KR0176786B1 - Focus error signal detection circuit of disk reproducing device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus error signal detection circuit of a disc player. In the conventional single-layer disc, a focus error can be detected and accurate servo can be performed. There is a problem that an accurate servo cannot be performed because an error is not detected. In order to solve this problem, the present invention has been devised to detect the correct focus error by applying an offset to the focus error during reproduction of a multi-layer disc, and to perform an accurate servo. By outputting the combined focus error signals through different detection paths, an error-free focus error signal can be obtained regardless of the thickness and type of the disc, thus enabling precise servo.

Description

Focus error signal detection circuit of disc player

1 is a reflection beam detection system diagram of a general disc player.

(A) and (b) of FIG. 2 are exemplary views of a general detector.

3 is a scanning form of the CD detection beam according to the distance between the objective lens and the disk.

(a) is a scanning pattern of the beam when it is close to the disk.

(b) is a scanning pattern of the beam when moving away from the disk.

(c) is the scanning pattern of the beam at the focal point.

4 is a scanning form of a high density detection beam according to the distance between the objective lens and the disk,

(a) is a scanning pattern of the beam when it is close to the disk.

(b) is a scanning pattern of the beam when moving away from the disk.

(c) is the scanning pattern of the beam at the focal point.

5 is a circuit diagram showing an embodiment of a conventional focus error signal detection circuit.

FIG. 6 is a waveform diagram of an uncorrected focus error signal in FIG.

7 is a circuit diagram showing another conventional embodiment.

8 is a waveform diagram showing a focus error signal in FIG.

9 is a circuit diagram showing an embodiment of the present invention.

FIG. 10 is a waveform diagram showing detection of a focus error signal in FIG.

* Explanation of symbols for main parts of the drawings

101: disk 102: objective lens

103: reflection mirror 104: sensor lens

105: detector 401 to 403: current amplifier

404,405: Adder 406 to 408: Focus error signal output unit

The present invention relates to a technique for detecting a focus error signal in a disk player, and in particular, in detecting a focus error signal during playback of a high density disc (DVD: Digital Video Disc) and a CD, a difference in sensitivity between the high density disc and the CD is reduced. A focus error signal detection circuit of a disc player is provided.

In general, in a disc player, an objective lens of a pickup designed to be suitable for an optical disc having a thickness of 0.6 mm becomes larger in spherical aberration when reading an existing CD disc of 1.2 mm, and thus stable playback is impossible.

Therefore, when reading a disc of 1.2 mm with a pickup designed for a thickness of 0.6 mm, a separate means is required.

One way to read a 1.2mm disc is to read both high density discs and CDs by blocking some of the light, reducing the effective numerical aperture of the objective lens, and reducing spherical aberration.

In the general zoom detection system, as shown in FIG. 1, a beam reflected from the disk 101 is scanned through the objective lens 102 to the reflection mirror 103, and then, by the reflection mirror 103, at a predetermined angle. It is configured to be scanned by the detector 105 through the sensor lens 104 after being reflected at (90 °).

The detector 105 is in the form of a bull's eye or a quadrangle divided by an arc having a predetermined radius (x) (y) (z) as shown in FIG. It will be located at the front or rear with respect to the focus position of.

In the conventional focus error signal detecting circuit, as shown in FIG. 5, a detection signal of a beam divided by an arc having a predetermined radius x (y) (z) and scanned by the sensor lens 104 ( a detector (105) for respectively outputting a) (b) and (c), an amplifying unit (201 to 203) for amplifying the detection signals (a) (b) and (c) to an appropriate level, and the amplifying unit ( A high density focus error signal output unit 204 for combining the output signals 201 to 203 and amplifying to an appropriate level and outputting a high density focus error signal [FE: (a + b) -c]; And a CD focus error signal output section 205 for combining the output signals 201 to 203 and amplifying the signals to an appropriate level to output CD focus error signals [FE: a- (b + c)].

Referring to the operation of the prior art as follows.

In the optical system of FIG. 1 for beam detection, the detector 105 may be located at either the front or the rear position based on the focal point of the sensor lens 104, and the detector 105 may have a circular or rectangular shape. Regardless of whether it is used, a circular detector will be described as an example for convenience of description.

The ratio of the radius x and y of each cell in the size of the cell of the detector 105 is set to be proportional to the size of the beam reflected from the CD and the high density disk.

For example, in the case of CD, the diameter of the beam focused on the detector 105 is 2x = y when the diameter of the beam is 1/2 of that of the high density disk.

Here, the diameter z of the outermost cell of the detector 105 is sufficiently large in consideration of the sensitivity.

In addition, when the size of the beam formed on the detector 105 is a high density disk when the focus of the sensor lens 105 is fixed after the detector 105 is fixed, the position of the sensor lens 105 is adjusted. , For CDs To be

In this way, a beam is displayed as shown in (a) to (c) of FIG. 3 according to the separation distance between the disk 101 and the objective lens in the case of a high density disk, and (a) to (c) in FIG. The beam is displayed.

