Details
Event:
Reading of T7 symbologies often tends to fail.
Probable Causes:
- Due to the physical parameters of the Wafer ID camera as well as the T7 specification, there is very little safety margin in the resolution for the following reasons.
In-Sight 1701/In-Sight 1721/In-Sight 1722/In-Sight 1741/In-Sight 1742's Wafer ID cameras have an image sensor resolution of 1024x768 pixel. The physical field of view is designed to be 31.0mm laterally (because of the special optical system, the field of view remains 31.0mm even when the working distance is changed), that is, the resolution is about 0.03mm per 1pixel, so that one of the dots (diameter 0.100mm) of T7 standard is expressed by approximately 3 pixels. This is a symbol reading that is really close to the limit and tends to require focus and lighting adjustments to be reliable. - The optical system could be designed to increase the resolution, however, as the field of view becomes narrower, it would became difficult to ensure the 31.0mm lateral span required for T7. In M12/M13 OCR(SEMI) system, 12-digit character strings were 16.431mm in terms of specifications. If the positioning accuracy of the system was poor, some of the character strings might be out of the field of view at worst.
In other words, we can imagine that the resulting resolution and field of view were designed as a compromise for OCR and T7 with the size of the light receiving elements at that time.
Solution:
- Ver4.5.2 Firmware features enhanced image filter functions. By devising image filters and illumination adjustment, T7 and DataMatrix codes have satisfactory performance for practical use. After carefully adjusting the focus, try the image filter functions.
