Abstract: A method and apparatus for mapping the character and location of medium conditions for a planar surface. Energy is supplied to a head in close proximity to the planar surface to thereby raise the temperature of the object. The head is moved with respect to the planar surface while keeping the distance from the planar surface substantially constant. An increase, decrease or a rapid variation containing positive and negative temperature excursions is distinguished by electronic means. These variations are used to categorize disturbances or contact with the medium, and the location and type of condition is recorded in hard copy or by computer acquisition for later consideration in the file manufacture process. Additionally, magnetic and thermal information may be combined to provide an even more complete description of the nature of the condition, since the magnetic and thermal signals are descriptive of different physical phenomenon.

Abstract: Apparatus and methods for calibrating a thermal proximity sensor are disclosed. Thermal responses from a thermal proximity sensor are used to sense the instantaneous distance between the sensor and a medium over which the sensor is moved, in a data storage system. Sensing the instantaneous distance results in detection of topographical variations on the medium. Calibration techniques for the sensor are disclosed herein and involve, in one aspect, using primarily electrical measurements to calibrate the sensor; and in another aspect, varying the distance between the sensor and the medium, obtaining actual thermal responses from the sensor, and using the actual responses (via direct comparison or curve fitting) to calibrate the sensor. In one embodiment, the sensor is a magnetoresistive access element used to access data on the medium.

Abstract: Apparatus and methods for improved thermal proximity imaging are provided. A data storage medium surface is moved relative to a sensor, in one embodiment a magnetoresistive read/write element. Topographical variations on the storage medium induce temperature changes in the sensor. These temperature changes are monitored to detect the location and nature (e.g., height) of the topographical variations on the medium surface. A feedback circuit using an impedance bridge is disclosed for sensing instantaneous changes in the temperature of the sensor, correcting for the changes and, therefore, keeping the temperature of the sensor substantially constant. By keeping the temperature of the sensor constant, the topographical variations can be detected without any adverse impacts of the surrounding thermal environment on the detection response time.