Discussion

Exercise 7. Work in pairs or in small groups. Share in the discussion. Use the following questions as prompts:

1) What is a laser rangefinder?

2) Could you describe the most common principle of its work?

3) What conditions are necessary to range any object within a few millimeters?

4) Could you name the effects to be taken into account concerning the work of a laser rangefinder?

5) Could you give the characteristic to the time-of-flight technology?

6) What is the advantage of a laser rangefinder as compared to any stereoscopic methods?

7) How can a laser rangefinder be used in forestry? And in sports?

8) Why can we consider a tape measure an out-of-date and inconvenient tool nowadays?

Lesson 2 all the truth about microscopes

Lexical units:

scanning probe microscope – сканирующий зондовый микроскоп

to magnify – увеличивать с помощью микроскопа

magnification – увеличение

transmitted light – проходящий свет

condenser lens – конденсорная линза

eyepiece – окуляр

objective turret – турель объектива

stage – предметный столик

focus wheel – винт микроскопа

comparison microscope – сравнительный микроскоп

inverted microscope – инвертированный микроскоп

to be a household name – быть на слухý

in essence – по сути

transillumination – трансиллюминация, просвечивание

incident light – падающий свет

charge-coupled device camera –

камера с зарядовой связью (для сканирования)

to omit – не включать, пропускать

specimen – образец

particle beam – пучок частиц

resolving power – разрешающая способность

failure analysis – анализ отказов/повреждений

raster scan – растровое сканирование

piezoelectric actuator – пьезоэлектрический регулятор

TEXT

A microscope is an instrument to see objects too small for the naked eye. Thereafter, the science of investigating small objects using such an instrument is called microscopy.

Of course, you may guess that there are many types of microscopes. The most common and first to be invented (in 1590) is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope and the scanning probe microscope.

The optical microscope, often referred to as the "light microscope," uses visible light and a system of lenses to magnify images of small samples. Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast. Historically optical microscopes were easy to develop and are popular because they use visible light, so the sample can be directly observed by eye.

All modern optical microscopes designed for viewing samples by transmitted light share the same basic components of the light path, listed here in the order the light travels through them: 1) light source, usually a mirror; 2) diaphragm and condenser lens; 3) objective; 4) ocular lens (eyepiece). In addition the vast majority of microscopes have the same structural components: objective turret to hold multiple objective lenses, stage to hold the sample, and focus wheel to move the stage.

There are many variants of the basic compound optical microscope design for specialized purposes. Some of these are stereo microscope, comparison microscope, inverted microscope, etc. But we’d better pay attention to the USB microscope and to the digital microscope as they are now household names just everywhere.

A USB microscope is a low-powered digital microscope which is connected to a computer, normally via a USB port. They are widely commercially available. In essence, USB microscopes are a webcam with a high-powered macro lens and generally do not use transillumination but rely on incident light instead. As the camera attaches directly to the USB port of a computer, eyepieces are not required and the images are shown directly on the monitor. They offer modest magnifications (up to about 200×) without the need to use eyepieces at very low cost, although lack of illumination optics limits their use. USB microscopes are most useful when examining flat objects such as coins or banknotes. They can be used even in the field, attached to a laptop computer.

A digital microscope is a variation of a traditional optical microscope that uses optics and a charge-coupled device (CCD) camera to output a digital image to a monitor, sometimes by means of software running on a computer. A digital microscope differs from an optical microscope in that there is no provision to observe the sample directly through an eyepiece. Since the optical image is projected directly on the CCD camera, the entire system is designed for the monitor image. The optics for the human eye are omitted.

An electron microscope is a type of microscope that produces an electronically-magnified image of a specimen for detailed observation. The electron microscope uses a particle beam of electrons to illuminate the specimen and create a magnified image of it. The microscope has a greater resolving power than an optical microscope, because it uses electrons that have wavelengths about 100,000 times shorter than visible light (photons), and can achieve magnifications of up to 2,000,000x, whereas light microscopes are limited to 2,000x magnification. Industrially, the electron microscope is primarily used for quality control and failure analysis in semiconductor device fabrication.

With the use of scanning probe microscopes, an image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen. The resolution varies somewhat from technique to technique, but some probe techniques reach a rather impressive atomic resolution. They owe this largely to the ability of piezoelectric actuators to execute motions with accuracy at the atomic level.