Time-of-Flight Sensor Reducing A/D Converter Cost via Signal Mixing
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Solution Overview
Problem
Conventional time-of-flight (TOF) sensors require expensive hardware, particularly a large number of analog-to-digital (A/D) converters, which increases manufacturing costs despite the use of compressive sensing methods to reduce sampling rates.
Innovation Solution
A TOF sensor architecture that combines time and spatial modulation of optical signals, allowing for a reduced number of A/D converters by modulating signals electronically before sampling, enabling reconstruction of a scene with a single A/D converter while preserving spatial and time modulation information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If compressive sensing methods are used to reduce sampling rate, then the acquisition rate is reduced, but the manufacturing cost remains high due to the need for multiple expensive A/D converters
Solution Approach 1:
The patent merges multiple A/D converters into a single A/D converter by combining the outputs of multiple optical converters into one mixed signal. This consolidation maintains the benefits of compressive sensing (reduced acquisition rate) while eliminating the need for multiple expensive A/D converters, thereby reducing manufacturing cost.
Solution Approach 2:
The patent introduces a signal mixing mechanism as an intermediary between the optical converters and the single A/D converter. This intermediary combines multiple analog signals into one mixed signal that preserves the spatial and temporal modulation information needed for compressive sensing reconstruction, enabling the use of a single inexpensive A/D converter.
2Ease of manufacture
If the number of A/D converters is reduced, then the manufacturing cost is reduced, but the ability to preserve spatial and time modulation information is compromised
Solution Approach 1:
The patent applies preliminary modulation to the optical signal before it reaches the optical converters. By encoding spatial and temporal modulation information into the optical signal in advance, the system ensures that this information is preserved in the mixed signal even when multiple optical converters feed into a single A/D converter, preventing information loss.
Solution Approach 2:
The patent changes the temporal parameters of the optical signal by modulating it at different frequencies or phases before detection. This parameter modulation allows the system to encode multiple pieces of information (spatial and temporal) into a single mixed signal that can be processed by one A/D converter without losing critical modulation information.
3Ease of manufacture
If a single A/D converter is used to sample mixed signals, then the manufacturing cost is minimized, but the sampling rate must be increased to preserve time modulation
Solution Approach 1:
The patent uses periodic modulation of the optical signal at known frequencies before detection. By modulating the signal periodically, the system creates distinct frequency components that can be separated through correlation or Fourier analysis after sampling. This allows a single A/D converter sampling at a lower rate to capture the necessary information, as the periodic structure enables signal separation without requiring ultra-high sampling rates.
Solution Approach 2:
The patent replaces the need for high-speed mechanical or electronic switching between multiple A/D converters with a signal processing approach. Instead of physically routing different signals to different converters at high speed, the system uses mathematical operations (correlation, filtering) to separate the mixed signals after they are combined, substituting complex high-speed hardware with simpler, lower-speed hardware plus computational processing.
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 reduces the manufacturing cost of TOF sensors by minimizing the number of A/D converters required while maintaining the ability to generate data samples suitable for scene reconstruction, such as three-dimensional depth maps, through effective compressive sensing methods.
Implementation Method 1
a set of optical converters, each optical converter, in response to transmitting an optical pulse modulated in time to a scene, is configured to convert a reflection of the optical pulse from an object in the scene into an analog signal indicative of a time-of-flight of the optical pulse to the object
Data Source
AI summary
A time-of-flight (TOF) sensor includes a set of optical converters; each optical converter is configured to convert a reflection of the optical pulse from an object in the scene into an analog signal indicative of a time-of-flight of the optical pulse to the object. To that end, the set of optical converters produces a set of analog signals. The TOF sensor also includes at least one modulator to uniquely modulate each analog signal from the set of analog signals to produce a set of modulated signals, a mixer to mix the modulated signals to produce a mixed signal, and an analog to digital converter to sample the mixed signal to produce a set of data samples indicative of the TOF to the scene.