3D Camera Timestamp Calibration for Depth Precision
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Solution Overview
Problem
Existing 3D imaging technologies face challenges such as high power consumption, limited resolution at short distances, vulnerability to ambient light, and computational complexity, making them unsuitable for low-power, compact image sensors in devices like smartphones.
Innovation Solution
A low-power 3D imaging system using a CMOS image sensor with a laser point scan and timestamp calibration for depth measurements, which operates in both 2D and 3D modes with visible light, allowing for compact and efficient depth sensing in portable devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-of-flight (TOF) based range imaging is used, then depth measurement capability is achieved, but power consumption increases
Solution Approach 1:
The patent uses periodic laser pulse emission where the laser emits light in pulsed intervals rather than continuous operation. The image sensor captures reflected light only during these periodic pulses, enabling depth measurement through time-of-flight calculation while significantly reducing power consumption compared to continuous illumination methods
Solution Approach 2:
The patent segments the imaging function by using a single image sensor that operates in different modes: capturing reflected laser light for depth measurement during 3D mode, and capturing ambient light for standard 2D imaging during 2D mode. This segmentation allows the system to achieve depth measurement capability without requiring a separate dedicated 3D sensing subsystem that would increase overall power consumption
2Measurement precision
If structured light methods are used, then 3D shape measurement is achieved, but computational complexity increases
Solution Approach 1:
The patent replaces complex computational structured light methods with a simpler time-of-flight measurement approach. Instead of projecting complex light patterns and performing computationally intensive pattern matching and phase calculation, the system uses direct time measurement of light travel based on laser pulse emission and detection, significantly reducing computational complexity while maintaining 3D shape measurement capability
Solution Approach 2:
The patent extracts only the essential depth measurement function from complex structured light systems by using simple laser pulse timing. Rather than implementing full structured light projection and analysis, the system extracts the core time-of-flight measurement principle, eliminating unnecessary computational complexity while preserving the ability to measure 3D shape
3Measurement precision
If stereo vision systems are used, then depth information is obtained, but device size and complexity increase
Solution Approach 1:
The patent makes the image sensor universal by enabling it to perform both standard 2D color imaging and 3D depth measurement functions. The same image sensor captures reflected laser light for depth calculation and ambient light for 2D imaging, eliminating the need for separate dedicated sensors and reducing overall device size and complexity
Solution Approach 2:
The patent merges the 2D imaging and 3D depth measurement functions into a single integrated system. The image sensor simultaneously or alternately captures both types of data, and the processor combines this information to produce both 2D images and 3D depth maps, reducing device complexity compared to systems using separate sensors for each function
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 system achieves low-power, high-efficiency 3D depth measurements with improved resolution at short distances and reduced computational complexity, suitable for integration in smartphones and other portable devices.
Implementation Method 1
performing a one-dimensional (1D) point scan of a three-dimensional (3D) object along a scanning line using a light source, wherein the point scan projects a sequence of light spots on a surface of the 3D object
Implementation Method 2
for a pixel in the selected row of pixels, sensing a pixel-specific detection of a corresponding light spot in the sequence of light spots; in response to sensing the pixel-specific detection of the corresponding light spot, generating a timestamp value for the corresponding light spot
Implementation Method 3
determining a distance to the corresponding light spot on the surface of the 3D object based at least on the corrected timestamp value and on a scan angle used by the light source for projecting the corresponding light spot
Data Source
AI summary
Using the same image sensor to capture a two-dimensional (2D) image and three-dimensional (3D) depth measurements for a 3D object. A laser point-scans the surface of the object with light spots, which are detected by a pixel array in the image sensor to generate the 3D depth profile of the object using triangulation. Each row of pixels in the pixel array forms an epipolar line of the corresponding laser scan line. Timestamping provides a correspondence between the pixel location of a captured light spot and the respective scan angle of the laser to remove any ambiguity in triangulation. An Analog-to-Digital Converter (ADC) in the image sensor operates as a Time-to-Digital (TDC) converter to generate timestamps. A timestamp calibration circuit is provided on-board to record the propagation delay of each column of pixels in the pixel array and to provide necessary corrections to the timestamp values generated during 3D depth measurements.