Signal processing apparatus and method

An in vivo monitoring apparatus comprising:

• light sensitive detector means for receiving a first in vivo signal and a second in vivo signal, wherein said first signal has a first desired signal portion and a first undesired signal portion and said second signal has a second desired signal portion and a second undesired signal portion;
• and
• reference processors means having an input for receiving said first and second signals for combining said first and second signals to generate a reference signal having a primary component which is a function of said first and said second undesired signal portions.

A signal processing apparatus having a source of first and second signals, said apparatus comprising:

• a detector which receives said first signal after propation through a test medium to form a first received signal and said second signal after propagation through said test medium to form a second received signal, wherein said first received signal has a first desired signal portion and a second undesired signal portion, and said second received signal has a first desired sigal portion and a second undesired signal portion, wherein a first ratio of the first desired signal portion to said first undesired signal portion has a value ranging from less than one to greater than one, and a second ratio of said second desired signal portion to said second undesired signal portion has a value ranging from less than one to greater than one;
• and
• a reference processor coupled to said detector and responsive to said first received signal and said second received signal, said processor comprising a filter which combines said first and second received signals and generates a second reference signal that for any value of said first and second ratios, has a primary component which is a function of said first and said second undesired signal portions.

A signal processing apparatus having a source of first and second signals, said apparatus comprising:

• a detector which receives said first signal after said first signal has propagated through a test medium to form a first received signal and which receives said second signal after said second signal has propagated through said test medium to form a second received signal, wherein said first received signal has a first desired signal portion and a first undesired signal portion, and said second received signal has a second desired signal portion and a second undesired signal portion, wherein a first ratio of the first desired signal portion to said first undesired signal portion has a value ranging from less than one to greater than one, and a second ratio of said second desired signal portion and said second undesired signal portion has a value ranging from less than one to greater than one;
• and
• a reference processor coupled to said detector and resopnsive to said first received signal and said econd received signal, said reference processor comprising a filter which combines said first and said second received signal and generates a reference signal that, for any value of said first and second ratios, has a primary component which is a function of said first and said second undesired signal portions.

A signal processing apparatus having a source of first and second signals, said apparatus comprising:

• a detector which receives said first signal after propagation through a test medium to provide a first received signal and which receives said second signal after propagation through said test medium to provide a second received signal, said first received signal having a first ratio between a magnitude of a first desired signal portion and a magnitude of a first undesired signal portion, and said second received signal having a second ratio between a magnitude of a second desired signal portion and a magnitude of a second undesired signal portion;
• and
• a reference processor coupled to said detector and responsive to said first and second received signals, said reference processor comprising a filter which combines said first and second received signals and which generates from said first and second received signals a reference signal that, irrespective of said first and second ratios, has a primary component which is a function of said first and said second undesired signal portions.