The Washington herald., 1922-01-15
DEVICE DETECTS
HEADLIGHT GLARE
FOR NIGHT DRIVERS
Regarded in Many Quar-
tiers as the Real Solution
n;Of Difficulty.
GLARE VANS HE s
Horizontal Rays Projected
Through Plain, Polished


From the faculty Of the Massa-
chusetts Institute of Technology.
where many noted practical inven-
tionss Tor commercial use have orig
mated. now comes what is regarded
In many quarters as the real solu-
ton of the giaring headlight prob
lem. .
The device Is unlike anything
nounnon the market. 1t has been
deslgfied and developed to a point
Of Practical use by William sud-
dsrds Franklin. professor of phys
les and Elof Benson. curator OF ap-
paraths.
Both. men are authorities on the
sub5eotr Of light in the scientific
world. Each is the author Of i'm
poFtant textbooks and scientific
trestises on the subject.
In explaining the principle Of the
device to several practical automo-
bile men Professor Benson said:
IF 1t were possible to obtain a
perfece focus of the source of light,
which is the filament in the bulb,
and a perfect parabolie mirror.
there would be no glare problem,
as every ray Of light projected, by
ths-Szdector would then travel in a
horizontal plane. We could then,
by properly setting the lamp. OBJ
tain perfect road illumination. the
Intensity of same being governed
by candle-power generated.
Hegs1dless of the intensity: no light
woul1trise to the height OF the ap-
preaching drivers eye, and, of
course. IL the light does not strike
the eye there can be no glare.
However, this - an utterly imprac-
teal. Il not Impossible. solution.
Protection solved.
The problem that the illuminate
ing engineer has had to face in
considering the automobile head
light problem has been not only to
keep all light out of the eyes Of
the approaching driver, but at the
same time to project enough light
forward so that the operator could
see the road at least 200 feet ahead
Of his car. II he attempted to tilt
his lamps at a sharp enough angle
to keep the light out of the other
fellows eyes, he did not get the
distance, and IL he projected his
light at such an angle as to prop
eriy illuminate the road. while. he
might succeed In keeping the man
beam of light below the level of
the approaching eye. yet the out
of-focus rays would be strong
enough to dazzle the eye. except
on brightly-lighted streets. Exact
~ the same dificulties are tencoun-
tered in refracting. or bending the
rays, through glass prisms.
1.-The result has been that our
States have attempted to define
what they term dangerous glare
but that IL admittedly n compro-
nise, and. like most compromises,
unsatisfactory to all parties. The
driver thinks he does not get sum
Client light and the. party approach
ink, depending on the strength of
his eyes, the degree of darkness
obtaining. etc. Is certain that he Is
being -blindedt
How Glare In Eliminated.
when Professor Franklin and
mx1Uf,. attempted the solution Of
thtnWpblem, we decided that the
ou5Y way TO really eliminate glare
WIS to hide the source of light,
wEkh means not only the filament,
b2 1.-THE entire reflector, from the
apDrpaching drivers eye, for as
loRt as the eye can see any spot
onS that reflector some glare is
bond to be the result. Now this
coat be accomplished by visors.
sh slsrs. etc. but these devices. like
nucbrous others that you have un-
doSRtedly seen, bent down, or de-
iesRg all the rays, which would be
no Improvement on existing devices.
lie did not want to interfere
wia the projection of the direct or
hokEpntA rays, comprising the
m4Yr beam of light. yet IL was
ne Ssary to turn down all upward
ouedf- focus rays. In other words.
the. Upward, or glare rays must be
pl&sd out and DETECTED, without
inarfering with the horizontal or
di$abce rays. 1 think you can
really see how we have accom-
pIfshkd this by looking at the de-
vioS All direct, or horizontal rays,
arg projected through plain. poll
ish glass, while all upward rays
areo1enected, not refracted. down
wa@-.