Focusing controlled

Need to integrate and focus control systems for quality and safety... 

Establishing a focused control system on specific hazardous chemicals... 

Focus can be controlled by monitoring the image contrast with the two-dimensional CCD camera while using the AF actuator to move the objective lens back and forth along the optical axis. Very clear images can be obtained with this simple focus control. 

When the thiekness is above 1 mi it is best measured by a mierometer screw or by a micrometer calibrated focus control on an optical microscope. When the thickness is below 1 pm it is convenient to use light interference fringes (colored or monochromatic). Figure 4.4 shows color fringes taken just before perforation occurs. The appearance of colored fringes is due to the interference of incident and reflected light, and occurs when... 

The key factors driving the advancements in exposure tool technology are line width resolution, registration, and depth of focus. The ahdity to decrease device feature line width is heneficial in that it lowers cost, increases the number of dies produced per wafer, and also increases device speed. Registration helps to increase device yield and speed by accurately overlaying one layer on another. Depth of focus control helps to determine CD control and consequently device speed and yield. ... 

Crucial in the design of the instrument is the focusing control for the microscope objective. For TIRF applications it is necessary to place the centre of the depth of focus of the objective (the objective focal plane) near the glass water interface. For diffusion confocal and two-photon designs it is desirable to always... 

Continually scan over a range of focal planes (generally the upper 10 to 15 m of the filter surface) with the fine focus control during each field count. Spend at least 5 to 15 seconds per field. 

FIGURE 14.14 Focus control system (a) the quad detector, (b) the spot of light focused on the quad by the astigmatic lens (circular implies objective lens is in focus), and (c) the spot of light on the quad when the objective lens is out of focus. 

Finally, it may be necessary to focus control on a data set cortsidered critical to the analyzed system. It is then possible to write each of these critical data in two areas of the RAM (two different areas, two differerrt memory banks, etc.) and to perform a consistency check between the two copies of tire data. The copies may be identical or not. For example, if we choose to write the value and its counterpart, verification of consistency can be achieved through a sum and a comparison with 0. This technique improves the execution time of the check and uses the ALU, but its main disadvantage is an excessive use of memory. 

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