JPH07129979A - Optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To provide an optical recording/reproducing device capable of stably recording/reproducing data. CONSTITUTION:A light beam irradiates an optical card provided with plural tracks through an objective lens, and while detecting the deviation from a track center of the irradiated light beam as a track error signal, the objective lens is moved in the direction orthogonally intersecting with a track, and the track error signal 17 is scanned. A track error gain 52 is obtained based on the sensitivity measured within the prescribed range in the vicinity of the zero point of a track sum signal 18, a lens displacement signal 19 and the track error signal 17 at the time, and the gain of the track error signal 17 is controlled by a variable gain circuit 51.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically recording / reproducing data.

[0002]

2. Description of the Related Art Generally, in an optical recording / reproducing apparatus, concentric / spiral / parallel tracks are formed on an optical recording medium and data is recorded along the tracks. On the other hand, by providing a means for generating a deviation of the light beam from the track center as a track error signal and a means for moving the light beam in the direction perpendicular to the track, and by performing feedback control generally called tracking servo by these means, The recording / reproducing light beam is aligned with the center of the track of the optical recording medium to record / reproduce data.

However, conventionally, the sensitivity of the track error signal may change due to the difference in the optical recording medium due to the variation in the formation of the groove of the track on the optical recording medium, and for this reason, the tracking servo There was a problem that the loop gain was not constant and the operation became unstable or oscillated.

Therefore, as a means for solving such a problem, the amplitude of the track error signal is measured as disclosed in Japanese Patent Publication No. 4-1411, and the gain of the variable gain circuit is determined based on this measurement result. A method of changing the amplitude to make it constant has been considered.

However, such a conventional one is
As an optical recording medium, a track is always formed by a groove, and it is premised on an optical disc. By the way, recently, an optical card device for recording / reproducing information using an optical card as a recording medium has been used. Such an optical card has a recording capacity several thousand to 10,000 times that of a conventional magnetic card, and cannot be rewritten like an optical disk, but its storage capacity is 1
Since it is as large as ~ 2 Mbytes, it is considered to have a wide range of applications as a bank savings bank, a mobile map, a prepaid card used for shopping, and the like. Further, since it cannot be rewritten, it is also considered to be applied to an application such as a personal health care card that does not allow tampering of data.

[0006]

In such an optical card, the track on the medium is not always formed by the groove, but the track is formed by arranging the guide tracks having different reflectances. There is.
In the case where the track is formed by the guide tracks having different reflectivities as described above, the reflectivity and width of the guide track may change depending on the recording medium due to manufacturing standards or variations in manufacturing.

In this case, although the amplitude of the track error signal can be made constant by using the above-mentioned conventional technique with respect to the change in the reflectance of the guide track, the change in the width of the guide track is Since the shape of the track error signal changes, the amplitude of the track error signal is made the same and the sensitivities near the zero point of the track error signal do not become the same. Therefore, if the loop gain of the tracking servo is constant, There is a problem that recording and reproducing of data becomes unstable because of disappearing.

Further, due to a problem in forming the guide track, swelling may occur in the guide track portion. In this case as well, the shape of the track error signal changes depending on the amount of the swelling, and the loop gain of the tracking servo is constant. However, there is a drawback that the recording and reproduction of data may become unstable. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical recording / reproducing apparatus capable of stable recording / reproducing of data.

[0009]

According to the present invention, there is provided an optical recording / reproducing apparatus for recording / reproducing information by irradiating a card-shaped optical recording medium having a plurality of tracks with a light beam.
Track error signal detecting means for detecting a deviation of the light beam from the track center of the card-shaped optical recording medium as a track error signal; and moving the light beam in a direction perpendicular to a track of the card-shaped optical recording medium. Track error signal sensitivity measuring means for measuring the sensitivity of the track error signal detected by the track error signal detecting means in a predetermined range near the zero point, and the track error based on the measurement result of the track error signal sensitivity measuring means. And a gain control means for controlling the gain of the signal.

