Multi-head laser assembly

A laser device is provided for the co-axial positioning of plural laser beams of same or different wavelengths along a single axis. At least two laser oscillators are provided, each producing a laser beam. A rotary reflector is positioned for intercepting at least one of the produced laser beams and directing the intercepted laser beam separately from, but along a single axis defined by another laser beam.

TECHNICAL FIELD 
The present invention relates to devices and procedures for the controlled 
delivery of laser energy along a selected axis to a target or site. The 
present invention is especially suitable for use in a medical device for 
treating a site on the surface of, or inside, a patient's body, as well as 
for industrial applications. 
BACKGROUND OF THE INVENTION AND TECHNICAL PROBLEMS POSED BY THE PRIOR ART 
Various systems have been developed or proposed for utilizing laser beam 
energy for cutting, welding, engraving, etc. Surgical laser devices have 
also been developed for delivering laser energy from a laser to a site on 
or in a patient's body. In some applications, these surgical laser devices 
deliver laser radiation through a flexible, optical fiber from a laser to 
a target tissue. 
Laser energy may be employed to produce a desired effect on tissue, 
including various types of human tissue. For example, laser energy may be 
employed to denature proteinaceous components and to cauterize, ablate, or 
cut tissue. 
Typically, effects of a laser beam on human tissue (e.g., ablation, 
thermo-coagulation, denaturization, cutting, and the like) can be produced 
with pulses of laser radiation having, for example, at a wavelength of 
2,100 nm, an energy density of about 300 mJ/mm.sup.2 incident on the 
target site tissue. The effects on the tissue are, of course, dependent 
upon the amount of incident radiant energy that is absorbed by the tissue 
and on the absorption efficiency of the employed wavelength. Relatively 
hard tissues, such as calcified atherosclerotic plaque or bone, require 
relatively high energy levels for ablation to be effective. Likewise, 
relatively high average power is needed for ablating a cancerous tumor, 
for ablation of cartilage in arthroscopy, or like medical procedures where 
relatively large amounts or relatively hard tissue is to be removed. At a 
wavelength of 2,100 nm, for example, this would require a power delivery 
of 40 to 130 watts to the tissue (about 50 to 150 watts at the laser 
head). 
In a variety of surgical procedures involving the cutting of tissue with a 
laser beam, it is desirable to cut the tissue relatively quickly. In order 
to cut certain types of tissues at a relatively high rate, the incident 
laser energy at the tissue site, at a wavelength of 2,100 nm, for example, 
should preferably be delivered in pulses having a duration of about 200 to 
600 microseconds at a repetition rate of 5 to 60 Hertz. 
With many types of commercially available laser devices suitable for tissue 
cutting in medical applications, the production of such high energy 
levels, or such rapid pulse repetition rates, with a single laser 
resonator or oscillator (i.e., flash lamp, cavity, and crystal) is 
difficult or impossible, especially with an excimer, a holmium:YAG, 
erbium:YAG, ruby, alexandrite or similar lasers having limited output 
energy level and repetition rate capability. Indeed, many of the 
commercially available laser devices that are suitable for tissue cutting 
cannot be operated for extended time periods at such high energy levels or 
such repetition rates without creating excessive heat or placing excessive 
stress on the laser device or optical fiber waveguide, which can lead to 
premature component failure. 
Accordingly, it would be desirable to provide an improved system for 
employing suitable, commercially available laser devices for generating 
radiant energy at higher energy levels, longer pulse widths, or faster 
repetition rates for delivery to a tissue site. It would also be 
advantageous to provide an improved laser system that can accommodate 
plural laser heads or laser devices for delivering laser energy of 
different wavelengths in intermittent, or substantially continuous, joined 
pulses. 
Preferably, such an improved system should accommodate the use of 
commercially available, pulsed or continuous laser devices of the 
following types: neodymium:yttrium aluminum garnet (Nd:YAG), 
erbium:yttrium aluminum garnet (Er:YAG), holmium:yttrium aluminum garnet 
(Ho:YAG), ruby, alexandrite, carbon dioxide, excimer lasers such as argon 
fluoride (ArF), xenon chloride (XeCl), and other pulsed lasers. 
