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Speedometer optical projection system

  • US 3,887,273 A
  • Filed: 07/27/1973
  • Issued: 06/03/1975
  • Est. Priority Date: 07/27/1973
  • Status: Expired due to Term
First Claim
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1. In a vehicle with an instrument panel including a speedometer or the like having a movable scale with indicia providing vehicle condition information for the vehicle operator, a system for projecting said information as a luminous image at infinite focus substantially in the operator'"'"''"'"'s forward field of view comprising a transparent windshield concave to the interior of the vehicle and of substantially spherical curvature, a projection lens for projecting parallel light rays on the inside surface of said transparent windshield, a light source for illuminating said scale and located on the opposite side of the scale from the lens, and an optical correcting element in the system for sharply focusing said image to overcome aberration produced by the curvature of the windshield, said scale being positioned at less than the focal length of the projection lens to correct for focus shift produced by curvature of the windshield.

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