DYNAMIC CONTROL OF TRANSMISSION VALUE

Abstract

The disclosure relates to methods, controlling units, eyeglasses, computer programs and computer-readable storage media for controlling an optical transmission of a variable transmission ophthalmic lens. The method includes receiving from a light sensor a measured illuminance of the environment of a wearer, computing a change of illuminance measured during a predetermined time interval, comparing the computed change of illuminance with a first threshold, when the computed change of illuminance is greater than the first threshold, implementing first command configured for varying the transmission of the variable transmission ophthalmic lens from initial transmission value corresponding to a current transmission value to a first target transmission value, according to a first variation profile comprising a first phase during which the transmission overshoots the first target transmission value, and a second phase during which the transmission returns to the first target transmission value.

Claims

1-15. (canceled)

16. A method for controlling an optical transmission of a variable transmission ophthalmic lens, the method being implemented by control circuitry and comprising: receiving, from an ambient light sensor, values of a measured parameter related to an illuminance of an environment of a wearer; computing a change of illuminance from the values of the measured parameter during a predetermined time interval; comparing the computed change of illuminance with a first threshold; and when the computed change of illuminance is greater than the first threshold, implementing a first command configured to vary the transmission of the variable transmission ophthalmic lens from an initial transmission value corresponding to a current transmission value to a first target transmission value, the first command being varied according to a first variation profile including a first phase during which the transmission overshoots the first target transmission value, and a second phase during which the transmission returns to the first target transmission value.

17. The method according to claim 16, further comprising, when the absolute value of the computed change of illuminance is smaller than, or equal to, the absolute value of the first threshold, implementing a second command configured to vary the transmission of the variable transmission ophthalmic lens according to a monotonic variation profile.

18. The method according to claim 16, further comprising, when the absolute value of the computed change of illuminance is smaller than, or equal to, the absolute value of the first threshold, maintaining the transmission value of the variable transmission ophthalmic lens at the initial transmission value.

19. The method according to claim 16, further comprising, when the absolute value of the computed change of illuminance is smaller than, or equal to, the absolute value of the first threshold: comparing the computed change of illuminance with a second threshold, then when the absolute value of the computed change of illuminance is greater than the absolute value of the second threshold, implementing a second command configured to vary the transmission of the variable transmission ophthalmic lens from the initial transmission value to a second target transmission value according to a monotonic variation profile, and when the absolute value of the computed change of illuminance is smaller than, or equal to, the absolute value of the second threshold, maintaining the transmission value of the variable transmission ophthalmic lens at the initial transmission value.

20. The method according to claim 16, wherein the first command includes instructions for varying the transmission of the variable transmission ophthalmic lens over time according to a sum of a standard function and of an overshoot function, the standard function defining a monotonous variation of transmission from the initial transmission value to the first target transmission value, and the overshoot function defining the transmission overshoot value, a duration of an overshoot phase and a duration of a decay phase.

21. The method according to claim 17, wherein the first command includes instructions for varying the transmission of the variable transmission ophthalmic lens over time according to a sum of a standard function and of an overshoot function, the standard function defining a monotonous variation of transmission from the initial transmission value to the first target transmission value, and the overshoot function defining the transmission overshoot value, a duration of an overshoot phase and a duration of a decay phase, wherein the second command comprises instructions for varying the transmission of the variable transmission ophthalmic lens over time according to the standard function.

22. The method according to claim 19, wherein the first command includes instructions for varying the transmission of the variable transmission ophthalmic lens over time according to a sum of a standard function and of an overshoot function, the standard function defining a monotonous variation of transmission from the initial transmission value to the first target transmission value, and the overshoot function defining the transmission overshoot value, a duration of an overshoot phase and a duration of a decay phase, wherein the second command comprises instructions for varying the transmission of the variable transmission ophthalmic lens over time according to the standard function.

23. The method according to claim 20, wherein a different overshoot function is used depending on whether the sign of the computed change of illuminance ΔE1 is positive or negative.

24. The method according to claim 16, wherein the first target transmission value Tf1 is determined as a function of an illuminance.

25. The method according to claim 16, wherein the transmission overshoot value is determined as a function of a difference between the computed change of illuminance and the first threshold.

