Abstract:
An illuminant head assembly for a photographic film image scanner includes a linear light source, preferably a linear array of spectrally distinct illuminant elements combined with a main body having an elongate light conducting channel aligned with the light source and having a light pipe in the light conducting channel, the light pipe having a light diffusion material dispersed therein. The illuminant head assembly in a preferred embodiment includes additional light sources at one or both ends of the linear array and the main body includes additional light channels aligned with the additional light sources, the additional light sources and channels serving as illuminant sources for scanning marginal regions of the photographic film in the film scanner.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Cross reference is made to commonly assigned, copending U.S. Applications, filed concurrently herewith and entitled “ULTRAVIOLET CURABLE RIVETING OF PRECISION ALIGNED COMPONENTS”, and Ser. No. 09/083,604 filed concurrently herewith and entitled “IMAGING APPARATUS FOR A PHOTOGRAPHIC FILM IMAGE SCANNER”. 
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of photographic media image scanners. More specifically, the invention relates to small, low cost scanners adapted for use with personal computers by consumers who wish to generate digital images from processed film stored in a film cartridge as in the case of the Advanced Photo System (APS) film. 
     BACKGROUND OF THE INVENTION 
     Users of personal home computers are increasingly loading digital image files into their computer for viewing, communicating images through the Internet and printing hardcopies on personal color printers. With the introduction of the Advanced Photo System, which stores processed film in the film cartridge, there is a growing interest in being able to scan and digitize images from the stored film for use on the personal computer. Such a scanner should not only be low cost, to obtain broad acceptance as a consumer product, but also needs to be compact in size to be able to fit into a standard disk drive bay on a personal computer. 
     In designing a film scanner for this type of application, it is important to have a design that uses a minimum of parts, is simple to manufacture and yet creates and maintains critical, micro-precision alignment of the photosensor with the film plane in the scan gate. The design of the present invention fully meets these objectives. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention therefore, there is provided an illuminant head assembly for a photographic media image scanner which comprises a linear light source and a main body having a first elongate planar light conducting channel aligned with the linear light source, wherein the light conducting channel includes a planar light pipe therein, the light pipe having a light diffusion material dispersed throughout the light pipe. 
     In accordance with another aspect of the invention, an illuminant head assembly is provided for a film scanner of the type having a scan gate and a pair of support arms on opposite sides of the scan gate, at least one of the support arms having a notch formed therein. In this aspect of the invention, the head assembly comprises a linear light source and a main body having a first elongate planar light conducting channel aligned with the linear light source, the light conducting channel including a planar light pipe therein, the light pipe having a light diffusion material dispersed throughout the light pipe. The main body has opposite side portions adapted to mate with the support arms of the film scanner. At least one of the side portions has a spring finger positioned to mate and lock into the notch in the support arms when the illuminant assembly is mounted into position on the support arms. 
     These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is an isometric view showing a film scanner embodying the present invention; 
     FIG. 2 is a perspective view of a film scanner chassis embodying the present invention; 
     FIGS. 3 &amp; 3 a  partially exploded perspective view of an imaging apparatus and illumination head embodying principles of the present invention; 
     FIG. 4 is a cross section side elevation view of the imaging apparatus and illumination head of FIG. 3; 
     FIG. 5 is an exploded perspective view from above of the illumination head shown in FIGS. 3,  3   a  and  4 ; and 
     FIG. 6 is an exploded perspective view from below of the illumination head shown in FIGS. 3,  3   a  and  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, there is shown a compact film scanner  10  adapted for use with APS film cartridges to convert film images to digital images. The illustrated scanner comprises an outer casing  12  and a front bezel  14  which enclose an internal film drive chassis to be described in more detail below. The chassis is provided with an APS film cartridge chamber  16  for receiving a manually inserted APS film cartridge. A hinged, spring-loaded door  18  includes a locating device  20  which acts to engage the end of the inserted film cartridge (not shown) as the door is closed to aid in properly positioning the film cartridge in the chamber  16 . A latch hook  22  on the door engages an internal latching mechanism  24  to lock the door in the closed position. When it is desired to remove the film cartridge, a door release button  26  is actuated to unlock the latch mechanism allowing the door to spring open. An internal spring loaded mechanism (not shown) within the cartridge chamber forces the cartridge partially outward, allowing the user to grasp and remove the cartridge. 
