Optical: systems and elements – Mirror – Plural mirrors or reflecting surfaces
Patent
1994-07-28
1997-03-04
Dzierzynski, Paul M.
Optical: systems and elements
Mirror
Plural mirrors or reflecting surfaces
359866, 359868, G02B 508, G02B 510
Patent
active
056085818
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a rear view apparatus for vehicles, especially passenger cars, and bears a resemblance to periscopic viewing apparatuses.
2. Description of the Prior Art
Periscopic rear view apparatuses in themselves are known. Use in passenger cars, however, has taken place hardly or not at all, because the known appartuses have drawbacks attached to them. These drawbacks concern, among other things, the restricted horizontal angle of vision of the known periscope, consisting of a tubular housing containing an optical apparatus by which an upright rear view image is obtained by means of mirrors and/or prisms and/or lenses.
A drawback of enlarging the angle of vision by using convex or cylindrical mirrors and the like is that image reduction takes place, whereby distances to the rear can no longer be properly estimated, which can pose a threat to road safety. Enlarging the angle of vision by strongly widening the periscope raises the drawback of increasing air resistance of the periscope which rises above the car roof, while the large dimensions also hinder the fitting and positioning of the periscope tube. Apart from this, the high costs of the known apparatuses are also a consideration.
SUMMARY OF THE INVENTION
The drawbacks mentioned are avoided or greatly reduced in the apparatus according to the invention, characterized in that the apparatus consists of at least three mirrors of which the first mirror is placed higher than the car roof with the mirror surface inclined towards the rear, the third mirror is placed in the driver's cabin in front of the head of the driver and with the mirror surface directed towards the driver and the second mirror is placed in such a way that the rays of light inciding from the rear reach the eye of the driver via the first mirror, subsequently via the second mirror and finally via the third mirror, wherein the cabin roof is provided with a transparent part through which passes the course of the rays between the first and the third mirror.
A second important characteristic of the apparatus according to the invention is that at least two of the mirror surfaces of the mirrors which are used are twisted. This torsion makes it possible to obtain such a field of vision that an optimal part of the total rearward field of view can be seen by the driver when the first mirror has a limited height. The optical image blurr which is caused by torsion of one of the mirror surfaces is corrected by an opposed torsion of the second and/or the third mirror. The torsion also allows for correction of the inclination of the image as well as the optical effect of a limited non-parallelism of the longitudinal axes of the mirror surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described and explained in more detail by means of the following figures:
FIGS. 1a and 1b: illustrates the arrangement of the three mirrors,
FIGS. 2a and 2b: shows a second possible arrangement of the three mirrors,
FIG. 3: shows a third arrangement of the three mirrors,
FIG. 4: shows how use can be made of a transparent sliding- or tilting roof which is already present,
FIG. 5: illustrates the torsion of the mirrors and the effect thereof on the rearward field of vision,
FIG. 6: shows some constructional details for the assembly of the mirrors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, the first mirror (1) is secured higher than the car roof (4) as a separate mirror with the mirror surface directed backwardly and inclined downwardly. The second mirror surface (2) is secured immediately below the window (5) in the car roof, with the mirror surface directed towards the front. The third mirror (3) is situated in front of the head of the driver (6), with the mirror surface directed towards the driver. The course of the rays has been indicated in the figure (21). The figure shows that at its lower side, the bottom line of vision (7) is bordered by the rearside (8) of the car roof (4). The upper line of vision (9) has, for practi
REFERENCES:
patent: 3774996 (1973-11-01), Donnelly
patent: 3806233 (1974-04-01), Stefano
patent: 3827788 (1974-08-01), Clark
patent: 4490013 (1984-12-01), Pribis
patent: 4643544 (1987-02-01), Loughram
Dzierzynski Paul M.
Sikder Mohammad Y
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