Patent ID: 6927860
Filing Date: 2005-08-09
Classification: A61B,G01B,G01N

Abstract:
1. Apparatus for optical coherence tomography comprising a source of low coherence or adjustable coherence light, and at least one optical coherence tomography (OCT) interferometer, equipped with interface optics to transfer light to an object to be scanned and image display means; said at least OCT interferometer comprising an output beam splitter having object beam and a reference beam input ports, first and second photodetectors, and an input beam splitter having object beam and reference beam output ports; wherein said at least one OCT interferometer is equipped with depth adjusting means to adjust the optical path difference in the interferometer to permit the selection of a signal from different depths in the object; wherein said output beam splitter combines an object beam and a reference beam at its respective object beam and reference beam inputs, and is terminated at said first and second photodetectors so as to implement balance detection via a subtraction electronic amplifier, wherein the output splitter, the two photodetectors and subtraction electronic amplifier form a balance detection unit; wherein said input splitter transfers 1−γ of light input to it from said light source to the respective object beam output port, and the remainder γ to reference path at its respective reference beam output port; wherein the light from the reference beam output port of said input splitter is directed to the reference beam input port of said output beam splitter; wherein the light from the object beam output port of said input splitter is transferred through the said interface optics to the said object, and the light reflected and scattered back from said object is reinjected into the object beam output port of said input splitter and is cross transferred to said object beam input port of said output splitter; wherein said output splitter has a substantially 50/50 coupling ratio for at least one wavelength within the spectral range of the optical source and different coupling ratios for other wavelengths within said spectral range, resulting in a mismatch in the balance detection unit; and wherein the power of said light source and the splitting ratio ε=(1−γ)/γ of said input splitter are set at high values such that said apparatus operates in a regime where a plot of the signal-to-noise ratio versus optical power sent to the object is saturated.