Abstract:
A system and method is presented for performing optical measurements, including a light source configured to emit a light beam, a first pattern generator defining a first longitudinal axis and configured to project a first generated pattern, and a second pattern generator defining a second longitudinal axis and configured to project a second generated pattern. The first and second generated patterns have different angular divergency. The first pattern generator is a diffractive circle pattern generator, whereas the second pattern generator is a diffractive cross pattern generator. Adjustment of the first and second generated patterns with respect to each other cause the system to serve as an optical ruler for performing the optical measurements when the first and second generate patterns overlap or coincide with each other at certain points.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/777,000, filed Mar. 12, 2013, the entire disclosure of which is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a system and method for measuring a dimension of a target site. More particularly, the present disclosure relates to a system and method of projecting an image for use in measuring a dimension of a target site. 
         [0004]    2. Background of the Related Art 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. Thus, a continuing need exists for in-situ surgical metrology methods that operate with a stable focus and no moving parts. 
       SUMMARY 
       [0008]    The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is intended to neither identify key or critical elements of the claimed subject matter nor delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later. 
         [0009]    A system for performing optical measurements is presented. The system includes a light source configured to emit a light beam, a first pattern generator defining a first longitudinal axis and configured to project a first generated pattern, and a second pattern generator defining a second longitudinal axis and configured to project a second generated pattern. The first and second generated patterns have different angular divergency. 
         [0010]    In an exemplary embodiment, the light source is a laser. 
         [0011]    In another exemplary embodiment, the first pattern generator is a diffractive circle pattern generator, whereas the second pattern generator is a diffractive cross pattern generator. 
         [0012]    In yet another exemplary embodiment, the first pattern generator is located between the light source and the second pattern generator. 
         [0013]    In an exemplary embodiment, the first pattern generator is positioned at a first distance with respect to the light source and the second pattern generator is positioned at a second distance with respect to the light source, the second distance being greater than the first distance. 
         [0014]    In another exemplary embodiment, the first and second generated patterns are projected onto a target site in an overlapping manner. 
         [0015]    In yet another exemplary embodiment, the first generated pattern is a circle and the second generated pattern is a cross-hair that is adjusted with respect to the circle based on the distance of the system relative to the target site. Additionally, adjustment of the first and second generated patterns with respect to each other cause the system to serve as an optical ruler for performing the optical measurements when the first and second generated patterns overlap. 
         [0016]    In an exemplary embodiment, the first and second longitudinal axes are parallel to each other and are offset from each other by a predetermined distance to create the different angular divergency of the first and second generated patterns. 
         [0017]    Moreover, the system is configured to be mounted on a surgical device. 
         [0018]    In another embodiment, a surgical instrument is presented including a handle portion, a body portion extending distally from the handle portion and defining a longitudinal axis, an end effector assembly disposed at a distal end of the body portion and an optical measurement system. The optical measurement system includes a beam delivery element for projecting a beam along an illumination path and onto a plane and first and second diffractive optical elements positioned along the illumination path of the beam delivery device, the first and second diffractive optical elements configured to project first and second generated patterns, in an overlapping manner, onto the plane, and having different angular divergency. 
         [0019]    In an embodiment, the beam delivery element is a laser. 
         [0020]    In another embodiment, the first diffractive optical element is a diffractive circle pattern generator and the second diffractive optical element is a diffractive cross pattern generator. 
         [0021]    In yet another exemplary embodiment, the first diffractive optical element is located between the light source and the second diffractive optical element. 
         [0022]    In another embodiment, the first generated pattern is a circle and the second generated pattern is a cross-hair that is adjusted with respect to the circle based on the distance of the optical measurement system relative to the target site. Additionally, adjustment of the first and second generated patterns with respect to each other cause the optical measurement system to serve as an optical ruler for performing optical measurements when the first and second generated patterns overlap. 
         [0023]    In another embodiment, a method of performing optical measurements is presented. The method includes the steps of mounting an optical measurement system onto a surgical instrument, projecting a beam along an illumination path and onto a plane, via a beam delivery element, positioning first and second diffractive optical elements along the illumination path, and projecting first and second generated patterns, in an overlapping manner, onto the plane, and having different angular divergency, via the first and second diffractive optical elements. 
