Abstract:
An optical bench for processing laser light in a laser system, including an optical bench housing, a beam dump mounted to the optical bench housing so as to be in optical communication therewith, steering optics mounted within the optical bench housing for directing the laser light in a path from a laser light input to an output, and a mechanism for causing the laser light to deviate from the path and be directed into the beam dump upon recognition of a specified condition in the laser system, wherein the laser light is thermally isolated from the steering optics. The mechanism can either cause at least one optically reflective element to be inserted into the path, cause at least one optical element of the steering optics to have a change in position with respect to the path, and/or causes at least one optical element of the steering optics to be removed from the path.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an optical bench for a laser system and, more particularly, to a laser system having an optical bench with steering optics to direct a laser beam to a thermally managed beam dump upon recognition of certain conditions. 
     It is well known that energy generators in the form of laser systems have been utilized to treat many disease states through surgical procedures. Such laser systems typically have a safety mechanism included therein to block emission of the laser beam in case an emergency situation or other anomaly occurs. One exemplary safety mechanism for performing this function involves a metal plate which is movable into the laser light path when the laser system detects an abnormal condition. While this mechanism is able to perform its intended safety function by effectively blocking the laser light, the metal plate is unable to absorb the light energy from the laser without a corresponding temperature increase within the optical bench of the laser system. This has had the adverse effect of causing thermal damage to the optics of the laser system. The laser light may also discharge particles and debris from the metal plate, which can scatter over the optical elements and cause physical damage thereto. Accordingly, the optics of a laser system will typically need to be refurbished or replaced when such a safety device has been activated. 
     In light of the foregoing concerns, as well as the continued need for safety mechanisms in laser treatment systems, it would be advantageous to have a safety mechanism that does not cause damage to the laser optics when activated. An optical bench of a laser treatment system with such a safety mechanism would therefore have the ability to manage the thermal energy dissipated from the laser beam and keep damaging energy and damaging particles away from the optics. It would also be desirable in this regard for the laser treatment system to include a beam dump which is thermally separated from the optics. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention, an optical bench for processing laser light in a laser system is disclosed as including an optical bench housing, a beam dump mounted to the optical bench housing so as to be in optical communication therewith, steering optics mounted within the optical bench housing for directing the laser light in a path from a laser light input to an output, and a mechanism for causing the laser light to deviate from the path and be directed into the beam dump upon recognition of a specified condition in the laser system, wherein the laser light is thermally isolated from the steering optics. The mechanism can either cause at least one optically reflective element to be inserted into the path, cause at least one optical element of the steering optics to have a change in position with respect to the path, and/or cause at least one optical element of the steering optics to be removed from the path. 
     In accordance with a second aspect of the present invention, a laser system is disclosed as including a laser for providing laser light, a first optical fiber in optical communication with the laser light, a second optical fiber, and an optical bench for directing the laser light from the first optical fiber to the second optical fiber. The optical bench further includes an optical bench housing, a beam dump mounted to the optical bench housing so as to be in optical communication therewith, steering optics mounted within the optical bench housing for directing the laser light in a path from the laser to the second optical fiber, and a mechanism for causing the laser light to deviate from the path and be directed into the beam dump upon recognition of a specified condition in the laser system, wherein the laser light is thermally isolated from said steering optics. A processor is also provided for controlling the mechanism. The mechanism can either cause at least one optically reflective element to be inserted into the path, cause at least one optical element of the steering optics to have a change in position with respect to the path, and/or cause at least one optical element of the steering optics to be removed from the path. 
