There are various types of invisible ink marked playing cards and spy cameras in the market. Those tow kinds of cards are barcode marked cards and backside marked playing cards.
While the poker scanning camera is suitable for scanning sides marked deck. And the IR contact lenses or infrared sunglasses is fit for back marking playing cards.
For playing cards contact lenses, their base curve is 8.6mm and the center thickness is 0.04mm and center diameter is 4, 7 or 9mm. Our perspective sunglasses are made of high-quality HEMA. For barcode poker card scanner, we fix poker camera lens inside each item so that can scan the bar-codes juiced playing cards with fast speed.