JPS5948835A - Controller of servo loop characteristics - Google Patents

Abstract

PURPOSE:To regulate easily the loop characteristics, by comparing the input signal applied to an input terminal to an end of a prescribed separated part of a servo loop with the synthetic signal of said input signal and the output signal of an oscillator through a buffer circuit and a rectifying circuit. CONSTITUTION:A prescribed part of a focus servo loop is separated, and a terminal 31 is connected to this separated part. A focus signal Si is sent to a buffer circuit 43 via an operational amplifier 32, and at the same time a measuring frequency signal Ss is delivered from an oscillator 36 and synthesized with the signal Si via operational amplifiers 37 and 35 and sent to a buffer circuit 42. The outputs of circuits 42 and 43 are sent to a comparator 48 via BPF44 and 45 and rectifier circuits 46 and 47. Then the difference of the peak-to-peak value between the signal Si and the output signal So of the terminal of a servo amplifier 41 is fed to a null meter 49. This difference is measured to regulate easily the servo loop characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a device for adjusting the loop characteristics of a servo loose on an electrical circuit.

BACKGROUND TECHNOLOGY AND PROBLEMS There is known a digital audio disc reproducing apparatus that optically reproduces a PCM audio signal from a disc on which the audio signal is converted into PCM and recorded in the state of a digital signal.

In this type of playback device, a focus servo circuit is provided to ensure that the light is focused correctly on the signal recording position of the disc, and a focus servo circuit is provided to ensure that the light scans the signal recording position correctly. Toratsuki/gusavo is applied.

An example of this servo circuit is shown below.

FIG. 1 shows an example of an optical system of this digital audio disc reproducing apparatus, and (1) shows a disc. On this disc (1), pits are formed in accordance with the PCM audio signal, and the PCM audio signal is recorded thereon.

(2) is a semiconductor laser as a light source, and the laser beam enters the collimating lens (4) via the guiding plate (3), which converts it into a parallel beam, which is then transformed into a beam splitter (5). ) K: The beam passes through the incident wave plate (6) and enters the objective lens (7). On the other hand, the reflected beam from the disk (1) returns to the beam splitter (5), is reflected at the beam splitter (5), and enters the light receiving section (9) through the lens (8L) and the cylindrical lens (8).

The objective lens (7) is attached to the QOI so as to be movable in a direction perpendicular to the surface of the disk (1) and in a direction perpendicular to the surface of the disk (1).

This drive mechanism αQ includes a drive coil (IOA) for moving the lens (7) in a direction perpendicular to the disk surface, and a drive coil (IOA) for moving the lens (7) in a direction perpendicular to the disk surface. A driving coil (IOB) is provided for moving the object in a direction parallel to the , and a servo voltage is supplied to these driving coils (IOA) (IOB) to perform autofocus and tracking control.

In signal reproduction, it is well known that the light that hits the pits of the disk (1) is hardly reflected as light, whereas the light that hits the non-pits is totally reflected. Since the light returns through the objective lens (7) and enters the light receiving section (9), it is detected as the rOJ rlJ signal as the output of the light receiving section (9).

Next, the servo circuit will be explained. FIG. 2 shows a system diagram of the servo circuit.

By the way, in this case, the light receiving section (9) has four photodiodes A, B, C, and D arranged in a rectangular shape as shown in the figure, as shown in FIG. Four light-receiving elements, namely photodiodes A, B, and C
, D are provided with two other photodiodes E and F as light receiving elements.

First, the focus control servo will be explained.

As described above, the reflected light from the disk fl is incident on the light receiving section (9) via the silica/trical lens (8). This cylindrical lens (8) has a semicylindrical shape, and not only functions to focus the beam onto the light receiving section (9), but also determines the focus state of the beam on the disk (1). It also plays a role in knowing what is going on.

