A viewing chamber which permits observation of a sample retained therein includes a pair of double window assemblies mounted in opposed openings in the walls thereof so that a light beam can directly enter and exit from the chamber. A flexible mounting arrangement for the outer windows of the window assemblies enables the windows to be brought into proper alignment. An electrical heating arrangement prevents fogging of the outer windows whereas desiccated air in the volume between the outer and inner windows prevents fogging of the latter

Elkins, B. R.

Keller, V. W.

Owen, R. B.

White, W. T.

English

NASA Technical Reports Server

United States Patent [i i]  Patent Number: 4,61a,21s 
Keller et al. [45] Date of Patent: Oct. 21, 1986 
[54] DOUBLE WINDOW VIEWING CHAMBER 
[75] Inventors: Vernon W. Keller; Robert B. Owen; 
Bobby R. Elkins; William T. White, 
all of Huntsville, Ala. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
ASSEMBLY 
[73] Assignee: The United States of America as 
[21] Appl. No.: 729,766 
[22] Filed: May 2, 1985 
[51] Int. (3.4 ................................................ C02B 7/00 
[52] U.S. Cl. .................................................... 350/319 
[58] Field of Search ............... 350/319, 418, 419, 286, 
350/543,430; 356/244,246, 352 
~561 References Cited 
U.S. PATENT DOCUMENTS 
3,438,700 4/1969 Gillard ................................ 350/286 
3,782,809 Vi974 Shropshire .......................... 350/319 
3,894,795 7/1975 Laurens ............................... 350/319 
4,255,020 3/1981 Yukio .................................. 350/430 
4,436,375 3/1984 Meginnis ............................. 350/319 
Primary Examiner-John K. Corbin 
Assistant Examiner-Loha Ben 
Attorney, Agent, or Firm-Joseph H. Beumer; John R. 
Manning; Leon D. Wofford, Jr. 
[571 ABSTRACT 
A viewing chamber which permits observation of a 
sample retained therein includes a pair of double win- 
dow assemblies mounted in opposed openings in the 
walls thereof so that a light beam can directly enter and 
exit from the chamber. A flexible mounting arrange- 
ment for the outer windows of the window assemblies 
enables the windows to be brought into proper align- 
ment. An electrical heating arrangement prevents fog- 
ging of the outer windows whereas desiccated air in the 
volume between the outer and inner windows prevents 
fogging of the latter. 
17 Claims, 2 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19870004922 2020-03-23T15:15:06+00:00Z
U.S. Patent Oct. 21,1986 4,6 18,2 15 
FIG. 2 
4,618,215 
2 1 
DOUBLE WINDOW VIEWING CHAMBER 
ASSEMBLY 
ORIGIN O F  THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government, and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
FIELD OF THE INVENTION 
The present invention relates to viewing chambers 
which permit optical viewing of a sample contained 
therein and more particularly, to an improved viewing 
chamber assembly employing a pair of double window 
ports located on opposite sides of the chamber. 
BACKGROUND OF THE INVENTION 
The present invention is concerned with, but is not 
limited to, viewing chambers which require isothermal 
cooling to temperatures below freezing. Such chambers 
are employed, among other uses, in observation of crys- 
tal growth in connection with aircraft flight experi- 
ments. Prior art chambers characteristically use a single 
wall construction for the access ports thereof which has 
caused thermal non-conformity in the walls, thereby 
resulting in uneven cooling of the chamber. Such prior 
art chambers have also been subject to fogging of the 
viewing window as the chamber cools. 
Patents of possible interest in this general area in- 
clude: 
U.S. Pat. Nos. 4,242,589 (Sachs); 3,936,196 (Wicker- 
sheim); 3,966,297 (Vigreux et al); 3,899,243 (Haver- 
kamp); and 4,372,652 (Pontefract). 
SUMMARY OF THE INVENTION 
As set forth above, one important aspect of the inven- 
tion concerns the provision of chamber including a pair 
of double window viewing ports. One of the reasons 
that chambers with double windows have not been used 
in the past is that a slight misalignment of the windows 
results in multiple reflections and distorts the image. 
Further, if fogging is not eliminated, the use of multiple 
window surfaces accentuates the image degradation 
which results from such fogging. Generally speaking, as 
set forth above, one important aspect of the invention 
involves the provision of two double-window ports on 
opposite sides of the chamber, for a total of four win- 
dows, together with flexible, adjustable mounts for the 
windoas which permit the windows to be adjusted 
about two axes parallel to the window surfaces. These 
flexible mounts permit the outer windows of the sets of 
two windows to be aligned with the inner windows, 
thereby eliminating multiple reflection distortions of the 
chamber sample image. By locating the optical ports on 
opposing sides of the chamber, a light path is provided 
which permits a beam of light to enter and exit directly, 
thereby providing optimum optical access to the cham- 
S 
10 
1s 