     Referring to FIG. 2, a general description of the internal film drive chassis  30  of the scanner  10  is presented here. The illustrated chassis comprises a lower frame  32  and an upper plate  34  which, when assembled as shown, define the film cartridge chamber  16 , a film takeup chamber  36  and a film path  38  longitudinally extending between the two chambers. A film drive roller mechanism  40 , including nip roller sets  52  and  53 , is located near the film cartridge chamber  16 . A pair of elongated apertures  41   a ,  41   b  are provided in upper plate  34  to allow access by magnetic read/write heads (not shown) to magnetic data tracks on the magnetic recording layer formed on the APS film as the film is driven along the film path, thereby enabling data transfer to and from the film magnetic layer, in known manner, as part of the film scanning process. Lower frame  32  is provided with depending skirt walls  39  that form a cavity in which is mounted imaging apparatus  50 . 
     One end of the imaging apparatus  50 , as will be seen in reference to FIG. 3, comprises a film scanner end which is snap mounted into a film scanner opening  51  formed in the chassis  30 . The film scanner end is straddled by film drive nip roller sets  52  and  53 . The nip rollers are driven by a film drive stepper motor (not shown) which is directly coupled via drive gear  54  to main drive rollers beneath idler rollers  60  and, via main drive pulley  56 , elastic drive belt  57  and slave drive pulley  58  to slave rollers beneath idler rollers  60 ′. Idler rollers  60  and  60 ′ are held in place against their respect drive rollers by means of retention clamps  61  held under pressure by tension springs  62 . The film scanner end of imaging apparatus  50  includes a pair of upstanding support arms  120  integrally formed on the imaging apparatus  50 . The arms  120  comprise support mounts for an illuminant head assembly  200  (FIG. 3) constructed in accordance with the present invention as will be described more fully later. The other end of the imaging apparatus  50  comprises a sub-housing  64  which encloses a linear CCD photosensor device  66  (FIG.  3 ). The CCD is electrically mounted on a printed circuit board  63  but is physically supported directly from the sub-housing  64  as is more fully described in copending, commonly assigned U.S. application Ser. No. 09/083,359, the disclosure of which is incorporated herein by reference. The elongated housing of imaging apparatus  50  comprises the sole means of support of the CCD from the chassis frame  32 . Spaced apart film guide pins  65   a  and  65   b  are located along one edge of the film path  38  to aid in accurately aligning magnet recording tracks on the APS film with the magnetic read/write heads positioned in the apertures  41   a ,  41   b . The lower frame  32 , upper plate  34  and housing body  72  are molded in the desired configurations out of a suitable, preferably blackened, 30% glass filled polycarbonate material held together by suitable fastening means (not shown), such as screws, snaps, adhesives and the like. The use of this material is highly beneficial in this application because of its stability in the presence of humidity and temperature changes which is particularly important in this configuration wherein the photosensor relies on the housing as the sole means of support from the scanning film plane. 