26. The method according to claim 16, further comprising, after implementing the first command, the transmission function of the variable transmission ophthalmic lens having a temporary value, based on the received measurements, computing a further change of illuminance during a further time interval, comparing the computed further change of illuminance with the first threshold, when the absolute value of the computed further change of illuminance is greater than the absolute value of the first threshold, interrupting the transmission variation resulting of the first command and implementing a third command for varying the transmission of the variable transmission ophthalmic lens from a temporary transmission value to a third target transmission value, and when the absolute value of the computed further change of illuminance is smaller than, or equal to, the absolute value of the first threshold, proceeding with the transmission variation resulting of the first command.

27. The method according to claim 16, wherein the first threshold is based on a physiological parameter of the wearer.

28. An apparatus comprising: control circuitry configured to control an optical transmission of a variable transmission ophthalmic lens by being configured to: receive, from an ambient light sensor, values of a measured parameter related to an illuminance of an environment of a wearer, compute a change of illuminance from the values of the measured parameter during a predetermined time interval, compare the computed change of illuminance with a first threshold, and when the computed change of illuminance is greater than the first threshold, implement a first command configured to vary the transmission of the variable transmission ophthalmic lens from an initial transmission value corresponding to a current transmission value to a first target transmission value, the first command being varied according to a first variation profile including a first phase during which the transmission overshoots the first target transmission value, and a second phase during which the transmission returns to the first target transmission.

29. A pair of eyeglasses intended to be worn by a wearer, the pair of eyeglasses comprising: at least one variable transmission ophthalmic lens; an ambient light sensor configured to measure values of a parameter related to an illuminance of an environment; and control circuitry coupled to the variable transmission ophthalmic lens and to the ambient light sensor, the control circuitry being further configured to control circuitry configured to control an optical transmission of a variable transmission ophthalmic lens by being configured to: receive, from an ambient light sensor, values of a measured parameter related to an illuminance of the environment of the wearer, compute a change of illuminance from the values of the measured parameter during a predetermined time interval, compare the computed change of illuminance with a first threshold, and when the computed change of illuminance is greater than the first threshold, implement a first command configured to vary the transmission of the variable transmission ophthalmic lens from an initial transmission value corresponding to a current transmission value to a first target transmission value, the first command being varied according to a first variation profile including a first phase during which the transmission overshoots the first target transmission value, and a second phase during which the transmission returns to the first target transmission.

30. A non-transitory computer-readable storage medium, storing a computer program that when executed by the computer causes the computer to implement the method according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] For a more complete understanding of the description provided herein and the advantages thereof, reference is now made to the brief descriptions below, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0077] FIG. 1 illustrates an exemplary eyeglass device.

[0078] FIG. 2 depicts a flowchart of a general algorithm of an exemplary software for carrying out a proposed method for controlling the device of FIG. 1.

[0079] FIG. 3 depicts a superimposition of two variation profiles of a transmission function of a variable transmission ophthalmic lens according, respectively, to an exemplary first command and to an exemplary second command.

DETAILED DESCRIPTION OF THE INVENTION

[0080] It is now referred to FIG. 1 which illustrates an exemplary eyeglass device.

[0081] The eyeglass device comprises: [0082] a pair of variable transmission ophthalmic lenses (100) mounted on a spectacle frame, [0083] a light sensor (200) configured to sense a level of visible light, or an illuminance, incoming towards the lenses (100), and [0084] a controlling unit (300) coupled to the light sensor and to the lenses.

[0085] The eyeglass device may comprise one or more power sources (400) for providing electrical power to the lenses (100), to the light sensor (200) and to the controlling unit (300).

[0086] Each lens (100) has a transmission function which is, directly or indirectly, controllable by an electrical command signal.

[0087] For example, each lens (100) may comprise an electrochromic material, which visible light transmission properties are electrically switchable, for instance as a layer placed between two command electrodes. For example, each lens (100) may comprise a thermochromic material, which visible light transmission properties are thermally switchable, associated to an electrical conductor which temperature may be controlled by the passage of an electric current. More generally, each lens (100) may be based on any smart glass technology or combination thereof, such as electrochromic, thermochromic, photochromic, suspended-particle, micro-blind or polymer-dispersed liquid-crystal technologies.

[0088] Light sensors are photoelectric devices that converts light energy of visible light, detected by the device, to electrical energy. Examples include photoresistors, photodiodes, and phototransistors. The light sensor (200) may be mounted on the spectacle frame, such as on the nose bridge, on the lens mount, on a hinge, on an arm, etc. The eyeglass device may comprise one or more additional light sensors (200). For example, the eyeglass device may comprise a pair of identical light sensors (200), each mounted close to a corresponding ophthalmic lens, in order to sense separately the incoming light towards each of the eyeglasses (100). For example, the eyeglass device may comprise a plurality of light sensors (200), each being sensitive to different visible light wavelengths, in order to sense separately blue light and red light for example, in order to apply different control functions to the ophthalmic lenses depending on the spectrum of the incoming visible light.