[0010]

As a result, according to the present invention, the deviation of the light beam applied to the card-shaped optical recording medium having a plurality of tracks from the track center is detected as a track error signal, and the light beam goes straight to the track. In this case, the sensitivity of the track error signal at this time is measured in a predetermined range near the zero point, and the gain of the track error signal is controlled based on this measurement result. Even if the track error signal is deformed due to manufacturing standards, variations in manufacturing, or the like, the loop gain of the tracking servo can be made constant.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a schematic structure of an optical card applied to the first embodiment. In this case, the optical card indicated by reference numeral 1 is composed of ID sections 2a and 2b in which information such as a track address is recorded and a data recording section 3 for recording the information, and the data recording section 3 is as shown in FIG. A plurality of guide tracks 31 for guiding the light spot in the track direction and a track 32 are provided between the guide tracks, and a data pit 33 is arranged in the track 32. Is recorded and reproduced.

Such an optical card 1 is stopped at either one end of the card in a standby state in which the recording and reproducing of the information is not performed after the card is inserted, and the optical card 1 is recorded in the reproducing of the information. By moving in the track direction. In this case, the ID sections 2a and 2b and the data recording section 3 of the optical card 1 are controlled so that the moving speed becomes constant. In addition, recording / reproducing of this information is performed on the optical card 1.
This is performed by projecting light emitted from a light source such as a semiconductor laser (LD) or LED.

FIG. 3 shows an optical card recording / reproducing apparatus,
An optical system and a detection system are shown. In this case, the light emitted from the light emitting element 22 is shaped into parallel light by the collimator lens 23, diffracted light is taken by the diffraction grating 24, and focused on the optical card 1 by the objective lens 25. Then, the focused light is reflected by the optical card 1, reflected by the mirrors 26, 27, reflected by the mirror 29 by the detection system lens 28, and incident on the detector 30.

In this case, the light beam at the focal point on the optical card 1 is as shown in FIG. 2, and the beam 34 called the main beam diffracted by the diffraction grating 24 is used for reproducing and recording the data pits 33, and A focus error signal for focusing control is generated, and the beams 35 and 36 called sub-beams are arranged so as to cover the guide track 31 half by half, thereby generating a track error signal.

FIG. 4 is a diagram of a beam reflected from the optical card 1 in the detector 30, which includes beams 34a, 35a and 3a.
6a corresponds to the beams 34, 35, 36 of FIG.
Further, the detector 30 further includes 38a, 38b and 3
It is divided into 9 and 40, and when the beam on the optical card 1 is out of focus, the beam 34a is detected by the detectors 38a and 38b.
Since it moves in a direction orthogonal to the dividing line of
By taking the difference between 8a and 38b, it is possible to obtain a focus error signal indicating a deviation from the in-focus position. With this focus error signal, the objective lens 25 shown in FIG.
Focusing control that always keeps the in-focus state is performed by driving so as to move closer to or farther from.

When the beams 34, 35 and 36 move in the direction perpendicular to the track 32, the engagement of the guide track 31 with respect to each of the beams 35 and 36 changes. By taking the difference, it is possible to obtain a track error signal indicating the deviation of the beam from the track center, and the objective lens 25 shown in FIG. 3 is driven by the objective lens tracking drive unit 18 in the direction perpendicular to the track by this track error signal. By doing so, the tracking control for always keeping the beam at the track center is performed.

FIG. 5 shows a schematic structure of a position detector for detecting the position of the objective lens 25. In this case, the LED
The beam emitted from 41 is projected on the detectors 43a and 43b, and at this time, a part of the light flux is blocked by the light blocking portion 42 that is configured integrally with the objective lens 25. Then, when the light shielding part 42 moves together with the objective lens 25 in the direction of the arrow shown, the light shielding parts on the detectors 43a and 43b also move. As a result, a signal proportional to the position of the objective lens 25 can be obtained by taking the difference between the outputs of the detectors 43a and 43b. FIG. 6 shows the relationship between the position (displacement) of the objective lens 25 and the difference signal output of the detectors 43a and 43b at this time.

Next, FIG. 7 shows a characteristic circuit configuration of the first embodiment. In this case, the outputs from the detectors 39 and 40 described in FIG. 4 are given to the subtractor 4, and the track error signal 17A is obtained from the difference between them, and the track error signal 17 is obtained by passing through the variable gain circuit 51. I have to. The variable gain circuit 51 here is the CPU 12
It is set to an arbitrary gain by the signal track error gain 52 output from.

