Patent Publication Number: US-2017373454-A1

Title: Laser Safety Device

Description:
FIELD 
     This invention relates generally to a laser safety device. 
     BACKGROUND 
     Electromagnetic (EM) radiation has many forms, such as radio waves, microwaves, X-rays and gamma rays. EM radiation spans an enormous range of wavelengths and frequencies. This range is known as the electromagnetic spectrum. Lasers are devices that emit narrow beams of intense EM radiation. Laser is an acronym for “laser amplification by stimulated emission of radiation.” A laser beam has the special property that the light waves are coherent and usually of one wavelength or color. 
     In addition, a laser has a very small beam divergence over a distance, compared with a light source such as an ordinary filament lamp. This means that the same degree of hazard can be present both close to and far from the laser. 
     In general, laser light is not in itself harmful and behaves much like light from other sources in its interaction with the body. However, with sufficient power, laser in the visible to near-infrared range (400-1400 nm) can cause laser radiation to be concentrated into an extremely small spot on the retina which can destroy retinal photoreceptor cells. Exposure to laser radiation with wavelengths less than 400 nm and greater than 1400 nm are largely absorbed by the cornea and lens, leading to the development of cataracts or burn injuries. Infrared lasers are particularly hazardous since the body&#39;s protective “blink reflex” response is triggered only by visible light. 
     Accessible Emission Limit (AEL) is the maximum value of accessible laser radiation to which an individual should be exposed during the operation of a laser. The AEL values are in turn based on Maximum Permissible Exposure (MPE) levels. An MPE is a level of laser exposure or irradiance an individual could be exposed to without incurring an injury. MPE levels are specified for both the eye and skin as a function of the wavelength of the laser radiation and the duration of exposure. The Nominal Hazard Zone (NHZ) is a distance within which the irradiance of a beam is greater than the MPE. It is specific to a given wavelength and time of exposure. A different NHZ can also be defined for the beam&#39;s path to the eye—direct viewing, specular reflectance or diffuse reflectance. Nominal ocular hazard distance NOHD is used to determine how far away persons need to be from the laser source. NOHD is set at the distance where the laser irradiance falls below the MPE. 
     One way to control EM irradiance is through distance. Another way to control EM radiation is to increase beam divergence. The divergence, φ, of a laser beam, is the angle of the increase in the radius with distance from the optical aperture. Increased divergence allows power and visibility to be increased. 
     For a laser show, where there may be many different movement patterns, it may be nearly impossible to calculate the “worst case” location for viewing the show. 
     SUMMARY 
     The following presents a simplified summary of the disclosure to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure, nor does it identify key or critical elements of the claimed subject matter or define its scope. Its sole purpose is to present some concepts disclosed in a simplified form as a precursor to the more detailed description that is later presented. 
     The instant application discloses, among other things, a laser safety device which may be comprised of a light source capable of projecting a beam of electromagnetic radiation, for example a laser, distance measuring system, a control subsystem, and a beam steering device that may be interconnected with the source. The distance measuring system may be configured to determine a distance to objects (including people) in a path of the beam. The distance measuring system may use many different methods for determining the distance to objects. The distance may be communicated to the control subsystem. The control subsystem may then adjust one or more attributes of the light source to stay within safety limits. 
     Many of the attendant features may be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates geometry of a laser beam. 
         FIG. 2  is a block diagram of a Laser Safety Device according to one embodiment. 
         FIG. 3  illustrates a Laser Safety Device in use, according to one embodiment. 
         FIG. 4  illustrates a Laser Safety Device in use, according to another embodiment. 
     
    
    
