GB2126548A

GB2126548A - Rearview mirror assembly

Info

Publication number: GB2126548A
Application number: GB08318735A
Authority: GB
Inventors: Charles Vincent Kerr
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-07-12
Filing date: 1983-07-11
Publication date: 1984-03-28
Also published as: GB8318735D0

Abstract

A motor vehicle rearview mirror assembly has a primary mirror to give a motorist a primary rearward field of vision, and a secondary mirror continguous to the primary mirror, to give a secondary field of vision contiguous to the primary field of vision. The secondary mirror is convex to give a laterally extended field of vision. The primary and secondary fields of vision are continuous, i.e. they do not overlap and there is no gap therebetween. Conveniently the primary mirror is plane and the secondary mirror is piano convex, preferably piano circular convex. <IMAGE>

Description

SPECIFICATION Rear view mirror assembly This invention relates to a motorvehicle rear view mirror assembly.

Motor Vehicle rear view mirrors can be mounted externally or internally. They may be mounted on the door or window ofthe vehicle or on a special bracket.

Plane mirrors are often used as the dimensions of the imageformed by a plane mirror are the same as those of the object, and the image is formed at the same distance behind the mirror as the object is in front of the mirror. Hence the image of an object seen by reflection subtends more or less the same angle at the eye as would the object if it were viewed directly. A disadvantage is that such mirrors do not give as great a field of view as a convex mirror ofthe same size, and may give an inadequate field of view unless they are inordinately large.

Convex mirrors have been used to provide a greater field ofviewthan plane mirrors,thefield of view increasing as the convexity ofthe mirrors increases. A disadvantage is that the image is reduced with respect to the object and informed behindthe mirror at a distance of half the mirror's radius of curvature, for a distance object. The end result is a smaller retinal image than when the object is viewed directly and, in addition, the driver's eyes have to focus correctly in order to seethe image clearly. The greaterthe convexity, the more accentuated are the effects. Since the brain associates smallness with greater distance, faulty judgements of a potentially dangerous nature can occur if the driver judges that an object seen in the mirror isfurther away than it is.

The present invention aims to provide a motor vehicle component which will alleviate the above problems.

In accordance with the invention, there is provided a motor vehicle rear view mirror assembly comprising a mirror mounting means for mounting the mirror on a motorvehicle,the mirror including a primary mirrorfor providing a motorist in the motor vehicle with a primary rearward field of vision; and a secondary mirror, contiguous to the primary mirror, for providing the motorist with a secondary rearward field of vision contiguous to the primary field of vision, the secondary mirror being convex such as to have the secondary field of vision laterally extended remote from the primaryfield ofvision. For purposes ofthis specification, "convex" is to be interpreted as meaning "bulging" and is not limited to meaning part circularorpartspherical.

The mirror may be a composite mirror, the primary and secondary mirrors being separate and being arranged such thatthe primary and secondary fields of vision are continuous. By "Continuous" is meant thatthefieldsofvision provided bythetwo mirrors do notoverlap oneanotherandthatthere is no gap or blind spot between them.

lnstead,the primary and secondary mirrors may be integral, their adjacent margins being smoothly blended. Smooth blending ofthe adjacent margins will ensure that the primary and secondaryfields of vision are continuous.

Preferably, the primary mirror is plane. However, it may instead be convex. Then the secondary mirror will be significantly more convex than the primary mirror.

Preferably, the secondary mirror is plano-convex.

In a preferred embodiment, the primary mirror is plane, the secondary mirror is plano-convex, and the axis of curvature of the secondary mirror is parallel to the plane of the primary mirror. Without wishing to be bound by theory the Applicant believes that, when the secondary mirror is circular convex, the axis of curvature will be fixed, and will be in a plane which is perpendiculartothe extreme edge. Whenthesecondary mirror is not circular convex, the axis of curvature will bea moving axis, and its starting position corresponding to the edge ofthe secondary mirror at the interface of the mirrors will be in a plane which is perpendiculartotheadjacentedgeofthe primary mirror. The criteria immediately above are believed to be satisfied when the adjacent margins are smoothly blended.

The rearview mirror assembly may be adapted for mounting on the outside of the vehicle, the secondary mirror being arranged to be on the outer side of the primary mirror.

The rearview mirror assembly may include adjusting means permitting the angular disposition ofthe mirror to be adjusted such that the primary and secondary mirrors move in unison.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure lisa schematic view showing a motor vehicle having a rearview mirror assembly according to the invention mounted thereon; Figure 2 isafrontviewto a larger scale ofthe mirror of the mirror assembly of Figure 1; Figure 3 is a plan view showing the mirror of Figure 2; Figures 4 and 5 show three dimensional views of respectively a primary mirror and a secondary mirror which in combination form the mirror of Figure 2.

