U.S. patent application number 10/669984 was filed with the patent office on 2004-03-25 for system and method for registering motion picture film.
Invention is credited to Behrns, Don P., Goodhill, Dean K., Safreno, Ty.
Application Number | 20040057015 10/669984 |
Document ID | / |
Family ID | 23912616 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040057015 |
Kind Code |
A1 |
Goodhill, Dean K. ; et
al. |
March 25, 2004 |
System and method for registering motion picture film
Abstract
A system and method for registering the frames of film with
respect to an aperture in a motion picture projector. A
registration reference mark is applied to each frame corresponding
to the location of the frame on the film. When the film is
intermittently stopped in the projector's film gate, the
registration reference mark is read to determine the location of
that frame relative to the immediately preceding frame. If the
frame in the gate is misregistered, the gate is moved to correctly
register the frame prior to projection. By properly registering the
frames, the "jitter" and "weave" associated with conventional
projectors is eliminated and resolution of the projected film image
is enhanced.
Inventors: |
Goodhill, Dean K.; (Los
Angeles, CA) ; Safreno, Ty; (San Luis Obispo, CA)
; Behrns, Don P.; (Los Angeles, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
23912616 |
Appl. No.: |
10/669984 |
Filed: |
September 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10669984 |
Sep 24, 2003 |
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10242037 |
Sep 10, 2002 |
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10242037 |
Sep 10, 2002 |
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09481602 |
Jan 12, 2000 |
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6450644 |
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Current U.S.
Class: |
352/27 |
Current CPC
Class: |
G03B 1/42 20130101; G03B
21/52 20130101; G03B 21/46 20130101; G03B 9/10 20130101; G03B 1/44
20130101 |
Class at
Publication: |
352/027 |
International
Class: |
G03B 031/02 |
Claims
What is claimed is:
1. A method of registering frames of film with respect to an
aperture in a motion picture projector, comprising: a. applying
registration information to the film corresponding to the location
of the frames on the film; b. moving the film through the projector
and intermittently stopping the film frame-by-frame with respect to
the aperture; c. reading the registration information associated
with each frame prior to projection to determine the location of
the frame with respect to the aperture; d. determining the amount
of correction that is necessary to achieve proper registration of
the frame with respect to the aperture prior to projection; and e.
moving the frame into proper registration with respect to the
aperture prior to projection.
2. A system for registering frames of film in a motion picture film
projector having a gate for receiving film during intermittent
advancement of the film through the projector, comprising: a. an
actuator connected to the gate that is adapted to move the gate
relative to the aperture; b. a sensor that reads registration
information on the film associated with each frame to determine the
location of the frame with respect to the aperture prior to
projection; and c. a registration processor connected to the sensor
and the actuator that is adapted to determine the amount of
movement that is necessary to move the gate and thus the frame into
proper registration with respect to the aperture.
3. The system of claim 2, wherein the actuator comprises a
piezoelectric motor.
4. The system of claim 2, wherein the actuator comprises a
piezoelectric motor flexure stage.
5. The system of claim 2, wherein the actuator comprises a moving
coil motor.
6. The system of claim 2, wherein the registration information
applied to the film comprises a registration reference mark that is
read by the sensor.
7. The system of claim 6, wherein the registration reference mark
comprises a plurality of geometric shapes.
8. The system of claim 7, wherein the geometric shapes comprise at
least a circle and square.
9. The system of claim 8, wherein the geometric shapes further
comprise a triangle.
10. The system of claim 2, wherein the registration information is
applied to the film in a space between adjacent frames on the
film.
11. The system of claim 2, wherein the sensor comprises a
light-based sensor.
12. The system of claim 11, wherein the light-based sensor
comprises an LED array and a CCD array.
13. The system of claim 12, wherein the light-based sensor further
comprises a mirror for reflecting light transmitted from the LED
array onto the CCD array.
14. The system of claim 2, further comprising redundant sensors
adapted to read redundant registration information associated with
each frame.
15. The system of claim 2, wherein the registration processor
controls operation of the sensor and processes the registration
information for each frame to determine the location of successive
frames relative to the aperture.
16. The system of claim 15, wherein the registration processor
further determines the amount of film misregistration from one
frame to the next and generates an output signal that is delivered
to the actuator, and wherein the output signal commands the
actuator to move the gate such that the frames are correctly
registered with respect to the aperture.
17. The system of claim 16, wherein the output signal is a voltage
based signal.
18. The system of claim 16, wherein the output signal is a current
based signal.
19. The system of claim 2, wherein the actuator is configured to
move the gate in increments as small as approximately 0.000002
inches in about one millisecond or less.
20. The system of claim 2, wherein the actuator and gate are
configured such that the actuator can move the gate at least 0.006
inches in both the X direction and the Y direction.
21. A device for registering motion picture film in a projector,
comprising: a. a gate for receiving film and intermittently
stopping frames of the film relative to an aperture, wherein the
gate is moveable with respect to the aperture; b. an actuator
connected to the gate, wherein the actuator is configured to move
the gate relative to the aperture; and c. a processor that commands
the actuator to move the gate relative to the aperture based on
registration information on the film adjacent to the frames.
22. Motion picture film, comprising: a. a length of motion picture
film having a plurality of projectable images on the film, wherein
each image is defined by a frame; and b. registration information
applied to the film adjacent to a plurality of the frames, wherein
the registration information is located in the same position
relative to each of the frames.
23. The motion picture film of claim 22, wherein the registration
information comprises information that is capable of being read by
a sensor.
24. The motion picture film of claim 23, wherein the registration
information comprises a plurality of different shapes that are read
by a light-based sensor.
25. The motion picture film of claim 24, wherein the plurality of
different shapes comprises at least a circle and a square or
rectangle, and wherein the diameter of the circle is equal to the
width of the square or rectangle.
26. The motion picture film of claim 25, wherein the plurality of
different shapes further comprises a triangle adjacent to the
circle and the square or rectangle.
27. The motion picture film of claim 22, wherein the registration
information is located outside the frame.
28. The motion picture film of claim 26, wherein the registration
information is located in the space between adjacent frames.
29. The motion picture film of claim 22, wherein redundant
registration information is applied to the film for each frame.
Description
[0001] This is a continuation of application Ser. No. 10/242,037,
filed on Sep. 10, 2002, which is a continuation of application Ser.
No. 09/481,602, filed on Jan. 12, 2000, which is now issued as U.S.
Pat. No. 6,450,644, issued on Sep. 17, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to motion picture
film registration techniques and, more particularly, to a system
and method for correctly registering frames of motion picture film
during the projection process to provide enhanced resolution of the
projected images.
[0004] 2. Description of the Related Art
[0005] Film projectors and the motion pictures they project have
amazed and delighted audiences around the world for over a century.
However, the term "motion pictures" is really a description of an
illusion, for the pictures do not actually move at all. To the
contrary, still images, typically 24 per second, must be projected
in as static a manner as possible. This is not a simple proposition
given the fact that in one minute 1,440 images or "pictures" are
presented to the viewer. The illusion of motion is created by the
differences between succeeding still images and is dependent upon
the precise positioning or "registration" of these images with
respect to an aperture in the projector.
[0006] One of the problems associated with existing motion picture
film projectors occurs when succeeding images are positioned in
slightly different locations in the projector's aperture. When this
happens, a given point on those images will appear to be blurred,
even if individual images show that point to be perfectly sharp. Of
course, individual images in motion pictures are not viewed
separately, but, rather, over time in rapid succession.
[0007] In the context of motion picture technology, the word
"register" (the root for "registration") is not formally defined.
Perhaps the closest applicable general definition is provided in
the Random House Dictionary Of The English Language, Second Edition
Unabridged (1983): "(11b) Print. Correct relation or exact
superimposition, as of colors in color printing." In the art of
motion pictures, however, "registration" has a slightly different
meaning. Motion picture photographic "registration" means the
repeated placement of each image, one after another, in as precise
a manner as possible throughout the entire chain that comprises the
system of cinema imaging. As described below, there are several
steps in this chain, starting with creation of the image and ending
with its projection.
[0008] At the outset, film is moved through the camera
intermittently and positioned by "registration pins" in precisely
the same place, called the "aperture". In this way, a succession of
areas called "frames" are exposed to light, thus creating "latent
images" that become a visible image after development. Because the
"frame" defines the rectangular space on the film that is occupied
by the "image," the terms "frame" and "image" shall be used
interchangeably and synonymously with each other herein.
[0009] During editing and other post-production processes, images
created in the camera are modified when appropriate. Then they are
duplicated for distribution through a process that involves
intermediate steps. These intermediate steps include contact
printing of an inter-positive ("IP"), and using that IP to make
inter-negatives ("IN").
[0010] In the next step, the IN is transferred onto release print
film via high-speed contact printing, which is an unregistered
process that operates at up to 17.times.-play speed, or faster. The
"release prints" made by this process are distributed to theaters
for projection. When the release prints are projected, the frames
are intermittently positioned in a fixed position relative to the
"aperture" of a projector's "gate." Light from a lamphouse in the
projector projects the images onto a screen for viewing by an
audience.
