Abstract:
A connector to connect a fiber bundle probe to a light injection module including a tightening cam having an opening of a specified shape adapted to receive the fiber bundle probe, a cam driving coupled to the tightening cam, wherein the tightening cam is configured to translate in response to rotation of the cam driving until the tightening cam is blocked, at least one spring extending between the tightening cam and the cam driving, wherein the at least one spring is configured to resist when the cam driving is actuated by rotation and the tightening cam is blocked, and a locking mechanism to lock the cam driving into a selected position.

Description:
BACKGROUND 
     1. Field of the of the Present Disclosure 
     The disclosure relates to an optical probe based on a fiber bundle adapted to be connected to a light injection module and to a connector for such a probe. 
     2. Background Art 
     The Applicant has developed a confocal imaging system based on a fiber bundle probe for in vivo in situ imaging of biological tissues as described for example in U.S. Patent Application 2005/0242298 which is fully incorporated herein by reference. Such a system is, for example, represented schematically on  FIG. 8 . A laser  4  is scanned over a proximal face  112  of the fiber bundle probe  1  which is connected to a light injection module  3  via a connector  2 . The light injection module  3  comprises an objective ensuring that light from the laser is properly injected into each fiber of the fiber bundle probe. Scanning the proximal face of the fiber bundle results in a fiber per fiber injection of light and at a distal end  111  of the bundle in a point per point illumination of an object under observation. As a consequence, each illuminated point of the observed object may re-emit light which is collected and transported back to the proximal end  112  of the fiber bundle via the same fiber and finally transmitted to a detector through the same scanning process. In such a confocal system, the light of the laser is injected fiber per fiber into the whole field of view of the bundle, thereby requiring a high precision in light focusing and resulting in a tolerance of about 2 μm in the probe positioning relatively to the light injection module. 
     Several other systems currently integrate fiber bundles connected to light sources for imaging purposes. For example, U.S. Pat. No. 6,370,422 describes the use of a fiber probe based on a fiber bundle in reflectance imaging. U.S. Pat. No. 6,388,809 discloses an imaging system based on a fiber probe in which the scanning scheme is based on a specific Digital Micro-mirror Device (DMD) scanning architecture wherein each fiber core is addressed by individual mirrors of a DMD matrix. 
     These systems may integrate standard connectors such as Ferrule Connector/Physical Connector (FC/PC) or Sub Miniature A (SMA) connectors between the fiber bundle and the injection module. The longitudinal positioning of these connectors depends on a thread specification that may longitudinally displace about 15 μm. Therefore, using such connectors may require refocusing light and manually repositioning the fiber bundle relative to the light injection module. These manipulations may be done by skilled professionals but are not appropriate for use in a medical environment. In a medical environment, users expect an apparatus to be ready to use in a minimum amount of time and effort. Moreover, these connectors are not adapted to multiple reuse and present risks of scratching the fiber bundle proximal face. 
     The Applicant proposes hereinunder a connector between a fiber bundle probe and a light injection module capable of improving positioning accuracy, repeatability and resistance to shocks and vibrations. The Applicant also proposes a fiber bundle probe adapted to said connector. 
     SUMMARY OF THE CLAIMED SUBJECT MATTER 
     In at least one aspect, embodiments disclosed herein relate to a connector to connect a fiber bundle probe to a light injection module. The connector may include a tightening cam having an opening of a specified shape adapted to receive the fiber bundle probe and a cam driving coupled to the tightening cam, wherein the tightening cam is configured to translate in response to rotation of the cam driving until the tightening cam is blocked. The connector may include at least one spring extending between the tightening cam and the cam driving, wherein the at least one spring is configured to resist when the cam driving is actuated by rotation and the tightening cam is blocked. The connector may also include a locking mechanism to lock the cam driving into a selected position. 
     Other aspects and advantages of the disclosure will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an illustration of a longitudinal section of a connector between a light injection module and a fiber probe according to an embodiment of the present disclosure. 
         FIG. 2  represents a longitudinal section of a fiber probe in contact with a frame of a light injection module according to an embodiment of the present disclosure. 
         FIG. 3   a ,  FIG. 3   b  and  FIG. 3   c  are transverse sections of a connector illustrating several phases a probe locking according to an embodiment of the present disclosure. 
         FIG. 4   a  and  FIG. 4   b  are front and rear perspective views of a connector according to an embodiment of the present disclosure. 
         FIG. 5  represents a fiber probe in contact with a frame of a light injection module according to an embodiment of the present disclosure. 
         FIGS. 6A and 6B  are respectively a longitudinal section and a front view of a tip of a fiber probe according to an embodiment of the present disclosure. 
         FIG. 7  is a longitudinal section of a mount of a fiber probe according to an embodiment of the present disclosure. 
