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The plasma optical boundary reconstruction technique based on Hommen’s theory is promising for future tokamaks with high parameters. In this paper, we conduct detailed analysis and simulation verification to estimate the “logic loophole” of this technique. The finite-width effect and unpredictable errors will reduce the level of reliability of this technique, which lead to the “logic loophole”. Based on imaging theory, the photos of a virtual camera are simulated by integrating assumed luminous intensity of plasma. Based on Hommen’s theory, the plasma optical boundary is reconstructed from the photos. Comparing the reconstructed boundary with the one assumed, the “logic loophole” and its two effects are quantitatively estimated. The finite-width effect is related to the equivalent thickness of the luminous layer, which is generally about 2-4 cm but sometimes larger. The level of unpredictable errors is around 0.65 cm. The technique based on Hommen’s theory is generally reliable, but in some scenarios, finite-width effect and unpredictable errors have to be taken into consideration. The parameters of HL-2M are applied in this paper.