20 
25 
30 
3s 
40 
4s 
so 
5s 
assemblies are in optical alignment whereby a light 
beam can enter and exit from the chamber directly. The 
window assemblies each comprise inner and outer win- 
dows mounted in spaced relationship so as to define a 
volume therebetween, and a flexible mounting arrange- 
ment for the outer one of the windows so as to permit 
adjustment in the positioning of that window, whereby 
the inner and outer windows can be brought into proper 
optical alignment. The flexible mounting means prefera- 
bly includes a window holder for the outer window and 
a plurality of screws for securing the window holder to 
a mounting member for the inner window. Advanta- 
geously, the flexible mounting means further comprises 
a flexible connection between the window holder and 
the mounting member. The screws preferably extend 
through corresponding enlarged diameter bores in the 
window holder and in this embodiment,. the flexible 
mounting means each further comprise a bearing, lo- 
cated within the associated bore at the outer end 
thereof, in which the head of the corresponding screw 
is received, and a coil spring located between each 
window holder and the corresponding mounting mem- 
ber, and surrounding the associated screw. 
The inner window of each window assembly is pref- 
erably located in an associated one of the openings in 
the chamber wall, the window assemblies each includ- 
ing a retaining arrangement received in the correspond- 
ing opening for holding the inner window in place. The * 
openings referred to are preferably threaded and the 
portions of the walls defining the openings include a 
stepped portion against which one surface of the inner 
window is held. The retaining arrangements each pref- 
erably include a screw threaded retaining member 
threadably received in the associated opening and a 
locking ring for locking the retainer member into place. 
Advantageously, the retaining arrangement further 
comprises an O-ring located in the stepped portion of 
the wall for cushioning and sealing the one surface of 
inner window, and a spacer located between said re- 
tainer member and the other surface of the inner win- 
dow. A desiccated gas is preferably located in the vol- 
ume defined between the pairs of windows. 
As explained in more detail below, a heating means is 
provided for heating the outer windows to prevent 
fogging thereof. This heating means preferably com- 
prises an electrical heating coil mounted on the mount- 
ing fixture for the outer window. Further, an additional 
heating means is mounted within the chamber wall for 
providing fine adjustment of the chamber temperature. 
The latter preferably comprises an electrical heating 
arrangement and is used in conjunction with the cooling 
fluid which is circulated in the walls of the chamber to 
control the temperature in the chamber. 
Advantageously, the plurality of connecting screws 
extending between the window holder and the remain- - 
6o der of the window assembly, together with the flexible 
connector, constitute the sole connection between the 
window holder and the remainder of said window as- 
sembly. Low thermal conductivity screws reduce the 
heat transfer between the outer window assembly and 
Other features and advantages of the present h e n -  
tion will be set forth in, or apparent from, the detailed 
description of a preferred embodiment which follows. 
ber. 
Thus, in accordance with a preferred embodiment of 
the invention, an optical viewing arrangement is pro- 
vided in a viewing chamber apparatus having chamber 
walls in which a coolant is circulated to provide cooling 
of the chamber, the optical viewing arrangement corn- 65 the chamber. 
prising first and second window assemblies respectively 
mounted in first and second opposed openings on oppo- 
site sides of the chamber wall such that the window 
4,6 1 8,2 1 5 
4 3 
basic components, which are identified by the same 
reference numerals with the letter “b” attached. 
FIG. 1 is a side elevational view of a viewing cham- Turning again to the chamber proper, the walls 10 are 
ber apparatus constructed in accordance with a pre- preferably formed from a thick aluminum block the 
ferred embodiment of the invention; and 5 exterior of which is insulated as required and which 
FIG. 2 is a cross section view of the chamber appara- contains both heating coils, indicated schematically at 
tus of the FIG. 1, with the heating and cooling coils for 64 in FIG. 1, and cooling coils, indicated schematically 
the chamber walls removed. at 66 in FIG. 1. The heating and cooling coils are not 
shown in FIG. 2 for purposes of clarity. The heating 
DESCRIPT1oN OF THE PREFERRED 10 coils 64 are electrical coils and are preferably disposed 
EMBODIMENTS in grooves in walls 10 while the cooling coils 66 have a 
Referring to FIGS. 1 and 2, the chamber assembly of frigid liquid Coolant Circulating therein. The Coolant 
the invention includes a generally cylindrical, thick- Can be a liquid with a low temperature freezing point, 
