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US 7,009,642 B2Granted
Method and apparatus for detecting the presence of artificial illumination in a scene
AssigneeHewlett-Packard Development Company, L.P.
InventorsGregory V Hofer, Jason E Yost
Life of this patent
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Abstract
A method and apparatus for detecting the presence of artificial illumination in a scene powered by alternating current by sampling the light in a scene at a periodic rate.
Claims25
A method of detecting artificial illumination in a scene, comprising:
- predicting at least one frequency for a variation in the illumination in the scene;
- measuring light from the scene at a periodic rate, wherein the periodic rate is different than any of the predicted frequencies, using an exposure length that is different than any of the periods of the predicted frequencies;
- detecting the presence of an artificial illuminant when the measured light from the scene contains periodic changes;
- choosing one of the predicted frequencies;
- re-measuring the light from the scene using a periodic rate that is an integer multiple of the chosen frequency;
- and
- confirming the actual frequency of the artificial illuminant by comparing the re-measured light for a reduction in the variability of the light intensity.
4 more elements
A method of detecting artificial illumination in a scene, comprising:
- predicting a frequency for a variation in the illumination in the scene;
- measuring light from the scene at a periodic rate using an exposure length that is equal to the period of the predicted frequency;
- detecting the presence of an artificial illuminant when the variability of the measured light is high.
A method of detecting artificial illumination in a scene, the method comprising:
- predicting a frequency for a variation in the illumination in the scene;
- measuring light from the scene at a periodic rate, wherein the periodic rate is equal to an integer multiple of the predicted frequency, using an exposure time that is different than the period of any of the predicted frequencies;
- and
- detecting the presence of an artificial illuminant when the variability of the measured light is high.
1 more element
An apparatus for detecting artificial illumination in a scene, the apparatus comprising:
- a photo sensor array, the photo sensor array configured to measure light from the scene at a preselected frequency using a predetermined exposure time, wherein the preselected frequency is approximately twice a frequency of a power source supplying an artificial illuminate, but not equal to twice the frequency of the power source;
- and
- a processor, the processor configured to determine the presence of an artificial illuminant by examining the measured light from the scene for periodic intensity variations.
An apparatus for detecting artificial illumination in a scene, the apparatus comprising:
- a photo sensor array, the photo sensor array configured to measure light emitted from the scene at a preselected frequency using a predetermined exposure time, wherein the preselected frequency is approximately twice a frequency of a power source supplying an artificial illuminate, but not equal to twice the frequency of the power source;
- a lens configured to focus the light from the scene onto the photo sensor array;
- a processor, the processor configured to determine the presence of an artificial illuminant by examining the measured light from the scene for periodic contrast variations.
An apparatus for detecting artificial illumination in a scene, the apparatus comprising:
- a means for measuring light from the scene at a preselected frequency using a predetermined exposure time, wherein the preselected frequency is approximately twice a frequency of a power source supplying an artificial illuminate, but not equal to twice the frequency of the power source;
- and
- a means for determining the presence of an artificial illuminant by examining the measured light form the scene for periodic intensity variations.
A digital camera comprising:
- a photo sensor array, the photosensor army configured to measure light from a scene at a preselected frequency using a predetermined exposure length, wherein the preselected frequency is approximately twice a frequency of a power source supplying an artificial illuminate, but not equal to twice the frequency of the power source;
- a lens configured to focus the light from the scene onto the photo sensor array;
- and
- a processor, the processor configured to determine the presence of an artificial illuminant by examining the measured light from the scene for periodic variations.
1 more element
A method of determining the illumination type in a scene, the method comprising:
- predicting at least one frequency for a variation in the illumination in the scene;
- measuring light from the scene at a periodic rate, wherein the periodic rate is different than any of the predicted frequencies, using an exposure length that is different than any of the periods of the predicted frequencies;
- comparing the variability of the measured light to a first threshold;
- detecting natural illumination when the variability of the measured light is below the first threshold;
- and
- detecting artificial illumination when the variability of the measured light is above the first threshold.
3 more elements
Dependencies are inferred from the claim text.