Abstract:
An apparatus and method for visually enhancing the ability to perform a medical procedure. The apparatus and method relates to an optical device configured to superimpose a display image over an object, wherein the display image aligns and corresponds with a portion of the object. The optical device includes a partial reflective device and a display member having a display surface configured to display the display image. The display member is oriented with respect to the partial reflective device such that the display image appears superimposed to a viewer over the object. With this arrangement, the display member displays an image that reflects with the partial reflective device and into a viewer&#39;s optical viewing path so that the viewer can see the displayed image through the partial reflective device superimposed over the object. The viewer may change the displayed image to another displayed image representing a portion further in depth into the object to obtain additional information with respect to the object.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional application No. 60\391,356, filed Jun. 25, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to an apparatus and method for visually combining an image with an object. More particularly, the present invention relates to a device and method for interposing a reflected image between an object and an individual or apparatus viewing the object for providing a physical collocation in real space of the object and image.  
           [0004]    Visual perception is defined by both psychological (e.g. shading, perspective, obscuration, etc.) and physiological (convergence, accommodation, etc.) depth cues. Only the physiological depth cues are able to unambiguously discern the distance of points on an object from the viewer, since they arise from physiological changes in the vision system such as lens muscles contracting or expanding, or the movement of the eyes as they focus at different depths. If the vision system is to compare two objects, it is important they are perceived at the same depth, otherwise visual strain can result from differentially focusing between the objects. Strain arising from the visual system moving between the objects can be further reduced if the two objects are superimposed on each other. If one of these objects is a two-dimensional cross-section of a 3D object and is seen superimposed on the 3D object, it is important that the superimposed image is displayed at its correct distance within the object. Otherwise, the physiological depth cues will correctly inform the viewer that they are at different distances from the viewer, which can have serious consequences if the viewer is a surgeon.  
           [0005]    1. State of the Art  
           [0006]    Current techniques in the field of neurosurgery for displaying three-dimensional scanned information require the viewer to look away from the direct field of view to look at either two-dimensional cross-sectional or three-dimensional alternative representations of the anatomy on two-dimensional display devices. Typically these alternative representations are three-dimensional scans of the anatomy derived from a CT, MRI, PET or other types of three-dimensional scanners, and are displayed to aid the healthcare professional in navigating through the real anatomy.  
           [0007]    For example, U.S. Pat. No. 6,167,296 to Shahidi discloses a surgical navigation system including a surgical pointer and a tracking system interconnected to a computer having data from an MRI or CT volumetric scan. The surgical pointer may be positioned on a portion of the patient&#39;s body, wherein the position of the pointer may be tracked in real time and conveyed to the computer with the volumetric scans. The computer then provides the real time images from the viewpoint of the pointer in combination with the volumetric scans to be displayed on a display screen to, thereby, allowing a surgeon to positionally locate portions on the patient&#39;s body with respect to the volumetric scans. While the Shahidi reference provides a device for positionally locating portions of a patient&#39;s body with respect to a volumetric scan, such device requires the surgeon to look away from the patient to the display screen to make comparisons between the position of the surgical pointer and the volumetric scan.  
           [0008]    U.S. Pat. No. 5,836,954 to Heilbrum et al. discloses a device for defining a location of a medical instrument relative to features of a patient&#39;s body. The device includes a pair of video cameras fixed with respect to the patient&#39;s body to provide a real-time image on a display. The real-time image is aligned with a previously scanned image, such as an MRI, CT or PET scan, so that the medical instrument can be localized and guided to a chosen feature in the scan. In this manner, a surgeon can positionally locate the medical instrument with respect to the scan and the real-time image. However, such device requires the surgeon to look away from the patient to the display screen to locate the position of the medical instrument.  
           [0009]    In each of the references discussed above, the medical practitioner is not able to optimize physiological and psychological depth cues during an operational procedure. Such physiological and psychological depth cues are triggered by objects when seen in their true three-dimensional space. The human visual system uses both physiological and psychological depth cues to determine relative positions in a three-dimensional space. The physiological depth cues include convergence, accommodation, binocular disparity and motion parallax. These physiological depth cues are the most important to professionals making critical decisions, such as neurosurgeons, yet these depth cues are not available in their field of view, in typical stereo-tactic displays. Therefore, it would be advantageous to medical practitioners to conduct medical procedures without substantial hampering of physiological and psychological depth cues.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    The present invention relates to a method and apparatus for providing physical collocation of a real object and a projected image in real space. According to the present invention, the collocation of an object and a projected image may be accomplished by interposing a partially reflective device between an object and an individual viewing the object. An image to be collocated with the object may be projected to reflect from the partially reflective device such that an individual viewing the object through the partially reflected device also views the reflected image.  
