Lens design and selection

You get used to looking through lenses it is an acquired skill The microscope 

The heart of the acoustic microscope system is its acoustic objective. (Atalar and Hoppe 1986) 

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Until recently, all SEMs used a "pinhole objective lens and single SE detector located below the lens, as shown in fig. 6(a). A characteristic of the "pinhole" lens, in which the polepiece bore diameter closest to the specimen is smaller than the other bore, is that the stray magnetic field below the lens is very low. With the specimen in field-free space, the low energy SEs are readily collected by a SE detector located in the vicinity of the specimen. The other reason for selecting this particular lens design... 

In the acoustic microscope the required signal can be selected not only in the time domain but also in the frequency domain. The ability to select the specimen echo and separate it in time from the unwanted lens echo was the basis of the design considerations of the focal length of the lens, and hence the resolution available ( 3.2 and 4.3). But it is a feet of experience that smaller lens reverberations are always present that cannot be separated in time from the echo from the specimen. These lead to the kind of problem that was illustrated schematically in Fig. 4.5. Moreover, even if such reverberations... 

In the daily care of contact lenses, wearers are instructed to clean their hands with soap and to dry hands their hands with lint-free towels prior to handling their lenses. Selection of the specific soap product is important. In addition, to cleaning the hands thoroughly, it should be rinsing and should not cause ocular irritation even if residual amounts are transferred to the lens. With these considerations in mind, some hand soaps have, therefore, been designed specifically for contact lens users. 

In process design the basic teaching philosophy should be one of giving le student relatively free rein and the complete responsibility for progress id accomplishment. The students may have the option of selecting leir own problem or the instructor may do this. The students should len decide on the method of approach, analyze the facts and situations, an and carry out laboratory and calculation work, select equipment, ake economic studies, and display initiative throughout. 

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