Optical: systems and elements – Prism – With reflecting surface
Reexamination Certificate
2001-02-16
2002-06-18
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Prism
With reflecting surface
C211S201000, C211S071010
Reexamination Certificate
active
06407872
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention pertains to an optical device for scanning optical path length. In particular, the present invention relates to an optical device for scanning optical path length using a set of moving prisms.
BACKGROUND OF THE INVENTION
An optical path length scanner is an important component used in many applications including, for example and without limitation, optical auto-correlation applications, optical coherent tomography (“OCT”), and optical coherent domain reflectometer (“OCDR”), to name a few. Scanning amplitude, linearity, duty cycle, and repetition rate are key parameters used to determine the efficacy of optical path length scanners. For example, in many applications it is desirable to have simultaneously a large scanning amplitude (for example, >1 mm), good linearity (for example, >95%), a high duty cycle (for example, >75%), and a high repetition rate (for example, >200 Hz). In addition, compactness and simplicity are among further concerns that relate to manufacturing of an optical path length scanner.
FIG. 3
shows a conventional optical path length scanner
310
as it is commonly used in a conventional interferometer
300
. As is well known, optical path length scanner
310
comprises retro-reflector
311
that is back and forth along a linear path with a driving mechanism such as, for example and without limitation, a galvanometer or a driven voice coil (the driving mechanism is not shown in FIG.
3
).
As further shown in
FIG. 3
, radiation beam
325
is directed to impinge upon retro-reflector
311
, and is reflected thereby to produce returning beam
328
. As is well known by those of ordinary skill in the art, returning beam
328
is substantially parallel to incident beam
325
, regardless of its alignment with respect to retro-reflector
311
.
Limitations with prior art optical path length scanner
310
stem from difficulty in driving retro-reflector
311
in a back and forth motion. For example, one limitation of back-and-forth driving mechanisms is that the repetition rate is typically below a hundred hertz (100 Hz) if a scanning amplitude in the millimeter range is required. Another limitation of back-and-forth driving mechanisms is that good linearity can be obtained only for a small portion of a cycle.
Various other designs for optical path length scanners have been reported in the prior art. One example of another design relates to a scanning optical delay device having a helicoid reflecting mirror that is disclosed in U.S. Pat. Nos. 5,784,186; 5,886,806, and 5,907,423 (inventors Wang et al.). A further example of another design relates to a grating-based, phase control, optical delay line that is disclosed in U.S. Pat. No. 6,111,645 (inventor Tearney et al.). A still further example of another design relates to a scanning optical delay line comprised of a rotating-parallelogram prism that is disclosed in an article entitled “Scanning delay line with a rotating-parallelogram prism for low-coherence interferometry” by Giniunas et al. in
Applied Optics
, Vol. 38, No. 34, Dec. 1, 1999, pp. 7076-7079. A yet still further example of another design relates to a rapid depth scanner comprised of a rotating cube that is disclosed in an article entitled “Rapid and scalable scans at 21 m/s in optical low-coherence reflectometry” by Ballif et al. in
Optics Letters
, Vol. 22, No. 11, Jun. 1, 1997, pp. 757-759. However, none of these designs provide a practical optical path length scanner (i.e., an optical path length scanner having relatively low cost, having a long lifetime, and requiring little alignment) which has a repetition rate in the kilohertz range, and a scanning amplitude in the millimeter range with good linearity and a high duty cycle.
In light of the above, there is a need for an optical path length scanner capable of having a relatively high repetition rate (for example, up to the kilohertz range) and a scanning amplitude up to the millimeter range with good linearity and a relatively high duty cycle.
SUMMARY OF THE INVENTION
Embodiments of the present invention advantageously satisfy the above-identified need in the art, and provide an optical path length scanner. Specifically, in accordance with a first embodiment of the present invention, an optical path length scanner comprises: (a) a set of prisms mounted evenly along a movable carrier; and (b) a mechanism that drives the movable carrier to move. In addition, in accordance with a second embodiment of the present invention, the optical path length scanner further comprises a first prism held stationary relative to a predetermined direction and arranged in a complementary orientation and position with respect to the set of prisms. In further addition, in accordance with a third embodiment of the present invention, the optical path length scanner further comprises a mechanism that applies a beam of radiation at a minimum deviation angle of incidence to the prisms.
REFERENCES:
patent: 5255114 (1993-10-01), Kessler
patent: 5321501 (1994-06-01), Swanson et al.
patent: 5436986 (1995-07-01), Tsai
patent: 5459570 (1995-10-01), Swanson et al.
patent: 5784186 (1998-07-01), Wang et al.
patent: 5886806 (1999-03-01), Wang et al.
patent: 5907423 (1999-05-01), Wang et al.
patent: 5959784 (1999-09-01), Seki et al.
patent: 6111645 (2000-08-01), Tearney et al.
patent: 6134003 (2000-10-01), Tearney et al.
patent: 6178255 (2001-01-01), Scott et al.
“400-Hz mechanical scanning optical delay line” by K.F. Kwong et al.,Optics Letters, vol. 18, No. 7, Apr. 1, 1993, pp. 558-560.
“Rapid and scalable scans at 21 m/s in optical low-coherence reflectometry” by J. Ballif et al.,Optics Letters, vol. 22, No. 11, Jun. 1, 1997, pp. 757-759.
“High-spped phase- and group-delay scanning with a grating-based phase control delay line” by G. J. Tearney et al.,Optics Letters, vol. 22, No. 23, Dec. 1, 1997, pp. 1811-1813.
“Scanning delay line with a rotating-parallelogram prism for low-coherence interferometry” by L. Giniunas et al., Applied Optics, vol. 38, No. 34, Dec. 1, 1999, pp. 7076-7079.
Arianta Kabir M.
Kulkarni Manish D.
Lai Ming
Wei Jay
Carl Zeiss, Inc.
Einschlag Michael B.
Sikder Mohammad
LandOfFree
Optical path length scanner using moving prisms does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical path length scanner using moving prisms, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical path length scanner using moving prisms will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971016