Range Image Sensor Timing Shift to Curb Peak Current Ringing
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Solution Overview
Problem
In range image sensors, the simultaneous driving of light receiving circuits leads to a large peak current when starting the drive signal, causing ringing in the source voltage and inaccurate charge reading due to fluctuations, especially as the number of pixels increases.
Innovation Solution
A range image sensor with pixel circuits arranged in a two-dimensional grid, where the storage drive signal is shifted by a predetermined adjustment time between pixel circuits, using a charge storage portion with multiple storage areas to distribute electric charge based on different light quantities, and a timing adjustment circuit to synchronize clock signals for accurate distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a drive signal is simultaneously supplied to all light receiving circuits to enable synchronized charge reading, then measurement accuracy is improved, but a large peak current flows causing ringing in source voltage
Solution Approach 1:
The patent divides the simultaneous driving of all light receiving circuits into sequential phases. The pixel drive circuit supplies drive signals to different pixel circuits at different timings, segmenting the peak current generation across time. This is achieved by sequentially selecting and driving pixel circuits in groups or individually, preventing the simultaneous activation that causes large peak currents and ringing in the source voltage.
2Measurement precision
If the number of pixels is increased to enhance image resolution, then measurement precision is improved, but peak current increases causing inaccurate charge reading
Solution Approach 1:
The patent segments the control of multiple pixel circuits by introducing timing shifts in the drive signals. The pixel drive circuit supplies drive signals to pixel circuits at different timings rather than simultaneously, which distributes the current demand across time. This allows a larger number of pixel circuits to be operated without generating excessive peak currents that would cause ringing and measurement errors.
3Object-generated harmful factors
If drive signal timing is shifted between pixel circuits to curb peak current, then harmful factors are reduced, but charge reading accuracy may be affected
Solution Approach 1:
The patent implements preliminary timing adjustment in the pixel drive circuit before charge reading occurs. The circuit is designed to supply drive signals with optimized timing shifts that preemptively prevent peak current generation while maintaining proper synchronization for accurate charge transfer. The timing relationships are pre-configured to ensure that charge reading accuracy is preserved even with the shifted drive signal timings.
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 curbs peak current flow and allows for accurate reading of electric charge from light receiving circuits, enabling precise distance measurement between the sensor and subject even with increased pixel numbers.
Implementation Method 1
each pixel circuit including a photoelectric conversion element that receives reflected light which is emitted by a subject in a measuring space which is a space to be measured reflecting optical pulses with the same pulse width which are applied to the measuring space from a predetermined light source at intervals of a predetermined cycle and generates electric charge corresponding to the received reflected light
Data Source
AI summary
One aspect of the present invention is a range image sensor wherein a pixel drive circuit supplies a storage drive signal which is shifted by a predetermined adjustment time between pixel circuits and stores an electric charge from a photoelectric conversion element in a charge storage portion in each pixel circuit.