3848974 is referenced by 46 patents and cites 11 patents.

Head-up display apparatus to provide an indication of the speed of an automobile includes a curved windscreen on which the indication is displayed in the driver's line-of-sight. The apparatus includes a speedometer scale attached to the shaft of a speedometer movement, a light source, and an optical assembly, having a diverging lens and a curved mirror, to project the speedometer display on to the windscreen. The speedometer scale is positioned by the speedometer movement so that the numeral on the scale representing the speed of the automobile is illuminated by the light source. The combined optical characteristics of the optical assembly and the curved windscreen are arranged so that the image appears to the driver to be focussed at a position between 6 and 20 feet ahead. The colour of the display may be varied in accordance with the driving conditions.

Head-up display apparatus
Application Number
Publication Number
Application Date
January 29, 1973
Publication Date
November 19, 1974
Blackham Norman
Hosking John Trevor
Pollock Elliott I
G02b 27/18
G02B 27/00
G02B 27/01
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