Abstract:
An attachment for a light unit, which attachment comprises light-detecting means adapted to generate an output signal corresponding to the intensity of light incident thereon, and adjustable attaching means for removably attaching said attachment to an existing light unit such that the light detecting means are positioned within a beam of light emitted by the light unit when operated and are adapted to detect light that is directed towards the light unit, said attaching means being adjustable to allow the attachment to be selectively fitted to a range of different existing light units. Particularly, said light sensing means are adapted to sense light from the light unit that is retro-reflected back towards the light unit.

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/GB00/00744 which has an International filing date of Mar. 2, 2000, which designated the United States of America and was published in English. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an attachment for a light unit. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,017,770 and GB-B-2183889 (Sigalov) disclose interactive light-to-MIDI equipment comprising a support assembly and a plurality of light units. Said support assembly comprises a structure consisting of a plurality of telescopic arms which are pivoted on a central hub. Said hub may be suspended from a ceiling or other superstructure, and the arms may be manipulated such that they extend radially outwardly of the hub. Said light units are mounted on the arms, and each comprises a lamp that is adapted emit a beam of light generally downwardly, and an integrant light sensing element that is positioned in front of the lamp in the beam. Said light sensing element is shielded from direct light from the lamp, but is adapted to detect light that is retroreflected back towards the light unit. 
     Said light sensing element may comprise a photoresistive diode which is connected to an analogue to digital pulse generator. Said pulse generator converts the analogue output of the detector to a digital “trigger” signal which is MIDI compatible. In turn, the output of the pulse generator can be connected to a MIDI interface, and this can be connected to sound generator or other MIDI device of kinds well known to those skilled in the art. The MIDI interface can be set up to transmit a MIDI instruction to the sound generator or other MIDI-control device in response to a digital “trigger” pulse from the pulse generator. 
     In use, a user such, for example, as a musician or dancer operates the equipment by wearing or carrying on part of his or her body a piece of rectroreflective material. When the user cuts a beam of light from one of the light units with the rectroreflective material, then part of the beam is retroreflected back towards the light unit, thus activating the light sensing element. Alternatively the system can be operated in an “inverse mode” in which a piece of retroreflective material is disposed at a fixed, remote location in front of each light unit. Light from the light unit is thus constantly reflected back towards the light unit by the retroreflective material, and is incident on the light sensing element. In this case the user does not need to be equipped with retroreflective material, but will cause a discontinuity in the output of the light sensing element simply by interrupting the beam of light with a non-reflecting member such, for example, as part of his or her body, thus shading the fixed retroreflective material from the beam. Such interruption in the output of the light sensing element is converted by the pulse generator into a control signal. 
     Most commonly, the equipment will be used to drive a sound generator such, for example, as a music synthesizer or drum computer. The output of each respective light unit may be used to generate a different note or sound. U.S. Pat. No. 5,017,770 and GB-B-2183889 disclose that the outputs of a group of light units may be connected through appropriate electronic circuitry to provide control over a different MIDI parameter in addition to the digital trigger signal. Thus, the speed at which two juxtaposed beams are cut by a user may, for example, be used to provide volume control. U.S. Pat. No. 507,770 and GB-B-2183889 also disclose that the equipment may be used to control non-sound devices such as other lighting devices and devices which can move objects, release smoke or odours, provide temperature control or release stage snow, stage rain or balloons or the like. The light emitted by the lamp of each light unit may be visible or invisible, although for most music applications, it is envisaged that each lamp will generate a different colour of visible light. 
     U.S. Pat. No. 5,017,770 and GB-B-2,183,889 thus disclose an integrated light-to-MIDI system that comprises light units, light sensing elements and electronic equipment for converting the output of the light sensing elements to MIDI instruction code. Such equipment works well, but is self-contained and therefore difficult to integrate with pre-existing equipment. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the present invention there is provided an attachment for a light unit, which attachment comprises light-detecting means, adapted to generate an output signal corresponding to the intensity of light incident thereon, and adjustable attaching means for removably attaching said attachment to a light unit such that the light-detecting means are positioned within a beam of light emitted by the light unit in use and are adapted to detect light that is directed towards said light unit, said attaching means being adjustable to allow the attachment to be selectively fitted to a range of differently sized light units. 