     In accordance with a third aspect of the present invention, a method of preventing laser light from being directed in a path through an optical bench into optical communication with an optical fiber is disclosed as including the steps of sensing a specified condition in the laser system, causing the laser light to deviate from the path into a beam dump upon recognition of the specified condition, and thermally isolating the laser light from the optical bench. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the same will be better understood from the following description taken in conjunction with the accompanying drawings in which: 
     FIG  1  is an isometric view of a laser treatment system in accordance with the present invention having an optical fiber connectable thereto; 
     FIG. 2 is an isometric view of the laser treatment system of FIG. 1, where the housing has been removed so as to enable viewing of a controller board and the exterior of an optical bench therein; 
     FIG. 3 is a section view of the optical bench depicted in FIG. 2, where the steering optics therein are in a normal operating position so as to allow a laser beam used for medical treatment procedures to pass through the optical bench and into the optical fiber; 
     FIG. 4 is an isometric view of the optical bench depicted in FIGS. 2 and 3, where a connect block and a sensor board are shown as being attached thereto; and 
     FIG. 5 is a section view of the optical bench as depicted in FIG. 3, where the steering optics therein are in a fail-safe operating position so as to direct the laser beam into a thermally managed beam dump. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in detail, wherein identical numerals indicate the same elements throughout the figures, FIG. 1 depicts a laser treatment system  10  for transferring energy to human tissue by means of light from an optical fiber  20 . A first laser diode is provided in laser treatment system  10  to produce a first laser beam having a predetermined power (preferably in a range of approximately 2-20 watts) and a predetermined wavelength (preferably in a range of approximately 800-850 nanometers) useful for the medical treatment of disease. As further seen in FIG. 1, a connect block  16  is located within a front portion of a housing  18  for laser treatment system  10 . Connect block  16  assists first laser beam  14  in being optically linked with a first end  22  of optical fiber  20  via a connector  24  so that first laser beam  14  can be transmitted from a second end (or tip)  26  of optical fiber  20 . 
     FIG. 2 depicts laser treatment system  10  with housing  18  removed so as to expose an optical bench, identified generally by reference numeral  34 , in order to direct first laser beam  14  into optical communication with optical fiber first end  22  during normal operation. A controller board  28  is also shown that includes, among other components, a main processor  30  for receiving and processing electronic signals to control the operation of laser treatment system  10 . As explained in greater detail herein, main processor  30  provides energy to certain optical components within optical bench  34  when laser treatment system  10  is operational. In this way, main processor  30  is able to prevent first laser beam  14  from entering optical fiber  20  upon recognition of an anomalous condition by removing energy from such optical components. It will also be appreciated that the optical components of optical bench  34  will preferably prevent first laser beam  14  from entering optical fiber  20  when laser system  10  is not operational (i.e., not lasing) as a failsafe feature. While other anomalous conditions will be identified herein, it will be understood that main processor  30  will deactivate such optical components when laser treatment system  10  detects unwanted conditions such as high tissue temperature, charring of the tissue, or an over-stressed or broken fiber. 
     With regard to the operation of optical bench  34 , it will be seen from FIGS. 3 and 4 that the path of first laser beam  14  preferably enters optical bench  34  via an optical fiber  13  in optical communication with the first laser diode. Optical fiber  13  is positioned within a connector  35  in optical bench  34  to assure proper alignment. First laser beam  14  is transmitted through a beam collimator  54  containing a lens  56  and is preferably directed toward a total internal reflection (TIR) prism  58  mounted to a housing  60  for optical bench  34 . First laser beam  14  preferably reflects off TIR prism  58  and is received by a first beamsplitter  62 , which reflects first laser beam  14  toward a second beamsplitter  64 . First laser beam  14  is then reflected from second beamsplitter  64  through an output beam lens assembly  66  and an output lens  68  so as to place first laser beam  14  in optical communication with optical fiber first end  22  via connector  24 . It will be appreciated that a small percentage of first laser beam  14  (identified by reference numeral  15 ) is preferably transmitted by first beamsplitter  62  to a laser power detector  70  by means of a turning mirror  72  so that the power output of first laser beam  14  can be monitored. Further explanation of first beamsplitter  62 , laser power detector  70 , and laser beam  15  is provided in a related patent application filed concurrently herewith entitled “Apparatus And Method Of Monitoring And Controlling Power Output Of A Laser System,” having Ser. No. 09/877,275 which is owned by the assignee of the present invention and hereby incorporated by reference. Of course, various filters may be employed to better isolate and attenuate the wavelength of light provided by first laser beam  14 , as exemplified by filter  74 , correction filter  76 , and neutral density filter  78 . 
