JPS60134577A - Magnetic disc reproducing device - Google Patents

Abstract

PURPOSE:To eliminate disturbance of a pattern and to make a scanning line unremarkable by swithcing and outputting a digital video signal delayed by 0.5H while two-revolution of a disc is taken as 1 cycle and a video signal not delayed at a prescribed timing. CONSTITUTION:An output of an FM demodulator 11 is applied to an A/D converter 16, where an analog TV signal is converted into a digital video signal. The digital video signal of an output of the converter 16 is inputted to a digital memory circuit 17. The digital video signal is inputted to the circuit in the reproduced order from a magnetic disc, and the digital video signal delayed by 0.5H and the video signal not delayed are outputted switchingly in a prescribed timing while taking two-revolution of the disc 7 is taken as one cycle.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetic disk reproducing device, and particularly to a device for recording or reproducing still images of television signals using a magnetic disk as an information recording medium, such as in an electronic camera. The present invention relates to a reproduction signal processing circuit in the apparatus, particularly on the reproduction apparatus side.

[Prior Art] FIG. 1 is a schematic block diagram of the recording device side of an electronic camera, which is the backbone of the present invention. In the figure, the image of the subject of this electronic camera is transferred to a photoelectric conversion element 2 by an optical lens 1.
imaged on top. The photoelectric conversion element 2 includes a tube-type device such as a vidicon, a solid-state image sensor using a semiconductor, etc., and converts an input optical signal into an electrical signal, and further outputs it in the form of a so-called television signal. It has become. The output signal of the photoelectric conversion element 2 is subjected to FM modulation by an FM modulator 3, passes through an analog switch 4, a recorder 6 and an amplifier 5, is supplied to a magnetic helad 6, and is concentrically recorded on a magnetic disk 7. . The switch control circuit 8 controls the opening and closing of the analog switch 4, so that the analog switch 4 supplies the FM signal to the recording amplifier 5 for the time required for one rotation of the magnetic disk during recording.

In consideration of ease of handling, it is desirable for the electronic camera as described above to be as small and lightweight as the current optical camera.

Therefore, the magnetic disk 7, which is a recording medium, also needs to be small and lightweight.Currently, sheet-like magnetic disks 7 with a diameter of about 5QlRIIl and a thickness of about several tens of micrometers are used. There is. However, in the case of such small magnetic disks, it is not possible to obtain sufficient frequency characteristics to record high-quality image signals at low rotational speeds. The required frequency characteristics are obtained by rotating at high speeds per minute. In this case, the time required for one rotation is about 1/60 second, which is the same as the time for one field of the preview signal. Therefore, one field time worth of television signals is FM-modulated and recorded concentrically on the magnetic disk 7 per rotation to form a recording track. Furthermore, by intermittently moving the position of the head in the radial direction, multiple fields of television signals can be recorded.

FIG. 2 is a block diagram showing an example of a conventional magnetic disk reproducing apparatus for reproducing still image information recorded on a magnetic disk as described above. In the figure, the magnetic disk 7 rotates at about 3,600 revolutions per minute as in the case of recording, and when the magnetic disk 9 comes into contact with the position of the concentric recording track where signals are recorded in advance, the output of the magnetic disk 9 changes. , a weak FM signal of about 1 mvpp or less than that is reproduced. This signal is amplified to the required level by the head output amplifier 1O, and FM demodulated by the FMS modulator 11 to obtain a television signal.Furthermore, this television signal is sent to the output terminal 13 of the device via the output amplifier 12. Supplied.

FIGS. 3A and 3B are diagrams for explaining the operation of the conventional magnetic disk reproducing apparatus shown in FIG. 2. That is, FIG. 3A shows that in the recording device of the electronic camera described above,
An example is shown in which a television signal output from the photoelectric conversion element 2 is reproduced on a television receiver.

Further, FIG. 3B shows that the magnetic disk 7 on which the video shown in FIG. 3A is recorded is played back by the conventional magnetic disk playback device shown in FIG. An example of reproduction on a John receiver is shown. Normally, as shown in Fig. 3A, two lines should be seen vertically in a straight line, but in the case of Fig. 3B, which is played back by a conventional magnetic disk playback device, a portion of the screen, that is, from point a to point b. The two straight lines are played back with a bend in the area between the points, resulting in an image that lacks the fidelity of the original.

FIG. 4 is a diagram for explaining the cause of the above-mentioned defects. In the figure, FIGS. 4(a) and (b) are
2A and 2B illustrate the synchronization relationships of even and odd fields of a typical television signal, respectively. As is well known, in television signals, due to the 2:1 interlace relationship, the position of the horizontal synchronizing signal is relatively shifted by 0.5 horizontal frequency time between even and odd fields. When recording one field time of such a television signal on a magnetic disk, for example, the fourth
One field time from point C of the even field shown in FIG. 4(a) to point d of the odd field shown in FIG. 4(b) is recorded on the same circumference of the magnetic disk 7 in one rotation. When recording tracks for fields are formed, the television signal waveform obtained by continuously reproducing the recording tracks with the magnetic disk reproducing apparatus shown in FIG. 2 is as follows.
As shown in Figure 4 (0), with point C as the border, O,
5H (IH is one horizontal frequency time). When such a signal is applied to a television receiver,
The synchronization AFC circuit on the receiver side had been following the normally sent synchronization signal up to point C, but due to the 0.51-1 time difference in the horizontal synchronization signal occurring after point C, C is disturbed at synchronization Δ and starts to pull in again. As shown in Figure 3B, the disturbance in the reproduced image between point a and point b on the screen on the television receiver is caused by the synchronization AFC of the receiver being disturbed, but the pull-in ends again. The screen continues to be distorted until you reach the point where you want to do so. The period of this screen disturbance varies depending on the television receiver, but it ranges from several H to several 101-1, resulting in a screen that is extremely difficult to view.

Furthermore, since the reproduced television signal shown in Figure 4 (0) does not maintain the regular 2:1 interlacing, the section from point b to point C of the reproduced image shown in Figure 3B is Even in other sections that look normal, coarse scanning lines appear and make the image difficult to see.

FIG. 5 is a block diagram showing still another example of a conventional magnetic disk reproducing apparatus proposed to solve the above-mentioned drawbacks. In the figure, the output of the FM demodulator 11 is supplied to one input of a switch circuit 15 and also to the input of an analog delay circuit 14. The delay amount of the analog delay circuit 14 is exactly 0.5H, and a COD or the like is used for such a delay circuit. The output signal of the FM demodulator 11, which has been delayed by 0.5H in the analog delay circuit 14, is supplied to the other input of the switch circuit 15. The switch circuit 15 switches the two signals supplied to each input at a predetermined timing, with two revolutions of the magnetic disk 7 as one cycle, and selectively outputs the signals.

FIG. 6 is a diagram for further explaining the operation of the conventional magnetic disk reproducing apparatus shown in FIG. 5, and schematically shows the timing at which the switch circuit 15 is switched. Note that FIG. 6(a) schematically shows the television signal reproduced from the magnetic disk 7, where 0 is the equalization pulse section, h is the vertical synchronization signal section, 1 is the equalization pulse section, and j is the magnetic disk. 7 shows the recording start point when recording the signal.

Since video information for exactly 1-field time (262, 58) is concentrically recorded on the magnetic disk 7 during one rotation, the output signal of the FMI adjuster 11 in FIG. The same signal will be repeated every time. FIG. 6(b) shows the switching timing of the switch circuit 15. When the state is "0", the switch circuit 15
The output signal of 1 is output as is, and when the state is ``1'', a signal delayed by 0.5H by the analog delay circuit 14 is output. During an arbitrary rotation, when the switch circuit 15 is in the "0" state, when the reproduced signal starts outputting the equalization pulse g, the switch circuit 15 becomes "1" within the equalization pulse section Q. The state is set to "0" again within the equalization pulse section i that starts after the vertical synchronizing signal section. Furthermore, when the recording start point j is reached, the state is set to "1" again. The rotation of the magnetic disk 7 begins the next rotation, and the equalization pulse section l! I.O.

Even if the vertical synchronization signal section 1 equalization pulse section 1 is reproduced, the state does not change this time and rlJ continues until the next recording start point j.
, and at this recording start point j, the state is changed to rOJ again.
The state of rOJ is maintained until the next rotation starts and the equalization pulse section Q is reproduced. In this way, by switching the switch circuit 15 at a predetermined timing with two rotations of the magnetic disk 7 as one cycle,
The signal obtained at the output of the switch circuit 75 has the even and odd fields of the television signal in a pseudo manner, that is, it is in the form of a frame signal.

Therefore, when such a signal is reproduced on a television receiver, as shown in Figure 3B, there is no disturbance in the synchronous AFC circuit of the television receiver, and the 2:1 increment is maintained. As a result, the scanning lines are no longer noticeable.

However, in the conventional device having such a configuration, even if there is a slight difference in amplitude between the signal that is delayed by 0.5H and the signal that is not delayed by 0.5H, which appears at the output of the switch circuit 15, Even if there is an offset in the DC potential, when reproduced on a television receiver, flickering occurs in the image, making the screen extremely difficult to view. Regarding the input/output characteristics of the analog delay circuit 14, it is very unlikely that the input/output signals will have the same amplitude and the same DC potential due to variations in the elements used in the circuit or transmission efficiency. The possibility is slim. Therefore, although not shown in the apparatus of FIG. 5, an adjustment mechanism is provided at the signal input section of the switch circuit 13 to adjust the amplitude and DC potential between input double signs to be the same. However, this adjustment requires great precision, and even if it is adjusted under the same environmental conditions, changes in temperature, solubility, etc. will cause the adjustment to deviate and cause flicker, so it is impossible to suppress the residual flicker. The drawback was that it couldn't be done.

[Summary of the Invention] The present invention was made in view of the shortcomings of the conventional device, and the present invention converts the output signal of the FM demodulator from A/D, performs digital signal processing using a digital memory circuit, and then converts the output signal to D.
An object of the present invention is to provide a magnetic disk reproducing device which can obtain a reproduced image having an accurate 2:1 incrace relationship and flicker-free by performing /A conversion.

Hereinafter, this invention will be described in more detail with reference to embodiments shown in the drawings.

[Embodiment of the Invention] FIG. 7 is a schematic block diagram showing an embodiment of the invention. Note that in FIG. 7, the same parts as those in the device in FIG. 5 are given the same reference numerals. In the figure, FM
The output of the tI modulator 11 is given to an A/D converter 16, which converts the analog television signal into a digital video signal. In A/D conversion of television signals, the sampling frequency is generally three times the color subcarrier frequency <
The color subcarrier frequency (approximately 10.7 MHz) or four times the color subcarrier frequency (approximately 14.3 MHz) lfi is used, and the number of quantization bits is often 7 or 8 bits. A/
The digital video signal output from the D converter 16 is input to a digital memory circuit 17.

The digital memory circuit 17 includes a RAM (Random A
Semiconductor elements such as access memory (access memory) are used. The digital video signal is input to the digital memory circuit 17 in the order in which it was reproduced from the magnetic disk 7, but the output of the digital memory circuit 17 includes the digital video signal delayed by 0.5H and the other digital video signals. The rotation is assumed to be one cycle, and the output is switched at a predetermined timing. In the digital memory circuit 17, in order to output the digital video signal with a delay of 0.5H, it is sufficient to specify the memory read address by shifting the number by 0.5H. can be obtained. The timing of switching between the video signal delayed by 0.5H and the other video signal is as follows:
It may be the same as the example of the conventional device explained in the figure.

In order to read a digital video signal from the digital memory circuit as described above, that is, to specify a read address, this embodiment uses a synchronization signal separation circuit 18, a rotational position detection circuit 19, a timing signal generation circuit 2○, and an address. A designation circuit 21 is provided. Rotation synchronization signal separation circuit 18
separates the synchronization signal from the analog video signal output from the FMIa modulator 11 and supplies it to the timing signal generation circuit 20. The timing signal generation circuit 20 detects the above-mentioned equalization pulse section Q, vertical synchronization signal section, and equalization pulse section based on this synchronization signal.

On the other hand, the rotational position detection circuit 19 detects the rotational position of the magnetic disk 7. For example, machine-readable marks are attached to positions on the outer circumference of the magnetic disk 7.
The rotational position detection circuit 19 detects this mark. That is, the rotational position detection circuit 19 outputs a detection pulse every time the magnetic disk 7 rotates once. This detection pulse is
It is applied to the timing signal generation circuit 2O. Note that recording on the magnetic disk 7 is started from the position of the above-mentioned mark in one round of the recording track. Timing signal generation circuit 2
0 is based on the synchronization signal from the synchronization signal separation circuit 18 and the rotational position detection pulse from the rotational position detection circuit 19.
A timing signal as shown in FIG. 6(b) is generated.

