Patent GB-975282-A (GB)
Title: Improvements in or relating to optical photo-electric apparatus
IPC: G01C1/02
Filed: 1962-02-23
Abstract: 975,282. Photo-electric following apparatus. CONTINENTAL ELEKTROINDUSTRIE A.G., [trading as CONTINENTAL ELEKTROINDUSTRIE A.G. ASKANIA-WERKE]. Feb. 23, 1962 [Feb. 23, 1961], No. 7210/62. Heading H4D. [Also in Division G2] In a system whereby a member rotatably mounted about two co-ordinate axes is made to follow up movement of another similarly mounted member, one of the members is provided with a light source, a photo-electric device and light beam resolving means, whilst the other is provided with light reflecting means, the arrangement being such that with the two members in alignment a light beam from the source directed on to the reflecting means is coincident with the reflected light beam, the beam resolving means being placed in between the reflecting means and the photo-electric device and passing the light beam to the reflecting means but partially reflecting the reflected beam, the photo-electric device producing electric signals in response to the reflected light beam to control the servomotors effecting the follow-up movements. The invention is described as being used to cause a radiotelescope, Fig. 1 (not shown), to follow up the movements of an optical control device and comprises, mounted on the radio-telescope, a light source 20 sending a narrow beam of light into a prismatic beam resolving arrangement wherein the beam passes, after reflection by surface 22, through permeable mirror surfaces 23, 24 and 25 to be reflected by a mirror 7, mounted on the optical device, back on to the mirror surfaces 24 and 25 which split the beam into two equal portions. The two portions are reflected out of the resolving arrangement, via means (not shown) rotating one beam portion through 90 degrees with respect to the other, the two beam splitting means 27 and 41 comprising two prisms having their contacting surfaces formed on their lower halves with mirror coatings 28 and 42 such that the lower halves of the incident beams are reflected by the mirror coatings whilst the upper halves are totally reflected by the outer faces of the prisms. Each beam portion is thus split into two halves 29, 30 and 43, 44 the relative intensities of the two halves of one portion depending on the position of the light source image with respect to the inner edge of the respective mirror coating. Each pair of split beams are analysed in a differential photometer comprising a photoelectric device 32 or 45, the two split beams being presented to the respective photoelectric device in sequence by means of a rotating shutter 31 rotated by a constant speed arrangement comprising a motor M driving the shutter shaft and generator G which via a regulator R, feeds back a control signal to the motor. Any difference in the intensities of the two split beams caused by the mirror 7 not directing the reflected beams on to the edge of the mirror coatings 28 or 42, causes signals to be sent out by the appropriate photoelectric device to control the corresponding servomotor 17 or 18 performing the follow-up motions, the servomotors directing the followup motions in orthogonal axis due to the 90 degrees relative rotation of the reflected beam portions in the beam resolving arrangement. A second light source 20<SP>1</SP> may be provided where a more intense beam is required. Specification 975,283 is referred to.