The objective lens is a single element glass lens with one aspheric replicated surface and one flat surface. The manufacture of the aspheric surface by means of replication is suitable for high quality mass-production.

In this paper an overview is given of the PCVD process as applied for the large scale production of optical fibres for telecommunication. The specific merits and potentials. of the process, such as the profile independent high deposition rate and excellent controllability are discribed. The current state of the art of the process, as it is used in the Eindhoven production unit, is a deposition rate of 1 g/min., a preform size equivalent to 28 km of fibre and a drawing speed of 4 m/s. Fibre characteristics are well within the requirements imposed by the telecommunication market. The PCVD process has also proven to be suited for the production of dispersion flattened singlemode fibres and high NA graded index fibres for short distance applications. For both fibre types the high refractive index differences obtained with fluorine doping are exploited. Depending upon the market demands all fibre types can be manufactured at the same productivity. Some trends are given towards further increase of productivity and reduction of fibre costs.

An inexpensive device which enables Scanning Optical Microscopy to be undertaken in an SEM is described. This equipment (SOMSEM) is outlined, and its use is demonstrated by the presentation of results obtained by both O.B.I.C. and Reflective imaging modes.

A frequency response technique for measuring carrier and trap lifetimes in semiconductors has been developed for use with a scanning laser microscope. Electron-hole pairs are excited in the semiconductor specimen using a square-wave modulated focused laser beam. A vector lock-in amplifier measures the real and quadrature components of the induced photoresponse as a function of frequency. This frequency domain data is corrected to remove the square wave modulation harmonic effects, and Fourier transformed into time domain data to produce the time domain transient decay curve; this curve is then analyzed in the same way as the conventional transient photoresponse data resulting from a pulsed laser experiment. The spatial resolution obtained is two orders of magnitude better than previously obtained in pulsed laser experiments, and the increased signal-to-noise ratio achieved with a lock-in amplifier enables us to measure bulk lifetimes in crystalline semiconductors, or lifetimes near grain boundaries in polycrystalline semiconductors with extremely low sample bias and low laser intensity.

The use of scanning optical microscopy in the inspection and examination of electronic devices will be considered. In particular we will model the imaging of dislocations and defects present within a semiconductor via their influence on the reduction of the short circuit photocurrent as the laser beam of a scanning optical microscope scans over the device surface. The effects of parameters such as probe beam size, surface recombination velocity and minority carrier diffusion length will all be included. The predictions of the model will be compared with practically obtained results. We will also consider the various methods of measuring material parameters by optical beam scanning. Particular attention will be given to Schottky barrier devices from which the uncertainty in knowledge of surface recombinaton is removed. Analytical expressions will be presented for comparison with experimental data.

The confocal scanning optical microscope exploits three unique capabilities of a point probing light scanning system: differential phase contrast, confocal sectioning and optical beam induced current (OBIC) imaging. Applications of these capabilities in materials microscopy, semiconductor failure analysis and biological microscopy are described. The design considerations of the Lasersharp scanning confocal microscope are outlined.

This paper describes a technique in which an electrolyte solution is used to form a junction with the surface of a metal or semiconductor, and images are formed using phenomena stimulated by scanned illumination of the surface. Photocurrent images showing the spreading and then the breakdown of inhibitor films on copper, and images showing recombination centres, and other electronic features in the surface of gallium arsenide, are presented. The potential application of the method to the in-situ imaging of anodising and etching processes on semiconductors is described. In principle one may obtain information on the spatial distributions of donor density, surface state density and reaction kinetics, and surface film thickness.

This paper describes an optical system which separates an image into separate discrete scan lines. The system, combined with diffraction optics is the major component of an experimental color scanner using a single TDI CCD imager (ref. 1).

A CCD imager arrangement is employed as an optoelectrical transversal filter with the help of a specific image superposition method. It was proved experimentally, that in this way finite impulse response filters with several hundreds of coefficients at megahertz sampling rates can be realized.

Thermoacoustic imaging permits the detection of surface and subsurface inhomogeneities in solid samples. In the scanning transmission microscope the periodic heating of the sample is realized by a power modulated laser. The thermally induced elastic waves are detected, on the opposite face of the sample, by an heterodyne laser probe. The noncontact testing system is described and compared to the optical microscope. The images of defects in solid samples are presented.

We describe RASCALS* (RAster SCAn Laser System) a 2D and 3D scanning laser microscope and outline it's performance. This system, based on optical disk technology and a PC compatible computer offers an interesting cost/performance ratio compared to existing laser scanning microscopes.

