Patent Publication Number: US-11663794-B2

Title: Content presentation in head worn computing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/240,830, filed Apr. 26, 2021, which is a continuation of U.S. patent application Ser. No. 16/841,508, filed Apr. 6, 2020, now U.S. Pat. No. 11,022,810, issued Jun. 1, 2021, which is a continuation of U.S. patent application Ser. No. 14/299,474, filed Jun. 9, 2014, now U.S. Pat. No. 10,649,220, issued May 12, 2020, the contents of which are incorporated herein by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     Field 
     This invention relates to head worn computing. More particularly, this invention relates to technologies for the presentation of digital content in head worn computing. 
     Description of Related Art 
     Wearable computing systems have been developed and are beginning to be commercialized. Many problems persist in the wearable computing field that need to be resolved to make them meet the demands of the market. 
     SUMMARY 
     Aspects of the present invention relate to methods and systems for presenting digital content in a field of view of a head-worn computer. 
     These and other systems, methods, objects, features, and advantages of the present invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiment and the drawings. All documents mentioned herein are hereby incorporated in their entirety by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are described with reference to the following Figures. The same numbers maybe used throughout to reference like features and components that are shown in the Figures: 
         FIG.  1    illustrates a head worn computing system in accordance with the principles of the present invention. 
         FIG.  2    illustrates a head worn computing system with optical system in accordance with the principles of the present invention. 
         FIG.  3   a    illustrates a large prior art optical arrangement. 
         FIG.  3   b    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  4    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  4   a    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  4   b    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  5    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  5   a    illustrates an upper optical module in accordance with the principles of the present invention. 
         FIG.  5   b    illustrates an upper optical module and dark light trap according to the principles of the present invention. 
         FIG.  5   c    illustrates an upper optical module and dark light trap according to the principles of the present invention. 
         FIG.  5   d    illustrates an upper optical module and dark light trap according to the principles of the present invention. 
         FIG.  5   e    illustrates an upper optical module and dark light trap according to the principles of the present invention. 
         FIG.  6    illustrates upper and lower optical modules in accordance with the principles of the present invention. 
         FIG.  7    illustrates angles of combiner elements in accordance with the principles of the present invention. 
         FIG.  8    illustrates upper and lower optical modules in accordance with the principles of the present invention. 
         FIG.  8   a    illustrates upper and lower optical modules in accordance with the principles of the present invention. 
         FIG.  8   b    illustrates upper and lower optical modules in accordance with the principles of the present invention. 
         FIG.  8   c    illustrates upper and lower optical modules in accordance with the principles of the present invention. 
         FIG.  9    illustrates an eye imaging system in accordance with the principles of the present invention. 
         FIG.  10    illustrates a light source in accordance with the principles of the present invention. 
         FIG.  10   a    illustrates a back lighting system in accordance with the principles of the present invention. 
         FIG.  10   b    illustrates a back lighting system in accordance with the principles of the present invention. 
         FIGS.  11   a  to  11   d    illustrate light source and filters in accordance with the principles of the present invention. 
         FIGS.  12   a  to  12   c    illustrate light source and quantum dot systems in accordance with the principles of the present invention. 
         FIGS.  13   a  to  13   c    illustrate peripheral lighting systems in accordance with the principles of the present invention. 
         FIGS.  14   a  to  14   c    illustrate a light suppression systems in accordance with the principles of the present invention. 
         FIG.  15    illustrates an external user interface in accordance with the principles of the present invention. 
         FIGS.  16   a  to  16   c    illustrate distance control systems in accordance with the principles of the present invention. 
         FIGS.  17   a  to  17   c    illustrate force interpretation systems in accordance with the principles of the present invention. 
         FIGS.  18   a  to  18   c    illustrate user interface mode selection systems in accordance with the principles of the present invention. 
         FIG.  19    illustrates interaction systems in accordance with the principles of the present invention. 
         FIG.  20    illustrates external user interfaces in accordance with the principles of the present invention. 
         FIG.  21    illustrates mD trace representations presented in accordance with the principles of the present invention. 
         FIG.  22    illustrates mD trace representations presented in accordance with the principles of the present invention. 
         FIG.  23    illustrates an mD scanned environment in accordance with the principles of the present invention. 
         FIG.  23   a    illustrates mD trace representations presented in accordance with the principles of the present invention. 
         FIG.  24    illustrates a stray light suppression technology in accordance with the principles of the present invention. 
         FIG.  25    illustrates a stray light suppression technology in accordance with the principles of the present invention. 
         FIG.  26    illustrates a stray light suppression technology in accordance with the principles of the present invention. 
         FIG.  27    illustrates a stray light suppression technology in accordance with the principles of the present invention. 
         FIGS.  28   a  to  28   c    illustrate DLP mirror angles. 
         FIGS.  29  to  33    illustrate eye imaging systems according to the principles of the present invention. 
         FIGS.  34  and  34     a  illustrate structured eye lighting systems according to the principles of the present invention. 
         FIG.  35    illustrates eye glint in the prediction of eye direction analysis in accordance with the principles of the present invention. 
         FIG.  36   a    illustrates eye characteristics that may be used in personal identification through analysis of a system according to the principles of the present invention. 
         FIG.  36   b    illustrates a digital content presentation reflection off of the wearer&#39;s eye that may be analyzed in accordance with the principles of the present invention. 
         FIG.  37    illustrates eye imaging along various virtual target lines and various focal planes in accordance with the principles of the present invention. 
         FIG.  38    illustrates content control with respect to eye movement based on eye imaging in accordance with the principles of the present invention. 
         FIG.  39    illustrates eye imaging and eye convergence in accordance with the principles of the present invention. 
         FIG.  40    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  41    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  42    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  43    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  44    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  45    illustrates various headings over time in an example. 
         FIG.  46    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  47    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  48    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  49    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
         FIG.  50    illustrates light impinging an eye in accordance with the principles of the present invention. 
         FIG.  51    illustrates a view of an eye in accordance with the principles of the present invention. 
         FIGS.  52   a  and  52   b    illustrate views of an eye with a structured light pattern in accordance with the principles of the present invention. 
         FIG.  53    illustrates an optics module in accordance with the principles of the present invention. 
         FIG.  54    illustrates an optics module in accordance with the principles of the present invention. 
         FIG.  55    shows a series of example spectrum for a variety of controlled substances as measured using a form of infrared spectroscopy. 
         FIG.  56    shows an infrared absorbance spectrum for glucose. 
         FIG.  57    illustrates a scene where a person is walking with a HWC mounted on his head. 
         FIG.  58    illustrates a system for receiving, developing and using movement heading, sight heading, eye heading and/or persistence information from HWC(s). 
         FIG.  59    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  60    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  61    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  62    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  63    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  64    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  65    illustrates a presentation technology in accordance with the principles of the present invention. 
         FIG.  66    illustrates a location based presentation technology in accordance with the principles of the present invention. 
         FIG.  67    illustrates a presentation technology in accordance with the principles of the present invention. 
     
    
    
     While the invention has been described in connection with certain preferred embodiments, other embodiments would be understood by one of ordinary skill in the art and are encompassed herein. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Aspects of the present invention relate to head-worn computing (“HWC”) systems. HWC involves, in some instances, a system that mimics the appearance of head-worn glasses or sunglasses. The glasses may be a fully developed computing platform, such as including computer displays presented in each of the lenses of the glasses to the eyes of the user. In embodiments, the lenses and displays may be configured to allow a person wearing the glasses to see the environment through the lenses while also seeing, simultaneously, digital imagery, which forms an overlaid image that is perceived by the person as a digitally augmented image of the environment, or augmented reality (“AR”). 
     HWC involves more than just placing a computing system on a person&#39;s head. The system may need to be designed as a lightweight, compact and fully functional computer display, such as wherein the computer display includes a high resolution digital display that provides a high level of immersion comprised of the displayed digital content and the see-through view of the environmental surroundings. User interfaces and control systems suited to the HWC device may be required that are unlike those used for a more conventional computer such as a laptop. For the HWC and associated systems to be most effective, the glasses may be equipped with sensors to determine environmental conditions, geographic location, relative positioning to other points of interest, objects identified by imaging and movement by the user or other users in a connected group, and the like. The HWC may then change the mode of operation to match the conditions, location, positioning, movements, and the like, in a method generally referred to as a contextually aware HWC. The glasses also may need to be connected, wirelessly or otherwise, to other systems either locally or through a network. Controlling the glasses may be achieved through the use of an external device, automatically through contextually gathered information, through user gestures captured by the glasses sensors, and the like. Each technique may be further refined depending on the software application being used in the glasses. The glasses may further be used to control or coordinate with external devices that are associated with the glasses. 
     Referring to  FIG.  1   , an overview of the HWC system  100  is presented. As shown, the HWC system  100  comprises a HWC  102 , which in this instance is configured as glasses to be worn on the head with sensors such that the HWC  102  is aware of the objects and conditions in the environment  114 . In this instance, the HWC  102  also receives and interprets control inputs such as gestures and movements  116 . The HWC  102  may communicate with external user interfaces  104 . The external user interfaces  104  may provide a physical user interface to take control instructions from a user of the HWC  102  and the external user interfaces  104  and the HWC  102  may communicate bi-directionally to affect the user&#39;s command and provide feedback to the external device  108 . The HWC  102  may also communicate bi-directionally with externally controlled or coordinated local devices  108 . For example, an external user interface  104  may be used in connection with the HWC  102  to control an externally controlled or coordinated local device  108 . The externally controlled or coordinated local device  108  may provide feedback to the HWC  102  and a customized GUI may be presented in the HWC  102  based on the type of device or specifically identified device  108 . The HWC  102  may also interact with remote devices and information sources  112  through a network connection  110 . Again, the external user interface  104  may be used in connection with the HWC  102  to control or otherwise interact with any of the remote devices  108  and information sources  112  in a similar way as when the external user interfaces  104  are used to control or otherwise interact with the externally controlled or coordinated local devices  108 . Similarly, HWC  102  may interpret gestures  116  (e.g. captured from forward, downward, upward, rearward facing sensors such as camera(s), range finders, IR sensors, etc.) or environmental conditions sensed in the environment  114  to control either local or remote devices  108  or  112 . 
     We will now describe each of the main elements depicted on  FIG.  1    in more detail; however, these descriptions are intended to provide general guidance and should not be construed as limiting. Additional description of each element may also be further described herein. 
     The HWC  102  is a computing platform intended to be worn on a person&#39;s head. The HWC  102  may take many different forms to fit many different functional requirements. In some situations, the HWC  102  will be designed in the form of conventional glasses. The glasses may or may not have active computer graphics displays. In situations where the HWC  102  has integrated computer displays the displays may be configured as see-through displays such that the digital imagery can be overlaid with respect to the user&#39;s view of the environment  114 . There are a number of see-through optical designs that may be used, including ones that have a reflective display (e.g. LCoS, DLP), emissive displays (e.g. OLED, LED), hologram, TIR waveguides, and the like. In embodiments, lighting systems used in connection with the display optics may be solid state lighting systems, such as LED, OLED, quantum dot, quantum dot LED, etc. In addition, the optical configuration may be monocular or binocular. It may also include vision corrective optical components. In embodiments, the optics may be packaged as contact lenses. In other embodiments, the HWC  102  may be in the form of a helmet with a see-through shield, sunglasses, safety glasses, goggles, a mask, fire helmet with see-through shield, police helmet with see through shield, military helmet with see-through shield, utility form customized to a certain work task (e.g. inventory control, logistics, repair, maintenance, etc.), and the like. 
     The HWC  102  may also have a number of integrated computing facilities, such as an integrated processor, integrated power management, communication structures (e.g. cell net, WiFi, Bluetooth, local area connections, mesh connections, remote connections (e.g. client server, etc.)), and the like. The HWC  102  may also have a number of positional awareness sensors, such as GPS, electronic compass, altimeter, tilt sensor, IMU, and the like. It may also have other sensors such as a camera, rangefinder, hyper-spectral camera, Geiger counter, microphone, spectral illumination detector, temperature sensor, chemical sensor, biologic sensor, moisture sensor, ultrasonic sensor, and the like. 
     The HWC  102  may also have integrated control technologies. The integrated control technologies may be contextual based control, passive control, active control, user control, and the like. For example, the HWC  102  may have an integrated sensor (e.g. camera) that captures user hand or body gestures  116  such that the integrated processing system can interpret the gestures and generate control commands for the HWC  102 . In another example, the HWC  102  may have sensors that detect movement (e.g. a nod, head shake, and the like) including accelerometers, gyros and other inertial measurements, where the integrated processor may interpret the movement and generate a control command in response. The HWC  102  may also automatically control itself based on measured or perceived environmental conditions. For example, if it is bright in the environment the HWC  102  may increase the brightness or contrast of the displayed image. In embodiments, the integrated control technologies may be mounted on the HWC  102  such that a user can interact with it directly. For example, the HWC  102  may have a button(s), touch capacitive interface, and the like. 
     As described herein, the HWC  102  may be in communication with external user interfaces  104 . The external user interfaces may come in many different forms. For example, a cell phone screen may be adapted to take user input for control of an aspect of the HWC  102 . The external user interface may be a dedicated UI, such as a keyboard, touch surface, button(s), joy stick, and the like. In embodiments, the external controller may be integrated into another device such as a ring, watch, bike, car, and the like. In each case, the external user interface  104  may include sensors (e.g. IMU, accelerometers, compass, altimeter, and the like) to provide additional input for controlling the HWD  104 . 
     As described herein, the HWC  102  may control or coordinate with other local devices  108 . The external devices  108  may be an audio device, visual device, vehicle, cell phone, computer, and the like. For instance, the local external device  108  may be another HWC  102 , where information may then be exchanged between the separate HWCs  108 . 
     Similar to the way the HWC  102  may control or coordinate with local devices  106 , the HWC  102  may control or coordinate with remote devices  112 , such as the HWC  102  communicating with the remote devices  112  through a network  110 . Again, the form of the remote device  112  may have many forms. Included in these forms is another HWC  102 . For example, each HWC  102  may communicate its GPS position such that all the HWCs  102  know where all of HWC  102  are located. 
       FIG.  2    illustrates a HWC  102  with an optical system that includes an upper optical module  202  and a lower optical module  204 . While the upper and lower optical modules  202  and  204  will generally be described as separate modules, it should be understood that this is illustrative only and the present invention includes other physical configurations, such as that when the two modules are combined into a single module or where the elements making up the two modules are configured into more than two modules. In embodiments, the upper module  202  includes a computer controlled display (e.g. LCoS, DLP, OLED, etc.) and image light delivery optics. In embodiments, the lower module includes eye delivery optics that are configured to receive the upper module&#39;s image light and deliver the image light to the eye of a wearer of the HWC. In  FIG.  2   , it should be noted that while the upper and lower optical modules  202  and  204  are illustrated in one side of the HWC such that image light can be delivered to one eye of the wearer, that it is envisioned by the present invention that embodiments will contain two image light delivery systems, one for each eye. 
       FIG.  3   b    illustrates an upper optical module  202  in accordance with the principles of the present invention. In this embodiment, the upper optical module  202  includes a DLP (also known as DMD or digital micromirror device)computer operated display  304  which includes pixels comprised of rotatable mirrors (such as, for example, the DLP3000 available from Texas Instruments), polarized light source  302 , ¼ wave retarder film  308 , reflective polarizer  310  and a field lens  312 . The polarized light source  302  provides substantially uniform polarized light that is generally directed towards the reflective polarizer  310 . The reflective polarizer reflects light of one polarization state (e.g. S polarized light) and transmits light of the other polarization state (e.g. P polarized light). The polarized light source  302  and the reflective polarizer  310  are oriented so that the polarized light from the polarized light source  302  is reflected generally towards the DLP  304 . The light then passes through the ¼ wave film  308  once before illuminating the pixels of the DLP  304  and then again after being reflected by the pixels of the DLP  304 . In passing through the ¼ wave film  308  twice, the light is converted from one polarization state to the other polarization state (e.g. the light is converted from S to P polarized light). The light then passes through the reflective polarizer  310 . In the event that the DLP pixel(s) are in the “on” state (i.e. the mirrors are positioned to reflect light towards the field lens  312 , the “on” pixels reflect the light generally along the optical axis and into the field lens  312 . This light that is reflected by “on” pixels and which is directed generally along the optical axis of the field lens  312  will be referred to as image light  316 . The image light  316  then passes through the field lens to be used by a lower optical module  204 . 
     The light that is provided by the polarized light source  302 , which is subsequently reflected by the reflective polarizer  310  before it reflects from the DLP  304 , will generally be referred to as illumination light. The light that is reflected by the “off” pixels of the DLP  304  is reflected at a different angle than the light reflected by the “on” pixels, so that the light from the “off” pixels is generally directed away from the optical axis of the field lens  312  and toward the side of the upper optical module  202  as shown in  FIG.  3   . The light that is reflected by the “off” pixels of the DLP  304  will be referred to as dark state light  314 . 
     The DLP  304  operates as a computer controlled display and is generally thought of as a MEMs device. The DLP pixels are comprised of small mirrors that can be directed. The mirrors generally flip from one angle to another angle. The two angles are generally referred to as states. When light is used to illuminate the DLP the mirrors will reflect the light in a direction depending on the state. In embodiments herein, we generally refer to the two states as “on” and “off,” which is intended to depict the condition of a display pixel. “On” pixels will be seen by a viewer of the display as emitting light because the light is directed along the optical axis and into the field lens and the associated remainder of the display system. “Off” pixels will be seen by a viewer of the display as not emitting light because the light from these pixels is directed to the side of the optical housing and into a light trap or light dump where the light is absorbed. The pattern of “on” and “off” pixels produces image light that is perceived by a viewer of the display as a computer generated image. Full color images can be presented to a user by sequentially providing illumination light with complimentary colors such as red, green and blue. Where the sequence is presented in a recurring cycle that is faster than the user can perceive as separate images and as a result the user perceives a full color image comprised of the sum of the sequential images. Bright pixels in the image are provided by pixels that remain in the “on” state for the entire time of the cycle, while dimmer pixels in the image are provided by pixels that switch between the “on” state and “off” state within the time of the cycle, or frame time when in a video sequence of images. 
       FIG.  3   a    shows an illustration of a system for a DLP  304  in which the unpolarized light source  350  is pointed directly at the DLP  304 . In this case, the angle required for the illumination light is such that the field lens  352  must be positioned substantially distant from the DLP  304  to avoid the illumination light from being clipped by the field lens  352 . The large distance between the field lens  352  and the DLP  304  along with the straight path of the dark state light  354 , means that the light trap for the dark state light  354  is also located at a substantial distance from the DLP. For these reasons, this configuration is larger in size compared to the upper optics module  202  of the preferred embodiments. 
     The configuration illustrated in  FIG.  3   b    can be lightweight and compact such that it fits into a small portion of a HWC. For example, the upper modules  202  illustrated herein can be physically adapted to mount in an upper frame of a HWC such that the image light can be directed into a lower optical module  204  for presentation of digital content to a wearer&#39;s eye. The package of components that combine to generate the image light (i.e. the polarized light source  302 , DLP  304 , reflective polarizer  310  and ¼ wave film  308 ) is very light and is compact. The height of the system, excluding the field lens, may be less than 8 mm. The width (i.e. from front to back) may be less than 8 mm. The weight may be less than 2 grams. The compactness of this upper optical module  202  allows for a compact mechanical design of the HWC and the light weight nature of these embodiments help make the HWC lightweight to provide for a HWC that is comfortable for a wearer of the HWC. 
     The configuration illustrated in  FIG.  3   b    can produce sharp contrast, high brightness and deep blacks, especially when compared to LCD or LCoS displays used in HWC. The “on” and “off” states of the DLP provide for a strong differentiator in the light reflection path representing an “on” pixel and an “off” pixel. As will be discussed in more detail below, the dark state light from the “off” pixel reflections can be managed to reduce stray light in the display system to produce images with high contrast. 
       FIG.  4    illustrates another embodiment of an upper optical module  202  in accordance with the principles of the present invention. This embodiment includes a light source  404 , but in this case, the light source can provide unpolarized illumination light. The illumination light from the light source  404  is directed into a TIR wedge  418  such that the illumination light is incident on an internal surface of the TIR wedge  418  (shown as the angled lower surface of the TIR wedge  418  in  FIG.  4   ) at an angle that is beyond the critical angle as defined by Eqn 1. 
     
