feat: Compute front effective focal lengths

README.md

@@ -84,6 +84,7 @@ Cherry might be for you if:
 - [ ] **Help Wanted** 3D views
 - [ ] **Help Wanted** Fuzzy search for materials
 - [ ] [Cardinal lens](https://opg.optica.org/ao/fulltext.cfm?uri=ao-63-4-1110) surface type for ideal objective models
+- [ ] Cross-validate integration test results with Optiland
 
 ### Done
 

crates/cherry-rs/src/core/sequential_model/solves/fno.rs

@@ -205,7 +205,7 @@ mod tests {
         let target = 4.0;
         let (_, pv) = build_with_fno_solve(target);
         let sub = pv.get(0, 0).unwrap();
-        assert_abs_diff_eq!(sub.paraxial_fno(), target, epsilon = 1e-4);
+        assert_abs_diff_eq!(sub.paraxial_fno().abs(), target, epsilon = 1e-4);
     }
 
     #[test]
@@ -315,7 +315,7 @@ mod tests {
         let sub = pv.get(0, 0).unwrap();
 
         // F/# constraint satisfied.
-        assert_abs_diff_eq!(sub.paraxial_fno(), target_fno, epsilon = 1e-3);
+        assert_abs_diff_eq!(sub.paraxial_fno().abs(), target_fno, epsilon = 1e-3);
 
         // MarginalRaySolve constraint: marginal ray height at image ≈ 0.
         let bundle = marginal_ray_bundle(&model, 0).unwrap();

crates/cherry-rs/src/gui/app.rs

@@ -515,13 +515,19 @@ impl eframe::App for CherryApp {
                         self.load_specs(examples::f_theta_scan_lens());
                         ui.close();
                     }
+                    ui.separator();
+                    ui.label("Systems");
                     if ui
                         .button("Galvo and Scan Lens (Negrean and Mansvelder)")
                         .clicked()
                     {
                         self.load_specs(examples::galvo_scan_lens_negrean_mansvelder());
                         ui.close();
                     }
+                    if ui.button("Widefield Epifluorescence Excitation").clicked() {
+                        self.load_specs(examples::wf_epi_excitation());
+                        ui.close();
+                    }
                 });
                 ui.add_space(16.0);
 

crates/cherry-rs/src/gui/examples.rs

@@ -546,6 +546,59 @@ pub fn galvo_scan_lens_negrean_mansvelder() -> SystemSpecs {
     }
 }
 
+/// Reduced widefield epifluorescence microscope excitation path.
+///
+/// An object, a thin relay lens (f = 40 mm), a flat fold mirror at 45°, and a
+/// second thin lens (f = 3.3333 mm) that acts as the aperture stop, modelling
+/// a microscope objective back aperture immersed in oil (n = 1.5). The fold
+/// mirror contributes no power; only the unfolded track length of 150 mm
+/// between the two lenses matters for paraxial calculations.
+pub fn wf_epi_excitation() -> SystemSpecs {
+    SystemSpecs {
+        surfaces: vec![
+            SurfaceRow::new_object("40.0"),
+            SurfaceRow::new_thin_lens("25.0", "40.0", "100.0", "1.0"),
+            SurfaceRow {
+                variant: SurfaceVariant::Sphere,
+                boundary_variant: BoundaryVariant::Reflecting,
+                refractive_index: "1.0".into(),
+                thickness: "50.0".into(),
+                semi_diameter: "36.0".into(),
+                radius_of_curvature: "Infinity".into(),
+                conic_constant: String::new(),
+                focal_length: String::new(),
+                theta: "45".into(),
+                psi: "0".into(),
+                material_key: None,
+            },
+            SurfaceRow::new_thin_lens("4.25", "3.3333", "1.0", "1.5"),
+            SurfaceRow::new_image(),
+        ],
+        fields: vec![FieldRow {
+            chi: "1.5".into(),
+            phi: "90.0".into(),
+            x: "0.0".into(),
+        }],
+        aperture_semi_diameter: "1.5454".into(),
+        wavelengths: vec!["0.5876".into()],
+        field_mode: FieldMode::PointSource,
+        use_materials: false,
+        selected_materials: Vec::new(),
+        cross_section_n_rays: 11,
+        full_pupil_spacing: "0.1".into(),
+        n_fan_rays: 65,
+        background_n: "1.0".into(),
+        background_material_key: None,
+        stop_surface: Some(3),
+        solves: vec![SolveSpec::MarginalRayHeight {
+            gap_index: 3,
+            target_height: 0.0,
+            wavelength_id: 0,
+        }],
+        lens_groups: Vec::new(),
+    }
+}
+
 /// f = +100 mm concave mirror.
 pub fn concave_mirror() -> SystemSpecs {
     SystemSpecs {
@@ -625,6 +678,18 @@ mod tests {
             .expect("model");
     }
 