         [0024]    Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present disclosure will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    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: 
           [0026]      FIG. 1  is a side, schematic view of a metrology system; 
           [0027]      FIG. 2  is a side, perspective view of a method of use of the metrology system of  FIG. 1 ; 
           [0028]      FIG. 3  is a side, schematic view of a metrology system, according to another embodiment; 
           [0029]      FIG. 4  is a schematic view of a pattern projection metrology system, according to an embodiment of the present disclosure; 
           [0030]      FIG. 5  is a schematic view of a projection system used in metrology with an axial location of a light source, according to an embodiment of the present disclosure; 
           [0031]      FIG. 6  is a schematic view of the optical measurement system having a laser and two diffractive elements, in accordance with another embodiment of the present disclosure; 
           [0032]      FIG. 7  is a schematic view of generated patterns based on the distance of the optical measurement system from the target site, in accordance with an embodiment of the present disclosure; 
           [0033]      FIG. 8  is a side view of the optical measurement system mounted on a surgical instrument, in accordance with an embodiment of the present disclosure; 
           [0034]      FIG. 9  is a perspective view of the optical measurement system mounted on a surgical instrument of  FIG. 8 , in accordance with an embodiment of the present disclosure; 
           [0035]      FIG. 10  is a schematic view of the projected patterns created by various locations of the surgical instruments of  FIGS. 8 and 9 , in accordance with an embodiment of the present disclosure; 
           [0036]      FIG. 11  is a schematic view of the cross hair depicting tick marks to provide reading of the circle diameter, in accordance with an embodiment of the present disclosure; 
           [0037]      FIG. 12  is a graph illustrating pattern sizes as a function of distance of the projection system from the surgical site, in accordance with an embodiment of the present disclosure; 
           [0038]      FIG. 13  provides for a calculation of a tick mark on a cross-hair pattern for reading a circle diameter, in accordance with an embodiment of the present disclosure; and 
           [0039]      FIG. 14  is a schematic diagram of an optical measurement system having at least one moving diffractive element, in accordance with an embodiment of the present disclosure. 
       
    
    
       [0040]    The figures depict preferred embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the present disclosure described herein. 
       DETAILED DESCRIPTION 
       [0041]    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. 
         [0042]    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. 
         [0043]    The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. The word “example” may be used interchangeably with the term “exemplary.” 
         [0044]    Reference will now be made in detail to embodiments of the present disclosure. While certain embodiments of the present disclosure will be described, it will be understood that it is not intended to limit the embodiments of the present disclosure to those described embodiments. To the contrary, reference to embodiments of the present disclosure is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the embodiments of the present disclosure as defined by the appended claims. 
         [0045]    As seen in  FIG. 1 , a metrology system  10  includes a point source projector  100  having a point source light emitter  102  and a mask  104 . Mask  104  is at a distance, d 1 , from point source light emitter  102  and a distance, d 2 , from a target site “S.” Mask  104  is semi-transparent and has a substantially opaque mask pattern  106  thereon. Mask pattern  106  has markings of known distances therebetween. For example, mask pattern  106  may be a series of uniformly spaced concentric circles. Mask  104  may be translatable toward or away from point source light emitter  102 . 
         [0046]    Point source light emitter  102  emits a light beam  120  therefrom. Light beam  120  approximates a point at point source light emitter  102  and conically diverges therefrom at an angle α. Point source light emitter  102  may be any device capable of emitting light from a narrow point, such as a laser diode or an LED. Light beam  120  is partially blocked by mask pattern  106  upon incidence with mask  104 . An unblocked portion  122  of light beam  120  continues past mask  104  to reach target site “S.” Unblocked portion  122  creates a magnified pattern  116  on target site “S.” Magnified pattern  116  is magnified from mask pattern  106  according to formula: M=1+d 2 /d 1 , where, M, is a magnification factor between mask pattern  106  and magnified pattern  116 . A translation of mask  104  or point source projector  100  away from target site “S” increases magnification factor M. A translation of mask  104  or point source projector  100  toward target site “S” decreases magnification factor M. Magnified pattern  116  retains a substantially sharp focus as mask  104  and/or point source projector  100  is translated. 
         [0047]    A method of use of metrology system  10  is depicted in  FIG. 2 . Metrology system  10  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.” Endoscope “E” may be inserted through a seal anchor “R” positioned within the opening in tissue “T.” Endoscope “E” is inserted through a port in seal anchor “R” that is expanded to a width greater than a maximum combined width of endoscope “E” and point source projector  100 . Once the distal end of endoscope “E” is distal to seal anchor “R,” the port resiliently compresses to form a substantially airtight seal around endoscope “E.” Point source projector  100  is translated distally toward target site “S” until point source projector  100  arrives at a known distance, d, from target site “S.” The arrival of point source projector  100  at distance, d, may be determined through any appropriate means, such as triangulation. Distance, d 1 , may be fixed prior to insertion of endoscope “E.” Alternatively, endoscope “E” may include a mechanism, such as a rotatable knob (not shown), for altering distance d 1 . Distance, d 2 , is calculated by subtracting distance, d 1 , from distance d. Distance, d 1 , and distance, d 2 , may then be used to calculate magnification factor M. 
         [0048]    Point source projector  100  projects magnified pattern  116  onto target site “S.” A clinician may observe magnified pattern  116  through endoscope “E.” A dimension of target site “S” is measured by visually inspecting and counting a number, n, of uniformly spaced markings appearing along the dimension of target site “S.” The number, n, of uniformly spaced markings is multiplied by a uniform distance between individual markings of pattern  116 . The uniform distance between individual markings of pattern  116  is calculated by multiplying a uniform distance, d k , between individual markings of mask  104  by magnification factor M. Thus, a measure of the dimension of target site “S” is calculated according to formula: x=nMd k , where, x, is the measure of the dimension. 
         [0049]    Turning to  FIG. 3 , 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. 
         [0050]    Metrology system  20  includes a point source projector  200  having a light source  202 , a mask  204 , and a lens  208 . Mask  204  has a mask pattern  206 . Light source  202  emits a light beam  220  toward lens  208 . Lens  208  is a converging lens that focuses light beam  220  into a point  226 . Point  226  is a distance d 1  away from mask  204 . Light beam  220  diverges at an angle, α, from point  226  and is partially blocked by mask  204 . An unblocked beam  222  passes through mask  204  and travels a distance, d 2 , to a target site “S” to form a magnified pattern  216  thereon. 
         [0051]    Referring to  FIG. 4 , a schematic view of a pattern projection metrology system  300  is presented. 
         [0052]    The metrology system  300  includes a surgical instrument  310  having a laser diode  315  positioned at a distal end thereof. The laser beams  317  emitted from the laser diode  315  are received by an optical diffuser  320  that diffuses two beams  330  onto, for example, an organ  340 . The optical diffuser  320  further causes a light pattern  345  to be projected onto the organ  340 . The light pattern  345  may be, for example, a series of concentric circles. The surgical instrument  310  may be used for laparoscopic procedures. The surgical instrument  310  is designed to satisfy certain criteria. For example, the laser diode  315  may be adapted and dimensioned to be fixedly secured to the shaft portion of the surgical instrument  310 . Additionally, in a triangulation system, two or more beams may be received from different angles, which is usually achieved by keeping light sources (e.g., laser beams) apart from each other in a direction orthogonal to the axis of projection due to the small diameters of the shafts of the surgical instruments  310 , as will be discussed in further detail below with reference to  FIG. 5 . 
         [0053]    Referring to  FIG. 5 , a schematic view of a projection system  400  used in metrology with an axial location of a light source is presented. 
         [0054]    The projection system  400  includes a first light source  410  and second light source  420 . The two light sources  410  and  420  are located along an axis of projection  415 . Point source light emitter  410  emits a light beam  411  therefrom. Light beam  411  approximates a point at point source light emitter  410  and conically diverges from an angle of projection at an angle α. Point source light emitter  410  may be any device capable of emitting light from a narrow point, such as a laser diode or an LED. Point source light emitter  420  emits a light beam  421  therefrom. Light beam  421  approximates a point at point source light emitter  420  and conically diverges from an angle of projection at an angle β. Point source light emitter  420  may be any device capable of emitting light from a narrow point, such as a laser diode or an LED. 
