Autofocus Driver Calibration Using Comparator and Replica Circuits
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Solution Overview
Problem
Autofocus systems in electronic devices face challenges due to offset voltage in operational amplifiers, leading to variations in the output current produced by drivers, which affect image quality.
Innovation Solution
The implementation of a current comparator circuit and a replica circuit that work together to monitor the drive current, provide feedback, and adjust it to minimize offset, ensuring accuracy and alignment with ideal current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If operational amplifiers are used in autofocus systems, then signal propagation is facilitated, but offset voltage causes output current to differ from ideal current
Solution Approach 1:
The patent implements a feedback mechanism where the actual output current of the operational amplifier is measured and compared with the ideal current. The difference (offset) is detected and used to generate a correction signal that adjusts the operational amplifier's output, thereby compensating for the offset voltage and improving current accuracy.
Solution Approach 2:
The patent replaces the purely electrical offset voltage problem with an optical measurement system. By using photodetectors to convert current into light signals and then back to measurable electrical signals, the system achieves more precise current measurement and offset compensation than direct electrical measurement alone.
2Manufacturing precision
If driver output current is increased to improve autofocus performance, then lens positioning accuracy improves, but offset voltage variation increases
Solution Approach 1:
The patent employs continuous feedback monitoring of the driver output current. The measured current is compared with the expected ideal current, and any deviation due to offset voltage is compensated by adjusting the drive signal, ensuring consistent and reliable current output across different operating conditions.
Solution Approach 2:
The patent dynamically adjusts operational parameters (such as bias voltages or compensation currents) based on the detected offset voltage. By changing these parameters in real-time, the system maintains current consistency and reliability even when operating at different current levels for various lens positioning requirements.
Data Source
AI summary
Driver circuits, systems for driving actuators, and imaging systems with actuators. The driver circuit includes a current comparator circuit, a driver, and a replica circuit. The current comparator circuit includes a first node having a first voltage. The current comparator circuit also includes a second node having a second voltage. The driver includes a first terminal responsive to the second voltage. The driver also includes a second terminal connected to a reference voltage. The replica circuit includes a third terminal connected to the first node. The replica circuit also includes a fourth terminal connected to the second terminal of the driver. The replica circuit also includes a fifth terminal connected to the first terminal of the driver.