In other words, this cylindrical lens (8) causes the spot shape of the beam that passes through it to be as shown in Figure 3.
When the focus is exactly right, it becomes a perfect circle, but if it deviates from that point, it becomes an ellipse. Therefore, in this case, when the beam 7J'' is just focused on the recording surface of the disk (1), the light receiving section (9) is arranged at a position where the beam passing through the cylindrical lens (8) is just focused.

Furthermore, the four photodiodes A and B of this light receiving element
, C, and D so that the beam hits where they cross.

In this way, when the beam just focuses on the recording surface of the disk (1) (well, as shown in No. 4141 B, there are four photo dies *--) 'A, B, C, and D. . If the recording surface of the disk +1) is too close to the lens (7), the focal power will be focused in front of the light receiving part (9), so the beam spot will be a vertically long ellipse at the position of the light receiving part (9). So, there are 4 dies, 3--4゛A, B
.

Among C and D, the outputs of A and C are large, and the outputs of B and D are small. On the other hand, disk (1) H self record 1fIi
7! Since the beam that does not reach the l' lens (7) will be focused at 1111 behind the light receiving section (9), the beam splitter will also become a horizontally long ellipse at the position of the 1 light receiving section (9), and 4 ( Among the +41 third diodes A, B, C, and D, the outputs of B and D are large, and the outputs of A and C are small.

From the above, four photodiodes" A, 1
3.

Autofocus can be achieved by controlling the C and D outputs to be the same.

Therefore, in this example, it is configured like an arrow. That is,
The output SA to the photodiode and the output SC of the 7-A-to-diode C are added together in an adder (I).
The output SA + SC is supplied to the non-inverting input terminal of the differential Angumino, and the output sB of photodiode B and the output SD of photodiode D are added in an adder ([3), and the output sB + SD is differential amplifier 02)
is supplied to the inverting input terminal of

Therefore, as shown in Figure 4, the shape of the beam spot changes depending on the relative positional relationship between the disk (1) and the objective lens (7), so the disk (1) is too close to the differential amplifier Oa. If the disk (1) is too far away, a negative DC pressure -V is obtained (C), and at the focal position, the output is It becomes zero (B in the same figure).

The output of the differential amplifier 0 is supplied through the RF amplifier 04) to a gain adjustment section consisting of a variable resistor 0 and an amplifier (I6).

Then, the output of this amplifier (I6) passes through the focus drive amplifier (17) to drive the objective lens TN4'#
(fO) objective lens (driving coil for moving the force in the direction perpendicular to the disk (1) surface)
IOA).

The above loop controls the objective lens (7) to be at a position where the beam is just focused on the recording surface of the disk (1).

Next, the tracking servo will be explained. Before explaining this tracking servo, the beam from the optical image (2) is actually not one beam, but a grating grating (3).
It is divided into three beams by passing through it. Then, among the three beams, one beam is set so that it hits the bit of the disk (1) correctly, and the other two beams are spaced a little apart from each other, and the other two beams are set so that they hit half of the pit. They are arranged in a staggered manner. The state is shown in FIG. In the figure, P indicates a pit and B11B21B3 indicates a beam spot. Here, the beam (spot B1) that correctly hits the bit will be called the main beam, and the other two beams will be called the sub-beams.

'Then, for the photodiodes arranged as shown in FIG. One of the sub-beams is incident on photodiode E, and the other is incident on photodiode F.

If the beam tracking position is correct, as is clear from Figure 5, the output from the two sub-beams will be slightly attenuated compared to the main beam, but the output from both sub-beams will be approximately the same. balance. On the other hand, if the tracking position shifts, one sub-beam will be applied more to the pit, and the other will be applied less to the pit, resulting in a state where one sub-beam increases and the other attenuates, resulting in an unbalanced state. A balance arises. By correcting this by 1, tracking control can be achieved.

Therefore, as shown in FIG. It is supplied to the gain adjustment section consisting of the amplifier (c) and the amplifier (2).Then, the amplifier (24)
The output of the objective lens (7) is driven by the tracking drive amplifier (c), and the objective lens (7) of the objective lens (7) is moved in a radial direction within a plane that is half a line along the recording surface of the disk (1). Drive coil (IOB) for
supplied to In this way, a servo loose is formed, and tracking servo is applied to the objective lens (force position) so that the main beam hits the pit correctly.

