Patent Description:
<CIT> discloses a pyroelectric infrared detection element of dual twin type. The pyroelectric infrared detection element disclosed in <CIT> includes two H-shaped light receiving electrodes. The two light receiving electrodes are connected to separate detection circuits in one-to-one relation. The two light receiving electrodes have different infrared detection-target regions. More specifically, a detection-target region of a first light receiving electrode is a region where infrared light from a small animal, such as a dog, or a moving heat-source body (such as a self-propelled cleaner) is not detected, and where infrared light from a human being can be detected. A detection-target region of a second light receiving electrode is a region where the infrared light mainly from the small animal or the moving heat-source body can be detected.

In the pyroelectric infrared detection element disclosed in <CIT>, detection of the human being and detection of the small animal are discriminated by separately using outputs of two detection circuits.

However, the pyroelectric infrared detection element disclosed in <CIT> is required to include the detection circuit for each of the light receiving electrodes. Thus, the pyroelectric infrared detection has a complicated structure and a larger-sized shape.

Accordingly, we have appreciated that it is desirable to provide a pyroelectric infrared detection element having a small size and being able to reliably detect plural types of detection targets.

<CIT> provides means to correct a decrease of an infrared radiation reception amount at a peripheral part of a sensor array region, in an infrared sensor device including the sensor array region having a plurality of pixels each having an infrared absorption film and a temperature sensor arranged in line or in matrix and a condensing lens arranged opposite to the sensor array region. To do this an infrared sensor device is provided which comprises: a sensor array region having a plurality of pixels each having an infrared absorption film and a temperature sensor arranged in line; and a condensing lens arranged opposite to the sensor array region. The infrared detection sensitivity of a pixel is changed to be higher from a centre part to a peripheral part of the sensor array region <NUM> according to an area change of the infrared absorption film.

<CIT> provides a radiation sensor which comprises plural radiation sensing elements arranged along an arrangement line, a lens having an optical axis focusing radiation towards the sensing elements, and circuitry receiving the electric signal of the sensing elements and providing an output signal, in which the midpoint of the arrangement line is offset against the optical axis of the converging section. Some of the sensing elements may have different sizes and have different relative sensitivity compared to each other. Two or more pairs of adjacent sensing elements have a different pitch.

<CIT> provides an infrared detection element which includes first and second pyroelectric elements arranged in a single pyroelectric substrate. First pyroelectric element includes a first surface electrode, a first back face electrode, and a first portion interposed between first surface and back face electrodes. First portion is provided as part of pyroelectric substrate. Second pyroelectric element includes a second surface electrode, a second back face electrode, and a second portion interposed between second surface and back face electrodes. Second portion is provided as part of pyroelectric substrate. Pyroelectric substrate is provided in part thereof surrounding first pyroelectric element with a slit shaped along an outer periphery of first pyroelectric element. Slit is formed out of regions in which a first surface wiring and a first back face wiring are disposed. Part of pyroelectric substrate surrounding second pyroelectric element is continuously formed over an entire circumference of second portion.

An infrared detection device according to the present invention is disclosed in independent claim <NUM>.

In the infrared detection element according to the present invention, preferably, the light-sensitivity adjustment member is an infrared absorption film arranged only on a surface of the first light receiving electrode.

With the above-described feature, the difference between the infrared detection sensitivity for the first region and the infrared detection sensitivity for the second region is increased.

The infrared detection element according to the present invention may be constituted as follows. The light-sensitivity adjustment member is a first infrared absorption film arranged on a surface of the first light receiving electrode, and a second infrared absorption film arranged on a surface of the second light receiving electrode. The first infrared absorption film has a higher infrared absorbance than the second infrared absorption film.

With the above-described features, the difference between the infrared detection sensitivity for the first region and the infrared detection sensitivity for the second region is adjusted depending on the difference in infrared absorbance.

In the infrared detection element according to the present invention, a coverage of the first infrared absorption film with respect to the first light receiving electrode may be higher than a coverage of the second infrared absorption film with respect to the second light receiving electrode.

With the above-described feature, the difference between the infrared detection sensitivity for the first region and the infrared detection sensitivity for the second region is adjusted depending on the coverage.

In the infrared detection element according to the present invention, the first light receiving electrode has a higher infrared absorbance than the second light receiving electrode.

With the above-described feature, the difference in infrared absorbance is obtained depending on electrode materials.