[0011] Registration is not a factor in creating high resolution
still photographic images. The photographer and viewer of a still
photograph are concerned only with a single image recorded and
printed from a single piece of film containing that image. However,
registration is a crucial component required for high resolution
imaging in motion pictures. As noted above, motion pictures are
dependent on thousands of images seen one after another in rapid
succession. Thus, in motion pictures, the collective impression of
resolution or sharpness is highly dependent upon the repeatable,
accurate positioning in the projector of every image that is
photographed and projected.
[0012] "Resolution" is another term for sharpness or clarity. In
motion pictures, resolution is a function of several factors, which
include: (1) lens sharpness; (2) film negative granularity; (3)
repeatable, accurate registration of the film in the camera's
aperture; (4) repeatable, accurate registration during exposure of
film IP's, IN's, and release prints; (5) film print granularity;
and (6) repeatable, accurate registration of the release print in
the projector. Of all these factors, nos. 4 and 6 are the most
severely flawed in current motion picture technology. According, a
long-felt need has existed for a system and method that can address
these factors and thereby provide more precise registration and
enhanced resolution across the entire system of motion picture
imaging.
[0013] The final measurement of motion picture resolution must be
made by analysis of a projected image at 24 frames per second
(standard) or faster, not by inspection of individual frames as
with still photography. Ideally, the registration precision of the
projector should match that of the camera. Unfortunately, that is
not now and never has been the case. As noted above, motion
pictures cameras use highly precise, mechanically activated
"registration pins" to achieve and maintain final and repeatable
film positioning from frame to frame. On the other hand, theatrical
projectors use registration techniques that are, at best,
considerably inaccurate about both the longitudinal and lateral
axes. This inaccuracy gets progressively worse as various
mechanical parts in the projector's intermittent movement and gate
are subjected to normal wear over time. But the primary cause of
this inaccuracy is the 100-year-old design of the projector
movement itself. Projector gates, intermittent sprockets, and the
"Geneva" mechanism that turns these sprockets in a
pause-then-rotate cadence have failed to evolve in any meaningful
manner.
[0014] As described more fully below, projector registration in its
present state is primarily achieved by means of the friction
provided by spring tension in the projector gate, acting against
the film, which is advanced by the rotational movement of the
intermittent sprocket. This intermittent sprocket is typically
positioned about 2 to 4 inches or more below the aperture and pulls
the film through the gate. When the intermittent sprocket stops
pulling the film, the spring tension in the gate acts on the film
sandwiched within it and friction causes the film to stop. But this
is a highly passive design that lends itself to imprecision. For
example, gate friction varies due to adjustable spring tension.
Moreover, the film print itself exhibits variable "slickness" due
to waxing, wear and other environmental factors. Therefore, each
succeeding frame simply cannot be registered in the exact same
location as the preceding frame.
[0015] During projection, inaccurate longitudinal registration of
the film produces an up and down film movement called "jitter,"
while inaccurate lateral registration produces a side-to-side film
movement called "weave." Both jitter and weave are greatly
magnified by the extreme enlargement of projection. At a minimum,
jitter and weave in any noticeable amount will result in a
softening and blurring of detail and impair the resolution of the
projected images.
[0016] The use of larger images on film, as with the various 70 mm
formats, creates a sharper image on screen simply because less
enlargement is required to fill the screen.
[0017] Consequently, the jitter and weave of the image is less
noticeable with 70 mm release prints. However, the higher cost and
the lack of 70 mm projectors in most theaters renders the various
70 mm formats moot as an option, except in a few "special venue"
theaters. Indeed, if jitter and weave in the 70 mm projectors could
be reduced or eliminated, the projected image would be even
sharper.
[0018] Current theatrical motion picture projectors inherently
create jitter and weave because they lack any kind of positive film
registration technology. Furthermore, the high-speed printing
process used to manufacture most IP's and IN's and thousands of
release prints distributed to theaters creates yet another level of
jitter and weave in itself.
[0019] In order to understand the problems that this causes when
the film is finally projected, it is necessary to understand how
motion picture images are photographed. In a typical camera
movement, film is driven from the camera magazine by a constant
speed sprocket, which maintains an upper loop of film. A pulldown
claw driven by an eccentric cam-like movement penetrates the film's
perforations and pulls the film into precise registration in the
camera's aperture. The upper loop, much of which is taken up for
this operation, is replenished by the continuous rotation of the
constant speed sprocket. Next, with the film stopped, the
registration pins penetrate adjoining perforations in the film,
while simultaneously the pulldown claw retracts and begins moving
back into position to take hold of the next length of film to be
pulled down. Meanwhile, as the registration pins penetrate the
film's perforations, their tapered teeth gently move the film into
precise position. The registration pins are restricted to a simple
back and forth movement and are locked in a predictable, repeatable
accurate mechanical design. Also, the registration pins are located
immediately adjacent to and often surrounding the portion of the
film to be exposed. For these reasons, they are very accurate and
allow the camera to expose a continuous succession of images in
precise registration.
[0020] In a typical projector movement, however, there is very
little similarity to camera movements. Although a typical projector
has a constant speed sprocket that feeds film to maintain an upper
loop, all similarity to cameras ends at that point. Unlike a
camera, the film's advance into the projector gate is provided by a
powerful pull from an intermittent sprocket positioned below the
projector gate's aperture, through which light is passed during
projection. The projector gate is a gently curved, spring tensioned
"trap" that exerts friction on the film and thus acts in opposition
to the motive force that pulls film through it. When the
intermittent sprocket stops pulling the film through the gate, the
friction exerted by the gate stops the film. Unfortunately, this
mechanism cannot duplicate the precise registration provided by
cameras for several reasons.
[0021] First, the gate's friction, as applied to the movement of
the film, is adjustable and varies from projector to projector.
Higher friction provides heightened opposition to the film's
intermittent movement, but simultaneously demands that more torque
be applied to overcome this static friction for frame-to-frame
advance. This can cause film stretching or, in extreme cases,
breakage. Also, gate friction that is too high may cause so much
film resistance that the teeth of the intermittent sprocket will
deform the perforations in the film during pulldown, which leads to
deteriorating registration in every subsequent showing of the film.
But if gate friction is reduced too much, the film may continue
moving slightly after the rotation of the intermittent sprocket
stops. In these cases, the film overshoots the proper location in a
way that is prone to be erratic from frame-to-frame.
[0022] Second, film prints are often waxed or otherwise provided
with a slick surface in order to slide through the gate with
reduced resistance and/or to help prevent stretching of the film.
This prevents the film from stopping in the gate in precisely the
same place from one frame to the next.
[0023] Third, film often shrinks or expands due to age, humidity
and other factors. Thus, the distance from the image in the
aperture to the intermittent sprocket necessarily varies. The
effect of such shrinkage or expansion increases with greater
lengths of film. Therefore, the distance between the aperture and
the intermittent sprocket includes further margin for error.
[0024] Fourth, the mechanism that advances the intermittent
sprocket is driven by a "Geneva" movement, which is subject to
wear. The Geneva movement is well known and comprises a "Maltese"
cross-shaped device, with slots cut into each cross. A rotating
cam-like device turns within it, with a pin that engages the slots
in the cross. This produces a pause-then-rotate intermittent
movement, which is then applied to a shaft connected to the
intermittent sprocket that pulls the film through the aperture from
below the gate. Although the Geneva movement turns in an oil bath
that is designed to inhibit metal-to-metal contact, like any
mechanical device, there is always some wear. This wear causes
slight imprecision in the application of the motive power to the
connecting shaft, the intermittent sprocket and the film itself,
which is then magnified by the act of projection.
[0025] Fifth, the slightest bend in the shaft connecting the Geneva
movement to the intermittent sprocket will impart an eccentric
movement to the intermittent sprocket, so that instead of rotating
in a circular movement, it will rotate in a slight oval-shaped
pattern. This in turn exacerbates any imprecision in the Geneva
movement, which, in turn, impairs resolution of the projected
image.
[0026] Finally, release prints are made on non-registered,
high-speed printers that introduce additional imprecision by
placing the images in different positions with respect to the film
edges and perforations. In other words, this non-registered
printing process microscopically misplaces frames in such a way
that they are no longer located in a precise, repeatable
relationship to the edges and perforations of the film.
[0027] Certain special-purpose, pin-registered projectors have been
built for a type of special effects cinematography called "process
shots," but these projectors were not designed for theatrical
projection. Instead, they were designed to achieve precise
registration with the assumption that they would be showing prints
made on some type of relatively slow, highly accurate printer,
rather than release prints duplicated by high-speed, non-registered
contact printers.
[0028] Two new projector designs have recently appeared for 70 mm
special-venue applications that provide some equivalent of pin
registration. The Mega-Systems projector has two intermittent
sprockets, placed both above and below the aperture. A curved,
one-sided gate mechanism is brought into intimate contact with the
film by sliding back toward it. This design is intended to allow
for film shrinkage or expansion while still providing positive
registration. The Linear Loop projector by IWERKS seeks to achieve
the equivalent of positive pin-registration by using blasts of
controlled, compressed air to advance film across a parallel set of
linear sprockets placed on either side of the projector's aperture.
