Patent Publication Number: US-2023158189-A1

Title: Germicidal lighting system

Description:
TECHNICAL FIELD 
     Germicidal lighting systems. 
     BACKGROUND 
     A germicidal lighting system uses ultraviolet radiant energy, for example UVC, to inactivate microorganisms such as bacteria, mold spores, fungi, or viruses (germs). Germicidal effectiveness depends on the exposure dose (radiant exposure, typically in millijoules per square centimeter, mJ/cm 2 , or joules per square meter, J/m 2 ), which is the product of the dose-rate (irradiance, typically in mW/cm 2  or W/m 2 ) and time (from 1 μs to several hours). 
     Typically, a threshold dose of radiation such as UVC on an area can effectively inactivate the germs on that area. A larger dose of UVC radiation than the threshold may cause or worsen color fade, material damage, or equipment disorder in that area without significantly improving germicidal effect. A smaller dose of UVC radiation than the threshold may not meet the germicidal purpose. 
     Most commercially available germicidal UVC devices generate diffusing non controllable scattering UVC beams. The UVC doses on the radiated area are not evenly distributed. Some small area may receive overdose of UVC to damage things while another small area may receive not enough dose to effectively kill germs. If there are some objects which can block the UVC beams on the radiated area, shadowed parts of the objects (e.g. the inner parts of the handles of doors) may receive no UVC beams at all. 
     SUMMARY 
     Embodiments of this germicidal lighting system solve one or more of the problems mentioned in the background for example by providing directional UVC radiation beams and means to control the beams. In one example, a directional germicidal light source includes LEDs on one or both sides of a heat sink, light from the LEDs being directed by a concave mirror. In an example, plural directional germicidal light sources are rotatably mounted to a robot. In an example, the light sources are mounted for rotation around axes horizontal relative to the robot and longitudinal relative to the light sources. 
     Controlled directional beams may be used to provide desired amounts of light to varied surfaces, such as flat and curved surfaces, holes, channels or other regular or irregular subjects. The beams may also provide relative even intensity and provide doses close to a desired amount, which may for example be a germicidal threshold for UVC light shining on the surface of the subject. Embodiments may provide a high efficiency of germicidal tasks, optimize radiation time, and avoid over-exposure of UVC radiation on subjects that may degenerate under UVC light. 
     The germicidal lighting system may be controlled by an AI (artificial intelligent) control system implemented by software running on a processor incorporated into the germicidal lighting system itself or into device on the UVC lighting system to achieve automatic disinfecting tasks. The UVC lighting system may also be controlled, monitored, or transmit information through wired or wireless methods including with internet, local net, Bluetooth, or internet of things (IoT). 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which: 
         FIG.  1    is a schematic diagram showing an exemplary germicidal lighting system. 
         FIG.  2    is an isometric view of an example directional germicidal light source for the germicidal lighting system of  FIG.  1   . 
         FIG.  3    is a side view of the directional germicidal light source of  FIG.  2   , also including a lens. 
         FIG.  4    is a schematic diagram of a germicidal light source including a concave mirror positioned to cause the light source to produce parallel light. 
         FIG.  5    is a schematic diagram of the germicidal light source of  FIG.  4    with the concave mirror moved to cause the light source to produce converging light. 
         FIG.  6    is a schematic diagram of the germicidal light source of  FIG.  4    with the concave mirror moved to cause the light source to produce diverging light. 
         FIG.  7    is a schematic diagram of an example directional germicidal light source using an optical fiber to direct light. 
         FIG.  8    is a flow chart showing a method of controlling a dose provided to a surface by a germicidal lighting system. 
         FIG.  9    is a flow chart showing a method of irradiating first and second portions of a surface. 
         FIG.  10    is a flow chart showing a method of irradiating an object adjacent to a surface. 
         FIG.  11    is an isometric view of a germicidal lighting system with multiple light sources around a mast on a movable base. 
         FIG.  12    is a top view of a header for a germicidal lighting system as shown in  FIG.  11   , with an exemplary arrangement of sensors shown. 
         FIG.  13    is a schematic cross section view of an exemplary directional germicidal light source including UVC LEDs on a heat sink. 
         FIG.  14    is an isometric view of the directional germicidal light source shown in  FIG.  13   . 
         FIG.  15    is an isometric view of an exemplary germicidal lighting system including plural germicidal light sources substantially as shown in  FIG.  14   . 
     
    
    
     DETAILED DESCRIPTION 
     Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims. 
     Germicidal Lighting System 
     A germicidal lighting system may include a movable structure, for example a robot, trolley or handcart, on which a germicidal light source is mounted. 
       FIG.  1    is a schematic diagram showing an example germicidal lighting system  10 . In this example, a germicidal light source  12  is mounted on a robot arm  14 . The robot arm extends from movable structure  16 , in this example having wheels  18 . The germicidal light source  12  is shown in more detail in  FIGS.  2 - 3   . The light source  12  in this example is a linear shaped light having a direction of extent perpendicular to a direction of light emission. The robot arm  14  may move and orient the light source  12  to adjust the position and direction of light emission. The robot arm may be moved by actuators such as actuator  26  shown in  FIG.  1   , or may be moved manually. 
     The germicidal light source  12  may be, for example, a UVC light source. The UVC light source can be gas discharge lamps, LEDs, or lasers in any shapes. A germicidal light source can be a linear light, other special shaped light, or a spotlight. The UVC light source may comprise a single linear lamp as shown in  FIG.  1   , but could also use a spot lamp, a single lamp of a different shape or multiple lamps, each of which may be a linear or spot lamp or a lamp of a different shape. The mention of an element, such as a germicidal light source, in the singular does not exclude additional similar elements. 
     The lighting system may be powered by, for example, rechargeable batteries  20  or by mains power. The germicidal light source  12  may be directional. The directional germicidal light source may be mounted movably on the movable structure for adjusting an orientation of the directional germicidal light source relative to the movable structure. For example, in the embodiment shown in  FIG.  1    the germicidal light source  12  is mounted on robot arm  14  to control position and direction. In another example, the germicidal light source  12  may be mounted on a rotating mount to control direction only. 
     The germicidal lighting system may include one or more sensors, shown in  FIG.  1    as a sensor and alarm system  22 . Where the germicidal lighting system is controlled by a computer, information from the sensors may be sent to the computer for the computer to use in controlling the germicidal lighting system. Regardless of whether the system is computer-controlled, information from the sensors may be used to supply information to users, for example on a display or an alarm. A computer, whether or not controlling the system, may analyze information from the sensors and determine whether to generate an alarm based on the analysis. 
     An alarm system, for example using light or sound, may be provided, shown in  FIG.  1    as a sensor and alarm system  22 . For example, an alarm may be generated on the germicidal lighting system producing germicidal light, in order to alert people in the vicinity that such light is being produced. An alarm may also be provided in other circumstances such as on determining that a desired dose has been supplied to a surface. An alarm may be produced in any other circumstances which it is considered desirable to bring to the attention of people, such as for example the sensors have detected a potentially unsafe condition such as a person in a field of emission of the germicidal light. In the event of detecting an unsafe condition, the system may stop the emission of germicidal light immediately and generate the alarm in order to alert people of the need to remedy the unsafe condition or to override the halting of the system in the event that the detection is a false detection. 
     The germicidal lighting system may be automated and controlled by a computer that may be mounted on the moving structure, such as in a control box  24  as shown in  FIG.  1   , or located elsewhere. The computer may operate the germicidal lighting system following high-level instructions that may be presented to the computer for example by the means described above. 
     The germicidal lighting system may be configured with hardware or software to limit the germicidal lighting to selected disinfecting areas. The selections of disinfecting areas could be preprogrammed, for example by mapping and selecting areas for disinfection, or could be remote controlled, or controlled by an artificial intelligent system. 
     The germicidal lighting system may be self moving, e.g. using a motor, or manually pushed, and the germicidal light source may be moved and adjusted manually or using an actuator. The germicidal light source may be controlled by various means, including commanding from a control panel with push-button or touch screen; commanding from a wired remote controller; commanding from a infra-red remote controller; commanding from smart phones/pads via Bluetooth network; commanding from smart phones/pads via WIFI network; commanding from a computer via WIFI network or Bluetooth network or Ethernet or other wired/wireless network including wired or wireless IoT. The robotic arm and the scannable light fixture can also be controlled by a robot. The robotic arm and the scannable light fixture can be controlled by the combinations of the above controlling methods.  FIG.  1    schematically shows a remote controller  28  for controlling the germicidal lighting system. 
