INVESTIGATION OF RHOMBOID ARM MOTION

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B05171A000400030026-2
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 9
• Document Creation Date: December 28, 2016
• Document Release Date: June 6, 2005
• Sequence Number: 26
• Publication Date: September 1, 1971
• Content Type: MFR

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Declass review by NGA/DoD
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NPIC/TSG/L S1)/TE]>- J.?.5/'1:1
1. Septcnbr.r 1971
Jfi:~i'JRA]dUl)~1 FOR TII] RI CORD
SlI]>J) ('1 Investigation of Rhomboid Arm Noti.oli
1t1) l'1:1 Nc 1 5: I j IEG/Oi)/'i.'J'i,-130/71, dated 29 July 1971.
1 in A 18 71
1. In response to a request. by IE:G/OD/TPB (Ref. 1),
ES]) has- investigated possible causes of inability to focus
j7.oort 240 i`1od 28 system rhomboids using 2X objective lenses.
Reference. 2, which treated table alignment procedures, was
intended to reduce the potential problem. This memorandum
discusses another aspect of the_ 1140/1.1od 2,S system which is
a. contributing factor.
It had been conjectured that part of the pr. ob].em
2_;
=
stated in Reference 1 could. be caused. by the non-parallel ,
non-planar swing of rhomboid arms. In order to test this,
ES]) had to purchase a. surface plate to use as a .base--for
these measurements . The piatepur. chased was 12" x 18 granc,
with a surface flatness tolerance of +0.0001 inches.
3. An optics mount was found in ESD/EP13's parts
stock ilii.ch could be mounted over the surface plate. This
mount is identical in mottnt/pod interface to that used on
the I IMLT 1540. The mount iwras firmly fixed on the Sur-
face plate, braced so that the weight of the Optics cs would
not more it 111 any manner. The surface of the mount on
which the optics pod rests was aligned parallel to the sur-
face plate within 0..001. inches -Total Indicating Reading.-
This is the equivalent to. a colJ.imat,ion -error of. less than
1 minute of arc. - ~~~:?
4. Two pods were then placed on this-mount one at a
time. :: Fourteen arms were mounted on the left si- de of each
of th.e pods. The variations. in distance from positron 1 at
positions 2 and 3 were checked with each pod and rhombo.d.
These measurer ents and a drawing of the set-up are shoWD.
i.n Attachment 1. .
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2) TSG/J.,S1)/11:]3-1-J.~/LJ., daL.ec
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Ins esti.I;ation of It]lombo:id Arm Notion
SUBJECT;
JECSUBJECT;
The following information. should be noted.
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to that of the pod to excursions of swing . I L
was made to align the th.reu-point moult on the rhon!boi.C
same way that a. PI would mount them. That is, no after:
a. The rllomboi.ds were placed on the pods in the
'is possible to reduce the excursion by approx:i.nlat.ely
10% by determining whether the position 3 distance (se
attachment) was plus or. nl:inus, and compensating for tlli :.
at the time of ]counting the rhomboid.
b. Rhomboids t~cre placed on car. a7.le1- bars cliv ol c:
from the pod, and the swing of the rhomboid. arms alone
-we-re checked. - Two rhoinboicts , 101-LA and 7161';F, were
c.h cked in this manner. 101L11 showed a total devi-ation
of, only 0.0005 inches for 1.80? of rotation in this test_
deviation when not on the ,pod.
when mounted on pod 296RF, 'shotw,ed only a' 0 .0002 inch
716WF, which had deviated by as much as 0.062 inches
6 . ' The conclusion., to be drawn from these tests is
that rhomboid mounting hardware is critical.-- The rhomboid
is positioned by a dowel pin. on the slide elating with a
slot on. the rhomboid arm itself,., . A total. cumulative tol_e-r. -
ance in four critical areas - dowel diameter, dowel posi-
tioning, slot width, slot' position - of 0.0005 inches will.
result in an angular deviation from parallel of approximatcl..
19 minutes of arc for the r.homboi.d arm. It is entirely
possible that the prism pr.oblem.n.oted in Reference 2 does
. not exist; i.e., the symptoms -noted are caused by rhomboid
swing, not by prism deviations ..
both of. which. involve a redesign' of the rhomboid/pod
7, This problem might be a .l.eviated by two methods
even with gross deviations from parallel swi.ng.
into the. rhomboid arm, enabling refocus of objectives
a'. Greater focus range could possibly be built
b. Tighter tolerances on. the positioning hard ; r:
would uz'ov?de a more nearly- 1.1-rnI 1 ei?rincr of rhnT11)O
T i~~it}lo.ui rectesis,n=_of_opt.ics- Hot?;ever-, -the geometry of
 SU1~JFiC'1': Irlves i:.ignti.on of Rhomboid Arm Motion
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the system is such that a deviation of 0.00l i_nc.h. in.
positioning at the dowel Will cause an angular clevia-
ti on in excess of 3 minutes of arc along the rhomboid
arnl at position 1 (Sec Attaclvnent) Th:i.s i.'s a height
differential of 0.008 inches f3:
.0111 position 1 to
o
i
-
s
p
.
- lion 3.
8. Unfortunately, there are other areas on the power
pod and rhomboid system which affect the swing of the rh.om-
boici. If we assume that the mounting ring L s perfectly
aligned to the viewing surface, their, ill, order to have the
rhomboids swing in. a perfectly parallel path, the following
rtnrhm 4r~il c1 0'. mm~.~ ,__
e
_ . a
horizontal plane perfectly parallel to the mountinng:;,r.ing.
a. The -surf ace on the. poi-;ex.- pod 1,71)i r1 4 t f
i
9. The conditions stated in section 8 do not all hai e
to be satisfied. Section 8c1, if satisfied, will provide that
th.e rhomhoid.s swing in a plane parallel to the vievring sux-
face. But interchangeab]-e parts cannot be specified in that
wav
b. The dovetail slide must he oslt-iol
'
ex aces
with the mounting pod must be perfectly flat at.
d. The rhomboids must mount on the slide so that
a line through the center of the rhomboid movement
bearings is perfectly normal to the mounting ring
nl any
V wJ.J-c
h
the nc( ..;.oids butt must be perfectly parallel to each
other perfectly normal (i. e . , at 90 ? exactly) to
the,, plane of the mounting ring. -
c. -- The vertical surfaces on t}1C. slide t ~}
a. The rhomboid bearing is probably- tied to the
-dowel slot and slide mating surface, with some - tolerance . -
b. The
of: -the dowel
surfaces' and
tolerance.
rhomboi-d mating surface and the position
are probably tied to the dovetail slide:
rhomboid. prisni::_centerli_ne,. with s~]ie
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I.uvc:sti.g,-jti.on. of Rhomboid Arm Motion
c. The dovetail slide surfaces are probabl.}'
tied to the pod mounting surface, again with some
10. The situation found ill the optics today, 9.s
that, generally-, the- 0.056 inch focus adjustne-mt found -i.n
the 2X rhomboid system is adequate for PI use with the IS t10
system. However, if an attempt is made to use optics with
less focus accomodat:ioil, major redesign of the mechanical
parts supporting the optics will be necessary. It has been
stated that 3X objective.Tenses currently under consideration
will contain focus accomnlodati.on~~`of about 0.075 inches
- NPIC/TSG/ESD/TEB' (Chrono
- NPIC/TSG/ESD/EPB
NPIC/TSG/RI:D
- DI.A/DI _8
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ease 2005/06%23 : CIA-RDP78B05171 A000400030026-2 .
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