Industrial Technology Research Institute

University of Colorado

Industrial Technology Institute

Opto-electronics & Systems Laboratories

Mark O Freeman

Hsi-Fu Shih

Tzu-Ping Yang

Jinn-Kang Wang

Gary Dean Sharp

Kristina M Johnson

Der-Ray Huang

Jau-Jiu Ju

Robert T Weverka

Hung-Te Lee

Tyler Alan Brown

Carl Y Yang

Wei-Chih Lu

The invention provides a pickup head used in an optical data storage system. The pickup head contains a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors. The middle layer serving its function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate a polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.

Diffractive stack pickup head for optical disk drives and method to fabricate the pickup head

A focus/tracking method and system is provided for use in an optical drive with a possibly multiple-wavelength laser source for control of the focus/tracking of the pickup head of the optical drive. The use of a multiple-wavelength laser source allows the optical drive to read data from various types of optical discs. The focus/tracking method and system combines the use of a differential, dual optical channel method for focusing control of the laser beam used to read data from the optical disc and the use of the single-beam tracking method for tracking control of the same. The focus error signal and the tracking error signal can be obtained from the same set of multi-element photodetectors. The structure of the system can therefore be simplified to include a reduced number of constituent components thus allowing a reduction in manufacturing cost.

Robust and versatile focus/tracking method and system for optical pickup heads

The present invention discloses a multiple-beam holographic optical pick-up head, which has the advantages of the multiple-beam optical pick-up head and the holographic optical pick-up head and can increase the light usage efficiency. This invention uses the property that a polarized diffractive optical element can generate different optical effects for laser beam with different polarizations and places a polarized multiple-beam grating and polarized hologram on the optical path for splitting the incident light toward the disc into multiple reading beams by the multiple-beam grating. The returning laser beams reflected from the disc are diffracted and diverted by the hologram to reach a photodetector. Both the incident and reflective beams are diffracted once only; thus the light usage efficiency can be increased.

Multiple-beam holographic optical pick-up head

The invention provides a pickup head used in an optical data storage system. The pickup head contains a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors. The middle layer's function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate a polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.

A dual-wavelength holographic laser module is provided. The dual-wavelength holographic laser module includes a holographic optical element (HOE), a multiple-element photodetector, and a laser light source that can produce a laser light with a wavelength that has, for example, two desired quantities. The laser light emitted from the laser light source with a desired wavelength can travel through the HOE and an objective lens unit, which is used to focus the laser light onto an optical disk of the DVD system, the CD system, or the CD-R system, depending on which wavelength quantity is chosen. The objective lens unit includes a single lens with a changeable NA quantity or a two-lens system that can be switched to put one lens at a time in the optical path. The optical disk reflects the laser light back to the HOE along the same light path. The reflected laser light is diffracted by the HOE to reach to the multiple-element photodetector. The photodetector receives the reflected laser light to obtain a signal, which is used for focusing and tracking, and further reads the information in the DVD system, the CD system, or the CD-R system. The laser light has a single light path even though the laser light can have two different wavelength quantities.

Dual-wavelength optical pickup head

A two-wavelength laser diode package is provided, which can be utilized in the read/write head of an optical drive capable of reading data from different types of optical discs, such as CD (compact disc), CD-R (CD Recordable) and DVD (digital versatile disc). The laser diode package includes a pair of laser diodes of two different specifications in wavelength, which are disposed on one or two submounts, either horizontally or vertically oriented with each other. Further, a beam coinciding means, such as a micro dichroic prism, a micro dichroic plate, a micro dichroic beam-splitter, or an external dichroic beam-splitter, is used to make the two respective laser beams from the two laser diodes to propagate on the same propagation axis when in use.

Two-wavelength semiconductor laser diode package for use on the read/write head of an optical drive capable of reading different types of optical discs

An optical frequency shifter is provided to change the frequency of a coherent input light beam by imparting periodic increases in phase to the beam. This increase in phase is caused by ferroelectric liquid crystals (FLCs) in conjunction with quarter wave plates. The FLCs are repeatedly switched on and off by electrical signal generators, adding phase shift in steps, which in turn results in a higher output optical frequency.

Liquid crystal optical frequency shifter

An optical pickup device including a lighting source, a condensing apparatus, a diffracting means, and a light detector. The light source generates and emits a light beam to the diffracting means. The diffracting means includes a center region and an outer region which encloses the center region. As the light travels from the light source towards the optical storage medium the main zero-order beam which reads the information on the disk encounters only the center region of the diffracting means while the two sub-beams used for track following are created as +1 and -1 diffraction orders from the outer region of the diffracting means. The three beams reflected from the recording medium all pass through the center region of the diffracting means and are diffracted in the direction of the detector therefrom. The light detector consists of multiple detector elements which convert the light that shines upon them after reflection from the recording medium into electronic signals containing the information that was recorded on the medium.

Single surface diffractive element for optical pickup heads

A pickup head for use in optical disk systems such as compact disk players or CD-ROM computer memory includes a holographic optical element that has two decision regions that greatly simplify the design of the pickup head. The two decision regions diffract light that encounters the holographic optical element in two different directions, respectively. The amount of light power incident upon each decision region is utilized to determine a focus error signal and to interpret information stored on the compact or optical disk.

Holographic optical element for optical disk pickup head

The present invention provides optical modulators which comprise aligned chiral smectic liquid crystal cells within an optical resonance cavity. The cavity configurations include symmetric and asymmetric Fabry-Perot etalons. The liquid crystal cells can be planar- or homeotropically-aligned and can be discrete state or analog cells. The device configurations of the present invention provide discrete or continuous optical modulation of the phase, intensity, and wavelength of elliptically polarized light, without requiring polarization analyzers. The modulators are optically or electronically addressable in single pixels or arrays of multiple pixels. Certain homeotropically-aligned cells are provided as an aspect of this invention, as are certain variable retarders comprised of planar-aligned cells in combination with birefringent elements.

Growing community of inventors

Hsinchu, Taiwan

Mark O Freeman