     Referring jointly to FIGS. 3,  3   a  and  4 , details of the imaging apparatus  50  will be described. Imaging apparatus  50  comprises a hollow, two-piece molded housing  70  having an upper, main body portion  72  and a separable, lower body portion  74 . One end  80  of the housing  70  comprises a film scanning portion and the other end  82  comprises a light sensor portion. The film scanning end  80  includes an elongated light entry slot  83 . As best seen in FIG. 3 a , a pair of film rails  84  are integrally molded onto the end of the imaging apparatus so as to bridge the slot  83  longitudinally in the direction of film path  38  to thereby define a film plane  86 . For this purpose, the film rails  84  are spaced apart only slightly more than the lateral dimension of the negative image on the film strip so as to define a first scanning aperture  83   a  coincident with images on the film. The portions  83   b  and  83   c  extending beyond the rails  84  define secondary scan apertures, each of which is coincident with a respective edge region of the film. The other end  82  of the housing  70  includes sub-housing  64  which encloses linear CCD  66  mounted on printed wiring board  63 . As described in aforementioned copending application Ser. No. 09/083,359, CCD  66  is supported from sub-housing  64  by means of radiation, preferably UV, curable adhesive “rivets” (not shown). Notch  89 , and a similar notch on the far side of sub-housing  64 , allow access by the UV radiation to the adhesive material inside the sub-housing  64  during the curing step. 
     The upper body portion  72  of the housing  70  is formed at right angles between the scanning end  80  and the photosensor end  82  to provide a compact structure enabling mounting of the film scanner  10  in a drive bay of a personal computer. To this end, a mirror  90  is mounted internally against ridges  91  formed inside the upper housing body  72  at a 45° angle to serve as reference datum surfaces for mounting of the mirror  90 . The mirror is held in place against the ridges  91  by means of compressive spring fingers  92  formed on the housing lower body portion  74 . Internally of housing body portions  72  and  74 , about half way between mirror  90  and CCD  66 , a focusing lens assembly  76  is mounted in axial alignment with the light path from the scanning end  80  via the mirror  90  to the photosensor end  82 . The focusing lens assembly  76  includes a focusing lens set  77  positioned within a cylindrical lens mount  78 . The lens mount  78  is provided with a circumferential groove  79  for use in setting the focus position of the lens  76  during assembly and alignment of the imaging apparatus. To this end, the housing upper body portion  72  is provided with an adjustment slot  79   a  extending longitudinally of the housing  70 . During the assembly process, a probe can be inserted through the slot  79   a  into engagement with groove  79  to move the lens mount  78  axially to focus the film plane  86  onto the CCD sensor  66 . Flexible spring fingers with pressure pads  105  are molded into the lower body portion  74  to temporarily hold the lens mount  78  in place after the upper and lower body portions are assembled together until focusing alignment is completed, at which time the lens is permanently retained by adhesive injected through either one or both of the space bridging the spring fingers with the lens mount  78  and the lens adjustment slot  79   a  in the upper body portion  72 , preferably the latter. As is described more filly in copending application Ser No. 09/083,604, (U.S. Pat. No. 6,178,016) the disclosure of which is incorporated herein by reference, Upper and lower body portions  72  and  74 , when assembled together as shown, are held together by U-shaped spring clamp arms  106  on lower body portion  74  snapped over retention tabs  107  formed on upper body portion  72 . 
     Integrally formed on the outer lateral sides of the scanning end  80  of the housing  70  are a pair of support arms  120  that serve the dual functions of supporting the housing  70  on the chassis lower frame  32  and rigidly supporting a illuminant head assembly  200  in precise position over the light entry slot  83 . The support arms are preferably integrally molded on the upper body  72  and are mirror images of each other. The lower portion of the support arm  120  includes a recessed portion  121  at the bottom of which there is provided a ramp  122  leading to the lower retention edge  124 . The upper portions of each of the support arms  120  are provided with a channel  132  and notches  134 , the purpose of which is explained below. As is described more fully in copending application Ser. No. 09/083,604, the chassis lower frame  32  includes a pair of integrally molded, downwardly extending retention hook arms that are springlike and flex outwardly to permit insertion of the scanning end  80  of the illumination housing  70  onto the chassis lower frame  32 . During assembly of the imaging apparatus  50  to the lower chassis frame  32 , the chassis frame  32  is turned upside-down and the scanning end  80  is inserted into the opening  51 . During this snap-in step, the hooks at the end of the retention arms initially fall into the recessed portions  121  and eventually engage the ramps  122  at which point the retention arms are flexed outwardly until the retention hooks grab and hold the housing assembly by engagement with the retention edges  124 . The scanning end of the housing is now rigidly and securely captured between the retention arms. Once this is completed, the lower frame  32  can be turned right side up for addition of the drive roller sets  52  and  53  and the upper chassis plate  34 . As can best be seen in FIG. 2, the upper portions of the support arms extend above the chassis  30 . As will be seen, this allows insertion of an illuminant head assembly  200  into the channels  132  of the support arms. 
