Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1997-07-28
2000-11-07
Kim, Robert H.
Optics: measuring and testing
By particle light scattering
With photocell detection
356357, 356360, G01B 902
Patent
active
061444499
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a low coherence interferometer apparatus for the investigation of a sample, in particular for multi-dimensional imaging in medical applications.
Low coherence interferometer methods are used for a variety of applications. They are normally referred to in the art as LCI (Low Coherence Interferometry) methods or as OCDR (Optical Coherence Domain Reflectometry). The abbreviation LCI is used below for reasons of simplicity.
LCI methods are utilized or are at least discussed for a variety of applications. For example, reference can be made to the following citations: Applied Optics, 26 (1987), 2836-2842. by Low-Coherence Reflectometry", Applied Optics, 32 (1993), 6032-6042
All LCI methods have the common property that light from a low coherence (wide spectral band width emitting) light source is split into two partial beams--a measuring light beam and a reference light beam. The two beams are joined upstream of a detector to produce an interference signal containing the desired information. A principal component in the low coherence interferometry apparatus (designated below as "LCI apparatus") is an interferometer configuration comprising, in addition to the low coherence light source, an optical coupler, a reference reflector, a probe head having a light exit opening for irradiating light into the sample, and the detector.
The optical paths between these interferometer elements form so-called interferometer arms. Light from the light source passes through the light source arm and is incident on the optical coupler where it is split. One part, constituting measuring light, passes through a sample arm and the probe head and is irradiated into the sample. The second part of the light, constituting reference light, passes through a reflector arm and is incident on the reference reflector. Both fractions of the light are reflected (the measuring light in the sample and the reference light at the reference reflector) and are guided back to the optical coupler along the same optical path (sample arm and reference arm respectively) where they are joined together and introduced through the detector arm to the detector. The light-sensitive surface of the detector can measure an interference signal caused by the interference between the two parts of the beam.
In order for an interference to occur, the optical path length in the reference arm (between the optical coupler and the reference reflector) differs by at most the coherence length of the light source from the optical path length of the measuring light between the optical coupler and the point of reflection in the sample. An interference signal is measured only if this condition is fulfilled. This fact is utilized to limit the investigation to one particular measuring depth, designated below as the LCI measuring depth, through appropriate adjustment of the length relationships between the reference arm and the sample arm.
This fundamental principle of the LCI measuring technique is used to allow various applications through variation of certain measurement details and through analysis of the interference signal.
For example, reference 1) concerns the investigation of the structure of optical fibers, in particular for localizing optical defects. References 2) and 3) concern various aspects of investigations in biological tissue (in particular skin tissue). These authors are only concerned with obtaining information in dependence on the LCI measuring depth defined by the interference criterion. These publications therefore perform a pure depth scan (also termed "longitudinal scan"), i.e. the length of the reference arm is varied to adjust the LCI measuring depth.
In contrast thereto, references 4) through 6) describe methods and apparatuses with which an additional lateral scan is carried out in order to obtain in various ways a picture of the distribution of the information of interest in the lateral direction (parallel to the surface of the sample) These methods therefore pertain to multi-dimensional imaging . In addition to a depth scan, a
REFERENCES:
patent: 5073023 (1991-12-01), Valette et al.
patent: 5289256 (1994-02-01), Gramling
patent: 5459570 (1995-10-01), Swanson et al.
Danielson et al., Applied Optics, vol. 26, No. 14, Jul. 15 1987, Guided-wave reflectometry with micrometer resolution.
Schmitt et al., Applied Optics, vol. 32, No. 30, Oct. 20 1993, "Measurement of optical properties of biological tissues by low-coherence reflectometry".
PCT International Application No. WO 95/30368 published Nov. 16, 1995.
PCT International Application No. WO 92/19930 published Nov. 12, 1992.
Article by Prof. Dr. Karl Joachim Ebeling.
Jungbluth et al., Laser Focus World, Apr. 1994, "Optical waveguides advance to meet fiberoptic demands".
Proceedings of the Third European Conference, ECIO'85, Berlin, Germany, May 6-8, 1985, Integrated Optics.
Rickman, Sensor Review, vol. 14, No. 1, 1994, pp 27-29, "Silicon Integrated Optics and Sensor Applications".
Brooks et al., Optics Letters, vol. 20, No. 4, Feb. 15, 1995, "Integrated-optic dispersion compensator that uses chirped gratings".
Youngquist et al., Optics Letters, vol. 12, No. 3, Mar. 1987, "Optical coherence-domain reflectometry: a new optical evaluation technique".
Hill et al., Optics Letters, vol. 19, No. 17, Sep. 1, 1994, "Chirped in-fiber Bragg gratings for compensation of optical-fiber dispersion".
Missig et al., Applied Optics, vol. 34, No. 14, May 10, 1995, "Diffractive optics applied eyepiece design".
Shibata et al., J. Opt. Soc. Am. A., vol. 4, No. 3, Mar. 1987, "Temporal coherence properties of a dispersively propagating beam in a fiber-optic interferometer".
Hebden et al., Physic World, Aug. 1993, "Infrared lasers muscle in on medical imaging".
Takada et al., Applied Optics, May 1, 1987, vol. 26, No. 9, "New measurement system for fault location in optical waveguide devices based on an interferometric technique".
Saleh et al., Journal of Lightwave Technology, vol. 6, No. 3 Mar. 1988, "Reflective Single-Mode Fiber-Optic Passive Star Couplers".
Himeno et al., Journal of Lightwave Technology, Jan. 6, 1988, No. 1, vol. 6, "Loss Measurement and Analysis of High-Silica Reflection Bending Optical Waveguides".
Boecker Dirk
Knuettel Alexander
Boehringer Mannheim GmbH
Kim Robert H.
Lee Andrew H.
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