cel, the maximum value Rvmax of the voltage sensitivity is an approximation of Rvmax = ε × p × S × Rth / Cel The combined capacitance value Cel is adjusted by the variable capacitance circuit by adjusting the capacitance value of the variable capacitance circuit, and the maximum value of the voltage sensitivity is adjusted by adjusting the combined capacitance value Cel. Rvmax may be adjusted.

  In this way, the detection device can increase the combined capacitance value by increasing the capacitance value of the variable capacitance circuit, and can decrease the maximum value of voltage sensitivity. On the other hand, the detection device can reduce the combined capacitance value by reducing the capacitance value of the variable capacitance circuit, and can increase the maximum value of voltage sensitivity.

  In one aspect of the present invention, the maximum value of the voltage sensitivity is Rvmax, the absorption rate of the pyroelectric element is ε, the pyroelectric coefficient is p, the area of the pyroelectric element is S, and the thermal resistance of the pyroelectric element is Rth, Rel, the combined resistance value of the pyroelectric element and the variable resistance circuit, Rel, the combined capacitance value of the pyroelectric element and the variable capacitance circuit, and the internal electricity of the pyroelectric element The maximum value Rvmax of the voltage sensitivity is an approximation of Rvmax = ε × p × S × Rel × Rth / τel, where τel is the electrical time constant that is the product of the combined resistance value of the resistor and the variable resistance circuit. The combined resistance value Rel is adjusted by the variable resistance circuit by adjusting the resistance value of the variable resistance circuit with the electric time constant τel constant, and the combined resistance value Rel is adjusted. The maximum voltage sensitivity Value Rvmax may be adjusted.

  In this way, the detection device can increase the combined resistance value and increase the maximum value of voltage sensitivity by increasing the resistance value of the variable resistance circuit while keeping the electrical time constant constant. On the other hand, the detection device can reduce the combined resistance value and reduce the maximum value of voltage sensitivity by making the electrical time constant constant and reducing the resistance value of the variable resistance circuit.

  Another aspect of the present invention relates to a sensor device including any one of the detection devices described above.

  Another aspect of the present invention includes a sensor array having a plurality of sensor cells, one or more row lines, one or more column lines, and a row selection circuit connected to the one or more row lines, A readout circuit connected to the one or more column lines, each sensor cell of the plurality of sensor cells being connected to the pyroelectric element and the pyroelectric element, and the voltage of the output voltage of the pyroelectric element It includes a sensitivity adjustment circuit for adjusting sensitivity and a detection circuit connected to the pyroelectric element, and the sensitivity adjustment circuit relates to a sensor device including a variable capacitance circuit for sensitivity adjustment.

  According to another aspect of the present invention, the voltage sensitivity of the sensor device can be adjusted by setting the capacitance value to be variable by the sensitivity adjustment circuit. As a result, it is possible to adjust the voltage sensitivity suitable for the temperature range of the object, or to correct variations in sensitivity between sensor cells.For example, the object image at night and the temperature distribution of the object It is possible to detect accurately and stably.

  Another aspect of the present invention relates to an electronic apparatus including any of the sensor devices described above.

1A and 1B are diagrams illustrating the principle of a detection device. FIG. 2A shows frequency characteristics of voltage sensitivity. FIG. 2B shows frequency characteristics of voltage sensitivity when the combined resistance is reduced. FIG. 3A shows frequency characteristics of voltage sensitivity when the combined capacitance is increased. FIG. 3B shows the frequency characteristics of voltage sensitivity when the electrical time constant is constant and the combined capacity is increased. The basic structural example of a detection apparatus. FIG. 5A and FIG. 5B are detailed configuration examples of pyroelectric elements. An example of the configuration of a sensitivity adjustment circuit. 7A and 7B show first and second configuration examples of the detection circuit. The 1st structural example of a sensor device. 9A and 9B show a second configuration example of the sensor device. 6 is a configuration example of an electronic device including a sensor device.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Voltage Sensitivity of Detection Device FIGS. 1A and 1B are diagrams illustrating the principle of the detection device of the present embodiment. In the detection apparatus of the present embodiment, a pyroelectric element 10 (thermal sensor element, infrared detection element, thermal photodetection element, ferroelectric element) is used as an element for detecting infrared rays or the like. The pyroelectric element 10 has a configuration in which a ferroelectric material FE (pyroelectric material) such as lead zirconate titanate (PZT) is sandwiched between an upper electrode EA and a lower electrode EB. As shown in FIG. 1A, the pyroelectric element 10 is electrically equivalent to a circuit in which three of spontaneous polarization, internal capacitance CA, and internal electrical resistance RA are connected in parallel. One end of the pyroelectric element 10 is connected to the detection node ND, and the other end is connected to the first power supply node VSS (low potential power supply node).