     The light source may be movable in a scanning motion. A scanning motion may include, e.g. translational motion of the light source, for example perpendicular to the direction of extent. A scanning effect may also be achieved by changing the direction of light emission. In an embodiment, the direction of extent of a linear light source may also be rotatable. 
     A germicidal light source may include a mirror, a lens or both for directing the light from the germicidal light source.  FIG.  2    shows an example light source  30  having a light producing element  32  with a mirror  34 , and  FIG.  3    shows the light source  30  of  FIG.  2    also including a lens  36 . A relative position of the lens  36  and the light producing element  32  may be adjustable, for example by moving the light producing element. A germicidal light source could also be directional by producing light in a collimated manner, as in a laser, or by blocking light traveling in unintended directions. Directionality may also be provided by directing the light using a waveguide, such as an optical fiber as shown in  FIG.  7    or multiple optical fibers separately or in a bundle.  FIG.  7    shows a germicidal light producing element  50  which sends germicidal light into an optical fiber  52 . The germicidal light  54  exits from an end of the optical fiber opposite from the light producing element  50 . The waveguide may be moved as a whole unit or may be flexible such that an exit of the waveguide may be moved separately from a light producing element, as shown for the optical fiber  52  in  FIG.  7   .  FIG.  7    also shows an optional additional optical fiber  56  directing germicidal light  58 . 
     The position and direction of a directional germicidal light source may be considered to be the position of, and direction of light emitted from, an exit optical element or aperture, regardless of the positioning of the light producing element or any intermediate optical elements. The exit of the additional optical fiber  56  shown in  FIG.  7    is positioned and oriented independently of the first optical fiber and thus forms an additional directional germicidal light source. In this case, the different germicidal light sources share the same light producing element  50 , but they could also have different respective light producing elements. 
     Where the directional germicidal light source includes a mirror  34 , the mirror can be, for example, a concave mirror. In an embodiment, the relative distance between mirror  34  and light-producing element  32  can be adjusted as shown in  FIGS.  4 - 6   . The mirror  34  may be shaped so that, for some relative distance between the mirror and a light producing element  32 , the output from the mirror forms a beam of generally parallel light  38 , as shown schematically in  FIG.  4   . In the example shown in  FIGS.  4 - 6   , the relative distance between mirror and a light-producing element is increased in  FIG.  5    to produce a convergent beam  40 , and reduced in  FIG.  6    to produce a divergent beam  42 . In other embodiments, adjustments in distance could produce varying degrees of convergence or divergence. A convex mirror or a flat mirror could also be used and would produce divergent light regardless of distance. 
     A lens  36  such as shown in  FIG.  3    may also be used to adjust a focus of the directional germicidal light source. In an embodiment a focus of the germicidal light source may be adjusted by adjusting the lens, for example by varying a position of the lens. 
     In an embodiment, the light may be adjusted in direction by rotating the mirror around the light producing element. 
     Germicidal Lighting Methods 
       FIG.  8    is a flow chart showing an example method of managing dose when disinfecting using germicidal lighting. In step  100 , a germicidal light source is provided in conjunction with a processor and a sensor. The mention of an element in the singular does not exclude others being present, here or in the claims. The germicidal light source may be operated in step  102  to apply germicidal light to a surface, in step  104  the processor receiving signals from the sensor relating to the surface and in step  106  the processor determining an intensity of the germicidal light on the surface based on the signals. The processor may then in step  108  calculate a dose provided to the surface based on the determined intensity of the germicidal light on the surface and a time during which the germicidal light was applied to the surface. The processor may in step  110  produce a stop signal when the dose reaches a threshold. The stop signal can be for example, a signal to the germicidal light source to cause the germicidal light source to turn off. Note, a “signal” can include an absence of an expected signal, for example, the ceasing of providing a signal to the light source to turn off. The germicidal light source may be movable in position or orientation in response to movement signals from the processor, and the stop signal can be a movement signal, causing the germicidal light source to no longer irradiate the same surface. The stop signal can also be an alarm presented to a user, so that the user can cause the germicidal light source to cease to provide germicidal light to the surface, for example by turning off or moving the germicidal light source. 
