An apparatus for measuring a subject's cornea, comprising (A.) a slit projection subsystem comprising a light source, (B.) a mask subsystem disposed in a path of light from the light source, comprising a first slit mask defining a plurality of apertures, (C.) a movement apparatus adapted to move at least a portion of the slit projection subsystem, the movement apparatus configured and arranged such that, by moving the portion of the slit projection subsystem, portions of the light can be selectively transmitted through an aperture of the plurality of apertures toward the cornea, (D.) an imaging element configured and arranged to image at least one of the plurality of apertures onto the cornea, and (E.) an image capture subsystem arranged to capture images of the portions of light after the light impinges on the cornea.