Fig. 1. Flow charts of (a) dictionary learning algorithm and (b) photoacoustic signal reconstruction algorithm based on dictionary learning

Fig. 2. Schematic of simulation

Fig. 3. (a) Simulated photoacoustic data; (b) signal at where marked with white line in Fig. 3 (a)

Fig. 4. (a) Initial random dictionary; (b) learned dictionary from sample set

Fig. 5. (a) Original image; (b) photoacoustic image reconstructed by measurement with 160 detector locations; (c) photoacoustic image reconstructed by measurement with 40 detector locations; (d) photoacoustic image reconstructed by measurement with 40 detector locations based on proposed algorithm in this paper