These linear sprockets, which are analogous to railroad tracks,
hold the film's perforations as succeeding frames are advanced by
means of a "standing wave" of film that rolls across the sprockets,
propelled by the air blast. Though these two projectors provide
registration that duplicates, somewhat, the positive registration
found in cameras, they do not address the misalignment created by
non-registered high-speed contact printers.
[0029] In another area of motion picture technology called
"telecine," where motion picture images are transferred to
videotape, various methods have been developed to achieve a stable
image. While there are differences in the devices and methods used
to achieve image stabilization in these telecine-based systems
(sometimes called "electronic pin registration"), they all have one
thing in common--they all seek to stabilize the film image by
reference to the film edges and/or perforations on the film. This
is acceptable in telecine, because telecine uses "low contrast"
prints that are made at 180 feet per minute in "wet gate" contact
printers. Thus, the image position on low contrast prints used in
telecine bears a relatively accurate relationship to the film's
edges and/or perforations. However, the technique of using the
edges and/or perforations on release prints as a reference to
stabilize the film image wrongly assumes that the images on the
film are correctly registered with respect to the edges and
perforations, as they are in the camera or with prints made on
relatively slow, highly accurate printers. As discussed above,
theatrical release prints are made on non-registered contact
printers at speeds often in excess of 1,500 feet per minute. This
high-speed, non-registered printing process microscopically
misplaces frames in such a way that they are no longer located in a
precise, repeatable relationship to the edges and perforations of
the film.
[0030] While various types of electronic pin registration and/or
image stabilization methods and technologies work well when
scanning prints made on registered printers, they cannot correct
for improper placement of the image relative to the edges and/or
perforations of the film. As discussed above, such improper
placement is a common occurrence due to errors engendered in
high-speed contact printing of theatrical release prints.
Consequently, electronic pin registration has limited value for
theatrical projection. In fact, none of these systems were designed
with that purpose in mind. Rather, they all declare to be directed
toward the process of scanning film to video or digital electronic
form.
[0031] Accordingly, there has existed a definite need for a system
and method that can achieve precise image stabilization and
enhanced resolution for theatrical motion picture film projection,
that corrects for misplacement of images on the release print film
(compared to the original negative), and which does not rely on the
edges of the film or its perforations to do so. The present
invention satisfies these and other needs and provides further
related advantages.
SUMMARY OF THE INVENTION
[0032] The present invention provides a system and method for
precisely registering frames of film with respect to an aperture in
a motion picture film projector. The projector comprises a gate for
receiving and guiding film during intermittent advancement of the
film through the projector. In accordance with the invention,
information is applied to the film corresponding to the location of
the frames on the film. The information associated with each frame
is read by a sensor prior to projection to determine the location
of the frame with respect to the aperture. If the frame is
misregistered with respect to the aperture once the film stops in
the gate, an actuator moves the film relative to the aperture to
achieve the correct registration. By repeatedly registering the
frames in the exact same location with respect to the aperture, the
resolution of the projected motion picture image is substantially
and advantageously enhanced.
[0033] In conventional projector designs, the gate is connected to
the projector in a fixed manner relative to the aperture. In
accordance with one embodiment of the present invention, however,
the gate is adapted to move relative to the aperture. Movement of
the gate relative to the aperture is provided by an actuator
connected to the gate. In one form of the invention, the actuator
comprises a piezoelectric motor or a moving coil motor. Both of
these types of motors can be used in conjunction with a flexure
stage to provide the required gate movement. The actuator
preferably is configured to move the gate in increments as small as
approximately 0.000002 inches in about 1 millisecond or less,
depending on the frame rate. In addition, the actuator and the gate
are configured such that the actuator can move the gate at least
about 0.006 inches in both the X direction and the Y direction.
[0034] The information necessary to move the gate by the required
amount is provided by the registration information applied to the
film. In one form of the invention, the registration information
comprises a registration reference mark that is capable of being
read by a sensor. The registration reference mark preferably
comprises a plurality of different shapes that are read by the
sensor. In one aspect of the invention, the plurality of different
shapes comprises at least a circle and a square or rectangle, where
the diameter of the circle is equal to the width of the square or
rectangle. In addition, a triangle may be positioned adjacent to
the circle and the square or rectangle to provide further
registration information.
[0035] The registration information is applied to the film in the
same location relative to each frame. In this regard, the
registration information preferably is located on the film in an
area outside the frame, and, most preferably, the registration
information is located in the space between adjacent frames.
Furthermore, if desired, redundant registration information may be
applied to the film for each frame.
[0036] The sensor that reads the registration information on the
film may take a variety of forms. In one embodiment, the sensor
comprises a light-based sensor. For example, the sensor may
comprise an LED array on one side of the gate that transmits light
through the registration reference mark on the film. The
transmitted light is received by a CCD array on the other side of
the gate. If desired, one or more mirrors may be used to reflect
the light transmitted from the LED array onto the CCD array. In
addition, redundant sensors may be used to read redundant
registration information associated with each frame.
[0037] A registration processor controls the operation of the
sensor and processes the registration information for each frame to
determine the location of each frame with respect to the aperture.
The location of these frames is determined by reading the
registration information associated with each frame. The
registration processor then uses the registration information to
compare the location of a frame in the gate relative to the
immediately preceding frame. If a frame is not properly registered
with respect to the aperture in the same place as the immediately
preceding frame, then the registration processor calculates the
amount of film misregistration. Based on the amount of
misregistration, the registration processor generates an
appropriate output signal that is delivered to the actuator. This
output signal commands the actuator to move the gate in such a
manner that the frame is correctly registered relative to the
immediately preceding frame. In this way, each of the frames will
be registered in the same location relative to the aperture. The
output signal may comprise a voltage-based signal, a current-based
signal, or other suitable signal configured to move the actuator
and thus the gate.
[0038] Other features and advantages of the present invention will
become apparent from the following detailed description, taken in
conjunction with the accompanying drawings, which illustrate, by
way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The accompanying drawings illustrate the invention. In such
drawings:
[0040] FIG. 1 is a diagrammatic representation of the six degrees
of freedom for defining any location in three-dimensional
space.
[0041] FIG. 2 is a schematic view of film travelling through a
motion picture projector.
[0042] FIG. 3 is another schematic view of film travelling through
the projector, showing the maximum amount of roll of the film in
the projector gate.
[0043] FIG. 4 is an elevational side view of a conventional motion
picture film projector, showing film travel through the
projector.
[0044] FIG. 5 is a schematic view showing the position of the
projector gate relative to an aperture of the projector.
[0045] FIG. 6 is a schematic view of a piezo crystal according to
one embodiment of the present invention.
[0046] FIG. 7 is a graph depicting the relationship between applied
voltage and the length of the piezo crystal.
[0047] FIG. 8 is a schematic illustration of a piezoelectric motor
flexure stage, shown partly in cut-away section, used to move the
projector gate and correct for film frame misregistration, in
accordance with one embodiment of the invention.
[0048] FIG. 9 is a schematic illustration of a moving coil motor
used to move the projector gate, in accordance with another
embodiment of the invention.
[0049] FIG. 10 shows a registration reference mark according to one
embodiment of the invention.
[0050] FIG. 11 is a section of film showing the location of a
registration reference mark between the frames of the film.
[0051] FIG. 12 shows a matrix CCD array according to one embodiment
of the invention.
[0052] FIG. 13 shows a line CCD array according to another
embodiment of the invention.
[0053] FIG. 14 is a rear elevational schematic view of a projector
gate and associated projector structure embodying the novel
features of the present invention.
[0054] FIG. 15 is a side elevational view of the projector gate and
associated projector, taken along the line A-A of FIG. 16.
[0055] FIG. 16 is a front elevational view of the projector gate
and associated projector structure, similar to FIG. 14.
[0056] FIG. 17 shows selected portions of a registration reference
mark according to one embodiment of the invention.
[0057] FIG. 18 shows additional aspects related to the registration
reference mark.
[0058] FIG. 19 shows another selected portion of the registration
reference mark, including reference lines for calculation of frame
misregistration.
[0059] FIG. 20 is a schematic illustration of one alternative for
illuminating the registration reference marks.
[0060] FIG. 21 is a schematic illustration of another alternative
for illuminating the registration reference marks.
[0061] FIG. 22 is a block diagram showing a registration processor
and other related processor components in accordance with the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] In accordance with the present invention, film frame
misregistration is detected and corrected on a frame-by-frame basis
to ensure precise registration of each frame with respect to the
projector's aperture. By registering each frame in the same
position with respect to the aperture, the resulting motion
picture, comprised of these individual projected images, has
dramatically enhanced resolution. Proper frame registration is
achieved, and misplacement of images on release print film is
corrected, by making corrective film movements while the film is
intermittently stopped in the projector gate. As explained below,
this precise film registration and the resulting enhanced film
resolution is provided by making corrective film movements in only
two directions, corresponding to the X direction and the Y
direction.
