JPS60258733A - Erasable optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain complete erasure of an optical recording medium over the entire range by increasing always an erasure optical beam irradiating section than a recording optical beam irradiating section. CONSTITUTION:An erasure optical beam irradiation start position 7 is controlled to come earlier than the recording optical beam irradiation start position 8 by a half r/2 of the major radius of the erasure optical spot M or over and the erasure optical beam irradiation end position 9 is controlled always to come later than the recording optical beam irradiation end position 10 by r/2 or over. Then the erasure optical beam irradiation section is always larger than the recording optical beam irradiation section. Then the energy of the erasure optical beam given to a medium is constant during the recording light beam irradiating section and a sufficient erasure energy is given to the medium. Thus, complete erasure without uneveness is attained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an erasable optical recording and reproducing device.

Conventional configuration and its problems As an optical recording/reproducing device, light from a laser or the like is condensed into a minute light beam with a diameter of about 1 μm using a lens, etc., and is irradiated onto an optical recording medium to record and reproduce signals at high density.1- In addition, an erasable optical recording and reproducing device has been proposed which can repeatedly record and reproduce signals by erasing once recorded signals by irradiation with laser light or the like. This optical recording and reproducing device has high recording density, low memory cost per bit, high-speed access, and stable recording and reproducing without contact between the optical head and the optical recording medium. It is attracting attention as a new memory medium for the future information society.

As an erasable optical recording and reproducing method, a method has been proposed in which thermal energy such as laser light is used to cause a reversible change in optical density by transition between an amorphous state and a crystalline state of an optical recording medium. ing.

In other words, when the temperature of an amorphous optical recording medium with low reflectance and high transmittance is raised to near its melting point and then slowly cooled,
It utilizes the phenomenon that an optical recording medium in a crystalline state transitions to a crystalline state with high reflectance and low transmittance, and conversely, when the temperature of a crystalline optical recording medium is raised in a trench near its melting point and then rapidly cooled, it transforms to an amorphous state. A specific method for obtaining the transition conditions is shown in FIG. FIG. 1a shows a substantially circular minute optical spot L formed by a laser beam or the like on an optical recording medium that moves relatively in the direction of the arrow. When the light intensity of this optical spora) L is increased by the furnace time to raise the temperature of a local part of the optical recording medium, the temperature rise in this local area quickly diffuses to the surroundings, and a rapid heating and cooling condition is obtained, and the optical recording medium Transforms into an amorphous state. On the other hand, as shown in FIG. The heated portion of the optical recording medium is cooled much more slowly than in case a, temperature raising and slow cooling conditions are obtained, and the optical recording medium is transformed into a crystalline state.

Now, in the conventional erasable optical recording/reproducing apparatus using the above-mentioned principle, control is performed so that the recording light beam irradiation section and the erasing light beam irradiation section on the optical recording medium are equal. Figure 2 shows the situation. On the optical recording medium 1, the recording light beam irradiation start position 2 and the erase light beam irradiation start position 3 are controlled to coincide, and the recording light beam irradiation end position 4 and the erase light beam irradiation end position 6 are controlled to coincide. . Strictly speaking, irradiation start positions 2, 3, end position 4.
In No. 5, the centers of the recording light spot) L and the erasing light spot M coincide. In this section, the recording light spot L or the erasing light beam M scans the medium 1 in the direction of the arrow at a constant speed V to perform recording and erasing.

Here, the recording light beam is intensity-modulated and the spot is very small and narrowed, so its diameter can be ignored, so the energy distribution applied by the recording light beam to the medium 1 is as shown in Figure 2 a. It will be like that. On the other hand, since the erasing light spot M has a long elliptical shape, near the erasing light beam irradiation start position 2,
In the vicinity of the erase light beam irradiation end position 4, the energy given by the erase light beam to the medium 1 becomes somewhat small. In other words, if the major axis of spot M is r, the time for which the erasing light irradiates point 6 is , while the time for irradiating points 2 and 4 with the erasing light is -. Therefore, the energy given by v is halved. Figure 2 shows the energy distribution. Therefore, sufficient erasing light energy is not applied near the erasing light irradiation start position 2 and near the erasing light irradiation end position 4, so that sufficient transfer of the medium does not occur.
It is possible that it cannot be completely erased.

OBJECTS OF THE INVENTION An object of the present invention is to provide an erasable optical recording/reproducing device that enables complete erasing over the entire area of an optical recording medium.

DESCRIPTION OF THE INVENTION The present invention is an erasable optical recording/reproducing apparatus in which the erasing light beam irradiation section is always larger than the recording light beam irradiation section.

Description of examples The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing a control system for a recording light beam and an erasing light beam in an embodiment of the present invention. In this embodiment, the erase light beam irradiation start position 7 is controlled so that it is located half the length of the long axis of the erase light spot (M) before the recording light beam irradiation start position 8, and the erase light beam irradiation start position 7 Control is performed so that the end position 9 is located above and behind the recording light beam irradiation end position 1o. Then, the erasing light beam irradiation section is always larger than the recording light beam irradiation section. The energy given to the medium by the erasing light beam is constant during the recording light beam irradiation period, as shown in Figure 3, and sufficient erasing energy can be given to the medium, making it possible to erase evenly and completely. become.

Note that FIG. 3a shows the energy given to the medium by the recording light beam.

Now, FIG. 4 shows a specific example of the configuration of the present invention using the above method. 11 is a disk made of an optical recording medium, which rotates at a constant speed.

On this disk, grooves are formed in a spiral or concentric manner to function as optically detectable guide tracks, and recording, reproduction, and erasing are performed along these grooves.

