Abstract: A marine auto pilot employing a compass with a Hall-effect sensing element in conjunction with a magnetic circuit designed to provide a high intensity magnetic field; electrical circuitry designed to produce high servo-loop gain at frequencies lower than the normal sea wave frequencies, and lower gain at the normal sea wave frequencies; a D.C. Linear Motor drive system in conjunction with a rudder position feedback signal; and a linear ball-screw and nut gearing system for converting the high-speed output of the direct current drive motor to a low-speed high-torque drive at the rudder, having the nut and ball-screw connected through rolling contact balls.

Abstract: The rotation of a motor is sensed and a signal indicative of any error in desired motor speed or phase is multiplied by the angular position of the motor shaft. The resulting product defines a sinusoidal drive signal which is amplified and introduced to the motor windings. As the error signal varies, the sinusoidal drive signal amplitude varies therewith to slow down or speed up the motor accordingly. Thus the invention provides both drive and servo control to a motor from a multiplier device disposed within the servo circuit. The multiplication process provides the ideal drive signal since the motor windings are driven with continuously varying drive signals, which provides accordingly a constant motor torque output inherently free from velocity variations.

Abstract: An optical assembly defines a reflector or refractor element installed behind the film plane of an optical scanner or fixed beam system. Its function is to image the rear nodal plane of a spot forming lens of the optical beam system, onto a split diode photodetector. The optical assembly is split into at least two facing optical sections with a thin reflective interface formed therebetween, whereby is defined a very precise intersection between the two optical sections at the surface of entrance of the beam. A fixed or scanning spot impinging the precise intersection is divided into two parts, and each is focused and directed to separate diode photodetector means. The relative intensity between the two parts of the divided beam is used to indicate the lateral deviation of the spot position with respect to the intersection. The images formed at the photodetector may be made essentially stationary regardless of the position of a scanning spot as it moves along the line of intersection.