Projectors for producing scanning laser light show displays (laser projectors, laser projection systems, and so forth) can be generally defined as belonging to one of two groups: conventional laser light show projectors (conventional scanning laser projectors), and audience-scanning laser light show projectors (audience-scanning laser projectors). Both types of projectors typically utilize high powered laser sources (e.g., U.S. Food and Drug Administration (FDA) Class 3b or 4 laser sources) of various colors that can be directed (e.g., via an optical system) to, for example, a pair of mirrors that are attached to a pair of galvanometer scanners. Such galvanometer scanners can form an X-Y pair and be used to direct a laser beam or laser beams from the laser sources (e.g., through one or more lenses) to various pre-determined locations. The projections produced by the laser(s) may be used to produce graphics (static images) such as corporate logo designs and/or to produce (dynamic) animated images.
Graphics and/or animated images produced by conventional scanning laser projectors are intended to be projected onto a destination surface, such as a projection screen. In other instances, the graphics or images produced by such conventional scanning laser projectors can be projected onto/through an atmospheric scattering medium (e.g., fog from a fog machine) to make the beams of the laser(s) visible in mid-air. Laser beam projections produced by such conventional laser light projectors should terminate in a “safe” area that is away from viewers or audience members, such as onto a ceiling, onto a projection screen, or into open air (e.g., a night sky, assuming proper clearance from any appropriate regulatory agencies). The laser beams from such conventional scanning laser projectors should not be allowed to enter, or terminate in viewer or audience areas due to the potential eye hazards associated with high levels of irradiance which may occur from exposure to light from the high power laser sources.
Audience-scanning laser projectors, as compared to conventional scanning laser projectors, are designed to allow graphics and animated images produced by their laser beams to terminate in audience areas. For example, graphics or animated images produced by such audience-scanning laser projectors may be projected directly onto viewers or audience members. Similarly, an audience-scanning laser projector may be used to produce aerial beam effects through an atmospheric scattering medium, and those effects could then be directed toward audience areas, effectively immersing viewers in a laser projection effect (which can be referred to as “audience-scanning effects”). However, viewer eye safety and other legal liabilities may be concerns associated with the use of audience-scanning laser projectors. Accordingly, in some countries, it has been difficult to gain approval from regulatory agencies for the use of so-called “audience-scanning effects” produced by such audience-scanning laser projectors and procedures for verifying safe operation of such audience-scanning laser projectors.
A safety concern associated with the use of audience-scanning laser projectors is the possibility of retinal damage which may occur from exposure (e.g., a single exposure or multiple exposures) to the projected laser beam(s). For instance, if a laser beam of a sufficiently high irradiance is permitted to dwell at one point in space, e.g., where a viewer's eye may be located, for a sufficiently long period of time (e.g., remains at a given X-Y location for a specific period of time), retinal damage may occur. In some cases, even a few milliseconds of direct retinal exposure to a high power laser beam may be sufficient to cause injury.
Current approaches (e.g., procedures approved by the FDA) for evaluating the safety of a set of graphics and/or animated images that are to be used as audience-scanning effects are highly complex and highly prone to error. For example, such current approaches require the use of a beam power meter capable of measuring irradiance (beam power per unit area), a fast silicon photodiode, an oscilloscope, a scientific calculator, and sufficient skill of a user to properly use these instruments. Also, a number of current safety verification procedures actually require that a safety system of a laser projection system be disabled in order to obtain proper measurements, e.g., using the tools discussed above. Such approaches can be extremely time consuming and also can create a risk of the safety system not being reinitialized properly prior to use to produce audience-scanning effects. Accordingly, alternative, less complicated approaches for evaluating safe operation of audience-scanning laser projectors are desirable.