1. An acousto-optical tunable filter, comprising:
a planar optical waveguide (2) for propagation of light beam (14), and
arranged sequentially along the path of the light radiation-means for forming a light beam,
transducer (16) for acoustic waves suited to generate an acoustic wave (15) that is capable of interacting with the light beam waves to cause their diffraction within a predetermined wavelength range, and
means for selecting a diffracted portion of the light beam, characterized in that
at least one of the light beam forming means and selecting means is in the form of at least one stripe waveguide (3) disposed in a plane of the planar waveguide (2), within said waveguide itself, or in the vicinity thereof, and in the form of a multiple unit reflectors (10) that overlap an aperture of stripe waveguide (3), the relative position and inclination angle of said unit reflectors being selected to maintain a phase difference at the operating radiation wavelength for any pair of beams (13) reflected from different unit reflectors (10), where said phase difference is essentially a multiple of 2\u03c0.
2. The acousto-optical filter as claimed in claim 1, characterized in that both the forming means and selecting means are in the form of stripe waveguides (3 and 4), unit reflectors (10) of the beam forming means’ stripe waveguide are inclined in the direction that is opposite to inclination of unit reflectors (10) of the selecting means.
3. The acousto-optical filter as claimed in claim 2, characterized in that the selecting means comprises a plurality of analogous stripe waveguides (4-7), the arrangement and inclination angle of unit reflectors (11) of each of said waveguides being chosen such that a predetermined wavelength is selected unique to a particular waveguide.
4. The acousto-optical filter as claimed in claim 3, characterized in that the stripe waveguide (7), that is the last on the radiation path, is implemented as identical to stripe waveguide (3) of the beam forming means.
5. The acousto-optical filter as claimed in claim 4, characterized in that said filter is provided with additional transducer (20) of acoustic waves, which transducer is suited to generate the acoustic wave that is directed opposite to the acoustic wave of main transducer (16) and capable of interacting with the beam light waves within the interval between the last and next to last stripe waveguides (6 and 7) of the selecting means.
6. The acousto-optical filter as claimed in any of claims 1, 2, characterized in that the inclination angle of the unit reflectors (3-7) is about 45 degrees with respect to axis of the corresponding stripe waveguide.
7. The acousto-optical filter as claimed in any of the preceding claims, characterized in that unit reflectors (10, 11) have different reflectance whose value decreases from the middle portion of a stripe waveguide to its ends.
8. The acousto-optical filter as claimed in any of the preceding claims, characterized in that unit reflectors (10, 11) are disposed at different intervals from one another.
9. The acousto-optical filter as claimed in any of the preceding claims, characterized in that along at least one stripe waveguide (5), electrode (23) is positioned, ends of which electrode being connected to controlled source (25) of alternating or direct current.
10. The acousto-optical filter as claimed in any of claims 1-8, characterized in that along at least one stripe waveguide (6) disposed is a pair of electrodes (22) connected to controlled source (24) of direct current.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A computer-implemented method for displaying information about items available from a web site, comprising:
for each of a set of items having rank values not exceeding a rank value threshold and associated with a consumption ranking exceeding a consumption threshold:
identifying a first and second rank value for selected item for a predetermined number of time periods immediately preceding the current time period, the first rank value corresponding to a rank value of the selected item at a first time period preceding the current time period and the second rank value corresponding to a rank value of the selected item at a second time period preceding the current time period;
characterizing a change in consumption ranking for a selected item based on a comparison between a current rank value associated with the selected item and at least one of the first and second rank values;
determining scores for the selected item based upon the current rank value of the selected item and the first and second rank value of the selected item, the scores characterizing the change in consumption ranking undergone by the selected item; and
causing the display of an indication of the characterization of change in the selected item;
wherein the method is performed by a computer system.