JPS6346624A - Optical disk index mark detector - Google Patents

Abstract

PURPOSE:To prevent the occurrence of malfunction due to dust or dirt adhered to a disk by arranging two mark sensors at a prescribed interval in the broadwise direction of an index mark and ANDing the detection signals of the two mark sensors. CONSTITUTION:The two mark sensors 20, 30 are arranged at a prescribed distance in the broadwise direction (radial direction of the disk 10) of the index mark 12 at the position corresponding of the optical disk 10 to detect an index mark 12 at each respective position. That is, a light beam (a) is radiated to the prescribed position of a disc face and its reflected light beam (b). Outputs of both the mark sensors 20, 30 are subject to binary coding by comparators 21, 31 respectively and ANDed by an AND circuit 40. Even if dust or dirt exists on the disk face, it is detected by any of the two mark sensors 20, 30 but seldom detected simultaneously. Thus, the occurrence rate of malfunction as the index mark detector is much small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc device for recording and reproducing information on an optical disc, and particularly relates to an improvement in a device for detecting index marks on a set optical disc.

In the case of a conventional CAV (constant rotational speed) type optical disc, an annular index mark 12 is provided at a predetermined position from the center of the optical disc 10, as shown in FIG. The index marks 12 are linear optical marks arranged radially at a constant width.0 On the optical disk device side, as shown in FIG.
An index mark detection device is provided which includes a mark sensor 14 disposed at a position corresponding to the mark sensor 14 and a comparator 16 that binarizes the output of the mark sensor 14.

The mark sensor 14 is a reflective optical sensor that irradiates the surface of the disk 10 with a thin light beam a and receives the reflected beam b. This allows index mark 1
2 black and white (high and low reflectance) is detected, comparator 1
6, the corresponding binarization code is obtained.

The control unit of the optical disk device recognizes the position information of the rotating optical disk 0 based on the signal from the comparator 16, and uses it for control such as generating a track address gate signal, generating a jumping timing, and generating a trunking control on timing. do.

Problems to be Solved by the Invention The index mark 12 is made up of thin linear marks arranged at a constant pitch, but if there is small dust or dirt attached between the linear marks, The output of the mark sensor 1, ↓ may be at the same level as the linear mark due to the dirt. In other words, dust or dirt attached to the index mark 12 portion may be mistakenly detected as a regular linear mark. □ When the above-mentioned erroneous signal is output from the index mark detection device, the control section of the optical disk device Since the rotational position of the optical disk is incorrectly recognized and the above-mentioned timing control is performed according to the incorrect position information, information cannot be read/written correctly.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide an index mark detection device for a comb optical disc that is less likely to malfunction due to dust or dirt adhering to the disc.

Means for Solving the Problem Therefore, in the present invention, two mark sensors are arranged at a predetermined interval in the width direction of the index mark of the optical disc (radial direction of the optical disc), and the detection signals of these two mark sensors are The structure was designed to take the logical product of .

Operation: The two mark sensors are arranged in the width direction of the index mark and detect the same linear mark at each position at the same timing. Therefore, the AND of the detection signals is established for a regular linear mark. Even if a detection signal is output from only one of the two mark sensors, the above-mentioned AND does not hold.

Embodiment FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 10 denotes an optical disk set on a rotary table, and as shown in FIG. 2, an annular index mark 12 is provided at a predetermined position from the center of the optical disk 10.

The index marks 12C are linear optical marks arranged radially at a constant pitch.

Mark sensors 20 and 30 each consist of a reflective optic sensor as in the prior art. 2 mark sensors 20.3
0 is a position corresponding to the index mark 12 of the optical disc 10, which is arranged at a predetermined interval in the width direction of the index mark 12 (radial direction of the disc 10), and the index mark 12 is detected at each position. In other words, the outputs of both mark sensors 20 and 30, which irradiate a predetermined position on the disk surface with a light beam a and receive its reflected beam b, are binarized by a comparator 2] and 31, and then output by an AND circuit 40. The logical AND is performed.

In the above configuration, under normal conditions, as the optical disc 0 rotates, both mark sensors 20 and 30 detect the same linear mark at the same timing, and at that time, the outputs of both mark sensors 20% and 30 are equal to the torque. becomes, AND circuit 4
The input condition of 0 is satisfied and the output becomes H level. This is the mark detection signal.

When dust or dirt adheres to the disk surface and reaches the detection position by the mark sensor 20.30, the output of the mark sensor 20.30 becomes H level. However, it is extremely rare for large dust or dirt to adhere to both the detection position by the mark sensor 20 and the detection position by the mark sensor 30.

Even if the optical disk 10 is set in the device with dust or dirt attached to the index mark 12, in most cases the dust or dirt is minute (and therefore overlooked), and the two mark sensors 20 30 degrees, but it is extremely rare for them to be detected at the same time.

Even if an erroneous detection occurs in only one of the mark sensors m 30, the output of the AND circuit 4o will be at L level, and this will not result in a final erroneous detection. Therefore, the incidence of malfunction as an index mark detection device is extremely low.

In addition, in the embodiment of the queen, mark sensors 20, 3
Although the output of 0 is binarized only by level discrimination,
The present invention is not limited to this. index mark 12
Since the thickness of the linear mark constituting the mark is constant, marks or other stains may be distinguished from the time width of the output of the mark sensor 20, 30 and then binarized. By doing so, malfunctions due to dirt or the like can be further reduced.

Effects of the Invention As explained in detail above, according to the present invention, with a simple configuration of appropriately arranging two mark sensors and calculating the logical product of their outputs, it is possible to detect dust and dirt attached to an optical disk. The probability of misrecognizing dirt as a genuine mark is greatly reduced, greatly contributing to improving the reliability of optical disk devices.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an outline of an apparatus according to an embodiment of the present invention;
FIG. 2 is a plan view of an optical disc, and FIG. 3 is a schematic diagram of a conventional apparatus. 10... Optical disc, 12... Index mark, 20. 30... Mark sensor, 40... Name of AND circuit agent Patent attorney Toshio Nakao and 1 other name 1 Figure

Claims (1)

[Claims] A plurality of mark sensors are arranged at predetermined intervals in the radial direction of the optical disc at positions corresponding to the index marks of the optical disc set on the rotary table, and detect the index marks at respective positions; 1. An index mark detection device for an optical disc, comprising means for calculating a logical product of detection signals of mark sensors.