Thin film partial reflectors for generating contrast in millimeter wave images

Depth resolution and contrast (grayscale) resolution test objects have been proposed for incorporation into an ANSI standard for image quality of active millimeter wave (MMW) imagers for screening humans. A design for a depth resolution target has required the need for a thin film to generate a reflection while allowing for metal targets behind it to be visible to MMW imagers. Materials to accomplish this task have been identified, essentially acting as a millimeter wave beam splitter. Images obtained with a wide-bandwidth MMW imaging system are discussed. Additionally, by altering the resistivity of the thin film, the reflection coefficient of the film changes, allowing these films to be used as a contrast phantom for the testing of millimeter wave imaging systems. Measurements using laboratory millimeter wave systems are in good agreement with theory, and an image collected with a commercially-available MMW imaging systems is presented.