Unknown part heights can automatically be detected by autofocussing on its underside. The nozzle will servo up and down to find the optimum.

As a pre-requisite, the Part Dimensions must be defined on each nozzle tip (Configuration tab). Both the Max. Part Diameter and Max. Part Height are used to determine the autofocus range and sensitive area.

To enable the auto focus on the camera, select the Focus Sensing Method. It is only available on up-looking cameras:

Once you press Apply, a new Auto Focus tab appears:

Focal Resolution determines the maximum step size for the Auto Focus servo.

Averages Frames lets you run the autofocus for multiple frames and average the results. This will improve the accuracy by effectively averaging out image noise etc.

Focus Speed sets the relative motion speed for the focus stepping.

Show Diagnostics? switches on auto focus edge highlighting and status info in the camera view.

Last Focus Distance indicates the last live or test focus distance measured. If there is a part on the nozzle, this is the part height.

Press the button to test the auto focus.

The auto focus can help you calibrate the precise up-looking camera Z position. This will make sure your bottom vision happens at optimum distance.

CAUTION: this procedure will change the subject to camera distance, which will change the scale of subjects. You will need to readjust the Units per Pixel after performing it.

1. Use a Z calibrated nozzle tip with no part on.
2. Auto focus it, using the button in the Auto Focus camera tab. .
3. Press the Adjust Camera Z button to set the camera Z Position to the detected distance.
4. Go to the General Configuration tab to adjust Units per Pixel.

Whenever Alignment (a.k.a. Bottom Vision) encounters a part with unknown part height, it will employ the auto focus. The detected part height is then stored on the part. This will take some additional time (but hardly longer than manually measuring and entering the data). All subsequent vision and placement operations will reuse the height directly, with no further speed penalty incurred.

The job processor knows when a camera has auto focus capability and bottom vision is enabled for the part. It will then allow starting a Job with unknown part heights. As an alternative, part heights can also be auto-learned using a ContactProbeNozzle. Note that when bottom vision is enabled for the part, either auto focus needs to be enabled for the up-looking camera or the part heights need to be entered manually, even when a ContactProbeNozzle is available. This is because bottom vision requires the component height to be known, and contact probing with the nozzle only happens after that when the component is placed on the PCB.