Accordingly, in the circuit of FIG. 5, the current amplifiers 201, 202, 203 output voltages proportional to the detection signals (a), (b), and (c) detected in each cell of the detector 105. The high density focus error signal output unit 204 sums the output signals of the current amplifiers 201 and 202 in the adder OP4 and then adds the adder OP4 and the current amplifier in the differential amplifier OP6. The difference (a + b) -c of the output signal of 203 is obtained and output as the focus error signal FE2, and the CD focus error signal output unit 204 is the current amplifier 201 (in the adder OP5). After the sum of the output signals of the 203, the differential amplifier OP7 calculates the difference a- (b + c) between the output signal of the adder OP5 and the current amplifier 202 and outputs it as the focus error signal FE1.

Accordingly, the focus error signals FE2 and FE1 of the high density disk and the CD appear as shown in FIG. 6, and focus servo is performed using the focus error signals FE1 and FE2.

However, when outputting the focus error signal FE through the above process, an imbalance occurs in the positive (+) and the negative (-) portions of the focus error signal FE as shown in FIG. It can be seen.

Another conventional embodiment proposed to compensate for this is as shown in FIG. 7, each of the variable gain VR1 for gain adjustment to the high density focus error signal output unit 304 and the CD focus error signal output unit 305. ), (VR2) is added. The size of the positive and negative portions of the focus error signal FE may be similar by adjusting the gain of the negative portion (-) in the focus error signal FE.

That is, the focus error signal FE2 of the high density disk is output as (a + b) -kc, and the focus error signal FE1 of the CD is output as ak (b + c) to make the positive and negative levels similar. Can be.

This allows the focal point portion of the detector 105 to be a high density disk, as in a conventional embodiment. Is not formed at the point where Formed at a smaller point, using sensor lens 104 Adjust to form at a slightly smaller point.

As an example, the gain of one end is adjusted so that the level of the focus error signal FE is similar at both sides of the positive part (+) and the negative part (-), and then (a + b + c) of the detector 105. The point at which the signal is maximized can be considered to be the point where focus is best on the disk 101. This point is zero when the focus error signal FE crosses from the negative part (-) to the positive part (+). The sensor lens 104 may be adjusted so that it appears at the instant of (0).

As a result, the level of the focus error signal FE can be precisely adjusted so that stable servo can be performed and a good signal can be reproduced.

The waveforms of the focus error signals FE1 and FE2 whose errors have been adjusted by the above operation are as shown in FIG.

In the conventional single-layer disc, however, a focus error can be detected and precisely performed. However, in the case of a multi-layer disc, since a separation distance exists between two recording planes, the correct focus error cannot be detected. There is this.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a focus error signal detection circuit of a disc player designed to detect an accurate focus error and to perform an accurate servo by applying an offset to a focus error during reproduction of a multilayer disc in order to solve the conventional problems. have.

The present invention provides a detection means for outputting a plurality of detection signals for a beam divided and scanned by a plurality of arcs having a predetermined radius to achieve the above object, and converting the plurality of detection signals to a corresponding voltage, respectively First to third current amplifying means, first adding means for summing output signals of the first and second current amplifying means, and second adding means for summing output signals of the second and third current amplifying means. A first focus error signal output means for obtaining a difference between the outputs of the first current amplifying means and the second adding means and outputting a focus error signal for a CD; and the outputs of the outputs of the first adding means and the third current amplifying means. The second focus error signal output means for obtaining the difference and outputting the focus error signal of the single-layer high-density disc, and the difference between the outputs of the first adding means and the third current amplifying means is obtained to give an offset. Constitute a third focus error signal output means for outputting the first and second focus error signals of the multi-layer high-density disk.

Hereinafter, the present invention will be described in detail with reference to the drawings.

9 is a focus error signal detection circuit diagram of the present invention, as shown therein, a detection signal (a) of a beam divided by an arc having a predetermined radius (x) (y) (z) and scanned through a sensor lens, respectively (a). a detector 105 for outputting (b) (c), current amplifiers 401 to 403 for converting the detection signals a, b and c into corresponding voltages, and the current amplifiers A first adder 404 for summing the output signals of 401 and 402, a second adder 405 for summing the output signals of the current amplifiers 402 and 403, and the current amplifier. A CD focus error signal output unit 406 for obtaining an output difference between the 401 and the adder 405, and outputting the CD focus error signals FE1: a- (b + c), and the adder 404; ) And the focus error signal output unit 407 for the single-layer high-density disc which calculates the output difference between the current amplifier 403 and the output of the focus error signal FE2: (a + b) -c of the single-layer high-density disc; Part (404 ) And a focus error signal output unit for outputting the first and second focus error signals FE3 and FE4 of the multilayer high density disk by offsetting the output difference between the current amplifier 403 and the current amplifier 403. 408.