         FIG. 8  is a schematic illustration of a confocal imaging system based on a fiber bundle probe. 
     
    
    
     DETAILED DESCRIPTION 
     Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying Figures. Like elements in the various Figures may be denoted by like numerals. Embodiments of the present disclosure relate an optical probe with a fiber bundle adapted to be connected to a light injection module and to a connector for connecting such a probe to a light injection module. 
       FIG. 1  represents a fiber bundle probe  1 , a light injection module  3  and a connector  2 , according to an embodiment of the present disclosure. The fiber probe  1  is to be brought in contact with the light injection module  3  through the connector  2  along a longitudinal axis Δ. Notably, when the probe is brought in contact with the light injection module, the connector  2 , according to embodiments disclosed herein, may enable tightening the fiber probe against the light injection module with a predetermined amount of coupling force. 
     The fiber bundle probe  1  comprises a fiber bundle  10 , a collar  11 , a mount  12  (e.g., made of stainless steel) and a guiding shoulder  13 . The collar  11 , the mount  12  and the guiding shoulder  13  form the tip of the probe. The (stainless steel) mount  12  may protect the tip of the fiber bundle  10  and collar  11  may enable pressure to be applied by the connector  2  to the probe  1  when the tip of the probe  1  is brought in contact with the light injection module  3  through the connector  2 . The collar may also have a specific shape, for example an oriented slot, to allow the probe  1  to be inserted in the connector  2  at a desired orientation. In another embodiment, the fiber probe  1  may comprise a specific oriented slot. Furthermore, the guiding shoulder  13  may have a tubular shape and may, in one embodiment, allow the attachment of a plastic handle to the probe. The mount  12 , the collar  11  and the guiding shoulder  13  may be coaxially assembled together, the mount  12  being at the extremity of the tip of the probe backed by the collar  11  to which is juxtaposed the guiding shoulder  13 . In another embodiment, the collar may be alternatively placed, for example on the guiding shoulder  13 . The guiding shoulder  13 , the collar  11  and the mount  12 , may comprise a hollow conduit for the fiber bundle to fit inside. The fiber bundle  10  fits inside the hollow conduit and arises at the extremity of the stainless steel mount  12 . An example of a probe according to the disclosure will be described below. 
     In selected embodiments, the fiber probe  1  may be connected to a (tubular) frame  30  of the light injection module  3 . When the fiber probe is connected to the light injection module  3 , a first side of a wall  321  of the frame  30  may act as an end stop for an extremity of the probe. A mount  31 , for example being tubular and comprising at least a lens  33 , may be inserted in the frame  30  close to a second side of the wall  321  for the lens  33  to be close to the probe when the probe is brought in contact with the first side of the wall  321 . The second side of the wall  321  may be in the inner part of the frame  30 . The mount  31  and the at least one lens  33  form an objective. In selected embodiments, the lens  33  may be designed in a mushroom shape. In alternative embodiments, lens  33  may have a conical shape. These varied shapes may allow the objective to be placed at the right longitudinal position where light focus is optimized for each fiber on the whole field of view of the fiber bundle  10 . The wall  321  may comprise a hole  322  and the objective may be centered relatively to the hole  322 . The objective may be used to focus light from a light source (not shown) in the fiber bundle  10 . When the probe is brought in contact with the wall  321 , the fiber bundle  10  may face the hole  322 . The first side of the wall  321  facing the probe  1  may be shaped in order to form a cavity  32 . The cavity  32  may be geometrically adapted to receive both the mount  12  and the collar  11  of the probe  1  and for the fibers of the fiber bundle  10  to face the hole  322  when the mount  12  of the probe is inserted therein. A bottom part of the cavity  32  to receive the mount  12  when the probe is brought in contact with the light injection module may have a cylindrical shape, said cylinder having a diameter of about 10 mm and a length of about 7.2 mm. An upper part of the cavity to receive the collar when the probe is brought in contact with the light injection module may have an equilateral triangular prism shape, an edge of the triangle being of about 13 mm to 14 mm and a length of the prism being of about 3 to 5 mm. 
     The connector  2  may comprise a cam driving  20 , a tightening cam  21  and elastic means  22  coupling the cam driving  20  and the tightening cam  21 . In selected embodiments, the elastic means  22  may include one or more springs arranged tangentially and symmetrically with regard to the longitudinal axis along which the cam driving may be rotationally actuated. When the connector  2  is assembled to the light injection module  3 , the connector  2  covers the wall  321  of the frame  30 . The cam driving  20  and the tightening cam  21  respectively comprise a cam driving opening  26  and a tightening cam opening  25  for the tip of the probe  1  to be inserted through the connector in the light injection module  3 . 
