JPH0468826B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a reproducing device for an optical disc, a magneto-optical disc, a magnetic disc, etc. The present invention relates to a playback device that plays back a disk-shaped recording medium (hereinafter simply referred to as a disk) that has been digitally recorded at a recording density while rotating it at a constant rotational speed.

(Background of the Invention) Conventionally, constant angular velocity method (hereinafter referred to as CAV method) and constant linear velocity method (hereinafter referred to as CLV method) are known as methods for digitally recording onto a disk.

Compared to the CLV method, the CAV method does not require a device for variable rotational speed control of the disk, so the recording/reproducing device is simpler. It also has the advantage of short access time during playback, but has the disadvantage that the recording density of the entire disk is smaller than that of the CLV method because the recording density decreases toward the outer periphery of the disk.

On the other hand, the CLV method has a larger recording capacity than the CAV method because there is no difference in recording density between the inner and outer peripheries of the disk, but since the rotation speed of the disk, which has a large inertial mass, must be controlled according to the radius of the disk, the recording and reproducing device Both are complicated and expensive. Another disadvantage is that the access time during playback becomes long.

Therefore, an optical disk device that has the advantages of both types, that is, a still image optical disk device that allows high-speed access and has a large storage capacity, has been proposed. For example, the tracks on an optical disk are divided into multiple groups depending on the distance from the center of rotation, and within each group
CAV method is adopted, and CLV is gradually increased between groups.
It takes a method. However, with this method, a variable rotation speed control device is still required for both the recording and playback devices, and in the end, the CLV method is sufficient for accessing widely separated groups, such as accessing from the innermost track to the outermost track. The disadvantage was that it required an access time of

(Objective of the Invention) The purpose of the present invention is to solve these drawbacks and provide a still image signal reproducing device that has both the simple configuration and high-speed access function of the CAV system and the large recording capacity (high recording density) of the CLV system. do.

(Summary of the Invention) In order to achieve the above object, the present invention rotates a disk at a constant rate, stores one screen worth of reproduced still image signals in a temporary memory, and uses a clock that is compatible with various output devices such as televisions and printers. By reading out the reproduced still image signal from the memory, a still image signal with a normal time axis is obtained, and the still image is reproduced using the still image signal.

Here, when pits are formed at the same recording density on all tracks as in the CLV method, when pits are formed at a frequency f on a disk rotating at a rotation speed ni at a disk radius ri, f=2πrini/ 2d, and from this, the pit length d is expressed by equation (1).

d=πrini/f...(1) Here, the fact that the recording density is constant on all tracks means that if the same frequency is recorded, the pit length d is constant regardless of the disk radius. Therefore, it is necessary to keep the product ri・ni of the disk radius and rotation speed constant. That is, the rotational speed ni is controlled according to changes in the disk radius ri to keep the product ri·ni constant. Next, the pit length d formed in this way is rotated at a constant speed, that is,
Consider playing in CAV format.

The frequency F obtained by rotating at a constant rotation speed N and having a pit length d on the disk radius r is F=
Since 2πrN/2d, it is expressed by equation (2).

F=πrN/d...(2) Substitute equation (1) into equation (2) to obtain equation (3).

F=rN/rini f...(3) Equation (3) shows the frequency F obtained when a signal with a frequency f recorded by the CLV method is reproduced at a constant rotation speed N and a disk radius r. Here ri・ni
is an arbitrarily determined constant, and is the pit length d on the disk of the highest frequency f _nax of the signal to be recorded.
Its value is determined by how large it should be. For example, if f _nax =5 MHz and d = approximately 1 μm, ri·ni = 1500 mm/sec.
In this case, if ri=50mm, ni is 1800rpm (30rps)
It is. Further, N is also a constant arbitrarily determined.
When reproducing, frequency F is reproduced by the CAV method (constant rotation speed N). This is described above
A signal of frequency f is reproduced by performing inverse transformation (f=rini/rNF) using equation (3).

The present invention is based on the above principles.

(Example) An example in which the present invention is applied to an optical disk still image recording and reproducing device will be described below with reference to FIGS. 1 and 2. In FIG. 1, an optical disk 1 is rotated at a constant rotation speed N by a spindle motor 2, and the rotation speed N is measured by a pulse generator 3.
The optical pickup 4 is moved in the radial direction of the disk by a slider, and its position r is measured by a linear scale 5.

7 is an arithmetic circuit that converts the frequency of data according to the above equation (3) using the radius r and the rotation speed N, and outputs a voltage or digital value according to the radius r. Configure with software. Reference numeral 15 denotes a variable frequency pulse generation circuit whose pulse output frequency changes depending on the input value, and when the output of the arithmetic circuit 7 is a voltage, the VCO
(voltage control oscillator), and when the output of the arithmetic circuit 7 is a digital value,
Each consists of a PD (programmable divider).

The timing signal detection circuit 6 extracts a timing signal from the signal reproduced by the optical head 4 and generates a timing pulse.

The clock generating circuit 8 divides the frequency of the pulse from the timing signal detecting circuit 6 or the variable frequency pulse generating circuit 15 by switching the switch 18, and generates a clock.

The output device clock generation circuit 10 is the output device 1.
Generates a clock compatible with 4.

The memory control circuit 9 switches memory input/output,
It supplies clocks to the memory and controls memory refresh, etc. The clock to the memory control circuit 9 is supplied from the clock generation circuit 8 or the clock generation circuit 10, and the selection is made by the switch 2.
Follow step 3. The memory 11 has a capacity for one still image, and is composed of dynamic RAM or static RAM. The output of the memory 11 is configured to be connectable to either the laser diode drive circuit 12 or the demodulation circuit 17 by a switch 21. The input device 13 is a TV camera or a still image reading device using a linear sensor array (for example, an input section of a facsimile), and its output is digital.

The modulation circuit 16 performs digital modulation (for example, MFM) suitable for recording on an optical disk device, and also generates an error correction signal and a timing signal based on the timing pulse from the timing pulse generator 25 in order to reproduce signals from the optical disk without errors. It is added. Reference numeral 22 denotes a switch that can be switched during recording and reproduction. The demodulation circuit 17 demodulates the digitally modulated signal into a signal that can be input to the output device 14.

The output device 14 is a CRT or a printer.
The laser drive circuit 12 drives a laser diode (LD) according to the output of the memory 11 and modulates the intensity of the laser beam.

The operation of the optical disk device configured as above will be described below. First, the recording mode will be explained. Switches are connected as shown in solid lines in Figure 1. That is, switch 22 is moved to the 16 side, switch 21 is moved to the 12 side, switch 18 is moved to the 15 side, and switch 23 is moved to the 8 side.
Connect to each side. Still image input device 13
The signal is converted into an electrical signal and input to the modulation circuit 16 as a digital signal. The signal is digitally modulated by a modulation circuit 16 and added to a timing signal etc. based on a timing pulse of frequency _f1 . FIG. 2a shows the output of the modulation circuit 16. 24 is a timing signal, 2
0 is an image signal including an error correction signal.

In order to distinguish the timing signal 24 from the signal 20, for example, a signal consisting of a certain number of consecutive pulses with a certain duty ratio is defined as a timing signal (of course, the frequency of the timing signal 24 is _f1 ), and this is stored in the memory 11. .

Move the optical head to the position to be recorded. The position is read by the linear scale 5. Since the disk rotation speed N and ri×ni are constants as described above, F can be obtained from the above equation (3). When the arithmetic circuit 7 outputs a voltage corresponding to F, this output is input to the variable frequency pulse generation circuit 15, which generates a pulse having a frequency of F. A clock generating circuit 8 divides the frequency F to obtain a clock having a frequency nF.
The laser beam is outputted from the memory 11 with a clock having a frequency of nF, and the intensity of the laser beam is modulated by the laser drive circuit 12 to form a pit on the optical disk 1, and recording is completed.

Next, the reproduction mode will be explained.Reproduction switches 18, 21, and 22 are connected to the side shown by the dotted line in FIG.

The signal reproduced by the optical pickup is as shown in FIG. 2a when read out at a disk radius r. The frequency of the timing signal 24 is F. The timing signal detection circuit 6 extracts the timing signal 24 from the signal shown in FIG. 2a and converts it into the signal shown in FIG. 2b.
It is converted into a timing pulse 19 as shown in FIG. The timing pulse 19 is input to the clock generation circuit 8 via the switch 18. The clock generating circuit 8 performs frequency division and outputs the nF clock shown in FIG. 2c. The signal of the optical pickup 4 is stored in the memory 11 at the clock frequency nF.
Next, the switch 23 is switched to the output device clock generation circuit 10 side to generate a clock of frequency nf. Here, the switching of the switch 23 is performed after the image signal for one screen is stored in the memory 11, and then the clock generation circuit 1 for the output device is transferred from the clock generation circuit 8 to the clock generation circuit 1 for the output device.
It is controlled so that it switches to 0. The fact that one screen worth of image signals has been stored in the memory 11 can be known by various known means. For example, this can be determined by storing a signal at a specific address in the memory 11, or by recording a specific signal at the end of one screen in advance and detecting this. The image signal is output from the memory 11 at a clock frequency nf and input to the demodulation circuit 17. The demodulation circuit 17 demodulates the signal into a signal that can operate the output device 14 and outputs it to the output device 14,
Obtain a playback image.

In this embodiment, both recording and reproduction were carried out at a constant disk rotational speed, but it goes without saying that even a disk recorded by the conventional CLV system can be reproduced in exactly the same way.

In the embodiment shown in FIG. 1, the position r of the optical pickup was determined using a linear scale 5. However, when using an optical disk with a guide track, it is not necessary to use the linear scale 5. This is because the track pitch of the disk is kept constant, so once the track address is known, its position can be calculated by, for example, a microcomputer. Further, the variable frequency pulse generation circuit 15 may be constructed of a plurality of circuits having different oscillation frequency ranges, and the circuit to be used may be selected according to the frequency F.

Further, in the embodiment, the timing signal 24 is added at the time of modulation.
Frequency Modulation, PE: Phase Encoding
etc.), there is no need to add the timing signal 24.

(Effects of the Invention) As described above, according to the present invention, since the disk is driven by rotating at a constant speed, the configuration is simple and high-speed access is possible. A disk having a constant recording density can be used over all recording tracks recorded by the method shown in this embodiment.

[Brief explanation of the drawing]

FIG. 1 shows an optical disk still image recording and reproducing apparatus to which a reproducing apparatus according to the present invention is applied, and FIG. 2 is a diagram of signal waveforms at various points in FIG. 1.

Claims (1)

[Claims] 1. In a playback device that rotates and plays back a disk-shaped recording medium on which a modulated still image signal is digitally recorded on a spiral or concentric recording track at a uniform recording density, the recording medium is rotated at a constant rate. a rotation driving means, a pick-up for reading out signals from the recording tracks, a memory means to which the output of the pick-up is input and has a storage capacity for one screen, and demodulating the output of the memory means and outputting it to an output device. demodulating means; timing signal detecting means for detecting a timing signal included in the output of the pickup; storing one screen of the still image signal in the memory means in accordance with the output of the timing detecting means; A still image signal reproducing device comprising: memory control means for controlling the still image signal to be outputted to the demodulating means at a timing suitable for the output device.