One or more embodiments of the invention provide for a lens package comprising a housing having a vacuum compatible interior space, a base coupled to the housing, a lens coupled to the housing, and an infrared detector within the housing for providing infrared images representative of infrared energy received through the lens. The housing, base, and lens are adapted to form an infrared detector vacuum package assembly. The housing may include a focal alignment feature that allows for focal adjustment of the lens relative to the infrared detector by applying pressure to at least a portion of the housing.