With the improvement of people's health awareness, portable fundus cameras for health monitoring are popular. In order to solve the problem of non-mydriasis in fundus cameras based on new smart phones, we propose a dual channel lighting non-mydriasis method. The system focus with 680nm light, and captures color images with white light flash. In this study, a group of orthogonal polarizers were used to eliminate the stray light caused by the front eyepiece, and a circular light source was used to suppress corneal reflection. The system performs well with a field of view of 45° and a pupil diameter of 3mm, when refractive error ranges from -10D to +10D. The imaging quality of the system is good in 480- 700nm band. This study provides a reliable scheme for telemedicine of senile ophthalmic diseases.
Miniaturization and compactness are the development direction of imaging spectrometer. More and more imaging spectrometers cannot be miniaturized because of traditional optical components. Thus, the optical design space that can highly benefit from the developments in transmission imaging spectrometer based on the metasurface. In this manuscript, we introduce the concept of transmission imaging spectrometer based on metasurface. The spectrometer has a high resolution from 700-800nm spectrum. The key element of the spectrometer is composed of dielectric metasurface, which is used to divide the incident light-spectrum. Meanwhile, the energy of the ultrasurface diffraction order is higher than that of the dispersion order of the traditional grating. The transmission metasystem design can be applied to many optical systems, interferometers, hyperspectral imagers, and computational optical systems, significantly reducing their sizes and increasing their mechanical robustness and potential for integration.
With the improvements of the spatial and spectral resolution, Compressive Sensing (CS) is applied to spectral imaging. CS-based spectral imaging reduces the requirements for data acquisition, storage and processing capabilities, while reducing the pressure of subsequent data transmission and storage. At present, the research on CS system is mostly in the stage of simulation, mainly focusing on the image algorithm. We studied the CS projection measurement optical system using Digital Micromirror Devices (DMD) as the image compression devices. We proposed a new dual-channel optical system that acquired the low-resolution coded image by DMD at both the reflection direction of +12°and -12°. We use shelf lenses to design a DMD-based dual-channel optical system and perform tolerance analysis on the optical system. The system has good tolerances, which reduces the cost of the system. Then, the dual optical path optical system was simulated and the principle prototype was built. Both obtain low-resolution coded images of two channels, which are complementary in energy. And the amount of image data is low, which are used to restore high-resolution images. This construction method can not only restore the encoded image of one channel to obtain a high-resolution spectral image, but also fuse the restored images of two channels to obtain a higher-resolution spectral image. Therefore, this construction method can be applied to spectral imaging technology.
Colour diagnosis of traditional Chinese medicine (TCM) is the main content of “looking” inspection in the four-diagnosis methods of "looking, listening, asking and feeling the pulse". The action of light on the face is a very complex process, it is difficult to distinguish reflected light from internally reflected light by human eyes alone. In this paper, we discuss the relationship between TCM facial colour diagnosis and optics, integrate imaging spectroscopy to improve the objectified development of facial colour diagnosis in TCM. A visible band snapshot hyperspectral imaging spectrometer is designed based on a grating dispersion module. This imaging spectrometer is a snapshot system with 34° field of view and a measured spectrum from 400 nm to 680 nm. The spectral resolution reaches 3nm. The total length of the optical system is only 165mm, which can realize the miniaturization of products.
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