Tackling Heterogeneous Color Registration: Binning Color Sensors.

Paul Myland,Sebastian Babilon,Tran Quoc Khanh

doi:10.3390/s21092950

Abstract

Intelligent systems for interior lighting strive to balance economical, ecological, and health-related needs. For this purpose, they rely on sensors to assess and respond to the current room conditions. With an augmented demand for more dedicated control, the number of sensors used in parallel increases considerably. In this context, the present work focuses on optical sensors with three spectral channels used to capture color-related information of the illumination conditions such as their chromaticities and correlated color temperatures. One major drawback of these devices, in particular with regard to intelligent lighting control, is that even same-type color sensors show production related differences in their color registration. Standard methods for color correction are either impractical for large-scale production or they result in large colorimetric errors. Therefore, this article shows the feasibility of a novel sensor binning approach using the sensor responses to a single white light source for cluster assignment. A cluster specific color correction is shown to significantly reduce the registered color differences for a selection of test stimuli to values in the range of 0.003–0.008 , which enables the wide use of such sensors in practice and, at the same time, requires minimal additional effort in sensor commissioning.

Highlights

In each case, the indicated values describe the differences between the color perceived by a standardized human observer and the sensor outputs after previous classification and cluster-wise color correction
We focus on the performance evaluation of the proposed sensor binning approach using a simple 3 × 3 transformation matrix for color correction, as this is the method of choice applied by the majority of manufacturers and, seems to be of the most practical relevance
By adopting a cluster-wise color correction, the registered color differences for the selection of test stimuli could be limited to values in the range of 0.003–0.008 ∆u0 v0, which is approximately a factor of two smaller than the deviations obtained for the standard color correction procedure and corresponds with the binning specifications standardized for white LEDs

Summary

Introduction

A closed-loop feedback design with input from optical sensors seems to be most expedient and has already been adopted successfully in practical research [2,3,4,5,6,7,8] in order to ensure that such systems are capable of monitoring and dynamically adapting to continuous changes in the environmental conditions and the lighting parameters, e.g., caused by variations of the natural daylight entry through windows and skylights [9,10,11] or by degradation and temperature processes in the luminaires [12,13,14]. In extension of simple occupancy monitoring, recent studies have shown the great energy saving potentials that emerge from such sensor-driven daylight harvesting strategies [15,16,17,18,19]

Methods

Results

Discussion

Conclusion