Optical reading apparatus and method of reading data

2- An apparatus as claimed in claim 1, wherein said master source is a laser.

3- An apparatus as claimed in claim 1 or 2, wherein said non-linear optical element is constituted by a second laser or slave laser into which the reflected light is injected so as to emit light to a light detector for providing said detected information, said emitted light having a magnitude related to the reflected light in a non-linear, monotonic fashion.

4- An apparatus as claimed in claims 1 or 2 or 3, in wherein the second light beam of said non-linear element has a wavelength different from the wavelength of said first light beam.

5- An apparatus as claimed in any of the preceding claims, wherein the second laser is a high-power laser as compared with the first laser.

6- An apparatus as claimed in any of the preceding claims, wherein the second laser changes its polarization in accordance with the polarization of the light which is injected into it.

7- An apparatus as claimed in any of the preceding claims, wherein the second laser changes its transverse mode depending on the amount of light injected from the light source.

8- A method of reading an optical data carrier, comprising the steps of:

• injecting into a slave laser the light coming from a master light source after reflection at a data carrier,
• providing detection means for detecting the light coming from the data carrier by using a non-linear optical element providing an improvement of the signal to noise ratio of the detected information.

9- An optical disc drive suitable for an apparatus as claimed in claims 1-7.