CN100513994C - Method for measuring displacement gain value between light storage device and driving voltage and apparatus therefor - Google Patents

Abstract

This invention relates to a method for measuring shift gain values of a light storage device. The device includes a fetch head containing an object glass, first and second light sources on it, said object glass can focus the first light source on the first focal point and the second on the second focal point with a first distance from the first focal point, a drive voltage can alter positions of said object glass including: a, changing said drive voltage to alter position of said object glass, b, registering a first factor when said first focal point passes through a preset layer in the disc, c, registering a second factor when the second passes through said preset layer and d, computing a shift gain value with them.

Description

The method and the device of relativeness between decision object lens position difference and driving voltage

Technical field

The present invention relates to a kind of light storage device, particularly a kind of in order to the alternate position spike of decision object lens and the method and the relevant apparatus of the relativeness between driving voltage in light storage device.

Background technology

Light storage device (optical storage device) is common a kind of medium in the computer system now.See also Fig. 1, Fig. 1 is the simple block diagram of prior art one light storage device 100.Include an axle center motor (spindle motor) 110, one CD 120, a read head (pickup) 130, a signal processing unit (signal processing unit) 140, one focus controller (focusing controller) 150, one micro-control unit (microcontrollerunit, MCU) 160 and one analog line driver (power driver) 170 in the light storage device 100.CD 120 can be the CD of CD or DVD kind; it can include two-layer at least: a superficial layer and a reflection horizon; for instance; this superficial layer be CD 120 near the superficial layer of read heads 130, this reflection is to connect surface layer (junction layer) between protection material (protective material) and metal surface (in order to recorded information groove (informationpits)).Have one or more different light sources (a CD light source and a DVD light source are arranged usually, be not shown on the figure) on the read head 130; One object lens (object lens is not shown on the figure) are used for a light-resource fousing wherein reading the data that are stored on the CD 120 with the light signal by reflection on CD 120; An and focus actuator (not being shown on the figure), be used for a driving voltage according to analog line driver 170 output (in the middle of this example, this driving voltage is a driving voltage (driving voltage)) move up and down (directions) these object lens in vertical CD 120 surfaces, and control the position of this light-resource fousing point.

Carrying out skip floor, or during the work of optical disc recognition, generally speaking all need input to the size of the driving voltage of this focus actuator by change, to change the position of these object lens, to control the position of this light-resource fousing point accurately.And the distance that moves up and down of these object lens can be represented with a displacement yield value with respect to the difference of this driving voltage haply, and unit of this displacement yield value then be apart from divided by voltage.

With optical disc recognition work is example, prior art system can be used a kind of light source, move to the required time of a reflection horizon (reflective layer) variable quantity of this driving voltage (or measure) by the focus point of measuring this light source from the superficial layer (surface layer) of CD 120, use this displacement yield value to calculate distance between this superficial layer and this reflection horizon, the CD type that then the is identified as CD that the be identified as DVD type CD that distance is short, distance are long.(certainly, real recognition methods meeting is more than above-mentioned complexity)

And the prior art system yield value that will be shifted is considered as a fixing constant, and the reference data of using this fixing displacement yield value to carry out skip floor, this class work of optical disc recognition.But because in the process of producing light storage device, can't make produced each light storage device all have identical displacement yield value (partly cause is because the fine difference of focus actuator), have at each light storage device under the situation of different displacement yield values, using fixing displacement yield value is the unadvisable practice as the reference data of each light storage device of control, focus actuator for the control action of object lens position also can thereby become not accurate.This is not that the deviser of a light storage device system finds pleasure in the situation of seeing.

Summary of the invention

Therefore fundamental purpose of the present invention is to provide a kind of in order to the alternate position spike of decision object lens and the method and the relevant apparatus of the relativeness between driving voltage in light storage device.

According to an aspect of the present invention, be to disclose a kind of displacement gain value method for measurement that is used in the light memory device, this light memory device includes a read head, include object lens on this read head, one first light source and a secondary light source, these object lens can be with this first light-resource fousing in one first focus point, maybe this secondary light source is focused on one second focus point, and the position of this first focus point and this second focus point is at a distance of one first distance, one driving voltage can change the position of these object lens, this method is to be used for measuring the displacement gain value of the displacement of these object lens with respect to this driving voltage, and this method includes: (a) change this driving voltage to change the position of these object lens; (b) when this first focus point during, write down one first parameter by default layer of one in the CD; (c) when this second focus point is preset layer by being somebody's turn to do in this CD, write down one second parameter; And (d) use this first distance, this first parameter, and this second calculation of parameter goes out this displacement gain value.

