U.S. patent application number 13/488806 was filed with the patent office on 2013-12-05 for high angle rear projection system.
This patent application is currently assigned to 3M Innovative Properties Company. The applicant listed for this patent is Rolf W. Biernath, Gary T. Boyd, John C. Schultz, Brian T. Weber. Invention is credited to Rolf W. Biernath, Gary T. Boyd, John C. Schultz, Brian T. Weber.
Application Number | 20130321910 13/488806 |
Document ID | / |
Family ID | 49640768 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130321910 |
Kind Code |
A1 |
Weber; Brian T. ; et
al. |
December 5, 2013 |
HIGH ANGLE REAR PROJECTION SYSTEM
Abstract
A system for projecting content at an angle to a rear projection
screen. The system includes a projector configured for projecting
changeable electronic content and a rear projection screen for
receiving the projected content at an angle and displaying the
projected content. The rear projection screen includes a turning
film having prisms facing toward or away from the projector. For
prisms facing toward the projector, a protective film covers the
turning film. When the projected content is displayed on the rear
projection screen, the content has a substantially uniform
appearance.
Inventors: |
Weber; Brian T.; (Saint
Paul, MN) ; Biernath; Rolf W.; (Wyoming, MN) ;
Schultz; John C.; (Afton, MN) ; Boyd; Gary T.;
(Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Weber; Brian T.
Biernath; Rolf W.
Schultz; John C.
Boyd; Gary T. |
Saint Paul
Wyoming
Afton
Woodbury |
MN
MN
MN
MN |
US
US
US
US |
|
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
49640768 |
Appl. No.: |
13/488806 |
Filed: |
June 5, 2012 |
Current U.S.
Class: |
359/454 |
Current CPC
Class: |
G03B 21/625
20130101 |
Class at
Publication: |
359/454 |
International
Class: |
G03B 21/62 20060101
G03B021/62 |
Claims
1. A system for projecting content at an angle to a rear projection
screen, comprising: a projector configured for projecting content;
and a rear projection screen for receiving the projected content at
an angle off a normal axis of the rear projection screen and
displaying the projected content, wherein the rear projection
screen comprises as arranged in the following order: a protective
film; a turning film having prisms facing toward the projector; a
spacer; and a rear projection film or plate, wherein the projected
content has a substantially uniform appearance when displayed on
the rear projection screen, wherein the rear projection screen
receives the projected content within an angular range of 30
degrees to 80 degrees off the normal axis.
2. (canceled)
3. The system of claim 1, wherein the rear projection screen is
shaped and the projected content has a shape substantially matching
the shape of the rear projection screen.
4. The system of claim 1, further comprising adhesive bonding the
protective film to the turning film.
5. The system of claim 1, wherein the protective film covers the
turning film, the spacer, and the rear projection film,
6. The system of claim 1, further comprising adhesive bonding the
spacer to the rear projection film.
7. The system of claim 1, further comprising an optically clear
adhesive securing the turning film to the spacer.
8. The system of claim 1, wherein the spacer comprises a polymeric
film or plate.
9. A system for projecting content at an angle to a rear projection
screen, comprising: a projector configured for projecting content;
and a rear projection screen for receiving the projected content at
an angle off a normal axis of the rear projection screen and
displaying the projected content, wherein the rear projection
screen comprises as arranged in the following order: a protective
film; a turning film having prisms facing toward the projector with
the prisms having a pitch between 5 microns and 80 microns; and a
rear projection film or plate, wherein the projected content has a
substantially uniform appearance when displayed on the rear
projection screen, wherein the rear projection screen receives the
projected content within an angular range of 30 degrees to 80
degrees off the normal axis.
10. (canceled)
11. The system of claim 9, wherein the rear projection screen is
shaped and the projected content has a shape substantially matching
the shape of the rear projection screen.
12. The system of claim 9, further comprising adhesive bonding the
protective film to the turning film.
