Color corrected viewfinder including a negative power lens component having a diffractive surface

• US 5,715,090 A
• Filed: 02/20/1996
• Issued: 02/03/1998
• Est. Priority Date: 02/20/1996
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Meyers, Mark M.
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US08/602,516
• Time in Patent Office: 714 Days
• Field of Search: 359/558, 359/565, 359/570, 359/16, 359/19, 359/742, 359/743, 359/744, 359/793, 359/784
• US Class Current: 359/565
• CPC Class Codes: G02B 27/0037 with diffracting elements G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence

Abstract

A viewfinder having an optical axis and comprising a negative lens component including a lens element having a first diffractive surface which introduces a phase modification φ(r) into a light wavefront passing through this diffractive surface and a positive lens component receiving phase modified light from the negative power lens component.

Claims

1. A color corrected viewfinder having an optical axis, said viewfinder comprising in order from an object side:

a negative power lens component having a diffractive surface which introduces a phase modification φ

(r) into a light wavefront passing through said diffractive surface, wherein ##EQU3## a) r is a height from the optical axis on the diffractive surface of the lens component,

b) λ

₀ is a wavelength of light,

c) i is an integer from 1 to n,

d) C_i is a set of coefficients defining the diffractive surface, and

e) C₁ is positive; and

a positive power lens component receiving phase modified light from said negative power lens component;

said negative power lens component and said positive power lens component together form a demagnified, achromatized image of an object.

2. A viewfinder according to claim 1 wherein said diffractive surface is a surface facing said positive power lens component.

3. A viewfinder according to claim 1 wherein at least two of said C_i coefficients are non zero to retard the edges of the outgoing wavefront emanating from said negative lens component.

4. A viewfinder according to claim 1, wherein said diffractive surface is curved.

5. A viewfinder according to claim 4, wherein said diffractive surface is concave.

6. A viewfinder according to claim 1, wherein said positive power lens component has a second diffractive surface which is also described by the phase modification φ

(r) of claim 1.

7. A viewfinder according to claim 6 wherein said diffractive surface is a surface facing said negative power lens component.

8. A viewfinder according to claim 6, wherein said second diffractive surface is curved.

9. A viewfinder according to claim 7, wherein said second diffractive surface is convex.

10. A viewfinder according to claim 6, wherein said second diffractive surface is defined by the phase modification φ

(r) in which the C₁ coefficient is negative.

11. A viewfinder according to claim 9, wherein at least two of said C_i coefficients are non zero to retard the edges of the outgoing wavefront emanating from said positive lens component.

12. A viewfinder according to claim 11 wherein each of said coefficients C_i has a sign opposite to the sign of its immediately preceding non-zero coefficient.