Such an improved system should preferably operate to subject the tissue to 
pulses of laser energy at a sufficiently high average power and/or 
repetition rate within a relatively short time span so as to produce the 
desired effect in the tissue. In particular, it would be desirable to 
raise the temperature of the tissue to a desired elevated level, 
notwithstanding the tendency of the tissue temperature to decay or drop 
over time. In this regard, it will be appreciated that the temperature of 
tissue that has been initially raised to an elevated temperature T.sub.o 
decreases approximately according to the following equation: 
EQU T.sub.t =T.sub.o e.sup.-t/k 
where T.sub.o is the maximum elevated temperature to which the tissue has 
been raised by a preceding pulse, e is the natural logarithm base, t is 
any selected time period following the establishment of the temperature 
T.sub.o, k is the tissue thermal diffusion time constant, and T.sub.t is 
the resulting time-dependent temperature at the end of the time period t. 
When tissue is subjected to an initial pulse of laser energy, the tissue 
temperature rises to a maximum temperature T.sub.o, and then the tissue 
temperature begins to decrease. As the tissue temperature is initially 
rising, it would be desirable to provide increased energy to the tissue. 
It is believed that the efficiency of the laser ablation by the tissue can 
be increased by subjecting the tissue to pulses of laser energy in a way 
that results in little or no time temperature decay between laser energy 
pulses. Accordingly, the time span between pulses should be relatively 
short, preferably much shorter than the tissue thermal diffusion time 
constant. 
For example, when a target site of a typical tissue is elevated to an 
initial temperature of about 100.degree. C., the tissue temperature decays 
to about 97.degree. C. in 5 milliseconds, and it would be desirable to 
subject the tissue to a plurality of laser energy pulses within such a 
time period or within an even shorter time. Preferably, an improved system 
should accommodate the emission of energy pulses from two or more 
conventional, medical lasers within such a time period wherein the laser 
energy pulses have a typical temporal separation of less than 5 
milliseconds--and a pulse width of about 200 to 600 microseconds. The 
pulse width may vary depending upon a specific application. For example, 
for the fragmentation of ureteral, kidney or gall stones, a pulse width of 
about 10 to 1000 nanoseconds may be desirable. 
While laser energy from two laser sources can be delivered through two 
independent optical fibers as known in the art, it would be beneficial to 
provide such an improved laser energy delivery system which could deliver 
such substantial laser energy through a single optical fiber or a bundle 
of optical fibers, a single hollow waveguide or an articulated arm. Such a 
system could also operate with two or more different laser types for 
subjecting the tissue sequentially to laser energy of different 
wavelengths to produce different effects on the tissue, such as 
cauterization by one wavelength, and cutting or ablation by another. 
The present invention provides an improved laser energy delivery system 
which can accommodate designs having the above-discussed benefits and 
features. 
SUMMARY OF THE INVENTION 
The present invention provides a unique multiple laser system for 
subjecting a target site to laser energy of a relatively greater average 
power, and/or longer pulse width, or higher pulse repetition rate at the 
site, than is possible with a single laser. 
The present invention is especially suitable for use in a medical system 
for delivering radiant laser energy pulses to a selected tissue site in a 
controlled manner. The invention is particularly well suited for use in 
surgical procedures for rapidly coagulating or cutting relatively soft 
tissues, as well as for ablating relatively hard tissues. Further, a 
plurality of different wavelengths of laser energy having different 
absorption characteristics can be delivered seriatim along a single axis 
directly or through one or more optical fibers or through an articulated 
arm to a target site. 
In accordance with a preferred aspect of the invention, a laser device is 
provided for co-axial positioning of plural laser beams along a single 
axis. At least two laser resonators or oscillators are provided for 
producing a laser beam by each such resonator or oscillator. A rotary 
reflector means is positioned for intercepting at least one of the 
produced laser beams and for directing the intercepted laser beam 
separately from, but along a single axis defined by, the other laser beam. 
Numerous other advantages and features of the present invention will become 
readily apparent from the following detailed description of the invention, 
from the claims, and from the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides an improved laser delivery system which is 
especially suitable for use in surgery and other medical as well as 
industrial applications. The system includes plural laser resonators or 
oscillators which are uniquely arranged to emit beams of laser radiation 
seriatim along a single axis to a target site. The system can thus deliver 
laser energy at a higher average power and greater energy density, without 
damage to the transmitting waveguides, or at a relatively faster pulse 
repetition rate, to a tissue site or workpiece through a single waveguide, 
an articulated arm, a hollow waveguide or the like without requiring a 
change in the numerical aperture of the system. 
While this invention is susceptible of embodiments in many different forms, 
this specification and the accompanying drawings disclose only some 
specific forms as examples of the invention. The invention is not intended 
to be limited to the embodiments so described, however. The scope of the 
invention is pointed out in the appended claims. 
For ease of description, the laser device of this invention is described in 
a selected operating position, and terms such as upper, lower, horizontal, 
etc., are used with reference to this position. It will be understood, 
however, that the laser energy device of this invention may be 
manufactured, stored, transported, used, and sold in an orientation other 
than the position described. 
