DIFFRACTIVE OPTICAL ELEMENT AND OPTICAL SYSTEM INCLUDING THE SAME

• US 20080043335A1
• Filed: 10/17/2007
• Published: 02/21/2008
• Est. Priority Date: 04/01/2004
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nakai, Takehiko
• Granted Patent: US 7,554,735 B2
• Time in Patent Office: Days
• US Class Current: 359/570
• 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 27/42 Diffraction optics , i.e. systems including a diffractive element being designed for providing a diffractive effectG02B27/60 takes precedence
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 5/1895 such optical elements having dioptric power

Abstract

A diffractive optical element includes a plurality of diffraction gratings. A diffraction grating within the plurality of diffraction gratings includes a plurality of grating parts having a curved grating surface and grating tips which connect to define a curved envelope face. The grating surface has a radius of curvature larger than a radius of curvature of the envelope face. In addition, two diffraction gratings within the plurality of diffraction gratings are composed of different materials having different dispersions. Therefore, even when the radius of curvature of the envelope face is small, the degradation of the diffraction efficiency is suppressed.

Claims

1. An optical system comprising:

a diffractive optical element including a plurality of diffraction gratings laminated and being composed of at least two materials having different dispersions,

wherein at least one of the diffraction gratings includes a plurality of grating parts having a curved grating surface and grating tips which connect to define a curved envelope face,

wherein the grating surface has a radius of curvature larger than a radius of curvature of the envelope face;

a refractive optical element, and

wherein an absolute value of the radius of curvature of the envelope face is between one-fifteenth of a focal length of the optical system to one-half of the focal length of the optical system, inclusive.