JP2583273C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for optically recording and reproducing information, and more particularly to a method and an apparatus used for a card-shaped optical information recording medium. (Prior Art) Conventionally, as this type of optical information recording medium, an optical card called a write-once type, which can be recorded once and reproduced many times, is known. In this write-once optical card (hereinafter, abbreviated as an optical card), information is focused on a light beam modulated according to recording information to a minute light spot by a lens, and the minute light spot (hereinafter, abbreviated as a light spot) is written on the optical card. A pit row (information track) that can be optically detected by irradiating the information recording section with the information and scanning the information recording section is recorded in such a manner that the light reflectance of the pit portion is smaller than that of other portions. Further, an information spot is irradiated and scanned with a light spot having lower light energy than that at the time of recording on the information track, and reflected light from the information track is detected by a light receiving diode to reproduce information. (Problems to be Solved by the Invention) In order to record and reproduce information by irradiating an optical spot with an optical spot, an ordinary optical head is used, and scanning of the optical spot is performed by using either the optical head or the optical card. This is performed by reciprocating. However, the optical head is a precision device composed of a large number of optical elements and driving elements, so that the optical head is not sufficiently resistant to sudden movements such as sudden acceleration and sudden deceleration. Since the setting error must be kept to a minimum, the shuttle on which the optical card is mounted must have a rigid structure that can press the optical card and correct the optical card's warpage, etc. to some extent, and there is a limit to weight reduction. . Therefore, high-speed movement is difficult regardless of whether the optical head side or the optical card side (shuttle side) is reciprocated, and it is difficult to realize high-speed information recording / reproducing. However, especially in the case of reproducing information, the frequency of use is large, and there is a strong demand for high speed, and the conventional technology has a problem that such a demand cannot be satisfied. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to record information using an optical head of a known three-beam system (also referred to as a three-spot system). It is an object of the present invention to provide an optical information recording / reproducing apparatus in which the reading speed of information is increased by a factor of two or four while the speed of the reciprocating motion on the optical head side or the shuttle side remains unchanged with the same optical head. In this specification, taking out information from an information track by a light spot is referred to as information reproduction, and taking out the reproduced information into a memory and then taking it out is referred to as information reading. (Means for Solving the Problems) In order to achieve the above object, the present invention uses an optical head having a diffraction grating and an optical information recording medium having a guide track. Recording of information and tracking with ± 1st-order diffracted light are performed. When reproducing information, tracking is performed with 0th-order diffracted light, and information is reproduced with higher-order odd-order diffracted light including ± 1st-order diffracted light or ± 1st-order diffracted light. An optical information recording / reproducing method, and a diffraction grating, wherein a plurality of beams composed of each order diffracted light including 0th-order diffracted light, ± 1st-order diffracted light, and higher-order diffracted light from parallel rays are formed and placed at predetermined positions. An optical means for irradiating the plurality of beams to the optical card and condensing the plurality of beams reflected from the optical card at a predetermined focal position; Four elements for receiving the zero-order diffracted light in the plurality of beams and forming an electric signal, and at least one pair of elements arranged at positions sandwiching the four elements and receiving the ± first-order diffracted light and forming an electric signal A photoelectric conversion unit having an element, arranged at the predetermined focal position of the optical unit, receiving the plurality of beams and forming an electric signal for each of the diffracted light beams, and a diagonal direction among the four elements. A circuit for forming a focusing signal by calculating a difference between the sum of electric signals due to the 0-order diffracted light of two elements;
A circuit for forming a tracking signal at the time of recording by obtaining a difference between electric signals of the pair of elements due to ± 1st-order diffracted light, and an electric signal of 0-order diffracted light of each of two elements on the same side of the four elements. And a circuit for forming a tracking signal at the time of reproduction by obtaining a difference. At the time of recording information, information is recorded with 0th-order diffracted light, tracking is performed with ± 1st-order diffracted light, and at the time of reproducing information, tracking is performed with 0th-order diffracted light. ±
An optical information recording / reproducing apparatus which reproduces information using first-order diffracted light or ± first-order diffracted light. (Operation) To record information on an optical information recording medium, a high-energy light beam is required. Therefore, recording is performed by irradiating the medium with high-energy 0th-order diffracted light formed by a diffraction grating. At this time, ± 1st-order diffracted light having lower energy than the 0th-order diffracted light is used for tracking,
Focusing is performed using zero-order diffracted light reflected from the surface of the medium. In order to reproduce the information recorded on the optical information recording medium in this way, it is necessary to simultaneously reproduce the information from a plurality of tracks on the medium. For this purpose, the medium surface is irradiated with a plurality of light beams composed of ± 1st-order diffracted light or higher-order odd-order diffracted light including ± 1st-order diffracted light. As higher order diffracted light is used, information can be reproduced from multiple tracks simultaneously and in parallel, and as a result, the reproduction speed can be increased. (Embodiment of the Invention) FIG. 1 shows the relationship between an optical card and a light spot when information is recorded on the optical card by the apparatus of the present invention. In FIG. 1, for example, an optical card 1 includes a guide track 2 (2a, 2b, 2c,...) Having a reduced light reflectance and an information recording section 3 (3a, 3b, 3c) sandwiched between the guide tracks 2. , ...). The optical spot 1 is applied to the information recording section 3a by an optical head using a known three-beam method.
