US 3096767 A
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"United States areas 3,096,767 PHOTO-CAUTERIZER WITH COHERENT LIGHT SOURCE Herbert D. Gresser, Plainview, Gerard M. Grosof, New
York, Leonard R. Solon, Yonkers, and Theodore S. Shultz, New York, NX., assignors to TRG, Incorporated, Syosset, N.Y., a corporation of New York Filed May 11, 1961, Ser. No. 109,325 7 Claims. (Cl. 12S-395) The present invention relates to medical apparatus utilizing high intensity electromagnetic radiation to produce cauterizing or similar effects in the human body (or in other animals). More particularly, the invention relates lto such apparatus using a coherent light source (Stich apparatus is variously known as an optical maser, laser, or coherent light generator).
Apparatus for photo-cauterizing which utilizes as a cauterizing energy source a source of incoherent light, such as an arc or discharge lamp, has previously been known and used with some degree of success. One important use of photo-cauterizing apparatus is in the attachment of detached retinas in .the humanmye. This riotminfrlunet causofblindness obviously is not of a character which is suitable for ordinary surgical treatment, due to the delicate nature of the human eye. lt is possible, however, by burning a tiny point on the retina, to reattach it to the chorioid in its proper position due to the `adhesion of the lesion or scar tissue at the burned area.
it is obviously desirable that lthe point or points which are cauterized to, in effect, weld the retina in piace should be small relative -to the area of the retina, as they will likely be destroyed with the resulting blind spots on the retina. Previous -photo-cauterizing apparatus was incapable of producing a sutiiciently tiny focal spot to avoid damaging a substantial area of the retina and'thus the success of Ithe photo-cauterizing technique was limited.
By the present invention a coherent light source is utilized which has, among .other properties, an exceptionally high degree of parallelism .in the rays emitted from the source. This allows the light to be concentrated on a much smaller area than heretofore possible, so Ithat a high intensity spot of substantially less than one millimeter in diameter, tfor example, can be produced.
Suclfhiglidegreefconcentration of the light energy also obviously allows greater local intensity for the same total amount of light power. This allows the cauterizing operation to be performed in a shorter interval of time. rthis is advantageous due to the fact that when the cauterizing temperature must be built up by integration of the heating effect over a period of several seconds, there is undesirable heat transfer tending to enlarge the lesion produced by the photo-cauterizing beyond the area of the focal spot. There is also the apparent advantage in speed of operation that the area to be cauterized need be immobilized for a shorter period of time and the danger of injury from accidental movement during the period of cauterization is minimized.
While the most promising present use -for the photocauterizing apparatus according to the present invention is in treatment f detached retinas, or other diseases or malformations in the eye, the apparatus is by no means limited to such treatment, and photo-cauterization of other external or internal parts of the human body is also within contemplation of the invention.
In addition to providing the foregoing features and advantages, it is a further object of the present invention to provide a photo-cauterizing apparatus utilizing a coherent light source to provide the cauterizing energy.
It is another object of the invention to provide apparatus of the foregoing type where an auxiliary incoherent light source is provided and arranged to have a' beam coincident with coherent light source beam for preliminary focussing and positioning of the Optical system to produce photo-cauterization at the desired point.
lt is another object ofthe present invention to provide apparatus of the foregoing ltype wherein the incoherent light source is provided with a tilter or other means to limit its final light output to a region of the light spectrum in proximity to the wavelength ofthe coherent light source to substantially avoid problems of chromatic aberration.
it lis still another obiect of the present invention to provide apparatus of the foregoing type wherein the beams from the coherent and incoherent light sources are directed onto a coincident path by means of a dichroic mirror.
It is still another object of the present invention to provide apparatus of the foregoing type wherein means is provided for viewing the subject to which the photocauterizing process is to be applied andA including means for blocking the light from the coherent light source from the user ofthe viewing appara-tus in order vto protect the operator from possible damage due to such light.
Other objects and advantages will be apparent from a consideration 0f the following description in conjunction with the appended drawings, in wh-ich:
FIGURE l is a partially schematic diagram of optical apparatus according to the present invention; and
.FIGURE 2 is a sectional view taken along the line 2 2 in FIGURE l.
Referring now to the drawing, a focusing light source 1l is provided which is. illustrated as a conventional incandescent lamp. vThe form of light source l1 is not critical since the auxiliary light source 11 does not furnish the energy for cauterization, but merely provides light beams for initially indexing and focusing the optical system.
A red filter 12 may be provided to cause the light output from source l1 to be in approximately the same portion of the light spectrum as that produced by the coherent light generator. In the illustration given here, it is assumed that -a ruby type coherent light generator will be utilized, having an output of 6,943 Angstroms wave-` length. ln such case, preferably the filter 12 will substantially limit the output from source 11 Vto a range of approximately 0-l0% less than the 6,943 Angstrom output of the coherent light generator. (Longer wavelengths would in this specific case tend to extend beyond the visiblespectrum into the infra red.)
