JPS5862833A - Optical head feed device - Google Patents

Abstract

PURPOSE:To simplify the constitution of a titled device, and also to make it inexpensive, by forming an optical head part provided with a semiconductor laser light source, and an optical means for executing focus control and tracking control, and sticking it to a turning arm. CONSTITUTION:A titled device is constituted of a pivotally supported turning arm 30 to which an optical head part 10 containing a semiconductor laser light source 11, and an optical means which makes laser light from this laser light source 11, 11 incident to a recording medium and also executes focus control and tracking control has been stuck, and an arm driving means which turns this turning arm 30 around the pivot and moves the optical head part 10 to the recording medium with a prescribed locus. According to such constitution, there is no part which moves complicatedly, therefore, the whole constitution is simplified, by which the number of parts is reduced, and an inexpensive device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical head feeding device in an apparatus for optically reproducing a recording medium such as a digital audio disc or video disc.

Generally, in this type of recording medium, pits are formed on the surface of the disk according to information such as audio signals or video signals. Predetermined information can be read by detecting light with a photodetector. An example of this is shown in FIG.

In the figure, a pit track l formed in a spiral shape on a disk is provided with a large number of bits formed in correspondence with recorded information, and an information reading light beam is tracked along this bit track l. Focus control is performed so that the information reading light beam 2 is accurately focused.

When reading information, there is a method in which three light beams arranged in a straight line are used, as shown in Fig. 1. In this case, the central light beam J scans the pit 2 while the focus is controlled. As a result, the information on the pin 30 is read, and tracking control is performed by the light beams on both sides of the central light beam 30. This tracking control separately detects the reflection of the light beam from the disk, and if the detected values (light intensity) of both match, it is assumed that accurate tracking is being performed, and if they do not match, tracking is performed. Assuming that the values are biased, correcting can be done by moving the optical axis of the focus lens and controlling the detected values to match. Here, the tangent of bitttrazug l and the light beam 3. V
If the intersecting angle θ with the line connecting the two lines is at a preset value, it will not have any negative effect on tracking control, but if this intersecting angle θ becomes larger than the set value, is the bit track t on which bit 2 is to be read.
The light beam or beam beamer will hit the bit of the pit track adjacent to the pit track, and there is a risk that an erroneous tracking control operation will be performed. Conversely, if the crossing angle θ is smaller than the set value, the optical beam sensor or optical beam sensor will move to the pit track l where the bit unit is to be read.
Similarly, there is a risk that an erroneous tracking control operation may be performed. The interval between pit tracks l adjacent to each other is extremely small, for example, about 6 μm.1. Since the permissible deviation of the above-mentioned crossing angle θ becomes a very small value, in a method using such three light beams, light beam 3. LI,! Accurate information reading cannot be achieved unless the optical system that generates the information is equipped with a drive system that provides a drive that keeps the intersection angle θ substantially constant.
For this reason, it was inevitable that the structure would become complicated.
On the other hand, instead of using three light beams to perform information reading and accompanying focus control and tracking control, one light beam from the optical head is used to read information, focus control, and tracking control. A method for performing tracking control has also been proposed. In this case, the light beam of the book is irradiated onto the bit of the pit track, and the reflected light beam from the bit is received by, for example, a photodetector divided into light-receiving areas, and is detected based on the output signal of each light-receiving area. ,
In addition to obtaining the information reading signal, electrical signals for performing focus control, tracking control, and furthermore, feed control of the optical head are obtained, and each control is performed using these control electrical signals. Further, in this case, both the tracking control and the optical head feeding control are performed using the same drive mechanism. Here, the driving range required for tracking control is the driving range IiI[! , is different from the encirclement. That is, the driving range for tracking control is sufficient if the disk is stably driven within the eccentricity error (for example, about ±0.7 mrn), and the driving range for optical head feed control is the width of multiple pit tracks ( Ef'lJ is a few cm
), and when comparing the driving accuracy of tracking control and the driving accuracy of feed control, tracking control requires much higher accuracy. Therefore, in conventional devices in which tracking control and optical head feed control are performed by the same drive mechanism, it is impossible to perform two types of drive control with different drive ranges and required precision as described above. This makes the mechanism complicated and extremely expensive. In addition, the tracking control and the optical head feed control interfere with each other, making it easy to generate multiple resonances, making it difficult to obtain a very wide servo band, and furthermore, there is the disadvantage that it tends to be vulnerable to external photography. .

The present invention has been made to solve the above-mentioned problems, and includes forming an optical head section that includes a semiconductor laser light source and optical means for performing focus control and tracking control. An object of the present invention is to provide a simple, low-cost optical head feeding device configured to control the feeding of an optical head by being fixed to a pivotally supported rotary arm.

Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent figures.

FIG. 2 is a schematic diagram showing an example of the optical system of a disc playback device to which the present invention is applied. In the same figure, 10
indicates an optical head section, and the optical head section io houses various optical components described below. That is, // is a semiconductor laser light source, and t is a collimator lens that collimates the light from the light source //. 13 is a side beam splitter, /14 is a mirror, /& is a t/V wavelength plate that rotates the polarization axis of the light, and /A is a focus lens. The light from the light source fl is sent to the disk 20 by the focus lens t6. It is made to be incident on.

t7 is a prism designed to substantially extend the optical path length, and the reflected light from the disk 20 is separated by the polarizing beam splitter 13 and enters the prism. tg is a photodetector that receives reflected light from the prism 17;

In addition, lq is a focus lens drive unit, and a focus lens tb is used for focus control and tracking control.
Position control is performed in the direction along the f optical axis and in the direction orthogonal to it. In this case, the focus nozzle 16 and the focus lens drive section f9 constitute an optical system that performs focus control and tracking control.

In the optical system configured in this way, the nose light generated by the light source // is converted into a parallel beam by the collimator nozzle 12 and directed to the mirror /p by the polarizing beam splitter t3. After the optical path is bent upward by the mirror/F, it passes through the t/e wavelength plate 15 and then passes through the focus lens 16.
Enter, forf)xvy, :/A by diZp'
20 (7:) The reflected light from the disk 20 is focused on the bit track and is converted into a parallel light beam by the focus lens L, and is further collimated by the t/la wavelength plate IS and the mirror/K.
The reflected light returns through the polarizing beam splitter 13 and enters the polarizing beam splitter 13. Since this reflected light has a different polarization axis from the light from the light source //, it goes straight through the polarizing beam splitter 13, passes through the prism t7, and enters the photodetector /g. enter.

The photodetector/g is divided into parts according to the light receiving area, and is connected to a circuit as shown in FIG.
In g, the light receiving area is divided into one area so that it has area al bI c + d, the output end of area a and the output end of area C are connected to adder 2/, and the output end of area b and the output end of area d are added. 22. An adder 23 and a subtracter 2LI are connected in parallel to both output terminals of the adders 2/22, and an information reading output signal (RF multiplied signal is derived from the output terminal of the adder 13. Subtractor 2
A tracking error output is obtained from the output end of LI. This tracking □ error output also has 1, . 1
:11 Control signal for tracking control can be obtained 1, On the other hand,
The outputs of area a and area b of photodetector/g are added to adder 25.
The FB power of area C and area d is connected to adder 2.
connected to Party B. Adder 2! Output end of r and adder 2
The output terminal of B is connected to the subtracter 27, and a focus control signal for focus control is obtained from the output terminal of the subtracter 27. Then, the focus lens drive section/9 is controlled based on the obtained focus control signal and tracking control signal, and the focus lens drive section/? The position of the focus nozzle/A is controlled by , and focus control and tracking control are performed.

The optical head unit 10 which has the above-mentioned various (reinvented materials) and performs the above-mentioned operations can be operated by the optical head feeding device 1j according to the present invention as shown in FIGS. 7 and 5. , driven 3. Firstly, to clarify the structure 5y, 8 and 1, as shown by the dashed line in FIG. rotation is performed.

Describing the MJ mechanism this time, the worm 33 connected to the rotating shaft of the feed motor 32 engages with the worm gear 3μ, and this worm gear, ? A small diameter gear 35 is fixed to the lower part of tI, and is engaged with the fixed gear 3g. The gear 3S consists of two gears 33k and 33f3, which are divided into two gears to eliminate backlash, and these are given rotational forces in opposite directions by springs (not shown). Similarly gear 37
A, Gear 3 is a gear for removing balaclaran divided into BK and 2. On the top side of the optical head section 10, there is a disk 2.
0 is attached to the Chuck knob part tI0, which is rotated by the motor 39 for rotating the disc. Next, the operation will be described. The motor 32 rotates in the direction of arrow A, for example, under the control of a control signal from a servo circuit (not shown) for controlling the movement of the optical head. This rotation is worm 33→
Three stages of deceleration are transmitted through the path of worm gear 3S □Gear 3S □Gear 3A □Gear 37 □Gear 3g,
Rotating arm 3θ is integrated with the rotation of gear 3g to rotate shaft 3/
It is rotated around.