           [0011]    The ability of the present invention to visually create a collocated image with an object provides a tool and method for visually exploring the interior of an object without altering the physical characteristics of the object. For instance, the interior of an opaque object may be digitally represented as images produced by an electronic scan such as a CT scan, MRI scan, or the like. A series of scans may be combined to define a three-dimensional image of the object, including portions of the interior of the object. Cross-sections of the three-dimensional image may be projected onto the partially reflective device such that an individual viewing the object through the partially reflective device may see the cross-sectional image collocated within the object. This provides the viewer a unique look into the interior of the object.  
           [0012]    The present invention may also be configured to accurately collocate an image of an interior portion of the object at a point in space corresponding with the actual portion of the object represented by the image. This provides an individual the ability to view a three-dimensional characterization of the object without altering the state of the object. Stated otherwise, the instant invention permits the user to “look” into the interior of an object without the need to cut into the object to reveal its interior. The invention provides a two-dimensional view of the interior of the object which can be transformed into a three-dimensional characterization through the viewing of multiple images over an extended period of time.  
           [0013]    The partially reflected device for use with the various embodiments of the present invention may be part of an image projection device that also includes a display device, a computing system coupled to the display device, and a tracking system for tracking a position of the partially reflective device in a three-dimensional field about an object being viewed in accordance with the present invention. The display device may be used to project a desired image onto the partially reflective device and may include such things as computer displays, flat panel displays, liquid crystals displays, projection apparatuses, and the like. An image created by or stored in the computing system may be displayed on the display device and reflected off of the partially reflected device. The tracking system may be coupled with the computing system to track movement of the partially reflective device and to provide a reference point for determining the image to be displayed on the display device. Movement of the image projection device or the partially reflective device may be tracked by the tracking system and relayed to the computing system for updating the image displayed on the display device in accordance with the movement of the image projection device or partially reflective device.  
           [0014]    In one embodiment of the present invention an image projection device includes a partially reflective device mounted a fixed distance from a display device. A computing system coupled with the display device includes one or more memories for storing data corresponding to images of an object. The computing system creates and displays images from the data stored in the memory of the computing system. A tracking system coupled to the computing system may be used to track the position of the partially reflective device within a three-dimensional space. The images created by the computing system and displayed on the display device may be altered by the movement of the partially reflected device as monitored by the tracking system. As the partially reflective device is moved, either manually or automatically, the display device also moves in a corresponding fashion such that the fixed distance and position between the partially reflected device and the display device remains constant. As the partially reflective device is moved within space around an object, the tracking system monitors the position of the partially reflective device and relays the position to the computing system. Based upon the position of the partially reflective device within space, the computing system creates a two-dimensional image of the object from the data stored in memory. The two-dimensional image is displayed on the display device and is reflected off of the partially reflective so that it may be viewed by a viewer. In this embodiment of the present invention, the image created by the computing system corresponds to the image that would appear a second fixed distance from the partially reflective device, the second fixed distance being the distance between the partially reflected device and a portion of the object being viewed. The second fixed distance is equal to the fixed distance between the partially reflective device and the display device. Thus, the image reflected off of the partially reflected device appears within the object a second fixed distance from the partially reflective device.  
           [0015]    In another embodiment of the present invention, the partially reflective device and the display device may be operably coupled to a movement mechanism for controlling the movement of the partially reflective device and the display device. For instance, the movement mechanism may include a foot pedal control coupled to devices for moving the partially reflective device and display device as the foot pedal control is used. Alternatively, the movement mechanism may be controlled with a mouse-like control, a joystick, voice command system, or other device for receiving movement instructions and moving the partially reflective device and display device in accordance with the movement instructions. In this way preprogrammed view paths can be traced through the object.  
           [0016]    In yet another embodiment of the present invention, the display device maybe moved relative to the partially reflective device such that the fixed distance between the display device and partially reflective device is altered. As the fixed distance between the display device and the partially reflective device is changed, the image reflected by the partially reflected device appears to move relative to the increase or decrease in distance between the partially reflective device and display device. The displayed images displayed by the display device may be altered in conjunction with the movement of the display device to reflect an image off of the partially reflective device corresponding to the distance between the partially reflective device and the display device.  
           [0017]    In another embodiment of the present invention, the display device and computer system may be configured to change the display of an image without movement of the partially reflective device. An image displayed on the display device may include an image not associated with the object at the second fixed distance from the partially reflective device. The image displayed on the display device, and reflected from the partially reflective device, may instead be an image associated with a defined positive or negative distance from the second fixed distance. When displayed on the display device, the reflected image appears collocated with the object at a second fixed distance although the actual image being displayed is of that portion of the object a distance equal to the second distance plus or minus the defined distance. Using this embodiment of the present invention, a user may step forward or backward through reflected images to see portions of the object a further or shorter distance from the partially reflective device. In this way the viewer has a look-ahead capability without changing their focus from the current position. However, such disassociation of the reflected image position and the actual position within the object should be used with caution.  
