Multi-angle colorimeter

1. A multi-angle colorimeter comprising:

a light emitter that emits light onto an object;

a light amount detector that receives the light emitted from the light emitter and reflected by the object in a plurality of directions of angles, and detects a reflected light amount in each of the angle; and

a hardware processor that obtains optical parameters, which are used in color evaluation of metallic coating or pearl coating on a surface of the object, based on the reflected light amount, and calculates, using the optical parameters, an index corresponding to a particle diameter of a glittering material used in the metallic coating or the pearl coating, wherein

the hardware processor calculates index B expressed by a following equation as the index corresponding to the particle diameter of the glittering material,

when

n is an integer equal to or greater than 2,

the plurality of angles are θ 1 to θ n respectively,

the optical parameters obtained for the respective angles θ 1 to θ n based on the reflected light amount are I(θ 1 ) to I(θ n ) respectively, and

weighting coefficients of the respective optical parameters I(θ 1 ) to I(θ n ) are two types of a 1 to a n and b 1 to b n respectively,

B={a 1 ·I (θ 1 )+ a 2 ·I (θ 2 )+ . . . + a n ·I (θ n )}/{ b 1 ·I (θ 1 )+ b 2 ·I (θ 2 )+ . . . + b n ·l (θ n )}

where,

regarding the weighting coefficients a 1 to a n , one is positive, another is negative, and rest is positive, negative, or zero, and

each of the weighting coefficients b 1 to b n is positive, negative or zero, except a case where all are zero.

2. The multi-angle colorimeter according to claim 1 , wherein

the respective optical parameters I(θ 1 ) to I(θ n ) are all brightness L*.

3. The multi-angle colorimeter according to claim 2 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect to the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a positive weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

4. The multi-angle colorimeter according to claim 2 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect to the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a negative weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

5. The multi-angle colorimeter according to claim 2 , wherein each of the weighting coefficients b 1 to b n is 1.

6. The multi-angle colorimeter according to claim 2 , further comprising

a display that displays the index B or the summed value, which is calculated by the hardware processor.

7. The multi-angle colorimeter according to claim 1 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect to the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a positive weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

8. The multi-angle colorimeter according to claim 1 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect t9o the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a negative weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

9. The multi-angle colorimeter according to claim 1 , wherein

each of the weighting coefficients b 1 to b n is 1.

10. The multi-angle colorimeter according to claim 1 , further comprising

a display that displays the index B or the summed value, which is calculated by the hardware processor.

11. A multi-angle colorimeter comprising:

a light emitter that emits light onto an object;

a light amount detector that receives the light emitted from the light emitter and reflected by the object in a plurality of directions of angles, and detects a reflected light amount in each of the angle; and

a hardware processor that obtains optical parameters, which are used in color evaluation of metallic coating or pearl coating on a surface of the object, based on the reflected light amount, and calculates, using the optical parameters, an index corresponding to a particle diameter of a glittering material used in the metallic coating or the pearl coating, wherein

the hardware processor calculates index B expressed by a following equation as the index corresponding to the particle diameter of the glittering material,

when

n and m are respectively an integer equal to or greater than 2,

the plurality of angles are θ 1 to θ n respectively,

the optical parameters obtained for the respective angles θ 1 to θ n based on the reflected light amount for each different wavelength band or each different wavelength are I′ 1 (θ 1 ) to I′ 1 (θ n ), I′ 2 (θ 1 ) to I′ 2 (θ n ), . . . , I′ m (θ 1 ) to I′ m (θ n ) respectively, and

weighting coefficients of the respective optical parameters I′I(θ 1 ) to I′ 1 (θ n ), I′ 2 (θ 1 ) to I′ 2 (θ n ), . . . , I′ m (θ n ) to I′ m (θ n ) are two types of a 1 to a n and b 1 to b n respectively,

B′ 1 ={a 1 ·I′ 1 (θ 1 )+ a 2 ·I′ 1 (θ 2 )+ . . . + a n ·I′ 1 (θ n )}/{ b 1 ·I′ 1 (θ 1 )+ b 2 ·I′ 1 (θ 2 )+ . . . + b n ·I′ 1 (θ n )}

B′ 2 ={a 1 ·I′ 2 (θ 1 )+ a 2 ·I′ 2 (θ 2 )+ . . . + a n ·I′ 2 (θ n )}/{ b 1 ·I′ 2 (θ 1 )+ b 2 ·I′ 2 (θ 2 )+ . . . + b n ·I′ 2 (θ n )}

. . .

