Apparatus and method for measuring light transmittance or reflectance
First Claim
1. Scanning apparatus for taking transmittance or reflectance measurements from a light transmitting or reflecting sheet comprising:
- means for supporting the sheet in an operative position so that the sheet is exposed for being scanned along a line by a radiation beam;
a radiation source;
means movable relative to said supporting means for directing a beam of radiation onto the sheet and along a line in scanning relationship thereto when the sheet is in said operative position;
means defining an elongated cavity having a radiation-receiving slot therein to allow radiation from the line scanning across the sheet to pass into the cavity, the cavity defining means having a radiation-reflecting surface to allow the radiation entering the cavity to be reflected thereby;
photodetector means for sensing, at the ends of the cavity, the radiation reflected in the cavity and for generating an electronic signal corresponding to the sensed radiation; and
circuit means coupled with the photodetector means for correcting the signal for variations in the intensity of the radiation entering the cavity as a function of the distance along the slot during scanning of the beam.
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Accused Products
Abstract
Apparatus and a method for providing measurements of the diffuse transmittance or reflectance of a sheet at a set of points arranged along a pattern line on the sheet. In accordance with the invention, the sheet, such as a photographic film, is moved with respect to a cylinder with a slot cut in its wall parallel to its central axis. A beam of radiation is swept parallel to the slot and into the cylinder after scanning along a line on the sheet. The inner wall surface of the cylinder is coated with a high reflectance material so that a fraction of the directly transmitted and scattered radiation in the cylinder enters one or more electronic radiation detectors coupled to the cylinder. The fraction of the radiation measured depends on the position along the slot of the radiation beam, and the data are corrected by dividing the measurement at each point by the measured radiation at that point when no object is in the beam. Several embodiments of the cylinder are disclosed.
39 Citations
20 Claims
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1. Scanning apparatus for taking transmittance or reflectance measurements from a light transmitting or reflecting sheet comprising:
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means for supporting the sheet in an operative position so that the sheet is exposed for being scanned along a line by a radiation beam; a radiation source; means movable relative to said supporting means for directing a beam of radiation onto the sheet and along a line in scanning relationship thereto when the sheet is in said operative position; means defining an elongated cavity having a radiation-receiving slot therein to allow radiation from the line scanning across the sheet to pass into the cavity, the cavity defining means having a radiation-reflecting surface to allow the radiation entering the cavity to be reflected thereby; photodetector means for sensing, at the ends of the cavity, the radiation reflected in the cavity and for generating an electronic signal corresponding to the sensed radiation; and circuit means coupled with the photodetector means for correcting the signal for variations in the intensity of the radiation entering the cavity as a function of the distance along the slot during scanning of the beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In scanning apparatus for taking transmittance or reflectance measurements from a radiation transmitting or reflecting sheet mounted in an operative position so that the sheet can be exposed for being scanned along a line by a radiation beam comprising:
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means for directing a beam of radiation onto the sheet and along a line in scanning relationship thereto when the sheet is in said operative position; means defining an elongated cavity having a radiation-receiving slot therein to allow radiation from the line scanning across the sheet to pass into the cavity, the cavity defining means having a radiation-reflecting surface to allow the radiation entering the cavity to be reflected; photodetector means for sensing at the ends of the cavity the radiation reflected in the cavity and for generating an electronic signal corresponding to the sensed radiation; and circuit means coupled with the photodetector means for correcting the signal for variations in the intensity of the radiation entering the cavity as a function of the distance along the slot during scanning of the beam. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of taking radiation measurements from a light transmitting or reflecting sheet comprising:
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exposing the sheet for being scanned along a line by a radiation beam; directing a beam of radiation onto the sheet and along a line in scanning relationship thereto when the sheet is in the operative position; collecting radiation from the line across the sheet within a cylindrical region and directing the collected light to a predetermined location in said region; generating an electronic signal corresponding to the collected radation; correcting the signal for variations in the radiation entering said cylindrical region as a function of the distance along the slot during scanning of the beam and; repeating the directing, collecting, generating and correcting steps until at least a part of the area of the sheet has been scanned by the beam.
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Specification