TAKS II, ITEM 5, FIRST TECHNICAL REPORT LAMPS FOR REAR PROJECTION VIEWERS
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Publication Date:
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MAILING ADDRESS
July 15, 1965
Taks It, Item 5, First Technical Report
Lamps For Rear Projection Viewers
Work Statement
Review literature and make an economic and
performance per watt profile of the types of lamps
applicable to rear projection viewers, such as:
1000 watt xenon, mercury xenon, quartz iodine, and
tungsten. Performance analysis to include estimates
of heat rejection, visible light level and spectral
distribution obtainable from band pas filters.
The analysis and report preparation will be accomplished
jointly be
Declass Review by NGA.
Submitted by:
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Task II, Item 5, First Technical Report
Page
1.
Summary
.1.1 I
ntroduction
1
1.2 D
iscussion Summary
1
1.3 D
ata Summary
1
2.
Definition of Terms
6
2.1 Units and Equations
6
2.2 Visibility
10
3.
Technical Discussion
15
3.1 Source Characteristics 15
3.2 Lamp Efficiency 18
3.3 Requirements for Cooling at Film 19
3.4 Cooling at Lamp 21
3.5 Form Factor 22
3.6 Filters 27
3.7 Lamp Tolerance and Replacement Time 29
3.8 Spectral Distribution 29
3.9 Screen Illumination from B and A. 31
3.10 Screen Illumination from Total Lamp Luminance 36
3.11 Summary of Screen Illumination and Heat
Rejection Factors 40
4. Data Sheets for Specified Lamps
1000 Watt Tungsten C-13 42
1000 Watt Tungsten C-13D 43
900 Watt Xenon 44
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Task It, Item 5, First Technical Report
List of Tables
Table I Sumcr-ary Tabulation of Lamp Data for Rear
Projection Viewers
Page
Table II Table of Units 7
List of Figures
Fig. 1 Standard Observer, Relative Visibility, V(A) 11
Fig. 2 Spectral Distribution of Sunlight 12
Fig. 3 Spectral Distribution of Black Body
Radiation at 3250?K 13
Fig. 4 Spectral Distribution of Quartz Iodide Lamp 16
Fig. 5 Brightness of Tungsten 17
Fig. 6 Black Body Radiation for various color
temperatures 17a
Fig. 7 Radiation Lobe of C-13 Tungsten Filament 26
Fig. 8 Radiation Lobe of C-13D Tungsten Filament 28
Fig. 9 Filter Transmission 30
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1. Summary
1.1 Introduction
In this report an attempt has been made to
(a) gather basic data and representative information
on several 1000 watt lamps;
(b) define terms and calculate representative
performance;
(c) establish a format for presentation of the data.
There are many gaps. For example there is no good information
on the conversion efficiency of Tungsten and it was estimated.
Some of the arc brightness data appears to be inconsistent
and needs further checking. We are not satisfied with the
presentation of screen illumination data (especially the
projection lens aperture) in Table I and will give it added
consideration. With the further cautionary note that all of
the data is preliminary and subject to revision we submit
this first report.
1.2 Discussion Summary
Photometry deals with the response of the eye to
light. Thus radiant power from a source or.a surface must
always be multiplied by the relative spectral sensitivity
function of the eye to obtain values in photometric units.
All tungsten lamps of whatever size and power when
operated at the same color temperature have the same
spectral distribution. The spectral distribution depends
only upon the filament color temperature. Two filament
shapes C-13 and C-13D are of greatest interest in projection
work. The radiation lobes of these filaments are quite dif
ferent but all lamps which use C-13 filaments will have
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approximately the same radiation lobe and all lamps which
use the C-13D filaments will have approximately-the same
radiation lobes.
The xenon high pressure arc lamps have the same
spectral distribution regardless of wattage and the spectral
distribution of other high pressure arc lamps depends on the
gas used.
The conversion efficiency (radiated watts per input
watt) of the compact high pressure arc lamps is approximately
507,. No good data is available for tungsten but the conversion
efficiency is believed to be about 807..
1.3 Data Summary
Lamp data are summarized in Table I for ready
reference.
The color temperature, lamp life and lamp cost are
manufacturer's published data. Note that the color tem-
perature of the compact high pressure arc lamps are only
approximate correlations to black body radiation, dis-
regarding spectral lines. The luminance in lumens is
from manufacturer's published data. The luminance in
visible watts is lumens divided by 621* and is the area
under the visibility curve expressed in watts. Note that
this is quite different from the watts radiated in the
visible region of the spectrum.
The radiation conversion efficiency is an estimate
for tungsten and for the arc lamps is taken from manufac-
turer's data. The heat dissipated at the lamps and the
* The quoted conversion value of lumens per watt varies from
621 to 692 depending on the source of information.
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n
Lang
Type
Summary Tabulation of Lamp Data for Rear Projection Viewers, Table I
Color
Temp.
Power Required
Lamp Lamp Cost Total Visible
Life Cost Per Hr. Radiation Cost
?K ,Hours
Life-Cost Luminance
Visible C Per
/Hr Lumens Watts 1000 im.
