Abstract:
A structured light 3D scanner comprising multiple pattern projectors each projecting a unique pattern onto an object by passing radiation through a stationary imaging substrate and one or more cameras for capturing the projected patterns in sequence. A processor processes the projected patterns based on a predetermined separation between the cameras. The processor uses this information to determine the deviation between the projected patterns and the reflected patterns captured by the camera or cameras. The deviation may be used to determine the three dimensional surface geometry of the object within the capture volume of the cameras. Surface geometry may be used to create a point cloud with each point representing a location on the surface of the object with respect to the 3D scanner.

Description:
[0001]    This application is based upon U.S. Provisional Application Ser. No. 61/806,175 filed Mar. 28, 2013, the complete disclosure of which is hereby expressly incorporated by this reference. 
     
    
     BACKGROUND 
       [0002]    Engineers and digital artists often use three-dimensional (3D) scanners to create digital models of real-world objects. An object placed in front of the device can be scanned to make a 3D point cloud representing the surface geometry of the scanned object. The point cloud may be converted into a mesh importable into computers for reverse engineering, integration of hand-tuned components, or computer graphics. 
         [0003]    Various methods of illumination, capture, and 3D mesh generation have been proposed. The most common illumination methods are structured light and laser line scanning. Most systems employ one or more cameras or image sensors to capture reflected light from the illumination system. Images captured by theses cameras are then processed to determine the surface geometry of the object being scanned. Structured light scanners have a number of advantages over laser line or laser speckle patterns, primarily a greatly increased capture rate. The increased capture rate is due to the ability to capture a full surface of an object without rotating the object or sweeping the laser. Certain techniques in structured light scanning enable the projection of a continuous illumination function (as opposed to the discrete swept line of a laser scanner) that covers the entire region to be captured; the camera or cameras capture the same region illuminated by the pattern. Traditionally, structured light scanners consist of one projector and at least one image sensor (camera). The projector and camera are typically fixed a known distance apart and disposed in such a fashion that the field of view of the camera coincides with the image generated by the projector. The overlap region of the camera and projector fields of view may be considered the capture volume of the 3D scanner system. An object placed within the capture volume of the scanner is illuminated with one or more patterns generated by the projector. Each of these patterns is often phase-shifted (i.e. a periodic pattern is projected repeatedly with a discrete spatial shift). Sequential images may have patterns of different width and periodicity. From the perspective of the camera, the straight lines of the projected image appear to be curved or wavy. Image processing of the camera&#39;s image in conjunction with the known separation of the camera and projector may be used to convert the distortion of the projected lines into a depth map of the surface of the object within the field of view of the system. 
         [0004]    Among structured light scanners, pattern generation methods wherein a repeating pattern is projected across the full field of view of the scanner are the most common. An illumination source projects some periodic function such as a square binary, sinusoidal, or triangular wave. Some methods alter the position of an imaging substrate (e.g. a movable grating system) (See U.S. Pat. Nos. 5,581,352 and 7,400,413) or interferometers (See U.S. Pat. No. 8,248,617) to generate the patterns. The movement of the imaging substrate in these prior art methods requires very precise movement and the patterns generated will often have higher order harmonics which introduces spatial error. These disadvantages limit the applicability of movable grating systems for mass appeal. 
         [0005]    Digital projection methods are an alternative to these hardware approaches, and allow better control over the patterns that are projected. However, while digital projectors are useful in a lab, they too suffer from several disadvantages, including: (1) variable spatial light modulators (SLM) such as Digital Light Projection (DLP) or Liquid Crystal Display (LCD) projectors are often heavy and bulky; (2) complicated electronics limit low cost production on a large scale; and (3) speed of projection is limited by either the movement of mirrors (as in a DLP) or the changing of polarization states (as in an LCD), thereby fundamentally limiting the speed of a 3D scanner producing patters with this method. 
         [0006]    The methods disclosed herein seek to solve the problems posed by both movable imaging substrates and variable SLM projections methods by creating a solid state 3D scanner having a stationary imaging substrate, and which calculates 3D geometry in a way which requires little or no calibration of the projectors and is tolerant to imperfect projection patterns. The present invention reduces cost, increases manufacturability and increases projection speed and thereby 3D capture speed over current systems. 
