Dual Beam Low Coherence Interferometer with Improved Signal-to-Noise Ratio and Imaging Depth

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Component set-up of a preferred embodiment of the dual beam low-coherence interferometer system
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Aristide Dogariu, Ph.D.
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John Miner
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Dual-beam low-coherence interferometer with improved signal-to-noise ratio

US Patent 6,256,102 B1

A novel design for a dual-beam low coherence interferometer with improved signal-to-noise ratio

This novel apparatus is capable of simultaneously measuring a collimated cylindrical beam and a focused beam centered on a target (such as human tissue cells). The invention then detects the multiscattering induced by the target, measuring both the intensity and magnitude values of the beam. These values are used to create an image of the target, while improving the signal-to-noise ratios. An example of a biomedical application is capturing depth-resolved images of a tissue by scanning the optical head over the region of interest. The resolution of these images, usually captured through OCT (optical coherence tomography), is limited by the speckle noise produced by multiple scattering in the sample. This invention can account quantitatively for such background scattering noise, delivering an enhanced imaging resolution that can penetrate deeper into the tissue sample.

Technical Details

Speckle is a random, deterministic, interference pattern in an image formed with coherent radiation of a medium containing many sub-resolution scatterers. Speckle-type noise is generally present in signals recorded when low-coherence interferometry is applied to characterize targets that are surrounded by random media such as tissue and bodily fluid samples. Reduction of speckle noise is one of the most important obstacles to overcome in order to increase the quality of coherent imaging. Due to the high level of noise, prior art low coherence techniques lack substantial quantitative capabilities, such as improvement in quantifying the optical contrast between a targeted region and its surroundings. Various types of interferometers have been proposed over the years, but have failed to overcome the background scattering noise in order to enhance imaging resolution. The employment of a dual beam low coherence interferometer, the current invention, greatly reduces background noise resulting in enhanced resolution and increased penetration depth.

Benefits

  • Enhances image resolution and depth of penetration into the sample
  • Improves signal to noise ratio and an images diagnostic value
  • Allows for deep non-invasive and non-destructive testing of a sample without sacrificing quality of the image

Applications

  • Optical coherence tomography and microscopy
  • Tissue characterization
  • Diagnosis
  • Materials characterization,
  • Subsurface defects visualization in inhomogeneous media
  • High power applications where much smaller wavelengths are desirable, such as extreme ultraviolet (EUV) and soft X-ray regions