Film frame registration and correction by means of film prerecorded track

Automatic metering and registration, between exposures, relative to an exposure station in a still camera of a next available unexposed frame of a perforationless filmstrip is achieved by reading frame number identifying cues, including stop point flags, magnetically encoded on the film. Continuation of registration is confirmed and, if necessary, corrected automatically in preparation for the next exposure by reading the same cues and comparing a stored cue for a desired next frame with a cue read from a registered unknown frame. The direction of film movement for misalignment correction is set based on the frame number comparison.

The present invention relates generally to film frame metering and 
registration in a still film camera; and, more particularly, to automatic 
film frame initial registration and pre-exposure correction using film 
prerecorded frame specific identifying cues. 
BACKGROUND OF THE INVENTION 
In a still camera, the importance of achieving accurate metering and 
registration of each image frame with the exposure gates in the 
frame-to-frame advance between exposures of a film strip has long been 
recognized Proper frame alignment with the picture-taking optical axis not 
only ensures correct frame-to-frame spacing and avoidance of overlap in a 
series of exposed images, but also correctly positions the film frame for 
properly locating exposure data and the like relating to a specific frame 
and recorded adjacent thereto on the film at the time of exposure for 
later reference in producing prints from the developed negatives. Harvey 
U.S. Pat. No. 4,639,111, for example, discloses marginal encoding by 
optical means adjacent a frame at the time of exposure of frame specific 
field of view identification information in a tele/pan camera. 
Cameras incorporating an automatic wind-up drive mechanism for the 
frame-to-frame film transport between supply and take-up reels have means 
for stopping the advance of the film at a point of registration of the 
next available frame with a camera exposure station in alignment with the 
picture-taking optical axis. A common practice of achieving accuracy of 
metering and registration is to utilize film resident, frame correlated 
marginal fiducials, such as single or multiple perforations per frame, 
which can be detected to determine the correct positioning for the next 
frame. One system uses a single perforation per frame film and a 
mechanical claw or pawl that detects the perforation corresponding to the 
next frame and disengages the wind-up motor drive when that perforation 
reaches a desired stopping point (see, e.g., Beach U.S. Pat. No. 
3,186,322). In another system (see, e.g., Takahashi U.S. Pat. No. 
4,431,292), the film travel distance is tracked by counting the number of 
multiple perforations per frame which pass by a given point, such as over 
a toothed sprocket wheel in engagement therewith. 
Once registration is achieved, it is desirable to provide means to maintain 
such registration until commencement of the next exposure. In the absence 
of such provision, the film is subject to creep out of registration due to 
vibration or physical shock forces exerted on the camera body or residual 
torque forces in the drive mechanism. For cameras designed to operate with 
a single perforation per frame film, registration can be maintained by 
continuing to engage the pawl at its stopping point through the 
perforation and into a slot located in the camera wall or film cartridge, 
until the next exposure. For sprocket wheel drives, the wheels can be 
locked to hold the frame in registration. It is a desirable objective to 
be able to achieve initial frame registration, as well as pre-exposure 
reassurance of continuation of registration, even for films that contain 
no marginal perforations at all and, thus, for which such pawl and 
sprocket drive systems are inadequate. 
It is known to provide periodic film frame correlated fiducials or cues 
other than perforations for various post-exposure purposes. Yamada U.S. 
Pat. No. 3,622,235, for example, discloses a framing adjustment device 
which responds to a transparent optical locator signal spaced at periodic 
intervals along a marginal edge of a motion picture for automatically 
repositioning the picture during projection. In Staudacher U.S. Pat. No. 
4,198,136 a motion picture film projector responds to interrupt-transport 
frame markings to signal a transition between those images which are to be 
sequentially displayed and those which are to be displayed as still 
images. Butler U.S. Pat. No. 4,215,920 shows marginal frame specific 
fiducials in the form of optically scannable binary representations of the 
sequential numerical identifications of successive frames. And, Williams 
U.S. Pat. No. 2,674,009 shows the use of marginal magnetic cue marks in 
the form of microscopicly thin metal disks which can be detected by 
magnetic scanning heads for the purpose of instituting an event or series 
of events (control or variation of printing light intensity, etc.) when a 
predetermined point or points are reached during the course of travel of a 
motion picture film. 
The provision of a magnetic recording track on a still camera roll film for 
the purpose of storing various frame specific data relating to image 
exposure information (such as the photographing day, exposure conditions, 
photographing place, photographer, data for photographic laboratory use, 
and the like) is disclosed in Ohta U.S. Pat. No. 4,613,911. Ohta suggests 
the use of such a track as a recording medium for providing the camera 
with information regarding film sensitivity or the number of exposed or 
unexposed frames. There is, however, no disclosure or suggestion of using 
such a magnetic track for wind-up motor control to achieve initial frame 
registration, or for confirming and, if necessary, correcting a previously 
achieved alignment in preparation for a next exposure. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus and a method for accomplishing 
the frame-to-frame film transport metering and registration procedure, 
suitable for use with a marginally unperforated film strip, utilizing 
frame specific identifying cues respectively prerecorded in correlation 
with the frames at periodic intervals along a film strip. 
