This paper proposes the Top-View Transformation Model for image coordinate transformation, which involves transforming a perspective projection image into its corresponding bird's eye vision. A fitting parameters searching algorithm estimates the parameters that are used to transform the coordinates from the source image. Using this approach, it is not necessary to provide any interior and exterior orientation parameters of the camera. The designed car parking assistant system can be installed at the rear end of the car, providing the driver with a clearer image of the area behind the car. The processing time can be reduced by storing and using the transformation matrix estimated from the first image frame for a sequence of video images. The transformation matrix can be stored as the Matrix Mapping Table, and loaded into the embedded platform to perform the transformation. Experimental results show that the proposed approaches can provide a clearer and more accurate bird's eye view to the vehicle driver.

No abstract

No abstract

This paper presents a robust copyright protection scheme based on discrete cosine transform (DCT) and secret sharing techniques. The scheme cannot only use a binary image of arbitrary size as the watermark, but also generate shares without the need of a codebook. The scheme first performs the DCT on a host image to obtain the image features and uses these features to generate a master share. The master share and a binary watermark are then used to generate an ownership share, according to the secret sharing technique. The hidden watermark, used for copyright verification, can be revealed by combining the master share with the ownership share. It is shown that the hidden watermark can be effectively revealed by the proposed scheme, even if the visual quality of protected images has been greatly degraded. Moreover, the proposed scheme achieves superior resistance to several image processing operations, compared with existing schemes. © 2008 SPIE and IS&T.

Geometric errors, such as straightness, perpendicularity, and parallelism errors are determinant factors of both the accuracy and service life of a linear guideway. In this study, a multipurpose geometric error measurement system was mainly composed of a laser source and an in-lab-developed optical module is proposed. Two adjustment methods were used for the in-lab-developed optical module to calibrate the altitude angle of the pentaprism: The first one is designed for ease of operation based on Michelson principle using a laser interferometer as the light receiver, and the second is aimed at high calibration repeatability based on the autocollimator principle using the quadrant detector (QD) to replace the light receiver. The result shows that the residual errors of the horizontal straightness and the vertical straightness are within ±1.3 µm and ±5.3 µm, respectively, when referred to as the commercial laser interferometer. Additionally, the residual errors of perpendicularity and parallelism are within ±1.2 µm and ±0.1 µm, respectively, when referred to as the granite reference blocks