Waveguide Optics

The AR waveguide optic engine is a crucial part of modern AR technology, allowing users to experience virtual images superimposed over the real world. These engines can be classified into two categories: Geometric Waveguide and Diffractive Waveguide.

Geometric Waveguides use the concept of total internal reflection to propagate light waves through a substrate. This category is known for its high brightness, contrast, and color uniformity, making it suitable for high-quality AR experiences. However, geometric waveguides require precise manufacturing and are typically less flexible than diffractive waveguides.

Diffractive Waveguides use diffraction gratings to redirect and reflect the incident light at various angles. This category can be further divided into two subcategories: Surface Relief Grating and Volumetric Holographic Grating.

Surface Relief Grating diffracts incoming light through a patterned surface relief grating. The patterned grating consists of a series of mutually parallel lines with depths proportional to the square root of the modulation function. Surface Relief Grating has high optical efficiency, minimal chromatic dispersion, and can provide good angular selectivity. However, this type of waveguide suffers from low transverse resolution, strong reflection, and color aberration.

Volumetric Holographic Grating uses interference patterns formed in the volume of the substrate to diffract incoming light to create the display image. This category provides high angular selectivity, broad spectral response, and low chromatic dispersion. It also has excellent optical quality and is highly customizable for different applications. However, the manufacturing process of Volumetric Holographic Grating is more complex than that of Surface Relief Grating.

So, what parameters should you consider when choosing a suitable waveguide optic engine? Here are some tips.

Color

Different from other AR optic engines, waveguide optic engines have a higher design and processing difficulty, and the problem of chromatic dispersion is challenging to solve (as seen in Magic Leap). Therefore, there are two types of optic engines available in the market, mono-color and color. For AR glasses used in applications such as information prompting, navigation, and translation assistants, it is recommended to use a mono-color waveguide optic engine (paired with a mono-color micro-display panel). Meanwhile, VISGLASS can also provide color waveguide optic engines.

FOV

The Field of View, or FOV, is an essential specification of AR glasses. It determines the range of virtual objects that a user can see through the display of their glasses. In simplified terms, it's like the "window" through which the user sees the virtual world.

Exit pupil distance

Exit pupil distance, also known as eye relief, is the optimal distance between the eyepiece and the user's eye that provides the best viewing experience. In AR glasses, it's critical to ensure that the exit pupil distance is optimized to maximize comfort and minimize eye strain without affecting the quality of the image.

Eyebox

The Eyebox, or exit pupil diameter, is the area where a user's eyes can be positioned while still seeing the full field of view. If the eyebox is too small, it can cause discomfort and disorientation, while too large an eyebox can lead to decreased image quality and a bulkier design.

MTF

MTF, or Modulation Transfer Function, is a measure of the optical system's ability to transfer contrast from the object to the image plane. In AR glasses, MTF determines the clarity and sharpness of the display, which is essential for providing the user with a realistic and seamless AR experience.

Please contact sales@visglass.com for details. Make sure to mention your order quantity, expected price, and packing requirements, among others.