Physiological study points out that the early stage of human visual system works like a filter bank on the retinal image. The filters in such a filter bank can be seen as being obtained by rotation and modulation from an original prototype filter. This paper concentrates on the design of local bases obtained by unitary transformation of a single prototype filter. In order to be able to construct such a basis, an equation is extended to a more general case. Based on this, the design of the filters is discussed.
