# Feasibility of LED-Assisted CMOS Camera: Contrast Estimation for Laser Tattoo Treatment
## 3 Results  
Figure 2 shows the captured images of the tattoos before and two weeks after laser treatment. Each tattoo band was imaged using a CMOS camera with LED irradiation (red, green, and blue lights; monochrome image). The total number of captured images was six for each tattoo. The black dotted boxes represent the locations for image analysis. Regardless of the tattoo and LED colors, the treated area on the mouse skin appeared fainter than the non-treated area. The change in the black tattoo band was clearly observed before and after the treatment under the three LED colors (Figure 2a). However, unlike the black tattoo band, the red tattoo band yielded various responses to the LED colors (Figure 2b). In particular, the red tattoo band (from pre- and post-laser treatments) was hardly detected under the red LED, whereas the red tattoo was evident under both the green and the blue LEDs. Based on the captured images under three LED colors (Figure 2), we analyzed and compared the intensity values of the black tattoo measured from the pre and post treatment. The results are shown in Figure 3. All the intensity values are displayed from 10 measurements in the dotted box in Figure 2a and compared between the pre and the post treatment (Figure 3a). Apparently, the black tattoo yielded considerably lower Iattoo (i.e., tattooed area) than I\({}_{\text{BGD}}\) (i.e., non-tattooed area) under all the LED colors for the pre-treatment (e.g., Iattoo = 45 \(\pm\) 12 vs. I\({}_{\text{BGD}}\) = 125 \(\pm\) 8 under red LED; \(p<0.001\)). Under each LED color, I\({}_{\text{BGD}}\) was almost invariant between the pre and the post treatment (\(p\) = 0.08-0.17). Nevertheless, Iattoo from the pretreatment was lower than Iattoo from the post treatment for all the LED colors. The intensity variation between the pre and the post treatment was found to be up to 80 under all the LED colors (e.g., Iattoo = 45 \(\pm\) 12 for pre vs. 125 \(\pm\) 8 for post under red LED; \(p<0.001\)). To quantify the variations in the intensity value after the laser treatment, the contrast between the black tattoo and the background were calculated and compared, as shown in Figure 3b. Irrespective of the LED color, Contrast\({}_{\text{pre}}\) was four-fold higher than Contrast\({}_{\text{post}}\) (\(p<0.001\)). However, the contrast values for either the pre or post treatment were comparable under all the LED colors (i.e., Contrast\({}_{\text{pre}}\) = 0.81-0.83; \(p=0.65\), and Contrast\({}_{\text{post}}\) = 0.21-0.25; \(p=0.32\)). Figure 4 shows the intensity and contrast values measured from the red tattoo. Figure 4a presents the spatial variations in the intensity profiles between the pre and post treatment under all the LED colors (i.e., measurements of dotted boxes in Figure 2b). For the pretreatment condition, the red tattoo case presented a markedly lower Iattoo than I\({}_{\text{BGD}}\) under green and blue LEDs, but no difference between Iattoo and I\({}_{\text{BGD}}\) was found under the red LED. I\({}_{\text{BGD}}\) was almost comparable between the pre and the post treatment under all the LEDs (\(p\) = 0.1-0.28). We also observed that the variation in Iattoo between the pre and the post treatment was significant under the green and blue LEDs, which was  
Figure 2: CMOS images of (**a**) black and (**b**) red tattoo pre- and post-laser treatment under various LED colors (red, green, and blue lights): Each black dotted box represents a region for image analysis. approximately 35 for the green LED (i.e., Iatto0 = 66 \(\pm\) 8 for pre vs. 101 \(\pm\) 6 for post; \(p\) < 0.001) and 30 for the blue LED (i.e., Iatto0 = 104 \(\pm\) 11 for pre vs. 134 \(\pm\) 12 for post; \(p\) < 0.001). However, the red LED showed an insignificant change in Iatto0 between the pre and the post treatment (i.e., Iatto0 = 142 \(\pm\) 2 for pre and 145 \(\pm\) 2 for post; \(p\) = 0.83). Figure 4b exhibits the quantitative comparisons of the contrast estimated from the red tatto0 between the pre and the post treatment under all the LEDs.