JPH0737267A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform a stable reproduction even for the pit edge system. CONSTITUTION:When an optical card 1 is irradiated by an optical spot 102 for reproduction, the information modulated with the pit 105 is detected by a light receiving part 107 of an optical detector, and at this time, the shape and size of the light receiving part 107 of optical detector are made to be the same as those of an optical spot 101 for recording. By the constitution made in such a manner, the stable reproduction is attained even for the case of pit edge system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for optically recording / reproducing information on / from an information recording medium such as an optical card.

[0002]

2. Description of the Related Art Optical cards have attracted attention as recording media that are easy to carry because they can write large amounts of data into credit cards. Recording and reproduction of information with respect to this optical card are performed by a laser beam generated from an optical head, and there is, for example, a single light source system in which an information recording light beam and an information reproducing light beam are generated by the same light source. There is also a two-light source system in which a first light source for generating an information recording light beam and a second light source for generating an information reproducing light beam are independently provided.

Compared to the single light source method, the dual light source method can perform a recording operation and a verify operation at the same time during recording, and can simultaneously read out a plurality of tracks at the time of reproduction, and thus has an advantage of shortening the reproduction time. Yes, this method is often used.

There are also two types of recording methods, a pit position recording method and a pit edge recording method. The pit position recording method is a method in which information is provided in the interval between pits. This is a method that has information on the length of the gap.

FIG. 4 shows a state in which an optical card of the pit position recording system is being accessed by a recording / reproducing apparatus of the two light source system. Optical card 1
Has a recording area 100 in a part thereof, and the recording area 100 has a plurality of track guides 103 formed in parallel in the longitudinal direction as shown in an enlarged view on the right side. An information track 104 is formed between the guide tracks 103.

At the time of information recording, a pit 105 is formed by the recording light spot 101, and at the time of reproduction, a reproduction light spot 102 extending over three tracks in this example is irradiated, and the reflected light is reflected by a photodetector. The light receiving unit 106 detects the light. The optical card 1 and the light beam spots 101 and 102 are configured to relatively move in a card feeding direction, which is a direction parallel to the track extending direction, for example.

FIG. 5 shows a state in which information recorded by such a pit position recording system is being reproduced. FIG. 5A shows recording pits, and each pit is a position corresponding to the information. It is recorded in. FIG. 5B shows a reproduction signal when this recording pit is reproduced by the light receiving section of the photodetector having a square shape, and FIG. 5C shows the reproduction signal by the light receiving section of the photodetector having a round shape. The reproduced signal when reproduced is shown.

In the pit position recording system, in order to detect the interval between the pits, the peak of the light fluctuation when the pits pass through the light receiving part of the photodetector is detected, and the peak-to-peak interval is detected. Playing information.
In this method, it is sufficient if the distance between the pits and the center of the pits can be detected.
The shape and size can be freely selected within the range of twice. Then, as shown in FIGS. 5B and 5C, although there is a difference in the detection signal waveform due to the difference in the shape of the photodetector,
There is no difference in the peak position of the waveform that detects the pit center,
Both can reproduce the information correctly.

FIG. 6 is a diagram showing a pit edge recording method. FIG. 6A shows recording pits, and pits having a length corresponding to information are recorded. FIG. 6B shows a reproduction signal when the recording pit is detected by the photodetector of the photodetector having a rectangular shape, and the information of the edge of the pit is extracted. In FIG. 6, the alternate long and short dash line indicates the position where information is detected.

[0010]

However, in the pit edge method, as shown in FIG. 6, if the no-signal time continues for a predetermined time or longer, the detection timing may deviate from the edge position of the pit, and this deviation occurs. However, there is a problem that it affects the determination of "1" or "0" of the data after the signal processing.

The present invention has been made in view of such a situation, and is intended to enable stable reproduction even in the pit edge recording system.

[0012]

In order to solve such a problem, the invention of claim 1 according to the present invention is a first light source for generating light for recording information and a first light source for generating light for reproducing information. In the optical information recording / reproducing apparatus having two light sources, a semiconductor laser in which a reference pit length is defined as a shape and a size when a light receiving portion of a photodetector for detecting a reproduction signal is projected on an optical recording medium. It is characterized by being the same as the spot.

According to a second aspect of the present invention, a reproduction signal is detected in an optical information recording / reproducing apparatus having a first light source for generating light for recording information and a second light source for generating light for reproducing information. The shape and size of the light receiving portion of the photodetector projected onto the optical recording medium are the same as the standard value of the minimum pit.

According to a third aspect of the invention, a reproduction signal is detected in an optical information recording / reproducing apparatus provided with a first light source for generating information recording light and a second light source for generating information reproducing light. The shape and size of the light receiving portion of the photodetector projected on the optical recording medium are the same as the spot of the first light source for recording information.

