Configuration Reference¶

The Params object holds all shared configuration for the reconstruction. It is created once and passed to both the Reconstruction and the engine.

from PtyLab import Params

params = Params()
params.propagatorType = "Fraunhofer"
params.positionOrder = "random"

Propagation¶

Parameter	Default	Options	Description
`propagatorType`	`"Fraunhofer"`	`"Fraunhofer"`, `"Fresnel"`, `"ASP"`, `"scaledASP"`	Wave propagation method from sample to detector
`fftshiftSwitch`	`False`	`bool`	Pre-shift FFT for slight performance gain; changes coordinate convention

Note

"Fraunhofer" (far-field) is the standard choice for most experiments. Use "ASP" (Angular Spectrum) for near-field or when the Fraunhofer approximation breaks down.

Update control¶

Parameter	Default	Options	Description
`probeUpdateStart`	`1`	`int`	Iteration at which probe updates begin
`objectUpdateStart`	`1`	`int`	Iteration at which object updates begin
`positionOrder`	`"random"`	`"random"`, `"sequential"`, `"NA"`	Order in which scan positions are visited each iteration

Momentum acceleration¶

Parameter	Default	Description
`momentumAcceleration`	`False`	Enable momentum-based acceleration (used by mPIE/mqNewton)
`adaptiveMomentumAcceleration`	`False`	Automatically adjust momentum strength during reconstruction

Object regularization¶

Parameter	Default	Description
`objectSmoothenessSwitch`	`False`	Apply smoothness regularization to the object
`objectSmoothenessWidth`	`2`	Smoothing kernel width (pixels)
`objectSmoothnessAleph`	`1e-2`	Smoothness regularization strength
`absObjectSwitch`	`False`	Constrain object to be real-valued (absorption only)
`absObjectBeta`	`1e-2`	Relaxation parameter for abs-only constraint
`objectTVregSwitch`	`False`	Enable total variation regularization on the object
`objectTVfreq`	`5`	How often (iterations) to apply TV update
`objectTVregStepSize`	`1e-3`	TV gradient step size
`l2reg`	`False`	Enable L2 regularization
`l2reg_object_aleph`	`0.001`	L2 regularization strength for the object

Probe regularization¶

Parameter	Default	Description
`probeSmoothenessSwitch`	`False`	Apply smoothness regularization to the probe
`probeSmoothenessWidth`	`3`	Smoothing kernel width (pixels)
`probeSmoothenessAleph`	`5e-2`	Smoothness regularization strength
`probeBoundary`	`False`	Apply a soft boundary constraint to the probe
`absorbingProbeBoundary`	`False`	Zero the probe outside its support (hard boundary)
`absorbingProbeBoundaryAleph`	`5e-2`	Boundary strength
`probePowerCorrectionSwitch`	`False`	Normalize probe power to match measured intensity
`modulusEnforcedProbeSwitch`	`False`	Enforce probe modulus from an empty-beam measurement
`absProbeSwitch`	`False`	Constrain probe to be real-valued
`absProbeBeta`	`1e-2`	Relaxation parameter for abs-only probe constraint
`binaryProbeSwitch`	`False`	Enforce a binary probe support
`l2reg_probe_aleph`	`0.01`	L2 regularization strength for the probe

Probe orthogonalization¶

Parameter	Default	Description
`orthogonalizationSwitch`	`False`	Orthogonalize incoherent probe modes during reconstruction
`orthogonalizationFrequency`	`10`	How often (iterations) to orthogonalize

Orthogonal Probe Relaxation (OPR)¶

Parameter	Default	Description
`OPR_modes`	`[0]`	Which probe modes to include in OPR relaxation
`OPR_subspace`	`4`	Number of subspace vectors for OPR
`OPR_alpha`	`0.05`	OPR feedback strength
`OPR_orthogonalize_modes`	`True`	Orthogonalize all modes within OPR

Intensity constraint¶

Parameter	Default	Options	Description
`intensityConstraint`	`"standard"`	`"standard"`, `"sigmoid"`	How to apply the Fourier modulus constraint

Autofocusing¶

Parameter	Default	Description
`TV_autofocus`	`False`	Enable TV-based autofocusing
`TV_autofocus_metric`	`"TV"`	Focus metric: `"TV"`, `"std"`, or `"min_std"`
`TV_autofocus_stepsize`	`5`	Step size (µm) between focus planes
`TV_autofocus_range_dof`	`11`	Number of planes to test (should be odd)
`TV_autofocus_roi`	`[0.4, 0.6]`	Region of interest (fractional) for metric computation
`TV_autofocus_run_every`	`3`	Run autofocus every N iterations

Other constraints¶

Parameter	Default	Description
`couplingSwitch`	`False`	Couple adjacent wavelengths in polychromatic mode
`couplingAleph`	`0.5`	Coupling strength
`backgroundModeSwitch`	`False`	Estimate and subtract a background term
`comStabilizationSwitch`	`False`	Stabilize center of mass of the probe
`adaptiveDenoisingSwitch`	`False`	Adaptive noise clipping during intensity projection
`CPSCswitch`	`False`	Constrained Pixel Sum Correction
`CPSCupsamplingFactor`	—	Upsampling factor for CPSC

GPU¶

Parameter	Default	Description
`gpuSwitch`	`False`	Move all arrays to GPU (requires CuPy and a CUDA GPU)
`saveMemory`	`False`	Reduce GPU memory usage at slight performance cost

See GPU Acceleration for setup and usage.

Output¶

Parameter	Default	Description
`dump_obj`	`False`	Save the object estimate to disk at every iteration