System and method for determining the state of a traffic signal

• US 8,692,996 B2
• Filed: 07/28/2011
• Issued: 04/08/2014
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: Mesa Engineering, Inc.
• Original Assignee: Mesa Engineering, Inc.
• Inventors: Davis, Clint A.
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): Gray, Sunghee Y
• Application Number:
  US13/192,762
• Publication Number:
  US 20130027704A1
• Time in Patent Office: 985 Days
• Field of Search: 356/402, 356405-406, 356 72- 73
• US Class Current: 356/402
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01J 3/505 measuring the colour produced by lighting fixtures other than screens, monitors, displays or CRTs
• CPC Class Codes: G08G 1/081 Plural intersections under common control

Abstract

A system and method for determining a state of a traffic signal. In one embodiment, a traffic signal state detector includes a lens, a color sensor, and a processor. The color sensor is configured to identify a plurality of colors of light directed to the color sensor by the lens, and a field of view of the color sensor is restricted based on dimensions of a traffic signal. The processor is coupled to the color sensor. The processor is configured to determine a color of light emitted by the traffic signal based on the colors of light identified by the color sensor.

Claims

1. A traffic signal state detector, comprising:

a lens;

a color sensor configured to identify a plurality of colors of light directed to the color sensor by the lens;

an aperture plate disposed between the lens and the color sensor, the aperture plate comprising an aperture having a shape and orientation corresponding to a traffic signal to be monitored by the traffic signal state detector, wherein the lens is configured to focus gathered light at the aperture; and

a processor coupled to the color sensor, the processor configured to;

determine a color of light emitted by the traffic signal based on the colors of light identified by the color sensor; and

anticipate a change in state of the traffic signal based on a determined timing of previous state changes of the traffic signal.

2. The traffic signal state detector of claim 1, wherein the field of view of the color sensor is restricted by the aperture to a field approximately four times the area of the traffic signal.

3. The traffic signal state detector of claim 1, wherein the processor is configured to identify a state change of the monitored traffic signal within a maximum of approximately one millisecond after the state change.

4. The traffic signal state detector of claim 1, wherein the processor is configured to determine the color of light emitted by the traffic signal based on a relative luminosity of different light colors emitted by the monitored traffic signal and detected by the color sensor.

5. The traffic signal detector of claim 1, wherein the processor is configured to track modulation of intensity of light emitted by the monitored traffic signal, wherein the modulation is due to instantaneous phase of voltage of the power line powering the traffic signal.

6. A method for determining a state of a monitored traffic signal, comprising:

directing, via a lens, a plurality of colors of light to a color sensor;

limiting a field of view of the color sensor, via an aperture positioned between the lens and the color sensor, to an area defined by a location, shape, orientation, and dimensions of the monitored traffic signal;

focusing light gathered by the lens at the aperture;

determining a state of the monitored traffic signal based on relative luminosity of light colors emitted by the monitored traffic signal and detected by the color sensor of the plurality of colors of light directed to the color sensor; and

anticipating a change in state of the monitored traffic signal based on a determined timing of previous state changes of the monitored traffic signal.

7. The method of claim 6, further comprising focusing gathered light at an aperture disposed between the lens and the color sensor.

8. The method of claim 6, further comprising providing traffic light state information updates at a rate of at least one update per millisecond.

9. The method of claim 6, wherein determining the state of the traffic signal comprises determining a hue, saturation, and lightness of a light color emitted by the monitored traffic signal and detected by the color sensor.

10. The method of claim 6, further comprising tracking modulation of intensity of light emitted by the monitored traffic signal, wherein the modulation is due to instantaneous phase of voltage of the power line powering the traffic signal.

11. An apparatus, comprising:

a lens;

an aperture plate disposed so that light from the lens passes through an aperture in the aperture plate, wherein the aperture is shaped and oriented in correspondence with a first traffic signal from which the lens gathers light, and the aperture is sized to be a multiple of the size of an image of a traffic signal provided by the lens at a predetermined distance from the first traffic signal;

a color sensor configured to detect colors of light passing through the aperture and to generate a color signal indicating an intensity of each of the colors of light detected by a plurality of red photodetectors, a plurality of blue photodetectors, and a plurality of green photodetectors that are irregularly arranged on the color sensor;

a processor coupled to the color sensor for processing the color signal; and

a traffic signal controller coupled to the processor;

wherein the signal controller is configured to synchronize a second traffic signal with the first traffic signal based on a state of the first traffic signal determined by the processor based on the color signal.