The light spot 5a is radiated over the information recording section 3a and the guide track 2a, and the light spot 5b is radiated over the information recording section 3a and the guide track 2b. The light spot 4 is a light spot for information recording and focusing by the 0th-order diffracted light of the diffraction grating, and forms an information pit 6 with the 0th-order diffracted light having the highest energy among the respective diffracted lights, and is a reflected light from the optical card 1. , For performing automatic focus control by a known astigmatism method or the like. The light spots 5a and 5b are used for tracking by the ± 1st-order diffracted light of the diffraction grating, and have lower light energy than the light spot 4 by the 0th-order diffracted light, and partially irradiate the guide tracks 2a and 2b, respectively. The light spot 4 has a role of controlling so that the central portion of the information recording section 3a is correctly scanned. FIG. 2 shows a configuration example of an optical head for irradiating the optical card 1 with a plurality of light spots and recording / reproducing information. In the optical head shown in FIG. 2, a divergent laser beam emitted from a semiconductor laser 7 is converted into a parallel beam by a collimator lens 8 and then converted to a diffraction grating 9.
Are formed into a plurality of beams composed of 0th-order diffracted light, ± 1st-order diffracted light, and higher-order diffracted light. These beams pass through the beam splitter 10 and are guided in a direction perpendicular to the surface of the optical card 1 and for guiding the optical card 1. The light is focused by a focusing lens 11 that moves in two axial directions perpendicular to the application track 2 to become light spots 4, 5 a, and 5 b, which are radiated to the optical card 1. The plurality of laser beams applied to the optical card 1 are reflected in accordance with the light reflectance of the irradiating section of the optical card 1, return to the focusing lens 11, and return to the beam splitter 10.
Is reflected to the right and is directed to the right.
Gives astigmatism and reaches the light receiving diode 14. Here, optical information of the reflected laser light from the optical card 1 is converted into electrical information. FIG. 3 shows the relationship between an optical card and a light spot when information is read from an optical card at twice the speed by the apparatus of the present invention. In FIG. 3, an optical card 1 has a guide track 2 (
2a, 2b, 2c,...) And information pits 6 (15a, 1a).
5b, 15c,...) Are formed on the optical card 1, and the optical head irradiates the light spot 4 on the guide track 2b, the light spot 5a on the information track 15a, and the light spot 5b on the information track 15b. . The light spot 4 is used to obtain focusing and tracking control signals. The focusing control signal is extracted using a known method such as an astigmatism method, and the tracking control signal is extracted using a known method such as a push-pull method. The light spots 5a and 5b are for obtaining information signals,
For example, by moving the optical card 1 from right to left, the light spots 5a and 5b are relatively scanned in the direction of the arrow S, and the information signal of the information track 15a from the light spot 5a and the information signal of the information track 15b from the light spot 5b. Reproduce the information signal. FIG. 4 shows an example of the element configuration of the light-receiving diode 14 and three light-receiving spots. Elements 14A, 14B, 14C and 14D are arranged in a central part in the shape of a Chinese character, and elements 14E and 14F are provided on both sides thereof. Are located. The three laser beams reflected from the optical card 1 pass through the light receiving lens 12 and the cylindrical lens 13 to form light receiving spots 16, 17a and 17b as shown in FIG. . Elements 14A, 14B, 14C, 14D, 14E and 1 of light receiving diode 14
The electrical outputs of 4F are VA, VB, VC, VD, VE and VF, respectively.
