本研究主要在於利用一轉換方式來對打光光源作用於取像目標上亮度分配 不均勻而產生的誤差作調整。在研究中取像目標以物體表面為主,而且取 像的材質也以不易反光的材質為主。研究中所探討的目標在於調整光源作 用於取像表面上亮度不均勻情形以減少因光源作用亮度不均勻而產生的雜 訊。本研究沒有限定特定的打光光源。 調整光源作用於取像表面上的亮度不均勻情形的方法,首先需決定打光光 源作用於表面上的亮度分佈狀況,針對此一部份在研究中採用 CCD直接量 測的方式,也就是在光源不變動的情況下用 CCD先對一純色平面(材質與 目標材質相似)取像,如此可得光源作用於目標表面上大致的亮度分配。 決定了亮度分佈狀況後,利用沒環境光下打光光源亮度分配和打光後目標 取像的標準化資料經下列轉換方程式就可得到一減低光源亮度分佈不均勻 影響的調整影像。 (N2( i, j)-N1( i, j))*σ2+ (P2( i, j)+μ2)/2 式中:N1( i, j)表純粹光源亮度標準化後位置於 (i, j)的資料 N2( i, j)表打光後,取像結果標準化後位置於 (i, j)的資料 P2( i, j) 表打光後,取像結果位置於 (i, j)的灰階值 σ2表打光後,取像結果整體的標準差值 μ2表打光後,取像結果整體資料的平均值 本研究的主要目的在於調整打光光源亮度不均勻的分配,在調整過後的影 像中依影像性質的不同可得到下列不同效果: 1)、減少因打光光源亮度不均勻而產生的雜訊 2)、加強因打光光源亮度不均勻而減弱的特徵 3)、凸顯因打光光源亮度不均勻而消失的特徵。
The illumination system is a very important part of a machine vision system. The nonuniform brightness is a significant factor of the illumination system. The objective of this research was to adjust the nonuniform brightness and decrease the noise generated by the nonuniform brightness. The method of adjust nonuniform brightness has two steps. The first step is to determine the nonuniform situation from the lighting source. At this step, we measured the brightness by a CCD camera. After this, we can use it and the image with lighting to simulate an image with an uniform lighting source. In this research, after adjusting the nonuniform brightness, get the three advantages can be shown: 1. Decrease noise generated by the nonuniform brightness 2. Enhance the features which was covered by the nonuniform brightness 3. Emphasize disappear feature which was product by nonuniform brightness Several examples were used to demonstrate the developed lighting adjustment system. The developed system can be used for surface defects inspection.