JPH0589481A - Focus controller - Google Patents

Abstract

PURPOSE:To quickly draw in an objective lens to a focal position by selecting and holding prescribed positive or negative polarity voltage outside a linear area even for a focus error signal (FE signal) with a zero-cross point besides a focal point. CONSTITUTION:While an analog switch 23 is opened, and a focus servo system is opened, the analog switch 27 is closed by making an FST signal 19-1 a high level for a prescribed period of time, and prescribed voltage is supplied to a drive circuit 25 through an addition circuit 24, and the objective lens is made more distant from a secondary zero-cross point. Next, the analog switch 23 is closed by making the signal 19-1 a low level, and the servo system is closed. At that time, only output Y3 becomes high, and the analog switch 21-4 is closed, and the output voltage 42 is made the prescribed positive polarity voltage, and is supplied to the drive circuit 25 through a phase compensation circuit 22, the switch 23, and the addition circuit 24, and the objective lens is made to approach to an optical card, and is made to reach the vicinity of the focal position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical information for optically recording / reproducing information by projecting a light beam through an objective lens onto an optical information recording carrier such as an optical disk, a magneto-optical disk or an optical card. The present invention relates to a focus pull-in method in a recording or reproducing device.

[0002]

2. Description of the Related Art Heretofore, as an optical information recording unit, for example, a card-shaped one called an optical card as shown by reference numeral 1 in FIG. 7 has been proposed. On the optical card 1, information is recorded by the presence / absence of light reflection, the shade of reflected light or the presence / absence of holes, etc., and is optically reproduced. This information is
For example, as indicated by reference numeral 52, recording or reproduction is performed in units called tracks, and one optical card 1 is configured by arranging a plurality of tracks 52 which are parallel to each other. For example, in the optical card 1 shown in FIG. 7, the ID parts 52a and 52b are arranged at both ends of the track 52, and the ID part 52c is provided at the center.
Are arranged, and each track number is recorded in this area to facilitate the search for the target track. Further, the data portions 52d and 52e store previously recorded data and recorded data. As such an optical card 1, the applicant of the present invention has disclosed, for example, Jitsukai Sho 63-1.
It is proposed as shown in Japanese Patent No. 45669.

An apparatus for recording or reproducing information on the optical card 1 has a structure as shown in, for example, FIGS. 8 (A) and 8 (B). The optical card 1 is placed on the frame 55, and the card motor 56 drives the rubber rollers 57a, 5
It is reciprocated corresponding to the data part 52d or the data part 52e via 7b. An optical pickup 58 for recording or reproducing information on the optical card 1 is arranged so as to face the optical card 1 and is moved by a seek motor 59 through a screw screw 60 in a seek direction which is a direction substantially perpendicular to a track. Driven.

FIG. 9 shows an example of a track format in the optical card 1 shown in FIG. The truck 5
2, a guide pattern 63 consisting of a black-and-white pattern extending in the track direction is formed on the clock / servo line 62 at the center thereof, and 8 bits each in the track width direction on both sides of the clock servo line 62. A total of 16-bit data 64-1 to 64-16 is recorded.

As shown in FIG. 10, the photodetector 69 of the optical pickup 58 includes 16 data reading light-receiving areas 69-A1 to 69-A1 arranged corresponding to 16-bit data recording positions in the track width direction. 69-A16 and five pairs of light receiving regions 69-B1 to 69 for clock generation which are spaced apart in the track direction so as to receive the image of the guide pattern 63.
-B10 and four pairs of servo signal detection light-receiving regions 69-C1 to 69-C4, 69-D1 to 69-D4 arranged facing each other in the track width direction of the guide pattern 63. .. Reference numeral 66 indicates an image of a light emitting portion (not shown) of the optical pickup 58 which is reflected by the optical card 1 and is formed on the photodetector 19.