  The temperature of the pyroelectric element 10 can be changed by periodically blocking the infrared rays irradiated to the pyroelectric element 10 by a chopper or the like. When the temperature changes, the spontaneous polarization of the pyroelectric element 10 changes and pyroelectric current is generated. This pyroelectric current is charged into the internal capacitance CA, and this pyroelectric current flows through the internal electrical resistance RA, thereby detecting An output voltage VA is generated at the node ND. This output voltage VA depends on the capacitance value (capacitance value) of the internal capacitance CA and the resistance value of the internal electrical resistance RA.

  In the detection apparatus of the present embodiment, as shown in FIG. 1B, the voltage sensitivity of the detection apparatus is adjusted by connecting the external capacitance CX and the external electrical resistance RX in parallel to the pyroelectric element 10. can do. That is, the combined capacitance of the internal capacitance CA and the external capacitance CX and the combined electrical resistance of the internal electrical resistance RA and the external electrical resistance RX are parameters that determine the voltage sensitivity, so that CX and RX can be varied. By setting to, voltage sensitivity can be adjusted. Hereinafter, how the voltage sensitivity is adjusted will be described.

  Assuming that the capacitance values of the internal capacitance CA and the external capacitance CX are Ca and Cx, respectively, and the resistance values of the internal electrical resistance RA and the external electrical resistance RX are Ra and Rx, respectively, the capacitance values Cel and The resistance value Rel of the combined electric resistance is given by the following equation.

Cel = Ca + Cx (1)
Rel = Ra × Rx / (Ra + Rx) (2)
The voltage sensitivity Rv is defined by the following equation, where Φ is the radiant flux (light flux) of the infrared light irradiated on the pyroelectric element 10, that is, the energy per unit time.

Rv = VA / Φ (3)
Hereinafter, how the voltage sensitivity Rv changes when the capacitance value Cel of the combined capacitance and the resistance value Rel of the combined electric resistance change will be described. In the following description, when there is no particular need to distinguish, the capacitance value Cel of the combined capacitance is simply expressed as a combined capacitance Cel, and the resistance value Rel of the combined electric resistance is simply expressed as a combined resistance Rel. .

  Known documents by Arnold Daniels, Mitsunobu Koyama, “Field Guide Infrared System”, Optronics, Inc., p. According to 64-65, the voltage sensitivity Rv is given by:

  Here, ε is the absorption rate of the pyroelectric element, p is the pyroelectric coefficient, S is the area of the pyroelectric element, Rth is the thermal resistance of the pyroelectric element, and ω is the angular frequency (chopping frequency) of the chopper. Also, τel is an electrical time constant and τth is a thermal time constant, which are given by the following equations, respectively.

τel = Cel × Rel (5)
τth = Cth × Rth (6)
Here, Cth is the thermal capacity of the pyroelectric element, and Rth is the thermal resistance of the pyroelectric element.

FIG. 2A shows frequency characteristics of the voltage sensitivity Rv. Here, a case where τth <τel is shown, but generally τth <τel holds because of the electrical characteristics of the pyroelectric element material and the structural design. For example, τel is in the range of 10 ⁻² to 10 ² s, and τth is in the range of 10 ⁻³ to 10 s.

  As shown in FIG. 2A, the voltage sensitivity Rv is

The maximum value Rvmax is taken. Rvmax can be obtained from the equations (4) and (7) as follows.

  In the range where the chopping frequency ω is 1 / τel ≦ ω ≦ 1 / τth, the voltage sensitivity Rv is substantially constant, and Rvmax exists in this range.

  FIG. 2B shows frequency characteristics of the voltage sensitivity Rv when the combined resistance Rel is reduced. As Rel decreases, the electrical time constant τel decreases, and therefore 1 / τel shifts to the high frequency side as indicated by D1 and D2 in FIG. That is, the range in which the voltage sensitivity Rv is almost constant becomes narrow. On the other hand, the maximum value Rvmax is small, but the amount of decrease is small.

  FIG. 3A shows the frequency characteristics of the voltage sensitivity Rv when the combined capacitance Cel is increased. As Cel increases, the electrical time constant τel increases, and therefore 1 / τel shifts to the lower frequency side. On the other hand, although the maximum value Rvmax is small, as shown by E1 and E2 in FIG. 3A, the amount of decrease is larger than that when the combined resistance Rel is small (FIG. 2B).

  It can be understood from the following approximate expression that the maximum value Rvmax of the voltage sensitivity changes greatly when the combined capacitance Cel is increased. When τth << τel, Rvmax can be approximated by the following equation.

  As can be seen from this equation, the maximum value Rvmax of the voltage sensitivity is adjusted by adjusting the combined capacitance value Cel. Further, the maximum value Rvmax of the voltage sensitivity is adjusted by adjusting the combined resistance value Rel while keeping the electric time constant τel constant.

  FIG. 3B shows frequency characteristics of the voltage sensitivity Rv when the electrical time constant τel is constant and the combined capacitance Cel is increased. In this case, since τel is constant, the frequency region where the voltage sensitivity Rv is substantially constant does not change. On the other hand, as indicated by F1, F2, and F3 in FIG. 3B, the maximum value Rvmax decreases as the combined capacity Cel increases.

