Optical information recording/reproducing apparatus

Abstract: An optical information recording/reproducing apparatus includes a first spot forming system for forming a first recording light spot (W1) and a second recording light spot (W2) for information record on an information record medium, a second spot forming system for forming a first reproducing light spot (R1) and a second reproducing light spot (R2) for information reproduction on the information record medium, and a moving device for effecting a relative reciprocating motion between the first and second spot forming systems and the information record medium.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an optical information recording/reproducing apparatus, for example a reader-writer for optical card, in which a plurality of beams are guided simultaneously to irradiate a reciprocating information record medium and to form light spots thereon, so as to enable record and verification (immediate reproduction of recorded information) both forward and backward in the reciprocating motion of the record medium. Related Background Art A typical example of such optical information recording/reproducing apparatus is an optical card information recording/reproducing apparatus is described in European Patent Application No. EP-A-0 558 249, forming prior art for the purpose of Art. 54(3) EPC, which has the structure as shown in Fig. 1, which is conventionally used. Figures 2-7 also reflect the prior art known from this document. In the apparatus, record and reproduction of information is carried out with beams from separate light sources (which is generally called as double light source method) to avoid degradation of reproducing light and to achieve high speed record with verification. An information record medium used herein (as denoted by reference numeral 1 in Fig. 1) is of a disk or card which is composed of a substrate such as glass and plastic, and a record layer formed thereon. Semiconductor lasers 21, 22 are used as the two light sources in the information recording/reproducing apparatus in order to record information in the information record medium 1 and to reproduce the information therefrom or in order to reproduce the information at the same time as the record to verify the recorded information. One laser emits light with wavelength of 780 nm and the other does light with wavelength of 830 nm. Each emitted light is collimated by a collimator lens 23 or 24. The former light passes through a diffraction grating 25 to be split into zeroth-order diffracted light and ± first-order diffracted light, while the latter light directly enters a dichroic prism 26. The prism 26 is so designed that dielectric multilayers layered on a prism bond surface as shown in Fig. 2 transmit the light with wavelength of 780 nm in the form of p-polarization component and reflects the light with wavelength of 830 nm in the form of p-polarization component. Each beam outgoing from the prism 26 passes through a beam shaping prism 27 to be shaped to have a predetermined light distribution. Then the shaped beam enters a polarization beam splitter 28 having the property as shown in Fig. 3 then to enter a quarter-wave plate 29 to be circularly polarized. The circularly polarized beam reaches an objective lens 30. Each beam is converged by the objective lens 30 on the information record medium 1, so that the light with wavelength of 780 nm forms three light spots S 1 (+ first-order diffracted light), S 2 (zeroth-order diffracted light) and S 3 (- first-order diffracted light), and that the light with wavelength of 830 nm forms a light spot S w . The light spots are positioned on an information track 2 on the information record medium 1 in an example of information record medium of card as shown in Fig. 4 and Fig. 5. Specifically, information tracks 2 are arranged from a home position 3 in the order of 2-1, 2-2, 2-3,... and tracking tracks 4-1, 4-2, 4-3,... are juxtaposed adjacent to the information tracks. Address portions 6-1, 6-2,... and 7-1, 7-2,... are prepared for track identification on either side-of the information tracks. The light spots S 1 , S 3 are positioned on two tracking tracks 4 adjacent to each other, and the light spot S 2 on an information track 2 between the two adjacent tracking tracks. Numeral 51 denotes a drive motor for moving the information record medium 1 forward and backward (in the direction F and in the direction L), which effects a relative reciprocating motion of the information record medium 1 to an optical head 50 in parallel with the information tracks 2. Reflected light from the information record medium passes through the same optical path up to the polarization beam splitter 28 and is then deflected thereby. The deflected light passes through a band pass filter 31 having the property equivalent to that shown in Fig. 2 and then reaches a toric lens 33 having a special film with the property shown in Fig. 6. The toric lens 33 transmits only light with wavelength of 780 nm, and the transmitted light reaches a photodetector 34. Numeral 32 designates a stopper for receiving light reflected by the band pass filter 31. The photodetector 34 has receptor elements 11, 13 for obtaining tracking control signals and a receptor element 12 sectioned into four segments for detecting focus control signals and reproduction signals, as shown in Fig. 7. In the conventional example as described, however, the verification is possible only in one direction (in the direction F in Fig. 5) on the reciprocating (moving in the direction F and in the direction L) information record medium. The verification is impossible in the return direction (in the direction L in Fig. 5), since the reproducing light spot S 2 is leading