SPATIAL MODULATION OF LIGHT TO DETERMINE OBJECT LENGTH
First Claim
1. A system, comprising:
- a spatial filter having a plurality of mask features;
at least one detector positioned to sense light emanating from at least one object moving in a flow path along a flow direction, an intensity of the sensed light being time modulated according to the mask features, the detector configured to generate a time varying electrical signal comprising a sequence of pulses in response to the sensed light; and
an analyzer configured to measure a pulse width of at least some of the pulses at a fraction of an amplitude extremum of the pulses and to determine a length of the object along the flow direction based on the measured pulse widths.
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Abstract
Spatially modulated light emanating from an object moving along a flow path is used to determine various object characteristics including object length along the flow direction. Light emanating from at least one object moving along in a flow path along a flow direction of a spatial filter is sensed. The intensity of the sensed light is time modulated according to features of the spatial filter. A time varying electrical signal is generated which includes a plurality of pulses in response to the sensed light. Pulse widths of at least some of the pulses are measured at a fraction of a local extremum of the pulses. The length of the object along the flow direction is determined based on the measured pulse widths.
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Citations
29 Claims
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1. A system, comprising:
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a spatial filter having a plurality of mask features; at least one detector positioned to sense light emanating from at least one object moving in a flow path along a flow direction, an intensity of the sensed light being time modulated according to the mask features, the detector configured to generate a time varying electrical signal comprising a sequence of pulses in response to the sensed light; and an analyzer configured to measure a pulse width of at least some of the pulses at a fraction of an amplitude extremum of the pulses and to determine a length of the object along the flow direction based on the measured pulse widths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method, comprising:
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sensing light emanating from at least one object moving in a flow path along a flow direction of a spatial filter, the spatial filter having a plurality of mask features comprising first features alternating with second features along the flow direction, the first features having first light-transmission characteristics and the second features having second light transmission characteristics, different from the first light transmission characteristics, an intensity of the sensed light being time modulated according to the mask features; generating a time varying electrical signal comprising a plurality of time modulated pulses in response to the sensed light; measuring pulse widths of the pulses at a fraction of a maximum extremum of the pulses; and determining a length of the object along the flow direction based on the measured pulse widths. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A system, comprising:
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a spatial filter having a plurality of mask features; at least one detector positioned to sense light emanating from at least one object moving in a flow path along a flow direction, an intensity of the sensed light being time modulated according to the mask features, the detector configured to generate a time varying electrical signal comprising a sequence of pulses in response to the sensed light; and an analyzer configured to measure a pulse width of at least some of the pulses at in a range of about 10% to 40% or 60% to 90% of an amplitude extremum of the pulses and to determine, based on the pulse widths, one or more of; a length along the flow direction of the object; an instantaneous velocity of the object; whether the object is accelerating or decelerating.
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Specification