BH-A51 Hot Mirror & UV-IR Cut Filter

The BH-A51 is a compact hot mirror with a narrower visible pass-band spanning 431 nm to 696 nm (50 % crossover points) and peak transmission of 92.1 % at 656 nm. It features a distinctly gradual blue onset-blue transmission is notably low at 55.6 %-which is intentional for applications where blue noise or UV/blue stray light contamination must be minimized. Green (89.5 %), yellow (90.7 %), and red are partially limited (86.9 %), reflecting the filter's design priority: mid-red-light dominance. NIR(700-850) is suppressed to 3.3 % and NIR(850-1000) to 1.5 %, providing solid thermal blocking. BH-A51 suits applications where red-dominated visible light and minimal blue cross-talk are essential.

Key Advantages

• Controlled blue suppression - Blue transmission (55.6 %) is substantially lower than standard HM filters, minimizing blue-light noise and blue-induced autofluorescence in sensitive biological and medical imaging.
• Red-dominant illumination - The 431-696 nm pass-band with red at 86.9 % (slightly clipped) provides predominantly red-yellow light useful for tissue visualization and applications where red penetration is diagnostic.
• Hard-oxide ion-assisted coating - Durable optical coating withstands thermal stress, mechanical handling, and long-term exposure to medical-grade lighting and high-intensity light sources.
• Deep NIR rejection - NIR(700-850) drops to 3.3 % and above 850 nm to 1.5 %, providing clean thermal blocking suitable for heat-sensitive sensors and optics.
• Versatile custom fabrication - Round, square, free-form blanks from 5 mm to 450 mm diameter, thickness 0.21-3.8 mm, on Borofloat, soda-lime, Schott D263 T, or Corning Eagle XG substrates.

Typical Applications

• Medical endoscopy and surgery - The red-dominated spectrum with minimal blue reduces reflected blue light artifacts and blue-induced tissue autofluorescence, improving diagnostic visibility in surgical and endoscopic imaging.
• Dermatology and skin imaging - Red-yellow light with suppressed blue penetrates skin effectively while the low blue transmission reduces melanin-related artifacts and UV-induced background noise.
• Retinal and ophthalmology imaging - Red light is optimal for retinal visualization; the low blue transmission minimizes macular photostress and blue-light-induced artifacts in diagnostic fundus imaging.
• Dental visualization systems - Red-yellow illumination provides excellent soft-tissue and tooth visibility; minimal blue transmission reduces blue-light glint from enamel and reduces patient light exposure.
• Scientific microscopy with reduced cross-talk - The controlled blue suppression enables clean red-channel imaging with minimal green-red cross-excitation in multi-fluorophore microscopy and spectroscopic applications.

KUPO Optics manufactures BH-A51 in fully custom configurations-your choice of diameter, shape, thickness, and substrate-with rapid prototyping and scalable production capability.