When recording information on the optical card 1, as shown in FIG. 5, adders 18 and 19 and subtractors 20 and 21 use VFO = (VA + VB)-(VC + VD), VFO
TR = VE-VF is determined, and VFO and VTR are used as a focusing control signal and a tracking control signal, respectively, as is well known. Next, when reproducing information from the optical card 1, as shown in FIG.
VFO = (VA + VB)-(VC + VD) and VTR = (VA + VD)-(VB + VC) are obtained from 8, 19, 22 and 23 and the subtracters 20 and 21. Control signal. The electrical outputs VE and VF from the elements 14E and 14F are reproduced information signals from the information tracks 15a and 15b, respectively. In the present invention, the information read speed is obtained by performing signal processing on these two reproduced information signals VE and VF. Increase. That is, as shown in FIG. 7, for example, the forward reproduction information signal VE (time T) of the relative reciprocating motion of the optical card is input to the memory 24, and the forward reproduction information signal VF (time T) is also input to the memory 25. And accumulate. In the return path of the optical card, the information stored in the memories 24 and 25 on the outward path is read out from the memory 24 and then from the memory 25 at a clock frequency twice as high as the clock frequency included in the reproduced information signals VE and VF. Therefore, the reading of the stored information from the memory 24 ends at the time of T / 2,
Subsequently, the reading of the stored information from the memory 25 ends in the time of T / 2. In this manner, the information for two information tracks stored in the memories 24 and 25 is continuously read during the time T on the return path of the optical card, so that the information reading speed can be reduced from one information track. It can be increased twice as fast as the speed. On the return path of the optical card, as described above, when information stored in the memories 24 and 25 is read at twice the speed, information on two adjacent tracks is reproduced at the same time so that the memory 24 Information stored in the optical card 2
The reading is performed at twice the speed in the first outward pass, and thereafter such an operation is repeated. FIG. 8 shows the relationship between an optical card and a light spot when information is read from an optical card at 4 × speed by the apparatus of the present invention. In this case, the diffraction grating 9 of the optical head shown in FIG.
The five light beams of the first-order diffracted light, the ± 1st-order diffracted light, and the ± 3rd-order diffracted light are formed, and these five beams are directed perpendicular to the surface of the optical card 1 and the guide track 2 of the optical card 1.
Are focused by a focusing lens 11 that moves in a direction perpendicular to the light spots 4, 5a, and 5b.
, 5c and 5d. In this case, the light spots 5m and 5n due to the ± 2nd-order diffracted light actually occur, but these are not particularly related to the present invention, and the description is omitted. In FIG. 8, a light spot 4 is radiated on a guide track 2b of the optical card 1, and the reflected laser light is provided with focusing information and tracking information. The light spots 5a, 5b, 5c and Reference numeral 5d irradiates the information tracks 15a, 15b, 15c and 15d of the optical card 1, and the laser light reflected from the information track is provided with the recording information recorded on the information tracks 15a, 15b, 15c and 15d. The five laser beams reflected from the optical card 1 reach the light receiving diode 14, where the optical information of the reflected laser beam is converted into an electrical information signal. FIG. 9 shows an example of the element configuration of the light receiving diode 14 in the case of the five beams shown in FIG. Elements 14G and 14H are arranged on both sides of the light receiving diode shown in FIG. The five laser beams reflected from the optical card 1 form light-receiving spots 16, 17a, 17b, 17c, and 17d as shown in FIG. As shown in FIG. 10, the focusing control signal VFO and the tracking control signal VTR are extracted from the light receiving diode 14, as shown in FIG.
