Patent ID: 7286229

Claim:
A system to detect multi-domain regions in a soft under layer of perpendicular magnetic media, comprising: a radiation targeting assembly to target a polarized radiation beam onto a surface of a substrate covered by a the soft under layer of a perpendicular magnetic media; and a radiation collecting assembly that collects radiation reflected from the surface; a processor coupled to the first radiation collecting assembly; a memory module coupled to the processor and comprising logic instructions which, when executed by the processor, configure the processor to: record signal values from radiation reflected by the radiation beam at different positions on the surface; analyze the signal values to detect a region of multiple magnetic domains in the soft under layer of a perpendicular magnetic media; establish a baseline noise value over a region of the surface; subtract a baseline noise value from a signal value generated at a specific location to obtain a noise-compensated signal value; and compare the noise-compensated signal value to a threshold.