DIFFRACTIVE OPTICAL ELEMENT

• US 20090052040A1
• Filed: 02/08/2006
• Published: 02/26/2009
• Est. Priority Date: 02/22/2005
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Miyakawa, Akiko, Suzuki, Kenzaburo
• Granted Patent: US 7,821,715 B2
• Time in Patent Office: Days
• US Class Current: 359/576
• CPC Class Codes: G02B 27/0056 by using a diffractive optical element
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4288 having uniform diffraction efficiency over a large spectral bandwidth
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02B 5/1847 Manufacturing methods
• 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 10 is constituted by sandwiching and closely bonding first and second optical element components 13, 14 which have different refractive indices and are adhered via a relief pattern 20, between third and fourth optical element components 11, 12.

Claims

1. A diffractive optical element, comprising:

a first optical element component on which a relief pattern for generating a desired diffraction effect is formed;

a second optical element component bonded to a surface of said first optical element component on which said relief pattern is formed; and

a third optical element component bonded to a surface opposite the surface on which said second optical element component is bonded to said first optical element component, wherein

said first and second optical element components comprise a relatively high refractive index and low dispersion material, and a relatively low refractive index and high dispersion material.

2. The diffractive optical element as claimed in claim 1, further comprising a fourth optical element component bonded to a surface opposite the surface on which said relief pattern of said first optical element component is formed.

3. The diffractive optical element as claimed in claim 2, wherein said third and fourth optical element components are refractive lenses having a curved surface shape of positive refractive power at the surfaces that are an interface with the environment.

4. The diffractive optical element as claimed in claim 3, satisfying the condition:

L<

dx

wherein L is the optical length difference, along the optical axis direction, of the most phase-advanced and most phase-delayed portions of a wavefront after diffraction of a light beam passing through said relief pattern, and dx is the thickness of one of the first or second optical element components positioned at the exit of said relief pattern.

5. The diffractive optical element as claimed in claim 4, satisfying the condition:

(d3+d4)/d<

0.5

wherein d3 is the thickness of said first optical element component along the optical axis, d4 is the thickness of said second optical element component along the optical axis, and d is the sum of the thicknesses along the optical axis of said first, second, third and fourth optical element components.

6. The diffractive optical element as claimed in claim 3, satisfying the condition:

0.00001<

P/f<

0.03

wherein P is the minimum pitch of said relief pattern and f is the focal distance of the diffractive optical element.

7. The diffractive optical element as claimed in claim 3, satisfying the condition:

1.0<

fd/(f1·

f2)1/2<

20.0

wherein f1 is the focal distance of said third optical element component, f2 is the focal distance of said fourth optical element component and fd is the inverse of the refractive power (focal distance) of said relief pattern.

8. The diffractive optical element as claimed in claim 3, further satisfying the condition:

0.03<

|{(nd3−

1)/ν

d3−

(nd4−

1)/ν

d4}/(nd3−

nd4)|<

3.0

wherein nd3 is the d-line refractive index of said first optical element component, nd4 is the d-line refractive index of said second optical element component, ν

d3 is the d-line Abbe number of said first optical element component and ν

d4 is the d-line Abbe number of said second optical element component.

9. The diffractive optical element as claimed in claim 3, wherein the optical material forming said third optical element component comprises a refractive index that is closer to that of an optical material of the optical element component to be formed later, than to that of an optical material of the optical element component to be formed first, among said first and second optical element components.

10. The diffractive optical element as claimed in claim 3, wherein

the optical material forming said third and fourth optical element components is a resin, and

the optical materials forming said first and second optical element components are UV-curable resins having mutually different refractive indices.

11. The diffractive optical element as claimed in claim 3, wherein said third or fourth optical element components comprise the same resin material.

12. The diffractive optical element as claimed in claim 3, wherein

the surface closest to an object side and the surface closest to an image side have predetermined curvatures respectively,

surfaces other than these surfaces have flat surfaces perpendicular to the optical axis, and

said relief pattern is planarly formed perpendicular to the optical axis.

13. An eyepiece optical system for forming a virtual image, comprising a diffractive optical element, said diffractive optical element including:

a first optical element component on which a relief pattern for generating a desired diffraction effect is formed;

a second optical element component bonded to a surface of said first optical element component on which said relief pattern is formed; and

a third optical element component bonded to a surface opposite the surface on which said second optical element component is bonded to said first optical element component, wherein

said first and second optical element components comprise a relatively high refractive index and low dispersion material, and a relatively low refractive index and high dispersion material.