Method of measuring light levels and device for implementing this method
First Claim
1. A method of monitoring exterior light levels in a zone of approach to a tunnel in which vehicles are moving, for adjusting levels of minimum illumination inside the tunnel, comprising:
- measuring light levels in the zone of approach to the tunnel by using a photo-sensitive cell which is axially recessed in a tube relative to an end of the tube, the tube having a longitudinal axis which intersects said cell and on which said cell is centered and having first structure effectively defining a cone having an apex on said axis at said cell, coaxial with said tube and increasing in diameter towards said end of said tube;
whilelimiting the quantity of light rays entering into said cone at said end of said tube by placing effectively across said end of said tube a second structure having a preselected pattern of light transmissivity which pattern is centered on said axis.
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Accused Products
Abstract
A method of measuring light levels, particularly the measurement of exterior light levels in the zone of approach to a tunnel in which vehicles are moving, and from which exterior light levels the minimum light level to be programed inside the tunnel can be calculated, by means of a photo-sensitive cell installed in a recessed tube in order to sense light levels contained within a cone defined by the center of the cell, which constitutes the apex of the cone, and by at least the open end of the tube. The method includes limiting the quantity of light rays entering into tube via the cone, and a device is provided for implementing the method.
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Citations
19 Claims
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1. A method of monitoring exterior light levels in a zone of approach to a tunnel in which vehicles are moving, for adjusting levels of minimum illumination inside the tunnel, comprising:
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measuring light levels in the zone of approach to the tunnel by using a photo-sensitive cell which is axially recessed in a tube relative to an end of the tube, the tube having a longitudinal axis which intersects said cell and on which said cell is centered and having first structure effectively defining a cone having an apex on said axis at said cell, coaxial with said tube and increasing in diameter towards said end of said tube;
whilelimiting the quantity of light rays entering into said cone at said end of said tube by placing effectively across said end of said tube a second structure having a preselected pattern of light transmissivity which pattern is centered on said axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for monitoring light levels in a zone of approach to a tunnel in which vehicles are moving, for adjusting levels of minimum illumination inside the tunnel, comprising:
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a photo-sensitive cell which is axially recessed in a tube relative to an end of the tube, the tube having a longitudinal axis which intersects said cell and on which said cell is centered and having first structure effectively defining a cone having an apex on said axis at said cell, coaxial with said tube and increasing in diameter towards said end of said tube; and a second structure limiting the quantity of light rays entering into said cone at said end of said tube, said second structure being placed effectively across said end of said tube and having a preselected pattern of light transmissivity which pattern is centered on said axis; said preselected pattern includes a plurality of spots of relatively high light transmissivity provided on a ground of relatively low light transmissivity. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification