Tunable Hyper-Spectral Illumination System Using DMD and Integrating Sphere
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Solution Overview
Problem
Existing illumination sources lack the flexibility and precision to provide accurate calibration for sensors, leading to issues like metamerism due to inadequate spectral control.
Innovation Solution
An illumination system comprising a source, a dispersive optical element, focusing optics, a digital micro-mirror device (DMD), and an integrating sphere, controlled by a system that calculates and activates specific reflective elements to achieve a target spectral power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single adjustable LED or multiple LEDs are used to provide adjustable illumination output, then the device complexity is reduced, but the spectral precision and flexibility are insufficient for accurate sensor calibration
Solution Approach 1:
The illumination source is segmented into multiple LED chips emitting at different spectral bands (violet, blue, cyan, green, yellow-green, yellow, orange, red). Each LED chip group can be independently controlled to provide precise spectral composition, resolving the contradiction by dividing the illumination function into spectrally distinct segments rather than using a single adjustable source.
Solution Approach 2:
The system changes the operational parameters of multiple LED chips simultaneously, adjusting their individual drive currents to achieve desired spectral power distribution. This allows precise control over the intensity and spectral composition of each band, providing calibration accuracy that cannot be achieved with a single adjustable LED.
2Adaptability or versatility
If existing illumination sources are used, then the device complexity is low, but the adaptability to generate diverse spectral power distributions is limited
Solution Approach 1:
The illumination device achieves multi-functionality by integrating eight different LED chip groups that can be independently controlled. This universal design allows the single device to generate diverse spectral power distributions suitable for calibrating various types of sensors (color sensors, spectral sensors, imaging sensors), eliminating the need for multiple specialized light sources.
Solution Approach 2:
The system implements dynamic spectral control by independently adjusting the drive current of each LED chip group in real-time. This dynamic capability allows the illumination output to be continuously tuned to match target spectral power distributions, providing adaptability that static or singly-adjustable sources cannot achieve.
3Reliability
If spectral calibration is not accomplished with adequate flexibility, then the illumination source is simpler, but metamerism and inaccurate calibration curves occur
Solution Approach 1:
The illumination device applies local quality control by assigning specific spectral characteristics to each LED chip group position. Each group targets a specific wavelength region with optimized spectral output, allowing precise local adjustment of spectral components to eliminate metamerism and achieve accurate calibration curves for different sensor types.
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
The system generates a highly stable and tunable illumination output that accurately matches user-defined spectral power distributions, enhancing sensor calibration and applications in imaging, chemical analysis, and material identification.
Implementation Method 1
a dispersive optical element configured to generate an angularly dispersed optical signal from the illumination light
Implementation Method 2
a focusing optics system configured to generate a spectral image from the angularly dispersed optical signal
Implementation Method 3
a digital micro-mirror device (DMD) comprising an array of reflective elements. The DMD is configured to receive the spectral image and direct a portion of the spectral image
Implementation Method 4
A collection optics system is configured to direct the illumination optical signal to an entrance port of an integrating sphere
Data Source
AI summary
An illumination system includes an illumination source configured to emit illumination light and a dispersive optical element configured to generate an angularly dispersed optical signal from the illumination light that is used to generate a spectral image. A digital micro-mirror device (DMD) includes an array of reflective elements that receive the spectral image and direct a portion of the spectral image to an integrating sphere. A controller is configured to calculate a subset of an array of reflective elements of the DMD to activate based on a target illumination output signal using a calibration model of the illumination system. The controller is also configured to activate the subset of the array of reflective elements to change the portion of the spectral image directed to the integrating sphere to generate an illumination output signal that substantially matches the target illumination output signal.