CA2081224C - Full spectrum polarized lighting system and ultraviolet transmitting multilayer polarizer - Google Patents
Full spectrum polarized lighting system and ultraviolet transmitting multilayer polarizer Download PDFInfo
- Publication number
- CA2081224C CA2081224C CA002081224A CA2081224A CA2081224C CA 2081224 C CA2081224 C CA 2081224C CA 002081224 A CA002081224 A CA 002081224A CA 2081224 A CA2081224 A CA 2081224A CA 2081224 C CA2081224 C CA 2081224C
- Authority
- CA
- Canada
- Prior art keywords
- light
- full
- polarized
- spectrum
- fluorescent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Polarising Elements (AREA)
Abstract
A full spectrum polarized lighting fixture for general commercial, institutional, and industrial use, and for use in offices with computer terminals and video display terminals.
The lighting fixture contains an electronic solid state ballast, a polarizing lense, and a full spectrum color corrected lamp.
The lense is a polarized diffuser to provide glare free light with excellent contrast. The fixture contains a full spectrum color corrected lamp to simulate daylight. The combination of the full spectrum lamp and the polarized diffuser provides for light with the spectral energy distribution characteristics and light polarization of natural daylight.
The lighting fixture contains an electronic solid state ballast, a polarizing lense, and a full spectrum color corrected lamp.
The lense is a polarized diffuser to provide glare free light with excellent contrast. The fixture contains a full spectrum color corrected lamp to simulate daylight. The combination of the full spectrum lamp and the polarized diffuser provides for light with the spectral energy distribution characteristics and light polarization of natural daylight.
Description
FULL, SPEC~'RUM POLARIZED LIGHTING SYSTEM AND
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a full spectrum polarized fluorescent lighting fixture for general purpose lighting for commercial, institutional, and industrial use. The lighting fixture will provide flicker free, glare free light of excellent color rendition. This fixture is also designed to be used in spaces with ,personal computers or video display terminals.
.Tlte polarizing lense provides glare free light that gives excellent contrast and sharp images. The lighting fixture is equipped with a full spectrum lamp to provide light that will match the color rendering properties of natural daylight, and to eliminate eyestrain. The lighting fixture also has a solid state ballast that does not flicker.
Ever since the invention of the incandescent light bulb, attempts have been made to reproduce natural light. Full spectrum lamps have been developed utilizing a combination of phosphors which produce ultraviolet as well as visible light in approximately the same proportion as found in natural daylight. Full spectrum lamps are defined as a lamp with a Color Rendition Index of 90 or above and a Color Temperature of 5,000 degrees or above. Such a fluorescent lamp is disclosed, E'or example, in U. S. Pat. No. 3,670,193.
'' ,', ~ i, r.~
The novel illuminating sysa.em according to my invention makes it possible for the first time expediently to provide artificial light which has the spectral energy distribution and light polarization characteristics of natural daylight.
Such an artificial lighting system was first noted in "Designing Efficient Full Spectrum Polarized Lighting Systems for the Electronic Office, by Daniel Karpen, P. E., in Strategies For Reducing Natural Gas, Electric, and Oil Costs (Proceedings of the 12th World Energy Engineering Congress, October 24-27, 1989, published by the Association of Energy Engineers, Atlanta, Georgia). Such a combination comprises a lighting system which will produce light providing great visual acuity.
It is well known that light scattered by the atmosphere is highly polarized (see for example, "Light Scattering in the Atmosphere and the Polarization of Light", by Z. Sekera, Journal of the Optical Society of ~nerica, June, 1957, Vol.
47, p. 484). The degree of light polarization. in the atmosphere was carefully measured by Z. Sekera, and it is of the same order of magnitude as the amount of light polarization produced by commercially available polarized diffusers for fluorescent lighting fixtures. It is easy to demonstrate that daylight from the sky is polarized by the atmosphere: take a linear palaxizer and rotate while looking at the sky. One will notice a darkening and lightening of the linear polarizes as it is xotated through 90 degrees. Maximum polarization is seen while looking in the sky at an angle of 90 from the direct beam of the sun.
~,~~_~.~' However, full spectrum lamps used by themselves are lacking,) the polarizing characteristics of natural daylight, and produce glare when used in lighting fixtures without polarized diffusers.
The subject of the invention is a fixture that contains both the full spectrum lamp and the polarized diffuser to achieve the desired result of an artificial lighting system that has both the spectral energy distribution and light polarization characteristics of natural daylight.
For some time, there. has been a great deal of dissatisfaction with conventional fluorescent lighting systems. for the computerized office, with personal computers and video display terminals, 'there is a great deal of glare from conventional fluorescent fixtures. The present technology of using core coil ballasts, cool-white or warm-white lamps, and prismatic or parabolic lenses contributes to fatigue, eyestrain, and glare in interior lighting, resulting~in a substantial loss of employee productivity.
While it has been known that visibility is related to the amount of light present (measured foot-candles), there are other fundamental characteristics concerning vision, task visibility, and lighting which are of equal or greater importance thin quantity alone. "Seeing" is not related to foot-candles per se. It is mostly a function of the luminance (brightness) of the task detail and its contrast with the background. The first of these factors is dependent on the task detail reflectance -how much of the light reaching the task has been absorbed by it and re-reflected, so it can be seen.
~~~' ' -~
The other factor, contrast, is the difference in task brightness between the Cask detail and its background. Gray printing on lighter gray background can be very difficult to see. Contrast is very important to "Seeing".
The nature of light and the lighting system can affect both the brightness of the task detail and its contrast. One can easily see just how much difference it makes. If one takes a printed object, such as a magazine or book, and places it on a table under a light source located slightly to the front of it, one will notice ~tha.t the print detail ..
looks "washed out".
IE one moves around to the side, the print will appear darker. What has happened ps that the contrast of. the print to the background l:as increased. In the first instance, the ligizt bouncing o.ff the task reduced its contrast due to reflected glare, also called "veiling reflections." These reflections are due to light which is reflected from the task surface without actually obtaining information on them. In the second instance, the reflections went off in the other directions than to the eye, so they did not wash out the contrast between the object detail and the background.
The portion of the light rays which cause reflected glare or veiling reflections is that which is horizontally polarized.
The vertically polarized portion of the .Light penetrates into the task (instead of bouncing off its surface) and returns to the eye carrying .information about the task, detail and color. If, therefore, one illuminates an object so the horizontally polarized component of the light is not present, one obtains a much higher contrast and one is able to see detail and color ~ni:3~~ ~t.~
much better. This is how multi-layer polarizing diffusers function. 'They convert the horizontally vibrating light rays emitted from the lamp to vertically polarized light, thus increasing the amount of vertically polarized light rays available for penetrating into the task. As a result, the reflections are reduced, and the visual contrasts enhanced significantly.
The visual effectiveness and "Seeing" are thus improved significantly.
If contrast is improved, then one requires "Less light"
to see tasks equally as well. If one improves the contrast, one can reduce the amount of light (measured foot-candles) one needs to achieve equivalent visu al performance. This is ho~o vertically polarized light .functions. Test results indicate a reduction of as much as 50 percent in measured foot-candles to achieve equivalent visual performance as noted in report .LRL 188-9, prepared by Lighting Research Laboratory, P. U. Box 6193, Orange, California 92667, dated January 13, , 1988.
Thus the substitution of polarized diffusers in place of prismatic or parabolic diffusers immediately solves the veiling reflection problem. It has been known since 1973 that polarizing diffusers increase contrast as compared with I
prismatic or louvred (including parabolic diffusers), as noted in "Progress in Solving Veiling Reflections", Lighr_ing Design and Application, May, 1973. The correct solution to solving tire glare problem is to use vertically polarized light. Using vertically polarized .Light also eliminates the bright spots 1 t directly under a fixture as there is a more even and wider light distribution.
r ;yo 6 ~,, 9 ~ iV ~ f7 y .~~~v 'The importance of the color rendering quality of light sources has been well established for applications where color identification or comparison is involved, and some studies have been made to determine the importance of color rendition for general illumination.
Berman examined the visual effectiveness of a number of light sources under photopic (day vision) and scotopic (night vision) environments (Energy Efficiency Consequences of Scotopic Sensitivity, Lighting Systems Research Group, Lawrence Berkeley Laboratory, Berkeley, California 94720, dated htay 13, 1991). 1-le found that at the light levels typical of interior illumination, the eye functions more in the scotopic region than i.n the photopic region.
Tile human eye is a light sensing system with an aperature (pupil) and a photoreceptive medium (retina). 'fhe i:etina contains two basic types of photoreceptors, cones and rods.
Tlte rod photoreceptors are generally associated with night vision and have been assumed to not participate in the visual process at light levels typical of building interiors. The cone receptors which are responsible for seeing fine detail and fox color vision, provide the photopic visual spectral efficiency of the eye which is captured by the V( ~ function.
Under conditions of very dim light, such as starlight, there is not enough light energy to stimulate the cone photoreceptors, but there is enough to stimulate the rod system as stars can be readily observed. The spectral response of the rod photoreceptors, the scotopic response function V'(~ ), differs i:rom the cone A
spectral response in that its wavelength peak response is at about 508 nm rather than the 555 nm of the V( 1) function.
6 3 ~
W 7 'Y'. ~ ~ f; ~ ~~) ~j n1G
~J t ) _.
Reductions in visual acuity occur with increasing pupil size for the normally sighted under conditions of moderate to low contrast but not necessarily at high contrast. However, individuals who need optical corrections, i. e., those who should be using spectacles because of myopia (nearsightedness) show decrements in visual acuity even at high levels of contrast.
Many tasks in the workplace do not possess high contrast.
Changes in acuity axe similar to changes in threshold contrast as both are major determinants of visual performance potential.
Conversely, at normal office lighting levels, photopic adaptation luminance is a weak determinant of visual performance potential.
'fhereEore two sources with equal scotopic illumination, but moderately different photopic illumination (within a factor of two), should be 'very close in their performance potential.
On the other hand, two sources with equal photopic illumination, buz moderately different scotopic illumination, may have significantly c i different visual performance potentials.
By using the V(~ ) and V'(~) functions, one can calculate , the photopic and scotopic lumens for a number ~f light sources.
The scotopic output can be determined by folding the lamp ., spectral power distribution with the scotopic sensitivity function V'(~ ) as given by Wyszecki and Stiles (Color Science, 2nd ed., Wi:ley, New York City (see page 105), 1982). Pupil ' size is then determined by a combination of photopic and scotopic lumens that can be thought of as a "pupil lumen" (see Berman et, al. "Spectral Determinants of Steady-State Pupil Size with Full Field of View", Lighting Systems Research Group, r Lawrence Berkeley Laboratory, Berkeley, California 94903 Report Number 31113, dated February 19, 1991). .
., Pupil lumens are determined by the factor P(S/P)'78, where P and S are the photopic and scotopic output of the lamp.
The ratio of the scotopic to photopic luminance (or lumens) is referred to here as the (S/P) ratio. This ratio is a property of the lamp spectral power distribution (SPD). Generally, the pupil lumen is determined by the measured photopic output multiplied by the S/P ratio which is calculated from the measured SPD which is then folded'with V( r) and V'(~ ). Based on the scotopic and photopic lumen outputs, the third column in Table 1, lists the values of the pupil lumens from each of the different spectral distributions. The fourth column in Table 1 shows the relative amounts of power required by these lamps for the condition of equal average pupil size, assigning a value of 100 to the cool white lamp. The last and most significant column compares the lamps on the basis of pupil lumens per watt which is proposed here as the measure of the visual effectiveness per watt for various 40 watt lamps.
