Achromatic beam shaping prism

Optical: systems and elements – Diffraction – From grating

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C359S837000

Reexamination Certificate

active

06552851

ABSTRACT:

BACKGROUND OF THE INVENTION
In an optical disc recording system, the equalization of intensity distribution (hereinafter termed “beam shaping”) of a laser beam that is output from a semiconductor laser source is desired in order to optimize the shape of a light spot on a disc. For example, beam shaping prisms may be used to either compress or expand the diameter of an incident beam in a specific direction by refracting the beam. Specific examples of such beam shaping prisms are disclosed in Japanese Laid Open Applications H10-268112 and H10-62611. All of these beam shaping prisms are designed so that they not only perform beam shaping, but also can compensate for recording performance degradation caused by wavelength fluctuations of a semiconductor laser that is used to read the optical disc.
Wavelength fluctuations of a semiconductor laser frequently occur at the start of operation of a laser or when the luminous power of the laser is changed. Such wavelength fluctuations are said to be an unavoidable phenomenon in an optical disc system for recording signals on a disc medium when turning the laser ON/OFF. However, in the case where the output of a laser fluctuates from a reference wavelength, the output beam from a beam shaping prism will be emitted at a slightly different inclination as compared with the output beam at the reference wavelength, due to the index of refraction of the beam shaping prism being dependent on wavelength. For a recording-type optical disc system, this becomes a problem in that the position of a reading light spot that is formed on a disc will vary with a change in wavelength. This will cause signal degradation in recording onto a disc as well as in reading from a disc using a photo head.
In the above conventional examples, this problem is solved by using two prisms which are formed of materials that have different, refractive indexes and different dispersions. Thus, by using a pair of prisms that form an achromatic beam shaping system, the angle of an output beam is kept roughly constant so as to prevent a positional fluctuation of a light spot on a disc even when the wavelength of the incident beam fluctuates. Further, a beam shaping optical system that uses two cylindrical lenses in lieu of a pair of prisms has also been known.
An optical system is disclosed in U.S. Pat. No. 5,101,458 which enables the output direction of a beam emitted from a prism to be made substantially constant when the wavelength of an input light beam and the incident angle thereof vary. The technique disclosed in this patent leads light that is output from a waveguide into a prism arranged opposite to the waveguide. The output direction of this light is made constant for a change in wavelength by the action of a diffraction grating formed on the output face of the prism. However, the invention described in the above prior art patent employs both a waveguide and a prism, wherein the prism requires a change of the angle of incidence of the input beam to the prism. Therefore the basic idea of that invention is different from that of the present invention. In the present invention the angle of incidence of the input beam is constant and no waveguide path is needed as a necessary component.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide an achromatic beam shaping prism in which the output angle of an emitted beam remains substantially the same even when the wavelength of the incident beam changes and which uses a construction that enables both miniaturization and low cost.


REFERENCES:
patent: 5101458 (1992-03-01), Spaulding et al.
patent: 5625499 (1997-04-01), Chen
patent: 5652681 (1997-07-01), Chen et al.
patent: 10-62611 (1998-03-01), None
patent: 10-268112 (1998-10-01), None

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Achromatic beam shaping prism does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Achromatic beam shaping prism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Achromatic beam shaping prism will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3069076

All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.