Phase-Detection Pixel Shield Layout for Autofocus Sensitivity
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Solution Overview
Problem
The image-plane phase difference autofocus system in digital cameras faces challenges with reduced sensitivity due to the use of light shield films and walls, which limit the amount of light incident on the image sensor, affecting the accuracy and speed of focus detection.
Innovation Solution
The implementation of a focus detecting device with a microlens, a photoreceptor, and a light shield film with strategically placed light shield walls to control the amount of light and maintain or enhance sensitivity, including configurations where the light shield walls are provided on the surface of the light shield film facing the microlens or photoreceptor to optimize sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a light shield film is used to control light incident on microlenses for phase difference autofocus, then focus detection speed is improved, but sensitivity is degraded due to reduced light amount
Solution Approach 1:
The light shield film is divided into multiple regions with different transparency levels. Specifically, a first light shield film with higher transparency and a second light shield film with lower transparency are arranged in different regions, allowing different portions of light to pass through at different rates. This segmentation enables simultaneous optimization of sensitivity (by allowing more light through in certain regions) and focus detection speed (by controlling light distribution across the sensor array).
Solution Approach 2:
Different regions of the light shield film are assigned different transparency characteristics to serve different functional purposes. The first light shield film region provides higher transparency to maintain sensitivity, while the second light shield film region provides lower transparency to control light distribution for accurate phase difference measurement. This local differentiation of quality allows the system to achieve both high sensitivity and fast focus detection.
2Measurement precision
If light is limited to separate left and right flux for phase difference measurement, then focus detection accuracy is improved, but total light incident on sensor decreases
Solution Approach 1:
The light shield film is segmented into multiple transparency regions that strategically direct light flux. The first light shield film with higher transparency allows more total light to reach the sensor while still maintaining the separation of left and right flux patterns needed for phase difference measurement. The second light shield film with lower transparency provides additional control over light distribution, ensuring that sufficient light reaches both left and right sensor regions for accurate focus detection.
Solution Approach 2:
The transparency parameter of the light shield film is varied across different regions. By changing the transparency parameter from the first light shield film (higher transparency) to the second light shield film (lower transparency), the system optimizes the balance between total light quantity and light flux separation. This parameter variation allows more light to reach the sensor while maintaining the spatial distribution needed for accurate phase difference autofocus.
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 configuration allows for improved sensitivity and focus detection accuracy by adjusting the light shield film's cover area and wall height to maintain maximum and minimum sensitivity values, enabling high-speed autofocus without compromising image quality.
Implementation Method 1
a microlens; a photoreceptor configured to receive light entering through the microlens
Implementation Method 2
a light shield film provided between the microlens and the photoreceptor and configured to limit an amount of light on the photoreceptor
Data Source
AI summary
The present technology relates to a focus detecting device and an electronic device that can adjust the maximum value and the minimum value of sensitivity in phase detection pixels. The focus detecting device and an electronic device each include a microlens, a photoreceptor configured to receive light entering through the microlens, a light shield film provided between the microlens and the photoreceptor and configured to limit an amount of light on the photoreceptor, and a light shield wall provided vertical to the light shield film. The light shield wall or the light shield walls having a predetermined height are provided on any one or both of surfaces of the light shield film facing the photoreceptor and the microlens. The present technology can be applied to an imaging device configured to detect a focus by detection of phase difference.