       SUMMARY 
       [0007]    Various embodiments of the present invention include systems and methods for structured light 3D imaging using a scanner having multiple projectors in conjunction with one or more cameras. In some embodiments the projectors generate a sequence of patterns by projecting light through a stationary imaging substrate to illuminate a target object and the reflected light is captured by the cameras. Any suitable imaging substrate may be used to generate the sequence of patterns, including a transmissive pattern, a diffraction grating, or a holographic optical element. In particular, according to some embodiments, each projector produces a single pattern of fixed structure with variable or fixed intensity. In some embodiments, the projectors each consist of a light source, condensing optics, a transmissive pattern, and projection optics. In some embodiments, the projector consists of a light source and a diffraction grating or a holographic optical element, eliminating the need for condensing or projection optics. In some embodiments, multiple light sources may be used in conjunction with a single imaging substrate. In some embodiments, the cameras and projectors are disposed such that a portion of the cameras&#39; field of view coincides with the spatial region illuminated by all of the projectors, the overlapping region constituting the capture volume of the scanner. In some embodiments, the projectors are activated sequentially. As each projector is illuminated one or both of the cameras capture images in such a fashion that a sequence of images is captured which allows for the generation of a set of three dimensional points representing the surface of any objects within the capture volume of the scanner system. 
         [0008]    The use of multiple projectors to generate a sequence of fixed patterns using any suitable imaging substrate (transmissive pattern, diffraction grating, or holographic optical element) eliminates the need for a variable spatial light modulator (e.g. digital micro-mirror device or liquid crystal on silicone device) or the translation (movement) of a pattern or grating, reducing the complexity and cost inherent in current structured light projection systems for 3D scanning. Further, the fixed pattern projectors may exhibit higher image contrast than is possible with a projector relying on a variable SLM. Still further, the use of two separate images captured by two cameras eliminates the need to calibrate the projectors because both cameras are viewing the same part of the same pattern the same time. 
         [0009]    In some embodiments, the speed of projecting and capturing the patterns is limited only by the time to turn on or off an illumination source such as an LED or laser diode, which is often measured in nanoseconds and therefore orders of magnitude faster than a changeable SLM. Further, solid-state projection patterns can be produced using common print shop tools to a high precision equivalent to a 25,000 dpi to 100,000 dpi printer, eliminating higher-order harmonics present in diffraction gratings or the need for expensive optics. In some embodiments, a monolithic set of patterns on an imaging substrate, each illuminated by a different light source, eliminates the need for complex control of a moving diffraction grating or highly precise manufacturing techniques to align multiple separate patterns, thereby reducing manufacturing cost. 
         [0010]    In some embodiments a phase-shifting method is employed to solve many of the problems inherent in existing methods using a single pattern. In some embodiments, the system described herein uses the three-step phase shifting method, wherein three periodic projected patterns are each shifted by 2 pi/3 radians from one another. Using this method the phase measurement and triangulation can be achieved independently from the intensity of the projected patterns or object color. The most significant limitation of using this method with previous 3D scanner designs was the difficultly of achieving proper phase-shifting alignment. Variable SLMs ensure proper alignment but are expensive and slow to actuate, translatable diffraction gratings or patterns can be less expensive but introduce positioning errors which reduce system accuracy. In one embodiment of the present invention, multiple phase shifted patterns are disposed on a single monolithic imaging substrate, thereby ensuring proper alignment between each pattern. In another embodiment of the present invention each of the patterns on the monolithic imaging substrate are illuminated by a different source, thereby allowing the projection of a single pattern at a time while simultaneously insuring proper alignment between the projected patterns. In another embodiment, the direction of the phase shifting of the patterns is perpendicular to the direction of separation of the patterns. This orientation ensures the phase shift of the projected patterns is not dependent on the distance from the projectors to the illuminated plane, thereby increasing 3D scanner measurement precision over a system which does not incorporate this constraint. 
         [0011]    In some embodiments a plurality of identical patterns are each rotated with respect to one another rather than phase shifted. This method allows significant tolerance in the placement of the discrete patterns such that they do not need to be on a monolithic substrate. Similar to the phase shifted patterns, the rotated patterns are projected one at a time and captured by one or more cameras and the images are processed to determine the 3D measurements of the surface onto which the patterns are projected. 
         [0012]    In some embodiments an additional pattern is projected to establish correspondence between the camera images. This correspondence pattern may be attached to a monolithic imaging substrate along with other patterns or may be a discrete pattern disposed separately from other projected patterns. In some embodiments a correspondence pattern captured by one or more cameras may be used to enhance the performance of the scanner by enabling the calculation of correspondence between the pixels of two or more cameras. By identifying the pixels in each camera which detect the same portion of the projected correspondence pattern, the correspondence between the two cameras can be used in the processing of the projected images to precisely calculate the 3D geometry of a captured surface. Any suitable correspondence pattern may be used, including a random pattern, a deBruijn sequence, or a minimum Hamming distance pattern. 
         [0013]    The components of the system may be any suitable size. In some embodiments the components are handheld or attached to a mobile device such as a mobile phone or tablet. 
