(Un-)sharpening deflectometry simulations by camera aperture ray tracing

Phase-measuring deflectometry facilitates accurate inspection of reflective free-form surfaces by analyzing deformations of reflected sinusoidal patterns. However, the limited depth of field of the camera causes an inherent blurring of the light source, which leads to contrast variations and systematic phase errors that degrade measurement quality. This contribution shows how this blurred imaging can be realistically simulated by ray tracing the camera aperture. An efficient method based on analytical boundary integration is proposed to obtain more realistic camera images. These are compared to the standard ray tracing of chief rays to quantify and correct phase errors induced by the blurred imaging of the reference (screen) in deflectometry systems. The improved accuracy of this approach is demonstrated by analyzing real measurement data.