Here, the positions of the optical card 1 and the optical pickup 58 are set so that the recording surface of the optical card 1 is at the in-focus position of an objective lens (not shown), and in this state, it is connected to the photodetector 69. The illuminance distribution in the diametrical direction of the image 66 of the light emitting portion to be imaged is the light receiving area 69-D1 for servo signal detection inside.
, 69-D2, 69-D3, 69-D4, a protruding portion is formed near the outside.

By doing so, when the optical card 1 comes closer to the objective lens than the in-focus position of the objective lens (not shown), the illuminance distribution on the photodetector 69 has a value for detecting the outer servo signal. Light receiving area 69-C1, 69-C2, 6
As the amount of light incident on 9-C3 and 69-C4 increases, the light receiving areas 69-D1, 69-D2 and 6 for servo signal detection inside
The amount of incident light on 9-D3 and 69-D4 decreases. When the optical card 1 is moved further away from the objective lens than the in-focus position of the objective lens, the illuminance distribution on the photodetector 19 is such that the outer servo signal detecting light receiving regions 69-C1 and 6 are present.
The amount of light incident on 9-C2, 69-C3, and 69-C4 decreases, and the inner light receiving regions 69-D1 and 6 for servo signal detection are used.
The incident light quantity increases on 9-D2, 69-D3, and 69-D4.

In the servo circuit of the optical information recording / reproducing apparatus, for example, due to the characteristics of the illuminance distribution on the photodetector 19 described above, the light receiving area 69-C1 for servo signal detection on the outer side is provided.
, 69-C2, 69-C3, 69-C4 output sum and the inner servo signal detection light receiving area 69-D1, 69-D2, 69-D
3 and 69-D4 output sum, and the focus error signal (FES) is obtained based on the difference between the former and latter output sums, and the output sum of servo signal detection light-receiving areas 69-D1 and 69-D3 And the light receiving areas 69-D2 and 69-D4 for servo signal detection
Then, the tracking error signal (TES) is obtained based on the difference between the output sums of the former and the latter.
Also, one of the pair of light receiving regions 69-B for clock generation is used.
1, 69-B3, 69-B5, 69-B7, 69-B9 output sum, and the other light receiving area 69-B2, 69-B4, 69-B6, 6
9-B8 and 69-B10 output sums are obtained, a clock signal is obtained based on the difference between the former and latter output sums, and a light receiving area 69-A1 for reading data is synchronized with this clock signal.
16-bit data is read simultaneously from the output of 69-A16.

Further, as a conventional focus control device,
For example, the applicant of the present application has also proposed the following focus pull-in method in Japanese Patent Application No. 2-28185. 11
In the case where the focus error signal (FES) has a secondary zero-cross point O ′ as a zero-cross point in addition to the focused point O, the objective lens is first set to the secondary zero-cross point in the direction causing the error pull-in. The focus error signal is monitored by moving the objective lens in a direction that does not cause erroneous pull-in by moving the objective lens in a direction that does not cause erroneous pulling, by moving the objective lens in a direction that does not cause erroneous pulling, by moving the objective lens in a direction that does not cause erroneous pulling, by applying a predetermined voltage Vc and then applying a predetermined voltage Vc. When the value reaches a predetermined value Vt, the target voltage is switched from the predetermined voltage Vc to the original focus error signal and the objective lens is pulled into the in-focus position of the optical information record carrier.

[0010]

However, the conventional focus control device described above has the following problems. That is, in FIG. When the focus servo system is closed with a predetermined voltage Vt to drive the objective lens, the driving speed increases and the objective lens passes the focal point O against the braking force and exceeds the minimum value L,
Further, it may reach the point B and collide with the optical information recording carrier to damage the recording surface.

2. On the contrary, when the objective lens is stopped near the minimum value L and is driven in a different direction, 1. Similarly, the driving speed increases and the objective lens passes the focal point O against the braking force and exceeds the maximum value U, and further passes through the secondary zero-cross point O'to reach the point A to cause an error pull-in. I will end up.

