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A Novel Keystone Correction Method Using Camera-Based Touch Interface for Ultra Short Throw Projector

Ultra-short throw projectors (USTPs) that reduce throw distance greatly with a high resolution have been widely developed. However, the hardware characteristics of the USTP make projected image distorted easily comparing to the typical long throw projectors (LTPs). Therefore, keystone correction is an important feature to ensure the usability of the USTPs. Although many automatic keystone correction methods have been presented for the LTP, they are limited to be directly applied to the USTP. Due to this limitation, the commercial USTPs adopted a manual keystone correction. The manual method requires users to be familiar with keystone distortion and correction mechanism, otherwise it takes lots of time to complete and results are unsatisfactory. To solve this problem, we propose a novel keystone correction method with the touch interface. As a prerequisite of keystone correction, we need to know the optimal projected shape without distortion. In the proposed method, the user-specified shape which obtained from the touch interface is used as the optimal shape. In addition, we present the projection model which can explain the cause and the solution of the keystone distortion. Experimental results show that the proposed method outperforms the manual keystone correction in terms of correction performance and usability.