Imagine taking a photograph and then being able to seamlessly change the focus of the image once the image has been captured. This is what technologists from Hitachi have developed. The associated hardware also means that the camera is much lighter and thinner than comparable technology, making the camera a plus for the next generation of smartphones.
The camera works, Phys.org explains, by reproducing an image at an arbitrary point of focus even after the image has been captured. This is possible due to a new field called “computational photography” and it is based on image processing being undertaken after images have been captured.
The science behind the technology is based on the principle of moiré fringes (these are generated from superposition of concentric circles). Often these effects are distracting. Think about watching television. Sometimes curved and shimmering fringes on fabrics like the distracting flashing colors on a television newsreader’s check jacket occur. These are a manifestation of moiré patterns and fringes. However, this same distraction can provide the basis of a new camera technology.
With the camera, moiré fringes can be analyzed to determine the incident angle of light. The camera can then use a computer program based on a mathematical function called the Fourier transform to capture a final image. The Fourier transform decomposes a function of time (a signal) into the frequencies that make it up.
This process combines a function for adjusting focus after images are captured in the same manner as a conventional light-field camera. In physics, moiré fringes are large scale interference patterns produced when an opaque ruled pattern with transparent gaps is overlaid on another similar pattern. In a different application, many banknotes exploit the tendency of digital scanners to produce moiré patterns.
The success with developing such a lensless camera is with knowing which measurements to take and how to reassemble them. Cameras of this design use only a single sensing pixel to take photographs. For this there are only two key components: an aperture assembly and a sensor. An image is formed by a sensor recording the light from a scene that has passed through a random array of apertures in a liquid crystal display panel.
As well as mobile platforms, CNET reports that Hitachi aims to utilize lensless photography in automated driving, vehicles, robotics and with CCTV. With surveillance CCTV, for example, the faces of people are often blurred due to low focal ranges. With lensless camera technology still images can be adjusted from a range of depths to identify people more clearly.
The new technology was presented at the International Workshop on Image Sensors and Imaging Systems (IWISS16), which took place at the Tokyo Institute of Technology during November 17th to 18th, 2016. The company is planning to commercialize this technology in 2018.