     In selected embodiments, at least one of the tightening cam opening  25  and the cam driving opening  26  may be adapted to enable orientating the probe longitudinally by, for example, having a specified shape corresponding to the shape of the collar  11 . This may enable to determine how to insert the probe  1  into the connector  2 . For example, the tightening cam  21  may have a triangular opening of certain dimensions and the collar  11  on the probe may have a plain triangular shape of same dimensions. In selected embodiments, the collar may have a rhombical shape. In alternative embodiments, the collar  11  may have an equilateral triangular shape. When the oriented slot and the tightening cam opening  25  have an equilateral triangular corresponding shape, the probe  1  may be inserted in the connector  2  according to three possible orientations along the longitudinal axis Δ. Additional geometric elements may be added to determine a preferred orientation among the three orientations. 
     The cam driving  20  may be actuated by a rotation relative to the longitudinal axis Δ. The elastic means  22  may couple the tightening cam  21  and the cam driving  20  so that rotation of the cam driving  20  rotates the tightening cam  21  and causes the tightening cam  21  to move towards the wall  321 , thereby pushing on the collar  11  and squeezing the probe against the wall  321  of the frame  30 . Turning the cam driving  20  may cause the tightening cam  21  to move helically towards the frame  30  so that when the tightening cam  21  and the collar are in contact, the triangular shapes of the tightening cam opening  25  and of the collar  11  do not match. Thus, the tightening cam may push on the collar. This may be performed using helical grooves  27  drawn on the tightening cam  21  and pins or screws mechanically coupling the tightening cam  21  and the frame  30  through said helical grooves. In selected embodiments, the cam driving  20  may translate together with the tightening cam  21 . 
     In alternative embodiments, the cam driving  20  may not translate together with the tightening cam  21 . When the movement of the tightening cam  21  is blocked, for example because of a contact between the tightening cam and the collar  11  of the probe  1  inserted in the cavity  32 , a rotation of the cam driving  20  may further drive the tightening cam  21  and therefore may cause the elastic means  22  to strain. The elastic means  22  may establish a linearly increasing elastic force during the squeezing of the tip of the probe  1  on the frame  30 . The elastic means  22  may also allow a repeatable force to be applied to lock the probe longitudinally. In selected embodiments, the elastic means  22  may be arranged in order to first unfold when the tightening cam  21  translates and then to start straining when the tightening cam  21  arrives in a position where it should be in contact with the collar  11  of the probe  1  if the probe was inserted in the connector  2 . Further, blocking the elastic means  22  by for example blocking the cam driving  20  on a determined tightening position, may result in applying a constant tightening force to the locking. This may, for example, ensure a strong mechanical resistance to shocks and vibrations and increase repeatability of the probe  1  positioning. A locking device (not shown) may then ensure locking of the connector  2 . This may allow the probe  1  to stay at an operating position and may ensure that a preliminary calibration process remains valid during a use of the probe  1  with an imaging system. In an embodiment, the probe  1  is plugged in the cavity  32  through the connector  2  assembled to the light injection module  3 , the tightening cam  21  performs an helical movement when the cam driving  20  is actuated and a distance between the extremity of the probe and the collar  11  may be adapted for the tightening cam  21  to come into contact with the collar  11  when the tightening cam has turned of about 180°. 
       FIG. 2  depicts the tip of the fiber bundle probe  1  in contact with the frame  30  of the light injection module; the connector ( 2  from  FIG. 1 ) is not shown in  FIG. 2 . As shown, the mount  31  inserted in the frame  30  comprises a conical lens  34 . In another embodiment (e.g., in  FIG. 1 , above), the lens may have a mushroom shape. The wall  321  of the frame  30  may comprise a centered hole and the thickness of the wall  321  around the hole may be about 1 mm to resist deformations. In order to properly inject light in the fibers of the fiber bundle  10 , the surface of the last lens  34  of the objective  31  may be placed at a distance of around 0.5 mm from the fiber bundle surface corresponding to a working distance of said objective  31 . The objective  31  may be adjusted close to the inner side of the wall of the frame  321  and the lens may be designed in a conical shape. This design allows the objective  31  (or lens  34 ) to be close to the fibers of the bundle and light to focus correctly on a plane corresponding to a face of the bundle. 
       FIGS. 3A to 3C  illustrate several phases of the probe connection according to embodiments of the present disclosure. Element  23  is a male projection of a locking device placed on the cam driving  21 . Element  24  is a corresponding female receptacle part of the locking device placed on a support of the frame (not shown). The locking device enables to lock the cam driving  21  into a determined tightening position. It may therefore allow one to intuitively determine when a probe is properly positioned with respect to the light injection module. In selected embodiments, the locking device may be any of push-lock device, a push-push device and a push-eject device. Such configurations allow for the easy and intuitive unlocking of the probe from the light injection module. The cam driving opening  26  may be wide, and the cam driving  20  may have a substantially circular shape. 
