JPS59187255A - Detecting method of kind of magnetic tape - Google Patents

Abstract

PURPOSE:To discriminate the kind of a magnetic tape accurately, by detecting a recorded current optimum for the magnetic tape, by comparing this current with a reference level in accordance with the kind of the magnetic tape, and by discriminating the kind of the magnetic tape based on the comparison. CONSTITUTION:In a recording mode, a counter 18 shifts the counting of the rotation pulse of a cylinder upward with every one rotation of a rotary head 11. The level of a current recorded on a magnetic tape through a digital attenuator 13 and an amplifier 14 is raised in stages with every one field. When the count of the counter 18 reaches a maximum count value which is set beforehand on the basis of the amount of variation of the recorded current, VTR stops recording and rewinds the magnetic tape. Next, in a playback mode, the counter 18 holds a count value corresponding to a recorded current recorded in a field in which a playback level is at the maximum, while a playback signal current is monitored by a maximum value detecting circuit 17. This count value is compared with a count value from a reference level counter 20 by a comparator 19, and the two kinds of magnetic tapes are discriminated on the basis of this comparison.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for detecting the type of magnetic tape used in a magnetic tape recording/reproducing device such as a video tape recorder.

(Conventional structure and its problems) At present, the magnetic tapes used in consumer video tape recorders (hereinafter referred to as VTRs) are regulated to be almost the same type, for example, according to the VH8 standard. For example, the magnetic tape to be stored in a VHS cassette is said to have a holding force of 600 degrees and an optimum recording current no different from that of a standard tape. In fact, legiler tape and H
Although G tapes are commercially available, the optimum recording current and other recording/reproducing conditions may be the same for all tapes. In this way, in current VTRs, there is no need to detect the type of magnetic tape because there are no magnetic tapes with extremely different characteristics. However, recently, research has been conducted to improve the performance of magnetic tapes, and for example, metal-coated tapes with a holding force of about 1,300 per cent and metal-coated tapes with a maximum magnetic flux density several times that of conventional magnetic tapes have been developed. has been done.

These high-performance tapes are basically capable of high-density recording and have excellent performance such as signal-to-noise ratio, so it is clear that if applied to existing formats, it will be possible to obtain playback signals that are several orders of magnitude superior to current VTRs. It is.

In addition, a new format of VTR using these high-performance tapes was the small cassette 7, called 8mm video.
A digital VTR has been proposed, and the magnetic tape used therein is either a metal-coated tape or a metal-deposited tape. In this way, in systems that can use multiple types of magnetic tape, or systems that use a new type of magnetic tape within an existing format to improve performance, the recording current may vary depending on the type of magnetic tape. The recording/playback conditions must be changed.

Therefore, in order to automatically switch the recording/playback conditions according to the type of magnetic tape, it is necessary to detect the type of magnetic tape. Mechanical or electrical tape type detection methods have been proposed, as applied to cassette tape recorders.Mechanical tape type detection methods detect the type of magnetic tape stored in a cassette. A tape type detection hole is provided to indicate the magnetic tape type, and when a cassette is loaded into the device, the tape type detection hole is mechanically detected to determine the type of magnetic tape.However, such conventional mechanical In the tape type detection method,
The device must be equipped with a mechanism to mechanically detect the tape type detection hole, and there are space limitations when applying it to VTRs, and it is not always possible to apply it to existing formats. There were drawbacks such as the need to unify standards among manufacturers. The clever electrical tape type detection method utilizes the difference in frequency vs. output characteristics of the conventional iron oxide tape A, metal coated tape B, and metal evaporated tape C, as shown in Figure 1.
A signal of a predetermined frequency is recorded in advance on the magnetic tape to be used, and as shown in FIG. Then, a part of the reproduced signal is extracted and the level detection circuit 4 detects the reproduced signal level, and the level of the reproduced signal is compared with a predetermined level from the reference level generator 6 in the control rake 5. According to
It is used to determine the type of magnetic tape. However, in such a conventional electrical tape type detection method, as shown in FIG. It is difficult to set a reference level for discrimination, and the type of magnetic tape cannot be accurately detected.

