An apparatus comprising: a display panel configured to emit display light representative of a display image; and a lens assembly disposed along an optical axis between the display panel and an expected position of a user's eye, the lens assembly comprising: a first phase mask plate having a first major surface facing the display panel and a second major surface opposite the first major surface, the second major surface implementing a first freeform Fresnel lens structure; a second phase mask plate adjacent and parallel to the first phase mask plate and having a third major surface facing the second major surface and an opposing fourth major surface, the third major surface implementing a second freeform Fresnel lens structure, wherein a pose of at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates is configured to be adjusted to adjust an optical power of the lens assembly; and an actuator configured to adjust the pose of the at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates; and a lens control module configured to manipulate an amount of adjustment of the pose by the actuator based on depth information associated with the display image. a display panel configured to emit display light representative of a display image; and a lens assembly disposed along an optical axis between the display panel and an expected position of a user's eye, the lens assembly comprising: a first phase mask plate having a first major surface facing the display panel and a second major surface opposite the first major surface, the second major surface implementing a first freeform Fresnel lens structure; a second phase mask plate adjacent and parallel to the first phase mask plate and having a third major surface facing the second major surface and an opposing fourth major surface, the third major surface implementing a second freeform Fresnel lens structure, wherein a pose of at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates is configured to be adjusted to adjust an optical power of the lens assembly; and an actuator configured to adjust the pose of the at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates; and a lens control module configured to manipulate an amount of adjustment of the pose by the actuator based on depth information associated with the display image. a first phase mask plate having a first major surface facing the display panel and a second major surface opposite the first major surface, the second major surface implementing a first freeform Fresnel lens structure; a second phase mask plate adjacent and parallel to the first phase mask plate and having a third major surface facing the second major surface and an opposing fourth major surface, the third major surface implementing a second freeform Fresnel lens structure, wherein a pose of at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates is configured to be adjusted to adjust an optical power of the lens assembly; and an actuator configured to adjust the pose of the at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates; and a lens control module configured to manipulate an amount of adjustment of the pose by the actuator based on depth information associated with the display image. wherein a pose of at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates is configured to be adjusted to adjust an optical power of the lens assembly; and an actuator configured to adjust the pose of the at least one of the first and second phase mask plates relative to the other of the first and second phase mask plates; and a lens control module configured to manipulate an amount of adjustment of the pose by the actuator based on depth information associated with the display image.