Friday, March 16, 2007

The Hoffman modulation contrast (HMC) microscope is another method how transparent, or close to it, objects can be visualized. Hoffman modulation contrast accentuates phase gradients within the sample, and displays them in the image as levels of gray modulated lighter or darker than an average background gray. A special filter, the modulator, is placed in the objective and a special aperture. It is available as new standard equipment or for upgrading compound microscopes. The modulator filter is constructed so as to have three regions of different neutral densities, ranging from low to a high attenuation. The condenser slit is adjusted so that light transmission through the slit falls on the gray region of the modulator. HMC offers, at moderate cost, virtually all of the capabilities of the other contrast systems, plus important additional advantages. Hoffman Modulation Contrast System is a cost effective upgrade to 3-dimensional appearing images for both the inverted and upright compound microscope.