Abstract:
A compact real-image projection apparatus is used for a portable device ( 140 ). An optical projector ( 110 ) emits light that is capable of forming an image. A collapsible screen ( 120 ) has a collapsed surface area no larger than substantially the surface area of a side of the portable device and an expanded surface area capable of receiving the light emitted from the optical projector ( 110 ). A retractable connecting member ( 150 ) is coupled between the screen ( 120 ) and the optical projector ( 110 ) and has at least a stowed position and an extended position. The extended position is configured to hold the screen ( 120 ) and the optical projector ( 110 ) relative to one another such that the light emitted from the optical projector forms a real image on the screen.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention relates to projection systems and, more particularly, relates to compact projection systems for portable devices.  
           [0003]    2. Description of the Related Art  
           [0004]    Projectors have been used in rooms to display images for many years. Slide projectors and projection televisions are examples of large-scale projection systems. These projection technologies, however, are unsuitable for compact portable applications.  
           [0005]    Miniature optics using a series of lenses and mirrors have been proposed for virtual image viewers on telephones handsets for example, in U.S. Pat. Nos. 6,073,034, 5,867,795 and 5,048,077. These systems provide a personal image viewable by the telephone user through an eye hole or eye piece. These systems can cause user eyestrain over long periods of time. These systems are incapable of presenting large amounts of screen data at once without scrolling an image. These systems are incapable of use by a group of people such as for demonstration purposes at a meeting.  
           [0006]    What is needed is a large screen projection system, for use with a portable electronic device, to present to groups of people or allow large amounts of data to be presented without user eyestrain.  
         SUMMARY OF THE INVENTION  
         [0007]    A compact real-image projection apparatus is used for a portable device. An optical projector emits light capable of forming an image. A collapsible screen has a collapsed surface area no larger than substantially the surface area of a side of the portable device and an expanded surface area capable of receiving the light emitted from the optical projector. A retractable connecting member is coupled between the screen and the optical projector and has at least a stowed position and an extended position. The extended position is configured to hold the screen and the optical projector relative to one another such that the light emitted from the optical projector forms a real image on the screen. The collapsible screen can be unfolding or rolling, for example. In two alternative embodiments, collapsible screen can be either reflective or transmissive for viewing from either the front or the back of the optical projector. The collapsible screen can have multiple layers with a Fresnel surface and be a gain screen that concentrates reflected or transmitted light in a viewing zone.  
           [0008]    The details of the preferred embodiments of the invention may be readily understood from the following detailed description when read in conjunction with the accompanying drawings wherein: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 illustrates a side view of the compact projection system according to one embodiment in an extended position according to the present invention;  
         [0010]    [0010]FIG. 2 illustrates a side view of the compact projection system according to the one embodiment in a retracted position according to the present invention;  
         [0011]    [0011]FIG. 3 illustrates a detailed diagram of the internal components for an image projection system according to an example of the present invention;  
         [0012]    [0012]FIG. 4 illustrates a diagram of the internal components for a point light source projection system according to an example of the present invention;  
         [0013]    [0013]FIG. 5 illustrates a prospective view of a telescoping projector and an unfolding screen embodiment on a portable device in an extended position according to the present invention;  
         [0014]    [0014]FIG. 6 illustrates a prospective view of a telescoping projector and an unfolding screen embodiment on a portable device in a retracted position according to the present invention;  
         [0015]    [0015]FIG. 7 illustrates a prospective view of an extensible, rotating projector and an unfolding screen embodiment on a portable device in an extended position according to the present invention;  
         [0016]    [0016]FIG. 8 illustrates a prospective view of an extensible, rotating projector and an unfolding screen embodiment on a portable device in a retracted position according to the present invention;  
         [0017]    [0017]FIG. 9 illustrates a prospective view of an extending projector and a roll-up screen embodiment on a portable device in an extended position according to the present invention;  
         [0018]    [0018]FIG. 10 illustrates a prospective view of a extending projector and an unfolding screen embodiment on a portable device in an extended position according to the present invention;  
         [0019]    [0019]FIG. 11 illustrates a prospective view of an axially rotating projector and an unfolding screen embodiment on a portable device in an extended position according to the present invention;  
         [0020]    [0020]FIG. 12 illustrates a prospective view of a radially rotating projector and an unfolding screen embodiment on a portable device in an extended position according to the present invention;  
         [0021]    [0021]FIG. 13 illustrates a prospective view of an extending, folding screen embodiment for a projector on a portable device in an extended position according to the present invention;  
         [0022]    [0022]FIG. 14 illustrates a prospective view of a different extending, folding screen embodiment for a projector on a portable device in an extended position according to the present invention; and  
         [0023]    [0023]FIG. 15 illustrates a prospective view of a different extending, folding screen embodiment for a projector on a portable device in a retracted position according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    [0024]FIG. 1 illustrates a side view of the compact projection system according to one embodiment in an extended position according to the present invention. A projector  110  projects light onto a screen  120 . The screen  120  is extended out of and pivots upwards on a pivot  125  when in the extended position illustrated in FIG. 1 The screen  120  can be modified to unfold in a horizontal or vertical direction. An outer portion  130  of a pivoting cover  135  slides downwards when extended. The projector  110  is connected to a housing  140  by a retractable connecting member  150 . The connecting member  150  is preferably thin such that it does not consume volume of the portable device in the closed position. The connecting member is also preferably thin in the alternate embodiments of this invention for the same reasons.  
