Patent GB-1408078-A (GB)
Title: Method of controlling a motion of a land vehicle
IPC: B60K31/18
Filed: 1973-03-21
Abstract: 1408078 Photo-electric speed measurement ERNST LEITZ GmbH 21 March 1973 [30 March 1972 20 Nov 1972 (3)] 13527/73 Heading G1A [Also in Division H4]  In the automatic control of a motor vehicle e.g. by application of the brakes to overcome a skid Fig. 1 or the correction of the steering to overcome a front wheel skid Fig. 8 or the automatic application of the brakes to stop a collision with a vehicle following or preceding the vehicle, the velocity of the vehicle relative to the road and/or the other vehicle is optically detected by projecting an image of the road or the other vehicle on to an optical grating in such a manner as to produce, in pairs of photo-detectors, pairs of antiphase useful signals and pairs of in-phase interference signals whereby by subtracting the outputs of the photo-detectors an interference free indication of the velocity of the vehicle relative to the ground and the rate of increase of the image of the other vehicle is detected and when determined as indicating a dangerous condition causes said brake actuation or said steering correction. In the anti-skid embodiment Fig. 1 the output of the optical correlation speed detector 10 is fed to a comparator and servo-mechanism 26, 29 whereby the determined rate of speed is compared with safe thresholds and any detected danger causes actuation of one or more of the brake cylinders. The comparator and servomechanism 26, 29 is also fed with signals from means 30, 33, 31, 32 detecting the rotational speed of the road wheels, undue slip being determined as an unduly high difference between the rotational speed of the wheels and the relative speed of the vehicle to the ground. The detector 10 may comprise a single dimension embodiment Fig. 3 wherein an image of the road 1 is projected via a Wollaston prism 16 producing two slightly displaced images with different polarizations on a grating 5 having the grating aligned at right angles to the direction of movement of the vehicle. The two images after passing through the grating are separated out by polarization divider 7 and detected by respective photo-detectors 8 whereby the desired signals having their anti-phase wanted signals and in-phase interference signals are produced. A second one dimensional embodiment of detector 10 is shown at Fig. 4 whereby the grating is in this form a structure of aligned and adjacent prisms 5a, the image of the road 1 being split in two for the respective detectors 8 by refraction at the two surfaces of each prism. In a third one dimensional embodiment of detector 10 Fig. 4a the grating 5 may comprise sets of four stripes one transparent, one with one direction of polarization, one opaque and one with an orthogonal direction of polarization, the two images of the road being then separated out by polarization separating prisms 7. A slit aperture 6 may be inserted in the image path to improve the resolution. A two dimensional embodiment of the detector 10 uses a grating formed of pyramidal prisms Fig. (9). The four images are then detected by corresponding four detectors 8. A cross shaped aperture (6') Fig. 10 (not shown) may be inserted in the image path to improve resolution. The two dimensional detector 10' is used in the steering correction embodiment Fig. 8 whereby the lateral as well as axial relative velocity of the vehicle is detected and fed to a computer servo-mechanism 25' where it is compared with the actual steering position from detector 24 and with the rotational speed of the wheels from detector 30, 33 whereby any needed correction of the steering is produced for feeding to box 26. In the collision avoiding embodiment Figs. 11g and 12 the grating Fig. 11g is in the form of concentric circles with their spacing increasing with distance from the centre. Such a grating is placed in front of a quadrant detector 10 Fig. 12 whereby signals are produced indicating the rate of increase of the size of the image of the other vehicle such signals being produced from adder 34 and 34' and subtractor 35 and 35' the resulting vertical change and horizontal change of image size signals being fed to a computer 25' for possible comparison with a distance measuring system 27 and any necessary actuation of speed or brake servosystem 26', an approach speed indicator 40 and an audible or visual alarm 28'.