Autofocusing technologies for whole slide imaging and automated microscopy

Abstract

Whole slide imaging (WSI) has moved digital pathology closer to diagnostic practice in recent years. Due to the inherent tissue topography variability, accurate autofocusing remains a critical challenge for WSI and automated microscopy systems. The traditional focus map surveying method is limited in its ability to acquire a high degree of focus points while still maintaining high throughput. Realtime approaches decouple image acquisition from focusing, thus allowing for rapid scanning while maintaining continuous accurate focus. This work reviews the traditional focus map approach and discusses the choice of focus measure for focal plane determination. It also discusses various real-time autofocusing approaches including reflective-based triangulation, confocal pinhole detection, low-coherence interferometry, tilted sensor approach, independent dual sensor scanning, beam splitter array, phase detection, dual-LED illumination and deep-learning approaches. The technical concepts, merits and limitations of these methods are explained and compared to those of a traditional WSI system. This review may provide new insights for the development of high-throughput automated microscopy imaging systems that can be made broadly available and utilizable without loss of capacity.

Automated Confluence Measurement Method for Mesenchymal Stem Cell from Brightfield Microscopic Images

“…The second layer (green component) (Awad et al, 2019) of the image was taken as an input grayscale image for further processing. Some existing focus measurement functions (FMF) (Bian et al, 2020) provide nonunique maximum values for brightfield microscopic images in our application. We proposed an autofocusing algorithm using the first derivative of variance of the image as FMF to determine the best focal plane for TIE processing, which can be described as follows:where I ( x ) is the intensity value at x when the image matrix is rearranged to an array.…”

Review of bio-optical imaging systems with a high space-bandwidth product

“…Despite challenges described above, the stepand-repeat scanning method has achieved a remarkable success in whole-slide pathological imaging. [62][63][64][65] To address these issues, Weinstein et al 7 developed a parallelization scheme using an array of microscopes [Figs. 2(a) and 2(b)].…”

High throughput slanted scanning whole slide imaging system for digital pathology

“…This greatly reduces the total time for WSI. Due to limited depth of field, accurate and high‐speed autofocusing for WSI and automated microscopy [9, 10] plays a very important role for conventional 1‐layer WSI approach.…”