Miniature confocal sensor measures parts other sensors cannot

Miniature confocal sensor measures parts other sensors cannot reach

A world first in optical sensor miniaturisation has been launched by Micro-Epsilon.

Renowned as a leader in the field of both optical sensor technology and sensor miniaturisation, Micro-Epsilon’s new range of miniature confocal displacement measurement sensors have a diameter of just 4mm (standard sensor diameters are 27mm) and are therefore ideal for measuring inside confined spaces such as narrow cavities, drilled holes and bores.

As well as axial measurement, the new range of sensors also includes a 90-degree version, which enables the user to measure (radially) the inner surfaces of small components. The sensor head can be rotated inside the bore, enabling the user to measure surface defects inside and to check the concentricity or roundness of a bore or drilled hole.

Other potential applications include the checking of liquid fill levels in medical test tube racks and trays; inspecting drilled holes and recesses; measuring grooves inside pipes; measuring the thickness of any transparent material, including glass and film; mirrored or highly reflective surfaces (which are difficult to measure with laser sensors) can be measured easily and with very high stability.

The sensor is targeted at a range of industry sectors, including medical, biotechnology, pharmaceuticals, aerospace component inspection, electronics components and PCB measurement, machine gauging/inspection and general engineering.

The new ‘optoNCDT 2402’ range of sensors, developed and manufactured by Micro-Epsilon, is a confocal miniature displacement sensor based on the company’s unique, patented lens design. Manufactured using Micro-Epsilon’s own special optical production technology, the sensor is currently the smallest diameter confocal displacement sensor available on the market.

At a measuring range of 1.5mm, the sensor has a resolution of 0.06mm at 0.004% FSO (full scale output). Measuring rate is from 30Hz up to 30kHz and operating temperature is from 10°C up to 50°C.

Designed with a titanium housing, the ‘optoNCDT 2402’ sensor weighs just 50g and so is ideal for machine builders and design engineers that require a lightweight, miniature displacement sensor for their application. The sensor head comprises precision optical parts without any electrical components that enable very high stability not possible with other laser optical devices.

Micro-Epsilon’s complete measurement system consists of a sensor, an optical cable and a controller. Up to six different sensors can be factory-calibrated for one corresponding controller.

The ‘optoNCDT2402’ sensor is the latest product in Micro-Epsilon’s ‘optoNCDT 2400’ range of confocal displacement sensors. All sensors in the range have no moving parts and can therefore be considered wear-free. The sensors work on the confocal measurement principle.

The confocal measurement principle

Polychromatic white light is focused onto the target surface by a multi-lens optical system. The lenses are arranged such that the white light is dispersed into a monochromatic light by controlled chromatic aberration. A specific distance is assigned to each wavelength by factory calibration. Only the wavelength that is exactly focused on the target 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.

The spot size of the device is very small, in the region of 7-10 microns, depending upon measurement range, and is always constant in diameter. This unique measuring principle enables displacements and distances to be measured with high precision and exact spatial resolution. Both diffuse and specular surfaces can be measured. With transparent materials such as glass, a one-sided thickness measurement can be achieved along with the distance measurement. Shadowing is also avoided because the emitter and receiver are arranged in one axis.

The white light technology also gives greater stability than laser-based technologies against shiny metal, transparent and mirrored surfaces.

For more information on Micro-Epsilon’s range of confocal displacement sensors, call the marketing department on 0151 260 9800 or email: info@micro-epsilon.co.uk

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