An optical system comprising lens 13, diaphragm 14, and lens i6 is provided to collimate the light beam from source 11. Diaphragm 14 is provided with a simili aperture 15 so that the light rays indicated by dashed lines l from source 11 reach lens i6 as if from a nearly point. source represented by the aperture 15. Lens 16 is spaced from diaphragm 14 by a distance equal to its focal length thus substantially collimating light rays 1 originating at source 11.
A 4mask i7 is provided having openings 18 -therein which, for example, muy be placed in a rectangular array as illustrated in FIGURE 2. As will later be more fully explained, the"l provision ot' the mask 17 facilitates focusing the collimated beam emerging from openings 18 and indicated by dashed lines 2 in FlGURE l.
A dichroic mirror I9 is placed in the path of light rays 2 at an angle (for example v45") with respect thereto. The dichroic mirror 19 may be provided with a coating 2.1 of the multi-layer interference type in order to provide a surface which is transparent to light of wavelength 6,943 Angstroms (and of course in the immediate vicinity of that wavelength), but which will substantially retlect most of the light rays 2 from the source 1l. lt
should be pointed out that the dichroic mirror 19 is much more selectively transparent than the red filter l2, so that most of the light passing through iilter 12 will not be transmitted but rather be rellected by the dichroic mirror 19. lt should also be noted that throughout FIGURE l, only the rays which are usefulv in the operation of the system are illustrated. and those which are not utilized by virtue of being reflected or transmitted out of the designed optical .path have been omitted in FIGURE l (and in the apparatus would be absorbed by suitable nonretlective internal coating, or the like).
rl'he path of rays from dichroic mirror 19 is indicated by dashed lines 3. The dashed lines 3 indicate the path of rays from auxiliary light source 11, and as later will be seen. also indicate the coincident path of rays from the coherent light generator.
A variable focal length optical system is schematically illustrated by lenses 22 and 23 in FIGURE l. The former is a gogvexleps and the latter is a concave lens.
Movement Iof respective lenses 22 and 23 (or their couni terparts in an equivalent opticabsystem) will allow cong trol ot' various parameters associated with the focal spot obtaining at the end of the optical train` such as its posi- Etion along the direction of propagation, the angle .of convergen, and the size of the spot in the focal plane.
' lt Should be noted at this point that in the illustration of FIGURE 1 the subject ot' the cauterization process is a human eye 26 and the lens 27 of the eye 26 is in effect a part of the optical train. ln fact, in the illustration of FIGURE l, lens 27 is assumed to provide the primary converging eect to produce the focal spot, and lenses 22 and 23 provide relatively fine focusing adjustment to correct for failure of lens 27 to focus parallel rays on the retina.
Where the apparatus is used to cauterize other areas than within the eye, an auxiliary lens or focusing means may be provided to contribute the focusing ellect provided by the lens 27 of the eye 26 in FIG. l.
A dichroic mirror 24 is located in the path of rays 3 to direct these rays as they emerge from lenses 22 and 23 to the subject of the cauterization process, which is illustrated as a human eye 26 having a lens 27. The dichroic mirror 24 is different from mirror 19 with essentially the opposite color discrimination characteristic, that is, it retlects light of 6,943 Angstroms while transmitting approximately one-half of other wavelengths. The dichroic mirror 24 may also be made with a coating 2S of the multilayer interference type according to known optical techniques.
Rays directed from mirror 24 to the eye 26 are indicated by dashed lines 4 (which also represent the path of light reected back from the eye which is seen by the operator and enables him to properly position and focus the beam originating at auxiliary light source 11). Accordingly, the beam emerging from lens 23 may diverge or converge to compensate for the characteristics of lens 27, and variable focal length will thus be understood to include negative and positive focal lengths.
As has been previously seen, light rays originating at auxiliary light source 11 may be focused by means of the apparatus thus far described. Accordingly, a pattern of light will fall on the retina of the eye, for example, and if the light beam is not focused on the retina the pattern will resemble the pattern in the mask as shown in FIGURE 2. However, when the beam is focused the dots 18 will appear to merge in the light pattern projected on the retina. Light from this pattern is visible by virtue of light reflected out through the lens 27 of the eye and along a path indicated by dashed lines 4. The light rei lected from the eye passes in part through dichroic mirror 24 which, as previously explained, is partially transparent to a light other than that of wave-length 6,943 Angstroms or at least to light from source 1I.
