JPS615446A - Erasable optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To average the intensity distribution inside a light spot for erasion and to eliminate a local intensity fluctuation, by providing a diffracting means which diffracts the output light of a laser array which is a light source for erasion in the direction, in which the light spot scans a recording medium. CONSTITUTION:An optical beam (l) outputted from a semiconductor laser 101 for recording and reproducing which produces light having a wavelength lambda1 is transformed into an almost parallel optical beam by a condenser lens 102 and passed through an optical beam synthesizer 105 and beam splitter 106. After passing through the beam splitter 106, the optical beam is reflected by a reflecting mirror 107 and forms an almost circular light spot L on the guide track 51 of an optical recording disk after passing through a diaphragm lens 108. Another optical beam (m) outputted from a laser array 103 for erasion which produces light having a wavelength lambda2 is transformed into an almost parallel optical beam having an oval cross section by a condenser lens 104 and reflected by the synthesizer 105 after passing through a diffraction element 118. After reflection, the optical beam forms an oval light spot M, the direction of whose major axis coincides with the longitudinal direction of a groove 51, on the groove 51. The element 118 gives a diffracting effect to the beam (m) in the direction of groove 51 and the intensity fluctuation inside the light spot M for erasion can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device. More specifically, light from a laser or the like is irradiated with a diameter of 1 mm using a lens or the like.
Focusing the light beam into a minute light beam of about μm, irradiating it onto the optical recording medium,
The present invention relates to an erasable optical recording and reproducing device that can record and reproduce signals at high density and repeatedly record and reproduce signals by erasing the once recorded signals by irradiating with laser light or the like.

Conventional configuration and problems This optical recording/reproducing device has the advantages of high recording rate, low memory cost per bit, high-speed access, and stable contact between the optical head and the optical recording medium. Because it can perform recording and playback, it is attracting attention as a new storage 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 to near its melting point and then rapidly cooled, it transforms into 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 light spot L is strengthened for a short period of time to raise the temperature of a local part of the optical recording medium, the temperature increase in the local part quickly diffuses to the surroundings, and a rapid heating and cooling condition is obtained, and the optical recording medium becomes non-stick. Transition to crystalline state. On the other hand, as shown in FIG. The heated portion of the recording medium is cooled much more slowly than in case a, temperature raising and slow cooling conditions are obtained, and the optical recording medium transforms into a crystalline state.

Based on the above principle, as an example of an erasable optical recording/reproducing device, for example, as shown in FIG. A method has been proposed in which two light beams are arranged in a guide groove (Japanese Patent Application No. 59-52607).
No.)0 In Fig. 2, 61 indicates a known guide groove coated with an optical recording material provided on an optical recording disk, and arrow A
indicates the direction in which the optical recording medium moves relative to the irradiated light spots, M, L, and X indicates one point on the optical recording medium. The signal recorded on point It is done.

Recording and erasing are performed in this manner. The feature of this method is that it has a very simple configuration and can erase records in real time. In order to ensure the transition of the recording material to a crystalline state during erasing and to perform complete erasing, it is necessary to allow a long slow cooling time after the temperature is raised above the melting point. That is, it is necessary to increase the length of the spot M in the groove direction. As one way to avoid this, conventionally it has been proposed to use a laser array as an erasing light source and arrange the light emitting points so that the direction in which they are lined up coincides with the direction of the groove, thereby increasing the length of the spot M. ing. The situation is schematically shown in FIG. Output l from laser array 31.

The light is focused by the condensing lens 32. A spot M is formed on the guide groove 61 by the aperture 9 lens 33. The laser array 31 is
Image A' of light-emitting points A, B, and C within spot M,
B' and C' are arranged so as to line up along the guide groove 61. In this way, the long axis of the spot M becomes larger than when using a laser with a single light emitting point. However, in the case of a laser array, if each light emitting point is driven independently, and in consideration of suppressing the amount of heat generated and extending the life, a certain distance between each light emitting point is required. Therefore, if the interval is large, the intensity distribution profile of the spot M will become as shown in FIG. The dotted line represents the intensity distribution of each light emitting point alone, and the overall intensity distribution is represented by the solid line. In this case, 75,1
．． Local intensity fluctuations occur between B1 and between B' and C', and this fluctuation becomes more significant as the distance between the light emitting points of the laser array increases.

