Abstract: A closed-loop, temperature-controlled cooling system includes a Stirling cycle refrigerator driven by a dc motor, wherein the motor excitation derives from pulse width modulation. Temperature control of the cooling system is provided by a temperature-sensitive bridge circuit which responds to variations in temperature by generating an error voltage which effects a change in the modulator duty cycle. The amount of cooling is directly related to the average voltage applied to the motor, which is a function of the modulator duty cycle and the amplitude of the supply voltage. A compensation circuit is disclosed which responds to variations in the voltage amplitude of an unregulated supply by coupling an error signal to the bridge circuit to thereby affect the modulator duty cycle.

Abstract: A temperature-controlled thermoelectric cooling system regulates the flow of electric current into the thermoelectric cooler in order to maintain a desired cold-side temperature without directly measuring the temperature of the device affixed to the cold side of the cooler. The system includes an apparatus for periodically interrupting the current flowing to the cooler, and during these interruptions measuring the open circuit voltage across the cooler induced by the temperature difference between the hot and cold sides. Computational means use this voltage measurement in conjunction with the temperature of the hot side of the cooler to determine the cold side temperature. From the cold side temperature determination, a controller regulates the current flow to the cooler to maintain a desired cold side temperature.

Abstract: Timing pulses generated by an incremental optical encoder disc may be nonuniformly spaced due to eccentricity in the disc mounting and inaccuracies in the pulse generating marks. An apparatus and method are disclosed wherein pulse width measurements are made during one revolution of the disc, and from these measurements data relating to pulse delay information are computed and stored in a memory. During operation the leading edge of each encoder pulse is delayed by a period of time related to the stored delay information corresponding to that specific pulse.

Abstract: A camera including a solid-state imager has a cooler for controlling cooling of the imager. A thermal servo regulates the cooling of the imager to a set point. A cooling control means changes the cooling set point in response to changes in the sensitivity of the camera.

Abstract: The focus actuator, turntable and translation stage in an optical disc record/playback system may effect relatively large reaction forces on the components of the system. These reaction forces can cause vibrations which interfere with or distort information recording or retrieving operations which occur at the same time that high speed access is being effected. A momentum compensating mass is coupled to the focus actuator, turntable and other moving elements to reduce or eliminate the reaction forces which can affect system operation.

Abstract: A rapidly-spinning motor-driven disc is quickly brought to a halt by utilizing the motor in a controlled current dynamic feedback mode. An electrical signal is provided to cut off the motor braking current when the rotating motor shaft reaches substantially zero velocity, thereby avoiding any residual rotation of the disc. As the disc slows at a constant deceleration rate, the apparatus measures the relative time durations of two consecutive pulses which represent equal displacement arcs on the disc. From these data the time at which zero velocity will be achieved is computed, and the motor current cutoff signal is generated at the proper instant.

Abstract: Eccentricity control apparatus is provided in a system for optically recording and reading information on a rotating disc medium. The information may be recorded on concentric or spiral tracks. The eccentricity control apparatus includes a detector for detecting track crossings as an optical scanning head scans the disc surface. The detector provides pulses representative of track crossings. The number of pulses in a once-around is representative of the amplitude of an eccentricity control signal. The angle measured between a once-around pulse and a minimum pulse rate of the track crossings indicates the phase of the error. An eccentricity error signal which is generated by suitable circuitry is applied to affect the manner in which the optical scanning head scans the disc surface such that number of track crossings is reduced.