Holographic stop sign

#The present invention relates generally to holographic lighting devices, and more particularly, to a holographic stop light for use in vehicular applications.

#Every time a school bus comes to a stop and lets out child pedestrians, there is a potential for tragic fatal accidents between oncoming traffic and the child pedestrians. Last year alone, a large number of children in the United States were killed by vehicles passing by school buses.

#Therefore, there is a great need in school buses to display a warning to oncoming vehicles that the bus is at a stop and the approaching vehicle should stop also. Prior art apparatus for providing "STOP" warning in school buses, for example, include mechanical "STOP" arms that move down when the driver comes to a stop. The mechanical arm is visible during the day but not very visible at night. Another apparatus is the use of flashing red warning lights on the bus to indicate the bus is stopped.

#The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like structural elements, and in which

#FIGS. 1a and 1b illustrate perspective and top views, respectively, of a warning indicator in accordance with the principles of the present invention;

#FIG. 1c illustrates a side view the warning indicator particularly illustrating its use in a school bus;

#Referring to the drawing figures, FIGS. 1a and 1b illustrate perspective and top views, respectively, of a warning indicator 10 in accordance with the principles of the present invention. FIG. 1c illustrates a side view the warning indicator 10 and specifically illustrates its use in a school bus 20. The preferred embodiment of the warning indicator 10 is designed for use with school busses 20, and the following discussion relates to this application.

#The warning indicator 10 comprises a holographic "STOP" sign 10. In a preferred embodiment of the holographic STOP sign 10, it is comprised of an array of four compact halogen lamps 11 having red colored filters 12 in front of them mounted adjacent a roof of the bus 20 (FIG. 1c) out of view occupants of the bus 20. Each of the compact halogen lamps 11 may have a shroud 18 surrounding it to control the light emitted thereby. A decal 14 comprising a transmission hologram 15 is mounted on an interior surface of a window 21 of the bus 20, such as a front windshield 21 or a rear window 21 of the bus 20 that is illuminated by the halogen lamps 11. A beam of light 13 from each halogen lamp 11 is projected down onto one-quarter of the area of the hologram decal 14 corresponding to a position of the holographic image 15 of one of the four letters in the word "STOP".

#For example, a halogen lamp 11 for illuminating the letter "S" projects a beam of light 13 down onto a leftmost one-quarter of the hologram decal 14 which contains a holographic image 15 of the letter "S". The same situation exists for the halogen lamps 11 that illuminate the letters "T", "O", and "P", respectively. The hologram 15 diffracts the incident light 13 (diffracted light 16) and projects it into a specified, predetermined angular field of view which in general is asymmetric about a normal 17 to the hologram 15 and is custom-shaped to match a desired angular coverage. Furthermore, an electric signal supplied to the lamps 11 may be coupled to a flashing circuit 22 so that the halogen lamps 11 are made to flash with a desired period and duty cycle.