JPH07141029A - Gain controller - Google Patents

Abstract

PURPOSE:To enable gain control so as not to listen to any noise of a disturbance source by supplying a disturbance signal to a servo loop when a regenerative output level corresponding to a read signal is higher than a prescribed value. CONSTITUTION:A reading means 2 reads information from a recording medium 1, a servo means 9 controls the position of the reading means 2 so that the reading means 2 can be positioned away from the recording medium 1 just for a prescribed distance, and a gain control means 8 changes the control by injecting the disturbance signal to the servo loop. Then, a level detection part 7 existent inside the gain control means 8 detects an audio signal level corresponding to the read signal provided from the reading means 2 and sets the gain control means 8 so as to generate disturbance when this level gets higher than an audio level at a certain degree so as not to make obvious noise caused by the injection of disturbance at the time of automatic gain control and therefore, the automatic gain control is performed only when the level is higher than that value. Thus, the noise caused by disturbance injection can be decreased in the sense of hearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called servo control device, and more particularly to a gain adjustment time control of a servo control device in an optical recording / reproducing device or the like.

[0002]

2. Description of the Related Art Usually a CD (Compact disk) or L
In an apparatus for recording and reproducing a disc such as a D (Laser disk), in order to accurately read information from a recording track on the disc, a pickup for reading, the speed of the disc, a track position, a lens focus, etc. are closed. Servo technology for driving and controlling by forming a circuit loop is important. In such servo technology, it is necessary to generate an error signal for a signal input from the pickup, and the error signal generating means needs to adjust the gain of the input voltage to an appropriate input voltage value. Therefore, an automatic gain adjustment (auto gain control) circuit that adjusts the gain according to the input signal is often provided.

Several devices have been devised as the automatic gain adjustment circuit. For example, there is a method in which the magnitude of the error signal is checked and the gain is adjusted to a magnitude suitable for input to the servo equalizer circuit. However, due to variations in the characteristics of pickups and circuits, and further temperature characteristics, the gain after servo closing may fluctuate significantly, making it impossible to perform optimum adjustment. In that case, a method of performing automatic gain adjustment using the disturbance source. Is excellent. this is,
Inject a disturbance whose magnitude and oscillation frequency are known using the disturbance source into the servo loop at an appropriate time, detect the disturbance signal that has passed through the loop at a certain time, and check the level to include the disk. The inherent gain of the loop is known, and the gain of the signal level is adjusted by an attenuator or the like to a level suitable for input to the servo equalizer as an error signal.

Conventionally, in the automatic gain adjustment device, the above-described gain adjustment is performed at an appropriate time before the reproduction of the disc is started. An example of this conventional timing is shown in FIG.
Shown in.

[0005]

However, in the conventional automatic gain adjusting device using the disturbance source, since the disturbance source is the oscillation of the audible frequency band, the pickup after the disturbance is injected is mechanically operated in accordance with this disturbance. Vibrate. However,
Because the vibration of the pickup due to disturbance occurs before the performance, there is a high possibility that the disturbance will leak as annoying noise,
In this case, there is a problem that the noise itself is heard as an offensive sound.

In FIG. 6 (a), the disc is set at, focus close is performed at, and the position of the lens in the pickup is focused on the track. Tracking is closed by and the pickup will follow the track. When the focus and tracking are controlled, automatic gain adjustment is performed (pulse in the automatic gain in the figure). However, the music starts to be heard from the speaker or the like after the beginning of the reproduced music is completed, and at the time of automatic gain adjustment immediately after, the MUTE signal is valid and still silent. In other words, the noise is heard as an offensive sound here.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic gain adjusting device that adjusts the gain without hearing the noise of the disturbance source.

