Ryoichi Imanaka

Ultrahigh accuracy 3-D profilometer

An ultrahigh accuracy 3-D profilometer using a laser heterodyne interferometer has been developed. The profiles of aspheric lenses and their molds have been measured. It can measure not only the rectangular coordinates but also the polar coordinates of the surface profile. The measuring accuracy of each of the three axes is 0.01-0.05 microm if the inclination of the investigated surface is less than +/-25 degrees . The accuracy of the polar coordinate measurement is also better than 0.05 microm when the inclination of the aspheric surface is less than +/-55 degrees . The dynamic range of the X-Y-Z measurement is 40 x 40 x 20 (mm).

Reproducing-only and recordable-reproduceable optical discs and common optical disc player therefor

The combination of recordable-reproduceable optical discs and reproducing-only optical discs and an optical disc player which is capable of reproducing recorded signals both from the recordable-reproduceable optical disc possessing pregrooves and the reproducing-only optical disc possessing recording pits by means of a common optical system. The common optical system has a common laser for irradiating both types of discs with a laser beam used for reading the discs. The wavelength of the laser is λ and the depth or height of the pregrooves of the recordable-reproduceable optical disc is made equal to or less than λ/8n, and the depth or height of the recording pits of the reproducing-only optical disc is made equal to or greater than λ/8n but less than λ/4n, wherein n is the refractive index of the substrate of the disc or the protective layer provided on the surface thereof.

Video And Audio Disk File System

A new disk format and a new recorder were developed, based on the still picture disk file system which was put on the market a few years ago, whereby a video disk system that permits concurrent continuous recording of video and audio signals has been developed. In order to achieve a prolonged. recording time, the disk track pitch was narrowed from the conventional 2.5 μm to 1.6 μm and a contrivance was also made circuit-wise to eliminate the resulting cross talk interference. Because of these innovations, 13.3 minutes (24,000 frames) of continuous recording is now realized on a disk 20 cm in diameter. For a continuous recording of sound signals, a continuous track is necessary. To solve this problem, a spiral track was developed in lieu of the conventional concentric track. To indicate addresses, this track is locally interrupted. Such interruptions would normally interfere with sound recording but such interferences could be prevented by selecting the optimum relation between, the length of interruptions and the sound carrier frequency.

A High-Density Phase-Change Optical Disk System Possessing Read/Write Compatibility with 90 mm Magneto-Optical Disks

High-density recording characteristics of phase-change optical disks were studied using 2-7 pulse-position-modulation (ppm) in-groove recording. Carrier-to-noise-ratio (CNR) was over 50 dB at a mark length of 0.60 µm and the crosstalk at the track pitch of 1.10 µm was less than -30 dB. In addition, a 256 MB 90 mm overwritable PC optical disk system having read/write compatibility with the ISO 128 MB MO disk has been developed based on the acquired results. The drive is based on the 90 mm MO drive at a wavelength of 780 nm and NA of 0.53. The user capacity of 256 MB was achieved using a mark length of 0.63 µm, track pitch of 1.25 µm, 2-7 ppm in-groove recording, and MCAV with 10 zones. The number of sectors per track was varied from 31 to 49.

Recording and Playing (R/P) System Having a Compatibility with Mass Produced Replica Disc

It has now been several years since the first laser video disc system made its debut on the market and the years since then have seen the development of many new applications utilizing various features of the system. The most outstanding features of the laser video disc system are high recording density, high speed of information retrieval, and high speed of copying of information.