Short-wave pass filter, also called short-wave filter, low-pass filter, long-wave cut-off filter, is a type of cut-off filter. It is an optical filter that only allows short-wavelength light to pass through and blocks long-wavelength light, that is, it is mainly used to block the interference wavelength light above a certain specific band and allow the light under the specific specified band to pass through. Its spectral characteristics are opposite to those of long-wave pass filter, and it has the function of “short-wave pass, long-wave cut-off”.
Manufacturing process
Short-wave pass filter is usually prepared by multi-layer film stacking. By controlling the thickness and refractive index of each film layer, selective transmission or reflection of light of different wavelengths can be achieved. General short-wave pass filter rarely passes ultraviolet light, and short-wave pass filter that can pass ultraviolet light needs to be made of special materials.
Application characteristics
Short-wave pass filters have the characteristics of high transmittance, high cut-off depth, and high background light density. Generally, the center wavelength is half of the peak transmittance.
Optical beauty: When the specific band is in the beauty band of the beauty instrument, the short-wave pass filter can be used on home beauty instruments with certain specific functions.
Fluorescence analysis: When the specific band is in the fluorescence emission band, the short-wave pass filter can be used to filter and limit the emission wavelength to meet the emission wavelength requirements and be used together with the excitation filter.
Raman spectroscopy application: In Raman spectroscopy analysis, the short-wave pass filter helps to separate the excitation light from the scattered light and improve the signal-to-noise ratio of the spectrum.
Spectral grouping application: Short-wave pass filters can be used to group light of different wavelengths for subsequent spectral analysis or processing.
Imaging optical system: Short-wave pass filters can be used in imaging optical systems to eliminate interference light outside the available band and improve the clarity of imaging and the sensitivity of the system.
Machine vision system: In machine vision system, short-wave pass filter helps to enhance the contrast of light and dark of the object photographed by the camera, improve the resolution of the system, and make the observed features clearer.
Fiber optic lighting: In fiber optic lighting system, short-wave pass filter can be used to adjust the wavelength range of light to achieve specific lighting effects.
Surveillance camera: The common IR-CUT double filter is a combination of full-spectrum filter and infrared cut-off filter. When the light interference is strong during the day, the infrared cut-off filter (a kind of short-wave pass filter) can effectively filter the interference of infrared light on the color reproduction of CCD or CMOS and restore the true color.
