Method for out-coupling grating for AR optical waveguide, and design method for AR optical waveguide

A design method of an augmented reality AR optical waveguide, the AR optical waveguide comprising a coupling-in grating, an optical waveguide body, and a coupling-out grating, and the design method characterized by comprising:

• optimizing grating parameters of the coupling-in grating according to an angle at which a light bean is incident to the coupling-in grating and a wavelength of the light beam, the grating parameters comprising a grating period, a grating depth and a grating duty ratio;
• determining a grating period and a grating depth of the coupling-out grating according to the grating period and the grating depth of the coupling-in grating:
• partitioning the coupling-out grating by employing a design method of the coupling-out grating;
• and obtaining grating duty ratios of respective partitions of the coupling-out grating by taking a total coupling-out optical power and non-uniformity of the coupling-out grating as optimization objectives, wherein the design method of the coupling-out grating comprises:
• calculating a diffraction coupling-in angle, at which a light beam is diffracted and coupled into the optical waveguide body through the coupling-in grating, according to an angle at which the light beam is incident to the coupling-in grating, a wavelength of the light beam and a grating period of the coupling-in grating;
• calculating a distance between two adjacent coupling-out positions of the light beam on the coupling-out grating according to the diffraction coupling-in angle and a thickness of the optical waveguide body;
• calculating a brightness difference rate of the light beam after being coupled out multiple times through the coupling-out grating according to a maximum diffraction efficiency of the coupling-out grating;
• and calculating a number of partitions of the coupling-out grating according to a length of the coupling-out grating, a sensitivity of a human eye to the light beam, the brightness difference rate, and the distance between the two adjacent coupling-out positions.

An optical waveguide for augmented reality AR glasses, designed and manufactured by employing the design method the AR optical waveguide comprising a coupling-in grating, an optical waveguide body, and a coupling-out grating, and the design method comprising:

• optimizing grating parameters of the coupling-in grating according to an angle at which alight beam is incident to the coupling-in grating and a wavelength of the light beam, the grating parameters comprising a grating period, a grating depth and a grating duty ratio;
• determining a grating period and a grating depth of the coupling-out grating according to the grating period and the grating depth of the coupling-in grating;
• partitioning the coupling-out grating by employing a design method of the coupling-out grating;
• and obtaining grating duty ratios of respective partitions of the coupling-out g rating by taking a total coupling-out optical power and non-uniformity of the coupling-out grating as optimization objectives, wherein the design method of the coupling-out grating comprises:
• calculating a diffraction coupling-in angle, at which a light beam is diffracted and coupled into the optical waveguide body through the coupling-in grating, according to an angle at which the light beam is incident to the coupling-in grating, a wavelength of the light beam and a grating period of the coupling-in grating;
• calculating a distance between two adjacent coupling-out positions of the light beam on the coupling-out grating according to the diffraction coupling-in angle and a thickness of the optical waveguide body;
• calculating a brightness difference rate of the light beam after being coupled out multiple times through the coupling-out grating according to a maximum diffraction efficiency of the coupling-out grating;
• and calculating a number of partitions of the coupling-out grating according to a length of the coupling-out grating, a sensitivity of a human eye to the light beam, the brightness difference rate, and the distance between the two adjacent coupling-out positions.