Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2000-01-04
2002-05-07
Hudspeth, David (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S112290, C369S124020, C369S053310
Reexamination Certificate
active
06385147
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to simultaneously reading and writing on an optical medium such as an optical tape.
BACKGROUND OF THE INVENTION
Direct Read After Write (DRAW) has been recognized as a design option for optical recording systems since the earliest introduction of the technology. (See Marchant,
Optical Recording: a Technical Overview
, Addison Wesley, 1990, p304.) As illustrated in
FIG. 1
, a prior art optical head
10
is schematically shown. A record laser
12
directs a beam of light through an objective lens
14
which is focused on a recording spot
16
on a moveable optical medium
18
that is moving in a direction
25
relative to the optical head. Also, a read laser
20
directs a beam of light through a beam splitter
22
and the objective lens
14
onto the surface of the moveable optical medium
18
to form a read spot
24
. This beam of light is reflected back to the beam splitter
22
which directs the light beam to a detector
26
shown as a photodiode.
More particularly, the beam from the read laser
20
is unmodulated and is focused on the moveable medium
18
downstream from the recording spot. Reflection of the read laser beam from the medium is modulated by the presence of marks on the recording medium newly recorded by the record laser beam. The detector
26
reconstructs the recorded data for comparison with the data just processed for recording. This is why this process is called Direct Read After Write, or DRAW. DRAW provides nearly instantaneous verification of recorded data reliability, eliminating the latency encountered with conventional, second-pass verification.
In optical recording, there must be some level of verification that the recording medium will support error free recording and reproduction. When optical tape is the medium of choice, there is also a requirement that the recording system can record and read bi-directionally, that is, when the tape is either moving in a forward or reverse direction. A problem with optical tape recording systems is that existing DRAW heads do not have this functionality.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide apparatus which provides DRAW functionality when the optical recording medium is moveable bi-directionally in either forward or reverse directions.
This object is achieved by an apparatus for simultaneously recording and reading information on a medium moveable in forward and reverse directions, comprising:
a) means including a first record laser and establishing a first beam path for recording information on the moveable medium;
b) means including a second read laser and at least one read-out detector and establishing a beam path over which light from the second laser illuminates the medium and is reflected to the detector which reads recorded information; and
c) means for adjusting the relative position of the first and second laser beam paths so that, in a first position, when the medium is moving in the forward direction, the first and second laser paths are arranged in close proximity so that the detector reads information which was just previously recorded by the record laser and that, in the second position, when the medium is moving in the reverse direction, the first and second laser paths are arranged in close proximity so that the detector reads information which was just previously recorded by the record laser.
ADVANTAGES
The present invention has as an advantage that it permits the DRAW read beam to be focused at a position downstream from the recording beam, with respect to scanning of the medium during recording. In the prior art, if the media velocity is reversed, as in serpentine recording on optical tape, the DRAW beam is sometimes positioned on the upstream side of the recording beam, and therefore cannot detect the recorded pattern.
A feature of the present invention is that it provides verification without requiring prior art methods of pre-scanning for media defects or multiple-pass readout for data verification.
REFERENCES:
patent: 5105403 (1992-04-01), Knado et al.
patent: 5191204 (1993-03-01), Dickson et al.
patent: 5216562 (1993-06-01), Luecke et al.
patent: 5948288 (1999-09-01), Treves et al.
patent: 6058092 (2000-05-01), Masters et al.
“Optical Recording: a Technical Overview” by Alan B. Marchant, Addison-Wesley Publishing, 1990, p304.
Eastman Kodak Company
Hudspeth David
Owens Raymond L.
Patel Gautam R.
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