KR930008146B1 - Off-axis compensating device of multi-disk player - Google Patents

Abstract

This invention consists of the radial beam light detection means (1), (2), current voltage convertor (3), (4), addition curcuit (5), comparator (6) and motor driver (7). The light detection means (1), (2) measures the current proportional to the light amount of radials (A), (C) among three beams reflected from the disk surface when the light irradiated the disk. The current voltage convertor converts the current from the light detection means to voltage. The addition curcuit adds the output from the current voltage converter (3), (4) and outputs voltage proportional to the tortal light amount of radial beam (A), (C). Comparator (6) compares the output value from the addition curcuit (5) with the reference value which detects the off axis direction. The motor driver controls the driving of the pick-up moving motor (8) according to the output signal of the comparator (6).

Description

Off-axis Compensator for Multi-disc Players

1 is a positional characteristic diagram of a track and three beams in a typical MDP.

2 is a characteristic diagram in which three beams are formed on a disk when off-axis occurs in a general MDP.

3a and 3b are track and beam position characteristics according to off-axis in a typical MDP. FIG. 3a is a case where the off-axis occurs above the center of rotation of the disc, and FIG. If it occurs below the center.

4 is a positional characteristic diagram of a track and a beam for explaining tracking in a general MDP.

5 is a block diagram of an off-axis correction device in an MDP according to the present invention.

6 is a detailed configuration of an embodiment of the present invention according to FIG.

7 is a configuration diagram of another embodiment of the off-axis correction apparatus of the MDP according to the present invention.

* Explanation of symbols for main parts of the drawings

1, 2: radial beam light quantity detecting means 3, 4: current-voltage conversion circuit

5: addition circuit 6: comparison circuit

7: motor driving circuit 8: motor

11: Tracking Error Detection Circuit 12: Error Gain Correction Circuit

13 tracking compensation circuit 14 off-axis amount detection circuit

OP ₁ -OP ₄ : Operational Amplifier CP ₁ : Comparator

R ₁ -R ₁₁ : Resistor T _r1 , T _r2 : Transistor

C ₁ , C ₃ : Capacitor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-axis correction apparatus for a multi disc player (hereinafter referred to as MDP), and more particularly to an MDP for playing a compact disc, a LD (laser disc), or the like. In detecting the signal from the disc, the off-axis that detects the disc rotation axis center and the optical pick-up movement path that detects the signal does not coincide with each other and properly corrects the information signal from the disc. An off-axis correction device for a multi-disc player for detecting.

In general, in the MDP, Off-Axis means that the center of the rotation axis of the disc and the movement path of the optical pickup that detect a signal from the disc do not coincide with each other. As shown in the positional relationship diagram of the 3 beams generated in the optical pickup, the beams are formed on the disk carrying the information signal, and the A beam and the C beam are radial beams, and pickup is performed correctly. Used to follow the track, the B beam is used to detect the information signal itself carried on the disc. Here, t _1-1 , t ₁ , t _{1 + 1} show the track.

FIG. 2 is an explanatory view showing that three beams are formed on the disc in the case of the off-axis Δx in the conventional MDP. As shown in FIG. 2, the pickup detecting the signal is separated from the center of the disc rotation axis by x (A, B, C) (A ', B', C '), (A ", B", C ") represents three beams from the pickup, and (r _K-1 , r _K , r _{K + 1} ), (r _j-1 , r _j , r _{j + 1} ) represent each track of the inner and outer circumferences of the disc, and (Q _k ), (Q _j ) indicate that the pickup will be off if there is no off-axis The moving line and the straight line extending from the center of the disc (O) indicate the angle between the pick-up meets the moving track in the presence of off-axis, and (Q ₀ ) indicates the angle between the pick-up moving line and the three beams. (Q _X ) (Q _{X '} ) and (Q _{X "} ) are three beams (A, B, C) (A', B ', C') and (A", B "C"), respectively. Shows the angle of the track.

As shown in FIG. 2, when off-axis occurs, the three beams A, B, and C proceed to (A ', B', C '), where the pickup moves and the three beams (A, B). The angle formed by, C) and (A ', B', C ') is constant at Q ₀ , respectively. However, the relationship between each Q _X that the three beams (A, B, C) make up the signal track and each Q _{X 'that the} three beams (A', B ', C') make with the signal track is Q _X 〉 Q _{X '} The more off-axis, i.e., the larger Δx in FIG. 2, the greater the difference between Q _X and Q _{X '} , which actually means that the three beams rotate right about the track. Will appear.

