Nanometre resolution confocal sensors

Confocal sensor

Large working distances are offered with a new range of high precision nanometre resolution confocal chromatic sensors.

Micro-Epsilon has launched a range of high precision confocal chromatic sensors for displacement, distance, position and thickness measurement. The compact sensors offer better linearity, nanometre resolution and a large offset/working distance of up to 220mm.

With a compact footprint and a small measuring spot size (6 to 60µm diameter), the new confocalDT IFS2405 series of confocal sensors are ideal for high accuracy distance measurements on reflecting or transparent surfaces, as well as one-sided thickness measurement of transparent film, plates or layers. 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, mirrors and glass production, medical devices and R&D laboratory projects.

Larger working distance

The latest addition to the confocalDT IFS2405 series is the confocalDT IFS2405-28, a confocal sensor with a diameter of just 62mm and a long measuring range of 28mm. This sensor offers a larger offset (working) distance from the target of up to 220mm. The sensor is therefore ideal when a large working distance from the measurement object is required, for example, when measuring hot surfaces. The IFS2405-28 has better linearity, a smaller tilt error and higher intensity than its predecessor, the IFS2400-24.

Controller and interface options

IFS2405 sensors are offered alongside the new confocalDT IFC2471 controller from Micro-Epsilon. This controller is currently the fastest available in the world, achieving measurement rates of up to 70kHz on highly reflective surfaces. 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.

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 focused 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 IFS2405 series offers measuring ranges of 0.3mm up to 30mm, with maximum resolution of 0.01µm (0.006% F.S.O.) and maximum linearity of 0.30µm (+/- 0.025% F.S.O.).

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