  As described above, while keeping the electrical time constant τel constant, the combined capacitance Cel is increased and the combined resistance Rel is decreased simultaneously, or the combined capacitance Cel is decreased and the combined resistance Rel is increased at the same time. Sensitivity adjustment of the detection device can be performed without changing the frequency region in which the sensitivity Rv is substantially constant. When the voltage sensitivity Rv is controlled and adjusted while keeping the electrical time constant τel constant, the voltage sensitivity Rv is proportional to the combined resistance Rel, as can be seen from the equation (9) which is an approximate expression of Rvmax. Fine and precise control / adjustment of the sensitivity Rv is possible.

  Furthermore, by setting the chopping frequency in a frequency region where the voltage sensitivity Rv is almost constant, more preferably near the center of the region, the influence of the frequency characteristics when the voltage sensitivity Rv is controlled / adjusted is reduced. Can do. At this time, the width of the frequency region where the voltage sensitivity Rv is substantially constant can be regarded as a margin for fluctuations and variations in the chopping frequency. The chopping frequency is set in a range of several tens to several hundreds Hz, for example.

  According to the detection apparatus of the present embodiment, as shown in FIG. 1B, the external capacitance CX and the external electrical resistance RX connected in parallel to the pyroelectric element 10 are variably set. While maintaining the electrical time constant τel constant, the combined capacitance Cel can be increased and simultaneously the combined resistance Rel can be decreased, or the combined capacitance Cel can be decreased and the combined resistance Rel can be increased simultaneously. By doing so, the voltage sensitivity Rv of the detection device can be adjusted without changing the chopping frequency region where the voltage sensitivity Rv becomes substantially constant. By adjusting the voltage sensitivity Rv, for example, it is possible to adjust to a sensitivity suitable for the temperature range (high temperature, normal temperature, low temperature, etc.) of the object (detection target).

2. Configuration of Detection Device FIG. 4 shows a basic configuration example of the detection device of the present embodiment. The detection device of this embodiment includes a pyroelectric element 10, a detection circuit 20, and a sensitivity adjustment circuit 30. In addition, the detection device of this embodiment may further include a control unit 60. Note that the detection apparatus according to the present embodiment is not limited to the configuration shown in FIG. 4, and various modifications may be made such as omitting some of the components, replacing them with other components, or adding other components. Is possible.

  As described above, the pyroelectric element 10 includes a ferroelectric material FE (pyroelectric material) such as lead zirconate titanate (PZT), and detects infrared rays or the like. The detailed configuration of the pyroelectric element 10 will be described later.

  The detection circuit 20 is connected to the pyroelectric element 10. Specifically, the detection circuit 20 is connected to a detection node ND that is a node on one end side of the pyroelectric element 10, detects the output voltage VA generated at the detection node ND, and outputs a detection signal VDET. The detailed configuration of the detection circuit 20 will be described later.

  The sensitivity adjustment circuit 30 is connected to the pyroelectric element 10 and adjusts the voltage sensitivity Rv of the output voltage VA of the pyroelectric element 10. Specifically, the sensitivity adjustment circuit 30 is provided between a detection node ND that is a node on one end side of the pyroelectric element 10 and a first power supply node VSS (low potential power supply node), and is a variable for adjusting sensitivity. A capacitance circuit 40 is included. The sensitivity adjustment circuit 30 may further include a variable resistance circuit 50 connected in parallel to the variable capacitance circuit 40. In the variable capacitance circuit 40 and the variable resistance circuit 50, the capacitance value and the resistance value are variably set based on the adjustment signal SAJ for sensitivity adjustment from the control unit 60.

  The variable capacitance circuit 40 may be composed of variable capacitance elements such as variable capacitance diodes (varicaps, varactors), or may be provided with a plurality of capacitance elements (capacitors) having different capacitance values from each other by switching elements. You may make it the structure which selects one of them. The variable resistance circuit 50 may be constituted by a variable resistance element such as a variable resistor (variohm), or a plurality of resistance elements having different resistance values are provided, and one of them is provided by a switch element. You may make it the structure which selects.

  The sensitivity adjustment circuit 30 may be configured by a combination of the above configurations of the variable capacitance circuit 40 and the variable resistance circuit 50. For example, it may be a combination of a variable capacitance element and a plurality of resistance elements selected by a switch element, or a combination of a plurality of capacitance elements selected by a switch element and a variable resistance element.

  The variable capacitance circuit 40 corresponds to the external capacitance CX shown in FIG. 1B, and the variable resistance circuit 50 corresponds to the external electric resistance RX shown in FIG. As described above, the combined capacitance Cel and the combined resistance Rel can be adjusted by variably setting the capacitance value Cx of the external capacitance CX and the resistance value Rx of the external electrical resistance RX. The voltage sensitivity Rv can be adjusted. As shown in FIG. 3A, the voltage sensitivity Rv can be adjusted even if only the combined capacitance Cel is changed. Therefore, the variable resistor circuit 50 can be omitted in FIG.

