System for identifying surface conditions of a moving medium

摘要

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.