     Referring jointly to FIGS. 3-6, the illuminant head assembly  200  of the present invention will now be described. The illuminant head assembly  200  comprises a main body  202 , a planar light pipe  204 , a printed circuit board  206  on which are mounted a linear array of red, green and blue LEDs  206   a  and additional LEDs  206   b  and  206   c  positioned at opposite ends of the linear array  206   a . The linear array provides spectral red, green and blue illuminant for scanning of image areas on the film. The additional LEDs serve as respective sources of light for reading of bar code data (LED  206   b ) and for sensing of reference perforations in the film (LED  206   c ). Preferably, LED  206   b  emits in the red spectrum. However, since Dmin density of the film is almost transparent in the red spectrum, LED  206   c  is selected to emit in another color spectrum such as green or blue. A heat sink panel  208  is mounted on the opposite side of the circuit board from the LEDs  206   a - 206   c . An apertured panel  207  is mounted over the LEDs on the circuit board and is provided with an elongated aperture  207   a  aligned with the linear LED array  206   a  and two smaller apertures  207   b  and  207   c  aligned with LEDs  206   b  and  206   c , respectively. Panel  207  serves as a dam to retain a clear silicone sealant disposed in each of the apertures  207   a - 207   c . The circuit board  206  also carries a connector  212  providing power connections to the LEDs from a microcontroller (not shown). 
     The main body  202 , made of a suitable highly reflective, white polycarbonate material, is provided with an elongated, planar light channel  214   a  into which light pipe  204  is inserted. Light pipe  204  is preferably made from a clear polymethylmethacrylate material loaded with a diffusion material such as barium sulfate at loadings of about 0.1% to about 1.0% by weight and preferably about 0.25% by weight. The particle size of the barium sulfate ranges between about 5-20 microns. The balancing of the interaction of the length of the light pipe, the loading of barium sulfate and the particle size of the barium sulfate allow for a diffuse light output at the bottom outlet of the elongated light channel  214   a  without the need for any special surface finish on the light pipe or the addition of a separate diffusion component. Thus the barium sulfate loaded light pipe  204  serves as the sole light diffusing agent for exposure of the LED light sources to the film being scanned. Smaller side channels  214   b  and  214   c , which do not have light pipes therein, serve to convey the illumination from LEDs  206   b  and  206   c , respectively, to the bar coded data and reference perforations along the longitudinal edges of the film. The sides  215  of the main body  202  are shaped to fit into the channels  132  of the previously described support arms  120 . Pointed crush ribs  216 , which engage the edges  132   a  of the channels  132 , ensure a tight fit of the body sides  215  in the channels as well as align edge surfaces  215   a  to edge surfaces  132   c  of the channels  132 . By dimensioning and controlling, during manufacture, the position of surface  215   a  to the elongate light channel  214   a , the alignment of the elongate light channel  214   a  to the elongate light entry slot  83  is maintained without subsequent adjustment. 
