► Cognex Wafer ID 產品參考
問題：
T7 符號的讀取常常會失敗。
Reading of T7 symbologies often tends to fail.
可能的原因：
• 由於WaferID相機的物理參數以及T7規格，解析度的安全裕度很小，原因如下。
In-Sight 1701/1721/1722/1741/1742 的 WaferID 相機的影像感測器解析度為 1024x768 像素。 物理視場設計為橫向31.0mm（由於特殊的光學系統，即使改變工作距離，視場仍保持31.0mm），即分辨率約為每1pixel 0.03mm，這樣T7標準的1個點（直徑0.100mm）用大約3個像素表示。這是一個非常接近極限的符號讀取，並且往往需要對焦和照明調整才能可靠。
• Due to the physical parameters of the WaferID camera as well as the T7 specification, there is very little safety margin in the resolution for the following reasons.
In-Sight 1701/1721/1722/1741/1742's WaferID 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.
• 光學系統可以透過設計來提高分辨率，但隨著視野變窄，很難保證T7所需的31.0mm橫向跨度。在M12/M13 OCR(SEMI)系統中，12位元字串的規格為16.431mm。如果系統的定位精度較差，在最壞的情況下，部分字串可能會超出視野。
• 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.
• 換句話說，我們可以想像，最終的解析度和視野是OCR和T7與當時的光接收元件尺寸的折衷設計。
• 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.
解決方案：
• Ver4.5.2 韌體具有增強的影像過濾功能。透過設計影像濾波器和照明調節，T7和DataMatrix碼具有令人滿意的實際使用效能。仔細調整焦點後，請嘗試影像濾鏡功能。
• 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.