Some of the figures illustrating embodiments of the apparatus show 
structural details and mechanical elements that will be recognized by one 
skilled in the art. However, the detailed descriptions of such elements 
are not necessary to an understanding of the invention, and accordingly, 
are not herein presented. 
Further, the apparatus of this invention is used with, or incorporates, 
certain conventional components, the details of which are not fully 
illustrated or described in detail. For example, the apparatus of this 
invention may be employed with suitable conventional laser sources (laser 
resonators or oscillators), articulated arms, mirrors, hollow waveguides, 
optical fibers and coupling systems therefor, the details of which, 
although not fully illustrated or fully described, will be apparent to 
those having skill in the art and an understanding of the necessary 
functions of such components. The detailed descriptions of such components 
are not necessary to an understanding of the invention and are not herein 
presented because the structural and operational details of such 
components per se form no part of the present invention. 
A first type of laser device or system embodying the present invention is 
illustrated in FIGS. 1 and 2. The device is suitable for directing beams 
or pulses of laser radiation along a single axis 10 to a target or site 
12. The system is particularly suitable for directing laser radiation to a 
target 12 of human tissue on the surface of a body, within a natural lumen 
or cavity, or in a surgically created area, cavity, or passage in body 
tissue. Typically, in surgical or other medical applications, the tissue 
at which the laser energy is directed may be characterized as defining a 
body site containing a material which is to be altered by the application 
of laser radiant energy. The material may be part of the tissue per se or 
may be an altered form of the tissue, such as cancerous tissue or 
atherosclerotic plaque. The material could also be an additional deposit 
on the tissue, or material to be removed for industrial purposes. 
The laser radiation may be transmitted along the axis 10 to, and then 
through, a suitable optical fiber or like waveguide (not illustrated) as 
mentioned hereinabove, as desired. Such a waveguide can be a conventional, 
elongate, flexible, optical fiber which may assume a curved configuration 
and which functions as a laser energy-transmitting conduit. Such a fiber 
can be connected or coupled at its proximal end to a conventional lens or 
coupling assembly 16 into which the laser energy is directed from at least 
two laser sources or laser oscillators: a first laser oscillator 21 and a 
second laser oscillator 22. The waveguide can also be a hollow, flexible 
tube having a reflective inner lumen, such as is utilized for transmission 
of CO.sub.2 laser energy. 
The design, construction, and operation of laser oscillators, optical 
fibers, waveguides, laser reflecting mirrors, and coupling assemblies are 
well known in the art and are not described in detail herein. The details 
of the design, construction, and operation of such components .per se form 
no part of the present invention. 
The terms "laser energy", "laser radiation", "laser beam," and variants 
thereof as used in this specification disclosure and in the claims will be 
understood to encompass pulsed wave or intermittent (chopped) continuous 
wave laser energy having a broad range of frequencies, pulse width and 
repetition rate characteristics, and energy densities or fluxes, and 
powers. The laser radiation may be suitably produced by a conventional 
laser device that generates pulses of the desired wavelength. Examples of 
laser types that can produce energies suitable for surgical applications 
include the following: excimer (e.g., 193 nanometers and 308 nanometers 
wavelength), alexandrite, titanium sapphire, argon, neodymium:yttrium 
aluminum garnet (Nd:YAG), frequency-doubled Nd:YAG (KTP laser), 
holmium:yttrium aluminum garnet (Holmium:YAG), erbium:yttrium aluminum 
garnet (Er:YAG), carbon dioxide (CO.sub.2), ruby, alexandrite, and the 
like. 
The laser oscillators 21 and 22 are arranged and controlled, in conjunction 
with other components, to produce separate, pulsed laser beams which are 
directed seriatim along the single axis 10. In the embodiment illustrated 
in FIG. 1, the two laser oscillators 21 and 22 are identical and are 
positioned so as to emit the pulsed laser beams from the emission ports in 
a substantially parallel configuration. The laser energy of the first 
laser oscillator 21 is transmitted in a pulsed beam 26 in a straight line 
which is coincident with, and which defines, the axis 10. 
The second laser oscillator 22 produces a pulsed beam that travels along a 
first path 30 which is spaced from, but which is parallel to, the first 
laser oscillator beam 26. At the end of the first path 30, the second 
laser oscillator beam 28 is reflected by a reflector device, such as a 
conventional, laser energy-reflecting mirror 32 of a suitable type. The 
second beam 28 is reflected by the mirror 32 from the first path 30 along 
a second path 34 which is generally perpendicular to the first path 30 and 
which is thus also perpendicular to the first laser oscillator beam 26 on 
the axis 10. In operation, the mirror 32 is normally stationary. However, 
the mirror may include suitable, conventional means for adjusting the 
angle of the mirror relative to the first beam path 30 so as to facilitate 
alignment of the second beam path 34. 
