Flaw detector for detecting flaws in a sheet
AssigneeFutec Inc.
InventorShizuo Nishioka
Life of this patent
Estimating the term…
Abstract
A flaw detector, for detecting a flaw in a sheet, picks up, by means of a plurality of linear array cameras, the light of rays transmitted through a sheet. The video signals from the linear array cameras, which are appropriately processed, are used for checking whether a flaw is present or not. A sensitivity-difference correcting section corrects sensitivity differences amoung the cameras and among photosensitive elements of each camera, which sensitivity differences are contained in the video signal. Automatic gain control sections, for transparent and opaque flaws, respectively, control the sensitivities of the video signals. These signals are differentiated, and then compared with a predetermined slicing level, thereby to check whether transparent and opaque flaws are present or not.
Claims30
A flaw detector for detecting flaws in a sheet, comprising:
- a light source for illuminating a sheet being subjected to flaw detection;
- a plurality of linear array image cameras for picking up the light rays transmitted through said sheet, and converting them into a video signal, said linear cameras being arrayed so as to cover the full width of said sheet, and each of said linear array cameras including a linear array image sensor made up of a number of photosensitive elements linearly arrayed;
- memory means corresponding to said linear array cameras, for storing the corrected sensitivity values thereof;
- correcting means corresponding to said linear array cameras, for amplifying the video signal derived from the corresponding linear array camera, at a degree of amplification corresponding to the corrected value as stored in said memory means, and for producing a sensitivity-corrected video signal;
- wave-shaping means for receiving said corrected video signal and shaping the waveform thereof, so as to clearly show a flawed portion of a sheet;
- and
- first flaw-check means for checking a flaw according to the shaped waveform, and for outputting the result of said check.
A flaw-detecting method for detecting flaws in a sheet, comprising the steps of:
- illuminating a sheet to be flaw-detected, by use of a light source;
- picking up the light rays transmitted through said sheet by a plurality of linear cameras being arrayed so as to cover the full width of said sheet, each of said linear array cameras including a linear array image sensor made up of a number of photosensitive elements linearly arrayed, and further producing a video signal corresponding to the amount of transmitted light;
- amplifying the video signal, derived from the corresponding linear array cameras, at a degree of amplification corresponding to the corrected value, as stored in memory means corresponding to said linear array cameras, thereby to obtain a sensitivity-corrected video signal;
- shaping the waveform of said corrected video signal, by said waveform-shaping means, so as to clearly show a flawed portion of a sheet;
- and
- checking a flaw, according to the shaped waveform, by first flaw-check means.
Dependencies are inferred from the claim text.