Abstract:
An underwater diving light has a rotatable front filter ring for selecting light filtration as needed for underwater still or video photography conditions. The filter ring is removable and interchangeable with different rings. Another important feature is efficient cooling of the LEDs and other internal electronics of the diving light assembly. The water is in contact with a metallic front face that conducts heat directly away from a metal core circuit board carrying the LED array or arrays. In one form of the diving light water channels are provided so that the ambient water can enter the assembly to spaces behind the LCD circuit board to efficiently cool the LEDs and associated electronics. The front plate assembly can be removable, for rinsing the internal cooling cavities, for interchange with different front face assemblies, and for air travel when the LCDs must be removed from driving electronics for safety concerns.

Description:
[0001]    This application claims benefit of provisional application Ser. No. 61/414,873, filed Nov. 17, 2010. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
       [0002]    The invention concerns underwater video lighting, and particularly a unit producing a powerful beam from LED sources, with the ability to adjust light filtration by rotation of a front filter ring. The underwater light may produce flood light at about 4000 lumens and weighs less than two pounds. 
         [0003]    A number of underwater lighting devices are available for divers, some with rechargeable batteries and some also including flip-down color filters, such as red filters. 
         [0004]    When an underwater photographer, including a video photographer, dives below about thirty feet during daylight, virtually all red has been filtered out of the ambient light. Because of the color adjustment (white balance) that is usually made by the diver&#39;s video camera, the colors in the video images will be adjusted to replace the red, but light projected from a diving light will compete with ambient light and areas of the video image that include the artificial light will appear overly red when color-balanced by the camera. The situation is different in night diving, in which the only light available is that from the diving light, and unbalance of color in different areas of the image is not a problem. 
         [0005]    Most diving lights previous to this invention have been little more than waterproof flashlights. None has included any filter to address the color balance problem noted above, nor has any included a convenient multi-filter manual selection on a powerful video diving light as in the current invention described below. 
         [0006]    The diving light of the invention, particularly for video support, is a relatively large underwater device, yet light in weight, with a beam which can be about 4000 lumens of flood light. Within the light&#39;s casing is a battery providing for about one hour of light at 4000 lumens (or about two hours of light at 2000 lumens, or about four hours of light at 1000 lumens). 
         [0007]    The dive light of the invention has a snap-on front filter ring, interchangeable with other filter rings as selected, the filter ring being rotatable about the face of the light casing and having several selectable filters. Light projection is from an off-center position on the face of the housing, enabling different filters to be placed in front of the light beam by rotation of the bezel. One important filter preferably included on the dive light is a blue/green filter, which can be used to approximately match the projected light beam to the ambient lighting when diving in conditions of near-total red depletion from the natural light. 
         [0008]    The light source of the device is a very tight cluster of LEDs, which may be sixteen in number. The tight cluster enables the off-center positioning of the light source as noted above. The tight LED array generates considerable heat, making the LED mounting board and surrounding areas hotter than would be the case if the LEDs were spread around the entire face of the housing. To dissipate the heat the LEDs are mounted onto a metal core board, and the face of the unit preferably is mostly metal and contacts the LED board. This provides an efficient heat sink for the LED array. Only a small sealed window is provided, directly in front of the LED cluster. 
         [0009]    Federal Aviation Administration (FAA) regulations require that devices generating significant amounts of heat must have the power source and heat generating element physically disconnected for air travel. So the device must allow a user easily to physically disconnect the LED cluster from the battery at some point in the circuit. Most dive lights do this by either (a) allowing the user to disconnect and/or remove an internal battery, or (b) using a separate battery housing with a cable and connector leading to the light head. The former requires opening a part of the device that is typically sensitive to water intrusion. Opening and closing a pressure seal repeatedly can and does introduce physical damage or dirt and grime to the seal, providing a path to potential flooding and corrosion. The latter adds a second pressure hull and a flexible cable, both of which are additional potential failure points. 
