Patent ID: 11863879
Assignee: AMS SENSORS GERMANY GMBH
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 13:
14. A method of using a camera system to characterize ambient illumination, the camera system having an image sensor to capture a view of a scene, a flash to provide flash illumination of the scene, and a multispectral sensor to capture a spectrum of light from the scene in a plurality of wavelength channels, the method comprising:
capturing a first spectrum of light (DTFA) from the scene using the multispectral sensor whilst the flash is operating to illuminate the scene in addition to ambient illumination;
capturing a second spectrum of light (DTA) from the scene using the multispectral sensor whilst the flash is not operating and the scene is illuminated by the ambient illumination;
determining a difference between the first and second spectra representing a scene flash spectrum (DTF), wherein the scene flash spectrum represents a spectrum of the scene when illuminated by the flash without the ambient illumination;
compensating the scene flash spectrum using a spectrum of the flash illumination (E(λ)) to determine a colour-compensated scene flash spectrum (RT(λ)), wherein the colour-compensated scene flash spectrum represents an average reflectance spectrum of the scene when compensated for the spectrum of the flash illumination; and
processing the second spectrum of light from the scene using the colour-compensated scene flash spectrum to estimate a spectrum of the ambient illumination (RA(λ));
wherein processing the second spectrum of light from the scene using the colour-compensated scene flash spectrum comprises dividing each of a set of values (RTA(λ)) representing the second spectrum of light at each of a respective set of wavelength points by a corresponding value for the colour-compensated scene flash spectrum (RT(λ)) at the respective wavelength point.