[0063] In this regard, and by way of further background, any type
of motion can be described with reference to six degrees of
freedom. As shown in FIG. 1, these six degrees of freedom comprise
three degrees of linear movement commonly known as X, Y and Z, and
three degrees of angular movement commonly known as yaw, pitch and
roll. Because film is flat, and because of the way it is captured
in the projector gate, there can be no discernable yaw or pitch
movements of the film. Although there is some thermal shock
defocusing of the film in the Z direction, due to the heat absorbed
by the film from the projector's lamphouse, which causes the film
to deflect slightly, any movement in the Z direction is considered
to be a very minor aspect of misregistration, as compared to the
misregistration of the film in the X and Y directions.
[0064] Further, while it is possible to correct for possible
misregistration due to roll, the magnitude of this movement is also
considered to be relatively small. In this regard, as shown in FIG.
2, film 10 that travels through the gate is mechanically guided
past the aperture 12 over a long distance compared to the width of
the film. In most projector designs, the film 10 is guided by
mechanical guide means 14, such that the film has the capacity to
deviate in the gate in the X direction by only about 0.003 inches.
As shown in FIG. 3, film 10 that moves by this amount would result
in a maximum roll component of only about 0.049 degrees. This small
angular rotation component is relatively insignificant and is
unlikely to have any noticeable impact on resolution. Thus, the
necessity and cost of correcting it is subject to question.
[0065] In view of the foregoing, and the fact that jitter and weave
are the most significant factors that contribute to film
misregistration, the system and method of the present invention is
designed to detect and correct film misregistration in the X
direction (weave) and the Y direction (jitter). It should be
understood, however, that the principles of the invention can be
applied to detect and correct film misregistration in other
directions as well. Therefore, the description that follows should
not be construed as limiting the invention to correct
misregistration in the X and Y directions only.
[0066] Referring to FIG. 4, a typical 35 mm projector 16 has two
constant speed sprockets, comprising a feed sprocket 18 and a
hold-back sprocket 20, located on opposite sides of a film gate 22.
An intermittent sprocket 24 is also located between the gate 22 and
the hold-back sprocket 20, approximately two to four inches (or
more) below the gate. The intermittent sprocket 24 pulls the film
10 intermittently, frame by frame, through the film gate 22 in a
well-known manner. Slack in the film 10, in the form of loops of
loose film 26 and 28, is provided, respectively, between the feed
sprocket 18 and the film gate 22 and between the intermittent
sprocket 24 and the hold-back sprocket 20 to prevent film
breakage.
[0067] The film gate 22 also includes an aperture plate 30 with an
aperture 32 designed to be in optical alignment with a projection
light source 34 (such as a lamp house) on one side of the gate and
a lens 36 on the other side of the gate. A rotating shutter blade
(not shown) between the aperture 32 and the lamp house 34 blocks
light from the lamp house during pull down and registration of the
film 10 and permits passage of light through the aperture upon
registration of a frame 40 with respect to the aperture. The
shutter blade or counter-rotating blades are rotated in a well
known manner by a shutter motor (also not shown).
[0068] The gate 22 serves several functions during the projection
process. One of these functions is to mechanically guide the film
10 through the projector 16. In this sense, the gate 22 acts as a
mechanical alignment system, whose purpose is to control film
movement in the X direction or "weave." The weave present in
today's projectors primarily occurs as a result of variations in
film width and mechanical deviations in the gate width.
[0069] Another purpose of the gate 22 is to apply friction to the
film 10, which stops the film in the gate when the intermittent
sprocket 24 stops pulling the film. In this context, the gate 22 is
mechanically similar to a constant drag system and must have drag
components large enough to quickly stop the film 10. Although the
film 10 does not create a large inertial force, because film is a
light material and there is only a small amount of it moving when
the intermittent sprocket 24 advances the film, a static friction
of up to several pounds is still required to overcome this inertia
effect and stop the film. As between misregistration of the frames
40 in the X direction and the Y direction, however, misregistration
in the Y direction is usually the largest of the two.
[0070] Because the gate 22 in conventional projectors is designed
to register the frame 40 with respect to the aperture 32, the gate
is an important aspect of the film registration process. However,
for the reasons previously explained, it is virtually impossible
for conventional projector gate designs to precisely register the
frame 40 in proper alignment with the aperture 32. Accordingly, to
correct for this constant misregistration from one frame to the
next, the system and method in accordance with one embodiment of
the present invention is designed to physically move the gate 22,
after the film 10 has been stopped in the gate by friction, to
precisely register the frame 40 with respect to the aperture
32.
[0071] FIG. 5 schematically illustrates the position of the gate
22, which, in accordance with the invention, is moveable in the X
direction and the Y direction relative to the aperture plate 30 of
the projector 16 and its corresponding aperture 32. The
intermittent sprocket 24 is located below the gate 22 and is driven
by an intermittent motor 38. In conventional projectors, as shown
in FIG. 4, the gate 22 is attached to the projector 16 in a fixed
position and therefore does not move. In accordance with the
present invention, however, the gate 22 is configured so that it
can be moved to provide for the necessary corrective movements that
will result in precise registration of the frame 40 with respect to
the aperture 32. In the preferred embodiment, the gate 22 is
configured to move in the X direction and the Y direction, as
necessary, to precisely register the film 10.
[0072] The range of gate movement in the X and Y directions
preferably is sufficient to allow enough movement in each direction
to correct for a "worst case" situation of misregistration. A worst
case situation is believed to be a maximum deviation of about
+/-0.003 inches, although it could be more or less than this
amount. Therefore, to correct for these deviations, the gate 22
should be able to move at least about 0.006 inches in both the X
direction and the Y direction. However, it will be understood that
a larger range of gate movement is possible and that the invention
is not limited to the specific ranges of movement set forth herein.
In any event, in order for the range of gate movement to be able to
provide enhanced resolution through precise frame registration, the
corrective movements of the gate 22 preferably should be at a level
and in increments that are at least on par with the obtainable film
grain resolution available.
[0073] According to today's standards, typical film 10 has the
capacity to resolve approximately 4,850 lines per inch in any axis.
In order to correct misregistration and project an image as a
steady picture, gate movement should ideally be at least ten to one
hundred times more precise than the smallest film grain size. Gate
movement at this level of precision would not only allow the system
to accurately position one frame relative to the next, but it would
also allow for future improvements in film stock technology.
Accordingly, in one aspect of the invention, gate movement
preferably can move the film in increments of {fraction (1/20)} of
a micron, or 0.000002 inches.
[0074] Movement of the gate 22 to correct misregistration of the
film 10 preferably occurs during the period in which the film is
stopped, after the pull down from the intermittent sprocket 24 and
before the shutter opens. During this period of time, several
operations must be performed. As explained in more detail below,
these operations include determining the position of the film frame
40 relative to the previous frame, calculating the amount of
corrective gate movement, and then moving the gate 22
accordingly.
[0075] Because the frames 40 will be registered at a rate of at
least 24 frames per second (i.e., one frame about every 41.6
milliseconds), all of these operations, and particularly the
movement of the gate 22, needs to be performed as quickly as
possible. Movement of the gate 22 is accomplished mechanically and,
therefore, is subject to certain physical limitations. Of course,
the shutter will not open until the film 10 has been pulled down
and stopped in the gate 22. If the amount of time to pull down each
frame 40 is approximately 8.0 milliseconds, then the operations
necessary to move the gate 22 and register the frame 40 must be
performed in approximately 2.5 milliseconds after the film 10 has
stopped and before the shutter opens. By allowing approximately 1.5
milliseconds to determine the location of the frame 40 and to
calculate the amount and direction of corrective gate movement
necessary, there is approximately 1.0 millisecond of time remaining
to actually move the gate 22. If the frame rate is 48 frames per
second, then the amount of time to move the gate 22 will be the
same as those set forth above. Similar calculations can be made to
budget the proper amount of time to move the gate 22 based on other
frame rates that may be used.
[0076] In order to move the gate 22 within the time available to do
so, the inertia of the gate ideally should be as small as possible.
Accordingly, the intermittent motor 38 should not be attached to
the gate 22, and the aperture plate 30 should remain fixed relative
to the lens 36 and intermittent motor 38, with the gate 22 moving
independently of both. The actual configuration to permit the gate
22 to move can be accomplished in several ways, so long as it has
the freedom to move at least about 0.006 inches in the X and Y
directions. For example, flexure stages, bearings, slides, and
other suitable configurations can be used in conjunction with an
appropriately configured gate 22.