     Like reference numerals are used to designate like parts in the accompanying drawings. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates geometry of a laser beam. Laser Projector  110  may include Light Source  220 , which may generate a laser beam. Light Source  220  may generate a continuous, pulsed, or modulated laser beam. Beam Source Diameter  120  is the diameter of the narrowest portion of the laser beam. Divergence  150  is an angle the laser beam spreads over distance. Beam Diameter  140  (DL) is the diameter of the laser beam at Distance  160 . Laser Projector  110  may also include Beam Steering Device  240 , which may be one or more moveable mirrors, diffraction gratings, or other technology, which may allow moving or aiming of the laser beam. 
     Laser Projector  110  may also include Control Subsystem  210 . Control Subsystem  210  may control attributes of Laser Source  110 , including, for example, power output of Light Source  220 , a frequency of pulses, Beam Source Diameter  120 , or a velocity which Beam Steering Device  240  is effectively moving the laser beam. 
     Laser Projector  110  may also include Distance Measuring System (DMS)  230 . DMS  230  may use radar, LIDAR, sonar, or other technology to determine a distance from Light Source  220  to an object. 
       FIG. 2  illustrates Laser Safety Device  200  according to one embodiment. In this example, Laser Safety Device  200  may include Control Subsystem  210 , Light Source  220 , DMS  230  and Beam Steering Device  240 . 
     Many types of light sources are contemplated, including laser, LED (Light Emitting Diode), OLED (Organic Light Emitting Diode), Xenon, incandescent, discharges, or plasma. Utilizing the correct optics, such as lenses, collimators, mirrors, and reflectors, almost any sufficiently bright illumination source may be focused into a defined beam. Examples in the instant disclosure use a laser source, but that is not intended as a limitation. 
     Beam Steering Device  240  may be any means of changing where Light Source  220  is effectively aimed, for example, mirrors, motors moving Light Source  220 , rotating diffraction gratings, or lenses. 
     One embodiment of the instant disclosure may provide DMS  230  the ability to automatically measure distances to various locations. DMS  230  may have the ability to distinguish Audience  350  members from other objects or structures in real time. Using these values, Control Subsystem  210  may automatically monitor and make adjustments to various parameters in Light Source  220 , for example optical power, Divergence  150 , or beam velocity, to automatically adjust irradiance at the point of closest viewer access to be within limits of applicable MPE for example. Adjustments may account for average, single pulse, or multiple pulses. Adjustments may account for eye levels or exposed skin of any sitting or standing observer whenever possible along the laser&#39;s intended path accounting for possible changes in its path due to reflections, refractions, etc. for example. 
     In some embodiments, DMS  230  may calculate distance using active means such as electromagnetic (EM) radiation or sound (pressure) waves. The distance to objects may be communicated to Control Subsystem  210 . Control Subsystem  210  may then adjust one or more parameters in Light Source  220  such as optical power, Divergence  150 , Beam Source Diameter  120 , beam velocity, pulse length, or pulse frequency, based on distance to the object and may further adjust these parameters based on the objects&#39; properties such as whether the object is a person, an inanimate object, or whether, for example, the object may reflect or refract the light beam. Adjustment may allow for the Light Source  220  to be at a high intensity while remaining within safety regulations. In some embodiments, DMS  230  may continually scan and communicate to Control Subsystem  210  any changes in the landscape, for example, a member of Audience  350  suddenly standing up. The Control Subsystem  210  may then adjust Light Source  220  to enhance safety. 
     Control Subsystem  210  may be able to change many attributes of Light Source  220 . One method may be to reduce the output power of Light Source  220 . A reduction in output power of Light Source  220  may reduce the overall light that is produced by Light Source  220  and consequently, the output illumination. In another embodiment, Control Subsystem  210  may control, for example, Beam Source Diameter  120 , diffraction of the beam, Divergence  150 , diffusion, beam shutter, beam focus, beam velocity, pulse frequency, pulse length, or other attributes that may be adjusted. 
     Distance Measuring System  230  may be able to measure the distance to objects in the beam path. This may allow Control Subsystem  210  to adjust Light Source  220  beam attributes to enhance safety. In some cases, some methods may determine more information than just distance such as density of an object, velocity of an object, vector of an object, or other attributes. 
     In some instances, DMS  230  may continuously determine object distances through all possible beam paths. By determining object distance continuously in real-time, Light Source  220  may be adjusted to allow a high intensity in a safe manner. For instance, a laser may shine on Audience  350  at the brightest setting that is still within safety requirements. 
     In another embodiment, DMS  230  may determine distances to people or objects in advance of a laser show, and store distances in different directions, providing Control Subsystem  210  with distance measurements based on where the beam is pointing. In another embodiment, Control Subsystem may be programmed in advance with distances in various directions, and may adjust attributes appropriately. 
     In yet another embodiment, DMS  230  may determine a closest distance for any objects for a location at which a beam is aimed. Control Subsystem  210  may adjust Laser Projector  110  to enhance safety for the closest object at the location. 
     In yet another embodiment, Beam Steering Device  240  may be adjusting over a path where a beam is aimed. Distance Measuring System  230  may receive the path from Control Subsystem  210 , and may determine a closest object across the path. Control Subsystem  210  may adjust Laser Projector  110  to an acceptable level for the closest object to enhance safety to all objects in the path. 
     One having skill in the art will recognize that many approaches may be used to provide distance measurements to enhance safety for laser use. 
     In other embodiments, the laser projector may have more than one Light Source  220 . For example, if Light Source  220  is an RGB laser projector, there may be three laser sources: one for each primary color: red, green, and blue. In this configuration, multiple colors may be mixed to together in different output amplitudes to create a large gamut of the colors capable of being seen by the human eye. Each laser source may comprise a single laser emitter or multiple laser emitters. It may be preferable that these lasers are color-balanced, but they may have a maximum power output that is not uniform. In this embodiment, Control Subsystem  210  may take each laser&#39;s power into consideration when determining the proper attribute adjustments for each laser and the attribute adjustments for the projector. In some cases, Control Subsystem  210  may adjust beam velocity or a shutter module. 
       FIG. 3  illustrates a Laser Safety Device  200  in use, according to one embodiment. Laser Projector  110  may include Beam Steering Device  240  to move a beam through Beam Movement  360 , changing where the beam is aimed. Beam Movement  360  may be any shape. Lenses, mirrors, shutters, absorbers, and other accessories may be added to Laser Projector  110  to obtain more power, pulses, modulation, or special beam shape. DME  230  may measure Distance  320 ,  330 ,  340  and provide Control Subsystem  210  the resulting measurements, which may allow Control Subsystem  210  to adjust attributes of Laser Projector  110  to enhance safety for members of Audience  350 . 
       FIG. 4  illustrates a Laser Safety Device  200  in use, according to another embodiment. DMS  230  may measure a distance to the nearest object over Distance Measuring Angle  410 , which may be a wider angle than Divergence  150 . When Beam Steering Device  240  is moving a beam, distances to objects within the range of Distance Measuring Angle  410  may be measured before the beam hits them. This may allow time for Control Subsystem  210  to adjust power appropriately before an object is hit by the beam. 
     The foregoing description of various embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples, and data provide a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.