Method and apparatus for detecting universal and selectively concentration gradients, and for deflecting a light beam in a controlled fashion

Abstract

Concentration gradients in samples to be evaluated are detected by measuring the deflection of a probe light beam passed through the sample using the principals of Shlieren optics. Specific chemical compounds in a sample can be detected and identified by supplying excitation energy to the sample where such energy is selected to be absorbed by the chemical compound to be specifically identified and not by other compounds in the sample. The absorption of the excitation energy by the absorbing compound produces a temperature gradient within the sample which causes deflection of the probe light beam and signals representative of such deflection may be separated from signals representative of deflections caused by other refractive index gradients present in the sample. A light emitting diode may be used to generate the probe light beam. Rather than detecting movement of the probe light beam caused by an unknown gradient, by passing the probe light beam through a known gradient, with or without excitation energy present, the light beam can be deflected in a controlled manner.

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