13. The system of claim 9, further comprising adhesive bonding the
turning film to the rear projection film.
14. A system for projecting content at an angle to a rear
projection screen, comprising: a projector configured for
projecting content; and a rear projection screen for receiving the
projected content at an angle off a normal axis of the rear
projection screen and displaying the projected content, wherein the
rear projection screen comprises as arranged in the following
order: a turning film having prisms facing away from the projector;
and a rear projection film or plate, wherein the projected content
has a substantially uniform appearance when displayed on the rear
projection screen, wherein the rear projection screen receives the
projected content within an angular range of 30 degrees to 80
degrees off the normal axis.
15. (canceled)
16. The system of claim 14, wherein the rear projection screen is
shaped and the projected content has a shape substantially matching
the shape of the rear projection screen.
17. The system of claim 14, further comprising adhesive bonding the
turning film to the rear projection film.
18. A system for projecting content at an angle to a rear
projection screen, comprising: a projector configured for
projecting content; and a rear projection screen for receiving the
projected content at an angle off a normal axis of the rear
projection screen and displaying the projected content, wherein the
rear projection screen comprises as arranged in the following
order: a turning film having prisms facing away from the projector;
a spacer; and a rear projection film or plate, wherein the
projected content has a substantially uniform appearance when
displayed on the rear projection screen, wherein the rear
projection screen receives the projected content within an angular
range of 30 degrees to 80 degrees off the normal axis.
19. (canceled)
20. The system of claim 18, wherein the rear projection screen is
shaped and the projected content has a shape substantially matching
the shape of the rear projection screen.
21. The system of claim 18, further comprising adhesive bonding the
turning film to the spacer.
22. The system of claim 18, further comprising adhesive bonding the
spacer to the rear projection film.
23. The system of claim 18, wherein the spacer comprises a
polymeric film or plate.
Description
BACKGROUND
[0001] Rear projection films are increasingly used in digital point
of purchase signage. One of the challenges with using these rear
projection films in point of purchase applications relates to the
long throw distance of most projectors, typically measuring two to
three times the long axis of the display. The expansion angle of
the image emanating from the projector increases dramatically when
the throw distance is shortened. When the entrance angle of the
image projected onto the rear projection screen is increased, the
light capture efficiency of the screen decreases rapidly. This
phenomenon results in significant uniformity and view angle loss,
and it can lead to an observable hot spot in the center of the
image, which moves around as the viewer changes position, leading
to poor useful view angle. Accordingly, a need exists for an
improved rear projection screen, particularly for digital
signage.
SUMMARY
[0002] A first system for projecting content at an angle to a rear
projection screen, consistent with the present invention, includes
a projector configured for projecting content and a rear projection
screen for receiving the projected content at an angle and
displaying the projected content. The rear projection screen
comprises a protective film, a turning film having prisms facing
toward the projector, a polymeric film, and a rear projection film
or plate.
[0003] A second system for projecting content at an angle to a rear
projection screen, consistent with the present invention, includes
a projector configured for projecting content and a rear projection
screen for receiving the projected content at an angle and
displaying the projected content. The rear projection screen
comprises a protective film, a turning film having prisms facing
toward the projector with the prisms having a pitch between 5
microns and 80 microns, and a rear projection film or plate.
[0004] A third system for projecting content at an angle to a rear
projection screen, consistent with the present invention, includes
a projector configured for projecting content and a rear projection
screen for receiving the projected content at an angle and
displaying the projected content. The rear projection screen
comprises a turning film having prisms facing away from the
projector and a rear projection film or plate.
[0005] A fourth system for projecting content at an angle to a rear
projection screen, consistent with the present invention, includes
a projector configured for projecting content and a rear projection
screen for receiving the projected content at an angle and
displaying the projected content. The rear projection screen
comprises a turning film having prisms facing away from the
projector, a spacer, and a rear projection film or plate.
