A 69-element Hadamard mask is used to encode a line-focused excimer laser beam to obtain spatially multiplexed photothermal deflection signals. The spatial distribution and relative quantities of potassium chromate samples on silica are recovered by Hadamard transformation.
Fotios K. Fotiou and Michael D. Morris, "Hadamard Transform Photothermal Deflection Imaging," Appl. Spectrosc. 40, 704-706 (1986)