Per Hr,
1000 Watt
Tungsten C-13
ASA #DPW
3200
50 9.80 19.6
28,000:
45.1 0.7
ASA #DRC
3250
50 7.50 15.0
30,000"
40.3 0.5
ASA #DRB
3350
25 6.90 27.6
32,000
51.5 0.86
Tungsten C-13D
ASA #DRS
3325
25
6.75 27.0
.28,500
45.9 0.95
ASA #DFD
3375
10
5.75 57.5
.30,500:
49.1 1.89
ASA #DGS
3375
10
7.25 72.5
33,000;
53.2 2.20
Quartz Iodine
ASA #DXW ;
3200
150
16.95 11.3 `
26,000:
41.9 0.43
ASA #DXN
3400
30
14.95 50.0
:33,000 -1
53.1 1.52
Xenon-Mercury
D.C Hanovia 528B9
5500
1000 If
200.00 20.0
40 , 000
63.4 0.5
A.C Hanovia 537B9
5500
:1000
200.00 20.0 ,
.50,000
80.5 0.4
}
900 Watt
D. C Hanovia 538C9
5500
1000
1
200.00, 20.0
1
35,000
56.4 0.57
D.C OSRAM XB0900
870 W. Rated Va lue sj
6000
1500
245.00'4 16.3
;30,500
49.1 0.53
1105 W. Maximum
s
j
Values 1
6000
2000
245.00 12.3
41,500
66.9 0.30
( Appr ' ed For R lease 2004/02/17: C411 -RDP78B
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
115-120 VAC Line Power
58-72 Volts 16 amps, D.C.
60-70 Volts 18 amps. A.C.
}
29-35 Volts 28-amps.
D.C. Power Supply-
70-110 Volts 30-50 amps.
I.C. Power Supply.
70-110 Volts 30-50 amps.
D.C. Power Supply.
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Summary Tabulation of Lamp Data for Rear Projection Viewers, Table I (cont'd)
Lamp
Type
1000.Watt
Tungsten C-13
Color`Lumin
Temp.
Conver Total
sion Radia-
Effie ._ . _ j can
ASA #DPW
3200
28,000
ASA #DRC
3250
30,000
ASA #DRB
3350
32,000
Tungsten C-13D
ASA #DRS
3325
28,500
ASA #DFD
3375
30,500
ASA #DGS
3375
33,000
Quartz Iodine
ASA #DXW
3200
,26,000
ASA #DXN
3400
;33,000
Xenon-Mercury
D.C Hanovia 528B9
5500
40,000
A.C Hanovia 537B9
5500
5 0,000
900 Watt
Xenon
D.C Han
ovia 538C9
5500
35 , 000 iH
D.C OSR
AM XB0900
870 W.
Rated Values.
6000
30,500
1105 W.
Maximum
Values
6000
41
500
,
?4
7 Watts
80 800
80 800
80 800
80 800
80 800
80 800
80 800
80 800
50 500
50 500
50 450
53
53
585
Heat
Watts
Scr_eeni -~- rojec
Non- Collect Per ' Projeci P
Filter tin Bright Cost tion
Visible at Gate'
----- - Ea c1 Qr Eactm .- ne s s Pna-
Watts - %.
672 .044
Screen Illumination
per ? Aper-
%Q ; Ft-L .100 ft-L ture
25.6
8.4
376
5.2
8.4
403
3.7
8.4
430
6.4
8.4
383
7.1
8.4
410
; 14.0
8.4
444
16.4
7.1
296
3.8
7.1
375
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4.4
3.5
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radiation are derived from the conversion efficiency. The
radiation power in the non-visible and the radiated power
in the visible were measured on the black body spectral
distribution curves for tungsten and were taken from the
manufacturer's data for xenon and xenon-mercury lamps.
The power at the gate depends upon the collection efficiency
and filter efficiency and is dervied from both the visible
and non-visible radiation.
The screen illumination data is based on total lamp
lumens, the projection efficiency and a 30" square screen.
In turn the projection efficiency is based on the product
of a number of factors standardized for this report:
a.) Collection efficiency (900 Collection angle)
b.) Condenser transmission efficiency
c.) Filter efficiency
d.) Film gate blocking factor
e.) Projection lens aperture blocking factor
f.) Screen transmission 75:, screen gain 1.0.
It was assumed that screen brightness would not
change with magnification. This of course is an approxi-
mation which is good only over a reasonable range of
magnification such as up to 48x. The approximation results
from the requirement to add condenser elements at higher
magnifications. In addition for large filaments and large
projection lens magnifications, the projection lens f/number
may be unavailable.
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2. Definition of Terms
2.1 Units and Equations
There has been much unnecessary confusion with regard
to photometry largely owing to the existence of an un-
necessary number of terms that have found their way into the
vocabulary. Actually there are four quantities that suffice
to handle any problem that may arise in either radiometry
or photometry. These disciplines together with the basic
quantities are defined herein. (See also Table II)
a.) Radiometry is the science of measurement of
radiant energy.
b.) Photometry is the science of measurement of
visible radiant energy.
c.) Radiant Flux is radiant energy transferred per
unit of time. It is measured in units of power.
d.) Luminous Flux is radiant flux evaluated with
respect to the luminous efficiency of the radiation.
e.) Radiant Intensity is the radiant flux emitted
from a point per unit solid angle in a specified
direction.
f.) Luminous Intensity is the luminous flux emitted
from a point per unit solid angle in a specified
direction.
g.) Radiance is the radiant intensity per unit area
of an extended source.
h.) Luminance is the luminous intensity per unit area
of an extended source. Synonymous with brightness
the term has been adopted to maintain analogous
terminology between photometry and radiometry.
i.) Irradiance is the radiant flux received per unit
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TABLE II TABLE
OF UNITS
Radiometry
(Total
Radiation)
Photometry
(Visible
Radiation)
S
TERM
BOL
UNITS
TERM
BOA.
UNITS
COMMENTS
Radiant
Luminous
Energy
U
Joule
Energy
Q
Talbot
Also talbots/sec.
gib.)
1 watt - 621 lumens at 0.555
Radiant Flux
P
Watt
Luminous Fluid
F
Lumen
microns
1. 7
1c
Also called luminosity
Radiant
Watt per
Luminous
Lumen per
Intensity
J
Steradian
Instensity i
I
Steradian
a.)
