NATIONAL BUREAU OF STANDARDS REPORT

4449

Analysis of Mercury Lamps and Filter Combinations

for Dse as Aviation-Green Lights

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201-20-2331 December 21, 1955 4449

Analysis of Mercury Lamps and Filter Combinations

for Use as Aviation-Green Lights

by

I. Nimeroff

Prepared for

Equipment Laboratory

Wright Air Development Center

Department of the Air Force

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, reprir

unless permission Is ob

25, D.C. Such permis

cal ly prepared If that

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

)art, is prohibited

lards, Washington

t has been specif!-

rt for its own use,
’ ' f
4449

Analysis of Mercury Lamps and Filter Combinations

for Use as Aviation-Green Lights

1. PURPOSE OF ANALYSIS

The purpose of this analysis is to compute the luminous

transmittance and chromaticity coordinates of present aviationgreen filters (designed for use with incandescent lamps) when they

are used in combination with currently available mercury lamps.

Should these combinations fail to meet either the present or proposed aviation-green light specification, suitable filters would

then be designed.

2. MERCURY UMPS

The energy radiated in the visible region by mercury lamps

consists of spectral lines and a continuum. The spectralemittance data for mercury lamps used in this analysis were

obtained from General Electric Company's brochure LS-103, June

1955. The performance of the following lamp types was analyzed:

H250-A5, BH6, H400-E1 and H1000-A15. The relative spectralemittance data for these lamps are shown in figure 1 .

The luminous efficiency index of each of these lamps and of an incandescent lamp operated at 2854°K, listed in table I,

indicates that the mercury lamps are relatively efficient in the

production of visible radiant energy. The luminous-efficiency

index of a lamp is defined as:

p

x

p

x

d>.

where P^ is the spectral radiant flux and 7^is the CIE relative

luminous-efficiency function.

Also listed in table I are the chromatid ties of mercury

lamps, H250-A5 and BH6 and of an incandescent lamp operating at

2854 °K. The chromaticity coordinates of these lamps are plotted
(

• ! V "

.

'T

'

‘

‘

'

r' ,!

** -
-2 -

on figure 2. Detailed analysis s of the H250-A5 lamp was undertaken

because its spectral distribution closely resembles that for H400-E1

and H1000-A15. Detailed analysis of the BH6 lamp was undertaken

because this lamp differs from the others by having a higher spectral

continuum.

Table I Chromaticity, Luminous-Efficiency Index, and Efficiency

of Mercury and Incandescent Lamps

Chromati city Coordinates

LuminousEfficiency

Efficiency

(Rated Lumens

Lamp Type X y

z Index per Watt)

H250-A5 0.318 0.379 0.303 54 44

BH6 .277 .330 .393 40 65

H400-E1 —

55 50

H100Q-A15 — .

—— 55 52

Incandescent .448 .408 .144 25 20

2.1 Performance of Mercury Lamps with Conventional Aviation-Green

Filters.

In computing the performance of the lamps with aviation-green

filters, spectral transmittance data, T^, for the transmittance

standard, WF590, were used. Luminous transmittance, T, of this

filter was computed for an incandescent tungsten lamp operated at

2854°K as well as for the mercury lamps. Chromaticity coordinates,

x, y, and z, and luminous transmittance were computed for the

H250-A5 and 8H6 mercury lamps and the incandescent lamp. These computed. results are listed in table II. The chromaticity coordinates

are plotted on figure 2.

Table II

Luminous Transmittance and Chromaticity Coordinates

of Lamp and Aviation-Green Filter Combinations

Chromaticity Coordinates

Lamp Type

i x y z T

(percent)

H250-A5 0.232 0.276 0,492 22

BH6 .192 .249 .559 27

H400-E1 —

—

21

H1000-A15 — —

22

Incandescent .205 .400 .395 20
I

'

. M

.

’ Mli

i - -

r
-3-

The colors of the combination of the aviation-green filter

and the mercury lamps are obviously too blue for use as aviationgreen lights. The mercury lamps provide little increase in

luminous transmittance over the incandescent lamp.

