Abstract: An optical scanner comprising an aimer light source to emit highly polarized light, a window, and a linear polarizer positioned between the aimer light source and the window. Further, the linear polarizer receives the highly polarized light and converts into linear polarized light. Further, a quarter-wave plate is positioned between the linear polarizer and the window. Further, the quarter-wave plate receives the linear polarized light and converts into circularly polarized light. Therefore, the linear polarizer and the quarter-wave plate prevent back reflection of the circularly polarized light from the window from reaching the aimer light source for preventing an aimer ghost light.

Abstract: A pre-alignment measurement device includes, disposed in a direction of propagation of light, a laser, a first cylindrical lens, a first imaging lens, an illumination diaphragm, a second imaging lens, a second cylindrical lens and a CCD detector. The laser, an object under measurement and the CCD detector are arranged at respective apexes of a triangle formed by the measurement device for pre-alignment. A light beam is emanated by the laser and is transformed into a line beam. The line beam is reflected by the object under measurement and then passes through the second cylindrical lens to form a CCD image which has different horizontal and vertical magnifications, allowing horizontal and vertical resolutions to be matched with horizontal and vertical measuring ranges, respectively. The CCD image contains information of a position and a height of a step defined by the object under measurement and the wafer stage.

Abstract: A pre-alignment measurement device includes, disposed in a direction of propagation of light, a laser, a first cylindrical lens, a first imaging lens, an illumination diaphragm, a second imaging lens, a second cylindrical lens and a CCD detector. The laser, an object under measurement and the CCD detector are arranged at respective apexes of a triangle formed by the measurement device for pre-alignment. A light beam is emanated by the laser and is transformed into a line beam. The line beam is reflected by the object under measurement and then passes through the second cylindrical lens to form a CCD image which has different horizontal and vertical magnifications, allowing horizontal and vertical resolutions to be matched with horizontal and vertical measuring ranges, respectively. The CCD image contains information of a position and a height of a step defined by the object under measurement and the wafer stage.