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EP-3721288-B1 - METHOD AND SYSTEM FOR SELECTING A COLOR FILTER, OPTICAL ARTICLE COMPRISING SUCH A COLOR FILTER

EP3721288B1EP 3721288 B1EP3721288 B1EP 3721288B1EP-3721288-B1

Inventors

  • ALLARD, Rémy
  • SILVESTRE, Daphné
  • CHENGUITI, Yannis

Dates

Publication Date
20260506
Application Date
20181206

Claims (12)

  1. Method for selecting a color filter intended to be worn by a subject in order to improve his/her visual performance for a given visual task to be realized in a given environment, said method using a system and comprising the steps of: - submitting, by a display means of the system, said subject to a colored spatio-temporal visual stimulus adapted to evaluate said visual performance for said given visual task, said visual stimulus being designed to stimulate differently the M- and L-cones stimulation pathways of the eyes of the subject and so that its chromaticity may be modified, the chromaticity of the visual stimulus taking at least two distinct values, each chromaticity being uniform ; - evaluating, by an evaluating means of the system, the visual performance of the subject based on his/her visual perception of said visual stimulus; and - selecting, by a selecting means of the system, said color filter based on the results of said evaluation of the visual performance, the selected color filter optimizing the visual perception of said visual stimulus, wherein the visual stimulus VS presented to the subject is of the form: VS(x,y,t,λ) = C(λ) * L(x,y,t), where: - C(λ) is the spectral density of the visual stimulus; and - L(x,y,t) represents the spatial and temporal luminance profiles of the visual stimulus, said spectral density C(λ) of the visual stimulus is such as C(λ) = w 1 *C 1 (λ) + w 2 *C 2 (λ), where: - C1(λ) and C 2 (λ) are different spectra designed to stimulate differently the L- or M-cones stimulation pathways of the eyes of the subject; and - w 1 and w 2 are respective weights of said spectra.
  2. Method according to claim 1, wherein the visual stimulus is designed so that, while its global chromaticity is modified during the submission step, its spatial and temporal luminance profiles are unchanged.
  3. Method according to anyone of claims 1 to 2, wherein the spatial and temporal luminance profiles of the visual stimulus are predetermined according to the subject's need for the given visual task.
  4. Method according to anyone of claims 1 to 3, wherein it further comprises a comparison step consisting in comparing at least one of said visual performance evaluation results with a predetermined reference value, the selection of said color filter being further based on the result of this comparison.
  5. Method according to claim 4, wherein, at the selection step: - when the result of the comparison shows that the visual performance of the subject is improved, one chooses said color filter as having a spectral response T λ so that the spectral content C E (λ) of the environment surrounding the subject seen through said color filter is globally conform to said spectral density C(λ) of the visual stimulus during the corresponding submission step; and - when the result of the comparison shows that the visual performance of the subject is degraded, one chooses another color filter.
  6. Method according to claim 5, wherein the color filter is chosen so that the L-/M- cones excitation ratio of the subject when he/she sees the given environment through said filter is substantially equal to his/her L-/M- cones excitation ratio when he/she is submitted to the relevant visual stimulus during the corresponding submission step.
  7. Method according to anyone of claims 1 to 6, wherein the selection step further takes into account the spectral content of said given environment.
  8. Method according to anyone of claims 4 to 7 in dependence of claim 4, wherein the predetermined reference value is a value of visual performance previously evaluated using said selection method.
  9. Method according to anyone of claims 1 to 8, wherein the evaluated visual performance is one of the following: - spatial and/or temporal contrast sensitivity; - visual acuity; - chromatic sensitivity; - spectral sensitivity; - critical fusion frequency; and/or - reading or driving ability.
  10. Method according to anyone of claims 1 to 9, wherein said visual stimulus is generated by a color display.
  11. Method according to anyone of claims 1 to 9, wherein, at evaluation step, the visual performance is evaluated by using a test chart illuminated by ambient light source, the spectral density of said ambient light source being modified during the submission step.
  12. System for selecting a color filter intended to be worn by a subject in order to improve his/her visual performance for a given visual task to be realized in a given environment, said system comprising: - display means configured to submit said subject to a colored spatio-temporal visual stimulus adapted to evaluate said visual performance for said given visual task, said visual stimulus being designed to stimulate differently the M- and L-cones stimulation pathways of the eyes of the subject and so that its chromaticity may be modified, the chromaticity of the visual stimulus taking at least two distinct values, each chromaticity being uniform; - evaluation means for evaluating the visual performance of the subject based on his/her visual perception of said visual stimulus displayed to the subject; - selection means for selecting said color filter based on the results of said evaluation of the visual performance performed by the evaluation means, the selected color filter optimizing the visual perception of said visual stimulus, wherein the visual stimulus VS presented to the subject is of the form: VS(x,y,t,λ) = C(λ) * L(x,y,t), where: - C(λ) is the spectral density of the visual stimulus; and - L(x,y,t) represents the spatial and temporal luminance profiles of the visual stimulus, said spectral density C(λ) of the visual stimulus is such as C(λ) = w 1 *C 1 (λ) + w 2 *C 2 (λ), where: - C1(λ) and C 2 (λ) are different spectra designed to stimulate differently the L- or M-cones stimulation pathways of the eyes of the subject; and - w 1 and w 2 are respective weights of said spectra.

