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 fig1 , 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 ( fig2 ) 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 fig2 , 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 fig3 , 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 fig4 , 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 ( fig2 ) 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 fig5 , 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 ( fig6 ). 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 : 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 fig6 , 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 .
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 .