  The smaller the capacitance value Cx of the variable capacitance circuit 40 is, the larger the resistance value Rx of the variable resistance circuit 50 is set. On the contrary, the resistance value Rx of the variable resistor circuit 50 is set to a smaller value as the capacitance value Cx of the variable capacitor circuit 40 is larger. More preferably, the capacitance value Cx of the variable capacitance circuit 40 and the resistance value Rx of the variable resistance circuit 50 are set such that the product of the capacitance value and the resistance value is constant. Here, the constant product of the capacitance value and the resistance value may be not only a strictly constant value but also a substantially constant value.

  Although not shown, the variable capacitance circuit 40 can be configured by, for example, a plurality of capacitance elements having different capacitance values and a first switch circuit that selects any one of the plurality of capacitance elements. Although not shown, the variable resistance circuit 50 can be configured by, for example, a plurality of resistance elements having different resistance values and a second switch circuit that selects any one of the plurality of resistance elements. . The first and second switch circuits are controlled based on the adjustment signal SAJ from the control unit 60.

  As described above, while maintaining the electric time constant τel constant, it is possible to increase the combined capacitance Cel and simultaneously decrease the combined resistance Rel, or to decrease the combined capacitance Cel and simultaneously increase the combined resistance Rel. By doing so, the voltage sensitivity Rv of the detection device can be adjusted without changing the frequency region in which the voltage sensitivity Rv is substantially constant.

  Therefore, according to the detection device of the present embodiment, the capacitance value Cx of the variable capacitance circuit 40 and the resistance value Rx of the variable resistance circuit 50 are set variably while keeping the product of both constant (or substantially constant). Thus, the voltage sensitivity Rv of the detection device can be adjusted without changing the frequency region in which the voltage sensitivity Rv is substantially constant.

  Strictly speaking, in order to keep the electric time constant τel constant, the product of the combined capacitance value Cel and the combined resistance value Rel is made constant in consideration of the internal capacitance CA and the internal resistance RA of the pyroelectric element 10. There is a need. However, when the internal capacitance CA is sufficiently small and the internal resistance RA is sufficiently large, the combined capacitance value Cel is substantially equal to the capacitance value Cx of the variable capacitance circuit 40, and the combined resistance value Rel is equal to that of the variable resistance circuit 50. Since the resistance value Rx is almost equal, the electric time constant τel can be kept substantially constant by making the product of Cx and Rx constant. Further, the internal capacitance CA and the internal resistance RA of the pyroelectric element 10 are measured, and Cx and Rx are calculated using the equations (1) and (2) that give the measured value, the combined capacitance value Cel, and the combined resistance value Rel. Thus, Cx and Rx can be set more accurately.

  5A and 5B show a detailed configuration example of the pyroelectric element 10 of the present embodiment. The pyroelectric element 10 of the present embodiment is not limited to the configuration shown in FIGS. 5A and 5B, and some of the components may be omitted or replaced with other components. Various modifications such as adding components are possible.

  FIG. 5A is a plan view of the pyroelectric element 10 as viewed from above. Here, upward refers to a direction perpendicular to the substrate and on the side where pyroelectric elements, transistors, etc. are formed (the side where circuits are formed). The term “lower” refers to the direction opposite to the upper side. FIG. 5B shows a cross section along B-B ′ of FIG.

  The pyroelectric element 10 includes an upper electrode EA, a ferroelectric (pyroelectric) FE, and a lower electrode EB. The ferroelectric (pyroelectric) FE is provided between the upper electrode EA and the lower electrode EB. The pyroelectric element 10 is formed on a membrane (support member) MB.

The membrane (support member) MB is, for example, a silicon oxide film (SiO ₂ ), and is for supporting the pyroelectric element 10.

  The cavity area CAV is an area provided below the membrane MB, and is for thermally separating the pyroelectric element 10 from the substrate (silicon substrate) SUB.

  The post portions (connection portions) PS1 and PS2 are for connecting the membrane MB to a region outside the pyroelectric element 10. These post portions PS1 and PS2 are provided with wirings LA1 and LA2, respectively. The pyroelectric element 10 is connected to the sensitivity adjustment circuit 30, the detection circuit 20, and the first power supply node VSS via the wirings LA1 and LA2.

  The internal capacitance CA of the pyroelectric element 10 is a capacitance of a capacitor formed by the upper electrode EA, the ferroelectric (pyroelectric body) FE, and the lower electrode EB, and the internal electric resistance RA is a ferroelectric material. (Pyroelectric body) The electrical resistance of the path from the upper electrode EA to the lower electrode EB of the FE.

  The heat capacity Cth of the pyroelectric element 10 is mainly a combined heat capacity of each heat capacity of the ferroelectric (pyroelectric) FE, the upper electrode EA, the lower electrode EB, and the membrane MB. The thermal resistance Rth of the pyroelectric element 10 is mainly a combined thermal resistance of the thermal resistances of the post portions PS1 and PS2.