[0089] The controlling unit (300) may comprise one or more processors operably coupled to one or more memories and to one or more communication interfaces with the lenses (100) and with the light sensor (200). Communication between the controlling unit, the lenses and the light sensor may be wired or wireless.

[0090] At an initial instant the eyeglass device being worn by a wearer, the lenses (100) each have an initial transmission value T.sub.i. The initial transmission value T.sub.i may be preset in accordance with the illuminance of the environment at the initial instant. For example, in a bright environment, the initial transmission value T.sub.i may be preset to a low value, such as 20% or less, in order to dim the incoming light and protect the wearer from glare. For example, in a dark environment, the initial transmission value T.sub.i may be preset to a high value, such as 80% or more, in order to allow the incoming light to pass and enhance the comfort of the wearer.

[0091] It is now referred to FIG. 2 which illustrates an algorithm of a software that may be stored on a memory and executed by a processor of the controlling unit (300) to carry out a method for driving the transmission of the lenses (100).

[0092] The controlling unit (300) obtains REC E (S1), from the light sensor (200), successive measurements of an illuminance of the environment of the wearer over time. The measurements may be collected for example at fixed time intervals dt, such as every second.

[0093] In the context of the disclosure, a measurement of the illuminance indicates a total quantity of incoming light energy, in a predetermined wavelength domain which the light sensor (200) may sense. The predetermined wavelength domain is specific to the light sensor (200) and corresponds to at least a portion of the visible light wavelength domain.

[0094] Each obtained measurement may be stored by the controlling unit as a time-stamped measurement indicating the illuminance of the environment of the wearer at the time of the measurement.

[0095] Based on the obtained measurements, the controlling unit (300) computes CPT ΔE.sub.1 (S2) a change of illuminance ΔE.sub.1=E.sub.cur−E.sub.i between an initial illuminance E.sub.i at the initial instant t.sub.i and a current illuminance E.sub.cur at a current instant t.sub.cur The time interval between the initial instant t.sub.i and the current instant t.sub.cur may comprise an integration time for filtering significative variations of illuminance from glitches.

[0096] The absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 indicates the amplitude of the change.

[0097] The sign of the change of illuminance ΔE.sub.1 indicates whether the illuminance has increased (if the sign is positive) or decreased (if the sign is negative) between the initial instant t.sub.i and the current instant t.sub.cur.

[0098] The controlling unit (300) compares CMP ΔE.sub.1/ΔE.sub.lim1 (S3) the computed change of illuminance with a first threshold ΔE.sub.lim1.

[0099] The first threshold ΔE.sub.lim1 is a preset non-null value corresponding to a limit above which a change of illuminance is considered steep, or brutal.

[0100] The first threshold ΔE.sub.lim1 may be preset for example as an absolute value, or a computed value, for example as a relative value of the initial illuminance.

[0101] The first threshold ΔE.sub.lim1 may be preset for example based on physiological parameters of the wearer, such as sensitivity to glare, average contrast recovery time after glare, pupil size and kinetic.

[0102] The first threshold ΔE.sub.lim1 may be adjusted through interaction with the wearer, possibly based on artificial intelligence, machine learning, deep learning, supervised learning, etc.

[0103] In an example, the first threshold is different whether the change of illuminance ΔE.sub.1 is positive or negative. For instance, a positive value ΔE.sub.lim1+ and a negative value ΔE.sub.lim1− of the first threshold may each be predetermined. Then, the first threshold ΔE.sub.lim1 may be selected as the predetermined value which sign matches the sign of the change of illuminance ΔE.sub.1.

[0104] Based on the result of the comparison, the processing circuit (300) controls the transmission of the lenses according to a different variation profile whether a detected change of illuminance is considered brutal or not.

[0105] More precisely, when the absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 is greater than the absolute value |ΔE.sub.lim1| of the first threshold ΔE.sub.lim1, the controlling unit (300) implements GEN CMD1 (S4) a first command for varying the transmission of the ophthalmic lenses (100).

[0106] The first command allows controlling the transmission of the ophthalmic lenses (100) from the initial transmission value T.sub.i to a first target transmission value T.sub.f1, according to a variation profile comprising a succession of two phases, namely an overshoot phase during which the transmission overshoots the first target transmission value and a decay phase during which the transmission returns towards the first target transmission value.

