Device for reading and/or writing optical recording media
AssigneeThomson Licensing
InventorsSoren Dambach, Hartmut Richter
Life of this patent
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Abstract
The present invention relates to an appliance for reading from and/or writing to optical recording media 1 having a first laser diode LD1 for producing a first scanning beam AS1 at a first wavelength λ1 and having a second laser diode LD2 for producing a second scanning beam AS2 at a second wavelength λ2, with the scanning beams AS1, AS2 running along a common optical axis 9, scanning an information layer 6 on the recording medium 1 and falling on a single photodetector 8 in order to produce an information signal IS, with a beam combination element being arranged at one point on the optical axis 9. According to the invention, the beam combination element is a diffraction grating 12.
Claims15
1) appliance for reading from and/or writing to optical recording media (1) having a first laser diode (LD1) for producing a first scanning beam (AS1) at a first wavelength (λ1) and having a second laser diode (LD2) for producing a second scanning beam (AS2) at a second wavelength (λ2), with the scanning beams (AS1, AS2) running along a common optical axis (9), scanning an information layer (6) on the recording medium (1) and falling on a single photodetector (8) in order to produce an information signal (IS), with a beam combination element being arranged at one point on the optical axis (9), characterized in that the beam combination element is a diffraction grating (12) which is optimized for higher than zero-order diffraction for both wavelengths (λ1, λ2).
6) Appliance according to one of the preceding claims, characterized in that the diffraction grating (12) is optimized to first-order diffraction for both wavelengths (λ1, λ2).
7) Appliance according to one of the preceding claims, characterized in that the first laser diode (LD1) and the second laser diode (LD2) are arranged tilted with respect to the optical axis (9).
8) Appliance according to one of the preceding claims, characterized in that the diffraction grating (12) is arranged tilted with respect to the optical axis (9).
9) Appliance according to one of the preceding claims, characterized in that the diffraction grating (12) is oriented such that side spots are oriented at right angles to information tracks on the optical recording medium (1).
10) Appliance according to one of the preceding claims, characterized in that the first laser diode (LD1), the second laser diode (LD2) and the diffraction grating (12) are integrated in one module (14).
13) Appliance according to one of the preceding claims, characterized in that a further diffraction grating (15), in particular a Ronchi grating, is arranged in the beam path.
14) Appliance according to one of the preceding claims, characterized in that both laser diodes (LD1, LD2) are operated simultaneously in order to record information on the optical recording medium (1), while only one of the laser diodes (LD1, LD2) is in each case operated for reading.
15) Method for producing a diffraction grating (12), in particular for use in an appliance according to one of the preceding claims, characterized in that the grating structure and the grating line profile (h1, h2, h3) are defined, the corresponding height profile is subdivided into surfaces of equal height, and the surfaces of equal height are transferred to a blank by means of lithography and an etching process.
Dependencies are inferred from the claim text.