Abstract:
A system, apparatus and method for spatially distributed, spectrally neutral optical attenuation. One embodiment of the apparatus can include: an attenuator fin plate; a set of attenuator fins, wherein each of the fins is operably coupled to the fin plate at a preset fin angle to the fin plate normal such that the attenuator fins maintain their position relative to the fin plate as the fin plate moves; and a motor for rotating the fin plate a set angular distance around an axis of rotation, wherein the axis of rotation is at a preset fin plate angle to a light beam direction of travel and wherein the attenuator fins block varying amounts of the light beam as the fin plate is rotated through the set angular distance. The attenuator fin plate and attenuator fins can be a single, integral component, wherein the attenuator fin plate is etched and stamped to form the attenuator fins, or separately formed components that are attached, for example, to a separate frame. The embodiments of the attenuator of this invention can be configured for use within an ophthalmic high brightness illumination system.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    This application claims priority from U.S. patent application Ser. No. 60/601,364 filed Aug. 13, 2004. This application also claims priority from, and is a continuation of U.S. patent application Ser. No. 11/204,305 filed on Aug. 15, 2005. 
         [0002]    The present invention relates generally to surgical instrumentation. In particular, the present invention relates to surgical instruments for illuminating a surgical area during eye surgery. Even more particularly, the present invention relates to spatially distributed, spectrally neutral optical attenuators for such surgical instruments that can homogeneously attenuate an optical beam. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many ophthalmic surgical procedures performed on a patient&#39;s eye require illuminating a portion of the eye so that a surgeon can properly observe the surgical site. In ophthalmic surgery, various different types of instruments are known and available for use by a surgeon to illuminate the interior of the eye. The handheld (probe) portion of a typical ophthalmic illuminator comprises a handle having a projecting tip and a length of optical fiber that enters a proximal end of the handle and passes through the handle and the tip to a distal end of the tip, from which light traveling along the optical fiber can project. The proximal end of the optical fiber can be optically coupled to a light source, such as in a high brightness illuminator, as known to those having skill in the art, to provide the light that is transmitted through the fiber. This type of handheld illuminator is typically used by inserting the probe tip through a small incision in the eye. In this way, light from the illuminator light source is carried along the optical fiber though the handpiece and emitted from the distal end of the probe to illuminate the surgical site for the surgeon. Ophthalmic illuminators that use a length of optical fiber to direct light from the light source to a surgical site are well known in the art. 
         [0004]    A typical ophthalmic illumination system comprises the handheld portion, or probe, to deliver illumination from a light source housed in an enclosure. Along with the light source, the enclosure typically houses optics that guide light from the light source to the optical fiber of the probe, a power supply, electronics with signal processing, and associated connectors, displays and other interfaces as known in the art. In addition, a typical ophthalmic illumination system includes an attenuator. Attenuators are used to vary the intensity of an optical beam to control the intensity profile of the light spot (focal spot) provided by the optical beam. Attenuating an optical beam provides the surgeon a means to attain a desired light intensity at a surgical site. Further, beam attenuation is typically configured such that the surgeon can vary the degree of attenuation as needed. 
         [0005]    Optical attenuators are known in the art for attenuating a collimated beam from an ophthalmic illumination system&#39;s light source. Some prior art optical attenuators have a design that changes the degree of attenuation across the cross-section of the light beam. For example, the attenuator disclosed in U.S. Pat. No. 4,425,599, issued to Volpi, performs in this manner. This non-homogeneous attenuation across the cross-section of the light beam, however, is not desirable in many applications, in particular in systems that focus light into multimode fibers, as it can result in different modes (angles) being attenuated in a non-equal manner. This can result in ring structures appearing in the beam output focal spot. 
         [0006]    Some large scale prior art attenuators are exemplified by the well-known Venetian blind and marine signal lights, such as the well-known naval signal lamps in use by navies around the world. Both these systems use rotating plates to block a light beam. These systems, however, use individually rotating fins (blinds) to attenuate the light beam. Other prior art small scale attenuators used in ophthalmic illumination systems are disclosed in U.S. Pat. Nos. 6,404,970 to Gransden et al., and 6,367,958 and 5,006,965 to E. M. Jones. These prior art attenuators, however, do not provide color neutrality, compact size, a direct motor drive or homogeneous attenuation across the entire light aperture. 