[0008]

In order to achieve the above object, it is necessary to have a configuration in which an automatic gain adjustment is performed after detecting an audio level. Therefore, an object of the present invention is to provide a reading unit that reads information from a recording medium, a servo unit that controls the position of the reading unit so that the reading unit is located at a predetermined position corresponding to the recording medium, and a gain of the servo unit that is a disturbance signal. In an automatic gain adjusting device having gain adjusting means for adjusting and changing by injecting into a servo loop, the gain adjusting means determines whether or not a reproduction output level corresponding to a read signal obtained from the reading means becomes a predetermined value or more. This is achieved by a gain adjusting device that has a level detecting unit that detects whether or not, and supplies a disturbance signal to the servo loop when the reproduction output level is greater than or equal to a predetermined value.

[0009]

According to the present invention, the reading means reads information from the recording medium, the servo means controls the position of the reading means so that the reading means is located at a predetermined distance from the recording medium, and the gain adjusting means servo-loops the disturbance signal. Change the adjustment by injecting. Then, the level detection section existing inside the gain adjusting means detects the reproduction output level (audio signal level) corresponding to the read signal obtained from the reading means, and this level makes noise due to disturbance injection in the automatic gain control conspicuous. By setting the gain adjusting means so as to generate a disturbance when the audio level exceeds a certain level, the automatic gain control can be performed only when the audio level is higher than that.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to the drawings. In this embodiment, in the CD reproducing apparatus, the audio level is detected by the signal processing circuit, and the automatic gain adjusting circuit is activated when the audio level exceeds a predetermined volume level.

1 and 2 show the configuration of this embodiment. FIG. 1 relates to the whole form of a servo system. Regarding the flow of audio signal demodulation, a disc 1 of a recording medium on which a signal is recorded and a signal recorded from an information track of the disc 1 are read through a lens (not shown). Pick up 2
A feed (carriage) motor 3 for driving the pickup 2 in the diameter direction of the disc 1, a spindle motor 4 for rotating the disc 1, and a read-out signal read by the pickup 2 and binarized RF signal. In addition, a preamplifier 5 that outputs a focus error signal, a tracking error signal, and the like, and a signal (CLV) for speed control of the spindle motor 4 are generated from the binarized RF signal, and EFM demodulation is performed from the RF signal. , A signal processing circuit 7 which performs error correction decoding by CIRC and converts it into a 16-bit digital signal and sends it to the D / A converter 11, and which is inside the signal processing circuit 7 and detects the level of digital audio data, The 16-bit digital signal and the audio level detection unit 7'which outputs the detection signal to the microcomputer 6 are output. The D / A circuit 11 for converting into an analog signal and the audible frequency band is passed from the analog signal,
A low-pass filter (LPF) 12 that removes noise components and outputs an audio signal, a volume 13 whose actual output volume is adjusted by control of the microcomputer 6, an amplifier 14 that amplifies power of an audio signal, and an audio signal. And a speaker 15 that converts a signal into sound. The signal processing circuit 7 is connected to the data buffer 18 and reads / writes predetermined data.

The signal flow relating to the servo system includes the automatic gain adjustment block 8 for adjusting the gains of various error signals supplied from the preamplifier 5 and adjusting the gain to a predetermined signal level to the servo system, and for the servo. A servo equalizer 9 for adjusting the frequency of the pickup, a focus / tracking coil (not shown) of the pickup 2 for current amplification of the generated drive signal, a feed motor 3, and a spindle motor 4
A driver 10 for driving the computer, a microcomputer 6 for controlling the entire system, a key 17 for the user to control the microcomputer 6,
And a display system 16 for performing a simple status display.

The lens in the pickup 2 is the disc 1
Driven by a tracking coil (not shown) in the diametrical direction, and a focus coil (not shown) for focus control, servo information is sent from the track so that it has a proper positional relationship with a light receiving part (not shown). Driven by the system.