[0077] In order to move the gate 22 by the distance necessary to
accurately correct frame to frame misregistration, a movement
mechanism is connected to the gate. This gate movement mechanism is
referred to herein as an "actuator." Given the gate movement
parameters discussed above, the actuator must be able to move the
gate 22 rapidly (i.e., in about one millisecond or less). The
actuator also must be able to move the gate 22 in a precise manner
(i.e., preferably in increments of 0.000002 inches). An actuator
capable of meeting these gate movement parameters may take several
different forms. For example, it may comprise a system that
utilizes fluids, air pressure, mechanical devices or
electromechanical devices to provide the required movement. Of
these options, electromechanical devices are presently preferred,
due to the high level of control and the higher speed response that
they provide.
[0078] Electromechanical devices come in many different forms, such
as rotary or linear motors, piezoelectric motors, bi-material
actuators, and other devices that change shape or size based upon
an electrical influence. Rotary motors represent a common system
that transfers rotary motion into linear motion through the use of
a screw, cam or similar device. Linear motors, such as moving coil
motors or speaker coil motors, are also candidates for the actuator
due to their precise movements and quick response time. Bi-material
actuators rely upon the dissimilar nature of two materials to cause
a bowing or shape change that can be converted into precise linear
motion. Of these options, piezoelectric motors or moving coil
motors are presently preferred actuators.
[0079] The piezoelectric motor has several attributes that make it
a very capable actuator. Among these attributes are the
piezoelectric motor's high speed capability and its high positional
accuracy. In fact, accurate moves in increments as small as one
nanometer (i.e., one billionth of a meter), or less, can be
achieved, provided proper mechanics and electronics are
employed.
[0080] As shown schematically in FIG. 6, a piezoelectric motor 42
employs a piezo crystal 44 that increases or decreases in length in
proportion to the voltage that is applied across the crystal. When
the voltage across the crystal 44 is increased, the length of the
crystal increases, whereas reduced voltage decreases crystal length
(see FIG. 7). One advantage of using the piezoelectric motor 42 as
the actuator is that it is not necessary to have a feedback loop or
to constantly monitor the actual position and the commanded
position of the gate 22. Feedback systems of this nature are
commonly deployed in motor control applications and would be
required if a moving coil motor (discussed below) is used as the
actuator.
[0081] By eliminating the feedback loop, the amount of
microprocessor power required by the piezoelectric motor 42 to both
initially move the gate 22 and then keep it in the correct position
during the time the shutter is open is reduced. Moreover,
piezoelectric motors 42 have a highly reliable and predictable move
distance based upon the applied voltage. As noted above, and as
represented in FIGS. 6-7, voltage applied to the piezo crystal 44
causes it to increase or decrease by a very precise distance in a
linear manner along the axis of the crystal. Therefore, a simple
calculation or the use of available conversion tables will indicate
the exact amount of voltage that must be applied to increase or
decrease the length of the crystal 44 by any given distance with
very high accuracy. While piezo crystals 44 are known to have a
rebound affect, this effect occurs over an extended period of time
and does not start to occur until at least several seconds have
passed. Therefore, the rebound effect of the crystals is a very
small factor because the time period between each corrective move
is so small.
[0082] In one form of the invention, the piezoelectric motor 42
comprises a high-resolution piezoelectric motor flexure stage 46.
As shown schematically in FIG. 8, the stage 46 comprises two
piezoelectric motors 42 protected by an outer metal frame 48. The
peizoelectric motors 42 have one end connected to the outer frame
48, which is fixed against movement, and another end connected to
an inner frame 50 that is moveable with respect to the outer frame
48. As explained later in conjunction with FIGS. 14-16, the
moveable inner frame 50 is connected to the projector gate 22, and
the fixed outer frame 48 is connected to a suitable fixed structure
of the projector 16 that surrounds the gate.
[0083] The stage 46 also includes a plurality of flexures 52, which
are frictionless, stictionless devices that rely upon the elastic
deformation or "flexing" of a solid material. The flexures 52 are
connected between the outer frame 48 and the inner frame 50 and
advantageously eliminate sliding and rolling. These flexures 52
essentially act like springs that bias the moveable inner frame 50
with respect to the fixed outer frame 48. They are capable of
providing the small increments of movement in response to the
linear motion of the piezoelectric motor 42, in accordance with the
principal of material elastic flexing, to provide mechanical
movement translation. The flexures 52 are also particularly
advantageous because they eliminate the common linear path errors
associated with linear bearings. Therefore, such flexure-type
positioners are superior to traditional positioners, such as ball
bearings, cross roller bearings, etc., in terms of resolution,
straightness and flatness.
[0084] The peizoelectric motor flexure stage 46 is preferably
equipped with at least two piezoelectric motors 42. The flexure
stage 46 also may be provided with two high-resolution capacitive
displacement sensors 54, but they are not required. The
piezoelectric motors 42 provide the motion required to move the
gate 22 with sub-nanometer resolution in the X direction and the Y
direction. The capacitive displacement sensors 54 comprise a probe
56 and a slightly larger target plate 58. The sensors 54 also have
sub-nanometer resolution and insensitivity to lateral motion.
Digital control electronics connected to the stage 46 by a cable 60
can evaluate the combined information of the capacitive
displacement sensors 54 and transform that information into two
individual signals proportional to X and Y linear displacement.
[0085] High resolution piezoelectric motor flexure stages 46 of the
type described above, and which have the capability of moving the
gate 22 by the required range of motion, and in the required
increments, are commercially available and can be obtained from,
for example, Physik Instrumente GmbH & Co., Polytec Platz 1-7,
76337 Waldbronn, Germany. Piezoelectric motor flexure stages 46
available from this company can provide sub-nanometer movements and
virtually unlimited resolution that is not limited by stick-slip
effects or by threshold voltages. These stages 46 also have
piezoelectric motors 42 that have an extremely fast expansion and
thus provide an extremely fast responding positional element, with
microsecond time constants. Furthermore, the piezoelectric motors
42 in these stages 46 have the further advantage that they are
solid-state. Thus, they require no maintenance and are not subject
to wear and tear.
[0086] A moving coil motor 62 also may serve as a suitable
actuator. The moving coil motor 62 uses a system very similar to a
speaker. As shown schematically in FIG. 9, the moving coil motor 62
comprises a magnet 64 and a wire coil 66 surrounding the magnet.
Like the piezoelectric transducer flexure stage 46 discussed above,
the moving coil motor 62 also may be used in conjunction with a
flexure stage having a plurality of flexures and high-resolution
capacitive displacement sensors, including a probe 68 and a
slightly larger target plate 70 to determine position. The wire
coil 66 is connected to the inner frame 72 of the flexure stage
that, in turn, is connected to the projector gate 22.
[0087] The magnet 64 is stationary and fixed to the surrounding
metal outer frame 74 of the stage. In use, current is passed
through the wire coil 66. By varying the intensity of the current,
the wire coil 66 will be moved relative to the stationary magnet 64
until an equilibrium is met between the stage flexures and the
force of the magnet pull. In this way, the inner frame 72 of the
stage and thus the gate 22 will be moved with respect to the outer
frame 74 to properly position the gate 22 and register the frames
40 of the film 10.
[0088] The actuator preferably is moved or driven in a linear
manner by an actuator driver. The actuator driver may comprise any
suitable arrangement that allows control over the actuator in
response to either a straight analog signal, a digitally processed
signal, or another suitable signal. When the piezoelectric motor 42
serves as the actuator, the actuator driver comprises a voltage
controlled system. If the moving coil motor 62 serves as the
actuator, then the actuator driver is a current controlled system.
Other suitable types of actuator drivers will be apparent and can
be selected based on the type of actuator that is used.
[0089] The voltage control system for the piezoelectric motor 42
includes an electronic system capable of handling the bandwidth
required to move the actuator by its required distance, i.e., at
least 0.006 inches, in one millisecond or less. For example, a high
voltage amplifier-based design taking a control signal from an
analog front end circuit can be used. The analog front end circuit
can be either an analog control circuit or a digital control
circuit that converts to analog through an analog to digital
converter.
[0090] The current control system for the moving coil motor 62 is
similar to the voltage control system for the piezoelectric motor
42, except for the addition of a feedback loop to monitor the
current output of the amplifier stage, either through an analog
circuit or a digital circuit. The feedback loop monitors the
current and adjusts it to follow a proportional gain value to the
control signal coming from the analog front end circuit. If the
current is too low, the feedback loop increases the voltage until
the appropriate current is reached. Likewise, if the current is too
high, the voltage is decreased until the correct current level is
reached.
[0091] Having described the electromechanical aspects for
physically moving the gate 22, the portion of the system that
governs how far the gate must move, and which direction it must
move, will now be described.
[0092] In order to move the gate 22 and position the frames 40 in
proper registration with respect to each other and the aperture 32,
it is necessary to determine the location of the frames once the
film stops moving at the conclusion of each intermittent pull down
by the intermittent sprocket 24. This determination of frame
location from one frame to the next will reveal the amount of
misregistration that needs to be corrected. In accordance with the
present invention, registration information is applied to the film
10 corresponding to the location of the frames 40 on the film 10.
This information is sensed or "read" in order to determine the
frame's location relative to the frame that preceded it.
