Apparatus is disclosed for determining the speed of a moving object by conducting an image of the object through a lens to a mirror and exciting the mirror with variable frequency oscillations from a light source or a vibrating source, until the image on the mirror becomes substantially steady. The frequency of oscillations exciting the mirror are proportional to the speed of rotation of a wheel driving the moving object. The apparatus may be mounted in a handheld housing.
An inspection device for detecting faulty prints on a printed matter running at a high speed. The prints on the printed matter are held as if they were stopped on account of the employment of an even-numbered polygonal prism which rotates in synchronism with the running speed of the printed matter and which allows an inspector's eye to catch successively the prints on an optical axis not only at their positions on said optical axis but also at their moving positions before and behind said optical axis.
An improved dental hand piece which has a driven tool which either is rotated or reciprocated and includes an illumination arrangement for projecting light from an exit end at a tip of the tool and the work area includes a stroboscopic device for creating light pulses having a light frequency which coincides with a motion frequency of the tool in such a manner that the surface of the tool is visible during motion. The stroboscopic device can either be a mechanical stroboscope or be a high-speed flash stroboscope.