On the other hand, when off-axis occurs downwardly with respect to the disk, the opposite phenomenon occurs as described above. In other words, the relationship between each Q _X of the three beams A, B, and C with the signal track and each Q _{X "} of the three beams A", B ", and C" with the signal track is Q _X <Q _{X ".} This means that the more off-axis, the greater the difference between Q _X and Q _{X &quot};, and in practice the three beams rotate to the left about the track. This rotation is as shown in Figs. 3a and 3b, where 3a is the case where off-axis occurs above the center of rotation of the disc, and 3b is the off-axis case below the center of rotation of the disc. The case is shown.

In order to reduce such off-axis, conventionally, a pickup that detects a signal uses a method of mechanically measuring and fixing the path of movement so as to match the center of rotation of the disk. do. First, not only can it not be mechanically perfect, but even if it is perfect there is a residual error that cannot completely eliminate off-axis. Second, after mechanically fixed, when the external user is inadvertently impacted from the outside, there is a possibility that the fixed part is distorted to cause off-axis. Third, in the manufacture of a disc carrying a signal, a result such as off-axis may occur due to the bending of the disc.

Therefore, the off-axis could not be completely eliminated. If off-axis occurs, the radial beam (see FIG. 3), which reads the signal, correctly tracks the track around the beam B while the signal is read. When A) and (C) rotate, the area of the radial beams (A) and (C) becomes larger when the off-axis occurs above the center of rotation, so that the area of the track containing the signal becomes larger as shown in the 3a diagram. If the off-axis occurs below the center of rotation, the area of the track containing the signal becomes smaller, as in the third diagram.

On the other hand, the principle of the tracking servo to correctly follow the track is to detect the difference in the amount of light between the radial beam C and the light amount difference between the beams A and C. Compensation is performed so as to correspond to, so as to follow the track correctly.

For example, when the left side of the three beams (A, B, C) is biased around the track as shown in the fourth diagram, the light quantity difference between the radial beams (A) and (C) is generated by the difference between the hatched portions. The compensation corresponding to the car will be performed.

However, when the three beams are rotated as shown in FIG. 3 when the off-axis is present, when the three beams are biased in one direction about the track, when the light quantity difference between the A beam and the C beam is normal, the off-axis Occurs at the top of the disk rotation center, and is different at the bottom.

Therefore, if the tracking servo is configured on the basis of the normal case, the tracking servo may not be correctly performed when off-axis occurs, thereby making it difficult to detect the signal correctly. By detecting the amount of off-axis in the normal case by using the method to compensate for the normal signal detection is possible. However, in the prior art, it is difficult to accurately detect a signal when off-axis occurs because it cannot compensate for off-axis in such a normal case.

In view of the above problems, the present invention detects the amount of light of radials (A) and (C), converts them to voltages, adds them, and detects the direction in which off-axis occurs according to the added values. An off-axis correction apparatus of a multi-disc player that compensates for off-axis by compensating driving is created. The detailed description will be given below with reference to the accompanying drawings.

5 is a block diagram of an off-axis correction device of the MDP according to the present invention, and FIG. 6 is an embodiment block diagram according to FIG. 5, which is irradiated from the pickup to the disk and reflected from the surface of the disk. Radial beam light amount detecting means (1), (2) for detecting a current amount proportional to the light amount of radial (A), (C) of the three beams, and radial beam light amount detecting means (1), (2) The current-voltage conversion circuits 3 and 4 for converting the output current into voltages and the outputs of the current-voltage conversion circuits 3 and 4 are added to the radial beams A and C. The addition circuit 5 outputs at a voltage proportional to the amount of light, and the output value of the addition circuit 5 and the reference value for detecting in which direction the up-down direction occurs based on the center of rotation of the disk. A motor driving circuit for driving control of the pickup moving motor 8 in accordance with the comparison circuit 6 and the output of the comparison circuit 6. It consists of (7).

