Time-of-flight sensor distance calculation using pulse ratio method
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Solution Overview
Problem
Time-of-flight (TOF) image sensors face limitations in distance determination, requiring ambient light correction and being incompatible with pixel binning, which restricts their range and efficiency in depth sensing applications.
Innovation Solution
A time-of-flight camera system that generates an emitted light wave and determines distance based on the ratio of specific differences between response signals, eliminating the need for ambient light correction and allowing compatibility with pixel binning, using a two-four pulse ratio method for accurate distance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TOF distance determination methods are used, then distance can be measured, but ambient light correction is required which complicates the system and reduces measurement accuracy
Solution Approach 1:
The patent extracts and eliminates the ambient light correction step from the TOF distance determination process. By using a ratio-based calculation method that compares response signals at different phases, the system directly calculates distance without needing to separately measure and subtract ambient light contributions, thereby simplifying the system while maintaining or improving measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from absolute response signal values (which require ambient light correction) to a ratio of response signal differences at different phases. This parameter transformation inherently eliminates ambient light effects, as the ratio method compares relative signal changes rather than absolute values, thus improving accuracy without adding complexity.
2Adaptability or versatility
If traditional TOF methods are used, then distance determination is possible, but compatibility with pixel binning operations is lost
Solution Approach 1:
The patent creates a universal distance determination method that works with both individual pixel measurements and binned pixel measurements. The ratio-based calculation approach is inherently compatible with averaging operations used in pixel binning, allowing the same algorithm to reliably determine distance whether applied to single pixels or groups of binned pixels, thus achieving multi-functionality without sacrificing reliability.
3Measurement precision
If ambient light correction is implemented in TOF systems, then measurement accuracy may be maintained, but the maximum detection range is reduced
Solution Approach 1:
The patent transforms the measurement approach from using absolute response signal levels (which are sensitive to ambient light and limit range) to using ratios of signal differences at different phases. This parameter change enables accurate distance measurement at longer ranges because the ratio method is insensitive to overall signal amplitude variations caused by distance attenuation, thereby extending maximum detection range while maintaining precision.
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 enables accurate distance determination without ambient light correction and maintains compatibility with pixel binning, achieving a maximum range comparable to continuous wave methods while being commutative with binning operations, thus enhancing depth sensing capabilities.
Implementation Method 1
a light generator configured to generate an emitted light wave; a light sensor configured to receive a reflected light wave, the reflected light wave corresponding to the emitted light wave reflected from an object
Data Source
AI summary
A time-of-flight camera includes a light generator that generates an emitted light wave, a light sensor that receives a reflected light wave that corresponds to the emitted light wave reflected from an object, and distance determination circuitry. The distance determination circuitry determines response signals based on the reflected light wave, calculates signs corresponding to differences between pairs of the response signals, determines a phase region based on the signs, and determines a distance between the time-of-flight camera and the object based on a ratio of the differences.