         [0025]    [0025]FIG. 2 illustrates a side view of the compact projection system according to the one embodiment in a retracted position according to the present invention. The retractable member  150  slides into the housing  140  when the compact projection system is in a retracted position. The housing  140  accommodates space for the retracted member  150  inside. The retracted member  150  can be rectangular or tubular in volume or, alternatively, a flat member that does not consume much volume within the housing  140  in a retracted position. The screen  120  folds shut between the housing  140  and an outer portion  130  and the cover  135  when closed in a retracted position. The cover  135  and the outer portion  130  protect the screen from damage in the closed position when the portable device is carried. The housing  140  contains electronics for controlling the projector  110 .  
         [0026]    [0026]FIG. 3 illustrates a detailed diagram of the internal components for an image projection system according to an example of the present invention. A lensed halogen bulb  210  provides light reflected by a reflector  220  through a hot mirror  230  and an imager  240  for focusing by a lens system  250  on a screen  260 . The imager provides a source of an image for projection on the screen  260 . The imager could be a microdisplay driven with the appropriate signal to project temporally changing images on the screen. Alternatively, the microdisplay could be an emissive type such as an Organic Light Emitting Diode (OLED) that would negate the need for a bulb and reflector illuminator. A computer or other controller drives the microdisplay to create desired static or dynamic images. The screen  260  can be either reflective or be transmissive for viewing from either the front or the back of the optical projector. Front projection systems can be designed to have increased contrast over transmission systems by using films such as holograms so that ambient light is not diffracted into the viewing cone and is absorbed behind the films by an absorbing layer. However, with a front projection system the optical projector is located on the viewer side of the device and in some situations could be blocking the view of the display or interaction with the portable device. Rear projection systems require specialized screens that reduce the amount of the unwanted light reaching the viewer. Ambient light typically reduces the contrast of the image in rear projection systems. Typically, light baffles or encasing the system is used in projection systems to reduce this ambient light. For either front or rear projection systems, multiple layer compositions are preferred in a projection screen for a compact device to improve optical characteristics as will be described herein. Front projection systems require reflective screens while rear projection systems require transmissive screens.  
         [0027]    Typically, projection screens are diffusers that can be classified as gain or Lambertian. A Lambertian diffuser is one that scatters light equally into a solid angle of 4 pi steradians (half of a sphere). Common screens used for large audiences such as slide projectors or theatres diffuse incident light over a broad range of angles and are close to Lambertian.  
         [0028]    A gain screen scatters the incident light non-uniformly. Typically most of the light is diffused into predetermined range of angles centered about the screen normal. Directing light away from some angles and concentrating it into desired angles increases the brightness of the image. The amount of gain for a screen is typically measured by the magnification in intensity of the light relative to a Lambertian diffuser. For example, a 5× gain diffuser would provide an intensity of light 5 times that of a Lambertian diffuser at a specific viewing angle. Gain screens can be used in applications such as handheld devices where the screen is viewed by one or two people within a small range of viewing angles. See U.S. Pat. No. 5,663,816, which is incorporated herein by reference.  