+    #[test]
+    fn wf_epi_excitation_example_converts_to_valid_model() {
+        let specs = wf_epi_excitation();
+        let parsed = parse(&specs);
+        SequentialModelBuilder::new()
+            .gap_specs(parsed.gaps)
+            .surface_specs(parsed.surfaces)
+            .wavelengths(parsed.wavelengths)
+            .build()
+            .expect("model");
+    }
+
     /// The M solve on the lens-to-image gap must resolve to the lens's back
     /// focal distance (== focal length, for a thin lens in air with an
     /// object at infinity), demonstrating that the image plane tracks the

crates/cherry-rs/src/gui/windows/paraxial.rs

@@ -130,59 +130,65 @@ fn render_table_body(
         tb_sep(body, n_cols);
     }
 
-    tb_row(body, row_h, "EFL", ids, pv, |sv| {
+    tb_row(body, row_h, "Effective focal length", ids, pv, |sv| {
         *sv.effective_focal_length()
     });
-    tb_row(body, row_h, "BFD", ids, pv, |sv| *sv.back_focal_distance());
-    tb_row(body, row_h, "FFD", ids, pv, |sv| *sv.front_focal_distance());
-    tb_row(body, row_h, "Paraxial F/#", ids, pv, |sv| sv.paraxial_fno());
-    tb_row(body, row_h, "Image space F/#", ids, pv, |sv| {
-        sv.image_space_fno()
+    tb_row(body, row_h, "Back focal distance", ids, pv, |sv| {
+        *sv.back_focal_distance()
     });
-
-    tb_sep(body, n_cols);
-
     tb_row(
         body,
         row_h,
-        "Entrance pupil dist. from first surface",
+        "Back principal plane location",
         ids,
         pv,
-        |sv| sv.entrance_pupil().location,
+        |sv| *sv.back_principal_plane(),
     );
-    tb_row(body, row_h, "Entrance pupil semi-diameter", ids, pv, |sv| {
-        sv.entrance_pupil().semi_diameter
+    tb_row(body, row_h, "Front focal length", ids, pv, |sv| {
+        *sv.front_focal_length()
+    });
+    tb_row(body, row_h, "Front focal distance", ids, pv, |sv| {
+        *sv.front_focal_distance()
     });
     tb_row(
         body,
         row_h,
-        "Exit pupil dist. from last surface",
+        "Front principal plane location",
         ids,
         pv,
-        |sv| sv.exit_pupil().location,
+        |sv| *sv.front_principal_plane(),
     );
-    tb_row(body, row_h, "Exit pupil semi-diameter", ids, pv, |sv| {
-        sv.exit_pupil().semi_diameter
+
+    tb_sep(body, n_cols);
+
+    tb_row(body, row_h, "Paraxial F/#", ids, pv, |sv| sv.paraxial_fno());
+    tb_row(body, row_h, "Image space F/#", ids, pv, |sv| {
+        sv.image_space_fno()
+    });
+
+    tb_row(body, row_h, "Lagrange invariant", ids, pv, |sv| {
+        let stop = *sv.aperture_stop();
+        sv.lagrange_invariants()
+            .get(stop)
+            .copied()
+            .unwrap_or(f64::NAN)
+            .abs()
     });
 
     tb_sep(body, n_cols);
 
-    tb_row(
-        body,
-        row_h,
-        "Front principal plane dist. from first surface",
-        ids,
-        pv,
-        |sv| *sv.front_principal_plane(),
-    );
-    tb_row(
-        body,
-        row_h,
-        "Back principal plane dist. from last surface",
-        ids,
-        pv,
-        |sv| *sv.back_principal_plane(),
-    );
+    tb_row(body, row_h, "Entrance pupil location", ids, pv, |sv| {
+        sv.entrance_pupil().location
+    });
+    tb_row(body, row_h, "Entrance pupil semi-diameter", ids, pv, |sv| {
+        sv.entrance_pupil().semi_diameter
+    });
+    tb_row(body, row_h, "Exit pupil location", ids, pv, |sv| {
+        sv.exit_pupil().location
+    });
+    tb_row(body, row_h, "Exit pupil semi-diameter", ids, pv, |sv| {
+        sv.exit_pupil().semi_diameter
+    });
 
     tb_sep(body, n_cols);
 
@@ -331,9 +337,9 @@ mod tests {
             ParaxialWindow::show(ctx, &mut open, Some(&result));
         });
         harness.step();
-        harness.get_by_label("EFL");
-        harness.get_by_label("BFD");
-        harness.get_by_label("FFD");
+        harness.get_by_label("Effective focal length");
+        harness.get_by_label("Back focal distance");
+        harness.get_by_label("Front focal distance");
     }
 
     #[test]
@@ -388,6 +394,17 @@ mod tests {
         harness.get_by_label("Image space F/#");
     }
 
+    #[test]
+    fn paraxial_data_shows_lagrange_invariant_row() {
+        let result = make_result(&["0.567"]);
+        let mut harness = Harness::new(|ctx| {
+            let mut open = true;
+            ParaxialWindow::show(ctx, &mut open, Some(&result));
+        });
+        harness.step();
+        harness.get_by_label("Lagrange invariant");
+    }
+
     #[test]
     fn single_wavelength_no_primary_axial_color() {
         let result = make_result(&["0.567"]);