The word "bandpass" refers to a filter that allows only a specific range of frequencies to pass through while blocking others. It is like a gate that only allows certain sounds or signals to get through, while excluding the rest. Full definition
A key part of the prototype's design is the use of a custom optical bandpass filter to capture sunlight that is normally wasted by commercial solar cells on towers and convert it to electricity at a higher efficiency than the solar cells themselves ever could. (sciencedaily.com)
For Kepler - 20c and Kepler - 20d, the blend scenario is independently disfavored by the achromaticity of the transit: From Spitzer data gathered at 4.5 um, we infer a ratio of the planetary to stellar radii of 0.075 + -0.015 (Kepler - 20c) and 0.065 + -0.011 (Kepler - 20d), consistent with each of the depths measured in the Kepler optical bandpass. (arxiv.org)
While its mandate was only to take color pictures, Junocam uses precision bandpass filters produced by Barr Associates of Westford, Massachusetts, including a red channel that sees into the near infrared to penetrate more deeply into the jovian atmosphere, and a fourth narrowband near - IR channel to map the abundance of methane. (msss.com)