76mm N-BK7 plano-convex lens long focal length

Product Description

Premium High-Quality Uncoated 3″ (76mm) Diameter N-BK7 Plano-Convex Lens – Long Focal Length, Excellent Condition

A professional-grade, large-aperture plano-convex lens crafted from genuine Schott N-BK7 optical glass. With a 76mm clear aperture and a long nominal focal length of 900–1000mm, this lens delivers low-aberration performance ideal for beam expansion, collimation, telescope objectives, and educational demonstrations. Uncoated surfaces offer cost-effective visible-light transmission with the flexibility to apply custom AR coatings if desired.

---

🔍 Key Specifications:

• Diameter: 3″ (76mm) clear aperture

• Focal Length: ~900–1000mm (f/12–f/13 focal ratio)

• Edge Thickness: 3mm (thin, lightweight profile)

• Sagitta: ~1.6mm (gentle curvature)

• Material: Genuine Schott N-BK7 borosilicate crown glass

• Design: Plano-convex – one flat surface, one gently curved convex surface

• Coating: Uncoated (~4% reflection loss per surface)

• Edge Finish: Precision-ground, ready for mounting

• Condition: Excellent – Used/Surplus, clean surfaces

---

✅ Condition & Notes:

• Condition: Excellent – no scratches, chips, or haze

• Origin: Surplus from professional laboratory or industrial optical stock

• Optical Quality: Surfaces are clean and polish is intact; glass is homogeneous with no bubbles or striae

• Mounting: Fits standard 3″ (76mm) lens cells and holders

• Includes: Lens only – no mounting cell or hardware

---

⚙️ Why This Lens is Exceptional:

🔬 Genuine Schott N-BK7:
Not generic crown glass—this is authentic Schott N-BK7, the industry standard for precision optical components. Delivers:

• Excellent transmission from 400–700nm (>90% uncoated)

• Superior homogeneity – no striae, minimal bubbles

• Stable, predictable performance across temperature ranges

📏 Long Focal Length Advantage:
The 900–1000mm focal length provides:

• Low angular magnification – ideal for beam expansion

• Reduced spherical aberration vs. short-focus singlets

• Comfortable working distance for optical bench setups

💡 Uncoated Flexibility:
Uncoated surfaces offer 4% natural reflectivity – perfect for:

• Cost-sensitive applications where 90% transmission is sufficient

• Custom coating – apply your own AR for specific wavelengths

• Polarization experiments – no coating-induced birefringence

🪶 Lightweight Profile:
At only 3mm edge thickness, this lens is surprisingly lightweight and easy to mount – no heavy glass block to support.

---

🛠️ Applications & Uses:

💫 Beam Collimation & Expansion:

• Collimate divergent sources (laser diodes, LEDs, fiber outputs)

• Beam expander output lens in Galilean or Keplerian configurations

• Long working distance alignment and targeting systems

🔭 DIY Telescopes & Optics:

• Objective lens for low-power, wide-field refractor telescopes

• Galilean beam expander ocular component

• Finder scope or spotting scope objective

🔬 Laboratory & Educational:

• Demonstrate lensmaker’s formula and focal length measurement

• Relay lens in optical relay systems

• Field lens in multi-element optical trains

• Physics classroom demonstrations of refraction and focusing

📷 Imaging & Projection:

• Large-format magnifier for inspection or viewing

• Projection lens in custom enlargers or solar projectors

• Schlieren imaging optics component

🎯 Laser & Light Experiments:

• Visible laser beam control (HeNe, 532nm, 635nm)

• Light collection for sensors or photodiodes

• Prototype optical systems for R&D