The structured lighting approach in range sensing is a collection of various methods where a laser or conventional light source projects a pattern of light onto the environment.
This technique is a fundamental method for acquiring three-dimensional (3D) data from the real world. Unlike active sensors that emit a single point or line of light and scan the scene, structured light sensors illuminate the entire scene or a significant portion of it simultaneously with a known pattern.
How Structured Light Works
The core principle involves projecting a specific, known pattern onto the surface of an object or scene. This pattern, when cast onto a 3D surface, becomes deformed or distorted according to the shape of the surface.
Here's a breakdown of the process:
- Pattern Projection: A projector (using a laser or conventional light source) emits a pre-defined pattern onto the target environment. This pattern can be simple, like a grid or a set of lines, or more complex, such as coded light patterns.
- Light Recognition: A sensor, typically a camera, captures the image of the projected pattern as it appears on the surface.
- 3D Reconstruction: By analyzing the distortions in the captured pattern compared to the original projected pattern, the system calculates the depth or distance to points on the surface. This allows the sensor to determine the three-dimensional structure of the environment.
The reference specifically highlights that structured light is a collection of various methods where a laser or conventional light source projects a pattern of light onto the environment. The reflected light is recognized by a sensor and used to determine the three-dimensional structure of the environment.
Key Components
A typical structured light system consists of:
- Projector: To cast the specific light pattern (laser or conventional light source).
- Sensor (Camera): To capture the image of the deformed pattern.
- Processing Unit: Software algorithms to analyze the captured pattern, calculate depth, and reconstruct the 3D model.
Types of Structured Light Patterns
Various patterns can be used, each with its own advantages:
- Single Shot Patterns: Patterns like speckles or complex coded patterns (e.g., gray codes) that allow capturing a 3D scene in a single image, suitable for dynamic scenes.
- Multi-Shot Patterns: Sequences of patterns (e.g., varying stripe widths or phases) that require multiple images to gather depth information, offering higher accuracy but less suitable for moving objects.
Applications
Structured lighting is widely used in many fields:
- Industrial Inspection: Checking the dimensions and defects of manufactured parts.
- Reverse Engineering: Creating 3D models of existing objects.
- Medical Imaging: Scanning body parts for prosthetic design or analysis.
- Quality Control: Automated inspection lines.
- Robotics: Enabling robots to perceive their environment in 3D.
- Entertainment: Motion capture and 3D scanning for special effects.
In essence, the structured lighting approach provides a non-contact way to measure distance and shape by observing how a known light pattern interacts with the surface of objects.
