In focus near and far – at the same time

Charles T. Troy, charlie.troy@photonics.com

Researchers at the University of Toronto have developed a new distance-mapping principle that delivers automatic real-time focus of both near- and far-field images, simultaneously and in high resolution. Called the Omni-focus Video Camera, it is described as a “breakthrough in video camera design.” The researchers say that this capability can be broadly applied in industry, including manufacturing, medicine, defense and security – and ultimately in the consumer market.

Inventor and principal investigator of the Omni-focus Video Camera, professor Keigo Iizuka of the Edward S. Rogers Sr. Department of Electrical and Computer Engineering explains that “the intensity of a point source decays with the inverse square of the distance of propagation. This variation with distance has proven to be large enough to provide depth mapping with high resolution. What’s more, by using two point sources at different locations, the distance of the object can be determined without the influence of its surface texture.” This principle led Iizuka to develop the Axi-Vision, a distance-mapping camera. Abbreviated “Divcam,” the divergence-ratio camera is a key component of the new device.

The images of the doll (taken with a prototype using two-color video cameras) clearly demonstrate how the omnifocused output, on the left, dramatically differs from that of a conventional camera, shown at right.

The Omni-focus is produced in collaboration with consulting investigator Dr. David Wilkes, president of Wilkes Associates, a Canadian high-tech product development company. It contains an array of color video cameras, two Sony XC color cameras and an XCR150 IR camera, each focused at a different distance, and an integrated Divcam. The Divcam maps distance information for every pixel in the scene in real time. Iizuka said that the number of cameras can be increased using additional beamsplitters.

A software-based pixel correspondence utility, using prior intellectual property invented by Wilkes, employs the distance information to select individual pixels from the ensemble of outputs of the color video cameras to generate the final “omni-focused” single-video image.

“The Omni-focus Video Camera’s ability to achieve simultaneous focus of all of the objects in a scene, near or far, multiple or single, without the usual physical movement of the camera’s optics, represents a true advancement that is further distinguished in terms of high resolution, distance mapping, real-time operation, simplicity, compactness, lightweight portability and a projected low manufacturing cost,” Wilkes said.

This image illustrates the Omni-focus Video Camera’s high-pixel resolution. Although the two sewing needles were photographed approximately 1.2 m apart, both are in sharp focus. Note that the eye of the back needle is actually viewed through the eye of the front needle.

Iizuka predicts that the device, although still in the research phase, could have an impact on several industries, such as in the following applications:

TV studio cameras. One example is a musical concert that is being televised by a major network. Even though the singer is in sharp focus, band members in the background are invariably blurry. Conventional video cameras are unable to focus on both simultaneously, but the Omni-focus Video Camera would remove this limitation and allow higher-quality video images.

Medical applications. Iizuka said, “I’d like to apply the principle of the Omni-focus Video Camera to the design of a laparoscope. It would help doctors at the operating table if they can see the entire view without touching optics of the laparoscope, especially if dealing with a large lesion.” This would work “because the size of endoscopic cameras is shrinking, and not all of the components need to be on the shaft of the laparoscope.”