JPH01179227A - Position detector for objective lens - Google Patents

Abstract

PURPOSE:To surely perform servo pull-in by holding an objective lens at an original balance position at the time of performing the servo pull-in, etc., by providing a travel means to move the objective lens to a one-valued function characteristic area detectable for the position of a position detecting sensor. CONSTITUTION:A light emitting means LED18 and a bi-sected optical detector 19 are provided so as to sandwich a plate shape flag 16 extending from a lens barrel 15 in a direction of Y-axis intersecting orthogonally to an X-axis and a Z-axis. At the time of assembling the optical detector 19, the LED18, and the flag 16, initial adjustment is performed so that the output of the differential amplifier 21 of photodetectors A and B which form the bi-sected optical detector 19 can go to zero. Also, the flag 16 shields the light of the LED18, and is set so as to form the photodetectors A and B symmetrically with respect to the Y-axis. In such a way, it is possible to generate a one-value functional characteristic in which the differential output of the detector 19 becomes a linear characteristic for the displacement of the objective lens 14 in a direction of the X-axis, and to lock the objective lens 14 at a position where the differential output goes to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a position detection device for an objective lens, in which the position detection means includes means for self-aligning the objective lens to an equilibrium position.

[Prior Art] In recent years, instead of recording and reproducing information using a magnetic head, information has been recorded and reproduced at high density on an optical recording medium using a light beam sent to an optical pickup. The optical information of the recording and reproducing device was put into practical use11.

The above-mentioned optical information recording 'irf't: 1.1, focusing ↑J-bo means and tracking lever in the V position, focusing the light beam on the 3Y, optical recording medium. The objective lens that shines is held in focus to focus and illuminate QJ, and the target track can be tracked and closed.

In addition, in the above device, when randomly accessing any concentric or spiral track on which information is recorded or for recording, the tracking servo is removed and an optical pickup equipped with an objective lens is targeted. After moving it to the vicinity of the track, set the trunning navigation to the retracted state again. In this case, if the objective lens is largely deviated from the equilibrium position, retraction cannot be performed safely if the tracking servo system is turned on.

In order to eliminate the above-mentioned problems, for example,
Publication No. 2235f discloses a conventional example in which the position of an objective lens can be detected as shown in FIG. 9.

That is, the total reflection prism 3 is attached to the lens barrel 2 to which the objective lens 1 is attached. This total reflection prism 3 reflects the light beam of the light emitting element 4, and divides the light receiving area into two areas 5a,
The output of this photodetector 6 is input to a differential amplifier 7, and a position detection signal is obtained from this differential output. In this case, in the total reflection prism 3, when the objective lens 1 (or [12) is in an equilibrium position, the light beam hits the center of both light receiving areas 5a and 5b, the output of both light receiving areas becomes equal, and from this position When there is a shift in the tracking direction, the amount of light beam hitting both light receiving areas changes depending on the shift.

Therefore, the differential amplification in the above conventional example! i7 output V
R exhibits a characteristic as shown in Fig. 10, and the linear region in this figure, that is, the region between It becomes a locking area.

[Problems to be Solved by the Invention] In the conventional example described above, generally: Since the lens barrel 2 is held in place during focusing and tracking by an elastic member (not shown), if the elastic member becomes slack due to fatigue over time, etc. , the objective lens is held at a position deviated from the initially set equilibrium position. Therefore, at that shifted position, the output of the differential amplifier 7 causes the objective lens 1 to
Even if you try to lock it to the center of the optical axis, it will come off, or it will be set near a position where it is easy to come off. This J
In such a case, even if you try to perform tracking servo, it may not be possible to perform tracking servo because it is outside the l-racking servo retraction area, or if the small 15 We
Even if J etc. are present, problems such as not being able to pull in the servo will occur.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an objective lens position detection device that can reliably servo retract the objective lens during a servo retraction operation or the like.