Table 1 Effective Relative Power Pupil Photopic Scotopic Pupil L~~ens Level for Equal Lumens Lamn Lumens Lumens P(S/P) Pupil Sizes Per Watt Warm White Fluorescent 3200 3100 3125 136 78 Cool White Fluorescent 3150 4630 4254 100 106 F40iT10 5500° CRT 91 2750 5913 4996 85 125 Thus, from the point of view of providing opti:,~um lighting l;or visual function, the F40/T10 5,500° c;RI 91 lamp would require percent less energy than the cool white lamp, and percent less energy than the warm wh~.te fluorescent lamp.
rr c~ ~E
~u LW ~~ ro ':,t By the use of the full spectrum lamps with the multi-layer polarized diffuser, the energy savings potential increases as compared with the cool white or warm white lamp. As discussed above, by utilizing a polarized diffuser, light levels can be cut in half for equal visual performance. Thus, when the full spectrum lamp replaces the cool white lamp, one needs only 82 percent of the energy to produce equivalent illumination;
by placing a polarized diffuser with the full spectrum lamp, one needs only42.5 percent of the original amount of energy for equivalent visual performance. Likewise, the use of the full spectrum lamp with the polarized diffuser in place of warm white lamps results in needing only 30 percent of the energy needed for equivalent illumination. This reduction in energy use in the full spectrum polarized lighting system can only occur when the polarized diffuser is used with the full spectrum lamp.
i Use of electronic solid state ballasts is necessary to eliminate the flickering associated with fluorescent lamps driven by conventional core coil electromagnetic ballasts.
Standard core coil ballasts produce a 60 cycle flicker at the ends of a fluorescent lamp and a 120 cycle flicker in j.
the middle of the fluorescent lamp. Both types of flickering are subliminally noticeable. When video display terminals ate viewed with fluorescent fixtures driven by standard core Boil ballasts, both the VDT and the fluorescent lamps flicker at the line frequency, but rarely exactly in phase since both 2 t the VD'f and the ballast are inductive devices. This out of please flickering, called the strobe effect, is causing discomfort for VDT operators. The high frequency ballast eliminates~this ~i~ ~ ~~1~
entirely. Evidence exists that the use of electronic ballasts improves productivity by about 10 percent, as noi.G~ in "Electronic Ballasts Produce Substantial Cost Savings", by Karen Haas Smith, Building Design & Construction, November, 1986 and "Superior Uffice Lighting - An Unusual Approach", by Arthur Freund, Electrical Construction & Management, November, 1983.
A solid state ballast with a 40 watt bipin four foot fluorescent lamp will consume approximately 40 watts. A solid state ballast driving two~40 watt bipin four foot fluorescent lamps will consume approximately %2 watts. A standard 4 lamp F40 Eluorescent fixture driven by core coil ballasts will consume approximately 192 watts.
By the use of the full spectrum lamp with the multi-layer polarized diffuser, as mentioned above, one can achieve essentially the same degree of visual performance with a single four foot F4G%T10 foil spectrum lamp as with four F40 warm white lamps. Thus, it is possible to save a significant amount of electrical energy by the use o~ the full spectrum fluorescent lamp with the multi-layer polarized diffuser in place of the use of warm white lamps alone. If one drives the full spectrum lamp by a solid state ballast, lrlStalling it a fluorescent Fixture with the multi-layer polarized diffuser, one can save 15~ watts of lighting instead of using a four foot fluorescent Fixture with 4.warm white lamps.
s Tlie fi:cture housinø is free of ventilation holes whi~oi~3J~~~~l permit air to ventilate the fixture. lfowewer, a solid state ballast produces far less heat, normally 1 to 3 watts compared with 8 to 16 watts produced by a conventional core coil type ballast. Thus, there is no need for ventilation holes. A
major problem with ventilation holes is while they work well to cool the fixture, they do permit substantial amounts of dirt and dust to accumulate on the prism side of the polarized diffuser. Such accumulation of dirt and dust becomes difficult and costly to clean compared to simply wiping the smooth surface a.E a conventional prismatic diffuser which is installed with the flat side towards the lamps and the prism side towards the objects being illuminated by the fixture. The fully sealed Fixture housing is an essential part of the fixture and the full spectrum polarized lighting system. The fixture also contains a gasket mounted on the door frame of the fixture between the door and the door frame to prevent dirt from entering around the door and door frame'. The gasketing is also ultraviolet resistant to prevent deterioration subsequently preventing dixt from entering the fixture housing. Since a full spectrum lamp gives off ultraviolet light (see for example U. S. Pat.
No. 3,670,193), one needs to use an ultraviolet light resistant gasketing, as otherwise the gasketing materials would deteriorate when ultraviolet light hits the gasketing materials.
.~csm,aswm.~_ ~~~...~ ".. . u.=.......~.....,. .,.
°~'-- _. .........~..........,a......,..r...... ..
-° 12 Description of Prior Art Scott (U. S. Pat. No. 3,201,576) teaches the use of several different fluorescent lamps in a fixture, each of which lamps produces a different spectral energy distribution, but when tl~e lamps are turned on in combination, so called "north light"
results. Semotan (U. S. Pat. No. 3,517,180) teaches the use of arrays of lamps of different colors intersecting at right angles to produce an artificial daylight effect. Thorington (U~ S~ Pat. No. 3,670,193) teaches the use of various combinations of phosphors znside a fluorescent lamp to obtain a light source providing light matching natural light. Ott (U. S. Pat. No.
4,091,441) shows tt:e use of full spectrum fluoresce~at Lamps in a lum.inaire in combination with a gas discharge lamp producing ultraviolet light to provide for a luminaire that produces .artificial light with the light spectral energy distribution and ultraviolet distribution of natural Light. Note that both Scott and Sematon use a combination of lamps to produce the full spectrum light, whereas Thorington and Ott use a single lamp that provides the spectral distribution of natural light in the visable light. Neither Thorington nor Ott use '. tt~e mufti-layer polarized diffuser in combination with the Fu,l1 spectrum lam s to P produce a light source that has both tt~e spectral energy distribution and li ht g polarization characteristics o~ natural light. Kahn (U. S. Pat. No. 3,124,639) teaches the use of light polarizing materials and specifically to materials capable of polarizing light incident thereon through refraction and reflection. Kahn (U. S:. Pat. No. 4,796,160) teaches a polarized lighting panel as an improved Radialens light control panel with a smooth bottom layer consisting ~f light polarizing materials. '1']~is polarizing lighting panel r ft:
provides polarized light that is preferentially distributed to provide higher visual effectiveness and contrast, less reflective glare, increased visual comfort and less direct glare that could be obtained with a Radialens panel alone or from the polarizing sheet alone without the preferential distribution offered by the Radialens panel. However, in neither of Kahn's patents is it taught the use of the polarized diffuser with the full spectrum lamp to produce a lighting system with both the light polarization characteristics and spectral energy distribution of natural light as the combination of the full spectrum lamp with the polarized diffuser is necessary to duplicate natural light.
Referring now to a further embodiment, the invention also provides a polarizing fluorescent lighting system with improved ultraviolet light transmission. In this respect, it has long been recognized that in order to provide glare free illumination, light polarization is~essentral.
By the use of polarized lighting, glare is minimized and contrast is increased. Lighting in most non-residential buildings is largely fluorescent.
Materials that can provide polarized light were a laboratory curiosity until the development of di.chroic linear polarizers in sheet form by Land,(see for example, LAND, "Polarizers Containing Aligned Crystals of Herapathite", U. S. Pat. No.
1,918,848 (1933)), and by Marks (see for example, MARKS, "Crystalline Formation", U. S. Pat. No. 2,1U4,949 (1938)).
A
~~~i.'~.~~~'~
The linear dichroic polarizers, while useful in many applications, were not suitable for use in commercial lighting fixtures for general illumination purposes. First of all, the polarization was only in one direction. A second major problem was the increase in electrical power needed for lighting as the linear dichroic polarizers absorbed between 60 and 72 percent of the incident light energy being transmitted through them. In particular, the linear dichroic polarizers absorbed most of the ultraviolet light, and much of the purple and blue light in the visible spectrum.
It took the invention of the so called "radial polarizer"
by Marks and Kahn in the years after World War II 'to solve both of these problems (see for example, MATZKS, "Multi-layered Light Polarizers", U. S. Pat. No. 3,069,974 (1962) and .K.AfIN
"Light Polarizing Structures", U. S. Pat. No. 3,124,639 (1964)).
The invention of the radialens style lighting panel by Jones (see JONES, "Lighting Panel", U. S. Pat. No. 3,829,680 (1974)), provided a diffuser for use in a lighting fixture that could minimize : glare from vei.l~.ng .ref~.e~ti.Qns. This panel contained a continuous pattern of triangular projections, aach having three mutually substantially perpendicular surfaces projecting upward .towards the light source. . "_ The base lines of the mutually perpendicular surfaces are co-planar and the pattern of projections is such that the base lines of ali projections on the panel form continuous straight lines directed in specific directions. This results in a light panel which minimizes veiling reflections from the illuminated mat;ter. The panel provides a radial distribution of light with a high lighting efficiency and with a maximum of light in the area which is 30° to 60° from vertical.
Kahn combined the prismatic structure of the JONES Radialens manufactured according to the methodologies and structure of KAHN's polarizing panel (see KAHN, "Light Polarizing Structures", U.S. Pat. No. 3,124,639, (1964), cited above) to obtain the 10 higher visual acuity realized with polarized light with the wider angle distribution of the Radialens panel and the desirable Visual Comfort Probability of 70 or more into an integral structure. What was achieved is not merely the expected advantages of polarized ~~nd Radialens light distribution, but also a marked improvement in Visual Comfort Probability and also a reduction in glare at wide angles as disclosed in U.S. Pat. No.
4, 796, 160 (1989) to KAHN.
A major problem with the Polarized Radialens and all of the radial multi-.layer polarizers manufactured for commercial lighting fixtures is the apparent reduction in brightness. This reduction in brightness is so severe as to be noted by a number of lighting practioners (see, Lovins, Amory, et al. STATE OF THE
ART: LIGHTING, Rocky Mountain Institute, Snowmass, Colorado 81654, (1988), page 157). The objection sometimes encountered with the multi-layer polarized diffusers is that they are so effective that they can give room lighting a "dull" subtly flat quality by suppressing the specular highlights which harsh lighting has led us to expect as visual cues.
~J 6-I I
An unrecognized problem with all multi-layer polarized diffusers used fcr commercial lighting fixtures is the type of acrylic plastic used as the supporting material for the polarizer which is adhered to the bottom side of the acrylic sheet. Typically, these multi-layer polarized ~difPusers are manufactured by extrusion using Type V Series. acrylic molding~powders as manufactured by Rohm and Haas (Philadelphia, Pennsylvania) or a similar product. The polarizing material is adhered by heat to the bottom of the sheet (see KAHN, "Machine for Continuously Producing Large Area Light Polarizing Panels", U, S, Pat. No. 3,772,128 (1973)). Figure 2 shows the transmission properties of the Type V Series acrylic molding powder when used to produce an acrylic sheet 0.125 inches thick (taken fxom Rohm and Haas Technical Bulletin PL-612, (1988)). The light transmission properties of the Type V Series acrylic ,.
molding powders is shown for wavelengths between 250 and ~E50 manometers. This 0.125 inch thickness is the thickness of the commercially available mufti-layer polarized diffusers.