Also candles
I
E
Lumen/sera-
b
t
/
2
l
l
Al
dl
than cm
a.)
er
am
e
cm
, a
so
so can
Radiance
' Watta/5tera-
--- - - - --
+-__
-_ _._____--~_.---------
N
than m
Luminance
B
a.)
Also candle/ft2, also foot
Lumen/stera-
lambert
}
than ftZ
b.)
Also called Brightness
c.)
Density of Inteesity emitted
from a surface
2
Lumen/m
a.)
Also meter candle
Illuminance
E
2
a.)
Also foot candle-
Lumen /ft
b.)
Density of luminous flux
falling on a surface
Radiant
Watts/m2
Luminous
L
Lumen/m2
Density of luminous flux emitted
emittance
Lumen/ft2
from a surface
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area of a surface. It is also sometimes known as
flux density.
3.) Illuminance is the luminous flux received per
unit area of a surface. Also referred to as
illumination, or flux density, it has been
adopted to maintain analogous terminology
between photometry and radiometry.
The above are the quantities essential for solving
problems. Other quantities of interest are:
a.) Radiant Emittance is the radiant flux emitted
per unit area of an extended source.
b.) Luminous Emittance is the luminous flux emitted
per unit area of an extended source.
c.) Luminosity. Total luminous flux expressed in
lumens. Mathematically expressed as
L s 62 if V(() E(21) d;
where VW is the relative visibility function
standard which has been adopted as most re-
presentative of the human eye, and E(7)is the
spectral emittance function of the source.
d.) Luminous Efficiency : The ratio of luminosity to
total radiant flux. Expressed in lumens per
radiated watt.
e.) Luminous Coefficient : Ratio of luminous power
(I.e. luminous flux) in watts to radiant power
(i.e. radiant flux) in watts.
f.) Radiant Efficiency Ratio of radiated power in
watts to input power in watts. Also called con-
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version efficiency.
g.) Lumen - Unit of luminous flux. That amount of
light that produces the visual response provided
by .00161 watt of mono"hromatic light at 555
millimicron.
h.) Foot-Lambert - A unit of luminance (applied to
screens) that is numerically equal to the
illuminance in lumens per square foot incident
on the screen, if the screen is perfectly
diffuse and perfectly transmitting or reflecting.
The terms Lambert and Foot-Lambert used in reference
to brightness of screens deserve some explanation. The
difference between the Lambert and Foot-Lambert is the unit
area of screen referred to. Lambert refers to cm-2 as unit
area and foot-lambert refers to ft-2 as unit area.
The lambert is a convenient term for expressing the
transmission or reflection of the visible light falling
on a screen. The assumption is that the visible light
falling on a screen is transmitted (or reflected) over a
full hemisphere (i.e. 2ir steradians). The intensity lobe
of a Lambertian screen is therefore shown as:
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Thus a lambertian screen is considered to be perfectly trans-
mitting (or reflecting) and perfectly diffuse. If a screen is
not Lambertian, then the transmission (or reflection) and
the screen gain must be taken into account.
i.) Diffuse - Descriptive of an emitting, reflecting
or transmitting surface. A surface whose in-
tensity varies as the cosine of the angle of
emission of transmitted (or reflected) light.
In consequence of this property, the brightness
of a diffuse surface is independent of the
viewing angle.
j.) Screen Gain - The ratio of the length of the
intensity lobe of an actual screen to that of a
perfectly diffusing screen. The "length" is
the radius vector of the polar plot in the
direction of the light for transmitting. screens.
2.2 Visibility
The relative visibility function, V(k) of the stand-
ard observer is given in Fig. 1.
The eye is well adapted to the peak of the spectral
distribution of sunlight as shown in Fig. 2. Sunlight is
approximately equivalent to Black Body radiation at about
6000?K. At lower color temperatures, a much lower fraction
of radiant power is visible-, as illustrated in Fig. 3 for
Black Body Radiation at 3250?K. Note in Fig. 3 that the
cross hatched area, which is the multiplication of ordinates
of the visiblity function and the radiated power, is the
visible power in watts/cm2. Multiplying by 621 gives the
visible power in lumens/cm2. The visible power is quite
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Standard-Observer
Relative. Visibility-'
V(a)
10X I O TO THE INCH 35o-3
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Radiant Power!,
Visible Power
4-Black- Body- At
..~ ..
'6000"K
(Arbitrary Or inate'
Scole)
brad. nc- -.Normal- _to. _ suns _Tays.at sea level.---
Table 16-.2 Page 16-19 of USA) Handbook of
Geophysicp, Revised Edition, 1960 2
Air;Mass 2 Solar; Constant I- 1322 watts/m
(does. not include effect of absorption bands)
WAVE LENGTH OF LIGHT, MICRONS
Y'_ T'.' 1 0 X 1 0 TO THE INCH 359-5
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0.2 0.4 0.7 1.0
2.0
WAVE LENGTH OF LIGHT, MICRONS
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different from the radiant power in the visible region of
the spectrum which is the area under the radiant power
curve between 0.4 to 0.7 microns.
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3. Technical Discussion
3.1 Source Characteristics
All present lamps use a hot gas or a hot solid as
their radiation source (with the exception of lasers).
All incandescent lamps using tungsten filaments (regard-
less of wattage or filament geometry) will have a spectral
distribution and brightness determined by the color tem-
perature at which the filament is operated. Tungsten radiates
much like a black body as shown in Fig. 4. The brightness
of tungsten rises rapidly with color temperature as shown
in Fig. 5. The luminous coefficient also increases with
color temperature, however, filament life goes down.
