Aperture-coded confocal profilometry

This Letter introduces a novel principle to the confocal profilometry for simultaneous measurement of surface position and tilt. The principle relies on an angle-dependent coding of the illumination of the surface-under-test, achieved by dividing the pupil into several subapertures. The reflected light is decoded to perform an angle-resolved analysis by measuring the intensity contributions of each individual subaperture. By comparing their contributions, additional information of surface tilt can be inferred. For our demonstration experiment the subapertures are encoded with specific spectral distribution, which may be called wavelength division encoding. Alternate coding procedures such as temporal or code division encoding are also feasible.