  Although not shown, the detection circuit 20, the sensitivity adjustment circuit 30, and the control unit 60 can be formed on the same substrate SUB, and the pyroelectric element 10 can be connected to the wirings LA1 and LA2. Alternatively, the detection circuit 20, the sensitivity adjustment circuit 30, and the control unit 60 may be formed on another substrate, and these and the pyroelectric element 10 may be connected by appropriate connection means.

  FIG. 6 shows a configuration example of the sensitivity adjustment circuit 30 of the present embodiment. The sensitivity adjustment circuit 30 of this embodiment includes a plurality of adjustment units AJ1 to AJ3 and a switch circuit SW as the variable capacitance circuit 40. Note that the sensitivity adjustment circuit 30 of the present embodiment is not limited to the configuration of FIG. 6, and various components such as omitting some of the components, replacing them with other components, and adding other components. Can be implemented.

  Each unit of the plurality of adjustment units AJ1 to AJ3 includes capacitive elements having different capacitance values. Each of the plurality of adjustment units AJ1 to AJ3 further includes a resistance element connected in parallel to the capacitive element. For example, as shown in FIG. 6, the adjustment unit AJ1 includes a capacitive element (capacitor) CX1 and a resistance element RX1, the adjustment unit AJ2 includes a capacitance element (capacitor) CX2 and a resistance element RX2, and the adjustment unit AJ3 is A capacitance element (capacitor) CX3 and a resistance element RX3 are included.

  The switch circuit SW selectively connects any one of the plurality of adjustment units AJ1 to AJ3 to the pyroelectric element 10. Specifically, for example, the switch circuit SW selects one end of the adjustment unit AJ1 based on the adjustment signal SAJ from the control unit 60 and electrically connects it to the detection node ND. Alternatively, one end of the adjustment unit AJ2 is selected and electrically connected to the detection node ND, or one end of the adjustment unit AJ3 is selected and electrically connected to the detection node ND. The switch circuit SW can be composed of, for example, a CMOS transistor.

  By presetting the product of the capacitance value and resistance value of each of the adjustment units AJ1 to AJ3 to be constant (or almost constant), the capacitance value and resistance value of the sensitivity adjustment circuit 30 are set to the product of both ( The electric time constant τel) can be variably set while being kept constant (or almost constant). By doing so, as described above, the voltage sensitivity Rv of the detection device can be adjusted without changing the frequency region in which the voltage sensitivity Rv is substantially constant.

  For example, when the capacitance values (capacitance values) of the capacitive elements CX1 to CX3 are Cx1 to Cx3 and the resistance values of the resistive elements RX1 to RX3 are Rx1 to Rx3, Cx1 <Cx2 <Cx3, Rx1> Rx2> Rx3, and , Cx1 × Rx1 = Cx2 × Rx2 = Cx3 × Rx3. In this way, if the maximum values of voltage sensitivity when the adjustment units AJ1 to AJ3 are selected are Rvmax1 to Rvmax3, as can be seen from the equation (9), Rvmax1> Rvmax2> Rvmax3. On the other hand, the frequency region where the voltage sensitivity Rv is substantially constant does not change regardless of which of the adjustment units AJ1 to AJ3 is selected.

  As described above, according to the sensitivity adjustment circuit 30 illustrated in FIG. 6, the switch circuit SW selectively connects any one of the plurality of adjustment units AJ1 to AJ3 to the detection node ND based on the adjustment signal SAJ. The voltage sensitivity Rv of the detection device can be adjusted without changing the frequency region in which the voltage sensitivity Rv is substantially constant.

  The number of the plurality of adjustment units is not limited to three, and may be two or four or more.

  FIGS. 7A and 7B show first and second configuration examples of the detection circuit 20 of the present embodiment. The detection circuit 20 of the present embodiment is not limited to the configuration shown in FIGS. 7A and 7B, and some of the components are omitted or replaced with other components. Various modifications such as adding elements are possible.

  The first configuration example shown in FIG. 7A includes an N-type depletion transistor TN and a resistor R. The N-type depletion transistor TN and the resistor R are provided in series between the second power supply node VCC (high potential side power supply node) and the first power supply node VSS (low potential side power supply node), and are a source follower circuit. Is configured.

  The voltage signal ΔV from the pyroelectric element is input to the gate (detection node ND) of the N-type transistor TN, and the source of the N-type transistor TN is connected to one end of the resistor R. These transistors TN and resistors R constitute a source follower circuit, and its gain is almost 1. A detection signal VDET that changes with the voltage signal ΔV is output from the output node NQ corresponding to the source of the N-type transistor TN.

  The detection circuit of the second configuration example illustrated in FIG. 7B includes a first P-type transistor TP1 and a second P-type transistor provided in series between the second power supply node VCC and the first power supply node VSS. Type transistor TP2. These first and second P-type transistors TP1 and TP2 constitute a source follower circuit. That is, for a small signal amplitude change of the voltage signal ΔV from the pyroelectric element, a voltage having an amplitude with a gain of approximately 1 is output as the detection signal VDET (output voltage).