       
         
           
             
               
                 
                   
                     
                       Critical 
                       ⁢ 
                           
                       angle 
                     
                     = 
                     arc 
                   
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     sin 
                     ⁡ 
                     ( 
                     
                       1 
                       / 
                       n 
                     
                     ) 
                   
                 
               
               
                 
                   Eqn 
                   ⁢ 
                       
                   1 
                 
               
             
           
         
       
     
     Where the critical angle is the angle beyond which the illumination light is reflected from the internal surface when the internal surface comprises an interface from a solid with a higher refractive index (n) to air with a refractive index of 1 (e.g. for an interface of acrylic, with a refractive index of n=1.5, to air, the critical angle is 41.8 degrees; for an interface of polycarbonate, with a refractive index of n=1.59, to air the critical angle is 38.9 degrees). Consequently, the TIR wedge  418  is associated with a thin air gap  408  along the internal surface to create an interface between a solid with a higher refractive index and air. By choosing the angle of the light source  404  relative to the DLP  402  in correspondence to the angle of the internal surface of the TIR wedge  418 , illumination light is turned toward the DLP  402  at an angle suitable for providing image light  414  as reflected from “on” pixels. Wherein, the illumination light is provided to the DLP  402  at approximately twice the angle of the pixel mirrors in the DLP  402  that are in the “on” state, such that after reflecting from the pixel mirrors, the image light  414  is directed generally along the optical axis of the field lens. Depending on the state of the DLP pixels, the illumination light from “on” pixels may be reflected as image light  414  which is directed towards a field lens and a lower optical module  204 , while illumination light reflected from “off” pixels (generally referred to herein as “dark” state light, “off” pixel light or “off” state light)  410  is directed in a separate direction, which may be trapped and not used for the image that is ultimately presented to the wearer&#39;s eye. 
     The light trap for the dark state light  410  may be located along the optical axis defined by the direction of the dark state light  410  and in the side of the housing, with the function of absorbing the dark state light. To this end, the light trap may be comprised of an area outside of the cone of image light  414  from the “on” pixels. The light trap is typically made up of materials that absorb light including coatings of black paints or other light absorbing materials to prevent light scattering from the dark state light degrading the image perceived by the user. In addition, the light trap may be recessed into the wall of the housing or include masks or guards to block scattered light and prevent the light trap from being viewed adjacent to the displayed image. 
     The embodiment of  FIG.  4    also includes a corrective wedge  420  to correct the effect of refraction of the image light  414  as it exits the TIR wedge  418 . By including the corrective wedge  420  and providing a thin air gap  408  (e.g. 25 micron), the image light from the “on” pixels can be maintained generally in a direction along the optical axis of the field lens (i.e. the same direction as that defined by the image light  414 ) so it passes into the field lens and the lower optical module  204 . As shown in  FIG.  4   , the image light  414  from the “on” pixels exits the corrective wedge  420  generally perpendicular to the surface of the corrective wedge  420  while the dark state light exits at an oblique angle. As a result, the direction of the image light  414  from the “on” pixels is largely unaffected by refraction as it exits from the surface of the corrective wedge  420 . In contrast, the dark state light  410  is substantially changed in direction by refraction when the dark state light  410  exits the corrective wedge  420 . 
     The embodiment illustrated in  FIG.  4    has the similar advantages of those discussed in connection with the embodiment of  FIG.  3   b   . The dimensions and weight of the upper module  202  depicted in  FIG.  4    may be approximately 8×8 mm with a weight of less than 3 grams. A difference in overall performance between the configuration illustrated in  FIG.  3   b    and the configuration illustrated in  FIG.  4    is that the embodiment of  FIG.  4    doesn&#39;t require the use of polarized light as supplied by the light source  404 . This can be an advantage in some situations as will be discussed in more detail below (e.g. increased see-through transparency of the HWC optics from the user&#39;s perspective). Polarized light may be used in connection with the embodiment depicted in  FIG.  4   , in embodiments. An additional advantage of the embodiment of  FIG.  4    compared to the embodiment shown in  FIG.  3   b    is that the dark state light (shown as DLP off light  410 ) is directed at a steeper angle away from the optical axis of the image light  414  due to the added refraction encountered when the dark state light  410  exits the corrective wedge  420 . This steeper angle of the dark state light  410  allows for the light trap to be positioned closer to the DLP  402  so that the overall size of the upper module  202  can be reduced. The light trap can also be made larger since the light trap doesn&#39;t interfere with the field lens, thereby the efficiency of the light trap can be increased and as a result, stray light can be reduced and the contrast of the image perceived by the user can be increased.  FIG.  4   a    illustrates the embodiment described in connection with  FIG.  4    with an example set of corresponding angles at the various surfaces with the reflected angles of a ray of light passing through the upper optical module  202 . In this example, the DLP mirrors are provided at 17 degrees to the surface of the DLP device. The angles of the TIR wedge are selected in correspondence to one another to provide TIR reflected illumination light at the correct angle for the DLP mirrors while allowing the image light and dark state light to pass through the thin air gap, various combinations of angles are possible to achieve this. 
       FIG.  5    illustrates yet another embodiment of an upper optical module  202  in accordance with the principles of the present invention. As with the embodiment shown in  FIG.  4   , the embodiment shown in  FIG.  5    does not require the use of polarized light. Polarized light may be used in connection with this embodiment, but it is not required. The optical module  202  depicted in  FIG.  5    is similar to that presented in connection with  FIG.  4   ; however, the embodiment of  FIG.  5    includes an off light redirection wedge  502 . As can be seen from the illustration, the off light redirection wedge  502  allows the image light  414  to continue generally along the optical axis toward the field lens and into the lower optical module  204  (as illustrated). However, the off light  504  is redirected substantially toward the side of the corrective wedge  420  where it passes into the light trap. This configuration may allow further height compactness in the HWC because the light trap (not illustrated) that is intended to absorb the off light  504  can be positioned laterally adjacent the upper optical module  202  as opposed to below it. In the embodiment depicted in  FIG.  5    there is a thin air gap between the TIR wedge  418  and the corrective wedge  420  (similar to the embodiment of  FIG.  4   ). There is also a thin air gap between the corrective wedge  420  and the off light redirection wedge  502 . There may be HWC mechanical configurations that warrant the positioning of a light trap for the dark state light elsewhere and the illustration depicted in  FIG.  5    should be considered illustrative of the concept that the off light can be redirected to create compactness of the overall HWC.  FIG.  5   a    illustrates an example of the embodiment described in connection with  FIG.  5    with the addition of more details on the relative angles at the various surfaces and a light ray trace for image light and a light ray trace for dark light are shown as it passes through the upper optical module  202 . Again, various combinations of angles are possible. 
       FIG.  4   b    shows an illustration of a further embodiment in which a solid transparent matched set of wedges  456  is provided with a reflective polarizer  450  at the interface between the wedges. Wherein the interface between the wedges in the wedge set  456  is provided at an angle so that illumination light  452  from the polarized light source  458  is reflected at the proper angle (e.g. 34 degrees for a 17 degree DLP mirror) for the DLP mirror “on” state so that the reflected image light  414  is provided along the optical axis of the field lens. The general geometry of the wedges in the wedge set  456  is similar to that shown in  FIGS.  4  and  4     a . A quarter wave film  454  is provided on the DLP  402  surface so that the illumination light  452  is one polarization state (e.g. S polarization state) while in passing through the quarter wave film  454 , reflecting from the DLP mirror and passing back through the quarter wave film  454 , the image light  414  is converted to the other polarization state (e.g. P polarization state). The reflective polarizer is oriented such that the illumination light  452  with its polarization state is reflected and the image light  414  with its other polarization state is transmitted. Since the dark state light from the “off” pixels  410  also passes through the quarter wave film  454  twice, it is also the other polarization state (e.g. P polarization state) so that it is transmitted by the reflective polarizer  450 . 
     The angles of the faces of the wedge set  450  correspond to the needed angles to provide illumination light  452  at the angle needed by the DLP mirrors when in the “on” state so that the reflected image light  414  is reflected from the DLP along the optical axis of the field lens. The wedge set  456  provides an interior interface where a reflective polarizer film can be located to redirect the illumination light  452  toward the mirrors of the DLP  402 . The wedge set also provides a matched wedge on the opposite side of the reflective polarizer  450  so that the image light  414  from the “on” pixels exits the wedge set  450  substantially perpendicular to the exit surface, while the dark state light from the “off” pixels  410  exits at an oblique angle to the exit surface. As a result, the image light  414  is substantially unrefracted upon exiting the wedge set  456 , while the dark state light from the “off” pixels  410  is substantially refracted upon exiting the wedge set  456  as shown in  FIG.  4     b.    
     By providing a solid transparent matched wedge set, the flatness of the interface is reduced, because variations in the flatness have a negligible effect as long as they are within the cone angle of the illuminating light  452 . Which can be f #2.2 with a 26 degree cone angle. In a preferred embodiment, the reflective polarizer is bonded between the matched internal surfaces of the wedge set  456  using an optical adhesive so that Fresnel reflections at the interfaces on either side of the reflective polarizer  450  are reduced. The optical adhesive can be matched in refractive index to the material of the wedge set  456  and the pieces of the wedge set  456  can be all made from the same material such as BK7 glass or cast acrylic. Wherein the wedge material can be selected to have low birefringence as well to reduce non-uniformities in brightness. The wedge set  456  and the quarter wave film  454  can also be bonded to the DLP  402  to further reduce Fresnel reflections at the DLP interface losses. In addition, since the image light  414  is substantially normal to the exit surface of the wedge set  456 , the flatness of the surface is not critical to maintain the wavefront of the image light  414  so that high image quality can be obtained in the displayed image without requiring very tightly toleranced flatness on the exit surface. 
     A yet further embodiment of the invention that is not illustrated, combines the embodiments illustrated in  FIG.  4   b    and  FIG.  5   . In this embodiment, the wedge set  456  is comprised of three wedges with the general geometry of the wedges in the wedge set corresponding to that shown in  FIGS.  5  and  5     a . A reflective polarizer is bonded between the first and second wedges similar to that shown in  FIG.  4   b   , however, a third wedge is provided similar to the embodiment of  FIG.  5   . Wherein there is an angled thin air gap between the second and third wedges so that the dark state light is reflected by TIR toward the side of the second wedge where it is absorbed in a light trap. This embodiment, like the embodiment shown in  FIG.  4   b   , uses a polarized light source as has been previously described. The difference in this embodiment is that the image light is transmitted through the reflective polarizer and is transmitted through the angled thin air gap so that it exits normal to the exit surface of the third wedge. 
       FIG.  5   b    illustrates an upper optical module  202  with a dark light trap  514   a . As described in connection with  FIGS.  4  and  4     a , image light can be generated from a DLP when using a TIR and corrective lens configuration. The upper module may be mounted in a HWC housing  510  and the housing  510  may include a dark light trap  514   a . The dark light trap  514   a  is generally positioned/constructed/formed in a position that is optically aligned with the dark light optical axis  512 . As illustrated, the dark light trap may have depth such that the trap internally reflects dark light in an attempt to further absorb the light and prevent the dark light from combining with the image light that passes through the field lens. The dark light trap may be of a shape and depth such that it absorbs the dark light. In addition, the dark light trap  514   b , in embodiments, may be made of light absorbing materials or coated with light absorbing materials. In embodiments, the recessed light trap  514   a  may include baffles to block a view of the dark state light. This may be combined with black surfaces and textured or fibrous surfaces to help absorb the light. The baffles can be part of the light trap, associated with the housing, or field lens, etc. 
       FIG.  5   c    illustrates another embodiment with a light trap  514   b . As can be seen in the illustration, the shape of the trap is configured to enhance internal reflections within the light trap  514   b  to increase the absorption of the dark light  512 .  FIG.  5   d    illustrates another embodiment with a light trap  514   c . As can be seen in the illustration, the shape of the trap  514   c  is configured to enhance internal reflections to increase the absorption of the dark light  512 . 
       FIG.  5   e    illustrates another embodiment of an upper optical module  202  with a dark light trap  514   d . This embodiment of upper module  202  includes an off light reflection wedge  502 , as illustrated and described in connection with the embodiment of  FIGS.  5  and  5     a . As can be seen in  FIG.  5   e   , the light trap  514   d  is positioned along the optical path of the dark light  512 . The dark light trap  514   d  may be configured as described in other embodiments herein. The embodiment of the light trap  514   d  illustrated in  FIG.  5   e    includes a black area on the side wall of the wedge, wherein the side wall is located substantially away from the optical axis of the image light  414 . In addition, baffles  5252  may be added to one or more edges of the field lens  312  to block the view of the light trap  514   d  adjacent to the displayed image seen by the user. 
       FIG.  6    illustrates a combination of an upper optical module  202  with a lower optical module  204 . In this embodiment, the image light projected from the upper optical module  202  may or may not be polarized. The image light is reflected off a flat combiner element  602  such that it is directed towards the user&#39;s eye. Wherein, the combiner element  602  is a partial mirror that reflects image light while transmitting a substantial portion of light from the environment so the user can look through the combiner element and see the environment surrounding the HWC. 
     The combiner  602  may include a holographic pattern, to form a holographic mirror. If a monochrome image is desired, there may be a single wavelength reflection design for the holographic pattern on the surface of the combiner  602 . If the intention is to have multiple colors reflected from the surface of the combiner  602 , a multiple wavelength holographic mirror maybe included on the combiner surface. For example, in a three-color embodiment, where red, green and blue pixels are generated in the image light, the holographic mirror may be reflective to wavelengths substantially matching the wavelengths of the red, green and blue light provided by the light source. This configuration can be used as a wavelength specific mirror where pre-determined wavelengths of light from the image light are reflected to the user&#39;s eye. This configuration may also be made such that substantially all other wavelengths in the visible pass through the combiner element  602  so the user has a substantially clear view of the surroundings when looking through the combiner element  602 . The transparency between the user&#39;s eye and the surrounding may be approximately 80% when using a combiner that is a holographic mirror. Wherein holographic mirrors can be made using lasers to produce interference patterns in the holographic material of the combiner where the wavelengths of the lasers correspond to the wavelengths of light that are subsequently reflected by the holographic mirror. 
     In another embodiment, the combiner element  602  may include a notch mirror comprised of a multilayer coated substrate wherein the coating is designed to substantially reflect the wavelengths of light provided by the light source and substantially transmit the remaining wavelengths in the visible spectrum. For example, in the case where red, green and blue light is provided by the light source to enable full color images to be provided to the user, the notch mirror is a tristimulus notch mirror wherein the multilayer coating is designed to reflect narrow bands of red, green and blue light that are matched to the what is provided by the light source and the remaining visible wavelengths are transmitted through the coating to enable a view of the environment through the combiner. In another example where monochrome images are provided to the user, the notch mirror is designed to reflect a single narrow band of light that is matched to the wavelength range of the light provided by the light source while transmitting the remaining visible wavelengths to enable a see-thru view of the environment. The combiner  602  with the notch mirror would operate, from the user&#39;s perspective, in a manner similar to the combiner that includes a holographic pattern on the combiner element  602 . The combiner, with the tristimulus notch mirror, would reflect the “on” pixels to the eye because of the match between the reflective wavelengths of the notch mirror and the color of the image light, and the wearer would be able to see with high clarity the surroundings. The transparency between the user&#39;s eye and the surrounding may be approximately 80% when using the tristimulus notch mirror. In addition, the image provided by the upper optical module  202  with the notch mirror combiner can provide higher contrast images than the holographic mirror combiner due to less scattering of the imaging light by the combiner. 
     Light can escape through the combiner  602  and may produce face glow as the light is generally directed downward onto the cheek of the user. When using a holographic mirror combiner or a tristimulus notch mirror combiner, the escaping light can be trapped to avoid face glow. In embodiments, if the image light is polarized before the combiner, a linear polarizer can be laminated, or otherwise associated, to the combiner, with the transmission axis of the polarizer oriented relative to the polarized image light so that any escaping image light is absorbed by the polarizer. In embodiments, the image light would be polarized to provide S polarized light to the combiner for better reflection. As a result, the linear polarizer on the combiner would be oriented to absorb S polarized light and pass P polarized light. This provides the preferred orientation of polarized sunglasses as well. 
     If the image light is unpolarized, a microlouvered film such as a privacy filter can be used to absorb the escaping image light while providing the user with a see-thru view of the environment. In this case, the absorbance or transmittance of the microlouvered film is dependent on the angle of the light. Where steep angle light is absorbed and light at less of an angle is transmitted. For this reason, in an embodiment, the combiner with the microlouver film is angled at greater than 45 degrees to the optical axis of the image light (e.g. the combiner can be oriented at 50 degrees so the image light from the file lens is incident on the combiner at an oblique angle. 
       FIG.  7    illustrates an embodiment of a combiner element  602  at various angles when the combiner element  602  includes a holographic mirror. Normally, a mirrored surface reflects light at an angle equal to the angle that the light is incident to the mirrored surface. Typically, this necessitates that the combiner element be at 45 degrees,  602   a , if the light is presented vertically to the combiner so the light can be reflected horizontally towards the wearer&#39;s eye. In embodiments, the incident light can be presented at angles other than vertical to enable the mirror surface to be oriented at other than 45 degrees, but in all cases wherein a mirrored surface is employed (including the tristimulus notch mirror described previously), the incident angle equals the reflected angle. As a result, increasing the angle of the combiner  602   a  requires that the incident image light be presented to the combiner  602   a  at a different angle which positions the upper optical module  202  to the left of the combiner as shown in  FIG.  7   . In contrast, a holographic mirror combiner, included in embodiments, can be made such that light is reflected at a different angle from the angle that the light is incident onto the holographic mirrored surface. This allows freedom to select the angle of the combiner element  602   b  independent of the angle of the incident image light and the angle of the light reflected into the wearer&#39;s eye. In embodiments, the angle of the combiner element  602   b  is greater than 45 degrees (shown in  FIG.  7   ) as this allows a more laterally compact HWC design. The increased angle of the combiner element  602   b  decreases the front to back width of the lower optical module  204  and may allow for a thinner HWC display (i.e. the furthest element from the wearer&#39;s eye can be closer to the wearer&#39;s face). 
       FIG.  8    illustrates another embodiment of a lower optical module  204 . In this embodiment, polarized image light provided by the upper optical module  202 , is directed into the lower optical module  204 . The image light reflects off a polarized mirror  804  and is directed to a focusing partially reflective mirror  802 , which is adapted to reflect the polarized light. An optical element such as a ¼ wave film located between the polarized mirror  804  and the partially reflective mirror  802 , is used to change the polarization state of the image light such that the light reflected by the partially reflective mirror  802  is transmitted by the polarized mirror  804  to present image light to the eye of the wearer. The user can also see through the polarized mirror  804  and the partially reflective mirror  802  to see the surrounding environment. As a result, the user perceives a combined image comprised of the displayed image light overlaid onto the see-thru view of the environment. 
     While many of the embodiments of the present invention have been referred to as upper and lower modules containing certain optical components, it should be understood that the image light and dark light production and management functions described in connection with the upper module may be arranged to direct light in other directions (e.g. upward, sideward, etc.). In embodiments, it may be preferred to mount the upper module  202  above the wearer&#39;s eye, in which case the image light would be directed downward. In other embodiments it may be preferred to produce light from the side of the wearer&#39;s eye, or from below the wearer&#39;s eye. In addition, the lower optical module is generally configured to deliver the image light to the wearer&#39;s eye and allow the wearer to see through the lower optical module, which may be accomplished through a variety of optical components. 
       FIG.  8   a    illustrates an embodiment of the present invention where the upper optical module  202  is arranged to direct image light into a TIR waveguide  810 . In this embodiment, the upper optical module  202  is positioned above the wearer&#39;s eye  812  and the light is directed horizontally into the TIR waveguide  810 . The TIR waveguide is designed to internally reflect the image light in a series of downward TIR reflections until it reaches the portion in front of the wearer&#39;s eye, where the light passes out of the TIR waveguide  812  into the wearer&#39;s eye. In this embodiment, an outer shield  814  is positioned in front of the TIR waveguide  810 . 
       FIG.  8   b    illustrates an embodiment of the present invention where the upper optical module  202  is arranged to direct image light into a TIR waveguide  818 . In this embodiment, the upper optical module  202  is arranged on the side of the TIR waveguide  818 . For example, the upper optical module may be positioned in the arm or near the arm of the HWC when configured as a pair of head worn glasses. The TIR waveguide  818  is designed to internally reflect the image light in a series of TIR reflections until it reaches the portion in front of the wearer&#39;s eye, where the light passes out of the TIR waveguide  812  into the wearer&#39;s eye. 
       FIG.  8   c    illustrates yet further embodiments of the present invention where an upper optical module  202  is directing polarized image light into an optical guide  828  where the image light passes through a polarized reflector  824 , changes polarization state upon reflection of the optical element  822  which includes a ¼ wave film for example and then is reflected by the polarized reflector  824  towards the wearer&#39;s eye, due to the change in polarization of the image light. The upper optical module  202  may be positioned to direct light to a mirror  820 , to position the upper optical module  202  laterally, in other embodiments, the upper optical module  202  may direct the image light directly towards the polarized reflector  824 . It should be understood that the present invention comprises other optical arrangements intended to direct image light into the wearer&#39;s eye. 
     Another aspect of the present invention relates to eye imaging. In embodiments, a camera is used in connection with an upper optical module  202  such that the wearer&#39;s eye can be imaged using pixels in the “off” state on the DLP.  FIG.  9    illustrates a system where the eye imaging camera  802  is mounted and angled such that the field of view of the eye imaging camera  802  is redirected toward the wearer&#39;s eye by the mirror pixels of the DLP  402  that are in the “off” state. In this way, the eye imaging camera  802  can be used to image the wearer&#39;s eye along the same optical axis as the displayed image that is presented to the wearer. Wherein, image light that is presented to the wearer&#39;s eye illuminates the wearer&#39;s eye so that the eye can be imaged by the eye imaging camera  802 . In the process, the light reflected by the eye passes back though the optical train of the lower optical module  204  and a portion of the upper optical module to where the light is reflected by the “off” pixels of the DLP  402  toward the eye imaging camera  802 . 
     In embodiments, the eye imaging camera may image the wearer&#39;s eye at a moment in time where there are enough “off” pixels to achieve the required eye image resolution. In another embodiment, the eye imaging camera collects eye image information from “off” pixels over time and forms a time lapsed image. In another embodiment, a modified image is presented to the user wherein enough “off” state pixels are included that the camera can obtain the desired resolution and brightness for imaging the wearer&#39;s eye and the eye image capture is synchronized with the presentation of the modified image. 
     The eye imaging system may be used for security systems. The HWC may not allow access to the HWC or other system if the eye is not recognized (e.g. through eye characteristics including retina or iris characteristics, etc.). The HWC may be used to provide constant security access in some embodiments. For example, the eye security confirmation may be a continuous, near-continuous, real-time, quasi real-time, periodic, etc. process so the wearer is effectively constantly being verified as known. In embodiments, the HWC may be worn and eye security tracked for access to other computer systems. 
     The eye imaging system may be used for control of the HWC. For example, a blink, wink, or particular eye movement may be used as a control mechanism for a software application operating on the HWC or associated device. 
     The eye imaging system may be used in a process that determines how or when the HWC  102  delivers digitally displayed content to the wearer. For example, the eye imaging system may determine that the user is looking in a direction and then HWC may change the resolution in an area of the display or provide some content that is associated with something in the environment that the user may be looking at. Alternatively, the eye imaging system may identify different users and change the displayed content or enabled features provided to the user. Users may be identified from a database of users eye characteristics either located on the HWC  102  or remotely located on the network  110  or on a server  112 . In addition, the HWC may identify a primary user or a group of primary users from eye characteristics wherein the primary user(s) are provided with an enhanced set of features and all other users are provided with a different set of features. Thus in this use case, the HWC  102  uses identified eye characteristics to either enable features or not and eye characteristics need only be analyzed in comparison to a relatively small database of individual eye characteristics. 
       FIG.  10    illustrates a light source that may be used in association with the upper optics module  202  (e.g. polarized light source if the light from the solid state light source is polarized such as polarized light source  302  and  458 ), and light source  404 . In embodiments, to provide a uniform surface of light  1008  to be directed into the upper optical module  202  and towards the DLP of the upper optical module, either directly or indirectly, the solid state light source  1002  may be projected into a backlighting optical system  1004 . The solid state light source  1002  may be one or more LEDs, laser diodes, OLEDs. In embodiments, the backlighting optical system  1004  includes an extended section with a length/distance ratio of greater than 3, wherein the light undergoes multiple reflections from the sidewalls to mix of homogenize the light as supplied by the solid state light source  1002 . The backlighting optical system  1004  can also include structures on the surface opposite (on the left side as shown in  FIG.  10   ) to where the uniform light  1008  exits the backlight  1004  to change the direction of the light toward the DLP  302  and the reflective polarizer  310  or the DLP  402  and the TIR wedge  418 . The backlighting optical system  1004  may also include structures to collimate the uniform light  1008  to provide light to the DLP with a smaller angular distribution or narrower cone angle. Diffusers or polarizers can be used on the entrance or exit surface of the backlighting optical system. Diffusers can be used to spread or uniformize the exiting light from the backlight to improve the uniformity or increase the angular spread of the uniform light  1008 . Elliptical diffusers that diffuse the light more in some directions and less in others can be used to improve the uniformity or spread of the uniform light  1008  in directions orthogonal to the optical axis of the uniform light  1008 . Linear polarizers can be used to convert unpolarized light as supplied by the solid state light source  1002  to polarized light so the uniform light  1008  is polarized with a desired polarization state. A reflective polarizer can be used on the exit surface of the backlight  1004  to polarize the uniform light  1008  to the desired polarization state, while reflecting the other polarization state back into the backlight where it is recycled by multiple reflections within the backlight  1004  and at the solid state light source  1002 . Therefore by including a reflective polarizer at the exit surface of the backlight  1004 , the efficiency of the polarized light source is improved. 
       FIGS.  10   a  and  10   b    show illustrations of structures in backlight optical systems  1004  that can be used to change the direction of the light provided to the entrance face  1045  by the light source and then collimates the light in a direction lateral to the optical axis of the exiting uniform light  1008 . Structure  1060  includes an angled sawtooth pattern in a transparent waveguide wherein the left edge of each sawtooth clips the steep angle rays of light thereby limiting the angle of the light being redirected. The steep surface at the right (as shown) of each sawtooth then redirects the light so that it reflects off the left angled surface of each sawtooth and is directed toward the exit surface  1040 . The sawtooth surfaces shown on the lower surface in  FIGS.  10   a  and  10   b   , can be smooth and coated (e.g. with an aluminum coating or a dielectric mirror coating) to provide a high level of reflectivity without scattering. Structure  1050  includes a curved face on the left side (as shown) to focus the rays after they pass through the exit surface  1040 , thereby providing a mechanism for collimating the uniform light  1008 . In a further embodiment, a diffuser can be provided between the solid state light source  1002  and the entrance face  1045  to homogenize the light provided by the solid state light source  1002 . In yet a further embodiment, a polarizer can be used between the diffuser and the entrance face  1045  of the backlight  1004  to provide a polarized light source. Because the sawtooth pattern provides smooth reflective surfaces, the polarization state of the light can be preserved from the entrance face  1045  to the exit face  1040 . In this embodiment, the light entering the backlight from the solid state light source  1002  passes through the polarizer so that it is polarized with the desired polarization state. If the polarizer is an absorptive linear polarizer, the light of the desired polarization state is transmitted while the light of the other polarization state is absorbed. If the polarizer is a reflective polarizer, the light of the desired polarization state is transmitted into the backlight  1004  while the light of the other polarization state is reflected back into the solid state light source  1002  where it can be recycled as previously described, to increase the efficiency of the polarized light source. 
       FIG.  11   a    illustrates a light source  1100  that may be used in association with the upper optics module  202 . In embodiments, the light source  1100  may provide light to a backlighting optical system  1004  as described above in connection with  FIG.  10   . In embodiments, the light source  1100  includes a tristimulus notch filter  1102 . The tristimulus notch filter  1102  has narrow band pass filters for three wavelengths, as indicated in  FIG.  11   c    in a transmission graph  1108 . The graph shown in  FIG.  11   b   , as  1104  illustrates an output of three different colored LEDs. One can see that the bandwidths of emission are narrow, but they have long tails. The tristimulus notch filter  1102  can be used in connection with such LEDs to provide a light source  1100  that emits narrow filtered wavelengths of light as shown in  FIG.  11   d    as the transmission graph  1110 . Wherein the clipping effects of the tristimulus notch filter  1102  can be seen to have cut the tails from the LED emission graph  1104  to provide narrower wavelength bands of light to the upper optical module  202 . The light source  1100  can be used in connection with a combiner  602  with a holographic mirror or tristimulus notch mirror to provide narrow bands of light that are reflected toward the wearer&#39;s eye with less waste light that does not get reflected by the combiner, thereby improving efficiency and reducing escaping light that can cause faceglow. 
       FIG.  12   a    illustrates another light source  1200  that may be used in association with the upper optics module  202 . In embodiments, the light source  1200  may provide light to a backlighting optical system  1004  as described above in connection with  FIG.  10   . In embodiments, the light source  1200  includes a quantum dot cover glass  1202 . Where the quantum dots absorb light of a shorter wavelength and emit light of a longer wavelength ( FIG.  12   b    shows an example wherein a UV spectrum  1202  applied to a quantum dot results in the quantum dot emitting a narrow band shown as a PL spectrum  1204 ) that is dependent on the material makeup and size of the quantum dot. As a result, quantum dots in the quantum dot cover glass  1202  can be tailored to provide one or more bands of narrow bandwidth light (e.g. red, green and blue emissions dependent on the different quantum dots included as illustrated in the graph shown in  FIG.  12   c    where three different quantum dots are used. In embodiments, the LED driver light emits UV light, deep blue or blue light. For sequential illumination of different colors, multiple light sources  1200  would be used where each light source  1200  would include a quantum dot cover glass  1202  with a quantum dot selected to emit at one of the desired colors. The light source  1100  can be used in connection with a combiner  602  with a holographic mirror or tristimulus notch mirror to provide narrow transmission bands of light that are reflected toward the wearer&#39;s eye with less waste light that does not get reflected. 
     Another aspect of the present invention relates to the generation of peripheral image lighting effects for a person wearing a HWC. In embodiments, a solid state lighting system (e.g. LED, OLED, etc), or other lighting system, may be included inside the optical elements of a lower optical module  204 . The solid state lighting system may be arranged such that lighting effects outside of a field of view (FOV) of the presented digital content is presented to create an immersive effect for the person wearing the HWC. To this end, the lighting effects may be presented to any portion of the HWC that is visible to the wearer. The solid state lighting system may be digitally controlled by an integrated processor on the HWC. In embodiments, the integrated processor will control the lighting effects in coordination with digital content that is presented within the FOV of the HWC. For example, a movie, picture, game, or other content, may be displayed or playing within the FOV of the HWC. The content may show a bomb blast on the right side of the FOV and at the same moment, the solid state lighting system inside of the upper module optics may flash quickly in concert with the FOV image effect. The effect may not be fast, it may be more persistent to indicate, for example, a general glow or color on one side of the user. The solid state lighting system may be color controlled, with red, green and blue LEDs, for example, such that color control can be coordinated with the digitally presented content within the field of view. 
       FIG.  13   a    illustrates optical components of a lower optical module  204  together with an outer lens  1302 .  FIG.  13   a    also shows an embodiment including effects LED&#39;s  1308   a  and  1308   b .  FIG.  13   a    illustrates image light  1312 , as described herein elsewhere, directed into the upper optical module where it will reflect off of the combiner element  1304 , as described herein elsewhere. The combiner element  1304  in this embodiment is angled towards the wearer&#39;s eye at the top of the module and away from the wearer&#39;s eye at the bottom of the module, as also illustrated and described in connection with  FIG.  8    (e.g. at a 45 degree angle). The image light  1312  provided by an upper optical module  202  (not shown in  FIG.  13   a   ) reflects off of the combiner element  1304  towards the collimating mirror  1310 , away from the wearer&#39;s eye, as described herein elsewhere. The image light  1312  then reflects and focuses off of the collimating mirror  1304 , passes back through the combiner element  1304 , and is directed into the wearer&#39;s eye. The wearer can also view the surrounding environment through the transparency of the combiner element  1304 , collimating mirror  1310 , and outer lens  1302  (if it is included). As described herein elsewhere, various surfaces are polarized to create the optical path for the image light and to provide transparency of the elements such that the wearer can view the surrounding environment. The wearer will generally perceive that the image light forms an image in the FOV  1305 . In embodiments, the outer lens  1302  may be included. The outer lens  1302  is an outer lens that may or may not be corrective and it may be designed to conceal the lower optical module components in an effort to make the HWC appear to be in a form similar to standard glasses or sunglasses. 
     In the embodiment illustrated in  FIG.  13   a   , the effects LEDs  1308   a  and  1308   b  are positioned at the sides of the combiner element  1304  and the outer lens  1302  and/or the collimating mirror  1310 . In embodiments, the effects LEDs  1308   a  are positioned within the confines defined by the combiner element  1304  and the outer lens  1302  and/or the collimating mirror. The effects LEDs  1308   a  and  1308   b  are also positioned outside of the FOV  1305 . In this arrangement, the effects LEDs  1308   a  and  1308   b  can provide lighting effects within the lower optical module outside of the FOV  1305 . In embodiments the light emitted from the effects LEDs  1308   a  and  1308   b  may be polarized such that the light passes through the combiner element  1304  toward the wearer&#39;s eye and does not pass through the outer lens  1302  and/or the collimating mirror  1310 . This arrangement provides peripheral lighting effects to the wearer in a more private setting by not transmitting the lighting effects through the front of the HWC into the surrounding environment. However, in other embodiments, the effects LEDs  1308   a  and  1308   b  may be unpolarized so the lighting effects provided are made to be purposefully viewable by others in the environment for entertainment such as giving the effect of the wearer&#39;s eye glowing in correspondence to the image content being viewed by the wearer. 
       FIG.  13   b    illustrates a cross section of the embodiment described in connection with  FIG.  13   a   . As illustrated, the effects LED  1308   a  is located in the upper-front area inside of the optical components of the lower optical module. It should be understood that the effects LED  1308   a  position in the described embodiments is only illustrative and alternate placements are encompassed by the present invention. Additionally, in embodiments, there may be one or more effects LEDs  1308   a  in each of the two sides of HWC to provide peripheral lighting effects near one or both eyes of the wearer. 
       FIG.  13   c    illustrates an embodiment where the combiner element  1304  is angled away from the eye at the top and towards the eye at the bottom (e.g. in accordance with the holographic or notch filter embodiments described herein). In this embodiment, the effects LED  1308   a  is located on the outer lens  1302  side of the combiner element  1304  to provide a concealed appearance of the lighting effects. As with other embodiments, the effects LED  1308   a  of  FIG.  13   c    may include a polarizer such that the emitted light can pass through a polarized element associated with the combiner element  1304  and be blocked by a polarized element associated with the outer lens  1302 . 
     Another aspect of the present invention relates to the mitigation of light escaping from the space between the wearer&#39;s face and the HWC itself. Another aspect of the present invention relates to maintaining a controlled lighting environment in proximity to the wearer&#39;s eyes. In embodiments, both the maintenance of the lighting environment and the mitigation of light escape are accomplished by including a removable and replaceable flexible shield for the HWC. Wherein the removable and replaceable shield can be provided for one eye or both eyes in correspondence to the use of the displays for each eye. For example, in a night vision application, the display to only one eye could be used for night vision while the display to the other eye is turned off to provide good see-thru when moving between areas where visible light is available and dark areas where night vision enhancement is needed. 
       FIG.  14   a    illustrates a removable and replaceable flexible eye cover  1402  with an opening  1408  that can be attached and removed quickly from the HWC  102  through the use of magnets. Other attachment methods may be used, but for illustration of the present invention we will focus on a magnet implementation. In embodiments, magnets may be included in the eye cover  1402  and magnets of an opposite polarity may be included (e.g. embedded) in the frame of the HWC  102 . The magnets of the two elements would attract quite strongly with the opposite polarity configuration. In another embodiment, one of the elements may have a magnet and the other side may have metal for the attraction. In embodiments, the eye cover  1402  is a flexible elastomeric shield. In embodiments, the eye cover  1402  may be an elastomeric bellows design to accommodate flexibility and more closely align with the wearer&#39;s face.  FIG.  14   b    illustrates a removable and replaceable flexible eye cover  1404  that is adapted as a single eye cover. In embodiments, a single eye cover may be used for each side of the HWC to cover both eyes of the wearer. In embodiments, the single eye cover may be used in connection with a HWC that includes only one computer display for one eye. These configurations prevent light that is generated and directed generally towards the wearer&#39;s face by covering the space between the wearer&#39;s face and the HWC. The opening  1408  allows the wearer to look through the opening  1408  to view the displayed content and the surrounding environment through the front of the HWC. The image light in the lower optical module  204  can be prevented from emitting from the front of the HWC through internal optics polarization schemes, as described herein, for example. 
       FIG.  14   c    illustrates another embodiment of a light suppression system. In this embodiment, the eye cover  1410  may be similar to the eye cover  1402 , but eye cover  1410  includes a front light shield  1412 . The front light shield  1412  may be opaque to prevent light from escaping the front lens of the HWC. In other embodiments, the front light shield  1412  is polarized to prevent light from escaping the front lens. In a polarized arrangement, in embodiments, the internal optical elements of the HWC (e.g. of the lower optical module  204 ) may polarize light transmitted towards the front of the HWC and the front light shield  1412  may be polarized to prevent the light from transmitting through the front light shield  1412 . 
     In embodiments, an opaque front light shield  1412  may be included and the digital content may include images of the surrounding environment such that the wearer can visualize the surrounding environment. One eye may be presented with night vision environmental imagery and this eye&#39;s surrounding environment optical path may be covered using an opaque front light shield  1412 . In other embodiments, this arrangement may be associated with both eyes. 
     Another aspect of the present invention relates to automatically configuring the lighting system(s) used in the HWC  102 . In embodiments, the display lighting and/or effects lighting, as described herein, may be controlled in a manner suitable for when an eye cover  1408  is attached or removed from the HWC  102 . For example, at night, when the light in the environment is low, the lighting system(s) in the HWC may go into a low light mode to further control any amounts of stray light escaping from the HWC and the areas around the HWC. Covert operations at night, while using night vision or standard vision, may require a solution which prevents as much escaping light as possible so a user may clip on the eye cover(s)  1408  and then the HWC may go into a low light mode. The low light mode may, in some embodiments, only go into a low light mode when the eye cover  1408  is attached if the HWC identifies that the environment is in low light conditions (e.g. through environment light level sensor detection). In embodiments, the low light level may be determined to be at an intermediate point between full and low light dependent on environmental conditions. 
     Another aspect of the present invention relates to automatically controlling the type of content displayed in the HWC when eye covers  1408  are attached or removed from the HWC. In embodiments, when the eye cover(s)  1408  is attached to the HWC, the displayed content may be restricted in amount or in color amounts. For example, the display(s) may go into a simple content delivery mode to restrict the amount of information displayed. This may be done to reduce the amount of light produced by the display(s). In an embodiment, the display(s) may change from color displays to monochrome displays to reduce the amount of light produced. In an embodiment, the monochrome lighting may be red to limit the impact on the wearer&#39;s eyes to maintain an ability to see better in the dark. 
     Referring to  FIG.  15   , we now turn to describe a particular external user interface  104 , referred to generally as a pen  1500 . The pen  1500  is a specially designed external user interface  104  and can operate as a user interface, such as to many different styles of HWC  102 . The pen  1500  generally follows the form of a conventional pen, which is a familiar user handled device and creates an intuitive physical interface for many of the operations to be carried out in the HWC system  100 . The pen  1500  may be one of several user interfaces  104  used in connection with controlling operations within the HWC system  100 . For example, the HWC  102  may watch for and interpret hand gestures  116  as control signals, where the pen  1500  may also be used as a user interface with the same HWC  102 . Similarly, a remote keyboard may be used as an external user interface  104  in concert with the pen  1500 . The combination of user interfaces or the use of just one control system generally depends on the operation(s) being executed in the HWC&#39;s system  100 . 
     While the pen  1500  may follow the general form of a conventional pen, it contains numerous technologies that enable it to function as an external user interface  104 .  FIG.  15    illustrates technologies comprised in the pen  1500 . As can be seen, the pen  1500  may include a camera  1508 , which is arranged to view through lens  1502 . The camera may then be focused, such as through lens  1502 , to image a surface upon which a user is writing or making other movements to interact with the HWC  102 . There are situations where the pen  1500  will also have an ink, graphite, or other system such that what is being written can be seen on the writing surface. There are other situations where the pen  1500  does not have such a physical writing system so there is no deposit on the writing surface, where the pen would only be communicating data or commands to the HWC  102 . The lens configuration is described in greater detail herein. The function of the camera is to capture information from an unstructured writing surface such that pen strokes can be interpreted as intended by the user. To assist in the predication of the intended stroke path, the pen  1500  may include a sensor, such as an IMU  1512 . Of course, the IMU could be included in the pen  1500  in its separate parts (e.g. gyro, accelerometer, etc.) or an IMU could be included as a single unit. In this instance, the IMU  1512  is used to measure and predict the motion of the pen  1500 . In turn, the integrated microprocessor  1510  would take the IMU information and camera information as inputs and process the information to form a prediction of the pen tip movement. 
     The pen  1500  may also include a pressure monitoring system  1504 , such as to measure the pressure exerted on the lens  1502 . As will be described in greater detail herein, the pressure measurement can be used to predict the user&#39;s intention for changing the weight of a line, type of a line, type of brush, click, double click, and the like. In embodiments, the pressure sensor may be constructed using any force or pressure measurement sensor located behind the lens  1502 , including for example, a resistive sensor, a current sensor, a capacitive sensor, a voltage sensor such as a piezoelectric sensor, and the like. 
     The pen  1500  may also include a communications module  1518 , such as for bi-directional communication with the HWC  102 . In embodiments, the communications module  1518  may be a short distance communication module (e.g. Bluetooth). The communications module  1518  may be security matched to the HWC  102 . The communications module  1518  may be arranged to communicate data and commands to and from the microprocessor  1510  of the pen  1500 . The microprocessor  1510  may be programmed to interpret data generated from the camera  1508 , IMU  1512 , and pressure sensor  1504 , and the like, and then pass a command onto the HWC  102  through the communications module  1518 , for example. In another embodiment, the data collected from any of the input sources (e.g. camera  1508 , IMU  1512 , pressure sensor  1504 ) by the microprocessor may be communicated by the communication module  1518  to the HWC  102 , and the HWC  102  may perform data processing and prediction of the user&#39;s intention when using the pen  1500 . In yet another embodiment, the data may be further passed on through a network  110  to a remote device  112 , such as a server, for the data processing and prediction. The commands may then be communicated back to the HWC  102  for execution (e.g. display writing in the glasses display, make a selection within the UI of the glasses display, control a remote external device  112 , control a local external device  108 ), and the like. The pen may also include memory  1514  for long or short term uses. 
     The pen  1500  may also include a number of physical user interfaces, such as quick launch buttons  1522 , a touch sensor  1520 , and the like. The quick launch buttons  1522  may be adapted to provide the user with a fast way of jumping to a software application in the HWC system  100 . For example, the user may be a frequent user of communication software packages (e.g. email, text, Twitter, Instagram, Facebook, Google+, and the like), and the user may program a quick launch button  1522  to command the HWC  102  to launch an application. The pen  1500  may be provided with several quick launch buttons  1522 , which may be user programmable or factory programmable. The quick launch button  1522  may be programmed to perform an operation. For example, one of the buttons may be programmed to clear the digital display of the HWC  102 . This would create a fast way for the user to clear the screens on the HWC  102  for any reason, such as for example to better view the environment. The quick launch button functionality will be discussed in further detail below. The touch sensor  1520  may be used to take gesture style input from the user. For example, the user may be able to take a single finger and run it across the touch sensor  1520  to affect a page scroll. 
     The pen  1500  may also include a laser pointer  1524 . The laser pointer  1524  may be coordinated with the IMU  1512  to coordinate gestures and laser pointing. For example, a user may use the laser  1524  in a presentation to help with guiding the audience with the interpretation of graphics and the IMU  1512  may, either simultaneously or when the laser  1524  is off, interpret the user&#39;s gestures as commands or data input. 
       FIGS.  16 A-C  illustrate several embodiments of lens and camera arrangements  1600  for the pen  1500 . One aspect relates to maintaining a constant distance between the camera and the writing surface to enable the writing surface to be kept in focus for better tracking of movements of the pen  1500  over the writing surface. Another aspect relates to maintaining an angled surface following the circumference of the writing tip of the pen  1500  such that the pen  1500  can be rolled or partially rolled in the user&#39;s hand to create the feel and freedom of a conventional writing instrument. 
       FIG.  16 A  illustrates an embodiment of the writing lens end of the pen  1500 . The configuration includes a ball lens  1604 , a camera or image capture surface  1602 , and a domed cover lens  1608 . In this arrangement, the camera views the writing surface through the ball lens  1604  and dome cover lens  1608 . The ball lens  1604  causes the camera to focus such that the camera views the writing surface when the pen  1500  is held in the hand in a natural writing position, such as with the pen  1500  in contact with a writing surface. In embodiments, the ball lens  1604  should be separated from the writing surface to obtain the highest resolution of the writing surface at the camera  1602 . In embodiments, the ball lens  1604  is separated by approximately 1 to 3 mm. In this configuration, the domed cover lens  1608  provides a surface that can keep the ball lens  1604  separated from the writing surface at a constant distance, such as substantially independent of the angle used to write on the writing surface. For instance, in embodiments the field of view of the camera in this arrangement would be approximately 60 degrees. 
     The domed cover lens, or other lens  1608  used to physically interact with the writing surface, will be transparent or transmissive within the active bandwidth of the camera  1602 . In embodiments, the domed cover lens  1608  may be spherical or other shape and comprised of glass, plastic, sapphire, diamond, and the like. In other embodiments where low resolution imaging of the surface is acceptable. The pen  1500  can omit the domed cover lens  1608  and the ball lens  1604  can be in direct contact with the surface. 
       FIG.  16 B  illustrates another structure where the construction is somewhat similar to that described in connection with  FIG.  16 A ; however this embodiment does not use a dome cover lens  1608 , but instead uses a spacer  1610  to maintain a predictable distance between the ball lens  1604  and the writing surface, wherein the spacer may be spherical, cylindrical, tubular or other shape that provides spacing while allowing for an image to be obtained by the camera  1602  through the lens  1604 . In a preferred embodiment, the spacer  1610  is transparent. In addition, while the spacer  1610  is shown as spherical, other shapes such as an oval, doughnut shape, half sphere, cone, cylinder or other form may be used. 
       FIG.  16 C  illustrates yet another embodiment, where the structure includes a post  1614 , such as running through the center of the lensed end of the pen  1500 . The post  1614  may be an ink deposition system (e.g. ink cartridge), graphite deposition system (e.g. graphite holder), or a dummy post whose purpose is mainly only that of alignment. The selection of the post type is dependent on the pen&#39;s use. For instance, in the event the user wants to use the pen  1500  as a conventional ink depositing pen as well as a fully functional external user interface  104 , the ink system post would be the best selection. If there is no need for the ‘writing’ to be visible on the writing surface, the selection would be the dummy post. The embodiment of  FIG.  16 C  includes camera(s)  1602  and an associated lens  1612 , where the camera  1602  and lens  1612  are positioned to capture the writing surface without substantial interference from the post  1614 . In embodiments, the pen  1500  may include multiple cameras  1602  and lenses  1612  such that more or all of the circumference of the tip  1614  can be used as an input system. In an embodiment, the pen  1500  includes a contoured grip that keeps the pen aligned in the user&#39;s hand so that the camera  1602  and lens  1612  remains pointed at the surface. 
     Another aspect of the pen  1500  relates to sensing the force applied by the user to the writing surface with the pen  1500 . The force measurement may be used in a number of ways. For example, the force measurement may be used as a discrete value, or discontinuous event tracking, and compared against a threshold in a process to determine a user&#39;s intent. The user may want the force interpreted as a ‘click’ in the selection of an object, for instance. The user may intend multiple force exertions interpreted as multiple clicks. There may be times when the user holds the pen  1500  in a certain position or holds a certain portion of the pen  1500  (e.g. a button or touch pad) while clicking to affect a certain operation (e.g. a ‘right click’). In embodiments, the force measurement may be used to track force and force trends. The force trends may be tracked and compared to threshold limits, for example. There may be one such threshold limit, multiple limits, groups of related limits, and the like. For example, when the force measurement indicates a fairly constant force that generally falls within a range of related threshold values, the microprocessor  1510  may interpret the force trend as an indication that the user desires to maintain the current writing style, writing tip type, line weight, brush type, and the like. In the event that the force trend appears to have gone outside of a set of threshold values intentionally, the microprocessor may interpret the action as an indication that the user wants to change the current writing style, writing tip type, line weight, brush type, and the like. Once the microprocessor has made a determination of the user&#39;s intent, a change in the current writing style, writing tip type, line weight, brush type, and the like may be executed. In embodiments, the change may be noted to the user (e.g. in a display of the HWC  102 ), and the user may be presented with an opportunity to accept the change. 
       FIG.  17 A  illustrates an embodiment of a force sensing surface tip  1700  of a pen  1500 . The force sensing surface tip  1700  comprises a surface connection tip  1702  (e.g. a lens as described herein elsewhere) in connection with a force or pressure monitoring system  1504 . As a user uses the pen  1500  to write on a surface or simulate writing on a surface the force monitoring system  1504  measures the force or pressure the user applies to the writing surface and the force monitoring system communicates data to the microprocessor  1510  for processing. In this configuration, the microprocessor  1510  receives force data from the force monitoring system  1504  and processes the data to make predictions of the user&#39;s intent in applying the particular force that is currently being applied. In embodiments, the processing may be provided at a location other than on the pen (e.g. at a server in the HWC system  100 , on the HWC  102 ). For clarity, when reference is made herein to processing information on the microprocessor  1510 , the processing of information contemplates processing the information at a location other than on the pen. The microprocessor  1510  may be programmed with force threshold(s), force signature(s), force signature library and/or other characteristics intended to guide an inference program in determining the user&#39;s intentions based on the measured force or pressure. The microprocessor  1510  may be further programmed to make inferences from the force measurements as to whether the user has attempted to initiate a discrete action (e.g. a user interface selection ‘click’) or is performing a constant action (e.g. writing within a particular writing style). The inferencing process is important as it causes the pen  1500  to act as an intuitive external user interface  104 . 
       FIG.  17 B  illustrates a force  1708  versus time  1710  trend chart with a single threshold  1718 . The threshold  1718  may be set at a level that indicates a discrete force exertion indicative of a user&#39;s desire to cause an action (e.g. select an object in a GUI). Event  1712 , for example, may be interpreted as a click or selection command because the force quickly increased from below the threshold  1718  to above the threshold  1718 . The event  1714  may be interpreted as a double click because the force quickly increased above the threshold  1718 , decreased below the threshold  1718  and then essentially repeated quickly. The user may also cause the force to go above the threshold  1718  and hold for a period indicating that the user is intending to select an object in the GUI (e.g. a GUI presented in the display of the HWC  102 ) and ‘hold’ for a further operation (e.g. moving the object). 
     While a threshold value may be used to assist in the interpretation of the user&#39;s intention, a signature force event trend may also be used. The threshold and signature may be used in combination or either method may be used alone. For example, a single-click signature may be represented by a certain force trend signature or set of signatures. The single-click signature(s) may require that the trend meet a criteria of a rise time between x any y values, a hold time of between a and b values and a fall time of between c and d values, for example. Signatures may be stored for a variety of functions such as click, double click, right click, hold, move, etc. The microprocessor  1510  may compare the real-time force or pressure tracking against the signatures from a signature library to make a decision and issue a command to the software application executing in the GUI. 
       FIG.  17 C  illustrates a force  1708  versus time  1710  trend chart with multiple thresholds  1718 . By way of example, the force trend is plotted on the chart with several pen force or pressure events. As noted, there are both presumably intentional events  1720  and presumably non-intentional events  1722 . The two thresholds  1718  of  FIG.  4 C  create three zones of force: a lower, middle and higher range. The beginning of the trend indicates that the user is placing a lower zone amount of force. This may mean that the user is writing with a given line weight and does not intend to change the weight, the user is writing. Then the trend shows a significant increase  1720  in force into the middle force range. This force change appears, from the trend to have been sudden and thereafter it is sustained. The microprocessor  1510  may interpret this as an intentional change and as a result change the operation in accordance with preset rules (e.g. change line width, increase line weight, etc.). The trend then continues with a second apparently intentional event  1720  into the higher-force range. During the performance in the higher-force range, the force dips below the upper threshold  1718 . This may indicate an unintentional force change and the microprocessor may detect the change in range however not affect a change in the operations being coordinated by the pen  1500 . As indicated above, the trend analysis may be done with thresholds and/or signatures. 
     Generally, in the present disclosure, instrument stroke parameter changes may be referred to as a change in line type, line weight, tip type, brush type, brush width, brush pressure, color, and other forms of writing, coloring, painting, and the like. 
     Another aspect of the pen  1500  relates to selecting an operating mode for the pen  1500  dependent on contextual information and/or selection interface(s). The pen  1500  may have several operating modes. For instance, the pen  1500  may have a writing mode where the user interface(s) of the pen  1500  (e.g. the writing surface end, quick launch buttons  1522 , touch sensor  1520 , motion based gesture, and the like) is optimized or selected for tasks associated with writing. As another example, the pen  1500  may have a wand mode where the user interface(s) of the pen is optimized or selected for tasks associated with software or device control (e.g. the HWC  102 , external local device, remote device  112 , and the like). The pen  1500 , by way of another example, may have a presentation mode where the user interface(s) is optimized or selected to assist a user with giving a presentation (e.g. pointing with the laser pointer  1524  while using the button(s)  1522  and/or gestures to control the presentation or applications relating to the presentation). The pen may, for example, have a mode that is optimized or selected for a particular device that a user is attempting to control. The pen  1500  may have a number of other modes and an aspect of the present invention relates to selecting such modes. 
       FIG.  18 A  illustrates an automatic user interface(s) mode selection based on contextual information. The microprocessor  1510  may be programmed with IMU thresholds  1814  and  1812 . The thresholds  1814  and  1812  may be used as indications of upper and lower bounds of an angle  1804  and  1802  of the pen  1500  for certain expected positions during certain predicted modes. When the microprocessor  1510  determines that the pen  1500  is being held or otherwise positioned within angles  1802  corresponding to writing thresholds  1814 , for example, the microprocessor  1510  may then institute a writing mode for the pen&#39;s user interfaces. Similarly, if the microprocessor  1510  determines (e.g. through the IMU  1512 ) that the pen is being held at an angle  1804  that falls between the predetermined wand thresholds  1812 , the microprocessor may institute a wand mode for the pen&#39;s user interface. Both of these examples may be referred to as context based user interface mode selection as the mode selection is based on contextual information (e.g. position) collected automatically and then used through an automatic evaluation process to automatically select the pen&#39;s user interface(s) mode. 
     As with other examples presented herein, the microprocessor  1510  may monitor the contextual trend (e.g. the angle of the pen over time) in an effort to decide whether to stay in a mode or change modes. For example, through signatures, thresholds, trend analysis, and the like, the microprocessor may determine that a change is an unintentional change and therefore no user interface mode change is desired. 
       FIG.  18 B  illustrates an automatic user interface(s) mode selection based on contextual information. In this example, the pen  1500  is monitoring (e.g. through its microprocessor) whether or not the camera at the writing surface end  1508  is imaging a writing surface in close proximity to the writing surface end of the pen  1500 . If the pen  1500  determines that a writing surface is within a predetermined relatively short distance, the pen  1500  may decide that a writing surface is present  1820  and the pen may go into a writing mode user interface(s) mode. In the event that the pen  1500  does not detect a relatively close writing surface  1822 , the pen may predict that the pen is not currently being used to as a writing instrument and the pen may go into a non-writing user interface(s) mode. 
       FIG.  18 C  illustrates a manual user interface(s) mode selection. The user interface(s) mode may be selected based on a twist of a section  1824  of the pen  1500  housing, clicking an end button  1828 , pressing a quick launch button  1522 , interacting with touch sensor  1520 , detecting a predetermined action at the pressure monitoring system (e.g. a click), detecting a gesture (e.g. detected by the IMU), etc. The manual mode selection may involve selecting an item in a GUI associated with the pen  1500  (e.g. an image presented in the display of HWC  102 ). 
     In embodiments, a confirmation selection may be presented to the user in the event a mode is going to change. The presentation may be physical (e.g. a vibration in the pen  1500 ), through a GUI, through a light indicator, etc. 
       FIG.  19    illustrates a couple pen use-scenarios  1900  and  1901 . There are many use scenarios and we have presented a couple in connection with  FIG.  19    as a way of illustrating use scenarios to further the understanding of the reader. As such, the use-scenarios should be considered illustrative and non-limiting. 
     Use scenario  1900  is a writing scenario where the pen  1500  is used as a writing instrument. In this example, quick launch button  122 A is pressed to launch a note application  1910  in the GUI  1908  of the HWC  102  display  1904 . Once the quick launch button  122 A is pressed, the HWC  102  launches the note program  1910  and puts the pen into a writing mode. The user uses the pen  1500  to scribe symbols  1902  on a writing surface, the pen records the scribing and transmits the scribing to the HWC  102  where symbols representing the scribing are displayed  1912  within the note application  1910 . 
     Use scenario  1901  is a gesture scenario where the pen  1500  is used as a gesture capture and command device. In this example, the quick launch button  122 B is activated and the pen  1500  activates a wand mode such that an application launched on the HWC  102  can be controlled. Here, the user sees an application chooser  1918  in the display(s) of the HWC  102  where different software applications can be chosen by the user. The user gestures (e.g. swipes, spins, turns, etc.) with the pen to cause the application chooser  1918  to move from application to application. Once the correct application is identified (e.g. highlighted) in the chooser  1918 , the user may gesture or click or otherwise interact with the pen  1500  such that the identified application is selected and launched. Once an application is launched, the wand mode may be used to scroll, rotate, change applications, select items, initiate processes, and the like, for example. 
     In an embodiment, the quick launch button  122 A may be activated and the HWC  102  may launch an application chooser presenting to the user a set of applications. For example, the quick launch button may launch a chooser to show all communication programs (e.g. SMS, Twitter, Instagram, Facebook, email, etc.) available for selection such that the user can select the program the user wants and then go into a writing mode. By way of further example, the launcher may bring up selections for various other groups that are related or categorized as generally being selected at a given time (e.g. Microsoft Office products, communication products, productivity products, note products, organizational products, and the like). 
       FIG.  20    illustrates yet another embodiment of the present invention.  FIG.  2000    illustrates a watchband clip on controller  2000 . The watchband clip on controller may be a controller used to control the HWC  102  or devices in the HWC system  100 . The watchband clip on controller  2000  has a fastener  2018  (e.g. rotatable clip) that is mechanically adapted to attach to a watchband, as illustrated at  2004 . 
     The watchband controller  2000  may have quick launch interfaces  2008  (e.g. to launch applications and choosers as described herein), a touch pad  2014  (e.g. to be used as a touch style mouse for GUI control in a HWC  102  display) and a display  2012 . The clip  2018  may be adapted to fit a wide range of watchbands so it can be used in connection with a watch that is independently selected for its function. The clip, in embodiments, is rotatable such that a user can position it in a desirable manner. In embodiments the clip may be a flexible strap. In embodiments, the flexible strap may be adapted to be stretched to attach to a hand, wrist, finger, device, weapon, and the like. 
     In embodiments, the watchband controller may be configured as a removable and replaceable watchband. For example, the controller may be incorporated into a band with a certain width, segment spacing&#39;s, etc. such that the watchband, with its incorporated controller, can be attached to a watch body. The attachment, in embodiments, may be mechanically adapted to attach with a pin upon which the watchband rotates. In embodiments, the watchband controller may be electrically connected to the watch and/or watch body such that the watch, watch body and/or the watchband controller can communicate data between them. 
     The watchband controller may have 3-axis motion monitoring (e.g. through an IMU, accelerometers, magnetometers, gyroscopes, etc.) to capture user motion. The user motion may then be interpreted for gesture control. 
     In embodiments, the watchband controller may comprise fitness sensors and a fitness computer. The sensors may track heart rate, calories burned, strides, distance covered, and the like. The data may then be compared against performance goals and/or standards for user feedback. 
     Another aspect of the present invention relates to visual display techniques relating to micro Doppler (“mD”) target tracking signatures (“mD signatures”). mD is a radar technique that uses a series of angle dependent electromagnetic pulses that are broadcast into an environment and return pulses are captured. Changes between the broadcast pulse and return pulse are indicative of changes in the shape, distance and angular location of objects or targets in the environment. These changes provide signals that can be used to track a target and identify the target through the mD signature. Each target or target type has a unique mD signature. Shifts in the radar pattern can be analyzed in the time domain and frequency domain based on mD techniques to derive information about the types of targets present (e.g. whether people are present), the motion of the targets and the relative angular location of the targets and the distance to the targets. By selecting a frequency used for the mD pulse relative to known objects in the environment, the pulse can penetrate the known objects to enable information about targets to be gathered even when the targets are visually blocked by the known objects. For example, pulse frequencies can be used that will penetrate concrete buildings to enable people to be identified inside the building. Multiple pulse frequencies can be used as well in the mD radar to enable different types of information to be gathered about the objects in the environment. In addition, the mD radar information can be combined with other information such as distance measurements or images captured of the environment that are analyzed jointly to provide improved object identification and improved target identification and tracking. In embodiments, the analysis can be performed on the HWC or the information can be transmitted to a remote network for analysis and results transmitted back to the HWC. Distance measurements can be provided by laser range finding, structured lighting, stereoscopic depth maps or sonar measurements. Images of the environment can be captured using one or more cameras capable of capturing images from visible, ultraviolet or infrared light. The mD radar can be attached to the HWC, located adjacently (e.g. in a vehicle) and associated wirelessly with the HWC or located remotely. Maps or other previously determined information about the environment can also be used in the analysis of the mD radar information. Embodiments of the present invention relate to visualizing the mD signatures in useful ways. 
       FIG.  21    illustrates a FOV  2102  of a HWC  102  from a wearer&#39;s perspective. The wearer, as described herein elsewhere, has a see-through FOV  2102  wherein the wearer views adjacent surroundings, such as the buildings illustrated in  FIG.  21   . The wearer, as described herein elsewhere, can also see displayed digital content presented within a portion of the FOV  2102 . The embodiment illustrated in  FIG.  21    is indicating that the wearer can see the buildings and other surrounding elements in the environment and digital content representing traces, or travel paths, of bullets being fired by different people in the area. The surroundings are viewed through the transparency of the FOV  2102 . The traces are presented via the digital computer display, as described herein elsewhere. In embodiments, the trace presented is based on a mD signature that is collected and communicated to the HWC in real time. The mD radar itself may be on or near the wearer of the HWC  102  or it may be located remote from the wearer. In embodiments, the mD radar scans the area, tracks and identifies targets, such as bullets, and communicates traces, based on locations, to the HWC  102 . 
     There are several traces  2108  and  2104  presented to the wearer in the embodiment illustrated in  FIG.  21   . The traces communicated from the mD radar may be associated with GPS locations and the GPS locations may be associated with objects in the environment, such as people, buildings, vehicles, etc, both in latitude and longitude perspective and an elevation perspective. The locations may be used as markers for the HWC such that the traces, as presented in the FOV, can be associated, or fixed in space relative to the markers. For example, if the friendly fire trace  2108  is determined, by the mD radar, to have originated from the upper right window of the building on the left, as illustrated in  FIG.  21   , then a virtual marker may be set on or near the window. When the HWC views, through its camera or other sensor, for example, the building&#39;s window, the trace may then virtually anchor with the virtual marker on the window. Similarly, a marker may be set near the termination position or other flight position of the friendly fire trace  2108 , such as the upper left window of the center building on the right, as illustrated in  FIG.  21   . This technique fixes in space the trace such that the trace appears fixed to the environmental positions independent of where the wearer is looking. So, for example, as the wearer&#39;s head turns, the trace appears fixed to the marked locations. 
     In embodiments, certain user positions may be known and thus identified in the FOV. For example, the shooter of the friendly fire trace  2108  may be from a known friendly combatant and as such his location may be known. The position may be known based on his GPS location based on a mobile communication system on him, such as another HWC  102 . In other embodiments, the friendly combatant may be marked by another friendly. For example, if the friendly position in the environment is known through visual contact or communicated information, a wearer of the HWC  102  may use a gesture or external user interface  104  to mark the location. If a friendly combatant location is known the originating position of the friendly fire trace  2108  may be color coded or otherwise distinguished from unidentified traces on the displayed digital content. Similarly, enemy fire traces  2104  may be color coded or otherwise distinguished on the displayed digital content. In embodiments, there may be an additional distinguished appearance on the displayed digital content for unknown traces. 
     In addition to situationally associated trace appearance, the trace colors or appearance may be different from the originating position to the terminating position. This path appearance change may be based on the mD signature. The mD signature may indicate that the bullet, for example, is slowing as it propagates and this slowing pattern may be reflected in the FOV  2102  as a color or pattern change. This can create an intuitive understanding of wear the shooter is located. For example, the originating color may be red, indicative of high speed, and it may change over the course of the trace to yellow, indicative of a slowing trace. This pattern changing may also be different for a friendly, enemy and unknown combatant. The enemy may go blue to green for a friendly trace, for example. 
       FIG.  21    illustrates an embodiment where the user sees the environment through the FOV and may also see color coded traces, which are dependent on bullet speed and combatant type, where the traces are fixed in environmental positions independent on the wearer&#39;s perspective. Other information, such as distance, range, range rings, time of day, date, engagement type (e.g. hold, stop firing, back away, etc.) may also be displayed in the FOV. 
     Another aspect of the present invention relates to mD radar techniques that trace and identify targets through other objects, such as walls (referred to generally as through wall mD), and visualization techniques related therewith.  FIG.  22    illustrates a through wall mD visualization technique according to the principles of the present invention. As described herein elsewhere, the mD radar scanning the environment may be local or remote from the wearer of a HWC  102 . The mD radar may identify a target (e.g. a person) that is visible  2204  and then track the target as he goes behind a wall  2208 . The tracking may then be presented to the wearer of a HWC  102  such that digital content reflective of the target and the target&#39;s movement, even behind the wall, is presented in the FOV  2202  of the HWC  102 . In embodiments, the target, when out of visible sight, may be represented by an avatar in the FOV to provide the wearer with imagery representing the target. 
     mD target recognition methods can identify the identity of a target based on the vibrations and other small movements of the target. This can provide a personal signature for the target. In the case of humans, this may result in a personal identification of a target that has been previously characterized. The cardio, heart beat, lung expansion and other small movements within the body may be unique to a person and if those attributes are pre-identified they may be matched in real time to provide a personal identification of a person in the FOV  2202 . The person&#39;s mD signatures may be determined based on the position of the person. For example, the database of personal mD signature attributes may include mD signatures for a person standing, sitting, laying down, running, walking, jumping, etc. This may improve the accuracy of the personal data match when a target is tracked through mD signature techniques in the field. In the event a person is personally identified, a specific indication of the person&#39;s identity may be presented in the FOV  2202 . The indication may be a color, shape, shade, name, indication of the type of person (e.g. enemy, friendly, etc.), etc. to provide the wearer with intuitive real time information about the person being tracked. This may be very useful in a situation where there is more than one person in an area of the person being tracked. If just one person in the area is personally identified, that person or the avatar of that person can be presented differently than other people in the area. 
