| 摘要 |
An apparatus measures the reflectivity of a selected region of a surface. A first light beam (122) is reflected from the selected region and substantially focused on a photodetector (106). A second light beam (124) is reflected from the selected region and is substantially unfocused on the photodetector (106). A signal is derived representative of the direct reflectance of light reflected from the surface onto the photodetector (106) as a function of the intensities of the focused light beam (122) and the unfocused light beam (124) detected by the photodetector (106). <IMAGE> |