Therefore, at the time of erasing, between A' and Bz, 33/,
Between C and C, the slow cooling condition of the recording medium is not maintained, and the recording medium becomes rapidly cooled or almost rapidly cooled, and the transition to the crystalline state does not occur, and erasing may not be possible.

OBJECTS OF THE INVENTION It is an object of the present invention to average the intensity distribution within an erasing spot by a laser array to eliminate local intensity fluctuations.

Structure of the Invention The present invention uses a diffraction element or the like to disperse light from each light emitting point of a laser array into a spot, thereby averaging the intensity distribution within the spot and eliminating local intensity changes. It is an erasable optical recording and reproducing device.

DESCRIPTION OF EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows an embodiment of an optical recording/reproducing apparatus in which the present invention is implemented. In the figure, reference numeral 101 indicates a recording/reproducing semiconductor laser that generates light of wavelength λ1, and reference numeral 4 indicates its output light beam. Reference numeral 102 denotes a condensing lens, which condenses the output light of the semiconductor laser having a spread into a substantially parallel light beam.

105 is a light beam combiner that transmits light with wavelength λ1 and reflects light with wavelength λ2, which will be described later; 106 is a beam splitter;
Reference numeral 107 indicates a reflecting mirror. The light beam l of the semiconductor laser 1o1 passes through these optical elements and enters the aperture lens 108. The aperture lens 108 narrows down the incident light beam L to form a substantially circular light spot L on the guide track 51 on the optical recording disk. Reference numeral 109 denotes an actuator for driving the aperture lens 108, which drives the aperture lens in the optical axis direction in response to surface wobbling of the disk to perform known focus control. This actuator still performs known tracking control by driving the aperture lens 108 in the radial direction of the disk.

In FIG. 5, 103 is a laser array that generates a light beam m of wavelength λ2, and 104 is a condenser lens thereof. The condensing lens 104 collects the output light beam m of the laser array 103.
is converted into approximately parallel light with an elliptical cross section. This light beam m
is reflected by the beam combiner 105 and enters the aperture lens 108 through almost the same optical path as the light beam L, and an elliptical shape is formed on the same groove 61 as the light spot L, as shown in FIGS. 3 and 4. A light spot (M) whose major axis direction coincides with the longitudinal direction of the groove 51 is formed.

In Figure 5, the light reflected by the optical recording disk is the aperture lens 1.
08. The light passes through the mirror 107 and enters the beam splitter 106, the optical path of which is changed, and the light enters the filter plate 111. Here, only the light C1) with wavelength λ1 is transmitted, and the wavelength λ2
indicates a filter plate through which the light (m) is not transmitted. A single lens 112 converts the reflected light beam l into an aperture beam. 1
Reference numeral 13 denotes a reflecting mirror, which serves to block and reflect about half of the light focused by the single lens 112 and guide it toward the photodetector 115.

Reference numeral 114 denotes a two-split photodiode for detecting a focus error signal, which is placed at the focus point of the single lens 112 and detects a conventionally known focus error signal in response to movement of the split light 41.

115 is a two-split photodiode for detecting a tracking error signal, and the reflected light β by the mirror 113 is
2, the conventional tracking (error signal is detected).
The signal recorded in the guide groove 51 on the optical recording disk is reproduced by a photodetector 114 or 115.

A laser drive circuit 117 that drives the laser array 103 is a laser drive circuit that drives the laser 101 . 118 is a diffraction element used in the present invention to control the light intensity distribution of the light spot M.

The diffraction element 118 is directed mainly in the direction of the guide groove 51 on the disk (mainly only in one-dimensional direction) with respect to the incident light beam m.
This is a diffraction element that gives a diffraction effect to the guide groove, and is used for the purpose of changing the intensity distribution of the erasing light spot created by each light emitting source of the laser array on the guide groove. The function and configuration of this diffraction element will be specifically explained below.

