Distance Measurement Using Dynamic Focus and Rolling Shutter Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Depth from Defocus (DFD) methods require capturing multiple images with different in-focus positions, which increases time and puts a load on actuator devices, leading to higher power consumption and inaccurate distance measurements due to the rolling shutter system's limitations.
Innovation Solution
A distance measurement apparatus with a CMOS imaging element that moves the in-focus position at a constant speed while capturing blurred images, using a correction process to account for the movement range, allowing for efficient and accurate distance measurement with a reduced number of images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images with different in-focus positions are captured using conventional DFD, then distance measurement is possible, but measurement time increases and power consumption increases
Solution Approach 1:
The patent applies dynamics by moving the in-focus position continuously at constant speed during the exposure period instead of capturing discrete images at different focus positions. The imaging element captures a single image while the in-focus position dynamically changes, effectively obtaining multiple blurred images with different defocus amounts simultaneously during the rolling shutter readout process.
Solution Approach 2:
The patent implements continuity of useful action by maintaining continuous movement of the in-focus position throughout the entire exposure and readout period. This allows the system to continuously capture light information at different focus positions without interrupting the imaging process, thereby reducing measurement time while maintaining distance measurement capability.
2Measurement precision
If multiple images with different in-focus positions are captured using conventional DFD, then distance measurement is possible, but actuator load increases and power consumption increases
Solution Approach 1:
The patent reduces power consumption by implementing continuous, smooth movement of the in-focus position at constant speed rather than repeatedly adjusting focus between discrete positions. This dynamic approach eliminates the need for multiple actuator activation cycles, reducing both mechanical load and energy consumption while still providing the necessary varied defocus information for distance measurement.
3Device complexity
If rolling shutter system is used for capturing images during in-focus position movement, then device complexity is reduced, but measurement accuracy decreases due to in-focus position movement during exposure
Solution Approach 1:
The patent applies feedback by introducing a correction unit that calculates correction values based on the relationship between the in-focus position movement amount and the rolling shutter readout timing. The correction unit uses the known constant speed movement parameter and timing information to compute accurate distance measurements despite the continuous focus shift during exposure, thereby maintaining measurement precision while using the simpler rolling shutter system.
Solution Approach 2:
The patent changes the parameter of in-focus position from static to dynamically moving at constant speed, and compensates for this change through mathematical correction. By modeling the relationship between focus position, time, and defocus amount, the system can accurately determine object distance even though the in-focus position continuously changes during the rolling shutter readout process.
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
Enables fast and accurate distance measurement by simplifying the control of the in-focus position, reducing power consumption, and improving the accuracy of distance calculations using a rolling shutter system.
Implementation Method 1
an imaging element that includes photoelectric conversion elements arranged in rows and columns, and images an object by performing exposure and readout of electric charges sequentially
Data Source
AI summary
A distance measurement apparatus includes: an imaging element that images an object by performing exposure and readout of electric charges sequentially for each row or column; an optical system that has a controllable in-focus position; an imaging control unit that moves the in-focus position at constant speed, and causes the imaging element to image the object sequentially while the in-focus position is being moved, to obtain blurred images; a distance measurement unit that measures a distance from a reference position in the optical system to the object using the blurred images and a point spread function dependent on object distance; and a correction unit that performs a correction process on the distance for each row or column according to a movement range of the in-focus position in which the in-focus position is moved during the exposure for each row or column when the blurred images are obtained.