Autofocus Control via Time-of-Flight Distance Measurement
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Solution Overview
Problem
Conventional imaging devices, such as smartphones, face difficulties in autofocus, especially on blank colored surfaces and in low-light environments, due to the iterative and resource-intensive nature of contrast AF, and the limited illumination area of active AF, which restricts accurate focus across the entire scene.
Innovation Solution
The implementation of a time-of-flight technique that actively illuminates the scene, allowing for the determination of distances to all objects within a range, enabling the display of distance values for each region of the image, and automatic adjustment of the optical assembly for optimal focus based on user selection, using a modulated or pulsed optical radiation and a receiver to generate output signals for distance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast AF is used for autofocus control, then the device can focus on subjects with sufficient contrast, but it becomes time-consuming and computationally intensive
Solution Approach 1:
The patent replaces the iterative contrast-based autofocus mechanism with a direct time-of-flight distance measurement system. Instead of repeatedly adjusting the lens and evaluating image contrast, the system uses optical radiation to directly measure distance to the subject, then positions the lens accordingly in a single step, dramatically reducing autofocus time while maintaining accuracy.
Solution Approach 2:
The patent introduces a time-of-flight measurement system as an intermediary between the user's focus selection and the actual focusing action. This intermediary provides direct distance information about the selected subject, eliminating the need for iterative contrast evaluation and enabling rapid, accurate autofocus control.
2Illumination intensity
If active AF with limited illumination is used, then distance measurement works in low-light environments, but only a limited area in the scene has known distance information
Solution Approach 1:
The patent makes the distance measurement system universal by allowing the user to select any region in the captured image for distance measurement. Instead of being limited to a predetermined illuminated area, the system can measure distance to any subject within the image frame, providing versatile autofocus control across the entire scene while maintaining low-light capability.
3Measurement precision
If repeated distance measurements are taken for different areas, then accurate focus can be achieved for each area, but the process becomes time-consuming
Solution Approach 1:
The patent performs preliminary distance measurement for the entire scene or selectable regions before the user makes their focus selection. By having distance information readily available for multiple areas in advance, the system can immediately adjust focus when the user selects a subject, eliminating the need for repeated measurements and significantly speeding up the autofocus process while maintaining measurement 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
This approach enables rapid and efficient autofocus across the entire scene, reducing computational resources and time, allowing for accurate focus on selected regions without the need for repeated distance measurements, even in low-light conditions.
Implementation Method 1
calculating the respective distance value for each of the regions of the displayed first image based on an optical time-of-flight technique. The method includes emitting modulated or pulsed optical radiation signals toward the scene, sensing, by a time-of-flight receiver, signals of the modulated or pulsed optical radiation reflected by one or more objects in the scene
Data Source
AI summary
The present disclosure describes imaging techniques and devices having improved autofocus capabilities. The imaging techniques can include actively illuminating a scene and determining distances over the entire scene and so that a respective distance to each object or point in the scene can be determined. Thus, distances to all objects in a scene (within a particular range) at any given instant can be stored. A preview of the image can be displayed so as to allow a user to select a region of the scene of interest. In response to the user's selection, the imager's optical assembly can be adjusted automatically, for example, to a position that corresponds to optimal image capture of objects at the particular distance of the selected region of the scene.