Black body radiation for a number of color-tem-
peratures is shown in Fig. 6 and can be taken as a close
approximation of the radiation distribution of tungsten
filament lamps at the given color temperatures. As the
color temperature increases the peak moves up and to the
left (towards the blue end of the spectrum). The curve
becomes more peaked with less radiation in the infra-red.
The area, P, under the radiated curve increases markedly
with color temperature.
P m T4
where:
P a Radiant flux, watts per unit radiating area
'T s Stefan-Boltzmann radiation constant ,
5.709 x 10-12 watts/cm2 deg4
T = Absolute temperature, degrees Kelvin
Thus for higher color temperatures, less radiating area is
required to radiate a given amount of power. The above
equation neglects ambient temperature.
* The quoted figures for the Stefan-Boltzmann constant vary
from 5.67 to 5.735 depending on the source of information.
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''Spectral giatribution.of uartz
;;,Iodide Lamp at.32O0;K
1.I(Measured by NASA, GSFC)
f
'
0 Black Body 3200
?K
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1000 2000. 30 0 4090 . 5.000
Color T 1 Temperate a K.
r 1 1~~ I! t
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__
Fig. 5
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.24.71-
04
0.3
0.2
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All the common high pressure arc lamps, regardless
of wattage, have the same spectral distribution of radiation
which is determined by the gas used. Spectral radiation lines
are superimposed on the black body radiation of the hot gas.
3.2 Lamp Efficiency
There are two kinds of efficiency that must be con-
sidered in the evaluation of a lamp, conversion efficiency
and luminous efficiency. That fraction of the electrical
input power that is converted into radiant power is termed
the conversion efficiency. The remainder of the power is
converted into heat in the base, connecting leads, envelope,
etc. Thus conversion efficiency is an indication of the
cooling that must take place at the source. Comparing
the data of several manufacturers, the conversion
efficiency of the compact are is approximately-50%,
.although General Electric claims 607. for their 5 KW Xenon
lamp.
Good information regarding conversion efficiency
of tungsten filament lamps has not been found to date.
According to Hardy and Perrin, "Principles of Optics,"
the losses may amount to "20 percent or more of the power
input."
In the course of preparing the present report, an
effort was made to find a more exact number, but with
questionable results. According to the Stefan-Boltzmann
law, a black body at 32500K radiates a total of 640 watts/cm2.
The distribution curve was calculated from Planck's equation
for a black body at that temperature, and the ordinates
multiplied by those of the relative spectral sensitivity
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curve of the eye. The resulting data were plotted, and the
area under the curve was measured with a planimeter. It
showed the luminous power to be 31 x 108 ergs/sec/cm2, or
31 watts/cm2. Over several measurements the average deviation
from the value was 77., but the maximum deviation was 14.57.
and in the positive direction. The greatest negative de-
viation was 87.. Based on 31 watts/cm2, the luminous
efficiency is 30 lumens/radiated watt.
Information in the G. E. projection lamp catalogue
indicates that lamps burning at approximately 3250?K provide
28 lumens/input watt. Similar information from Sylvania
varies from 23.8 to 29 lumens/input-watt.
Using 30 lumens/watt calculated above as the luminous
efficiency, the resulting conversion efficiency varies from
977. to 79.57. depending on the manufacturers data used. Taking
the uncertainty of the planimeter measurements into account,
the value can be in excess of 1007. or as low as 687..
While the value was not established with accuracy,
it can be reasonably concluded that the conversion efficiency
of the incandescent lamp is higher than that of the arc and
has been tentatively assumed to be 807..
No information is available on other lamp types.
3.3 Requirements for Cooling at Film
Despite the fact that infra-red radiation is common-
ly referred to as "heat waves," radiant power of any wave-
length, , including the visual region, is converted to heat
upon being absorbed. The problem of determining the amount
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of heat to be dissipated at the film is one of the finding the
power in watts, rather than lumens, that reaches the film.
The most reliable approach is to start with the
electrical input and calculate the ultilization as follows:
1. Radiant power - Conversion Efficiency x input power
2. Collection efficiency - Solid angle collected
Total solid angle
the solid angle collected is established by the numerical
aperture of the condenser, and can be taken as -7T(NA)2
.
The total solid angle depends on the type of lamp. The gas
arc lamps characteristically radiate through a meridional,
plane angle of 1200, which amounts to about 11 steradians.
The obscuration is generally less in incandescent lamps and
12 steradians is a reasonable approximation.
3. Collected power - Collection efficiency x radiant
power
The transmission is the product of the transmission
factors of all the elements in the illuminating system.
Filtering is used to reduce the non-visible radiation and
the filter factors are different for the visible and non-
visible power, and the appropriate filter factor applied to
each.
4. Luminous ,per - Luminous coefficient x radiant
power
5. Non-Luminous power - Radiant power - luminous
power
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Infra-red rejecting interference filters begin to
lose their effectiveness at slightly over 1 micron, and
the heat absorbing glass is used to absorb the longer
wavelengths. Transmission curves are presented in section 3.6.
From these curves we estimate that approximately 757. of the
luminous power and 37. of the non-luminous power will be
transmitted.
Roughly one percent will be absorbed by every one
centimeter of glass in the condenser. (The refinement of
the increased IR absorption of the condenser lenses has not
been included.) Each air-glass surface will reflect 47.
at normal incidence and more at larger angles if they are
not coated. With coatings this is reduced to 17. -27..
Aluminum mirrors reflect approximately 887. of the visible
spectrum.
