Integral ambient light and occupancy sensor having a linear array of sensor element and a segmented slit aperture device

• US 5,834,765 A
• Filed: 07/08/1997
• Issued: 11/10/1998
• Est. Priority Date: 07/08/1997
• Status: Expired due to Term

• Current Assignee: Ledalite Architectural Products
• Original Assignee: Ledalite Architectural Products
• Inventors: Ashdown, Ian E.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/889,789
• Time in Patent Office: 490 Days
• Field of Search: 250/221, 250/214 AL, 250/214.1, 250/578.1, 250/206.1, 250/206.2, 250/203.1
• US Class Current: 250/221
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0437 using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 1/4204 with determination of ambient light solar light G01J2001/4266
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01V 8/20 using multiple transmitters or receivers

Abstract

A sensor implemented with a single light sensing device detects ambient light levels and object motion. The sensor comprises an optical component assembly composed of a linear array of light sensitive elements, preferably photodiodes, positioned downstream of a segmented slit aperture device comprising a single, segmented slit, the slit length of which is oriented perpendicular to the length of the linear array. The individual photodiodes of the array provide motion detection capability in a direction perpendicular to the slit length. The slit aperture is segmented along the slit length to form multiple zones of sensor light responsivity that provide motion detection capability in a direction parallel to the slit length. An object moving in a direction parallel to the multiple slit aperture passes through one or more zones of sensor responsivity and thereby produces from the photodiodes a varying electrical signal from which object motion can be detected. A processor in a first mode detects an ambient light level and in a second mode detects object motion. In the first mode, the processor determines the average amount of light received by the entire photodiode array by computing an average of light signal data values derived from the photodiodes in response to the quantities of light they receive during an exposure time. In the second mode, the processor compares light signal data values acquired at different times for corresponding photodiodes to detect differences in light intensities of adjacent zones of sensor responsivity to detect object motion. The processor is capable of concurrently performing the first and second modes.

Claims

1. An integral ambient light and occupancy sensor having an overall angular field of view, comprising:

a linear array of light sensitive elements, the array having an array length and the light sensitive elements producing light signals representing quantities of light incident on them;

a segmented slit aperture device having a slit aperture defined by a slit length and a slit width that is much smaller than the array length, the slit aperture device positioned a distance away from the linear array and oriented so that the slit length crosses the linear array in a transverse direction, the distance between the linear array and the slit aperture device contributing to the overall angular field of view of the sensor, and the slit aperture being segmented along the slit length to form multiple zones of light responsivity for the linear array along the slit length; and

a processor operatively connected to the linear array to process light data values corresponding to the light signals, the processor operable in first and second modes, in the first mode the processor determining from the light data values a quantity representing an average measure of the light incident on the linear array, and in the second mode the processor determining from light data values acquired at different times for corresponding light sensitive elements to detect the existence of object motion within the overall angular field of view of the sensor.

2. The sensor of claim 1, further comprising a visible light filter having a spectral response approximating that of the human visual system and positioned in optical association with the linear array to cause the linear array to have a spectral response approximating that of the human visual system.

3. The sensor of claim 2 in which the visible light filter is positioned either upstream or downstream of the segmented slit aperture device to intercept incident light before it propagates to the linear array.

4. The sensor of claim 1 in which the segmented slit aperture device comprises a substrate having alternate areas of different light transmissivity along the slit length to form the zones of light responsivity.

5. The sensor of claim 4 in which the substrate comprises exposed photographic film having different gray shades forming the areas of different light transmissivity.

6. The sensor of claim 1 in which the slit width determines for any one of the light sensitive elements a width of an angular field of view in a direction parallel to the linear array, the slit width being set so that the angular fields of view of adjacent light sensitive elements do not overlap appreciably and do not by diffraction effects distribute appreciable amounts of incident light to adjacent light sensitive elements.

7. The sensor of claim 1 in which the light sensitive elements comprise photodiodes.

8. The sensor of claim 1 in which the light data values correspond to light signals developed during an exposure time and in which, in the first mode, the processor computes an average of the light data values corresponding to light signals developed during the exposure time to determine the average measure of the light incident on the linear array.

9. The sensor of claim 1 in which, in the second mode, the processor compares the light data values for corresponding light sensitive elements at different times to detect differences in light intensities of adjacent zones of light responsivity along the slit length to determine the existence of object motion.

10. The sensor of claim 1 in which the processor performs the first and second modes concurrently.

11. An integral ambient light and occupancy sensor optical component assembly having an overall angular field of view, comprising:

a linear array of light sensitive elements, the array having an array length and the light sensitive elements producing light signals representing quantities of light incident on them; and

a segmented slit aperture device having a slit aperture defined by a slit length and a slit width that is much smaller than the array length, the slit aperture device positioned a distance away from the linear array and oriented so that the slit length crosses the linear array in a transverse direction, the distance between the linear array and the slit aperture device contributing to the overall angular field of view of the sensor optical component assembly, and the slit aperture being segmented along the slit length to form multiple zones of light responsivity for the linear array along the slit length.

12. The optical component assembly of claim 11, further comprising a visible light filter having a spectral response approximating that of the human visual system and positioned in optical association with the linear array to cause the linear array to have a spectral response approximating that of the human visual system.

13. The optical component assembly of claim 12 in which the visible light filter is positioned either upstream or downstream of the segmented slit aperture device to intercept incident light before it propagates to the linear array.

14. The optical component assembly of claim 11 in which the segmented slit aperture device comprises a substrate having alternate areas of different light transmissivity along the slit length to form the zones of light responsivity.

15. The optical component assembly of claim 14 in which the substrate comprises exposed photographic film having different gray shades forming the areas of different light transmissivity.

16. The optical component assembly of claim 11 in which the slit width determines for any one of the light sensitive elements a width of an angular field of view in a direction parallel to the linear array, the slit width being set so that the angular fields of view of adjacent light sensitive elements do not overlap appreciably and do not by diffraction effects distribute appreciable amounts of incident light to adjacent light sensitive elements.

17. The optical component assembly of claim 11 in which the light sensitive elements comprise photodiodes.