Lamp and corresponding control method

Abstract

Lamp and corresponding control method 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 gaze of the user, - one or more light sensors (6), - 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 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, and - the emitted light intensity (IE) is lower than said first value. Figure for abstract: Fig. 2.

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 already exist headlamps comprising, 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 as a function of 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, in particular 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 consequently 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 the latter is faced with a reflective object such as a map.

[0007] Document FR 2 792 594 relates to a lamp comprising in particular a control module with 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 the luminous power being restricted to situations during which the user finds himself facing an object reflecting the light of the lamp in the direction of the sensor. Presentation 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 autonomy 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 autonomy.

[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 sensor(s), 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).

[0011] The control circuit is configured to increase the intensity of emitted light 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.

[0012] The lamp according to the present invention takes into account the adaptation of the eye to the 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 light detected on 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. Only when the control circuit detects the end of the glare, in this case when the detected brightness falls below the determined threshold again, is the lamp intensity modified and increased to compensate for the loss of sensitivity linked to the 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 decrease 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 visual adaptation period of the user. 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 again. 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 autonomy of the battery, while remaining barely perceptible 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 duration, the intensity of the lamp can be initially reduced to an initial value, for example the user's setpoint 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 duration, the intensity emitted can be reduced again, below this initial value, to continue to adapt to the user's visual sensitivity and save the 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 provided to take place over a fourth duration, more or less long, corresponding substantially to the simultaneous increase in the visual sensitivity of the user.

[0022] Preferably, the control circuit is also configured to maintain the intensity of light emitted 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.

[0023] Here again, and in order to limit the energy consumption of the lamp, the increase in the emitted intensity is not triggered systematically 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 high 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 light intensity of the lamp, compared to the user's initial setting. The energy saving is therefore significant for a relatively low impact, in use, for the user.

[0026] According to another aspect, there is also provided 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), in which 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 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.

[0028] In particular, the intensity of light emitted may be increased to a first intensity value when the intensity of light emitted is lower than said first value before and / or during the increase in the intensity of light detected 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, there is also provided 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), 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 intensity of light detected 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), in which 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 in- less than a first fixed term. Brief description of the drawings

[0036] [Fig.l] [Fig.l] represents a headlamp according to the present invention;

[0037] [Fig.2] [Fig.2] schematically represents the different means of a headlamp as illustrated in [Fig.l];

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

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

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

[0041] [Fig.l] 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. The sensor 6 thus makes it possible to measure the light intensity Ic received by the user's eyes, and therefore to detect any glare or, on the contrary, constant darkness in the ambient environment. The 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 [Fig.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 IE of 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 brightness conditions ambient measured by sensor 6.

[0045] As will be detailed below, the control circuit 8 is configured to determine the emitted light intensity control IE as a function of the visual adaptation (or retinal habituation) of the user. More precisely, 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 really 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] [Fig. 3] illustrates an example of the control signal IE supplied by the control circuit 8 to the light source(s) 2, as a function of the light intensity Ic detected by the sensor 6.

[0048] On the curves of [Fig.3], it is assumed that the lamp 1 is lit at time t0. At t0, the intensity of the light source(s) 2 is for example equal to IE0, and corresponds for example to a specific light intensity desired by the user, among several predetermined ones. The choice of the intensity IE0 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 can 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 the 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 [Fig.3], the light intensity Ic detected by the sensor 6 remains lower than a threshold value ICs 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 accordingly. consequently the control of the light sources 2. Thus, after a determined duration, the control circuit 8 provides the light sources 2 with a setpoint of emitted light intensity IE which decreases over time from the initial value IE0 to a value IE2 smaller than the initial value IE0. The user's sight having had time to adapt to the darkness during this reduction in the emitted light intensity IE, such a reduction remains substantially imperceptible for the user who maintains the same comfort of use, while preserving the electrical energy of his lamp 1.

[0051] It is considered that the lamp 1 is now in permanent mode.

[0052] At time tb it is observed that the light intensity Ic detected by the sensor 6 exceeds a threshold ICs determined by the control circuit 8. The threshold ICs corresponds to a light intensity for which there could be dazzling of the user. It is also observed that the light intensity Ic detected by the sensor 6 remains above the threshold ICs for a continuous duration corresponding to a first determined duration DSi. In this case, the control circuit 8 considers that the intensity of the ambient light Ic, 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 determined duration DSi can 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 Ic detected by the sensor 6 falls below the threshold I es, 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 IE2. For example, the emitted light intensity IE can be increased to the initial value IE0, or even to a first value IEi (see [Fig.3]) greater than the initial value IE0. It is then easier for the user to see what is illuminated by the 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, it can be seen in [Fig.3] that the light Ic detected by the sensor 6 remains below the determined threshold ICs. In this case, and as during the transient phase of the switching on of the lamp 1, the control circuit 8 can provide a procedure for progressively reducing the light intensity IE emitted by the light sources 2, over time.