[0107] On the contrary, the first command is not implemented when the absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 is smaller than, or equal to, the absolute value |ΔE.sub.lim1| of the first threshold ΔE.sub.lim1.

[0108] To sum up, upon detecting a change of illuminance, said change of illuminance is compared to a first threshold to detect if the change is brutal.

[0109] Then, in the case that the change of illuminance is brutal, a first command is implemented to vary the transmission of the ophthalmic lenses.

[0110] Otherwise, the first command is not implemented.

[0111] A possible further course of action is described thereafter in the case that the change of illuminance is smoother. It is thus considered, in this case, the following result of the comparison: the absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 is smaller than, or equal to, the absolute value |ΔE.sub.lim1| of the first threshold ΔE.sub.lim1.

[0112] The controlling unit (300) proceeds with comparing CMP ΔE.sub.1/ΔE.sub.lim2 (S51) the computed change of illuminance with a second threshold ΔE.sub.lim2.

[0113] The second threshold ΔE.sub.lim2 is a preset non-null value which is lower than the first threshold ΔE.sub.lim1.

[0114] Similarly to the first threshold ΔE.sub.lim1, the second threshold ΔE.sub.lim2 may be a preset absolute or relative value, and may also be different depending on the sign of the computed change of illuminance.

[0115] The value of the second threshold ΔE.sub.lim2 may be related to a physiological parameter of the wearer, such as a perception threshold of the wearer.

[0116] For instance, the second threshold may correspond to a limit above which the detected change of illuminance is perceptible by the wearer and requires a compensation by adapting the transmission of the ophthalmic lenses.

[0117] Based on the result of the comparison, the processing circuit (300) may implement a second command and vary the transmission of the lenses.

[0118] More precisely, when the absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 is greater than the absolute value |ΔE.sub.lim2| of the second threshold ΔE.sub.lim2, the controlling unit (300) implements GEN CMD2 (S52) a second command for varying the transmission of the ophthalmic lenses (100).

[0119] The second command allows controlling the transmission of the ophthalmic lenses (100) from the initial transmission value T.sub.i to a second target transmission value T.sub.f2, according to a variation profile not comprising any overshoot phase.

[0120] On the contrary, when the absolute value |ΔE.sub.1| of the change of illuminance ΔE.sub.1 is smaller than, or equal to, the absolute value |ΔE.sub.lim2| of the second threshold ΔE.sub.lim2, no command is implemented.

[0121] To sum up: [0122] if the change of illuminance is brutal, then a first command is implemented to vary the transmission of the ophthalmic lenses, the first command implying overshooting a first target transmission value during an overshoot phase then returning towards the first target transmission value during a decay phase, [0123] if the change if illuminance is perceptible without being brutal, then a second command is implemented to vary the transmission of the ophthalmic lenses, the second command implying reaching a second target transmission value without overshooting said value, and [0124] if the change of illuminance is imperceptible, then no command is implemented and the value of the transmission of the ophthalmic lenses remains equal to the initial transmission value T.sub.i.

[0125] It is now referred to FIG. 3, which illustrates an exemplary illuminance as a function of time as a solid line labeled E.sub.1=f(t).

[0126] It is seen in this example that the level of light intensity varies, during a time interval, from an initial light intensity value to a first light intensity value. Said values may correspond for example to two successive measurements.

[0127] For simplicity's sake, the illumination E is considered to have two stable states during the considered period of time.

[0128] In this example, the first light intensity value is significantly greater than the initial light intensity value, resulting in a brutal light intensity increase during the time interval, thus to a positive value of ΔE.sub.1, greater than the absolute value of the first threshold ΔE.sub.lim1. As a result, a first command is implemented by the controlling unit (300).

[0129] A schematic representation of an exemplary transmission as a function of time according to a first variation profile which results of the implementation of such first command is represented on FIG. 3 as a solid line labeled τ.sub.v=f.sub.EE′t(E,E′,t).

[0130] According to the first variation profile, the transmission value of the ophthalmic lenses (100) varies from the initial transmission value T.sub.i to a first target transmission value T.sub.f1. The first target transmission value T.sub.f1 may for example be determined as a function of a measured illuminance, for instance as a function of the first light intensity value.

[0131] The first variation profile comprises a succession of two phases.

[0132] The first phase is an overshoot phase (11) from the initial transmission value T.sub.i to a transmission overshoot value T.sub.OS exceeding the first target transmission value T.sub.f1.