According to a further aspect in the invention, be to disclose a kind of displacement gain value method for measurement that is used in the light memory device, this light memory device includes a read head, include object lens and one first light source on this read head, these object lens can be with this first light-resource fousing in one first focus point, one driving voltage can change the position of these object lens, this method is to be used for measuring the displacement gain value of the displacement of these object lens with respect to this driving voltage, and this method includes: (a) change this driving voltage to change the position of these object lens; (b) when one first signal arrives one first state, note one first parameter of this moment; (c) when this first signal arrives one second state, note one second parameter of this moment; And (d) use a predeterminable range, this first parameter and this second calculation of parameter go out this displacement gain value.

In accordance with a further aspect of the present invention, be to disclose a kind of light memory device that measures displacement gain value, this light memory device includes: a read head includes on this read head: object lens and are used for determining the focus actuator of the position of these object lens according to a driving voltage; One signal processing unit is coupled in this read head; One focus controller is coupled in this signal processing unit; One analog line driver is coupled in this focus controller and this focus actuator, is used for producing this driving voltage; And a gain calculating unit, being coupled in this signal processing unit and this focus controller, the displacement that is used for calculating these object lens is with respect to a displacement gain value of this driving voltage.

An advantage of the present invention is, can accurately determine the alternate position spike of object lens and the relativeness between the driving voltage.Use the relativeness that is determined, can further proofread and correct, so total system can be more more accurate than prior art in control light storage device.

Description of drawings

Fig. 1 is the simple block diagram of prior art one light storage device 100.

Fig. 2 is the be shifted first embodiment process flow diagram of yield value measuring method of the present invention.

Fig. 3 is when using method shown in Figure 2, and driving voltage and focus error signal change the sketch of situation.

Fig. 4 is the be shifted second embodiment process flow diagram of yield value measuring method of the present invention.

Fig. 5 is when using method shown in Figure 4, and driving voltage and focus error signal change the sketch of situation.

Fig. 6 can measure the embodiment synoptic diagram of the light storage device of displacement yield value for the present invention.

The reference numeral explanation

100,600 light storage devices

110,610 axle center motors

120,620 CDs

130,630 read heads

140,640 signal processing units

150,650 focus controllers

160,660 micro-control units

170,670 analog line drivers

665 decision unit

680 amplifying units

Embodiment

At first introduce method proposed by the invention.Method of the present invention mainly is to use a specific distance as standard, to calculate a displacement yield value (that is the relativeness between the alternate position spike of object lens and the driving voltage).In first embodiment proposed by the invention, this light storage device includes a read head.Include a CD light source (it is one first light source of this light storage device) on this read head, a DVD light source (it is a secondary light source of this light storage device), and object lens.These object lens can with this CD light-resource fousing in one first focus point, maybe with this DVD light-resource fousing in one first focus point.One driving voltage then can move these object lens, to determine the position of these object lens.In the middle of example of the present invention, be to use a driving voltage to be used as this driving voltage, yet, can also in the present invention, use the driving voltage (for example drive current) of other kind to control the position of these object lens.

Because the progress of optical technology, when making these object lens, can make these object lens that the focal length (focal length) that this CD light source or this DVD light source are produced is all had high degree of accuracy (promptly this first focus point or this second focus point are to the distance of these object lens).And also therefore can be so that the distance between first focus point and second focus point, i.e. one first distance W D_delta, be a fixing value (being worth accurately and can derive this first distance W D_delta according to the characteristic of read head) haply, this first distance W D_delta i.e. the employed specific range of first embodiment (or be called " predeterminable range ") for this reason.

See also Fig. 2, Fig. 2 is the be shifted first embodiment process flow diagram of yield value measuring method of the present invention.Below will introduce each step among Fig. 2 in detail.

Step 200: open this CD light source, change this driving voltage so that these object lens are moved down on earth.

Step 210: continue to change this driving voltage, so that these object lens continue to move up.

