Optical information reproducing apparatus

Abstract: The present invention relates to the improvement in an apparatus for reproducing information from a card-like optical information recording medium including tracks for guiding and tracks for information. At least three light spots are formed in said card-like recording medium by light-spot forming means. Signal detection means then detects focusing control signals and tracking control signals by scanning said tracks for guiding with a spot among said light spots. Further, signal reproducing means reproduces information signals (V E , V F ) of plural tracks by scanning the information tracks with the remain­ ing at least two light spots. The reproduced information signals of the plural tracks are stored in plural memories (22, 23) separately for each track. Subsequent­ ly, read-out means sequentially and successively reads the stored information by the time sharing system from each of the plural memories with a speed larger than that when said reproduced information has been input. By such a configuration, it is possible to largely increase the amount of information read-out per unit time from the optical card.

Description: BACKGROUND OF THE INVENTION Field of the Art This invention relates to an apparatus for optically reproducing information, and more particularly relates to an apparatus used for card-like optical information recording media. Prior Art Heretofore, in the card-like optical information recording medium (termed the optical card hereinafter), tracks for guiding and tracks for information are alternately disposed on a card surface. The tracks for information are scanned utilizing the tracks for guiding, and information is taken out. However, when tracks for guiding and tracks for information are alternately disposed as described above, the recording density of the area which can be utilized for information recording within the card surface does not exceed a certain extent. As a result, in order to increase the amount of information reproduction per unit time, the speed of the optical head or optical cards (or the shuttle for carrying the cards) should be increased. All of these countermeasures require, however, mechanical solutions, and hence the problems are complicated. FR-A-2575568 which is appreciated in the precharacterizing portion of the main claim 1 comprises light spot forming means with a diffraction grating. The diffraction grating divides the incident beam into three beams. Although no information concerning the nature of these beams are given in FR-A-2575568 it is obvious that these beams represent respectively the zero and the two first order sub-beams produced by the diffraction grating. Furthermore, it is suggested in this citation that a first beam is used for reading a track information and that at least two beams are used for reproducing data information. It is also known to give an astigmatism to the zero-order, first-order and third-order diffraction light for taking out focusing control signals. Furthermore, it is suggested to convert the zero-order diffraction light into electrical signals for determining the focusing control signals and tracking control signals and to use the reflected first-order and third-oder diffraction lights to reproduce at least two information tracks concurrently. Patent Abstracts of Japan, Vol. 8, No. 171,(P-293), August 8, 1994, & JP-A-59065948 (Canon K.K.) April 14, 1984 discloses that informations recorded at plural tracks of an optical disk are concurrently read out by plural photoelectric conversion devices integrated to each other in an element array, and informations thus read out are once recorded in three buffer memories, and then sequentially read out at a high speed to reproduce an information. Patent Abstracts of Japan, Vol. 9, No. 239 (P-391) (1962), September 25, 1985, & JP-A-60093646 (Suwa Seikosha K.K.) disclose that a semiconductor laser array having plural light emitters is used as a light source, and at least a light beam from the laser array is used for detecting a servo signal at both recording and reproducing, whereby a plurality of signals are concurrently recorded and reproduced by using other light beams, carrying out focusing and tracking. SUMMARY OF THE INVENTION The present invention has been done for solving the above-described problems. It is an object of the present invention to provide an optical information reproducing apparatus in which the read-out speed of information is increased without changing the speed of the reciprocating movement of the optical head side or the shuttle side. The present invention provides an apparatus for reproducing information from a card-like optical information recording medium including guiding tracks and information tracks being provided on a surface of said medium, comprising: light spot forming means comprising a diffraction grating for forming at least three light spots on a card-like recording medium including guiding tracks and information tracks; signal detection means comprising light spot receiving means and first photoelectric conversion means for detecting focusing control signals and tracking control signals by scanning said guiding tracks with a spot among said light spots; signal reproducing means comprising light spot receiving means and second photoelectric conversion means for reproducing information signals of plural tracks by scanning the information tracks with the remaining at least two light spots; wherein: zero-oder, first-order and third-order diffraction lights of said grating are used; said light spot receiving means give an astigmatism to said zero-order, first-order and third-order diffraction light reflected by said recording medium for taking out focusing control signals; said first photoelectric conversion means convert the reflected zero-order diffraction light from said light spot receiving means into electrical signals for determining said focusing control signals and tracking control signals; and said second photoelectric conversion means convert the reflected first-order and third-order diffraction lights from said light spot receiving means to reproduce at least two information tracks concurrently, characterized in that plural storage means are provided for storing reproduced information signals of the plural tracks separately for each track during forward and backward movements of a reciprocating scanning; and that read-out means are provided for sequentially and successively reading the stored information from each of the plural storage means during the backward and forward movements with a time sharing system such that the stored information is read-out at a speed higher than the speed at which the reproduced