1. AUTOMATIC VISUAL INSPECTION OF ZIRCONITE BLOCKS

2. raw zirconite blocksfinished zirconites Zirconite blocks : the problem Raw zirconite blocks are polished and converted into zirconites for use in jewelry. About 15% of blocks exhibit shape and dimensional defects, which interrupt the transformation process if they reach the machines. Human visual inspection is infeasible because millions of blocks per month are processed. How to view, illuminate and inspect blocks ?

3. Zirconite blocks : approach I. The first step is the requeriments analysis : what must exactly be done, why and under which operational restrictions ?  Requirements Specification Document. II. Once we have concluded that... a machine vision approach is feasible  lighting is critical! machine vision is the best approach the devised solution may be affordable for the customer and cost effective for the developer then design a system prototype  Preliminary Design Document evaluate its cost : hardware, software, risk, licenses, copies … formulate an economic proposal sometimes prepare a convincing demo = implement prototype III. Propose either... an in-depth study (more analysis) that is not for free  Formal Report to sign a contract and start the project  Contract, Plannification Document,...

4. Possible shape defects Zirconite blocks : defect characterization Possible dimensional defects non-square base | length or width  nominal size | > tolerance, tolerance = 0.1 mm nominal sizes from 1.70 to 3.00 mm (height from 1.25 to 2.00 mm)

5. Backlight Zirconite blocks : Lighting

6. FLD from Doal&Jenner (coaxial) Zirconite blocks : Lighting

7. 1234 5678 910 Correct blocks The “museum of horrors” Zirconite blocks : Lighting

8. 1234 5678 910 11 12 Zirconite blocks : Lighting

9. 1313bis1415 16171819 20212223 Zirconite blocks : Lighting

10. 24252627 28 Zirconite blocks : Lighting

11. Background : the different of shades of black velvettire rubberblack mate spray paint We must maximize the difference between backgound and black grey levels so as to correctly and reliabily segment and measure the blocks. “Black” must be really black, not just dark very diffuse Zirconite blocks : Lighting

12. 2: progressive camera, with wide open aperture and shutter 1/1000 5: rectified coaxial lighting 6: fiberoptic photosensor 7: rotation motor and painted platform 8: manual speed control 3: extensor tube 20mm 4: lens f=50mm 1 2 4 1: closed dome with black painted inner walls 3 5 6 7 8 Zirconite blocks : Lighting

13. fiber optic to photosensor fiber optic from infrared LED beamsplitter Zirconite blocks : Lighting

14. Zirconite blocks : Defect detection X 2 = A 1 / (A 1 + A 2 ) A1A1 A2A2 L1L1 L2L2 D2D2 D1D1 X 1 = 1  D 2 / D 1

15. right X 1 = 1  D 2 / D 1 Zirconite blocks : Defect detection

16. Zirconite blocks What would we do if... not only the upper face had to be examined but also lower or side faces in order to detect lack of material not visible from above ? the height of the block must also conform to a certain tolerance ? Height varies 2 mm. (depth from focus ?) 6 parts per second have to be safely inspected ? That means high base speed, less time to acquire each image or otherwise the camera will yield blurred images we are later told that blocks can be o several grey shades ? And how much would the proposed solutions cost in terms of hardware and labour time ? There is not such a thing as a simple machine vision problem : the risk of a project should never be underestimated