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.

为了实现多路无源液晶光学器件的驱动，设计开发了低成本、低复杂度及幅频可调的多路驱动电路。首先，为了便于控制液晶器件，在PC机和驱动板之间采用USB数据传输方式进行控制信号的传输。其次，驱动板卡采用母板加多子板模式，每个子板可输出32路驱动信号，其可依据实际需求灵活选取子板数目，从而降低成本。母板与子板均采用STM32作为主控芯片，子板通过SPI接口与母板进行数据传输。每个子板通过2个SPI接口将数据分组分发给DAC芯片，每个DAC芯片可控制16路数模转换，最终实现192路模拟信号的输出。最后，进行制板和测试。结果显示，输出模拟电压与灰度值符合线性比例关系，其绝对误差在0.010 V左右，符合10 bit、1 024级电压灰度值调制精度。该驱动板卡可以实现多路驱动信号的输出，满足多路无源液晶光学器件驱动控制的需求。