I11111 111111ll111 Ill11 Ill11 IIIII IIIII IIIII 11111 .

5,897,18434FIG. 10 is a top view of an alternate embodiment forlightguide surface 16, and the widths and shapes of itsreflecting surfaces, may vary depending on what position theilluminating three dimensional displays of the present invengrooves 20 occupy on the surface 16 of the lightguide 10.tion with the possibility of alternating back and forthLight transmitted from illuminated edge 14 will reflect offbetween 3-D and 2-D displays.5elongated reflecting surfaces 24 of the grooves 20 and willFIG. 11 illustrates a plan view of one embodiment of abounce off towards the second surface 18.variable diffuser for enabling a 3-D display of the presentAs can also be seen in FIG. 2, the second surface 18 of theinvention to display segments in 2-D.light transmissive slab 12 has a plurality of lenticular lensesFIG. 12 illustrates a top view of another alternate embodi26. The lenses 26 preferably cover the entire second surfacement for illuminating three dimensional displays of the18 of the lightguide 10 except for a very small border areapresent invention with the possibility of alternating back andon each side. The lenticular lenses 26 are present on theforth between 3-D and 2-D displays.surface of the lightguide opposite the grooves 20. TheFIGS. 13A-13C illustrate top views of another alternatelenticular lenses 26 are oriented parallel to both the groovesembodiment for illuminating three dimensional displays of20 and the short sides of the lightguide corresponding to thethe present invention with the possibility of alternating back 15 illuminated edge 14. The dimensions of the lenticular lensesand forth between 3-D and 2-D displays.26 preferably do not vary substantially across the entiresurface 18, in other words, they should remain constantDETAILED DESCRIPTION OF THEother than a small tolerance factor.INVENTIONThe lenticular lenses 26 and the grooves 20, which mayFIG. 1 an autostereoscopic display according to the inven- 2o each be referred to collectively as microstructures, may betion. A transmissive light valve display 62, such as a liquidfabricated directly into the light transmissive slab 12, or theycrystal display (LCD), is situated in front of and spaced apartmay be contained in a layer such as plastic or epoxy bondedfrom an illuminating lightguide 10 which produces on aor otherwise attached to the slab 12.surface a large number of thin, bright, parallel vertical lightTurning to FIG. 3 it can be seen that there is not a 1 to 1lines 2. There is at least one light line 2 for every pair of 2s correspondence between the grooves 20 and the lenticularpixel columns 4 in the transmissive display 62. The lightlenses 26. There should usually be more lenticular lenses 26lines 2 are spaced apart from each other and from thethan there are grooves 20. As can be seen in FIG. 3, there aretransmissive display 62 at such a distance that an observerat least three times as many lenticular lenses 26 as there are6 seated at some viewing distance directly in front of thegrooves 20, however the dimensions of these figures are nottransmissive display 62 screen, sees all of these lines 30 to scale and should therefore not be construed as limiting.through the odd numbered columns of pixels 4 with his orEach groove 20 is provided with two side walls, a first sideher left eye 6a and all of the lines through the even numberedwall 32 and a second side wall 34. If both edges 14 arecolumns of pixels 4 with his or her right eye 6b. Thus, theilluminated by light sources 36 (shown in FIG. 4), bothleft eye 6a sees only what is displayed on the odd columnsreflecting surfaces 32 and 34 of each groove 20 will reflectof pixels 4, and the right eye 6b sees only what is displayed 35 light from the illuminated edges 14 towards the lenticularon the even columns of pixels 4. If the left eye 6a view oflenses 26. The reflecting surfaces 32 and 34 are preferablya stereoscopic image pair is displayed on the odd columnsprovided with a reflective coating, such as aluminum orand a right eye 6b view on the even columns, a stereoscopicsilver, while the land areas or flat surfaces 22 between theimage with apparent depth is perceived by the observer 6.grooves 20 are not provided with a reflective coating, e.g.The observer 6 will see the correct left eye 6a and right eye 40 the flat surfaces 22 may be left light transmissive.6b images as long as his or her eyes are near an ideal viewingAlternatively, the reflecting surfaces 32 and 34 may beplane 7 and within certain viewing zones 8 and 9 whosecoated with a diffuse material such as diffuse silver, ink, orboundaries are defined by lines running from the light linespaint.2 through the pixel column 4 boundaries, as shown in FIG.As can be seen in FIG. 4, the lightguide 10 will receive1.45 light from either or both light sources 36. The light sourcesFIG. 