A detailed block diagram of the automatic gain adjustment block is shown in FIG. The automatic gain adjustment block 8 includes the preamplifier 5
Various error signals supplied from the servo equalizer 9
Attenuator 20 which functions to perform gain adjustment to an optimum level for input to the input terminal, appropriately changes the gain of the error signal by the attenuator control signal supplied from the microcomputer 6, and outputs the error signal, and the first branch from the output of the attenuator 20 (Y A gain change amount detection block 21 for detecting a gain change amount of an error signal including a disturbance that has made a loop, and an adder 30 for adding the disturbance from the disturbance source 29 to the signal from the Y branch. And a gain change amount detection block 21 ′ that branches (X-branch) from the output of the adder 30 and detects the gain change amount immediately after the disturbance is applied.
And, The disturbance source 29 is for adding a disturbance element having a fixed value (a constant frequency having a constant amplitude by an oscillator or the like) to the error signal and checking the level of the error signal which changes by the disturbance element. It is supplied to the adder 30 by a switch SW ₁ which can be disconnected.

Gain change amount detection blocks 21, 21 '
Has switches SW ₂ and SW ₃ for switching the circuit block to be used between coarse adjustment and fine adjustment. One of the fine adjustment (automatic gain adjustment) blocks is a bandpass filter 22 that passes the frequency band of the disturbance signal. And an absolute value circuit 23 for converting the signal into an absolute value signal, and a low-pass filter unit 24 for removing the frequency component of the disturbance signal and converting it into a digital signal for A / D conversion, and the other coarse adjustment block. Is a peak hold circuit 25 that holds the maximum value of the input signal, a bottom hold circuit 26 that holds the minimum value of the input signal, and a differential amplifier 27 that converts the difference (dynamic range) between the maximum and minimum values to a predetermined level. And an A / D converter 28 for A / D converting the dynamic range
And,

Next, the operation of this embodiment will be described based on the sequence of FIG. First, a disc is mounted (step S1). The microcomputer 6 controls the spindle servo system of the servo equalizer circuit 9 to start the spindle motor 4 (step S2). Next, the light reception of the pickup 2 is enabled and a focus search is performed (step S3). Here, although it is not the optimum value, the focus gain is roughly adjusted in order to apply the focus servo for the time being (step S4).

FIG. 4 shows a subroutine sequence for coarse adjustment of the focus gain. When coarse adjustment is started (step S
30), the level of the focus error signal is read (step S31). A signal having this level is input to the gain change amount detection block 21 (or 21 ') in FIG. The microcomputer 6 has a switch SW ₂ ,
SW ₃ is switched to the coarse adjustment block (b side), and the gain for the attenuator 20 is calculated according to the dynamic range input from the A / D converter 28 at this time.
The level is adjusted by the attenuator control signal (step S32), and this subroutine ends (step S33).

That is, the focus error signal level is F
If E, then FE = peak hold value−bottom hold value, from which the attenuator gain ATT may be calculated and controlled by ATT gain = FE standard target level / FE.

When the coarse adjustment of the focus gain is completed, the focus is closed and the focus servo can be performed (step S5). Next, in order to roughly adjust the tracking gain, a subroutine for rough adjustment is called as in the focus servo (step S6). The subroutine sequence for performing the coarse adjustment of the tracking gain is the same as the procedure for the coarse adjustment of the focus gain, and therefore will be omitted. As the tracking gain coarse adjustment sequence, the focus error in step S31 in FIG. 4 is changed to a tracking error and FE is changed to TE. The set value for the attenuator 20 in this case is also obtained from ATT gain = TE standard target level / TE.

The above-mentioned coarse adjustment of focus and tracking is necessary for a device or the like having a narrow attenuator setting range on the circuit, and can be omitted depending on the mode of the device.

Now, tracking close (step S
7) Then, the microcomputer 6 is the TOC of the disk.
Read the information (step S8). Then, based on the read TOC information, the beginning of the music is performed from the track number of the music to be reproduced, etc. (step S9), and the performance of the music is started (step S10). At that time, the microcomputer 6
Starts a timer whose length can be freely set by an internal clock (step S11). This timer may be operated to determine the time for performing automatic gain adjustment, and an interrupt process may be applied to the microcomputer 6 by using a timer-dedicated circuit, or the microcomputer 6 may count.