[0006] For any of these systems, the rear projection screen is
configured such that when the projected content is displayed on the
rear projection screen, the content has a substantially uniform
appearance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The accompanying drawings are incorporated in and constitute
a part of this specification and, together with the description,
explain the advantages and principles of the invention. In the
drawings,
[0008] FIG. 1 is a perspective view of system having a shaped rear
projection screen;
[0009] FIG. 2 is a perspective view of system having a shaped rear
projection screen and having content projected at an angle to the
film;
[0010] FIG. 3 is a perspective view of a system for high angle
projection onto a rear projection screen;
[0011] FIG. 4 is a side sectional view of a first rear projection
screen for high angle projection;
[0012] FIG. 5 is a side sectional view of second rear projection
screen for high angle projection;
[0013] FIG. 6 is a side sectional view of a third rear projection
screen for high angle projection;
[0014] FIG. 7 is a side sectional view of a fourth rear projection
screen for high angle projection;
[0015] FIG. 8 is a flow chart of a method for image correction for
high angle projection;
[0016] FIG. 9 is a diagram of an alternative embodiment for a
protective film on a rear projection screen; and
[0017] FIG. 10 is a diagram of another alternative embodiment for a
protective film on a rear projection screen.
DETAILED DESCRIPTION
[0018] Embodiments of the present invention include particular
constructions of rear projection screens for at least substantially
uniformly displaying content projected to the screen at an
angle.
[0019] FIG. 1 is a perspective view of system 10 having a shaped
rear projection screen. System 10 includes a projector 12 for
projecting changeable electronic content, a processor-based device
11 for electronically providing content to projector 12, a virtual
mask 14 having a projection area 18, and a shaped rear projection
screen 20. Processor-based device 11 can implement virtual mask 14
in software to effectively block content in region 16 such that the
displayed content, as represented by line 21, is projected within
projection area 18 and substantially conforms to the shape of
projection screen 20 as defined by its outer edge 22. Rear
projection screen 20 can optionally include a shaped optically
active light redirecting film, such as a Fresnel lens sheet, having
a shape corresponding with outer edge 22.
[0020] FIG. 2 is a perspective view of system 24 having a shaped
rear projection screen and having content projected at an angle to
the film. System 24 includes a projector 26 for projecting
changeable electronic content, a processor-based device 27 for
electronically providing content to projector 26, a virtual mask 28
having a projection area 32, and a shaped rear projection screen
34. Processor-based device 27 can implement virtual mask 28 in
software to effectively block content in region 30 such that the
displayed content, as represented by line 35, is projected within
projection area 32 and substantially conforms to the shape of
projection screen 34 as defined by its outer edge 36. Rear
projection screen 34 can optionally include a shaped optically
active light redirecting film, such as a Fresnel lens sheet, having
a shape corresponding with outer edge 36. In system 24, the content
is projected from projector 26 to projection screen 34 at an angle
38. Projecting the content at an angle allows, for example,
locating the projector out of view or to the side or above objects
so that the objects remain accessible.
[0021] In FIGS. 1 and 2, a bottle shape is used as the shape of the
rear projection screen for illustrative purposes only. The rear
projection screens can be shaped to conform to any desired content
to be projected upon them. Although a virtual mask having a
projection area to create the particular shape of the content is
described above, a physical mask can also be used to create the
particular shape of the content, or both a virtual and a physical
mask can be used.
[0022] FIG. 3 is a perspective view of a system 40 for high angle
projection onto a rear projection screen. System 40 includes a
projector 42 for projecting changeable electronic content, a
processor-based device 41 for electronically providing content to
projector 42, a turning film 44, and a rear projection screen 46.
Projector 42 projects content to turning film 44 at an angle off
the normal axis of rear projection screen 46, as represented by
lines 48, and turning film 44 redirects the projected content
through rear projection screen 46. Turning film 44 can be arranged
with prisms facing in away from projector 42 or facing out toward
projector 42.
