U.S. patent application number 11/870162 was filed with the patent office on 2008-04-10 for optpo-mechanical filter for blending of images from a digital projector.
This patent application is currently assigned to Christie Digital Systems Canada, Inc.. Invention is credited to Brock Eccles, Bruno GILBERT, Gord Harris.
Application Number | 20080084543 11/870162 |
Document ID | / |
Family ID | 37693921 |
Filed Date | 2008-04-10 |
United States Patent
Application |
20080084543 |
Kind Code |
A1 |
GILBERT; Bruno ; et
al. |
April 10, 2008 |
OPTPO-MECHANICAL FILTER FOR BLENDING OF IMAGES FROM A DIGITAL
PROJECTOR
Abstract
A filter mounting apparatus for use with an optical filter
placed between a projector lens and screen. The filter mounting
apparatus comprises a metallic disk connected to the projector
lens, and an assembly magnetically connected to the metallic disk
for mounting the optical filter a predetermined distance from the
projector lens.
Inventors: |
GILBERT; Bruno; (Waterloo,
CA) ; Harris; Gord; (Georgetown, CA) ; Eccles;
Brock; (Kitchener, CA) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Christie Digital Systems Canada,
Inc.
Kitchener
CA
|
Family ID: |
37693921 |
Appl. No.: |
11/870162 |
Filed: |
October 10, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11189836 |
Jul 27, 2005 |
7296902 |
|
|
11870162 |
Oct 10, 2007 |
|
|
|
Current U.S.
Class: |
353/30 ;
353/84 |
Current CPC
Class: |
G03B 21/14 20130101;
G03B 21/26 20130101 |
Class at
Publication: |
353/030 ;
353/084 |
International
Class: |
G03B 21/14 20060101
G03B021/14; G02B 5/22 20060101 G02B005/22 |
Claims
1. An optical filter adapted for placement between a projector lens
and screen, said filter comprising a plurality of layers of
transparent polymer film incorporating a neutral density (ND) color
dye and having respective edges profiled to conform to the shape of
the edge of an image as it exits the projection lens, and wherein
said edges are positioned relative to each other with an offset to
create a stepped graduation of cumulative color dye density.
2. The optical filter of claim 1, wherein said polymer film is pre
fabricated from one of transparent polycarbonate and polyester.
3. The optical filter of claim 1, wherein the density of the ND dye
is selected for optimizing black image generation with different
combinations of lenses, projector screen gains and geometries to
minimize impact on mid tone and light scenes.
4. The optical filter of claim 1, wherein the density of the ND dye
on respective filter layers is relative to ND dye densities of
other ones of said filter layers to vary said stepped graduation of
cumulative color dye density.
5. The optical filter of claim 1, wherein an edge of the film is
profiled to conform to the shape of the edge of the light image
leaving the projector.
6. The optical filter of claim 1, wherein colour density of each
said ND dye in said layers is selected to optimize light roll-off
slope for filtering the light density of different images projected
from different projectors having different power lamps and
brightness.
7. Use of a filter assembly having a pair of optical filters, each
in accordance with claim 1, to create a single projected image from
two overlapping projected images having an imperceptible blend
region therebetween.
8. The optical filter of claim 1, wherein said plurality of layers
is variable in number to vary said stepped graduation of cumulative
color dye density.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/189,836, filed Jul. 27, 2005, the disclosure of which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to projection systems, and
more particularly to an apparatus for blending of images from
multiple digital projectors, as are used, for example, in
simulation systems with day/night scenarios.
[0004] 2. Description of the Related Art
[0005] Multiple projection displays are well known in the art,
having been used for many years in the film industry to create
high-resolution images on large variously shaped screens (e.g.
domes, cylinders and toroids, in addition to large flat screens).
For example, the CINERAMA system developed in the 1950s used three
separate projectors to project three images which were then
combined to form a single panoramic image. More recently, video
based multiple projector display systems have been used for flight
simulators, wherein multiple video screens are placed next to each
other to form a large tiled image display.
[0006] Because of the difficulty in `butting` multiple images
edge-to-edge, a significant disadvantage of such multiple projector
display systems is that the images often do not appear as one
single continuous image on the display screen. When multiple images
are projected side-by-side and/or top-to-bottom on a single screen,
a seam or overlapping region is typically created between the
images. Consequently, the final display image appears either as
multiple images placed side-by-side with a gap between images or,
if the images are made to overlap on a single screen, with a bright
line or band there between. When the images of two projectors
overlap, the amount of light in the overlapped regions of the
images is approximately double the amount of light observed on the
screen in regions where only a single projector image resides.
Therefore, the region of overlap is brighter than the balance of
the image.
[0007] The above described problem applies equally to black
projector output levels, and is particularly relevant to DMD type
displays with a finite black level off state (unlike CRT
projectors). Specifically, when displaying a black image, instead
of protecting a generally uniformly black area across the entire
displayed image the black image tends to brighten in the regions of
overlap, giving rise to objectionable artifacts.
[0008] Attempts have been made to hide such artifacts, one such
example being to electronically reduce light intensity in the
regions of over lap to the same brightness levels as the regions of
non-overlap. Such practices are usually implemented by adjusting
the input video level to obliterate the visibility of the regions
of overlap. Although electronic blending does work for CRT
projectors (because the "off" state is completely black), it does
not work as well for light valve LCD or DMD/DLP type micromirror
projectors when generating black images, which is a matter of
importance when projecting quality simulated night scenes (such as
required, for example, in aircraft and ship simulators).
Specifically, because the off-state (i.e. black) brightness is a
minimum 000 video code value, electronic reduction of light
intensity cannot occur since it is already as low as it can go
(zero) so it cannot eliminate the bright region of overlap without
adversely affecting the contrast ratio of the projection system.
Approaches such as boosting the black level of the non-blended
regions degrade contrast rather significantly.
[0009] Another prior art solution is set forth in U.S. Pat. No.
6,017,123 (Bleha et al), wherein a blending device is located in
the path of light between the projection lens and the screen. The
blending device smoothes off-state and on-state illumination levels
in the region of overlap without reducing the contrast ratio of the
projector. The blending device includes physical devices such as
filters, solid masks, and/or a combination thereof as a substitute
for electronic blending.
[0010] A matte box type solution has also been used wherein a hard
mechanical edge slides in and out of the light path of the
projector, usually in a strict linear and parallel fashion.
Although this solution effectively hides the edge of a projected
DMD micromirror device between the imaged area and the non-imaged
DMD mask, it cannot create a convincing black blend across the
entire overlap region since the density of penumbra (blurred
shadow) is fixed by the projector and lens pupil geometry and
distance from the lens. Consequently, the matte box type solution
does not work well for both dark and light scenes and is not
sufficiently controllable, nor does it work well for short throw
lenses. Furthermore, it does not handle keystoned projection setups
whereby the overlapped regions are not necessarily in the form of
vertical or parallel lines.
[0011] Another method of creating a softer edge in the overlap
region is to use optical filters, fabricated using photomask
techniques or solid fabrication techniques such as
stereolithography, wherein the filters incorporate comb-like or
serrated edges. Typically, these masks control the blending of
light by selecting the size, shape, length and density of teeth.
The main disadvantages of this method are quality of the light
blending, cost, size, weight and the difficulty in customizing for
particular lenses, projectors, or for unique projection geometries.
Mechanical light attenuators can help disguise the blend edges
(similar to tape) but are not as controllable or flexible as a
custom optical filter.
[0012] A further method involves placing glass plates in front of
the lens, either with Neutral Density (ND) graduated filters
incorporated therein, or simulated with print screen patterns of
various dot density similar to the method used for printing
half-screen photographs in newspapers. Various densities may be
created by photographically changing dot screen density on a coarse
scale, or by variable density dyes, etc. The main disadvantage of
such ND filter methods is the loss of light due to back reflection
on each glass or plastic surface. For seams (overlapped regions)
that involve top, bottom, left and right in a dome simulator this
requires a very complex single filter, or for best adjustment
flexibility, multiple sheets of glass each of which affects not
just the blend overlap region, but the entire image area. Such
methods are also very expensive to customize, and heavy to
mount.
SUMMARY OF THE INVENTION
[0013] It is an aspect of the present invention to provide an
apparatus for optical blending of images from multiple projectors
which overcomes the disadvantages of the prior art. According to a
preferred embodiment, an optical blending device is mounted to the
lens of a projector so as to maintain a constant distance from the
lens, where the distance is optimized for proper edge blending and
temperature considerations, where variations in width, height,
size, shape (edge curve), and density of the device are
accommodated for optimization with different lens, throw, projector
and screen combinations. In one embodiment, the device is
magnetically mounted for virtually unlimited flexibility in terms
of angling, curving, cutting contours etc. on any side of the
image. As such, the apparatus according to the present invention
benefits from simplicity, low-cost, no-tool adjustment and zero
backlash or play (i.e. high accuracy).
[0014] In one variation, the optical blending device is connected
to a disk mounted around the lens bezel. In another variation, the
optical blending device is connected to a steel frame which, in
turn, is attached to the disk by rigid polymer standoffs having
magnetized ends. In a further variation, overspill masks are added
to the steel frame. In yet another variation, the standoffs are
replaced by micro-actuators for independent control of the distance
between the blending device and lens.
[0015] The above aspects can be attained by a filter mounting
apparatus for use with an optical filter placed between a projector
lens and screen. The filter mounting apparatus comprises a metallic
disk connected to the projector lens, and an assembly magnetically
connected to the metallic disk for mounting the optical filter a
predetermined distance from the projector lens.