         [0010]    An important second aspect and form of the invention therefore encompasses an advanced sealing setup. In use it is an entirely self-contained assembly, but it allows disconnection for FAA compliance, and when disconnected the separate assemblies are themselves completely sealed. Specifically, in this form the face plate assembly containing the LEDs is an individual pressure hull, but it can be easily removed by unthreading the bezel ring and pulling the face plate assembly off of the body unit. The body unit is itself an individual pressure hull. As an added benefit for easy storage and to prevent possible damage, the bezel ring allows the face plate assembly to be flipped over and stored backward, so that the device is electrically disconnected but physically in one piece. 
         [0011]    In order to allow this easy disconnect, the back of the metal core circuit board is equipped with a series of exposed contact pads on the rear face. These pads are plated with a corrosion-resistant material, typically gold, and they are contacted by a series of spring-loaded knee-type contacts attached to an intermediary plate on the front of the body unit. The knee-type contacts are also plated with corrosion-resistant material. A heavy-gauge nonconductive alignment pin is used to help the user align the face plate assembly to the body unit so the connections are made reliably. The face plate assembly is sealed to the body unit by a large bore o-ring so that the entire area between the face plate assembly and the body unit is dry. 
         [0012]    Another important part of the face plate assembly and body unit structure is cooling of electronics contained in the body unit. While the LEDs produce most of the heat in the system, the drive electronics can produce upwards of 10%, or about 6 watts when running at 4000 lumens. Without proper heat dissipation the drive electronics can overheat and fail. For this reason, in this second form of the invention, the intermediary plate is equipped with thermal transfer pads that interface to wide areas on the rear of the face plate assembly, providing a relatively short thermal path from hot components to intermediary plate to face plate to water. In this form, both the metal core circuit board and the intermediary plate are passing heat through the face plate to the water, which is fairly efficient. 
         [0013]    In order to output the maximum amount of light possible, LEDs must be cooled as much as possible. In a typical case, cooling the LEDs from 55 down to 45 degrees Celsius will increase output approximately 100 lumens when running at 4000 lumens, with no other changes, so the shortest heat path from LED to water is desirable. 
         [0014]    In the first and second forms of the invention, the metal core circuit board is connected around its edges to the face plate. Thus all the heat must travel laterally across the metal core circuit board to be conducted away. In a third form of the invention, the face plate assembly is not sealed to the body unit, but instead it has large holes to allow water flow into the cavity between body unit and face plate assembly. The face plate assembly has a large rear cap that encloses the metal core circuit board to protect it from corrosion. This rear cap also has a collared area that extends toward the intermediary plate and creates a sealed volume around the connector pads and connector. Thus the heat path is through the thickness of the metal core circuit board and the thickness of the rear cap, rather than along a greater lateral distance. 
         [0015]    In a fourth form of the invention, the metal core circuit board is allowed to directly contact the water, for even better cooling. This can introduce corrosion on the metal core circuit board, but if the device is properly rinsed in fresh water and dried between uses (typical and customary for this type of equipment) the corrosion is minimal and the heat path is reduced further to just metal core circuit board to water. In this form, the rear cap takes a different form and is just the collar bolted to the central area of the metal core circuit board, to form the sealed volume around the connector. Additional benefits of this form are reduction in overall weight, and increased volume of cooling water inside the head, due to the smaller sealing collar instead of the fully enclosing cap of the third form. 
         [0016]    Another form of the invention that is compatible with any of the four sealing and thermal solutions discussed above, employs a second array of LEDs added to a larger metal core circuit board. The multi-function switch on the body unit provides the user the ability to easily turn on one or the other array of LEDs. The second array can be a different color such as red, can be electromagnetic energy outside the visible spectrum such as infrared or UV light, or can be any wavelengths of light focused by dedicated optics, such that the upper array can provide a wide flood light and the lower array a focused spot beam. The advantage of the clustered arrays is that the blue or red filters held by the rotating filter ring enable use of light either filtered or unfiltered, by rotating the filter ring into various positions. 
