Patent ID: 7929857

Claim:
A method for aligning a telecentric on-axis darkfield (TOAD) lighting device with a substantially specular surface, the TOAD lighting device having a plurality of concentric illumination arrays, the method comprising: adjusting an angle of incidence between the TOAD lighting device and an object plane in a first direction until an area of intense brightness is substantially removed from a first side of an image of the specular surface; recording the adjusted angle of incidence as a first measurement; adjusting the angle of incidence between the TOAD lighting device and the object plane in an opposite direction as compared to the first direction until the area of intense brightness is substantially removed from a second side of the image of the specular surface; recording the readjusted angle of incidence as a second measurement; determining an aligned angle of incidence for the first direction as an approximate difference between the first measurement and the second measurement; and aligning the TOAD lighting device according to the determined aligned angle of incidence for the first direction.