The present invention has been made in view of such a problem. Even if the focus error signal has a zero cross point other than the focus point, the objective lens is accurately positioned at the focus position of the optical information recording carrier. It is an object of the present invention to provide a focus control device configured so that it can be pulled in quickly.

[0013]

In order to achieve the above object, according to the present invention, an objective lens for projecting a light beam onto an optical information recording carrier is fitted to the optical information recording carrier based on a focus error signal. In a focus control device for driving and controlling the focus state, a first comparing means for comparing the focus error signal with a reference value of positive polarity and a first comparing means for comparing the focus error signal with a reference value of negative polarity 2 comparing means, a first signal generating means for generating a positive polarity constant signal based on the output of the first comparing means, and a negative polarity constant signal based on the output of the second comparing means. When the focus error signal is within the positive reference value and the negative reference value, the focus error signal is generated based on the output of the second signal generating means and the output of the first and second comparing means. Signal selecting means for selecting the output of the first signal generating means when the positive polarity reference value or more is selected, and selecting the output of the second signal generating means when the negative polarity reference value or more And the focus control of the objective lens is performed by the signal selected by the signal selection means.

[0014]

EXAMPLES Examples of the present invention will be described in detail below.

1 to 5 relate to the first embodiment, and FIG. 1 is a block diagram showing the overall structure of a focus control device, and FIG.
Is a circuit diagram showing the configuration of the focus control circuit, FIG. 3 is a truth table at the input / output of the decoder, FIG. 4 is an explanatory diagram for explaining the FE characteristic and the drive amount characteristic of the objective lens, and FIG. 5 is the focus control circuit. It is a signal waveform diagram showing the timing of the signal of each part.

As shown in FIG. 1, the light emitted from the light source 3 in the optical pickup 2 is converted into substantially parallel light by the collimator lens 4 and is applied to the half prism 5. The light transmitted through the half prism 5 is condensed on the recording surface of the optical card 1 by the objective lens 6, and the recording surface is physically changed to record information.

The reflected light from the recording surface is again condensed by the objective lens 6 and reflected by the half prism 5. The light reflected by the half prism 5 is received by the photodetector 8 through the imaging lens 7, converted into an electric signal, and then added to the demodulation circuit 12, and the reproduction signal reproduced by the demodulation circuit 12 is reproduced. It is output to the controller 17.

The output of the photodetector 8 is further applied to the focus error signal (FE) generating circuit 13 and the tracking error signal (TE) generating circuit 15 to output the focus error signal 18 and the tracking error signal. It has become.

The focus servo system is composed of the optical pickup 2, the FE generation circuit 13, the focus control circuit (including the phase compensation of the system and the functions of opening / closing, pulling in, and driving) and the focus coil 10, and the objective. The lens 6 is driven in the distance direction of the optical card 1 based on the FE signal 18, and auto focus control for accurately focusing the light beam on the recording surface of the optical card 1 is performed.

Similarly, the tracking servo system is composed of the optical pickup 2, the TE generation circuit 15, the tracking control circuit 16 and the tracking coil 9, and the objective lens 6 is moved in the track width direction of the optical card 1 based on the TE signal. It is driven by performing auto-tracking control for correcting the recording / reproducing position of the optical pickup 2 and the deviation between the tracks.

The light source 3 is controlled by the controller 7 via the drive circuit 11.

The focus control circuit 14 is constructed as shown in FIG. 2, that is, the FE signal 18 from the FE generation circuit 13 is added via the analog switch 21-1, the phase compensation circuit 22 and the analog switch 23. Circuit 2
4 and one input terminal of each of the comparators 34, 39 and 40. To the other input terminal of the adder circuit 24, a predetermined voltage of negative polarity which separates the objective lens 6 from the optical card 1 via the analog switch 27 is applied to the resistor 28-.
1 and 28-2 are divided and supplied.

The analog switch 27 is opened / closed by a control signal FST19-1 from the controller 17.

