HPI Metal Halide lamp Quality Inspection.

The HPI is a high pressure sodium lamp used for outdoor lighting e.g. street lamps but also for agriculture 'grow' lighting. These long life heavy duty industrial lamps are produced at a high quality level (quality level is a few ppm!). HPI-T_10 HPI lamp overview HPI 250MH4k lamp
These lamps are 100% inspected by one vision systems and several cameras.
Damaged cement lamp holder Lamp_Holder Cement Inspection  

J.A.I.M.S. also realised the 'Lamp Holder Cement Inspection'
system for this type of lamps.

Burner Philips_03
The burner inside the glass bulb is the most complex
and critical part of the whole lamp. On this page the most important inspection of this burner are briefly described. Of course several burner types can be measured, on this page a burner with and without an iqnite electrode is shown. Also of few panels of the user interface are shown.
    Electrode Chamber contour measurement.
    Compression joint, including the metal parts and the surface quality of the metal parts.
    User interfaces of the vision system.

Electrode chamber contour measurement

It's difficult to create always the correct electrode chamber contour within a few ppm's. This complex process depends on several parameters, so a 100% inspection is required.
Camera set up
For this inspection a telecentric lens a digital cameras and a diffuse back light is used.
To solve unwanted reflections at the measurement area on the glass, the shape of the back light matches roughly the contour of the burner. Once a good, accurate and reliable contour is realised accurate measurement with subpixel accuracy can be performed. Electrode Chamber incl measurements
And of course, before measuring the shape the whole system is calibrated.
Software detection, inspection sequence:
First of all, the availability of the back light is checked by measuring the intensity on the two small green areas (left and right top. In the green large area on the top of the burner the availability of the burner is checked by also measuring the intensity.
After locating the rough position of the burner, using an edge detection algorithm and detecting the cylindrical contour (red straight lines), the exact middle line is calculated.
In the green segments around the electrode chamber the edge is very accurate measured and the shape is calculated. Shown is a circle fit (red circle) but a better result is achieved by a polynomial fit.

Compression joint, back light image

The compression joint is a very complicated part of the burner. Inside the glass the metal parts are positioned before the heated quarts glass is pressed to a well defined 3D shape. Shown is a burner with a ignition electrode (electrode on the bottom in the joint) included. Because of the required resolution only one half of the burner is inspected by one camera.
The other side is inspected by a second camera. A back light is used for the required contour and 2D measurements. The shape of the back light matches roughly the shape of the burner, necessary for all required measurements.
Software detection, inspection sequence:
In almost every measurement algorithm J.A.I.M.S. checks first the availability of the backlight (1)and next the availability of the product (here the burner, measurement area not shown). When the intensity of the back light is too low or when the intensity in the product detection area is too high an error (including an error code) is given. HPI Compression joint measurements 02
Next step (3) the position of the burner in the image is measured and the middle line is calculated (yellow). The horizontal position of the burner is detected by a double edge detection algorithm (4). The edge of the joint (red vertical line) is difficult to detect, so a double detection is necessary.
The metal contact strips (5) are detected and of course if one is missing an error (including an error code) is generated. The middle line (white line) of this metal contact strip is also used for the broad metal tape inside the joint.

Important to know is the position and the quality of the joint. Therefore the position of the dark lines (6, actually the end of the compressed joint)is detected using more then one edge detection algorithm. Thanks to a well designed back light contour the end of the compressed joint area is shown with a very good contrast. Bad and good joint JAIMS Not all the burners does have such a perfect contrast. When the hot glass is not well pressed the contrast is significant lower, the edge detection reliability is decreasing dramatically.

Next step is the detection of the electrode chamber (7), the contrast of this contour is depend also of the hot glass compression. So the shape is not always so nice as shown in this image. To achieve the required reliability more than one detection algorithm is used.

The quality of the metal tapes (8 and 9) is very important for the operation lifetime of the burner, realise the burner is getting hot during operation. The position and shape of the tape is measured very accurate (subpixel accuracy).
The corners of the tape has to be visible, so no corner of the tape is folded. As shown in the image (several crosses on the edges of the tape) at least 3 detection techniques are to inspect the quality.
These measurements are also used to calculate the exact position of the tape with respect to the references of the burner. Also a crack detection algorithm is performed to detect cracks in the tape. The connection between the metal strip and the tape is also checked.

In the electrode chamber the electrode (11) (and the ignition electrode, 13) is detected and measured. When the dimension of the electrode does not compare the required dimension the operation lifetime is decreasing.
The angle between the electrode and the middle of the compression joint is also calculated.
Of course when one of these measurements does not compare the required dimensions an error (including an error code and an error explanation) is given.

Here a few examples of detected errors, only clear visible errors are shown, mostly the errors are hardly visible but still detectable:
First image: Broken electrode, this one clearly visible.
Second image: Ignition pole shifted into the electrode chamber.
Third image: Folded strip.
Fourth image: Crack over the whole strip.
Fifth image: three quarter crack.
and the last image: a few crack around the weld hole.
When a crack exceeds a certain limit is will be rejected. It is difficult to detect the start or end of a crack. A hole in the strip is not a problem, the burner will work anyway, only a too large hole can cause a problems and increase a starting crack.
Error broken electrode and bad joint JAIMS Error ignition pole JAIMS Error strip JAIMS Example strip crack 02 JAIMS Example strip crack 01 JAIMS Examples strip crack JAIMS

Compression joint, front light image

HPI Oxidation measurements 03 Error oxidized electrode JAIMS To meet the required burner quality it's not allowed to have any oxidation spot on the tape or electrode. To perform this quality inspection an extra image is acquired using front lights.
Once the exact position and contour of the tape and electrode are measured a smart oxidation algorithm is performed.
This algorithm measures any disturbance in the intensity at the tape. The oxidation detection on the electrode is more difficult because the electrode is a spiralised wire.

Vision system user interface.

The production system is controlled by a PLC. The vision system receives a start command when the burner is in position and start the inspection. HPI front panel 02 HPI front panel vision 1_01 HPI front panel vision 3_01 HPI zoom image and comm data
The Vision system receives when the start command is given which burner type is produced and also the accept/reject limits. So the vision system is capable to show if the burner will be accepted or rejected by the PLC but does not accept or reject itself.
When the vision system has finished the inspection the measured results are send to the PLC. Finally the PLC accepts or rejects the burner. The PLC is responsible for this final decision.
The information of the vision system is shown on the usere interface monitor and a few panel images are shown here. The front panel shows 5 camera images including several measurement areas and if the burner is oke of not oke. A lot of extra features are available and can be activated by pressing the appropriate button. These buttons (and corresponding actions) are visible as well as a message area. Errors wil be visible within this area.

The operator can get all the measured results by selection the tab: Vision 1, Vision 2 or Vison 3.
The program contains also a Calibration possibility, logging data, change settings panel (password protected), communication between PLC and vision data panel(see picture) etc..

Also some extra features:
    When clicking on the image the software enlarges the image.
    Change monitor setting separate for normal mode, calibration mode and tuning/maintenance mode. So the maintenance or vision engineer can change the layout of the panel (Password protected).
    Change vision settings by pop up the vision software panels, only for maintenance and vision engineers (Password protected).
    Change communication between PLC and Vision system (Password protected).
    Simulation of the vision software without communication with the PLC (Password protected).