Scale the FPM object plot by its real-space pixel size, not dxo

PtyLab/Monitor/Monitor.py

@@ -205,6 +205,14 @@ def initializeMonitors(self):
         if self.verboseLevel == "high":
             self.diffractionDataMonitor = DiffractionDataPlot()
 
+    @property
+    def objectPixelSize(self):
+        """Pixel size of the object estimate that is plotted.
+        """
+        if self.reconstruction.data.operationMode == "FPM":
+            return self.reconstruction.dxo_fpm
+        return self.reconstruction.dxo
+
     def updateObjectProbeErrorMonitor(
         self,
         error,
@@ -226,7 +234,7 @@ def updateObjectProbeErrorMonitor(
             object_estimate,
             self.reconstruction,
             objectPlot=self.objectPlot,
-            pixelSize=self.reconstruction.dxo,
+            pixelSize=self.objectPixelSize,
             axisUnit="mm",
             amplitudeScalingFactor=self.objectPlotContrast,
         )

PtyLab/Reconstruction/Reconstruction.py

@@ -651,6 +651,17 @@ def Lo(self):
         """Field of view (entrance pupil plane)"""
         return self.No * self.dxo
 
+    @property
+    def dxo_fpm(self):
+        """Real-space object pixel size for FPM.
+        """
+        return self.dxp * self.Np / self.No
+
+    @property
+    def Lo_fpm(self):
+        """Real-space field of view of the FPM object, equal to that of the raw images."""
+        return self.No * self.dxo_fpm
+
     @property
     def xo(self):
         """object coordinates 1D"""

tests/Reconstruction/test_fpm_sampling.py

@@ -0,0 +1,70 @@
+import h5py
+import numpy as np
+import pytest
+from numpy.testing import assert_allclose
+
+from PtyLab.ExperimentalData.ExperimentalData import ExperimentalData
+from PtyLab.Monitor.Monitor import Monitor
+from PtyLab.Params.Params import Params
+from PtyLab.Reconstruction.Reconstruction import Reconstruction
+
+
+@pytest.fixture
+def fpm_reconstruction(tmp_path):
+    """A minimal FPM dataset, sampled like the LED-array microscope examples."""
+    rng = np.random.default_rng(42)
+    Nd, N_frames = 64, 25
+
+    # LEDs on a 5x5 grid, 60 mm below the sample
+    led = np.linspace(-4e-3, 4e-3, 5)
+    encoder = np.stack(np.meshgrid(led, led), axis=-1).reshape(-1, 2)
+
+    hdf5_path = tmp_path / "fpm.hdf5"
+    with h5py.File(hdf5_path, "w") as hf:
+        hf.create_dataset(
+            "ptychogram", data=rng.random((N_frames, Nd, Nd)).astype(np.float32)
+        )
+        hf.create_dataset("encoder", data=encoder)
+        hf.create_dataset("dxd", data=np.array(5.5e-6))
+        hf.create_dataset("magnification", data=np.array(4.0))
+        hf.create_dataset("wavelength", data=np.array(625e-9))
+        hf.create_dataset("zled", data=np.array(60e-3))
+        hf.create_dataset("NA", data=np.array(0.1))
+
+    data = ExperimentalData(hdf5_path, operationMode="FPM")
+    return Reconstruction(data, Params())
+
+
+def test_fpm_object_sampling_preserves_field_of_view(fpm_reconstruction):
+    """The enlarged FPM object adds bandwidth, not field of view."""
+    reconstruction = fpm_reconstruction
+    assert reconstruction.No > reconstruction.Np
+
+    assert_allclose(
+        reconstruction.dxo_fpm,
+        reconstruction.dxp * reconstruction.Np / reconstruction.No,
+    )
+    assert reconstruction.dxo_fpm < reconstruction.dxp
+    assert_allclose(reconstruction.Lo_fpm, reconstruction.Np * reconstruction.dxp)
+
+
+def test_monitor_plots_fpm_object_with_fpm_pixel_size(fpm_reconstruction):
+    monitor = Monitor()
+    monitor.reconstruction = fpm_reconstruction
+
+    assert_allclose(monitor.objectPixelSize, fpm_reconstruction.dxo_fpm)
+    # the plotted extent is the field of view of the raw images, not No * dxo
+    assert_allclose(
+        fpm_reconstruction.No * monitor.objectPixelSize,
+        fpm_reconstruction.Np * fpm_reconstruction.dxp,
+    )
+
+
+def test_monitor_plots_cpm_object_with_dxo(generate_simu_hdf5):
+    data = ExperimentalData("example:simulation_cpm")
+    reconstruction = Reconstruction(data, Params())
+
+    monitor = Monitor()
+    monitor.reconstruction = reconstruction
+
+    assert_allclose(monitor.objectPixelSize, reconstruction.dxo)