Lamp and corresponding control method

Abstract

The invention relates to a lamp (1), in particular a portable lamp such as a headlamp, comprising: - one or more light sources (2), intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors (6), and - a control circuit (8). The control circuit (8) is configured to increase the emitted light intensity (IE) to a first intensity value, when: - the detected light intensity (IC) is less than a determined threshold after having been greater than or equal to said determined threshold for a duration greater than or equal to a first determined duration, and - the emitted light intensity (IE) is less than said first value.

Description

Description Title of the invention: Lamp and corresponding control method Technical Field

[0001] The present invention relates to the field of sports equipment and in particular to the field of individual lighting. More particularly, the present invention relates to portable lamps, in particular headlamps. Prior art

[0002] There are already headlamps which include, in addition to the lighting means, a brightness sensor and means for controlling the lighting means, making it possible to adjust the brightness emitted by the lighting means according to the brightness received by the sensor.

[0003] Document US 6,966,668 discloses a lamp with a sensor, in which the power of the lamp is notably reduced, in proportion, when the intensity of the light captured by the sensor increases. The purpose of such a lamp is to limit energy consumption, by reducing the power of the lamp when external conditions allow it.

[0004] However, such a lamp does not always give satisfaction, especially when the ambient intensity illuminates the user of the lamp more than the area he is looking at. In such a case, not only is the user dazzled by the ambient brightness, but in addition the area illuminated by the lamp is less illuminated, which makes it even less visible to the user.

[0005] In document FR 2 930 706, the lamp measures, via a sensor, the reflection of the light emitted by an object more or less close to the user, and accordingly adapts the power of the lamp so that the intensity of the light reflected towards the user corresponds to the lighting level desired by the user, without the user needing to change the lighting mode of the lamp.

[0006] Such a lamp makes it possible in particular to avoid self-dazzling of the user when they are faced with a reflective object such as a map.

[0007] Document FR 2 792 594 concerns a lamp comprising in particular a control module with an image sensor: an image of an illuminated area is generated in order to determine the appropriate control signal for the lamp.

[0008] However, such lamps still have a limited autonomy, the reduction of light power being restricted to situations during which the user finds himself facing an object reflecting the light from the lamp in the direction of the sensor. Statement of the invention

[0009] The present invention aims to solve the various technical problems stated above. In particular, the present invention aims to provide a lamp, in particular a headlamp, allowing for improved battery life while maintaining the same comfort of use for the user. The present invention aims in particular to provide a lamp, in particular a headlamp, taking into account the physiology of the user to increase its battery life.

[0010] Thus, according to one aspect, a lamp is proposed, in particular a portable lamp such as a headlamp, comprising: - one or more light sources, preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors for detecting light arriving at said one or more sensors, the lamp also comprising a control circuit configured to modify the intensity of the light emitted by the one or more light sources as a function of the intensity of the light detected by the one or more sensors.

[0011] The control circuit is configured to increase the intensity of light emitted to a first intensity value, : - when the detected light intensity is lower than a threshold determined after have been greater than or equal to said determined threshold for a duration greater than or equal to a first determined duration, for example greater than or equal to 0.5 seconds, preferably 1 second and more preferably 5 seconds, and - when the intensity of light emitted is less than said first value.

[0012] The lamp according to the present invention takes into account the adaptation of the eye to brightness, to modify the intensity of the light sources. More precisely, the lamp according to the present invention is configured to identify glare of the user, then to increase the light intensity of the light sources when this glare is over. The intensity of the lamp therefore adapts to the sensitivity of the eye, in particular when the latter has just been dazzled and is therefore less sensitive to light: the intensity of the lamp is then increased at the end of the glare, to compensate for such a drop in sensitivity of the eye. On the other hand, and in order to limit the energy consumption of the lamp, such an increase in the intensity of the lamp is only provided at the end of the glare of the user, and for a limited duration corresponding to the duration of visual adaptation (or retinal habituation) of the user.This limits the energy consumption of the lamp, without reducing the comfort of use for the user.

