For different optical measurement techniques in our department so called Scheimpflug mounts for CCD- and CMOS-cameras from various companies and distributors have been constructed and built. These mounts enable the possibility to tilt the focal plane relative to the image sensor. If image capturing of the object plane (e.g. a PIV light sheet) have to be realized in a non-normal viewing direction, the application of a Scheimpflug mount can assure a focussed image over the whole field of view. In that case a variation of the magnification factor over the field of view has to be accepted according to the local projection angles and distances of the imaging geometry. By imaging a calibration plane with a regularly distributed marker pattern located at the object plane a rectification matrix can be determined enabling an exact mapping of the image to a uniform magnification factor for each camera viewing separately.
The principle of the Scheimpflug mount is dated from a patent of the Austrian officer and cartographer Theodor Scheimpflug in 1904 and results from an application of the general lens equation. The corresponding Scheimpflug condition defines that image-, lens- and object- or focus-plane have to intersect in one line. In compliance with this condition it is possible to focus images where the object plane is tilted to the image plane by using a Scheimpflug mount (e.g. for Stereo PIV see Fig. 1). In the formulation of the Scheimpflug condition no statement is made regarding the direction of the intersection line. The viewing direction to the object plane is often restricted by limited optical access so that the mounts at our department are constructed in a way that the tilting axis can be chosen freely. In order to optimize the field of view for rectangular sensors for a chosen Scheimpflug condition in our mounts the camera body can be rotated in an axis normal to the sensor plane. Furthermore, Scheimpflug mounts constructed for large sensors with a holder for the application of optical filters are constructed (shown in Fig. 2).
At measurement campaigns in large industrial facilities and wind tunnels Scheimpflug mounts additionally need to carry remotely controlled motors e.g. for the focussing of the lens and shall enable a robust and oscillation-free fixation of the cameras in order to minimize vibrations for a reliable repeatability of the optical measurements. Our long-term experiences in applications of optical measurement techniques in industrial facilities have been taken into account as far as possible at the planning and realization of the Scheimpflug mounts in our department.
Our Scheimpflug mounts are in use with C- mount and F-mount and in various sizes and ways of fixation for different camera models (e.g. PCO- Sensicam, QE, 1600, 2000, 4000, Pixelfly, Photron APX-RS, SA*, etc.)