Research Of Single-pixel Imaging Experiment Based On Spatial Light Modulator

Single-pixel imaging is a technology to achieve image of a two-dimensional scene using a single-point photo-detector.Compared to traditional imaging systems based on lenses and CCDs,single-pixel imaging systems not only have advantages in non-visible light imaging and scattering media imaging,but also own a low cost.Single-pixel imaging systems usually contain a spatial light modulator,which can make the unique modulation for the incident light according to its species.For example,DMD can make a high contrast modulation,but the modulation is usually confined to binary.Although LC SLM is able to achieve 256 gray-scale modulation,its contrast is not as high as DMD's.In addition,the modulation of LC SLM relies on the deflection of the liquid crystal molecules,so between loading the mask and light intensity data acquisition the deflection time of the liquid crystal needs to be reserved.In this paper,single-pixel imaging experiments based on different imaging theories are completed,including the computational ghost imaging experiment,the compressed sensing single-pixel camera,and the four-step phase shift single-pixel experiment.Their imaging system and imaging quality are compared and evaluated respectively.Specifically,the following research work is completed in this paper:1.Single-pixel photo-detector and spatial light modulator are the distinct optoelectronic devices in single-pixel imaging system compared with traditional imaging system.This paper introduces the commonly used avalanche photodiode,liquid crystal spatial light modulator and digital micro-mirror device.Their working principle,working mode and the characteristics are presented respectively,and the specific parameters of the devices used in this paper are described in detail.2.Three typical single-pixel imaging theories are introduced,namely,the computational ghost imaging based on intensity fluctuation statistics,single-pixel camera based on compressed sensing theory,and the four-step phase shift imaging by the Fourier spectrum acquisition.Although the backgrounds and the principles of the three imaging theories are different,all of them can achieve single-pixel imaging in a similar device system.Therefore,in this paper these three imaging methods are discussed in the framework of single-pixel imaging.3.The simulation and experiment results on computational ghost imaging and compressed singing imaging are compared.The computational ghost imaging uses second-order correlation algorithm to reconstruct,while the compressed sensing uses OMP algorithm.Both methods load random binary masks on DMD,so the same group of masks and the same set of data are used for both reconstruction.The results show that the computational ghost imaging usually requires more sampling to achieve high signal-to-noise ratio,and under sub-Nyquist sampling,the reconstruction of single-pixel camera based on CS performs superiorly to the computational ghost imaging.4.Despite the compressed sensing is able to recover the object under sub-Nyquist sampling,the reconstruction process takes a long time because of its high computational complexity,especially facing the high-pixel object reconstructed at high sampling rate.The four-step phase shift single-pixel imaging uses inverse fast Fourier transform(IFFT)to recover,which is accurate and high speed.On the basis of the proposed using the projector to illuminate the object with the sinusoidal fringe light,this paper realizes the imaging of transmissive object using the amplitude liquid crystal spatial light modulator to load the sinusoidal stripes masks.Furthermore,this paper uses LCD to display sinusoidal structured light stripe to achieve LCD-based lensless single-pixel imaging.Applying LCD to replace the projector or LC SLM can lower the hardware requirements,saving costs and simplifying the optical path.In the experiment the influence of the Gamma curve of the LCD on the results is analyzed.It is suggested that reserving the deflection time of the LCD liquid crystal molecules can increase the signal to noise ratio,and improve the reconstruction quality greatly.