JPS58153253A - Capstan servo circuit of vtr - Google Patents

Abstract

PURPOSE:To facilitate adjusting operation, by providing plural frequency dividers between a rotation-relative signal generating means and an error detector, and switching them on the basis of the display output of a display signal generating means. CONSTITUTION:A signal generator 1 outputs a standard speed signal A and +(n)-fold speed signals B and C; the rotary phase of a head motor 3 is brought under the servocontrol of a servo circuit 2 and the phase of a capstan motor 5 is brought under the servocontrol of a servo circuit 4. A signal G from the rotation-relative signal generating means 16 is frequency-divided 31-33 by a frequency dividers 30, and a frequency division ratio is selected 34. Said output is inputted to the error detector to detect an error, and then adjustment 41, addition 14, and amplification 15 are carried out to control a cpastan 5. Thus, the adjusting operation is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a servo capstan circuit for a VTR, and aims to simplify the adjustment process.

The VTR has a standard playback mode in which the magnetic tape is played back while being transported at a first speed (b) equal to the feed speed during recording.
forward high-speed regeneration in which regeneration is performed while transporting at a second speed (n ma) that is an integer (ns, e.g., n fin 9) times faster in the transport direction than the first speed M; and a fifth speed in which the regeneration is performed at the same speed in the opposite direction. ,
There is a device that can selectively perform reverse high-speed playback in which the data is played back while being transferred (-nv). For high-speed playback, there are cases in which the magnetic tape is driven by a reel motor (without a servo mechanism) and a capstan motor.
...Although there are cases where it is confusing, the former simplifies the circuit configuration.
On the other hand, the magnetic head has the disadvantage that the noise par displayed on the screen fluctuates when it straddles the rack.The latter can fix the noise par as a capstan servo system, but on the other hand, the capstan motor cannot be phased. Requires a servo circuit to lock. The present invention relates to the latter method.

First, an overview of the conventional VTR chip type will be explained with reference to FIG. (l) is a means for generating signals that individually display the feeding speed of the magnetic tape; for example, when the operator commands the standard playback mode, forward high-speed playback mode, or reverse high-speed playback mode, the display signal A is generated. , B
, C are configured to be output separately. (2) is a phase servo circuit for the five-point motor (3), (4) is a phase servo circuit for the capstan motor (5), and (6) is a speed servo circuit for the motor (5).

The phase servo circuit (2) includes a circuit (7) that generates the rotational phase (R number) of the Herad motor (3), and a display signal generation means (
1) A reference signal generator (8) whose oscillation frequency can be adjusted in response to display signals 9A and B%C output from the generator (8), and a reference signal E and rotational phase value @D from this generator (8). It is equipped with a comparator (9) that inputs the input signal and derives the phase difference output between the two, and the output of the comparator (9) is amplified by the amplifier signal and is connected to the head motor (3).
The phase is controlled. Here, the reference signal Nv
The reason why the J wave number is changed in accordance with the display signal is to prevent the image on the screen from flowing in the horizontal direction due to changing the feeding speed of the magnetic tape. For example, NTS
Adjacent horizontal synchronizing signals in C method [difference between ranks is 17
If the data is distributed so that there are two line periods, the number of scanning lines (c) scanned in one field period is H-262,5--(n-1 lines) according to the above integer n. Tonashi, n-±9(
positive for the forward direction and negative for the reverse direction], the forward direction high-speed playback mode results in a deviation of -152< and +19%, respectively, compared to the standard playback mode, which is the same as that of a general television receiver. This is because it is close to the limit of the pull-in range of the horizontal synchronizing signal. Yes, the oscillation frequency of the reference signal generator (8) is displayed above! j) To change according to K, for example, change the reference signal generator to the color subcarrier (nominal frequency 558MH2
) may be configured with a frequency dividing circuit using a manual trigger, and its division ratio may be controlled by the above display signal.

Capstan motor (5) phase nervo rotation 1d1114
) is the playback control signal (50H for NTSCcD)
2) and the circuit αυ that generates the signal A, which in the case of the above display signal A transmits the output of the generation circuit W1 (11) as it is, and in the case of the above display signal B or C, divides the nuclear generation circuit αυ output by 1/n and derives it. A variable division ratio circuit (comprising a comparator ([3) with the circuit 12 output F as a comparison input and an ε generation circuit (7J output rotation phase value @D as a quasi-input), The output of the device aa is given to the capstan motor (53K +1) via the mixing circuit Q4 and the amplifier class $.In this phase servo circuit, one single signal (rotational phase signal D) is in the positive direction or Reverse high speed playback
In the case of r, the deviations are -tszs and +t9%, respectively.

