GB2174531A

GB2174531A - Optical head positioning

Info

Publication number: GB2174531A
Application number: GB08608345A
Authority: GB
Inventors: Kazuhiko Matsuoka; Hideki Hosoya; Akio Aoki; Masahiko Enari; Masayuki Usui; Hiroshi Matsuoka; Kazuo Minoura; Kenichi Suzuki; Satoshi Shikichi; Fumiaki Kawaguchi
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1985-04-05
Filing date: 1986-04-04
Publication date: 1986-11-05
Anticipated expiration: 2006-04-04
Also published as: CH671475A5; DE3611334C2; FR2580085A1; CH674681A5; DE3611334A1; JPS61230629A; JP2556465B2; GB2174531B; FR2580085B1; CA1270059A; GB8608345D0

Abstract

In a method for positioning an optical head before data are recorded on an optical card or the data recorded on the card are reproduced, an optical head for applying a light beam (producing data scanning spot 14a and tracking spot 15a) to the optical card and the optical card are displaced relative to each other in the direction of track of the optical card. Whereby the spots become aligned with the respective data and tracking tracks as spots 14b, 15b, and the spots traverse to the data track I.D. area 13a to read the track number to thereby detect the position of the optical head relative to the optical card. The head can then be moved to the track with the required track number. A plurality of data spots (14a) may be provided (Figure 3) allowing A or B side insertion (Figure 1). The head or card may be moved. <IMAGE>

Description

SPECIFICATION Method of detecting the position of an optical head Background of the invention Field of the invention This invention relates to a method of detecting the position of an optical head in a recording-reproducing apparatus for recording or reproducing data on a card-like recording medium (hereinafter referred to as the optical card) by the use of a light beam, that is, detecting the relative positional relation of the optical head to the optical card before recording or reproduction of data is effected. The recording-reproducing apparatus referred to herein means an apparatus for effecting only one or both of recording and reproduction.

Related background art In recent years, along with the advance of the informational age, attention has been paid to optical cards as information storing means. The main features of the optical cards are that as compared with optical discs and optical tapes, they are of a card-like shape which is easy to carry and handle and that as compared with magnetic cards and IC cards, they have a great storage capacity.

Now, in recording reproducing data through a storing medium such as an optical card, the relative positional relation between the optical card and the optical head in the initial state need be apparent before the recording or reproducing operation is started. For example, generally, most recording-reproducing apparatus are in such a form that before said operation is started, the information of the area of contents which is provided in the optical card and in which the data situation or the like in the optical card is written is read and the operation is performed on the basis of that information.Accordingly, to shorten the time required for the recording or reproduction of data, it is necessary that after the optical card has been inserted into the apparatus or when the recording or reproducing operation once interrupted is to be resumed, the relative position of the optical head and the optical card be quickly moved to bring about a state in which the information of said area of contents can be reproduced. Herein, the position in which the optical head is positioned in such a state relative to the optical card is called the home position of the optical head.

Summary of the invention It is the object of the present invention to provide a method of quickly detecting the position of an optical head to enable the optical head to quickly stand by at a predetermined position.

In the method according to the present invention, before data are recorded on an optical card or the data recorded on the card are reproduced, an optical head for applying a light beam to the optical card and the optical card are displaced relative to each other in the direction of track of the optical card and a track number written on the optical card is read to thereby detect the position of the optical head relative to the optical card.

The invention will hereinafter be described in detail.

Brief description of the drawings Figure 1 shows an embodiment of the optical card.

Figures 2 and 3 illustrate the detecting method according to the present invention.

Figure 4 shows an embodiment of the optical card recording-reproducing apparatus using the detecting method according to the present invention.

Description of the preferred embodiment Figure 1 is a schematic view showing an embodiment of the otpical card. Reference numeral 1 designates the optical card, reference numeral 2 denotes an area in which data are recorded, and reference characters 3a, 3b and 3c represent track units. The track unit herein referred to means a combination of minimum necessary various tracks including, in addition to a data track on which data are written, a track for tracking for effecting thereon reliable writing and reading of data and a track for clock.

