Glass and Optics
Cleaning Dirty Filters
Carbon dioxide has been used extensively to clean glass and optical surfaces. This includes removing contamination before applying optical coatings, cleaning surfaces before or after assembly, and many other applications. One of the first examples we published (see Sherman - 1991), was the removal of extensive debris from neutral density and bandpass filters. These filters, all one inch in diameter and about a 1/4" thick, were loaded with dirt and grease from handling after being used in a laboratory. We cleaned the surfaces with CO2 Snow. The surface compositions, as found by XPS and given below, and optical inspections, indicated effective cleaning. Visually, they were "clean" and this was verified by examination by bright field and dark field images.
XPS Data for Filters
|
Element
|
Filter #1 Initial
|
Filter #1 Cleaned
|
Filter #2 Initial
|
Filter #2 Cleaned
|
Filter #3 Initial
|
Filter #3 Cleaned
|
| Si |
12 |
26 |
8 |
21 |
9 |
21 |
| O |
29 |
50 |
16 |
45 |
24 |
43 |
| C |
55 |
20 |
72 |
28 |
65 |
32 |
| Na |
3 |
2 |
2 |
2 |
2 |
2 |
| Mg |
0 |
1 |
0 |
1 |
0 |
1 |
| S |
1 |
0 |
2 |
0 |
0 |
0 |
| N |
0 |
0 |
0 |
2 |
0 |
2 |
Coated and Uncoated Plate Glass
We have studied several items within this category including cleaning coated and uncoated glass, quartz, and also compared solvent cleaning to snow cleaning. Overall, with optics, substrates, and other glass objects, cleaning is effective with proper attention to processing parameters. Other items cleaned include IR and UV optics, gyroscopes, sensors, 3-5 Si and Ge optics, mirrors, grating, telescopes, gratings, and others.