[0133] Since in this example, the change of illuminance is positive, resulting in the first target transmission value T.sub.f1 being smaller than the initial transmission value T.sub.i, the transmission overshoot value T.sub.OS is smaller than the first target transmission value.

[0134] In another example, not represented, the change of illuminance is negative, resulting in the first target transmission value T.sub.f1 being greater than the initial transmission value T.sub.i. In this other example, the transmission overshoot value T.sub.OS is greater than the first target transmission value.

[0135] In both cases, the variation of transmission during the overshoot phase has the same sign as for attaining the first target transmission value, and a greater amplitude. Formally,

[00001]$\frac{T_{\mathrm{OS}}-T_i}{T_{f1}-T_i}>1.$

[0136] The transmission overshoot value (T.sub.OS) may be determined as a fixed offset from the first target transmission value T.sub.f1. Alternatively, such offset may be determined as a function of a difference between the computed change of illuminance ΔE.sub.1 and the first threshold ΔE.sub.lim1.

[0137] Reaching the transmission overshoot value T.sub.OS corresponds to reaching an inflexion point on the variation profile and marks the start of the second phase.

[0138] The second phase is a decay phase (12) from the transmission overshoot value T.sub.OS to the first target transmission value T.sub.f1. From what precedes, the variation of transmission during the decay phase (12) has a sign opposite to that during the overshoot phase (11).

[0139] The duration of the decay phase may be one or two orders of magnitude greater than the duration of the overshoot phase. For instance, if the overshoot phase lasts a few seconds, the subsequent decay phase may last about a few minutes.

[0140] This succession of the overshoot phase and of the decay phase allows: [0141] cushioning a brutal variation of luminosity by quickly averting the wearer against the risk of immediate glare, then [0142] recovering some dynamic in transmission to get ready for a future brutal variation of luminosity while following the eye adaptation to the light and improving contrast.

[0143] In some embodiments, the first variation profile may be represented as the sum of a standard function and of an overshoot function, [0144] the standard function defining a monotonous variation of transmission from the initial transmission value T.sub.i to the first target transmission value T.sub.f1, and [0145] the overshoot function defining the transmission overshoot value T.sub.OS, a duration of the overshoot phase (11) and a duration of the decay phase (12).

[0146] Formally, this equates to τ.sub.V=f.sub.EE′t(E,E′,t)=f.sub.Et(E,t)+h(E,E′,t), with h(E,E′,t) being a boost function divided in two parts: an overshoot period followed by a decay period.

[0147] h(E,E′,t) may depend (in time, in intensity, in shape . . . ) on the wearer and on some of its specific physiological parameters (ie: sensitivity to glare, average contrast recovery time after glare, pupil size and kinetic, or else) and may be adjusted through interaction with the wearer using AI, machine learning, deep learning, supervised learning, or else.

[0148] h(E,E′,t) may be different depending on the sign of the variation of light intensity, so that different overshoot managements are implemented for darkening and for bleaching.

[0149] Regarding the overshoot period, h(E,E′,t) may tend to zero when the first derivative E′ of the light intensity over time tends to zero, meaning that the amplitude of the overshoot is minimized when the speed of variation of the light intensity is contained.

[0150] The duration of the overshoot period may be predetermined so that the decay period occurs at expiration of a specific time interval.

[0151] The duration of the overshoot period may be predetermined based on specific rules, such as management rules specific to class 4 eyewear in a driving situation for example, and/or according to the amplitude of the change of illuminance ΔE.sub.1 and/or according to previous values of transmission of the ophthalmic lenses (100) prior to detecting the change of illuminance ΔE.sub.1 and/or according to physical limitations of the eyewear, such as the maximal possible bleaching or darkening speed of the ophthalmic lenses (100).

[0152] Regarding the decay period, h(E,E′,t) may tend to zero at an infinite time, meaning that the transmission of the ophthalmic lenses evolves towards the first target transmission value T.sub.f1. The shape of the decay phase may be of a linear type, of an exponential type, of an arctan type, or else.

[0153] An alternate exemplary illuminance as a function of time is illustrated on FIG. 3 as a discontinued line labeled E.sub.1′=f(t).

[0154] In this example, a smoother light intensity increase is detected during the time interval, resulting in a positive value of ΔE.sub.1′, which is greater than the absolute value of the second threshold ΔE.sub.lim2, but smaller than the absolute value of the first threshold ΔE.sub.lim1. As a result, a second command is implemented by the controlling unit (300).

