Scientific Photography and Applied Imaging

34 Holography

34.1 Outline theory

34.1.1 Wavefront reconstruction

Conventional photography uses a lens to image a subject as a similar intensity distribution which is recorded after exposure on to photographic material and subsequently processed as optical density variations (D). This essentially non-linear system is represented by the characteristic curve of the processed material, a graph of D against log exposure (H), where H = Et; E is image illumination and t is exposure duration (see Chapter 10).

Photographic film is a square-law detector in that it records only intensity E, which is the square of the convoluted wavefront amplitudes (A) at any point on the material. No phase information is recorded. Playback is by viewing the intensity ...