information is simultaneously stored in the storage means. Accordingly the optical information reproducing apparatus according to the present invention inputs the reproduced information signals of the plural tracks (for example three or five light spots on said medium) in plural memories (for example two or four semiconductor memories), and then sequentially and continuously reads out information from these plural memories with a higher speed (for example twice or four times) than the reproduced information signals which have been input in the memories, and thus the read-out speed of information is increased. Accordingly it is possible to increase the speed of information read-out from the optical card without changing the scanning speed of the light spots which are projected on and scan the optical card. Hence, the present invention has effects such that the performance of the information reproducing apparatus can be improved, and the miniaturization and economization of the apparatus become also possible. Features of preferred embodiments of the invention are defined in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view showing the relationship between the optical card and three light spots when information is reproduced by an apparatus of the present invention; FIG. 2 is a schematic diagram showing a configurational example of an optical head used in an apparatus of the present invention; FIG. 3 is a diagram showing a configurational example of a photodiode element and three reflected-light spots; FIG. 4 is a block diagram showing a configurational example of a circuit which takes out focusing control signals, tracking control signals and two reproduced information signals from the photodiode in FIG. 3; FIG. 5 is a schematic diagram showing a configurational example of a circuit which doubles the reproducing speed of information; FIG. 6 is a schematic plan view showing the relationship between the optical card and five light spots when information is reproduced by an apparatus of the present invention; FIG. 7 is a diagram showing a configurational example of a photodiode element and five reflected-light spots; FIG. 8 is a block diagram showing a configurational example of a circuit which takes out focusing control signals, tracking control signals and four reproduced information signals from the photodiode in FIG. 7; FIG. 9 is a schematic diagram showing a configurational example of a circuit which increases the reproducing speed of information by four times; and FIG. 10 is a diagram when the five light spots shown in FIG. 6 are arranged in the direction perpendicular to information tracks. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the relationship between the optical card and light spots when information is reproduced by an apparatus of the present invention. In FIG. 1, tracks 2 (2a, 2b, 2c, ...) for guiding and information tracks 3 (3a, 3b, 3c, ...) are formed in an optical card 1. On the optical card 1, light spots 4, 5a and 5b are projected on the track 2b for guiding, the information tracks 3a and 3b, respectively, by an optical head. The light spot 4 is for obtaining control signals for focusing and tracking. Both the focusing control signals and tracking control signals are taken out by well-known methods: for example, the astigmatism method for the focusing control signals; and the push-pull method for the tracking control signals. 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 relatively scan in the direction of the arrow S, and information signals on the information tracks 3a and 3b are reproduced from the light spots 5a and 5b, respectively. FIG. 2 shows a configurational example of an optical head for reproducing focusing control signals and tracking control signals and two information signals by irradiating the light spots 4, 5a and 5b on the optical card 1. The optical head shown in FIG. 2 comprises a semiconductor laser 6, a collimating lens 7, a diffraction grating 8, a half-prism (or a half-mirror) 9, a focusing lens 10, a light-receiving lens 11, a cylindrical lens 12 and a photodiode 13. In FIG. 2, divergent laser light emitted from the semiconductor laser 6 is converted into parallel light by the collimating lens 7, and then forms three beams consisting of the 0-order diffraction light and the ± 1st-order diffraction lights. The three beams are transmitted through the half-prism 9, and are focused by the focusing lens 10 which moves in the direction vertical to the surface of the optical card 1 and in the direction perpendicular to the tracks 2 for guiding in the optical card 1, and become the light spots 4, 5a and 5b. The light spot 4 is projected on the track 2b for guiding in the optical card 1. Here, when a part of the laser light is reflected, focusing information and tracking information are given. The light spots 5a and 5b are projected on the information tracks 3a and 3b in the optical card 1, respectively. Here, the information recorded on the information tracks 3a and 3b is given to the reflected laser lights. The three laser lights reflected from the optical card 1 move back through the focusing lens, are reflected at the half-prism 9 toward right, and are focused by the light-receiving lens 11. Then, astigmatism is given at the cylindrical lens 12, and the laser lights reach the photodiode 13. Here, the optical information which the reflected laser lights have is converted into electric information signals. FIG. 3 shows a configurational example of the photodiode 13. Four elements, 13A, 13B, 13C and 13D are disposed in the form closely aligned in two rows and two columns, and elements 13E and 13F are disposed on both sides thereof. The three laser lights reflected from the optical card 1 pass through the light-receiving lens 11 and the cylindrical lens 12, and then are projected on each element of the photodiode 13 as reflected-light spots 14, 15a and 15b as shown in FIG. 3. Electric outputs V A , V B , V C , V D , V E and V F are obtained from the elements 13A, 13B, 13C, 13D, 13E and 13F of the photodiode 13, respectively, as shown in FIG. 4. V FO = (V A + V B ) - (V C + V D ), V TR = (V A + V D ) - (V B + V C ) are obtained by adders 16, 17, 19 and 20, and subtracters 18 and 21. The V FO and V TR are made as the focusing control signal and the tracking control signal, respectively, as well known to the public. The electric signals V E and V F from the elements 13E and 13F are reproduced information signals from the information tracks 3a and 3b, respectively. In the present invention, the reproducing speed of information is increased by performing signal processing of these two reproduced information signals V E and V F . That is, as shown in FIG. 5, the