A contrast technique, in which phase contrast and inclined unilateral illumination are mixed, has been developed for the examination of living cells in culture vessels. An additional stop shaped like a ring sector is used on the illumination side, permitting unilateral inclined illumination. Unilateral darkfield, VAREL contrast superimposed on phase contrast and inclined brightfield are set by shifting the stop in the radial direction from the outside to the inside. This is a very low-price method of imaging cells in culture vessels.
The image below shows pseudo-relief. Even vessels with a curved bottom allow a useful image to be produced. Phase contrast alone sometimes fails in such cases because a curved chamber base acts like a lens and impairs the superimposition of phase rings. The method is successfully used for the examination of living objects (micromanipulation).
A slider contains two of the mentioned sectors to allow illumination to be performed from the left or right, as required. This makes it possible to contrast cells even in the “holes” of microtiter plates in the vicinity of the “hole” edges.