Canon EOS-1 - Manual (Page 37)

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Double Electrical Contacts
monitored by the main micro­
processor for dependability.
There’s no problem with power,
either. Pressing the battery check
button under the palm door gives
an instant readout of battery power
on the display panel. The display
panel also presents a row of blink­
ing dashes as a warning if the film
is not loaded properly. A row of
dashes coming out of the cartridge
symbol indicates correct film ad­
vance and film rewind, too.
TTL-CT-SIR ranging system
TTie TTI,CT-SIR (TTL Crosse
Type Secondary Image Registra­
tion) phase detection system deter­
mines focus by driving the lens
after completing a sophisticated
process of signal detection and
calculations. The system splits
light rays into four beams — two
horizontal and two vertical — that
form images on the surfaces of
four sensors. Focus is determined
, first by comparing the differences
in the data received by the two pairs
of images, then by deciding which
is the more reliable. Once this has
been determined — a matter of
microseconds — the lens motor
focuses the lens.
Cross ranging sensor BASIS
In order io develofTaTi AF sys­
tem accurate enough and reliable
enough to meet the standards pro­
fessional photographers insist on.
Canon had to develop a new cross
ranging sensor to replace the con­
ventional sensor used in the past.
This new BASIS (Base-Stored
Image Sensor) was the result of
extensive research, and consists of
two 47-bit horizontal line sensors
and two 29-bit vertical line sensors,
plus associated amplifier circuitry
that is housed in a clear-molded
package. By integrating an ampli­
fier with each individual element
of the sensor instead of just having
an amplifier section at the output
stage as CCDs do, BASIS preserves
signal integrity by amplifying the
electrical signals before they are
read out through switching. Signal
purity is thus maintained, with
minimum noise and minimum loss
of information. In addition, the
new BASIS is equipped with an
extra circuit that amplifies the
signal ten times in order to improve
sensitivity and S/N ratio. The
sensor pitch is also 10% finer than
that of previous BASIS sensors,
providing improved narrow-line
detection ability. Also, an anti­
reflection film coats the sensor in
order to stabilize signal detection.
This innovative cross ranging
sensor BASIS results in improved
accuracy and better efficiency,
making possible reliable low-light
level operation down to -1 EV.
Two microprocessors
The EOS'l employs an informa­
tion processing system composed
of two microprocessors. One is a
high-speed super-microprocessor
that is dedicated to AF operation
only. The other microprocessor is
in charge of AE and sequence con­
trols. The two microprocessors can
handle data independently and
simultaneously. As a result, elec­
tronic operation and AF speed and
accuracy are obviously superior.