[0016] These together with other aspects and advantages which will
be subsequently apparent, reside in the details of construction and
operation as more fully hereinafter described and claimed,
reference being had to the accompanying drawings forming a part
hereof, wherein like numerals refer to like parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows a generally rectangular filter component used
in the preferred embodiment;
[0018] FIG. 2 shows a graduated filter constructed from layers of
rectangular filter components shown in FIG. 1;
[0019] FIG. 3 shows a filter holder for the graduated filter of
FIG. 2;
[0020] FIG. 4 is an exploded view of the filter holder shown in
FIG. 3;
[0021] FIGS. 5A and 5B show front and rear surfaces of a disk for
mounting one or more filter holders of FIG. 3, according to a first
embodinierit;
[0022] FIG. 6 shows a filter holder mounted to a projector lens
using the disk of FIGS. 5A and 5B;
[0023] FIG. 7 shows a standoff for mounting a rectangular frame
shown in FIG. 8 for supporting one or more filter holders of FIG.
3, according to a second embodiment;
[0024] FIG. 9 shows a pair of overspili masks for optional
attachment to the disk of FIGS. 5A and 5B over the rectangle or
frame of FIG. 8;
[0025] FIG. 10 shows a filter holder with overspill masks mounted
to a projector lens using the standoffs of FIG. 7 and rectangular
frame of FIG. 8; and
[0026] FIG. 11 shows a further alternative embodiment wherein a
pair of filter holders may be positioned into repositioned in and
out of the projected light frustum by means of an electrically
powered actuator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] With reference to FIG. 1, a generally rectangular filter
component 1 is shown cut from a commercial transparent polymer
(polycarbonate or polyester) film impregnated or coated with a
neutral density (ND) color dye, such as described in U.S. Pat. No.
6,531,230 (Weber et al). As is known in the art, one of the longer
edges of the filter component is profiled to conform to the shape
of the edge of the image as it exits the projection lens of a
projector. Typically, the profile follows the shape of a shallow
curve 3.
[0028] In FIG. 2, a graduated filter 5 is shown made from layers of
cut film filter components of FIG. 1, wherein the curved edges are
offset, as indicated by reference numeral 7, to create a `stepped`
graduation of the density of the color dye. The width of the cut
filter components and graduated stepped offsets may be varied to
best conform to the width of the image area to be blended. Also,
the number of layers of cut filter components can be varied (three
layers being shown in FIG. 2) to refine the graduation or
`drop-off` profile to best conform to the light intensity of the
associated projector. Furthermore, the color density of the ND dies
can be specified to optimize filtering the light density of the
image projected from different projectors having different power
lamps.
[0029] Preferably, pre-fabricated ND filter gels are utilized,
which can be economically cut, shaped, spaced and created with
differing light roll-off slopes or gradients by combining any
combination of densities in discrete steps. This provides
significant flexibility for customization and very low-cost
compared to ND coatings over an entire sheet of glass or plastic,
as set forth in U.S. Pat. No. 6,017,123.
[0030] The layered graduated filter is protectively secured within
a filter holder 9, as shown in FIGS. 3 and 4. The filter holder 9
preferably comprises a profile-cut strip of rare earth magnetic
sheet 11 coated with adhesive on one face, and a profile-cut strip
of polycarbonate sheet 13 between which the film filter layers 5
are sandwiched. In a successful prototype, the thickness of
polycarbonate sheet 13 was 0.03 inches.
[0031] As discussed above, the filters 7 and magnetic filter
holders 9 are positioned in front of the vertical and/or horizontal
edges of the light images as they exit the projection lens 14 of a
projector 16. As shown in FIG. 5, the filters 7 and magnetic filter
holders 9 are magnetically connected to a steel disk 15 which, in
turn, is secured to the projector lens bezel 14 via a rigid polymer
(e.g. Delrin.RTM.) ring 17 by nylon tipped set screws 19.
[0032] Unlike the optical filter set forth in U.S. Pat. No.
6,017,123, the optical filter 7 does not cover the entire projected
image area and therefore does not produce back reflections that may
be considered annoying to a user in a simulation environment and
also reduces light transmission and MTF due to dust, dirt,
fingerprints etc. on the cover glass or plastic. In contrast with
U.S. Pat. No. 6,017,123, applicant's filter 7 is constructed from
low cost complete ND layers of chosen densities, custom selected to
match the ideal density required for good black image generation
with any particular combination of lens, projector, screen gain and
geometry, with minimal impact on mid tone and light scenes.
