Light Detection System Using Rolling Shutter for Coded Light
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Solution Overview
Problem
Existing illumination systems face challenges in detecting embedded data from multiple light sources in a 2D scene using conventional low-cost camera sensors, which are unable to capture high-frequency coded light due to low acquisition rates.
Innovation Solution
A light detection system that captures images line by line using a rolling-shutter image sensor, increasing the temporal sample rate and allowing for the detection of high-frequency coded light, while also providing spatial information about separate light contributions, using a combination of pixel values along each line and optional filtering to improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional low-cost camera sensors are used to detect embedded data from multiple light sources, then device cost is reduced, but acquisition rate is too low to capture high-frequency coded light
Solution Approach 1:
The patent transforms the temporal sampling problem into a spatial-temporal solution by utilizing the rolling shutter's sequential line-by-line image acquisition. Each line in the image corresponds to a different time instant, effectively converting temporal information into spatial patterns across the image rows. This allows detection of high-frequency modulations without requiring high frame rates, resolving the contradiction between low cost and high acquisition rate.
Solution Approach 2:
The invention exploits the dynamic nature of the rolling shutter readout process, where different rows of pixels are read at different times. By synchronizing the light modulation frequency with the line readout rate, the system dynamically captures temporal variations in light intensity across successive lines, enabling high-frequency detection with low-cost sensors.
2Measurement precision
If high-frequency coded light is detected using conventional camera acquisition methods, then measurement precision is improved, but measurement time increases due to multiple sequential acquisitions
Solution Approach 1:
The rolling shutter provides continuous sampling across the image frame, with each line capturing a successive time instant of the light modulation. This continuous action across spatial dimensions allows the system to capture complete modulation cycles within a single image exposure, eliminating the need for multiple sequential acquisitions and reducing measurement time while maintaining precision.
3Loss of information
If multiple light sources are detected simultaneously in a 2D scene, then spatial information is provided, but separating and identifying individual codes becomes more complex
Solution Approach 1:
The patent segments the detection problem by associating different spatial regions of the image with different light sources. The rolling shutter's temporal-spatial mapping allows each light source's modulation to be isolated in specific rows or regions of the image, enabling independent decoding of multiple codes simultaneously without cross-interference, thus reducing separation complexity.
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 efficient detection of embedded codes from multiple light sources in a 2D scene using low-cost cameras, significantly shortening measurement time and enabling the use of smartphones for coded-light detection, while providing spatial information about light contributions.
Implementation Method 1
The image is acquired by a plurality of temporal shifted line instances, each comprising an instance of the temporal sequence of modulations of the first embedded code
Data Source
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AI summary
There is provided a light detection system which is capable of determining in light embedded codes by detecting light in a scene which is illuminated by an illumination system (110) comprising one or more light sources (111,112,113) each providing a light contribution (I111, I112, I113) comprising an embedded code (ID#1, ID#2, ID#3) emitted as a temporal sequence of modulations in a characteristics of the light emitted and wherein the embedded code is repeated periodically. The light detection system comprises light detection means (220), which are arranged for acquiring a plurality of images of the scene, where the images are acquired at a plurality of temporal shifted line instances. Each line of the acquired images comprise an instance of the temporal sequence of modulations of the first embedded code where the light footprint is imaged. The light detection system further comprises means (230) for determining embedded codes from the spatial pattern of modulations from the plurality of images, by determining bits of the first embedded code from the respective ones of the plurality of images until each bit of the first embedded code has been determined.