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

The disclosure describes a particle analysis system that performs geometric hydrofocusing for imaging particles in a blood fluid sample within a flowcell. The flowcell includes a flowpath with an injection tube and an imaging window along an imaging axis, and a decrease in flowpath size comprising a narrowing zone, so that blood fluid injected into flowing sheath fluid at the narrowing zone is compressed to form a sample flowstream having a width greater than its thickness.

An illumination window and a viewport window are positioned on opposite walls of the flowcell, and the viewport window is positioned between the image capture device and the illumination window on the imaging axis. The system includes an image capture device with an objective lens, a flowcell control mechanism that varies a distance between the flowcell and the objective lens, and an autofocus pattern fixed relative to the flowcell.

The autofocus pattern includes a transparent portion with a high contrast pattern having sharply contrasting features and edges surrounded by an opaque border. The autofocus pattern and the sample flowstream define a displacement distance along the imaging axis, and the data processing module uses the autofocus pattern to determine a focus position and generate a focused image.

The processor causes the flowcell control mechanism to adjust the position of the flowcell relative to the objective lens based on the displacement distance so that the sample flowstream at the imaging axis is aligned with a focal plane of the objective lens, and then causes the image capture device to acquire an image suitable for particle characterization and counting after the flowcell position is adjusted.

Claims Coverage

The partial content provides one independent claim, which covers geometric hydrofocusing particle analysis with an autofocus pattern fixed relative to the flowcell and displacement-distance-based flowcell-to-objective adjustment for focusing imaging on a compressed sample flowstream. Four inventive features are identified, with dependent claims refining optical and flowstream parameters and an autofocus comparison workflow.

Across the partial content, the independent claim centers on geometric hydrofocusing at a narrowing zone to create a compressed sample flowstream, an autofocus pattern fixed relative to the flowcell, and a displacement-distance-based adjustment of flowcell position relative to the objective lens so the sample flowstream aligns with the objective focal plane for particle characterization and counting.

Stated Advantages

Documented Applications