The major problem is that the acrylic manufactured from the Type V Series acrylic molding powder transmits less than 50 percent of the ultraviolet light with a wavelength of less than 380 manometers.
i E? '~ a The present invention solves this problem by providing a Type UVT acrylic molding powder or a similar material. The multi-layer polarized diffuser which results from the use of the Type UVT acrylic molding powder is capable of transmitting ultraviolet light with wavelengths as low as 290 nanometers.
The resulting transmission of ultraviolet wavelengths all the way down to 290 nanometers provides a substantial improvement in the quality of the illumination.
In addition to solving the problem~of absorption of ultraviolet in the 290 to 380 nanometer range, it is noteworthy that none of the patents by darks or Kahn cited above make any mention of the unrecognized need to polarize the ultraviolet tight given off by fluorescent, metal halide, or a number of other light sources as a way of improving the contrast and apparent brightness of objects viewed under a combination of visible and ultraviolet light. The present invention not only transmits the ultraviolet in the 290 to 380 nanometer range, but also polarizes it as well.
4. Theory of the Tnvention ' ' The key to the present invention is.that virtually all paper and textile materials, and many paints and pigments have substances such as opticalbrighteners that fluoresce under ultraviolet light between 290 and 420 nanometers.
The fluorescent effects add to brightness by transforming the ultraviolet radiation between 290 and 420 nanometers into longer wavelength radiation in the visible spectrtun (see Barrows, tdilliam E., Light, Photometry, and Illuminating En~ineerin , McGraw-Hill Book Company, New York, (198), p. 26).
l8 '~ s ~~i3~.~.~~~~~
Thus, if the multi-layer polarizers were so modified to be manufactured with an acrylic supporting material that could transmit ultraviolet light so it could be polarized by the multi-layer polarizing material on the bottom of the Light polarizing structure, the advantage of the invention is that it would be possible to increase the apparent brightness of paper and te:~tile materials being illuminated by a light source giving off ultraviolet as well as visible light. It should be noted that when compared to an unpolarized light source, the ultraviolet light will be vertically polarized as well, so it will be glare free, as it is well known that glare from unpolarized radiation is detrimental to one's eyes and the ability to see.
Figure ~ also shows the transmission properties of an ..
ultraviolet transmitting acrylic made from an acrylic molding powder such as the UVT type acrylic molding powder as manufactured by Rohm and Haas (taken from Rohm and Haas Technical Bulletin PL-612e, (1985), p. 5) from 250 to 450 nanometers. It should be noted that acrylic sheets manufactured from this acrylic molding powder will transmit 85 percent of the ultraviolet light with a wavelength greater than 315 nanometers.
Thus, the application of an ultraviolet transmitting acrylic would permit the transmission of the ultraviolet light emitted from a light source through the supporting acrylic so the ultraviolet light would then be polarized by the multi-layer polarizing~materials which are adhered to the bottom of the acrylic sheet, which is the side of the sheet facing towards the objects being illuminated.
It should be noted that ultraviolet light is not detectable by a standard photopic light meter which measures visible light according to the Standard Observer Curve ( ~) as established by the International Commission on Illumination. Thus, using the present invention, objects will appear brighter, even though the measured foot-candles will be virtually the same for a light source in the visible as compared with a light source which emits the same visible light plus some ultraviolet light. It will then be necessary to develop new photometric instruments that will integrate the fluorescent effects of ultraviolet light into the Standard Observer Curve V(~) for Che photopic region.
It is also not generally.known that the eye responds to ultraviolet light. In the young healthy eye the ocular media are sufficiently transparent to allow a substantial amount of ultraviolet energy (so-called "invisible") of wavelength as short as 350 nanometers to reach the retina and evoke a visual sensation. Smaller amounts of wavelengths as short as 300 manometers may be transmitted, but this effect is not important in ordinary vision at high levels of luminance (see The Science of Color, Optical Society of America, Washington, D. C. (1953), p. 76).
Therefore, since my invention provides an increase in ultraviolet illumination in polarized lighting installations, there will be an increase in visual sensation for normal healthy eyes.
Most fluorescent lamps produce a certain amount of u:ltrav-iolet light, and many of the spectra of such lamps contain a peak in the ultraviolet at 305 manometers. Full-spectrum lamps are defined as lamps having a color rendition index of 90 or above and a correlated color temperature of 5,000 degrees Kelvin or above. The visually effective F40/T12 Color Classes 75, with a correlated color temperature of 7,500 degrees Kelvin, and a color rendition index of 93, is a full-spectrum fluorescent lamp currently available from Duro-Test Corporation, Fairfield, New Jersey, and provides illumination not only in the visible range from 380 to 780 manometers, but also provides a significant amount of ultraviolet light from 290 to 380 manometers. This ultraviolet light is exactly the radiation capable of producing ".fluorescent effects . , , Thus, the use of the Type V Series acrylic molding powder in the manufacture of the supporting layer for the multi-layer polarizing material ~e1_iminate~.much .of the benefit of: the ultrav2.ol~~C flight in improving the apparent brightness of paper and textile objects -.since a mufti-Iayer polarized ...__.. .
diffuser made from the Type V Series acrylic molding powder or a similar product would absorb most of the ultraviolet sight between 290 and 380 manometers.
Figure ~ shows the spectral energy distribution of the "'FGO/T12 Color Classes 75 fluorescent lamp, as provided to Che inventor by the Duro-Test Corporation. As shown, there is production of much ultraviolet light between 290 and 380 manometers.
_. _ In comparison to the 'type V Series acrylic molding powder which absorbs much of the valuable ultraviolet light, use of the 'type UVT acrylic molding powder or a similar product in the manufacture o~ the supporting acrylic of the multi-layer polarized diffuser would then allow almost all of the valuable ultraviolet light emitted from lamps between 290 and 380 nanometers to pass through the acrylic supporting structure and hence the ultraviolet light would be then vertically polarized where it could increase the apparent brightness of paper and textile materials .without_ the harmful glare that results from unpolarized ultraviolet as well as unpolarized visible light.
The polarization effects would be expected to be greater in the ultraviolet than in the visible portion of the electromagnetic spectrum. It is known that the index of refraction of many materials varies with the wavelength of light, and the index of refraction increases with a decrease in the wavelength , of light -( see, .far exa~mple,~ Hal~fi~day,T David, and Re snick, Robert, Physics, John Wiley & Sons, New York, 1966, p. 1014-1015). As the index of.refraction increases, the amount of polarization increases, especially for multi-layer type polarizing Cype materials. The multi-layer poTarizers provide vertically polarized visible and ultraviolet light by means of reflection and refraction; the polarization effects are greater with an increase in the index of refraction, hence the degree of polarization will be greater in the ultraviolet region as compared with light in the visible portion of the spectrum. .
It is also known that the ultraviolet light which is scattered in the sky is very highly polarized (see, for eYampie, Feynman, Richard, et. al., The Feynman Lectures on Physics, Volume I. Addison-Wesley Publishing Company, Reading, Massachusetts, (1963), p. 32-8). The scattering of ultraviolet light increases as the fourth power of the frequency of the spectrum. Thus, one should e:cpect that the sky should be blue, since the blue light is more highly scattered than the light at the red end o~ the spectrum, This scattering is known as the Raleigh scattering in honor of the person who first discovered it.
Daylight contains radiation down to 290 manometers (see, l~uffie, John, A, et, al., Solar Eneray Thermal Processes, John Wiley & Sons, New York, 1974, p. 14, and Cayless, M. A., and Marsden, A. M., Lamps and Lighting, Edward Arnold, London, 1983, p.
4). Thus, the present invention of an ultraviolet transmitting polarized diffuser, when used in conjunction with full-spectrum Fluorescent lamps, will provide a lighting system which is ~ - -~ ..
s:~bstantially duplicates natural daymgnz, ana ~an~ch contains ..
vertically polarized ultraviolet light in addition to vertically polarized visible light. The previously available multi-layer polarized diffusers which are made from a Type V Series ox s::nilar acrylic molding powder block much of the ultraviolet light with wavelengths below about 380 manometers.
An e:cample of the use of the present invention which in no way limits its potential application is for~-the~p'roduction of so called "north sky" lighting that artists prefer. Irr north sky lighting, one combines a 7,500 degree fluorescent lamp with an ultraviolet transmitting multi-layer polarized diffuser. A mufti-layer polarized diffuser made from the Type V Series. acrylic molding powder or a similar rzeaterial would produce: an inferior "north sity" effect due to the absence of u;ltravioiet light below 380 naizvmeters.
Passage of the ultraviolet Light through the acrylic supporting Layer of the present invention and through the mult__-layer palarizer will reduce degradation of the acrylic materials, since the ultraviolet light is passing through the diffuser, rather than having an opportunity to interact with it. Thus, the need for periodic replacement of the lighting diffusers is reduced significantly, along with a reduction of Che solid waste that would otherwise be added to the solid wasCe stream when materials ere discarded in the trash.
Another benefit of the use o.f an ultraviolet transmitting polarized dif::user (as compared to ultraviolet absorbing polarized diffusers of the prior art) is the energy saving potential. Since objects will appear brighter due to fluoresce effects, one can install fewer lighting fixtures and spread them farther apa-rt, . ' - .
A secondary energy sa~rings occurs because when the Type V Series acrylic molding powder is used to manufacture the mufti-layer polarizer, the acrylic absorbs the ultraviolet Light and is v.ltimately converted to heat. The diffuser heats up, which traps the heat from the fluorescent lamps inside the fixture. Sy allowing the u:Ltravivlet light to easily pass through the ultraviolet transmitting mufti-layer polarize:r, additional heat can be rejected from the lighting fixture, and the heat build-up is reduced significantly, lowering the ** TOTAL PAGE.02 **
~ Y n' 1 C~ ~ ~! ~ it lamp operating temperature. It is known that reduced light output from a fluorescent fixture results from operating a fluorescent lamp above its optimum lamp wall temperature (sea Jerome, Charles W., "Effect of Bulb Wall Temperatures on Fluorescent Lamp Parameters", Illuminating Engineering, February, 1956, pp. ?05-213).
It has been shown by Cobb (see, Cobb, Percy W, and Moss, Frank E., "Lighting and Contrast", Transact-ions of the Illuminating Engineering Society, February, 1927, p. 195-204, also see Marks, Alvin, "Multilayer Polarizers and Their Application to General Polarized Lighting", Illuminating Engineering, February, 1959, p. 127) that visual acuity increases with contrast. Marks provided proof using a set of algebraic equations that contrast will always be improved using polarized illumination.
With the use of the ultraviolet transmitting mufti-layer polarizer, contrast, and hence visual acuity, will be greater than when-using a mufti-layer polarizer with a supporting acrylic made of a Type V Series acrylic molding powder or a similar material, since the effect of the ultraviolet light will be to increase 'brightness of the paper which contains the optical brighteners which fluoresce under ultraviolet light. Note that the areas df paper covered by black print will not fluoresce, so there will be a definite increase in contrast between the print anti the paper it is printed on when compared to illuminating the same paper with a light source giving off ult'raviol:et light and having the ultraviolet light blocked by a mufti-layer polarized diffuser made of the Type V Series or similar acrylic molding powder.