     The invention thus provides an attachment which can be fitted to a pre-existing light unit to convert the light unit into an interactive light-operated controller. It is envisaged that said adjustable attaching means may be adapted to attach the attachment to a wide variety of different kinds of light units without restriction. In particular, the attaching means may be adapted for connecting the light sensing means to known kinds of theatre lighting, including ellipsoidals, pars, fresnels and pinspots. 
     Preferably, said light sensing means comprises a light sensing element and shielding means for shielding the light sensing element from direct light emitted by the light unit and/or ambient light, so as to avoid false positive readings. Said shielding means may comprise an opaque, elongate housing that is arranged substantially co-axially with the beam when the attachment is fitted to a light unit, which housing is closed at one end that is disposed closest to the light unit and is open at its other end, the light sensing element being disposed within the housing. In some embodiments, said housing may comprise a tube that is closed at said one end, with the light sensing element being mounted within the tube. Said housing serves to ensure that the only retroreflected light impinges on the light sensing element to provide stable operation of the attachment. Operation of the light sensing element may be further enhanced by the provision of lens means for concentrating said retroreflected light onto the light sensing element. 
     Said attaching means may be adapted such that, when fitted to a light unit, said light sensing means is positioned generally centrally within the beam emitted by the light unit. In some embodiments, said attaching means may comprise adjustable positioning means for adjusting the position of the light sensing means relative to the light unit. 
     It will be appreciated that the present invention is not limited to any particular form or configuration of attaching means. The invention embraces a wide variety of different kinds of attaching means suitable for attaching the light sensing means to a wide variety of different kinds of theatre lighting as mentioned above. Furthermore, said attaching means may comprise mechanical fastening means for fastening the attachment to a light unit, or alternatively other kinds of releasable fastening means may be employed such, for example, as magnetic fasteners and adhesive pads. In some embodiments, the attaching means may be adapted simply to allow the attachment to be placed on the light unit or a part connected thereto such that the light unit is retained in position by gravity and optionally one or more stops to prevent lateral movement. 
     In some embodiments of the invention, said attachment may further comprise pulse generating means for converting the output signal of the light sensing means into a digital or analogue signal, particularly a control signal. Typically, said signal may be a MIDI compatible signal. 
     Said attachment may further comprise signal transmitting means for transmitting the output signal of said light detecting means to a suitable remote receiver. Said transmitting means may comprise electromagnetic wave transmitting means for transmitting said control signal to a remote receiver on an electromagnetic carrier wave. In some particularly preferred embodiments of the invention, said transmitting means may be adapted to provide an infra-red carrier signal for carrying the control signal. Of course, the invention does not preclude the possibility that the output of the light sensing means or pulse generating means may be hard-wired into a suitable receiver. 
     The attachment of the invention may be provided with appropriate power leads for connecting the light sensing means and optional pulse generating means to a source for electrical power. However, in some embodiments, the attachment may further comprise photovoltaic generator means to provide electrical power to the attachment, which photovoltaic generator means are positioned in the beam of light emitted by the light unit in use, when the attachment is attached to said light unit. Said photovoltaic generator may comprise at least one photovoltaic cell. 
     Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Following is a description by way of example only with reference to the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention, and of methods of carrying the present invention into effect. 
     FIG. 1 shows a first embodiment of an attachment in accordance with the present invention which is adapted to be supported on a pair of powered lamp bars. 
     FIG. 2 shows a second embodiment of an attachment in accordance with the present invention. 
     FIG. 3 shows a third embodiment of an attachment in accordance with the present invention. 
     FIG. 4 shows the attachment of FIG. 3 as fitted to a theatre light. 
     FIG. 5 shows a fourth embodiment of an attachment in accordance with the present invention which is adapted to be held in the colour frame of a theatre light unit. 
     FIG. 6 is an end view of a fifth embodiment of an attachment in accordance with the present invention. 
     FIG. 7 is an end view of a sixth embodiment of the invention. 
     FIG. 8 is an end view of a seventh embodiment of the invention. 