The infrared detection element according to the present invention may be constituted as follows. A polarizability of the pyroelectric body is different between a first region in which the first light receiving electrode is formed on the surface of the pyroelectric body and a second region in which the second light receiving electrode is formed on the surface of the pyroelectric body. The first region has a higher polarizability than the second region.

The infrared detection element according to the present invention may be constituted as follows. A thickness of the pyroelectric body is different between a first region in which the first light receiving electrode is formed and a second region in which the second light receiving electrode is formed. The pyroelectric body in the first region has a smaller thickness than that of the pyroelectric body in the second region.

With the above-described features, the difference in sensitivity for the infrared light between detection signals is obtained depending on the constitution of the pyroelectric body.

An infrared detection device according to the present invention includes a first element, a second element, a connection portion, an impedance conversion element, and a determination unit. The first element includes a first light receiving electrode and a pyroelectric body. The second element includes a second light receiving electrode and a pyroelectric body. The connection portion interconnects the first element and the second element. The impedance conversion element generates detection signals from electric charges in the first element and the second element through the connection portion. The determination unit determines detection of infrared light on the basis of the detection signals.

With the above-described features, detection of the infrared light from the first region and detection of the infrared light from the second region are realized with one impedance conversion element and one determination unit.

According to the present invention, the pyroelectric infrared detection element capable of reliably detecting plural types of detection targets can be realized in a small size.

An infrared detection element and an infrared detection device according to a first embodiment of the present invention will be described below with reference to the drawings. <FIG> is a plan view of the infrared detection element according to the first embodiment of the present invention. <FIG> is a sectional view taken along A-A in <FIG>.

As illustrated in <FIG>, the infrared detection element <NUM> includes a pyroelectric body <NUM>, a light receiving electrode <NUM>, a light receiving electrode <NUM>, a blackened film <NUM>, a blackened film <NUM>, and connection electrodes <NUM> and <NUM>. The light receiving electrode <NUM> corresponds to a "first light receiving electrode" in the present invention, and the light receiving electrode <NUM> corresponds to a "second light receiving electrode" in the present invention. The blackened film <NUM> corresponds to a "first blackened film" in the present invention, and the blackened film <NUM> corresponds to a "second blackened film" in the present invention.

The pyroelectric body <NUM> is made of a material generating the pyroelectric effect. The pyroelectric body <NUM> is made of, for example, a ferroelectric material. The pyroelectric body <NUM> is in the form of a flat plate.

The light receiving electrode <NUM> and the light receiving electrode <NUM> are formed on a front surface of the pyroelectric body <NUM>.

The light receiving electrode <NUM> includes detection electrodes <NUM> and <NUM>, and a wiring electrode <NUM>. The detection electrodes <NUM> and <NUM> are each rectangular when viewed in plan. The detection electrodes <NUM> and <NUM> are arranged in spaced relation along a first direction. The wiring electrode <NUM> is a linear electrode extending along the first direction. The wiring electrode <NUM> interconnects the detection electrode <NUM> and the detection electrode <NUM>. A length of the wiring electrode <NUM> along a second direction is shorter than that of the detection electrode <NUM> along the second direction and that of the detection electrode <NUM> along the second direction. Thus, the light receiving electrode <NUM> is an H-shaped electrode when viewed in plan. The detection electrode <NUM> and the detection electrode <NUM> preferably have the same shape. With the detection electrode <NUM> and the detection electrode <NUM> having the same shape, infrared detection accuracy is improved because both the detection electrodes are balanced to each other and stabilized with respect to variations of outside air temperature.

The light receiving electrode <NUM> includes detection electrodes <NUM> and <NUM>, and a wiring electrode <NUM>. The detection electrodes <NUM> and <NUM> are each rectangular when viewed in plan. The detection electrodes <NUM> and <NUM> are arranged in spaced relation along the first direction. The wiring electrode <NUM> is a linear electrode extending along the first direction. The wiring electrode <NUM> interconnects the detection electrode <NUM> and the detection electrode <NUM>. A length of the wiring electrode <NUM> along the second direction is shorter than that of the detection electrode <NUM> along the second direction and that of the detection electrode <NUM> along the second direction. Thus, the light receiving electrode <NUM> is an H-shaped electrode when viewed in plan. The detection electrode <NUM> and the detection electrode <NUM> preferably have the same shape. With the detection electrode <NUM> and the detection electrode <NUM> having the same shape, infrared detection accuracy is improved.