By the way, when adjusting the gain characteristics of such a servo loose, conventionally a servo analyzer was used for one loop, the human output characteristics were measured against disturbances, and the adjustment was made by reciting the values. was. Incidentally, the adjustment is performed using the above-mentioned adjustment port and resistor (151).

However, this conventional method has the disadvantage that the servo analyzer is a very expensive % measurement, ltz, and must read the measured values. Therefore, the setting is very troublesome and the adjustment is very difficult.

Purpose of the Invention The present invention enables the A adjustment of the loop characteristic in one -v-water circuit of the loop circuit as described above to be easily and accurately adjusted using a simple device with extreme pressure. This is what we are trying to provide.

SUMMARY OF THE INVENTION The present invention includes an input terminal to which a servo loop is separated at a predetermined portion and one end thereof is connected;
It has an output terminal connected to the other end and a built-in oscillator, and the input signal through the input terminal is supplied to the rectifier circuit @1 via the first buffer circuit, and the input signal is supplied to the rectifier circuit @1 according to the level of the human input signal. On the other hand, the input signal and the output signal of the oscillator are combined, and the combined signal is supplied to the output terminal, and the combined signal is supplied to the first DC signal via the second buffer circuit. The first DC signal and the second DC signal are supplied to a level comparison circuit, and the comparison output is used as a null meter. The present invention provides a servo loop characteristic adjusting device in which a servo loop characteristic is driven, and thereby the servo loose characteristic can be adjusted easily, inexpensively, and accurately.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking as an example a case in which an embodiment of the present invention is applied to a focus control servo circuit and a tracking servo circuit of an optical disk reproducing apparatus as described above.

In this process, an adjustment jig according to the present invention is connected to a part of the servo yarn loop.

For example, in the circuit shown in FIG. 2, for the focus servo loop, the RF amplifier (141) and the variable resistor a4 are disconnected, the terminals U31Q and I are provided at the disconnected part, and the RF amplifier (1, 4) Connect a jig between the terminal (1) and the variable resistor (terminal H on the I51 side. Similarly, for tracking servo looseness, connect the jig between the RF amplifier (2) and the variable resistor (c). Cut it, install terminals (26) (27) on the cut part, and connect a jig between the terminal C41iJ on the smell side of this RF' amplifier and the terminal (5) on the variable resistor (second theory side). It is.

Next, FIG. 7 shows an example of a jig for connecting between terminals -H and 06) (2D) as described above.

In the same figure, 0D is an input terminal connected to the terminal - or terminal (A) of the servo loop to be adjusted, and this input terminal C
31) is supplied to the operational amplifier C33. The output end of this operational amplifier (33) is grounded through a series circuit of a resistor (T) and C34. Then, the signal obtained at the connection point between the resistor and (34) is the operational amplifier c
351 is supplied to one input terminal.

(g) is the oscillator of the signal of the frequency to be measured in this servo loop, and the output signal SS of this oscillator 06) is an operational amplifier. ) and this op amp 6
The output of 7) is supplied to the other input terminal of operational amplifier G39 via a resistor. A resistor 01 is connected between the output terminal of this operational amplifier I3■ and the other input terminal.

From the operational amplifier (c), the signal S from the input terminal C31)
A signal is obtained by combining i and the oscillation output SS of the oscillator (to), and this combined signal SO is supplied to the output terminal (4υ) through the operational amplifier (40).This output terminal (41) is connected to the servo loop to be adjusted. terminal 09 or terminal (27
).

In this adjustment jig, the level of the human input output at that time is compared and the difference is displayed to know and adjust the gain of the servo loop.