     FIG. 9 is an end view of an eighth embodiment of the invention. 
     FIG. 10 is an isometric view of a screw-fitting attachment in accordance with a ninth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, an attachment  10  in accordance with a first embodiment of the present invention comprises a light sensor  11  comprising an opaque, elongate tube  12  which is closed at one end  13  and accommodates a light sensing element (not shown) such as a photo-resistive diode. 
     Said light sensor  11  is mounted substantially co-axially within an annular shield member  14  by means of a radial vane  15 . Said annular shield member  14  carries two opposing elongate supporting arms  16 , 17 , each of which is provided with an undercut channel  18  remote from the annular shield member  14  to engage a respective powered lamp bar (not shown). Within each recess, said arm  16 , 17  carries a conducting contact element that is adapted to form an electrical contact with said bar. Said contact element is connected to the electrically operated component of the attachment to provide power thereto. 
     The light sensing element within the elongate tube  12  is connected to a pulse generator (not shown) which is configured to generate a MIDI compatible trigger pulse when light impinges on the light sensing element. The output of said pulse generator is connected to an infra-red transmitter device  19  which is secured to the annular shield member  14  between the supporting arms  16 , 17  as shown in FIG.  1 . 
     In use, said attachment  10  can be mounted on a pair of spaced lamp bars in juxtaposition with a pre-existing light unit, such that the light sensor  11  is mounted substantially centrally within a beam of light generated by the light unit. The attachment  10  is mounted on the lamp bars, such that the closed end  13  of the elongate tube  12  is oriented towards the light unit, and the other open end is directed away from the light unit. The elongate tube  12  serves to shield the light sensing element from ambient light and direct light emitted by the light unit. 
     A user may be equipped with a piece of retroreflected material. When the user cuts the beam of light from the light unit with said retroreflective material, some of the light is retroreflected back towards the light unit and impinges on the light sensing element within the tube  12 , thereby generating a trigger pulse from the pulse generator which is transmitted by the infra-red transmitter  19  to a central receiving hub (not shown). (Alternatively, the system can be operated in an “inverse mode” as described above). Typically such a receiving hub would include a MIDI interface for converting the trigger pulse to MIDI instruction code for controlling a music synthesizer, drum computer or other MIDI-controlled device. 
     With reference to FIG. 2, an attachment  20  according to a second embodiment of the invention comprises a light sensor  21  which is substantially the same as the light sensor  11  included in the attachment  10  of the first embodiment described above. Said sensor carries  3  radially extending arms  22 , 23 , 24  which are pivoted to the open end  25  of the sensor. (Alternatively, the arms  22 , 23 , 24  could be pivoted to the closed end  26 ). Each of said radially extending arms  22 , 23 , 24  is marked with a graduated scale and carries a slider  27  which is fitted with an elongate finger  28 . Said slider  27  includes a grub screw or the like  29  for releasably securing the slider  27  in a selected position along the respective arm  22 , 23 , 24 . Said arms  22 , 23 , 24  are adapted to embrace the body of a light unit (not shown) such, for example, as ellipsoidal, par, pinspot or fresnel lamp, and the arms  22 , 23 , 24  can be pivoted about the sensor  21  and the sliders  27  adjusted, so that the attachment  20  can be fitted to a variety of different sizes of light unit. Said arms  22 , 23 , 24  may be provided with suitable fixing means for releasably securing the arms to the light unit. For example, the fingers  28  may be equipped with screws or bolts for engaging cooperating components on the light unit. Alternatively, each finger  28  may be equipped with a magnetic element or strip. As a further possibility, a strap may be used which may be secured around all the fingers when fitted to a light unit to hold the fingers securely to the body of the light unit. 
     Said light sensor  21  may be equipped with a pulse generator of the kind referred to above in connection with the first embodiment of the invention, and the output of the pulse generator may be connected to a central hub by wires, alternatively, by an infra-red transmitter  19  which may be mounted on one of the fingers  28 . 
     Advantageously, one or more the radially extending arms  22 , 23 , 24  may be equipped with one or more photovoltaic cells  100  which are arranged to face the lamp unit, when the attachment  20  is fitted to the lamp unit. The photovoltaic cells may be used to provide power to the sensor and optional infra-red transmitter  19 . 
