Overview of the main classifications and uses of filters

Optical components used to select the desired radiation band. One commonality of filters is that no filter can make the imaging of celestial bodies brighter, because all filters absorb certain wavelengths, making objects darker.

Divided by spectral band, visible filter, ultraviolet filter
Classified by spectral characteristics; Bandpass filter; Cut off filter, long wave pass (low-pass), short wave pass (high pass), dichroic filter, neutral density filter, reflector, anti reflection mirror
Classified by application type, ITO transparent conductive glass biochemical analyzer, interference filter, enzyme-linked immunosorbent assay analyzer, interference filter; Beauty device filter; Fluorescence detection filter Laser wavelength filter CCD digital gel filter Two way splitting prism Processing of various prisms and lenses

Filter products are mainly classified according to spectral bands, spectral characteristics, film materials, and application features.
Spectral bands: UV filter, visible filter, infrared filter;
Spectral characteristics: bandpass filter, cutoff filter, spectral filter, neutral density filter, reflective filter;
Film layer materials: soft film filter, hard film filter;
Hard film filter not only refers to the hardness of the thin film, but more importantly, its laser damage threshold, so it is widely used in laser systems, while soft film filter is mainly used in biochemical analyzers.
Band pass type: Light in the selected wavelength band passes through, while light outside the passband is cut off. Its optical indicators mainly include center wavelength (CWL) and full width at half maximum (FWHM). Divided into narrowband and broadband. For example, narrowband 808 filter NBF-808.
Short wave pass type (also known as low-pass): Light shorter than the selected wavelength passes through, and light longer than that wavelength is cut off. For example, an infrared cut-off filter, IBG-650。
Long wave pass type (also known as high wave pass); Light longer than the selected wavelength passes through, while light shorter than that wavelength is cut off, such as through an infrared filter, IPG-800。
Between 380-780nm; Visible to the human eye, infrared band greater than 780nm; Less than 380nm ultraviolet band.

Narrowband filter
Narrowband filter is a subdivision of bandpass filter, and its definition is the same as bandpass filter. This type of filter allows light signals to pass through a specific frequency band, while blocking light signals on both sides outside of this band. The passband of narrowband filter is relatively narrow, generally less than 5% of the center wavelength value.
Its main parameters include: center wavelength, full width at half maximum (bandwidth), peak transmittance, cutoff range, and cutoff depth (OD value)
Center wavelength: The center wavelength of a narrowband filter is generally the operating wavelength of the instrument or device, which refers to the wavelength at the center of the passband.
Half width (bandwidth): Bandwidth refers to the distance between two positions in the passband where the transmittance is half of the peak transmittance, sometimes also called half width (not half bandwidth), and is often represented by FWHM (Full Width at Half Maximum) in English letters.
Peak transmittance: refers to the highest transmittance of a bandpass filter in the passband.
Cut off range: Cut off range refers to the wavelength range that is required to be cut off, except for the passband. For narrowband filters, there is a front cutoff, which is the segment where the cutoff wavelength is less than the center wavelength, and a long cutoff, which is the segment where the cutoff wavelength is higher than the center wavelength.
Cut off depth (OD value): Cut off depth refers to the maximum transmittance allowed for light to pass through the cut-off band. Different application systems have different requirements for the cut-off depth, for example, in the case of excitation fluorescence, the cut-off depth is generally required to be between T< Below 0.001%, in ordinary monitoring and recognition systems, the cut-off depth T is less than or equal to; 0.5% is sometimes sufficient. For simplicity, OD value is often used to represent the cut-off depth. OD=-lgT
Application: Machine vision, biochemical analysis, optical instruments, spectral measurement and other fields

Product Features
Single piece without adhesive bonding
Plated hard film, long service life
Accurate wavelength positioning
Ion evaporation with minimal temperature drift
High transmittance
High cut-off depth

Thoroughly filter out visible light and retain only the near-infrared 940nm light needed for CCD or CMOS photosensitive chips to produce black and white images. Through biometric system calculations, test features such as human eyes, iris, and facial features To identify different people's characteristics, it plays a role in access control and security, hotel and entertainment venue monitoring, factory or office attendance.

Bandpass filter
A bandpass filter only allows light in a narrow wavelength range to pass through, commonly known as a Fabry Perot filter, which is essentially a Fabry Perot standard (see Fabry Perot interferometer). The specific structure is as follows: a semi transparent metal layer is coated on a glass substrate, followed by a layer of magnesium fluoride interlayer, and then a semi transparent metal layer is coated. The two metal layers form the two parallel plates of the Fabry Perot etalon. When the distance between the two poles is of the same order of magnitude as the wavelength, the interference peaks of different wavelengths in the transmitted light are very separated. Using other absorption filters can filter out the light that is not allowed to pass through, thus obtaining a narrow passband filter with a much narrower passband width than ordinary absorption filters. In addition, there are Fabry Perot filters with all dielectric materials, two typical structures of which are gHLHLLHH a and gHLHL HH LHLH a1. As needed, the passband of the bandpass filter can range from infrared to ultraviolet. In the visible light range, color television cameras can use this filter to separate images into different colors; In the infrared region, it is commonly used for carbon dioxide lasers, missile guidance systems, and satellite sensors.

Product Features:
Imported ultra-thin optical glass with high transparency, good smoothness, small thickness tolerance, and good flatness, among other optical characteristics
Adopting imported coating equipment ion sputtering coating process, it has the characteristics of high film hardness, good spectral uniformity, and strong center wave stability
We can customize specifications and sizes according to customer requirements, including square and round shapes.

Product Advantages:

Single piece without adhesive bonding
The glass is ultra-thin, with a thickness of only 1.1mm
Plated hard film, long service life,
Accurate wavelength positioning
Ion evaporation with minimal temperature drift
High penetration rate
High cut-off depth

Application fields:
Fluorescence analyzer, enzyme-linked immunosorbent assay (ELISA) reader, cable TV upgrade equipment, wireless transmission equipment, mobile barcode scanning, infrared electronic whiteboard, infrared camera, infrared touch screen, iris recognition, infrared medical instrument, infrared ink recognition, red film recognition, facial recognition sensor system. Handheld infrared laser rangefinder, laser rangefinder, optical instrument, medical and health equipment, and detection instrument.

Infrared filter

Infrared filters are mainly used in the field of security monitoring, infrared gas analyzers, night vision products, infrared detectors, infrared receivers, infrared sensing, and infrared communication products. Specific products include surveillance cameras, remote controls, infrared curtain wall products, infrared sensing toilets, faucets, hand sanitizer devices, infrared thermometers, infrared printers, interactive electronic whiteboards, infrared touch screens, fingerprint recognition machines, facial recognition systems, etc.