Patent GB-1070655-A (GB)
Title: Method and system for determining the angle of deviation of an axis
IPC: G01S3/782
Filed: 1964-09-25
Abstract: 1,070,655. Axis direction determination. BOLKOW G.m.b.H. Sept. 25, 1964 [Sept. 25, 1963], No. 39219/64. Heading H4D. The angle of deviation of an axis Z, Fig. 1, with respect to the direction of a celestial body 33, is determined, by forming an image 31 of the body on the screen of a television camera tube by means of a lens 30 having a field of view of 180 degrees, and by scanning the screen by means of two groups of ellipses, of which the major axes are perpendicular in respect of one another, and the minor axes, starting from a value of zero, are increased in accordance with a circular sinusoidal function up to the value of the major axis, the interval of time between the moment when a minor axis of an ellipse starts from a value of zero, and the moment when a scanning ellipse of the same group passes the image, being a direct measure for the magnitude of an angle of deviation # or #. It is shown in the Specification that the equation in the X, Y plane of the image 31 of a body 33 lying in a plane containing the X axis and at an angle # with the Z, X plane is the ellipse where 1/m is the focal length of lens 30, and it is likewise shown that the equation in the X, Y plane of the image 31 of a body 33 lying in a plane containing the Y axis and at an angle # with YZ plane is the ellipse Thus be determining the minor axis of the ellipse which passes through the image 31, the angle # or # may be directly determined. Referring to Fig. 3, lens (4) focusses the image (2) of the celestial body on the screen (3) of the television camera tube (1). The scanning spot of the camera tube is deflected by X and Y deflector plates, having sinusoidal deflecting voltages applied thereto from generator (6), that applied to the Y plates being phase shifted by means (8) with respect to that applied to the X plates. As such voltages would merely cause the spot to describe a circle, the deflection voltages are amplitude modulated in modulation stages (7) and (9). The modulation waveform consists of half sine waves alternating with rectangular pulses having the same amplitude and width, the sine waves being produced by generator (11) and the rectangular pulses by multivibrator (12). The modulation waveform applied to modulation stages (7) in 180 degrees out of phase with that applied to modulation stage (9) such that when the X plates are being energized with a deflection voltage of constant amplitude, the Y plates being energized with a deflection voltage whose amplitude varies in a sinusoidal manner, and vice versa. The result is that the screen is scanned with a first series of ellipses, starting as a line along say the X axis, and broadening out from ellipse to ellipse to finally give a circle, and then narrowing down again to the straight line. This is then repeated along the Y axis. Each series of ellipses thus scans the image twice and produces two output signals from the camera tube. Only the first sig. nal however is used. To determine the minor axis of the ellipse which passes through the image (13) a bi-stable multivibrator (16) is used, which is triggered on a synchronism with the start of the series of ellipses, and is triggered off by the first output signal from the camera tube, to give a pulse having a width indicating the minor axis. This width is converted to a pulse height by means of integrator (17) and differentiator (18). To determine whether the pulse height represents the angle # or the angle #, the pulse passes to gates (19) and (20), which are opened alternately in corresponding synchronism with the changeover of the alignment of the major axes of the ellipse series. To determine on which side of the X or Y axis the image lies, the outputs of gates (19) and (20) are fed to gate pairs (21/22) and (23/24). The first pair are alternately opened by the output of generator (6) such that a pulse represented by its height will pass through gate (21) if it is on the positive side of the X axis and through gate (22) if it is on the negative side of the X axis. Pulses represent + # and - # likewise come from gates (23) and (24) respectively. Generator (6) is synchronized at frequency f/400 by a pulse train at that frequency from trigger (5) via pulse divider (10) and multivibrators (12) and (16) are triggered by pulses f at frequency --- from trigger (5), via pulse 200 divider (10). If the field of view of the lens is less than 180 degrees the minor axis of the ellipse increases to a value proportionally less than the major axis.