         [0055]    The second light beam  421  located at a distal end of a surgical instrument  310  (as shown in  FIG. 4 ), has a larger angle, β, whereas the first light beam  411 , located at a proximal end of a surgical instrument  310 , has a smaller angle, α. As noted in  FIG. 5 , the light sources  410 ,  420  are positioned axially on the same axis  415 , such that the light beams  411 ,  421  are coincident with the axis  415 . Light beams  411 ,  421  are partially blocked by mask pattern or image plane  430  upon incidence with plane  430 . An unblocked portion of light beams  411 ,  421  continues past plane  430  to reach a target site “S.” The unblocked portion creates a magnified pattern  440  on target site “S.” The pattern  440  may be a series of concentric circles or a cross-hair  441  with a plurality of marks  443 . One skilled in the art may contemplate a plurality of different patterns to be projected having a number of different tick marks. The exemplary embodiments of the present disclosure are not limited by the shape or size of the projected patterns. 
         [0056]    Referring to  FIG. 6 , a schematic view of an optical measurement system  500  having two diffractive elements  540 ,  550 , in accordance with an embodiment of the present disclosure is presented. 
         [0057]    In the system  500 , a point source light emitter  510  emits a light beam  511  therefrom. A first portion of light beam  511  is received by a diffractive circle pattern generator  520  located at a proximal end of, for example, a surgical instrument. A second portion of the light beam  511  is received by a diffractive cross-pattern generator  530 . The light beam  521  emitted from the diffractive circle pattern generator  520  conically diverges therefrom at an angle, a. The light beam  531  emitted from the diffractive cross-pattern generator  530  conically diverges therefrom at an angle, b. 
         [0058]    Light beam  521  is partially blocked by image plane  540  upon incidence with plane  540 , whereas light beam  531  is partially blocked by at least image plane  550  upon incidence with plane  550 . Unblocked portions of light beams  521 ,  531  continue past planes  540 ,  550  to reach a target site. Unblocked portions create a magnified pattern  560  on the target site. The magnified pattern  560  may include a circle  562  having an outer perimeter greater than the outer perimeters of the image planes  540 ,  550 . 
         [0059]    Image pattern  550  is a distance, l a , from the first diffractive pattern generator  520  and a distance, l, from a target site “S” or from the third plane  560 . Additionally, the image pattern  550  is a distance, l b , from the second diffractive pattern generator  530 . Thus, the first pattern generator  520  is located between the light source and the second pattern generator  530 . This results in the first pattern generator  520  being positioned at a first distance with respect to the light source and the second pattern generator being positioned at a second distance with respect to the light source, the second distance being greater than the first distance. 
         [0060]    Therefore, as shown in  FIG. 6 , the projection system includes a laser  510  and two diffractive optical elements  520 ,  530  having different angular divergency (a and b). The first diffuser  520  receives a portion of the laser beam  511  and the other diffuser  530  receives the remaining portion of the laser beam  511 . Since angular divergences (a and b) are different, patterns are overlapped in a space in such a way that they have equal size only at a location B, on image plane  550 , as depicted in  FIG. 6 . At longer distances, the cross pattern  624  becomes larger than the circle pattern  622 , whereas at shorter distances the cross pattern  624  becomes smaller than the circle pattern  622 . At location B, on image plane  550 , they have the same exact size or, stated differently, they have the same pre-engineered size (a o =b o ), where the patterns  562 ,  564  provide accurate measurements, thus allowing the system  500  to act as an accurate optical ruler. Therefore, the medical professional needs to move the surgical instrument  510  such that the circle pattern  562  and the cross pattern  564  coincide or overlap with each other in order to obtain accurate measurements of the object (e.g., an organ) to be measured. Stated differently, the end points of the cross hair align with the outer periphery of the circle for optimizing measurements of target sites, such as an organ. 
         [0061]    In operation or use, the medical professional moves the surgical instrument  510  toward the site to be measured until both patterns  562 ,  564  (i.e., the circle pattern and the cross hair pattern) overlap or coincide. At the point of coincidence or overlap, the two patterns  562 ,  564  serve as an accurate optical ruler where tick marks  443  are equally spaced apart at predefined distances, as shown on magnified pattern  440  on target site “S” (see  FIG. 5 ). In other words, by using such exemplary patterns, the end points of the cross hair are designed to coincide or align with the circle, thus indicating that an accurate measurement is achievable at that point. 
         [0062]    Referring to  FIG. 7 , a schematic view of generated patterns  600  based on the distance of the optical measurement system from the target site, in accordance with an embodiment of the present disclosure is presented. 
