Key Takeaways This case study examines the high NA infinity conjugate long working distance microscope objective, designed for optical tweezers and other precision applications. With a 16 mm focal length, 14 mm working distance, and 0.7 NA, this objective balances resolution and depth. Covering wavelengths from 420-900 nm, it supports various laser sources. The lens corrects for a 3 mm quartz window and requires precise machining due to high sensitivity to tolerances.  Performance testing ensures optimal imaging by adjusting eccentricity and air gaps. Overview of Optical Tweezers Technology  Optical tweezer technology is a tool that utilizes highly focused laser beams to capture and manipulate tiny particles, such as cells and nanoparticles. This technology generates force through the transfer of light, enabling non-contact control of small objects. The focused laser beam creates a strong gradient field near its focal point, attracting tiny particles to the region with high light intensity and thus facilitating capture.  Optical tweezers can manipulate nano-scale particles without causing physical damage to the samples and have demonstrated promising applications across various fields. To achieve effective particle capture in atom capture experiments, lasers typically need to converge to the micron level. Therefore, the microscope objective used in optical tweezer systems must possess high resolution. Increasing the numerical aperture (NA) is one useful method for obtaining high-resolution objective lenses. Since the samples for atom capture experiments are often placed in a vacuum chamber, the microscope objective must also provide a long working distance.  In recent years, microscope objective developers have focused on achieving both high NA and long working distances. High NA microscope objectives are extensively employed in fields such as biology, materials science, and semiconductor detection due to their high resolution and light-gathering ability. Generally, microscope objectives with high NA have shorter working distances. Achieving both high NA and long working distances necessitates the correction of numerous higher-level aberrations during the design phase, leading to complex structures, larger sizes, increased sensitivity to tolerances, and significant design and production challenges. Description of the High NA Objective This specific high NA microscope objective features a numerical aperture of 0.7 and a working distance of 14 mm, resulting in a larger diameter than conventional objectives. Its wide working band, which covers wavelengths from 420 nm to 900 nm, makes it versatile for different laser sources. It is important to note that this objective is designed to correct a quartz window with a thickness of 3 mm; any deviation from this thickness during actual use may diminish the performance of the objective. Working distance is the distance between the observed or processed object and the front end of the lens.  In practical applications, taking into account working distance is crucial when selecting a microscope objective. Typically, a longer working distance offers greater flexibility in application. However, for a fixed NA, increasing the working distance necessitates a larger lens size, while also increasing advanced aberrations within the optical path and complicating the manufacturing process. Additionally, a smaller ratio of focal length to working distance can result in increased spherical error from the rear lens due to the expansion of the optical path aperture, further complicating design efforts. Taking all this into account, the lens is designed with a focal length closely matching the working distance, which is 16 mm, and exhibits low magnification. Specification of the NA0.7 infinitely conjugated long working distance microscope objective Focal length 16mm NA 0.7 Wavelength 420-900nm FOV Φ0.5mm Working distance 14mm(including 3mm fused silica) NA0.7 Infinite conjugate long working distance microscope objective design structure Spot and WFE performance Performance Criteria of the Microscope Objective  The performance of the microscope objective is evaluated based on the size of the dispersion spot and the trans-wavefront error. The design value for the spot radius along the optical axis of this lens is less than 0.4 µm, indicating effective spot convergence at the micron level. Analysis of the transmit-wavefront diagram shows that this objective achieves diffraction-limited performance across various wavelengths, although the off-axis performance slightly exceeds the diffraction limit at 421 nm. Focal shift curve Chromatic Aberration and Wavelength Range  One unique feature of this lens is its operation across a wide range of wavelengths, from violet to near-infrared. Although the correction of chromatic aberration does not meet the diffraction limit, this objective lens has been specifically designed to perform well with laser sources. Only minimal post-focusing adjustments are required when using different light sources, helping to mitigate performance degradation caused by chromatic aberration. For the 421 nm band, the transmission wavefront design performance after focusing is as follows. transmission wavefront error@421nm Design Summary of High NA and Long Working Distance Microscope Objective Lenses The magnification of this micro objective lens is low, approximately 12X when paired with a 200 mm tube lens. The numerical aperture is significant, reaching 0.7, and the working distance extends to 14 mm, with correction for a 3 mm thick quartz window. The objective operates across a broad range of wavelengths from 421 to 900 nm, is compatible with various laser sources, and represents a special type of high-end objective. Optical Component Machining  Given the specific parameters of this objective lens, the effect of tolerance is highly sensitive, requiring precise machining tolerance for all components. The high NA and long working distance further heighten the challenges associated with manufacturing such optical components.  