[0023] High angle projection includes, for example, the projected
content being projected within the angular range of 30 degrees to
80 degrees off the normal axis of the rear projection screen. A
desired angular range for projection of content can be determined,
for example, by a cut-off acceptance angle for high contrast rear
projection screens that transmit on-axis light and at least
partially reject off-axis light. For a desired luminance of the
rear projection screen, the corresponding cut-off acceptance angle
providing for such luminance can be selected. Other methods are
also possible for selecting the desired angular range for
projection of content.
[0024] Rear projection screen 46 can be a shaped screen, as
described with respect to FIGS. 1 and 2, or a non-shaped screen. In
particular, the screens for high angle projection can use a
conventional outline of a screen (e.g., rectangular and not
conforming to the projected content) or arbitrary shapes to enhance
the visual appearance of the screen. Such shapes can be relatively
simple such as the outline of circles, ovals, rectangles with
rounded corners and the like, or more complex shapes such as stars,
outlines of humans, outlines of animals, animated characters and
the like. Acceptable shapes can also include outlines with interior
features (e.g., holes) such that no projected content is visible
within the interior features.
[0025] The combination of turning film 44 and rear projection
screen 46 can include additional components or a particular
construction, as explained below, to provide substantial uniformity
of the projected content and reduce sparkle in the content. Sparkle
is generally an exaggerated graininess in the image where small
regions appear variably brighter and darker, which changes with
viewing angle.
[0026] Rear projection screens, including shaped screens, are
described in the following, all of which are incorporated herein by
reference as if fully set forth: U.S. Pat. No. 7,923,675; U.S. Pat.
No. 6,870,670; and U.S. patent application Ser. No. 13/407,053,
entitled "Shaped Rear Projection Screen with Shaped Fresnel Lens
Sheet," and filed Feb. 28, 2012.
[0027] The projectors for projecting the changeable electronic
content can include mercury bulb based projectors (e.g., X56
projector from 3M Company), LED based projectors (e.g., MP180 and
MP410 projectors from 3M Company), and laser based projectors
(e.g., SHOWWX+ scanning laser projector from MicroVision, Inc.). In
some systems, use of a laser projector is advantageous because of
its very long depth of focus, resulting in little degradation of
the image quality from the top-to-bottom or side-to-side of the
projected image.
[0028] FIG. 4 is a side sectional view of a first rear projection
screen 50 for high angle projection. Rear projection screen 50
includes a protective film 52, a turning film 56, a spacer 60, and
a rear projection film (or plate) 64. Protective film 52 is secured
to turning film 56 with tape 54, which would be placed around the
edges of those two films. Turning film 56 is secured to spacer 60
with an optically clear adhesive 58. Spacer 60 is secured to rear
projection film 64 with tape 62, which would be placed around the
edges of those two films. Rear projection film 64 can include an
optically clear adhesive on the viewer side for securing the film
to a support substrate such as a window. Turning film 56 is
arranged with its prisms facing out toward the projector, and
protective film 52 protects the prisms from damage. Spacer 60
typically has a thickness in the range of 10 mils to 30 mils,
preferably about 20 mils for turning film prism pitches of 50
microns, and creates a space between turning film 56 and rear
projection film 64 in order to help reduce sparkle in the displayed
image. For a 5 micron prism pitch, the spacer typically has a
thickness in the range of 1 mil to 10 mils. For an 80 micron prism
pitch, the spacer typically has a thickness in the range of 20 mils
to 30 mils. In some embodiments, the prisms can be coated onto
thicker substrates to provide the required separation where the
turning film substrate functions as the spacer.