         [0017]    Another benefit of the removable front plate is the ability to provide interchangeable face plate assemblies to a user. A user might choose to switch face plates (a) to upgrade to a new brighter set of LEDs, (b) to replace a failed face plate or body unit, (c) to switch between colors or types of single-mode face plate units, for instance spot-only for flood-only, (d) to switch from a single-mode face plate unit to a multi-mode face plate unit such as spot plus flood. The body unit electronics can be designed to recognize the available use modes of the attached face plate unit by a detector circuit, and adjust the type of switching available to increase ease of use. 
         [0018]    A typical equipment setup for underwater still photography includes a sealed camera housing and one or more underwater strobe units. In the past, film photography required the intense output of powerful flashbulbs; these flashbulbs produced very short bursts of light typically 8-10 times as bright as video lights. Digital photography increasingly allows use of much less powerful lighting to achieve the same results. As self-contained underwater lights increase in power, it is possible to completely replace dedicated flash units with video lights in some situations. Replacing strobes is even more practical if the video lights are capable of producing short bursts at increased power levels, for instance two times the maximum constant output of the light for video use. The final form of the invention, which is compatible with all other forms previously discussed, addresses this need. In this form, one or more large capacitors are added to the electronic circuit to provide a short, powerful burst of energy, which along with the power available directly from the battery, is capable of generating the flash output. The battery charges the capacitor(s) in between flashes. The flash is timed to the shutter of the camera by a synch cable. The synch cable can be a fiber optic cable carrying light from the camera&#39;s flash unit, or an electronic cable carrying an industry-standard synch signal. 
         [0019]    The light unit of the invention is charged using external wet style connectors, allowing the body unit to be sealed at the factory and never opened in the field, improving reliability for the diver. 
         [0020]    It is an object of the invention to improve over previous dive lights available for video support, including in brightness, duration, cooling efficiency, and convenient filtering of the light beam as needed. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective view showing a diving light of the invention. 
           [0022]      FIG. 2  is a partially exploded view of the first form of the diving light, showing a front filter ring removed. 
           [0023]      FIG. 3  is a side elevation view in section showing the assembly of the first form of the diving light, particularly the front. 
           [0024]      FIG. 4  is an exploded view of the separate assemblies in the second form of the invention. 
           [0025]      FIG. 5  is a view of the back side of the face plate assembly in the second form of the invention. 
           [0026]      FIG. 6  is an exploded view of the face plate assembly in the second form of the invention. 
           [0027]      FIG. 7  is an exploded view of the intermediary plate in the second, third, and fourth form of the invention. 
           [0028]      FIG. 8  is a partially exploded side elevation view, in section, of the second form of the invention. 
           [0029]      FIG. 9  is a side elevation view, in section, of the second form of the invention, at the front. 
           [0030]      FIG. 10  is an exploded view of the face plate assembly showing the third form of the invention. This figure also shows a face plate with two LED arrays. 
           [0031]      FIG. 11  is a rear view of the face plate assembly showing the third form of the invention. 
           [0032]      FIG. 12  is a side elevation view in section showing the main assemblies of the third form of the invention exploded by assembly. 
           [0033]      FIG. 13  is a side elevation view in section showing the assembled third form of the invention. 
           [0034]      FIG. 14  is a partial side elevation section view of the front of the third form of the invention, showing flow of water into the assembly. 
           [0035]      FIG. 15  is a partial top plan section view of the front of the third form of the invention, showing flow of water into the assembly. 
           [0036]      FIG. 16  shows the front of the face plate assembly of the fourth form of the invention. 
           [0037]      FIG. 17  shows the rear of the face plate assembly of the fourth form of the invention. 
           [0038]      FIG. 18  shows an exploded view of the face plate assembly of the fourth form of the invention. 
           [0039]      FIG. 19  shows a side elevation section view of the complete unit with large capacitors added to the electronic circuit. 