         [0063]    The first pattern  540  includes a circular outer perimeter  612  and a cross hair  614 . The end points of cross hair  614  do not intersect the circular outer perimeter  612 . The end points of the cross hair  614  are determined by the distance of the diffractive cross-pattern generator  530  from the image plane  540 , as shown in  FIG. 6 . At location A, an accurate measurement is not obtained since there is no overlap or coincidence of the two patterns. 
         [0064]    The second pattern  550  includes a circular outer perimeter  622  and a cross hair  624 . The end points  626  of cross hair  624  coincide with the circular outer perimeter  622 . The end points  626  of the cross hair  624  are determined by the distance of the diffractive cross-pattern generator  530  from the image plane  550 , as shown in  FIG. 6 . At location B, an accurate measurement is obtained since the two patterns coincide or are overlapped. This is the point at which accurate, real-time, in-body cavity optical metrology may be achieved. This visual indication enables a medical professional to obtain an accurate reading or measurement of a target site (e.g., an organ), via for example, tick marks placed on portions or segments of the pattern  550  (see  FIG. 8 ). 
         [0065]    The third pattern  560  includes a circular outer perimeter  632  and a cross hair  634 . The end points of cross hair  634  intersect the circular outer perimeter  632  and extend beyond the circular outer perimeter  632 . The end points of the cross hair  634  are determined by the distance of the diffractive cross-pattern generator  530  from the image plane  560 , as shown in  FIG. 6 . At location C, an accurate measurement is not obtained since there is no overlap or coincidence of the two patterns. There is merely an intersection of the cross-hair  634  with the circle  632 . 
         [0066]    Referring to  FIGS. 8 and 9 , side and perspective views  700 ,  800  of the optical measurement system  715  mounted on a surgical instrument  710 , in accordance with an embodiment of the present disclosure are presented. 
         [0067]    In  FIGS. 8 and 9 , a projection device  715  is mounted on a distal end of a shaft  712  of a surgical instrument  710 . A light beam  720  is emitted from the projection device  715  at an angle γ. Light beam  720  is partially blocked by image plane  730  upon incidence with plane  730 . Unblocked portions of the light beam  720  continue past image plane  730  and onto a target site, S, forming a pattern  740 . The pattern  740  is circular in nature and includes a cross hair  742  having a plurality of marks  744 . The projection device  715  acts as an optical ruler. In  FIG. 8 , the end points  726  of the cross hair  742  overlap or coincide with or align with the outer periphery of the circle  740 . This overlap or alignment indicates or signifies that an accurate measurement may be made by the medical professional. 
         [0068]    Referring to  FIG. 10 , a schematic view of the projected patterns  900  created by various locations of the surgical instruments of  FIGS. 8 and 9 , in accordance with an embodiment of the present disclosure are presented. 
         [0069]    The first pattern  910  includes a circular outer perimeter  912  and a cross hair  914 . The end points of cross hair  914  do not intersect the circular outer perimeter  912 . The end points of the cross hair  914  are determined by the distance of the diffractive cross-pattern generator  715  from the image plane  730 , as shown in  FIGS. 8 and 9 . 
         [0070]    The second pattern  920  includes a circular outer perimeter  922  and a cross hair  924 . The end points  926  of cross hair  924  coincide or overlap or align with the circular outer perimeter  922 . The end points  926  of the cross hair  924  are determined by the distance of the diffractive cross-pattern generator  715  from the image plane  730 , as shown in  FIGS. 8 and 9 . 
         [0071]    The third pattern  930  includes a circular outer perimeter  932  and a cross hair  934 . The end points of cross hair  934  intersect the circular outer perimeter  932  and extend beyond the circular outer perimeter  932 . The end points of the cross hair  934  are determined by the distance of the diffractive cross-pattern generator  715  from the image plane  730 , as shown in  FIGS. 8 and 9 . 
         [0072]      FIG. 11  is a schematic view  1000  of the cross hair  1020  depicting tick marks  1022  to provide reading of the circle diameter, in accordance with an embodiment of the present disclosure. 
