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Unformatted text preview: Thick Lens Imaging and Depth of Field An object is plaCed to the left of the macro lens shown in the diagram below.
Light propagates from left to right. The focal length of this lens is 55 mm. The f-no. of
this lens is set at f / 11. All dimensions on the diagram are given in mm. It is desired to
form a real image of an object (an assembled printed circuit board) such that the object- to—image reproduction ratio is 20 to 1. For a high resolution image, the tolerable blur
spot is taken to be (1 = 0.05 mm. 55 37. 4 27. 9 38. 3
103. 6 Calculate, showing all work, the distance of the object from the left—most glass
surface. Calculate, showing all work, the distance of the image from the right—most glass
surface. Calculate the depth of ﬁeld and the depth of focus for this arrangement. De—
termine the depth of ﬁeld from the table supplied with the lens (in the class notes). Ex—
press your answers in mm accurately to four signiﬁcant ﬁgures. Put your answers in the spaces provided. Distance of object from left—most glass 2 min
Distance of image from right—most glass 2 mm
Calculated depth of ﬁeld = mm Depth of ﬁeld from table = mm Calculated depth of focus 2 mm Thick Lens Imaging and Depth of Field Focal length, f = 55.0mm 'Real image, m < 0 Linear magniﬁcation, m = —1/2() = —0.05
f-no. -—- 11 Tolerable blur spot, d = 0.05 mm Object distance
3 = (1 — 51).)“ = 21f = 21 (55.0mm) = 1155.0mm Distance of object from left-most glass = 1155.0 — (55.0 —~ 37.4) = 1137.4 mm Image distance
3’ = -ms 2 -(-1/20) 1155.0 mm = 57.75 mm
Distance of image from right-most glass = 57.75 — (55.0 - 38.3) = 41.05 mm Depth of ﬁeld calculated 2w # no.) (1 + |m|) A: m2 = 462 mm Depth of ﬁeld from table
A = 1.37m — 1.07m = 0.30m = 300mm Depth of focus
6 = Am? = 1.155mm ...
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- Spring '08