title: Integrated High Resolution Digital Color Light Sensor in 130 nm CMOS Technology.
abstract: This article presents a color light detection system integrated in 130 nm CMOS technology. The sensors and corresponding electronics detect light in a CIE XYZ color luminosity space using on-chip integrated sensors without any additional process steps, high-resolution analog-to-digital converter, and dedicated DSP algorithm. The sensor consists of a set of laterally arranged integrated photodiodes that are partly covered by metal, where color separation between the photodiodes is achieved by lateral carrier diffusion together with wavelength-dependent absorption. A high resolution, hybrid, ∑∆ ADC converts each photo diode's current into a 22-bit digital result, canceling the dark current of the photo diodes. The digital results are further processed by the DSP, which calculates normalized XYZ or RGB color and intensity parameters using linear transformations of the three photo diode responses by multiplication of the data with a transformation matrix, where the coefficients are extracted by training in combination with a pseudo-inverse operation and the least-mean square approximation. The sensor system detects the color light parameters with 22-bit accuracy, consumes less than 60 μA on average at 10 readings per second, and occupies approx. 0.8 mm(2) of silicon area (including three photodiodes and the analog part of the ADC). The DSP is currently implemented on FPGA.
authors.affiliation: University of Ljubljana, Electrical Engineering Department, Tržaška 25, Ljubljana 1000, Slovenia. drago.strle@fe.uni-lj.si.
authors.forename: Drago
authors.initials: D
authors.lastname: Strle
authors.affiliation: University of Ljubljana, Electrical Engineering Department, Tržaška 25, Ljubljana 1000, Slovenia. uroš.nahtigal@fe.uni-lj.si.
authors.forename: Uroš
authors.initials: U
authors.lastname: Nahtigal
authors.affiliation: Carinthia University of Applied Sciences, Europastrasse 4, Villach 9585, Austria. g.batistell@fh-kaernten.at.
authors.forename: Graciele
authors.initials: G
authors.lastname: Batistell
authors.affiliation: Infineon Technologies Austria AG, Siemensstrae 2, Villach 9500, Austria. VincentChi.Zhang@infineon.com.
authors.forename: Vincent Chi
authors.initials: VC
authors.lastname: Zhang
authors.affiliation: Carinthia University of Applied Sciences, Europastrasse 4, Villach 9585, Austria. E.Ofner@fh-kaernten.at.
authors.forename: Erwin
authors.initials: E
authors.lastname: Ofner
authors.affiliation: Infineon Technologies Austria AG, Siemensstrae 2, Villach 9500, Austria. andrea.fant@infineon.com.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fant
authors.affiliation: Carinthia University of Applied Sciences, Europastrasse 4, Villach 9585, Austria. j.sturm@fh-kaernten.at.
authors.forename: Johannes
authors.initials: J
authors.lastname: Sturm
keywords: CMOS-integrated color light sensor system; RGB color sensor; color light detection; color signal processing; high-resolution photo current measurements; measurements of light in CIE XYZ color luminosity space