The track error signal 17 is sent to the adder 8 via the analog switch 6 and the phase compensating circuit 7, where it is summed with the scanning signal 20 and via the power amplifier 9 the objective lens tracking drive section. 10 is driven in the tracking direction.

In this tracking servo state, the track servo ON signal 21 is turned on, and the analog switch 6 selects the track error signal 17 to
Closed loop control is executed. At this time, the CPU 12
The scan signal 20 set by the D / A 11 to the adder 8 is set to zero (neutral value). When the track servo ON signal 21 is OFF, the analog switch 6 selects the midpoint potential to open the tracking servo.

On the other hand, the track error signal 17 is A / D1.
4, the output of the detectors 39, 40 is summed by the adder 5 and the track sum signal 18 is added via A / D 15.
The outputs of the detectors 43a and 43b described in FIG.
The signal lens displacement signal 19 obtained by
It is adapted to be digitized via the and input to the CPU 12.

Next, the operation of the embodiment configured as described above will be described. FIG. 8 shows a flowchart for explaining such an operation. In this case, when the optical card 1 is inserted into the optical card recording / reproducing apparatus, the optical card 1 is moved to the objective lens 25.
Is set so that the areas outside the ID portions 2a and 2b are located under the. In this case, no data is recorded in the areas outside the ID sections 2a and 2b, so that only the guide tracks 31 and 32 exist there.

Normally, here, a process called a focus search for searching for the in-focus position which is the zero point of the focus error signal 17 is performed, and then the focusing control state is set.

At this point, the sensitivity of the track error signal 17 to the inserted optical card 1 is unknown. From this state, the process for measuring the sensitivity of the track error signal, which is the object of the present invention, starts.

First, the track servo ON signal 21 shown in FIG. 7 is turned off and the tracking servo is opened (step 801). Next, a predetermined value TG1 is set as the track error gain signal 52, and the variable gain circuit 5
A gain of 1 is set (step 802).

From this state, the CPU 12 causes the D / A 11
The scanning is started by changing the value set in (1) to change the scanning signal 20 (step 803). In this case, the scanning signal 20 repeatedly changes as shown in FIG. 9D, and the objective lens tracking drive unit 10 is driven via the power amplifier 9 by the signal added by the adder 8.

As a result, the objective lens 25 moves in the direction orthogonal to the track 32, and the beam spot 3
4, 35 and 36 cross the track 32, and the track error signal 17 of the variable gain circuit 51 and the track sum signal 18 of the adder 5 are caused by the output fluctuations of the detectors 39 and 40 shown in FIG. 5, respectively. It changes as shown in (a) and (b).

During this time, the CPU 12 sets the maximum value S1 and the minimum value S2 of the track sum signal 18 by the output from the A / D 15 and measures the maximum value S1 and the minimum value S2. , And obtain the value S by dividing each sum by 2 (steps 805-80).
6).

In this state, the detectors 43a, 4 shown in FIG.
Until the difference signal output of the subtracter 13 to which the output of 3b is given, that is, the absolute value of the lens displacement signal 19 shown in FIG. 9C becomes smaller than the range of the predetermined value GE set near the zero point of this signal 19. Wait (step 807). This is because the lens displacement signal 19 is not a completely straight line as shown in FIG. 6, and therefore the measurement is performed near zero, which is the closest to the straight line.

Next, the track sum signal 18 is smaller than the previously obtained value S, and the absolute value of the track error signal 17 is set to a predetermined value near the zero point of the track error signal 17 as shown in FIG. Wait until it becomes smaller than the value GT (steps 808 and 809). This is to search for the vicinity of the zero point of the track error signal 17, and the condition that the track sum signal 18 is smaller than S is that the track error signal 17 has two zero points, as shown in FIG. Since one zero point is detected in such a positional relationship, the track sum signal 18 becomes larger than S at the other zero point.

If such a condition is satisfied, the level of the track error signal 17 is set to T1 within the range of the positive predetermined value GT, the level of the lens displacement signal 19 is set to E1 (steps 810 and 811), and thereafter, for a fixed time. Then, the level of the track error signal is again set to T2 in the range of the predetermined negative value GT.
Then, the level of the lens displacement signal 19 is set to E2 (steps 813 to 814). The correspondence with each signal waveform at this time is as shown in FIG.

