Temperature-Dependent Reference Image Correction for Light Projectors
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Solution Overview
Problem
Temperature-induced distortion of projected light patterns in depth sensing systems, caused by thermal expansion and refractive index changes, leads to erroneous depth measurements due to changes in the effective focal length of projectors, which existing techniques struggle to correct effectively.
Innovation Solution
A method for image thermal correction that involves determining the effective focal length adjustment based on temperature changes and applying this adjustment to a reference image to generate a corrected reference image, using temperature measurements and diffraction models to account for distortions in the projector's numerical aperture space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature-dependent correction is applied to the reference image, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by adjusting the reference image based on temperature-dependent effective focal length changes. The system measures temperature, determines the corresponding EFL change, and corrects the reference image accordingly to maintain measurement precision across varying temperatures.
Solution Approach 2:
The patent replaces complex mechanical calibration systems with a computational approach. Instead of physically recalibrating the projector at different temperatures, the system uses temperature measurements and EFL correction algorithms to achieve the same effect, reducing mechanical complexity.
2Reliability
If effective focal length correction is applied, then reliability is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs self-correction by automatically measuring its own temperature and applying the appropriate EFL correction to the reference image. This self-service mechanism maintains reliability without requiring external calibration equipment or complex operational procedures from the user.
Solution Approach 2:
The patent implements a feedback loop where temperature measurements are continuously monitored, and the reference image is dynamically corrected based on the measured temperature. This closed-loop feedback ensures consistent performance while automating the correction 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
This approach provides accurate depth measurements by compensating for temperature-induced distortions, ensuring consistent performance across varying projector temperatures without the need for complex and time-consuming calibration processes.
Implementation Method 1
heat can cause distortion of the projected light pattern, for example, due to thermal expansion of components of the light projector
Implementation Method 2
changes in the refractive index in the projector's lens and/or laser cavity
Implementation Method 3
receiving an indication of a temperature of a projector, e.g., an indication of an amount of change in temperature of the projector relative to the measured temperature of the projector
Data Source
AI summary
One disclosed embodiment includes techniques for temperature-dependent reference image correction in structured light projectors that may be used for generating three-dimensional (3D) scene depth maps. The techniques disclosed herein include receiving an indication of a temperature (e.g., an actual current operating temperature or a change in the current operating temperature relative to an established reference temperature) associated with one or more components of a projector and then determining, based on the temperature indication, an amount of adjustment needed to correct a reference pattern image based on an estimated effective focal length change of the projector. Next, a reference pattern image may be appropriately adjusted, e.g., based on the determined amount of effective focal length adjustment caused by the current operating temperature of the projector, to generate a corrected reference image, which may then be used to generate a more accurate 3D scene depth maps at the projector's current operating temperature.