JPH03268231A - Brake circuit for optical pickup - Google Patents

Abstract

PURPOSE:To obviate the generation of an unnecessary signal in a brake signal by turning on and off the brake circuit at the timing of the edge of the output signal of a servo filter circuit. CONSTITUTION:The input to a waveform shaping circuit connecting to the clock input of an FF is made into not a TE (track error) signal but the output of the servo filter circuit where a phase delay already arises. All the tracking outputs act to be braked and the unnecessary signals are no longer generated if such constitution is adopted. The generation of the unnecessary part in the brake signal is, therefore, obviated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tracking servo for an optical pickup.
Especially regarding the brake circuit during truck jumps.

[Conventional technology]

FIG. 2 shows the brake circuit of a conventional optical pickup.

The optical pickup's RF' signal envelope circuit, the waveform shaping circuit 1 connected to it, and the tracking error signal (
A waveform shaping circuit 2 that receives the TE multiplied signal as input, an edge detection circuit connected to it, a data flip-flop that uses the output of the waveform shaping circuit 1 as data input, and the output of the edge detection circuit as clock input; It consists of a switch that allows the output of the tracking servo filter circuit that receives the double signal input to be output as is or to turn it off.

Next, the operation will be explained.

FIG. 5 is a diagram when a photodiode traces a pick on a track. RF double signal photodiode A
, B, C, and D, and similarly, it is obtained from the difference between the TE multiplied signal photodiodes E and F. Therefore, when the pickup is on the track, the RF multiplied signal amplitude becomes maximum and the TE multiplied signal becomes zero. Conversely, when the pickup is between tracks, the RF multiplied signal amplitude is minimum, and when the TE multiplied signal is exactly between tracks, it becomes zero, but otherwise it deviates from zero.

FIG. 4 is a timing chart of FIG. 3, showing that the pickup is jumping the truck. As the pickup moves on and off the track, the amplitude waves like the RF multiplied signal ■, and similarly, the TE multiplied signal zero is also sandwiched between them, as shown in ■.The envelope detection and waveform shaping circuit produce ◎ and ■. The output of the flip-flop becomes as shown in ■. The output signal of the flip-flop is used to turn off the output of the servo filter. When the pickup moves from the inner circumference to the outer circumference, the output of the tracking servo filter becomes like @, when it moves away from the track, it acts inward, and when it approaches the track, it acts outward. However, when the desired track jump is completed and the brakes are applied, this effort to move toward the outer circumference ends up being a hindrance. Therefore, the tracking servo is turned off during the period when the object is heading toward the outer circumference by the output of the flip-flop mentioned above.

Moreover, in the case of moving from the outer circumference to the inner circumference, this is completely reversed, and the operation to move toward the inner circumference becomes unnecessary and is turned off by the output of the flip-flop.

This is how the brakes are applied after a track jump.

[Problem to be solved by the invention]

In this conventional optical pickup brake circuit, there is a phase delay caused by the tracking servo circuit, so the tracking output waveform (■) has an unnecessary part that differs from the originally expected output, as shown in Figure 4. However, since this unnecessary part works to accelerate rather than control, there is a drawback that the pickup control period becomes long.

[Means to solve the problem]

The brake circuit of the optical pickup of the present invention includes an RF double signal envelope detection circuit of the optical pickup and a waveform shaping circuit connected thereto.1. A tracking servo filter circuit that receives a tracking error signal as an input, a waveform shaping circuit 2 that receives the output of this filter circuit as an input, and an edge detection circuit connected thereto, the output of the waveform shaping circuit 1 as a data input,
It is equipped with a data flip-flop that receives the output of the edge detection circuit as a clock input, and a switch that switches whether to output the output of the servo filter as it is or to turn it off based on the output of this flip-flop.

〔Example〕

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

FIG. 1 shows a brake circuit of an optical pickup according to an embodiment of the present invention.

The difference from the conventional example is that the input of the waveform shaping circuit 2 connected to the clock input of the flip-flop is not a TE multiplied signal, but is the output of a servo filter circuit in which a phase lag has already occurred. With this more configuration, all the tracking outputs act as if they were to be braked, as shown in FIG. 2, and no unnecessary signals are generated.

〔Effect of the invention〕

As explained above, the present invention has the effect that unnecessary portions are not generated in the brake signal because the brake circuit is turned on and off at the edge timing of the output signal of the servo filter circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a timing chart thereof. FIG. 3 is a block diagram of the conventional example, and FIG. 4 is its timing chart. FIG. 5 is a diagram when the optical pickup traces a track.

Claims (1)

[Claims] An envelope detection circuit for an RF signal of an optical pickup and a waveform shaping circuit 1 connected thereto, a tracking servo filter circuit that receives a tracking error signal as an input, a waveform shaping circuit 2 that receives the output of this filter circuit as an input, and an edge detection circuit connected thereto; It is characterized by comprising a data flip-flop which uses the output of the waveform shaping circuit 1 as a data input and the output of the edge detection circuit as a clock input, and a switch that switches whether the output of the servo filter is outputted as is or turned off according to the output of this flip-flop. Brake circuit for optical pickup.