The second beam path 34 and the path of the first laser oscillator beam 26 
intersect at a right angle generally at an intersection region 36. 
Although the paths of the beams are aligned to intersect in the region 36 
(FIG. 1), the two laser oscillators are operated at different times, as 
will be described in detail hereinafter, so that the beam pulses do not 
coincide in time but only in space. 
A reflector means 40 is provided at the path intersection region 36 for 
intercepting the second laser oscillator beam 28 and directing the beam 
along the axis 10. The reflector means 40 includes a rotary chopper means 
42 mounted on a shaft 44 extending from a drive motor 46. The reflector 
means 40 may be a special or conventional light beam chopper. Choppers 
that are suitable for this application are commercially available under 
the designation Model 220 Light Beam Chopper from Ithaco, 735 West Clinton 
Street, P.O. Box 437, Ithaca, N.Y. 14851-6437. 
With reference to FIG. 2, the rotary chopper means 42 includes a plurality 
of arms or blades 50. In the illustrated embodiment, five such blades 50 
radiate outwardly and are equally spaced to define slots or voids 52. Each 
blade 50 has a front surface (i.e., the surface facing the incoming second 
laser oscillator beam 28) that is defined by a reflective surface, such as 
a coated glass mirror. 
Preferably the motor 46 is an adjustable speed electric motor which is 
capable of rotating the chopper means 42 through a range of rotational 
speeds. For one presently contemplated mode of operation for the 
embodiment illustrated in FIGS. 1 and 2, the chopper means 42 can be 
rotated at a speed in the range of about 12 revolutions/minute to about 
10,000 revolutions/minute. 
A conventional reference pick up photosensor or position sensor 54 is 
located in a conventional manner adjacent the rotating member 42 for 
registering the presence or absence of a blade 50. 
A conventional control system is provided and includes a revolution counter 
56 for receiving a signal 58 from the position sensor 54. The revolution 
counter 56 registers the frequency or rate at which the blades 50 rotate 
past the sensor 54. A control signal 60 corresponding to this frequency is 
transmitted to a central processing unit 62. The chopper means motor 46 is 
preferably controlled through a conventional control signal 64 which can 
be responsive to the revolution counter signal 60 and a conventional 
frequency control system. 
The first laser oscillator 21 is controlled from the central processing 
unit 62 via a control signal 71, and the second laser oscillator 22 is 
controlled from the central processing unit 62 through a control signal 
72. 
In operation, the central processing unit 62 alternately operates (i.e., 
actuates or fires) the first laser oscillator 21 and the second laser 
oscillator 22. For convenient operation, the motor 46 is typically 
operated at a constant, selected speed. When one of the five blades 50 is 
sensed by the position sensor (photosensor) 54, the slot or void 52 that 
is 180.degree. away from the sensed blade 50 accommodates passage of the 
first laser oscillator beam 26 along the axis 10 to the target 12. The 
central processing unit 62 actuates the first laser oscillator 21 at this 
time to emit the laser energy beam or pulse 26. The pulse terminates by 
the time a blade 50 rotates into the beam path. 
When the rotating member 42 carries a blade 50 into the path of the beam 26 
and, hence, also into the second laser oscillator beam path 34, the 
position of that blade 50 is determined by the position sensor 54 which 
senses the corresponding void or slot 52 which is 36.degree. away. The 
central processing unit 62 then actuates the second laser oscillator 22 to 
emit a pulsed laser beam 28 which is reflected off mirror 32 as beam 34 
which in turn is reflected off of the blade 50 of member 42 in the 
intercept region 36 and directed along the axis 10 to the target 12. This 
process is repeated as the reflecting member 42 rotates, and the laser 
beam pulses are thus transmitted alternately, and in a seriatim 
relationship, from the two laser oscillators to the target 12. This is 
graphically illustrated in FIG. 8 where the output signals of photosensor 
54 are shown by waveform trace (1). "High" in the waveform (1) corresponds 
to the detection of the mirror parts of the rotary chopper means 42. "Low" 
in the waveform (1) corresponds to the detection of the open or aperture 
portions of rotary chopper 42. Waveform (2) of FIG. 8 shows the fire 
command signal 71 as issued by the central processing unit or controller 
62. Waveform (3) of FIG. 8 shows the fire command signal 72 as issued by 
controller 62. The fire command signal 71 is issued to fire the oscillator 
21 during the "low" portion of waveform (1) as shown in FIG. 8. This is 
the portion of time in which the laser pulse from oscillator 21 can 
propagate through to the coupling assembly 16 uninterrupted. The fire 
command signal 72 is issued only during the "high" portion of waveform 
(1), however. This is the portion of time in which a reflective blade 50 
or the like is presented by the rotary chopper 42 in the path of a laser 
pulse from oscillator 22. This allows the pulse from oscillator 22 to be 
reflected by the reflective blade 50 at a coincidental intersecting point 
in space with the pulse from oscillator 21. 