Step 220: measure the characteristic of a focus error signal (FE signal), whether pass through a ground floor of a CD to judge this first focus point.Measure one first magnitude of voltage V1 of this driving voltage when this first focus point passes through the ground floor of this CD.Be to judge herein, and can also use the signal of a radio frequency level signal (RFL signal) or other kind as the benchmark of judging during actual enforcement with " whether in this focus error signal, sensing the change curve (being S-curve) of S type ".In addition, this ground floor can be a superficial layer or a reflection horizon herein.

Step 230: close this CD light source, open this DVD light source then, measure the characteristic of this focus error signal, whether pass through the ground floor of this CD to judge this second focus point.Measure one second magnitude of voltage of this driving voltage when this second focus point passes through the ground floor of this CD.

Step 240: use this first magnitude of voltage V1, this second magnitude of voltage V2 and this first distance W D_delta, calculate the displacement yield value D_gain of the displacement of these object lens with respect to this driving voltage.

Clearly, because the position of this ground floor remains unchanged, so between the step 230, the distance that these object lens moved will be this first distance W D_delta in step 220, therefore use the first distance W D_delta can calculate displacement yield value D_gain as standard.See also Fig. 3, Fig. 3 then is that this driving voltage and this focus error signal change the sketch of situation when using method shown in Figure 2.

When this ground floor was a superficial layer of this CD, this displacement yield value can be expressed as: $D\_\mathrm{gain}=\frac{\mathrm{WD}\_\mathrm{delta}}{|V2-\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">V</figure-callout>}1|};$ When being a reflection horizon of this CD when this ground floor, because the influence that refractive index n caused in the CD, this displacement yield value then can be represented as: $D\_\mathrm{gain}=\frac{\mathrm{WD}\_\mathrm{delta}}{|V2-\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">V</figure-callout>}1|\&CenterDot;n}.$

Note that above-mentioned second formula situation that to be hypothesis CD or DVD light beam all equate the CD refractive index of CD or DVD derives (can suppose n=1.55 usually), for the convenience on illustrating, below mentioned refractive index all herewith suppose.As for working as refractive index not simultaneously, second above-mentioned formula then is false, but prior art person still can derive a comparatively complicated formula from the focal length and the operating distance (workingdistance) of each light source, perhaps count this multiplier via great deal of experiment data, therefore method proposed by the invention still can be suitable for.

In addition, in step 220 and 230, can also measure the very first time T1 when this first focus point passes through the ground floor of this CD respectively, and second time T 2 when this second focus point passes through the ground floor of this CD.Again according in the step 210, this driving voltage is with respect to counter this driving voltage variable quantity of releasing of the variable quantity of time, if driving voltage is first a fixing slope C with respect to the rate of change of time, then calculate can be suitable easily.To be that the situation of fixed value explains below at the first slope C.

When this ground floor was a superficial layer of this CD, this displacement yield value can be expressed as: $D\_\mathrm{gain}=\frac{\mathrm{WD}\_\mathrm{delta}}{|T2-\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">T</figure-callout>}1|\&CenterDot;C};$ As for when being a reflection horizon of this CD when this ground floor, because the influence that refractive index n caused in the CD, this displacement yield value then can be represented as: $D\_\mathrm{gain}=\frac{\mathrm{WD}\_\mathrm{delta}}{|T2-\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">T</figure-callout>}1|\&CenterDot;C\&CenterDot;n}.$

Next then will introduce second embodiment of the inventive method.Be different from first embodiment of the invention, need be used in the light storage device that has two kinds of light sources at least, second embodiment of the invention can also be used in the light storage device with single kind of light source.In second embodiment proposed by the invention, this light storage device includes a read head.Include one first light source (can be a CD light source or a DVD light source) and these object lens on this read head.These object lens can be with this first light-resource fousing in one first focus point.One driving voltage (in following example, this driving voltage is a driving voltage, yet this does not limit claim of the present invention) can move these object lens, to determine the position of these object lens.

And in this one second embodiment, when employed specific range (also can be described as " predeterminable range ") then is this first focus point by a ground floor of a CD (this ground floor can be a superficial layer or a reflection horizon), this focus error signal produces the size of the linear zone in the S type curve (be above-mentioned S-curve).

See also Fig. 4, Fig. 4 is the be shifted second embodiment process flow diagram of yield value measuring method of the present invention.Below will introduce each step among Fig. 4 in detail.

