JPS63214930A - Tracking error correcting circuit - Google Patents

Abstract

PURPOSE:To always obtain the constant amplitude of a tracking error signal by providing a differential amplifier which generates a control signal for controlling the amplification factor of a multiplier by subtracting an output from a sample hold circuit with a reference voltage. CONSTITUTION:The higher the amplification factor of the differential amplifier 1 is, the better it is, so that it is used at more than several tens fold factor. Thus, the variation of the amplitude of the corrected tracking error signal can be decreased. The output 9 from the differential amplifier 1 is increased as the amplitude of the tracking error signal 5 is lowered. Therefore, in the multiplier 2 the coefficient by which the tracking error signal is multiplied increases and the amplitude of the signal inputted in an envelope detector 3 increases, so that the control signal 9 is increased until the output 8 from the sample hold circuit 4 becomes nearly equal to the reference voltage. Thus, the amplitude of the corrected tracking error signal is kept always constant even if the amplitude of the tracking error signal 5 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording/reproducing device, and more particularly to an amplitude correction circuit for a tracking error signal.

[Conventional technology]

Conventionally, in this type of tracking/king control circuit, in order to keep the amplitude of the tracking error signal at a certain level in setting the servo gain during tracking/king, detecting track/off, etc. Trouble caused by light intensity fluctuations or media reflective curtain fluctuations.

The error signal is divided by the sum signal of the output of the sensor and the sensor so as to suppress the amplitude fluctuation of the error signal. Using a division type amplitude correction circuit to suppress fluctuations in the tracking error signal and adjusting the imaging width using a variable resistor etc., the Taboroog gain can be set to within a certain standard value. In addition, in detection of tracking errors, if the tracking error signal exceeds a certain level in millimeter, for example 50%, a error occurs.

The operating conditions of the device were set based on the amplitude of the tracking error signal, such as detecting an abnormality in the tracker or king servo.

Here, it is relatively easy to set the servo gain by keeping the amplitude of the tracking error signal constant if there are small variations in the shape of the track, crack, chip, group shape, etc. This is because it is easier to set the detection distance than by measuring the relationship between the detection distance and the signal amplitude.

[Problems to be Solved by the Invention] The conventional tracking error amplitude correction circuit described above only performs amplitude correction using a dividing type amplitude hydraulic circuit that divides by the amount of reflected light that causes a tracking error and a variable resistor. Although it is possible to correct variations in the amount of emitted light, such as fluctuations in the amount of emitted light, variations in medium characteristics, such as differences in the Bruch shape of the medium, differences in group formats, and inclination of the medium.

Damage to tracking error signals such as amplitude reduction due to bit formation! If @ fluctuates, it becomes difficult to correct it, and this causes a fluctuation in the Taborogue gain, resulting in a decrease in the compression ratio, or a decrease in the gain margin and phase margin, making it difficult to obtain stable tracking characteristics. I couldn't do it anymore.

In addition, when detecting tracking error, the amplitude of the tracking error signal fluctuates, so if the signal amplitude becomes too large, the detection range becomes relatively narrow. is more likely to occur. In the opposite case, the reliability of the device will be lowered as a result of failure to detect tracking or misalignment, and it is necessary to strictly control the medium conditions for device operation to reduce amplitude fluctuations of the tracking error signal. This was a factor that led to a decrease in fractionation.

[Means for solving problems]

The tracking error correction circuit of the present invention includes: a multiplier that multiplies a tracking error signal and a control signal to generate a corrected tracking error signal; an envelope detector that detects an envelope of the multiplier output; It has a sample hold circuit that holds the output of the wave detector, and a differential amplifier that subtracts the output of the sample hold circuit and a reference voltage to generate a control signal that controls the amplification factor of the multiplier.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention.

