DIFFRACTIVE OPTICAL ELEMENT, OPTICAL SYSTEM AND OPTICAL APPARATUS

• US 20100134889A1
• Filed: 11/25/2009
• Published: 06/03/2010
• Est. Priority Date: 11/28/2008
• Status: Abandoned Application

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takayama, Hidemi
• Application Number:
  US12/625,685
• Publication Number:
  US 20100134889A1
• Time in Patent Office: Days
• US Class Current: 359/576
• 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 27/4283 having a diffractive element with major temperature dependent properties
• CPC Class Codes: G02B 27/4288 having uniform diffraction efficiency over a large spectral bandwidth
• 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

Abstract

The diffractive optical element is constituted by a glass material and a resin material whose dn/dT representing refractive index variation with temperature is larger than that of the glass material, the resin material being in close contact with or facing the glass material, and a diffractive grating formed at a close contact portion or a facing portion between the glass material and the resin material. The resin material is a mixture material of (a) a resin base material, (b) first fine particles formed of a first material whose dn/dT is equal to or higher than −1×10⁻⁵(/° C.) and (c) second fine particles formed of a second material whose Abbe constant is lower than that of the glass material. The diffractive optical element can maintain high diffraction efficiency in a wide wavelength region even if temperature changes, without generating unnecessary diffracted light.

Claims

1. A diffractive optical element comprising:

a glass material;

a resin material whose dn/dT representing a refractive index variation with temperature is larger than that of the glass material, the resin material being in close contact with or facing the glass material; and

a diffractive grating formed at a close contact portion or a facing portion between the glass material and the resin material,

wherein the resin material is a mixture material of (a) a resin base material, (b) first fine particles formed of a first material whose dn/dT satisfies a condition of dn/dT≧

−

1×

10<sup>−

5</sup>(/°

C.) and (c) second fine particles formed of a second material whose Abbe constant is lower than that of the glass material.

2. A diffractive optical element according to claim 1, wherein at least one of the first fine particles and the second fine particles are particles whose particle diameter is equal to or smaller than 100 nm.

3. A diffractive optical element according to claim 1, wherein a mixing ratio in volume of the first fine particles to the resin base material is equal to or higher than 20%.

4. A diffractive optical element according to claim 1, wherein the resin material has a lower refractive index and a lower Abbe constant than those of the glass material.

5. A diffractive optical element according to claim 1, wherein the glass material is a low melting point glass whose glass transition temperature is equal to or lower than 600°

C.

6. An optical system comprising:

a diffractive optical element,

wherein the diffractive optical element comprising;

a glass material;

a resin material whose dn/dT representing a refractive index variation with temperature is larger than that of the glass material, the resin material being in close contact with or facing the glass material; and

a diffractive grating formed at a close contact portion or a facing portion between the glass material and the resin material,

wherein the resin material is a mixture material of (a) a resin base material, (b) first fine particles formed of a first material whose dn/dT satisfies a condition of dn/dT≧

−

1×

10<sup>−

5</sup>(/°

C.) and (c) second fine particles formed of a second material whose Abbe constant is lower than that of the glass material.

7. An optical apparatus comprising:

an optical system including a diffractive optical element,

wherein the diffractive optical element comprising;

a glass material;

a resin material whose dn/dT representing a refractive index variation with temperature is larger than that of the glass material, the resin material being in close contact with or facing the glass material; and

a diffractive grating formed at a close contact portion or a facing portion between the glass material and the resin material,

wherein the resin material is a mixture material of (a) a resin base material, (b) first fine particles formed of a first material whose dn/dT satisfies a condition of dn/dT≧

−

1×

10<sup>−

5</sup>(/°

C.) and (c) second fine particles formed of a second material whose Abbe constant is lower than that of the glass material.