[0013] Glare is defined, in the present invention, by detected light above a determined threshold, for a determined duration, i.e. a temporary, or momentary, increase in the detected light. The determined threshold and duration are chosen to correspond substantially to a stimulus causing a physiological adaptation of the user's eye, for example a pupillary reaction. During the duration of the glare, i.e. at the start of the eye's adaptation and after the eye has adapted to the glare, the lamp control can remain unchanged. It is only when the control circuit detects the end of the glare, in this case when the detected brightness falls below the determined threshold again, that the intensity of the lamp is modified and increased to compensate for the loss of sensitivity linked to glare.

[0014] Furthermore, adapting the intensity of the lamp to glare also implies that the intensity of the lamp is not at a maximum value, so as to be able to allow an increase in the intensity of the lamp. Thus, the lamp provides that the intensity of the light emitted, before or during glare, is lower than the value emitted after glare. In other words, the control circuit is configured to increase the intensity of light emitted to a first intensity value, in particular when the intensity of light emitted was lower than said first value before and / or during the increase in the intensity of light detected above said determined threshold.

[0015] Preferably, the control circuit is also configured to reduce the intensity of light emitted from said first value to a second value when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the intensity of light detected is: - below the said determined threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

[0016] As indicated previously, the increase in the intensity of the lamp is only provided from the end of the glare, and for a period corresponding substantially to the user's visual adaptation period. Indeed, once the glare is over, the user's eye will again adapt to the decrease in brightness, for example by pupillary reaction, to become more sensitive to light. The control circuit is thus configured to reduce the intensity emitted by the lamp, when the detected light has remained below the determined threshold, for a second determined duration, or when the brightness peaks occurring during the second determined duration have remained sufficiently short not to cause a corresponding reaction from the user's eye.

[0017] Reducing the intensity of the lamp thus leads to better battery life, while remaining barely noticeable to the user whose eye sensitivity increases at the same time as the intensity of the lamp decreases.

[0018] Preferably, the control circuit is configured to decrease the intensity of light emitted from said first value to said second value, while maintaining said intensity at a third intensity value between said first value and said second value, for a third determined duration.

[0019] It is possible to provide a specific lighting intensity in the event of glare, for example a maximum intensity. In this case, when the light intensity decreases after the second determined period, the intensity of the lamp can be initially reduced to an initial value, for example the user's set value or the value of the intensity emitted before glare, or even the value of the intensity emitted before increase. Then, after a third determined period, the intensity emitted can be reduced again, below this initial value, to continue to adapt to the user's visual sensitivity and save energy consumed.

[0020] Preferably, the control circuit is configured to reduce the intensity of light emitted from said first value to a second value, for a fourth determined duration, for example less than or equal to 10 minutes, preferably 5 minutes and more preferably less than 3 minutes.

[0021] The decrease in the intensity emitted by the lamp can be planned to take place over a fourth duration, more or less long, corresponding substantially to the simultaneous increase in the user's visual sensitivity.

[0022] Preferably, the control circuit is also configured to maintain the intensity of light emitted at said second value, when the detected light intensity is: - below the said determined threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

[0023] Here again, and in order to limit the energy consumption of the lamp, the increase in the emitted intensity is not systematically triggered as soon as the detected brightness exceeds a threshold, but only when the detected brightness exceeds a threshold for a determined duration. It is in fact not useful to increase the luminous intensity of the lamp if the user's eyes have not had time to adapt to very brief strong brightness. The control circuit thus adjusts the control of the intensity of the lamp according to the physiological response of the user.

[0024] Preferably, the second intensity is less than or equal to 40% of the first intensity of light emitted, preferably 30% and more preferably 20%.

[0025] The reduction in light intensity can represent 60 to 80% of the lamp's light intensity, compared to the user's initial setting. The energy savings are therefore significant for a relatively low impact on the user.

[0026] According to another aspect, there is also provided a method of controlling a lamp, in particular a portable lamp such as a headlamp, comprising: - one or more light sources, preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors for detecting light arriving at said sensor(s), wherein the intensity of the light emitted by the light source(s) is modified as a function of the intensity of the light detected by the sensor(s).

[0027] According to the method, the intensity of the emitted light is increased to a first intensity value: - when the detected light intensity is lower than a determined threshold after having been greater than or equal to said determined threshold for a duration greater than or equal to a first determined duration, for example greater than or equal to 0.5 seconds, preferably 1 second and more preferably 5 seconds, and - when the intensity of light emitted is less than said first value.

