JP2806559B2 - Focusing device and method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing device for focusing light on an optical disk and an optical disk determining device for determining the state of the optical disk.

[Prior Art] The operations of a conventional focusing device and an optical disc discriminating device are described below.
This will be described with reference to FIGS. FIG. 4 shows the optical system of this device. 2 is an optical disk,
2a is a pit. A laser light source 4 is provided on the lower surface of the optical disc 2, and emits laser light toward the optical disc 2. This laser light is focused on the optical disk 2 by the objective lens 6.

The laser light reflected on the optical disk 2 is directed to the cylindrical lens 10 by the half mirror 8. Near the focal point of the cylindrical lens 10, a four-division photodiode 12 is provided. Cylindrical lens 10
Since the vertical cross section is a parallelogram, no refraction occurs in the vertical direction. Since the cross section has a convex lens shape, refraction occurs in the left-right direction. Therefore, the focus of the cylindrical lens 10 is a vertical line (called a focal line).

When the optical disk 2 is focused, the reflected light returns as a parallel beam and returns to a four-division photodiode.
12 produces a circular beam image. FIG. 6A shows this state, and .alpha. In FIG. 5 shows the position of the four-division photodiode 12 at that time. At this time, the amount of light received by each of the four divided photodiodes 12 is equal, and the FE signal becomes zero.

If the distance from the disk 2 is too short (corresponding to β in FIG. 5), the beam becomes a divergent beam, the focal line shifts backward, and the image becomes a vertically long ellipse (see FIG. 6B). At this time, the amount of light received by each diode of the four-division photodiode 12 changes, and the FE signal becomes +.

If the distance from the disk 2 is too long (corresponding to γ in FIG. 5), the beam becomes a convergent beam, the focal line shifts forward, and the image becomes a horizontally long ellipse (see FIG. 6C). At this time, the FE signal becomes-.

Note that if the distance is extremely close or extremely far, no light is received due to defocus, and the FE signal becomes 0. Therefore,
When the objective lens 6 is gradually moved away, the FE signal
It appears as in Figure A. Here, α is the just focus point. An RF signal indicating the total amount of light received by the photodiode is as shown in FIG. 7B.

FIG. 2 shows an example of a focusing circuit utilizing the properties as shown in FIGS. 7A and 7B. The operation is as follows. First,
The changeover switch 20 is set to the triangular wave oscillation circuit 22 to output a triangular wave. This triangular wave passes through a phase compensation drive amplifier 24 and a drive circuit 26, and is given to an objective lens drive coil 28. Thereby, the objective lens 6 is gradually moved away.
FIG. 7A shows the change of the FE signal in this case, and FIG. 7B shows the change of the RF signal.

Thus, when the objective lens 6 is gradually moved away, first,
The RF signal rises from 0 to +, becomes 0 again, and the FE signal changes from 0 → + → 0 → − → 0. The CPU 30 determines the focal point α by looking at this change. That is, the point at which the FE signal changes from + to 0 after the RF signal exceeds the predetermined threshold value _VTH is determined as the focal point. When the CPU 30 finds the focal point α, the CPU 30 switches the switch 20 to the focus error detection circuit 32.
Switch to the side. The focus error detection circuit 32 is the circuit shown in FIG. Therefore, the objective lens coil
28, a focus error detection circuit 32, a phase compensation drive amplifier 24, and a drive circuit 26 form a feedback control circuit. Thereby, even if the disk 2 moves up and down due to rotation, just focus is maintained.

By the way, during the above operation, as shown in FIG. 8A, there is a case where the noise X is added to the FE signal.

In such a case, the CPU 30 determines that the inflection point of the noise X is the focal point and switches the switch 20. Therefore, the feedback control does not work well.

Therefore, when the focusing fails, the focusing operation is repeated several times. If the cause of the focusing failure is sudden noise or the like, the focusing is achieved by the next focusing operation. If the cause of the focusing failure is a defect of the disc 2 (for example, when the disc 2 is turned upside down) or no insertion of the disc 2, the focusing cannot be achieved even if the focusing operation is repeated. Therefore, a predetermined circuit (usually 3
If focusing cannot be achieved even after repeating (about twice), a message such as NO DISC is displayed.