In the embodiment of the present invention configured as described above, as shown in FIG. 6, the radial beam light quantity detecting means (1) and (2) are used as photodiodes, and the current-voltage conversion circuits (3) and (4) are respectively a photodiode (1), calculating the output of the (2) an amplifier (OP _1), the inverting input terminal of the (OP ₂₎ (-) being applied, the operational amplifier (OP _1), the non-inverting input terminal of the (OP ₂₎ (+) Is grounded separately and connects resistors (R ₁ ) and (R ₂ ) between inverting input terminal (-) and output terminal of operational amplifier (OP ₁ ) and (OP ₂ ) respectively. The voltage follower is configured to output a voltage, and the addition circuit 5 passes the outputs of the current-voltage conversion circuits 3 and 4 through the resistors R ₃ and R _4, respectively, and then a common operational amplifier ( A resistor (R ₅ ) is connected between the inverting input terminal (-) and the output terminal of the operational amplifier (OP ₃ ) applied to the inverting input terminal (-) of OP ₃ ) and the non-inverting input terminal (+) is grounded. Radial beam through his output terminal The input / output is proportional to the total light amount of (A) and (C), and the comparison circuit 6 receives the output of the addition circuit 5 from the inverting input terminal (-) of the comparator CP ₁ . , the non-inverting input terminal of a resistor (R ₆₎ variable resistance (V _R1) and connected to the movable terminal that the variable resistance (V _R1) to said comparator (CP ₁₎ of the other side of the connection to the power supply terminal (Vcc) (+ Is connected between the ground and the ground, and outputs a signal according to the off-axis generating direction through the output terminal of the comparator CP ₁ , and the motor driving circuit 7 resists the output of the comparing circuit 6. (R _7), a ground capacitor (C ₁₎ and a resistor (R ₈₎ being applied to the non-inverting input terminal (+) of the operational amplifier (OP ₄₎ through, and the operational amplifier collector to an output terminal, each of (OP ₄₎ To the bases of transistors Tr ₁ and Tr ₂ connected to the power terminals of the motor 8 by connecting the power supply terminals (+ V) and (-V) to the power supply terminals of the motor 8. Tr ₁ ), (Tr ₂ Resistor (R ₉ ) and condenser (C ₃ ) are connected in parallel between the emitter common connection point, the base common connection point, and the inverting input terminal (-) connecting the ground resistance (R ₁₀ ) of the operational amplifier (OP ₄ ). It is configured to drive the pick-up movement motor 8 forward / reverse rotation according to the output of the comparison circuit (6).

The operation and effects of the off-axis correction apparatus of the present invention MDP configured as described above are as follows.

First, in the case of the principle of correcting off-axis, as shown in FIG. 3a, when the upper portion of the radial beams A and C occurs, the area occupied by the track does not occur. Since the amount becomes larger than the case, the light amount of the beam A and the beam C becomes smaller than when the off-axis does not occur.

In addition, when the off-axis occurs below the center of rotation of the disk as shown in FIG. 3b, the area occupied by the track among the areas of the beams A and C becomes smaller than the case where the off-axis does not occur. The amount of light in (A) and beam C becomes larger than in the case where off-axis does not occur.

Thus, by examining the light amounts of the beams A and C, it becomes possible to detect how much off-axis occurred in which direction relative to the center of rotation of the disc.

By using this principle, it is detected through the photodiode which is the radial light quantity detecting means (1) and (2). Among the three beams (A, B, C) irradiated from the pickup to the disk, the radial beams (A), ( C) is reflected from the disk and then received by the photodiodes 1 and 2. Accordingly, the output of the photodiodes 1 and 2 is determined by the amount of current proportional to the amount of light of the radial beams A and C reflected from the disk, and the amount of received light of the photodiodes 1 and 2 is determined. The current output proportional to is output as voltage through current amplifier (OP ₁ ), (OP ₂ ) and resistors (R ₁ ) and (R ₂ ) in the current follower (3) and (4) as voltage follower. The voltage outputs of the current-voltage conversion circuits 3 and 4 are added by the addition circuit 5, and are converted to a voltage proportional to the sum of the received light amounts of the radial beams A and C. The axis is output with a voltage value indicating how much is generated with respect to the center of rotation of the disc, and the addition circuit 5 is compared with the reference value in the comparison circuit 6. At this time, the reference value is set by the voltage _division of the supply voltage (V _CC ) of the resistor (R ₆ ) and the variable resistor (R _R1 ), which is the sum of the amounts of the radial beams (A) and (C) when no off-axis occurs. Since it is set to the voltage value corresponding to, the variable resistor V _R1 is adjusted to set the voltage value corresponding to the sum of the A and C beam light amounts when no off-axis occurs.

Accordingly, by comparing the voltage values proportional to the light quantity of the actually detected radial beams A and C, which are compared with this reference value, it is possible to know in which direction the off-axis generation occurred relative to the center of rotation of the disc. It becomes possible. In this way, when the off-axis occurs in the comparison circuit 6, a signal of information indicating in which direction the off-axis occurs on the basis of the center of the disk rotation is output, and the motor driving circuit ( 7) drives the pickup movement motor 8 in a direction in which the off-axis is compensated. I.e. off as in 3b also - if the axis caused by the lower than the disc rotation center, the ray amount of the radial beams (A), (C) is an off-so increases as the day has not been axis occurs, the comparator (CP ₁ As the input of the inverting input terminal (-) of the 1) becomes large and outputs a low potential signal accordingly, the output of the comparator CP ₁ becomes a low potential signal, so that the operational amplifier OP of the motor driving circuit 7 ₄ ) compensates for the off-axis since the PNP transistor T _r1 is turned on with the low potential output to drive the motor 8 in the reverse direction.