DESCRIPTION OF THE DRAWINGS
~~u~~~~~
Having thus generally described the invention, reference will now be made to the accompanying drawings in which:
FIGURE 1 is a side view of a two-lamp troffer mounted fixture.
FIGURE 2 is a graph chart comparing the transmission properties of the acrylic layer 2 of the ultraviolet transmitting multi-layer polarizer of the present invention and the prior art.
FIGURE 3 is a graph chart showing the spectral energy distribution of a prior art 7,500 degree full-spectrum fluorescent lamp.
FIGURE 4 is a side elevational view of the ultraviolet transmitting multi-layer polarizer of the present invention.
~~~~.~2. ~
A vast improvement in visual performance is achieved in the full spectrum polarized lighting system which comprises full spectrum lamps in combination with a polarized diffuser.
The fixture contains two full spectrum fluorescent lamps 1 mounted between the fixture housing 2 and a mufti-layer polarized diffuser 3. The prism side 4 of the mufti-layer polarized diffuser is towards the lamps and the smooth side 5 is towards the objects or room being illuminated by the fixture. The smooth side 5 is coated with a layer of polarizing material 6 which converts unpolarized light to preferentially vertically polarized light.
The mufti-layer polarized diffuser is mounted in the fixture door 7. There is an ultraviolet resistant gasket R which is between the fixture door 7 and the fixture housing 2. The lamps are driven by a solid state ballast 9.
'The prism side of the mufti-layer polarizer is towards the lamps to provide for proper light polarization. If the the smooth side which contains the polarized layer is towards the lamps, there will be some depolarization of the light as it emerges from the prism side. In addition, the light distribution will be altered since the prism side will be A
down instead of being up., ~~'~ ~.~~
~n the preterrec~ embodiment, the light polarization material used produces preferentially polarized light in a radial cone directly under any point in the fixture. A linear polarizes, such as the dichroic polarizers used in sunglasses, can only provide vertically polarized light in one direction. For an overhead lighting system, where viewing takes place from all directions, a linear polarizing material would provide for extremely uneven lighting in a room or an office, and would be highly unsatisfato,ry. In addition, the linear polarizers axe only about 40 percent in transmitting light, as compared with efficiencies in the 70 to 85 percent range achieved by using a polarizing film which produces vertically polarized light. As one of the objectives of the full spectrum polarized lighting system is to improve vision and to be an energy efficient lighting system, such an approach using dichroic polarizing materials would not. achieve the objectives of energy conservation and a visually efficient lighting system.
~fexence will now be made to Figures 2 through 4 as follcxvs.
A vast improvement~in visual performance and brightness of objects being illuminated is achieved by the use of the ultraviolet transmitting multi-layer polarizes. Referring now to Figure $, the prism side l~of the ultraviolet transmitting mufti-layer polarizes faces towards the full-spectrum fluorescent i lamps. The supporting acrylic~layer 2 transmits the ultraviolet light from the lamps to the mufti-layer polarizing layer 3~
on the bottom of the ultraviolet transmitting mufti-layer polarizes. The function of the acrylic layer 2 is to support i the thin polarizes 3 which is itself comprised of multiple layers as described in prior art. The assemblage of the: supporting i acrylic 2~and the polarizes 3 is manufactured in flat sheets for use in commercial fluorescent lighting fixtures.
s~~a ~'? - °I
28 Fa ;f tJ ~ ~a ~ ~~
Figure ~ shows the transmission properties of the Type V Series acrylic molding powder of acrylic layer 2, when used to produce an acrylic sheet 0.125 inches thick (taken from Rohm and Haas Technical Bulletin PL-612, (1988)). The light transmission properties of the Type V Series acrylic molding a powders of acrylic layer 2 is shown for wavelengths between 250 and 450 nanometers. This 0.125 inch thickness of acrylic layer 2 is the thickness of the commercially available multi-layer polarized diffusers.
The present invention not only transmits the ultraviolet in the 290 to 380 nanometer range but also polarizes as caell.
Figure ~ also shows the transmission properties of a 0.125 inches thick ultraviolet transmitting acrylic layer 2 made from an acrylic molding powder such as the UVT type acrylic molding powder manufactured by Rohm and Haas (taken from Rohm and Haas Technical Bulletin PL-612e, (1985), p.5) from 250 to 450 nanometers. It should be noted that acrylic sheets manufactured the Type UVT acrylic molding powder, will transmit 85 percent of the ultraviolet light with a wavelength greater than 315 nanometers.
29 y~~~ ~.~, Acrylic layer 2 includes a type UVT acrylic molding powder or a similar material. The multi-layer polarized diffuser which results from the use of the Type UVT acrylic s molding powder of acrylic layer 2 is capable of transmitting ultraviolet light with wavelengths as low as 290 nanometers.
The resulting transmission of ultraviolet wavelengths all the way down to 290 nanometers provides a substantial improvement in the quality of the illumination.
The application of an ultraviolet transmitting acrylic layer 2~permits the transmission of the ultraviolet light emitted from a light source through the supporting acrylic layer 2 so the ultraviolet light would then be polarized by the multi-layer polarizing materials of thin polarizer 3r which are adhered to the bottom of the acrylic sheet of acrylic layer 2;~ which is the side of the sheet facing towards the objects being illuminated.
Figure 3 shows the spectral energy distribution of the F40/T12 Color Classer 75 fluorescent lamp (not shown) as provided to the inventor by the Duro-Test Corporation. As shown, there is production of much ultraviolet light between 290 and 380 nanometers.
30 ~ S3 ~ '~
~: t 9 .~. ~ ~ '-~
Thus, the present invention of an ultraviolet transmitting polarized diffuser, when used in conjunction cdith full-spectrum fluorescent lamps, provides a lighting system which substantially duplicates natural daylight, and which contains vertically polarized ultraviolet light in addition to vertically polarized visible light.
Passage of the ultraviolet light through the acrylic supporting layer 2~of the present invention and through the multi-layer polarizes reduces degradation of. the acrylic materials, since the ultraviolet light pass through the diffuser, rather than having an opportunity to interact with it.
Modifications can be made to the method used for making the device, the device itself as well as the process described for the ultraviolet transmitting mufti-layer polarizes without departing .fram the spirit and scope of the invention as exemplified below in the appended claims.
A novel use of the ultraviolet transmitting multi-layer polarized diffuser would be for illumination using so called "black lights" that only give off ultraviolet light. Lighting fixtures using the ultraviolet transmitting polarized diffuser could be used for special effects lighting for nightclubs and other places of entertainment. As mentioned above, use of the ultraviolet transmitting multi-layer polarizer with an ultraviolet light source pith provide vertically polarized ultraviolet light, as it is well known that glare from unpo.larized radiation is detrimental to one's eyes and the ability, to see
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a full spectrum polarized fluorescent lighting fixture for general purpose lighting for commercial, institutional, and industrial use. The lighting fixture will provide flicker free, glare free light of excellent color rendition. This fixture is also designed to be used in spaces with ,personal computers or video display terminals.
.Tlte polarizing lense provides glare free light that gives excellent contrast and sharp images. The lighting fixture is equipped with a full spectrum lamp to provide light that will match the color rendering properties of natural daylight, and to eliminate eyestrain. The lighting fixture also has a solid state ballast that does not flicker.
Ever since the invention of the incandescent light bulb, attempts have been made to reproduce natural light. Full spectrum lamps have been developed utilizing a combination of phosphors which produce ultraviolet as well as visible light in approximately the same proportion as found in natural daylight. Full spectrum lamps are defined as a lamp with a Color Rendition Index of 90 or above and a Color Temperature of 5,000 degrees or above. Such a fluorescent lamp is disclosed, E'or example, in U. S. Pat. No. 3,670,193.
'' ,', ~ i, r.~
The novel illuminating sysa.em according to my invention makes it possible for the first time expediently to provide artificial light which has the spectral energy distribution and light polarization characteristics of natural daylight.
Such an artificial lighting system was first noted in "Designing Efficient Full Spectrum Polarized Lighting Systems for the Electronic Office, by Daniel Karpen, P. E., in Strategies For Reducing Natural Gas, Electric, and Oil Costs (Proceedings of the 12th World Energy Engineering Congress, October 24-27, 1989, published by the Association of Energy Engineers, Atlanta, Georgia). Such a combination comprises a lighting system which will produce light providing great visual acuity.
It is well known that light scattered by the atmosphere is highly polarized (see for example, "Light Scattering in the Atmosphere and the Polarization of Light", by Z. Sekera, Journal of the Optical Society of ~nerica, June, 1957, Vol.
47, p. 484). The degree of light polarization. in the atmosphere was carefully measured by Z. Sekera, and it is of the same order of magnitude as the amount of light polarization produced by commercially available polarized diffusers for fluorescent lighting fixtures. It is easy to demonstrate that daylight from the sky is polarized by the atmosphere: take a linear palaxizer and rotate while looking at the sky. One will notice a darkening and lightening of the linear polarizes as it is xotated through 90 degrees. Maximum polarization is seen while looking in the sky at an angle of 90 from the direct beam of the sun.
~,~~_~.~' However, full spectrum lamps used by themselves are lacking,) the polarizing characteristics of natural daylight, and produce glare when used in lighting fixtures without polarized diffusers.
The subject of the invention is a fixture that contains both the full spectrum lamp and the polarized diffuser to achieve the desired result of an artificial lighting system that has both the spectral energy distribution and light polarization characteristics of natural daylight.
For some time, there. has been a great deal of dissatisfaction with conventional fluorescent lighting systems. for the computerized office, with personal computers and video display terminals, 'there is a great deal of glare from conventional fluorescent fixtures. The present technology of using core coil ballasts, cool-white or warm-white lamps, and prismatic or parabolic lenses contributes to fatigue, eyestrain, and glare in interior lighting, resulting~in a substantial loss of employee productivity.
While it has been known that visibility is related to the amount of light present (measured foot-candles), there are other fundamental characteristics concerning vision, task visibility, and lighting which are of equal or greater importance thin quantity alone. "Seeing" is not related to foot-candles per se. It is mostly a function of the luminance (brightness) of the task detail and its contrast with the background. The first of these factors is dependent on the task detail reflectance -how much of the light reaching the task has been absorbed by it and re-reflected, so it can be seen.
~~~' ' -~
The other factor, contrast, is the difference in task brightness between the Cask detail and its background. Gray printing on lighter gray background can be very difficult to see. Contrast is very important to "Seeing".
The nature of light and the lighting system can affect both the brightness of the task detail and its contrast. One can easily see just how much difference it makes. If one takes a printed object, such as a magazine or book, and places it on a table under a light source located slightly to the front of it, one will notice ~tha.t the print detail ..
looks "washed out".
IE one moves around to the side, the print will appear darker. What has happened ps that the contrast of. the print to the background l:as increased. In the first instance, the ligizt bouncing o.ff the task reduced its contrast due to reflected glare, also called "veiling reflections." These reflections are due to light which is reflected from the task surface without actually obtaining information on them. In the second instance, the reflections went off in the other directions than to the eye, so they did not wash out the contrast between the object detail and the background.
The portion of the light rays which cause reflected glare or veiling reflections is that which is horizontally polarized.
