Sequential Light Source Grouping for ToF Depth Measurement
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Solution Overview
Problem
The Time of Flight (ToF) method for acquiring depth information is limited by the total average power of the output light, which restricts the intensity of the light and decreases the measurement distance due to signal attenuation.
Innovation Solution
A camera device with a light output unit comprising multiple light sources arranged in a predetermined pattern, divided into at least two light source groups, and an image sensor with corresponding pixel groups, where the output light signal is controlled to be output sequentially from each light source group, and the input light signal is collected sequentially in each pixel group, allowing adaptive adjustment of the number of light source groups based on the measurement distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the total average power of the output light is limited to satisfy the eye safety standard, then the intensity of the output light is limited, but the measurement distance decreases due to signal attenuation
Solution Approach 1:
The light sources are divided into multiple groups that operate sequentially rather than simultaneously. Each group emits light at high intensity for a brief period, then switches to the next group. This temporal segmentation allows the system to maintain high instantaneous intensity for accurate depth measurement while keeping the total average power within eye safety limits.
Solution Approach 2:
The light source groups operate in periodic cycles, with each group emitting light for a specific duration followed by a pause before the next group activates. This periodic operation pattern enables the system to deliver high-intensity light pulses necessary for ToF measurement while controlling the duty cycle to maintain compliance with average power safety standards.
2Length of stationary object
If the intensity of the output light is increased to extend measurement distance, then the measurement distance increases, but the eye safety standard may be violated
Solution Approach 1:
By segmenting the light sources into multiple groups that activate sequentially, the system can concentrate power into shorter, more intense pulses from each group. This segmentation allows achieving the necessary peak intensity for extended measurement distance while distributing the total energy delivery over time to maintain safe average power levels.
Solution Approach 2:
The system dynamically adjusts the operating parameters of the light source groups, including the duty cycle, pulse width, and intensity level of each group. By optimizing these parameters, the system achieves maximum measurement distance with the highest safe peak intensity while ensuring the time-averaged power remains within eye safety standards.
3Length of stationary object
If multiple light sources operate simultaneously to increase measurement distance, then the signal strength increases, but the total average power consumption increases
Solution Approach 1:
Instead of all light sources operating simultaneously, the system segments them into multiple groups that activate in sequence. This approach maintains the signal strength needed for extended measurement distance by ensuring adequate light intensity from active groups, while reducing total power consumption by having only a fraction of light sources active at any given moment.
Solution Approach 2:
The light source groups operate in periodic cycles with controlled duty ratios. Each group emits light at high intensity for a portion of the measurement period, then remains inactive while other groups operate. This periodic operation maintains sufficient average signal strength for accurate depth measurement while significantly reducing the overall power consumption compared to continuous operation of all light sources.
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
This solution enables an increase in the measurement distance for depth information while adhering to eye safety standards, allowing for adaptive adjustment of light source intensity and number based on the distance to the object, thereby improving the accuracy of depth information extraction at both short and long distances without significant increases in power consumption.
Implementation Method 1
an image sensor which generates an electric signal from the input light signal collected by the lens unit
Implementation Method 2
The distance to an object is calculated by measuring the flight time, i.e., the time it takes for emitted light to return by being reflected
Data Source
AI summary
A camera device according to an embodiment of the present invention a light output unit which outputs output light signals to be emitted to an object; a lens unit which includes an infrared (IR) filter and at least one lens disposed on the IR filter, and focuses input light signals reflected from the object; an image sensor which generates electrical signals from the input light signals focused by the lens unit; an image processing unit which acquires depth information about the object by using the input light signals received in the image sensor; and a control unit which controls the output light signals to be output sequentially for a plurality of light source groups included in the light output unit, and the input light signals to be received sequentially for a plurality of pixel groups included in the light input unit.