Diffractive optical element

• US 20050264887A1
• Filed: 07/28/2005
• Published: 12/01/2005
• Est. Priority Date: 06/07/2000
• Status: Abandoned Application

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Sato, Hideki
• Application Number:
  US11/190,870
• Publication Number:
  US 20050264887A1
• Time in Patent Office: Days
• US Class Current: 359/566
• CPC Class Codes: G02B 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner
• CPC Class Codes: G02B 5/1852 using mechanical means, e.g. ruling with diamond tool, moulding
• CPC Class Codes: G02B 5/1871 Transmissive phase gratings
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08

Abstract

A diffractive optical element includes a first diffractive optical part having a phase type diffractive grating, and a second diffractive optical part having a phase type diffractive grating formed of a material differing from that of the first diffractive optical part. The first diffractive optical part and the second diffractive optical part are disposed in proximity to each other with an air layer. Each of the first diffractive optical part and the second diffractive optical part has a mark for aligning them with the optical effective areas thereof.

Claims

1-9. -9. (canceled)

10. A diffractive optical element comprising:

a diffractive optical part having a phase-type diffractive grating,

said diffractive optical part having a mark for aligning with another member, said mark being in an area where the diffractive grating is provided,

wherein the depth or height of said mark is 10% or less of the depth or height of the diffractive grating of said diffractive optical part.

11. The diffractive optical element of claim 10, wherein the diffractive grating of said diffractive optical part is a diffractive grating formed into a concentric circular shape, and said mark has a size of 0.1% or less of a projection area of a first diffractive grating area as counted from the center.

12. The diffractive optical element of claim 11, wherein the influence of said mark upon the optical performance of said diffractive optical element is smaller than the reduction of optical performance caused by manufacturing imperfections.

13. An optical system provided with the diffractive optical element of claim 10.

14. A diffractive optical element comprising:

a diffractive optical part having a phase-type diffractive grating,

said diffractive optical part having an alignment mark,

said mark being in an area where the diffractive grating is provided,

wherein the depth or height of said mark is 10% or less of the depth or height of the diffractive grating of said diffractive optical part.

15. An optical system provided with the diffractive optical element of claim 14.