Industrial Technology Research Institute

Tsung-Ming Yang

Jau-Jiu Ju

Shin-Ter Tsai

Pei-Yih Liu

Zu-Wen Chao

Tsung-Kai Chang

Jiin-Shyan Tzeng

Pei-Yuh Liu

Chien-Chung Pien

A focusing and tracking method and system for use on the read/write head of an optical drive is provided. The focusing and tracking method and system is capable of detecting both the focusing error and the tracking error of the read/write head to thereby control the focusing and tracking of the same during read operation. In particular, this focusing and tracking method and system combines the use of a knife-edge focusing method and a push-pull tracking method respectively for focusing and tracking of the read/write head. A specially designed photo detector is used to obtain both the focusing error signal and the tracking error signal. This allows the focusing and tracking system to be simplified in structural complexity, thereby saving manufacturing cost. Moreover, since the focusing error signal and the tracking error signal are obtained respectively in perpendicular directions, the undesired effect of cross-talk between the two error signals can be avoided.

Focusing and tracking method and system for the read/write head of an

A two-wavelength laser pick-up head used for accessing DVD, CD, CD-R and CD-E systems. The two-wavelength laser pick-up head includes a shorter wavelength laser optical path for reading the data from a DVD system, and a longer wavelength laser optical path for reading the data from a CD or CD-R system. The above two optical paths use the same collimator and the same objective lens. There is a compensator lens which is used in the longer wavelength laser optical path for correcting the spherical aberration due to the thick substrate of the CD or CD-R.

Two-wavelength laser pick-up head for a DVD

A grating pattern for a bifocal optical pick-up head assembly of an optical compact disc drive device is disclosed. The device is capable of accessing data on the surface of compact discs arranged in either the DVD or the CD formats. The optical head assembly has an optical system that includes a grating plate and an objective, wherein the grating plate contains the grating pattern, and the objective focuses a light beam onto the data surface of the accessed compact disc. The grating pattern includes a first region that contains no grating and a second region that contains grating. The first region substantially surrounds the second region. The light beam that passes through the first region of the grating pattern is incident to the cross-sectional aperture of the objective for the DVD format of the accessed optical disk. The light beam that passes through the second region of the grating pattern is incident to the cross-sectional aperture of the objective for the CD format of the accessed optical disk.

Optical grating for a bifocal access head of optical disk drive devices

An objective lens for an optical disk drive is disclosed. The objective lens comprises four portions each having a aspherical surface for focusing a light beam of a designated wavelength to a designated focal point. The first portion has a first aspherical surface that focuses the light beam to a first focal point. The second portion has a second aspherical surface that focuses the light beam to a second focal point. The third portion has a third aspherical surface featuring the same surface curvature characteristics as that of the first aspherical surface and focuses the light beam to the first focal point. And, the fourth portion has a fourth aspherical surface featuring the same surface curvature characteristics as that of the second aspherical surface and focuses the light beam to the second focal point. The objective lens can be made as a single-piece lens that suffers no energy loss for either focusing.

Objective lens for optical pick-up head of optical disk drive

A single-lens optical pick-up head has a laser diode, a beam splitter, a collimator, a polarizing light converter, a polarization controller, a polarizing beam splitter, a first quarter-wavelength plate, a mirror, a second quarter-wavelength plate, a convex mirror, an objective lens and a photodetector, for use in accessing DVD and CD discs by switching its optical property between two states.

Single-lens optical pick-up head for accessing a DVD disc and a CD disc

A beam shaper device for an optical read/write head on an optical disc drive is provided. This beam shaper device is particularly useful for shaping a laser beam originally emitted with an elliptical cross section, into having a substantially circular cross section. The beam shaper device includes only one prism and one plane mirror. The shape of the prism and the orientation of the plane mirror are specifically devised in such a way as to allow the output beam shaper device to have a circular cross section and to have its propagation axis orthogonal to that of the input laser beam.

Beam shaper device for optical read/write heads

An equivalent Wollaston prism is disclosed for splitting an incident light beam into two adjacent beams which are S-polarized and P-polarized respectively. The polarized light beams are at approximately a right angle with the incident light beam, therefore the structure of optical pick-up head will not be limited to a straight line configuration. The entire structure is compact, easy to align, and economical.

Growing community of inventors

Chilung, Taiwan

Tsung-Ming Yang