Dual Pixel Autofocus Infrared Filter Design
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Solution Overview
Problem
Existing autofocus systems are inefficient under low-light conditions, requiring additional light sources and multiple components, and are limited to specific points on the image, making them unsuitable for compact and reliable performance across the entire image.
Innovation Solution
A compact autofocus system utilizing dual pixel sensors sensitive to both visible and infrared light, with an infrared light source and filter, allowing for phase contrast autofocusing across the entire image without continuous pre-flash, reducing component count and enhancing reliability in low-light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an infrared autofocus system is used to avoid long or continuous pre-flash light, then the harmful effect of unwanted pre-flash is reduced, but the system requires an additional sensor and works only at selected points rather than over the complete image
Solution Approach 1:
The image sensor is designed to perform dual functions: capturing visible light images and detecting infrared light for autofocus. The sensor array can operate in different modes (visible light imaging, infrared autofocus, or combined) without requiring separate dedicated sensors, thereby reducing component count while maintaining autofocus functionality across the complete image
Solution Approach 2:
An infrared filter is introduced as an intermediary component in the light path between the aperture and image sensor. This filter selectively transmits infrared light to the sensor while blocking visible light during autofocus operations, enabling the sensor to detect infrared phase differences without being overwhelmed by visible light, thus achieving full-image autofocus without additional sensors
2Device complexity
If a compact autofocus system with reduced components is implemented, then the device complexity is reduced, but the reliability of autofocus function under low light conditions may be compromised
Solution Approach 1:
The system changes the operational parameter from visible light to infrared light for autofocus operations. By detecting infrared light emitted or reflected from the scene, the system can perform phase contrast autofocus reliably even in low visible light conditions, as infrared detection is not limited by visible light availability
Solution Approach 2:
The single image sensor is designed to handle both visible light imaging and infrared autofocus detection. The sensor array can switch between or combine these functions, ensuring reliable autofocus performance across varying light conditions without requiring separate dedicated infrared sensors or additional components
3Manufacturing precision
If the image sensor records image data as a sum signal from both pixel sensors, then the image quality is maintained, but the autofocus system cannot obtain individual infrared signals from each pixel sensor for phase contrast autofocusing
Solution Approach 1:
The sensor array is segmented into multiple dual-pixel units, where each unit contains two separate pixel sensors (first and second pixel sensors). This segmentation allows the system to separately capture infrared light at different phases while maintaining the ability to combine signals for visible light imaging, enabling both high-quality imaging and precise autofocus
Solution Approach 2:
Different regions or configurations of the sensor array are optimized for different functions. The first and second pixel sensors of each dual-pixel unit are positioned to capture infrared light from slightly different angles or phases, creating local variations in signal characteristics that enable phase contrast autofocus while the combined output maintains overall image quality
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 system provides reliable autofocus functionality across the entire image even in low-light conditions, reducing the number of components and eliminating the need for continuous pre-flash, while maintaining accurate focus and color reproduction.
Implementation Method 1
an infrared filter arranged in the light path between the aperture and the imaging sensor and adapted to locally transmit only a portion of the infrared light or less along the light path to the imaging sensor
Implementation Method 2
providing infrared data as individual signals from each of the two pixel sensors to the autofocus system for phase contrast autofocusing
Data Source
AI summary
The invention describes an imaging device (1) comprising an image sensor (2), an imaging lens (3), an infrared light source (5) to illuminate a scene (SC), and an infrared autofocus system (6) for providing an autofocus function, wherein the image sensor (2) comprises an array (21) of sensor pixels each arranged as dual pixel (22) comprising two separate pixel sensors (22a, 22b) per dual pixel (22) to record the image data (D1) as a sum signal from both pixel sensors (22a, 22b) and providing infrared data (D2) as individual signals from each of the two pixel sensors (22a, 22b) for phase contrast (PC) autofocusing, wherein an infrared filter (7) arranged between an aperture (4) of the imaging device (1) and an imaging sensor (2) and is adapted to locally transmit only a portion of the infrared light (IR) to the imaging sensor (2) by comprising at least one first area (71) arranged as infrared blocking area and at least one second area (72) arranged as infrared bandpass area. The invention further relates to a method (100) to automatically focusing this device (1).