such a way that the point to be measured shall be brought within the circle of
10 mm in diameter marked on the glass plate directly under the pricking needle
and then X', Y', X", and Y" shall be precisely adjusted so as to bring the mea
sured point of the stereo model to coincidence with the floating mark by the aid
of observation through the optical system. In this case the stereo model shall be
adjusted by rotating (K\ K") the Amici prisms mentioned in (A) (1).)
(C) Pricking Needle
( a ) After the measured point is brought to coincidence with the floating mark
by the aid of stereoscopic observation, the said point on the diapositive
shall be pricked. In pricking, a minimotor is used as the power source in
order to maintain the uniform size of the pin hole and its form.
( b ) The pricking needle is operated in the following steps:
(1) A push-button switch shall be pressed for a short time (neary 1/2 second)
and then released.
(2) If the push-button is pressed, the opal glass for illumination will be in-
staneously turned outside from its position directly under the pricking
needle.
(3) After the opal glass will have completed its turning away, the mini
motor will start to operate.
(3) After once started, the mini-motor will be switched on the power source
by means of a cam and continue its revolution. (Then the push button
may be released.)
(4) After once started, the mini-motor will be switched on the power source
by means of a cam and continue its revolution. (Then the push button
may be released.)
(5) The pricking needle standing by at its top position will descend slowly
rotating by itself with the rotation of the motor until its tip will touch
the emulsion surface and it will make nearly three complete revolutions
and then slowly ascend until it will reach the top position.
(6) As soon as the pricking needle will reach the top position, the motor
will be switched off by itself by means of the cam and brought to a
stop.
(7) After the pricking needle will reach its top position, it will assume a
stand-by attitude for the next operation and it will come to stop after
completing one revolution for pricking (for nearly four seconds).
( c ) A balance weight is attached to the pricking needle in order to make it
lighter. The pressure given by this balance weight to the emulsion sur
face is adjustable. (When the tip of the pricking needle touches the
emulsion surface, the film base may be free from scratch when film is
used whereas the tip of the needle may be free from damage when dry
plate is used by the aid of making the weight of the pricking needle
properly light. Specifically when film is used, if the needle would prick
its base, the material of the base would rise around the pin-hole, or would
make its density change; therefore, if the base would be looked at its
back, the pin-hole looks indistinct because of refraction of light occurred
thereabout. In consequence, it is necessary to prick the pin-hole only on