Cinema laser projection

WHITEPAPER
Cinema laser projection
Illumination options for your cinema
whitepaper
Cinema laser projection
For over 10 years, our industry has transformed
from film to digital projection with the objective
of improving and providing a consistent motion
picture experience for your audience.
Simultaneously, the creative community has
expanded their storytelling techniques with
technology advancements such as 3D, High
Frame Rate and High Dynamic Range. These
advancements in storytelling have at times
required an upgrade or replacement of the
existing digital projector in order to showcase
these movies to your audience. For exhibitors who
are thinking about replacing their digital projection
equipment or outfit a new build, one technology
that has created new questions is laser projection.
What makes a great image on screen?
The answer is simple. Brighter is better, accurate colors appear
more natural, higher contrast is critical, and high resolution
displays finer details. In 2007, when studios defined the original
DCI specifications for digital cinema projectors they specified
these standards for on-screen brightness, color gamut, contrast
ratio, and exact pixel resolutions based on the technology
at the time.
What was known then:
›› How to light up screens to 14 fL (though not in 3D)
›› Xenon lamps could easily reproduce the P3 color gamut
›› Imaging chips could achieve a certain contrast ratio
and resolution
So these became the standards.
Today’s digital projectors have several illumination
options (Xenon lamp, laser phosphor, and RGB
laser) available. However, not all light sources
provide the presentation experience you or your
audience expect.
This illumination overview explores the reasons
why, when considering a laser projection solution,
RGB laser will soon become the dominant
illumination technology for lighting cinema
screens, provide a foundation for future
technology advancements, and enhance
the cinema experience.
Since then, the display industry has advanced rapidly.
Consumers can now purchase display technology for the home
with higher resolution, improved color and contrast that’s
comparable to many cinemas. The younger generation has
become more tech-savvy and will begin to notice these visual
differences, or lack of, if our industry fails to invest in keeping up
with technological advancements.
Is red truly red?
Color is perhaps one of the most misunderstood aspects
of the cinema experience.
0.9
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0.8
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0.7
560
0.6
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0.5
y
0.4
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0.3
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0.2
0.1
480
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0
0.1 380 0.2
0.3
0.4
0.5
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0.8
The outer curved boundary is the spectral locus representing
all the colors that can typically be perceived by the human eye.
Note the triangles that are plotted on the curve. These triangles
indicate the capabilities of various display technologies with
respect to the entire visible spectrum. The innermost triangle
defines the Rec.709 standard. This is a color standard defined
in 1990 by the television industry for HDTVs. It is also very close
to the capabilities of a typical computer display or conference
room projector. The next triangle out is the DCI P3 color gamut
for digital cinema projectors. Note the increased volume of
colors in this triangle versus the innermost one, especially
in various shades of green and deep reds. Of particular
importance here is the red color. Most people can easily spot
the difference between the orange-red in the Rec.709 triangle
versus the deeply saturated reds in the DCI P3 specification.
Not only is this a color which exists commonly in the world
off-screen, but is also critical for reproducing natural skin tones.
The largest triangle on the curve is the Rec.2020 color space,
recently developed by the television industry as an aspirational
goal for future UHDTVs. Note the significantly increased
coverage of the CIE color diagram, bringing in many new
colors that cannot be reproduced in the other color spaces.
There are currently no TVs that can perfectly reproduce this
gamut of colors. The only technology that can fully achieve this
is an RGB laser projector.
x
Rec. 2020
DCI P3
Rec. 709
Currently, every compliant digital cinema projector is built
to cover the DCI P3 standard to within reasonably tight
tolerance. To achieve this, most projectors need a device
called a Yellow Notch Filter (YNF), which is a glass optical
element that cuts out yellow light, hence increasing the relative
contribution of green, and more importantly, red light in
the displayed image. However, by cutting out yellow light,
we are also reducing the overall brightness of the projector.
As a result, cinema projector engineers must carefully balance
the design of YNFs to achieve the right color capabilities
without sacrificing too much brightness.
Laser phosphor projection
One interesting innovation seen in the projection market
recently is laser phosphor or blue-pumped phosphor.
On the surface, this seems like a revolution as it allows us to
create white projection light using only blue lasers, which are
based on a mature and economical laser device technology
that needs far less cooling than other lasers. This allows
manufacturers to build relatively inexpensive projectors
that need less maintenance than conventional projectors,
since there are no lamps to be changed.
However, there are some major drawbacks with respect to laser
phosphor technology, especially in a cinema environment. For
example, laser phosphor projectors use a lot of energy (>50%)
in the conversion of blue light to white light. Furthermore,
the native color gamut produced by this type of projector is
typically smaller than the Rec.709 triangle shown in the CIE
diagram and is particularly deficient in the critical green and red
colors that are essential for a natural looking image. As a result,
projector engineers using a laser phosphor light source need
to make tough decisions regarding the design of YNFs to retain
brightness while still achieving some essence of acceptable
color performance. For laser phosphor technology, the YNF
will waste as much as 50% of the available light to achieve the
demanding DCI P3 specification for cinema.
