Apparatus and method for reducing headlight glare

An improved glare control system usable on a vehicle for reducing headlight glare from oncoming vehicles traveling along an adjacent path of travel, said control system including a headlight for illuminating the vehicle's path of travel, means for interrupting the light output of said headlight cyclically at a fixed frequency with each headlight cycle consisting of a fixed light emissive interval followed by a fixed nonemissive interval, a visor switchable between light transmissive and opaque states for, respectively, unblocking and blocking the operator's view of his vehicle's path of travel and said adjacent path of travel, and visor switching means operating cyclically in synchronism with said headlight cycle for automatically switching said visor to said transmissive state for a transmissive interval that coincides with said headlight emissive interval and thereafter being responsive to a visor modulation signal for switching said visor to said opaque state wherein said improvement comprises:

• means for measuring the headlight glare intensity of said adjacent path of travel and providing a glare level signal that is proportional to the measured intensity;
• and
• means responsive to said glare level signal for selectively providing said modulation signal to said visor switching means to vary the opaque interval and thereby adjust the transmissive-to-opaque interval ratio of said visor cycle in accordance with measured glare intensity so that when said glare intensity is below a predetermined lower limit said modulation signal is withheld and said visor remains in said transmissive state for the entire visor cycle, as said glare intensity progressively increases above said lower limit said opaque interval is progressively increased proportionally to decrease said ratio, and when said measured intensity exceeds a predetermined upper limit said opaque interval is set at a maximum thereby establishing said ratio at a minimum for maximum glare reduction.

A method of reducing headlight glare from oncoming vehicles traveling along an adjacent path of travel comprising the steps of:

• periodically interrupting the light output of a vehicle's headlight so it operates cyclically at a fixed frequency with each headlight cycle consisting of a fixed light emissive interval followed by a fixed nonemissive interval;
• providing a visor that is cyclically switchable between light transmissive and opaque states for, respectively, unblocking and blocking the vehicle operator's view of his vehicle's path of travel and said adjacent path of travel and is adjustable to vary the transmissive-to-opaque interval ratio of a visor cycle to change the apparent density of the visor;
• operating said visor cyclically in synchronism with said headlight cycle so that said visor is automatically switched to said transmissive state for a transmissive interval that coincides with said headlight emissive interval and thereafter is switchable to said opaque state;
• measuring the headlight glare intesity of said adjacent path of travel;
• and
• varying said transmissive-to-opaque interval ratio in accordance with the measured glare intensity level by selectively switching said visor to said opaque state so that at least between predetermined upper and lower glare intensity limits the apparent density of said visor increases with increasing glare intensity and decreases with decreasing glare intensity.