T1, T2, E measured in this way
In 1 and E2, the sensitivity of the track error signal 17 is
Since the track error signal 17 changes by T2-T1 with respect to the deviation of E2-E1 which is the difference between the two points of the lens displacement signal 19, it can be easily obtained.

Therefore, the set value TG of the track error gain 52 after the correction of the variable gain circuit 51 becomes TG = {(E2-E1) K1 / (T2-T1)}. TG1 ... (1). Here, K1 is a constant calculated in advance.

Then, when the scanning signal 20 becomes zero, the scanning is ended, and the set value TG is set to the track error gain 52.
Then, the track servo ON signal 21 is turned on to start the tracking servo (steps 815 to 818).

Next, a description will be given by tentatively setting a value. In this case, the track error gain 52 is 1 to 256.
It takes a value up to twice, and here, TG1 is set to 128 times. Further, assuming that the sensitivity of the track error signal 17B after passing through the variable gain circuit 51 is TS [V / μm], here, when TS = 4 [V / μm], the tracking servo has an optimum loop gain. And In addition, the lens displacement signal 19 has a sensitivity ES of 2 [V /
[μm].

If K1 = TS / ES = 2 and T1, T2, E1, and E2 are measured to have the following values, T1 = 0.2 [V] T2 = 0.6 [V] E1 = 0.1 [V] E2 = 0.2 [V] The sensitivity of the track error signal in this case is TS1 [V /
[μm] has changed by T2-T1 = 0.4 [V] with respect to the deviation of (E2-E1) / ES = (0.2-0.1) /2=0.05 [μm]. , TS1 = 0.4 / 0.05 = 8 [V / μm], which is twice the target sensitivity TS = 4 [V / μm], so TG is 1/2 the value of TG1. Of 64.

When this is calculated using the equation (1), TG = {(0.2-0.1) 2 / (0.6-0.2)} * 128 = 64.

Therefore, in this way, the sensitivity in a predetermined range near the zero point of the track error signal when the objective lens 25 for irradiating the light beam is moved in the direction perpendicular to the track is measured, and from this result, the track is detected. Since the gain of the error signal is controlled, even if the track is formed by guide tracks with different reflectivity, and the reflectivity and width of the guide track differ depending on manufacturing standards and manufacturing variations. The sensitivity of the track error signal can be corrected, the loop gain of the tracking servo can be made constant, and the data recording / reproducing can be stabilized.

In the first embodiment, the TG is obtained by one scan and calculation, but if there is a time margin, the scan and calculation are repeated several times, and the TG value is calculated from these results. Of course, if the focusing is performed, the result with higher accuracy can be obtained.

(Second Embodiment) In the above-described first embodiment, the scanning signal is generated and supplied to the objective lens tracking drive section to scan the track error signal.

However, in this method, if there is external vibration during scanning, the objective lens moves due to the vibration,
It may not be possible to scan correctly, and when the optical card is inserted, vibration due to the operation of the insertion mechanism occurs, so it is necessary to wait for the scanning until this vibration subsides. Problems such as increased time until it becomes possible and increased waiting time for users can be considered.

Therefore, the second embodiment is constructed as shown in FIG. In this case, the detector 39 described in FIG.
The outputs of 40 and 40 are given to the subtractor 4, and the track error signal 17A is obtained from the difference between these and the variable gain circuit 51
The track error signal 17 is obtained by passing through. The variable gain circuit 51 here is set to an arbitrary gain by the signal track error gain 52 output from the CPU 12.

The track error signal 17 is input to the power amplifier 9 via the analog switch 6 and the phase compensation circuit 7 and further via the analog switch 44 so as to drive the objective lens tracking drive section 10 in the tracking direction. There is.

In this tracking servo state, the track servo ON signal 21 is turned on, the analog switch 6 selects the track error signal 17, and the analog switch 44 selects the output of the phase compensation circuit 7, whereby the closed loop control is executed. It When the track servo ON signal 21 is off, the analog switch 6 selects the midpoint potential to open the tracking servo.

