Autofocus systems and methods for particle analysis in blood samples

Inventors

Wanders, Bart J. • Jordan, Brett • Farrell, Gregory A. • Adams, Thomas H. • Groner, Warren

Assignees

Iris International Inc

Abstract

Particles such as blood cells can be categorized and counted by a digital image processor. A digital microscope camera can be directed into a flowcell defining a symmetrically narrowing flowpath in which the sample stream flows in a ribbon flattened by flow and viscosity parameters between layers of sheath fluid. A contrast pattern for autofocusing is provided on the flowcell, for example at an edge of a rear illumination opening. The image processor assesses focus accuracy from pixel data contrast. A positioning motor moves the microscope and/or flowcell along the optical axis for autofocusing on the contrast pattern target. The processor then displaces microscope and flowcell by a known distance between the contrast pattern and the sample stream, thus focusing on the sample stream. Blood cell images are collected from that position until autofocus is reinitiated, periodically, by input signal, or when detecting temperature changes or focus inaccuracy in the image data.

Core Innovation

A biological sample fluid particle analysis system uses a flowcell having a flowpath and a viewport window, with a sample flowstream flowing through the flowpath. An imaging target is fixed to the flowcell, and an imaging capture device includes an objective lens aligned with the viewport window. The system includes a focusing mechanism configured to vary a distance between the flowcell and the image capture device, enabling particle characterization and counting of the sample flowstream.

The system acquires a first image of the imaging target and analyzes the first image for a level of contrast. Using the level of contrast, the system determines a first position of the image capture device from the imaging target where an image of the imaging target is focused. The system then adjusts the distance between the flowcell and the image capture device or objective lens by a displacement distance that is a non-zero distance difference between a first focal distance to the imaging target and a second focal distance to the sample flowstream, and acquires an image of the biological sample fluid.

The described arrangement is implemented for automated blood analysis using a symmetrically narrowing flowcell that hydrodynamically flattens the sample into a thin ribbon enveloped by a higher-viscosity sheath/PIOAL, with optional geometric and viscosity hydrofocusing to improve alignment of cells and intracellular organelles. Refocusing can be reinitiated based on temperature changes or focus-quality metrics, and representative system components include motor drive, processor, motor control, and a temperature sensor to address thermal drift. The approach supports particle characterization/counting of ribbon-shaped sample streams for imaging such as WBC differential counting and RBC/platelet imaging.

Claims Coverage

The partial content provides one independent claim (clm-00001). Its inventive features focus on a fixed imaging target on the flowcell and a contrast-based autofocus sequence that uses a displacement distance between two focal distances to focus on the sample flowstream, enabling particle characterization and counting.

Across the provided independent claim, the coverage is centered on using a flowcell-fixed imaging target and contrast analysis to compute a focus reference, then applying a non-zero displacement distance defined by two focal distances to shift focus from the imaging target to the sample flowstream for particle characterization and counting.

Stated Advantages

Documented Applications