JPH046629A - Track actuator position detector - Google Patents

Abstract

PURPOSE:To attain adjustment automatically against a temperature characteris tic change or a secular change and a to obtain a PE signal with same sensitivity at all times by controlling an output of a light emitting diode so as to make the total light receiving quantity of a photodetector constant. CONSTITUTION:A total light receiving quantity is obtained from a photodetector 21, which is fluctuated due to a warp of a disk 1 or a displacement of a track actuator 17. The total light receiving quantity is compared with a setting object value, and when the total light receiving quantity is more than the object value, a drive power of a light emitting diode 20 is decreased and conversely when the total light receiving quantity is less than the object value, the drive power of the light emitting diode 20 is increased, resulting the feedback is applied so that the total light receiving quantity of the photodetector 21 is always kept constant. Thus, the luminous quantity lost fill the light radiating from the light emitting diode 20 reaches the photodetector 21 is compensated. Thus, a track actuator position detection signal with always stable sensitivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a track actuator position detection device used in an optical information reproducing device.

[Prior art] Optical disk devices concentrically and
Alternatively, in order to record or reproduce signals in a spiral manner, it is necessary to generate a tracking error signal. Various methods have been proposed for generating this tracking error signal, and there is a method called a push-pull method that utilizes diffracted light from signal pits or guide grooves.

FIG. 3 is a diagram illustrating the principle of tracking error signal generation using the push-pull method. In the figure, (1) is an information recording medium, (2) is a guide groove on the information recording medium (1), and (3) is a guide groove on the information recording medium (1). (5) is an objective lens that forms a focused spot (4) at the center of the guide groove (2) of the information recording medium (1);
(6) is a convex lens that is arranged parallel to the outgoing light side of the objective lens (3), and (6) is composed of two light receiving surfaces (6a) and (6b), and is arranged on the outgoing light side of the convex lens (5). 2-split photodetector (7) is a 2-split photodetector (6
) has input terminals (+) and (-) connected to the two light-receiving surfaces (6a) and (6b), respectively, and this light-receiving surface (6a
), (6b) generates a tracking error signal (TE) based on the outputs from the TE.

When the focused spot (4) is diffracted by both edges of the guide groove (2), it produces diffracted light distributions (8) and (9), and is also projected onto the surface of the two-split photodetector (6). This results in diffracted light distributions (10) and (11).

When the objective lens (3) is at the center position of the guide groove (2), the intensities of the diffracted light distributions (10) and (11) are equal according to the diffracted light distributions (8) and (9), and the difference is The output of the dynamic amplifier (7) becomes zero.

However, if the relative positional relationship between the objective lens (3) and the guide groove (2) shifts due to eccentricity of the information recording medium (1), etc., the diffracted light distributions (8) and (9) will not be uniform. Therefore, the output of the differential amplifier (7) becomes positive or negative. Therefore, the servo operates to make this output zero, and the objective lens (3) is displaced in the X direction shown in the figure.

Next, the problems of the tracking error signal generation method using the push-pull method will be explained. Figure 4 shows the objective lens (3
) to the neutral point (on the dashed line in the figure) of the guide groove (2).
FIG. 3 is a diagram showing a state in which is displaced by a distance d.

In this state, the projected diffracted light distributions (10), (11 )
is no longer evenly incident on the two light-receiving surfaces (6a) and (6b), and as a result, the output of the differential amplifier (7) is no longer zero.

In other words, a tracking offset occurs.

FIG. 5 is a diagram showing the tracking error signal TE with respect to the displacement d of the objective lens (3), and as the displacement d increases, the amount of tracking offset also increases.

As described above, the tracking error signal generation method using the push-pull method is a simple method that uses diffracted light, but an offset occurs in the tracking error signal (TE) due to the displacement X of the objective lens (3) in the tracking direction. , Therefore, there was a problem that a wide movable range in the tracking direction could not be achieved.

Conventionally, there has been an objective lens position detecting device shown in FIGS. 6 and 7, for example, as a device for improving such inconveniences.

