Rearview mirror control circuit
US4793690A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 27, 1987 |
| Grant date | Dec 27, 1988 |
| Priority date | — |
| Expiry date | Apr 27, 2007 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB60R1/088
- WIPO fieldTransport
- WIPO sectorMechanical engineering
Abstract
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 amb…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.