Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-07-28
2002-02-26
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S372000, C359S382000, C359S383000, C359S389000, C359S393000, C359S900000
Reexamination Certificate
active
06351325
ABSTRACT:
SUMMARY OF THE INVENTION
This invention provides an angled-dual-axis confocal scanning microscope, comprising an angled-dual-axis confocal head and a vertical scanning unit. The angled-dual-axis confocal head further comprises a first end of a first single-mode optical fiber serving as a point light source, an angled-dual-axis focusing means, and a first end of a second single-mode optical fiber serving as a point light detector.
From the first end of the first optical fiber an illumination beam emerges. The angled-dual-axis focusing means serves to focus the illumination beam to a diffraction-limited illumination focal volume along an illumination axis within an object. The angled-dual-axis focusing means further receives an observation beam emanated from an observation focal volume along an observation axis within the object, and focuses the observation beam to the first end of the second optical fiber. The angled-dual-axis focusing means is designed such that the illumination axis and the observation axis intersect at an angle &thgr; with the object, whereby the illumination and observation focal volumes intersect optimally at a confocal overlapping volume. The vertical scanning unit comprises a vertical translation means and a compensation means. The vertical translation means is mechanically coupled to the angled-dual-axis confocal head, such that it causes the angled-dual-axis confocal head to move towards or away from the object, thereby providing a vertical scan that deepens into the interior of the object. The compensation means keeps the optical path lengths of the illumination and observation beams substantially unchanged, thereby ensuring the optimal intersection of the illumination and observation focal volumes in the course of vertical scanning. Altogether, the angled-dual-axis confocal scanning microscope of the present invention is capable of performing vertical scanning with enhanced axial (i.e., vertical) resolution, while maintaining a workable working distance and a large field of view.
The angled-dual-axis confocal scanning microscope described above may be further equipped with a transverse stage mechanically coupled to the object, serving to translate the angled-dual-axis confocal head relative to the object in a transverse plane perpendicular to the vertical direction. Alternatively, the object itself may be moved (e.g., driven by an external mechanism) transversely relative to the angle-dual-axis confocal head in various directions perpendicular to the vertical direction. As such, the angled-dual-axis confocal scanning microscope of the present invention is capable of providing vertical scans and transverse scans in various ways. Moreover, by assembling an assortment of the vertical and/or transverse scans in a suitable manner, two-dimensional transverse and/or vertical cross-section scans of the object can be obtained. A three-dimensional volume image of the object can also be accordingly constructed.
It is to be understood that the term “emanating” as used in this specification is to be construed in a broad sense as covering any light transmitted back from the object, including reflected light, scattered light, and fluorescent light. It should be also understood that when describing the intersection of the illumination and observation beams in this specification, the term “optimal” means that the illumination and observation focal volumes (i.e., the main lobes of the illumination beam's point-spread function and the observation beam's point-spread function) intersect in such a way that their respective centers substantially coincide and the resulting overlapping volume has comparable transverse and axial extents. This optimal overlapping volume is termed “confocal overlapping volume” in this specification.
In an angled-dual-axis confocal head of the present invention, the angled-dual-axis focusing means generally comprises an assembly of beam focusing, collimating, and deflecting elements. Such elements can be selected from the group of refractive lenses, diffractive lenses, GRIN lenses, focusing gratings, micro-lenses, holographic optical elements, binary lenses, curved mirrors, flat mirrors, prisms and the like. A crucial feature of the angled-dual-axis focusing means is that it provides an illumination axis and an observation axis that intersect at an angle &thgr;. The optical fibers can be single-mode fibers, multi-mode fibers, birefrigent fibers, polarization maintaining fibers and the like. Single-mode fibers are preferable in the present invention, for the ends of single-mode fibers provide a nearly point-like light source and detector.
An important advantage of the angled-dual-axis arrangement of the present invention is that since the observation beam is positioned at an angle relative to the illumination beam, scattered light along the illumination beam does not easily get passed into the observation beam, except where the beams overlap. This substantially reduces scattered photon noise in the observation beam, thus enhancing the sensitivity and dynamic range of detection. This is in contrast to the direct coupling of scattered photon noise between the illumination and observation beams in a transmission or reciprocal confocal microscope, due to the collinear arrangement between the beams. Moreover, by using low NA focusing elements (or lenses) in an angled-dual-axis confocal scanning system of the present invention, the illumination and observation beams do not become overlapping until very close to the focus. Such an arrangement further prevents scattered light in the illumination beam from directly “jumping” to the observation beam, hence further filtering out scattered photon noise in the observation beam. Altogether, the angled-dual-axis confocal system of the present invention has much lower noise and is capable of providing much higher contrast when imaging in a scattering medium than the prior art confocal systems employing high NA lenses, rendering it highly suitable for imaging within biological specimens.
Another advantage of the present invention is that the entire angled-dual-axis confocal head can be mounted on a silicon substrate etched with precision V-grooves which host various optical elements. Such an integrated device offers a high degree of integrity, maneuverability, scalability, versatility, simple construction, and easy alignment.
The present invention further provides a first angled-dual-axis confocal scanning system, comprising an angled-dual-axis confocal scanning microscope of the present invention, a light source, and an optical detector. The light source is optically coupled to the second end of the first optical fiber of the angled-dual-axis confocal scanning microscope, providing an illumination beam; and the optical detector is optically coupled to a second end of the second optical fiber of the angled-dual-axis confocal scanning microscope, receiving an observation beam collected from an object. The light source can be a continuous wave (CW) or a pulsed source such as a fiber laser, a semiconductor optical amplifier, an optical fiber amplifier, a semiconductor laser, a diode pumped solid state laser, or other suitable fiber-coupled light source known in the art. The optical detector can be a PIN diode, an avalanche photo diode (APD), or a photomultiplier tube. Such an angled-dual-axis confocal scanning system provides a simple and versatile imaging tool with high resolution and fast scanning capability.
It is known in the art that many biological tissues, such as tendons, muscle, nerve, bone, cartilage and teeth, exhibit birefrigence due to their linear or fibrous structure. Birefrigence causes the polarization state of light to be altered (e.g., rotated) in a prescribed manner upon refection. Skin is another birefrigent medium. Collagen contained in skin is a weakly birefrigent material. At temperatures between 56-65° C., collagen denatures and loses its birefrigence. Thus, by detecting induced changes in the polarization state of light reflected from a skin sample, an image representing the reg
Garrett Mark H.
Kino Gordon S.
Mandella Michael J.
Lumen Intellectual Property Services Inc.
Optical Biopsy Technologies, Inc.
Phan James
LandOfFree
Fiber-coupled, angled-dual-axis confocal scanning... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fiber-coupled, angled-dual-axis confocal scanning..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fiber-coupled, angled-dual-axis confocal scanning... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2970453