referring to fig1 , a treatment apparatus 10 includes a handpiece 12 coupled to a treatment console 14 which includes a user interface 13 , a power supply 16 and a controller 19 . power supply 16 may be a high voltage power supply of the type provided by cutera , inc . ( brisbane calif .) in consoles for use with its laser product lines , and in particular the power supply used with the pearl ™ laser . the exterior of handpiece 12 includes a protective window 15 through which treatment energy exits the handpiece . a distance guide 17 sets the distance between the handpiece 12 and the target treatment site . during use , the distance guide is placed in direct contact with the patient &# 39 ; s skin . features housed within the handpiece 12 are shown in fig2 a and 2b . these features include a semi - monolithic laser resonator comprising a laser rod 18 and a planar minor 20 . the laser rod 18 is preferably a er : ysgg or a cr , er : ysgg rod . this gain medium has a primary output at 2 . 79 μm . in one embodiment , rod 18 has a length of 86 mm and a diameter of 3 mm , and the length of the resonator is 106 mm . as best shown in fig2 b , laser rod 18 includes first and second planar ends . first end 22 , which serves as the output coupler , includes a polished surface coated with a partially transmissive coating . second end 24 , which is positioned in alignment with the minor 20 , has an anti - reflective coating . mirror 20 is a planar mirror aligned with the second end 24 to permit light to circulate between the minor 20 and the first end 22 . minor 20 is supported in a mount 21 which permits the tilt angle of the mirror to be adjusted during assembly to facilitate alignment with the resonator axis . this semi - monolithic resonator design , with the output coupler 22 formed on the gain rod 18 and the second minor 20 being spaced from the end of the rod was developed to improve the m 2 output of the laser to increase the depth of focus of the beam . more specifically , in the laser resonator used in the assignee &# 39 ; s pearl laser system was fully monolithic wherein both ends of the gain rod were coated for reflection . in such a fully monolithic laser resonator , the ends of the rod were curved for stability purposes . curved minors tend to produce a higher m 2 output with a short depth of focus . this short depth of focus was not a problem with the pearl system because of its large spot size at the tissue . the semi - monolithic design reduces the m 2 because it uses two flat mirrors and is longer than the prior art resonator . by mounting minor 21 on a tiltable support , alignment is facilitated . the increased depth of focus is very useful for maintaining the desired spot size on the tissue for multiple small spots . the rod 18 is side - pumped flashlamp 26 to generate a pulsed output . a portion of the beam 100 exiting the laser resonator may be diverted to a photodetector ( not shown ) by a beam splitter 27 for use in monitoring output power . mirrors 28 , 29 and 31 are positioned to direct the output beam from the laser to a pair of scanning mirrors 30 a , 30 b . each of the scanning mirrors 30 a , 30 b is coupled to a corresponding stepper motor 32 a , 32 b . stepper motors 32 a , 32 b are simultaneously or independently operable to scan the output beam 100 in x - and / or y - directions across a diffractive element 34 . diffractive element 34 splits the scanned beams into a fixed number ( e . g . 6 , 8 , or 10 ) of sub - beams 200 having fixed angles between them ( fig3 ). the diffractive element may be manufactured in a number of ways to optimize uniformity of the sub - beams . for example , the diffractive element may be one that eliminates the effect of the zero order and / or that skips the even orders to maintain symmetry around the zero order . off - axis diffractive elements may also be used . suitable diffractive elements are manufactured by mems optical of huntsville , ala . optics 36 focus the sub - beams 200 to a predetermined spot size onto the tissue to be treated . in the illustrated embodiment , optics 36 includes a meniscus lens 36 a and — a double convex lens 36 b , each of which is made of sapphire . see also fig3 a - 3c . the separation distance between the spots impinged onto the target tissue is determined by the focal length of the optics 36 and the angles of the sub - beams 200 formed by the diffractive element . the arrangement of the optics 36 also determines the working distance ( defined as the distance between the tissue surface and the output of the optics 36 ). for example , in one embodiment illustrated in fig3 b , the lenses 36 a , 36 b are designed to impinge 300μ diameter spots onto the tissue surface , with a 20 mm working distance , and a 1 . 3 mm depth of focus . this arrangement gives a 0 . 44 mm spot offset / degree beam angle , meaning that if the diffractive element gives angles of 1 degree between each beam , the center - to - center separation distance between the spots will be 0 . 44 mm . in contrast , fig3 c illustrates another design of lenses 36 a , 36 b which create 300μ diameter spots with a 41 mm working distance , a 3 mm depth of focus , and a 0 . 