Abstract:
The invention relates to a portable electric lamp with a light source generating at least one light beam; and a pane of glass arranged in front of the light source. The pane of glass has an electro-optical diffusion device controlled by an electrical signal in order to generate electrically adjustable diffusion. This diffusion generates a light beam with variable geometry from the single narrow beam. This results in headlamps with improved control of the geometry of its lightbeams.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to portable electric lamps, and in particular to a headlamp having an improved control of the geometry of the light beam. 
       BACKGROUND 
       [0002]    The Applicant of the present application has contributed significantly to the development of new portable lamps, improving comfort and lighting of their users in all is kind of sports situations (caving, climbing, jogging, etc...) or professional (rescue, pruning, mine etc . . . ) 
         [0003]    In French patent application FR2893811 filed Nov. 21, 2005, the Applicant has proposed a portable electric lamp as shown in  FIG. 1 , including at least two light sources with distinct beams—respectively narrow/long and wide/short—respectively generated by a central light source  1 d and an annular light source 1e. Combining their respective beams by means of a single control allows the generation of an effect of “zooming.” This effect of “zoom” remains fairly limited with a relative variation of the beam angle. Furthermore , this embodiment requires two separate sources of light, which can significantly increase the manufacturing costs and also the size of the light source. Finally, and this was not the least annoying inconvenience, in order to have a homogeneous light output , it is necessary that the light sources are perfectly matched, which can be difficult. And even more, when considering that, in general, LEDs have different aging profiles causing very quickly a loss of homogeneity in the production of the respective luminous fluxes of the two (or more) LED lamps, thus reducing the effectiveness of the “zooming” effect being searched. 
       SUMMARY 
       [0004]    The invention solves a number of problems. One solved problem is the opportunity to integrate the zoom effect in the “dynamic” or “reactive” lighting invented by the Applicant of the present application. Indeed, in application WO2009/133309, the Applicant has invented the so-called concept of “dynamic lighting” or “reactive lighting” which, briefly and as shown in  FIG. 2 , is based on a headlamp comprising at least one light emitting diode  11  (LED) and an optical sensor  14  located in its vicinity for sensing a signal representative of the light reflected by the surface of an object  16  being illuminated by the lamp. A control circuit  13  processes this signal so as to automatically control the power of the LED according to a predetermined threshold. In this manner, automatic control of the light beam emitted by the lamp is achieved is without further manual action so as to adjust the lighting to the environment, while also optimizing the power consumption and the life of the battery. If the principle of this “dynamic” lighting undeniably is a significant advance in the field of headlamps and more generally of the portable lighting, however, it remains necessary to combine this light with a powerful zoom effect, allowing constant effective and flexible adaptation of the illumination in accordance with the lighting conditions. 
         [0005]    Moreover finally, in the international patent application WO2012/119756, the Applicant has introduced a headlamp with a variable geometry beam device controlled by an analysis of an image generated by an image sensor. For such a highly sophisticated lamp, it also appears desirable to have a “zoom” allowing the control of the geometry of the light beam that is particularly efficient and flexible to greatly benefit the possibilities offered by this new lamp technology . 
         [0006]    It can thus be seen that there is still a wish for an effective and flexible mechanism for controlling the beam geometry and which allows easy and effective integration into the latest portable lamp technologies, and especially the so-called “dynamic” lighting lamp. In addition, it is desirable to provide an effective solution to problems of space, cost and finally the problem of aging of the light sources. 
         [0007]    The present invention proposes to significantly improve this situation by achieving a new device for controlling the geometry of the beam which is perfectly suited to the new requirements introduced with the new facilities offered by modern headlamps. 
         [0008]    It is an object of the present invention to carry out a portable lamp structure, such as a headlamp, allowing easier control of the geometry of the light beam. 
         [0009]    It is another object of the present invention to provide a device for controlling the geometry of the beam generated by a portable lamp, reducing manufacturing costs but also the lamp clutter. 
         [0010]    It is still another object of the present invention to provide a portable lamp device enabling fine control of the geometry of the beam and adapted to dynamic lighting. 
