Project 029 – Inventing new measurement equipment

Creation of new opto-electronic measurement equipment

This equipment was developed from the ground up to determine the field-of-view and spatial sensitivity of passive infrared motion detectors.

Not seldom there are large differences between the specifications and the actual view properties of passive infrared (PIR) motion detectors. With the equipment shown here, you can analyse the actual performance of such detectors. The analysis can be done on all types of detectors: indoor, outdoor, wall, ceiling and more.

This opto-electronic lens meter measures not just the individual parts such as the lens or the sensor, but the complete long-wave infrared optical system of these detectors, including the pyroelectric sensors, (Fresnel) lenses and mirrors.

To perform the measurement, one can move a heat source around a PIR detector and measure the detector (sensor) output signal as it changes. This output signal change can be measured for the whole view of the detector. From the combined responses of all angles a digital 3D beam pattern model can be composed. Because this model is not the result of a simulation but includes the complete electro-optical system, it reflects the device's true performance. For example, the performance of a segmented Fresnel lens strongly depends on its the rotation angle in respect to the pyroelectric sensor.

The shape of the beam pattern stays valid even after changing the signal processing electronics for lower cost, different range or better performance.

The advantages:

• Check if your injection mold results match your simulations;
• Use the 3D beam pattern models in CAD programs to compare the part design specifications with their actual performance;
• Use the 3D beam pattern models to choose between different available pyroelectric sensor types and different lenses, for example to match the desired coverage area for a particular application;
• Save time on walk-tests by using the sensitivity plots to determine the detection zones and the focal length of a lens;
• Use the measurement data inside electronic simulation software to watch the signal response of your detector as it reacts to different object sizes, shapes and speeds;
• Use the 3D beam pattern model for use in building design software to find the optimal location for the detectors to make sure no burglars can sneak by;
• Use the sensitivity information to optimize individual components such as pyroelectric sensors, (Fresnel) lenses, mirrors and optical filters;
• Determine the horizontal angle of view;
• Determine the optimum installation height;
• See how the device performance drops as the lens material weathers and ages.

The equipment was used by Pirlabs to perform the various measurements for clients worldwide.

You can download a PDF example measurement report here.

You can view a 3D interactive beam pattern here.