A signal lens displacement signal 19 obtained by subtracting the outputs of the detectors 43a and 43b described in FIG.
Is supplied to the subtracter 45 together with the lens displacement target value 47 set by the CPU 12 using the D / A 46, and here the difference output is supplied to one input of the analog switch 44.

On the other hand, when the steady-state servo-on signal 48 output from the CPU 12 is given to the analog switch 44, the analog switch 44 selects the output of the subtractor 45 and gives it to the power amplifier 9.

In this case, instead of the tracking servo state, the objective lens position is controlled so that the lens displacement signal 19 is equal to the lens displacement target value 47, and the shake-stop servo state is set. Here, when the lens displacement target value 47 is changed, the position of the objective lens is changed accordingly.

On the other hand, the track error signal 17 is A / D1.
The output signals of the detectors 39 and 40 are summed by the adder 5 via 4 and the track sum signal 18 is digitized via the A / D 15 and input to the CPU 12.

Next, the operation of the embodiment configured as described above will be described. FIG. 12 shows a flowchart for explaining such an operation. In this case, when the optical card 1 is inserted into the optical card recording / reproducing apparatus, the optical card 1 is replaced by the objective lens 2
It is set so that the area outside the ID portions 2a and 2b is located under 5. In this case, since no data is recorded in the area outside the ID sections 2a and 2b, only the guide track 36 and the track 35 exist therein.

Normally, here, a process called a focus search for searching for the in-focus position which is the zero point of the focus error signal is performed, and then the focusing control state is set.
At this point, the sensitivity of the track error signal to the inserted optical card 1 is unknown. From this state, the process for measuring the sensitivity of the track error signal, which is the object of the present invention, starts.

First, the track servo-on signal 21 shown in FIG. 11 is turned off and the shake-preventing servo signal 48 is turned on to set the shake-preventing servo state (step 1201). next,
A predetermined value TG1 is set as the track error gain signal 52, and the gain of the variable gain circuit 51 is set (step 1202).

From this state, the CPU 12 causes the D / A 46
The scanning is started while changing the value set in to increase the lens displacement target value 47. As a result, the objective lens 2
5 moves in a direction orthogonal to the track 35, the beam spots 34, 35, 36 cross the track 35, and the output error of the detectors 39, 40 shown in FIG. The track sum signal 18 of the adder 5 also changes.

During this period, the CPU 12 sets the maximum value S1 and the minimum value of the track sum signal 18 by the output from the A / D 15 to S2 and increases the lens displacement target value 47 to measure the maximum value S1 and the minimum value S2. At the same time, when this is completed, the sum S of each is taken and divided by 2 to obtain a value S (steps 1203 to 1206).

Next, the lens displacement target value 47 is set to zero,
The objective lens 27 is moved to near the zero point of the lens displacement signal 19 (step 1207). This is because the lens displacement signal 19 is not perfectly linear as shown in FIG. 6 described above, and therefore the measurement is performed near zero, which is the closest to the straight line.

Next, after waiting for a predetermined time (step 120)
8) Scan again while increasing the lens displacement target value 47 again, and perform track sum signal 1 in the same manner as described in the first embodiment.
It waits until 8 is smaller than S previously obtained and the absolute value of the track error signal 17 is smaller than a predetermined value GT (steps 1209 to 1211). This is to search for the vicinity of the zero point of the track error signal, and the reason why the track sum signal 18 is made smaller than S is that the track error signal has two zero points.

When such a condition is satisfied, the level of the track error signal 17 is set to T1 within the range of the positive predetermined value GT, and the level of the lens displacement signal 19 is set to E1 (steps 1212 and 1213).

Further, since the anti-sway servo state is set here, the level E1 of the lens displacement signal 19 becomes equal to the lens displacement target value 47 at this time. Thereafter, a value obtained by adding a predetermined value D to E1 is set as the lens displacement target value 47, and after waiting for a predetermined time, the level of the track error signal 17 is set to T2 (steps 1214 to 1216).

At T1 and T2 thus measured, the sensitivity of the track error signal is determined by the lens displacement signal 19
Since the track error signal 17 changes by T2-T1 with respect to the deviation of D which is the difference between the two points, it can be easily obtained.