[0028] In particular, the emitted light intensity may be increased to a first intensity value when the emitted light intensity is lower than said first value before and / or during the increase in the detected light intensity above said determined threshold.

[0029] Preferably, the intensity of light emitted is reduced from said first value to a second value when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the intensity of light detected is: - below the said determined threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

[0030] Preferably, the intensity of light emitted is reduced from said first value to a second value, for a fourth determined duration, for example less than or equal to 10 minutes, preferably 5 minutes and more preferably less than 3 minutes.

[0031] Preferably, the intensity of light emitted is maintained at said second value, when the intensity of light detected is: - below the said determined threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

[0032] According to another alternative or complementary aspect, a lamp is also proposed, in particular a portable lamp such as a headlamp, comprising: - one or more light sources, preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors for detecting light arriving on said or said sensors, the lamp also comprising a control circuit configured to modify the intensity of the light emitted by the light source(s) as a function of the intensity of the light detected by the sensor(s).

[0033] The control circuit is configured, in particular in permanent operating mode of the lamp, to reduce the intensity of light emitted to a second intensity value, when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the detected light intensity is: - below a specific threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

[0034] According to another alternative or complementary aspect, there is also proposed a method for controlling a lamp, in particular a portable lamp such as a headlamp, comprising: - one or more light sources, preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors for detecting light arriving at said sensor(s), wherein the intensity of the light emitted by the light source(s) is modified as a function of the intensity of the light detected by the sensor(s).

[0035] According to the alternative or complementary method, in particular in permanent operating mode of the lamp, the intensity of light emitted is reduced to a second value, when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the intensity of light detected is: - below the said determined threshold, - or greater than or equal to said threshold determined for a continuous period less than a first determined period. Brief description of the drawings

[0036] [Fig. 1] Figure 1 shows a headlamp according to the present invention;

[0037] [Fig. 2] Figure 2 shows, schematically, the different means of a headlamp as illustrated in Figure 1;

[0038] [Fig. 3] Figure 3 represents an example of control of the lamp according to the present invention, as a function of the external brightness;

[0039] [Fig. 4] Figure 4 shows a control flowchart for increasing the intensity emitted by the lamp according to the present invention, and

[0040] [Fig. 5] Figure 5 shows a control flowchart for decreasing the intensity emitted by the lamp according to the present invention. Description of the embodiments

[0041] Figure 1 illustrates a portable lamp 1, in particular a headlamp, according to the present invention. The lamp 1 conventionally comprises one or more light sources 2, for example LEDs, as well as a carrying means 4, or fixing means, for example a tightening strap. The carrying means 4 makes it possible in this case to hold the portable lamp 1 on the user, in this case on the user's head.

[0042] The lamp 1 according to the present invention is preferably an individual lamp, and the light source(s) 2 are intended to illuminate in the user's direction of observation. In other words, the light source(s) 2 are configured to emit light generally parallel to the user's direction of gaze. The lamp 1 is thus intended to illuminate the space in front of the user, so that the user can see it.

[0043] The lamp 1 finally comprises a light sensor 6 arranged near the light sources 2, in order to capture the ambient light arriving in the direction of the user, and more particularly in the direction of the user's gaze. sensor 6 thus makes it possible to measure the light intensity received by the user's eyes, and therefore to detect possible glare or, on the contrary, constant darkness in the ambient environment. Sensor 6 is notably used to modify the control of the light sources 2, in order to adapt the intensity of the light sources 2 to the ambient brightness.

[0044] Thus, as illustrated in Figure 2, the lamp 1 comprises a control circuit 8 receiving as input the value Ic of the light intensity detected by the sensor 6, and providing a value I Eof the light intensity to be emitted by the light source(s) 2 of the lamp 1. In particular, the control of the light source(s) 2 by the control circuit 8 is determined as a function of the ambient light conditions measured by the sensor 6.

[0045] As will be detailed below, the control circuit 8 is configured to determine the emitted light intensity command I E depending on the visual adaptation (or retinal habituation) of the user. More specifically, the control circuit 8 is configured to decrease the light power of the light source(s) 2 when the visual sensitivity of the user increases, for example after a prolonged period of exposure to low light intensity, and / or to increase the light power of the light source(s) 2 after the user is dazzled, for example after temporary exposure to high light intensity.

