Coherent light generators – Particular resonant cavity – Specified output coupling device
Reexamination Certificate
2000-11-21
2003-03-04
Ip, Paul (Department: 2828)
Coherent light generators
Particular resonant cavity
Specified output coupling device
C606S013000, C606S016000, C606S017000
Reexamination Certificate
active
06529543
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the use of electromagnetic wave energy to alter a substrate, e.g., by heat, ablation, and/or photochemical reaction.
BACKGROUND OF THE INVENTION
Lasers are useful in medical, materials processing, and other applications to cause heating and/or ablation, i.e., substance removal, within a substrate, e.g., biological tissue or other material. In addition, certain lasers, e.g., ultraviolet (UV) lasers, can be used to cause photochemical alterations, e.g., polymerization, in a substrate, with or without simultaneous ablation.
Laser energy is typically delivered as a beam or illumination in which the electromagnetic energy propagates directly into the tissue or other substrate. Ablation of biological tissue by lasers occurs predominantly by the rapid thermal vaporization of tissue water. However, secondary processes may coexist with this thermal vaporization. For example, explosive mechanical removal is caused by short laser pulses when laser energy intensity is high enough to initiate a plasma that produces shock waves and mechanical fracture, e.g., greater than about 10
8
W/cm
2
. Additionally, UV pulsed laser ablation can cause concurrent photochemical reactions in tissue. When present, these secondary processes can change the efficiency of pulsed laser ablation.
The ablation depth within tissue or other materials depends upon the depth to which the electromagnetic waves penetrate. For some applications, e.g., treatment of large tumors, deep or subsurface penetration is required, and appropriate wavelength regions, e.g., red or near infrared, are preferable. For other applications, a well-controlled superficial effect is desired, e.g., skin resurfacing, ablation of the outer surface of the cornea to correct vision, or of the inner surface of diseased arteries. Typically, laser energy is delivered to a patient at normal incidence, and the wavelength of the laser energy is selected to produce the desired penetration depth based on the optical absorption of the target tissue and any intermediate tissue.
SUMMARY OF THE INVENTION
The invention features systems and tools for controlling the optical penetration depth of laser energy, e.g., when delivering laser energy to target tissue in a patient. The systems and tools control the optical penetration depth (OPD) by controlling the incident angle at which the laser energy is delivered to the target area of the patient. Embodiments of the invention include an optical coupler that permit a user to vary the incident angle and thereby selectably control the OPD of incident laser energy. Fabricating the optical coupler to have a refractive index greater than that of the target tissue can enhance the range of selectable OPDs. The laser energy, which is delivered to the desired depth, can cause alteration of the target tissue by, e.g., heating, ablation, and/or photochemical reaction.
In general, in one aspect, the invention features an apparatus delivering laser radiation to a substrate at a controlled penetration depth, the substrate having a first refractive index and an absorption coefficient &mgr;
a
. The apparatus includes an optical coupler for receiving optical energy from a optical energy source and a positioning mechanism. The optical coupler has a second refractive index higher than the first refractive index and is adapted to contact and form an interface with the substrate. It also has a contoured surface such that an angle of refraction &thgr;
r
of the optical energy into the substrate at the interface can be varied by adjusting relative positions of the optical coupler and the optical energy entering the optical coupler. Selection of a particular angle of refraction produces a desired penetration depth &dgr;
r
according to the equation &dgr;
3
≈(1/&mgr;
a
)cos &thgr;
r
. The positioning mechanism couples the optical coupler and the optical energy to adjust the relative positions of the optical coupler and the optical energy entering the optical coupler.
The optical coupler may have, e.g., a hemispherical shape or a hemicylindrical shape. The positioning mechanism can be angular positioning mechanism, for example, it can include a gimbal mounted to the optical coupler. Alternatively, the positioning mechanism can be a translational positioning mechanism, e.g., it can include a support structure slidably connected to the optical coupler. Furthermore, the optical coupler can be configured to receive the optical energy at substantially normal incidence and deliver the optical energy to the interface at non-normal incidence.
In general, in another aspect, the invention features, another apparatus delivering laser radiation to a substrate at a controlled penetration depth, the substrate having a first refractive index n
1
and an absorption coefficient &mgr;
a
. The second apparatus includes an optical coupler for receiving optical energy from a optical energy source. The optical coupler has a second refractive index n
2
higher than the first refractive index. The optical coupler also has at least two surfaces adapted to contact and form an interface with the substrate. It is shaped to internally direct the optical energy received from the optical energy source to the first surface at a first acute incident angle, and direct optical energy internally reflected from the first surface to the second surface at a second acute incident angle different from the first acute incident angle. Contacting the substrate with the first surface produces an optical penetration depth &dgr;
r1
≈(1/&mgr;
a
)cos &thgr;
r1
, whereas contacting the substrate with the second surface produces an optical penetration depth &dgr;
r2
≈(1/&mgr;
a
)cos &thgr;
r2
, where &thgr;
r1
is the refraction angle corresponding to the first acute incident angle and &thgr;
r2
is the refraction angle corresponding to the second acute incident angle.
The optical coupler may further include a third surface adapted to contact and form an interface with the substrate. In this case, the optical coupler is shaped to direct the optical energy internally reflected from the second surface to the third surface at a third acute incident angle. In some embodiments, the first and second acute incident angles can both greater than arcsin(n
0
2
), n
0
being the refractive index for air, and/or they can both be less than arcsin(n
1
2
). Furthermore, the first and second acute incident angles can be each greater than about 10°.
In general, in another aspect, the invention features another apparatus delivering laser radiation to a substrate at a controlled penetration depth, the substrate having a first refractive index n
1
and an absorption coefficient &mgr;
a
. The third apparatus includes: an optical coupler base; and a plurality of optical coupler tips each configured to be mechanically attached to the optical coupler base to form an optical coupler for delivering optical energy from a optical energy source to a substrate. The optical coupler includes a surface adapted to contact and form an interface with the substrate. Each optical coupler tip, when attached to the optical coupler base, is shaped to internally deliver the optical energy to the interface at an incident angle, wherein the incident angles corresponding to each of the plurality of optical coupler tips differ from one another. Selecting one of the optical coupler tips specifies a desired penetration depth &dgr;
r
, according to the equation &dgr;
r
≈(1/&mgr;
a
)cos &thgr;
r
, where &thgr;
r
is the refraction angle corresponding to the incident angle defined by the selected optical coupler tip.
In some embodiments, each of the optical coupler tips has a refractive index greater than the first refractive index n
1
. Moreover, the plurality of optical coupler tips may include at least three optical coupler tips. The incident angle defined by each optical coupler tip may be greater than about 10°. Furthermore, the incident angle defined by each optical coupler tip may be greater than arcsin(n
0
2
), where n
0
is the refractive index for air and n
2
i
Anderson R. Rox
Domankevitz Yacov
Ip Paul
Menefee James
The General Hospital Corporation
LandOfFree
Apparatus for controlling laser penetration depth does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for controlling laser penetration depth, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for controlling laser penetration depth will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3033479