JPH0550074B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-speed search method for a disc reproducing device, and more particularly, to a high-speed search method for a disc reproducing device that detects the scanning speed during disc reproducing.

2. Description of the Related Art Conventionally, there has been a disc playback device for playing back a disc on which digital audio signals have been recorded.
A digital audio signal is recorded on the above disk at a constant linear velocity, and the disk playback device compares the synchronization signal reproduced from the disk with a reference frequency signal to determine that the scanning speed is constant (same as the linear velocity of the disk). The speed of the disk rotation motor is controlled to ensure that

Problems to be Solved by the Invention The linear velocity of a disc is approximately constant within a single disc, but this linear velocity is standardized to be 1.20 to 1.40 m/sec, and the linear velocity of each disc is within this standard. It can be any value within. As described above, the permissible range of linear velocity is wide, and the scanning speed of the disc reproducing apparatus also changes depending on the linear velocity of the disc to be reproduced.

When performing a high-speed search, conventional disc playback devices use the absolute address (A time) of the target song and the current playing position, as described in "Toshiba Review Vol. 38, No. 3," pages 248 to 249. The absolute address (A time) is converted into the number of tracks, and the pick-up is transferred by this number of tracks. The above track number N _T is calculated using the following formula.

N _T = (Rt-Rn)/P... (1a) However, V _L is the scanning speed of the playback device, P is the track pitch of the disk (=1.6 μm), At is the A time of the search target device, An is the A time of the current playback position, and Ro is the radius of the program start position. (=24.9mm), Rn is the radius of the current position, and Rt is the radius of the target point.

The above equations (1a) and (1b) were derived from the equations below.

An・V _L・P=πRn ² −πRo ² ...(2a) At・V _L・P=πRn ² −πRo ² ...(2b) In the conventional device, V _L , P, Ro in equation (1b)
was treated as a constant and the number of tracks N _T was calculated.

Here, the track pitch P is 1.6 ± 0.1 μm with an error of ±0.1%, the radius Ro is 24.9 ± 0.2 mm and the error is ±0.4%, which is quite small, but the linear velocity V _L is 1.3
At ±0.1m/sec, the error is ±7.7%, which is quite large. For this reason, the number of tracks N _T obtained using equation (1b) has a large error, and time is required to correct this error, resulting in a problem that the search time becomes long.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-speed search method for a disc playback device that solves the above problems by measuring and detecting the scanning speed of the disc and using this scanning speed to calculate the number of tracks. do.

Means for Solving the Problems FIG. 1 shows the overall configuration of the system of the present invention. In the figure, the recorded signal on disk 1 is transmitted through playback mechanisms 2, 3,
4, 5, 21, 24, and 25, and demodulated by the demodulation circuit 7. The microcomputer 19 has playback mechanisms 2 to 5, 21,
24, 25 and demodulation circuit 7, and generates a control signal to control the servo circuits 17, 1.
8, 20, 22, and the reproduction mechanism 2 to 5, 2
1, 24, and 25 are controlled. The detection means A controls the microcomputer to pick up the pickup 5 from the program start position of the disk 1 to be played back by the playback mechanisms 2 to 5, 21, 24, and 25.
The scanning speed of the disk 1 is detected by counting the reproduction frame synchronization signals from when the track pitch is forcibly moved to the inner circumferential side until the program start position is detected again. Calculating means B calculates the number of tracks to be transferred using the detected scanning speed during high-speed search, and the microcomputer operates the reproduction mechanisms 2 to 5, 21, 24, 25 by the number of tracks.
Playback mechanism 2 to transfer the pick-up inside
5, 21, 24, and 25.

Function: The detection means A detects the scanning speed specific to the disk 1 with high precision. Further, calculation means B calculates the number of tracks using the above scanning speed during high-speed search,
As a result, the number of tracks obtained has good accuracy and its error is small, so less time is required to correct the error, and the search time is shortened.

Embodiment FIG. 2 shows a block system diagram of an embodiment of a device to which the method of the present invention is applied. In the figure, 1 is an eight-to-fourteen modulation (hereinafter referred to as "EFM") digitalized two-channel audio signal.
This is a compact disc in which signals are recorded from the inner circumference to the outer circumference of the spiral track. After the disk 1 is installed in a mounting section (not shown) of a playback device, it is driven by a drawer motor 2 and loaded into a predetermined position.
It is supported by and rotated. Further, 5 is a pickup of the optical system, and the laser beam emitted from the pickup 5 is reflected by the disk 1 and enters the optical system again. This reflected light is detected by an optical sensor built into the pickup 5, and the strength of the reflected light, which changes depending on the presence or absence of pits on the disk 1, is converted into an electrical signal.