       FIG.  23    illustrates an mD scanned environment  2300 . An mD radar may scan an environment in an attempt to identify objects in the environment. In this embodiment, the mD scanned environment reveals two vehicles  2302   a  and  2302   b , en enemy combatant  2309 , two friendly combatants  2308   a  and  2308   b  and a shot trace  2318 . Each of these objects may be personally identified or type identified. For example, the vehicles  2302   a  and  2302   b  may be identified through the mD signatures as a tank and heavy truck. The enemy combatant  2309  may be identified as a type (e.g. enemy combatant) or more personally (e.g. by name). The friendly combatants may be identified as a type (e.g. friendly combatant) or more personally (e.g. by name). The shot trace  2318  may be characterized by type of projectile or weapon type for the projectile, for example. 
       FIG.  23   a    illustrates two separate HWC  102  FOV display techniques according to the principles of the present invention. FOV  2312  illustrates a map view  2310  where the mD scanned environment is presented. Here, the wearer has a perspective on the mapped area so he can understand all tracked targets in the area. This allows the wearer to traverse the area with knowledge of the targets. FOV  2312  illustrates a heads-up view to provide the wearer with an augmented reality style view of the environment that is in proximity of the wearer. 
     An aspect of the present invention relates to suppression of extraneous or stray light. As discussed herein elsewhere, eyeglow and faceglow are two such artifacts that develop from such light. Eyeglow and faceglow can be caused by image light escaping from the optics module. The escaping light is then visible, particularly in dark environments when the user is viewing bright displayed images with the HWC. Light that escapes through the front of the HWC is visible as eyeglow as it that light that is visible in the region of the user&#39;s eyes. Eyeglow can appear in the form of a small version of the displayed image that the user is viewing. Light that escapes from the bottom of the HWC shines onto the user&#39;s face, cheek or chest so that these portions of the user appear to glow. Eyeglow and faceglow can both increase the visibility of the user and highlight the use of the HWC, which may be viewed negatively by the user. As such, reducing eyeglow and faceglow is advantageous. In combat situations (e.g. the mD trace presentation scenarios described herein) and certain gaming situations, the suppression of extraneous or stray light is very important. 
     The disclosure relating to  FIG.  6    shows an example where a portion of the image light passes through the combiner  602  such that the light shines onto the user&#39;s face, thereby illuminating a portion of the user&#39;s face in what is generally referred to herein as faceglow. Faceglow be caused by any portion of light from the HWC that illuminates the user&#39;s face. 
     An example of the source for the faceglow light can come from wide cone angle light associated with the image light incident onto the combiner  602 . Where the combiner can include a holographic mirror or a notch mirror in which the narrow bands of high reflectivity are matched to wavelengths of light by the light source. The wide cone angle associated with the image light corresponds with the field of view provided by the HWC. Typically the reflectivity of holographic mirrors and notch mirrors is reduced as the cone angle of the incident light is increased above 8 degrees. As a result, for a field of view of 30 degrees, substantial image light can pass through the combiner and cause faceglow. 
       FIG.  24    shows an illustration of a light trap  2410  for the faceglow light. In this embodiment, an extension of the outer shield lens of the HWC is coated with a light absorbing material in the region where the converging light responsible for faceglow is absorbed in a light trap  2410 . The light absorbing material can be black or it can be a filter designed to absorb only the specific wavelengths of light provided by the light source(s) in the HWC. In addition, the surface of the light trap  2410  may be textured or fibrous to further improve the absorption. 
       FIG.  25    illustrates an optical system for a HWC that includes an outer absorptive polarizer  2520  to block the faceglow light. In this embodiment, the image light is polarized and as a result the light responsible for faceglow is similarly polarized. The absorptive polarizer is oriented with a transmission axis such that the faceglow light is absorbed and not transmitted. In this case, the rest of the imaging system in the HWC may not require polarized image light and the image light may be polarized at any point before the combiner. In embodiments, the transmission axis of the absorptive polarizer  2520  is oriented vertically so that external glare from water (S polarized light) is absorbed and correspondingly, the polarization of the image light is selected to be horizontal (S polarization). Consequently, image light that passes through the combiner  602  and is then incident onto the absorptive polarizer  2520 , is absorbed. In  FIG.  25    the absorptive polarizer  2520  is shown outside the shield lens, alternatively the absorptive polarizer  2520  can be located inside the shield lens. 
       FIG.  26    illustrates an optical system for a HWC that includes a film with an absorptive notch filter  2620 . In this case, the absorptive notch filter absorbs narrow bands of light that are selected to match the light provided by the optical system&#39;s light source. As a result, the absorptive notch filter is opaque with respect to the faceglow light and is transparent to the remainder of the wavelengths included in the visible spectrum so that the user has a clear view of the surrounding environment. A triple notch filter suitable for this approach is available from Iridian Spectral Technologies, Ottawa, ON: http://www.ilphotonics.com/cdv2/Iridian-Interference%20Filters/New%20Filters/Triple%20Notch%20Filter.pdf 
     In embodiments, the combiner  602  may include a notch mirror coating to reflect the wavelengths of light in the image light and a notch filter  2620  can be selected in correspondence to the wavelengths of light provided by the light source and the narrow bands of high reflectivity provided by the notch mirror. In this way, image light that is not reflected by the notch mirror is absorbed by the notch filter  2620 . In embodiments of the invention the light source can provide one narrow band of light for a monochrome imaging or three narrow bands of light for full color imaging. The notch mirror and associated notch filter would then each provide one narrow band or three narrow bands of high reflectivity and absorption respectively. 
       FIG.  27    includes a microlouver film  2750  to block the faceglow light. Microlouver film is sold by 3M as ALCF-P, for example and is typically used as a privacy filter for computer. See http://multimedia.3 m.com/mws/mediawebserver?mwsld=SSSSSuH8gc7nZxtUoY_x_1Y_eevUqe 17zHvTSevTSeSSSSSS-&amp;fn=ALCF-P_ABR2_Control_Film_DS.pdf. The microlouver film transmits light within a somewhat narrow angle (e.g. 30 degrees of normal and absorbs light beyond 30 degrees of normal). In  FIG.  27   , the microlouver film  2750  is positioned such that the faceglow light  2758  is incident beyond 30 degrees from normal while the see-through light  2755  is incident within 30 degrees of normal to the microlouver film  2750 . As such, the faceglow light  2758  is absorbed by the microlouver film and the see-through light  2755  is transmitted so that the user has a bright see-thru view of the surrounding environment. 
     We now turn back to a description of eye imaging technologies. Aspects of the present invention relate to various methods of imaging the eye of a person wearing the HWC  102 . In embodiments, technologies for imaging the eye using an optical path involving the “off” state and “no power” state, which is described in detail below, are described. In embodiments, technologies for imaging the eye with optical configurations that do not involve reflecting the eye image off of DLP mirrors is described. In embodiments, unstructured light, structured light, or controlled lighting conditions, are used to predict the eye&#39;s position based on the light reflected off of the front of the wearer&#39;s eye. In embodiments, a reflection of a presented digital content image is captured as it reflects off of the wearer&#39;s eye and the reflected image may be processed to determine the quality (e.g. sharpness) of the image presented. In embodiments, the image may then be adjusted (e.g. focused differently) to increase the quality of the image presented based on the image reflection. 
       FIGS.  28   a ,  28   b  and  28   c    show illustrations of the various positions of the DLP mirrors.  FIG.  28   a    shows the DLP mirrors in the “on” state  2815 . With the mirror in the “on” state  2815 , illumination light  2810  is reflected along an optical axis  2820  that extends into the lower optical module  204 .  FIG.  28   b    shows the DLP mirrors in the “off” state  2825 . With the mirror in the “off” state  2825 , illumination light  2810  is reflected along an optical axis  2830  that is substantially to the side of optical axis  2820  so that the “off” state light is directed toward a dark light trap as has been described herein elsewhere.  FIG.  28   c    shows the DLP mirrors in a third position, which occurs when no power is applied to the DLP. This “no power” state differs from the “on” and “off” states in that the mirror edges are not in contact with the substrate and as such are less accurately positioned.  FIG.  28   c    shows all of the DLP mirrors in the “no power” state  2835 . The “no power” state is achieved by simultaneously setting the voltage to zero for the “on” contact and “off” contact for a DLP mirror, as a result, the mirror returns to a no stress position where the DLP mirror is in the plane of the DLP platform as shown in  FIG.  28   c   . Although not normally done, it is also possible to apply the “no power” state to individual DLP mirrors. When the DLP mirrors are in the “no power” state they do not contribute image content. Instead, as shown in  FIG.  28   c   , when the DLP mirrors are in the “no power” state, the illumination light  2810  is reflected along an optical axis  2840  that is between the optical axes  2820  and  2830  that are respectively associated with the “on” and “off” states and as such this light doesn&#39;t contribute to the displayed image as a bright or dark pixel. This light can however contribute scattered light into the lower optical module  204  and as a result the displayed image contrast can be reduced or artifacts can be created in the image that detract from the image content. Consequently, it is generally desirable, in embodiments, to limit the time associated with the “no power” state to times when images are not displayed or to reduce the time associated with having DLP mirrors in the “no power” state so that the affect of the scattered light is reduced. 
       FIG.  29    shows an embodiment of the invention that can be used for displaying digital content images to a wearer of the HWC  102  and capturing images of the wearer&#39;s eye. In this embodiment, light from the eye  2971  passes back through the optics in the lower module  204 , the solid corrective wedge  2966 , at least a portion of the light passes through the partially reflective layer  2960 , the solid illumination wedge  2964  and is reflected by a plurality of DLP mirrors on the DLP  2955  that are in the “no power” state. The reflected light then passes back through the illumination wedge  2964  and at least a portion of the light is reflected by the partially reflective layer  2960  and the light is captured by the camera  2980 . 
     For comparison, illuminating light rays  2973  from the light source  2958  are also shown being reflected by the partially reflective layer  2960 . Where the angle of the illuminating light  2973  is such that the DLP mirrors, when in the “on” state, reflect the illuminating light  2973  to form image light  2969  that substantially shares the same optical axis as the light from the wearer&#39;s eye  2971 . In this way, images of the wearer&#39;s eye are captured in a field of view that overlaps the field of view for the displayed image content. In contrast, light reflected by DLP mirrors in the “off” state form dark light  2975  which is directed substantially to the side of the image light  2969  and the light from eye  2971 . Dark light  2975  is directed toward a light trap  2962  that absorbs the dark light to improve the contrast of the displayed image as has been described above in this specification. 
     In an embodiment, partially reflective layer  2960  is a reflective polarizer. The light that is reflected from the eye  2971  can then be polarized prior to entering the corrective wedge  2966  (e.g. with an absorptive polarizer between the upper module  202  and the lower module  204 ), with a polarization orientation relative to the reflective polarizer that enables the light reflected from the eye  2971  to substantially be transmitted by the reflective polarizer. A quarter wave retarder layer  2957  is then included adjacent to the DLP  2955  (as previously disclosed in  FIG.  3   b   ) so that the light reflected from the eye  2971  passes through the quarter wave retarder layer  2957  once before being reflected by the plurality of DLP mirrors in the “no power” state and then passes through a second time after being reflected. By passing through the quarter wave retarder layer  2957  twice, the polarization state of the light from the eye  2971  is reversed, such that when it is incident upon the reflective polarizer, the light from the eye  2971  is then substantially reflected toward the camera  2980 . By using a partially reflective layer  2960  that is a reflective polarizer and polarizing the light from the eye  2971  prior to entering the corrective wedge  2964 , losses attributed to the partially reflective layer  2960  are reduced. 
       FIG.  28   c    shows the case wherein the DLP mirrors are simultaneously in the “no power” state, this mode of operation can be particularly useful when the HWC  102  is first put onto the head of the wearer. When the HWC  102  is first put onto the head of the wearer, it is not necessary to display an image yet. As a result, the DLP can be in a “no power” state for all the DLP mirrors and an image of the wearer&#39;s eyes can be captured. The captured image of the wearer&#39;s eye can then be compared to a database, using iris identification techniques, or other eye pattern identification techniques to determine, for example, the identity of the wearer. 
     In a further embodiment illustrated by  FIG.  29    all of the DLP mirrors are put into the “no power” state for a portion of a frame time (e.g. 50% of a frame time for the displayed digital content image) and the capture of the eye image is synchronized to occur at the same time and for the same duration. By reducing the time that the DLP mirrors are in the “no power” state, the time where light is scattered by the DLP mirrors being in the “no power” state is reduced such that the wearer doesn&#39;t perceive a change in the displayed image quality. This is possible because the DLP mirrors have a response time on the order of microseconds while typical frame times for a displayed image are on the order of 0.016 seconds. This method of capturing images of the wearer&#39;s eye can be used periodically to capture repetitive images of the wearer&#39;s eye. For example, eye images could be captured for 50% of the frame time of every 10 th  frame displayed to the wearer. In another example, eye images could be captured for 10% of the frame time of every frame displayed to the wearer. 
     Alternately, the “no power” state can be applied to a subset of the DLP mirrors (e.g. 10% of the DLP mirrors) within while another subset is in busy generating image light for content to be displayed. This enables the capture of an eye image(s) during the display of digital content to the wearer. The DLP mirrors used for eye imaging can, for example, be distributed randomly across the area of the DLP to minimize the impact on the quality of the digital content being displayed to the wearer. To improve the displayed image perceived by the wearer, the individual DLP mirrors put into the “no power” state for capturing each eye image, can be varied over time such as in a random pattern, for example. In yet a further embodiment, the DLP mirrors put into the “no power” state for eye imaging may be coordinated with the digital content in such a way that the “no power” mirrors are taken from a portion of the image that requires less resolution. 
     In the embodiments of the invention as illustrated in  FIGS.  9  and  29   , in both cases the reflective surfaces provided by the DLP mirrors do not preserve the wavefront of the light from the wearer&#39;s eye so that the image quality of captured image of the eye is somewhat limited. It may still be useful in certain embodiments, but it is somewhat limited. This is due to the DLP mirrors not being constrained to be on the same plane. In the embodiment illustrated in  FIG.  9   , the DLP mirrors are tilted so that they form rows of DLP mirrors that share common planes. In the embodiment illustrated in  FIG.  29   , the individual DLP mirrors are not accurately positioned to be in the same plane since they are not in contact with the substrate. Examples of advantages of the embodiments associated with  FIG.  29    are: first, the camera  2980  can be located between the DLP  2955  and the illumination light source  2958  to provide a more compact upper module  202 . Second, the polarization state of the light reflected from the eye  2971  can be the same as that of the image light  2969  so that the optical path of the light reflected from the eye and the image light can be the same in the lower module  204 . 
       FIG.  30    shows an illustration of an embodiment for displaying images to the wearer and simultaneously capturing images of the wearer&#39;s eye, wherein light from the eye  2971  is reflected towards a camera  3080  by the partially reflective layer  2960 . The partially reflective layer  2960  can be an optically flat layer such that the wavefront of the light from the eye  2971  is preserved and as a result, higher quality images of the wearer&#39;s eye can be captured. In addition, since the DLP  2955  is not included in the optical path for the light from the eye  2971 , and the eye imaging process shown in  FIG.  30    does not interfere with the displayed image, images of the wearer&#39;s eye can be captured independently (e.g. with independent of timing, impact on resolution, or pixel count used in the image light) from the displayed images. 
     In the embodiment illustrated in  FIG.  30   , the partially reflective layer  2960  is a reflective polarizer, the illuminating light  2973  is polarized, the light from the eye  2971  is polarized and the camera  3080  is located behind a polarizer  3085 . The polarization axis of the illuminating light  2973  and the polarization axis of the light from the eye are oriented perpendicular to the transmission axis of the reflective polarizer so that they are both substantially reflected by the reflective polarizer. The illumination light  2973  passes through a quarter wave layer  2957  before being reflected by the DLP mirrors in the DLP  2955 . The reflected light passes back through the quarter wave layer  2957  so that the polarization states of the image light  2969  and dark light  2975  are reversed in comparison to the illumination light  2973 . As such, the image light  2969  and dark light  2975  are substantially transmitted by the reflective polarizer. Where the DLP mirrors in the “on” state provide the image light  2969  along an optical axis that extends into the lower optical module  204  to display an image to the wearer. At the same time, DLP mirrors in the “off” state provide the dark light  2975  along an optical axis that extends to the side of the upper optics module  202 . In the region of the corrective wedge  2966  where the dark light  2975  is incident on the side of the upper optics module  202 , an absorptive polarizer  3085  is positioned with its transmission axis perpendicular to the polarization axis of the dark light and parallel to the polarization axis of the light from the eye so that the dark light  2975  is absorbed and the light from the eye  2971  is transmitted to the camera  3080 . 
       FIG.  31    shows an illustration of another embodiment of a system for displaying images and simultaneously capturing image of the wearer&#39;s eye that is similar to the one shown in  FIG.  30   . The difference in the system shown in  FIG.  31    is that the light from the eye  2971  is subjected to multiple reflections before being captured by the camera  3180 . To enable the multiple reflections, a mirror  3187  is provided behind the absorptive polarizer  3185 . Therefore, the light from the eye  2971  is polarized prior to entering the corrective wedge  2966  with a polarization axis that is perpendicular to the transmission axis of the reflective polarizer that comprises the partially reflective layer  2960 . In this way, the light from the eye  2971  is reflected first by the reflective polarizer, reflected second by the mirror  3187  and reflected third by the reflective polarizer before being captured by the camera  3180 . While the light from the eye  2971  passes through the absorptive polarizer  3185  twice, since the polarization axis of the light from the eye  2971  is oriented parallel to the polarization axis of the light from the eye  2971 , it is substantially transmitted by the absorptive polarizer  3185 . As with the system described in connection with  FIG.  30   , the system shown in  FIG.  31    includes an optically flat partially reflective layer  2960  that preserves the wavefront of the light from the eye  2971  so that higher quality images of the wearer&#39;s eye can be captured. Also, since the DLP  2955  is not included in the optical path for the light reflected from the eye  2971  and the eye imaging process shown in  FIG.  31    does not interfere with the displayed image, images of the wearer&#39;s eye can be captured independently from the displayed images. 
       FIG.  32    shows an illustration of a system for displaying images and simultaneously capturing images of the wearer&#39;s eye that includes a beam splitter plate  3212  comprised of a reflective polarizer, which is held in air between the light source  2958 , the DLP  2955  and the camera  3280 . The illumination light  2973  and the light from the eye  2971  are both polarized with polarization axes that are perpendicular to the transmission axis of the reflective polarizer. As a result, both the illumination light  2973  and the light from the eye  2971  are substantially reflected by the reflective polarizer. The illumination light  2873  is reflected toward the DLP  2955  by the reflective polarizer and split into image light  2969  and dark light  3275  depending on whether the individual DLP mirrors are respectively in the “on” state or the “off” state. By passing through the quarter wave layer  2957  twice, the polarization state of the illumination light  2973  is reversed in comparison to the polarization state of the image light  2969  and the dark light  3275 . As a result, the image light  2969  and the dark light  3275  are then substantially transmitted by the reflective polarizer. The absorptive polarizer  3285  at the side of the beam splitter plate  3212  has a transmission axis that is perpendicular to the polarization axis of the dark light  3275  and parallel to the polarization axis of the light from the eye  2971  so that the dark light  3275  is absorbed and the light from the eye  2971  is transmitted to the camera  3280 . As in the system shown in  FIG.  30   , the system shown in  FIG.  31    includes an optically flat beam splitter plate  3212  that preserves the wavefront of the light from the eye  2971  so that higher quality images of the wearer&#39;s eye can be captured. Also, since the DLP  2955  is not included in the optical path for the light from the eye  2971  and the eye imaging process shown in  FIG.  31    does not interfere with the displayed image, images of the wearer&#39;s eye can be captured independently from the displayed images. 
     Eye imaging systems where the polarization state of the light from the eye  2971  needs to be opposite to that of the image light  2969  (as shown in  FIGS.  30 ,  31  and  32   ), need to be used with lower modules  204  that include combiners that will reflect both polarization states. As such, these upper modules  202  are best suited for use with the lower modules  204  that include combiners that are reflective regardless of polarization state, examples of these lower modules are shown in  FIGS.  6 ,  8     a ,  8   b ,  8   c  and  24 - 27 . 
     In a further embodiment shown in  FIG.  33   , the partially reflective layer  3360  is comprised of a reflective polarizer on the side facing the illumination light  2973  and a short pass dichroic mirror on the side facing the light from the eye  3371  and the camera  3080 . Where the short pass dichroic mirror is a dielectric mirror coating that transmits visible light and reflects infrared light. The partially reflective layer  3360  can be comprised of a reflective polarizer bonded to the inner surface of the illumination wedge  2964  and a short pass dielectric mirror coating on the opposing inner surface of the corrective wedge  2966 , wherein the illumination wedge  2964  and the corrective wedge  2966  are then optically bonded together. Alternatively, the partially reflective layer  3360  can be comprised of a thin substrate that has a reflective polarizer bonded to one side and a short pass dichroic mirror coating on the other side, where the partially reflective layer  3360  is then bonded between the illumination wedge  2964  and the corrective wedge  2966 . In this embodiment, an infrared light is included to illuminate the eye so that the light from the eye and the images captured of the eye are substantially comprised of infrared light. The wavelength of the infrared light is then matched to the reflecting wavelength of the shortpass dichroic mirror and the wavelength that the camera can capture images, for example an 800 nm wavelength can be used. In this way, the short pass dichroic mirror transmits the image light and reflects the light from the eye. The camera  3080  is then positioned at the side of the corrective wedge  2966  in the area of the absorbing light trap  3382 , which is provided to absorb the dark light  2975 . By positioning the camera  3080  in a depression in the absorbing light trap  3382 , scattering of the dark light  2975  by the camera  3080  can be reduced so that higher contrast images can be displayed to the wearer. An advantage of this embodiment is that the light from the eye need not be polarized, which can simplify the optical system and increase efficiency for the eye imaging system. 
     In yet another embodiment shown in  FIG.  32   a    a beam splitter plate  3222  is comprised of a reflective polarizer on the side facing the illumination light  2973  and a short pass dichroic mirror on the side facing the light from the eye  3271  and the camera  3280 . An absorbing surface  3295  is provided to trap the dark light  3275  and the camera  3280  is positioned in an opening in the absorbing surface  3295 . In this way the system of  FIG.  32    can be made to function with unpolarized light from the eye  3271 . 
     In embodiments directed to capturing images of the wearer&#39;s eye, light to illuminate the wearer&#39;s eye can be provided by several different sources including: light from the displayed image (i.e. image light); light from the environment that passes through the combiner or other optics; light provided by a dedicated eye light, etc.  FIGS.  34  and  34     a  show illustrations of dedicated eye illumination lights  3420 .  FIG.  34    shows an illustration from a side view in which the dedicated illumination eye light  3420  is positioned at a corner of the combiner  3410  so that it doesn&#39;t interfere with the image light  3415 . The dedicated eye illumination light  3420  is pointed so that the eye illumination light  3425  illuminates the eyebox  3427  where the eye  3430  is located when the wearer is viewing displayed images provided by the image light  3415 .  FIG.  34   a    shows an illustration from the perspective of the eye of the wearer to show how the dedicated eye illumination light  3420  is positioned at the corner of the combiner  3410 . While the dedicated eye illumination light  3420  is shown at the upper left corner of the combiner  3410 , other positions along one of the edges of the combiner  3410 , or other optical or mechanical components, are possible as well. In other embodiments, more than one dedicated eye light  3420  with different positions can be used. In an embodiment, the dedicated eye light  3420  is an infrared light that is not visible by the wearer (e.g. 800 nm) so that the eye illumination light  3425  doesn&#39;t interfere with the displayed image perceived by the wearer. 
