JPS6252989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data recording system for video discs.

One example of a video disk is a system in which video information is recorded in the form of pits on a thin film on the disk using a laser beam and then reproduced. The video information at this time uses the NTSC method, which is a standard TV signal,
This is subjected to FM modulation, and the modulated signal is recorded in the form of a pit using a concentric or spiral laser beam. When one round of this pit row is one track, one track on the TV screen is
The field is recorded, and during playback, the disk is rotated from the TV transmission speed of 30 screens/second to 1/30 second/rotation, or 1800 rotations/minute. In such a recording/reproducing system, the minimum circumferential length of a track required to record one frame is limited by the recording pit diameter, the readout light spot diameter, etc. Therefore, at present, the minimum recordable radius is generally around 50 mm to 100 mm. The maximum radius to be recorded is around 150mm to 200mm, and if the track pitch is 0.002mm, it will be around 25000mm.
It is possible to record 75,000 tracks. This means that if we assume that still images are output one screen at a time, the screen will be 25,000 to 75,000 frames, and if we look at it as a general moving image, the screen will be about 14 to 40 minutes. However, in the above method, when the track moves to the outside,
The recording density decreases as the circumference length increases, and when the radius doubles, the recording density becomes half. Therefore, if the disk rotation speed is halved and two frames of video are recorded on one track, the data capacity on the disk will increase, but when using it as a still image, generally each screen There is a function to search randomly, and each time this boundary is moved, the rotation speed of the disk must be changed in a short period of time. Also, when using it as a video, the rotation speed must be changed in an even shorter period of time, and with this method, changing the inner side to 1 screen/1 track and changing it to 2 screens/1 track from the radius 2r is a sudden change. This is not practical because it involves speed switching. It also has the disadvantage that the number of storage screens cannot be increased compared to the number of trucks.

An object of the present invention is to provide a video disc data recording system that enables high-density recording without speed switching.

The gist of the present invention is to select a recording area of a video disc so as to record n frames on one track, and to perform recording and reproduction. below,
The invention will now be described in detail.

The basic idea for increasing the recording capacity of a video disc is to increase (R-r), where R is the maximum recording diameter and r is the minimum recording diameter. In order to increase (R-r), it is necessary to increase R and decrease r. However, there is a certain limit because the vertical fluctuation width of the rotating disk becomes large and the autofocus function, which minimizes the diameter of the laser beam spot during recording and playback, lacks tracking ability. . Regarding this, the diameter of the light spot cannot be easily reduced depending on the wavelength of the laser beam used, the numerical aperture of the lens used, etc.

Based on the above, the present invention focuses on the difference in recording density between the inside and outside of the video disc without changing R and r, and in this invention, the radius nr (where n is a positive integer of 2 or more) is By the way, the recording density is 1/n, so in order to make the density at this radius nr the same as r, the rotation speed of the video disk should be reduced to 1/n.
as n screens/1 track, and nr
The recording density is increased by three points: Even if the inner area is excluded from the recording schedule, n screens/1 track recording is performed only on the area outside nr.

FIG. 1 is a diagram for explaining the recording/reproducing method of the present invention when n=2, and shows a video disc main body 1 having a recording thin film. Information can be recorded between a maximum recording radius 4 and a minimum recording radius 5 between the disk outer diameter 2 and the disk inner diameter 4 of the disk body 1. Here, the minimum recording radius is r and the maximum recording radius is R. In the disk body 1, the area between the minimum recording radius r and twice this minimum recording radius, ie, 2r, is set as a non-recordable area, and the area between the radius 2r and the maximum recording radius R is set as a recordable area. . Further, the rotational speed in this recordable area is set to 1/2 of the rotational speed in the recording area from radius r to radius R.
By setting the recording area and setting the rotational speed, each track of the newly set recordable area is recorded every two screens.

Next, FIG. 2 shows the overall configuration including the recording and reproducing system. In the figure, a video disc main body section 10 has a video disc main body and constituent elements related to the disc main body related to recording and reproduction thereof.
The recording optical system 12 is an optical system for modulating recording data and writing it into the video disc main body 10 during recording. The reproducing optical system 13 is an optical system for reproducing recorded data recorded on the video disc body. The disk drive system 11 is a motor drive system for rotationally driving the disk body during recording and reproduction of the video disk.

What concerns the present invention in this configuration is the rotational speed _VR applied to the disk drive system 11 from the outside.
This rotation speed V _R is set to 1/2 of the speed determined by the size of the disk body. Further, the recording optical system 12 and the reproducing optical system 13 are also set to exclude the area from r to 2r from being scanned. With this configuration, it is possible to record two screens per track in the area from radius 2r to radius R.

Next, the operation and effects of this embodiment will be explained by setting actual numerical values. R=180mm, r=50mm, track pick 0.002mm in 1 screen/1 track
Then, (180-50)1/0.002=65000 screens can be recorded. On the other hand, in this example, 2r=100mm
Since 2 screens/1 track are recorded only on the outer side and the rotation speed is halved, the number of recorded screens is
100) x 1/0.002 x 2 = 80000 screens. Therefore, the number of screens will increase by 15,000 compared to the previous version.

In this embodiment, n=2, but n>2 may be possible.

According to the present invention, the area between nr and R can be set as a recordable area, and n screens can be recorded for each track within the area, so that substantial high-density recording has become possible. At the same time, from the viewpoint of autofocus followability, the advantage of being able to increase the outer diameter R can be expected. Furthermore, since the recording area width has been reduced by (n-1)r, the movement range of the screen search mechanism can now be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the main body of a video disk for explaining this embodiment, and FIG. 2 is a diagram of an embodiment of the present invention including recording and reproduction. DESCRIPTION OF SYMBOLS 1... Video disk main body, 10... Video disk main body part, 11... Disk drive system, 12... Recording optical system, 13... Reproducing optical system.

Claims (1)

[Claims] 1 The minimum recordable radius of a video disc is r,
Let the maximum recording radius be R, and when (R-r) < n (R-nr) holds when n≧2 is given as an integer, the minimum recording radius of the video disc is nr, and the rotation speed of the disc is 1/ A video disc recording method in which n videos are recorded on one track.