The ultra-thin diameter imaging endoscope developed in this research is about the thickness of a human hair, and is characterized by its "lensless" design. In addition, by applying the "ghost imaging method," it is possible to image the most clinically important area, which is a distance of several millimeters to several tens of millimeters from the tip of the optical fiber, and is sensitive to the effects of light scattering in blood. It also has the characteristic of being difficult.

　Rather than directly photographing the object, the ghost imaging method illuminates the object with a light intensity distribution (speckle pattern) whose structure is known in advance, and reconstructs an image of the object from the information of the scattered light. This is a method to do so. Lensless single-fiber ghost imaging records the scattered light from the measurement target via an optical fiber, making it possible to capture the measurement target more clearly than with conventional endoscopes. Furthermore, in an experiment assuming a light scattering field caused by blood, conventional endoscopes cannot capture the image well, but using this method, we demonstrated that the measurement target can be reconstructed from the correlation with diffused light.

　Lensless single-fiber ghost imaging is expected to enable direct observation of pathological conditions deep within a patient's body, such as inside ultra-thin blood vessels. In conventional optical angioscopy, blood removal (flushing) using physiological saline was essential to remove the influence of light scattering by red blood cells, but in small-diameter blood vessels, the pressure inside the blood vessel Flushing that causes a sudden increase in the temperature is contraindicated. Lensless single fiber ghost imaging is expected to open the door to ultra-minimally invasive medical care that does not use flash.

Paper information:【Applied Optics】Lensless single-fiber ghost imaging