For a filter or thin-film coating, the wavelength range over which transmission is allowed and possibly maximized. Transmission above or below the bandpass range is restricted by design through absorption and/or reflection.
SPHERICAL VS. ASPHERIC LENSES
HOW THEY’RE USED IN IMAGING APPLICATIONS
Optical Lenses are often categorized by their shape. Two common surface shapes are spherical and aspherical. Each offers unique characteristics that make it suitable for different use cases.