Double-Pyramid Wavefront Sensors: Tolerance Relaxation and Cheaper Alternatives using Achromatic Double-Roof Prisms
Bibliographic record
Abstract
We present the current design of the double-pyramid planned for the TMT-NFIRAOS Visible Natural Guide Star WFS and its manufacture challenges to meet all the requirements in terms of tip size, pupil image quality and mapping on the detector pixels. We show that the angular tolerance of the pyramid can be relaxed from 6 arcsec. to 2 arcmin. without significant impact on the AO performance, which is within the capabilities of most optical suppliers and reduces the fabrication cost by a factor 10 or more. Then we compare the pyramid design to a new concept using two double-roof prisms, optically equivalent to an achromatic double-pyramid and offering very similar performance. Roof prisms are easier to manufacture to tolerance than pyramids since there is no tip. We also present an adjustable version of the achromatic double-roof prism allowing very fine adjustments of the positions of the four pupils onto the detector pixels, which can relax the manufacture tolerance of the prisms even more.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".