Canon EOS DIGITAL REBEL XTI Service Manual page 71

４）Energy saving
To minimize the increased power consumption due to the high-speed reading, the output
amp's power consumption was absolutely minimized. Also, during long exposures, power
to the output amp is cut off and the standard current for the circuit drive is also cut off as
with the EOS KISS DIGITAL N.
５）Infrared-blocking, low-pass filter
The construction of the infrared-blocking, low-pass
filter is as shown in Fig. 002.
With the EOS D REBEL XTI / EOS 400D D, low-pass
filter 1 is part of the Self Cleaning Sensor Unit.
⑴Low-pass filter 1
This separates the subject image into two images
horizontally. The front of the filter is coated with a
dichroic mirror to reflect infrared light.
⑵Phase plate
The images separated by low-pass filter 1 are
converted from linear polarization to circular
polarization. The phase plate is for preparing the
polarized components, enabling low-pass filter 2 to
correctly separate the subject image into four square
images.
⑶Infrared-absorption glass
Together with the dichroic mirror coated on the
front of the low-pass filter, this infrared-absorption
glass has a hybrid construction to reflect and absorb
infrared light. Red ghosting and color casts caused by
reflections on the sensor surface, etc., are effectively
suppressed by the infrared-blocking filter.
⑷Low-pass filter 2
The subject image separated into two images horizontally by the low-pass filter is
separated vertically into two images by this low-pass filter 2. The image is thereby
properly separated into four square images. The image separation width for the vertical
and horizontal images is optimized for the sensor pitch. This minimizes color artifacts
caused by minute horizontal- and vertical-line patterns.
As with the EOS 5D, low-pass filter 2 also serves as the CMOS sensor package's cover
glass. This eliminates having a relatively expensive glass cover and reduces the cost.
Dichroic mirror
(Reflects infrared rays)
3. Infrared-absorbing glass
2. Phaser layer
1. Low-pass filter 1
(Separates image in horizontal
direction)
Fig. 002 Cross section of infrared
2
Technical Information
CMOS
sensor
4. Low-pass filter 2
(Separates image in
vertical direction)
(Converts linear polarized
light into circular polarized light)
cut, low-pass filter