Due to the customized IC and optical design, high precision detection is fulfilled with directivity and visibility achievable only by laser. The laser adopted is Class 1 (IEC / JIS / FDA) laser that is safe to use, so that there is no need to separate the areas of sensor usage. Panasonic EX-L211 ø0.5 mm ø0.020 in light receiving slit cuts out any unnecessary beam. As only the beam which enters into the slit becomes valid, an accurate and precise detection is possible. This is effective for minute object detection or small difference in level detection. Also, the aspheric surface adopts a glass module lens to deliver a high quality spot beam. A repeatability of 0.02 mm 0.0008 in or less at a range of from 100 mm to 200 mm 3.937 to 7.874 in makes this type best suitable for positioning applications. Moreover, it boasts a top-class detection precision in the compact laser sensor category with its min. sensing object being ø0.01 mm ø0.0004 in. The same aspheric surface glass lens used in the thru-beam type is adopted to minimize aberration and deliver a high quality beam spot. Panasonic EX-L200 series has the same mounting pitch as ultra-compact photoelectric sensor EX-20 series so that the time taken in designing is saved.