[0046] Such an adaptation of the control of the light source(s) 2 makes it possible in particular to provide the user with the light power that he actually needs, taking into account the light environment in which he finds himself, and in particular to have a high light power of the lamp 1 especially, or even only, when the visual sensitivity of the user is low or reduced. Conversely, when the visual sensitivity of the user is high, then the light power of the lamp 1 is reduced so as to save its battery or batteries.

[0047] Figure 3 illustrates an example of the control signal I E supplied by the control circuit 8 to the light source(s) 2, depending on the light intensity detected by the sensor 6.

[0048] In the curves of figure 3, we assume that lamp 1 is on at time t0. At to, the intensity of the light source(s) 2 is for example equal to I E o, and corresponds for example to a specific light intensity desired by the user, among several predetermined ones. The choice of the intensity IEO can for example be made by successive presses on a control button of the lamp 1.

[0049] The start-up of the lamp 1 corresponds to a period of transient operation, or transient regime, of the lamp 1 during which specific controls of the light intensity emitted by the light sources 2 may be provided, for example for regulatory or standard reasons. Outside the start-up (or ignition) period of the lamp 1, it is considered that the lamp is in permanent operation, or permanent regime, that is to say that the control of the light sources 2 is determined independently of the constraints linked to start-up but, for example, solely as a function of the user's controls and the external light conditions.

[0050] As can be seen in Figure 3, the light intensity Ic detected by the sensor 6 remains below a threshold value Ic during and after the lighting phase of the lamp 1, so that the control circuit 8 can consider that the user's vision is gradually adapting to the ambient darkness, and adjust the control of the light sources 2 accordingly. Thus, after a determined duration, the control circuit 8 provides the light sources 2 with an emitted light intensity setpoint I E which decreases over time from the initial value I E0 up to a value I E2 smaller than the initial value I E0 . The user's vision having had time to adapt to the darkness during this reduction in the emitted light intensity I E , such a reduction remains significantly imperceptible for the user who maintains the same comfort of use, while preserving the electrical energy of his lamp 1.

[0051] Lamp 1 is now considered to be in steady state.

[0052] At time ti, it is observed that the light intensity 1e detected by the sensor 6 exceeds a threshold 1s determined by the control circuit 8. The threshold 1s corresponds to a light intensity for which there could be a glare of the user. It is also noted that the light intensity detected by the sensor 6 remains above the threshold for a continuous duration corresponding to a first determined duration D S i. In this case, the control circuit 8 considers that the intensity of the ambient light le, for a duration Dsi, is sufficient to create dazzling of the user and in particular a contraction of the pupil reducing his visual sensitivity.

[0053] The first fixed term D Sican for example be chosen to be greater than or equal to 0.5 seconds, preferably 1 second and more preferably 5 seconds.

[0054] At time t2, the light intensity I c detected by the sensor 6 falls below the threshold les, which means that the ambient light becomes low again around the user even though the latter has reduced visual sensitivity. The control circuit 8 then modifies the value of the intensity of the emitted light IE in order to compensate for this drop in visual sensitivity which occurs at the end of the glare: the light intensity emitted by the light sources 2 is then increased, at time t2, to a value greater than the value I E2 . For example, the emitted light intensity I E can be increased to the initial value I E0 , OR even to a first value I Ei (see figure 3) greater than the initial value I E0. It is then easier for the user to see what is illuminated by lamp 1, despite the recent glare.

[0055] It is therefore understood that the control circuit 8 is configured to identify glare and determine its end, in order to be able to increase the intensity of the light emitted by the lamp 1 and thus compensate for the reduction in visual sensitivity of the user following the glare.

[0056] From t2, we see in figure 3 that the light detected by the sensor 6 remains below the determined threshold I C s- In this case, and as during the transient phase of switching on the lamp 1, the control circuit 8 can provide a procedure for progressively reducing the emitted light intensity I E by light sources 2, over time.

[0057] Thus, at time ta, after a second determined duration D2, the control circuit 8 can decrease the value IE of the luminous intensity emitted since the first determined value I E i. In the example shown in Figure 3, the emitted light intensity I E is reduced by the first value I Ei to a third determined value I E3 which can be for example equal to the initial value I E0 or which can be equal to the average of the first and second values ​​I Ei and I E2 .

