An optical device is disclosed for expanding input light in two dimensions in an augmented reality display. The device comprises a waveguide (12) and three linear diffraction grat-ings H0, H1, H2. An incident beam from a projector illuminates an input grating H0 with polychromatic light, and the light is coupled into the waveguide (12). The other two gratings H1, H2 are overlaid on top of one another. Light can be diffracted by one grating H1 into a first diffracted order and towards the other grating H2 which can couple the light out of the waveguide (12) towards a viewer. In another arrangement the crossed gratings H1, H2 may be replaced by a photonic crystal (19) having a regular array of pillars (20) which create a number effective diffraction gratings.
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机译：公开了一种用于在增强现实显示器中以二维方式扩展输入光的光学装置。该设备包括一个波导（ 12 ）和三个线性衍射图H 0， H 1， H 2。来自投影仪的入射光束用多色光照射输入光栅H 0 ，该光耦合到波导（ 12 ）中。其他两个光栅H 1， H 2 彼此重叠。光可以被一个光栅H 1 衍射成第一衍射级，并朝另一个光栅H 2 衍射，该光栅可以将光耦合出波导（ 12 < / B>）。在另一种布置中，交叉的光栅H 1， H 2 可以由具有规则的柱阵列（< B> 20 ），可以产生许多有效的衍射光栅。
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