Homal

Homal, Homal, an ocular used in microphotography instead of regular oculars, represents a system of lenses which collectively form a negative lens similar to a binocular ocular. It serves like compensating oculars to correct image defects due to chromatic aberration and especially to straighten the curvature of the image plane. Focal length - 20 mm. Not suitable for subjective observation. Since the degree of field correction depends on the magnification of the objective, Zeiss manufactures Homal in three numbers adapted to its objectives: I - for apochromats 10, 20 and achromats 6 to 20; III - for apochromats 40, 60, for achromats 40 to 90, as well as for achromatic homogeneous immersion; and IV - for immersion apochromats. Negative lenses of this type are also included in the ocular microphotographic apparatus 'Phocu' (Zeiss) and others. Price of each Homal - 75 marks.