Abstract: An apparatus for detecting streaks in a moving sheet of material utilizes the signal generating and processing means of an existing spot/hole detection system which provides a series of spot measurement signals generated sequentially as a machine direction series of cross-machine sets and assigns a cross-direction location to each signal. Means are provided for calculating an exponential average of the signals for each of the cross-machine locations. This average is compared with a predetermined standard and an output signal, including a cross-machine location, is generated when the average exceeds the standard.

Abstract: The stack reflectance is predicted from an on-line, wavelength dependent measurement of the sheet reflectance and the on-line measurement of the sheet opacity at a wavelength interval. The stack reflectance Rst is then used to predict and/or control stack color, preferably by using the parameter K/S=(1-Rst.sup.2)/2 Rst where K is the dye absorption coefficient and S is the dye scattering coefficient.

Abstract: A light source module for use with a multi-camera array in a video surface inspection system includes a first light emitter which extends lengthwise across the entire width of a sheet to be inspected. Light from the first light emitter, which preferably comprises one or more fluorescent lamps, is received by a light guide and carried by the guide to uniformly illuminate a band extending entirely across the width of the moving sheet. The light guide comprises a transparent thermoplastic such that the light receiving end of the guide can be bent to define a plurality of sections which can be axially aligned with a corresponding plurality of fluorescent lamps. The fluorescent lamps may be powered by individual inverter ballasts which may be driven inturn by one or more variable dc power supplied to control the intensity of light emitted by the lamps.

Abstract: Apparatus for inspecting sheet material having known characteristics is disclosed. The apparatus comprises means for providing a plurality of pixel signals each having a magnitude representing the intensity of electromagnetic radiation received from a corresponding point on the sheet material. The apparatus also comprises signal processing means for comparing the magnitude of each one of the pixel signals to a corresponding reference range defined by the known characteristics of the sheet material and generating a characteristic signal. The characteristic signal includes an event signal for each of the magnitudes falling outside of the corresponding reference range and a data signal for each of the magnitudes falling within the range, wherein the data signal represents the magnitude of the pixel signal. The signal processing means also generates an address signal representing the point on the sheet material at which the characteristic signal is generated.

Abstract: Apparatus (10) and methods for measuring dark and bright reflectances of translucent sheet material (2) are disclosed. The apparatus (10) comprises first optical means for illuminating one side of the sheet material (2) with a source of electromagnetic radiation. A portion of the radiation is transmitted through the sheet material (2) and another portion of the radiation is reflected by the sheet material. The apparatus (10) also comprises optical gating means (30) that is positioned adjacent the other side of the sheet material (2) in a fixed position relative to the first optical means. The optical gating means (30) absorbs substantially all of the transmitted portion of the radiation when switched to a dark state and reflects substantially all of the transmitted portion of the radiation back through the sheet material (2) when switched to a bright state.

Abstract: Disclosed are sheet inspection apparatus and methods for rapid, repetitive measurement of a quality attribute in each of a plurality of measurement zones of a continuously-manufactured sheet of material, wherein measurement is based on the interaction of one or more radiation wavelength bands with one or more constituents of the sheet. Simultaneous resolution of measurement zones is provided in both scanning and non-scanning applications.

Abstract: Disclosed are apparatus and methods for producing electrical signals that can be used to measure the speed of ultrasound in a moving web of paper. The apparatus employs a hollow cylinder in which a plurality of transducers are positioned to contact the web. Power supplied to the cylinder through mercury slip is filtered by power conditioning circuitry in the interior of the cylinder, thus enabling the delivery of clean electrical pulses to the emitting transducers. Signals from the receiving transducers are delivered to voltage-to-frequency converter circuitry in the interior of the cylinder, and the resulting electrical frequency signals are converted to optical frequency signals. The optical signals are then communicated across an air gap to receptors which are external to the cylinder. Thus, signals from which measurements of the speed of ultrasound can be derived are provided substantially free from noise generated by transmission through slip rings.