In the event that the film has large areas of
density 2 or thereabouts, it is necessary to provide cooling
at the film for 997. of radiant watts reaching it. We
therefore assume that cooling required at the film equals
the full number of watts reaching the film.
6. Power at film - Transmission x collected power
3.4 Cooling at Lamp
In most cases manufacturers state the cooling re-
quirements at the lamp, "for ordinary circumstances." If
the information is not given, or if the circumstances are
not ordinary and if the conversion efficiency is known,
the watts to be dissipated are
PD - (l-E) P1
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where:
PD - Power to be dissipated, watts
E - Conversion efficiency of the lamp
P1 - Power input, watts
For example, a 1KW Xenon lamp is report to have an
efficiency of 0.5. Thus provision must be made for dissi-
pating 'KW by convection or conduction.
Uhen considering cooling of both the lamp and the
lamp house (including condensers and filters), only the
power reaching the film gate can be excluded. Since about
909'. of the input power does not reach the film gate, it is
a safe approximation to provide cooling capacity for the
entire input power.
3.5 Form Factor
The geometrical form of the light source is an im-
portant consideration in the design of projection illuminating
systems. For the projection of large formats it is man-
datory that the illuminating system be of the type that
forms the source image at or near the entrance pupil of the
projection lens rather than at the film, as in the case
of commercial cinema projection.
The projection lens is utilized to the extent that
its aperture is uniformly filled with the image of the
source. Thus, for optimum utilization, the source should
be a round disc, uniformly luminous, and sufficiently
large for the condenser to magnify it to the diameter of
the projection lens aperture.
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It is shown in section 3.9 that the merit function
of a light source is the product of its average brightness
and its useful projected area. If a source has a long narrow
aspect ratio, and the designer is successful in filling the
projection lens aperture with the narrow dimension of the
source, that portion of the length that falls outside the
projection lens aperture is not useful. The following is a
discussion of various-lamp types in terms of the above
considerations.
3.5.1 Flat Disc Sources
The flat disc source is typical of two series of
lamps manufactured by Sylvania. The Zirconium arc and the
RF lamp both satisfy the conditions of being round and
uniformly bright, and some of them are sufficiently large
to satisfy the requirement of filling the projection lens
aperture. Since the sources are flat, the polar intensity
distribution varies as the cosine of the angle of emittance,
and the illuminance at the entrance pupil of the condenser
drops off according to the cos4 law. For large aperture
condensers the problem of obtaining uniform illuminance at
the film is difficult.
3.5.2 Compact Arcs
The compact arc is a luminous volume, roughly in
the form of a truncated cone. While there are severe
brightness gradients across both its length and its width,
the use of a spherical mirror to return the backward radia-
tion to the arc has some tendency to improve the uniformity
by reflecting the more intense (cathode) portion back into
the less intense (anode) portion. Even though the brightness
is not uniform, it is continuous, as opposed to that of a
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filament. While the arcs are not large enough to permit
filling the aperture of a projection lens, their average
brightness is so great that the highest wattage versions
provide the largest amount of total luminous flux of any
of the lamps found in the course of this investigation.
3.5.3 Plasma Are
.According to figures obtained from Plasmadyne Corp.
early in 1963, the shape of the vortex-stabilized plasma
arc closely approaches a cylinder, and has less of a
gradient along the length of the are than does the ordinary
compact arc. Its polar distribution of intensity varies in
much the same way, with a strong peak on the cathode side.
3.5.4 Long Narrow Cylinder
Both the quartz-iodine lamp and the mercury
capillary can be classed as long narrow cylinders. With
the axis of the cylinder normal to the optical axis the
form factor is unfavorable in the light of the above
remarks on useful area. For any practical sizes of field
and projection lens aperture it is impossible for the con-
denser to fill the lens aperture with the narrow dimension
of the source image, and to the extent that the length is
magnified beyond the diameter of the lens it represents
watts consumed to no other effect than the-production of
heat to be dissipated.
Conceivably the form might be used to better
advantage if it is coaxial with the optical system. If
so used at the first focus of an illipsoidal reflector, a
conically shaped image volume is formed at the second focus,
and this image might be used as the object for a refracting
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-25
condenser. Without investigating such a system it is not
possible to evaluate it fairly, but it is doubtful that
it would have advantages.
Polar plots of intensity distribution are not
available for lamps of this type, but it is anticipated that
there would be approximately a cosine variation in the plane
containing the axis, and it may safely be assumed that it
is uniform in the plane normal to the axis.
3.5.5 Tungsten Filament C-13 Type
The C-13 type of filament is a single row of
Tungsten coils with a format that is almost square. Used
with a spherical back-up mirror to form a filament image
placed between the actual coils, a typical C-13 filament
can be expected to have an average brightness over its area
of almost 907. of the actual coil brightness. On such a
filament measured in this laboratory, the average coil
diameter was 897. of the width of the spaces between coils,
and allowing a reflectivity of 887. for the reflector, the coil
images will be 787. as effective as if the filament were
solidly filled. Fig. 7 shows the radiation lobe of the C-13
filament as measured by Wallin Optical Systems.
3.5.6 Tungsten Filament C-13D Type
The C-13D filament is constructed with two rows
of coils, staggered so that the rear row fills the gaps
between those of the front row. Thus, viewed axially, or
through a narrow angle, it is almost a solid luminous
area. However, for large acceptance angles, i.e. for
high numerical aperture condensers, the front row shadows
the roar row, with the result that the polar distribution
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Appr ced: o rcRelease' 2005/02/1741 IA-RDP78BO477OA001500050003-9
,I.
1111111!
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falls off more rapidly than a cosine function. Fig. 8 shows
the radiation lobe of the C-13D filament as.measured by
Wallin Optical Systems.
