Fluorescent filters generally include three combinations, namely excitation filter, emission filter and dichroic mirror.
Excitation filter (excitation filter, exciter filter, excitation filter): in fluorescence microscope, only the wavelength of excitation fluorescence can pass through the filter. In the past, short wave pass filters were used, but now band-pass filters are basically used. The shell is engraved with an arrow to indicate the recommended direction of light propagation.
Emission filter (emitting filter, emission filter, barrier filter, emitter): select and transmit the fluorescence emitted by the sample, and cut off the light in other ranges. The wavelength of the emitted light is longer than that of the excitation light (closer to red). A bandpass filter or a long wave pass filter can be selected as the emission filter. The shell is engraved with an arrow to indicate the recommended direction of light propagation.
Dichroic mirror, dichroic beamplitter, dichromatic beamplitter: also known as dichroic filter or color splitter. Placed at an angle of 45 ° to the optical path of the microscope. This filter reflects one color light (excitation light) and transmits another color light (emission light). The reflectivity of excitation light is greater than 90% and the transmittance of emission light is greater than 90%. The opaque part of the spectrum is reflected rather than absorbed. The colors of the filter under transmitted light and reflected light are complementary to each other, so it is also called dichroic filter.
Fluorescence filters are the abbreviation of fluorescence imaging filters. They are the key components used in biomedical and life science instruments. Their main function is to separate and select the characteristic band spectra of excitation light and emission fluorescence of substances in biomedical fluorescence inspection and analysis system. Generally, the cut-off depth of the filter is required to be above od5 (optical density, OD = – LGT). The core requirements of the filter used in the fluorescence detection system are high cut-off steepness, high transmittance, high positioning accuracy, high cut-off depth and excellent environmental stability.