  The first P-type transistor TP1 (P-type MOS transistor) is provided between the output node NQ of the detection circuit and the first power supply node VSS (low potential side power supply node). For example, in FIG. 7B, the source of TP1 is connected to the output node NQ, the drain is connected to the first power supply node VSS, and the voltage signal ΔV from the pyroelectric element is input to the gate.

  The second P-type transistor TP2 (P-type MOS transistor) is provided between the second power supply node VCC (high potential side power supply node) and the output node NQ. For example, in FIG. 7B, the source of TP2 is connected to the second power supply node VCC, the drain is connected to the output node NQ, and the gate is set to the reference voltage VR = Vcc−Vconst. Here, Vcc represents the voltage of the high potential side power supply VCC, and Vconst is a constant voltage (fixed voltage).

  Further, the substrate potential of the P-type transistor TP1 is set to the potential of the source of TP1. For example, in FIG. 7B, the substrate potential of TP1 is connected to the output node NQ. The substrate potential of the P-type transistor TP2 is set to the potential of the source of TP2. For example, in FIG. 7B, the substrate potential of TP2 is connected to the second power supply node VCC. Since the substrate potentials of the P-type transistors TP1 and TP2 are set to their source potentials in this way, fluctuations in the threshold voltages of TP1 and TP2 due to the substrate bias effect can be prevented. , Can be closer. It is also possible to perform a modification in which the substrate potentials of the P-type transistors TP1 and TP2 are both set to the VCC potential.

  The P-type transistors TP1 and TP2 have the same gate length and / or gate width. More preferably, both TP1 and TP2 have the same gate length and gate width. In this way, it is possible to make the device characteristics such as the threshold voltages of the P-type transistors TP1 and TP2 closer to each other, and the fluctuation of the detection signal VDET due to the manufacturing process fluctuation or the like can be suppressed.

3. Sensor Device FIG. 8 shows a first configuration example of the sensor device of this embodiment. The sensor device includes a pyroelectric element 10, a detection circuit 20, a sensitivity adjustment circuit 30, a control unit 60, a signal processing circuit 70, a control mode switching unit 80, a chopper 90, a chopper drive unit 91, and a chopping control circuit 92.

  Since the pyroelectric element 10, the detection circuit 20, the sensitivity adjustment circuit 30, and the control unit 60 are as described above, the description thereof is omitted here.

  The signal processing circuit 70 receives the detection signal VDET from the detection circuit 20 and performs necessary signal processing. Specifically, for example, a detection signal VDET that is an analog signal is converted into a digital signal and output as digital data DOUT, or a setting signal for setting detection sensitivity according to the intensity of infrared light from the object Generate and output. The setting signal is generated according to the signal level (voltage level) of the detection signal VDET, and the control unit 60 outputs the adjustment signal SAJ based on the setting signal. By doing so, the voltage sensitivity Rv of the detection device can be automatically adjusted so that the detection signal VDET has an appropriate signal level.

  The control mode switching unit 80 can switch whether the voltage sensitivity Rv is adjusted automatically or manually. That is, when the control mode is the automatic mode, the voltage sensitivity Rv is automatically adjusted based on the setting signal from the signal processing circuit 70, while when the control mode is the manual mode, the user inputs it. The voltage sensitivity Rv is adjusted based on the setting signal.

  The chopper 90 is for periodically blocking infrared light incident on the pyroelectric element 10 at a predetermined frequency (chopping frequency). By doing so, since the temperature of the pyroelectric element 10 changes periodically, a pyroelectric current is generated and an output voltage VA is generated. The chopper 90 is driven by a chopper driving unit 91.

  The chopping control circuit 92 controls the chopper driving unit 91 so that the chopping frequency becomes a predetermined frequency.

  9A and 9B show a second configuration example of the sensor device according to the present embodiment. The sensor device includes a sensor array 100, a row selection circuit (row driver) 110, and a readout circuit 120. An A / D conversion unit 130, a column scanning circuit 140, and a control circuit 150 can be included. By using this sensor device, for example, an infrared camera used in a night vision device or the like can be realized.

  A plurality of sensor cells are arranged (arranged) in the sensor array 100 (focal plane array). A plurality of row lines (word lines, scanning lines) and a plurality of column lines (data lines) are provided. One of the row lines and the column lines may be one. For example, when there is one row line, a plurality of sensor cells are arranged in a direction (lateral direction) along the row line in FIG. On the other hand, when there is one column line, a plurality of sensor cells are arranged in a direction (vertical direction) along the column line.

  As shown in FIG. 9B, each sensor cell of the sensor array 100 is arranged (formed) at a location corresponding to the intersection position of each row line and each column line. For example, the sensor cell of FIG. 9B is disposed at a location corresponding to the intersection position of the row line WL1 and the column line DL1. The same applies to other sensor cells.

