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1.
Opt Express ; 17(5): 3619-29, 2009 Mar 02.
Article in English | MEDLINE | ID: mdl-19259202

ABSTRACT

Point of care (POC) medical technologies require portable, small, robust instrumentation for practical implementation. In their current embodiment, optical frequency domain imaging (OFDI) systems employ large form-factor wavelength-swept lasers, making them impractical in the POC environment. Here, we describe a first step toward a POC OFDI system by demonstrating a miniaturized swept-wavelength source. The laser is based on a tunable optical filter using a reflection grating and a miniature resonant scanning mirror. The laser achieves 75 nm of bandwidth centered at 1340 nm, a 0.24 nm instantaneous line width, a 15.3 kHz repetition rate with 12 mW peak output power, and a 30.4 kHz A-line rate when utilizing forward and backward sweeps. The entire laser system is approximately the size of a deck of cards and can operate on battery power for at least one hour.


Subject(s)
Lasers , Optical Devices , Point-of-Care Systems , Biopsy, Fine-Needle/instrumentation , Equipment Design , Fiber Optic Technology , Humans , Miniaturization , Optical Fibers
2.
Opt Express ; 16(22): 17186-95, 2008 Oct 27.
Article in English | MEDLINE | ID: mdl-18957999

ABSTRACT

Spectral-domain optical coherence phase microscopy (SD-OCPM) measures minute phase changes in transparent biological specimens using a common path interferometer and a spectrometer based optical coherence tomography system. The Fourier transform of the acquired interference spectrum in spectral-domain optical coherence tomography (SD-OCT) is complex and the phase is affected by contributions from inherent random noise. To reduce this phase noise, knowledge of the probability density function (PDF) of data becomes essential. In the present work, the intensity and phase PDFs of the complex interference signal are theoretically derived and the optical path length (OPL) PDF is experimentally validated. The full knowledge of the PDFs is exploited for optimal estimation (Maximum Likelihood estimation) of the intensity, phase, and signal-to-noise ratio (SNR) in SD-OCPM. Maximum likelihood (ML) estimates of the intensity, SNR, and OPL images are presented for two different scan modes using Bovine Pulmonary Artery Endothelial (BPAE) cells. To investigate the phase accuracy of SD-OCPM, we experimentally calculate and compare the cumulative distribution functions (CDFs) of the OPL standard deviation and the square root of the Cramér-Rao lower bound (1/ square root 2SNR ) over 100 BPAE images for two different scan modes. The correction to the OPL measurement by applying ML estimation to SD-OCPM for BPAE cells is demonstrated.

3.
Opt Lett ; 33(15): 1741-3, 2008 Aug 01.
Article in English | MEDLINE | ID: mdl-18670522

ABSTRACT

A compact high-speed tuning laser source is demonstrated in two different configurations using a polygonal mirror scanner without a telescope. It is shown that the filter configuration finesse increases by utilizing multiple reflections from the polygon facet(s) and grating illumination(s). Theoretically, the free spectral range (FSR), the instantaneous linewidth, and the finesse of each filter configuration are derived. For single grating illumination, the measured coherence length, FSR, and power were 2.8 mm, 184 nm, and 40 mW at the scanning frequency of 50 kHz, respectively. Coherence length, FSR, and power of the second laser configuration were 6.2 mm, 117 nm, and 35 mW, respectively. Finally, images of a human finger were acquired in vivo using two proposed swept-source configurations.


Subject(s)
Fingers/anatomy & histology , Lasers , Tomography, Optical Coherence/instrumentation , Fiber Optic Technology/instrumentation , Fiber Optic Technology/methods , Humans , Tomography, Optical Coherence/methods
4.
Opt Lett ; 32(19): 2768-70, 2007 Oct 01.
Article in English | MEDLINE | ID: mdl-17909567

ABSTRACT

A technique for increasing the ranging depth in optical frequency domain imaging utilizing frequency encoding is presented. Ranging depth is enhanced by using two interferometer reference arms with different path lengths and independent modulation frequencies (25 and 50 MHz). With this configuration, the sensitivity decreases by 6 dB over a depth range of 7 mm, approximately a threefold improvement over the conventional optical frequency domain imaging technique. We demonstrate that the reference arm frequency separation, tuning speed, center wavelength, and instantaneous coherence length determine the signal-to-cross-talk ratio.


Subject(s)
Algorithms , Data Compression/methods , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Signal Processing, Computer-Assisted , Tomography, Optical Coherence/methods , Fourier Analysis , Sensitivity and Specificity
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