DE2413318A1 - Marking drop-outs in flexible magnetic tapes - by recording electronic marks in separate track as drop-outs are registered - Google Patents

Abstract

In magnetic tape manufacture, so-called "drop-outs" may occur owing to dust or fibre on the surface or insufficient coating. These cause interference, e.g. horizontal lines on screens in the case of video tapes. The present arrangement makes marks electronically on a separate track of the tape by means of an audio head at the same time as the drop-out is registered by scanning the tape with a rotating head. The mark is made at a given distance from the drop-out and is subsequently located by a rotating magnetic head so that the drop-out can be evaluated by means of a microscope or magnifier.

Description

Non-destructive marking of defects in ban-shaped flexible magnetic storage media For magnetic recording of data and images errors can arise from drop-outs. For example, they generate when recording a video stripes running horizontally across the screen. Therefore, magnetic tapes become instantaneous after manufacture checked for freedom from imperfections. The cause of such Defects can be in an inadequate casting quality of the magnetic tapes or in the deposition of foreign bodies such as dust, fibers, lie on the belt surface. In order to find these errors and to record them quantitatively, appropriate measuring devices are used (such as drop-out counters) are used that enable the manufacturer to take measures to avoid or

Take action to eliminate these errors. In addition to registering the For drop-outs, it is useful to mark the points of failure in order to remove them if necessary cut out of the tape. This can be done mechanically, e.g. by notching on the edge of the web happen.

This will damage the tape at this point and will no longer be sold in full length. If, on the other hand, it is a at this point Drop-out, which is caused by dust adhering to the surface of the layer, can do that Drop-out can be eliminated by cleaning the tape without cutting it out.

The present invention is therefore based on the object of fault locations to mark non-destructively This goal is achieved according to the invention, that the drop-out detected by means of a recording device and the drop-out formed in the process Pulse fed to a pulse converter and the converted pulse on an auxiliary track of the tape is recorded. The signal stored in this way is then known per se Can be scanned in a way and can be made audible or visible via suitable devices will. For the detection of drop-outs will be on the tape Test signal recorded. Any imperfections that may be present are displayed during playback of the signal is registered and counted in a known manner.

When used to carry out the method according to the invention Facility is used in an advantageous manner that the determination of the drop-outs occurring counting impulses of the disturbance point counter are used at the same time to be on the recording medium at a defined distance from the head drum to set a signal on the memory lane.

The method according to the invention is explained in more detail with the aid of a drawing explained. They show: FIG. 1: The top view of a video tape with playback of a Drop-outs and the simultaneous setting of the associated mark on the memory lane (at a distance from the place of origin).

Figure 2: A schematic signal flow diagram.

In Figure 1, a section of a video tape 1 according to DIN 15 900 is reproduced, in a known manner in addition to the video tracks 2 a memory 3 and a control track 4 carries. The sound track 7 runs parallel to the upper edge of the tape 6 on an image recording system based on the four-head method from Ampex the tape or the video track passed a rotating head drum 8 and scanned. The tape head is located at a defined distance A from the head drum 9 for recording and playing back freely selectable signals for memory track 3. With 11 indicates a fault (drop-out) on one of the video tracks 2. With the Sound head 9 is electronically a mark of this disturbance on the memory track 3 12 set.

According to FIG. 2, the high-frequency signal picked up by the video head 8 is (FM) in a known manner in one of an amplifier, equalizer and electromagnetic Switch existing subsequent electronics 13 of a conventional video recording device, which is used to merge the single head signals, processed further. This signal is fed to a drop-out registration device 14, which in the presence of an interference point a pulse for the counter 15 supplies. As mentioned above, this impulse is im In the sense of the method according to the invention, a magnetic marking is used to be stored in memory track 3.

The low-energy counting pulse is in a pulse converter 16, which is on Pulse output of the registration device 14 is connected, shaped into a rectangle. The square-wave pulse is then transmitted via the recording amplifier 16a and the recording head 9 laid down on the memory lane. Now the marking is on the memory lane in one defined distance from the point of disturbance corresponding to the distance from the head drum 8 and recording head 9. The marking on the measuring track 3 is now scanned via a rotating magnetic head 17 or via a Hall probe, and is after amplification 18 made visible by a display 19.

Located at the same distance as the head drum 8 and the speaking head 9 a viewing device 20 such as a microscope or magnifying glass. By moving of the crosshair perpendicular to the tape edges appears the cause of the drop-out Disturbance in the field of vision. A conventional image cutting device can also be used for viewing for video tapes, with the memory track being scanned from the back of the tape will.

The procedure allows the tape to be used for determination and assessment to mark of imperfections without cutting a part of it out of the roll must be, whereby the tape would lose sales value or for sale would be completely unusable, since splices are not permitted in video tapes.

Claims (1)

Claim experienced in the non-destructive marking of defects (drop-out) in the case of tape-shaped, flexible, magnetizable storage media, especially in the case of video tapes, whereby the drop-outs are registered by means of counters, characterized in that that the counting pulses of the counter are fed to a pulse converter and the transformed impulses on the Aufsprechtonkopf an image recording system set an auxiliary track of the storage medium electronic marks, and that these marks corresponding signals are sampled in a known manner and connected & can be made audible via the amplifier or visualized by means of a visual display.