         [0073]    In some embodiments, it may be desirable to obtain a reading of the diameter of the circle pattern  1010  without moving the surgical instrument (see  FIGS. 8 and 9 ). For example, a surgeon may move the surgical instrument toward the object to be measured until the circle pattern  1010  covers the entire object, at which point it may be desirable to read the diameter of the circle  1010 . In the view  1000  of  FIG. 11 , there are two separate patterns, that is, a circle pattern  1010  and a cross hair pattern  1020 . The cross hair pattern  1020  includes a plurality of tick marks  1022 , which provide a reading of the circle diameter. For example, as shown in  FIG. 11 , a medical professional may read the circle diameter as “6,” since the circle intersects a mark designating the distance as being 6 cm. It is noted that the tick marks  1022  need not be equally spaced apart. One skilled in the art may include any number of tick marks in any number of shapes or colors for providing accurate distance indications to a medical professional. 
         [0074]      FIG. 12  is a graph  1100  illustrating pattern sizes as a function of the distance of the surgical instrument from the target site (e.g., an organ), in accordance with an embodiment of the present disclosure. 
         [0075]    The graph  1100  has an x-axis  1110  representing distance and a y-axis  1120  representing projected size. Plot  1130  illustrates a first pattern size, whereas plot  1140  illustrates a second pattern size. The first and second pattern sizes  1130 ,  1140  may be calculated via the equations or formulas presented above with reference to  FIGS. 1 and 2 . For example, if it assumed that la=5 cm, lb=2.5 cm, a o =b o =2.5 cm, as illustrated in  FIG. 7 , then the projected size of the patterns  1130 ,  1140  may be calculated in accordance with the following formula or equation: 
         [0000]    
       
         
           
             
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         [0076]      FIG. 13  provides for a calculation of a tick mark  1222  on a cross-hair pattern  1220  for reading a circle diameter, in accordance with an embodiment of the present disclosure. 
         [0077]    In  FIG. 13  the x-axis  1205  represents the ratio b/a and the y-axis  1210  represents the circle diameter (Φ=2*a). The line  1230  represents the change of the patterns with respect to each other as the surgical instrument is moved in and out of the surgical site. The tick marks  1222  in a cross pattern  1220  may be designed as demonstrated in  FIG. 13 . In the example shown, the diameter is derived to be 6 cm, thus enabling the medical professional to estimate or approximate the size of the measured structure or organ or target site with accuracy. 
         [0078]      FIG. 14  is a schematic diagram of an optical measurement system  1300  having at least one moving diffractive element  520 ,  530 , in accordance with an embodiment of the present disclosure. 
         [0079]    According to  FIG. 14 , in some exemplary embodiments, one of the diffractive elements  520 ,  530  may have translational motion along the laser axis  525 . At a given position of the instrument  510 , rotation of the knob  1310  at the proximal end of the surgical instrument  510 , causes a change in size of the projected patterns  562 ,  564 . The knob  1310  should be rotated until both patterns  562 ,  564  have the same size or coincide or overlap. For example, if it assumed that the diameter of the circle pattern  562  at the site of projection is, Φ, and the second diffuser  530  is at distance, l 1 , then at this distance the projected cross pattern  564  has a size, b, and is larger than the circle diameter  562 . By rotating the knob  1310 , in the direction “x,” the medical professional may achieve an equal size of the two patterns  562 ,  564  (i.e., b=Φ) at the location of the second diffuser  530  at distance, l 2 . Since the size of the cross pattern  564 , b, is proportional to the distance between the diffuser  530  and the target site  560 , the knob  1310  may be calibrated in units of circle diameter. Thus, the reading of the knob&#39;s scale provides a desired value for the circle diameter. Additionally, the motion or movement of one of the elements  520 ,  530  is associated with a change of the size of the projected patterns  562 ,  564 . Thus, a direct relationship is established between the size of the projected pattern and the distance of the surgical instrument/projection system from the target site. 
         [0080]    One advantage of the present disclosure is to create a small form factor, inexpensive projection device for real-time, in-body cavity optical metrology, in order to reduce overall surgery time and cognitive burden on a surgeon, as well as potentially improve patient outcomes with more accurate and smaller incision procedures, which are less prone to human errors or miscalculations. 
         [0081]    While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of presently disclosed embodiments. Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given. 
         [0082]    Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the present disclosure based on the above-described embodiments. Accordingly, the present disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 
         [0083]    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.