Abstract:
A display device for large scale billboard displays comprises a set of image carriers each defining a respective sequence of image frames and each having directional properties such that different image frames are viewable from different viewing directions relative to the image carrier. A support device supports the image carriers such that they together form a composite display and an adjustment device is provided operable to adjust the orientation of the image carriers relative to the support device such that corresponding frames of each image carrier are simultaneously viewable by an observer at a predetermined position relative to the display apparatus. The image carriers may be lenticular members in which lenticular lenses overlay interdigitated strips of image elements.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to display devices of the type in which relative movement between an observer and the display presents successive frames of a moving image by virtue of directional properties of an image carrier forming part of the display device. The invention relates in particular, but not exclusively, to display devices comprising large scale advertising hoardings formed from a set of panels, and wherein the image carrier displaying the moving image comprises a lenticular member having a plurality of lenticular lenses which overlay an image hearing member upon which inter-digitated image elements are formed. Examples of such lenticular media are described in U.S. Pat. No. 5,699,190 and U.S. Pat. No. 5,959,718 and are commercially marketed by Eastman Kodak (Trade Mark) as Dynamic Imaging materials. 
     It is known to provide an advertising hoarding formed of a number of panels in which an image carrier is mounted on a single one of the panels and defines a moving image by virtue of the directional properties of the image carrier. Such displays are effective in attracting the attention of pedestrians and travellers in moving vehicles, the moving image typically being formed by animated photographic or graphics techniques or by use of actual events captured using a cine-camera or video camera. 
     Typically in such advertising hoardings the image carrier on the single panel providing the moving image is accompanied by a series of fixed image panels carrying text or other fixed images not having directional properties to complete the advertising message. Typically, the entire hoarding cannot practically be formed of a single image carrier having directional properties because of cost and the technical implications of introducing a single large scale lenticular image medium. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention seeks to provide an improvement whereby more than one of the panels of the display may comprise an image carrier providing part of the same moving image. A problem anticipated with such composite displays is that the panels will generally be required to extend in a planar array, as for example along the side of a building, and the observer will observe the display at a distance which is determined by local topography such as the locations of a pavement, pathway or traffic lane. If for example more than one identical image carriers are simply mounted against the wall of the building in co-planar relationship and spaced apart in the direction of observer travel, the portions of moving image which the respective panels provide will not in general be simultaneously viewable from the same direction and therefore will not be in sync. 
     According to the present invention, a composite display is formed by a set of image carriers displaying multiple frames which are selectively viewable depending upon viewing direction and wherein the image carriers are supported such that their orientations can be adjusted. The image carriers each include at least one frame recognisable as being a reference frame so that during an on-site alignment procedure the image carriers can be adjusted in orientation such that the reference frames of each image carrier are simultaneously viewable by an observer at an alignment position. This ensures that the frames of the moving image provided by each image carrier are in sync with the frames of the moving image provided by the other image carriers of the set. 
     A further aspect of the invention provides image carriers for which the viewing angle corresponding to the reference frame is determined during a manufacturing process according to the position which the image carrier will adopt when assembled into the array of image carriers forming the composite display, thereby minimising the need for adjustment in orientation during the onsite alignment procedure. Typically therefore, image carriers which are to be located at an array position at the centre of the composite display may have a viewing angle for the reference frame which is at or about 90° relative to the planar extent of the image carrier whereas those image carriers which are intended to be located at the periphery of the composite image may have a viewing angle which is less than 90°. 
     During the onsite alignment procedure, it is necessary for the reference frame to be readily recognised by operatives performing the alignment and therefore a further aspect of the invention relates to providing means for recognising the reference frames such as by the inclusion in the reference frame image of indicia such as a symbol. In the preferred embodiment, the symbols are square markers, such symbol being placed at suitable locations in the image frame so as not to obscure the image information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will now be disclosed by way of example only and with reference to the accompanying drawings of which; 
     FIG. 1 is a schematic plan view of a composite display; 
     FIG. 2 is a schematic front elevation of the composite display of FIG. 1; 
     FIG. 3 is an enlarged plan view of part of the composite display of FIG. 1; 
     FIG. 4 is a view as seen by an observer located at an alignment position relative to the part of the display shown in FIG. 3; 
     FIG. 5 is a plan view of one of the image carriers of FIG. 3 showing successive frames of a sequence of frames viewable at different viewing directions relative to the image carrier; 
     FIG. 6A is a side elevation of two image carriers on panels supported adjustably on a supporting frame; 
     FIG. 6B is a rear elevation of the panels and the supporting frame of FIG. 6A; 
     FIG. 7 is a detail from FIG. 6A of the adjusting mechanism between one of the panels and the supporting frame; 
     FIG. 8A is a sectional view of a lenticular image carrier; 
     FIG. 8B is a front elevation of the image carrier of FIG. 8A; 
     FIG. 8C is a view of the image bearing member of the image carrier of FIG. 8A showing the image strips; and 
     FIG. 9 is a front elevation of an alternative display in which some of the panels do not have image carriers with directional properties. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates in plan view a composite display  1  for use as an advertising hoarding formed by a set of image carriers  2  which are supported by a support frame  3  so as to be viewable in a generally horizontal direction by an observer  4 . 
     FIG. 2 illustrates in front elevation the image carriers  2  being twelve in number and arranged to form a 6×2 array in which an upper row  5  of six image carriers is supported above a lower row  6  of a further six image carriers. 
     The display  1  is intended to be viewed by the observer  4  at any of a number of viewing positions along a horizontally extending viewing path  7  which runs parallel to and at a distance d from the display  1 . Movement of the observer  4  along path  7  results in successive image frames in the sequence being viewable, thereby enabling the appearance of a moving image to be created. 
     Each of the image carriers  2  is mounted on a rectangular panel  64  having a long axis which is vertical and a short axis which is horizontal. Each panel  64  is mounted to the support frame  3  by adjustable couplings  8  which facilitate adjustment of the orientation of the panel through a range of about ±5 degrees about both vertical and horizontal axes. The panel  64  can therefore be adjusted in orientation about the vertical axis to a tilt angle A between the plane of the image carrier  2  and a vertical plane defined by the support frame  3 . In FIG. 1, the size of angle A is exaggerated for illustration purposes and this figure is therefore not to scale in this respect. 
     Each of the image carriers  2  has directional characteristics by virtue of lenticular Dynamic Imaging materials, described below, such that the observer  4  sees the composite image of the display  1  as a sequence of different image frames when the observer moves along the viewing path  7 . In the present example, the sequence of image frames is recorded using a video camera and processed to form a pattern of interlaced image strips suitable for lenticular imaging before being transferred to the image carriers by exposure of photographic emulsion. 
     In the display  1  of the present example, the image carriers  2  are arranged such that the longitudinal axis of the lenticular material (i.e. the lenticular axis) extends vertically. 
     FIG. 3 shows in greater scale the image carriers  2   a  and  2   b  of FIG.  1 . Image carrier  2   a  is manufactured to display a sequence of 21 image frames, each of which is viewable at a respective horizontal viewing direction represented schematically in FIG. 3 by a number of lines  30  radiating from a vertical axis in the image carrier, each line representing a viewing direction at which one of the image frames of the moving image is viewable. Vertical movement of the observer  4  does not change the viewing direction in the above sense since it is the angle about the lenticular axis of the lenticular material which determines which image frames are viewable. 
     As illustrated in FIG. 2, an image presented by a composite image area  20  is formed from a set of image segments  25  provided by respective image carriers  2 . Each image segment  25  however can at a given time be selectively viewed as any one of frames 1 to 21 of the image frames provided by its respective image carrier  2 . There is therefore a requirement for the observer  4  on the viewing path  7  to simultaneously view image segments  25  having the same frame number in the sequence which defines the moving image. Each of the image carriers  2  is manufactured to have directional properties selected with the intention that this requirement should be met for a given value of distance d when the image carriers are mounted in co-planar relationship thereby requiring zero adjusting angle A in each case. However, manufacturing tolerances associated with the lenticular material typically do not achieve this degree of alignment. Furthermore, the manufacture will set the viewing angles for each image carrier with a particular value of distance d in mind. If the value of d is to be changed for a particular application of the display, image segments having the same frame number will no longer be simultaneously viewable along the new viewing path  7 . 
     For the above reasons, the adjustable couplings  8  generally need to be set on site to ensure that for any given position along the viewing path  7 , image segments having the same frame number are simultaneously viewable in each of the image carriers  2 . This synchronisation process will now be described as part of the overall process of forming the image carriers  2  and mounting them in the composite display  1 . 
     The process of manufacturing the image carriers  2  begins by obtaining a series of 21 images which are to constitute the composite image area  20  and which when viewed in numerical sequence are perceived as a moving image. Each image is divided into the twelve image segments  25  shown in FIG. 2 so as to correspond to the image areas which will be presented by respective image carriers  2  when mounted in array on the support  3 . 
     For each image carrier  2 , a sequence of 21 image frames then corresponds to the sequence of image segments  25  for that image carrier. The frames are numbered sequentially in the order in which they are to be viewed. 
     The design parameters for the display  1  then need to be determined as shown in FIG. 1 since it is necessary to have knowledge of the dimensions of the panels  64  and the distance d from which the display  1  will be viewed. As a reference position for alignment purposes, an alignment position  9  on the viewing path  7  is selected. This allows calculation of the angles B relative to each image carrier  2  at which it is to be viewable from the alignment position  9 . One of the frames is selected during manufacture to be used in the on-site alignment process. In the present example, an alignment reference frame number 10 is chosen. As an aid to recognition of the alignment reference frame 10, the number 10 frame of each image carrier  2  is modified during manufacture by the addition of one or more reference symbols  40 , as illustrated in FIG. 4 where the reference symbols are in the form of squares with one symbol being located in each corner of the frame. 
     Using the values of angle B for each of the image carriers  2 , it is also possible to determine for a given image carrier the number of the frame which would be viewable at a viewing angle of 90°. Frames of this number are marked with a different symbol, referred to hereafter as a manufacturing reference symbol, so that it is also possible to recognise these frames during manufacture. For example, image carrier  2   c  in FIG. 1 requires a viewing direction of B=45° to view the alignment reference frame 10. If however image carrier  2   c  is viewed in a direction at right angles to the plane of the image carrier, frame 15 is viewable. Frame 15 is therefore marked for recognition purposes with the manufacturing reference symbol  50  which in this example is a circle as shown in FIG.  5 B. 
     For each of the image carriers  2 , a lenticular member  80  in the form of an extruded sheet  81  of Polyethylene Terethphalate having a shape defining parallel lenticles  82  is mounted in contact with an image bearing member  83  carrying inter-digitated image strips  84  as shown in FIGS. 8A,  8 B and  8 C. 
     Each image strip  84  consists of a sequence of frame elements belonging to different frames as illustrated in the lower portion of FIG. 8C which shows an image strip having frame elements F 1  to F 21 . The order of frame elements corresponds to the sequence of image frames seen by the observer  4 . For those image carriers  2  which are peripheral in the array, the sequence of frame numbers is modified for example so as to commence with F 5  to F 21 , followed by frames F 1  to F 4 . Such shifting of the frame numbers allows the image carriers to be substantially coplanar and avoids the need for large values of tilt angle A during assembly. 
     In FIG. 8C, the complete image frame number 1 for example will be formed by the composite image formed by viewing the inter-digitated frame elements F1 from each of the image strips  84  through the lenticular member  80 . 
     An alcohol based lubricant is used to allow the lenticular member  80  to be adjusted in position in contact with the image bearing member  83 , the adjustment being carried out until the manufacturing reference symbols  50  are viewable in a viewing direction of 90°. The relative position of the lenticular member  80  and image strips affects the directional properties of the image carrier  2  so that this alignment step during manufacture requires high tolerance. Inevitably however, some residual error may remain. 
     Once the required position has been determined for the lenticular member  80 , a hardening process utilising exposure to ultraviolet light is used to bond the lenticular member  80  to the image bearing member  83  in fixed relationship. This process is repeated for each of the image carriers  2 . 
     The image carriers  2  are then mounted on the rigid panels  64  which in turn are mounted on the support frame  3  in their allotted array positions as shown in FIG.  1 . The observer  4  at the alignment position  9  should be able to see in each image segment  25  provided by the image carriers  2  the alignment reference symbols  40 . For each image carrier  2  where this is not the case, adjustment of the orientation of the image carrier relative to the support frame  3  is necessary and this requires actuation of the adjustable coupling  8  attached to each corner of the panel  64  upon which the image carrier is mounted. 
     The adjustable couplings  8  are illustrated in FIGS. 6A,  6 B and  7 . As shown in FIG.  6 B and in greater detail in FIG. 7, the support frame  3  is formed from a steel box frame to which a number of flanges  60  are mounted, each flange defining an aperture through which a screw studding  61  slidably extends. Each studding  61  has a first end portion  62  which is fixedly secured by a lock nut  63  to the panel  64  upon which the image carrier  2  is mounted. The panel  64  is formed of rigid plywood of sufficient thickness to substantially prevent bending in use. The studding  61  has a second end portion  65  which projects rearwardly from the flange  60 , thereby facilitating adjustment of the separation between the panel  64  and the flange  60 . 
     During the alignment procedure, the panel  64  is adjusted in orientation by an operative until the observer  4  confirms visibility of the alignment reference symbols  40 . 
     The position of the studding  61  relative to the support frame 2 is then secured by tightening locking nuts  66  and  67  on opposite sides of the flange  60 . 
     The second end portion  65  may then be cut so as to no longer project rearwardly of the support frame  3 . The alignment procedure may require adjustment of each of the four adjustable couplings  8  located at corners of the panel. 
     In the above description, a single image frame (number 10) is selected to be the reference frame for alignment purposes. Alternatively, two adjacent image frames in the sequence may be selected for reference purposes and may each be marked with the alignment reference symbols  40  as shown in FIG.  5 A. In FIG. 5A, a series of image segments  25  corresponding to successive image frames are illustrated for a single one of the image carriers  2 . Adjacent reference frames  51  and  52  each include alignment reference symbols  40 . 
     The provision of such multiple adjacent reference frames makes it easier for the observer to recognise the presence of a reference frame and allows greater tolerance in adjusting the position of the panels  64  during onsite alignment. 
     In an alternative embodiment, not all of the panels  64  carry image carriers  2  having directional viewing properties. In FIG. 9 for example, those panels  90  marked with an X do not carry direction dependent image carriers and may simply carry conventional posters with images carrying text or other matter which complements the moving image provided by the direction dependent image carriers  2  occupying the remainder of the display 
     In the example of FIG. 9, image carriers  2   e  and  2   d  have viewing angles B of 90° and 45° respectively when observed during the alignment process described above. 
     In the embodiment of FIG. 1, the size of the display is approximately 10 ft in height and 20 ft in length with a typical value of distance d of 2 ft. The lenticular material is dimensioned to have 22 lenticles per inch. 
     The above described embodiments refer to image carriers in the form of lenticular media. Other forms of image carrier may alternatively be utilised as for example holographic devices or fly-eye lenses. Alignment about both horizontal and vertical axes may then be desirable. 
     In the case of lenticular material, the lenticular axis may in alternative embodiments be aligned horizontally for viewing by passengers moving vertically as in the case of an ascending escalator. 
     The panels  64  may alternatively be formed from a rigid plastics material. 
     Although in general it will be necessary to adjust the coupling  8  on site as described above, the alignment may be pre-set during an alignment procedure carried out at a manufacturing site and the panels then shipped together with the support frame to the actual site for deployment. 
     In the above described embodiments, the images forming the sequence of frames may be produced using animated photographic techniques using still cameras, cine cameras or video cameras. Other techniques may also be used including the use of graphics, either generated by hand or by computer, or any combination of the above.