IF you have an impression from the nightly news that Japanese homes are filled with high-definition televisions (HDTV) - the sets with cinema-shaped screens and crystal-clear pictures, touted as the video revolution of the '90s - please adjust your mental screen. Japan is not awash in HDTV, not even a pixel's worth. In fact, no Japanese consumer can yet buy HDTV in a store, and it could well be into the 21st century before any sets are available to consumers here.
Yet HDTV is more visible in this country than almost anywhere else: At the Toto, Ltd., showroom on the 27th floor of a spanking-new Tokyo high-rise, customers choose kitchen and bathroom fixtures displayed on an HDTV screen. The screen is linked to a computer that can show what a kitchen set would look like in, say, 28 different colors.
In the lobby of the Sezon Museum of Art across town, museumgoers sit before a 9-by-15-ft. projection screen, examining detailed images of the museum's collection of ceramics and a featured exhibit of works by Gustav Klimt. Visitors ``ooh'' and ``ahh'' at video enlargements as breathtakingly vivid as if seen through a window.
From 2 to 3 p.m. each weekday at Tokyo's downtown central post office, people can watch HDTV telecasts (known here as ``Hi-Vision'') from NHK, this country's public broadcasting system. A mixture of sports, nature films, dramas, and more are shown on the screen, while images from the nation's eight other stations flicker from a conventional TV nearby. Similar HDTV demonstrations are shown in about 90 public locations nationwide.
But walk into any of the booming, multistoried electronics outlets here, and you will get blank stares if you ask to purchase an HDTV set. Ask for printed information, and the salesman will tell you, ``We have no such thing.''
In-home use of HDTV here is still five to 10 years away, by most accounts. Even then, due to the $20,000 price of receiving sets, regular use may be far more limited than that of conventional TV. Apart from the HDTV sets placed by NHK in public locations for experiment and display, there are about 100 other sets in the industrial showrooms of such electronics giants as Sony, Matsushita, Sanyo, Hitachi, Sharp, and Toshiba.
In an interview in his office at the Ministry of Industry and Trade (MITI), Yoshiki Mikami, senior officer for visual industry planning, waxes enthusiastic about the industrial, medical, and educational uses of HDTV.
He mentions a hookup that offered Japanese buyers superior images of paintings in a recent two-continent auction conducted in France. He says local universities are using HDTV images in medical lectures and video libraries. He shows me a book of photographs, striking in detail, as evidence of the kind of image-processing HDTV can offer and suggests the technology may revolutionize publishing.
But HDTV in the home? ``That is secondary,'' he says. ``Not widespread until the 21st century.''
NHK has taken the lead in developing HDTV since 1970. Yutaka Masuko, spokesman for NHK, predicts that 1 million sets will be in use by 1995.
He mentions the one-hour daily demonstration programming as a catalyst for the industry to produce cheaper sets. A satellite to be launched next year will devote one channel to round-the-clock HDTV broadcasts.
Mr. Masuko also mentions other special events, such as horse races and concerts, which have been distributed in HDTV format to isolated areas by cable or satellite. And he mentions coverage of the Seoul Olympics, from which stunning HDTV images were transmitted to Japan and elsewhere.
``It is the unstoppable wave of the future,'' he says.
Both MITI and NHK are engaged in public-relations offensives to capture the attention of the Japanese public. They are also working closely with manufacturers to make the sets affordable.
Interviews with executives from such companies as Matsushita, Mitsubishi, and others put the timetable for widespread use somewhere between those of MITI and NHK, at 5 to 10 years. Even then, they say, the sets will be far more expensive than today's standard sets, perhaps three times the price.
So far public enthusiasm seems muted.
``We are not so excited about it,'' says Kazuyoshi Momohara, an executive of Fuji Keizai Company, an international marketer. ``The programming is not so interesting.... So who cares if the pictures are so good?''
``I've never heard of it,'' says Prof. Tsutomu Tsukamoto, who teaches biochemistry in Kyoto. ``It's not part of the daily life. Maybe they are testing, but I know nothing about it.''
The Japanese have poured an estimated $1 billion into developing HDTV since 1970, compared to an estimated $100 million spent in the United States and about $200 million invested by European governments and companies.
Despite a relatively slow start, recent reports in the US have shown interest in an entirely different form of digital technology that could make the Japanese analog technology seem outdated by comparison.
Since there are as yet no international broadcast standards, the race to develop HDTV goes beyond the goal of superior images and sound to that of product development: television sets; video systems for educational, military, and industrial uses; and the computer chips that drive them.
``The companies and countries that control the development of HDTV will have a huge lead in the coming competition for leadership in the electronics world,'' said Rep. Edward J. Markey (D) of Massachusetts, chairman of the House subcommittee on telecommunications, in recent Congressional hearings.
The sole surviving US builder of television sets, Zenith, recently sold its personal-computer business to focus on HDTV development. Estimates as to when Zenith's digital technology will be ready for transmission are also 5 to 10 years.
It is hard to find anyone who denies that an affordable HDTV system would rapidly gain a place as the next generation of TV equipment for our video culture.
``Not since the introduction of color into the world of black and white over 30 years ago has TV in this country been on the threshold of as dramatic a change as it is today,'' says Brenda Fox, general counsel and vice-president for special policy projects at the National Cable Television Association.
Not to be confused with IDTV (improved definition television) or ARTV (advanced resolution TV) - both of which are marketing catchwords used by various companies - HDTV increases the number of TV scanning lines from the current 525 to 1,125. The width-to-height ratio of the screen has been changed to match the wide screens in movie theaters.