A light-emitting device, comprising: a plurality of light-emitting elements, each of the plurality of light-emitting elements configured to emit light upon receiving electric current; driving circuitry coupled to the plurality of light-emitting elements, the driving circuitry configured to supply electric current to each of the plurality of light-emitting elements; a light-mixing region configured to receive light emitted by the plurality of light-emitting elements; a plurality of photodetectors arranged at a plurality of locations of the light-mixing region, wherein each of the plurality of photodetectors is configured to detect an intensity of light present at a location of the light-mixing region and generate a corresponding detection signal; test circuitry coupled to the driving circuitry, the test circuitry configured to perform a test sequence and control the driving circuitry to supply electric current to a plurality of groups of light-emitting elements in sequence, wherein each of the plurality of groups of light-emitting elements includes one or more of the plurality of light-emitting elements, said test sequence being such that only one individual group of said plurality of groups of light-emitting elements emits light at a step of said test sequence and that the plurality of photodetectors detect, during said step of said test sequence, an intensity of light emitted by said one individual group of said plurality of groups of light-emitting elements at said plurality of locations of said light-mixing region, characterised in that the intensity of light detected by a particular photodetectors i and emitted by a particular group j of light-emitting elements correpsonds to the electric current supplied to that particular group of light-emitting elements multiplied by a coupling coefficient C i,j obtained upon performing the test sequence, and in that said light-emitting device further comprises process circuitry coupled to the plurality of photodetectors and the driving circuitry, wherein the process circuitry is configured to process the detection signals generated by the plurality of photodetectors and adjust an electric current supplied to each of the plurality of light-emitting elements based on the processing such that at least one characteristic of light emitted by all of the plurality of light-emitting elements is substantially the same at each of the plurality of locations of the light-mixing region, wherein said electric current I [1,m] supplied to each of the plurality of light-emitting elements is determined on a least squares basis by solving the equation I Least Squares = (C T C) -1 C T D, where C is the matrix of coefficients C [1,n][1,m] and D is the matrix of desired brightness levels D [1,n] at photodetectors [1,n]. a plurality of light-emitting elements, each of the plurality of light-emitting elements configured to emit light upon receiving electric current; driving circuitry coupled to the plurality of light-emitting elements, the driving circuitry configured to supply electric current to each of the plurality of light-emitting elements; a light-mixing region configured to receive light emitted by the plurality of light-emitting elements; a plurality of photodetectors arranged at a plurality of locations of the light-mixing region, wherein each of the plurality of photodetectors is configured to detect an intensity of light present at a location of the light-mixing region and generate a corresponding detection signal; test circuitry coupled to the driving circuitry, the test circuitry configured to perform a test sequence and control the driving circuitry to supply electric current to a plurality of groups of light-emitting elements in sequence, wherein each of the plurality of groups of light-emitting elements includes one or more of the plurality of light-emitting elements, said test sequence being such that only one individual group of said plurality of groups of light-emitting elements emits light at a step of said test sequence and that the plurality of photodetectors detect, during said step of said test sequence, an intensity of light emitted by said one individual group of said plurality of groups of light-emitting elements at said plurality of locations of said light-mixing region, characterised in that the intensity of light detected by a particular photodetectors i and emitted by a particular group j of light-emitting elements correpsonds to the electric current supplied to that particular group of light-emitting elements multiplied by a coupling coefficient C i,j obtained upon performing the test sequence, and in that said light-emitting device further comprises process circuitry coupled to the plurality of photodetectors and the driving circuitry, wherein the process circuitry is configured to process the detection signals generated by the plurality of photodetectors and adjust an electric current supplied to each of the plurality of light-emitting elements based on the processing such that at least one characteristic of light emitted by all of the plurality of light-emitting elements is substantially the same at each of the plurality of locations of the light-mixing region, wherein said electric current I [1,m] supplied to each of the plurality of light-emitting elements is determined on a least squares basis by solving the equation I Least Squares = (C T C) -1 C T D, where C is the matrix of coefficients C [1,n][1,m] and D is the matrix of desired brightness levels D [1,n] at photodetectors [1,n].