The invention also provides an apparatus and a method for automatically 
rechecking a previously set frame registration in order to confirm and, if 
necessary, correct the alignment of a desired frame with an exposure gate, 
prior to making the next exposure. 
In one aspect of the invention, a camera having a drive means for 
automatically transporting a film strip, after loading in the camera and 
completion of a previous image frame exposure cycle, between supply and 
take-up positions to bring a next unexposed frame into registration with 
an exposure gate, includes a sensor for reading a frame specific 
identifying cue correlated with the next frame and located in proximity 
thereto, and means responsive to said sensor reading for stopping the film 
transport at a location in which the next frame is aligned at an exposure 
station with the exposure optical axis. In another aspect of the 
invention, means is also provided for storing the frame specific 
identifying cue associated with the initially registered next frame, and 
for reading the frame number of the frame in line with the exposure 
station just prior to making the next exposure and for comparing the cue 
of that unknown frame with the stored cue in order to confirm that the 
desired next exposure frame has remained in registration. Means is 
provided for correcting the alignment of the desired next frame to bring 
it back into registration, if it has been displaced. 
A preferred embodiment of the invention, discussed in greater detail below, 
utilizes a magnetic read head to read frame specific identifying cues 
respectively correlated with each frame and spaced at frame length 
intervals along the film which take the form of binary representations of 
successive frame numbers magnetically prerecorded on a magnetic strip 
running lengthwise along one edge of the film. Film metering and 
registration is initially controlled automatically by wind-up drive means 
initiated upon completion of the previous frame exposure, with the next 
frame alignment stopping point determined by detection of the arrival of a 
stopping point identifier at the read head. Circuitry including a 
microcomputer responds to initiation of preparation for a next exposure 
cycle to compare the identification number of the frame nearest the 
aperture station with the previously stored identification number of the 
desired next exposure frame to assure their identity. If they are not the 
same, the microcomputer activates the film transport drive to make an 
adjustment in frame position to correct registration prior to undertaking 
the next exposure. 
A frame metering and registration, and subsequent preexposure registration 
confirmation and correction method and apparatus in accordance with the 
invention is particularly useful for ensuring registration for the rapid 
exposure and high speed transport of a succession of image frames of a 
roll film having no perforations.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The principles of the apparatus and method of the invention are described 
with reference to an exemplary implementation of a film frame metering and 
registration system in a still film camera that cooperates with a film 
strip F having a plurality of image frames n-1, n, n+1, etc., and a 
corresponding plurality of frame specific, film resident identifying cues 
exp n-1, exp n, exp n+1, etc., respectively correlated with the frames, 
and spaced at periodic intervals along the strip. 
As shown in FIG. 1, the film F is loaded in a lightproof body 10 of a still 
camera for movement between a supply reel 12 located in a film cartridge 
14 and a take-up reel 15 spaced laterally therefrom across an exposure 
station or window 16, shown in dashed lines. The station 16 is located in 
alignment with an optical axis O--O' so that when a frame n of the film F 
is positioned in registration with the station 16 it can be exposed by 
light passing from a subject to be photographed through a lens L when the 
exposure gate E is actuated, such as in response to full depression of a 
shutter release button 17. After exposure of the frame n, it is desired to 
move the loaded film F between the reels 12 and 15 for a distance 
corresponding to one frame interval to bring a next available unexposed 
frame n+1 into registration with the exposure station 16, and so forth, 
for a series of successive film exposures. Unlike conventional film 
transport mechanisms which control frame-to-frame film transport using 
perforation frame determining fiducials, however, the film frame metering 
and registration apparatus of the shown embodiment avoids the use of 
sprocket wheels and pawls, and acts in other ways to effect the advance of 
film F which does not have the usual marginal perforations. 
The unperforated film F has a magnetic recording layer or strip 18 applied 
to at least one edge surface thereof in the longitudinal direction of the 
film F. The strip 18 is prerecorded at frame length intervals 19 along 
film F with magnetically encoded data in binary form corresponding to the 
sequential frame numbers exp n-1, exp n, exp n+1 of the respectively 
adjacent successive image frames n-1, n, n+1, etc. It is preferable that 
the prerecorded cue data be in a usual identifiable numerical sequence 
such as 1, 2, 3, 4, etc. However, it is enough that the frame identifying 
data be sufficiently frame specific so that a particular frame in a given 
plurality of frames can be separately identified from adjacent frames in 
the same plurality. 
