Modular head-mounted device

A modular sensor and display module comprises an enclosure with a rigid frame and front and back visor lens encapsulating sensors, waveguide optics, and display/projection devices that provide various functions for a typical head-mounted device. A front visor may conceal sensors and other components and may further provide dimming for holographic displays. The modular sensor and display module may include a standard interface for attachment to various fit systems, including, for example, headband, VR headset, glasses temples, helmet, and the like. A further module, such as a rear-attachment module, may be provided that can provide auxiliary compute, storage, and power resources for the modular sensor and display module.