         [0029]    A gain screen will conserve battery power for a portable, compact device because the gain screen concentrates light in a predetermined viewing zone. For instance, if a group of persons needs to view the screen, the gain screen can asymmetrically concentrate light in a horizontal but not in a vertical viewing zone thus conserving power for battery operated device. For a personal viewing, a gain screen could be used to concentrate light in both horizontal and vertical directions to conserve power. With some types of diffusers such as surface relief diffusers, the high gain screens may also contribute to problems of speckle in the image. Methods for reducing the speckle introduced with this type of screen can be reduced by continuously moving or vibrating the diffuser. Other methods for reduction in speckle are known to those skilled in the art. Some volumetric diffusers have reduced speckle and may be preferred in some cases. The amount of gain chosen is related to the viewing angles desired, the increase in brightness and image quality desired, the amount of speckle introduced, manufacturing constraints, and cost. The gain screen should have a gain greater than about 5× and preferably greater than about 10× measured within 10 degrees from the normal of the screen.  
         [0030]    Typically screens for projection systems may have several layers or components. The screen should contain a diffusing (or scattering) element  266 . The diffusive element may be a volumetric scattering film (such as those made by introducing scattering regions of different index of refraction into a film) or surface relief (such as those formed from embossing microstructures as in Physical Optics Corporation Light Shaping Diffusers). Volumetric scattering can also be diffractive in nature such as the case of diffraction from a diffuse hologram.  
         [0031]    Projection screens may also have other components such as a Fresnel lens  264  to improve the uniformity, brightness or contrast of the image on the screen. The diffusing structure of the film may direct incident light into a narrow viewing angle, thus providing gain. This may be done symmetrically or asymmetrically (such the case with Physical Optics Corporation Light Shaping Diffusers). In a television projector application, the diffuser may scatter light more horizontally than vertically such that light is not wasted by directing it toward the ceiling. Alternatively, the angular spread of the light can be controlled by adding additional films such as lenticular screens or prismatic films. In order to reduce ambient reflections from the screen, the screen component or support layer may be tinted or specialized diffusing screens  266  such as the BlackScreen™ made by Jenmar Visual Systems may be used to reduced ambient light reflections. In systems where the light reaching the diffusing element arrives from steep angles, typically, a Fresnel lens, such as those manufactured by Fresnel Optics, is used to substantially collimate the incident light. This results in an image where the brightness at the corners of the screen is closer to the brightness at the center of the screen.  
         [0032]    Screens for front (reflection) based projectors may also contain multiple different layers. One such screen could consist of a reflection hologram layer laminated onto a black absorptive layer. The reflection hologram could be recorded to be a substantially monochrome diffuse reflection hologram or could contain multiple exposures allowing for polychromatic diffuse reflections such as a red, green and blue reflection for a full-color display Alternatively, multiple layers of holograms could be recorded and laminated together to provide a multicolor reflection for a full-color display. Prismatic films with controlled diffusing layers and a reflective layer can also be used to diffuse light from the projector into a predetermined range of viewing angles. Prismatic films can be designed to tailor the light reflection across the screen to enable off-axis designs and increase the uniformity of the brightness.  
         [0033]    In front or in rear screens, any or all of the components may contain anti-reflection layers (such as anti-reflection coatings or moth-eye structures) or anti-glare components to reduce unwanted reflections. The film components comprising the screen could be made substantially thin such that they could be folded or rolled-up into a smaller form factor.  
         [0034]    [0034]FIG. 4 illustrates a detailed diagram of the internal components for a scanning projection system according to an example of the present invention. Rather than use of an imager to modulate light capable of forming an image, a laser or LED  270  or other point light source and one or more moving mirrors  280  can be used in the embodiment of FIG. 4 to draw an image on the screen  260 . Electronics in the housing of the compact device control the point light source  270  and moving mirror  280  to draw the image on the screen  260 .  
         [0035]    FIGS.  5 - 15  illustrate various alternative embodiments for constructing the compact projection system of the present invention on the housing of a compact device such as a battery-powered, handheld electronic computer or wireless radio telephone.  
         [0036]    [0036]FIG. 5 illustrates a prospective view of a telescoping projector  310  and an unfolding screen  320  on a portable device  330  in an extended position and FIG. 6 illustrates a prospective view of the telescoping projector  310  and the unfolding screen  320  on the portable device  330  in a retracted position according to an alternate embodiment of the present invention. The unfolding screen  320  is a transmissive screen viewable from a side opposite the telescoping projector  310 . The screen unfolds in a horizontal direction as viewed by the viewer and increases the viewable surface area of the screen. The projector  310  is connected to the portable device  330  by a retractable telescopic member  340 . The retractable telescopic member  340  retracts from within the housing or beneath the housing of the portable device  330 . The unfolding screen  320  is attached to the portable device  330  using a hinge such that the angle of the screen matches the angle of rotation of the projector  310 . In order for proper illumination of the screen, the angle of the screen  320  is not perpendicular to the front face  350  of the housing of the portable device  330  but matched to the angle of illumination from the projector  310 . A detent or spring can be used to urge the angle of the screen  320  to an optimum angle that matches the angle of the projector  310 .  
