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Sandbox Physics

Optics 072 · Diffraction, Fourier optics, and computational imaging

Ptychography & Coherent Diffraction Imaging

An independently initialized three-dimensional apparatus connects Overlapping probe scan, Diffraction-only detector, Iterative object recovery. Two dimensional physical controls, direct probe dragging, a detector trace, and three quantitative checks are recalculated from the stated equation.

Interactive modelPtychography & Coherent Diffraction Imaging
Primary prediction P1\mathcal P_10.500.50
Physical scale P2\mathcal P_250%50\%
Limit check V\mathcal V0.00π0.00\pi
Model regimevalid model regime\text{valid model regime}

Physics tutorial

How to investigate Ptychography & Coherent Diffraction Imaging

BackgroundPtychography & Coherent Diffraction Imaging is one independently initialized apparatus with three linked investigations: Overlapping probe scan, Diffraction-only detector, Iterative object recovery. Its two controls—Scan step and Probe diameter—feed the governing relation Ij(q)=∣F{P(r−Rj)O(r)}∣2I_j(\mathbf q)=\left|\mathcal F\{P(\mathbf r-\mathbf R_j)O(\mathbf r)\}\right|^2. Scalar, paraxial, or sampled-field assumptions are stated by the validity indicator; vector and nonparaxial effects are outside that boundary.

Why it mattersHow does overlapping illumination make a lensless amplitude-and-phase reconstruction possible?

Start with the essentials

Focus question
How does overlapping illumination make a lensless amplitude-and-phase reconstruction possible?
One-sentence intuition
The detector curve and all three numerical readouts are recomputed from Ij(q)=∣F{P(r−Rj)O(r)}∣2I_j(\mathbf q)=\left|\mathcal F\{P(\mathbf r-\mathbf R_j)O(\mathbf r)\}\right|^2. Geometry and glow are presentation encodings; the equation, units, conservation or limit check, and validity indicator are the quantitative evidence.

Core mathematical model

Governing relation

Ij(q)=∣F{P(r−Rj)O(r)}∣2I_j(\mathbf q)=\left|\mathcal F\{P(\mathbf r-\mathbf R_j)O(\mathbf r)\}\right|^2

The implementation evaluates this relation with dimensional inputs and an executable analytic or numerical benchmark. Scalar, paraxial, or sampled-field assumptions are stated by the validity indicator; vector and nonparaxial effects are outside that boundary.

Common difficulties

Mistaking glow for measured power

Typical misconceptionA brighter cinematic trail must represent proportionally more optical power.

Better mental modelUse the detector and normalized readouts for comparison. Glow is deliberately nonlinear so weak structure stays visible.

Run the experiment

  1. 01

    Scene 1: Overlapping probe scan

    Select Overlapping probe scan. Sweep Scan step, hold Probe diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  2. 02

    Scene 2: Diffraction-only detector

    Select Diffraction-only detector. Sweep Scan step, hold Probe diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  3. 03

    Scene 3: Iterative object recovery

    Select Iterative object recovery. Sweep Scan step, hold Probe diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.