GB2175123A

GB2175123A - Information recording method

Info

Publication number: GB2175123A
Application number: GB08609393A
Authority: GB
Inventors: Satoshi Shikichi; Fumiaki Kawaguchi; Kenichi Suzuki; Masayuki Usui; Hiroshi Matsuoka; Kazuhiko Matsuoka; Hideki Hosoya; Akio Aoki; Masahiko Enari; Kazuo Minoura
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1985-04-17
Filing date: 1986-04-17
Publication date: 1986-11-19
Also published as: GB8609393D0; DE3612815A1; FR2580850B1; FR2580850A1; CH672856A5; CA1268252A; GB2175123B

Abstract

An information recording method comprises recording information on a record medium (card) by a recording head during forward movement, reading the recorded information in the opposite sequence to the recording sequence (during backward movement), and checking if the information has been correctly written or not based on the information read during the backward movement. Information on two adjacent information tracks may be simultaneously reproduced by two light beams (Fig. 4a-c) and the total verification time reduced. The signal from a memory facility is preferably read in opposite time sequence and recorded (Fig. 3). An indicia may be provided indicating incorrect recording, and reproduction not then necessary. Verification methods include bit by bit comparison, error check codes, and error correction codes. <IMAGE>

Description

SPECIFICATION Information recording method BACKGROUND OF THE INVENTION The present invention relates to a recording method for verifying if information has been correctly recorded in an apparatus which records and reproduces information by a relative linear reciprocal movement between the recording and reproducing apparatus and a recording medium. Recently, information has been optically or magnetically recorded by relatively and linearly reciprocating a write unit of the recording and reproducing apparatus (hereinafter called a recording head) relative to a card-like recording medium. In this case, it is important to rapidly verify if the information has been correctly recorded after write operation.

Fig. 1 shows a technique to verify if the information has been correctly recorded or not. Numeral 1 denotes an information track on a recording medium on which the information is to be recorded, numeral 2 represents a relative movement direction of a recording head to the recording medium in writing operation, and numeral 3 represents a relative movement direction of the recording head relative to the recording medium in a period between the writing operation and information read operation for verifying the recorded information. When the recording head is moved in the direction 3, the writing operation and the reading operation are not performed. The head movement in this period is called an idling movement.Numeral 4 represents a relative movement direction of the recording head relative to the recording medium when the recorded information is verified, and numeral 5 represents a relative movement direction of the recording head relative to the recording medium when the recording head is returned to a home position is preparation to the next writing operation. In the writing operation which uses such a record check method, two times of relative movement between the recording head and the recording medium are required to record information on one information track and two times of idling movement are performed during the two times of reciprocal movement. Accordingly, recording and verification read times are long.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information recording method which reads information recorded on a recording medium to verify it.

It is another object of the present invention to provide an information recording method which requires a short recording time in spite of verification reading.

The information recording method of the present invention comprises steps of recording information on a recording medium by a recording head during forward movement, reading the information recorded during the forward movement in the opposite sequence to the recording sequence during backward movement, and checking if the information has been correctly written or not based on the information read during the backward movement.

In the information recording method of the present invention, when the information recording medium is made of an unrewritable medium and an information track has been determined to include information recorded incorrectly, an indicia indicating that the track has the information incorrectly recorded and need not be reproduced in a reproducing operation may be recorded on the recording medium.

The indicia may be recorded on an extended line of the track on the recording medium. By recording such an indicia, it is immediately determined in the reproducing operation that the track need not be read.

In the information recording method of the present invention, there are various methods to verify if the information has been correctly recorded or not. In a first method, a data to be recorded and a data read from the recorded track are compared bit by bit. In a second method, an error check code such as a cyclic redundancy check code is added to an end of a data to be recorded and they are recorded on the recording medium, and in the verification step, an error is checked based on the reproduced data and the error check code.