         [0011]    The invention achieves these objects by means of a portable electric lamp, such as a headlamp, comprising:
       a light source generating at least one light beam generates a narrow beam;   a panel arranged in front of said light source, said panel having an electric-optical diffusion device controlled by an electric signal for producing an electrically adjustable diffusion,       
 
         [0014]    so as to generate a light beam of variable geometry from the single narrow beam. 
         [0015]    The electro-optical device may be a liquid crystal diffuser controlled either by a current or by a control voltage. 
         [0016]    In one embodiment, the panel consists of a Diffusion Polymer Liquid Cristal (DPLC) film through which passes said narrow beam, the DPLC film comprising biasing electrodes for receiving a control voltage for controlling the transparency of said film. 
         [0017]    Preferably, the portable lamp includes:
       a light source comprising at least one LED generating a narrow beam;   a source of power for powering the LEDs;   a control unit for generating a control potential for controlling the transparency of said DPLC film.       
 
         [0021]    In a particular embodiment, the control voltage is generated from a manually controlled actuator. 
         [0022]    Alternatively, the control voltage is generated from an information generated by a sensor sensing a fraction of the light being reflected on an object illuminated by the beam. 
         [0023]    Alternatively, the control voltage is generated from an information generated by an accelerometer sensor, allowing the control of lamp lighting as the user is running or jogging. 
         [0024]    In a particular embodiment, the control voltage is generated from an information generated by an image sensor. 
         [0025]    More specifically, the portable lamp comprises communication means for receiving a control information which can be used for deriving the adjustable transparency control potential. This information can come from either another lamp—being interconnected and which may be configured in master mode—or from a data processing device such as a mobile phone, tablet etc .. which may also be used for controlling the features of the portable lamp. 
         [0026]    In a specific embodiment, the portable lamp is particularly suitable for producing a headlamp. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Other features of one or more embodiments of the invention will appear from the following description of embodiments of the invention, with reference being made to the accompanying drawings. 
           [0028]      FIG. 1  illustrates the principle of a conventional lamp fitted with an “electric zoom” facility. 
           [0029]      FIG. 2  represents the general principle of a conventional lamp fitted with the so-called “dynamic lighting”. 
           [0030]      FIG. 3  illustrates a first preferred embodiment of a portable lamp comprising is an electrically adjustable transparent glazing. 
           [0031]      FIG. 4  illustrates a second embodiment combining an electro-optical diffuser with dynamic lighting lamp. 
           [0032]      FIG. 5  illustrates a third embodiment of a portable lamp comprising an accelerometer used for generating the control potential of the electro-optical diffuser. 
           [0033]      FIG. 6  shows a fourth embodiment of a portable lamp comprising an image sensor and an image processor for generating a control information for generating the control potential of the electric optical diffuser . 
           [0034]      FIG. 7  shows a fifth embodiment of a portable lamp comprising communication means for receiving information for generating the control potential of the electro-optical diffuser. 
       
    
    
     DESCRIPTION 
       [0035]    There will now be described, in relation to  FIG. 3 , a particular embodiment of a lamp, such as a headlamp generating a light beam, and provided with an improved device for controlling the geometry of the light beam. 
         [0036]    The lamp includes a light source  31  which produces a light beam  31  generated for example by means of one or more LED(s). The light source  31  may be provided with a primary optics for providing first collimating so as to allow the formation of a rather narrow beam. 
         [0037]    Optionally, a secondary optics  32  may be provided to improve, as necessary, the collimation of the source and thus increase, as appropriate, the narrow beam geometry. 
         [0038]    The lamp furthermore has an electro-optical device  33  disposed in front of the light source, such as an electro-optical diffuser allowing electrical control transparency/opacity, so as to control the geometry of the light beam generated by the LED or (s). 
         [0039]    Preferably the electro-optical device  33  is made of a panel of Diffusion Polymer 
         [0040]    Liquid Cristal (DPLC) film (Liquid crystals dispersed in polymer or polymer dispersive liquid crystal) which, as known by a skilled man, consists of a particular implementation of crystals liquid heterogeneous dispersion in a polymer matrix. 
         [0041]    This DPLC film may advantageously replace the glass conventionally disposed in front of the light source and protecting the latter, and which comprises two biasing terminals  34  and  35  receiving a control signal, for example a control voltage Vc generated by a control unit  36  . 