the recording light spot S w . Also, Japanese Laid-open Patent Application No. 61-240408 discloses an optical information recording/reproducing apparatus which can perform record and reproduction of information in a relative reciprocating motion between a record reproducing apparatus and a record medium, in which information recorded in the forward motion is read out in the backward direction during return, and the thus read information is compared with information desired to be recorded thereby to check whether information is correctly recorded on the medium. This method, however, cannot enable the record and verification of information in the both directions in a reciprocating motion of information record medium. The present invention has been accomplished considering the above circumstances. It is a concern of the present invention to provide an optical information recording/reproducing apparatus which can perform record with verification in both directions in a reciprocating motion of information record medium. In accordance with the present invention, there is provided an optical information recording/reproducing apparatus as set out in claim 1. In accordance with a second aspect there is provided a recording and reproduction method as set out in claim 6. In the present invention, an optical information recording/reproducing apparatus has a first light source for information reproduction and second and third light sources for information record, in which beams emitted from the light sources are guided to irradiate an information record medium reciprocating relative to the beams and to form light spots on information tracks on the information record medium thereby to carry out record and reproduction of information, wherein the relative positional relation between the light spots from the first light source and from the second and third light sources is determined such that a recording light spot is located on each of two information tracks and that two reproducing light spots are obliquely positioned before and after the two recording light spots with respect to the moving direction of the record medium. The light sources for recording light spots are selectively turned on depending upon the moving direction of the record medium so that a beam emitted from the light source turned on may be guided to irradiate the information record medium. In order that the present invention may be more readily understood, embodiments thereof will now be described by way of example and with reference to the accompanying drawings in which : Fig. 1 is a drawing to show a conventional optical information recording/reproducing apparatus; Fig. 2 is a spectral distribution diagram of a dichroic prism 26; Fig. 3 is a spectral distribution diagram of a polarization beam splitter 28; Fig. 4 is a schematic plan view to show a WORM (Write Once Read Many) type card record medium; Fig. 5 is a partially enlarged view of Fig. 4; Fig. 6 is a spectral distribution diagram of a film on the surface of toric lens 33; Fig. 7 is an enlarged view to show receptor elements in a photodetector; Fig. 8 is a drawing showing an embodiment optical information recording/reproducing apparatus of the present invention; Fig. 9 is a drawing to show an arrangement of light spots in the present invention; and Fig. 10 is a drawing to show an arrangement of light spots in another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the optical information recording/reproducing apparatus of the present invention will be described in detail with reference to the drawings. Fig. 8 is a drawing to illustrate the structure of an optical system in the optical information recording/reproducing apparatus of the present invention. The same reference numerals denote the same members as those in Fig. 1, which are omitted to explain herein. Fig. 9 schematically shows an arrangement of light spots in the present invention. In this example a card information record medium is employed for explanation purpose, similarly as in Fig. 5. A semiconductor laser 21 emits a beam of 780 nm used for reproducing light spot, similarly as in Fig. 1. The beam of 780 nm is collimated by a collimator lens 23 and split into three beams by a diffraction grating 25. The three split beams are guided to irradiate an optical card 1 as information record medium. The present invention, however, is different from Fig. 1 in that among the three split reproducing light spots a center light spot R 2 (zeroth-order light) is located on a tracking track 4-2 and that two remaining reproducing light spots R 1 , R 3 (± first-order light) are located near the center of information track 2-2 and near the center of information track 2-1, respectively, as shown in Fig. 9. Three reflected beams from the light spots R 1 , R 2 , R 3 on the optical card are guided to a photodetector 34, similarly as described with Fig. 1. The three beams respectively enter receptor elements 11, 12, 13 as shown in Fig. 7. The reflected light from light spot R 2 entering the quarter-sectioned receptor element 12 is used to obtain control signals for autotracking (as will be referred to as AT) and for autofocus (as will be referred to as AF). In this case, AT is controlled by the generally well-known push-pull method and AF by the astigmatic method. Also, the reflected light from light spots R 1 , R 3 entering the receptor elements 11, 13 is used to detect reproduction signals. As for AF, either or both of the receptor elements 11, 13 may be a quarter-sectioned element or quarter-sectioned elements for AF control. Such an arrangement can remove negative influence of AF offset or card inclination arisen from a height difference between tracking tracks and information tracks, assuring excellent