Corporate Japan is on display here at this country's third international exposition, the technology-oriented Science Expo '85. The expo site is 32 miles north of Tokyo in Tsukuba, a city the Japanese created in 1963 for scientific research. It's a one-hour, 45-minute trip from downtown Tokyo hotels by subway, train and bus.

Halfway through a six-month run that will end in mid-September, Tsukuba Expo has had 10 million visitors, precisely on schedule for the expected 20 million total.

Admission is 2,700 yen (about $11), less than that for younger people and kids. The train and bus fares from Tokyo's central station add another 2,900 yen (or $12). Travel bureaus offer tourists a one-day package for 13,000 yen, or about $52.

Ryo Saji, assistant manager of the foreign press office for Expo, told me that the typical crowd on a busy Saturday or Sunday will run between 120,000 and 150,000. The peak attendance so far was 230,000 on a special day for children last May.

But Expo '85 is rated as something less than a smashing success by the Japanese, who apparently were more excited by their first World's Fair at Osaka in 1970.

For one thing, despite the scientific theme, there are no spectacular innovations at Tsukuba, because the Japanese decided not to display their most advanced technology. Another complaint comes from the local community, whose hotels have remained mostly empty: The Japanese visitors come early in the morning with their kids, and go back to Tokyo in the evening.

Finally, it remains to be seen whether the government's hope that the publicity would focus attention on Tsukuba science city itself will pay off. It's not yet clear that private companies are scrambling for permanent locations on the fair site once the pavilions and futuristic exhibits are torn down.

But the people who come here enjoy the day, as I did, although there can be a wait for as much as two hours to get into one of the more popular pavillions, such as the Japan IBM, Fujitsu or NEC buildings, each of which boasts a large-screen show based on computerized images.

In a way, the whole scene, dominated by an 82-foot-high Sony "jumbotron" television screen, is a tribute to Japan's smashing successes in world trade. The jumbotron, equal to about 10,000 normal TV screens, can be seen from almost any place at the fair. A spokesman said Sony plans to make half-size models for racetracks and arenas.

For an American visitor, Tsukuba Expo doesn't have the noise and bustle generated by an American crowd. (I have the same complaint about Japanese baseball fans: Except for organized cheering sections, Japanese fans sit quietly in the stands, drink their beer and aren't very vocal. Japanese baseball is made to sound much more exciting by Japanese TV-hype than it really is.)

Even in the rain, the Japanese at the Expo wait patiently to get into the more popular exhibits. What they get for their patience is a magic world of voice-activated computers and robots, electronic marvels and gadgets, and huge screen shows simulating space travel generated by computers rather than conventional film, some of them using three-dimensional images.

It is all vaguely reminiscent of the Hayden Planetarium in New York, and of the big-screen shows at the National Air and Space Museum in Washington.

Among the more innovative pavilions I visited is NEC's C&C -- for computers and communications. The main C&C show is a journey to outer space: Each seat in the theater has a computer screen attached, allowing the audience (by touch control) to "vote" on the right course to take to avoid a meteor. NEC claims that there are 81 possible variations of the adventure.

But what caught my attention at NEC was a computer-edited daily newspaper, the Tsukuba Satellite Newspaper, published by ECC with the cooperation of the Asahi Shimbun. The news is edited at the Tokyo office of Asahi, converted into electronic signals, and fed by the Sakura 2 satellite to the NEC pavilion's color presses. NEC claims that this is the first time in Japan a communications satellite has been used for newspaper publication.

A popular exhibit in the Japanese theme pavilion is a piano-playing robot that, after putting a sheet-music display into its memory, fingers the keys into -- of all things -- "London Bridge Is Falling Down."

I admit to a sense of nationalistic pride in the United States pavilion, staffed by Japanese-speaking young Americans. For example, Lena Marshall of San Francisco was holding forth the day I attended, explaining the progression of computer technology from the first Eniac installation in 1944 to present-day miniaturization.

I asked the Japanese friend who accompanied me to Tsukuba how good Marshall's Japanese was. "Absolutely perfect," he said. If Marshall can do it -- three years of study, including one year in Tokyo -- why not American businessmen?