Conversion of analog images into digital data has become widespread for a variety of applications, including storing, manipulating, transmitting and displaying or printing copies of the images. For example, images captured in photographic media are converted to digital data and stored on compact discs for readout and display as a video image, as exemplified by the KODAK.RTM. Photo-CD system, or reproduced employing various types of color printers. In order to convert the photographic image into a set of digital line data, the film image frame is transported through a film scanning station past, and illuminated in each scan line with a linear light beam of uniform, diffuse illumination, typically produced by a light integrating cavity or integrator.
The light transmitted through the illuminated scan line of the image frame is focused by a lens system on a linear CCD array, image detector which typically produces three primary color light intensity signals for each image pixel that are digitized and stored. The digitized signal values for each scan line may be formatted to a standard for video recording and display and stored on compact disc or magnetic media. Such film scanners take a variety of forms, and the various common aspects of film image frame digitizing, particularly line illumination and linear CCD array-based digitizers, are described in greater detail in commonly assigned U.S. Pat. No. 5,155,596.
In order to perform line scanning of an image frame of photographic negative filmstrips, it is necessary to provide an accurate film transport mechanism to transport a filmstrip into a scanning gate and hold the image frame flat in alignment with a scanning aperture. Typically, the linear CCD array and scanning light beam are stationary so that the light beam illuminates a line of the filmstrip image frame, and a line of digitized data is stored. The scanning gate is incrementally moved or translated line-by-line by a translation stage until the entire image frame is digitized. Then a new image frame is positioned and flattened for scanning and digitizing. Such a scanning and digitizing system for Photo-CD conversion is embodied in the KODAK.RTM. PIW Model 2400 Photo-CD scanner system marketed by the assignee of this application.
In the Model 2400 film scanner, the scanning plane is vertical and the stationary scanner components are oriented horizontally. Negative filmstrips are scanned in a process described more completely in the above referenced, co-pending applications that involves a low resolution pre-scan in a first pass and a high resolution main-scan in a second pass.
The filmstrip scanning gate includes the filmstrip scanning aperture, a clamp for flattening the image frame, the filmstrip drive roller assembly and a sensor for deriving perforation signals for use in re-positioning the image frames for high resolution scanning. It is possible to scan positive color transparencies in mounts, i.e. slides, in the Model 2400 Photo-CD scanner employing common components of the same film scanner station. To do so, it is necessary for the operator to manually replace the filmstrip scanning gate and substitute a slide clamp and scanning gate, in its place on the translation stage. The slides are manually inserted into a clamp so that one side of the slide mount is fitted against a fixed aperture frame. Thus, the slide scanning plane varies with the thickness of the slide mount, requiring re-focus of the scanning lens to the image plane.
The scanning area is left open in this film scanner to allow frequent replacement of the scanning gates, and the scanning station is therefore open to the infiltration of dust particles. The exchange of the scanning gates is tedious and mechanical breakdowns are possible in attempting the exchange. Moreover, the scanning gates are subject to damage when they are carelessly handled or stored when not in use. Finally, the process is slow and productivity in scanning slides is low.
When inserting slides manually, operator fatigue sets in, thus decreasing the number of slides that can be scanned per hour. At best, about seventy-two slides can be inserted manually and scanned per hour by a skilled operator.
A lower resolution scanning and digitizing system of either a negative filmstrip or a positive slide for direct display as a video image is generally disclosed in commonly assigned U.S. Pat. No. 4,858,003. The '003 patent describes a mechanism for introducing and ejecting individual slides from a slide receiver frame in the scanning gate. The slides are held flat with one side against a fixed frame surrounding the scanning window, which defines a first scanning plane, regardless of the thickness of the slide. Negative filmstrips are fitted into an elongated carrier so that-individual image frames are introduced into and aligned with a second scanning plane. The optical system is adjusted to the first and second scanning planes when slides and negative filmstrip carriers, respectively, are presented for scanning. However, there is no provision for adjusting the optical system to the thickness of the slide mount, and the positive film image frame is not always aligned to the first scanning plane due to the varying slide mount thicknesses.
In this film scanner, a conventional Kodak.RTM. Carousel 80 slide tray, or equivalent, is employed to select, position, and eject the individual slides to and from the first scanning plane relying on gravity feed and a conventional ejection mechanism.
In a further Kodak.RTM. RFS 2035 scanner, an auto feed slide device made by MARON, INC. feeds slides from a spring-loaded, horizontal hopper into a slide track. The parade of vertically standing slides move horizontally along their edge and are pushed out of the hopper and through a hopper slot with a shuttle device. The shuttle cannot feed slides from the hopper to the slide gate unless all the slides in the hopper are the same thickness and can pass through the hopper slot. The hopper slot can be manually adjusted for various slide thicknesses, but does not automatically do so. The slides are pushed toward the CCD area array so that one side of the slide mount is forced against a frame.
In the RFS 2035 scanner, the shuttle cycle time is set to insure a slide is present and aligned to the aperture during scanning. The slide device does not communicate with the Rapid Scanner and therefore cannot stop moving slides if any scanner error occurs. The scanned slides are pushed into another spring loaded horizontal hopper after scanning is completed.
Slide projectors made by Eastman Kodak Co., 3M, Inc., Bell and Howell, Inc., and other companies accept either a rotary or box type slide tray from which slides are fed into the projector. Shuttle mechanisms of various types are used to push a slide from the tray. For example, the KODAK.RTM. Carousel slide projectors rely on gravity for the slide to "fall" into the projector and uses a solenoid activated arm to lift the slide back into the tray. A slide projector does not move the slide once the slide has been inserted between the lamp and lens.
In contrast, in the film image scanners described above, it is necessary to move the slide relative to the linear illumination and CCD array and imaging components during scanning. An automatic slide loading and returning apparatus is needed to increase the slide scanning rate from that achieved with operator loading and removing of scanned slides.