[0093] In one form of the invention, the information is embodied in
a registration reference mark 76 adjacent to the frame 40. In the
preferred embodiment, there is at least one registration reference
mark 76 associated with each frame 40. By detecting the location of
the registration reference mark 76 and comparing its location
relative to the location of the immediately preceding registration
reference mark, it is possible to determine the amount of movement
necessary to correct misregistration on a frame by frame basis.
With this comparative information, the difference between the
locations of two successive registration reference marks 76 can be
calculated and a signal sent to the actuator commanding it to move
the gate 22 so that the two marks lay on top of each other. Once
the registration reference marks 76 lay on top of each other, then
the frames 40 will also.
[0094] When the film registration process starts, the first frame
40 with a registration reference mark 76 acts as a "benchmark" for
the subsequent registration of every frame 40 that follows. In
other words, the location of the first frame 40 relative to the
aperture 32 is determined by sensing the location of a first
registration reference mark associated with that first frame. The
location of the next or second registration reference mark is also
determined, and the gate 22 is moved so that the second mark lays
on top of the first mark, at the same location as the first mark.
Once the second registration reference mark has been aligned with
the first registration reference mark (at the same location as the
first registration reference mark), then the first and second
frames will also be equally aligned or "registered." By precisely
registering subsequent frames 40 of the film "on top" of each other
in this manner, substantially all jitter and weave will be
eliminated, and the resolution of the projected image will be
substantially enhanced.
[0095] It will be appreciated that, at the beginning of the
registration process, the first "benchmark" frame should be
"centered" as much as possible with respect to the aperture 32. In
other words, the center of the first frame 40 should be aligned as
much as possible with the optical axis of the projector lens 36,
which should also be in optical alignment with the aperture 32. In
this way, all subsequent frames 40, which are registered with
respect to the first frame, will be equally and correctly
registered.
[0096] The registration references mark 76 can take a variety of
different forms. The main requirement of the registration reference
mark 76 is that it must be capable of being detected by a process
that can determine the location of the mark and then compare that
location to the location of the previous mark. For example, a
circle is capable of functioning as one aspect of a registration
reference mark. The circle can be located by a sensor and then
compared to the location of the circle associated with the previous
frame. Once the distance between the two circles and their
direction relative to each other have been calculated, the actuator
can move the gate 22 by the corresponding distance and direction to
lay the two circles on top of each other in the manner described
above.
[0097] The registration reference mark 76 in accordance with one
embodiment of the invention employs multiple shapes. As shown in
FIG. 10, these shapes may comprise geometric shapes, such as a
square 78, a circle 80 and a triangle 82. The square 78, by
definition, has a constant dimension on all four sides, i.e., from
top to bottom and from side to side. The circle 80 is placed
adjacent to the square 78 and is the geometric shape used to
calculate the amount of misregistration of each frame 40. The
diameter of the circle 80 is the same as the width of the square
78. Alternatively, a rectangle may be used instead of the square
78, so long as the width of the rectangle is the same as the
diameter of the circle 80. The triangle 82 is placed on the other
side of the square 78 from the circle 80. The base of the triangle
82 is shown aligned with the bottom of the square 78 and has a
length that is the same as the width of the square, although
triangles having other dimensions may be used.
[0098] If desired, the registration reference mark 76 may also
include additional information. With reference again to FIG. 10,
optional additional information is set forth to the left of the
three geometric shapes. This other information may include, for
example, binary information 84 indicating the frame size, film
speed, movie title, lab origin, or any other appropriate
information. The binary information may also include information
signaling the start 86 of the information band at the beginning and
a checksum 88 at the end. The type of message 90 also may be
provided. However, this additional information is not needed or
used to determine the location of the frame 40.
[0099] Rather, as set forth above, frame location is determined by
the three geometric shapes.
[0100] One aspect of the registration reference marks 76 involves
the location of these marks on the film 10 and the number of marks
that are used. Preferably, there is one registration reference mark
76 associated with each frame 40. In this way, each and every frame
40 will be precisely registered and resolution of the projected
images will be maximized. Alternatively, registration reference
marks 76 may be applied to every other frame 40, or in some other
number or convention, to achieve better registration and resolution
than conventional systems, although not as good as the resolution
provided when each frame 40 is registered.
[0101] With respect to the location of the registration reference
marks 76, each mark is preferably located on a portion of the film
closely adjacent to each frame 40. In one embodiment shown in FIG.
11, the registration reference mark 76 is located in the
longitudinal space 92 between each frame 40. This space 92 is large
enough to fit the registration reference marks 76 in most film
formats. The registration reference marks 76 also could be located
on the outside of the film's perforations 94, or between the
perforations. However, this is not a preferred location because it
is ordinarily occupied by sound track information.
[0102] In the alternative, the registration reference mark 76 may
be located within the image itself, but this would require an image
capture system that could scan an image and then interpret the
location of the mark from the entire frame 40. Accordingly, this
approach has certain drawbacks. The registration reference marks 76
also could be applied with ink or a magnetic charge that is
invisible to the naked eye, but that could be read by an
appropriate sensor. However, the preferred location of the
registration reference marks 76 is immediately outside the frame
40. By placing the registration reference marks 76 outside the
frame 40, they can be read by the sensor without affecting the
image to be projected. The most preferred location of the
registration reference marks 76 is in the space 92 between each
frame 40.
[0103] The registration reference marks 76 may be placed on the
film 10 in any suitable manner, preferably during the manufacture
of IN's, IP's or other intermediate printing process, or in the
equivalent digital version of that process ("digital
intermediate"), wherein fades, dissolves, titles, effects, color
"timing," density corrections, and other intermediate processes are
handled digitally before scanning back out to film. For example,
the registration reference marks 76 may be applied to the film by a
laser device precisely mounted on a registered contact "step"
printer. The precise method of mounting the laser device to such a
printer will vary with the different types of printers, and various
techniques exist to modify step printers for placement of such
laser devices. Other suitable devices may be used to apply the
registration reference marks 76, in particular, the outline of the
three geometric shapes. Regardless of the device that is selected,
it must be able to apply the registration reference marks 76 to the
film 10 such that the square 78, circle 80 and triangle 82 are
transparent and surrounded or outlined by a non-transparent
portion. Alternatively, the square 78, circle 80 and triangle 82
may be non-transparent and surrounded or outlined by a transparent
portion. Laser devices are capable of providing these types of
registration reference marks by use of appropriate masking and the
like, but other suitable devices may be used as desired.
[0104] In applying the registration reference marks 76 to the film
10, it is important to position each registration reference mark in
a location that most closely tracks the exposure of each frame 40
onto the intermediate film. Accordingly, each registration
reference mark 76 should be applied to the film 10 as close as
possible to its corresponding frame 40 and the operative
registration pins of the contact "step" printer. In this manner,
the laser device, or other suitable device, can precisely apply the
registration reference marks 76 in the same location as each frame
40 is exposed onto the intermediate film stock.
[0105] If the registration reference marks 76 are applied during
the "digital intermediate" process, the marks can be placed in the
correct position by means of the imaging computer and its
associated software. They can then be placed on the film elements
generated thereby using the same film recorder technology as is
used to duplicate the film images themselves.
[0106] Alternatively, if the registration reference marks 76 are
applied in the context of dye-transfer (imbibition, "IB") printing
(e.g. the original TECHNICOLOR 3-strip process), the marks may be
placed prior to making the separation matrixes, or otherwise as
appropriate to insure that they maintain alignment with the frames
40 themselves throughout the duplication process. The IB process is
fully pin-registered, unlike standard duplication using multi-layer
Eastmancolor-type film. Therefore, the registration reference marks
76 applied in this instance will have a less involved function, in
that they need not be used to correct for printing misalignment,
but function simply to insure correct projector registration by
compensating for any possible shrinkage, expansion or other such
variables.
[0107] No matter how the registration reference marks 76 are
applied, they should be placed in repeatable precise position
relative to the frame 40. In this regard, prior to the manufacture
of release prints, the image is still precisely located on the film
10 relative to the perforations. The subsequent process of
high-speed contact printing will produce errors in image placement
relative to the film edges and perforations, for the reasons
described above, such as the variable high-speed printer transport
and inevitable misalignment of the bi-packed film moving through
the printer. However, because the registration reference marks 76
are aligned to the images themselves, they will be duplicated in
the same manner, right next to their respective frame 40.
Accordingly, one can still correctly position the image by simply
tracking the registration reference marks 76 and by moving the gate
22 to correctly reposition the film 10 accordingly. Hence, even
though the images may no longer be precisely located relative to
the perforations 94 and the film's edges, they will always be
located with precise reference to their respective registration
reference marks 76. These registration reference marks 76, though
they are located between the projected frames 40 and thus will
never appear on the screen, are duplicated with the images
themselves during the high-speed contact printing process.
