JPH0793772A - Device for automatically correcting focal point - Google Patents

Abstract

PURPOSE:To correctly focus and converge even when an offset occurs in a focusing state due to the change in the environment by detecting the out-of-focus and an offset amount according to an enviromental condition also with a focal point condition detection means and correcting a focus error signal. CONSTITUTION:A reflected beam from a recording medium 1 is made incident on the quadlipartite photodetector 9 of the focal point condition detection means through an objective lens 2, beam splitters 3, 7 and a luminous flux divider 8. The offset amounts due to the change in the environment of a temp. etc., together with the out-of-focus are detected by the photodetector 9, and the focus error signal is corrected according to the offset amount by a focus signal processing circuit 11. Then, a position of a lens 2 is servo controlled through a driving amplifier 13 and a driving coil 12. Thus, even when the offset occurs in the focusing state due to the change in the environment, correct focusing and converging control is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an automatic focus control mechanism in an apparatus which records or reproduces information by utilizing light.

[0002]

2. Description of the Related Art In the conventional automatic focus control mechanism in an optical disk device, the in-focus point is usually detected optically.
For example, when the light beam reflected from the optical disk is optically divided into two, and the light spots of each of the divided light beams are detected by the four-division light receiving element, the state shown in FIG. 2 is obtained.

Here, when the objective lens 2 is in focus with respect to the recording medium (optical disk) 1 as shown in FIG. 2B, the light spots of the two divided light beams on the four divided light receiving element are , As shown in FIG. 2 (e), they are evenly located on the central vertical division line of the light receiving element. In this case, the focus error signal FES = 0.

If the recording medium 1 is used as shown in FIG.
On the other hand, when the objective lens 2 is too close and is out of focus, the light spots of the two-divided light fluxes on the four-divided light receiving element are the central vertical division lines of the light receiving element as shown in FIG. Located non-uniformly with respect to. In this case, the focus error signal FES <0.

On the contrary, as shown in FIG. 2C, the recording medium 1
On the other hand, when the objective lens 2 is too far away and is out of focus, the light spots of the two-divided light fluxes on the four-divided light receiving element are the central vertical division lines of the light receiving element as shown in FIG. 2 (f). Located non-uniformly with respect to. In this case, the focus error signal FES> 0.

That is, the polarity (>) of the focus error signal FES
From 0, <0), it becomes clear in which direction the objective lens 2 is out of focus. When this deviation direction is known, the position of the objective lens 2 is controlled so that the deviation in that direction is minimized (that is, the focus error signal FES becomes zero). This is the basic operation of the conventional automatic focus control mechanism.

The automatic focus control mechanism includes an essentially precise optical system (lens, prism, mirror, light receiving element, etc.). Since the mechanism including the precision optical system is accurately adjusted in the final adjustment process of the product, the mechanism shown in FIG.
The state (e) (FES = 0) is obtained.

[0008]

However, the ambient environment that differs from the final adjustment process of the product (mainly the difference in ambient temperature)
If the product is used, or if a slight positional shift occurs in the optical system due to vibration during use of the device for a long period of time, the following situation occurs.

That is, when the optical system is displaced, if the objective lens 2 is in the focused position with respect to the recording medium 1 as shown in FIG. The light spots of the respective divided light fluxes are offset by ΔX from the center vertical division line of the light receiving element as shown in FIG. In this case, the focus error signal FES
≠ 0. However, the automatic focus control system has a focus error signal F
Since the control operation is such that ES becomes zero,
The position of the objective lens 2 is changed so that FES = 0.

That is, if the optical system is displaced, the automatic focus control system will perform an erroneous control operation that converges to a non-focus point. When such non-focus point convergence control is performed, normal recording or reproduction of information on the recording medium (optical disc) 1 cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic focus correction device capable of performing accurate focus focus control even if an offset occurs in the focus detection state due to changes in the surrounding environment.

[0012]

According to the present invention, the deviation information (offset ΔX) from the in-focus point due to environmental changes such as temperature changes is the same as the portion (9) for detecting the focus error signal (FES). Then, the focus error signal (FES) is corrected with this shift information. Control is performed to obtain the in-focus point with this corrected focus error signal (FESC).

