Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-03-30
2001-05-01
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044250, C369S112040
Reexamination Certificate
active
06226238
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an optical disc master recording device which is used to make an optical disc master.
As is conventional, various optical disc master recording devices have been used for creating an optical disc master of a compact disc, laser disc, or the like. These commonly known optical disc master recording devices have been constituted such that information is helically recorded on an optical disc master composed of a glass plate having an abraded surface on which a photoresist layer is formed. This recording operation is performed by rotation controlling the optical disc master so as to rotate at a predetermined rotational speed and by sequential feed controlling laser light gathered with an objective lens in an optical head in the radial direction of the optical disc master.
Coarse and fine adjustments are performed so that a spot position of the laser light is caused to agree with a target spot position. The coarse adjustment is performed by causing the entire optical head to drive in the radial direction of the optical disc master and the fine adjustment is performed by causing the objective lens to drive in the radial direction with an actuator in the optical head. In this case, a center position of the objective lens is made the spot position of the laser light, so that the coarse and fine adjustments described above are performed by detecting the center position of the objective lens and then by causing the optical head and actuator to drive so as to eliminate the amount of space between the center position of the objective lens and the target spot position.
Over the years, in order to significantly improve a recording density of the optical disc, information has to be recorded with extremely small track pitch and bit as compared with conventional techniques. However, there is a limit to form a significantly small light spot only with the objective lens as compared with a current light spot.
Incidentally, a method using a solid immersion lens (hereinafter referred to as SIL) is known as a method for further converging the laser light gathered by an objective lens.
FIG. 1
in accompanying drawings illustrates the condition in which a laser light gathered by an objective lens is further converged by an SIL. The laser light from a light source (not shown) is converged by the objective lens A to be incident on the SIL C which is held in a floating head B. The incident laser light is further converged by the SIL C and exposed on an optical disc master D. Incidentally, the objective lens A and SIL C are configured such that they can be driven independently. The number of aperture of the objective lens A can be substantially increased by the SIL C, resulting in the formation of a minute light spot on the optical disc master.
Since two kinds of lenses are provided in an optical disc master recording device having an optical head with the objective lens and SIL shown in
FIG. 1
, the center position of the objective lens or SIL does not correspond to the spot position of the laser light, respectively. In other words, the positional relationship between the objective lens and SIL causes the position of the light spot to change. Therefore, the position of the light spot on an optical disc master can not be determined only by detecting the center position of the objective lens, as with the devices having been proposed in the prior art. Accordingly, there was a problem in which the current position of the light spot can not be controlled to approach the target spot position in the conventional method.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described background, and therefore, has an object to provide an optical disc master recording device which can ensure to control a position of a light spot even if both an objective lens and SIL are attached to an optical head thereof.
In order to achieve the object described above, according to one aspect of the present invention, an optical disc master recording device is provided which comprises an objective lens for gathering a recording light irradiating an optical disc master, a solid immersion lens for further converging the recording light gathered by the objective lens, first drive means for driving the objective lens to a radial direction of the optical disc master, second drive means for driving the solid immersion lens to the radial direction of the optical disc master, means for determining a center position of the objective lens from a reference position in the radial direction, means for determining a center position of the solid immersion lens from the reference position in the radial direction, means for calculating a spot position of the recording light on the optical disc master according to the center positions of the objective lens and the solid immersion lens, and control means for controlling the first and second drive means so as to approach the calculated spot position to a target spot position.
According to another aspect of the present invention, an optical disc master recording device is provided which comprises an objective lens for gathering a recording light irradiating an optical disc master, a solid immersion lens for further converging the recording light gathered by the objective lens, first drive means for driving the objective lens to a radial direction of the optical disc master, second drive means for driving the solid immersion lens to the radial direction of the optical disc master, means for determining a center position of the solid immersion lens from a reference position in the radial direction, means for detecting amount of space of the center position of the objective lens with respect to the center position of the solid immersion lens, means for calculating a spot position of the recording light on the optical disc master according to the amount of space and the center position of the solid immersion lens, and control means for controlling the first and second drive means so as to approach the calculated spot position to a target spot position.
The control means is preferably configured such that the difference between the calculated spot position and the target spot position is formed as a tracking error signal and the first and second drive means are controlled in accordance with the tracking error signal.
In addition, the control means is configured to control the second drive means in accordance with low frequency components of the tracking error signal.
In the optical disc master recording device according to the present invention, even if the objective lens and the solid immersion lens deviate from the respective target spot positions during recording, the control means may control the first and second drive means so as to adjust the spot positions calculated in accordance with the center positions of the objective lens and solid immersion lens to the target spot positions, so that it is ensured that the light spot position on the optical disc master can be adjusted to the target spot position.
REFERENCES:
patent: 5729393 (1998-03-01), Lee et al.
patent: 6157598 (2000-12-01), Mowry et al.
Arent Fox Kintner & Plotkin & Kahn, PLLC
Edun Muhammad
Pioneer Electronic Corporation
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