Method and apparatus for detecting asperities on magnetic disks using thermal proximity imaging

A method for mapping the character and location of surface variations of relatively small height on a substantially planar surface comprising the steps of:

• supplying energy to an object in close proximity to the planar surface to thereby raise its temperature;
• moving the object with respect to the planar surface while keeping the object a substantially constant distance from the planar surface;
• and
• detecting a decrease in temperature of the object when it is in proximity to a surface variation to define the location and character of the variation,
• wherein pulses of energy are supplied to the object to obtain peak temperatures and to avoid mechanical distortion of the object.

A method for detecting the presence of asperities on a planar surface comprising the steps of:

• supplying energy to an object in close proximity to the planar surface to thereby raise its temperature, said energy being supplied in the form of pulses of sufficient magnitude to increase peak temperature and avoid mechanical distortion of said object;
• moving the object with respect to the planar surface while keeping the object at a substantially constant distance from the planar surface;
• and
• detecting a change in the temperature of the object when it is in proximity to an asperity.

An apparatus for detecting the presence of surface variations on a planar surface comprising:

• a slider;
• means for flying said slider over the planar surface at a substantially constant fly height;
• a sensor object carried by said slider in close proximity to said planar surface;
• energy means for supplying energy to said object to thereby raise its temperature;
• and
• means for detecting a drop in temperature of the object when it is in proximity to a surface variation.

An apparatus for detecting the presence of surface variations on a planar surface comprising:

• an object to be placed in close proximity to said planar surface;
• energy means for supplying energy to said object to thereby raise its temperature;
• means for moving the object with respect to the planar surface so as to maintain the object at a substantially constant distance therefrom;
• and
• means for detecting a drop in temperature of the object when it is in proximity to a surface variation,
• wherein the energy means supplies pulses of energy of sufficient amplitude to obtain high peak temperatures and to avoid mechanical distortion of said object.

An apparatus for detecting the presence of surface variations on a planar surface comprising:

• an object to be placed in close proximity to said planar surface;
• energy means for supplying energy to said object to thereby raise its temperature;
• means for moving the object with respect to the planar surface so as to maintain the object at a substantially constant distance therefrom;
• and
• means for detecting a drop in temperature of the object when it is in proximity to a surface variation,
• wherein said energy means includes an adjusting means for adjusting an amount of energy supplied, whereby said apparatus may be used to distinguish between magnetic and topographic surface variations.