The vertically polarized portion of the .Light penetrates into the task (instead of bouncing off its surface) and returns to the eye carrying .information about the task, detail and color. If, therefore, one illuminates an object so the horizontally polarized component of the light is not present, one obtains a much higher contrast and one is able to see detail and color ~ni:3~~ ~t.~
much better. This is how multi-layer polarizing diffusers function. 'They convert the horizontally vibrating light rays emitted from the lamp to vertically polarized light, thus increasing the amount of vertically polarized light rays available for penetrating into the task. As a result, the reflections are reduced, and the visual contrasts enhanced significantly.
The visual effectiveness and "Seeing" are thus improved significantly.
If contrast is improved, then one requires "Less light"
to see tasks equally as well. If one improves the contrast, one can reduce the amount of light (measured foot-candles) one needs to achieve equivalent visu al performance. This is ho~o vertically polarized light .functions. Test results indicate a reduction of as much as 50 percent in measured foot-candles to achieve equivalent visual performance as noted in report .LRL 188-9, prepared by Lighting Research Laboratory, P. U. Box 6193, Orange, California 92667, dated January 13, , 1988.
Thus the substitution of polarized diffusers in place of prismatic or parabolic diffusers immediately solves the veiling reflection problem. It has been known since 1973 that polarizing diffusers increase contrast as compared with I
prismatic or louvred (including parabolic diffusers), as noted in "Progress in Solving Veiling Reflections", Lighr_ing Design and Application, May, 1973. The correct solution to solving tire glare problem is to use vertically polarized light. Using vertically polarized .Light also eliminates the bright spots 1 t directly under a fixture as there is a more even and wider light distribution.
r ;yo 6 ~,, 9 ~ iV ~ f7 y .~~~v 'The importance of the color rendering quality of light sources has been well established for applications where color identification or comparison is involved, and some studies have been made to determine the importance of color rendition for general illumination.
Berman examined the visual effectiveness of a number of light sources under photopic (day vision) and scotopic (night vision) environments (Energy Efficiency Consequences of Scotopic Sensitivity, Lighting Systems Research Group, Lawrence Berkeley Laboratory, Berkeley, California 94720, dated htay 13, 1991). 1-le found that at the light levels typical of interior illumination, the eye functions more in the scotopic region than i.n the photopic region.
Tile human eye is a light sensing system with an aperature (pupil) and a photoreceptive medium (retina). 'fhe i:etina contains two basic types of photoreceptors, cones and rods.
Tlte rod photoreceptors are generally associated with night vision and have been assumed to not participate in the visual process at light levels typical of building interiors. The cone receptors which are responsible for seeing fine detail and fox color vision, provide the photopic visual spectral efficiency of the eye which is captured by the V( ~ function.
Under conditions of very dim light, such as starlight, there is not enough light energy to stimulate the cone photoreceptors, but there is enough to stimulate the rod system as stars can be readily observed. The spectral response of the rod photoreceptors, the scotopic response function V'(~ ), differs i:rom the cone A
spectral response in that its wavelength peak response is at about 508 nm rather than the 555 nm of the V( 1) function.
6 3 ~
W 7 'Y'. ~ ~ f; ~ ~~) ~j n1G
~J t ) _.
Reductions in visual acuity occur with increasing pupil size for the normally sighted under conditions of moderate to low contrast but not necessarily at high contrast. However, individuals who need optical corrections, i. e., those who should be using spectacles because of myopia (nearsightedness) show decrements in visual acuity even at high levels of contrast.
Many tasks in the workplace do not possess high contrast.
Changes in acuity axe similar to changes in threshold contrast as both are major determinants of visual performance potential.
Conversely, at normal office lighting levels, photopic adaptation luminance is a weak determinant of visual performance potential.
'fhereEore two sources with equal scotopic illumination, but moderately different photopic illumination (within a factor of two), should be 'very close in their performance potential.
On the other hand, two sources with equal photopic illumination, buz moderately different scotopic illumination, may have significantly c i different visual performance potentials.
By using the V(~ ) and V'(~) functions, one can calculate , the photopic and scotopic lumens for a number ~f light sources.
The scotopic output can be determined by folding the lamp ., spectral power distribution with the scotopic sensitivity function V'(~ ) as given by Wyszecki and Stiles (Color Science, 2nd ed., Wi:ley, New York City (see page 105), 1982). Pupil ' size is then determined by a combination of photopic and scotopic lumens that can be thought of as a "pupil lumen" (see Berman et, al. "Spectral Determinants of Steady-State Pupil Size with Full Field of View", Lighting Systems Research Group, r Lawrence Berkeley Laboratory, Berkeley, California 94903 Report Number 31113, dated February 19, 1991). .
., Pupil lumens are determined by the factor P(S/P)'78, where P and S are the photopic and scotopic output of the lamp.
The ratio of the scotopic to photopic luminance (or lumens) is referred to here as the (S/P) ratio. This ratio is a property of the lamp spectral power distribution (SPD). Generally, the pupil lumen is determined by the measured photopic output multiplied by the S/P ratio which is calculated from the measured SPD which is then folded'with V( r) and V'(~ ). Based on the scotopic and photopic lumen outputs, the third column in Table 1, lists the values of the pupil lumens from each of the different spectral distributions. The fourth column in Table 1 shows the relative amounts of power required by these lamps for the condition of equal average pupil size, assigning a value of 100 to the cool white lamp. The last and most significant column compares the lamps on the basis of pupil lumens per watt which is proposed here as the measure of the visual effectiveness per watt for various 40 watt lamps.
Table 1 Effective Relative Power Pupil Photopic Scotopic Pupil L~~ens Level for Equal Lumens Lamn Lumens Lumens P(S/P) Pupil Sizes Per Watt Warm White Fluorescent 3200 3100 3125 136 78 Cool White Fluorescent 3150 4630 4254 100 106 F40iT10 5500° CRT 91 2750 5913 4996 85 125 Thus, from the point of view of providing opti:,~um lighting l;or visual function, the F40/T10 5,500° c;RI 91 lamp would require percent less energy than the cool white lamp, and percent less energy than the warm wh~.te fluorescent lamp.
rr c~ ~E
~u LW ~~ ro ':,t By the use of the full spectrum lamps with the multi-layer polarized diffuser, the energy savings potential increases as compared with the cool white or warm white lamp. As discussed above, by utilizing a polarized diffuser, light levels can be cut in half for equal visual performance. Thus, when the full spectrum lamp replaces the cool white lamp, one needs only 82 percent of the energy to produce equivalent illumination;
by placing a polarized diffuser with the full spectrum lamp, one needs only42.5 percent of the original amount of energy for equivalent visual performance. Likewise, the use of the full spectrum lamp with the polarized diffuser in place of warm white lamps results in needing only 30 percent of the energy needed for equivalent illumination. This reduction in energy use in the full spectrum polarized lighting system can only occur when the polarized diffuser is used with the full spectrum lamp.
i Use of electronic solid state ballasts is necessary to eliminate the flickering associated with fluorescent lamps driven by conventional core coil electromagnetic ballasts.
Standard core coil ballasts produce a 60 cycle flicker at the ends of a fluorescent lamp and a 120 cycle flicker in j.
the middle of the fluorescent lamp. Both types of flickering are subliminally noticeable. When video display terminals ate viewed with fluorescent fixtures driven by standard core Boil ballasts, both the VDT and the fluorescent lamps flicker at the line frequency, but rarely exactly in phase since both 2 t the VD'f and the ballast are inductive devices. This out of please flickering, called the strobe effect, is causing discomfort for VDT operators. The high frequency ballast eliminates~this ~i~ ~ ~~1~
entirely. Evidence exists that the use of electronic ballasts improves productivity by about 10 percent, as noi.G~ in "Electronic Ballasts Produce Substantial Cost Savings", by Karen Haas Smith, Building Design & Construction, November, 1986 and "Superior Uffice Lighting - An Unusual Approach", by Arthur Freund, Electrical Construction & Management, November, 1983.
A solid state ballast with a 40 watt bipin four foot fluorescent lamp will consume approximately 40 watts. A solid state ballast driving two~40 watt bipin four foot fluorescent lamps will consume approximately %2 watts. A standard 4 lamp F40 Eluorescent fixture driven by core coil ballasts will consume approximately 192 watts.
By the use of the full spectrum lamp with the multi-layer polarized diffuser, as mentioned above, one can achieve essentially the same degree of visual performance with a single four foot F4G%T10 foil spectrum lamp as with four F40 warm white lamps. Thus, it is possible to save a significant amount of electrical energy by the use o~ the full spectrum fluorescent lamp with the multi-layer polarized diffuser in place of the use of warm white lamps alone. If one drives the full spectrum lamp by a solid state ballast, lrlStalling it a fluorescent Fixture with the multi-layer polarized diffuser, one can save 15~ watts of lighting instead of using a four foot fluorescent Fixture with 4.warm white lamps.
s Tlie fi:cture housinø is free of ventilation holes whi~oi~3J~~~~l permit air to ventilate the fixture. lfowewer, a solid state ballast produces far less heat, normally 1 to 3 watts compared with 8 to 16 watts produced by a conventional core coil type ballast. Thus, there is no need for ventilation holes. A
major problem with ventilation holes is while they work well to cool the fixture, they do permit substantial amounts of dirt and dust to accumulate on the prism side of the polarized diffuser. Such accumulation of dirt and dust becomes difficult and costly to clean compared to simply wiping the smooth surface a.E a conventional prismatic diffuser which is installed with the flat side towards the lamps and the prism side towards the objects being illuminated by the fixture. The fully sealed Fixture housing is an essential part of the fixture and the full spectrum polarized lighting system. The fixture also contains a gasket mounted on the door frame of the fixture between the door and the door frame to prevent dirt from entering around the door and door frame'. The gasketing is also ultraviolet resistant to prevent deterioration subsequently preventing dixt from entering the fixture housing. Since a full spectrum lamp gives off ultraviolet light (see for example U. S. Pat.
No. 3,670,193), one needs to use an ultraviolet light resistant gasketing, as otherwise the gasketing materials would deteriorate when ultraviolet light hits the gasketing materials.
.~csm,aswm.~_ ~~~...~ ".. . u.=.......~.....,. .,.
°~'-- _. .........~..........,a......,..r...... ..
-° 12 Description of Prior Art Scott (U. S. Pat. No. 3,201,576) teaches the use of several different fluorescent lamps in a fixture, each of which lamps produces a different spectral energy distribution, but when tl~e lamps are turned on in combination, so called "north light"
results. Semotan (U. S. Pat. No. 3,517,180) teaches the use of arrays of lamps of different colors intersecting at right angles to produce an artificial daylight effect. Thorington (U~ S~ Pat. No. 3,670,193) teaches the use of various combinations of phosphors znside a fluorescent lamp to obtain a light source providing light matching natural light. Ott (U. S. Pat. No.
