JPH0428019A - Servo circuit for optical information recording and/or reproducing device - Google Patents

Abstract

PURPOSE:To always stably perform appropriate servo without generating out-of- servo by performing servo control by selecting a servo signal on which no defective part is affected based on the output of a defect detecting means. CONSTITUTION:Plural detecting systems which detect the servo signals based on reflected light at different positions on the same servo line of a recording medium, and the defect detecting means 66 which detects the defective part on the servo line based on the servo signal not being used in the servo control out of detected servo signals are provided. A selection means 67 which selects the detecting system not being affected by the defective part from the plural detecting systems based on the output of the defect detecting means is provided, and the detecting system can be switched to the one not being affected by the defective part even when the defect exists on the recording medium by performing the servo control by the servo signal by the detecting system selected by the selection means 67. In such a way, it is possible to prevent the out-of- servo occurring and to always maintain an appropriate servo state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording and/or recording medium for recording information on an optical recording medium such as an optical card through an objective lens, and for reproducing recorded information. Or regarding the servo circuit of a playback device.

[Prior Art] In an optical head of an optical information recording and/or reproducing device, focus control and track control are required to maintain the relative position between the objective lens and the recording medium, and an error signal detection device for this purpose is required. Various methods have been proposed in the past. In addition, the applicant also applied for example in Japanese Patent Application No. 63-204.
No. 819, illumination light is projected onto a recording medium in a defocused state from the normal direction thereof, and in the reflected light from the recording medium, the illuminance of the unchanging portion hardly changes even if the defocus state of the illumination light changes. They have proposed a system in which photodetectors are placed on the inside and outside to generate error signals.

3 and 4 are a cross-sectional front view and a cross-sectional plan view showing the configuration of an optical head in an optical information recording/reproducing apparatus already proposed by the applicant. This optical information reproducing apparatus reads data recorded on the tracks of the optical card 11 by relatively moving the optical card 11 and the optical head in the track direction of the optical card 11. The LED 12 as an illumination light source is arranged slightly behind the focal position fO of the collimator lens 13, and the illumination light from the LED 12 is sent to the optical card through the collimator lens 13, half mirror 14, reflection mirror 15, and objective lens 16. 11 from the normal direction to illuminate the tracks of the optical card 11 in a defocused state. Further, the reflected light from the optical card 11 is collected by an objective lens 16, passes through a reflecting mirror 15, a half mirror 14, and a lens 17, and is received by a photodetector 18.

The objective lens 16 is held in a holder 21, and this holder 2
1 through four parallel wires 22 in a focus direction F, which is the optical axis direction of the objective lens 16, and in a tracking direction T, which is orthogonal to the focus direction F and the tracks of the optical card 11 (not shown). It is supported by a wire stand 23 fixed to the base. The holder 21 is equipped with focus coils 24A and 24B on opposite end faces in the tracking direction T, and also includes a flexible substrate 26 on which tracking coils 25A and 25B made of printed coils are formed. Attach it so that it is located outside of 24B.

Also, a focus coil 24A is provided on the base (not shown).
Inner yokes 27A and 27B are inserted into the inner yokes 24B, and a pair of outer yokes 28A are provided opposite to these inner yokes 27A and 27B via focus coils 24A and 24B and tracking coils 25A and 25B, respectively.
, 28B and 29A, 29B are provided, and these outer yokes 2
Permanent magnets 30A, 30B and 31A, 31B are attached to the inside of 8A, 28B and 29A, 29B, respectively, and the tracking coil 25A is connected by the permanent magnets 30A, 30B.
The magnetic flux that crosses the focus coil 24A is generated by the permanent magnets 31A and 31B, and the magnetic flux that crosses the tracking coil 25B and the focus coil 24B are generated, respectively. In this way, four parallel wires 22
Forky coil 24A through two wires of
, 24B, the objective lens 16 is moved integrally with the holder 21 in the focus direction F.
By displacing the objective lens 16 in the tracking direction T together with the holder 21 by supplying a tracking error signal to the tracking coils 25A and 25B via the other two wires, tracking servo is performed. Make sure to do the following. In addition, LED
12, a collimator lens 13, a half mirror 14, a reflecting mirror 15, a lens 17, and a photodetector 18 are fixedly held on a base (not shown).

FIG. 5 shows an example of a rack format of the optical card 11 shown in FIG. A guide pattern 36 consisting of a black and white pattern is formed in the center of the track 35 and extends in the track direction, and 8-bit data is recorded on each side of the guide pattern 36 in the track width direction. .

FIG. 6 shows the configuration of the photodetector 18 shown in FIG. 4. The photodetector 18 has data reading light receiving areas 41-1 to 41-16 arranged corresponding to 16 data recording positions in the track width direction, and is spaced apart in the track direction so as to receive the image of the guide pattern 36. four pairs of clock generation light-receiving areas 42-1 to 42-8 arranged as shown in FIG. Focus/tracking error detection light receiving area 43-
1 to 43-8.

Here, as described above, if the LED 12 is placed slightly behind the focal position fO of the collimator lens 13 and the optical card 11 is illuminated in a defocused state, the illumination light will be closer to the objective than the focal position of the objective lens 16. The light is focused on the lens 16 side. Therefore, in a focused state where the focal position of the objective lens 16 is located on the optical card 11, the illuminance distribution of the illumination light on the optical card 11 is as shown by the solid line in FIG. 7, and the optical card 11 is As you approach the objective lens, the spot diameter becomes smaller, and the illuminance distribution becomes as shown by the broken line in FIG. 7, and conversely, as you move away from the objective lens, the spot diameter becomes larger, as shown by the two-dot chain line. In this way, the illuminance distribution of the illumination light on the card 11 changes depending on the distance between the objective lens 16 and the optical card 11, but as is clear from FIG. lens 16
A ring-shaped part (indicated by numeral 4 in FIG. 7) in which the illuminance hardly changes even if the distance between
5) occurs, and changes in illuminance due to changes in the focal state of the objective lens 16 are opposite between the inside and outside of this unchanged portion 45. That is, as the optical card 11 approaches the objective lens side, the illuminance increases on the inside of the unchanged portion 45 compared to when in focus, but decreases on the outside; As the distance from the focal point increases, the illuminance decreases inside the unchanged portion 45 compared to when it is in focus, whereas it increases outside the constant portion 45.

Here, as shown in FIG. 6, a data reading light receiving area 41-1 corresponding to the data recording position of the track 35 is
- 41-16 are arranged along the diameter direction of the unchanged portion 45 inside the unchanged portion 45 of the spot image of the optical card 11 caused by the illumination light formed on the photodetector 18, and the first light receiving means is Two pairs of focus/tracking error detection light receiving areas 43-3.43-4 and 43-5.43 constitute
-6, inside the unchanged part, the center of each of which is the arrangement central axis of the light receiving areas 43-1 to 43-16, and the unchanged part 4
along a diametrical straight line perpendicular to the center of 5, and arranged at symmetrical positions with respect to the center.

Further, the two pairs of focus/tracking error detection light receiving areas 43-1, 43-2 and 43-7, 43-8 constituting the second light receiving means are arranged so that their respective centers are outside the unchanged portion 45. They are placed at symmetrical positions about the center along a straight line. In addition, these light receiving areas 43-3, 43-4
and 43-5, 436, four pairs of clock generation light receiving regions 42-1 to 42-8 are arranged. Note that the paired clock generation light receiving areas 42-1.42-2.43,
. . , 42-7, 42'-8, the pitch is 1/2 of the pitch of the black and white pattern image constituting the guide pattern 36. In each of the focus/tracking error detection light receiving areas 43-1 to 43-8, the spot center of the illumination light (optical axis of the objective lens 16) is located at the track 35.
The white part between the guide pattern 36 and the data part (high reflectance They are each made of the same size so that they have a width that can sufficiently receive the reflected light from the other parts.

In this way, the sum of the outputs of one pair of clock generation light receiving areas 42-1.42-3.42-5 and 42-7, and the output of the other clock generation light receiving area 42-2.42-4.
．． A clock signal is obtained based on the difference between the sum of the outputs of 42-6 and 42-8.

Further, as shown in FIG. 8, a light receiving area 4 receives an image of one edge portion of the guide pattern 36 in the track width direction.
The differential amplifier 51 detects the difference between the sum of the outputs of 3-3 and 43-5 and the sum of the outputs of the light-receiving areas 43-4 and 43-6, which receive the image of the other edge part. A tracking error signal is obtained based on the center of the unchanged portion 4.
Light receiving area 43-3.43-4.43 located inside 5
The sum of the outputs of -5 and 43-6 is added to adder 54゜5.
5, and adders 52 and 53 add these sums and the sums of the outputs of the light receiving areas 43-1, 43-2, 43-7 and 43-8 whose centers are located outside the unchanged portion 45, respectively. and detecting the difference between these sums using the differential amplifier 56.
A focus error signal is obtained based on this difference.