           [0040]      FIG. 20  shows an aspect view of the intermediary plate and the face plate assembly, showing the capacitors on the connector PCBA. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]    In the drawings,  FIG. 1  shows a dive light  10  having a housing  12  formed of a casing  14 , a front section or face assembly  16  attached to the casing, which can be by sealed threaded connection, a mounting interface device  17  and a rotatable filter ring  18 . The device  17  is shown as a standard interface, to be received in a socket on a camera light arm accessory. On the casing is a switch assembly  20  with slide switch  22 , for switching the dive light on and off and selecting a desired power level. At the front of the dive light device a beam is projected by an array  24  of LEDs in a tight cluster as shown. These may be sixteen in number. 
         [0042]    With reference to both  FIGS. 1 and 2 , the filter ring  18  snaps onto and off a position of covering the front face  26  of the unit. The front of the unit has a bezel ring  28 , forming an annular recess  30 , which is gripped by overhanging structure (not shown in  FIGS. 1 and 2 ) on the rim  18   a  of the filter ring to hold the filter ring in place on the housing, and to allow its snap-off removal and interchanging with another filter ring when desired. The purpose of the rotatable filter ring  18  is to provide different filtration for light emitted from the LED array  24 . Light filters  32  and  34  are shown, secured in filter ring openings  32   a  and  34   a . A third filter ring opening  36  can be fitted with another filter or can be left open, as shown, for a selection of no filtration. 
         [0043]    As noted above, one of the filters  32  preferably is a blue/green (cyan) filter, for filtering out most of the red component of the light beam to match the artificial light closely with ambient light filtering through relatively deep water. The blue/green or cyan filter, used at depth, makes the LED light beam close to the color of natural light at depth, and the user&#39;s video (or still) camera will light balance the image correctly so that objects illuminated from the dive light will look normal in the video or photograph. This is a great advantage in daytime wide angle photography and video where ambient light is the dominant light; without the cyan filtration the dive light will produce different color lighting from the ambient light, creating an unbalanced and undesired appearance in the picture or video. 
         [0044]    The other filter  34  can be a diffuser, which will spread and disperse the flood light more widely. Preferably, any of the optical filters are mounted in industry-standard threaded rings that can be assembled or disassembled from the filter ring simply by threading in or out. 
         [0045]    The slide switch  22  is a toggle switch. It operates within the non-waterproofed switch assembly or sub-housing  20 , by magnetic interface with magnetic pickups inside a sealed casing  14 . In a preferred embodiment of a single-mode LED face plate, the switch is effective as follows: a momentary push forward will turn the light on, preferably at a medium power level, or power level  4 ; a series of further momentary pushes forward will change the beam to levels  5 , then  6 , then  7  or high power; a momentary push back will lower the light level among the seven different settings successively; and a forward or back push with a hold (e.g. two seconds) will turn the power off. When using multi-mode LED face plates, such as spot-flood, a momentary push forward or backward will change the power level upward or downward among the available number of power settings in the current array, a push and hold forward will switch between LED arrays (e.g. from spot to flood), and a push backward with a hold, will turn the light off. 
         [0046]      FIG. 3  is a side elevation view of the first heat path option in section illustrating the dive light  10  and particularly positioning and connection of components at the front of the unit. The face plate is seen at  26 . Within the upper opening of the face plate is a circular glass window  40  retained within a recess of the face plate using a retaining ring indicated at  42 . A water tight seal is made with a seal ring or O-ring  43 . A metal core circuit board  44  has soldered to it all of the LEDs (preferably sixteen) of the LED array  24 , as shown. The LED array produces a flood beam, approximately 80° spread in water, approximately 110° spread in air (although the spread could be different). Thus, the optics are simple. A reflector  46 , best seen in  FIG. 2 , is incorporated within the recess having the glass window  40  at front. The reflector, preferably conical, may be formed as a surface on the face plate  26 , which preferably extends inward as shown. The glass window  40  is indicated as “port” in  FIG. 3 . 