Scanning Optical Microscopy, able to reconstruct, pixel after pixel, low noise images with the expected microscope resolution, is especially suitable for quantitative microscopy. Use of a bright, monochromatic spot of light extends its field of application to fluo-rescence Microscopy. Description of a typical device is given and the problems encountered to realize the scan of the laser beam are discussed. Results relating to transmitted light images as well as to epifluorescence images and spectral analysis are shown.

An X-ray sensitive detector of 1024 pixels for non-destructive testing is described. The detection pitch is 0.45 mm and the total sensitive length is 460 mm. In standard operation, the detector is in the path of an X-ray beam collimated with a 0.45 mm slit. The detector delivers a digital video signal as an object is displaced at constant speed through the X-ray beam. The image is displayed on a TV monitor using a frame memory. Each line is read in 7.8 ms. A 1024 x 512 pixels image is read in 4.4 s. The detector is an assembly of 16 arrays of 64 silicon photodiodes. A scintillating screen converts the X-ray flux into visible photons to which the silicon photodiodes are sensitive. The photodiode arrays are multiplexed by silicon Charge Transfer Devices. The functions of the detector are as follows : multiplexing of the 1024 pixels signals, analog to digital conversion and level compensations. The correction levels are stored in a digital memory. The main characteristics of the detector are as follows - energy detection range : 10 keV - 250 keV - nominal X-ray energy : 60 keV - noise equivalent X-ray dose : 5 X photons at 60 keV on the detector - saturation level : 300 p,11. at 60 keV - dynamic range : > 4000. Some applications of these detectors are given.

A serious disadvantage of most confocal optical scanning microscopes is that they use mechanical scanning methods, which lead to long frame times. Here we describe an off-axis CLSM in which scanning of the laser focal point is achieved with the aid of a fast acousto-optical deflector for line scanning, and a scanning mirror for frame scanning. This arrangement affords short frame-times of 0.05 seconds, and 0.02 seconds is within easy reach. A more or less three-dimensional image of the object can be built up at high speed by combining a number of confocal image sections. The system is suitable for reflection as well as fluorescence microscopy.

In this paper the combination of differential phase contrast microscopy and confocal microscopy is presented. When the energy from one half of the pupil of the collector lens is subtracted from the energy of the other half we get conventional differential phase contrast detection, a simple and powerful way to measure phase structures. One of the disadvantages of the conventional case is the fact that out-of-focus amplitude structures also give a large differential phase contrast signal. By focussing the light of both pupil halves onto point detectors we are able to combine differential phase contrast and confocal microscopy. We can therefore make use of the well known advantage of confocal microscopy, namely the insensitivity to objects out of focus, to reduce the crosstalk between signals due to out-of-focus objects and the signals due to in-focus phase objects. The confocal signal for amplitude structures can also easily be obtained. The real and imaginary parts of the optical transfer function for both confocal and conventional differential phase contrast detection are calculated for different degrees of defocus. The results clearly show the advantages of the confocal option. The implementation of this detection scheme in a scanning optical microscope and experimental results are presented.

Confocal imaging systems rely on the use of an accurately positioned axial point detector. We discuss in this paper the effects on the various confocal imaging modes of using a misaligned or finite sized detector. We show, in particular, that the axial resolution of the system is considerably less sensitive to detector size than is the lateral resolution.

Confocal laser microscopy extends the applicability of optical methods to sub-micron structure measurements. A beam scanning system developed by Heidelberg Instruments GmbH is presented. The contribution includes a detailed comparison between beam scanning and object scanning microscopes. A number of practical applications of the beam scanning system in the field of biology and integrated circuit metrology are presented.

A new type of real-time confocal scanning optical microscope, with the same measured resolution as a conventional confocal scanning optical microscope, is described. The system uses a rotating Nipkow disk with 150,000 pinholes etched in it, to yield a 640 frame/sec, 7000-line image. The transverse definition is of the order of 0.3 μm, and the 3 dB range resolution, with a 0.8 N.A. objective lens, is better than 0.75 μm.

Various first kind Fredholm integral equations, occurring in confocal scanning microscopy, are investigated and numerical methods for their solution are described.

Parallel processing allows super-resolution based on prolate spheroidal functions to be extended to two-dimensional systems where object and pupil differ in shape.

The depth-discriminating property of confocal laser microscope scanners can be used to record the three-dimensional structure of specimens. A number of thin sections (approx. 1 μm thick) can be recorded by a repeated process of image scanning and refocusing of the microscope. We have used a confocal microscope scanner in a number of feasibility studies to investigate its possibilities and limitations. It has proved to be well suited for examining fluorescent specimens with a complicated three-dimensional structure, such as nerve cells. It has also been used to study orchid seeds, as well as cell colonies, greatly facilitating evaluation of such specimens. Scanning of the specimens is performed by a focused laser beam that is deflected by rotating mirrors, and the reflected or fluorescent light from the specimen is detected. The specimen thus remains stationary during image scanning, and is only moved stepwise in the vertical direction for refocusing between successive sections. The scanned images consist of 256*256 or 512*512 pixels, each pixel containing 8 bits of data. After a scanning session a large number of digital images, representing consecutive sections of the specimen, are stored on a disk memory. In a typical case 200 such 256*256 images are stored. To display and process this information in a meaningful way requires both appropriate software and a powerful computer. The computer used is a 32-bits minicomputer equipped with an array processor (FPS 100). The necessary software was developed at our department.

