Proceedings Article | 25 February 2010
Proc. SPIE. 7570, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XVII
KEYWORDS: Confocal microscopy, Microscopes, Gaussian beams, Microscopy, Reflectivity, Fourier transforms, Skin cancer, Biopsy, Objectives, Line scan image sensors
Confocal reflectance microscopy may enable screening and diagnosis of skin cancers noninvasively and in real-time,
as an adjunct to biopsy and pathology. Current instruments are large, complex, and expensive. A simpler, confocal
line-scanning microscope may accelerate the translation of confocal microscopy in clinical and surgical
dermatology. A confocal reflectance microscope may use a beamsplitter, transmitting and detecting through the
pupil, or a divided pupil, or theta configuration, with half used for transmission and half for detection. The divided
pupil may offer better sectioning and contrast.
We present a Fourier optics model and compare the on-axis irradiance of a confocal point-scanning microscope in
both pupil configurations, optimizing the profile of a Gaussian beam in a circular or semicircular aperture. We
repeat both calculations with a cylindrical lens which focuses the source to a line. The variable parameter is the fillfactor,
h, the ratio of the 1/e2 diameter of the Gaussian beam to the diameter of the full aperture. The optimal values of h, for point scanning are 0.90 (full) and 0.66 for the half-aperture. For line-scanning, the fill-factors are 1.02
(full) and 0.52 (half).
Additional parameters to consider are the optimal location of the point-source beam in the divided-pupil
configuration, the optimal line width for the line-source, and the width of the aperture in the divided-pupil
configuration. Additional figures of merit are field-of-view and sectioning. Use of optimal designs is critical in
comparing the experimental performance of the different configurations.
