Note: Descriptions are shown in the official language in which they were submitted.
1~7(305~
1 TITLE OF THE INVENTION
Method of Detecting the Position of an Optical
Head
BACKGROUN~ OF THE INVENTION
Field of the Invention
This invention relates to a method of deteoting
the position of an optical head in a recording-reproduc-
ing 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 anapparatus for effecting only one or both of recording
and reproduction.
Related Background A~t
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
lX70059
1 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 ~uickly 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,
,~
'' , ': ' ',, ~ "'; ' ~ '" :
,
, .. ... . . .
. . . , -
,,- ~ ~ ,
1.270~353
an optical head, for recording or reproducing information on
or from an optical card having a plurality of linearly
extending tracks and position information written
correspondingly to each end area of each track, is positioned
to a target position relative to the optical card by the
steps of:
instructing the optical head to move relative to the
optical card and to record or reproduce information;
reciprocatively and linearly displacing the optical
head relative to a track of the optical card on the basis of
an instruction produced by said instructing step;
reading the position information written on the end
area of the track on the optical card; and
positioning the optical head to a target position
relative to the optical card on the basis of the position
information so read.
The invention will hereinafter be described in more
detail with reference to the accompanying drawings, in which:
Figure 1 shows an embodiment of the optical card.
Figures 2 and 3 illustrate the accessing method
according to the present invention.
Figure 4 shows an embodiment of the optical card
recording-reproducing apparatus using the accessing method
according to the present invention.
Figure 1 is a schematic view showing an embodiment of
the optical 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 types of track including, in
addition to a data track on which data are written, a
tracking track for effecting reliable writing and reading of
data to and from the data track, and a clock track.
Figure 2 is a view illustrating the method according
to the present invention by reference to an optical card one
which exemplary track units are shown. These track units, as
B
..
~270059
shown in Figure 2, consists of tracking tracks lla, llb, llc
and data tracks 12a, 12b. At the opposite ends of the data
tracks 12a and 12b, there are data track identification areas
13a and 13b in which data track numbers for identifying the
data tracks are recorded.
Before writing or reading of data is effected, a beam
spot 14a for scanning the track for data and a beam spot 15a
for scanning the track for tracking may lie at any positions
on the optical card. On initiation of a reading or writing
operation, an optical head of a recording-reproducing
apparatus, not shown, is moved in the left and right
direction as viewed in Figure 2 (the direction of movement of
the track) and auto-focusing and auto-tracking functions of
the recording-reproducing apparatus are caused to act by
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 tracking track
lla respectively. The light spots in this state are
designated by reference characters 14b and 15b, respectively.
As the light spots move to the end of the track, the
spot 14b passes the data track identification area and as a
result the data track number 13a is read. This informs the
apparatus of 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
accomplish a required writing or reading of data. For
example, when data track number is read and the relative
positional relation between the optical head and the optical
card is recoqnized, the mutual positional relation of the
card and the head is modified so that the optical head moves
to a directory area, and from this home position, a further
command can be issued.
Means for giving a command to start the relative
movement in the track direction to ascertain the positional
relation between the optical card and the optical head may be
B
, . . . . .. .
........ . .
. ,. ~,~ ."
,. ` ,. .
. .-~ . . ,
- . .. .. . ..
- ,;
.: -: ..,., ~
.
lZ~0059
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
ends of each data track, so that 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, the
present invention enables access of the optical head to be
accomplished by a simple system. Further, the present
invention can cope with different types of optical cards in
which the shapes of the track units are the same but which
differ from one another in the position and size of the data
area 2 shown in Figure 1.
Figure 3 is a view further illustrating the method of
the present invention with reference to an optical card
having track units as shown in Figure 2. In Figure 3,
elements functionally similar to those in Figure 2 are given
similar reference characters. The difference 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 may be at any positions on the optical card,
but by a similar operation to that previously described, the
light spots 14a for reading 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 llb for
tracking. As a result, both of the data track numbers 13a
and 13b can be read at the same time. Accordingly, not only
can the position of the optical head be ascertained by
reading the data track numbers 13a and 13b, but it becomes
possible to know also the direction in which the next track
unit to be accessed is to be found. This provides a
practically very useful advantage in that the optical card
shown in Figure 1 may be inserted into the optical recording-
~ - .
30',~
reproducing apparatus with either the A side or the B side
leading.
Although the foregoing description has been made with
respect to apparatus of the type in which the optical head is
moved, the optical card may of course be moved relative to
the head in the direction of movement of the track. As
regards the specific means for realizing the auto-focusing
and the auto-tracking functions, the critical angle method,
the knife edge method, the astigmatism method, are examples
of known techniques for the former and the 3-beam method, the
push-pull method, the heterodyne method are examples of known
techniques for the latter, and any of these methods may be
used. Furthermore, although the foregoing description has
been made use of data track numbers, it is also possible to
set a tracking track number corresponding to the track for
tracking and utilize that number to detect the position of
the optical head.
Figure 4 is a schematic diagram showing an embodiment
of 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 reciprocating a table (not shown) supporting the
optical card 1 thereon in the track directions of the card
(the directions shown by the bilateral arrow), and reference
numeral 24 denotes an optical head for simultaneously
applying three light beams to the optical card as shown in
Figure 3. The construction of this optical head is similar
to that of the optical head used with a conventional optical
disc except that a diffraction grating for separating the
light beam from a light source into three light beams is
provided, and its detailed construction is not described
herein. Reference numeral 25 designates a circuit for
recovering information recorded on the tracks from a signal
.,
'
read by the optical head, as described in connection 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
determining a position to which the optical head is to be
subsequently moved relative to the optical card, reference
numeral 29 designates a stepper pulse, motor driver, and
reference numeral 30 denotes a stepper 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 outputs 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,
on the basis of a further detection signal from the sensor
21, the optical head 24 reads the information on two tracks
of the optical card 1 while performing the auto-focusing and
the auto-tracking function. From this information, the
reproducing circuit 25 identifies the track number of each
track and this information 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 puls~ motor driver 29 drives the
pulse motor 30 the optical head 24 to access a predetermined
track.
With the above-described apparatus, it is possible to
carry out the method according to the present invention. In
Figure 4, an arrangement in which the insertion of the
optical card into the apparatus is detected to start a series
of operations has been shown, whereas this need not always be
the case. Thus the present method is of course applicable
also to a case in which the optical card is already inserted
in the apparatus, recording or reproduction of data has been
carried out, and operation has been interrupted, whereafter
~70(~59
further recording or reproduction is again required.
~'