[0013]

Since the deviation information (offset) from the in-focus point is detected from the same part as the focus error signal detection portion, the detected offset amount is proportional to the offset amount (FES ≠ 0) in the focus error signal. And change. Therefore,
No matter how the offset in the focus error signal changes, the corrected focus error signal (FES
C) can be obtained. Such a corrected focus error signal (FESC) is used for in-focus point convergence control instead of the focus error signal (FES) before correction.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an optical system of an optical disc device including an automatic focus correction device according to an embodiment of the present invention.

The laser beam emitted from the light source (laser diode) 5 is sent to the surface (information recording surface) of the recording medium (optical disk) 1 through the collimator 4, the beam splitter 3 and the objective lens 2.

The objective lens 2 can be moved up and down at a high speed in the perpendicular direction of the recording medium 1 by the drive coil 12, and has a function of focusing the laser beam on the information recording surface of the recording medium 1.

The laser beam reflected by the recording medium 1 is sent to the light receiving element 10 via the beam splitter 3, the condenser lens 6 and the beam splitter 7. Light receiving element 10
Is to read recorded information from the laser beam reflected by the recording medium 1.

The laser beam reflected by the recording medium 1 is further guided from the beam splitter 7 to the divided light receiving element 9 via the beam splitter 8. The divided light receiving element 9 has four light receiving areas A, B, C, D, and electric signals A, B, C, D having a magnitude corresponding to the intensity of the incident laser beam are emitted from the respective light receiving areas. You can get it.

Electric signals A, B from the divided light receiving element 9,
C and D are processed by the focus signal processing circuit 11 to obtain the signal E1.
It becomes 1. This signal E11 becomes the offset-corrected corrected focus error signal FESC which will be described in detail later.

The signal E11 from the focus signal processing circuit 11
The frequency characteristics and the phase characteristics are compensated by the drive amplifier 13, and then the power is amplified. The power-amplified signal (driving current) is given to the driving coil 12, and the position of the objective lens 2 is controlled so that the corrected focus error signal FESC becomes minimum.

Now, assume that the divided light-receiving element 9 of FIG. 1 has a four-divided structure as shown in FIG. 2 (e). In this case, 2
Information of one beam spot of the split laser beam is output as signals A and D from the light receiving regions A and D, and information of the other beam spot of the two split laser beams is received from the light receiving regions B and C. It is output as C.

From the signals A, B, C and D, the focus error signal FES before offset correction is obtained by the following calculation.

FES = (A + C) − (B + D) (1) When the objective lens 2 is too close to the recording medium 1 and is out of focus as shown in FIG. Light receiving area A,
The beam spots projected on B, C, and D are as shown in FIG. 2D, and D> A and B> C. Then (B + D)
> (A + C), the FES of the formula (1) is negative (FES <0). In this case, a drive current that causes the objective lens 2 to separate from the recording medium 1 is applied from the drive amplifier 13 to the drive coil 12.

As shown in FIG. 2C, when the objective lens 2 is too far from the recording medium 1 and is out of focus, the beam spots projected on the light receiving areas A, B, C and D of the divided light receiving element 9. Is as shown in FIG. 2F, and D <A and B <C. Then, since (B + D) <(A + C), the FE of the formula (1) is
S becomes positive (FES> 0). In this case, a drive current such that the objective lens 2 approaches the recording medium 1 is applied to the drive amplifier 1.
3 to the drive coil 12.

As described above, the objective lens 2 is moved away from the recording medium 1 if it is too close to the recording medium 1 and is moved too close to the recording medium 1. As a result, the position of the objective lens 2 is controlled so that the FES of the expression (1) becomes zero.

When there is no offset, this FES = 0 point coincides with the focal point, as shown in FIG. 2 (e).

However, when the relative positions of the components of the optical system (beam splitter, light receiving element, etc.) change slightly due to changes in ambient temperature, the positions of the two beam spots at the original focus point are shown in FIG. 2 (h). It will be as shown. That is, the light receiving areas A and B and the light receiving areas C,
A line in the central portion of the divided light receiving element 9 that forms a boundary with D;
The line connecting the centers of the two beam spots is offset by ΔX at the original focus. In this case, D> A,
C> B.

Rewriting the right side of equation (1) gives (AD) +
(CB). Substituting D> A and C> B into these results in (AD) <0 and (CB)> 0. If (AD) <(CB), then FES> 0.

That is, when an offset as shown in FIG. 2 (h) occurs, FES> 0, the original in-focus point is recognized as a non-in-focus point (too far), and a position too close as shown in FIG. 2 (a). Wrong focus control will be performed.

