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 6025 which accepts a full 6"×6"×0.25" photomask substrate. For applications where a smaller aperture will suffice, our Model 50R accepts a CGH substrate measuring Ø50.8 mm and up to 4 mm thick. Finally, the Model 50 is identical in overall dimensions to the 50R but accepts square substrates measuring 38 x 38 mm.
| CGH Frames | ||||
|---|---|---|---|---|
| Model | Clear Aperture | Glass Size | Drawing | Image |
| 6025 | 127×127 mm | 6"×6"×0.25" (photomask) | 6025.dxf | M6025_dwg.jpg |
| 50R | Ø48 mm | Ø50.8x4 mm | 50R.dxf | 50R.2D.gif |
| 50 | 35x35 mm | 38x38x2.3 mm | N/A | N/A |
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 |
| M6025 | 5 or 6-axis | Ø158 mm | 125±3 mm | Inquire | M6025_dwg.jpg |  Pricing |
| M506 | 6-axis | Ø48 mm | 51±3 mm | M506.dxf | M506.2D.gif | Pricing |
| 1206R | Adapter | Ø55 mm | N/A | M1206R.dxf | M1206R.2D.gif | Pricing |
Our Model M506 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. 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.
