Apparatus and method for producing very small microchannels in tissue

Abstract

A lens system includes: a plurality of aligned lenses; a first lens having negative refractive power; a second lens having negative refractive power; a third lens with positive refractive power; and, a fourth lens with positive refractive power; a light beam transmitted through the first, second, third and fourth lenses is first diverged by the first and second lenses, collimated by the third lens and focused by the fourth lens to form a small spot at the focal plane.

What we claim is: 
     
         1 . A lens system comprising:
 a plurality of aligned lenses;   a first lens having negative refractive power;   a second lens having negative refractive power;   a third lens with positive refractive power; and,   a fourth lens with positive refractive power;   wherein, a light beam transmitted through the first, second, third and fourth lenses is first diverged by the first and second lenses, collimated by the third lens and focused by the fourth lens to form a small spot at the focal plane.   
     
     
         2 . The lens system of  claim 1 , wherein the plurality of lenses act as a reverse telephoto lens system. 
     
     
         3 . The lens system of  claim 1 , wherein the back focal length (BFL) of the lens system is longer than the effective focal length (EFL). 
     
     
         4 . The lens system of  claim 1 , wherein the spot size of the small spot is about 70 u at a distance of about 50 mm from the vertex of the fourth lens to the focal plane. 
     
     
         5 . The lens system of  claim 3 , wherein the long BFL is about 50 mm 
     
     
         6 . The lens system of  claim 1 , further comprising one or more scanning mirrors in line with and upstream of the plurality of aligned lenses and a source of laser energy upstream of the one or more scanning mirrors, wherein laser light beam from the laser source is transmitted from the source of laser energy, deflected by the one or more scanning mirrors and then transmitted through the aligned lenses. 
     
     
         7 . The lens system of  claim 6 , wherein the laser light beam is about 7 mm in diameter, diverges to about 12 mm after being transmitted through the first and the second lenses, enters the third lens with about a 12 mm diameter, and converges to 70 microns on the focal plane after being transmitted through the third and fourth lenses. 
     
     
         8 . The lens system of  claim 7 , wherein the radii of curvature of each of the first, second, third and fourth lenses are selected to diverge and then converge a laser light beam to a spot size of 70 microns. 
     
     
         9 . The lens system of  claim 6 , further comprising one or more motors to control the one or more scanning mirrors, a programmed controller in operative connection to the one or more motors, wherein the controller is programmed to move the one or more scanning mirrors in a selected pattern. 
     
     
         10 . The lens system of  claim 1 , wherein the first lens is of meniscus shape with radii of curvature of 20.61 mm and 50.15 mm, the second lens is of meniscus shape with radii of curvature of 35.1 mm and 28.35 mm, the third and fourth lenses are identical and of meniscus shape with radii of curvature of 163.35 mm and 61.19 mm. 
     
     
         11 . A method of producing small microchannels on skin tissue comprising:
 providing the lens system of  claim 1 ;   transmitting a light beam of about 7 mm in diameter to impinge on the first lens;   transmitting the light beam through the first and second lenses, whereby the light beam diverges to about 12 mm;   transmitting the diverged light beam to the third lens, the third lens collimating the light beam; and,   transmitting the light beam from the third lens to the fourth lens, the fourth lens converging the light beam on the focal plane to 70 u.