A Low Cost Time-Coded Confocal Microscope

Abstract

Confocal microscopy is a high resolution microscope technique, which operates by scanning a diffraction limited focal spot over a sample. This focal point on the sample is then imaged through an objective lens and a pinhole to ensure that only the information coming from the focal plane is captured and the information from the other planes are blocked by the pinhole. Although this gives better lateral resolution, this method is inefficient in terms of the amount of light required and the scanning time. In this paper, we discuss an alternative solution using digital micromirror device (DMD) to perform multiple focal points scanning simultaneously. This is done by projecting a series of orthogonal codes onto the DMD. The corresponding images obtained from the orthogonal codes are then saved and processed offline in a computer to calculate a confocal image. We use incoherent illumination rather than a laser source as used previously. We also discuss a key issue in this confocal system, which is a suitable separation between each focal spots and a crosstalk between them. We demonstrate that the proposed confocal configuration with the DMD device improves the light efficiency, the scanning time through the parallel confocal spots and a laser source is not required.