The present invention generally relates to method and apparatus for preventing duplex recording on information recording mediums, and more particularly to a method and apparatus for preventing duplex recording of an information signal in a portion of an information recording medium pre-recorded with an address signal and another information signal.
There are information recording mediums pre-recorded with an address signal before an information signal is recorded thereon, and information recording mediums recorded with an information signal together with an address signal. In such information recording mediums, it is not only possible to record an information signal on successive tracks, but it is also possible to skip a predetermined number of tracks and leave unrecorded tracks which may be later recorded with another information signal. It is possible to divide a total recording region of the information recording medium into a plurality of divided regions which are to be recorded with different kinds of information signals, so that the recording can be carried out for each kind of information signal. In other words, the information signals may be recorded on these information recording mediums in a variety of ways.
However, when recording the information signals on the information recording mediums in the variety of ways, it is necessary to accurately discriminate the pre-recorded tracks and the unrecorded tracks so as to prevent a duplex recording in which an information signal is erroneously recorded on a pre-recorded track which is pre-recorded with another information signal. It is essential that the duplex recording is prevented in a type of an information recording medium which can be recorded only once with an information signal, because the signal recorded on the pre-recorded track of this type of information recording medium cannot be erased. In other words, if the information signal is newly recorded on the pre-recorded track which is recorded with the previously recorded information signal, both the previously recorded information signal and the newly recorded information signal will be destroyed and neither the previously recorded information signal nor the newly recorded information signal can be reproduced at the time of a reproduction.
In order to prevent the duplex recording, there is a conventional recording apparatus provided with detection head which leads a recording head along a scanning direction of the recording head. According to this conventional recording apparatus, a warning is displayed when the detection head detects the pre-recorded track. The recording head itself is shifted mechanically or the channel of the recording head is switched over so as to record the information signal on only the unrecorded track. For example, a recording apparatus of this type is disclosed in a Japanese Laid-Open Patent Application No. 54-140515.
However, the conventional recording apparatus detects the unrecorded track by simply detecting whether or not a reproduced output signal is obtained from the detection head. For this reason, the pre-recorded track and the unrecorded track cannot be discrimnnated from each other with a high accuracy. But in order to prevent the duplex recording, it is absolutely necessary that the discrimination between the pre-recorded track and the unrecorded track is accurately carried out at a border where the track changes from the pre-recorded track to the unrecorded track or vice versa.