Rotating Polygon Light Pattern Generation for Depth Mapping

The patent applies periodic action by using a rotating polygon mirror to scan the laser beam across the scene in a periodic manner. This scanning approach converts continuous illumination into periodic line scans, allowing the use of shorter effective integration times for each line while maintaining continuous scene coverage. The periodic scanning enables the system to achieve good signal-to-noise ratio without requiring the laser to operate in complex high-power short pulse modes.

The patent implements dynamics by transitioning from a static staring camera approach to a dynamic scanning approach using a rotating polygon mirror. The mirror rotates at controlled speeds to sweep the laser beam across multiple lines sequentially. This dynamic scanning enables the system to reduce ambient light accumulation by limiting exposure to brief intervals for each scanned line, thereby improving signal-to-noise ratio while using standard continuous-wave lasers.

The rotating polygon mirror creates periodic line scans that allow the laser to illuminate each line for a brief duration. This periodic scanning approach achieves short effective exposure times for each line without requiring the laser to operate in complex pulsed modes. The continuous-wave laser simply follows the scanning pattern, maintaining reliability while achieving good signal-to-noise ratio through the temporal separation of line scans.

The patent introduces the rotating polygon mirror as an intermediary device between the continuous-wave laser and the scene. This intermediary component performs the time-multiplexed scanning function, allowing the laser to operate continuously at low power while the mirror creates the effective short-duration line scans. This intermediary approach eliminates the need for complex laser pulsing electronics and improves overall system reliability.

The periodic line scanning approach allows the system to achieve sufficient illumination intensity by concentrating laser power into brief sequential line scans rather than continuous illumination. Each line receives intense illumination for a short duration, creating a bright visible pattern, while the duty cycle remains low enough to maintain eye safety. This temporal concentration of energy achieves the desired brightness without requiring continuously high power levels.

The dynamic scanning approach distributes the total laser energy across multiple sequential line scans rather than concentrating it continuously in one location. This dynamic time-multiplexed illumination allows each line to be brightly illuminated during its scan interval while the average power density over time remains below eye safety thresholds. The rotating mirror enables this dynamic energy distribution, achieving both brightness and safety.