(Object of the Invention) The present invention has been made in view of the drawbacks of the conventional examples described in 2. In a magnetic tape recording/reproducing device such as a VTR, the type of magnetic tape can be accurately detected by partially detecting the characteristics of the magnetic tape used. The purpose of the present invention is to provide a tape type detection method that can determine the type of magnetic tape and set the optimum recording conditions for the magnetic tape at the same time.

(Structure of the Invention) In order to achieve the above object, the present invention utilizes the recording current vs. output characteristic of a magnetic tape to record a recording current of increasing level sequentially on the magnetic tape used, and the reproduction level The optimum recording current is set by detecting the recording current when the maximum value is reached, and the type of magnetic tape is determined by comparing this optimum recording current with a predetermined level.

(Explanation of Examples) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing the recording current versus output characteristics of a magnetic tape, and shows the characteristics of iron oxide tape a, metal coated tape b, and metal vapor deposited tape C when the recording wavelength is 1 μm. In Figure 3, the optimal recording current for each magnetic tape is the recording current when each output is maximum,
By comparing the optimum recording currents, the type of magnetic tape can be determined.1 The optimum recording currents of the metal-coated tape B and the metal-deposited tape C have a sufficient level difference. Therefore, the present invention utilizes the characteristics of the magnetic tape as described above to detect the type of magnetic tape as shown in FIG. 4 is a block diagram showing a tape type detection method in a VTRK as an embodiment of the present invention, in which 11 is a rotary head, 12 is a recording/reproducing switch, 13 is a digital attenuator, 14 and 15 are amplifiers, and 16 1 is a level detection circuit, 17 is a maximum value detection circuit, 18 is a counter, 19 is a comparator, and 2o is a reference level counter. Note that the VT to which this embodiment is applied
R is configured to input a signal indicating loading of the cassette tape to the system control circuit 9, and automatically perform detection with a period for detecting the optimum recording current.

In the above configuration, in this embodiment, the recording/reproducing switch 12 is set to the recording side without switching, the recording current is completely supplied to the rotary head 11 via the digital attenuator I3 and the amplifier 14, and recording is performed on the magnetic tape. mode.

At this time, a reset pulse is applied to the reset terminal R of the counter 18, and the counter 8 is reset. In addition,
The clock terminal CK of the counter 18 is connected to the clock terminal CK of the counter 18 as shown in FIG.
A rotation pulse is applied to the cylinder on which the rotary head 11 is mounted as shown in K, and as soon as the recording mode is entered, the counter 18 increases the count every time the rotary head 11 rotates once. The digital attenuator 13
This is a circuit whose attenuation amount is digitally set by a count value of 8. Therefore, the recording current supplied to the rotary node 11 via the digital attenuator 13 and the amplifier 14 and recorded on the magnetic tape is as follows. As shown in FIG. 5(b), the level increases step by step for each field. Then, when the count of the counter 18 reaches the maximum count value set in advance from the amount of change in the recorded current,
The VTR stops recording and rewinds the magnetic tape to the recording start position. In this case, the argument value of the tape counter at the recording start position may be used, or a start signal may be recorded on the magnetic tape. Next, the recording/reproducing switch 12 is switched to the playback side 1, and a playback mode is entered in which the recording on the magnetic tape is played back and the playback signal from the rotary head 11 is supplied to the playback signal processing system via the amplifier 15. . At this time, the counter 18 is reset and starts counting again in the same way as when recording. Then, the throat to rotate 11
The output of the amplifier 15 which amplified the reproduced signal is shown in Fig. 5 (C
), Km changes in accordance with the magnetic tape recording current vs. output characteristic, and takes a maximum value when the recording current recorded on the magnetic tape is at a level of . The amplitude of this reproduced signal is detected by a level detection circuit 6, and the output level of the level detection circuit 16, which changes for each field, is monitored by a series value detection circuit 17. The maximum value detection circuit 17 outputs a low binary signal when the input level is higher than the level of the previous field, and outputs a high signal when the input level is lower than the level of the previous field. This binary signal is applied to the stop input terminal S of the counter 18, which continues counting when the input is low and stops counting when the input goes high. As a result, the count value of the counter 18 is maintained at a count value corresponding to the recording current recorded in the field where the reproduction level is maximum, that is, the optimum recording current, as shown in FIG. 5(d). A divisor value corresponding to this maintained optimum recording current is applied to one input terminal of the comparator 19, and a divisor value corresponding to the level of a predetermined recording current from the reference level multiplier 2° is applied to the other input terminal of the comparator 19. By applying the count value, the comparator 19 outputs a high signal if the optimum recording current is above a predetermined level, and a low signal if it is smaller than a predetermined level, making it possible to discriminate between two types of magnetic tape. Here, the output of the reference level counter 20 may be set to a count value corresponding to the intermediate level of the optimum recording current for each of the magnetic tapes as soon as the determination is made. Counter 18
is held at a count value that is the optimum recording current for the magnetic tape, so if recording is to be performed after detecting the tape type, the argument value of the counter 18 should be set to that one! It is possible to record on magnetic tape at an optimal level by using the method.

