How It Works: 3D Sensing | The Glass Age | Corning

The mobile phone of the future depends on glass. But next-gen devices are getting even smarter thanks to cutting-edge imaging technology that senses a phone’s environment in three dimensions. Corning Precision Glass Solutions enables this technology. Here’s how.

How does 3D sensing work?

There are two main technologies that power 3D sensing applications: Time of Flight and Structured Light Illumination (SLI).

In Time of Flight, an infrared strobe emits a bright, short pulse, and a custom detector with a very fast shutter speed measures the time that the light travels before hitting an object.

In SLI, a specific pattern of infrared light is projected onto an object.  The light pattern bends to match the inconsistencies in the surface of that object.  A camera with an infrared filter observes the distortion of that pattern. In other words, Time of Flight directly measures the time that light travels, while SLI utilizes the distortion of a known pattern of infrared light to calculate the distance to an object.

Why does that difference matter? Time of Flight-based 3D sensing systems typically generate lower resolution images due to heat generation and packing density.  They also typically require higher power consumption to operate the shutter.

SLI-based systems enable higher accuracy imaging because of the higher spatial resolutions of the projected patterns. SLI also results in lower power consumption – enabling more precise 3D sensing applications such as facial recognition, while conserving battery life.                

Why is glass important for SLI-based 3D sensing?

3D sensing device makers have two key considerations when choosing an optical material for the SLI projector.

1.) The material must have the lowest coefficient of thermal expansion (CTE), so that it’s least susceptible to changes in temperature. This ensures that the device consistently delivers the most accurate pattern due to heat generation in the light source, or whether it’s operated on a hot, summer afternoon or a cold, winter night.

2.) The material must have extremely high purity. This ensures that it can be introduced seamlessly into the semiconductor front-end foundry lines for high-volume production.

Corning HPFS® fused silica meets these requirements better than other materials. That’s because it has a near-zero CTE, meaning it’s extremely insensitive to changes in temperature. And it’s composed of 100% silicon dioxide. This means it’s additive-free and compatible with existing semiconductor manufacturing requirements. 

Why is Corning HPFS® fused silica ideal?

Corning pioneered the first fused silica in the 1930s. Since then, the material properties of HPFS® fused silica have made it the material of choice for extreme applications including NASA’s space shuttle windows, the International Space Station Destiny Window, and the Hubble Telescope’s corrective optics.

Corning HPFS® fused silica is one result of Corning’s more than 160 years of glass science expertise. In addition to low CTE and high purity, this material offers low birefringence and exceptional refractive index uniformity. These attributes enable optimal performance in the micro-optics required by emerging, high-resolution SLI-based 3D sensing devices.

Corning has demonstrated significant capacity for producing high volumes of Corning HPFS® fused silica for 3D sensing and other applications requiring wafer-format material. Utilizing internally developed state-of-the art metrology systems, Corning is able to achieve champion polish, thickness uniformity, and surface flatness specifications, and meet the stringent quality requirements of the demanding consumer electronics customers.

Learn more about how Corning Precision Glass Solutions powers smarter consumer devices and Internet of Things applications here.