Xenon’s total cost of operation
Cinema lamp technology has been in use for decades now
and represents a solid value for exhibitors. The industry is
familiar with lamps and cinema operations are established
with lamp changes in the plan. Lamps can also provide an easy
brightness boost on screen to maintain even brightness over
years of operation or for special events like opening nights
for the next new blockbuster. Reference the brightness over
illumination lifetime chart below which demonstrates the total
cost of ownership between Xenon and laser phosphor by
outlining the benefit of restored brightness with Xenon lamps.
Lamp-based projectors will continue to be installed for the next
3-5 years which will require the use of replacement lamps for
10-15 years following.
Another important fact about Xenon lamps is that they offer
a very high-value proposition for cinemas operating in the 20K
lumen range for medium-sized screens. This is where 65% of
the world’s cinemas operate, and as such, new lower Xenon
prices and longer lifetimes have played an important role in
cost reduction of lamps, improved performance, and longevity.
Medium-sized screens really are the “sweet spot” where Xenon
lamps provide the best value for those concerned about total
cost of ownership.
Setting aside the image performance for a moment, some
projector manufacturers are pitching elusive financial benefits
of laser phosphor projectors for cinema use. However, when
calculating the net present value cost of all the lamps required
over the expected lifetime of a projector, in most cases, the actual
cost will be less than the cost of the laser phosphor projector.
Brightness over 30,000 hours
20K lumen-class, Xenon versus laser phosphor*
110%
1
(14 fL) 100%
2
3
4
5
(Number of lamps used)
6
7
8
80%
Percent of DCI
required brightness
70%
10
11
Xenon
90%
(11 fL)
9
11 fL typical
â Below DCI standards
Just over 1 year á
of operation (based on
10 hours per day)
60%
Laser phosphor
7.0 fL typical
50%
0%
0
2,800
5,600
8,400
11,200
14,000
16,800
Hours of operation
19,600
22,400
25,200
28,000
30,800
* ~20m wide screen * ~1.8 gain screen
The efficiency of laser
There is no doubt that lasers hold the promise of dramatically
improving the image quality on cinema screens, and RGB laser
projectors help the industry achieve those goals. With RGB
laser projectors, the white light comes from combining red,
green, and blue laser light sources in a precise way that can
cover up to and include the Rec.2020 color gamut. At the same
time, having red and green lasers means that there is absolutely
no conversion efficiency loss that is observed in laser phosphor
projectors. For cinema applications, a YNF is not needed so
there is no brightness loss from this device required to achieve
the DCI P3 color spec. If more red light is needed in an RGB
laser projector, more red lasers could be added. In fact, an
RGB laser system is over four times more efficient than a laser
phosphor projector at converting laser light into cinema quality
white light. As a result, RGB laser projectors can achieve much
higher brightness levels than laser phosphor projectors and
also offer advantages in terms of the contrast ratio that can be
achieved. Commercially, RGB lasers are the only cinema
illumination technology that currently delivers High Dynamic
Range (HDR) on cinema screens.
Next generation RGB laser projection
Recent advancements in red and green laser technology
are far more efficient than those currently operating in
premium cinemas around the world. These next generation
lasers don’t need to be cooled like today’s lasers, allowing
a huge reduction in system complexity, size, reliability issues,
and cost. Manufacturers will soon begin introducing RGB laser
projectors for mainstream cinema screens that can operate
at an equivalent cost of ownership to a comparable lamp
or laser phosphor-based projector. These new RGB laser
projectors will put a dramatically better image on screen
in terms of brightness, color, and contrast ratio.
With consumers being introduced to a variety of technologies
and devices to consume content, our industry must continue to
strive to provide spectacular on-screen experiences audiences
can only enjoy in cinema. The creative vision of today’s
directors’ takes advantage of these technologies, such as
high dynamic range and high contrast. RGB lasers are the
presentation engine to achieve these visions and improve
cinema for everyone. Exhibitors must be aware that laser
phosphor for cinema is a short-term solution and only suitable
for small cinema screens, where projectors require less lumens
or can operate at low brightness with the YNF intact. In
addition, laser phosphor projectors cannot take advantage
of high dynamic range and high contrast content. As
manufacturers’ ramp up RGB laser production to achieve
economies of scale and next generation RGB laser projectors
are being introduced to the market, RGB laser will soon
dominate the cinema industry as the primary illumination
source. The benefits in RGB laser illumination will continue
to make cinema the primary motion picture experience
for audiences.
Summary
›› N
ot all laser projectors are the same – exhibitors in the
market for laser projectors must understand the differences
between laser phosphor and RGB.
›› L
aser phosphor projectors are a step backwards in image
quality and the cinema experience.
›› R
GB laser projectors can dramatically improve the image
quality on cinema screens.
›› T
he cost of a Christie® Xenon lamp projector with inclusion
of all Christie lamps required over the expected lifetime is
less than the cost of a laser phosphor projector.
›› N
ext generation RGB laser projectors, which exist as
prototypes in labs today, will soon become the dominant
illumination technology in cinema.
Connect with an expert
If you have additional questions, or if
you need some help in selecting the right
solution, please contact us. We can connect
you with a network of experts who will be
happy to help you work through the final
steps of your procurement process.
Contact us
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Copyright 2017 Christie Digital Systems USA, Inc. All rights reserved. All brand names and product names are trademarks, registered trademarks
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Performance specifications are typical. Due to constant research, specifications are subject to change without notice.
Printed in Canada on recycled paper. 4560 Sep 17
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