Optical see-through --Waveguide

         We know that the core of AR glasses is the optical module and the optical module consists of micro-display, optical components and fixed components. The optical components can be divided into prism, free surface, Birdbath and waveguide in terms of technical implementation.Today we're going to talk about waveguide technology.

      Waveguide technology is not a new invention. In the optical communication system we are familiar with, the optical fiber used to transmit signals consists of numerous undersea optical cables that connect to the other side of the ocean.It's a kind of waveguide, but it's transmitting light in infrared wavelengths that we can't see.

       For light to travel loss-free and leak-free, "total reflection" is the key, meaning that  meaning that light does not come out as it bounces back and forth.

     This feature of optical waveguide has great advantages in optimizing the design of the glass or HMD and beautifying the appearance.

     With the waveguide as the transmission channel, the display and imaging system can be moved away from the glasses to the top or side of the forehead, which greatly reduces the optical system's blocking of external vision and makes the weight distribution more ergonomic, thus improving the wearing experience of the device.

 

Advantage

  • Increase the range of FOV (Field of View) to accommodate more people and promote the realization of consumer products --- Pupil dilation technology increases FOV.

  • The imaging system is side-mounted, does not block the line of sight and improves redistribution -- Waveguide lenses work like optical cables to transmit images to the human eye.

  • The appearance is more like traditional glasses, which is conducive to design -- It is a flat, thin piece of glass whose outline can be cut.

  • Provides the possibility of "real" 3d images  --  Multiple waveguides can be stacked together, each providing a virtual image.

Weakness

  • Optical efficiency is relatively low  -- Light is lost during transmission, and the large FOV reduces the single-point output brightness.

  • High cost -- Redundant manufacturing processes result in low overall yield.

  • High design threshold -- Diffraction dispersion results in "rainbow" phenomenon and halo.

 

Back to blog

Leave a comment