Next, it is checked whether or not there is an audio level detection signal input to the microcomputer 6 from the audio level detection section 7'of the signal processing circuit 7 (step S12). That is, it is determined whether or not the music information of the piece of music started to be reproduced and a predetermined signal level is sent to the analog system.

When the audio level is equal to or higher than the predetermined value (step S12: YES), the music level transmitted from the speaker 15 is equal to or higher than the predetermined level, and thus the automatic gain adjustment is started (step S13).

If the audio level is less than the predetermined value (step S12: NO), the sound heard from the speaker 15 is still small, so it is checked whether the timer has a margin without performing the automatic gain adjustment (step S14). If the timer has not timed out (step S14: NO), it waits until the audio level continues to rise (step S12). When time out occurs (step S
14: YES), it is determined that the audio level of the song does not rise, and automatic gain adjustment is started (step S1).
3).

When the automatic gain adjustment is completed, the next process is started (step S15). Now, a sequence of automatic gain adjustment is shown in FIG. First, the microcomputer 6 closes the switch SW ₁ and injects the disturbance signal generated by the disturbance source 29 into the adder 30 (step S21). At the same time, the switches SW ₂ and SW ₃ of the gain change amount detection block are switched to the side a so that the automatic adjustment block becomes effective. The error signal to which this disturbance value has been added is input from the X branch to the gain change amount detection block 21 'and measured by the microcomputer 6 (step S2).
2). At the same time, the signal subjected to the disturbance from the X branch is supplied to the servo equalizer 9 and applied from the driver 10 to the pickup 2. Then, the lens is driven according to the disturbance to cause a slight change. The error signal changes according to this slight change, and is input again to the automatic gain adjustment block 8 via the preamplifier 5. The microcomputer 6 sets the value of the attenuator 20 to a fixed value (for example, gain 1) by the attenuator control signal. Then, the signal input to the Y branch through the servo loop is examined by the gain change amount detection block 21 (step S22). The disturbance source oscillates a constant frequency with a constant amplitude, but since the bandpass filter 22 passes only the oscillation frequency of this disturbance source, even if there is information in the track,
Only the disturbance value can be input and measured. Here, the gain of this loop is from the X branch to the microcomputer 6
If the input to the microcomputer 6 is X and the input to the microcomputer 6 from the Y branch is Y, then gain = Y / X is obtained. The X and Y measurement results are stored in the data buffer 18.

Next, the gain calculation in step S22 is measured several times (five times in this embodiment) and averaged, so the number of measurements is recorded (step S23). This counter is an operation in which the initial value is set to zero and the counter is incremented by one (count is incremented by 1). Then, the number of measurements is checked (step S23), and a predetermined number of times (5 in this embodiment)
Times. ) Less (step S24: NO), the measurement is performed again (step S22). When the predetermined number of times has been reached (step S22: NO), a calculation for averaging the measured values of the past number of measurements from the data buffer 18 is performed (step S25).

Since it has been experimentally known that a stable servo condition is that the fluctuation range of the input gain is within 1 dB, the gain width of the calculated values averaged in this way is checked (step S26). ), If the fluctuation range due to the vibration of the lens due to the disturbance is larger than ± 1 dB (step S26:
NO), the gain of the attenuator 20 is readjusted in the direction in which the fluctuation range is within ± 1 dB (the direction in which the gain is decreased) (step S27), and the average value is calculated again (step S2).
2).

When the fluctuation range is within ± 1 dB (step S26: YES), the switch SW ₁ is cut off and the injection of the disturbance source is stopped (step S28). Subsequently, the gain set in the attenuator 20 at this time is stored in a RAM or the like (not shown) and the process proceeds to the next step (step S29).