FIG. 6 is a configuration diagram of a conventional objective lens position detection device. In FIG. 6, (12) is a light source such as a semiconductor laser, and (13) is a light beam (14) emitted from the light source (12).
) is a collimator lens that makes parallel light, (15) is a beam splitter that splits the emitted light beam (14) into two directions, (16
) is a reflecting mirror that reflects the unidirectional light beam (14X) emitted from the beam splitter (15), and (17) is the axis (1
8) is an actuator rotatably and slidably supported, (20) is a light emitting diode provided at an eccentric position of the actuator (17), and (21) is a light emitting diode (2).
0), two light receiving surfaces (21a) and (2l
b) a two-split photodetector for detecting the position of the objective lens, having (
22) are two light-receiving surfaces (6a), (
(23) is an input terminal (+) connected to the two light-receiving surfaces (21a) and (2l b) of the two-split photodetector (21), respectively; (-), and these light-receiving surfaces (21a), (2
A differential amplifier (24) generates an actuator position detection signal (PE) based on the output from 1b). a differential amplifier having connected input terminals (+) and (-) and generating a tracking error signal (TE) based on outputs from the light receiving surfaces (6a) and (6b);
25) has input terminals (+) and (-) connected to the differential amplifiers (23) and (24), respectively, and the actuator signals output from the differential amplifiers (23) and (24), respectively. This is a differential amplifier that outputs a tracking error signal (CTE) without tracking offset based on a position detection signal (PE) and a tracking error signal (TE).

Next, the operation of the objective lens position detection device shown in FIG. 6 will be explained. The emitted light flux (14) from the light source (12) passes through the collimator lens (13) and the beam splitter (15), and is reflected by the reflection mirror (16), and this reflected light flux (
26) passes through the objective lens (3) and the information recording medium (1
) is reflected.

This reflected light flux returns to the original optical path and returns to the beam splitter (1
5) and enters the two light-receiving surfaces (6a) and (6b) of the two-split photodetector (6) for tracking error detection. The differential amplifier (7) generates a tracking error signal (TE) based on the outputs from the two light receiving surfaces (6a) and (6b) of the two-split photodetector (6) for tracking error detection. This tracking error signal (TE) is the seventh
As shown in Figure (a), the waveform has a tracking offset with respect to the displacement d of the objective lens (3).

On the other hand, the actuator (1) that holds the objective lens (3)
7) performs a tracking operation by rotating in the tracking direction about the shaft (18). The light beam (35) emitted from the light emitting diode (20) provided on this actuator (17) is transmitted to the two light receiving surfaces (21a) and (2l b) of the two-split photodetector (21) for detecting the position of the objective lens.
) is received by the The differential amplifier (23) operates as shown in FIG. 7(b) based on the output difference from the two light receiving surfaces (21a) and (2l b) of the two-split photodetector (21) for tracking position detection. Actuator position detection signal (
PE) is generated.

The differential amplifier (25) receives the tracking error signal (T) obtained from the differential amplifier (23) and the differential amplifier (7).
By calculating E) and the actuator position detection signal (P E), corrected tracking with no tracking offset is always achieved regardless of the displacement d of the objective lens (3) in the tracking direction, as shown in FIG. 7(c). It is possible to obtain an error signal (CTE), and therefore it is possible to have a wide movable node l in the tracking direction.

[Problems to be Solved by the Invention] Since the conventional actuator position detection device is configured as described above, the output of the actuator position detection signal changes for the following reasons.

The first reason is that the actuator position detection sensitivity fluctuates due to movement of the actuator in the focus direction. Generally, an optical disk has a surface wobbling component, and as the disk rotates, the disk information surface moves perpendicularly to the objective lens (3) and the actuator (17).

Therefore, the actuator (17) is controlled to move in the focusing direction in order to connect the focused spots on the disc information surface. Therefore, the distance between the track position detector light emitting diode (20) and the track position detector (21) changes, and the amount of light received by the track position detector (21) changes. The actuator (17) follows the surface runout of the disk,
As the distance between the position detection light emitting diode (20) and the track position detection detector (21) increases, the amount of light received decreases.
As the distance approaches, the amount of light received will increase.

