TOF Dot Projector Layout for Optical Distortion Compensation
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Solution Overview
Problem
Conventional TOF cameras suffer from substantial optical distortion due to non-ideal lenses, leading to increased energy consumption and computational efforts in existing distortion compensation methods.
Innovation Solution
Optically compensate for distortion by engineering the arrangement of light emitters and transfer functions of projection and camera lenses to minimize optical distortion without additional components or digital processing, ensuring each dot is captured by a corresponding sensor pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional lenses are used in TOF cameras, then the optical system is simple to manufacture, but substantial optical distortion occurs in the dot pattern and captured images
Solution Approach 1:
The patent applies preliminary anti-action by pre-distorting the dot pattern before projection so that the distortion introduced by conventional lenses is compensated. The dot pattern is intentionally designed with distortion characteristics that are opposite to those introduced by the lenses, thereby canceling out the optical distortion and achieving accurate depth measurements without requiring complex distortion-free lenses
2Measurement precision
If the number of pixels of the optical sensor is increased to overcome distortion, then measurement precision improves, but energy consumption increases excessively
Solution Approach 1:
The patent replaces the mechanical approach of increasing sensor pixel count with an optical-preprocessing approach. Instead of using more pixels to capture the distorted pattern and then processing it digitally, the system substitutes this with a pre-distorted dot pattern that naturally compensates for lens distortion, thereby maintaining measurement precision while avoiding the energy cost of operating additional pixels and performing complex digital corrections
3Manufacturing precision
If digital pre-distortion is used to compensate for lens distortion, then optical distortion is reduced, but computational efforts increase significantly
Solution Approach 1:
The patent applies preliminary action by performing distortion compensation in the optical domain before detection, rather than computing it after detection. The dot pattern is pre-distorted during the projection phase, so that when captured by the sensor, the distortion is already compensated. This eliminates the need for computationally intensive digital pre-distortion algorithms, reducing computational complexity while maintaining distortion compensation effectiveness
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
Reduces the number of emitters needed, lowers costs, improves optical power throughput, and enhances robustness against tolerances, maintaining efficient and reliable TOF measurements.
Implementation Method 1
the target is illuminated by means of a light pulse from a light emitter of the camera
Implementation Method 2
a projection lens configured to project a dot pattern onto a target
Implementation Method 3
a sensor element of the camera captures the reflected light from the target
Implementation Method 4
an optical sensor, which is formed from an array of sensor pixels and a camera lens. The optical sensor is configured to capture the dot pattern projected onto and reflected from the target
Implementation Method 5
a processing unit determines the time it takes for the light to reach the target and back again for each pixel. Therein, the determined time is directly proportional to the distance to the target
Data Source
AI summary
A time-of-flight, TOF, camera comprises a dot projector formed from an array of light emitters and a projection lens, the dot projector being configured to project a dot pattern onto a target. The TOF camera further comprises an optical sensor formed from an array of sensor pixels and a camera lens, the optical sensor being configured to capture the dot pattern projected onto the target. A distortion of the array of light emitters, a transfer function of the projection lens and/or a transfer function of the camera lens is set such that the captured dot pattern is free of optical distortion.