JPS63167441A - Information memory medium - Google Patents

Abstract

PURPOSE:To permit detection of the absolute position on a recording medium with an optical head and miniaturization of an information memory medium by using an optically specific point provided to a point where information memory is possible as a revolution mark. CONSTITUTION:The optically specific point which generates double refraction is provided to part of the inside circumferential edge in the memory part A of an information recording medium 1 to constitute the revolution mark 2. Laser light from the head receives the double refraction and increases the quantity of the return light when the mark 2 is brought to the position of the optical head by the rotation of the medium 1. The rotating position of the medium 1 is, therefore, detected by detecting the quantity of the return light increasing periodically at every one rotation of the medium 1. There is thus no need for providing a sensor or the like to be exclusively used for detecting the revolution mark and the information memory and reproduction device is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a revolution mark for an information storage medium from which information can be read from, for example, reflected light of an irradiated laser beam.

(Prior Art) Conventionally, information storage media that use optical means for recording and reproducing information can be roughly divided into read-only media.
), recording/reproduction type (Writc Qnce) J
'3 and a rewritable form (E rasable).

In a read-only information storage medium, such as an optical disk, bits (holes) corresponding to the information are formed on a disc-shaped optical disk plate by thermal or optical action, and when the information is to be reproduced, the bits are filled with holes. It irradiates laser light, detects physical changes in the laser light, and reads information.

A record-and-playback type information storage medium uses an optical disk board made of non-erasable material, and when recording, additional information is sequentially added to the unrecorded areas. It is almost the same as the case.

Examples of rewritable information storage media include magneto-optical disks, which are magnetic thin film storage media that use magnetic thin films as information storage media, and phase change discs that utilize changes in reflectance, etc. due to phase change from crystal to amorphous, etc. It is a type disc.

Further, magneto-optical disks can be divided into two types based on differences in recording and erasing methods: an optical modulation method (not shown in FIG. 4) and a magnetic field modulation method (not shown in FIG. 5).

The optical modulation method is magnetized perpendicularly and in the same direction to the 7 surfaces of the magneto-optical disk! r! A weak magnetic field H is applied to the directly magnetized λ9 film 7a in the same direction (and in the opposite direction) using the external magnetic field generator 5, and a focused laser beam is irradiated by the objective lens 37 to the part where information is to be recorded. , the temperature of this part is raised to near the Curie point to avoid reversal of the perpendicular magnetization 'a film body magnetization of this part.In other words, by forming a bit with reversed magnetization only in the part irradiated with strong leave light. A binary signal can be recorded on a magneto-optical disk.

Next, in the case of reproduction, a laser beam with a weaker output (approximately 10%) than the laser beam used for recording is irradiated, and when this linearly polarized laser beam is reflected, it is curved depending on the direction of magnetization of the bit. Because the (Kerr) effect rotates the plane of polarization, this reflected light is detected as the intensity of light through an analyzer. Further, as mentioned above, when the light passes through the perpendicularly magnetized thin film medium, the plane of polarization rotates.
There is a method of using the Kerr effect and the Faraday effect, in which the SE 11 light that has once passed through the perpendicularly magnetized thin film medium is reflected and detected again.

In the magnetic modulation method, when reversing the magnetization of the perpendicularly magnetized thin film 7a, a laser beam is continuously irradiated with a constant intensity, and an external magnetic field generator is used to apply a magnetic field that is reversed according to information. Information is recorded on a magnetized thin film, and reproduction is performed using a method similar to the above-mentioned optical modulation method.

In such a disc-shaped information storage medium,
Information is stored by forming a revolution mark at a predetermined position on the information storage medium to indicate the position of the O-cellar 9 on the information storage medium, and detecting the rotational position of the information storage medium from this revolution mark. It was possible to store, play and erase data in a given sector.

(Problems to be Solved by the Invention) However, in conventional information storage media, the disk substrate of the non-storage portion inside the information storage portion is partially deformed mechanically, or a portion of the information storage portion is Since the revolution mark was created by cutting away the unique parts, it was necessary to construct a dedicated sensor separate from the optical head to detect these unique parts.

