: Filtering in which two sets of filters are used e.g. Odd and Even Gabor filters, whose receptive field profiles are said to be in 'Quadrature Phase'.

: Used in image compression. A QMF pair splits an image into two orthogonal components. One filter defines a convolution kernal that blurs and reduces the image. The second filter, which is orthogonal to the first is used to create a representation of the error signal. The representation is more eficient than normal pyramidal schemes as the resulting reduced image and error signal are orthogonal. In continuous rather than discrete form, the convolution kernals are called orthogonal wavelets.