         [0014]    Various systems and methods are disclosed herein to solve the alignment and phase-shifting problems of the prior art or circumvent phase shifting altogether. The systems and methods disclosed herein provide a low-cost and high-quality 3D scanning system using triangulation of projected patterns to capture the surface profile of objects within the scanner field of view. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0015]    Having thus described various embodiments of the invention in general terms, references will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0016]      FIG. 1  is a perspective view illustrating a 3D structured light scanner according to various embodiments of the invention. 
           [0017]      FIG. 2  is a cross-sectional view of the illumination module taken along lines A-A of  FIG. 1 . 
           [0018]      FIG. 3  is a cross-sectional view of the projection module taken along lines A-A of  FIG. 1 . 
           [0019]      FIG. 4  is a side view illustrating an embodiment wherein the imaging substrate is a stationary diffractive grating. 
           [0020]      FIG. 5  is a rear perspective view illustrating a 3D structured light scanner projecting a pattern according to various embodiments of the invention. 
           [0021]      FIG. 6  is a cross-sectional view of the 3D structured light scanner taken along lines A-A in  FIG. 1 . 
           [0022]      FIG. 7  illustrates a circuit board containing illumination sources and a plurality of other electronic components according to various embodiments of the invention. 
           [0023]      FIG. 8  is a front view of an imaging substrate having several transmissive patterns and a correspondence pattern combined thereto according to various embodiments of the invention. 
           [0024]      FIG. 9  is an exploded view of the structured light 3D scanner according to various embodiments of the invention. 
           [0025]      FIG. 10  is a functional block diagram of the components within the structured light 3D scanner according to various embodiments of the invention. 
           [0026]      FIG. 11   a  shows a monolithic phase shifted transmissive pattern projected onto a surface. 
           [0027]      FIG. 11   b  shows discrete rotated transmissive patterns projected onto a surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Various embodiments of the invention are described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown in the figures. Indeed, these inventions many be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will satisfy applicable legal requirements. 
         [0029]      FIG. 1  illustrates one embodiment of the invention. In this embodiment, 3D scanner  10  comprises four projectors  20  each used to project a different static pattern when activated, mounting locations  30  for two cameras (one shown)  60 , and a cable  135  to connect the scanner to an external computer  340  and/or a power source. In other embodiments, 3D scanner  10  may comprise any suitable number of projectors  20  and any number of cameras  60 . More specifically, in this embodiment, 3D scanner  10  comprises two modules, an illumination module  50  containing the illumination sources  140  for each projector  20 , and a projection module  40  containing the imaging substrate  120 . In one embodiment the camera(s)  60  are part of the projection module  40 . The illumination sources  140  may emit any suitable type of radiation at any wavelength. Light (or other types of radiation) from the illumination sources  140  is passed through the imaging substrate  120  to project patterns onto the object being scanned. The imaging substrate  120  may be a transmissive projection pattern  70 , a diffractive element  85 , or a holographic optical element. In the embodiments where the imaging substrate  120  is a transmissive projection pattern  70 , the transmissive projection pattern  70  may be adapted to project patterns  80 ,  90 ,  100 ,  400 ,  510 ,  520 ,  530  through projection lenses  210 ,  200  which help project the illuminated pattern on to the object being scanned (not shown). As described below, the transmissive projection pattern  70  is typically comprised of several individual patterns such as patterns  80   a ,  90   a ,  100   a ,  110   a  which correspond to the projected patterns  80 ,  90 ,  100 ,  110  shown in  FIG. 12 . 
         [0030]      FIG. 2  illustrates a cross sectional view of an illumination module  50 . In some embodiments, illumination module  50  comprises housing  240  adapted to receive four condensing lenses  230  disposed in line with four illumination sources  140 . In some embodiments, illumination sources  140  are mounted on printed circuit board (PCB)  130  as further described with reference to  FIG. 7 . In some embodiments, condensing lens  230  collimates the light emitted by illumination source  140 . In further embodiments the condensing lenses  230  collect a large portion of the light from illumination source  140  and focus it into a narrower beam in such a manner that a large portion the light falls on the imaging substrate  120 . In one embodiment illumination source  140  is a white light emitting diode (LED). In some embodiments, illumination source  140  may produce any color of light, or incoherent radiation of any wavelength. In some embodiments, illumination source  140  may be a coherent light source such as, but not limited to, a laser diode of any wavelength. In some embodiments, illumination source  140  emits viable light. In some embodiments, illumination source  140  may emit light outside of the human visible range such as infrared or ultraviolet. 
