OKYO, March 23 — Enveloped in a green plastic raincoat, Kazutoshi Obana slowly raised his arms. Then, with a click of a button, Mr. Obana, a graduate student at Tokyo University, faded away.

In his place, a ghostly image of the cityscape directly behind him came into view.

Graduate students may be resigned to some invisibility, particularly in the eyes of their advisers, but this was something else entirely: an “invisible” raincoat, under development at the university.

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It is the brainchild of Susumu Tachi, a professor of computer science and information physics.

While invisibility has long been a plot element in films like “The Invisible Man” and the Harry Potter series, Dr. Tachi said his device was far removed from movie magic.

In his office at the university, he scoffed at Hollywood’s special-effects type of invisibility, represented most recently by the vanishing sports car in the latest James Bond movie.

“That is science fiction,” Dr. Tachi said. “But this,” he added, “is true scientific development.”

As with many true scientific developments, however, Dr. Tachi’s raincoat is clunky and cumbersome. And it is something of a special effect of its own.

Basically, a camera films a scene behind the raincoat, and a projector projects it on the garment’s front, which is covered with tiny reflective beads called retroreflectors. The process creates an illusion of invisibility.

While a raincoat may not be the most useful application of the technology — it is more for demonstration purposes — there are many potential practical uses, Dr. Tachi said. A plane could be turned into a high-tech glass-bottomed boat, for instance, with the floor a projection screen displaying images of the ground below. Or images from within the body could be projected on the skin, to aid surgeons.

“This would allow minimally invasive surgery,” Dr. Tachi said. “Now, brain surgeons often have to cut off the top of a head. This could allow a very small hole, which would be nice for the patient.”

“We are working with several surgeons, also a company that makes cockpits,” he said.

Dr. Tachi suggested another application: home builders could embed microchips containing blueprints of wiring and piping in the walls of buildings. When a repair was needed, a worker could flip a switch and see the blueprint superimposed on the wall.

Asked if this invisible technology could have military applications, say in a desert war, the 57-year-old professor flinched, quite visibly. Reflecting Japan’s deeply held pacifist ethic, universities generally shun military research.

Sukeyasu S. Yamamoto, a retired Tokyo University physics professor, explained, “There is a real allergy to anything to do with military research.”

But in the United States, where such allergies are not as widespread, the technology is called “adaptive camouflage,” and research has progressed in fits and starts, according to flows of military financing.

“We dreamed that up in 1998,” Maurice L. Langevin, a military researcher in Maryland, said of a projection concept that he said he developed with Philip I. Moynihan at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Before the military financing ran out, Mr. Langevin said, he had developed a camera projection system that “at a distance of 50 yards would make something unrecognizable and in certain conditions invisible.”

The key is a series of small cameras and the cloaking of the object in a material suitable for projection of images.

“On a tank, there were places where you would see things, like the treads,” he said from Maryland, where he runs a small military research company, Tracer Round Associates. “So we put skirts on the treads.”

In an e-mail, Dr. Moynihan, now a principal engineer at the Jet Propulsion Laboratory, said that this kind of cloaking would work best with “stationary vehicles, positions, or equipment that troops wish to hide.”

Dr. Moynihan said the use of “small and inexpensive cameras” to project a background image was accurately described by “Q,” the gadget buff, in the latest James Bond movie, “Die Another Day.” But, the real life scientist added, studio special effects created the vanishing Aston Martin that left tire tracks magically crunching through the snow.

Japanese and American scientists admit that their invisibility devices, whether cloaks or shields of walls, are really just optical illusions.

“People like to fool people,” said Steven K. Feiner, a Columbia University computer science professor who experiments in the field. Then, lowering his voice as if giving away a big secret, he added: “Magicians do this all the time. A lot of the vanishing women and the sawing of people in half — that’s done with mirrors.”