           [0018]    Other features and advantages of the present invention will become apparent to those of skill in the art through a consideration of the ensuing description, the accompanying drawings and the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0019]    While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the invention may be further understood from the following description of the invention when read in conjunction with the accompanying drawings, wherein:  
         [0020]    [0020]FIG. 1 illustrates a side perspective view of an optical space combining device in communication with an electronic system and tracking system, according to a first embodiment of the present invention;  
         [0021]    [0021]FIG. 2 illustrates a front perspective view of an optical space combining device in communication with the electronic system and tracking system, according to a first embodiment of the present invention;  
         [0022]    [0022]FIG. 3 illustrates a perspective side view of the optical space combining device in communication with an electronic system and tracking system, according to a second embodiment of the present invention; and.  
         [0023]    [0023]FIG. 4 illustrates a perspective side view of the optical space combining device in communication with the electronic system, according to a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    The various embodiments of the present invention are hereinafter described with reference to the accompanying drawings. It is understood that the drawings and descriptions are not to be taken as actual views of any specific apparatus or method of the present invention, but are merely exemplary, idealized representations employed to more clearly and fully depict the present invention than might otherwise be possible. Additionally, elements and features common between the drawing figures retain the same numerical designation.  
         [0025]    One embodiment of an image projection device  100  of the present invention that may be used to carry out the various methods embodied in the present invention is illustrated in FIG. 1. The image projection device  100  may include a partially reflective device  110 , a display device  120 , an imaging system  160 , and a tracking system  170 . The image projection device  100  may also include a carrier  130  to which the partially reflective device  110  and display device  120  may be moveably attached. Also illustrated in FIG. 1 are an object  150  and a view point  140 .  
         [0026]    The partially reflective device  110  may include any device that is transparent and is also able to reflect light. For instance, the partially reflective device  110  may include a device commonly referred to as a half-silvered mirror. A half-silvered mirror allows light to pass through the mirror while reflecting a portion of the light impinging on one surface of the mirror. As illustrated, the partially reflective device  110  includes both a first surface  112  and a second surface  114 . If the partially reflective device  110  is a half-silvered mirror, light reflected off of object  150  passes from the object  150  through second surface  114  of the half-silvered mirror towards view point  140 . A portion of light directed from display device  120  towards first surface  112  of the half-silvered mirror is reflected off of the first surface  112  back to the view point  140 . Thus, light passes through the half-silvered mirror and is also reflected by the half-silvered mirror.  
         [0027]    Additional devices capable of partially reflecting light and partially transmitting light through the device may be used as the partially reflective device  110  of the present invention. Like partial mirrors, such as a half-silvered mirror, polarized glass, glass plates, or plastic plates configured to both reflect and transmit light could be used. Furthermore, glass or plastic plates may be etched to alter the refractive qualities of the plate such that it could be used as a partially reflective device  110 . Other devices, such as a liquid crystal container filled with liquid crystals, may be used as the partially reflective device  110  such that the amount of reflectance and transmittance may be controlled by a user of the partially reflective device  110 . For example, variation of an electrical impulse to a liquid crystal container could alter the state of the liquid crystals in the container, thereby changing the amount of reflectance and transmittance realized by the liquid crystal container. The various embodiments of the present invention are not limited by the descriptions of the partially reflective devices  110  given herein.  
         [0028]    The partially reflective device  110  may also include refraction altering films applied to one or more surfaces of the partially reflective device  110 . For instance, an antireflecting film  116  may be applied to a second surface  114  of the partially reflective device  110  to prevent the reflection of light reflecting off of object  150 . The use of an antireflective film  116  on a second surface  114  of the partially reflective device  110  helps to ensure that as much light as possible is transmitted through the partially reflective device  110  from object  150  to view point  140 . Other filtering films, polarization films, and the like may also be used with or applied to the partially reflective device  110 .  
         [0029]    The display device  120  of the image projection device  100  may include any device capable of projecting or displaying an image. Any number of available display devices  120  may be used with the present invention, including such devices as a monitor screen, a flat panel display screen, a television tube, a liquid crystal display, an image projection device, and the like. The example display device  120  illustrated in FIG. 1 includes a display surface  122  recessed in a display housing  124 . An input port  126  in the display housing  124  may accept or transmit data, input power to the display device  120 , or provide other data communications. Data received at input port  126  may be converted to an image for display on display surface  122 .  
         [0030]    The partially reflective device  110  and the display device  120  may be moveably attached to a carrier  130  such that the display device  120  may be positioned a distance d, from the partially reflective device  110 . Fastening devices such a bolts, screws, clamps, or other devices may be used to moveably attach the display device  120  and partially reflective device  110  to carrier  130 . Alternatively, the display device  120  and partially reflective device  110  may be moveably attached to or fitted into defined portions of carrier  130  for holding or supporting the display device  120  or partially reflective device  110 . In one embodiment, the carrier  130  may include two ends where one end terminates with the attachment to the partially reflective device  110  as illustrated in FIG. 1. In another embodiment, carrier  130  may include a track upon which a movable attachment device connected to display device  120  may be moved and fixed such that the display device  120  may easily move up and down carrier  130  to lengthen or shorten distance d 1 .  