84 mm spot offset / degree beam angle . referring again to fig2 a and 2b , the handpiece additionally includes an aiming diode 38 positioned to generate a visible aiming beam of light that is combined with the laser output beam 100 . the aiming beam is likewise diffracted into sub - beam so that the aiming sub - beams are parallel and coincident with the treatment sub - beams . in a preferred mode of operation , the scanning minors scan the pulsed output beam across the diffractive element . as a result , the sub - beams 200 generated by the diffractive element form a matrix of small diameter ( e . g . approximately 200 - 400μ ) treatment spots on a treatment area of the skin . treatment spots may have a depth of approximately 200μ to 1 mm , and the energy per pulse of each treatment sub - beam is approximately 30 - 150 mj . an optimal treatment speed is approximately 1 cm 2 / sec . the stepper motors may be operated in a number of treatment modes to produce spot matrices having a variety of spot densities . three exemplary modes will be described with reference to fig4 a - 4c , which illustrate three examples of treatment patterns that can be produced using the disclosed laser . each of the illustrated treatment patterns represents a pattern generated in a 14 mm by 18 mm treatment area using a diffractive element that yields eight treatment sub - beams . in fig4 a , treatment begins with the formation of column 102 of treatment spots when the eight sub - beams are in their initial position . scanning motors 32 a , 32 b are energized between laser pulses to step the mirrors 30 a , 30 b , causing a shift in the sub - beam orientations . activation of the scanning motors causes one of the scanning minors to shift the orientation of the sub - beams along the x - axis , and causes the other one of the scanning minors to shift the orientation of the sub - beams downwardly along the y - axis , forming column 104 of treatment spots . the minors are again scanned , this time to move the sub - beams to the right along the x - axis and upwardly along the y - axis , so that the next pulse of energy from the laser 18 generates column 106 of treatment spots . the process is repeated ( toggling the array of spots up and down ) to produce multiple columns of treatment spots . fig4 a shows a matrix of 80 treatment spots with a spot density of approximately 4 %. the system is capable of forming the matrix in less than 1 second , and preferably approximately 0 . 5 sec . the fig4 b treatment pattern may be formed using a mode similar to that described with respect to fig4 a , but by shortening the x - direction scanning distance by half to form a denser spot array . here , a matrix of 160 treatment spots with a spot density of approximately 8 % is shown . in one embodiment , the treatment time to form this matrix of spots may be approximately one second . in the treatment pattern shown in fig4 c , the spot density is further increased to 16 %. as shown , although the diffractive element produces eight sub - beams , each column includes sixteen treatment spots . in column 110 , boxes are drawn around alternate spots to identify the initial eight treatment spots . the y - axis stepper motor is then activated between treatment pulses to reorient the eight treatment sub - beams to form additional spots between the initial eight treatment spots . the x - axis stepper motor is then used to orient the sub - beams to form additional treatment columns . as with the fig4 a and 4b patterns , the pattern is created by repeatedly stepping the x - axis and y - axis motors to re - orient the eight treatment sub - beams . the sequence of the x - axis and y - axis shifts needed to complete the pattern is not critical , but is generally optimized to minimize the treatment time , which in this mode is ideally about 2 sec or less for the entire matrix . in use , the operator would select the desired spot density through the user interface 13 on the console 14 . based on this input , the controller 19 sends signals to the flashlamp to generate the laser pulses and coordinates the pulsed operation with the movement of the scanning minors 30 a and 30 b . some additional details of control circuitry suitable for implementing the design is set forth in u . s . publication 2007 / 026504 with particular reference to fig3 . it should be recognized that a number of variations of the above - identified embodiments will be obvious to one of ordinary skill in the art in view of the foregoing description . accordingly , the invention is not to be limited by those specific embodiments and methods of the present invention shown and described herein . rather , the scope of the invention is to be defined by the following claims and their equivalents .
a dermatological treatment device is disclosed for generating a matrix of two dimensional treatment spots on the tissue . a handpiece carries a laser which generates a beam of laser pulses . the pulses are focused onto the tissue with a lens system . a diffractive element is positioned between the laser and the lens system for splitting the laser beam into a plurality of sub - beams . a scanner translates the beam over the diffractive element to generate the two dimensional spot pattern . the laser has a semi - monolithic resonator design with one integral end minor defining the output coupler and a second , independent mirror for adjustment .