Abstract: An electro-optical distance meter has a light-emitting element that is directed through a shutter to a target and returned from the target to a photodetector. Internal and external optical paths are continuously switched by the shutter with a predetermined time ratio. The internal optical path is used for calibrating the distance being measured. The meter reduces the measurement time and enhances accuracy. In one form, the shutter comprises a disc having a C-shaped opening with an index thereon for providing a reference signal. In another form, the shutter comprises a liquid crystal switch.

Abstract: An equipment for measuring difference in elevation employing a leveling pole and a level is disclosed. The leveling pole comprises divisions of coded marks each indicating height at a unit interval. The level comprises a telescope and an image sensor. The output signal of the sensor is decoded for display of digital height value. A plate glass is provided in front of an object lens for vertical compensation of an optical axis of the telescope. An inclination angle of the plate glass required for compensation is used for interpolation between two adjacent coded marks.

Abstract: Known absolute type position encoders have poor resolution due to bits density of tracks formed on an encoding member and mechanical size of sensors opposed to the encoding member for reading absolute position data from the tracks. This invention provides a position encoder comprising a laser scanning type encoding member on which data tracks aligned at equal intervals in a moving direction of a part to be position-measured. A sensor with a single laser beam deflectable along the track is used for reading the position data. High resolution is obtained since it depends upon recorded pitch of tracks. Many data can be recorded on each track, including error correction code for the position code. It improves reliability of the encoder.