In this paper we study a spiral illusion generated by fractal islands. Furthermore, by a neuro-scientific consideration we present a new class of geometrical illusions. In order to analyse these illusions, we propose a new mathematical method.

In this paper we will construct compactly supported tight framelets with orientation selectivity and Gaussian derivative like filters. These features are similar to one of simple cells in V1 revealed by recent vision science. In order to see the orientation selectivity, we also give a simple example of image processing of a test image.

As is well known in neuroscience, simple cells of the mammalian's striate cortex possess both orientation and spatial-frequency selectivity, and are similar to the Gabor filters or Gaussian derivative filters in shape. The purpose of this paper is to propose a method of designing perfect reconstruction 2D filterbanks which act on finite dimensional linear spaces consisting of 2D signals of a certain size, and have several analogous features to simple cells: (1) the filterbanks consist of several spatial-frequency channels with orientation selectivity, (2) the filterbanks have shift-invariant multiresolution (multiscale) structures, (3) filters contained in them are FIR, and are similar in appearance to not only Gaussian derivatives of 1st and 2nd order, but also ones of higher order. Moreover, they are constructed by finite linear combinations of separable filters. As is described in the text, by virtue of these properties, our 2D filterbanks can become bases of constructing computational nonlinear models of visual information processing. In this paper we construct the 2D filterbanks, and discuss them from the viewpoint of vision science. For example we disclose a possible role of ''Gaussian-derivative-like'' filters of higher order in our filterbanks. Practical applications of our 2D filterbanks to vision science and image processing will be given in our subsequent papers.