Optimized multiwavelength combination sources for interferometric use

Abstract

We present the use of multiwavelength combination sources in a direct method for improved central fringe identification in a white-light interferometric system. The optimum wavelength combinations of such sources can be obtained by the use of the results of a simple analysis. We find that this multiwavelength technique can greatly reduce the minimum signal-to-noise ratio required by the systemwhen used to identify the central fringe, and thus it offers an increased signal resolution. As a result, it is suitable for high-precision measurement purposes as well as for applications in coherence multiplexed interferometric sensor systems.

Resolution-improved dual-beam and standard optical coherence tomography: a comparison

“…To improve the axial resolution, we used a synthesized light source generated by superimposing two SLDs (EG&G C86142E, EG&G Optoelectronics, Canada) with different center wavelengths (λ 01 =830 nm, ∆λ 1 =26 nm, λ 02 =855 nm, ∆λ 2 =25 nm). Due to a beat effect [7,28,34] these two combined light sources have an effective spectral width of ∆λ eff =50 nm. The coherence length of this synthesized light source is l c ≅8 µm [2], corresponding to an axial resolution of ≅6 µm after division by the mean group refractive index 1.354 of the ocular media [12].…”

Ultrahigh Resolution Optical Coherence Tomography

“…However, biological imaging could not be performed with these light sources due to their low brightness. By multiplexing spectrally displaced superluminescent diodes to increase optical bandwidth [24][25][26], OCT tomograms with improved $7 mm axial resolution in the retina were demonstrated several years ago [27]. More recently, cost-effective, broad bandwidth advanced SLD light sources have become available which approach the image resolutions achieved by femtosecond lasers [28,29].…”

<title>Peculiarities of interferometer temporal signal in partially coherent light of multiple sources</title>

“…Under the condition of mutual spatial coherence of interfering waves, we can write the following simplified expression for the interferometer signal u (At) (e.g., for the signal ofthe Michelson interferometer): u(z1t) 'R 'S +2Ir(At)Icos(4t+a), (1) where 'R' 's and F(zlt) are respectively intensities and temporal coherence function of interfering waves; a = arg P(4t) -?iY4t; zlt is the time delay of light waves in the interferometer; and is the average light frequency, which can be defined by expression4…”