[Means and effects for solving the problem] The present invention C is a device J3 that is provided with a position detection sensor for an objective lens movably held by an elastic member, and a position detection sensor for detecting the position of the objective lens is provided. By providing a moving means that moves within the possible single-value function characteristic region, when performing 1-nervo pull-in, etc., the objective lens is held at its original equilibrium position, so that servo pull-in can be performed reliably.

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

FIGS. 1 to 4 relate to a first embodiment of the present invention.
The figure is a block diagram of the first embodiment, Figure 2 is a perspective view showing the part where the flag is removed from the objective lens in the first embodiment, and Figure 3 is a perspective view of the part where the flag is removed from the objective lens in the first embodiment. A characteristic diagram showing differential output with respect to deviation, and FIG. 4 is a timing diagram for explaining the operation of each part of the first embodiment.

As shown in FIG. 2, a flag detector 11 forming the objective lens position detection device 10 of the first embodiment is arranged facing an optical disk 13 that is rotationally driven by a spindle motor (not shown). objective lens 14
A flag 16 is provided protruding from the lens barrel 15 to which the lens barrel 15 is attached, and the position of this flag 16 is detected.

The tube 15 to which the objective lens 14 is attached is elastically held in the housing (not shown) of the optical pickup by a leaf spring 17, 17 serving as an elastic member.

The leaf springs 17.17 are arranged parallel to the radial direction (or tracking direction) R of the optical disc 13, and the objective lens 14 is elastically held in the radial direction R (X-axis direction in the coordinate system shown in FIG. 1). has been done. The objective lens 14 is also held by an elastic member (not shown) in the optical direction (Z-axis direction) including the objective lens 14.

"-2 Y perpendicular to the X-axis direction and the Z-axis direction from the lens barrel 15
so as to sandwich the plate-shaped flag 16 extending in the axial direction.
An LED 18 serving as a light emitting means and a two-part photodetector 19 are provided (fixed to the housing of the optical pickup, etc.).

The objective lens 14 can be moved in the X-axis direction and the zllth direction by a tracking actuator and a forcing actuator (not shown), respectively.

The above two-divided photodetector 19 and LED 18, and the flag 1
When assembling the optical pickup, install with 2.
The differential output through the differential amplifier 21 of the light receiving elements Δ and B forming the divided photodetector 18 is initially adjusted so that Vs=VA−VBh(O.Furthermore, the flags 16 and f
The light of E D 16 is blocked from being received by the light receiving elements A and B, and the blocking in this case is set to be symmetrical with respect to the Y axis (with respect to the positive and negative Bouff directions of the X axis).

Therefore, the differential output characteristics of the two-split photodetector 19 C1 are as follows:
As shown in FIG. 3, the displacement of the objective lens 14 in the X direction increases monotonically from negative to positive between x1 and x2.
It exhibits linear, monovalent functional characteristics, and outside A, the output voltage decreases or becomes saturated. Therefore, 2
Due to the output of one divided photodetector, differential output 5=VA-
Apply 1 Nervo so that Vll becomes 0, and set objective lens 1.
The range in which the retraction lock can be stably achieved in 4 is a linear characteristic region where the differential output VS is between x1 and x2.

(It doesn't have to be a linear 'C'; it can be a numeric value.) By the way, the objective lens 14 may shift in the X direction from the initially adjusted equilibrium position due to aging of the elastic member, etc. However, in the first embodiment, the configuration as shown in FIG. 1 is adopted so that the objective lens 14 can be locked at the position where the differential output VS becomes O.

The output of the differential amplifier 21 is phase-compensated by the phase compensation circuit 23 and then passed through the ablog switch SW1 (inputted to the drive amplifier 24. The output of the drive amplifier 24 is input to the radial actuator coil 25 applied.

The above analog switch SW1 has an L″ at the switch control end.
It is turned on by applying the signal.

At this control end, the output of the matching circuit 26 is connected to an inverter 27.
applied via. Further, the output of this coincidence circuit 26 is output from the analog switch SW2 and the flag narch generation circuit 2.
The sample and hold circuit 29 to which the output of 8 is input performs sampling and hold control.

