The Elwi-Ger 3000 makes it easy to measure, adjust and record the results. © IDS

It sees a crosshair or a vignetted illuminated area, i.e. with shading towards the edge of the image, in monochrome LED light. These result mathematically from the correlation function of two circular areas of the same diameter. The latter, in turn, are created during autocollimation, as mentioned above, by reflection of the emitted light cone on a distant mirror.

The intensity distribution in the image or on the camera results in a regular circular cone, whereby several so-called V-SPOTs can also be visible in various applications. The precise position of the V-SPOTs is calculated with sub-pixel accuracy (< 1/50 pixel peak-to-valley and 1/100 deviation from the root mean square). Based on this, corresponding angles are determined in up to three dimensions (degrees of freedom) and simultaneously up to three degrees of positional freedom.

Thanks to the patented vignetting method, Hofbauer is the only company in the world capable of overcoming the problems of the classic autocollimation method and measuring lengths of over 100 meters even at extremely large angles (1,000 seconds = 17 millimeters per meter) with angular second accuracy and evaluating them using the tilt method.

Two possible measuring methods
Two possible measuring methods are available to the user: With the inclination method, a measuring mirror on a mirror base or on the guide carriage of a linear guide is moved over the test specimen in equal steps and the change in inclination is measured. The straightness is determined and displayed by summing (integrating) the height differences determined from the partial sections. This method achieves the highest accuracy with the lowest measurement uncertainty.

Alternatively, depending on the application, the height method can also be used for measurement. In this case, the reflector is also attached to a suitable base or to the linear slide or the moving axis (machine table, traverse) and can be positioned anywhere on the path. The deviation from the ideal straight line (optical axis) is measured and displayed immediately and directly. The advantage here is that adjustment processes can be carried out directly.

Camera models
The Elwimat-Ger 3000 contains one industrial camera from the uEye camera family, depending on the customer application. There is a choice of different models with GigE or USB 3.1 Gen 1 interface, as a board level version or with housing. Whether a cost-effective project camera or a compact powerhouse, all models are quality-tested and pre-calibrated. With the IDS software and Plug & Play, they can be integrated quickly and are therefore particularly economical.

The UI-3272LE-M-VU is mounted on the central element of the sensor. © IDS

Specifically, the UI-3272LE-M-VU, a cost-effective and versatile project camera from the uEye LE USB 3.1 Gen 1 series with a torsion-proof USB Type-C connection, is used. USB Power Delivery makes it possible to offer a variable peripheral power supply at the I/O port. It is equipped with the Sony IMX265 area sensor - one of the best image sensors in the 3 MP pixel class. The 1/1.8" size of the global shutter CMOS sensor provides a choice of suitable lenses. The industrial camera delivers frame rates of up to 57 fps at full resolution (3.2 MP: 2056 x 1542 px) and 80 fps at Full HD resolution. The USB 3.1 Gen 1 camera is therefore suitable for visualization tasks in machine vision applications. The board level variants are available with upright (-VU) - as in the Elwimat - or horizontal USB Type-C orientation and also have a ten-pin I/O SMD connector for GPIO, trigger and flash.

With the fast USB 3.1 Gen 1 technology, the data transfer rate could be increased from 480 MBit/s to five GBit/s, with the same or longer cable length. The measurement frequency in full screen mode increased by a factor of five from just under twelve frames per second to 57 fps. For special applications in vibration and frequency analysis, the clock rates can be extended into the KHz range using AOI technology as well as subsampling and binning methods.

Software
Hofbauer uses the IDS Software Development Kit to integrate the industrial camera into its system. "With the IDS SDK, we have the advantage of a standardized programming interface for all IDS cameras. Programming is therefore independent of the model connection, regardless of whether it is USB 2, USB 3.1 Gen 1 or GigE," explains Dr. Hofbauer, adding: "New camera models are also supported without any software changes. This fits in with our goal of reconciling the highest demands on measurement technology with user-friendly operability." Another reason for using the IDS software was the simple use of additional functions such as EEPROM and GPIOs. The SDK is compatible with Windows and Linux.

Outlook
Straightness and alignment are essential in mechanical and plant engineering. The Elwi-Ger 3000 makes it easy to measure, adjust and record the results for different applications. It does not miss even the smallest changes in angle. In contrast to the competition, it achieves measuring lengths of over 100 meters with an accuracy in straightness measurement of 0.5 micrometers per meter, i.e. 0.05 millimeters at 100 meters measuring distance. The flexible and mobile usability as well as the extensive range of accessories provide additional customer benefits. as