walled housing 10 forming a central chamber 12. A pair such as ethylene glycol, or, if either rapid cooling Or a 
of dual optical window assemblies, denoted 14p and 15 very low temperature is required, the coolant can even 
14b, are respectively mounted in stepped openings be liquid nitrogen. The liquid coolant provides coarse 
and 166 formed in opposite walls of the housing. The temperature control of the temperature of chamber 12 
optical window assemblies are while electrical heating coils 64 provide fine adjustment 
chamber 12, while still permitting optimum optical ac- 
cess for measurement and observational purposes. In 
~ ! h ~ o ~ t r ~ $ & ~ ~ ~ ~ ~ ~ ~  ,?$E ~~~~r~ 
25 reasonably close to the freezing point of the coolant by 
cooling the liquid coolant to an appropriate value, cir- 
coils 66 as described above until the temperature within 
chamber 12 is slightly below the desired temperature, 
A lock- 30 and then using the electrical heating coils 64 to provide 
DESCRIPT1oN OF THE 
identical and corresponding p m  of each have been Of this temperature. This arrangement pennits an ex- 
given the =me numbefi with the letter a or letter b 20 tremely uniform temperature to be set UP within the 
attached. Because of this only one of the 
window assemblies will be described below. 
Considering window assembly 14u, one flat surface of 
a generally cylindrical inner window 1& is held against 
an O-ring seal mounted in a groove in a shoulder 22u 
is located between the other flat surface and a threaded 
cylindrical retainer member 2Q which is screwed into 
Opening 16a so as to window in 
serves in locking retainer member 26a in place in open- 
windows & and 486 enables these windows to be tilted ing 16a 
A plug member 28a is threaded at One end and this around two axes parallel to the surfaces thereof so as to 
threaded end is received in retainer member 26a as 35 for midignment. ln particular, relative adjust- 
illustrated. A laterally extending flange 3Oa includes ment of & and 346 enables the tilt of windows 
three threaded bores 320 (only one of which is shown in e and ub to be so that these windows can 
FIG. 2), in which are received three screws * Screws be brought into proper alignment with the fixed, inner 
34a each form Part of an adjustment Screw assembly windows 1& and 18b, while the flexible connection 
and extend between flange 3Oa and a window holder 40 provided by flexible connecting tubes 5oa and Sob per- 
member 3612. Considering a typical one Of the adjust- mits this to & done. B~ bringing the inner and outer 
ment screw assemblies, as shown in FIG. 2, a spring 3& windows into optical alignment, multiple reflection 
surrounds a Portion Of screw & and iS captured be- distortions ofthe image of the chamber sample are elim- 
tween flange 3 0 ~  and window holder 36a9 between inated. Further, by providing dual window assemblies 
washers 400 and The outermost Portion of Screw 45 on both sides, a light path is provided which allows a 
& is mounted by a bearing 44a in an enlarged bore 46u beam to enter and exit directly, thus affording optimum 
in window holder 36a optical access to the chamber 12. In addition, the con- 
struction ofthe window mounting assemblies minimizes 
dow and is further connected to Plug member 28a the thermal conduction between the mounting fixtures 
by a flexible connector tube 5 k  mounted on facing 5.0 for the outer windows e and 48b and the chamber 
opposed flanges on window holder 36a and Plug mem- walls 10, thereby reducing the amount of heating re- 
ber 28a. One flat surface of window bears against an quired and lessening the impact of the mounting fixtures 
O-ring 52u disposed in a groove in an end wall defining on the thermal uniformity provided in chamber 12. As 
a bore * in window holder 36a and is held in place mentioned above, desiccated air placed in the volumes 
within bore Mu by a threaded retaining ring 56a and an 55 formed between windows &, 1& and 486, 186 respec- 
intermediate washer 58a tively, ensures that fogging of inner windows 1& and 
A pair of stainless steel tubes 6Ou and 61a (see FIG. 1) 18b does not occur. This air is supplied to assembly 14a, 
are brazed or soldered in place in flange 3Oa of plug 28a for example, through inlet and outlet tubes 6Oa and 61a 
These tubes form an inlet and outlet for an inert gas, It will be understood by those skilled in the art that 
such as desiccated air, which is supplied to the volume 60 although the invention has been described relative to an 
between windows 48u and 18a exemplary embodiment thereof, variations and modifi- 
A heating coil, located around the mounting fixture cations can be effected in this exemplary embodiment 
for window 48u and indicated schematically at 62u in without departing from the scope and spirit of the in- 
FIGS. 1 and 2, provides selective heating of window vention. 
48n so as to eliminate fogging thereof. Electrical con- 65 
nections to coil 620 are indicated at 63a 
As stated above, the other double window assembly 
14b is similar to assembly 14p and includes the same 
defining One step in stepped Opening 16a A ‘pacer 24a culating the coolant through the walls 10 in 