     Similarly, a second laser diode preferably provides a second laser beam  82 , also known herein as a marker laser beam, to optical bench  34  by means of an optical fiber  81 . Optical fiber  81  is positioned within a connector  85  in optical bench  34  to assure proper alignment. Second laser beam  82  is transmitted through a marker beam collimator  84 , a marker lens  86 , and a marker filter  87  attached to optical bench housing  60 . Marker laser beam  82  preferably has a predetermined power (preferably in a range of approximately 0.5-2 milliwatts) and a predetermined wavelength (preferably in a range of approximately 600-650 nanometers). It will be appreciated that marker laser beam  82  is preferably used as the light source to optically stimulate a fluorescent slug in optical fiber  20  so as to generate a desired optical fluorescent response therefrom. In order to place marker laser beam  82  in optical communication with optical fiber first end  22  via connector  24 , it is directed toward a first laser turning mirror  88  which reflects it to a second laser turning mirror  90 . Marker laser beam  82  then impacts first beamsplitter  62 , which transmits most of marker laser beam  82  (as a function of its wavelength) so that it passes therethrough to second beamsplitter  64 . Marker laser beam  82  then reflects off second beamsplitter  64  and through output beam lens assembly  66  and output lens  68 . Accordingly, both first (treatment) laser beam  14  and second (marker) laser beam  82  are routed from first beamsplitter  62  to second beamsplitter  64 , as indicated by reference numeral  92 , into first end  22  of optical fiber  20  during normal operation of laser treatment system  10 . 
     It will be appreciated that marker laser beam  82  provides an optical stimulus to the fluorescent slug in optical fiber second end  26 , which absorbs the energy of marker laser beam  82  and fluoresces in response thereto. The time delay from stimulation of the fluorescent slug by marker laser beam  82  to the fluorescence of such fluorescent slug is a function of the temperature of optical fiber second end  26  and can be measured and used to calculate such temperature. The optical fluorescent response, indicated by reference numeral  94 , is transmitted back through optical fiber  20  and out optical fiber first end  22  into optical bench  34 . Optical fluorescent response  94  preferably has extremely low power (in a range of approximately 5-100 nanowatts) and has a preferred wavelength of approximately 680-780 nanometers. Optical fluorescent response  94  then passes through output lens  68  and output beam lens assembly  66  to second beamsplitter  64 . Second beamsplitter  64  is constructed so that optical fluorescent response  94  is transmitted therethrough to a signal filter set  96 , which functions to block any reflected marker and treatment light. The remaining signal, filtered to pass only the fluorescent and blackbody wavelengths, passes through a focussing lens  98  held together with the signal filter set  96  in a signal optical assembly  99  onto a fluorescence/blackbody detector  100 . It will be understood that the blackbody radiation returns along the same path as optical fluorescent signal  94 , but is passed in a fourth waveband through second beamsplitter  64 . Florescence/blackbody detector  100  thus captures and analyzes this signal as a secondary temperature mechanism for a fail-safe mode, where blackbody radiation indicating a temperature too high for proper operation will shut down power to the first laser diode. 
     It will be seen that a sensor board  102  is provided adjacent to optical bench housing  60  so as to interface with fluorescence/blackbody detector  100  and laser power detector  70 . Circuitry on sensor board  102  is connected to and communicates with controller board  28  in order to calculate the temperature of optical fiber second end  26 . Optical bench housing  60  also serves to cover optical bench  34  and keep stray light out. In the present embodiment of the invention, black anodized 6061-T6 aluminum is utilized for optical bench housing  60  to minimize reflection and scattering of ambient light. It will be appreciated, however, that optical bench housing  60  can be created from a reflective material coated by an absorptive material, as it is not purposely placed in a direct path with first laser beam  14 . 