This timing signal is used for address specified times v! Given to I21. The addressing circuit 21 performs addressing so that the undelayed digital video signal is read out from the digital memory circuit 17 when the timing signal is rOJ, and vice versa. Addressing is performed so that the digital video signal delayed by 0.5H from the address is read out.

The output of the digital memory circuit 17 is sent to the D/A converter 22.
and converted to the original analog television signal. This television signal is output from an output terminal 13 via an output amplifier 12.

By the way, the 0 output from the digital memory circuit 17
The digital video signals that have been delayed by 5 days are exactly the same as the original digital video signals that have not been delayed by 0.5H, and even if they are converted into analog signals by the D/A converter 22, There is no difference in amplitude or DC level. Therefore, the television signal output from the output terminal 13 is a television signal that has been interlaced at an exact ratio of 2:1, and if this signal is reproduced on a television receiver, scanning lines will be visible. Furthermore, stable reproduced images without flicker can be obtained.

[Effects of the Invention] As described above, according to the present invention, a video signal reproduced from a magnetic disk is divided into a digital video signal delayed by 1/2H and an undelayed video signal, with two rotations of the magnetic disk being one cycle. Since the output is switched and output at a predetermined timing, the 1
It is possible to convert a field's worth of television signals into one frame of television 23218 with accurate 2=1 interlacing, eliminating screen disturbances and making scanning lines less noticeable. Furthermore, in the present invention, the video signal reproduced from the magnetic disk is converted into a -H digital video signal and then stored in the digital memory circuit before the above processing is performed.
There is no difference in amplitude or DC level between the signal and the undelayed video signal, and a stable reproduced image without flicker can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing a magnetic disk recording device for an electronic camera, which is the background of the present invention. FIG. 2 is a block diagram showing an example of a conventional magnetic disk reproducing apparatus. FIGS. 3A and 3B are illustrative views for explaining the drawbacks of the conventional magnetic disk reproducing apparatus, based on FIG. 2. FIG. 4 is a diagram for explaining the cause of the defect in the @ position in FIG. 2. FIG. 5 is a block diagram showing another example of a conventional magnetic disk reproducing apparatus. 6th
The diagram is shown in Figure 5'! There are diagrams for explaining the operation of the J magnetic disk reproducing apparatus, and in particular, the timing for switching the switch circuit 15 is schematically shown. FIG. 7 is a schematic block diagram showing one embodiment of the present invention. In the figure, 7 is a magnetic disk, 9 is a magnetic head, and 10 is a magnetic disk.
is a head output amplifier, 11 is an FM demodulator, and 16 is an A/D
Converter, 17 is a digital memory circuit, 18 is a synchronization signal separation circuit, 19 is a rotational position detection circuit, 20 is a timing signal generation circuit, 21 is an addressing circuit, 22 is a beam, /
A converter is shown. Representative Masuo Oiwa, Commissioner of the Japan Patent Office 1. Display of the case Japanese Patent Application No. 5S-243258F2゜Name of the invention Magnetic disk reproducing device 1 3. To the representative Hitoshi Katayama of the person making the amendment Section 5. Detailed description of the invention in the specification subject to the amendment 6. Contents of the amendment (1) "Can be done" in the first line of page 6 of the specification. ” is corrected. (2) "Rotation synchronization signal separation circuit" on page 14, line 4 of the specification is corrected to "synchronization signal separation circuit." (3) "On the outer periphery" on page 14, line 12 of the specification is corrected to "on the circumference." (4) Correct "timing signal as shown" in lines 2 and 3 of page 15 of the specification to "timing signal j in the positional relationship as shown."

Claims (1)

[Scope of Claims] A reproducing device for a magnetic disk in which video information of a still image for one field of a television signal is FM-modulated and recorded concentrically for each rotation period, the magnetic disk comprising: a magnetic head for reproducing information from the magnetic head; a head output amplifier for amplifying the output signal of the magnetic head; an FM demodulator for performing FMTL modulation on the output of the head output amplifier; a D converter; a digital memory circuit that stores the output signal of the A/D converter; two revolutions of the magnetic disk as one cycle; digital video signal information that is delayed by 1/'2 of a horizontal scanning period; and digital video signal information that is not delayed. A magnetic disk reproducing device comprising: means for switching and reading digital video signal information from the digital memory circuit at a predetermined timing; and a D/A converter for converting the digital video signal information read by the reading means into an analog signal. Device.