The light receiving electrode <NUM> and the light receiving electrode <NUM> are arranged side by side in the second direction. The light receiving electrode <NUM> and the light receiving electrode <NUM> are spaced from each other.

The blackened film <NUM> is arranged over an entire surface of the detection electrode <NUM> in the light receiving electrode <NUM>. The blackened film <NUM> is arranged over an entire surface of the detection electrode <NUM> in the light receiving electrode <NUM>. In other words, the blackened films <NUM> and <NUM> are arranged only on the surfaces of the detection electrodes <NUM> and <NUM> in the light receiving electrode <NUM>. The blackened films <NUM> and <NUM> correspond to "infrared absorption films" in the present invention.

With the above-described constitution, infrared reception sensitivity of the light receiving electrode <NUM> becomes higher than that of the light receiving electrode <NUM>. Each of the blackened films <NUM> and <NUM> corresponds to a "light-sensitivity adjustment member" in the present invention.

Thus, detection sensitivity for infrared light detected by the light receiving electrode <NUM> becomes higher than that for infrared light detected by the light receiving electrode <NUM>. Accordingly, infrared detection sensitivity in a first infrared-detection target region (corresponding to a "first region" in the present invention) assigned to the light receiving electrode <NUM> is different from that in a second infrared-detection target region (corresponding to a "secondregion" in the present invention) assigned to the light receiving electrode <NUM>. The infrared detection element <NUM> constituted as described above enables detection of infrared light to be performed for plural regions providing different detection sensitivities with a simple constitution. As a result, a size of the infrared detection element <NUM> can be reduced.

The connection electrodes <NUM> and <NUM> are formed on a rear surface of the pyroelectric body <NUM>. The connection electrode <NUM> is opposed to the detection electrode <NUM> in the light receiving electrode <NUM> and the detection electrode <NUM> in the light receiving electrode <NUM> with the pyroelectric body <NUM> interposed therebetween. The connection electrode <NUM> is opposed to the detection electrode <NUM> in the light receiving electrode <NUM> and the detection electrode <NUM> in the light receiving electrode <NUM> with the pyroelectric body <NUM> interposed therebetween.

The infrared detection element <NUM> constituted as described above is used in an infrared detection device illustrated in <FIG> is a circuit diagram of the infrared detection device according to the first embodiment of the present invention.

As illustrated in <FIG>, the infrared detection device <NUM> includes an infrared detection element <NUM>, an impedance conversion element <NUM>, and a determination unit <NUM>. The infrared detection element <NUM> and the impedance conversion element <NUM> constitute an infrared sensor <NUM>. The infrared sensor <NUM> has a ground terminal PG, a drive-voltage input terminal PD, and an output terminal PO.

The infrared detection element <NUM> has the above-described constitution illustrated in <FIG>. The infrared detection element <NUM> includes a first element E1 including the light receiving electrode <NUM> and the pyroelectric body <NUM>, and a second element E2 including the light receiving electrode <NUM> and the pyroelectric body <NUM>. The first element E1 and the second element E2 are connected in parallel by the connection electrode <NUM> and the connection electrode <NUM>.

The infrared detection element <NUM> is connected to the impedance conversion element <NUM> through the connection electrode <NUM>. The connection electrode <NUM> corresponds to a "connection portion" in the present invention. The infrared detection element <NUM> is connected to the ground terminal PG through the connection electrode <NUM>. The ground terminal PG is grounded.

The impedance conversion element <NUM> is constituted by an n-type FET, for example. A gate G of the n-type FET is connected to the connection electrode <NUM>. A drain of the n-type FET is connected to the drive-voltage input terminal PD. A source of the n-type FET is connected to the output terminal PO.

The determination unit <NUM> is constituted by a microcomputer, etc. The determination unit <NUM> is connected to the output terminal PO of the infrared sensor <NUM>.

When the infrared detection element <NUM> detects infrared light, a voltage depending on generated electric charges is applied to the gate of the n-type FET constituting the impedance conversion element <NUM>. A drive voltage VDD is applied to the impedance conversion element <NUM> via the drive-voltage input terminal PD. The impedance conversion element <NUM> outputs a source voltage having a magnitude depending on the gate voltage. This source voltage signal corresponds to a "detection signal" in the present invention.

