US-12619107-B2 - Photography and thermography combining method of obtaining a fitting parameter to fit an ophthalmic lens into a spectacle frame

US12619107B2US 12619107 B2US12619107 B2US 12619107B2US-12619107-B2

Abstract

A photography and thermography combining method of obtaining, for a chosen spectacle frame model of a spectacle wearer, at least one fitting parameter to fit an ophthalmic lens into the spectacle frame model. The method includes taking a photograph of the wearer's face with spectacles having the chosen spectacle frame model, taking a thermogram of the wearer's face with the spectacles, identifying the spectacles' contour in the thermogram, overlaying the identified contour or a boxing shape derived from the identified contour onto the photograph, thus obtaining a composite image, and obtaining the at least one fitting parameter from the composite image.

Inventors

Stéphane Perrot
Shuang DING

Assignees

ESSILOR INTERNATIONAL

Dates

Publication Date: 20260505
Application Date: 20220525
Priority Date: 20210528

Claims (15)

1 . A photography and thermography combining method of obtaining, for a chosen spectacle frame model of a spectacle wearer, at least one fitting parameter to fit an ophthalmic lens into the spectacle frame model, the method comprising: a. taking a photograph of the wearer's face with spectacles having the chosen spectacle frame model; b. taking a thermogram of the wearer's face with said spectacles; c. identifying the spectacles' contour in the thermogram; d. overlaying 1) the identified contour, or 2) a boxing shape derived from the identified contour onto the photograph, thus obtaining a composite image; and e. obtaining the at least one fitting parameter from the composite image.
2 . The method of claim 1 , wherein at least c) is carried out by a computer-implemented image processing algorithm.
3 . The method of claim 2 , wherein, when carrying out c), the image processing algorithm comprises: i) converting the thermogram into a binary image by classifying each of the thermogram's pixels into a first pixel category if the pixel's intensity is above a predetermined threshold, or into a second pixel category if the pixel's intensity is below the predetermined threshold; and ii) identifying the spectacles' contour in the binary image by edge detection.
4 . The method of claim 3 , wherein, when carrying out c), the image processing algorithm comprises, after i) and prior to ii), assigning pixel clusters in the binary image of one pixel category, which are below a predetermined size, to the other pixel category.
5 . The method of claim 3 , further comprising detecting a face boundary in the photograph, and wherein, when carrying out c), the image processing algorithm comprises, after i) and prior to ii), assigning all pixels in the binary image, which belong to the second pixel category and are located outside the face boundary, to the first pixel category.
6 . The method of claim 3 , further comprising identifying eyes region in the photograph, and wherein, when carrying out c), the image processing algorithm applies i) only to a part of the thermogram that corresponds to the identified eyes region.
7 . The method of claim 2 , wherein at least a part of the image processing algorithm is based on supervised machine learning.
8 . A non-transitory computer-readable storage medium including computer executable instructions, wherein the instructions, when executed by a computer, cause the computer to perform the method according to claim 2 .
9 . The method of claim 1 , wherein, in 1) of d), d) involves detection of a same section of a spectacle frame in both the photograph and the identified contour, and using the detected frame section for positioning the identified contour on the photograph.
10 . The method of claim 1 , wherein the obtained at least one fitting parameter is a measure of a position of the wearer's eyes relative to the spectacles.
11 . A non-transitory computer-readable storage medium including computer executable instructions, wherein the instructions, when executed by a computer, cause the computer to perform the method according to claim 1 .
12 . The method of claim 1 , wherein, in 1 ) of d), d) involves detection of a frame bridge of a spectacle frame in both the photograph and the identified contour, and using the detected frame bridge for positioning the identified contour on the photograph.
13 . The method of claim 1 , wherein the obtained at least one fitting parameter is a fitting height.
14 . An electronic device for obtaining, for a chosen spectacle frame model of a spectacle wearer, at least one fitting parameter to fit an ophthalmic lens into the spectacle frame model, the device comprising: a photographic camera configured to take a photograph of the wearer's face with spectacles having the chosen spectacle frame model; a thermographic camera configured to take a thermogram of a wearer's face with said spectacles; a memory storing an image processing algorithm comprising: i) identifying the spectacles' contour in the thermogram; ii) overlaying the identified contour or a boxing shape derived from the identified contour onto the photograph, thus obtaining a composite image; and iii) obtaining the at least one fitting parameter from the composite image; and a processor configured to execute the image processing algorithm stored in the memory.
15 . The electronic device of claim 14 , wherein the electronic device is a smartphone, a tablet or a measuring instrument dedicated for eye care professionals.