Step 400: open this first light source, change this driving voltage so that these object lens are moved down on earth.

Step 410: continue to change this driving voltage, so that these object lens continue to move up.

Step 420: the characteristic of measuring a focus error signal.Measure after this focus error signal passes through a predetermined threshold value threshold, and when arriving a maximum value MAX, one first magnitude of voltage V1 of this driving voltage.The signal that can also use radio frequency level signal or other kind herein on the implementation is as the benchmark of judging; Predetermined threshold value threshold is used for guaranteeing can not causing erroneous judgement because of the noise in this focus error signal.

Step 430: the characteristic of this focus error signal of test constantly.Measure when this focus error signal arrives a minimal value MIN one second magnitude of voltage V2 of this driving voltage.And this focus error signal is so-called linear zone from maximum value MAX to the varied sections the minimal value MIN.

Step 440: use this first magnitude of voltage V1, this second magnitude of voltage V2 and a predeterminable range Def_delta, calculate the displacement yield value D_gain of the displacement of these object lens with respect to this driving voltage.

See also Fig. 5, Fig. 5 then when using method shown in Figure 4, the variation situation of this driving voltage and this focus error signal.

Method shown in Figure 4, can also be modified as the interlude that uses in the linear zone (promptly from maximum value MAX*A to the interval the minimal value MIN*B, wherein A and B are absolute value less than 1 numerical value), or from MAX-C to the interval the MIN+D, or the section of whole S type curve, this is the design alternative of system designer, but uses linear zone to have preferable degree of accuracy.Then can from experimentation, measure easily as for predeterminable range Def_delta.

When this ground floor was a superficial layer of this CD, this displacement yield value can be expressed as: $D\_\mathrm{gain}=\frac{\mathrm{Def}\_\mathrm{delta}}{|V2-\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">V</figure-callout>}1|};$ When being a reflection horizon of this CD when this ground floor, because the influence that refractive index n caused in the CD, this displacement yield value then can be represented as: $D\_\mathrm{gain}=\frac{\mathrm{Def}\_\mathrm{delta}}{|V2-\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">V</figure-callout>}1|\&CenterDot;n}.$

In addition, in step 420 and 430, can also measure the very first time T1 when this focus error signal arrives this maximum value MAX respectively, and one second time T 2 when this focus error signal arrives this minimal value MIN.Again according in the step 410, this driving voltage is with respect to counter this driving voltage variable quantity of releasing of the variable quantity of time, if driving voltage is first a fixing slope C with respect to the rate of change of time, then calculate can be suitable easily.To be that the situation of fixed value explains below at the first slope C.

When this ground floor was a superficial layer of this CD, this displacement yield value can be expressed as: $D\_\mathrm{gain}=\frac{\mathrm{Def}\_\mathrm{delta}}{|T2-\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">T</figure-callout>}1|\&CenterDot;C};$ As for when being a reflection horizon of this CD when this ground floor, because the influence that refractive index n caused in the CD, this displacement yield value then can be represented as: $D\_\mathrm{gain}=\frac{\mathrm{Def}\_\mathrm{delta}}{|T2-\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C200310120478E00151.png"\; state="\{\{state\}\}">T</figure-callout>}1|\&CenterDot;C\&CenterDot;n}.$

The method of using the present invention to propose, calculate after the displacement yield value, just can carry out the action that transfer in the school to light storage device, carrying out optical disc recognition no matter be, or during the work of skip floor, can significantly increase the degree of accuracy (this mode also can make object lens into and move up earlier on earth, moves down again, and alternate manner is then with aforementioned listed identical) of system.In addition, the displacement yield value that calculates can also be used for the controller in the light storage device (controller) is carried out the correction work (especially proofreading and correct the frequency response of low frequency part) of frequency response.

