Product Description
Research Lab Surplus – Precision N-BK7 Plano-Convex Lens, 50mm Diameter, 800mm EFL, Visible Broadband AR Coated
A high-quality plano-convex lens sourced directly from a research laboratory clearout, featuring premium visible broadband anti-reflection (BBAR) coating and precision N-BK7 substrate. With a 50mm clear aperture and 800mm effective focal length (EFL) , this lens delivers low-aberration, high-transmission performance ideal for beam collimation, gentle focusing, and experimental optical systems.
🔍 Key Specifications:
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Material: N-BK7 optical glass – borosilicate crown, excellent homogeneity
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Diameter: 50 mm
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Effective Focal Length (EFL): 800 mm (f/16 focal ratio)
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Edge Thickness: ~4 mm (lightweight profile)
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Design: Plano-convex – one flat surface, one gently curved convex surface
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Coating: Multi-layer broadband AR (BBAR) for visible spectrum – <1% reflectivity per surface, >99% transmission
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Coating Range: 400–700 nm optimized
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Condition: Excellent – clean surfaces, no scratches or chips
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Equivalent Models: OptoSigma SLB-50-800PM, Thorlabs LA1908-A, Edmund Optics #32-334
✅ Condition & Notes:
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Condition: Excellent – Research Lab Surplus
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Origin: Direct from university or government research laboratory decommission
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Optical Surfaces: Clean, no coating defects, haze, or cleaning marks
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Edge: Precision-ground, ready for standard 50mm lens cells
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Includes: Lens only – no mounting hardware or original packaging
⚙️ Why This Lens is Exceptional:
🔬 Genuine Research-Grade Pedigree:
This is not commercial overstock or consumer-grade optics—it is laboratory-surplus hardware from active research environments. These lenses were selected, inspected, and used by professional scientists and engineers for demanding experimental work.
💎 Premium BBAR Coating:
Unlike economy single-layer MgF₂ coatings, this multi-layer broadband AR coating delivers:
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<1% reflectivity across entire visible spectrum (400–700 nm)
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>99% transmission – maximizes throughput in photon-starved systems
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Durable hard coating – resistant to cleaning and environmental exposure
📏 Long Focal Length Advantage:
The 800 mm EFL at f/16 provides:
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Minimal spherical aberration – near-diffraction-limited on-axis performance
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Gentle focusing power – ideal for collimation over extended working distances
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Forgiving alignment tolerances – perfect for educational and prototyping applications
🪶 Lightweight Profile:
At only 4 mm edge thickness, this lens is easy to mount and places minimal stress on lens cells and translation stages.
🛠️ Applications & Uses:
💫 Beam Collimation & Expansion:
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Collimate divergent sources (laser diodes, SLEDs, fiber outputs) with minimal wavefront error
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Beam expander output lens – low divergence over long paths
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Alignment telescope objective – precision autocollimation and targeting
🔭 DIY Telescope & Optics:
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Objective lens for low-power, wide-field refractor telescopes
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Finder scope or guide scope objective
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Galilean beam expander ocular component
🔬 Laboratory & Experimental:
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Focusing lens for optical bench setups
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Relay lens in multi-element imaging trains
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Field lens for pupil relay systems
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Spatial filter output collimator
🎯 Laser Alignment & Beam Steering:
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Visible laser beam control (HeNe, 532 nm, 635 nm, 405 nm)
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Long working-distance focusing for alignment tasks
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Beam routing in prototype optical systems
🧪 Educational Demonstrations:
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Measure focal length with nodal slide or conjugate methods
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Demonstrate spherical aberration vs. aperture
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Compare AR-coated vs. uncoated transmission
📷 Projection & Imaging:
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Low-power magnifier for inspection tasks
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Projection lens in custom enlargers or solar projectors
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Condenser system component