         [0047]    As mentioned above, the LED array  24  is a very tight cluster and generates considerable heat, particularly at high power setting. This is dissipated using a heat sink which comprises the metal core circuit board  44  and metal face plate  26 , including the portion extending rearwardly to contact the circuit board  44  as shown. The metal core circuit board  44  is screwed onto the face plate  26 , both of which can be aluminum. The large aluminum plate  26  at the face of the unit contacts water on the outside surface, which immediately cools the attached metal core LED board and prevents overheating. 
         [0048]    The filter ring  18  is also shown in  FIG. 3 , rotatable on the housing and retained thereon via the annular groove  30  in the bezel ring  28 . 
         [0049]    The dive light unit  10  is self-contained, including a rechargeable battery indicated at  50 . A wet style recharging terminal (not shown) enables sealing of the unit without need to open it after manufacture. 
         [0050]      FIG. 4  shows the assemblies a user will encounter when operating a second form of the invention. The filter ring  18  comes off as previously described. The user then unthreads the bezel ring  28 , exposing the edge of a face plate  26   a  of the face assembly  16   a . Pulling on the face plate  26   a  removes it from the body unit  12   a . An intermediary plate  60  encloses the housing or body unit  12   a  together, being secured to the body  14   a , and provides a mounting location for a multi-contact electrical connector  62 . The intermediary plate  60  also has two symmetrical thermal transfer pads  66  that contact the back of the face plate  26   a  to provide an escape path for heat from the electronics inside the body unit. Finally, it has a steel alignment pin  64  so that the user can easily orient the face plate  26   a  so that the connectors are properly aligned. 
         [0051]      FIGS. 4 and 6  shows grooves  27  formed in the front of the face plate. These grooves or recesses expand the surface area available for cooling by water contact; they do not extend through the face plate. 
         [0052]      FIG. 5  shows the reverse side of the face plate assembly. The previously described LED array is mounted to a metal core circuit board  44 , similar to the metal core circuit board described previously. On the back side of that board are gold plated contact pads  44   a , which interface with the connector  62  from  FIG. 4 . Two wide areas  26   b  provide broad contact for thermal transfer from the thermal pads  66  shown in  FIG. 4 . An alignment feature  26   c  accepts the alignment pin  64  shown in  FIG. 4  to ensure connector alignment. To help the user remove the front plate assembly from the body unit, there are two stepped areas  26   d  in face plate  26   a  that are sized to accept common coins such as a U.S. quarter dollar. Inserting and twisting the coin allows the user to overcome the significant friction of the main bore seal o-ring (part  51  in  FIG. 6 ). 
         [0053]      FIG. 6  shows the face plate assembly  16   a  for this second form of the invention. The face plate  26   a  holds the reflector  46  and glass port or window  40 , sealed by an o-ring  43  and retained by a retaining ring  42 , as previously described. The main seal o-ring  51  is installed on the plate  26   a  to seal against the inner bore of the body unit. The metal core circuit board  44  is sealed to the face plate by an o-ring  41 , and held on by four screws S that lie outside the seal groove. This keeps the LED components on the circuit board from any contact with water, even if the main seal o-ring  51  fails at some point. 
         [0054]      FIG. 7  shows the intermediary plate  60  that is installed in the front of the casing or body  14   a . It is permanently sealed into the body by a main bore o-ring  52 , and held in with two screws S, which are sealed by two small o-rings  69 . At the center of the intermediary plate  60  is an opening for mounting a connector circuit board  65 , which is sealed to the intermediary plate by an o-ring  68  and held in place with two screws S. Thus the connector board  65  is exposed at the front of the housing or body unit  12   a  so it can contact the connector pads  44   a  on the metal core circuit board  44 , but otherwise the body unit  12   a  is completely sealed. 
         [0055]      FIGS. 8 and 9  show the bezel ring  28 , face plate assembly  16   a , and casing or body  14   a  exploded and then assembled in cross section to illustrate the electrical path and assembly method. The battery  50  is connected to a main driver electronics circuit board  71  by a cable (not shown). The driver  71  controls the amount of power routed to the LED cluster, and outputs current through a cable  70 , through a header  67  on the back of the connector circuit board  65 , through the board, to spring loaded contacts of the connector  62  exposed at the front of the unit  12   a . See also  FIG. 4 . The intermediary plate  60  is sealed into the body  14   a  by the o-ring  52 . The face plate assembly is sealed into the body by the o-ring  51 . 