Thus the fire command signals 71 and 72 appearing in waveforms (2) and (3) 
of FIG. 8 respectively, are at least 180 degrees apart in phase. The mode 
of operation where two succeeding fire command signals are 180 degrees 
apart provides for the shortest possible interpulse delay, dictated by the 
angular velocity of the rotating member. This is useful in achieving twice 
the energy of a single pulse as far as photothermal ablation is concerned. 
As stated earlier, the interpulse delay is selected long enough to allow 
the acoustic effects of a first laser pulse to dissipate before a second 
laser pulse is introduced. In this manner of operation, the acoustic 
pulses from two succeeding laser pulses are not additive. 
In another mode of operation, where a high repetition rate is desired, the 
two laser oscillators 21 and 22 are caused to fire with a relatively 
longer delay between their two corresponding pulses. For example, if a 
repetition rate of 50 pulses per second is desired, the laser oscillator 
21 fires a pulse through an open part, at a repetition rate of 25 pulses 
per second, and approximately 20 milliseconds later, laser oscillator 22 
fires a pulse, at a repetition rate of 25 pulses per second, into a mirror 
part. In this manner, the pulses are equally spaced from one another and a 
total of 50 pulses per second is achieved. 
In any given instance, the pulse width must not exceed the time period that 
either the aperture or the beam reflecting surface is available to 
transmit or reflect the entire beam. 
In one presently contemplated mode of operation, wherein a conventional 
five blade reflecting member 42 is employed, the laser oscillators 21 and 
22 both can be holmium:YAG lasers that are each operable at least at about 
a 1-Hertz pulse repetition rate with a 10 to 10,000 microsecond typical 
pulse width (at a power output of about 8,000 milliJoules per pulse and at 
a wavelength of about 2,100 nanometers when operating at a maximum average 
power per oscillator of about 75 watts). 
In general, as a trailing edge of a blade moves out of the path of the 
first laser oscillator beam 26 to permit the first beam 26 to pass to the 
target, a 800 microsecond margin time delay is preferably provided by the 
central processing unit 62 to insure that the first laser oscillator 21 is 
actuated when the beam path is completely open. Similarly, when the 
leading edge of the next blade 50 begins to move into the path defined by 
beam 34 for the second laser oscillator beam 28, an 800 microsecond time 
delay margin is provided by the central processing unit 62 before the 
second laser oscillator 22 is actuated. This insures that the entire beam 
28 will be reflected by the reflecting blade 50. Of course this delay 
period is dependent upon the angular velocity of the blade. 
The spacing of individual pulses can be utilized to modulate the acoustic 
effects of the applied, pulsed laser beam. In order to maximize the 
available acoustic effects, for example, for fragmenting a relatively hard 
material such as a urinary or biliary stone, the pulse spacing is 
minimized, i.e., the pulses are generated relatively close to one another. 
By spacing the consecutive pulses relatively close to one another, the 
pulse width is substantially increased, thus enabling a relatively higher 
average power to be delivered to a target without damage to the optical 
fiber used to transmit the same. This is particularly beneficial for the 
delivery of relatively high energy pulses from excimer lasers. 
On the other hand, to minimize the acoustic effects, the individual pulses 
are spaced by at least 800 microseconds. 
To maximize the thermal effects while minimizing the acoustic effects, the 
individual consecutive pulses are spaced by at least 800 microseconds but 
are cascaded within a time period that is less than the time period during 
which the heat generated by the preceding pulse is substantially 
dissipated. The duration of this latter time period varies with the type 
of tissue to be cut or ablated and is a function of the temperature 
integration time constant for the particular tissue. For example, when the 
thermal diffusion time constant k value is 150 milliseconds, utilization 
of the aforestated formula 
EQU T.sub.t =T.sub.o e.sup.-t/k 
reveals that starting with a tissue temperature of 100.degree. C. the 
tissue temperature after 5 milliseconds is 
EQU T.sub.t =100.times.e.sup.-0.005/0.15 =96.7.degree. C. 
Accordingly, the delivery of a second laser energy pulse within 5 
milliseconds from the delivery of the preceding pulse will cause an 
accumulation of the respective thermal effects. 
The present invention permits employment of commercially available medical 
lasers that produce laser beam energies subject to significant attenuation 
during transmission. In one mode of operation contemplated by the present 
invention, two such identical, conventional, medical lasers can be 
employed for the laser oscillators 21 and 22, and each oscillator is 
operated to produce laser radiation, for example, with a power of about 75 
watts at the emission port so as to deliver about 65 watts to the target. 
The two laser oscillators can be operated to produce the pulses at a 
frequency of about 15 Hertz so that one pulse from one laser oscillator 
and the next pulse from the other laser oscillator occur sequentially and 
co-axially in a relatively short time span. This subjects the target to a 
total of 130 watts of average power, at a repetition rate of 30 pulses per 
second. 
Preferably, the target 12, such as tissue, can be more efficiently cut by 
the laser beam pulses if the two pulses are transmitted to the tissue with 
a relatively short time interval between the two pulses. For example, for 
pulses each having a pulse width of about 250 microseconds and a 
repetition rate of 15 Hertz, it would be desirable to initiate the second 
pulse within 0.25 to 5 milliseconds of the end of the first pulse. By 
appropriate selection of the configuration of the rotary reflector or 
chopper (i.e., the number of reflecting surfaces and number of voids) and 
by appropriate selection of the rotational speed, pairs of consecutive 
laser beam pulses can be produced such that the time period between the 
two pulses is as small as a few hundred microseconds. The delivery of 
successive pulses with a relatively short time interval therebetween has 
the same thermal effect vis-a-vis the tissue target site in a 
thermodynamic sense as if it were a single pulse having the combined 
energies of the plural pulses. From an acoustic sense, however, the 
delivered pulses remain as two separate pulses inasmuch as acoustic shock 
and the generated vapor bubble dissipate within about 800 to 900 
microseconds. That is, the emission of consecutive laser energy pulses can 
be controlled so that such pulses are emitted sufficiently close in time 
to one another to elicit an additive acoustic effect at a target site, 
e.g., kidney or gall stones. Similarly, two consecutive laser energy 
pulses can be emitted spaced in time from one another to elicit an 
additive thermal effect but without eliciting an additive acoustic effect 
at a target site, e.g., on a knee cartilage or at a blood vessel 
obstruction. 
If desired, a detector 76 may be provided on the axis 10 downstream of the 
rotary reflector means 40 to monitor the energy levels of the beams. The 
detector 76 can be connected to supply a signal 77 to the central 
processing unit 62. The detector 76 may be of any suitable special or 
conventional design well known to those of skill in the art. The detailed 
design, construction, and operation of such a detector forms no part of 
the present invention. 
An aiming beam may also be provided if desired. To this end, a helium-neon 
(HeNe) laser 80 may be provided for directing a beam 82 to a mirror 84 
which reflects the beam 82 through the focusing lens 16 (when used). The 
helium-neon laser may be of the conventional type which, as known in the 
art, provides a low power aiming beam. The detailed design, construction, 
and operation of such an aiming beam laser forms no part of the present 
invention. 
The system illustrated in FIG. 1 may also include additional components, 
such as other mirrors, coatings, focusing elements, housings, 
automatically-operated beam blocking devices or shutters, and the like 
(not illustrated). The detailed design, construction, and operation of 
such components per se form no part of the present invention. 
It will also be appreciated that modifications may be made to the system 
illustrated in FIG. 1. For example, the second laser oscillator 22 need 
not be oriented to emit the beam 28 along a first path 30 which is 
parallel to the first laser oscillator beam 26. Instead, the mirror 32 
could be eliminated and the second laser oscillator 22 could be oriented 
so as to initially emit its beam 28 directly along the beam path 34 in the 
direction generally perpendicular to the first laser oscillator beam 26. 
The second laser oscillator 22 could also be oriented at other oblique 
angles, depending upon the orientation of the mirror 32 and rotary 
reflector means 40. 
Various modifications or alternatives may be employed with respect to the 
design and operation of the rotary reflector means 40. For example, the 
rotary reflecting member 42 may be provided in the form of a disk with 
individual posts or apertures (not illustrated), rather than with blades 
50 and slots 52 as illustrated in FIG. 2. Moreover, the laser oscillators 
can be Q-switched or mode locked in a known manner to produce relatively 
short pulses in synchronism with the rotary reflector means and at a 
repetition rate in the nanosecond, or picosecond, range so as to produce a 
greater acoustic effect and be suitable for fragmentation of kidney 
stones, gall stones, and the like. 
