Card preview
This tool prints a card of dots arranged in a 2D lattice. Hold the printed card in front of the Fourier Camera and observe the diffraction pattern — a known crystal structure produces a recognisable Fourier transform.
Pick a preset (square, rectangular, hexagonal, oblique) or tune by hand. Spacing along a and spacing along b are the distances between neighbouring rows in two directions; angle is the angle between those two directions. A 60° angle with equal spacings produces a hexagonal (triangular) lattice; 90° gives a rectangular grid.
By default the dots scale with the spacing — about 0.4× the nearest-neighbour distance, capped at 2 mm. Click Auto size to turn this off and use the slider directly. Manual mode is useful if you want a particular dot/spacing ratio for the diffraction pattern.
Optional thin grey lines along the a and b directions through every lattice point. Helpful for students learning to read the lattice; turn off for a clean dots-only sample.
Choose 1, 2, or 4 cards per Letter page depending on how big a sample your camera needs. The preview always shows one card at true mm scale, so what you see is what prints.
Click Save PDF and print at 100 % scale — uncheck "fit to page" in your printer dialog. Cut along the grey lines between cards. The printed dot spacing will match what's shown on screen, and each card carries a small label with its parameters so a stack of printed cards stays organised.