Patent ID: 9654746
Date: 2017-05-16
CPC Classifications: G01N,H04N

Claim:
1. A color lighting control method for improving image quality of a vision system comprising a lighting device having a plurality of lighting units for irradiating lights of different wavelengths to an inspection subject and a lighting control unit for controlling a light irradiation intensity by respectively adjusting input voltages applied to the lighting units and a camera for shooting an image of the inspection subject to generate a monochrome digital image, the method comprising the steps of: (a) applying predetermined input voltages to the plurality of lighting units respectively; (b) obtaining image data through the camera; (c) calculating an image histogram that is a distribution graph for displaying the number of pixels corresponding to each monochrome level intensity through the image data; (d) calculating a standard deviation of the image histogram; and (e) calculating an optimal input voltage value for each of the plurality of lighting units within an adjustment range of the predetermined input voltages, wherein the optimal input voltage value maximizes the standard deviation, wherein the optimal input voltage value that maximizes the standard deviation is calculated through a steepest decent method in which an operation of calculating an amount of change of the standard deviation according to an input voltage change and applying the input voltage adjusted in consideration of the calculated change amount is repeated.