[Problems to be Solved by the Invention] However, in the above-described conventional apparatus, even when the disc is not inserted or the disc is defective (inverted, etc.), the focusing operation is performed a predetermined number of times. repeat. Therefore, there is a problem that it takes time to determine that the disk is not inserted or the disk is defective.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a disk determination device capable of quickly determining whether a disk is not inserted or a disk is defective. It is still another object of the present invention to provide a focusing device which can quickly determine whether a disc is not inserted or a disc is defective, and can repeatedly perform a focusing operation when the disc is normal.

[Means for Solving the Problems] FIG. 1 shows the overall configuration of a focusing device according to claim 1.

This focusing device includes: a light emitting unit 42 for irradiating light toward the optical disc 2; a focus position moving unit 70 for moving a focal position of light emitted from the light emitting unit 42 based on an input signal; Reflected light information detecting means for receiving reflected light and outputting reflected light information indicating the intensity of the reflected light
62, receiving the reflected light information, determining the level of the intensity of the reflected light according to a predetermined threshold, and outputting level determination information 64; level determining means 64 for receiving the light reflected from the optical disk and detecting an error indicating a defocus Error information detection means 60 for outputting information; continuous change signal output means 22 for outputting a continuous change signal; switching means 20 for inputting the error information and the continuous change signal and providing one of them to the focus position moving means; Moving means 70, error information detecting means 60, switching means
A lock success / failure judging means 68 for judging whether or not the control loop is properly locked by looking at the state of the control loop constituted by 20, and outputting success / failure judgment information, level judgment information, lock success / failure judgment information and error A judgment control means 66 for receiving information and performing processing.

3. The focusing method according to claim 2, further comprising irradiating the optical disk with irradiation light while moving a focal position, detecting reflected light from the optical disk, and detecting the reflected light. If the intensity exceeds a predetermined threshold value, error information indicating defocus is detected,
A focusing method for performing a focusing process so that a focal position is focused on an optical disc. When a reflected light intensity for determining whether to perform the focusing process does not exceed the threshold value, the focusing method is performed. Without performing the focusing process, it is detected that the optical disk is defective or the optical disk is not inserted.

[Operation] In the focusing apparatus according to the first aspect, the determination control means determines whether or not to form the control loop during output of the continuous change signal when the reflected light intensity does not exceed the threshold value. In this case, it is determined that the disk state is defective without performing the control loop forming process. Therefore, it is possible to determine the disk state failure based on the reflected light intensity that determines whether to form the control loop.

In the focusing method including the disk state detection according to claim 2, when the reflected light intensity for determining whether to perform the focusing process does not exceed the threshold value, the focusing process is performed. Instead, it detects that the optical disk is defective or that the optical disk has not been inserted. This makes it possible to detect that the optical disk is defective or that the optical disk has not been inserted, based on the reflected light intensity that determines whether or not to perform the focusing processing.

Embodiment FIG. 2 shows a hardware configuration of a focusing apparatus according to an embodiment of the present invention. I / O port 3 on bus line 40
8, ROM34, RAM36 and CPU30 are connected. CPU30 is R
In accordance with the program stored in the OM, the control unit controls the changeover switch 20 as the changeover means and the triangular wave oscillation circuit 22 as the continuous change signal output means via the I / O port.

The disk 2 is rotated by a motor 46. The laser light emitted from the laser diode 42, which is a light emitting means,
The light is emitted to the back surface of the disk 2 via the collimator lens 44, the half mirror 48, and the objective lens 6. The reflected light is reflected by the half mirror 48 and is provided to a focus mirror detection circuit 32 which is an error information detecting means and a reflected light information detecting means. This focus error detection circuit 32
It is a circuit as shown in the figure. The FE signal, that is, the signal obtained by subtracting the amount of light received from the amount of light received by the photodiode is supplied to the changeover switch 20. The sum of the RF signal, that is, the amount of light received by the photodiode is I /
Input to O port 38.

The phase compensation drive amplifier 24 performs phase compensation on the signal from the changeover switch 20 and then provides the signal to the drive circuit 26. The output of the drive circuit 26 is provided to an objective lens drive coil 28. A magnet 80 is arranged around the coil 28, and the objective lens 6 moves up and down according to the current flowing through the coil 28. That is, the coil 28 and the magnet 80 form a focus position moving unit.