Here, the objective lens 16 is set to the focal position of the optical card 1 based on the focus error signal obtained as described above.
Focus servo is performed by displacing the optical card 1 in the optical axis direction so that the spot center of the illumination light is located on the optical card 11 based on the tracking error signal.
While performing tracking servo so as to be located at the center of the desired track 35, the outputs of the data reading light receiving areas 41-1 to 41-16 are taken in in synchronization with the clock signal, and at the same time 16 bits of data are read. I try to read it.

[Problems to be Solved by the Invention] However, in the above-mentioned optical head, as shown in FIG. 9, the guide pattern has defects caused by air bubbles, etc., which are accidentally created between the protective layer and the recording surface during card manufacturing. 37, this is the light receiving area 43-1 to 43 for servo signal detection.
-8, a large protrusion occurs in the track error signal, and the objective lens 16 is largely displaced in the track width direction, or servo deviation occurs where it is removed from the desired track, causing data to be recorded and/or reproduced. The problem is that it cannot be done.

Furthermore, a similar problem arises in that control is disrupted with respect to focus servo.

The present invention has been made in view of the above-mentioned points, and provides an optical information recording and/or system that functions to always perform proper servo without causing the servo to come off even if there is a defect such as a bubble in the guide pattern. The purpose is to provide a servo circuit for a playback device.

[Means and effects for solving the problem] In the present invention, a recording medium having servo lines formed in the track direction is irradiated with a light beam, and the relationship between the recording medium and the light beam is determined based on the reflected light from the servo line. In a servo circuit of an optical information recording and/or reproducing device that detects an error signal representing a relative positional deviation and performs servo control to correct the relative positional deviation based on the error signal, the recording medium a plurality of detection systems that detect servo signals based on reflected light at different positions of the same servo line, and among the detected servo signals,
Based on servo signals not used for servo control,
a defect detection means for detecting a defective portion on the servo line; and a selection means for selecting a detection system unaffected by the defective portion from the plurality of detection systems based on the output of the defect detection means; By performing servo control using the servo signal from the detection system selected in , even if there is a defect on the recording medium, the detection system can be switched to a detection system that is not affected by the defect, preventing servo misalignment and always This allows the servo to be maintained in an appropriate state.

[Example code] Hereinafter, the present invention will be specifically explained with reference to the drawings.

1 and 2 relate to one embodiment of the present invention, FIG. 1 is a configuration diagram of a servo signal generation circuit in one embodiment, and FIG. 2 is a timing chart diagram explaining the operation of FIG. 1. .

The optical head in this invention has the same structure as in FIGS. 3 and 4, the format of the optical card is the same as in FIG. 5, and the photodetector shown in FIG. 6 is used.

That is, the optical head described in FIGS. 3 to 7 is used, and servo control is performed by the servo circuit section, that is, the servo signal generation circuit 61 shown in FIG. 1.

This servo signal generation circuit 61 includes a focus error signal generation circuit 63 including first and second focus error signal generation circuits 62a and 62b, and first and second track error signal generation circuits 64a and 64b. l. A racking error signal generation circuit 65, a defect detection circuit 66 that detects defects from the output signal of the first track error signal generation circuit 64a, and a focus error detection circuit 66 that detects defects from the output signal of the first track error signal generation circuit 64a, and a focus error signal used for servo control based on the output signal of this defect detection circuit 66. Selection control circuit 67 that performs selection control of signals and track error signals
It consists of

Light receiving area 4B- whose center is located outside the unchanged portion 45
The outputs of 1 and 43-2 are respectively supplied to the inverting input terminal of the differential amplifier constituting the adder 71 via the resistor R1R.
The non-inverting input terminal is grounded via a resistor R, and the inverting input terminal and output terminal are connected via a resistor R' (or R may be used). In FIG. 1, the reference numerals for the resistors R (or R') are omitted.

Similarly, the outputs of the light receiving regions 4B-7 and 43-8, whose centers are located outside the unchanged portion 45, are sent to the differential amplifier configuring the adder 72. The output of -3. The signals are respectively input to dynamic amplifiers.

The outputs of the adders 71 and 73 are sent to the differential amplifier 75 and the adder 7
The outputs of FB1.3.74 are respectively input to the differential amplifier 76, and the outputs of the first and second focus error signals FB1. FB2
are generated respectively. These focus error signals F
EI and FE2 are analog switches 77 and 7, respectively.
8 and is input to the differential amplifier constituting the adder 79,
A focus error signal FB is generated and sent to a focus coil 24A via a phase compensation circuit and a drive circuit (not shown).
24B (see FIG. 4) to perform focus control.

