JPH0467437A - Video signal recording/reproducing device - Google Patents

Abstract

PURPOSE:To realize the recording of a long period of time by changing the pulse width of a laser drive pulse, and simultaneously, controlling the pulse width of the laser drive pulse so that the optimum recording power of a laser light source becomes constant at the time of generating the laser drive pulse in accordance with a modulated FM modulation signal. CONSTITUTION:A recording part 21 is provided with a modulating means 23 to FM-modulate an inputted video signal 22, and a laser drive pulse generating means 24a to generate the laser drive pulse in accordance with the modulated FM modulation signal and in addition, output the generated laser drive pulse after changing its pulse width in conformity to some definite rule. A recording means 25 to focus and record laser light generated in conformity to this laser drive pulse at a prescribed position on an optical disk memory 27 as a recording medium is connected in order. The laser drive pulse generating means 24a is connected to a detecting means 24c to detect linear velocity or a recording diameter and a pulse generation control means 24b to control the recording power so as to make it constant on the basis of this signal. Thus, the recordable time can be prolonged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video signal recording and reproducing device for recording and reproducing video signals on and from an optical disk memory used as a large-capacity memory. .

[Conventional technology]

Conventionally, magnetic tapes, optical disk memories, and the like have been used as recording media for video signals.

In particular, optical disk memories have been increasingly used in recent years due to their ease of handling and operation.

Such optical disk memories include, for example, playback-only types such as compact disks and laser video disks, which are recorded during the manufacturing process of the optical disk memory, and punch-type optical disks that use Te-C or the like as a recording medium. There are known write-once types, such as memories, which allow recording only once, and rewrite types, such as magneto-optical disks, which can be recorded and erased any number of times.

For example, recording on a read-only optical disk memory is performed by canting a disk master with an Ar laser and copying it onto a plastic substrate by injection molding.

On the other hand, write-once and rewritable types use laser light generated by a semiconductor laser to perform recording and reproduction.

[Problem to be solved by the invention]

By the way, in the case of the above-mentioned optical disk memory, the recording area is limited, so in order to increase the recording capacity, it is necessary to increase the recording density as much as possible.

By the way, the recording density of the above-mentioned optical disk memory is determined by the condensed beam diameter of the Ar laser or semiconductor laser.
The diameter of this focused beam depends on the wavelength of the light emitted by the laser. Normally, the bit length that can be recorded and played back with sufficient playback performance is 0.5 for playback-only optical disk memory.
It is quite large, about 1 μm for write-once type and rewritable type.

Furthermore, when the track pitch of an optical disk memory is made as small as the diameter of a laser beam, crosstalk occurs, so the limit is usually about 1.6 μm.

Therefore, when recording a video signal, for example, a diameter of 30
On a 0 mm read-only laser disc, recording is possible only for a relatively short time of about 30 minutes in the case of a constant angular velocity force type (hereinafter referred to as CAV type) with a disc rotation speed of 1800 rpm. Further, for a laser disk with a diameter of 200 mm, the recording time is about 14 minutes in the case of the CAV method, and about 18 minutes in the case of the constant linear velocity force method (hereinafter referred to as the CLV method), which is -1 layer shorter.

As described above, a video signal having a particularly large amount of information has a problem in that it is difficult to record it for a long time.

[Means for Solving the Problems] In order to solve the above-mentioned problems, a video signal recording and reproducing device according to the present invention records and reproduces a video signal using a laser beam on a recording medium. In the playback device, a laser light source that generates a laser beam, an FM modulation means that performs FM modulation on a video signal, and a pulse width of the laser drive pulse is changed when generating the laser drive pulse in accordance with the modulated FM modulation signal. a pulse generation control means that controls the pulse width of the laser drive pulse in the laser drive pulse generation means so that the optimum recording power of the laser light source is constant; a condensing means for condensing a laser beam generated by the laser light source onto a recording medium; a driving means for driving the recording medium;
FM demodulation means for demodulating the M modulated signal.

[Function] As mentioned above, one of the reasons why it is difficult to record and reproduce video signals on a recording medium for a long time is that the length of the recording bits recorded on the recording medium is smaller than the laser beam diameter. If the length becomes too short, the amount of reproduced signal decreases rapidly. This is considered to be because the recording focus has an elliptical shape that is substantially elongated in the track direction.

In order to prevent the above-mentioned reduction in the amount of reproduced signals and obtain a reproduced image with sufficient image quality, the amount of reproduced signals greater than a certain value is required. Therefore, the amount of video signal that can be recorded on a recording medium is determined by the minimum recording bit length that allows a reproduced signal amount of a certain value or more to be obtained. By shortening this minimum recording bit length, video signals can be recorded and played over long periods of time.
In order to enable reproduction, it is necessary to increase the amount of reproduction signal with a short bit length.

In order to achieve this, the inventor considered changing the pulse width of the laser drive pulse (recording pulse) that drives the laser light source without changing the duty of the reproduction signal. Figure 1 shows the pulse duty of the laser drive pulse and the reproduced signal when a single frequency is recorded by generating a laser drive pulse by alternately switching the laser power of the laser light source between two levels, high level and low level. The results of determining the relationship with the amount using the recording diameter (the radial position at which recording is performed on the recording medium) as a parameter are shown. However, the recording medium was rotated using the CAV method. Furthermore, the reproduced signal amount at each point in FIG. 1 is the value obtained when the data is reproduced after recording with the optimum recording power, and is shown in relative display.

As is clear from the figure, the optimum recording power increases as the duty of the recording pulse decreases, in other words, as the pulse width of the recording pulse decreases. In this way, by reducing the pulse width of the recording pulse and increasing the recording laser power, the amount of the reproduced signal can be increased. becomes possible.

The reason why the reproduction signal amount increases due to the reduction in the pulse width of the recording pulse and the increase in the recording laser power as described above is considered to be because the recorded bits become approximately circular. On the other hand, as mentioned above, in the past, the recorded bits had a substantially elliptical shape, which led to a reduction in the amount of reproduced signals. Note that in the present invention, the duty of the recording pulse is set to 50.
%, but the duty of the recorded bits and ends (the ratio of the recording bit length to the length of the blank area between recording bits) that is actually recorded is approximately 50%, so the duty of the reproduced signal is the same as before. It will be about 50%.

Next, Figure 2 shows the linear velocity (proportional to the recording diameter in the CAV method) when a single frequency is recorded by alternating the laser power of the laser light source between two levels.
The results of measuring the relationship between the 1/2) power (square root) and the optimum recording power using the duty of the recording pulse as a parameter are shown. As you can see from this episode, by changing the recording pulse duty for each recording diameter, more specifically,
By increasing the duty of the recording pulse toward the outer circumference with a larger recording diameter, the recording power is kept constant and this recording power is made to correspond to the optimum recording power for each recording diameter. be able to.

As is clear from Figure 1, if the recording diameter becomes larger, a sufficient amount of reproduction signal can be obtained even if the duty of the recording pulse becomes somewhat larger. Increasing the duty does not adversely affect the quality of reproduced images.

As described above, by changing the duty of the recording pulse according to the recording diameter, the recording power can be easily controlled by keeping the recording power constant regardless of the recording diameter or linear velocity.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

The video signal recording and reproducing apparatus according to this embodiment is for recording and reproducing video signals on an optical disk memory. As shown in FIGS. 3 and 4, this device has a recording section 2.
As shown in FIG. 3, the recording section 21 includes a modulation means 23 for FM modulating the input video signal 22, and a laser drive pulse ( a laser drive pulse generating means 24a that generates a recording pulse) and outputs the generated laser drive pulse after changing its pulse width (for example, pulse duty) according to a certain rule; A recording means 25 having a condensing means for condensing the laser beam onto a predetermined position on an optical disk memory 27 serving as a recording medium is connected in sequence. Further, the recording section 21 is provided with a driving means 26 for driving the optical disk memory 27 in synchronization with the input video signal.

On the other hand, as shown in FIG.
and a demodulating means 33 for performing FM demodulation of the reproduced FM modulated signal are connected in this order, and the demodulating means 33 outputs a reproduced video signal 34. Further, during reproduction, the driving means 26 drives the optical disk memory 27 in synchronization with the reproduced video signal 34.

The detailed structure of the recording section 21 and the reproducing section 31 is explained in the fifth section.
This will be explained based on the diagram and FIG. However, here, as the optical disk memory 27, a magneto-optical disk 27° (recording is performed using a so-called optical modulation method) using DyFeCo as a recording medium is used.

In the recording section 21, as shown in FIG. 5, an input terminal 47 to which the video signal 22 is input is connected to a low-pass filter 41. This low pass filter 41
is connected to the mixer 42 via a modulation means 23 that performs FM modulation. This mixer 42 has input terminals 48 and 4.
The 1-channel and 2-channel audio signals 43 input through the audio signal processing circuit 45 and the audio modulation circuit 44
, where the audio signal 43 is mixed with the video signal 22 described above.

The mixer 42 includes the laser drive pulse generating means 24 described above.
a is connected, and this laser drive pulse generation means 24a is connected to, via an LD driver 25a in the recording means 25,
It is connected to a pickup 25b that includes a laser light source consisting of an LD (laser diode), a condensing means consisting of an objective lens, etc., and a magnetic field applying section. Note that the magnetic field applying section may be configured separately from the pickup 25b.

Further, the laser drive pulse generation means 24a is connected to a detection means 24c for detecting linear velocity or recording diameter, and furthermore, the laser drive pulse generation means 24a is connected to a detection means 24c for detecting linear velocity or recording diameter, and further, the laser drive pulse generation means 24a is configured to keep the recording power constant based on the signal from the detection means 24c. Pulse generation control means 24b that controls the laser drive pulse generation means 24a
It is connected to the.

A pickup control circuit 25c is connected to the pickup 25b, and this pink amplifier control circuit 25c allows the laser beam to be focused correctly on a predetermined position on the magneto-optical disk 27''. ing.

The reference clock generation circuit 46 that generates the reference clock includes:
It is connected to the modulation means 23, the audio modulation circuit 44, and the motor control circuit 26a in the drive means 26, and is connected to the FM modulation means 23 and the audio modulation circuit 44 based on the reference clock.
The synchronization signal is controlled by the motor control circuit 26a, and the rotational speed of the motor 26b is controlled by the motor control circuit 26a. Note that the driving means 26 includes a motor control circuit 26a.
and a motor 26b that rotationally drives the magneto-optical disk 27'.
It is composed of.

On the other hand, in the reproducing section 31, as shown in FIG. 6, a pickup 25b is connected to a big amplifier control wholesale circuit 25c and a preamplifier 32a to constitute a reproducing means 32, and the signal reproduced by the pickup 25b is transmitted to the preamplifier 32a.
It seems to be amplified by

The preamplifier 32a is a bandpass filter 5.
It is connected to 1.54. One bandpass filter 54 is connected to an audio signal processing circuit 56 via an audio demodulation circuit 55.
It is connected to the. Then, in the audio demodulation circuit 55, the audio signal that has passed through the bandpass filter 54 is demodulated,
Furthermore, in the audio signal processing circuit 56, 1 channel and 2
After being separated into channels, it is outputted as a reproduced audio signal 57 via output terminals 59.

Further, the other bandpass filter 51 includes an equalizer 52,
Demodulation means 33 and low pass filter 53 for performing FM demodulation
is connected to the output terminal 58 via the demodulating means 33.
The FM demodulated video signal is output as a reproduced video signal 34 via an output terminal 58.

The reference clock generation circuit 46 is also connected to the demodulation means 33 and the audio demodulation circuit 55, and the synchronization signals of the demodulation means 33 and the audio demodulation circuit 55 are controlled based on the reference clock. .

Next, an example of a specific configuration of the laser drive pulse generating means 24a will be explained based on FIG. 7.

The laser drive pulse generation means 24a has four input terminals 61.
a to 61d, and an FM modulation signal is inputted from a mixer 42 (FIG. 5) to an input terminal 61a.

The input terminal 61a is connected to an input comparator 62a that converts the FM modulation signal into pulses. The input comparator 62a compares the FM modulation signal with a slice level set by a variable resistor, thereby binarizing the FM modulation signal and converting it into a pulse.

The input comparator 62a is connected to one input terminal of the AND circuit 62b for inhibiting, and the input terminal 61b is connected to the other input terminal of the AND circuit 62b for inhibiting.
An inhibit signal is input from the input terminal.

That is, when the above inhibit signal is at a high level, the output of the input comparator 62a is output as is from the positive output terminal of the AND circuit 62b for inhibiting, and the signal obtained by inverting the output of the input comparator 62a is outputted from the AND circuit 62b for inhibiting. It is designed to be output from the negative output terminal. On the other hand, when the inhibit signal is at a low level, the positive output of the inhibit AND circuit 62b is fixed at a low level, and the negative output is fixed at a high level. In addition, the inhibit signal is sent to the pickup 25.
It is set to a high level when the LD is driven in b.

The positive output terminal of the inhibit AND circuit 62b is connected to the trigger input terminal of the trigger reset circuit 63c. Then, a pulse (see FIG. 8) is input from the inhibit AND circuit 62b to the trigger input terminal.
A sawtooth wave (see I in FIG. 8(C)) is generated by the timing control circuit 63d based on the rise of the signal (see a). Further, the above-mentioned sawtooth waveform is reset by the rise of a reset pulse (see FIG. 8(d)), which will be described later, which is input from the trigger reset circuit 63c to the reset input terminal of the timing control circuit 63d.

A DAC (digital to analog converter) 63e is connected to the timing control and saving circuit 63d. This DA
For example, 8-bit data is input to C63e from an input terminal 61d via a latch circuit 63f. A timing signal is input to the latch circuit 63f from the input terminal 61c. DAC based on the above 8-bit data.
Slice level made with 63e (■ in Fig. 8(C)
) is the output circuit 6 via the timing control circuit 63d.
Sent to 4. Then, the sawtooth wave generated in the timing control circuit 63d is sliced by the slice level, and at the first crossing point, a negative polarity output (M8 (e)
) changes from low level to high level, and the state of the positive polarity output changes from high level to low level. Next, the sawtooth wave (■ in Figure 8 (C)) is reset by the reset pulse (Figure 8 (d)), and at the same time the negative polarity output (the 8
(e) changes from high level to low level, and the state of the positive polarity output changes from low level to high level.

These outputs will be output from the output circuit 64.

The reset pulse (FIG. 8(d)) of the trigger reset circuit 63c is sent to the output circuit 64 in the AND circuit 63a.
AND circuit 62b for positive output pulse and inhibitor
AND with the positive output pulse of the resistor 67.
The AND circuit 63b calculates the AND of the result integrated by the integrating circuit consisting of a and the capacitor 67b and the negative output pulse (FIG. 8(b)) of the inhibit AND circuit 62b, and triggers the output of this AND circuit 63b. It is generated by inputting it to the reset input terminal of the reset circuit 63c.

In the above configuration, the 8 input from the input terminal 61d
By arbitrarily setting the slice level of the sawtooth wave in the timing control circuit 63d using bit data,
The pulse width of the binarized pulse of the FM modulation signal input from the input terminal 61a can be arbitrarily controlled.

This method reduces the pulse width by a certain amount in the pulse waveform, and does not depend on the frequency of the FM modulation signal input from the input terminal 61a. The negative polarity output of the output circuit 64 is sent to the output terminal 66 via the output huffer 65 as a laser drive pulse. This output terminal 66 is connected to the LD driver 25a in FIG. 5.

The results of actually recording and reproducing video signals using the video signal recording and reproducing apparatus configured as described above will be explained.

-g, S/N (SN ratio) is used as an index for evaluating the signal quality of the reproduced video signal 34. It is known that there is a relationship between this S/N and the C/N (CN ratio) at the carrier frequency of a luminance signal in a video signal as shown in the following equation (1).

S/N=C/N-Q ・・・・・・(1) Here, Q
The value is a constant determined by the system. Therefore, in order to improve the S/N of reproduced images, it is sufficient to obtain a high C/N.

As can be seen from FIG. 1, for example, the recording pulse, that is,
By reducing the duty of the laser drive pulse, the pulse width of the recording pulse can be reduced, thereby improving the C/N of the reproduced signal. Therefore, by using a video signal recording and reproducing apparatus configured as described above, the duty of the recording pulse (in this case, the FM video signal is
FIG. 9 shows the results of measuring the relationship between the duty (in terms of MHz) and the S/N of the reproduced image. Here, as the FM modulation method, a method proposed by Philips Corporation is adopted, and recording and reproduction are performed under the condition that the bit length at the carrier frequency of the luminance signal in the video signal corresponds to 0.73 μm. It can be seen from FIG. 9 that by shortening the pulse width of the recording pulse, the S/N at the middle circumference of the disk (at the open position in the radial direction) is improved from the conventional 38 dB to more than 40 dB.

With conventional technology, in order to obtain an S/N of 40 dB or more in the middle, a bit length of 0.84 μm or more is required, so for a disk with a diameter of 300 mm and a track pitch of 1.6 μm, the CAV method requires Recording and playback could only be performed for about 22 minutes, whereas with the CLV method it was only about 31 minutes. This time, by using a video signal recording and reproducing device with the above configuration, we achieved an S/N of more than 40 dB with a bit length of 0.73 μm.
Therefore, in the case of the above-mentioned disk with a diameter of 300 mm and a track pitch of 1.6 μm, recording/reproduction time of about 26 minutes is possible with the CAV method and about 40 minutes with the CLV method. In other words, in the case of the CAV method, the required bit length is shortened, making it possible to record to a position closer to the inner circumference of the disc than in the past, increasing the recording capacity. As the bit length decreases, the linear velocity of the disk decreases accordingly, or
Alternatively, since the recording frequency can be increased, the recording capacity can also be increased.

Similarly to the above, in the case of a disk with a diameter of 130 mm, the conventional CLV method could only record and reproduce for about 4.3 minutes, but with the configuration of this embodiment, it is possible to record and reproduce for about 5.2 minutes. Became.

At this time, if the amount of reduction in the pulse width of the recording pulse at the inner circumference of the magneto-optical disk 27'' is constant to the outer circumference, the second
As is clear from the figure, the recording power at the outer periphery is insufficient. However, as can be seen from FIG. 9, since the S/N on the outer circumference is already sufficiently secured compared to the inner circumference, the amount of recording pulse reduction by the laser drive pulse generation means 24a can be reduced on the outer circumference. .

Therefore, the pulse generation control means 24b gradually increases the duty of the recording pulse toward the outer circumference, in other words, decreases the reduction amount of the recording pulse.
By performing the control, it becomes possible to always record with the optimum recording power while keeping the recording power constant for each recording diameter. That is, for example, the pulse generation control means 24b including a converting section into which characteristics as shown in FIG. ), which simplifies the configuration of the laser power control section.

In the above embodiment, as an example of a method of changing the pulse width of the recording pulse, a method of reducing a certain amount of the recording pulse was shown, but the duty of the recording pulse may be changed.

In the above embodiment, a magneto-optical disk 27° on which recording is performed using an optical modulation method was illustrated as an example of the optical disk memory 27. It may be an optical disc. Furthermore, the present invention can also be applied to the cutting of master discs for read-only optical discs.

[Effects of the Invention] As described above, the video signal annotation playback device according to the present invention has the following effects.
Recording and recording of video signals on recording media using laser light
In a video signal recording and reproducing device that performs reproduction, a laser light source that generates a laser beam, an FM modulation unit that performs FM modulation on the video signal, and a laser drive unit that generates a laser drive pulse in response to the modulated FM modulation signal. A laser drive pulse generation means that can change the pulse width of the pulse; and a pulse generation control means that controls the pulse width of the laser drive pulse in the laser drive pulse generation means so that the optimum recording power of the laser light source is constant. , a focusing means for focusing laser light generated by the laser light source on a recording medium based on a laser driving pulse, a driving means for driving the recording medium, and an FM demodulating the reproduced FM modulation signal. The configuration includes demodulation means.

This allows the minimum recording bit length to be shortened, so CA
In the case of the V method, it is possible to use the recording medium to a position closer to the inner circumference, while in the case of CLVO, the driving speed of the recording medium can be lowered, so the recording time is increased in either method. It has the effect of being able to

Further, the recording power is always fixed at a constant value without changing the recording power depending on the linear velocity or the recording diameter, and
Since the pulse width of the laser drive pulse is adjusted so that this recording power becomes the optimum recording power for each recording diameter, the laser drive system can be simplified.

Note that in order to keep the recording power constant, it is necessary to increase the pulse width of the laser drive pulse toward the outer periphery of the recording medium, but on the outer periphery, even if the pulse width is originally large, it is Since the amount of reproduced signal is obtained, no inconvenience occurs.

[Brief explanation of the drawing]

FIGS. 1 to 9 show one embodiment of the present invention. FIG. 1 is a graph showing the relationship between the duty of the recording pulse and the amount of reproduced signal when recording a single frequency. FIG. 2 is a graph showing the results of measuring the square root of the linear velocity and the optimum recording power when recording a single frequency by changing the duty of the recording pulse. FIG. 3 is a block diagram showing the configuration of the recording section. FIG. 4 is a block diagram showing the configuration of the playback section. FIG. 5 is a block diagram showing the detailed configuration of the recording section. FIG. 6 is a block diagram showing the detailed configuration of the playback section. FIG. 7 is a circuit diagram showing the detailed configuration of the laser drive pulse generation means. FIG. 8 is a timing chart showing the operation of the laser drive pulse generating means. Figure 9 shows the duty of the laser drive pulse and the S of the reproduced image.
It is a graph showing the relationship with /N. 23 is an FM modulation means, 24a is a laser drive pulse generation means, 24b is a pulse generation control means, 26 is a drive means, 2
7 is an optical disk memory (recording medium), 27' is a magneto-optical disk (recording medium), and 33 is an FM demodulating means.

Claims (1)

[Claims] 1. A video signal recording and reproducing device that records and reproduces video signals on a recording medium using a laser beam, comprising: a laser light source that generates a laser beam;
FM modulation means for modulating, laser drive pulse generation means capable of changing the pulse width of the laser drive pulse when generating the laser drive pulse according to the modulated FM modulation signal, and an optimum recording power of the laser light source. pulse generation control means for controlling the pulse width of the laser drive pulse in the laser drive pulse generation means so that the pulse width of the laser drive pulse is constant; A video signal recording and reproducing apparatus comprising a light condensing means, a driving means for driving the recording medium, and an FM demodulating means for demodulating the reproduced FM modulated signal.