| 摘要 |
PROBLEM TO BE SOLVED: To communicate data appropriately regardless of close distance or far distance by equipping an optical means for forming the image of communication light with a diffraction optical member with at least a 0-order beam. SOLUTION: A light reception optical means with a diffraction optical member 20 is provided at the front of a photo detector 7 of a data communication part 16. When range-finding light 5 enters the diffraction optical member 20 from an oblique direction at a close distance, parallel components are transmitted and reach the photo detector 7. In this case, since the spread of luminous flux is small, luminous flux density is high, which is sufficient for operating the photo detector 7. On the other hand, when a surveying machine is located at a far distance and the luminous flux of the range-finding light 5 enters while being spread widely, the diffraction optical member 20 condenses the range- finding light 5 on a light reception surface, so that a sufficient quantity of light enters the photo detector 7. |
