Viewfinder - Canon EOS 20D Service Manual

Technical Information

1.5 Viewfinder

1) Viewfinder optics
The basic configuration of the viewfinder optics is the same as the EOS 10D's.
Only the pentaprism and eyepiece optics have been optimized so that the
viewfinder magnification is slightly better (from 0.880 to 0.90).
The other specifications (95% coverage, 20mm eye point, dioptric adjustment
range from -3.0 to +1.0 dpt) are the same as the EOS 10D.
The dioptric adjustment mechanism is based on the EOS 10D's. However,
since the movement of the lens during dioptric adjustment is larger, the -3.0 to
+1.0 dpt range is retained even while the effects of the moving lens' inclination
and eccentricity are reduced. Thus, even when there is dioptric adjustment, the
eyepiece optics still make it easy to see.
Acrylic reflective plate
Focusing screen
Secondary mirror
2) Superimposition display
The newly-developed superimposition
display optics have been incorporated. The
light from the superimposition LED
positioned on the upper rear of the
pentaprism goes through the SI prism and
pentaprism. Then it is projected in the
configuration of the AF points on the fine
reflective surface of the acrylic reflective plate
between the pentaprism and focusing screen.
This is how the SI illumination is produced.
LCD prism
Pentaprism
Built-in flash
45 main mirror
AF mirror
Infrared cut filter
Fig. 022 Cross section at center.
Metering sensor
Metering lens
Eyepiece lens 1
Eyepiece lens 2
Eyepiece lens 3
LCD
Shutter
Imaging base board
Large color LCD
Image sensor
AF sensor
Secondary image-formation lens
Fixed diaphragm
SI prism
Acrylic reflective plate
Fig. 023 SI optics
14
SI-LED
Pentaprism