The focus error signal output units 407 and 408 have variable resistors VR1 having fixed terminals connected to voltages (+ 5V) (-5V) to offset the focus error signals FE2 (FE3, FE4). Add (VR2, VR3) respectively.

Referring to the operation and effect of the present invention configured as described above are as follows.

In the optical system as shown in FIG. 1, a beam reflected from the disk 101 is sequentially scanned through the objective lens 102, the reflection mirror 103, and the sensor lens 104 to the detector 105 to be detected from the detector 105. Signals (a), (b), and (c) are outputted, and the phase formed on the detector 105 is different depending on the type and thickness of the disk.

For example, in the case of a multi-layer high density disk, since there is a separation distance between two recording surfaces, the image size of the beam formed on the detector 105 is different, so that the focus error is slightly different.

That is, the waveform of FIG. 10 illustrates the waveform of the error error of the single-layer digital video disc. In case of the double layer, the 10 (a) is a distance error of two layers with the signal of FIG. 10 (a). A signal as shown in FIG. 10 (b) is summed and output as a signal as shown in FIG. 10 (c).

In this case, the points at which the focus error signal becomes zero in the waveforms of FIGS. 10A and 10B correspond to marker points in the waveforms of FIG. 10C, which are caused by the sum of the two signals. .

Therefore, a focus error occurs depending on the case of reproducing the first and second surfaces of a single-layer disc or a double-layer disc. Thus, an offset is given to the focus error signal generated in each case, regardless of the thickness and type of the disc. A focus error signal can be obtained.

That is, as shown in FIG. 9, the fixed terminal has a voltage (+ 5V) (-5V) at the non-inverting terminal of the differential amplifiers OP6 (OP8, OP9) constituting the focus error signal output units 407 and 408, respectively. The variable resistance VR11 (VR12, VR13, VR13) connected to each other is connected to the variable resistance to give an offset to the focus error signal.

Referring to FIG. 9, when the beam reflected from the disk 101 is scanned by the detector 105 and the detection signals a, b, and c are output, the current amplifiers 401, 402, 403 are output. ) Outputs a voltage proportional to the signals (a), (b), and (c) detected in each cell of the detector 105.

At this time, the first adder 404 adds the output voltages of the current amplifiers 401 and 402 to the focus error signal output units 407 and 408 for the high density disk, and the second adder 405. The sum of the output voltages of the current amplifiers 402 and 403 is output to the CD focus error signal output unit 406.

Accordingly, the CD focus error signal output unit 406 may vary the output voltage a- (b + c) of the second amplifier 405 from the output voltage of the current amplifier 401 in the differential amplifier OP7. To obtain the CD focus error signal FE1.

In addition, the focus error signal output unit 407 for the single-layer high-density disk has an output difference ((a + b) -c) between the output voltage of the first adder 404 and the current amplifier 403 in the differential amplifier OP6. Is obtained and output as a focus error signal FE2 for a single layer high density disk.

In addition, the multi-layer high density disk focus error signal output unit 408 uses the differential amplifiers OP8 and OP9 to obtain the difference between the output voltage of the first adder 404 and the output of the current amplifier 403, respectively. Is output as a focus error signal FE3 (FE4) for the first and second floor surfaces of the "

Therefore, by obtaining the focus error by the above operation, accurate servo can be performed by using the focus error signals FE1 (FE2) (FE3, FE4) in each case.

As described in detail above, the present invention outputs a combined focus error signal through different detection paths so as to be suitable for the characteristics of a high-density disk or CD, thereby obtaining an error-free focus error signal regardless of the thickness and type of the disk. There is an effect that can perform precise servo.

Claims (2)

Detection means for outputting detection signals (a) (b) (c) for beams divided and scanned by a plurality of arcs having a predetermined radius, and outputs (a) (b) (c) of the detection means A first to third current amplifying means for converting the first to third current amplification means, a first adding means for summing output signals of the first and second current amplifying means, and a second summation of the output signals of the second and third current amplifying means. A first focus error signal output means for obtaining a difference between the output means of the second adding means, the output of the first current amplifying means and the output of the second adding means, and outputting a CD focus error signal FE1; A second focus error signal output means for obtaining a difference between the output and the output of the third current amplifying means and outputting a focus error signal FE2 of the single-layer high density disk, an output of the first adding means and an output of the third current amplifying means The difference between the first and second recording surfaces of the multi-layer high density disc The third focus the focus of the disk player, characterized in that the error signal output means configured error signal detecting circuit for outputting a call. The focus error signal detection circuit of a disc player according to claim 1, wherein the second and third focus error signal output means is configured to give an offset to the focus error signal.