A modification of a rotary reflecting member is illustrated in FIG. 3 
wherein it is designated generally by the reference numeral 42A. The 
rotary reflecting member 42A is adapted to be rotated on a shaft in the 
same manner as the blade reflecting member 42 described above with 
reference to FIG. 2. However, the reflecting member 42A does not include 
separate blades per se. Rather, the member 42A has the form of a single 
disk provided with a transparent region 41A and a coplanar reflecting 
region 43A. Each region 41A and 43A has a substantially semicircular 
shape. The transparent region is preferably coated with an anti-reflection 
coating, and the reflecting region 43A is preferably coated with a 
dielectric reflective coating, as known in the art. 
The single rotating disk 42A illustrated in FIG. 3 could also be modified 
by providing a number of pie-shaped transparent segments separated by 
pie-shaped reflecting segments (not shown). 
The principles of the present invention can also be applied to systems 
employing more than two laser oscillators. FIG. 4 illustrates a system in 
which three laser oscillators are employed: a first laser oscillator 221, 
a second laser oscillator 222, and a third laser oscillator 223. The first 
laser oscillator is oriented to emit a pulsed laser beam 226 along an axis 
210 which passes through a site or target 212. The second laser oscillator 
222 is oriented to emit a beam 228 to a mirror 232 for reflection along a 
path 234 which intersects the path of the beam 226 along the axis 210. 
Similarly, the third laser oscillator 223 emits a beam 229 for reflecting 
off of a mirror 233 along a path 235 to intersect the path of the beam 226 
(along the axis 210) at a right angle. 
A first rotary reflector means or chopper 240 is disposed at the 
intersection region of the paths of the beams 226 and 228, and a second 
rotary reflector means or chopper 245 is disposed at the intersection of 
the paths of the beams 226 and 235. Each chopper 240 and 245 includes a 
reflecting member 242 (FIG. 5) which includes four blades 250. The angular 
measurement or peripheral distance between the leading edge of one blade 
250 and the leading edge of the next adjacent blade 250 is designated by 
reference letter P. The angular measurement of each blade 250 is 1/3 P, 
and the angular measurement of the space between adjacent blades 250 is 
2/3 P. 
As in the first embodiment illustrated in FIG. 1, a control system is 
provided for controlling the operation of the laser oscillators and rotary 
reflector choppers 240 and 245. Control signals are generally illustrated 
schematically by dashed lines in FIG. 4. 
Each rotary reflector chopper 240 and 245 is operated in conjunction with 
position sensors 254 and a control system that includes a revolution 
counter 256 and central processing unit 262. The control system operates 
the first laser oscillator 221 to emit the first beam 226 between the 
blades 250 in both rotary reflector choppers 240 and 245. As the rotary 
reflector choppers 240 and 245 rotate, the generation of the laser beam 
pulse from the first laser oscillator 221 is terminated, and the second 
laser oscillator 222 is operated to generate the second laser beam pulse 
228 which is reflected off of blade 250 which has now been rotated into 
the beam path interception region. The rotary reflector choppers 240 and 
245 are regulated so as to rotate at a phase difference equal to the 
angular measurement of one of the blades 250. The rotary reflector means 
245 lags the rotary reflector choppers 240 by an angle equivalent to 1/3 
P. Thus, when the reflector chopper 240 has rotated a blade to reflect the 
second beam 228, the reflector means 245 still presents a void or slot 252 
at the beam path along the axis 210. 
Upon further rotation of the reflector choppers 240 and 245, the reflector 
chopper 245 presents a blade 250 to reflect the third beam 229 which is 
emitted by the third laser oscillator 223 in response to control by the 
central processing unit 262. 
A laser energy detector 276 may be provided in the path of the beams for 
monitoring the energy level and/or providing a feedback signal to the 
central processing unit for control of the laser oscillator power. 
It will be appreciated that the system illustrated in FIG. 4 can be 
operated to provide a series of three laser pulses consecutively from 
three separate laser oscillators in a relatively short time span. While in 
the system illustrated in FIG. 4 two of the three provided laser 
oscillators interact with the rotary reflector means constituted by 
reflector choppers 240 and 245, the principles of the system illustrated 
in FIG. 4 may also be employed with four or more laser oscillators by 
altering the spacings of the chopper reflector surfaces or blades and 
making appropriate modifications to the control system. 
