Abstract:
A first metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size, and determining a dimension of a target object by comparing the aligned image to the target object. A second metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size by synchronously adjusting a zoom factor for projecting the first image and an angle for projecting the second image, and determining a dimension of a target object by comparing the aligned image to the target object.

Description:
This application is a continuation of U.S. patent application Ser. No. 13/448,429, filed Apr. 17, 2012, which claims the benefit of and priority to U.S. Provisional Patent Application No. 61/487,750, filed May 19, 2011, the entire disclosure of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a method for measuring a dimension of a target site. More particularly, the present disclosure relates to a method of triangulation for creating an image of a predetermined size for use in measuring a dimension of a target site. 
     2. Background of the Related Art 
     Minimally invasive surgery, e.g., laparoscopic, endoscopic, and thoroscopic surgery, has many advantages over traditional open surgeries. In particular, minimally invasive surgery eliminates the need for a large incision, thereby reducing discomfort, recovery time, and many of the deleterious side effects associated with traditional open surgery. 
     The minimally invasive surgeries are performed through small openings in a patient&#39;s skin. These openings may be incisions in the skin or may be naturally occurring body orifices (e.g., mouth, anus, or vagina). In general, insufflation gas is used to enlarge the area surrounding the target surgical site to create a larger, more accessible work area. 
     During minimally invasive procedures, it is often difficult for a surgeon to determine sizes of various organs, tissues, and other structures in a surgical site. Various in-situ surgical metrology methods exist for measurement in a surgical site. Such methods require many moving parts and projection images that change size and/or focus quickly as projectors move in or out of a surface of projection. A continuing need exists for in-situ surgical metrology methods that operate with a stable focus and no moving parts. 
     SUMMARY 
     A first metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size by moving an instrument towards and away from a target object, and determining a dimension of a target object by comparing the aligned image to the target object. The aligned image may include aligned circles. The aligned image may include a single point aligned with a center point of a circle. The projecting of at least one of the first image and second image may be achieved by a point source projector. A single beam may be split to project the first image and the second image. 
     A second metrology method includes the steps of projecting a first image and a second image, aligning the first image and the second image to form an aligned image of a known size by synchronously adjusting a zoom factor for projecting the first image and an angle for projecting the second image, and determining a dimension of a target object by comparing the aligned image to the target object. The aligned image may include aligned circles. The aligned image may include a single point aligned with a center point of a circle. The projecting of at least one of the first image and second image may be achieved by a point source projector. A single beam may be split to project the first image and the second image. 
     In other embodiments the metrology system may be a standalone device, while projected pattern is observed through a separate endoscope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a side, schematic view of a metrology system according to the principles of the present disclosure; 
         FIG. 2  is a side, schematic view of a projector of the metrology system of  FIG. 1 ; 
         FIG. 3  is a side, perspective view of a method of use of the metrology system of  FIG. 1 ; 
         FIG. 4  is a side, schematic view of a metrology system according to another embodiment of the present disclosure; 
         FIG. 5  is a side, schematic view of a metrology system according to another embodiment of the present disclosure; and 
         FIG. 6  is a side, perspective view of a method of use of the metrology system of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
     Like reference numerals may refer to similar or identical elements throughout the description of the figures. As shown in the drawings and described throughout the following description, as is traditional when referring to relative positioning on a surgical instrument, the term “proximal” refers to the end of the apparatus which is closer to the user and the term “distal” refers to the end of the apparatus which is farther away from the user. The term “clinician” refers to any medical professional (i.e., doctor, surgeon, nurse, or the like) performing a medical procedure involving the use of embodiments described herein. 
     As seen in  FIG. 1 , a metrology system  10  according to an embodiment of the present disclosure is illustrated. Metrology system  10  utilizes projectors  100  for projecting light beams  110  at intersecting angles. Projectors  100  include a projector  100   a  and a projector  100   b . Some embodiments may utilize more than two projectors  100 . Other embodiments may only have one projector  100 , as will be described in greater detail hereinbelow. In metrology system  10 , projector  100   a  and projector  100   b  are substantially identical and project substantially identical light beams  110   a ,  110   b , respectively. 
     Light beams  110  form an image  120  including an image  120   a  from light beam  110   a  and an image  120   b  from light beam  110   b . Images  120   a ,  120   b  substantially align to form a substantially aligned image  122  having a predetermined size on an image plane p 2  at a distance d 2  from point sources  102  ( FIG. 2 ) of projectors  100 . Image plane p 2  is the only image plane on which images  120   a ,  120   b  align. On an image plane p 1  at a distance d 1  less than distance d 2  from point sources  102  of projectors  100 , an unaligned image  121  is formed. Likewise, on an image plane p 3  at a distance d 3  greater than distance d 2  from point sources  102  of projectors  100 , an unaligned image  123  is formed. Distance d 2  may be calculated geometrically using a distance between point sources  102  and angles of projectors  100 . Distance d 2  may also be determined experimentally. Similarly, the predetermined size of aligned image  122  may be determined geometrically or experimentally. 
     Images  120   a ,  120   b  may be any shapes appropriate for determining an alignment of thereof. For example, images  120   a ,  120   b  may be circles that concentrically overlap on image plane p 2 . Images  120   a ,  120   b  have uniformly spaced markings. In other embodiments, an endoscope or other device may provide uniformly spaced markings. When image  122  is formed, the uniformly spaced markings have a predetermined distance therebetween to assist in determining a measurement of a dimension on image plane p 2 . The predetermined distance of the uniformly spaced markings may be determined geometrically or experimentally. Although images  120   a ,  120   b  are substantially identical in metrology system  10 , other embodiments may have differing shapes of images  120   a ,  120   b.    