[0058] The second determined duration D2 can for example be chosen to be greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds,

[0059] At time t4, the value of the emitted light intensity I E is equal to the third determined intensity I E3 , and the control circuit 8 can then maintain the emitted light intensity I E to the said third determined value I E3for a certain duration, for example for a third determined duration D3. The third emitted light intensity value I E3 thus constitutes an intermediate level in the decrease in the emitted light intensity.

[0060] At time t5, after a third determined duration D3, the control circuit 8 can decrease the value I E of the luminous intensity emitted from the third determined value I E3 . In the example shown in Figure 3, the emitted light intensity I E is reduced by the third value I E3 to the second determined value I E2 .

[0061] At time t6, the value of the emitted light intensity I E is equal to the second determined intensity I E2 , and the control circuit 8 can then maintain the emitted light intensity I E to the said second determined value I E2 until the next glare.

[0062] In the end, the control circuit 8 decreased the emitted light intensity I E of the first value I Ei to the second value I E2 for a total duration corresponding to a fourth fixed duration D4 extending between t3 and te.

[0063] The fourth fixed duration D4 can for example be chosen to be less than or equal to 10 minutes, preferably 5 minutes and more preferably less than 3 minutes.

[0064] Furthermore, the value of the second intensity IE2 can be chosen to be less than or equal to 40% of the value of the first intensity I Ei of emitted light, preferably 30% and more preferably 20%.

[0065] It is thus understood that in the absence of glare, the control circuit 8 is configured to progressively reduce the light intensity emitted by the lamp 1, according to characteristics corresponding to the visual adaptation mechanisms of the user. Such a progressive reduction can be implemented when the lamp 1 is started, during the transient regime, or after glare or a change in the lighting mode of the lamp 1 by the user, in permanent regime.

[0066] As can be seen in Figure 3, the determined threshold I Cs is not necessarily a constant value, but can instead be a value that is modified according to the value of the ambient intensity. Indeed, we understand that a user's eyes can be more easily dazzled when the ambient brightness is very low, rather than when the ambient brightness is dimmed. In this case, the threshold determined les, at very low ambient intensity, may be smaller than the threshold determined les, at dimmed ambient brightness. This is what is represented in Figure 3 by the straight line segments.

[0067] Figure 4 illustrates a first method 20 for controlling a lamp, in particular a lamp 1 as described previously. In particular, the first control method 20 is configured to adapt the light intensity of the lamp following glare.

[0068] In a first step 22, it is determined whether the intensity of the light detected by the sensor 6 is greater than or equal to a determined threshold les, for a duration greater than or equal to the first determined duration D. S i. Step 22 therefore consists of detecting glare.

[0069] If the conditions of step 22 are met, then it is determined, during a second step 24, whether the intensity of the light detected by the sensor 6 becomes lower than said determined threshold. Step 24 therefore consists of detecting the end of the glare.

[0070] In a third step 26, for example simultaneous, it is determined whether the emitted intensity I E is less than a first value I E i. Such a step 26 makes it possible to know if it is possible to increase the emitted brightness I E to the value I Ei or if it is already equal to the value I Ei and can therefore no longer be increased.

[0071] If the conditions of steps 24 and 26 are met, then in step 28 the emitted intensity I is increased E to the first value I Ei .

[0072] Figure 5 illustrates a second method 30 for controlling a lamp, in particular a lamp 1 as described previously. In particular, the second control method 30 is configured to adapt the light intensity of the lamp in the absence of glare.

[0073] In a first step 32, we determine whether the intensity I E emitted by light sources 2 is greater than the second value I E2 . Such a step 32 makes it possible to know if it is possible to reduce the emitted brightness I E to the value I E2 or if it is already equal to the value I E2 and can therefore no longer be reduced.

[0074] In particular, the first step 32 may correspond to the last step 28 of the first method 20: when the emitted intensity I E is increased to the first value I Ei , it actually becomes greater than the second value I E2 , so that the second method 30 can be implemented in continuity with the first method 20, or independently of the first method 20, for example when the lamp is switched on or when the user changes the lighting mode of the lamp.

[0075] In a second step 34, for example simultaneous, it is determined whether, during the second determined duration D2, the intensity le of the light detected by the sensor 6 is less than the determined threshold les, or greater than or equal to a determined threshold les for a continuous duration less than the first determined duration D S i. Step 34 therefore consists of detecting the absence of glare.

