Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Of record carrier
Reexamination Certificate
2000-03-16
2004-10-19
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Of record carrier
C369S053200
Reexamination Certificate
active
06807136
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for reading from and/or writing to optical recording media which has a disk type identification means for identifying the type of recording medium, and also to a corresponding method.
2. Prior art
An apparatus of this type is disclosed in U.S. Pat. No. 5,414,684. In the case of this known apparatus, in order to identify the type of recording medium first of all an attempt is made to read the list of contents thereof, the so-called TOC or Table of Contents. If it is not possible to read the TOC, then one or a number of renewed attempts are made to read information at one or a number of other locations on the recording medium. The type of optical recording medium is inferred from the success or lack of success of these attempts.
What is disadvantageous about the known apparatus is that a complete set-up operation has to be performed for each attempt to read information. This operation includes, inter alia, the closing of focus regulating circuit, track regulating circuit, drive regulating circuit and the like. This procedure is relatively complicated and time-consuming.
SUMMARY OF THE INVENTION
An object of the invention is to propose an apparatus having disk type identification means which is able to reliably identify the type of the recording medium inserted into the apparatus within a short-time. A further object of the invention is to specify a corresponding method.
According to the invention, these objects are achieved by means of the features specified in the independent claims. Advantageous developments thereof are specified in the dependent claims.
According to the invention, the disk type identification means has a mirror signal detector, a threshold value generator, a counter and an evaluation unit. This has the advantage that rapid identification of the type of recording medium is attained. The disk type identification means has elements with a relatively simple function which enable information about the type of disk to be obtained even when the recording medium cannot yet be read even though the focus regulating circuit is closed. The mirror signal is a signal which assumes different values if the scanning means is scanning an information track or a region between two information tracks. In this case, the region located between two information tracks may be free of information, but it may also itself carry information, for example control information or else information of a kind which corresponds to that of the information tracks.
According to the invention, an input of the mirror signal detector is connected to an output of the scanning means and a further input is connected to the threshold value generator, and the counter is connected to an output of the mirror signal detector and to an input of the evaluation unit. In the case of this advantageous combination of the individual elements, the threshold value generator specifies a threshold value for the formation of the mirror signal. The counter counts the occurrence of specific states of the mirror signal, for example the number of high or low states, corresponding transitions, zero crossings or the like. The evaluation unit evaluates the counter reading for the purpose of determining the type of recording medium.
An advantageous development of the invention provides for the apparatus to have a layer thickness identification means. This has the advantage that the layer thickness identification means supplies an additional criterion by means of which specific settings of the apparatus are suitably preselected in order further to accelerate the identification of the type of disk. In addition or as an alternative, the additional criterion also serves as a criterion for the identification of the type of disk, thereby accelerating the identification or increasing its reliability. The layer thickness identification means serves for determining the thickness of a protective layer which is superposed on an information-carrying layer of the recording medium.
A further variant of the invention provides for the apparatus to have a spacing identification means for determining the spacing of different layers of the recording medium from one another. This additional criterion also contributes to accelerating and/or to increasing the reliability of the identification of the type of disk. In this case, the various levels are advantageously two or more information layers. However, it is also likewise within the scope of the invention for the layers to be other layers which are present in the structure of the optical recording medium and can be detected.
The invention's method for identifying the type of an optical recording medium has the following method steps: aa) focusing onto an information layer of the recording medium; bb) setting of a threshold value for the generation of a mirror signal; cc) counting of transitions of the mirror signal; dd) determination of the type of the recording medium using the count. This has the advantage that a tracking mode and signal identification, that is to say reading of the information stored on the recording medium, are not necessary, which enables the type of disk to be identified rapidly. As soon as the type of recording medium has been identified, apparatus settings which are adapted to this type of recording medium, in particular for focus, tracking and other regulating circuits, are selected. As a result, the start-up phase, that is to say the time from the insertion of the recording medium into the apparatus or from the issuing of a start command until the beginning of playback or recording, can be kept short. Consequently, the waiting time for the user is advantageously shortened.
According to the invention, in step dd), the recording medium is determined as being associated with an nth type if the count lies in an nth range of values, where n is an integer. This has the advantage that, if appropriate, a multiplicity of different types of recording media can be identified without the counts necessarily having to be exact. In the simplest case a check is made to see whether the count is greater or less than a limit value. This limit value is regarded as the limit between two ranges of values. In the extreme case, a single type of recording medium is identified for example by virtue of the fact that the count is greater than a limit value. For n=2, by way of example, the recording medium is determined as being associated with a first type if the count lies between zero and a first value m
1
, while it is determined as being associated with a second type if the count lies between a second value m
2
and a third value m
3
. In this case, it is perfectly possible for the start value m
0
also to be a value other than zero, or for the first value m
1
and second value m
2
to be identical. The same applies correspondingly to three or a larger number of disk types to be identified.
An advantageous development of the method provides for the scanning beam of the scanning means of the apparatus to be moved across a region of the recording medium which is larger than a region which corresponds to the maximum eccentricity that occurs. This had the advantage that more rapid and more reliable identification is made possible by the large number, achieved as a consequence, of information tracks crossed by the scanning beam. In this case, the eccentricity includes both the production-dictated eccentricity of the recording medium, that is to say the circular or spiral information tracks thereof which are not centred exactly with respect to the axis of rotational symmetry, and eccentricity engendered by operation, for example due to inexact centring of the recording medium in the apparatus. The eccentricity is subject to tolerance ranges which, in practice, are generally not exceeded and which serve here as a lower limit for the induced movement of the scanning beam.
An advantageous refinement of the invention provides for steps bb) to cc) to be performed a number of times, a different th
Davenport Francis A.
Fried Harvey D.
Psitos Aristotelis M.
Thomson Licensing S.A.
Tripoli Joseph S.
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