Further, the output of the light receiving area 43-3 that receives the image of one edge portion of the guide pattern 36 in the track axis direction and the output of the light receiving area 43-4 that receives the image of the other edge portion are connected to a resistor R, respectively. R to the inverting and non-inverting inputs of a differential amplifier 81, and the difference between these outputs is detected to generate a first tracking error signal.

Similarly, a light receiving area 43-5 receives the image of one edge portion.
A light receiving area 43- receives the output of the edge part and the image of the other edge part.
6 is input to a differential amplifier 82, and the difference between these outputs is detected and generated as a second tracking error signal TE2.
is generated.

The tracking error signal TE2 is input to a differential amplifier constituting an adder 85 via analog switches 83 and 84, respectively, and a tracking error signal TE is generated from the adder 85.
The signal is supplied to tracking coils 25A and 25B via an off switch, a phase compensation circuit, and a drive circuit, and is used for tracking control.

The output of the differential amplifier 81, that is, the first tracking error signal device, is connected to a window comparator, that is, the first and second comparators 86a that constitute the defect detection circuit 66.
, 86b, respectively. The non-inverting input terminal of the first comparator 86a and the inverting input terminal of the second comparator 86b are connected to variable terminals of variable resistors 87a and 87b, respectively, and levels Vl and V2 for detecting defects (see FIG. 2(a) ). Therefore, by passing through this defect detection circuit 66, if a defect exists, a defect detection signal DEF is output. The output of this circuit 66 is a monostable multivibrator (hereinafter abbreviated as OMV) 88 that constitutes the selection control circuit 67.
is applied to the trigger input terminal B of. This OMV88 is designed so that the signal to this input terminal B rises from "L" to "H".
outputs a Q output that remains "H" for a predetermined period of time set by the values of capacitor C and resistor r.

This Q output is supplied to analog switches 77 and 83 and to on/off control ends of ζ (inversion) output analog switches 78 and 84. These analog switches 77.78,
83 and 84 are controlled so that they are turned on when the level to the control terminal is "°H" and turned off when the level is "L".

In addition, the read signal R is connected to the clear terminal CLR of OMV88.
EAD is applied and this OMV8 in read mode.
8 works.

In one embodiment configured in this way, when the defect detection signal DEF is not output from the defect type output M66, since the analog switches 78 and 84 are on, Signal FE2. T.E.
2 performs focus control and tracking control, and when the defect detection signal DEF is output, the analog switches 77.83 are turned on, so the signals FBI and TE1 that pass through these analog switches 77.83 are Focus control and tracking control are performed.

The operation of one embodiment configured in this manner will be described below.

When the read mode is entered, the read signal READ becomes "H" as shown in FIG. 2(f), and this signal READ becomes O.
Put MV88 into operation state.

In normal use, where no defects are detected as mentioned above, the OM
Since the Q output of V88 is "L" and the output of V88 is "H", analog switches 78 and 84 are on.

Therefore, by the adder 74, the light receiving areas 43-5 and 43-
6, the adder 72 detects the sum of the outputs of the light receiving areas 43-7 and 43-8, and the difference between these is detected by the differential amplifier 76 to generate a focus error signal FE2. It is output as a focus error signal FE.

Further, the difference between the output of the light receiving area 43-5 and the output of the light receiving area 43-6 is detected by the differential amplifier 82, and a tracking error signal TE2 is generated! - Output as racking error signal TE.

However, as shown in FIG. 9, there is a defect 37 due to bubbles or the like on the guide pattern 36 of the optical card 11, and this defect extends from the light receiving area 43-1, 43-2 to the light receiving area 43-7.
43-8, the tracking error signals TEI and TE2 are as shown in Fig. 2(a), (
As shown in b), first, the level of the I/racking error signal device changes in a mountain shape due to the defect 37, and then the level of the tracking error signal TE2 also changes in a mountain shape.

When the level that has changed in the shape of a mountain exceeds one level V1 of the defect detection circuit 66, the output of the comparator 86a becomes "
The defect detection signal DEF is output from this circuit 66 as shown in FIG. 2(C).This signal DEF triggers the OMV88 and the defect detection signal DEF is output as shown in FIG. 2(d) and (e). Q output changes from “L” to “H”, ?) output goes from “H” to “H”.
'' to "L" for a predetermined period of time.