The other input terminal of the comparator 34 is supplied with the reference voltage VR, which is the operating point of the circuit, and its output is supplied to the clock (CK) terminal of the D type-flip prop (DF). The -Q output is one input of the OR gates 29 and 30. DF / F3
The output of the OR gate 32 that receives the control signal FST19-1 from the controller 17 as one input via the inverter 33 and the other as the −RESET signal is connected to the reset terminal of No. 1.

The other input terminals of the comparators 39 and 40 are respectively supplied with the positive reference voltage VH and the negative reference voltage VL, and the respective outputs are sent to the sample and hold (S / H) circuits 37 and 38. It is supplied and becomes a sampling signal.

The drive signal FDS20, which is the output of the drive circuit 25 input from the adder circuit 24, is supplied to the focus coil 10 in the optical pickup 2 and the objective lens 1 is supplied.
While driving in the direction (focus direction) perpendicular to
It is input to the low-pass filter (LPF) 41, and its output is regarded as the drive amount in the focus direction of the objective lens 6, and is input to one input terminal of each of the comparators 35 and 36 and the S / H circuits 37 and 38. It is like this.

The S / H circuits 37 and 38 supply the respective voltages held by the sampling signals (outputs of the comparators 39 and 40) to the other input terminals of the comparators 35 and 36, and the respective outputs are OR gates 29 and 30. Is the other input of.

The outputs of the OR gates 29 and 30 are supplied to the input terminals A and B of the decoder 26, and their outputs Y
0, Y1, Y2, Y3 are analog switches 21-1,
21-2, 21-3, and 21-4 are output to the respective control terminals. This analog switch 21
The FE signal 18, the predetermined voltage Va of the positive polarity, the predetermined voltage Vb of the negative polarity, and the predetermined voltage Vc of the positive polarity are connected to the input terminals of -1, 21-2, 21-3, and 21-4, respectively, and the output terminals thereof are connected. Are all connected to the phase compensation circuit 22. The controller 1 for opening and closing the focus servo system is connected to the control terminal E of the decoder 26 and the control terminal of the analog switch 23.
The control signal (FON) 19-2 from 7 is connected. Here, when the FE signal 18 exceeds the positive reference voltage VH and the negative reference voltage VL, the positive predetermined voltage Va, the negative predetermined voltage Vb, and the positive predetermined voltage Vc are as follows. The voltage is a voltage capable of forcibly giving a pulling force to the focal point while the distance from the focal point is farther than the lens position at that time.

FIG. 3 is a truth table for input / output of the decoder 26, and analog switches 21-1, 21-2, 21-.
3 shows the relationship between the open / closed states of Nos. 3 and 21-4 and the output voltage FE ′ 42 supplied to the phase compensation circuit 22.

The operation of this embodiment will be described below with reference to the FE characteristic shown in FIG. 4A, the drive amount characteristic of the objective lens 6 shown in FIG. 4B, and the signal waveform chart of each part of the focus control circuit shown in FIG. It will be explained with reference to FIG.

In FIG. 5, first, the analog switch 2
With 3 turned off and the focus servo system open,
The controller 17 sets the FST signal 19-1 to the Hi-level for a predetermined period to turn on the analog switch 27, and supplies a predetermined voltage to the drive circuit 25 via the adder circuit 24 to move the objective lens 6 to the state shown in FIG. ) The optical card 1 is further distanced from the secondary zero-cross point O ′.

The controller 17 uses the FST signal 19-1.
Is set to Lo-level to turn off the analog switch 27, and the FON signal 19-2 is set to HI-level to turn on the analog switch 23 to close the focus servo system. At this time, only the output Y3 of the decoder 26 is Hi-
It becomes a level and the analog switch 21-4 is turned on,
The output voltage FE ′ 42 is set to a predetermined positive voltage Vc, and the phase compensation circuit 22, the analog switch 23 and the addition circuit 24
The objective lens 6 is driven in a direction of approaching the optical card 1 through the drive circuit 25, passes through the secondary zero-cross point O ′ of FIG. 4 (A), and is further driven in a direction of approaching the optical card 1. Reach near focus.

