an optical phenomenon resulting from the failure of a lens or mirror to produce a good image
質のよい像を作るはずのレンズや鏡にできた欠損から生じる光学系の現象
distortion
a change (usually undesired) in the waveform of an acoustic or analog electrical signal; the difference between two measurements of a signal (as between the input and output signal); "heavy metal guitar players use vacuum tube amplifiers to produce extreme distortion"