Keiji Kataoka

Holographic video disk: an alternative approach to optical video disks

Optical video disks employing time sequential coding are superior to mechanical video disks because of their noncontact reproducing capability. One drawback in the optical systems is the necessity of precise focusing and tracking adjustments. To solve this problem, an alternative approach, using a holographic technique that makes it possible to store a frame of information in a specified area redundantly, is proposed. A design concept and experiments relating to the breakthroughs are described. A combination of random phase sampling holography and coherently superimposing holography makes it possible to store color-encoded images sufficient for about a 30-min motion picture on a disk of 300 mm in diameter. A sound recording technique suitable for the holographic video disk, constituting one-dimensional hologram-type, pulse-coded-modulation signals, is proposed.

Laser printer optics with use of slant scanning of multiple beams

Simultaneous scanning of multiple beams in an array is an effective method to realize high-speed and high-resolution printers. The arrayed multiple beams can be generated by devices such as grating, Wollaston prism, fiber array, and laser diode array. In any of these devices, the focused spots in an array have a period several tens of times larger than the spot diameter. We propose a simultaneous scanning method suitable for these devices in which the arrayed multiple beams are arranged in a slant angle to the scanning direction to produce consecutive scan lines. Laser print experiments with two or four beams were carried out, and high-performance printing of a 431.8-mm print width, 23.6 dot/mm (i.e., 600 dot/in.) resolution, and of 541-mm/s speed were realized.

Optics for modulating multiple beams using an asymmetric multilevel phase grating and a multichannel acousto-optic modulator.

Asymmetric multilevel phase gratings for generating even numbered beams have been designed, assuming that their phase patterns are formed by overlapping plural binary-phase patterns, each of which has an arbitrary phase height. The grating for four beams, which produces uniform and high intense diffraction orders of the minus first to the plus second order, is fabricated. The efficiency is 75.5%, although the theoretical efficiency is 79.9%. It is also demonstrated that the optics in which the beams from the grating are fed into a multichannel acousto-optic modulator through a Fourier-transform lens makes their successful modulation possible for pulse signals of 20-ns pulse duration.

Bit Shift Measurement and Overwriting in a Sampled Servo Format Magneto-Optical Recording

A new direct overwrite method, which uses oscillating laser pulses and magnetic field pulses modulated by code data, is demonstrated and the characteristics of bit shifts are discussed. A bit shift correction method is also demonstrated. In this method, preamble pits are written in the open space of the header area when data pits are recorded. In reconstruction, the phase of PLL clocks is adjusted automatically using the signal from the preamble pits.

Position sensing of a grating mark by heterodyne detection using a Zeeman laser

A way to detect with high resolution the position of a wafer and a mask is proposed and evaluated. In this method, a grating mark on a wafer or a mask is detected by heterodyne interference using a He-Ne Zeeman laser. Experiments show that the position of a wafer or a mask could be detected with a resolution of approximately 0.01 microm.