Phase Detect Autofocus Module Using Dedicated Sensor Segmentation
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Solution Overview
Problem
Existing imaging systems with semiconductor image sensors face challenges in autofocus speed and image quality due to mechanisms that require long times to find the appropriate focal distance or devote pixels for phase detection, leading to user perceptible latency and reduced image quality.
Innovation Solution
A phase detection (PD) module with a dedicated PD image sensor and controller determines focus parameters to control the image capture module's lens assembly, allowing for fast and accurate autofocus without dedicating primary image sensor pixels to phase detection, enabling quick focus adjustment and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sweep through a range of focal lengths is used to find the appropriate focal length, then the focus accuracy is improved, but the autofocus time increases significantly
Solution Approach 1:
The patent divides the image sensor pixels into two distinct groups: phase detection pixels arranged in a specific pattern for measuring focus accuracy, and imaging pixels for capturing the actual image. This segmentation allows the phase detection pixels to quickly determine focus offset without requiring a time-consuming sweep through multiple focal lengths, thereby resolving the contradiction between focus accuracy and autofocus time.
2Speed
If some pixels of the image sensor are devoted to phase detection, then the autofocus speed is improved, but the image quality deteriorates
Solution Approach 1:
The patent segments the image sensor into dedicated phase detection pixels and imaging pixels. The phase detection pixels are arranged in a specific pattern (e.g., alternating rows or columns) and are used solely for measuring focus offset. The imaging pixels capture the actual image. This segmentation allows fast autofocus while maintaining image quality because the imaging pixels are not compromised for phase detection functions.
Solution Approach 2:
The patent extracts the phase detection function from the imaging pixels by dedicating specific pixels solely to phase detection. This extraction allows the imaging pixels to focus entirely on capturing high-quality images without the interference or degradation that would result from using the same pixels for both imaging and phase detection purposes.
3Measurement precision
If a dedicated PD module is added for phase detection, then the autofocus accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent merges the phase detection module with the image sensor by integrating phase detection pixels directly into the sensor array. This integration allows the phase detection function to be performed using the same sensor hardware that captures images, eliminating the need for a completely separate dedicated PD module and reducing overall system complexity while maintaining autofocus accuracy.
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
The solution enables rapid and accurate autofocus, enhancing user experience by avoiding the need for time-consuming focal length sweeps and reducing image processing overhead, while maintaining high image quality with a separate PD module optimizing autofocus and image capture processes.
Implementation Method 1
perform phase detection (PD) on a PD image signal
Implementation Method 2
determine a focus point of the object to be focused in the PD image
Data Source
AI summary
An phase detect (PD) module including a phase detect (PD) lens, PD image sensor, and a PD controller is disclosed. The PD module may be configured to provide a control signal to an electromechanical device, such as a voice coil motor (VCM), of an image capture module to move a lens assembly to focus an image of an object to be imaged onto a primary image sensor. The PD module may direct the capture of a PD image by the PD image sensor and perform a phase detect (PD) technique on the captured AF image to identify a focus point of the lens assembly. This determined focus point may be used to displace the lens assembly relative to the primary image sensor to achieve focus of the object onto the primary image sensor.