Dichroic Longpass Filter
Dichroic Longpass Filters are precision optical filters designed to transmit wavelengths above a specified cut-on wavelength while reflecting shorter wavelengths. Using multilayer dielectric coatings, these filters provide high spectral selectivity with high transmission in the passband and efficient reflection in the rejection band. Chenyu Optics manufactures dichroic longpass filters in BK7 and fused silica with custom cut-on wavelength design.
Dichroic Longpass Filter Overview
Dichroic Longpass Filters are precision optical filters designed to transmit wavelengths above a specified cut-on wavelength while reflecting shorter wavelengths.
Using multilayer dielectric coatings, these filters provide high spectral selectivity with high transmission in the passband and efficient reflection in the rejection band. They are widely used for wavelength separation in fluorescence imaging, microscopy, spectroscopy, laser systems and optical sensing applications.
Chenyu Optics supports custom dichroic longpass filter manufacturing according to customer drawings, including substrate, dimensions, cut-on wavelength, blocking range, AOI and coating design. Explore our Optical Filters, Dichroic Filter, Longpass Filter, Fluorescence Filter and Emission Filter pages, or review our Optical Coating capability.
Key Advantages of Dichroic Longpass Filter
Fluorescence Imaging & Microscopy Systems
Dichroic longpass filters are widely used for wavelength separation in fluorescence imaging systems, microscopy systems, spectroscopy equipment and multispectral imaging systems.
Typical Specifications of Dichroic Longpass Filter
| Filter Type | Multilayer dielectric dichroic longpass filter; transmits the long-wave band and reflects the short-wave band |
|---|---|
| Passband Transmission | Typical design target Tavg ≥ 90% in the specified passband; final guaranteed value is defined with wavelength range, AOI and polarization |
| Blocking / Reflection Band | Typical transmitted-light blocking OD3–OD4 over the specified rejection band, or high reflection when the rejected beam is reused; OD5+ is subject to coating review |
| Custom Cut-on Wavelength | UV, visible or NIR cut-on available according to coating design and substrate transmission |
| Cut-on Tolerance | Typically ±2% of the specified cut-on wavelength; tighter tolerances such as ±1% are subject to design and measurement review |
| Angle of Incidence | Specify 0°, 45° or another operating AOI together with AOI tolerance, beam cone and polarization |
| Spectral Shift with AOI | Increasing AOI generally shifts the spectral edge toward shorter wavelengths; s- and p-polarized responses may separate at oblique incidence |
| Available Size | Custom round, square or rectangular parts; final range depends on substrate, coating uniformity, clear aperture and quantity |
| Thickness | Custom and drawing-defined according to stiffness, transmitted wavefront, mounting and substrate availability |
| Substrate Options | N-BK7 or equivalent optical glass for general visible/NIR use; fused silica for UV transmission, lower thermal expansion and demanding laser or thermal environments |
| Surface Quality | Typically 40-20 or 20-10 scratch-dig; tighter requirements subject to substrate and size review |
| Clear Aperture | Drawing-defined; specify the usable coated aperture and edge exclusion |
| Spectral Inspection | Transmission/reflection is measured over the agreed wavelength range and AOI; a measured lot-specific curve can be supplied when included in the quotation |
Spectral Transmission Curve & Test Data
Why Choose Chenyu Optics for Dichroic Longpass Filter
Chenyu Optics focuses on drawing-based precision filter manufacturing for fluorescence, microscopy, spectroscopy and laser optical systems. We support prototype verification, small-batch production and repeat manufacturing for non-standard dichroic longpass filters.
Manufacturing Capability for Dichroic Longpass Filter
Precision Polishing
High surface quality processing for stable filter performance.
Dielectric Coating
High performance dichroic longpass coating for precise cut-on wavelength control.
Inspection & Packaging
Strict quality control on cut-on wavelength and spectral performance, with clean protective packaging before shipment.
Custom Dichroic Longpass Filter Options
Bandpass Filter Type Comparison
| Filter Type | Typical FWHM | Peak Transmission | Blocking (OD) | Typical Applications |
|---|---|---|---|---|
| Dichroic Longpass Filter | N/A — longpass edge | >90% above cut-on | High reflection below cut-on | Fluorescence imaging, microscopy, laser systems |
| Narrow Bandpass Filter | 1 – 10 nm | >90% | OD4 – OD6+ | Laser line selection, fluorescence |
| Standard Bandpass Filter | 10 – 50 nm | >90% | OD4 – OD6+ | Machine vision, instrumentation |
| Wide Bandpass Filter | 50 – 200 nm | >90% | OD4 – OD6 | Imaging, spectroscopy |
Applications of Dichroic Longpass Filter
Fluorescence Imaging Systems
Wavelength separation for fluorescence excitation and emission paths.
Microscopy Systems
Precise spectral separation for microscopy imaging setups.
Spectroscopy Equipment
Wavelength separation for spectroscopic measurement systems.
Laser Optical Systems
Spectral separation for laser system beam paths.
Optical Sensing Systems
Precision wavelength separation for optical sensor design.
Multispectral Imaging Systems
Spectral channel separation for multispectral imaging platforms.
Dichroic Longpass Filter FAQ
What is the function of a dichroic longpass filter?
A dichroic longpass filter transmits longer wavelengths while reflecting shorter wavelengths, enabling precise spectral separation.
What is the difference between a standard longpass filter and a dichroic longpass filter?
Dichroic longpass filters use dielectric coatings to provide both transmission and reflection functions, while standard longpass filters mainly focus on wavelength blocking and transmission.
Can dichroic longpass filters be customized?
Yes. Cut-on wavelength, substrate material, dimensions, and coating performance can be customized.
Does incident angle affect filter performance?
Yes. The spectral transition wavelength may shift with incident angle, so coating design should match the optical system.
What information should I provide for a quotation?
Please provide passband and rejection-band limits, minimum transmission, required blocking OD or reflection, cut-on definition and tolerance, substrate, size, thickness, clear aperture, AOI and tolerance, beam cone, polarization, surface requirements, quantity, spectral-report requirement and drawing.
Where can I learn more about dichroic filter design?
Additional information on dichroic filter design can be found from Edmund Optics.
Related Products for Dichroic Longpass Filter
Need Custom Dichroic Longpass Filters?
Send the passband, blocking range or OD, cut-on tolerance, AOI, polarization, substrate, dimensions, thickness, spectral-test requirement and quantity. Chenyu Optics will review the optical and mechanical specifications and provide a suitable dichroic longpass filter manufacturing suggestion.