Magnitude Filtering
Roger L. Easton Jr. · 2010
This chapter begins with the discussion of filtering and concentrates on the 1-D case because the 2-D case usually is a simple generalization. The entire point of this discussion is to demonstrate how the transfer function H[ξ] modifies both the magnitude and phase of the spectrum of the input function. It is convenient to group filters into more restrictive classes based on similar performance. The transfer functions of the lowpass filters considered in this chapter are real valued and symmetric, though it is easy to construct lowpass filters with asymmetric modulation transfer functions (MTFs). The MTF of a strictly defined bandpass filter reaches its maximum at one (or more) nonzero frequencies and drops to zero at ξ = 0 and ξ = ±∞. If the transfer function has a single maximum, say at ξ =+|ξ0|, the transfer function has a single passband. Controlled Vocabulary Terms low-pass filters; optical transfer function