JPS586225B2 - tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape amount display device for displaying the amount of tape used, remaining amount of tape, etc. in a tape recorder or the like.

Conventionally, there is a tape amount display device that allows the amount of tape to be determined by counting the number of revolutions of a reel stand or the number of revolutions of a roller brought into contact with the tape.

However, in the former case, the relationship between the count and the counted tape length is non-linear, and in the latter case, due to slip between the tape and the roller that is in contact with it,
This method has disadvantages such as large errors.

The present invention has been made in view of the above-mentioned drawbacks.First, prior to explaining the embodiments of the present invention, the tape recorder. A general consideration will be made regarding the remaining tape time T of the reader.

Here, as shown in FIG. 1, the remaining tape time T when the magnetic tape 51 is wound from the supply reel 52 to the take-up reel 53 through the recording/reproducing magnetic head 54 will be considered.

Now, if the total length of the tape 51 wound on the supply side reel 52, that is, the total length of the remaining tape is expressed as ls, (where rs is the winding diameter of the tape wound on the supply side reel 52, , rh is the hub diameter of the supply reel 52, and δ is the tape 51.
thickness) is given as

On the other hand, if the running speed of the tape 51 is V, then the rotation speed Ps of the supply reel 52 is as follows.

Also, since the remaining tape time T is expressed as (4
) By substituting equations (1) and (3) into the equation, we get: (However, Ns=1/Ps means the rotation period of the reel 52.

Also, it is.

).

In this equation (5), the tape running speed v, the hub diameter rh of the supply reel 52, and the tape thickness δ are constants, so
It is understood that the remaining amount time T can be known by knowing the rotation speed Ps or the rotation period Ns.

Therefore, as one method of knowing the remaining amount time T, the method shown in FIG. 2 can be considered.

That is, a signal proportional to the rotational speed Ps is obtained by, for example, a frequency generator directly connected to the reel stand, and is applied to the input terminal 1 shown in FIG.

After making the amplitude of this input signal constant with limiter 2,
It is assumed that the third-order LPF is a low-pass filter with a second-order transfer function, and the frequency distribution range of the input signal is within the attenuation characteristic region a of this filter.

), an output proportional to 1/Ps2 is obtained.

After that, the A/D conversion circuit 5 or the display circuit 6 (5
) By correcting the other constant terms C1 and C2 in the equation, the display circuit 6 can display the remaining amount of tape in real time.

However, in this method, a second-order LPF 3 is used to obtain a signal proportional to 1/Ps2, but because of this, low-frequency wow and flutter components in the input signal enter the passband and are attenuated. Instead, it appears as the output of the secondary LPF 3.

This means that the wow and flutter components have an adverse effect on the accuracy of the above-mentioned tape amount display device.

FIG. 3 shows an embodiment of the invention to solve the above problem.

In this embodiment, a sampling circuit 30, a peak detection circuit 31, and an integrating circuit 32 are added to the circuit of the method of FIG. 2 described above.

A signal as shown in FIG. 9A is obtained from the secondary LPF 3.

The peak of this signal is detected by the peak detector 31, and the ninth
A detection output shown in FIG. B is obtained and applied to the sampling circuit 30 as a sampling signal.

As the sampling output, a PAM signal having a constant pulse width and different amplitudes as shown in FIG. 9C is obtained.

If this PAM signal is supplied to the integrating circuit 32, a staircase wave as shown in FIG. 9E is obtained as its output.

This staircase wave is sampled by a periodic signal generated every rotation of the reel as shown in FIG. 9D, and the display circuit 34
supply to.

According to the above configuration, the wow and flutter components of the signal sent to the display circuit 34 are averaged and canceled out within one cycle, so that the influence on the display value is reduced.

In particular, according to this method, the reel's 1
Effective in removing wow components during rotation.

Incidentally, the periodic signal may be generated every two or more revolutions of the reel.

In the embodiment, the remaining time is detected by detecting the rotation speed (period) of the supply side reel stand, but the remaining time is detected by detecting the rotation speed (cycle) of the take-up side reel stand. It is also possible to display the time.

Furthermore, if the system is configured to detect both, it is possible to know the total amount of tape, in other words, the recordable and reproducible time of the tape.

Further, although digital display is performed in the embodiment, it is of course possible to perform analog display without A/D conversion.

Furthermore, a changeover switch may be used to select between a conventional counter method that counts only the number of rotations of the reel stand and a real-time display method according to the present invention.

Further, the present invention can be applied not only to tape recorders and VTRs, but also to detecting the amount of tape-like material wound on a reel.

As described above, the present invention includes means for detecting the rotation period of the reel (for example, a frequency generator directly connected to the reel stand) and means for converting the detected rotation period signal into a level change (for example, a secondary LPF 3). ), and means (for example, an integrating circuit 32) for integrating this converted signal over n (n=integer) rotation periods of the reel.

Therefore, according to the present invention, highly accurate tape amount detection that is not affected by tape wow and flutter can be performed on a real-time display.

It is particularly effective in removing wow components caused by eccentricity of the reel.

Furthermore, you can know the remaining tape time or elapsed time simply by detecting the number of revolutions (period) of the reel stand at any point on the tape, so you can use the counter only when you want to know the amount of tape. You can also make it work.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a tape recorder, FIG. 2 is a block diagram showing one method for real-time display, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. FIG. 3 is a waveform diagram at each part of the figure. In addition, in the symbols used in the drawings, 3 is the secondary LP
F, 30 is a sampling circuit, 31 is a peak detection circuit,
32 is an integrating circuit.

Claims (1)

[Claims] 1. A detection means for detecting the rotation period of the reel, a conversion means for converting the rotation period signal obtained from this detection means into a level change, and a level change signal obtained from this conversion means as n (n = integer) of the reel. A tape amount display device comprising: an integrating means for integrating over a rotation period.