         [0056]    The form of diving light shown in  FIGS. 4-9  efficiently carries away heat, both from the LED array and from electronics inside the body unit  14   a . Heat from electronics inside the body unit is conducted through the contact pads  66  on the intermediate plate  60  to the wide areas  26   b  on the back of the face plate, via pressed and wide-area contact when the bezel  28  is tightened onto the body. Also, heat from the LED array on the front of the metal core circuit board  44  travels outwardly through the metal board to the tight connection between the metal board  44  and the back side of the face plate  26   a . The front of the face plate  26   a , cooled by direct contact with water and with enhanced surface area provided by the grooves  27 , dissipates the heat from the body  14   a  and from the LED array to the water. 
         [0057]    Note that the metal core circuit board in the embodiments of  FIGS. 1-9 , in thermal conductive contact with the face plate in both cases, is preferably in direct contact with the face plate, but the contact could be indirect, via intermediary conductive metal. 
         [0058]    As noted above, the face plate  26   a , for purposes of air travel, can be pulled out from the casing or body  14   a  after removal of the threaded bezel ring  28 . This can also be done for the purpose of interchanging a different face plate on the body, such as for different spot/flood characteristics or different light colors or an upgraded face plate. For air travel, where the LED array may have to be completely disconnected from electronics connected to the battery, the face plate  26   a  can be flipped around, placed against the front of the body and secured thereon using the bezel ring  28 . The exposed rear contacts  44   a  ( FIG. 5 ) of the face plate, now oriented forwardly, can be covered with a plastic cover or cap (not shown). 
         [0059]      FIGS. 10 and 11  show a modified assembly with two arrays of LEDs, and also the face plate setup for this third form of the invention. A two-array face plate  26   e  contains two large circular openings, top and bottom. The top opening contains an identical set of parts as previously described for the single array  24  of LEDs, including a reflector  46  for illustration, and a transparent window  40 , preferably a glass port. The bottom opening contains a molded window  75  that is flat on the front but contains seven integrated total-internal-reflection (TIR) optical cones designed to project light in a spot beam. A modified two-array metal core circuit board  44   b  is shown with an upper array  76  of 16 LEDs and a lower array  77  of seven LEDs in a preferred embodiment, though either number of LEDs could vary. 
         [0060]    In this form of the invention, the face plate  26   e  has two large side openings  26   f  which allow water to pass through the face plate to cool the internal electronics more directly. A rear cap  78  in this embodiment encloses the entire metal core circuit board, completely sealing the board against water intrusion. The rear cap  78  is sealed to the metal core circuit board at the center by an o-ring  80 , creating a small volume  78   a  to protect the contact pads on the back of the metal core circuit board. The rear cap is held on by screws S that are independently sealed by o-rings  82 , and then by a larger outer o-ring  84  shown in  FIG. 12 . The rear cap contains an o-ring  86  that forms a bore seal on the opening  18   a  in the intermediary plate (see  FIGS. 4 and 7 ) in use. Thus the entire front plate assembly is independently sealed, and it can connect to the intermediary plate and provide more direct cooling to the electronics. Water can enter through the front plate and extend into a space between the back of the rear cap  78  and the intermediate plate of the sealed body, cooling both directly. The rear cap draws some heat from the circuit board  44   b , and may be of relatively thin heat-conducting metal, directly contacting the metal core circuit board  44   b  to cool the board from the back. The metal board  44   b  is of thick metal, e.g. copper or aluminum, about ⅛ inch or greater in thickness. It is also in contact with the front panel of the face plate, the front side of which contacts the outside water, so it is cooled from both sides, which helps minimize temperature for best LED light output. 