To introduce system architecture proposed by the invention with next.See also Fig. 6, Fig. 6 can measure the embodiment synoptic diagram of the light storage device of displacement yield value for the present invention.Light storage device 600 includes: an axle center motor 610; One CD 620; One read head 630 includes object lens and a focus actuator (all not being presented on the figure), and this focus driver is to be used for determining the position (in the present embodiment, this driving voltage is a driving voltage) of these object lens according to a driving voltage; One signal processing unit 640 is coupled in read head 630; One focus controller 650 is coupled in signal processing unit 640; One amplifying unit 680 is coupled in focus controller 650; One analog line driver 670 is coupled between amplifying unit 680 and this focus actuator, is used for producing this driving voltage; And a micro-control unit 660, be coupled in signal processing unit 640 and this focus controller 650, include a decision unit 665, with the alternate position spike that decides these object lens and the relativeness between this driving voltage (that is one be shifted yield value).The main difference of system architecture proposed by the invention and prior art is: the decision unit 665 that has the yield value that can determine to be shifted in the micro-control unit 660 in the light storage device 600, decision unit 665 can control system use method proposed by the invention to determine a displacement yield value, in addition, the work that can also proofread and correct light storage device 600 according to the displacement yield value that is determined.

If do not consider the existence of amplifying unit 680, then determine unit 665 after determining this displacement yield value, can be to carry out the work that transfer in the school by any unit in read head 630, signal processing unit 640, focus controller 650 and the analog line driver 670 formed loops.The employed mode of present embodiment then is to have added amplifying unit 680 between focus controller 650 and analog line driver 670, decision unit 665 can directly carry out the school to amplifying unit 680 after determining this displacement yield value transfers, and this structure on the implementation can be more or less freely.In addition, decision unit 665 in the present embodiment is arranged among the micro-control unit 660, and system designer can also be independent from micro-control unit 660 with decision unit 665 when this light storage device of design, and becoming the block of independently working, this is the another kind of feasible practice on the implementation.

In prior art, the value that this displacement yield value is considered as fixing and the overall optical memory storage is controlled, displacement yield value measuring method proposed by the invention can be at single light storage device, measure and belong to this light storage device yield value that is shifted accurately, more can further use such displacement yield value that this light storage device is proofreaied and correct, so that relevant control action becomes more accurate.In addition, the system architecture of measuring the light storage device of displacement yield value proposed by the invention, have a decision unit in then in a micro-control unit, this decision unit can use method proposed by the invention to determine this displacement yield value, and the work that can use this displacement yield value that system is proofreaied and correct, therefore in relevant control action also can compared with the prior art system structure more precisely.

The above only is preferred embodiment of the present invention, and all equalizations of being done according to the present patent application claim change and modify, and all should belong to the covering scope of patent of the present invention.

Claims (21)

1. displacement gain value method for measurement that is used in the light memory device, this light memory device includes a read head, include object lens on this read head, one first light source and a secondary light source, these object lens can be with this first light-resource fousing in one first focus point, maybe this secondary light source is focused on one second focus point, and the position of this first focus point and this second focus point is at a distance of one first distance, one driving voltage can change the position of these object lens, this method is to be used for measuring the displacement gain value of the displacement of these object lens with respect to this driving voltage, and this method includes:

(a) change this driving voltage to change the position of these object lens;

(b) when this first focus point during, write down one first parameter by default layer of one in the CD;

(c) when this second focus point is preset layer by being somebody's turn to do in this CD, write down one second parameter;

And

(d) use this first distance, this first parameter, and this second calculation of parameter goes out this displacement gain value.

2. the method for claim 1, wherein, this first parameter be for this first focus point by in this CD should default layer time this driving voltage one first magnitude of voltage, this second parameter be for this second focus point by in this CD should default layer time this driving voltage one second magnitude of voltage.

3. method as claimed in claim 2, wherein, this default layer is the superficial layer for this CD, the calculating formula of using in step (d) is for: this displacement gain value=this is first apart from/one voltage difference; This voltage difference is the difference mutually that equals this second magnitude of voltage and this first magnitude of voltage.

4. method as claimed in claim 2, wherein, this default layer is the reflection horizon for this CD, the calculating formula of in step (d) in, using be for: this displacement gain value=this first apart from/(a voltage difference * one first refractive index); This voltage difference is the difference mutually that equals this second magnitude of voltage and this first magnitude of voltage.

The method of claim 1, wherein this first parameter be for this first focus point by in this CD should default layer time a very first time, this second parameter be for this second focus point by in this CD should default layer time one second time; This driving voltage is to be one first slope with respect to the rate of change of time in step (a).

6. method as claimed in claim 5, wherein, this default layer is the superficial layer for this CD, the calculating formula of in step (d) in, using be for: this displacement gain value=this first apart from/(this first slope of a mistiming *); This mistiming is the difference mutually that equals this second time and this very first time.

