Task lighting is lighting supplementary to general ambient lighting to provide additional illumination of a work area or surface, such as, for example, a desk top, work bench, or a counter top. Work surfaces located under cabinets or shelves will often have much of the ambient lighting, e.g., room lighting, at least partially blocked. Therefore, a task light is necessary to adequately illuminate those surfaces. Also, many times the ambient lighting is insufficient to provide adequate illumination of a work surface, and, therefore, a task light is necessary to supplement the ambient lighting.
Ideally, a task light will perform two major functions: (1) it will increase the overall illumination level on the work surface, and (2) it will produce a glare-free visual environment. In addition, the ideal task light will have other attributes, such as a low profile and high light output without significantly heating the work area.
Many common prior task light designs incorporate one or two fluorescent lamp tubes, e.g., in lengths ranging from 9 inches to 48 inches. The lamp was either exposed or was mounted in an enclosure having a clear lens, a prismed lens or an “egg-crate” baffle. Such task light fixtures are typically mounted under cabinets or shelves or are suspended above the work surface, and extend laterally along most of the length of the work surface. Such fixtures usually provide adequate illumination, but do not adequately address the problem of glare control. When such fixtures are located directly in an angular line with the eye, objectionable reflective glare will be experienced. This is annoying and tiring to the viewer.
There are three types of glare: direct, contrast, and indirect. Direct glare occurs when there are bright light sources directly in the operator's field of view. Windows are often a source of direct glare, or one may experience direct glare by looking straightly to the sun or a light bulb. Contrast glare is where one part of the vision area is much brighter than another. Usually it is caused by large differences in light levels within the visual field. For example, it may happen when there are two light sources illuminating a same general area, such as a study room, in that an area light such as the luminaire fitted on the ceiling is used for lighting the whole study room while a task light such as a desktop lamp is used for specifically lighting a working area on the desk, thereby, large differences in light levels will be caused in the visual field. Indirect glare occurs when light from windows or overhead lighting is reflected off shiny surfaces in the field of view, such as terminal screens, desks and other office equipment, which is considered to be the most commonly experienced glare and is the one that causes most discomfort to human eye.
U.S. Pat. No. 4,384,318 (Reibling) discloses a task lighting apparatus that includes light directing, preferably highly specular, louvers to provide a controlled light pattern of high illumination and high efficiency. U.S. Patent Publn. No. 2008/0253129 (Lin et al.) discloses a lamp fixture comprising a light-control microstructure for controlling the angle of light emission so as to reduce glare.
The need exists for improved task lighting that provides effective bright illumination with reduced glare.