         [0031]    Imaging system  160  provides data to display device  120  for producing an image on a display surface  122  of display device  120  or otherwise projecting an image from display device  120 . As illustrated in FIG. 1, imaging system  160  may include a computer  162  with one or more memories  163 , one or more storage devices  164 , and coupled to one or more input devices  166  and displays  168 . Computer  162  may include any type of computing system capable of storing and transmitting data. For instance, computer  162  may include a standalone computing system, a networked computing system, or other data storage and processing device capable of storing and transmitting image data to a display device  120 . Storage devices  164  may include data storage devices and readers such as disk drives, optical drives, digital video disc drives, compact disc drives, tape drives, flash memory readers and the like. In an alternate embodiment of the present invention, the imaging system  160  may be incorporated with display device.  
         [0032]    Image data corresponding to an object  150  may be stored in one or more memories  163  of the imaging system  160  or on media readable by storage devices  164 . Image data may include data for constructing three-dimensional representations of objects or for creating two-dimensional planar views of a three-dimensional image. For instance, image data may include data developed from a CT scan of a portion of a human being, such as a CT scan of a person&#39;s head. The image data may be utilized, i.e. integrated, to construct a three-dimensional image of the person&#39;s head. Alternatively, the image data from the CT scan may be used to compile two-dimensional “slices” of the larger three-dimensional image. Each two-dimensional slice image created from the data represents a particular portion of the person&#39;s head at a definite location about the person&#39;s head. Other types of image data may include data developed from MRI scans, ultrasound scans, PET scans, and the like. Methods for collecting and storing image data that can be used with the various embodiments of the present invention are known. Furthermore, software and hardware for integrating image data into two-dimensional slices or three-dimensional images as used by the present invention are also known. Such software or hardware may operate on or with computer  162  to create images for display on display device  120  from the image data accessible to the imaging system  160 .  
         [0033]    The image projection device  100  of the present invention may also include a tracking system  170  for locating the position of the partially reflective device  110  or display device  120  within a three-dimensional space. The tracking system  170  may include any system capable of tracking the position of the partially reflective device  110  based upon coordinates along x, y, and z axes in a three-dimensional space. Furthermore, the tracking system  170  may also be configured to track the rotation of the partially reflective device  110  about the x, y, and z axes. The tracking system  170  may be operably coupled to the imaging system  160  to provide the location of the partially reflective device  110  such that the imaging system  160  may adjust the data sent to the display device  120  to alter the displayed image to correspond with the view of an object  150  from a view point  140  through the partially reflective device  110 .  
         [0034]    The tracking system  170  of the present invention monitors the position of the partially reflective device  110  relative to the object  150  and communicates the position to the imaging system  160 . The imaging system  160  creates an image for display on display device  120  based upon the position of the partially reflective device  110  as monitored by the tracking system  170 . For instance, tracking system  170  may include a receiver  172  and a transmitter  174 . Transmitter  174  may transmit a magnetic field about object  150  and image projection device  100 . The receiver  172  may include a device that disrupts the magnetic field created by transmitter  174 . As the receiver  172  passes through the magnetic field created by transmitter  174 , the transmitter  174  detects the interruption in the magnetic field and determines the position of the disruption. Coordinates corresponding with the disruption in the magnetic field may be passed by the transmitter  174  to the imaging system  160  to relay the position of the partially reflective device  110  within the magnetic field. Images created by imaging system  160  and displayed on display device  120  are based upon the position of the partially reflective device  110  within the magnetic field. For example, the transmitter  174  may be placed next to an object  150  to create a magnetic field about the object  150  and the image projection device  100 . A receiver  172  mounted to the partially reflective device  110  creates disturbances in the magnetic field created by the transmitter  174 . The transmitter detects the disturbances and the tracking system  170  communicates the coordinates of the disturbances to the imaging system  160 . The imaging system  160  uses the coordinates received from the tracking system  170  to determine the data for creating an image on display device  120  and passing the data to the display device  120 . The tracking system  170  of the present invention is not limited to a magnetic field disturbance tracking system as described. Other tracking methods or systems capable of monitoring the position of the partially reflective device  110  about an object  150  may be used.  