     In a preferred embodiment, a solenoid  36  is attached to optical bench housing  60  and holds a mirror  38  at the end of a shutter arm  40 . It will be seen that solenoid  36  is able to actuate shutter arm  40  to move mirror  38  into and out of the path of first laser beam  14  after being passed by beam collimator  54 . FIG. 3 depicts mirror  38  as being positioned outside the path of first laser beam  14  during normal operation of laser treatment system  10 , thereby allowing laser light to pass into the rest of optical bench  34 . While shutter arm  40  is shown as having been rotated approximately 90° from the position shown in FIG. 5, it will be appreciated that solenoid  36  need rotate shutter arm  40  only an amount necessary to move mirror  38  out of the path of first laser beam  14 . A position detection mechanism, identified generally by reference numeral  42  (see FIG.  5 ), is provided to continually monitor the position of shutter arm  40 . More specifically, position detection system  42  preferably includes a pair of Hall-effect sensors  44  located near a magnet  46  placed on shutter arm  40 . It will be appreciated that Hall-effect sensors  44  sense the position of mirror  38  and communicate the position thereof to main processor  30 . In particular, only one of Hall-effect sensors  44  will sense the presence of magnet  46  when mirror  38  deflects first laser beam  14  into beam dump  50  (i.e., the closed or blocked position) and only the other of Hall-effect sensors  44  will sense the presence of magnet  46  when mirror  38  permits first laser beam  14  to continue to laser filter  74  (i.e., the open position). 
     It will be noted that laser filter  74  is preferably mounted adjacent to mirror  38  in order to filter the sidebands of first laser beam  14  (when permitted to pass thereto) so as to allow an optimal wavelength of laser light to pass. At the same time, light (identified by reference numeral  11  in FIG. 3) in wavelengths slightly longer or shorter than the optimal wavelength are preferably reflected into a beam dump  50  located adjacent to optical bench  34  and attached to housing  60  thereof. 
     More specifically, beam dump  50  preferably includes a layer  51  of light absorbing material having an inverted cone shape and a beam dump housing  52  (made out of aluminum, for example) encasing absorber layer  51 . The cone angle and light absorption of layer  51  enable beam dump  50  to contain nearly all of the light entering it from an opening  55  therein oriented toward the inside of optical bench  34 . A transparent window  57  made of coated glass preferably covers opening  55  in order to cause a seal within a cavity  65  of beam dump  50 , thereby assuring that out-gassing from absorber layer  51  will not deposit on the sensitive internal optics of optical bench  34 . Fins  59  are preferably placed on an exterior surface  61  of beam dump housing  52  so as to better dissipate heat therefrom. In this way, it will be appreciated that heat contained within absorber layer  51  is thermally conducted to beam dump housing  52  and to fins  59 . 
     Absorber layer  51  preferably is a single material (e.g., carbon graphite) throughout beam dump  50  so that a light absorptive surface is always present to capture any incoming light beam, even if material on the surface of the conically-shaped depressions  63  is removed. This type of absorber layer  51  is advantageous over an absorber comprising only an absorptive coating on a reflective material, which scatters the laser light instead of capturing it for conversion to heat energy when the coating is removed. Absorber layer  51  preferably contains conically shaped depressions  63  which are oriented so that the wider end is adjacent beam dump housing opening  55  and faces toward the direction from which laser light enters beam dump  50 . Conically-shaped depression  63  are designed to direct the extremely small amount of unabsorbed light into, rather than out of, beam dump  50 . All internal surfaces of absorber layer  51  are preferably absorptive, rather than reflective, to eliminate backscattering of any light energy that enters absorber layer  51 . 
     FIG. 3 shows that when laser treatment system  10  is operational and first laser beam  14  is used, first laser beam  14  enters optical bench  34  via optical fiber  13  and travels through lens  56  of beam collimator  54 . When laser treatment system  10  is operating without a detected error, as shown in FIG. 3, solenoid  36  holds mirror  38  out of the path of first laser beam  14  so that it can proceed past mirror  38  to laser filter  74 . As stated herein, laser filter  74  blocks sideband wavelengths close to the wavelengths of optical fluorescent response  94  emitted by the fluorescent slug in optical fiber  20 . 