     There may be one or more sensors. The one or more sensors may include, for example, video cameras, temperature sensors, humidity sensors, infrared sensors, sound sensors, microwave sensors and lidar. In an embodiment a distance sensor is used. A distance sensor can include any sensor that may send to the processor signals indicative of a distance between the germicidal light source and the surface, including video cameras, infrared sensors, sonar or lidar. The processor may determine the intensity of the germicidal light on the surface based on the signals indicative of the distance between the germicidal light source and the surface. With a distance sensor, the control box can measure the area and the distance of the surface in front of the light fixture which the germicidal light, e.g. UVC, beams radiate. The control box can then calculate the UVC dose needed and control the radiation time so that the radiating UVC dose passes the germ-killing threshold, but does not overdose. 
     Other uses of sensors include detecting that a surface is being damaged by germicidal light, detecting that germicidal light is not reaching an intended surface, detecting an intensity of germicidal light being reflected from a surface, or detecting that an object or person is present that the system should avoid irradiating with germicidal light. 
     Sensors may also be used to detect infected or polluted areas to be targeted specifically or exclusively by the germicidal lighting system. Data from one or more sensors may be supplied to a processor to identify infected or polluted areas, for example using AI, or displayed to a human user. The one or more sensors can include video imagery or other sensors. 
     The germicidal lighting system can disinfect the infected areas according to the directly input commands of a user, following preprogrammed routines in the system, or using AI results or wired or wireless signals from a remote controlling system. 
       FIG.  9    is a flow chart showing a method of disinfection of a surface. In step  120  a germicidal lighting system is provided comprising a directional germicidal light source movably mounted on a structure. The structure may be, for example, a movable structure. The germicidal lighting system may be a germicidal lighting system as described above. The germicidal lighting system may be used to sequentially irradiate a first surface portion and then a second surface portion. For example, as shown in  FIG.  9   , the germicidal lighting system may irradiate the first surface by in step  122  positioning the directional germicidal light source in facing relation to a first surface, e.g. so that the first surface generally faces the germicidal lighting system, in step  124  adjusting an orientation of the directional germicidal light source towards the first surface portion, and in step  126  operating the directional germicidal light source to irradiate the first surface portion. The germicidal lighting system may irradiate the second surface portion by in step  128  positioning the directional germicidal light source in facing relation to the second surface portion, in step  130  adjusting the orientation of the directional germicidal light source towards the second surface portion; and in step  132  operating the germicidal light source to irradiate the second surface portion. 
     Where the structure is a movable structure, the step  128  of positioning the directional germicidal light source in facing relation to the second surface portion may comprise moving the movable structure. Regardless of whether the structure is movable, this step may comprise adjusting a position of the directional germicidal light source relative to the structure. 
     Where the structure is a movable structure, the step  130  of adjusting the orientation of the directional germicidal light source towards the second surface portion may comprise moving the movable structure. Regardless of whether the structure is movable, this step may comprise adjusting the orientation of the directional germicidal light source relative to the structure. 
     The directional germicidal light source may remain active between the steps of operating the directional germicidal light source to irradiate the first surface portion and operating the directional germicidal light source to irradiate the second surface portion. This allows smoothing of the average light intensity over time as a field of irradiation of the germicidal light source moves over any given point on surfaces to be irradiated. 
     In an embodiment, the first surface portion and the second surface portion may form parts of a scanned surface. The directional germicidal lighting system sequentially irradiates different portions of the scanned surface, which may occur for example in a series of discrete steps or in one continuous motion. 
     In an example, a robot arm moves the directional germicidal light across the surface, and as the robot arm moves, the directional germicidal light source rotates relative to the robot arm to keep the directional germicidal light source directed substantially perpendicularly to the surface. 
