Abstract
Although the single-shot focus scanning technique (SSFS) has been experimentally demonstrated for extended depth of field (EDOF) imaging, few work has been performed to characterize its imaging properties and limitations. In this paper, based on an analytical model of a SSFS system, we examined the properties of the system response and the restored image quality in relation to the axial position of the object, scan range, and signal-to-noise ratio, and demonstrated the properties via a prototype of 10 × 0.25 NA microscope system. We quantified the full range of the achievable EDOF is equivalent to the focus scan range. We further demonstrated that the restored image quality can be improved by extending the focus scan range by a distance equivalent to twice of the standard DOF. For example, in a focus-scanning microscope with a ± 15 μm standard DOF, a 120 μm focus scan range can obtain a ± 60 μm EDOF, but a 150 μm scan range affords noticeably better EDOF images for the same EDOF range. These results provide guidelines for designing and implementing EDOF systems using SSFS technique.
Highlights
Standard optical techniques for microscopy typically are limited to a small depth of field (DOF)
We examined the properties of the system response, quantified the achievable Extended depth of field (EDOF) and the variance of the deconvolution kernel, suggested the operated scan range for a desired EDOF, and examined the limitations of the EDOF range via using an 8-bit 48 dB detector as an example (Sec. 3)
Through analytical modeling under the condition of being aberration free except defocus we have examined the properties and limitations of a single-shot focus scanning (SSFS) system, and quantified the achievable EDOF range and restored image quality in relation to the axial position of the object being imaged, the operated scan range, and signal-to-noise
Summary
Standard optical techniques for microscopy typically are limited to a small depth of field (DOF). Known as focus stacking, is a technique where multiple images of a thick specimen taken at different focal depths are combined to reconstruct an EDOF image with a greater DOF than any of the individual source images This technique requires a method to suppress the out-of-focus signals when capturing the individual source images [2] or post-process the images via deconvolution before they are fused [2,5]. The SSFS technique shares similarity to the well-known wavefront coding as a hybrid imaging approach In both methods, the optical system acquires a blurred image of a specimen with an extended depth range through a well-defined pre-blur imaging mechanism, and a digital image processing is applied to remove the blur effect and restore a clear EDOF image. The main aim is to provide valuable guidelines in designing and implementing an EDOF imaging system through single-shot focus scanning technique
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