International travelers may be in for a small suprise when it's time to revew their passports. New passports issued in Washington are machine-readable, the first step of an effort to standardize passports all over the world.

The passports, which have been issued since February, look the same as the old ones, except that the number on the front is not punched out and the photograph is not embossed. Also, on the bottom of the page with the photo are two new lines with the bearer's name and date of birth, printed so that they can be read by an optical scanner, as well as a customs official.

The only passport scanner operating now is in the passport agency in Washington to make sure that the newly issued documents have been printed correctly. But eventually, all U.S. and West European passports will be machine-readable and scanners will be installed in airports and other points of entry, said Norpert Krieg, head of the federal passport office.

The International Civil Aviation Organization has studied standardized passports since 1968, and in 1980 it recommended uniform specifications for them. The United States is the first country to issue the machine-readable passports, but all Common Market countries have agreed to use them by 1985.

Heathrow Airport near London will install scanners next February on a trial basis, although no machine-readable passports will be issued in Britain until at least next year, Krieg said. West Germany also will issue the new passports and install readers next year, he said.

Scanners will not make their debut in the United States for several years, said John Keefe, deputy assistant commissioner of the Immigration and Naturalization Service, which is responsible for installing the machines. Although the technology exists, a high-quality scanner still must be developed and marketed, he said.

Border crossing cards, used on the Mexican and Canadian borders, have been machine-readable for almost a year, and the "green cards" required of aliens have been for two years, Keefe said. But scanning equipment will not be installed at the borders for several more years, he said.

Even though some countries will not institute the new passports for some time, scanners will be used for their vistors to this country, because the United States will be issuing them machine-readable visas.

Krieg said the new passports are cheaper to produce than the old ones, because they are made by a computer process that uses less labor. One reason the new passports was that the equipment to produce passports was wearing out and a new system was needed, he said.

The new passports are being developed under a $14.8 million contract with Planning Research Corp. here, Krieg said. They may be issued in Chicago and Los Angles later this year, and across the country in three or four years, he said.