         [0037]    [0037]FIG. 7 illustrates a prospective view of an extensible, rotating projector  410  and an unfolding screen  420  on a portable device  430  in an extended position and FIG. 8 illustrates a prospective view of the extensible, rotating projector  410  and the unfolding screen  420  on the portable device  430  in a retracted position according to an alternate embodiment of the present invention. Phantom lines in FIG. 8 illustrate the projector  410  being extended and rotated from the housing of the portable device  430 . The optical projector is rotated upward so that the light is directed toward the screen in a substantially perpendicular direction such that keystone distortion is reduced. This on-axis illumination prevents the projection of a square or rectangular image into a trapezoidal shape.  
         [0038]    [0038]FIG. 9 illustrates a prospective view of an extending projector  510  and a rollup screen  520  on a portable device  530  in an extended position according to an alternate embodiment of the present invention. The roll-up screen  520  collapses by automatically rolling in and out under the force of an internal spring and locking mechanism  540 . Side ends of the roll-up screen  520  are supported by a roll-out metal band  550  attached to the backside of the screen. The metal band  550  rolls-out similar to a tape measure and thus provides rigidity for the screen when in an extended position. The roll-up screen  520  displays the real image projected from the optical projector  510  in a rear projection format. Alternatively, the screen could be pull-out such that it is substantially co-planar with the front face  560  of the housing of the portable device  530  with the retractable member  570  extending in a direction perpendicular to the screen. The roll-up screen can be substituted for the folding screens used in a front or rear projection format as an alternative to the other collapsing screen approaches in the other embodiments of this invention.  
         [0039]    [0039]FIG. 10 illustrates a prospective view of an extending projector  610  and an unfolding screen  620  on a portable device  630  in an extended position according to an alternate embodiment of the present invention. The position of the retractable connecting member  640  is on the side of the portable device  630  such that the projector  610  is centrally located to projection light perpendicular to the screen  620 .  
         [0040]    [0040]FIG. 11 illustrates a prospective view of an axially rotating projector  710  and an unfolding screen  720  on a portable device  730  in an extended position and in phantom lines being closed to a retracted position according to an alternate embodiment of the present invention. The retractable connecting member  740  is stored in a recess on the bottom surface of the housing of the portable device  730 . To extend the retractable connecting member  740 , it is axially pulled out of the recess before rotating.  
         [0041]    [0041]FIG. 12 illustrates a prospective view of a radially rotating projector  810  and an unfolding screen  820  on a portable device  830  in an extended position according to an alternate embodiment of the present invention.  
         [0042]    [0042]FIG. 13 illustrates a prospective view of an extending, folding screen  920  for a projector  910  on the near end of the portable device  930  relative to the screen in an extended position according an alternate embodiment of to the present invention. The extending, folding screen  920  pulls out from the portable device  930 .  
         [0043]    [0043]FIG. 14 illustrates a prospective view of an extending, folding screen  1020  for a different projector  1010  on the far end of the portable device  1030  relative to the screen in an extended position and FIG. 15 illustrates a prospective view of the extending, folding screen  1020  for a different projector  1010  on the portable device  1030  in a retracted position according to an alternate embodiment of to the present invention. The projector  1010  may be in-between the ends to give the greatest throw distance for the projector with the users fingers on buttons blocking the projection.  
         [0044]    Although the invention has been described and illustrated in the above description and drawings, it is understood that this description is by example only, and that numerous changes and modifications can be made by those skilled in the art without departing from the true spirit and scope of the invention. Although the examples in the drawings depict only example constructions and embodiments, alternate embodiments are available given the teachings of the present patent disclosure. For example the portable device could be miniature or of other electronic kind (such as a personal data assistant or electronic game) or the projector and screen could be located on alternate locations and surfaces of the device housing. The projection apparatus describe herein could function as an accessory to a portable electronic device. The drawings are for illustrative purposes and although relative sizes can be seen among the elements, they are not drawn to scale.