The output of the coincidence circuit 26 is applied to the switch control end of the analog switch SW2 and also to the switch control end of the analog switch f-SW1 via the inverter 27, so that the output of the matching circuit 26 is applied to the switch control end of the analog switch f-SW1. 1j
When /l<ON, the other is held OFF.

An analog switch SW3 is provided in parallel with the blogging switch SW2, and is turned on by a signal CCOU R8E for random access.

Note that "I-X" in the signal does not indicate that "I-"r is active.

Tokorogu, the drive amplifier 24 is a differential amplifier 2/
The J1 inverting input terminal of this amplifier 2/Ia is grounded via a resistor R1, and is also connected to an analog switch SWI. U is connected to the output end via a resistor R2, and is also connected to one terminal of the analog switches SW2 and SW3 via a resistor R3.

The output of the matching circuit 26 is further connected to an analog switch.
It is applied to the switch control end of SW4. The differential output VS that has passed through the ablog switch SW4 is applied to one input terminal of the matching circuit 2 (3) through the Δ/D-1 inverter 31, where a signal of ε is applied and a signal of 0 is applied to the other input terminal. is input.

Thus, the coincidence circuit 26 outputs a signal of "LII" when the digital signals applied to both input terminals do not match, and outputs a signal of 1 when they match.

Therefore, the output of the coincidence circuit 26 is initially "yes", and the analog switch SW2 is turned on to output the output signal of the flag leave generation circuit 28 to the drive amplifier 24 side via the hot number hold circuit 29.

Note that this ripple hold circuit 29 has a control terminal "'
L ”-(' indicates rimbling mode, II
Hold when it reaches 11. Therefore, if the output of the above-mentioned matching circuit 26 is L'', the analog switch S
WI is held off, and analog switch S~■4
is held on, and the difference 9J+output VS is Δ/l)] It is converted into a digital signal via the inverter 31 and input to the digital -/matching circuit 26.

Here, the flag search generation circuit 28 is configured, for example, as a triangular wave generator, and as shown in FIG. 4(a),
A triangular waveform (No. 5 Vd is output) from negative to positive and from 1 to negative.

Therefore, the output signal ■d of the flag search generation circuit 28
is the (radial) Aquayu 1 via the drive amplifier 24.
- the root spring 17. by being applied to the coil 25;
At 17, the objective lens 14, which is elastically held in the X direction, is moved in the X direction against the elastic force of the objective lens 14, and along with this movement, the flag 16 is also moved.

For example, even if the holding position of the objective lens 14 moves due to aging of the elastic part and is in the state shown in FIG. 4(b),
According to the output signal Vd of the flag search generation circuit 28,
The objective lens 14 is moved and passes through the initial adjustment position of the objective lens 14, that is, the position where the differential output Vs becomes O. When this differential output reaches the position where Vs=O, the matching circuit 26 detects this and as shown in FIG. .

When the output of the coincidence circuit 26 becomes l-1'', the 7 analog switch SW2 is turned off. ゛) Therefore, the flag reach output signal Vd is no longer input to the drive amplifier 24, and the sample hold circuit 29 is turned off. It becomes a bold state and holds the triangular wave level VO which makes Vs = 0.

Furthermore, since the analog switch SW4 is also turned off, the match circuit 26 maintains the 'H' state.Furthermore, due to the output of the match circuit 26, the analog switch SW2h<' Phase compensation circuit 23 for A
The differential output Vs that has passed through is inputted to the drive amplifier 24 and applied to the actuator coil 25.

In this state, the differential output VS is O(.), so the objective lens 14 is kept in the state where the differential output Vs is O.

