Video High Density

Video High Density (VHD) was an analog video disc format storing up to 60 minutes per side, predominantly marketed by JVC in Japan. In contrast to the optical LaserDisc format, the VHD format was read with a physical conductive stylus. Facing numerous competing formats both in and outside of Japan, the reach of VHD remained very limited.

VHD was first demonstrated in 1978 and was eventually released in Japan on April 21, 1983. Despite demonstrating the player at several Consumer Electronics Shows, JVC opted not to release VHD as a consumer product in North America.

In the UK, Thorn EMI, which was the leading consumer provider of the VHS tape system, saw VHD as the next step in the market and committed to the system. In 1981 it invested in a factory to press discs (in Swindon) and a production unit to develop a catalogue of "interactive" titles to support a planned 1984 launch, but canceled the investment in late 1983. VHD remained on the market in the UK primarily as an educational and training tool, usually linked to a computer, but attracted few customers.

It found its main niche as a karaoke system, and was also used in video games and interactive training systems. Commercial versions were available in the UK for training, demonstration and fault diagnosis.

A stereoscopic system was also sold in Japan. These 3D VHD systems achieved the 3D effect using double-speed discs with alternate-eye images and LCS glasses to pass the correct view to each eye.

While discs continued to be manufactured in the 1980s, the format saw its last new release in 1990.^{[citation needed]}

VHD discs are 25 centimetres (9.8 in) in diameter, and store up to 60 minutes of video per side. As with CED, each disc is stored in a caddy: the user never handles the disc directly. The entire caddy is inserted into the player, and then withdrawn, leaving the disc inside where it will be loaded and start playing. At the end of the side the disc must be removed, turned over and re-inserted.

Like the RCA CED system, the signal is recorded on the discs as variations in capacitance, a conductive coating on the disc itself forming part of a resonant circuit. A diamond stylus reads the signal, though unlike CED there are no actual grooves – the stylus follows the tracks electronically, like a compact disc. This means less wear, though there is still physical contact (unlike LaserDisc) so some wear would still occur.