Reference Waveguide for Depth Camera Timing Error Correction
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Solution Overview
Problem
Existing depth camera systems face challenges in accurately determining depth information due to errors in the signal path and turn-on delay of the light source, particularly in the nano-second and pico-second regime.
Innovation Solution
A source-camera assembly is introduced, comprising a projector, a camera assembly, a reference waveguide, and an overmold. The reference waveguide guides light from the projector's source array to a reference pixel in the camera assembly, providing an optical reference for light emission, which helps correct errors in the signal path and turn-on delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct time-of-flight measurement is used to determine depth information, then depth measurement capability is achieved, but measurement precision deteriorates due to errors in signal path and turn-on delay of the light source
Solution Approach 1:
A reference waveguide is introduced as an intermediary optical path that guides light from the light source to a reference pixel. This reference path serves as a mediator to establish an accurate temporal reference for when light is emitted, allowing the system to subtract out errors in the signal path and turn-on delay of the light source, thereby improving depth measurement precision
Solution Approach 2:
The patent creates an optical copy of the light emission event by guiding light through the reference waveguide to the reference pixel. This optical copy serves as a reference signal that replicates the timing characteristics of the main light emission, enabling accurate time-of-flight measurement by comparing the reference signal timing with the reflected light timing
2Measurement precision
If the light source operates in the nano-second and pico-second regime for accurate depth measurement, then depth resolution is improved, but the system becomes more sensitive to turn-on delay errors
Solution Approach 1:
The reference waveguide system is self-contained within the camera assembly, using the same light source and detector infrastructure. The reference pixel captures light directly from the source through the waveguide, creating an automatic timing reference that eliminates the need for external timing equipment or complex synchronization systems, thus managing complexity while enabling high-precision measurement
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 solution enhances the accuracy of depth information determination by providing an optical reference that mitigates residual electrical-to-optical errors, ensuring precise timing between light emission and pixel readiness, even in the nano-second and pico-second regime.
Implementation Method 1
The reference waveguide is a light path through which light from a source array of the projector propagates to a reference pixel of the camera assembly
Implementation Method 2
The overmold is opaque to light emitted by the projector and prevents stray light from reaching the camera assembly from the projector
Implementation Method 3
Direct time-of-flight (dToF) measures distance to a target based on the time delta between when light is emitted from the light source and when the light returns back to the sensor due to reflection
Data Source
AI summary
A source-camera assembly with an isolated light path for a reference pixel is described. The assembly may include a projector, a camera assembly, a reference waveguide, and an overmold. The projector may include a source array configured to emit light and a lens assembly configured to direct the light into a local area. The camera assembly may include a sensor and a reference pixel. The sensor may be configured to detect the emitted light reflected from an object within the local area. The reference waveguide is configured to guide a portion of the light emitted by the projector from the source array to the reference pixel. The light detected by the sensor and the light detected by the reference pixel may be used to determine depth information for the object. The overmold is opaque to the emitted light and covers portions of the projector, the camera assembly, and the reference waveguide.