         [0042]    Thus, one can achieve an advantageous combination of a specifically narrow light source and an electro-optical DPLC diffuser which can be electrically controlled so as to generate light beams various shapes of light beams, since the narrowest beam (when the film DPLC is completely transparent) to a maximum diffusion providing light scattering in all directions, as illustrated in  FIG. 3 . 
         [0043]    With this particularly advantageous arrangement, it is thus possible to generate, by means of a single narrow beam light source, for example less than 10 degrees, a large variety of angles or beamwidths. The portable lamp can therefore ensure new features (floodlight—lantern—dawn simulator alarm). 
         [0044]    And these new features will be permitted while significantly reducing the size of the lamp since, in the best case, only one single LED will be required to produce a wide variety of light beams. 
         [0045]    Furthermore, the problem of matching the LEDs and their profiles aging is also solved since one single LED can be used for generating a plurality of beams which always present an homogenous color. 
         [0046]    The invention can thus be used for effectively solving quite a number of problems arising in the development of an ‘electrically controlled zoom’. 
         [0047]    One can further note an aesthetic advantage since, in the absence of any control voltage Vc and when the lamp is switched off, the latter is fully grained and has, therefore, quite a nice appearance. 
         [0048]    In one particularly simple embodiment, the control voltage Vc is controlled via a switch or a manual actuator which can be operated by the lamp user, which may thus set—as desired—the angle of the generated beam. 
         [0049]    Alternatively—and this shows the great flexibility of the device being described—it will automatically adjust the potential Vc from various information data. 
         [0050]      FIG. 4  illustrates a second embodiment of a lamp  100 , assumed to be a headlamp, which advantageously combines the use of an electro-optical diffuser in a “dynamic” or “reactive” type lamp. 
         [0051]    The lamp  100  includes a power module  450  associated with a control module  400  and a light source  460  having one or more LED (s) which has/have, when appropriate, its/their own focal system (not shown in the figure). 
         [0052]    In the example in  FIG. 4 , one shows, for the sake of simplification, a single LED  460  which is powered by leads  461  being connected to power module  450 , which clearly represents the most compact embodiment. 
         [0053]    However, where the compactness is critical, one can consider, particularly for the purpose of increasing the brightness of the lamp, to use several diodes into a single focal optical system, or even multiply the number of optical systems so as to increase the possibilities of use of the lamp. In particular, one can consider theh use of more imposing LEDs, for instance of the multi-chip type (Creates XLM 2 ) combined with the most impressive optics, enabling a more sophisticated embodiment. 
         [0054]    In a specific embodiment, the powering of LED diode  460 —via leads  461 —is carried out under the control information or a control signal  401  generated by the control module  400 . 
         [0055]    Power module  450  specifically includes all components that are conventionally found in an LED illumination lamp for producing a light beam of high intensity, and in general based on Pulse Width Modulation PWM, well known to the skilled man and similar to that known and used in class audio circuits D. The PWM modulation is controlled by the control signal  401 . Generally speaking, the term “signal” mentioned above refers to an electrical quantity—current or voltage—that can cause control of the power module  450 , including the PWM modulation used to supply power to the LED  460 . This is only one particular embodiment, with the understanding that it will be possible to substitute to “control signal  401 ” any “control information” such a logical information stored in a register and transmitted by any appropriate means to power module  450  in order to control the transmission power of the light beam. In one particular embodiment, we can even consider the two control modules  400  and power  450  are integrated within the same integrated circuit. 
         [0056]    A skilled person can therefore easily understand that that when we refer to a “control signal  401 ” is indiscriminately encompasses embodiments using an electrical quantity control—current or voltage—and the embodiments in which the command is effected by means of a logic information transmitted within the power module  450 . For this reason, one will hereinafter indiscriminately use the wordings “control signal” or “control information”. 
         [0057]    In general, switches and switching components that constitute power module  450 —which can be either bipolar transistors, FETs (Field Effect Transistor) or MOS (Metal Oxide Semiconductor) or MOSFET—are well known to a skilled man and the presentation will be deliberately reduced in this regard for brevity. Likewise, we invite the reader to refer to the general literature on various aspect of the PWM modulation. 