[0057] Thus, at time t3, after a second determined duration D2, the control circuit 8 can reduce the value IE of the emitted light intensity from the first determined value IE1. In the example illustrated in [Fig.3], the emitted light intensity IE is reduced from the first value IEi to a third determined value IE3 which can be for example equal to the initial value IE0 or which can be equal to the average of the first and second values ​​IEi and IE2.

[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 IE is equal to the third determined intensity IE3, and the control circuit 8 can then maintain the emitted light intensity IE at said third determined value IE3 for a certain duration, for example for a third determined duration D3. The third emitted light intensity value IE3 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 IE of the emitted light intensity from the third determined value IE3. In the example illustrated in [Fig.3], the emitted light intensity IE is decreased from the third value IE3 to the second determined value IE2.

[0061] At time t6, the value of the emitted light intensity IE is equal to the second determined intensity IE2, and the control circuit 8 can then maintain the emitted light intensity IE at said second determined value IE2 until the next glare.

[0062] Ultimately, the control circuit 8 has reduced the emitted light intensity IE from the first value IEi to the second value IE2 for a total duration corresponding to a fourth determined duration D4 extending between t3 and t6.

[0063] The fourth determined 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 IEi 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 [Fig.3], the determined threshold ICs is not necessarily a constant value, but can on the contrary be a value which is modified depending on 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 ICs, at very low ambient intensity, may be smaller than the threshold determined ICs, at dimmed ambient brightness. This is what is represented in [Fig.3] by the straight line segments.

[0067] [Fig.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 Ic of the light detected by the sensor 6 is greater than or equal to a determined threshold ICs, for a duration greater than or equal to the first determined duration DSi. 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 Ic of the light detected by the sensor 6 becomes lower than said determined threshold ICs. 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 IE is less than a first value IEi. Such a step 26 makes it possible to know whether it is possible to increase the emitted brightness IE to the value IEi or whether it is already equal to the value IEi and can therefore no longer be increased.

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

[0072] [Fig. 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, it is determined whether the intensity IE emitted by the light sources 2 is greater than the second value IE2. Such a step 32 makes it possible to know whether it is possible to reduce the emitted brightness IE to the value IE2 or whether it is already equal to the value IE2 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 IE is increased to the first value IEb it in fact becomes greater than the second value IE2, so that the second method 30 may be implemented in the continuity of 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 Ic of the light detected by the sensor 6 is less than the determined threshold ICs, or greater than or equal to a determined threshold ICs for a continuous duration less than the first determined duration DSi. Step 34 therefore consists of detecting the absence of glare.

[0076] If the conditions of steps 32 and 34 are met, then in a step 36, the emitted intensity IE is reduced from the first value IEi to the second value IE2, possibly via a step to a third value IE3.

[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 sensor(s), the lamp (1) also comprising a control circuit (8) configured to modify the intensity of the light emitted (IE) by the light source(s) as a function of the intensity of the light detected (Ic) by the sensor(s) (6), characterized in that the control circuit (8) is configured to increase the intensity of the light emitted to a first intensity value (IEi),: - when the detected light intensity (Ic) is lower than a determined threshold (ICs) after having been greater than or equal to said determined threshold (les) 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 emitted light intensity is lower than said first value (IE1).,

2. Lamp (1) according to claim 1, wherein the control circuit (8) is also configured to decrease the intensity of light emitted from said first value (IE1) to a second value (IE2) 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 (ICs), - or greater than or equal to said determined threshold (ICs) for a continuous duration less than said first determined duration (DSi).

3. Lamp (1) according to the preceding claim, wherein the control circuit (8) is configured to decrease the intensity of light emitted from said first value (IE1) to said second value (IE2), while maintaining said intensity at a third intensity value (IE3) between said first value and said second value, for a third fixed term (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 from said first value (IE1) to a second value (IE2), for a fourth determined 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, in which the control circuit (8) is also configured to maintain the intensity of light emitted at said second value (IE2), when the detected intensity of light is: - lower than said determined threshold (les), - or higher than or equal to said determined threshold (ICs) for a continuous duration less than said first determined duration (DSi).

6. Lamp (1) according to any one of the preceding claims, in which the second intensity (IE2) is less than or equal to 40% of the first intensity (IEi) of light emitted, 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 light emitted (IE) by the light source(s) is modified as a function of the intensity of the light detected (Ic) by the sensor(s), characterized in that the intensity of the light emitted is increased to a first intensity value,: - when the intensity of the detected light 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 one decreases 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: - less than said determined threshold, - or greater than or equal to said determined threshold for a continuous duration less than said first determined duration.

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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