Achromatic lens systems with telecentric objectives enhance precision in optical coherence tomography for freeform surface metrology
Institute Reference: 2-18091
Background
Freeform optical components provide high performance but are challenging to measure with low uncertainty due to their complex shapes. Conventional metrology tools like Optical Coherence Tomography (OCT) systems struggle to meet the desired measurement precision, especially with components featuring steep slopes and varying surface sags. Traditional lenses fail to achieve optimal results due to limitations in telecentricity, field of view (FOV), and numerical aperture (NA), resulting in higher uncertainty.
Technology Overview
This invention introduces an advanced objective lens system featuring two telecentric objectives designed for OCT metrology. One lens has a large FOV, ideal for broadband laser scanning, and the other provides high NA, useful for microscopic or probing tasks. These lenses can be configured in a pseudo-bistatic setup, allowing separate paths for the probing and reflected signals, maximizing precision. The configuration ensures low signal loss and enables measurements over a wide range of slopes.
The design achieves telecentricity and flat-field imaging, correcting for aberrations and distortions that impact measurement accuracy. By supporting a 300 nm bandwidth (720–1080 nm), these lenses allow precise depth scanning with minimal wavefront error. This technology also reduces the impact of signal-to-noise issues, commonly encountered in OCT, by allowing reflected beams to follow optimized, distinct paths.
Benefits
This technology reduces measurement uncertainty to the nanometer scale, making it ideal for the complex geometries of freeform optics. It allows both wide field of view (FOV) and high numerical aperture (NA) objectives, ensuring adaptability for various metrology tasks. The system maintains low aberration, achieving diffraction-limited performance with a wavefront error of ≤ 0.07λ. Its pseudo-bistatic configuration enhances depth focus, allowing it to capture signals from steep or irregular surfaces with greater accuracy. Additionally, the lenses provide reliable broadband achromatic performance over a spectral range of 720 to 1080 nm, ensuring precision across multiple wavelengths.
Applications
This technology offers significant potential in optical metrology by enabling precise quality control for advanced optics, including freeform lenses and mirrors. It can enhance high-precision imaging in microscopy, particularly within optical coordinate measurement machines (CMMs), where accurate dimensional analysis is crucial. Its ability to support broadband laser scanning makes it well-suited for both industrial applications and scientific research. Furthermore, it can improve optical coherence tomography (OCT) systems by delivering the precision required for medical imaging tasks, such as retinal diagnostics and in-depth tissue analysis.
Opportunity
The University of Rochester is open to exploring funded research collaborations, licensing agreements, and other partnership opportunities.