FIG. 6 illustrates yet another embodiment of the present invention which 
employs a first laser oscillator 331, a second laser oscillator 332, and a 
third laser oscillator 333, each interacting with a rotary reflector 
means. To that end, rotary reflector means 340 is provided to direct the 
beams from the individual laser oscillators along a common axis 310 to a 
target 312. As shown in FIG. 7, the reflector means 340 includes three 
mirrors 351, 352, and 353. The mirrors 351, 352, and 353 are mounted at 
oblique angles as shown in detail for mirrors 351 and 352 in a portion of 
FIG. 6 which includes a cross-sectional view taken along two planes 6--6 
in FIG. 7. The reflector means 340 is rotated by a motor 346 about a 
central axis 355 in the direction of the arrow 357. 
The rotary reflector means 340 is positioned to receive a first laser beam 
pulse 326 emitted from the first laser oscillator 331 and reflected to the 
reflector means 340 by a mirror 302, a second laser beam pulse 328 emitted 
from the second laser oscillator 332 and reflected to the reflector means 
340 by a mirror 304, and a third laser beam pulse 329 emitted from the 
third laser oscillator 333 and reflected to the reflector means 340 by a 
mirror 306. 
The three beams 326, 328, and 329 are directed to a common point into which 
each mirror 351, 352, and 353 is carried as the reflector means 340 
rotates. The three reflecting mirrors 351, 352, and 353 each define a 
concave mirror surface. Each mirror 351, 352, and 353 is disposed at a 
different angle relative to the central axis 355 about which the rotary 
reflector means 340 rotates. As illustrated in FIG. 6, the mirror 351 is 
oriented at an angle A, and the mirror 352 is oriented at a greater angle 
B. The angle of orientation of the mirror 353 is not represented in the 
figures but is greater than the angle B. 
The mirror angle A is selected so that the mirror 351, when located in the 
illustrated position, can reflect the laser beam 329 along the axis 310 to 
the target 312. The angle B of the mirror 352 is selected so that when the 
mirror 352 is rotated to the beam interception position (the position 
shown occupied by mirror 351 in the FIGURES), the mirror 352 will reflect 
the laser beam 328 from the second laser oscillator 332 along the same 
axis 310 to the target 312. Finally, the orientation angle for the mirror 
353 is selected so that when the mirror 353 is in the beam interception 
position (the position shown occupied by mirror 351 in the figures), the 
mirror 353 will reflect the beam 326 from the first laser oscillator 331 
along the axis 310 to the target 312. 
A position sensor 354 is provided adjacent the rotating reflector means 340 
for detecting spaced reference notches 361 which are each associated with 
one of the mirrors 351, 352, and 353. A controller 362, which can include 
a conventional central processing unit and counter responsive to the 
position sensor 354, is employed to control the rotational speed of the 
rotary reflector means 340 and the operation of the laser oscillators 331, 
332, and 333. Control signal paths are generally illustrated schematically 
by dashed lines in FIG. 6. 
In particular, as each mirror 351, 352, and 353 is rotated into the beam 
interception position, the controller 362 operates the laser oscillator 
associated with that mirror for generating a laser beam pulse. The 
generated beam pulses from the three lasers are produced seriatim and 
reflected seriatim to the target 312 so as to efficiently provide the 
pulses of laser energy in a relatively short time span. 
Of course, more than three laser oscillators may be employed by adding 
additional mirrors to the rotary reflector means 340 and modifying the 
control system as necessary. 
Further, it will be realized that the laser oscillators need not be 
positioned as shown to transmit the laser beams along the paths defined by 
the stationary mirrors 302, 304, and 306. If desired, the laser 
oscillators could be positioned to emit the laser beams along straight 
line paths directly to the rotating mirror interception point. However, 
the use of mirrors 302, 304, and 306 as illustrated accommodates alignment 
procedures by requiring merely the adjustment of relatively small mirrors 
rather than the special positioning of each entire laser oscillator. 
Other modifications of the illustrated embodiments of the present invention 
may be made. It will be appreciated, however, that the present invention 
provides a novel means for directing laser beam pulses from a plurality of 
laser oscillators seriatim along a common axis. This system permits a 
number of pulses of laser energy to be directed to a target in a 
relatively short time period so as to efficiently cut or ablate tissues of 
different hardness. Further, the system accommodates the exposure of a 
target to a number of different types of laser energy from different types 
of laser oscillators where such a mode of operation is desired. 
It will be readily apparent from the foregoing detailed description of the 
invention and from the illustrations thereof that numerous variations and 
modifications may be effected without departing from the true spirit and 
scope of the novel concepts or principles of this invention.