For the example shown in FIG. 1, image frame n-1 is identified by a 
marginal recording exp n-1 (shown as a series of dashes) recorded along a 
length interval 19a of the film F corresponding to the length of frame 
n-1, plus an associated desired marginal spacing increment 21. A 
neighboring strip portion 19b to the right of portion 19a has data exp n 
recorded thereon (shown as a series of alternating dots and dashes) for a 
frame length correlated with the frame n shown located in registration 
with the exposure station 16. To the right of the data exp n for the frame 
n is located data exp n+1 (shown as a series of dots) prerecorded in a 
frame length 19c correlated with the frame n+1. This scheme is continued 
at a frame length interval 19d for frame n+2, and so on for successive 
frames in a given plurality of frames, preferably for the entire length of 
exposable film, each cue location being recorded with a cue that is 
specific to identify and distinguish a particular frame in the plurality. 
Frame registration film transport stop point identifiers or flags 22 can 
be either separately recorded or incorporated within the code format of 
the precoded frame numbers themselves in accordance with known computer 
related magnetic media drive technology. 
For the shown embodiment, a cue sensor in the form of a magnetic read head 
25 is positioned within the camera body 10 at a location to be in a data 
reading position adjacent the magnetic strip 18 when the roll film F is 
loaded. The read position of the head 25 is laterally offset from the 
optical axis O--O', and thus the center of the frame exposure station 16, 
by a distance D as seen in FIG. 1. Accordingly, the respective frame 
registration stop points 22 and frame specific cue prerecording portions 
19 are likewise displaced the same distance with respect to the frames 
n-1, n, n+1, etc., so that the flag 22 for a particular frame will be 
located at the sensor read head 25 when that frame is in its position of 
correct registration with the exposure station 16. FIG. 1 shows frame n in 
proper registration for exposure at the station 16 when the flag 22b at 
the trailing edge of portion 19b of magnetic strip 18 is disposed adjacent 
the head 25. 
Circuitry, including a microcomputer 28 and a memory 29, is electrically 
interfaced with the sensor 25 and with a film transport drive assembly 
which comprises a bidirectional drive motor M. The motor M is connected 
for control by a drive circuit 30 and is mechanically coupled to drive the 
reels 12 and/or 15 to advance the film F from an exposed frame n in the 
forward direction toward a next unexposed frame n+1 (direction of arrow) 
in response to an exposure completion signal received by the microcomputer 
28 from an exposure circuit 31, or retract the film F, if necessary, in 
the opposite (backward) direction from frame n toward frame n-1. 
Transport in the frame-to-frame advance of the film strip F between 
exposures is effected by activating the motor M under control of the 
microcomputer 28 to drive the spool of the one of the reels 12, 15 in 
rotation about its axis which will wind the strip F around the 
circumference of its associated spool spindle to move the film in the 
desired direction. The other spool may be left freewheeling to rotate 
about its axis in response to drawing of the film therefrom. For the 
arrangement shown, frame-to-frame advance occurs by driving the cartridge 
reel 12 to wind the film F to the left by successive single frame length 
intervals back into the cartridge 14, with the film being retrieved into 
the cartridge directly after exposure. It is to be understood, however, 
that the same principles apply in systems wherein frame-to-frame advance 
occurs in a direction from the supply reel 12 onto the take-up reel 15, 
such as by driving the take-up reel 15 and letting the supply reel 12 
rotate freely. 
Frame advance is initiated after completion of exposure of a frame n by 
receipt of a signal from the exposure circuit 31 indicating the end of 
actuation of the shutter mechanism of exposure gate E. The motor M will 
normally be operated to drive the film F in a direction (i.e. forward 
direction) to bring the next available unexposed frame n+1 toward the 
exposure station 16. The stopping point of the film F will occur when the 
sensor 25 detects the stopping point flag 22c (shown as the trailing edge 
of the strip portion 19c) which is correlated with the number 
identification cue exp n+1 for the frame n+1. This will place frame n+1 in 
the position shown now occupied by the frame n in FIG. 1, and ensure its 
registration with the exposure station 16. By dispensing with mechanical 
interaction of pawls and sprocket wheels with the film margins, a smooth 
and rapid frame-to-frame film advance is achievable. It will of course be 
appreciated, that other flags may be placed ahead of the stopping point 
flag 22 or other provision made to slow the film transport speed prior to 
reaching the stopping point. 
In accordance with a feature of the invention, means are provided for 
automatically confirming and, if necessary, correcting the previously 
achieved alignment of a frame n of the film strip F relative to the 
exposure station 16 to ensure that registration has been maintained during 
any delay that occurs between the time of initial registration and the 
time that the exposure gate E is actuated to expose that frame. 
FIG. 2 indicates a position of the frame n of a film F following a delay in 
which a vibration or shock to the camera body 10 has caused the film F to 
creep by a distance d in the backward direction, thereby taking the frame 
n out of registration with the shutter station 16 before exposure. As 
shown in FIG. 2, film movement relative to the camera exposure station 16 
has resulted in the prerecorded data portion 19b being correspondingly 
shifted so that the registration stop point flag 22b is no longer aligned 
with the sensor 25. 
In accordance with the invention, upon initiation of a next exposure cycle, 
during preexposure setting of camera parameters, pretravel of release, 
ranging, lens cover opening, etc., sensor 25 acts under control of the 
microcomputer 28 to detect any shift in the stop point 22b. The 
microcomputer 28 responds to a detected shift by actuating the motor M to 
wind the film F in which direction is necessary to bring the desired cue 
22b back to its previously established registration position in front of 
the read head 25. When no frame is in registration during the confirmation 
process, the microcomputer 28 controls the drive circuit 30 as indicated 
in FIG. 3 to retract the film F in the backward direction to bring an 
unknown frame (in this case frame n-1) into registration with the station 
16 and the associated frame number cue (in this case exp n-1) is read by 
the sensor. The shown embodiment looks for registration of the next left 
frame; however, it is understood that seeking to the right may also be 
done. 
A comparison is then conducted between the unknown frame cue (i.e., exp n-1 
and the desired frame cue (i.e., exp n) previously stored in memory 29 
(FIG. 1) at the time of initial registration of the frame n. If the two 
coincide, correct registration of the desired frame is confirmed and the 
exposure gate E is enabled to complete the exposure cycle. If the two do 
not coincide, the motor M is activated, as indicated in FIG. 4, to drive 
the film F in the direction necessary, as determined by the comparison, 
until the stop point cue 22b is adjacent the head 25, at which time the 
exposure gate E is then reenabled. 
The logic to accomplish the registration and automatic confirmation and 
correction processes may be implemented in a software or hardware embedded 
program in accordance with the flow chart rendition thereof shown in FIG. 
5. As shown by blocks 40, 41, 42, upon detection of a signal indicating 
completion of an exposure cycle by the circuit 30, the exposure gate E is 
disabled and the microcomputer 28 signals the drive circuit 30 to actuate 
the motor M in the forward direction to advance the next available 
unexposed frame toward the exposure station 16. As the film F advances, 
read head 25 reads the next frame number cue from the track 18 (block 43) 
and the process continues until the stop point 22 for that frame reaches 
the read head 25 (block 44). The motor M is then stopped (block 45) with 
the next frame in proper registration with the exposure station 16, and 
the frame number read from track 18 is stored for later reference in the 
memory 29 (block 46). 
When the next exposure cycle is to be initiated and preexposure is 
signalled (block 47), such as when button 17 is partially depressed to the 
dot-dash position indicated in FIG. 1, track 18 is again read by sensor 25 
(block 48) in a sequence of steps to confirm that the frame whose frame 
number was stored in memory 29 as a reference is still in registration 
with the station 16. If no stop point 22 is located at the sensor head 25, 
the film F is driven in a given direction (backward in the shown 
embodiment) until an unknown frame stop point cue is adjacent the head 25 
(blocks 49,50) and, thus, an unknown frame is in registration with the 
exposure station 16. The read identification number of the unknown frame 
is then compared with the stored reference number of the desired next 
frame and, if the same are equal, identity of the unknown frame with the 
desired frame is confirmed and the gate is enabled for completion of the 
exposure (blocks 51, 52). If identity does not exist, the film F is driven 
to a next stopping point where the comparison is repeated until the 
correct registration of the desired next frame has been restored. The 
direction in which to drive the film F is determined based on whether the 
compared unknown frame number is lower or higher than the stored reference 
frame number (blocks 53, 54, 55). 
A film frame metering and registration system in accordance with the 
foregoing description provides a mechanism readily adaptable for the 
smooth high speed frame-to-frame advance between exposures in a still 
camera useful to achieve a rapid succession of sequential exposures, such 
as needed in sport photography or the like. As already indicated, the 
prerecordings in the frame correlated positions 19 can be formatted to 
give cues in addition to stopping points 22 as, for example, to give cues 
to one or more reductions in film transport speed from an initial high 
speed prior to searching the stopping point. 
Those skilled in the art to which the invention relates will understand 
that the foregoing detailed description is intended to be merely exemplary 
and not exclusive, and that various substitutions and modifications may be 
made to the described embodiment without departing from the spirit and the 
scope of the invention as defined by the claims below. It is noted, for 
example, that the reference to a bidirectional motor M, above, is intended 
to include a single motor M which may be rotated in forward or reverse 
directions, two separate motors each rotatable in its own opposite 
direction, or a motor which cooperates with gearing, clutching or other 
mechanism to provide film drive in either the forward or backward 
direction as selected.