FILM SCANNER

Abstract: A film scanner is disclosed which comprises a dynamic film gate (11). The film gate (11) includes a pair of rollers (12) for supporting the film (16) at an imaging station (18) and a pair of drive belts (20) which clamp the film (16) against the rollers (12). The belts (20) are driven to advance the film (16) through the imaging station (18). An integrating cylinder (41) located above the film gate (18) produces a line of light on the film (16), and light transmitted through the film is imaged onto a linear CCD image sensor (23).

Description: FILM SCANNER This invention relates to a film scanner, and more particularly, to such a scanner having a dynamic film gate. In various types of imaging apparatus, a photographic film must be clamped in a workstation while a particular operation is performed on the film. In certain types of apparatus, for example, film scanners, the film must be held extremely flat in order for an image on the film to be recorded properly. One problem in maintaining the film flat is that photographic film has a natural curl due to an emulsion coated on one side of the film. In one known type of film gate, a film is clamped against a flat platen, and the film and platen are moved relative to an image sensor to scan the film. In the use of such a film gate, the film must be clamped and undamped for each film frame, and the film platen must be moved to a home position after each frame is scanned. Such a technique requires a significant number of moving parts, and it is relatively slow. Further, devices of this type are likely to scratch the film, and the motion of the platen introduces the possibility of vibrations into the system. It is also known to use a rotary film gate, as disclosed, for example, in U.S. Pat. No. 4,281,351. U.S. Pat. No. 4,281,351 discloses apparatus for the line-by-line optical scanning of a film. In order to reduce friction of the film adjacent the scanning region, rollers or endless belts support the film at positions on the film outside of the film frames. A disadvantage of the apparatus disclosed in this patent is that the only means for maintaining the film flat in the scan region is through the tension in the film. Thus, any irregular motion in the drive system is transmitted to the film, and this tends to produce blurring in the scanned image. Further, the arrangement disclosed in the patent is not suitable for use with film strips which are too short to be mounted on the feed rollers. It is an object of the present invention to overcome the problems in the prior art discussed above and to provide an improved film scanner. In accordance with the present invention, there is provided a film scanner comprising: means for supporting a film at an imaging station; belt means for urging film against the support means, the belt means contacting the film along an edge thereof; illumination means for producing a line of light on the film as it is contacted by the supporting means and the belt means; and means for driving the belt means to advance the film relative to the illumination means. In one embodiment of the present invention, the film scanner comprises a pair of rollers which support the film as it passes through an imaging station. The film is pressed against the rollers by a pair of belts, and the belts are driven to advance the film through the imaging station. An integrating cylinder provides a line of light on the film at the imaging station, and light transmitted through the film is imaged onto a CCD image sensor. An advantage of the present invention is that the film is advanced at a constant rate through the imaging station. The film can be driven at a selected scan speed and at a fast frame—to—frame advance, since the same motion serves to scan the film and advance the film to the next scan area. Drive belts provide for dynamic clamping of the film in the imaging station, and use of the belts eliminates the need for tensioning the film in the imaging station. Further, the belts are arranged to wrap the film around a portion of the rollers in a direction to remove the inherent curl of the film; this makes the film very flat in the imaging station, and as a result, imaging optics having a smaller depth of field can be used. The illumination device is located above the film so that line illumination can be provided across the entire width of the film image. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: FIG. 1 is a perspective view of the film scanner of the present invention; FIG. 2 is a front elevational view of the film scanner shown in FIG. 1; FIG. 3 is a side elevational view of the film scanner shown in FIG. 1; and FIG. 4 is a schematic view illustrating the shape assumed by the film as it passes through the imaging station. With reference to FIG. 1, there is shown a film scanner 10 which is constructed in accordance with the present invention. Film scanner 10 comprises a dynamic film gate 11 which is adapted to support a film 16 as it is moved through an imaging station indicated at 18, an illumination source 40 which is adapted to provide a line source of light at station 18, an imaging lens 21, and a linear CCD image sensor 23. Film gate 11 comprises a pair of rollers 12 and a pair of drive belts 20 which are adapted to clamp the film 16 against rollers 12 as the film is advanced through station 18. As shown in FIG. 3, each of the rollers 12 includes an outer cylindrical portion 14 and an inner cylindrical portion 15 of a reduced diameter. Each roller 12 includes a stub shaft 17 which is journalled in support structure (not shown) in the scanner 10. The rollers 12 are spaced such that the film 16 rides on the portions 15. Belts 20 are made of a length sufficient to provide a wrap angle a. (FIG. 4) of about 60° on a roller 12. Each of the belts 20 is trained around idler pulleys 30, a roller 12, and a shaft 24 which is connected to a drive motor 26 (FIG. 3). Motor 26 can be, for example, a DC servo motor of a type well known in the art. Each belt 20 is relatively narrow so that it only contacts an edge of the film 16 and does not extend into the image area. The belts 20 can be constructed of a fiberglass core, or similar non—stretch material, which is coated on both sides with a urethane or similar high friction material. When film is fed to a nip 27 (FIG. 1) defined by rollers 12 and belts 20, a pinching action on the film 16 will capture the film 16 and pull it into the interface; the film 16 will be driven in the direction of arrow 29 as shaft 24 and rollers 12 move in the direction of arrows 31 and 33, respectively. The film 16 will be advanced a constant rate of speed which is controlled by the speed of motor 26. Illumination source 40 is mounted above the film 16 and is adapted to provide a line of illumination at the imaging station 18. Light transmitted through the film is imaged onto linear CCD sensor 23 by means of lens 21. The illumination source 40 includes an integrating cylinder 41 and a lamp (not shown) such as a 24V DC tungsten halogen lamp, type ELC, sold by General Electric Co. The integrating cylinder 41 can be, for example, an integrating cylinder as disclosed in U.S. Pat. No. 4,868,383, to Kurtz et al., granted September 19, 1989. The integrating cylinder disclosed therein produces a line of diffuse illumination which has a uniform linear and angular distribution. Image sensor 23 can be a linear CCD image sensor such as a No. KLI—5001A/B sensor, manufactured by Eastman Kodak Co., Rochester, New York. The image sensor can also include an array which consists of three separate photodiode linear arrays for capturing red, green, and blue signals. The image sensor 23 must be precisely located relative to scanning station 18, and to this end, it can be supported in a mount as disclosed in U.S. Patent No. 4,972,079. Signals from image sensor 23 can be processed in a well known manner in order to produce an electronic record of the images on film 16. In the operation of film scanner 10, a film 16, for example, a 35 mm film, is threaded into the gate 11, and the film is advanced therein by means of the belts 20 bearing on rollers 12. As the film 16 is advanced, the image is scanned in a page scan direction, and the line scan is performed by the clocking of the individual image elements in the sensor 23.

