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Appendix
XCD-SX910CR/X710CR
XCD-SX910UV
XCD-SX910/X710
Deterioration in CCD sensitivity
The sensitivity of the CCD in this camera can
deteriorate over time.
Because ultraviolet light contains higher energy
compared to visible light, the elements making up the
CCD can suffer damage; so depending on the amount
of ultraviolet light energy accumulated, a lowering of
the sensitivity may occur. The amount of radiated
energy is equal to the amount of light radiated and the
length of time it is radiated, thus the total accumulated
radiated energy is the sum total of all the radiated
energy accumulated over time.
The total accumulated radiated energy [J/cm
2
] =
Σ (Amount of radiated light [W] × length of
time it is radiated [in seconds])
As an example of this particular characteristic, see the
following.
Characteristic Example 1:
With ultraviolet light having a wavelength of
266 nm, and total accumulated radiated energy of
100 J/cm
2
, the sensitivity of the CCD will be
reduced by about 1%.
As an easy guideline to calculate the duration of time
which causes a 1% reduction in the sensitivity with a
226 nm ultraviolet light source (Characteristic
Example 1), we will introduce a simpler version of the
formula used above to calculate the total amount of
accumulated radiated energy.
Time which causes a 1% reduction in the
sensitivity (in years) =
3.17/ amount of radiated light [
µ
W]
This formula is based on the amount of radiated light
under one light source, with the camera being used
continuously for 24 hours a day. For example, with
1.5
µ
W of radiated light, which is the high-power
output from one light source, the number of years it
would take a 1% deterioration in sensitivity to occur
is 2.11 years. So if the camera is used 8 hours a day,
then the period is three times that, or 6.33 years.
Characteristic Example 2:
With ultraviolet light having a wavelength of
196 nm, and total accumulated radiated energy of
15 J/cm
2
, the sensitivity of the CCD will be
reduced by about 15%.
As an example of the decision standard, you can think
of a 15% reduction in sensitivity as a guideline to use
to decide when to replace the CCD. However, even
though the conditions under which you use your
camera change (for example, how wide you open the
lens, how long the exposure time is, how high the gain,
etc.), it is not absolutely necessary to change the CCD
as long as the desired standard of image quality
continues to be produced.
As an easy guideline to calculate the duration of time
which causes a 15% reduction in the sensitivity with a
196 nm ultraviolet light source (Characteristic
Example 2), we will introduce a simpler version of the
formula used above to calculate the total amount of
accumulated radiated energy.
Time which causes a 15% reduction of the
sensitivity (in years) =
0.48/ amount of radiated light [
µ
W]
This formula is based on the amount of radiated light
under one light source, with the camera being used
continuously for 24 hours a day. For example, with
0.5
µ
W of radiated light, which is the standard output
from one light source, the number of years it would
take the CCD to suffer the 15% deterioration in
sensitivity necessary to require replacement is 0.96
years. So if the camera is used 8 hours a day, then the
time to replacement of the CCD is three times that, or
2.88 years.
This is how the sensitivity of the CCD deteriorates
from the effects of the radiation of ultraviolet light.
When the wavelength of the radiated ultraviolet light
changes, it can be assumed that the total amount of
accumulated radiated energy which causes the
deterioration in the sensitivity will vary greatly.
Please be aware that it is possible for the sensitivity to
deteriorate in a short time, too, especially when a large
amount of ultraviolet light is used. (When an
ultraviolet laser is shined directly into the camera and a
portion of the usable picture element area of the CCD
receives a significant amount of ultraviolet light, that
portion of the CCD alone can suffer from deterioration
in sensitivity.)
Even when there isn’t a significant amount of light
entering the camera, but the exposure to the light
continues for a long time, the sensitivity can be
affected. So close the shutter when not actually
shooting, and protect the CCD from ultraviolet light as
much as possible.
Because the CCD is replaceable, when you want to
replace it due to deterioration in sensitivity, contact the
store where you purchased the camera. However, you
cannot replace just the CCD, you will have to replace
the front panel block as a unit, at additional expense.