Illumination – Plural light sources – With modifier
Reexamination Certificate
1998-08-07
2001-03-27
O'Shea, Sandra (Department: 2875)
Illumination
Plural light sources
With modifier
C362S084000, C362S223000, C362S222000, C362S225000, C362S217060, C362S219000, C362S221000, C362S268000, C362S331000, C313S493000, C313S487000, C359S694000, C359S704000
Reexamination Certificate
active
06206544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to luminescent illumination systems for television, video and film sets and studios.
2. Description of the Prior Art
In U.S. Pat. Nos. 5,012,396 and 5,235,497 the Applicant, Paul D. Costa describes luminescent lighting fixtures and illumination systems providing omni-directional sustained luminescent (florescent and phosphorescent) light emission of desired color/chromaticity from phosphors in an emulsion coating the interiors of luminescent light tubes for television and film studios.
It is important to understand that there are both prompt or fluorescent and delayed or phosphorescent luminescent light emissions excited from the phosphors lining the light tubes. The prompt or fluorescent light emission begins within 10 nsec (10
−9
sec.) of the exciting stimulus and ceases within 10 nsec after excitation stops. The delayed or phosphorescent light emissions can begin after 10 nsec of the exciting stimulus but persists beyond 10 nsec once excitation stops [See
Van Nostrand's Scientific Encyclopedia
6
Th
. Ed. 1983 pp.
1237, 1788 & 2204
.] The bandwidths of prompt or fluorescent light emissions in many instances are different than the bandwidths of the delayed or phosphorescent light emissions. Also, the phosphor compounds which fluoresce may be different from those that phosphoresce.
As noted in U.S. Pat. No. 5,235,497, luminescent lighting fixtures have relatively large light apertures that generally frustrate efforts to direct and shape the emitted light. Even with the geometry for shaping the light from sustained luminescent lighting fixtures as disclosed in U.S. Pat. No. 5,235,497, the apertures can be unacceptably large, particularly when appropriate variations of shadows, and areas of differing luminosity, brightness, shade, tint and hue are required for providing a believable perception of dimensional depth to a two dimensional (flat) video or film image.
Color television cameras, video cameras, color photography films, digital electron scanning cameras and the human eye each sense or perceive discrete bandwidths of light which are then recombined, integrated and interpreted in a nonlinear fashion as a particular color. In contrast to incandescent lighting fixtures that are characterized with reference to Stefan-Boltzman “blackbody emission temperatures” or ‘color temperatures’, luminescence light consists of relatively narrow bandwidths of light emissions which do not follow blackbody laws. (A laser is a common example of a luminescent light source producing a coherent amplified light emission in very narrow bandwidths.)
Spectral output of luminescent light sources are better characterized in terms of an index which provides a comparison of colors illuminated (by the luminescent light) to those same colors illuminated, for example, by direct ‘white’ noon sunlight. (Direct ‘white’ sunlight typically between noon and 2:00 P.M. is the practical standard for determining color for human vision.) Manufacturers of luminescent light tubes try to blend phosphors to produce different bandwidth distributions of radiant energy usually identified with a proprietary trademark, e.g., LUMILUX®. Descriptive terms such as cool white, warm white, daylight are also frequently relied upon. However, most luminescent light tube manufacturers ultimately resort to characterizing the distribution of different bandwidths of light emitted by their blends of phosphors as producing an effect of illumination equivalent to that produced by incandescent Tungsten filaments at particular temperatures expressed in degrees Kelvin (°K), in tacit recognition of the predominance of Stefan-Boltzman blackbody emission standards.
A better index for characterizing the light output of luminescent light tubes having a selected blend of phosphors emitting a distribution of different narrow spectral bandwidths of light would be the SRGB® standard developed by the Applicant which characterizes the relative radiance of respective red, blue and green primary color bandwidths of sustained luminescent light emanated by a blend of phosphors reflecting from known sets of standard gray scale charts and color band charts.
In particular, the color of a surface is the bandwidths of light reflected from that surface. Such reflected light can be captured, digitally imaged and then sampled using conventional eye dropper tools associated with most computer graphics, design, and image processing software programs. The software eye dropper tools measure and/or characterize such parameters as brilliance, saturation, hue, tint, shade or whatever, in terms of the various color-model systems used by the particular program for specifying color. In a sense, the optical capture system, and associated computer and software tools function as a reflection meter. Diffusely reflected light from a standard chart can be sampled to provide a quantitative color evaluation of its spectral in terms of color(s) reproduced and observed by a human being directing the optical capture system and controlling the computer system.
For example, in the RGB additive model, typical CRT television or computer monitor screens reproduce the color yellow, not spectrally present, by combining various brightness values of red, green, and blue light. James Clerk Maxwell initially demonstrated this effect to the Royal Institute in London in 1861. The L*a*b* (Lab) model developed by CIE
1
mathematically specifies a luminance or lightness (L) value and two chromatic components values (a) specifying a range from green to magenta, and (b) specifying a range from blue to yellow in a way that is supposed to be device independent. The CMY and CMYK color-model system for photography and printing are subtractive/multplicative models that specify values for cyan (C), magenta (M), yellow (Y) filters and ink which absorb light. Values for black (K) inks are specified in printing because available C, M & Y inks combine to reflect a muddy brown. [See
Van Nostrand's Scientific Encyclopedia
7
th Edition
, Vol. 1, pp.
36 & 701
, Vol. 2 pp. 2203, 2714] In HSB and HLS color models, an achromatic ‘gray scale’ value termed ‘brilliance’ (B) or ‘lightness’ (L) is specified along with two chromatic values specifying ‘hue’ (H) and ‘saturation’ (S). Saturation is a parameter relating to purity of the color, gray being zero. In the HSB model, colors having a more pronounced hue are more chromatic, i.e., differ more from a gray of the same ‘brilliance’ or ‘lightness’ ‘Brilliance’ and ‘hue’ can in turn be related by using such terms as ‘tints’ and ‘shades.’ A chromatic color having little ‘hue’ but high ‘brilliance’ is termed a ‘tint’, e.g., pink, whereas color of low ‘hue’ and low ‘brilliance’ is termed a ‘shade’, e.g. brown.
1
Centre Internationale d'Eclairage, an international organization which began establishing specifications for color in 1931. CIE has developed a number of comparable standards including CIE XYZ, CIE xyY, CIE L*u*v* and CIE L*a*b*. The television broadcast industry in fact specifies desired chromaticities in picture tube output which then relate to gamma corrected voltages corresponding to red green and blue signals. See 47 CFR § 73.682(20) (iv).
Modern personal computers and associated graphics, design and imaging software programs and tools provide RGB image displays which allow users to manipulate and evaluate color by varying values in one or more of the common and proprietary color modeling schemes using side-by-side color comparison boxes. Such computers and software tools thus, in a very real sense, allow the bandwidth sensitivity of human perception to be integrated into the evolution of illumination standards for producing images of studio subjects and talent.
Titanium dioxide also in the emulsion coatings of luminescent light tubes scatters and mixes the light emissions from the different phosphor compounds in the coating. Ad Lagendijk of the University of Amsterdam and the FOM-Institute for Atomic and Molecular Physics in the Netherlands at t
Newhouse David E.
O'Shea Sandra
Ton Anabel M.
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