A card-scale loader substitute built on the Foucault knife-edge test: a knife edge racks through a mirror's focus, sweeping the aperture's shadow pattern from one side to a flat null and back, with four baked zonal errors crossing that null at their own moment.
npx shadcn@latest add https://design.helpmarq.com/r/knife-edge-rack-focus.jsonknife-edge-rack-focus