大方廣圓覺修多羅了義經略疏 2.1188

2.1188

明設像之意。謂大師去世，不覩真儀，設像諦觀，引心入法。相即無相，即見如來。亦可想佛真身常在不滅。若稱理說者，觀行無間是佛現在，間斷之時是佛滅後。斷後復作觀行思惟，是設像存想。今且依事行釋也。次下明禮懺儀式。

This clarifies the purpose of setting up images. It means that when the Great Master has departed the world and one does not behold his true appearance, one sets up an image and contemplates it closely, drawing the mind into the Dharma. Marks are themselves markless, and thereby one sees the Tathāgata. Alternatively, one may visualize the Buddha's true body as constantly present and unextinguished. If explained in accord with principle: uninterrupted contemplation practice is the Buddha being present; when there is interruption, it is after the Buddha's extinction. Engaging in contemplation and reflection again after an interruption is setting up images and visualizing. Here we explain it for now according to phenomenal practice. Next below, the ritual of worship and repentance is clarified.