At this time, the optical axis of the optical head unit 10, that is, the optical axis X of the focus lens 16 through which the laser beam enters and exits, moves in the direction of arrow B, drawing a movement trajectory as shown by the dashed line in FIG. Become. On the other hand, when the motor 32 is rotated in the direction opposite to the arrow A in FIGS. 9 and S by a control signal from a servo circuit for controlling the feed of the optical head (not shown), the optical head IQ The rotating arm 30 is rotated so that the axis X moves in the direction opposite to the arrow B on the above-mentioned movement trajectory.

In this way, when the motor 32 is rotated in response to the feed control signal of the optical head, the rotating arm 30 rotates in response to this rotation, and the optical axis X of the optical head section 10 is aligned as shown in FIG. The optical head section 10 follows a bit track of the disk 20 rotating at high speed, drawing a movement locus like a dashed line. Further, within the optical head section fθ, focus control and tracking control are performed to ensure information reading. Note that the low frequency component of the tracking control signal generated by combining the control signal for sending the optical head unit 10 with the output of the photodetector housed within the optical head unit 10 is also involved. Alternatively, the feed motor 32 may be rotated in forward and reverse directions, or a servo motor that rotates depending on the rotation of the disk 20 may be used.
The motor may be used as a feeding motor 432.Next, another example of the optical head feeding device according to the present invention shown in FIGS. 6 and 7 will be described.

In this example, a rotating arm 30 to which an optical head portion to is fixed is shown.
The means for driving the motor is constructed using an electromagnetic segment motor. First, to explain the configuration, the optical head section 10 has a rotating arm 12 that is pivotally supported by an axis U/.
The coil part 13 is fixed to the other end of the rotating arm '42. This coil part q3 is composed of a coil v3A and a topobin p3B, and includes a magnet °: 11 ψV and two Yofugu 5 provided on its upper and lower surfaces.
In the magnetic loop formed by the yoke part qS consisting of A and prB, the magnet retarder, and the yokes p and tA.

G'5B! :Similar magnet vsu' and yoke! f
fA'.

It is arranged in a magnetic loop formed by a yoke portion vy' made of LItB'.

Next, the operation of the apparatus configured as described above will be explained. A drive signal from a drive control circuit (not shown) is sent to the coil F.
When the current is supplied to the coil section II3, the current flows through the coil section II3, causing the magnet pμ, the yoke section star, the magnet lsu', and the yoke t1. t' rotates to the left or right about the axis 'l/' under the force of the magnetic field in the magnetic loops formed respectively. As a result, the rotating arm v2 rotates about the axis F/the entire center, and the optical axis X of the optical head section 10 moves along a trajectory as shown by the dashed line in FIG. Therefore,
The feeding of the optical head section 10 can be controlled in accordance with the control signal supplied to the coil ρ3A.

As is clear from the description of the embodiments described above, the optical head feeding device according to the present invention includes a semiconductor laser light source and an optical system that makes the laser light from the laser light source enter a recording medium and performs focus control and tracking control. A pivotably supported rotating arm to which an optical head unit having a built-in means is fixed; Since it consists of an arm drive means that moves the arm with a hand, there are no parts that move complicatedly, and the overall structure is extremely simple. Along with this, the number of parts can be reduced to a small extent, and a significant cost reduction can be achieved.

Furthermore, since the optical head feeding device according to the present invention is separated from the drive mechanism for tracking control, it is not subject to restrictions from the tracking control system and has the advantage of being able to perform stable optical head feeding control. be.

[Brief explanation of the drawing]

FIG. f is a diagram for explaining an example of a method of reading information from a disc, FIG. FIG. 1 is a plan view showing an example of the optical/rad feeder according to the present invention; FIG. 3 is a circuit connection diagram showing an example of the photodetector and the circuit connected thereto; f
FIG. 6 is a plan view showing another row of the optical head feeding device according to the present invention, and FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. In the figure, 10 is an optical head section, // is a semiconductor laser light source,
12 is a collimator lens, /3 is a polarizing beam splitter, / is a mirror, 15 is //'I wavelength plate, /A is a focus lens, /7 is a prism, ig is a photodetector, t9 is a focus lens drive unit, 20 is a disk, 30. 'I
U is the rotating arm, 31°S is the shaft, 3.2.39 is the motor, 33 is the worm, 3 is the worm gear, 3S to 3g
is the gear, 110 is the chucking part, @,? are the coil, lily, sl' magnet, geta, and geta' are the yoke parts. 311 411 511 Figure 6, 7F! ! J

Claims (1)

[Claims] An optical head section incorporating a semiconductor laser light source and an optical means for making the laser light from the laser light source enter the recording medium and performing focus control and tracking control of the laser light is fixed and arranged in a pivotably supported manner. An optical head feeding device comprising: a rotating arm; and arm driving means for rotating the rotating arm to move the optical head portion along a predetermined trajectory relative to the recording medium.