[0076] If the conditions of steps 32 and 34 are met, then in step 36 the emitted intensity I is reduced E of the first value I Ei to the second value I E2 , possibly via a level to a third value I E3 .

[0077] Thus, thanks to the lamp according to the present invention, it becomes possible to have lighting which adapts both to external conditions, but also and above all to the physiological variations in the visual sensitivity of the user, to reduce the electrical consumption of the lamp while providing the same comfort of use for the user.

Claims

Claims

1. Lamp (1), in particular portable such as a headlamp, comprising: - one or more light sources (2), preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors (6) for detecting the light arriving at said one or more sensors, the lamp (1) also comprising a control circuit (8) configured to modify the intensity of the emitted light (I E ) by the light source(s) as a function of the intensity of the light detected by the sensor(s) (6), characterized in that the control circuit (8) is configured to increase the intensity of light emitted to a first intensity value (IEI),: - when the detected light intensity (I c) is less than a determined threshold (the) after having been greater than or equal to said determined threshold (the) for a duration greater than or equal to a first determined duration (Dsi), for example greater than or equal to 0.5 seconds, preferably 1 second and more preferably 5 seconds, and - when the intensity of light emitted is lower than said first value (IEI).

2. Lamp (1) according to claim 1, wherein the control circuit (8) is also configured to decrease the intensity of light emitted by said first value (I E i) to a second value (I E2 ) when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the detected light intensity is: - lower than said determined threshold (I C s), - or greater than or equal to said determined threshold(s) for a continuous period less than said first determined period (D S i).

3. Lamp (1) according to the preceding claim, wherein the control circuit (8) is configured to decrease the intensity of light emitted by said first value (I E (i) to the said second value (I E 2), maintaining said intensity at a third intensity value (I E s) between said first value and said second value, for a third determined duration (D3).

4. Lamp (1) according to the preceding 2 or 3, in which the control circuit (8) is configured to decrease the intensity of light emitted by said first value (I E i) to a second value (I E2), for a fourth fixed duration (D4), for example less than or equal to 10 minutes, preferably 5 minutes and more preferably less than 3 minutes.

5. Lamp (1) according to claim 1, wherein the control circuit (8) is also configured to maintain the intensity of light emitted at said second value (I E2 ), when the detected light intensity is: - below the said determined threshold(s), - or greater than or equal to said determined threshold(s) for a continuous period less than said first determined period (D S i).

6. A lamp (1) according to any preceding claim, wherein the second intensity (I E2 ) is less than or equal to 40% of the first intensity (I E i) of emitted light, preferably 30% and more preferably 20%.

7. Method for controlling a lamp (20, 30), in particular a portable lamp (1) such as a headlamp, comprising: - one or more light sources (2), preferably in the visible range, for example LEDs, and intended to emit light generally parallel to the direction of the user's gaze, - one or more light sensors (6) for detecting the light arriving at said sensor(s), in which the intensity of the emitted light (I) is modified. E ) by the light source(s) as a function of the intensity of the light detected by the sensor(s), characterized in that the intensity of the light emitted is increased to a first intensity value,: - when the detected light intensity is less than a determined threshold after having been greater than or equal to said determined threshold for a duration greater than or equal to a first determined duration, for example greater than or equal to 0.5 seconds, preferably 1 second and more preferably 5 seconds, and - when the intensity of light emitted is less than said first value.

8. Method (30) according to the preceding claim, in which the intensity of light emitted is reduced from said first value to a second value when, for at least a second determined duration, for example greater than or equal to 15 seconds, preferably 20 seconds and more preferably 30 seconds, the intensity of light detected is: - below the said determined threshold, - or greater than or equal to said determined threshold for a continuous period less than said first determined period.

9. Method (30) according to the preceding claim, in which the intensity of light emitted is reduced from said first value to a second value, for a fourth determined duration, for example less than or equal to 10 minutes, preferably 5 minutes and more preferably less than 3 minutes.

10. Method (20, 30) according to any one of claims 7 to 9, in which the intensity of light emitted is maintained at said second value, when the intensity of light detected is: - less than said determined threshold, - or greater than or equal to said determined threshold for a continuous duration less than said first determined duration.

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