     Sides  215  of the main body are also provided with locking tabs  218  which engage notches  134  in the support arms to rigidly lock the head assembly into the support arm structure. The locking tabs  218  are integrally molded as part of the main body. The length width and depth of the locking tabs are such that, during assembly, the tabs deflect to allow insertion then spring back into position and contact the notches  134  preventing any movement up and out of the channels  134 . This action maintains alignment of surfaces  217   a  and  217   b  (FIG. 6) to surfaces  132   b  at the bottom of the channels  132 . The parts of the head assembly are easily snapped together by slipping end  220  of the printed wiring board under a capture hook  222  formed on the main body  202  and rotating the printed wiring board down until the under surface of the printed wiring board rests on the upper surfaces of support pads  232 ,  233  and  234 . Aperture panel  207  is provided with a semicircular shaped notch  235  which mates with the semicircular shaped support pad  232 . Support pad  232  and notch  235  serve to initial locating means for assembly of the light sources to the main body. Support pad  233  is provided with a diamond shaped locating pin  226  and support pad  234  is provided with a circular locating pin  227 . Each of the pins mate with corresponding locating holes  228  on the circuit board. As such, both pins serve to set the alignment of the LEDs  206   a ,  206   b  and  206   c  to the elongate light channels  214   a ,  214   b  and  214   c  during assembly. When the board is fully rotated into position on the support pads, snap locking hooks  224  on the main body engage mating locking holes  230  in the printed wiring board to securely hold the board in place on the main body. The arrangement described is a simple, practical self-aligning mounting arrangement for attaching the head assembly  200  in a secure and rigid manner to the imaging apparatus  50 . 
     It will be appreciated from the foregoing description that what has been described is an illuminant head assembly of simple and compact design that is provided with snap lock features that facilitate rapid assembly and that precisely and rigidly positions the LED light elements in place over the scanning aperture  83  of the imaging aperture without the requirement for additional fasteners. The use of an elongated light pipe with diffusion material in the light pipe simplifies the cost and complexity of the head design by eliminating the need for a separate diffusion element at the outlet of elongated channel  214 . Additionally, the incorporation of spectrally discrete, e.g. red, green and blue, separate illumination elements enables independent adjustment of the spectral components of the film scanning illumination. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
       10  film scanner 
       12  outer casing 
       14  front bezel 
       16  film cartridge chamber 
       18  spring-loaded door 
       20  locating device 
       22  door latch hook 
       24  door latching mechanism 
       30  film drive chassis 
       32  lower frame 
       34  upper plate 
       36  film takeup chamber 
       38  film path 
       40  film drive roller mechanism 
       41   a,b  read/write head apertures 
       50  imaging apparatus 
       51  film scanner opening 
       52  nip roller set 
       53  nip roller set 
       54  drive gear 
       56  main drive pulley 
       57  elastic drive belt 
       58  slave drive pulley 
       60 , 60 ′ idler rollers 
       61  retention clamps 
       62  retention springs 
       63  printed circuit board 
       64  sub-housing 
       65   a,b,c  film guide pins 
       66  linear CCD photosensor 
       70  imaging apparatus housing 
       72  upper body portion 
       74  lower body portion 
       76  focusing lens assembly 
       77  focusing lens set 
       78  lens mount 
       79  lens mount groove 
       79   a  lens adjustment slot 
       80  film scanning end 
       82  photosensor end 
       83  elongated light entry slot 
       84  film rails 
       86  film plane 
       89  sub-housing notch 
       90  mirror 
       91  mirror mount ridges 
       92  compressive spring fingers 
       102  lens mount collar segment 
       105  pressure pads 
       106  cantilevered retention arm 
       107  retention tabs 
       120  support arms 
       121  recesses 
       122  ramp 
       132   a,b,c  channel 
       134  locking notch 
       200  illuminant head assembly 
       202  main body 
       204  planar light pipe 
       206  printed circuit board 
       206   a  linear R, G, B LED array 
       206   b,c  red LEDs 
       207  apertured panel 
       207   a,b,c  apertures 
       208  heat sink panel 
       212  connector 
       214   a,b,c  light channels 
       215  body sides 
       216  crush ribs 
       218  locking tabs 
       220  end of printed wiring board 
       222  capture hook 
       224  locking hooks 
       226 - 7  locating pins 
       228  alignment holes 
       230  locking holes 
       232 - 4  support pads 
       235  locating notch