3.6 Filters ?
Three types of filters are available to eliminate
the infra-red.
The so-called cold mirror is a multi-layer inter-
ference filter that transmits the near infra-red and ultra-
violet and reflects the visible radiation. In a folded system,
this type of filter permits transmitting the infra-red into
a heat sink.
The reverse type of interference filter, known as
a hot mirror, can be used when no fold in the optical
path is desired. In that case, the near infra-red and ultra-
violet are reflected off to the side into a heat sink, and
the visible passes straight through.
In both cases, the effectiveness is only for the
near infra-red. Good data are not available beyond 1 micron,
but it may be presumed that the effectiveness fails some-
where between 1 and 2 microns. Since tungsten and Xenon
have a considerable portion of their radiation in the
longer infra-red, it is advisable to use a heat absorbing
glass in conjunction with the interference filter. In such
a case the interference filter should be nearer to the lamp
in order to reject as much of the unwanted radiation as
possible before it is absorbed by the heat absorbing glass,
because a portion of what is absorbed will be re-radiated
as longer wavelength infra-red.
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POLAR CO-ORDINATE 46 4410
tlO?
'!''__L.LI_LLl_LLL(I_.J__LLi(.lI_IJ_!_i(_I_!._'_LI_!.I_~J1_!_I_!JIB"(I~,~'~_~_~!i~!I!I~!i!ili!ii~~+i~~
? rr? -- --? ? -. . --?- -- ---~ --? --? ? --- .. -? ?-- --------- -
I ~
( I (
o
C o
W
11
O O
p - N
00 O~ cp ?~ ..GG C - J -N -N
0 0 O O C O 0 0 0 0 0 0 0 0
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-29-
Filtering capability is illustrated in Fig. 9. The
Balzer heat reflecting filter transmits about 907. of the
visible and about 67 of the near infra-red. There is no data
on the far infra-red. The transmission drops steeply above
0.64 microns.
The Corning Glass infra-red absorbing, visible trans-
mitting filter absorbs about 977. of the infra-red above 1
micron.
3.7 Lamp Tolerances and Replacement Time
No attempt has as yet been made to take into account
the fact that replacement cost includes not only the pur-
chase price of the lamp, but also the labor cost of making
the replacement. In high numerical aperture condensing
systems, use is necessarily made of aspheric elements,
which tend to make alignment extremely critical. Thus, where
dimensional tolerances of the lamps are known, those lamps
made to the tighter tolerances are favored. Replacement time
is highly specific to a particular projector design. No
suitable general assumption has been found so far.
3.8 Spectral Distribution
Tungsten lamps in the higher wattages have very close
to a black body spectral distribution with color temperatures
ranging from 28000 to 3400?K. Some are available with rated
lives as long as 50 hours, while 25 hours is more common.
The carbon arc has the very desirable property of a
black body distribution whose color temperature can be in-
creased to that of sunlight by operating under pressure.
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1.0
0.8
0.6
0.4
0.2
-Balzers . Heat:_ Reflecting _.--- - _ ' _- _- - -
Interference Filter; Type Calflex B1JKX
-Corning. G].ass.In#ralred Absorbing_
Visible Tlransmitting Filters
(AKLO Type) Color Specification No. 1-69
80% Minimum Luminous; Transmispion
pproximape Combined Transmispion Efficiency:
40.7 Vsible Range: 0.85 x, 0:90 0.765
r tt
4771041
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-31-
According to Sylvania's literature on their RF lamp,
it has a gray body distribution, and its color temperature
can be varied, with a corresponding difference in lamp life.
This relationship is tabulated as follows:
?K
Hours Life
2700
1000
2800
750
2900
600
3000
5 00
3100.
400
3200
300
3300
250
3400
180
3500
125
3600
100
3700
50
4100
Melting Point
Xenon and Xenon-Mercury lamps are characterized by
having a line spectrum superimposed on an approximation to
a black body distribution of about 5500 to 6000?K. According
to Hanovia data, a Xenon lamp has 23.67. of its radiated energy
in the visible region while a Xenon-Mercury lamp has 41% in
the visible. While these data make the Xenon-Mercury lamp
sound attractive, it becomes less attractive when one con-
siders that the quality of the light is blue-green.
3.9 Screen Illumination from B and A.
Evaluation of a lamp cannot actually be made without
reference to the optical system with which it is used.
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One method of expressing the illumination falling on
the screen is:
k B AL
where:
k - Transmission factor of the entire optical system
B - Lamp brightness
AL - Utilized area of the entrance pupil of the
projection lens
t - Distance from film to projection lens
m = The projection magnification to the screen
The equation deceptively u.akes it appear that the brightness
is the only lamp parameter of importance.
Actually if the condenser magnification does not fill
the projection lens with the source image, AL must depend on
As, the projected area of the source. In case of a compact
arc the image of which is unlikely to fill the lens in either
direction, the relationship is simply
AL - mc2 A.
where:
me - Condenser magnification
As = Projected area of the source
For a long narrow source, AL will be roughly rect-
angular limited by the projection lens diameter along its
length, while its width is the product of the source width
and the condenser magnification.
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Considering the case of the compact arc, the screen
illumination is then
k B me As
E _ ------2 --2
m t
The condenser magnification may be expressed as
m NA
c tan uL
where::
NA = Numerical aperture of the condenser
uL - Half field angle of the projection lens
In turn:
tan uL= -t -
where: y = semi-diagonal of film
Thus:
k B As (NA) 2
M y
But for a square screen, m2 y2 is half the area of the screen.
