Lecture 1 Flashcards
(34 cards)
What are the key characteristics of laser measurement technology?
Non-contact measurement, high flexibility, high measuring speed, high precision.
What triggered the evolution of optical measurement techniques?
Inventions like the microscope (16th century), telescope (17th century), and later, photography and spectroscopy.
Why is laser measurement favored in manufacturing?
It enables real-time, non-contact, inline measurements for process and quality control.
What are the three main components of a laser measuring system?
Laser, measuring object, detector.
What elements are used between the components to guide the beam?
Focusing optics, beam expanders, and optical fibers.
What is the principle behind interferometry?
Superposition of light waves traveling different paths to measure path difference via resulting irradiance.
What is the key advantage of interferometry?
It can measure path differences with accuracy less than half a wavelength.
What does the principle of superposition state?
Multiple light waves can overlap without disturbing each other.
What does irradiance represent in a light wave?
Time-averaged square of amplitude, linked to the Poynting vector.
Why is complex notation used in interferometry?
Simplifies vector addition and calculation.
What are the two main types of laser interferometers?
Polarization interferometers and dual-frequency interferometers.
What type of laser is used in polarization interferometers?
Helium-Neon (HeNe) laser.
What component converts linear polarization to circular?
Quarter-wave plate.
How is displacement direction identified?
By the rotational direction of signals on an oscilloscope in X-Y mode.
What physical phenomenon causes dual frequencies in lasers?
Zeeman effect.
What does the Doppler effect influence in this setup?
The beat frequency at the detector, reflecting movement.
What does the counter difference indicate?
Displacement in quarter-wavelength steps and direction of movement.
What laser is typically used and why?
HeNe laser – good beam quality, stable wavelength, long life.
What factors affect the refractive index of air?
Temperature, pressure, humidity, and presence of gases.
What is the parameter method?
Measuring environmental conditions along the beam path to adjust wavelength.
What limits the measuring range of interferometers?
Coherence length of the laser.
What is the dominant source of measurement error?
Environmental effects on air refractive index.
What is the typical resolution of a HeNe laser interferometer?
150–300 nm, down to 1 nm with interpolation.
How are angular displacements measured?
By detecting the relative displacement of two retroreflectors.
