JPS6171781A - Control circuit for tape intermittent drive - Google Patents

Abstract

PURPOSE:To ensure the stable intermittent slow reproduction of a tape with no tracking shift by giving the intermittent drive to the tape with the 1st control signal containing a prescribed start signal and a control signal and correcting the tape intermittent drive state with the 2nd control signal obtained from comparison performed between the level of an ideal tracking error signal and the level of a tracking error signal to be detected. CONSTITUTION:An ideal tracking error E is stored previously in a reference error signal generating circuit 12, and the degree of the error E is decided by a correction signal generating circuit 13. Then a correction signal is supplied to a drive circuit 9 for the 2nd control signal DT in accordance with the degree of the error E. Thus the drive output accordant with an addition output level of the 1st control signal containing a start pulse MP and a damping pulse BP and the correction signal is supplied to a capstan motor. Then the error E is eliminated by the correction signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an intermittent tape running control circuit for intermittent slow motion playback of 8 mm video.

(b) Conventional technology Intermittent slow motion playback of a video tape recorder is disclosed in Japanese Patent Laid-Open No. 5945786 and others.

These conventional techniques start the tape using an RF switching valve associated with the rotation of the head, and apply braking to the tape using a playback foot roll signal.

(c) Problems to be Solved by the Invention However, in the case of 8mm video, accurate tape running position corresponding to the playback control signal! There is no detection signal, and the braking is forced to be applied by the RF switching device (1).
It is expected that the tracking state will continue to deviate.

(d) Means for Solving the Problems Therefore, the present invention makes the tape run intermittently using a first control signal consisting of a predefined starting signal and a braking signal, and also provides an ideal trunking error signal. The intermittent running state of the tape is corrected by a second control signal obtained by comparing the tracking error signal level detected with the tracking error signal level.

(E) Effect -C1 In the present invention, tracking is made possible by correcting the running error of the tape running by the RF switching pulse using the second control signal.

(f) Example Hereinafter, the present invention will be explained according to an illustrative example. First, in the pattern diagram shown in FIG. 1, the scanning trace indicated by solid line C is an ideal reproduction scanning trace.

A tracking error caused by scanning this scanning trace has a waveform as shown in FIG. 1E.

In order to derive the trunking error, the reproduced Byrond signal is amplified in a preamplifier 1) and mixed in a mixing circuit 2 with a reference signal having a frequency equal to the reproduced pilot signal frequency of the track to be reproduced. still,
This reference signal frequency is switched and derived from a reference signal generation circuit (3) which inputs an RF switching pulse (RF) and a slow ratio setting output (MO) in accordance with the slow ratio.

The 16KHz and 46KHz beat components in the mixed output are
They are selected by filters 16 (4) and 46 (5) in the next stage, and the output levels of these filters are compared by a level comparison circuit (6) in the subsequent stage. Further, since the polarity of this comparison output is inverted for each field, the polarity is made uniform in a polarity inverting circuit (7) which uses an RF switching pulse (RF) as a control input, and the polarity is derived as a tracking error signal. The above-mentioned configuration is a well-known configuration for 8 mm video, and detailed explanation will be omitted.

In order to perform the above-mentioned ideal reproduction scan, in this embodiment, when starting the tape, the starting pulse generation circuit (8) waits for a predetermined period (1+) at the rise of the RF switching pulse (RF).
) A starting pulse (MP) that becomes positive level for a certain period of time (t2) after a delay is supplied to the drive circuit (9>), and the capstan motor (10) is driven for a certain period of time to normally reproduce one frame.

Furthermore, the braking pulse generation circuit (11) generates a braking pulse (BP) to the drive circuit (9) that is delayed by a predetermined period (t3) from the rising edge of the RF switching pulse (RF) and remains at a negative level for a certain period of time. Supply, cab stan motor (1
0) is reversely driven to apply braking to the running tape and complete the movement of the tape by one frame.

The above-mentioned configuration is also the same as that of a normal VTR, but is slightly different from the conventional configuration in that the starting point of brake pulse generation is the rising edge of the RF switching pulse. In addition, the starting pulse generation circuit (8) and the braking pulse generation circuit (1)
1) is the first control circuit in the present invention. Although the above-described configuration enables intermittent slow playback, the RF switching pulses control the intermittent running of the tape, which may cause tracking deviations.

For example, if reproduction scanning traces as shown in the pattern diagram of FIG. 1 occur and tracking deviation occurs, the reproduced image will deteriorate.

Therefore, in this embodiment, in order to eliminate this tracking thread, the following steps are taken.

Well, if you scan the playback scan trace as shown by the dotted line,
The tracking error exhibits a waveform as shown in E'). Therefore, in this embodiment, the ideal tracking error (E) is stored in advance in the reference error signal generation circuit (12), and the error amount of the tracking error is determined in the correction signal generation circuit (13). , a correction signal corresponding to this error amount (second control signal>(0>> is input to the drive circuit (9),
The first pulse consists of a starting pulse (MP) and a braking pulse (BP).
The control signal and the correction signal are added together and outputted, and a drive output corresponding to the health is supplied to the capstan motor. Therefore, this correction signal eliminates the tracking error.

(G) Effects of the Invention According to the present invention, by effectively using the trunking error signal instead of the playback control signal, stable intermittent slow playback without tracking/king deviation is possible; It's a dog.

[Brief explanation of the drawing]

Each of the drawings shows an embodiment of the present invention; FIG. 1 is an explanatory diagram of a reproduced signal scanning trace and signal waveform, and FIG. 2 is a block diagram of the main circuit of this embodiment. (8) Starting pulse generation circuit, (11) Braking pulse generation circuit, (13)... Correction signal generation circuit.

Claims (1)

[Claims] (1) In an 8mm video tape recorder that performs intermittent slow motion playback by intermittently running a videotape on which a tracking pilot signal is multiplexed on a video track, predetermined starting pulses and braking are applied in synchronization with the rotation of the video head. a first control circuit that emits pulses; a second control circuit that compares a tracking error signal obtained from a regenerated pilot signal with a preset ideal tracking error signal; A tape intermittent running control circuit consisting of a drive circuit and a drive circuit for driving the tape.