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Holographic analogue indicating means

  • US 4,834,475 A
  • Filed: 11/06/1986
  • Issued: 05/30/1989
  • Est. Priority Date: 03/07/1985
  • Status: Expired due to Fees
First Claim
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1. Analogue indicating means comprising two relatively movable components (FIGS. 1-3:

  • 26/28 and

         12) respectively having associated therewith a reference marker (30/32), and a scale portion (46) bearing a series of scale markings (48) spaced apart along the scale portion (46), the position of the reference marker (30/32) relative to said scale markings (48) being indicative to an observer of the relative positions of the two components (26/28 and

         12), wherein at least one (26/28 or

         12) of said two components comprises a hologram which, when illuminated by a source of a predetermined reference light, (33) portrays to the observer a holographic image of said reference marker (30/32) or holographic images of said scale markings (48), as appropriate to the said one component, for comparison with, respectively, the said scale markings (48) or the said reference marker (30/32) of the other (12 or 30/32) of said two components when the two components lie in cooperating positions, said hologram being arranged so as to project the said holographic image or images into a plane disposed near or at the plane of the scale markings (48) or reference marker (30/32) respectively of the said other (12 or 26/28) of said two components, so as to diminish parallax errors when determining the position of said reference mark relative to said scale markings.

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