AF properties. Recording light spots are next described. A semiconductor laser 20 for recording beams has two radiative points to emit rays of 830 nm. Beams from the semiconductor laser 20 are collimated by the collimator lens 24, and the collimated beams pass through the optical components and are converged by the objective lens 30 to irradiate the optical card as information record medium, similarly as in Fig, 1. W 1 and W 2 shown in Fig. 9 are recording light spots, and the arrangement thereof is as shown. As seen from the arrangement in Fig. 9, the light spots W 1 , W 2 are arranged at the center of information tracks 2-2, 2-1 adjacent to each other, and a distance between W 1 and W 2 is uniquely determined by the distance between the radiative points in LD array, the collimator lens 24, the objective lens 30, and the beam shaping prism 27. The operation of recording light spots during recording is briefly described in the following. When the optical card is moved by the drive motor 51 in the direction L in Fig. 9, only the light source in laser 20 corresponding to the light spot W 2 is actuated to emit a beam. The emitted beam is converged on the information track 2-1 to effect record of information therein. The light spot R 3 follows the light spot W 2 to effect verification of recorded information at the same time. Conversely, when the optical card is moved by the drive motor 51 in the direction F, only the light source in laser 20 corresponding to the light spot W 1 is actuated to emit a beam. The emitted beam is converged on the information track 2-2 to effect record of information therein. The light spot R 1 effects simultaneous verification with the recording. After a cycle of forward and backward recording is completed as described, the beams are shifted onto two tracks next to the recorded tracks, on which another cycle-of information record and verification is repeated in the same manner of operation. Accordingly, bi-directional record and verification can be carried out on the information tracks on optical card, doubling the recording speed. As described above, the present invention provides an optical information recording/reproducing apparatus having a first light source (21) for information reproduction and a second light source (20) and a third light source (20) for information record, in which beams emitted from the light sources are guided to irradiate an information record medium (1) made reciprocating relative to the beams by the moving means (51) and to form light spots on information tracks on the information record medium thereby to carry out record and reproduction of information, wherein the relative positional relation between the light spots from the first light source and from the second and third light sources is determined such that a recording light spot is located on each of two information tracks and that a reproducing light spot is located on each of the said two information tracks while the reproducing light spots are positioned on either side of the alignment line of the two recording light spots as before and after the alignment line. The light sources (20) for the recording light spots are arranged to be selectively turned on depending upon the moving direction of the record medium so that a beam emitted from the light source turned on may be guided to irradiate the information record medium. In an aspect, the light sources for the recording light spots are selectively turned on such that a corresponding recording light spot is on behind a reproducing light spot with respect to the moving direction of the information record medium. In another aspect, the selection timing of a light source to be turned on for a recording light spot is between the time of completion of information recording and the time of start of next information recording. Namely, the selection is preferably carried out during reversal of the reciprocating motion. In another aspect, the first light source and the second and third light sources are semiconductor lasers, and the wavelength of the first light source is different from that of the second and third light sources. In another aspect, the second and third light sources for information record are arrayed semiconductor lasers. Fig. 10 shows another embodiment of the present invention, in which the arrangement of light spots is modified by changing the distance between radiative points in LD array (but there is no change made except for the LD array). This embodiment is effective to double the record capacity. In this embodiment, record and reproduction may be conducted with two lines of information being recorded in each information track (2-1, 2-2). In a further embodiment, the light with wavelength of 830 nm used for recording may be also used for reproduction instead of the light with wavelength of 780 nm for reproduction. Although the two recording light spots are produced by the 2-beam LD array in the present invention, light from 1-beam LD may also be used by splitting it into two beams by means of an optical component such as a diffraction grating and an acousto-optic element, achieving the same operation and effect. Three (or more) separate light sources may also be employed as an alternative. Further, the recording light spots are located inside the reproducing light spots with respect to the moving direction of optical card in the present invention, but the recording light spots may be located outside the reproducing light spots with the same operation and effect. The present invention is described above in detail, which enables the information record and verification in the both directions in a reciprocating motion of information record medium, whereby the recording speed may be doubled.