         [0035]    According to the various embodiments of the present invention, an image displayed by display device  120  may be reflected off of the partially reflective device  110  such that a viewer positioned at view point  140  views a collocation of the displayed image with an object  150 . The image projection device  100  may be positioned proximate an object  150  such that the object  150  may be viewed through the partially reflective device  110  from view point  140 . In particular, the partially reflective device  110  and display device  120 , preferably connected to carrier  130 , are positioned proximate to object  150  for viewing object  150  through the partially reflective device  110  from view point  140 . The position of the imaging system  160  is less important and the only requirement is that the imaging system  160  is capable of relaying data to display device  120  and receiving positioning coordinates from the tracking system  170 . For instance, the imaging system  160  may be located remote to the display device  120  and partially reflective device  110  while remaining in communication with the display device  120  and tracking system  170  through wired communications, wireless communications, or other data exchange communications. Alternatively, the imaging system  160  may be incorporated with display device  120  such that the display device  120 , partially reflective device  110 , and carrier  130  are moveable about object  150  without any hindrance. The tracking system  170  may be integrated with the carrier  130  or positioned about object  150  and partially reflective device  110  so that the position of the partially reflective device  110  with respect to the object  150  may be monitored and coordinates relayed to the imaging system  160 .  
         [0036]    The positioning of the image projection device  100  about object  150  as monitored by the tracking system  170  dictates the image displayed by display device  120 . The imaging system  160  constructs an image from data based upon the position of the image projection device  100  about the object  150  and more particularly, based upon the position of the partially reflective device  110  with respect to object  150 . The image, or data representing the image constructed by the imaging system  160 , is communicated to the display device  120  and the image is displayed on the display surface  122  of the display device  120 . The displayed image is reflected off of the partially reflective device  110  in the viewing path  142  with the view of the object  150  from view point  140 . The reflection of the displayed image off of the partially reflective device  110  in the viewing path  142 , combined with the reflection of light off of the object  150  which passes through the partially reflective device  110  in viewing path  142 , creates a dual image at view point  140  for a person or camera viewing the object  150  from view point  140 . For instance, a person viewing object  150  through partially reflective device  110  from view point  140  would see both the object  150  and a reflection of the displayed image from display device  120 . The combination of the reflection of the displayed image and the image of the object  150  as viewed through the partially reflective device  110  creates a physical collocation of the object  150  with the reflected image displayed on display device  120 .  
         [0037]    The various embodiments of the present invention provide methods for viewing imaged portions of an object  150  collocated, or superimposed, with the object  150 . For example, an object  150  may be scanned using a CT scan and the data from the CT scan stored in an imaging system  160  or made accessible to the imaging system  160 . The data from the CT scan may be constructed into images for display on display device  120 . When an image created from a CT scan of an object  150  is displayed by display device  120 , the image is also reflected off of partially reflective device  110 . A viewer viewing the object  150  through the partially reflective device  110  views both the object  150  and the reflected image. To the viewer, the reflected image appears to be superimposed on, or within, the object  150 . The apparent location of the image within the object  150  depends upon the distance between the display device  120  and the partially reflective device  110 . In certain embodiments of the present invention, the display device  120  is mounted a fixed distance d 1  from the partially reflective device  110  as illustrated in FIG. 1. A reflected image of the display of the display device  120  off of partially reflective device  110  will appear to be a distance d 1 ′ from the partially reflective device  110  where distance d 1 , and d 1 ′ are equal. If the distance between display device  120  and partially reflective device  110  is altered, the distance d 1  changes and the apparent location of an image reflected off of the partially reflective device  110  will also change to appear a distance d 1 ′ from the partially reflective device  110  where distance d 1  and d 1 ′ remain the same. Therefore, as the display device  120  is moved closer to the partially reflective device  110  the reflected image off of the partially reflective device  110  appears to move closer to the view point  140 . Similarly, as the display device  120  is moved away from the partially reflective device  110  the reflected image appears to move further away from view point  140 .  
         [0038]    In certain embodiments of the present invention the distance between the display device  120  and the partially reflective device  110  is held at a constant distance d 1 . The images displayed by display device  120  and reflected off of partially reflective device  110  in viewing path  142  appear to a viewer at a view point  140  to be a distance d 1 ′ from the partially reflective device  110 . If a viewer is viewing an object through the partially reflective device  110 , the reflected image is superimposed in the object  150  at a distance d 1 ′ from the partially reflective device  110 . If the partially reflective device  110  and display device  120  are moved closer to the object  150 , the reflected image appears to move through the object  150 , maintaining a distance d 1 ′ from the partially reflective device  110 . Likewise, if the partially reflective device  110  and display device  120  are moved away from the object  150  the reflected image appears to move through object  150  towards view point  140 . At all times, the reflected image appears to be superimposed on the object  150  at a distance d 1 ′ from the partially reflective device  110 .  
         [0039]    Imaging systems, such as the imaging system  160  used with the present invention, provide the ability to create two-dimensional or three-dimensional images of an object  150  based upon imaging data taken of the object  150 . For instance, data from a CT scan of an object may be constructed to create images of two-dimensional slices of the object  150 . One example of such a system is used for medical purposes. A CT scan of a human&#39;s head may be conducted and the data used to recreate images of the interior portions of the head. Typically, the images created are two-dimensional images representing slices through the head. Three-dimensional images may also be created from the data. The data may be combined such that the two-dimensional images may be created from any angle. In other words, the images may be constructed to represent slices appearing along multiple planes, from multiple angles. Thus, images may be constructed as if a person was looking at the head from the side of the head, from the top of the head, from the bottom of the head, or from any other angle. Based upon the desired viewing angle, the imaging system  160  is capable of constructing an image of the head.  
