METHOD FOR CHARACTERIZING THE APPEARANCE OF A PARTICULAR OBJECT, FOR PREDICTING THE APPEARANCE OF AN OBJECT, AND FOR MANUFACTURING AN OBJECT HAVING A PREDETERMINED APPEARANCE WHICH HAS OPTIONALLY BEEN DETERMINED ON THE BASIS OF A REFERENCE OBJECT

• US 6,788,413 B2
• Filed: 11/09/2001
• Issued: 09/07/2004
• Est. Priority Date: 11/20/2000
• Status: Expired due to Term

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: Dow Global Technologies, Inc. (Dow, Inc.)
• Inventors: Dedeyne, Evelien M., Goethals, Eric G., Brands, Gerrit J., Torfs, Jan C.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): LAUCHMAN, LAYLA G
• Application Number:
  US09/990,687
• Publication Number:
  US 20020118357A1
• Time in Patent Office: 1,033 Days
• Field of Search: 356/402, 356/408, 356/421, 356/422, 356/425
• US Class Current: 356/408
• CPC Class Codes: G01J 3/504 Goniometric colour measurements, for example measurements of metallic or flake based paints
• CPC Class Codes: G01N 21/25 Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
• CPC Class Codes: G01N 21/57 Measuring gloss

Abstract

The surface contribution to appearance of an object is characterized using a plurality of viewing and illumination angles. The color determining and surface contribution are determined to aid in the predicting of the appearance of an object as well as matching an object to another object.

Claims

1. A method for characterizing a surface contribution to an object'"'"'s appearance;

the method comprising determining from the object surface reflection values k₁(w,h,i), from a plurality of reflectance values R_m(w,h,i) which are established for at least one light frequency (w) and a plurality of combinations of viewing (h) and illumination (i) angles.

2. The method according to claim 1 wherein the surface reflection values k₁(w,h,i), are calculated from at least two different reflectance values R_m(w,h,i) established for a predetermined combination of viewing and illumination angles using directional light.

3. The method of claim 1 wherein k₁(w,h,i) values are calculated from idealized reflectance value(s) R_i(w) for light frequency or frequencies (w), and the measured reflectance values R_m(w,h,i) using a color theory equation.

4. The method of claim 3 wherein the color theory equation has been assumed to be independent of the viewing and illumination angles and defines a relation between the idealized reflectance value(s) R_i(w), a viewing and illumination angle-independent surface reflection value(s) k₁(w), and reflectance value(s) R_m(w) which are measurable independently of the viewing and illumination angles, with k₁(w,h,i) being calculated by substituting one occurrence of k₁(w) with k₁(w,h,i) and replacing R_m(w) with R_m(w,h,i) in this equation, and subsequently calculating k₁(w,h,i) from this equation.

5. The method of claim 4 characterized in that each surface reflection value k₁(w,h,i) is calculated by solving k₁(w,h,i) from said equation for each value of R_m(w,h,i) and the value(s) of R_i(w).

6. The method of claim 4 wherein the object has a black color.

7. A method for predicting an appearance of an object wherein the method comprises predicting the appearance of the object at predetermined viewing (h) and illumination (i) angles and at least one light frequency (w) based on color determining parameters of the material from which the object is manufactured and a plurality of surface reflection values k₁(w,h,i) that represent a surface contribution to the appearance for a predetermined plurality of combinations of viewing and illumination angles and at least one light frequency (w).

8. The method according to claim 7 wherein, an idealized reflectance value R_i(w) of the object is calculated based on the color determining parameters of the material from which the object is manufactured and subsequently a prediction of observed appearances for the object as viewed at a plurality of combinations of viewing and illumination angle(s) by calculating a plurality of reflectance values R_p(w,h,i) using the viewing and illumination angle(s), the reflectance value R_p(w,h,i) being calculated using an equation from a color theory, the equation being assumed to be independent of the viewing and illumination angles and defining a relation between the idealized reflectance value R_i(w), an angle-independent surface reflection k₁(w) and an angle-independent reflectance value R_p(w), with R_p(w,h,i) being calculated at a combination of viewing and illumination angles and by setting R_p(w,h,i) equal to R_p(w) and replacing one k₁(w) with k₁(w,h,i) in this equation and by subsequently solving R_p(w,h,i) from this equation using the idealized reflectance R_i(w) and the surface reflection k₁(w,h,i).

