VEHICLE REVERSING DEVICE

Abstract: A vehicle (1) includes an optical device (3) mounted on the exterior of the vehicle at the rear corner thereof. The device (3) consists of a part only of a Fresnel lens having a negative focal length with the optical centre of the lens lying adjacent to or outside of the outer side of the lens. The device (3) gives a driver good vision of the area behind the vehicle when reversing.

Description: Vehicle Reversing Device This invention relates to an optical device for deflecting the view of a person in a vehicle to allow that person to view an area behind the vehicle when reversing. When reversing a vehicle, particularly one without rear windows, a serious problem can be caused because vision of the area behind the vheicle is very restricted. Various devices have been proposed to enable a driver to see behind the vehicle when reversing. British patent specification No. 2 085 382 proposes the use of a mirror mounted on the rear corner of a vehicle to enable the driver to see the rear of the vehicle and the area immediately behind it. Such a device suffers from the dis¬ advantage that the field of view covered by the mirror is inevitably very restricted so that the driver can see only a short distance behind the vehicle. Consequently if a driver is reversing at speed, an obstruction behind the vehicle may not come into view until a moment before impact leaving the driver insufficient time to stop. To some extent this problem could be avoided by the use of a prism and a negative Fresnel lens disposed adjacent to the prism. If such an arrangement were mounted on the rear corner of a vehicle then the prism would operate ir. a similar manner to the mirror of British patent, specification No. 2 085 382 but the additier, cf the negative Fresnel lens would expand the field cf view so that the driver would be able to see further behind the vehicle. Such an arrangement would, however, have various drawbacks. First, the use of both a Fresnel lens and a prism would make the arrangement relatively expensive: secondly the-re would be difficulty in obtaining the necessary clarity and range of vision and while this ight be improved to some extent by using a large lens and a large prism, a large arrangement would increase costs and also stick out from the vehicle a long way. It is an object of the invention to provide an improved optical arrangement for viewing to the rear of a motor vehicle. According to the invention a motor vehicle includes an optical device mounted on the exterior of the vehicle at a rear corner thereof, the device consisting of a Fresnel lens having a negative focal length. By using a Fresnel lens both to deflect the line of vision and to expand the field of view the need for a prism is dispensed with. For seeing inwardly behind the vehicle only the inner part of the lens is used and it is therefore most advantageous to provide a part only of the Fresnel lens. Accord¬ ing to the preferred form of the invention there¬ fore, the device comprises part only of a Fresnel lens having a negative focal length, the optical centre of the Fresnel lens lying adjacent to or outside of the outer side of the lens. Omitting the remaining part of the lens reduces the width of the device so that it does not project too far beyond the sides of the vehicle. The part of the Fresnel lens may be substantially a quadrant or two quadrants. In this case a driver is able to see straight through the lens (through the optical centre) and also to see in a direction lying at an acute angle to OMPI the rear of the vehicle (through the side of the lens adjacent the vehicle). The lens may comprise more than one lens element of negative focal length, the elements being stacked one on another. For example, if two identical lens elements, each of which individually provide a deviation in the line of view at their periphery of a given angle, are stacked together OMPI •fr^ IPO they will provide a deviation of substantially twice that angle at the periphery of the composite element. For example two lens elements each having a maximum angle of deviation of 40o may be stacked together to provide a lens having a maximum angle of deviation of 80 , enabling a driver to see almost directly behind the vehicle. Preferably the lens provides a maximum angle of deviation of at least about 45°. Thus if two lens elements are employed they preferably each provide a maximum angle of deviation of at least about 22 . The plane of the Fresnel lens may extend outwardly perpendicular to the side of the vehicle. Alternatively the plane of the lens may be inclined to the perpendicular direction such that the outer side of the lens is to the rear of the inner side; such an arrangement facilitates view¬ ing of the area immediately to the rear of the vehicle. A second optical device similar or identical to the first mentioned device may be mounted on the exterior of the vehicle at the other rear corner thereof. The Fresnel lens may be movably mounted on the vehicle being movable between a stored position in which the device lies along the side of the vehicle