Hitachi Lensless Camera Adjusts Focus after Image Capture

JCN Newswire: Hitachi develops a camera technology that can capture video without using a lens and adjust focus after the capture by using a film imprinted with a concentric-circle pattern instead of a lens. Since it acquires depth information in addition to planar information, it is possible to reproduce an image at an arbitrary point of focus even after the image has been captured. Hitachi is aiming to utilize this technology in a broad range of applications such as work support, automated driving, and human-behavior analysis with mobile devices, vehicles and robots.

Hitachi camera is based on the principle of Moiré fringes (that are generated from superposition of concentric circles)−that combines a function for adjusting focus after images are captured in the same manner as a light-field camera and features of thinness and lightness of a lensless camera which computational load incurred by image processing is reduced to 1/300. The two main features of the developed camera technology are described as follows.

(1) Image processing technology using Moiré fringes

A film patterned with concentric circles (whose interval narrow toward the edge of the film) is positioned in front of an image sensor, and the image of a shadow formed by a light beam irradiated onto the film is captured by the image sensor. During the image processing, a similar concentric-circle pattern is superimposed on the shadow and Moiré fringes with spacing dependent on the incidence angle of a light beam are formed. By utilizing the Moiré fringes, it is possible to capture images by Fourier transform.

(2) Focus adjustment technology of captured images

The focal position can be changed by changing the size of the concentric-circle pattern superimposed on the shadow formed on the image sensor by a light beam irradiated onto the film. By superposing the concentric-circle pattern by image processing after image capturing, the focal position can be adjusted freely.

To measure the performance of the developed technology, an experiment with a 1-cm2 image sensor and a film imprinted with a concentric-circle pattern positioned 1 mm from the sensor was conducted. The results of the experiment confirmed that video images could be captured at 30fps when a standard notebook PC was used for image processing.