Varying focal length provides measurement accuracy

The research laboratory of Makoto Sato, graduate student Michio Sanwa, and others in the engineering department of the Tokyo Institute of Technology has developed a new method of measuring the distance to objects by taking multiple pictures with different focal points. By analyzing the degree to which the objects are out of focus, the distance can be estimated. Previously, this type of method measured objects up to 5 m away, but this new variation can measure distances up to 20 m.

An image taken by shifting the focal point over many shots is known as a multiple-focal-point image. After focusing on a single point of an object, a change in the focal point causes a degree of blurring. By tracking this change in focus, the distance to the object can be estimated. The research group has developed a camera that effectively increases the resolution, so a shallow object depth can be achieved. In this experiment, an object depth of 4 m was achieved with an object 20 m distant.

Courtesy O plus E magazine, Tokyo