High Precision BK7 Glass Achromatic Doublet Lens for Microscope/Telescope

1. Material

• Core Elements: Precision-bonded pair of optical elements.

• Primary Material: Crown Glass: High-quality BK7 (Schott designation) borosilicate glass for the positive (converging) element. Renowned for excellent homogeneity, transmission (approx. 92% in visible spectrum), and low bubble/inclusion content.

• Secondary Material: Flint Glass: Typically a higher dispersion glass (e.g., F2, SF2) for the negative (diverging) element.

• Bonding: Cemented using high-transparency, low-stress optical adhesive (e.g., Canada balsam historically, modern epoxies/UV-cured adhesives).

2. Key Properties

• Achromatic Design: Significantly reduces chromatic aberration by bringing two primary wavelengths (e.g., red/C & blue/F lines) to a common focal point. Minimizes color fringing ("purple haze").

• High Precision: Features tight tolerances on centering (<3 arcmin), surface figure (λ/4 or better), surface quality (scratch-dig 40-20 or finer), and focal length.

• Wavefront Accuracy: Optimized for minimal wavefront distortion.

• Low Stress: Manufacturing and bonding processes minimize internal stress, preserving optical performance.

• Durability: BK7 offers good chemical resistance and mechanical stability.

3. Primary Function

• Chromatic Aberration Correction: The core purpose is to eliminate color blur caused by dispersion in single-element lenses, providing sharper, truer color images.

• Spherical Aberration Reduction: The doublet design also helps minimize spherical aberration, improving overall image sharpness and contrast, especially off-axis.

• Precision Focusing: Delivers high-resolution, high-contrast images by focusing a broad spectrum of light accurately onto a single plane.

4. Critical Applications

• • Microscopes:

    • Essential in objective lenses (especially higher magnifications like 40x, 60x, 100x oil immersion) for crisp, color-accurate specimen imaging (biology, pathology, materials science).

    • Used in eyepieces for enhanced viewing clarity and reduced eye strain.

  • Telescopes:

    • Fundamental component in objective lenses for refracting telescopes (achromats).

    • Key element in high-quality eyepieces (e.g., Kellner, Plössl designs) for planetary and lunar observation, minimizing false color.

    • Used in Barlow lenses and correctors.

  • Collimators & Other Instruments: Used where precise, color-corrected collimation or imaging is required (e.g., laser alignment, inspection systems).