Structured light is a technique where a known pattern of light is projected onto a scene, allowing for the measurement of its 3D shape. An example method involving structured light includes the use of infrared light. Another involves employing extremely high frame rates alternating between two exact opposite patterns.
How Structured Light Works
The core principle behind structured light is projecting a specific, known pattern onto an object or scene. The way this pattern distorts when it hits the surface reveals information about the surface's three-dimensional geometry. By analyzing these distortions with a camera, 3D data can be captured.
Examples of Structured Light Methods
Based on the application and required precision, various types of structured light patterns and methods are used. The provided reference highlights two key approaches:
- Using Infrared Light: While visible light patterns are common, structured light systems can also utilize infrared (IR) light. This is particularly useful in applications where visible light might be distracting or where sensing needs to occur in low-light conditions. Infrared light, projected in a specific pattern (like dots, grids, or lines), behaves similarly to visible structured light, allowing for 3D scanning or depth sensing.
- Alternating Patterns at High Frame Rates: Another method involves projecting patterns, such as stripes or grids, and rapidly switching between complementary or opposite versions of these patterns at very high speeds. Analyzing how these rapidly changing patterns interact with the scene allows for robust and often faster 3D data acquisition. This high-speed alternation helps distinguish between the projected pattern and ambient light, improving accuracy.
Practical Application: Fingerprint Photography
Structured light techniques have practical applications in various fields. As mentioned in the reference, structured light is used by a number of police forces. Specifically, they use it for the purpose of photographing fingerprints in a 3D scene. By projecting a structured light pattern onto a crime scene, forensic investigators can capture detailed 3D information about fingerprints, which can be crucial for analysis and identification.
This application showcases how structured light provides depth and shape information that traditional 2D photography cannot capture, offering a more comprehensive view of the evidence.
