For the head of a vehicle occupant exclamation

摘要

1533859 Head-up display ELLIOTT BROS (LONDON) Ltd 27 April 1976 [29 April 1975] 17812/75 Heading G2J A helmet has a display device (light-emitter diode array 33) collimated and presented to the wearer by a prism 37 and the visor 29. The optics are such that spherical aberration introduced by the visor is corrected and preferably astigmatism is also corrected e.g. by modifying the otherwise plane internally reflecting surfaces 41, 43 of the prism.