the constraint rollers 611 and 612 would be a hard non deformable plastic although the composition of the constraint rollers 611 and 612 could be composed of any non deformable material capable of providing a light clamping force to the substrate media 608 the non deformable constraint rollers 611 and 612 ensure that the substrate media 608 is held tangent to the constraint rollers 611 and 612 on the substrate media path 603 the drive speed of the constraint rollers 611 and 612 is controlled such that the lead edge constraint rollers 611 and 612 are driven at a slightly higher speed than that of the drive rollers 609 and 610 to keep the substrate media 608 taunt and under tension as it enters the curl sensor 100 alternatively in an additional embodiment drive rollers 611 and 612 can be composed of a deformable material such that each roller 611 and 612 has similar elastic modulus or stiffness the nip thus formed by rollers 611 and 612 provides a consistent sheet ejection angle over a wide range of substrates and nip normal forces the trailing edge constraint system 602 functions in a manner that is similar to the lead edge constraint system 601 the trailing edge constraint system 602 holds the substrate media 608 as it exits the curl sensor 100 such that the trailing edge curl of the substrate media 608 can be accurately measured.