Structured Light Projector LC Lens Temperature Compensation
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Solution Overview
Problem
Conventional structured light projectors experience tilt deviations in depth measurement due to temperature-induced expansion of speckle patterns, affecting the accuracy of depth information calculation.
Innovation Solution
A structured light projector equipped with a liquid crystal (LC) lens and a processor that adjusts the equivalent curvature of the LC lens based on environmental temperature, using a temperature sensor and look-up table to generate control signals for the LC lens driver, ensuring accurate focusing of optical patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional laser element is used to generate optical patterns, then the structure is simple, but the wavelength changes due to temperature variation causing speckle expansion and depth measurement deviation
Solution Approach 1:
An LC lens is introduced as an intermediary component between the laser source and the target. This LC lens acts as a mediator that compensates for temperature-induced wavelength changes by dynamically adjusting its optical power based on temperature feedback, thereby correcting speckle expansion without requiring changes to the fundamental laser source structure.
Solution Approach 2:
The system changes the optical power parameter of the LC lens based on temperature variations. By adjusting the voltage applied to the LC lens, the system dynamically modifies its focal length and optical power to compensate for wavelength drift, thereby maintaining measurement accuracy despite temperature-induced laser wavelength changes.
2Measurement precision
If the optical power of the LC lens is increased to compensate for speckle expansion, then depth measurement accuracy is improved, but the response time of the LC lens becomes a limiting factor
Solution Approach 1:
The system performs preliminary actions by pre-charging storage capacitances before each frame period and pre-calculating compensation values based on temperature trends. This preliminary preparation reduces the actual response time required during active projection by having the LC lens and control system ready in advance.
Solution Approach 2:
A temperature sensor provides continuous feedback to the control system, which then adjusts the LC lens optical power in real-time. This feedback loop enables the system to respond dynamically to temperature changes, optimizing the balance between compensation accuracy and response speed by adjusting compensation magnitude based on actual temperature drift rates.
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
Compensates for temperature-induced speckle expansion, enhancing the accuracy of depth information measurement by dynamically adjusting the LC lens curvature.
Implementation Method 1
an LC lens and a processor. The projection module is configured to project an optical pattern. The LC lens is disposed over the projection module, and is configured to focus the optical pattern onto a region of space
Implementation Method 2
a processor configured to generate a control signal depending on an environment temperature of the projection module for controlling the LC lens
Implementation Method 3
The projection module includes a light source and a diffractive optical element (DOE). The light source is configured to generate a light beam. The DOE is configured to convert the light beam into the optical pattern
Data Source
AI summary
A structured light projector and a method for structured light projection are disclosed. The structured light projector includes a projection module, a liquid crystal (LC) lens and a processor. The projection module is configured to project an optical pattern. The (LC) lens module is disposed over the projection module, and is configured to focus the optical pattern onto a region of space. The processor is configured to generate a control signal depending on an environment temperature of the projection module for controlling the LC lens.