584 IMAGE FORMATION, INVERSION OF IMAGES [Ch. XIV’
Image Formation with the Magic Lantern
§ 811. Ideal case.—When using transparent lantern slides
with a magic lantern and a small source of light the ideal arrange¬
ment is that shown in fig. 325.
L. is a point source of light (crater of the arc light). The con¬
denser C, focuses this light at the point O, in the optical center of
the objective. The slide-carrier S, is placed just in front of the
condenser. The objective 0,is at the proper distance from S,to
form a real image of the slide on the screen. All of the raj’s of
light from S pass directly through the center of the objective O.and
Fig. 325. Lantern-Slide Projection; No Spherical Aberration.
This shows an ideal case where there is a point source of light, and a con¬
denser without spherical aberration. The light from the condenser crosses at
the renter of the objective (O) and goes on without deviation to the image
screen.
L Light source.
C Condenser.
S Lantern slide.
O Projection objective.
hence undergo practically no deviation. If the source of light L,
were really a j joint source, and the condenser C, had no spherical
aberration, the shadow of the lantern slide S,in the screen without
an objective would be just like the image which is projected by the
objective.
§ 812. Inversion of the image.—In their passage from the
lantern slide to the screen the rays pass from the top of the slide
to the bottom of the screen, and from the bottom of the slide to the
top of the screen. In like manner the rays from the two sides of
the slide cross before reaching the screen (fig. 1.)
This crossing of the rays gives what is known as an inverted
image.