         [0007]    Therefore, a need exists for an optical attenuator for use within an ophthalmic illumination system that can provide for variable attenuation of wide aperture optical (e.g., UV, Visible, IR) beams in a homogeneous manner over the entire aperture. Further still, a need exists for such an attenuator that can provide spectrally neutral attenuation within the desired range of attenuation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The embodiments of the system, apparatus and method for spatially distributed, spectrally neutral optical attenuation of the present invention substantially meet these needs and others. One embodiment of the apparatus of the present invention is an attenuator for attenuating a light beam, comprising: an attenuator fin plate; a set of attenuator fins, wherein each of the fins is operably coupled to the fin plate at a preset fin angle to the fin plate normal such that the attenuator fins maintain their position relative to the fin plate as the fin plate moves; and a means for rotating the fin plate a set angular distance around an axis of rotation, wherein the axis of rotation is at a preset fin plate angle to the light beam direction of travel and wherein the attenuator fins block varying amounts of the optical beam as the fin plate is rotated through the set angular distance. 
         [0009]    The attenuator fin plate and attenuator fins can be a single, integral component, wherein the attenuator fin plate is etched and stamped to form the attenuator fins, or separately formed components that are attached, for example, to a separate frame. The means for rotating the fin plate would then comprise means to rotate the attenuator frame. Means for rotating the attenuator fin plate or frame can include a stepper motor, for discrete step positions, or a continuously variable motor for infinitely variable positioning. The means for rotating the attenuator fin plate or frame can be electronically controlled, for example, by a microprocessor on a printed circuit board or other such controller as known to those having skill in the art. 
         [0010]    The preset fin angle can be 31 degrees, and the preset fin plate angle can be 90 degrees. Each of the attenuator fins can be operably coupled to the fin plate at the same preset fin angle and the fin plate and/or frame centered on the axis of rotation. Each fin&#39;s major axis can be parallel to every other fin&#39;s major axis, and the axis of rotation can be parallel to each fin&#39;s major axis. The set of attenuator fins can comprise eight attenuator fins and the attenuator fins can be spaced equally apart from one another. The attenuator fin plate and set of attenuator fins can be sized so as to interfere with the entire light beam cross-section/aperture at a position along the set angular distance corresponding to zero percent of the optical beam passing through the attenuator fins. The embodiments of the attenuator of this invention can be configured for use within an ophthalmic high brightness illumination system. 
         [0011]    Other embodiments of the present invention can include a system and a method for spatially distributed, spectrally neutral optical attenuation of an optical beam using an optical attenuator in accordance with the teachings disclosed herein. 
         [0012]    Embodiments of this invention can be implemented within a surgical machine or system for use in ophthalmic or other surgery. In particular, it is contemplated that the system, apparatus and method for spatially distributed, spectrally neutral optical attenuation of this invention can be implemented or incorporated into any ophthalmic illumination system in which it is desirable to attenuate an optical beam in a homogeneous and spatially neutral manner. Other uses for the embodiments of this invention will be apparent to those having skill in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features and wherein: 
           [0014]      FIG. 1  is a simplified block diagram illustrating an exemplary high-brightness illuminator system  10  comprising an embodiment of the present invention; 
           [0015]      FIG. 2  is a simplified block diagram illustrating in greater detail an embodiment of an optical attenuator according to the present invention; 
           [0016]      FIG. 3  is a simplified drawing of an exemplary stamping tool for shaping a fin-plate of an embodiment of an optical attenuator of this invention; 
           [0017]      FIGS. 4 and 5  show a MathCAD plot of two dependences used to calculate the fin angle on an embodiment of the attenuator of the present invention; and 
           [0018]      FIG. 6  illustrates another embodiment of an attenuator of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Preferred embodiments of the present invention are illustrated in the FIGURES, like numerals being used to refer to like and corresponding parts of the various drawings. 
         [0020]    The various embodiments of the present invention provide for spatially distributed, spectrally neutral optical attenuation of an optical beam. In ophthalmic surgery there is often a need to attenuate a wide aperture optical beam (e.g., ultra-violet, Visible, Infra red, etc.) in a homogeneous manner (equal attenuation per square area) over the beam aperture. Further, there is a need to be able to vary the degree of attenuation as needed and to have the attenuation be spectrally neutral within the desired range of attenuation. The embodiments of the apparatus, method and system for spatially distributed, spectrally neutral optical attenuation of this invention can provide these functions by following simple principles analogous to those of Venetian blinds mounted on a solid frame. 
         [0021]    Rotating a frame changes an angle between the frame fins and an optical beam passing between the fins. This varies the attenuation from a maximum transmission of the optical beam, which can be as high as 95% or more, to complete or near complete blockage of the beam. One purpose of the present invention is to provide ophthalmic illumination systems implementing an embodiment of this invention a means to attenuate an optical beam in a spatially distributed, spectrally neutral manner and to provide the surgeon a means to variably control the desired illumination scheme at a surgical site. 
