JPS6190354A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To obtain stable noise transfer and to simplify and reduce the cost of circuit structure, by shaping the waveform of noise, making a dropout pulse, detecting the peak of noise and stopping noise transfer. CONSTITUTION:Shaping the waveform of noise into a pulse shaped signal by a dropout pulse generator 15, and input a positive dropout pulse to Tr19. Then noise transfer is started and the noise starts to move towards the direction of noise transfer. When a dropout signal stops, Tr19 is turned off, and charging is started by a load resistor 17 and capacitor 20. at the next dropout signal, the Tr19 is turned on, and the capacitor 20 starts discharging, and charge/ discharge pulse is formed at a peak detecting circuit 16. At the fall of that pulse (edge of the noise), a comparative pulse is generated by a comparative pulse generator 6, and when it coincide with the reference pulse generated by a reference pulse generator 7, a noise transfer halt signal is outputted from the generator 7, and noise transfer is stopped. Thus, the noiseless still reproduction picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording/reproducing device, and particularly to a noise detecting means and a noise sending stopping means for sending noise using a field still method in the device.

[Conventional technology]

A conventional device of this type is the one shown in FIG. Here, in FIG. 3, since the field still type noise sending means is well known, its structure is omitted, and the schematic structure of the noise sending stopping means related to the present invention is shown.

In the figure, ■ is an FM envelope detection circuit that detects the envelope of the FM playback signal obtained from navel and do during playback, and 5 is a comparator block, which is a differential amplifier 4 that takes out the square wave pulse by inputting the FM envelope.
．． and a reference resistor 2.3 that determines the bias of this differential amplifier 4. 6 is a comparison pulse generator that generates a comparison pulse at the falling edge of the pulse waveform output by the differential amplifier 4; 7 is a comparison pulse generator that generates a comparison pulse at the falling edge of the pulse waveform output by the differential amplifier 4; A reference pulse ordering device for setting a reference pulse at a time delayed by approximately one field from the rising point of the pulse; 8 generates a drum rotation pulse obtained by inputting a signal outputted as the drum rotates to a flip-flop; This is a drum rotation pulse ordering device.

4 is a timing chart showing waveforms of various parts of the device shown in FIG. 3. FIG.

Next, the operation will be explained.

During normal playback, the FM envelope detection circuit 1 outputs a signal f as shown in FIG. 4(b), which is an amplified weak signal from the video head. Further, during still playback, an FM envelope g as shown in FIG. 4(C) is obtained by the still playback head having the same azimuth as the one-side channel head provided separately from the recording/reproducing head. The FM envelope g during normal reproduction is input to the differential amplifier 4 of the comparator block 5, and when the level of the signal from the FM envelope detection circuit 1 reaches the bias determined by the resistors 2 and 3, the differential The amplifier 4 outputs a pulse h as shown in FIG. 4+d). Here, since noise feeding is started at the same time as the still signal is input, the waveform of signal g moves in the direction of noise feeding, and the pulse h also moves at the same time. Further, the comparison pulse generator 6 generates a comparison pulse j as shown in FIG. 4(f) at the falling edge of the pulse h generated by the differential amplifier 4. On the other hand, the reference pulse generator 7 stops feeding the reference pulse at a position close to 100% of one field of the drum rotation pulse a (see Fig. 4 (a)), and this allows noiseless still regeneration. You can get a picture.

[Problem that the invention seeks to solve]

Since the conventional apparatus is constructed as described above, there was a problem in that unless the video tape running was stabilized, the envelope of the FM reproduction signal would be subject to fluctuations, making stable noise transmission difficult.

Further, since the noise is sent using an FM envelope, a differential amplifier is required for accuracy, which poses problems such as the circuit is complicated and expensive.

This invention was made in order to solve the above-mentioned problems, and its purpose is to provide a magnetic recording and reproducing device that can send stable noise and can easily and inexpensively configure a circuit. There is.

[Means for solving problems]

The magnetic recording and reproducing device according to the present invention includes a dropout pulse generator that outputs noise as a dropout pulse train, a noise front end detection circuit that includes a transistor or the like and receives the dropout pulse as input and detects the front end of the noise, and A noise feeding stop means is provided for stopping noise feeding when the tip has been fed by a predetermined amount.

