377 results about "Optical frequencies" patented technology

Apparatus, method, logic arrangement and storage medium are provided for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source can be split into N spectral bands. The N spectral bands can be individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band may be detected by a separate photo detector and amplified. For each spectral band, the signal can be band p3 filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is likely reduced by a factor equal to the number of spectral bands, while the signal amplitude can remain the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

Apparatus, method, logic arrangement and storage medium are provided for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source can be split into N spectral bands. The N spectral bands can be individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band may be detected by a separate photo detector and amplified. For each spectral band, the signal can be band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is likely reduced by a factor equal to the number of spectral bands, while the signal amplitude can remain the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split into N spectral bands. The N spectral bands are individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band is detected by a separate photo detector and amplified. For each spectral band the signal is band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is reduced by a factor equal to the number of spectral bands. The signal remains the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

The present invention is directed to a heterodyne reflectometer system and method for obtaining highly accurate phase shift information from heterodyned optical signals, from which extremely accurate film depths can be calculated. A linearly polarized light comprised of two linearly polarized components that are orthogonal to each other, with split optical frequencies, is directed toward a film causing one of the optical polarization components to lag behind the other due to an increase in the optical path in the film for that component. A pair of detectors receives the beam reflected from the film layer and produces a measurement signal, and the beam prior to incidence on the film layer and generates a reference signal, respectively. The measurement signal and reference signal are analyzed by a phase detector for phase shift. The detected phase shift is then fed into a thickness calculator for film thickness results. A grating interferometer may be included with the heterodyne reflectometer system with a grating, which diffracts the reflected beam into zeroth- and first-order bands, which are then detected by separate detectors. A detector receives the zeroth-order beam and generates another measurement signal. Another detector receives the first-order beam and generates a grating signal. The measurement signal from the grating and reference signal may be analyzed by a phase detector for phase shift, which is related to the thickness of the film. Conversely, either measurement signal may be analyzed with the grating signal by a phase detector for detecting a grating phase shift. The refractive index for the film may be calculated from grating phase shift and the heterodyne phase shift. The updated refractive index is then used for calculating thickness.