Practically, if the set value of the corrected track error gain 52 is TG, then TG = {DK2 / (T2-T1)} TG1 (2) Here, K2 is a constant calculated in advance.

Then, TG is set to the track error gain 52.
, Turn on the track servo ON signal 21,
The steady rest servo-on signal 48 is turned off and the tracking servo is started (steps 1217 to 12).
19).

Next, a description will be given by tentatively setting a value. In this case, the track error gain 52 is 1 to 256.
It takes a value up to twice, and here, TG1 is set to 128 times. Assuming that the sensitivity of the track error signal 17 after passing through the variable gain circuit 51 is TS [V / μm], here, T
When S = 4 [V / μm], it is assumed that the tracking servo has an optimum loop gain. Also, the lens displacement signal 1
It is assumed that 9 is adjusted in advance so that the sensitivity ES near the zero point is 2 [V / μm].

Then, D is 0.1 [V] and K2 = TS
If / ES = 2 and T1, T2, E1, and E2 are measured to the following values, T1 = 0.2 [V] T2 = 0.6 [V] In this case, the sensitivity of the track error signal 17 is , TS1
Since [V / μm] changes by T2-T1 = 0.4 [V] with respect to the deviation of D / ES = 0.1 / 2 = 0.05 [μm], TS1 = 0.4 / 0.05 = 8 [V / μm], which is twice the target sensitivity TS = 4 [V / μm], so that TG is 64, which is half the value of TG1.

When this is calculated using equation (2), TG = {0.1 × 2 / (0.6−0.2)} × 128 = 64.

Therefore, even in this way, due to the difference in the inserted optical card (manufacturer, lot, material of medium),
The difference in the sensitivity of the track error signal can be completely corrected. In addition, since the steady-state servo state is always present, feedback control works, and the position of the objective lens 27 is controlled to be equal to the lens displacement target value 47.
The correction process can be performed without being affected by the vibration, and the vibration generated when the card is inserted can be immediately started without waiting for the vibration to subside. Furthermore, waiting for the time after setting the lens displacement target value is also the time until the objective lens settles at the target position, so at most 1
It also has the effect of requiring a short time of about 0 msec.

In the second embodiment, the TG was calculated by one scan and calculation, but if there is a time margin, the scan and calculation are repeated several times, and the TG value is converged from these results. Of course, if this is done, higher precision results can be obtained.

(Third Embodiment) The first and second embodiments described above.
In the embodiment, a detector for detecting the position of the objective lens is required.

However, the provision of these detectors may complicate the structure of the objective lens and increase the cost, and the sensitivity of the lens displacement signal, which is the output of the detector, is constant. Problems such as the need for adjustment work in advance are possible.

Therefore, the third embodiment is constructed as shown in FIG. In this case, the detector 3 described in FIG.
The outputs of 9 and 40 are given to the subtractor 4, and the track error signal 17A is obtained from the difference between these and the variable gain circuit 5
The track error signal 17 is obtained by passing 1 through. The variable gain circuit 51 here is set to an arbitrary gain by the signal track error gain 52 output from the CPU 12.

The track error signal 17 passes through the analog switch 6 and the phase compensation circuit 7 and is given to the adder 8 where the sum with the scanning signal 20 is taken and inputted to the power amplifier 9 for the objective lens tracking drive section. 10 is driven in the tracking direction.

In the tracking servo state, the track servo ON signal 21 is turned on, and the analog switch 6 selects the track error signal 17 to execute the closed loop control. At this time, the CPU 12 causes the D / A 11
The scan signal 20 set via the is set to zero (neutral value). On the other hand, when the track servo ON signal 21 is OFF, the analog switch 6 selects the potential at the middle point to open the tracking servo.

On the other hand, the track error signal 17 from the variable gain circuit 51 is given to the comparator 48, where it is compared with the comparison value 49, and the track error signal 17 is compared with the comparison value 49.
When it is larger than the above, a high level is outputted as the comparison signal 50, and when it is larger than the above, a low level is outputted respectively. Then, the comparison signal 50 is input to the CPU 12. The track error signal 17 of the variable gain circuit 51 is A
It is digitized via / D14 and input to the CPU 12.

