JPH02265026A - Optical recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing apparatus using an optical disk or the like.

BACKGROUND OF THE INVENTION In recent years, there has been a demand for a recording/reproducing apparatus that can perform high-speed searches and store a huge amount of information, and optical recording/reproducing apparatuses have been developed.

Therefore, the conventional example of such an optical recording/reproducing device was developed as a second example.
This will be explained based on FIGS. 5 to 5. In this optical recording and reproducing apparatus 1, an optical system formed from various lenses 3, 4, a reflecting mirror 5, a beam splitter 6, etc. is arranged on the optical axis of a laser diode 2, and an optical disc 7, which is an optical recording medium, is An optical head 9 is formed to converge a laser beam onto the formed concentric recording track 8. Also, on the optical axis of the laser beam reflected from the recording track 8 and having its optical path changed by the beam splitter 6, there are
Four light receiving elements 10a to 10d arranged in a lattice pattern are arranged via a correction lens 11 and a cylindrical lens 12.

Note that this optical recording/reproducing device 1 has the optical disc 7.
A driving mechanism (not shown) for the optical disk 7 that causes the optical head 9 to optically scan the recording track 8 by rotating the optical disk 7, and a drive mechanism (not shown) for the optical disk 7 that causes the optical head 9 to optically scan the recording track 8, and controls the tracing state of the recording track 8 by moving the optical head 9 in the radial direction of the optical disk 7. It also includes a tracking mechanism (not shown).

In such a configuration, the laser beam emitted from the optical head 9 is focused on the recording track 8 of the optical disk 7 rotated by the drive mechanism, and information is recorded and reproduced by this optical scanning.

Here, in this optical recording/reproducing device 1, the recording track 8
Information is recorded and reproduced using a laser beam focused on the optical disk 7. However, since the distance between the optical head 9 and the recording track 8 changes every moment due to undulation of the optical disk 7, etc., this is corrected. A means is necessary.

Therefore, such a focal position correction mechanism will be explained based on FIG. 3. First, a cylindrical lens 12 gives astigmatism to the laser beam reflected from the recording track 8 of the optical disk 7, and four light receiving elements 10a are arranged in a grid pattern.
~] Detected at Od.

Therefore, the detected values a to d of these light receiving elements 10a to ]Od
The optical system and the like are controlled so that the sum of detected values at diagonal positions becomes the same value. In other words, (Δ+G)-(B + D
)=F. At this time, as illustrated in FIG. 3, the calculated value F is proportional to the difference 2S in the light receiving areas of adjacent light receiving elements 1.0a to 10d, so the optical value is adjusted so that the calculated value F=O. By sliding the converging lens 4 of the head 9 in the optical axis direction, the light spot becomes a substantially perfect circle and the focal point of the laser beam coincides with the recording track 8''.

Problems to be Solved by the Invention In the optical recording/reproducing apparatus 1 as described above, focusing of the optical head 9 is performed based on the detection values A-D of the four light receiving elements 10a to 10d. It is assumed that the optical axis of the laser beam incident on the light receiving elements 10a to 10d coincides with the center of the light receiving elements ]Oa to ]Od, and as illustrated in FIGS. If the light receiving elements 10a to 10lod are off the center, false detection will occur. That is, FIGS. 4 and 5(a).

As shown in (c), even if the light spot is elliptical, there are cases where the difference in the value obtained by adding the detected values A-D at the diagonal positions is O, so focusing using the above-mentioned calculation may result in malfunction. It tends to occur.

As a solution to such problems,
There is a method disclosed in Japanese Patent No. 92. This performs a predetermined calculation based on the detection values obtained from the four light receiving elements, and compensates for optical axis deviation through calculation processing to obtain an appropriate value.

However, this method requires a complicated arithmetic circuit, which hinders the mass production of the device, and also makes it complicated to determine each coefficient required for the arithmetic operation.

In addition, there are other methods, such as arranging a large number of light-receiving elements so that optical axis misalignment can be overlooked, and correcting the position of the light spot incident on the light-receiving element using two-way control, but these methods require a complicated structure. It is not practical as it may lead to problems such as

Means for Solving the Problems An optical head relatively scans a recording track formed on an optical recording medium, and the astigmatic light emitted from the optical head and reflected from the recording track is scanned in a lattice pattern. The first comparator calculates the difference between the detected values of two predetermined adjacent ones of these light receiving elements, and based on the output value of this first comparator, The optical axis displacement means linearly moves the light spot on the light receiving element perpendicular to the optical axis, and the second comparator detects the difference between the two light receiving elements other than the light receiving element to which the first comparator is connected. The focusing means moves the focal position of the optical head in the optical axis direction based on the output value of the second comparator.