     The portion of first laser beam  14  blocked by laser filter  74 , indicated by reference numeral  11 , is preferably reflected into beam dump  50 . Beam dump  50  is therefore placed near laser filter  74  to capture at least a portion of laser light reflected thereby. It will be appreciated that laser light energy captured by beam dump  50  is converted to heat and moved away from the optics in optical bench  34  to keep such optics cool. Removing rejected wavelengths of treatment light from optical bench  34  also has the advantage of keeping such light from first laser beam  14  away from fluorescence/blackbody detector  100 , whereby measurements using information generated by fluorescence/blackbody detector  100  become more accurate. 
     If main processor  30  on controller board  28  detects an anomalous condition, it will preferably remove a signal holding solenoid  36  open, thus causing mirror  38  to move into the path of first laser beam  14 . This is a fail-safe configuration since solenoid  36  will divert first laser beam  14  to beam dump  50  by default instead of allowing the light therefrom to pass through the rest of optical bench  34 . Alternatively, when no signal is required to maintain solenoid  36  in an open position, main processor  30  could send a signal to solenoid  36  causing mirror  38  to move into the path of first laser beam  14 . In either case, first laser beam  14  will be reflected into beam dump  50 . This position, with solenoid-actuated mirror  38  in the path of first laser beam  14 , is shown in FIG.  5 . 
     FIG. 5 depicts mirror  38  in the path of first laser beam  14 . It will be seen that first laser beam  14  is reflected from mirror  38  and passes through window  57  to absorber layer  51  in beam dump  50 . Beam dump  50  then absorbs first laser beam  14 , converts the light energy thereof to heat energy, and dissipates the heat energy away from the optics in optical bench housing  60 . Absorber layer  51 , made of a material with a high coefficient of heat transfer and absorptive to light in the waveband of first laser beam  14  (e.g., carbon graphite), absorbs nearly all of the impinging light energy. It will be appreciated, however, that any small portion of reflected light energy travels to another highly absorptive surface within absorber layer  51  because the angle of the conically shaped depression  63  creates an angle of reflection that directs the energy deeper therein. The thermal conductivity of absorber layer  51  then moves thermal energy through beam dump housing  52  to fins  59 , where convection occurs to take the heat into the surrounding air and away from optical bench  34 . It will be understood that such convection could be natural convection, utilizing the natural air movements caused by temperature differences between fins  59  and ambient air, or forced convection, caused by air moved by an external source such as a fan. Window  57  serves to protect the optical elements of optical bench  34  from debris or particles created by impinging absorber layer  51  with laser light, as well as acts in the capacity of a thermal insulator in helping to keep heat away from optical bench  34 . 
     It will be recognized that equivalent structures may be substituted for the structures illustrated and described herein and that the described embodiment of the invention is not the only structure that may be employed to implement the claimed invention. As one example of an equivalent structure that may be used to implement the present invention, any cooling means may be substituted for fins  59 . For example, circulating water could be used in place of the fins  59  to move heat away from beam dump housing  52 . However, the heat transfer abilities of absorber layer  51  and beam dump housing  52  allow the use of fins  59  in a medical laser application where expense and close proximity of electronics may proscribe the use of potentially leaky water cooling. 
     As a further example of an equivalent structure that may be used to implement the present invention, any steering optics to deflect first laser beam  14  into beam dump  50  could be substituted for solenoid-activated mirror  38 , such as a prism. Moreover, it will be understood that the steering optics may automatically deflect first laser beam  14  into beam dump  50  until it receives a signal indicating normal operation of laser treatment system  10  from main processor  30 . In this scenario, for example, mirror  38  will initially be positioned in the path of first laser beam  14  as seen in FIG.  5 . Once laser treatment system  10  is considered to be operating normally, mirror  38  is removed from such path to permit first laser beam  14  to enter optical fiber  20 . It will also be appreciated that one or more of the reflecting surfaces already present within optical bench  34  may be rotated, removed or otherwise repositioned so as to cause first laser beam  14  to be deflected into beam dump  50  upon recognition of a specified condition. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.