     If a linear germicidal light source is substantially uniform in brightness along its length, but non-uniform perpendicular to its length, e.g. by more brightly illuminating a central line of focus and less brightly illuminating away from the line, then the above method of scanning makes the applied dose more uniform by applying the different brightness levels over time to each point on the surface. 
     Non-uniformity perpendicular to the direction of scanning can also be smoothed by moving the field of illumination of the germicidal light source on a path forming substantially parallel lines during the scanning, the substantially parallel lines overlapping. For example, if a light source forms a spotlight with greater illumination in the center, overlapping subsequent passes can result in smoother application of the dose. Even a highly irregular field of illumination could be smoothed by many closely overlapping passes. 
     Multiple germicidal light sources may also be used to smooth the application of the dose of germicidal light. By orienting the different germicidal light sources separately, they can have similar cumulative effect as a single germicidal light source at different positions at different times. The multiple sources can reduce the total amount of motion needed to achieve a given amount of smoothing, relative to a single germicidal light source. 
     The speed and path of the scanning may also be adjusted to control the dose. For example, where different portions of a surface are at different distances, the light may be moved slower when directed at more distant portions of the surface. The processor may also monitor the dose provided, and adjust the path of scanning to avoid further illuminating portions that have already received the desired dose. 
     A higher dose may also be applied to surfaces for which disinfection is particularly important or which are likely to be able to withstand higher levels of radiation. For example, a higher dose may be applied to doorknobs than walls. 
     As described above, a directional germicidal light may have adjustable focus by adjusting the distance between a light source and a mirror, or by adjusting a lens in front of the light fixture. This changes the lighting area, hence the exposure time. 
     Some special objects on the radiated surface, such as the handles of the doors, can be scanned by moving the light fixture to each side of the object, and be directionally radiated with divergent beams so that inner portions of the object can receive enough UVC radiation. The divergent beams can spread the light across portions of the object that may be difficult to reliably irradiate with focused beams. A divergent focus may be useful to illuminate a nearby surface with higher intensity than a more distant surface. For example, a divergent beam may illuminate the doorknob more strongly than more distance surfaces across the room. A highly convergent beam may also be used, as it becomes divergent beyond a distance of focus of the convergent beam. 
     Focus may also be adjusted for example depending on the apparent size of a surface to be disinfected or to be avoided. For example, focus may be adjusted to avoid overexposing a sensitive surface. Nearby surfaces may be disinfected with tighter focus to avoid spillage onto the sensitive surface. 
       FIG.  10    is a flow chart showing a method of irradiation of an object. In step  140 , a germicidal lighting system is provided, which may have one or more directional germicidal light sources movably mounted on a movable structure. In step  142 , a directional germicidal light source is positioned adjacent to the surface in view of a first side of the object. In step  144 , the directional germicidal light source is oriented towards the first side of the object and in step  146  the directional germicidal light source is operated to irradiate the first side of the object. In step  148 , a directional germicidal light source is positioned adjacent to the surface in view of the second side of the object. This may be the same directional germicidal light source used to irradiate the first side of the object, or a different directional germicidal light source. In step  150 , this directional germicidal light source is oriented towards the second side of the object, and in step  152  this directional germicidal light source is operated to irradiate the second side of the object. The surface may also be irradiated in step  156  using the directional germicidal light source or sources. Optionally, in step  154  the focus of the directional germicidal light source or sources may be adjusted between irradiating the first and second sides of the object and irradiating the surface. 
     A germicidal lighting system may also scan a surface without changing the position of the directional germicidal light source. In an example, the directional germicidal light source has a linear extent as shown in  FIG.  1   , and the scanning comprises rotating the direction of light emission while keeping the direction of linear extent the same. For example, where the directional germicidal light source includes a mirror as shown in  FIGS.  2 - 6   , the direction of light emission may be rotated by rotating the mirror  34  around the light producing element  32 . 
     The germicidal lighting system may be applied to deactivate human pathogens, for example in a hospital, or may be used in other contexts such as horticultural. 
