How to eliminate noise and the audio enhancement technologies are also proposed, especially the analyzing of the character of audio and frequencysubtraction for eliminating noise.
With a phase grating located at Fourier frequency plane, optical image subtraction is obtained as a result of the coherent superposition of the zeroth and the first order of the diffracted light.
置一位相光栅于相干光学处理系统频谱平面，利用其零级与一级衍射光的相干迭加实现图象相减。
3
As the mine hoist on the speed of addition and subtraction accuracy and speed requirements of high precision, variable-frequency control system must be used.