Long working distance microscope with a low obscuration aspherical Schwarzschild objective.

For fine stitching of multiwindow wide-spectrum detectors, an aspherical Schwarzschild objective with an effective working distance of 525 mm has been realized for chromatic aberration-free imaging in 400-900 nm wavelength range and with a numerical aperture of 0.13. A theoretical approach for analytical design of an initial configuration has been modeled using an on-axis Taylor series expansion, and the beam obscuration ratio (OR) has been controlled down to 4%. In comparison against the theoretical spherical-based Schwarzschild objective, 77.5% of the OR has been reduced for improved contrast.