Microscopic Lenses

Small probed regions down to 1-2 pm are possible using microscope lenses. Lasers can supply as much pump power as needed to compensate for weaker signals, but a limit is reached when sample heating or nonlinear optically induced processes become significant. 

Khuri-Yakub, B. T. and Chou, C.-H. (1986). Acoustic microscope lenses with shear wave transducers. IEEE 1986 Ultrasonics Symposium, pp. 741-4. IEEE, New York. [69]... 

Important ongoing developments in HRTEM that are expected to be valuable in catalysis research include the correction of spherical aberrations in electron microscope lenses and monochromatization of the electron beam for improvement of the spatial and spectral resolution. Recently, scanning-TEM (STEM) of atomically dispersed lanthanum atoms on alumina (63) has provided e.x situ aberration-corrected images, but it is noteworthy that there is no technical limitation in applying the correction devices to instruments used for making measurements of samples in reactive environments. 

The next question is How do we write it We have no standard technique to do this now. But let me argue that it is not as difficult as it first appears to be. We can reverse the lenses of the electron microscope in order to demagnify as well as magnify. A source of ions, sent through the microscope lenses in reverse, could be focused to a very small spot. We could write with that spot like we write in a TV cathode ray oscilloscope, by going across in lines, and having an adjustment which determines the amount of material which is going to be deposited as we scan in lines. 

A simpler way might be this (though I am not sure it would work) we take light and, through an optical microscope running backwards, we focus it onto a very small photoelectric screen. Then electrons come away from the screen where the light is shining. These electrons are focused down in size by the electron microscope lenses... 

Never clean the microscope lenses or stand with cloths that have been used for removing surplus of alkali, acid or other reagent from slides. 

However, electron microscope lenses are far from ideal, and the probe is broadened by spherical aberration (proportional to the cube of the aperture size) and by diffraction (inversely proportional to the aperture size). Balancing the two effects by finding an optimal aperture size (ao) gives the theoretical minimum probe sizes at the specimen plane. However, the current within the probe size may be too small for useful signal to be collected within an acceptable time. Thus, while many manufacturers will claim smaller probe sizes, in reality the useful minimum probe size, one that yields enough... 

The collection efficiency of the optical system increases with the square of the effective numerical aperture of the microscope objective lens. A good lens is therefore essential in order to obtain a high coincidence rate. If the sample is transparent the light can be collected from both sides, either by the condenser lens of the microscope or by a second microscope lens. Theoretically, the collection efficiency can be doubled and the coincidence rate increased by a factor of four. Moreover, in a microscope with two aligned microscope lenses exciting and detecting from both sides of the sample, the focal volume can be considerably decreased [64, 448]... 

Microscopic lenses are used to enlarge the image of an object. They can be purchased as complete lens systems in microscopic objectives. 

We meet this case in technics. For instance, in an optical microscope, lenses fulfil the direct and inverse Fourier transforms the light is focused by a condenser onto the object, then diffracted, then collected by an objective, and finally the image is taken by a video camera and seen on a screen. The form of the object is seen as an intensity pattern that is a flat distribution of the optical density, because the phases of the waves forming the image are lost. A holographic technique, which always uses an interference of scattered rays with a reference beam having a known phase, allows the restoration of a volume image of the object. 

All optical microscope lenses are corrected for chromatic and spherical aberration and will give... 

When illuminated, the TLCs reflect the light in a special way an opalescent color play occurs, strongly dependent on temperature. These light reflections, a narrow band of wavelengths, can be recorded with the usual color cameras and microscopic lenses. With a special calibration technique the RGB information of the color images is converted into the scalar hue-value and from that into a temperature value for each pixel of the frame. Thus, it is possible to determine entire temperature fields with high spatial resolution. 

All optical microscope lenses are corrected for chromatic and spherical aberration and will give a resolution close to the diffraction limit described above. Table 3.2 shows the diffraction limit for typical high and low power objective lenses. 

Microscope lenses Microscope lenses are complex assemblies that are designed to balance the requirements for magnification, focal length, and light collection with various factors that degrade image fidelity (note that the optics in Figure 2 are... 

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