JPS592210A - Tape type detecting method - Google Patents

Abstract

PURPOSE:To ensure the high performance of a video tape recorder, by providing a level detector for tape reproduction output and a level deciding device to a reproducing system to detect automatically the type of a tape and switching the recording/reproducing condutions in response to the type of the using tape. CONSTITUTION:In a reproduction mode of a video tape recorder, the output of a head amplifier 2 is applied to a level detector 5 to detect the level of reproduced output. This detected level is supplied to the input terminal at one side of a comparator 7; while a prescribed level is fed to the input terminal at the other side of the comparator 7 from a reference level generator 6. In such a constitution, the output of the comparator 7 is set at H and L when the reproduction output level is higher and lower than the prescribed level respectively. The type of the using tape is detected from the relationship between the reproduction level and a reference level. Based on the type of the tape, the switching is carried out between the recording current suited to the using tape and other recording/reproducting conditions in order to ensure the normal recoding and reproduction. For this purpose, the electric circuit system is especially constituted for a video tape recorder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically detecting the type of magnetic tape on which recording or reproduction is to be performed, for example in a tape recorder.

Currently, the magnetic tapes (hereinafter simply referred to as tapes) used in consumer video tape recorders are generally defined to be of the same type.

For example, according to the VH3 standard, tapes to be stored in VHS cassettes must have a holding force of 600 degrees and have an optimum recording current no different from that of standard tapes.

In reality, regular tapes and HCi tapes are commercially available, but both may have the same recording and reproducing conditions including the optimum recording current. In such a system, since there are no extremely different tape types, there is no need for a tape type detection method such as the one according to the present invention.However, recently, the performance of magnetic tapes has been improved, for example. Metal tapes with a holding force of about 1300 and vapor-deposited tapes with a maximum magnetic flux density several times that of conventional tapes have been developed. These high-performance tapes are basically capable of high-density recording and have excellent performance such as signal-to-noise ratio, so if applied to existing formats, it is possible to obtain playback signals that are several orders of magnitude better than conventional video tape recorders. it is obvious.

Also, new format video tape recorders can be considered using these high-performance tapes.

A small cassette (VTR) called 8mm video has been proposed, and the tape used for this is metal tape or vapor-deposited tape.

In systems that allow the use of multiple types of tape, or systems that attempt to improve performance by using a new tape type within an existing format, recording current and other factors may vary depending on the tape type. The playback conditions must be changed.

Conventionally, the tape type has usually been detected mechanically by providing a tape type detection hole in the cassette, as seen in the example of an audio cassette, and with the hole attached. However, in the case of video tape recorders, it is difficult to install a conventional detection mechanism due to space constraints, and when introducing a new tape to an existing format, it is not always possible to use the detection hole method. do not have.

In consideration of the above-mentioned points, the present invention measures some of the characteristics of the tape itself used in a video tape recorder, determines the tape type based on the results, and then performs normal recording and playback under recording and playback conditions that match the tape type. It is possible to record and play back.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows the relative speed of the tape and head at 3.75 m/s.
This is the frequency vs. playback output characteristics of various tapes when ec is set. A is a conventionally used γ-Fe203 tape, b is a metal-coated tape, and C is a metal-deposited tape. From this, for example, if you want to distinguish between the conventional tape (a) and the metal-coated tape (b), you can easily tell by looking at the reproduction output level. That is,
Since there is an output difference of 7 to sdB over most frequency bands, if the reproduced output level is above a predetermined level, it can be determined that it is a metal-coated tape, and if it is below a predetermined level, it can be determined that it is a conventional tape.

FIG. 2 shows an embodiment of a tape type detection method in the playback mode of a video tape recorder, and it is assumed that the tape to be detected has regular recording. The reproduced output from the rotary head 1 is amplified by a nodal amplifier 2, processed by a reproduced signal processing system 3, and an output signal is provided to an output terminal 4, as in a normal video tape recorder.

The output of the head amplifier 2 is applied to a level detector 5 to detect a reproduction output level, and this is input to one input terminal of a comparator 7. A predetermined level is input from the reference level generator 6 to the other input terminal of the comparator 7 . With this configuration, the output of the comparator 7 will be H'' if the reproduced output level is higher than the predetermined level, and will be L I+ if it is lower.

Here, the reference level should be selected at a level that corresponds to approximately the middle between the conventional tape and the metal-coated tape in FIG. As shown in FIG. 2, it is not necessary to constantly detect the tape type during playback, but rather to do so in the initial stage after the tape is loaded, and there is no need to re-detect υ unless the tape is replaced.

Next, a method for detecting the tape type during recording will be described. In this case, for example, a signal indicating that a tape cassette is installed and a signal instructing a recording mode by an operation switch are input into the system control circuit of the video tape recorder, and a tape type detection period is automatically established.

Then, recording is performed at least once during the tape type detection period.

Playback is performed, and the type of tape is determined based on the playback output. For rotating head video tape recorders,
During the tape type detection period, for example, it is sufficient to simply stop the running of the tape and switch the electric self-pressure system to the recording and reproducing states.

FIG. 3 shows the recording current versus reproduction output characteristics of iron oxide tape and metal tape.

Now, to determine whether the tape is iron oxide tape d or metal tape e, the problem is where to set the recording current during the tape type detection period. As far as we can see in Figure 3, the output of tape e is twice the output of tape d at any recording current, but when comparing the playback output level with the reference level, the reference level setting is the output of two types of tapes. The wider the difference, the easier it is and the less likely detection errors will occur. Therefore, the recording current should be selected to be large, and it is desirable to select the magnitude near the optimum recording current for a tape with a large output (corresponding to tape e in this case). As a practical matter, a tape whose optimum recording current is completely unknown is never loaded, and for example, if either a regular tape or a metal tape is loaded, the optimum recording current for the metal tape can be selected. As explained in Figure 2, the type of tape can be easily detected by playing back a tape recorded with a larger recording current and determining the magnitude relationship between the current level and the reference level. be.

In FIG. 3, a method for distinguishing between two types of tapes has been described, but this method can also be carried out for three or more types of tapes, and in that case, a plurality of reference levels may be set.

Based on the tape type detected in this way, the electrical circuit system of the video tape recorder is configured to switch to the recording current and other recording and playback conditions that are compatible with the tape and perform regular recording and playback. .

Next, a detection method for two types of tapes having relatively similar reproduction outputs will be described. It is determined whether the tape is metal coated tape b or metal vapor deposited tape C shown in FIG. What can be said from Fig. 1 is that the metal evaporated tape C is I
Although the output at MHz is smaller than the output at 3 MHz, the output at 1 MHz of metal coated tape b is thicker than the output at 3 MHz. By distinguishing between these differences, the tape type can be detected.

FIG. 4 is a configuration diagram showing one embodiment, and FIG. 5 is a time chart for explaining its operation.

The tape type detection period (abbreviated as TEST period) is the fifth
As shown in Figure (b), a minimum of three field periods are required, during which the tape is stopped. In a rotating head type VTR, it is sufficient to detect the tape type using only one head; in this case, the head switch signal (H5W
) has a recording mode (REC) and a playback mode (PB) as shown in FIG. 6(C). recording mode during the TEST period, i.e. the first
In the field, the frequencies shown in Figure 4 are fl and f
The outputs of oscillators 11 and 12 of 2 are connected to analog switch 1
3 and 14, amplified by a recording amplifier 16, and then supplied to rotary heads 17 and 18 as a recording current. The analog switches 13 and 14 are controlled by the mono multi-by break 19 and the mono multi-by break 21.
The signal f in FIG. 6(f) that rises at the H8W signal and the signal I in FIG. 5(f) that rises at the fall of the signal f are formed. As shown in the figure, one field period is divided into two, and signals fl and f2 are respectively recorded on the tape.Note that 20 is an inverter.When the recording is finished, the recording/playback switch 16 switches to the P side playback mode. When the signal is recorded, the rotating head scans the same track as recorded and reproduces the previously recorded signal.