     As seen in  FIG. 2 , a projector  100  includes a point source  102  and a mask  104 . Point source  102  emits a light beam  110 . Various embodiments of point source  102  include a laser diode, a light-emitting diode, and a lens for shaping a beam of light. Mask  104  is positioned between point source  102  and the target site. Mask  104  has a pattern  106  disposed thereon in a shape of a desired image  120 , such as a series of concentric, uniformly spaced circles. Light beam  110  may be collimated for increased sharpness of image  120 . Light beam  110  is partially blocked upon incidence with mask  104 . A portion of light beam  110  that passes through mask  104  forms a magnified pattern  116  as a portion of image  120 . 
     A magnification factor of pattern  106  to pattern  116  is calculated according a formula: M=1+x b /x a , where M is the magnification factor, x a  is a distance between point source  102  and mask  104 , and x b  is a distance between mask  104  and the target site. Accordingly, image  120  may be enlarged when x b  is increased or x a  is decreased. Image  120  may shrink upon an increase of x a  or a decrease of x b . Mask  104  may be translated with respect to the target site to increase or decrease x a  and x b . Metrology system  10  may be translated to increase or decrease x b . Point source  102  is sufficiently small for edges of image  120  to remain substantially sharp as a size of image  120  changes. 
     A method of use of metrology system  10  will now be described. As seen in  FIG. 3 , metrology system  10  may be attached to a distal end of an endoscope “E”. Endoscope “E” is inserted into a body cavity “C” through an opening in a tissue “T”. Endoscope “E” may be inserted through a seal anchor “R” positioned in the opening in tissue “T”. Projectors  100  project image  120  onto a target site “S” within cavity “C”. A clinician may observe image  120  through endoscope “E”. If images  120   a ,  120   b  are not aligned, endoscope “E” is translated distally or proximally until point sources  102  of projectors  100  are at distance d 2  from target site “S”. Once aligned image  122  is formed on target site “S”, the predetermined size of aligned image  122  and the predetermined distance of the uniformly spaced markings thereon may be used to measure a dimension of target site “S”. A dimension of target site “S” is measured by visually inspecting and counting a number of uniformly spaced markings appearing along the dimension of target site “S”. The number of uniformly spaced markings is multiplied by the predetermined distance therebetween to calculate the measure of the dimension of target site “S”. 
     Turning to  FIG. 4 , a metrology system in accordance with an alternate embodiment of the present disclosure is generally designated as  20 . Metrology system  20  is similar to metrology system  10  and thus will only be discussed as necessary to identify the differences in construction and operation thereof. 
     Metrology system  20  has a projector  200 , a splitter  212 , and a reflector  214 . Projector  200  is substantially identical to projector  100  ( FIG. 2 ) and projects a light beam  210 . Splitter  212  splits light beam  210  into light beams  210   a ,  210   b . Embodiments of splitter  212  include prisms and mirrors. Light beam  210   a  passes through splitter  212 . Light beam  210   b  is reflected by splitter  212  onto reflector  214 . Reflector  214  reflects light beam  210   b  at an angle {acute over (α)} for intersection with light beam  210   a.    
     Light beams  210  form a substantially aligned image  222  on an image plane p 2  at a distance d 2  from a point source of projector  200 . Image plane p 2  is the only image plane on which a substantially aligned image is formed. Light beams  210  project a pattern having uniformly spaced markings onto image plane p 2 . Distance d 2 , a distance of the uniformly spaced markings, and a size of aligned image  222  may be determined geometrically or experimentally. 
     Light beams  210  produce images of any shapes appropriate for determining an alignment of thereof. In some embodiments, a total overlap of certain elements of the images of light beams  210  may not occur due to light beam  210   a  travelling a shorter total distance than light beam  210   b  to reach image plane p 2 . In such embodiments, an alignment of a point or a line may be an ideal indicator of alignment. For example, light beam  210   a  may project a circle with a center point, and light beam  210   b  may project a single point for aligning with the center point of the image projected by light beam  210   a.    
     A method of use of metrology system  20  is substantially identical to the method of use of metrology system  10  described hereinabove. 
     Turning to  FIG. 5 , a metrology system in accordance with an alternate embodiment of the present disclosure is generally designated as  30 . Metrology system  30  is similar to metrology system  20  and thus will only be discussed as necessary to identify the differences in construction and operation thereof. 
     Metrology system  30  includes a projector  300 , a splitter  312 , a reflector  314 , and an actuator  330  ( FIG. 6 ). Projector  300  includes a point source  302  and a mask  304 . Mask  304  is a distance x an  away from point source  302  and distances x bn  away from image planes p n . Point source  302  emits a light beam  310  that passes through a pattern  306  on mask  304 . Splitter  312  splits light beam  310  into light beams  310   a ,  310   b . Light beam  310   a  passes through splitter  312  and forms a first image on an image plane p n . Light beam  310   b  is reflected by splitter  312  onto reflector  314 . Reflector  314  is rotatable to reflect light beam  310   b  at any of angles α n  onto image planes p n  to form a second image. The first image and the second image form a substantially aligned image  322  on an image plane p n  having a distance d n  from point source  302  when reflector  314  reflects light beam  310   b  at a particular angle {acute over (α)} n . For each image plane p n , only angle α n  provides for a projection of substantially aligned image  322 . Substantially aligned image  322  has a magnified pattern  316  thereon. Magnified pattern  316  is a magnification of pattern  306  and includes uniformly spaced markings thereon having a predetermined distance on image plane p n . 
     Actuator  330  is operably coupled to mask  304  and reflector  314 . A manipulation of actuator  330  rotates reflector  314 , thus changing an angle α n  and an image plane p n  on which aligned image  322  is formed. Actuator  330  translates mask  304  a distance to maintain a predetermined size of image  322 . The translation of mask  304  and the rotation of reflector  314  are synchronous upon a manipulation of actuator  330 . A relationship between the translation of mask  304  and the rotation of reflector  314  is described according to the following formulas:
 
