High-speed microscopy of continuously moving cell culture vessels
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We report a method of high-speed phase contrast and bright field microscopy which permits large cell culture vessels to be scanned at much higher speed (up to 30 times faster) than when conventional methods are used without compromising image quality. The object under investigation moves continuously and is captured using a flash illumination which creates an exposure time short enough to prevent motion blur. During the scan the object always stays in focus due to a novel hardware-autofocus system.Keywords:
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In this paper, we report our experience in looking for effective autofocus functions for automatic image acquisition in ImmunoFluorescence Assay (IFA). We propose to use two functions that greatly improve the performance with respect to functions commonly proposed in the literature. The first function is based on the image histogram and it is suited to in the coarse phase of autofocus, when the z-axis steps are larger to speedup the identification of the interval where lies the focus position. The second function is a popular autofocus function properly modified to compensate the effects of photo-bleaching. It is best suited to be used in the other phases of the autofocus process when smaller steps are taken to precisely identify the focus position. Effectiveness of the proposed functions has been assessed on real images both quantitatively and qualitatively, confirming that they allow obtaining a high quality images, in most cases better than those manually acquired.
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Deblurring
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Computational photography
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Auto-focusing is essential for the detection of minute defects in inspection equipments. We propose an optical system that can autofocus on a glass substrate and an algorithm that can adjust the focus quickly and accurately. The optical system uses Koehler illumination to measure the contrast of the field of view aperture, which is effective for plain glass. The auto-focusing algorithm using random forest is learned by setting the target value for the input image with the estimated focal length. When a new image is given, the focal length estimate is calculated. Various experiments have been performed on focus measurement using images acquired from various locations and show better results than others.
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An autofocus circuit, based on measurement of the high spatial frequency image components, was designed for automated microscopic scanning of biological specimens. By careful consideration of the system transfer function, elimination of video end-of-line filter artifacts, correction for illumination instability, and incorporation of autogain, the focus measurement circuit attained the sensitivity and dynamic range necessary for robust operation even at the extremes of biological specimen detail encountered in exhaustive raster scans of thousands of fields. This new circuit exhibited a 25-fold improvement in dynamic range over a previous analog implementation, matched real-time digital performance at an order of magnitude lower cost, resulted in autofocus precision of 56 nm (or 10-fold better than the depth of field of the objective) in scanning experiments comprising over 10 000 microscope fields, and tracked focus at scanning speeds of up to 3.45 fields/s. Focus was correctly maintained in these scanning experiments without additional compensation for low-detail images. This circuit makes possible the widespread inclusion of high-performance autofocus as a low cost option in video microscopy systems.
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Raster scan
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We report a method of high-speed phase contrast and bright field microscopy which permits large cell culture vessels to be scanned at much higher speed (up to 30 times faster) than when conventional methods are used without compromising image quality. The object under investigation moves continuously and is captured using a flash illumination which creates an exposure time short enough to prevent motion blur. During the scan the object always stays in focus due to a novel hardware-autofocus system.
Autofocus
Depth of field
Motion blur
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Wearable Video See-Through (VST) devices for Augmented Reality (AR) and for obtaining a Magnified View are taking hold in the medical and surgical fields. However, these devices are not yet usable in daily clinical practice, due to focusing problems and a limited depth of field. This study investigates the use of liquid-lens optics to create an autofocus system for wearable VST visors. The autofocus system is based on a Time of Flight (TOF) distance sensor and an active autofocus control system. The integrated autofocus system in the wearable VST viewers showed good potential in terms of providing rapid focus at various distances and a magnified view.
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Optical head-mounted display
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In this paper, we propose a technique for multiregion autofocusing. The objective is to make the objects of interest at the different distance locations well focused while maintaining the shallow depth of field. Based on the image sharpness analysis of interested regions, we determine the camera's best lens position and largest aperture size such that the depth of field encompasses all objects selected by the user. Thus, in addition to emphasize the objects of interest in photography, our method can also reduce the exposure for image stabilization. Experiments with real scene images are presented.
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Computational photography
Camera lens
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Field of view
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The presented vision system integrates a focus tunable lens allows to perform fast autofocus and distance measurement at the same time. By deriving the best focus from the maximum position of a fitted distribution, it is not required to capture the image with the actual best focus during the autofocus sweep, resulting in high speed and robustness of the algorithm. In this work, we demonstrate that a focus tunable lens in conjunction with an autofocus algorithm can reliably measure distance to an arbitrary object in less than a second (depth from focus). The accuracy of the distance measurement is in line with the depth of field of the imaging system. No additional hardware is required apart from the imaging system comprising camera, objective lens and focus tunable lens. The fast and accurate focus and distance measurement enables and simplifies various applications ranging from robot vision to smart manufacturing control. The optics can be tailored to reach the desired precision and focus range, whereas there is generally a trade-off between the two.
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Depth of field
Ranging
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Machine Vision
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