JPH0468827B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to an apparatus for digitally recording still image signals on a rotating disk-shaped recording medium (hereinafter simply referred to as a disk) such as an optical disk, magneto-optical disk, or magnetic disk. It is related to.

(Background of the Invention) Conventionally, the constant angular velocity method (hereinafter referred to as CAV method) and the 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 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, with the CLV method, there is no difference in recording density between the inner and outer circumference of the disk, and the recording capacity is larger than with the CAV method, but the rotation speed of the disk, which has a large inertial mass, must be controlled according to the radius of the disk, so the equipment is complicated and expensive. becomes. 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, this system has the disadvantage that a device for variable rotational speed control is still required.

(Objective of the Invention) The present invention solves the above-mentioned drawbacks, and provides a simple configuration of the CAV system and a large recording capacity (high recording density) of the CLV system.
The purpose of the present invention is to obtain a still image signal device having the following features.

(Summary of the Invention) In order to achieve the above object, the present invention maintains a constant rotation speed, that is, the CAV method, and controls the pit recording state.
The frequency of the timing signal is controlled according to the distance r from the rotation center of the disk to the relevant track (hereinafter simply referred to as the disk radius), so that the recording density is kept constant for all tracks. More specifically, during recording, the disk is rotated at a constant rate, and the frequency of the timing signal is increased toward the outer periphery. Of course, at this time, the time axis of the image signal between the timing signals is also compressed toward the outer periphery, so that all tracks are recorded at the same recording density. Here, when pits are formed at the same recording density on all tracks as in the present invention and the CLV method, the disk radius
When a pit is formed at a frequency f on a disk rotating at a rotation speed ni at a location ri, f=2πrini/2d, and from this, the length d of the pit 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.
In other words, the rotational speed ni changes depending on the change in the disk radius ri.
control to keep seri and ni constant. Next, let us consider reproducing the pit length d formed in this manner using constant speed rotation, that is, the CAV method.

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/rinif...(3) Equation (3) is the frequency f recorded by the present invention or the CLV method.
It shows the frequency F obtained when the signal is reproduced at a constant rotation speed N and a disk radius r. Furthermore, if the frequency is converted according to equation (3) and recorded, pits will be formed on all tracks at the same density even if the disk is rotated at a constant speed, similar to recording by the CLV method. Here, ri・ni is a constant that is arbitrarily determined, and its value is determined depending on the size of the pit length d on the disk of the highest frequency f _nax of the signal to be recorded. . 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). Further, N is also a constant arbitrarily determined by the method of the present invention.

When playing, CAV method (constant rotation speed N)
When this is done, frequency F is reproduced. By inversely transforming this using equation (3) (f=rini/rNF), a signal of frequency f is reproduced.

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/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 determined by a linear scale 5.
Measure with.

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. Or configure it 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,
Generate 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 converts the digitally modulated signal into
It demodulates 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 drives a laser diode (LD) according to the output of the memory 11 to modulate 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. Digitally modulated by the modulation circuit 16, based on the timing pulse of frequency _f1 ,
Add timing signals, etc. 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 memorized. 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 generation 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 playback mode will be explained. The playback switches 18, 21, and 22 are connected to the side shown by the dotted line in FIG.

The signal reproduced by the optical pickup 4 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 a timing pulse 19 as shown in FIG. 2b.
The timing pulse 19 is input to the clock generation circuit 8 via the switch 18. The clock generating circuit 8 performs frequency division to obtain nF as shown in FIG. 2c.
Outputs the clock. 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 controlled so that after one screen's worth of image signals is stored in the memory 11, the clock generation circuit 8 is switched to the clock generation circuit 10 for the output device. 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 known 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. Demodulation circuit 17
The demodulated signal is demodulated into a signal that can operate the output device 14, and is output to the output device 14 to obtain a reproduced image.

In this embodiment, the disc rotation is kept constant during reproduction, but it is of course possible to reproduce using a conventional CLV type reproduction apparatus. However, in this case, the access time during playback is the same as CLV.

The position r from the center of rotation of the optical pickup 4 was determined using the 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 frequency variable pulse generation circuit 15 is composed of a plurality of circuits with different oscillation frequency regions, and has a frequency F
The circuit to be used may be selected depending on the situation.

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, the rotation of the disc plate can be kept constant, so a variable rotation speed control device like the CLV system is not required, the configuration is simple, and the rotation speed can be kept constant over the entire track. As a result, the recording density is constant, and unlike the CAV method, the recording density does not become lower as the outer tracks become smaller, so it is possible to achieve the same large recording capacity as the CLV method.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. In a recording device that digitally records a still image signal so as to form a spiral or concentric recording track of uniform recording density on a rotating disc-shaped recording medium, a rotation driving means for causing the recording medium to rotate at a constant rate; , a modulation means for converting a still image signal into a digital signal and outputting a modulation signal including a timing signal, a memory means having a storage capacity for one screen of the output of the modulation means, and a memory means for converting the still image signal into a digital signal and outputting a modulation signal including a timing signal; a recording head for recording a still image signal on each of the recording media; a recording head position detection means for detecting the position of the recording head from the center of rotation of the recording medium; and a timing added by the modulation means. calculation means for converting the frequency of the signal so that it has a constant density over all tracks according to the output of the recording head position detection means; and the calculation means for converting the still image signal for one screen stored in the memory means. 1. A still image signal recording apparatus comprising: memory control means for controlling output to each of the recording heads according to the output of the means.