Elliptical Structured Light for Time-of-Flight Range Imaging
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Solution Overview
Problem
Time-of-flight range imaging devices face challenges in achieving high resolution and accurate distance measurement due to the use of dot light sources, which result in low resolution areas where dot light is not applied, and the saturation of pixels at intersections of perpendicular lines of light, leading to signal output differences and reduced measurable distances.
Innovation Solution
The implementation of a range imaging device that emits structured light with elliptical patterns of dot light and periodically formed lines of light, where the light source unit includes elements that can independently adjust the orientation and overlap of light patterns to reduce unlit areas and pixel saturation, using a pixel drive circuit to synchronize charge integration with light pulses and a charge discharge unit to manage charge during non-integration periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If dot light sources are used in time-of-flight range imaging devices, then the device structure is simplified, but the resolution is reduced in areas where dot light is not applied
Solution Approach 1:
The light source is divided into multiple independently controllable light emitting elements arranged in a matrix, allowing selective activation of specific elements to create various light patterns including elliptical dots and lines, thereby improving resolution without requiring a completely different light source structure
Solution Approach 2:
The patent transitions from conventional circular dot patterns to elliptical dot patterns with adjustable aspect ratios, adding a dimensional parameter (ellipse orientation and ratio) to the light pattern design, which enables better coverage and resolution improvement while maintaining the simplicity of dot light sources
2Area of stationary object
If perpendicular lines of light are used to improve coverage, then the unlit areas are reduced, but pixel saturation occurs at intersections leading to signal output differences
Solution Approach 1:
The patent uses elliptical light patterns with controlled aspect ratios instead of symmetric circular dots or perpendicular lines. By adjusting the ellipse orientation and ratio, the system achieves better area coverage while avoiding the intersection saturation problem that occurs with perpendicular line patterns
Solution Approach 2:
Different regions of the object surface receive differently oriented and shaped light patterns. The system adaptively adjusts the ellipse orientation and ratio based on the local measurement requirements, allowing optimal light distribution without causing pixel saturation at specific locations
3Length of stationary object
If light source output is increased to improve measurable distance, then the measurable distance range is extended, but the light source power consumption increases
Solution Approach 1:
The light source emits light in pulsed intervals rather than continuous emission. The pixel circuits integrate charge during specific time windows corresponding to light pulse arrivals, allowing extended measurable distance through time-gated detection while maintaining low average power consumption
Solution Approach 2:
The pixel circuits perform charge integration during predetermined time windows before the actual light pulse arrives. This preliminary charge accumulation enables the detection of weak return signals from distant objects without requiring high light source power
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 approach enhances resolution by minimizing unlit areas and preventing pixel saturation, thereby improving the accuracy and range of distance measurements while maintaining low light source output.
Implementation Method 1
each of the pixel circuits includes a photoelectric conversion element that generates charge according to incident light
Data Source
AI summary
A range imaging device includes a light source unit that emits light pulses to an object, a light-receiving unit including pixel circuits each including a photoelectric conversion element that generates charge according to incident light and charge storage units that integrates the charge, a pixel drive circuit that distributes the charge to the charge storage units for integration therein, and a charge discharge unit that discharges the charge, and a distance calculation unit that calculates a distance to the object. The light pulses include structured light including patterns of dot light, and at least one first pattern of dot light among the patterns of dot light has an elliptical shape in which a ratio of a major axis length to a minor axis length is a threshold or more.