Canon EOS 55 Service Manual page 48

Part 2: Technical Information
2) Horizontal or Vertical Orientation
The camera's orientation is detected by optical orientation switches (same as EOS
5/A2E) fitted on each side of the eyepiece. As shown in Fig. 2-4. a steel ball rolls
between an LED and LED sensor. In the horizontal shooting position, light emitted by
the LED in both switches 1 and 2 is blocked by the ball (indicated by• when closed).
However, when the grip is turned upward, the ball in switch 2 rolls down, allowing the
LED sensor to sense the emitted light (indicated by O when open). In this way, the
open-and-close combinations enable the camera to detect orientation.
The ball's path inclines by about 15' from an upright position. Therefore, when the
camera is upright, both switches are closed, and when the camera is upside down, both
are open. Horizontal orientation is detected in both cases.
Table 2-2 Orientation detection
Holder
.!Orientation / Switch ➔
(!) @
Upright
• •
Horizontal
LED sensor
(2)
Upside down*
0 0
Vertical
Grip up
•
0
Grip down
0
•
Steel ball (2)
LED (2)
* Calibration disabled.
Fig. 2-4 Camera Orientation Switches
3) Improved Response
With improved CPU performance, a different Eye-Controlled Autofocus sensor (Eye-
Controlled Autofocus BASIS instead of a CCD), and a revamped Eye-Controlled
Autofocus algorithm, the Eye-Controlled Autofocus and calculation times have been
shortened to about half that of the EOS 5/A2E. (120ms vs 220ms). This improved speed
contributes to easier picture-taking and expands photographic possibilities.
4) Vertical Eye-Controlled Autofocus
The EOS 5 / A2E could not adequately detect the edge of the pupil when the camera was
vertical. Vertical Eye-Controlled Autofocus was therefore not provided. In this camera,
more precise pupil edge detection and the incorporation of vertical-orientation calibra-
tion have made vertical Eye-Controlled Autofocus possible.
5) Eye-Controlled Autofocus BASIS
To attain precise, high-speed eye-controlled operation, a new BASIS area sensor devel-
oped by Canon has been incorporated.
Replacing the EOS 5/ A2E's CCD with the new BASIS enabled high-speed and high-pre-
cision eye-controlled operation with less power:
a. The drive logic section and signal-processing circuit have been integrated in the
BASIS to save space.
b. The power requirement of only 5 V has cut power consumption to 1/6 of what the
EOS 5/A2E's CCD required (which was 18
V).
c. Signal reading speed is twice as fast as the EOS 5/ A2E's CCD.
2-4