Figure 2 is a view for illustrating the method according to the present invention by the use of an optical card having a certain track unit. This certain track unit, as shown in Figure 2, consists of a track 11 for tracking and a data track 12. At the opposite ends of a data track 12, there are data track identification areas 13 in which data track numbers for identifying the data tracks are recorded. Considering the initial state before writing or reading of data is effected, a beam spot 14a for scanning the track for data and a beam spot 1 5a for scanning the track for tracking lie generally at any positions on the optical card.In subsequence to this state, the optical head of an apparatus, not shown, is moved in the left to right direction as viewed in Figure 2 (the direction of movement of the track) and the auto-focusing function and the auto-tracking function of a recording-reproducing apparatus are made to act by the reflected light from the beam spot 15a, whereby the light spot 14a for data and the light spot 15a for tracking are positioned on the nearest data track 12a and the track 11a for tracking, respectively. The light spots 14a and 15a showing this state are designated by reference characters 14b and 15b, respectively. Further, the light spots move and pass the data track identification area and as a result, the data track number 13a is read and thus, it becomes possible to know the relative positional relation between the optical head and the optical card at the current point of time.Accordingly, after the above-described operation, the optical head can be moved to a desired track unit to thereby accomplish writing or reading of data easily. For example, it becomes possible to read the data track number and known the relative positional relation between the optical head and the optical card. Accordingly, after the above-de scribed operation, the optical head can be moved to a desired track unit to thereby accomplish writing or reading of data easily. For example, the data track number is read and the relative positional relation between the optical head and the optical card is recognized, whereafter the mutual positional relation is modified so that the optical head comes to the area of contents, and in this home position, a further command is had.

Means for giving a command for starting the relative movement in the track direction to know the positional relation between the optical card and the optical head may be for example, a signal from a sensor for confirming that the optical card has entered a predetermined position, or a manual signal given by the operator. As shown in Figure 2, data track identification areas are provided at the opposite sides of the data track, whereby it is conveniently possible to read the data track number by the movement of the optical head relative to the optical card either from right to left or from left to right.

As can be seen from the foregoing description, according to the present invention, access of the optical head can be accomplished by a simple system. Further, the present invention can cope with plural types of optical cards in which the shapes of the track units are the same but which differe from one another in the position and size of the data area 2 shown in Figure 1.

Figure 3 is a view for illustrating the method according to the present invention by the use of an optical card having the track units shown in Figure 2. In Figure 3, elements functionally similar to those in Figure 2 are given similar reference characters. The difference of the present embodiment from the embodiment shown in Figure 2 is that there are a plurality of light spots 14a for data.

Again in Figure 3, in the initial state, the two light spots 14a for data and the light spot 15a for tracking are at any positions on the optical card, but by the same operation as that previously described, the light spots 14a for data can be positioned on the nearest data tracks 12a and 12b, respectively, and the light spot 15a for tracking can be positioned on the track 15 for tracking and as a result, both of the data track numbers 13a and 14b can be read at a time. Accordingly, in addition to the aforementioned advantage that by the read data track. numbers 13a and 13b being compared, the then position of the optical head can be judged, it becomes possible to know also the direction in which the track unit to be accessed in the next state is present.This gives rise to a practically very useful effect that the optical card shown in Figure 1 may be inserted into the optical recording-reproducing apparatus with either the A side or the B side of the optical card as the leading side.

Although the foregoing description has been made with respect to the type in which the optical head is moved, the optical card may of course be moved in the direction of movement of the track.

Also, as regards the specific means for realizing the autofocusing and the auto-tracking function, the critical angle method, the knife edge method, the astigmatism method, etc. are known for the former and the 3-beam method, the push-pull method, the beterodyne method, etc. are known for the latter, and any of these methods is applicable. Furthermore, although the foregoing description has been made by the use of the data track numbers, it is also possible to set a tracking track number corresponding to the track for tracking and utilize it to detect the position of the optical head.

