For decades now, the medical industry has been automating to improve throughput, yield, and performance of medical devices. Slide scanning, for example, has been automated to reduce the time required to process each sample and collect test data. Today, slide scanning is used in a variety of applications including cancer screening, cytometry, and cellometry. These systems utilize cameras to capture hundreds and even thousands of images of a single sample for future review, feature recognition, detection, or identification. The technologies used to execute these tasks are rapidly evolving and always changing. One recent development, motivated largely by the consumer peripheral market, promises to have a positive impact on the price-performance ratio of automated slide scanning solutions.

Fig. 1 — Bio- and chemiluminescence (BL/CL) in microtiter plates.
System builders focus on several key requirements when selecting cameras for an automated slide scanning solution. The image processing required is highly demanding while the platform for software deployment needs to be flexible. To address these needs, an automated slide scanning solution will typically rely on a PC connected to cameras using a commonly available digital interface. Ideally, the software can be deployed on a variety of operating systems, so machine builders can offer their end users the flexibility of using their own PCs and avoid having to bundle a PC into the solution. While the image processing is executed on the PC, the cameras are focused on capturing high-resolution, high-quality images very quickly. Low noise and high dynamic range are both critical characteristics for this kind of imaging. This allows the system to maximize the initial detail extracted from an image to improve the success rate of a given algorithm.

Automated slide scanning system commonly uses a combination of monochrome and color cameras. The monochrome images are used for processing and analysis while the color camera captures overview images for reference. The slide itself is mounted on a motorized precision stage. The monochrome camera focuses on a smaller field of view. The stage is shifted under the camera and successive images are stitched together to form a much higher resolution, much more detailed image. At each field of view, the camera may capture multiple images in order to achieve focus, apply various optical filters and averaging techniques. Throughout the process, the monochrome camera may capture hundreds or even thousands of images of a single slide.

One of the most popular camera interfaces in automated slide scanning systems is USB. Although originally developed for peripheral components and portable hard drives, the technology has been adapted to industrial cameras. The next generation of this popular interface, USB 3.0, offers increased available bandwidth and reduced CPU processing required to capture images. This allows automated slide scanning systems to capture higher resolution images at faster frame rates while reducing the CPU processing needed to pass these images to the image processing application. More CPU bandwidth can be dedicated to the image processing algorithms, enabling them to execute faster, increase their complexity, and quality of output. In addition to higher bandwidth, lower power draw of USB 3.0 compared to other interfaces allows machine builders to minimize heat, and reduce read noise, dark noise, and dark current.

Machine builders are always looking for ways to be more competitive. By leveraging a technology like USB 3.0 which offers both increased performance and the ability to provide end users more flexibility, early adopters have the opportunity to minimize time to market while new players can use this technology to leapfrog established competitors.

This article was written by Paul Kozik, Product Manager for Point Grey, Richmond, BC, Canada. For more information, visit http://info.hotims.com/40437-163.

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