Photoneo is a manufacturer of industrial 3D scanners. Its PhoXi scanners and MotionCam-3D cameras are used wherever an accurate 3D image is needed: for robots locating parts, for shape measurement and for product inspection. We work with both families and use them together with industrial robots. This article explains how they differ and when to choose which.
How Photoneo scanners work
Both families are based on structured light. The scanner projects a pattern onto the object, a camera observes how the pattern is distorted by the surface, and depth is calculated from that. The result is a point cloud with the precise position of every point, plus a 2D image. For a general comparison of 3D technologies, see 3D machine vision in industry.
The key difference is sensitivity to motion. Classic structured light, as used by PhoXi, is sensitive to motion, so the object has to stay still during the scan. MotionCam-3D uses what the manufacturer calls "parallel structured light" and a special mosaic-shutter CMOS sensor, so it can also scan moving objects.
PhoXi: for static objects where accuracy comes first
PhoXi scanners are designed for stationary objects when maximum accuracy and resolution are needed. According to the manufacturer, the PhoXi 3D Scanner M offers:
- a scanning range of approx. 458-1118 mm;
- up to 3.2 million points per scan;
- calibration accuracy of approx. 0.1 mm (1 sigma);
- a scanning time of 250-2500 ms.
According to the manufacturer, the accuracy of the PhoXi family as a whole ranges from 25 to 500 µm, depending on the model.
PhoXi is a good fit when:
- the part is stationary during the scan - in a bin, on a table or on a pallet;
- high accuracy is needed for measurement or shape inspection;
- a robot is looking for parts in a random pile and needs a precise pick point;
- a few hundred milliseconds or a few seconds of scanning does not limit the cycle.
MotionCam-3D: for moving objects
MotionCam-3D is designed for cases where classic structured light falls short - when the object is moving. According to the manufacturer:
- it scans moving objects - the manufacturer states up to 40 m/s without motion blur;
- resolution of up to approx. 2 Mpx;
- approx. 20 frames per second (depending on the model).
MotionCam-3D is a good fit when:
- parts travel on a conveyor and cannot be stopped;
- the scanner is mounted on a moving robot and scans while it moves;
- you need a continuous stream of 3D images rather than individual scans.
A simple rule: if the object can be stopped and accuracy matters most, choose PhoXi; if the object or the scanner is moving, choose MotionCam-3D. If you need to cover a large scene and millimetre or centimetre accuracy is enough, consider ToF 3D cameras.
How we use Photoneo scanners with robots
Hand-eye calibration
For a robot to use the scanner data, hand-eye calibration is carried out: it establishes the exact position of the scanner relative to the robot. A point found by the scanner can then be converted into robot coordinates. This step decides whether the scanner's high accuracy actually turns into accurate robot motion, so we always verify the calibration separately.
The robot points the scanner
The scanner can be mounted above the work area or carried by the robot. In the second case the robot itself points the scanner where it is needed, can scan the object from several sides and choose an angle at which the important surfaces are visible. Scans from several poses are merged into a single point cloud.
This approach is especially useful for shiny metal parts. We scan shiny surfaces without matting spray - we describe how in 3D scanning of shiny surfaces.
Trials on our own equipment
We have our own KUKA KR 60-3 and Yaskawa Motoman MH5F robots for testing, so a solution can be tried out before it is installed at the customer's site. We integrate KUKA, Yaskawa Motoman and FAIRINO robots.
What to consider before choosing a scanner
- Working volume. This determines the model: a scanner that is too large for a small part will give lower accuracy, while one that is too small will not cover the whole area.
- Whether the object moves. This is the main criterion for choosing between PhoXi and MotionCam-3D.
- Cycle time. Scanning, processing and robot motion all have to fit into the production cycle.
- Surface. Shiny, dark or transparent surfaces need additional measures.
Try it on your own parts
Datasheets show what is possible, but only a trial shows the real result. We start vision projects with a trial on your real parts, so that before any larger investment you can see what the scanner actually sees. More under machine vision services; to discuss the details, use our contact page.