Granted Patent B2

US 12,730,331 · App. 18/401,763 · Granted Sep 8, 2026

Inventor: Mikio Kobayashi (Tochigi, JP)

Assignee: CANON KABUSHIKI KAISHA

G02B27/4205

Abstract

Claims (191)

1 . A diffractive optical element comprising:

a diffractive area including annular sections concentrically arranged,

wherein at least one of the annular sections has a non-circular shape,

wherein the annular sections are rotationally symmetric and concentric, and

wherein the following inequalities are satisfied:

6

<

P

⁢

min

×

Rdc

/

Re

<

65

0.5

<

Rdc

/

Re

<

0.95

0.7

<

Rdc

/

RPm

<

1

.

5

⁢

0

where Rdc (mm) is a shortest one of distances from a center of the annular sections to an outer circumference of the diffractive area, Re (mm) is a radius of one of the annular sections which is farthest from the center, Pmin (μm) is a minimum value of an array pitch of the diffractive optical element, and RPm (mm) is a radius of the annulus having the minimum value Pmin.

2 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

0.8

<

1000

×

(

R

⁢

2

2

-

R

⁢

1

2

)

/

(

Re

×

Pmin

)

<

2

.

4

where R1 (mm) is a radius of a first annulus counted from the center, and R2 (mm) is a radius of a second annulus counted from the center.

3 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

0.4

<

fd

×

λ0

/

(

Re

×

P

⁢

min

)

<

1

.

2

⁢

0

where λ0 (μm) is a design wavelength of the diffractive optical element, and fd (mm) is a focal length on a diffractive surface.

4 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

0

.

0

⁢

5

<

Dm

/

Pmin

<

1.

where Dm (μm) is a grating height in an annulus having the minimum value Pmin.

5 . The diffractive optical element according to claim 1 , wherein annular ends are points where an outer peripheral area intersects with each annular section, where the annular sections have a non-circular shape, and wherein the following inequality is satisfied:

1.

5

<

P

⁢

o

⁢

u

t

⁢

m

/

Pmin

<

6

.

0

where Pout (μm) is an interval between adjacent annular ends among the annular sections in which the circumference is non-circular, and Pou tm (μm) is a minimum value of the interval Pout.

6 . The diffractive optical element according to claim 1 , wherein an outermost annulus in the diffractive optical element has the circumference that is non-circular, and the following inequality is satisfied:

3.

<

Lae

/

Re

<

6

.

0

where Lae (mm) is a length of an arc in the outermost annulus.

7 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

1

⁢

5

⁢

0

<

N

⁢

R

<

8

⁢

0

⁢

0

where NR is the number of annuli in the annular sections.

8 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

20

<

Ndc

<

300

where Ndc is the number of annuli having a radius larger than the shortest distance Rdc and smaller than the radius Re among the annular sections.

9 . The diffractive optical element according to claim 1 , wherein an optical material of the diffractive optical element includes a thermoplastic resin.

10 . The diffractive optical element according to claim 1 , wherein the diffractive optical element includes layers of a first diffraction grating made of a first material, and a second diffraction grating made of a second material different from the first material.

11 . The diffractive optical element according to claim 1 , wherein the diffractive optical element has an outer circumferential area in which no diffraction grating is formed outside an annulus having the radius Re.

12 . The diffractive optical element according to claim 1 , wherein the following inequality is satisfied:

-

5

.

0

<

(

Ψ

⁢

2

⁢

(

h

)

-

2

×

C

2

)

/

C

2

<

-

0

.

5

where h (mm) is a distance in a direction perpendicular to an optical axis in the diffractive optical element, an optical path difference function Ψ of a diffractive surface is Ψ(h)=C 2 h 2 +C 4 h 4 +C 6 h 6 . . . , Ψ2(h) is a second derivative value of the optical path difference function Ψ with respect to h, and Ci is a phase coefficient (i=2, 4, 6 . . . ).

13 . The diffractive optical element according to claim 1 , wherein the diffractive optical element has a gate portion, and

wherein in the diffractive area, a direction of a shortest length from the center and a direction of the gate portion are opposite to each other with respect to an annular rotation center.

14 . An optical system comprising the diffractive optical element according to claim 1 .

15 . An image pickup apparatus comprising:

the optical system according to claim 14 ; and

an image sensor configured to receive an optical image formed by the optical system.

16 . A display apparatus comprising:

a display element configured to display an image; and

the optical system according to claim 14 configured to guide light from the display element.

Assignments (1)

Priority Claims (1)

Continuity (1)

References Cited (11)