Fig. 3

Imaging performance. A 1951 USAF resolution target (63 × 63 × 2 mm) on the stereo microscope stage. Red arrow highlights the group element used for optical benchmarking; B and C depict groups 6 and 7 from both positive B and negative C chrome patterns, respectively. The contrast of the modulation frequency of 114 lp/mm obtained from the resolution target was evaluated on the negative group 6—element 6 using the imaging setup and stereo microscope. The contrast tests were performed at maximum native 5:1 and 4:1 magnifications for D the imaging setup and F stereomicroscope systems, respectively; E and G are crops from D and F, respectively. The vertical and horizontal intensity line probes on element 6 are depicted in (E-v) and (E–h) and in (G-v) and (G-h) for the imaging setup and Stemi 508, respectively; (H) an average three-fold superior contrast between the imaging setup (E-v) and (E–h) (29.4%) compared to the Stemi 508 (G-v) and (G-h) (10.1%) is shown in the intensity gradient from horizontal and vertical line pairs. The line probe intensity values for (G-v) and (G-h) have a higher absolute value, despite the lower contrast. This attenuated brightness was challenging to control due to the intense chromatic aberration in the brightfield illumination using the Stemi 508; I field of view (FOV) comparison between the two imaging systems depicting the much larger FOV in the imaging setup across the entire corresponding magnification range. Scale bars: B and C 0.02 mm