In the highly competitive smartphone market, screen flatness is a critical quality indicator. A perfectly flat screen not only enhances the aesthetic appeal of the device but also significantly impacts the user's touch experience and overall visual enjoyment. Deviations from flatness, such as bows, creases, or dents, can lead to assembly issues, stress on glued joints, and decreased housing life. 

Therefore, smartphone manufacturers face the challenge of efficiently and accurately measuring screen flatness to ensure only screens meeting stringent quality standards proceed to assembly. Subtle undulations, often imperceptible to the naked eye, need to be detected with micron-level precision. Traditional methods are often inefficient or lack the necessary accuracy for today's demanding production environments.