BH-A21 UV-Cut Longpass Filter
Wide-passband filter transmitting a broad red window (771 – 1100 nm) with steep edges and deep blocking on both sides for clean spectral isolation.
- Passband: 771 – 1100 nm
- Bandwidth (FWHM): ~751 nm
- Centre wavelength: ~724 nm (nominal)
- Passband transmittance: ≥ 67.4 % T (± 7.4 % ripple)
- Short-wave edge (T50): ≈ 349 nm, ~20 nm steepness
- Long-wave edge (T50): ≈ 1100 nm, ~1 nm steepness
- Short-wave blocking: OD ≥ 2.6 below 319 nm
- Long-wave blocking: OD ≥ 2.0 above 1130 nm
- AOI: 0° (normal incidence); custom angles available
- Construction: Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick
- Custom options: Edge shifting, passband widening/narrowing, asymmetric blocking, rapid prototypes
Learn more
BH-A21 Bandpass Extended delivers Passband 771 – 1100 nm, Bandwidth (FWHM) ~751 nm, and Centre wavelength ~724 nm (nominal).
The hard-oxide coating is built for repeated handling, heat, and cleaning.
Best suited for:
Near-infrared imaging and sensing applications — including silicon-sensor camera systems, LIDAR receivers, and night-vision optics — where the wide NIR passband maximises signal collection across the sensor's peak sensitivity range
Description
The BH-A21 is a broadband 50/50 beam splitter specifically designed for 45-degree angle of incidence operation, delivering approximately equal transmission and reflection across the visible and near-infrared spectrum. With consistent 60 % transmission across visible wavelengths (Blue: 60 %, Green: 60 %, Red: 59 %) and rising to 74.8 % peak at 859 nm in the near-infrared, the BH-A21 provides balanced photon distribution for dual optical pathways. This dichroic element functions as a primary beam splitter in stereo imaging, beam combining, and multi-wavelength detection systems requiring equal intensity distribution between two optical paths. The 45-degree angle-of-incidence specification ensures optimal performance in compact optical layouts.
Key Advantages
- Balanced 50/50 Split Performance - ~60 % transmission with 40 % reflection across visible spectrum provides near-equal intensity distribution to transmitted and reflected optical paths.
- 45-Degree Angle of Incidence Optimization - Dichroic design optimized for 45 deg AOI delivers peak performance at the most compact optical geometry, reducing system size and cost.
- Broadband Visible-NIR Coverage - Sustained 60 % transmission across full visible spectrum (Blue: 60 %, Green: 60 %, Red: 59 %) with rising NIR response (74.8 % at 859 nm).
- Hard-Oxide Ion-Assisted Coating - Multilayer hard-oxide construction maintains dichroic performance across environmental stress and high-intensity laser illumination at 45 degrees.
- Custom Format Flexibility - Round, square, and free-form geometries from 5-450 mm with Borofloat, soda-lime, Schott D263 T, and Corning Eagle XG substrate options.
Typical Applications
- Stereo Imaging Systems - Divides single image pathway into two equal-intensity paths for stereoscopic 3D vision and depth reconstruction in compact cameras.
- Beam Combining - Combines illumination from two separate sources into single optical path while maintaining equal intensity balance for symmetrical imaging.
- Dual-Channel Detection - Splits sensor signal between two detectors for simultaneous parallel processing, real-time cross-validation, or redundant detection.
- Laser Beam Splitting - Divides laser beam into two equal-intensity beams for multiplex processing or simultaneous two-wavelength measurement.
- Compact Optical Layout - 45-degree geometry enables miniaturized optical arrangements in portable instruments, microscopes, and hand-held devices.
Deploy the BH-A21 50/50 Beam Splitter in your dual-pathway optical system with rapid prototyping and full production capability.
FAQ
BH-A21 FAQ
What is BH-A21 and what is it used for?
BH-A21 is a 50/50 Beam Splitter, AOI=45 deg. The BH-A21 is a broadband 50/50 beam splitter specifically designed for 45-degree angle of incidence operation, delivering approximately equal transmission and reflection across the visible and near-infrared spectrum. With consistent 60 % transmission across visible wavelengths (Blue: 60 %, Green: 60 %, Red: 59 %) and rising to 74.8 % peak at 859 nm in the near-infrared, the BH-A21 provides balanced photon distribution for dual optical pathways. Common uses include Stereo Imaging Systems, Beam Combining, Dual-Channel Detection, and Laser Beam Splitting.
What are the key optical specs of BH-A21?
Key published specs for BH-A21 include Passband: 771 – 1100 nm; Bandwidth (FWHM): ~751 nm; Centre wavelength: ~724 nm (nominal); Passband transmittance: ≥ 67.4 % T (± 7.4 % ripple); Short-wave edge (T50): ≈ 349 nm, ~20 nm steepness.
What applications is BH-A21 best suited for?
BH-A21 is commonly used for Stereo Imaging Systems, Beam Combining, Dual-Channel Detection, and Laser Beam Splitting. Stereo Imaging Systems - Divides single image pathway into two equal-intensity paths for stereoscopic 3D vision and depth reconstruction in compact cameras.
Can BH-A21 be customized for size, substrate, or coating requirements?
KUPO lists the construction for BH-A21 as Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick. Published custom options include Edge shifting, passband widening/narrowing, asymmetric blocking, rapid prototypes. Custom Format Flexibility - Round, square, and free-form geometries from 5-450 mm with Borofloat, soda-lime, Schott D263 T, and Corning Eagle XG substrate options.
What should I know about angle of incidence and durability for BH-A21?
The published angle of incidence for BH-A21 is 0° (normal incidence); custom angles available. The hard-oxide coating is built for repeated handling, heat, and cleaning.