         [0031]      FIG. 3  is a cross-sectional view of a projection module  40  wherein the imaging substrate  120  comprises a transmissive pattern  70 . In some embodiments, projection module  40  comprises a housing  245 , transmissive pattern  70 , and four sets of lenses, each set including first lens  210  and second lens  200 . In some embodiments, light passes through transmissive pattern  70  and then through lenses  210  and  200 . In some embodiments lenses  210  and  200  are positioned in such a fashion that they reimage transmissive pattern  70  onto a real image plane (not shown) on the other side of lenses  210  and  200  from transmissive pattern  70 , and in this fashion project transmissive pattern  70  onto the object being scanned. In some embodiments, the orientation of lenses  210  and  200  may have any relationship with one another as well as with transmissive pattern  70 ; the orientation of lenses  210  and  200  in the present embodiment represent one potential orientation with respect to one another and to transmissive pattern  70  and should not be construed as the only possible orientation. In some embodiments, transmissive pattern  70  may be combined with a monolithic component such as substrate  120  comprising one or more distinct patterns  80   a ,  90   a ,  100   a ,  110   a  thereby ensuring proper alignment between the patterns. In some embodiments, transmissive pattern  70  may comprise several patterns each separate from one another and disposed in a specific relationship with one another. In some embodiments, two or more different patterns  80   a ,  90   a ,  100   a ,  110   a  comprising transmissive pattern  70  may each be disposed such that light or radiation emitted from each illumination source  140  passes through only one of the patterns  80   a ,  90   a ,  100   a ,  110   a . In some embodiments, light or radiation from multiple illumination sources  140  may pass through a single pattern  80   a ,  90   a ,  100   a ,  110   a  that is a component of transmissive pattern  70 , thereby allowing the activation of different illumination sources to cause the projection of slightly different patterns. In some embodiments, lenses  210  and  200  are disposed with respect to transmissive pattern  70  in such a fashion that the projected real image (not shown) maintains an acceptable degree of focus within a desired range of distances from projection module  40 , ensuring the projected pattern  80 ,  90 ,  110 ,  110 ,  400 ,  510 ,  520 ,  530  has the desired level of focus or defocus when it illuminates the object being scanned. In some embodiments, inclusion of condensing lens  230  increases the brightness of projector  20  by ensuring more light or radiation from illumination source  140  passes through transmissive pattern  70  and projection optics  210  and  200  than in a system without a condensing lens. In some embodiments, projection lenses  210  and  200  enable more control of the level of focus of projected pattern  80 ,  90 ,  110 ,  110 ,  400 ,  510 ,  520 ,  530  within the functional region of 3D scanner  10  than a system without projection optics; increased control of the focus or defocus level of projected pattern  80 ,  90 ,  110 ,  110 ,  400 ,  510 ,  520 ,  530  enables a system with lower error and higher precision and accuracy. 
         [0032]      FIG. 4  illustrates a diagram of projection module  40  according to various embodiments of the invention wherein the imaging substrate  120  comprises a diffractive element  85  which eliminates the need for lenses  210  and  200 . In some embodiments, projection module  40  may contain a single diffractive element  85  and one or more coherent illumination sources  140 , in such a fashion that the activation of each illumination source  140  causes the projection of a different pattern as the light (or other radiation) passes through the stationary diffractive element  85 . In some embodiments, diffractive element  85  may comprise several patterns each separate from one another and disposed in a specific relationship with one another. The patterns in this embodiment are small openings or slits in the generally opaque diffractive element  85  which cause light transmitted therethrough to project a pattern  410 ,  412 ,  414 ,  416  on the object. In some embodiments, different patterns comprising diffractive element  85  may each be disposed such that light or radiation emitted from each illumination source  140  passes through separate patterns to create distinct projected patterns  410 ,  412 ,  414 ,  416 . In some embodiments, light or radiation from multiple illumination sources  140  may pass through a single pattern (not shown) that is a component of diffractive element  85 . In some embodiments radiation or light emitted from illumination source  140  may pass through diffractive element  85  and generate patterns  410 ,  412 ,  414 ,  416  at some position in front of 3D scanner  10  (not shown) and on the opposite side of diffractive element as illumination source  140 . In some embodiments, multiple patterns  410 ,  412 ,  414 ,  416  generated by radiation or light emitted by illumination source  140  passing through diffractive element  85  may all have the same structure but be shifted spatially with respect to one another; the degree of spatial shifting of the patterns  410 ,  412 ,  414 ,  416  with respect to one another may be related to the spacing and relative orientation of illumination sources  140  with respect to one another. In some embodiments, diffractive element  85  may be transmissive. In some embodiments diffractive element  85  may be reflective such that patterns  410 ,  412 ,  414 ,  416  may be generated on the same side of diffractive element  85  as illumination source  140 . 
