Correction of second‐order‐diffraction errors in spectrophotometry

Conventional diffraction gratings are designed so that most of the light striking the grating is diffracted toward the “first‐order beam” direction, but in practice, some of the light may be diffracted towards the “second‐order beam” direction, so that the light striking a particular sensor pixel may be a combination of both first‐ and second‐order components. This causes errors in the output of diffraction‐grating based UV–visible spectrometers. A new method has been developed to correct such errors by calibrating the optical system with a UV‐excluded standard (such as an orange tile) and a UV‐included standard (such as a white tile). These two calibrations can predict the relationship between first‐order‐only signals and first‐and‐second‐order combined signals at sensor pixels (nominal wavelengths) where there is second‐order light, and thus help correct the second‐order diffraction error. This compensation method applied on the reflectance measurement of a set of color ceramic tiles showed significant improvement on the accuracy of the result. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 189–192, 2017