Abstract: A beam projecting apparatus which includes a light source emitting a laser beam; and a beam projecting device which includes a beam projecting portion from which the laser beam is projected outwardly so that the laser beam has a beam waist position at a predetermined position apart from the beam projecting apparatus. The beam projecting apparatus further includes a beam waist position adjusting optical system which is disposed along a light path from the light source to the beam projecting portion, at least one lens element of the beam waist position adjusting optical system being movable along an optical axis thereof; a temperature detecting device for detecting a temperature in the beam projecting apparatus; and a controller for controlling a movement of the at least one lens element in association with the temperature detected by the temperature detecting device so that a deviation of the beam waist position from the predetermined position due to a temperature change is minimized.

Abstract: A beam projecting apparatus has a light source and a reflecting device for reflecting and rotating a bundle of light emitted from the light source for forming a reference plane. A shape converting optical system is provided in an optical path from the light source to the reflecting device for converting the bundle of light from an elliptical sectional shape to a circular sectional shape.

Abstract: A device for measuring a characteristic of an optical element which forms an interference fringe pattern using a reference light beam reflected from a reference surface and a test light beam that is guided from the optical element by a light refracting element. The interference fringe pattern is detected and data corresponding to the interference fringe pattern is output. The outputted data is processed such that information of wave front aberration representative of the interference fringe pattern is output. The information includes mathematical terms representative of position errors and of the characteristic of the optical element. The mathematical terms are calculated, and the mathematical terms representative of the characteristic of the optical element are corrected based on a value of at least one of the mathematical terms representative of the position errors. The corrected mathematical terms are then displayed.