[0029] FIG. 5 is a side sectional view of a second rear projection
screen 66 for high angle projection. Rear projection screen 66
includes a protective film 68, a turning film 72, and a rear
projection film (or plate) 76. Protective film 68 is secured to
turning film 72 with tape 70, which would be placed around the
edges of those two films. Turning film 72 is secured to rear
projection film 76 with tape 74, which would be placed around the
edges of those two films. Rear projection film 76 can include an
optically clear adhesive on the viewer side for securing the film
to a support substrate such as a window. Turning film 72 is
arranged with its prisms facing out toward the projector, and
protective film 68 protects the prisms. This embodiment eliminates
the need for spacer 60 used in rear projection screen 50 by using a
turning film with a small pitch compared with turning film 56. In
particular, turning film 72 has a prism pitch in the range of 5
microns to 80 microns. The thickness of tape 74 can be increased as
the turning film pitch increases in order to provide for a larger
space between turning film 72 and rear projection film 76 as the
pitch increases.
[0030] FIG. 6 is a side sectional view of a third rear projection
screen 78 for high angle projection. Rear projection screen 78
includes a turning film 80 and a rear projection film (or plate)
84. Turning film 80 is secured to rear projection film 84 with tape
82, which would be placed around the edges of those two films. Rear
projection film 84 can include an optically clear adhesive on the
viewer side for securing the film to a support substrate such as a
window. Turning film 80 is arranged with its prisms facing in
toward the rear projection film (away from the projector), which
eliminates the need for a protective film over the prisms.
[0031] FIG. 7 is a side sectional view of a fourth rear projection
screen 83 for high angle projection. Rear projection screen 83
includes a turning film 85, a spacer 87, and a rear projection film
(or plate) 89. Turning film 85 is secured to spacer 87 with tape
86, which would be placed around the edges of those two films.
Spacer 87 is secured to rear projection film 89 with tape 88, which
would be placed around the edges of those two films. Rear
projection film 89 can include an optically clear adhesive on the
viewer side for securing the film to a support substrate such as a
window. Turning film 85 is arranged with its prisms facing in
toward the spacer and rear projection film (away from the
projector), which eliminates the need for a protective film over
the prisms.
[0032] FIG. 8 is a flow chart of a method 90 for image correction
for high angle projection. In method 90, one or more test images
are projected at an angle onto a rear projection screen such as the
screens described above (step 92). Examples of test images include
a four dot grid, a moving or expanding single pixel, a moving or
expanding column or row of light, or a grid test pattern. When
projecting the test image, the focus of the projected image should
be optimized for the rear projection screen being used. An image is
captured of the content projected onto the rear projection screen
(step 94). The position of the boundaries of the projected content
is compared with ideal or desired screen boundaries (step 96). The
comparison can be performed manually through a visual inspection or
automatically through use of an image sensor and software
processing.
[0033] If necessary, the projected image is compensated based upon
the comparison in step 96 such that widths of the projected image
at the top and bottom of the rear projection screen are at least
substantially equal in terms of perceived size (step 98). If
necessary, the compensation can also include compensating for
changes in resolution at adjacent edges of the rear projection
screen (step 100). This compensation for resolution changes can
include comparing the relative pixel sizes at adjacent edges of the
rear projection screen and compensating accordingly in order to
resize the image to obtain at least a substantially uniform
projected image. For example, the pixels can be resized in
particular portions of the image in order to obtain uniformity. The
pixels can also be adjusted to compensate for brightness
non-uniformity due to changes of incidence angle to the rear
projection screen.
[0034] The high angle rear projection screens can include optional
coatings on the protective films or on the non-structured side of
the turning films, such as hard coat, anti-fog, anti-fingerprint,
easy to clean, and antireflection coatings.
[0035] The following are exemplary components and materials for
implementing high angle rear projection screens. Polyethylene
terephthalate (PET), polyethylene terephthalate glycol (PETG), or
polycarbonate can be used for the spacer, as can other transparent
materials such as transparent plastics or glasses, or an air gap.
Alternatively, the spacer can be implemented with a polarizer.
