Differential Interference Contrast Microscope with Continuously Variable Wavefront Shear and Pupilar Compensation

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Abstract
A trans-illumination double-refracting interference microscope with pupilar compensation and continuously variable amount of wavefront shear has been developed. A combination of two birefringent prisms separated by a half-wave plate is placed in the image space of the objective. One of these prisms is, together with the half-wave plate, rotatable round the objective axis. This enables the amount of wavefront shear to be changed. The other prism can be translated in a direction perpendicular to the microscope axis. This translation serves for shifting the phase of interfering light waves. Construction parameters of both prisms are fixed so as to bring their interference fringes into coincidence with the back focal point of the objective. Another combination of two birefringent prisms, separated also by a half-wave plate, is placed in front of the condenser. Both these prisms are set so as to bring their own interference fringes into coincidence with the front focal point of the condenser. One of the subcondenser prisms is, together with the half-wave plate, rotatable round the condenser axis, and it acts as compensator for the rotatable birefringent prism placed above the objective, whereas the other subcondenser prism is immovable and it acts as compensator for the slidable birefringent prism located in the microscope tube.