Abstract : Linear interpolation methods have the characteristics of low computational complexity which makes them widely developed in CFA (color filter array) demosaicking. However, the trichromatic nature of colour images enables CFA demosaicking algorithms to take advantage of the luminance-chrominance representation to interpolate the colour planes efficiently and effectively. It seems, however, this does not apply to multispectral images in a straightforward manner. In this paper, we first propose a linear interpolation method for SFA (spectral filter array) demosaicking drawing on the mathematical analysis of mosaicking, demosaicking processes and the idea of residual interpolation. We then compare the performance of the proposed method with that of five other techniques by means of the SSIM index. The result shows that our new algorithm has a good performance with less computing time.