The determination unit <NUM> executes detection of the infrared light on the basis of the magnitude of the source voltage signal.

In the infrared detection element <NUM>, infrared detection sensitivity is different between the first element E1 including the light receiving electrode <NUM> and the second element E2 including the light receiving electrode <NUM>. Accordingly, electric charges generated in detecting the infrared light are different between the first infrared-detection target region, i.e., a detection target of the first element E1, and the second infrared-detection target region, i.e., a detection target of the second element E2. Hence the magnitude (amplitude) of the detection signal output from the impedance conversion element <NUM> is also different therebetween.

By detecting the magnitude of the detection signal, the determination unit <NUM> can easily determine in which one of the first infrared-detection target region and the second infrared-detection target region the infrared light has been detected.

Furthermore, the determination unit <NUM> previously stores a threshold for the magnitude of the detection signal, and compares the detection signal with the threshold. Depending on a comparison result, if the magnitude of the detection signal is not smaller than the threshold, the determination unit <NUM> determines that the infrared light has been detected. Thus, the infrared detection device <NUM> can realize the detection of the infrared light in a manner of restricting (or exclusively aiming at) the detection target.

<FIG> illustrates an application example of the infrared detection device according to the present invention. In the example of <FIG>, the infrared detection device <NUM> includes an optical element OE. In the infrared detection device, the first infrared-detection target region TGR1 is set as a region targeting a human being, but not targeting a small animal, such as a dog, or a moving low-height heat source body. The second infrared-detection target region TGR2 is set to mainly target the small animal, such as the dog, or the moving low-height heat source body, and to allow part of the human being to be included therein.

With the above-described setting, in the infrared detection element <NUM> and the infrared detection device <NUM>, the detection sensitivity can be increased for the region targeting the human being, but not targeting the small animal, and can be reduced for the region targeting the small animal. Accordingly, the infrared detection element <NUM> and the infrared detection device <NUM>, each reliably detecting the human being and reliably not detecting the small animal, can be realized. Moreover, the infrared detection device <NUM> is not required to include the detection circuit for each element, i.e., for each detection-target region. As a result, the infrared detection device <NUM> can be realized in a small size with a simple constitution.

An infrared detection element according to a second embodiment of the present invention will be described below with reference to the drawing. <FIG> is a plan view illustrating a constitution of the infrared detection element according to the second embodiment of the present invention.

As illustrated in <FIG>, the infrared detection element 10A according to the second embodiment is different from the infrared detection element <NUM> according to the first embodiment in adding blackened films <NUM> and <NUM>. Other constituent elements of the infrared detection element 10A are similar to those of the infrared detection element <NUM>, and description of the same constituent elements is omitted.

The infrared detection element 10A includes the blackened films <NUM> and <NUM>. Each of the blackened films <NUM> and <NUM> corresponds to the "light-sensitivity adjustment member" in the present invention. The blackened film <NUM> is formed on a surface of the detection electrode <NUM> in the light receiving electrode <NUM>. The blackened film <NUM> covers part of the detection electrode <NUM>. More specifically, the blackened film <NUM> is formed along sides of the detection electrode <NUM>. The blackened film <NUM> is not formed in a central region of the detection electrode <NUM>. The blackened film <NUM> is formed on a surface of the detection electrode <NUM> in the light receiving electrode <NUM>. The blackened film <NUM> covers part of the detection electrode <NUM>. More specifically, the blackened film <NUM> is formed along sides of the detection electrode <NUM>. The blackened film <NUM> is not formed in a central region of the detection electrode <NUM>.

With the above-described constitution, a coverage of the blackened films <NUM> and <NUM> with respect to the surface of the light receiving electrode <NUM> can be made different from that of the blackened films <NUM> and <NUM> with respect to the surface of the light receiving electrode <NUM>. Accordingly, the light sensitivity of the light receiving electrode <NUM> can be made different from that of the light receiving electrode <NUM>. Furthermore, with the above-described constitution, the sensitivity difference between the light sensitivity of the light receiving electrode <NUM> and the light sensitivity of the light receiving electrode <NUM> can be adjusted by adjusting the coverage of the blackened films <NUM> and <NUM> with respect to the surface of the light receiving electrode <NUM>.

An infrared detection element according to a third embodiment of the present invention will be described below with reference to the drawing. <FIG> is a plan view illustrating a constitution of the infrared detection element according to the third embodiment of the present invention.