Electrical information signals VE, VF, VG and VH are extracted from E, 14F, 14G and 14H. The electric information signals VE, VF, VG and VH are reproduction information from the information tracks 15a, 15b, 15d and 15c, respectively. In the present invention, these four reproduction information signals VE, VF, VG and VH are subjected to signal processing. To increase the information reading speed. That is, as shown in FIG. 11, for example, the reproduction information signal VE (time T) of the forward path of the relative reciprocating motion of the optical card is stored in the memory 2.
4, the reproduction information signal VF (time T) is stored in the memory 25, and the reproduction information signal VG (time T) is stored in the memory 25.
) Is input to the memory 26 and the reproduction information signal VH (time T) is input to the memory 27 and stored. In the return path of the optical card, the information stored in the memories 24, 25, 26 and 27 on the outward path is transferred to the memories 26, 24, and 24 at a clock frequency four times the clock frequency included in the reproduced information signals VE, VF, VG and VH. The data is read continuously in the order of 25 and 27. Therefore, the reading of the stored information from the memory 26 ends in the time of T / 4,
Subsequent to this, reading from the memories 24, 25 and 27 also ends at T / 4. In this way, the information of four information tracks stored in the memories 26, 24, 25 and 27 is continuously read during the time T on the return path of the optical card, so that the information reading speed can be reduced by one. The speed can be increased four times as compared with the reproduction speed from the information track. In the return path of the optical card, as described above, the memories 26, 24, 25 and 2
7 is read out at four times the speed while simultaneously reproducing information from four adjacent information tracks and storing the information in the memories 26, 24, 25 and 27. Further, the information stored in the memories 24 to 27 on the return path of the optical card is read at four times the speed on the second outward path of the optical card, and such an operation is sequentially repeated. If it is desired to further increase the information reading speed, as can be easily inferred from the above description, the diffraction grating 9 may be used including odd-order high-order diffracted light such as ± 5th order and ± 7th order. In the above description, the information on the outward path of the optical card stored in the memories 24 to 27 is read at twice or four times the speed in the return path of the optical card. Since the reproduction of information is not performed during the period, the reading of the information from the memories 24 to 27 may be completed instantaneously at a high speed during the transition period. In the case where the information of the outward path is stored in the outward path of the optical card, and the information of the outward path is read out and the information of the return path is stored in the return path, the memories 24 to 27 each have a memory capacity enough to store the information of the outward path and the information of the return path. That is, it is necessary to have a memory capacity twice as large as the information on the outward path. However, when the information stored in the memories 24 to 27 is to be read out instantaneously during the switching period of the moving direction of the optical card, the memories 24 to 27 respectively have the optical capacity. What is necessary is just to have a memory capacity for the information of the outward path of the card. In the above description of the present invention, the light spot 5 irradiating the optical card 1 is shown in FIG.
It is assumed that the guide tracks 2 to the information tracks 15 are arranged obliquely with respect to the information tracks 15 as shown in FIGS. However, the light spots 5 may be arranged at right angles to the guide track 2 or the information track 15 if there is no inconvenience such that adjacent light spots partially overlap each other. In the present invention, since even-order diffracted light such as ± 2 order and ± 4 order by the diffraction grating 9 is unnecessary, it is necessary to design the diffraction grating 9 so that the intensity of the even-order diffracted light is as small as possible. Is desirable. In the optical information recording / reproducing apparatus of the present invention, when reproducing information, when irradiating the optical card 1 with the light spot 5 and reciprocally irradiating the information, the information is input to the memory on the outward path, and the accumulated information of the outward path is stored on the outward path. The information is read out while performing the operation of inputting the information of the return path to the memory at the same time as outputting at the reading speed of 2 times, 4 times or the like. When information is recorded on the optical card 1, it is normal to perform reciprocal recording with one optical spot. Therefore, when information is reproduced using a plurality of spots as in the present invention, the information is reproduced for each information track. The time series of the information is reversed. Whether the reproduction is in the forward direction or in the reverse direction can be easily detected by the address signal recorded at the end of the information track, so that the correction may be made when the information is output from the memory. According to the present invention, the recording of information and the high-speed reading of information are performed by the same optical head. Therefore, it is necessary to switch the electric circuit and the optical system between the case of recording the information and the case of reading the information at high speed. There is. First, regarding the electric circuit, in the case of recording information, the semiconductor laser 7 shown in FIG.
