FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of optics. More particularly, the invention relates to an optical element for illumination of the eye in an ophthalmic laser device. 
       BACKGROUND TO THE INVENTION 
       [0002]    Lasers are well accepted as essential tools for ophthalmic treatments. A laser treatment device requires four basic elements in order to effectively deliver laser energy into the eye for medical treatment. The four essential elements are:
       An illuminator delivering light to the target treatment area to assist viewing;   A microscope (preferable binocular) for viewing the target treatment area;   Optics to deliver aiming beams to the target treatment area to assist with accurate targeting of the treatment; and   Optics to deliver the treatment laser beam to the target treatment area.       
 
         [0007]    It is known to use a slit lamp to provide the illumination and to view the target treatment area with a binocular microscope. It is also known to use a dichroic mirror to reflect the treatment laser beam and aiming beams into the microscope viewing path. In order to deliver the illumination, aiming beams and treatment beams without blocking the binocular viewing path, it is usual to provide the illumination from a position outside the main optical path. The aiming beams, treatment laser beam and viewing path are focused by an objective lens. A typical prior art arrangement is shown in  FIG. 1 . 
         [0008]    The arrangement in  FIG. 1  is functional but does not provide illumination of the treatment area coaxially with the viewing or laser paths. This is mot usually a problem for anterior treatments of the eye since the illumination adequately illuminates the treatment area. For posterior treatment areas there is a problem since the optical path for the treatment laser beam, aiming beams, illumination and viewing must pass through the aperture created by the iris. A typical dilated iris is about 7.8 mm and is located about 20 mm from the retina. The angles are such that for treatment of the posterior of the eye virtually coaxial delivery of the treatment laser beam, aiming laser beam, illumination and viewing is required. This is not possible with the geometry of  FIG. 1 . 
         [0009]    One approach to overcome this problem has been to use dual illumination mirrors placed between the binocular viewing paths (JP10328226) with a small spacing to allow laser beams to be delivered between them, thus providing almost coaxial illumination. The problem with this approach is that the illumination is not quite coaxial and the reduced aperture for the treatment laser beam restricts the laser beam diameter. 
         [0010]    The restricted treatment laser beam diameter is a particular problem for short pulse photo-disruptor lasers that require a full cone angle of 14 to 18 degrees and a working distance of 90 to 100 mm. These parameters require the laser beam emitted from the microscope to have a diameter approximately the same diameter as the viewing objective lens, so that coaxial illumination with the existing arrangements is not possible without blocking a portion of the treatment laser beam. 
       SUMMARY OF THE INVENTION 
       [0011]    In one form, although it need not be the only or indeed the broadest form, the invention resides in a reflex coaxial illuminator for an ophthalmic laser device comprising a reflex mirror movable on an axis from a position in a treatment laser beam path to a position out of the treatment laser beam path. 
         [0012]    Suitably the reflex mirror is rotated about an axis to move from the position in the treatment laser beam path to the position out of the treatment laser beam path. 
         [0013]    Alternatively, the reflex mirror is translated along an axis to move from the position in the treatment laser beam path to the position out of the treatment laser beam path. 
         [0014]    In another form the invention resides in an ophthalmic treatment device comprising: 
         [0015]    one or more aiming lasers producing aiming laser beams that are directed into a treatment path to a target treatment area by at least a first mirror; 
         [0016]    a treatment laser producing a treatment laser beam that is directed into the treatment path by a second mirror; 
         [0017]    a viewing microscope that views the target treatment area along a viewing path coaxial with the treatment path; and a reflex mirror directing illumination from a source of illumination into an illumination path coaxial with the treatment path. 
         [0018]    Suitably the reflex mirror is biased to maintain a position in the treatment path but is movable to a position out of the treatment path by an actuator. The reflex mirror is preferably biased by a spring and the actuator is preferably a motor. Alternatively the actuator may be a solenoid or a piezoelectric device. 