[0108] An appropriate sensor must be used to detect and "read" the
registration reference marks 76. Preferably, the sensor is
fast-acting and triggerable. The sensor also is one that preferably
operates on the principle of detecting deviations between light and
dark. For example, photocells can not only determine if something
is light or dark, but also shades of gray between the two. Solar
cells can detect varying light levels and respond at very high
speeds. Magnetic pickup heads can read a portion of the film 10
which has been coded, and this information may used to determine
the film's location. For the reasons set forth below, LED and CCD
technology is the currently preferred sensor-based system, However,
it will be understood that LED and CCD technology is not the only
suitable sensor system, and other types of suitable sensors may be
used.
[0109] CCDs are well-known devices having defined pixels that can
be exposed by light and read digitally. They are not only very
fast, but they also allow direct connection to most digital
systems. Both an X and Y matrix CCD or line CCD are suitable. As
shown in FIGS. 12-13, the difference between them is only in the
number and arrangement of pixels. The matrix CCD 96, shown in FIG.
12, has a number of pixels 98 in both the X and Y directions,
resulting in an X-Y matrix. This type of CCD usually takes longer
to evaluate due to the larger number of pixels 98 on the cell. The
line CCD 100, shown in FIG. 13, uses the same technology, but with
only a single row of pixels 98. This single row of pixels 98 is
quicker to read and contains less data to sort and analyze.
[0110] In order for the line CCD array to work, the film 10 must be
illuminated to cast the outline of the three geometric shapes,
i.e., the square 78, the circle 80 and the triangle 82, onto the
CCD array 96 or 100. There are several options available to
illuminate the film 10. Of course, the opening of the shutter will
illuminate the mark 76 and thereby expose the CCD. However, if the
film 10 is moving while the shutter is open, it will cause a
blurring of the image on the screen, which is unacceptable.
[0111] Therefore, the registration reference mark 76 preferably is
illuminated while the shutter is closed so the corrective move can
be completed before the shutter opens. One way to illuminate the
registration reference marks is by utilizing an LED array 102. This
array can turn on briefly and expose the CCD array 100 through the
film 10 while the shutter is still closed. The LED array 102 may be
either visible-light based or invisible-light based. The benefit of
the invisible light array is that it prevents any bleed-through
light from the LED array 102 from being projected and thus visible
to the audience. For example, this array could flash 2.5 ms prior
to the opening of the shutter, allowing enough time for the
actuator to move the gate 22 before the shutter opens. The LED
array 102 is the presently preferred way to illuminate the CCD
array 100.
[0112] One embodiment of the sensor, using arrays of LEDs and CCDs,
is illustrated in FIGS. 14-16. In this embodiment, there are two
sets of arrays of LEDs 102 and CCDs 100, with one set above and one
set below the aperture 32 in the aperture plate 30 of the projector
16. This arrangement provides redundancy and increased reliability
when, for example, there are two registration reference marks 76
associated with each frame 40 and both sets of arrays 100 and 102
are in use. Alternatively, only one of the sets of arrays could be
used, and if one of the sets malfunctioned, the other set could be
activated to keep the system operating. However, it is not
necessary or required to use multiple sets of LED and CCD arrays.
Therefore, FIGS. 14-16 will be discussed with reference to only one
of the LED/CCD arrays, and it will be understood that the
description applies equally to both sets of arrays.
[0113] FIG. 14 is a rear elevational view of the projector gate 22,
and FIG. 15 is an elevational side view of the projector gate taken
along the line A-A of FIG. 16, which is a front elevational view of
the projector gate. Before discussing the LED/CCD arrays 100 and
102, the piezoelectric motor flexure stage 46 shown in FIGS. 14-16
will be discussed briefly. As shown in these drawings, the stage 46
has its moveable inner frame 50 connected to the projector gate 22,
which has been disconnected from its conventional projector support
structure. The inner frame 50 may be connected to the gate 22 in
any suitable manner, such as by bolts, screws or the like that will
provide a secure connection between the inner frame of the stage
and the gate. The outer frame 48 of the stage 46 surrounds the
inner frame 50 and is connected to the adjacent projector structure
that is fixed against movement relative to the gate 22. Thus,
movement of the inner frame 50 of the stage 46 will result in
corresponding movement of the gate 22, in accordance with the
principles of the invention.
[0114] There is an LED array 102 on the front side of the gate 22,
which is to the right in FIG. 15. This array 102 is adapted to
transmit light through an aperture in the gate 22 and another
aperture 32 in the aperture plate 30 so that light from the LED
array 102 passes through the film 10 when the film is stopped in
the gate 22 during the intermittent pulldown. Thus, once the film
10 has stopped in the gate 22, the LED array 102 is quickly
activated to pass light through the registration reference mark 76
associated with the frame 40 that is about to be projected. As a
result, certain pixels 98 in the CCD array 100 will be illuminated
and others will not, depending on whether the geometric shapes are
transparent or non-transparent. In either case, the light will pass
through the film 10 to the back side of the gate 22, which is to
the left in FIG. 15.
[0115] With reference to FIGS. 14 and 15, as the light passes
horizontally through the film 10, the light that passes through the
registration reference mark 76 is received by a first mirror 104.
As shown in FIG. 14, this first mirror 104 reflects the light
vertically downwardly toward a second mirror 106. The reference
numeral 108 represents the line of travel of the light, and the
reference numeral 110 represents the band of the total light that
is transmitted. The second mirror 106 then reflects the transmitted
light along a generally horizontal path outwardly to one side of
the aperture 32, where it is received by the CCD array 100. As a
result, the transmitted light will illuminate certain pixels 98 in
the CCD array 100. With this information, the location of the
registration reference mark 76 can be determined.
[0116] In the first step of this determination, the number of
pixels 98 illuminated in the CCD array 100 by the first
registration reference mark 76 (associated with the first frame)
establishes the "benchmark" for the registration of all subsequent
frames 40. As noted previously, this "benchmark" frame should be
centered as much as possible with respect to the optical axis of
the projector lens 36. With this information, the location of the
first registration reference 76 mark with respect to the aperture
32 is determined. This location will correspond to the center of
the circle 80 and the geometric center of the square 78 for all
future calculations. In other words, this will be the location of a
frame 40 that is properly registered with respect to the aperture
32.
[0117] When the LED array 102 is activated again for the next
succeeding frame 40, the light passes through the registration
reference mark 76 associated with that frame and certain pixels 98
of the CCD array 100 are illuminated again. The number of pixels 98
illuminated by the circle 80 are compared to the number of pixels
98 illuminated by the square 78. As shown in FIG. 17, if the number
of pixels 98 illuminated by the square 78 and the circle 80 are
equal (i.e., when W.sub.1=W.sub.2), then the CCD array 100
necessarily falls directly through the center of the circle 80 and
the geometric mid-point of the square 78, meaning that the frame 40
is properly registered in the Y direction with respect to the
aperture 32 and no corrective movement in the Y direction is
required. However, when the number of pixels 98 illuminated by the
circle 80 is less than the number illuminated by the square 78
(i.e., when W.sub.2<W.sub.1), as shown in FIG. 18, then the
frame 40 is misregistered with respect to the aperture 32 and gate
movement in the Y direction is required to properly register the
frame.
[0118] To determine whether the CCD array 100 is located above or
below the center of the circle 80, the pixels 98 illuminated by the
triangle 82 are also read. Depending on the number of pixels 98
that are illuminated by the triangle 82, it can be determined
whether the frame 40 needs to be moved in the positive Y direction
or the negative Y direction to achieve proper registration of the
frame. For example, if the number of pixels 98 illuminated by the
triangle 82 is above a certain value, then it can be determined
that the CCD array 100 is located below the center of the circle
80. Thus, by comparing all of the CCD array data generated from
each geometric shape, it is possible to determine the amount of
movement and the direction of movement necessary to properly
register each frame 40.
[0119] FIG. 19 helps illustrate the calculations associated with
the circle 80 that need to be made to determine the extent of any
misregistration in the Y direction. In FIG. 19, DC represents the
diameter of the circle 80 and the width of the square 78. L.sub.c
represents the length of a chord of the circle 80 and the location
of the CCD array 100 relative to the center of the circle. Y.sub.d
represents the offset of the CCD array 100 in the Y direction, as
measured from the center of the circle 80. R represents the radius
of the circle 80, or 1/2 of Dc. To calculate the amount of
misregistration in the Y direction, simple mathematics using the
Pythagorean theorem is used according to the following equation,
where Y.sub.d equals the amount of misregistration in the Y
direction: 1 Y d = ( D c 2 ) 2 - ( L c 2 ) 2
[0120] To calculate the amount of misregistration in the X
direction, it is necessary simply to know the location (i.e., the
pixel) on the CCD array 100 corresponding to the center of the
circle 80 of the first registration reference mark 76. This
location will correspond to the center of the circle 80 and the
midpoint on the CCD array 100 for all subsequent circles. When
light from the LED array 102 passes through subsequent circles 80
and illuminates the CCD array 100, the midpoint of the chord Lc for
those circles will be calculated and compared to the midpoint of
the CCD array 100 as determined by the first circle 80. If there is
a difference between the midpoint of a subsequent circle 80 and the
midpoint of the CCD array 100, then the amount of misregistration
in the X direction can be calculated based on the difference in
distance between these two points.
