Application Of Optical Fibers In The Single-pixel Imaging System

Optical fiber is a kind of transmission medium,which has the advantages of non-interference from ambient light,anti-electromagnetic interference,small size,light weight,small loss,low cost and long-life cycle.Optical fiber has been widely used in communication,laser,sensor and other fields.Recently,optical fiber has become more and more attractive in the field of imaging.In some extreme conditions,the traditional electrical imaging devices are not convenient to work,but optical fiber imaging devices are possible to have some unique advantages.Optical fiber can work in high temperature,high humidity and even high corrosive environment,and can also freely penetrate into various small corners,so it is relatively easy to achieve endoscopic imaging,remote imaging,high-resolution imaging,etc.Therefore,optical fiber has great value and potential in imaging applications.Single-pixel imaging(SPI)system is a kind of computational imaging method different from traditional imaging system.It only needs one pixel to realize the restoration and reconstruction of a image.SPI has the advantages of fast imaging speed,high signal-to-noise ratio in bad environment and low cost.It has made a series of progress in biomedical imaging,terahertz imaging,holographic imaging,microscopic imaging,hyperspectral imaging,three-dimensional imaging,information encryption.However,SPI still has many shortcomings in light source generation,computing speed,system stability,imaging distance,detector size,system integration package and so on.The typical SPI system is generally based on free space optical components and devices,mainly including two types of functions: light modulation and signal detection.If the optical fiber devices are applied to these two types of functions of SPI,the advantages of optical fiber can be brought into full play to realize the functions and applications that the general SPI system cannot achieve.Aiming at the application of optical fiber in SPI system,this paper focuses on low-cost SPI system based on an optical fiber detection device,and optimizes both the light modulation and signal detection devices.The main contents of this paper include:1.The low-cost light modulation device is investigated: the single-pixel system usually needs to use various spatial light modulators to generate structured light.These devices are expensive,which limits the wide application of SPI.We propose to use commercialized display screens to generate structured light to achieve low-cost SPI.Compared with other commonly used structured light modulation devices,the cost is reduced by more than 100 times.We compared the performance characteristics of different kinds of spatial light generation and modulation devices commonly used in SPI,including liquid crystal spatial light modulator,digital micro mirror array and display screen.The display screen has the advantages of flexible size change,active lighting,low cost,non-mechanical movement,convenient drive integration,etc.We also discuss the encoding method of light source and image restoration algorithm.We use ordinary computer display screen to build a SPI system,carry out experiments on numbers,letters,insects and other objects.In the case of random coding of light source,the restoration effects of different restoration algorithms and different sampling rates are compared.In addition,Hadamard coding is used for image restoration.In the future,different speckle patterns generated by multi-mode fiber can also be used as structural light in SPI to realize all-optical fiber imaging system.2.Combined with the method of generating structured light based on the display screen,the optical fiberized detection device is proposed and discussed: the traditional detector must be placed in a range that can receive the reflected or transmitted light of the target object,so that the SPI system can work normally.The detector has a certain volume,which limits the application of SPI system in narrow space,such as smallslits,closed small pipes and other corners that is difficult to be accessed directly.We first analyze the acceptance angle of an ordinary flat-end fiber and single inclined face fiber(SIFF)(the field of view of SPI).We discuss the angle of light entering the SIFF from both the end face and the sidewall in detail.Then,the SPI experiments are carried out with ordinary flat-end fibers and single inclined face fibers,respectively.Finally,the SPI based on the SIFF in 6mm diameter tube is demonstrated.The feasibility of optical fiber as a detection device in SPI is verified.And non-direct,remote and multi-dimensional SPI in narrow space is realized.