OPTICAL DATA READER

Abstract: A plurality of converging light beams (20) are focused on the same area of an optical recording medium (40) to sequentially scan data recorded on the medium. A plurality of detectors (22), one associated with each light beam (20), detect the scanned data and provide an output signal (A to D). A logic gate (50) receives the outputs from each of the plurality of detectors (22) and provides an output only when each detector (22) is sensing data so as to eliminate the effects of random surface irregularities (45) (e.g. dust particles) which may be in the beam path of one or more, but not all, of the light beams (20).

Description: - i - OPTICAL DATA READER Technical Field The present invention relates to an optical data reader and, more particularly, to a laser system for reading data recorded on optical media such as a rotatable disk. Background Art Optical disks are manufactured in multiple layers with the layer containing the recording medium protected by a transparent layer or thin film. Under conditions of normal usage, the surface of the transparent layer accumulates dirt particles, which particles, to an optical read system, reflect light similar to the recorded data. When such a disk is used in a computer or other sensitized data system, errors are introduced. A number of techniques can be used to remove the accumulated dust particles and/or to prevent their accumulation on the surface of the disk. All of these methods require elaborate precautions. Short focal-length lenses having an extremely limited depth of field tend to focus solely upon the data plane containing the data and obscure (disfocus) particles which appear in other planes. A disadvantage of such a system is the relatively high cost for the lensing and the power requirements for the laser to properly illuminate the data. Disclosure of the Invention It is an object of the invention to provide a relatively inexpensive optical readout system wherein slight imperfections such as dust and particle accumulations on the surface of the optical disk would not affect data readout. Thus, according to the invention, there is provided an optical data reader for use in conjunction with a record member on which data is stored in the form of reflective and non-reflective areas, characterized by a combination of generating means for generating a plurality of light beams converging on said record member to illuminate an area corresponding to one unit of data; a plurality of light detectors each associated with a corresponding light beam, for detecting reflections of the corresponding light beam; and logic means coupled to each of said plurality of detectors for providing an output when all of said plurality of detectors are detecting reflections. According to another aspect of the invention, there is provided an optical data reader for use in conjunction with a record member on which data is stored in the form of transparent and non-transparent areas, characterized by a combination of generating means for generating a plurality of light beams converging on said record member; a plurality of light detectors each positioned to receive the light from an individual light beam which passes through a transparent area of said record member; and logic means coupled to each of said plurality of light detectors for providing an output when all of the light beams pass through a transparent area. Brief Description of the Drawings Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram illustrating one embodiment of the present invention; Fig. 2 is a group of waveforms illustrating the operating signals associated with the embodiment of Fig. l; Fig. 3 is a schematic diagram illustrating a second embodiment of the invention; and Fig. 4 is a schematic diagram illustrating a third embodiment of the invention. Best Mode for Carrying Out the Invention Fig. 1 illustrates a plurality of semi¬ conductor lasers 10. Each laser is angularly positioned so as to direct a beam of light 20 onto a recording layer 30. The recording layer is one component of an optical data recording member 40 which in the preferred embodiment is an optical disk. The recording member 40 is comprised of a glass layer 41 which is both transparent and optically homogeneous and has highly parallel and flat surfaces. The recording layer 30 may be a light-absorbing sub-oxide of metal or semi-metal. A protective film 42 is deposited on the recording layer 30 to protect the recording layer from damage. The beam 20, emanating from the laser 10, is directed to a first lens 12 and from the first lens to a one-half silvered mirror 14. The beam traverses the mirror to a second lens 16 and is focused on the recording layer 30. A third lens 18 is positioned, with regards to the one-half silvered mirror 14, so as to receive reflected light from the recording layer. A semi-conductor light detector 22 is positioned to detect the image formed by lens 18. Each of the remaining laser beam-generating systems shown is identical in construction to the one just described. The output signal provided by each of the light detectors, labeled A, B, C and D is directed as inputs to an AND gate 50. The AND gate 50 provides an output when all of its inputs are of a high level. The recording layer 30 is conditioned such that data is represented by the reflectance or lack of reflectance from the layer. The shaded areas 47 signify light-absorbing portions and the non-shaded areas signify light-reflective portions. Referring now to Fig. 2 in conjunction with Fig. 1, in operation, as the optical recording medium moves in the direction indicated by the direction arrow F, the optical beams will be reflected by the areas 46 or absorbed by the areas 47. The output of each of the detectors labeled A through D in Fig. 2 are illustrated as positive-going waveforms when the beams reflect from the area 46. In all other instances, the waveform will remain low and relatively flat. An imperfection such as a particle of dust and/or fingerprint, shown as a dark projection 45 on the surface of the glass substrate 41 may cause a reflection in the absence of a reflective area 46. For the position of the recording member 40 shown in Fig. 1, the output signal A, although caused by the dust spot, is substantially similar to the signals B, C and D, caused by a true reflection from area 46. The presence of a positive pulse from all detectors indicates that the light beams are focused on, and are, in fact, reflecting from, a true reflective area 46. As the recording member continues on in direction F, a light absorbing area 47 will come into the focal point of the beams. As the dust particle 45 moves between the first beam and the second beam, the detector outputs will remain flat because the beams will be focused on the light-absorbing film 47. When the dust spot is in the second beam, the output signal B from the detector will go high, but the other detectors, not reflecting the light beam, will remain low. In a similar fashion, as the recording member 40 continues to move forward the dust spot is positioned in the third beam, and the output signal C from the detector will go high. A like response will be obtained as evidenced by the output signal D, when the dust spot enters the fourth beam. The AND gate 50 detecting, in the second instance, no positive pulses will result in outputting a low-level signal. Simi¬ larly, for the conditions of positioning the spot in the third and fourth beams, all of the outputs are not at the high level; therefore, the presence of the reflective particle on the surface of the optical data recording member will be ignored by the AND gate 50. Obviously, if the contaminate on the surface of the glass layer 41 covers an area which encompasses all of the light beam impinging points, an erroneous indication will be outputted. The likelihood of such a large contaminate appearing on the surface is quite remote and, as such, the system of the present inven¬ tion eliminates all of the problems associated with prior art systems while permitting the use of rela¬ tively inexpensive long focal-length lenses and low power laser sources. Although four laser beam systems are shown in the preferred embodiment of the invention, it would be obvious to a person skilled in the art that more or less units could be used with increasing and/or de¬ creasing resolution of the dust problem. Referring to Fig. 3, wherein a second embodiment of the invention is shown: the recording member 40 is modified such that the glass layer 41 supports the data layer, which consists of transparent areas 61 and non-transparent areas 60. The lenses 18 are positioned on the side of the recording member opposite the semiconductor lasers 10, lens 12 and lens 16. The operation of the second embodiment is identical to that of the first embodiment with the exception that the 1/2 reflective mirrors are not required. Referring to Fig. 4, wherein a third embodiment of the invention is shown: a single semiconductor laser 10 is shown with its output directed through lens 12 to a fully reflecting 90° prism 51. The prism 51 splits the impinging laser beam into two equal beams and directs the beams to 1/2 reflective mirrors 52 and to the fully reflective mirrors 53. The beams reflected from mirrors 52 and 53 then are directed through the remainder of the system which corresponds to the system shown and described in conjunction with Fig. 1.