The speed servo circuit (6) of the middle Yagustan motor (5) is
Means 1e for generating a signal G related to the rotation of a capstan that selectively drives the magnetic tape at various speeds T;
Speed error detection WIIL that detects the amount of variation with respect to the quasi-pigeon season
Then, the response characteristic of this detector is expressed by the above display signal A%B%G.
It is equipped with an adjusting means (19) that adjusts according to K, and the output of the detection section η is applied to the upper mixer α4.
/! FIG. i2 shows the internal structure of this detector αD and the adjustment means 0, and FIG. 5 is a waveform diagram of each part in FIG. 2. In Figure 2, ■ is an input terminal for rotation-related signal 0, Qυ is a delay circuit, and ■
is a triangular wave forming circuit, (c) is a chimple hold circuit, @
is the output terminal, - is the input terminal for the display signal, (19M), (19B), and (19G) are used together with the capacitor (C) to change the slope of the triangular wave (3rd waveform), standard playback and positive playback, respectively. This is a polycum for high-speed playback in the direction and high-speed playback in the reverse direction.
19B) (190).

When the capstan motor (5) is phase-locked, the rotation-related signal G will also be shifted by the amount that the rotational phase signal of the head servo is shifted. Therefore, first, set the magnetic tape to the first speed (7) [standard playback mode] and adjust the potukum (19A) so that the output of comparator 0 falls within the specified value.
Next, set the magnetic tape to the second speed (nV) (forward high-speed playback mode) and adjust the volume (19B) to II!l, and similarly adjust the volume (19C) so that the output of the comparator α3 falls within the specified value. In this way, it is necessary to set the magnetic tape to each running mode and adjust each polyum (19A) to (19C) for each mode.In this example, the magnetic tape running mode It required adjustment work five times by changing the setting, and there was a problem with workability.

The present invention allows the first turn related signal to be input to the speed error detector to remain almost the same even if the running speed of the magnetic tape is changed to correspond to the standard playback mode or the n-times speed playback mode. The present invention aims to provide a capstan tivo circuit for a VTR that allows the time constant to be adjusted only once. Rounding The present invention is provided with a separator between the rotation-related signal generating means and the error detector, the dividing ratio of which is changed based on the control of the output of the display signal generating means, and the separator is provided with a divider whose frequency division ratio is changed based on control of the output of the display signal generating means. A VT characterized in that the signal generating means outputs a 1211-degree detection side signal of a nominal frequency (f) or a second speed detection signal 45Kff of a frequency (f) equal to or close to this nominal frequency.
The present invention aims to provide an H capstanchibo circuit.

FIG. 4 shows one embodiment of the circuit of the present invention. In the figure, the same figure numbers as in FIG. 1 indicate the same functional elements.

(to) is a divider W4 whose frequency division ratio is changed according to the display signal from the display signal generating means (1), and the division ratio is z.

A first branching unit c311 with a branching ratio of 17!1" and a second branching unit c311 with a branching ratio of 17!1"
A separator (to) and a third separator (to) with a division ratio of 1788
and a display signal from the display signal generating means (1), B,
The output signal from the 0-time light signal generating means, which is equipped with a switch circuit (to) in which one of the first to fifth frequency dividers is selected by the CK signal, is output from the first speed (to) of the standard playback mode, for example.
) and 1200Hz (referred to as the first light signal),
At the 2nd and 5th speeds (9v) and (-97), the H numbers within one field period are 258.5 and 26, respectively, as mentioned above.
7.5, so they become 10947.117Hz (second light signal) and 105913.15H2 (third light signal), respectively. Therefore, the output of the frequency divider (to) is 120Hz and 1 for the first, second, and third light signals, respectively.
Derive 2 csHz and 12α4Hz. That is, a first speed detection signal with a nominal frequency f (120Hz), a second speed detection signal with a frequency f' (12115Hz) close to this nominal frequency, and a third speed detection signal (12α4H2).
Outputs. The mutual frequency difference between these is the above-mentioned 1st to 5th
This difference is extremely small compared to the difference between the rotational signals and can be considered to be virtually non-existent. Therefore, when the magnetic tape is set to the standard playback mode, the speed error detector (for example, rcmFIltii) controls the time constant that determines the slope of the 4G triangular wave. Lord Boricum for only one phase Chibo circuit (4)
If T is adjusted so that the output of the comparator σJ is within the specified value, then
*j to other playback modes! There is no need to adjust the polyurethane for each mode, and the adjustment work can be significantly simplified.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventional circuit, FIG. 2 is a circuit diagram of an example of a speed error detector, and FIG. 5 is a waveform diagram of each part thereof. 450 is a schematic circuit configuration diagram of one embodiment of the present invention. Explanation of main drawing numbers α・Rotation related (l! No. generation means, (1)...display signal generation means, (to)...frequency divider, l?14Q-・speed error detector. Application Person Sanyo tlIA Co., Ltd., I Figure 2

Claims (1)

[Claims] t Magnetic tape as standard W! 11 speed (to) and this 1st
means for generating a signal related to the rotation of the capstan selectively driven by an integral number (b) times the 211th degree (nv) of the speed; and means for generating a signal for individually indicating the feeding speed of the magnetic tape. , inputs the output of the related signal generating means and generates the first speed detection signal of the nominal wave number (f) or this nominal ll! inputting the first or second speed detection signal and a frequency dividing ratio for outputting a 2j1 degree detection signal with a frequency P equal to or close to the wave number; A capstan servo circuit for a VTR, comprising a speed error detector common to both speed detection signals, which derives an output (!1g) corresponding to the speed error of each speed detection signal.