Achieving High Sensitivity |
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As we mentioned at the beginning of this article,
constantly striving for high sensitivity and
even lower noise is important in the security
camera field.
By introducing the forming and design technologies
fostered in the finer pixel sizes used
in recent years, Sony was able to improve the
CCD structure in the “Super HAD CCD II” and
achieve a sensitivity of 1000 mV or higher per
square micron (F5.6 for color sensors, F8 for
black and white, 1 s accumulation time). This
corresponds to a +6 dB improvement over
Sony’s current products. In particular, the percentage
of light focused on the photodiode was
increased significantly by increasing the aperture
size and improving the form and height of
the microlenses. Sony also succeeded in suppressing
the reduction in focusing ratio that
occurs when the lens is used at its wide open
F number.
Furthermore, the photosensor area was increased
making highly efficient optoelectronic conversion
possible. (See figure 1.)
Figure 1 “Super HAD CCD II” Elemental Technologies that Improve Sensitivity
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Achieving both Improved Spectral
Sensitivity Characteristics and Light
Resistance |
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While achieving high sensitivity in the ”Super
HAD CCD II”, we also designed this device
with concern for color reproduction.
By adopting new complementary color pigment
materials in the color filters, we increased
the blue (short wavelength) sensitivity and
achieved balanced spectral sensitivity characteristics.
These spectral sensitivity characteristics lead
to reduced color noise.
Furthermore, this new device maintains the
strong light resistance of the proven current
ICX408AK/409AK products. Even in locations
subject to strong ambient illumination for extended
periods, the color filters remain strongly
resistant to fading. |
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Compatibility with Sony’s Current Products |
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Security camera products have an extremely
long life; in some cases the same model will
be sold for over ten years. Therefore, compatibility
of the parts used is an extremely important
factor in this product area. These new
devices maintain the same image size, pixel
count, drive timing, package, and pin arrangement
as Sony's current products, while improving
sensitivity by over +6 dB compared to those
products.
Due to this compatibility, customers can create
new models without changing the design
simply by switching to a new CCD.
Furthermore, in addition to the same 5.0 V (Typ.)
as the current products, the ICX638AKA/639AKA
additionally support 3.3 V (Typ.) as the drive
voltage for the horizontal transfer clock and
reset gate clock. Thus these devices maintain
compatibility with existing product models
while at the same time contributing to lower
power in new models.
Figure 2 Characteristics Comparison
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all articles with figures and tables.  |
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Vol.52 |
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