         [0033]      FIG. 5  illustrates one embodiment of the present invention. In some embodiments, exemplary pattern  400  is generated by projector  20  of 3D scanner  10 . In some embodiments, 3D scanner  10  comprises at least two projectors  20  each projecting a single distinct pattern (See, e.g. the projected patterns shown in FIGS.  4 , 11   a , and  11   b ). In some embodiments, projected patterns  80 ,  90 ,  110 ,  110 ,  400 ,  410 ,  412 ,  414 ,  416   510 ,  520 ,  530  may be a plurality of monochromatic lines of uniform intensity; two-dimensional monochromatic binary patterns; or a plurality of monochromatic patterns with a sinusoidal intensity pattern in two dimensions. In some embodiments, projected patterns  80 ,  90 ,  110 ,  110 ,  400 ,  410 ,  412 ,  414 ,  416   510 ,  520 ,  530  may be a plurality of colored lines of uniform intensity; two dimensional colored binary patterns; or a plurality of colored patterns with a sinusoidal intensity pattern in two dimensions. In some embodiments, projector  20  produces a monochrome pattern of random intensity levels in one axis, or a monochrome pattern of random intensity levels in two axes. In some embodiments, projector  20  produces a color pattern of random intensity levels in one axis, or a color pattern of random intensity levels in two axes. In some embodiments, cameras  60  are disposed such that their fields of view substantially overlap with the pattern  400  as well as the patterns from the other projectors  20 . 
         [0034]      FIG. 6  illustrates a cross-sectional view of one embodiment of the present invention. In one embodiment of the present embodiment, 3D scanner  10  is comprised of four projectors  20 , wherein the front half of each projector  20  is defined by projection module housing  245 , and the back half of each projector is defined by illumination module housing  240 . In one embodiment, printed circuit board  130  contains four illumination sources  140  and is attached to the rear of illumination module housing  240 . In some embodiments there may be any number of illumination sources  140 . In some embodiments, condensing lens  230 , first projection lens  210  and second projection lens  200  may be disposed in front of the illumination source  140  and centered on, and normal to optical axis  420 . In some embodiments, condensing lens  230 , first projection lens  210  and second projection lens  200  may be disposed in a position other than centered on, or normal to optical axis  420 . In some embodiments, condensing lens  230  may be disposed so as to collimate the radiation or light emitted by illumination source  140 . In some embodiments, condensing lens  230  may be disposed in a fashion that does not collimate the radiation or light emitted by illumination source  140 . In some embodiments, transmissive pattern  70  may be disposed in such a fashion that the light or radiation emitted from illumination source  140 , and passing through condensing lens  230  passes through a portion of transmissive pattern  70  containing a single pattern  80   a ,  90   a ,  110   a ,  110   a . In some embodiments, transmissive pattern  70  may be disposed in such a fashion that the light or radiation emitted from illumination source  140 , and passing through condensing lens  230  passes through a portion of transmissive pattern  70  containing more than one pattern  80   a ,  90   a ,  110   a ,  110   a . In some embodiments, first lens  210  and second lens  200  may be disposed in such a fashion that they reimage a portion of transmissive pattern  70  into a real image plane (not shown) on the other side of lenses  210  and  200  from transmissive pattern  70 . In some embodiments, lenses  210  and  200  may be disposed is such a fashion that they are centered on and normal to optical axis  420 . In some embodiments, lenses  210  and  200  may be disposed is such a fashion that they are not centered on or normal to optical axis  420 . In some embodiments, transmissive pattern  70  may be replaced with diffractive or holographic element  80  as discussed above. In some embodiments, condensing lens  230  may not be present. In some embodiments first lens  210  may not be present, in other embodiments second lens  200  may not be present; in further embodiments neither first lens  210  nor second lens  200  may be present. In some embodiments, additional projection lenses (not shown may be present and disposed in relationship to lenses  210  and  200  so as to reimage transmissive pattern  70 ). In some embodiments, projection lenses  210  and  200  may reimage a plane other than the plane where transmissive pattern  70  is located. In some embodiments 3D scanner  10  may contain more fewer than four projectors  20 , in further embodiments 3D scanner  10  may contain more than four projectors  20 . 
         [0035]      FIG. 7  illustrates printed circuit board  130  containing illumination sources  140 , microcontroller  160 , voltage regulator  170 , current driver  180  and external connection port  150 . In some embodiments four illumination sources  140  may be attached to printed circuit board  130 . In some embodiments printed circuit board  130  may contain more than four illumination sources  140 . In further embodiments, printed circuit board  130  may contain fewer than four illumination sources  140 . In some embodiments, multiple printed circuit boards  190  (only one shown) may each contain one or more illumination sources  140 . In some embodiments, printed circuit board  130  may have a thermally conductive backing (not shown) that conducts heat from the illumination sources  140  and acts as a heat sink. In some embodiments, printed circuit board  130  may contain additional circuitry including, but not limited to, resistors, capacitors, inductors, transformers, diodes, fuses, batteries, digital signal processors, oscillators, crystals, and integrated circuit components. In some embodiments, illumination sources  140  may be disposed along the center line (not shown) of the printed circuit board  130  and separated by a uniform distance. In further embodiments, illumination sources  140  may be disposed on the printed circuit board  130  in a non-uniform fashion. 
