PMD Sensor Shift Register Matrix for Distance Measurement
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Solution Overview
Problem
Time-of-flight light sensors for triangulation systems have complex structures that complicate the measurement of object distances, particularly due to the need for precise wiring and handling of multiple pixel columns, which increases parasitic capacitance and leakage currents, affecting performance.
Innovation Solution
The solution involves using a common shift register to drive pixels in sensor columns, switching diode nodes to column lines or a discard/reset potential, and combining groups of pixels to reduce wiring effort and parasitic effects, with a switch matrix routing charges to differential amplifiers for signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple pixel columns are precisely wired and handled in time-of-flight sensors for triangulation systems, then measurement precision is improved, but device complexity increases due to complex wiring structures
Solution Approach 1:
Multiple pixel columns are combined and connected to a common readout circuit. The patent integrates several pixel columns that detect light from different distance ranges into a single readout path, reducing the number of separate wiring connections while maintaining the ability to distinguish signals from different columns through temporal or spatial multiplexing techniques.
Solution Approach 2:
A single readout circuit is designed to handle multiple pixel columns universally. The common readout circuit can process signals from any of the multiple pixel columns, making it a multi-functional component that replaces what would otherwise require multiple dedicated readout circuits, thereby simplifying the overall wiring structure.
2Measurement precision
If multiple pixel columns are precisely wired and handled in time-of-flight sensors, then measurement precision is improved, but parasitic capacitance and leakage currents increase
Solution Approach 1:
By merging multiple pixel columns into a common readout circuit, the total number of separate wiring connections is reduced. This consolidation decreases the cumulative parasitic capacitance and leakage currents that would arise from numerous individual connections, while the common readout circuit is designed to maintain signal integrity through careful impedance matching and shielding.
Solution Approach 2:
The harmful parasitic effects are extracted and managed at the common readout circuit level rather than being distributed across multiple individual connections. The common readout circuit incorporates compensation techniques that isolate and counteract the parasitic capacitance and leakage currents, preventing them from degrading measurement precision.
3Device complexity
If wiring complexity is reduced by combining pixel columns, then device complexity is reduced, but signal processing difficulty increases
Solution Approach 1:
Pixel columns are pre-assigned to specific distance ranges and the common readout circuit is pre-configured with timing and gain settings optimized for each column's expected signal characteristics. This preliminary configuration reduces the complexity of real-time signal processing by establishing known parameters for each pixel column before measurement begins.
Solution Approach 2:
The common readout circuit incorporates dynamic adjustment capabilities that automatically adapt its parameters based on which pixel column is currently active or which distance range is being measured. This dynamic behavior simplifies signal processing by optimizing the readout circuit's response characteristics for the specific measurement conditions without requiring complex manual configuration.
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 simplifies the sensor structure, reduces wiring complexity, and enhances signal-to-noise ratio by discarding unlit pixels and optimizing pixel dimensions for each distance range, thereby improving measurement accuracy and reducing interference from background light and noise.
Implementation Method 1
obtain time-of-flight information or distances from the phase shift of emitted and received radiation
Implementation Method 2
obtain time-of-flight information or distances from the phase shift of emitted and received radiation
Implementation Method 3
PMD cameras with photonic mixing detectors (PMD)
Implementation Method 4
a switch matrix routing charges to differential amplifiers for signal processing
Data Source
AI summary
The invention relates to a PMD light transit time sensor (22) for an optical distance measurement system, comprising an array of PMD light transit time pixels (21), said light transit time pixels having diode nodes (Ga, Gb) for an A channel and a B channel (A, B) and being connectable to a corresponding column line (cola, colb) via a first switch (S1) and to a reset potential (vreset) via a second switch (S2). The PMD light transit time sensor comprises multiple shift registers, which are constructed and connected to the pixels such that the two switches (S1, S2) can be switched in an alternating manner on the basis of register entries of the individual registers (FF), wherein multiple columns or rows are at least partly assigned to a shift register; and a switch matrix (80), which is designed such that the column lines (cola, colb) can be connected to one of a plurality of amplifiers (100) and multiple column lines (cola, colb) can be connected to a common amplifier (100). The light transit time sensor (22) is designed such that during an integration time period, the charges photogenerated on the light transit time pixel are accumulated on the diode nodes (diode a, diode b) and the connected column lines (cola, colb).