Optical metrology

Triangulation

Measurement of range by determining the angles between sensor, illumination and object. Example of triangulation techniques are stereo cameras, laser line triangulation, projected patterns and photogrammetry.

 

Stereo cameras

Using two cameras and by identifying disparities between the two images calculating the distance to the object.

 

Laser line triangulation

Illuminating an object with a laser line and observing it from an angle. The distance to and shape of the object can then be determined from the perceived deformation of the laser line.

 

Projected patterns

By projecting visible or infrared lines, squares or dots on the object and decoding images captured from an angle the 3D shape/range can be calculated.

 

Time-of-Flight

Time-of-flight (ToF) is a family of techniques where the time it takes for the light to travel a distance is measured, which can then be used to calculate the distance or other quantities.

 

Interferometry

A set of techniques that utilizes the wave nature of light and that a super position of two coherent light beams cause constructive or destructive interference. Interferometry can be used to very precisely measure distances, vibrations, movements, deformations, pressure change, etc.

 

Digital Holography

An technique based on interferometry where a hologram is recorded by a digital camera. The hologram can then be used to in software refocus the image or to extract shape or changes in refractive index.

 

Photometry/Radiometry

Measurement of light and quantities like e.g. luminance and illuminance, which for example is important when designing different types of illuminations or signal lights.

 

Photometric Stereo

Calculation of the surface slope by measurement of the light reflected from an object. Using a camera and illumination from two or more directions and calculating the surface slope by measuring the scattered light.

 

Spectroscopy

A family of techniques that uses the spectra of light and different wavelength to determine physical and chemical properties of an object.

 

Plenoptic cameras

By placing an array of small lenses in front of a camera sensor both the direction and the intensity of the light can be recorded. This gives the possibility to in software refocus or measure the distance to an object.