When the objective lens 6 is brought close to the position of the in-focus point O to the optical card 1, the output of the comparator 34 (rising edge) sets the D-F / F31, and the -Q output changes from the Hi-level to the Lo-level. Change. At this time,
Only the output Y0 of the decoder 26 becomes Hi-level to turn on the analog switch 21-1, and the FE signal 18 is fed to the phase compensation circuit 22, the analog switch 23 and the adder circuit 2.
4 to the drive circuit 25. Therefore, after the FE signal 18 is selected, a characteristic having a zero-cross point only at the focal point O is exhibited, so that the focus servo system operates so that the objective lens 6 will eventually settle at the focal point O.

However, when the driving speed of the objective lens 6 is high against the braking force of the focus servo system, FIG.
Of the FE signal 18 becomes VL because the FE signal 18 becomes lower than the negative reference voltage VL because the FE signal 18 becomes closer to the optical card 1 after passing the Q point or Q'point.
It becomes Hi-level in the following cases. At this time, the S / H circuit 38
Is the driving voltage (LPF4) of the objective lens 6 using the output (rising edge) of the comparator 40 as a sampling signal.
1 output) is held (voltage at point V in FIG. 4B),
Output to the comparator 36. The output of the comparator 36 becomes Hi-level when the drive voltage is equal to or higher than the hold voltage, and only the output Y2 of the decoder 26 becomes Hi-level to turn on the analog switch 21-3 to output the output voltage F.
E'42 is a predetermined negative polarity voltage Vb, for example, the peak value of the negative polarity voltage of the FE signal 18 at this time, and is supplied to the drive circuit 25 via the phase compensation circuit 22, the analog switch 23 and the addition circuit 24. The objective lens 6 is moved away from the optical card 1.

When the objective lens 6 is moved to the point Q in FIG. 4A, the output of the comparator 36 becomes Lo level, and only the output Y0 of the decoder 26 becomes Hi-level and the analog switch 21-1 is turned on. FE signal 18
Is selected.

Also, due to disturbance or the like, the driving speed of the objective lens 6 is large against the braking force of the focus servo system so that it passes point P or point P'in FIG. When the FE signal 18 is more than VH, the output of the comparator 39 becomes Hi-level when the FE signal 18 is VH or more. At this time, the S / H circuit 37 uses the output of the comparator 39 as a sampling signal to hold the drive voltage of the objective lens 6 (voltage at point U in FIG. 4B) and outputs it to the comparator 35. The output of the comparator 35 becomes Hi-level when the driving voltage is lower than the hold voltage, and only the output Y1 of the decoder 26 becomes Hi-level and the analog switch 21.
-2 is turned on, the output voltage FE'42 is set to a predetermined positive polarity voltage Va, for example, the peak value of the positive polarity voltage of the FE signal 18 at this time, and the phase compensation circuit 22, the analog switch 23, and the adder circuit 24 are used. Supply to the drive circuit 25,
The objective lens 6 is brought close to the optical card 1.

When the objective lens 6 is brought close to the point P in FIG. 4A, the output of the comparator 35 becomes Lo-level, and only the output Y0 of the decoder 26 becomes Hi-level and the analog switch 21-1 is turned on. Turn on and FE signal 1
8 is selected, the braking force of the focus servo system is higher than the driving speed of the objective lens 6, and the focus servo system operates so that the objective lens 6 will eventually settle at the focal point O.

As described above, the predetermined voltage Va is applied outside the linear region (between P and Q) of the FE signal 18 shown in FIG.
Since (positive polarity) or Vb (negative polarity) is selected to direct the objective lens 6 to the focal point O, the objective lens 6 collides with the recording surface of the optical card 1 or erroneous pulling occurs. The optical card 1 can be accurately and quickly drawn into the focal point O of the optical card 1.

Next, FIG. 6 is a block diagram of a focus control circuit according to the second embodiment of the present invention, and the same reference numerals as those in FIG. 2 have the same functions.

