Control and evaluation of room interior lighting using digital camera as the sensor

Susan G Varghese,Ciji Pearl Kurian,T S Sudheer Kumar,V I George

doi:10.14419/ijet.v7i2.21.11844

Abstract

This paper reports the results of measurements performed in a test room to test how digital camera can be used as luminance meter and thus to investigate the lighting control scheme based on the inputs coming from camera. An indoor lighting control scheme which adapts according to the daylight availability is presented in this work. The camera calibration procedure based on High Dynamic Range Imaging technique is used to obtain the camera response function which allows to relate pixel values obtained from the image and the photopic luminance values. Luminance gradient evaluation for the uniformity analysis is discussed for the test room.

Highlights

This paper presents a method for the usage of digital still cameras as luminance meter
Wuller and Gabele [4] presents a method for the replacement of camera as luminance meter .The measurement is not dependent on exposure settings, instead the camera calibration factor .With the help of calibration procedure the OECF was measured .Using the image from the camera RGB values and OECF were used to calculate the luminance value
A lighting control system that adjusts the artificial light depending upon the availability of daylight based on the inputs from camera as sensor that provides luminance information of the test room is presented here

Summary

Methodology & system description

HDRI is used for luminance measurement so as to develop an image that closely resembles to what a human eye can see. Minimum error curve is obtained with the color checker chart here and the steps are mentioned for calibration These options are based on the ranges required to be measured [6]. The luminance from the actual scene is proportional to the pixel values from the HDRI image obtained from the camera. Which is termed as the luminance obtained from the HDR image This software luminance is found for all those pixel coordinates for which the actual values of the region are measured by luminance meter[6,9]. Depending upon the digital output of the comparator that is given to the I/O pins of ardiuno controller, different duty cycles are generated This generated PWM signal with varying duty cycle is fed to the LED driver circuit. These R,G,B values are used to find the software luminance using equation (3)

B Luminance

Findings

Conclusion