 Method for making hologram ornamental sticker |
| The main object of the present invention is to provide a method for making ornamental hologram ... |
|
| Method for forming spatially-varying distributed Bragg reflectors in optical media |
| We have discovered a new method for making gratings, such as Bragg gratings, having spatially ... |
|
| Cascaded self-induced holography |
| To address the foregoing problems, the present invention provides a method and apparatus for ... |
|
| Writing Bragg gratings in optical waveguides |
| It is an object of the present invention to provide a method of writing a Bragg reflection grating ... |
|
| Optical logic device and optical memory device |
| The invention has been developed in view of the circumstances described above, and an object of the ... |
|
| Non-aqueous electrolyte cell |
| An object of the present invention, therefore, is to provide a non-aqueous electrolyte cell capable ... |
|
| Incandescent light with parallel grooves encompassing a bulbous portion |
| In accordance with the illustrative embodiments illustrating features and advantages of the present ... |
|
| Cable grid spectral lighting system |
| OF THE INVENTION As shown in FIGS. 1 and 2, the basic components of the trapeze grid lighting ... |
|
| LTG AlGaAs non-linear optical material and devices fabricated therefrom |
| The foregoing problems are overcome and the objects of the invention are realized by a light ... |
|
|
Optical disc readout apparatus for different types of optical discs
| Details |
Inventors: Tsuchiya, Yoichi; Kajiyama, Seiji; Kanou, Yasuyuki;
Assignee: Sanyo Electric Co., Ltd. (Osaka, JP)
Primary Examiner: Tran; Thang V.
Assistant Examiner:
Attorney, Agent or Firm: Loeb & Loeb LLP
An optical disc readout apparatus having an optical system which guides a laser beam onto a signal recording surface of a loaded disc through an objective lens and guides a reflected laser beam onto a photo detector. An effective numerical aperture of the objective lens is adjusted according to the thickness between a substrate surface of the loaded disc and the signal recording surface, and the laser spot with a diameter suitable to a recording density of the loaded disc is focused on the signal recording surface. Therefore, the data recorded in a plurality of optical discs with different thickness or recording densities can be read out. |
|
DETAILED DESCRIPTION : It is presumed that a disc type of standard density with a thickness of 1.
2 mm (CD, CDROM), a disc type of high density with a thickness of 1.
2 mm (HDMCD), and a disc type of high density with a thickness of 0.
6 mm (SD) will continue to exist.
It is an object of embodiments of the present invention to provide an apparatus which can record data on optical discs, each being one of two or more different thicknesses and to provide an apparatus which can read out data from optical discs having one of two or more different thicknesses.
An optical disc readout apparatus irradiates a laser beam onto the signal recording surface of an optical disc through an objective lens and guides the laser beam reflected from the signal recording surface into a photodetector, and thereby reads out the signal.
The object of embodiments of the present invention is fulfilled by constructing such optical disc readout apparatus comprising a means for adjusting the effective numerical aperture of the objective lens through the adjustment of the optical system, and guiding the laser beam output from the laser source into the objective lens according to the thickness of the optical disc.
In this construction, when the effective numerical aperture of the objective lens has been adjusted according to the thickness of the substrate of the loaded optical disc, the laser spot with a diameter suitable to the recording density of the loaded optical disc is focused on the signal recording surface of the loaded optical disc.
The adjustment described above can be realized by, for example, interposing a stopping down means within the beam path between the laser source and the objective lens.
The adjustment described above can also be realized by, for example, constructing the optical disc readout apparatus so that two different types of laser sources having mutually orthogonal directions of polarization are switched from one to the other in operation, and a polarization selection means which stops down the diameter of the beam path for one polarization but does not stop down for the other polarization
|
|
Optical Systems 