As shown in Fig. 1, the relationship between the track on the optical card and the light spot is shown in Fig. 1 because a large current close to the standard value is supplied to the device to emit a high-power laser beam, and the light spot is tracked using a three-beam method. The tracking control signal output VTR is extracted by the circuit configuration shown in FIG. In the case of high-speed reading of information, the current supplied to the semiconductor laser 7 shown in FIG. 2 is reduced, a low-output laser beam is emitted, and the push-pull method is used for tracking the light spot. 3 to FIG. 8, the tracking control signal output VTR has the circuit configuration shown in FIG. 6 to FIG. FIG. 12 shows an example of switching the signal output side electric circuit for recording information and reading information at high speed. FIG. 12 shows an example in which FIG. 5 and FIG. 6 are combined. In the case of recording information, switches 28 and 29 are connected to the terminals in conjunction with each other to electrically connect the light receiving diode elements 14E and 14F. The difference VE-VF = VTR between the outputs VE and VF is extracted as a tracking control signal. In the case of high-speed reading of information, the switches 28 and 29 are connected to the terminals in conjunction with each other, and the light receiving diode elements 14A, 14B, 1
From the electrical outputs VA, VB, VC and VD of 4C and 14D, (VA + VD)-(VB + VC) = VTR is used as a tracking control signal, VE and V
F is extracted as a reproduction information signal. FIG. 13 shows the difference between the angle formed by the guide track 2 and the straight line connecting the light spots 5a, 4 and 5b on the optical card 1 when recording information and when reading information at high speed. FIG. 13 (a) shows the case of recording information, and FIG. 13 (b) shows the case of high-speed reading of information. A straight line 3 connecting the centers of the light spots 5a, 4 and 5b.
Assuming that the angle between 0 and the center line 31 of the guide track 2a is θW and θR, respectively, θW = sin ⁻¹ (W ₃ / W ₁ ) and θR = sin ⁻¹ ｛(W ₂ + W ₃ ) / W ₁ ｝ And θ
W <θR. Here W ₁ interval of the light spot 5a and 5b, W _two the guide track 2 width, W ₃ is the width of the information recording section 3. W ₁ , W ₂ and W ₃ are constant values when the optical head and the optical card are the same, so that the optical head itself or θR becomes θW for recording information and θR for high-speed reading of information. It is necessary to change the installation angle of the optical element in the optical head. Specifically, as shown in FIG. 14 (a), the optical head housing 32 is slightly rotated around the optical axis 33 of the focusing lens 11 in the direction of arrow 34, or as shown in FIG. 14 (b). A method of slightly rotating the diffraction grating 9 in the direction of the arrow 36 about the optical axis 35 may be used. Various known methods using an electromagnetic force can be applied to the minute rotation. In the above description of the present invention, a write-once optical card has been described as an example of the optical information recording medium. However, the present invention is not limited to a write-once optical card, and may be an erasable / re-recordable optical card. The present invention is also applicable to optical discs and the like. [Effects of the Invention] As described above, the optical information recording / reproducing apparatus of the present invention records information while performing tracking by a three-beam method using the 0th-order diffracted light and ± 1st-order diffracted light by the diffraction grating, and Is a device that performs push-pull tracking using the 0th-order diffracted light from the diffraction grating and reproduces information using ± 1st-order diffracted light and higher-order diffracted light. Information can be read at high speed simply by recording information and switching with a switch, etc., without changing the scanning speed of the optical spot that irradiates and scans the optical information recording medium. It is possible to realize the miniaturization and economical production of.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view showing the relationship between an optical card and an optical spot when information is recorded on the optical card by the apparatus of the present invention, and FIG. FIG. 3 is a schematic diagram showing a configuration example of an optical head for irradiating and recording / reproducing information, and FIG. 3 is a schematic diagram showing a relationship between an optical card and a light spot when reading information from an optical card at double speed by the apparatus of the present invention. FIG. 4 is a plan view, FIG.