That is, for example, the terminal - in the focus servo loop is connected to the input terminal c31), and the terminal 091 is connected to the output terminal (4).
When detected at υ, the human input signal Si through operational amplifier c (2) and the composite signal SO from operational amplifier OQ are transferred to From this, only the measurement frequency component from the oscillator (to) is obtained, which is then supplied to the rectifier circuits (46) and (47) to obtain DC voltages corresponding to the respective signal levels.These rectifier circuits The output voltages of (46) and (47) are supplied to the comparator circuit (mark 4) to obtain the difference between the two voltages, which is supplied to the null meter (mark 4) and appears as its swing.

That is, what corresponds to the difference in peak-to-peak value between the input signal 8i to the terminal C31) and the output signal So of the terminal (4υ) appears in the null meter (4ω).

In this case, the variable resistor 6 is used to stop the value of the null meter 09) at that time according to the frequency to be measured.
[Adjust bias offset.

After calibrating the null meter (4Q) in this way, the gain of the servo, that is, the one-loop characteristic can be adjusted by simply measuring the deflection of this meter (49).

In this case, when the m anti-G33 (341G31H31(') values are R1, R2, R3, and R4, R1= R2=
It3==Selected as R4.

As a result, the operational amplifier 69 and these resistors (Kari G34)
The gain G of the amplifier consisting of c3al and C41 is as follows.

With this configuration, open loop characteristics can be measured and adjusted without adversely affecting the servo circuit path.

In other words, in order to measure and adjust the open-loop gain characteristics, it is sufficient to find the voltage difference between point A and point B (buffer circuit (4th floor output end is also acceptable) in Figure 7. ,
To do this, it is sufficient to insert a resistor between the image points and measure the pressure between the two ends of the resistor and the ground. However, when doing so, there are 5 small sections where the servo circuit path becomes impaired.

On the other hand, in this case, the gain G=
1 buffer amplifier is provided, which makes it possible to measure the ground pressure at both points A and B, and mix the oscillation output of the oscillator 06) without adversely affecting the servo circuit. It is something that can be done.

In addition, the i?f signal obtained at each of the output terminals of the measuring points A and B (Fig. 7) or the buffer circuit (4a) is supplied to the phase comparator, and the null meter is operated by the comparison output. By doing so, the phase adjustment of the servo yarn can be easily performed.

Effects of the Invention As described above, according to the present invention, loop characteristics can be easily adjusted without using an expensive servo analyzer. Moreover, in this invention, the open loose gain can be adjusted in a closed loop state.

Furthermore, since adjustments can be made while looking at the null meter, adjustments can be made even if one is not an experienced adjustment person, and the coffin preparation time is also extremely shortened. Another advantage is that setting for adjustment is much easier than in the past.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of a main part of a device to which this invention is applied, FIG. 2 is a system diagram of an example of a servo loop to which this invention is applied, and FIGS. 3, 4, and 5 6 and 6 are diagrams for explaining the servo operation, and FIG. 7 is a system diagram of an example of the main part of the present invention. 81) is the input terminal, country! 9 t37) is an operational amplifier,
(1) is an oscillator, (4I) is an output terminal, and (49) is a null meter. Same as Hidemori Matsukuma-3 (1°I... PaI) 1. Figure 1. Figure 2. Figure 4. Please follow the instructions. Figure 5.

Claims (1)

[Claims] The servo loose is separated at a predetermined portion and includes an input terminal to which one end is connected, an output terminal to which the other end is connected, and a built-in oscillator. An input signal through the input terminal is supplied to a first rectifier circuit via a first buffer circuit and converted into a first DC signal according to the level of the input signal, while the input signal and the oscillator are The output signals of are synthesized, and the synthesized signal is supplied to the output terminal, and the synthesized signal is also supplied to the second rectifier circuit via the second buffer circuit, and a second rectifier corresponding to the level of the synthesized signal is supplied. is converted into a DC signal. A servo loop characteristic adjusting device, wherein the first DC signal and the second DC signal are supplied to a level comparison circuit, and a null meter is driven by the comparison output.