Diffraction grating, diffractive optical element, and optical system using the same

• US 20030058538A1
• Filed: 09/23/2002
• Published: 03/27/2003
• Est. Priority Date: 09/25/2001
• Status: Abandoned Application

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Sugiyama, Takayuki, Fukasawa, Motomu
• Application Number:
  US10/252,041
• Publication Number:
  US 20030058538A1
• Time in Patent Office: Days
• US Class Current: 359/570
• 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 27/4216 correcting geometrical aberrations
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44

Abstract

An ultraviolet-permeable resin is used for a substrate of a diffraction grating, and at least one grating portion formed from ultraviolet cured resin is provided onto a surface of the substrate, thereby alleviating performance deterioration that is caused by heat expansion and the like due to environmental changes and enabling a large angle of view and cost reduction due to the simple construction. Further, a diffractive optical element using the diffraction grating, and an optical system using the diffractive optical element, are also obtained.

Claims

1. A diffraction grating wherein an ultraviolet-permeable resin is used for a substrate, and at least one grating portions comprising of an ultraviolet cured resin and being provided onto a surface of the substrate.

2. A diffraction grating according to claim 1, wherein a thermal expansion coefficient of the substrate is 9.4×

10<sup>−

6</sup> (cm/cm°

C.) or greater and 1.1×

10<sup>−

4</sup> (cm/cm°

C.) or less.

3. A diffraction grating according to claim 1, wherein the substrate is made of an ultraviolet-permeable-type acrylic.

4. A diffraction grating according to claim 1, wherein the diffraction grating has a concave power, and dispersion by the material of the grating portion is 30 or less.

5. A diffraction grating according to claim 1, wherein the diffraction portion has a convex power, and dispersion by the material of the grating portion is 45 or greater.

6. A diffractive optical element in which a plurality of diffraction gratings including at least one diffraction gratings as set forth in claim 1 are arranged close to each other.

7. A diffractive optical element according to claim 6, wherein at least two of the plurality of diffraction gratings are joined with their grating surfaces facing each other with a layer of air in between.

8. A diffractive optical element according to claim 6, wherein the plurality of diffraction gratings include at least:

one diffraction grating having a concave power and in which dispersion by the material of the grating portion is 30 or less; and

one diffraction grating having a convex power and in which dispersion by the material of the grating portion is 45 or greater.

9. A diffractive optical element in which a diffraction grating as set forth in claim 1 is provided on one side thereof, and a diffraction grating in which a substrate and its grating portion are integrally molded is provided on the other side thereof.

10. A diffractive optical element according to claim 6, wherein the plurality of diffraction gratings are formed by molding a convex portion and a concave portion on the periphery of the substrate, and combining the convex portion and the concave portion to thereby stack a plurality of diffraction gratings.

11. A diffractive optical element according to claim 9, wherein the diffraction grating is integrally molded with a substrate and grating portion therein by means of injection molding.

12. A diffractive optical element according to claim 9, wherein the diffraction grating with its substrate and its grating portion integrally molded is made of plastic material.

13. A diffraction grating according to claim 1, wherein the substrate is one of a parallel flat plate and a member that has a curved surface.

14. A diffractive optical element according to claim 6, wherein the substrate is one of a parallel flat plate and a member that has a curved surface.

15. An optical system using a diffraction grating as set forth in claim 1.

16. An optical system using a diffractive optical element as set forth in claim 6.

17. An image reading device in which image information from an original is formed onto a surface of reading means using an image reading lens having a diffraction grating as set forth in claim 1.

18. An image reading device in which image information from an original is formed onto a surface of reading means using an image reading lens having a diffractive optical element as set forth in claim 6.