Add FZP telescope tutorial to docs#153
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Adds docs/tutorials/fzp_focus.ipynb, a new Jupyter tutorial demonstrating how to model a Fresnel Zone Plate (FZP) as a holographic grating using HolographicRulingSpacing. The tutorial covers: - Recording geometry: x1 at 1 AU (sun distance) and x2 at the focal point, producing an ideal on-axis FZP for 171 Å EUV light - Solar disk source (0.5° full diameter) as the object surface - Known limitation with SequentialSystem backward-trace normalization for transmissive gratings, and the workaround (override rayfunction_default with physical coordinates) - Spot diagrams across the ±0.19° field of view - Diffraction-limited performance verification: geometric RMS spot 0.33 pm vs Airy disk radius 0.149 μm (ratio ~2×10⁻⁶) - Chromatic aberration demo: defocused disks at 169 Å (r=0.82 mm) and 174 Å (r=1.23 mm) vs diffraction-limited point at 171 Å Also registers the new tutorial in docs/index.rst. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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roytsmart
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May 21, 2026
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| "source": "FZP Telescope Tutorial\n======================\n\nA `Fresnel Zone Plate (FZP) <https://en.wikipedia.org/wiki/Zone_plate>`_\nis a diffractive optical element that focuses light by encoding the\ninterference pattern of two spherical waves on a flat surface.\nIn :mod:`optika`, an FZP is modeled as a transmissive surface with\n:class:`~optika.rulings.HolographicRulingSpacing` rulings, where the\ntwo recording-beam origins define the focal geometry.\n\nThis tutorial builds a single-element FZP telescope that focuses\ncollimated 171 Å EUV light onto a detector and examines the resulting\nspot diagrams." |
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| "source": "and the focal length" |
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| "source": "Holographic recording geometry\n^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n\nAn FZP is equivalent to a holographic grating whose rulings were\nrecorded by interfering two coherent beams.\nTo focus incoming collimated light (a plane wave from :math:`z = -\\infty`)\nonto a focal point at :math:`z = +\\text{focal\\_length}`, we choose:\n\n- **Recording beam 1** (``x1``): originates very far away on the optical\n axis, representing a plane wave. With ``is_diverging_1=True`` and\n :math:`x_1 \\to -\\infty`, the unit vectors from :math:`x_1` to every\n point on the surface become parallel, so the ruling pattern is\n identical to that produced by a true plane wave. We place ``x1`` at\n 1 AU (the Earth–Sun distance) so that the residual defocus\n :math:`\\delta f = f^2 / |x_1| \\approx 7\\ \\mathrm{pm}` is far below\n the diffraction limit.\n- **Recording beam 2** (``x2``): converges *to* the desired focal point\n at :math:`z = +\\text{focal\\_length}`. ``is_diverging_2=False`` means\n rays are directed toward :math:`x_2`, i.e. the second recording beam\n is a converging spherical wave.\n\nThe :class:`~optika.rulings.HolographicRulingSpacing` class computes\nthe spatially-varying ruling vector :math:`\\mathbf{d}(\\mathbf{r})` from\nthese two source points." |
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So is 7 pm really correct?
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| "source": "Holographic recording geometry\n^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n\nAn FZP is equivalent to a holographic grating whose rulings were\nrecorded by interfering two coherent beams.\nTo focus incoming collimated light (a plane wave from :math:`z = -\\infty`)\nonto a focal point at :math:`z = +\\text{focal\\_length}`, we choose:\n\n- **Recording beam 1** (``x1``): originates very far away on the optical\n axis, representing a plane wave. With ``is_diverging_1=True`` and\n :math:`x_1 \\to -\\infty`, the unit vectors from :math:`x_1` to every\n point on the surface become parallel, so the ruling pattern is\n identical to that produced by a true plane wave. We place ``x1`` at\n 1 AU (the Earth–Sun distance) so that the residual defocus\n :math:`\\delta f = f^2 / |x_1| \\approx 7\\ \\mathrm{pm}` is far below\n the diffraction limit.\n- **Recording beam 2** (``x2``): converges *to* the desired focal point\n at :math:`z = +\\text{focal\\_length}`. ``is_diverging_2=False`` means\n rays are directed toward :math:`x_2`, i.e. the second recording beam\n is a converging spherical wave.\n\nThe :class:`~optika.rulings.HolographicRulingSpacing` class computes\nthe spatially-varying ruling vector :math:`\\mathbf{d}(\\mathbf{r})` from\nthese two source points." |
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replace +\\text{focal\\_length} with :math:f and define
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Need "Source" heading and short explanation
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| "source": "Because the internal normalization algorithm in\n:class:`~optika.systems.SequentialSystem` traces rays *backward* through\nthe system to establish the field-of-view scale, and because this\nbackward trace re-applies the grating equation of a transmissive FZP\n(doubling the deflection angle), we must compute the default ray function\ndirectly with physical coordinates and cache the result manually.\n\n.. note::\n\n This is a known limitation when ``object_is_at_infinity=True`` with\n a transmissive grating as the pupil stop. Reflective systems (e.g.\n the prime-focus telescope) are not affected." |
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Is this really true? Check if the normalization algorithm works here
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Summary
docs/tutorials/fzp_focus.ipynb: a new Jupyter tutorial modeling a Fresnel Zone Plate (FZP) as a holographic grating withHolographicRulingSpacing, designed to focus 171 Å EUV light (MUSE science wavelength)docs/index.rstTutorial contents
HolographicRulingSpacingwith recording beamx1at 1 AU so residual defocus δf = f²/|x1| ≈ 7 pm, far below the diffraction limitSequentialSystem's backward-trace normalization re-applies the grating equation for transmissive surfaces (doubling the deflection angle); fix: overriderayfunction_defaultwith physical coordinates