High performance confocal chromatic sensors

| Information and Communication Technology

Compact confocal sensors

A new range of sensors has been introduced using a compact footprint using the confocal chromatic principle for thickness measurements.

Precision sensor manufacturer Micro-Epsilon has launched a series of high performing yet compact confocal chromatic sensors. Typically, for high performance confocal sensor measurements, a large optical sensor head is required. However, the new confocal IFS2406 sensors are almost 60% smaller, enabling simpler integration into restricted spaces.

The performance of the confocal IFS2406 series is almost as high as the IFS2405 range of sensors, yet has a much more compact sensor footprint and a small measuring spot size, making it ideal for high accuracy distance measurements on reflecting or transparent surfaces, as well as one-sided thickness measurement of transparent film, plates or layers. The sensors are also suitable for vacuum applications in semiconductor and microelectronics production. As well as distance measurements on highly reflective, shiny surfaces, the sensors can also be used to measure on dark, diffuse materials. Typical applications include displays and glass production, medical devices and R&D laboratory projects.

Confocal measuring principle

The confocal chromatic measuring principle works by focusing polychromatic white light onto the target surface using a multi-lens optical system. The lenses are arranged in such a way that the white light is dispersed into a monochromatic light by controlled chromatic deviation (aberration). A certain deviation (specific distance) is assigned to each wavelength by a factory calibration. Only the wavelength that is exactly focussed on the target surface or material is used for the measurement. This light reflected from the target surface is passed through a confocal aperture onto a spectrometer, which detects and processes the spectral changes. Both diffuse and specular surfaces can be measured using the confocal chromatic principle.

Confocal measurement offers nanometre resolutions and operates almost independently of the target material. A very small, constant spot size through the measurement range of the sensor is achieved. Radial and axial confocal versions are available for measuring the internal surfaces of drilled or bored holes, as well as the measurement of narrow apertures, small gaps and cavities. The IFS2406 series offers measuring ranges of 2.5mm and 10mm, with maximum resolution of 0.024µm (0.001% FSO) and maximum linearity of 0.75µm (+/- 0.03% FSO).

Controller and interface options

IFS2406 sensors can be used with the confocalDT measurement system from Micro-Epsilon. This controller is currently the fastest available in the world, achieving measurement rates of 10kHz using an LED light source and 70kHz using a Xenon light source. A wide range of confocal sensors can be used with the controller and various interface options are available including Ethernet, EtherCAT, RS422 and analogue output. Measurement channels can be set up and configured via an intuitive web browser interface, which means there is no need to install any separate software.

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