For example, in the case of optical discs, a notch was formed near the center of a disc-shaped transparent disc substrate to form the Revolution mark, so a sensor was placed near the rotational drive shaft (center spindle) of the optical disc. This makes it difficult to miniaturize the information storage/reproduction device due to mounting constraints.

Therefore, in information storage and reproducing devices, etc., which are becoming smaller and smaller, there has been a strong desire to improve the detection means.

The present invention has been made in view of the above, and an object thereof is to provide an information storage medium equipped with a simple detection means that can reliably detect the rotational position of the information storage medium.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides an information storage medium capable of reading recorded information using optical means. It was constructed by providing an optical singularity in the part.

(Function) In the information storage medium of the present invention, by using an optical singular point provided in a portion where information can be stored as a revolution mark, the revolution mark can be set using conventional optical means such as an optical head. The absolute position on the information storage medium-L can be detected from the John mark.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of an information storage medium 1 that uses optical means to read information from an optical disk, etc., and an optical singularity that causes birefringence is provided at a part of the inner peripheral edge of the information storage portion. The revolution mark 2 is composed of optical singularities.

FIG. 3 is a partial cross-sectional view showing a general configuration of an information storage medium 1 that uses optical means for reading information, and the material of the disk substrate 11 is transparent acrylic with low birefringence (
PMMA), polycarbonate (PC), polyvinyl chloride, or the like is used, and the recording layer 13 is formed with guide grooves 15 for assisting the tracking operation of the optical head and pits 17 for recording information.

To read out the information detected in the bit 17 from the information storage medium 1 configured in this manner, the laser beam 6 focused by the objective lens 4 of the optical head 8 is irradiated from the bottom side of the information storage medium 1, and the disk substrate 11 is This is done by capturing the laser beam that is transmitted through the storage layer 13 and reflected at the storage layer 13.

Similarly, when detecting revolution mark 2,
This is done by measuring the amount of return light of the laser beam 6 that is incident on the optical head 8.

That is, as is clear from the graph showing the change in the return point in FIG. 2, when the revolution mark 2 reaches the position of the optical head due to the rotation of the information storage medium 1, light is emitted from the optical head 8. Since the laser beam undergoes birefringence while being reflected by the recording layer 13 and returning to the optical head, the return tip increases.

Therefore, the rotational position of the information storage medium 1 can be detected by detecting the return opening W which periodically increases every rotation of the information storage medium 1.

In this embodiment, the return tip is increased using birefringence as an optical singularity, but it is also possible to increase or decrease the return light m or to block it by providing optical scratches or distortions. good.

The configuration of the revolution mark shown in this embodiment is applicable to all information storage media using optical means for storing, reproducing, and erasing information, and is compatible with conventional optical heads. can be used to detect the revolution mark, there is no need to provide the above-mentioned sensor or the like exclusively for detection of the revolution mark, and the information storage/reproduction device can be constructed in a small size and at low cost.

[Effects of the Invention] As explained above, according to the present invention, an optical singularity is provided in the information storage portion of an information storage medium that uses optical means for storing and reproducing information. When used as a revolution mark, there are effects such as the ability to simplify the mechanism of an information recording/reproducing device, etc., since there is no need to provide a detection means.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show an example of this embodiment.
The figure is a plan view showing the position of the optical singularity on the information storage medium, Figure 2 is a graph showing the change in return light due to the optical singularity, and Figure 3 is a cross-sectional view without showing the structure of the optical disc. . 1... Information storage medium 2... Optical singularity A... Information storage part Yasuo Miyoshi, apprentice patent attorney Figure 1 Figure 2

Claims (2)

[Claims] (1) An information storage medium from which at least recorded information can be read using optical means, characterized in that an optical singularity is provided in a portion of the information storage medium where information can be stored. storage medium. (2) The information storage medium according to claim 1, wherein the optical singularity of the information storage medium is due to birefringence.