Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1979-02-28
1981-09-01
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250206, 351 7, A61B 310, H01J 4014
Patent
active
042874106
ABSTRACT:
An eye tracker measures the point in space on which the eye is fixated. An input mirror reflects an input image into the eye and directs the Purkinje images so formed in the eye back into the eye tracker mechanism. The images are gathered by a collimating objective and directed through focusing and deflecting optics so as to be incident on light flux measuring devices (photodetectors). The optics and detectors are connected in closed loop servo systems which keep the first and fourth Purkinje images centered on their respective photodetectors, keep the input beam properly positioned in the eye, and at the same time generate signals responsive to movement of the first Purkinje image to give a measure of both translational and rotational horizontal and vertical eye movement and movement of the fourth Purkinje image to give a measure of purely horizontal and vertical eye movement. Circuitry combines the signals to generate a measure of purely translational horizontal and vertical signals. The first Purkinje image is also directed to be focused nominally at a given focal distance. Light flux measuring devices are positioned equal distances before and behind the given focal distance, whereby the output signal from the devices provides a measure of focus and axial position of the eye and the difference in output signals is used in a servo system to drive the collimating objective, thereby to focus the first Purkinje image at the given focal distance.
REFERENCES:
patent: 3712716 (1973-01-01), Cornsweet et al.
patent: 3724932 (1973-03-01), Cornsweet et al.
patent: 3804496 (1974-04-01), Crane et al.
patent: 3925603 (1975-12-01), Naruse et al.
patent: 3967110 (1976-06-01), Rogers et al.
Crane Hewitt D.
Steele Carroll M.
Faubion Urban H.
Nelms David C.
SRI - International
Westin Edward P.
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