Pixel Array Autofocus Design Without Light Shield
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Solution Overview
Problem
Existing autofocus systems in digital cameras, particularly those without a mirror or prism, face challenges in achieving fast and accurate focus due to the limitations of contrast-based autofocus and the inability to use secondary phase detect autofocus sensors in live view or video modes, leading to slower focusing times.
Innovation Solution
A pixel array design that eliminates the need for a light shield over phase detect autofocus pixels, allowing for improved selectivity in light angle and reduced internal reflections, enabling faster and more accurate focus detection without the need for additional manufacturing steps or complex spacing adjustments, and allowing these pixels to function for both focusing and normal image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light shield is used to create an exit pupil for phase detect autofocus pixels, then focus detection accuracy is improved, but manufacturing complexity increases and light reception is reduced
Solution Approach 1:
The patent removes the light shield component from the pixel structure, extracting the problematic element that caused manufacturing complexity. Instead of adding a light shield to create an exit pupil, the invention uses the natural optical properties of the microlens and photodiode structure to achieve phase detect autofocus functionality without requiring additional shielding components.
Solution Approach 2:
The patent makes the pixels universal by enabling them to perform both normal imaging and phase detect autofocus functions without requiring separate dedicated pixels or additional components like light shields. The same pixel structure serves multiple purposes, eliminating the need for specialized autofocus pixels with complex light shield arrangements.
2Measurement precision
If a light shield is positioned at specific distances from the photodiode and microlens, then phase detect autofocus performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent extracts and removes the light shield component that required precise spacing control. By eliminating this component, the invention removes the manufacturing precision constraints associated with positioning the light shield at specific distances from the photodiode and microlens.
Solution Approach 2:
The patent changes the optical parameters by removing the light shield, thereby altering the optical path and exit pupil formation mechanism. This parameter change eliminates the need for precise spacing control of the light shield, as the optical functionality is achieved through the inherent properties of the microlens-photodiode structure.
3Measurement precision
If a light shield is used to block certain light paths, then focus direction detection is improved, but light reception and low-light performance deteriorate
Solution Approach 1:
The patent converts the potential harm of light loss into a benefit by using the natural angular selectivity of the microlens-photodiode structure instead of blocking light with a shield. The system achieves focus direction detection by measuring light from different angles that naturally reach the pixel, turning the limitation of no light shielding into an advantage for maintaining light reception.
Solution Approach 2:
The patent enables pixels to universally perform both imaging and phase detect autofocus functions without light shields, allowing the same pixel structure to maintain full light reception capability while still providing focus direction detection through angularly selective light collection.
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
This design simplifies the manufacturing process, enhances focus accuracy and speed, and improves performance in low-light conditions by allowing phase detect autofocus pixels to receive a similar amount of light as standard pixels, eliminating the need for interpolation and enabling differential autofocus signals from pairs of pixels.
Implementation Method 1
Each pixel may include a microlens positioned above the photo-sensitive element
Implementation Method 2
A second photo-sensitive element and a third photo-sensitive element may be provided in the pixel and arranged side by side... Each photo-sensitive element may be arranged to receive light rays over an angular range
Data Source
AI summary
A pixel array for imaging comprises an array of pixels of a first pixel type (50) and a second pixel type (60, 70; 80). Each pixel of the first pixel type (50) comprises a first photo-sensitive element (51) having a first area. Each pixel of the second pixel type (60, 70; 70) comprises a second photo-sensitive element (61, 71; 81) and a third photo-sensitive element (62, 72; 82). The second photo-sensitive element (61, 71; 81) has a second area, which is smaller than the first area. Only the second photo-sensitive element in the pixel of the second pixel type is connected to a readout circuit. The third photo-sensitive element is connected to a charge drain via a permanent connection or a switchable connection. Outputs of the second photo-sensitive elements (61, 71; 81) can be used to perform phase detect autofocussing.