Referringfirstlyto Figure 1,a motorvehicle 10 has mounted on itsoutsidea rearview mirror assembly 12 according to the invention. The mirror assembly 12 may be mounted on the vehicle in any suitable manner. A driver 14 sits within the vehicle 10 and, by viewing the mirror assembly 12, is provided with a primary field of rearward vision indicated at 16 and a secondary field of rearward vision indicated at 18.

With reference to Figure 2 and Figure 3, in order to provide the primary and secondary fields 16, 18 of vision, the mirror of the mirror assembly 12 includes a primary mirror 20 and a secondary mirror 22 disposed outside the primary mirror 20. The mirrors 20,22 may be mounted in a suitable mounting, the outline of which is illustrated schematically at 24. The mounting may be provided with any suitable means for attaching the componentto the vehicle.

The primary mirror 20 in the embodiment shown is plane, and the secondary mirror 22 is plano-convex and more specifically convex cylindrical. The mirrors 20,22 are arranged edgeto edge, and the axis 28 of curvature ofthesecondary mirror22 lies in the plane (indicated at 30) which is normal to that edge ofthe primary mirror20touching the edge ofthesecondary mirror 22.

In Figure 4 it is shown that, when the back surfaces of the mirror 20 is to be silvered than both the back and front surfaces of the primary mirror are made plane and parallel. Forthe secondary mirror22, the back surface is made concave cylindrical corresponding to the front surface which is convex cylindrical.

With th is arrangement, the primary m irror 20 provides the motorist in the vehicle 10 with the primary field of vision 16 as shown in Figure 1, and the convex cylindrical secondary mirror 22, provides the motorist with the field of vision 18 which is laterally extended in a region remote from the primary field of vision 16. The field of vision 18 is continuous with and outwardly of the field ofvision 16. It does not overlap the field of vision 16 and there is no gap between the two fields of vision.

The primary mirror20 may serve as the main mirror for rearward viewing. The secondary mirror 22 may serve to extend the rearward vision laterally to warn the motorist when a vehicle is in the laterally extended field of vision, which would, butforthe secondary mirror22, be in his "blind spot". The advantages ofthe embodiment illustrated are:1) Forthesame horizontal field of viewthe compo- site mirror is smallerthan would be a plane mirror.

2) Accuracy in judging distances is not compromised as the primary mirror is plane.

3) There is no vertical parallax between the images of the same object formed by the primary and secondary mirrors.

4) There 5 no difference in vertical image size between the images of the same object formed by the primary and secondary mirrors because the secondary mirror is piano-convex.

5) For the same object, light reflected by the secon- darymirrorin meridians parallel to the axis meridian has the same vergence as light reflected by the primary mirror because the secondary mirror is convex cylindrical. Hence there is no extra focussing effort required in order to see horizontally disposed detail ofthe secondary mirror image.

It will be appreciated that the dimensions and curvatures ofthe mirrors will be selected bearing in mind their intended application.

Claims

1. A motor vehicle rear view mirror assembly comprising a mirrorand mounting meansformounting the mirror on a motorvehicle, the mirror including a primary mirrorfor providing a motorist in the motorvehiclewith a primary rearward field of vision; and a secondary mirror, contiguous to the primary mirror, for providing the motorist with a secondary rearward field of vision contiguous to the primary field of vision, the secondary mirror being convex such as to have the secondary field of vision laterally extended remote from the primary field of vision.

2. A rearview mirror assembly as claimed in Claim 1, in which the mirror is a composite mirror, the primary and secondary mirrors being separate and being arranged such that the primary and secondary fields of vision are continuous.

3. A rear mirror assembly as claimed in Claim 1 in which the primary and secondary mirrors are integral, their adjacent margins being smoothly blended.

4. A rearview mirror assembly as claimed in any one of Claims 1,2 or3 in which the primary mirror is plane.

5. A rearview mirror assembly as claimed in any one ofthe prececing claims in which the secondary mirror is plano-convex.

6. Arearviewmirrorassemblyasclaimed in any one of Claims 1,2 and 3 in which the primary mirror is plane, the secondary mirror is plano-convex, and the axis of curvature of the secondary mirror is parallel to the plane ofthe primary mirror.

7. A rearview mirror assembly as claimed in any one ofthe preceding claims which is adapted for mounting on the outside of the vehicie, the secondary mirror being arranged to be on the outerside ofthe primary mirror.

8. A rearview mirror assembly as claimed in any one ofthe preceding claims which includes adjusting means permitting the angular disposition of the mirrorto be adjusted such that the primary and secondary mirrors move in unison.

9. A motor vehicle rearview mirror assembly substantially as herein described and illustrated.