Such a change in sensitivity is shown by the broken line in FIG.

The broken line in Fig. 8 Ca) indicates the amount of light received by the track position detection detector (21) when the light emission amount of the light emitting diode for position detection is kept constant and the position of the actuator in the focus direction is shifted (detector 21). a + 2 l b
, ).

In addition, the broken line in (b) indicates the track position detection detector←2
1) represents the output of the track position detection detector (detectors 21a-21b) when the amount of received light changes. It can be seen that as the amount of light received by the track position detection detector (21) decreases, the track position detection sensitivity (PE) also decreases.

Therefore, when surface runout occurs in the disk (1) due to the disk (1) or the disk rotation mechanism system, the optimum value of the offset correction circuit for the tracking error signal from the tracking position detector changes, causing A new offset will occur in the servo system.

In addition, when the track actuator follows the guide groove (2) on the disk that is displaced in the track direction due to the eccentric component of the disk (1), the track position detection detector (21) of the track actuator position detection device and the track position By shifting the position of the light emitting diode for detection (20), the total amount of light received by the position detection detector increases as shown in Fig. 9(a).
may decrease as shown by the broken line. Then, Figure 9 (
As shown by the broken line in b), the position detection sensitivity of the track actuator decreases as the total amount of received light decreases.

Furthermore, a light emitting diode (20) for a truck position detector.
The track position detection detector (21) has been a factor that increases the sensitivity variation of the track position detection device due to sensitivity variations, temperature changes, changes over time, and the like.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a track position detection device that is highly reliable and does not require adjustment and maintenance.

[Means for Solving the Problems] A track actuator position detection device according to the present invention is provided with a device that controls the driving power of the amount of light emitted from the light emitting diodes to a target value so that the sum of the outputs of the photodetectors remains constant. It is.

[Function] In the track actuator position detection device according to the present invention, the total amount of light received by the photodetector is obtained, which varies depending on the surface runout of the disk and the displacement of the track actuator.
The total amount of light received is compared with the set target value, and when the total amount of light received is large compared to the target value, the driving power of the light emitting diode is lowered, and on the other hand, when the total amount of light received is small, the driving power of the light emitting diode is increased. Feedback is applied to keep the total amount of light received from the photodetector output constant. This makes it possible to compensate for the amount of light emitted from the light emitting diode that is lost before it reaches the photodetector, and it is possible to always obtain a track actuator position detection signal with stable sensitivity.

[Embodiments] Hereinafter, embodiments of the present invention will be described based on the drawings. 1st
In the figures and FIG. 2, the members indicated by (1) to (26) correspond to those shown in FIG.

Further, in this embodiment, (27) is a track position detection detector addition circuit that adds the outputs of the track position detector detectors (21a) and (21b), and (28) is a track position detection detector addition circuit. The output comparator for position detection (30) compares the output of the circuit (27) with the output of the reference voltage sources (two) and outputs the deviation thereof. 27), a position detection detector output comparator (28), and a reference voltage (29).

In FIG. 2, (31) and (32) are track position detection detector iv conversion circuits for converting the current output of the track position detection detector into voltage, and (33) is a track position detection detector iv conversion circuit. This is a drive circuit for driving a light emitting diode (20).

Next, the operation will be explained. Assume that the track actuator is misaligned in the focus direction or track following direction due to eccentricity or wobbling of the disk. At this time, the amount of light emitted from the track position detection light emitting diode (20) decreases before reaching the track position detection detector (21), which is a light receiving surface.

Therefore, the output level of the track position detection detector addition circuit (27) that handles the sum of the detectors (21) also decreases. If the output level at this time is lower than the reference voltage (29), the output of the position detection output comparator (28) will be a voltage of 10. In response to this ten signal, the LED drive circuit (33
) operates in the direction in which the LED emits light. As a result, the amount of light received by the track position detection detector (21) increases, the output of the track position detection detector addition circuit (28) increases, and the output voltage of the position detection output comparator (28) decreases. The amount of light received is controlled so as to always be constant (same as the reference voltage). In other words, feedback control is working so that the output of the track position detection detector addition circuit (27) is always constant. As a result, the output sensitivity of the PE signal differential amplifier (PE signal sensitivity) also remains constant.

