Optic flow sensor with negative iris photoreceptor array

• US 6,493,068 B1
• Filed: 09/28/2001
• Issued: 12/10/2002
• Est. Priority Date: 09/28/2001
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Barrows, Geoffrey
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/965,246
• Time in Patent Office: 438 Days
• Field of Search: 356/28, 250/237.R
• US Class Current: 356/28
• CPC Class Codes: G01P 5/001 Full-field flow measurement, e.g. determining flow velocity and direction in a whole region at the same time, flow visualisation
• CPC Class Codes: G06T 7/269 using gradient-based methods

Abstract

An improved optic flow sensor is provided which affords enhanced bandwidth without the use of a lens. A plurality of photoreceptor circuits, arranged in a linear array, sense light received from a visual field and produce a plurality of photoreceptor signals in accordance with the light sensed. A negative iris, disposed between the visual field and the photoreceptor circuits, blocks a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits. The photoreceptor signals are used in determining optic flow in the visual field. The invention is useful for implementation using micro electromechanical system (MEMS) techniques.

Claims

1. An optic flow sensor comprising:

a plurality of photoreceptor circuits for sensing light received from a visual field and for producing a plurality of photoreceptor signals having contrast levels in accordance with the light sensed said photoreceptor circuits being arranged in a linear array;

a negative iris comprising a plurality of light blocking elements disposed between the visual field and the photoreceptor circuits for blocking a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits;

a contrast level enhancing means for receiving the photoreceptor signals for computing a mean value for the photoreceptor signals and for computing the difference between the photoreceptor signal for that photoreceptor circuit and said mean value and for enhancing the contrast levels of the photoreceptor signals; and

optical flow determining means responsive to said photoreceptor signals from said contrast level subhousing means for determining optic flow in the visual field.

2. An optic flow sensor according to claim 1 wherein said negative iris comprises a rectangular light blocking element.

3. An optic flow sensor according to claim 2 wherein said photoreceptor circuits comprise rectangular photoreceptors.

4. An optic flow sensor according to claim 3 wherein said rectangular photoreceptors extend parallel to said rectangular iris.

5. An optic flow sensor according to claim 1 wherein said light blocking elements are rectangular in shape.

6. An optic flow sensor according to claim 1 wherein said negative iris comprises a substantially point shaped light blocking element and said photoreceptor circuits comprise rectangular photoreceptors.

7. An optic flow sensor according to claim 1 wherein said negative iris comprises a colored iris element for blocking a sub-band of white light.

8. An optic flow sensor according to claim 1 wherein the optic flow determining means comprises a plurality of feature detectors for receiving said photoreceptor signals and said contrast level enhancing means comprises amplifying means for increasing the amplification of said feature detectors.

9. An optic flow sensor according to claim 1 wherein said optic flow sensor is implemented in micro-electromechanical systems technology and said negative iris comprises an etched iris structure.

10. An optic flow sensor comprising:

a plurality of photoreceptor circuits for sensing light received from a visual field and for producing a plurality of photoreceptor signals in accordance with the light sensed said photoreceptor circuits comprising photoreceptors defining a sensor orientation vector, said photoreceptors each having a response function of a rectangular shape defining a longitudinal axis extending perpendicular to said sensor orientation vector and being arranged in a linear array;

a negative iris of a rectangular shape comprising a plurality of light blocking elements, disposed between the visual field and the photoreceptor circuits and extending perpendicular to said sensor orientation vector, for blocking a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits; and

a contrast level enhancing means for receiving the photoreceptor signals for computing a mean value for the photoreceptor signals and for computing the difference between the photoreceptor signal for that photoreceptor circuit and said mean value, and for enhancing the contrast levels of the photoreceptor signals; and

optic flow determining means responsive to said photoreceptor signals from said contrast level subhousing means for determining optic flow in the visual field.

11. An optic flow sensor according to claim 10 wherein said negative iris comprises a colored iris element for blocking a sub-band of white light.

12. An optic flow sensor according to claim 10 wherein said optic flow sensor is implemented in micro-electromechanical systems technology and said negative iris comprises an etched iris surface.