Thus calling the screen area AI, the illumination is
2 k B As (NA)2
In the above equation, the characteristics of the
projection lens and film size have been completely eliminat-
ed, and it is seen that for a source that does not fill the
projection lens, the screen illumination depends on the
numerical aperture of the condenser, on the screen size, and
on the transmission factor of the entire optical system.
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The necessary diameter of the projection lens will be
DL - ds c
where:
ds = Length of the source
Replacing me as before,
d (NA) t
jL - U
But from a paraxial relationship
t= (1-++m) f andyi=my
where:
y1 = Semi-diagonal of the screen
Thus the f/no of the projection lens must be
YL
ds m +
While a faster lens may be used, this f/no is adequate,
and a faster lens does not increase screen brightness.
When a C-13 or C-13D filament is used it is generally
possible to fill the projection lens aperture, and the avail-
able lens speed becomes the limiting factor. In that case the
screen illumination may be expressed
E - 1 1 B D 2
4(1+m)2 f
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The trade off that follows from the preceding dis-
cussion is that with a small source of high brightness,
the condenser should be of high numerical aperture, but a
relatively slow projection lens may be used. With a large
source, having a lower brightness, a lower condenser magni-
fication and accordingly a lower numerical aperture of the
condenser lens will serve to fill the aperture of existing
projection lenses, but the burden is imposed on the pro-
jection lens, which must be of correspondingly higher speed.
In order to evaluate and compare screen brightness
obtainable from the various lamps, certain standard con-
ditions were assumed. For the equation:
2 k B As (NA)
AI
assumptions were:
E - Illumination falling'on screen, lm!ft2
k - Total transmission factor of the entire optical
system - 0.3
B - Source brightness from manufactures data, lm/mm2
As s Source area from manufactures data, mm
NA - Numerical aperture of condenser lens a 0.707
for a 900 collecting angle
AI = Screen area - 6.25 ft2 for a 30" square screen
When screen brightness was computed, it was found
that tungsten lamps were several times brighter than the
Xenon or Xenon-Mercury lamps and this result was not con-
sistent with the comparative total luminous flux output of
the lamps as quoted by the manufactures.
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The B and As data were suspect. For the compact
arc lamps, the average source brightness, B, is dependent
upon what source area, As, the brightness is averaged over.
The manufactures data for B and As varied greatly for lamps
which, it appeared, should be nearly equal.
The total lumen output data for the lamps appeared
to be more consistent and probably more reliable since
measurement by the lamp manufacturer was relatively easy
in an integrating sphere. Therefore an alternate method of
computing screen illumination was sought.
3.10 Screen Illumination from Total Lamp Luminance
The alternate method of predicting screen illumination.
consists of determining the fraction of the total lumens
collected and transmitted and dividing by the area of the
screen over which it is spread.
where:
E - Density of the luminous flux falling on the screen,
lumens/ft2
k - Total collection and transmission factor,
dimensionless
A Q Area of the screen, ft2 a 6.25 ft2 for a 30
inch square screen
The density of the luminous flux falling on a screen
in lumens/ft2 is numerically equal to the brightness in ft.
lamberts of a perfectly transmitting (or reflecting) and
perfectly diffusing screen.
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To determine the collection factor we will consider
two idealized radiation patterns for which nearly all actual
lamps will be well approximated.
One pattern consists of two tangent spherical lobes.
It is representative of planar type tungsten filaments. In
both plan view and Side elevation, the lobes are lsmbe--tian
distributions. The total radiation is the volume of the two
spheres. For each sphere this is
Ifr3
where:
r - The radiation intensity vector
The radiation collected is represented by a right
circular cone with apex at the filament and the base at the
condenser lens. The collected radiation is thus the inter-
section volume of the cone and the sphere.. The intersection
volume is:
V = 3 r3 sin2 (2u) cos2u + 4 7(r3 sin4u (3 sin 2u - 2 sin2u)
where:
V = Volume of intersection = collected flux
r = Radius of the lambertian sphere
u = Half angle of the collection cone
To permit a standardized comparison of lamps, we
have arbitrarily selected a condenser lens with a"90? plane
collection angle. Thus:
NA- 0.7 and u= 450
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and the collected flux is:
V a IIf r3 + 22 r3 wr3
The fraction collected will therefore be the ratio
of volume of intersection to the total volume of the two
spheres:
r3
11 -
-
- 0.375
4 3
Ile
The other radiation pattern to be considered is a
toroidal shape.
A compact arc radiates uniformly through 360? in
the plane normal to its axis, while in the meridional
section (side elevation) the distribution is roughly
Lambertian. Thus the total radiation may be represented
approximately by a toric volume.
V - 2 2r3
where:
V - Volume of toroid - total flux
r = Radius of lambertian cross section and radius of
revolution of the toroid
The flux collected is that portion of the torus
intercepted by the cone of acceptance of the condenser.
A condenser of NA.7 has a 900 collection cone. A
90? plane wedge would take in 0.25 of the flux. Thus the
90? cone is accepting approximately (and somewhat less than)
257. of the flux.
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Two other factors must be considered in collection.
One factor is the light blocked by the film-format shape
which we call format blocking. For a square film format
inscribed in circular condenser lens the flux falling in the
circular segments outside the square format is not used.
The flux falling inside the square format is found by:
Format blocking factor 2r - 0.637 Z 71'
Ir
where:
r - Radius of condenser lens
also:
r-- Semi-diagonal of film format
The other factor to be considered is projection lens
aperture blocking. When the condenser magnifies the source,
so that it fully fills the projection lens aperture (as it
normally does for tungsten filament lamps), then the flux
falling outside the circular projection lens aperture is
not used. For a square filament shape, such as C-13 and
C-13D, the flux falling inside the projection lens cir-
cular aperture is found by:
Aperture blocking factor
(2r)
- v - 0.786.