and an operative position in which the device projects outwardly from the side of the vehicle. Preferably, a remote control system is provided for moving the device between the stored and operative positions; the remote control system may be operable by the driver in his normal driving position. OMP " " -*~ < ■ """ ■ "T """ ? ■ "_" By way of example an illustrative embodiment of the invention will now be described with reference to and as illustrated by the accompanying schematic drawings, of which: Fig. 1 is a plan view of a motor vehicle with optical devices mounted at the rear corners thereof; Fig. 2 is a side view of the vehicle; Fig. 3 is a side view of one of the optical devices mounted on the vehicle; Fig. 4 is a sectional view along the lines 1V-1V of Fig. 3; and Fig. 5 is a plan view showing the field of vision provided to the rear of the vehicle. Referring first to Figs. 1 to 3, a motor vehicle 1, for example a commercial van, has a pair of conventional wing mirrors 2 and a pair of optical devices 3 movably mounted at the rear corners of the vehicle on the outside thereof and a remote control system involving a control 8 fitted within reach of the driver and a pair of motors 9 associated with respective optical devices 3. As illustrated in Fig. 1 the optical devices 3 have an operative position (shown in solid out¬ line in Fig. 1) in which they extend away from the sides of the vehicle at an angle inclined slightly to the perpendicular such that the outer sides of the devices 3 are to the rear of the inner sides. As indicated by the dotted lines in Fig. 1, the devices 3 are pivotally mounted and can be moved to a stowed position in which they lie alongside the vehicle. If desired, shallow recesses may be provided in the sides of the vehicle OMPI WIPO to accommodate the devices 3 in the stowed position. Each optical device 3 consists of part of a Fresnel lens 6 made up of a pair of quadrants 4 of two Fresnel lens elements, each having a nega- tive focal length, stacked one on another and mounting means 5 connected to a side edge of the lens and used to mount the lens pivotally on the vehicle 1. The exact form of mounting means employed is not an important feature of the present invention. Those skilled in the art will be aware of many suitable methods for pivotally mounting the lens 6 on the vehicle. In the example shown the optical axes of the lens elements 4 are coincident and lie at a corner 7 of the device 3, the corner 7 being at the top of the outside edge of the device. It should be understood that although the optical centres of the lens elements are shown at the corner 7 they could actually be spaced a little inside of the corner or alternatively they could lie outside the lens elements, for example the lens elements could consist only of the rectangle defined by chain dotted lines in Fig. 3. In one particular example of the invention each of the lens elements 4 provides an angle of deviation of 40 at its edge furthest from its optical centre so that the lens 6 provides a maximum deviation of about 80 The remote control system 8,9 is used to control the pivotal movement of the optical devices 3 between their stored and operative positions. The exact form of remote, control system employed is not an important feature of the present inven¬ tion. Those skilled in the art will be aware of TITUTE SHEET many suitable methods for controlling the movement of the devices 3. For example the devices 3 may be pivoted by respective electric motors 9 operated by a common push button switch 8; the motors 9 may be solenoids. Under normal forward driving.conditions the devices 3 are kept in their stowed positions and therefore are less inclined to become dirty and also do not add to the drag on the vehicle. When a driver wishes to see immediately to the rear of his vehicle, for example when he is reversing, he actuates the control 8 pivoting the devices 3 into their operative position shown in Fig. 1. The driver is then able to see through either of devices via the wing mirrors 2 or directly by putting his head through a window of the vehicle and looking backwards. When the driver looks through the portion of the lens elements at or close to their optical axes (i.e through the upper and outer portion of the lens) his line of vision is not substantially altered, but when he looks through the portion of the lens elements adjacent the side of the vehicle, which are remote from the optical axis, his line of vision is deflected away from the optical axis, namely around the rear corner of the vehicle and, when looking through the lower parts of the lens, also downwards. Figs.2 and 3 show in dotted outline the boundaries of the field of view provided by the optical devices for the driver. It can be seen from this that the driver is able to see not a only the ar /immediately behind his vehicle but also all the space behind that area. Thus if a driver is reversing towards an obstruction he is TE SHEET able to see that obstruction all the time he is approaching it. Once the driver has finished using the devices 3 he actuates the control 8 again