Optical: systems and elements – Glare or unwanted light reduction – With mirror
Patent
1994-10-24
1997-04-15
Shafer, Ricky D.
Optical: systems and elements
Glare or unwanted light reduction
With mirror
359604, 359864, 359866, 359868, G02B 508, G02B 510, B60R 104, B60R 108
Patent
active
056215690
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a rear-view mirror for motor vehicles, comprising a plane-mirror section and at least one convexly curved side section contiguous with the sides of the plane-mirror section and sloping steadily, and having a curvature of zero at the transition line to the plane-mirror section, the curvature of the side section increasing progressively with increasing distance from the plane-mirror section.
A rear-view mirror of this type is known from Netherlands Patent Document NL-A-6 400 067 as an outside mirror for a vehicle. In this case the flat mirror makes a continuous changeover into a spherical mirror with a decreasing curvature radius. Because the outside mirror is disposed under the eye level of the driver and only the lateral space is perceived from the vehicle, the visual distortions of the horizontal line that result in the transitional area into the spherical mirror are tolerable. For an inside mirror disposed above the eye level of the driver and offset from it toward the vehicle center, and which also encompasses at least the viewing area behind the vehicle, double images and a severe distortion of the horizontal line result with a dimensioning of this type, leading to visual errors.
A further rear-view mirror is already known from European Patent Document 0 210 757 A 2. In this mirror it is provided that the flat mirror section changes over tangentially into the curved section, whose curvature increases suddenly at the transition line and is further increased in spiral fashion. The sudden change in curvature is disadvantageous not only for recognizability of a reflected image due to resulting double images, but also for production.
Further, inside rear-view mirrors are known from German Patent Document DE 17 55 828 A1 in which a horizontally and vertically curved side-mirror section is contiguous with a plane-mirror section. The curvature radii of the side-mirror section are intended to become smaller with increasing distance from the mirror center. Although the curvature of this side-mirror section increases outwardly, this increase in curvature takes place in steps, not in a steady manner. This steplike increase in curvature causes a transition that is noticeable as a kink, not merely at the transition line from the plane-mirror section into the side-mirror section, but at each changeover of curvature radius, thus preventing a side view adequate to fulfill safety requirements, because as the number of radius changeovers increases, an equal number of kinks that distort the reflected image and cause double images is present on the side-mirror section. An embodiment of the side mirror curvature may permit a virtually distortion-free side view for the driver if the respective difference of the curvature radii is set to be appropriately low; however, even with this determination of curvature, no seamless changeover of curvature is provided from the plane-mirror section into the curved side-mirror section, so that the rear view is impaired at least at the transition line, which has a negative overall effect on the performance capability of this rear-view mirror.
Further, inside rear-view mirrors are known from German Patent Document DE 28 49 468 A 1 in which the plane-mirror section changes over, with respect to its horizontal axis, to a convexly curved side-mirror section shaped uniformly in the manner of a shell of a cylinder, by means of which the viewing angle is enlarged by the convex curvature of the side-mirror section in comparison to the plane-mirror section. This mirror permits a side view from the vehicle, but has the disadvantage of a distorted reflection of the side viewing field because of the cylinder shell-shaped curvature. An assessment of the position of overtaking vehicles is exceedingly difficult. Moreover, there is no seamless changeover from the plane-mirror section into the curved side-mirror section, because the curvature of the side-mirror section changes suddenly at the transition line. For this reason the transition line is always perceived by the driver as
REFERENCES:
patent: 3764201 (1973-10-01), Haile
patent: 4258979 (1981-03-01), Mahin
patent: 4264144 (1981-04-01), McCord
patent: 4331382 (1982-05-01), Graff
patent: 4449786 (1984-05-01), McCord
patent: 5005962 (1991-04-01), Edelman
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