A frame for adjusting this micro objective lens Objective Focusing and Performance Testing  When adjusting the micro objective lens, it is essential to obtain an image of the object and adjust the lens’s eccentricity and air gap based on the imaging results. This process helps eliminate coma and spherical aberration that may arise from manufacturing deviations. The objective in question is a low-magnification microscope lens with a high numerical aperture (NA) and a large entrance pupil. When used with a standard microscope frame, the imaging results may be inadequate, making proper adjustment challenging. To ensure optimal performance, it is important to align the microscope with the object being observed. Measurement Graph: MTF vs. Frequency Customize

Key Takeaways A global leader in agricultural genetics sought durable, cost-effective UV microscope objectives.  Challenges included optical design complexity, wavefront control, and fabrication precision.  By optimizing coatings, manufacturing, and materials, we extended the lens lifespan from 3 to 18 months, reducing replacement costs and downtime.  Avantier’s customized optical coatings improved both performance and durability, ensuring reliable genetic analysis. This collaboration set a new standard for high-performance, cost-efficient UV microscope objectives in genetics and reproduction. Project Background:  UV Microscope Objectives for Genetic Analysis A global leader in agricultural genetics and reproduction services approached us to address problems they were facing related to the cost and durability of microscope objective lenses. These lenses play a pivotal role in analyzing genetic data, directly impacting the company’s efficiency and operational costs. By partnering with us, they hoped to enhance the performance and longevity of their UV microscope objectives. Challenges in Designing and Manufacturing UV Microscope Objectives Optical Design Complexity Designing UV microscope objectives involves navigating the unique properties of UV light, such as shorter wavelengths, higher photon energy, and lower transmittance. Advanced optical design techniques needed to be employed to deliver optimal imaging across the entire field of view. One aspect of this was the development of apochromatic equation systems to correct chromatic and spherical aberrations. Material Selection and Manufacturing Processes UV-grade fused silica, prized for its high damage threshold and minimal scattering properties, was selected as the primary substrate. A specialized process was implemented during manufacturing to ensure the highest levels of cleanliness and mitigate potential contamination that could compromise imaging quality. Wavefront Aberration Control Maintaining wavefront aberration below λ/5 across the full wavelength range was crucial for achieving high-resolution, low-distortion imaging. This required meticulous optimization in both the design and manufacturing stages. Precision Fabrication and Testing The high photon energy associated with UV light demands exceptional surface quality and precision in optical components. Advanced fabrication techniques, coupled with state-of-the-art metrology technologies, were employed to meet these exacting requirements. Cost and Efficiency Challenges High production costs traditionally limit the widespread adoption of UV microscope objectives. Addressing this, we focused on reducing manufacturing expenses while maintaining stringent quality standards and optimizing production efficiency. Solutions and Outcomes Customized Optical Coatings To meet the company’s specific needs, a customized optical coating solution was developed in collaboration with Avantier. These coatings enhanced the durability and performance of the microscope objectives, enabling them to withstand the demanding conditions under which they were used.  Significant Longevity Improvements Through the implementation of advanced materials, coatings, and precision manufacturing processes, the operational lifespan of the UV microscope objectives was extended from 3 months to 18 months—a sixfold increase in durability.  Cost and Time Savings The extended longevity of the lenses drastically reduced the frequency of replacements, leading to substantial cost savings and minimized instrument downtime. This improvement streamlined the operations of the genetic analysis company, enabling them to allocate resources more effectively. UV Microscope Objectives for Genetic Analysis Enhancing UV Microscope Objectives  By addressing the complexities of UV light, selecting the best materials, and employing cutting-edge manufacturing techniques, we successfully delivered a robust solution that exceeded our client’s expectations. The collaboration not only resolved their immediate challenges but also set a new benchmark for cost-efficient, high-performance UV microscope objectives in the field of genetics and reproduction. Please contact us if you’d like to request a quote on your next project. Related Content

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