Optical: systems and elements – Signal reflector
Patent
1997-01-30
1998-10-06
Phan, James
Optical: systems and elements
Signal reflector
359527, 359532, 359547, 359552, 404 9, 116 63R, G02B 512
Patent
active
058186409
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a system for and a method of illuminating a sign, particularly road signs, billboards, bicycle riding path signs, walking path signs, and the like.
BACKGROUND
Retroreflective road signs presently employed for road signs are often installed at a relatively high position above the roadway and typically do not have a wide observation angle. Motor vehicles typically run with their headlights directed downward, i.e., low beams, particularly when in areas having large volumes of traffic, such that the quantity of light emitted from the headlights toward a sign is often relatively small. As a result, drivers may have trouble in recognizing and reading the road sign. In urban areas there are typically many street lights, building illuminations, and neon lights that interfere with the ability of drivers to see and read road signs. To improve the ability of drivers to recognize and read road signs, the road signs are often provided with an illumination source.
FIGS. 5 and 6 show examples of conventional illumination systems for road signs. In FIG. 5, sign 10 is illuminated by illumination source 20, e.g., a lamp (usually, a fluorescent lamp), both sign 10 and illumination source 20 being mounted on pole 30. Illumination source 20 illuminates sign 10 from above. In FIG. 6, illumination source 20 illuminates road sign 10 from below, both sign 10 and illumination source 20 being mounted on pole 30. These illumination sources and methods of illuminating the road sign are based on JIS and the Japan Road Sign Installation Standards Act.
U.S. Pat. No. 4,726,134 (Woltman) discloses an improved roadway sign in which the retroreflective properties of the indicia and background portions of a sign face are separately selected to optimize the conspicuity of the sign at relatively longer distances and legibility of the sign at relatively shorter distances. U.S. Pat. No. 4,957,335 (Kuney) discloses selection of microspheres in microsphere-based retroreflective articles to optimize retroreflective brightness at narrow observation angles. Japanese Application No. 6-9426/94 (Nakajima), filed Apr. 7, 1994, discloses a microsphere-based retroreflective sheeting comprising two classes of microspheres intended to impart good retroreflective performance at both narrow observation angles and wide observation angles.
The need exists for better systems of sign illumination.
SUMMARY OF INVENTION
The present invention provides an illuminated sign system and a method for illuminating a sign. It is particularly well suited for road signs, billboards, bicycle riding path signs, walking path signs, and the like.
In brief summary, the illuminated sign system of the invention comprises a sign having a retroreflective sign face and an illumination source. The illumination source is positioned relative to the sign face such that it emits light that is incident to the sign face at an incidence angle in the range of about 0.degree. to about 30.degree.. The sign face comprises retroreflective portions which have a wide effective incidence angle and wide effective observation angle. A glossary of some of the terms used to define the geometry of retroreflection is provided at the end of this specification.
Briefly summarizing, the method of the invention comprises providing a sign having a face that comprises a retroreflective portion, providing an illumination source, positioning the illumination source relative to the sign face such that light emitted from the illumination source is incident to the sign face at an incidence angle of between about 0.degree. and 30.degree.. The retroreflective portions of the sign face exhibit wide effective incidence and observation angles. The illumination source then illuminates the sign face, rendering it more easily read and understood while not blocking the view of observers. Preferably the retroreflective portions, and positioning of the illumination source are such that substantially no portion of the sign face is blocked from view by an observer in the int
REFERENCES:
patent: 2326634 (1943-08-01), Gebhard et al.
patent: 3712706 (1973-01-01), Stamm
patent: 4505967 (1985-03-01), Bailey
patent: 4726134 (1988-02-01), Woltman
patent: 4957335 (1990-09-01), Kuney, Jr.
Proceedings of the 49th Annual Conference of the Japan Society of Civil Engineers VI-102 (Sep., 1994) w/translation.
Kakishita Satoshi
Momozawa Muneo
Nakajima Toshitaka
Watanabe Yoshio
Minnesota Mining and Manufacturing Company
Olson Peter L.
Phan James
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