Structured illumination microscopy (SIM) is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity. The spatial resolution of SIM is typically limited to two times of the diffraction limit and the depth of field is small. In this work, we propose and experimentally demonstrate a low cost, easy to implement, novel technique called speckle structured illumination endoscopy (SSIE) to enhance the resolution of a wide field endoscope with large depth of field. Here, speckle patterns are used to excite objects on the sample which is then followed by a blind-SIM algorithm for super resolution image reconstruction. Our approach is insensitive to the 3D morphology of the specimen, or the deformation of illuminations used. It greatly simplifies the experimental setup as there are no calibration protocols and no stringent control of illumination patterns nor focusing optics. We demonstrate that the SSIE can enhance the resolution 2–4.5 times that of a standard white light endoscopic (WLE) system. The SSIE presents a unique route to super resolution in endoscopic imaging at wide field of view and depth of field, which might be beneficial to the practice of clinical endoscopy.

In this Letter, we present a low-cost, high-resolution spectrometer design for ultra-high resolution optical coherence tomography (UHR-OCT), in which multiple standard achromatic lenses are combined to replace the expensive F-theta lens to achieve a comparable performance. For UHR-OCT, the spectrometer plays an important role in high-quality 3D image reconstruction. Typically, an F-theta lens is used in spectrometers as the Fourier lens to focus the dispersed light on the sensor array, and this F-theta lens is one of the most expensive components in spectrometers. The advantage of F-theta lens over the most widely used achromatic lens is that the aberrations (mainly spherical aberration, SA) are corrected, so the foci of the dispersed optical beams (at different wavelengths) with different incident angles could be placed on the sensor array simultaneously. For the achromatic lens, the foci of the center part of the spectrum are farther than those on the side in the longitudinal direction, causing degradations of the spectral resolution. Furthermore, in comparison with the achromatic lens with the same focal length, those with smaller diameters have stronger SA, but small lenses are what we need for making spectrometers compact and stable. In this work, we propose a simple method of using multiple long-focal-length achromatic lenses together to replace the F-theta lens, which is >8-fold cheaper based on the price of optical components from Thorlabs, US. Both simulations and in vivo experiments were implemented to demonstrate the performance of the proposed method.