A capsule employing components for detecting blood content or hemoglobin
concentration within tissue forming a lumen in vivo advantageously
permits screening or diagnosis of certain diseases. In one embodiment,
the capsule includes a light source for intermittently illuminating a
region of tissue and a light detector for receiving interacted light from
the tissue and hemoglobin therein. Methods of validating data of
interacted light signal are also disclosed. A power conservation method
of detecting the blood content values at different rates is further
disclosed.