         [0058]    As seen in  FIG. 4 , control module  400  particularly comprises a sensor  410  having its own focal optical module, which is used for sensing a portion of the light being reflected on the illuminated object or zone, so as to generate an useful information for carrying out the so-called “dynamic” or “reactive” lighting . 
         [0059]    The information produced by sensor  410  is processed by control module  400  so as to derive a control voltage Vc by means of appropriate logic and analog circuits. This control voltage Vc is transmitted via appropriate leads  471  to a DPLC film  470  so as to control the diffusion of the light beam passing through the latter. 
         [0060]    More specifically, the diffusion control is such that, in the absence of any control voltage Vc, the diffusion of the DPLC film  470  is maximum, thus producing the light rays in all directions (shown by the beam  473  in  FIG. 4 ). On the contrary, when control module  400  generates a significant control voltage Vc—in the order of 75 volts today but with the aim of lowering in the value of 24 volts—the DPLC film will show a perfect or almost full transparency, so that only a narrow beam  472  will be generated by the portable lamp. 
         [0061]    With such a device, one can therefore automatically control the coefficient of diffusion of the DPLC film via control voltage Vc, and such control is derived from the reflection of light on an illuminated object sensed by sensor  410 . 
         [0062]    One thus significantly improves the conventional “dynamic” or “reactive” lamp by integrating in the latter an electrically controllable DPLC film. More specifically, the io possibility of electrically controlling the electro-optical diffuser greatly simplifies the feedback loop allowing the control of the diffusion based on the light sensed by the sensor  410 . 
         [0063]    This makes lamp  100  of  FIG. 4  particularly flexible for quite a large number of control loops which can be used. 
         [0064]    But this certainly does not exhaust the possibilities of the described embodiment, which can allow a wide variety of different controls, as this is illustrated in  FIG. 5 , wherein all components identical to those of  FIG. 4  retain their references. This device of  FIG. 5  further includes a speed sensor or accelerometer sensor  420  which can be added, or substituted to sensor  410 . Such acceleromter sensor is particularly useful for detecting a situation where the lamp user makes significant moves, for instance if he is running, in which case, it can be useful to automatically control, through the control unit  400 , the generation of a narrower and stronger beam. 
         [0065]      FIG. 6  shows another example of a more sophisticated embodiment in which the lamp includes an image processor  435  such as that described in patent application WO 2012/119756 dated Mar. 6, 2012, and allowing control of the geometry the beam from an image analysis performed by an image processor  435  shown in  FIG. 6 . Such analysis of the image sensed leads, thanks to an appropriate image processing, to the generation of an control voltage Vc which can be used for controlling the diffusion factor of the DPLC film  470 . The reader is particularly invited to refer to the developments described in this patent application for carrying out such a particular portable lamp incorporating an image sensor. 
         [0066]      FIG. 7  shows another embodiment wherein one adds, to the elements described in the embodiment of  FIG. 4 , and which—for the sake of brevity—shall keep their reference numerals, a wireless communication unit  440 , and particularly transmission/reception circuits for receiving a control information from a device being external to the lamp, said information being used for generating the control voltage Vc for controlling the diffusion of the electro-optical diffusion device. 
         [0067]    In a particular embodiment, the communication circuits may be Bluetooth or equivalent type and allow an exchange of information between two portable lamps so that a type of master/slave control between the two lamps. 
         [0068]    It is thus possible, thanks to this arrangement to produce centralized control of the diffusion of the DPLC film. 
         [0069]    Alternatively, the wireless communication circuits  440  are used for the exchange of data between the portable lamp and an external data processing device, such as a mobile phone or a touch pad  500  that will thus be able to take advantage of all the processing power available in these external devices, but also their communication capabilities. This allows control of the brightness of the beam but also its geometry thanks to the DPLC film  470 . 
         [0070]    This arrangement can be particularly advantageous as it will become possible to use the computing power which is available in these external devices, as well as the extended communication facilities which are thus permitted, so as to achieve a fine and effective tuning of the beam geometry. 
         [0071]    With this communication capability, quite a number of new facilities and possibilities may be considered for the headlamp.