JPH10112040A - Offset and balance correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely compensate for the offset and the unbalance in a short time in the device which is used in an optical disk recording and reproducing device that normally requires a long compensation data deciding time. SOLUTION: The device consists of two head amplifier output signal amplifying sections, two offset correcting sections 4 and 5 which correct the offsets in the outputs of the amplifying sections above, two balance correcting sections 8 and 9 which correct the gain unbalance of the outputs of the sections 4 and 5 and a differential section 12 which takes the difference of the outputs of the sections 4 and 5. By conducting the offset and the balance correction data changing operations in a completely independent manner, the offset and the balance correction data are precisely determined in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset and balance correction device for an information recording / reproducing apparatus such as an optical disk.

[0002]

2. Description of the Related Art In recent years, offset and balance correction devices have been used for improving the servo performance of optical disk recording and reproducing devices. Hereinafter, a conventional offset and balance correction device will be described. FIG. 2 shows a block diagram of this conventional offset and balance correction device. In FIG. 2, 21 is an optical head, 22 and 23 are amplification units, 24 and 25 are balance correction units, 26 and 27 are balance correction data, 28 is a differential unit, 29 is an offset correction unit, and 30 is offset correction data. is there.

The two outputs output from the optical head 21 are amplified by amplifiers 22 and 23, and then the gain balance is corrected by balance correctors 24 and 25. The difference between the two signals is output by a differential unit 28. And then the offset correction unit 2
At 9, the offset is corrected and output as an error signal. The offset correction data 30 is determined so that the error signal is zero when there is no reflected light from the optical disk and there is no input from the optical head, that is, when the defocus state or the read beam is off.
And 27 are determined so that the state of the reproduced signal when the optical disk is reproduced is optimized.

[0004]

However, in the above-described conventional configuration, the offset correction data 30 is determined in a defocused state, and the order in which the balance correction data 26 and 27 are determined after the reproduction of the optical disk is performed. Since the balance correction section is provided before the offset correction section, if the balance correction data 26 and 27 are changed, the offset correction data 30 must also be changed, and the offset correction data 30 and the balance correction data 26 and 27 are alternately driven. I have to adjust it. For this reason, it is necessary to repeat the optical disk reproduction state and the defocus state, and the time for determining the correction data becomes extremely long.

[0005] Further, when a method of turning off the read beam for a short time is used, it is impossible to correct an offset due to stray light inside the optical head. When the balance correction processing is performed by an analog circuit, there are many disadvantages that a large offset is added and a dynamic range of an error signal output is narrowed.

An object of the present invention is to provide an offset and balance correction apparatus capable of determining offset correction data and balance correction data in a short time and with high accuracy.

[0007]

In order to achieve this object, an offset and balance correction device according to the present invention comprises two head amplifier output signal amplifiers, two offset correction units for correcting the output offset, and It has a configuration including two balance correction units for correcting the gain balance of the output and a differential unit for obtaining the difference between the outputs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, two head amplifier output signal amplifying sections, two offset correcting sections for correcting an output offset, and a gain balance of the output are corrected. And a differential unit for obtaining a difference between the outputs of the offset and balance correction units. Since the offset correction unit is disposed in front of the balance correction unit, an offset correction data change operation and an offset correction data change operation are performed. The operation of changing the balance correction data can be performed completely independently, and has the effect that the offset correction data and the balance correction data can be determined in a short time and with high accuracy.

According to a second aspect of the present invention, there is provided the offset and balance correcting apparatus according to the first aspect, wherein the error signal amplifying section is constituted by an AD converter, and all subsequent processing is digitally processed. Digital processing can accurately realize offset correction and balance correction, and has an effect that a large dynamic range can be secured.

According to a third aspect of the present invention, the data for offset correction and balance correction determine a plurality of data for a plurality of conditions, and use the data in accordance with each condition. Item 1. The offset and balance correction device according to Item 1, which has an effect that a stable operation can be realized even when a laser power for recording and reproduction changes and a correction condition changes.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an offset and balance correction device according to a first embodiment of the present invention. In FIG. 1, 1 is an optical head,
Includes a laser as a light emitting source, an incident optical system for focusing the laser on the information recording medium, a reflecting optical system for guiding the reflected light from the information recording medium to the photodetector, and an amplifier that amplifies the outputs of multiple photodetectors. However, it is not shown here because the configuration is not directly related. Reference numerals 2 and 3 denote an AD converter, 4 and 5 denote offset correction units, 6 and 7 denote offset correction data, 8 and 9 denote balance correction units, 10 and 11 denote balance correction data, and 12 denotes a differential unit.

