Apparatus for non-invasively detecting and measuring electrical field or potential in e.g. opto-electronic components, employs confocal microscope to map phase differences

摘要

A confocal microscope (15) is used to map phase differences in the light beam (7). The zone under inspection is located in the beam so that a planar image of it is formed. An interferometer (5) divides the source beam (19) into a reference beam (21) and an inspection beam (23). It measures phase shift between the reference- (21) and inspection beam (23) having passed through the inspection zone. In the interferometer, control of reference and inspection beam lengths is active up to a cut-off frequency fc. The mapping system (7) has a signal sampling frequency fa exceeding the cut-off frequency fc. The medium can be displaced along three spatial axes under the inspection beam (23). A scanner (33) sweeps the inspection- and a reference zone (36). Image acquisition frequency f of images registered by beam (7) phase variation, exceeds the cut off frequency fc. The scanner operates in two directions at frequencies fx and fy respectively, to form an image of n x m pixels, satisfying fx = fy/n and fy = fa/m. Four acousto-optical deflectors scan the beam along the axes and re-align the beams ahead of and following the confocal microscope. A Galilean lens increases the angle between the first order and the optical axis. Polarization of the incident beam is controlled ahead of the microscope.