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

• Current Assignee: David Griffiths
• Original Assignee: David Griffiths
• Inventors: Griffiths, David
• Primary Examiner(s): Aegerter, Richard E.
• Assistant Examiner(s): Mirabito, A. J.
• Application Number:
  US05/383,244
• Time in Patent Office: 676 Days
• Field of Search: 353/13,14,69,11,98
• US Class Current: 353/14
• CPC Class Codes: B60K 2360/334 Projection means
• CPC Class Codes: B60K 37/00 Dashboards as road-vehicle superstructure sub-units B62D25/14
• CPC Class Codes: G01P 1/08 Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers
• CPC Class Codes: G02B 2027/0169 Supporting or connecting means other than the external walls
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G03B 21/20 Lamp housings

Abstract

A system for projecting a speedometer or other instrument reading as a virtual image, focused at infinity, into the field of view of a vehicle operator includes the windshield and a lens system containing a lens that substantially corrects aberrations caused by curvature of the windshield.

Claims

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.

2. The invention as set forth in claim 1 wherein said correcting element is a cylindrical lens.

3. The invention as set forth in claim 2 wherein said cylindrical lens is negative and positioned so that its curvature is along the length of the vehicle.

4. The invention as set forth in claim 2 wherein said cylindrical lens is positive and positioned so that its curvature is across the width of the vehicle.

5. 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 correcting element being a negative cylindrical lens positioned so that its curvature is along the length of the vehicle.