| 摘要 |
PURPOSE:To enhance detection accuracy, by a simple structure wherein the light of a light source is brought to parallel light or approximate parallel light by an illumination apparatus to irradiate an object to be inspected. CONSTITUTION:In an illumination apparatus 13, three parallel illumination guide plates 15 are provided to the light path between a light source 11 and the setting stand 12A of an object 12 to be inspected and the distance l between the light source 11 and the stand 12A is set to a predetermined value to bring the light of the light source 11 to light approximate to parallel light 16 to irradiate the object 12 to be inspected. Even when the setting position of the object 12 to be inspected is positionally shifted by DELTAl toward the light source from a reference position l by the cause of the setting error of the stand 12A, since no change is generated in the quantity of the light allowed to irradiate the unit irradiation area of the object 12 to be inspected, the change in the quantity of the irregular reflected beam from the object 12 to be inspected is zero or near to zero and the quantity of the light received by a photodetector 14 also becomes same. By this method, the effect of the change in the relative distance between the light source 11 and the setting position of the object 12 to be inspected on the light receiving result of the apparatus 14 is suppressed and detection accuracy can be enhanced by a simple structure not enhancing the relative positioning accuracy of the light source 11 and the stand 12A even when the object to be inspected has slight warpage. |