Claims: Claims : 1. A film scanner comprising: means (12) for supporting a film (16) at an imaging station (18); belt means (20) for urging film against said supporting means (12), said belt means (20) contacting said film (16) along an edge thereof; illumination means (40) for producing a line of light on said film (16) as it is contacted by said supporting means (12) and said belt means (20); and means (24,26) for driving said belt means to advance the film (16) relative to said illumination means (40). 2. A film scanner, as defined in claim 1, wherein said supporting means includes roller means (12). 3. A film scanner, as defined in claim 2, wherein said roller means includes two rollers (12) which are spaced to contact opposite edges of said film (16). 4. A film scanner, as defined in claim 1, wherein said belt means includes two belts (20) which are spaced to contact opposite edges of said film (16). 5. A film scanner, as defined in claim 3, wherein said belt means includes a first belt (20) which is operable to hold film (16) onto one of said rollers (12). 6. A film scanner, as defined in claim 5, wherein said belt means includes a second belt (20) which is operable to hold film (16) onto the other of said rollers (12). 7. A film scanner, as defined in claim 1, wherein said drive means includes a rotatably driven element (24) which contacts said belt means (20). 8. A film scanner, as defined in claim 2, wherein said roller means (12) is driven by said belt means (20). 9. A film scanner, as defined in claim 1, wherein said illumination means (40) is located adjacent said belt means (20). 10. A film scanner, as defined in claim 9, wherein said illumination means (40) includes an integrating cylinder (41). 11. A film scanner, as defined in claim 10, wherein said cylinder (41) is located within said belt means (20). 12. A film scanner comprising: a pair of spaced-apart rollers (12) for supporting a film (16) at an imaging station (18); belt means (20) for urging the film against said rollers (12), said belt means including a first endless belt (20) which urges one edge of said film (16) against one of said rollers (12) and a second endless belt (20) which urges an opposite edge of said film (16) against the other of said rollers (12); illumination means (40) for producing a line of light on said film at said imaging station (18), said line of light extending between said edges, and said light being transmitted through said film; means (24,26) for driving said belt means (20) to advance the film (16) relative to said illumination means (40); an image sensor (23) for receiving light transmitted through said film (16); and means (21) for imaging said light onto said sensor (23). 13. A film scanner, as defined in claim 12, wherein each of said rollers (12) includes a first portion (14) of one diameter and a second portion (15) of a diameter less than said one diameter (14), and said film (16) is supported on said second portions (15). 14. A film scanner, as defined in claim 13, wherein each of said belts (20) is adapted to extend around a predetermined circumferential portion (α) of a roller (12) in order to clamp said film (16) against the roller (12) in said portion. 15. A film scanner, as defined in claim 14, wherein said circumferential portion (α) extends around an angle of about 60°.

Inventors: WAKEFIELD EDWARD HENRY, WAKEFIELD, EDWARD, HENRY
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1991
Main classification: H04N3
IPC codes: H04N1, H04N3