The decoder 26 sets the output of the comparator 39 to the Hi-level only when the FE signal 18 is equal to or higher than the positive reference voltage VH, or sets the output of the comparator 40 to the Hi-level only when the FE signal 18 is equal to or lower than the negative reference voltage VL. To a predetermined voltage Va (positive polarity) or Vb (negative polarity)
Is supplied to the drive circuit 25 via the phase compensation circuit 22, the analog switch 23, and the addition circuit 24 so that the objective lens 6 is brought closer to or away from the optical card 1. Therefore, as shown in FIG. 4A, Va is selected between P and P ', Vb is selected between Q and Q', and the FE signal 18 is selected otherwise, and the focus servo system operates. In this way, the same focus servo pull-in can be realized with a simple configuration having no hold function.

[0041]

As described above, according to the present invention, even if the FE signal has a zero cross point other than the in-focus point, the F
In a region other than the linear region of the E signal, a predetermined voltage Va (positive polarity) or Vb (negative polarity) is selected and held, and the objective lens 6
Since the objective lens is made to face the focusing position, the objective lens can be accurately, quickly and with a simple configuration drawn to the focusing position of the optical card without colliding with the recording surface of the optical card or causing wrong drawing. Can be made. Further, even if the objective lens is shaken in a region other than the linear region of the FE signal due to the vibration due to the disturbance, the objective lens tends to be returned to the in-focus direction with a predetermined voltage having both polarities, so that it can have a limiting action.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a focus control device according to a first embodiment.

FIG. 2 is a circuit diagram showing a configuration of a focus control circuit according to the first embodiment.

FIG. 3 is a truth table at the input / output of the decoder 26 according to the first embodiment.

FIG. 4 is an explanatory diagram illustrating an FE characteristic and a driving amount characteristic of an objective lens according to the first example.

FIG. 5 is a signal waveform diagram showing timings of signals of respective parts of the focus control circuit according to the first example.

FIG. 6 is a circuit diagram showing a configuration of a focus control circuit according to a second embodiment.

FIG. 7 is an explanatory diagram of an optical card according to a conventional example.

FIG. 8 is an explanatory diagram of an optical information recording and / or reproducing apparatus according to a conventional example.

FIG. 9 is an explanatory diagram of a recording format of an optical card according to a conventional example.

FIG. 10 is an explanatory diagram of a photodetector according to a conventional example.

FIG. 11 is an explanatory diagram illustrating an FE characteristic and a drive amount characteristic of an objective lens according to a conventional example.

[Explanation of symbols]

 14 ... Focus control circuit 21-1 ... Analog switch 21-2 ... Analog switch 21-3 ... Analog switch 21-4 ... Analog switch 22 ... Phase compensation circuit 24 ... Addition circuit 25 ... Drive circuit 26 ... Decoder 31 ... D-flip floc 34 ... Comparator 39 ... Comparator 40 ... Comparator

Claims (2)

[Claims] 1. A focus control device for driving and controlling an objective lens for projecting a light beam onto an optical information recording carrier so as to bring the optical information recording carrier into a focused state based on a focus error signal, First comparing means for comparing the focus error signal with a reference value of positive polarity, second comparing means for comparing the focus error signal with a reference value of negative polarity, and output of the first comparing means First signal generating means for generating a positive polarity constant signal based on the above, and second signal generating means for generating a negative polarity constant signal based on the output of the second comparing means; Based on the output of the second comparison means, the focus error signal is selected when the focus error signal is within the positive reference value and the negative reference value, and when the focus error signal is equal to or more than the positive reference value, the focus error signal is selected. First signal Selects the output of the raw unit, the focus control unit when the above reference value of the negative polarity, characterized in that a signal selection means for selecting an output of said second signal generating means. 2. The outputs of the first and second comparison means are:
The focus control device according to claim 1, wherein the focus control device is held based on an output of a driving unit that drives the objective lens in the optical axis direction.