Fig. 1. Experimental setup for laser nonlinearity measurement^[15]

Fig. 2. Calibration diagrams of pinhole aperture attenuation factor. (a) Spectral radiance of high luminance source and response of the reflectance transfer spectrometer with a pinhole aperture are measured; (b) spectral radiance of low luminance source and response of the reflectance transfer spectrometer without a pinhole aperture are measured

Fig. 3. Spectral radiance of integrating sphere light source measured by wide dynamic spectrometer. (a) High luminance; (b) low luminance

Fig. 4. Measurement results of pinhole aperture attenuation factor. (a) Signal value of reflectance transfer spectrometer; (b) pinhole aperture attenuation factor calculated from Eq. (13)

Fig. 5. Experiment diagram of measuring reflectance outdoor. (a) Directly imaging the solar; (b) observing the white diffusing plate

Fig. 6. Experimental test results. (a) Oversampled image of the solar disk; (b) spectral response of reflectance transfer spectrometer to solar and diffuse reflector

Fig. 7. Influence of non-full-aperture imaging on the uniformity of attenuation factor

Fig. 8. Results of non-uniformity correction. (a) Ratio of solar response signal of reflectance transfer spectrometer to white diffusing plate response signal; (b) normalized result of ratio non-uniformity corrected by pinhole aperture attenuation factor

Table 1. Evaluation of uncertainty in measurement of pinhole aperture attenuation factor