2 illustrates the lightguide in one embodiment of theare preferably fluorescent and cylindrical, although alternatepresent invention. The lightguide 10 may be a lightembodiments may be accommodated. The light sources aretransmissive, preferably clear rectangular substrate plate asgenerally coplanar with the lightguide 10, meaning that theshown by light transmissive slab 12. The slab 12 may becentral axes of the light sources preferably lies within themade from any light transmissive material, such as glass or SO same plane as a plane dividing the thickness of the lightfused silica, or any other known material such as plastics orguide 10. Also, the diameter of the light sources and theany other light transmissive or at least partially light transthickness of the lightguide 10 may be substantially equal.missive material. The slab 12 includes four edges which mayThe light may be directed towards the edges 14 by approbe illuminated, however the slab shall include at least onepriate reflectors 37, also preferably coplanar with the lightilluminated edge shown generally at 14, and preferably ss guide 10 so as not to enlarge the thickness of the backlightincludes two opposing illuminated edges. The slab furthering system of the present invention. The reflectors may, forincludes two parallel opposed surfaces, a first surface 16 andexample, comprise reflecting tape. Light from the lighta second surface 18.source 36 will be captured by the light transmissive slab 12The first surface 16 has a plurality of thin preferablyof the lightguide 10 by refraction at the end faces, will reflectevenly spaced grooves formed in or on the surface of the 60 off the reflecting surfaces 32 and 34, and will be directed bylightguide and preferably parallel to the short dimension ofthe reflecting surfaces 24 towards the lenticular lenses 26.By total internal reflection, light rays, not striking the microthe guide and the illuminated edge 14. As shown in FIG. 2,the grooves 20 are separated by spaces shown as land areasstructures, propagate in the slab 12. Rays traveling internallyor flat surfaces 22. The grooves 20 each have elongatedin the lightguide and striking the grooves 20 are reflectedreflecting surfaces 24. Although the grooves 20 each have 65 across the thickness of the slab towards the second surface18. The lenticular lenses 26 collect this light and focus it tothe same length, the other dimensions of the grooves, suchas the depth into the lightguide, the width it takes up on thelines outside the lightguide, as at the intersection of the rays

5,897,18456in FIG. 4. Preferably, the lines are all of the same intensity,evenly in front of the display, approximately where anand the intensity of the light lines is uniform along the lengthobserver would sit. Alternatively, in another embodiment ofthe invention, FIGS. 6A-6C illustrate that the elongatedof the lines. Thus each groove is a light source that is relayedto strips outside the lightguide. As can be seen, the lightreflecting surfaces 24 may be curved or bowed reflectingguide will create multiple thin vertical light emitting lines S surfaces 42, although the cross-section of the grooves shownwhen the guide is illuminated through one or two sides. Thein FIGS. 6A-6C is still roughly triangular in shape. Thelines are spaced apart from each other and the transmissivecurvature of the reflecting surfaces 42 serves to spread lightdisplay, or LCD, pixels according to a very preciseout more evenly in front of the display, approximately wheregeometry, which is dependent upon the horizontal pitch ofan observer would sit, in a more controlled manner than thethe LCD pixels and the desired viewing zone width and 10 rough planar reflecting surfaces 40. An alternative method ofdistance.and device for spreading light out more evenly in front of thedisplay would be to make each reflecting surface 24 aThe required pitch of the light line images formed by themulti-faceted surface, i.e. have more than one planar orlenticular lenses 26 can be expressed by the formula:curved secondary surface per reflecting surface 24.s 2/[l/n-l/z]1s Both FIGS. 5A-5C and 6A-6C show embodiments of theinvention in which the grooves 20 have different dimensionswheredepending on their location within the first surface 16 of thelight transmissive slab 12. In particular, the grooves in thes is the pitch of the light lines,center portion of the first surface 16 have reflecting surfacesn is the width of a single pixel (or color