Method and apparatus for providing strobed image capture
Inventors
Lolacono, Dominick • Matey, James R. • Naroditsky, Oleg • Tinker, Michael • Zappia, Thomas
Assignees
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Publication Number
US-7542628-B2
Publication Date
2009-06-02
Expiration Date
Abstract
A method and apparatus for strobed image capture includes stroboscopic illumination synchronized with one or more cameras to improve a signal to noise ratio, reduce motion blur and avoid object damage in sensor systems used to analyze illumination sensitive objects.
Core Innovation
A strobed image-capture system and method are provided in which a controller controls at least one strobed illumination source to limit an amount of radiation applied to an illumination sensitive object. The illumination sensitive object is an iris, and the controller synchronizes at least one camera with the strobed illumination source so that the camera captures images illuminated by a plurality of photons from the strobed illumination source. During a strobe, a light intensity of the strobed illumination source is increased while an average irradiance remains below a safety threshold.
The system architecture includes at least one camera, an illumination controller, at least one illumination source, and an illumination synchronization function with the controller for camera operation. The controller provides illumination during camera operation and strobes the illumination source, including synchronization of the strobe with camera shuttering. The captured plurality of images may include at least a portion of an iris as a subject moves through an image capture volume.
An iris recognition apparatus and method process at least one of the plurality of images containing at least a portion of an iris with a processor to perform iris recognition. The controller strobe the illumination source for a series of short pulses over a period of time with an intensity greater than a threshold limit value for a continuous wave output. Illumination and synchronization are configured to generate sufficient reflected photons to produce a clear iris image while using a large distance between the camera and the subject.
Claims Coverage
The independent claims include four core inventive aspects across a method, a system, an apparatus, and a method: synchronized strobed illumination for an iris while keeping average irradiance below a safety threshold; capturing iris images illuminated by photons from the strobed source; processing captured iris images for iris recognition; and, for recognition at distance, strobing with pulsed intensity relative to a continuous-wave threshold while enabling clear iris image output.
Synchronizing a camera with a strobed illumination source while increasing strobe intensity under a safety threshold
Controlling, with a controller, at least one strobed illumination source to limit an amount of radiation applied to an illumination sensitive object; synchronizing the controller with at least one camera with the strobed illumination source; capturing at least one image where a light intensity of the strobed illumination source is increased during a strobe while an average irradiance remains below a safety threshold.
Strobed image-capture system with camera/illumination synchronization under safety-limited average irradiance
Providing at least one camera and at least one illumination controller for synchronizing with the camera at least one illumination source; capturing at least one image from photons reflected from the illumination sensitive object; where the object is an iris; and where a light intensity of the strobed illumination source is increased during a strobe while an average irradiance remains below a safety threshold.
Iris recognition apparatus using strobed illumination pulses with intensity relative to continuous-wave threshold
Providing an apparatus with at least one camera arranged to define an image capture volume and capture a plurality of images of a subject moving through the image capture volume with at least one image containing at least a portion of an iris; an illumination source; a controller coupled to the illumination source and the camera to provide illumination during camera operation; a processor for processing at least one iris-containing image to perform iris recognition; where the controller is configured to strobe the illumination source for a series of short pulses over a period of time having an intensity greater than a threshold limit value for a continuous wave output over the period of time.
Iris recognition method with synchronized strobed illumination to produce a clear iris image at a large distance under safety-limited average irradiance
Capturing, with at least one camera, a plurality of images of a subject moving through an image capture volume with at least one image containing at least a portion of an iris; synchronizing, with a controller, illumination from an illumination source with operation of the camera to generate sufficient reflected photons to produce a clear iris image while using a large distance between the camera and the subject; processing with a processor to perform iris recognition; and strobing with the controller; where a light intensity is increased during a strobe while an average irradiance remains below a safety threshold.
Across the independent claims, the core coverage centers on synchronizing camera capture with stroboscopic illumination of an iris, increasing intensity during strobe while keeping average irradiance below a safety threshold, and processing iris-containing images for iris recognition. For recognition with a large camera-to-subject distance, the claims further cover strobing as a series of short pulses having intensity greater than a continuous-wave threshold limit value.
Stated Advantages
Improved signal-to-noise ratio (S/N) for strobed image capture.
Reduced motion blur compared with conventional lighting.
Reduced ambient illumination impact.
Stroboscopic synchronized capture enables larger capture volumes.
Improved safety/illumination customization by keeping average irradiance below a safety threshold while increasing strobe peak intensity.
Documented Applications
Iris recognition using strobed image capture and processor-performed iris recognition from captured iris-containing images.
Pupillometry and analysis of saccadic motion using captured iris/pupil images in a strobed, synchronized system.
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