In FIG. 1, a tracking error signal 5 is input to a multiplier 2 and multiplied by a control signal 9 which is the output of a differential amplifier l. The output of multiplier 2 is the corrected tracking error signal l
It is output as O and is also input to the envelope detector 3. The output 6 of the envelope detector 3 is input to the sample hold circuit 4 and held only when the hold signal 7 is HIGH, and when the hold signal 7 is LOW, a signal equal to the input is output. The output 8 of the sample hold circuit 4 is subtracted from the reference voltage input to the differential amplifier IK, and is amplified to output a control signal 9. Here, hold signal 7 is a tiger,
When the king servo is OFF, it is LOW, and just before the reed, rear, and king servos turn ON, it becomes K) 11GH and holds the output of the envelope detector.

Next, the circuit operation will be explained with reference to FIG. First, consider the case where the tracking error signal crosses the track, and suppose that the amplitude changes as shown in 5. The output of the multiplier 2 is detected by the envelope detector 3, and the signal is detected as shown in the solid line of the signal 6. The output passes through the sample and hold circuit 4, is subtracted from the reference voltage input to the differential amplifier IK, and is amplified. At this time, the higher the amplification factor of the differential amplifier 1, the better, and it is used at several tens of times or more. By doing K like this, it is corrected.

Amplitude fluctuations in the king error signal can be reduced. The output 9 of the differential amplifier 1 is the tracking error signal 5
increases with decreasing amplitude. Therefore, the coefficient multiplied by the tracking error signal in multiplier 2 increases.
The signal amplitude entering the envelope AM waveform generator 3 increases, and the control signal 9 increases until the output 8 of the sample hold circuit 4 becomes approximately equal to the reference voltage #1. In this way, even if the amplitude of the tracking error signal 5 changes, the amplitude of the corrected tracking error signal always remains constant. Also, when turning on the tiger and king servos, turn on the hold signal 7 of the sample hold circuit 4 just before turning on 0NIC)
With IGHK, the previous state can be held, so it is possible to always obtain a constant amplitude of the tracking error signal.

Although the sample and hold circuit 4 is used in this embodiment, it is also possible to implement a configuration in which analog-to-digital conversion is performed, the output is stored in the hold IK register, and the register output is digital-to-analog converted and input to the differential amplifier l. .

〔Effect of the invention〕

As explained above, the present invention inputs a tracking error signal using a variable amplification amplifier using a multiplier, and changes the amplification factor of the multiplier so that the output envelope detection output always has a constant amplitude. With this configuration, even if the input tiger and dP songler signal amplitudes fluctuate, a stable constant amplitude can always be obtained. In addition, the sandal hold circuit is held when turning on the tiger and king servos. (Yofi) Since the amplitude can be maintained at the level just before it goes into the error, a stable amplitude error signal can be obtained. Therefore, there is no fluctuation in Taboroog gain due to fluctuations in the amplitude of the tracking error signal, and stable tracking characteristics can be obtained, as well as accurate setting and detection of the amount of positional deviation in level detection of the tracking and deviation detection circuits. It is possible. In addition, since there are no fluctuations in the amplitude of the tracking error signal due to medium reflectance fluctuations, group shape fluctuations, media rows (tilts), etc., there is no need to strictly adhere to the media specifications, improving the fractionation of the media and reducing the cost. In addition to being able to supply the medium, it also eliminates the need to adjust the amplitude of the tracking error signal, resulting in the advantage that an inexpensive device can be provided.

[Brief explanation of the drawing]

Figure 1 shows a diagram of the tracking error correction circuit of the present invention.
2 is an explanatory diagram of the operation of the present invention. 1... Differential amplifier, 2... Multiplier, 3
...Envelope detector, 4...Sample hold-path. +1++~ Agent Patent Attorney Susumu Uchihara 13 θ□ ff5;z Chu

Claims (1)

[Claims] A multiplier that multiplies a tracking error signal and a control signal to generate a corrected tracking error signal, an envelope detector that performs envelope detection on the output of the multiplier, and a sample hold circuit that holds the output of the envelope detector. and a differential amplifier that generates a control signal that subtracts the output of the sample and hold circuit from a reference voltage to control the amplification factor of the multiplier.