As described above, according to the first embodiment, even if the holding position of the objective lens 14 deviates from the Honto equilibrium position due to aging of the elastic member and reaches a range that deviates from the flag servo retraction range, the flag reach When the movement of ``J'' is due to heavy pressure, the equilibrium position can be moved to a state where it passes through, and the flag 4 novo is performed at the timing when the differential output of the photodetector 19 becomes O when passing through the equilibrium position. The objective lens 14 can be reliably locked in the equilibrium position. Therefore, for example, when performing random access, first, the level Vo held by the two sample and hold circuits is applied to the actuator coil 25 by the signal *course to the coarse movement H, 7 of moving the optical pickup, and the equilibrium position is reached. To, Rock C Saru. Thereafter, this actuator 25 is connected to a tracking servo system to establish a tracking servo system, thereby allowing tracking to a track near the target 1-rack. Therefore, the target track can be randomly accessed by the close movement after step A.

In this way, according to the first embodiment, tracking can be reliably skipped when the tracking servo system is closed, such as during random access. Therefore, 11 random accesses etc. can be reliably performed in a short period of time.

FIG. 5 shows the configuration of a second embodiment of the present invention.

1-The first embodiment includes an analog output Vs [1 analog switch SW4, Δ/[)] inverter 31 and matching circuit 26.
In contrast, in this embodiment, as shown in FIG. 7, a linear area VAD capable of retracting the flag servo is used.
The flag servo is carried out inside. Therefore, in this case, the window comparator 41 and the flip 70 knob 4 to which the output of the window comparator 41 is input are connected.
2 are provided, and this output is used as an analog switch SW1. SW
2 is controlled to turn on and off.

The f window comparator 41 includes two comparators 43a and 43b, both of these comparators 43a,
It is composed of an AND circuit 44 to which the output signal of 43b is input.

As shown in FIG. 6, the non-inverting input terminal of the comparator 43a is applied with an appropriate voltage Vc on the positive side within the linear region in which the differential output Vs exhibits linear characteristics, while the inverting input terminal of the comparator 43b is A negative voltage -VC is applied, and the dynamic outputs Vs applied to the inverting and non-inverting input terminals of these comparators 438 and 43b are compared.

By passing these two comparators 43a,=13bG, and the two-man-operated AND circuit 44, the differential output ■S is -
It becomes 1-bi only when Vc<Vs<Vc, and becomes "L" otherwise. Therefore, the flip-flop 42 to which the output of the window comparator 41 is inputted, when the output of the comparator 1 rises from L'' to 11H11, the flip-flop 42 at the f-all input end is
'' data is output from output end Q. In other words, output end Q
, Φ is ゛1-bi゛ from °"1" and °1" when the output of comparator 1 rises from "L" to "H11".
Transfers to 11″.

The above output terminals Q and Q are "HLIT, nL-do"
The operation in the case of no is the same as that of the first embodiment.

This embodiment operates in the same way as the first embodiment when the differential output Vs becomes 01 or 1 outside the linear region as shown in FIG. In particular, according to 4. Note that even if the differential output VS is not saturated, +Vc,
The same application can be made by reducing the absolute value of -Vc.

FIG. 7 shows a third embodiment of the invention.

In the first embodiment described above, the output voltage of the flag search generation circuit 28 is held by two sample and hold circuits at the voltage ∆O when the differential output Vs becomes 0, but in this embodiment, instead of △ A feature is that a /D converter 51 and a D/A converter 52 are provided.

A clock signal [1] is applied to both the converters 51 and 52 from the clock generator, and the A/V converter is synchronized with this clock.
Perform D conversion and D/△ conversion. Also, the D/Δ converter 52
The analog switch %S'I is connected to the D/△conversion control terminal of
V2 control end and its) A-cass (J-ion signal *F
This allows S RON to be applied.

When this signal *FSRON reaches 11 LIT, the D/A converter 52 synchronizes with the clock and converts the D/A
A conversion is performed, and when it reaches 11 HII, the D/Δ conversion output is latched.

In this embodiment, the analog switch SW1 is controlled by the flag-on signal = CF L G ON, and when this signal *FIGON becomes L'°, the analog switch SW1
turns on.

When the focus search on signal * F S RON becomes passive, the flag ('') signal generator circuit 28 outputs a triangular wave signal vd as shown in FIG. It is applied to the Akubuko ball-tacoil 25 via the amplifier 24, and moves the RJ object lens held elastically.

Since the flag is moved along with this, the differential output VS changes. Therefore, even if the objective lens is at a position deviated from its original position due to changes in the member's perspiration, etc., this triangular wave signal V i4 causes
- It passes through the I device where the dynamic output VS becomes O. 8th
As shown in FIG. 3(b), at a timing to when this X dynamic output Vs becomes O, the detection means for the differential output S (the matching circuit 2G in the first embodiment) detects the flag (Narch A). ：I：r S RON inactive,
In other words, as shown in (C) of the same figure, the flag A signal: l: is turned on as shown in (d) of the same figure.
Set F L G ON to °“L II. The above flag surge signal: k When F RS ON becomes H II, D/
The Δ converter 52 wraps the D/A converted signal.

Furthermore, when the flag-on signal FLGON becomes "L", the differential output VS is applied to the actuator 25 via the drive amplifier 24, thereby locking the objective lens at its original equilibrium position.

The operation of this second embodiment is similar to that of the first embodiment.

In each of the above embodiments, the objective lens 14 (
Although the flag 16 is provided on the vA tube 15), it can also be applied to the conventional example shown in FIG. If the differential amplifier 7 in FIG. 9 is regarded as the differential amplifier 21, the present invention can be applied in exactly the same way.

Note that although the above description has been made regarding the radial direction, a similar means may be provided in the focusing direction also when performing focus focusing.

[Effects of the Invention] As described above, according to the present invention, the objective lens is locked at the equilibrium position by the output of the lens position detection lever (
・Since the moving means for moving the objective lens within the linear region where the object lens can be moved is locked in the equilibrium position within this linear region, the elastic f1 member that holds the objective lens becomes a deformed tube. Even if you do so, you can reliably reach the equilibrium position.

[Brief explanation of the drawing]

FIGS. 1 to 4 relate to the first embodiment of the present invention.
Fig. 2 is a block diagram of the first embodiment, Fig. 2 is a perspective view showing the part where the objective lens in the first embodiment has a flag (=J < J, and Fig. 3 is an optical A characteristic diagram showing the differential output with respect to the deviation from the equilibrium position of the detector, FIG.
FIG. 5 is a configuration diagram showing the second embodiment of the present invention, FIG. 6 is a characteristic diagram showing the differential output of the photodetector in J3 in the second embodiment,
FIG. 7 is a configuration diagram of the third embodiment of the present invention, FIG. 8 is a timing diagram for explaining the operation of each part in the third embodiment, and FIG. 9 shows the configuration of a conventional example. Explanatory diagram,
FIG. 10 is a characteristic diagram showing the differential output of the photodetector with respect to deviation from the equilibrium position in the conventional example. 10...Objective lens position detection device 11...Flag acticoator 13...Optical disk 14...Objective lens 15
... Lens barrel 16 ... Flag 17 ... Leaf spring 18 ... One LED ... Photodetector
21...Differential amplifier 24...Drive amplifier 25...Radial actuator coil 26...-
Several circuits 28...Flag search generation circuit 29...Sample and hold circuits SWI, SW2. SW3. SW4...Analog switch tree Course Figure 3 Figure 4 d Figure 5 Course Figure 7 Book FSRON Figure 6 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1. The position of an objective lens, which has an elastic member that movably holds the objective lens with respect to the optical pickup, and a plurality of detection elements that detect the position of the objective lens with respect to the optical pickup. The detection device includes an objective lens drive unit that moves the objective lens to a position in a region where the output of the detection element has a substantially linear relationship with the position of the objective lens. Lens position detection device. 2. The objective lens driving unit drives the objective lens to a position where the optical axis of the objective lens and the optical axis of the optical pickup coincide with each other. Objective lens position detection device. 3. Claim 2, further comprising a storage means for storing a drive signal when the objective lens is driven to a position where the optical axis of the objective lens and the optical axis of the optical pickup coincide. The objective lens position detection device described in .