Minnesota Mining and Manufacturing Company

Literal Corporation

Laserdrive Ltd.

Chi H Chung

Theodore D Rees

Sun Lu

Ian Turner

David B Chung

A method and apparatus for increasing the information storage capacity of optical recording structures by utilizing a laser beam of different powers to produce a selected one of a plurality of different physical states. These states each produce a different optical contrast. If the number of different optical contrasts is greater than two, then encoding schemes based on three or more bits may be used to store the information thus increasing the data density on the optical recording structure, such as an optical disc. In order to promote the stability of the physical states and to enhance the speed of transition between the states, a stabiliment layer is added adjacent and covering the photosensitive layer of the disc. The stabiliment layer itself is ablated in the ablation state of the photosensitive layer.

Multi-state optical contrasts in optical recording media for data

A system for storing and retrieving encoded data on an optical recording medium using pit edge detection is disclosed. The pit extension characteristics of a given medium are determined by first using laser beam test write pulses to form one or more pits on the medium and then detecting the time durational difference between the pulse width of the test write pulses and the duration of the leading edge transitions to trailing edge transitions of the corresponding pits formed on said medium. This difference value may be stored in a certification sector of the medium. Subsequent write pulses are modified in duration in an amount equal to this detected durational difference. For forming a pit that is longer than a predetermined minimum length, the corresponding write pulse is made non-continuous in order to minimize cumulative pit extension. The number of non-continuous pulses used to form a given pit is a function of the desired length, the on time of each pulse and the duration of the off time between adjacent write pulses, said off time being a predetermined length to cause pit extension overlap between the portions of the pit formed during the one time of each said write pulse, thereby forming a continuous pit.

Apparatus and method for detecting and compensating for pit extension in

Quadrilayer optical DRAW medium which differs from prior trilayer optical DRAW media by having a thin triggering layer adjacent each of the optical spacer and light-absorbing layers. The triggering layer is a material, preferably organic, which when heated by a modulated laser-diode beam to a temperature less than the melting point of the optical spacer layer develops substantial vapor pressure or otherwise rapidly expands to implement or enhance the formation of pits or bubbles in the light-absorbing layer without disturbing the optical spacer layer or its function of protecting the substrate of the medium.

Quadrilayer optical draw medium

High brightness internal reflector for liquid crystal displays and its

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San Jose, CA, United States of America

Chi H Chung