       FIG.  11    shows a germicidal lighting system  200  with multiple directional germicidal light sources  202  supported by a tower  204  mounted on a base  206 . The base  206  may be movable using, for example, wheels  208 . The tower  204  in the embodiment shown comprises a rotating structure  210  that rotates around a column  212  fixed to the base  206 . This may allow 360 degree horizontal rotation of the lights around the axis defined by the column. In this embodiment, a header  214  is fixed to the top of the column  212 . Each light source  202  may be directional, for example a directional germicidal light source  30  including a mirror  34  as shown in  FIGS.  2 - 6   . For example, it may be configured to direct light in parallel manner as shown in  FIG.  4   . Any configuration or variant of directional germicidal light source disclosed in this document may also be used. In the embodiment shown in  FIG.  11   , there are eight directional germicidal light sources arranged in two tiers each having one light source  202  at each of four sides of the rotatable structure. Each directional germicidal light source  202  shown is supported on a respective shaft  216  extending from the rotational structure and is rotatable around an axis longitudinal to the shaft  216 . In the embodiment shown, the shaft  216  is oriented horizontally and the directional germicidal light sources extend substantially perpendicularly to the shaft, with the direction of light oriented substantially perpendicularly to both the shaft and the light source, so that the rotation occurs in the manner of the hands of a clock. The rotation may be caused by an actuator (not shown) controlled by a processor within the germicidal lighting system  200 , or by any other means disclosed in this document. This rotation may be up to, in this embodiment, 45 degrees in either rotational direction from a position where the directional lights are vertically oriented, and direct light substantially horizontally. This allows the light to be directed upwards or downwards in a 90 degree range of angles. In other embodiments, the lights may have greater range of motion, for example to face down, up or other directions. The robot may rotate the structure  210  at the same time as rotating the light sources relative to the structure. 
     The base  206  may contain a battery (not shown). Any other means of powering the germicidal lighting system disclosed in this document may also be used. The germicidal lighting system  200  may include a processor at any suitable location, in an example within the header  214 . The germicidal lighting system  200  may also, in this or any other embodiment of a germicidal lighting system including computer control, operate autonomously. The germicidal lighting system  200  may also include a control panel  216 . The autonomous operation may use a suite of sensors included in the robot. 
     An example suite of sensors is described in relation to the embodiment of  FIG.  11   . The arrangement of the sensors on the header  214  is shown schematically in  FIG.  12   , which shows a top view with the upward direction on the page corresponding to a frontward direction for the robot. In this example, the header  214  includes five pairs of video cameras  220 , four arranged at corners of the header and one at the top of the header for stereo vision in all directions. The header also includes here five passive infrared (PIR) sensors  222 , four arranged on the respective vertical surfaces of an octagonal prism forming the header and one on top of the header. These sensors may be used to detect the presence of humans. There may also be two optical sensors  234 , one at the front and one at the back. The optical sensors are used to avoid collisions with obstacles. The optical sensors send out and detect infrared light. The optical sensors can be used to detect obstacles in 3D space, and measure the distance to the obstacle. Optical sensors are typically cheaper than cameras. In some embodiments, the optical sensors can be used to detect and measure characteristics of obstacles on their own, rather than a processor receiving raw sensor data and detecting the obstacle and determining its characteristics. The video cameras may be used for example to check the environment for humans and measure the positions of, distance to and trend of motion of the humans, and the video cameras and optical sensors may be used separately or together to avoid collision with the top of the robot. This embodiment also includes four cameras  224  mounted on the base  206 , including two cameras at the front  218  of the base  206  and two cameras at the rear for depth perception in front and rear directions for 3D navigation. The embodiment also includes Lidar sensors mounted in cavities  226 , one at the front and one at the back of the base  206 , to provide 2D navigation. This embodiment also includes four ultrasonic sensors  228  in the base, again two at the front and two at the rear, to detect obstacles. Eight optical sensors  230 , two on each corner surface  232  of the base  206 , are used to avoid collisions with obstacles. All sensors may be provided in a symmetric arrangement (front and back) to enable the robot to move in both directions equally well. 
     This embodiment or any other embodiment of a germicidal lighting system may be used with germicidal light in a range of wavelengths selected to cause reduced harm to humans, for example at or near 222 nm. 
