Armored 
Medical. Research Laboratory 
Fort Krgoxc; Kentucky 
INDEXED 
Report On 
PROJECT NO. 6 - VISION IN TANKS 
Subject: Binocular Modification Providing Quick Adjustment 
of Interpupillary Distance and Diopter Setting 
Project No, 6 
15 October 1945 ARKOHED MEDICAL RESEARCH LABOKATOn'l 
Fort Knox, Kentucky 
Project No, 6 
SPMSA 741 
15 October 1945 
BINOCULAR MODIFICATION PROVIDING ADJUSTMENT 
OF INTSRPUPILLARY DISTANCE AND DIOPTER SETTING 
P. PROJECT NO. 6 - Vision in Tanks. 
a. Authority: Letter Commanding General, Headquarters Armored 
Force, Fort Knox, Kentucky, File 400,112/6 GNOHD, dated September 24, 1942. 
b, Purposes To discuss need for binocular IPD and diopter adjust- 
ments especially for night operations and to describe one method of meeting 
the requirements. 
2, DISCUSSION? 
For efficient use of binoculars at night or during daylight it is 
necessary that both the IPD and diopter setting of the binoculars be adjusted 
for the person using them. Scales are provided for making the adjustments in 
daylight, and the scales are adequate for daylight use provided the user 
remembers the various settings. (It is surprising how few people remember 
their setting and depend on rough adjustment each time the binoculars are used). 
At night the scales are no longer readable, consequently this method of adjust- 
ment cannot be made without the use of artificial illumination. For security, 
artificial illumination cannot be used during most night operations, and it is 
of course, at such times that the need for proper adjustment of the binoculars 
is most important, Sven if artificial illumination can be used for making the 
settings, its use is undesirable because of the risk of loss of dark adaptation. 
In combat the binoculars may be taken out of the case, used and 
returned to the case many times in a short period. They must be adjusted each 
time they are used. 
Clearly there is needed some means to permit quick and positive set- 
ting of the binocular IPD and diopter adjustments in total darkness. One method 
of doing this has been developed at this Laboratory and has been tried on GI 
6x30-M3 Binoculars, The simple modifications made have proven quite adequate 
and have the virtue that they can be applied to existing binoculars without 
change. As they stand they represent an expression of an idea and not neces- 
sarily a fully designed item. 
Essentially the modifications are adjustable detents which once 
adjusted can be reset by feel. Figure 1 shows modified binocular parts required 
and method of making initial adjustments. The Modified 6 x 30-l£3 Binoculars are shown in Figure 1, the modifi- 
cation parts in Figure 2, 
Figures 3, 4, 5 and 6 show method of initial adjustment and use. 
Figure 7 shows range scale for correct individual focus at short range 
for daytime use. It is a useful but not essential feature. 
3. CONCLUSIONS; 
a# There is a definite need for some means of quickly and positively 
making binocular IPD and diopter adjustment in complete darkness, 
b. The binocular modifications suggested meet the requirements of a , 
above, 
3 
c. The modifications suggested can be easily applied to existing 
binoculars, 
d. As a production item the modifications could probably be more simply 
built into the binocular, 
e. The modifications are usable and advantageous for daytime use as well 
as night use, 
f. The distance scale incorporated in the diopter adjustment is useful 
for close-in viewing, 
g. The detent method of stop is considered superior to positive stops 
for the reason that the binoculars may be handed to someone else who can make 
adjustments without altering the adjustment setting of the principal user. 
4. RECOMMENDATIONS; 
a. That the suggested modification (or variation accomplishing the 
same ends) for IPD and diopter setting be applied to binoculars for use by 
ground troop engaged in night operations, 
b. That, for future procurement, simplified version be designed into 
production binoculars for ground troop use# 
NOTE: The recommendations as set forth in this project have been 
concurred in by Brigadier General George W0 Reed, Jr0, President, Army Ground 
Forces Board No. 2, 
Submitted by: 
Frederick S, Brackett, Lt, Col#, SnC 
Lester B. Roberts, Major, SnC 
John W, Weymouth, Tec 3 
A1 PROVED *3- & 
WILLI All B. BEAN 
Major, Medical Corps 
Commanding 
1 IncI. (Figs. 1 thru 8) Fig. 1 
BINOCULAR WITH IPD AND DIOPTER ADJUSTMENT MODIFICATIONS 
one diopter adjustment in detent—one out) FIGURE Z 
SIDE VIEW BINOCULAR IPD AND DIOPTER ADJUSTMENT PARTS FIGURE 3 
TOP VIEW BINOCULAR I PD AND DIOPTER ADJUSTMENT PARTS FIGURE U 
(a) LOOSENING IPD ADJUSTER PRIOR TO MAKING ADJUSTMENT 
(b) TIGHTENING IPD ADJUSTER AFTER MAKING ADJUSTMENT FIGURE 5 
ADJUSTING I PD OF BINOCULARS I FIGURE 6 
(si) LOOSENING EYE CUP PRIOR TO BINOCULAR DIOPTER ADJUSTMENT 
(fc) TIGHTENING EXE CUP AFTER DIOPTER ADJUSTMENT FIGURE 7 
MAKING DIOPTER ADJUSTMENT I.RD, 8 DIOPTER ADJUSTMENT 
PARTS FOR M6 BINOCULARS