04793690 is referenced by 510 patents and cites 23 patents.

The specification discloses an automatic rearview mirror control circuit which models the physiological response of the human eye to fluctuating light levels as observed in typical driving conditions. The control circuit calculates an ambient light signal representative of light levels within the driver's field of view and a rear light signal representative of light levels in a direction generally incident to the reflective element. The reflectivity of the reflective element is controlled to optimize rear image information while minimizing on rear image glare at the driver's eyes. The control circuit includes a multiple-rate filter for time-averaging an ambient light signal over a shorter time period during increasing ambient light intensities than during decreasing ambient light intensities to simulate the more rapid adaptation of the human eye to increasing light intensities than to decreasing light intensities. The control circuit automatically alters or adjusts the sensitivity of the mirror to rear light based on the ambient light level. The mirror is more sensitive to rear light in relatively low ambient light, such as experienced on rural highways, than in relatively high ambient light, such as is experienced on urban highways. The control circuit calculates ambient light within the driver' s field of view. The calculation takes into account the forward light, rear light reflected from the interior rearview mirror, and/or rear light reflected from the windshield, pillars, headliner, and exterior rearview mirrors.

Title
Rearview mirror control circuit
Application Number
888129
Publication Number
4793690
Application Date
April 27, 1987
Publication Date
December 27, 1988
Inventor
Kenneth Schofield
Holland
MI, US
Keith W Molyneux
Ballymore Eustace
IE
Edward A Gahan
Holland
MI, US
Agent
Price Heneveld Cooper DeWitt & Litton
Assignee
Donnelly Corporation
MI, US
IPC
G02B 17/00
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