In the G2 MVE, a 405-nm laser diode (Nichia Corporation, Tokyo, Japan) was installed to provide illumination in VFI mode. As in the G1 system, the diode replaced the auxiliary white light LED in the EPK-i and was powered by a laser driver (Wavelength Electronics, Bozeman, Montana). Since the diode has an optical output of (to our knowledge, it is the most powerful 405-nm diode laser at the time of system development), a customized aluminum heatsink was installed and air-cooled. Through mechanical control, the illumination source could be switched between a Xenon lamp for WLI and the laser diode for VFI. Although the absorption of proflavine is reduced at 405 nm, shifting the illumination to 405 nm allowed for the installation of a 435-nm LPF (Schott North America, Duryea, Pennsylvania) in place of the original 500-nm LPF, permitting more blue light to reach the CCD and allowing WLI without removal of the VFI module. As in the G1 MVE, the filter was installed in a customized stainless steel cap and secured to the distal endoscope tip by a commercially available halo cap (Covidien, Sunnyvale, California), as shown in Figs. 1(a) and 1(b). The LPF combined a colored absorption glass (GG435, thick) with a custom coating to accommodate angular fields of view (FOVs) up to . At a typical working distance of 5 to 10 mm, the FOV ranges from 15 to 25 mm. The laser diode excitation and the emission filter spectra of the G1 and G2 systems are measured using an Ocean USB2000 spectrometer (Ocean Optics, Dunedin, Florida) and a Cary 5000 spectrophotometer (Agilent Technologies, Santa Clara, California), respectively, and shown in Fig. 1(c). A detailed comparison of the two systems, including the excitation source, emission filter, light guide transmission, and proflavine absorption, is shown in Table 1.