Fig. 2.
Configuration geometry of the Schwarzschild scan objective which consists of concentric Mirror 1 and Mirror 2. Only one scanner was shown here for simplicity. (a) Ray-tracing for an arbitrary chief ray with the scan angle of θ. R1 and R2 are the radii of curvature, and T1 and T2 are the center thickness for Mirror 1 and Mirror 2, respectively. O is the mutual center point of the curvatures of the mirrors. S is the pivot point of the scanner. The distance between point S and Mirror 1 is d1, the distance between Mirror 2 and Mirror 1 is d2. The chief ray interacts with the two mirrors at points A and B with incident angles I1 and I2, respectively. The chief ray is incident on the focal plane (θ’) before the point C (exit pupil position). f is the focal length of the Schwarzschild scan object, and equals to the distance from point O to the focal plane. L is the total length. dwork and dexp are the working distance and exit pupil distance, respectively. (b) Ray-tracing of the scan beams with the minimal and the maximal scan angles (θmin and θmax, respectively). The reserved central area of loading is in a central zone of ± Hmin, while the peripheral area of scanning is in the annular zone of ± (Hmin – Hmax) at the focal plane. D0 is the input beam size, D1 is the diameter of Mirror 1, and D2_out and D2_in are the outer and inner diameters of Mirror 2, respectively. RH1 to RH5 are the specific marginal ray heights.