Method and apparatus for cerebral oximetry

1. A method for measuring oxygen level in a human brain comprising:

generating a digital modulation signal associated with a code sequence;

generating a modulated optical signal based on said digital modulation signal;

transmitting said modulated optical signal to said human brain;

receiving a modified version of said modulated optical signal after transmission through said human brain;

deriving a temporal transfer characteristic for said modified version of said modulated optical signal;

calculating said oxygen level based on said temporal transfer characteristic;

delaying said code sequence to generate a second code sequence;

generating a second digital modulation signal associated with said second code sequence;

generating a second modulated optical signal based on said second digital modulation signal;

transmitting said second modulated optical signal to said human brain;

receiving a second modified version of said second modulated optical signal after transmission through said human brain; and

deriving a second temporal transfer characteristic for said second modified version of said second modulated optical signal.

2. The method of claim 1 further comprising:

delaying said modulated optical signal to reduce noise effects.

3. The method of claim 1 further comprising:

determining an absorption coefficient of said human brain from said temporal transfer characteristic.

4. The method of claim 1 wherein said code sequence is circular.

5. The method of claim 1 wherein said code sequence is unipolar.

6. The method of claim 1 wherein said code sequence is orthogonal.

7. The method of claim 1 wherein said code sequence is a pseudorandom binary sequence.