Abstract:
Current apparatuses and methods for analysis of spectroscopic optical coherence tomography (SOCT) signals suffer from an inherent tradeoff between time (depth) and frequency (wavelength) resolution. In one non-limiting embodiment, multiple or dual window (DW) apparatuses and methods for reconstructing time-frequency distributions (TFDs) that applies two windows that independently determine the optical and temporal resolution is provided. For example, optical resolution may relate to scattering information about a sample, and temporal resolution may be related to absorption or depth related information. The effectiveness of the apparatuses and methods is demonstrated in simulations and in processing of measured OCT signals that contain fields which vary in time and frequency. The DW technique may yield TFDs that maintain high spectral and temporal resolution and are free from the artifacts and limitations commonly observed with other processing methods.
Abstract:
One aspect of the invention concerns a method for characterization of a light beam, comprising the following steps: - separation of the light beam by means of a separator optic into a first sub-beam and a second sub-beam; - propagation of the first sub-beam over a first optic and of the second sub-beam over a second optic, said first and second optics being respectively arranged so that the first sub-beam on leaving the first optic, referred to as the "reference beam", and the second sub-beam on leaving the second optic, referred to as the "characterized beam", are separated by a time delay τ; - recombination of the reference beam and the characterized beam by means of a recombiner optic, in such a way that the beams spatially interfere and form a two-dimensional interference pattern, the two-dimensional interference pattern extending along a first plane; - measurement of the spectral frequency of at least one part of the two-dimensional interference pattern by means of a measurement system, - calculation of the Fourier transform in the time domain of at least one spatial point of the frequency spectrum, said Fourier transform in the time domain having a time central peak and first and second time side peaks; - calculation of the Fourier transform in the frequency domain for one of said first and second time side peaks; - calculation of the spectral amplitude A R (ω) and of the space-spectrum phase φ R (χ,γ,ω) for said Fourier transform in the frequency domain.
Abstract:
Un aspect de l'invention concerne un procédé de caractérisation d'un faisceau de lumière comprenant les étapes suivantes : - séparation au moyen d'une optique séparatrice du faisceau de lumière en un premier sous-faisceau et un deuxième sous-faisceau; - propagation du premier sous-faisceau sur une première optique et du deuxième sous-faisceau sur une deuxième optique, lesdites première et deuxième optiques étant respectivement agencées de sorte que le premier sous-faisceau en sortie de la première optique, dit « faisceau de référence », et le deuxième sous-faisceau en sortie de la deuxième optique, dit « faisceau à caractériser », présentent entre eux un délai temporel τ; - recombinaison au moyen d'une optique recombinatrice du faisceau de référence et du faisceau à caractériser de telle manière qu'ils interfèrent spatialement et forment un motif d'interférence bidimensionnel, le motif d'interférence bidimensionnel s'étendant suivant un premier plan; - mesure au moyen d'un système de mesure du spectre fréquentiel d'au moins une partie du motif d'interférence bidimensionnel; - calcul de la transformée de Fourier dans le domaine temporel d'au moins un point spatial du spectre fréquentiel, ladite transformée de Fourier dans le domaine temporel présentant un pic temporel central et des premier et deuxième pics temporels latéraux; - calcul de la transformée de Fourier dans le domaine fréquentiel pour l'un desdits premier et deuxième pics temporels latéraux; - calcul de l'amplitude spectrale A R (ω) et de la phase spatio-spectrale φ R (χ,γ,ω) pour ladite transformée de Fourier dans le domaine fréquentiel.
Abstract:
Verfahren und Vorrichtung zur optischen Überprüfung einer Probe mittels spektraler Interferometrie, wobei ein von einer Strahlungsquelle (1) abgegebener Strahl (2'') auf die Probe (5) sowie ein Referenzstrahl (2') auf eine Referenzprobe (4) gerichtet werden und die spektrale Interferenz der beiden Strahlen nach Reflexion an den Proben oder Passieren der Proben mittels eines Spektrographen (6) aufgenommen wird; das so erhaltene Interferogramm I (ω) wird numerisch nach der Kreisfrequenz ω abgeleitet, wonach für die so erhaltene Funktion I `(ω) die Nullstellen ω i numerisch als Lösungen der Gleichung I `(ω) = 0 berechnet werden und danach aus den Nullstellen ω i die frequenzabhängige Gruppenverzögerung τ (ω) entsprechend der Gleichung τ (ω n ) = π/ (ω i+1 -ω i ), mit i = 1,2... und ω n = (ω i+1 + ω i ) /2, berechnet wird.
Abstract:
One aspect of the invention concerns a method for characterization of a light beam, comprising the following steps: - separation of the light beam by means of a separator optic into a first sub-beam and a second sub-beam; - propagation of the first sub-beam over a first optic and of the second sub-beam over a second optic, said first and second optics being respectively arranged so that the first sub-beam on leaving the first optic, referred to as the "reference beam", and the second sub-beam, on leaving the second optic, referred to as the "characterized beam", are separated by a time delay τ sweeping a time interval T1 with step P1; - recombination of the reference beam and the characterized beam by means of a recombiner optic in such a way that the beams spatially interfere and form a two-dimensional interference pattern; - measurement of said two-dimensional interference pattern by means of a measurement system, as a function of the time delay τ sweeping the time interval T1 with step P1, in order to obtain a temporal interferogram; - calculation of the Fourier transform in the frequency domain of at least one spatial point of the temporal interferogram, said Fourier transform in the frequency domain having a frequency central peak and first and second frequency side peaks; - calculation of the spectral amplitude A R(ω) and of the space-spectrum phase φR(x,y,ω) for one of said first and second frequency side peaks of said Fourier transform in the frequency domain.
Abstract:
The present invention causes measurement light emitted from an object to be measured to enter a fixed mirror unit and a movable mirror unit and forms interference light of measurement light reflected by the fixed mirror unit and measurement light reflected by the movable mirror unit. At this time, a change of the intensity of the interference light of measurement light is obtained by moving the movable mirror unit, and an interferogram of measurement light is acquired based on the change. At the same time, reference light of a narrow wavelength band included in a wavelength band of the measurement light is caused to enter the fixed mirror unit and the movable mirror unit, and interference light of the reference light reflected by the fixed mirror unit and the reference light reflected by the movable mirror unit is formed. At this time, the movable mirror unit is moved to correct the interferogram of measurement light based on an amplitude of the change of the interference light of the reference light and based on a phase difference between measurement light, which is at the same wavelength as the reference light in the measurement light, and the reference light, and a spectrum of the measurement light is acquired based on the corrected interferogram.