As illustrated in <FIG>, the infrared detection element 10B according to the third embodiment is different from the infrared detection element <NUM> according to the first embodiment in adding blackened films 151B and 152B. Other constituent elements of the infrared detection element 10B are similar to those of the infrared detection element <NUM>, and description of the same constituent elements is omitted.

The infrared detection element 10B includes the blackened films 151B and 152B. Each of the blackened films 151B and 152B corresponds to the "light-sensitivity adjustment member" in the present invention. The blackened film 151B is formed over the entire surface of the detection electrode <NUM> in the light receiving electrode <NUM>. The blackened film 152B is formed over the entire surface of the detection electrode <NUM> in the light receiving electrode <NUM>.

An infrared absorbance of the blackened films 151B and 152B is lower than that of the blackened films <NUM> and <NUM>.

Also with the above-described constitution, the light sensitivity of the light receiving electrode <NUM> can be made different from that of the light receiving electrode <NUM>.

Furthermore, with the above-described constitution, the difference between the light sensitivity of the light receiving electrode <NUM> and the light sensitivity of the light receiving electrode <NUM> can be adjusted by adjusting the difference between the infrared absorbance of the blackened films <NUM> and <NUM> and the infrared absorbance of the blackened films 151B and 152B.

An infrared detection element according to a fourth embodiment of the present invention will be described below with reference to the drawing. <FIG> is a side sectional view illustrating a constitution of the infrared detection element according to the fourth embodiment of the present invention.

As illustrated in <FIG>, the infrared detection element 10C according to the fourth embodiment is different from the infrared detection element <NUM> according to the first embodiment in including a light receiving electrode 120C instead of the light receiving electrode <NUM>. Other constituent elements of the infrared detection element 10C are similar to those of the infrared detection element <NUM>, and description of the same constituent elements is omitted.

The infrared detection element 10C includes the light receiving electrode 120C. The light receiving electrode 120C has the same shape as the light receiving electrode <NUM> in the first embodiment. An infrared absorbance of the light receiving electrode 120C (i.e., the electrode including the detection electrode 122C in <FIG>) is lower than that of the light receiving electrode <NUM> (i.e., the electrode including the detection electrode <NUM> in <FIG>).

Also with the above-described constitution, the light sensitivity of the light receiving electrode <NUM> can be made different from that of the light receiving electrode 120C. Furthermore, with the above-described constitution of the infrared detection element 10C, the difference in infrared detection sensitivity between the first element E1 and the second element E2 can be further increased due to the synergetic effect of both the difference in light sensitivity between the light receiving electrode <NUM> and the light receiving electrode <NUM>, which is caused by the presence of the blackened films <NUM> and <NUM>, and the difference in light sensitivity between the light receiving electrode <NUM> and the light receiving electrode 120C, which is caused by materials of those electrodes.

Moreover, with the above-described constitution, the sensitivity difference between the light sensitivity of the light receiving electrode <NUM> and the light sensitivity of the light receiving electrode 120C can be adjusted by adjusting the difference between the infrared absorbance of the light receiving electrode <NUM> and the infrared absorbance of the light receiving electrode 120C.

An infrared detection element according to a fifth embodiment of the present invention will be described below with reference to the drawing. <FIG> is a side sectional view illustrating a constitution of the infrared detection element according to the fifth embodiment of the present invention.

As illustrated in <FIG>, the infrared detection element 10D according to the fifth embodiment is different from the infrared detection element <NUM> according to the first embodiment in constitution of a pyroelectric body 101D. Other constituent elements of the infrared detection element 10D are similar to those of the infrared detection element <NUM> according to the first embodiment, and description of the same constituent elements is omitted.

The infrared detection element 10D includes the pyroelectric body 101D. The pyroelectric body 101D includes a first region <NUM> and a second region <NUM>. The first region <NUM> and the second region <NUM> are arrayed side by side in the second direction. A polarizability of the first region <NUM> is higher than that of the second region <NUM>. The light receiving electrode <NUM> is formed on a surface of the first region <NUM>. The light receiving electrode <NUM> is formed on a surface of the second region <NUM>.

With the above-described constitution, the difference in infrared detection sensitivity between the first element E1 and the second element E2 can be increased. Moreover, with the constitution of the infrared detection element 10D, the difference in infrared detection sensitivity between the first element E1 and the second element E2 can be further increased due to the synergetic effect of both the difference in light sensitivity between the light receiving electrode <NUM> and the light receiving electrode <NUM>, which is caused by the presence of the blackened films <NUM> and <NUM>, and the difference in polarizability between the first region <NUM> and the second region <NUM> of the pyroelectric body 101D.