Although not shown, each sensor cell of the plurality of sensor cells includes a pyroelectric element 10, a sensitivity adjustment circuit 30, and a detection circuit 20. The sensitivity adjustment circuit 30 includes a variable capacitance circuit 40 for sensitivity adjustment. The row selection circuit 110 is connected to one or a plurality of row lines. Then, each row line is selected. For example, taking a QVGA (320 × 240 pixel) sensor array 100 (focal plane array) as shown in FIG. 9B as an example, row lines WL0, WL1, WL2,... WL239 are sequentially selected (scanned). Perform the action. That is, a signal (word selection signal) for selecting these row lines is output to the sensor array 100.

  The read circuit 120 is connected to one or more column lines. Then, a read operation for each column line is performed. Taking the QVGA sensor array 100 as an example, an operation of reading detection signals (detection current, detection charge) from the column lines DL0, DL1, DL2,.

  The A / D conversion unit 130 performs a process of A / D converting the detection voltage (measurement voltage, ultimate voltage) acquired in the readout circuit 120 into digital data. Then, the digital data DOUT after A / D conversion is output. Specifically, the A / D converter 130 is provided with each A / D converter corresponding to each of the plurality of column lines. Each A / D converter performs A / D conversion processing of the detection voltage acquired by the reading circuit 120 in the corresponding column line. Note that one A / D converter is provided corresponding to a plurality of column lines, and the detection voltage of the plurality of column lines can be A / D converted in a time division manner using this one A / D converter. Good.

  The column scanning circuit 140 performs an operation for sequentially selecting (scanning) each column (row) and outputting digital data after A / D conversion of each column as time series data. Note that the digital data of each column may be output in parallel (in parallel) without providing the column scanning circuit 140.

  The control circuit 150 (timing generation circuit) generates various control signals and outputs them to the row selection circuit 110, the readout circuit 120, the A / D conversion unit 130, and the column scanning circuit 140. For example, a charge or discharge (reset) control signal is generated and output. Alternatively, a signal for controlling the timing of each circuit is generated and output. The control circuit 150 may generate and output an adjustment signal SAJ for sensitivity adjustment.

  As described above, according to the sensor device of the present embodiment, the voltage sensitivity Rv of the sensor device can be adjusted by variably setting the composite capacitor Cel by the sensitivity adjustment circuit 30. By adjusting the voltage sensitivity Rv, for example, it is possible to adjust to a sensitivity suitable for the temperature range (high temperature, normal temperature, low temperature, etc.) of the object (detection target). Further, in the sensor array, it is possible to correct the sensitivity variation between the sensor cells. As a result, it is possible to accurately and stably detect the nighttime object image, the temperature distribution of the object, and the like.

4). Electronic Device FIG. 10 shows a configuration example of an electronic device including the sensor device of the present embodiment. The electronic apparatus is, for example, an infrared camera, and includes an optical system 200, a sensor device 210, an image processing unit 220, a processing unit 230, a storage unit 240, an operation unit 250, and a display unit 260. Note that the electronic apparatus according to the present embodiment is not limited to the configuration shown in FIG. Can be implemented.

  The optical system 200 includes, for example, one or a plurality of lenses and a driving unit that drives these lenses. Then, an object image is formed on the sensor device 210. If necessary, focus adjustment is also performed.

  The sensor device 210 is the one described with reference to FIG. 9A and the like, and performs an object image capturing process. The image processing unit 220 performs various image processing such as image correction processing based on digital image data (pixel data) from the sensor device 210.

  The processing unit 230 controls the entire electronic device and controls each block in the electronic device. The processing unit 230 is realized by a CPU or the like, for example. The storage unit 240 stores various types of information, and functions as a work area for the processing unit 230 and the image processing unit 220, for example. The operation unit 250 serves as an interface for the user to operate the electronic device, and is realized by various buttons or a GUI (Graphical User Interface) screen, for example. The display unit 260 displays, for example, an image acquired by the sensor device 210, a GUI screen, and the like, and is realized by various displays such as a liquid crystal display and an organic EL display, a projection display device, and the like.

  The present embodiment can be applied to an infrared camera using an FPA (Focal Plane Array) and an electronic device using the infrared camera. Electronic devices to which infrared cameras are applied include, for example, night vision devices that capture night-time object images, thermographic devices that acquire the temperature distribution of objects, intrusion detection devices that detect human intrusions, and analysis (measurement of physical information on objects) Analysis equipment (measuring equipment), security equipment that detects fire and heat generation, FA (Factory Automation) equipment installed in factories, etc. can be assumed. If a night vision device is applied to an in-vehicle device, it is possible to detect and display the appearance of a person at night when the vehicle is running. If applied to a thermographic device, it can be used for influenza quarantine.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Therefore, all such modifications are included in the scope of the present invention. For example, in the specification or drawings, terms (membrane, post portion, etc.) described together with different terms (supporting member, connection portion, etc.) having a broader meaning or the same meaning at least once are used in any part of the specification or drawings. It can be replaced by that different term. Further, the configurations and operations of the detection device, the sensor device, and the electronic apparatus are not limited to those described in this embodiment, and various modifications can be made.