FIG. 5 is a block diagram showing a configuration example of a circuit for extracting a focusing control signal and a tracking control signal from the light receiving diode of FIG. 4, and FIG. 6 is a block diagram showing a focusing control signal, a tracking control signal and two signals from the light receiving diode of FIG. FIG. 7 is a block diagram showing a configuration example of a circuit for extracting a reproduction information signal, FIG. 7 is a conceptual diagram showing a circuit configuration example for doubling the information reading speed, and FIG. FIG. 9 is a schematic plan view showing the relationship between an optical card and a light spot when reading at 4 × speed. FIG.
FIG. 0 is a block diagram showing a configuration example of a circuit for extracting a focusing control signal, a tracking control signal, and four reproduction information signals from the light receiving diode of FIG.
FIG. 1 is a conceptual diagram showing an example of a circuit configuration for increasing the information reading speed by four times, and FIG.
Fig. 13 is a block diagram showing an example of switching of an electric circuit on the signal output side for recording information and reading information at high speed. Fig. 13 shows a straight line connecting light spots and a guide track for recording information and reading information at high speed. And FIG. 14 is a diagram for explaining a specific method for changing the angle as shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Optical card, 2 ... Guide track, 3 ... Information recording part, 4, 5 ... Light spot,
6 information pit, 7 semiconductor laser, 8 collimator lens, 9 diffraction grating, 1
0: beam splitter, 11: focusing lens, 12: light receiving lens, 13: cylindrical lens, 14: light receiving diode, 15: information track, 16, 17: light receiving spot, 18, 19, 22, 23 ... adder, 20, 21: subtractor, 24, 25
, 26, 27... Memory.

Claims (1)

[Claims] 1. Using an optical head having a diffraction grating and an optical information recording medium having a guide track, information is recorded with 0-order diffracted light and tracking is performed with ± 1st-order diffracted light when information is recorded. An optical information recording / reproducing method in which tracking is performed with a first-order diffracted light, and information is reproduced with a higher-order odd-order diffracted light including a ± 1st-order diffracted light or a ± 1st-order diffracted light. 2. An optical card having a diffraction grating, forming a plurality of beams composed of each order diffracted light including a 0th-order diffracted light, ± 1st-order diffracted light, and a higher-order diffracted light from a parallel ray, and forming the plurality of beams on an optical card placed at a predetermined position An optical means for irradiating a beam and condensing the plurality of beams reflected from the optical card at a predetermined focal position; and
Four elements for receiving the first-order diffracted light to form an electric signal, and receiving the higher-order odd-order diffracted light including the ± 1st-order diffracted light or the ± 1st-order diffracted light arranged at a position sandwiching the four elements and forming the electric signal. A photoelectric conversion unit having at least a pair of elements to be formed, arranged at the predetermined focal position of the optical unit, receiving the plurality of beams, and forming an electric signal for each of the diffracted lights; and the four elements. A circuit for forming a focusing signal by calculating the difference between the electric signals of the 0th-order diffracted light of each of the two elements in the diagonal direction in the middle, and calculating the difference between the electric signals of the pair of elements by the ± 1st-order diffracted light during recording A circuit for forming a tracking signal; and a circuit for forming a reproduction-time tracking signal by obtaining a difference between a sum of electric signals generated by 0-order diffracted light of two elements on the same side of the four elements. When information is recorded, information is recorded with the 0th-order diffracted light and tracking is performed with ± 1st-order diffracted light. When information is reproduced, tracking is performed with the 0th-order diffracted light, and higher-orders including ± 1st-order diffracted light or ± 1st-order diffracted light are included. An optical information recording / reproducing apparatus that reproduces information using odd-order diffracted light. 3. 3. The optical information recording / reproducing apparatus according to claim 2, wherein focusing is performed with 0-order diffracted light both during recording and during information reproduction. 4. 3. The apparatus according to claim 2, wherein at the time of reproducing the information, after sequentially inputting a plurality of information signals reproduced from ± 1st-order diffracted light or higher-order odd-order diffracted light including ± 1st-order diffracted light to a plurality of memories, An optical information recording / reproducing apparatus configured to sequentially read information from the plurality of memories using a clock that is an integral multiple of 2 at the time of writing.