Fig. 3
a Reconstructed images with different excitation current frequencies. The frequency was 1 KHz (A1), 50 KHz (A2), 100 KHz (A3) or 150 KHz (A4). The rose stem diameter was 5.68 mm, and the excitation current was 250 μA. b Reconstructed images with different diameters of rose stems. The diameter of rose stems was 2.45 mm (B1), 3.23 mm (B2), 4.44 mm (B3), 5.63 mm (B4) or 6.29 mm (B5). The excitation current was 250 μA, the excitation frequency was 1 kHz. The radius of the test device was 8 cm. The blue area on the lower part of each image represented the stem of the rose, the green area represented the background salt solution, and the other colours indicated that serious noise occurred