Definitions for

**"Spatial Frequency"**the number of lines per unit length of the interference pattern; used to compute resolution requirements for film used in holography

A measure of how rapidly a property changes in space. A commonly used form of visual stimulus consists of vertical bars where the lightness varies according to a sinusoidal function. In this simple case the spatial frequency of the stimulus is just the frequency of the sinusoid used to generate the pattern. In general stimuli with fine detail including sharp edges have high spatial frequency while those where the stimulus properties change more slowly in space have low spatial frequency.

(a) a vector giving the frequency components (number of cycles per unit length, kx and ky ) of a general 2D sine wave in x- and y-direction; or (b) the length of a spatial frequency vector. In the 2D Fourier transform plane, the spatial frequency vector gives the location of any point. Points that have the same [absolute] spatial frequency lie on a circle with radius sqrt(kx**2 + ky**2). For representation of 3D objects or images, the spatial frequency vector is three-dimensional, with components (kx , ky , kz), corresponding to 3D sine waves, and points with the same [absolute] spatial frequency lie on the surface of a sphere with radius sqrt(kx**2 + ky**2 + kz**2).