OPTICAL SYSTEM FOR MEASURING INSTRUMENT

PURPOSE:To utilize light energy from a light emitting element effectively by inserting a convex cylindrical lens which ha linear light convergence effect into parallel luminous flux. CONSTITUTION:The optical-axis direction of an optical system is denoted as Z, the arrangement direction of a line sensor 15 is denoted as Y, and a direction crossing it at right angles is denoted as X. Then, divergent light from a light source 11 such as an LED is converted by a spherical lens 12 into parallel light, which is converged by the cylindrical lens 13. The lens 13 is so arranged s to have convergence effect in the direction X. Namely, the light convergence effect is obtained in the X, Z section, but the light is still parallel in the Y, Z section. Further, when the utilization of energy from a spot light source is considered, luminous flux having an angle theta as to divergent luminous flux from the light source is all converged on the sensor 15 through lenses 12 and 13, so a light source with low output can be utilized. Then, when the focus of the lens 13 is set on the sensor 15, the utilization efficiency of the light is maximized. Further, when an infrared-light LED is used, a filter 14 for removing an unnecessary spectrum, e.g. light in the visible ray range is inserted.