Precisely Crafting Innovative Objective Lenses for Microscopes

Feb. 7, 2024

Shanghai Optics, a leading optical solutions provider, excels in designing objective lenses for microscopes with a focus on innovation and precision. The lens design process involves close collaboration with clients to determine optimal specifications, ensuring tailored solutions for specific imaging needs.

Shanghai Optics’s advanced manufacturing techniques yield optical components with unparalleled precision. Quality control measures are implemented throughout the process, ensuring accuracy and consistency. Specialized coatings, such as anti-reflective coatings and ion-assisted deposition techniques, enhance lens performance.

In assembly, skilled technicians meticulously align and bond components, emphasizing stability and precision. Shanghai Optics’s objective lenses, designed for various applications, offer superior resolution, clarity, and aberration correction.

 

Insights into Physical Design

The assembly drawing categorizes lenses into components like the front group, first group, front pressure cap, middle two groups, back group, spacer ring, mirror body, objective lens shell, pressure ring, spring, and rear light bar. With five lenses, the first is in the front group, the second and third are together, the fourth in the middle two groups, and the fifth in the back group. Spacers in the mirror body are secured by a pressure ring in the front, one, two, and rear groups, with the mirror body rotating with an objective lens shell and front pressure cap. This ensures high coaxial accuracy. Smaller fit spaces between groups and the mirror body are preferred, marked around 5um for outer and inner diameter tolerances. A clearance of 0.1 to 0.2 is maintained between the middle two groups and the lens body for adjusting coma. Threads inside spacer rings of the front, one, two, and rear groups reduce stray light, enhancing optical precision.

 

Assembly Technology

In the assembly process for this lens, the adjustment of aberrations such as spherical aberration, coma, astigmatism, field curvature, distortion, and color differences is crucial. The widely used “star point method” involves utilizing transmitted light to generate diffraction spots on an aluminum-coated glass plate, observed through a microscopic system with a lens for tuning. Ideally, aberration-free lenses should display airy patches with thin circles in the eyepiece field. Adjusting the lens involves real-time modifications to parameters while observing the diffraction spot shapes. Experienced lens adjusters quickly identify and address aberrations, but for beginners, mastering this skill is challenging. It often requires hands-on experience, as exemplified by spending months in workshops learning glass wiping techniques. The shape of diffraction spots corresponds to specific aberrations, including:

  • Spherical aberration: Incorrect brightness proportion of airy disk in the total diffraction spot or a too-thick diffraction ring. Solutions involve adjusting the air interval by turning the lens holder or adding gaskets.
  • Coma: Adjustment of alignment is necessary for this comet-like tail diffraction pattern. Initial focus on the specified clearance of 0.1 to 0.2 in the two groups and lens body, with subsequent correction of coma aberration followed by observing other aberrations.
  • Astigmatism: Observation requires rotating the lens, often improved by replacing the glass due to the difficulty in adjusting the lens’s internal glass surface aberration.
  • Field curvature: Defocus is employed to observe spots in central and peripheral visual fields.
  • Distortion: The irregular shape of the diffraction spot, if not inherent to the design, may require addressing the lens’s plane shape.

 

Objective Lens Types and Considerations

  • Immersion Objectives: Enhance resolution and numerical aperture using fluid.
  • Achromatic Objectives: Correct chromatic aberration, improving image quality.

 

Optical Coatings and Design Considerations:

Ion-assisted deposition techniques are used to apply coatings, contributing to superior optical quality. Other considerations include field of view, long working distance, and infinity correction.

Do not hesitate to contact Shanghai Optics today. We’d be more than happy to discuss your projects and how best they can become a success.

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