Abstract

In their 1970 patent [1], Luis Alvarez and William Humphrey invented a pair of conjugate, rotationally asymmetrical, aspheric surfaces such that the lateral movement of these surfaces across the optical axis resulted in an element of variable optical power. This paper presents two designs, which use these basic concepts to extend capabilities of a miniature, multi-modal microscope (4M) device by providing it with an additional object depth sampling ability. The 4M devices are miniaturized microscopes first developed by Michael Descour et al for the detection of pre-cancer [2]. The pre-cancer tissues to be imaged have a finite depth and experiments have suggested that in order to study the various morphologic and biochemical changes in tissue, we need to have the ability to sample object depths up to 200 microns. Thus in order to fully develop the various modalities envisioned by Descour et al [2] such as optical sectioning, it is necessary to have a 4M device which can image object planes at different depths on to a stationary image plane. The two designs discussed in this paper present different ways of solving the same problem. The first design is a variable power 4M device, which exactly applies the Alvarez-Humphrey principle to vary the optical power, thus enabling it to image different object depths on a fixed image plane. The second design presents a novel and indirect application of the Alvarez-Humphrey device. In this design, lateral movement of one of the plates enables us to image different object depths on the same image plane at constant magnification, i.e. without changing the optical power. This is done by moving the image laterally on a fixed image plane.

© 2003 Optical Society of America