Optical characteristics of optical systems, such as the eye, are measured including vision defects of the eye using a collimated beam from a diode laser focused onto the anterior surface of the cornea of the eye for providing a finite source of secondary radiation on the retina of the eye, the image...http://www.google.se/patents/US6270221?utm_source=gb-gplus-sharePatent US6270221 - Apparatus and method for measuring vision defects of a human eye
