Nov 14 2019
A technique for capturing moving objects using the unconventional imaging method called ghost imaging has been developed by scientists. The new technique could enable practical use of the imaging method for innovative applications like video compression and storage, biomedical imaging, and security checks.
Researchers used ghost imaging to capture images of the translating and rotating object in the first row. They used information in the blurry images (middle row) to create the reconstructed images in the bottom row. Image Credit: Wei-Tao Liu, National University of Defense Technology.
Ghost imaging offers a range of benefits, one of which is the ability to create an image by illuminating the object with lower levels of light than conventional imaging methods. Yet, ghost imaging has been restricted to stationary objects since it takes much more time to project the light pattern sequence onto the object that is required to reconstruct an image. This makes a moving object’s images to appear blurry.
In the Optics Letters journal, published by The Optical Society (OSA), scientists from the National University of Defense Technology in China illustrate how they could integrate information in the blurry images with details related to the location of the object, to develop high-quality images of moving objects using ghost imaging.
Our work shows that blurred images contain useful information. With further improvements, this approach could make ghost imaging useful for applications such as biomedical imaging of human beings. If used with x-rays, for example, it could help reduce the radiation dose needed for imaging.
Wei-Tao Liu, Research Team Leader, National University of Defense Technology
Creating a Clear Image
The ghost imaging method involves forming an image through the correlation of a beam that interacts with the object and a reference beam that does not interact with it. On an individual basis, the beams do not transfer any meaningful information related to the object.
The imaging method works with X-rays, visible light, and other parts of the electromagnetic spectrum. By computationally producing the structured light beams using spatial light modulators, this method can be carried out using an inexpensive single-pixel detector rather than a complex, high-cost camera.
The new technique applies ghost imaging to moving objects by using a small number of light patterns to learn the trajectory and position of the object. The team created an algorithm to cross-correlate such positional information with blurred images obtained at different positions, enabling a clear image to be formed gradually.
This approach relaxes the requirement for fast imaging, and because the algorithm is linear, it doesn’t require a large amount of computing power. The method can be performed with a typical ghost imaging system without any additional devices and allows the image to be reconstructed in a timely manner.
Wei-Tao Liu, Research Team Leader, National University of Defense Technology
Standard Setup Captures New Information
The new technique was demonstrated using a standard ghost imaging system, where a random light field produced by a rotating diffuser was split into two beams. A CCD camera recorded one of the beams, a moving object created by the researchers using a digital micromirror device was illuminated by the other beam. A single-pixel detector collected the light discharged from the moving object.
We demonstrated that our method captured the trajectory of the image and formed a high-quality image. With these same experimental conditions, traditional ghost imaging approaches would have lost most of the object information due to blurring from movement.
Wei-Tao Liu, Research Team Leader, National University of Defense Technology
At present, the researchers are involved in their efforts to enhance the performance of the method so that it would hold good for objects that move at higher speeds. They also intend to further minimize the amount of light required to expand the applications of the technique.