Abstract: We attempted to understand the rule of fusion on the spatial frequencydomain in binocular stereopsis.Two sets of random-dot stereograms withdifferent texture were optically filtered by low,high and band pass filters.Filtered stereograms were paired in various combinations and examined undera stereoscope to see if any depth could be perceived. We observed that: 1. All the stereograms that passed the same filter could produce stereopsisperfectly. 2. Generally speaking,two sets with different texture have commontendency but in some cases they gave different results. 3. Sofar the overlap of spatial frequency spectra between the twohalf pictures of a stereogram could not be simply used as a rule to explain thefusing mechanism of stereo perception.

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