More specifically, a data U(x) including a data to be recorded and an error check code is selected such that it is always divided by a generation polynominal G(x) without residue. If there is not recording error, the data U(x) reproduced from the recording medium can be divided by the generation polynominal G(x) without residue, but if an error is included during recording operation, a data U'(x) reproduced from the recording medium cannot be divided by G(x) without residual. In this manner, any error during the recording operation can be detected. In a third method, an error correction code such as Reed-Solomon code is added to the data to be recorded and they are recorded, and in the verification step, an error is corrected based on the read data and the error correction code, and an error flag for indicating whether the correction was made or not is set.If an error which is beyond the correction ability is included in the recording operation, the error flag indicates that the correction was not made so that incorrect recording is indicated. In the following description of an embodiment, the first method is described.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a prior art information recording method, Fig. 2 illustrates an information recording method of the present invention, Fig. 3 shows an embodiment of an optical information recording and reproducing apparatus in accordance with the present invention, and Figs. 4A, 4B and 4C show another embodiment of the information recording method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODI MENTS Fig. 2 illustrates a method of the present invention. Numeral 1 denotes an information track, -numeral 6 represents a relative movement direction of a recording head relative to a recording medium during a recording operation, and numeral 7 represents a relative movement direction of the recording head relative to the recording medium during a verification operation. As shown in Fig. 2, since the verification reading operation is performed immediately after the recording operation, a signal is read out on the opposite time axis to that of the recording operation, and the recording and the verification are performed in one time of reciprocation of the recording head. Accordingly, the idling movement time of the head is saved and the recording and verification times can be reduced.

The signal read out in the verification operation is of the opposite sequence to that of the signal applied to the recording head during the recording operation. Accordingly, it is advisable to read out the signal from memory means in the opposite sequence to the signal sequence applied in the recording operation, when the reproduced signal is compared with the recording signal during the verification operation.

In general, it is advisable that the signal is read from the information track of the recording medium in the verification operation such that the reproduced signal can be used as it is. If the signal is read from the memory means in the opposite sequence on the time axis and it is recorded, the signal read during the verification operation can be used without reversing the sequence.

Fig. 3 shows one embodiment of an optical information recording and reproducing apparatus in accordance with the present invention.

Numeral 11 denotes a central processing unit (CPU) which controls an overall operation of the recording and reproducing apparatus, numeral 12 denotes a card-like optical recording medium (optical card), numeral 13 denotes an optical head for irradiating a light beam to the optical card 12 to optically record and reproduce information, numeral 14 denotes drive means for reciprocating a shattle unit (not shown) on which the optical card 12 is mounted in a direction of an arrow, numeral 15 denotes main memory means which stores information to be written into the optical card 12 such as a personal computer, and numeral 16 denotes an address type memory which can store one information track line of record signal. The signals stored in the memory 16 can be read either forwardly or backwardly.

Numeral 17 denotes a compare circuit.

In a recording operation,# one information track line of record signal is sent to the address type memory 16 and stored therein in response to an instruction from the CPU 11.

Then, the one line of record signal is backwardly read from the memory 16 by a signal from the CPU 11. Thus, the signal which is reversed on a time axis is applied to the optical head 13 to intensitymodulate a semiconductor laser light source (not shown) of the optical head 13. In synchronism therewith, the drive circuit 14 is activated by a signal from the CPU 11 so that information is recorded on an information track of the optical card 12 by the modulated light beam from the optical head 13 while the optical card 12 is driven in the direction of the arrow A. At the end of the recording operation, the drive circuit 14 backwardly drives the optical card 12 in the direction of the arrow B by a signal from the CPU 11.In synchronism therewith, the optical head 13 reproduces the information which has been recorded on the information track during the forward movement, and the reproduced signal is sent to the compare circuit 17. In synchronism therewith,-a signal from the CPU 11 is applied to the memory 16 so that the one track of record signal stored in the memory 16 is forwardly read out and applied to the compare circuit 17. The signal read from the memory 16 and the signal read from the optical head 13 are compared by the compare circuit 17. If the information has been correctly recorded, the signal from the compare circuit 17 is applied to the CPU 11 so that the record signal in the memory 16 is erased by an instruction from the CPU 11 and a new one line of record signal is sent to the memory 16 and stored therein by a signal supplied from the CPU 11 to the main memory means 15. If the compare circuit 17 detects that the information has not been correctly recorded, the signal from the compare circuit 17 is sent to the CPU 11 and the recording and verification operations are repreated.

A relative speed between the optical head 13 and the optical card 12 in the verification operation is higher than a relative speed between the optical head 13 and the optical card 12 in the recording operation, because a light intensity of the optical head 13 in the verification operation may be lower than that in the recording operation. Thus, in the verification operation, the light intensity from the optical head 13 is selected to be lower than that in the recording operation.

The record signal to be applied to the optical head 13 in the recording operation and the record operation to be applied to the compare circuit 17 in the verification operation may be generated by software or hardware.

In Fig. 3, the optical head 13 may be one of various known devices such as optical disk and compact disk, and detailed explanation thereof is omitted here.

Figs. 4A, 4B and 4C show another embodiment of the information recording method of the present invention. In the present embodiment, information on two adjacent information tracks are simultaneously reproduced by two independent light beams.