 d   2   /d   1 =tan(α 1 )/tan(α 2 )= M   1   /M   2  
 
 M= 1+ x   b   /x   a  
 
 d=x   a   +x   b  
 
     In the formulas above, the values of d 1 , α 1 , and M 1  respectively represent an initial distance d n , angle α n , and magnification M n  of system  30 . The values of d 2 , α 2 , and M 2  respectively represent a resulting distance d n , angle α n , and magnification M n  of system  30  after actuator  330  is manipulated. 
     A method of use of metrology system  30  is similar to the method of use of metrology system  10  described hereinabove. As seen in  FIG. 6 , metrology system  30  is attached to a distal end of an endoscope “E”. Endoscope “E” is inserted into a body cavity “C” through an opening in a tissue “T”. Projector  300  projects light beams  310   a ,  310   b  onto a target site “S” within cavity “C”. A clinician may observe an image formed by light beams  310   a ,  310   b  through endoscope “E”. If substantially aligned image  322 , is not formed on target site “S”, actuator  330  is rotated until substantially aligned image  322  is formed on target site “S”. The predetermined size of substantially aligned image  322  and the uniformly spaced markings of magnified pattern  316  may then be used to measure a dimension of target site “S”. 
     It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications and variances. The embodiments described with reference to the attached drawing figs. are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods and techniques that are insubstantially different from those described above and/or in the appended claims are also intended to be within the scope of the disclosure.