Sky Luminance Mapping with Sun-Shading Pyranometer Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional high dynamic range imaging (HDRi) technology struggles to capture accurate sky luminance maps during daylight due to the overwhelming luminance of the sun, which can damage camera sensors and introduce noise, and requires manual filter replacement, leading to inefficiencies and costs.
Innovation Solution
A sky luminance mapping system comprising a digital camera with a fisheye lens, pyranometer units, and light-shading devices that block the sun's direct light, allowing for separate measurement of sun-blocked and total sky illuminance, enabling correction of image luminance and distribution without manual filter changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional HDRi technology is used to shoot sky dome images, then the luminance distribution of the sky dome can be documented, but the direct sunlight will overheat the photo sensor and exceed the luminance range
Solution Approach 1:
The patent introduces a light-shading device as an intermediary element between the sun and the photo sensor. This device selectively blocks direct sunlight while allowing diffuse sky radiation to reach the sensor, thereby preventing overheating and overexposure while maintaining measurement capability. The light-shading device acts as a mediator that separates the harmful direct sun light from the useful sky dome luminance information.
Solution Approach 2:
The patent segments the sky dome measurement into two distinct components: direct sunlight measurement and diffuse sky radiation measurement. By using separate measurement paths—one with the light-shading device blocking direct sun and another without shading for total sky measurement—the system can process and combine these segmented measurements to achieve accurate overall luminance mapping without sensor damage.
2Object-affected harmful factors
If a filter is used to reduce the luminance of direct sunlight, then the sensor can capture sky images, but baseband noises interfere with signals and signals are distorted
Solution Approach 1:
Instead of using optical filters that introduce noise and distortion, the patent employs a light-shading device as a physical intermediary that geometrically blocks direct sunlight before it reaches the sensor. This mechanical shading approach avoids the signal degradation and baseband noise interference associated with optical filtering, maintaining signal quality while achieving the same protective effect.
3Measurement precision
If manual filter replacement is performed to adapt to different sunlight conditions, then measurement accuracy can be maintained, but significant costs and time are incurred
Solution Approach 1:
The light-shading device is designed to automatically track and follow the sun's movement across the sky, eliminating the need for manual intervention. The device self-adjusts its position to maintain optimal shading of direct sunlight throughout the day, enabling continuous automated operation without manual filter replacement while maintaining measurement precision across varying sunlight conditions.
Solution Approach 2:
The patent implements a dynamic light-shading device that can move and adjust its position in real-time to track the sun's changing position in the sky. This dynamic adaptation allows the system to maintain effective sunlight blocking throughout the day without manual intervention, contrasting with static filter systems that would require manual replacement as lighting conditions change.
4Measurement precision
If exposure bracketing is used to capture sky dome images at different exposure levels, then luminance distribution can be documented, but the process takes significant time and cannot operate continuously
Solution Approach 1:
The light-shading device enables single-exposure capture by acting as a mediator that pre-conditioning the light before it reaches the sensor. By blocking direct sunlight at the source, the device allows the sensor to capture the entire sky dome luminance distribution in a single exposure without requiring multiple bracketed shots, thereby dramatically reducing measurement time and enabling continuous operation.
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 accurate and efficient sky luminance mapping in daylight conditions, reducing noise and manual intervention, allowing continuous outdoor operation and improved data updating frequency.
Implementation Method 1
a location of the first light-shading device corresponds to an instant location of a sun at an instant time, such that the first light-shading device blocks the sun from the digital camera
Implementation Method 2
The first pyranometer measures the daylight illuminance from the sun-blocked sky dome to output a first intensity signal
Data Source
AI summary
A sky luminance mapping system includes a camera unit, two pyranometer units and a processing unit. Camera unit includes a fisheye lens to shoot image of sky dome and is equipped with light-shading devices which block the sun from the camera unit corresponding to instant location of the sun at instant time. First pyranometer unit measures daylight illuminance from the sky dome and outputs first intensity signal while the light-shading device is applied to block the sun. Second pyranometer unit measures daylight illuminance from the sky dome and outputs second intensity signal without blocking the sun. A reference intensity value is obtained by subtracting a value of the first intensity signal from a value of the second intensity signal. According to the value of the first intensity signal and the reference intensity value, a total luminance of and the luminance distribution in the image of the sky dome are corrected.