High-speed camera

Abstract: A high-speed framing camera is disclosed. The camera includes an optical tunnel of rectangular cross section for forming an extended array of virtual images of an event to be recorded. An objective lens system of limited aperture projects a cone of image-forming rays onto a face of a rotating mirror upon which face a real image of the event is formed. These rays are recollected by another lens to form an additional real image at the entrance of the tunnel. A copy lens at the exit of the tunnel forms rows of real images of these virtual images on an image surface outside of the tunnel. As the face of the mirror rotates through its recording angle, the images are sequentially illuminated.

Abstract: Although the melt pool convection currents influence the dilution, porosity and distribution of potentially included hard phase particles such as carbide or other ceramic particles, which are added to increase the wear resistance of the deposited material, there is only limited knowledge of melt pool dynamics within blown powder additive manufacturing processes. In the pursuit of a deeper understanding, a high-speed camera has been used to observe melt pool dynamics during laser cladding at a frame rate of up to 67’000 frames per second, allowing for the particles that swim on the surface to be traced automatically. The resulting videos allow for the melt pool surface behavior to be investigated using a specifically developed automated high-speed camera image evaluation technique. This method has been tested for reliability and applied to investigate the process parameter influence on melt pool dynamics. The results show, that there is no pronounced laminar flow on the melt pool surface, instead a remarkable randomness to the direction of particle flow can be observed. That being said, it is still possible to identify certain flow tendencies that can be explained by surface tension phenomena like the Marangoni effect and which depend on the process parameters.

Abstract: As one of ITS technique, a new visible light road-to-vehicle communication system at intersections is proposed. In this system, the communication between a vehicle and an LED traffic light is conducted using an LED traffic light as a transmitter, and an on-vehicle high-speed camera as a receiver. The LEDs in the transmitter emit light in high frequency and those emitting LEDs are captured by the high-speed camera for making communication. Here, the luminance value of LEDs in the transmitter should be captured in consecutive frames to achieve effective communication. For this purpose, first the transmitter should be found, then it should be tracked in consecutive frames by processing the images from the high-speed camera. In this paper, we propose new effective algorithms for finding and tracking the transmitter, which result in a increased communication speed, compared to the previous methods. Experiments using appropriate images showed the effectiveness of the proposals.