reproduced information signals V E (for time T) and V F (for time T) are input in memories 22 and 23, respectively. From the memories 22 and 23, information is successively read out, first from the memory 22, and then from the memory 23 with a clock frequency twice the clock frequency contained in the reproduced information signals V E and V F to produce an information signal V E+F (for time T). Thus, the reproducing speed of information is doubled compared with the reproducing speed from a single information track. FIG. 6 shows the relationship between the optical card and light spots when information signals are reproduced from four information tracks 3a, 3b, 3c and 3d, and thus the reproducing speed of information is increased by four times compared with the reproducing speed of a single information track. In this case, five light beams, i.e., the 0-order diffraction light, the ± 1st-order diffraction lights and the ± 3rd-order diffraction lights, are formed by the diffraction grating 8 in the optical head shown in FIG. 2. These five beams are focused by the focusing lens 10 which moves in the direction vertical to the surface of the optical card 1 and in the direction perpendicular to the tracks 2 for guiding in the optical card 1, and become light spots 4, 5a, 5b, 5c and 5d. Actually, in this case, light spots 5m and 5n due to the ± 2nd-order diffraction lights are also produced, but since these have no particular relation with the present invention, the explanation thereof will be omitted. The light spot 4 is projected on the track 2b for guiding in the optical card 1. Here, focusing information and tracking information are given to the reflected laser light. The light spots 5a, 5b, 5c and 5d are projected on the information tracks 3a, 3b, 3c and 3d in the optical card 1. Here, information recorded in the information tracks 3a, 3b, 3c and 3d is given to the reflected laser lights. The five laser lights reflected from the optical card 1 reach the photodiode 13, where the optical information which the reflected laser lights have is converted into electric information signals. FIG. 7 shows a configurational example of the photodiode 13 in the case of five beams. Elements 13G and 13H are disposed at both sides of the photodiode shown in FIG. 3. The five laser lights reflected from the optical card 1 become reflected-light spots 14, 15a, 15b, 15c and 15d as shown in FIG. 7, and are projected on each element of the photodiode. From the photodiode 13, as shown in FIG. 8, the focusing control signal V FO and the tracking control signal V TR are taken out like in FIG. 4. Electric information signals V E , V F , V G and V H are also taken out from the elements 13E, 13F, 13G and 13H. The electric information signals V E , V F , V G and V H are reproduced information from the information tracks 3a, 3b, 3c and 3d, respectively. In the present invention, the reproducing speed of information is increased by performing the signal processing of these four reproduced information signals V E , V F , V G and V H . That is, as shown in FIG. 9, the reproduced information signals V E (for time T), V F (for time T), V G (for time T) and V H (for time T) are input in memories 22, 23, 24 and 25, respectively. From the memories 22, 23, 24 and 25, information is sequentially and successively read out, first from the memory 24, then from the memories 22, 23 and 25 with a clock frequency four times the clock frequency contained in the reproduced information signals V E , V F , V G and V H to produce an information signal V G+E+F+H (for time T). Thus, the reproducing speed of information is increased by four times compared with the reproducing speed from a single information track. When it is desired to further increase the reproducing speed of information, the odd and higher-order, such as the ± 5th-order, the ± 7th-order and the like, diffraction lights of the diffraction grating 8 may also be utilized, as can easily be analogized from the above-described explanation. In the above-described explanation of the present invention, it is assumed that the light spots 5 projected on the optical card 1 are arranged in a direction oblique to the tracks 2 for guiding and the information tracks 3, as shown in FIGS. 1 and 6. The light spots 5 may be arranged, however, in the direction perpendicular to the tracks 2 for guiding and the information tracks 3 as shown in FIG. 10, unless inconvenience does not exist such that adjacent light spots partially overlap one another. Further, in the present invention, the even-order, such as the ± 2nd-order, the ± 4th-order and the like, diffraction lights of the diffraction grating 8 are unnecessary. Hence, it is desirable to take care in designing the diffraction grating 8 so that the intensities of these even-order diffraction lights become as small as possible. In the optical information reproducing apparatus of the present invention, when reciprocating scanning is performed with projecting the light spots 5 on the optical card 1, information is input in memories at the forward movement, and the information is reproduced with performing the operations such that the information stored at the forward movement is output with a reproducing speed, such as twice, four times and the like, at the backward movement, and at the same time the information at the backward movement is input in memories. When information is recorded in the optical card 1, recording is usually performed by reciprocating a single light spot. Hence, when information is reproduced using plural spots as in the present invention, the time series of the reproduced information is reversed at every information track. Whether the reproduction in question is at the forward movement or at the backward movement can easily be detected by address signals recorded in an edge of the information track. Accordingly, correction may be performed when the information is output from the memory. In the above-described explanation of the present invention, the optical card has been exemplified. However, it goes without saying that the optical information reproducing apparatus of the present invention is applicable not only to the optical card, but also to the optical disk or the like. As described above, according to the optical information reproducing apparatus of the present invention, it is possible to increase the speed of information read-out from the optical card without changing the scanning speed of the light spots which are projected on and scan the optical card. Hence, the present invention has effects such that the performance of the information reproducing apparatus can be improved, and the miniaturization and economization of the apparatus become also possible.

Claims: An apparatus for reproducing information from a card-like optical information recording medium (1) including guiding tracks (2a, 2b, 2c ...) and information tracks (3a, 3b, 3c ...) being provided on a surface of said medium, comprising: light spot forming means (6, 7, 8, 9, 10) comprising a diffraction grating (8) for forming at least three light spots (4, 5a, 5b) on a card-like recording medium including guiding tracks and information tracks; signal detection means (9, 10, 11, 12, 13) comprising light spot receiving means (12) and first photoelectric conversion means (13A, 13B, 13C, 13D) for detecting focusing control signals (V FO ) and tracking control signals (V TR ) by scanning said guiding tracks with a spot (4) among said light spots; signal reproducing means (6, 7, 8, 9, 10, 13) comprising light spot receiving means (12) and second photoelectric conversion means (13F, 13E) for reproducing information signals (V E , V F ) of plural tracks by scanning the information tracks with the remaining at least two light spots (5a, 5b); wherein: zero-order, first-order and third-order diffraction lights of said grating (8) are used ; said light spot receiving means (12) give an astigmatism to said zero-order, first-order and third-order diffraction light reflected by said recording medium (1) for taking out focusing control signals; said first photoelectric conversion means (13A, 13B, 13C, 13D) convert the reflected zero-order diffraction light from said light spot receiving means (12) into electrical signals for determining said focusing control signals (V FO ) and tracking control signals (V TR ); and said second photoelectric conversion means (13F, 13E) convert the reflected first-order and third-order diffraction lights from said light spot receiving means (12) to reproduce at least two information tracks concurrently; characterized in that plural storage means (22, 23) are provided for storing reproduced information signals of the plural tracks separately for each track during forward and backward movements of a reciprocating scanning; and that read-out means are provided for sequentially and successively reading the stored information from each of the plural storage means during the backward and forward movements with a time sharing system such that the stored information is read-out at a speed higher than the speed at which the reproduced information is simultaneously stored in the storage means. An optical information reproducing apparatus according to claim 1, wherein the number of said light spots (4, 5a, 5b) is three. An optical information reproducing apparatus according to claim 1, wherein the number of said light spots (4, 5a, 5b, 5c, 5d) is five. An optical information reproducing apparatus according to claim 1, wherein said optical signal detection means (9, 10, 11, 12, 13) is configured such that an element (13A, 13B, 13C, 13D) disposed at the center scans said tracks for guiding, and other elements (13E, 13F) disposed at both sides of said element disposed at the center scan said tracks for information. An information reproducing apparatus according to claim 4, wherein said optical signal detection means is configured such that a combination element (13A, 13B, 13C, 13D) consisting of four square elements closely arranged in two rows and two columns is disposed at the center, and focus error signals (V FO ) are formed by signals from two pairs (V A , V B ; V C , V D ) of elements in the diagonal direction in the combination element. An information reproducing apparatus according to claim 5, wherein said optical signal detection means is configured such that tracking error signals (V TR ) are formed by signals from two pairs of elements, each pair (V A , V D ; V B , V C ) being on the identical side. An information reproducing apparatus according to claim 1 wherein said information recording medium is provided with four information tracks (3a, 3b, 3c, 3d) and said light spot forming means (8) forms five spots (5a, 5b, 5c, 5d) which are projected on at least one guiding track and said four information tracks. An information reproducing apparatus according to claim 7 wherein said second photoelectric conversion means reproduces four information signals concurrently.

Inventors: NODA KAZUO, YAMAZAKI KOICHI, NODA, KAZUO, YAMAZAKI, KOICHI
Applicants: NIPPON CONLUX CO LTD, NIPPON CONLUX CO., LTD.
Application year: 1988
Main classification: G11B7
IPC codes: G11B7