UC Irvine

Confocal microscopy is a powerful tool that has been used in the development of 3D profilometers for depth-section image capture and surface measurements. Previously developed confocal microscopes operate by scanning a single point, or array of points, over the surface of a sample. The 3D profilometer we constructed acquires measurement data using a confocal microscopy technique, where transverse surface (x, y) scanning is performed by a digital micromirror device (DMD). The DMD is imaged onto the object's surface allowing for confocal surface scanning of the field of view at a rate faster than video rate without physical movement of the sample. 3D reconstruction is performed a posteriori from stacks of 2D image planes acquired at different depths. A description of the experimental setup with system design issues and solutions are presented. Backscatter noise and diffraction noise due to the periodic micromirror structure is minimized using spatial filtering and polarization coding techniques. Using a 100× objective, the longitudinal point spread function (FWHM) was measured at 2.1 μm, with simultaneous transverse resolution of 228.0 lines/mm. The optical resolution performance of our microscope with real-time scanning provided by the DMD, is shown to be effectively equivalent to those of conventional confocal microscopes. The 3D image capabilities of our scanning system using the DMD were demonstrated on various objects.