Description

TECHNICAL FIELD OF THE INVENTION The invention pertains to the domain of optometry and to the selection of a chromatic filter according to the wearer's sensitivity. More precisely, the invention relates to a method for selecting a color filter intended to be worn by a subject in order to improve his/her visual performance for a given visual task to be realized in a given environment. The invention also proposes an optical article comprising a color filter chosen using such a selection method. Another object of the invention is to provide a system for selecting a color filter using said selection method. BACKGROUND INFORMATION AND PRIOR ART It is well known in the art of ophthalmic filters that color, also known as "chromatic", filters can improve, or degrade, the visual sensitivity of a wearer of this color filter, depending on the environment conditions (luminance levels, spectral content of surrounding lighting, spatial and/or temporal frequencies), visual task (reading, driving, ...) and observer's factors (e.g. age, ethnicity, pathologies, ...). Usually, the color of a filter is chosen subjectively by the wearer among many possible color filters according to wearer's qualitative judgment or belief: preferred perception, aesthetic consideration, belief in enhanced vision (e.g. orange for fog and brown for sunny days). However, the correlation between qualitative preference and visual performance is low. It is known from document US2013/176534A1, a method for adaptively determining a model of visual performance of a test subject. It is also known from document Rabin Jeff et AL "Rapid quantification of color vision: the cone contrast test" a method based on the cone contrast test. It is also known from document WO2016/148984A1, an optical filter that provides regulation and/or enhancement of chromatic and luminous aspects of the color appearance of light to human vision. A document in this field is WO2017/194898A1. Therefore, the true needs of the wearer for a given visual task is often not (or little) considered to optimize his/her visual performance for this task in a given environment. In other words, there is no objective quantification of visual performance to select optimal color filter. SUMMARY OF THE INVENTION Therefore one object of the invention is to provide a solution for optimizing the spectrum prescription in order to select the optimal color filter for specific visual functions and conditions. A further object of the invention is to provide a color filter selection method which can reduce the subjective appreciation of color filters and to guide color filter prescription to optimize contrast sensitivity by choosing the best chromaticity for each wearer. The above objects are achieved according to the invention by providing a method as claimed in claim 1. The method is a method for selecting a color filter intended to be worn by a subject in order to improve his/her visual performance for a given visual task to be realized in a given environment, said method comprising the steps of: submitting said subject to a colored spatio-temporal visual stimulus adapted to evaluate said visual performance for said given visual task, said stimulus being designed so that its chromaticity may be modified, the chromaticity of the visual stimulus taking at least two distinct values, each chromaticity being uniform;evaluating the visual performance of the subject based on his/her visual perception of said visual stimulus, the chromaticity of the visual stimulus taking at least two distinct values, each chromaticity being uniform; andselecting said color filter based on the results of said evaluation of the visual performance. The above "chromaticity" of the visual stimulus is defined as a colorimetric quantity according to CIE 1931 color space (CIE stands for "Commission Internationale de l'Éclairage"): it basically represents the "color sensation" of the eye, i.e. the eye's response to a specific colored visual stimulus, i.e. a colored visual stimulus having a specific spectral density or spectral power distribution. It should be stressed that two distinct colored visual stimuli, hence having different spectral densities, may cause the same response from the eye of the subject, that is the same color sensation. This phenomenon is called metamerism. It is understood by the term "metamerism", a perceived matching of the colors with different spectral power distributions. Despite CIE standard, the perceived chromaticity of a visual stimulus is personal and depends on individual physiology of color perception. For instance, the actual spectral sensitivity of different retinal photoreceptors (short S, medium M or long L), or how information from these photoreceptors are combined in retina and brain. In the same manner, the chromaticity at which the visual performance is optimal varies from one person to another. This is why we assess visual skill for different uniform chromaticity to select the best chromatic filt