Abstract:
An optical connector for use with a light separator, the optical connector including a first portion and a second portion, the first portion being optically couplable by first optical transmitter to a first input of the light separator and by second optical transmitter to a second input of the light separator. The first and second portions are detachably couplable to couple the first and second optical transmitter to third and fourth optical transmitters, respectively, provided in or coupled to the second portion. The first and second inputs of the light separator can thereby be optically coupled to a first optical instrument coupled to the third optical transmitter and a second optical instrument coupled to the fourth optical transmitter.

Description:
RELATED APPLICATIONS  
       [0001]     This application is based on and claims the benefit of the filing date of U.S. provisional application Ser. No. 60/470,874 filed 16 May 2003, the contents of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to an optical connector, of particular but by no means exclusive application with endoscopes, endomicroscopes, microscopes, colonoscopes and scanning devices for connecting an optical coupler to both a laser and a detector unit.  
       BACKGROUND OF THE INVENTION  
       [0003]     An arrangement typical of existing endoscopes is shown schematically at  10  in  FIG. 1 . The laser  12  provides the excitation light for a fluorescent dye with which a sample has been stained or for reflection from the sample. A light separator in the form of coupler  14  couples laser light from the laser  12  to both endoscope head  16  and a power monitor  18 . The power monitor  18  includes a power monitor device, and allows the operator to obtain some measure of the power being delivered to the endoscope head  16 . The coupler  14  also couples the light returned by the sample (from low level excited fluorescence and/or reflection) back to a detection unit  20 , which contains a barrier filter and a photomultiplier tube (not shown) to detect this return light. The core of optical fiber  22  between the endoscope head  16  and the coupler  14  is the transmission medium for both the excitation light and the return signal but, in some prior art systems, also constitutes a spatial filter (or, in effect, a pinhole) so that confocal detection may be effected.  
         [0004]     In such arrangements, the laser  12 , coupler  14 , power monitor  18  and detection unit  20  are provided in a control box  24 . Optical fiber  22  is detachably coupled to the control box  24  by means of an optical connector (not shown), so that the endoscope head  16  can be detached, such as for cleaning, between successive patients, or the like, by detaching the single optical connection between the control box  24  and that portion of the endoscope (i.e. optical fiber  22  and endoscope head  16 ) outside the control box.  
         [0005]     Such arrangements have a number of problems. The relative power between the endoscope head  16  and the photodiode of the power monitor  18  is dependent on any joint loss at the connection between control box  24  to optical fiber  22  (due, for example, to dust in the connection). This means that the power monitor  18  needs, in principle, to be calibrated each time a new or replacement endoscope head  16  is connected. Where a 488 nm laser is used, it is necessary to ensure low loss at this interface for both the 488 nm excitation light and the 488 to 585 nm return light, as light of all these wavelengths is carried by optical fiber  22 ; the connection is between single mode fiber and requires low loss in both directions.  
         [0006]     Further, this connection can affect the mode mix and hence the optical power distribution in optical fiber  22 , which has the potential to produce image instability, noise and reduced resolution. In addition, reflection from this connection can cause instability in laser  12  resulting in image noise, and increase noise in the ultimate image by reflecting excitation light into the detection unit  20 .  
       SUMMARY OF THE INVENTION  
       [0007]     In a first broad aspect, the present invention provides an optical connector for use with a light separator, the optical connector comprising: 
        a first portion and a second portion, said first portion being optically couplable by first optical transmitter to a first input of said light separator and by second optical transmitter to a second input of said light separator;     wherein said first and second portions are detachably couplable to couple said first and second optical transmitters to respectively third and fourth optical transmitters provided in or coupled to said second portion, whereby said first and second inputs of said light separator can be optically coupled to a first optical instrument coupled to said third optical transmitter and a second optical instrument coupled to said fourth optical transmitter.        
 
         [0010]     It will be understood, however, that—while the connector may generally be used with at least two optical instruments—in some applications only one optical instrument may be so coupled. Also, it will be understood that an optical instrument can comprise any device that is adapted to provide optical output or receive optical input.  
         [0011]     In one embodiment, said optical instruments respectively comprise a laser source and a light detector, wherein said laser source is optically couplable by the third optical transmitter to said second portion and said light detector is optically couplable by the fourth optical transmitter to said second portion, whereby said first optical transmitter can be coupled via said third optical transmitter to said laser source and said second optical transmitter can be coupled via said fourth optical transmitter to said light detector.  
         [0012]     The light separator is typically in the form of an optical coupler.  
         [0013]     In this embodiment, at least a portion of each of said first and second optical transmitter is preferably integral with, or permanently connected during manufacture to, said light separator (or coupler).  
         [0014]     Each optical transmitter preferably comprises an optical fiber (though possibly incorporating a join). More preferably, each of said optical fibers is single or few mode with the exception of said fourth optical transmitter which can be multimode, few mode or single mode for coupling to a light detector.  
         [0015]     When multimode the fourth optical transmitter has a greater diameter and many more guided modes than the second optical transmitter, so that alignment of the second and fourth optical fibers is more readily effected while achieving low loss.  