4,091,441) shows tt:e use of full spectrum fluoresce~at Lamps in a lum.inaire in combination with a gas discharge lamp producing ultraviolet light to provide for a luminaire that produces .artificial light with the light spectral energy distribution and ultraviolet distribution of natural Light. Note that both Scott and Sematon use a combination of lamps to produce the full spectrum light, whereas Thorington and Ott use a single lamp that provides the spectral distribution of natural light in the visable light. Neither Thorington nor Ott use '. tt~e mufti-layer polarized diffuser in combination with the Fu,l1 spectrum lam s to P produce a light source that has both tt~e spectral energy distribution and li ht g polarization characteristics o~ natural light. Kahn (U. S. Pat. No. 3,124,639) teaches the use of light polarizing materials and specifically to materials capable of polarizing light incident thereon through refraction and reflection. Kahn (U. S:. Pat. No. 4,796,160) teaches a polarized lighting panel as an improved Radialens light control panel with a smooth bottom layer consisting ~f light polarizing materials. '1']~is polarizing lighting panel r ft:
provides polarized light that is preferentially distributed to provide higher visual effectiveness and contrast, less reflective glare, increased visual comfort and less direct glare that could be obtained with a Radialens panel alone or from the polarizing sheet alone without the preferential distribution offered by the Radialens panel. However, in neither of Kahn's patents is it taught the use of the polarized diffuser with the full spectrum lamp to produce a lighting system with both the light polarization characteristics and spectral energy distribution of natural light as the combination of the full spectrum lamp with the polarized diffuser is necessary to duplicate natural light.
Referring now to a further embodiment, the invention also provides a polarizing fluorescent lighting system with improved ultraviolet light transmission. In this respect, it has long been recognized that in order to provide glare free illumination, light polarization is~essentral.
By the use of polarized lighting, glare is minimized and contrast is increased. Lighting in most non-residential buildings is largely fluorescent.
Materials that can provide polarized light were a laboratory curiosity until the development of di.chroic linear polarizers in sheet form by Land,(see for example, LAND, "Polarizers Containing Aligned Crystals of Herapathite", U. S. Pat. No.
1,918,848 (1933)), and by Marks (see for example, MARKS, "Crystalline Formation", U. S. Pat. No. 2,1U4,949 (1938)).
A
~~~i.'~.~~~'~
The linear dichroic polarizers, while useful in many applications, were not suitable for use in commercial lighting fixtures for general illumination purposes. First of all, the polarization was only in one direction. A second major problem was the increase in electrical power needed for lighting as the linear dichroic polarizers absorbed between 60 and 72 percent of the incident light energy being transmitted through them. In particular, the linear dichroic polarizers absorbed most of the ultraviolet light, and much of the purple and blue light in the visible spectrum.
It took the invention of the so called "radial polarizer"
by Marks and Kahn in the years after World War II 'to solve both of these problems (see for example, MATZKS, "Multi-layered Light Polarizers", U. S. Pat. No. 3,069,974 (1962) and .K.AfIN
"Light Polarizing Structures", U. S. Pat. No. 3,124,639 (1964)).
The invention of the radialens style lighting panel by Jones (see JONES, "Lighting Panel", U. S. Pat. No. 3,829,680 (1974)), provided a diffuser for use in a lighting fixture that could minimize : glare from vei.l~.ng .ref~.e~ti.Qns. This panel contained a continuous pattern of triangular projections, aach having three mutually substantially perpendicular surfaces projecting upward .towards the light source. . "_ The base lines of the mutually perpendicular surfaces are co-planar and the pattern of projections is such that the base lines of ali projections on the panel form continuous straight lines directed in specific directions. This results in a light panel which minimizes veiling reflections from the illuminated mat;ter. The panel provides a radial distribution of light with a high lighting efficiency and with a maximum of light in the area which is 30° to 60° from vertical.
Kahn combined the prismatic structure of the JONES Radialens manufactured according to the methodologies and structure of KAHN's polarizing panel (see KAHN, "Light Polarizing Structures", U.S. Pat. No. 3,124,639, (1964), cited above) to obtain the 10 higher visual acuity realized with polarized light with the wider angle distribution of the Radialens panel and the desirable Visual Comfort Probability of 70 or more into an integral structure. What was achieved is not merely the expected advantages of polarized ~~nd Radialens light distribution, but also a marked improvement in Visual Comfort Probability and also a reduction in glare at wide angles as disclosed in U.S. Pat. No.
4, 796, 160 (1989) to KAHN.
A major problem with the Polarized Radialens and all of the radial multi-.layer polarizers manufactured for commercial lighting fixtures is the apparent reduction in brightness. This reduction in brightness is so severe as to be noted by a number of lighting practioners (see, Lovins, Amory, et al. STATE OF THE
ART: LIGHTING, Rocky Mountain Institute, Snowmass, Colorado 81654, (1988), page 157). The objection sometimes encountered with the multi-layer polarized diffusers is that they are so effective that they can give room lighting a "dull" subtly flat quality by suppressing the specular highlights which harsh lighting has led us to expect as visual cues.
~J 6-I I
An unrecognized problem with all multi-layer polarized diffusers used fcr commercial lighting fixtures is the type of acrylic plastic used as the supporting material for the polarizer which is adhered to the bottom side of the acrylic sheet. Typically, these multi-layer polarized ~difPusers are manufactured by extrusion using Type V Series. acrylic molding~powders as manufactured by Rohm and Haas (Philadelphia, Pennsylvania) or a similar product. The polarizing material is adhered by heat to the bottom of the sheet (see KAHN, "Machine for Continuously Producing Large Area Light Polarizing Panels", U, S, Pat. No. 3,772,128 (1973)). Figure 2 shows the transmission properties of the Type V Series acrylic molding powder when used to produce an acrylic sheet 0.125 inches thick (taken fxom Rohm and Haas Technical Bulletin PL-612, (1988)). The light transmission properties of the Type V Series acrylic ,.
molding powders is shown for wavelengths between 250 and ~E50 manometers. This 0.125 inch thickness is the thickness of the commercially available mufti-layer polarized diffusers.
The major problem is that the acrylic manufactured from the Type V Series acrylic molding powder transmits less than 50 percent of the ultraviolet light with a wavelength of less than 380 manometers.
i E? '~ a The present invention solves this problem by providing a Type UVT acrylic molding powder or a similar material. The multi-layer polarized diffuser which results from the use of the Type UVT acrylic molding powder is capable of transmitting ultraviolet light with wavelengths as low as 290 nanometers.
The resulting transmission of ultraviolet wavelengths all the way down to 290 nanometers provides a substantial improvement in the quality of the illumination.
In addition to solving the problem~of absorption of ultraviolet in the 290 to 380 nanometer range, it is noteworthy that none of the patents by darks or Kahn cited above make any mention of the unrecognized need to polarize the ultraviolet tight given off by fluorescent, metal halide, or a number of other light sources as a way of improving the contrast and apparent brightness of objects viewed under a combination of visible and ultraviolet light. The present invention not only transmits the ultraviolet in the 290 to 380 nanometer range, but also polarizes it as well.
4. Theory of the Tnvention ' ' The key to the present invention is.that virtually all paper and textile materials, and many paints and pigments have substances such as opticalbrighteners that fluoresce under ultraviolet light between 290 and 420 nanometers.
The fluorescent effects add to brightness by transforming the ultraviolet radiation between 290 and 420 nanometers into longer wavelength radiation in the visible spectrtun (see Barrows, tdilliam E., Light, Photometry, and Illuminating En~ineerin , McGraw-Hill Book Company, New York, (198), p. 26).
l8 '~ s ~~i3~.~.~~~~~
Thus, if the multi-layer polarizers were so modified to be manufactured with an acrylic supporting material that could transmit ultraviolet light so it could be polarized by the multi-layer polarizing material on the bottom of the Light polarizing structure, the advantage of the invention is that it would be possible to increase the apparent brightness of paper and te:~tile materials being illuminated by a light source giving off ultraviolet as well as visible light. It should be noted that when compared to an unpolarized light source, the ultraviolet light will be vertically polarized as well, so it will be glare free, as it is well known that glare from unpolarized radiation is detrimental to one's eyes and the ability to see.
Figure ~ also shows the transmission properties of an ..
ultraviolet transmitting acrylic made from an acrylic molding powder such as the UVT type acrylic molding powder as manufactured by Rohm and Haas (taken from Rohm and Haas Technical Bulletin PL-612e, (1985), p. 5) from 250 to 450 nanometers. It should be noted that acrylic sheets manufactured from this acrylic molding powder will transmit 85 percent of the ultraviolet light with a wavelength greater than 315 nanometers.
Thus, the application of an ultraviolet transmitting acrylic would permit the transmission of the ultraviolet light emitted from a light source through the supporting acrylic so the ultraviolet light would then be polarized by the multi-layer polarizing~materials which are adhered to the bottom of the acrylic sheet, which is the side of the sheet facing towards the objects being illuminated.
It should be noted that ultraviolet light is not detectable by a standard photopic light meter which measures visible light according to the Standard Observer Curve ( ~) as established by the International Commission on Illumination. Thus, using the present invention, objects will appear brighter, even though the measured foot-candles will be virtually the same for a light source in the visible as compared with a light source which emits the same visible light plus some ultraviolet light. It will then be necessary to develop new photometric instruments that will integrate the fluorescent effects of ultraviolet light into the Standard Observer Curve V(~) for Che photopic region.
It is also not generally.known that the eye responds to ultraviolet light. In the young healthy eye the ocular media are sufficiently transparent to allow a substantial amount of ultraviolet energy (so-called "invisible") of wavelength as short as 350 nanometers to reach the retina and evoke a visual sensation. Smaller amounts of wavelengths as short as 300 manometers may be transmitted, but this effect is not important in ordinary vision at high levels of luminance (see The Science of Color, Optical Society of America, Washington, D. C. (1953), p. 76).
Therefore, since my invention provides an increase in ultraviolet illumination in polarized lighting installations, there will be an increase in visual sensation for normal healthy eyes.
Most fluorescent lamps produce a certain amount of u:ltrav-iolet light, and many of the spectra of such lamps contain a peak in the ultraviolet at 305 manometers. Full-spectrum lamps are defined as lamps having a color rendition index of 90 or above and a correlated color temperature of 5,000 degrees Kelvin or above. The visually effective F40/T12 Color Classes 75, with a correlated color temperature of 7,500 degrees Kelvin, and a color rendition index of 93, is a full-spectrum fluorescent lamp currently available from Duro-Test Corporation, Fairfield, New Jersey, and provides illumination not only in the visible range from 380 to 780 manometers, but also provides a significant amount of ultraviolet light from 290 to 380 manometers. This ultraviolet light is exactly the radiation capable of producing ".fluorescent effects . , , Thus, the use of the Type V Series acrylic molding powder in the manufacture of the supporting layer for the multi-layer polarizing material ~e1_iminate~.much .of the benefit of: the ultrav2.ol~~C flight in improving the apparent brightness of paper and textile objects -.since a mufti-Iayer polarized ...__.. .
diffuser made from the Type V Series acrylic molding powder or a similar product would absorb most of the ultraviolet sight between 290 and 380 manometers.
Figure ~ shows the spectral energy distribution of the "'FGO/T12 Color Classes 75 fluorescent lamp, as provided to Che inventor by the Duro-Test Corporation. As shown, there is production of much ultraviolet light between 290 and 380 manometers.
_. _ In comparison to the 'type V Series acrylic molding powder which absorbs much of the valuable ultraviolet light, use of the 'type UVT acrylic molding powder or a similar product in the manufacture o~ the supporting acrylic of the multi-layer polarized diffuser would then allow almost all of the valuable ultraviolet light emitted from lamps between 290 and 380 nanometers to pass through the acrylic supporting structure and hence the ultraviolet light would be then vertically polarized where it could increase the apparent brightness of paper and textile materials .without_ the harmful glare that results from unpolarized ultraviolet as well as unpolarized visible light.