The aperture blocking factor is not applicable to
the compact arc lamps since the image of the source normally
lies wholly within the projection lens aperture. For other
source shapes, the factor will be the area of the source image.
falling inside the lens aperture divided by the total area
of the source image at the projection lens aperture.
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3.11 Summary of Screen Illumination and Heat
Rejection Factors
Visible Light
Tangent Lambertian Lambertia1
Spheres (Planar Toroid
Filament) (Compact Arc)
1. Collection Factors
Condenser Collection
Factor without mirror 0.375 0.25
857. Refectance mirror 1. 85 1.85
Format Blocking Factor
(square format) 0.637 0.637
Aperture Blocking Factor
(square filament) 0.786 1.0
Product .0.348 0.294
2. Filter Factors, Visible
Light
Dichroic hot mirror 0.90 0.90
Heat absorbing glass 0.85 0.85
Product 0.765 0.765
3. Transmission Factors
12 surface condenser
with 27. per coated surface
reflectance loss 0.785 0.785
25 cm of condenser glass
with 17. per cm absorption
loss 0. 75 0.75
Projection lens estimated
transmission efficiency 0. 90
0.90
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-41-
Two projection mirrors,
one dichroic, one rear
surface coated
0. 79
0. 75
0.79
0.75
0.315
0.315
0.084
0.071
Screen Transmission
Product
4. All Factors Product
1.
2.
3.
4.
Infra-red Tangent
Lambertian
Spheres
Lambertian
Toroid
Collection Factors
Condenser collection factor
0.375
0.25
107. reflecting
cold mirror
1. 10
1.10
0.413--
0.275
Filter Factors
Dichroic hot mirror
0. 06
0.06
Heat absorbing glass
0. 03
0.03
0.0018
0.0018
Transmission Factors
12 surface condenser
0.785
0.785
25 cm condenser glass
0. 75
0. 75
0. 59
0.59
All Factors Product
0.000438
0.000266
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C SIG" IO I LAMP TYPE
General Electric #DPW 1000 Watt
Sylvania Type lm/t20p C-13 Tungsten
Y 115-120 VAC Line Power P?OJ CTLO:N FACTORS
A 7 AMPC Hot
Li _'E 50 Hours
P;?0_0: `T ZIC DATA
Color Temperature
Luminous 'lux
Intensity
Brightness'
Area
Utilization
3200?K
28,000 lumens
21.1 candles/sq. mm.
238 sq. r.n.
of Arca or Brightness
0.78
%_Q tieLL.luii V. V7
Filter 0.76
Transmission 0,32
Format Blocking 0.64
Aperture Blocking 01i9
PRODUCT 0.084
L_OTATIO\' LOBE 91 PLAN VIE-k,1 ; SOURCE ;
`~~-~ I Monoplane Tungsten Coil
Approved For Release 2005/02/17: CIA-RDP78B04770A00150005009
- \UI'' C +.liR R AND DESIGNATION LAMP TYPE
General Electric ASA IiDFD
r'~E 115 -120 VAC Line Power
8.7 AMPS, Hot
LIP iE 10 Hours
PHOTO`m' RIC DATA
Color Ter:.',erature 3375?K
Luminous Flux 30,500 lumens
Intensity
Brightness' 24 candles/sq. mm.
Area 97 sq, r m,
Utilization of Area or Brightness
0.95
`1000 Watt
1C-13D Tungsten
P ROJfCTION FA""-ORS
Collection 0.69
Filter 0.76
Transmissio:1 0.32
Format Blocking 0.64
PECT.?RAL DISTRIBUTION
3375?K
Radiated
5~_ .
I v.~ V.7 1.v
2005/02/17: IA-Rdpj8 04770A00
A proved For Release
Sylvania Type lm/tl2p
j Aperture Blocking 0.79
Approved For, felease 2005/02/17: CIA-RDP78B0477001500050QQQ4.9
.AMP MANUFACTURER AND DESIGNATION
LAMP TYPE
OSRAM XBO 900W
900 Watt
Xenon
POWER SUPPLY COST :
PROJECTION FACTORS
70-110 Volts with 30 to-50 amps.
Collection 0.462
D.C Power Supp v.
IGNITER OSRAM #25103 igniter
Filter 0.765
Transmission 0
315
with #L726, $180.00
.
Format Blocking 0.637
33,000 Volt Spark Gap.
Aperture Blocking ltq
LAMP LIFE Warranted 1500 Hrs. $245.00
Average 2000 Hrs.
PRODUCT 0.071
PHOTOMETRIC DATA: Rated Maximum
SPECTRAL DATA -
Current 42 50 AMPS
UV 0.2-0.38p 3%
Luminous Flux 30,500 41,500 LM
Visible 0.38-0.76p 147.
Intensity , 3,300 4,100 LM/STE
.IR to 1.3u 227.
Brightness 550 730 cd/sq
IR Beyond 1.3$1 147.
Area 6.6 6.6 sq.n4n.
Envelope, Leads, Etc 477,
Utilization of Area or Brightness
Input T
RADIATION LOBE, PLAN VIEW
SOURCE : Xenon Compact Arc
'r
Anode
-~" 20
?
3
-50
1 M
-
'
100 cd/sqq
- M4
200 at 42AM
rated
c 1
1000 cutren
--1500
0
2
2000
1 0 1 z 25 00
3000.
Cathode
RADIATION LOBE, SIDE ELEVATI N
SPECTRAL DISTRIBUTION
Radiated
Visible
100
.
i 4-
so
J j-3
5 / 7
8 04770A001500050003-9