| 摘要 |
An apparatus for photoelectrically detecting the position of each of the edges of a line having the opposite edges thereof formed substantially parallel to each other on an a substrate thereby to measure the width of the line, comprises a source of coherent light, means for condensing the coherent light into a tiny light spot which illuminates the line, means for imparting to the tiny light spot a minute oscillation having an amplitude less than the width of the line, means for providing relative movement of the tiny light spot and the line so that diffracted light may be created at each of the edges of the line, a first photoelectric conversion element for receiving chiefly the diffracted light created at one of the edges of the line, a second photoelectric conversion element for receiving chiefly the diffracted light created at the other edge of the line, and a circuit for producing position signals corresponding to the edges of the line from the output signals from the first and second photoelectric conversion elements. |
