Direct current (DC) level shifting circuit for use in the detection of media defects within a magnetic recording media

A method for processing input signals from an apparatus for detecting a condition of a surface region of a magnetic recording medium, the method comprising:

• receiving a plurality of input signals from a plurality of optical sensors of the apparatus;
• generating a summed output signal based on the plurality of input signals using a first circuit that is configured to generate first and second components of the summed output signal, the first component representative of the condition and the second component representative of a power of an optical transmitter of the apparatus;
• and
• performing dynamic level shifting of the second component of the summed output signal using a second circuit that is coupled to the first circuit and is configured to perform the level shifting based on an offset signal and the plurality of input signals, wherein the level shifting is performed to set a slope of the second component as a function of the power of the optical transmitter of the apparatus to a selected slope value.

An apparatus for detecting a condition of a surface region of a magnetic recording medium, the apparatus comprising:

• means for receiving a plurality of input signals from a plurality of optical sensors of a magnetic recording media scanning device;
• means for generating a summed output signal based on the plurality of input signals, the summed output signal having first and second components, the first component representative of the condition and the second component representative of a power of an optical transmitter of the apparatus;
• and
• means for level shifting the second component of the summed output signal based on an offset signal and the plurality of input signals, wherein the level shifting is performed to set a slope of the second component as a function of the power of the optical transmitter of the apparatus to a selected slope value.