This is amplified by the head amplifier 22, for example, as shown in FIG.
It exhibits the output shown in e). This means that the output of fl is lower than the output of f2. That is, f1=I
If we choose MHZ + f 2 =3 MHz, this tape is a metallized tape. The sample and hold circuit (S/H) determines this electrically.
24, the signal 1 in FIG. 6(b) in which the level of the first half of the third field is held and the signal 1 in FIG. In addition, the output of the comparator 26 is connected to the latch circuit 2.
7 data input terminal. As a result, in the second half of the third field, if the output of f is smaller than fl, then
The output j of the latch circuit 27 [see FIG. 5(i)] is It
LI+, and if -5 is opposite, it becomes L''. In order to read out this output j and hold the above readout output except during detection, an AN is connected to the gate input terminal G of the latch circuit 27.
The configuration is such that the output of the D gate circuit 28 is added, only the data of the third field is read out, and the others are latched. Thereby, if the detection output is "HI+It", it can be determined that it is a metal coated tape, and if it is "L" level, it can be determined that it is a metal evaporated tape.

In FIG. 5(i), the detection output j is at the °L' level, indicating that this tape is a metal-deposited tape.

In the embodiments shown in FIGS. 4 and 6, two frequencies are recorded and the magnitude of their outputs is directly compared to determine the magnitude of the output. It is also possible to determine whether the tape is dog or small for a predetermined level, and to detect the type of tape based on the result.

The above-described tape type detection method according to the present invention only needs to set a stop state for at least three field periods, and the detection time is about 50 m1iec. Even if this is done before starting regular recording, there is almost no practical problem; the tape type is detected completely automatically, and the recording and playback conditions are automatically adjusted to match the tape type. A videotape recorder can be configured to switch to .

As detailed above, the present invention is based on the fact that the playback system is equipped with a level detector that detects the playback output of the tape and a determiner that judges the magnitude relationship of the levels to automatically detect the tape type. For unrecorded tapes, recording is performed using a relatively large recording current, and the type of tape is determined based on the playback output.

Two frequencies are recorded, and the type of tape can be reliably detected from the magnitude relationship of the reproduction output level for each frequency.

This is especially true for rotating video tape recorders because the above detection can be performed by stopping the tape and switching to the recording and playback states.

The type detection period can be automatically set and executed in a short time.

According to the present invention, the tape type can be automatically detected without providing a hole for detecting the type in the case/nod case in which the tape is stored. This is particularly effective when trying to improve the performance of a conventional system by using a new tape.

[Brief explanation of drawings]

Fig. 1 is a frequency vs. output characteristic diagram of various tapes for video tape recorders, Fig. 2 is a principle diagram of an example of the tape type detection method according to the present invention, and Fig. 3 is a recording current vs. output of iron oxide tape and metal tape. FIG. 4 is a block configuration diagram for explaining a specific embodiment of the present invention, and FIG. 5 is a signal waveform diagram of each part for explaining its operation. 1...Magnetic head, 3...Reproduction signal processing system, 6 @@@11111 Lebel detector, 6.0...
・Reference level generator, 7e@II... comparator,
11.12...0...Oscillator, 13.14...
・Analog switch, nochi, 16.0...recording/playback switch, 17
, 18...Life, ◆, Rotating bellybutton)", 19,21...eI
I... Mono multi-high inflator, 23... @ conflict, Φ level detector, 24, 25eI111, φφ sample hold circuit, 26 ****e** comparator, 27... conflict... latch circuit, 28... ...AND gate circuit.

Claims (1)

[Claims] (1) A playback system that plays back a tape on which a signal is recorded and uses a level detector that detects the playback output level from the magnetic head and a determiner that judges the magnitude relationship of the output from the level detector. A tape type detection method characterized in that the tape type is detected from. (2) The determiner is configured to receive a predetermined reference level and a level detector output as input, and to detect the tape type based on the magnitude relationship thereof. How to detect tape type. (Scream) Before starting regular recording in the video tape recorder, a tape type detection period is automatically set, and the tape type is detected by recording and playing the tape, and the recording that matches the tape type used. A tape type detection method characterized in that regular recording is performed under playback conditions. Range 1 (Method for detecting tape type as described in section 1) (When recording with the largest recording current among the optimum recording currents for various tapes, and detecting the tape type by comparing the playback output level with the reference level. (→ A tape type detection method characterized by recording a plurality of signals with known frequencies and detecting the tape type by comparing the playback output level of each frequency.