returning the devices 3 to their stored position. The lens elements 4 may be simply constructed from plastics material, although other materials may also be used. As an alternative to providing a composite lens, the lens may be made from a single lens element. A typical size for the element 4 is about 10 cm by 7 cm but larger sizes may be used, particularly on long vehicles. Instead of making each lens element from a single quadrant as described, the element may be made from two quadrants as illustrated in dotted outline in Fig. 3. The addition of the second quadrant enables a driver to see upwardly as well as down¬ wardly around the back of his vehicle and may be useful particularly in the case of a tall vehicle. In. certain applications of the invention it may be desirable to mount the devices 3 in fixed positions on the vehicle. It may also be desirable to mount the devices 3 perpendicular to the sides of the vehicle as this may give a clearer view through the lenses. Although two devices are shown mounted on the vehicle a single device, preferably mounted on the driver's side of the vehicle, may be provided. The optical device embodying the invention may be used on a wide variety of vehicles including trailers and caravans. • While it is clearly of value on a vehicle without rear windows or a rear windscreen it may also be of assistance on a " " - -- - CCMMPP vehicle with a rear window, for example if vision through the window is poor or is sometimes obstructed. Thus the device may for example be used on a bus or a coach. A hood may be provided to protect the device 3 in its stowed positions. The hood may be operated automatically as the device 3 is moved between its operative and stowed positions. A suitable height for the device 3 is substantially the same height as the wing mirror 2 but in certain circumstances it may be desirable to provide the device 3 at some other level. For example if the wing mirror is relatively high it may be useful to have the device 3 at a lower level. In such a case it is also advantageous to include at least part of the upper quadrant of the lens, that is at least part of the quadrant shown in dotted outline in Fig. 3, so as to extend the view rearwardly of the vehicle. In the case where the Fresnel lens is made up of two elements stacked one an another it is preferable to stack the elements with a grooved face of one element in contact with a plain face of the other element and with the grooved faces of each element facing forwards (so that the driver looks through the grooved face of the front element) . This gives the clearest view through the elements.

Claims: Claims : 1. A vehicle including an optical device mounted on the exterior of the vehicle at the rear corner thereof, characterized in that the device consists of a Fresnel lens having a negative focal length. 2. A vehicle as claimed in claim 1 further characterized in that the optical device comprises part only of a Fresnel lens having a negative focal length, the optical centre of the Fresnel lens lying adjacent to or outside of the outer side of the lens. 3. A vehicle as claimed in claim 2 further characterized in that the part of the lens is sub¬ stantially a quadrant. 4. A vehicle as claimed in claim 2 further characterized in that the part of the lens is sub- stantially two quadrants. 5. A vehicle as claimed in claim 1 further characterised in that the Fresnel lens comprises more than one lens element of negative focal length, the elements being stacked one on another. 6. A vehicle as claimed in claim 1 further characterized in that the plane of the Fresnel lens extends outwardly perpendicular to the side of the vehicle. 7. A vehicle as claimed in claim 1 further characterized in that the plane of the Fresnel lens is inclined to the perpendicular direction such that the outer side of the lens is tc the rear cf the inner side. 8. A vehicle as claimed in claim 1 further characterized in that the Fresnel lens is mcvably mounted on the vehicle and is movable between a stored position in which the device lies along the CMPI .IPO side of the vehicle and an operative position in which the device projects outwardly from the side of the vehicle. 9. A vehicle as claimed in claim 8 further characterized in that movement of the Fresnel lens is controlled by a remote control system operable by the driver. 10. A vehicle as claimed in claim 1 further characterized in that a second optical device similar or identical to the first mentioned device is mounted on the exterior of the vehicle at the other rear corner thereof. 11. An optical device to be mounted on the exterior of a vehicle at the rear corner thereof and mounting means for mounting the device, characterized in that the device comprises a part only of a Fresnel lens having a negative focal length, the optical centre of the Fresnel lens lying adjacent to or out¬ side of a side of the lens opposite the mounting means .

Inventors: FOX ARNOLD JEFFREY, FOX, ARNOLD, JEFFREY
Applicants: FOX ARNOLD JEFFREY, FOX, ARNOLD, JEFFREY
Application year: 1983
Main classification: B60R1
IPC codes: B60R1