초록 ▼

A vehicle video imaging system comprises a white-light LED array for illuminating retro-reflective painted parts of a vehicle's license plate, a powerful flash with a visual spectrum cutout filter and a polarizing filter for illuminating any non-retro-reflective license plate paint and the vehicle i

A vehicle video imaging system comprises a white-light LED array for illuminating retro-reflective painted parts of a vehicle's license plate, a powerful flash with a visual spectrum cutout filter and a polarizing filter for illuminating any non-retro-reflective license plate paint and the vehicle itself. A video camera with a polarizing filter turned 90° relative to the one in front of the flash receives the illuminated image of the vehicle and its license plate. The retro-reflective paint of a license plate will return polarized light as it is received, so the white-light LED array will provide all the illumination needed by the camera to get a good high-contrast picture of the license plate. The polarizing filters will combine to block out most of the light from the flash that was returned still-polarized by the retro-reflective-paint license plate. All other surfaces that do not have retro-reflective paint will bounce-back and scatter the light from both the polarized flash and non-polarized light.

대표청구항 ▼

A vehicle video imaging system comprises a white-light LED array for illuminating retro-reflective painted parts of a vehicle's license plate, a powerful flash with a visual spectrum cutout filter and a polarizing filter for illuminating any non-retro-reflective license plate paint and the vehicle i

A vehicle video imaging system comprises a white-light LED array for illuminating retro-reflective painted parts of a vehicle's license plate, a powerful flash with a visual spectrum cutout filter and a polarizing filter for illuminating any non-retro-reflective license plate paint and the vehicle itself. A video camera with a polarizing filter turned 90° relative to the one in front of the flash receives the illuminated image of the vehicle and its license plate. The retro-reflective paint of a license plate will return polarized light as it is received, so the white-light LED array will provide all the illumination needed by the camera to get a good high-contrast picture of the license plate. The polarizing filters will combine to block out most of the light from the flash that was returned still-polarized by the retro-reflective-paint license plate. All other surfaces that do not have retro-reflective paint will bounce-back and scatter the light from both the polarized flash and non-polarized light. aid central member has a transverse cross-sectional area which increases in said direction of sound propagation within said channel and said second portion of said central member has a transverse cross-sectional area which decreases in said direction of sound propagation within said channel. 3. A loudspeaker as claimed in claim 1, in which said throat has a transverse cross-sectional area which increases at a first rate in said direction of sound propagation within the channel. 4. A loudspeaker as claimed in claim 3, in which said horn has a transverse cross-sectional area which increases at a second rate greater than said first rate in said direction of sound propagation within said channel. 5. A loudspeaker as claimed in claim 1, in which said central member has a fourth portion extending into said horn. 6. A loudspeaker as claimed in claim 5, in which said fourth portion of said central member has a substantially hemispherical end. 7. A loudspeaker as claimed in claim 1, in which said central member has a substantially circular transverse cross-sectional shape throughout its extent in said direction of sound propagation within said channel. 8. A loudspeaker as claimed in claim 1, in which said housing has a substantially rectangular transverse cross-sectional shape throughout its extent in said direction of sound propagation within said channel. 9. A loudspeaker as claimed in claim 1, in which said housing has a substantially parallel pair of internal surfaces. 10. A loudspeaker as claimed in claim 1, in which said channel is folded. 11. A loudspeaker as claimed in claim 10, in which said channel is folded at or adjacent said transition between said second region and said throat. 12. A loudspeaker as claimed in claim 1, comprising an enclosure at a rear of said driver defining therewith a substantially sealed chamber.