Patent ID: 6654048
Filing Date: 2003-11-25
Classification: G01J,H04N

Abstract:
A method for calibration of an imaging system having a camera for capturing colour data for a viewed scene, the method including a primary calibration to enable compensation for variations in the camera operation or characteristics, the primary calibration including providing a number of standard colour specimens and presenting these to the camera under controlled illumination conditions and with extraneous or external light being substantially excluded from illuminating the standard colour specimens, capturing image data for the standard colours including colour data and calculating a primary transform comprising compensation factors or transformation parameters for relating the actual measured colour data to known standard colour data for the particular standard colour specimens; the method further including a secondary calibration to enable compensation for local lighting conditions during capture and processing of colour data for captured images to be analysed, the secondary calibration process comprising presenting to the camera reference colour specimens exposed to the lighting conditions that the object to be imaged and analysed is being or is to be exposed followed by capturing image data for the reference colour specimens and determining a secondary transform comprising compensation factors or transformation parameters for relating the measured colour data for the reference colour specimens to known colour data for those specimens, the method further including a preliminary calibration in which the primary calibration standard colour specimens and associated controlled light source are calibrated against centralised standard colours by using the camera to capture image data for the centralised standard colours and determining a preliminary transform comprising compensation factors or transformation parameters for relating the actual measured colour data for the standard colour specimens to known standard colour data for the centralised standard colours.