When the objective lens 2 is too close to the recording medium 1, the two beam spots are as shown in FIG. 2 (g) and FES <0 is obtained. In this case, the objective lens 2
Is controlled to be released. If the objective lens 2 is too far away from the recording medium 1, two beam spots will appear in FIG.
And FES> 0 is obtained. In this case, control for bringing the objective lens 2 closer is performed.

In order to prevent the control system from erroneously recognizing that the original in-focus point (FIG. 2 (b)) is a non-in-focus point when an offset as shown in FIG. A new focus error signal FESC is needed that is corrected to be zero at focus and positive or negative at out-of-focus.

The corrected focus error signal FESC when the four-division light receiving element 9 is used as in the embodiment of FIG. 1 is as follows.

FESC = (A + C)-(B + D) -k [(A + D)-(B + C)]-[(A + B)-(C + D)] ......... (2 ) Here, k is a proportional coefficient obtained experimentally in an actual implementation device (product). The first and second terms on the right side of the equation (2) correspond to the FES (focus error signal before correction) of the equation (1), and the third term thereof is a portion for canceling the component due to the offset ΔX in FIG. 2 (h). Is.

When there is no offset ΔX as shown in FIG. 2 (h), [(A + B)-(C + D)] in the third term becomes zero. In this case, the corrected focus error signal F of equation (2)
The ESC becomes the same as the focus error signal FES of the equation (1).
Therefore, even if the offset does not occur, there is no problem in the automatic focus control by the corrected focus error signal FESC of the formula (2).

FIG. 3 shows an example of a circuit configuration for producing the corrected focus error signal FESC expressed by the equation (2) from the 4-division light receiving element 9. The four-division light receiving element 9 is composed of photodiodes 9A, 9B, 9C and 9D, the cathodes of which are connected to the bias power supply VR and the anodes of which are connected to the inverting input terminals of the operational amplifiers 111 to 114, respectively.

The light receiving areas A, B, C and D in FIG.
The photodiodes 9A, 9B, 9C of FIG.
Corresponds to 9D. The current signal corresponding to the size of the laser beam spot detected by the photodiode 9A in the area A is converted into the voltage signal EA (-A) via the operational amplifier 111 and the inverting amplifier circuit by the feedback resistor R11. Similarly, the current signal corresponding to the size of the laser beam spot detected by the photodiode 9B in the region B is converted into the voltage signal EB (−B) via the operational amplifier 112 and the inverting amplifier circuit by the feedback resistor R12. , The current signal corresponding to the size of the laser beam spot detected by the photodiode 9C in the region C is the operational amplifier 1
A current signal corresponding to the size of the laser beam spot detected by the photodiode 9D in the region D is converted into a voltage signal EC (-C) through an inverting amplifier circuit formed of the feedback resistor R13 and the feedback resistor R13. It is converted into a voltage signal ED (-D) via the inverting amplifier circuit by the feedback resistor R14.

The voltage signals EA and EC are sent to the inverting input terminal of the operational amplifier 115 via the resistance network RA, and the voltage signals EB and ED are sent to the non-inverting input terminal of the operational amplifier 115 via the resistance network RA. To be The operational amplifier 115 amplifies the voltage signal EA + EC and the voltage signal EB + ED with a gain distribution determined by the ratio of each resistance value of the resistance network RA and the negative feedback resistor R15, and corresponds to the difference between the voltage signal EA + EC and the voltage signal EB + ED. The voltage signal E115 is output. This voltage signal E115
Corresponds to the focus error signal FES of Expression (1) or the first and second terms on the right side of Expression (2).

The voltage signals EA and ED are resistor networks R
It is sent to the inverting input terminal of the operational amplifier 116 via B, and the voltage signals EB and EC are sent to the non-inverting input terminal of the operational amplifier 116 via the resistor network RB. The operational amplifier 116 has a voltage signal EA + ED and a voltage signal EB +.
EC is amplified by gain distribution determined by the ratio of each resistance value of the resistance network RB and the negative feedback resistance R16, and the voltage signal E
The voltage signal E116 corresponding to the difference between A + ED and the voltage signal EB + EC is output.

The voltage signals EA and EB are resistor networks R
The voltage signals EC and ED are sent to the inverting input terminal of the operational amplifier 117 via C, and are sent to the non-inverting input terminal of the operational amplifier 117 via the resistor network RC. The operational amplifier 117 has a voltage signal EA + EB and a voltage signal EC +.
ED is amplified by gain distribution determined by the ratio of each resistance value of the resistance network RC and the negative feedback resistance R17, and the voltage signal E
A voltage signal E117 corresponding to the difference between A + EB and the voltage signal EC + ED is output.

The voltage signals EA to ED are connected to the resistor network R.
It is sent to the inverting input terminal of the operational amplifier 118 via D, and the non-inverting input terminal of the operational amplifier 118 is grounded. The operational amplifier 118 outputs the voltage signals EA to ED to the resistance network R.
Amplification is performed with a gain distribution determined by the ratio of each resistance value of D and the negative feedback resistor R18, and a voltage signal E118 corresponding to the voltage signal EA + EB + EC + ED is output.

The voltage signals E116 to E118 are input to the analog multiplication circuit 110. The circuit 110 uses the third term k [(A + D) − (B + C)] ·
An analog calculation process corresponding to [(A + B)-(C + D)] is performed and an offset correction signal E110 is output.

The offset correction signal E110 corresponding to the third term on the right side of the equation (2) is applied to the non-inverting input terminal of the operational amplifier 119 via the resistor R20. This amplifier 119
A voltage signal E115 corresponding to the first and second terms on the right side of the equation (2) (corresponding to the FES of the equation (1)) is applied to the inverting input terminal of the. The operational amplifier 119 uses the voltage signal E11 with an amplification degree corresponding to the ratio of the resistors R19 and R21.
5 and the offset correction signal E110 are amplified and the focus error signal E corrected by the offset correction signal E110 is amplified.
11 is output. This signal E11 corresponds to the corrected focus error signal FESC of Expression (2).

By applying this signal E11 to the drive amplifier 13 of FIG. 1, the objective lens 2 can be moved to the position shown in FIG. 2 regardless of the presence or absence of the offset ΔX as shown in FIG.
The in-focus state as shown in (b) can be automatically controlled.

FIG. 4 shows a specific example of the analog multiplication circuit 110 shown in FIG. Here, the transistors Q10, Q14,
The exponential function characteristic between the base-emitter voltage of Q16 and the collector current is applied to the negative feedback circuit of the operational amplifiers 120, 121, 122 to perform logarithmic conversion on the input voltages E116 to E118, and the subsequent analog synthesis processing result. Is passed through the antilogarithm circuit (Q12, 123) to perform the multiplication process. By these processes, the offset correction signal E1
10 is obtained.

Although the analog calculation is performed in the configurations of FIGS. 3 and 4, the calculation of the equation (2) can be performed by digital processing. FIG. 5 shows a configuration example in the case of digitally processing a part of Expression (2). 6 is a flow chart for explaining the operation of the offset amount calculator 1102 in FIG.

First, the four voltage signals EA to ED obtained from the operational amplifiers 111 to 114 of FIG.
It is digitized by 4 bits or 8 bits in the / D converter 1101 and passed to the offset amount calculator 1102. After taking in the voltage signals EA to ED (ST10), the CPU of the computer 1102 calculates the third term on the right side of the equation (2) and outputs the result (digital value of the offset correction signal E110) (ST20).

The calculated value output from the CPU of the computer 1102 is converted into an analog offset correction signal E110 by the D / A converter 1103, and the operational amplifier 1 shown in FIG.
At 19, it is combined with the signal E115 corresponding to the FES of equation (1).

The combination of FIGS. 3 and 5 is analog /
FE of formula (2), though it is a digital hybrid configuration
It is also possible to perform all the processing until the signal E11 corresponding to SC is obtained by the computer 1102 in FIG. However, in this case, the computer 1102 needs a CPU with a high processing speed.

In the hybrid configuration combining FIG. 3 and FIG. 5, there is no strict requirement for the processing speed of the CPU of the computer 1102. The offset correction amount E by the CPU
This is because the analog focus control using the FES of the formula (1) is performed even when the time-consuming offset correction amount E110 has not yet been calculated for the calculation of 110. Once the offset correction amount E110 is obtained, the FES of equation (2)
Focus control based on C is quickly performed by the operation of the analog control circuit.

Once the offset correction amount E110 is obtained, this correction amount E110 does not fluctuate in a short period, so this correction amount E110 can be temporarily replaced with a fixed value. Then, the CPU of the computer 1102 can be used for other work. Conversely speaking, it is possible to obtain the offset correction amount E110 by utilizing the idle time of the processing of the CPU which is not originally provided for focus control.