[0036] The rear projection films or plates can be implemented with
beaded or microreplicated non-beaded screens. An example of a
beaded rear projection screen is the VIKUITI Rear Projection Film
(available from 3M Company, St. Paul, Minn.). Examples of
microreplicated non-beaded screens are disclosed in U.S. Pat. Nos.
7,184,210 and 7,057,810, both of which are incorporated herein by
reference as if fully set forth.
[0037] The turning films can be implemented with microreplicated
prism films, as further illustrated in the Example. The turning
films can also be implemented with optically active light
redirecting films (or plates) configured to function as a turning
film for the projection systems.
[0038] The tape, or other ways to bond together the edges of the
films, can be implemented with double-side adhesive films,
thermoset adhesive films or dispensed thermoset liquids, and
thermoplastic adhesive films or dispensed thermoplastic
liquids.
[0039] The cover sheet (protective film) is typically a transparent
film layer that provides protection for the rest of the film stack.
A typical protective film is 1 mil PET film (available from DuPont
Teijin Films, Hopewell, Va. This protective layer may not be needed
in all screen constructions. The cover sheet may be adhered at the
edges of the underlying adjacent film using RIM tape such as 3M
8150 tape (available from 3M Company, St. Paul, Minn.), a dispensed
liquid clear or opaque adhesive which may be thermoset, or a UV
cured adhesive. Only the edges of the cover sheet are adhered to
the turning film, creating an air gap and preserving the optical
properties of the turning film. This construction offers increased
durability, an environmentally stable film stack, and easy cleaning
with the turning film prisms protected by the cover sheet. The
sealing adhesive may be contained entirely within the outline of
the rear projection film, outside the edges of the rear projection
film, or a combination of those two positions.
[0040] Alternatively as shown in FIG. 9, the cover sheet can be
substantially larger than the turning film and rear projection film
layers. In FIG. 9, a rear projection screen 102 corresponds with
screens 50 and 66, or other screen with the prisms of the turning
film facing toward the projector. In this case, a protective film
106 need not be adhered to the optical stack of screen 102. Rather,
protective film 106 covers the optical stack and is adhered to the
supporting transparent structure 104 for the rear projection film,
such as a glass or plastic window, using tape 108 around a
periphery of protective film 106.
[0041] As another alternative as shown in FIG. 10, the cover sheet
can be substantially larger than the turning film and rear
projection film layers. In FIG. 10, protective film 106 covers the
optical stack and is adhered to a supporting transparent adhesive
film 109 that extends beyond the edges of rear projection screen
102, using tape 108 around a periphery of protective film 106. This
allows for the film stack to be completely sealed after
fabrication, simplifying system set-up on supporting transparent
structure 104 such as a glass or plastic window. In particular, the
film stack can be secured to supporting transparent structure 104
using an optically clear (removable) adhesive 111.
[0042] The sealing adhesive for the protective film can be opaque,
transparent, or of a particular color to coordinate, enhance, or
otherwise make the displayed images more noticeable. While a
rectangular protective film can be used, the protective film can be
cut to the same outline as the shaped screen or cut to the same
general outline and slightly larger (e.g., 0.25 inches larger) to
seal the edges of the film stack to the mounting surface or the
underlying adhesive coated film surface.
[0043] For any stack sealing method the stack edges can be
preserved through alignment of the individual layers during stack
assembly. In another method, the stack can be shaped after final
assembly for any of these sealing methods by cutting through the
edge seal layer. Various methods can be used to cut through the
edge seal including use of a laser, shaped steel rule die,
programmable knife cutting with one or more passes, or using other
techniques known for cutting irregular shapes in relatively thick
materials.
[0044] The protective film can include an adhesive layer on its
inner surface in place of the edge sealing tape. The adhesive layer
can be uniformly coated on the protective film layer and press
against the turning film prism peaks without an adverse optical
effect, or a second layer of optically clear film can be applied to
the uniformly coated adhesive and selectively removed around the
edges of the shaped protective screen in order to seal the edges as
illustrated by tape 108.