pixel element in20 24 which are equal in length, as shown in FIGS. 5b and 6b.the case of a vertical stripe color display), andGrooves located on a left side portion of the first surface 16,z is the maximum viewing zone width, which is usuallysuchas grooves 48 and 50, will have left reflecting surfacesset equal to the average interpupillary distance betweenwhich are longer than their right reflecting surfaces.human eyes, about 63 mm.Likewise, grooves 20 located on the right side area of theGiven this required pitch, the relationship between thepitch of the grooves 20 (or other light reflecting, scattering, 2s first surface 16, such as grooves 52 and 54, will have rightreflecting surfaces which are longer than their left reflectingor emitting elements), and the pitch of the lenticular lensessurfaces. In addition, as can be seen in FIGS. 5A-5C and26 is given by:6A-6C the depths of the grooves vary according to theirlocation within the first surface 16. In particular the centera l/[l/L-l/sl,30 grooves 44 and 46 will have the greatest or deepest depthwithin the first surface 16. The grooves located on the rightwheremost and the left most edges of the first surface, will havea is the pitch (center to center distance) of the lenses 26,the least or most shallow depths. The purpose for varying theLis the pitch (center to center distance) of the grooves 20,dimensions of the grooves depending on their location onand3s the first surface 16 is to insure that the brightness of the lights is the required pitch of the light lines.reflected from the illuminated edges 14 will be even acrossGiven that the above relationship holds, the relationshipthe second surface 18. If the grooves 20 were of equalbetween the focal length of the lenses and the distancedimensions throughout the first surface 16 the edges of thebetween the front of the lenses and the grooves (taking thesecond surface 18 would receive a greater amount of lightrefractive index of the light guide material into account) is 40 and would thus be brighter than the central area of thegiven by:second surface 18.Following are measurements for a preferred embodimentD (f/a) xL,of this invention when utilized with an LCD having a 31centimeter diagonal with a 0.08 millimeter horizontal pixelwhere4s element pitch and 1024x768 resolution. Of course, theD is the distance between the grooves 20 and the lensesmeasurements of the lightguide of this invention could26,obviously be altered to accommodate differently sizedf is the focal length of the lenses 26,LCD's. The lightguide 10 for a preferred embodiment of thisa is the pitch of the lenses 26 as given above, andinvention, when used with the above described LCD, isL is the pitch of the grooves 20 as given above.so made of a light transmissive slab 12 having the dimensionsThese conditions provide a correct light line pitch andof 247 millimeters /-1 millimeter for the length, 186also ensure that light lines formed by each lens 26 aremillimeters /-1millimeter for the width (corresponding tosuperimposed on the light lines formed by adjacent lensesthe length of illuminated edge 14), and 4 millimeters /-0.0526.millimeters for the thickness. There may be 274 thin groovesThe thin light lines created by the apparatus with dark 5s evenly spaced across the first surface 16. The grooves mayspaces in between are necessary for autostereoscopic viewbe 186 millimeters /-1millimeter long and will, as dising. The geometry of this lightguide is important for accomcussed previously, have different depths depending on whatplishing this autostereoscopic feature. For example, if theposition the grooves are in on the lightguide. The centergrooves were not spaced apart at least five times their width,most grooves may have a depth of 0.09 millimeters /-0.009the lightlines shown would be wider than desirable and thus 60 millimeters. The edge grooves, either on the right side or thewould decrease the 3-D effect. Also, for example, the depthsleft side, may have a depth of 0.015 millimeters /-0.0015millimeters, and the depth of the grooves may vary betweenof the grooves are important because otherwise the lines atthe lowest and the highest value depending on the groove'sthe edges would be brighter than the lines at the center, asdistance from the edge. As also previously discussed, the tiltdiscussed in more detail below.FIGS. 5A-5C show that the elongated reflecting surfaces 65 of the grooves may vary according to groove position. The24 may be planar reflecting surfaces 40. The planar reflecttwo central grooves may be symmetrical, with each sideing surfaces may be rough for spreading light out moremaking an angle of 43" with the surface of the lightguide.