B′ m ={a m ·I′ 1 (θ 1 )+ a 2 ·I′ m (θ 2 )+ . . . + a n ·I′ m (θ n )}/{ b 1 ·I′ m (θ 1 )+ b 2 ·I′ m (θ 2 )+ . . . + b n ·I′ m (θ n )}

B=B′ 1 + . . . +B′ m

where,

regarding the weighting coefficients a 1 to a n , one is positive, another is negative, and rest is positive, negative, or zero, and

the respective weighting coefficients b 1 to b n are positive, negative, or zero, except a case where all are zero.

12. The multi-angle colorimeter according to claim 11 , wherein

the optical parameters are tristimulus values XYZ, and

when

I′ 1 (θ 1 ) to I′ 1 (θ n )= X (θ 1 ) to X (θ n ),

I′ 2 (θ 1 ) to I′ 2 (θ n )= Y (θ 1 ) to Y (θ n ),

I′ 3 (θ 1 ) to I′ 3 (θ n )= Z (θ 1 ) to Z (θ n ),

B′ 1 =B′ x ={a 1 ·X (θ 1 )+ a 2 ·X (θ 2 )+ . . . + a n ·X (θ n )}/{ b 1 ·X (θ 1 )+ b 2 ·X (θ 2 )+ . . . + b n ·X (θ n )}

B′ 2 =B′ y ={a 1 ·Y (θ 1 )+ a 2 ·Y (θ 2 )+ . . . + a n ·Y (θ n )}/{ b 1 ·Y (θ 1 )+ b 2 ·Y (θ 2 )+ . . . + b n ·Y (θ n )}

B′ 3 =B′ z ={a 1 ·Z (θ 1 )+ a 2 ·Z (θ 2 )+ . . . + a n ·Z (θ n )}/{ b 1 ·Z (θ 1 )+ b 2 ·Z (θ 2 )+ . . . + b n ·Z (θ n )}

and,

B=B′ x +B′ y +B′ z .

13. The multi-angle colorimeter according to claim 11 , wherein

the optical parameters are spectral reflectances Ref(λθ) in a plurality of wavelengths λ, and

when

I′ 1 (θ 1 ) to I′ 1 (θ n )=Ref(λ 1 θ 1 ) to Ref(λ 1 θ n )

I′ 2 (θ 1 ) to I′ 2 (θ n )=Ref(λ 2 θ 1 ) to Ref(λ 2 θ n )

. . .

I′ m (θ 1 ) to I′ m (θ n )=Ref(λ m θ 1 ) to Ref(λ m θ n )

where the plurality of wavelengths λ are λ 1 , λ 2 , . . . λ m ,

B′ 1 ={a 1 ·Ref(λ 1 θ 1 )+ a 2 ·Ref(λ 1 θ 2 )+ . . . + a n ·Ref(λ 1 θ n )}/{ b 1 ·Ref(λ 1 θ 1 )+ b 2 ·Ref(λ 1 θ 2 )+ . . . + b n ·Ref(λ 1 θ n )}

B′ 2 ={a 1 ·Ref(λ 2 θ 1 )+ a 2 ·Ref(λ 2 θ 2 )+ . . . + a n ·Ref(λ 2 θ n )}/{ b 1 ·Ref(λ 2 θ 1 )+ b 2 ·Ref(λ 2 θ 2 )+ . . . + b n ·Ref(λ 2 θ n )}

. . .

B′ m ={a 1 ·Ref(λ m θ 1 )+ a 2 ·Ref(λ m θ 2 )+ . . . + a n ·Ref(λ m θ n )}/{ b 1 ·Ref(λ m θ 1 )+ b 2 ·Ref(λ m θ 2 )+ . . . + b n ·Ref(λ m θ n )},

and

B=B′ 1 +B′ 2 + . . . +B′ m .

14. The multi-angle colorimeter according to claim 11 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect to the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a positive weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

15. The multi-angle colorimeter according to claim 11 , wherein

when the specular reflection direction is 0° on a plane including an incident direction and a specular reflection direction of a principal light beam of the light emitted from the light emitter with respect to the object, and an angle direction inclined from the specular reflection direction toward the incident direction is defined as a positive direction,

at least one of angles corresponding to the optical parameters multiplied with a negative weighting coefficient of the weighting coefficient a 1 to a n is an angle in a range from −15° to +45° with respect to the specular reflection direction.

16. The multi-angle colorimeter according to claim 11 , wherein

each of the weighting coefficients b 1 to b n is 1.

17. The multi-angle colorimeter according to claim 11 , further comprising

a display that displays the index B or the summed value, which is calculated by the hardware processor.