New technique for super-resolution images

A new technique called speckle structured illumination endoscopy (SSIE) to provide images with a wide field of view (FOV) and a large depth of field (DOF) has been explored in a new study.

In the study, published in Opto-Electronic Advances, the authors introduce two fibres in a standard white light endoscope (WLE) to deliver high-resolution speckles to illuminate the object. The random speckle patterns are generated from the interference between the laser light from the two fibres. A number of images with standard resolution are collected by the WLE camera and then subjected to an image reconstruction algorithm to yield a single super-resolution image.

The speckle structured illumination refers to the usage and direction of random optical illumination patterns originating from a coherent light source, such as a laser, onto the sample under study.

Both planar and non-planar surfaces were examined, attesting to the SSIE’s objective of imaging at large DOF. In addition, from a theoretical perspective, the FOV and the DOF can be extended to as large as a WLE may allow. Furthermore, the SSIE does not require a stringent control of the illumination patterns, calibration protocols or that of the focusing optics as in the case of SIM, thereby, greatly simplifying the experimental set-up.

A demonstration of 2–4.5 times enhancement in resolution at wide FOV and DOF over the systemic limit of a standard WLE was shown. The experimental results indicate the potential of the SSIE in presenting a unique route to super resolution in endoscopic imaging at wide FOV and DOF which may be beneficial to the practice of clinical endoscopy. In a broader perspective, this technique of imaging can also be adopted into other similar domains of biomedical, medical and camera-based systems where high resolution at wide FOV and DOF is preferred or critical.

The authors said this study can potentially benefit the endoscopic imaging community in clinics, health centres and similar because no specialist equipment or stringent imaging control is needed for the acquisition and processing of image data. This makes the speckle structured illumination endoscopic system fairly easy to be translated and adopted into imaging fields broader than just endoscopy.

The method has potential to be translated into similar imaging fields that implement an incoherent imaging modality; typically, methods that make use of fluorescent dyes which stain the sample under study. In addition, the speckle structured endoscopic illumination demonstrations are independent of the internal structure, type or specifications of the scope or probe used; the imaging technique can be translated into any white light endoscopic modality with similar resolution improvement factors whether its application is clinical or industrial, since the working principle remains the same.

The study explores the possibility of imaging three-dimensional nonplanar surfaces by random optical illuminations; a direct translation of the imaging concept adopted in this study to other imaging fields such as biomedical, medical or camera-based imaging systems is possible. Any imaging system that has a camera to acquire images and that can employ the facility and routing of random pattern-based optical illuminations onto the sample by a fashion as demonstrated in this study will be able to achieve super resolution at optimal imaging parameters, the authors said.

Image credit: iStock.com/Lan Zhang