Tom N. Cornsweet

Servo-Controlled Infrared Optometer*

A device is described that provides an electrical signal proportional to the instantaneous refractive power of the human eye. Infrared light illuminates a target whose optical distance from the subject’s eye can be changed rapidly. The position of this target is servo controlled in such a way that it remains conjugate with the retina regardless of changes of the subject’s state of accommodation. The position of the target provides a direct measure of refractive power. The device may be used on an undrugged eye and does not interfere with normal visual tasks.

Ocular-Focus Stimulator*

Author(s): Cornsweet, TN; Crane, HD | Abstract: The simple instrument described in this letter performs the following function. When it is pointed at any object, test pattern, or other form of visual display, the optical distance between the observer and the object can be changed at will while the brightness and visual angle of the object are invariant. Further, the observer sees the object through a pupil of any desired shape and transmittance.