On the other hand, another embodiment for compensating off-axis in accordance with the present invention is to provide an error gain correction circuit 12 to the output of the tracking error detection circuit 11 for detecting the tracking error from the pickup as shown in FIG. In the tracking correction device for correcting the tracking in the tracking correction circuit 13 by correcting the error gain, the off-axis amount output from the fifth degree addition circuit 5, which is the off-axis amount detection circuit 14, is output. Is input to the error gain correction circuit 12 to correct the tracking error gain in accordance with the off-axis amount and output to the tracking correction circuit 13.

In another embodiment of the present invention thus constructed, when off-axis occurs, it is intended to correct this by influencing the tracking to actually follow the track correctly. Tracking correction does not drive the pickup itself by the amount of off-axis, but adjusts the gain value of the tracking servo. When the off-axis occurs above the disk rotation center as shown in FIG. 3a, the servo gain value is turned off. If the off-axis occurs below the center of rotation of the disc as shown in FIG. 3b, the servo gain value is higher than the absence of the off-axis to compensate for the tracking, thereby effectively reducing the off-axis. You can compensate.

As described above, conventionally, a method of mechanically measuring and fixing a pickup so that the movement path of a pickup that detects a signal coincides with the center of rotation of the disk is used. Although it was not possible to remove and change the position of the pickup during use, or the disc itself was bent, it was difficult to accurately detect the signal by off-axis. By driving the axis in the direction to be calibrated, the tracking servo gain is adjusted, and the set is continuously performed during the operation according to the off-axis amount, so that the signal can be detected more accurately. It has the effect of improving sound quality.

Claims (5)

Radial beam light amount detecting means (1), (2) for detecting the amount of light reflected from the disk of the radial beams (A) and (C) as the amount of current among the three beams (A, B, C) irradiated to the disk from the pickup. And the current-voltage conversion circuits 3 and 4 for converting the output of the radial beam light quantity detecting means 1 and 2 into voltage, and the current-voltage conversion circuits 3 and 4, respectively. And an output circuit 5 for outputting a voltage proportional to the sum of the amounts of the radial beams A and C, and the output and off-axis of the adder circuit 5 are not generated. The comparison circuit 6 for comparing the reference voltages corresponding to the radial beams (A) and (C) amounts of light at the time and the pickup movement control motor 8 according to the output of the comparison circuit 6 The off-axis correction device for a multi-disc player, characterized in that the motor drive circuit (7) for driving in the direction to be corrected. An off-axis correction apparatus for a multi-disc player according to claim 1, wherein the radial beam light amount detecting means (1) and (2) are photodiodes, respectively. 2. The motor driving circuit (7) according to claim 1, wherein the motor driving circuit (7) applies the output of the comparing circuit (6) to the non-inverting input terminal (+) through a resistor (R ₇ ), a ground capacitor (C ₁ ) and a resistor (R ₈ ). receiving an operational amplifier (OP ₄₎ outputs, each power supply terminal (+ V), the terminal to the collector of the (- V) commonly connected to the base of a transistor (T _r1) connected to a, (T _r2) and the transistor (T _r1) Connect the emitter of (T _r2 ) to the drive power supply terminal of the motor (8), and connect the resistor (R ₁₁ ) and the capacitor (C ₂ ) in parallel with the base common connection point. And a resistor (R ₉ ) and a capacitor (C ₃ ) connected in parallel between the common connection point and the inverting input terminal (-) connecting the ground resistance (R ₁₀ ) of the operational amplifier (7). Player's off-axis correction device. The tracking correction device detects the tracking error from the pickup through the tracking error detection circuit 11 and then corrects the tracking surge gain through the error gain correction circuit 12 to perform tracking correction through the tracking correction circuit 13. The amount of light reflected from the disks of the radial beams A and C through the off-axis amount detection circuit 14 is detected and detected as a voltage proportional to the sum of the amount of light. 12) The apparatus for compensating for off-axis in a multi-disc player, characterized in that the tracking servo gain is corrected in the direction of correcting the off-axis amount when the tracking error gain is corrected. 4. The radial beam light quantity detecting means (1) or (2) according to claim 3, wherein the off-axis amount detecting circuit (14) detects the amount of light reflected from the disk of the radial beams (A) and (C) as a current. And current-voltage conversion circuits 3 and 4 for converting the outputs of the radial beam light quantity detection means 1 and 2 into voltages, and the current-voltage conversion circuits 3 and 4, respectively. And an addition circuit (5) which adds the output of the circuit and outputs the voltage in proportion to the total amount of light detected.