Although the Charge-Coupled Device (CCD) imaging chip is the standard in today's video and digital cameras, things may change during the coming year. The CCD chip is being challenged by a competing device, the CMOS ("C-moss") chip.

CMOS is the most widely used type of integrated circuit for memory and digital processing, virtually everything in computers is CMOS based. The economies of scale and production of CMOS devices are the main reasons why computer prices have continued to drop during the past few years. If a device or an instrument has a microprocessor in it, chances are it includes CMOS technology..

Confocal microscopy is a collection of optical techniques that are applied in a variety of hardware configurations. Design strategies for the application of these techniques have generally used laser light (Pawley, 1990). In most laboratories, basic research use has employed laser light in conjunction with a fluorescent substrate to generate an optical signal, either through direct application of a fluorescent material to cells or by the stimulation of a chromophore associated with an antibody which will identify a cellular protein under some specified experimental conditions, The use of confocal microscopy in this type of situation generally requires a standard research microscope, and the tissue may be situated on a slide or other type of container that will provide a stable, controlled environment.

Driven by the analytical needs of microelectronics, magnetic media and micro-fabrication industries, focused ion beam (FIB) systems are now capable of milling and manipulating samples for the analysis of microstructure features having dimensions of 180 nm or less, A technique for locating and extracting site specific specimens for examination by transmission electron microscopy (TEM) has been developed. An identified feature can be located and precisely milled with an FIB system from two sides to prepare an ultrathin sample, and then extracted from the region with a glass rod micromanipulator onto a grid for TEM analysis. This specimen preparation method has been applied to semiconductor failure analysis and to the study of metallic and ceramic microsiructures with irregular topographies and complex mufti-layered components.

Now you would probably think that I was joking if I were to tell you that there are microscopes made of precious metals, such as silver, rather than brass, and objectives made with diamonds and rubies, rather than glass. But yes, Virginia, prodigal items such as these do actually exist - and not at the end of the rainbow. All right, suppose they do exist, who could afford one? Well, kings for one, Figure 1 shows what is perhaps the most elaborately decorated microscope ever constructed. It was made in 1761 by the wellknown instrument maker George Adams for King George III. George III placed great value on science throughout his long reign, as reflected in his collection of scientific instruments, which can be seen today in the Science Museum at South Kensington in London.

In Medieval Europe, manuscripts and formulas on the preparation of colors and dyes used by chemists and artists contained many references to natural plant extracts, The yellow stigmas of aromatic saffron (Crocus sativus) were crushed and used both as a medicine and colorant as far back as the ninth century BCE. In 1437 CE, a manual was written by Cennini, II Libro del Arte, a collection of recipes on the preparation of tempera and block-printing inks from saffron and brazilwood (Caesalpinia echinata), Finely divided brazil wood was prepared by scraping sticks with a knife.

Recently, a question surfaced on the Microscopy list server regarding preparation of insect eggs for EM evaluation. While the electron microscopy approach involved considerable sample preparation (mounting, coating, etc.), our experience indicated that, for some of these applications, a combination of reflected and fluorescent confocal microscopy provided valuable information with little or no sample preparation required, provided there are not other considerations such as the extended resolution provided by electron microscopy.

In the biological arena, most confocal work is done in fluorescence mode, There have been some forays into imaging silver-stained structures using reflected light confocal but those applications have not been very prevalent in the literature. With the judicious addition of a quarter wave plate (a polarizing accessory) in the light path, the disruptive artifact from the laser beam can be removed from the image, converting any confocal into a dual purpose instrument.

In the course of both physical and failure analysis of semiconductor chips (i.e., verifying what you actually deposited as a layer, vs, what caused the circuit to fail), it is essential to have appropriate deprocessing tools at your disposal in order to evaluate complex semiconductor structures, Deprocessing techniques are developed for each product manufactured and involve multi-step procedures that reveal the layer-by-layer secrets of the chip, These techniques require constant tweaking in duration and procedure as the manufacturing process imposes changes and as the architecture of the semiconductor changes. While there are many tools that assist in these analytical pursuits, such as RIE (reactive ion etching - a dry etching technique), ion milling, and microcleaving, the wet chemical etching of tungsten is sometimes more reproducible than RIE techniques.

In scanning microscopes, like the Atomic Force Microscope (AFM), used in contact mode, scanning begins with engaging the tip with the sample at some contact force, which can be adjusted by the setpoint* (this is common to Digital Instruments' AFMs). It may differ for other brands. For a system that detects the motion of the cantilever with a laser beam, the setpoint basically gives an idea of the voltage difference between the top and bottom photo detectors, When the tip comes into contact, the feedback circuit adjusts the tip deflection according to the required contact force, This is the method commonly followed for the constant deflection method.

Learning how to operate the microscope has dominated the TEMteaching process in a way that is perhaps unparalleled by any other common scientific instrument. The TEM column is so complex that the arcane aspects of its manual manipulation become the main points to be learned by the student, rather than the use of the instrument to solve materials problems. In other words, command of the instrument often becomes an end in itself. Such an approach would preach that it is better to be able to produce a striking CDF image that is well aligned and focused than it is to be able to interpret that image in terms of the materials processing responsible for the microstructure!

Today, charge coupled devices (CCDs) have become the de-facto standard for scientific imaging, In fact, their potential for high resolution, sensitivity, wide dynamic range and low noise has made them the device of choice for most fluorescent microscopy imaging applications, This is especially true for quantitative microscopy applications such as ratio imaging, fluorescent in-situ hybridization and image deconvolution.

However, choosing the most appropriate CCD camera for each application can be quite challenging given the broad range of features and performance specifications. This month's article focuses on a single characteristic of the CCD: the chip grade.

A perennial favorite debate among TEM users is which side of the grid to use, the dull side or the shiny side. This question popped up again on the Microscopy tistserver, and received several welt-informed replies, tn the past, the answer has typically been "whichever works" or "Welt, I learned it this way". Now opinion seems to be leaning towards a particular side. Read on for the answers

From John Bozzola, Director, Center for Electron Microscopy, Southern Illinois University:

This is a good basic question - one that many microscopists have asked when coating grids with various plastic substrates.