7. method as claimed in claim 6, wherein, this default layer is the reflection horizon for this CD, and the calculating formula of using in step (d) is: this displacement gain value=this first distance/(this first slope of mistiming * * one first refractive index); This mistiming is the difference mutually that equals this second time and this very first time.

8. displacement gain value method for measurement that is used in the light memory device, this light memory device includes a read head, include object lens and one first light source on this read head, these object lens can be with this first light-resource fousing in one first focus point, one driving voltage can change the position of these object lens, this method is to be used for measuring the displacement gain value of the displacement of these object lens with respect to this driving voltage, and this method includes:

(a) change this driving voltage to change the position of these object lens;

(b) when one first signal arrives one first state, note one first parameter of this moment;

(c) when this first signal arrives one second state, note one second parameter of this moment; And

(d) use a predeterminable range, this first parameter and this second calculation of parameter go out this displacement gain value.

9. method as claimed in claim 8, wherein, in step (b), this first signal is meant this first signal by after the predetermined threshold value when arriving this first state, and when arriving one first particular value; In step (c), this first signal is meant this first signal by behind this first particular value when arriving this second state, and when arriving one second particular value.

10. method as claimed in claim 9, wherein, this first particular value is the maximum value for this first signal; This second particular value is the minimal value for this first signal.

11. method as claimed in claim 9, wherein, this first particular value is that the maximum value for this first signal is multiplied by one first multiplying power; This second particular value is that the minimal value for this first signal is multiplied by one second multiplying power.

12. method as claimed in claim 9, wherein, this first parameter is when arriving this first state for this first signal, one first magnitude of voltage of this driving voltage; This second parameter is when arriving this second state for this first signal, one second magnitude of voltage of this driving voltage.

13. method as claimed in claim 12, wherein, between step (b), (c), this first focus point is the superficial layer by a CD; The calculating formula used in step (d) is to be this displacement gain value=this a predeterminable range/voltage difference; This voltage difference equals the difference mutually of this second magnitude of voltage and this first magnitude of voltage.

14. method as claimed in claim 12, wherein.Between step (b), (c), this first focus point is the reflection horizon by a CD; The calculating formula of using in step (d) is: this displacement gain value=this predeterminable range/(a voltage difference * one first refractive index); This voltage difference equals the difference mutually of this second magnitude of voltage and this first magnitude of voltage.

15. method as claimed in claim 9, wherein, this first parameter is the very first time when arriving this first state for this first signal; This second parameter is one second time when arriving this second state for this first signal; This driving voltage is to be one first slope with respect to the rate of change of time in step (a).

16. method as claimed in claim 15, wherein, between step (b), (c), this first focus point is the superficial layer by a CD; The calculating formula of using in step (d) is: this displacement gain value=this predeterminable range/(this first slope of a mistiming *); This mistiming equals the difference mutually of this second time and this very first time.

17. method as claimed in claim 15, wherein, between step (b), (c), this first focus point is the superficial layer by a CD, and the calculating formula of using in step (d) is: this displacement gain value=this predeterminable range/(this first slope of mistiming * * one first refractive index); This mistiming equals the difference mutually of this second time and this very first time.

18. the light memory device that can measure displacement gain value, this light memory device includes:

One read head includes on this read head:

One object lens; And

One focus actuator is used for determining the position of these object lens according to a driving voltage;

One signal processing unit is coupled in this read head;

One focus controller is coupled in this signal processing unit;

One analog line driver is coupled in this focus controller and this focus actuator, is used for producing this driving voltage; And

One gain calculating unit is coupled in this signal processing unit and this focus controller, and the displacement that is used for calculating these object lens is with respect to a displacement gain value of this driving voltage.

19. light memory device as claimed in claim 18, wherein, this gain calculating unit can be according to the displacement gain value that calculates, the work that this light memory device is proofreaied and correct.

20. light memory device as claimed in claim 18, wherein, this gain calculating unit can be according to the displacement gain value that calculates, the work that this analog line driver is proofreaied and correct.

21. light memory device as claimed in claim 18, wherein, this light memory device includes an amplifying unit in addition, is coupled between this focus controller and this analog line driver; This gain calculating unit can be according to the displacement gain value that calculates, the work that this amplifying unit is proofreaied and correct.

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