The polarization effects would be expected to be greater in the ultraviolet than in the visible portion of the electromagnetic spectrum. It is known that the index of refraction of many materials varies with the wavelength of light, and the index of refraction increases with a decrease in the wavelength , of light -( see, .far exa~mple,~ Hal~fi~day,T David, and Re snick, Robert, Physics, John Wiley & Sons, New York, 1966, p. 1014-1015). As the index of.refraction increases, the amount of polarization increases, especially for multi-layer type polarizing Cype materials. The multi-layer poTarizers provide vertically polarized visible and ultraviolet light by means of reflection and refraction; the polarization effects are greater with an increase in the index of refraction, hence the degree of polarization will be greater in the ultraviolet region as compared with light in the visible portion of the spectrum. .
It is also known that the ultraviolet light which is scattered in the sky is very highly polarized (see, for eYampie, Feynman, Richard, et. al., The Feynman Lectures on Physics, Volume I. Addison-Wesley Publishing Company, Reading, Massachusetts, (1963), p. 32-8). The scattering of ultraviolet light increases as the fourth power of the frequency of the spectrum. Thus, one should e:cpect that the sky should be blue, since the blue light is more highly scattered than the light at the red end o~ the spectrum, This scattering is known as the Raleigh scattering in honor of the person who first discovered it.
Daylight contains radiation down to 290 manometers (see, l~uffie, John, A, et, al., Solar Eneray Thermal Processes, John Wiley & Sons, New York, 1974, p. 14, and Cayless, M. A., and Marsden, A. M., Lamps and Lighting, Edward Arnold, London, 1983, p.
4). Thus, the present invention of an ultraviolet transmitting polarized diffuser, when used in conjunction with full-spectrum Fluorescent lamps, will provide a lighting system which is ~ - -~ ..
s:~bstantially duplicates natural daymgnz, ana ~an~ch contains ..
vertically polarized ultraviolet light in addition to vertically polarized visible light. The previously available multi-layer polarized diffusers which are made from a Type V Series ox s::nilar acrylic molding powder block much of the ultraviolet light with wavelengths below about 380 manometers.
An e:cample of the use of the present invention which in no way limits its potential application is for~-the~p'roduction of so called "north sky" lighting that artists prefer. Irr north sky lighting, one combines a 7,500 degree fluorescent lamp with an ultraviolet transmitting multi-layer polarized diffuser. A mufti-layer polarized diffuser made from the Type V Series. acrylic molding powder or a similar rzeaterial would produce: an inferior "north sity" effect due to the absence of u;ltravioiet light below 380 naizvmeters.
Passage of the ultraviolet Light through the acrylic supporting Layer of the present invention and through the mult__-layer palarizer will reduce degradation of the acrylic materials, since the ultraviolet light is passing through the diffuser, rather than having an opportunity to interact with it. Thus, the need for periodic replacement of the lighting diffusers is reduced significantly, along with a reduction of Che solid waste that would otherwise be added to the solid wasCe stream when materials ere discarded in the trash.
Another benefit of the use o.f an ultraviolet transmitting polarized dif::user (as compared to ultraviolet absorbing polarized diffusers of the prior art) is the energy saving potential. Since objects will appear brighter due to fluoresce effects, one can install fewer lighting fixtures and spread them farther apa-rt, . ' - .
A secondary energy sa~rings occurs because when the Type V Series acrylic molding powder is used to manufacture the mufti-layer polarizer, the acrylic absorbs the ultraviolet Light and is v.ltimately converted to heat. The diffuser heats up, which traps the heat from the fluorescent lamps inside the fixture. Sy allowing the u:Ltravivlet light to easily pass through the ultraviolet transmitting mufti-layer polarize:r, additional heat can be rejected from the lighting fixture, and the heat build-up is reduced significantly, lowering the ** TOTAL PAGE.02 **
~ Y n' 1 C~ ~ ~! ~ it lamp operating temperature. It is known that reduced light output from a fluorescent fixture results from operating a fluorescent lamp above its optimum lamp wall temperature (sea Jerome, Charles W., "Effect of Bulb Wall Temperatures on Fluorescent Lamp Parameters", Illuminating Engineering, February, 1956, pp. ?05-213).
It has been shown by Cobb (see, Cobb, Percy W, and Moss, Frank E., "Lighting and Contrast", Transact-ions of the Illuminating Engineering Society, February, 1927, p. 195-204, also see Marks, Alvin, "Multilayer Polarizers and Their Application to General Polarized Lighting", Illuminating Engineering, February, 1959, p. 127) that visual acuity increases with contrast. Marks provided proof using a set of algebraic equations that contrast will always be improved using polarized illumination.
With the use of the ultraviolet transmitting mufti-layer polarizer, contrast, and hence visual acuity, will be greater than when-using a mufti-layer polarizer with a supporting acrylic made of a Type V Series acrylic molding powder or a similar material, since the effect of the ultraviolet light will be to increase 'brightness of the paper which contains the optical brighteners which fluoresce under ultraviolet light. Note that the areas df paper covered by black print will not fluoresce, so there will be a definite increase in contrast between the print anti the paper it is printed on when compared to illuminating the same paper with a light source giving off ult'raviol:et light and having the ultraviolet light blocked by a mufti-layer polarized diffuser made of the Type V Series or similar acrylic molding powder.
DESCRIPTION OF THE DRAWINGS
~~u~~~~~
Having thus generally described the invention, reference will now be made to the accompanying drawings in which:
FIGURE 1 is a side view of a two-lamp troffer mounted fixture.
FIGURE 2 is a graph chart comparing the transmission properties of the acrylic layer 2 of the ultraviolet transmitting multi-layer polarizer of the present invention and the prior art.
FIGURE 3 is a graph chart showing the spectral energy distribution of a prior art 7,500 degree full-spectrum fluorescent lamp.
FIGURE 4 is a side elevational view of the ultraviolet transmitting multi-layer polarizer of the present invention.
~~~~.~2. ~
A vast improvement in visual performance is achieved in the full spectrum polarized lighting system which comprises full spectrum lamps in combination with a polarized diffuser.
The fixture contains two full spectrum fluorescent lamps 1 mounted between the fixture housing 2 and a mufti-layer polarized diffuser 3. The prism side 4 of the mufti-layer polarized diffuser is towards the lamps and the smooth side 5 is towards the objects or room being illuminated by the fixture. The smooth side 5 is coated with a layer of polarizing material 6 which converts unpolarized light to preferentially vertically polarized light.
The mufti-layer polarized diffuser is mounted in the fixture door 7. There is an ultraviolet resistant gasket R which is between the fixture door 7 and the fixture housing 2. The lamps are driven by a solid state ballast 9.
'The prism side of the mufti-layer polarizer is towards the lamps to provide for proper light polarization. If the the smooth side which contains the polarized layer is towards the lamps, there will be some depolarization of the light as it emerges from the prism side. In addition, the light distribution will be altered since the prism side will be A
down instead of being up., ~~'~ ~.~~
~n the preterrec~ embodiment, the light polarization material used produces preferentially polarized light in a radial cone directly under any point in the fixture. A linear polarizes, such as the dichroic polarizers used in sunglasses, can only provide vertically polarized light in one direction. For an overhead lighting system, where viewing takes place from all directions, a linear polarizing material would provide for extremely uneven lighting in a room or an office, and would be highly unsatisfato,ry. In addition, the linear polarizers axe only about 40 percent in transmitting light, as compared with efficiencies in the 70 to 85 percent range achieved by using a polarizing film which produces vertically polarized light. As one of the objectives of the full spectrum polarized lighting system is to improve vision and to be an energy efficient lighting system, such an approach using dichroic polarizing materials would not. achieve the objectives of energy conservation and a visually efficient lighting system.
~fexence will now be made to Figures 2 through 4 as follcxvs.
A vast improvement~in visual performance and brightness of objects being illuminated is achieved by the use of the ultraviolet transmitting multi-layer polarizes. Referring now to Figure $, the prism side l~of the ultraviolet transmitting mufti-layer polarizes faces towards the full-spectrum fluorescent i lamps. The supporting acrylic~layer 2 transmits the ultraviolet light from the lamps to the mufti-layer polarizing layer 3~
on the bottom of the ultraviolet transmitting mufti-layer polarizes. The function of the acrylic layer 2 is to support i the thin polarizes 3 which is itself comprised of multiple layers as described in prior art. The assemblage of the: supporting i acrylic 2~and the polarizes 3 is manufactured in flat sheets for use in commercial fluorescent lighting fixtures.
s~~a ~'? - °I
28 Fa ;f tJ ~ ~a ~ ~~
Figure ~ shows the transmission properties of the Type V Series acrylic molding powder of acrylic layer 2, when used to produce an acrylic sheet 0.125 inches thick (taken from Rohm and Haas Technical Bulletin PL-612, (1988)). The light transmission properties of the Type V Series acrylic molding a powders of acrylic layer 2 is shown for wavelengths between 250 and 450 nanometers. This 0.125 inch thickness of acrylic layer 2 is the thickness of the commercially available multi-layer polarized diffusers.
The present invention not only transmits the ultraviolet in the 290 to 380 nanometer range but also polarizes as caell.
Figure ~ also shows the transmission properties of a 0.125 inches thick ultraviolet transmitting acrylic layer 2 made from an acrylic molding powder such as the UVT type acrylic molding powder manufactured by Rohm and Haas (taken from Rohm and Haas Technical Bulletin PL-612e, (1985), p.5) from 250 to 450 nanometers. It should be noted that acrylic sheets manufactured the Type UVT acrylic molding powder, will transmit 85 percent of the ultraviolet light with a wavelength greater than 315 nanometers.
29 y~~~ ~.~, Acrylic layer 2 includes a type UVT acrylic molding powder or a similar material. The multi-layer polarized diffuser which results from the use of the Type UVT acrylic s molding powder of acrylic layer 2 is capable of transmitting ultraviolet light with wavelengths as low as 290 nanometers.
The resulting transmission of ultraviolet wavelengths all the way down to 290 nanometers provides a substantial improvement in the quality of the illumination.
The application of an ultraviolet transmitting acrylic layer 2~permits the transmission of the ultraviolet light emitted from a light source through the supporting acrylic layer 2 so the ultraviolet light would then be polarized by the multi-layer polarizing materials of thin polarizer 3r which are adhered to the bottom of the acrylic sheet of acrylic layer 2;~ which is the side of the sheet facing towards the objects being illuminated.
Figure 3 shows the spectral energy distribution of the F40/T12 Color Classer 75 fluorescent lamp (not shown) as provided to the inventor by the Duro-Test Corporation. As shown, there is production of much ultraviolet light between 290 and 380 nanometers.
30 ~ S3 ~ '~
~: t 9 .~. ~ ~ '-~
Thus, the present invention of an ultraviolet transmitting polarized diffuser, when used in conjunction cdith full-spectrum fluorescent lamps, provides a lighting system which substantially duplicates natural daylight, and which contains vertically polarized ultraviolet light in addition to vertically polarized visible light.
Passage of the ultraviolet light through the acrylic supporting layer 2~of the present invention and through the multi-layer polarizes reduces degradation of. the acrylic materials, since the ultraviolet light pass through the diffuser, rather than having an opportunity to interact with it.
