PIR motion sensor

• US 20040169145A1
• Filed: 06/20/2003
• Published: 09/02/2004
• Est. Priority Date: 01/21/2003
• Status: Active Grant

• Current Assignee: Suren Systems, Ltd.
• Original Assignee: Suren Systems, Ltd.
• Inventors: Micko, Eric Scott
• Granted Patent: US 7,399,970 B2
• Time in Patent Office: Days
• US Class Current: 250/342
• CPC Class Codes: G08B 13/19 using infrared-radiation detection systems G08B13/194 takes precedence
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

A passive infrared sensor uses two detectors having elements of different configurations such that each element outputs a respective frequency when an object moves in front of it. Based on the presence of two frequencies with similar peak and/or slope characteristics, a motion signal is output to, e.g., activate an alarm. In another embodiment the detectors have plural elements with the elements of one detector being wired in a dimension that is orthogonal to the dimension in which the elements of the other detector are wired. The signals from the detectors are combined to determine motion and size of object. The detector elements can also be configured differently from each other as in the first embodiment, and the polarities of signals can be used to determine direction of motion. In yet another embodiment the detectors can be of the same size but have optics of different focal lengths.

Claims

1. A passive infrared (IR) motion sensor, comprising:

at least a first IR detector outputting a first signal having a first frequency when a moving object passes in a detection volume of the first detector;

at least a second IR detector outputting a second signal having a second frequency when the moving object passes in a detection volume of the second detector, the second frequency being different than the first; and

a processing system receiving the first and second signals and at least partially based on the first and second signals, outputting a detection signal representative of the moving object, wherein the detectors have the same size as each other, the first detector being provided with a first optics defining a first focal length and the second detector being provided with a second optics defining a second focal length different than the first focal length.

2. The sensor of claim 1, wherein the first and second-detectors are housed separately from each other and the first detector monitors a first volume of space that is at least partially optically superposed with a second volume of space monitored by the second detector.

3. The sensor of claim 1, wherein each detector has two and only two respective elements with the elements being of equal size with each other and with the spacing between the elements of the first detector being the same as the spacing between the elements of the second detector.

4. A method for discriminating a moving object in a monitored space from a non-moving object characterized by non-constant radiation, comprising:

receiving a first frequency from a first passive IR detector;

receiving a second frequency from a second passive IR detector, the first and second frequencies not being equal, the detectors being of equal size and configuration but having respective optics of different focal lengths; and

outputting a signal indicating the presence of the moving object only if both the first and second frequencies are substantially simultaneously received, and otherwise not outputting the signal indicating the presence of the moving object.

5. The method of claim 4, comprising arranging the detectors in respective separate housings.

6. The method of claim 4, comprising optically superposing a first volume of space monitored by the first detector with a second volume of space monitored by the second detector.

7. The method of claim 4, wherein each detector has two and only two respective elements with the elements being of equal size with each other and with the spacing between the elements of the first detector being the same as the spacing between the elements of the second detector.

8. A motion sensor, comprising:

at least a first passive IR detector having two and only two elements defining a first spacing therebetween, the first passive IR detector monitoring a first subvolume of space;

at least a second passive IR detector having two and only two elements defining a second spacing therebetween, the second spacing being equal to the first spacing and all four elements having the same size as each other, the second passive IR detector monitoring a second subvolume of space; and

an optics system at least partially optically superposing the first and second subvolumes, the optics system defining a first focal length associated with the first detector and a second focal length associated with the second detector, the first and second focal lengths not being equal to each other.

9. The sensor of claim 8, further comprising a processor receiving signals from the detectors.