JPS63201972A - Information retrieving method - Google Patents

Abstract

PURPOSE:To reduce a memory capacity, necessary for retrieving an information by dividing an address to number of tracks function by the interval of the prescribed number of tracks. CONSTITUTION:The function to show a relation between the address on an information track and the number of tracks, for which a reading means traverses, is divided by the interval of the prescribed number of tracks, and a divided division region is attached with a step number, and the step number and an address region, corresponding to this step number, are stored in a memory. In the case of retrieving a bit of information, the step number, to which a present address belongs, and the step number, to which an object address belongs, are read out from the memory, and the reading means is shifted according to the number of tracks, calculated by multiplying the difference of these two step numbers by the number of tracks. Thus, the reading means can be positioned at a position, where an error for the object address is less than the prescribed number of tracks, after the retrieval, and the memory of a comparatively small capacity is enough.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information retrieval method for a device 1, such as a compact disc player (hereinafter referred to as an OD player), which reads and reproduces information by rotating a disc at a constant linear velocity. It is something.

tpl Background Art In recent years, compact disks (hereinafter referred to as disks) have become popular as high-density, large-capacity recording media. Information is recorded in a spiral on such a disk, and this information is read by irradiating the spiral information track with a laser beam emitted from a pickup and depending on the state of the reflected light. Furthermore, during playback, the disk is driven to rotate at a constant linear velocity.

On the other hand, in order to cause the laser beam to follow the information track, the pickup is moved in a direction perpendicular to the information track, that is, in the radial direction of the disk. Positional information (address) representing the position on the disc is recorded on such a disc, and this positional information represents the absolute time from the start end of the information at the time of reproduction.

Here, the relationship between the absolute time (X) during reproduction and the distance (y) of the pickup position from the center of the disk is expressed as the following equation.

x, vl, tpw 5r2f rarWf (7-rO)
(1) However, V/ is linear velocity and tap is track pitch.

r is the radius of the disk, and ro is the radial distance to the information start end.

If we transform the above formula (13).

2 vl-zp 2...
・(2) y−□・x+r O π is obtained, and by dividing both sides of this equation (2) by the square of the track pitch (tp), the number of tracks in the radial direction (T) and the absolute time [x ] to find the relationship.

T2-(-≦!Uni 2w -J-x+('') 2m
A3C+B...-(3)tp
gtp tP is obtained, and the absolute time (X) is the number of tracks in the radial direction (T)
It can be seen that it can be expressed as a quadratic function.

Now, for an OD player that operates as described above.

When searching for predetermined information, the absolute time of the pickup position at the time of the search and the absolute time of the target position are calculated using the above formula 5, and the number of tracks in the disk radial direction at each corresponding pickup position is calculated. There is a method of calculating the moving distance of the pickup as the number of tracks traversed in the radial direction by subtracting these values. However, since such a method requires arithmetic processing time during the search, the search time is long, and a microcomputer with a relatively large ROM capacity is required to store the program for the calculation.

As an information retrieval method other than Kamishi, for example, Tokuko Sho 61-14
No. 590 (011B21108) is publicly known. Such a search method includes a coarse search in which the reading means is moved widely from the current address to a position near the target address, and a fine search in which the reading means is accurately positioned at the target address by moving, for example, several tens of tracks from the neighboring position. be.

In this type of search method, if the reading means can be moved to a position relatively close to the target address by coarse search, the time required for fine search can be shortened, and the overall search time can be shortened.

As a method for the rough search, for example, Japanese Patent Application Laid-Open No. 60-5076
The technique disclosed in Publication No. 0 (()11B21108) can be used. Such a technique involves dividing the function expressed by the above equation (3) at a constant absolute time [ΔX] and determining the start of a track number region corresponding to this divided region (for example, the absolute time at the start of each region). A technique is disclosed in which the starting track number of the corresponding track number area is read out from a divided value range that includes the absolute time indicating the target position at the time of retrieval (see FIG. 6).

This starting track number can be used as the rough search position in the above search method.