Next, the operation of the embodiment configured as described above will be described. FIG. 14 shows a flowchart for explaining such an operation. In this case, when the optical card 1 is inserted into the optical card recording / reproducing apparatus, the optical card 1 is replaced by the objective lens 2
It is set so that the area outside the ID portions 2a and 2b is located under 5. In this case, since no data is recorded in the area outside the ID sections 2a and 2b, only the guide track 36 and the track 35 exist therein.

Normally, here, a process called a focus search for searching for the in-focus position which is the zero point of the focus error signal is performed, and thereafter the focus control state is set.
At this point, the sensitivity of the track error signal to the inserted optical card 1 is unknown. From this state, the process for measuring the sensitivity of the track error signal, which is the object of the present invention, starts.

First, the track servo ON signal 21 is turned off and the tracking servo is opened (step 1).
401). Next, a predetermined value TG1 is set as the track error gain signal 52, and the gain of the variable gain circuit 51 is set (step 1402). From this state, CP
U12 changes the value set in D / A11 to change the scanning signal 20 (step 1403).

Then, the scanning signal 20 repeatedly changes as shown in FIG. 15C, and the signal added by the adder 8 is passed through the power amplifier 9 to the objective lens tracking drive section 1.
Drive 0. As a result, the objective lens 25 shown in FIG.
Moves in a direction orthogonal to the track 32, the beam spots 34, 35, 36 cross the track 32, and the track error signal 17 and the comparison signal 50 are shown in FIGS.
It changes as shown in.

In this state, the process waits until the scanning direction of the scanning signal 20 becomes the determined direction (step 1404). Here, the direction in which the scanning signal 20 shown in FIG. 15B decreases is defined as the forward direction. In this direction, the comparison signal 5
It is determined that the first zero point of the track error signal 17 after the rise of 0 becomes the target position of the tracking servo.

Next, a predetermined value GS is set in the vicinity of the zero point of the scanning signal 20, and the process waits until the absolute value of the scanning signal 20 becomes smaller than this value GS (step 1405). This is because the scanning speed is most stable in the vicinity of the zero point of the scanning signal during scanning.

Next, the process waits until the rising edge of the comparison signal 50 is detected (step 1406). Then, at the same time as detecting the rising edge, a timer for measuring time is started (step 1407).

Next, wait until the absolute value of the track error signal 17 becomes smaller than the predetermined value GT (step 140).
8) If the above conditions are met, track error signal 1
The level of track error signal 7 is set to T1, the level of the track error signal is set to T2 again after a predetermined time P1 (step 140).
9-1411).

Further, the process waits until the rising edge of the comparison signal 50 is detected, and the time measured by the timer at this time is set to P (steps 1412 and 1413). The correspondence with each signal waveform at this time is shown in FIG.

In T1 and T2 thus measured, it is assumed that scanning is performed at a constant speed in the period from the rising edge of the comparison signal 50 to the next rising edge, and the track pitch on the card is known. , And the moving distance TL in the period P1 is TL = (P1 / P) TP. Further, the sensitivity of the track error signal 17 is TL
Track error signal 17 is T2-T1
Since it has changed only, it can be easily obtained.

Practically, if the set value of the corrected track error gain 52 is TG, then TG = {P1 · K3 / (T2-T1) P} · TG1 (3) Here, K3 is a constant calculated in advance.

Then, the scanning signal 20 is set to zero to end the scanning, the TG is set to the track error gain 52, the track servo ON signal 21 is turned ON, and the tracking servo is started (step 1414).
~ 1417).

Next, a description will be given by tentatively setting a value. In this case, the track error gain 52 is 1 to 256.
It takes a value up to twice, and here, TG1 is set to 128 times. Assuming that the sensitivity of the track error signal 17 after passing through the variable gain circuit 51 is TS [V / μm], here, T
When S = 4 [V / μm], it is assumed that the tracking servo has an optimum loop gain. Also, the track pitch TP
Is 12 [μm].