         [0040]    Furthermore, imaging systems may be used to step through an object  150  and create images of the object  150  based upon the desired location within the object  150 . The ability of the imaging system  160  to create an image may depend upon the amount of data available to the imaging system  160  from the scan performed of the object  150 . For instance, with respect to a human&#39;s head, a CT scan may be performed wherein the equivalent of twenty scans at a distance of 5 millimeters are taken. Images created from the data are limited to the data available. Thus, if a person wished to step through the images of the scanned head they may be limited to twenty images corresponding to the twenty scans performed. However, if one hundred scans were performed at a distance of 1 millimeter, one hundred images could be stepped through using the imaging system  160 . In some instances, the imaging system  160  may be able to create a three-dimensional image from the scan data or be able to interpolate additional images based upon the overall three-dimensional structure of the object. An imaging system  160  capable of interpolating scan data into a three-dimensional image may be capable of creating as many images from the data as desired. Thus, a user could indicate that they wished to view two-dimensional images in one millimeter steps through the object  150  or in ⅕ millimeter steps through the object  150 .  
         [0041]    The combination of the imaging system  160  capabilities with the partially reflective device  110  and display device  120  of the present invention provides methods for altering the displayed images on the display device  120  so that different portions of the object  150  may be viewed as reflections off of the partially reflective device  110 . Changing the displayed image changes the reflection so that a viewer viewing an object  150  through the partially reflective device  110  also sees the displayed portion of the object as it appears on the display device  120  superimposed on the object  150  at a distance d 1 ′ from the partially reflective device  110 . Thus, the imaging system  160  may be instructed to create two-dimensional images of the object  150  from scan data of the object  150 , and step through the data, creating and displaying images of each step through the object  150  on the display device. Thus, as a viewer views the object  150  through the partially reflective device  110  they may also see and step through the images created by the imaging system  160 . However, unless the partially reflective device  110  and display device  120  are moved as images corresponding to different portions of the object  150  are displayed by imaging system  160 , all of the images will appear superimposed on the object  150  at a distance d 1 ′ from the partially reflective device  110 .  
         [0042]    The tracking system  170  of the present invention may be combined with the imaging system  160 , display device  120 , and partially reflective device  110  to provide a dynamic system that allows a user to alter the reflected images based upon the positioning of the partially reflective device  110  with respect to an object  150 . For instance, as the partially reflective device  110  is moved closer to the object  150  a reflected image created by the imaging system  160  and displayed on display device  120  appears to move through the object  150 , maintaining a distance d 1 ′ from the partially reflective device  110 . If the movement of the partially reflective device  110  with respect to the object  150  is tracked by tracking system  170 , the tracking system  170  may communicate the distance moved to the imaging system  160  so that the imaging system  160  may alter the displayed image to correspond with an image of the object  150  at the distance d 1 ′ from the partially reflective device  110 . Therefore, as the partially reflective device  110  is moved closer to the object  150  the displayed image changes to reflect that portion of the object  150  at the distance d 1 ′ from the partially reflective device  110 . A person using the present invention to view an object  150  through partially reflective device  110  along with a reflected image of an interior portion of the object  150  could therefore “step through” the object  150  and view superimposed scanned images of the object by moving the partially reflective device  110  closer to or away from the object  150 .  
         [0043]    The collocation of a reflected image displayed by display device  120  with an object  150  such that a displayed image corresponds exactly with a portion of the object  150  a distance d 1 ′ from the partially reflective device  110  may be accomplished by coordinating the scanned images with the object  150 . Coordination of the images with the movement of the partially reflective device  110  may be accomplished by aligning registration points of the object  150  with registration points recorded with the scanned data and setting the tracking system  170  to monitor movement based upon the registration. The coordination of the images with the object  150  may be accomplished by aligning known common points, such as registration points  152 , appearing on the object  150  and in the displayed images. Two or more registration points  152  associated with object  150  may be aligned with registration points  152  appearing on images created from scanned data. Once aligned, the tracking system  170  may be set to monitor the movement of the partially reflective device  110  with respect to the object  150  based upon the registration. This provides a correlation between distance d 1 ′ from the partially reflective device  110  with the image displayed by imaging system  160  on display device  120  such that the displayed and reflected image viewed by a user is an image of the object  150  at the distance d 1 ′ from the partially reflective device  110 .  