[0033] The filter 7 may be positioned at the lens bezel 14, as
shown in FIG. 6, or further away from the lens 14. Preferably, the
filter 7 is located between 0 inches and 6 inches from the lens
bezel 14. In order to mount the filters 7 further from the lens
bezel, a plurality of standoffs 21 (FIG. 7) may be magnetically
attached to the steel disk 15, and a rectangular steel frame 23
may, in turn, be mounted to the standoffs 21 for holding the
filters 7, as shown in FIG. 8. The standoffs 21 are also preferably
fabricated from rigid polymer (Delrin.RTM.) of desired length into
the ends of which rare earth magnets are disposed of sufficient
strength to attach the standoffs 21 to the steel disk 15 and steel
frame 23. The magnetic standoffs 21 enable the rectangular sheet
steel frame 23 to be variably positioned around the projected light
frustum anywhere in the range of the lens offset (i.e. due to
projector lens shift adjustments).
[0034] As shown in FIG. 9, thin sheet magnet overspili masks 25 can
optionally be adhered to the sheet steel disk 15 or steel frame 23
to mask extraneous or overspill light. As shown by reference
numeral 27, the mask edges can optionally be profiled to create a
desired image geometry.
[0035] FIG. 10 shows a filter mount assembly according to the
preferred embodiment, fitted to a digital projector 16 with
magnetic standoffs 21, rectangular steel frame 23, overspill masks
25, magnetic filter holder 9 and graduated filter 7.
[0036] Additional advantages of the invention may be achieved by
selectively controlling the linear position of the optical blend
filters 7 in and out of the projected light frustum, for switching
from day to night simulation. For example, if no dark scenes (i.e.
black) are necessary, such as during daytime flight simulation, the
filters 7 can be positioned for best edge blending in non-black
conditions or optionally may be completely removed from the image
so that only electronic blending is performed. By way of contrast,
for nighttime or other dark images, the optical filters 7 are
typically required to be fully inserted into the image. For
mid-tone scenes, an intermediate filter position may be desirable.
Also, for domes (e.g. 3.times.3 array of projected images),
adjustment of the filters 7 may be required both left and right as
well as up and down to accommodate four sided seams (top, bottom,
left, right).
[0037] To that end, FIG. 11 shows an embodiment of the invention
for electrically controlling the linear position of the optical
filters 7 in an interactive, controlled fashion, rather than simply
fixing the position of the filters relative to the lens by magnetic
adherence, as discussed in connection with the embodiments above.
An electrically powered, incremental micro adjust linear actuator
29 is controlled by an electronic controller (not shown), such as a
PC. The filter holders 9 are connected to respective linear
actuator mount brackets 31, before moving laterally in and note of
the image under control of the actuator 29. Typical image blends
from 12.5% to 35% of the image width typically require a filter
movement range of from 0.3 inches to 1.5 inches (maximum). Although
not shown, it will be appreciated that additional filter holders 9
may be disposed and selectively positioned in a vertical
orientation using the depicted methodology to permit construction
of systems with up to four independently adjustable blend filters 7
per projector (i.e. top, bottom, right and left), for use with dome
simulators or large tiled arrays.
[0038] In summary, the filter mounting apparatus of the present
invention is characterized by simple and compact deployment (i.e.
the assembly is smaller than the envelope of the range of
adjustment that it is able to cover), and light weight construction
(i.e. no heavy glass components or complex adjustments mechanisms)
which enables it to be mounted directly to the lens without pulting
undue strain on the lens offset adjustment motors. The mounting
apparatus is cost effective (few parts, simple to manufacture) and
the profile of the filters 7 and the setup of the mount is readily
adapted to the requirements of different screen geometries and edge
blending (including multiple projector arrays on flat, spherical,
toroidal or cylindrical screens with a range of different blend
lengths, widths and non orthogonal horizontal and vertical blend
relationships).
[0039] A person of skill in the art who will appreciate that the
linear actuator 29 can be any one of a number of conventional
devices, such as a solenoid, a step or motor with lead screw, a DC
motor with lead screw, etc. Micro switches may be incorporated at
each end of a desired range of motion. Also, in addition to the
contemplated lateral horizontal and vertical positioning of the
filters holders 9, the electrically powered actuator 29 may also
operate on a pivoted lever on which the filters holders 9 are
mounted so as to rotate through a 90.degree. rotation.
[0040] As an alternative to the electrically powered actuator of
FIG. 11, other devices may be employed such as a small rotary motor
with belt or gear drive in conjunction with a sliding rod, a
computer disk drive motor for positioning the filters 7, etc., all
of which would be well known to a person of skill in the art.
[0041] The many features and advantages of the invention are
apparent from the detailed specification and, thus, it is intended
by the appended claims to cover all such features and advantages of
the invention that fall within the true spirit and scope of the
invention. Further, since numerous modifications and changes will
readily occur to those skilled in the art, it is not desired to
limit the invention to the exact construction and operation
illustrated and described, and accordingly all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *