Abstract: A display source emits light. A first hologram receives the light from the display source and diffracts the received light. The light from the display source is applied to the first hologram at an incident angle A1 and moves from the first hologram at an outgoing angle B1. A second hologram receives the light from the first hologram and diffractively reflects the received light. The light diffractively reflected by the second hologram forms an image of the display source in viewer's field of view. The light from the first hologram is applied to the second hologram at an incident angle A2 and moves from the second hologram at an outgoing angle B2. The first and second holograms are nonparallel to remove a ghost image of the display source which would result from at least one of surface reflections at the first and second holograms. The first hologram has an angle .theta. relative to the second hologram. The angles A1, B1, A2, B2, and .theta.

Abstract: A columnar vortex generator is set in a duct communicating with an intake pipe of an engine, to extend across the airflow in the duct. A vortex sensor is arranged in a downstream surface of the vortex generator. The sensor generates a signal corresponding to the frequency of Karman vortexes generated at the downstream side of the vortex generator. A turbulence generator for generating a turbulent flow in that part of intake air flowing against the vortex generator is set at the upstream side of the vortex generator. The vortex generator consists of stationary and movable units. The movable unit is moved in accordance with elongation/contraction of a bellows so as to vary the typical dimension D of the surface of the vortex generator against which air flows.

Abstract: An ignition device for use with internal combustion engines is adapted for conducting a light beam into the combustion chamber of the engine to ignite a fuel-air mixture. The ignition device includes a light emission apparatus opened to the combustion chamber to emit a light beam into the chamber, and a particle supply apparatus disposed in opposed relation with the light emission apparatus for supplying into the combustion chamber particles of a high light absorption index separately from the fuel-air mixture. The particles from the particle supply apparatus are emitted along the optical axis of the light beam into the combustion chamber and are heated at a position suitable for ignition of the fuel-air mixture within the combustion chamber to serve as an ignition source.

Abstract: An ignition apparatus for an internal combustion engine comprises an intake path supplying a mixture of air and fuel into the combustion chamber of the engine, a particle supplying unit having an ejection port opening into the combustion chamber for supplying minute particles of a material which is not the fuel and has a high light absorption factor, and a light source radiating a laser beam through a light focusing unit toward a suitably selected position in the internal space of the combustion chamber, so that the laser beam can strike the minute particles of high light absorption factor supplied from the particle supplying unit thereby producing a torch for igniting the air-fuel mixture.

Abstract: A laser ignition apparatus includes a laser oscillator which generates at least two successive pulse-shaped laser beams during each compression stroke of the engine. A first pulse-shaped laser beam is generated by a Q switching action of the laser oscillator and thus has a high peak output and a second pulse-shaped laser beam is generated without the Q switching action and has a low peak output but a larger pulse duration than the first laser beam. The first and second pulse-shaped laser beams are guided and directed into the combustion chamber of the engine and the first laser beam of a high energy density causes the breakdown of the air-fuel mixture in the combustion chamber to develop a plasma and the second laser beam further increases the energy of the plasma thereby to ensure the setting fire of the air-fuel mixture.