The operation of the offset and balance correction apparatus of the present embodiment configured as described above will be described below. In FIG. 1, the same processing is performed for the output of the optical head 1 used for focus servo, tracking servo, tilt servo, and the like. Here, the focus servo will be described as an example. The two outputs of the optical head 1 are A / D converted by the A / D converters 2 and 3, and then the offset is corrected by the offset correctors 4 and 5, then the balance is corrected by the balance correctors 8 and 9, and the difference is calculated. The difference is taken by the moving unit 12 and output as an error signal.

At the stage before the reproduction of the optical disk, the AD conversion unit 2
And 3, the offset correction data 6 and 7 are determined by adding and subtracting the correction data so that the outputs of the offset correction units 4 and 5 become zero. The product magnification is determined so that the amplification factor of the balance correction data 10 and 11 is changed so that is best. Since the offset and balance correction operations are now completed, the correction operations are completed in a much shorter time than in the conventional example. Here, the quality of the reproduced signal is such that the amplitude of the signal is maximum and the error rate is minimum in the case of a digital signal, but the more important one can be selected under the conditions required for the apparatus.

According to the present invention, it is not necessary to turn off the read beam during the offset correction processing, so that the offset due to stray light in the optical head can be corrected at the same time. However, when the power of the read beam changes, such as when recording on an information recording disk, the amount of stray light also changes accordingly. Therefore, a plurality of offsets corresponding to various read beam outputs are provided before the optical disk is reproduced. The correction data may be determined and used by switching between reading and writing.

Further, the output of the optical head 1 is digitized by the AD converters 2 and 3, which are the first stage of the error signal generation processing, and the subsequent offset correction processing and balance correction processing are carried out by digital calculation, whereby each processing block is processed. A large dynamic range can be secured by setting the occurrence of offset at 0 to zero. As described above, according to the present embodiment, two head amplifier output signal amplifiers, two offset correctors for correcting the output offset, two balance correctors for correcting the output gain balance, With the configuration including the differential section that takes the difference between the outputs, the offset correction section is arranged before the balance correction section, so that the offset correction data change operation and the balance correction data change operation can be performed completely independently. The offset correction data and the balance correction data can be determined in a short time and with high accuracy. In the above description, two head amplifier outputs are taken as an example. However, even when four outputs are added two by two and differential operation is performed after that, four offset corrections are provided or two outputs are added after addition. A similar effect can be obtained by a configuration such as performing balance correction after addition after performing one offset correction, and the scope of the present invention is obvious even in the case of a servo system using two or more head amplifier outputs. It is.

[0016]

As described above, the present invention provides two head amplifier output signal amplifiers, two offset correctors for correcting the output offset, and two balance correctors for correcting the output gain balance. And a differential section that takes the difference between the outputs, the offset correction section is arranged before the balance correction section, so that the offset correction data change operation and the balance correction data change operation are completely independent. Therefore, an excellent offset and balance correction device that can determine offset correction data and balance correction data in a short time and with high accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an offset and balance correction device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional offset and balance correction device.

[Explanation of symbols]

 Reference Signs List 1 optical head 2, 3 AD conversion unit 4, 5 offset correction unit 6, 7 offset correction data 8, 9 balance correction unit 10, 11 balance correction data 12 differential unit

Claims (3)

[Claims] 1. A difference between two head amplifier output signal amplifiers, two offset correctors for correcting an output offset, two balance correctors for correcting a gain balance of the output, and a difference between the outputs. An offset and balance correction device including a differential unit. 2. The offset and balance correction device according to claim 1, wherein said error signal amplifier is constituted by an AD converter, and all subsequent processing is digitally processed. 3. The offset and balance according to claim 1, wherein a plurality of data is determined for a plurality of conditions for the offset correction and the balance correction, and the data is selectively used in accordance with each condition. Correction device.