Af System - Canon EOS 7 Service Manual

Part 2: Technical Information
1.2 AF S
YSTEM
(1) Basic Configuration of Focusing Optics
The basic configuration of the focusing optics, AF sensor, and AF unit are the same
as the EOS 300/Rebel 2000/EOS Kiss III's. The actual focusing optics are shown in
Fig. 2-7. The light comes through the camera lens, the focusing light flux passes
through the semi-silvered mirror (40% transmittance), then it is refracted downward
by 81 deg. by the secondary mirror (flat and fully reflective). Then it goes through the
field lens, AF mirror (fully reflective), infrared filter, fixed diaphragm, and the
secondary image-formation lens before reaching the AF sensor.
(2) AF Sensor
As with the EOS 300/Rebel 2000/EOS Kiss III, the EOS ELAN 7 E / EOS 30 uses a
7-point CMOS sensor. For technical details on the AF sensor, see the EOS 300/Rebel
2000/EOS Kiss III's Service Manual.
AF sensor
Secondary image-
formation lens
Fig. 2-7 Focusing Optics
(3) AF Speed and AF Processing
1) Faster AF speed
A high-speed
microcomputer
with a 33.554
MHz clock speed
and a command
execution time of
only 0.03 ms
makes the AF
speed during automatic focusing point selection just as fast as the EOS-3's.
Table 2-2 compares the CPU performance of recent EOS cameras.
Main mirror
Secondary mirror
Primary image-
formation plane
Field lens
AF mirror
Infrared filter
Fixed diaphragm
Camera
EOS ELAN 7 E / EOS 30
EOS ELAN II E / EOS 50 E
EOS-3
EOS 300 / Rebel 2000 / EOS Kiss III
Table 2-2 CPU Performance Comparison
2-4
4.5
7.5
Fig. 2-8 Focusing Points
Fig. 2-9 AF Sensor
Clock Speed Command Execution Time
u
33.554MHz 0.03
0.0625 u
16.0MHz
0.04 u
24.576MHz
16.0MHz 0.12 u