A linearly-overlapping light measurement system “measurement head” having one or more linearly-overlapping modular light sources each having individual light sources arranged in a geometric pattern, the light sources being single- or multi-wavelength and programmable to generate light that is transmitted through and/or reflected from a work piece to be detected by linearly-overlapping modular light detectors having individual light detectors arranged in a geometric pattern. The “measurement head” also has linearly-overlapping modular light detectors arranged in a geometric pattern to receive light emitted by the light sources. A computer controller coordinating the operation of the light source array and light detector array to automatically sense and record the light transmittance and/or reflectance of one or more spectral ranges in real time from the work piece and then adjust the work being performed on the work piece to attain pre-determined standards. Reference feedback circuitry is provided for monitoring the light sources in each light source module. The reference feedback circuitry adjusts the operating parameters of a light source module to ensure that the intensity and the chromatic output of the light therefrom remains at a consistent level.