How the Garmin LIDAR-Lite Products Work with Reflective Surfaces

Reflective characteristics of an object's surface can be divided into three categories (in the real world, a combination of characteristics is typically present):

• Diffuse Reflective
• Specular
• Retro-reflective

Diffuse Reflective Surfaces:

Purely diffuse surfaces are found on materials that have a textured quality that causes reflected energy to disperse uniformly. This tendency results in a relatively predictable percentage of the dispersed laser energy finding its way back to the device. as a result, these materials tend to read very well.

Materials that fall into this category are paper, matte walls, and granite. It is important to note that materials that fit into this category due to observed reflection at visible light wavelengths may exhibit unexpected results in other wavelengths. The near infrared range used by the device may detect them as nearly identical. For example, a black sheet of paper may reflect a nearly identical percentage of the infrared signal back to the receiver as a white sheet.

Specular Surfaces:

Specular surfaces are found on materials that have a smooth quality that reflect energy instead of dispersing it. It is difficult or impossible for the device to recognize the distance of many specular surfaces. Reflections off of specular surfaces tend to reflect with little dispersion which causes the reflected beam to remain small and, if not reflected directly back to the receiver, to miss the receiver altogether. The device may fail to detect a specular object in front of it unless viewed from the normal.

Examples of specular surfaces are mirrors and glass viewed off-axis.