Description

TECHNICAL FIELD This disclosure generally pertains to the field of ophthalmic optics. More precisely, the present disclosure relates to the manufacturing, ordering and adjustment of spectacle frames as well as the exact mounting of spectacle lenses into spectacle frames. BACKGROUND ART Document WO 2020/064755 A1 discloses a method of determining the fitting height of a spectacle frame for a given wearer, cf. in particular page 16, lines 4 ff., as well as FIGS. 2 and 4. In this method, a photograph of the wearer's head 50 with the chosen spectacle frame is taken using the camera 12 of a smart phone 10. The fitting height is then determined by measuring, in the taken photograph, the distance between the centre of one pupil and the bottom edge of the frame or of the corresponding lens. This method has the drawback that it is sometimes difficult to clearly identify said bottom edge in the photograph. Indeed, under poor lighting conditions and/or in case of little contrast between skin colour and frame colour, a given spectacle frame is barely visible in the photograph. This problem is even worse with spectacles that have a rimless frame where one must identify the bottom edge of a transparent lens. Further background art is mentioned in the citation list at the end of the present description. SUMMARY It is therefore an object of the present disclosure to provide a more robust photographic method of obtaining fitting parameters. According to the present disclosure, this object is achieved with a photography and thermography combining method of obtaining, for the chosen spectacle frame model of a spectacle wearer, at least one fitting parameter to fit an ophthalmic lens into the spectacle frame model, the method comprising the following steps: a) taking a photograph of the wearer's face with spectacles having the chosen spectacle frame model;b) taking a thermogram of the wearer's face with said spectacles;c) identifying the spectacles' contour in the thermogram;d) overlaying 1) the identified contour or 2) a boxing shape derived from the identified contour onto the photograph, thus obtaining a composite image;e) obtaining the at least one fitting parameter from the composite image. Indeed, by not only taking a photograph but also a thermogram, one obtains a much better image of the outline of the spectacles. This is because the thermal infrared radiation, which is emitted by the whole face of the spectacle wearer, is blocked in the facial regions that are covered by the spectacles. Accordingly, in the thermogram, the outline of the spectacles appears clearly and can be easily derived therefrom. The following features can be optionally implemented, separately or in combination: at least step c) is carried out by a computer-implemented image processing algorithm;when carrying out step c), the image processing algorithm comprises the steps of, i) converting the thermogram into a binary image by classifying each of the thermogram's pixels into a first pixel category if the pixel's intensity is above a predetermined threshold, or into a second pixel category if the pixel's intensity is below the predetermined threshold, ii) identifying the spectacles' contour in the binary image by edge detection;when carrying out step c), the image processing algorithm comprises the further step of, after step i) and prior to step ii), assigning pixel clusters in the binary image of one pixel category, which are below a predetermined size, to the other pixel category;detecting the face boundary in the photograph, and wherein, when carrying out step c), the image processing algorithm comprises the further step of, after step i) and prior to step ii), assigning all pixels in the binary image, which belong to the second pixel category and are located outside the face boundary, to the first pixel category;identifying the eyes region in the photograph, and wherein, when carrying out step c), the image processing algorithm applies step i) only to the part of the thermogram that corresponds to the identified eyes region;at least a part of the image processing algorithm is based on supervised machine learning;in alternative 1) of step d), step d) involves the detection of the same section of the spectacle frame, such as the frame bridge, in both the photograph and the identified contour, and using the detected frame section for positioning the identified contour on the photograph;the obtained at least one fitting parameter is a measure of the position of the wearer's eyes relative to the spectacles, such as the fitting height. The present disclosure also relates to an electronic device for obtaining, for the chosen spectacle frame model of a spectacle wearer, at least one fitting parameter to fit an ophthalmic lens into the spectacle frame model, the device comprising: a photographic camera adapted for taking a photograph of the wearer's face with spectacles having the chosen spectacle frame model;a thermographic camera adapted for taking a