Modifications can be made to the method used for making the device, the device itself as well as the process described for the ultraviolet transmitting mufti-layer polarizes without departing .fram the spirit and scope of the invention as exemplified below in the appended claims.
A novel use of the ultraviolet transmitting multi-layer polarized diffuser would be for illumination using so called "black lights" that only give off ultraviolet light. Lighting fixtures using the ultraviolet transmitting polarized diffuser could be used for special effects lighting for nightclubs and other places of entertainment. As mentioned above, use of the ultraviolet transmitting multi-layer polarizer with an ultraviolet light source pith provide vertically polarized ultraviolet light, as it is well known that glare from unpo.larized radiation is detrimental to one's eyes and the ability, to see
Claims (25)
1. A full spectrum polarized lighting system which produces artificial light that is of the spectral energy distribution and light polarization characteristics of natural daylight comprising in combination:
a ceiling mounted fluorescent fixture;
a flat multi-layer polarized diffuser mounted in a door of said fixture; said flat multi-layer polarized diffuser is mounted in said door with a top prism side towards one or more full spectrum lamps and a smooth bottom side facing towards objects being illuminated; said fixture includes a means for providing light which is glare free and preferentially vertically polarized; said means comprises said multi-layer polarized diffuser; and said full spectrum fluorescent lamps mounted inside said fixture; said full spectrum lamps comprise a means for providing light of excellent color rendition matching the spectral energy distribution of natural daylight;
said full spectrum lamps being full spectrum fluorescent lamps with a color rendition index of 90 or above and a correlated color temperature of 5,000 degrees Kelvin or above; and a gasket mounted on a door frame of said fluorescent fixture between said door and said door frame; said gasket comprises a means to keep dirt and dust out of said fixture and from collecting on the said top prism surface facing towards said full spectrum fluorescent lamps of said multi-layer polarized diffuser; said gasketing materials ara ultraviolet resistant; and a fixture housing free of ventilation holes; said fluorescent fixture to be sealed for dust and light leaks; and a solid state electronic ballast; said ballast comprises a means of providing flicker free lighting; said means including said solid state ballast.
a ceiling mounted fluorescent fixture;
a flat multi-layer polarized diffuser mounted in a door of said fixture; said flat multi-layer polarized diffuser is mounted in said door with a top prism side towards one or more full spectrum lamps and a smooth bottom side facing towards objects being illuminated; said fixture includes a means for providing light which is glare free and preferentially vertically polarized; said means comprises said multi-layer polarized diffuser; and said full spectrum fluorescent lamps mounted inside said fixture; said full spectrum lamps comprise a means for providing light of excellent color rendition matching the spectral energy distribution of natural daylight;
said full spectrum lamps being full spectrum fluorescent lamps with a color rendition index of 90 or above and a correlated color temperature of 5,000 degrees Kelvin or above; and a gasket mounted on a door frame of said fluorescent fixture between said door and said door frame; said gasket comprises a means to keep dirt and dust out of said fixture and from collecting on the said top prism surface facing towards said full spectrum fluorescent lamps of said multi-layer polarized diffuser; said gasketing materials ara ultraviolet resistant; and a fixture housing free of ventilation holes; said fluorescent fixture to be sealed for dust and light leaks; and a solid state electronic ballast; said ballast comprises a means of providing flicker free lighting; said means including said solid state ballast.
2. The full spectrum polarized lighting system as in Claim 1 whereas said full spectrum fluorescent lamps are F40/T10.
3. The full spectrum polarized lighting system as in Claim 1 whereas said full spectrum fluorescent lamps are F40/T12.
4. The full spectrum polarized lighting system as in Claim 1 whereas said full spectrum fluorescent lamps are F32/T8.
5. The full spectrum polarized lighting system as in Claim 1 whereas said ceiling mounted fluorescent fixture is surface mounted.
6. The full spectrum polarized lighting system as in Claim 1 whereas said ceiling mounted fluorescent fixture is troffer mounted.
7. The full spectrum polarized lighting system as in Claim 1 whereas said ceiling mounted fluorescent fixture is flange mounted.
8. The full spectrum polarized lighting system as in Claim 1 whereas said ceiling mounted fluorescent fixture is pendent mounted.
9. A polarizing fluorescent lighting system with improved ultraviolet light transmission, the improvement comprising:
a fluorescent lighting fixture having at least one full-spectrum fluorescent lamp, and a thin multi-layered polarizer capable of transmitting all wavelengths of polarized visible light and all wavelengths of polarized ultraviolet light;
the thin multi-layered polarizer being disposed between the at least one full-spectrum fluorescent lamp and an area to be illuminated.
a fluorescent lighting fixture having at least one full-spectrum fluorescent lamp, and a thin multi-layered polarizer capable of transmitting all wavelengths of polarized visible light and all wavelengths of polarized ultraviolet light;
the thin multi-layered polarizer being disposed between the at least one full-spectrum fluorescent lamp and an area to be illuminated.
10. The device of claim 9, wherein the thin multi-layered polarizer is capable of transmitting wavelengths of polarized light of wavelengths between about 290 nanometers and about 800 nanometers.
11. The device of claim 10, the fluorescent lighting fixture having an enclosure for enclosing the full-spectrum lamps, the enclosure having receptacle means for receiving and fixably holding the thin multi-layer polarizer.
12. The device of claim 11, wherein the multi-layered polarizer comprises a light transmitting support layer and a light polarizing layer.
13. The device of claim 12, wherein the light transmitting support layer is composed of material capable of transmitting light of wavelengths between about 290 and about 800 nanometers.
14. The device of claim 13, wherein the light transmitting support layer comprises a light diffuser for directed scattering of incident light emanating from the at least one full-spectrum fluorescent lamp.
15. The device of claim 14 wherein the light polarizing layer is comprises a thin sheet of light transmissible material, the thin sheet being capable of transmitting and polarizing light of wavelengths between about 290 and about 800 nanometers.
16. The device of claim 15 wherein further the support layer comprises a flat light diffuser, the support layer comprising a first substantially flat and smooth surface and a second substantially textured surface and at least one edge, the at least one edge being disposed at the perimeter of the flat light diffuser; and further wherein the second substantially textured surface of the flat light diffuser faces toward the at least one full-spectrum fluorescent lamp, the textured surface being for refracting incident light emanating from the at least one full-spectrum fluorescent lamp and further for providing a directed scattering of the incident light, the directed scattering comprising diffusion of the incident light; and further wherein the first substantially flat and smooth surface of the flat light diffuser faces toward the area to be illuminated by the fluorescent lighting fixture.
17. The device of claim 16, wherein the thin sheet light polarizing layer is disposed upon and supported by the light transmitting support layer, the thin sheet light polarizing layer being disposed upon and adhered to the first substantially flat and smooth surface of the flat light diffuser.
18. The device of claim 17 wherein the light transmitting support layer is composed of molded acrylic polymer.
19. The device of claim 18, wherein the lighting fixture is a metal halide lighting fixture, the source of light being at least one metal halide lamp.
20. A method of artificial fluorescent illumination which approximates natural daylight, comprising the steps of:
a. generating light using at least one full-spectrum fluorescent lamp capable of producing a spectrum of light wavelengths which substantially duplicates the light wavelengths found in natural daylight;
b. passing the full-spectrum fluorescent light through a light transmitting diffuser, the diffuser being capable of transmitting substantially all of the wavelengths found in natural daylight and further being capable of transmitting substantially all of the light wavelengths emanating from the at least one full-spectrum fluorescent lamp; and c. polarizing the full-spectrum light after it has been diffused and before the full-spectrum light is permitted to strike an area of intended illumination.
a. generating light using at least one full-spectrum fluorescent lamp capable of producing a spectrum of light wavelengths which substantially duplicates the light wavelengths found in natural daylight;
b. passing the full-spectrum fluorescent light through a light transmitting diffuser, the diffuser being capable of transmitting substantially all of the wavelengths found in natural daylight and further being capable of transmitting substantially all of the light wavelengths emanating from the at least one full-spectrum fluorescent lamp; and c. polarizing the full-spectrum light after it has been diffused and before the full-spectrum light is permitted to strike an area of intended illumination.
21. The method of claim 20, wherein the full-spectrum fluorescent light contains substantially all light wavelengths of between about 290 and about 800 manometers.
22. The method of claim 21, wherein the light transmitting diffuser is capable of transmitting light wavelengths of between about 290 manometers and about 800 manometers.
23. The method of claim 22, wherein the light transmitting diffuser produces a directed scattering of light emanating from the at least one full-spectrum fluorescent lamp.
24. The method as in claim 20, the fluorescent lamp having a color rendition index of at least 90 and a correlated color temperature of at least 5,000 degrees Kelvin.
25. The method as in claim 23, wherein the artificial illumination is metal halide lamp illumination, the light source being a metal halide lamp.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/781,844 US5184881A (en) | 1990-03-07 | 1991-10-24 | Device for full spectrum polarized lighting system |
| US07/781,844 | 1991-10-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2081224A1 CA2081224A1 (en) | 1993-04-25 |
| CA2081224C true CA2081224C (en) | 2002-04-16 |
Family
ID=25124137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002081224A Expired - Fee Related CA2081224C (en) | 1991-10-24 | 1992-10-23 | Full spectrum polarized lighting system and ultraviolet transmitting multilayer polarizer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2081224C (en) |
-
1992
- 1992-10-23 CA CA002081224A patent/CA2081224C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2081224A1 (en) | 1993-04-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5184881A (en) | Device for full spectrum polarized lighting system | |
| US8430548B1 (en) | Enhanced light fixture with volumetric light scattering | |
| US7431489B2 (en) | Enhanced light fixture | |
| EP3589884B1 (en) | Sunlight-based sun imitating illumination | |
| RU2642138C2 (en) | Artificial lighting system for imitation of natural lighting | |
| US5426879A (en) | Wall hangable window simulating unit | |
| US8164844B2 (en) | Optical filter and lighting apparatus | |
| US6019476A (en) | Full spectrum filtering for fluorescent lighting | |
| US4649462A (en) | Viewing angle color sensitive lighting accessory | |
| CN1132558A (en) | Light source for back lighting | |
| IT201800005680A1 (en) | Adjustable white light illumination | |
| US5359498A (en) | Ultraviolet transmitting multi-layer polarizer | |
| US20080062323A1 (en) | High Intensity Display Screen Based Electronic Window | |
| CA2081224C (en) | Full spectrum polarized lighting system and ultraviolet transmitting multilayer polarizer | |
| CN209540576U (en) | A kind of headlamp of the electric operating with light guide plate | |
| JP2004518260A (en) | Lighting equipment | |
| RU2309441C1 (en) | Liquid crystal screen | |
| KR20020070243A (en) | Desk lamp with the condensed ray of plane surface illuminant system | |
| JP2944915B2 (en) | Indoor lighting fixtures | |
| KR102515714B1 (en) | Anti-glare lighting and manufacturing method thereof | |
| KR20110109737A (en) | Front plate for light lamp and lighting apparatus having the same | |
| CN2589809Y (en) | Lamp shade spreading film | |
| Lank | The function of natural light in picture galleries | |
| JP2000057821A (en) | Luminaire | |
| CN109578833A (en) | A kind of headlamp of the electric operating with light guide plate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20101025 |