The signal read by the optical sensor of the pickup 5 is amplified by an amplifier 6 and then supplied to a demodulation circuit 7, where it is FEM demodulated. The 192 data bits and 64 error correction bits of each frame of the demodulated signal are supplied to a correction circuit 8. The correction circuit 8 uses the RAM 9 to de-interleave the 256-bit signal, detects and corrects code errors, and extracts the right channel and left channel digital signals whose time bases have been corrected. This digital signal is converted into an analog audio signal by a D/A converter 10, and unnecessary high-frequency components are removed from the right channel and left channel audio signals by low-pass filters 11 and 12, respectively, and amplified by amplifiers 13 and 14. After that, terminals 15 and 16
output from each.

Further, the read signal from the pickup 5 is supplied to a focus servo circuit 17 and a tracking servo circuit 18, respectively, and the user's bits from the demodulation circuit 7 are supplied to a microcomputer 19. The focus servo circuit 17 displaces the objective lens of the optical system in the pickup 5 in response to the read signal and the control signal from the microcomputer 19 to focus the laser beam on the recording surface of the disk 1. The tracking servo circuit 18 detects a tracking error from the read signal, and further displaces the laser beam emitted by the pickup 5 in the radial direction of the disk 1 in accordance with the control signal from the microcomputer 19, so that the laser beam performs recording on the disk 1. Automatically adjusts to scan tracks.

Further, the radial servo circuit 20 drives the radial motor 21 in accordance with the scanning track information from the tracking servo circuit 18 and the control signal from the microcomputer 19 to move the pickup 5 in the radial direction of the disk 1. The disk servo circuit 22 rotates the disk motor 3 in response to an error signal obtained by phase comparison between the frame period signal from the demodulation circuit 7 and the clock signal from the microcomputer 19, and reproduces the disk 1 at a predetermined linear velocity. Automatically adjust so that When the sensor 24 detects that the disk 1 is mounted, the drive circuit 23 drives the drawer motor 2 in response to a control signal from the microcomputer 19 to load the disk. The sensor 25 supplies a detection signal to the microcomputer 19 when the pickup 5 is at the innermost scanning position of the disk 1. Signals generated by operating the operation panel 26 are supplied to the microcomputer 19, which controls the operation of the disc playback device.
Further, a display signal from the microcomputer 19 is supplied to the display 27 to display the playback device of the disc 1, the track number, etc.

Next, the processing executed by the microcomputer will be explained.

When the microcomputer 19 is supplied with a detection signal detected by the sensor 24 when the disk 1 is attached to the attachment section (not shown) of the playback device,
The process shown in FIG. 3A is executed. In FIG. 3A, first, a control signal is supplied to the drive circuit 23, the drawer motor 2 is driven, and a disk is loaded (step 30). When loading of the disk is completed, the radial motor 21 is driven to move the pickup 5 toward the inner circumference of the disk 1 until the sensor 25 generates a detection signal (step 31). Thereafter, the focus servo, tracking servo, and radial servo are activated (step 32), and reproduction of the digital signal recorded on the disk 1 is started.

By starting the playback described above, the TOC (Table of Contents) recorded on the lead intratrack on the inner circumferential side of the program start position on disk 1 is played back (step 33), and as a result, the table of contents recorded on disk 1 is played back (step 33). The A times at the start positions of all songs are read and stored. The above A time represents the playback time from the program start position, is assigned to an absolute address on disk 1, and is recorded in the user's bit during the program recording period of disk 1. Next, the diameter of disk 1
A program start position located at a position of 50 mm and having an A time value of zero is searched for (step 34). When the program start position is reproduced, the scanning speed, that is, the linear speed of the disk 1 is detected in step 35.

In step 35, the process shown in FIG. 3B is executed. In step 36 of FIG. 3B, the counter
_NL is reset. Furthermore, the pick-up 5 is forcibly moved (jumped) one track pitch inward from the program start position (step 3).
7), you will be prompted to continue playing. Thereafter, the counter N _L counts up the frame synchronization signal that is reproduced at a frequency of 7350 Hz, and when the program start position where the A time is zero is detected (step 38), the process moves to step 39. Step 3
At step 9, the count value of the counter N _L is read out. Thereafter, the scanning speed V _L of the playback device, that is, the linear velocity of disk 1 is calculated using the following equation (step 4).
0).