FIG. 7 shows another embodiment of the automatic focus correction device. FIG. 8 is a diagram for explaining the operation of this automatic focus correction device.

The laser beam emitted from the light source 5 is sent to the surface of the recording medium 1 via the collimator 4, the beam splitter 3 and the objective lens 2. The laser beam reflected by the recording medium 1 is a beam splitter 3 and a condenser lens 6.
Then, the light is transmitted to the light receiving element 10 via the beam splitters 7a and 7b.

The laser beam reflected by the recording medium 1 is further divided by the beam splitters 7a and 7b.
a, 9b. The divided light receiving element 9b has three light receiving areas A, B, and C, and an electric signal A having a magnitude corresponding to the intensity of the incident laser beam from each light receiving area,
B and C can be obtained. Further, the divided light receiving element 9a has three light receiving regions D, E, F so that electric signals D, E, F having a magnitude corresponding to the intensity of the incident laser beam light can be obtained from the respective light receiving regions. Has become.

Electric signals A, B from the divided light receiving element 9b,
The electric signals D, E and F from C and the divided light receiving element 9a are processed by the focus signal processing circuit 11 to become a signal E11. In this embodiment, the signal E11 is the second corrected focus error signal F.
Includes ESC. Signal E11 from the focus signal processing circuit 11
The frequency characteristics and the phase characteristics are compensated by the drive amplifier 13, and then the power is amplified. This power-amplified signal (driving current) is given to the driving coil 12, and the position of the objective lens 2 is controlled so that the second corrected focus error signal FESC is minimized.

Now, the three of the divided light receiving elements 9a and 9b in FIG.
It is assumed that the division structure is as shown in FIG. In this case, information on one beam spot of the two laser beams from the two beam splitters 7a and 7b is given to the light receiving regions A to C, and information on the other beam spot is given to the light receiving regions D to F. In this case, the three-division light receiving element 9
The signals A to C are obtained from b, and the signals D to F are obtained from the three-divided light receiving element 9a.

From the signals A to F, the following calculation is performed.
A focus error signal FES before offset correction is obtained.

FES = (B−A−C) − (E−D−F) (3) If the objective lens 2 is too close to the recording medium 1 and is out of focus, the divided light receiving elements 9 a, The beam spots projected on the light receiving areas A to F of 9b are as shown in FIG. 8A, and the FES of the expression (3) is negative (FES <0). In this case, a drive current that causes the objective lens 2 to separate from the recording medium 1 is applied from the drive amplifier 13 to the drive coil 12.

When the objective lens 2 is too far from the recording medium 1 and is out of focus, the light receiving area A of the divided light receiving elements 9a and 9b is obtained.
The beam spots projected on to F are as shown in FIG. 8C, and the FES of the equation (3) is positive (FES> 0). In this case, a drive current that causes the objective lens 2 to approach the recording medium 1 is applied from the drive amplifier 13 to the drive coil 12.

As described above, the objective lens 2 is moved away from the recording medium 1 if it is too close to the recording medium 1 and is moved too close to the recording medium 1. As a result, the position of the objective lens 2 is controlled so that the FES of the expression (3) becomes zero.

When there is no offset, as shown in FIG. 8B, this point of FES = 0 coincides with the focal point.

Next, as shown in FIG. 8 (e), the case where the center line CL of the light receiving regions B and E and the line connecting the centers of the two beam spots are offset by ΔX at the original focus point. Considering this, FES ≠ 0.

In order to prevent the control system from erroneously recognizing that the original focusing point is the non-focusing point when the offset shown in FIG. A new focus error signal FESC corrected to be positive or negative at the focus is required.

Corrected focus error signal FESC when two sets of three-divided photodetectors 9a and 9b are used as in the embodiment of FIG.
Is as follows.

FESC = (BAC)-(EDF) -k [(A + D)-(C + F)]-[(A + B + C)-(D + E + F)] ......... (4 ) Here, k is a proportional coefficient obtained experimentally in an actual implementation device (product). The first and second terms on the right side of the equation (4) correspond to the FES (focus error signal before correction) of the equation (3), and the third term is a portion for canceling the component due to the offset ΔX in FIG. 8 (e). Is.

When there is no offset ΔX as shown in FIG. 8E, the third term on the right side of the equation (4) becomes zero. In this case, the corrected focus error signal FESC of equation (4) is
Of the focus error signal FES. Therefore, even if the offset does not occur, there is no problem in the automatic focus control by the corrected focus error signal FESC of the formula (4).