FIG. 6B shows a timing chart of the result of this embodiment. Assuming that the audio level determined in step S12 is Gs, cueing of the reproduced music starts as shown in the figure, the MUTE signal is invalidated, and sound is output from the speaker 15, which is determined by the signal processing circuit 7. When the level exceeds Gs, automatic gain adjustment is performed. Since the audio level is above a certain level, the noise related to the automatic gain adjustment is inconspicuous.

As described above, according to the present embodiment, it is possible to know the timing at which the automatic gain adjustment due to the disturbance in which noise occurs should be performed by detecting the audio level, and when the audio level is high, the noise is not noticeable. Automatic gain adjustment is possible.

Further, even if the audio level is low, the gain adjustment is performed in a closed manner, so that stable servo performance can be prioritized. Further, since the gain adjustment value is stored, the stored value can be used at the time of replay (replay) unless the disc is removed, and the procedure for automatic adjustment can be omitted, and the time until playback can be reduced. Can be shortened. Other Modifications The invention of the present application is not limited to the above embodiment and can be applied to various devices. For example, the audio level detection is detected by the signal processing circuit 7. However, the audio level detection may be detected at any place after the signal processing, and determination is made by simply inputting the high-order few bits of the digital audio signal to the microcomputer 6. Yes, in this case the circuit is simple. Further, in order to make the disturbance frequency particularly inconspicuous, the specific frequency may be detected by a bandpass filter or the like from the analog system, and may be performed when the corresponding frequency level is high.

[0032]

As described above, according to the present invention, since the coarse gain adjustment and the automatic gain adjustment by the disturbance can be used together, the coarse gain adjustment is performed at the start, and when the audio level is high, the automatic gain adjustment by the disturbance input is performed. Therefore, it is possible to reduce the noise due to the disturbance injection in the sense of hearing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a disc reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an automatic gain adjustment block according to an embodiment of the present invention.

FIG. 3 is an operation sequence according to an embodiment of the present invention.

FIG. 4 is a sequence of focus coarse gain adjustment according to an embodiment of the present invention.

FIG. 5 is an automatic gain adjustment basic sequence according to the embodiment of the present invention.

FIG. 6 is a timing chart during reproduction of a conventional example and an example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Pickup 3 ... Feed (carriage) motor 4 ... Spindle motor 5 ... Preamplifier 6 ... Microcomputer 7 ... Signal processing circuit 7 '... Audio level detection unit 8 ... Automatic gain adjustment block 9 ... Servo equalizer 10 ... Driver 11 ... D / A converter 12, 24 ... Low-pass filter (LPF) 13 ... Volume adjustment volume 14 ... Amplifier 15 ... Speaker 16 ... Display system 17 ... Key operation unit 18 ... Data buffer 20 ... Attenuator 21, 21 '... Gain change amount Detection block 22 ... Band pass filter 23 ... Absolute value circuit 24 ... Low pass filter 25 ... Peak hold circuit 26 ... Bottom hold circuit 27 ... Differential amplifier 28 ... A / D converter 29 ... Disturbance source 30 ... Adder SW _{1 to} SW ₃ … switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kamo Shigeru Kawagoe City, Saitama Prefecture 25, Nishida, Yamada, Nishimachi 1 Pioneer Co., Ltd. Kawagoe Plant (72) Inventor Takehiro Takada 25, Nishimachi, Kawagoe, Saitama Prefecture 1 Pioneer Corporation Kawagoe Factory

Claims (1)

[Claims] 1. A reading unit for reading information from a recording medium, a servo unit for controlling the position of the reading unit so that the reading unit is located at a predetermined position corresponding to the recording medium, and a gain of the servo unit for a disturbance signal. In the servo loop, the gain adjustment means for adjusting and changing the gain, and the gain adjustment means has a reproduction output level corresponding to the read signal obtained from the reading means of a predetermined value or more. A gain adjusting device, comprising: a level detecting unit for detecting whether or not the noise occurs, and supplying the disturbance signal to the servo loop when the reproduction output level is equal to or larger than a predetermined value.