Filing in this space is concentrated among large biologics originators, with the leading assignee holding 386 of the 1,827 records in scope and the top five combined accounting for 45.0% of all records. The remainder is spread across a long tail of companies and research institutions with far fewer filings each, several holding only a handful of records. This concentration reflects that most claims bundle formulation-stability language with particle-count specifications tied to a company’s own protein therapeutics.

Filings rose from 59 in 2017 to a peak of 168 in 2021, then eased to 159 by 2024 — a 5% decline over that three-year window, which reads as a plateau rather than a collapse. Counts for 2025 and 2026 appear lower still, but publication typically lags filing by around 18 months, so those most recent years understate real filing activity and should not be read as a continuing downward trend. A clearer read on 2025-2026 activity will only be available once those cohorts finish publishing.

Both terms appear as search criteria in this dataset because they represent competing subvisible particle detection methods, and many families reference both to establish method orthogonality — using two independent techniques to confirm a particle count or characterization result. Light obscuration is the more established, count-based method, while flow imaging microscopy adds image capture and morphology analysis, which is part of why image-recognition classes (G06V) appear, albeit in only 1.4% of records. Claims combining both methods, or claiming a correction for known discrepancies between them such as silicone oil droplet interference, are a recurring pattern worth checking specifically rather than searching for either method alone.