         [0016]     In certain embodiments, the optical connector is adapted to couple more than two pairs of optical transmitters, each of said first and said second portions being optically couplable by one or more further optical transmitters to one or more respective further inputs of said light separator.  
         [0017]     The invention also provides in a further aspect an optical apparatus comprising: 
        a light separator;     a power monitor;     a first portion of an optical connector that comprises said first portion and a second portion, said first portion being optically couplable by first optical transmitter to a first input of said light separator and by second optical transmitter to a second input of said light separator, said first portion being detachably couplable to said second portion to couple said first and second optical transmitters to respectively third and fourth optical transmitters provided in or coupled to said second portion;     wherein said light separator is optically coupled or couplable to an optical head, said power monitor and said first portion, whereby said apparatus is detachably couplable to said second portion.        
 
         [0022]     In one particular embodiment, the optical apparatus further comprises a housing enclosing said light separator and said power monitor, and either supporting said first portion or at least partially enclosing said first portion.  
         [0023]     Thus, the second portion will typically be coupled in use to a laser source and a light detector, but such an arrangement can be used to facilitate cleaning or sterilisation; this apparatus can be decoupled from the laser source and light detector and another comparable apparatus substituted while the first is cleaned.  
         [0024]     The optical apparatus may further comprise the optical head.  
         [0025]     The light separator may be permanently coupled to said power monitor. This permits more reliable calibration of the system, as the efficiency of light transmission between the light separator and the power monitor should remain constant.  
         [0026]     In another aspect, the invention provides an optical scanning system including an optical connector as described above.  
         [0027]     In a still further aspect, the invention provides an endoscope including an optical connector as described above.  
         [0028]     In a still further aspect, the invention provides an endomicroscope including an optical connector as described above.  
         [0029]     In yet another aspect, the invention provides a microscope including an optical connector as described above.  
         [0030]     The invention also provides a method for providing an optical connection comprising employing an optical connector as described above. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     In order that the invention may be more clearly ascertained, an embodiment will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0032]      FIG. 1  is a schematic view of a background art endoscope;  
         [0033]      FIG. 2  is a schematic view of an endoscope incorporating an optical connector according to an embodiment of the present invention;  
         [0034]      FIG. 3  is another schematic view of the endoscope of  FIG. 2 ; and  
         [0035]      FIG. 4  is a schematic view of the connector of the endoscope of  FIG. 2 .  
     
    
     DETAILED DESCRIPTION  
       [0036]     An optical scanning system incorporating an optical connector according to an embodiment of the present invention is shown generally at  28  in  FIG. 2 . The components of scanning system  28  are, in some cases, comparable with those of endoscope  10  of  FIG. 1 , so like reference numerals have been used to indicates like features.  
         [0037]     Scanning system  28 , which might be in the form of an endoscope or microscope, includes a laser  12  with 488 nm wavelength output, a light separator in the form of coupler  14 , a scanning optical head  30 , power monitor  18 , and detection unit  20 . Laser  12  and detection unit  20  are contained in control box  32 .  
         [0038]     Scanning system  28  is also provided with an optical connector  34  for connecting the coupler  14  to the control box  32 . Referring to  FIG. 3 , which is a more detailed schematic view of scanning system  28  of  FIG. 2 , the connector  34  comprises two portions, first portion  36   a  and second portion  36   b.  The first portion  36   a  is coupled to first and second inputs  38   a,    38   b  of the coupler  14  by means of optical transmitters in the form of, respectively, first optical fiber  42  and second optical fiber  44 , while the second portion  36   b  forms a part of the control box  32  and is coupled to the laser  12  and the detection unit  20  by means of optical transmitters in the form of, respectively, third optical fiber  46  and fourth optical fiber  48 . It will be understood that first and second inputs  38   a,    38   b  of coupler  14  are points that may equivalently be referred to as “outputs” since light can—in principle even if not in this embodiment—pass in both directions past these points, and because first optical fiber  42  and second optical fiber  44  are integral with the coupler  14  at these points. Further, it will be understood that second portion  36   b  need not be a part of or directly connected to the control box  32 .  
         [0039]     The coupler  14  is coupled to the scanning optical head  30  by means of an optical transmitter in the form of fifth optical fiber  50 , and to power monitor  18  by means of an optical transmitter in the form of sixth optical fiber  52 . In this embodiment, fifth optical fiber  50  and sixth optical fiber  52  are integral with coupler  14 .  
         [0040]     All the optical fibers (with the exception of fourth optical fiber  48 ) are single mode (in fact of SM450 fiber) at the wavelength of laser  12 .  
         [0041]     Consequently, the connection from third optical fiber  46  to first optical fiber  42  provides a stable split ratio of the light from the laser  12 , to provide class compliance, stable illumination of the sample at the scanning system  28 , and a power distribution of light illuminating the sample that minimizes degradation of optical resolution.  
         [0042]     Similarly, this means that only one fiber is used in the coupler  14 , which provides strong optical power exchange from one fiber to the other in the coupler waist region, though—in some applications—dissimilar fibers forming an asymmetric coupler could be used acceptable or indeed advantageous.  
