Phase Contrast Attachment PSAW This equipmant is useful for viewing detailed atructure of unstained or living organisms. This is due to the unique ability of phase contrast to convert small difference in thickness and refractive index of the specimen into difference in brightness. The assembly consists of phase turret condenser having glass of numerical aperture 1.25 with iris diaphragm, phase achromatic objectives 10x,20x, 40x and 100x (oil immersion) having 45mm par focal distance, Phase centering telescopic eye piece, green filter and turret condenser key.