When such a method is used, only a few divided areas and the number of starting troubles are memorized at most when searching, so a relatively small memory capacity is required and it is effective. Among the divided areas, in the divided area corresponding to the inner circumference of the disk, the corresponding track number area has a relatively large width, so if the starting track number is taken as the coarse search position, this rough search position is the target There are cases where there is a large difference between the addresses, and for this reason, it takes a long time to perform a fine search, which may lengthen the overall search time.

(c) Problems to be Solved by the Invention The present invention seeks to provide a table information retrieval method that can reduce the memory capacity required for information retrieval and further shorten the retrieval time.

B) Means for Solving the Problems The information retrieval method of the present invention uses an address and the above-mentioned address to advance the reading means in order to retrieve information at a constant linear velocity from concentric or spiral information tracks formed on a disk. A function indicating the relationship with the number of tracks crossed by the reading means is divided into intervals of a fixed number of tracks, and step numbers are assigned to the divided areas thus divided, and the step numbers and the corresponding address areas are recorded. When searching for information, the step number to which the current address belongs and the step number to which the target address belongs are read from the memory, and the number of tracks is calculated by multiplying the difference between these two step numbers by the number of tracks. The pre-start reading υ means was moved.

According to the information retrieval method of the present invention, it is only necessary to memorize several types of step numbers and address areas for retrieval, and the address vs. track number function is divided at constant track number intervals. Therefore, the number of tracks corresponding to the divided areas on the inner and outer peripheries of the disk is constant, and therefore the error in positioning with respect to the target address does not become significantly large.

(F) Embodiment One embodiment of the present invention will be described below using a compact disc as an example.

A compact disc (hereinafter referred to as a disc) has an information track formed in a spiral shape with a certain number of tracks.If this information track is divided into a certain number of tracks in the radial direction from the center of the disc, the track area The relationship between and the corresponding absolute time domain is as shown in FIG.

Here, the track is divided into 16 color gamuts for each rack (1280) racks as the number of divided tracks (MS), and the final absolute time (16 from 'I'1) of these divided areas is RO
When a disc in which the step numbers (8TP1 to 8TP16) for the 160 divided areas are stored in correspondence with the absolute time is set in the player, the steps are recorded in the disc prior to playback. T which is the table of contents of the songs being played,
O, O(Ta'ble-□f-(3ontente)
is read. At this time, each start time is compared with the absolute time (Tl to TM6). Among the 16 divided areas of 1lrl, song numbers corresponding to predetermined addresses (TNO8'1 to TNO816) in the RAM are stored in sequence in association with predetermined areas. At this time, if there is no corresponding start time within the 16 divided areas, the corresponding address ('
f'N081 to TNO816) are empty addresses and, on the other hand, if multiple start times correspond to one divided area, they correspond to the start time closest to the final absolute time (T1-T16) of that divided area. The song number is stored in the RAM (see FIG. 3). FIG. 4 is a diagram showing a state in which a large number of songs are recorded on a disc and one divided area includes a plurality of start times. That is, divided area (8TP1)
The first song and the second song.

The start time of the third song is included, and one divided area (8TP2) includes the fourth, fifth, and sixth songs. In this case, the address ('1'N081) in lRAM is the absolute time (
The song number ``3s'' of the third song closest to 'I'1) is stored, and the song number 6.degree. of the sixth song is similarly stored at address 1 CTNO82).

Next, a method of searching for and playing a predetermined song during playback will be explained according to the flowchart of FIG.

Assume that the player is currently playing the second song in FIG. 4 and a command is issued to play the sixth song. Then, the currently playing song number and the song number to be searched are R.
A divided area (8TP1) is created for the song number stored in AM.
), and the step numbers of the largest divided area not exceeding the song number in the RAM are read out one by one. That is, for the second song currently being played, the step number (s'rp1) is read out corresponding to the song number "3@," while for the sixth song to be searched, the step number is "6".
The step number (8TP3) is read in response to -. When the two divided areas are read out in this way, the step difference (Δ8T) between the divided area of the target song and the current divided area is calculated.
P ) is calculated.