An imaging lens 28 is provided to form an image of the patt'ern projected on the retina by converging the rellected rays as indicated by dashed lines 4, which `pass through an obliquely oriented partially transparent mirror 29 and thence through a 6,943 Angstrom blocking filter 31, to binocular viewing apparatus 32. Two sets of optics indicated at 33 and 34 together with separate eye pieces 36 and 35 are provided for binocular viewing ot` the eye. Ililter 31 is an optional added protection against the possibility of light from the coherent light generator reaching the eyes of the operator or viewer which could obviously be very injurious.
Since the light from the focusing source 11 is directed into the eye in a restricted pattern by reason of the mask 17, it is desirable to provide other general illumination for the eye to facilitate viewing thereof and location of the Spot to be cauterized. Partially reecting mirror 29 provides means for retlecting light provided by general il lumination source 37. rl'his light is collimated by lens 38 and further directed by eld lens 39 into the eye. General illumination light source 37 -is preferably a white light and partially reflecting mirror 29 may be a partially transmissive mirror with little or no color selectivity. As may be seen from FIGURE l, the light from source 37 passes along the path indicated by dashed lines 7 through mirror 29, thence to the left through lens 28 and through dichroic mirror 24 to illuminate the eye 26. Dichroic mirror 24 will partially transmit all except a narrow band of frequencies in the vicinity of 6,943 Angstroms, thus causing relatively little attenuation of the light from source 37.
The reliected light from the eye due to source 37 will return along the path indicated by the dashed lines 7 to dichroic mirror 24 and lens 28. A portion of the reilected light will pass through partially reecting mirror 29 and lter 3l tothe binocular viewing apparatus 32. Separate optical paths indicated by dashed lines 5 and 6, respectively, are associated with each of the Optic systems of the binocular viewing apparatus 32.
The apparatus thus far described allows the viewer utilizing binocular viewing apparatus 32 to view the eye 26 as illuminated by general illumination source 37 and also to locate and focus a spot or pattern of` spots pr duced by focusing source 11 and the optical system associ-ated therewith. As will now be seen, a coherent light generator 41 is provided and arranged to produce a beam of light which -is effectively coincident with the beam from focusing source 11 along the path indicated by dashed lines 3. The coherent light generator 41 comprises ya volume of working medium 42 which may, for example, be a ruby crystal as in the present example. A gaseous discharge lamp 43 is provided for optically pumping the ruby crystal. Electrical energy for the discharge lamp 43 is provided by leads 45 and 46 connected to a generator control circuit 44 which may include provision for timing the duration or number of pulses from the generator and also their intensity. The design and operation of coherent light generators is known and will not be explained here. Information concerning such generators will be found in the literature in various places includmg:
Physical Review, vol. 112, No. 6, page 1940, December l5, 1958, Infrared and Optical Masers,by A. L. Schawlow and C. H. Townes;
Nature vol. 187, page 493 (1960) article by T. H. Maiman;
Physical Review Letters, vol. 5, page 303 (1960), article by R. J. Collins et al.
Coherent light generators are also commercially available, for example from TRG, Incorporated, Syosset, New York.
It will be understood that other than ruby light generators of the coherent type may be utilized in apparatus according to the present invention and in particular it may be desirable in some instances to utilize coherent light generators employing gaseous working mediums rather than a solid working medium such as ruby. The ruby`light- .3 generator has one advantage in that it produces red light which is Ia color and wave-length more readily transmitted by human tissue, both in the eye and elsewhere.
As indicated in FIGURE l, the coherent light generator 4l is arranged to transmitlight along a path indicated by dashed lines 8 through dichroic mirror i9 which is transparent to such iight (in the example illustrated 6,943 Angstroms wavelength) so that it becomes coincident with a beam from focusing source il along a path indicated by dashed lines 3.
As previously explained, the light from source 11 is passed thruogh a collimating optical system so that the beam from source 11 is substantially collimated along path 3. The light from the coherent light generator emerges therefrom inherently collimated, that is with a high degree of parallelism of the rays of light. The coherent light generator beam from a ruby type apparatus may, for example, have rays parallel to within less than .005 radian of angle (compared to an angle of about 1/2 degree for light fro-m the stm). it is this characteristic of the coherent light which is principally responsible for its being susceptible of being focused into a very small (and thus very intense) spot.
It will be obvious that since the beam from the focusing source i1 and the beam from the coherent light generator 41 are coincident along the path 3 and are both parallel (they are also nearly the same wavelength, within approximately they will be focused at the same spot by the optical train comprising lens 22, lens 2-3 and the lens of the eye 27. Accordingly, it is possible to deter- :mine the location and focus of the coherent light generator beam spot indirectly by means of the spot pattern produced by the focusing source 11. This will normally be accomplished with the coherent light generator 41 inoperative.