FIG. 6a shows the relationship between the diffraction element 118 in FIG. 6, the aperture lens 1o8, and the guide groove 61 on the optical recording disk. Arrow A indicates the direction in which the groove 51 moves.

In this figure, the substantially parallel light (m) incident on the diffraction element 118 has an intensity distribution as shown in Figure 6, diagram 1, and Xl, x
2. x3 indicates the position of its maximum. i.e. xl, x2
．． X3 corresponds to the center of each light emitting point of the laser array. The angle of incidence on the diffraction element 118 is xl.

x2. Since there is a slight difference in X3, the arrival point of each 0th order light on the aperture lens is different from X1. X2 and Xs exist to some extent. Conventionally, since there is no diffraction element 118, there is only 00th order light, resulting in an intra-spot intensity distribution as shown in FIG. Therefore, the diffraction element 118 is arranged so that each of the ±1st-order lights fills the space between points X1, X2, and X3 on the aperture lens, and the intensity of each diffracted light is the same.
The intensity distribution within the erased spot at that time is shown in FIG. 7a. The broken line shows the intensity distribution of each diffracted light alone, and the solid line shows the intensity distribution of the whole eyedropper M. In this case, there will be no local intensity fluctuations within the erasing light spot M, and when the point X on the recording medium passes under the erasing light spot y'-M, the slow cooling conditions will not be disturbed on the way. The transition to the crystalline state is complete and complete erasure is possible.

Furthermore, if the intensity distribution of the substantially parallel light m incident on the diffraction element 118 is configured to become 2 in Figure 6 by increasing the intensity of one light emitting point of the laser array, the intensity within the light spot M is The distribution is shown in Figure 7. The broken line shows the intensity distribution of each diffracted light alone, and the solid line shows the intensity distribution of the entire spot M. When point X passes through this spot M, the time required for the temperature of point X to rise above the melting point becomes shorter, so
Since the annealing time is longer than in Figure a and the annealing state is not disturbed, a transition to a more perfect crystalline state occurs and complete erasure is possible.

In this way, by using the diffraction element, even if the distance between the light emitting points of the laser array is large, the intensity distribution within the erasing light spot can be averaged and local intensity fluctuations can be eliminated.

Specific examples of the diffraction element 118 include, for example, one that has stripes with a density on a transparent glass and the width and interval of the stripes are changed, and one that has grooves on a transparent glass and the width and pitch of the grooves. Possible examples include changes in the .

Effects of the Invention As described above, according to the present invention, when a laser array is used, it is possible to always average the intensity distribution within the erasing light spot and eliminate local intensity fluctuations, regardless of the distance between the light emitting points. As a result, it becomes possible to maintain a stable slow cooling state, and complete erasure is achieved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the erasable optical recording method used in the present invention, Fig. 2 is a diagram showing the arrangement of the light spot on the optical recording thin film and the direction of movement of the optical recording thin film, and Fig. 3 is a diagram showing the conventional laser recording method. A diagram showing a spot forming method using an array, FIG. 4 is a diagram showing the intensity distribution of a conventional erasing spot, and FIG. 6 is a configuration diagram showing an example of the erasable optical recording/reproducing device of the present invention. , FIG. 6 is an explanatory diagram of the diffraction element in the same example, and FIG. 7 is a characteristic diagram showing the intensity distribution of the erase spot on the optical recording thin film according to the present invention. L... Recording light spot, M... Erasing light spot, 31.103... Laser array, 1
o1... Laser for recording and reproduction, 118...
・Name of agent for diffraction element 01' Patent attorney Satoshi Nakao
Figure 1 C'b) Figure 4 A'B'(/' Figure 5 Figure 6 (Illusion)

Claims (1)

[Claims] It has a laser array as an erasing light source and a diffraction means for diffracting the output light of the laser array in a direction in which a light spot scans on a recording medium, and the intensity distribution within the light spot formed by the laser array is 1. An erasable optical recording and reproducing device characterized in that it is configured to average and eliminate local intensity fluctuations.