That is, in one embodiment.

AI3TP=l(STPn)-(87Pm)l
The step difference 2 is calculated as -+21 1 (3TP3) - (8TP1) 1 Maro2. At the same time, 7 lags are set according to the sign within the absolute value of the above equation (2), and the direction in which the pickup should be moved is determined by this. In other words, if the sign in the absolute value is positive, the pickup moves toward the outer circumference of the disk.

If it is negative, it is moved toward the inner circumference of the disk. Then, when the step difference (ΔS'I'P) is determined in this way, this step difference (Δ8TP) is multiplied by the number of divided tracks (MS) to calculate the number of tracks (Mi+) that the pickup should cross during the search. Ru. That is.

MRxMflXΔBTP-Ml 1(8TPn)-(s
'rpm)1·-+31 In this embodiment, from the above equation (3), it is Ml-1280X2-2560() rack). Since the sign in the absolute value of equation (2) is positive, the pickup is moved by 2560 tracks in the outer circumferential direction during the search.

In this embodiment, the search operation allows the pickup to be located near the target song.

Also, the error at that position with respect to the starting point of the target song is 412
80) Since it is less than a rack, the time required for a subsequent fine search, for example, is short, and thus the overall search time can be shortened. Also, the only contents that need to be memorized for searching are 16 types ('j'1 to T16) of absolute times and track numbers, and a simple calculation rule for calculating the number of tracks to cross from these. Therefore, it is possible to use a memory having a relatively small capacity.

(G1) Effects of the Invention According to the information retrieval method of the present invention, in order to search for information at a constant linear velocity from concentric or spiral information tracks formed on a disk, the address on the read track and the A function indicating the relationship with the number of tracks crossed by the reading means is divided into intervals of a fixed number of tracks, and step numbers are assigned to the divided areas thus divided, and the step numbers and the corresponding address areas are stored in memory. When retrieving information, the step number to which the current address belongs and the step number to which the target address belongs are read from the memory, and the number of tracks is calculated by multiplying the difference between these two step numbers by the number of tracks. Since the reading means is moved, the reading means can be positioned at a position with an error of less than a certain number of tracks with respect to the target address after the search.

A complicated calculation process is not required for the search, and the memory only stores this calculation format, the step number, and the address prefix, so the memory only needs to have a relatively small capacity.

Furthermore, by reducing the above-mentioned fixed number of tracks, the reading means can be positioned at the target address with relatively high accuracy. Therefore, for example, if a so-called fine search is performed to accurately position the reading means at the target address after such a search, the amount of time required at this time is time is reduced.

Therefore, the overall search time required can be significantly shortened.

Incidentally, if the fixed number of tracks is reduced in this way, the step number and the type of address area to be stored in the memory will be increased accordingly, but as mentioned above, this point depends on the memory capacity required for information retrieval of the present invention. This can be compensated in that it only needs to be relatively small.

[Brief explanation of the drawing]

Factors 1 to 5 show an embodiment of the present invention.
Figure 1 and the second factor show a state in which the function representing the relationship between absolute time and the number of tracks is divided into 16 by a constant number of tracks. FIG. 3 is a diagram showing the contents of the memory, FIG. 4 is a diagram showing the relationship between each divided area and the included song numbers, and FIG. 5 is a flowchart showing the search operation. FIG. 6 is a diagram showing the conventional technique.

Claims (1)

[Claims] (1) An information retrieval method in an information retrieval device in which a reading means is scanned across the information track in order to retrieve information from concentric or spiral information tracks formed on a disk at a constant linear velocity; Then, a function indicating the relationship between the address on the information track of the information and the number of tracks traversed by the reading force means is divided into intervals of a constant number of tracks, and further step numbers are assigned to the divided regions thus divided. Then, this step number and the corresponding address area are stored in memory, and when retrieving information, the step number to which the current address belongs and the step number to which the target address belongs are read from the memory, and the difference between these two step numbers is An information retrieval method characterized in that the reading means is moved according to the number of tracks calculated by multiplying the number of tracks.