AUTOMOTIVE CONVEX MIRRORS - OPTICAL PROPERTIES
This study reporesents an attempt to bring under one cover as many of the optical properties of convex mirror systems that are accessibile by computational tehcniques. No claim can be made that the assumptions made in this report actually describe a realistic set of assumptions for automotive use of convex mirrors, but act as a conservative starting point. Convex mirrors represent a most promising cost effective means for improving driver vision. When a person observes an object through a convex mirror, the object is seen by a left and right eye from different areas on the mirror surface. The mirror surface is aportion of a sphere and hence the image of the observed object seen by each eye could be separated vertically or horizontally from each other. Also, if the radius of the surface is different at the two points where the eyes observe the object, one image could be larger or smaller than the other or rotated with respect to each other. These optical defects could cause an observer to process the information differently than if he were looking at an object directly. Under centain conditions, any one or a combination of the defects listed above could make it difficult for an observer to focus on or accommodate to the images. The magnitude of the effects will be a function of the image distance from the observer's eyes and the visula capability of the observer. In this report, the magnitude of the four optical defects (devergence, dipvergence, differential magnification, and cyclo rotation) were determined for a series of mirror radii and locations appropriate to their use as indirect vision devices on an automobile. Also, the accommodation of subjects to viewing images in convex mirrors which are closer than those seen through a plane mirror is considered. Tolerances were determined for the various optical defects and accommodation and converted the tolerances into recommendations for mirror radii, the location of mirror on the vehicle, and mirror surface quality. No tolerance data could be found that pertained directly to optical devices associated with the driving task. Although a direct relationship cannot be shown between these tolerance recommendations and the driving task, this study does determine the conclusions which could be drawn if visual performance form convex mirrors were presumed to be comparable to optical instruments and eyeglasses. However, a glance into a mirror to note the position of a vehicle is a decidedly different visual task those associated with optical instruments (microscope, binoculars, etc.) and eyeglasses. It is recommended that these conclusions and recommendations be placed in their proper perspective before applying them to convex mirrors on motor vehicles.
Donnelly Mirrors, Incorporated60 Fenton Street
Holland, MI United States 49423
- Seeser, J
- Publication Date: 1974-2
- Features: Figures; References; Tables;
- Pagination: 59 p.
- TRT Terms: Convex mirrors; Curvature; Lenses (Optics); Mirrors; Optical properties; Photometry
- Old TRIS Terms: Optical lenses
- Subject Areas: Highways; Safety and Human Factors;
- Accession Number: 00125415
- Record Type: Publication
- Report/Paper Numbers: TR 201
- Files: TRIS
- Created Date: Oct 18 1975 12:00AM