Single-pixel Imaging Based On Mask Plate Modulation And Its Application In Methane Optical Detection

Since the single-pixel imaging theory was proposed,,the research of related theory and application has become a major hot issue because of its special imaging mechanism.Different from planar array imaging,single-pixel imaging has only a barrel detector without spatial resolution.However,in the visible band,due to the increasingly mature array detectors such as CCD and CMOS,the application of single-pixel imaging is greatly limited in the pain points of long imaging time and low resolution.The proposed algorithms such as compressed sensing make it possible to reduce the time cost of single-pixel imaging.At the same time,single-pixel imaging has natural advantages over planar array detectors in areas such as non-visible band imaging,microscopic imaging and phase imaging.Therefore,single-pixel imaging is gradually emerging.Single-pixel imaging relies on optical field modulator as the core module of imaging to carry out a large number of structural light illumination.Traditional optical field modulator mainly includes liquid crystal spatial light modulator(LCSLM)and digital micromirror device(DMD).The refresh rate of the working target surface of the two modulators becomes the bottleneck of the frame rate of the imaging system,and is usually only applicable to the visible band.A few spatial light modulators working in the near infrared region not only have low transmittance but also high price,which limits the further development of single-pixel imaging.It is urgent to acquire new light field modulators to break the restrictions.In this paper,we propose a ring mask as a light field modulator for single-pixel imaging.Using quartz crystal and other materials with wide spectrum and high transmittance as the base,the pre-designed modulation pattern is processed onto the ring mask plate,and the stepper motor drives it to rotate at a constant speed to realize the periodic modulation of the target.Active structural light illumination can be completed and passive structure detection can be completed,thus completely replacing the role of traditional light field modulator.Not only will the modulation rate be greatly increased,but also will use the spectrum to extend to near ultraviolet and middle and far infrared.In this paper,the effects of different modulation matrices on imaging quality and the errors in practice are discussed.Firstly,a matrix that can be used for continuous optical field modulation is selected,and the imaging results at a low sampling rate are compared and analyzed,and its robustness is compared by adding noise.Finally,a 40%sampling rate random binary matrix and a full sampling cyclic S-matrix is designed.Due to the soft synchronization of the sampled signal,the problem of measurement matrix offset often occurs in the experiment.The corresponding reconstructed image quality is analyzed by simulation calculation.In this work,we build two passive single-pixel imaging systems based on two different matrices.After adjusting and solving the problem of coaxiality caused by machining accuracy,single-pixel imaging experiments in visible and infrared bands were carried out.In order to further expand the imaging application of this system in infrared band,based on the methane infrared absorption spectrum detection method,a tunable laser is used for differential absorption measurement of methane,combined with a single-pixel imaging system modulated by ring mask,the imaging experiment of methane absorption spectrum is completed.Experimental results show the superiority of the system in modulation rate and spectral detection range.