[0045] The protective film can also be used to hold the film stack
in position, eliminating the need for the edge sealing tape shown
in FIGS. 4-6. In particular, the rear projection film can be
adhered to a supporting surface such as a window. A turning film of
the same size or shape as the rear projection film can then be
aligned to the rear projection film and held in place by a
protective film larger than the turning film and rear projection
film shape.
Example
[0046] These examples are merely for illustrative purposes only and
are not meant to be limiting on the scope of the appended claims.
Beaded rear projection screens in combination with various turning
films were assembled and evaluated for sparkle, and image content
corrections were made to high angle projection content.
Sparkle Reduction--Test Methods
[0047] All characterization was done with an MPro 410 DLP based
projector, available from 3M Company, St. Paul, Minn. Various
optical films were used to turn light. The projector angle was also
varied for each film to optimally turn light through a VIKUITI Rear
Projection Film (available from 3M Company, St. Paul, Minn.).
Sparkle was quantified utilizing a Minolta A2 camera (available
from Konica Minolta Holdings, Inc, Tokyo, Japan) in manual mode to
maintain consistent exposure between pictures. Settings were chosen
to ensure the test region was not oversaturated. The settings were
as provided in Table 1.
TABLE-US-00001 TABLE 1 Exposure time: 1/60.sup.th second F11 ISO 64
Camera was set 1 meter from screen, fixed on a tripod Focus set to
1.1 meter as this was sharpest Zoom was set to 35 +/1.5 millimeters
for the range of the data set Images were set to highest
resolution, each image ~4 mb
[0048] ImageJ Version 1.45S software was used to quantify sparkle
of the images. Image J is open source software available from the
National Institutes of Health (NIH), Bethesda, Md. A rectangular
region was selected toward the center of the highest contrast
region of the photo measuring approximately an area of 16,500
pixels, and then brightness standard deviation and mean brightness
were measured within the rectangle. The standard deviation (Std
Dev) was divided by the mean to normalize the data with respect to
overall brightness, and this is reported as Normalized Standard
Deviation (Std Dev/Mean).
Sparkle Reduction--Sample Preparation
[0049] Turning films were examined in two orientations, prisms
facing out toward the projector, and prisms facing in toward the
VIKUITI Rear Projection Film. The turning films contained 60 degree
included-angle prisms with 18 micron and 50 micron pitch on 5 mil
and 2 mil PET backings, respectively. The prisms had no canting and
were symmetric.
[0050] Prisms consisted of microreplicated structures on one side
of a roll of a clear 2 mil PET or 5 mil PET (refractive index
.about.1.64) film (MELINEX 454 film from DuPont Teijin Films,
Hopewell, Va., 2 mil and 5 mil thicknesses). The microreplicated
structures were formed on the substrate from a UV curable acrylate
resin (refractive index .about.1.49, 85% by weight PHOTOMER 6210
product available from Cognis, Monheim, Germany, and 15% by weight
1,6-hexanedioldiacrylate available from Aldrich Chemical Co,
Milwaukee, Wis. and a photoinitiator 1% LUCIRIN TPO photoinitiator,
BASF Corporation, Florham Park, N.J.) using a roll based tool. The
microreplication tool used for this experimental example was a
metallic cylindrical tool with one-dimensional structure (linearly
extending prisms with a 50 micron pitch, and a second tool with 18
micron pitch). The one-dimensional structure was created by cutting
into the copper surface of the cylindrical tool using a precision
diamond turning machine. The resulting copper cylinder with
precision prismatic cut features was chrome plated. The plating
process of the copper master cylinder is used to promote release of
cured resin during the microreplication process. The film replicate
was made using an acrylate resin composition comprising acrylate
monomers that was cast onto a PET support film and then cured
against the precision patterned cylindrical tool using an LED based
ultraviolet curing unit.
[0051] Various glossy inserts were utilized to separate the rear
projection film and prisms to characterize any change in sparkle.