[0121] In view of the above, it will be appreciated that the CCD
array also can be configured to act as the "benchmark" for the
registration of the frames 40, in conjunction with the registration
reference marks 76. For example, a predefined location on the CCD
array can be selected as the location to which all frames will be
moved. By using the registration reference marks 76 to move all
frames 40 a predefined location on the CCD array, the undesirable
jitter and weave will be eliminated.
[0122] One of the advantages of using geometric shapes to comprise
the registration reference mark 76 is that fluctuations that occur
during the film production process, or fluctuations in the
illumination of the marks, will not affect the results of the gate
movement calculations. For example, if film exposure and reprinting
makes the square 78 smaller or larger than its original size, the
circle 80 and triangle 82 will change in size by the exact same
ratio. Furthermore, lower or higher power illumination will not
affect the ability to calculate the center of the circle 80 because
of the corrective nature of the other two geometric shapes, namely
the square 78 and the triangle 82.
[0123] Another possible way to illuminate the CCD array 100, shown
in FIG. 20, is to provide a notch 112 in the shutter 114 in a way
that allows exposure of the CCD array 100 before the shutter opens.
However, this method may cause a ghosting image across the film
while the notch 112 moves across the film frame 40, which would be
unacceptable.
[0124] Alternatively, light from the lamp house 34 may be directed
around the film 10 and used to expose the registration reference
mark 76 while the shutter is closed, as shown in FIG. 21. This
system would require mirrors 116 or a light pipe, for example, to
channel the light to the appropriate location.
[0125] Each of the registration reference marks 76 is read by the
sensor as soon as the film 10 has stopped in the gate 22. However,
sensing the registration reference marks 76 at a different time is
possible and opens some advanced processing possibilities. For
example, if the registration reference mark 76 is sensed before the
frame 40 associated with that mark has stopped in the gate 22, a
period of time longer than 1.5 milliseconds can be used to analyze
the mark. By increasing the time available for analysis, a slower,
less expensive registration processor (discussed below) may be
used. Moreover, if the registration reference mark 76 can be read
and analyzed before the frame 40 is stopped in the gate 22, the
gate can be commanded to move toward the correct position during
the pull down of the frame by the intermittent sprocket 24. This
would allow approximately 10 milliseconds of time to move the gate
22 instead of 1 millisecond or less if the registration reference
mark 76 is not read until the film 10 fully stops in the gate
22.
[0126] In another aspect of the invention, corrective gate movement
could be at least partially determined by searching for and
determining the existence of a trend of misregistration of the film
10 from one frame 40 to the next. Based on the nature of the
"trending," basic corrective gate movements could be predicted and
executed. While a trending system does not cancel all error when
the film 10 stops, it should at least eliminate the errors
associated with the film duplication process. By analyzing how
several successive frames 40 have stopped in the gate 22, a film
stop deviation may be trended and corrected by appropriate gate
movement. Although this method could possibly correct for the major
deviations causing misregistration of the frames 40, it is unlikely
to be as accurate as analyzing the registration reference marks 76
once the film 10 has stopped in the gate 22 and before the shutter
114 has opened.
[0127] In accordance with the invention, a registration processor
118 governs the operation of the system. With reference to FIG. 22,
the registration processor 118 communicates with a host processor
120 to receive information related to film format (e.g., a
four-perforation per frame format or a three-perforation per frame
format), frame rate, brightness, and so forth. The host processor
120, in turn, communicates with a motion processor 122 that
controls operation of the projector 16. The host processor 120 will
inform the registration processor 118 if the film 10 contains
registration reference marks 76 and, if so, the type of
registration reference marks being used. The connection between the
host processor 120 and the registration processor 118 also will
provide a line of communication for determining registration status
and correct operation.
[0128] Upon a command from the host processor 120, the registration
processor 118 commences its operation to precisely register the
frames 40. The registration processor 118 will activate the LED
array 102, for example, to illuminate the registration reference
marks 76 which, in turn, project the outline of the three geometric
shapes onto the sensor, such as a line CCD array 100, in the manner
described above. The registration processor 118 then analyzes the
pixel information gathered from the sensor, sorts through the
information and determines the location of the frame 40 being
registered relative to the previous frame. Once this information is
known, the registration processor calculates the distance, in both
the X direction and the Y direction, by which the frame 40 is
misregistered with respect to the previous frame. This calculation
can be in the form of a vector direction and length, which
determines the corrective direction and distance needed to move the
gate 22.
[0129] Depending upon the direction and the length of the vector,
the amount of voltage or other signal needed to move the gate 22 in
the X direction and/or the Y direction is calculated. A command
signal containing the necessary information is then transferred to
an actuator processor and driver 124 to generate an appropriate
signal. For example, if the actuator is the piezoelectric motor 42,
then the signal will be a voltage signal. The actuator processor
and driver 124 amplifies the voltage signal to produce a precise
voltage that is applied, for example, through the cable 60 to the
piezoelectric motor flexure stage 46, which then moves the gate 22
in the X and/or Y directions to move the frame 40 into precise
alignment with respect to the previous frame.
[0130] The registration processor 118 may take several forms. For
example, commercially available microprocessors, digital signal
processors, microcontrollers, analog circuits and other suitable
processors may be used. In addition, a combination of these various
types of processors can be used to determine and send the
corrective move signal to the actuator.
[0131] In other aspects of the invention, the registration
processor 118 may default to a lower level of frame registration
accuracy, as may be appropriate. For example, if the host processor
120 informs the registration processor 118 that the film 10 in the
projector 16 does not have registration reference marks 76, the
registration processor 118 may default to a mode in which the
sensor reads the position of perforations 94 instead of
registration reference marks 76 on the film 10. In this default
mode, the sensor would determine the location of a particular
perforation 94 associated with a frame 40 and place each successive
perforation (associated with each successive frame) in overlapping
relation to the one that preceded it. Even though this default mode
would be less accurate than systems that read the registration
reference marks 76, an increase in film registration accuracy
nevertheless can be achieved as compared to conventional projectors
having no such system.
[0132] In another more detailed aspect of the invention,
information regarding the location of the registration reference
marks 76 and the corresponding corrective movements of the gate 22
may be analyzed and stored in the registration processor 118. By
analyzing and storing this information for enough frames 40, the
registration processor 118 may provide an estimate of the
corrective move that will be required before a frame 40 enters the
gate 22. This provides several advantages.
[0133] First, as mentioned previously, this "trending" allows
movement of the gate 22 prior to the correct analysis as the frame
40 is being pulled into the gate. This minimizes the distance the
gate 22 has to move once the actual move has been calculated. If
the majority of the misregistration can be corrected by gate
movement during the actual pulldown of the frame 40 into the gate
22, then only a minor correction will be necessary once the film 10
has stopped moving. Accordingly, if the distance of this final
corrective move is small, it can be performed more quickly than a
longer corrective move.
[0134] Second, this trending allows corrective moves to be made
with respect to film frames 40 that do not have any registration
reference marks 76, or where the registration reference marks have
been corrupted in some way and cannot be read. For example, if the
film 10 is damaged or dust or other contaminants obliterate a
registration reference mark 76, either in whole or in part, it may
not be possible to read the registration reference mark. In these
circumstances, an accurate determination of the corrective action
necessary with respect to that particular frame 40 will not be
possible. However, instead of bypassing corrective action with
respect to this frame 40 altogether, the trend in misregistration
of the immediately preceding frames will allow the registration
processor 118 to predict the proper location of the film frame 40
to correct for as much misregistration as possible.
[0135] As an additional feature, the design of the gate 22, in
conjunction with the motion processor 122 and the registration
processor 118, may include a system to permit high-speed computer
control over the resistance to film movement in the gate. For
example, after the film 10 has stopped in the gate 22, the
resistance may be decreased to provide a low starting friction
component when the film is pulled down by the intermittent sprocket
24. This reduced gate friction would allow lower peak intermittent
sprocket torque and would reduce the stresses placed on the film 10
by the gate 22 during the intermittent pull down move. Near the end
of the intermittent pull down move, appropriate friction necessary
to stop the film 10 may be reapplied back to the gate 22. This
repeated cycle of decreasing and increasing gate friction would
accomplish the objectives of stopping the film 10 accurately at the
end of each pulldown move, while reducing the work required to move
the film at the beginning of each move.
[0136] In view of the foregoing, it will be appreciated that the
principles of the present invention can be applied in numerous ways
to eliminate jitter and weave. For example, instead of using the
registration reference marks 76 to move the gate 22, these marks
can be used to manipulate other components in the projector as
appropriate to eliminate the jitter and weave. These manipulations
can be accomplished by mechanical, optical and other appropriate
means. Therefore, while a particular form of the invention has been
illustrated and described, it will be apparent that various
modifications can be made without departing from the spirit and
scope of the invention. Accordingly, it is not intended that the
invention be limited, accept as by the appended claims.
* * * * *