Optical pickup device emitting linear polarized light with a 45 degree phase difference

The present invention relates to an optical device which includes a first laser diode, a beam splitter, a first objective lens, a photo-detector, a second laser diode, a wedged plate beam splitter, a second objective lens and a collimator. The present invention deploys two independent transmitting paths. The retrieving paths share the beam splitter and the photo-detector commonly at the returning route.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an optical pickup device. There is 90 degree phase shift between linear polarization light from an laser diode reflected by an optical disk, which feedback to the original laser diode and linear polarization light from the original laser diode.

2. Background Description

FIG. 1shows all components in an ordinary optical disk system. At first, laser diode11emits a p-type linear polarized light to polarized beam splitter12. Through polarized beam splitter12and quarter wave plate13, the light becomes circular polarized light to optical disk16. Corrected by collimator lens14and objective lens15, the light reflected by optical disk16comes back with original optical path. That is to say, through objective lens15and collimator lens14, the reflected light with left-hand circular polarization enters into quarter wave plate13and polarized beam splitter12. Finally, the light with s-type linear polarization enters to photodetector17.

In this optical path with disk signal from optical disk, there are few signals which feedback to laser diode11by the property of polarized beam splitter12. The partial signa with p-type linear polarization through polarized beam splitter12enters the laser diode11. It makes intensity noise and influences the original p-type polarized light from laser diode11. InFIG. 2, the photodetector17detects the related intensity noise which makes the bad influences of precision of detecting signals.

According to the defect of used optical pickup system, this invention has been implemented an optical pickup system and its optical path by the optical property to reduce the signal intensity noise and increase the precision of detecting signal, which can improve the defect of used optical pickup system.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to reduce the signal intensity noise and to increase the precision of detecting signal to improve the defect of used optical pickup system, the invention of optical pickup head includes laser diode11which emits an original polarized light with 45 degree phase angle, polarized beam splitter12which reflects the original polarized light to circular polarized light and passes through reflective light with left-hand circular polarized light, a collimator which makes the circular-polarized light to parallel light, an objective lens which focus the circular-polarized light to disk to let the reflective light which has one signal from optical disk and one photodetector which detect the relative signal. In this invention, the polarized beam splitter can produce one feedback light with −45 degree phase angle to laser diode, which can has one phase shift 90 degree between feedback light and original linear polarized light.

The followings are the list of detailed legends presented in the present invention.

The following is a description of the present invention. However, other than the detailed description, the present can also be widely implemented in other embodiment, and the scope of the present invention is not limited and is based on the future patent scope.

A preferred embodiment according to the invention will be described hereunder with reference toFIGS. 1 to 3.

At first, laser diode21emits the linear polarized light with 45 phase angle to polarized beam splitter22. By effect of separating and reflecting light of polarized beam splitter22, the emitting light becomes right-hand circular polarized light to collimator23. The light passing through the collimator23focuses on optical disk25by an objective lens24. The reflective light with left-hand circular polarization by optical disk25is reflected with original optical path from objective lens24and collimator23to polarized beam splitter22. The light is changed the polarization from left-hand circular polarization to linear polarization by passing through polarized beam splitter22to photodetector26.

From this optical path which contains optical disk signal, there are few signals light which feedback to laser diode22because of the property of polarized beam splitter22. But the feedback light with −45 degree phase angle increases the 90 degree phase shift compared with original light with +45 degree phase angle, the intensity noise can be removed.

However, the influence of yield rate of making optical component, (like beam splitter, collimator, objective lens and laser diode) can change the optical property of optical component. The foregoing phase shift can not be 90 degree by influence of yield rate. When it existing a phase shift in optical system, the intensity noise can still be reduced.

According to real operation and the existent optical component testing, in this invention, there is a tolerance +/−30 degree with 90 degree.

In this invention, the non-polarized beam splitter or some composed of polarized beam splitters can be used in place of polarized beam splitter. In this invention, it can reduce the specific optical component, like quarter wave plate which reduce the noise and increase the precision of detecting optical signal and to reduce the cost.

According to the foregoing description, this invention has one kind of method to reduce the signal intensity noise and increase the precision of detecting signal in optical pickup head system.

Although preferred embodiments of the present invention have been described in the forgoing description and illustrated in the accompanying drawings, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substituting of parts and elements without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to encompass such rearrangements, modifications, and substitutions of parts and elements as fall within the scope of the appended claims.