The glossy inserts identified in Table 2 were used to examine
various separations of rear projection film beads and turning film
prisms.
TABLE-US-00002 TABLE 2 4 mil: Mylar 400-A102: DuPont Teijin,
Chester, VA 5 mil: Mylar 500-J102 PE: DuPont Teijin, Chester, VA 7
mil: GE 8010MC 112 Polycarbonate (PC): General Electric Company,
Pittsfield, MA 10 mil: DE1-1D Polycarbonate: Bayer MaterialScience,
Pittsburgh, PA 20 mil: PETG: Professional Plastics Inc, Fullerton,
CA
[0052] The total spacer thickness reported includes the PET
substrate that the films were on for the prisms out configurations.
The samples with 18 micron pitch were on a 5 mil PET substrate, and
the samples with 50 micron pitch were on a 2 mil PET substrate. The
material reported as the spacer is the additional glossy insert.
Because the film turns light differently in each orientation the
projector angle was varied. With prisms facing in toward the rear
projection film, the MPro 410 projector was set to 57 degrees above
normal. For prisms out (facing the projector), the 410 projector
was set to 68 degrees above normal incidence. The films and spacers
were all pressed together using a tool in order to minimize error
from any inadvertent air gaps between the films.
Sparkle Reduction--Results
[0053] The sparkle of each different pitch turning film as a
function of spacer thickness is shown in the data of Table 3.
Sparkle was noticeably reduced in the samples as indicated by the
Std/Mean values with lower Std/Mean values resulting in noticeably
less sparkle.
TABLE-US-00003 TABLE 3 Prisms facing inward or outward Prism
relative to rear Insert Total Pitch projection film Insert Material
(mil) Std/Mean 18 In None 0 0.19 18 In PET 4 0.13 18 In PET 5 0.13
18 In PC 7 0.11 18 In PC 10 0.11 18 In PETG 20 0.10 18 Out None 5
0.10 18 Out PC 9 0.09 18 Out PC 10 0.08 18 Out PET 15 0.07 18 Out
PETG 25 0.06 50 In None 0 0.14 50 In PET 5 0.14 50 In PC 7 0.14 50
In PC 10 0.14 50 In PETG 20 0.12 50 Out None 2 0.17 50 Out PET 6
0.16 50 Out PC 7 0.14 50 Out PC 12 0.12 50 Out PETG 22 0.10
Image Correction
[0054] Projecting at high angles degrades the projected image
quality because of issues such as depth of focus and image
distortion. The following method was used to correct content for 60
degree high angle projection. A test image of a checkerboard was
projected onto the projection screen. The projection screen was
moved up until the center of the screen was located optimally in
terms of image brightness and focus. Optimal location in terms of
image brightness and focus was assessed subjectively. A Canon
POWERSHOT SD780 image sensor (available from Canon Inc, Tokyo,
Japan) was used to capture an image of the projected pattern. Using
this captured image, pixels were identified which corresponded to
(or appeared at) the four corners of the projection screen.
Keystone distortion correction was performed on the image using
these identified pixel locations as the new (or keystone corrected)
image pixel corners. This correction was implemented using the
PHOTOSHOP CS4 program (available from Adobe Systems Inc. San Jose,
Calif.) using the transform/distort function keyed to the four
points. The resulting image was improved since the entire image was
not noticeably distorted.
[0055] This same technique was used on video content. In this case
a sequence of still images was extracted from the video, keystone
corrected, and then composited into a keystone corrected video
clip. An alternative was to use the FINAL CUT PRO X program
(available from Apple Inc. Cupertino, Calif.). This software
keystone corrected a video sequence without separating the video
into individual image frames. The keystone correction was most
conveniently calculated from the (x,y) coordinates of the four
points at the corners of a rectangular displayed image the same
size or larger than the screen size. Arbitrarily shaped screens
could also be keystone corrected using this technique.
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