Study On The Method Of Quality Assessment For Digital Holographic Image Of Cell

With the development of modern computer and image sensor technology,digital holography has become a new holographic imaging technology different from traditional holographic imaging technology. Owing to the unique characteristics and advantages, it has found a wide range of applications in particle size analysis, transparent field measurements, microcircuit testing, measurement of objects in small aperture and small field, and cell observation etc. As the quality of digital holographic images may be influenced in the process of acquisition, compression, storage, transmission and reconstruction, e.g. noise and blur introduced to the images, image distortion would be caused, and the quality of reconstruction images would be further affected. This makes it difficult to meet the application requirements. In addition, the digital hologram shows the interference fringes, rather than the morphology of objects familiar to observers. Therefore it is difficult to judge its quality directly and reconstruction is often needed prior to the evaluation of image quality. Such an indirect evaluation method is undoubtedly time-consuming and laborious, particularly in the applications requiring the significant timeliness, e.g. lensless holographic imaging for biological living cells. Accordingly, the objective quality assessment method for directly judging the quality of digital lensless holographic image, has great potentials to solve these problems. It is not only helpful to realize real-time screening of the holographic images, but also helpful to improve the quality of the reconstruction image. Following that, it is of great significance to promote the wide applications of digital holographic image.In this paper, according to the characteristics of digital holographic image, the in-depth research was conducted to investigate the suitable image quality assessment methods for digital holographic. It mainly included three parts :quality assessment of holographic image, reconstruction of holographic image, quality assessment of reconstruction image. Two types of no reference quality assessment algorithms based on the masking effect and structure definition were used to evaluate the holographic image with the distortion caused by noise and blur. Then the convolution algorithm was adopted to reconstruct the digital holographic images and with the microscopic images serving as the reference images, the full-reference image quality assessment method based on the gradient information of structural similarity was applied. Finally, the results of the quality assessment of reconstruction images were compared with those of the digital holographic images to verify the consistence.The correctness of all the algorithms was preliminarily proved by using the conventional digital images from the LIVE Database Release2 image library and the holographic images from the foreign literature. Moreover, the holographic images of different qualities, recorded by the self-developed holographic image acquisition device, were selected to further verify these assessment algorithms. The experimental results indicate that the proposed evaluation system can achieve the purpose of screening digital holographic images, and also confirm its feasibility and effectiveness.