We aim to analyze and correct stray light in spectrally modulated polarization spectrometers to enhance their measurement accuracy. Spectrally modulated polarization spectrometers are advanced instruments designed to perform high-precision measurements of continuous spectral radiation and polarization characteristics. These instruments are widely used in various scientific and industrial applications where accurate radiation and polarization measurements are crucial. However, stray light presents a significant challenge, as it can cause errors that compromise the overall precision and reliability of the instrument. Stray light occurs when light outside the desired optical path reaches the detector, causing unwanted signals that interfere with the measurements. Thus, it is critical to address stray light through systematic analysis, measurement, and correction methods. We investigate the effect of stray light on radiation and polarization measurement accuracy. In addition, a novel correction method is proposed to minimize stray light effects. The correction method involves three-dimensional adjustment of the field of view, polarization angle, and wavelength to create a stray light distribution matrix. The application of this matrix can significantly reduce stray light’s influence during actual measurements. Furthermore, a stray light quantification testing system based on linearly polarized monochromatic parallel light is designed for experimental validation of the correction method, which enables precise calibration of the spectrometer.

To begin, we construct a model of the spectrometer using LightTools, based on both measured data and the information available in the product manuals. The model is used to simulate the distribution of stray light paths within the instrument. During the simulation, several critical components of the spectrometer are considered, including the spectral modulation module, the telescope module, filters, the spectrometer itself, the protective window, and the detector. These components are crucial to understanding how stray light propagates through the system and affects the final measurements. The simulation results provide valuable insights into the distribution characteristics of stray light, forming the basis for the subsequent correction methodology. Next, stray light coefficients are determined through black tape method experiments. This experimental approach involves two distinct types of measurements. In the first experiment, black velvet is placed at the opening of an integrating sphere to measure the stray light coefficient in the spatial dimension of the instrument. The integrating sphere helps quantify the stray light coming from unintended directions, which is essential for understanding its effect on the measurements. The second experiment involves using a notch filter placed at the front of the optical system, which allows for the measurement of stray light in the spectral dimension. The notch filter works by selectively blocking certain wavelengths of light, thereby isolating and measuring the stray light that affects the spectrometer’s spectral measurements. These two experiments provide quantitative data on the stray light’s effect in both spatial and spectral dimensions, thus contributing to a deeper understanding of its overall effect on the instrument’s accuracy. Finally, based on the simulation results and experimental data, we introduce a new correction method involving three-dimensional adjustments of the field of view, polarization angle, and wavelength. This method is designed to generate a stray light distribution matrix, which could be applied during actual measurements to correct for the influence of stray light. By adjusting these three parameters, the stray light distribution matrix accounts for variations in the optical system’s configuration, thereby offering a flexible approach to stray light correction. To test and implement this correction method, we design a stray light distribution matrix testing system based on linearly polarized monochromatic parallel light. This system allows for precise measurements of stray light distribution and facilitates the validation of the correction method.

The simulation of stray light paths in the spectrometer is conducted by adjusting various parameters in LightTools [Fig. 3(a)]. Simultaneously, a measured image is obtained with a 3° field of view and a full-wavelength, unpolarized light source [Fig. 3(b)]. The comparison between the simulated image and the measured image reveals a high degree of similarity, which confirms the accuracy of the simulation model and validates its use for constructing the stray light mathematical model. This comparison is crucial for establishing the reliability of the simulation results and ensuring the validity of the stray light distribution characteristics identified through the model. Next, the black tape method experiments provide stray light coefficients for both the spatial and spectral dimensions of the instrument. The stray light coefficients for the spatial dimension are obtained (Fig. 5), and the coefficients for the spectral dimension are also determined (Fig. 7). These experimental results provide quantitative data on the levels of stray light affecting the instrument, offering insights into the magnitude of the stray light issue. Such measurements are essential for understanding how stray light interacts with the instrument and influences the accuracy of measurements. The experimental results demonstrate that the proposed three-dimensional adjustment method (incorporating the field of view, polarization angle, and wavelength) is highly effective in reducing stray light. Specifically, the method can eliminate more than 86.6% of stray light (Fig. 13). This significant reduction in stray light is shown to enhance the accuracy of radiation intensity and polarization measurements (Figs. 14 and 15).

We address the problem of stray light in spectrally modulated polarization spectrometers by utilizing the principles of spectral modulation to analyze the distribution of stray light and quantify its effects on measurement accuracy. Through a combination of simulation and experimental methods, we successfully demonstrate the necessity of correcting stray light in these instruments. The new correction method, based on three-dimensional adjustments of the field of view, polarization angle, and wavelength, is shown to be highly effective in minimizing the impact of stray light. By employing a linearly polarized monochromatic parallel light scanning experimental setup, we also develop a testing system for measuring the stray light distribution matrix. This system enables precise calibration and further validates the correction method. The experimental results confirm that the proposed correction technique could effectively reduce stray light by over 86.6%, which leads to significant improvements in radiation and polarization measurement accuracy. This work provides valuable theoretical insights and technical support for addressing stray light in spectrally modulated polarization spectrometers, contributing to the enhancement of their performance. By reducing stray light, we overcome a long-standing challenge in optical instrumentation, thus offering a promising solution for improving the precision of these advanced instruments.