Optical configurations for head-worn see-through displays

An optical system configured for use with a wearable head device, the optical system comprising:

• a first combiner, the first combiner adapted to visually present image content such that a surrounding environment is visible to a user of the wearable head device through the first combiner while the image content is presented, wherein the first combiner comprises a first surface having a reflectivity that is adjustable;
• one or more light sources, the one or more light sources adapted to project image light onto the first combiner,
• a first camera configured to capture a portion of first ambient light reflected by the first combiner;
• and
• a processor configured to:
• determine whether a brightness of the first ambient light exceeds a first threshold value,
• in accordance with a determination that the brightness of the first ambient light exceeds the first threshold value, increase the reflectivity of the first surface of the first combiner,
• in accordance with a determination that the brightness of the first ambient light does not exceed the first threshold value, forgo increasing the reflectivity of the first surface of the first combiner,
• wherein the first combiner is adapted to reflect, with the reflectivity and toward a first eye of a user, a first portion of the image light projected by the one or more light sources.