Fig. 4

Photo image (a), typical Raman spectra (b), and Raman intensity images (c–f) collected from the paint branches distributed on a glass surface. In a, the area of 10 μm × 10 μm is scanned. Raman spectra were collected under an objective lens of 100×, integration time of 1 s for each pixel of 0.33 μm × 0.33 μm (to create a spectrum matrix of 30 × 30). b Shows the Raman spectrum of ABS (with intensity off-setting for presentation), to compare with 3 typical spectra collected from the positions marked in a, and the scanning average spectrum. The intensity images (c–f) are mapped at the peak of acrylic at ~ 2910 cm⁻¹ (c) and colourant at ~ 440 cm⁻¹ (e), as marked under each image (and the peak width) and in b, after 20% colour off-setting. e Merges (c, d) using logic-OR. f Is another version of e, using 3D presentation and white background