In Fig. 4A, numerals 21, 22, 23 and 24 denote information tracks, numerals 21-0, 220, 23-0 and 24-0 denote record paths, numerals 21-1 and 23-1 denote return paths after recording, numerals 21-2, 22-2, 23-2 and 24-2 denotes verification paths, and ar rowsf represent relative movement direction of a head to a recording medium. The record paths, return paths and verification paths are shown separately for a purpose of illustration although they are actually on one line, that is, on an information track. The head is backwardly moved on the information track 21 at the end of the return path 21-1 for the previous track, and in the record path 21-0, the original information is recorded on the information track 21 in the reverse arrangement.

At the end of the recording onto the information track 21, the direction of the head movement is again reversed, and in the verification path 21-2, the recorded information is verified and the head is moved to the information track 22.

Then, in the record path 22-0, the original information is recorded on the information track 22 in the reverse arrangement. At the end of the recording operation, the direction of the head movement is reversed. In the verification path 22-2, at the end of the verification operation, the head is moved to the information track 23.

In the subsequent sequences, odd numbered tracks are identical to the track 21, and the even numbered tracks are identical to the track 22. In the odd numbered track, there is the return path but the even numbered track does not need the return path. In any information track, the relative speed between the head and the card in the verification operation is essentially equal to that in the reproducing operation.

Fig. 48 shows arrangement of information recorded on the information tracks. Numerals 21-3, 22-3, 23-3 and 24-3 denote arrangement of information on the information tracks 21 to 24, respectively. They are opposite to the directions of the record paths 21-0 to 240 and of the same direction to the verification paths 21-2 to 24-2. As a result, any special process is required in processing the signal produced in the verification operation.

Fig. 4C illustrates simultaneous reading of two tracks. Numerals 21-4, 22-4, 23-4 and 24-4 represent directions of the reproduction paths for the information tracks 21, 22, 23 and 24, respectively. In the reproducing operation, the information tracks 21 and 22 are reproduced in pair, and the information tracks 23 and 24 are reproduced in pair. As seen from Fig. 4C, the directions 21-4 to 24-4 of the reproduction paths in the respective tracks are same as the arrangement of the information recorded on the information tracks. Accordingly, no special process is required in the reproduction operation.

In the present embodiment, the return path in which no information is processed occurs once for every two tracks. Thus, a total verification time can be reduced over the previous embodiment.

If the relative speed between the head and the recording medium in the verification operation is equal to that in the reproducing operation, a circuit for reproducing the information can be shared.

In the embodiment shown in Fig. 4, two tracks are simultaneously read and the arrangement of the information is reversed for every two tracks. The larger the number of tracks which are simultaneously read is, the smaller is the number of times of idling movement and the more is the total time for recording and verification reduced. When n tracks are simultaneously read and the arrangement of information is reversed for every n tracks, the idling movement occurs once for every n tracks.

Claims

1. An information recording method for recording information on an information recording medium by relative reciprocal movement between a recording head and the information recording head, comprising the steps of; recording information on the information recording medium by the recording head in forward movement; reading the information recorded in the forward movement, in an opposite sequence to the recording sequence in backward movement; and verifying if the information has been correctly recorded based on the information read in said step.

2. An information recording method according to Claim 1 further comprising a step of recording an indicia on the information recording medium for indicating that the information has not been correctly recorded if such is detected.

3. An information recording method according to Claim 1 wherein said verification step compares information to be written and the information read, bit by bit, to verify if the information has been correctly recorded.

4. An information recording method according to Claim 1 wherein an error check code is added to the information to be recorded, and said verification step checks if an error has occurred in the recording operation based on the error check code.

5. An information recording method according to Claim 1 wherein an error correction code is added to the information to be recorded, an error is corrected by the information reproduced in the forward movement and the error correction code, and an error flag is set to indicate whether the correction was made or not.

6. An information recording method for recording information on an optical card by relative reciprocal movement between an optical head and the optical card, comprising the steps of; recording information on the optical card by a light beam from the optical head in forward movement; reading the information recorded in the forward movement, in an opposite sequence to the recording sequence in backward movement, a relative speed between the optical head and the light beam in said read step being higher than a relative speed between the optical head and the light beam in said recording step; and verifying if the information has been correctly recorded based on the information read in said read step.

7. An information recording method according to Claim 6 wherein arrangement of information recorded on tracks is opposite to the direction of the relative movement between the optical head and the optical card in the recording operation.

8-. An information recording method sub stantiaily as herein described with reference to any of the accompanying drawings.

9. An information recording apparatus arranged to operate as described with reference to any of the accompanying drawings.