ToF Auto-Focus Tracking for Low-Light Depth Measurement
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Solution Overview
Problem
Existing auto-focus systems in photographic equipment struggle to accurately and rapidly determine focusing distance in varying lighting conditions and subject positions, especially in low-light settings and when dealing with human subjects.
Innovation Solution
An active auto-focus solution utilizing a Time-of-Flight (ToF) sensor, combined with a Single Shot Multi-Box Detector (SSD), Hungarian algorithm, compressive tracking algorithm, and Kalman filter, to acquire subject depth information and track object movement effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast measurement technique is used for auto-focusing, then focusing accuracy can be achieved, but the system is not suitable for video and performs poorly in low-light conditions
Solution Approach 1:
The patent introduces a ToF sensor as an intermediary device that actively emits light and measures the time of flight to obtain depth information. This mediator enables the system to acquire focusing distance independently of ambient lighting conditions and subject visual patterns, resolving the contradiction between measurement precision and adaptability to different conditions
Solution Approach 2:
The patent replaces the passive optical contrast measurement system with an active time-of-flight measurement system. By substituting the mechanical/optical contrast detection with electronic time measurement of light travel, the system achieves focusing capability that works in both still images and video, and performs reliably in low-light conditions
2Measurement precision
If phase difference method is used with beam splitter, then focusing distance can be determined, but additional parts are required and light intensity is greatly reduced
Solution Approach 1:
The ToF sensor performs multiple functions: it acts as both the depth measurement device and the primary imaging sensor. By making the sensor universal, the system eliminates the need for separate beam splitters and additional image sensors, reducing device complexity while maintaining focusing distance determination capability
Solution Approach 2:
The patent extracts the depth measurement function from the complex phase difference system with beam splitters and separates it into a dedicated ToF sensor. This extraction simplifies the overall system by removing unnecessary optical components while preserving the essential focusing distance determination capability
3Measurement precision
If phase difference method splits light, then two images can be captured for comparison, but the amount of light striking the sensor is greatly reduced
Solution Approach 1:
The ToF sensor uses periodic modulation of the emitted light signal to encode depth information in the time domain. By modulating the light source periodically and measuring the phase shift or time of flight of the reflected signal, the system achieves phase difference measurement without physically splitting the light path, thereby maintaining full light intensity at the sensor
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate and rapid acquisition of focusing distance in both normal and low-level lighting conditions, providing stable focus on moving subjects and improving user experience by adapting to different lighting and subject scenarios.
Implementation Method 1
An active auto-focus solution with a ToF sensor that can acquire subject depth information regardless of lighting conditions
Data Source
AI summary
The invention discloses an active auto-focus tracking system using a time-of-flight (ToF) depth sensor. The ToF sensor serves as a rangefinder and also provides environmental depth information. The active auto-focus system includes a compressive tracking algorithm to track the movement of an object. The active auto-focus tracking system can acquire subject depth information regardless of various lighting conditions, subject positions, and visual patterns. Moreover, the system can perform an improved acquisition of focusing distance in both normal and low-level lighting conditions.