The first comparator calculates the difference between the detected values of two predetermined adjacent light receiving elements among the four light receiving elements arranged in a grid pattern, and the optical axis displacement is calculated based on the output value of this first comparator. The means is a light receiving element.”
The second light spot is linearly moved perpendicular to the optical axis, and the second comparator calculates the difference between the two light receiving elements other than the light receiving element to which the first comparator is connected. The focusing means moves the focal position of the optical head in the direction of the optical axis based on the output value of the device, so even if the light spot deviates from the center of the four light receiving elements, the optical axis displacement means linearly moves it to the predetermined position. Since a substantially accurate correction signal can be obtained even if the lens is moved and remains deviated in a direction perpendicular to this, accurate focusing can be performed with a simple structure.

Example An embodiment of the present invention will be described based on FIG.

In this optical recording/reproducing device 13, four light receiving elements 10
Two adjacent light receiving elements among a to lod] Oa, 10
b, an optical axis displacement means (which linearly moves the light spot on the light receiving elements 10a to 10d perpendicular to the optical axis via the comparator 14);
(not shown) are connected. Further, the light receiving element 10
Two adjacent light receiving elements other than a and 10b]Oc, 10
d, a focusing means (not shown) for moving the focal position of the optical head 9 in the optical axis direction via the comparator 15;
is connected.

In addition, as the optical axis displacement means, a solenoid or the like is used to move various optical components such as the reflecting mirror 5 and the light receiving element]Oa~
1. A conceivable focusing means may be one that displaces the Od, and the focusing means may be one that slides the converging lens 4 in the optical axis direction.

Further, the other structure is the same as that of the optical recording/reproducing apparatus 1 described above.

In such a configuration, this optical recording/reproducing device 13
functions in the same way as the conventional optical recording/reproducing device 1.

Note that focusing of the optical recording/reproducing device 13 of this embodiment is performed by directing a laser beam having astigmatism to the light receiving elements 10a to 10a.
10d, and adjacent predetermined light receiving elements 10a to 10
The optical axis displacement means and the focusing means are driven so that the detected values A, B and C, D of d become the same value. Therefore, an example will be described in which the focus of the laser beam does not coincide with the recording track 8 and the light spot has an elliptical shape elongated in the direction of the light receiving elements 10a and 10c.

First, A-B = X is calculated by the comparator 13, and when the optical axis displacement means is operated so that this value It will be in a shifted state.

Therefore, when CD=F' is calculated by the comparator 14, F'2S is obtained as illustrated in FIG. This detected value F' is approximately the same value as the value F detected by the optical recording/reproducing apparatus 1 illustrated in FIG. By sliding the lens 4, the focus of the laser beam will be aligned on the recording track 8. Therefore, in this method, the optical axis is displaced by simple one-way control of the optical axis displacement means, so there is no problem even if the light spot shifts to the left or right in the figure, and even if it shifts downward by 1. , the state as illustrated in FIG. 4(b) is reached, and substantially accurate focusing is performed.

Furthermore, by performing the above-mentioned two types of control simultaneously or alternately at short intervals, it is possible to maintain the light spot in a perfect circle at all times and achieve extremely accurate focusing.

Effects of the Invention As described above, in the present invention, the first comparator calculates the difference between the detected values of two predetermined adjacent light receiving elements among the four light receiving elements arranged in a lattice pattern, and this first comparison Based on the output value of the detector, the optical axis displacement means linearly moves the light spot on the light receiving element perpendicular to the optical axis, and the difference between the two light receiving elements other than the light receiving element to which the first comparator is connected is detected. The second comparator calculates the value, and the focusing means moves the focal position of the optical head in the optical axis direction based on the output value of the second comparator, so that the light spot is moved from the center of the four light receiving elements. Even if the optical axis is misaligned, it is linearly moved to a predetermined position by the optical axis displacement means, and a nearly accurate correction signal can be obtained even if the optical axis remains misaligned in the direction perpendicular to this, so accurate focusing can be performed with a simple structure, and it is easy to calculate. It is extremely simple and does not require complicated arithmetic circuits, nor does it require the formation of a large number of light-receiving elements or a mechanism for moving the light spot in two directions, so the structure of the device is simple and mass production is good. It has the following effects.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is a side view showing the optical structure of a conventional example, and Figs. 3 to 5 show a state in which a light receiving element is receiving a light spot. FIG.

Claims (1)

[Claims] An optical head that relatively optically scans a recording track formed on an optical recording medium, and four lenses arranged in a lattice shape that receive astigmatic light emitted from this optical head and reflected from the recording track. a first comparator that calculates the difference between detected values of two predetermined adjacent ones of these light receiving elements; an optical axis displacement means for linearly moving the spot perpendicular to the optical axis; a second comparator for calculating the difference between two light receiving elements other than the light receiving element to which the first comparator is connected; An optical recording/reproducing apparatus comprising: focusing means for moving the focal position of the optical head in the optical axis direction based on the output value of the second comparator.