         [0044]    An example of a process that may be used to register the tracking system  170  involves the placement of registration points on an object before obtaining scan data. For instance, an object  150 , such as a human head, may be fixed with two or more registration points prior to a scan to obtain image data. The scanned data picks up and includes the positions of the registration points on the head. Viewing the head through the partially reflective device  110 , the registration points on the head may be seen. Images created from the scan data and displayed by imaging system  160  on the display device  120  may be adjusted to show images corresponding to the scanned data of the registration points. The partially reflective device  110 , with display device  120  fixed a distance d 1  from the partially reflective device  110 , may be moved with respect to the object  150  until the registration points  152  on the object align with and correspond to the registration point images reflected off of the partially reflective device  110 . Once the registration points  152  of the object  150  are aligned in space with the registration points on the images created by the imaging system  160 , the tracking system  170  may be configured to base movement instructions sent to the imaging system  160  based upon the registration alignment.  
         [0045]    As the tracking system  170  monitors the movement of the partially reflective device  110  with respect to an object  150 , the tracking system  170  communicates the movement to the imaging system  160  which in turn alters the data sent to the display device  120  to alter the displayed image to correspond with the position within the object a distance d 1 ′ from the partially reflective device  110 . The images displayed and reflected in viewing path  142  create a collocated image within object  150 . This allows a user to explore the images of the interior of the object  150  from scan data collocated with the object  150 .  
         [0046]    The various embodiments of the present invention may be used in numerous applications where it is desirable to view an object  150  while simultaneously viewing scanned data representing images of portions of the object  150  collocated with the object. As an example, use of the present invention in the medical field is explained, however, it is understood that the examples do not limit the scope of the invention or the claims.  
         [0047]    Neurosurgery is a delicate procedure, often requiring precise movements and attention to detail. To facilitate neurosurgical procedures imaged data of a person&#39;s head is often viewed before and during the neurosurgical procedure. Scanned images of the head may be stepped through and viewed on a monitor as the neurosurgeon performs an operation. To view the scanned images, the neurosurgeon glances away from the head, or operating object, to view a monitor displaying the scanned images. Although alternating views of the operating object and the monitor allow the surgeon to view scanned images, it is difficult to correlate the images with the operating object because they are not in the same view path or superimposed on each other.  
         [0048]    At least one embodiment of the present invention may be used to improve neurosurgical techniques. An image projection device  100  may be used during neurosurgery as illustrated in FIG. 2. The image projection device  100  may be used to display images of the scanned operating object  150  in the view path  142  of the surgeon  140 . This allows the surgeon to view both the operating object  150  and images of the interior of the operating object during the surgery.  
         [0049]    In one embodiment of the present invention, the head of a patient may be scanned, such as by a CT scan, MRI scan, PET scan, or the like, and the data stored in an imaging system  160  for creating two-dimensional images of the head. Registration points  152  may be applied to the head  150  prior to scanning to provide images with registration point  142  for calibrating the image projection device  100 . In the operating room, the image projection device  100  may be located proximate to the head  150  of the patient such that a surgeon  140  may view the head  150  through the partially reflective device  110  of the image projection device  100 . Before use, registration or calibration of the tracking system  170  is performed. The surgeon  140  aligns the registration points  142  on the head  150  with registration point  142  images created by the imaging system  160 , displayed by display device  120  and reflected off of the partially reflective device  110 . The tracking system  170  may be set or configured once the registration points  142  on the head and the images are aligned.  
         [0050]    During surgery, the image projection device  100  may be used to view scanned images of the portions of the head  150  that the surgeon wishes to view. For instance, if the surgeon is working within the head  150  and they wish to see what is coming up next, in other words a portion of the head  150  that is not yet exposed by surgery, the surgeon may move the partially reflective device  110  closer to the head  150  thereby causing a displayed image associated with a portion of the head  150  a distance d 1 ′ from the partially reflective device  110  to be collocated with the head  150  by reflection off of the partially reflective device  110 . The surgeon may move the partially reflective device  110  back, away from the head  150  to again view the portion of the head  150  where the surgery is taking place. Use of the partially reflective device  110  to perform such operations during surgery allows the surgeon to view, simultaneously, both the head  150  and a collocated image of a scan of the head  150 .  
         [0051]    Movement of the partially reflective device  110  during surgery may be accomplished manually or mechanically. The image projection device  100 , and more importantly the partially reflective device  110 , may be equipped with handles or other devices so that the partially reflective device  110  may be moved along and about an x-axis, y-axis, and z-axis. Alternatively, the partially reflective device  110  may be controlled by a mechanical device also capable of moving the partially reflective device  110  along and about an x-axis, y-axis, and z-axis. The control system may include movement controls such as a foot pedal, mouse, joystick, control panel, voice operated system, or other control mechanism for initiating movement of the partially reflective device  110 . The amount of movement associated with a certain command issued to a mechanical control system may be altered and programmed as desired by the user. For instance, a surgeon may set the control system to provide one millimeter movements of the partially reflective device  110  upon each movement command issued to the control system. The movement distance could also be altered for another surgery or during a surgery if smaller or larger movement was desired. For example, once a surgeon reaches the portion of the head  150  where finer detail and more precision is required, the movement could be adjusted to one-half millimeter movement increments rather than one millimeter movement increments.  