ing ring 27n located in portion Of Opening 16a fine adjustment of the chamber temperature. 
The flexible mounting described above for 
Window holder 36a serves to mount an outer win- 
We claim: 
1. In a viewing chamber apparatus having a chamber 
wall in which a coolant is circulated to provide cooling 
of the chamber, an optical viewing arrangement com- 
4,618,215 
5 6 
prising first and second window assemblies respectively between said retainer member and the other surface of 
mounted in first and second opposed openings in the said inner window. 
chamber wall such that said window assemblies are in 8. A viewing chamber apparatus as claimed in claim 
optical alignment whereby a light beam can enter and 1 wherein a desiccated gas is located in said volume 
exit from the chamber directly, said window assemblies 5 defined between said windows. 
each comprising inner and outer windows mounted in 9. A viewing chamber apparatus as claimed in claim 
spaced relat_onship so as to define a volume therebe- 1 further comprising heating means for heating the 
tween, and flexible mounting means for the outer one of outer windows to prevent fogging thereof. 
the windows for permitting adjustment of the position- 10. A viewing chamber apparatus as claimed in claim 
ing of said outer window whereby the inner and outer 10 9 wherein said heating means comprises an electrical 
windows can be brought into optical alignment. heating coil mounted on the flexible mounting means 
2. A viewing chamber apparatus as claimed in claim for said outer window. 
1 wherein said flexible mounting means includes a win- 11. A viewing chamber apparatus as claimed in claim 
dow holder member and a plurality of screws for secur- 1 further comprising heating means mounted within 
ing said window holder member to a mounting member 15 said chamber wall for providing fine adjustment of the 
for said inner window. chamber temperature. 
3. A viewing chamber apparatus as claimed in claim 12. A viewing chamber apparatus as claimed in claim 
2 wherein said flexible mounting means further com- 11 wherein said heating means comprises electrical 
prises a flexible connection between said window heating means. 
holder member and said mounting member. 13. A viewing chamber apparatus as claimed in claim 
4. A viewing chamber apparatus as claimed in claim 1 wherein each said flexible mounting means includes a 
3 wherein said screws extend through corresponding window holder for the outer window, and adjustable 
bores in said window holder member and said flexible mounting means for providing adjustment of the posi- 
mounting means further comprises a bearing, located tion of said window holder relative to the remainder of 
within each of said bores at the outer end thereof, in 25 the window assembly. 
which the head of the corresponding screw is received, 14. A viewing chamber apparatus as claimed in claim 
and a spring located between each window holder 13 wherein said adjustable mounting means includes a 
member and the corresponding mounting member. flexible connector located between said window holder 
5. A viewing chamber apparatus as claimed in claim and the remainder of said window assembly which 
1 wherein the inner window of each member assembly 30 serves in defining said volume between said inner and 
is located in a corresponding one of said openings in the outer windows. 
chamber wall, said window assemblies each including 15. A viewing chamber apparatus as claimed in claim 
retaining means received in the corresponding said 14 wherein said adjustable mounting means includes a 
opening for holding said inner window in place. plurality of connecting screws extending between said 
6. A viewing chamber apparatus as claimed in claim 35 window holder and the remainder of the window as- 
5 wherein each of said openings is threaded and the sembly which, together with said flexible connector, 
portions of the wall defining the openings include a constitute the sole connection between said window 
stepped portion against which one surface of said inner holder and the remainder of said window assembly. 
window is held, and said retaining means each com- 16. A viewing chamber apparatus as claimed in claim 
prises a screw threaded retaining member threadably 40 15 further comprising bearing means for mounting one 
received in the corresponding one of said openings and end of each of said screws in an enlarged bore in said 
a locking ring for locking said retainer member into window holder. 
place. 17. A viewing chamber apparatus as claimed in claim 
7. A viewing chamber apparatus as claimed in claim 15 further comprising a coil spring surrounding each of 
6 wherein said retaining means further comprises an 45 said screws and extending between said window holder 
O-ring located in said stepped portion for cushioning and the remainder of said window assembly. 
said one surface of inner window and a spacer located 
20 
I * * * *  
50 
55 
60 
65 


Double window viewing chamber assembly

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server