         [0036]      FIG. 8  illustrates a diagram of transmissive pattern  70 . In some embodiments, transmissive pattern  70  may comprise a transmissive substrate  125  having four transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  combined therewith. In some embodiments, transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  may be made of a transmissive film affixed to the surface of transmissive substrate  125 . In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  may comprise a coating applied directly to the surface of transmissive substrate  125 . In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  may formed from the same material as the transmissive substrate  125  and be created by optical, chemical or other treatment to transmissive substrate  125 . In some embodiments, transmissive substrate  125  may contain more than four transmissive patterns. In further embodiments, transmissive substrate  125  may contain fewer than four transmissive patterns. In some embodiments, transmissive substrate  125  may comprise a monolithic material. In other embodiments transmissive substrate  125  may comprise multiple transmissive substrate sections (not shown). In some embodiments, transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  may all be portions of a monolithic substrate. In other embodiments, transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  may each be separate patters individually affixed to transmissive substrate  125  or transmissive substrate segments (not shown). In some embodiments, alignment of transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  with respect to one another may be critical; alignment may be achieved by fabricating all portions of transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  on a single monolithic transmissive film; alternatively, alignment may be achieved by placing separate segments of transmissive film, each containing one or more transmissive patterns  80   a ,  90   a ,  100   a ,  110   a  onto transmissive substrate  125  with proper orientation during manufacturing. In some embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may depict a sinusoidal or triangular wave of transmissivity. In further embodiments, patterns  80   a ,  90   a ,  100   a  may be phase-shifted. In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may be phase-shifted by a value of 2*pi/3 radians. In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may be phase-shifted by pi/2 radians. In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may be phase-shifted by pi/4 radians. In further embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may be phase-shifted by any other radian value. In some embodiments, transmissive patterns  80   a ,  90   a ,  100   a  may each be phase-shifted by different radian values. In further embodiments, more than four transmissive patterns may be phase-shifted by any radian value; fewer than four transmissive patterns may be phase-shifted by any radian value. 
         [0037]      FIG. 9  illustrates an embodiment of an exploded diagram of 3D scanner  10 . In some embodiments, 3D scanner  10  comprises a printed circuit board  130  with illumination sources  140 , illumination module  50  containing condensing lenses  230 , projection module  40  including an imaging substrate  120 , first projection lenses  210 , second projection lenses  200 , camera mounts  30  and camera lenses  32 , and cameras  60 . In the embodiment shown in  FIG. 9 , the imaging substrate  120  is preferably a transmissive pattern  70  due to the inclusion of lenses  200 ,  210 . In some embodiments, printed circuit board  130  and condensing lenses  230  may be mounted into illumination module housing  240 , first lenses  210  and second lenses  200  as well as imaging substrate  120  may be inserted and mounted into projection module housing  245 , camera lenses  32  may be inserted and mounted into camera mounts  30 , and cameras  60  may also be inserted and mounted into camera mounts  30  in the projection module housing  245 . In this fashion, components of 3D scanner  10  may be assembled into two modules, illumination module  50  and projection module  40 . In some embodiments, decoupling projection module  40  from illumination module  50 , while incorporating imaging substrate  120  in projection module  40  ensures proper orientation between imaging substrate  120  with first and second projection lenses  210  and  200  without requiring perfect alignment between illumination source  140 , condensing lens  230  and transmissive pattern  70 , thereby reducing manufacturing complexity. In other embodiments, illumination sources  140 , condensing lens  230 , imaging substrate  120 , and first and second projection lenses  210  and  200  may all be incorporated into a single housing without separate illumination module  50  or projection module  40 . In further embodiments, camera  60  may be incorporated into printed circuit board  130 . In some embodiments, lenses  210 ,  200 ,  32 ,  230  may be fixed in place with adhesive; alternatively lenses  210 ,  200 ,  32 ,  230  may be held in place by a retaining ring (not shown). In some embodiments, the imaging substrate  120  may be fixed to projection module housing  245  with adhesive or any other permanent or temporary means. In some embodiments, cameras  60  may be fixed to projection module housing  245  with adhesive; alternatively, cameras  60  may be held in place by a retaining ring (not shown). In further embodiments, camera  60  may be fixed to illumination module housing  240 . In some embodiments, 3D scanner  10  may include a stand (not shown); alternatively 3D scanner  10  may include a removable stand. In some embodiments, 3D scanner  10  may include a stand with an attached turn table (not shown) to rotate an object being scanned (not shown). In further embodiments, turn table (not shown) may not be connected to either the stand (not shown) or the 3D scanner  10 . 