5,897,18478The two edge grooves may be tilted so that the sides closestto the edge make an angle of 29 /-1 degree with the surface,and the sides away from the edge make an angle of 57 /-1degrees with the surface. The angle of tilt will vary from thelowest to the highest value depending upon the distance ofeach groove from the center. Note, however, that the angleat the tip of the groove remains constant at 94 degrees. Thesurfaces of the grooves may be sufficiently rough such thatlight reflecting off them is scattered with a half maximumwidth of at least /-9 degrees from the direction of specularreflection. Although ideally constant, the width of any singlegroove may vary by no more than one-tenth its averagewidth along its length. The angle between the groovereflecting surfaces may be a constant 94 degrees /-0.5degrees. The surface of the grooves may be aluminized so asto reflect light with no more than a /-5% reflectancevariation. The surface area (land area or flat surface 22)between the grooves may not be aluminized. The groovesmay have an average pitch of 0.9 millimeters. No point onthe left edge of the nth groove from the left may deviate fromits ideal position by more than /-0.045 millimeters, wherethe ideal position is defined as a vertical line situated at adistance (N-l)x0.9 millimeters from the left edge of the leftmost light emitting region, as measured along lines runningperpendicular to the center line of the left most light emittingregion. 1,831 lenticular lenses may be present on the side ofthe lightguide opposite the grooves. The lenticular lensesmay be oriented parallel to both the grooves and the shortsides of the lightguide. The lenticular lenses may cover thesecond surface of the lightguide, except for a very smallborder area on each side. Each lens may have a length of 186millimeters /-1 millimeter and a width of 0.13483 millimeters /-0.01 millimeters. The transmittance of the lensesmay vary by no more than 5% across their surface. Thelenses may have an average pitch of 0.13483 millimeters.No point on the center line of the nth lens from the left maydeviate from its ideal position by more than /-0.007millimeters, where the ideal position is defined as a verticalline situated at a distance (N-l)x0.13484 millimeters fromthe center line of the left most lens, as measured along linesrunning perpendicular to the center line of the left most lens.The lens may have a focal length of 0.4 millimeters /-0.04millimeters. The lens may be aligned parallel to the groovesto within /-5 minutes of arc.The thickness of the light transmissive slab 12 of thelightguide 10 may be 4 millimeters /-0.1 millimeter. Thesurfaces of the substrate may not deviate from two idealparallel planes by more than /-0.025 millimeters. Thelightguide 10 may weigh no more than 0.5 kilograms. Thelightguide may be manufactured from clear materials without tinting or other discoloration. The apparent luminanceseen within areas on the surface of the lightguide betweenthe grooves, due to stray light leaking from the systemthrough these areas due to scratches, surface roughness, andother blemishes, may be no more than 0.5% of the luminance within the light emitting lines. The lightguide may bedesigned to transmit white light with peaks in the red, green,and blue spectral regions without noticeably changing thecolor coordinate of such white light due to filtering of thevarious colors. Blemishes and discolorations may not bevisible when the lightguide is viewed with the naked eyefrom a distance of 53 centimeters.The lightguide and the materials used to create the lightlines should be capable of operating reliably for 10,000hours MTBF (mean time between failure) without degradation in transmittance or discoloration over that period, whilebeing illuminated by fluorescent lamps along one or moresides, and under use conditions typically associated withportable computer display illumination systems. Preferablythe light sources used are cylindrical fluorescent bulbshaving a diameter of approximately 2 mm and not greaterthan 5 mm. Because the preferred embodiment of the presentinvention utilizes only two light sources, the chances forfailure are decreased thus increasing the lifespan of thebacklighter. In addition, the backlighter requires less powerto run itself because of the limited amount of light sourcesneeded to effectively operate.In an alternative embodiment, two lightguides could bestacked together as shown generally at 98 in FIG. 7 forgenerating a uniform radiance. Both lightguides 100, 120preferably would have similar surface relief containinglenticular lens arrays 106, 126 on the second surfaces 104,124, respectively. Arrays of grooves 108,128 would also becommon to both first surfaces 102,122, however the secondadditional lightguide 100 would contain densely packedgrooves 108. Both sets of grooves 108,128 would be coatedwith reflective films, or otherwise made to reflect light. Inoperation, light striking the first surface 102 of the second,stacked lightguide 100 reflects across the width of its slab.Incident the opposite surface 104 of lenticular lenses 106,this light is focused to a point inside the first lightguide 120.If this focus is close to the grooves of the first lightguide 120then the lenticular lenses 126 of the first lightguide 120 willrefocus this light into a second set of lightlines.FIG. 8 illustrates the lightguide in another embodiment ofthe present invention. The lightguide 210 may be a lighttransmissive, preferably clear rectangular substrate plate asshown by light transmissive slab 212. As with slab 12 inFIG. 2, the slab 212 may be made from any light transmissive material, such as glass or fused silica, or any othermaterial known in the prior art such as plastics or any otherlight transmissive or at least partially light transmissivematerial. The slab 212 includes two edges which may be

each section capable of becoming diffuse or transparent independently of the others so that one can cause some 30 sections of the display to display 3D images and some sections to display 2D images. In another embodiment, a conventional 2-D planar backlighter may be employed in