3. DESIGN OF FILTERS FOR MERCURY LAMPS TO YIELD AVIATION-GREEN LIGHT

If the radiant energy emitted by the mercury lamp in the

visible region of the spectrum were composed entirely of spectral

lines 404,7, 435.8, 546.1, and 578.0 mp, the color of any mercury

lamp-filter combination would lie within a chromaticity region

defined by these spectral lines. This chromaticity region is shown by

dashes on figure 2. If we wish to obtain a color that will lie in

the aviation-green chromaticity region, a filter is required that will

almost completely absorb the energy of line 578.0 mp and will partially absorb the energy of lines 404.7 and 435.8 mp.

As no single filter known can satisfy these requirements, twocomponent filter combinations of Didymium and Noviol filters were

tried. Didymium filters have an absorption band in the region of

578 mp and Noviol filters absorb energy in the blue and violet

regions of the spectrum.

The design data for the two combinations that show promise of

usefulness are listed in table III. The thickness of each filter

component is designed on the basis of spectral data published in

Glass Color Filters, Corning, 1948, for stock thickness t

0

. Table III

Filter Design Data

Filter Corning Relative

Designation Xdent. No. Thickness Name

A 1-63 0.4 t

0 Didymium

3-72 0.5 t

0 Noviol B

B 1-63 1.0 Didymium

3-73 1.0 t

0

Noviol A

Figure 3 shows the computed spectral transmittance of the

components and the combination of designed filter A. Figure 4

shows the computed spectral transmittance of the components and

%
r , cv -* 1

"{ m

.

.

1

•

i

0
-4-

the combination of designed filter B„ The location of each mercury spectral line is indicated by an arrow on figures 3 and 4.

The chromaticity coordinates and luminous transmi ttance of

filters A and B in combination with lamps H250-A5 and BH6 were

computed. The results of these computations are listed in table IV.

The chromaticity coordinates are plotted on figure 2,

Table IV

Chromaticity Coordinates and Luminous Transmittance

of Mercury Lamps and Designed Filter Combinations

Chromaticity Luminous

Filter Lamp Coordinates Transmi tta

Designation Type X y z (percent)

A H250-A5 0.356 0.587 0.057 60

A BH6 .313 .522 . 165 66

B H250-A5 .273 .425 .302 48

B BH6 .267 .376 .358 56

4. DISCUSSION

The chromaticity coordinates for mercury lights show that the

color of each light lies on the green side of the Planckian Locus

near 6QQ0°K. The chromaticity of the mercury lamps in combination

with the present aviation-green filter indicates that the resulting

color is too blue for aviation green. The H25Q-A5 lamp in combination with designed filter B and the BH6 lamp in combination

with designed filter A satisfy the proposed aviation green limits.

Designed filter A shifts the color of mercury lamps toward yellowgreen,, while designed filter B shifts the color of the mercury

lamp toward green.

The mercury lines plotted as points on the spectrum locus of

figure 2 serve to define approximately the chromaticity region

within which chromatici ties of mercury lamp-filter combinations

will lie. The BH6 lamp in combination with the present aviationgreen filter fails just outside of this region because of the high

spectral continuum in the spectral region of 490 mp.

The chromaticity region defined by the mercury lines indicates

that use of mercury lamps is theoretically possible for lunar white,

-5-

aviation blue, and aviation green. For lunar white, line 546 mp

needs to be eliminated. For aviation blue, lines 546 mp and

578 mp need to be greatly reduced. For aviation green, line

578 mp needs to be eliminated, and lines 405 mp and 436 mp

reduced.

In the use of mercury lamps, precaution should be taken

to dissipate the heat produced by the ultraviolet radiation that

will be absorbed by the filter. The absorbed radiation might

heat the filter to the cracking point. Incandescent lamps emit

very little ultraviolet radiant energy but have much infrared.

The filters in use with incandescent lamps generally transmit

the infrared so no special precautions need be taken.

I

Wavelength (mti) Figure 1

- Figure 2 - 


-

I Equal Energy

I I 1 1 ± 1 I j U i I II 1 ,1





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