[Effect]

In this invention, a dropout pulse train is created by waveform-shaping the noise generated during still playback, the dropout pulse is used to detect the leading edge of the noise, and when the leading edge of the noise is sent a predetermined amount, Stop feeding.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an embodiment of the part related to the present invention in the magnetic recording and reproducing device, that is, the noise detection means and the noise feed stop means of the noise sending device.
1 is a dropout pulse generator that generates a dropout pulse signal obtained by shaping noise into a pulse shape; 16 is a noise tip detection circuit that receives the dropout pulse as input and detects the tip of the noise; this noise tip detection circuit 16 , 19 is a transistor for driving charging and rapid discharging, and 18 is a transistor 19.
The base resistor 17 is a load resistor connected between the collector of the transistor 19 and the power supply Vcc, which together with a capacitor 20 whose one end is connected to the connection point between the load resistor 17 and the collector of the transistor 19, It is up to you to decide. Further, 6 is a comparison pulse generator that generates a comparison pulse when the output of the noise leading edge detection circuit 16 falls, and 7 is a comparison pulse generator that generates a comparison pulse at the falling edge of the output of the noise leading edge detection circuit 16, and 7 is a pulse generator that generates a comparison pulse when the output of the noise leading edge detection circuit 16 falls. A reference pulse generator 8 is a drum rotation pulse generator for providing a reference pulse at a time delayed by approximately one field period from the comparison pulse generator 6, reference pulse generator 7. The drum rotation pulse generator 8 constitutes noise feed stopping means.

Further, FIG. 2 is a timing chart diagram accompanying the operation of the apparatus shown in FIG. 1.

Next, the operation will be explained.

When switching from normal playback to still playback, noise is generated when the video head crosses the track due to the guard band on the video track.

The dropout pulse generator 15 shapes the noise into a pulse shape, thereby causing the noise to be dropped. When this dropout pulse b is present, an H level is input to the base of the transistor 19, and the collector of the transistor 19 becomes an L level.

Here, since noise feeding is started at the same time as the still signal is input (noise feeding starting means is not shown), the noise moves in the direction of noise feeding. When the noise is sent and the dropout pulse b disappears, the transistor 19 is completely turned off and charging is started by the resistor 17 and capacitor 20. Then, the transistor 19 is turned on again by the dropout pulse b at the beginning of the next field part, and the charge stored in the capacitor 20 is rapidly discharged, and the charge/discharge pulse C shown in FIG. 2(C) is generated. is formed by the level tip detection circuit 16.

The falling edge of this charging/discharging pulse C is the leading edge of the noise, and the comparison pulse d, which received the pulse C, is placed at a position near 100% of one field of the drum rotation pulse a by the reference pulse generator 7. A noise feed stop signal is output from the reference pulse generator 7 when it matches the provided reference pulse e (see FIG. 2(e)). This noise feed stop signal is then supplied to the capstan motor drive circuit of the noise feed means (not shown), noise feed is stopped, and a still reproduced image without noise is obtained.

In this way, in the device of this embodiment, noise detection during still playback is performed using a dropout pulse, and the transistor 1
Since this is done using a charging/discharging circuit (noise leading edge detection circuit) consisting of 9 etc., the circuit can be easily and inexpensively constructed, and the tolerance for tape fluctuations, tape hits, etc. is increased, and noise leading edge detection is possible. This allows for highly accurate noise feeding.

〔Effect of the invention〕

As described above, according to the present invention, a dropout pulse is created by shaping the waveform of noise generated during still playback,
Since the dropout pulse is used to detect the leading edge of the noise and thereby stop the noise feed, it is possible to stably send the noise, and the circuit configuration can be made simple and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the apparatus, and FIG. 3 is a diagram of a conventional magnetic recording/reproducing apparatus. 1 is a block diagram of a portion corresponding to FIG. 1, and FIG. 4 is a timing chart for explaining the operation of this conventional device. 6... Comparison pulse generator, 7... Reference pulse generator, 8... Drum rotation pulse generator, 15... Dropout pulse generator, 16... Noise tip detection circuit, 17...・Load resistance, 19...transistor, 20
...Capacitor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a magnetic recording and reproducing device, a noise sending means for performing noiseless field still reproduction during reproduction, a dropout pulse generator for generating a dropout pulse train by shaping noise generated during still reproduction, and a dropout pulse generator for generating a dropout pulse train by shaping noise generated during still reproduction; A noise leading edge detection circuit receives an out pulse train as input and detects the leading edge of noise from the pulse at the leading edge thereof; and a noise feeding stop circuit which stops the noise feeding means when the noise leading edge detected by the noise leading edge detection circuit is sent by a predetermined amount. 1. A magnetic recording and reproducing device comprising: means. (2) The noise tip detection circuit has a transistor whose base receives the dropout pulse train, whose collector is connected to a power supply via a load resistor, and whose one end is a connection point between the collector of the transistor and the load resistor. and a capacitor whose other end is grounded, the capacitor is charged when the dropout pulse is not input, and rapidly discharged when the dropout pulse is input. The magnetic recording and reproducing device according to item 1.