[0015]

The spot on the optical recording medium by the light receiving portion is set so that the shape and size of the recording light spot are the same, the track is scanned by the spot, and the pit information is reproduced along with the scanning. It

[0016]

1 is a diagram showing the structure of an optical head to which the present invention is applied. A recording beam generated by a laser diode 2 is collimated by a collimator lens 3 and enters a polarizing beam splitter 4. .

Since the parallel beam for recording has a linearly polarized component due to the property of the laser diode 2,
The parallel beam passes through the polarization beam splitter 4 as it is and enters the objective lens 5. This light is the objective lens 5
Are converged to form a circular spot on the optical card 1, locally increase the energy density, and cause a thermal irreversible change in the recording layer of the optical card 1 to form a recording pit.

On the other hand, as a light source of the reproducing light beam, for example, a light emitting diode 10 is used, and the reproducing light beam generated from the light emitting diode 10 becomes substantially parallel light by the collimator lens 9 and passes through the non-polarizing beam splitter 8. Then, it enters the polarization beam splitter 4.

After being reflected by the polarization beam splitter 4, it is incident on the optical axis of the objective lens 5. This light is converged by the objective lens 5 and applied onto the optical card 1. In the optical card 1, the reflected light is modulated by the difference in reflectance depending on the presence or absence of pits, and the reflected light is detected by the photodetector 6 via the polarization beam splitter 4, the beam splitter 8 and the condenser lens 7. To be done.

FIG. 2 is a diagram showing an embodiment of the present invention in which a recording light spot 101 of a laser diode 2 and a reproducing light spot 102 of a light emitting diode 10 are formed on an optical card 1. The same symbols are used for the same parts as in FIG.

In this example, the shape and size of the light receiving portion 107 of the photodetector 6, that is, when the light receiving portion of the photodetector 6 is projected onto the optical card 1 through the optical system shown in FIG. The shape and size of the recording spot are the same as the shape and size of the recording spot for recording information. The diameter of the circular light receiving portion actually formed in the photodetector 6 is A,
When the focal length of the condenser lens 7 is fa and the focal length of the objective lens 5 is fb, the diameter B of the circle projected by the light receiving unit is
It is expressed by the following equation. B = A × (fb / fa)

With this structure, as shown in FIG. 3, stable reproducing performance can be obtained even in the pit edge reproducing system.

The shape and size of the recording light spot 101 are almost the same as the shape and size of the spot light of the laser diode that defines the reference pit defined by the standard of the optical card 1, and the standard. It is almost equal to the shape and size of the minimum pit defined in. Therefore, the shape and size of the light receiving portion 107 of the photodetector may be the same as the shape and size of the semiconductor laser spot defining the standard pit length defined by the standard, and also defined by the standard. The shape and size of the smallest pit may be used.

[0024]

As described above, in the optical information recording / reproducing apparatus according to the present invention, the shape of the light receiving portion of the optical head is set to be approximately the same as the shape and size of the recording light spot.
The effect is that stable reproduction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a relationship between a light spot and a track when the present invention is applied.

FIG. 3 is a diagram showing a reproduction signal when reproducing information recorded by the pit edge recording system of the present invention.

FIG. 4 is a diagram showing a relationship between a light spot and a track of a conventional device.

FIG. 5 is a diagram showing a reproduction signal when reproducing information recorded by a pit position recording system.

FIG. 6 is a diagram showing a reproduction signal when reproducing information recorded by a pit edge recording system.

[Explanation of symbols]

 1 Optical Card 2 Laser Diode 3, 9 Collimating Lens 4 Polarizing Beam Splitter 5 Objective Lens 6 Photodetector 7 Condensing Lens 8 Beam Splitter 10 Light Emitting Diode 100 Optical Recording Section 101 Recording Optical Spot 102 Playback Optical Spot 103 Track Guide 104 Track 105 Pit 106, 107 Light receiving part of photodetector

Claims (3)

[Claims] 1. An optical information recording / reproducing apparatus provided with a first light source for generating light for recording information and a second light source for generating light for reproducing information, comprising a photodetector for detecting a reproduction signal. An optical information recording / reproducing apparatus characterized in that the shape and size of a light receiving portion projected onto an optical recording medium are the same as the spot of a semiconductor laser defining a reference pit length. 2. An optical information recording / reproducing apparatus provided with a first light source for generating information recording light and a second light source for generating information reproducing light, wherein a photodetector for detecting a reproduced signal is provided. An optical information recording / reproducing apparatus characterized in that a shape and a size of a light receiving portion projected on an optical recording medium are made to be the same as a standard value of a minimum pit. 3. An optical information recording / reproducing apparatus provided with a first light source for generating light for recording information and a second light source for generating light for reproducing information, comprising: a photodetector for detecting a reproduction signal. First information for recording the shape and size of a light receiving unit projected onto an optical recording medium
The optical information recording / reproducing apparatus is the same as the spot of the light source of.