Vision systems, components

Fig. 7.8.2 shows the basic components of a camera system, and the signal flow. A vision system or optical measurement system consists of the elements illustrated in the figure. A lens collects radiation from a source, such as a light bulb or an illuminated object. A sensor converts the collected radiation into an electronic charge, which can be preprocessed by electronics. The preprocessed information is con-... 

Fully automatic wiring of luminaires is made possible by the integration of previously presented components into the whole system. Luminaire cases are supplied by a feeding system. The luminaire case type is selected by the vision system identifying the bar code on the luminaire case. Next, luminaire components are assembled in the luminaire case and then directed to the wiring station (Figure 43). 

Automated deburring of aeroengine components using a vision system-driven cutting tool (Jayaweera and Webb 2011)... 

The change to Pb-free solders does not have an explicit impact on component placement machine technology. Indirectly, however, the need for alternative surface finishes on both the components and circuit board fiducials, which have different reflectance characteristics, can affect the performance of the vision systems used to locate accurately both the circuit board and the tooling that delivers the component to the board. 

In addition, there has been a steady increase of odd-shaped devices that include inductors as well as LEDs, surface-mount connectors,etc. The result has been circuit boards with a greater mix of package types and sizes. Consequently, it is considerably less expensive and time-consuming to reprogram a computer-based, machine vision system to recognize these components than it is to retool a machine based on mechanical relays, detents, and such for component placement. 

FIGURE 40.22 Vision system images (a) a flip chip component (b) a printed circuit board fiducial. (Courtesy of Universal Instruments.)... 

Vision system limitations are determined by the speed with which the computer can process information (e.g., circuit board coordinates, component geometries, defects). The more information to be processed, the slower is the component placement step. For products requiring the placement of thousands of parts per circuit board, even an additional few tenths of a second per component can add up to a significant loss of production throughput. 

This technique consists of directing a heated stream of air or other process gas such as nitrogen at the component to be removed. Modem hot-gas repair stations are sophisticated, with computer control, predictive reflow profiling, vision systems to assist in component alignment to bonding pads on the printed wiring board (PWB), preheating stations, and accommodations for component removal. Hot-gas repair is most often used for SMT components but can be adapted for PTH component removal. 

Vision System. This is used to aUgn component leads to PWB bonding pads manually. Usually a split-image video system is used to view both component leads and board bonding pads simultaneously. The images are superimposed and the operator manually adjusts them for the best lead-to-pad alignment. 

For ergonomic design of new system components, these have to be adapted to the abilities and skills of people [62, p. 969]. Therefore, this section shows the state of research regarding information acquisition and processing based on established model approaches. To fulfill the task of driving the visual sensory channel is by far the most comprehensive [1, p. 6], [76, p. 1]. The design and study relevant characteristics of the human eye are therefore summarized briefly. This is followed by consideration of the vision task and the related vision restrictions from commercial vehicles. 

Checking detection of missing, incorrect, misshapen or wrongly orientated components by electronic vision systems, tactile/pressure sensors and proximity sensors. 

A serious limitation of the STM technique so far is its lack of chemical sensitivity. Generally, STM is not specific for the elemental species in multi-component systems, though there are special cases where the direction of charge flow is well known as shown for the GaAs(llO) surface. The surface area which one is looking at by STM is typically quite small. The problem of how representative the obtained tunnel vision is, is at least partly solved by considerably increasing the total scan range of STM/SPM instruments. 

For catalyst testing, conventional small tubular reactors are commonly employed today [2]. However, although the reactors are small, this is not the case for their environment. Large panels of complex fluidic handling manifolds, containment vessels, and extended analytical equipment encompass the tube reactors. Detection is often the bottleneck, since it is still performed in a serial fashion. To overcome this situation, there is the vision, ultimately, to develop PC-card-sized chip systems with integrated microfluidic, sensor, control, and reaction components [2]. The advantages are less space, reduced waste, and fewer utilities. 

Thus far in this book we have discussed one- or two-component photochemical systems which because of their relative simplicity lend themselves quite well to laboratory study. Consequently the mechanisms of many of the photoreactions we have discussed have been elucidated in exquisite detail. As we turn our attention in this chapter to some photochemical aspects of living systems, we shall find much more complex situations in which mechanistic details are just now beginning to be obtained. In some systems, such as those which exhibit phototaxis or phototropism, so little is known that our treatment must as a consequence be limited to only a brief discussion of these phenomena. The topics we will consider here are photosynthesis, vision, phototaxis and phototropism, and damage and subsequent repair of damage by light. Due to space limitations, a discussion of the very fascinating area of bioluminescence must be omitted. 

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