Terahertz Real-time Off-axis Digital Holography With Zoom Microscopy Function

Terahertz(THz) wave features of detecting hidden objects,nondestructive detection for organism and so forth.Based on the characters of THz wave,THz imaging technique plays a significant role in the areas of cancer cell observation,defect detection and security check,making it possesses a quite broad prospect in theoretical research and industrial application.THz digital holography is a combinative production of THz imaging technique and digital holography technique.Compared with conventional imaging technique,this kind of interferometry is able to obtain the amplitude and phase information simultaneously of THz wave transmission or reflection from the object.Moreover,it can improve the image quality and enhance the resolution of the system to some extent.In this paper,a off-axis holography system worked at 0.17TTHz is constructed by utilizing digital holography theory.The part of light path employs the combination of 4f lens,which uses the method of frequency domain filtering to restore object light wavefront on image plane.When CCD is placed on different plane,the object light complex amplitude is acquired by inverse operation of difffraction.Then the author provides a comparison between the images obtained by holography and original focal plane imaging.The resolution of the image reconstructed from the holography is estimated by a home-made THz resolution card.On this basis5 the light path is reformed by adding a lens which comprise the zoom system.The system not only possesses the capacity of adjusting focal length ratio flexibly which make the specimen be full of the window of CCD,but also promotes the lateral resolution of the system,as a result of the function of microscopy.Besides,the system is estimated the resolution by the home-made resolution card as well,which is demonstrated close to the theoretical limitation.