The present invention relates to stereoscopic photographic slide viewers and filmstrip holders therefor. More particularly, the present invention relates to disposable, collapsible stereoscopic photographic slide viewers and disposable filmstrip holders therefor.
Various types of photographic slide viewers are known in the art, including stereoscopic slide viewers, which may be folded or collapsed. Conventionally, slide viewers include a front wall having a light-admitting opening for illuminating a photographic slide, and a rear wall having a viewing aperture which routinely houses a magnification lens. Collapsible viewers are similarly well known, certain designs being adapted for disposable use by virtue of construction from cardboard or like materials. Routinely, some means for insuring cooperation between an inserted filmstrip or filmstrips, which may be disposed in a holder, and the viewer itself are provided, often in the form of a filmstrip receiving channel adjacent to the front wall of the viewer. Light diffusing elements are conventionally incorporating into the light-admitting opening. Examples of these optical viewers and filmstrip holders are those disclosed in U.S. Pat. Nos. 2,543,240, 2,768,554, 2,789,460, 2,933,015, 2,934,999, 2,986,830, 3,019,691, 3,386,194, 3,553,866 and 3,562,939.
While each of the cited patents discloses a viewer suitable for its intended purpose, various of them require elaborate assembly of a foldable blank to yield a finished viewer. Most of the disclosed viewers involve a blank that folds about an axis generally perpendicular to the side walls of the viewer. Such a folding axis results in a relatively complex structure and complex assembly steps for folding and closure of the side walls. Conversely, those of the viewers disclosed in the patents cited above which are of simpler design fail to yield a finished article which possesses sufficient structural integrity to withstand extended use. Yet other designs require the attachment of an independent film-receiving channel to a completed optical viewer.
The filmstrip elements for retaining and positioning the photographic slides for observation disclosed in the cited patents also suffer design deficiencies. In stereoscopic slide systems where two separate slides are used to form the stereographic pair, providing accurate registration between the two photographic slides in order to obtain the stereoscopic effect is particularly troublesome. One conventional approach to solving the registration problem employs a filmstrip holder blank having a pair of longitudinal slots formed therein to receive the photographic filmstrips. In some of these holders, the filmstrips are placed on the blank coincident with the longitudinal slots and the assembly is folded and joined together. In other holders, the filmstrips are inserted after the holder is assembled. While these filmstrip holders are quite simple, none fully solves the problem of registering pairs of stereographic images.
Consequently, the need exists to provide a collapsible, preferably disposable, stereoscopic optical viewer which is of simple physical design, is easily assembled from a blank, and which (although disposable) possesses sufficient structural integrity to allow for extended use. Similarly, the need exists to provide a cooperative filmstrip holder for this stereoscopic viewer which accurately secures and positions stereographic pairs of photographic slides in proper registration for stereoscopic viewing.