         [0019]    In a yet further form, the invention resides in a method of performing ophthalmic laser treatment including the steps of: 
         [0020]    illuminating a target treatment area with illumination directed coaxially along a treatment path by a reflex mirror; 
         [0021]    directing aiming laser beams along the treatment path to the target treatment area; 
         [0022]    viewing the target treatment area and adjusting the aiming laser beams to be aimed at a selected treatment zone; and 
         [0023]    activating a treatment laser to produce a treatment laser beam that is directed into the treatment zone; 
         [0024]    wherein the reflex mirror is moved out of the treatment path prior to treatment laser emission and then moves back into the treatment path after treatment laser emission ceases. 
         [0025]    Suitably the reflex mirror is moved automatically when the treatment laser is activated and is released back to the biased position when activation of the treatment laser ceases. 
         [0026]    Further features and advantages of the present invention will become apparent from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, in which: 
           [0028]      FIG. 1  is a sketch of a prior art arrangement; 
           [0029]      FIG. 2  is a sketch of a side view of one embodiment of the invention in a first configuration before treatment; 
           [0030]      FIG. 3  is a sketch of a side view of the invention of  FIG. 2  in a second configuration during emission of the treatment laser; 
           [0031]      FIG. 4  is a sketch of a side view of the invention of  FIG. 2  in a third configuration after treatment; 
           [0032]      FIG. 5  is a top view of the embodiment of the invention of  FIG. 2  showing a binocular viewing path; 
           [0033]      FIG. 6  shows one form of an actuator of one embodiment of the invention; 
           [0034]      FIG. 7  shows another form of an actuator; and 
           [0035]      FIG. 8  shows a linear actuator; 
           [0036]      FIG. 9  shows a block diagram of an ophthalmic laser treatment system; and 
           [0037]      FIG. 10  shows a timing diagram for operation of the system of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    Embodiments of the present invention reside primarily in ophthalmic laser device. Accordingly, the elements have been illustrated in concise schematic form in the drawings, showing only those specific details that are necessary for understanding the embodiments of the present invention, but so as not to obscure the disclosure with excessive detail that will be readily apparent to those of ordinary skill in the art having the benefit of the present description. 
         [0039]    In this specification, adjectives such as first and second, left and right, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Words such as “comprises” or “includes” are intended to define a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed, including elements that are inherent to such a process, method, article, or apparatus. 
         [0040]    Referring to  FIG. 1  there is shown a prior art ophthalmic slit lamp microscope laser system  10  in which a treatment laser beam  11  is directed to a targeted treatment area in an eye  12  by a mirror  13  and objective lens  14 . An aiming laser beam  15  is directed by, in this case, a pair of mirrors  16  through the objective lens  14  to the same targeted treatment area in the eye  12 . The dichroic mirror  13  reflects at the treatment laser wavelength but transmits at the aiming laser wavelength. A light source  17  produces broad spectrum (white) light that is directed by mirror  18  to the eye  12  from an off-axis position. The target treatment area is viewed through a microscope  19 . 
         [0041]    A side view of one embodiment of the invention is shown in  FIG. 2 . A reflex coaxial illuminator  20  comprises a reflex mirror  21  that directs light from a light source  22  to an eye  23 . As with the prior art the light source  22  is suitably a broad spectrum (white) light source. 
         [0042]    The mirror  21  is of a size and shape to be located between a pair of laser aiming beams  24  that are directed to the eye  23  by an objective lens  25 . The user positions the aiming beams  24  by moving the slit lamp microscope system to target a treatment zone while viewing the eye through the microscope. 
         [0043]    Referring to  FIG. 3 , the user then activates a treatment laser beam emission that follows a treatment path  26  through the objective lens  25  to the selected treatment zone. Upon activation of the treatment laser the reflex mirror  21  is moved out of the treatment path prior to emission by an actuator  27 . 