       FIGS.  13  and  14    show a further example of a directional germicidal light source  330  using a concave mirror  334 .  FIG.  13    shows a schematic end view of this example light source  330  and  FIG.  14    shows an isometric view. The light source  330  includes a concave mirror  334  in combination with light producing elements  332  which may be, for example, LEDs producing UVC light. As shown in  FIG.  13   , light rays  338  may be reflected using the mirror  334  to be generally parallel, though the light source  330  could also be configured to produce for example converging or diverging light. The LEDs  332  are shown mounted on panels (for example circuit boards)  344  here located on opposite sides of a heat sink  346 ;  FIG.  14    shows such a circuit board on one side (the other side would be behind the heat sink). In the embodiment shown, the concave mirror  334  comprises a backing structure  348  which includes the mirror surface  334  as a coating or as a supported mirror on the backing structure  348 . The backing structure  348  may be contiguous with the heat sink  346  as shown. The mirror surface  334  may be a single mirror surface extending to both sides of heat sink  346 , or in the embodiment shown, be split into mirror surfaces on each side of the heat sink  346 . A one-sided embodiment would also be possible in which the mirror  334  extends only to one side of the heat sink and the LEDs  332  and panel  344  may also be only present on that side. Where there are LED panels on different sides the LED panels may face oppositely, for example mounted to opposite sides of a substantially flat or planar heat sink, or the heat sink could have a different shape such that the LED panels are at different angles. The LED germicidal light source may have a linear shape as shown, with the heat sink and backing structure extending linearly in a first direction labeled with arrow A, the LED panels facing in directions labeled by arrows B and D, and light from the LEDs reflecting from the mirror  334  generally in a direction labeled by arrow C. The term “generally” is used to indicate that there may be some variation in direction, for example including converging or diverging light. A cover (not shown) may also be included on the germicidal light source. 
     Embodiments of a directional germicidal light source as shown in  FIGS.  13  and  14    and as described above may be used as a directional germicidal light source in any germicidal lighting system using a concave mirror described in this document, for example, installed on a robotic arm as a germicidal light source  12  as shown in  FIG.  1   , mounted on transverse rotational axes as shown in  FIG.  11   , or mounted on longitudinal rotational axes as shown in  FIG.  15   , described below. 
       FIG.  15    is an isometric view of an exemplary germicidal lighting system  400  with multiple directional germicidal light sources  402 . The germicidal lighting system  400  may include a header  414  and base  406  which may include features, such as for example sensors, as described above in relation to  FIG.  11   . The germicidal lighting system  400  may, as with  FIG.  11   , include a control system configured to operate the system as an autonomous ground vehicle (AGV). A body frame  404  is here shown without any configuration for movement relative to the base and, in the embodiment shown, mounts the germicidal light sources  402 . The germicidal lighting sources  402  in the embodiment shown are mounted for rotation about axes  436  which are longitudinal relative to the directional germicidal light sources and horizontal relative to the germicidal lighting system  400 . This allows tilting of the light sources  402  to control vertical orientation of light from the light sources  402  and movement of the robot to control azimuthal orientation, without the additional complexity of the embodiment of  FIG.  11   . In the embodiment shown, the light sources  402  include first light sources  402 A having shorter axes and located adjacent to thinner faces of the body frame  404 , and second light sources  402 B having longer axes and adjacent to wider faces of the body frame  404 . The second light sources  402 B are shown on one side of the robot, but a symmetrical arrangement may also be present on the other side. Similarly, first light sources  402 A may be present on both front and back as shown in  FIG.  15   . A control panel  416  is shown mounted in a different location than control panel  216  of the embodiment of  FIG.  11   , in order to accommodate a germicidal lighting source  402 A; in various embodiments, the control panel could be located in any of various locations. 
     In any of the embodiments shown using linear, directional germicidal light sources, for example in any of the robots shown in  FIGS.  1 ,  11  and  15   , either UVC LED lights as shown in  FIGS.  13 - 14    may be used, or any linear UVC light source combined with a mirror as shown in  FIGS.  2  and  4 - 6    or a lens as shown in  FIG.  3   . Other examples of linear UVC light sources include mercury vapour lamps and excimer lamps. The robot shown in  FIG.  1    may be used to disinfect difficult to reach areas, whereas the robot shown in  FIG.  15    is more suitable to disinfect large open areas. 
     In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.