A scanner is operative with an imaging system for inducing a mechanical movement of a subject during an optical scanning of the subject to provide an image of the subject. The subject which is in the shape of a card is advanced along a travel path past an optical viewing site by means of a drum, the scanner including a first roller and a second roller which urge the subject against the drum. Initially, the first roller is located between the viewing site and the entry port for receipt of the subject in a first nip between the first roller and the drum. The second roller is positioned fixed on the opposite side of the viewing site. The first roller is supported by an arm which swings about a rotational axis of the drum to vary the spacing between the two rollers. Upon rotation of the drum in a forward direction for induction of the subject, a brake located between the drum and the arm drags the arm and the first roller towards the second roller to facilitate a transference of a leading edge of the subject from the first nip to a second nip defined by the second roller and the drum. Preparatory to optical scanning of the subject which is accomplished during reverse rotation of the drum, the arm swings the first roller away from the second roller to present the viewing site to the optical scanning beam.
Jeffrey E. Beck, Lawrence E. Green William K. Smyth
Original Assignee: Polaroid Corporation
BACKGROUND OF THE INVENTION
This invention relates to a scanner operative in an imaging system for moving a subject past an optical beam to accomplish an optical scanning of the subject and, more particularly, to the use of a drum and a pair of rollers for guiding the subject along a path of travel past a viewing site at the light beam, and wherein a spacing between the rollers can be varied in synchronism with rotation of the drum to facilitate transfer of a leading edge of the subject between rollers prior to presentation of the subject to the light beam for the optical scanning.
Scanners providing for optical scanning of a subject are constructed frequently with mechanical components which move a subject along a path of travel past a viewing site where the subject is scanned by an optical beam. One form of apparatus for accomplishing the movement of the subject includes a drum having a cylindrical surface disposed at the viewing site, and includes two rollers disposed in contact with the drum and located at opposite sides of the viewing site. Rotation of the drum brings successive portions of the subject into the viewing site while pressure between the rollers and the drum secures the subject to the drum to enable accurate positioning of the successive portions of the subject during the scanning procedure.
It may be desirable to construct the scanning apparatus in a manner which admits the subject into the scanner by rotation of the drum in a forward direction for the purpose of ascertaining the physical size of the subject, this being followed by retraction of the subject by rotation of the drum in the reverse direction. The scanning of the subject by the optical beam takes place during the retraction of the subject. Such a scanning procedure is useful because an image processor operative in conjunction with the movement of the subject can be provided with information as to the physical size of the subject prior to the actual optical scanning.
A problem arises in the use of such a scanner in that the spacing between the rollers requires that the subject have a physical form which facilitates advancement of the subject from a first nip between a first of the rollers and the drum to a second nip between the second of the rollers and the drum. Typically, the subject is in the form of a photograph or a picture postcard, such card-shaped subject having a leading edge, a trailing edge, and opposed side edges. The card may be inserted manually into the first nip such that, upon rotation of the drum, the card is drawn past the viewing site to be engaged in the second nip. However, should the leading edge portion of the card be bent or otherwise disfigured by handling by persons viewing the card, or by other causes, there is a chance that the leading edge, during advancement of the subject, may deflect away from the second nip and pass over the second roller rather than through the nip. This would disrupt the scanning procedure.
SUMMARY OF THE INVENTION
The foregoing problem is overcome and other advantages are provided by a scanner incorporating a drum for movement of a subject having the general shape of a card past a viewing site for optical scanning of the subject. Also included within the scanner are a first roller and a second roller providing respectively a first and a second nip with the drum, and being disposed respectively before and after the viewing site with respect to movement of the subject along a path of travel through the viewing site. The scanner is operative to advance the subject initially past the viewing site to ascertain the physical size of the subject prior to the optical scanning, the optical scanning being accomplished during a retraction of the subject along the travel path.
It is an object of the invention to have the two rollers spaced apart at a sufficiently large distance to insure clearance of the optical beam during the generation of a scan line, while providing a sufficiently small distance between the rollers during a passage of a leading edge of the subject from the first nip to the second nip prior to the scanning. In accordance with the invention, this is accomplished by physically moving at least one of the rollers so as to vary the spacing. The variation in spacing provides for a relatively large distance during the optical scanning, and a relatively small distance during the initial advancement of the subject from the first nip to the second nip.
In accordance with a preferred embodiment of the invention, an axis of rotation of the second roller is maintained fixed relative to the travel path of the subject, while the axis of rotation of the first roller is moved so as to provide the variation in spacing. The first roller is carried by an arm which is made to swing back and forth between two fixed stops. The two stops define limits in the swinging movement of the arm, and set corresponding limits on the spacing between the two rollers. Movement of the swing arm is synchronized with movement of the drum by pivoting the swing arm about the drum axis and by connecting the swing arm to the drum by means of a slip clutch or brake. The brake produces a frictional force between the arm and the drum during a rotation of the drum which swings the arm from one of the stops to the other of the stops during an initial stage of rotation of the drum in the forward direction and during an initial stage of rotation of the drum in the reverse direction. Also included within the scanner are two optical sensors for sensing the location of the subject, a first of the sensors being located ahead of the first roller along the travel path, and a second of the sensors being located beyond the second roller on the travel path.
During operation of the scanner, a person places the leading edge of the subject in an entry port of a housing enclosing the scanner, and advances the subject along the path of travel past the first sensor to the first nip. The person then pushes a button to start operation of the scanner. Thereupon, the drum rotates in the forward direction to advance the leading edge of the subject towards the second nip. During the initial stage of rotation of the drum, the arm moves with the drum and swings the first roller towards the second roller to decrease the spacing between the rollers, thereby to ensure a smooth and safe transference of the leading edge of the subject from the first nip to the second nip. The drum continues to rotate while an inner one of the stops holds the arm against further rotation. The subject advances past the second sensor, and continues to advance until the trailing edge is at the first sensor. The length of the subject is now known. The subject is advanced a predetermined distance further to bring the trailing edge within the first nip.
The operation continues with reversal of the rotation of the drum for retraction of the subject. During the initial reverse rotation of the drum, the arm swings the first roller away from the second roller to expose the viewing site to the optical beam. Scanning with the optical beam is initiated. The arm contacts an outer one of the two stops which holds the roller spacing at the maximum position. Further reverse rotation of the drum passes the subject along the travel path between the two roller nips to expose successive portions of the subject to the optical scanning. At the conclusion of the optical scanning, the leading edge of the subject has returned to the first nip to allow either manual removal of the subject from the scanner or a rescan, if desired.