On the basis of the analysis of the existing pupil diameter estimation models, the changes in pupil diameter of all subjects under different light environments are measured. The comparison among all existing models are made by use of the measurement data. The relationship of luminance and visual angle with pupil diameter is established according to the corneal flux density. Moreover, based on the Stanley-Davies model, the original calculation formulas are corrected and optimized, and thus the calculation precision of this model is improved. Via experiments, the field of view area is extended and the maximum field of view is increased to 40 degrees.