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Optical System Considerations 65
Figure 4.5 (a) Schematic of an optical system and (b) the corresponding
y-ybar diagram.
4.5 The Scheimpflug Condition
To this point we have assumed that the object is defined by a plane
surface which is normal to the optical axis. However, if the object plane
is tilted with respect to the vertical, then the image plane is also
tilted. The Scheimpflug condition is illustrated in Fig. 4.6a, which shows
the tilted object and image planes intersecting at the plane of the lens.
Or, stated more precisely for a thick lens, the extended object and
image planes intersect their respective principal planes at the same
height.
For small tilt angles in the paraxial region, it is apparent from
Fig. 4.6a that the object and image tilts are related by
s′
′ m (4.29)
s
where m is the magnification. For finite (real) angles
s′
tan ′ tan m tan (4.30)
s