       FIG.  35    shows a series of illustrations of captured eye images that show the eye glint (i.e. light that reflects off the front of the eye) produced by a dedicated eye light. In this embodiment of the invention, captured images of the wearer&#39;s eye are analyzed to determine the relative positions of the iris  3550 , pupil, or other portion of the eye, and the eye glint  3560 . The eye glint is a reflected image of the dedicated eye light  3420  when the dedicated light is used.  FIG.  35    illustrates the relative positions of the iris  3550  and the eye glint  3560  for a variety of eye positions. By providing a dedicated eye light  3420  in a fixed position, combined with the fact that the human eye is essentially spherical, or at least a reliably repeatable shape, the eye glint provides a fixed reference point against which the determined position of the iris can be compared to determine where the wearer is looking, either within the displayed image or within the see-through view of the surrounding environment. By positioning the dedicated eye light  3420  at a corner of the combiner  3410 , the eye glint  3560  is formed away from the iris  3550  in the captured images. As a result, the positions of the iris and the eye glint can be determined more easily and more accurately during the analysis of the captured images, since they do not interfere with one another. In a further embodiment, the combiner includes an associated cut filter that prevents infrared light from the environment from entering the HWC and the camera is an infrared camera, so that the eye glint is only provided by light from the dedicated eye light. For example, the combiner can include a low pass filter that passes visible light while absorbing infrared light and the camera can include a high pass filter that absorbs visible light while passing infrared light. 
     In an embodiment of the eye imaging system, the lens for the camera is designed to take into account the optics associated with the upper module  202  and the lower module  204 . This is accomplished by designing the camera to include the optics in the upper module  202  and optics in the lower module  204 , so that a high MTF image is produced, at the image sensor in the camera, of the wearer&#39;s eye. In yet a further embodiment, the camera lens is provided with a large depth of field to eliminate the need for focusing the camera to enable sharp image of the eye to be captured. Where a large depth of field is typically provided by a high f/#lens (e.g. f/#&gt;5). In this case, the reduced light gathering associated with high f/#lenses is compensated by the inclusion of a dedicated eye light to enable a bright image of the eye to be captured. Further, the brightness of the dedicated eye light can be modulated and synchronized with the capture of eye images so that the dedicated eye light has a reduced duty cycle and the brightness of infrared light on the wearer&#39;s eye is reduced. 
     In a further embodiment,  FIG.  36   a    shows an illustration of an eye image that is used to identify the wearer of the HWC. In this case, an image of the wearer&#39;s eye  3611  is captured and analyzed for patterns of identifiable features  3612 . The patterns are then compared to a database of eye images to determine the identity of the wearer. After the identity of the wearer has been verified, the operating mode of the HWC and the types of images, applications, and information to be displayed can be adjusted and controlled in correspondence to the determined identity of the wearer. Examples of adjustments to the operating mode depending on who the wearer is determined to be or not be include: making different operating modes or feature sets available, shutting down or sending a message to an external network, allowing guest features and applications to run, etc. 
       FIG.  36   b    is an illustration of another embodiment using eye imaging, in which the sharpness of the displayed image is determined based on the eye glint produced by the reflection of the displayed image from the wearer&#39;s eye surface. By capturing images of the wearer&#39;s eye  3611 , an eye glint  3622 , which is a small version of the displayed image can be captured and analyzed for sharpness. If the displayed image is determined to not be sharp, then an automated adjustment to the focus of the HWC optics can be performed to improve the sharpness. This ability to perform a measurement of the sharpness of a displayed image at the surface of the wearer&#39;s eye can provide a very accurate measurement of image quality. Having the ability to measure and automatically adjust the focus of displayed images can be very useful in augmented reality imaging where the focus distance of the displayed image can be varied in response to changes in the environment or changes in the method of use by the wearer. 
     An aspect of the present invention relates to controlling the HWC  102  through interpretations of eye imagery. In embodiments, eye-imaging technologies, such as those described herein, are used to capture an eye image or series of eye images for processing. The image(s) may be processed to determine a user intended action, an HWC predetermined reaction, or other action. For example, the imagery may be interpreted as an affirmative user control action for an application on the HWC  102 . Or, the imagery may cause, for example, the HWC  102  to react in a pre-determined way such that the HWC  102  is operating safely, intuitively, etc. 
       FIG.  37    illustrates a eye imagery process that involves imaging the HWC  102  wearer&#39;s eye(s) and processing the images (e.g. through eye imaging technologies described herein) to determine in what position  3702  the eye is relative to its neutral or forward-looking position and/or the FOV  3708 . The process may involve a calibration step where the user is instructed, through guidance provided in the FOV of the HWC  102 , to look in certain directions such that a more accurate prediction of the eye position relative to areas of the FOV can be made. In the event the wearer&#39;s eye is determined to be looking towards the right side of the FOV  3708  (as illustrated in  FIG.  37   , the eye is looking out of the page) a virtual target line may be established to project what in the environment the wearer may be looking towards or at. The virtual target line may be used in connection with an image captured by camera on the HWC  102  that images the surrounding environment in front of the wearer. In embodiments, the field of view of the camera capturing the surrounding environment matches, or can be matched (e.g. digitally), to the FOV  3708  such that making the comparison is made more clear. For example, with the camera capturing the image of the surroundings in an angle that matches the FOV  3708  the virtual line can be processed (e.g. in 2d or 3d, depending on the camera images capabilities and/or the processing of the images) by projecting what surrounding environment objects align with the virtual target line. In the event there are multiple objects along the virtual target line, focal planes may be established corresponding to each of the objects such that digital content may be placed in an area in the FOV  3708  that aligns with the virtual target line and falls at a focal plane of an intersecting object. The user then may see the digital content when he focuses on the object in the environment, which is at the same focal plane. In embodiments, objects in line with the virtual target line may be established by comparison to mapped information of the surroundings. 
     In embodiments, the digital content that is in line with the virtual target line may not be displayed in the FOV until the eye position is in the right position. This may be a predetermined process. For example, the system may be set up such that a particular piece of digital content (e.g. an advertisement, guidance information, object information, etc.) will appear in the event that the wearer looks at a certain object(s) in the environment. A virtual target line(s) may be developed that virtually connects the wearer&#39;s eye with an object(s) in the environment (e.g. a building, portion of a building, mark on a building, GPS location, etc.) and the virtual target line may be continually updated depending on the position and viewing direction of the wearer (e.g. as determined through GPS, e-compass, IMU, etc.) and the position of the object. When the virtual target line suggests that the wearer&#39;s pupil is substantially aligned with the virtual target line or about to be aligned with the virtual target line, the digital content may be displayed in the FOV  3704 . 
     In embodiments, the time spent looking along the virtual target line and/or a particular portion of the FOV  3708  may indicate that the wearer is interested in an object in the environment and/or digital content being displayed. In the event there is no digital content being displayed at the time a predetermined period of time is spent looking at a direction, digital content may be presented in the area of the FOV  3708 . The time spent looking at an object may be interpreted as a command to display information about the object, for example. In other embodiments, the content may not relate to the object and may be presented because of the indication that the person is relatively inactive. In embodiments, the digital content may be positioned in proximity to the virtual target line, but not in-line with it such that the wearer&#39;s view of the surroundings are not obstructed but information can augment the wearer&#39;s view of the surroundings. In embodiments, the time spent looking along a target line in the direction of displayed digital content may be an indication of interest in the digital content. This may be used as a conversion event in advertising. For example, an advertiser may pay more for an add placement if the wearer of the HWC  102  looks at a displayed advertisement for a certain period of time. As such, in embodiments, the time spent looking at the advertisement, as assessed by comparing eye position with the content placement, target line or other appropriate position may be used to determine a rate of conversion or other compensation amount due for the presentation. 
     An aspect of the invention relates to removing content from the FOV of the HWC  102  when the wearer of the HWC  102  apparently wants to view the surrounding environments clearly.  FIG.  38    illustrates a situation where eye imagery suggests that the eye has or is moving quickly so the digital content  3804  in the FOV  3808  is removed from the FOV  3808 . In this example, the wearer may be looking quickly to the side indicating that there is something on the side in the environment that has grabbed the wearer&#39;s attention. This eye movement  3802  may be captured through eye imaging techniques (e.g. as described herein) and if the movement matches a predetermined movement (e.g. speed, rate, pattern, etc.) the content may be removed from view. In embodiments, the eye movement is used as one input and HWC movements indicated by other sensors (e.g. IMU in the HWC) may be used as another indication. These various sensor movements may be used together to project an event that should cause a change in the content being displayed in the FOV. 
     Another aspect of the present invention relates to determining a focal plane based on the wearer&#39;s eye convergence. Eyes are generally converged slightly and converge more when the person focuses on something very close. This is generally referred to as convergence. In embodiments, convergence is calibrated for the wearer. That is, the wearer may be guided through certain focal plane exercises to determine how much the wearer&#39;s eyes converge at various focal planes and at various viewing angles. The convergence information may then be stored in a database for later reference. In embodiments, a general table may be used in the event there is no calibration step or the person skips the calibration step. The two eyes may then be imaged periodically to determine the convergence in an attempt to understand what focal plane the wearer is focused on. In embodiments, the eyes may be imaged to determine a virtual target line and then the eye&#39;s convergence may be determined to establish the wearer&#39;s focus, and the digital content may be displayed or altered based thereon. 
       FIG.  39    illustrates a situation where digital content is moved  3902  within one or both of the FOVs  3908  and  3910  to align with the convergence of the eyes as determined by the pupil movement  3904 . By moving the digital content to maintain alignment, in embodiments, the overlapping nature of the content is maintained so the object appears properly to the wearer. This can be important in situations where 3D content is displayed. 
     An aspect of the present invention relates to controlling the HWC  102  based on events detected through eye imaging. A wearer winking, blinking, moving his eyes in a certain pattern, etc. may, for example, control an application of the HWC  102 . Eye imaging (e.g. as described herein) may be used to monitor the eye(s) of the wearer and once a pre-determined pattern is detected an application control command may be initiated. 
     An aspect of the invention relates to monitoring the health of a person wearing a HWC  102  by monitoring the wearer&#39;s eye(s). Calibrations may be made such that the normal performance, under various conditions (e.g. lighting conditions, image light conditions, etc.) of a wearer&#39;s eyes may be documented. The wearer&#39;s eyes may then be monitored through eye imaging (e.g. as described herein) for changes in their performance. Changes in performance may be indicative of a health concern (e.g. concussion, brain injury, stroke, loss of blood, etc.). If detected the data indicative of the change or event may be communicated from the HWC  102 . 
     Aspects of the present invention relate to security and access of computer assets (e.g. the HWC itself and related computer systems) as determined through eye image verification. As discussed herein elsewhere, eye imagery may be compared to known person eye imagery to confirm a person&#39;s identity. Eye imagery may also be used to confirm the identity of people wearing the HWCs  102  before allowing them to link together or share files, streams, information, etc. 
     A variety of use cases for eye imaging are possible based on technologies described herein. An aspect of the present invention relates to the timing of eye image capture. The timing of the capture of the eye image and the frequency of the capture of multiple images of the eye can vary dependent on the use case for the information gathered from the eye image. For example, capturing an eye image to identify the user of the HWC may be required only when the HWC has been turned ON or when the HWC determines that the HWC has been put onto a wearer&#39;s head, to control the security of the HWC and the associated information that is displayed to the user. Wherein, the orientation, movement pattern, stress or position of the earhorns (or other portions of the HWC) of the HWC can be used to determine that a person has put the HWC onto their head with the intention to use the HWC. Those same parameters may be monitored in an effort to understand when the HWC is dismounted from the user&#39;s head. This may enable a situation where the capture of an eye image for identifying the wearer may be completed only when a change in the wearing status is identified. In a contrasting example, capturing eye images to monitor the health of the wearer may require images to be captured periodically (e.g. every few seconds, minutes, hours, days, etc.). For example, the eye images may be taken in minute intervals when the images are being used to monitor the health of the wearer when detected movements indicate that the wearer is exercising. In a further contrasting example, capturing eye images to monitor the health of the wearer for long-term effects may only require that eye images be captured monthly. Embodiments of the invention relate to selection of the timing and rate of capture of eye images to be in correspondence with the selected use scenario associated with the eye images. These selections may be done automatically, as with the exercise example above where movements indicate exercise, or these selections may be set manually. In a further embodiment, the selection of the timing and rate of eye image capture is adjusted automatically depending on the mode of operation of the HWC. The selection of the timing and rate of eye image capture can further be selected in correspondence with input characteristics associated with the wearer including age and health status, or sensed physical conditions of the wearer including heart rate, chemical makeup of the blood and eye blink rate. 
       FIG.  40    illustrates an embodiment in which digital content presented in a see-through FOV is positioned based on the speed in which the wearer is moving. When the person is not moving, as measured by sensor(s) in the HWC  102  (e.g. IMU, GPS-based tracking, etc.), digital content may be presented at the stationary person content position  4004 . The content position  4004  is indicated as being in the middle of the see-through FOV  4002 ; however, this is meant to illustrate that the digital content is positioned within the see-through FOV at a place that is generally desirable knowing that the wearer is not moving and as such the wearer&#39;s surrounding see-through view can be somewhat obstructed. So, the stationary person content position, or neutral position, may not be centered in the see-through FOV; it may be positioned somewhere in the see-through FOV deemed desirable and the sensor feedback may shift the digital content from the neutral position. The movement of the digital content for a quickly moving person is also shown in  FIG.  40    wherein as the person turns their head to the side, the digital content moves out of the see-through FOV to content position  4008  and then moves back as the person turns their head back. For a slowly moving person, the head movement can be more complex and as such the movement of the digital content in an out of the see-through FOV can follow a path such as that shown by content position  4010 . 
     In embodiments, the sensor that assesses the wearer&#39;s movements may be a GPS sensor, IMU, accelerometer, etc. The content position may be shifted from a neutral position to a position towards a side edge of the field of view as the forward motion increases. The content position may be shifted from a neutral position to a position towards a top or bottom edge of the field of view as the forward motion increases. The content position may shift based on a threshold speed of the assessed motion. The content position may shift linearly based on the speed of the forward motion. The content position may shift non-linearly based on the speed of the forward motion. The content position may shift outside of the field of view. In embodiments, the content is no longer displayed if the speed of movement exceeds a predetermined threshold and will be displayed again once the forward motion slows. 
     In embodiments, the content position may generally be referred to as shifting; it should be understood that the term shifting encompasses a process where the movement from one position to another within the see-through FOV or out of the FOV is visible to the wearer (e.g. the content appears to slowly or quickly move and the user perceives the movement itself) or the movement from one position to another may not be visible to the wearer (e.g. the content appears to jump in a discontinuous fashion or the content disappears and then reappears in the new position). 
     Another aspect of the present invention relates to removing the content from the field of view or shifting it to a position within the field of view that increases the wearer&#39;s view of the surrounding environment when a sensor causes an alert command to be issued. In embodiments, the alert may be due to a sensor or combination of sensors that sense a condition above a threshold value. For example, if an audio sensor detects a loud sound of a certain pitch, content in the field of view may be removed or shifted to provide a clear view of the surrounding environment for the wearer. In addition to the shifting of the content, in embodiments, an indication of why the content was shifted may be presented in the field of view or provided through audio feedback to the wearer. For instance, if a carbon monoxide sensor detects a high concentration in the area, content in the field of view may be shifted to the side of the field of view or removed from the field of view and an indication may be provided to the wearer that there is a high concentration of carbon monoxide in the area. This new information, when presented in the field of view, may similarly be shifted within or outside of the field of view depending on the movement speed of the wearer. 
       FIG.  41    illustrates how content may be shifted from a neutral position  4104  to an alert position  4108 . In this embodiment, the content is shifted outside of the see-through FOV  4102 . In other embodiments, the content may be shifted as described herein. 
     Another aspect of the present invention relates to identification of various vectors or headings related to the HWC  102 , along with sensor inputs, to determine how to position content in the field of view. In embodiments, the speed of movement of the wearer is detected and used as an input for position of the content and, depending on the speed, the content may be positioned with respect to a movement vector or heading (i.e. the direction of the movement), or a sight vector or heading (i.e. the direction of the wearer&#39;s sight direction). For example, if the wearer is moving very fast the content may be positioned within the field of view with respect to the movement vector because the wearer is only going to be looking towards the sides of himself periodically and for short periods of time. As another example, if the wearer is moving slowly, the content may be positioned with respect to the sight heading because the user may more freely be shifting his view from side to side. 
       FIG.  42    illustrates two examples where the movement vector may effect content positioning. Movement vector A  4202  is shorter than movement vector B  4210  indicating that the forward speed and/or acceleration of movement of the person associated with movement vector A  4202  is lower than the person associated with movement vector B  4210 . Each person is also indicated as having a sight vector or heading  4208  and  4212 . The sight vectors A  4208  and B  4210  are the same from a relative perspective. The white area inside of the black triangle in front of each person is indicative of how much time each person likely spends looking at a direction that is not in line with the movement vector. The time spent looking off angle A  4204  is indicated as being more than that of the time spent looking off angle B  4214 . This may be because the movement vector speed A is lower than movement vector speed B. The faster the person moves forward the more the person tends to look in the forward direction, typically. The FOVs A  4218  and B  4222  illustrate how content may be aligned depending on the movement vectors  4202  and  4210  and sight vectors  4208  and  4212 . FOV A  4218  is illustrated as presenting content in-line with the sight vector  4220 . This may be due to the lower speed of the movement vector A  4202 . This may also be due to the prediction of a larger amount of time spent looking off angle A  4204 . FOV B  4222  is illustrated as presenting content in line with the movement vector  4224 . This may be due to the higher speed of movement vector B  4210 . This may also be due to the prediction of a shorter amount of time spent looking off angle B  4214 . 
     Another aspect of the present invention relates to damping a rate of content position change within the field of view. As illustrated in  FIG.  43   , the sight vector may undergo a rapid change  4304 . This rapid change may be an isolated event or it may be made at or near a time when other sight vector changes are occurring. The wearer&#39;s head may be turning back and forth for some reason. In embodiments, the rapid successive changes in sight vector may cause a damped rate of content position change  4308  within the FOV  4302 . For example, the content may be positioned with respect to the sight vector, as described herein, and the rapid change in sight vector may normally cause a rapid content position change; however, since the sight vector is successively changing, the rate of position change with respect to the sight vector may be damped, slowed, or stopped. The position rate change may be altered based on the rate of change of the sight vector, average of the sight vector changes, or otherwise altered. 
     Another aspect of the present invention relates to simultaneously presenting more than one content in the field of view of a see-through optical system of a HWC  102  and positioning one content with the sight heading and one content with the movement heading.  FIG.  44    illustrates two FOV&#39;s A  4414  and B  4420 , which correspond respectively to the two identified sight vectors A  4402  and B  4404 .  FIG.  44    also illustrates an object in the environment  4408  at a position relative to the sight vectors A  4402  and B  4404 . When the person is looking along sight vector A  4402 , the environment object  4408  can be seen through the field of view A  4414  at position  4412 . As illustrated, sight heading aligned content is presented as TEXT in proximity with the environment object  4412 . At the same time, other content  4418  is presented in the field of view A  4414  at a position aligned in correspondence with the movement vector. As the movement speed increases, the content  4418  may shift as described herein. When the sight vector of the person is sight vector B  4404  the environmental object  4408  is not seen in the field of view B  4420 . As a result, the sight aligned content  4410  is not presented in field of view B  4420 ; however, the movement aligned content  4418  is presented and is still dependent on the speed of the motion. 
     In a further embodiment, in an operating mode such as when the user is moving in an environment, digital content is presented at the side of the user&#39;s see-through FOV so that the user can only view the digital content by turning their head. In this case, when the user is looking straight ahead, such as when the movement heading matches the sight heading, the see-through view FOV does not include digital content. The user then accesses the digital content by turning their head to the side whereupon the digital content moves laterally into the user&#39;s see-through FOV. In another embodiment, the digital content is ready for presentation and will be presented if an indication for its presentation is received. For example, the information may be ready for presentation and if the sight heading or predetermined position of the HWC  102  is achieved the content may then be presented. The wearer may look to the side and the content may be presented. In another embodiment, the user may cause the content to move into an area in the field of view by looking in a direction for a predetermined period of time, blinking, winking, or displaying some other pattern that can be captured through eye imaging technologies (e.g. as described herein elsewhere). 
     In yet another embodiment, an operating mode is provided wherein the user can define sight headings wherein the associated see-through FOV includes digital content or does not include digital content. In an example, this operating mode can be used in an office environment where when the user is looking at a wall digital content is provided within the FOV, whereas when the user is looking toward a hallway, the FOV is unencumbered by digital content. In another example, when the user is looking horizontally digital content is provided within the FOV, but when the user looks down (e.g. to look at a desktop or a cellphone) the digital content is removed from the FOV. 
