After assembly, the requirements are: Lens decentration: ±0.01 mm, tilt: ±30 arcseconds, air gap: ±0.01 mm. After assembly, the wavefront of the entire lens group shall be tested with an interferometer.

355nm UV Objective Lens The 355nm UV objective lens is a precision optical objective optimized specifically for the 355nm near-ultraviolet band (the third harmonic of an Nd:YAG laser). It is mainly used in UV laser precision machining, microscopic observation and ultraviolet imaging. Featuring high transmittance, high resolution, low aberration and high laser damage resistance, it serves as the core imaging and focusing component in ultraviolet optical systems. ## I. Core Definition and Band Positioning Operating wavelength: Centered at 355nm, compatible with multiple wavelengths including 266nm (deep UV) and 532nm (visible light), covering the near-ultraviolet to visible light range. Optical type: Mostly infinity-corrected and Plan Apochromatic (Plan APO) design; some versions are specialized for long working distance (LWD) and high resolution (HR). Core applications: Focusing 355nm pulsed laser for micromachining, or microscopic observation and coaxial imaging inspection of UV-sensitive samples. ## II. Key Technical Features ### 1. Optical Design and Aberration Correction Apochromatic correction: Precisely compensates chromatic aberration, spherical aberration and field curvature for 355nm ultraviolet light and 532nm visible light, ensuring sharp imaging across the entire field of view without edge blurring. High numerical aperture (NA): Typical NA ranges from 0.4 to 0.65, which directly determines the resolution (up to 0.4–0.7μm at 355nm) and focused spot size, suitable for precision micromachining. Long working distance (WD): Standard WD is 5–15mm, and long-working-distance versions can reach over 65mm, suitable for thick samples, machining with protective glass or non-contact observation. Infinity conjugate design: Compatible with microscope bodies, laser scanning systems, and can be flexibly matched with tube lenses, cameras, galvanometers and other components. ### 2. Material and Coating Performance UV high-transmission materials: Made of UV-grade optical glass or fused silica, with transmittance ≥50% at 355nm, avoiding strong ultraviolet absorption by ordinary glass. Laser damage-resistant coating: Coated with broadband ultraviolet anti-reflection (AR) coating. Typical laser-induced damage threshold at 355nm is 0.05J/cm² (10ns pulse), suitable for high-power pulsed lasers. Non-cemented structure: High-end models adopt air-spaced non-cemented lenses to improve laser durability and reduce aging and damage risks of cemented layers. ### 3. Resolution and Imaging Performance Theoretical resolution: At 355nm, resolution ≈0.42μm at NA=0.65, meeting the requirements of semiconductor processing, micro-nano machining and biological UV fluorescence observation. Coaxial observation compatibility: Corrects both ultraviolet and visible light simultaneously, enabling laser machining with real-time coaxial imaging and in-process inspection, improving manufacturing accuracy. Large sensor compatibility: Supports C-mount and M4/3-mount interfaces, compatible with 1/2-inch to 1.2-inch high-resolution CMOS/CCD cameras (pixel size ≤3μm).