An Acousto-Optic Colorimeter
Uniform color spaces and color-difference formulae rest on visual data obtained almost entirely with surface samples and conventional displays, whose primaries confine the measurements to a limited chromaticity range. The highly saturated region of color space is therefore the least measured part of human color perception, at the moment when quantum-dot, microLED, and laser displays have begun to operate inside it. Closing this gap requires stimuli more saturated than any fixed-primary device can produce, together with the stability and uniformity demanded by visual experiments. We present an acousto-optic colorimeter built for this purpose. A four-channel acousto-optic tunable filter selects narrow spectral components from a supercontinuum laser over the calibrated range of 443--660~nm, with measured linewidths of 1.37--3.20~nm; the wavelength and radiance of every component are set electronically, so the primary set itself becomes an experimental variable. A compact diffuser--light-pipe homogenizer combines the selected components into a uniform observation field, and spectral feedback stabilizes their intensities. The calibrated primary set covered 95\% of the area enclosed by the CIE 1964 $10^{\circ}$ spectral locus in the $x,y$ chromaticity plane. The calculated maximum luminance reached 1406~cd\,m$^{-2}$, with 328~cd\,m$^{-2}$ available at the gray Robertson chromaticity. Across an 18-mm observation field the mean spatial $ΔE_{00}$ difference was 0.913, and five Robertson color centers reproduced under continuous feedback gave mean target errors of 0.34--1.26~$ΔE_{00}$ over 10-min intervals. The instrument thus delivers calibrated, uniform, and stable highly saturated stimuli, and is intended to extend the empirical basis of color-difference measurement into the region where data are still absent.