Focusing system comprising acousto-optic deflectors for focusing an electromagnetic beam
A focusing system for focusing an electromagnetic beam for three-dimensional random access applications comprises a first pair of acousto-optic deflectors for focusing an electromagnetic beam in an X-Z plane, and a second pair of acousto-optic deflectors for focusing an electromagnetic beam in a Y-Z plane substantially perpendicular to the X-Z plane. The second pair of acousto-optic deflectors is arranged between the acousto-optic deflectors of the first pair of acousto-optic deflectors such that the first and fourth acousto-optic deflectors of the system belong to the first pair of acousto-optic deflectors and the second and third acousto-optic deflectors of the system belong to the second pair of acousto-optic deflectors.
1. Focusing system for focusing an electromagnetic beam for three-dimensional random access applications, the system comprising a first pair ( 10 ) of acousto-optic deflectors ( 12 , 12 ′) for focusing an electromagnetic beam in an X-Z plane, and a second pair ( 20 ) of acousto-optic deflectors ( 22 , 22 ′) for focusing an electromagnetic beam in a Y-Z plane being substantially perpendicular to the X-Z plane, characterised in that the second pair ( 20 ) of acousto-optic deflectors ( 22 , 22 ′) is arranged between the acousto-optic deflectors ( 12 , 12 ′) of the first pair ( 10 ) of acousto-optic deflectors, such that the acousto-optic deflectors together form an array of deflectors with acousto-optic deflectors ( 12 , 12 ′) of the first pair ( 10 ) being the first and fourth acousto-optic deflectors in the array and acousto-optic deflectors ( 22 , 22 ′) of the second pair ( 20 ) being the second and third acousto-optic deflectors in the array.
2. The focusing system according to claim 1 , wherein the acousto-optic deflectors ( 12 , 22 , 12 ′, 22 ′) comprise anisotropic crystals and the deflectors are used in shear acoustic mode.
3. The focusing system according to claim 1 , wherein the acousto-optic deflectors ( 12 , 12 ′, 22 , 22 ′) of each pair ( 10 , 20 ) are arranged substantially parallel to each other.
4. The focusing system according to claim 1 , wherein a polariser is arranged between the first and second acousto-optic deflectors ( 12 , 22 ), and/or between the second and third acousto-optic deflectors ( 22 , 22 ′), and/or between the third and fourth acousto-optic deflectors ( 22 ′, 12 ′).
5. The focusing system according to claim 1 , wherein a telecentric relay system ( 60 ) is arranged between the first and second acousto-optic deflectors ( 12 , 22 ), and/or between the second and third acousto-optic deflectors ( 22 , 22 ′), and/or between the third and fourth acousto-optic deflectors ( 22 ′, 12 ′).
6. The focusing system according to claim 1 , wherein optical elements present between the acousto-optic deflectors maintain polarisation of a transmitted portion of an electromagnetic beam.
7. The focusing system according to claim 1 , wherein optical aperture of one of the second, third or fourth acousto-optic deflectors ( 22 , 22 ′, 12 ′) is increased and the acousto-optic deflector with the increased optical aperture is separated from an adjacent upstream acousto-optic deflector by a telecentric relay system ( 60 ) with magnification adjusted to aperture difference therebetween.