Once the desired location, focus and spot size are set the coherent light generator 41 is actuated for a predetermined time interval and a predetermined power to produce the desired cauterizing effect. Variable filter 47 provides a means for controlling the amount of energy in the beam, which could also be controlled within limits by the amount of power provided by generator control circuit 44. Ruby-type coherent light generators typically operate in pulsed fashion with a pulse of approximately l millisecond. In a single such pulse an energy of .l Joules is readily obtainable, which is quite adequate to produce cauterization of a spot approximately one millimeter in diameter. Obviously, higher energy generato-rs could be utilized and .may be desirable in the event that it is desired to cauterize below the surface of body areas more opaque than the human eye. The variable iilter 47 could, of course, be replaced by any other means tor wasting or attenuating part of the light generator beam, such as an adjustable iris, for example.
lt should be understood that the illustration of the apparatus as vbeing used for photo-cauterization of the eye is only one ot' many uses of the apparatus, some of which would be facilitated by slight modications in the apparatus within the ability of those of ordinary skill in the art.
For example, the intensity of light available from coherent light generators is such that it would readily be possible to penetrate a few millimeters or more of the skin on portions of the body other than the eye t'or the eradication of undesirable growths or other treatments. ln such a case, it may be desired that the optical system be arranged so that the focusing spot from focusing source l1 be longitudinally displaced a predetermined or a controllable distance from the spot produced by the coherent light generator.
it should further be understood that the use of the apparatus is not limited to the exterior of the body, but that rigid or articulated optical trains may be utilized to cgnvey the light beams of the apparatus into the interior 6 of the -body through natural or surgical openings within the scope of the invention.
It should also be noted that the present invention admits of the utilization of tiber optics in addition to or in place of the conventional lens optics shwn by way of illustration.
lt will be apparent that in addition to the various alternatives and modifications suggested that numerous other variations of the present invention will be apparent to those of ordinary skill in the art. Accordingly, it is intended that the scope of the present invention not be limited to those alternatives, modifications and variations shown or suggested but that it be limited solely by the appended claims.
What is claimed is:
l. Photo-cauterizing apparatus comprising a coherent light generator for producing a beam of light with rays having a high degree of parallelism, a variable focal length optical system for controlling the position of the focal point of said beam and the angle of convergence of said beam to cauterize a small area of matter, a focusing light` source, means for directing a beam from said focusing light source along a path substantially coincident with the -beam of light from said generator passing through said optical system, with the rays of said focusing light beam respectively parallel with the rays of said coherent light generator beam, the last said means including a reector element for at least partially reflecting one of said two beams and for at least partially transmitting the other of said two beams along said coincident path whereby a spot to be cauterized may accurately be determined by observation of the beam from said focusing light source and thereafter cauterized by energy from said generator, the coincidence of the focal spot of said coherent light generator beam with the focal spot of said focusing light beam being assured by the parallelism of the respective rays of said beams.
2. Apparatus as claimed in claim 1 wherein said reilector element is a dichroic reflector.
3. Apparatus as claimed in claim l wherein said light from said focusing light source is limited substantially to a range of wave-lengths between 0.9 times and 1.1
times the wave-length of said generator.
4. Apparatus as claimed in claim l further including a mask with a plurality of apertures placed in the path of the beam from said focusing light source to facilitate fine focusing of said beam.
5. Apparatus as claimed in claim 1 further including an observers position and means for blocking light of the wave-length of said generator from reaching said position to prevent injury to the observer.
6. Photo-cauterizing apparatus comprising a coherent light generator for producing a beam of light with rays having a high degree of parallelism, a variable focal length optical system for controlling the position of the focal point of said beam and 'the angle of convergence of said beam, a focusing light source having a range of output of wavelengths within approximately 10% of the Wavelength of said generator output, means for directing a beam from said focusing light source along a path substantially coincident with the beam of light from said generator passing through said optical system, said means comprising a dichroic mirror substantially transmitting one of said beams and substantially retiecting the other of said beams, means for collimating the light from said focusing light source arranged between said source and said dichroic mirror, a mask having a plurality of apertures placed in the collmated beam from said focusing light source between said dichroic mirror and said collimating means, beam splitting means for directing to an observers position a portion of the light from said focusing light source after reflection from the subject being cauterized, and means for blocking direct or reected light of the wave-length emitted by said generator from said observers position.
References Cited in the le of this patent UNITED STATES PATENTS Schawlow Mar, 22 1960 Dopp Mar. 29, 1960 OTHER REFERENCES Mann: Popular Science, pp. 2S, 26, Oct. 1960. Colyear: American Journal of OphthalmologyM-pg., 474-479, Oct. 96l.