In the above example, a method for distinguishing between two types of magnetic tapes was explained, but this can also be applied to the case of discriminating magnetic tapes on three types of furnace plates. In that case, the reference level is You can set more than one.

Based on the type of magnetic tape detected in this way, the electric circuit of the VTR is configured to switch to the recording current and other recording/playback conditions suitable for the magnetic tape to perform normal recording/playback.

Furthermore, in the embodiment shown in FIG. 4, it takes about 1 second to detect the type of magnetic deso, including recording, rewinding, and reproducing. It is possible to shorten this time by superimposing the recording current waveform shown in Fig. 5(b) on the horizontal synchronizing signal of the NTSC system.
With TR, recording can be completed during one rotation of the rotary head, and the type of magnetic tape can be detected while the magnetic tape is in a stopped state.

(Effects of the Invention) As explained above, the present invention detects the optimum recording current by measuring some of the characteristics of the magnetic tape, and determines the type of magnetic tape based on the value. There is no need to perform processing such as providing a hole for detecting the tape type, and it is possible to freely use magnetic tapes from various manufacturers and accurately detect the type. Since it is possible to set the recording current, it has the advantage of being able to automatically perform recording under optimal conditions at all times, even against variations in the characteristics of the magnetic tape and magnetic head, and wear of the magnetic head. It is something.

[Brief explanation of drawings]

Figure 1 is a diagram showing the frequency vs. output characteristics of various magnetic tapes, Figure 2 is a block diagram showing a conventional tape type detection method, and Figure 3 is a diagram showing the recording current vs. output characteristics of various magnetic tapes. 4 is a block diagram of an embodiment of the present invention,
FIG. 5 is a diagram showing a time chart in FIG. 4. 11 ・・・・・・Rotating hend, 12・・・・・・
Recording/playback switch, 13... Digital attenuator, 16... Level detection circuit, 1
7... Maximum value detection circuit, 18...
...Counter, 19...Comparator. Fig. 1 Ill 51 ILfMHz Fig. 2 Fig. 3 □ 1f

Claims (2)

[Claims] (1) After loading a magnetic tape into a magnetic tape recording/reproducing device, detect the optimum recording current for the magnetic tape during a predetermined period, and compare the detected optimum recording current with a reference level according to the type of magnetic tape. A method for detecting a tape type, characterized in that the type of magnetic tape is determined by using the magnetic tape. (2) During the period for detecting the optimum recording current, the first
In this mode, a predetermined pulse is counted and a recording current that is sequentially increased according to the counted value is recorded on the magnetic tape,
in a second mode, reproducing the recording on the magnetic tape and counting predetermined pulses in the same manner as in the first mode;
Claims characterized in that the optimum recording current is detected by stopping the counting of the noise pulses and holding the counted value when the reproduction level of the recording on the magnetic tape reaches a maximum. The tape type detection method described in paragraph (1).