The artist who painted this ca. 1605 (date estimated based on dress) would be Frans Poubus the Younger. The chin is not as wide in this portrait and the one in this image as in the other images in this Subalbum.
From the lost gallery's photostream on flickr; removed spots throughout image and fixed left, upper, and right edges with Photoshop. Also posted to Margarita de Austria, Queen of Spain’s Subalbum.