Abstract:
A digital still camera for receiving a optical tape cassette having optical tape including an image sensor for capturing an image; focusing an image of a subject onto the image sensor which in response thereto captures such image; a structure for receiving the optical tape cassette; an optical writer for effecting a change in the optical properties of the optical tape. The optical tape is movable into operative relationship with the optical head; the image sensor and the optical writer causes the optical head write to effect changes in the optical properties of the optical tape in accordance with the image captured by the image sensor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to digital still cameras which capture and store images. 
     BACKGROUND OF THE INVENTION 
     Digital still cameras exist that capture an image with a sensor, and store captured images within the digital still camera. Various media storage systems have been developed that permit the storage of one or more of the capture images in a removable media cassette. The cassettes can hold a flexible (“floppy”) or rigid (“hard”) rotating disk having a magnetically or optically sensitive coating. U.S. Pat. No. 5,264,457 is one such system, wherein a digital still camera stores captured still images on a removable optical disk. 
     Digital images are data, and other systems have been disclosed that record data onto writable optical or magnetic tape. Such a method is shown in U.S. Pat. No. 4,541,021. A magnetic tape is stored on two reels, and individual images are recorded in separate areas on the tape. A magnetic head having a plurality of writing elements is used to record digital image information. 
     Conventional photographic film can be considered an optical media that can stores image information onto light sensitive silver halide grains using an optically focused image. Such grains are limited in recording density compared to an optical tape medium. In the Advanced Photographic System (APS) standard, a removable cassette carries a strip of light sensitive film in a light tight cassette. Features on the film strip and in the cassette permit the film strip to be stored on a single spool. The film is accessed by thrusting the film from the cassette, passing the film through an exposing area and taking the film up onto a take-up spool. The film is advanced for reading or writing an image and the film is wound back into the cassette for removal. The APS cassette has a small size than optical tape spool-to-spool systems, and protects the media using a single spool. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an efficient storage arrangement for digital still cameras. 
     This object is achieved in a digital still camera for receiving a optical tape cassette having optical tape comprising: 
     (a) an image sensor for capturing an image; 
     (b) optical means for focusing an image of a subject onto the image sensor which in response thereto captures such image; 
     (c) means for receiving the optical tape cassette; 
     (d) an optical head including write means for effecting a change in the optical properties of the optical tape; 
     (e) means coupled to the optical tape cassette for moving such optical tape into operative relationship with the optical head; and 
     (f) means coupled to the image sensor and the optical head write means for causing the optical head write means to effect changes in the optical properties of the optical tape in accordance with the image captured by the image sensor. 
     It is an advantage of the present invention to provide a digital still camera that can convert images captured by an image sensor into a format which is stored on optical tape. 
     An important feature of the present invention is that images can be captured on optical tape stored in an optical tape cassette which can readily be inserted and removed from the digital still camera. 
     It is another advantage of the present invention to provide an improved removable image storage means for a digital still camera that stores multiple digital images in a optical tape cassette. The optical tape cassette can be conventional that protects optical tape from damage. A single recording element is needed to write to the optical phase change on the optical tape. Surface contact problems are eliminated by non-contact writing to the optical tape. High resolution images are written to each frame by micro-stepping the recording head to create a plurality of partial circular tracks. A plurality of frames permits storage of multiple images. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top sectional view of a digital still camera, an optical tape cassette and a writing mechanism; 
     FIG. 2 is a rear view of the digital still camera of FIG. 1; 
     FIG. 3 is a back view of the optical tape cassette of FIG. 1; 
     FIG. 4 is a magnified portion of the tape of the optical tape cassette of FIG. 3; and 
     FIG. 5 shows a printer using the optical tape cassette of FIG. 3 to print images from the optical tape cassette of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is concerned with digital still cameras which use optical tape. Turning now to FIGS. 1 and 2, an optical tape cassette  12  is inserted in a digital still camera  10  according to the present invention. The optical tape cassette  12  stores optical tape which will be discussed in more detail later. It will be understood that the optical tape cassette  12  can have the form and features meeting the specifications for what is known as the Advanced Photographic System (APS). The APS structure has the advantage of protecting an optical tape  16 . An important feature of the present invention is that images can be captured on optical tape stored in an optical tape cassette  12  which can readily be inserted and removed from the digital still camera  10 . Optical tape cassette  12  has a optical tape cassette spool  14  on which supports optical tape  16 . 
