Canon EOS Camera

1
Canon EOS Camera

• A Mechatronics Case Study
• Pei Chong Luke Stone
• Lee Sheldon Ewan Panter

2
Topics

• Introduction to the Canon EOS System
• Auto Focus
• Exposure Control
• Diaphragm Drive System
• Miscellaneous Systems
• Motor Drive, DX coding and Eye tracking
• Summary

3
EOS - an overview

• EOS - Electro Optical System
• EOS 650 Launched March 1987
• Key Features
• Advanced Auto Focus functions
• Ultra Sonic motor drive
• Automated exposure control

4
Auto Focus System Advantages

• Expanded degrees of freedom
• Greater number of focus points
• Fast and near silent operation
• New ultra sonic motor system
• Predictive auto focus
• Possible due to focus update speed

5
Auto Focus System Layout
SW1
SWITCH SENSING CIRCUIT

• CMOS area sensor
• 32 bit micro processor
• USM Motor

SW2
SW3
FOCUS DETECING CIRCUIT
APERTURE
LENS CONTROL CIRCUIT
SHUTTER CONTROL CIRCUIT
6
Auto Focus Operation Process
START
CLOSE-DOWN APERTURE
NO
SW1 ON?
FIRE SHUTTER
YES
OPEN-UP APERTURE
(PREDICTIVE) FOCUS
SW2 ON?
ADVANCE FILM
NO
YES
7
Auto Focus Ultra-Sonic Motor
A.C. -

• Piezoelectric element ring bonded to elastic
  stator
• Alternating current applied to ring causes a
  rippling effect in the stator
• This, in turn, drives the rotor in a circular
  motion

Stator
Rotor
8
Exposure Control
A main subject and central area of image B
main subject and adjacent background C
peripheral areas of image

• If B A and C - B lt 0 then exposure set on value
  A
• If B A and C - B 0 then exposure set on value
  C

9
Shooting Modes

• Automatic mode
• Shutter speed priority mode
• Aperture priority mode
• Depth of field priority

10
Diaphragm Drive System

• Arc form drive
• uses a brushless permanent magnet d.c. motor.
• Hall sensors being used to detect the position of
  the rotor.
• The drive from the motor is transmitted through
  gears to move the focusing lens along the optical
  axis.
• Ultrasonic motor
• As previously explained

11
The Motor Drive

• Twin purpose
• Advances film one frame at a time
• Rewinds film when fully exposed
• Replaces manual advance
• Negates need for film rewind handle

12
The Motor Drive cont.

• Two motors
• High performance coreless DC motor
• PMDC motor
• Controlled by 32 bit microprocessor
• Max 10 fps
• Near silent operation

13
DX Coding

• Describes ISO speed
• Allows Automatic film speed setting
• Removes need for manual adjustment
• Auto-detects speeds 25-5000 ISO

14
Eye Tracking System

• Allows off-centre focal point
• Removes need for focus lock
• Consists of
• 8 infra red LEDs (IRED)
• system of prisms, mirrors and lenses
• CMOS sensor (view sensor)

15
Eye tracking cont.

• Controlled by 32 bit microprocessor
• Incorporates learning function

16
Conclusion

• Design Evolution of Advance Auto Focus Features
• Eye controlled focus selection
• Multi-point focusing
• Automatic shooting modes
• Advanced diaphragm drive
• Automated film drive control