An infrared detection element according to a sixth embodiment of the present invention will be described below with reference to the drawing. <FIG> is a side sectional view illustrating a constitution of the infrared detection element according to the sixth embodiment of the present invention.

As illustrated in <FIG>, the infrared detection element 10E according to the sixth embodiment is different from the infrared detection element <NUM> according to the first embodiment in constitution of a pyroelectric body 101E. Other constituent elements of the infrared detection element 10E are similar to those of the infrared detection element <NUM> according to the first embodiment, and description of the same constituent elements is omitted.

The infrared detection element 10E includes the pyroelectric body 101E. The pyroelectric body 101E includes a first region <NUM> and a second region <NUM>. The first region <NUM> and the second region <NUM> are arrayed side by side in the second direction. A thickness of the first region <NUM> is smaller than that of the second region <NUM>. The light receiving electrode <NUM> is formed on a surface of the first region <NUM>. The light receiving electrode <NUM> is formed on a surface of the second region <NUM>. Because of having the above-described constitution, a capacitance formed in the first region <NUM> between the light receiving electrode <NUM> and each of the connection electrodes <NUM> and <NUM> is greater than that formed in the second region <NUM> between the light receiving electrode <NUM> and each of the connection electrodes <NUM> and <NUM>.

With the above-described constitution, the difference in infrared detection sensitivity between the first element E1 and the second element E2 can be increased. Moreover, with the constitution of the infrared detection element 10E, the difference in infrared detection sensitivity between the first element E1 and the second element E2 can be further increased due to the synergetic effect of both the difference in light sensitivity between the light receiving electrode <NUM> and the light receiving electrode <NUM>, which is caused by the presence of the blackened films <NUM> and <NUM>, and the difference in thickness between the first region <NUM> and the second region <NUM> of the pyroelectric body 101E.

The constitutions of the above-described embodiments can be combined with each other as appropriate. Various advantageous effects can be obtained depending on the combinations of the constitutions.

The first embodiment illustrates the constitution in which the first element E1 and the second element E2 are connected in parallel. However, the constitution may be modified as illustrated in <FIG> is a circuit diagram of an infrared detection device in another form according to an embodiment of the present invention.

As illustrated in <FIG>, in an infrared detection element 10F, the first element E1 and the second element E2 are connected in series. In an infrared detection device 30F, the serial circuit is connected between the impedance conversion element <NUM> and the ground terminal PG.

The above-described constitution can also provide similar advantageous to those obtained with the infrared detection element <NUM> and the infrared detection device <NUM>, illustrated in <FIG>, according to the first embodiment.

Claim 1:
An infrared detection device (<NUM>) comprising;
an infrared detection element (<NUM>), which comprises:
a pyroelectric body (<NUM>);
a first light receiving electrode (<NUM>) formed on a surface of the pyroelectric body (<NUM>);
a second light receiving electrode (<NUM>) formed on a surface of the pyroelectric body (<NUM>); and
a light-sensitivity adjustment member (<NUM>, <NUM>, <NUM>, <NUM>) comprising an infrared absorption film arranged on a surface of at least the first light receiving electrode (<NUM>), and configured to make infrared reception sensitivity of the first light receiving electrode (<NUM>) higher than that of the second light receiving electrode (<NUM>); wherein the infrared detection device (<NUM>) further comprises
an optical element (OE);
characterised in that the optical element is configured to direct light from a first infrared- detection target region (TGR1), set as a region targeting a first detection target,
to the first light receiving electrode (<NUM>), wherein the first electrode (<NUM>) is configured to receive light from the first infrared-detection target region (TGR1), and to direct light from a second infrared-detection target region (TGR2), set as a region targeting mainly a second detection target and part of the first detection target, to the second light receiving electrode (<NUM>) wherein the second light receiving electrode (<NUM>) is configured to receive light from the second infrared-detection target region (TGR2); and
wherein the detection sensitivity is increased for the first infrared-detection target region (TGR1) and is reduced for the second infrared-detection target region (TGR2), such that the first detection target in the first infrared-detection target region is distinguished from the second detection target in the second infrared-detection target region.