     Another aspect of the present invention relates to collecting and using eye position and sight heading information. Head worn computing with motion heading, sight heading, and/or eye position prediction (sometimes referred to as “eye heading” herein) may be used to identify what a wearer of the HWC  102  is apparently interested in and the information may be captured and used. In embodiments, the information may be characterized as viewing information because the information apparently relates to what the wearer is looking at. The viewing information may be used to develop a personal profile for the wearer, which may indicate what the wearer tends to look at. The viewing information from several or many HWC&#39;s  102  may be captured such that group or crowd viewing trends may be established. For example, if the movement heading and sight heading are known, a prediction of what the wearer is looking at may be made and used to generate a personal profile or portion of a crowd profile. In another embodiment, if the eye heading and location, sight heading and/or movement heading are known, a prediction of what is being looked at may be predicted. The prediction may involve understanding what is in proximity of the wearer and this may be understood by establishing the position of the wearer (e.g. through GPS or other location technology) and establishing what mapped objects are known in the area. The prediction may involve interpreting images captured by the camera or other sensors associated with the HWC  102 . For example, if the camera captures an image of a sign and the camera is in-line with the sight heading, the prediction may involve assessing the likelihood that the wearer is viewing the sign. The prediction may involve capturing an image or other sensory information and then performing object recognition analysis to determine what is being viewed. For example, the wearer may be walking down a street and the camera that is in the HWC  102  may capture an image and a processor, either on-board or remote from the HWC  102 , may recognize a face, object, marker, image, etc. and it may be determined that the wearer may have been looking at it or towards it. 
       FIG.  45    shows an example set of data for a movement heading versus time. The movement heading starts at 0 degrees and ends with a movement heading of 114 degrees during which time the speed of movement varies from 0 m/sec to 20 m/sec. The sight heading can be seen to vary on either side of the movement heading. Large changes in sight heading occur when the movement speed is 0 m/sec, followed by step changes in movement heading. 
       FIG.  46    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
       FIG.  47    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
       FIG.  48    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
       FIG.  49    illustrates content position dependent on sensor feedback in accordance with the principles of the present invention. 
       FIG.  50    illustrates a cross section of an eyeball of a wearer of an HWC with focus points that can be associated with the eye imaging system of the invention. The eyeball  5010  includes an iris  5012  and a retina  5014 . Because the eye imaging system of the invention provides coaxial eye imaging with a display system, images of the eye can be captured from a perspective directly in front of the eye and inline with where the wearer is looking. In embodiments of the invention, the eye imaging system can be focused at the iris  5012  and/or the retina  5014  of the wearer, to capture images of the external surface of the iris  5012  or the internal portions of the eye, which includes the retina  5014 .  FIG.  50    shows light rays  5020  and  5025  that are respectively associated with capturing images of the iris  5012  or the retina  5014  wherein the optics associated with the eye imaging system are respectively focused at the iris  5012  or the retina  5014 . Illuminating light can also be provided in the eye imaging system to illuminate the iris  5012  or the retina  5014 .  FIG.  51    shows an illustration of an eye including an iris  5130  and a sclera  5125 . In embodiments, the eye imaging system can be used to capture images that include the iris  5130  and portions the sclera  5125 . The images can then be analyzed to determine color, shapes and patterns that are associated with the user. In further embodiments, the focus of the eye imaging system is adjusted to enable images to be captured of the iris  5012  or the retina  5014 . Illuminating light can also be adjusted to illuminate the iris  5012  or to pass through the pupil of the eye to illuminate the retina  5014 . The illuminating light can be visible light to enable capture of colors of the iris  5012  or the retina  5014 , or the illuminating light can be ultraviolet (e.g. 340 nm), near infrared (e.g. 850 nm) or mid-wave infrared (e.g. 5000 nm) light to enable capture of hyperspectral characteristics of the eye. 
       FIG.  53    illustrates a display system that includes an eye imaging system. The display system includes a polarized light source  2958 , a DLP  2955 , a quarter wave film  2957  and a beam splitter plate  5345 . The eye imaging system includes a camera  3280 , illuminating lights  5355  and beam splitter plate  5345 . Where the beam splitter plate  5345  can be a reflective polarizer on the side facing the polarized light source  2958  and a hot mirror on the side facing the camera  3280 . Wherein the hot mirror reflects infrared light (e.g. wavelengths 700 to 2000 nm) and transmits visible light (e.g. wavelengths 400 to 670 nm). The beam splitter plate  5345  can be comprised of multiple laminated films, a substrate film with coatings or a rigid transparent substrate with films on either side. By providing a reflective polarizer on the one side, the light from the polarized light source  2958  is reflected toward the DLP  2955  where it passes through the quarter wave film  2957  once, is reflected by the DLP mirrors in correspondence with the image content being displayed by the DLP  2955  and then passes back through the quarter wave film  2957 . In so doing, the polarization state of the light from the polarized light source is changed, so that it is transmitted by the reflective polarizer on the beam splitter plate  5345  and the image light  2971  passes into the lower optics module  204  where the image is displayed to the user. At the same time, infrared light  5357  from the illuminating lights  5355  is reflected by the hot mirror so that it passes into the lower optics module  204  where it illuminates the user&#39;s eye. Portions of the infrared light  2969  are reflected by the user&#39;s eye and this light passes back through the lower optics module  204 , is reflected by the hot mirror on the beam splitter plate  5345  and is captured by the camera  3280 . In this embodiment, the image light  2971  is polarized while the infrared light  5357  and  2969  can be unpolarized. In an embodiment, the illuminating lights  5355  provide two different infrared wavelengths and eye images are captured in pairs, wherein the pairs of eye images are analyzed together to improve the accuracy of identification of the user based on iris analysis. 
       FIG.  54    shows an illustration of a further embodiment of a display system with an eye imaging system. In addition to the features of  FIG.  53   , this system includes a second camera  5460 . Wherein the second camera  5460  is provided to capture eye images in the visible wavelengths. Illumination of the eye can be provided by the displayed image or by see-through light from the environment. Portions of the displayed image can be modified to provide improved illumination of the user&#39;s eye when images of the eye are to be captured such as by increasing the brightness of the displayed image or increasing the white areas within the displayed image. Further, modified displayed images can be presented briefly for the purpose of capturing eye images and the display of the modified images can be synchronized with the capture of the eye images. As shown in  FIG.  54   , visible light  5467  is polarized when it is captured by the second camera  5460  since it passes through the beam splitter  5445  and the beam splitter  5445  is a reflective polarizer on the side facing the second camera  5460 . In this eye imaging system, visible eye images can be captured by the second camera  5460  at the same time that infrared eye images are captured by the camera  3280 . Wherein, the characteristics of the camera  3280  and the second camera  5460  and the associated respective images captured can be different in terms of resolution and capture rate. 
       FIGS.  52   a  and  52   b    illustrate captured images of eyes where the eyes are illuminated with structured light patterns. In  FIG.  52   a   , an eye  5220  is shown with a projected structured light pattern  5230 , where the light pattern is a grid of lines. A light pattern of such as  5230  can be provided by the light source  5355  show in  FIG.  53    by including a diffractive or a refractive device to modify the light  5357  as are known by those skilled in the art. A visible light source can also be included for the second camera  5460  shown in  FIG.  54    which can include a diffractive or refractive to modify the light  5467  to provide a light pattern.  FIG.  52   b    illustrates how the structured light pattern of  5230  becomes distorted to  5235  when the user&#39;s eye  5225  looks to the side. This distortion comes from the fact that the human eye is not spherical in shape, instead the iris sticks out slightly from the eyeball to form a bump in the area of the iris. As a result, the shape of the eye and the associated shape of the reflected structured light pattern is different depending on which direction the eye is pointed, when images of the eye are captured from a fixed position. Changes in the structured light pattern can subsequently be analyzed in captured eye images to determine the direction that the eye is looking. 
     The eye imaging system can also be used for the assessment of aspects of health of the user. In this case, information gained from analyzing captured images of the iris  5012  is different from information gained from analyzing captured images of the retina  5014 . Where images of the retina  5014  are captured using light  5357  that illuminates the inner portions of the eye including the retina  5014 . The light  5357  can be visible light, but in an embodiment, the light  5357  is infrared light (e.g. wavelength 1 to 5 microns) and the camera  3280  is an infrared light sensor (e.g. an InGaAs sensor) or a low resolution infrared image sensor that is used to determine the relative amount of light  5357  that is absorbed, reflected or scattered by the inner portions of the eye. Wherein the majority of the light that is absorbed, reflected or scattered can be attributed to materials in the inner portion of the eye including the retina where there are densely packed blood vessels with thin walls so that the absorption, reflection and scattering are caused by the material makeup of the blood. These measurements can be conducted automatically when the user is wearing the HWC, either at regular intervals, after identified events or when prompted by an external communication. In a preferred embodiment, the illuminating light is near infrared or mid infrared (e.g. 0.7 to 5 microns wavelength) to reduce the chance for thermal damage to the wearer&#39;s eye. In another embodiment, the polarizer  3285  is antireflection coated to reduce any reflections from this surface from the light  5357 , the light  2969  or the light  3275  and thereby increase the sensitivity of the camera  3280 . In a further embodiment, the light source  5355  and the camera  3280  together comprise a spectrometer wherein the relative intensity of the light reflected by the eye is analyzed over a series of narrow wavelengths within the range of wavelengths provided by the light source  5355  to determine a characteristic spectrum of the light that is absorbed, reflected or scattered by the eye. For example, the light source  5355  can provide a broad range of infrared light to illuminate the eye and the camera  3280  can include: a grating to laterally disperse the reflected light from the eye into a series of narrow wavelength bands that are captured by a linear photodetector so that the relative intensity by wavelength can be measured and a characteristic absorbance spectrum for the eye can be determined over the broad range of infrared. In a further example, the light source  5355  can provide a series of narrow wavelengths of light (ultraviolet, visible or infrared) to sequentially illuminate the eye and camera  3280  includes a photodetector that is selected to measure the relative intensity of the series of narrow wavelengths in a series of sequential measurements that together can be used to determine a characteristic spectrum of the eye. The determined characteristic spectrum is then compared to known characteristic spectra for different materials to determine the material makeup of the eye. In yet another embodiment, the illuminating light  5357  is focused on the retina  5014  and a characteristic spectrum of the retina  5014  is determined and the spectrum is compared to known spectra for materials that may be present in the user&#39;s blood. For example, in the visible wavelengths 540 nm is useful for detecting hemoglobin and 660 nm is useful for differentiating oxygenated hemoglobin. In a further example, in the infrared, a wide variety of materials can be identified as is known by those skilled in the art, including: glucose, urea, alcohol and controlled substances.  FIG.  55    shows a series of example spectrum for a variety of controlled substances as measured using a form of infrared spectroscopy (ThermoScientific Application Note  51242 , by C. Petty, B. Garland and the Mesa Police Department Forensic Laboratory, which is hereby incorporated by reference herein).  FIG.  56    shows an infrared absorbance spectrum for glucose (Hewlett Packard Company 1999, G. Hopkins, G. Mauze; “In-vivo NIR Diffuse-reflectance Tissue Spectroscopy of Human Subjects,” which is hereby incorporated by reference herein). U.S. Pat. No. 6,675,030, which is hereby incorporated by reference herein, provides a near infrared blood glucose monitoring system that includes infrared scans of a body part such as a foot. United States Patent publication 2006/0183986, which is hereby incorporated by reference herein, provides a blood glucose monitoring system including a light measurement of the retina. Embodiments of the present invention provide methods for automatic measurements of specific materials in the user&#39;s blood by illuminating at one or more narrow wavelengths into the iris of the wearer&#39;s eye and measuring the relative intensity of the light reflected by the eye to identify the relative absorbance spectrum and comparing the measured absorbance spectrum with known absorbance spectra for the specific material, such as illuminating at 540 and 660 nm to determine the level of hemoglobin present in the user&#39;s blood. 
     Another aspect of the present invention relates to collecting and using eye position and sight heading information. Head worn computing with motion heading, sight heading, and/or eye position prediction (sometimes referred to as “eye heading” herein) may be used to identify what a wearer of the HWC  102  is apparently interested in and the information may be captured and used. In embodiments, the information may be characterized as viewing information because the information apparently relates to what the wearer is looking at. The viewing information may be used to develop a personal profile for the wearer, which may indicate what the wearer tends to look at. The viewing information from several or many HWC&#39;s  102  may be captured such that group or crowd viewing trends may be established. For example, if the movement heading and sight heading are known, a prediction of what the wearer is looking at may be made and used to generate a personal profile or portion of a crowd profile. In another embodiment, if the eye heading and location, sight heading and/or movement heading are known, a prediction of what is being looked at may be predicted. The prediction may involve understanding what is in proximity of the wearer and this may be understood by establishing the position of the wearer (e.g. through GPS or other location technology) and establishing what mapped objects are known in the area. The prediction may involve interpreting images captured by the camera or other sensors associated with the HWC  102 . For example, if the camera captures an image of a sign and the camera is in-line with the sight heading, the prediction may involve assessing the likelihood that the wearer is viewing the sign. The prediction may involve capturing an image or other sensory information and then performing object recognition analysis to determine what is being viewed. For example, the wearer may be walking down a street and the camera that is in the HWC  102  may capture an image and a processor, either on-board or remote from the HWC  102 , may recognize a face, object, marker, image, etc. and it may be determined that the wearer may have been looking at it or towards it. 
       FIG.  57    illustrates a scene where a person is walking with a HWC  102  mounted on his head. In this scene, the person&#39;s geo-spatial location  5704  is known through a GPS sensor, which could be another location system, and his movement heading, sight heading  5714  and eye heading  5702  are known and can be recorded (e.g. through systems described herein). There are objects and a person in the scene. Person  5712  may be recognized by the wearer&#39;s HWC  102  system, the person may be mapped (e.g. the person&#39;s GPS location may be known or recognized), or otherwise known. The person may be wearing a garment or device that is recognizable. For example, the garment may be of a certain style and the HWC may recognize the style and record its viewing. The scene also includes a mapped object  5718  and a recognized object  5720 . As the wearer moves through the scene, the sight and/or eye headings may be recorded and communicated from the HWC  102 . In embodiments, the time that the sight and/or eye heading maintains a particular position may be recorded. For example, if a person appears to look at an object or person for a predetermined period of time (e.g. 2 seconds or longer), the information may be communicated as gaze persistence information as an indication that the person may have been interested in the object. 
     In embodiments, sight headings may be used in conjunction with eye headings or eye and/or sight headings may be used alone. Sight headings can do a good job of predicting what direction a wearer is looking because many times the eyes are looking forward, in the same general direction as the sight heading. In other situations, eye headings may be a more desirable metric because the eye and sight headings are not always aligned. In embodiments herein examples may be provided with the term “eye/sight” heading, which indicates that either or both eye heading and sight heading may be used in the example. 
       FIG.  58    illustrates a system for receiving, developing and using movement heading, sight heading, eye heading and/or persistence information from HWC(s)  102 . The server  5804  may receive heading or gaze persistence information, which is noted as persistence information  5802 , for processing and/or use. The heading and/or gaze persistence information may be used to generate a personal profile  5808  and/or a group profile  5810 . The personal profile  5718  may reflect the wearer&#39;s general viewing tendencies and interests. The group profile  5810  may be an assemblage of different wearer&#39;s heading and persistence information to create impressions of general group viewing tendencies and interests. The group profile  5810  may be broken into different groups based on other information such as gender, likes, dislikes, biographical information, etc. such that certain groups can be distinguished from other groups. This may be useful in advertising because an advertiser may be interested in what a male adult sports go&#39;er is generally looking at as opposed to a younger female. The profiles  5808  and  5810  and raw heading and persistence information may be used by retailers  5814 , advertisers  5818 , trainers, etc. For example, an advertiser may have an advertisement posted in an environment and may be interested in knowing how many people look at the advertisement, how long they look at it and where they go after looking at it. This information may be used as conversion information to assess the value of the advertisement and thus the payment to be received for the advertisement. 
     In embodiments, the process involves collecting eye and/or sight heading information from a plurality of head-worn computers that come into proximity with an object in an environment. For example, a number of people may be walking through an area and each of the people may be wearing a head worn computer with the ability to track the position of the wearer&#39;s eye(s) as well as possibly the wearer&#39;s sight and movement headings. The various HWC wearing individuals may then walk, ride, or otherwise come into proximity with some object in the environment (e.g. a store, sign, person, vehicle, box, bag, etc.). When each person passes by or otherwise comes near the object, the eye imaging system may determine if the person is looking towards the object. All of the eye/sight heading information may be collected and used to form impressions of how the crowd reacted to the object. A store may be running a sale and so the store may put out a sign indicating such. The storeowners and managers may be very interested to know if anyone is looking at their sign. The sign may be set as the object of interest in the area and as people navigate near the sign, possibly determined by their GPS locations, the eye/sight heading determination system may record information relative to the environment and the sign. Once, or as, the eye/sight heading information is collected and associations between the eye headings and the sign are determined, feedback may be sent back to the storeowner, managers, advertiser, etc. as an indication of how well their sign is attracting people. In embodiments, the sign&#39;s effectiveness at attracting people&#39;s attention, as indicated through the eye/sight headings, may be considered a conversion metric and impact the economic value of the sign and/or the signs placement. 
     In embodiments, a map of the environment with the object may be generated by mapping the locations and movement paths of the people in the crowd as they navigate by the object (e.g. the sign). Layered on this map may be an indication of the various eye/sight headings. This may be useful in indicating where people were in relation to the object when they viewed the object. The map may also have an indication of how long people looked at the object from the various positions in the environment and where they went after seeing the object. 
     In embodiments, the process involves collecting a plurality of eye/sight headings from a head-worn computer, wherein each of the plurality of eye/sight headings is associated with a different pre-determined object in an environment. This technology may be used to determine which of the different objects attracts more of the person&#39;s attention. For example, if there are three objects placed in an environment and a person enters the environment navigating his way through it, he may look at one or more of the objects and his eye/sight heading may persist on one or more objects longer than others. This may be used in making or refining the person&#39;s personal attention profile and/or it may be used in connection with other such people&#39;s data on the same or similar objects to determine an impression of how the population or crowd reacts to the objects. Testing advertisements in this way may provide good feedback of its effectiveness. 
     In embodiments, the process may involve capturing eye/sight headings once there is substantial alignment between the eye/sight heading and an object of interest. For example, the person with the HWC may be navigating through an environment and once the HWC detects substantial alignment or the projected occurrence of an upcoming substantial alignment between the eye/sight heading and the object of interest, the occurrence and/or persistence may be recorded for use. 
     In embodiments, the process may involve collecting eye/sight heading information from a head-worn computer and collecting a captured image from the head-worn computer that was taken at substantially the same time as the eye/sight heading information was captured. These two pieces of information may be used in conjunction to gain an understanding of what the wearer was looking at and possibly interested in. The process may further involve associating the eye/sight heading information with an object, person, or other thing found in the captured image. This may involve processing the captured image looking for objects or patterns. In embodiments, gaze time or persistence may be measured and used in conjunction with the image processing. The process may still involve object and/or pattern recognition, but it may also involve attempting to identify what the person gazed at for the period of time by more particularly identifying a portion of the image in conjunction with image processing. 
     In embodiments, the process may involve setting a pre-determined eye/sight heading from a pre-determined geospatial location and using them as triggers. In the event that a head worn computer enters the geospatial location and an eye/sight heading associated with the head worn computer aligns with the pre-determined eye/sight heading, the system may collect the fact that there was an apparent alignment and/or the system may record information identifying how long the eye/sight heading remains substantially aligned with the pre-determined eye/sight heading to form a persistence statistic. This may eliminate or reduce the need for image processing as the triggers can be used without having to image the area. In other embodiments, image capture and processing is performed in conjunction with the triggers. In embodiments, the triggers may be a series a geospatial locations with corresponding eye/sight headings such that many spots can be used as triggers that indicate when a person entered an area in proximity to an object of interest and/or when that person actually appeared to look at the object. 
     In embodiments, eye imaging may be used to capture images of both eyes of the wearer in order to determine the amount of convergence of the eyes (e.g. through technologies described herein elsewhere) to get an understanding of what focal plane is being concentrated on by the wearer. For example, if the convergence measurement suggests that the focal plane is within 15 feet of the wearer, than, even though the eye/sight headings may align with an object that is more than 15 feet away it may be determined that the wearer was not looking at the object. If the object were within the 15 foot suggested focal plane, the determination may be that the wearer was looking at the object.  FIG.  59    illustrates an environmentally position locked digital content  5912  that is indicative of a person&#39;s location  5902 . In this disclosure the term “BlueForce” is generally used to indicate team members or members for which geo-spatial locations are known and can be used. In embodiments, “BlueForce” is a term to indicate members of a tactical arms team (e.g. a police force, secret service force, security force, military force, national security force, intelligence force, etc.). In many embodiments herein one member may be referred to as the primary or first BlueForce member and it is this member, in many described embodiments, that is wearing the HWC. It should be understood that this terminology is to help the reader and make for clear presentations of the various situations and that other members of the BlueForce, or other people, may have HWC&#39;s  102  and have similar capabilities. In this embodiment, a first person is wearing a head-worn computer  102  that has a see through field of view (“FOV”)  5914 . The first person can see through the FOV to view the surrounding environment through the FOV and digital content can also be presented in the FOV such that the first person can view the actual surroundings, through the FOV, in a digitally augmented view. The other BlueForce person&#39;s location is known and is indicated at a position inside of a building at point  5902 . This location is known in three dimensions, longitude, latitude and altitude, which may have been determined by GPS along with an altimeter associated with the other BlueForce person. Similarly, the location of the first person wearing the HWC  102  is also known, as indicated in  FIG.  59    as point  5908 . In this embodiment, the compass heading  5910  of the first person is also known. With the compass heading  5910  known, the angle in which the first person is viewing the surroundings can be estimated. A virtual target line between the location of the first person  5908  and the other person&#39;s location  5902  can be established in three dimensional space and emanating from the HWC  102  proximate the FOV  5914 . The three dimensionally oriented virtual target line can then be used to present environmentally position locked digital content in the FOV  5914 , which is indicative of the other person&#39;s location  5902 . The environmentally position locked digital content  5902  can be positioned within the FOV  5914  such that the first person, who is wearing the HWC  102 , perceives the content  5902  as locked in position within the environment and marking the location of the other person  5902 . 