     Optical tape  16  has a film base such as polyethylene-terepthalate (PET) or acetate or similar film support approximated 100 microns thick. An optically written, phase changing material is coated on the surface of optical tape  16  to receive digital data. The phase change media can be an antimony-tin alloy incorporating a third element to facilitate the change from an amorphous to crystalline state, such as set forth in commonly assigned U.S. Pat. No. 4,981,772, the disclosure of which is incorporated herein by reference. Such films can be phase changed with less than 3 milli-watts of energy applied for 50 nano-seconds. 
     Optical tape  16  permits significantly higher recording densities than a silver halide emulsion. Phase change coatings are not sensitive to light energies associated with recording photographic images, and the new optical tape cassette structure is dedicated to digital image storage alone. The use of phase change optical tape  16  as a replacement for a silver halide coating permits writing resolutions of less than 3 microns, compared with greater than 3 micron for photographic emulsions. The phase change optical tape  16  in the preferred embodiment is designed to record 1 micron diameter bits. In addition, the phase change coating does not require the chemical development which is required for readable silver halide coatings. The phase change coating is uniform and write-only within digital still camera  10  to provide a simple writing mechanism. 
     The phase change optical tape  16  is opaque, and data are read from the material using the variable reflectance from written track areas. Writing is done by using a 790 mm laser diode which selectively applies a 5 milli-watt pulse to each write area to change reflectance by up to 22%. A conventional optical feedback and servo maintain the focus on the surface of optical tape  16 . Optical writing is done non-contact, and has reduced sensitivity to environmental contamination and higher writing resolution. 
     For a further discussion of optical tapes and structures for writing on such optical tapes see U.S. Pat. No. 4,815,067. This patent discloses an optical tape, which is wrapped around a drum, and writes the data as a series of linear, helical scan tracks on the tape. Such optical write systems require significant volume to accommodate the drum and write electronics. 
     It is important to protect the surface of optical tape  16 . Optical tape  16  can be configured according to the APS specification and stored on optical tape cassette spool  14  for storage. Optical tape cassette  12  keeps optical tape  16  from contact except when in reading and writing apparatus. When optical tape  16  is secured in digital still camera  12 , it is thrust from optical tape cassette  12  across a writing area  18  and is taken up by a take-up spool  30 . After the initial thrust from optical tape cassette  12 , optical tape  16  is pulled by take-up motor  32 . Common mechanisms in the art for the APS cassette are disclosed in for thrusting and pulling optical tape  16 . In certain cases, a separate motors provide the initial thrust; in other cases, a mechanical coupling permits take-up motor  32  to provide both the initial thrust and take-up drive to optical tape  16 . 
     Images are captured by digital still camera  10  using imager  22  under control of camera controller  24 . Imager  22  is a conventional charge coupled device or a CMOS device, having a plurality of imaging sites in an orderly array configured to convert an image focused on the array by imager optics  20  into a set of data representing a captured image. Imager optics  20  are aligned to imager  22  to focus the image on imager  22 . Image data from imager  22  is transmitted to camera controller  24 , which formats the image data into a format for recording onto optical tape  16 . 
     The take-up motor  32  under the control of camera controller  24  drives the take-up spool  30  to position the optical tape  16  in a recording position under the optical write head  40 . Camera controller  24  actuates a write motor  44  to spin optical write head  40  at 1800 revolutions per minute. Data are recorded as a series of 1 micron bits on 18 millimeter diameter data track 48 Megahertz. The 18 mm track diameter permits a compact writing mechanism, and the 1 micron bits provide a fault-tolerant recording. The rotation speed and track diameter permit writing of pixels in 590 nano-seconds. The write time permits data writing at the relatively slow rate of 1.7 megahertz. The optical write head  40  includes a 790 mm laser diode and associated optics that provide a modulated, focused point of energy represented by light beam  42  onto a data track  48  in response to the stored image in response to camera controller  24 . Optical write head  40  records a bit of data as a 1 micron phase change to the recording surface on optical tape  16 . 
     A single circular data track  48  is preferable and contains 56,000 bits. That amount of data is insufficient for typical imaging applications. A write displacement actuator  46  is attached to write motor  44  and is driven in response to camera controller  24  to displace write motor  44  to create 100 data tracks  48  per recorded image, with each data track  48  displaced 10 micron. Write displacement actuator  46  can be for instance, a piezo motor or electromagnetic stepper motor that is capable of 30 displacements a second that corresponds to 30 rotations per second of optical write head  40 . The 100 tracks are written in 3.3 seconds. The 100 tracks provide 700,000 bytes worth of data, sufficient for many consumer imaging applications. 