10 pyroelectric elements, 20 detection circuits, 30 sensitivity adjustment circuits, 40 variable capacitance circuits,
50 variable resistance circuit, 60 control unit, 70 signal processing circuit, 80 control mode switching unit,
90 chopper, 91 chopper drive, 92 chopping control circuit,
100 sensor array, 110 row selection circuit (row driver),
120 readout circuit, 130 A / D converter, 140 column scanning circuit,
150 control circuit, 200 optical system, 210 sensor device, 220 image processing unit,
230 processing unit (CPU), 240 storage unit, 250 operation unit, 260 display unit,
AJ1 to AJ3 adjustment unit, SAJ adjustment signal, SW switch circuit,
ND detection node, VSS first power supply node

Claims (13)

A pyroelectric element;
A sensitivity adjustment circuit that is connected to the pyroelectric element and adjusts the voltage sensitivity of the output voltage of the pyroelectric element;
A detection circuit connected to the pyroelectric element,
The sensitivity adjustment circuit includes:
A detection device comprising a variable capacitance circuit for sensitivity adjustment. In claim 1,
The sensitivity adjustment circuit includes:
The detection apparatus further comprising a variable resistance circuit connected in parallel to the variable capacitance circuit. In claim 2,
The detection device, wherein the resistance value of the variable resistance circuit is set to a larger value as the capacitance value of the variable capacitance circuit is smaller. In claim 3,
The detection device characterized in that the capacitance value of the variable capacitance circuit and the resistance value of the variable resistance circuit are set so that a product of the capacitance value and the resistance value is constant. In any of claims 2 to 4,
The sensitivity adjustment circuit, as the variable capacitance circuit,
A plurality of adjustment units each having a capacitive element having a capacitance value different from each other;
A detection apparatus comprising: a switch circuit that selectively connects any one of the plurality of adjustment units to the pyroelectric element. In claim 5,
Each of the plurality of adjustment units further includes a resistance element connected in parallel to the capacitive element. In any one of Claims 3 thru | or 6.
Including a control unit that outputs an adjustment signal for sensitivity adjustment;
The detection device, wherein a capacitance value of the variable capacitance circuit is variably set based on the adjustment signal. In claim 7,
The detection device, wherein a resistance value of the variable resistance circuit is variably set based on the adjustment signal. In any of claims 2 to 8,
The maximum value of the voltage sensitivity is Rvmax, the absorption rate of the pyroelectric element is ε, the pyroelectric coefficient is p, the area of the pyroelectric element is S, the thermal resistance of the pyroelectric element is Rth, the inside of the pyroelectric element When the combined capacitance value of the capacitance and the variable capacitance circuit is Cel,
The maximum value Rvmax of the voltage sensitivity is given by an approximate expression of Rvmax = ε × p × S × Rth / Cel,
By adjusting the capacitance value of the variable capacitance circuit, the combined capacitance value Cel is adjusted by the variable capacitance circuit,
The detection apparatus, wherein the maximum value Rvmax of the voltage sensitivity is adjusted by adjusting the combined capacitance value Cel. In any of claims 2 to 8,
The maximum value of the voltage sensitivity is Rvmax, the absorption rate of the pyroelectric element is ε, the pyroelectric coefficient is p, the area of the pyroelectric element is S, the thermal resistance of the pyroelectric element is Rth, the inside of the pyroelectric element Rel is the combined resistance value of the electrical resistance and the variable resistance circuit, and the combined capacitance value of the internal capacitance of the pyroelectric element and the variable capacitance circuit, and the internal electrical resistance of the pyroelectric element and the variable resistance circuit. When the electrical time constant that is the product of the combined resistance value is τel,
The maximum value Rvmax of the voltage sensitivity is given by an approximate expression of Rvmax = ε × p × S × Rel × Rth / τel,
The combined resistance value Rel is adjusted by the variable resistance circuit by adjusting the resistance value of the variable resistance circuit while keeping the electric time constant τel constant.
The detection device characterized in that the maximum value Rvmax of the voltage sensitivity is adjusted by adjusting the combined resistance value Rel.   A sensor device comprising the detection device according to claim 1. A sensor array having a plurality of sensor cells;
One or more row lines;
One or more column lines;
A row selection circuit connected to the one or more row lines;
A readout circuit connected to the one or more column lines,
Each sensor cell of the plurality of sensor cells is
A pyroelectric element;
A sensitivity adjustment circuit that is connected to the pyroelectric element and adjusts the voltage sensitivity of the output voltage of the pyroelectric element;
A detection circuit connected to the pyroelectric element,
The sensitivity adjustment circuit includes:
A sensor device comprising a variable capacitance circuit for sensitivity adjustment.   An electronic apparatus comprising the sensor device according to claim 11.

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