Asymmetric metrology tool for reflective waveguide

A optical metrology system, comprising:

• a light engine comprising:
• a light source disposed over one or more microlens arrays;
• one or more condenser lens disposed under the one or more microlens arrays, wherein the one or more condenser lens are disposed over a reticle;
• and
• a projection lens, having a first focal length, disposed under the reticle, wherein the projection lens is configured to align with an in-coupler of an optical device;
• and
• a reflection detector comprising:
• a camera lens, having a second focal length, wherein the camera lens is configured to align with an out-coupler of the optical device;
• and
• a camera disposed over the camera lens, the camera configured to receive light from the camera lens,
• wherein the first focal length is about 10 mm to about 20 mm, and the second focal length is about 20 mm to about 40 mm.

A method, comprising:

• aligning a light engine with an in-coupler of an optical device, the light engine comprising one or more microlens arrays, one or more condenser lens disposed under the one or more microlens arrays, a reticle disposed under the one or more condensers, and a projection lens disposed under the reticle, wherein the projection lens comprises a first focal length;
• projecting a test pattern onto the optical device using the light engine;
• aligning a reflection detector with an out-coupler of the optical device, the reflection detector comprising a camera lens and a camera disposed over the camera lens, wherein the camera lens comprises a second focal length, wherein the first focal length is less than the second focal length;
• receiving a reflected test pattern from the optical device using the reflection detector;
• and
• determining one or more metrology metrics for the optical device based on the reflected test pattern.