         [0061]      FIGS. 12 and 13  further illustrate the dual array LED embodiment, as well as this third form of the invention. Upper LED array  76  and lower LED array  77  are mounted on the metal core circuit board  44   b . The TIR optic  75  is placed in front of the lower array. The outer rim of the rear cap  78  is sealed to the face plate  26   e  by the o-ring  84 . The inner face of the rear cap is sealed to the circuit board by an o-ring  88 . These are permanent seals, all within the face plate. The rear cap also contains an o-ring  86  which seals on the bore in the center of the intermediary plate  60 . This view also shows a modified body  14   b , which has channels  14   c  at the top and bottom to provide more water flow through the front of the unit. Also, the body  14   b  is shorter than the previously described version of the body  14   a  ( FIG. 4 ), both because it does not need to provide a bore seal to the face plate assembly, and because the shorter body provides for better water flow. 
         [0062]      FIGS. 14 and 15  show the openings that allow water to flow through the assembly.  FIG. 14  is a side elevation cross section which shows the cuts in the body identified above as  14   c , that allow water to travel from the top and bottom behind the front bezel ring. The male threads (not shown but seen in  FIG. 12 ) at the front of the body  14   b  are interrupted at these cuts or channels  14   c .  FIG. 15  shows a top plan cross section which shows the larger openings  26   f  which allow water to enter from the front. The areas shown are all connected, so water can freely flow through and circulate via these four openings. More openings could be provided if desired. The water cooling space between the intermediate plate  60  and the rear cap  78  is seen at  89 . 
         [0063]      FIGS. 16 through 18  show a fourth form of the invention. A modified face plate  91  has openings  91   a  that function similarly to the openings  26   f . The shape difference compared to  26   f  is cosmetic.  FIGS. 17 and 18  show the metal core circuit board  44   c , now exposed to flowing water (not covered by a rear cap as in  FIGS. 10-15 ), with a smaller, modified form  92  of rear cap. In this form, the cap forms a volume  92   a  exactly like  78   a  described above, to enclose the connector pads  44   a . However, this cap only seals off a small area of the metal core circuit board with an o-ring  53 , leaving the rest exposed to water. The rear cap  92  is sealed to the intermediary plate by a bore seal o-ring  86 . The rear cap and metal core circuit board are bolted to the face plate  91  with four screws S to form a permanently sealed face plate assembly. The cooling water enters the space behind the face plate via the openings  91   a  and directly contacts the metal core circuit board  44   c  as well as the intermediate plate  60  of the main casing or body. Again, the face plate is easily removable from the main body for interchanging a different face plate or for air travel safety requirements, and also for rinsing salt water off these inner components; rinsing is important for all embodiments. 
         [0064]    As noted above, cooling of the metal core circuit board by contact with ambient water is important and preferred, for optimum LED performance. With the water entering the assembly and directly contacting the metal board from behind, the front panel of the face plate might even be formed of plastic. 
         [0065]      FIG. 19  shows the complete assembly with a single LED array, with the addition of two large capacitors  94  attached to the connector circuit board. In this embodiment, the capacitors shown are rated at 1 microfarad at 100 volts. The battery and driver electronics charge up the capacitor between pulses, and then the capacitors discharge into the LED array on a timing signal, producing approximately 8000 lumens for 1-3 microseconds, as a flash. 
         [0066]      FIG. 20  shows a detailed view of the intermediary plate  60  and a face plate  26   a  assembled together, with the capacitors  94  attached to the connector board  65 , with the connector  67  that brings power and timing signal from the control electronics. 
         [0067]    In a preferred embodiment the dive light  10  produces a maximum flood light output (level  7 ) power of 4000 lumens, which can be maintained for about 50 minutes to one hour. At a medium power setting (level  4 ) of 1500 lumens, the duration is about 150 minutes. At a low setting (level  1 ) of 500 lumens, the flood beam will last for about 10 hours. Charge time: 85% at 90 minutes, 100% at 150 minutes. The unit preferably weighs no more than about 750 grams (about 1.65 lb.). 
         [0068]    The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention.