| In order that an image may be processed accurately and effectively, it is necessary to know the properties of image formation of the particular system, i.e. whether the system is coherent or incoherent, the transfer f$nction of the imaging system, etc. In many applications such information is unknown and it is therefore necessary to estimate the imaging properties. At other times the transfer function may be known but so complex that simpli@ing approximations are applied, e.g. for optical microscopy incoherent imaging may be assumed even though for high resolution the imaging is necessarily partially coherent. In a confocal imaging system’, the object is illuminated by focussing a coherent source and the signal is received by a point detector, the back projected image of which is arranged to coincide with the illumination on the object as shown in Figure 1. Confbcal imaging has several desirable properties for digital image processing. These include l purely coherent imaging 0 range information ofthe object may be obtained, i.e. the relative distance of its surface fEom the observer 0 improved resolution over a conventional imaging system using the same aperture and wavelength is attainable A confbcal system, by its very nature, must scan the object in order to produce an image. Thus the image may be digitized very simply. |
