Carl Amos, an inventor in Atlanta, anticipates a return to the cash economy but without the computer-generated visual effects. Mr. Amos recently patented a way to pay for online transactions with bills and coins rather than credit or banking cards.

“In upwards of three-quarters of the world, most money transactions are cash only,” said Mr. Amos, who envisions a big market for his invention.

Basically, what Mr. Amos has patented is a new combination of existing technologies.

His patent, No. 6,554,184, covers a modified A.T.M. that not only dispenses money but, like a vending machine, accepts cash, which can be used to transfer money from one person to another or to pay for online purchases.

It’s a method patent, a new way of doing business,” Mr. Amos said. “These are off-the-shelf components. All I had to do was build the machine and write the software.”

Mr. Amos is a rare breed: an independent inventor who actually makes a living off his inventions. A former electrical engineer at I.B.M., he left corporate life to develop his idea for a holographic lens. Since he patented the lens in 1994, he estimates, he has received about $1 million in royalties.

Mr. Amos, one of six children, grew up on a farm in Ohio, where he set up his own skunk works in a shed. Not all his inventions were successful. One was a parachute to be worn while leaping off the garage. “I survived, obviously,” Mr. Amos said. “My siblings survived, too, thank goodness.”

Mr. Amos said his latest invention, should it become widely available, would obviate the need for services provided by Western Union and other money-transfer companies.

Another big market in the United States, Mr. Amos said, might be teenagers. Though they do not usually have their own credit cards, they usually have cash and are more than willing to spend it to download music or games.

Mr. Amos also said his system should appeal to those who were worried about identity theft on the Internet or who simply wanted the privacy it provided.

Gamblers may be interested in the technology. Many credit-card companies, for example, will not authorize payments to gambling sites. Nor will PayPal, the biggest third-party payment option on the Internet.

Tom Turano, a law partner specializing in banking patents at Testa Hurwitz & Thibeault in Boston, called the invention a “cute idea.”

“It’s like a funky A.T.M.,” Mr. Turano said. But the patent itself, he said, is “fairly narrow” and may be easy for others to come up with similar inventions that do not infringe the patent.

Mr. Amos, who is represented by a licensing firm in Connecticut, said he was approaching banks about licensing his patent. “Western Union and Moneygram haven’t called me yet,” Mr. Amos said. “But I don’t expect them to.”

More here.