For example, if the CPU of the computer 1102 shown in FIG. 5 executes a program for calculating the formula (4), the corrected focus error signal FESC of the formula (4) can be obtained.

[0068]

EFFECT OF THE INVENTION Offset ΔX showing deviation from the in-focus point
Information is detected from the same divided light receiving element 9 as the focus error signal detection portion, the detected offset amount changes in proportion to the offset amount (FES ≠ 0) in the focus error signal FES. Therefore, no matter how the offset in the focus error signal FES changes, the corrected focus error signal FESC can be obtained by canceling the change.
Such a corrected focus error signal FESC is used for in-focus point convergence control.

Therefore, in the in-focus focusing control system using the automatic focus correction device of the present invention, defocusing due to changes in ambient temperature does not occur.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of an automatic focus correction device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the automatic focus correction device in FIG.

FIG. 3 is a circuit diagram illustrating an example of the focus signal processing circuit of FIG.

4 is a circuit diagram illustrating a specific example of the analog multiplication circuit of FIG.

5 is a circuit diagram illustrating another example of the focus signal processing circuit of FIG.

6 is a flowchart illustrating the operation of the offset amount calculator of FIG.

FIG. 7 is a diagram illustrating a configuration of an automatic focus correction device according to another embodiment of the present invention.

FIG. 8 is a view for explaining the operation of the automatic focus correction device in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording medium (optical disk), 2 ... Objective lens, 3 ... Beam splitter, 4 ... Collimator, 5 ... Light source, 6 ... Condensing lens, 7, 7a, 7b ... Beam splitter, 8 ... Light beam splitter, 9, 9a , 9b ... Divided light receiving element (focus error detector / divided light detector), 10 ... Light receiving element, 11 ... Focus signal processing circuit, 12 ... Driving coil, 13 ... Driving amplifier, 11
0 ... Analog multiplication circuit, 111-123 ... Operational amplifier,
1101 ... A / D converter, 1102 ... Offset amount calculator (CPU), 1103 ... D / A converter, Q10-Q1
6 ... NPN transistor, RA, RB, RC, RD ... Resistor network.

Claims (3)

[Claims] 1. A light beam supplying means for supplying a light beam to an information recording surface of an information recording medium utilizing light; and a focusing for focusing the light beam on the information recording surface of the information recording medium. Focus means for detecting the focus state of the light beam on the information recording surface of the information recording medium and outputting a focus error signal indicating a deviation from the focused state; and an information recording surface of the information recording medium. An offset amount detecting means for detecting the offset amount together with a deviation from the in-focus state, when the focus error signal includes an offset amount with respect to the focus state of the light beam; Focus error signal correction means for outputting a corrected focus error signal obtained by correcting the focus error signal by adding an offset amount to the deviation from the in-focus state; An automatic focus correction apparatus comprising: a means for focusing the light beam on an information recording surface of the optical disc by controlling the focusing means based on a focus error signal. 2. The corrected focus error signal is FESC,
In the case where the signal FESC is detected by a divided photodetector composed of four divided photodetectors, A is the amount of light detected in the first portion of the divided photodetector, and B is in the second portion of the divided photodetector. When the detected light amount is C, the detected light amount in the third portion of the divided photodetector is D, the detected light amount in the fourth portion of the divided photodetector is D, and the proportionality coefficient is k, FESC = (A + C)-(B + D) ー k [(A + D)-(B + C)] ・ [(A + B)
The automatic focus correction device according to claim 1, wherein the offset amount detection means is configured so that a relationship of-(C + D)] is established. 3. The corrected focus error signal is FESC,
In the case where the signal FESC is detected by a first divided photodetector composed of three-divided light receiving elements and a second divided photodetector composed of three divided light receiving elements, A is the first divided photodetector. The amount of light detected on one side is B
Is the amount of light detected at the central portion of the first split photodetector, C is the amount of detected light at the other side of the first split photodetector, and D is the amount of detected light at one side of the second split photodetector. Where E is the detected light amount in the central portion of the second split photodetector, F is the detected light amount in the other side portion of the second split photodetector, and the proportionality coefficient is k, FESC = (BAC )-(EDF) ー k [(A + D)-(C + F)] ・
The automatic focus correction device according to claim 1, wherein the offset amount detection means is configured so that a relationship of [(A + B + C)-(D + E + F)] is established.