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Optical pickup

A technology of lasers and optical discs, applied in the direction of instruments, optics, diffraction gratings, etc., can solve problems such as insufficient luminous efficiency and reduced light quantity of servo signals, and achieve the effect of small light loss and reduced number of components

Inactive Publication Date: 2007-06-13
SHARP KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the holographic optical element 15 acts on both the forward path and the return path, the result is a reduction in the amount of light used as a servo signal.
[0013] The luminous characteristics of blue-violet semiconductor lasers are not sufficient in terms of luminous efficiency compared with red semiconductor lasers and infrared semiconductor lasers used in CDs and DVDs in the current situation.

Method used

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Experimental program
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Embodiment approach 1

[0048] Next, the optical pickup of Embodiment 1 will be described with reference to FIGS. 1 to 7 .

[0049] As shown in FIG. 1 , light emitted from a semiconductor laser 1 is converted by a collimator lens 2 into a parallel beam having an effective beam diameter φeff (2 mm in this embodiment). Then, after passing through the diffraction grating 3 and the light splitting element 4, the spherical aberration compensating element 5 composed of two lenses magnifies the effective beam diameter by m times. In the present embodiment, since m=1.5, the effective beam diameter of the light passing through the spherical aberration compensating element 5 becomes φeff·m=3 millimeters (mm). Furthermore, after the reflection mirror 6 changes the optical path, it is guided to the objective lens 7 of the 2-piece group, and converged on the optical disk 8 .

[0050] After passing through the objective lens 7, the reflected light from the optical disc 8 travels on the optical path opposite to th...

Embodiment approach 2

[0070] Next, refer to FIG. 8 to FIG. 11 of Embodiment 2 of the gate surface.

[0071] As shown in FIG. 8, the light emitted from the semiconductor laser 1 passes through the diffraction grating 3 and the beam splitter 4, and is collimated by the collimator lens 2 into an effective beam diameter φeff (2 mm in this embodiment). Then, the spherical aberration compensating element 5 composed of two lenses enlarges the effective beam diameter by m times. In the present embodiment, since m=1.5, the effective beam diameter of the light passing through the spherical aberration compensating element 5 becomes φeff·m=3 millimeters (mm). Furthermore, after the reflection mirror 6 changes the optical path, it guides to the objective lens 7 of the 2-piece set, and makes it converge on the optical disc 8 .

[0072] The reflected light from the optical disk 8 passes through the objective lens 7 , travels on the optical path opposite to the incident light, is collected by the collimator lens 2 ...

Embodiment approach 3

[0085] An optical pickup according to Embodiment 3 will be described with reference to FIGS. 12A to 14 .

[0086] In this embodiment, as shown in FIG. 12A , the diffraction grating 3 is arranged in the converging optical path as in Embodiment 2. Therefore, for example, if L=8.1 mm and x=4.5 mm, it is the same as Embodiment 2 and also forms φgr = 1.1 mm. Assuming that the horizontal component θ / / =9 degrees of the FFP half-value total width of the light emitted by the semiconductor laser 1, and the vertical component θ⊥=18 degrees, then the irradiation area becomes an ellipse with a minor axis of 0.7 millimeters and a major axis of 1.43 millimeters in the Y direction. shape. Furthermore, the effective diameter (φgr) of the diffraction grating becomes the shape of the center portion of the laser irradiation area. In this embodiment, the semiconductor laser 1 of Embodiments 1 and 2 is rotated by 90 degrees around the optical axis. By rotating in this way, the polarization axis ...

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Abstract

An optical pickup in which the grating constant of diffraction grating (3) is made constant over the entirety, and the duty ratio referred to as L / G duty between the land L and the groove G defined by L / G duty(%)=L / (L+G)100 is varied continuously along the direction orthogonally intersecting the grating groove of the diffraction grating. For example, the L / G duty is set to nearly 50% in the central part of the diffraction grating and set to nearly 100% at the outer edge part of the diffraction grating (3). According to the above arrangement, quantity of light loss can be minimized at the time of recording and reproducting while decreasing the number of components of the optical pickup.

Description

technical field [0001] The present invention relates to an optical pickup for recording information on the recording surface of the information recording medium or reproducing information written on the recording surface of the information recording medium by irradiating light from a semiconductor laser to an information recording medium such as an optical disk. Background technique [0002] In recent years, in the field of information recording, studies on optical information recording methods have been widely conducted. This optical information recording method has many advantages such as non-contact recording and reproduction, and compatibility with various memory forms of reproduction-only type, additive recording type, and rewritable type. Therefore, as an optical information recording system capable of realizing an inexpensive large-capacity medium, a wide range of applications from industrial use to consumer use can be considered. [0003] As the latest trend of thes...

Claims

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Application Information

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IPC IPC(8): G11B7/135G02B5/18G11B7/09
CPCG11B7/13925G11B7/1378G02B27/14G11B2007/13727G02B5/1866G11B7/1398G11B7/1353
Inventor 寺岛健太郎三宅隆浩
Owner SHARP KK