Linear integrating cavity light source for infra-red illumination of sensitized media
First Claim
1. A linear light integrator for use in illuminating a web with an elongated stripe of diffuse illumination comprising:
- an elongated housing formed with side and end walls defining a light integrating cavity having diffusely reflecting interior wall surfaces, said housing side wall having a longitudinally extending slit through which diffuse light exits said cavity;
an elongated array comprising a plurality of discrete light sources supported with respect to the elongated housing to emit light into said cavity, whereby the emitted light is integrated within the cavity by reflection from the interior wall surfaces thereof and the integrated light forms a linear light beam exiting the elongated slit having a varying longitudinal intensity profile; and
means for modulating the intensity of the light emitted by said discrete light sources in a predetermined intensity pattern for altering the varying longitudinal intensity profile of the linear light beam to provide a desired longitudinal intensity profile of the stripe of diffuse illumination, said intensity modulating means further comprises;
means for providing a set point control signal defining an illumination intensity level of said stripe of illumination;
means for connecting said plurality of light sources into a further plurality of groups in a predetermined relationship; and
a plurality of drive circuits for driving each of said plurality of groups of light sources at a plurality of light intensities corresponding to said predetermined intensity pattern as a function of said set point control signal for altering the varying longitudinal intensity profile of the linear light beam to provide the desired longitudinal intensity profile of the stripe of diffuse illumination.
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Accused Products
Abstract
A highly uniform infrared illumination source for illuminating a stripe of a moving sensitized web for line scan imaging of imperfections in the coating on the web by a CCD imaging camera. A light integrator having an elongated housing formed with side and end walls defines a linear light integrating cavity having diffusely reflecting interior wall surfaces. An elongated array of infrared LEDs is spaced along the side wall for emitting light into the cavity for integration within the cavity. A longitudinally extending slit is formed in the side wall through which a diffuse, linear light beam exits the elongated slit having a varying longitudinal intensity profile. The intensity of the light emitted by the LEDs is modulated in an intensity pattern that alters the varying longitudinal intensity profile of the linear light beam to provide a desired longitudinal intensity profile of the stripe of diffuse illumination. Preferably, the intensity modulation renders more uniform the longitudinal intensity profile of the linear light beam illuminating the web as viewed by the imaging camera. The desired light intensity profile along the length of the emitted light beam is achieved by clustering the LEDs with LED drive circuits operated at different drive currents as a function of a set point control signal appropriate to the characteristics of the imaging camera and a transmitted light intensity feedback signal to maintain the intensity pattern of the LEDs and the uniform intensity profile as viewed by the imaging camera regardless of the optical density of the web.
41 Citations
23 Claims
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1. A linear light integrator for use in illuminating a web with an elongated stripe of diffuse illumination comprising:
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an elongated housing formed with side and end walls defining a light integrating cavity having diffusely reflecting interior wall surfaces, said housing side wall having a longitudinally extending slit through which diffuse light exits said cavity; an elongated array comprising a plurality of discrete light sources supported with respect to the elongated housing to emit light into said cavity, whereby the emitted light is integrated within the cavity by reflection from the interior wall surfaces thereof and the integrated light forms a linear light beam exiting the elongated slit having a varying longitudinal intensity profile; and means for modulating the intensity of the light emitted by said discrete light sources in a predetermined intensity pattern for altering the varying longitudinal intensity profile of the linear light beam to provide a desired longitudinal intensity profile of the stripe of diffuse illumination, said intensity modulating means further comprises; means for providing a set point control signal defining an illumination intensity level of said stripe of illumination; means for connecting said plurality of light sources into a further plurality of groups in a predetermined relationship; and a plurality of drive circuits for driving each of said plurality of groups of light sources at a plurality of light intensities corresponding to said predetermined intensity pattern as a function of said set point control signal for altering the varying longitudinal intensity profile of the linear light beam to provide the desired longitudinal intensity profile of the stripe of diffuse illumination. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A scanner for scanning an illuminated stripe of a moving web for detecting defects in the web comprising:
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a linear light integrator for use in illuminating said web with a stripe of diffuse illumination at a web scanning plane further comprising; an elongated housing formed with side and end walls defining a light integrating cavity having diffusely reflecting interior wall surfaces, said housing side wall having a longitudinally extending slit through which diffuse light exits said cavity; and an elongated array of a plurality of discrete light sources supported with respect to the elongated housing for emitting light into said cavity, whereby the emitted light is integrated within the cavity by reflection from the interior wall surfaces thereof and the integrated light forms a linear light beam exiting the elongated slit having a varying longitudinal intensity profile; a line imaging camera imaged on an image scan line of said illuminated stripe of said web for developing an output image signal varying in magnitude as a function of the transmission of light through areas of said web that exhibit normal and defective densities; and means for modulating the intensity of the light emitted by said discrete light sources in an intensity pattern to provide a desired longitudinal intensity profile of said stripe of diffuse illumination illuminating the web as viewed by said line imaging camera, said intensity modulating means further comprises; means for providing a set point control signal defining an illumination intensity level of said stripe of illumination for the imaging camera being used; means for connecting said plurality of light sources into a further plurality of groups in a predetermined relationship; a plurality of drive circuits for driving each of said plurality of groups of light sources at a plurality of light intensities corresponding to said predetermined intensity pattern as a function of said set point control signal for altering the varying longitudinal intensity profile of the linear light beam to provide the desired longitudinal intensity profile of said stripe of diffuse illumination. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification