Optical waveguide comprising a beam in-coupling region and a beam coupling-out region each provided with a coupling grating and display device

An optical waveguide, comprising an optical waveguide body having a beam in-coupling region and a beam coupling-out region, wherein:

• the beam in-coupling region is provided with a coupling grating configured to couple a beam into the optical waveguide body, and have the beam propagate in a total reflection manner in the optical waveguide body;
• the beam coupling-out region is provided with an out-coupling grating configured to couple the light beam propagating to the beam coupling-out region out of the optical waveguide body, such that the beam does not undergo secondary diffraction at the coupling grating and have continuous exit pupil expansion;
• the out-coupling grating comprises a transmissive out-coupling grating and a reflective out-coupling grating disposed on two sides of the optical waveguide body parallel to a beam propagation direction;
• and
• parameters of the in-coupling grating and the out-coupling grating satisfy:
• 2T·tan{arcsin[λ/(nd)+sin imin/n]}≥D (1)
• T·tan[arcsin(sin imax/n)]+T·tan {arcsin[λ/(nd)+sin imax/n]}≤D (2)
• wherein:
• n is a refractive index of the optical waveguide body;
• T is a thickness of the optical waveguide body;
• d is a period of the coupling grating;
• periods of the in-coupling grating and the out-coupling grating are same;
• D is a width of the in-coupling grating in the beam propagation direction;
• λ is a wavelength of the light beam incident on the optical waveguide body;
• imin is a minimum field of view angle of the light beam incident on the optical waveguide body;
• and
• imax is a maximum field of view angle of the beam incident on the optical waveguide body.

A display device comprising an optical waveguide, comprising an optical waveguide body having a beam in-coupling region and a beam coupling-out region, wherein:

• the beam in-coupling region is provided with a coupling grating configured to couple a beam into the optical waveguide body, and have the beam propagate in a total reflection manner in the optical waveguide body;
• the beam coupling-out region is provided with an out-coupling grating configured to couple the light beam propagating to the beam coupling-out region out of the optical waveguide body, such that the beam does not undergo secondary diffraction at the coupling grating and have continuous exit pupil expansion;
• the out-coupling grating comprises a transmissive out-coupling grating and a reflective out-coupling grating disposed on two sides of the optical waveguide body parallel to a beam propagation direction;
• the display device comprises an augmented reality (AR) device;
• and
• a maximum misalignment interval between a first end of the transmissive out-coupling grating and a first end of the reflective out-coupling grating is half of a propagation step that the light beam incident on the optical waveguide body at a maximum field of view angle and propagating within the optical waveguide body in a total reflection manner, i.e., Smax/2,
• Smin=2T·tan {arcsin[λ/(nd)+sin imin/n]}. (a)
• wherein imax is the maximum field of view angle.