Spectrophotometer Design Using Single-Grating, Single-Sensor, Double-Beam Spectroscope

Abstract

The double beam structure in existing spectrophotometers is traditionally realized using two spectroscopes. Owing to inconsistencies in gratings, optical path mechanical structures, and sensors, the two spectroscopes tend to mismatch as the temperature varies, which leads to poor measurement reproducibility. This paper proposes a single-sensor, single-grating, double-beam spectrophotometer design that simultaneously samples both optical paths to reduce the effect of temperature on the measurement reproducibility. Wavelength and energy calibration were implemented to further improve the instrument’s reproducibility. Experiments were performed to evaluate the effectiveness of this design. The results suggest that the spectrophotometer denoted DS-36D, can significantly improve measurement reproducibility when the temperature varies. At fixed temperature and humidity, the standard deviation of measurement repeatability is 0.001, and the maximum smallest color deviation is 0.005. When the temperature varies from 15 to 30 °C, the maximum Allan deviation of color difference δ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ΔE</sub> =1.509×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> , with a maximum smallest color deviation of 0.036. The novel spectrophotometer design shown in this study outperforms other existing technologies.