#### Transcript Maestro Lens Mounting - University of Arizona

```Maestro Lens Mounting
• Lenses 4 and 6
– Mounting method: Potted on OD with elastomer (athermalized)
– Lens diameter
= 10.63 inches
– Lens CTE (l)
= 3.5x10-6/F
– Elastomer
• CTE (e)
• 
= 178.0x10-6/F
= 0.4992
– Cell, Aluminum (to match L5 CTE)
• CTE (c)
= 13.0x10-6/F
1
Athermalization Calculation
• Assume elastomer layer is constrained
– Thermal expansion of elastomer (h = thickness of elastomer layer)
= e*((1+)/(1-  ))*T*h = 2.994 e T*h
– Thermal expansion of cell (D = diameter of lens)
= c*T*(D/2+h)
– Thermal expansion of lens
= l*(D/2)*T
– The mounting is athermalized if the expansion of the elastomer
equals the cell expansion less the lens expansion:
– 2.994 e T*h = c*T*(D/2+h) - l*(D/2)*T
• This is true if:
– h = (c- l)*(D/2)/(2.994 e - c) = 0.097 inches
• After adjusting for shape effects (finite width)
– h = 0.102” for L4 and 0.102” for L6
2
Finite Element Model of Lens L4
Lens L4
Elastomer Layer
3
Finite Element Model of Lens L6
Lens L6
4
Lens L4 Results, No Axial Locators
– 1 g Z cases are on elastomer and on elastomer supplemented by
axial supports.
– 1 g Y and Z hydro cases do not include gravitational acceleration
Item
Units
1gZ
1gZ
3 spts
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
15.5
0.088
19.3
0.14
15
0.089
45.7
0.299
8
0.047
189
1.099
waves
waves
waves
waves
waves
waves
3.99
0.37
0.16
1.07
40.57
0.04
0.04
0.04
9.79
15.70
0.12
0.02
0.51
0.01
0.11
0.04
0.01
0.05
0.01
0.01
0.03
5
Lens L6 Results, No Axial Locators
• 1 g Z cases are on elastomer and on elastomer
supplemented by axial supports.
1 g Y and Z hydro cases do not include gravitational
acceleration
Item
Units
1gZ
1gZ
3 spts
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
11.3
0.061
18.6
0.129
11.2
0.066
44.8
0.286
15.2
0.084
185
1.016
waves
waves
waves
waves
waves
waves
4.33
0.13
0.13
4.05
53.05
0.03
0.03
0.03
12.04
22.30
0.12
0.04
0.49
0.01
0.06
0.04
0.07
0.01
6
Lens L4 Results, Three Axial Locators
1 g Y and Z hydro cases do not include gravitational
acceleration
Item
Units
1gZ
3 spts
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
100 F
Change
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
19.1
138
15.4
0.095
65.6
0.538
8.6
0.609
221
1.611
9982
48.76
waves
waves
waves
waves
waves
waves
0.20
0.12
0.08
2.21
62.36
0.04
0.04
0.56
1.01
0.12
0.15
0.02
0.12
0.03
0.02
0.51
27.01
0.01
0.01
0.51
0.11
0.33
1.67
0.05
0.01
0.01
7
Lens L6 Results, Three Axial Locators
1 g Y and Z hydro cases do not include gravitational acceleration
Item
Units
1gZ
3 spts
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
100 F
Change
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
19
0.131
11.5
0.068
80.5
0.726
20.8
0.151
261
1.879
4724
25.6
waves
waves
waves
waves
waves
waves
0.18
0.10
0.20
2.53
0.88
0.03
0.03
0.52
2.53
0.12
0.20
0.03
0.19
0.02
0.04
0.50
12.68
0.06
0.01
0.80
0.07
0.31
0.11
0.07
8
Lens L4 Results, Six Axial Locators
1 g Y and Z hydro cases do not include gravitational
acceleration
Item
Units
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
100 F
Change
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
15.6
0.121
45.2
0.394
8.1
0.056
190
1.438
16354
68.32
waves
waves
waves
waves
waves
waves
0.12
0.35
0.27
0.12
0.08
1.44
68.06
0.02
0.52
14.17
0.01
0.12
1.80
0.04
0.02
0.01
0.03
9
Lens L6 Results, Six Axial Locators
1 g Y and Z hydro cases do not include gravitational acceleration
Item
Units
1gZ
6 spts
1gY
hydro
hydro
1gz
1 psi
100 F
Change
Distortion
P-V distortion
Zernekes
Piston
tilt
focus
astig
coma
trifoil
spherical
nm-rms
Waves
11.5
0.068
44.96
0.299
15.5
0.092
187.5
1.106
4723
25.3
waves
waves
waves
waves
waves
waves
0.09
0.36
0.69
0.12
0.12
0.32
77.61
0.04
0.50
12.68
0.01
0.07
0.11
0.03
0.03
0.02
10
Residual Deformation if Bonded on Three Points
Assume 500*sin(3*) -inch deformation when bonded
(Actual 1 g trifoil is < 1.75 -inch)
Residual trifoil in lens L4 is 2.7 -inch (0.54%)
Residual trifoil in lens L6 is 3.05 -inch (0.61%)
Conclusion:
The lens can be supported on 3 OD points while bonding.
When the weight is removed from the 3 support points 99.4%
of the trifoil present during bonding will disappear.
11
Thermal Stress and Elastomer Thickness
Lens 4
Bond Thickness
Support Points
inches
0.098
3
0.1
3
0.102
3
0.1
3
u-inches
1237
1154
1080
1149
Stress in elastomer
psi
36
14
-37
10
Max Glass stress
psi
358
352
346
50
Surface distortion
waves
8.83
8.62
8.42
8.03
Uz at 100 deg F delta
12
Thermal Distortion, 100 deg F Change, L4
Lens and Cell
Lens and Cell
Cell
Z
X
Y
1
Elastomer (a narrow strip with the
same shape factor is required).
AESTRO L4 with elastomer at OD, 3 point axial Support
Z
Z
X
X
Y
Y
13
MAESTRO L4 with elastomer at OD, 3 point axial Support
Thermal Results, 100 deg F Change, L4
• To investigate large thermal distortions an aluminum cell
was added to the model and the methodology revised to
allow accurate distortion calculation (I.e. normalize CTE’s
to the glass value to remove large dimensional changes
related only to thermal expansion).
• Results for various configurations of the elastomer layer:
– Case
– Full lens height
– Half lens height
– Half height, half circumf.
Lens distortion
0.81 waves P-V
0.092 waves P-V
0.058 waves P-V
14
```