Visualization of oriented hemoglobin S in individual erythrocytes by differential extinction of polarized light

The distribution of oriented, polymerized sickle cell hemoglobin (hemoglobin S) in erythrocytes is visualized with a microscope that produces an image proportional to linear dichroism. Monochromatic light alternately polarized along two perpendicular directions is incident on the sample. The image is focused on a diode array, and the digital output is used to form two images. One is the usual image proportional to the average transmitted light intensity of the two incident polarizations of light; the other is a linear differential image proportional to the linear dichroism of the sample. This quantitative image can specifically reveal oriented hemoglobin molecules with a sensitivity of about 4000 oriented molecules per picture element of the image.