The flowchart of the program stored in the ROM 34
As shown in FIG. The CPU 30 controls each unit according to this flowchart.

First, in step S _1, CPU 30 has the RF flag 0
To Next, the selector switch 20 is controlled via the I / O port 38 to switch to the triangular wave oscillation circuit side (step
S _2). Next, in step S _2, via the I / O port 38, to control the triangular wave oscillation circuit 22, increase the triangular wave standing. This triangular wave is output from the phase compensation drive amplifier 24 and the drive circuit.
The signal is supplied to a coil 28 via 26. Thereby, the objective lens 6 gradually moves away from the disk 2. At this time,
The FE signal and the RF signal change as shown in FIGS. 7A and 7B.

The CPU 30 receives the FE signal and the RF signal at a predetermined cycle via the I / O port 38. Then, RF signals to determine whether it exceeds the threshold value V _TH (Step S _4). If not exceed, jump to step S _9, again returns to the step S _4.
Repeat this, the RF signal exceeds the threshold value V _TH, the process proceeds to step S _5, sets the RF flag.

Then, the process proceeds to step S _6, CPU 30 from the I / O port 8 FE
The signal is taken in, and it is determined whether or not the FE signal has fallen. If it has not fallen (for example, point α in FIG. 7A)
If), the process returns to step S _4, repeat the same operation.
When FE signal falls (for example, if a point in FIG. 7 A gamma), the process proceeds from step S ₆ to S _7, it switches the switch 20 to the side of the focus error detection circuit 32. As a result, a control loop including the coil 28, the focus error detection circuit 32, the phase compensation drive amplifier 24, and the drive circuit 26 is formed. Since this control loop operates so that the FE signal becomes 0, just focus (that is, point α in FIG. 7A) is always maintained.

The CPU 30 checks any signal in the control loop to determine whether the lock has succeeded. In this embodiment, the success or failure of the lock is determined by looking at the FE signal. If the lock is successful, the focusing operation is completed and the focusing operation by the control loop is continued. In this way, the focusing operation is performed.

Next, as shown in FIG. 8A, the operation when the noise X rides on the FE signal will be described. In this case, at the point X, the switch 20 is switched, and a control loop is formed. Therefore, the lock does not succeed, the switch 20 in step S ₁₅ is switched to the triangular wave oscillation circuit side. Then, the process proceeds to step S _9, again, step S _4, S _5, and repeats the loop of S _6. Thus, at the point γ, the switch
20 is switched to the focus error detection circuit 32 side, and a correct control loop is formed.

In addition, noise is large due to dirt on the disk surface, etc.
If the control loop does not work well, go from step S ₉ to step S _10. Here, if RF flag is set, the process proceeds to step S _11. In step S _11, it is counted the number of times a triangular wave or was raised. Now, because it is the first time, the process proceeds to step S _13, lowers the triangle wave. When falling is completed, the process returns to step S _1, the same operation is repeated. Such a repetition is effective because the lock may be successful by the second and third rises of the triangular wave. However, repeated 3 times, if the lock is not successful, then branches from step S ₁₁ to step S _12, it is determined that the disk failure.

Next, the operation when no disc is inserted will be described. In this case, as shown in FIG. 9B, since the RF signal does not rise, step S ₉ is performed while the RF flag remains 0.
Through. Accordingly, in step S _10, the program jumps to step S _12, is determined to be a bad disk (in this case, no disk). That is, it is possible to determine a disk defect only by raising the triangular wave once.

The same applies to the case where the disc is turned upside down.
In this case also, as shown in FIG. 10 B, since the RF signal does not rise, leaving the left step S ₉ RF flag is 0. Therefore, as described above, a disk failure can be determined only by raising the triangular wave once.

In the above embodiment, a triangular wave is used as the continuous change signal. However, any signal may be used as long as it is a signal that changes continuously (including a step change and a small step width). For example, a SIN wave or the like can be used.

In the above embodiment, the focus position is moved by moving the objective lens 6, but the light emitting means 42 and the disk 2 may be moved.

Furthermore, a focus error detection circuit using astigmatism
Although 32 was used, a Foucault method or a critical angle method may be used.

