Contrast enhancement by oblique illumination microscopy with an LED array

Abstract

Oblique illumination microscopy is a contrast-enhancing technique accomplished by changing the illumination angle. Conventionally, oblique illumination is achieved by illuminating the sample with a part of the light coming from the condenser lens. This paper describes a low-cost oblique illumination microscope with an LED array. The LED array can electrically change asymmetric illumination patterns. By oblique illumination, we enhanced the contrast of obtained images compared with that of a bright-field image. The contrast obtained by oblique illumination was approximately 3.5 times higher than those of bright-field images obtained by a standard bright-field microscope. The feasibility of oblique illumination microscopy with an LED array is demonstrated by observing diatom cells and buccal epithelial cells.