Recording head clogging detection method and its device

Details Recording head clogging detection method and its device Recording head clogging detection method and its device

2001-05-25

2004-10-12

Hudspeth, David (Department: 2651)

Dynamic magnetic information storage or retrieval

Monitoring or testing the progress of recording

Reexamination Certificate

active

06804072

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a device for detecting clogging of a video tape recorder recording head that carries out recording helically with respect to the longitudinal direction by means of a head provided on a rotating cylinder.
BACKGROUND ART
Conventionally, as shown in
FIG. 17
, a camcoder records by means of a rotating head along a magnetic tape
31
around a cylinder
36
. In order to verify the recorded state upon recording, as for a signal recorded on recording tracks
37
of the magnetic tape
31
, an information signal
35
, which has been recorded by a recording head
33
immediately before, is reproduced by a reproducing head
32
for detecting clogging. The reproducing head
32
is positioned to follow the recording head
33
. When a recording failure results from clogging of the head, etc., the clogging is detected immediately and cleaning and so on is performed on the head. Reference numeral
38
denotes a running direction of the magnetic tape
31
and reference numeral
39
denotes a tracing direction of the recording head
33
and so on. An erase head
34
erases an area in advance for recording the information signal
35
ahead of the recording head
33
. Thus, it is possible to eliminate the influence of a previously recorded signal.
As equipment decreases in size, a VTR system having a small cylinder diameter has been put into practice. Meanwhile, in accordance with the trend toward high-quality images, the signal transfer rate increases. Hence, it has been necessary to reduce the number of heads per cylinder to maintain the same number of revolutions of the cylinder. Meanwhile, it is difficult to mount a number of sets of heads on a single cylinder where each set includes an erasing head, a recording head, and a reproducing head.
However, regarding a recording/reproducing apparatus, it is quite important for the device to operate normally by recording and verifying the recording. Except in cases where recorded information can be read repeatedly, for example, when recording an event taking place only one time for news reports and so on, it is important to verify the operating state of the recording device upon recording. As a conventional technique for collecting materials for news reports using a camera and a VTR, the following method has been mainly used: just before recording, recording and playback is performed for a short time on a tape to be recorded, and then the recording/reproducing operation is verified. Or a recording head and a reproducing head, which reads recorded information immediately after the recording, are provided in the functionality of the VTR, and the recording operation is verified by reading recorded information while recording.
The above function, which verifies recorded information by performing reproduction immediately after recording, is a function essential to an external memory for a computer and a camcorder for acquisition by broadcasters.
Moreover, as a simple method of verifying the recording operation, the following method has been also adopted as a conventional technique: when the recording operation is verified by reproduction immediately after recording, instead of playback all recorded data to make a comparison with the original data, the presence or absence of an envelope of reproduction output is detected after recording.
As for the verification of the recording function, the method of performing recording and reproducing on a tape just before recording is actually limited by the amount of time available. Additionally, no solutions are possible in the event of a malfunction during the recording process.
Also, when information is read immediately after recording, a reproducing head is necessary for verifying the recording process in addition to a recording head.
In general, a means for achieving high-quality recording/reproducing output is that an erasing head completely demagnetizes a tape just before recording; the tape is initialized; and recording is carried out. Thus, in order to realize more reliable recording, three kinds of heads are necessary which include a recording head, a reproducing head, and an erasing head.
Generally in a VTR using a helical scanning method, by which a tape is wrapped around 180-degrees of the cylinder and is recorded and reproduced, a pair of heads (two heads) are positioned opposing each other at 180-degree angles on the rotary cylinder, and the heads are switched at every half turn for recording. In this case, six heads are necessary in total.
Furthermore, in the case where recorded information has a high data rate and recording is not carried out by a single recording head system but by a two heads system, twelve heads are required in total. Hence, a problem appears in packaging so many heads together. Additionally, in the case of n-channel recording system, since 6×n heads in total need to be installed on the cylinder, it is not possible to mount all the heads when building a VTR.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a recording head clogging detection method, by which the above clogging can be detected without providing a reproducing head for detecting clogging of the recording head. Therefore, the recording head clogging detection method of the present invention is characterized in that an erasing head records a test signal in a specific section of a recording track, evaluation is made on a reproduced test signal obtained by reproducing the test signal in the recording head, and the occurrence of clogging is evaluated. According to the present invention, it is possible to detect the occurrence of clogging of the recording head without the necessity for a reproducing head used for detecting clogging of the recording head.
Furthermore, a preceding first head records sub information in a second area. When a second head records main information in a first area, the sub information is reproduced from the second area. It is possible to detect the presence or absence of adherents on the head based on the reproduction output. Furthermore, at the same time, verification is made on the reliability of the recording operation by verifying recording current, which is applied when the second head records main information. Hence, even if the number of heads installed in a rotary cylinder is reduced, it is possible to verify the recording. Namely, the present invention is realized as follows: regarding contamination (adherent such as tape fillings adhered to a surface of the head) that degrades the reliability of a recording/reproducing system of the tape head, a detection signal is recorded and reproduced in a predetermined area by using the positional relationship between the first head (e.g., an erasing head) and the second head (e.g., a recording head).
The following will discuss the detail of the present invention.
The recording head clogging detection method of the present invention is characterized in that a magnetic recording/reproducing apparatus reproduces from a magnetic tape having an information signal recorded by rotating and scanning the heads in sequence, the signal being provided helically with respect to the longitudinal direction of a magnetic tape. When detecting clogging of a recording head, a test signal is recorded on the magnetic tape by applying current with a frequency lower than an erasing frequency to an erasing head which erases an area for recording an information signal before the recording head records information in a recording track for each recording track, every specified number of two or more recording tracks, or every specified time, at a timing when the erasing head traces a specific section of the area for recording an information signal in the recording track; and the presence or absence of clogging of the recording head is determined by evaluating the reproduced test signal obtained by reproducing the test signal, which is recorded by the erasing head, by means of the recording head.
Moreover, the method of the present invention is characterized in that the specific section for recordin

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