PASSIVE INFRARED SENSOR AND METHOD OF CONTROL

Abstract

A method of controlling a field of view of a passive infrared sensor, the method comprising: providing a passive infrared sensor comprising: an infrared detector configured to detect infrared signals from a plurality of detection zones; and an electrochromic mask comprising a plurality of electrochromic sections; and applying a voltage to one or more of the plurality of electrochromic sections to control transmission of a predetermined range of infrared signals to the detector from one or more of the plurality of detection zones.

Claims

1. A method of controlling a field of view of a passive infrared sensor, the method comprising: providing a passive infrared sensor comprising: an infrared detector configured to detect infrared signals from a plurality of detection zones; and an electrochromic mask comprising a plurality of electrochromic sections; and applying a voltage to one or more of the plurality of electrochromic sections to control transmission of a predetermined range of infrared signals to the detector from one or more of the plurality of detection zones.

2. A method according to claim 1, comprising: setting a desired field of view of the infrared sensor, wherein the desired field of view comprises a viewing angle; and determining which of the plurality of electrochromic sections a voltage needs to be applied to provide the desired field of view of the infrared sensor.

3. A method according to claim 1, comprising: setting a desired range of the infrared sensor, determining which of the plurality of electrochromic sections a voltage needs to be applied to provide the desired range of the infrared sensor.

4. A method according to claim 1, wherein the controlling of the field of view delimits the field of view into at least two separate detection areas.

5. A method according to claim 1, wherein the application of voltage reduces the transparency of the electrochromic section(s) for infrared signals in the predetermined range.

6. A method according to claim 1, wherein the application of voltage increases the reflectance of the electrochromic section(s) for infrared signals in the predetermined range.

7. A method according to claim 1, wherein the predetermined range of infrared signals has a wavelength of between 0.7 and 10 μm.

8. A passive infrared sensor comprising: an infrared detector configured to detect infrared signals from a plurality of detection zones, and an electrochromic mask comprising a plurality of electrochromic sections, wherein each electrochromic section is electrically connected to a voltage source, and wherein the electrochromic mask is arranged such that the application of a voltage from the voltage source to one or more of the plurality of electrochromic sections changes the field of the view of the infrared sensor.

9. A passive infrared sensor according to claim 8, wherein the electrochromic sections comprise any one or a combination of: titanium dioxide (TiO.sub.2), (amorphous) tungsten trioxide (WO.sub.3), neodymium-Niobium (Nd-Nb), and tin (IV) oxide (SnO.sub.2), other metal oxides, acid doped polyaniline (PANI) films, polycrystalline, organic small molecules, triphenylamine-based polymers, conducting polymers, metal complexes, and plasmonic nanocrystals.

10. A passive infrared sensor according to claim 8, comprising a mirror arranged to reflect infrared signals to the infrared detector, wherein the electrochromic mask is positioned between the mirror and the infrared detector.

11. A passive infrared sensor according to claim 10, wherein the electrochromic mask is a layer on a surface of the mirror.

12. A passive infrared sensor according to claim 8, comprising a lens arranged to focus infrared signals on the infrared detector, wherein the lens is positioned between the electrochromic mask and the infrared detector or the electrochromic mask is positioned between the lens and the infrared detector.

13. A passive infrared sensor according to claim 12, wherein the electrochromic mask is a layer on a surface the lens.

14. A passive infrared sensor according to claim 8, wherein the voltage source is a controller and the controller is arranged to control the magnitude of a voltage applied to each electrochromic section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Certain example embodiments will now be described by way of example only and with reference to the accompanying drawings, in which:

[0036] FIG. 1 shows schematic view of a first passive infrared sensor;

[0037] FIG. 2 shows a schematic view of a second passive infrared sensor; and

[0038] FIG. 3 shows a schematic view of a third passive infrared sensor.

DETAILED DESCRIPTION

[0039] With reference to FIG. 1, a passive infrared (PIR) sensor 100 is shown.