[0155] An exemplary transmission as a function of time according to a second variation profile which results of the implementation of such second command is represented on FIG. 3 as a discontinued line labeled τ.sub.V=f.sub.Et(E,t).

[0156] According to the second variation profile, the transmission value of the ophthalmic lenses (100) varies from the initial transmission value T.sub.i to a second target transmission value T.sub.f2 without overshooting said second target transmission value T.sub.f2.

[0157] For example, the second variation profile may consist of a single monotonic phase (20) according to a standard function defining a monotonous variation of transmission from the initial transmission value T.sub.i to the second target transmission value (T.sub.f2).

[0158] Such a variation profile allows following the eye adaptation to the light without any brutal variation in transmission since there is no risk of immediate glare.

[0159] Therefore, thanks to the selective implementation of the first command and of the second command, it is possible to always provide to the wearer a variation of transmission which is adapted to the current speed of variation of the ambient light intensity.

[0160] In exemplary embodiments, it may be possible to interrupt the implementation of the first command. Triggering such an interruption may be based on a predefined criterion related to detecting a further evolution of the ambient light intensity.

[0161] In an example, the light sensor (200) performs repeated measurements of the ambient light intensity over time and transmits the measurements to the processing circuit (300). It is further considered in this example that an increase in ambient light intensity from an initial value to a first, greater, value has been detected. It is further considered that the processing circuit (300) has determined that the detected increase exceeds a first threshold. As a result, an implementation of a first command has been triggered.

[0162] In this example, it is considered that, at a current instant: [0163] the implementation of the first command is in progress, [0164] the transmission of the ophthalmic lenses (100) has a temporary value, and [0165] a further measurement of the ambient light intensity by the light sensor (200) is obtained by the processing circuit (300) and indicates a second value.

[0166] Based on the second value, it is possible to either confirm that the change of illuminance from the initial value is brutal or, on the contrary, indicate that the first value reflects merely a brief, transient, state, and that the change of illuminance from the initial value to the second value is actually not brutal.

[0167] To do so, the processing circuit may be further configured to compute CPT ΔE.sub.2 (S41) the difference ΔE.sub.2 between the initial value and the second value of light intensity.

[0168] The processing circuit may be further configured to compare CMP ΔE.sub.2/ΔE.sub.lim1 (S42) the computed difference ΔE.sub.2 with the first threshold ΔE.sub.lim1.

[0169] The result of the comparison indicates whether the change of light intensity between the initial value and the second value is brutal or not.

[0170] Then, based on the result of the comparison, the processing circuit (300) may either proceed with the implementation of the first command or interrupt the implementation of the first command.

[0171] More precisely, when the absolute value |ΔE.sub.2| of the change of illuminance ΔE.sub.2 is greater than the absolute value |ΔE.sub.lim1| of the first threshold ΔE.sub.lim1, the controlling unit (300) proceeds PROC CMD1 (S45) with the implementation of the first command for varying the transmission of the ophthalmic lenses (100).

[0172] In such a case, both the variation of light intensity from the initial value to the first value and the variation of light intensity from the initial value to the second value exceed the first threshold. It is thus confirmed that the variation of light intensity is brutal and requires an immediate adaptation of the transmission of the ophthalmic lenses (100) to prevent glare.

[0173] On the contrary, when the absolute value |ΔE.sub.2| of the change of illuminance ΔE.sub.2 is smaller than, or equal to, the absolute value |ΔE.sub.lim1| of the first threshold ΔE.sub.lim1, the controlling unit (300) interrupts INT CMD1 (S43) the implementation of the first command for varying the transmission of the ophthalmic lenses (100).

[0174] In such a case, the variation of light intensity from the initial value to the second value does not exceed the first threshold, and is not considered brutal. As a consequence, the variation of transmission of the ophthalmic lenses (100) may be performed without an overshoot.

[0175] In such a case, the controlling unit (300) further generates GEN CMD3 a third command (S44) for varying the transmission of the ophthalmic lenses (100) from the temporary transmission value to a third target transmission value.

[0176] The third target transmission value is determined based on the second value of light intensity. For example, if the absolute value |ΔE.sub.2| of the change of illuminance ΔE.sub.2 is smaller than, or equal to, the absolute value |ΔE.sub.lim2| of the second threshold ΔE.sub.lim2, then this means that the change of illuminance ΔE.sub.2 does not require a variation of transmission from the initial value. In such a case, the third target transmission value is set at the initial transmission value T.sub.i.