In the above embodiment, the functions shown in FIG. 1 are realized by software using the CPU 30, but a part or all of them may be constituted only by hardware logic.

[Effect of the Invention] In the focusing apparatus according to the first aspect, the determination control means determines that the reflected light intensity for determining whether or not to form the control loop exceeds the threshold value during the continuous change signal output. If not, the control loop forming process is not performed, and it is determined that the disk state is defective. Therefore, it is possible to quickly determine a disk state defect based on the reflected light intensity that determines whether or not to form the control loop.

In the focusing method including the disk state detection according to claim 2, when the reflected light intensity for determining whether to perform the focusing process does not exceed the threshold value, the focusing process is performed. Instead, it detects that the optical disk is defective or that the optical disk has not been inserted. Therefore, it is possible to quickly detect that the optical disk is defective or that the optical disk has not been inserted, based on the reflected light intensity that determines whether or not to perform the focusing processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a focusing device according to the present invention, FIG. 2 is a diagram showing a hardware configuration according to one embodiment, FIG. 3 is a diagram showing a flowchart of a program stored in a ROM 34, 4 is a perspective view showing an optical pickup portion, FIG. 5 is a diagram showing a light receiving position of a four-division photodiode, FIG. 6 (A to C) is a diagram showing details of a focus error detection circuit 32, FIG. , B is the FE signal and RF when a normal disc is inserted
FIGS. 8A and 8B show a state in which noise is superimposed on the FE signal. FIGS. 9A and 9B show the FE signal and RF when no disc is inserted.
FIGS. 10A and 10B are diagrams showing a change in a signal, and FIGS. 10A and 10B are diagrams showing an RF signal and a change in the RF signal when the disk is turned over. 2 optical disk 20 switching means 22 continuous change signal output means 42 light emitting means 60 error information detecting means 62 reflected light information detecting means 64 level determining means 66 determination control means 68 ...... Lock success / failure determination means

Claims (2)

(57) [Claims] 1. A light emitting means for irradiating light toward an optical disk, a focus position moving means for moving a focal position of light emitted from the light emitting means based on an input signal, and a light receiving means for receiving light reflected from the optical disk A reflected light information detecting means for outputting reflected light information indicating the intensity of the reflected light; a level for receiving the reflected light information, discriminating the intensity of the reflected light by a predetermined threshold, and outputting the level discrimination information. Discriminating means, error information detecting means for receiving error light reflected from the optical disc and outputting error information indicating defocus, continuous change signal output means for outputting a continuous change signal, inputting the error information and the continuous change signal, The state of the control loop constituted by the switching means for giving one of them to the focus position moving means, the focus position moving means, the error information detecting means, and the switching means is determined. Lock success / failure determination means for determining whether or not the lock has been securely performed and outputting success / failure determination information, and determination control for performing the following processes i) to iv) upon receiving the level determination information, the lock success / failure determination information and the error information. I) controlling the continuous change signal output means and the switching means;
A continuous change signal is given to the focus position moving means, and it is determined whether or not the reflected light intensity exceeds a threshold value by looking at the level determination information during the output of the continuous change signal. If the light intensity exceeds the threshold value, the control means controls the switching means based on the error information, and forms a control loop so that the error information output from the error information detecting means is given to the focus position moving means; iii) Looking at the lock success / failure determination information, if the control loop is properly locked, it is determined that focusing is completed. Iv) If the lock is not properly performed, it is determined that focusing cannot be performed. returning to i), repeating the same operation again, and if focusing cannot be performed even after repeating the predetermined number of times, determines that focusing has failed. Form the control loop If the reflected light intensity of determining whether does not exceed the threshold value, without performing the control loop forming process, it is determined that the disc state poor focusing device according to claim. 2. The method according to claim 1, further comprising: irradiating the optical disk with irradiation light while moving the focal position, detecting reflected light reflected by the optical disk, and determining whether the intensity of the reflected light exceeds a predetermined threshold value. Detects error information indicating defocus,
A focusing method for performing a focusing process so that a focal position is focused on an optical disc, wherein the reflected light intensity for determining whether or not to perform the focusing process does not exceed the threshold value. Detecting a defect of the optical disk or the fact that the optical disk has not been inserted without performing a focusing process.