         [0022]      FIG. 1  is a simplified block diagram of a high brightness ophthalmic illumination system incorporating an embodiment of a spatially distributed, spectrally neutral attenuator of the present invention. Illuminator system  10  comprises power supply  12  and illumination source  14 , cold mirror  16 , a hot mirror  18 , a beam splitter  20 , mirror  21 , optical fiber ports  24  and attenuators  22 . Illuminator system  10  also typically comprises one or more optical fiber probes  26 . Optical fiber probes  26  comprise the handheld portion of the illuminator system  10 , including optical fiber  34 , which is optically coupled to the illumination source  14  within enclosure  11 . High brightness illuminator system  10  is exemplary only and is not intended to limit the scope of the present invention in any way. The embodiments of the present invention can be used in any such ophthalmic illuminator, medical laser, or any other system or machine in which it is desirable to attenuate an optical beam in a homogeneous and spectrally neutral manner. 
         [0023]    Optical source  14  of illuminator system  10  in this example comprises a xenon lamp, but it can comprise any suitable light source as known to those having skill in the art. Xenon lamp  14  emits light beam  28 , which is directed along the optical path comprising cold mirror  16 , hot mirror  18 , beam splitter  20 , mirror  21 , attenuators  22 , and optical fiber ports  24 . In this example, beam splitter  20  splits light beam  28  into two optical paths to provide for two optical probes  26  if desired. Cold mirror  16  and hot mirror  18  combine to remove the infrared components of light beam  28  (heat) and provide a cool visible light beam  28  to the downstream optical components, as will be familiar to those skilled in the art. Attenuators  22  attenuate optical beam  28  in the manner disclosed herein. Attenuators  22  can each be custom designed for its respective optical path and need not be identical, though they can be. Further, each attenuator  22  can be independently controlled via, for example, PCB  30 . Although high brightness illuminator system  10  is shown comprising two optical fiber ports  24 , it will be obvious to those having skill in the art single optical port  24  or multiple optical ports  24  can be implemented within illuminator system  10 . Illuminator system  10  further comprises a printed circuit board (“PCB”)  30 , or its electronic equivalent, to provide signal processing and control functions. PCB  30  can be implemented in any manner and configuration capable of performing the desired processing and control functions described herein, as will be apparent to those having skill in the art. Optical ports  24  comprise a receptacle to receive the proximal end of the fiber corresponding to fiber probes  26 , which are inserted into the high brightness illuminator enclosure  11  and optically coupled to illumination source  14  to direct light onto a desired site. 
         [0024]      FIG. 2  is a simplified block diagram illustrating in more detail an attenuator  22  of  FIG. 1 . Attenuator  22  comprises an attenuator frame  50  to which is attached an attenuator fin-plate  52 . Attenuator fin-plate  52  comprises fins  54  that are tilted at a preset angle to the attenuator fin-plate  52  normal. Attenuator frame  50  and fin-plate  52  can be driven by a means for rotating fin-plate  52  and/or frame  50 , such as a motor  56 , such that they can be rotated through a range of angles and stopped at a desired angle. As the attenuator fin-plate  52  and fins  54  are rotated, attenuation (transmission) of the light beam  28  can range between a preset maximum to a preset minimum, e.g., 95% transmission to 0% transmission. Motor  56  can be any suitable stepper motor, for discrete step positions, or a continuously variable motor for infinitely variable positioning, as will be known to those having skill in the art. Motor  56  can be electronically controlled, for example, by a microprocessor on PCB  30 , or by another such controller as known to those having skill in the art. 
         [0025]    In one embodiment of the present invention, attenuator fin-plate  52  and fins  54  of attenuator  22  are made by first photo-etching a flat pattern onto an initially flat attenuator fin-plate  52  comprising copper beryllium plate. Copper beryllium alloys are known for their good shape memory, even at elevated temperatures, and are a suitable material for attenuator  22 &#39;s attenuator fin-plate  52 . Initially flat attenuator fin-plate  52  is then plated with bright tin coat and stamped with a tool designed for this purpose. An exemplary stamping tool  100  is shown in  FIG. 3 . Stamping tool  100  comprises an upper plate  101  and lower plate  102  having respective fin forms  103  and  104  tilted at an angle to the attenuator normal operable to shape fins  54  of fin-plate  52  to a desired angle (in this example, 31°). The two stamping tool  100  plates  101  and  102  are brought together forcibly in a manner that will be known to those skilled in the art to produce fins  54  on attenuator fin-plate  52  having a tilt from normal corresponding to the angle of stamping tool  100  fin forms  103  and  104 . This method of manufacture is well-known in the art and stamping tool  100  can be produced by any tool forming technology as known to those skilled in art. Stamping tool  100  includes appropriate pin forms  106  and guiding pins  108  to produce fastener holes  110  in attenuator fin-plate  52  and to guide the separate portions of stamping tool  100  into position with one another. 
