Camera Module Actuator Drive Signal Timing for Noise Reduction
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Solution Overview
Problem
Camera modules using alternating-current drive systems face challenges in maintaining high image quality while reducing power consumption, as existing techniques often result in image degradation.
Innovation Solution
A camera module configuration that includes an imaging unit, a lens unit with an actuator, and a driver unit, where the driver unit generates a drive signal that transitions during specific terms to enhance image quality and reduce power consumption by correlating double sampling and adjusting the duty ratio and timing of the drive signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an alternating-current drive system is used to drive the actuator, then power consumption is reduced, but image quality degrades due to noise from actuator operation
Solution Approach 1:
The patent applies preliminary action by performing reset signal generation and correlated double sampling before the actuator operates during the exposure period. The reset signal is generated in advance during the first period, and the imaging unit captures reference data before actuator activation, allowing noise from alternating-current drive to be subtracted from the final image signal, thereby maintaining image quality while enabling power-efficient actuator operation.
Solution Approach 2:
The patent introduces an intermediary mechanism through the reset signal and correlated double sampling process. This intermediary approach captures a reference signal that includes the actuator noise, then subtracts this reference from the actual image signal, effectively mediating between the power-saving alternating-current drive and the quality requirements of the imaging sensor.
2Speed
If the drive signal transitions during the exposure period, then the actuator can respond quickly to focusing requirements, but noise is introduced into the captured image
Solution Approach 1:
The patent performs preliminary action by capturing a reference signal before the actuator transitions during exposure. The imaging unit records data during a first period when the drive signal is stable, then uses this reference to subtract noise from subsequent measurements taken during actuator operation, enabling fast response without degrading image quality.
Solution Approach 2:
The patent implements feedback through correlated double sampling, where the reference signal captured before actuator operation is continuously subtracted from the image signal during exposure. This feedback mechanism dynamically removes noise introduced by drive signal transitions, allowing the actuator to respond quickly to focusing requirements while maintaining image quality.
3Measurement precision
If correlated double sampling is performed with multiple terms, then noise components can be reduced, but the complexity of the driver unit increases
Solution Approach 1:
The patent applies periodic action by structuring the correlated double sampling process around repeating cycles of four distinct terms: reset signal generation, first image signal capture, second reset signal generation, and second image signal capture. This periodic structure enables systematic noise reduction through consistent reference subtraction while maintaining manageable driver unit complexity through pattern repetition.
Data Source
AI summary
A camera module of the disclosure includes: an imaging unit that includes a plurality of pixels, acquires a first detection value in one of the pixels in a second term out of a first term, the second term, a third term, and a fourth term that are set in order, acquires a second detection value in the relevant one of the pixels in the fourth term, and obtains a pixel value of the relevant one of the pixels on the basis of a difference between the first and second detection values; a lens unit including a lens and an actuator that drives the lens; and a driver unit that generates a drive signal and drives the actuator using the drive signal, in which the drive signal makes a transition in each of the first and third terms.