Optical Coding Imaging Of X-ray Scintillator Imager

Among all kinds of X-ray imaging technologies,X-ray indirect imager is a very important technology because of its high detection efficiency.The X-ray indirect imager transforms the incident X-ray into visible light through the scintillator,and then the object image is transmitted to the imaging detection array through the subsequent optical lens system to realize image visualization and reading.Therefore,the performance of scintillator is the basis of the performance of X-ray detector.Scintillator affects the spatial resolution,time resolution and detection efficiency of X-ray indirect imaging detector.As we all know,scintillators can absorb high-energy rays and emit visible light,which has the advantages of non-deliquescence,high and low temperature resistance,stable thermodynamic performance,practicability,strong applicability,and micron level imaging resolution.They play an important role in scientific research and medical treatment,luggage security inspection,industrial flaw detection,radiation detection,equipment nondestructive testing,etc.However,the difference between the refractive index of the scintillator and that of the air is large.The total reflection of the laser acceptor inside the scintillator occurs at the interface between the scintillator and the air,which results in the loss of a large number of laser acceptors,especially the information of medium and high frequency,resulting in the poor imaging quality of the X-ray indirect imaging detector.Therefore,the demand for high-performance X-ray indirect imaging detector attracts many scientific researchers to conduct in-depth research from many aspects.In order to improve the imaging quality of X-ray indirect imaging detector,improve the signal-to-noise ratio of image details,and solve the shortcomings of X-ray imaging methodology,we put forward innovative solutions,and carried out a lot of experimental work,the specific work is as follows:1.In order to study the high-performance hard X-ray indirect scintillationimaging detector,improve the imaging quality of the detector,and solve the problem of the loss of medium and high frequency information due to the diffraction limitation caused by the high refractive index of the scintillator,we propose a technology to restore the medium and high frequency information in these images.In this technology,the two-dimensional high-density grating is used as the encoder to cover the emitting surface of the scintillator,and the medium and high frequency information is transferred to the low frequency area through the first-order diffraction,so that the medium and high frequency information can be emitted from the interior of the scintillator.Finally,we approximate the effect of the encoder to the modified point spread function(PSF).The modified PSF is used to decode the image recorded by the camera,and the high-frequency information transferred to the low-frequency area is converted to the high-frequency area again,thus greatly improving the signal-to-noise ratio.We call it HSFER.Finally,experiments are carried out to verify the effectiveness,practicability and applicability of HSFER method.The experimental results show that the HSFER method can greatly improve the signal-to-noise ratio of image details and make the image details clearer.At the same time,the method can reduce the exposure dose in the imaging experiment and achieve high signal-to-noise ratio reconstruction at a lower dose.In many practical applications,HSFER technology is expected to achieve high signal-to-noise ratio,high spatial resolution imaging,and high fidelity imaging,especially in high spatial resolution X-ray indirect imaging based on large synchrotron radiation device or desktop X-ray tube.Compared with the indirect X-ray imaging under the same experimental conditions,HSFER technology has higher contrast and signal-to-noise ratio.2.In HSFER technology,it is necessary to build PSF which only depends on the system to describe the encoder,but in the measurement of PSF,it is often affected by the image.Therefore,in HSFER technology,it is necessary to build image independent encoder PSF.In order to eliminate the influence of specific image,we propose a method to reconstruct PSF by using iterative algorithm,so as to obtain encoder PSF under incoherent illumination.We reconstruct the central region of PSFusing the nonlocality of light information distribution under incoherent light,and successfully apply it to the complex X-ray indirect imaging system based on HSFER method.According to the comparison of the results of the synchrotron radiation imaging experiment,the PSF constructed by the iterative algorithm can accurately restore the image,and the image fidelity is high,the signal-to-noise ratio is improved significantly,and one-step imaging is realized.3.Based on the above theory,we have developed a set of large numerical aperture imaging detector which is suitable for our HSFER method,to ensure the continuity of the spectrum,and successfully carried out the X-ray indirect imaging experiment.The experimental results show that the signal-to-noise ratio is increased by 52 times,and the final imaging experimental results show that the HSFER technology has strong practicability.4.EUV interference lithography is suitable for the preparation of large-area nanostructures with precise period.We use the existing technology of our research group to apply in HSFER imaging experiment,and do the following work: we use large area splicing technology to prepare centimeter level two-dimensional high-density grating as encoder for imaging experiment,and obtain high signal-to-noise ratio image,which is expected to be applied in CT imaging;we use photoresist containing metal oxide to directly prepare two-dimensional high-density grating,forming pattern It does not need graphics transfer,and has strong stability,avoiding the distortion of graphics transfer caused by post-processing.