ToF Camera Signal Timing Circuit for Switchable Modulation Frequency
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Solution Overview
Problem
In distance image sensors of indirect ToF type, the modulation frequency and distance measurement error have an inverse proportional relationship, making it challenging to increase measurement accuracy without reducing the distance measurement range.
Innovation Solution
A signal generation apparatus for ToF camera systems that adopts the indirect system, capable of handling various modulation frequencies with a simple configuration, utilizing a pulse generator with programmable counters and a D-type flip-flop to adjust phase and division settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the modulation frequency is increased to improve distance measurement accuracy, then the measurement precision is improved, but the distance measurement range becomes narrower
Solution Approach 1:
The patent applies dynamics by making the modulation frequency adjustable rather than fixed. The signal generation apparatus can dynamically change the modulation frequency based on the required measurement range, allowing the system to adapt between high-frequency operation for accurate short-range measurement and low-frequency operation for extended range measurement.
Solution Approach 2:
The patent implements parameter changes by varying the modulation frequency as a controllable parameter. The system can switch between different frequency parameters (e.g., 10MHz for short range high accuracy, 20MHz for extended range) depending on the measurement requirements, thus resolving the contradiction between accuracy and range.
2Device complexity
If a fixed modulation frequency is used to simplify the system configuration, then the device complexity is reduced, but the adaptability to different measurement ranges is limited
Solution Approach 1:
The signal generation apparatus is designed with multi-functionality to generate multiple modulation frequencies using a unified circuit structure. The same apparatus can operate at different frequencies (10MHz, 20MHz, or other values) by adjusting the division ratio of the counter, eliminating the need for separate frequency generation circuits and achieving versatility without proportionally increasing complexity.
Solution Approach 2:
The system incorporates dynamic configurability through a programmable counter that can be set to different division ratios. This allows the modulation frequency to be dynamically adjusted based on application requirements while maintaining a single, relatively simple hardware configuration that serves multiple frequency needs.
Data Source
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AI summary
To provide a signal generation apparatus for use with a ToF camera system that especially adopts the indirect system, which can be ready for various modulation frequencies with a simple configuration. A signal generation apparatus is provided which includes a first pulse generator configured to generate a pulse to be supplied to a light source that irradiates light to a distance measurement target, a second pulse generator configured to generate a pulse to be supplied to pixels that receive light reflected by the distance measurement target, and a switching section configured to switch a setting of a modulation frequency of the first pulse generator and the second pulse generator within a predetermined period.