Claims: CLAIMS 1. An optical data reader for use in conjunction with a record member (40) on which data is stored in the form of reflective (46) and non- reflective (47) areas, characterized by a combination of generating means (10) for generating a plurality of light beams (20) converging on said record member (40) to illuminate an area corresponding to one unit of data; a plurality of light detectors (22) each associated with a corresponding light beam (20), for detecting reflections of the corresponding light beam (20); and logic means (50) coupled to each of said plurality of detectors (22) for providing an output when all of said plurality of detectors (22) are detecting reflections. 2. An optical data reader for use in conjunction with a record member (40) on which data is stored in the form of transparent (61) and non- transparent (60) areas, characterized by a combination of generating means (10) for generating a plurality of light beams (20) converging on said record member (40); a plurality of light detectors (22) each positioned to receive the light from an individual light beam (20) which passes through a transparent area (61) of said record member (40); and logic means (50) coupled to each of said plurality of light detectors (22) for providing an output when all of the light beams pass through a transparent area (61). 3. An optical reader according to either claim 1 or 2, characterized in that said generating means (10) includes a plurality of focused beam- generating means each generating a beam (20) of light directed onto a point on said record member (40). o — 4. An optical reader according to either claim 1 or 2, characterized in that said generating means (10) includes a semiconductor laser for emitting a laser beam; and a lens system (51, 52, 53) for splitting the laser beam into a plurality of beams (20) convergent on said record member (40). 5. An optical reader according to claim 1, characterized by a plurality of reflector means (14) for directing reflected light from the illuminated area to an associated light detector (22). 6. An optical reader according to claim 1, characterized in that said record member (40) is arranged to move with respect to said light beams (20) to cause a sequential scanning of the stored data and in that said light beams (20) are aligned in a plane parallel with the direction of motion of the record member (40) . 7. An optical reader according to claim 1, characterized by a plurality of lens means (16) interposed in each generated beam of light (20) for focusing and converging said beam to illuminate an area on said record member (40). 8. An optical reader according to either claim 1 or 2, characterized in that said record member (40) is an optical disk.

Inventors: BARNES RONALD LEIGH, BARNES, RONALD, LEIGH
Applicants: NCR CO, NCR CORPORATION
Application year: 1985
Main classification: G11B7
IPC codes: G06K7, G11B7