         [0043]     Fourth optical fiber  48  could also be single or few mode, but as it is merely necessary that there be low loss for light travelling to the detection unit  20 , a larger core multimode fiber is used so that the alignment tolerance is relaxed. Care should be exercised, however, to avoid excessive mode dispersion in fourth optical fiber  48  or imaging sensitivity may be reduced.  
         [0044]     Thus, in this embodiment fourth optical fiber  48  is a multimode fiber having a considerably greater core diameter than have the other optical fibers, by at least an order of magnitude. In particular, it has a substantially larger core diameter than the second optical fiber  44  to which—in use—it is optically coupled. Consequently, when the connector  34  is connected (that is, portions  36   a  and  36   b  are coupled), the fourth optical fiber  48  and the second optical fiber  44  will be readily aligned as long as the more difficult alignment—between single mode first optical fiber  42  and single mode third optical fiber  46 —has been effected. This reduces the engineering challenge associated with constructing such a connector if only single mode fibers (with core diameters of perhaps 5 μm or less) were employed; this would require, during the physical coupling of the two portions  36   a  and  36   b  of the connector  34 , precise alignment of exceedingly small cores.  
         [0045]     The connector  34  is shown schematically in greater detail in  FIG. 4 . Within each of the two portions  36   a  and  36   b  of connector  34 , the tips of first, second, third, and fourth fibers  42 ,  44 ,  46  and  48  are located within metal ferrules (such as ferrule  54  of third optical fiber  46 ), so that each tip can be positioned accurately for alignment with the opposite tip. The two portions  36   a  and  36   b  of connector  34  are aligned by means of a pair of positioning pins  56   a,    56   b  accessible for coupling and decoupling via a pair of slots  58   a,    58   b  in the sides of the connector  34 .  
         [0046]     The two portions  36   a  and  36   b  of connector  34  are held together by any suitable means; this could be in the form of pins, grub screws, or an external clip attached to one portion for engaging the other portion.  
         [0047]     First and second optical fibers  42  and  44  transmit light to and from coupler  14  (see  FIG. 3 ), so are enclosed in a common protective sheath  62 .  
         [0048]     Thus, in use the connector  34  allows the quick detachment of the scanning optical head  30 , power monitor  18  and coupler  14  as a single unit. This means that replacement units must include more components than the endoscope head  16  of the background art arrangement of  FIG. 1 , but with the following advantages that—in some applications—are expected to make this approach desirable.  
         [0049]     Indeed, first portion  36   a  of connector  34 , coupler  14  and power monitor  18  and associated fibers  42 ,  44 ,  52  can all be contained in a physical housing  40  (from which fifth optical fiber  50  and hence optical head  30  would protrude) that an operator can easily attach and detach from second portion  36   b  of connector  34 . The housing  40  can consequently be sealed for ready sterilisation and cleaning. In such an embodiment, the scanning system  28  might be in the form of an endoscope or colonoscope, where sterilisation and cleaning are particularly important considerations. The physical housing  40  and its contents thus constitute an optical apparatus for use as a part of, for example, an endoscope, endomicroscopes or colonoscope.  
         [0050]     Input excitation light transmitted to power monitor  18  and scanning optical head  30  passes through only one connection that, in use, is decoupled and recoupled (i.e. the connection from third optical fiber  46  to first optical fiber  42 ). Consequently, the power delivered to both the power monitor  18  and the scanning optical head  30  will have a constant relationship that is independent of loss in connector  34 : this relationship will not be affected by a change in the total power delivered to first optical fiber  42  (such as due to dust coming between the tips of third optical fiber  46  to first optical fiber  42 ). As a result, it is not necessary to provide an additional set-up test when connecting a (possibly) sterilised scanning optical head  30  before use to ensure class compliance or accurate power setting.  
         [0051]     Wavelength performance of the optical joint formed by the connector  34  is easier to achieve. This is because the connection between third optical fiber  46  and first optical fiber  42  is from single mode fiber to single mode fiber and only needs low loss at the 488 nm wavelength of laser  12  in the forward direction, while the connection between second optical fiber  44  and fourth optical fiber  48  is only required to have low loss for 488 to 585 nm wavelength light transmitted in the return direction only. In the background art arrangement of  FIG. 1 , low loss would be required for both 488 nm excitation light and 488 to 585 nm return light, so the connection in optical fiber  22  at the outside of control box  24  is necessarily (in this example) between two segments of single mode fiber requiring low loss in both directions.  
         [0052]     Further, optical loss at the connection between second and fourth optical fibers  44 ,  48  for low level fluorescence may, in some applications, be lower in the present embodiment than at a connection in optical fiber  22  at the outside of control box  24  in the background art arrangement of  FIG. 1 .  
         [0053]     Modifications within the scope of the invention may be readily effected by those skilled in the art. For example, the embodiment illustrated in FIGS.  2  to  4  comprises a scanning system, but the same approach can clearly be employed in an endoscope, a microscope and an endomicroscope. It is to be understood, therefore, that this invention is not limited to the particular embodiments described by way of example hereinabove.  
         [0054]     Further, any reference herein to prior art is not intended to imply that such prior art forms or formed a part of the common general knowledge.