If K3 = TS · TP = 48 and T1, T2, E1, and E2 are measured to the following values, T1 = 0.2 [V] T2 = 0.6 [V] P1 = 0.2 [msec] P = 12 [msec] The sensitivity of the track error signal 17 in this case is TS1.
Since [V / μm] changes by T2-T1 = 0.4 [V] with respect to the deviation of (P1 / P) TP = (0.2 / 12) × 12 = 0.2 [μm] , TS1 = 0.4 / 0.2 = 2 [V / μm], which is 1/2 of the target sensitivity TS = 4 [V / μm], so TG is twice the value of TG1. Of 256
Becomes

When this is calculated using equation (3), TG = {0.2 × 48 / (0.6−0.2) 12} × 128 = 256.

Therefore, even in this way, due to the difference in the inserted optical card (manufacturer, lot, material of medium),
The difference in the sensitivity of the track error signal can be completely corrected. The present invention is not limited to the above-mentioned embodiments, and can be carried out with appropriate modifications without departing from the scope of the invention.

[0088]

As described above, according to the present invention, the deviation from the track center of the light beam applied to the card-shaped optical recording medium having a plurality of tracks is detected as a track error signal while Since the beam is moved in the direction perpendicular to the track, the sensitivity of the track error signal at this time in a predetermined range near the zero point is measured, and the gain of the track error signal is controlled from this measurement result. In an optical recording medium such as an optical card in which tracks are formed by guide tracks having different reflectances, even if the shape of the track error signal changes due to changes in the width and swell of the guide track, the track error signal By measuring the sensitivity in the vicinity of the zero point of, the loop gain of the tracking servo can be made constant and data recording / reproduction is stable. It can be to those were.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical card applied to a first embodiment.

FIG. 2 is a diagram showing a data recording unit of an optical card applied to the first embodiment.

FIG. 3 is a diagram showing an optical system and a detection system of the optical card recording / reproducing apparatus applied to the first embodiment.

FIG. 4 is a diagram showing a beam reflected from an optical card in a detector of the optical card recording / reproducing apparatus applied to the first embodiment.

FIG. 5 is a diagram showing a schematic configuration of a position detection unit that detects the position of the objective lens applied to the first embodiment.

FIG. 6 is a diagram showing the relationship between the position (displacement) of the objective lens and the difference signal output of the detector in the first example.

FIG. 7 is a diagram showing a characteristic circuit configuration of the first embodiment.

FIG. 8 is a flowchart for explaining the operation of the first embodiment.

FIG. 9 is a diagram for explaining the operation of the first embodiment.

FIG. 10 is a diagram for explaining the operation of the first embodiment.

FIG. 11 is a diagram showing a schematic configuration of a second embodiment of the present invention.

FIG. 12 is a flowchart for explaining the operation of the second embodiment.

FIG. 13 is a diagram showing a schematic configuration of a third embodiment of the present invention.

FIG. 14 is a flowchart for explaining the operation of the third embodiment.

FIG. 15 is a diagram for explaining the operation of the third embodiment.

FIG. 16 is a diagram for explaining the operation of the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical card, 2a, 2b ... ID part, 3 ... Data recording part, 4 ... Subtractor, 5 ... Adder, 51 ... Variable gain circuit, 6
... Analog switch, 7 ... Phase compensation circuit, 8 ... Adder,
9 ... Power amplifier, 10 ... Objective lens tracking drive unit, 11 ... D / A, 12 ... CPU, 13 ... Subtractor, 1
4, 15, 16 ... A / D, 25 ... Objective lens, 31 ... Guide track, 32 ... Track, 33 ... Data pit,
34, 35, 36 ... Beam, 41 ... LED, 42 ... Shading section, 43a, 43b ... Detector, 48 ... Comparator.

Claims (1)

[Claims] 1. An optical recording / reproducing apparatus for irradiating a card-shaped optical recording medium having a plurality of tracks with a light beam to record and reproduce information, wherein a deviation of the light beam from a track center of the card-shaped optical recording medium. Of the track error signal detected by the track error signal detecting means by moving the light beam in a direction perpendicular to the track of the card-shaped optical recording medium. A track error signal sensitivity measuring means for measuring the sensitivity in a predetermined range near the point; and a gain control means for controlling the gain of the track error signal based on the measurement result by the track error signal sensitivity measuring means. Characteristic optical recording / reproducing device.