Aspheric metrology using CGH nulls requires precise multi-axis alignment of the CGH, either within the interferometer itself or within its test beam. Pre-alignment of CGHs in interchangeable frames speeds this alignment process and improves its accuracy.
Our versatile CGH frames and positioners provide 6-axis positioning while allowing easy and rapid interchangeability of CGHs with virtually no degradation of alignment. They are easily integrated with other optical fixturing and instrumentation already in your lab.
We offer three sizes of CGH frame. Our Model 50R accepts a CGH substrate measuring 50 to 50.8 mm diameter and up to 3 mm thick. For applications requiring a larger aperture, we offer the Model 120R which accepts a Ø112.5 mm substrate up to 6.35 mm thick. Finally, the Model 50 is identical in overall dimensions to the 50R but accepts substrates measuring 38 x 38 mm.
| CGH Frames | ||||
|---|---|---|---|---|
| Model | CGH Size | Clear Aperture | Drawing | Image |
| 50 | 38x38x3 mm | 35x35 mm | N/A | N/A |
| 50R | Ø50.8x3 mm | Ø48 mm | 50R.dxf | 50R.2D.gif |
| 120R | Ø112.5x6 mm | Ø105 mm | 120R.dxf | 120R.2D.gif |
Each CGH frame includes four precision hardened steel balls, any three of which register against six carbide rod bearing surfaces of the CGH positioner to provide exactly six mechanical constraints. A CGH frame can be repeatedly removed and reattached to its positioner with virtually no change in alignment.
CGH frames are held against a positioner’s carbide bearing surfaces by magnetic coupling. The coupling force is sufficient to hold the CGH securely, but not so great as to degrade system alignment when the CGH frame is pulled free.
Each framed CGH can be attached in any of eight discrete orientations. Decentration on switching mounting orientations is typically less than 20 µm.
Our CGHs are permanently aligned and bonded to their frames. Tilt, tip and focus are controlled by locating the CGH optical surface to within about 10 µm of its design position relative to the plane of the four precision balls. Using fiducial marks incorporated into the CGH and a proprietary alignment tool, centering and rotation are controlled to a few µm.
Because our alignment technique does not depend on the CGH substrate thickness or its optical transmission properties, we can prealign transmission, reflection, visible and infrared CGHs.
Verification of CGH alignment and kinematic mounting can be performed by the user with standard metrology techniques. We will be glad to show you how.
| CGH Positioners | |||||||
|---|---|---|---|---|---|---|---|
| Model | Type | Aperture | Axis Height | Drawing | Image | Price* | Export* |
| 506 | 6-axis | Ø48 mm | 51±3 mm | M506.dxf | M506.2D.gif | $1045 | $1150 |
| 1206 | 6-axis | Ø140 mm | 90±3 mm | M1206.dxf | M1206.2D.gif | $1375 | $1510 |
| 1206R | Adapter | Ø55 mm | 90±3 mm | M1206R.dxf | M1206R.2D.gif | $495 | $545 |
Our Model 506 positioner offers a full six axes of precision adjustment from a single stable base. This positioner is useful for aligning a CGH to a spherical reference wavefront while also aiming and orienting the diffracted beam. The Model 506 positioner accepts Model 50 and Model 50R CGH frames as well as Ø50-50.8 mm optics. The three face screws control tilt, tip and focus; pure tilt or tip is achieved by turning two adjacent screws an equal amount, whereas focus requires turning all three screws. Vertical translation is controlled by the top edge screw. Horizontal translation requires turning both side edge screws and equal amount. Clock rotation requires turning the top and bottom most edge screws an equal amount.
With a bolt key in place, the CGH frame can only be attached in a single, unique orientation providing maximum alignment accuracy.
The open profile of our large Model 1206 positioner allows a CGH null to be positioned in close proximity to a 4-inch Fizeau transmission sphere for testing of large convex aspheres. This positioner accepts any of our CGH frames. The Model 120 frames attach directly, whereas Model 50 and 50R frames require use of reducer plate Model 1206R.
Use our CGH Bracket to attach a Model 1206 positioner to the optional rail kit of your Zygo GPI or ADE MiniFIZ interferometer.
