Systems and methods for non-invasive material analysis are disclosed in which a material (e.g., a liquid such as blood) is illuminated at a plurality of discrete wavelengths. Measurements of the intensity of reflected light at such wavelengths are taken, and an analysis of reflection ratios for various wavelengths is performed. Changes in the reflection ratios can be correlated with specific material properties such as the concentration of analytes (e.g., oxygen content, glucose levels, cholesterol or drugs in a subject's circulatory system).

An apparatus for photo-optically detecting transducer motion using a photodetector resiliently suspended inside the transducer housing and photo-optically coupled to a light source. During movement the inertia effect of the photodetector along with the resilient suspension system causes the changes in the photo-optical coupling between the photodetector and the light source. The inertia effect of the photodetector is enhanced by adding a mass to the photodetector. Either the magnitude or the phase of the photodetector output is monitored to detect movement. In another embodiment, a light emitter is resiliently suspended so that movement induced changes in the position of the light emitter alter the coupling of light to one or more light detectors.

An apparatus for photo-optically detecting transducer motion in a transducer using a photodetector elastically suspended inside the transducer housing and photo-optically coupled to a light source. During movement the inertia effect of the photodetector along with the elastic suspension system causes the changes in the photo-optical coupling between the photodetector and the light source. The inertia effect of the photodetector is enhanced by adding a mass to the photodetector. Either the magnitude or the phase of the photodetector output is monitored to detect movement.

The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example oxyhemoglobin and deoxyhemoglobin in living tissue.

An oximeter for non-invasively measuring the oxygen saturation in blood with increased speed and accuracy is disclosed. The oximeter includes a number of features which increase the functionality of the device including: a dynamic range control for monitoring a range of inputs from low level signals encountered in fetal and other applications to typical or high level signals; light emitting devices of different wavelengths for filtering noise and providing additional medial monitoring functions; and an improved method for calculating the oxygenation levels without the need to take peak and valley measurements. The device includes a sensor unit which can be attached to a patient and an oximeter which determines the oxygen saturation in the blood based on signals received from the sensor. The sensor can include light emitting devices in three or more wavelengths to provide additional functions. In the present invention, the detected signal is immediately converted to a digital value.