in fig1 , a first embodiment of an endoscopic device for generating acoustic waves is shown . a first transducer 40 and a second transducer 30 are contained within an endoscope sheath 10 , having an opening to allow the exit of acoustic energy to an outside of the endoscope . the first transducer 40 generates a first beam 51 of acoustic energy , which preferably exits the endoscope under a predetermined angle , preferably under a right angle to the center axis 16 of the endoscope . the second transducer 30 generates a second beam 50 of acoustic energy , which preferably exits the endoscope under an angle different to the exit angle of the first transducer . the first beam 51 and the second beam 50 intersect under an intersecting angle 53 outside of the endoscope at an intersecting point 60 , also referred as focus spot . preferably , the second transducer 30 is mounted to a first slider 20 , which may be moved in the direction 17 of the center axis 16 of the endoscope . the slider may contain at least one conduit 21 for liquids and / or electrical lines . there may be a cover 11 covering the opening of the endoscope sheath 10 and further enclosing an inner volume 14 , which preferably is filled with an acoustic coupling fluid . preferably there is at least one sealing 12 for sealing the inner volume at a gap of movement of the first slider 20 against the endoscope sheath 10 . when moving the first slider 20 , the inner volume 14 changes . accordingly acoustic fluid must be filled in or removed , which may be done through the at least one conduit 21 . the cover 11 may also be an elastic cover , which may extend or shrink , when the first slider 20 is moved . in fig2 , the basic function of the endoscope device is shown . the first slider 20 as shown in the previous figure may be moved to second position 22 , which is more distant from the first transducer 40 than the first position . from the second position , it radiates a second beam 55 of acoustic energy , basically under the same angle as from the first position . the second beam 55 is intersecting with the first beam 51 of the first transducer under a second intersecting angle 56 resulting in the second focus spot 61 . as there was only a linear displacement of the second transducer , the second beam 55 from the second position is parallel to the second beam 50 from the first position . consequently the second intersecting angle 56 is the same or approximately the same as the first intersecting angle 53 . the second focus spot 61 has moved outward from the first focus spot 60 . accordingly , a linear movement of the second transducer 30 by moving the slider 20 results in a preferably radial displacement of the focus spot . the focus spot may also be moved by moving the first transducer and keeping the second transducer fixed or even by moving both transducers . when moving the first transducer , the focus spot not only moves radially , but it also moves laterally in the direction of the center axis 16 . in fig3 , another embodiment with modified radiation sources is shown . here the radiation sources 40 and 30 are focused transducers emitting narrower beams 51 and 50 resulting in a smaller focus spot 60 . here the energy density at the surface of the endoscope defined by the cover 11 is comparatively low and prevents unwanted effects like coagulation of the tissue at the surface of the endoscope . in fig4 , a further embodiment with a mirror is shown . herein the second emitter is a reflector 32 . the acoustic energy is generated by a transducer 31 , which may be located in the end section 13 of the endoscope . this transducer 31 radiates acoustic energy towards the reflector 32 which itself deflects the acoustic energy into a second beam 50 to form a focus spot 60 together with a first beam 51 . the basic function is the same , as if there would be a transducer 30 instead of the reflector 32 . in fig5 , an embodiment with two movable radiation sources is shown . this embodiment is based on the previous embodiments . furthermore , a third transducer 70 has been added . this first transducer 70 generates a third beam 52 intersecting first beam 51 under a third intersecting angle 54 . the focus spot accumulates the energy of all three beams 50 , 51 , 52 . the first transducer 70 may be supported by a second slider 25 , which may also be moved parallel to the center axis 16 of the endoscope . this second slider may be moved for the same amount , but in the opposite direction of the first slider to keep a small focus spot . it may also be used independently of the first slider to form a variable and / or increased focus spot . in fig6 , a similar embodiment , but without the stationary emitter 40 is shown . this embodiment permits to adjust the position of the focus spot not only radially but also in the whole z - x plane . here , the first slider 20 may be moved into first directions 17 , preferably by a first drive means 80 and preferably parallel to the center axis 16 as shown by the arrow 17 . furthermore , the second slider 25 may be moved into second directions 18 , preferably by a second drive means 81 and preferably parallel to the center axis 16 as shown by the arrow 18 . such a drive means may be a linear motor preferably having at least one coil and / or at least one permanent magnet . it may also be a drive wire , driven by an external motor or hand operated . if the first and second sliders 20 and 25 are moved in opposite directions and of the same quantity , the focus spot moves in the radial direction 63 . if the first and second sliders 20 and 25 are moved in the same direction and of the same quantity , the focus spot moves laterally in the direction 62 . when moving only one slider , the focus spot not only moves radially , but it also moves laterally . in fig7 , an endoscope is shown . the endoscope has a sheath 10 defining a center axis 16 . there is a proximal end having a handle 15 and a distal end bearing the transducers , which are covered by a cover 11 . it will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide endoscopic devices for generating acoustic waves . further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description . accordingly , this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention . it is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments . elements and materials may be substituted for those illustrated and described herein , parts and processes may be reversed , and certain features of the invention may be utilized independently , all as would be apparent to one skilled in the art after having the benefit of this description of the invention . changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims .
an endoscopic device for generating acoustic waves with a sheath defining a center axis contains a first transducer for generating a first beam of acoustic energy radiating outwards of the endoscope sheath and a second transducer for generating a second beam of acoustic energy radiating outwards of the endoscope sheath . both beams have different directions and intersect outside of the endoscope forming a focus spot . the second transducer is linearly movable parallel to the center axis with respect to the first transducer to displace the second beam and therefore to displace the intersection of the beams and therefore of the focus spot .