         [0038]      FIG. 10  illustrates a schematic depiction of a number of functional components of 3D scanner  10 . In some embodiments, 3D scanner  10  may be a handheld or table mounted device comprising projector sub-system  270 , imaging sub-system  260 , power sub-system  250 , processor  280 , and may contain standalone scanner components  390 . In some embodiments, 3D scanner  10  may not contain standalone scanner components  390 . 
         [0039]    In some embodiments, projector sub-system  270  may contain one or more projectors  20  and one or more current drivers  320 . In some embodiments, sub-system  270  may contain four projectors  20  and one current driver  320 . In some embodiments, current driver  320  may supply projectors  20  with a constant current at a constant voltage; alternatively, current driver  320  may supply projectors  20  with any current or voltage. In some embodiments, current driver  320  may supply power to one projector  20  at a time. In further embodiments, current driver  320  may supply projectors  20  with power sequentially, one projector  20  receiving power at a given moment to illuminate and project a single pattern  80 ,  90 ,  100 ,  110 ,  400 ,  410 ,  412 ,  414 ,  416 ,  510 ,  520 , or  530 . In an alternative embodiment, current driver  320  may supply more than one projector  320  with power at a given moment and then supply power to a different set of projectors  20  at another moment. In another embodiment, current driver  320  may supply a current of constant value to one or more projectors  20  while using pulse width modulation, varying the duty cycle of power application to projectors  20 ; in this fashion, the brightness of projectors  20  may be controlled by varying the duty cycle of the power provided by current driver  320 . In some embodiments, two or more projectors  20  may be illuminated simultaneously each receiving power from current driver  320  at a different duty cycle, thereby independently controlling brightness of multiple projectors  20  simultaneously. 
         [0040]    In some embodiments, current driver  320  may be controlled by processor  280 ; in this fashion, the state of illumination and brightness of each projector  20  may be controlled. In some embodiments, processor  280  may be connected to imaging sub-system  260 ; in this fashion processor  280  may trigger the capture of cameras  60  as well as the illumination state of projectors  20 . In another embodiment, camera  60  capture rates may be fixed and processor  280  may trigger the illumination state of projectors  20  to coincide with the capture rate of cameras  60 . In some embodiments, processor  280  may facilitate a state of camera  60  capture and illumination of projector  20  such that images generated by projectors  20  may be captured by cameras  60 . In some embodiments, a first frame captured by cameras  60  may contain an image generated by first projector  20 , a second frame captured by cameras  60  may contain an image generated by a second projector  20 . In some embodiments, a first frame captured by cameras  60  may contain images generated by the simultaneous illumination of a set of two or more projectors  20 , a second frame captured by cameras  60  may contain images generated by the simultaneous illumination of a different set of two or more projectors  20 . In some embodiments, processor  280  may perform image processing on captured frames from cameras  60 . In some embodiments, processor  280  may perform image processing on captured frames from cameras  60  thereby generating three dimensional point clouds; generated point clouds may represent objects imaged by 3D scanner  10 . In some embodiments, processor  280  may perform compression of three dimensional point clouds or models. 
         [0041]    In some embodiments, 3D scanner  10  may connect to host computer  340  wirelessly. In some embodiments, 3D scanner  10  may wirelessly connect to host computer  340  via Bluetooth transceiver  370 . In another embodiment, 3D scanner  10  may wirelessly connect to host computer  340  via WLAN transceiver  370 . In some embodiments, 3D scanner  10  may wirelessly connect to host computer  340  via Bluetooth transceiver  370  and via WLAN transceiver  370 . In some embodiments, 3D scanner  10  may connect with a smart phone (not shown) via Bluetooth transceiver  370  and/or WLAN transceiver  360 . In some embodiments, 3D scanner  10  may include onboard memory  350  for storage of two dimensional images or videos, and/or three dimensional point clouds or models. In some embodiments, 3D scanner  10  may be connected via one or more cables to host computer  340 ; host computer  340  may perform computational tasks central to the function of 3D scanner  10  including processing and rendering of three dimensional models. In other embodiments, host computer  340  may be used to display three dimensional models, images and/or videos captured and rendered by 3D scanner  10 . In further embodiments, 3D scanner  10  may be connected to host computer  340  via WLAN transceiver  360  and/or Bluetooth transceiver  370 . In further embodiments, 3D scanner  10  may not be attached to host computer  340 . In further embodiments, all processing and rendering may be performed by 3D scanner  10 ; three dimensional models, images and/or may be displayed by touch screen  380  contained within 3D scanner  10 . In some embodiments, touch screen  380  may react to user touch and gestural commands. In some embodiments, touch screen  380  may not respond to user touch or gestural commands. In some embodiments, 3D scanner  10  may not include touch screen  380 . 