         [0044]    A typical treatment modality requires a short pulse from the treatment laser of around 1 msec or less. As soon as the treatment laser emission ceases the reflex mirror is immediately returned to the original position, as shown in  FIG. 4 . This can be achieved quickly if the reflex mirror is biased to the original position by, for example, a spring or other biasing means  28 . The out-of-path time is less than 1 second and typically less than 0.2 seconds. 
         [0045]    As can be seen in the top view of  FIG. 5 , the reflex mirror  21  is of a size and shape to not block the viewing paths  29  of a binocular microscope. Because the reflex mirror  21  is biased by a spring to a position within the treatment path  26  but without blocking the aiming beams  24  or viewing paths  29 , it permits the user to view the target treatment area under coaxial illumination and accurately direct the aiming beams to the target treatment zone. Upon activation of the treatment laser beam the mirror is moved out of the beam path prior to emission but snaps back as soon as the treatment laser ceases treatment. This can be achieved by electrical connection between the treatment laser and the actuator. 
         [0046]    The time taken for the reflex mirror to move is very short so that the interruption to illumination is barely noticeable by a user in most cases. 
         [0047]    The reflex mirror can be moved by any suitable form of actuator. One form of the actuator  27  is shown in  FIG. 6 . In  FIG. 6  the actuator  27  is a small electric motor that is activated to rotate an axle mounting the reflex mirror  21 . A biasing means  28  in the form of a coil spring has one end fixed and the other end acts against a mirror arm  21   a  as shown in  FIG. 6 . 
         [0048]    An alternate form of the actuator is shown in  FIG. 7 . In this case a linear actuator  30  acts on one end  31  of the mirror arm  21   a . Upon release the biasing means  28  in the form of a coil spring acts to rotate the mirror arm  21   a  back to the original position, as previously described. 
         [0049]    A further form of actuator is shown in  FIG. 8 . In this case a linear actuator  32  translates the mirror  21  into and out of position between the binocular viewing path  29 . In  FIG. 8  the mirror  21  is shown out of the beam and the location in the beam is shown in dotted outline  21   b.    
         [0050]    Other forms of actuation, such as piezoelectric devices or manual actuation by a user, will also be suitable. 
         [0051]    For an added level of safety a position sensor may be employed to detect that the reflex mirror  21  is completely out of the treatment laser beam path before the treatment laser is activated. An alternate approach is for the mirror arm  21   a  to close a contact to activate the treatment laser as it moves out of the treatment laser beam path. 
         [0052]    An ophthalmic laser treatment system  40  incorporating a reflex coaxial illuminator  20  is shown in  FIG. 9  and an operation timing diagram is shown in  FIG. 10 . The system is activated by a treatment laser fire switch  41 , which is indicated as A in the timing diagram. A system timing control circuit  42  sends a signal B to open a safety shutter  47  and actuate the reflex coaxial illuminator  20  out of the path of the treatment laser beam  48 . The system timing control circuit also receives a signal C from a mirror position sensor  44  and shutter open sensor  46  that indicates that the mirror and shutter are out of the path before firing the laser system  43 . The system timing control circuit  42  sends a signal D that fires a laser pulse from the laser system  43 . The signal B is then switched off which releases the shutter  47  and reflex coaxial illuminator  20 . A shutter closed sensor  45  provides a positive safety indication. 
         [0053]    It will be appreciated that, unlike the prior art arrangements, the invention provides coaxial illumination of the eye without obstructing the viewing path, the aiming beams or the treatment laser path, without noticeable interruption to viewing by the user. The inventors envisage the invention finding particular application in posterior membranectomy or hyaloidotomy using an Nd:YAG laser. 
         [0054]    The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this invention is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.
A mirror for an ophthalmic laser treatment device that is movable on an axis from a position in a treatment laser beam path to a position out of the treatment laser beam path. The mirror reflects light from a light source into the eye of a patient. The mirror is biased towards a position in the path and is moved out of the path by an actuator just long enough for the laser treatment to be applied and without noticeable interruption to viewing by a user.