Event Sensor Autofocus via Pixel Threshold Counting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Event-based sensors face challenges in implementing autofocus due to their output format, which uses +1, -1, and 0 to represent luminance changes, making it difficult to determine the in-focus position using existing contrast evaluation methods, as both positive and negative changes occur frequently, resulting in the same evaluation value regardless of focus achievement.
Innovation Solution
An imaging apparatus with a control unit to manage the focus lens position, an acquisition unit to gather event signals indicating pixel luminance changes and their timing, and a determination unit to calculate an evaluation value for each focus lens position, allowing the system to determine the in-focus position by integrating the number of pixels with luminance changes within a specific time frame and controlling the focus lens accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If event-based sensor output format (+1, -1, 0) is used to represent luminance changes, then real-time luminance change detection is achieved, but contrast evaluation becomes difficult as both positive and negative changes occur frequently resulting in the same evaluation value regardless of focus achievement
Solution Approach 1:
The patent changes the evaluation parameter from simple luminance change values (+1, -1, 0) to the number of pixels exceeding a specific threshold value within a predetermined time period. This parameter transformation allows the system to differentiate between in-focus and out-of-focus states by counting threshold-exceeding pixels, thereby resolving the contradiction between real-time detection speed and focus determination accuracy
Solution Approach 2:
The patent creates a temporal copy of luminance change events by accumulating pixel threshold exceedances over a predetermined time period. Instead of evaluating instantaneous luminance changes, the system copies and counts threshold-exceeding events within a time window, enabling accurate focus determination while maintaining real-time processing capability
2Use of energy by moving object
If aperture value is reduced to increase light reception in low illuminance environment, then more light reaches the sensor, but depth of field is reduced making focusing more critical and difficult
Solution Approach 1:
The patent replaces traditional contrast-based mechanical focus evaluation with an event-based counting mechanism. Instead of relying on contrast metrics that fail in low-light conditions, the system substitutes a threshold-exceeding pixel count approach that remains effective regardless of aperture settings, enabling accurate focus detection even when depth of field is reduced due to low illuminance requirements
Data Source
AI summary
An apparatus includes a control unit configured to control a position of a focus lens of the apparatus, an acquisition unit configured to acquire an event signal indicating a position of a pixel in which a luminance change has occurred and a time when the luminance change has occurred, and a determination unit configured to determine an in-focus position of the focus lens by acquiring, for each position of the focus lens, an evaluation value based on the event signal.