Safety countermeasures, such as protective gear, etc., are not required since Panasonic LD-600 uses a Class 1 laser as per JIS standards, and LD-601 uses a Class II laser as per FDA standards. Troublesome optical beam alignment is not required since the emitter and the receiver are mounted on one body. FDA standard (Class II) conforming model LD-601 is available. A red semiconductor laser is used as the emitting device and CCD is used as the receiving device. An ideally parallel optical beam is emitted achieving highly accurate measurement. Shading correction function which compensates for receiver sensitivity variation and generates a uniform sensitivity distribution has been incorporated. Stable sensing over extended periods of time is possible. The sensor can be used for various applications with its binary data output with four different sensing modes.