OPTICAL HEAD APPARATUS

Abstract: In case that the light beam emitted from a light source mounted on a base element is focused to a spot litht on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read write the data on the storage media. In order to resolve the above pro­ blem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being re­ flected toward the data storage media and focused thereon.

Description: The present invention relates to an optical head apparatus in which data may stored on and read from an optical storage media, and more particularly to a system which employs a so-called twin-spot method as a track displacement detection technique for scanning data tracks of such optical storage means. Earlier European application EP-A-l71 929 falling under Art.54(3) already describes an optical head apparatus having a light source mounted on a base element containing a mount in, a manner that a light emitting end face of said light source is made flush with a front end face of said base element; optical incident means for diffracting a light beam emitted from said light source into a plurality of diffracted light beams and for focusing said diffracted light beams to a plurality of spot lights on a data storage media; splitter means interposed in said optical incident means, for separating light beams coming from the side of said light source from reflected light beams coming from said data storage media; and photodetection means constructed of a plurality of photoreceptors for receiving light beams having been separated by said splitter means, whereby a light beam treating means is provided in a portion of said base element on which portion re-incident light beams not having been separated by said splitter means are incident again, said light beam treating means preventing said re-incident light beams from being reflected toward said optical incident means, said light beam treating means being constructed of a serrated surface formed in said front end face of said base element for reflecting the incident light beams out of said optical incident means. In this apparatus the light treating means is constructed as an oblique, rough surface, which causes an irregular reflection of the light beam incident on the front end face of the mount or the buffer layer, resp. It is the object of the invention to provide an optical head apparatus in which the oblique surfaces causes a regular reflection of the light beam. According to the invention this object is solved in that said serrated surface comprises a plurality of small oblique faces each of which crosses a vertical plane at an angle of Θ so that the light beam incident on the front end face of said mount or the front end face of said buffer layer is reflected in a direction deviated by an angle of 2 Θ from the light path of such incident beam. The present invention will become more apparent from the following detailed description in conjunction with the drawings, in which: Fig. 1 is a schematic view of the LD chip employed in a first embodiment of the invention, and Fig. 2 is a schematic view of the LD Chip employed in a second embodiment of the invention. In Fig. 1 the light treating means is constructed of a serrated surface formed in the front end face 300 of mount 4, which serrated surface comprises a plurality of small oblique faces each of which crosses a vertical plane at an angle of Θ, so that the light beam incident on the front end face 300 of the mount 4 is reflected in a direction deviated by an angle of 2 Θ from the light path of such incident beam to make it possible to eliminate/reduce the interference. The first order light beam 82 having been reflected form the disk (not shown) toward the side of the LD chip 1 is reflected from the front end face 300 of the mount 4 in a direction deviated from the optical axis of such incident beam 82 by an angle of 2 Θ to become a light beam 92. Consequently, in case that a half angle if the light beam emitted from the LD chip 1 and to be focused is designated by the reference character u, when the angle of Θ is larger than the half angle u, the thus reflected light beam 92 does not pass through the light path of the incident beam 82 at all, to make it possible to prevent the reflected beam 92 from being focused on the the disk by the objective lens (not shown), so that the interference is prevented from occurring. It is naturally possible to decrease the amount of light of the beam 92 returning again to the position of the 1st order light beam on the disk when the angle of Θ is slightly smaller than the half angle u. Therefor, in this case, such provisions of the surface formed in the front end face 300 of the mount 4 with a plurality of such oblique faces is advantageous to reduce the influence of the interference. In Fig. 2 the base element is constructed of said mount 4 and a buffer layer 3. The light treating means is constructed of a serrated surface formed in the front end face 200 of a buffer layer 3, which serrated surface comprises a plurality of small oblique faces each of which crosses a vertical plane at an angle of Θ, so that the light beam incident on the front end face 200 of the buffer layer 3 is reflected in a direction deviated by an angle of 2 Θ from the light path of such incident beam to make it possible to eliminate or to reduce the interference.

Claims: Optical head apparatus having a light source (1) mounted on a base element containing a mount (4) in a manner that a light emitting end face of said light source (1) is made flush with a front end face (300) of said base element or the front end face (200) of a buffer layer (3); optical incident means for diffracting a light beam (5) emitted from said light source (1) into a plurality of diffracted light beams and for focusing said diffracted light beams to a plurality of spot lights on a data storage media; splitter means interposed in said optical incident means, for separating light beams coming from the side of said light source (1) from reflected light beams coming from said data storage media; and photodetection means constructed of a plurality of photoreceptors for receiving light beams having been separated by said splitter means, whereby a light beam treating means is provided in a portion of said base element on which portion re-incident light beams not having been separated by said splitter means are incident again, said light beam treating means preventing said re-incident light beams from being reflected toward said optical incident means, said light beam treating means being constructed of a serrated surface formed in said front end face (300) of said base element (4) or said front end face (200) of said buffer layer (3) for reflecting the incident light beams out of said optical incident means, said serrated surface comprising a plurality of small oblique faces each of which crosses a vertical plane at an angle of Θ so that the light beam incident on the front end face (300) of the mount (4) or the front end face (200) of said buffer layer (3) is reflected in a direction deviated by an angle of 2 Θ from the light path of such incident beam.

Inventors: IWATA, KAZUO, SHIKAMA, SHINSUKE
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1986
Main classification: G11B7
IPC codes: G11B7, H01S5