Frames is an important part in research of wavelet analysis and its definition was formally advanced by Duffin and Schaefer when they studied the problems of nonharmonic Fourier expansions in 1952.

• 框架理论是小波分析的重要组成部分，其概念是由Duffin和Schaefer于1952年在研究非调和Fourier分析中提出来的。