Imaging through a biological medium using speckle noise removal techniques

摘要

Experimental work has been carried out to extend a recently introduced technique, namely non-invasive optical imaging by speckle ensemble (NOISE), to non-invasively image a structure embedded beneath a 2.5mm thick layer of biological tissue (bacon). This method uses a microlens array and a coherent light source in transmission mode. Image reconstruction is achieved by averaging individual images from selected microlenses, thus reducing the speckle noise created due to the tissue layers. We advance on previous work by use of a more powerful laser source (75mW HeNe) and a higher resolution camera (2048x2048). Further advancement led to the introduction of a rotating ground glass diffuser into the system, which additionally reduced the speckle noise and enhanced the image quality. Leading on from this, an even simpler method of imaging beneath biological tissue is devised using the same setup, but without the microlens array. The principle is the same as the NOISE technique, except instead of taking a spatial average of independent speckle patterns a time average is taken within the exposure time of the CCD camera. Experimental results and comparisons are provided that support the theory.