1. A spectral camera for producing a spectral output, the spectral camera comprising: an objective lens for producing an image; an array of lenses for producing optical copies of segments of the image on different optical channels; an array of filters for the different optical channels and having an interleaved spatial pattern of different passbands across the array; and one or more sensor arrays arranged to detect the copies of the image segments on the different filtered optical channels, the interleaved spatial pattern of the array of filters being arranged so that detected segment copies of spatially adjacent optical channels have different passbands and represent segments of the image which at least partially overlap each other, and so that at least some of the detected segment copies of the same passband on spatially non-adjacent optical channels represent segments of the image which are adjacent and fit together.