Figure 4 is a schematic diagram showing an embodiment of the optical card recording-reproducing apparatus using the detecting method according to the present invention.

In Figure 4, reference numeral 21 designates a sensor for mechanically or electrically detecting the insertion of the optical card 1 into the apparatus, reference numeral 22 denotes a DC motor driver, reference numeral 23 designates a DC motor for moving a table (not shown) supporting the optical card 1 thereon in the track directions of the card (the directions of bilateral arrow), and reference numeral 24 denotes an optical head for applying three light beams to the optical card at a time as shown in Figure 3. The construction of this optical head is similar to that of the optical head used with the conventional optical disc with the exception that a diffraction grating for separating the light beam from a light source into three light beams is provided, and the detailed construction thereof need not be described herein.Reference numeral 25 designates a circuit for reproducing the information recorded on the tracks from a signal read by the optical head as described in convention with Figures 2 and 3, reference numeral 26 denotes a comparator, reference numeral 27 designates a pulse operating circuit, reference numeral 28 denotes a setting circuit for setting to what position the optical head is to be subsequently moved relative to the optical card, reference numeral 29 designates a pulse motor driver, and reference numeral 30 denotes a pulse motor for moving the optical head 24 relative to the optical card 1.

When it detects the insertion of the optical card 1, the sensor 21 gives a detection signal to the DC motor driver 22 and on the basis of this signal, the DC motor driver 22 drives the DC motor 23 to move the optical card 1 in the direction of movement of the track. Simultaneously therewith, on the basis of a further detection signal from the sensor 21, the optical head 24 reads the information on two tracks on the optical card 1 at a time while performing the auto focusing and the auto-tracking function. From this reproduction signal, the reproducing circuit 25 indentifies the track number of each track and the information thereof is supplied to the comparator 26.

When it receives the result of comparison from the comparator 26, the pulse operating circuit 27 supplies the pulse motor driver 29 with a signal of the next track to be accessed by the optical head, with the value set by the setting circuit 28 as a reference, and the pulse motor driver 29 drives the pulse motor 30 to access the optical head 24 to a predetermined track.

By the above-described construction, it is possible to realize the method according to the present invention. In the description made with reference to Figure 4, an example in which the insertion of the optical card into the apparatus is detected to thereby start a series of operations has been shown, whereas this is not always restrictive. That is, the present method is of course applicable also to a case where with the optical card already inserted in the apparatus, recording or reproduction of data is done and the operation is once interrupted, whereafter recording or reproduction is again started.

The details and effect of the present invention have been described above with reference to the drawings. According to the present invention, before data are written into or read from the optical card, the optical card and the optical head are moved relative to each other in the direction of movement of the data track and the then relative positional relation between the two is known to thereby make it possible to quickly shift to the next operation.

Claims

1. A method of detecting the position of an optical head for recording information on an optical card or reproducing the information recorded on the optical card, comprising the steps of: instructing the optical head to record or reproduce; and displacing the optical head relative to the optical card in the direction of track of the optical card on the basis of said instruction and reading the position information written on the optical card.

2. A method of detecting the position of an optical head for recording information on an optical card or reproducing the information recorded on the optical card, comprising the steps of: detecting the recording or the reproduction being effected; causing a light beam from the optical head to be accurately applied onto a track on the optical card; moving the optical head and the optical card relative to each other in the direction of track of the optical card and reading the position information written on the optical card.

3. A method according to claim 2, further comprising the step of moving said optical head to its home position on the basis of the read position information.

4. An apparatus capable of detecting the position of an optical head and effecting optical recording or reproduction, comprising: means for instructing the optical head to record or reproduce; and means for moving the optical head and an optical card relative to each other in the direction of track of the optical card on the basis of a signal from said instructing means.

5. Method of detecting the position of an optical head substantially as herein described with reference to Figures 2 to 4 of the accompanying drawings.

6. Apparatus for detecting the position of an optical head substantially as herein described with reference to Figures 2 to 4 of the accompanying drawings.