Abstract
We report the development of a high-throughput whole slide imaging (WSI) system by adapting a cost-effective optomechanical add-on kit to existing microscopes. Inspired by the phase detection concept in professional photography, we attached two pinhole-modulated cameras at the eyepiece ports for instant focal plane detection. By adjusting the positions of the pinholes, we can effectively change the view angle for the sample, and as such, we can use the translation shift of the two pinhole-modulated images to identify the optimal focal position. By using a small pinhole size, the focal-plane-detection range is on the order of millimeter, orders of magnitude longer than the objective's depth of field. We also show that, by analyzing the phase correlation of the pinhole-modulated images, we can determine whether the sample contains one thin section, folded sections, or multiple layers separated by certain distances - an important piece of information prior to a detailed z scan. In order to achieve system automation, we deployed a low-cost programmable robotic arm to perform sample loading and $14 stepper motors to drive the microscope stage to perform x-y scanning. Using a 20X objective lens, we can acquire a 2 gigapixel image with 14 mm by 8 mm field of view in 90 seconds. The reported platform may find applications in biomedical research, telemedicine, and digital pathology. It may also provide new insights for the development of high-content screening instruments.
Highlights
Whole slide imaging (WSI) system is one important tool for biomedical research and clinical diagnosis
We report the development of a high-throughput whole slide imaging (WSI) system by adapting a cost-effective optomechanical add-on kit to existing microscopes
We can expand their capability for handling different samples and integrate other image recognition strategies for better and affordable laboratory automation
Summary
Whole slide imaging (WSI) system is one important tool for biomedical research and clinical diagnosis. Different from the laser-reflection method, image-contrast-related method [2, 4,5,6] is able to track topographic variations and identify the optimal focal position through image processing. If the sample is placed at an out-of-focus position, the sample will be projected at two different view angles, causing a translational shift in the two captured images (Fig. 1(b1) and 1(b3)). By identifying the translational shift of the two captured images, we can recover the optimal focal position of the sample without a z-scan. By putting the sample at different positions, we can see different translational shift from the two pinhole-modulated images (Fig. 2(a) and 2(b)). We first identify the translational shift of the two pinhole-modulated images and use this calibration curve to recover the focal position
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