Above, the output turns the analog switch 78.84 from on to off, while the Q output turns the analog switch 77
．． Since the signal 83 is turned on from off, the first focus error signal FBI and the first tracking error signal device are switched to be output as the focus error signal FE and the tracking error signal TE, respectively.

That is, at first, the servo is performed by the focus error signal FE2 and the tracking error signal TE2, and then the pulse of the defect detection signal DEF rises again, and the defect 37 hits the light receiving areas 43-1, 43-2, 43-3 and 43-4. When a passage is detected, the error signal switches to FEI.

After a predetermined time, the defect is detected in the light receiving section 43-5.43-643-7.
and 43-8, the error signal passes through FE2. T.E.
Return to 2.

Therefore, even if a defect exists, after the defect is detected, the signals FE2 and TE2 used as the focus error signal FE and track error TE are switched to the signals FEI and TEl, which are not affected by the defect 37. It is possible to prevent servo control from being affected by defects, and to maintain an appropriate servo state at all times without causing servo disconnection.

In the above-mentioned first embodiment, the level of the 1 to racking machine signal position, whose level changes temporally earlier due to the influence of a defect, is detected, and the signal used for servo control is switched for a certain period of time. However, the defect (end of portion) may also be detected using the other tracking signal TE2, and the switching may be returned to the original state after this detection.

Further, when switching, the switching may be performed after detecting that the level has reached a level smaller than the level used for the detection signal DEF.

Furthermore, the focus error signal FBI may be used instead of the tracking error signal GoE1 for defect detection.

Furthermore, defect detection may be performed from the tracking error signal device and the focus error signal FBI, respectively, and switching may be performed based on either detection signal.

Note that when the defect 37 passes in the direction opposite to the above-mentioned direction from the light receiving areas 4B-7 and 43-8 to the light receiving areas 43-1 and 43-2, the tracking error signal T
Defect detection is performed using E2, and initially one error signal F
Servo is performed by BI and TEI, and when the defect passes, the other error signal FE2. What is necessary is to switch to TE2 and return to one of the error signals FEI and TEI after passing.

[Effects of the Invention] As described above, according to the present invention, the same type of servo signals are detected based on the reflected light at different positions of the same servo line on the recording medium, and the servo signals that are used among the servo signals are detected. The defective part is detected based on the error signal that is not detected, and the servo control is performed by selecting a servo signal that is not affected by the defective part based on the output of this defect detection means. Even when the servo is off, the servo does not come off, and the servo can always be properly and stably performed.

[Brief explanation of the drawing]

1 and 2 relate to one embodiment of the present invention, FIG. 1 is a circuit diagram showing the configuration of a servo signal generation circuit in one embodiment, and FIG. 2 is a timing chart diagram for explaining the operation of FIG. 1. , FIG. 3 and FIG. 4 are cross-sectional views showing the configuration of essential parts of the optical head in the first embodiment and the preceding example, and FIG. 5 is an explanation showing an example of the track format of the optical card used in FIG. 3. 6 is an explanatory diagram showing an example of the photodetector used in FIG. 4, FIG. 7 is a distribution diagram showing changes in the illuminance distribution of illumination light on the optical card in FIG. The figure is a circuit diagram of an error signal generation circuit in a prior example by the applicant.
FIG. 9 is an explanatory diagram showing an example of a defect in a guide pattern portion of an optical card. 11... Optical card 12... LED16
...Objective lens 18...Photodetector 24A,
24B... Focus coil 25A, 25B... Tracking coil 35... Track 36.
...Guide patterns 43-1 to 43-8...Focus/tracking error detection light receiving area 61...Servo signal generation circuit 63...Focus error signal generation circuit 65...Tracking error signal generation circuit 66... ...Defect detection circuit 67...Selection control circuit Fig. 11111 41 constant g'l possible --- (f) EAD Fig. 4B Fig. 7B Fig. 8

Claims (1)

[Claims] A recording medium having servo lines formed in the track direction is irradiated with a light beam, and a relative positional shift between the recording medium and the light beam is determined based on the light reflected from the servo line. In a servo circuit of an optical information recording and/or reproducing device that detects an error signal representing the error signal and performs servo control to correct the relative positional deviation based on the error signal, A plurality of detection systems detect servo signals based on reflected light at different positions, and a defective portion on the servo line is detected based on a servo signal that is not used for servo control among the detected servo signals. a defect detection means; and a selection means for selecting a detection system unaffected by the defective part from among the plurality of detection systems based on the output of the defect detection means, and based on the detection system selected by the selection means. A servo circuit for an optical information recording and/or reproducing device, characterized in that it performs servo control.