9. The method according to claim 8 wherein the values of k₁(w,h,i) are determined from a test object manufactured from a material and with a surface texture corresponding to the kind of material and predetermined surface texture of a sample object to be made in a later stage.

10. The method according claim 9 wherein an appearance of the sample object is predicted at a plurality of combinations of predetermined viewing and illumination angles based on the color determining parameters of the material from which the sample object is manufactured and the plurality of reflection values k₁(w,h,i) obtained from the test object for a plurality of combinations of viewing and illumination angles.

11. The method according to claim 10 wherein the plurality of surface reflection values k₁(w,h,i) obtained from the test object are respectively determined from a plurality of corresponding reflectance values R₁(w,h,i) of the test object.

12. The method of claim 11 wherein the test object has a black color.

13. A method for matching an appearance of an object with a reference object;

the method comprising the steps of;

(a) measuring or otherwise selecting reflectance values Rm_ref(w,h,i) of the reference object using at least one light of frequency (w) and a plurality of predetermined viewing angles (h) and illumination angles (i);

(b) measuring reflectance values R_mtest(w,h,i) of a test object manufactured by a pre-selected method from a pre-selected material having a pre-selected amount and type of colorant(s) and/or other additive(s);

(c) calculating values for a surface contribution to appearance k₁(w,h,i) of the test object from reflectance values Rm_test(w,h,i);

(d) making a sample object with predicted reflectance values R_p(w,h,i) by selecting a surface texture similar to that of the test object and characterized by k₁(w,h,i) values and a composition such that R_p(w,h,i) values that are predicted to be similar to R_ref(w,h,i) values;

(e) comparing the reflectance values measured on the sample object from step (d) with those the reference object; and

(f) repeating, as desired, steps (b), (c), (d), and (e) changing the surface texture the amount or type of colorants, other additives or manufacturing process until the appearance match between the first and second object is acceptable.

14. The method according to claim 13 wherein the test object in step (b) has a black color.

15. The method of claim 13 wherein the surface reflection values k₁(w,h,i) of the test object are determined based on a preselected material and surface texture.

16. The method according to claim 13 wherein a test object is manufactured from a preselected material and surface texture and the value(s) k₁(w,h,i) for the viewing and illumination angle(s) is calculated by solving k₁(w,h,i) for each value of R_m(w,h,i) and an idealized reflectance value R_i(w) from a color theory equation that has been assumed to be independent of viewing and illumination angles and that defines a relation between R_i(w), a viewing and illumination angle-independent surface reflection k₁(w), and a reflectance value R_m(w) which is measurable independently of the viewing and illumination angles, where k₁(w,h,i) substitute for k₁(w) in one occurrence and R_m(w) is replaced by R_m(w,h,i) in the equation.

17. The method according to claim 13 wherein the surface reflection values k₁(w,h,i) do not change in step (f).

18. The method according to claim 13 wherein the material does not change in step (f).

19. The method of claim 13 wherein:

step (c) comprises the steps of calculating an idealized reflectance value R_i(w) of the test object using an equation from a color theory, independent of the viewing and illumination angles h,i, using color determining parameters of the material from which the test object is manufactured that are dictated by what material and added colorants and/or other additives comprise the test object, and

step (d) comprises calculating R_p(w,h,i,) using an equation from a color theory, which equation has been assumed to be independent of the viewing and illumination angles and that defines a relation between the idealized reflectance value(s) R_i(w), angle-independent surface reflection value(s) k₁(w) and angle-independent reflectance value(s) R_p(w) such as it would be measured, with R_p(w,h,i) being determined using this equation by setting R_p(w,h,i) equal to R_p(w) and one k₁(w) is changed to k₁(w,h,i) in this equation and by subsequently solving R_p(w,h,i) from this equation on the basis of the idealized reflectance value(s) R_i(w) and the surface reflection k₁(w,h,i).

20. The method of claim 19 wherein the color determining parameters are calculated from absorption coefficient K_pol and scattering coefficient S_pol of a polymer comprising an object and absorption coefficient K_pig and scattering coefficient S_pig colorants and/or other additives comprising an object, wherein the object is the test object for step (c) and the sample object for step (d).

21. The method of claim 19 wherein the R_mref(w,h,i) values are determined from a reference object.

22. The method of claim 19 wherein the method is carried out for a plurality or a range of values for the frequency (w).

23. The method of claim 13 wherein the sample object is transparent or translucent.