     The three dimensionally positioned virtual target line can be recalculated periodically (e.g. every millisecond, second, minute, etc.) to reposition the environmentally position locked content  5912  to remain in-line with the virtual target line. This can create the illusion that the content  5912  is staying positioned within the environment at a point that is associated with the other person&#39;s location  5902  independent of the location of the first person  5908  wearing the HWC  102  and independent of the compass heading of the HWC  102 . 
     In embodiments, the environmentally locked digital content  5912  may be positioned with an object  5904  that is between the first person&#39;s location  5908  and the other person&#39;s location  5902 . The virtual target line may intersect the object  5904  before intersecting with the other person&#39;s location  5902 . In embodiments, the environmentally locked digital content  5912  may be associated with the object intersection point  5904 . In embodiments, the intersecting object  5904  may be identified by comparing the two person&#39;s locations  5902  and  5908  with obstructions identified on a map. In embodiments the intersecting object  5904  may be identified by processing images captured from a camera, or other sensor, associated with the HWC  102 . In embodiments, the digital content  5912  has an appearance that is indicative of being at the location of the other person  5902 , at the location of the intersecting object  5904  to provide a more clear indication of the position of the other person&#39;s position  5902  in the FOV  5914 . 
       FIG.  60    illustrates how and where digital content may be positioned within the FOV  6008  based on a virtual target line between the location of the first person  5908 , who&#39;s wearing the HWC  102 , and the other person  5902 . In addition to positioning the content in a position within the FOV  6008  that is in-line with the virtual target line, the digital content may be presented such that it comes into focus by the first person when the first person focuses at a certain plane or distance in the environment. Presented object A  6018  is digitally generated content that is presented as an image at content position A  6012 . The position  6012  is based on the virtual target line. The presented object A  6018  is presented not only along the virtual target line but also at a focal plane B  6014  such that the content at position A  6012  in the FOV  6008  comes into focus by the first person when the first person&#39;s eye  6002  focuses at something in the surrounding environment at the focal plane B  6014  distance. Setting the focal plane of the presented content provides content that does not come into focus until the eye  6002  focuses at the set focal plane. In embodiments, this allows the content at position A to be presented without when the HWC&#39;s compass is indicative of the first person looking in the direction of the other person  5902  but it will only come into focus when the first person focuses on in the direction of the other person  5902  and at the focal plane of the other person  5902 . 
     Presented object B  6020  is aligned with a different virtual target line then presented object A  6018 . Presented object B  6020  is also presented at content position B  6004  at a different focal plane than the content position A  6012 . Presented content B  6020  is presented at a further focal plane, which is indicative that the other person  5902  is physically located at a further distance. If the focal planes are sufficiently different, the content at position A will come into focus at a different time than the content at position B because the two focal planes require different focus from the eye  6002 . 
       FIG.  61    illustrates several BlueForce members at locations with various points of view from the first person&#39;s perspective. In embodiments, the relative positions, distances and obstacles may cause the digital content indicative of the other person&#39;s location to be altered. For example, if the other person can be seen by the first person through the first person&#39;s FOV, the digital content may be locked at the location of the other person and the digital content may be of a type that indicates the other person&#39;s position is being actively marked and tracked. If the other person is in relatively close proximity, but cannot be seen by the first person, the digital content may be locked to an intersecting object or area and the digital content may indicate that the actual location of the other person cannot be seen but the mark is generally tracking the other persons general position. If the other person is not within a pre-determined proximity or is otherwise more significantly obscured from the first person&#39;s view, the digital content may generally indicate a direction or area where the other person is located and the digital content may indicate that the other person&#39;s location is not closely identified or tracked by the digital content, but that the other person is in the general area. 
     Continuing to refer to  FIG.  61   , several BlueForce members are presented at various positions within an area where the first person is located. The primary BlueForce member  6102  (also referred to generally as the first person, or the person wherein the HWC with the FOV for example purposes) can directly see the BlueForce member in the open field  6104 . In embodiments, the digital content provided in the FOV of the primary BlueForce member may be based on a virtual target line and virtually locked in an environment position that is indicative of the open field position of the BlueForce member  6104 . The digital content may also indicate that the location of the open field BlueForce member is marked and is being tracked. The digital content may change forms if the BlueForce member becomes obscured from the vision of the primary BlueForce member or otherwise becomes unavailable for direct viewing. 
     BlueForce member  6108  is obscured from the primary BlueForce member&#39;s  6102  view by an obstacle that is in close proximity to the obscured member  6108 . As depicted, the obscured member  6108  is in a building but close to one of the front walls. In this situation, the digital content provided in the FOV of the primary member  6102  may be indicative of the general position of the obscured member  6108  and the digital content may indicate that, while the other person&#39;s location is fairly well marked, it is obscured so it is not as precise as if the person was in direct view. In addition, the digital content may be virtually positionally locked to some feature on the outside of the building that the obscured member is in. This may make the environmental locking more stable and also provide an indication that the location of the person is somewhat unknown. 
     BlueForce member  6110  is obscured by multiple obstacles. The member  6110  is in a building and there is another building  6112  in between the primary member  6102  and the obscured member  6110 . In this situation, the digital content in the FOV of the primary member will be spatially quite short of the actual obscured member and as such the digital content may need to be presented in a way that indicates that the obscured member  6110  is in a general direction but that the digital marker is not a reliable source of information for the particular location of obscured member  6110 . 
       FIG.  62    illustrates yet another method for positioning digital content within the FOV of a HWC where the digital content is intended to indicate a position of another person. This embodiment is similar to the embodiment described in connection with  FIG.  62    herein. The main additional element in this embodiment is the additional step of verifying the distance between the first person  5908 , the one wearing the HWC with the FOV digital content presentation of location, and the other person at location  5902 . Here, the range finder may be included in the HWC and measure a distance at an angle that is represented by the virtual target line. In the event that the range finder finds an object obstructing the path of the virtual target line, the digital content presentation in the FOV may indicate such (e.g. as described herein elsewhere). In the event that the range finder confirms that there is a person or object at the end of the prescribed distance and angle defined by the virtual target line, the digital content may represent that the proper location has been marked, as described herein elsewhere. 
     Another aspect of the present invention relates to predicting the movement of BlueForce members to maintain proper virtual marking of the BlueForce member locations.  FIG.  63    illustrates a situation where the primary BlueForce member  6302  is tracking the locations of the other BlueForce members through an augmented environment using a HWC  102 , as described herein elsewhere (e.g. as described in connection with the above figures). The primary BlueForce member  6302  may have knowledge of the tactical movement plan  6308 . The tactical movement plan may be maintained locally (e.g. on the HWCs  102  with sharing of the plan between the BlueForce members) or remotely (e.g. on a server and communicated to the HWC&#39;s  102 , or communicated to a subset of HWC&#39;s  102  for HWC  102  sharing). In this case, the tactical plan involves the BlueForce group generally moving in the direction of the arrow  6308 . The tactical plan may influence the presentations of digital content in the FOV of the HWC  102  of the primary BlueForce member. For example, the tactical plan may assist in the prediction of the location of the other BlueForce member and the virtual target line may be adjusted accordingly. In embodiments, the area in the tactical movement plan may be shaded or colored or otherwise marked with digital content in the FOV such that the primary BlueForce member can manage his activities with respect to the tactical plan. For example, he may be made aware that one or more BlueForce members are moving towards the tactical path  6308 . He may also be made aware of movements in the tactical path that do not appear associated with BlueForce members. 
       FIG.  63    also illustrates that internal IMU sensors in the HWCs worn by the BlueForce members may provide guidance on the movement of the members  6304 . This may be helpful in identifying when a GPS location should be updated and hence updating the position of the virtual marker in the FOV. This may also be helpful in assessing the validity of the GPS location. For example, if the GPS location has not updated but there is significant IMU sensor activity, the system may call into question the accuracy of the identified location. The IMU information may also be useful to help track the position of a member in the event the GPS information is unavailable. For example, dead reckoning may be used if the GPS signal is lost and the virtual marker in the FOV may indicate both indicated movements of the team member and indicate that the location identification is not ideal. The current tactical plan  6308  may be updated periodically and the updated plans may further refine what is presented in the FOV of the HWC  102 . 
       FIG.  64    illustrates a BlueForce tracking system in accordance with the principles of the present invention. In embodiments, the BlueForce HWC&#39;s  102  may have directional antenna&#39;s that emit relatively low power directional RF signals such that other BlueForce members within the range of the relatively low power signal can receive and assess its direction and/or distance based on the strength and varying strength of the signals. In embodiments, the tracking of such RF signals can be used to alter the presentation of the virtual markers of persons locations within the FOV of HWC  102 . 
     Another aspect of the present invention relates to monitoring the health of BlueForce members. Each BlueForce member may be automatically monitored for health and stress events. For example, the members may have a watchband as described herein elsewhere or other wearable biometric monitoring device and the device may continually monitor the biometric information and predict health concerns or stress events. As another example, the eye imaging systems described herein elsewhere may be used to monitor pupil dilatations as compared to normal conditions to predict head trauma. Each eye may be imaged to check for differences in pupil dilation for indications of head trauma. As another example, an IMU in the HWC  102  may monitor a person&#39;s walking gate looking for changes in pattern, which may be an indication of head or other trauma. Biometric feedback from a member indicative of a health or stress concern may be uploaded to a server for sharing with other members or the information may be shared with local members, for example. Once shared, the digital content in the FOV that indicates the location of the person having the health or stress event may include an indication of the health event. 
       FIG.  65    illustrates a situation where the primary BlueForce member  6502  is monitoring the location of the BlueForce member  6504  that has had a heath event and caused a health alert to be transmitted from the HWC  102 . As described herein elsewhere, the FOV of the HWC  102  of the primary BlueForce member may include an indication of the location of the BlueForce member with the health concern  6504 . The digital content in the FOV may also include an indication of the health condition in association with the location indication. In embodiments, non-biometric sensors (e.g. IMU, camera, ranger finder, accelerometer, altimeter, etc.) may be used to provide health and/or situational conditions to the BlueForce team or other local or remote persons interested in the information. For example, if one of the BlueForce members is detected as quickly hitting the ground from a standing position an alter may be sent as an indication of a fall, the person is in trouble and had to drop down, was shot, etc. 
     Another aspect of the present invention relates to virtually marking various prior acts and events. For example, as depicted in  FIG.  66   , the techniques described herein elsewhere may be used to construct a virtual prior movement path  6604  of a BlueForce member. The virtual path may be displayed as digital content in the FOV of the primary BlueForce member  6602  using methods described herein elsewhere. As the BlueForce member moved along the path  6604  he may have virtually placed an event marker  6608  such that when another member views the location the mark can be displayed as digital content. For example, the BlueForce member may inspect and clear an area and then use an external user interface or gesture to indicate that the area has been cleared and then the location would be virtually marked and shared with BlueForce members. Then, when someone wants to understand if the location was inspected he can view the location&#39;s information. As indicated herein elsewhere, if the location is visible to the member, the digital content may be displayed in a way that indicates the specific location and if the location is not visible from the person&#39;s perspective, the digital content may be somewhat different in that it may not specifically mark the location. 
     Another aspect of the present invention relates to the physical location at which digital content is going to be presented to a person wearing a HWC  102 . In embodiments, content is presented in a FOV of a HWC  102  when the HWC  102  is at a physical location that was selected based on personal information particular to the wearer of the HWC  102 . In embodiments, the physical location is identified by a geo-spatial location and an attribute in the surroundings proximate the geo-spatial location. The attribute may be something that more precisely places the content within the environment located at the geo-spatial location. The attribute may be selected such that content appears in a hallway, office, near a billboard, rooftop, outside wall, object, etc. Personal information relating to the person may be stored such that it can be retrieved during a process of determining at what physical location in the world certain digital content should be presented to the person. In embodiments, the content may relate to the physical location. In other embodiments, the content does not necessarily relate to the physical location. In instances where the physical location is selected based on personal information and the content does not relate to the location, the location may have been selected because the location is of the type that the person may spend more time viewing or interacting with content of the type to be presented. 
     In embodiments, a method of presenting digital content in a FOV of a HWC  102  may include identifying that the HWC  102  has arrived at a physical location, wherein the physical location is pre-determined based on personal information relating to the person wearing the HWC, and presenting the digital content in relation to an attribute in the surroundings where the attribute was pre-selected based on the personal information. The personal information may relate to personal attributes, demographics, behaviors, prior visited locations, stored personal locations, preferred locations, travel habits, etc. For example, the person wearing the HWC  102  may frequent a venue often (e.g. a place of work), and the system may present content to the person when he arrives at the venue. The type of content may also be particular to the venue, or other location selection criteria, such that the person is more apt to view and/or interact with the content. The content, for example, may relate to services or products relating to the person&#39;s work and as such the system may present the content at or near the person&#39;s place of work under the assumption that the person is going to be more interested in content relating to his work when he is at or near his place of work. In another example, content may be presented to the person when the person is passing by a sports complex because the person is generally characterized as being interested in sports. This presentation may be based on the assumption that the person may be more interested in content presented in connection with a venue that he finds interesting. 
     In embodiments, the placement of the digital content may be based on the selection of an environment&#39;s attribute, which was selected based on personal information relating to the person wearing the HWC  102 . The personal information may suggest that the person would be more apt to interact with content if it is presented indoors, outdoors, in a room, in a hallway, on a blank wall, over a TV, near a table, near a chair, near a vehicle, while sitting, while standing, while walking, etc. For example, a 50-year-old man may be more apt to interact with content that is presented in an area where he will likely be sitting, while a 17-year-old man may be more apt to interact with content while he is moving. This may cause the system to choose an internal wall of a building for the presentation to the 50-year-old and an external wall of the building for the presentation to the 17-year-old. The 50-year-old may be more apt to interact with content presented near an entrance to his place of work and the 17-year-old may be more apt to interact with content when presented proximate a vehicle. Each of these attributes near the geo-spatial location are eligible candidates for the presentation of the content and the selection of the one(s) to be used may be based on the personal information known about the person wearing the HWC  102 . 
       FIG.  67    illustrates a content presentation technology in accordance with the principles of the present invention.  FIG.  67    illustrates a person entering a location proximate to his place of work  6702 . This location has been pre-selected  6704  as a physical location for the presentation of digital content in the HWC  102  based on stored personal information  6708 . The physical location may be further refined by identifying a wall, object or other more specific location for the presentation of the content. For example, a work wall  6714  proximate to the geo-spatial location of work  6702  may be identified for placement of the content presentation  6712  to be viewed within the FOV of the HWC  6710 . The wall may then be used as a virtual marker or a virtual marker or physical marker may be identified on the wall such that the HWC  102  identifies the marker and then presents the content proximate the marker. A virtual marker may be based on physical markers, objects, lines, figures, etc. For example, the intersection of a top edge and side edge of a doorway at the place of work may be used as a virtual marker and the digital content in the FOV of the HWC  102  may be presented proximate the intersection. A virtual marker may also be established at some point distant from an object (e.g. a foot from the intersection). A virtual marker may also be set based on the person&#39;s physical location and the sight heading of the HWC  102  (e.g. as determined by an eCompass on the HWC). For example, once the person arrives at the physical location that was pre-selected based on the person&#39;s personal information, the content may be displayed in the FOV of the HWC  102  when the HWC  102  is aligned with a predetermined direction. So, for example, if the person is standing in a hallway and then looks north the content may be displayed. In embodiments, the HWC  102  identifies a physically present attribute in the surroundings and then associates the content with the attribute such that the content appears locked to the attribute from the person&#39;s perspective. For example, the person, once at the physical location, looks north and then the HWC  102  performs an analysis of the surroundings in the north direction (e.g. by imaging the surroundings with an onboard camera) to select a physical attribute to be used as a virtual marker. In embodiments, the physical marker may be pre-determined. For example, the doorway in a particular hallway may be presented as the object to key off of when setting the virtual world-locked position of the digital content. In embodiments, the physical attribute is selected based on a pre-determined criteria. For example, the system may have a list of priority placements such as being proximate a painting, picture, television, doorway, blank wall, etc., and the head-worn computer may review the physical location and select one of the priority placements for the virtual placement of the digital content. 
     As illustrated in  FIG.  67   , the physical location of the content presentation may be dependent upon personal information particular to the person wearing the HWC  102 . For example, personal information, such as gender, height, weight, age, date of birth, heritage, credit history, etc. may be used as a selection criteria for the physical location. If the person is male, aged 50, the physical location may be selected from a set of locations that generally suits a man of that age. It could be that a male of that age does not generally interact with content when it is presented proximate his home, so the home location may be eliminated from the selection. It could also be that a male of that age tends to interact with content when he is taking public transportation so locations relating to public transportation may be given a higher priority in the physical location selection process. Similarly, a male that is 17 years of age may typically interact with content when he is home so the home location may be rated high when making the selection of physical location. 
     As illustrated in  FIG.  67   , the physical location of the content presentation may be dependent upon demographic information particular to the person wearing the HWC  102 . For example, demographic information, such as statistically inferred information relating to a population, may be used in the selection of the physical location. If it is determined that the person is in a population of people that moves often, votes a particular way, is within a certain age range, etc. physical locations for the presentations of the content may be dependent thereon. 
     As illustrated in  FIG.  67   , the physical location of the content presentation may be dependent upon behavior information particular to the person wearing the HWC  102 . For example, if the person tends to spend money at particular establishments, eat at particular venues, drive a certain type of car, play certain sports, work particular hours, etc., the tendencies or behaviors may influence the physical location for the content presentation. 
     In embodiments, a person&#39;s movements may be traced to identify the areas of general or particular interest to the person. The traced movements may indicate a place of work or workday place of interest, evening or home locations, driving habits, transportation habits, store locations and identities, etc. and the traced movements may influence the physical location for the content presentation. The movements may be traced by tracing GPS movements, IMU movements, or other sensor feedback from the HWC  102  or other device, for example. 
     In embodiments, external user interfaces and gestures as described herein elsewhere may be used to interact with the content and/or assist in the positioning of the content. For example, the content may be set to appear when a user is at a particular location based on the user&#39;s personal traits or information and the user may then use an external user interface to interact with the content to reposition the content within the environment, for posting at another environment, sharing the content, storing the content for later viewing, etc. The content, for example, may appear in proximity to a doorway, as illustrated in  FIG.  67   , and the user may use an external interface or gesture to move the content from its pre-set position to an alternate position (e.g. another wall, another location on the same wall, an internal wall, an external wall, an office wall, personal wall, etc.). 
     In embodiments, the display presentation technologies as described herein elsewhere may be used in connection with the presentation technologies based on physical placement based on personal information. For example, the content may be presented at a physical location selected based on the person&#39;s personal information and the content may be presented to be viewed at a particular focal plane such that the user perceives it in focus when the user looks at a distance associated with the focal plane. The content may also be presented when the person is at the physical location; however, the content presentation may further be based on obstacle management technologies. In the event that the user is proximate the physical location where the content is to be presented, an evaluation of obstacles in the area may be completed and then the content presentation may be altered based on any obstacles that obscure the user&#39;s view of the content presentation location. 
     In embodiments, the content presented at a physical location based on personal information may further be positioned in the FOV of the HWC  102  based on sensor information as described herein elsewhere. For example, the sensor may indicate that the person is moving and the content may be re-positioned within the FOV, out of the FOV, or removed entirely, based on the detected movement. In the event that the person is deemed to be moving forward quickly, for example, it may be assumed that the person wants the center of the FOV clear so the content may be shifted towards the side of the FOV. The content may be of a type that is sensor dependent, or not sensor dependent, and it may be presented with other content that is of the opposite dependency. In embodiments, the content position may move depending on the sight heading and if the sight heading is rapidly moving the position of the content in the FOV may move but the positioning may also be damped, as described herein elsewhere. The physical location presentation based on personal information may be presented in a ‘side panel’ such that it is presented when the person looks to the side or turns his head to a side when the person is at the physical location. 
     In embodiments, eye imaging and sight heading technologies as described herein elsewhere may be used in connection with the physical location content presentation based on personal information. For example, the content may be ready for presentation once the person has reached the physical location identified but the presentation may be conditioned on the person looking in a particular direction. The direction may be indicative of the person&#39;s eye heading or sight heading. 
     Although embodiments of HWC have been described in language specific to features, systems, computer processes and/or methods, the appended claims are not necessarily limited to the specific features, systems, computer processes and/or methods described. Rather, the specific features, systems, computer processes and/or and methods are disclosed as non-limited example implementations of HWC. All documents referenced herein are hereby incorporated by reference.