       FIG. 3A  represents an unlocked position of the connector  2 . The male part  23  of the locking device is down, the tightening cam opening  25  is aligned with the hole of the frame (not shown) and the springs  22  are not strained. In this position, a fiber probe  1  having a collar  11  whose shape corresponds to the shape of the tightening cam opening  25  may be brought in contact with the wall  321  of the frame  30  and plugged in the cavity  32 . 
       FIG. 3B  represents an intermediate phase of the probe  1  connection. In this phase, the cam driving  20  may be turned, resulting in a movement of the tightening cam  20  towards the frame  30 . The cam driving  20  stays in a plane. The tightening cam  21  may be progressively brought in contact of the collar  11  of the probe  1  in this phase. The tightening cam  21  may perform a helical movement so that when the tightening cam  21  and the collar  11  are to be in contact, the triangular shapes of the tightening cam  21  and of the collar  11  do not match, enabling the tightening cam  21  to push on the collar. When the movement of the tightening cam  21  may be blocked by a contact with the collar  11  of the probe  1  and the cam driving  20  is further turned, the tightening cam  21  may push on the collar  11  resulting in squeezing the tip of the probe  1  against the frame with a linearly increasing elastic force due to springs  22  straining.  FIG. 3B  represents an intermediate phase before a contact between the tightening cam  21  and the collar  11  of the probe. The springs  22  may be unfolded along a helical movement (not shown), following the movement of the tightening cam  21 . 
       FIG. 3C  represents a locked position of the connector  2 . In this position, the male and female part of the locking device may block the cam driving  20  in a tightening position. This position may be determined to allow the tightening cam  21  to enter in contact with the collar  11  and to push the probe  1  on the frame, resulting in straining the springs  22  with a determined force. Blocking the system on the tightening position may allow a determined constant force to squeeze the fiber probe  1  on the frame of the objective. This constant force may depend on the spring rate and on the tightening position determined by the position of the female locking device  24 . 
       FIGS. 4A and 4B  depict front and back perspective views of the connector  2  in accordance with embodiments disclosed herein. The opening  25  of the tightening cam  21  may have a triangular shape. The male and female parts  23  and  24  of the locking device may form a push-lock device. Helical grooves  27  may be used to receive pins and to couple the tightening cam  21  to the frame  30 . In selected embodiments, the cam driving  21  may be actuated by a motor. 
       FIG. 5  depicts a fiber probe  1  in contact with an advanced frame  35  (connector  2  not shown). In this embodiment, a linear micro-motor  38  may be added to automatically translate a mount  36  relative to a wall of frame  35 . A soft spring  37  may permit the mount to perform a movement back towards an opposite direction. 
     A fiber probe according to the present disclosure is now described in reference to  FIG. 6A ,  FIG. 6B  and  FIG. 7 . 
     The probe according to embodiments in accordance with the present disclosure may comprise a fiber bundle  10  protected by a ferrule  123  mounted in a hollow conduit of a mount  12  made of, for example, stainless steel. It may also comprise a collar  11  having a shape adapted to a geometry of an opening in the connector so as to act as a orienting slot. Advantageously, the shape of the collar  11  may be a triangle, the corners of which may be rounded, as shown proximate to item  11  in  FIG. 6B . According to embodiments disclosed herein, an end of the probe may be polished resulting in a polished surface  121  that may be brought in contact with the frame of the light injection module when the probe is inserted in the connector. The polishing may be performed using known polishing techniques to obtain the polished surface  121  with a flatness of less than 2.5 μm over a surface of a diameter of around 10 mm. A tilt of the polished surface may be of less than 0.19° using specific tools developed specifically for the polishing. In selected embodiments, the ferrule  123  may be made of a material having substantially the same mechanical properties than the fiber bundle in order to ease the polishing. In alternative embodiments, the fiber bundle  10  may be mounted directly in the hollow conduit of the mount  12 . The mount  12  may have a cylindrical shank and a flat ogive tip, the collar  11  may have an equilateral triangular prism shape. In selected embodiments, a length Lh between the polished end of the probe  121  and the triangular collar may be about 7.2 mm, a diameter D 1  of the flat tip of the probe may be about 6.4 mm, a large diameter D 2  of the mount may be about 10 mm, a total length Lt of the mount including the collar  11  may be about 11.6 mm, and the collar may have a length of about 4.4 mm. 
     Embodiments disclosed herein may also relate to an imaging system comprising a light source, a fiber bundle probe according to the present disclosure, connected to a light injection module using the connector as described above. In an embodiment, the imaging system further comprises a laser isolator such as a quarter-wave plate. This may prevent interference between a face of the bundle and an optical cavity of the light source, particularly when the light source is a laser with a large coherence length. 
     While the disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the disclosure as disclosed herein. Accordingly, the scope of the disclosed invention should be limited only by the attached claims.