         [0026]    Although the exemplary embodiment of attenuator  22 , and in particular attenuator fin-plate  52  shown in  FIGS. 2 and 3 . have been described with reference to a particular manufacturing technique and material (e.g., copper beryllium plate), it is contemplated to be within the scope of this invention and will be familiar to those having skill in the art that attenuator  22  and attenuator fin-plate  52  can be manufactured using any appropriate material, stepper motor, and fin angle, or any combination thereof suitable to meet the requirements of a particular attenuator  22  implementation. In particular, various fin angles are contemplated for the embodiments of the present invention to achieve varying degrees of attenuation. 
         [0027]    The fins  54  of an attenuator  22  of the present invention should be thin enough so that when the fins  54  are aligned along the collimated optical beam, such as light beam  28 , the relative cross-section taken by the fins should be small. In the embodiment shown in  FIGS. 2 and 3 , maximum transmission achieved with an eight fin design is approximately 95% of the optical beam intensity. Minimum transmission is 0%, (i.e. the beam is blocked entirely). 
         [0028]    Another consideration is to select an angle (α max ) of maximum attenuator rotation and the period of the fins  54  in such a way that a relatively small angle of rotation results in a considerable attenuation change in the light beam  28 .  FIGS. 4 and 5  show a MathCAD plot of two dependences—projection of fin period on optical beam cross-section as a function of attenuator tilt D(α); and, projection of the fin period on cross-section of the optical beam  28  as a function of angle of rotation d(α). At the angle that achieves D(α)=d(α), the attenuator  22  is blocking light beam  28 . Calculations in  FIGS. 4 and 5  are shown for fins  54  rotated by 30° from the attenuator fin-plate  52  normal. Other fin  54  angle and maximum angle of rotation combinations may be suitable for different applications and are contemplated to be within the scope of the present invention. 
         [0029]      FIG. 6  shows another embodiment of an attenuator  22  in accordance with the present invention. Attenuator mounting plate  126  of this embodiment comprises an enclosure attached to and housing fin-plate  128 . Attenuator mounting plate  126  comprises an enclosure having an elliptical in this example, although the shape can be arbitrarily selected) opening through which fins  130  of attenuator fin-plate  128  will receive and attenuate an optical beam  28 . Attenuator mounting plate  126  can be operably connected to and driven by a stepper motor, such as stepper motor  56  of  FIG. 2 . Various other such embodiments of a mounting plate  126  and attenuator fin-plate  128  combinations are contemplated to be within the scope of this invention. For example, attenuator fin-plate  52  and attenuator fins  54  can be a single, integral component, as described above, or separately formed components. In either case they can be attached to a frame, such as frame  50 , or stand alone. 
         [0030]    In contrast to the prior art, the various embodiments of the attenuator  22  of this invention can provide homogeneous attenuation of the light beam  28 , which is important in, for example, systems that focus light into multi-mode fibers. This is because different modes (angles) can be attenuated equally. Thus, no ring structures appear in the output of the optical beam upon attenuation. Periodicity of the attenuator fins is used to control how fine (how homogeneous) the attenuation will be. For the purposes of an ophthalmic illuminator, an embodiment such as the eight fin embodiment of  FIG. 2  is sufficient to provide homogeneous attenuation, although a greater or lesser number of fins can be used depending on the application. 
         [0031]    Embodiments of the apparatus, method and system for spatially distributed, spectrally neutral optical attention of the present invention provide an attenuator  22  in which the fins are mounted on a rotatable frame as opposed to some prior art attenuators in which individual fins (blinds) are rotated. Rotating the frame changes the angle between all the fins and the collimated optical beam  28  passing between them. This action can be used to vary the amount of attenuation from a maximum transmission to potentially complete blockage of the optical beam. 
         [0032]    The various embodiments of the present invention provide various advantages, including homogeneous attenuation of an optical beam across the entire light aperture, color neutrality, a compact design and direct motor drive. Other advantages of the present invention include the ability to include a right angle between the attenuated light beam and the axis of the attenuator location (allows positioning of the attenuator motor close to the optical beam). Further, in an ophthalmic illumination system incorporating multiple attenuators  22  in accordance with the embodiments of the present invention, individual attenuators  22  can be controlled independently of one another to provide, for example, varying amounts of attenuation along different optical paths (e.g., to different optical ports  24 ). This independent control can be accomplished, for example, by PCB  30  in a manner that will be known to those having skill in the art. 
         [0033]    Although the present invention has been described in detail herein with reference to the illustrated embodiments, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments of this invention and additional embodiments of this invention will be apparent to, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the spirit and true scope of this invention as claimed below.