Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Patent
1993-11-18
1998-03-24
Phan, James
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
359640, 359837, G02B 2710
Patent
active
057319006
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an optical reflector suitable for a wide range of use including, for example, use as an external vehicle rear view mirror.
A conventional reflector, or plane mirror, such as used, for example, as an external rear view mirror of a vehicle, can present problems due to its substantial lateral extent, that is, its extent in the plane of the reflector. Such problems include aerodynamic drag exerted by laterally projecting exterior mirrors. At medium and high speeds, the aerodynamic drag factor may account for up to 80% of the total mechanical energy loss resulting in both increased fuel consumption and noise. Furthermore, although exterior rear-view mirrors are designed to yield under impact, they remain a traffic hazard. Mirror yield is of most benefit in very low speed impacts. In higher speed impacts, whether against another mirror or a pedestrian, mirror inertia plays an important role and considerable damage and/or injury can occur.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical reflector. The optical reflector of the present invention is suitable for use as a motor vehicle rear-view mirror, but this example is given without prejudice to the generality of the invention which can also be applied to a wide range of other uses.
According to one aspect of the present invention, there is provided an optical reflector having a plurality of elongate elemental reflectors in an array spaced from one another in a direction generally parallel to the optical axis of each individual elemental reflector whereby to provide a composite image of an object viewed from at least a limited range of angles to one side of the array, in which each elemental reflector is formed as a transparent face or facet of a transparent body having two opposed surfaces, such that light entering the reflector through one said surface and approaching the face or facet through the body at a certain angle or range of angles thereto is reflected by total internal reflection and exits the reflector through the other of the said surfaces, and such that light approaching the face or facet through the body at angles other than the said certain angle or range of angles is transmitted therethrough.
The elemental reflectors preferably all lie generally parallel to one another, with the optical axis of the reflector as a whole parallel to the optical axis of the individual elemental reflectors.
With such an arrangement, the main extent of the optical reflector is generally parallel to the optical axis of the reflector array (this being normal to the plane of reflection of the elemental reflectors which facilitates the use of the reflector in applications such as for a vehicle rear view mirror.
The transparent body consists of refractive material chosen such that a medium of lower refractive index, typically defining the interface at the said transparent face or facet, allows total internal reflection to take place.
Embodiments of the reflector may be formed in which, at least one of the entry and exit faces is provided with slots in the refractive-material body, these slots extending towards the opposite face and being so arranged that one surface of each slot constitutes a respective one of the said surfaces.
The size and/or inclination of the elemental reflecting surfaces may vary progressively along the array of reflecting surfaces. Furthermore, the axis of the array may be curved to enhance the viewing of close objects.
Preferably, the entry and/or exit faces on the refractive-material body has a respective elemental refractor facet associated with each said reflecting surface, each such facet being angled to the main axis of the array such as to modify the optical characteristics of the reflector. The physical parameters of the elemental refractor facet may be such that they vary progressively along the array.
The optical reflector can be combined with one or more refracting devices positioned across the entry and/or exit faces of the
REFERENCES:
patent: 4989964 (1991-02-01), Meise
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