         [0042]      FIGS. 11   a  and  11   b  illustrate two exemplary projected patterns for 3D scanner  10 , specifically in  FIG. 11   a  shows a monolithic pattern, and  FIG. 11   b  shows a plurality of separate patterns. 
         [0043]    In one embodiment  FIG. 11   a  comprises substrate  120  that is a transmissive substrate  125  containing precisely phase shifted and periodic patterns  80   a ,  90   a , and  100   a  as well as correspondence pattern  110   a  (shown on the substrate in  FIG. 8 ). When projected, patterns  80 ,  90  and  100  generate an image with periodically varying intensity on the surface being scanned, and correspondence pattern  110  generates a known image used to establish correspondence between the camera images. By disposing patterns  80   a ,  90   a ,  100   a  and  110   a  on a single monolithic transmissive substrate  125 , proper alignment between patterns  80 ,  90  and  100  may be ensured without highly precise and costly manufacturing methods.  FIG. 11   a  illustrates the embodiment wherein the direction of the phase shifting of the projected patterns  80 ,  90 , and  100  is generally perpendicular to the direction of separation of the patterns. As shown, the projected patterns  80 ,  90 ,  100  are phase shifted along the x-axis while the projected patterns  80 ,  90 ,  100  are separated from each other along the y-axis. This orientation helps ensure the phase shift of the projected patterns  80 ,  90 ,  100  is not dependent on the distance from the projectors to the illuminated plane, thereby increasing 3D scanner measurement precision over a system which does not incorporate this constraint. In other embodiments, patterns  80 ,  90 , and  100  may not be periodic. In other embodiments pattern  110  may not be random. 
         [0044]    In one embodiment  FIG. 11   b  comprises a plurality of separate periodic patterns  510 ,  520 ,  530  projected onto a surface as well as a separate correspondence pattern  110 . In one embodiment the projected periodic patterns  510 ,  520 ,  530  may be rotated with respect to one another, in such a fashion that when they are projected a camera capturing images of the projected patterns is able to distinguish between the different patterns. In the embodiment shown, the lines in projected patterns  510 ,  520 ,  530  are rotated at about forty-five degrees relative to each other. In one embodiment projected periodic patterns  510 ,  520 ,  530  and correspondence pattern  110  may have any arbitrary spacing and relative rotation between them so long as periodic patterns  510 ,  520 ,  530  are sufficiently rotated with respect to one another so as to allow their projected patterns to be distinguished from other another. In one embodiment periodic patters  510 ,  520 ,  530  and correspondence pattern  110  may all lay on the same plane. In another embodiment, periodic patterns  510 ,  520 ,  530  and correspondence pattern  110  may lie on different planes than one another. In another embodiment patterns  510 ,  520 ,  530  may not be periodic. In some embodiments any suitable correspondence pattern  110  may be used, including a random pattern, a deBruijn sequence, or a minimum Hamming distance pattern. 
         [0045]    Some embodiments include a method of using the correspondence pattern  110  to help generate the 3D image. As discussed above, some embodiments include the use of two separate cameras  60 . Each camera  60  captures an independent image of the patterns projected onto the object. It should be noted that as few as two patterns may be used in the present invention—one correspondence pattern  110  and one non-correspondence pattern (such as  80 ,  90 ,  100 ,  400 ,  410 ,  412 ,  414 ,  416 ,  510 ,  520 , or  530 ). The various patterns, including the correspondence pattern  110 , are sequentially projected onto the object and captured and processed by the system. The correspondence pattern  110  includes one or more definable unique areas which may be easily identified by both cameras  60  (in contrast to the non-correspondence patterns whose periodic characteristics may make it difficult for the system to distinguish between different regions of the pattern). The one or more unique areas of the correspondence pattern  110  are identified and stored by the system in a memory so their position on the object can be identified when the other (non-correspondence  110 ) pattern(s) is (are) projected. The unique area of the non-correspondence  110  pattern(s) is (are) captured by both cameras  60  and compared by the processor. Triangulation is obtained by determining the optimal shift for each pixel in the unique area for each non-correspondence pattern. At first, the cross-section of the lines in the non-correspondence pattern will not line up since each camera  60  sees the pattern from a different angle. By shifting each pixel and knowing the separation distance between the cameras, the correct shift can be obtained for each non-correspondence pattern. Once this shift is computed, the processor uses this information to create the 3D image of the object through conventional means. 
         [0046]    Having thus described the invention in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein without departing from the spirit and scope of the invention. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included within the scope of the following claims.