[0040] The PIR sensor 100 comprises a detector 102, an electrochromic mask 108 comprising a plurality of electrochromic sections 110, a mirror 114, and a controller 112. The controller 112 is a voltage source and is electrically connected to each of the electrochromic sections 110 in parallel.

[0041] The PIR sensor 100 is arranged such that passive infrared signals 104 from a plurality of detection zones 106 are reflected by the mirror 114 and detected at the detector 102. The electrochromic sections 110 are used to optionally mask any given detection zone 106 by selectively blocking or transmitting infrared signals from the given detection zone.

[0042] To do so, each electrochromic section 110 has an operating state and a non-operating state. In this arrangement, the operating state occurs when the controller supplies a voltage to the electrochromic section 110. The electrochromic sections 110 are transparent in the non-operating state. However, application of a voltage by the controller 112 causes the electrochromic section 110 to become opaque, thereby blocking infrared signals, preventing them from pass through to the mirror 114 and reaching the detector 102. For anyone electrochromic section 110 his essentially masks off a given detection zone 106, thereby controlling the field of view of the PIR sensor 100.

[0043] The PIR sensor 100 with no voltages applied, and so no electrochromic sections 110 in the operating state is shown in the top left of FIG. 1 at reference 100a. It can be seen that signals from every detection zone 106 can reach the detector 102. In the main FIG. 1, voltage has been applied to the third to sixth and eight electrochromic sections 108, causing these to become opaque and masking the field of view into two distinct viewing areas. The first viewing area on the left comprising of two detection zones, the second on the right comprising of one detection zone. In this way the single PIR sensor 100 can be used to monitor two distinct areas.

[0044] FIG. 2 shows a similar PIR sensor 200 but with a different optical arrangement. The PIR sensor 200 comprises a detector 202, an electrochromic mask 208 comprising a plurality of electrochromic sections 210, an infrared absorber 216 and a controller 212. The controller 212 is a voltage source and is electrically connected to each of the electrochromic sections 210 in parallel.

[0045] Here, the electrochromic sections 210 are reflective in their non-operating state and opaque in the operating state. In FIG. 2, voltage is being applied to the third to sixth and eight electrochromic sections.

[0046] The PIR sensor 200 is arranged such that passive infrared signals 204 from a plurality of detection zones 206 are reflected by the electrochromic sections when in the non-operating state and detected at the detector 102. The electrochromic sections 110 are used to optionally mask any given detection zone 106 by selectively blocking infrared signals from the given detection zone when in the operating state. There is therefore no need for a separate mirror component, as the electrochromic sections 210 fulfil the function of a mirror (as previously described) when in the non-operating state and an electrochromic mask when in the operating state.

[0047] The infrared absorber 216 absorbs and dissipates any infrared signals that pass through the electrochromic sections in either state (this occurs as the materials may not be 100% reflective or opaque). This prevents the PIR sensor 200 from overheating.

[0048] FIG. 3 shows another similar PIR sensor 300, but again with a different optical arrangement.

[0049] The PIR sensor 300 comprises a detector 302, an electrochromic mask 308 comprising a plurality of electrochromic sections 310, a Fresnel lens 318 and a controller 312. The electrochromic mask 308 is applied to the lens 318 as a coating. The controller 312 is a voltage source and is electrically connected to each of the electrochromic sections 310 in parallel. In contrast to the arrangements shown in FIGS. 1 and 2 it can be seen that the detector 302 is positioned behind the electrochromic mask due to the use of a Fresnel lens 318 rather than a reflective mirror.

[0050] Here, the electrochromic sections 310 are transparent in their non-operating state and opaque in the operating state. In FIG. 3, voltage is being applied to the third to sixth and eight electrochromic sections.

[0051] The PIR sensor 300 is arranged such that passive infrared signals 304 from a plurality of detection zones 306 are transmitted through the electrochromic sections 310 when in the non-operating state, focussed by the lens 318 and detected at the detector 302. The electrochromic sections 310 are used to optionally mask any given detection zone 306 by selectively blocking infrared signals from the given detection zone 306 when in the operating state.