Sectional multi spectral sensor with optical blurring

Multi-spectral optical sensor 102 comprises monolithic semiconductor chip 110 defining multiple subarrays 112 of optical detector regions 111, multiple optical filters 160 and multiple lens elements 162. The number and relative spatial arrangement of optical detector regions 111 is the same in each subarray. Each filter is positioned between a corresponding lens element and subarray. Light from a scene incident on one of the lens elements along an incidence direction propagates through the corresponding filter towards an optical detector region of the corresponding subarray, the optical detector region corresponding to the incidence direction. An out-of-focus image of the scene is formed at a plane (1105, Fig. 11) of the optical detector regions. An ambient light source classification may be determined for each incidence direction by comparing with known spectra, and used to white-balance an image from an image sensor in a known spatial relationship relative to the optical sensor.