Reference numeral 12 denotes a recording/reproducing laser of wavelength λ1, which is controlled by a laser drive circuit 12'. Reference numeral 13 denotes an erasing laser of wavelength λ2, which is controlled by a laser drive circuit 13'. During recording, the light emitted from the recording/reproducing laser 12 is passed through the condenser lens 14. Wavelength selection filter 16° polarizing beam splitter 1
6, changes direction with a mirror 17, passes through a wavelength plate 18, and passes through an aperture lens 19, with a diameter of 171? ? Aperture to 2 or less and guidance of the wrinkling disk 11] - A substantially circular spot L is formed on the rack, and recording is performed by lowering the reflectance of that portion. During erasing, the light from the erasing laser 13 passes through the condensing lens 2o, is reflected by the wavelength selection filter 5, and then follows the same path as the recording/reproducing light to illuminate the guide track as an elongated spot. Erasing is performed by restoring the reflectance. During reproduction, only the reproduced light is transmitted to the photodetector 22 by the wavelength selection filter 21.
The change in reflectance on the disk is output. 2
3 is a recording/erasing gate generation circuit, which generates a recording gate signal d.
is inputted to the laser drive circuit 12', and the erase gate signal q is inputted to the laser drive circuit 13', and a recording light beam and an erasing light beam are respectively irradiated in the section where this input signal is H'''.

j In Fig. 4, the solid line represents the recording/reproducing optical path, and the broken line represents the erasing optical path.

FIG. 5 schematically shows the relationship between the two optical spots L and M formed on the guide track of the disk 11 with the above configuration and the guide track. The guide track 24 is moving in the direction of the arrow at a speed V, and two light spots (L, M) are arranged on the guide track 24 with an interval l. Also,
The guide track 24 has pre-engraved addresses 25.
26, it is divided into several register intervals l',
Recording, reproduction, and erasing are performed for each recording section by specifying an address so that a recording/erasing gate is generated from the recording/erasing gate generating circuit 13.

The process from specifying the address of the section to be recorded/erased to generating the recording/erasing gate will be explained in detail. FIG. 6 is a block diagram of the write/erase gate generating circuit. 27 is an address match detection circuit, which detects the time 1 from the input of the address read from the disk and the specified address counter activation signal a.
Pulses b, c, e, and f are generated at 1, 12, and 13 degrees t4 edge.

11.12 and 13.14 can be set arbitrarily. 32 is a recording flip-flop, 33 is an erasing flip-flop, and when a pulse is input when the output of both is "L",
The output becomes HII, and if a pulse is input when the output is HII, the output becomes LII.Thus, a recording gate signal d and an erasing gate signal q are generated from pulses b, c, e, and f.

FIG. 7 shows the recording gate signal in the circuit of FIG. 6.

This is a time chart up to the generation of the erase gate signal. The waveforms in Figures 7a-q are the same as those in Figure 6.
−q signals respectively. As can be seen from FIG. 7, recording begins after t1 and ends after t2 after address matching is detected, and begins after erasure utB and ends after t4. Here, consider the conditions for establishing the relationship between the recording light irradiation section and the erasing light irradiation section as shown in FIG. The explanation will be given with reference to FIG. First, on the medium, the recording light irradiation start position 34 must be located later than the erase light irradiation start position 35. Therefore, vtl〉vt3+ljugo・・・・・・・・・・・・(1)
Next, the erase light irradiation end position 36 must be located before the next address 37, and the recording light irradiation end position 38 must be located one or more places before the erase light irradiation end position 36. .

Therefore, No. 13'>vt4+A! 〉vt2+'−−−−・−(
2) Also, 1 > 1 , 14 > 13 ...... river (
3) 1 Therefore, formulas (1), (2), and (3) are satisfied.
By setting 12, 13, and 14, the erasing light beam irradiation section will always be larger than the recording light beam irradiation section, and sufficient erasing energy will always be given to the recorded section, so complete erasure is possible. .

Effects of the Invention As described above, the present invention has the advantage that the erasing light beam irradiation section is
Since the recording light beam irradiation section is always set to be larger than the recording light beam irradiation section, a constant and sufficient erasing energy is always applied to the recording light beam irradiation section, making complete erasure possible.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the recording light and erasing light spots, Fig. 2 is an explanatory diagram of the conventional recording light and erasing light beam irradiation sections and energy distribution, and Fig. 3 is a diagram showing the recording light and erasing light beam irradiation sections in the present invention. FIG. 4 is a configuration diagram showing an embodiment of the erasable optical recording/reproducing device of the present invention. FIG. 5 is a schematic diagram of a light spot formed on a disk. FIG. 7 is a block diagram of a recording/erasing gate generation circuit, FIG. 7 is a time chart for recording/erasing gate generation, and FIG. 8 is an explanatory diagram of recording light and erasing light beam irradiation control in the present invention. L: Recording light spot, M: Erasing light spot, 8.34: Recording light beam irradiation start position, 1
0°38... Recording light beam irradiation end position, 7,
35... Erase light beam irradiation start position, 9.36.
...Erasing light beam irradiation end position, 25.26.37.
. . . address section, 2 . . . recording/reproducing laser, 3 . . . erasing laser. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure α 1-4-y l-barrel Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] It is configured to record and reproduce signals at high density by irradiating an optical recording medium with output light from a laser, etc., and to repeatedly record and reproduce signals by erasing the once recorded signal by irradiating the output light from a laser or the like again. An erasable optical recording/reproducing apparatus characterized in that the erasing light beam irradiation section is always larger than the recording light beam irradiation section.