1.8.0 Image Tracking:As the picture 21cm across, The distance of glass to picture is about 30cm, I need to close to picture

As the picture 21cm across, The distance of glass to picture is about 30cm, I need to close to picture, then the recognition result can appear.

How can I get the recognition result with the distance about 1meters , keep the picture 21cm across?

Thanks a lot.