Optical Demodulation Using Diffractive Phase Elements
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Solution Overview
Problem
Conventional phase-based time-of-flight (ToF) sensors in machine vision have lower resolution due to the circuitry required for demodulating reflected signals to determine phase differences, limiting their effectiveness in depth sensing applications.
Innovation Solution
The use of a matrix of variable-phase optical elements, such as diffractive optical elements, to introduce phase delays into light signals, allowing for optical demodulation and increasing the area dedicated to photosensing while reducing circuitry, enabling improved resolution and depth sensing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circuitry is used for demodulating reflected signals to determine phase difference, then depth sensing capability is achieved, but resolution is reduced and sensor area is consumed by circuitry
Solution Approach 1:
The patent replaces electronic circuitry with optical elements (diffractive optical elements) to perform the demodulation function. The DOE introduces phase delays directly in the optical domain, substituting the need for complex electronic demodulation circuits and enabling higher resolution depth sensing.
Solution Approach 2:
The patent introduces diffractive optical elements as an intermediary between the lens and the optical sensor. These DOE elements mediate the light signal by introducing controlled phase delays, enabling optical demodulation without requiring extensive circuitry on the sensor.
2Area of stationary object
If circuitry is used for demodulation, then phase difference determination is possible, but sensor area available for photosensing is reduced
Solution Approach 1:
The patent replaces electronic demodulation circuitry with optical phase modulation using diffractive optical elements. This substitution eliminates the need for complex per-pixel circuitry, thereby increasing the area available for photosensing while maintaining depth sensing capability.
3Measurement precision
If optical demodulation is implemented, then resolution and photosensing area are improved, but device structure becomes more complex
Solution Approach 1:
The patent segments the optical path by inserting diffractive optical elements at specific positions between the lens and sensor. This segmentation allows independent optimization of the imaging optics and the depth sensing function, achieving high resolution without proportionally increasing overall device complexity.
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 the resolution of ToF sensors by partially demodulating signals in the optical domain, allowing for higher precision in depth measurement and increased angular resolution, while also reducing the need for extensive circuitry, thus enabling more efficient and accurate depth sensing.
Implementation Method 1
The matrix of variable-phase optical elements may include a diffractive optical element that directs a portion of the light signal having a first phase delay
Data Source
AI summary
An exemplary imaging device includes an optical sensor having an optical axis, a lens positioned to focus light from a scene onto the optical sensor, a matrix of variable-phase optical elements that are dimensioned to introduce at least two different phase delays into a wavefront of a light signal received from the scene through the lens, a housing that secures the matrix of variable-phase optical elements between the optical sensor and the lens, and a processing subsystem programmed to determine a phase difference associated with the light signal based on the at least two different phase delays. Related systems and methods are also provided.