👉 Etchers, in optics and electronics, are a class of lenses that allow light to pass through them while blocking out other wavelengths. These lenses can be used for various applications such as optical fiber cables, light sources, and displays. Etchers are commonly used in semiconductor manufacturing processes where they are used to align the wafer onto the substrate, or to ensure that the wavelength profile of a laser beam is correctly aligned with the material being processed.