Modern molecular biologists and in particular cell biologists have a large set of experimental tools at their disposal. Immunocytochemistry, fluorescence labels, and microscopy are only subsets of the entire spectrum of methods. Depending on the fields in which biologists work a lot of results are obtained with classical biochemistry, gel electrophoresis and blotting techniques. Gathering morphological data may not be the least important task, but will in many cases be considered only after all other methods have failed. With the advent of video microscopes and the availability of high speed image processing devices, microscopy can also be used for quantitation. Confocal scanning laser fluorescence microscopy (Ft-CSCM) [Cox 1984] is in fact another technique or method that is entering the rapidly developing field of quantitative microscopy. It is therefore very important to understand the physical properties of the CSCLM in detail and to compare a confocal microscope not only with other confocal microscopes, but also with all the other techniques and methods. The confocal microscope has to find its particular application and it should be understood that it will replace neither conventional microscopy, nor video microscopy, nor electron microscopy. It will not be used for every application and every type of investigation. The CSCM has to find its niche in the laboratories and this paper will present two applications in which it proves its usefulness.

A confocal scanning laser microscope of the on-axis type, directly coupled to an image processing system is described. Results of measurements of the actual response functions, both in fluorescence and reflection are presented. Applications of the confocal technique in the area of biology in combination with image processing are demonstrated.

A scanning laser microscope (SLM) has been constructed for use in imaging single living skeletal muscle fibers. The muscle fiber is kept alive and stimulated in a temperature-controlled chamber through which a nutrient solution flows. The fiber is attached at each end to force and displacement transducers which are in turn connected to electromagnetic (voice-coil type) linear motors. These motors scan the fiber in one axis (x-axis) and are also used to stretch and shorten the fiber during mechanical experiments. Each of the x-axis linear motors is in turn mounted on a micro-stepping motor which provides for rotation (r-axis) and twist of the muscle fiber. A laser beam is focused at a location within the fiber by high numerical aperture confocal optics which form one path of a mach-Zehnder interferometer. The position of the muscle fiber with respect to the laser beam may be further manipulated by two additional electromagnetic linear motors (y-and z-axis) to permit 3-linear and 1-rotary axis scanning. The scanning pattern is controlled by a Micro-VAX-II computer which is also used to sample the output of the photo-detector and the force and displacement transducers. A complex 3-D image is acquired and processed (e.g. SLM optical transfer function identification and deconvolution) on the VAX using NEXUS-plus a language for linear and nonlinear signal and system analysis.

Scanning electron acoustic microscopy (SEAM ) is an operation mode within scanning electron microscopy utilizing the sound or ultrasound generation within the sample due to the impact of a temporarily modulated electron beam current. This technique, which has already shown its large range of applicability in materials research and engineering, is now applied to medical research. Applications presented in this paper are shown for SEAM micrographs of human bone and brain.

Biomedical specimens can be considered as the most difficult type of samples for scanning acoustic microscopy, since modulation by structural properties is low, the coupling medium often cannot be heated up to improve its transmission properties, and small structural details call for high frequencies where the signal-to-noise ratio is low. A microscope developed at Ernst Leitz Wetzlar GmbH using state of the art technology to reduce these problems is described. Applicational examples are given proving both high resolution performance and high signal-to-noise ratio under critical conditions.

In XTH-2 cells (line derived from Xenopus laevis tadpole hearts) grown on glass, cyto-plasmic factors influencing acoustic impedance and attenuation were investigated using ultrasound of 1.6 GHz frequency. An overall correlation between the distribution of F-actin and zones with increased impedance is qualitatively assessed. Comparison of scanning acousto-microscope (SAM) images with those taken with a Mach-Zehnder type microinterferometer reveal a linear relationship between the amount of cytoplasmic mass penetrated by the sound waves, and sound attenuation. However, the attenuation coefficient for the cell periphery is considerably higher then that for the cell centre.

This paper reviews applications of wideband frequency modulation techniques to acoustic microscopy. The similarities and differences between chirped systems in which the waveform is recompressed with a matched filter and those in which non-linear mixing is used are discussed. Many of the considerations which determine the performance of the systems are presented.