Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1997-12-11
2000-01-04
Tran, Thang V
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369116, G11B 700
Patent
active
060117699
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical information recording/reproducing apparatus having means for reducing undesirable radiation generated in a high frequency imposing circuit, in particular, relates to a noise protection apparatus in such an apparatus.
BACKGROUND OF THE INVENTION
In recording or reproducing operation of an optical information recording/reproducing apparatus, a high frequency imposing method in which a laser diode is driven by current imposed with high frequency current has been known for preventing laser noise which is induced by return light. The optical information recording/reproducing apparatus using high frequency imposing method, has a high frequency imposing circuit having an oscillator for switching ON/OFF a laser output light with frequency of several hundred MHz, so that vertical mode of laser beam is transformed to multi-mode, and generation of said laser noise is prevented (for instance, JP patent publication 9086/1984).
However, if oscillation frequency component of said high frequency imposing circuit is leaked into air, it is undesirable radiation (line noise, radiation noise). Therefore, the leakage should be prevented.
The radiation of undesired wave is classified to that through air space, and through coupling lines with external circuits. The former is prevented by enclosing an apparatus by conductive shield case, and the latter is prevented by a capacitor coupled between an external coupling line and ground.
FIG. 10 shows a prior optical recording/reproducing apparatus which prevents undesired radiation. In the optical recording/reproducing apparatus in FIG. 10, a portion mounting high frequency imposing circuit is sealed with a shield case 4 (conductive case).
Further, in the optical recording/reproducing apparatus, a laser diode 6 is engaged with an opening on an optical base 7, and the terminals of the laser diode are on substrate 5 for a high frequency imposing circuit, as shown in FIG. 11, which is a view in C-direction in FIG. 10 with a shield case taken off.
The external connection lines for power supply of the high frequency imposing circuit, power supply for a laser diode, and control signal of the high frequency imposing circuit are coupled with an external circuit through a respective through-hole capacitor 11 which engages with a shield case 4. Thus, the high frequency imposing circuit itself is sealed with a shield case, and the external connection lines are coupled with an external circuit through a through-hole capacitor 11, therefore, undesired radiation is prevented.
No radiation leaks through a gap between a through hole capacitor 11 and a shield case 4, by fixing the through hole capacitor to a hole provided on the shield case 4.
The through hole capacitors are coupled with a substrate 5 of a high frequency imposing circuit either through a flexible printed circuit 12 (FIG. 11(a)), or directly (FIG. 11(b)).
However, the prior optical recording/reproducing apparatus which has facility to prevent undesired radiation has the following problems which should be solved.
(1) As shown in FIG. 11, one terminal (a) of a through hole capacitor 11 must be connected to a substrate 5 of a high frequency imposing circuit either through a flexible printed circuit 12 for inner connection, or directly, and the other terminal (b) of the through hole capacitor 11 must be connected to the other flexible printed circuit 13 for external connection, therefore, the operation for mounting a through hole capacitor is complicated, and further it is difficult to reduce cost for components. Further, as a through hole capacitor occupies large area, therefore, it is difficult to reduce size of an optical recording/reproducing apparatus itself.
(2) As a shield case must have a hole for fixing a through hole capacitor, the producing steps of a shield case are complicated, and the assembling steps of the shield case are also complicated.
(3) It is preferable that external connection lines are taken out on one surface of a shield case, when we consider the wi
REFERENCES:
patent: 5495464 (1996-02-01), Fujikawa et al.
TDK Corporation
Tran Thang V
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