         [0052]    In another embodiment of the present invention, the surgeon may wish to advance the images produced by the imaging system  160  without moving the partially reflective device  110 . In other words, the surgeon may wish to maintain the position of the partially reflective device  110  while viewing the next image or series of images that can be created by the imaging system  160 . A control system, such as a foot operated control, hand operated control, voice operated control, or the like, may be integrated with the image projection device  100  to allow the surgeon to request movement through scanned images without movement of the partially reflective device  110 . Based upon the request to the control system, the imaging system  160  may be instructed to advance or step through the scanned images. The amount of movement through the images, in other words, the step distance or increment, may be set to a desired amount using the control system. Using this system, a surgeon could move forward through the scanned images of an object without moving the partially reflective device  110 . In instances where the images are altered without movement of the partially reflective device  110 , the reflected image will appear superimposed on the object  150  but they will not be collocated within the object because the distance d 1 ′ does not change as the images are displayed. This function, however, allows a surgeon to view images of the object that they will be seeing as they move deeper into the head during surgery. Also, a reset function may be incorporated with the control system for resetting the image corresponding to the distance d 1 ′ on the display device  120  thereby providing collocation of the reflected image with the head  150 .  
         [0053]    In yet another embodiment of the present invention, the partially reflective device  110  of the image projection device  100  may be fixed to a neurosurgeons operating microscope or visual enhancement device. Images reflected off of the partially reflective device  110  are reflected into the microscope so that the surgeon views the images with the operating object, or head  150 , view. This allows the surgeon to view scanned images of the operating object superimposed on the operating object.  
         [0054]    In each of the embodiments of the present invention, the display of the images produced by the imaging system  160  may be terminated and reinstated at will. In other words, a user may turn the display on and off in order to view a superimposed or collocated image or to remove the image from view path  142 . The display of the images may be turned on and off using manual or mechanical devices which may be integrated with control systems to allow voice control or manual control so the view of the object does not have to be disturbed to operate the display.  
         [0055]    In an alternate embodiment of the present invention the image projection device  100  may be used in conjunction with real-time scanning equipment or an imaging system  160  conducting real-time scanning. Real-time scanning provides an image of an object in real-time. For instance, an ultrasound scan may be in progress while the image projection device  100  is being used. Images created from the ultrasound may be passed to the imaging system  160  and used with the image projection device  100 . In another embodiment, helical scanners may be used with an object to scan the object while viewing the object through the partially reflective device  110 . The integration of the image projection device  100  with real-time scanning is especially useful in surgical environments where a patient&#39;s body may be changing. For instance, during neurosurgery, portions of the brain may be altered by the surgery being performed or they may have changed since the time of the scan, such as with the growth of a tumor. Use of a real-time scanning device allows the imaging system  160  to produce images of the head or brain as the surgery is taking place. Thus, the image projection device  100  may be used to view real-time images collocated with the operating object during surgery.  
         [0056]    [0056]FIG. 3 illustrates a perspective side view of the image projection device  100  in communication with an electronic system and a tracking system, according to a second embodiment of the present invention. The second embodiment is substantially the same as the first embodiment, except the second embodiment includes a stepper  292  and a foot pedal  294 . The stepper  292  may be an automated movable connector that is secured to the display device  120  and is movable by depressing the foot pedal  294 . The stepper  292  and foot pedal  294  combination provide a controlled, stepped movement of the display device  120 , wherein the receiver  172  should be in a fixed position with respect to said display device  120 . As such, the tracking system  170  tracks the movement and position of the display device  120  and changes the scanned image  180  with respect to such movement as described in the first embodiment herein.  
         [0057]    In the second embodiment, the movability of the image projection device  100  in combination with the tracking device  170  may still be utilized to determine the optimal position or optimal directional viewing course to examine the patient and object  150 , by which the tracking system  170  provides the position of the image projection device  100  so that the computer  160  may generate a corresponding scanned image  180 . Once such optimal position is determined by the viewer  140 , the stepper  292  and foot pedal  294  combination provide the viewer  140  the ability to change the scanned image  180  along the optimal directional viewing course without having to manipulate the optical device manually, thereby, allowing the viewer to change the scanned image  180  with the viewer&#39;s hands free to continue performance of any medical procedures necessary.  
         [0058]    Although the various embodiments are described where the partially reflective device  110  may sit suspended between the viewer and object, it is also contemplated that the partially reflective device  110  may be integrated on an ultrasound wand or other scanning device so that the partially reflective device  110  is reduced in size.  
         [0059]    Having thus described certain preferred embodiments of the present invention, it is to be understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof as hereinafter claimed.