V _L = π・T _F・D ₀ /N _L ...(3) However, T _F is the frame period (= 1/7350), and D ₀ is the diameter of the program start position of disk 1 (= 49.8
mm) After determining the playback speed V _L in this way, the process shown in FIG.

where the diameter at the program start position is 50 ⁺⁰ _-0.4 mm
In other words, since the error is as small as 49.8mm±0.4%, the track length of one round of disk 1 including the program start position can be determined with high accuracy with an error of about 0.4%, and this track length can be calculated using the scanning time (N _L /T _F ), the scanning speed obtained by dividing by ) will be of high accuracy.

When, for example, a desired song number is input from the operation panel 26 shown in the second figure and high-speed search playback is instructed, the microcomputer 19 executes the process shown in FIG. 4. In FIG. 4, at step 41, time A in the user's bits reproduced from disk 1 is read and stored in variable An.
Thereafter, the process moves to step 42, where the number of tracks N _T is determined using equation (1b).

When the number N _T of tracks to be transferred is determined by equation (1b), it is determined whether the number N _T is positive or negative (step 43), and if it is positive, the process moves to step 44, and if it is negative, the process moves to step 45. If it is determined in step 44 that the number of tracks N _T is greater than "256", the tracking servo is turned off and the pickup 5 is turned off.
is sent toward the outer circumference of the disk 1 at high speed by the radial motor 21 (step 46). At this time, the number of times the envelope of the read signal from the pickup 5 exceeds a predetermined level (transfer track number) is counted, and this count value is used as the track number. At the time when the number becomes equal to the number N _T (step 47), the tracking servo is turned on to enter the normal playback state (step 48), and the process moves to step 41. Further, if the number of tracks N _T is less than "256", the number of tracks N _T is compared with "4" (step 49),
If it is larger than "4", the laser beam of the pickup 5 is shifted (jumped) to the outer circumferential side by (N _T -2) tracks (step 50), and then the process moves to step 41. If the value is smaller, the state is set to normal playback (step 51), and the values of the variable An and the A time At of the target position are compared (step 52), and if they do not match, the process moves to step 41.
Processing ends when a match occurs.

Also, in step 45, the number of tracks N _T is
256'', the tracking servo is turned off and the pick-up 5 is fed at high speed toward the inner circumference of the disk 1 (step 53), and when the number of phase shift tracks at this time becomes equal to the number of tracks N _T ( At step 54), the tracking servo is turned on and the normal playback state is established (step 55).
The process moves to step 41. Also, the number of tracks N _T
If is greater than "-256", the laser beam from the pickup 5 is shifted (jumped) to the inner circumferential side by (N _T -2) tracks (step 56), and the process then proceeds to step 41.

Here, assuming that the measurement error in the scanning period (N _L /T _F ) of one track of disk 1 in equation (3) is approximately 0.1%, the tolerance Do of the diameter D ₀ is 0.4%, so
The error ΔV _L in the scanning speed V _L is approximately 0.5%. Also,
The error ΔN _T of the track N _T is expressed as the following equation.

ΔN _T ≒ ΔP + (1 + ΔV _L −1) + ΔD ₀ ... (4) However, ΔP is the error in track pitch P (= 0.1%) The error in the number of tracks according to the method of the present invention determined by the above equation (4) is approximately 1%. , whereas in the conventional device it is approximately 4%. In this way, the error in the number of tracks N _T calculated by the method of the present invention becomes small.
Therefore, the time required to correct this error is shortened, and the search time is shortened.

Effects of the Invention As described above, the high-speed search method of the disc playback device according to the present invention measures and detects the scanning speed of the disc and uses this scanning speed to calculate the number of tracks, so that the error in the number of tracks is less than that of the conventional disc playback device. It has the advantage that it is much smaller than that, the time required to correct this error is shortened, and the search time is shortened.

[Brief explanation of the drawing]

Figure 1 shows the overall configuration of the system of the present invention, Figure 2 shows the overall configuration of the system of the present invention.
The figure is a block system diagram of an embodiment of an apparatus to which the method of the present invention is applied, and FIGS. 3 and 4 are flowcharts of the processing executed by the microcomputer shown in FIG. 2, respectively. 1...Disk, 5...Pickup, 18...
...Tracking servo circuit, 19...Microcomputer, 20...Radial servo circuit, 30
~56...Step.

Claims (1)

[Scope of Claims] 1. A high-speed search method for a disk playback device in which a disk on which information signals are recorded on a spiral track at a constant linear velocity is scanned by a pickup at a scanning speed equal to the linear velocity to read and reproduce the information signals. In this step, the scanning speed of the disk is determined by counting the playback frame synchronization signals during the period from when the pick-up is forcibly moved one track pitch inward from the program start position of the disk until the program start position is detected again. 1. A high-speed search method for a disk playback device, characterized in that the number of tracks for transporting the pickup in the radial direction of the disk during high-speed search is calculated using the scanning speed.