- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
120
10.6.6. AE Mechanical Iris Mode
This is an example of a lens with an automatic iris which operates using a power supply and video signal.
In AE mode, if MIRIS (CAT14_Byte1_bit1) is set to 1[h], then Mechanical Iris Mode is set.
In this mode, the shutter speed is always 1/60 sec for NTSC and 1/50 sec for PAL, and the backlight
compensation amount is output and supplied as a voltage to an external circuit using the CXD3172AR’s
internal EVR1. The AE operation is performed using AGC control based on the microcontroller’s AE, and the
mechanical iris inside the external lens.
Example configuration of mechanical iris using IRISVCNT
The CCDLEVEL signal of CXA2096N is used as the video signal. The amplitude of this signal can be
controlled by VCA, which is controlled by the IRISVCNT voltage after level adjustment by a pre-amp circuit.
This makes it possible to perform backlight compensation using the lens iris.
Fig 10.6-3 Example configuration of video servo mechanical iris
CCD
CXA2096N
15
Lens
CCDLEVEL
VCA
Pre AMP
Video Signal
EVR1
GND
Vdd
CXD3172AR
IRISVCNT
Backlight Compensation
Pin 64 (EVR1)
Motor
Driver
Circuit
0 - 3.3V