A see-through head-worn computer display, comprising: an image light production optical module with an upper portion and a lower portion; wherein the upper portion of the module includes a first flat reflective surface positioned in use above an eye of a user and arranged to reflect image light produced by an image display, from the upper portion of the module to the lower portion of the module along a first optical axis, wherein the lower portion of the module includes a second flat reflective surface arranged to change the direction of the image light from the upper portion of the module to a direction along a second optical axis towards an eye of the user which creates a compound angle in the image light path, the second flat reflective surface thereby reflecting image light to the user while simultaneously providing the user with a see-through view of a surrounding environment, wherein the display further comprises an image source configured to emit illumination light toward the upper portion of the module along an illumination light axis, the first optical axis and the second optical axis both being perpendicular to the illumination light axis in a non twisted state, and the first optical axis and the second optial axis both further being perpendicular to each other in the non twisted state, wherein the upper portion of the module is twisted about the first optical axis to change the fit of the optical module into a frame associated with the see-through head-worn computer display and thereby enable the frame to be thinner than when the upper portion of the module is not twisted, and wherein the lower portion of the module is twisted a corresponding amount about the second optical axis to introduce the compound angle between the first reflective surface and the second reflective surface to reduce distortion within the image due to the twisting. an image light production optical module with an upper portion and a lower portion; wherein the upper portion of the module includes a first flat reflective surface positioned in use above an eye of a user and arranged to reflect image light produced by an image display, from the upper portion of the module to the lower portion of the module along a first optical axis, wherein the lower portion of the module includes a second flat reflective surface arranged to change the direction of the image light from the upper portion of the module to a direction along a second optical axis towards an eye of the user which creates a compound angle in the image light path, the second flat reflective surface thereby reflecting image light to the user while simultaneously providing the user with a see-through view of a surrounding environment, wherein the display further comprises an image source configured to emit illumination light toward the upper portion of the module along an illumination light axis, the first optical axis and the second optical axis both being perpendicular to the illumination light axis in a non twisted state, and the first optical axis and the second optial axis both further being perpendicular to each other in the non twisted state, wherein the upper portion of the module is twisted about the first optical axis to change the fit of the optical module into a frame associated with the see-through head-worn computer display and thereby enable the frame to be thinner than when the upper portion of the module is not twisted, and wherein the lower portion of the module is twisted a corresponding amount about the second optical axis to introduce the compound angle between the first reflective surface and the second reflective surface to reduce distortion within the image due to the twisting.