Claims: An optical information recording/reproducing apparatus comprising: recording/reproducing means (20, 21) for forming a first recording light spot (W1) for recording of information and a first reproducing light spot (R1) for reproduction of information on a first information track (2-2) of an information recording medium (1); and for forming a second recording light spot (W2) for recording of information and a second reproducing light spot (R3) for reproduction of information on a second information track (2-1) different from the first information track (2-2) of the information recording medium; and moving means (51) for effecting a relative reciprocating motion between said recording/reproducing means and the information recording medium, said recording/reproducing means forming the first recording light spot (W1) and the first reproducing light spot (R1) and the second recording light spot (W2) and the second reproducing light spot (R3) such that the first reproducing light spot (R1) is located at a side opposite to the second reproducing light spot (R3) with respect to a line linking the first recording light spot (W1) with the second recording light spot (W2). Apparatus according to claim 1, wherein said recording/reproducing means comprise first and second semiconductor lasers (20, 21), and wherein said second semiconductor laser in operation produces said first and second reproducing light spots (R1, R3). Apparatus according to claim 2, wherein the output of said second semiconductor laser is split to provide said reproducing spots by a diffraction grating (25). Apparatus according to claim 3, wherein the diffraction grating (25) generates three light spots (R1, R2, R3), namely said first and second reproducing spots (R1, R3) and a spot (R2) located between said first and second reproducing spots, and wherein in operation said first and second reproducing spots are located on adjacent information tracks (2-2, 2-1) and the centre spot is located on a tracking track (4-2) located between said adjacent information tracks. Apparatus according to any one of claims 2 to 4, wherein said first semiconductor laser is adapted to emit two light spots (W1, W2) in operation located on the centre of said different information tracks (2-2, 2-1). A recording and reproduction method in an optical information recording/reproducing apparatus, said method comprising the steps of: using an optical head for forming a first recording light spot (W1) and a first reproducing light spot (R1) for recording and reproduction of information on a first information track (2-2) of an information recording medium; using the optical head for forming a second recording light spot (W2) and a second reproducing light spot (R3) for recording and reproduction of information on a second information track (2-1) different from the first information track of the information recording medium; and effecting a relative reciprocating motion between the optical head and the information recording medium, the optical head forming the first recording light spot (W1) and the first reproducing light spot (R1) and the second recording light spot (W2) and the second reproducing light spot (R3) such that a line linking the first and second recording light spots intersects a line linking the first and second reproducing light spots. A method according to claim 6, wherein said optical head comprises first and second semiconductor lasers (20, 21), and said second semiconductor laser produces said first and second reproducing light spots (R1, R3). A method according to claim 7, wherein the output of said second semiconductor laser is split to provide said reproducing spots by a diffraction grating (25). A method according to claim 8, wherein the diffraction grating (25) generates three light spots (R1, R2, R3), namely said first and second reproducing spots (R1, R3) and a spot (R2) located between said first and second reproducing spots, and wherein in operation said first and second reproducing spots are located on adjacent information tracks (2-2, 2-1) and the centre spot is located on a tracking track (4-2) located between said adjacent information tracks. A method according to any one of claims 7 to 9, wherein said first semiconductor laser emits two light spots (W1, W2) which are located on the centre of said different information tracks (2-2, 2-1).

Inventors: MIYAMOTO MORITOSHI, MIYAMOTO, MORITOSHI, MIYAMOTO, MORITOSHI, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: G11B7
IPC codes: G11B7, G11B20, G11B11