JPH04372757A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a magnetic recording and reproducing device with high reliability by dissolving a malfunction caused by the uniformity of light transmitivity or a helical translucent flow of a magnetic record tape. CONSTITUTION:Phototransistors 1 arranged with two pieces vertically in the longitudinal direction of the magnetic recording tape 5 are provided and light from a light emitting diode 2 is detected and a logical product is taken with an AND circuit 6 and then the device has such constitution to decrease the malfunction due to unexpected wear of the magnetic tape or the ununiformity of the light transmitivity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus using a magnetic recording tape as a recording medium.

0002

2. Description of the Related Art In a conventional magnetic recording/reproducing apparatus, a method for detecting a leader tape at the beginning of a magnetic recording tape and a trailer tape at the trailing end uses one light emitting diode and one light emitting diode at each of the beginning and end ends.
The mainstream method is to use individual phototransistors to detect the difference in light transmittance between the magnetic recording tape, the leader tape, and the trailer tape. In recent years, as magnetic recording and reproducing devices have become smaller, have higher image quality, and have longer operating times, magnetic recording tapes are also becoming thinner and have thinner magnetic layers. As the difference narrowed, new detection methods were desired.

0003

[Problems to be Solved by the Invention] However, as magnetic recording tapes become thinner, more dense, and have thinner magnetic layers, in the case of current helical scan type VTRs, magnetic heads or rotating Helical transmission scratches are more likely to occur due to the drum. In addition, the spread of the optical transmittance distribution of the magnetic recording tape itself, combined with the non-uniformity of phototransistor accuracy, causes phototransistors to
A phenomenon occurs in which light from a light emitting diode is detected.

[0004] This phenomenon results in malfunctions such as stopping or rewinding at a location other than the desired location when the magnetic recording/reproducing device is recording or reproducing the magnetic recording tape. Until now, in order to prevent such malfunctions from occurring, methods such as lowering the light transmittance of the magnetic recording tape to ensure a difference in light transmittance between the leader tape and trailer tape, and improving the detection accuracy of phototransistors have been taken. Improvements have been made, but these improvements are reaching their limits as magnetic recording tapes are becoming thinner, more dense, and have thinner magnetic layers.

The present invention solves the above problems, and aims to provide a magnetic recording/reproducing device that greatly reduces malfunctions caused by erroneous detection of light transmittance.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention has a configuration in which two or more detection phototransistors are arranged for each detection location.

[0007]

[Operation] With the above-described configuration, the present invention arranges two or more phototransistors for each detection location,
Since detection is performed using two or more points, the probability of detection errors due to helical transmission scratches on the magnetic recording tape or non-uniformity of light transmittance is reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking the case of an 8 mm VTR as an example.

FIG. 1 shows a phototransistor 1 for detecting start and end ends.
-a, 1-b, 1-c, 1-d are attached to the magnetic recording tape 5 on the supply reel 3-a side and the take-up reel 3-b side, respectively.
Two 8mm VTs arranged perpendicularly to the longitudinal direction of
2 is a schematic diagram of R, 2 is a light emitting diode, 4 is a rotating drum, 6 is an AND circuit, and 7 is a system control circuit.

During recording, reproduction, and fast forwarding of the magnetic recording tape 5, the magnetic recording tape 5 led out from the supply reel 3-a is wound around the rotating drum 4 and then transferred to the take-up reel 3.
-b is wound up. When rewinding the magnetic recording tape 5, it is wound from the take-up reel 3-b to the supply reel 3-a via the rotating drum 4. During recording, playback, and fast forwarding, the light from the light emitting diode 2 is blocked by the magnetic recording tape 5, and the four phototransistors 1-a, 1-b,
It is not detected in 1-c and 1-d. As recording, playback, and fast forwarding progress and the trailer tape provided at the end of the magnetic recording tape 5 appears, the light from the light emitting diode 2 passes through the tape 2.
The phototransistors 1-a and 1-b receive light, and the magnetic recording tape 5 stops and begins rewinding. During rewinding, the light from the light emitting diode 2 is blocked by the magnetic recording tape 5 and the four phototransistors 1-a, 1-b, 1-c
, 1-d are not detected. As the rewind progresses and the leader tape provided at the starting end of the magnetic recording tape 5 appears, the light from the light emitting diode 2 passes through and is received by the two phototransistors 1-c and 1-d, so that the magnetic recording tape 5 Stop.

[0011] The 8 mm of this embodiment configured as described above
Using both a VTR and a comparative 8mm VTR with only one conventional phototransistor, 100 rolls each of commercially available 8mm ME tape A without transmission scratches and 8mm ME tape B with helical transmission scratches were recorded. We played it back and compared the total number of malfunctions. The result (
Table 1) shows the results.

0012

[Table 1]

Since the conventional 8mm VTR has only one phototransistor each, the phototransistor detects the light from the light emitting diode 2 leaking through the transparent scratches on the magnetic recording tape 5, causing the magnetic recording tape to be wound at a place other than the designated location. This causes malfunctions such as returning or stopping. Furthermore, even if the detection accuracy of the phototransistor is poor, the above-mentioned malfunction may occur due to variations in the light transmittance of the magnetic recording tape 5. In comparison, in this example,
Even if a helical transmission scratch on the magnetic recording tape 5 passes through the phototransistor part, the two phototransistors 1
Since the probability that -a, 1-b (or 1-c, 1-d) simultaneously detect the light of the light emitting diode is low, the outputs of the two phototransistors are connected to the AND circuit 6-a (or 6-b).
If the logical product is calculated and inputted to the system control circuit 7, the probability of determining that no detection is detected can be improved. Furthermore, providing two phototransistors each has the effect of making the detection accuracy of the phototransistors uniform.

As described above, according to this embodiment, since a redundant design is adopted in which each phototransistor, which is a light-receiving element, has two phototransistors, as is clear from Table 1, the light transmittance in the case of tape A is It is possible to eliminate malfunctions due to non-uniformity of tape B and helical transmission scratches in the case of tape B.

[0015]

As is clear from the above embodiments, according to the present invention, malfunctions caused by accidental wear of the magnetic recording tape or non-uniformity of light transmittance due to manufacturing can be reduced, and false detection of light transmittance can be reduced. A magnetic recording/reproducing device with fewer malfunctions caused by this can be provided.

[Brief explanation of the drawing]

FIG. 1: Schematic diagram of an 8mm VTR according to an embodiment of the present invention

[Explanation of symbols]

1 Phototransistor 2 Light emitting diode 5 Magnetic recording tape 6 AND circuit

Claims (1)

[Claims] 1. A magnetic recording and reproducing apparatus comprising at least two detection devices for each detection location for detecting the presence or absence of a magnetic recording tape.