     Using sequentially displaced circular tracks of optically written material permits faster data recording than translation systems which must accelerate and decelerate The one hundred 10-micron steps are generated by write displacement actuator  46  stepping 10 microns for every rotation of optical write head  40 . The 100 data tracks  48  are written in 3.3 seconds. Using a single optical write head  40  is significantly less expensive than using multiple magnetic or optical heads. The use of a single optical write head  40  and write displacement actuator  46  to only write to optical tape  16  provides a simple, low cost way for storing digitally captured images in digital still camera  10 . 
     FIGS. 3 and 4 show portions of optical tape cassette  12  and optical tape  16 . In FIG. 4, a close up of data tracks  48  shows the convergence of data tracks  48  at the top and bottom of the recorded area. When the tracks converge, recorded data become unreadable. For a 1 micron pixel track, the acceptable data becomes unreadable when data tracks  48  are spaced 2 microns apart. In this embodiment, data are not recorded at the top and bottom 36 degrees of data tracks. The angle of non-recording can be varied depending on track diameter, bit size and the track spacing of data tracks  48 . In the exemplary embodiment, the angle of lost data reduces the maximum data capacity of 700,000 bytes of data tracks  48  by 20% to 560,000 bytes. 
     Optical tape  16  is designed to support a recording area for each captured image. To differentiate each recording area, one or more alignment perforations  50  can be disposed on optical tape  16  to aid detection of each recording area. In the exemplary case, dual perforations corresponding to the perforations in the APS specification are used to delimit each set of image data. 
     FIG. 5 is a side view of a printer for generating images from optical tape cassette  12 . Optical tape cassette  12  is held in printer  60  and optical tape  16  is thrust out of optical tape cassette  12  and onto take-up spool  30 . An optical read head  62  is spun by read motor  64  to acquire data tracks  48 . Read displacement actuator  66  micro-adjusts spinning optical read head  62  to data tracks  48 . Writing to optical tape  16  in digital still camera  10  using the proposed write mechanism creates irregular data tracks  48 . Conventional processes permit data received from optical read head  62  to be analyzed by printer controller  68  to control displacement actuator  66  and keep optical read head  62  in alignment with data tracks  48 . 
     Printer controller  68  collects the data for a given set of image data and re-constructs the image captured by digital still camera  10 . Printer controller  68  loads the image onto display  70 . Display  70  can be a liquid crystal display or a cathode ray tube of conventional design. Printer optic  72  focuses the image from display  70  onto print media  74 . In this embodiment, print media  74  is conventional silver halide media that is chemically processed after exposure to generate hard copy images from the image data stored in frames of optical tape  16 . Optical tape  16  is sequentially advanced to read each image. Print media  74  is advanced to a new printing area along with the advancement of optical tape  16 , and the process is repeated until all images on optical tape  16  have been printed. 
     The invention has been described in detail with particular reference to a certain preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 digital still camera 
               
               
                 12 
                 optical tape cassette 
               
               
                 14 
                 optical tape cassette spool 
               
               
                 16 
                 optical tape 
               
               
                 18 
                 writing area 
               
               
                 20 
                 imager optics 
               
               
                 22 
                 imager 
               
               
                 24 
                 camera controller 
               
               
                 30 
                 take-up spool 
               
               
                 32 
                 take-up motor 
               
               
                 40 
                 optical write head 
               
               
                 42 
                 light beam 
               
               
                 44 
                 write motor 
               
               
                 46 
                 write displacement actuator 
               
               
                 48 
                 data tracks 
               
               
                 50 
                 alignment perforations 
               
               
                 60 
                 printer 
               
               
                 62 
                 optical read head 
               
               
                 64 
                 read motor 
               
               
                 66 
                 read displacement actuator 
               
               
                 68 
                 printer controller 
               
               
                 70 
                 display 
               
               
                 72 
                 printer optics 
               
               
                 74 
                 print media