     An attachment  30  in accordance with the third embodiment of the invention is illustrated in FIG.  3 . The attachment  30  is similar in construction to the attachment  20  of FIG. 2, except that it includes only a single arm  31 , which arm  31  is equipped with a slider  32  and elongate finger  33  in the same way as each arm  22 , 23 , 24  of FIG.  2 . FIG. 4 shows the attachment  30  of FIG. 3 fitted to a theatre light unit  35 , such that the light sensor  34  is positioned substantially centrally of the lamp  36  of the light unit  35 . In this case, it can be seen that the elongate finger  33  is fixedly secured to a hanging bracket  37  of the light unit  35  and includes an infra-red transmitter  19  that is adapted to transmit MIDI compatible digital control signal to a receiver  38  connected to a MIDI interface and MIDI-controlled equipment such, for example, as a synthesizer. Another alternative attachment  40  in accordance with the fourth embodiment of the invention is illustrated in FIG.  5 . In this case, the light sensor  41  is mounted substantially centrally within a square frame  42  that is adapted to be received in the colour frame  43  of a light unit  44 . 
     A fifth embodiment of the invention is shown in FIG. 6 which illustrates an attachment  50  in which a light sensor  51  is mounted substantially co-axially within a circular band spring  52 . Said band spring  52  is open at  53 , so that the spring can be opened out and entered over or inside the body of a light unit (not shown). The elasticity of the band spring  52  allows the attachment  50  to be secured firmly to the light unit. 
     FIG. 7 shows a sixth embodiment of the invention in which an attachment  60  comprises a light sensor  61  that is mounted co-axially within a loop defined by an endless elastic band  62 . Said band is provided with a pair of opposing slide clips  63 . Said attachment  60  is configured such that it can be entered over the front of a circular light unit (not shown), and the clips  63  are adapted to sliderably engage a protruding annular flange on the light unit. The elasticity of the band  62  allows the attachment to accommodate the range differently sized units. 
     A seventh embodiment of the invention is illustrated in FIG.  8 . According to the seventh embodiment, an attachment  70  comprises a light sensor  71  which, in this case, is generally square. Said frame is formed from a sheet of structural material such as metal (e.g. aluminum or light steel) or plastics, and is provided with a central hole  73 . Said light sensor  71  is mounted within the hole  73  on a vane or other support  74 . Said frame  72  is equipped with a plurality of slide clips of the kind described above with reference to the sixth embodiment. In the embodiment shown, four clips are used, and these are mounted one each on each of the four sides of the frame. However, it is envisaged that more or fewer clips may be used as necessary. 
     An attachment  80  according to an eighth embodiment of the invention is shown in FIG. 9, which attachment  80  also comprises a light sensor  81  mounted substantially centrally within a rectilinear frame  82 . In the eighth embodiment as illustrated, the frame is provided with two clips  85  mounted on opposing sides of the frame. The other pair of opposing sides of the frame each carry a hinged wing  83  which can be used in conventional manner to control the spread of light from a light unit to which the attachment  80  is attached. Alternatively the wings  83  could be folded backwards for use in attaching the attachment to a light unit. 
     According to a ninth embodiment of the invention as illustrated in FIG. 10, an attachment  90  comprises a light sensor  91  of the kind described above which is mounted within a generally cylindrical, opened-ended barrel  92  which carries an internal lens  97 . Said light sensor  91  is mounted on said lens  97  within the barrel, such that the open end of the sensor faces one open end  93  of the barrel. The other open end  94  of the barrel is provided with a hollow threaded stem  95  which is suitable for attaching the attachment  90  to a cooperating threaded bore formed around a lamp orifice of a light unit (not shown). Said open end  93  of the attachment  90  may be equipped with a protruding cylindrical flange portion  96  which may be internally threaded to receive further threaded attachments such as lenses, colour filters and the like. The outer surface of the barrel  92  may be provided with a roughened or knurled finger engaging surface  96  to facilitate attachment of the barrel  92  to and detachment from a cooperating light unit. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.