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OPTICS / OPTICAL FILTERS
Types of Optical Filters
Optical filters are classified by how they function and the spectral range they affect. The two main functional categories are absorptive filters and interference filters.
Absorptive Filters: These filters absorb unwanted wavelengths of light, allowing only the desired ones to pass through. They are often simple in working principle and cost-effective. However, they have less precise control over the passband compared to interference filters.
Interference Filters (Dichroic Filters): These filters use the principle of thin-film interference to reflect unwanted wavelengths while transmitting the desired ones. They are made of multiple, thin layers of dielectric materials with different refractive indices. The thickness of each layer is precisely controlled to cause constructive interference for the desired wavelengths and destructive interference for the unwanted ones. These filters offer superior precision, higher transmission, and better blocking of unwanted light.
Laser Line Filters provide one of the simplest and most economical ways to transmit a well-defined wavelength band of light, while rejecting other unwanted radiation.
Laser Line Filters – Central Wavelengths from 350 nm to 1550 nm, 350nm, 488nm, 532nm, 632.8nm, 670nm, 780nm, 850nm, 980nm, 1060nm, 1310nm, 1550nm laser line typ.
1nm, 3nm, 10nm, 12nm, 25nm, 40nm, and 70 nm Bandpass Regions typ.
Nomenclature: LLF-DIAMETER-CWL-FWHM
DIA25.4mm Standard – BPF-10 | Assorted Blue Green Red types – BPF-A |
Narrowband types – BPF-C | Large-Area Custom-Shapes
Bandpass filters transmit a well-defined wavelength band of light, while rejecting other unwanted radiation. Optical bandpass filters allow the isolation of a band of wavelengths from the total spectrum, enabling higher energy throughput and greater out-of-band rejection, without the use of dispersing elements such as prisms or gratings.
Longpass type EPF-LP |
Shortpass type EPF-SP
The durable dielectric coating of LongPass Filters makes them instrumental in many industrial and Research & Development applications, due to the rejection band optical density of 3.0 and >85% transmission above the cut-on wavelength.
Shortpass filter transmission region is 0.7 x Cut-off-Wavelength to Cut-off-Wavelength (Unless 0.7 x Cut-off-Wavelength is < 400 nm, then 400 nm to Cut-off-Wavelength).
Shortpass filter rejection region is 1.3 times Cut-off-Wavelength.
Longpass Color Glass – CGF-LP |
Bandpass Color Glass CGF-BP
Customers may specify Schott Glass models and dimensions and Singapore Optics Shop customize per request.
Schott Colored Glass Available: N-WG280, GG400, GG435, GG495, OG515, OG550, OG590, RG610, RG665, RG715, RG780, RG850, RG1000
Color Glass Filter Dimension Available: Round or Square, 1inch(25.4mm), 2inch(50.8mm), 3inch(76.2mm), 4inch(101.6mm), 5inch(127mm), 6inch(152.4mm)
Absorptive ND type(Visible Light) | Circular Continuously Variable Metallic type | Absorptive ND type(NIR Band) | Linearly Reflective Variable type | Radially Variable ND Filters(OD 0@Center) | Metallized Reflective type(Broadband)
Because of variations between different lots of glass, Photonik recommends that the user calibrate the filter in their setup before taking quantitative measurements.
Hot Mirror IR Reflector | Cold Mirror IR Transmitter
Hot Mirrors are perfect for keeping unwanted heat from reaching sensitive areas of your setup. In applications where heat build up is a concern, a 0-deg incidence hot mirror provides a means of protection by blocking the IR.
Cold Mirrors work to transmit IR energy and reflect the visible light from your setup at 90-deg. These mirrors are perfect for applications where the IR energy can be dumped and the visible is reflected at 90-deg.
Notch filters are useful in applications where one needs to block light from a laser. For instance, to obtain good signal-to-noise ratios in Raman spectroscopy experiments, it is critical that light from the pump laser be blocked. This is achieved by placing a notch filter in the detection channel of the setup. In addition to spectroscopy, notch filters are commonly used in laser-based fluorescence instrumentation and biomedical laser systems.