How are doppleganger's used in Vertigo?

Doppleganger's are by definition a ghostly double of a living person that haunts its living counterpart. Within Vertigo Madeleine and Judy are the most obvious as it is he same person (Judy is payed by Gavin to act as Madeleine). From first instance Scottie sees Madeleine he is obsesses, the scene in Ernie's host a long tracking shot up to Madeleine a shot of her going through the doorway which frames her like a picture and a profile shot of her. The second half of the film after Madeleine has died shoes a shot in Ernie's where a woman with Madeleine shade of hair walks towards him and is framed once again in the doorway. The first time we see Judy just like Madeleine we get a profile shot of her. Hitchcock visually repeats theses series of actions taken by Scottie as he attempts to recreate the events associated with is trauma.

Hitchcock uses the same cinematic techniques to repeat key events in Scotties stalking of Madeleine. The shots in the art gallery is almost identical, Scottie watches Madeleine watch the painting of Carlotta and in the second half he watches a stranger. both shots of him are frames the same with him standing next to the pillar, the only difference is the different coloured suits.