Patent GB-732878-A (GB)
Title: Improvement in automatic computer
IPC: G06J1/00
Filed: 1953-07-01
Abstract: 732,878. Photo-electric computation of functions of independent variables. SCHLUMBERGER WELL SURVEYING CORPORATION. July 1, 1953 [July 1, 1952], No. 18244/53. Class 40(3). A computor apparatus for deriving the instantaneous value of a function of two dependent variables comprises a member inscribed with a family of curves depicting such function, means forming a beam of radiant energy impinging on the member, means for displacing the member and beam relatively on to the other in a first direction to effect modulation of the beam by the inscribed curves, means for positioning the member and the incident beam relatively to one another in a second direction perpendicularly to said first direction in accordance with instantaneous values of a first independently variable quantity, and utilization means operated in synchronism with the relative displacement between the member and the incident beam in the first direction operative to. establish a time interval dependent on the instantaneous values of a second independently variable quantity, for utilization of the beam subsequently to its modulation and for derivation of indications representing a characteristic of the modulation occurring during the time interval. In Fig. 1 an opaque endless belt 10 driven at constant velocity over rollers 11, 12 by motor 13 is divided longitudinally into plural frames 15 by lateral slits 17, and each frame is formed with slits 16a to 16n representing a family of curves representing different values 10; 1, 2 . . . n, of a predetermined function u=f (x, y) referred to a lateral x axis and a longitudinal y axis. An intense light beam 18 is focused on the belt by the optical system of a mirror galvanometer 21 energised by an electrical signal proportional to the instantaneous value of a variable x to correspondingly deflect the spot along the x axis, and an elongated photo-cell 25 receives light passing through the slits to produce a train of signal pulses whose frequency is a function of the belt speed and whose number and time position are functions of x given by u=f (x,y) for successive values of u; the belt velocity being such that no substantial variation 'of x occurs during passage of a single frame or the deflecting light spot source being arranged so that deflection takes place only between frame intervals and the spot is thereafter fixed during the remainder of the frame. Fig. 2A shows against a time axis the output waveform of the photo-cell which comprises trains of pulses 28 determined in number and timing by the value x, separated by synchronizing pulses 27 developed by the intersection of the light spot and the successive slits 17 separating the frames. A multivibrator gate pulse generator 30 is energized on occurrence of each synchronizing pulse 27 to generate a variable duration pulse 31 (Fig. 2B) terminating at an instant determined by the magnitude of a voltage on terminals 32 representing the instantaneous value of a variable y, which opens a gating amplifier 34 to allow pulses 28 to pass to a counter circuit 36 for the duration of the gating pulse, which by number registered on an indicating instrument 37 represents the instantaneous value of function u=f (x, y) for the instantaneous values of x, y ruling during the passage of a particular frame (Fig. 2C). The curves may be represented by slits in the periphery of a rotatory drum or darkened markings on a transparent drum or belt, while a single family of curves may occupy the entire surface of the latter. Synchronizing pulses may be derived from a pulse generator operatively coupled to the motor 13, while the x co-ordinate galvanometer 21 may be given a logarithmic characteristic and the gating pulse duration may be made to vary logarithmically with the y co-ordinate. Families of curve traces representing the function u with reference to a polar co-ordinate system may be angularly disposed on the surface of a rotating disc (Fig. 3, not shown) having a radial trace to establish synchronizing pulses, and the light spot may be traversed radially of the disc to illuminate a radially arranged photo-cell. Alternate frames of the belt shown in Fig. 1 may be impressed with families of curve traces representing functions u=f (x, y) and v=g (x, y) and two separate pulse counters and indicators may be rendered responsive to the appropriate frames by electronic or other switches synchronized with the belt movement to indicate the instantaneous values of u and v. A single pulse counter and indicator as shown in Fig. 1 will indicate the instantaneous value of (u+v). Fig. 4 shows a modification for obtaining continuously the value of a predetermined function u=f (x, y, z) in three independent variables, wherein the annular surface 44 of a drum 41 rotated by a motor 43 at constant speed is divided into plural similar frames 45a to 45n, each of which bear a family of curve traces of the function u=f (x, y, z) for different values of the function, inscribed as reflecting lines on a non-reflecting background, with refprence to a rectangular co-ordinate system having the x axis parallel to the drum axis and the y axis perpendicular thereto. Successive frames bear successive families of curves for different values of z, and a light beam 18 from a mirror galvanometer 21 deflected by a signal representing the instantaneous value of variable x traverses the drum surface and is reflected to a linear photo-cell 25 parallel to the x axis. A single contact 52 on a drum 51 driven in synchronism with drum 41 engages contact 53 once per revolution to start a gating pulse generator 49 to generate a pulse 57 (Fig. 5B) which is terminated after a time interval proportional to the instantaneous value of a signal representing variable z, and a series of contacts 62 on drum 51 engaging a contact 55 develop a train of synchronizing pulses 56 (Fig. 5C) corresponding to the beginning of successive frames which energize a second gate pulse generator 30<SP>1</SP> to generate a once per drum revolution pulse 58 (Fig. 5D) immediately following the completion of pulse 57, also fed to the generator 30<SP>1</SP> so as to open gating amplifier 34 to connect the pulse counter circuit 36 and its indicating instrument to the photo-cell 25. The pulse 58 is terminated after an interval of time proportionate to the instantaneous value of a signal representing the variable y. The trains of signal pulses in the photo-cell output (Fig. 5A) are thus gated by pulse 57 selecting the individual frame corresponding to the instantaneous value of z, and by pulse 58 to select for the pulse counter circuit the pulse train (Fig. 5E) produced by the traverse of beam 18 corresponding to the instantaneous value of x over the appropriate frame, whereby the counter indicating instrument registers the instantaneous value of u=f (x, y, z) as described in connection with Fig. 1. Synchronizing pulses may be alternatively derived from marks or slits in the surface 44 of drum 41, and the variable z may be used to determine the instant at which the variable signal becomes operative rather than the signal y, by application to connect the signal x to the ,galvanometer 21 when the required family of curves is appropriately positioned. Functions of more than 3 variables may be similarly determined by the use of additional sets of drums 41 each corresponding to a predetermined value of the 4th variable, which is used to select the appropriate gate amplifier 34 to pass pulses to the counter 36.