Detection apparatus

• US 8,164,437 B2
• Filed: 02/02/2006
• Issued: 04/24/2012
• Est. Priority Date: 02/02/2005
• Status: Active Grant

• Current Assignee: Pyronix Ltd. (Hangzhou Hikvision Digital Technology Company Limited)
• Original Assignee: Pyronix Ltd. (Hangzhou Hikvision Digital Technology Company Limited)
• Inventors: Cooper, Glyn
• Primary Examiner(s): PHAM, TOAN NGOC
• Application Number:
  US11/883,500
• Publication Number:
  US 20110169629A1
• Time in Patent Office: 2,273 Days
• Field of Search: 340/507, 340/506, 340/523, 340/526, 340/529, 340/541, 340/552, 340/565, 356/27, 356/29, 367/93, 367/94, 367/95
• US Class Current: 340/507
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G08B 13/2494 by interference with electro-magnetic field distribution combined with other electrical sensor means, e.g. microwave detectors combined with other sensor means
• CPC Class Codes: G08B 29/046 prevention of tampering with detection circuits
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

Embodiments of the present invention relate to a range reduction detection apparatus that is able to detect blocking of its field of view. Detection of an event, due to movement or intrusion within the field of view, is arranged to start a timer, which will time-out thereby providing an indication of such blocking unless a subsequent event is detected within the time-period.

Claims

1. A range reduction detection apparatus comprising means, responsive to at least a first input signal, to generate a blocking alarm signal, providing an indication that a field of view of a detector has been blocked, after a first period of time, unless a second input signal is generated within that first period of time, said blocking being associated with a reduction in detection range of the detector determined relative to a specified detection range of the detector.

2. The apparatus as claimed in claim 1 in which the means to generate the alarm signal comprises a timer arranged to time out after the first period of time and to generate, or cause to be generated, the blocking alarm signal and means to detect input of the second input signal to at least stop or reset the timer.

3. The apparatus as claimed in claim 1 in which the first and second input signals have the same type.

4. The apparatus as claimed in claim 1 in which the first and second input signals have different types.

5. The apparatus as claimed in claim 1 in which:

(a) the first input signal is derived from a microwave detector or the first input signal is derived from a passive infrared detector;

(b) the second input signal is derived from a microwave detector or the second input signal is derived from a passive infrared detector;

(c) the first input signal is derived from a microwave detector and the second input signal is derived from a passive infrared detector;

or

(d) the first input signal is derived from a passive infrared detector and the second input signal is derived from a microwave detector.

6. The apparatus as claimed in claim 1 further comprising at least one of a microwave detector and a passive infrared detector for producing at least one of the first input signal and the second input signal.

7. The apparatus as claimed in claim 1 further comprising an alarm to generate an alarm output in response to the range reduction detection alarm signal.

8. The apparatus as claimed in claim 1 wherein the first period of time is started by at least one of:

in response to the first input signal exceeding a threshold a predetermined number of times in a predetermined time period, or

in response to the first signal breaching a threshold for a cumulative percentage of time during a predetermined time period.

9. A non-transitory machine-readable storage storing a program comprising code for causing an apparatus to operate as a range reduction detection apparatus comprising means, responsive to at least a first input signal, to generate a blocking alarm signal, providing an indication that a field of view of a detector has been blocked, after a first period of time unless a second input signal is generated within that first period of time;

said blocking being associated with a reduction in detection range of the detector determined relative to a specified detection range of the detector.