In the above embodiment, the light emitting diode (20) for detecting the track position was attached to the actuator (17) of the optical pickup, and the detector (21) for detecting the track position was attached to the base part holding the actuator (17).
Any structure may be used as long as the deviation can be detected when the actuator (17) moves in the track direction, so there is no problem even if the detector (21) and the light emitting diode (20) are replaced.

Further, by disposing an actuator between the light emitting diode (20) and the detector (21), it is possible to use an actuator track position detection device.

Furthermore, in the above embodiment, the desired amount of light received by the detector (21) can be set by changing the output of the reference voltage source (29) using a semi-fixed resistor.

This makes it possible to absorb all variations in the characteristics of the light emitting diode (20), variations in the light receiving sensitivity of the detector (21), and variations in properties due to temperature characteristics.

Therefore, by installing this device, sensitivity adjustment and the like regarding the track actuator position detection device becomes unnecessary, eliminating adjustment errors and reducing adjustment time.

[Effects of the Invention] As described above, according to the present invention, the output of the light emitting diode is controlled so that the total amount of light received by the photodetector is constant, and the PE sensitivity decreases due to the movement of the actuator in the focus direction. It can prevent PE sensitivity from decreasing due to actuator track tracking, and automatically adjusts the gain in response to variations in light emitting diodes and photodetectors, which have different characteristics, as well as temperature characteristics and changes over time. PE signals with the same sensitivity can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a track actuator position detection device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of a track position detector output control circuit in this embodiment, and FIG. 3 is a tracking Figure 4 is a diagram explaining the principle of error signal generation. Figure 4 is a diagram explaining problems in tracking error signal generation. Figure 5 is a tracking error signal waveform diagram. Figure 6 is a configuration diagram of a conventional track actuator position detection device. Figure 7. are signal waveform diagrams of various parts of the conventional device, and FIG.
) is the waveform diagram of the normal tracking error signal TE, No. 7
Figure (b) is a waveform diagram of the objective lens position detection signal PH.
FIG. 8C is a waveform diagram of the corrected tracking error signal CTH, and FIGS. 8 and 9 are diagrams illustrating problems in the conventional technology. In the figure, (1) is the information recording medium, (2) is the guide groove on the information recording medium, (3) is the objective lens, (4) is the focused spot, (5) is the convex lens, and (6) is divided into two parts. photodetector,
(7) is a differential amplifier, (17) is an actuator, (2
0) is a light emitting diode, (21) is a two-split photodetector for detecting the objective lens position, (27) is a detector addition circuit for detecting track position, (28) is an output comparator for position detection, (29)
) is a reference voltage source, (30) is a track position detector output control circuit, (31) and (32) are track position detection detector iv conversion circuits, and (33) is an LED drive circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Patent Attorney Yoshi 1) Kenji (2 others) 1. Information storage medium 2. Guide groove on the information recording medium 3. Objective lens 4. Focusing spot 7. Differential amplifier Trunking Explanation of the principle of error signal generation Figure 3 Figure 1o: Diffracted light distribution on the 2-split detector 11° Diffracted light distribution on the 2-split detector Explanation of problems in tracking error signal generation Figure 4 Tracking error signal TE Tracking error signal waveform diagram Figure 5 21 Two-split photodetector for detecting objective position/zoo Position diagram No. 6: Configuration diagram of conventional Toranoku actuator position detection device

Claims (1)

[Scope of Claims] An optical device that focuses a light beam from a light source on the information surface of an optical information recording and reproducing medium, and an information track that displaces the light beam from the light source by an eccentric component of the optical information recording and reproducing medium. a track actuator that focuses light on the track actuator; a photodetector that is provided on the track actuator or a base for holding the track actuator and that receives light from a light emitting diode; and a total sum of outputs of the photodetector is constant. A track actuator position detection device comprising: a device for controlling drive power of a light source to a target value;