Figure 2(c), the histology image of the 5-μm thick section from the first specimen, illustrates the CAR, DCTs, and other lung components, such as epithelium (Epi) and loose connective tissue. Figure 2(a) shows an en-face OCT section close to the bottom of the 600-μm thick sample. As explained previously, the 3-D OCT image was constructed from individual OCT frames (Video 1: OCT B-scans of the 600-µm thick sample (MOV, 14782 KB), URI: CrossRef[[XSLOpenURL/10.1117/1.JBO.19.3.036022.1]]) and the en-face OCT images (Video 2: en-face OCT images of the 600-µm thick sample (MOV, 20370 KB), URI: CrossRef[[XSLOpenURL/10.1117/1.JBO.19.3.036022.2]]) were constructed by sectioning the 3-D OCT image perpendicular to the excitation beam. Coregistered with the AF image, these en-face OCT images are required for the identification of the lung components and thereby their corresponding AF signal. Cartilage and DCT areas along with the areas including loose connective tissue, basement membrane, and epithelium were segmented in the en-face OCT images as illustrated in Fig. 2(a). The five CAR were the distinct features in the en-face OCT images specified by the blue lines in Fig. 2(a). Given the histology image, we believe that the bright areas in the en-face OCT image specified by the black lines in Fig. 2(a) were DCTs since they had higher OCT scattering compared to the more interior loose connective tissue and, therefore, they appeared brighter in the OCT images. The darker areas closer to the center, specified by the red lines in Fig. 2(a), included loose connective tissues, the lamina propria, and the epithelium according to the histology image. The corresponding segments were transferred to the normalized AF image by ImageJ, as illustrated in Fig. 2(b). Since the AF signal of the epithelium, lamina propria, and loose connective tissue were significantly smaller than that of cartilage and DCT, the logarithmic scale was chosen for the AF image in order to reveal more details about the AF signals of different components. The highest AF intensity was generated in the cartilage. DCTs emitted a higher AF signal compared to the loose connective tissue adjacent to the epithelium. The epithelium and the lamina propria generate a small AF signal compared to the cartilage and DCTs.