Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2000-07-28
2002-08-20
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112280
Reexamination Certificate
active
06438088
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a light transmission system for transmitting a light beam of a variable wave-length from a light source to a light receiver, an apparatus for measuring a change in distance between an optical element and an object member movable with respect to each other by using the light transmission system, and an apparatus for exposing at least a part of a surface of the object member (for example, a recording medium) by using the light transmission system.
TECHNICAL DIJEST of INTERNATIONAL SYMPOSIUM ON OPTICAL MEMORY 1998 discloses on Pd-07 regarding Deep UV mastering using an all-solid-state 266 nm laser for an over 20 GB/layer capacity disk that a positional relationship between an objective lens and a recording disk is measured from a position on a light receiver at which position a first light beam projected through the objective lens to the recording disk and subsequently reflected by the recording disk is received by the light receiver, while a second light beam is projected through the objective lens to the recording disk to expose a surface of the recording disk.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a light transmission device for transmitting securely and efficiently a light beam with a variation of wavelength from a light source to a light receiver while restraining a position on the light receiver at which position the light beam impinges from changing according to the variation of wavelength of the light beam, an apparatus for measuring correctly irrespective of the variation of wavelength of the light beam a change in distance between an optical element and a surface of an object member movable relative to each other, and an apparatus for exposing securely irrespective of the variation of wavelength of the light beam at least apart of a surface oaf object member (for example, a recording medium).
A light transmission device for transmitting a light beam with a variation of wavelength from a light source to a light receiver, according to the present invention, comprises, an optical element for receiving the light beam and projecting the light beam wherein a deflection angle between the received light beam and the projected light beam varies according to the variation of wavelength of the light beam, and a compensation optical element for receiving the light beam and projecting the light beam wherein a compensating deflection angle between the received light beam and the projected light beam varies according to the variation of wavelength of the light beam, wherein the optical element and the compensation optical element are arranged optically in series between the light source and the light receiver (the light beam may proceed from the optical element to an object, and subsequently the light beam reflected by the object may return to the optical element to proceed further toward the light receiver), the deflection angle changes in a first direction according to an increase (decrease) of wavelength of the light beam, the compensating deflection angle changes in a second direction according to the increase (decrease) of wavelength of the light beam, and the change of the deflection angle in the first direction is compensated by the change of the compensating deflection angle in the second direction so that a position on the light receiver at which position the light beam impinges is restrained from changing according to the increase (decrease) of wavelength of the light beam.
Since the change of the deflection angle in the first direction at the optical element is compensated by the change of the compensating deflection angle in the second direction at the compensation optical element so that the position on the light receiver at which position the light beam impinges is restrained from changing according to the increase (decrease) of wavelength of the light beam, the light beam is transmitted securely and efficiently from the light source to the light receiver although the deflection angle of the optical element is changed according to the variation of wavelength of the light beam.
The optical element and the compensation optical element may be arranged in such a manner that the light beam r received by the optical element, the light beam projected by the optical element, the light beam received by the compensation optical element and the light beam projected by the compensation optical element proceed along an imaginary plane. The optical element may be a lens. The compensation optical element may be a prism, diffraction grating or lens.
It is effective for compensating the change of the deflection angle in the first direction at the optical element by the change of the compensating deflection angle in the second direction that the optical element and the compensation optical element are arranged in such a manner that on an imaginary plane to be traversed by the light beam with a predetermined angle between the imaginary plane and the light beam, a direction in which a position on the imaginary plane to be passed by the light beam is changed by the change of the deflection angle according to the increase (decrease) of wavelength of the light beam is opposite to a direction in which the position on the imaginary plane to be passed by the light beam is changed by the change of the compensating deflection angle according to the increase (decrease) of wavelength of the light beam.
It is preferable that the compensation optical element is arranged to receive the light beam projected by the optical element and to project the light beam toward the light receiver, that is, the compensation optical element is arranged at a downstream side of the optical element in a light beam proceeding direction.
It is effective for compensating the change of the deflection angle in the first direction at the optical element by the change of the compensating deflection angle in the second direction that a direction in which the position on the light receiver at which position the light beam impinges is changed according to the change of the deflection angle in the first direction is opposite to a direction in which the position on the light receiver at which position the light beam impinges is changed according to the change of the compensating deflection angle in the second direction.
It is effective for compensating the change of the deflection angle in the first direction at the optical element by the change of the compensating deflection angle in the second direction that the optical element and the compensation optical element are arranged in such a manner that the light beam received by the optical element, the light beam projected by the optical element, the light beam received by the compensation optical element and the light beam projected by the compensation optical element proceed along or on an imaginary plane, and the first direction is opposite to the second direction as seen in a proceeding direction of the light beam.
The optical element may be adapted to face to an object member, and the light beam projected by the optical element may be received by the light receiver after being reflected by the object member. When the optical element is a lens, the lens is arranged to prevent the light beam from proceeding along a symmetrical axis of the lens around which symmetrical axis the lens is substantially symmetrical, so that the deflection angle of the light beam at the optical element changes according to the change of wavelength of the light beam. The light transmission device may further comprise a supplemental lens arranged to convert the light beam projected by the light source to a convergent light to be received by the optical element. When the optical element and the object member are movable relative to each other, the optical element is arranged to prevent a direction in which the light beam proceeds from the optical element to the object member from being parallel to a direction in which the optical element and the object member are movable re
Kadotani Masanori
Sugiyama Toshinori
Birch & Stewart Kolasch & Birch, LLP
Hindi Nabil
Hitachi Maxell Ltd.
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